Method for detecting a gas leak in the intake circuit of a motorization device

Abstract

This method for detecting a gas leak in an air intake circuit of an internal combustion engine device equipped with a turbocharger comprises the following steps: Measurement (step 22) of a current boost pressure in the air intake circuit; Comparison (step 23) of a current turbocharger rotation speed with a theoretical turbocharger rotation speed or of a current position of a boost actuator with a theoretical position of said boost actuator, said theoretical turbocharger rotation speed or said theoretical position of said boost actuator allowing, in the absence of a leak, to obtain the measured current boost pressure;Determination (step 24) of the presence of a gas leak when the difference between the actual turbocharger speed and the theoretical turbocharger speed, or between the actual position of the boost actuator and the theoretical position of said boost actuator, is greater than a predetermined leak detection threshold for a predetermined period. Figure for the summary: Fig 2;

Description

Title of the invention: Method for detecting a gas leak in the intake circuit of a motorization device. Technical field

[0001] The invention relates, in general, to the detection of air leaks or intake gas mixture in a combustion engine of a motor vehicle.

[0002] The invention relates in particular to the detection of intake air leaks between an engine and a turbocharger of a compression-ignition (diesel) or supercharged spark-ignition engine. Previous techniques

[0003] Figure 1 schematically represents a motor vehicle engine 1 comprising an engine 2, here a four-cylinder engine, comprising an intake manifold 3 connected to an intake circuit 4 equipped with an air filter 5, a cooler 6, an air flap 7 and an exhaust manifold 8 recovering the exhaust gases from combustion to deliver them at the outlet to an exhaust circuit 9 equipped with a gaseous effluent aftertreatment system not shown.

[0004] The drive device 1 also includes a supercharging system comprising a turbocharger 10 equipped with a compressor 11 and a turbine 12 linked by a shaft 13 to the compressor 11.

[0005] The turbine 12 can be bypassed by means of a discharge valve 14.

[0006] The pressure downstream of the compressor 11 in the intake circuit 4 is the boost pressure.

[0007] In some variants, the discharge valve 14 is replaced by a variable geometry turbine whose blades can be oriented and allow the energy extracted from the exhaust gases to be regulated.

[0008] The exhaust gases can also be reinjected with the air from the intake circuit 4 using recirculation circuits not shown.

[0009] Generally, the boost pressure increases when the relief valve 14 closes and the exhaust gases pass through the turbine 12. Conversely, if the relief valve 14 is open, the exhaust gases do not rotate the turbine 12 and the boost pressure decreases due to a reduced effort of the compressor 11 connected by the shaft 13 to the turbine 12.

[0010] To produce the torque necessary to drive the vehicle according to a driver demand, materialized by pressing the vehicle's accelerator pedal, it is necessary to adjust the load of the motor 2, which depends on its Mass air flow rate. The mass air flow rate depends on the pressure in the intake manifold 3, which is the parameter to be measured to determine the mass air flow rate.

[0011] The mass air flow rate is adjustable by adjusting the air flap 7 or the discharge valve 14 which modifies the boost pressure.

[0012] However, at low load, the relief valve 14 is open and the air flap 7 is adjusted to regulate the pressure in the intake manifold 3 to a closed loop setpoint.

[0013] Conversely, at higher load, the air flap 7 is already fully open and the pressure in the intake manifold 3 is adjusted with the relief valve 14. In this situation, with the air flap 7 open, the boost pressure and the pressure in the intake manifold 3 are the same. The boost pressure is therefore set to a closed-loop setpoint, which is equivalent to setting the pressure in the intake manifold 3.

[0014] The fuel is injected so that the richness of the air-fuel mixture corresponds to a given value.

[0015] In a compression-ignition engine (of the diesel type), the air flap 7 is mostly open and the mass flow of air is adjusted by means of the discharge valve 14 as explained above in the case of a spark-ignition engine.

[0016] To detect leaks in the intake circuit 4, existing solutions rely on comparing the boost pressure with its setpoint, which depends on the engine operating point 2. This allows for the detection of an air leak when the system is no longer able to compensate for the decrease in boost pressure. A discrepancy between the setpoint and the measured value indicates the presence of a leak in the intake circuit 4.

[0017] Consequently, small leaks, causing a slight decrease in boost pressure, are compensated by an automatic closure of the relief valve 14 and are therefore not detectable unless the relief valve 14 is already fully closed and cannot compensate for the pressure loss.

[0018] Thus, only large leaks are reliably detected, with holes on the order of one centimeter in diameter diverting approximately 10% of the airflow. Small leaks go undetected, creating a safety hazard for the vehicle and its passengers. Description of the invention

[0019] The present invention therefore aims to overcome the aforementioned drawbacks and to facilitate the detection of small leaks in addition to the detection of larger leaks.

[0020] The present invention relates to a method for detecting a gas leak in an air intake circuit of an internal combustion engine equipped with a turbocharger, the method comprising the following steps: - Measurement of a current boost pressure in the air intake circuit; - Comparison of a current turbocharger rotation speed with a theoretical turbocharger rotation speed or of a current position of a boost actuator with a theoretical position of said boost actuator, said theoretical turbocharger rotation speed or said theoretical position of said boost actuator allowing, in the absence of leakage, to obtain the current measured boost pressure; - Determination of the presence of a gas leak when the difference between the current rotation speed of the turbocharger and the theoretical rotation speed of the turbocharger or between the current position of the boost actuator and the theoretical position of said boost actuator is greater than a predetermined leak detection threshold for a predetermined period.

[0021] Thus, this process makes it possible to detect in a non-intrusive way large as well as small leaks of intake gas downstream of the compressor in order to prevent any safety risk to the vehicle and the passengers of a motor vehicle.

[0022] In one embodiment, it is verified at the beginning of the implementation of the process that the boost pressure is equal to a pressure in an air intake manifold of the drive device and that a motor of the drive device is at a constant operating point.

[0023] Advantageously, a mapping makes it possible to link the values ​​of a turbocharger rotation regime to the positions of a boost actuator.

[0024] Advantageously, the boost actuator is a relief valve or a set of turbine blades of the turbocharger.

[0025] Advantageously, the possible theoretical values, in the absence of leakage, of turbocharger rotation speed and boost pressure are contained in a map.

[0026] In one embodiment, a process consolidation step is carried out by requiring the step of determining the presence of a gas leak to be repeated a number of times greater than a predefined threshold.

[0027] Advantageously, the process is implemented by an on-board computer of a motor vehicle. Brief description of the drawings

[0028] Other objects, features and advantages of the invention will become apparent from the following description, given solely by way of non-limiting example, and made with reference to the accompanying drawings in which:

[0029] [Fig. 1], which has already been mentioned, schematically illustrates various elements of a motor vehicle drive system involved in the implementation of a method according to the invention; and

[0030] [Fig.2] illustrates the different stages of the gas leak detection process according to the invention. Detailed description of at least one embodiment

[0031] Figure 2 shows the different stages of the leak detection process, an example of which is detailed below.

[0032] This method is intended to be implemented in an on-board computer 15 embedded in a motor vehicle, dedicated for example to engine control.

[0033] This on-board computer 15 is duly programmed to implement the various stages of the leak detection process.

[0034] The method being applied to the detection of a leak in a conventional motorization device, the following description will also be made with reference to [Fig.1].

[0035] In the implementation of the method for detecting a gas leak in the intake circuit of the drive device 1, it can first be verified in a step 21 that the boost pressure in the intake circuit 4 is equal to the pressure in the intake manifold 3 and that the motor 2 of the drive device 1 is at a constant operating point for a minimum time.

[0036] Indeed, when the boost pressure is identical to the pressure in the intake manifold 3, airflow control is simplified because only the boost actuator regulates it, with the air flap 7 then open. Depending on the configuration of the drive unit 1, the boost actuator is either the wastegate 14 or the set of adjustable turbine blades 12 of the turbocharger 10. Furthermore, when the engine 2 is at a constant operating point, measurements and subsequent steps are also facilitated since the parameters of the engine 2 do not change, or change very little, over time.

[0037] It is also verified that the relief valve 14 is not completely closed or that the turbine blades are not at their maximum orientation in the closed position. If this is the case, it is not possible to regulate the turbocharger's rotational speed, and this method does not allow for the identification of a leak.

[0038] A step 22 of measuring the current boost pressure is then carried out in the air intake circuit 4. This measurement can be carried out by measuring the pressure in the intake manifold 3 when it is identical to the boost pressure.

[0039] Then, from this pressure measurement and a map stored in the on-board computer 15, it is possible to determine the theoretical rotational speed of the turbocharger 10 required to obtain such a boost pressure. Indeed, the map contains the possible theoretical values, in the absence of leaks, of the turbocharger 10 rotational speed and the boost pressure.

[0040] A step 23 is then performed to compare the actual operating speed of the turbocharger 10 with the theoretical operating speed of the turbocharger 10 deduced using the mapping described above. This theoretical operating speed of the turbocharger 10 allows, in the absence of leaks, the measured actual boost pressure to be obtained. The actual operating speed of the turbocharger 10 is, for example, measured using a sensor whose primary purpose is to measure the speed of the turbocharger 10 in order to authorize or prevent the engine 2 from increasing its load.

[0041] Thus, if a leak is present in the intake circuit 4 and the boost pressure decreases, the turbocharger speed will automatically increase to compensate for this pressure loss. The comparison described above makes it possible to identify that such compensation is taking place and allows this leak detection method to be implemented.

[0042] By equivalence, it is possible to replace the turbocharger 10 speed values ​​with the position of the boost actuator. A map, either the same as before or a second map, allows the turbocharger 10 speed values ​​to be linked to the positions of the boost actuator, whether it be the wastegate 14 or the turbine vanes 12. Thus, the current turbocharger 10 speed is replaced by the current position of the boost actuator, and the theoretical turbocharger 10 speed is replaced by the theoretical position of the boost actuator, allowing, in the absence of leaks, the measured current boost pressure to be obtained.

[0043] A step 24 for determining the presence of a gas leak is then carried out. The on-board computer 15 concludes that there is a potential leak in the intake circuit 4 when the difference between the actual rotational speed of the turbocharger 10 and the theoretical rotational speed of the turbocharger 10, or equivalently between the actual position of the boost actuator and the theoretical position of said actuator, is significant. supercharger actuator, is above a predetermined threshold for a predetermined period, for example for more than a few seconds.

[0044] Finally, a step 25 consolidating the conclusion of the on-board computer 15 is performed if it is necessary to confirm the presence of a leak in the intake circuit 4. This step 25 requires repeating the preceding steps above a number of times exceeding a predefined threshold within a predefined period. For example, a threshold of five leak detections per minute may be defined to definitively establish that a leak is present in the intake circuit 4.

[0045] This method makes it possible in particular to detect leaks of 5% of the flow of the intake circuit 4, and originating from small holes of three millimeters.

Claims

1.

2. Demands Method for detecting a gas leak in an air intake circuit (4) of an internal combustion engine device (1) equipped with a turbocharger (10), characterized in that it comprises the following steps: - Measurement (step 22) of a current boost pressure in the air intake circuit (4); - Comparison (step 23) of a current rotational regime of the turbocharger (10) with a theoretical rotational regime of the turbocharger (10) or of a current position of a boost actuator (14) with a theoretical position of said boost actuator (14), said theoretical rotational regime of the turbocharger (10) or said theoretical position of said boost actuator (14) allowing, in the absence of leakage, obtaining the current measured boost pressure; - Determination (step 24) of the presence of a gas leak when the difference between the current rotational speed of the turbocharger (10) and the theoretical rotational speed of the turbocharger (10) or between the current position of the boost actuator (14) and the theoretical position of said boost actuator (14) is greater than a predetermined leak detection threshold for a predetermined period, the process comprising firstly a verification step (step 21) that the boost pressure is equal to a pressure in an air intake manifold (3) of the drive device (1) and that a motor (2) of the drive device (1) is at a constant operating point. Method according to claim 1, wherein a mapping makes it possible to link the values ​​of a turbocharger rotation regime (10) to the positions of a boost actuator (14).

3. A method according to any one of claims 1 and 2, wherein the boost actuator is a relief valve (14) or a set of turbine blades (12) of the turbocharger (10).

4. A method according to any one of claims 1 to 3, wherein the pairs of possible theoretical values, in the absence of leakage, of turbocharger (10) rotation speed and boost pressure are contained in a map.

5. A method according to any one of claims 1 to 4, wherein a step (25) of consolidating the method is carried out by requiring the repetition of step (24) of determining the presence of a gas leak a number of times greater than a predefined threshold.

6. A method according to any one of claims 1 to 5, characterized in that it is implemented by an on-board computer (15) of a motor vehicle.

Images