Bioethanol conversion device arranged to produce a modified injection signal

Abstract

The invention relates to a conversion device (1) for a direct injection engine, a conversion device enabling a user to use a fuel of their choice, for example unleaded fuel, bioethanol-type fuel, or a mixture of unleaded fuel and bioethanol-type fuel, a conversion device arranged to provide, from an initial injection signal (SI) received from an engine control unit (ECU), a modified injection signal (SM) to an injector (5) of the engine, a conversion device (1) characterized in that it comprises: - an analysis circuit (60) of the initial injection signal (SI) arranged to determine an end time (Tf) of the initial injection signal, - a signal generator (70) arranged to produce the complementary injection signal (SC) from the end time of the initial injection signal,the supplementary injection signal being a function of an enrichment ratio dependent on the composition of the fuel supplying the engine, and - an addition circuit (80) arranged to produce the modified injection signal (SM) from the supplementary injection signal (SC) and the initial injection signal (SI). Figure from the abstract: Figure 2,

Description

Title of the invention: Bioethanol conversion device arranged to produce a modified injection signal technical field

[0001] The invention relates to the field of bioethanol conversion devices for direct injection engines. These devices allow a user to choose between using unleaded fuel, bioethanol-type fuel, or a mixture of the two, to power the engine of a motor vehicle, for example. More specifically, these devices allow control of the injector opening time, since the use of bioethanol requires the injection of additional fuel to obtain performance similar to that obtained with unleaded fuel. These devices are designed not to interfere with the engine's normal ECU control unit, which must be able to function correctly whether the bioethanol conversion device is active or not, and whether the engine is running on unleaded fuel or bioethanol.

[0002] In a known manner, such a conversion device is arranged to receive an injection signal from the engine's ECU and transmit a modified injection signal to the engine injectors, appropriate for injecting more fuel into the engine. To modify the initial injection signal, the conversion device takes into account the engine type and the type of fuel used. The injection signal is most often a current control signal, which commands the opening of an injector and then its maintenance for a sufficient injection duration to supply the engine with the required fuel. In known conversion devices, the adaptation circuit is generally specific to a given engine type, and at most, manual adjustment via a potentiometer is considered.

[0003] Known conversion devices are generally inefficient, particularly for the following reasons.

[0004] For direct injection engines, which are used in most motor vehicles on the road today, depending on the technology and engine power, the injection signals are very specific and vary considerably from one engine or engine type to another, both in terms of the signal waveform, amplitude, and duration. These are periodic signals with a frequency proportional to the engine speed. Furthermore, for the same engine, over a period (also called an injection cycle), the injection signals can vary enormously in practice; they can have a voltage that can reach several The voltage ranges from tens to hundreds of volts, and the current can peak between a few amps and tens of amps, reaching zero or near zero at the end of the injection period. Therefore, a standard conversion device, fixed at the manufacturing stage, can only be used for one type of engine, and it is necessary to have as many conversion devices as there are engine types.

[0005] Furthermore, today, engine manufacturers optimize engine operation by developing real-time fuel consumption regulation methods, taking into account not only the fuel used but also the engine's usage and operating conditions. For example, in motor vehicles, the initial injection signals produced by the engine control unit take into account, in particular, the accelerator pedal depressor (i.e., the power demanded from the engine) and the ambient temperature, and are adapted accordingly. This results in initial injection signals whose waveform, amplitude, and duration vary in real time with each injection cycle during engine operation.Under these highly variable conditions, a conventional conversion device may alter the initial injection signal at an inopportune moment in the injection cycle, risking unnecessary overconsumption of fuel, or even damaging the engine. Description of the invention

[0006] The invention proposes a new conversion device not exhibiting all or part of the disadvantages of known prior conversion devices as described above.

[0007] To this end, the invention proposes a new conversion device (1) arranged to provide, from an initial injection signal (SI) received from an engine control unit (ECU), a modified injection signal (SM) to an injector (5) of the engine. The conversion device according to the invention (1) is characterized in that it comprises: - an analysis circuit (60) of the initial injection signal (SI) arranged to determine an end time (Tf) of the initial injection signal, - a signal generator (70) arranged to produce the supplementary injection signal (SC) from the moment the initial injection signal ends, the supplementary injection signal being a function of an enrichment ratio that is a function of the composition of the fuel supplying the engine, and - an addition circuit (80) arranged to produce the modified injection signal (SM) from the complementary injection signal (SC) and the initial injection signal (SI).

[0008] The device according to the invention thus makes it possible to provide a complementary injection signal at the end of the initial injection signal, i.e. at the most opportune time; the efficiency of the conversion device is thus optimized.

[0009] The signal generator can be arranged to produce the complementary signal The injection (SC) duration is a function of the enrichment ratio and the duration (DI) of the initial injection signal. The device according to the invention thus makes it possible to obtain a modified injection signal that takes into account, in real time, the initial injection signal as optimized and provided by the engine's ECU control unit. The efficiency of the conversion device is therefore further improved.

[0010] The enrichment ratio can be a function of intrinsic engine parameters and / or engine operating conditions and / or engine temperature. In one embodiment, the enrichment ratio has a first value (TX1) at engine start-up and takes on a second value (TX2): - after a predefined transition time (TPS1), or - when an engine temperature goes above a temperature threshold (TT).

[0011] According to one embodiment, the addition circuit comprises a first input terminal connected to the control unit to receive the initial injection signal SI, a second input terminal connected to the signal generator to receive the complementary injection signal SC, and an output terminal connected to the injector (5), the first input terminal and the second input terminal of the addition circuit being connected to the output terminal of the addition circuit, and the addition circuit also includes: - a first protection circuit (81) connected between the first input terminal and the output terminal of the addition circuit and arranged to prevent the initial injection signal received by the conversion device from disturbing the signal generator, and / or - a second protection device (82) connected between the second input terminal and the output terminal of the addition circuit and arranged to prevent the complementary signal produced by the signal generator from interfering with the engine control unit (ECU).

[0012] The invention also relates to a conversion method for a direct injection engine, the conversion method comprising the use of a conversion device as described above to receive an initial injection signal from an engine control unit (ECU) and produce a modified injection signal (MS) by carrying out the following steps, consisting of: - ET1: analyze the initial injection signal (SI), to determine an end time (Tf) of the initial injection signal (SI), - ET2: produce a complementary signal (SC) as a function of an enrichment ratio (TX1, TX2) which is itself a function of the composition of the fuel supplying the engine, and - ET3: produce the modified injection signal (SM) from the complementary injection signal (SC) and the initial injection signal (SI).

[0013] The production of the modified injection signal (MS) is repeated in a loop, at each injection cycle of the initial injection signal.

[0014] The modified injection signal generation step can be repeated for a transition period with a first enrichment rate (TX1), and then repeated with a second enrichment rate (TX2). For example, the transition period is defined based on engine temperature and / or ambient temperature. This is particularly useful during a cold engine start, or when the outside temperature is low, making fuel vaporization in the injector difficult.

[0015] The method according to the invention may also include a parameterization step performed by an operator, consisting of: - ET01: provide at least one parameter from a set of parameters including an engine identifying parameter, an engine type identifying parameter, a fuel identifying parameter, a fuel type identifying parameter, a high current threshold, a low current threshold, the first enrichment rate, the second enrichment rate, the transition time, a transition temperature threshold.

[0016] This step allows the conversion device to be adapted to the engine to which it is associated, in order to best take into account the intrinsic characteristics of the engine and the fuel used. This step is advantageously implemented via a Human-Machine Interface displayed on a computer terminal such as a PC, a smartphone, etc. Brief description of the figures

[0017] The invention will be better understood, and other features and advantages of the invention will become apparent from the following description of examples of implementations of the invention. These examples are given by way of non-limiting example. The description is to be read in conjunction with the accompanying drawings in which:

[0018] [Fig.1] is a simplified electrical diagram of the device according to the invention in its environment.

[0019] [Fig.2] is an electrical diagram detailing the device according to the invention.

[0020] [Fig.3] shows the evolution of the injection control signal supplied to an injector of a first engine.

[0021] [Fig.4] shows the evolution of the injection control signal supplied to an injector of a second engine, and the evolution of signals inside the conversion device.

[0022] [Fig.5] is a schematic representation of the essential steps of a process according to the invention.

[0023] Detailed description of embodiments of the invention

[0024] As stated previously, the invention relates to ([Fig. 1]) a conversion device 1 arranged to provide, from an initial injection signal (SI) received from an engine control unit (ECU), a modified injection signal SM to an injector 5 of the engine. According to the invention, the conversion device 1 comprises ([Fig. 2]): - an analysis circuit 60 of the initial injection signal SI arranged to determine an end time Tf of the initial injection signal, - a signal generator 70 arranged to produce the complementary injection signal SC from the moment the initial injection signal ends, the SC signal being a function of an enrichment ratio based on the composition of the fuel supplying the engine, and - an addition circuit 80 arranged to produce the modified injection signal SM from the complementary injection signal SC and the initial injection signal SI.

[0025] Figures 1-2 show a possible embodiment of a conversion device according to the invention, intentionally simplified for clarity. A pair of input cables connects the control unit U to the positive and negative (or ground) input terminals of the conversion device 1 and a pair of output cables connects the positive and negative (or ground) output terminals of the conversion device to the injector 5.

[0026] For the sake of simplicity, a single injector of an engine has been represented in [Fig. 1]. For an engine comprising N injectors, for example four or six injectors, the diagram of [Fig. 1] can be duplicated N times: the conversion device according to the invention comprises N pairs of input terminals, each connected to corresponding pairs of terminals of the ECU control unit, and N pairs of output terminals, each connected to a pair of terminals of an injector; within the conversion device, the analysis circuit, the current generator and the addition circuit can be duplicated in the same way, which allows each injector to be controlled independently of the others.

[0027] The analysis circuit 60 here ([Fig. 2]) comprises a current measurement circuit 61 and a detection circuit 62. The negative input and output terminals of the conversion device are electrically connected. The measurement circuit 61 is arranged to measure the instantaneous current flowing between the negative input and output terminals of the conversion device, i.e., in the return connection of the injection signal from injector 5 to the ECU control unit. In the example shown, the measurement device is a Hall effect current sensor. Such a sensor has the advantage of providing galvanic isolation between, on the one hand, the power circuit of the conversion device, including the signal generator 70 and the electrical connections between the ECU and injector 5, and, on the other hand, the analysis circuit 60 and the control circuit of said power circuit. The current sensor provides a measurement signal whose voltage is proportional to the current flowing between the negative input and output terminals of the conversion device.

[0028] Figure 3 shows a first example of the evolution over time (a single injection cycle is shown) of the image, as measured by the measuring circuit 61, of the initial injection signal SI (solid line) supplied by the ECU, and of the image of the complementary signal SC (dashed line) as supplied by the signal generator 70. The resulting signal corresponds to the image of the modified injection signal SM as supplied to the injector 5 by the conversion device according to the invention for an engine of a PEUGEOT 5008 type vehicle. Figure 4a, similar to Figure 3, shows a second example of the evolution over time of the image, as measured by the measuring circuit 61, of the modified injection signal SM for an engine of a VW Caddy type vehicle.

[0029] As can be seen in Figures 3 and 4a, the initial injection signals SI (dashed lines) are quite different from one engine to another, in terms of their waveforms, amplitudes, and durations. However, all exhibit a first part A corresponding to a command to open the injector, followed by a second part B, corresponding to a command to keep the injector open. In the first part, the current increases from a minimum value, typically zero Amperes, passes through a maximum value, and then decreases. The maximum value is on the order of ??? in the example in [Fig. 3], and on the order of ??? in the example in [Fig. 4]; in other examples, the maximum value may be lower, on the order of a few Amperes.In the second part, the current is regulated and oscillates between two values, a high value and a low value, with a jet of pressurized fuel being projected into the injector throughout the duration of the second part.

[0030] The detection circuit 62 is arranged to determine parameters of the initial injection signal. In the example shown, the detection circuit comprises: - a first comparator 63a, arranged to produce an active HS signal when the amplitude of the measurement signal applied to its input is less than a high threshold HT, - a second comparator 63b arranged to produce an active LS signal when the amplitude of the measurement signal applied to its input is less than a low threshold LT.

[0031] The first comparator detects the start time Td of the second part B of the initial injection signal SI, which corresponds to the current regulation phase; this second part begins when the HS signal becomes active, i.e., on a rising edge of the HS signal (Fig. 4b). The second comparator detects the end Tf of the second part B of the SI signal; this second part ends when the LS signal becomes active, i.e., on a rising edge of the signal LS (Fig. 4c). The detection circuit 60 can be supplemented by a measurement circuit 63c with an injection duration corresponding to the time between the rising edge of the HS signal and the rising edge of the LS signal. In one example, the circuit 63c is a counter configured to count pulses of a clock signal between a rising edge (at time Td) of the HS signal and a rising edge (at time Tf) of the LS signal (Fig. 4d). The detection circuit 60 can also be supplemented by a temperature measurement circuit 64a, and a third comparator 64b configured to generate an active temperature signal TS when the measured temperature exceeds a temperature threshold TT. The detection circuit 60 may further include a communication interface 66, configured to exchange information with a remote terminal by known means such as a wired connection (e.g., a connection via a USB cable) or a wireless connection (e.g., a Bluetooth connection).The significance of these circuits 63c, 64a, 64b, 66 will be discussed further below.

[0032] Finally, the detection circuit 60 may include a control circuit 65 arranged to receive all the signals supplied by the measuring circuits and comparators of the conversion device, to receive parameters supplied by a user, and to provide a control signal to drive the signal generator 70. The control circuit 65 includes, in particular, a data memory for storing data such as the upper current threshold, the lower current threshold, the enrichment ratio, etc. The data memory may also store a database containing, for each known motor (or type of motor) identified by an identifier, initial parameters associated with said motor such as the upper current threshold, the lower current threshold, the enrichment ratio, etc.The control circuit 65 also includes a program memory comprising a plurality of lines of code suitable for implementing the method according to the invention and for controlling all the circuits of the conversion device, as described below.

[0033] According to the invention, the signal generator 70 is arranged to produce the complementary injection signal SC. The signal generator 70 is in the example a power current generator arranged to produce a power current from an electrical energy external to the conversion device, for example an electrical energy supplied here by a battery (accumulators) of the vehicle.

[0034] Finally, the addition circuit 80 is arranged to add the complementary signal SC to the initial signal SI and provide the modified injection signal SM on the positive terminal of the injector. In the example shown, the addition circuit 80 comprises a first input terminal E1 connected to the control unit to receive the initial injection signal SI, a second input terminal E2 connected to the signal generator to receive the complementary injection signal SC, and an output terminal S connected to the injector (5). The first input terminal E1 and the second input terminal E2 of the addition circuit are connected to the output terminal S of the addition circuit. The addition circuit also includes a first protection circuit (81) connected between the first input terminal and the output terminal of the addition circuit and arranged to prevent the initial injection signal received by the conversion device from interfering with the signal generator, and a second protection device (82) connected between the second input terminal and the output terminal of the addition circuit and arranged to prevent the complementary signal produced by the signal generator from interfering with the engine control unit (ECU). In the example shown, both protection devices are power diodes that allow any signal flowing in the forward direction to pass but block any signal flowing in the reverse direction.

[0035] In a practical implementation example, the various elements of the conversion device can be implemented on a single electronic circuit board housed in a closed enclosure designed to be mounted in the immediate vicinity of the engine to which it is connected. The enclosure includes first input connectors (one per injector) intended to be connected to corresponding output connectors of an engine control unit (ECU), and first output connectors (one per injector) intended to be connected to corresponding connectors on the injectors. Each connector has two terminals, a positive terminal and a negative (or ground) terminal. The enclosure also includes a power supply connector, intended to be connected to the corresponding positive and negative terminals of a vehicle battery (or accumulators).Preferably, power components, such as ECU connection terminals, injector connection boxes, connections between power boxes, signal generator 70, etc., can be grouped on one part of the circuit board, and control components, such as the analysis circuit including measurement circuits and logic components, the control device, etc., can be grouped on a second part of the circuit board. This board layout, combined with an appropriate choice of components (e.g., a Hall effect current sensor), allows for electrical isolation of the power components from the control components.

[0036] The generator 70 provides the SC signal from the instant of the end of the initial injection signal, that is to say in the example shown when the LS signal becomes active (rising edge of the LS signal).

[0037] The SC signal is a function of an enrichment ratio TX, the latter being essentially a function of the composition of the fuel used to power the engine. The amplitude of the SC signal is chosen to be above the lower threshold to keep the injector open and continue injecting fuel, and below the upper threshold to avoid damaging the injector with excessive current.

[0038] According to one embodiment, the duration of the SC signal is a function of the enrichment rate TX and is, for example, equal to the product DM x TX, where DM is a constant representing an average injection duration. According to another embodiment, the duration of the SC signal is a function of the enrichment rate TX and the injection duration DI determined by the measuring circuit 63c of the detection circuit and is, for example, equal to DI x TX. The duration of the complementary signal can thus be adjusted for each injection cycle, and for each injector, to optimize overall fuel consumption.

[0039] The enrichment ratio TX is essentially a function of the fuel composition. The enrichment ratio can also depend on engine operating conditions and / or engine temperature. In practice, a bioethanol-type fuel or a fuel containing bioethanol vaporizes poorly when the engine temperature is below a temperature threshold TT of approximately 30 to 45°C. To account for this, depending on the implementation, the enrichment ratio can take an initial value TX1 at engine start-up, and a second value TX2 after a transition time chosen to be sufficiently long for the engine temperature to rise above the temperature threshold TT.

[0040] According to another embodiment, the enrichment ratio can take a first value TX1 at engine start-up, then a second value TX2 when the engine temperature exceeds a temperature threshold TT. The temperature measurement circuit 64a and the comparator 64b detect the moment when the temperature reaches the temperature threshold TT, and the control circuit selects TX1 and then TX2 to drive the signal generator 70.

[0041] As an indication, and depending on the engine or engine type, the TX1 rate can be in the range of 25 to 40% and the TX2 rate can be in the range of 10 to 25%

[0042] The conversion device according to the invention can be used to implement a conversion process according to the invention, the essential step of which is the production of a modified injection signal SM by carrying out the following steps, consisting of ([Fig.5]): - ET1: analyze the initial injection signal SI, to determine the end time of the initial injection signal, - ET2: produce a complementary signal SC starting from the end of the initial injection signal, the complementary signal being a function of an enrichment rate TX that depends on the fuel composition, and - ET3: produce the modified injection signal SM from the complementary signal SC and the initial injection signal SL

[0043] The modified injection signal production step is performed in a loop at each injection cycle, preferably throughout the entire engine operating time.

[0044] As mentioned previously, if the outside temperature is low, for example below 5 to 10°C, and / or if the engine temperature is low, for example below 5 to 10°C, the step of generating the modified injection signal can be repeated initially with a first enrichment rate TX1, then repeated with a second enrichment rate TX2. By choosing TX1 > TX2, it is thus possible to supply more fuel (rate TX1) at engine start-up, and then to limit fuel consumption (rate TX2) after a transition time TPS1. The first transition time TPS1 can be predefined, for example at TPS1 = 5 to 15 s.The transition time can also be defined as a function of an engine temperature, measured by circuit 64a; thus, for example, the first rate TX1 can be used as long as the engine temperature is below a temperature threshold TT beyond which the engine efficiency is optimal.

[0045] The method may also include a parameterization step, consisting of (ET01) selecting at least one parameter from a set of parameters including: a parameter identifying the engine, a parameter identifying the engine type, a parameter identifying a fuel, a parameter identifying a fuel type, an enrichment ratio, a high current threshold HT, a low current threshold LT, the first enrichment ratio TX1, the second enrichment ratio TX2, the transition time TPS1, the transition temperature threshold TT.

[0046] The ET01 parameterization step can be performed by a user, using a user interface (also called a human-machine interface or H / M interface) allowing the user to enter parameters necessary for the operation of the conversion device (in particular, information about the engine and / or fuel). If the conversion device's data memory stores parameters for known engines, the user interface can suggest default parameter values ​​when the user enters an engine identifier or engine type. The user interface can also inform the user of a possible connection fault in the conversion device or a possible malfunction of the conversion device, etc.

[0047] The user interface includes in particular a display and input terminal known elsewhere (for example a smartphone with a touch screen, a PC with a screen and keyboard, etc.) connected to the communication interface 66 of the conversion device by a wired connection known elsewhere (for example a USB cable) or a wireless connection (for example a Bluetooth connection) allowing an exchange of information between the display and input terminal and the communication interface 66 of the conversion device.

[0048] These initial parameters then allow the measurement circuits to be calibrated, pa- reconnect the detection circuit, the control circuit, etc.

[0049] Also, the method may include an initialization step ET02 may include a step (ET02) consisting of measuring an engine temperature and determining the first time TPS1 from a difference between the measured engine temperature and a predefined established operating temperature.

[0050] Alternatively, the modified injection signal production step may include a step ET4 consisting of measuring the engine temperature and replacing the first enrichment rate TX1 with the second enrichment rate TX2 when the temperature reaches the temperature threshold TT.

[0051] List of reference signs 5 injectors 6 control unit 60 analysis circuit 61 current measurement circuit 62 detection circuit 63a first comparator 63b second comparator 63c time measurement circuit 64a temperature measurement circuit 64b third comparator 65 control circuit 66 communication interface 70 signal generator 80 addition circuit 81, 82 first and second protective devices A, B: first part and second part of an initial injection signal SI initial injection signal SC complementary injection signal SM modified injection signal HT, LT high threshold and low threshold, of current HS, LS signals produced by comparators 63a, 63b TT temperature threshold TS temperature signal produced by comparator 64b TX, TX1, TX2 enrichment rates TPS1 transition time DI, DM injection duration, average injection duration

Claims

Demands

1. Conversion device (1) for a direct injection engine of a motor vehicle, conversion device arranged to allow a user to use a fuel of their choice, for example a first unleaded fuel, or a second fuel different from the first fuel, the second fuel being of the Bioethanol type or a mixture of unleaded fuel and Bioethanol type fuel, conversion device arranged to provide, from an initial injection signal (IS) received from an engine control unit (ECU), a modified injection signal (MS) to an injector (5) of the engine, conversion device (1) characterized in that it comprises: - an analysis circuit (60) of the initial injection signal (IS) arranged to determine an end time (Tf) of the initial injection signal, - a signal generator (70) arranged to produce the complementary injection signal (CS) from the end time of the initial injection signal,the supplementary injection signal being a function of an enrichment ratio dependent on the composition of the fuel supplying the engine, and - an addition circuit (80) arranged to produce the modified injection signal (SM) from the supplementary injection signal (SC) and the initial injection signal (SI).

2. Conversion device according to claim 1 in which the signal generator (70) is arranged to produce the complementary injection signal (SC) of duration as a function of the enrichment ratio and a duration (DI) of the initial injection signal.

3. A device according to claim 3, wherein the analysis circuit (60) comprises: - a current measurement circuit (61) for the current flowing in a return connection of the injection signal from the injector to the engine control unit (ECU), - a first comparator (63a), arranged to produce an active start signal HS when the measured current decreases and falls below a high threshold HT, and - a second comparator (63b), arranged to produce an active end signal LS when the measured current decreases and falls below a low threshold LT that is lower than the high threshold, and - a time measurement circuit (63c) arranged to determine a duration between the end signal LS and the start signal HS.

4. Device according to any one of claims 1 to 3 wherein the enrichment rate is a function of intrinsic engine parameters and / or engine operating conditions and / or engine temperature.

5. Device according to claim 4 in which the enrichment ratio has a first value (TX1) at engine start and takes a second value (TX2): - after a predefined transition time (TPS1), or - when an engine temperature goes above a temperature threshold (TT).

6. A conversion device according to any one of the preceding claims, wherein the addition circuit comprises a first input terminal connected to the control unit for receiving the initial injection signal SI, a second input terminal connected to the signal generator for receiving the complementary injection signal SC, and an output terminal connected to the injector (5), the first input terminal and the second input terminal of the addition circuit being connected to the output terminal of the addition circuit, and wherein the addition circuit also comprises: - a first protection circuit (81) connected between the first input terminal and the output terminal of the addition circuit and arranged to prevent the initial injection signal received by the conversion device from interfering with the signal generator,and / or - a second protection device (82) connected between the second input terminal and the output terminal of the addition circuit and arranged to prevent the additional signal produced by the signal generator from interfering with the engine control unit (ECU).

7. A conversion method for a direct injection engine of a motor vehicle, adapted to allow a user to use either a first unleaded fuel or a second fuel different from the first fuel, the second fuel being of the bioethanol type or a mixture of unleaded fuel and bioethanol-type fuel to power an engine, the conversion method comprising the use of a conversion device according to any one of the preceding claims for receiving an initial injection signal from an engine control unit (ECU) and supplying a modified injection signal (SM) to an injector (5) of the engine, by carrying out the steps the following, consisting of: - ET1: analyze the initial injection signal (SI), to determine an end time (Tf) of the initial injection signal (SI), - ET2: produce a complementary injection signal (SC) from the end time of the initial injection signal as a function of an enrichment rate (TX1, TX2) as a function of the composition of the fuel supplying the engine, and - ET3: produce the modified injection signal (SM) from the complementary injection signal (SC) and the initial injection signal (SI).

8. Method according to claim 7 wherein the production of the modified injection signal (MS) is repeated in a loop, at each injection cycle of the initial injection signal.

9. A method according to claim 8 wherein the modified injection signal production step is repeated for a transition time with a first enrichment rate (TX1), then is repeated with a second enrichment rate (TX2).

10. Method according to claim 9 wherein the transition time is defined as a function of an engine temperature and / or as a function of an ambient temperature.

11. A method according to any one of claims 7 to 10, also comprising a parameterization step carried out by an operator, consisting of: - ET01: providing at least one parameter from a set of parameters including a parameter identifying the engine, a parameter identifying the engine type, a parameter identifying a fuel, a parameter identifying a fuel type, a high current threshold, a low current threshold, the first enrichment rate, the second enrichment rate, the transition time, a transition temperature threshold.

12. A method according to any one of claims 10 to 60 also comprising an initialization step, consisting of: - ET02: measuring an engine temperature and determining the transition time (TPS1) from a difference between the measured engine temperature and the transition temperature.

Images