BRAKE MANAGEMENT METHOD ENSURING SELF-CLEANING OF BRAKES

Abstract

BRAKE MANAGEMENT METHOD ENSURING SELF-CLEANING OF BRAKES The present invention relates to a method for managing a friction braking system of an electric motor vehicle with regenerative braking, said method comprising automatic activation of the friction braking system as a function of a parameter K representing a state of usage frequency of said friction braking system, notable in that said parameter K is determined on the basis of a cumulative friction braking energy at each friction braking operation, said cumulative energy decreasing monotonically with time according to a predetermined law, and the automatic activation of the friction braking system occurs in the presence of a negative torque demand and when the parameter K is equal to or less than a threshold value Kthreshold so as to ensure maintenance of the braking system. (Figure to be published with the abstract: Figure 1)

Description

Title of the invention: BRAKE MANAGEMENT METHOD ENSURING SELF-CLEANING OF BRAKES technical field

[0001] The present invention relates to the field of motor vehicles, more particularly to the field of motor vehicle braking systems. Previous technique

[0002] Electric vehicles equipped with regenerative braking systems see a decrease in the use of their conventional friction braking systems against rotating elements such as discs or drums. However, this reduction leads to a problem of deposit development on these elements, including corrosion, affecting their integrity, braking performance, and the overall appearance of the brakes.

[0003] One possible solution would be to treat the brake discs organically to prevent the formation of these deposits, but this approach is costly and risks increasing the mass of the brake discs.

[0004] The published patent document WO 2020 / 21216 Al discloses a method for managing a vehicle braking system incorporating regenerative braking. This method proposes a self-cleaning operating mode defined by a predetermined fixed ratio between a deceleration torque applied by the friction brake and that applied by the regenerative braking to decelerate the vehicle.

[0005] However, there remain possibilities for improving this solution to optimize the efficiency of friction brake maintenance in a more targeted and precise manner, while optimizing the energy balance of electric vehicles. Description of the invention

[0006] The present invention aims to overcome at least one of the drawbacks of the aforementioned prior art. More particularly, the invention aims to provide a simple, efficient, and economical solution for effectively treating brake corrosion in electric motor vehicles that regularly use regenerative braking.

[0007] To this end, the invention relates to a method for managing a friction braking system of an electric motor vehicle with regenerative braking, said method comprising an automatic activation of the friction braking system as a function of a parameter K representing a state of use frequency of said friction braking system, remarkable in that the parameter K representing a state of use frequency of the friction braking system is determined on the basis of an accumulation of friction braking energy at each friction braking operation, said accumulation decreasing monotonically over time according to a predetermined law, and the automatic activation of the friction braking system takes place in the presence of a negative torque demand and when the parameter K is equal to or less than a threshold value KseuU so as to ensure maintenance of the braking system.

[0008] According to one embodiment, the activation of the friction braking system takes place in conjunction with regenerative braking.

[0009] According to one embodiment, said method includes an automatic deactivation of the friction braking system when the parameter K is equal to a maximum value Kmax, greater than the threshold value KseuU, and is reactivated when the parameter K becomes less than or equal to the threshold value Kseuii.

[0010] According to one embodiment, the conjunction includes a combination of friction braking and regenerative braking when the negative torque demand is expressed in the presence of a vehicle speed greater than a limit speed Vj.

[0011] Preferably, the combination of friction braking and regenerative braking is configurable between 0% and 100%. For example, friction braking can be used at 70% when regenerative braking is used at 30%.

[0012] According to one embodiment, the conjunction includes a decrease in regenerative braking at the same time as an increase in friction braking in the presence of a vehicle speed below a limit speed Vj.

[0013] Preferably, the limit speed Vi is greater than or equal to 20 km / h.

[0014] According to one embodiment, the maximum value Kmax of the parameter K is greater than the threshold value Kseun, said parameter K being bounded by the maximum value Kmax, and comprising a minimum value Kmin which is less than or equal to the threshold value Kseuii.

[0015] According to one embodiment, the demand for negative torque is conditioned by: - pressure on the brake pedal of the motor vehicle; and / or - an automatic vehicle driving assistance function; and / or - an engagement of engine braking during a release of the accelerator pedal of the motor vehicle.

[0016] The invention also relates to a computer program comprising computer-readable code instructions, notable in that said program leads the computer to implement the steps of the method for managing a braking system of an electric traction motor vehicle according to the invention, when said program is executed by a computer.

[0017] The invention also relates to a device comprising a computer-readable recording medium, notable in that the computer program according to the invention is recorded on the recording medium.

[0018] The invention further relates to a motor vehicle, remarkable in that said motor vehicle is configured to perform the method of managing a braking system of an electric traction motor vehicle according to the invention.

[0019] The measures of the invention are advantageous in that the method automatically actuating the friction braking of the motor vehicle in a manner correlated to the parameter K, makes it possible to further optimize the choice of the relevant moments in which the motor vehicle's braking system requires self-cleaning against corrosion, thus effectively limiting the appearance of corrosion on rotating elements of the braking system, and this at a lower cost and while optimizing the energy balance of the vehicle. Brief description of the drawings

[0020] [Fig.1] represents a graph illustrating an evolution of a parameter K representative of a state of frequency of use of a friction braking system, as a function of time and of the rolling of a corresponding motor vehicle;

[0021] [Fig.2] represents an enlarged view illustrating the evolution of the parameter K as a function of the driving of the motor vehicle, over a shorter time range than that visible in the graph of [Fig.1]. Detailed description

[0022] Figure 1 shows a graph illustrating the evolution of a parameter K representing a usage frequency state of a friction braking system of a motor vehicle. The latter preferably being electrically driven and comprising a braking system including at least one electric regenerative braking module, and at least one friction brake against a rotating element which may correspond to a brake disc or a drum.

[0023] The method proposed by the present invention makes it possible to ensure maintenance of the braking system, advantageously by self-cleaning of the rotating element, so as to eliminate deposits (including corrosion) on its surface.

[0024] In this regard, the method monitors the evolution of the parameter K, which is representative of a usage frequency state of said friction braking system. More precisely, the parameter K is determined based on the cumulative friction braking energy at each friction braking operation. More specifically, the parameter K quantifies the cumulative instantaneous braking energy dissipated by at least one friction brake of the motor vehicle.

[0025] The parameter K changes constantly over time, and is expressed in Kilojoules (kJ) on the ordinate axis to the right of graph 100.

[0026] To this end, the method of the invention predefines three levels of the parameter K: a threshold value Kseuii arranged between a maximum value Kmax and a minimum value Kmin. The value of parameter K is bounded by the maximum value Kmax, i.e., the value of parameter K is programmed to never exceed the maximum value Kmax. Preferably, parameter K is also bounded by the minimum value Kmin, i.e., the value of parameter K is preferably configured to never fall below the minimum value Kmin.

[0027] The K values ​​shown in the figures are only examples. For instance, it can be seen that the maximum value Kmax is approximately 110 kJ higher than the threshold value Kseuib and that the minimum value Kmin is approximately 250 kJ lower than said threshold value Kseuii. These values ​​are variable and depend, among other things, on the size of the brakes and / or the mass of the vehicle. Thus, the values ​​of the parameter K (in particular KseuU and the Kmax and Kmin limits) can be configured according to the desired application.

[0028] The energy accumulation (parameter K) is configured to decrease monotonically over time according to a predetermined law, said law being linear or non-linear, and in which the decrease of parameter K may, for example, be equal to about 110 kJ in 24 hours.

[0029] A negative torque demand from the motor vehicle corresponds to the activation of a deceleration phase of the motor vehicle, by pressing on the motor vehicle's brake pedal; and / or by an automatic driving assistance function of the motor vehicle; and / or by engaging engine braking during a release of the motor vehicle's accelerator pedal.

[0030] The motor vehicle according to the invention preferably includes a driving assistance system, commonly referred to by the acronym "AD AS", which can ensure the management of the automatic driving assistance function (for example, a distance regulation by radar, generally referred to as ACC, for "Assistant Cruise Control").

[0031] When there is a negative torque demand from the motor vehicle, then the method of the invention checks the state of the parameter K (if its value is less than or greater than KseuU) before deciding on the automatic activation of the friction braking system, in order to ensure the self-cleaning of said system.

[0032] Graph 100 shows six vertical bars T0 to T5, which correspond to journeys of the motor vehicle with an average duration of approximately 20 to 60 minutes. These journeys are represented as bars because it is a very wide and distant view over a relatively long time scale (several days).

[0033] Trace F visible at the bottom of graph 100 corresponds to the state of a computer flag (commonly referred to as "Flag") oscillating between 0 and 1, said flag corresponding to the automatic activation of the friction braking system (1) represented by an increment of trace F from 0 to 1, or to automatic deactivation of the friction braking system (0) represented by a decrease from 1 to 0 of the trace F. The trace F thus represents the connected or disconnected state of the active friction braking proposed by the invention.

[0034] Advantageously, when the parameter K is less than the threshold value KseuU, during negative torque demand, the friction braking of the motor vehicle is automatically activated. For example, it can be seen that during the journey Tl, the conditions were met to activate the friction braking, which increases the cumulative energy dissipated in the brakes (increase in the parameter K).

[0035] When the maximum value Kmax is reached during the second journey T2, the flag changes to 0 (trace F decreases), which corresponds to an automatic deactivation of the friction braking. Indeed, reaching Kmax means that a significant amount of energy has been dissipated by friction in the brakes, which is correlated with a low risk of corrosion on the rotating element.

[0036] Preferably, the method of the invention establishes as a rule the automatic deactivation of the friction braking system when the parameter K is greater than or equal to its maximum value Kmax. This is why, on the third journey T3, there was no increment of the parameter K, which continued to decrease; said journey T3 therefore experienced deceleration phases ensured solely by regenerative braking.

[0037] The flag switches to 1 as soon as the parameter K falls below its threshold value, so as to allow automatic activation of the friction braking for the next journey T4 of the motor vehicle, during which Kmax has again been reached.

[0038] After the last journey T5 of graph 100, the parameter K reaches its minimum level Kmin after several days (for example 8 days) without driving the motor vehicle, following which the risk of corrosion of the rotating braking elements is high.

[0039] Fig. 2 represents a graph 101 corresponding to an enlarged view illustrating the evolution of the parameter K as a function of the driving of the motor vehicle during the journey T4, i.e. over a shorter time range than that visible in graph 100 of Fig. 1.

[0040] Here, the T4 trace corresponds to a real-time evolution of the vehicle's speed, from which the different phases of deceleration and acceleration of the vehicle can be deduced. Since K was initially lower than its threshold value KSeuii, the flag is set to 1, and the friction brakes are then activated when the conditions are met, progressively increasing the value of the parameter K with each deceleration.

[0041] Advantageously, the activation of the friction braking system takes place in conjunction with regenerative braking, preferably when the conditions related to the parameter K and the negative torque demand are met, and also when the motor vehicle is traveling at a speed that is greater than a limit speed Vi which is preferably between 15 and 30 km / h (equal, for example, to about 20 km / h), and more preferably when the speed of the motor vehicle is between two limit speeds Vi and V2, said speed V2 corresponding, for example, to about 60 km / h (±10 km / h).

[0042] It should be noted that the present invention is not limited to the speed values ​​mentioned above; these are only examples that can be parameterized, for example, according to the motor vehicle.

[0043] Alternatively, the method of the invention can also activate the friction braking system (with or without regenerative braking) only when the conditions relating to parameter K are met, even without a negative torque demand, or even during a positive torque demand (during the acceleration phase of the motor vehicle).

[0044] Advantageously, the method of the invention comprises switching to friction-only braking (without regenerative braking) when the motor vehicle is at a speed below the speed limit Vb, which corresponds to a braking phase allowing the motor vehicle to come to a complete stop, commonly referred to as the "Blending" phase. The invention thus allows switching to 100% friction braking, starting from a speed Vi (for example, equal to 20 km / h) which is higher than that typically used in conventional vehicles (generally 10 km / h), thereby taking advantage of an additional 10 km / h to clean the rotating parts.

[0045] Preferably, each of the friction braking and regenerative braking being preferentially configurable between 0% and 100%.

[0046] The automatic activation of the friction braking system according to the method of the invention can be applied independently to the front axle and / or the rear axle of the motor vehicle. In this respect, the parameter K may differ between the front and rear axle brakes. For example, on a motor vehicle with drum brakes at the rear and disc brakes at the front, the evolution of the cumulative braking energy may differ (thus influencing the parameter K). The method is advantageously capable of taking this difference into account.

[0047] The method of the invention is preferably in the form of a computer program (algorithm) recorded in a recording medium of the motor vehicle, so as to allow its execution by a computer of said motor vehicle.

[0048] Advantageously, the management method according to the invention leads to the application of friction braking to clean the brake discs only when it is necessary necessary. Thus, the contribution of friction braking will be closely linked to the use made of the vehicle by the driver, leading to a variation in the frequency of this contribution as well as its intensity until it never has to be activated.

[0049] Automatic activation of the friction braking system (dissipative braking) according to parameter K can advantageously take place during all phases of the life of the motor vehicle in which a braking torque is produced, and this from any origin, i.e., by pressing the brake pedal, by lifting the foot (for example, driving of the type: "One-Pedal"), by a driving assistance function (ACC, etc.).

[0050] Advantageously, the invention makes it possible to ensure maintenance of the braking system of the motor vehicle in a simple and efficient manner, while optimizing the energy balance of said vehicle.

Claims

Demands

1. Method of managing a friction braking system of an electric traction motor vehicle with regenerative braking, said method comprising an automatic activation of the friction braking system as a function of a parameter K representing a state of use frequency of said friction braking system, characterized in that the parameter K representing a state of use frequency of the friction braking system is determined on the basis of a cumulative friction braking energy at each friction braking operation, said cumulative decreasing monotonically with time according to a predetermined law, and the automatic activation of the friction braking system takes place in the presence of a negative torque demand and when the parameter K is equal to or less than a threshold value KseuU so as to ensure maintenance of the braking system.

2. A method according to claim 1, wherein the activation of the friction braking system takes place in conjunction with regenerative braking.

3. Method according to claim 2, comprising an automatic deactivation of the friction braking system when the parameter K is equal to a maximum value Kmax, greater than the threshold value KseuU, and is reactivated when the parameter K becomes less than or equal to the threshold value Kseuii.

4. A method according to any one of claims 2 and 3, wherein the conjunction comprises a combination of friction braking and regenerative braking when the negative torque demand is expressed in the presence of a vehicle speed exceeding a limiting speed Vp

5. A method according to any one of claims 2 to 4, wherein the combination includes a decrease in regenerative braking along with an increase in friction braking when the vehicle speed is below a limiting speed Vp

6. A method according to any one of claims 3 to 5, wherein the maximum value Kmax of the parameter K is greater than the threshold value KseuU, said parameter K being bounded by the maximum value Kmax, and comprising a minimum value Kmin which is less than or equal to the threshold value Kseuii.

7. A method according to any one of claims 1 to 6, wherein the demand for negative torque is conditioned by: - pressure on the brake pedal of the motor vehicle; and / or - an automatic driving assistance function of the motor vehicle; and / or - the engagement of engine braking during a release of the accelerator pedal of the motor vehicle.

8. A computer program comprising computer-readable code instructions, characterized in that said program leads the computer to implement the steps of the method for managing a braking system of an electrically powered motor vehicle according to any one of claims 1 to 7, when said program is executed by a computer.

9. Device comprising a computer-readable recording medium, characterized in that the computer program according to claim 8 is recorded on the recording medium.

10. Motor vehicle, characterized in that said motor vehicle is configured to perform the method of managing a braking system of an electrically powered motor vehicle according to any one of claims 1 to 9.

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