FR3096638A1 - PROCESS FOR LIMITING THE RETURN ON A SLOPE OF A HYBRID MOTOR VEHICLE, WITH A CONTROL LAW - Google Patents

Abstract

The present invention relates to a method of limiting the backward slope of a hybrid motor vehicle when a heat engine is started by an automatic stopping and restarting device, for which the condition for switching off the engine is that the driver applies 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 brake system hill start aid applying a braking action to said vehicle, said hill start aid system incorporating a control law L using the value P of the gradient of the road to control the powertrain. Figure 1

Description

METHOD FOR LIMITING THE RECOIL ON SLOPE OF A HYBRID MOTOR VEHICLE, PROVIDED WITH A CONTROL LAW

The present invention relates to a method for automatic stopping and restarting assisted by a hill start aid of a hybrid vehicle, intended to limit the rollback on a slope of the vehicle by means of a strategy for managing the gearbox , the thermal engine and the clutch taking into account the gradient of the road.

It is known hybrid vehicles equipped with an automatic stop and restart device, to which is added a Hill Start Assistance system, known as "ADEC" in French or "Hill Assist" in English. .

Usually, the hill start assistance system authorizes the automatic stop and restart device to switch off the internal combustion engine when it is detected that the upward slope is sufficiently low and therefore that there is no need holding the vehicle against a rollback.

Otherwise, i.e. when a need for holding is detected, the hill start assistance system authorizes the automatic stop and restart device to switch off the combustion engine when the hold function slope is active.

To know in which situation the vehicle is, it must be stopped, in order to have an accurate measurement of the slope. This therefore imposes the stopping of the thermal engine for an automatic stop and restart device equipped with a starter at 0 km/H.

The "Hill Assist" strategy keeps the brakes applied to prevent rollback on a slope. However, the release of the brakes is based on a desire for torque, without taking into account the dynamics of obtaining said torque. Very often the torque threshold must be overestimated to authorize the release of the brakes in order to be certain that the torque will be installed. This uncertainty generates the inconvenience that the vehicle may remain held by the brakes while the components potentially already provide torque.

When the vehicle is stopped, in nominal conditions of temperature and battery charge level, the internal combustion engine is switched off and decoupled to improve consumption and reduce emissions.

In addition, on an application where the speed and torque demand are low, the gearbox is kept "open" in order to favor the rear axle for its best performance and therefore provide the energy necessary for the movement of the vehicle.

In these conditions and when the driver wants to start on a slope, the supply of power by the rear axle or by the front electric machine may prove to be too weak to ensure the desired take-off dynamics.

In addition, the supply of the power required by the thermal engine, made necessary, requires a certain time due to the starting procedure and the coupling of the clutch. It can then be observed a decline in the slope, which can cause untimely collisions.

This is why the invention proposes to overcome all or part of the risks mentioned above 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. , engine starting, and clutch pre-positioning.

The invention relates in particular to a method for limiting the recoil on a slope of a hybrid motor vehicle when starting a heat engine by an automatic stop and restart device, for which the extinction condition of the heat engine is that the driver presses the brake and that the speed of the vehicle is below a first speed threshold, while the condition for restarting the heat engine is that the driver releases the brake pedal, said vehicle further comprising a hill start assistance system applying a braking action to said vehicle, the automatic stopping and restarting device integrating the control law L defined by the following steps:

- Check that the vehicle is stationary then,

- Recovery of the P value of the road gradient then,

- Comparison of the value P of the gradient of the road with a first threshold value P1 beyond which the hill start assistance system controls the coupling of the gearbox then,

- Comparison of the value P of the gradient of the road with a second threshold value P2 beyond which the hill start assistance system controls the starting of the internal combustion engine then,

- Comparison of the value P of the gradient of the road with a third threshold value P3 beyond which the hill start assistance system controls the coupling of the clutch.

Optional characteristics of the invention, complementary or substitute, are set out below.

According to certain characteristics, the value P of the gradient of the road is obtained by direct measurement, and in particular by means of a sensor or else a GPS.

According to other characteristics, the value P of the gradient of the road is an estimate based on the 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 organs.

Preferably, the control law L is only applied if and only if the available power level of the alternative energy to that of the heat engine is lower than a limit value P0, so as not to start the engine unnecessarily. thermal motor.

Preferably, the result of the execution of the control law L is canceled when the vehicle is not in a driving situation after a time value T0 after 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 value D0.

Preferably, the state of the gear lever is used to apply the control law L to a rolling situation in forward gear and on an uphill slope or else to a rolling situation in reverse gear on a downhill slope.

According to a particular embodiment, the first, second and third threshold values of the gradient of the road are respectively of the order of 4, 6 and 8%.

The invention also relates to a motor vehicle comprising an automatic stopping and restarting device as well as a hill start assistance system, characterized in that the recoil of the vehicle during a stop on an ascending slope is limited by a method according to the invention.

Other advantages and particularities of the invention will appear on reading the detailed description of in no way limiting implementations and embodiments, and of the single figure:

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 being in no way limiting, variants of the invention may in particular be considered comprising only a selection of characteristics described, isolated from the other characteristics described (even if this selection is isolated within a sentence including these other features), if this selection of features is sufficient to confer a technical advantage or to differentiate the invention from the state of the prior art. This selection includes at least one feature, preferably functional without structural details, or with only part of the structural details if only this part is sufficient to confer a technical advantage or to differentiate the invention from the state of the prior art .

According to the invention, the method for limiting recoil on a slope according to the invention is intended for hybrid motor vehicles, that is to say vehicles equipped with hybrid propulsion which consists of combining one or more electric motors ( reversible to become generators) with a heat engine.

The method for limiting reverse on a slope according to the invention is more particularly intended for vehicles equipped with an automatic stop and restart device, for which the condition for switching off the engine is that the driver presses the brake and that the speed of the vehicle 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 assistance system capable of applying a braking action to said vehicle.

The method for limiting recoil on a slope according to the invention is intended more particularly for vehicles with complete hybridization, in which the vehicle can be driven by each motor separately or by the two motors together.

This operation requires powers greater than 20 kW3. A complex transmission management allows all combinations. The percentage of use of the electric motor depends on the capacity of the battery, the charge of which takes place while driving, by the internal combustion engine, as well as during slowing down, by the recovery of kinetic energy, or by recharging via the engine. thermal, or via electric charging if possible.

The different operating phases of a "full hybrid" are as follows:

- when the vehicle is stationary, the two motors (thermal and electric) are stopped;

- the car is set in motion 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 greater acceleration is required, the internal combustion engine is started to provide the additional power and gradually replace the electric motor;

- in the event of a high power demand (strong acceleration or steep gradient), the two motors operate simultaneously to add their motor torques;

- in the deceleration or descent phase, regenerative braking allows the motor/generator to convert part of the kinetic energy into electrical energy, recharging the battery. This role of engine braking can be increased by forcing the combustion engine to run without fuel injection, relieving the mechanical friction brakes. On the contrary, it can be stopped to reduce consumption and pollution, which deactivates its engine brake.

Management of the whole system is entrusted to the on-board electronics which take into account the state of charge of the battery, the temperature of the internal combustion engine and that of the catalyst, the needs for heating and air conditioning and the pressure on the the accelerator and brake pedals.

Still according to the invention, the automatic stop and restart device incorporates a control law L defined in FIG. 1 and by the steps detailed below.

As detailed in Figure 1, it is first necessary to verify that the vehicle is stationary or not, as indicated by the condition "Vehicle stopped?" YES NO ".

If the vehicle is stationary, the value P of the road gradient is retrieved.

Then, the control law L verifies whether the condition “ValeurPente > ValeurSeuil_1? YES/NO” is met or not, that is to say if the value P of the gradient of the road is greater than a first threshold value P1. If this is the case, the hill start assist system controls the coupling of the gearbox.

Then, the control law L verifies whether the condition “ValeurPente > ValeurSeuil_2? YES/NO” is fulfilled or not, that is to say if the value P of the gradient of the road is greater than a first threshold value P2. If this is the case, the hill start assistance system controls the starting of the internal combustion engine.

Finally, the control law L verifies whether the condition "ValeurPente > ValeurSeuil_3?" YES/NO” is fulfilled or not, that is to say if the value P of the gradient of the road is greater than a third threshold value P3. If this is the case, the hill start assist system controls clutch engagement.

The first threshold value P1 is less than or equal to the second threshold value P2, itself less than or equal to the third threshold value P3.

Thus, the control law L uses the information on the value of the gradient of the road in order to determine the level of power necessary for the setting in driving situation as well as the torque dynamics desired if necessary.

The P-value of the road gradient can be obtained by direct measurement or estimated by calculation.

It can be envisaged in particular to obtain a direct measurement of the gradient of the road by means of a sensor or else of a GPS.

The value P of the gradient of the road can alternatively be obtained by an estimate based on the 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 organs.

Preferably, the first, second and third threshold values of the gradient of the road are respectively of the order of 4, 6 and 8%.

In order not to start the heat engine unnecessarily, the control law L is only applied if and only if the power level available from the alternative energy (generally the battery of the electric motor) to that of the heat engine, is lower than a limit value P0.

Advantageously, this limit value P0 is of the order of 20 kW and depends on the slope and the will of the driver.

Preferably, the result of the execution of the control law L is canceled when the vehicle is not in a driving situation after a time value T0 after the execution of the control law L.

Advantageously, this limit value T0 is of 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 value D0.

Advantageously, this limit value D0 is of the order of 30 m to 1 km.

Advantageously, even if the value P of the gradient of the road is lower than the third threshold value P3, the hill start assistance system can control the coupling of the clutch, if the car is moving in the opposite direction to that defines in the coupling of the gearbox.

To know if it is necessary to apply the control law L to a rolling situation in forward gear and on an uphill slope or else to a rolling situation in reverse gear on a downhill slope, it is advantageous to use the state of the speed.

Thus, the criteria of available electrical power, battery charge levels, time and distance traveled make it possible to refine the control law L so as to optimize the consumption of the vehicle as well as its driving comfort.

It should be noted that the different characteristics, forms, variants and embodiments of the invention may be associated with each other, in various combinations insofar as they are not incompatible or exclusive of each other.

Claims (9)

Method for limiting the reversal on a slope of a hybrid motor vehicle when starting a heat engine by an automatic stop and restart device, for which the condition for switching off the heat engine is that the driver presses the brake and that the speed of the vehicle is lower than a first speed threshold, while the condition for restarting the heat engine is that the driver releases the brake pedal, said vehicle further comprising a hill start assistance system capable of applying a braking action to said vehicle, characterized in that the automatic stopping and restarting device incorporates the control law L defined by the following steps:
- Check that the vehicle is stationary then ,
- Recovery of the value P of the gradient of the road then ,
- Comparison of the value P of the gradient of the road with a first threshold value P1 beyond which the hill start assistance system controls the coupling of the gearbox then,
- Comparison of the value P of the gradient of the road with a second threshold value P2 beyond which the hill start assistance system controls the starting of the internal combustion engine then,
- Comparison of the value P of the gradient of the road with a third threshold value P3 beyond which the hill start assistance system controls the coupling of the clutch. Method for limiting the rollback on a slope of a hybrid motor vehicle according to Claim 1, characterized in that the value P of the slope of the road is obtained by direct measurement, and in particular by means of a sensor or else of a GPS. Method for limiting the rollback on a slope of a hybrid motor vehicle according to Claim 1, characterized in that the value P of the slope of the road is an estimate based on the 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 organs. Method for limiting the recoil on a slope of a hybrid motor vehicle according to one of the preceding claims, characterized in that the control law L is applied if and only if the power level available from the alternative energy to that of the motor thermal, is lower than a limit value P0, so as not to start the thermal engine unnecessarily. Method for limiting the recoil on a slope of a hybrid motor vehicle according to one of the preceding claims, characterized in that the result of the execution of the control law L is canceled when the vehicle is not in a driving situation at the end of a time value T0 after the execution of the control law L. Method for limiting the reversal on a slope of a hybrid motor vehicle according to one of the preceding claims, characterized in that the driving situation is defined when the distance traveled by the vehicle is greater than a determined value D0. Method for limiting the recoil on a slope of a hybrid motor vehicle according to one of the preceding claims, characterized in that the state of the gear lever is used to apply the control law L to a driving situation in forward gear and on an uphill grade or to a reversing situation on a downhill grade. Method for limiting the rollback on a slope of a hybrid motor vehicle according to one of the preceding claims, characterized in that the first, second and third threshold values of the slope of the road are respectively of the order of 4, 6 and 8%. Motor vehicle comprising an automatic stopping and restarting device as well as a hill start assistance system, characterized in that the recoil of the vehicle when stopping on an ascending slope is limited by a method according to the any of the preceding claims.