BRAKING MANAGEMENT METHOD ENSURING SELF-CLEANING OF THE BRAKES

Abstract

BRAKING MANAGEMENT METHOD ENSURING SELF-CLEANING OF THE BRAKES The present invention relates to a method for 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 representative of a state of frequency of use of said friction braking system, remarkable in that said parameter K is determined on the basis of an accumulation of friction braking energy at each friction braking operation, said accumulation 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 Kseuil so as to ensure maintenance of the braking system. (Figure to be published with the abstract: Figure 1)

Description

Title of the invention: BRAKING MANAGEMENT METHOD ENSURING SELF-CLEANING OF THE BRAKES Technical field

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

[0002] Electric motor 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. This reduction, however, leads to a problem of developing deposits on these elements, including corrosion, affecting their integrity, braking performance, and the overall aesthetics 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 expensive and risks increasing the mass of the brake discs.

[0004] Published patent document WO 2020 / 21216 A1 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 are still 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. Statement of the invention

[0006] The present invention aims to overcome at least one of the drawbacks of the aforementioned state of the art. More particularly, the invention aims to propose a simple, efficient and economical solution for effectively treating corrosion of the brakes of electric traction motor vehicles using regenerative braking on a recurring basis.

[0007] To this end, the invention relates to a method for 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 representative of a state of frequency of use of said friction braking system, remarkable in that the parameter K representative of a state of frequency of use 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 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.

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

[0009] According to one embodiment, said method comprises 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 lower than or equal to the threshold value Kseuii.

[0010] According to one embodiment, 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 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 comprises a reduction in regenerative braking at the same time as an increase in friction braking in the presence of a vehicle speed lower than 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 negative torque demand is conditioned by: - pressure on the brake pedal of the motor vehicle; and / or - an automatic driving assistance function for the motor vehicle; and / or - engagement of an engine brake during release of the accelerator pedal of the motor vehicle.

[0016] The invention also relates to a computer program comprising computer-readable code instructions, remarkable in that said program causes the computer to implement the steps of the method for managing a braking system of an electrically powered 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, remarkable 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 execute the method for 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 with the parameter K, makes it possible to further optimize the choice of the relevant times in which the braking system of the motor vehicle 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.l] 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 the running of a corresponding motor vehicle;

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

[0022] [Fig.l] represents a graph 100 illustrating an evolution of a parameter K representative of a state of frequency of use of a friction braking system of a motor vehicle. The latter preferably being electric traction and comprising a braking system comprising 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 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 state of frequency of use of said friction braking system. More precisely, the parameter K is determined on the basis of an accumulation of friction braking energy at each friction braking operation. More precisely, the parameter K quantifies the accumulation of the instantaneous braking energy dissipated by the at least one friction brake of the motor vehicle.

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

[0026] For this purpose, 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 the parameter K is bounded by the maximum value Kmax ie, the value of the parameter K is programmed to never exceed the maximum value Kmax. Preferably, the parameter K is also bounded by the minimum value Kmin ie, the value of the parameter K is preferentially configured to not fall below the minimum value Kmin.

[0027] The values of K visible in the figures are only examples. For example, it can be seen that the maximum value Kmax is approximately 110 kJ higher than the threshold value K seuib and that the minimum value Kmin is approximately 250 kJ lower than said threshold value Kseuii. These values are open 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 of KseuU and of the limits Kmax and Kmin) can be configured according to the desired application.

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

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

[0030] The motor vehicle according to the invention preferably comprises a driving assistance system, commonly designated by the acronym “AD AS”, capable of managing the automatic driving assistance function (for example, distance regulation by radar, generally designated by ACC, for “Assistant Cruise Control”).

[0031] When there is a presence of 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 lower or higher than KseuU) before deciding on the automatic activation of the friction braking system, with a view to ensuring the self-cleaning of said system.

[0032] On graph 100, six vertical bars T0 to T5 can be seen, these correspond to journeys of the motor vehicle having an average duration of approximately 20 to 60 min. These journeys are represented as bars given that this is a very broad and distant view over a relatively long time scale (several days).

[0033] The trace F visible in the lower part of the graph 100 corresponds to the state of a computer flag (commonly designated by “Flag”) oscillating between 0 and 1, said flag corresponding to the automatic activation of the friction braking system (1) represented by an incrementation of the trace F from 0 to 1, or to the automatic deactivation of the friction braking system (0) represented by a drop 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 the negative torque request, then the friction braking of the motor vehicle is automatically activated. For example, it can be seen that during the journey T1, the conditions were met to activate the friction braking, which causes the cumulative energy dissipated in the brakes to change (increase in the parameter K).

[0035] When the maximum value Kmax is reached during the second trip T2, the flag changes to 0 (drop in the F line), which corresponds to an automatic deactivation of the friction braking. Indeed, reaching Kmax means that there has been a lot of energy 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 the reason why in the third path T3, there was no increment of the parameter K, which continued to decrease, said path T3 therefore experienced deceleration phases ensured solely by regenerative braking.

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

[0038] After the last path 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 rolling of the motor vehicle during the journey T4, i.e. over a shorter time range than that visible in graph 100 of [Fig.l].

[0040] Here, the T4 plot corresponds to a real-time evolution of the speed of the motor vehicle, from which the different phases of deceleration and acceleration of the vehicle can be deduced. Given that K was initially lower than its threshold value KSeuii, the flag is at 1 so the friction brakes are actuated when the conditions are met, which progressively increments the value of the parameter K at each deceleration.

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

[0042] It should be noted that the present invention is not limited to the speed values cited above; these are only examples which can be parameterized, for example, depending on 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 the parameter K are met, even without a negative torque request, or even during a positive torque request (during the acceleration phase of the motor vehicle).

[0044] Advantageously, the method of the invention comprises switching to friction braking only (without regenerative braking) when the motor vehicle is at a speed lower than the speed limit Vb, which corresponds to a braking phase allowing the motor vehicle to be completely stopped, commonly referred to as a “Blending” phase. The invention therefore allows switching to 100% friction braking, and this from a speed Vi (for example, equal to 20 km / h) which is higher than that conventionally used in conventional vehicles (generally 10 km / h), thus taking advantage of an additional 10 km / h to clean the rotating elements.

[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 to the rear axle of the motor vehicle. In this respect, the parameter K can be different between the brakes of the front and rear axle. For example, on a motor vehicle comprising drum brakes at the rear and disc brakes at the front, the evolution of the cumulative braking energy can be different (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 provision of friction braking to clean the brake discs only when it is necessary. necessary. Thus the friction braking input will be closely linked to the use made of the vehicle by the driver, leading to a variation in the frequency of this input as well as its intensity until it never has to be activated.

[0049] The automatic activation of the friction braking system (dissipative braking) as a function of the 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, “One-Pedal” type driving), 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

Claims

1. Method for 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 representative of a state of frequency of use of said friction braking system, characterized in that the parameter K representative of a state of frequency of use 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 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. The method of claim 1, wherein the activation of the friction braking system occurs in conjunction with the 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 lower than or equal to the threshold value Kseuii.

4. Method according to one of claims 2 and 3, in which 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 greater than a limit speed Vp

5. Method according to one of claims 2 to 4, in which the conjunction comprises a reduction in regenerative braking at the same time as an increase in friction braking in the presence of a vehicle speed lower than a limit speed Vp

6. Method according to one of claims 3 to 5, in which 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. Method according to one of claims 1 to 6, in which the negative torque demand 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 - engagement of an engine brake during release of the accelerator pedal of the motor vehicle.

8. Computer program comprising computer-readable code instructions, characterized in that said program causes the computer to implement the steps of the method for managing a braking system of an electrically powered motor vehicle according to 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 execute the method for managing a braking system of an electrically driven motor vehicle according to one of claims 1 to 9.

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