METHOD FOR LIMITING THE SLOPE REVERSE OF A HYBRID MOTOR VEHICLE, EQUIPPED WITH A CONTROL LAW

Abstract

METHOD FOR LIMITING THE SLOPE REVERSE OF A HYBRID MOTOR VEHICLE EQUIPPED WITH A CONTROL LAW. The present invention relates to a method for limiting the slope reversal of a hybrid motor vehicle when starting a thermal engine by an automatic stop and restart device, for which the engine switching off condition is that the driver presses the brake and that the vehicle speed is lower than a first speed threshold, while the engine restart condition is that the driver releases the brake pedal, said vehicle further comprising a hill start assist system applying a braking action to said vehicle, said hill start assist system integrating a control law L using the value P of the road gradient to control the powertrain. Figure for abstract: Fig. 1

Description

Description Title of the invention: METHOD FOR LIMITING THE REVERSE ENGINE ON SLOPES OF A HYBRID MOTOR VEHICLE, EQUIPPED OF A LAW OF COMMAND

[0001] — The present invention relates to a method for automatic stopping and restarting assisted by hill start assist in a hybrid vehicle, designed to limit the reversing the vehicle on an incline using a gearbox management strategy of the internal combustion engine and clutch, taking into account the road gradient.

[0002] It is known from hybrid vehicles equipped with a stop-start device. automatic, to which is added a Hill Start Assist system, known as the The designation "ADEC" in French or "Hill Assist" in English.

[0003] Typically, the hill start assist system allows the device automatic stop and restart to shut off the internal combustion engine when it is detected that the upward slope is sufficiently shallow and therefore there is no need vehicle retention against rolling back

[0004] Otherwise, that is, when a maintenance need is detected, the system Hill start assist enables the automatic stop and restart device to switch off the internal combustion engine when the hill-hold function is active.

[0005] To determine the vehicle's status, it must be stopped, in order to to have a precise measurement of the slope. This therefore requires the combustion engine to be switched off. for an automatic stop and restart device equipped with a starter at 00 km / H.

[0006] — The "Hill Assist" strategy allows the brakes to be kept on in order to prevent the Reversal on a slope. However, releasing the brakes is based on a desire for torque. without taking into account the dynamics of obtaining said couple. Very often the threshold The torque must be overestimated to allow the brakes to be released in order to be certain that the couple will be installed. This uncertainty creates the inconvenience that the vehicle can to remain held back by the brakes while the organs are potentially already supplying couple.

[0007] — When the vehicle is stopped, under nominal temperature and level conditions Once the battery is charging, the internal combustion engine is switched off and decoupled to promote the consumption and reduce emissions.

[0008] = Moreover, in an application where the speed and torque demand are low, the The gearbox is held "open" to favor the rear axle for its better efficiency and therefore provide the energy necessary for the vehicle's movement.

[0009] — Under these conditions and when the driver wants to start on an incline, the supply of Power from the rear axle or from the front electric machine may prove too weak to ensure the desired takeoff dynamics. Furthermore, the necessary power delivery from the internal combustion engine requires a certain amount of time due to the starting procedure and clutch engagement. This can result in a slight rollback on the slope, potentially leading to unexpected collisions. Therefore, the invention proposes to mitigate all or part of the risks mentioned previously by using the value of the slope to anticipate the need for torque, and more particularly by requesting, in order of priority, the closing of the gearbox, the starting of the engine, and the pre-positioning of the clutch. The invention relates in particular to a method for limiting the rollback of a hybrid motor vehicle on an incline during the start of a combustion engine by means of an automatic stop-start device, wherein the condition for stopping the combustion engine is that the driver presses the brake and the vehicle speed is below a first speed threshold, while the condition for restarting the combustion engine is that the driver releases the brake pedal, said vehicle further comprising a hill start assist system applying a braking action to said vehicle, the automatic stop-start device incorporating the control law L defined by the following steps: - Verification that the vehicle is stationary, then, - Retrieving the P value of the road's slope, then, - Comparison of the road gradient value P with a first threshold value P1 beyond which the hill start assist system controls the gearbox engagement, then, - Comparison of the road gradient value P with a second threshold value P2 beyond which the hill start assist system commands the starting of the internal combustion engine, then, - Comparison of the P value of the road slope with a third threshold value P3 beyond which the hill start assist system controls the clutch engagement. Optional features of the invention, complementary or alternative, are set out below. Depending on certain characteristics, the P value of the road's slope is obtained by direct measurement, and in particular by means of a sensor or a GPS. According to other characteristics, the P value of the road slope is an estimate based on external forces, namely the difference between the actual acceleration of the vehicle and the theoretical acceleration that the vehicle would have with the torque produced by all the components. Preferably, the control law L is applied only if and only if the available power level of the alternative energy to that of the heat engine is less than a limit value PO, so as not to start the heat engine unnecessarily. Preferably, the result of the execution of the control law L is cancelled when the vehicle is not in a driving situation after a time value TO following the execution of the control law L. Preferably, the driving situation is defined when the distance traveled by the vehicle is greater than a determined DO value. Preferably, the state of the gear lever is used to apply the control law L to a driving situation in forward motion on an uphill slope or to a driving situation in reverse on a downhill slope. According to a particular embodiment, the first, second and third threshold values ​​of the road slope are respectively around 4, 6 and 8%. The invention also relates to a motor vehicle comprising an automatic stop and restart device and a hill start assist system, characterized in that the vehicle's rollback when stopped on an uphill slope is limited by a method according to the invention. Other advantages and features of the invention will become apparent upon reading the detailed description of implementations and embodiments, which are by no means limiting, and the single figure: [fig.1] This figure represents a schematic view of the control law applied to the automatic stop and restart device according to the invention. The embodiments described below are not exhaustive; variants of the invention may include, in particular, a selection of the described features, isolated from the other described features (even if this selection is isolated within a sentence containing these other features), provided that this selection of features is sufficient to confer a technical advantage or to differentiate the invention from the prior art. This selection includes at least one feature, preferably a functional feature without structural details, or with only a portion of the structural details if this portion alone is sufficient to confer a technical advantage or to differentiate the invention from the prior art. According to the invention, the method for limiting the rollback on slope according to the invention is intended for hybrid motor vehicles, that is to say for vehicles with hybrid propulsion which consists of combining one or more electric motors (reversible to become generators) with a thermal engine. The method for limiting setback on slopes according to the invention is aimed more specifically at related to vehicles equipped with an automatic stop and restart device, for which the condition for stopping the engine is that the driver presses the brake and the vehicle speed is below a first speed threshold, while the condition for restarting the engine is that the driver releases the brake pedal, said vehicle further comprising a hill start assist system capable of applying a braking action to said vehicle. The method for limiting rollback on slopes according to the invention is more particularly suited to fully hybrid vehicles, in which the vehicle can be driven by each motor separately or by both motors together. This operation requires power outputs exceeding 20 kW. A complex transmission management system allows for all possible combinations. The percentage of electric motor usage depends on the battery capacity, which is charged while driving by the internal combustion engine, as well as during deceleration through kinetic energy recovery, or by recharging via the internal combustion engine, or via electrical charging if available. The different operating phases of a "full hybrid" unfold as follows: - When the vehicle is stationary, both engines (thermal and electric) are off: - the car is started by the electric motor alone, up to a maximum speed varying between 70 and 130 km / h depending on the model; - beyond these speeds, or when stronger acceleration is required, the internal combustion engine is started to provide the additional power and gradually replace the electric motor; - in case of high power demand (strong acceleration or steep slope), the two motors operate simultaneously to add their motor torques; - During deceleration or descent, regenerative braking allows the motor / generator to convert some of the kinetic energy into electrical energy, recharging the battery. This engine braking effect can be enhanced by forcing the internal combustion engine to run without fuel injection, relieving the mechanical friction brakes. Conversely, the engine can be switched off to reduce fuel consumption and pollution, thus deactivating its engine braking function. The management of the whole system is entrusted to the on-board electronics which takes into account the state of charge of the battery, the temperature of the internal combustion engine and that of the catalytic converter, the heating and air conditioning requirements and the pressure on the accelerator and brake pedals. According to the invention, the automatic stop and restart device incorporates a control law L defined in Figure 1 and by the steps detailed below. As detailed in Figure 1, it is first necessary to check whether the vehicle is stopped or not, as indicated by the condition "Vehicle stopped? YES / NO". In the case where the vehicle is stationary, the P value of the road slope is retrieved. Next, the control law L checks whether the condition "Slope Value > Threshold Value_1? YES / NO" is met or not, that is, whether the value P of the road slope is greater than a first threshold value P1. If this is the case, the hill start assist system controls the transmission coupling. Next, the control law L checks whether the condition "Slope Value > Threshold Value_2? YES / NO" is met or not, that is, whether the value P of the road slope is greater than a first threshold value P2. If this is the case, the hill start assist system commands the start of the internal combustion engine. Finally, the control law L checks whether the condition "Slope Value > Threshold Value_3? YES / NO" is met or not, that is, whether the value P of the road slope is greater than a third threshold value P3. If this is the case, the hill start assist system controls the clutch engagement. The first threshold value P1 is less than or equal to the second threshold value P2, which is itself less than or equal to the third threshold value P3. Thus, the control law L uses information on the value of the road slope in order to determine the level of power required for the driving situation as well as the desired torque dynamics if needed. The P value of the road slope can be obtained by direct measurement or estimated by calculation. In particular, consideration can be given to obtaining a direct measurement of the road's slope using a sensor or a GPS. The value P of the road slope can alternatively be obtained by an estimation based on external forces, namely the difference between the actual acceleration of the vehicle and the theoretical acceleration that the vehicle would have with the torque produced by all the components. Preferably, the first, second and third threshold values ​​for the road gradient are respectively around 4, 6 and 8%. In order to avoid unnecessarily starting the internal combustion engine, the control law L is only applied if and only if the available power level of the alternative energy (generally the battery of the electric motor) to that of the internal combustion engine, is less than a limit value PO. Advantageously, this limit value PO is around 20 kW and depends on the slope and the driver's will. Preferably, the result of the execution of the control law L is cancelled when the vehicle is not in a driving situation after a time value TO following the execution of the control law L. Advantageously, this limit value TO is on the order of 5 s to 1 min. Preferably, the driving situation is defined when the distance traveled by the vehicle is greater than a determined DO value. Advantageously, this DO limit value is in the range of 30 m to 1 km. Advantageously, even if the P value of the road gradient is less than the third threshold value P3, the hill start assist system can control the clutch coupling, if the car is moving in the opposite direction to that defined in the gearbox coupling. To know whether to apply the L control law to a forward driving situation on an uphill slope or to a reverse driving situation on a downhill slope, it is advantageous to use the state of the gear lever. Thus, the criteria of available electrical power, battery charge levels, time and distance traveled allow the control law L to be refined in order to optimize the vehicle's consumption as well as its driving comfort. It should be noted that the different characteristics, forms, variants and embodiments of the invention can be associated with each other, according to various combinations insofar as they are not incompatible or exclusive of each other.

Claims

Demands

1. Method for limiting the rollback of a motor vehicle on a slope hybrid during the starting of a combustion engine by a device automatic stop and restart, for which the condition The method of shutting off the internal combustion engine is for the driver to press the brake and that the vehicle's speed is below a first threshold of speed, while the condition for restarting the internal combustion engine is that the driver releases the brake pedal, said vehicle comprising in addition to a hill start assist system capable of applying a braking action of said vehicle, characterized in that the device automatic stop and restart incorporates the L control law defined by the following steps: - Check that the vehicle is stationary, then, - Retrieving the P value of the road slope, then , - Comparison of the P value of the road slope with a first threshold value Pl beyond which the assistance system Starting on a hill triggers the gearbox coupling, then... - Comparison of the P value of the road slope with a second threshold value P2 beyond which the assistance system hill start control initiates the start of the internal combustion engine, then, - Comparison of the P value of the road slope with a third threshold value P3 beyond which the assistance system Hill start control engages the clutch.

2. Method for limiting the rollback of a motor vehicle on an incline hybrid according to claim 1, characterized in that the value P of the The road gradient is obtained by direct measurement, and in particular at by means of a sensor or a GPS.

3. Method for limiting the rollback of a motor vehicle on a slope hybrid according to claim 1, characterized in that the value P of the The road gradient is an estimate based on external forces, at to know the difference between the vehicle's actual acceleration and the acceleration theoretical value that the vehicle would have with the torque produced by all the organs.

4. Method for limiting the rollback of a motor vehicle on a slope hybrid according to one of the preceding claims, characterized in this that the L control law is applied if and only if the level of available power from alternative energy to that of the motor thermal, is less than a limit value PO, so as not to starting the internal combustion engine unnecessarily.

5. Method for limiting the rollback of a motor vehicle on a slope hybrid according to one of the preceding claims, characterized in this that the result of the execution of command law L is cancelled when the vehicle is not in motion after a time value TO after execution of control law L.

6. Method for limiting the rollback of a motor vehicle on a slope hybrid according to one of the preceding claims, characterized in this that the driving situation is defined when the distance traveled by the vehicle exceeds a predetermined DO value.

7. Method for limiting the rollback of a motor vehicle on a slope hybrid according to one of the preceding claims, characterized in this that the state of the gear lever is used to apply the law of command L in a forward driving situation on a slope uphill or in a reversing situation on a slope descending.

8. Method for limiting the rollback of a motor vehicle on a slope hybrid according to one of the preceding claims, characterized in this that the first, second and third threshold values ​​of the slope of the road are respectively around 4, 6 and 8%.

9. Motor vehicle comprising a stop and restart device automatic transmission and a hill start assist system, characterized in that the vehicle rolls backward when stopped on an uphill slope is limited by a process according to any one of the preceding claims previous.