Method for detecting a fuel leak in a high-pressure fuel injection circuit

Abstract

The invention relates to a method for detecting an external fuel leak in a high-pressure fuel injection circuit (130, 128, 120, 132) comprising a pump (130), a supply rail (120), at least one injector (132), a pressure sensor (25) in the rail (120), and a computer (10) configured to generate pump (130) activation events, the method being implemented during an injection cut-off phase and comprising the steps of comparing a pressure value measured by the sensor with a setpoint value of the fuel pressure; and if the measured value is lower than the setpoint value, running the high-pressure pump (130) in order to return the measured value to the setpoint value by triggering at least one pump event and by incrementing a pump event counter by at least one unit until the measured value is higher than or equal to the setpoint value. When the value of the pump event counter exceeds a threshold value, the method issues an alarm indicating a fuel leak.

Description

[0001] METHOD FOR DETECTING A FUEL LEAK IN A HIGH PRESSURE FUEL INJECTION CIRCUIT

[0002] DESCRIPTION

[0003] Technical field of the invention

[0004] The present invention relates to a method for detecting a fuel leak to the outside in a high pressure fuel injection circuit.

[0005] The invention also relates to a computer for implementing the method and a combustion engine comprising such a computer.

[0006] Technical background

[0007] The invention relates to the detection of fuel leaks to the outside in a high-pressure supply circuit of a combustion engine such as, for example, a diesel engine, or a dual-fuel engine, for example based on gasoline and liquefied petroleum gas (LPG) of a motor vehicle, or even a combustion engine integrated into a so-called "hybrid" propulsion system.

[0008] An injection engine typically comprises a fuel injection circuit, also called a high-pressure circuit, comprising a high-pressure pump adapted to put the fuel under high pressure (for example of the order of 100 bars), one or more fuel injectors in a combustion chamber, and an injector supply rail, which conveys the fuel from the outlet of the high-pressure pump to the injectors.

[0009] When controlling a high-pressure system of a combustion engine using dual fuel, functions for monitoring the behavior of the high-pressure fuel system are necessary to meet the requirements for supervising the operation of the whole system.

[0010] For this type of system, and particularly for safety reasons, it is necessary to have the ability to alert the user in the event of an external fuel leak.

[0011] Such a so-called external leak is a fuel leak to the outside of the high-pressure fuel injection circuit.

[0012] The special case of dual-fuel operating modes includes operating cases which are not controlled by the diagnostic functions available in the generic version of the pressure control system.

[0013] Indeed, when operating in pure LPG mode, the high pressure pump for the gasoline injection can continue to operate to satisfy a setpoint of the requested high pressure so as to anticipate and prepare the resumption of gasoline injection or dual fuel. During such a phase, if a fuel leak to the outside is present, it is amplified and continues because the control function of the high pressure pump tends to compensate for the loss of pressure induced by the fuel leak.

[0014] Currently, diagnostics used to detect a fuel leak can determine an external leak, problems with mechanical components of the high pressure system, problems with mechanical components of the low pressure system or leaks at the injectors.

[0015] These diagnostics are based on the analysis of the difference between the pressure setpoint that must prevail in the high-pressure circuit, for example in the injector supply rail, and the actual pressure, the value of which is known using a pressure measuring sensor. Document DE102013101850 discloses a device for detecting a leak in a high-pressure fuel injection circuit, which comprises a fuel pressure sensor in the circuit, and a leak detection circuit that analyzes the shape of the output signal from the fuel pressure sensor in the circuit, to determine a fuel injection period, and to determine a leak as a function of a pressure variation in the fuel injection circuit during an injection period, and during a longer period of time including the injection period.

[0016] In the case of a dual-fuel engine, for example when the engine is operating in pure LPG mode, such types of diagnostic procedures cannot be implemented because they require high-pressure pump activity and injection.

[0017] In fact, when operating in LPG mode, conventional gasoline injection is disabled. Normally, the fuel pressure in the rail remains stable in the rail, but this behavior may be slightly different.

[0018] Pressure can indeed:

[0019] - increase by thermal phenomenon, because the fuel sees its temperature increase in an enclosed space, and therefore sees its pressure increase;

[0020] - decrease by the same thermal phenomenon if the fuel temperature decreases;

[0021] - decrease due to internal system leaks that are tolerated such as leaks from the outlet valve or pressure reducing valve.

[0022] Since the temperature information is not sufficiently precise because it comes from a model and since internal leaks can vary from one component to another, it is not possible to base an external leak diagnosis directly on variations in the pressure value.

[0023] Known diagnostic methods do not allow detection of possible fuel leaks to the outside when injection is inactive.

[0024] Summary of the invention

[0025] The invention provides a method for detecting a fuel leak to the outside in a high-pressure fuel injection circuit in a combustion engine comprising: - a high-pressure pump;

[0026] - at least one fuel injector;

[0027] - a fuel supply rail extending between the outlet of the high pressure pump and each of at least one fuel injector;

[0028] - a sensor for measuring the value of the pressure prevailing in said rail;

[0029] - a computer configured to generate pump events each representative of an activation of the high pressure pump; the method being implemented during an operating phase during which a fuel injection by said injection circuit is cut off, and the method comprising the following cycle of steps:

[0030] - E3 compare a value of the pressure measured by the sensor, noted VPM, with a set value of the fuel pressure in the rail, noted VPC;

[0031] - E4) if VPM is less than VPC, operate the high pressure pump in order to bring the measured pressure value VPM back to the set pressure value VPC, by triggering at least one pump event and incrementing a pump event counter by at least one unit per pump event until VPM is greater than or equal to VPC; and

[0032] - E8) when the pump event counter value exceeds a threshold value generate an alarm indicating a fuel leak.

[0033] According to other characteristics of the process:

[0034] - when during a determined duration, no pump event is triggered, the method comprises a step E6) of decrementing the pump event counter by at least one unit per determined duration without pump event;

[0035] - the method is implemented each time the fuel injection is cut off by said fuel injection circuit;

[0036] - prior to the implementation of a said cycle of steps, the method comprises a step E7) of initializing the value of the pump event counter;

[0037] - each pump event is an activation of the high pressure pump for at least a short duration.

[0038] The invention also proposes a calculator characterized in that it is configured to implement a method for detecting a fuel leak according to the invention.

[0039] The invention also provides a combustion engine comprising a high pressure fuel injection circuit comprising:

[0040] - a high pressure pump;

[0041] - at least one fuel injector;

[0042] - a fuel supply rail extending between the outlet of the high pressure pump and each of at least one fuel injector;

[0043] - a sensor for measuring the value of the pressure prevailing in said rail,

[0044] - and a computer configured to implement a method for detecting a fuel leak to the outside in said circuit according to the invention. According to other characteristics of the combustion engine:

[0045] - it has a dual fuel injection system;

[0046] - it includes a dual injection system, direct for gasoline and indirect for liquid gas, particularly liquefied petroleum gas (LPG).

[0047] Brief description of the figures

[0048] Other characteristics and advantages of the invention will appear during the reading of the detailed description which follows for the understanding of which reference will be made to the appended drawings in which:

[0049] [Fig. 1] - Figure 1 is a schematic representation of a dual injection system, direct and indirect, of fuels into cylinders of a gasoline and LPG combustion engine;

[0050] [Fig. 2] - Figure 2 is a schematic representation of the steps of a fuel leak detection method according to an exemplary embodiment of the invention;

[0051] [Fig .3] - Figure 3 is a diagram illustrating an example of variation of different parameters during the implementation of the process.

[0052] Detailed description of the invention

[0053] In the following description, identical, similar or analogous elements will be designated by the same reference numbers.

[0054] Figure 1 schematically shows a dual injection system 1 of known general design.

[0055] In the system, gasoline is transferred from a tank 112 by a low pressure pump 114 which is for example an electric pump capable of compressing the fuel for example to a pressure of approximately 5 bars.

[0056] The high pressure zone comprises a supply rail 120 connected to a pipe 128 equipped with a high pressure pump 130 (for example with piston(s) actuated by at least one cam of a camshaft of the combustion engine equipped with such a double injection system) whose function is to increase the low pressure of approximately 5 bars prevailing in the supply pipe 116 up to a high pressure for example equal to approximately 100 bars.

[0057] The fuel, for example gasoline, is then injected directly into each of the cylinders (not shown) of the heat engine by a series of high-pressure injectors 132 ensuring direct injection from the high-pressure supply rail 120.

[0058] The supply line 116 may be equipped with a pressure regulator 122 which maintains the pressure in the supply line 116 at a substantially constant value. The low pressure zone 118 comprises a pipe 124 which is connected directly to a tank 113 of LPG gas.

[0059] A low pressure zone 118 is here in the form of a low pressure tubular ramp, which is connected to a series of low pressure injectors 126 which inject “gas” fuel into the intake duct, not shown, of the heat engine.

[0060] Alternatively, the low pressure zone may have only one low pressure injector that injects fuel into the intake tract.

[0061] The intake duct is connected to the various combustion chambers, not shown, of the combustion engine cylinders.

[0062] For implementing the method according to the invention for detecting a fuel leak to the outside, here in the high-pressure fuel injection circuit (130, 128, 120, 132) (also referred to as the high-pressure circuit), a sensor 25 is also provided for measuring the pressure value prevailing in the supply rail 120.

[0063] The leak detection system 1 also comprises at least one computer 10, which may be a controller, a microcontroller, processor, microprocessor, FPGA, or any other electronic component configured for implementing the leak detection method described below.

[0064] With reference to Figure 2, we will now describe the leak detection method implemented according to the invention.

[0065] The method is only implemented if the engine is running, which is verified by the computer 10 during a preliminary step E0, for example but not limited to, from a non-zero value of the engine speed Rpm.

[0066] In a non-limiting manner, the method preferably comprises a step E1 of verification, by the computer 10, that the operating context of the engine allows the implementation of fuel leak detection.

[0067] This step may, for example, include checking the following:

[0068] - the value of the engine speed;

[0069] - the quantity of fuel injected;

[0070] - the set value of the pressure gradient of the injected fuel;

[0071] - the time elapsed since start-up and the VPC value of the fuel pressure setpoint in rail 120.

[0072] The system must have been adapted at least once since its beginning of life, the adaptation aiming to eliminate the dispersion which can appear between several components on different vehicles.

[0073] If the check carried out in step E1 is positive, during a step E2, the computer 10 determines whether the engine is in a phase of its operation during which fuel injection by the injection circuit is cut off.

[0074] If the computer 10 determines that the engine is in a stable injection cut-off period, during a step E3, the computer 10 makes a comparison between a VPM value of the pressure measured by the sensor 25 with a VPC value of the fuel pressure in the rail 120.

[0075] If VPM < VPC, during a step E4, the computer 10 causes the high pressure pump 130 to start operating by:

[0076] - triggering at least one first EP pump event; and

[0077] - causing an increment E5 of a pump event counter CEP by at least one unit for each EP pump event triggered per time segment. If VPM remains lower than VPC, step E4 is repeated in a loop as a series of EP pump events until VPM >= VPC.

[0078] When the VCEP value of the CEP pump event counter is greater than a determined VCEP threshold value (VCEP > VCEP), during a step E8, the computer 10 then generates an alarm, or alert, which can be an audible or visual alarm.

[0079] For example, the leak detection system 1 may comprise an interface such as a screen or an indicator light 11, which may light up or display an alert message during step 120 to draw the attention of the driver of the vehicle to the detected leak. For example, a dashboard indicator light may light up and / or a message on the central display of the vehicle may be displayed, indicating the detection of a leak and encouraging the driver to stop as quickly as possible to have the vehicle checked. In embodiments, step E8 may also comprise the adoption by the vehicle of a degraded engine operating mode and / or a capping of the vehicle speed until the vehicle is taken to a control and maintenance center.

[0080] When for a determined duration T no EP pump event is triggered by the computer 10, the computer 10 causes a decrement E6 of the CEP pump event counter by at least one unit.

[0081] Prior to its implementation, the method may comprise a step E7 of initializing the VCPE value of the CPE pump event counter.

[0082] In Figure 3, as a function of the elapsed time indicated on the abscissa, we have represented from bottom to top:

[0083] - variations in the measured VPM value;

[0084] - the VPC setpoint value;

[0085] - variations in engine speed Rpm;

[0086] - variations in the CEP pump event counter representative of the activation of the high pressure pump.

[0087] As can be seen, when the measured value VPM is lower than the threshold value VPC, the pump is activated - here three times consecutively - with a corresponding increment of three units of the VCEP value of the CEP counter.

[0088] Then, for a determined duration T, VPM remains higher than VPC with the consequence of a decrement of one unit of the CEP counter.

Claims

CLAIMS 1. Method for detecting a fuel leak to the outside in a high pressure fuel injection circuit (130, 128, 120, 132) in a combustion engine comprising: - a high pressure pump (130); - at least one fuel injector (132); - a fuel supply rail (120) extending between the outlet of the high pressure pump (130) and each of at least one fuel injector (132); - a sensor (25) for measuring the value of the pressure prevailing in said rail (120); - a computer (10) configured to generate pump events (EP) each representative of an activation of the high pressure pump; the method being implemented during an operating phase during which a fuel injection by said injection circuit is cut off, and the method comprising the following cycle of steps: - E3 compare a value of the pressure measured by the sensor, noted VPM, with a set value of the fuel pressure in the rail (120), noted VPC; - E4) if VPM is less than VPC, operate the high pressure pump (130) in order to bring the measured pressure value VPM back to the set pressure value VPC, by triggering at least one pump event (EP) and incrementing (E5) a pump event counter (CEP) by at least one unit per pump event (EP) until VPM is greater than or equal to VPC; and - E8) when the value (VCEP) of the pump event counter exceeds a threshold value (VCEPthreshold), generate an alarm indicating a fuel leak.

2. Method according to claim 1, characterized in that, when during a determined duration (T), no pump event (EP) is triggered, the method comprises a step E6) of decrementing the pump event counter (CEP) by at least one unit per determined duration (T) without pump event (EP).

3. Method according to any one of the preceding claims, characterized in that it is implemented during each cutoff of the fuel injection by said fuel injection circuit (130, 128, 120, 132).

4. Method according to any one of the preceding claims, characterized in that, prior to the implementation of a said cycle of steps, it comprises a step E7) of initializing the value of the pump event counter (CPE).

5. Method according to any one of the preceding claims, characterized in that each pump event (EP) is an activation of the high pressure pump (130) for at least a short duration.

6. Calculator (10), characterized in that it is configured to implement a method for detecting a fuel leak according to any one of claims 1 to 5.

7. Combustion engine comprising a high pressure fuel injection circuit (130, 128, 120, 132) comprising: - a high pressure pump (130); - at least one fuel injector (132); - a fuel supply rail (120) extending between the outlet of the high pressure pump (130) and each of at least one fuel injector (132); - a sensor (25) for measuring the value (VPC) of the pressure prevailing in said rail (120), - and a computer (10) configured to implement a method for detecting a fuel leak to the outside in said circuit according to any one of claims 1 to 5.

8. Combustion engine according to the preceding claim, characterized in that it comprises a dual fuel injection assembly.

9. Combustion engine according to the preceding claim, characterized in that it comprises a dual injection assembly, direct injection of gasoline (130, 128, 120, 132) and indirect injection (113, 124, 118, 126) of liquid gas, in particular liquefied petroleum gas LPG.

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