Method and system for validating the phase of a vehicle engine

Abstract

Disclosed is a method for determining the configuration of a combustion engine of a motor vehicle including a step of detecting the reference position of the crankshaft, a step of controlling the control valve of the injection pump, after a predetermined time interval, a step of measuring a fuel pressure value in the injection rail, and a step of determining a first configuration of the engine when the fuel pressure value measured in the injection rail is greater than or equal to a first predetermined pressure threshold or determining a second configuration of the engine when the fuel pressure value measured in the injection rail is between a second predetermined pressure threshold and a third predetermined pressure threshold.

Claims

1. A method for determining the configuration of a combustion engine (10) of a motor vehicle, where the engine (10) has a plurality of cylinders (11) in connection with a crankshaft (13), a camshaft (15), a fuel injection rail (22) for injecting fuel into said cylinders (11), a high pressure hydraulic injection pump (21) that pumps fuel into said injection rail (22), a control valve (24) that controls opening and closing of said injection pump (21), a pressure sensor (25) that measures pressure of fuel flowing in said injection rail (22), and a control module (30), said crankshaft (13) having an angular position from a reference position (D.sub.0), said camshaft (15) being rigidly connected to the crankshaft (13) such that the crankshaft (13) performs two full revolutions when the camshaft (15) performs one full revolution, and said injection pump (21) equipped with a fuel pumping piston (210) that operates synchronously with said crankshaft (13) such that said fuel pumping piston (210) pumps fuel an odd number of times during one revolution of said camshaft (15), said method comprising: detecting (E1.sub.A) the reference position (D.sub.0) of the crankshaft (13); causing (E2.sub.A), by the control module (30), the control valve (24) of the injection pump (21) to close; after a first predetermined time interval, of measuring (E4.sub.A) by the pressure sensor (25) a first fuel pressure value (P) in the injection rail (22); comparing the first fuel pressure value (P) measured in the injection rail (22) with a predetermined initial pressure value (P.sub.i), the engine (10) determined to be in a first configuration when the fuel pressure value (P) measured in the injection rail (22) is greater than or equal to a first predetermined pressure threshold (S.sub.1), and in a second configuration when the fuel pressure value (P) measured in the injection rail (22) is between a second predetermined pressure threshold (S.sub.2) and a third predetermined pressure threshold (S.sub.3); measuring (E4.sub.B), when the first fuel pressure value (P) measured in the injection rail (22) is between the second predetermined pressure threshold (S.sub.2) and the third predetermined pressure threshold (S.sub.3) by the pressure sensor (25), a second fuel pressure value (P.sub.B) in the injection rail (22) after a second predetermined time interval; and determining the engine to be in the first configuration of the engine (10) when the second fuel pressure value (P.sub.B) measured in the injection rail (22) is greater than or equal to said first predetermined pressure threshold (S.sub.1), and detecting an engine anomaly when the second pressure value (P.sub.B) measured in the injection rail (22) is lower than the first predetermined pressure threshold (S.sub.1).

2. The method as claimed in claim 1, wherein the first predetermined threshold (S.sub.1) corresponds to the predetermined initial pressure (P.sub.i) plus at least 3 MPa.

3. The method as claimed in claim 1, wherein the second predetermined threshold (S.sub.2) and the third predetermined threshold (S.sub.3) correspond to the predetermined initial pressure (P.sub.i) minus 1 MPa and to the predetermined initial pressure (P.sub.i) plus 1 MPa, respectively.

4. The method as claimed in claim 1, further comprising, prior to the step of detecting the reference position (Do) of the crankshaft (13): measuring said initial pressure value (P.sub.i) in said injection rail (22).

5. The method as claimed in claim 1, wherein, as said at least one piston (210) of the injection pump (21) pumps fuel an odd number of times during one revolution of said at least one camshaft (15), each cam of said camshaft (15) comprises an odd number of lobes.

6. The method as claimed in claim 1, wherein the first time interval is between 20 and 500 ms.

7. A system (1) for determining a position of a crankshaft (13) of a combustion engine (10) of a motor vehicle, where the combustion engine (10) includes a plurality of cylinders (11), a crankshaft (13) having an angular position from a reference position (D.sub.0), a camshaft (15) rigidly connected to said crankshaft (13) such that the crankshaft (13) performs two full revolutions when said at least one camshaft (15) performs one full revolution, and a position sensor (16) that determines an angular position of said crankshaft (13), the system comprising: an injection module (20), comprised of: a high pressure fuel injection pump (21) with at least one fuel pumping piston (210) being mounted synchronously with said crankshaft (13) such that said at least one piston (210) pumps fuel an odd number of times during one revolution of said at least one camshaft (15), a control valve (24) configured to control opening and closing of said injection pump (21), a fuel injection rail (22) connected both to said injection pump (21) and to a plurality of injectors (23) for injecting the fuel into the cylinders (11) of the engine (10), and a pressure sensor (25), configured to measure a pressure value (P) in said injection rail (22); and a control module (30) configured to control the opening and closing of said control valve (24) and to determine the position of the crankshaft (13) by means of the position sensor (16) and the pressure sensor (25) in order to determine the configuration of the engine (10), the control module configured to: detect the reference position (D.sub.0) of the crankshaft (13), cause the control valve (24) of the injection pump (21) to close, after a first predetermined time interval, measure by the pressure sensor (25) a first fuel pressure value (P) in the injection rail (22); compare the first fuel pressure value (P) measured in the injection rail (22) with a predetermined initial pressure value (P.sub.i), the engine (10) determined to be in a first configuration when the fuel pressure value (P) measured in the injection rail (22) is greater than or equal to a first predetermined pressure threshold (S.sub.1), and in a second configuration when the fuel pressure value (P) measured in the injection rail (22) is between a second predetermined pressure threshold (S.sub.2) and a third predetermined pressure threshold (S.sub.3), measure, when the first fuel pressure value (P) measured in the injection rail (22) is between the second predetermined pressure threshold (S.sub.2) and the third predetermined pressure threshold (S.sub.3) by the pressure sensor (25), a second fuel pressure value (P.sub.B) in the injection rail (22) after a second predetermined time interval, and determine the engine to be in first configuration of the engine (10) when the second fuel pressure value (P.sub.B) measured in the injection rail (22) is greater than or equal to said first predetermined pressure threshold (S.sub.1), and detecting an engine anomaly when the second pressure value (P.sub.B) measured in the injection rail (22) is lower than the first predetermined pressure threshold (S.sub.1).

8. A motor vehicle, comprising the system (1) for determining a position of a crankshaft (13) of a combustion engine (10) as claimed in claim 7.

9. The method as claimed in claim 1, wherein the first predetermined threshold (S.sub.i) corresponds to the predetermined initial pressure (P.sub.i) plus 10 MPa.

10. The method as claimed in claim 1, wherein the first time interval is 70 ms.

11. The method as claimed in claim 2, wherein the second predetermined threshold (S.sub.2) and the third predetermined threshold (S.sub.3) correspond to the predetermined initial pressure (P.sub.i) minus 1 MPa and to the predetermined initial pressure (P.sub.i) plus 1 MPa, respectively.

12. The method as claimed in claim 2, further comprising, prior to the step of detecting the reference position (D.sub.0) of the crankshaft (13): measuring said initial pressure value (P.sub.i) in said injection rail (22).

13. The method as claimed in claim 3, further comprising, prior to the step of detecting the reference position (D.sub.0) of the crankshaft (13): measuring said initial pressure value (P.sub.i) in said injection rail (22).

14. The method as claimed in claim 2, wherein, as said at least one piston (210) of the injection pump (21) pumps fuel an odd number of times during one revolution of said at least one camshaft (15), each cam of said camshaft (15) comprises an odd number of lobes.

15. The method as claimed in claim 3, wherein, as said at least one piston (210) of the injection pump (21) pumps fuel an odd number of times during one revolution of said at least one camshaft (15), each cam of said camshaft (15) comprises an odd number of lobes.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 schematically illustrates one embodiment of the system according to the invention.

(2) FIG. 2 is a schematic view of the system in FIG. 1, detailing the engine of the vehicle.

(3) FIG. 3 is a schematic view of the system in FIG. 1, detailing the injection module.

(4) FIGS. 4A to 4C schematically illustrate an example of the operation of a piston pump actuated by a cam comprising three lobes.

(5) FIG. 5 depicts on a graph the evolution of the position of the piston in the high pressure pump during half of an engine cycle as a function of an open and closed state of the control valve connected to the injection pump, allowing the injection of fuel into the injection rail.

(6) FIG. 6 schematically illustrates one embodiment of the method according to the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

(7) The invention will be presented below for the purpose of implementation in a motor vehicle. However, any implementation in a different context, in particular for any vehicle comprising a combustion engine whose configuration it is necessary to determine is also covered by the invention. Likewise, the invention will be described with the aid of an example in which the injection of fuel into a combustion chamber is synchronized with the opening of the intake valve connected to this same intake chamber, that is to say during the intake phase of this combustion chamber; however, such synchronization could also be carried out during another operating phase, depending on the type of engine concerned.

(8) 1/System

(9) With reference to FIG. 1, the system 1, according to one form of representation of the invention, comprises a motor vehicle combustion engine 10, an injection module 20 and a control module for controlling the injection module 20, in this case in the form of a computer 30.

(10) a. Engine 10

(11) As shown schematically in FIG. 2, the combustion engine 10 comprises, in a known way, a plurality of cylinders 11 each delimiting a combustion chamber 11A in which a piston 12 slides, the movement of the piston being driven by compression and expansion of the gases resulting from the compression of a mixture of air and fuel introduced into the combustion chambers 11A.

(12) As a reminder, the air and the gases are introduced and expelled respectively via intake valves 14A and exhaust valves 14B, which are connected, in this example, to a single camshaft 15. However the engine 10 of the vehicle could just as easily comprise two camshafts 15, one for the intake valves 14A and the other for the exhaust valves 14B. Similarly, in this example, each cylinder 11 is connected to one intake valve 14A and one exhaust valve 14B; however, each cylinder 11 could also be connected to several intake valves 14A and several exhaust valves 14B. The camshaft 15, rotated, alternately allows the opening and closing of the intake and exhaust valves 14 of each combustion chamber 11A.

(13) The set of pistons 12 is connected to a crankshaft 13, which is rotated by the thrust of each piston 12, thus driving the rotation of the wheels of a vehicle. The crankshaft 13 comprises a toothed wheel 130 having a predetermined number of regularly spaced-apart teeth, and also a tooth-free space corresponding to a reference position D.sub.0 of the crankshaft 13. Since such a toothed wheel 130 is known per se, it will not be described in more detail here.

(14) A position sensor 16 is mounted next to the toothed wheel 130 so as to allow the detection of the reference position D.sub.0 and the counting of the number of teeth passing in front of the position sensor 16 from the reference position D.sub.0 by the computer 30 when the crankshaft 13 is driven in rotation. More specifically, the position sensor 16 delivers a signal representative of the passage of the teeth which allows the computer 30 to determine the angular position from 0° to 360° of the crankshaft 13. As an alternative, the position sensor 16 could itself detect the reference position D.sub.0, count the teeth and send this information to the computer 30 without this limiting the scope of the present invention.

(15) When the camshaft 15 and the crankshaft 13 are rotated, the camshaft 15 performs a full revolution from 0° to 360° while the crankshaft 13 performs two revolutions. This, as is known, is an engine cycle ranging from 0° to 720° in which four operating phases are performed for each of the combustion chambers 11A, for example in turn.

(16) To be specific, each combustion chamber 11A of the cylinders 11 of the engine 10 successively comprises the following operating phases: a phase of intake of air and fuel into the combustion chamber 11A, a phase of compression of the mixture until combustion thereof, a phase of expansion of the gases resulting from said combustion and a phase of exhaust of the gases out of the combustion chamber 11A.

(17) b. Injection Module 20

(18) The injection module 20 makes it possible to introduce the fuel into the combustion chambers 11A. In this example, the system 1 according to the invention makes it possible to synchronize the instant of injection of fuel into a combustion chamber 11A with the opening of the intake valve 14A of this same combustion chamber 11A. However, depending on the type of engine, the instant of injection of fuel could just as well be synchronized with another phase of the combustion chamber 11A, for example at the end of the combustion phase.

(19) To achieve this synchronization, the injection module 20 is connected to the computer 30, for example the main computer of the vehicle, and comprises, with reference to FIG. 3, an injection pump 21, configured to pump fuel into an injection rail 22, connected to a plurality of injectors 23. The injection module 20 further comprises a control valve 24 for controlling the opening and closing of the injection pump 21, and a pressure sensor 25.

(20) Preferably, the injection pump 21 comprises one or more internal piston(s) 210 (not shown), generally one piston 210, configured to control the flow of fuel, thereby regulating the pressure in the injection module 20.

(21) To this end, as shown in the example of FIGS. 4A, 4B and 4C, such a piston 210 slides regularly in the injection pump 21 The piston 210 is thus configured to move regularly in the injection pump 21, in order to allow the introduction (FIG. 4A) of fuel into the injection pump 21, then discharge of the fuel (FIG. 4B). As the control valve 24 is open, the injection pump 21 is thus not pressurized.

(22) To be specific, the fuel is introduced into the injection pump 21 via a control valve 24 for opening and closing the injection pump 21, thus making it possible to control the flow of fuel. Thus, when the control valve 24 is open, as shown in FIGS. 4A and 4B, the movement of the piston 210 causes the fuel to be introduced and discharged, without a rise in pressure in the injection pump 21. However, when the control valve 24 is closed, as shown in FIG. 4C, the piston 210 compresses the fuel introduced into the injection pump 21, the pressure increases, causing the opening of a valve 211 for connection with the injection rail 22, causing the introduction of fuel into the injection rail 22 and thus the rise in pressure inside the injection rail 22.

(23) Such a control valve 24 is preferably a digital flow valve, allowing more precise control of the flow of fuel in the injection pump 21 and thus regulation of the pressure in the injection rail 22. In addition, in this example, the control valve 24 is included in the injection pump 21; however, it goes without saying that the control valve 24 could be external to the injection pump 21, as shown in FIG. 3.

(24) In a preferred embodiment, the sliding movement of the piston 210 in the injection pump 21 is driven by a cam 150 of the camshaft 15 in rotation. However, the injection pump 21 could equally well include a rotary piston 210 comprising a plurality of lobes. In this example, the number of lobes of the rotary piston 210 would be odd.

(25) To be specific, in a preferred embodiment of the invention, during an engine cycle from 0° to 720°, the injection pump 21 is configured to allow the injection of fuel into the injection rail 22 an odd number of times. By way of example, the piston 210 of the injection pump 21 is configured to pump fuel three times during the engine cycle. The succession of six slides (for example three rises and three descents) of the piston 210 during an engine cycle thus allows three rises in pressure of the injection pump 21, and therefore three rises in pressure in the injection rail 22, during this engine cycle.

(26) The injection pump 21 is configured to operate in synchronization with the crankshaft 13. In particular, the injection pump 21 is configured to rise in pressure, by means of the control valve 24, in synchronization with one or more defined positions of the crankshaft 13.

(27) To be specific, during an engine cycle, as the crankshaft 13 performs two revolutions, the position sensor 16 is configured to detect the reference position D.sub.0 twice. In this example, when the control valve 24 is closed, as the cam 150 actuating the piston 210 of the injection pump 21 comprises three lobes, the first reference position D.sub.0 of the crankshaft 13 corresponds to a high position of the piston 210 and therefore to an increase in the pressure in the injection pump 21 and hence in the injection rail 22, while the second reference position D.sub.0 corresponds to a low position of the piston 210 and therefore to a value P of constant pressure of the fuel in the injection rail 22.

(28) Such an injection rail 22 is configured to allow the distribution of fuel, coming from the injection pump 21, into the set of cylinders 11 of the engine 10 via injectors 23.

(29) The injector 23 of the combustion chamber 11A of which the intake valve 14A is open is activated so as to allow, in this example, the simultaneous intake of the mixture of air and fuel into the combustion chamber 11A.

(30) In order to allow the implementation of the invention, the injection module 20 comprises a pressure sensor 25, connected to the injection rail 22 and configured to measure a pressure value P in the injection rail 22. Such a pressure sensor 25 is configured to transmit the pressure measurement values P to the computer 30 of the vehicle.

(31) To be specific, with reference to FIG. 5, during its operation, the position Z of the piston 210 of the injection pump 21 alternates successively between a high position H and a low position B. When the control valve 24 is closed (OFF), the high position H of the piston 210 corresponds to a first phase I.sub.1 of injection of fuel into the injection rail 22 during which the pressure in the injection rail 22 increases, and the low position B to a second phase I.sub.2 during which the fuel is not compressed in the injection pump 21, not resulting in the injection of fuel into the injection rail 22 in which the pressure then remains constant.

(32) Indeed, when the control valve 24 is open, the pressure in the injection pump 21 and therefore in the injection rail 22 corresponds to a minimum pressure referred to as the predetermined initial pressure P.sub.i which is generally close to atmospheric pressure. When the control valve 24 is closed, two cases arise: if the piston 210 of the injection pump 21 is in the low position B, that is to say the fuel is not compressed by the piston 210, then the pressure value P in the injection rail 22 is equivalent to the predetermined initial pressure P.sub.i; likewise, if the piston 210 is in the high position H, that is to say the fuel is compressed by the piston 210, then the pressure value P in the injection pump 21 and therefore in the injection rail 22 is greater than the predetermined initial pressure P.sub.i.

(33) In this example, in which the piston 210 of the injection pump 21 is configured to pump fuel three times during a complete engine cycle, the first revolution and the second revolution of the crankshaft 13, each corresponding to half of an engine cycle, each thus correspond to a different position of the piston 210. In fact, when the control valve 24 is closed, if the crankshaft 13 is in its first revolution of rotation, then the piston 210, synchronized with the crankshaft 13, is configured to be in the first phase I.sub.1 of rising to the high position H, in which the pressure value P measured in the injection rail 22 is greater than the predetermined initial pressure P.sub.i. Likewise, if the crankshaft 13 is in its second revolution of rotation, then the piston 210 is configured to be in the second phase I.sub.2 of descent to the low position B, in which the pressure value P measured in the injection rail 22 is similar to the predetermined initial pressure P.sub.i. “Similar” means in this example that the pressure value P is equal to the predetermined initial pressure P.sub.i±1 MPa (megapascal).

(34) The odd number of phases I.sub.1 during which the piston 210 pumps fuel into the injection rail 22 during a complete engine cycle thus makes it possible to ensure that the fuel pressure in the injection rail 22 is different for the same angular position of the crankshaft 13 during two consecutive revolutions of said crankshaft 13, corresponding to two different configurations of the engine 10.

(35) c. Computer 30

(36) The computer 30, for example the main computer of the vehicle, makes it possible to control the injection of fuel into a defined combustion chamber 11A at a precise instant. To this end, the computer 30 is configured to control the control valve 24 in order to control the flow of fuel into the injection pump 21 and to control the closing of such an injection pump 21, allowing the introduction of fuel into the injection rail 22. In other words, the computer 30 is configured to control the pumping of fuel into the injection rail 22 by means of the injection pump 21 controlled by the control valve 24 at a given instant corresponding to the predetermined position of the crankshaft 13 known and described previously.

(37) Lastly, the computer 30 of the vehicle is configured to receive the data supplied by the position sensor 16 of the crankshaft 13 and by the pressure sensor 25 of the injection rail 22.

(38) 2/Method

(39) The invention will now be described in an exemplary embodiment with reference to FIGS. 5 and 6. The method for determining the position of the crankshaft 13 makes it possible to determine the synchronization of the engine 10. As the crankshaft 13 and the camshaft 15 are connected so as to allow simultaneous rotation, such a method could in an equivalent manner be described for determining the position of the camshaft 15, the position of which can be ascertained by means of the position sensor 16 of the crankshaft 13.

(40) In this example, the method firstly comprises a step E0 of starting up the engine 10, making it possible to actuate the rotation of the camshaft 15 and of the crankshaft 13. An initial pressure value P.sub.i is then measured in the injection rail 22 by means of the pressure sensor 25.

(41) The position sensor 16 then detects, in a step E1.sub.A, the reference position D.sub.0A of the crankshaft 13, by detecting the tooth-free space on the toothed wheel 130. A signal of detection of a tooth of the toothed wheel 130 is thus regularly sent to the computer 30.

(42) In this example, the position sensor 16 detects each tooth of the toothed wheel 130 and regularly transmits to the computer 30 a signal of detection of the presence of a tooth. The computer 30 then detects the reference position D.sub.0 of the crankshaft 13 when no signal is sent by the position sensor 16 for a predetermined period. However, it goes without saying that the position sensor 16 could equally well directly detect the reference position D.sub.0 of the crankshaft 13 and transmit a signal of detection of such a reference position D.sub.0 to the computer 30, for example.

(43) When the computer 30 detects the reference position D.sub.0A of the crankshaft 13, said computer 30 commands, for example, the closing of the control valve 24, in a step E2.sub.A. Alternatively, the closing of the control valve 24 may be commanded by the computer 30 after a predetermined time interval, depending on the arrangement of the injection pump 21. The computer 30 then detects, in a step E3.sub.A, an angular rotation of the crankshaft 13, referred to as the offset D.sub.A of the angular position of the crankshaft 13, from the reference position D.sub.0A. Such an offset D.sub.A of the angular position of the crankshaft 13 is between 30° and 240°, preferably 120° in the example of an engine operating by means of a starter motor and thus running at a rotation speed of 300 rpm, and corresponds to a time interval. The computer 30 could thus also trigger a time delay T, the duration of which corresponds to a predetermined time interval, for example 10 milliseconds. As shown in the graph in FIG. 5, this time delay T corresponds to the time elapsing between the detection of the reference position D.sub.0 and the instant at which the piston 210 of the injection pump 21 is in the high position H.

(44) In a step E4.sub.A, the pressure sensor 25 measures the pressure in the injection rail 22 and transmits the pressure value P.sub.A measured to the computer 30.

(45) Thus, when the computer 30 controls the control valve 24 of the injection pump 21 so that said injection pump 21 injects fuel into the injection rail 22, the pressure value P.sub.A of the fuel in the injection rail 22, measured at the end of the offset D.sub.A of the angular position of the crankshaft 13, has increased to reach a maximum if the engine 10 is in a first configuration, or has remained constant, if the engine 10 is in a second configuration.

(46) The pressure value P.sub.A is then compared with the predetermined initial pressure value P.sub.i.

(47) When the pressure value P.sub.A measured in step E4.sub.A is greater than a first predetermined threshold S.sub.1 as in a step E5.sub.A1, for example equal to the predetermined initial pressure P.sub.i plus at least 3 MPa, preferably 10 MPa, then the computer 30 deduces therefrom, in a step E6.sub.A1, that the engine 10 is in the first configuration, that is to say that the crankshaft 13 is indeed in its first revolution. The engine 10 is synchronized (Y).

(48) When the pressure value P.sub.A measured in step E4.sub.A is between a second predetermined threshold S.sub.2 and a third predetermined threshold S.sub.3 in a step E5.sub.A2, then the computer 30 deduces therefrom, in the step E6.sub.A2, either that the engine 10 is in the second configuration, that is to say that the crankshaft 13 is in its second revolution, or that the engine 10 is out of synchronization and has an anomaly (W). In this example, the second predetermined threshold S.sub.2 and the third predetermined threshold S.sub.3 correspond respectively to the predetermined initial pressure P.sub.i minus 1 MPa and to the predetermined initial pressure P.sub.i plus 1 MPa. In other words, it is said that the pressure value P.sub.A measured is similar to the predetermined initial pressure P.sub.i, that is to say for example equal to the predetermined initial pressure P.sub.i ±1 MPa.

(49) In the latter case, the method then comprises a new step E1.sub.B of detecting the second reference position D.sub.0B of the crankshaft 13, corresponding to the next revolution of the crankshaft 13, followed by a new step E2.sub.B of closing the control valve 24. After a second offset D.sub.B of the angular position of the crankshaft 13 or a second predetermined time interval (step E3.sub.B), the pressure in the injection rail 22 is again measured in a new step E4.sub.B and compared with the predetermined initial pressure P.sub.i. If the pressure value P.sub.B measured is greater than or equal to the first predetermined threshold S.sub.1 in a step E5.sub.B1, then the engine is indeed in its first configuration, that is to say the crankshaft 13 is indeed in its first revolution. The method includes a step E6.sub.B1 of validating the synchronization of the engine 10 (Y). If the pressure value P.sub.B measured is lower than the first predetermined threshold S.sub.1 in a step E5.sub.B2, then the method detects that the engine 10 is out of synchronization and has an anomaly (N) in a step E6.sub.B2.

(50) Such a method advantageously makes it possible to determine the position of the crankshaft and hence the operating phase of the engine, thus making it possible to synchronize the engine without the need for fuel injection. The method according to the invention thus makes it possible to limit the deterioration of the exhaust system as well as the pollution emitted by the vehicle.