WO1988007131A1 - Mass flow fuel injection control system - Google Patents

Mass flow fuel injection control system Download PDF

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Publication number
WO1988007131A1
WO1988007131A1 PCT/US1988/000398 US8800398W WO8807131A1 WO 1988007131 A1 WO1988007131 A1 WO 1988007131A1 US 8800398 W US8800398 W US 8800398W WO 8807131 A1 WO8807131 A1 WO 8807131A1
Authority
WO
WIPO (PCT)
Prior art keywords
input
amplifier
amplifier means
output
chip driver
Prior art date
Application number
PCT/US1988/000398
Other languages
French (fr)
Inventor
Richard E. Staerzl
Original Assignee
Brunswick Corporation
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Brunswick Corporation filed Critical Brunswick Corporation
Priority to DE8888902305T priority Critical patent/DE3875345T2/en
Priority to BR888807409A priority patent/BR8807409A/en
Priority to AT88902305T priority patent/ATE81542T1/en
Publication of WO1988007131A1 publication Critical patent/WO1988007131A1/en

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Classifications

    • GPHYSICS
    • G01MEASURING; TESTING
    • G01FMEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/05Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects
    • G01F1/34Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by measuring pressure or differential pressure
    • G01F1/36Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by measuring pressure or differential pressure the pressure or differential pressure being created by the use of flow constriction
    • G01F1/363Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by measuring pressure or differential pressure the pressure or differential pressure being created by the use of flow constriction with electrical or electro-mechanical indication
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02BINTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B33/00Engines characterised by provision of pumps for charging or scavenging
    • F02B33/02Engines with reciprocating-piston pumps; Engines with crankcase pumps
    • F02B33/04Engines with reciprocating-piston pumps; Engines with crankcase pumps with simple crankcase pumps, i.e. with the rear face of a non-stepped working piston acting as sole pumping member in co-operation with the crankcase
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02DCONTROLLING COMBUSTION ENGINES
    • F02D41/00Electrical control of supply of combustible mixture or its constituents
    • F02D41/02Circuit arrangements for generating control signals
    • F02D41/18Circuit arrangements for generating control signals by measuring intake air flow
    • GPHYSICS
    • G01MEASURING; TESTING
    • G01FMEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/76Devices for measuring mass flow of a fluid or a fluent solid material
    • G01F1/86Indirect mass flowmeters, e.g. measuring volume flow and density, temperature or pressure
    • G01F1/88Indirect mass flowmeters, e.g. measuring volume flow and density, temperature or pressure with differential-pressure measurement to determine the volume flow
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02BINTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL
    • F02B75/00Other engines
    • F02B75/02Engines characterised by their cycles, e.g. six-stroke
    • F02B2075/022Engines characterised by their cycles, e.g. six-stroke having less than six strokes per cycle
    • F02B2075/025Engines characterised by their cycles, e.g. six-stroke having less than six strokes per cycle two
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02DCONTROLLING COMBUSTION ENGINES
    • F02D2400/00Control systems adapted for specific engine types; Special features of engine control systems not otherwise provided for; Power supply, connectors or cabling for engine control systems
    • F02D2400/04Two-stroke combustion engines with electronic control

Definitions

  • the invention relates to an electronic fuel njection control system for an internal combustion engine.
  • the object of the present invention is to provide a system by which the amount of fuel injected may be controlled without determination from a pre ⁇ programmed look-up table according to throttle setting; which, overcomes the above noted problems regarding reprogramming and recalibration upon alteration of the engine or use on different engine; and which eliminates the need for a throttle position sensor.
  • the present invention provides a mass flow fuel injection control system for an internal combustion engine having air intake means supplying combustion air to said engine, and fuel injector means supplying fuel to said engine, comprising means including a venturi sensing the flow velocity of said combustion air; means sensing the mass of said com ⁇ bustion air; and means responsive to said last two mentioned means and controlling said fuel injector means to control the amount of fuel injected accord ⁇ ing to said air flow velocity and said air mass.
  • the system which determines the amount of air coming into the engine by means of its velocity and mass. With this information, it is known how much fuel the engine needs.
  • the system automatically tracks and self- adjusts to the particular engine at hand, and can be used on an altered engine or on another different engine, and will automatically readjust to the en ⁇ gine's fuel requirements, all without a look-up table.
  • the automatic tracking is also desirable as the engine wears. As piston rings wear, the piston will pull in less air, and the electronic fuel in ⁇ jection control system-will automatically lower the amount of fuel injected. Without this automatic adjustment, the fuel-air mixture would become richer.
  • FIG. 1 is a sectional view through one of the cylinder banks of a V-6 marine internal combustion engine and control system in accordance with the in ⁇ vention.
  • Figure 2 is a sectional view through a portion of the structure of Figure 1.
  • FIG. 3 is a schematic block diagram of electronic control circuitry in accordance with the invention.
  • Figure 4 is a more detailed circuit diagram of the circuitry of Figure 3.
  • Figure 5 is a graph illustrating operation of a portion of the circuitry of Figure 4.
  • Figure 1 shows a two-cycle internal com ⁇ bustion engine 2 having a plurality of reciprocal pistons 4 connected to a vertical crankshaft 6 by connecting rods 8 in a cylinder block 10.
  • Figure 1 shows one bank of three cylinders in a V-6 engine. Piston 4 moves to the left during its intake stroke drawing a fuel-air rm ⁇ xture through one-way reed valves 12 into crankcase chamber 14. Piston movement to the left also compresses the fuel-air mixture in cylinder 16 for ignition by spark plug 18, which combustion drives piston 4 to "the right generating its power stroke.
  • crankcase chamber 14 During the movement of piston 4 to the right, the fuel-air mixture in crankcase chamber 14 is blocked by one-way reed valves 12 from exiting the crankcase and instead is driven through a trans ⁇ fer passage in the crankcase to port 20 in cylinder 16 for compression during the intake stroke, and so on to repeat the cycle, all as is well known.
  • the com ⁇ bustion products are exhausted at port 22.
  • Air intake manifold 24 is mounted by bolts 26 to crankcase 10 and defines the air intake flow path as shown at arrows 28.
  • the manifold includes an outer mouth 30 and a reduced inner diameter portion 5 32 providing a venturi through which the air flows.
  • Fuel is injected into the crankcase downstream of the reed valves, for example as shown in U.S. Patent 4,305,351 at fuel injectors 34 in Figures 2 and 3.
  • the fuel injector tips are shown at 36.
  • Venturi 32 includes a butterfly valve 40 on rotatable shaft 42 for controlling air flow into manifold 24.
  • Manifold 24 has a drilled pas ⁇ sage 44 therethrough, Figure 2, at venturi 32 which
  • Manifold 24 has another drilled passage 48 therethrough at outer mouth 30 which receives a tube 50 for sensing pressure thereat. As air flows through venturi 32, there is a pressure drop according to
  • Tube 46 is open at its end 45 and senses the reduced pressure in venturi 32.
  • Tube 50 senses the absolute pressure outside of the venturi.
  • Tube 50 is closed at its end 47 and has a sma.ll hole in its side 49 facing upstream.
  • butterfly valve 40 is closed, it is at an angle of approximately 30 relative to a plane normal to air flow path 28.
  • Tube 46 is adjacent shaft 42 and up ⁇ stream of valve 40.
  • Absolute pressure sensor 52 for example a Microswitch 136PC, measures absolute air" pressure P, outside of venturi 32 at tube 50.
  • Differential pressure sensor 54 for example a Microswitch 176PC, measures the dif-
  • the frequency of the ignition or trigger signals on line 64 corresponds to engine speed and hence cancels out the factor in the E MOD si 9 nal - S
  • the differential pressure P varies over a wide range, from a minimum at idle speed to a maximum at high engine speed.
  • the low end signal may be too small for the amplifier unless an inordinate amount of gain is provided.
  • the high end signal may saturate the amplifier unless the gain is reduced.
  • These factors limit the dynamic range.
  • One solution is to provide a greater pressure drop by further reducing the constriction of the venturi. However, it is not desirable to reduce the constric ⁇ tion of the venturi too much because this would hinder air flow and reduce power, etc.
  • the inner diameter at mouth 30 is about 12.7 cm. (about five inches) and the inner diameter at venturi 32 is about 7.62 cm. (.about three inches)..
  • the dynamic range dilemma is solved by reducing the differential pressure signal as engine speed increases. The amplifier can thus be provided with, enough gain to amplify the low end signals at idle speed, and yet not saturate at high
  • amplifier Al has an inverting input 70, a noninverting input 72 and an output 74.
  • the output of differential pressure sen ⁇ sor 54 is connected through resistor 76 to input 72 of amplifier Al.
  • the output 74 of amplifier Al is con- nected in a voltage divider network formed by re ⁇ sistors 78 and 80 in a feedback loop to input 70 to set the gain of amplifier Al.
  • An LED chip driver Ul for example an LM3914, has an input 82 from tacho ⁇ meter 56 through resistor 84, and has a plurality of outputs including respective resistors R1-R10 con ⁇ nected in parallel to input 72 of amplifier Al.
  • resistor Rl As engine speed increases, the voltage at Ul input 82 from tachometer 56 increases, which in turn sequentially turns on resistors Rl through R10 in stepwise manner. When the first output turns on, resistor Rl is connected in circuit with amplifier input 72 such that current flows from input 72 through resistor Rl to ground reference at 86. This sinking of current through resistor Rl from input 72 lowers the voltage at input 72 which in turn reduces the- voltage at amplifier output 74 because less gain is needed to keep the voltage at input 70 equal to that at input 72. As engine speed continues to increase, the voltage at Ul input 82 increases, and when it reaches the next threshold, the output at R2 is turned on to also connect resistor R2 in cir ⁇ cuit w.ith.
  • resistance values Rl through RIO are chosen to provide the noted quadradic squaring and p division function to yield _p_
  • the resistance values for resistors R1-R10 are, respec ⁇ tively: 909 K ohms; 30.1 K ohms; 17.8 ohms; 12.7 K ohms; 10.0 K ohms; 8.06 K ohms; 6.81 K ohms; 5.90 K ohms; 5.23 K ohms; and 4.64 K ohms.
  • Figure 5 shows a graph, of relative gain of amplifier Al for the output signal at 74 versus engine speed, and il ⁇ lustrates the decreasing quadradic relationship with increasing engine speed.
  • the smooth nature of the curve is facilitated by ramp generator 88 providing a superimposed ramp voltage through resistor 90 to Ul input 82 which periodically rises to a maxi ⁇ mum voltage level about 1/lOth that of the maximum tachometer voltage.
  • Ramp generator 88 is an RC oscillator running at a substantially higher fre ⁇ quency, e.g. 100 hertz, than the progression of threshold steps of Ul, i.e. the ramp generator will go through many cycles between each of the threshold steps for turning on Rl through R10.
  • the superimposed oscillatory higher frequency ramp voltage provides a small ripple in the voltage at input 82 which pro ⁇ vides a more gradual turning-on of the next threshold step, rather than an abrupt turn-on of the next resistance, and hence smooths out the otherwise 5 stepwise incrementation of voltage at amplifier input 72, and provides a more smoothly varying variable resistance attenuator.
  • Resistor 92 and capacitor 94 provide an RC filter filtering out the ramp genera ⁇ tor frequency at the output of amplifier Al.
  • Amplifier A2 has a noninverting input 96 receiving the an output 100.. in a feedback loop including a voltage divider network formed by resistor 102 and parallel resistors Rll-
  • resistances R11-R20 are chosen to provide a linear multiplying function, n order to multiply _ PD by PA.
  • Resistors R11-R20 s 2 each have the same resistance, 100 K ohms.
  • the 35 voltage from ramp generator 88 is applied through resistor 110 to be superimposed and added to the voltage at U2 input 106 smooth out the stepwise changing of resistance at the outputs of U2, in or ⁇ der to provide a smoother change.
  • the ramp generator frequency is later filtered out at the RC filter pro ⁇ vided by resistor 112 and capacitor 114 at the out ⁇ put of amplifier A2.
  • the divider function 58 of Figure 3 is provided at node 116 in Figure 4.
  • Temperature sen- sor 60 is a negative temperature coefficient ther ⁇ mistor 118 connected between node 116 and ground reference, and physically located at inlet mouth 30 to sense ambient air temperature.
  • a resistor 120 is connected in series between node 116 and NTC thermistor 118, and a resistor 122 is connected in parallel with NTC thermistor 118 between node 116 and ground reference.
  • Resistor 120 has a substantially lower resistance value than resistor 122.
  • Resistors 122 and 120 have a ratio of about a 100 to 1 and tend to linearize the response of thermis ⁇ tor 118, to provide a more linear divide by T func ⁇ tion, such that the output voltage from amplifier A2 is more linearly reduced with increasing tempera- ture.
  • Amplifier A3 has a noninverting input 124 connected to a voltage source +V through a voltage divider network formed by resistors 126 and 128. Amplifier A3 has an output 130 connected to non- inverting input 132 in a feedback loop including the 5 voltage divider network formed by resistor 134 and resistors R21-R30 which are connected to respective parallel outputs of LED chip driver U3, such as an LM3914.
  • the voltage at node 116, representing PDPA is supplied through resistor 136 to the input " '
  • resistances R21-R30 are chosen to provide the square root function and are respectively: 383 K ohms; 191 K ohms; 249 K ohms; 294 K ohms; 332 K ohms; 374 K ohms; 402 K ohms;
  • Oscillatory ramp voltage from ramp generator 88 through resistor 142 is. superimposed and added at input 138 to smooth out the step changes as the switching thresholds are reached for turn-on of the outputs having resistors
  • the ramp voltage frequency is later filtered out by the RC filter formed by resistor 144 and capacitor 146.
  • the output of amplifier A3 provides the E MOD signal on line 45 which is the E signal on line 35 45 in Figure 11 of U.S. Patent 4,305,351.
  • Figure 11 of U.S. Patent 4,305,351 shows two square wave pulse generators 46 and 47 in accordance with the timing system in Figure 5 thereof.
  • the timing system in Figure 6 of U.S. Patent 4,305,351 is preferred, with three square wave pulse generators each of which is supplied with the MOD signal, and each of which receives its respective injection trigger signal 64a, 64b, 64c provided by the respective ignition pulses indicated as FIRE #1, FIRE #3 and FIRE #5 in Figure 6 of incorporated U.S. Patent 4,305,351.
  • the present system includes three output injection pulses 66a, 66b, 66c respectively providing INJECT #3, 4, INJECT #5, 6, INJECT #1, 2 in Figure 6 of U.S. Patent 4,305,351.
  • the frequency of the ignition trigger pulses corresponds to engine speed and hence cancels the term — 1 in EMOD signal.
  • the square wave generators are triggered by the ignition trigger signals, and the length of—the injection pulses output therefrom equals k I_PD_PA where k is a con ⁇ stant.
  • the square root generator function provided by A3 and U3 includes a failsafe region in the event differential pressure sensor 54 fails or the voltage at U3 input 138 drops to zero. Even with a zero input at 118, it is still desired that a certain level voltage output be generated at the amplifier output on line 45 so that there will be at least some fuel injection pulse length generated in order to inject enough fuel to keep the engine running and at least get home albeit not as peak power. This minimum fuel supply is considered desirable and pro- vides a limp home feature so that the boat operator will not be stranded in the middle of the lake.
  • Am ⁇ plifier A3 is thus preferably provided " vrith a minimum gain even if each of the U3 outputs through respec ⁇ tive resistors R21-R30 is nonconductive, which gain is set by resistor 114. Because of this gain, the value of resistance R21 is selected out of sequence c with the other resistances R22-R30, as above noted.
  • the invention is preferably implemented in analog circuitry, as disclosed above, though it can also be implemented by digital circuitry including a microprocessor. Analog circuitry is preferred
  • an ignition spike in an anlog system may cause a momentary purturbation, but the system will keep running.
  • ignition spike may fill or lock-up a register such, that the next
  • the interfacing of the differen ⁇ tial pressure sensor be done after 'the sensor's analog output is reduced with increasing engine speed, to improve the sensor's dynamic range.

Abstract

A mass flow fuel injection control system is provided for an internal combustion engine and measures mass and flow velocity of combustion air. The length of fuel injection pulses is determined by formula (I), where PD is the air pressure drop produced by a Venturi (32), PA is absolute air pressure, and T is air temperature. The system directly determines fuel requirements from the air mass flow and automatically self-adjusts and tracks such requirements from engine to engine or with modifications to the engine, without a preprogrammed look-up table according to throttle setting, and eliminates the need for a throttle position sensor.

Description

MASS FLOW FUEL INJECTION CONTROL SYSTEM
The invention relates to an electronic fuel njection control system for an internal combustion engine.
In a fuel injected engine, it is necessary to know the amount of air going into the engine in order to determine the amount of fuel to be injected, in order to provide the proper air-fuel ratio mixture. In a speed density system, for example as shown in U.S. Patent 4, 305,351, the amount of air going into the engine is determined indirectly by knowing ahead of time the typical amount of air entering the engine for a given throttle setting. The fuel requirements are then programmed in a look-up table memory. This type of system works well if the engine is a constant. However, if the engine is altered, then the look-up table for the fuel requirements must be reprogrammed. This is. particularly objectionable in racing applica¬ tions where the engine may be changed from day to day, or race to race by providing different compression ratios, cylinder heads, camshafts, etc. The look-up table does not self-correct or automatically track the particular engine at hand.
It is common in marine racing applications to change cylinder heads, seeking higher compression ratios. This changes the operating and horsepower characteristics of the engine, and in turn requires that the speed density system be recalibrated in order to achieve optimum performance. In addition, it has been found in racing applications that the throttle position sensor has a very short life rating. With the high stresses and shock loading typical in racing particularly on engines running close to 10,000 rpm, it is not uncommon for throttle position sensors to fail within a half hour. It is not unusual to re- place the throttle position sensor after every race. The object of the present invention is to provide a system by which the amount of fuel injected may be controlled without determination from a pre¬ programmed look-up table according to throttle setting; which, overcomes the above noted problems regarding reprogramming and recalibration upon alteration of the engine or use on different engine; and which eliminates the need for a throttle position sensor. The present invention provides a mass flow fuel injection control system for an internal combustion engine having air intake means supplying combustion air to said engine, and fuel injector means supplying fuel to said engine, comprising means including a venturi sensing the flow velocity of said combustion air; means sensing the mass of said com¬ bustion air; and means responsive to said last two mentioned means and controlling said fuel injector means to control the amount of fuel injected accord¬ ing to said air flow velocity and said air mass. In accordance with the invention, the system which determines the amount of air coming into the engine by means of its velocity and mass. With this information, it is known how much fuel the engine needs. The system automatically tracks and self- adjusts to the particular engine at hand, and can be used on an altered engine or on another different engine, and will automatically readjust to the en¬ gine's fuel requirements, all without a look-up table. The automatic tracking is also desirable as the engine wears. As piston rings wear, the piston will pull in less air, and the electronic fuel in¬ jection control system-will automatically lower the amount of fuel injected. Without this automatic adjustment, the fuel-air mixture would become richer.
One manner known in the prior art for measuring air flow is to use a hot film or a hot wire. The denser the air moving by the film, the more heat will be removed from the film. Also, the faster the air moves by the film, the more heat will be removed. The amount of energy needed to maintain a constant temperature of the film is measured, to indicate the amount of heat being pulled off by the air flowing by the film. A drawback of the hot film is that it is a very fragile device. Another problem is that the film must be relatively free of contamina¬ tion. If there is dirt on the film, the dirt will act as an insulator and will change the measurement. It has also been found that water in the air stream dramatically adversely affects the hot film. Water is mucli denser than air, and extracts more heat. In marine applications, it is nearly impossible to keep water out of the engine, and hence such system is not suitable therefor.
Another approach known in the prior art for measuring air flow is to use a flapper valve. A spring loaded valve in the air stream is deflected by the air flow, and the amount of deflection measures the air flow. The disadvantage of this approach is that the flapper valve is in the air stream and.blocks some of the air, acting like a throttle and reducing maximum horsepower. It has also been found that in rough, vater applications, the flapper may start os¬ cillating or may even break off because of the shock loads experienced in racing. The rugged environment of marine racing thus rules out the flapper valve approach. In the present invention, flow velocity of combustion air is measured by sensing air pressure drop across a venturi in the air intake manifold, and the mass of combustion air is measured by sensing air pressure and temperature. In the drawings: Figure 1 is a sectional view through one of the cylinder banks of a V-6 marine internal combustion engine and control system in accordance with the in¬ vention.
Figure 2 is a sectional view through a portion of the structure of Figure 1.
Figure 3 is a schematic block diagram of electronic control circuitry in accordance with the invention.
Figure 4 is a more detailed circuit diagram of the circuitry of Figure 3.
Figure 5 is a graph illustrating operation of a portion of the circuitry of Figure 4.
Figure 1 shows a two-cycle internal com¬ bustion engine 2 having a plurality of reciprocal pistons 4 connected to a vertical crankshaft 6 by connecting rods 8 in a cylinder block 10. Figure 1 shows one bank of three cylinders in a V-6 engine. Piston 4 moves to the left during its intake stroke drawing a fuel-air rm±xture through one-way reed valves 12 into crankcase chamber 14. Piston movement to the left also compresses the fuel-air mixture in cylinder 16 for ignition by spark plug 18, which combustion drives piston 4 to "the right generating its power stroke. During the movement of piston 4 to the right, the fuel-air mixture in crankcase chamber 14 is blocked by one-way reed valves 12 from exiting the crankcase and instead is driven through a trans¬ fer passage in the crankcase to port 20 in cylinder 16 for compression during the intake stroke, and so on to repeat the cycle, all as is well known. The com¬ bustion products are exhausted at port 22. Air intake manifold 24 is mounted by bolts 26 to crankcase 10 and defines the air intake flow path as shown at arrows 28. The manifold includes an outer mouth 30 and a reduced inner diameter portion 5 32 providing a venturi through which the air flows. Fuel is injected into the crankcase downstream of the reed valves, for example as shown in U.S. Patent 4,305,351 at fuel injectors 34 in Figures 2 and 3. The fuel injector tips are shown at 36. Alternatively,
10 the fuel may be injected in plenum 38 upstream of the reed valves. Venturi 32 includes a butterfly valve 40 on rotatable shaft 42 for controlling air flow into manifold 24. Manifold 24 has a drilled pas¬ sage 44 therethrough, Figure 2, at venturi 32 which
15 receives a tube 46 for sensing pressure at venturi 32. Manifold 24 has another drilled passage 48 therethrough at outer mouth 30 which receives a tube 50 for sensing pressure thereat. As air flows through venturi 32, there is a pressure drop according to
20 Bernoulli's principle. Tube 46 is open at its end 45 and senses the reduced pressure in venturi 32. Tube 50 senses the absolute pressure outside of the venturi. Tube 50 is closed at its end 47 and has a sma.ll hole in its side 49 facing upstream. When
25 butterfly valve 40 is closed, it is at an angle of approximately 30 relative to a plane normal to air flow path 28. Tube 46 is adjacent shaft 42 and up¬ stream of valve 40.
As noted, venturi 32 in air intake manifold
30 24 produces a pressure drop. Absolute pressure sensor 52, Figure 3, for example a Microswitch 136PC, measures absolute air" pressure P, outside of venturi 32 at tube 50. Differential pressure sensor 54, for example a Microswitch 176PC, measures the dif-
35 ferential pressure PD between the absolute pressure outside of the venturi at tube 50 and the reduced pressure in the venturi at tube 46. Engine speed S measured by tachometer 56 is squared by amplifier Al and also divided by amplifier Al into P_, and the result is multiplied by P at amplifier A2, which result is divided at 58 by air temperature T from temperature sensor 60. Amplifier A3 performs a square root function whose output is the signal E on line 45 in Figure 11 of U.S. Patent 4,305,351. The signal E ΩD is supplied to the fuel injection controller 62 provided by the one or more square wave pulse generators in Figure 11 of U.S. Patent 4,305,351, which are triggered by one or more ignition pulses shown as FIRE CYL. #1 and FIRE CYL. #4 in Figure 11 of U.S. Patent 4,305,351. These ignition pulses provide the trigger signals on line 64, Figure 3, to the fuel injection controller which in turn out¬ puts injection pulses on line 66 to the fuel injec¬ tors, as shown at.the one or more lines 48, 49 in Figure 11 of U.S. Patent 4,305,351. The length of the injection pulses on line 66, Figure 3, is deter¬ mined byVp_ . —/p measures air flow velocity.
T air mass. The frequency of the ignition
Figure imgf000008_0001
or trigger signals on line 64 corresponds to engine speed and hence cancels out the factor in the EMOD si9nal- S
The differential pressure P varies over a wide range, from a minimum at idle speed to a maximum at high engine speed. The low end signal may be too small for the amplifier unless an inordinate amount of gain is provided. On the other hand, the high end signal may saturate the amplifier unless the gain is reduced. These factors limit the dynamic range. One solution is to provide a greater pressure drop by further reducing the constriction of the venturi. However, it is not desirable to reduce the constric¬ tion of the venturi too much because this would hinder air flow and reduce power, etc. In the pre¬ ferred embodiment, the inner diameter at mouth 30 is about 12.7 cm. (about five inches) and the inner diameter at venturi 32 is about 7.62 cm. (.about three inches).. The dynamic range dilemma is solved by reducing the differential pressure signal as engine speed increases. The amplifier can thus be provided with, enough gain to amplify the low end signals at idle speed, and yet not saturate at high
2 speed. P is reduced by a factor of S . Referring to Figure 4, amplifier Al has an inverting input 70, a noninverting input 72 and an output 74. The output of differential pressure sen¬ sor 54 is connected through resistor 76 to input 72 of amplifier Al. The output 74 of amplifier Al is con- nected in a voltage divider network formed by re¬ sistors 78 and 80 in a feedback loop to input 70 to set the gain of amplifier Al. An LED chip driver Ul, for example an LM3914, has an input 82 from tacho¬ meter 56 through resistor 84, and has a plurality of outputs including respective resistors R1-R10 con¬ nected in parallel to input 72 of amplifier Al. As engine speed increases, the voltage at Ul input 82 from tachometer 56 increases, which in turn sequentially turns on resistors Rl through R10 in stepwise manner. When the first output turns on, resistor Rl is connected in circuit with amplifier input 72 such that current flows from input 72 through resistor Rl to ground reference at 86. This sinking of current through resistor Rl from input 72 lowers the voltage at input 72 which in turn reduces the- voltage at amplifier output 74 because less gain is needed to keep the voltage at input 70 equal to that at input 72. As engine speed continues to increase, the voltage at Ul input 82 increases, and when it reaches the next threshold, the output at R2 is turned on to also connect resistor R2 in cir¬ cuit w.ith. amplifier input 72 such that additional cur¬ rent flows from input 72 through resistor R2 to ground reference at 86, thus further lowering the voltage at amplifier input 7-2 and hence lowering the voltage at amplifier output 74. As engine speed continues to increase, the voltage at input 82 increases, and the remaining resistors R3 through RIO are sequentially turned on.
The values of resistances Rl through RIO are chosen to provide the noted quadradic squaring and p division function to yield _p_ In Figure 4, the resistance values for resistors R1-R10 are, respec¬ tively: 909 K ohms; 30.1 K ohms; 17.8 ohms; 12.7 K ohms; 10.0 K ohms; 8.06 K ohms; 6.81 K ohms; 5.90 K ohms; 5.23 K ohms; and 4.64 K ohms. Figure 5 shows a graph, of relative gain of amplifier Al for the output signal at 74 versus engine speed, and il¬ lustrates the decreasing quadradic relationship with increasing engine speed. The smooth nature of the curve is facilitated by ramp generator 88 providing a superimposed ramp voltage through resistor 90 to Ul input 82 which periodically rises to a maxi¬ mum voltage level about 1/lOth that of the maximum tachometer voltage. Ramp generator 88 is an RC oscillator running at a substantially higher fre¬ quency, e.g. 100 hertz, than the progression of threshold steps of Ul, i.e. the ramp generator will go through many cycles between each of the threshold steps for turning on Rl through R10. The superimposed oscillatory higher frequency ramp voltage" provides a small ripple in the voltage at input 82 which pro¬ vides a more gradual turning-on of the next threshold step, rather than an abrupt turn-on of the next resistance, and hence smooths out the otherwise 5 stepwise incrementation of voltage at amplifier input 72, and provides a more smoothly varying variable resistance attenuator. Resistor 92 and capacitor 94 provide an RC filter filtering out the ramp genera¬ tor frequency at the output of amplifier Al.
10 Amplifier A2 has a noninverting input 96 receiving the an output 100..
Figure imgf000011_0001
in a feedback loop including a voltage divider network formed by resistor 102 and parallel resistors Rll-
15 20. in the outputs of LED chip driver U2, such as an LM3914. Absolute pressure sensor 52 is connected through, resistor 104 to U2 input 106. . As the ab¬ solute air pressure increases, the increasing voltage at U2 input 106 sequentially turns on resistors Rll- ώυ R-20 in stepwise manner as the various switching thresholds are reached. As more outputs of U2 are turned on, more resistors are connected in parallel between amplifier input 98 and ground reference 108, which in turn sinks more current through the. re- ώJ spective resistors from amplifier input 98, thus lowering the voltage at input 98. The lower voltage at amplifier input 98 causes the voltage at amplifier output 108 to increase because such increased gain is necessary to maintain the voltage at input 98
30 equal to that at amplifier input 96.
The values of resistances R11-R20 are chosen to provide a linear multiplying function, n order to multiply _ PD by PA. Resistors R11-R20 s2 each have the same resistance, 100 K ohms. The 35 voltage from ramp generator 88 is applied through resistor 110 to be superimposed and added to the voltage at U2 input 106 smooth out the stepwise changing of resistance at the outputs of U2, in or¬ der to provide a smoother change. The ramp generator frequency is later filtered out at the RC filter pro¬ vided by resistor 112 and capacitor 114 at the out¬ put of amplifier A2.
The divider function 58 of Figure 3 is provided at node 116 in Figure 4. Temperature sen- sor 60 is a negative temperature coefficient ther¬ mistor 118 connected between node 116 and ground reference, and physically located at inlet mouth 30 to sense ambient air temperature. A resistor 120 is connected in series between node 116 and NTC thermistor 118, and a resistor 122 is connected in parallel with NTC thermistor 118 between node 116 and ground reference. As temperature increases, the. resistance of NTC thermistor 118 decreases, and more current is conducted therethrough from node 116, which, in turn lowers the voltage at node 116, pro¬ viding the divide by T function. Resistor 120 has a substantially lower resistance value than resistor 122. At low temperature, the resistance value of thermis¬ tor 118 is high, and most of the current from node 116 flows through resistor 122. At high temperature, the resistance valve of thermistor 118 is low, and most of the current from node 116 flows through resistor 120 and thermistor 118, because such branch provides the lower resistance path at high temperature. Resistors 122 and 120 have a ratio of about a 100 to 1 and tend to linearize the response of thermis¬ tor 118, to provide a more linear divide by T func¬ tion, such that the output voltage from amplifier A2 is more linearly reduced with increasing tempera- ture.
Amplifier A3 has a noninverting input 124 connected to a voltage source +V through a voltage divider network formed by resistors 126 and 128. Amplifier A3 has an output 130 connected to non- inverting input 132 in a feedback loop including the 5 voltage divider network formed by resistor 134 and resistors R21-R30 which are connected to respective parallel outputs of LED chip driver U3, such as an LM3914. The voltage at node 116, representing PDPA is supplied through resistor 136 to the input " '
138 of U3. As the voltage at input 138 increases, the outputs of U3 are sequentially turned on in stepwise manner, to connect more resistors to ampli¬ fier input 132, to in turn sink more current through the respective parallel resistors from amplifier
15 input 132 to ground reference 140, to lower the voltage at amplifier input 132. The lower voltage at amplifier input 132 causes an increased voltage at amplifier output 130 because more gain is needed to
20 keep the voltage at input 132 equal to that at input 124.
The values of resistances R21-R30 are chosen to provide the square root function and are respectively: 383 K ohms; 191 K ohms; 249 K ohms; 294 K ohms; 332 K ohms; 374 K ohms; 402 K ohms;
25 432 K ohms; 475 K ohms and 487 K ohm. Oscillatory ramp voltage from ramp generator 88 through resistor 142 is. superimposed and added at input 138 to smooth out the step changes as the switching thresholds are reached for turn-on of the outputs having resistors
30 R21 through R30. The ramp voltage frequency is later filtered out by the RC filter formed by resistor 144 and capacitor 146.
The output of amplifier A3 provides the E MOD signal on line 45 which is the E signal on line 35 45 in Figure 11 of U.S. Patent 4,305,351. Figure 11 of U.S. Patent 4,305,351 shows two square wave pulse generators 46 and 47 in accordance with the timing system in Figure 5 thereof. In the present invention, the timing system in Figure 6 of U.S. Patent 4,305,351 is preferred, with three square wave pulse generators each of which is supplied with the MOD signal, and each of which receives its respective injection trigger signal 64a, 64b, 64c provided by the respective ignition pulses indicated as FIRE #1, FIRE #3 and FIRE #5 in Figure 6 of incorporated U.S. Patent 4,305,351. Likewise, instead of two output injection pulses shown as 48 and 49 in Figure 11 of U.S. Patent 4,305,351, the present system includes three output injection pulses 66a, 66b, 66c respectively providing INJECT #3, 4, INJECT #5, 6, INJECT #1, 2 in Figure 6 of U.S. Patent 4,305,351. The frequency of the ignition trigger pulses corresponds to engine speed and hence cancels the term — 1 in EMOD signal. The square wave generators are triggered by the ignition trigger signals, and the length of—the injection pulses output therefrom equals k I_PD_PA where k is a con¬ stant. T
The square root generator function provided by A3 and U3 includes a failsafe region in the event differential pressure sensor 54 fails or the voltage at U3 input 138 drops to zero. Even with a zero input at 118, it is still desired that a certain level voltage output be generated at the amplifier output on line 45 so that there will be at least some fuel injection pulse length generated in order to inject enough fuel to keep the engine running and at least get home albeit not as peak power. This minimum fuel supply is considered desirable and pro- vides a limp home feature so that the boat operator will not be stranded in the middle of the lake. Am¬ plifier A3 is thus preferably provided" vrith a minimum gain even if each of the U3 outputs through respec¬ tive resistors R21-R30 is nonconductive, which gain is set by resistor 114. Because of this gain, the value of resistance R21 is selected out of sequence c with the other resistances R22-R30, as above noted. The invention is preferably implemented in analog circuitry, as disclosed above, though it can also be implemented by digital circuitry including a microprocessor. Analog circuitry is preferred
,Q because of its better noise immunity. For example, an ignition spike in an anlog system may cause a momentary purturbation, but the system will keep running. In a digital system, such, ignition spike may fill or lock-up a register such, that the next
-, - component gets the wrong operational code, and the system may shut down. Marine racing applications involve high, speeds and extremely noisy environments, and hence the analog circuitry is desirable. If digital or microprocessor circuitry is used, it is
2 still preferred that the interfacing of the differen¬ tial pressure sensor be done after 'the sensor's analog output is reduced with increasing engine speed, to improve the sensor's dynamic range.
It is thus seen that a mass flow fuel
2c Injection control system is provided for an in¬ ternal combustion engine having air intake means sup¬ plying combustion air to the engine, and fuel injec¬ tor means supplying fuel to the engine. Flow velocity
30
Figure imgf000015_0001
responds to the measured values D, A control the amount of fuel injected according^tp air flow velocity and air mass
Figure imgf000015_0002
It is recognized that various equivalents, alternatives and modifications are possible.

Claims

1. A mass flow fuel injection control system for an internal combustion engine having air intake means supplying combustion air to said engine, and fuel injector means supplying fuel to said engine, comprising means including a venturi sensing the flow velocity of said combustion air; means sensing the mass of said combustion air; and means respon¬ sive to said last two mentioned means and controlling said fuel injector means to control the amount of fuel injected according to said air flow velocity and said air mass.
2. The system according to claim 1, wherein said venturi is in said air intake means and pro¬ duces an air pressure drop; said means sensing air flow velocity further comprises absolute pressure sensor means measuring absolute air pressure outside of said venturi; and differential pressure sensor means measuring the differential pressure between the absolute pressure outside of said venturi and the reduced pressure in said venturi; said means sensing air mass comprises temperature sensor means measuring air temperature; and said means controlling said fuel injector means responds to said absolute air pressure, said differential air pressure, and said air. tempera¬ ture, without input from a throttle position sensor.
3. The system of claim 2 wherein said air flow velocity sensing means includes means calculating said air flow velocity as a function of the differ¬ ential pressure CPD) ; and said air mass sensing means includes means, calculating said air mass as a function of (P ) absolute pressure outside the ven¬ turi and the air temperature (T) . 4. The system according to claim 3, wherein said air flow velocity sensing means measures P and calculates 'Λf P to determine said air flow velocity; said air mass sensing means measures P_ and T and
r-^T A calculates \ _ to determine said air mass; said
^ T means control ing said fuel injector means comprises means supplying injection pulses for said fuel in¬ jector means to control the amount of fuel injected, wherein the length of said injection pulses is controlled by fP and by]/P .
I
5. The system of claim 4, wherein the length, of said injection pulses is a factor of
Figure imgf000018_0001
6. The system according to claim 5, wherein P_ varies from a low value at idle speed of said engine to a high value at top speed of said engine, and comprising amplifier means responsive to said differential pressure sensor means and yielding an amplified P output; and means for increasing the dynamic range of said control system by preventing saturation of said amplifier means over said P range by reducing said amplified P_ output with increasing engine speed.
7. The system according to claim 6, comprising tachometer means for measuring engine speed S, and wherein said amplifier means divides P
Figure imgf000018_0002
8. The system according to claim 7, comprising chip driver means having a plurality of outputs connected in parallel to said amplifier means, each output having a given resistance, said chip driver means having an input responsive to said tachometer means to successively turn on more of said outputs with increasing engine speed to in turn connect more of said resistances in circuit with said amplifier means, wherein the values of said resistances are selected to provide an output of said amplifier means as a nonlinear decreasing quad¬ radic function of S to provide the function P .
9. The system according to claim 78, wherein said amplifier means has first and second inputs, and has an output connected in a voltage divider feedback network to said first input to set the gain of said amplifier means, and wherein the output of said differential pressure sensor means and the parallel outputs including said resistances of said chip driver means are connected to said second input of said amplifier means.
10. " The system according to claim 9, wherein the gain of said amplifier means is fixed as set by said voltage divider network in said feedback loop to said first input of said amplifier means, and wherein said chip driver means turns on said outputs according to given threshold speeds from said tachometer means, wherein a turned-on output of said chip driver means completes a circuit through its. respective resistance means from said second input of said amplifier means to a given ground reference, such that current flows from said second input of said amplifier means through said respective resistance means to said ground reference to reduce the voltage at said second input of said amplifier means and in turn reduce the voltage level at said output of said amplifier means, because less gain of said amplifier means is needed to keep the voltage at said first input of said amplifier means equal to that at said second input of said amplifier means. 11. The system according to claim 10 comprising ramp generator means supplying a periodic ramp voltage at said input of said chip driver means at a given frequency to smooth the transitions of the switching of said chip driver means outputs and pro¬ vide a more gradual transitioning between said resis¬ tances and in turn a smoother reduction of the vol¬ tage level at said output of said amplifier means with, increasing engine speed.
12. The system according to claim 5, comprising means for multiplying P by P compris¬ ing, amplifier means having first and second inputs, and an output, said first input of said amplifier :neans being responsive to Pn, said output of said amplifier means being connected in a voltage divider network in a feedback loop to said second input of 3aid amplifier means; chip driver means having a plurality of outputs connected in parallel to said second input of said amplifier means, each output having a given resistance, said chip driver means having an input responsive to said absolute pressure sensor means to successively turn on more of said outputs as said absolute pressure increases, to in turn connect more of said resistances to said second input of said amplifier means, the gain of said amplifier means being variable and determined ac¬ cording to the number of said outputs and their re¬ sistances connected to said second input of said amplifier means, wherein a turned-on output of said chip driver means completes a circuit through its respective resistance from said second input of said amplifier means to a given ground reference, such that current flows from said second input of said amplifier means through said respective resistance to said ground reference to reduce the voltage at said second input of said amplifier means, such that as more of said outputs of said chip driver means are turned on, more of said respective resistances are connected to said second input of said amplifier means to in turn reduce the voltage thereat and in turn increase the gain of said amplifier means to increase the voltage level at the output of said amplifier means with, increasing P , to in turn multiply P_ by P .
13. The system according to claim 12, wherein each of said resistances at the respective said outputs of said chip driver means has about the same value.
14. The system according to claim 13, comprising ramp generator-means supplying a periodic ramp voltage at said input of said chip driver means at a given frequency to smooth the transitions of the switching of said chip driver means outputs and provide a more gradual transitioning between said resistances and in turn a smoother increase of the voltage level at the output of said amplifier means with increasing
15. The system according to claim 5 comprising means for multiplying P D by P Α and supply- ing the product as an analog voltage level at a given node; means for dividing P P by T.
16. The system according to claim 15, wherein said last mentioned means comprises a thermis¬ tor connected in circuit with said node.
17. The system according to claim 20 wherein said thermistor comprises a negative tempera¬ ture coefficient thermistor connected between said node and a ground reference such that with increasing temperature the resistance of said thermistor .decreases and more current flows therethrough from said node to said ground reference, thus reducing the voltage at said node to provide said divide by T function. 18. The system according to claim 17 comprising a first resistor connected in series with said thermistor, and a second resistor connected in parallel with said thermistor between said node and said ground reference, said first resistor having a smaller valve than.said second resistor such that at low temperature and high resistance of said thermis¬ tor more current flows through said second resistor, and such that at high temperature and low resistance of said thermistor more current flows through said first resistor and said thermistor, to linearize the changing voltage value at said node as a function of T.
Figure imgf000022_0001
20. The system according to claim 19 wherein said last mentioned means comprises amplifier means having first and second inputs, and an output; chip driver means having an input connected to said node and having a plurality of outputs connected in parallel to one of said inputs of said amplifier means, each output having a given resistance, said input of said chip driver means being responsive to voltage at said node to successively turn-on more of said outputs of said chip driver means as PnP,
T changes, to in turn connect more of said resistances to said one input of said amplifier means, the gain of said amplifier means being variable and determined according to the number of said chip driver means outputs and their resistances connected to said one input of said amplifier means, wherein a turned-on output of said chip driver means completes a circuit through its respective resistance from said one input of said amplifier means to a given ground reference, such that current flows from said one input of said amplifier means through said respective resistance to said ground reference to reduce the voltage at said one input of said amplifier means and in turn reduce the voltage at said output of said amplifier means, such that as more of said outputs of said chip driver means are turned on, more of' said respective resistan¬ ces are connected to said one input of said amplifier means to in turn reduce the voltage thereat and in turn increase the gain of said amplifier means to increase the voltage at said output of said amplifier means, wherein the values of said resistances in said parallel outputs of said chip driver means are selected such that the output of said amplifier means changes as the one-half power of the volt ge at said node, to
Figure imgf000023_0001
21. The system according to clai: 20 wherein the other said input of said amplifier means is con¬ nected to a given reference voltage, and wherein said output of said amplifier means is connected in a voltage divider network in a feedback loop to said one input of said amplifier means.
22. The system according to claim 21 comprising ramp generator means for supplying a periodic ramp voltage at said input of said chip driver means at a given frequency to smooth the transition's of the switching of said chip driver means outputs and provide a more gradual transitioning between said chip driver means output resistances and in turn a smoother change of the voltage level at said output of said amplifier means.
23. The system according to claim 6 comprising tachometer means for measuring engine speed S, and variable resistance attenuator means responsive to said tachometer means and connected to said amplifier means and changing resistance with, in¬ creasing engine speed such that said amplifier means divides P by a given power of S. 24. The system according to claim 3, comprising tachometer means for measuring engine speed S, and variable resistance attenuator means responsive to said tachometer means and connected to said air flow velocity sensing means and changing resistance with increasing engine speed such that said air flow velocity sensing means divides P by a given power of S.
25. A mass flow fuel injection control system for an internal combustion engine having air intake means supplying combustion air to said engine, and fuel injector means supplying fuel to said engine, comprising, venturi means in said air intake means and producing an air pressure drop; absolute pressure sensor means measuring absolute pressure P. outside of said venturi means; differential pressure sensor means measuring the differential pressure P_. between the absolute pressure outside of said venturi means and the reduced pressure in said venturi means; tem¬ perature sensor means measuring air temperature T; tachometer means measuring engine speed S; squaring
2 and divider means dividing P by S ; multiplier means P u p p multiplying D by P ; divider means dividinα D A ,
~ cT2 A p p 2 — b xv -T ' : square root means providing the square root of . 2~ ax^L means supplying injection pulses for said fuel injector means in response to trigger signals to control the amount of fuel in¬ jected, wherein the length of said inj ection pulses is determined by . . . , _ _ times the frequency of said trigger signals.
Figure imgf000024_0001
26. The system according to claim 25, where¬ in said squaring and divider means comprises first variable resistance attenuator means responsive to said tachometer means; and first amplifier means responsive to said first variable resistance attenua¬ tor means and to said differential pressure sensor means; said multiplier means comprises: second vari¬ able resistance attenuator means responsive to said absolute pressure sensor means; and second amplifier means responsive to said second variable resistance attenuator means and to said first amplifier means; said square root means comprises: third variable resistance attenuator means responsive to said second amplifier means; and third amplifier means responsive to said third variable resistance attenuator means.
27. The system according to claim 26, wherein said squaring and divider means comprises first chip driver means having a plurality of outputs connected in parallel to said first amplifier means, each output having a given resistance, said first chip driver means having an input responsive to said tachometer means to successively turn on more of said outputs with increasing engine speed to in turn connect more of said resistances in circuit with said first amplifier means, wherein the values of said resistances are selected to provide an output of said first amplifier means as a nonlinear decreasing quad¬ radic function of S to provide the function P
said multiplier means comprises second chip driver means having a plurality of outputs connected in paral¬ lel to said second amplifier means, each output having a given resistance, said second chip driver means having an input responsive to said absolute pressure sensor means to successively turn on more of said outputs of said second chip driver means as said absolute pressure increases, to in turn connect more of said resistances of said second chip driver means to said second amplifier means, wherein the values of said resistances of said second chip driver means are selected to provide an output of said second amplifier means as an increasing function of P to pro¬ vide the function P^P, 72"
D A ; S
S2 said divider means comprises temperature responsive means in circuit with the output of said second amplifier means; said square root means comprises third chip driver means having a plurality of outputs connected in parallel with said third amplifier means, each output having a given resistance, said third chip driver means having an input responsive to said output of said second amplifier means to successively
Figure imgf000026_0001
in circuit with said third amplifier means, wherein the values of said resistances of said third chip driver means are selected to provide an output of said third amplifier means as the one-half power of the voltage at said input of said third chip driver means to provide the function 1 DPA
28. The system according to claim 27, wherein said first amplifier means has first and second inputs, and has an output connected in a voltage divider feedback network to said first input of said first amplifier means to set the gain of said first amplifier means; the output of said differen¬ tial pressure sensor means and the parallel outputs including said resistances of said first chip driver means are connected to said second input of said * •" first amplifier means; said first chip driver means successively turns on said outputs according to given threshold speeds from said tachometer means, wherein a turned-on output of said first chip driver means completes a circuit through its respective resistance from said second input of said first amplifier means to a given ground reference such that current flows from said second input of said first amplifier means through said respective resistance to said ground reference to reduce, the voltage at said second input of said first amplifier means and in turn reduce the voltage level at said output of said first amplifier means because less gain is needed to keep the voltage at said first input of said first amplifier means equal to that at said second input of said first amplifier means; said second amplifier means has first and second inputs, and an output, said first input of s.aid second amplifier means being responsive to said first amplifier means; said output of said second amplifier means being connected in a voltage divider network in a feedback loop to said second input of said second amplifier means; said second chip driver means has said plurality of outputs connected in para¬ llel to said second input of said second amplifier means, said input of said second chip driver means heing responsive to said absolute pressure sensor means to successively turn on more of said outputs of said second chip driver means as said absolute pres¬ sure increases, to in turn connect more of said resistance of said second chip driver means to said second input of said second amplifier means, the gain of said second amplifier means being variable and determined according to the number of said outputs and their resistances of said second chip driver means connected to said input of said second amplifier means,, wherein a turned-on output of said second chip driver means completes a circuit through its re¬ spective resistance from said second input of said second amplifier means to a given ground reference, such that current flows from said second input of said second amplifier means through said respective resistance to said ground reference to reduce the voltage at said second input of said second amplifier means, such that as more of said outputs of said second chip driver means are turned on, more of said respective resistances are connected to said second input of said second amplifier means to in turn reduce the voltage thereat and in turn increase the gain of said second amplifier means to increase the voltage level at said output of said second amplifier means with increasing P , to in turn multiply P
by P_; said third amplifier means has first and second inputs, and an output; said third chip driver means has an input connected to said output of said second amplifier means and has a plurality of outputs connected in parallel to one of said inputs of said third amplifier means, said input of said third chip driver means being responsive to voltage at said output of said second amplifier means to suc¬ cessively turn-on more of said outputs of said third chip driver means as — D= A increases, to in turn connect more of said Sr2eTspective resistances to said one input of said third amplifier means, the gain of said third amplifier means being variable and determined according to the number of said third chip driver means outputs and their resistances connected to said one input of said third amplifier means, wherein a turned-on output of said third chip driver means completes a circuit through its re¬ spective resistance from said one input of said third amplifier means to a given ground reference, such that current flows from said one input of said third amplifier means through said respective resistance to said ground reference to reduce the voltage at said one input of said third amplifier means and in turn reduce the voltage of said output of said third amplifier means, such that as more of said outputs of said third chip driver means are turned on, more of said respective resistances are connected to said one input of said third amplifier means to in turn reduce the voltage thereat and in turn increase the gain of said third amplifier means to increase the voltage at said output of said third amplifier means, wherein the values of said resistances in said parallel outputs of said third chip driver means are selected such, that the output of said amplifier means changes as the one-half power of the voltage at said input of said third chip driver means, to provide the function
Figure imgf000029_0001
The system according to claim 28, wherein said temperature responsive means connected in circuit with said output of said second amplifier means comprises a negative temperature coefficient thermistor connected between a ground reference and -a node connected in circuit with said output of said second amplifier means, such that with increasing temperature the resistance of said thermistor de¬ creases and more current flows therethrough from said node to said ground reference, thus reducing the voltage at said node to provide said divide by T function.
30. The invention according to claim 28, comprising ramp generator means supplying a periodic ramp voltage at each of said inputs of said first, second and third chip driver means at a given fre¬ quency to smooth the transitions of the switching of said outputs of said first, second and third chip driver means and provide a more gradual transitioning between said resistances and in turn a smoother change of the voltage level at respective said outputs of said first, second and third amplifier means.
PCT/US1988/000398 1987-03-12 1988-02-11 Mass flow fuel injection control system WO1988007131A1 (en)

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AT88902305T ATE81542T1 (en) 1987-03-12 1988-02-11 MASS FLOW FUEL INJECTION CONTROL SYSTEM.

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EP0352274A1 (en) 1990-01-31
DE3875345T2 (en) 1993-05-06
ATE81542T1 (en) 1992-10-15
BR8807409A (en) 1990-05-15
DE3875345D1 (en) 1992-11-19
JPH02503102A (en) 1990-09-27
EP0352274B1 (en) 1992-10-14
US4750464A (en) 1988-06-14

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