WO2010046574A1

WO2010046574A1 - Method for starting a combustion engine supplied with a fuel containing ethanol

Info

Publication number: WO2010046574A1
Application number: PCT/FR2009/051801
Authority: WO
Inventors: Daniel Santurbano
Original assignee: Peugeot Citroën Automobiles SA
Priority date: 2008-10-22
Filing date: 2009-09-23
Publication date: 2010-04-29
Also published as: FR2937381A1; BRPI0914037B1; FR2937381B1; EP2344741A1; BRPI0914037A2

Abstract

The invention relates to a method for starting a combustion engine (1) supplied with a first fuel that may contain ethanol, said engine being provided with a cold-start auxiliary system including a tank (5) for a second fuel having a low ethanol content, wherein said method comprises determining the temperature of the liquid coolant of the engine (1), and determining the ethanol proportion in the first fuel, characterised in that, if the temperature of the liquid coolant of the engine is lower than a predetermined critical temperature and if the ethanol proportion of the fuel is higher than a predetermined threshold, the second fuel is pre-injected at the inlet of the engine (1) in response to the occurrence of an event preceding the engine start request.

Description

METHOD FOR STARTING A COMBUSTION ENGINE SUPPLIED BY

A FUEL CONTAINING UETHANOL

The present invention claims the priority of the French application 0857152 filed October 22, 2008 whose content (text, drawings and claims) is here incorporated by reference.

The invention relates to the field of starting combustion engines operating with a fuel containing ethanol. These engines are often referred to as "Flex-Fuel".

Engines that can run on ethanol or a mixture of traditional fuel and ethanol have difficulty starting at low temperatures. By traditional fuel is meant in particular the fuel conventionally used in spark ignition engines, commonly known as gasoline, or premium gasoline.

In particular, when the engine is cold, the ignition of ethanol being more difficult than that of gasoline, starting is difficult. The concept of cold engine is understood vis-à-vis the temperature of the liquid contained in the cooling circuit of the engine.

It is known that depending on the proportion of ethanol contained in the fuel, and in particular when it is high, starting at low temperatures can be problematic, that is to say resulting in a longer, if not impossible, starting of the engine under particularly low temperature conditions.

It is also known a device for cold starting engines operating with a mixture of ethanol. The Brazilian patent application BRPI8801648 presents a particular variant of such a device. This device comprises an additional reservoir filled with a second fuel, low in ethanol content. This fuel may be conventional super-fuel, called EO, but may also be, for example, super-fuel comprising 22% by volume of ethanol, said E22, widely marketed on the Brazilian market, for example, or from 26 to 26% by volume. ethanol. During cold starts, and in the presence of a high concentration of ethanol in the fuel, the auxiliary starting device introduces fuel low ethanol concentration at the engine intake.

However, if the introduction of fuel poor in ethanol will allow the vehicle to start, it causes a relatively long startup time. Indeed, the fuel being introduced into the intake duct, the inventor has found that it took the fuel a certain time to arrive in the combustion chamber of the engine. This can result in a delay of one to two seconds for starting the engine.

In the present invention, the solution to these problems is to perform a pre-introduction of low ethanol fuel at the intake of the engine, even before the engine start request is made.

More specifically, the invention therefore relates to a method of starting a combustion engine powered by a first fuel that may contain ethanol, said engine being equipped with a cold start auxiliary system comprising a fuel tank. a second low ethanol fuel, wherein the temperature of the engine coolant is determined, the proportion of ethanol in the first fuel is determined, and characterized in that, if the engine coolant temperature is below a predetermined critical temperature and if the proportion of ethanol in the fuel is greater than a predetermined threshold, pre-introducing the second fuel to the engine intake in response to the observation of an event prior to the engine start request. Thus, the fuel introduced to the intake by the auxiliary starting system physically has time to reach the engine cylinder inlet when the latter receives the start command. The time elapsing the engine start request, that is to say the start of its rotation, for example by a starter and the arrival of low ethanol fuel is thus greatly reduced, which decreases all the time the engine starts, between the start order and the first combustion in the engine. The invention is all the more effective when the ethanol content in the auxiliary booster system tank is low, this data being otherwise conditional on the availability of low ethanol fuel in a given market. In Brazil, for example, for spark ignition engines, the marketed fuel with the lowest ethanol content still has 22% by volume of ethanol. In general, therefore, the term "low ethanol content" means a proportion of ethanol less than 40% by volume, and preferably less than 30% by volume, and preferably less than or equal to 22% by volume.

Preferably, the critical temperature is between 15 ° C and 20 ° C, and preferably equal to 18 ° C. The inventor has indeed found that a temperature below 18 ° C caused difficulties starting the engine, especially if it is fed with a fuel containing more than 22% by volume of ethanol.

[0012] Preferably, the predetermined threshold for the proportion of ethanol in the first fuel is between 22% and 100% by volume. Indeed, a fuel containing up to 22% by volume of ethanol is generally not problematic for starting the engine. Moreover, in certain markets such as Brazil, the so-called E22 fuel, that is to say containing 22% by volume of ethanol, is distributed in place of traditional fuel without ethanol. In the Flex-Fuel models, it is possible to make successive full fuel with fuels with very variable ethanol levels, for example EO (without ethanol) or E22 or E26, then E85 (containing 85 % by volume of ethanol), or even E100 (100% ethanol by volume). In fact, the main reservoir (first reservoir) of the engine may contain a fuel having 0 to 100% by volume of ethanol. Known specific devices make it possible to estimate the ethanol content of the fuel with an accuracy of the order of 5% by volume.

Preferably the amount of second fuel pre-introduced is dependent on the engine coolant temperature Indeed, the higher the engine temperature (estimated by the temperature of its coolant), the lower the starting is problematic Preferably the amount of second fuel pre-introduced is dependent on the proportion of ethanol in the first fuel. Indeed, the higher the ethanol content in the fuel of the main tank, the more the engine start is problematic.

[0015] Preferably, the quantity of second fuel pre-introduced is modulated by modulating the duration of the pre-introduction. As part of a pre-introduction system, a substantially constant flow injector is a simple device to implement. By modulating the injection time, we simply modulate the amount of fuel with low ethanol content introduced to the intake of the engine.

Preferably, the pre-introduction duration is modulated according to a pre-established cartography.

[0017] Preferably, a minimum predefined time delay is provided between two pre-introductions. Thus, if the event prior to starting the engine is observed more than once a short time before an actual start, only one pre-introduction will be performed.

In a variant of the invention where the method is applied to a vehicle with doors, the event observed prior to starting the engine is the unlocking or opening of at least one door. This event reflecting the accession to the vehicle thus makes it possible to assume that a successive start will probably occur, and that it is necessary to carry out the pre-introduction of fuel according to the invention. It is also possible to monitor in particular the opening of the door giving access to the driving position. This is the easiest event to detect, usually preceding the start of the engine, especially as current vehicles are generally equipped with door opening sensors.

In another variant of the invention where it is applied to a motor equipping a vehicle, the event observed prior to starting the engine is the detection of a transponder present in a free hand start card or in a key engine contact. If the vehicle is equipped with a free hand start system, the transponder detection of a starter card free hand is the prerequisite for the start authorization. This detection is perfectly appropriate to the control of the pre-introduction. In the case where the engine of the vehicle is started using a ignition key, a transponder is generally present in the key as a safety device, preventing the starting of the engine with a copy of the key. The detection of this transponder may serve as an event observed prior to starting the engine, although the time elapsing between the detection of the transponder and the starting order of the engine (turning the key) may be short.

In another variant of the invention where it is applied to a motor equipping a vehicle, the event observed prior to starting the engine is the detection of the depression of the brake pedal or the clutch pedal of the vehicle. Depending on the equipped vehicle, observation of these events may be particularly relevant. Indeed, on a vehicle equipped with an automatic gearbox, depressing the brake pedal is necessary to start the engine. Thus, on such a vehicle, depressing the brake pedal while the engine is at rest very likely translates a future start. Likewise, according to some legislation, the depressing of the clutch pedal of a vehicle equipped with a manual gearbox may be necessary for authorization to start the engine.

In another variant of the invention where it is applied to a motor equipping a vehicle, the event observed prior to starting the engine is the buckling of the seat belt of the driver or the detection of the presence of a driver. This is another simple event to detect, with sensors often pre-existing to the use of the method according to the invention.

The invention is described in more detail below and with reference to the figures schematically showing the system in its preferred embodiment.

Figure 1 schematically shows the general architecture of an auxiliary starting system of a fuel flex type motor. For a given application, FIG. 2 shows the pre-introduction time selected as a function of the engine temperature and the ethanol content in the fuel.

In Figure 1, a motor 1 flex fuel type, that is to say that can be powered by a fuel containing a certain proportion of ethanol, is fed with a first fuel by a first tank 2. The ethanol content present in the fuel can be determined using a probe 3, in connection with the engine control 4.

A device for measuring the temperature of the liquid flowing in the not shown cooling circuit of the engine 1. This information can be transmitted to the engine control.

An auxiliary starting device comprises a tank of a second fuel 5, and a metering device 6 controlled by the engine control 4, and allowing the introduction of the second fuel at the engine intake. Traditionally, this introduction of the second fuel is performed downstream of the throttle body 7, when the engine is equipped. The second tank is intended to be filled with spark ignition engine fuel ("premium fuel") containing the lowest possible level of ethanol. Depending on the market, it may be fuel called EO, containing 0% ethanol, or for example E22 containing 22% by volume of ethanol, or E26 containing 26% by volume of ethanol.

When an event preceding the start of the engine, which may be depending on the application and not exhaustive the opening of a door of the equipped vehicle or the opening of the door to access the driving position, the detection of a hands-free start transponder card, the detection of a transponder contained in the ignition key, the buckling of the driver's safety belt, or the depressing of the brake or clutch pedal , is detected, the engine control 4 integrates the temperature information of the liquid contained in the engine cooling circuit 1 and the ethanol content of the first fuel, contained in the first tank 2. If the temperature of the liquid contained in the cooling circuit of the engine 1, and which reflects the temperature of the engine 1, is less than a first predetermined threshold, and if the ethanol content of the first fuel is greater than a second predetermined threshold, the engine control will then control a pre-introduction of the second fuel contained in the second tank 5, at the intake of the engine via the auxiliary start system. The metering device 6 will ensure the introduction of the desired amount of second fuel at the inlet. In practice, it is the duration of the pre-introduction that is modulated to modulate the amount of second fuel.

For the application shown here, corresponding to a four-cylinder engine of 2.0L displacement and 16 valves, the inventor has empirically determined the optimal time of pre-introduction. FIG. 2 shows in a table the optimum pre-introduction time for the application in question, as a function of the temperature of the coolant of the engine cooling circuit, and of the ethanol content in the first fuel. In the case in question, the second fuel is IΕ22 to 22% by volume of ethanol. The temperatures (in columns) are expressed in degrees Celsius ( ⁰ C). The ethanol rate is based on an air / fuel ratio or A / F (in rows); stoichiometry being different for the EO super-fuel (ratio A / F = 14.7) and for ethanol at 100% E100 (ratio A / F = 9.0), the ratio A / F to stoichiometry reflects the ethanol content present in the fuel.

It is noted in Figure 2 that the pre-introduction time, and therefore the amount of second fuel pre-introduced, is even more important that the engine temperature is low and that the ethanol rate in the first fuel is important. However, at the cost of a pre-introduction for 1, 2 seconds, it is ensured a quick start at -10 ° C. with a first fuel containing 100% ethanol.

In contrast, the pre-introduction is still unnecessary, for the application in question, as soon as the temperature of the engine coolant equals or exceeds 18 ° C or the ratio A / F to the stoichiometry of the first fuel equals or exceeds 12.0. Thus, with the aid of a pre-introduction adapted to the start-up situation, it is possible to start almost instantaneously, that is to say from the start-up order of the engine, an engine operating with a fuel that can contain up to 100% ethanol, at low temperatures and in particular of the order of -10 ° C.

Claims

Claims:

1. A method of starting a combustion engine (1) powered by a first fuel that may contain ethanol, said engine being equipped with a cold start auxiliary system comprising a reservoir (5) of a second fuel low in ethanol, wherein the temperature of the engine coolant is determined, the proportion of ethanol in the first fuel is determined, and characterized in that, if the engine coolant temperature (1) is below a predetermined critical temperature and if the proportion of ethanol in the fuel is greater than a predetermined threshold, the second fuel is pre-introduced at the intake of the engine (1), in response to the observation of an event prior to the request to start the engine.

2. Method according to claim 1, characterized in that the critical temperature is between 15 ° C and 20 ° C, and preferably equal to 18 ° C.

3. Method according to claim 1 or claim 2, characterized in that the predetermined threshold is between 22% and 100% by volume.

4. Method according to any one of the preceding claims, characterized in that the amount of second fuel pre-introduced is dependent on the temperature of the engine coolant (1).

5. Method according to any one of the preceding claims, characterized in that the amount of second fuel pre-introduced is dependent on the level of ethanol in the first fuel.

6. Method according to claim 4 or claim 5, characterized in that modulates the amount of second fuel pre-introduced by modulating the duration of the pre-introduction.

7. Method according to any one of claims 4 to 6, characterized in that modulates the pre-introduction time according to a preset map.

8. Method according to any one of the preceding claims, characterized by a minimum delay predefined between two pre-introductions.

9. Method according to any one of the preceding claims, applied to a motor (1) fitted to a vehicle with doors, characterized in that the event observed prior to starting the engine is the unlocking or opening of at least a door.

10. Method according to any one of claims 1 to 8, applied to a motor (1) fitted to a vehicle, characterized in that the event observed prior to starting the engine is the detection of a transponder of a card. start free hand or present in a key engine contact.

1 1. Process according to any one of claims 1 to 8, applied to a motor equipping a vehicle, characterized in that the event observed prior to starting the engine is the detection of the depression of the brake pedal or the clutch pedal of the vehicle.

12. Method according to any one of claims 1 to 8, applied to a motor (1) fitted to a vehicle, characterized in that the event observed prior to starting the engine is the buckling of the driver's seat belt, or detection of the presence of a driver.