Method for increasing the torque of a heat engine, corresponding heat engine, and motor vehicle comprising such a heat engine

Abstract

This method for increasing the torque of a heat engine (4) comprising an air intake circuit (8) provided with a compressor (14) configured to modify an air intake mass flow rate of the heat engine (4) comprises at least the following steps: - a step of determining (40) a downstream air pressure increase setpoint (Pdownstream) of the compressor; - a step of decreasing (44) an upstream air pressure (Pupstream) of the compressor performed independently of the compressor (14); and - a step of increasing (46) a compression ratio (rc) of the compressor (14) so as to increase the downstream air pressure (Pdownstream) of the compressor according to said setpoint.

Description

[0001] DESCRIPTION

[0002] Method for increasing the torque of a heat engine, corresponding heat engine, and motor vehicle comprising such a heat engine

[0003] Technical field

[0004] The technical field of the present invention is petrol or diesel heat engines for motor vehicles.

[0005] In particular, the present invention relates to a method for increasing the torque of a heat engine, a heat engine comprising a computer configured to implement such a method, and a motor vehicle comprising such a heat engine.

[0006] Prior art

[0007] A heat engine of a motor vehicle generally comprises an air intake circuit, a fuel intake circuit, a plurality of combustion chambers and an exhaust circuit for the combustion gases of the heat engine.

[0008] Such a heat engine may comprise a turbocharger provided with a compressor, a turbine and a common shaft on which the compressor and the turbine are mounted. The compressor is arranged in the air intake circuit so as to increase the mass flow rate of air admitted into the combustion chambers. The turbine is arranged in the exhaust circuit of the combustion gases so as to expand the exhaust gases passing through it and drive the compressor.

[0009] During a sudden acceleration of the motor vehicle, a high torque is requested from the heat engine. To grant such torque, the compressor must provide a high compression ratio.

[0010] In certain situations, in particular when the heat engine is operating at low rpm, the high compression ratio requested from the compressor may be higher than the compressor's compression boundary, so the compressor cannot provide such a high compression ratio.

[0011] In addition, when such a high compression ratio is requested from the compressor, pressure oscillations may appear in the vicinity of the compressor and damage it.

[0012] Disclosure of the invention

[0013] Therefore, the objective of the present invention is to overcome all or part of the aforementioned drawbacks, to allow the torque of a heat engine to be increased, to allow the compression ratio of a compressor of the heat engine to be increased, and to reduce pressure oscillations occurring in the vicinity of the compressor of the heat engine.

[0014] The invention relates to a method of increasing the torque of a motor vehicle heat engine, the heat engine comprising an air intake circuit provided with a compressor configured to modify an air intake mass flow rate of the heat engine, the method comprising at least the following steps:

[0015] - a step of determining a compressor downstream air pressure increase setpoint;

[0016] - a step of decreasing an upstream air pressure of the compressor performed independently of the compressor; and

[0017] - a step of increasing a compression ratio of the compressor so as to increase the downstream air pressure of the compressor according to said setpoint.

[0018] By “a step of decreasing an upstream air pressure of the compressor performed independently of the compressor” is meant that the decrease in the upstream air pressure of the compressor is not performed by the compressor.

[0019] Decreasing the compressor upstream air pressure increases the compressor compression ratio, defined as the value of the compressor downstream air pressure divided by the value of the compressor upstream air pressure, and also increases a corrected air mass flow rate through the compressor.

[0020] Thus, an operating point of the compressor on a compressor field mapping is modified, the operating point being able to deviate from a maximum compression curve of the compressor and allowing a greater increase in the downstream air pressure of the compressor, the maximum compression curve of the compressor being an intrinsic feature of the compressor.

[0021] Decreasing the compressor upstream air pressure also changes the pressure oscillations or pressure pulsations occurring upstream of the compressor and may change the air spray conditions of a compressor impeller.

[0022] Advantageously, the step of determining a compressor downstream air pressure increase setpoint comprises a sub-step of determining a deviation between an initial compressor compression ratio and a maximum compressor compression ratio, the step of decreasing a compressor upstream air pressure being carried out when said deviation is insufficient to increase, at constant compressor upstream air pressure, the compressor downstream air pressure according to said setpoint.

[0023] Thus, the step of decreasing an upstream air pressure of the compressor is implemented only when the compressor cannot, at a constant upstream air pressure of the compressor, provide a compression ratio making it possible to increase the downstream air pressure of the compressor according to said increase setpoint.

[0024] Said deviation may be determined based on a compressor field mapping and an rricinitial corrected compressor air mass flow calculated as: rrirbeing the actual air mass flow rate of the compressor;

[0025] Prefbeing a reference pressure;

[0026] Tupstream being the air temperature upstream of the compressor;

[0027] Pupstream being the upstream air pressure of the compressor;

[0028] Tref being a reference temperature.

[0029] By determining the initial compressor operating point on the compressor field mapping from the initial compressor compression ratio and therricinitial corrected compressor air mass flow rate, said deviation between the initial compressor operating point and the maximum compressor compression ratio of the apartment compressor to the maximum compressor compression curve is determined.

[0030] It is also noted that a variation in the air temperature upstream of the compressor changes the value of the corrected air mass flow rate of the compressor and therefore the operating point of the compressor on the compressor mapping.

[0031] The step of decreasing an air pressure upstream of the compressor can comprise partially closing an air intake valve arranged upstream of the compressor.

[0032] Partial closing of the air intake valve can be performed incrementally, with an increase in the compressor compression ratio being calculated at each increment and then compared with a growth rate of a maximum compressor compression curve.

[0033] Thus, it is ensured that closing the air intake valve makes it possible to increase said deviation at each increment.

[0034] Alternatively, the partial closing position of the air intake valve is predetermined, during preliminary tests of the heat engine, and recorded.

[0035] Advantageously, the step of decreasing an upstream air pressure of the compressor is carried out such that the upstream air pressure of the compressor is between 0.95 bar and 1.00 bar, in particular between 0.97 bar and 1.00 bar, when the engine is operating at an altitude close to 0 m corresponding to sea level where the external pressure is slightly greater than 1 bar. More generally, the pressure decrease caused by the partial closure of the air intake valve is advantageously at most equal to 50 mbar, and preferably between 20 and 30 mbar.

[0036] The step of determining a compressor downstream air pressure increase setpoint may comprise calculating said setpoint based on a motor vehicle acceleration setpoint and a heat engine rpm.

[0037] The acceleration setpoint of the motor vehicle can be determined according to the depression of an accelerator pedal of the motor vehicle or a force value exerted on the accelerator pedal of the motor vehicle or of a PLC controlling the motor vehicle.

[0038] The present invention also relates to a heat engine for a motor vehicle, the heat engine comprising an air intake circuit provided with a compressor configured to modify an air intake mass flow rate of the heat engine and an air intake valve arranged upstream of the compressor, the heat engine further comprising a computer configured to implement a method for increasing the torque of the heat engine as defined above.

[0039] The heat engine may further comprise a combustion gas exhaust circuit of the heat engine and an exhaust gas recirculation circuit from the exhaust circuit to the air intake circuit so that the recirculation circuit opens outwards into the air intake circuit upstream of the compressor and downstream of the air intake valve.

[0040] The present invention also relates to a motor vehicle comprising a heat engine as defined above.

[0041] Brief description of the drawings

[0042] Other aims, characteristics and advantages of the invention will become apparent on reading the following description, given solely by way of non-limiting example, and made with reference to the appended drawings wherein:

[0043] [Fig 1 ] schematically illustrates a motor vehicle according to the present invention;

[0044] [Fig 2] schematically illustrates a heat engine according to a first exemplary embodiment of the invention;

[0045] [Fig 3] illustrates a compressor field mapping of the heat engine of Figure 2;

[0046] [Fig. 4] schematically illustrates a method for increasing the torque of the heat engine in Figure 2 according to the present invention;

[0047] [Fig 5] illustrates measurements made on a heat engine during the implementation of the method described in Figure 4; and

[0048] [Fig 6] illustrates a heat engine according to a second exemplary embodiment of the invention. Detailed description

[0049] Figure 1 schematically shows a motor vehicle 2 comprising an internal combustion heat engine 4, in particular a petrol or diesel heat engine 4.

[0050] As shown schematically in Figure 2, the heat engine 4 comprises a cylinder block 6, an air intake circuit 8 supplying air to the cylinder block 6, a fuel supply circuit (not shown) supplying fuel to the cylinder block 6, and a combustion gas exhaust circuit 10 of the cylinder block 6 of the heat engine 4. The cylinder block 6 is equipped with three in-line cylinders. Optionally, the cylinder block 6 may comprise camshaft phase shifters at the intake and exhaust.

[0051] The air intake circuit 8 comprises an air inlet, an air filter 12 capable of filtering the air coming from the air inlet, a compressor 14 capable of modifying, in particular increasing, the mass flow rate of the air coming from the air filter 12, an air cooler 16 capable of decreasing the temperature of the air coming from the compressor 14, a throttle box 18 capable of adjusting the flow rate of air coming from the air cooler 16, and an intake manifold (not referenced) capable of distributing the air coming from the throttle box 18 into the cylinders of the cylinder block 6.

[0052] The air intake circuit 8 further comprises an air intake valve 20 arranged upstream of the compressor 14 and downstream of the air filter 12, an upstream pressure sensor 22 arranged upstream of the compressor 14 and downstream of the air intake valve 20, an upstream temperature sensor 24 arranged upstream of the compressor 14 and downstream of the air intake valve 20, a downstream pressure sensor 26 arranged downstream of the compressor 14 and upstream of the air cooler 16, and an upstream air mass flow sensor 28 arranged upstream of the compressor 14 and downstream of the air intake valve 20.

[0053] The air intake valve 20 is capable of closing to prevent the air flow through the air intake circuit 8 and capable of opening at least in part to allow air to pass through the air intake circuit 8.

[0054] The combustion gas exhaust circuit 10 comprises an exhaust manifold (not referenced) able to collect the exhaust gases coming from the cylinder block 6, a turbine 30 able to expand the exhaust gases coming from the exhaust manifold, and a catalyst 32 able to reduce the polluting emissions of the exhaust gases coming from the turbine 30.

[0055] The heat engine 4 comprises a shaft 34 on which the compressor and the turbine 30 are mounted so as to form a turbocharger. The turbocharger is able to increase the torque of the heat engine 4 by increasing the mass flow rate of the air admitted into the cylinder block 6, the turbine 30 expanding the exhaust gases passing through it in order to return the energy taken from the compressor 14 compressing the intake air.

[0056] Optionally, the turbine 30 may have a variable geometry and thus be able to adjust the amount of energy taken from the exhaust gases passing through it.

[0057] The heat engine 4 further comprises a computer 36 able to communicate with the air intake valve 20, with the upstream and downstream pressure sensors 22, 26, with the upstream temperature sensor 24, and with the upstream air mass flow rate sensor 28.

[0058] The computer 36 is furthermore able to implement a method for increasing the torque of the heat engine 4 which will be detailed below.

[0059] Figure 3 shows a field mapping of the compressor 14 of the heat engine 4.

[0060] The x-axis of the mapping corresponds to the corrected air mass flow rate mcof the compressor 14 calculated as:

[0061] . PrefJPupstream mc= mr

[0062] ) / T upstream1ref

[0063] With:

[0064] - mrthe actual air mass flow rate of the compressor 14, e.g. the air mass flow rate measured by the upstream air mass flow sensor 28.

[0065] - Prefa reference pressure, e.g. 1 .00 bar.

[0066] - Tupstream the temperature of the air upstream of the compressor 14, e.g. the temperature measured by the upstream temperature sensor 24.

[0067] - Pupstream the upstream air pressure of the compressor, e.g. the pressure measured by the upstream pressure sensor 22.

[0068] - Trefa reference temperature, e.g. 20°C or 25°C.

[0069] The ordinate axis of the mapping corresponds to the compression ratio rcof the compressor 14 calculated as: r D downstream rc = ~ - r upstream

[0070] With Pdownstream the downstream air pressure of the compressor, e.g. pressure measured by the downstream pressure sensor 26.

[0071] The thick line curve 38 of the mapping shows the maximum compression curve 38 of the compressor 14 which is an intrinsic feature of the compressor 14, the compressor 14 not being able to operate in an operating mode located above the maximum compression curve 38 of the compressor 14.

[0072] The closed thin line curves in the mapping show constant performance curves of compressor 14, with the higher performance curves being the inner curves.

[0073] The open thick line curves of the mapping show constant speed curves of the compressor 14, the constant speed of the compressor 14 being higher for curves with archigher compression ratio of the compressor 14.

[0074] Figure 4 schematically shows the method for increasing the torque of the heat engine 4 implemented by the computer 36.

[0075] The method begins with a step 40 of determining a setpoint for increasing the downstream air pressure Pd0Wnstream of the compressor. For example, the computer 36 performs a calculation according to an acceleration setpoint of the motor vehicle 2 and a rpm of the heat engine 4 in order to determine the downstream air pressure Pd0Wnstream of the compressor required to allow the motor vehicle 2 to accelerate according to the acceleration setpoint.

[0076] The acceleration setpoint of the motor vehicle 2 is, for example, determined according to the depression of the accelerator pedal of the motor vehicle 2 or a force value exerted on the accelerator pedal of the motor vehicle 2 or a PLC controlling the motor vehicle 2.

[0077] Optionally, a sub-step 42 of determining a deviation between the initial compression ratio of the compressor 14 and the maximum compression ratio of the compressor 14 is carried out, the initial compression ratio of the compressor 14 being the compression ratio rcof the compressor 14 at the time of determining the setpoint for increasing the downstream air pressure Pd0Wnstream of the compressor, the maximum compression ratio of the compressor 14 being taken from the maximum compression curve 38 of the compressor 14.

[0078] For example, the deviation on the field mapping of the compressor 14 is calculated from an initial operating point P1 of the compressor 14, the x-axis of which is the mcinitial corrected air mass flow rate of the compressor 14 and the ordinate of which is the initial compression ratio of the compressor 14, the mcinitial corrected air mass flow rate of the compressor 14 being the corrected air flow rate mcof the compressor 14 at the time of determining the setpoint for increasing the downstream air pressure Pdownstream of fhe compressor. The deviation is, for example, calculated as the distance taken vertically or substantially vertically between the initial operating point P1 of the compressor 14 and the maximum compression curve 38 of the compressor 14.

[0079] The initial operating point P1 of the compressor 14 is shown here in the field mapping of Figure 3 close to the maximum compression curve 38 of the compressor 14.

[0080] A step of strict decrease 44 Pupstream of the compressor upstream air pressure is then carried out. Optionally, the step of strictly decreasing 44 the upstream air pressure Pupstream of the compressor is performed only if the calculated deviation between the initial compression ratio of the compressor 14 and the maximum compression ratio of the compressor 14 is insufficient to allow the compressor 14 to increase its compression ratio rcto meet the setpoint of increasing the downstream air pressure Pdownstream of the compressor without decreasing the upstream air pressure Pupstream of the compressor.

[0081] Advantageously, the air intake valve 20 arranged upstream of the compressor 14 is partially closed in order to decrease the air pressure upstream of the compressor 14. For example, the computer 36 communicates an opening position setpoint to the air intake valve 20.

[0082] By decreasing the air pressure upstream Pupstream of the compressor, the corrected air mass flow rate mcof the compressor 14 and the compression ratio rcof the compressor 14 are simultaneously increased. The compressor 14 therefore passes from the initial operating point P1 to an operating point P2 illustrated in Figure 3, the operating point P2 being further from the maximum compression curve 38 of the compressor 14 than the initial operating point P1 is, the performance of the compressor 14 at the operating point P2 also being greater than the performance of the compressor 14 at the initial operating point P1 . The compressor 14 is therefore now able to further increase its compression ratio rc.

[0083] Finally, a step 46 of increasing the compression ratio rcof the compressor 14 is carried out so as to strictly increase the downstream air pressure Pdownstream of the compressor in order to comply with the setpoint for increasing the downstream air pressure Pdownstream of the compressor, thus making it possible to increase the torque of the heat engine 4. The compressor 14 therefore passes from the operating point P2 to an operating point P3 illustrated in Figure 3 by approaching the maximum compression curve 38 of the compressor 14. For example, the computer 36 communicates a compression ratio setpoint rcof the compressor to the compressor 14. For reasons of understanding, the operating points P1 , P2 and P3 have been deliberately moved away on the field mapping of the compressor 14. Advantageously, the step 44 of decreasing the upstream air pressure Pupstream of the compressor is carried out such that the upstream air pressure Pupstream of the compressor is between 0.95 bar and 1 .00 bar, in particular between 0.97 bar and 1 .00 bar, when the engine is operating at an altitude close to 0 m corresponding to sea level where the external pressure is slightly greater than 1 bar. More generally, the pressure decrease caused by the partial closure of the air intake valve is advantageously at most equal to 50 mbar, and preferably between 20 and 30 mbar.

[0084] Figure 5 shows measurements made on a heat engine 4 during the implementation of the method, the x-axis being a time scale.

[0085] Before the time tO, the computer 36 implements the step 40 of determining the setpoint for increasing the downstream air pressure Pdownstream of the compressor and communicates a torque setpoint to the heat engine 4.

[0086] In the lower part of Figure 5, the dark line curve 48 shows the torque setpoint of the heat engine 4, the light line curve 50 shows the actual measured torque of the heat engine 4, the torque being shown in Newton meters.

[0087] An abnormal operating deviation is present between the torque setpoint of the heat engine 4 and the actual measured torque of the heat engine 4 at time tO. Indeed, the compressor 14 operates in a state of maximum compression, that is to say that the operating point of the compressor 14 is on the maximum compression curve 38 of the compressor 14 and does not allow the compressor 14 to supply the downstream air pressure Pdownstream of the compressor necessary for the heat engine 4 to operate according to the torque setpoint of the heat engine 4.

[0088] In the upper part of Figure 5, curve 52 in light line shows the downstream air pressure Pdownstream of the setpoint compressor, curve 54 in dark line showing the measured downstream air pressure Pdownstream of the compressor, the pressure being shown in kilopascals. The measured downstream air pressure Pdownstream of the compressor fluctuates strongly at time tO, with pressure oscillations being present in the vicinity of the compressor 14.

[0089] In the central part of Figure 5, the curve 56 shows the opening position of the air intake valve 20 as an opening percentage, the curve 58 representing the upstream air pressure Pupstream of the compressor measured. The computer 36 then performs the determination of the deviation between the compression ratio rcof the compressor 14 at time tO and the maximum compression ratio of the compressor 14.

[0090] Then, between times t1 and t2, the computer 36 implements the step 44 of decreasing the upstream air pressure Pupstream of the compressor. The initially fully open air intake valve 20 closes gradually until it is at least half closed, the air intake valve 20 here being only 40% open at time t2. Here, the air intake valve 20 is closed incrementally, in particular in steps of 5% of the open position.

[0091] During the gradual closing of the air intake valve 20, the measured upstream air pressure Pupstream of the compressor gradually decreases independently of the operation of the compressor 14, passing here from an upstream air pressure Pupstream substantially equal to 1 bar to an upstream air pressure Pupstream substantially equal to 0.98 bar.

[0092] The measured downstream air pressure Paownstream of the compressor gradually stabilises between times t1 and t2, with the pressure oscillations present near the compressor 14 decreasing between times t1 and t2.

[0093] At time t2, the computer 36 implements the step 46 of increasing the compression ratio rcof the compressor 14 so as to increase the downstream air pressure Pdownstream of the compressor according to the setpoint. At time t2, the compressor 14 no longer operates in the maximum compression state, the operating point of the compressor 14 on the field mapping of the compressor 14 having been changed as a result of the decrease in the upstream air pressure Pupstream of the compressor 14.

[0094] Between times t2 and t3, the compression ratio rcof the compressor 14 gradually increases. Before the time t3, the deviation between the curves 48, 50 of the torque setpoint of the heat engine 4 and the actual measured torque of the heat engine 4 is smaller than the abnormal operating mode deviation, the deviation between the curves 52, 54 of the compressor downstream air pressure setpoint and the measured compressor downstream air pressure being also smaller than the abnormal operating mode deviation.

[0095] At time t3, the torque setpoint of the heat engine 4 is increased again. The deviation between the compression ratio rcof the compressor 14 at time t3 and the maximum compression ratio of the compressor 14 is determined. Since the deviation is sufficient to increase the compression ratio rcof the compressor 14, the compression ratio rcof the compressor 14 is increased without changing the opening of the air intake valve 20.

[0096] Between times t3 and t4, the upstream air pressure Pupstream of the compressor decreases and the downstream air pressure Paownstream of the compressor increases, these two pressure variations depending on the increase in the compression ratio rcof the compressor 14.

[0097] At time t4, the measured actual torque of the heat engine 4 is stabilised on the torque setpoint of the heat engine 4, the measured downstream air pressure of the compressor also being stabilised on the downstream air pressure setpoint value of the compressor.

[0098] Optionally, during the step of decreasing 44 the upstream air pressure Pupstream of the compressor, the computer 36 performs the calculation of the increase in the compression ratio rcof the compressor 14, then a comparison of this increase with a growth rate of the maximum compression curve 38 of the compressor 14.

[0099] For example, at each increment of the position of the air intake valve 20, the computer 36 performs the calculation of a slope of evolution of the operating point of the compressor 14 and compares this slope of evolution with the slope of the maximum compression curve 38 of the compressor 14 in order to ensure that the closing of the air intake valve 20 moves the operating point of the compressor 14 away from the maximum compression curve 38 of the compressor 14.

[0100] Figure 6, wherein the identical elements bear the same references, shows another heat engine 4 comprising a computer 36 able to implement the method of increasing the torque.

[0101] The heat engine 4 comprises a cylinder block 6, an air intake circuit 8, a combustion gas exhaust circuit 10 and an exhaust gas recirculation circuit 60.

[0102] The air intake circuit 8 comprises an air inlet, an air filter 12 capable of filtering the air coming from the air inlet, a compressor 14 capable of increasing the mass flow rate of the air coming from the air filter 12, a throttle box 18 capable of adjusting the flow rate of air coming from the compressor 14, an air cooler 16 capable of decreasing the temperature of the air coming from the throttle housing 18, an intake manifold capable of distributing the air coming from the throttle box 18 into the cylinders of the cylinder block 6, and an air intake valve 20 arranged downstream of the air filter 12 and upstream of the compressor 14.

[0103] The combustion gas exhaust circuit 10 comprises an exhaust manifold able to collect the exhaust gases coming from the cylinder block 6, a turbine 30 able to expand the exhaust gases coming from the exhaust manifold, a catalyst 32 able to reduce the polluting emissions of the exhaust gases coming from the turbine 30 and a particulate filter 62 able to filter the exhaust gases from the catalyst 32.

[0104] Optionally, the particulate filter 62 may comprise a differential pressure sensor (not shown), and thus be able to determine the mass of particles stored in the particulate filter 62, and be able to purge the particulate filter 62 when the mass of particles stored in the particulate filter 62 reaches a predetermined threshold.

[0105] The exhaust gas recirculation circuit 60 is capable of sampling exhaust gases from the particulate filter 62 and distributing the sampled exhaust gases to the air intake circuit 8, the exhaust gas recirculation circuit 60 opening outwards into the air intake circuit 8 downstream of the air intake valve 20 and upstream of the compressor 14.

[0106] The exhaust gas recirculation circuit 60 further comprises an additional air cooler 64 capable of decreasing the temperature of the exhaust gases from the exhaust gas recirculation circuit 10, an additional filter 65 capable of filtering the exhaust gases from the additional air cooler 64, and an exhaust gas recirculation valve 66 capable of closing to prevent the circulation of exhaust gases through the exhaust gas recirculation circuit 60 and capable of opening at least in part to allow the circulation of exhaust gases through the exhaust gas recirculation circuit 60.

[0107] The heat engine 4 further comprises a bypass circuit 68 of the compressor 14 opening on the one hand into the air intake circuit 8 downstream of the air intake valve 20 and upstream of the compressor 14, and opening on the other hand into the air intake circuit 8 downstream of the compressor 14 and upstream of the throttle box 18.

[0108] The bypass circuit 68 of the compressor 14 comprises a bypass valve 70 of the compressor 14 able to close to prevent the circulation of air through the bypass circuit 68 and able to open at least in part to allow the circulation of air through the bypass circuit 68 in particular to avoid a backflow of air from the throttle box 18 towards the compressor 14 risking damage to the compressor 14.

[0109] The heat engine 4 also comprises an upstream pressure sensor 22 arranged upstream of the compressor 14 and downstream of the air intake valve 20, a first upstream temperature sensor 71 arranged in the air intake circuit 8 upstream of the air intake valve 20 and downstream of the air filter 12, a second upstream temperature sensor 72 arranged in the exhaust gas recirculation circuit 60 downstream of the exhaust gas recirculation valve 66, an upstream air mass flow rate sensor 74 arranged in the air intake circuit 8 upstream of the air intake valve 20 and downstream of the air filter 12, a downstream pressure sensor 26 arranged in the air intake circuit 8 downstream of the compressor 14 and upstream of the throttle box 18.

[0110] Optionally, the heat engine 4 comprises an additional upstream air mass flow sensor (not shown) arranged in the exhaust gas recirculation circuit 60 downstream of the exhaust gas recirculation valve 66 and able to measure the mass flow of the recirculated exhaust gases in the air intake circuit 8. Alternatively, the computer 36 is capable of estimating the mass flow rate of the exhaust gases recirculated in the air intake circuit 8 from the temperature measured by the second upstream temperature sensor 72 and the open position of the exhaust gas recirculation valve 66.

[0111] The actual air mass flow rate mrof the compressor 14 is calculated as the sum of the air mass flow rate from the air intake circuit 8 and the mass flow rate of the exhaust gas recirculated in the air intake circuit 8. Optionally, the exhaust gas recirculation valve 66 can be closed when performing the torque increasing method.

[0112] The corrected air mass flow rate mcof the compressor 14 is calculated with an ^upstream estimated upstream air temperature of the compressor and the upstream air pressure Pupstream of the compressor measured by the upstream pressure sensor 22. The temperature of the air upstream of the compressor Tupstreamis, for example, estimated from the mass flow rate of air from the air intake circuit 8, the temperature measured by the first upstream temperature sensor 71 , the mass flow rate of the exhaust gases recirculated in the air intake circuit 8 and the second upstream temperature sensor 72. Alternatively, the heat engine 4 comprises an upstream air mass flow sensor arranged in the exhaust gas recirculation circuit 60 downstream of the exhaust gas recirculation valve 66, downstream of the exhaust gas recirculation circuit 60 and upstream of the compressor 14.

[0113] The compression ratio rcof the compressor 14 is calculated with the downstream air pressure PdOwnstream of the compressor measured by the downstream pressure sensor 26, and with the upstream air pressure Pupstream of the compressor measured by the upstream pressure sensor 22.

Claims

CLAIMS1 . Method for increasing the torque of a heat engine (4) of a motor vehicle (2), the heat engine (4) comprising an air intake circuit (8) provided with a compressor (14) configured to modify an air intake mass flow rate of the heat engine (4), characterised in that it comprises at least the following steps:- a step of determining (40) a downstream air pressure increase setpoint (Pdownstream) of the compressor;- a step of decreasing (44) an upstream air pressure (Pupstream of the compressor performed independently of the compressor (14); and- a step of increasing (46) a compression ratio (rc) of the compressor (14) so as to increase the downstream air pressure (Pdownstream) of the compressor according to said setpoint.

2. Method according to claim 1 , wherein the step of determining (40) a compressor downstream air pressure increase setpoint comprises a sub-step of determining (42) a deviation between an initial compression ratio of the compressor (14) and a maximum compression ratio of the compressor (14), the step of decreasing (44) an upstream air pressure (Pupstream) of the compressor being performed when said deviation is insufficient to increase, at a constant upstream air pressure (Pupstream) of the compressor, the downstream air pressure (Pdownstream) of the compressor according to said setpoint.

3. Method according to claim 2, wherein said deviation is determined based on a field mapping of the compressor (14) and an mcinitial corrected air mass flow rate of the compressor calculated as:rrirbeing the actual air mass flow rate of the compressor (14);Prefbeing a reference pressure;Tupstream being the air temperature upstream of the compressor (14);Pupstream being the upstream air pressure of the compressor;Tref being a reference temperature.

4. Method according to any one of the preceding claims, wherein the step of decreasing (44) an upstream air pressure (Pupstream) of the compressor comprises partially closing an air intake valve (20) arranged upstream of the compressor (14).

5. Method according to claim 4, wherein the partial closing of the air intake valve (20) is performed incrementally, an increase in the compression ratio (rc) of the compressor (14) being calculated at each increment and then compared with a growth rate of a maximum compression curve (38) of the compressor (14).

6. Method according to any one of the preceding claims, wherein the step of decreasing (44) an upstream air pressure (Pupstream) of the compressor is performed such that the decrease in the upstream air pressure (Pupstream) of the compressor is at most 50 mbar, and preferably between 20 and 30 mbar.

7. Method according to any one of the preceding claims, wherein the step of determining (40) a compressor downstream air pressure increase setpoint (Pdownstream) comprises calculating said setpoint based on an acceleration setpoint of the motor vehicle (2) and a speed of the heat engine (4).

8. Heat engine (4) for a motor vehicle (2), the heat engine (4) comprising an air intake circuit (8) provided with a compressor (14) configured to modify an air intake mass flow rate of the heat engine (4) and an air intake valve (20) arranged upstream of the compressor (14), the heat engine (4) further comprising a computer (36) configured to implement a method according to any one of the claims 1 to 7.

9. The heat engine (4) according to claim 8, further comprising a combustion gas exhaust circuit (10) of the heat engine (4) and an exhaust gas recirculation circuit (60) from the exhaust circuit (10) to the air intake circuit (8) so that the recirculation circuit (60) opens into the air intake circuit (8) upstream of the compressor (14) and downstream of the air intake valve (20).1 0. Motor vehicle (2) comprising a heat engine (4) according to one of claims 8 and 9.

Images