WO1999025965A1

WO1999025965A1 - VEHICULAR ON-BOARD MONITORING SYSTEM SENSING COMBINED HC/NOx EMISSIONS FOR CATALYTIC CONVERTER EVALUATION

Info

Publication number: WO1999025965A1
Application number: PCT/US1998/022782
Authority: WO
Inventors: Patrick W. Blosser
Original assignee: Engelhard Corporation
Priority date: 1997-11-14
Filing date: 1998-10-27
Publication date: 1999-05-27
Also published as: WO1999025965A9; AU1282199A

Abstract

An on-board monitoring system senses hydrocarbon emissions produced by the internal combustion engine of a vehicle through qualifying condition sensors detecting selected vehicle operating conditions and a hydrocarbon sensor sensing HC emissions. The HC emission signals are counted and compared against a set HC concentration threshold to determine if an excessive emission has occurred only if the vehicle has met threshold limits for each qualifying condition sensor. By calculating the number of excessive emission signals against the total number of emission signals counted during an operating run of the vehicle, the vehicle is determined to be within or outside of emission regulatory standards. By selecting a qualifying condition to be a NOx concentration present at a set threshold concentration in the exhaust gas, the adverse impact of drive cycle variations on repeatable, consistent HC readings is eliminated.

Description

VEHICULAR ON-BOARD MONITORING SYSTEM SENSING COMBINED HC/NO_x EMISSIONS FOR CATALYTIC CONVERTER EVALUATION

This invention is a continuation-in-part of application Serial No. 08/903,524, filed 7/30/97, entitled "Automotive On-Board Monitoring System for Catalytic Converter Evaluation" .

FIELD OF THE INVENTION

This invention relates generally to an on-board system for monitoring vehicular emissions and more particularly to a diagnostic system for monitoring such emissions.

The invention is particularly relevant to an emissions monitoring system in compliance with government regulatory emissions standards such as OBD II mandated by the State of California and will be described with specific reference to such systems. However, those skilled in the art will recognize that the invention may have broader applications and could be used for monitoring, evaluating and/or predicting the functional operation of any number of vehicle components whether or not related to the vehicle's emissions.

INCORPORATION BY REFERENCE

The following United States patents are incorporated by reference herein so that details relating to the engine control module and the ability or sophistication of the engine control module to monitor emissions information need not be set forth nor explained in detail herein. The patents listed below or referenced in the specifications do not form part of the present invention. A) United States patent No. 5,431,042 to Lambert et al. entitled "Engine Emissions Analyzer";

B) United" States patent No. 5,426,934 to Hunt et al. entitled "Engine and Emission Monitoring and

Control System Utilizing Gas Sensors";

C) United States patent No. 5,490,064 to Minowa et al. entitled "Control Unit for Vehicle and Total Control System Therefor";

D) United States patent No. 5,237,818 to Ishii et al. entitled "Conversion Efficiency Measuring Apparatus of Catalyst Used for Exhaust Gas Purification of Internal Combustion Engine and the Method of the Same"; and,

E) United States patent No. 5,505,837 to Friese et al. entitled "Sensor Arrangement for Determining Gas Components and/or Gas Concentrations of Gas

Mixtures" .

In addition, my prior patent application S.N. 08/903,524, filed 7/30/97, entitled "Automotive On-Board Monitoring System for Catalytic Converter Evaluation" is hereby incorporated by reference and made a part hereof .

The present invention is also related to United States patent applications: EXHAUST GAS SENSOR (Docket No. 300.002); GAS SENSOR HAVING A POROUS DIFFUSION BARRIER LAYER AND METHOD OF MAKING SAME (Docket No. 300.003); and EXHAUST GAS SENSOR WITH FLOW CONTROL WITHOUT A DIFFUSION BARRIER (Docket No. 300.004); APPARATUS AND METHOD FOR DIAGNOSIS OF CATALYST PERFORMANCE (Docket No. 4077-A) , each application being filed of even date herewith and the disclosures of which are hereby expressly incorporated herein by reference. Additionally, this patent relates to United States application entitled "Apparatus and Method for Diagnosis of Catalyst Performance" filed on November 3, 1997 bearing attorney Docket No. 4077 incorporated by reference herein.

BACKGROUND OF THE INVENTION

As is well known, government regulations require vehicles equipped with internal combustion engines to have emission monitoring systems conventionally known as OBD (On-board Diagnostic Systems) to advise the operator of the vehicle when the gaseous pollutants or emissions produced by such vehicles exceed government regulatory standards. Government regulatory standards set emission threshold levels which the vehicle cannot exceed when operated pursuant to a specified driving cycle such as that set forth in a FTP (Federal Test Procedure). The FTP requires the vehicle be operated at various acceleration/deceleration modes as well as at steady state or constant velocity at various specified speeds in a standardized drive cycle. Specifically, the hydrocarbon emissions from the vehicle cannot exceed threshold limits during the standardized drive cycle.

One of the principal components of the vehicle ' s emission system is the catalytic converter, typically a TWC (Three Way Catalyst - NO_x, hydrocarbons and oxides, i.e., CO) . TWCs store oxygen when the engine operates lean and release stored oxygen when the engine operates rich to combust gaseous pollutants such as hydrocarbons or carbon monoxide. As the catalyst ages, its ability to store oxygen diminishes and thus the efficiency of the catalytic converter decreases. Conventional systems in use today monitor the ability of TWCs to store oxygen to determine failure of the catalyst. Typically an EGO (exhaust gas oxygen sensor) is placed upstream of the TWC and an oxygen sensor is placed either within or downstream of the TWC to sense the oxygen content in the exhaust gas .

The principal disadvantage of this method is simply that the oxygen storage capacity of the TWC has been demonstrated to poorly correlate with hydrocarbon conversion efficiencies. See J. S. Hepburn and H. S.

Gandhi "The Relationship Between Catalyst Hydrocarbon

Conversion Efficiency and Oxygen Storage Capacity", SAE paper 920831, 1992 and G. B. Fischer, J. R. Theis, M. V.

Casarella and S. T. Mahan "The Roll of Ceria in Automotive Exhaust Catalysis and OBD-II Catalyst Monitoring", SAE paper 931034, 1993. Another significant disadvantage of current monitoring systems is that for such methods to be applied to low emission vehicles (LEVs)and ultra-low emission vehicles (ULEVs), it will be necessary to monitor increasingly smaller portions of the TWC leading to less reliable correlations to total TWC performance. It should also be noted that monitoring smaller portions of the TWC require that the catalyst be canned, in sections, to facilitate insertion of the oxygen sensors at appropriate locations within the TWC further increasing the cost of the

TWC.

Any HC system which attempts to evaluate the efficiency of the catalytic converter by ascertaining the combustibles of an exhaust stream before and after the TWC is inherently flawed for a number of reasons. First, the pre-catalyst and post-catalyst signals have to be time adjusted to assure measurement of the same gas mixture. The speed of the gas has to be precisely determined even though the gas stream passes through a tortuous path within the converter conducive to producing uneven flow for various gas stream slips. Second, the pre-catalyst and post-catalyst sensors must make measurements in significantly different gas mixtures which produce different reactions over the sensors. This prevents optimization of- sensor sensitivity if a common sensor design is used or requires a multitude of sensor designs optimized to match the expected gas mixture present at the sensor placement position. Third, the hydrocarbon conversion efficiency is determined from the difference between a large signal developed by the pre-catalytic converter sensor resulting from the unburnt hydrocarbons compared to a small signal (typically on a ppm basis for ULEV applications) resulting from the post-catalytic converter sensor. Differentiation becomes increasingly difficult as hydrocarbon emission standards tighten. Finally, the two sensors are not expected to age at equal rates owing to different gaseous environments and temperatures experienced during operation. Thus, long term reliability using a direct, dual measurement to ascertain catalyst efficiency is suspect.

The prior art has already recognized limitations of using oxygen sensors to determine catalytic conversion efficiency. United States Patents Nos. 5,177,464 to Hamburg, 5,265,417 to Visser et al., and 5,408,215 to Hamburg, all disclose the use of a hydrocarbon sensor to determine emission compliance of the vehicle. However, the sampling system disclosed in the preferred embodiments of the aforementioned patents is to sequentially tap portions of the exhaust gas stream, upstream and downstream of the TWC, which gas portions are then analyzed by a single sensor to determine hydrocarbon concentrations . The upstream and downstream sensor readings are compared to establish ratios for hydrocarbon conversions which are stored and evaluated to determine an efficiency ratio in turn correlated to emission threshold regulated standards. As the catalyst ages, the ratios change to trigger the appropriate warning. This approach relies on valves and switches for sampling that will likely result in higher cost, added complexity, lower reliability, and a potentially slow response time. Obtaining good comparative samples of exhaust gas will also be complicated by the dynamic changes in exhaust flows, hydrocarbon concentrations, and exhaust gas pressure during normal vehicular operation. Thus, while this approach overcomes the limitations inherently present in the conventional EGO sensor systems because the hydrocarbons are directly measured vis-a-vis the hydrocarbon sensors, the before and after comparison inherently cause limitations in the sampling system proposed as noted above

United States patent No. 5,444,974 to Beck et al. and possibly, the schematic representation portrayed in Figure 6 of the Hamburg references cited above, disclose a fundamentally different approach than that discussed above. In Beck, an especially developed calorimetric sensor is used downstream of the TWC to sense hydrocarbon emissions. The readings from the sensor are correlated to emissions when the vehicle is operated at certain conditions specified to be constant speed and stoichiometric or lean engine conditions. Beck filters the signals developed by the calorimetric sensor so that only the signals occurring when the vehicle is at the specified operating conditions are selected to be processed. The filtering is done vis-avis the EGO sensor upstream of the TWC. The data is stored and built into histograms to provide an acceptance or rejection of the catalytic converter.

Engine microprocessors or ECMs (engine control modules) used in today's vehicles are sophisticated, high powered devices capable of processing input from any number of sensors depicting operating conditions of the vehicle and rapidly issuing engine control signals in response thereto. It is known to program the ECM to perform onboard monitoring of the emissions system. United States patent No. 5,490,064 to Minowa illustrates such a control unit which includes in its functions an on-board self diagnostic emissions monitoring process using conventional precatalytic and postcatalytic 0₂ sensors, digital filtering and exhaust gas speed to correlate the sensor readings to one another to determine failure of the catalytic converter. United States patent No. 5,431,011 to Casarella et al. likewise illustrates precatalytic and postcatalytic converter 0₂ sensors whose signals are processed by the CPU in the ECM along with other vehicle operational signals. In Casarella, a two-stage analyzing technique is utilized. Filtered signals are collected in a first stage and analyzed. If the first stage analysis indicates a failure, then a more thorough or rigorous second stage scrutiny of a number of signals which can effect performance of the catalytic converter is conducted before indicating failure of the converter.

More recently, artificial intelligence approaches have been used to avoid reliance on algorithms to calculate the converter Jactivity based upon the laws of physics and/or chemistry. United States patent Nos. 5,539,638 to Keeler et al. and 5,625,750 to Puskorius et al. illustrate use of sophisticated computerized neural networks utilizing training programs to predict failure of the catalytic converter. In Keeler, the parameters which control the operation of the vehicle's engine such as temperature, back pressure, valve position, etc. are detected by various sensors employed on the vehicle including the conventional EGO sensor upstream of the catalytic converter and are trained in the sense that the operating conditions vis-a- vis the vehicle's ECM are correlated to an emissions level produced by the vehicle's engine for the sensed operating conditions of the engine. The signals are stored on a time basis and factored and compared to a threshold value indicative of a regulatory standard at which an emissions failure is deemed to have occurred. In Keeler, training of the neural network is accomplished by simply inserting whatever sensor probe is used by the government regulatory agency in the vehicle's exhaust pipe to generate emissions data correlated to the sensed parameter. Puskorius discloses a more sophisticated neural network and additionally uses an EGO sensor position rearwardly of the catalytic converter to provide two neural artificial intelligence networks with feedback. One network establishes emissions before the catalytic converter and the' second network establishes emissions after the catalytic converter. Training data for the networks is provided from a data bank of a large number of similar vehicles with data accumulated over the expected vehicle life. In operation, then, a trained neural network provides an efficiency ratio accumulated over time which is compared against stored data to predict when failure of the catalytic converter will occur. While an artificial intelligence computerized network may appear theoretically sound, in practice, it is only as good as the training data which cannot be precisely correlated to that one specific vehicle which is being sampled. The assumption is made that any specific vehicle will produce emissions at the level of that produced by the vehicle(s) from which the training data was assimilated.

While the arrangements discussed above illustrate the sophistication and computing power of an ECM, they additionally require further expenses incurred in upgrading the computing power of the ECM to handle additional data storage and computational functions required of algorithm intensive emission monitoring systems. A more subtle problem results from extensive filtering employed in the monitoring system which in turn requires data from a number of different sensors, some of which may have to be recalibrated or refined in their sensing outputs to develop sensitive ranges suitable for emission sensing purposes in addition to their primary engine control f nctions . The use of multiple data sources for filters means the system is more likely to be less reliable over time since failure or calibration drift of any of the sensors will produce inaccurate system results.

SUMMARY OF THE INVENTION

It is thus a principal object of the invention to provide an on-board monitoring system for a catalytic converter equipped vehicle, which is able to directly sense emissions throughout the vehicle's operating range including the various drive cycles specified by emission regulatory standards .

This object along with other features of the invention is achieved in a system which includes a process (and apparatus) for on-board monitoring and detecting a failure of the catalytic converter of a vehicle. The process includes the steps of providing at least one emission sensor downstream of the catalytic converter generating emission signals indicative of the emissions in the vehicle's exhaust gas and providing at least one qualifying condition sensor for sensing at least one vehicular operating condition affecting the performance of the catalytic converter, the qualifying condition sensor generating qualifying condition signals indicative of the vehicle's operating condition. The qualifying condition signals are sampled at periodic intervals during an operating run of the vehicle and each sampled qualifying condition signal is compared to a set threshold which, if met or exceeded, establishes a validated qualifying condition signal. The process also samples the emission signals only at the time a validated qualifying condition signal is produced and each sampled or validated emission signal is compared against a set emission threshold to determine if the validated emission signal exceeds the set emission threshold to become an excessive emission signal. The process includes the final step of activating a warning indicator after completion of a vehicle run, (established either on a timed or validated condition signal count basis), if a statistical evaluation of excessive emission signal occurrence, i.e., frequency, exceeds a stored emission value corresponding to a regulatory emission standard. By selecting appropriate qualifying condition sensors, the process produces a reliable method for easily computing a failure of the catalytic converter system to meet emission standards based on actual emission sensor readings.

In accordance with a significant feature of the invention, the emission sensor senses NO_x separately from HC and simultaneously generates NO_x signals indicative of NO_x concentrations in the exhaust stream and HC signals indicative of the HC concentration in the exhaust stream. The emission signal is sampled or counted only when the emission signal exceeds a set threshold for N0_X, i.e., a validated emission signal, whereby variations in the driving cycle, such as speed or the air to fuel ratio, have no effect on the ability of the monitoring process to determine if the catalytic converter satisfies emission regulation requirements. More specifically, this aspect of the invention includes the discovery that the presence of NO_x emissions in the exhaust gas at or greater than a set limit allows direct sensing of hydrocarbon emissions to produce accurate and consistent hydrocarbon readings with the engine operating at lean, rich or stoichiometric conditions. In accordance with another aspect of the invention the stored value corresponding to a regulatory emission standard has an upper limit and a lower limit associated therewith, and in the event the system produces a calculated emission value falling between the upper and lower limits for any given run, additional operating runs are conducted and the calculated values for each run are statistically factored as a group to produce an average value of excessive emission signals compared to the actual stored value to determine if the warning mechanism is to be activated thereby avoiding false warnings of failure of the catalytic converter. Additionally should the calculated emissions for the run fall below the lower limit, sampling of additional runs can be delayed to prolong sensor life since the system indicates a measure of the effectiveness of the catalyst.

In accordance with yet another important feature of the invention, the set emission threshold can be varied to include a plurality of different hydrocarbon threshold concentrations, with each run producing different pluralities of excessive emission signals for each of the various hydrocarbon threshold concentrations. The process includes the additional step of comparing the frequencies at which the number of excessive emission signals exceeded each hydrocarbon threshold concentration to determine an actual sensed hydrocarbon emission level produced by the vehicle whereby the process senses actual hydrocarbon emissions which may be directly compared to regulatory hydrocarbon emission levels without the need for extrapolation and correlation present in other monitoring systems .

In conjunction with the foregoing inventive feature, a still more specific feature of the invention is the further step, after a failure has been detected, of determining whether the excessive emission signals in the run exceeded the stored value for all hydrocarbon threshold concentrations whereby the monitoring process determines whether or not the sensed emission failure is attributed to the catalytic converter or some other operating system within the vehicle without the necessity of having to undergo extensive diagnostic routines.

In accordance with yet another feature of the invention there is provided a system for on-board monitoring and detecting a failure of a vehicle's exhaust emission to meet governmental regulatory emission standards for various operating speeds and conditions of a vehicle powered by an internal combustion engine. The system includes a) a catalytic converter through which the vehicle's exhaust gasses pass; b) a qualifying condition sensor arrangement for sensing an operating condition of the vehicle and generating a qualifying condition signal indicative of the sensed operating condition; and c) an emission sensor - immediately downstream of the catalytic converter for sensing at least hydrocarbons in the exhaust gas and generating hydrocarbon emission signals indicative of the concentrations of hydrocarbon emissions in the exhaust gas . The vehicle ' s on-board computer causes periodic sampling of the qualifying condition sensor to generate a plurality of qualifying condition signals, with each qualifying condition signal compared against a stored qualifying condition threshold to determine if a validated qualifying condition signal has occurred. The computer also causes periodic sampling of the hydrocarbon emission signals but only the hydrocarbon emission signals generated when a simultaneously generated validated qualifying condition signal has occurred are counted each of which are compared against a set emission threshold whereby each hydrocarbon emission signal exceeding the set emission threshold is deemed an excessive emission signal. The computer calculates, by statistically factoring, the number of "excessive emission signals occurring during a given operating run of the vehicle to determine if a warning condition is present whereby a warning indicator mechanism is actuated to alert the operator of the vehicle of a failure of the vehicle to meet regulatory emission standards-? The monitoring system thus allows easily implemented counting routines established by relative signal size comparisons to determine vehicle emission compliance without the need of sophisticated algorithms requiring sophisticated computer systems.

A particularly unique feature of the invention resides in the catalytic converter arrangement which includes a close-coupled catalyst positioned in close proximity to the exhaust header of the vehicle for reacting with approximately 60 to 80% of the hydrocarbon emissions in the exhaust gas and a TWC catalytic converter downstream of the close-coupled catalyst. The sensor arrangement includes a first hydrocarbon sensor downstream of the close-coupled catalyst and a second emissions sensor downstream of the TWC catalytic converter with different stored emission values for each of the sensors whereby the first hydrocarbon sensor i) insures compliance with emission standards during "cold" or "warm-up" operation of the vehicles and/or ii) is a predictor, from statistical evaluation of its excessive emission signals, of the remaining life of the TWC and/or iii) aids the ECM in adjusting the A/F ratio of the vehicle as a result of the frequency of the excessive emission signals.

In accordance with yet another important feature of the invention, the second hydrocarbon sensor arrangement downstream of the TWC not only senses the hydrocarbon emissions but also separately senses the nitrous oxide emissions in the exhaust gas and generates HC and NO_x signals indicative, respectively, of the hydrocarbon emissions and nitrous oxide emissions in the exhaust gas prior to release to the atmosphere. The computer samples on a periodic basis simultaneously generated HC and NO_x signals produced by the second emission sensor and compares each simultaneously sampled HC and NO_x signal against a set emission HC and NO_x threshold, respectively, so that each simultaneously generated HC and NO_x signal pair exceeding each's respective stored emission threshold is an excessive emission signal whereby the warning arrangement is actuated when a set number or set frequency of excessive emission signals occur without regard to the operating speed or any other operating conditions of the vehicle.

It is thus an object of the present invention to provide an on-board system (process and apparatus) for a vehicle equipped with an internal combustion engine which monitors the exhaust emissions produced by the vehicle and indicates a failure of the catalytic converter(s) in the vehicle to satisfy emission regulatory standards characterized by any one or any combination of or all of the following: a) continuous monitoring of the vehicle's emissions irrespective of the operating condition of the vehicle such as its speed, it's A/F ratio, etc; b) actual sensing of hydrocarbon emissions assuring strict conformance with emission regulations including LEV and ULEV standards; c) recording specific levels of hydrocarbon emissions during vehicle runs corresponding to FTPs and other regulatory driving cycles; ' d) simple processing (algorithms) steps permitting implementation into existing ECM's without significant upgrading; e) monitoring of vehicle's compliance with emission standards during vehicle start-up or warm-up period; f) diagnosing emission failures attributed to failure of the catalytic converter or to other engine operating systems; g) reducing catalytic converter costs by minimizing canning requirements for the converter; h) controlling engine operating systems separately and apart from monitoring vehicular emissions; i) utilizing a signal generation and processing arrangement which is able to account for erratic and/or sporadic fluctuations in the engine operating conditions which would otherwise distort the emission readings; j ) having the flexibility to monitor emissions other than hydrocarbons when and if emission standards require control levels for other gaseous components emitted by an internal combustion engine; and/or k) monitoring emissions without regard to the A/F ratio, space velocity through the catalyst and other engine operating conditions.

It is a general object of the invention to provide a statistical system (method and apparatus) for catalyst monitoring that minimizes emission variabilities attributed to random vehicle operation by simultaneously monitoring both HC and NO_x tailpipe emissions using post catalyst sensing devices(s) to make a determination of catalyst performance .

In conjunction with the immediately preceding object, a further object of the invention is to provide a monitoring system for exhaust emissions which utilizes varying threshold evaluation levels to tailor the monitoring system to meet any specified range of emission limits resulting in a flexible monitoring system.

In conjunction with the immediately preceding object, a specific but important object of the invention is to provide a monitoring system of the afore described type which can be easily modified or refined through changes in qualifying conditions to further compensate for driving variables which render other monitoring systems unreliable. Another object of the invention is to provide a monitoring system which reduces the requirements of the hydrocarbon sensor by reliance on threshold levels thus minimizing to some extent the requirement that the hydrocarbon sensor sense absolute ppm measurements resulting in less expensive hydrocarbon sensors than otherwise required. Another object of the invention is to provide a monitoring system which produces a more reliable catalyst diagnosis than current EGO switching ratio approaches resulting in fewer erroneous malfunction indicator light (MIL) warnings for the catalyst and reduced warrantee repair bills for the automotive manufacturers.

Another object of the invention is to provide an emissions monitoring system which can quickly determine the presence of an adequately functioning catalytic converter and then be shut off to increase the life of the emission sensors.

Another object of the invention is to provide an emissions monitoring system which uses a process in which gas flow rate has minimal importance thus permitting utilization of economical sensors which measure gas concentrations and are flow independent.

- Another object of the invention is to provide an emissions monitoring system capable of being operated under rich or lean conditions so that the system can function with new engine control strategies being developed today, such as partial lean burn and gasoline direct injection engine control strategies.

An important object of the invention is to provide a generic emissions monitoring system capable of application to any vehicle platform thus avoiding tailoring of the OBD monitor and reducing time and money otherwise spent on qualifying new vehicular platforms for emission certification. Yet another object of the invention is to provide an emissions monitoring system which reduces or relaxes the requirements of correlating emission sensor readings with vehicular operating conditions permitting, among other things, the use of sensors in a cooler environment than what would otherwise be possible, thus prolonging sensor life and allowing utilization of a wider range of sensors including sensors capable of sensing both HC and N0_X gases simultaneously. These and other objects, features and advantages of the present invention will become apparent to those skilled in the art upon reading and understanding the Detailed Description of the Invention set forth below taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may take form in certain parts and an arrangement of certain parts taken together and in conjunction with the attached drawings which form part of the invention and wherein:

Figure 1 is a general diagrammatic illustration of the vehicular components of an emission system;

Figures 2 and 3 are graphs of TWC conversion efficiencies for emissions (HC, CO, NO_x) as a function of Lambda for "good" and "aged" catalysts, respectively;

Figure 4 is a graph of speed and speed change as a function of time for the FTP-75 driving cycle;

Figure 5 is a graph of speed and speed change as a function of time for a steady state (SS) driving cycle;

Figure 6 is a plot of HC concentrations as single data points resulting from the SS and FTP driving cycles with average HC concentrations plotted on the y-axis and calculated FTP g HC/mile plotted on the x-axis;

Figure 7 is a plot similar to Figure 6 but with low temperature data points for the SS run discarded;

Figure 8 is a diagrammatic flow chart of a simple statistical algorithm used in the present invention;

Figure 9 is a diagrammatic logic flow chart illustrating one method of analyzing data resulting from Fig. 8;

Figure 10 shows a series of trendline graphs indicating the percentage of times a set emission threshold is exceeded as the catalyst ages;

Figure 11 is a trendline plot of an FTP cycle and a trendline plot of a SS cycle indicating the percentage of times a common emission threshold for both cycles is exceeded as the catalyst ages;

Figure 12 is a graph similar to Figures 10 and 11 showing a common trendline for both FTP and SS drive cycles in accordance with the invention;

Figure 13 is a schematic representation indicative of the ' coupled effects of catalyst aging, depicted on the y axrs (vertical), and lambda, depicted on the x axis (horizontal) ;

Figure 14 is a plot of HC and NO_x emissions at various vehicle speeds for a fresh TWC; Figure 15 is a plot similar to Figure 14 but for an aged TWC :J

Figure 16 shows a series of trendline plots similar to

Figure 10 but with each trendline based on emissions exceeding a set NO_x level and a HC level, the HC levels being varied to produce the various trendline graphs illustrated;

Figure 17 shows a series of trendline plots similar to Figure 16 but at a higher set NO_x level than that used to construct the trendlines of Figure 16; and,

Figure 18 shows two trendline plots taken from Figures 16 and 17 with each trendline constructed at a fixed HC level.

DETAILED DESCRIPTION

I The General Structure of the Emission System

Referring now to the drawings wherein the showings are for the purpose of illustrating a preferred embodiment invention only and not for the purpose of limiting same, there is generally shown in diagrammatic form in Figure 1 the principal components of a vehicular emission control system 10. The vehicle has an internal combustion engine 12 which discharges gaseous pollutants or emissions through an exhaust system 14. Internal combustion engine 12 is conventionally under the control of an electronic control module or ECM 15 (controller or computer) .

_. Exhaust system 14 is conventional and includes an exhaust header 16, a close-coupled or light-off catalyst 17 closely adjacent header 16, a three-way catalyst or TWC 18 positioned downstream of exhaust header 16, a muffler 19 downstream of TWC 18 and a tailpipe 20 downstream of muffler 19 which is open to atmosphere for discharging or emitting the emissions or gaseous pollutants produced by internal combustion engine 12. ECM 15 is conventional and includes well known elements such as a central processing unit or CPU 22, RAM (Random Access Memory) 23, ROM (Read Only Memory) 24, and NVRAM (Non Volatile Random Access Memory) 25. Also included is a look-up table 29 separate and apart from ROM 24 (or alternatively included as a component of ROM 24). Also shown is a conventional input/output unit (I/O) unit 28 for receiving and transmitting appropriate instructions from and to ECM 15. I/O unit 28 typically transmits appropriate instructions to activate a display failure light or warning mechanism 30 situated in the vehicle. Communication between ECM 15 and actuation units on the vehicle including sensors associated therewith is typically carried out via conventional two-way communication links which may be, for example, bi-directional serial data links in 8-bit, 16-bit or 24-bit formats. ECM 15 operates in a well established known manner to control the engine and process engine control and diagnostic routines, such as that stored in step by step instructions in ROM 24. Essentially, engine operating parameters are read into ECM as input signals which are then processed into output signals or control signals outputted from ECM to actuation units on the vehicle controlling vehicular operation, specifically, the operation of internal combustion engine 12 "as well as warning mechanism 30. Insofar as the present invention is concerned, input sensor signals are read into ECM, processed by RAM 23 and NVRAM 25 under the control of CPU 22 from algorithm routines stored in ROM 24 and emission correlation data typically stored in look-up table (LUT) 29 to generate signals outputted by I/O unit 28 to display 30 and to optimally use the signals to either monitor or control engine 12.

Several sensors normally applied to the vehicle with their sensor signals inputted to ECM 15 are shown in Figure 1. Typical sensors which generate operative signals indicative of an operating condition of the vehicle include a vehicle speed sensor generating vehicle speed signals on line 34; an A/F sensor system (which includes several sensors sensing EGO, manifold air pressure, mass air flow) is shown schematically as generating signals on line 37 indicative of the estimated ratio of air to fuel fed to engine 12 controlling combustion at or above stoichiometric ranges in engine 12; and, an EGO sensor generating signals on line 38 indicative of the oxygen present in the exhaust gas upstream of TWC 18 for controlling several vehicular functions such as the exhaust gas recirculation (EGR) system on the vehicle.

In accordance with the invention certain of the operating signals conventionally generated to control engine 12 may be used to trigger the sampling of emission signals. For terminology purposes, when an operating condition sensor signal is used in the invention's monitoring system, it will be referred to as a qualifying condition signal. Examples of qualifying condition signals which can be used in the invention's monitoring system include, but are not necessarily limited to, time from engine start, exhaust gas and/or catalyst temperatures, vehicle speed (line 34), engine rpm, EGO sensor signals

(line 38), A/F (line 37), manifold air pressure (MAP), mass air flow (MAF) signals from hot wire anemometers, throttle position, exhaust gas recirculation (EGR) solenoid position, manifold inlet air temperature, engine coolant temperature, transmission position, and other gearing or drive shaft torque information.

Referring still to Figure 1, an emission sensor arrangement 40 is shown positioned immediately downstream of TWC 18 and a second emission sensor 40a is optionally positioned immediately downstream of light-off catalyst 17 also generating emission sensor signals on line 41a.

In the broad sense of the invention emission sensor 40 generates gas sensor signals which correspond to temperature or concentrations of non-methane hydrocarbon (NMHC), methane, total HC, NO_x, CO, SO_x, total combustibles, oxygen, carbon dioxide, or combinations of these gases. In the preferred embodiment of the invention, emission sensor includes any sensor or combination of sensors which can sense separately HC and NO_x emissions. Sensor 40, per se, does not form part of the invention and any conventionally designed sensor can be utilized in the invention. In fact, the inventive system contemplates that developments in the sensor art will further enhance its utilization and capabilities. In the preferred embodiment sensor arrangement includes a separate hydrocarbon sensor and a separate NO_x sensor spaced closely adjacent exit end of TWC 18 and at diametrically opposed, axially aligned positions in the exhaust so that both sensors are simultaneously sampling the same exhaust stream. Alternatively, a valving arrangement to siphon a stream of exhaust gas to a compartment for measuring same as disclosed in Hamburg United States patent numbers 5,177,464 and 5,408,215 may be utilized. A hydrocarbon sensor 40a is utilized for close-coupled catalyst 17. Hydrocarbon sensor of the type shown in United States patent numbers 5,265,417 to Visser et al. and 5,451,371 to Zanini-Fisher et al. (incorporated by reference herein) may be utilized. Nitrous oxide sensors of the type shown in United States patent numbers 4,927,517 to Mizutani et al. and 5,486,336 to Dalla Betta et al. (incorporated by reference herein) may be used. Electrochemical oxygen sources such as shown in U. S. patent No. 5,505,837 to Friese et al. may be utilized with such sensors, also incorporated by reference herein. Essentially, these electrochemical sensor devices are calorimetric or Pellistor type sensors in which the gas is passed over a catalyst portion of the sensor causing a chemical reaction producing a temperature change (in theory the reaction could cause other physical changes which could be measurable). The temperature change is measured electrically, usually by comparing the catalyst coated channel in the device to a non-coated reference channel, to produce a difference signal which is correlated to the concentration of the specific gaseous component which is being measured. An oxygen source, such as shown in Friese is provided to supply oxygen if needed to produce the catalyst reaction.

As is known to those skilled in the art, the vehicle emission control system will sample one or more qualifying condition sensor signals corresponding to regulatory standards dictating emission requirements of the vehicle at specified vehicle operating conditions, i.e., FTP (Federal Test Procedure) . ECM 15 senses the operating conditions and then reads and interpolates emission sensor signals on lines 41, 41a to determine the compliance with emission standards. Further, as noted above, a number of catalytic converters can be interposed within exhaust system 14 to assure compliance with emission standards such as light-off catalyst 17, which insures catalytic hydrocarbon reactions during warmup of the vehicle while also assisting in the efficiency of TWC 18. Insofar as the present invention is concerned, correlation of the various catalytic converters during the staged combustion of the exhaust gases is monitored by emission sensor 40 and, to some extent, the engine operation can be controlled by appropriate algorithms in response to the monitoring signals. The control algorithms for the internal combustion engine are beyond the scope of this invention and reference should be had to United States patent Numbers 5,426,934 to Hunt et al. and 5,490,064 to Miami et al. (incorporated by reference herein) in this regard.

As is well known, TWC 18 simultaneously catalyzes the oxidation of hydrocarbons and carbon monoxide and the reduction of nitrogen oxides in a gas stream by contacting the exhaust gas at reaction temperatures with a catalyst composition.

Such compositions typically comprise a catalytically active component. A useful and preferred component is a precious metal, preferably a platinum group metal and a support for the precious metal. Preferred supports are refractory oxides such as alumina, silica, titania, and zirconia. A catalyst system useful with the method and apparatus of the present invention comprises at least one substrate comprising a catalyst composition located thereon. The composition comprises a catalytically active material, a support and preferably an oxygen storage component .

Useful catalytically active components include at least one of palladium, platinum, rhodium, ruthenium, and iridium co ponents, with platinum, palladium and/or rhodium preferred. Precious metals are typically used in amounts of up to 300 g/ft³, preferably 5 to 250 g/ft³ and more preferably 25 to 200 g/ft³ depending on the metal. Amounts of materials are based on weight divided by substrate ( honeycomb) volume .

Useful supports can be made of a high surface area refractory oxide support. Useful high surface area supports include one or more refractory oxides selected from alumina, titan a, silica and zirconia. These oxides include, for example, silica and metal oxides such as alumina, including mixed oxide forms such as silica- alumina, aluminosilicates which may be amorphous or crystalline, alumina-zirconia, alumina-chromia, alumina- ceria and the like. The support is substantially comprised of alumina which preferably includes the members of the gamma or activated alumina family, such as gamma and eta aluminas, and, if present, a minor amount of other refractory oxide, e.g., about up to 20 weight percent. Desirably, the active alumina has a specific surface area of 60 to 300 m²/g. A useful and preferred catalyzed article can be a layered catalyst composite comprises a first (bottom) layer comprising a first layer composition and the second (top) layer comprising a second layer composition. Such articles are disclosed in WO95/00235, incorporated by reference herein.

Briefly, the first layer comprises a first platinum group metal component, which comprises a first palladium component, which can be the same or different than that in the second layer. For the first layer to result in higher temperature conversion efficiencies, an oxygen storage component is used in intimate contact with the platinum group metal. It is preferred to use an alkaline earth metal component believed to act as a stabilizer, a rare earth metal selected from lanthanum and neodymium metal components which is believed to act as a promoter, and a zirconium component. The second layer comprises a second palladium component and optionally, at least one second platinum group metal component other than palladium. Preferably the second layer additionally comprises a second zirconium component, at least one second alkaline earth metal component, and at least one second rare earth metal component selected from the group consisting of lanthanum metal components and neodymium metal components . Preferably, each layer contains a zirconium component, at least one of the alkaline earth metal components and the rare earth component. Most preferably, each layer includes both at least one alkaline earth metal component and at least one rare earth component. The first layer optionally further comprises a second oxygen storage composition which comprises a second oxygen storage component. The second oxygen storage component and/or the second oxygen storage composition are preferably in bulk form and also in intimate contact with the first platinum group metal component .

When the compositions are applied as a thin coating to a monolithic carrier substrate, preferably a honeycomb carrier, the proportions of ingredients are conventionally expressed as grams of material per cubic inch of catalyst as this measure accommodates different gas flow passage cell sizes in different monolithic carrier substrates. Platinum group metal components are based on the weight of the platinum group metal.

Any suitable carrier may be employed, such as a monolithic carrier of the type having a plurality of fine, parallel gas flow passages extending therethrough from an inlet or an outlet face of the carrier, so that the passages are open to fluid flow therethrough. The passages, which are essentially straight from their fluid inlet to their fluid outlet, are defined by walls on which the catalytic material is coated as a "washcoat" so that the gases flowing through the passages contact the catalytic material. The flow passages of the monolithic carrier are thin-walled channels which can be of any suitable cross- sectional shape and size such as trapezoidal, rectangular, square, sinusoidal, hexagonal, oval, circular. Such structures may contain from about 60 to about 600 or more gas inlet openings ("cells") per square inch of cross section. The ceramic carrier may be made of any suitable refractory material, for example, cordierite, cordierite- alpha alumina, silicon nitride, zircon mullite, spodumene, alumina-silica magnesia, zircon silicate, sillimanite, magnesium silicates, zircon, petalite, alpha alumina and aluminosilicates. The metallic honeycomb may be made of a refractory metal such as a stainless steel or other suitable iron based corrosion resistant alloys.

Such monolithic carriers may contain up to about 700 or more flow channels ("cells") per square inch of cross section, although far fewer may be used. For example, the carrier may have from about 60 to 600, more usually from about 200 to 400, cells per square inch ("cpsi").

The discrete form and second coats of catalytic material, conventionally referred to as "washcoats", can be coated onto a suitable carrier with, preferably, the first coat adhered to the carrier and the second coat overlying and adhering to the first coat. With this arrangement, the gas being contacted with the catalyst, e.g., being flowed through the passageways of the catalytic material-coated carrier, will first contact the second or top coat and pass therethrough in order to contact the underlying bottom or first coat. However, in an alternative configuration, the second coat need not overlie the first coat but may be provided on an upstream (as sensed in the direction of gas flow through the catalyst composition) portion of the carrier, with the first coat provided on a downstream portion of the carrier. Thus, to apply the washcoat in this configuration, an upstream longitudinal segment only of the carrier would be dipped into a slurry of the second coat catalytic material, and dried, and the undipped downstream longitudinal segment of the carrier would then be dipped into a slurry of the first coat catalytic material and dried. Alternatively, separate carriers may be used, one carrier on which the first coat is deposited and a second carrier on which the second coat is deposited, and then the two separate carriers may be positioned within a canister or other holding device and arranged so that the exhaust gas to be treated is flowed in series first through the catalyst containing the second coat and then through the catalyst containing the first coat thereon. However, as indicated above, it is preferred to utilize a catalyst composition in which the second coat overlies and adheres to the first coat because such configuration is believed both to simplify production of the catalyst composition and to enhance its efficacy

As noted, emission sensor 40 of the present invention is also used as a hydrocarbon sensor in combination with a stable close-coupled catalyst. A system comprising such a close-coupled catalyst and a related method of operation as disclosed in W096/17671 incorporated by reference herein.

Close-coupled catalysts have been designed to reduce hydrocarbon emissions from gasoline engines during cold starts. More particularly, the close-coupled catalyst is designed to reduce pollutants in automotive engine exhaust gas streams at temperatures as low as 350°C, preferably as low as 300°C and more preferably as low as 200°C. The close- coupled catalyst of the present invention comprises a close-coupled catalyst composition which catalyzes low temperature reactions. This is indicated by the light-off temperature. The light-off temperature for a specific component is the temperature at which 50% of that component reacts.

Close-coupled catalyst 17 is placed close to engine 12 to enable it to reach reaction temperatures as soon as possible. However, during steady state operation of the engine, the proximity of the close-coupled catalyst to engine 12, typically less than one foot, more typically less than six inches and commonly attached directly to the outlet of the exhaust manifold exposes the close-coupled catalyst composition to exhaust gases at very high temperatures of up to 1100°C. The close-coupled catalyst in the catalyst bed is heated to high temperature by heat from both the hot exhaust gas and by heat generated by the combustion of hydrocarbons and carbon monoxide present in the exhaust gas. In addition to being very reactive at low temperatures, the close-coupled catalyst composition should be stable at high temperatures during the operating life of the engine. TWC 18 downstream of the close-coupled catalyst can be an underfloor catalyst or a downstream catalyst. When TWC 18 is heated to a high enough temperature to reduce the pollutants, the reduced conversion of carbon monoxide in the close-coupled catalyst results in a cooler close-coupled catalyst 17 and enables the downstream catalyst TWC 18, typically the underfloor three-way catalyst to burn the carbon monoxide and run more effectively at a higher temperature. The downstream or underfloor catalyst preferably comprises an oxygen storage component as described above.

Close-coupled catalyst 17 preferably is in the form of a carrier supported catalyst where the carrier comprises a honeycomb type carrier. A preferred honeycomb type carrier comprises a composition having at least about 50 grams per cubic foot of palladium component, from 0.5 to 3.5 g/in³ of activated alumina, and from 0.05 to 0.5g/in³ of at least one alkaline earth metal component, most preferably, strontium oxide. Where lanthanum and/or neodymium oxide are present, they are present in amounts up to 0.6g/in³'

II. The Problem In Using an HC Sensor Alone to Sense Emissions

A) Discussion of factors adversely affecting the use of an HC sensor alone to sense emissions.

HC conversion is directly related to the air-to-fuel (A/F) ratio, space velocity and temperature. Understanding the significance of a signal obtained from an HC sensor requires some knowledge of these parameters. The A/F ratio varies according to operating conditions (such as speed and load) based upon look-up tables used for engine calibration in the ECM. Therefore, it is necessary to know the parameters and values associated with engine calibration.

Space velocity can be estimated in some vehicles using mass air flow (MAF) sensor signals, but many vehicles do not

J> have such a sensor and must rely upon manifold air pressure

(MAP), throttle position sensor (TPS), and engine rpm to estimate space velocity. Finally, at this time, production vehicles are not equipped to provide catalyst temperature measurements . A model for estimating temperature could be devised, but none are currently used in production vehicles. Considering these three factors, using a single HC sensor to correlate emissions to catalyst quality would be complex and likely would require additional equipment.

The HC conversion efficiency of a TWC decreases as the

A/F ratio decreases. This is shown in Figures 2 and 3 which show the A/F ratio as lambda, λ. Lambda is a dimensionless parameter used to define the mixture's A/F ratio. It can be expressed by the following equation 1.

Equation 1 : instantaneous A/R ratio λ = stoichiometric A/R ratio

When λ equals 1, the A/F ratio produces stoichiometric combustion. When lambda is greater than one(λ > 1) the A/F ratio supplied to the vehicle cause the engine to operate lean or at excess air. When lambda is less than one(λ < 1) the vehicle is operating rich or with excess fuel. Figure 2 is a plot of the efficiency of the TWC conversion of emissions for various lambda numbers. Specifically, HC emissions are shown by solid line designated as reference numeral 50; NO_x emissions are shown by dotted line designated by reference numeral 51 and CO emissions are shown by dash lines designated by reference numeral 52. Figure 2 illustrates the conversion efficiency for a new TWC while Figure 3 shows the conversation efficiency of a TWC which is aged. Conversion efficiency for HC decreases under rich operating conditions. As the catalyst ages, so do the EGO sensor(s) used for engine controls. Drift in the target control value of lambda could lead to increases or decreases in tail pipe HC concentrations and using an HC sensor alone, erroneous diagnosis of the catalyst could be made. Under this "type 2 error" the catalyst is still functional, but another engine parameter is out of calibration.

For these reasons, the use of an HC sensor alone to monitor catalytic converter efficiencies must address these variables.

B) The Adverse Impact of Drive Cycle Validity on HC Sensing.

Drive cycle variability must be overcome for an OBD catalyst strategy to be useful. Two significantly different drive cycles have been used in the examples that demonstrate this invention. Figure 4 is a plot of speed and speed change (acceleration) as a function of time for the FTP-75 driving cycle (FTP). Speed is shown by the trace indicated by reference numeral 54 at the lower portion of the graph and acceleration is indicated by a trace 55 at the mid-portion of the Figure 4 graph. As is readily apparent, the FTP drive cycle contains extensive transient driving with a high frequency of speed changes. This drive cycle should be compared with the speed and speed change traces likewise designated by reference numerals 54, 55 respectively, illustrated in the graph of Figure 5 which shows a "steady state" (SS) driving cycle. The SS cycle contains extensive constant speed driving with a low frequency of speed change. It is desirable to have a catalyst diagnostic strategy which yields equivalent results independent of the drive cycle.

The data used to construct the graphs shown which depict how the invention works was collected on a chassis dynometer and Horiba analytical bench at the assignee's Union Engine Lab using the FTP-75 and SS cycles depicted in Figures 4 and 5 on a 1996 production model Honda Accord EX model equipped with a 2.2 L VTEC engine, and a series of catalytic converters with varied compositions and varied degrees of accelerated aging. Details of the catalyst, aging, FTP g HC/mile performance, run numbers and dates are given in Table 1 set forth at the end of the specification. All tabular data referred to in the specifications is set forth at the end hereof.

Example 1. Demonstration of derived cycle variability under idle conditions.

Data from individual FTP and SS runs were processed to determine the average tail pipe HC concentration for each run during idle conditions of the vehicle's engine. To avoid considering data obtained during cold operation (defined as catalyst temperature being less than 350°C) at which the catalyst was inactive, all data points with a time of less than 200 seconds was discarded. For the FTP- 75 cycle, the car was shut off at a time equal to 1374 seconds. After five minutes, the car was restarted and data acquisition resumed. For the purposes of the graph shewn in Figure 4, time upon restart commenced at 1375 seconds. For the purposes of all calculations in this specification, time was reset to zero upon this restart. Thus, for the FTP runs, the first 200 seconds of data after engine start were discarded. This "start-up" procedure was done consistently for all the test data generated. For SS runs, the vehicle was not shut off until the end of the cycle. Thus, only the first 200 seconds of data were discarded. Under "real world" driving conditions, cool- down time after "key off" is randomized. A 200 second delay after "key on" and prior to OBD testing insures that a satisfactory catalyst operation temperature for every OBD test .

With these considerations in mind, average HC concentrations were calculated under idle conditions defined as time > 200 seconds, speed < 1 mph. As will be discussed further, the idle conditions defined as time and mph will be designated "qualifying conditions". These qualifying conditions were met for each run listed in Table 2 and the value plotted in Figure 6 as a single data point with the Y-axis being an average HC concentration and the X-axis being FTP g HC/mile calculated from the run. Specifically, data points in the form of a triangle indicated by reference numeral 57 are extracted from SS runs for various aged catalysts and data points shown as a diamond indicated by reference numeral 58 is data extracted from the FTP run for various aged catalysts. For SS runs, the value for X was taken from the equivalently aged FTP run (see Table 1). Inspection of Figure 6 reveals a trend that gradually increasing tail pipe HC concentrations exist indicative of the efficiency losses of the catalyst with aging. Inspection of Table 2 shows that the average idle temperature of the catalyst (measured 1 inch from the inlet face) for the FTP runs is typically 540-550°C. The data points in Figure 6 clearly show that the expected HC concentration increases with aging of the catalyst. However, the data points in Figure 6 that are associated with the SS runs do not follow the trend of the FTP runs. The data was reviewed to determine if any factor could cause this difference other than the driving cycle. In this regard, Table 2 shows that the average idle temperature of the catalyst (again measured one inch from the inlet face) for SS runs was typically 510-520°C. Because the temperature difference could account for the trend, elimination of lower temperature points (< 530°C) from the SS runs brought the average of the SS runs to within the range for the FTP runs as is shown in Table 3. However, the new average idle HC concentration points still remain above the trend associated with the FTP runs as shown in Figure 7. Figure 7 is the plot shown in Figure 6 with the SS data points 57 corrected for temperature. FTP points 58 are unchanged. From comparing Figures 6 and 7 the need for accurate temperature measurement of the catalytic converter when using an HC signal is obvious. However, even an effort to "temperature correct" the data failed to normalize two drive cycles with one another. Thus, the invention recognizes that OBD emission monetary systems using HC sensors alone will produce variations in HC sensor output depending on the drive cycle of the vehicle. This means that it is not possible to develop a monitoring system using HC sensors unless the drive cycle variability is accounted for. This forms one of the underpinnings of the invention. ' Other possible explanations for the differences observed between the cycles (especially for the aged catalyst) exist. Poisoning of the catalyst or EGO sensors by sulphur in the fuel could lead to differences such as those described under idle conditions. Such plausible explanations are inherent in the engine operation and cannot be removed from the system.

III. Statistical Sampling for Catalyst Diagnosis.

A) A Threshold Sampling Algorithm.

Owing to numerous operating variables mentioned in the preceding discussion, it is desirable to examine tailpipe emissions from a statistical approach to average out variations in emissions inherently occurring under similar conditions. Further, from a statistical approach, it is possible to consider fewer parameters thereby simplifying data acquisition, storage and analysis.

For definitional purposes and for consistency in terminology, the following definitions will apply to terminology used in explaining the invention as follows :

"Qualifying condition" with reference to a qualifying condition sensor, a qualifying condition threshold, or a qualifying condition signal means an operating condition of the vehicle which is being sensed. Examples of vehicular qualifying conditions include but are not necessarily limited to the time from the engine start, the exhaust gas and/or catalyst temperatures, the vehicle speed, the engine RPM, EGO sensor signals, A/F ratio, manifold air pressure (MAP), mass air flow (MAF), signals from hot wire anemometers, throttle position, exhaust gas recirculation (EGR), solenoid position, manifold inlet air temperature, engine coolant temperature, transmission position, and other gearing or drive shaft torque information. A qualifying condition can include an emission signal. In the preferred embodiment NO_x, even though an emission signal, can be viewed as a qualifying condition. "Validated qualifying condition" means a qualifying conditionJfeignal which meets or exceeds a set threshold. The threshold is established at a value which insures that an emission signal sampled at the time a validated qualifying condition is sensed will in turn be a valid emission signal suitable for use in the system of the invention. In other words, a validated qualifying condition means that emission signals being sampled have been filtered.

"Emission signal" is a signal indicative of the tailpipe emissions of the vehicle which include, but are not limited to exhaust gas sensor signals which correspond to either temperature or concentrations of non-methane hydrocarbon (NMHC), methane, total HC, N0_X, CO, SOX, total combustibles, oxygen, carbon dioxide, or any combination of such gases. As will be explained in further detail below, the emission signals in the preferred embodiment of this invention, will be HC or HC and NO_x. However, the invention in its broader application is not limited to the emissions HC, NO_x.

"Excessive emission signal" means a sampled emission signal or a validated emission signal occurring when a validated qualifying condition signal occurs which emission signal exceeds a set emission threshold which, in turn, bears a correlation to an emission regulatory standard. Assuming that a statistical approach was not used, an excessive emission signal would trigger the vehicle's warning indicator 30. In the preferred embodiment only the HC "signal can become an excessive emission signal.

"Stored value" means a value, typically stored in ECM 15, which corresponds to a regulatory emission level for a specific or alternatively, general, drive cycle, or still alternatively, a specific operating mode or condition of the vehicle. More specifically, the stored value is a number against which a calculated value resulting from a statistical analysis of the emission signals is compared to determine whether or not warning mechanism 30 should be activated, and in further embodiments or applications of the invention, whether or not additional diagnostic steps should be conducted. "Operating run" or "run" means a set operating period of the vehicle during which sensors are sampled at periodic intervals to produce qualifying condition signals and emission signals. A run could be either a fixed time of vehicle operation or a fixed distance over which the vehicle is driven, or a vehicle operating time which occurs until a set number of events have happened. Sampling rates are expected to be in the range of 0.3 to 10 Hz which is determined mainly by the response time of the sensors used and the speed at which conditions can be conveniently obtained from the vehicle's power control module or other sources. In the examples and tabulations a sampling rate of 1 Hz was used.

Example 2. A Statistical Algorithm for Catalytic

Diagnosis.

Referring now to Figure 8 , there is shown a flow chart 60 describing a simple statistical algorithm used in the system of the invention. First, the engine is started at block 62 and the operating condition and emission counters are reset to zero at block 63. The first filter or qualifying condition is shown to be at block 65 which is a wait block delaying processing of any further signals until the catalyst has been deemed sufficiently hot to be sensed. Wait block 65 of the preferred embodiment is simply a time delay arbitrarily set at 200 seconds. In the flow chart of Figure 8, once the warmup operating conditions have been met at block 65, periodic emission signals and qualifying condition signals are being sampled under the control of ECM 15 at set time intervals shown to be one Hz for illustrative purposes at start sample block 68. The qualifying condition signal is then compared against a set threshold operating condition at a speed qualifying condition threshold comparator 70. If the threshold is met or exceeded, a validated operating condition is determined to have occurred which, in turn, outputs a validated qualifying condition signal to a validated qualifying condition 72 counter to increase its numerical count by one and also, outputs the qualifying condition signal to actuate an emission (HC) threshold comparator 73. In Figure 8, speed qualifying condition threshold comparator 70 simply compares the speed of the vehicle developed on sensor speed line 34 against a set threshold of 50 mph. If the vehicle speed is less than 50 mph, the qualifying condition is validated and the hydrocarbon signal from sensor 40 sensed at the time of the validated qualifying condition signal is evaluated against a set emission threshold in emission (HC) threshold comparator 73. If vehicle speed is greater than 50 mph, the event is discarded. In the flow chart shown in Figure 8, the HC threshold is set at a concentration of 25 ppm or higher. If the emission signal exceeds a concentration 25 ppm HC, an "excessive emissions counter 75 records this event by increasing its count storage value by one. If the emission signal failed to exceed the set emission threshold of 25 ppm, the emission signal would not be counted. The flow chart of Figure 8 is thus keeping a count of two events. Validated qualifying condition counter 72 is keeping track of the total numbers of events or times that an emission signal was sampled. Excessive emission counter 75 keeps track of the number of times emission sensor 40 exceeded an HC concentration of a set level which is correlated to an emission regulatory standard.

The algorithm described in Figure 8 for counting is highly versatile. As noted, qualifying conditions include those listed above and any combination thereof.

B) Use of the Algorithm.

The system illustrated in Figure 8 lends itself easily to any number of statistical techniques based on simple counting routines. This could be as simple as determining whether or not a calculated percentage is reached according to the following equations 2, 3:

Equation 2 number of excessive emission signals calculated % = X 100 number of validated condition signals and

Equation 3 calculated % < stored set %

The number of validated condition signals can be set at some arbitrary number such as 100 but the value of the number of occurrences should be set high enough to insure catalyst evaluation within a reasonable amount of time for most drive cycles or runs. The stored set percentage is equal to a stored or "regulated" threshold percentage as determined for any particular vehicle platform through testing of catalyst aged to various FTP g HC/mile performance level. At this stored "regulated" percentage threshold value, the catalyst is performing at a level which is just allowable by governmental regulations. If the calculated value or calculated % is below the stored regulated threshold value of stored %, the catalyst passes the diagnostic test. If the calculated value or calculated % is above this regulated threshold value, the catalyst fails the diagnostic test and malfunctioning catalyst indicator display light 30 is illuminated to alert the driver of the problem. To minimize false indications the results of any operating run can be passed through an evaluation process such as that illustrated in Figure 9. Since the stored value represents a regulatory value, it lends itself easily to establishing upper and lower limits so that if the emission results, i.e., calculated %, was less than the lower limit, one would have a high confidence that the catalyst is performing in a satisfactory manner while if the calculated % for any run exceeded the upper limits of the stored value, one could be fairly comfortable that the catalyst had failed. More particularly, if an operating run passed the low threshold, the sensors could be turned off to extend the life of the sensors until the next scheduled operating run of the vehicle was to occur.

The flow diagram shown in Figure 9 illustrates a simple procedure for such evaluation. The calculated percentage for any given operating run indicated at block 80 is compared to the lower limit of stored value in low threshold block 81. If the low threshold is not exceeded the diagnosis is deemed complete and a signal is sent to pass block 83 whereat ECM 15 schedules the next operating run of the vehicle and sensor 40 can be turned off. If the lower stored limit is exceeded in low threshold block 81, the signal is compared against the upper limit of the stored value in high threshold block 84. If the upper limit is exceeded, the catalyst is deemed to fail and a signal is sent to fail block 86 whereat ECM 15 causes warning light 30 to be activated. If the upper limit is not exceeded in high threshold block 84, the signal is transferred to a stored summing block 87. In stored summing block 87, the calculated percentage for that specific run is stored as "value N" . Both the qualifying condition counter 72 and the excessive emission counter 75 in Figure 8 are reset to zero. The value of N is increased by one and data sampling resumes until another operating run is completed and the calculated percentage for that run is also stored in stored summing block 87. The counter are again reset and the process continues until a calculated percentage for a set number of runs has been sampled which, in the flow chart of Figure 9, total three operating runs. The average of the three operating runs as a percentage is computed by the equation 4 :

Equation 4

Average = (value 1 + value 2 + value 3)/3

The calculated average value is then compared to the stored value in final comparison block 88. If the value is below the stored value, pass block 83 is activated and if the value is above the stored value fail block 86 is activated.

Obviously, variations of the described method are possible and intended to be included under the scope of this invention. Examples of such variations include changing the value of the operating condition counter at which the percentage is calculated and changing the value of N at which the average is calculated.

One method to modify the overall catalyst evaluation is to simultaneously run multiple algorithms with different qualifying conditions and emission conditions. Combining the results is one method of adding reliability to the system and possibly tailoring the catalyst diagnosis to classes of driving styles and cycles. Comparison of different qualifying condition counters could be used to characterize the drive cycle. For example, the transient nature of the drive cycle could be determined by evaluating parameters such as speed change or throttle position movement. Thresholds can be set and a counter used to determine the frequency with which the threshold is exceeded. Adjusting emission thresholds may be appropriate based upon the nature of the drive cycle. More specifically, as demonstrated above with reference to Figures 6 and 7 by counting speed changes which occur during an operating run, the stored regulated value can be picked from any number of values correlated to specific regulated driving cycles and the results then used to indicate pass/fail of the catalytic converter. While somewhat complicated, relatively speaking, this is a simple approach to resolving what would otherwise be an unsolvable problem. In general summary, a validated qualifying condition counter counts the vehicle's speed within a set range and an excessive counter counts the number of acceleration/deceleration occurrences within the sensed speed range. A counting based algorithm determines an acceleration frequency which is matched vis-a-vis look-up tables 29 with a regulated drive cycle. This is done through a flow chart process similar to that illustrated in Figure 8 but separate and apart from the catalytic evaluation simultaneously performed in Figure 8. The stored value for the matched drive cycle is then used to evaluate catalytic performance.

Up to this point, an operating run of the vehicle was defined to include a collection of a fixed number of validated qualifying condition signals resulting from a number of operating signals taken at a fixed rate or period. Another method to modify the catalyst evaluation is used for the remaining examples in the specification. Instead of waiting for validated qualifying condition counter 72 to reach a set value, data can simply be collected for an entire driving cycle and at the end of the driving cycle, evaluated by a calculated % = 100 x (excessive emissions count/validated operating conditions count) using whatever values existed for the two counters 72, 75. For the sake of simplicity, time from engine start is used in the remaining examples as a qualifying condition. Sampling of signals is at 1 Hz throughout each drive cycle run. Additionally, the comparisons of percentage to a stored threshold are not made in the next several examples. Instead, values for percentage of time the threshold is exceeded are plotted versus FTP g HC/mile calculated using the standard bag weighting method where "g" is grams, "b" is bag and "dist" is distance in accordance with equation 5 :

Equation 5 wgt'd g/mile=[0.43(gb#l + gb#2)/(b#l dist + b#2 dist)] +[0.57 (gb#2 + gb#3)/(b#2 dist + b#3 dist)]

For SS runs, FTP g HC/mile values are assumed from the equally aged catalyst. It is worth noting that some run to run variability is expected and observed in the data of column "FTP HC" in Table 1. After the accelerated aging cycle used (a fuel cut strategy), the catalysts were regenerated by exposure to stoichiometric engine exhaust for one hour. Some of the variability comes from slight differences in the effectiveness of the regeneration process. Additionally, the data presented in the remaining examples come from multiple catalysts with varied metal loadings . Note that catalyst metal loading does not appear to affect catalyst evaluation using the system of this invention.

Example 3. Use of Emission Threshold to Shift Evaluation Curve.

Referring now to Figure 10 there is shown trendline curves when the emission threshold for determining excessive emission signals is changed for different levels of HC concentration. The emissions data used to construct the trendlines in Figure 10 was taken from multiple chassis dynamometer FTP drive cycle runs (no SS runs) and analyzed using the simple percentage algorithm based on a fixed number of validated operating condition events . The qualifying conditions were defined as time > 200 seconds and vehicle speed < 50 mph. Using the algorithm described, the results are presented in Table 4 and shown graphically in Figure 10. Calculations were based on four emission thresholds. The first threshold was set at 10 ppm HC and data representing the percentage of time that excessive emission signals were generated beyond the ten ppm HC threshold is represented by diamond s designated as reference numeral 90 producing trendline curve 91. Similarly, data indicating percentage of excessive emission signals exceeding a second hydrocarbon emission threshold set at 15 ppm HC is indicated by circles designated by reference numeral 92 producing trendline 93. Data indicated by squares designated by reference numeral 94 producing aging trendline 95 indicates the percentage of excessive emission signals exceeding a third hydrocarbon threshold set at 20 ppm HC while triangles indicated by reference numeral 96 producing trendline 97 indicates the percentage of excessive emission signals exceeding a fourth hydrocarbon level set at 25 ppm HC. Figure 10 demonstrates that the choice of a tailpipe emission condition threshold provides a useful means for tailoring the algorithm to maximize catalysts evaluation capabilities at specific "regulated" emission thresholds. For example, if the greater than 15 ppm HC threshold value is used, trendline 93 results in a "hockey stick" shaped curve which allows for easy differentiation of any catalyst performing below 0.12g HC/mile (percentage < 11) from one at 0.14g HC/mile (percentage > 70). Under these qualifying conditions, if the 25 ppm HC emission threshold is used, a much less reliable differentiation of catalyst at these performance levels can be made.

C) Drive Cycle Dependency Using HC Sensing Alone.

In this example, data was processed in the manner described for Figure 10 but a tailpipe emission threshold of HC > 25 ppm is considered. To demonstrate the problem of drive cycle variability on catalyst evaluation, the data, FTP runs and SS runs listed in Table 5, were used and the results of the analysis are plotted in Figure 11. Figure 11 is similar to Figure 10 but compares FTP runs to SS runs. Specifically, data calculated for FTP runs is indicated by triangles designated by reference numeral 100 generating an FTP aging trendline 101. Data obtained for SS runs is shown by squares indicated by reference numeral 102 generating SS aging trendline 103. Trendlines 101, 103 clearly demonstrate the influence of drive cycle using catalyst evaluation with qualifying conditions (time > 200 seconds and speed < 50 mph) and tailpipe emission threshold (> 25 ppm HC) conditions. It may be possible to merge the curve for the two drive cycles using an HC signal alone if sufficient operating condition restrictions were placed in the algorithm demonstrated in Figure 8. Alternatively, additional routines can be added to classify the run so that it can be correlated to a drive cycle and the stored value for that drive cycle used to evaluate the catalyst. At the same time, it has to be recognized that increasing the number of qualifying conditions or filters will inevitably require more time to obtain sufficient data points to make a fair statistical analysis of the data. If the conditions are too restrictive, a diagnosis would not be completed even during many drive cycles or runs. Further, Figures 6 and 7 demonstrate that even under conditions using restrictive operating conditions, evaluation data from the two driving cycles (FTP vs. SS) will not merge into a single evaluation curve. For this reasons, if a sole HC sensor were used in accordance with the invention, operating condition data would inevitably have to be obtained for each run and statistically evaluated to arrive at a set emission threshold correlated to that specific driving cycle.

IV. Removing Drive Cycle Variations

Example 5. Combined Use of HC and NO_x Sensing for

Catalyst Evaluation to Remove Drive Cycle Variation. This example overcomes the problems associated with catalyst evaluation resulting from different drive cycles. Evaluating the catalyst in accordance with the algorithm demonstrated in Figure 8, the qualifying condition signals were defined as time > 200 second, vehicle speed < 50 mph and NO_x > 15 ppm. The threshold tailpipe emission condition was defined as HC > 15 ppm. NO_x is an emission signal. For reasons which will be explained below, its presence, at least in a small concentration, removes drive cycle variabilities on HC sensor measurements. It is treated as a qualifying condition having a threshold which must be met to produce a validated qualifying condition signal to allow processing of the HC signal. Figure 8 would be modified by inclusion of an NO_x threshold comparator block positioned between speed qualifying condition comparator 70 and emission threshold comparator 73. Validated qualifying counter 72 would be moved and positioned adjacent NO_x threshold comparator block so that the HC signal would be sampled in excessive emissions counter 75 only if sensor signals had met the start-up delay imposed by wait block 65,^* the speed requirement imposed by speed qualifying condition comparator 70 and the NO_x concentration imposed by NO_x qualifying condition comparator. The validated qualifying counter signals and the excessive emission signals would then be factored as discussed with respect to Figure 8.^~

In any event, the data and list of runs used for constructing the graph shown in Figure 12 is presented in Table 6. Figure 12 is a plot of a trendline for steady state run data indicated by rectangles designated by reference numeral 105 and a plot of a trendline based on FTP run data indicated by circles designated by reference numeral 106. Both trendlines superimpose themselves as one curve shown by reference numeral 108. Figure 12 thus shows that if an additional filter requiring the presence of NO_x in a concentration > 15 ppm, variations in the drive cycle can be ignored. This significantly reduces the complexities of systems which otherwise have to account for the variations in the drive cycle to determine compliance with emission regulations.

In general summary, only when both HC and NO_x were simultaneously emitted was a tailpipe emission counted. This worked to eliminate the drive cycle dependency because two dissimilar functions of the catalyst were monitored simultaneously. While each function was dependent upon vehicle operating conditions, the two were not expected to happen simultaneously unless the catalyst had begun to lose performance for both functions. In this manner, the diagnostic was significantly independent of variables such as A/F ratio, engine calibration and vehicle speed (so long as space velocity through the catalyst was below an acceptable level). The speed restriction easily limited evaluation during sustained high space velocity periods through the catalyst which would be experienced under high speed driving. Catalyst evaluation during high speed driving is expected to be significantly more difficult than during low speed driving because of fuel enrichment dictated by engine calibration under such conditions.

While no claim is made as to the precise reasons why this discovery negating the adverse affects drive cycle variations on HC emission sensing works, a rationalization of the various factors affecting the discovery can be had by reference to Figure 13. Figure 13 is a pictorial representation of catalytic observations divided into four quadrants labeled clockwise as a first quadrant 110, a second quadrant 111, a third quadrant 112, and a fourth quadrant 113. Lambda designated by reference numeral 115, is shown increasing in the direction of first and fourth (rich) quadrants, 110, 113 to second and third (lean) quadrants 111, 112, respectively. Catalyst aging is shown increasing as indicated by reference numeral 116 from first and second (fresh) quadrants 110, 111 to third and fourth (aged) quadrants 112, 113, respectively. Figure 12 is thus a pictorial representation showing the coupled effects of aging (top/bottom) 116 and lambda (left-right) 115. In actual vehicle operation, the value of lambda is constantly switching between the rich first and fourth quadrants 110, 113 and the lean second and third quadrants 111, 112. Thus, the expected emissions result from combining the results of the lean and rich quadrants. As the catalyst ages, the probability that both HC and NO_x emissions will occur simultaneously increase, especially during rich excursions such as occurs during acceleration. Reference can be had to Figures 14 and 15 to demonstrate graphically the observations pictorially represented in Figure 13. Figure 14 shows plots of hydrocarbon emissions in ppm concentrations designated by solid line 120; NO_x emissions in ppm concentrations shown by dashed lines 121 for a vehicle operated at speeds shown by dotted line 122 for a fresh catalyst. Figure 15 likewise shows HC plots 120, NO_x plots 121 and speed plots 122 for an aged catalyst. Figure 14 is based on FTP run number 8299 and Figure 15 is based on FTP run number 8513. The loss of catalyst metal surface area and oxygen storage capacity combined with a constant A/F ratio perturbation were the causes. The most noteworthy differences are observed under accelerations. Before aging, the catalyst infrequently emitted N0_X during accelerations. After aging, N0_X was emitted consistently upon acceleration. During acceleration the A/F ratio was typically rich and HC emissions under these conditions were expected to increase as the catalyst aged. The net result during acceleration was an increased probability of simultaneous HC and N0_X tailpipe emissions.

Example 6. Combined Use of HC and NO_x Sensing to

Implement the Invention.

The data in this example used to construct the plots in Figures 16, 17 and 18 was obtained from the run numbers listed in Table 6 with HC and NO_x conditions as specified.

Figure 16 is a graph of trendlines for various hydrocarbon emission thresholds similar to that described above with reference to Figure 10. However, the additional qualifying condition requirement of NO_x being present in excess of 15 ppm is required before a validated qualifying condition occurs. When the hydrocarbon emission threshold is ^* set at HC > 10 ppm the percentage of time excessive emission signals occur is represented by data points in the form of a diamond indicated by reference numeral 130 and generates an HC > 10 aging trendline 131. Similarly, data points in the form of a block designated by reference numeral 132 indicate the percentage of times excessive emission signals exceeding an HC > 15 threshold occurs and produce an HC > 15 aging trendline on 133. Data points in the form of a triangle designated by reference numeral 134 generate an HC > 20 aging trendline 135 and data points in the form of a circle designated by reference numeral 136 generate an HC > 25 aging trendline 137. Trendlines 131, 133, 135 and 137 hold irrespective of the driving cycle so long as qualifying conditions indicative of a speed less than 50 mph occurs and the vehicle has been operated for at least 200 seconds and the NO_x emissions have a concentration greater than 15 ppm. As discussed above with reference to the algorithm derived from the flow chart illustrated in Figure .8, a stored value equal to some set percentage correlated to an emission regulatory standard determines when a failure of the catalytic converter has occurred. For explanation purposes, the stored percentage value is set at 50 percent (i.e., 50% of the validated emission signals or more turn out to be excessive emission signals) and is shown by line 140 in Figure 16. Intersection of line 140 with the various trendlines show that, depending upon the emission threshold (expressed as HC > X ppm), trendline aging curves can be tailored to cross the stored % = 50% line 140 at FTP g HC/mile values ranging from 0.10 to > 0.14. A direct correlation between stored value, set emission threshold and emission regulatory standard is thus established without significant computer modeling. For example, by counting the number of excessive emission signals occurring for various emission thresholds (i.e., HC > 10 ppm; HC > 15 ppm; HC > 20 ppm; HC > 25 ppm) the specific HC concentration can be extrapolated for any given run (or averaged for a plurality of runs) and directly compared as a hard number to the regulated HC emission standard.

Figures 17 and 18 illustrate the fact that changing the threshold limit for NO_x does not significantly impact the sensing of hydrocarbon emissions. In particular, Figure 17 shows a graph constructed in the same manner as that used to construct the trendlines shown in Figure 16 but with an NO_x emission threshold set as N0_X > 50 and reference numerals used in Figure 16 are also used to apply to the same data points and trendlines shown in Figure 17 but with the subscript (a) added to the numeral. Figure 18 is a graph showing trendline 133 (for HC > 15 and NO_x > 15) shown in Figure 16 and with trendline 133(a) (for HC > 15 and NO_x > 50) shown in Figure 17. The variation in FTP g HC/mile at a 50% stored value is not significant. This is because in general, NO_x is emitted in "bursts" with concentrations very often > 50 ppm. Thus, the ability to control the range is mainly controlled by changes in HC.

V. Further Applications .

The system as described in Part II is inherently suited for functioning as an OBD for light-off catalyst 17 and provides a system for monitoring emissions during cold start of the engine. As explained above, light-off catalyst is effective to convert hydrocarbons. Typically, the vehicle is not operated at hard acceleration during its first 200 seconds thus permitting formation of a drivability curve to establish a set HC emission limit and a stored value. Once the vehicle is at operating temperature, light-off catalyst 17 is used as an adjunct to TWC 18 and the algorithm monitoring systems employed for each can be used as a predictor for catalytic converter replacement. Thus, should emission standards require regulation of the hydrocarbon emissions during vehicle warm-up, the system disclosed herein can accommodate onboard monitoring by the addition of hydrocarbon sensor 40a. The on-board diagnostic requirements also require that the monitoring system determine whether or not the emission failure is attributed to a failure of the catalytic converter. The system of the present invention inherently provides this determination and this can be explained by reference to Figure 16. Assume that an emission threshold of HC > 15 and N0_X > 15 with a stored value of excessive emissions occurring over 50% of the time is chosen to indicate failure and that a failure occurs such that warning light 30 is to be triggered. At that time, all the other ranges, i.e., HC > 10, HC > 20 and HC > 25 are also checked and if the stored value is exceeded for all of the ranges, then the failure is not attributed to TWC 18. However, if one of the ranges such as HC > 25 does not indicate a failure, then TWC 18 has failed.

It should be clear that the basic algorithm described in part II can be easily implemented for other emission control systems in the vehicle such as the EGR system. Different operating condition filters will have to be employed as well as different sensors. The basic fundamental process remains the same however. A more subtle utilization of the system disclosed herein in addition to its primary function as an OBD monitoring system is its utilization in the control of internal combustion engine 12 itself and especially so in conjunction with new engine controls and engines currently under development by many vehicle manufacturers such as gasoline direct injection engines. More specifically, by counting excessive emission signals which occur over a protracted period of engine operation, a mechanism exists for adjusting the inevitable drift which occurs in the controls which are rapidly actuated to control such engine variables as the A/F ratio.

In addition, the use of both HC and NO_x sensing could eliminate the need for current sensors such as the rear HEGO sensor. Also, the N0_X sensor used for emission control can be used for engine control during lean operation.

Insofar as the emission monitoring system is concerned, the implementation of the system is believed entirely possible through software. Because of the relatively long sampling times (.3 Hz to 10 Hz) the only hardware required would be a conventional analog clock circuit (software controlled) which now exists in the ECM to sample the sensors at periodic intervals. The HC and N0_X samples have to occur at the same time as the operating condition signals which all can be done via the clock circuit and then digitized in an A/D converter. Space velocity is not a consideration. Processing of the digitized NO_x and HC signals can then wait the filtering of the qualifying condition signals given the long time between samples. Programming ECM 15 to accomplish the simple algorithms illustrated herein is believed within the skill of an ordinary artesian and is not described in any detail.

The invention has been described with reference to a preferred embodiment and alternative embodiments . Obviously, modifications and alterations will occur to those skilled in the art upon reading and understanding the Detailed Description of the Invention set forth above. For example, the invention is described with reference to HC sensors detecting hydrocarbons. Should emission regulations require control of SO_x or other gaseous emissions, the system can easily accommodate such regulations by the simple addition of a SO_x sensor. It is intended to include all such modifications and all alterations insofar as they come within the scope of the present invention.

The various tables and data set forth in the examples above are set forth below:

TABLE 1

HAA = Honda aging cycle - fuel cut aging . specified temperature - 4 mg Pb fuel TABLE 2

TABLE 3

TABLE 4 qualifying conditions time > 200 seconds, speed < 50 mph

TABLE 5

TABLE 6

Claims

Having thus defined the invention, it is claimed:

1) A process for on-board monitoring and detecting a failure of the catalytic converter of a vehicle comprising the steps of : a) providing at least one emission sensor downstream of the catalytic converter generating emission signals indicative of gaseous emissions in the vehicle's exhaust gas; b) providing at least one qualifying condition sensor for sensing at least one vehicular operating condition affecting the performance of said catalytic converter, said qualifying condition sensor generating qualifying condition signals indicative of said operating condition; c) sampling said qualifying condition signals at periodic time intervals during an operating run of said vehicle and determining if each sampled qualified condition signal exceeded a set operating condition threshold to produce a validated qualifying condition signal; said sampling continuing until a set number of validated qualifying condition signals have occurred during said run; d) sampling said emission signals at the time a validated condition signal is sensed and determining whether each sampled emission signal generated at the time of a validated condition signal exceeded a set emission threshold to produce an excessive emission signal; e) comparing the number of excessive emission signals generated during said run to a stored value in turn correlated to an emission regulatory standard to determine if a failure of the catalytic converter occurred; and, f) activating a warning indicator mechanism indicative of the vehicle's inability to meet emission requirements if such failure has occurred.

2 ) The process of claim 1 wherein said qualifying condition sensor is a sensor for monitoring at least one of the following of said vehicle's operating conditions: i) the air to fuel ratio; ii) the speed of the vehicle; iii) engine rpm; iv) timing; v) lambda; vi) EGO sensor signals; vii) manifold air pressure; viii) throttle position; ix) exhaust gas recirculation solenoid position; x) drive shaft torque; xi) mass air flow; xii) exhaust gas temperature; and, xiii) catalytic temperature.

3) The process of claim 2 further including the steps of providing a second qualifying condition sensor; generating second qualifying condition signals; additionally sampling said second qualifying condition signals during step (c) to determine if said second qualifying condition signals exceed a second set threshold value, said validated condition signal established only if simultaneously generated first and second operating condition signals exceed their respective threshold values.

4) The process of claim 3 wherein said first qualifying condition is the time elapsed from when the vehicle was initially started, said first qualifying condition threshold occurring when said vehicle has been operated after a set time from initial start-up has passed to insure warm up of said vehicle.

5) The process of claim 4 wherein said second qualifying condition is the speed of said vehicle, said second qualifying threshold occurring only when said vehicle is operated at a speed less than a set speed.

6) The process of claim 5 wherein said emission sensor senses at least one of the following emissions generated by the vehicle is i) non-methane hydrocarbon; ii) methane; iii) total HC; iv) N0_X; v) CO; vi) S0_X; vii) total combustibles; viii) oxygen; and, ix) carbon dioxide.

7) The process of claim 6 wherein said emission sampling step produces an excessive emission signal only when two or more different emissions are sensed and exceed a stored value for each of said two or more sensed emission signals.

8) The process of claim 7 wherein said two or more sensed emissions include HC and N0_X.

9) The process of claim 6 further including the additional step of comparing sequentially generated validated condition signals and determining the vehicle's rate of change in speed therefrom; establishing a second validated condition signal when the vehicle's rate of speed change is beyond a set limit; counting the number of sampled emission signals which exceeded a second set emission threshold when said second validated condition signals have been generated to produce a second excessive emission signal, said second emission threshold corresponding to a regulatory emission standard for the vehicle under a set acceleration level; and activating said warning mechanism when the number of said second excessive emission signals relative to the number of said second validated condition signals exceeds a set number.

10) The process of claim 6 wherein said stored value corresponds to a regulatory emission standard and has an upper limit and a lower limit associated therewith, said comparing step (e) activating said warning mechanism when said number of excessive emissions exceeds said upper limit and completing said process if said number of excessive emissions is less than said lower limit.

11) The process of claim 10 wherein in the event said emission sampling step (d) produces a number of excessive emissions falling between said upper and lower limits in step (e), said steps (c), (d) and (e) are repeated to produce a plurality of sets of excessive emission signals, said sets statistically factored to produce an accurate count of excessive emission signals compared to said stored value to determine if said warning mechanism is to be activated.

12) The process of claim 10 wherein said stored value is a set percentage expressed as number of excessive emission signals Set percentage < number of validated condition signals 100 and said warning mechanism is activated when a regulatory emission standard correlated to a specific set percentage is exceeded.

13) The process of claim 12 wherein said emission threshold correlates to grams of hydrocarbons emitted from the vehicle per mile driven, g HC/mile, as determined by the expression:

wgt'd g/mile=[0.43(gb#l + gb#2)/(b#l dist + b#2 dist)] +[0.57 (gb#2 + gb#3)/(b#2 dist + b#3 dist)]

where

"b" is bag as used in the Federal Test Protocol "dist" is distance "g" is grams and said specific set percentage corresponds to a fixed g HC/mile set by a governmental regulatory agency.

14) The process of claim 13 wherein said emissions sensed by said emission sensor are hydrocarbons, said set emission threshold corresponding to a plurality of different hydrocarbon ranges, each run producing different pluralities of excessive emission signals corresponding to various hydrocarbon ranges; said process including the additional step of conducting a plurality of runs and comparing the frequencies at which said number of excessive emission signals exceeded said set emission threshold for each hydrocarbon range to determine a sensed hydrocarbon emission level produced by said vehicle and comparing said sensed emission level to a regulatory emission level to determine if said warning mechanism is to be actuated.

15) The process of claim 14 wherein said pluralities of hydrocarbon ranges are set at less than 10 ppm, 15 ppm, 20 ppm, and 25 ppm of hydrocarbon concentrations in said exhaust gas respectively.

16) The process of claim 1 wherein said emission sensor senses at least one of the following emissions generated by the vehicle is i) non-methane hydrocarbon; ii) methane; iii) total HC; iv) N0_X; v) CO; vi ) SO_x; vii) total combustibles; viii) oxygen; and, ix) carbon dioxide.

17) The process of claim 16 wherein said emission sampling step produces an excessive emission signal only when two or more different emissions are sensed and exceed a stored value for each of said two or more sensed emission signals.

18) The process of claim 17 wherein said two or more sensed emissions include HC and N0_X.

19) The process of claim 18 wherein said set emission threshold for said HC includes a plurality of emission thresholds corresponding to a like plurality of HC ranges so that each threshold in said plurality corresponds to a specific range of HC emissions and each run produces a plurality of excessive emission signals for each HC range; said process including the additional step of comparing the frequency at which said number of excessive emission signals exceeded each emission threshold for each hydrocarbon range during an operating run to determine a specific, sensed emission level for said run, said specific sensed emission level compared to a regulatory emission level to determine if said warning mechanism is to be actuated.

20) The process of claim 19 wherein a plurality of specific sensed emission levels accumulated over a like plurality of runs are statistically evaluated before determining if said warning mechanism is to be actuated.

21) The process of claim 19 further including said vehicle having an engine control mechanism regulating the operation J) of the engine of said vehicle including the ratio of air to fuel supplied to said engine, said warning mechanism in communication with said engine control mechanism, said step of comparing said frequencies of said excessive emission signals for said HC ranges triggering a failure signal to said engine control mechanism while not activating said warning mechanism in the event said set thresholds are exceeded for all of said hydrocarbon ranges.

22) The process of claim 19 wherein said pluralities of hydrocarbon ranges are set at HC concentrations greater than 10 ppm, 15 ppm, 20 ppm, and 25 ppm of hydrocarbons respectively.

23) The process of claim 22 wherein said emission sensor senses NO_x separately from HC and generates NO_x signals indicative of NO_x concentrations in the exhaust stream, said emission signal being sampled only when a set threshold for NO_x emission has occurred whereby variations in the driving cycle do not affect the ability to determine if the catalytic converter satisfies emission regulation requirements .

24) The process of claim 23 wherein variations in levels of emission regulatory requirements are accounted for by selecting a set number of excessive emissions which must be exceeded in a run, a specific one of said pluralities of said HC threshold levels and a set NO_x threshold value.

25) The process of claim 24 wherein said stored value is a set percentage expressed as number of excessive emission signals Set percentage < number of validated condition signals x 100 and said warning mechanism is activated when a regulatory emission standard correlated to a specific set percentage is exceeded.

26) The process of claim 25 wherein said emission threshold correlates to grams of hydrocarbons emitted from the vehicle per mile driven, g HC/mile, as determined by the expression: wgt'd g/mile=[0.43(gb#l + gb#2)/(b#l dist + b#2 dist)] +[0.57 (gb#2 + gb#3)/(b#2 dist + b#3 dist)]

where

"b" is bag as used in the Federal Test Protocol

"dist" is distance "g" is grams and said specific set percentage corresponds to a fixed g HC/mile set by a governmental regulatory agency.

27) The process of claim 18 wherein said two or more sensed emissions are sensed by separate emission sensors.

28) The process of claim 27 wherein said catalytic converter includes a three way catalyst capable of sensing HC, carbon monoxide and NO_x carried on a ceramic or metal honeycomb substrate.

29) The process of claim 28 wherein said catalyst includes one or more precious metals selected from the group consisting of platinum, palladium, rhodium, ruthenium and iridium located on a support compound in turn affixed to said substrate.

30) The process of claim 29 further including an oxygen storage composition.

31) The process of claim 30 wherein said catalyst contains two or more layers of precious metals and said support includes at least alumina.

32) The process of claim 1 wherein said stored value corresponds to a regulatory emission standard and has an upper limit and a lower limit associated therewith, said comparing step (e) activating said warning mechanism when said number of excessive emissions exceed said upper limit and completing said process if said number of excessive emissions is less than said lower limit.

33) The process of claim 32 wherein in the event said emission sampling step (d) produces a number of excessive emissions falling between said upper and lower limits in step (e), said steps (c), (d) and (e) are repeated to produce a plurality of sets of excessive emission signals, said sets statistically factored to produce an accurate count of excessive emission signals compared to said stored value to determine if said warning mechanism is to be activated.

34) The process of claim 1 wherein said emission sensor senses NO_x separately from HC and generates N0_X signals indicative of N0_X concentrations in the exhaust stream and HC signals indicative of the HC concentrations in the exhaust stream; said qualifying condition sensor is activated only after said vehicle has been operated for a fixed time and only when the vehicle's speed is below a fixed limit; said sampling of said emission signal step proceeding in a sequencing step of comparing each of said NO_x and HC signals against a set threshold for the N0_X and HC emissions and counting the emission signal as an excessive emission signal only when both N0_X and HC signals exceed said set thresholds whereby variations in the driving cycle do not affect the ability to determine if the catalytic converter satisfies emission regulation requirements.

35) The process of claim 1 wherein said qualifying condition sensor senses the speed of said vehicle, said validated condition signals being established when said vehicle's speed is less than a set value.

36) The process of claim 35 further including the additional step of comparing sequentially generated validated condition signals and determining the vehicle's rate of change in speed therefrom; establishing a second validated condition signal when the vehicle's rate of speed change is beyond a set limit; counting the number of sampled emission signals which exceeded a second set emission threshold when said second validated condition signals have been generated to produce a second excessive emission signal, said second emission threshold corresponding to a regulatory emission standard for the vehicle under a set acceleration level; and activating said warning mechanism when the number of said second excessive emission signals relative to the number of said second validated condition signals exceeds a set number.

37) The process of claim 1 wherein said set number of validated condition signals in said run is a fixed number of signals occurring over a fixed time period after a set start-up period for the vehicle has elapsed.

38) The process of claim 1 wherein said set number of validated condition signals in said run is a varying number determined by the time said vehicle is continuously operated after a set start-up period has elapsed.

39) The process of claim 1 wherein said stored value is a set percentage expressed as nnuummbbeerr ooff eexxcceessive emission signals SSeett ppeerrcceennttaaggee << nnuummbbeerr ooff vvaalliicdated condition signals x 100 and said warning mechanism is activated when a regulatory emission standard correlated to a specific set percentage is exceeded.

40) The process of claim 39 wherein said number of validated condition signals in the expression is a fixed number .

41) The process of claim 39 wherein said number of validated condition signals in the expression is the number of validated condition signals when the vehicle has been operated for at least a set time.

42) The process of claim 1 wherein said emission threshold correlates to grams of hydrocarbons emitted from the vehicle per mile driven, g HC/mile, as determined by the expression:

where

"b" is bag as used in the Federal Test Protocol

"dist" is distance

"g" is grams and said specific set percentage corresponds to a fixed g HC/mile set by a governmental regulatory agency.

43) The process of claim 42 wherein said stored value has an upper limit corresponding to a high number of g HC/mile and a lower limit corresponding to a lower number of g HC/mile wherein said number of excessive emissions required to reach said upper limit is approximately a factor of at least twice the number of excessive emissions required to meet said lower limit. 44) The process of claim 1 wherein said set emission thresholds for said HC includes a plurality of emission thresholds corresponding to a like plurality of HC ranges so that each threshold in said plurality corresponds to a specific range of HC emissions and each run produces a plurality of excessive emission signals for each HC range; said process including the additional step of comparing the frequency at which said number of excessive emission signals exceeded each emission threshold for each hydrocarbon range during an operating run to determine a specific, sensed emission level for said run, said specific sensed emission level compared to a regulatory emission level to determine if said warning mechanism is to be actuated.

45) The process of claim 44 wherein a plurality of specific sensed emission levels accumulated over a like plurality of runs are statistically evaluated before determining if said warning mechanism is to be actuated.

46) The process of claim 44 further including said vehicle having an engine control mechanism regulating the operation of the engine of said vehicle including the ratio of air to fuel supplied to said engine, said warning mechanism in communication with said engine control mechanism, said step of comparing said frequencies of said excessive emission signals for said HC ranges triggering a failure signal to said engine control mechanism while not activating said warning mechanism in the event said set thresholds are exceeded for all of said hydrocarbon ranges.

47) The process of claim 44 wherein said pluralities of hydrocarbon ranges are set at HC concentrations greater than 10 ppm, 15 ppm, 20 ppm, and 25 ppm of hydrocarbons respectively.

48) The process of claim 44 wherein said emission sensor senses N0_X separately from HC and generates N0_X signals indicative of N0_X concentrations in the exhaust stream, said excessive emission signal occurring only when a set threshold for N0_X emission has occurred as well as said set threshold for HC emission whereby variations in the driving cycle do not affect the ability to determine if the catalytic converter satisfies emission regulation requirements .

49) The process of claim 48 whereby variations in levels of emission requirements can be accounted for by selecting a set number of excessive emissions which must be exceeded in a run, a specific one of said pluralities of said HC threshold levels and a set N0_X threshold stored value.

50) The process of claim 1 further including the step of periodically sensing one or more of the following operating conditions of said vehicle: i) air to fuel ratio; ii) timing; iii) lambda; iv) EGO sensor signals; v) manifold air pressure; vi) exhaust gas recirculation solenoid position; vii) mass air flow; viii) exhaust gas temperature; and, ix) catalytic temperature and counting the conditions sensed which exceed a stored threshold value indicative of an optimal engine operating condition, each instance in which said sensed operating condition exceeded said threshold during a vehicle run being an excessive operating condition signals .

51) The process of claim 50 further including the steps of statistically evaluating said excessive operating conditions when catalytic converter failure has been sensed; adjusting the engine operation of said vehicle to bring the sensed operating conditions within a set value of said operating condition threshold and repeating said method prior to activating said warning mechanism.

52) A vehicular on-board method for monitoring gaseous pollutants emitted by an internal combustion engine to determine failure of the vehicle's catalytic converter, said method comprising the step of: i) sampling at periodic intervals the exhaust gas downstream of the catalytic converter to determine from each sample the HC content of the exhaust gas and the N0_X content of the exhaust gas; ii) determining from said samples the number of samples in which the HC content and the NO_x content each exceeded set emission threshold limits therefor, each sample exceeding said emission threshold limits being an excessive emission sample; iii) statistically evaluating said excessive emission samples relative to the total number of samples to determine when a catalytic converter failure has occurred; and, iv) actuating a warning mechanism in the vehicle indicative of an inability of the vehicle to meet emission regulatory standards when said catalytic failure has occurred.

53) The method of claim 52 wherein said sampling occurs only when said vehicle is operated at preset operating conditions.

54) The method of claim 53 wherein said preset operating conditions include said vehicle being at a speed less than a set value and said vehicle having been operated for at least a set time to warm up.

55) The method of claim 54 wherein said exhaust gas is sampled for HC emissions by a pellistor type sensor.

56) The method of claim 55 wherein said exhaust gas is sampled by a N0_X sensor.

57) The method of claim 56 wherein said exhaust gas is sampled at periodic intervals between 0.3 and 10 Hz.

58) The method of claim 53 wherein said statistical evaluation is accomplished pursuant to a set percentage expressed as number of excessive emission signals Set percentage < number of validated condition signals x 100 where said validated condition signal is every periodic emission signal which occurs during the time said preset operating condition is present during a given run of said vehicle and said set percentage which actuates said warning mechanism when exceeded corresponds to an emission regulatory standard in turn correlated to said threshold limit.

59) The method of claim 58 wherein said emission threshold correlates to grams of hydrocarbons emitted from the vehicle per mile driven, g HC/mile, as determined by the expression:

where

"b" is bag as used in the Federal Test Protocol

"dist" is distance

60) The method of claim 59 wherein said number of validated condition signals in said set percentage expression is a fixed number.

61) The method of claim 60 wherein said number of validated condition signals in said set percentage expression is the number of validated condition signals when the vehicle has been operated for at least a set time.

62) The method of claim 54 wherein said set emission thresholds for said HC includes a plurality of emission thresholds corresponding to a like plurality of HC concentration ranges so that each threshold in said plurality corresponds to a specific range of HC emissions and each run produces a plurality of excessive emission signals for each HC range; said process including the additional step of comparing the frequency at which said number of excessive emission signals exceeded each emission threshold for each hydrocarbon range to determine a specific, sensed emission level for said run, said specific sensed emission level compared to a regulatory emission level to determine if said warning mechanism is to be actuated.

63) The method of claim 62 wherein a plurality of specific sensed emission levels accumulated over a like plurality of runs are statistically evaluated before determining if said warning mechanism is to be actuated.

64) The method of claim 62 further including said vehicle having an engine control mechanism regulating the operation of the engine of said vehicle including the ratio of air to fuel supplied to said engine, said warning mechanism in communication with said engine control mechanism, said step of comparing said frequencies of said excessive emission signals for said HC ranges triggering a failure signal to said engine control mechanism while not activating said warning mechanism in the event said set thresholds are exceeded for all of said hydrocarbon ranges.

65) The method of claim 62 wherein said pluralities of hydrocarbon ranges are set at less than 10 ppm, 15 ppm, 20 ppm, and 25 ppm of hydrocarbons respectively.

66) The method of claim 65 wherein variations in levels of emission requirements are accounted for by selecting a set number of excessive emissions which must be exceeded in a run, a specific one of said pluralities of said HC threshold levels and a set NO_x threshold value.

67) The method of claim 59 wherein said set percentage has an upper limit and a lower limit associated therewith, activating said warning mechanism when said number of excessive emissions exceeds said upper limit of said set percentage and completing said monitoring method if said number of excessive emissions is less than said lower limit.

68) The process of claim 67 wherein in the event said number of excessive emissions produces a percentage falling between said upper and lower limits of said set percentage, said method monitors additional runs to produce a plurality of sets of excessive emission signals, said sets statistically factored to produce an accurate percentage count of excessive emission signals compared to said set percentage to determine if said warning mechanism is to be activated.

69) The method of claim 52 further including the step of periodically sensing one or more of the following operating conditions of said vehicle: i) air to fuel ratio; ii) timing; iii) lambda; iii) EGO sensor signals; iv) manifold air pressure; v) exhaust gas recirculation solenoid position; vi) mass air flow; vii) exhaust gas temperature; and, viii) catalytic temperature and counting the conditions sensed which exceed a stored threshold value indicative of an optimal engine operating condition, each instance in which said sensed operating condition exceeded said threshold during a vehicle run being an excessive operating condition signals.

70) The method of claim 69 further including the steps of statistically evaluating said excessive operating conditions when a catalytic converter failure has been sensed; adjusting the engine operation of said vehicle to bring the sensed operating conditions within a set value of said operating condition threshold and repeating said method prior to activating said warning mechanism.

71) A system for on-board monitoring and detecting a failure of a vehicle's exhaust emission to meet regulatory standards promulgated by a regulatory agency for various operating-) speeds of a vehicle powered by an internal combustion engine, said system comprising: a) a catalytic converter through which the vehicle's exhaust gas passes; b) sensor means downstream of said converter for separately sensing the hydrocarbon emissions and nitrous oxide emissions in the exhaust gas and generating HC signals and N0_X signals indicative, respectively, of the hydrocarbon emissions and nitrous oxide emissions in the exhaust gas; c) computer means in said vehicle for sampling, after a warm-up period of said vehicle has expired, on a periodic basis simultaneously generated HC and NO_x signals produced by said sensor means irrespective of variation in operating speed of said vehicle and comparing each sampled signal against a set emission threshold having set NO_x and HC concentration values, said HC signal being compared against its threshold only if said N0_X signal exceeded said NO_x threshold, each HC signal exceeding said HC threshold being an excessive emission signal; d) warning indicator means in said vehicle for indicating failure of said vehicle to meet said emission standards, said warning signal means actuated by said computer means when said computer means determines that a set number of excessive emission signals have occurred during a set run time of said vehicle.

72) The system of claim 71 wherein said sensing means includes a hydrocarbon sensor for sensing HC emissions and a nitrous oxide sensor for sensing said NO_x emissions.

73) The system of claim 71 further including qualifying condition sensing means for periodically sensing and generating operating conditions signals simultaneously with said HC and NO_x signals which are indicative of at least one of the following operating conditions of the vehicle: i) air to fuel ratio; ii) the speed of the vehicle; iii) engine rpm; iv) timing; v) lambda; vi) EGO sensor signals; vii) manifold air pressure; viii) throttle position; ix) exhaust gas recirculation solenoid position; x) drive shaft torque; xi) mass air flow; xii) exhaust gas temperature; and, xiii) catalytic temperature; said computer means comparing said sensed qualifying condition signal to a stored operating condition value, to determine if a validated qualifying condition signal has occurred and processing said HC and N0_X signals only when a validated qualifying condition signal has occurred.

74) The system of claim 73 wherein said sensed qualifying conditions include a speed less than 50 mph and a time period indicative of a warm-up time for a cold engine.

75) The system of claim 74 wherein said computer means determines said set number of excessive emission signals which have exceeded said regulatory emission threshold in accordance with a set percentage expressed as number of excessive emission signals Set percentage < number of sampled emission signals ^x 1 0 and said set percentage corresponds to an emission regulatory standard in turn correlated to said regulatory emission threshold limit.

76) The system of claim 75 wherein said regulatory emission threshold correlates to grams of hydrocarbons emitted from the vehicle per mile driven, g HC/mile, as determined by the expression:

gt'd g/mile=[0.43(gb#l + gb#2)/(b#l dist + b#2 dist)] +[0.57 (gb#2 + gb#3)/(b#2 dist + b#3 dist)]

where

77) The system of claim 76 wherein said catalytic converter includes a three way catalyst capable of sensing HC, carbon monoxide and N0_X carried on a ceramic or metal honeycomb substrate.

78) The system of claim 77 wherein said catalyst includes one or more precious metals selected from the group consisting of platinum, palladium, rhodium, ruthenium and iridium located on a support compound in turn affixed to said substrate.

79) The system of claim 78 further including an oxygen storage composition.

80) The system of claim 79 wherein said catalyst contains two or more layers of precious metals and said support includes at least alumina.

81) The system of claim 76 wherein said number of validated emission signals in said set percentage expression is a fixed number.

82) The system of claim 81 wherein said number of sampled emission signals in said set percentage expression is the number of emission signals generated at a fixed frequency when the vehicle has been operated for at least a set time.

83) The system of claim 75 wherein said excessive emission threshold for said validated HC signals includes a plurality of regulatory emission thresholds corresponding to a like plurality of HC ranges so that each regulatory emission threshold corresponds to a specific range of HC emissions and each run produces pluralities of excessive emission signals for each HC range; said computer means interpolating the number of excessive emission signals which exceeded each regulatory emission threshold for each hydrocarbon range to determine a specific, sensed emission level for a given run and comparing said specific sensed emission level to a regulatory emission level to determine if said warning mechanism is to be actuated.

84) The system of claim 83 wherein said computer means statistically evaluates a plurality of said specific sensed emission levels accumulated over a like plurality of runs before determining if said warning mechanism is to be actuated.

85) The system of claim 83 wherein said pluralities of hydrocarbon ranges are set at less than 10 ppm, 15 ppm, 20 ppm, and 25 ppm of hydrocarbons respectively.

86) The system of claim 85 further including said vehicle having an engine control means under the control of said computer means for regulating the operation of said engine including the ratio of air to fuel supplied to said engine, and said computer means triggering a failure signal to said engine control mechanism while not activating said warning mechanism in the event said computer means determines that the number of excessive emission signals have exceeded said set percentage of regulatory emission thresholds for all of said hydrocarbon ranges.

87) The system of claim 71 further including at least one qualifying condition sensor on said vehicle for sensing and generating qualifying condition signals indicative of one or more of the following operating conditions of said vehicle: i) air to fuel ratio; ii) timing; iii) lambda; iv) EGO sensor signals; v) manifold air pressure; vi) exhaust gas recirculation solenoid position; vii) mass air flow; viii) exhaust gas temperature; and, ix) catalytic temperature and said computer means is operable to count said qualifying condition signals which exceed a stored optimal operating threshold value indicative of an optimal engine operating condition, each instance in which said sensed qualifying condition exceeded said optimal operating threshold during a vehicle run being an excessive operating condition signals.

88) The system of claim 87 wherein said computer means statistically evaluates said excessive operating conditions when a catalytic converter failure has been sensed and causes the generation of correction signals for adjusting the engine operation of said vehicle to bring the sensed operating conditions within a set value of said optimal operating condition threshold prior to activating said warning means .

89) A system for on-board monitoring and detecting a failure of the exhaust emission to meet governmental regulatory pollution standards for various operating speeds of a vehicle powered by an internal combustion engine, said system comprising: a) a catalytic converter through which the vehicle's exhaust passes; b) qualifying condition sensor means for sensing an operating condition of said vehicle and generating an qualifying condition signal indicative of said sensed operating condition; c) hydrocarbon emission sensor means immediately downstream of said catalytic converter for sensing hydrocarbons in said exhaust gas and generating hydrocarbon emission signals indicative of the hydrocarbon emissions in said exhaust gas; d) computer means in said vehicle for i) causing periodic sampling of said qualifying condition sensor to generate a plurality of qualifying condition signals, interpolating each qualifying condition signal and comparing each qualifying signal against a qualifying condition threshold to determine if a validated qualifying condition signal has occurred; ii) causing periodic sampling of said hydrocarbon emission sensor to generate a plurality of hydrocarbon emission signals; interpolating only the hydrocarbon emission signals generated when a simultaneously generated validated operating condition signal has occurred to generate a plurality of hydrocarbon emission signals and comparing each hydrocarbon emission signal against a set value correlated to an emission threshold, each hydrocarbon emission signal exceeding said emission threshold being an excessive emission signal; and iii) statistically factoring the number of excessive emission signals occurring during a given run of said vehicle to determine if a warning condition is present; and e) warning indicator means actuated when said computer -senses a warning condition to alert the operator of said vehicle of a failure of the vehicle to meet regulatory pollution standards.

90) The system of claim 89 wherein said catalytic converter includes close-coupled catalyst means positioned in close proximity to the exhaust header of said vehicle for reacting with approximately 60 to 80% of the hydrocarbon emissions in said exhaust gas and said sensor means includes a hydrocarbon sensor adjacent and downstream of said close- coupled catalyst to determine vehicle compliance with emission regulatory requirements during vehicle start-up.

91) The system of claim 90 wherein said close coupled catalyst means is effective to react with said hydrocarbons in said exhaust gas at temperatures as low as about 200°c.

92) The system of claim 91 wherein said close coupled catalyst means a honeycomb type carrier carrying a precious metal selected from the group consisting of platinum, palladium, rhodium, ruthenium and iridium, an activated alumina and at least one alkaline earth metal element, said close coupled catalyst means being void of any oxygen storage composition.

93) The system of claim 92 wherein said catalytic converter further includes a three way catalytic converter capable of sensing HC, carbon monoxide and N0_X carried on a ceramic or metal honeycomb substrate and located downstream of said close coupled catalysis means.

94) The system of claim 93 wherein said three way catalyst includes one or more precious metals selected from the group consisting of platinum, palladium, rhodium, ruthenium and iridium located on a support compound in turn affixed to said substrate.

95) The system of claim 94 further including an oxygen storage composition.

96) The system of claim 95 wherein said catalyst contains two or more layers of precious metals and said support includes at least alumina.

97) The system of claim 90 wherein said qualifying condition sensor is a sensor for monitoring at least one of the following of said vehicle's operating conditions: i) the air to fuel ratio; ii) the speed of the vehicle; iii) engine rpm; iv) timing; v) lambda; vi) EGO sensor signals; vii) manifold air pressure; viii) throttle position; ix) exhaust gas recirculation solenoid position; x) drive shaft torque; xi) mass air flow; xii) exhaust gas temperature; and, xiii) catalytic temperature.

98) The system of claim 97 wherein said qualifying condition is the temperature of said exhaust gas.

99) The system of claim 97 wherein said stored value corresponds to a regulatory emission standard and has an upper limit and a lower limit associated therewith, said comparing step (e) activating said warning mechanism when said number of excessive emissions exceeds said upper limit and completing said process if said number of excessive emissions is less than said lower limit.

100) The system of claim 99 wherein said stored value is a set percentage expressed as number of excessive emission signals Set percentage < number of validated condition signals x 100 and said warning mechanism is activated when a regulatory emission standard correlated to a specific set percentage is exceeded.

101) The system of claim 100 wherein said computer means causes a plurality of vehicle runs to occur in the event the number of excessive emission signals fall between said upper and lower limit for any given run before actuating said warning means, said computer means interpolating, in a statistically valid manner, the number of said excessive emission signals produced in said plurality of runs and comparing the results thereof with said stored value.

102) The system of claim 101 wherein said regulatory emission threshold correlates to grams of hydrocarbons emitted from the vehicle per mile driven, g HC/mile, as determined by the expression:

where

"b" is bag as used in the Federal Test Protocol

103) The system of claim 100 wherein said set regulatory emission thresholds for said validated HC signals includes a plurality of regulatory emission thresholds corresponding to a like plurality of HC ranges so that each regulatory emission threshold corresponds to a specific range of HC emissions and each run produces pluralities of excessive emission signals for each HC range; said computer means interpolating the number of excessive emission signals which exceeded each regulatory emission threshold for each hydrocarbon range to determine a specific, sensed emission level for a given run and comparing said specific sensed emission level to a regulatory emission level to determine if said warning mechanism is to be actuated. 104) The system of claim 103 wherein said computer means statistically evaluates a plurality of said specific sensed emission levels accumulated over a like plurality of runs before determining if said warning mechanism is to be actuated.

105) The system of claim 89 wherein said hydrocarbon emission sensors means is a calorimetric hydrocarbon sensor.

106) The system of claim 90 further including a three way catalytic converter downstream of said close coupled catalyst means; second emission sensor means downstream of said three way catalytic converter for separately sensing the hydrocarbon emissions and nitrous oxide emissions in the exhaust gas and generating HC and N0_X signals indicative, respectively, of the hydrocarbon emissions and nitrous oxide emissions in the exhaust gas prior to release to the atmosphere; said computer means further i) sampling on a periodic basis simultaneously generated HC and N0_X signals produced by said second emission sensor means irrespective of operating speed of said vehicle and comparing each sampled signal against a stored threshold value and ii) actuating said warning means when a set number of simultaneously generated HC and NO_x sampled signals have both exceeded their respective thresholds during a set run time of said vehicle, each simultaneously generated HC and NO_x signal pair exceeding said set threshold being an excessive emission signal.

107) The system of claim 106 wherein said sensing means includes a hydrocarbon sensor for sensing HC emissions and a nitrous oxide sensor for sensing said NO_x emissions. 108) The system of claim 106 wherein said qualifying condition signals are indicative of at least one of the following operating conditions of the vehicle: i) air to fuel ration; ii) the speed of the vehicle; iii) engine rpm; iv) timing; v) lambda; vi) EGO sensor signals; vii) manifold air pressure; viii) throttle position; ix) exhaust gas recirculation solenoid position; x) drive shaft torque; xi) mass air flow; xii) exhaust gas temperature; and xiii) catalytic temperature; said computer means comparing said sensed qualifying condition signal to a stored value to determine if a validated operating condition signal has occurred and processing said HC and N0_X signals only when a validated operating condition signal has occurred.

109) The system of claim 106 wherein said computer means statistically factors said excessive emission signals in accordance with a set percentage expressed as number of excessive emission signals Set percentage < number of sampled emission signals 100 and said set percentage corresponds to an emission regulatory standard in turn correlated to said threshold limit.

110) The system of claim 109 wherein said emission threshold correlates to grams of hydrocarbons emitted from the vehicle per mile driven, g HC/mile, as determined by the expression:

where

"b" is bag as used in the Federal Test Protocol "dist" is distance " g" is grams and said specific set percentage corresponds to a fixed g HC/mile set by a governmental regulatory agency.

111) The system of claim 109 wherein said set regulatory emission thresholds for said HC signals includes a plurality of regulatory emission thresholds corresponding to a like plurality of HC ranges so that each regulatory emission threshold corresponds to a specific range of HC emissions and each run produces pluralities of excessive emission signals for each HC range; said computer means interpolating the number of excessive emission signals which exceeded each regulatory emission threshold for each hydrocarbon range to determine a specific, sensed emission level for a given run and comparing said specific sensed emission level to a regulatory emission level to determine if said warning mechanism is to be actuated.

112) The system of claim 111 wherein said computer means statistically evaluates a plurality of said specific sensed emission levels accumulated over a like plurality of runs before determining if said warning mechanism is to be actuated.

113) The system of claim 112 wherein said pluralities of hydrocarbon ranges are set at less than 10 ppm, 15 ppm, 20 ppm, and -2^5 ppm of hydrocarbons respectively.

114) The system of claim 113 further including said vehicle having an engine control means under the control of said computer means for regulating the operation of said engine including the ratio of air to fuel supplied to said engine, and said computer means triggering a failure signal to said engine control mechanism while not activating said warning mechanism in the event said computer means determines that the number of excessive emission signals have exceeded said set percentage of regulatory emission thresholds for all of said hydrocarbon ranges.

115) The system of claim 112 wherein said computer means is operable to count said qualifying condition signals which exceed a stored optimal operating threshold value indicative of an optimal engine operating condition, each instance in which said sensed operating condition exceeded said optimal operating threshold during a vehicle run being an excessive operating condition signal.

116) The system of claim 115 wherein said computer means statistically evaluates said excessive operating conditions when a catalytic converter failure has been sensed and causes the generation of correction signals for adjusting the engine operation of said vehicle to bring the sensed operating conditions within a set value of said optimal operating condition threshold prior to activating said warning means .

AMENDED CLAIMS

[received by the International Bureau on 27 April 1999 (27.04.99); original claims 1-116 replaced by amended claims 1-113 (31 pages)]

Having thus defined the invention, it is claimed:

1) A process for on-board monitoring and detecting a failure of the catalytic converter of a vehicle comprising the steps of: a) providing an emission sensor downstream of the catalytic converter generating emission signals indicative of at least one specific gaseous pollutant, the concentration of which, in the vehicle's exhaust gas, is controlled by emission regulatory standards; b) providing at least one qualifying condition sensor for sensing at least one vehicular operating condition affecting the performance of said catalytic converter, said qualifying condition sensor generating qualifying condition signals indicative of said operating condition, said operating condition being specified as a vehicle operating condition during which regulatory emission requirements are to be met; c) sampling said qualifying condition signals at periodic time intervals during an operating run of said vehicle and determining if each sampled qualified condition signal exceeded a set operating condition threshold to produce a validated qualifying condition signal; said sampling continuing until a set number of validated qualifying condition signals have occurred during said run; d) sampling said emission signals at the time a validated condition signal is sensed and determining whether each sampled emission signal generated at the time of a validated condition signal exceeded a set emission threshold corresponding to a regulatory standard for the emission sensed by said emission sensor to produce an excessive emission signal; e) statistically factoring the number of excessive emission signals generated during said run relative to the total number of emission signals generated during said run and comparing the statistically factored number to a stored value in turn correlated to an emission regulatory standard to determine if a failure of the catalytic converter occurred; and, f) activating a warning indicator mechanism indicative of the vehicle's inability to meet emission requirements if such failure has occurred.

2) The process of claim 1 wherein said qualifying condition sensor is a sensor for monitoring at least one of the following of said vehicle's operating conditions: i) the air to fuel ratio; ii) the speed of the vehicle; iii) engine rpm; iv) timing; v) lambda; vi) EGO sensor signals; vii) manifold air pressure; viii) throttle position; ix) exhaust gas recirculation solenoid position; x) drive shaft torque; xi ) mass air flow; xii) exhaust gas temperature; and, xiii) catalytic temperature.

6) The process of claim 5 wherein step (a) includes a sensor or sensors measuring concentrations of two different but regulated gaseous pollutants, said emission sampling step producing an excessive emission signal only when said two different emissions each exceed a stored value.

7) The process of claim 6 wherein said two or more sensed emissions include HC and N0_X whereby cataytic conversion efficiency can be ascertained without reference to regulatory drive cycles.

8) The process of claim 5 further including the additional step of comparing sequentially generated validated condition signals and determining the vehicle's rate of change in speed therefrom; establishing a second validated condition signal when the vehicle's rate of speed change is beyond a set limit; counting the number of sampled emission signals which exceeded a second set emission threshold when said second validated condition signals have been generated to produce a second excessive emission signal, said second emission threshold corresponding to a regulatory emission standard for the vehicle under a set acceleration level; and activating said warning mechanism when the number of said second excessive emission signals relative to the number of said second validated condition signals exceeds a set number.

9) The process of claim 5 wherein said stored value corresponds to a regulatory emission standard and has an upper limit and a lower limit associated therewith, said comparing step (e) activating said warning mechanism when said number of excessive emissions exceeds said upper limit and completing said process if said number of excessive emissions is less than said lower limit.

10) The process of claim 9 wherein in the event said emission sampling step (d) produces a number of excessive emissions falling between said upper and lower limits in step (e), said steps (c), (d) and (e) are repeated to produce a plurality of sets of excessive emission signals, said sets statistically factored to produce an accurate count of excessive emission signals compared to said stored value to determine if said warning mechanism is to be activated.

11) The process of claim 9 wherein said stored value is a set percentage expressed as number of excessive emission signals Set percentage < number of validated condition signals 100 and said warning mechanism is activated when a regulatory emission standard correlated to a specific set percentage is exceeded.

12) The process of claim 11 wherein said emission threshold correlates to grams of hydrocarbons emitted from the vehicle per mile driven, g HC/mile, as determined by the expression:

where

13) The process of claim 12 wherein said emissions sensed by said emission sensor are hydrocarbons, said set emission threshold corresponding to a plurality of different hydrocarbon ranges, each run producing different pluralities of excessive emission signals corresponding to various hydrocarbon ranges; said process including the additional step of conducting a plurality of runs and comparing the frequencies at which said number of excessive emission signals exceeded said set emission threshold for each hydrocarbon range to determine a sensed hydrocarbon emission level produced by said vehicle and comparing said sensed emission level to a regulatory emission level to determine if said warning mechanism is to be actuated.

14) The process of claim 13 wherein said pluralities of hydrocarbon ranges are set at less than 10 ppm, 15 ppm, 20 ppm, and 25 ppm of hydrocarbon concentrations in said exhaust gas respectively.

15) The process of claim 1 wherein step (a) includes a sensor or sensors measuring concentrations of two different but regulated gaseous pollutants, said emission sampling step producing an excessive emission signal only when said two different emissions each exceed a stored value.

16) The process of claim 15 wherein said two or more sensed emissions include HC and N0_X whereby cataytic conversion efficiency can be ascertained without reference to regulatory drive cycles.

17) The process of claim 16 wherein said set emission threshold for said HC includes a plurality of emission thresholds corresponding to a like plurality of HC ranges so that each threshold in said plurality corresponds to a specific range of HC emissions and each run produces a plurality of excessive emission signals for each HC range; said process including the additional step of comparing the frequency at which said number of excessive emission signals exceeded each emission threshold for each hydrocarbon range during an operating run to determine a specific, sensed emission level for said run, said specific sensed emission level compared to a regulatory emission level to determine if said warning mechanism is to be actuated.

18) The process of claim 17 wherein a plurality of specific sensed emission levels accumulated over a like plurality of runs are statistically evaluated before determining if said warning mechanism is to be actuated.

19) The process of claim 17 further including said vehicle having an engine control mechanism regulating the operation of the engine of said vehicle including the ratio of air to fuel supplied to said engine, said warning mechanism in communication with said engine control mechanism, said step of comparing said frequencies of said excessive emission signals for said HC ranges triggering a failure signal to said engine control mechanism while not activating said warning mechanism in the event said set thresholds are exceeded for all of said hydrocarbon ranges.

20) The process of claim 17 wherein said pluralities of hydrocarbon ranges are set at HC concentrations greater than 10 ppm, 15 ppm, 20 ppm, and 25 ppm of hydrocarbons respectively.

21) The process of claim 20 wherein said emission sensor senses NO_x separately from HC and generates NO_x signals indicative of N0_x concentrations in the exhaust stream, said emission signal being sampled only when a set threshold for NO_x emission has occurred whereby variations in the driving cycle do not affect the ability to determine if the catalytic converter satisfies emission regulation requirements .

22) The process of claim 21 wherein variations in levels of emission regulatory requirements are accounted for by selecting a set number of excessive emissions which must be exceeded in a run, a specific one of said pluralities of said HC threshold levels and a set NO_x threshold value.

23) The process of claim 22 wherein said stored value is a set percentage expressed as

, number of excessive emission signals

Set percentage < number of validated condition signals 100 and said warning mechanism is activated when a regulatory emission standard correlated to a specific set percentage is exceeded. 24) The process of claim 23 wherein said emission threshold correlates to grams of hydrocarbons emitted from the vehicle per mile driven, g HC/mile, as determined by the expression:

where

25) The process of claim 16 wherein said two or more sensed emissions are sensed by separate emission sensors.

26) The process of claim 25 wherein said catalytic converter includes a three way catalyst capable of sensing HC, carbon monoxide and NO_x carried on a ceramic or metal honeycomb substrate.

27) The process of claim 26 wherein said catalyst includes one or more precious metals selected from the group consisting of platinum, palladium, rhodium, ruthenium and iridium located on a support compound in turn affixed to said substrate.

28) The process of claim 27 further including an oxygen storage composition.

29) The process of claim 28 wherein said catalyst contains two or more layers of precious metals and said support includes at least alumina.

30) The process of claim 1 wherein said stored value has an upper limit and a lower limit associated therewith, said comparing step (e) activating said warning mechanism when said number of excessive emissions exceed said upper limit and completing said process if said number of excessive emissions is less than said lower limit.

31) The process of claim 30 wherein in the event said emission sampling step (d) produces a number of excessive emissions falling between said upper and lower limits in step (e), said steps (c), (d) and (e) are repeated to produce a plurality of sets of excessive emission signals, said sets statistically factored to produce an accurate count of excessive emission signals compared to said stored value to determine if said warning mechanism is to be activated.

32) The process of claim 1 wherein said emission sensor senses N0_X separately from HC and generates N0_X signals indicative of N0_X concentrations in the exhaust stream and HC signals indicative of the HC concentrations in the exhaust stream; said qualifying condition sensor is activated only after said vehicle has been operated for a fixed time and only when the vehicle's speed is below a fixed limit; said sampling of said emission signal step proceeding in a sequencing step of comparing each of said N0_X and HC signals against a set threshold for the NO_x and HC emissions and counting the emission signal as an excessive emission signal only when both NO_x and HC signals exceed said set thresholds whereby variations in the driving cycle do not affect the ability to determine if the catalytic converter satisfies emission regulation requirements.

33) The process of claim 1 wherein said qualifying condition sensor senses the speed of said vehicle, said validated condition signals being established when said vehicle's speed is less than a set value.

34) The process of claim 33 further including the additional step of comparing sequentially generated validated condition signals and determining the vehicle's rate of change in speed therefrom; establishing a second validated condition signal when the vehicle's rate of speed change is beyond a set limit; counting the number of sampled emission signals which exceeded a second set emission threshold when said second validated condition signals have been generated to produce a second excessive emission signal, said second emission threshold corresponding to a regulatory emission standard for the vehicle under a set acceleration level; and activating said warning mechanism when the number of said second excessive emission signals relative to the number of said second validated condition signals exceeds a set number.

35) The process of claim 1 wherein said set number of validated condition signals in said run is a fixed number of signals occurring over a fixed time period after a set start-up period for the vehicle has elapsed.

36) The process of claim 1 wherein said set number of validated condition signals in said run is a varying number determined by the time said vehicle is continuously operated after a set start-up period has elapsed. 37) The process of claim 1 wherein said stored value is a set percentage expressed as number of excessive emission signals Set percentage < number of validated condition signals 100 and said warning mechanism is activated when a regulatory emission standard correlated to a specific set percentage is exceeded.

38) The process of claim 37 wherein said number of validated condition signals in the expression is a fixed number .

39) The process of claim 37 wherein said number of validated condition signals in the expression is the number of validated condition signals when the vehicle has been operated for at least a set time.

40) The process of claim 1 wherein said emission threshold correlates to grams of hydrocarbons emitted from the vehicle per mile driven, g HC/mile, as determined by the expression:

where

41) The process of claim 40 wherein said stored value has an upper limit corresponding to a high number of g HC/mile and a lower limit corresponding to a lower number of g HC/mile wherein said number of excessive emissions required to reach said upper limit is approximately a factor of at least twice the number of excessive emissions required to meet said lower limit.

42) The process of claim 1 wherein said set emission thresholds for said HC includes a plurality of emission thresholds corresponding to a like plurality of HC ranges so that each threshold in said plurality corresponds to a specific range of HC emissions and each run produces a plurality of excessive emission signals for each HC range; said process including the additional step of comparing the frequency at which said number of excessive emission signals exceeded each emission threshold for each hydrocarbon range during an operating run to determine a specific, sensed emission level for said run, said specific sensed emission level compared to a regulatory emission level to determine if said warning mechanism is to be actuated.

43) The process of claim 42 wherein a plurality of specific sensed emission levels accumulated over a like plurality of runs are statistically evaluated before determining if said warning mechanism is to be actuated.

44) The process of claim 42 further including said vehicle having an engine control mechanism regulating the operation of the engine of said vehicle including the ratio of air to fuel supplied to said engine, said warning mechanism in communication with said engine control mechanism, said step of comparing said frequencies of said excessive emission signals for said HC ranges triggering a failure signal to said engine control mechanism while not activating said warning mechanism in the event said set thresholds are exceeded for all of said hydrocarbon ranges.

45) The process of claim 42 wherein said pluralities of hydrocarbon ranges are set at HC concentrations greater than 10 ppm, 15 ppm, 20 ppm, and 25 ppm of hydrocarbons respectively.

46) The process of claim 42 wherein said emission sensor senses NO_x separately from HC and generates NO_x signals indicative of N0_X concentrations in the exhaust stream, said excessive emission signal occurring only when a set threshold for NO_x emission has occurred as well as said set threshold for HC emission whereby variations in the driving cycle do not affect the ability to determine if the catalytic converter satisfies emission regulation requirements .

47) The process of claim 46 whereby variations in levels of emission requirements can be accounted for by selecting a set number of excessive emissions which must be exceeded in a run, a specific one of said pluralities of said HC threshold levels and a set NO_x threshold stored value.

48) The process of claim 1 further including the steps of statistically evaluating said excessive operating conditions when catalytic converter failure has been sensed; adjusting the engine operation of said vehicle to bring the sensed operating conditions within a set value of said operating condition threshold and repeating said method prior to activating said warning mechanism.

49) A vehicular on-board method for monitoring gaseous pollutants emitted by an internal combustion engine to determine failure of the vehicle's catalytic converter, said method comprising the step of: i) sampling at periodic intervals the exhaust gas downstream of the catalytic converter to determine from each sample the HC concentration in the exhaust gas and the NO_x concentration in the exhaust gas at each periodic interval; ii) determining after an operating run the number of samples in which the HC concentration and the NO_x concentration each exceeded set emission threshold limits therefor, each sample exceeding said emission threshold limits for both HC and NO_x concentrations being an excessive emission sample; iii) statistically evaluating said excessive emission samples relative to the total number of samples taken during the run to determine, without regard to variations in engine operating conditions during the operating run, when a catalytic converter failure has occurred; and, iv) actuating a warning mechanism in the vehicle indicative of an inability of the vehicle to meet emission regulatory standards when said catalytic failure has occurred.

50) The method of claim 49 wherein said sampling occurs only when said vehicle is operated at preset operating conditions.

51) The method of claim 50 wherein said preset operating conditions include said vehicle being at a speed less than a set value and said vehicle having been operated for at least a set time to warm up.

52) The method of claim 51 wherein said exhaust gas is sampled for HC emissions by a pellistor type sensor. 53) The method of claim 52 wherein said exhaust gas is sampled by a NO_x sensor.

54) The method of claim 53 wherein said exhaust gas is sampled at periodic intervals between 0.3 and 10 Hz.

55) The method of claim 50 wherein said statistical evaluation is accomplished pursuant to a set percentage expressed as number of excessive emission signals Set percentage < number of validated condition signals x 100 where said validated condition signal is every periodic emission signal which occurs during the time said preset operating condition is present during a given run of said vehicle and said set percentage which actuates said warning mechanism when exceeded corresponds to an emission regulatory standard in turn correlated to said threshold limit.

56) The method of claim 55 wherein said emission threshold correlates to grams of hydrocarbons emitted from the vehicle per mile driven, g HC/mile, as determined by the expression:

where

57) The method of claim 56 wherein said number of validated condition signals in said set percentage expression is a fixed number.

58) The method of claim 57 wherein said number of validated condition signals in said set percentage expression is the number of validated condition signals when the vehicle has been operated for at least a set time.

59) The method of claim 50 wherein said set emission thresholds for said HC includes a plurality of emission thresholds corresponding to a like plurality of HC concentration ranges so that each threshold in said plurality corresponds to a specific range of HC emissions and each run produces a plurality of excessive emission signals for each HC range; said process including the additional step of comparing the frequency at which said number of excessive emission signals exceeded each emission threshold for each hydrocarbon range to determine a specific, sensed emission level for said run, said specific sensed emission level compared to a regulatory emission level to determine if said warning mechanism is to be actuated.

60) The method of claim 59 wherein a plurality of specific sensed emission levels accumulated over a like plurality of runs are statistically evaluated before determining if said warning mechanism is to be actuated.

61) The method of claim 59 further including said vehicle having an engine control mechanism regulating the operation of the engine of said vehicle including the ratio of air to fuel supplied to said engine, said warning mechanism in communication with said engine control mechanism, said step of comparing said frequencies of said excessive emission signals for said HC ranges triggering a failure signal to said engine control mechanism while not activating said warning mechanism in the event said set thresholds are exceeded for all of said hydrocarbon ranges.

62) The method of claim 59 wherein said pluralities of hydrocarbon ranges are set at less than 10 ppm, 15 ppm, 20 ppm, and 25 ppm of hydrocarbons respectively.

63) The method of claim 62 wherein variations in levels of emission requirements are accounted for by selecting a set number of excessive emissions which must be exceeded in a run, a specific one of said pluralities of said HC threshold levels and a set N0_X threshold value.

64) The method of claim 56 wherein said set percentage has an upper limit and a lower limit associated therewith, activating said warning mechanism when said number of excessive emissions exceeds said upper limit of said set percentage and completing said monitoring method if said number of excessive emissions is less than said lower limit.

65) The process of claim 64 wherein in the event said number of excessive emissions produces a percentage falling between said upper and lower limits of said set percentage, said method monitors additional runs to produce a plurality of sets of excessive emission signals, said sets statistically factored to produce an accurate percentage count of excessive emission signals compared to said set percentage to determine if said warning mechanism is to be activated.

66) The method of claim 49 further including the step of periodically sensing one or more of the following operating conditions of said vehicle: i) air to fuel ratio; ii) timing; iii) lambda; iii) EGO sensor signals; iv) manifold air pressure; v) exhaust gas recirculation solenoid position; vi) mass air flow; vii) exhaust gas temperature; and, viii) catalytic temperature and counting the conditions sensed which exceed a stored threshold value indicative of an optimal engine operating condition, each instance in which said sensed operating condition exceeded said threshold during a vehicle run being an excessive operating condition signals.

67) The method of claim 66 further including the steps of statistically evaluating said excessive operating conditions when a catalytic converter failure has been sensed; adjusting the engine operation of said vehicle to bring the sensed operating conditions within a set value of said operating condition threshold and repeating said method prior to activating said warning mechanism.

68) A system for on-board monitoring and detecting a failure of a vehicle's exhaust emission to meet regulatory standards promulgated by a regulatory agency for various operating speeds of a vehicle powered by an internal combustion engine, said system comprising: a) a catalytic converter through which the vehicle's exhaust gas passes; b) sensor means downstream of said converter for separately sensing the hydrocarbon emissions and nitrous oxide emissions in the exhaust gas and generating HC signals and NO_x signals indicative, respectively, of the hydrocarbon emissions and nitrous oxide emissions in the exhaust gas; c) computer means in said vehicle for sampling, after - I l l -

a warm-up period of said vehicle has expired, on a periodic basis simultaneously generated HC and N0_X signals produced by said sensor means irrespective of variation in operating speed of said vehicle and comparing each sampled signal against a set emission threshold having set N0_X and HC concentration values, said HC signal being compared against its threshold only if said N0_X signal exceeded said N0_X threshold, each HC signal exceeding said HC threshold being an excessive emission signal; d) warning indicator means in said vehicle for indicating failure of said vehicle to meet said emission standards, said warning indicator means actuated by said computer means when said computer means determines that a set number of excessive emission signals have occurred during a set run time of said vehicle irrespective of variations in operating speed occurring during said run time.

69) The system of claim 68 wherein said sensing means includes a hydrocarbon sensor for sensing HC emissions and a nitrous oxide sensor for sensing said NO_x emissions.

70) The system of claim 68 further including qualifying condition sensing means for periodically sensing and generating operating conditions signals simultaneously with said HC and NO_x signals which are indicative of at least one of the following operating conditions of the vehicle: i) air to fuel ratio; ii) the speed of the vehicle; iii) engine rpm; iv) timing; v) lambda; vi) EGO sensor signals; vii) manifold air pressure; viii) throttle position; ix) exhaust gas recirculation solenoid position; x) drive shaft torque; xi) mass air flow; xii) exhaust gas temperature; and, xiii) catalytic temperature; said computer means comparing said sensed qualifying condition signal to a stored operating condition value to determine if a validated qualifying condition signal has occurred and processing said HC and N0_X signals only when a validated qualifying condition signal has occurred.

71) The system of claim 70 wherein said sensed qualifying conditions include a speed less than 50 mph and a time period indicative of a warm-up time for a cold engine .

72) The system of claim 71 wherein said computer means determines said set number of excessive emission signals which have exceeded said regulatory emission threshold in accordance with a set percentage expressed as . , number of excessive emission signals Set percentage < number of sampled emission signals x 100 and said set percentage corresponds to an emission regulatory standard in turn correlated to said regulatory emission threshold limit.

73) The system of claim 72 wherein said regulatory emission threshold correlates to grams of hydrocarbons emitted from the vehicle per mile driven, g HC/mile, as determined by the expression:

where

"b" is bag as used in the Federal Test Protocol "dist" is distance "g" is grams and said specific set percentage corresponds to a fixed g HC/mile set by a governmental regulatory agency. 74) The system of claim 73 wherein said catalytic converter includes a three way catalyst capable of sensing HC, carbon monoxide and N0_X carried on a ceramic or metal honeycomb substrate.

75) The system of claim 74 wherein said catalyst includes one or more precious metals selected from the group consisting of platinum, palladium, rhodium, ruthenium and iridium located on a support compound in turn affixed to said substrate.

76) The system of claim 75 further including an oxygen storage composition.

77) The system of claim 76 wherein said catalyst contains two or more layers of precious metals and said support includes at least alumina.

78) The system of claim 73 wherein said number of validated emission signals in said set percentage expression is a fixed number.

79) The system of claim 78 wherein said number of sampled emission signals in said set percentage expression is the number of emission signals generated at a fixed frequency when the vehicle has been operated for at least a set time.

80) The system of claim 72 wherein said excessive emission threshold for said validated HC signals includes a plurality of regulatory emission thresholds corresponding to a like plurality of HC ranges so that each regulatory emission threshold corresponds to a specific range of HC emissions and each run produces pluralities of excessive emission signals for each HC range; said computer means interpolating the number of excessive emission signals which exceeded each regulatory emission threshold for each hydrocarbon range to determine a specific, sensed emission level for a given run and comparing said specific sensed emission level to a regulatory emission level to determine if said warning mechanism is to be actuated.

81) The system of claim 80 wherein said computer means statistically evaluates a plurality of said specific sensed emission levels accumulated over a like plurality of runs before determining if said warning mechanism is to be actuated.

82) The system of claim 80 wherein said pluralities of hydrocarbon ranges are set at less than 10 ppm, 15 ppm, 20 ppm, and 25 ppm of hydrocarbons respectively.

83) The system of claim 82 further including said vehicle having an engine control means under the control of said computer means for regulating the operation of said engine including the ratio of air to fuel supplied to said engine, and said computer means triggering a failure signal to said engine control mechanism while not activating said warning mechanism in the event said computer means determines that the number of excessive emission signals have exceeded said set percentage of regulatory emission thresholds for all of said hydrocarbon ranges.

84) The system of claim 68 further including at least one qualifying condition sensor on said vehicle for sensing and generating qualifying condition signals indicative of one or more of the following operating conditions of said vehicle: i) air to fuel ratio; ii) timing; iii) lambda; iv) EGO sensor signals; v) manifold air pressure; vi) exhaust gas recirculation solenoid position; vii) mass air flow; viii) exhaust gas temperature; and, ix) catalytic temperature and said computer means is operable to count said qualifying condition signals which exceed a stored optimal operating threshold value indicative of an optimal engine operating condition, each instance in which said sensed qualifying condition exceeded said optimal operating threshold during a vehicle run being an excessive operating condition signals.

85) The system of claim 84 wherein said computer means statistically evaluates said excessive operating conditions when a catalytic converter failure has been sensed and causes the generation of correction signals for adjusting the engine operation of said vehicle to bring the sensed operating conditions within a set value of said optimal operating condition threshold prior to activating said warning means .

86) A system for on-board monitoring and detecting a failure of the exhaust emission to meet governmental regulatory pollution standards for various operating speeds of a vehicle powered by an internal combustion engine, said system comprising: a) a catalytic converter through which the vehicle's exhaust passes; b) a qualifying condition sensor for sensing an operating condition of said vehicle and generating a qualifying condition signal indicative of said sensed operating condition; c) a hydrocarbon emission sensor immediately downstream of said catalytic converter for sensing hydrocarbons in said exhaust gas and generating hydrocarbon emission signals indicative of the hydrocarbon emissions in said exhaust gas; d) a computer in said vehicle for i) causing periodic sampling of said qualifying condition sensor to generate a plurality of qualifying condition signals, and comparing each qualifying signal against a qualifying condition threshold to determine if a validated qualifying condition signal has occurred; ii) causing periodic sampling of said hydrocarbon emission sensor to generate a plurality of hydrocarbon emission signals; interpolating only the hydrocarbon emission signals generated when a simultaneously generated validated operating condition signal has occurred to generate a plurality of validated hydrocarbon emission signals and comparing each validated hydrocarbon emission signal against a set value correlated to an emission threshold corresponding to a regulated hydrocarbon concentration for said operating condition and comparing the statistically factored number to a stored value corresponding to a regulated hydrocarbon concentration for said operating condition, each hydrocarbon emission signal exceeding said emission threshold being an excessive emission signal; and iii) statistically factoring the number of excessive emission signals occurring during a given run of said vehicle relative to the total number of validated hydrocarbon emission signals to determine if a warning condition is present; and e) a warning indicator actuated when said computer senses a warning condition to alert the operator of said vehicle of a failure of the vehicle to meet regulatory pollution standards.

87) The system of claim 86 wherein said catalytic converter includes a close-coupled catalyst positioned in close proximity to the exhaust header of said vehicle for reacting with approximately 60 to 80% of the hydrocarbon emissions in said exhaust gas and said system further includes a second hydrocarbon sensor adjacent and downstream of said close- coupled catalyst to determine vehicle compliance with emission regulatory requirements during vehicle start-up.

88) The system of claim 87 wherein said close coupled catalyst is effective to react with said hydrocarbons in said exhaust gas at temperatures as low as about 200°c.

89) The system of claim 88 wherein said close coupled catalyst includes a honeycomb type carrier carrying a precious metal selected from the group consisting of platinum, palladium, rhodium, ruthenium and iridium, an activated alumina and at least one alkaline earth metal element, said close coupled catalyst being void of any oxygen storage composition.

90) The system of claim 89 wherein said catalytic converter further includes a three way catalytic converter capable of sensing HC, carbon monoxide and NO_x carried on a ceramic or metal honeycomb substrate and located downstream of said close coupled catalysis means.

91) The system of claim 90 wherein said three way catalyst includes one or more precious metals selected from the group consisting of platinum, palladium, rhodium, ruthenium and iridium located on a support compound in turn affixed to said substrate.

92) The system of claim 91 further including an oxygen storage composition.

93) The system of claim 92 wherein said catalyst contains two or more layers of precious metals and said support includes at least alumina.

94) The system of claim 87 wherein said qualifying condition sensor is a sensor for monitoring at least one of the following of said vehicle's operating conditions: i) the air to fuel ratio; ii) the speed of the vehicle; iii) engine rpm; iv) timing; v) lambda; vi ) EGO sensor signals; vii) manifold air pressure; viii) throttle position; ix) exhaust gas recirculation solenoid position; x) drive shaft torque; xi) mass air flow; xii) exhaust gas temperature; and, xiii) catalytic temperature.

95) The system of claim 94 wherein said qualifying condition is the temperature of said exhaust gas.

96) The system of claim 94 wherein said stored value has an upper limit and a lower limit associated therewith, said computer activating said warning mechanism when said number of excessive emissions exceeds said upper limit and indicating said catalytic converter meets emission requirements if said number of excessive emissions is less than said lower limit.

97) The system of claim 96 wherein said stored value is a set percentage expressed as nnuummbbeerr ooff eexxcceessive emission signals SSeett ppeerrcceennttaaggee << nnuummbbeerr ooff vvaalliicdated condition signals x 100 and said warning mechanism is activated when a regulatory emission standard correlated to a specific set percentage is exceeded.

98) The system of claim 97 wherein said computer causes a plurality of vehicle runs to occur in the event the number of excessive emission signals fall between said upper and lower limit for any given run before actuating said warning indicator, said computer interpolating, in a statistically valid manner, the number of said excessive emission signals produced in said plurality of runs and comparing the results thereof with said stored value.

99) The system of claim 98 wherein said regulatory emission threshold correlates to grams of hydrocarbons emitted from the vehicle per mile driven, g HC/mile, as determined by the expression:

where

"b" is bag as used in the Federal Test Protocol

100) The system of claim 99 wherein said set regulatory emission thresholds for said validated hydrocarbon signals includes a plurality of regulatory emission thresholds corresponding to a like plurality of hydrocarbon ranges so that each regulatory emission threshold corresponds to a specific range of hydrocarbon emissions and each run produces pluralities of excessive emission signals for each hydrocarbon range; said computer means interpolating the number of excessive emission signals which exceeded each regulatory emission threshold for each hydrocarbon range to determine a specific, sensed emission level for a given run and comparing said specific sensed emission level to a regulatory emission level to determine if said warning mechanism is to be actuated.

101) The system of claim 100 wherein said computer statistically evaluates a plurality of said specific sensed emission levels accumulated over a like plurality of runs before determining if said warning mechanism is to be actuated.

102) The system of claim 86 wherein said hydrocarbon emission sensors means is a calorimetric hydrocarbon sensor.

103) The system of claim 87 further including a three way catalytic converter downstream of said close coupled catalyst; second emission sensors downstream of said three way catalytic converter for separately sensing the hydrocarbon emissions and nitrous oxide emissions in the exhaust gas and generating HC and NO_x signals indicative, respectively, of the hydrocarbon emissions and nitrous oxide emissions in the exhaust gas prior to release to the atmosphere; said computer further i) sampling on a periodic basis simultaneously generated HC and NO_x signals produced by said second emission sensors irrespective of operating speed of said vehicle and comparing each sampled signal against a stored threshold value and ii) actuating said warning means when a set number of simultaneously generated HC and NO_x sampled signals have both exceeded their respective thresholds during a set run time of said vehicle, each simultaneously generated HC and N0_X signal pair exceeding said set threshold being an excessive emission signal.

104) The system of claim 103 wherein said second sensor includes a hydrocarbon sensor for sensing HC emissions and a nitrous oxide sensor for sensing said N0_X emissions.

105) The system of claim 103 wherein said qualifying condition signals are indicative of at least one of the following operating conditions of the vehicle: i) air to fuel ratio; ii) the speed of the vehicle; iii) engine rpm; iv) timing; v) lambda; vi) EGO sensor signals; vii) manifold air pressure; viii) throttle position; ix) exhaust gas recirculation solenoid position; x) drive shaft torque; xi) mass air flow; xii) exhaust gas temperature; and xiii) catalytic temperature; said computer comparing said sensed qualifying condition signal to a stored value to determine if a validated operating condition signal has occurred and processing said HC and NO_x signals only when a validated operating condition signal has occurred.

106) The system of claim 103 wherein said computer means statistically factors said excessive emission signals in accordance with a set percentage expressed as number of excessive emission signals Set percentage < number of sampled emission signals x 100 and said set percentage corresponds to an emission regulatory standard in turn correlated to said threshold limit.

107) The system of claim 106 wherein said emission threshold correlates to grams of hydrocarbons emitted from the vehicle per mile driven, g HC/mile, as determined by the expression:

where

"b" is bag as used in the Federal Test Protocol

108) The system of claim 106 wherein said set regulatory emission thresholds for said HC signals includes a plurality of regulatory emission thresholds corresponding to a like plurality of HC ranges so that each regulatory emission threshold corresponds to a specific range of HC emissions and each run produces pluralities of excessive emission signals for each HC range; said computer interpolating the number of excessive emission signals which exceeded each regulatory emission threshold for each hydrocarbon range to determine a specific, sensed emission level for a given run and comparing said specific sensed emission level to a regulatory emission level to determine if said warning mechanism is to be actuated.

109) The system of claim 108 wherein said computer statistically evaluates a plurality of said specific sensed emission levels accumulated over a like plurality of runs before determining if said warning mechanism is to be actuated. 110) The system of claim 109 wherein said pluralities of hydrocarbon ranges are set at less than 10 ppm, 15 ppm, 20 ppm, and 25 ppm of hydrocarbons respectively.

111) The system of claim 110 further including said vehicle having an engine controller under the control of said computer for regulating the operation of said engine including the ratio of air to fuel supplied to said engine, and said computer triggering a failure signal to said engine controller while not activating said warning mechanism in the event said computer determines that the number of excessive emission signals have exceeded said set percentage of regulatory emission thresholds for all of said hydrocarbon ranges.

112) The system of claim 109 wherein said computer is operable to count said qualifying condition signals which exceed a stored optimal operating threshold value indicative of an optimal engine operating condition, each instance in which said sensed operating condition exceeded said optimal operating threshold during a vehicle run being an excessive operating condition signal.

113) The system of claim 112 wherein said computer statistically evaluates said excessive operating conditions when a catalytic converter failure has been sensed and causes the generation of correction signals for adjusting the engine operation of said vehicle to bring the sensed operating conditions within a set value of said optimal operating condition threshold prior to activating said warning means .