METHOD FOR REGULATING WHEEL TORQUE OF AN ELECTRIC OR HYBRID MOTOR VEHICLE IN CASE OF BRAKE OVERHEATING

Abstract

The invention relates to a method for regulating wheel torque in an electric or hybrid motor vehicle comprising a regenerative braking system, said brakes comprising a temperature estimation measurement means, a maximum positive torque being the maximum positive value of wheel torque achievable when the accelerator pedal is fully depressed, and a maximum negative torque being the maximum negative value of wheel torque achievable when the accelerator pedal is fully released. The method is characterized in that it comprises a step of calculating a brake temperature (E1) and a step of reducing the maximum positive torque and increasing the maximum negative torque (E2) when the brake temperature exceeds a first predetermined threshold value, the maximum positive torque being reduced to a first value, and the maximum negative torque being increased to a first value. Figure 1

Description

Title of the invention: METHOD FOR REGULATING WHEEL TORQUE OF AN ELECTRIC OR HYBRID MOTOR VEHICLE IN CASE OF BRAKE OVERHEATING

[0001] The invention relates to the wheel torques of electric or hybrid motor vehicles comprising a regenerative braking system.

[0002] Prior art patent application DE102007025926 is known, describing a method for managing the operation of a motor vehicle equipped with brakes when the brakes reach a high temperature. The method includes a step in which the maximum drive torque is reduced when the brake temperature exceeds a predetermined limit. The reduced maximum drive torque is determined based on the longitudinal incline of the road. The greater the incline of the road in the direction of vehicle travel, the higher the maximum drive torque. Conversely, the greater the incline of the road in the opposite direction of vehicle travel, the lower the drive torque. Thus, on an uphill slope, the drive torque is reduced, but it is higher than when the vehicle is traveling downhill. However, a drawback remains.Reducing the maximum drive torque prevents the brakes from overheating when they are already too hot. This compromises brake performance, and even overall brake function. This poses a danger to vehicle occupants.

[0003] The objective of the present invention is to remedy these drawbacks and improve the safety of vehicle occupants in the event of brake overheating.

[0004] To achieve this objective, the invention proposes a method for regulating the wheel torque of an electric or hybrid motor vehicle comprising a regenerative braking system, said vehicle comprising brakes and an accelerator pedal, said brakes comprising a means for measuring or estimating the temperature, a maximum positive torque being the maximum positive value of the wheel torque that can be reached when the accelerator pedal is fully depressed, a maximum negative torque being the maximum negative value of the wheel torque that can be reached when the accelerator pedal is fully released, notable in that said method comprises the following steps: - a step of calculating a brake temperature by said means of measuring or estimating temperature; - a step of reducing the maximum positive torque and increasing the maximum negative torque when the brake temperature is above a first predetermined threshold value and below a second predetermined threshold value, the maximum positive torque being reduced to a first predetermined value, the maximum negative torque being increased to a first predetermined value.

[0005] Thanks to the invention, occupant safety is improved in the event of brake overheating.

[0006] Advantageously, said vehicle has a driving speed, said vehicle having a limiter of the maximum driving speed, the maximum driving speed being limited to a predetermined maximum speed during the step of reducing the maximum positive torque and increasing the maximum negative torque.

[0007] Limiting the maximum driving speed reduces the risk of brake temperature increase and, consequently, prevents their malfunction.

[0008] Preferably, the predetermined maximum driving speed being equal to 100 km / h.

[0009] This is a speed that allows travel under normal conditions on the majority of roadways.

[0010] Advantageously, said method includes an additional step of reducing the maximum positive torque and increasing the maximum negative torque when the brake temperature is above the second predetermined threshold value, said second predetermined threshold value being above said first predetermined threshold value, the maximum positive torque being reduced to a second predetermined value, the second value of the maximum positive torque being below the first value of the maximum positive torque, the maximum negative torque being increased to a second value, the second value of the maximum negative torque being above the first value of the maximum negative torque.

[0011] Thus, if the brake temperature continues to rise despite the restrictions, the restrictions are strengthened.

[0012] Preferably, the maximum positive torque has a predetermined value, the maximum negative torque has a predetermined value, said first value of the maximum positive torque being reduced to 80% of the predetermined value of the maximum positive torque, said first value of the maximum negative torque being increased by 20% of the predetermined value of the maximum negative torque.

[0013] Such values ​​make it possible to avoid heating of the brakes without drastically impacting the driving of the vehicle.

[0014] Preferably, the second value of the maximum positive torque is reduced to 60% of the predetermined value of the maximum positive torque and the second value of the maximum negative torque is increased by 30% of the predetermined value of the maximum negative torque.

[0015] More drastic restrictions more effectively reduce the risks of brake overheating.

[0016] Advantageously, said vehicle includes a warning means, said method including a driver warning step during which said warning means is activated when the brake temperature is above the first predetermined threshold value.

[0017] In this way, the driver is informed of the change in torque at the wheel of his vehicle. This avoids the element of surprise, particularly during deceleration.

[0018] Preferably, said vehicle includes a dashboard, said warning means being a dashboard indicator light, said indicator light being configured to illuminate during said warning step.

[0019] A warning light on a dashboard is directly visible to the driver while driving.

[0020] Preferably, said vehicle includes a dashboard comprising a screen, said warning means being a message configured to be displayed on said screen during said warning step.

[0021] A message on a screen is clearer and does not require interpretation.

[0022] Furthermore, the invention relates to a computer program comprising instructions which, when the program is executed by a computer, lead the latter to implement the steps of the method of regulating the wheel torque of an electric or hybrid motor vehicle comprising a regenerative braking system previously described.

[0023] The invention will be further detailed by describing non-limiting embodiments, and based on the accompanying figures illustrating variants of the invention, in which: - [Fig.1] schematically illustrates, in the form of a logic diagram, a method for regulating the torque at the wheel of an electric or hybrid motor vehicle according to an embodiment of the invention; - [Fig.2] represents a graph illustrating the evolution of the wheel torque as a function of the accelerator pedal position in D mode, in B mode and in case of brake overheating.

[0024] A method for regulating wheel torque in an electric or hybrid motor vehicle comprising a regenerative braking system, according to an embodiment of the invention, is schematically illustrated in [Fig. 1] in the form of a flowchart. The vehicle includes brakes and an accelerator pedal. The brakes include a means for measuring or estimating temperature, enabling the determination of a brake temperature. The brakes are likely to experience a high temperature, particularly when the vehicle is traveling downhill. When the vehicle is loaded or during sporty driving, brake overheating reduces their performance and therefore poses a risk to vehicle occupants. Maximum wheel torque is the maximum value achievable when the accelerator pedal is fully depressed to the floor of the vehicle, i.e., when the driver is pressing the accelerator pedal to its maximum. Negative maximum wheel torque is the maximum value achievable when the accelerator pedal is fully released, i.e., when the driver is not applying any force to the accelerator pedal. When the accelerator pedal is partially or fully released, the regenerative braking system is activated.Indeed, regenerative braking is a system used in electric and hybrid vehicles to recover some of the kinetic energy generated during braking and convert it into electrical energy to recharge the vehicle's traction battery. This improves the vehicle's range. When the driver fully or partially releases the accelerator pedal, the vehicle brakes automatically. Therefore, in cases of poor brake performance due to overheating, it is advantageous to be able to brake effectively by releasing the accelerator pedal. The vehicle features a human-machine interface that allows the driver to select a driving mode. Among the different driving modes are D mode and B mode. D mode is characterized by moderate energy regeneration, with a minimal impact on the vehicle's braking performance.Conversely, mode B allows for more efficient energy regeneration, but stronger braking. Preferably, the maximum negative torque has a predetermined value equal to -5% of the maximum torque in mode D and -10% in mode B. The maximum positive torque also has a predetermined value. Figure 2 illustrates the evolution of wheel torque in mode D and mode B as a function of accelerator pedal position. During a brake temperature calculation step E1, the brake temperature measurement or estimation means calculates the brake temperature. During a maximum positive torque reduction and maximum negative torque increase step E2, the maximum positive torque is reduced to a first value and the maximum negative torque is increased to a first value when the brake temperature is above a first predetermined threshold value and below a second predetermined threshold value. Preferably, the first value of the maximum positive torque is reduced to 80% of the predetermined value of the maximum positive torque, while the first value of the maximum negative torque is increased by 20% of the predetermined value of the maximum negative torque.The evolution of wheel torque when brake temperature exceeds the first predetermined threshold value is illustrated in [Fig. 2] by curve HB. Excessive brake temperature is likely to cause [the problem]. Reduction in braking performance. By reducing the maximum positive torque, the risk of brake overheating is reduced, and the brakes remain functional. Furthermore, by increasing the maximum negative torque, regenerative braking is more effective, thus improving the safety of the vehicle's occupants. When the vehicle is moving, it has a cruising speed. Optionally, the vehicle is equipped with a maximum cruising speed limiter. The maximum cruising speed is limited by this limiter during the phase of reducing the maximum positive torque and increasing the maximum negative torque, i.e., when the brake temperature exceeds a predetermined threshold value. Preferably, the predetermined maximum cruising speed is 100 km / h.Optionally, the process includes an additional step of reducing the maximum positive torque and increasing the maximum negative torque, during which the maximum positive torque is further reduced following the initial reduction in step E2. The maximum positive torque is then reduced to a second value. This second value of the maximum positive torque is lower than the first value. Similarly, the maximum negative torque is again increased to a second value. The additional step is implemented when the brake temperature exceeds the second predetermined threshold value. This second predetermined threshold value is higher than the first predetermined threshold value. Preferably, the second value of the maximum positive torque is reduced to [value missing]. 60% of the maximum positive torque value and the second maximum negative torque value are increased by 30% of the maximum negative torque value. Optionally, the vehicle includes an instrument panel and a warning device. Preferably, the instrument panel includes a display. The warning device, preferably an instrument panel indicator light or a message, is designed to warn the driver of the reduction in maximum positive torque, the increase in maximum negative torque, and / or the limitation of the maximum driving speed during a warning phase. When the warning device is an indicator light on the instrument panel, that light is configured to illuminate during the warning phase. When the warning device is a message, that message is configured to be displayed on the instrument panel display during the warning phase.

[0025] Furthermore, the invention relates to a computer program configured to implement said method of regulating wheel torque of an electric or hybrid motor vehicle comprising a regenerative braking system previously described.

Claims

Demands

1. A method for regulating wheel torque of an electric or hybrid motor vehicle comprising a regenerative braking system, said vehicle comprising brakes and an accelerator pedal, said brakes comprising a means for measuring or estimating the temperature, a maximum positive torque being the maximum positive value of wheel torque that can be reached when the accelerator pedal is fully depressed, a maximum negative torque being the maximum negative value of wheel torque that can be reached when the accelerator pedal is fully released, characterized in that said method comprises the following steps: - a step of calculating a brake temperature (El) by said means for measuring or estimating the temperature;- a step of reducing the maximum positive torque and increasing the maximum negative torque (E2) when the brake temperature is above a first predetermined threshold value and below a second predetermined threshold value, the maximum positive torque being reduced to a first predetermined value, the maximum negative torque being increased to a first predetermined value.

2. The method according to claim 1 characterized in that said vehicle has a rolling speed, said vehicle comprising a limiter of the maximum rolling speed, the maximum rolling speed being limited to a predetermined maximum speed during the step of reducing the maximum positive torque and increasing the maximum negative torque.

3. The method according to claim 2 characterized in that the predetermined maximum rolling speed is equal to 100 km / h.

4. A method according to any one of claims 1 to 3 characterized in that said method comprises an additional step of reducing the maximum positive torque and increasing the maximum negative torque when the brake temperature is above the second predetermined threshold value, said second predetermined threshold value being above said first predetermined threshold value, the maximum positive torque being reduced to a second predetermined value, the second value of the maximum positive torque being below the first value of the maximum positive torque, the maximum negative torque being increased to a second value, the the second value of the maximum negative torque being greater than the first value of the maximum negative torque.

5. A method according to any one of claims 1 to 4 characterized in that the maximum positive torque has a predetermined value, the maximum negative torque has a predetermined value, said first value of the maximum positive torque being reduced to 80% of the predetermined value of the maximum positive torque, said first value of the maximum negative torque being increased by 20% of the predetermined value of the maximum negative torque.

6. Method according to claim 4 or 5 characterized in that the second value of the maximum positive torque is reduced to 60% of the predetermined value of the maximum positive torque and the second value of the maximum negative torque is increased by 30% of the predetermined value of the maximum negative torque.

7. A method according to any one of claims 1 to 6 characterized in that said vehicle comprises a warning means, said method comprising a driver warning step during which said warning means is activated when the brake temperature is above the first predetermined threshold value.

8. Method according to claim 7 characterized in that said vehicle comprises a dashboard, said warning means being a dashboard indicator light, said indicator light being configured to illuminate during said warning step.

9. Method according to claim 7 or 8 characterized in that said vehicle comprises a dashboard including a screen, said warning means being a message configured to be displayed on said screen during said warning step.

10. A computer program comprising instructions which, when the program is executed by a computer, cause the computer to implement the steps of the method for regulating wheel torque of an electric or hybrid motor vehicle comprising a regenerative braking system according to any one of claims 1 to 9.

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