FR3120590A1 - METHOD FOR CONTROLLING AN ELECTRIC PARKING BRAKE SUITABLE FOR NEW BRAKES - Google Patents

Abstract

The present invention relates to a method for controlling an electric parking brake (30) of a motor vehicle, said electric parking brake (30) comprising: - a braking control device (31), and - at least a geared motor (32) arranged on a brake chamber (17.2, 17.3) associated with a wheel of the motor vehicle, said geared motor (32) being controlled by the braking control device (31). According to this method, during a break-in period of wear elements of the brake chamber, a break-in braking force applied to at least one brake chamber (17.2, 17.3) to immobilize the motor vehicle is greater than a breaking-in force nominal braking applied to the brake chamber (17.2, 17.3) by the electric parking brake (30) outside the running-in period. Figure 2

Description

METHOD FOR CONTROLLING AN ELECTRIC PARKING BRAKE SUITABLE FOR NEW BRAKES

The present invention relates to a method for controlling an electric parking brake suitable for new brakes. The invention finds a particularly advantageous, but not exclusive, application with vehicles equipped with disc or drum brakes.

In a manner known per se, the parking brake of a motor vehicle comprises a braking control device and geared motors each arranged on a brake chamber associated with a wheel of the motor vehicle. The control device comprises a control button connected to a computer capable of controlling the geared motors. The computer may also be in communication with components external to the braking system.

When the driver wishes to leave his vehicle, the parking brake is activated to ensure that the vehicle is held stationary. This action can be initiated either by direct action on the control button or by switching off the engine or opening the driver's door at zero speed. The parking brake computer then receives an order to apply from these components outside the braking system.

There shows the evolution of a braking efficiency Eff_fr corresponding to a torque delivered by the brake receiver for a given clamping force of the pads on a disc or of segments on a drum as a function of the mileage of the vehicle. This figure shows that when the vehicle is new, there is a period of use of the braking systems, called the running-in period P_rod_1, during which the braking efficiency Eff_fr is lower than the nominal case. This is also the case each time the brake discs and pads or the shoes and drums are replaced in the life of the vehicle (cf. P_rod_2 on the graph).

It should be noted that on this graph, the running-in period P_rod_1, P_rod_2 has been exaggerated (the abscissa scale is not real), insofar as this running-in period represents a few hundred kilometers whereas the replacement of the brakes operates after several tens of thousands of kilometres. On the other hand, the ordinate scale is real, i.e. there is indeed a loss of braking efficiency of around 30% during a running-in period.

Thus, for a new vehicle or after each change of wearing elements, the braking force between the tire and the ground is reduced by approximately 30% for the same force delivered by the geared motor. The specificity of this life phase of the vehicle is not subject to a specific control law in vehicles. Indeed, there is generally a single control law that applies throughout the life of the vehicle.

This control law can lead to:

- non-immobilization of the vehicle, which is not acceptable in terms of safety. It is then necessary to provide an auxiliary device of the park pin type associated with a transmission device.

- organic oversizing of the parking brake to cover an infrequent life situation, or

- the implementation of a vehicle movement monitoring strategy based on wheel speed sensors of an anti-lock braking system (known as the "ABS" system for "Antiblockiersystem" in German). However, there are security risks related to an electrical problem or a simple disconnection of the battery making this monitoring impossible.

The invention aims to effectively remedy these drawbacks by proposing a method for controlling an electric parking brake of a motor vehicle, said electric parking brake comprising:

- a braking control device, and

- At least one gear motor disposed on a brake chamber associated with a wheel of the motor vehicle, said gear motor being controlled by the brake control device.

According to the invention, during a break-in period of wear elements of the brake chamber, a break-in braking force applied to the brake chamber to immobilize the motor vehicle is greater than a nominal braking force applied to the brake chamber by the electric parking brake outside the running-in period.

The invention thus makes it possible, thanks to the application of an exceptional tightening force during the running-in period, to guarantee the immobility of the vehicle during this phase of the life of the vehicle, without abnormally stressing, the rest of the time, the electric parking brake of the motor vehicle. The invention avoids oversizing the braking system in a costly manner. The invention also makes it possible to eliminate costly ancillary mechanical devices, such as the park finger on the transmission.

According to one implementation, a start of the running-in period corresponds to leaving the factory of the new motor vehicle or to replacing the wear elements of the brake chamber.

According to one implementation, a duration of the running-in period corresponds to a predetermined mileage.

According to one implementation, a duration of the break-in period corresponds to a predetermined accumulation of kinetic energy dissipated in the brake chamber.

According to one implementation, a duration of the running-in period corresponds to a dissipative braking efficiency threshold.

According to one implementation, the running-in braking force is between 1.2 and 1.4 times the nominal braking force and is preferably 1.3 times the nominal braking force.

According to one implementation, the running-in braking force is obtained solely by virtue of a tightening of the brake chamber carried out by the geared motor.

According to one implementation, the break-in braking force is obtained by combining a hydraulic pressure produced by a device for modulating the pressure of a hydraulic fluid circulating in hydraulic circuits simultaneously with a tightening of the brake chamber by the gear motor.

According to one implementation, the nominal braking force applied by the electric parking brake depends on an inclination of the motor vehicle, and/or on a hydraulic pressure in the braking circuits, and/or on an estimated temperature or measured from the brake chamber.

The invention further relates to a computer comprising a memory storing software instructions for implementing the method for controlling an electric parking brake of a motor vehicle as defined above.

The invention will be better understood on reading the following description and on examining the accompanying figures. These figures are given only by way of illustration but in no way limit the invention.

There , already described, is a graphic representation of a change in braking efficiency as a function of mileage of a motor vehicle;

There is a schematic representation of a braking system provided with an electric parking brake intended to implement the method according to the invention intended to adapt the braking force for new brakes;

There is a diagram of the steps of the method according to the invention intended to adapt the braking force for new brakes.

There represents a braking system 10 equipped with a pressure modulation device 16 of a hydraulic fluid flowing in the hydraulic circuits of the system 10, in particular a path control device, called ESC device for "Electronic Stability Control" in English.

The braking system 10 is supplied with hydraulic fluid, also called "braking fluid", by a master cylinder 11 connected to a braking amplifier 12 actuated by a brake pedal 13 on which a driver can act. These elements belong to a control device 14. As a variant, in the context of autonomous vehicle applications, the braking amplifier 12 can be actuated automatically by an electronic control module.

The master cylinder 11 has two chambers isolated from each other. Each of the two chambers of the master cylinder 11 independently supplies a first hydraulic circuit 15.1 and a second hydraulic circuit 15.2 of the device 16. The first circuit 15.1 and the second circuit 15.2 are distributed in "X", that is to say that the first circuit 15.1 supplies hydraulic fluid to a control chamber of a brake chamber 17.1 of a right front wheel and of a brake chamber 17.2 of a left rear wheel, and that the second circuit 15.2 supplies hydraulic fluid a chamber for controlling a brake chamber 17.4 of a left front wheel and a brake chamber 17.3 of the right rear wheel. As a variant, another type of architecture could be implemented according to which the first circuit 15.1 supplies the chambers of the two front brake chambers 17.1, 17.4 and the second circuit 15.2 supplies the chambers of the two rear brake chambers 17.2, 17.3. The brake chambers 17.1-17.4 may take the form of drum brakes or disc brakes.

The first circuit 15.1 and the second circuit 15.2 consist, for each brake chamber 17.1-17.4, of an inlet branch 20 and a discharge branch 21. An inlet branch 20 comprises an inlet solenoid valve 20.1. A discharge branch 21 comprises, positioned in series, a discharge solenoid valve 21.1 and a discharge pump 21.2.

Whether for the first circuit 15.1 or for the second circuit 15.2, a single common delivery pump 21.2 can be used for two delivery branches 21 connected to two brake receivers 17.1-17.4 powered by the same control chamber of the master- cylinder 11.

The device 16 also comprises, for each circuit 15.1, 15.2, a solenoid valve 23 for isolation from the master cylinder 11 as well as a solenoid valve 24 for supply from the master cylinder 11.

Furthermore, a sensor 13.1 is capable of measuring a displacement of the brake pedal 13 or of the pistons of the master cylinder 11 over all or part of its movement. A pressure sensor 25 is able to measure the pressure in the braking system 10.

A computer 27, which is for example that of the ESC, is capable of controlling the various components of the braking system 10, in particular the solenoid valves, according to the information coming from the sensors 13.1 and 25.

An electric parking brake 30 comprises a braking control device 31 and geared motors 32 each arranged on a braking receiver 17.2, 17.3 associated with a wheel of the motor vehicle. The geared motors 32 are controlled by the braking control device 31.

To this end, the braking control device 31 comprises a control button 33 connected to a computer 35 in communication with the geared motors 32 arranged on the braking receivers 17.2, 17.3. Generally, the gearmotors 32 are arranged on the brake chambers 17.2, 17.3 located at the rear of the vehicle, but they could be arranged on the brake chambers 17.1, 17.4 located at the front of the vehicle. The computer 35 may also be in communication with components 36 external to the braking system, such as the engine or the driver's door.

The communication between the computer 35 and the various elements is carried out via the links 37.1, 37.2, and 37.3. Link 37.1 is a wired signal link between control button 33 and computer 35. Links 37.2 are power and possibly signal links between computer 35 and geared motors 32. Link 37.3 is a signal link between the computer 35 and the external components 36.

When the driver wishes to leave his vehicle, the electric parking brake 30 is actuated to ensure that the vehicle is held stationary. This action can be initiated either by direct action on the control button 33 or by switching off the engine or opening the driver's door at zero speed. The computer 35 of the electric parking brake 30 then receives an order to apply from these external components 36.

The computer 35 includes a memory 35.1 storing software instructions for implementing the method according to the invention for controlling the electric parking brake 30 adapted to new brakes.

According to this method, during a break-in period of wear elements of the brake chambers 17.2, 17.3, a breaking-in braking force Fr applied to a brake chamber 17.2, 17.3 to immobilize the motor vehicle is greater than a breaking-in force nominal braking Fn applied to the braking receiver 17.2, 17.3 by the electric parking brake 30 outside the running-in period.

The wear elements are the pads and the disc for a brake chamber 17.2, 17.3 of the disc brake type or the shoes and the drum for a brake chamber 17.2, 17.3 of the drum brake type. The braking force is a tightening force between the pads and the brake disc for a brake chamber 17.2, 17.3 of the disc brake type or between the shoes and the drum for a brake chamber 17.2, 17.3 of the brake type. drum.

A start of the running-in period corresponds to leaving the factory of a new motor vehicle or to replacing the wear elements of the brake chambers. In a step 101 of the diagram of the , the computer 35 is thus informed that the vehicle leaving the factory has new wear elements or that the wear elements of the brake chambers 17.2, 17.3 have been replaced by the mechanic. The mechanic can communicate this information to the computer 35 via a communication interface of the motor vehicle.

A duration of the running-in period P_rod_1, P_rod_2 (cf. ) preferably corresponds to a predetermined mileage, in particular of the order of 1000 km. Once this mileage has been reached, we consider that we are outside the running-in period P_rod_1, P_rod_2.

As a variant, the duration of the running-in period P_rod_1, P_rod_2 may correspond to a predetermined accumulation of kinetic energy dissipated in the braking chambers. The cumulative kinetic energy can be calculated using information such as the speed of the motor vehicle, the deceleration of the vehicle during a braking phase and other parameters if necessary. Once this accumulation of dissipated kinetic energy has been reached, it is considered that the running-in period P_rod_1, P_rod_2 is outside.

As a variant, the duration of the running-in period P_rod_1, P_rod_2 may correspond to a dissipative braking efficiency threshold. This dissipative braking efficiency threshold can be determined through hydraulic pressure and vehicle deceleration information while taking into account a rate of electrical energy recovery in the case of an electric vehicle. Once this dissipative braking efficiency threshold has been reached, it is considered that the running-in period P_rod_1, P_rod_2 is outside.

During the break-in period P_rod_1, P_rod_2, the break-in braking force Fr applied in a step 102 to immobilize the parked vehicle is between 1.2 and 1.4 times the nominal braking force Fn and is preferably 1.3 times the nominal braking force, i.e. Fr = 1.3xFn.

The break-in braking force Fr can be obtained only by tightening the brake receivers 17.2, 17.3 performed by the geared motors 32. This is possible if the geared motors 32 are capable of providing more effort while consuming more energy without compromising their physical integrity given the low percentage of activation represented by running-in. Indeed, the running-in phase generally represents 1% of the total use made of the vehicle.

Alternatively, the running-in braking force Fr can be obtained by combining a high hydraulic pressure, typically of the order of 100bar=10^7Pa, produced by the device 16 of the ESC type, simultaneously with a tightening of the receivers of braking 17.2, 17.3 by the geared motors 32. The hydraulic pressure generated by the device 16 makes it possible to increase the final clamping force of the iso-force brake delivered by the geared motor 32 during the clamping phase. Once the application of the electric parking brake 30 has been completed, the hydraulic pressure of the ESC can be released.

Outside the running-in period P_rod_1, P_rod_2, the electric parking brake 30 applies, in a step 103, the nominal force Fn to immobilize the motor vehicle when parked. The nominal braking force Fn applied by the electric parking brake 30 may depend on a slope of the road (in other words the inclination of the vehicle), and/or on a hydraulic pressure in the braking circuits 15.1, 15.2, and/or an estimated or measured temperature of the brake chambers.

Claims (10)

Method for controlling an electric parking brake (30) of a motor vehicle, said electric parking brake (30) comprising:
- a braking control device (31), and
- at least one geared motor (32) arranged on a brake chamber (17.2, 17.3) associated with a wheel of the motor vehicle, said geared motor (32) being controlled by the braking control device (31),
characterized in that during a running-in period (P_rod_1, P_rod_2) of wear elements of the brake chamber, a running-in braking force (Fr) applied to the brake chamber (17.2, 17.3) to immobilize the motor vehicle is greater than a nominal braking force (Fn) applied to the brake chamber (17.2, 17.3) by the electric parking brake (30) outside the running-in period (P_rod_1, P_rod_2). Method according to Claim 1, characterized in that a start of the running-in period (P_rod_1, P_rod_2) corresponds to leaving the factory of the new motor vehicle or to replacing the wearing elements of the brake chamber (17.2, 17.3). Method according to Claim 1 or 2, characterized in that a duration of the running-in period (P_rod_1, P_rod_2) corresponds to a predetermined mileage. Method according to Claim 1 or 2, characterized in that a duration of the running-in period (P_rod_1, P_rod_2) corresponds to a predetermined accumulation of kinetic energy dissipated in the brake chamber (17.2, 17.3). Method according to Claim 1 or 2, characterized in that a duration of the running-in period (P_rod_1, P_rod_2) corresponds to a dissipative braking efficiency threshold. Method according to any one of Claims 1 to 5, characterized in that the running-in braking force (Fr) is between 1.2 and 1.4 times the nominal braking force and is preferably equal to 1.3 times the braking force nominal (Fn). Method according to any one of Claims 1 to 6, characterized in that the running-in braking force (Fr) is obtained solely by virtue of a tightening of the brake chamber (17.2, 17.3) carried out by the geared motor (32). Method according to any one of Claims 1 to 7, characterized in that the running-in braking force (Fr) is obtained by combining a hydraulic pressure produced by a pressure modulation device (16) of a fluid hydraulic flowing in hydraulic circuits (15.1, 15.2) simultaneously with a clamping of the brake chamber (17.2, 17.3) by the geared motor (32). Method according to any one of Claims 1 to 8, characterized in that the nominal braking force (Fn) applied by the electric parking brake (30) depends on an inclination of the motor vehicle, and/or on a hydraulic pressure in brake circuits (15.1, 15.2), and/or an estimated or measured temperature of the brake chamber (17.2, 17.3). Computer (35) comprising a memory (35.1) storing software instructions for implementing the method for controlling an electric parking brake (30) of a motor vehicle as defined according to any one of the preceding claims.