FR3078304A1 - METHOD FOR MANAGING APPLIED COUPLES ON VEHICLE ROLLING TRAINS COMPRISING EACH MOTORIZATION - Google Patents

Abstract

A method for managing the torques applied to the front and rear undercarriages of a vehicle, each comprising a motor (2, 10), this vehicle having an electronic ESP stability program for limiting the sliding of the wheels (6, 14), remarkable in that during the activation of the electronic stability program ESP, in case of braking setpoint on a first rolling train, or acceleration respectively on the first rolling train, it applies a negative torque setpoint saturated to the zero value on the second running gear, or respectively it applies a positive torque setpoint saturated with the zero value on the second running gear.

Description

"METHOD FOR MANAGING THE TORQUES APPLIED TO THE TRAINS

VEHICLE ROLLERS INCLUDING EACH MOTORIZATION ”The present invention relates to a method of managing the torques applied to the front axle and the rear axle of a motor vehicle each comprising a motorization, as well as a motor vehicle comprising means putting implement such a management process.

Some motor vehicles have a motorization on each undercarriage, which may in particular include a thermal motorization on the front and an electric motorization on the rear to produce a vehicle with hybrid traction.

These vehicles may also include an electronic stability program, called "ESP" for "Electronic Stability Program" in English, which uses a vehicle brake control system and a power management system to limit the slipping of the wheels which could compromise the traction or the stability of the vehicle.

In particular, the ESP program may, on a running gear during braking desired by the driver, request a function for regulating the engine torque, called "MSR" for "Motor Schleppmoment Regelung" in German, to increase slightly the torque delivered by the engine of this train, for example by increasing the idling speed of the heat engine, in order to reduce the engine brake applied to the wheels in the event of excessive braking of the wheels which may cause them to lock.

Conversely, the ESP program can on a running gear during an acceleration desired by the driver request a function for regulating the braking torque, called "ASR" for "Anti Slip Regulation" in English, to reduce the torque delivered by the engine or apply braking with the wheel brakes, in order to limit the engine torque on these wheels to avoid slipping.

However, the action of these functions on a running gear can have an opposite effect to that applied to the other running gear by its engine or its brakes. In particular, braking on one running gear and acceleration on the other running gear can be obtained, which leads to instability of the vehicle, giving the driver a feeling of insecurity.

In addition, these opposite effects of acceleration on one train and braking on the other cause energy losses. One can obtain in particular an electrical energy production by the electric motorization of a running train applying braking, and an electric energy consumption by a second electric motorization of the other running gear, leading to an overall energy efficiency which is not optimal.

Furthermore, a known method presented in particular by document FR-A12799417, for controlling two motorizations each acting on a running gear of a motor vehicle, comprising an electric motorization on the rear axle, performs a control of the distribution of torques on the two trains depending on the pulling force of the desired vehicle, in particular when the vehicle is started.

This known method achieves in particular according to the static and dynamic state of the vehicle, a distribution of torque between the two running gear giving a sum of torque corresponding to the request of the driver, and making it possible to avoid losses of grip on these wheels as well as excessive demand from the electric motor. However, this method does not present a solution in the case of a control with an ESP program requesting pairs of opposite signs on the two running gear.

The present invention aims in particular to avoid these drawbacks of the prior art.

To this end, it proposes a method for managing the torques applied to the front and rear undercarriages of a motor vehicle each comprising a motorization, this vehicle having an electronic stability program ESP for limiting the slip of the wheels, asking on each running gear to limit blocking during a request for braking by the driver, to increase the torque delivered by its engine, or to limit slippage during a request for acceleration of the driver, to decrease the torque delivered by its motorization or by applying braking to the brakes of its wheels, this process being remarkable in that during the activation of the electronic stability program ESP, in the event of a braking instruction on a first running gear, or respectively of acceleration on this first undercarriage, it applies a negative saturated torque setpoint to zero on the second undercarriage, or res pectively, it applies a saturated positive torque setpoint to the zero value on this second running gear.

An advantage of this process is that with the saturation at zero of the negative braking setpoint, or respectively positive acceleration setpoint, of the second running gear, it is no longer possible to obtain opposite setpoints between the two trains. Vehicle stability is improved, fuel efficiency is optimized.

The management method according to the invention may further include one or more of the following characteristics, which can be combined with one another.

Advantageously, the motorization of the second train comprising an electric traction motor, during the activation of the ESP stability program, in the event of a braking instruction on the first train the method sends a braking torque instruction with the electric motor on the second train with a negative or zero value.

Advantageously, the motorization of the second train comprising an electric traction machine, during the activation of the ESP stability program, in the event of an acceleration setpoint on the first train the method sends an acceleration torque setpoint with the electric motor on the second train including a positive or zero value.

Advantageously, the ESP stability program controls a function for regulating the torque MSR of a traction thermal engine, which increases the idling speed of this thermal engine in order to reduce its engine brake in the event of a risk of wheel lockup. driven by this motor.

Advantageously, the ESP stability program controls a function for regulating the braking torque ASR, which on a running gear reduces the torque delivered by its engine or applies braking with the wheel brakes, in order to limit the engine torque on its wheels to avoid slipping.

The invention further relates to a motor vehicle comprising a motorization on each undercarriage, remarkable in that it comprises means implementing a process for managing the torques applied on the front and rear axles comprising the any of the foregoing features.

In particular, the motorization of the front axle may include a heat engine and the motorization of the rear axle an electric traction machine.

The invention will be better understood, and other objects, characteristics, details and advantages thereof will appear more clearly in the explanatory description which follows, made with reference to the appended drawings given solely by way of example illustrating an embodiment of the invention, and in which:

- Figure 1 is a diagram of a motor vehicle comprising a motorization on each running gear, implementing a management method according to the invention;

- Figures 2 and 3 are graphs showing as a function of time, a method respectively according to the prior art and according to the invention, for managing the torques of the motorizations of this vehicle in the case of a braking request from the driver; and

- Figures 4 and 5 are graphs showing as a function of time, a method respectively according to the prior art and according to the invention, for managing the torque of the motorizations in the case of a request for acceleration of the driver.

Figure 1 shows a vehicle having at the front a heat engine 2 driving a gearbox 4, which is connected to the two front drive wheels 6 by the front wheel shafts 8. Similarly an electric machine 10 drives a transmission 12 which is connected to the two rear driving wheels 14 by rear wheel shafts 16.

An electronic powertrain management computer 18 delivers torque instructions for each engine 2, 10, in order to meet the driver's request while optimizing overall energy consumption. For each running gear, an electronic ESP stability program uses an MSR engine torque control function to modify the torque delivered by each engine 2, 10, in order to avoid locking of the wheels during braking requested by the driver.

Similarly for each running gear, the electronic stability program ESP also uses a function for regulating the braking torque ASR to reduce the torque delivered by its engine 2, 10 or apply braking with the wheel brakes, in order to '' avoid slipping of these wheels during acceleration requested by the driver.

On a vehicle equipped with two drive trains, the driver's will is divided between these two trains. By default, a target of torque to be achieved by the rear axle is established, then taking into account the distribution of the torque on the two trains, the rest of the driver's will is then achieved by the front axle.

When the driver requests for sufficiently high braking, the ESP electronic stability program activates the MSR engine torque control function to prevent the wheels from locking up. To do this, it sends a torque setpoint on a train whose wheels could lock, in order to reduce the negative torque coming from the distribution strategy between the two trains.

Similarly, when the driver requests a sufficiently high acceleration, the ESP electronic stability program activates the ASR braking torque regulation function to prevent wheel slip, which sends a setpoint torque to decrease the positive torque from the distribution strategy.

In some cases the torque requested on a running gear by the engine torque control function MSR, or ASR braking torque respectively, can become positive, or respectively negative. The ESP electronic stability program having priority, this torque is then rejected on the other running gear by giving two pairs of opposite signs on the two trains.

The invention consists in saturating the positive setpoint of the engine torque regulation function MSR, or respectively the negative setpoint of the braking torque function ASR, at zero to avoid two pairs of opposite signs. By calibration, it is possible to decide whether the saturation of the setpoint is applied to the front axle or the rear axle.

Figures 2, 3, 4 and 5 show as a function of time t, in the upper part an activation curve 20 of the electronic stability program ESP, which is deactivated at level 0 and activated at level 1. The lower part has different torques C on each running gear, brought to the level of the wheels of this train, which can be positive by forming an engine torque accelerating the vehicle or negative by forming a braking torque decelerating this vehicle.

In particular, a first curve represents the request from the driver 22 for positive acceleration or negative braking torque of the vehicle. A second front axle torque curve 24 represents the total torque applied to the front axle, a third rear axle unsaturated torque curve 26 represents the total torque applied to the rear axle with a management method according to the prior art, and a fourth curve of saturated rear axle torque 30 represents the total torque applied to the rear axle with a management method according to the invention. The total torque applied to the rear axle is given by the electric machine 10 and by the brakes of the rear wheels 14.

Figure 2 shows from time tO a request from the vehicle braking conductor increasingly strong, the driver demand torque 22 decreases regularly until time t1 to express the increasing negative torque to be applied to all of the wheels 6, 14 of the vehicle.

At time tO there is already a braking torque given by the rear electric machine 10 to recover electrical energy, the unsaturated rear axle torque 26 has a negative constant value C1. From the instant t0, the engine brake of the heat engine 2 and the front wheel brakes act, the front axle torque 24 decreases regularly, adding to the negative value C1 of unsaturated rear axle torque 26, progress towards braking the vehicle meeting the driver's request 22.

At time t1 the braking torque on the rear axle is too great with a risk of locking the rear wheels. The electronic stability program ESP is activated by going to level 1. The rear electric machine 10 instantaneously decreases its negative unsaturated rear axle torque 26 to reach the negative value C3 which joins the front axle torque 24.

Then there is a gradual rise in the negative unsaturated rear axle torque 26, corresponding to the gradual descent of the front axle torque 24 so as to obtain total braking of the vehicle corresponding to the request of the driver 22 which is stable at level C2.

At time t3 the unsaturated rear axle torque 26 stabilizes at a slightly positive value C4, compensated by a front axle torque 24 at level C5 which is slightly below level C2 of the driver's request 22 , to get this request. We then have a couple opposition, the couple being positive on the rear axle and negative on the front axle.

This situation giving both braking of the front axle and an acceleration of the rear axle can be felt by the driver. In addition, an overall poor energy efficiency of the vehicle is obtained, which is penalized by the energy consumption of the rear electric machine 10.

Figure 3 shows the saturated negative rear axle torque 30, which is saturated at the maximum zero value, to remain negative or zero. We then obtain after instant t2 a front axle torque 24 remaining negative at the constant value C2 which is precisely the value requested by the driver, the rear axle not adding positive engine torque.

There is no longer any opposition between the torques applied to the two undercarriages, which stabilizes the vehicle and optimizes energy consumption.

Figure 4 shows from the instant tO an increasing demand from the driver to accelerate the vehicle, the driver demand torque 22 increases regularly until time t1 to express the increasing positive torque to be applied to all of the wheels 6, 14 of the vehicle.

At time tO there is already an acceleration torque given by the rear electric machine 10, the unsaturated rear axle torque 26 has a positive constant value C1. From the instant tO the heat engine acts, the front axle torque 24 increases regularly so, in addition to the positive value C1 of unsaturated rear axle torque 26, progress towards the acceleration of the responding vehicle at the driver's request 22.

At time t1 the acceleration torque on the rear axle is too great with a risk of slipping of the rear wheels. The electronic stability program ESP is activated by going to level 1. The rear electric machine 10 instantly decreases its positive unsaturated rear axle torque 26, to reach the positive value C3 which joins the front axle torque 24.

Then there is a gradual descent of the positive unsaturated rear axle torque 26, corresponding to the gradual rise of the front axle torque 24 so as to obtain a total acceleration of the vehicle corresponding to the request of the driver 22 which is stable at level C2.

At time t3 the unsaturated rear axle torque 26 stabilizes at a slightly negative value C4, compensated by a front axle torque 24 at level C5 which is slightly above level C2 of the driver's request 22, to obtain this request. We then have a couple opposition, the couple being negative on the rear axle and positive on the front axle.

This situation giving both acceleration of the front axle and braking of the rear axle can be felt by the driver. In addition, a poor overall energy efficiency of the vehicle is obtained, which is penalized by the energy consumption of the rear electric machine 10.

Figure 5 shows the saturated rear axle torque 30, which is saturated at the minimum zero value to remain positive or zero. We then obtain after time t2 a front axle torque 24 remaining positive at the constant value C2 which is precisely that requested by the driver, the rear axle not adding negative engine torque. There is no longer any opposition between the torques applied on the two running gear.

With the management method according to the invention, it is achieved in a simple and economical manner, with only additional software installed in an existing computer, an improvement in the overall energy balance of the vehicle, as well as better stability of the vehicle. vehicle ensuring comfort and safety.

Claims (7)

1. Method for managing the torques applied to the front and rear undercarriages of a motor vehicle each comprising a motorization (2, 10), this vehicle having an electronic stability program ESP for limiting the slip of the wheels (6, 14), requesting on each running gear to limit blocking during a request for braking by the driver, to increase the torque delivered by its motorization (2, 10), or to limit slippage during a request for acceleration of the driver, to reduce the torque delivered by his motorization (2, 10) or to apply braking to the brakes of his wheels (6, 14), characterized in that during the activation of the electronic stability program ESP, in braking setpoint on a first undercarriage, or acceleration setpoint on this first undercarriage, respectively, it applies a saturated negative torque setpoint at zero (30) on the second undercarriage, or respectively It also applies a saturated positive torque setpoint to the zero value (30) on this second running gear. 2. Management method according to claim 1, the motorization of the second train (10) comprising an electric traction motor, characterized in that during the activation of the ESP stability program, in the event of a braking instruction on the first train there sends a braking torque setpoint with the electric motor on the second train comprising a negative or zero value. 3. Management method according to claim 1 or 2, the motorization of the second train (10) comprising an electric traction machine, characterized in that during the activation of the ESP stability program, in the event of an acceleration setpoint on the first train it sends an acceleration torque setpoint with the electric motor on the second train comprising a positive or zero value. 4. Management method according to any one of the preceding claims, characterized in that the ESP stability program controls a function for regulating the torque MSR of a thermal traction engine (2), which increases the idling speed of this thermal engine in order to reduce its engine brake in the event of a risk of the wheels driven by this engine locking (6). 5. Management method according to any one of the preceding claims, characterized in that the ESP stability program controls a function for regulating the braking torque ASR, which on a running gear reduces the torque delivered by its motorization (2, 10 ) or apply braking with the wheel brakes, in order to limit the engine torque on its wheels (6, 14) to avoid their slipping. 6. Motor vehicle comprising a motorization (2, 10) on each running gear, characterized in that it comprises means implementing a management process 5 of the torques applied to the front and rear axles according to any one of the preceding claims. 7. Motor vehicle according to claim 6, characterized in that the engine of the front axle (2) comprises a heat engine and the engine of the rear axle (10) an electric traction machine.