FR3065932A1 - BRAKING SYSTEM WITH INDEPENDENT ACTUATION OF AT LEAST TWO WHEELS OF AN AXLE OF A MOTOR VEHICLE - Google Patents

Abstract

The invention relates to a braking system (1) for a motor vehicle comprising: - an electronic control system (21); - a position sensor (28) of a brake pedal (29); According to the invention, the braking system (1) comprises two individual brake blocks (3) for at least one axle, each of said blocks (3) being intended to act on a wheel (4) of the axle under the electronic control system command (21, 31) when a movement of the brake pedal (29) is detected and each of said blocks (3) comprising a speed sensor (39) connected to the wheel (4).

Description

Holder (s):

RENAULT S.A.S ..

O Extension request (s):

® Agent (s): RENAULT TECHNOCENTRE.

® BRAKING SYSTEM WITH INDEPENDENT ACTUATION WITH AT LEAST TWO WHEELS OF AN AXLE OF A MOTOR VEHICLE.

FR 3,065,932 - A1 (57) The invention relates to a braking system (1) for a motor vehicle comprising:

- an electronic control system (21);

- a position sensor (28) of a brake pedal (29);

According to the invention, the braking system (1) comprises two individual braking blocks (3) for at least one axle, each of said blocks (3) being intended to act on a wheel (4) of the axle under the order of the electronic control system (21,31) when a movement of the brake pedal (29) is detected and each of said blocks (3) comprising a speed sensor (39) connected to the wheel (4).

Braking system independently actuated on at least two wheels of an axle of a motor vehicle

Field of the invention

The invention relates to a motor vehicle braking system. In particular, the invention relates to a braking system in which wheels of at least one axle are braked independently of one another.

State of the art

It is known, in the motor vehicle field, electronic trajectory correctors, often called by its equivalent in English Electronic Stability Control or ESC, which are associated with brake assist or servo-brake. This ESC system consists in improving the trajectory control of a motor vehicle, for example, during a turn. The ESC system detects loss of grip when cornering to compensate for it by braking one or more wheels of the vehicle.

However, this ESC system causes tremors or jolts and sudden ascent at the level of the brake pedal and the steering wheel. The feeling at the pedal of a driver of the vehicle is not pleasant. Above all, this management of the pressure at each of the wheels is often brutal and without fine management of the pressure at each of the wheels.

To resolve this first problem, there are decoupled braking systems which make it possible to suppress jerks and / or dampen the rise of the brake pedal. However, these systems do not allow fine individualized management of the braking torque for each of the vehicle wheels.

Thus, an objective of the invention is to propose a braking system allowing fine management of braking torque for each wheel of the vehicle with at least one axle.

General description of the invention

To this end, the invention proposes a braking system for a motor vehicle comprising:

- an electronic control system;

- a brake pedal position sensor;

According to the invention, the braking system comprises two individual braking blocks for at least one axle, each of said blocks being intended to act on an axle wheel under the order of the electronic control system when a movement of the brake pedal is detected and each of said blocks comprising a speed sensor connected to the wheel.

Thus, each wheel of the axle is equipped with its own brake block. In this way, the braking of the wheels of an axle is carried out independently of one another. In addition, thanks to the speed sensor, the braking of a wheel, as a function of the speed thereof, is different from the other wheel whose speed is not necessarily the same, for example in a turn of the vehicle. The braking torque is thus different for each wheel depending on the trajectory and / or the speed specific to each.

The braking system according to the invention therefore allows individualized management of the braking torque of each of the wheels of at least one axle. You can also install an individual brake block for each wheel of a vehicle, so two individual brake blocks per axle. As a result, the braking of the wheels is managed independently and differently for each of the vehicle wheels.

Furthermore, for hybrid electric or electric vehicles, individualized traction systems with several electric motors will be generalized, for example one motor per axle or even one per wheel. Thus, the management of the traction torque will be independent and different from one wheel to another. By installing the braking system according to the invention with the individualized traction system, optimized torque management is obtained, both in positive (traction) and in negative (braking) for each of the wheels.

According to a characteristic of the invention, a central braking block is connected to each of the individual braking blocks.

Furthermore, according to another characteristic of the invention, the central braking block is structurally decoupled from each of the individual braking blocks when a movement of the brake pedal is detected and therefore allows, in association with the management of the regenerative torque, cooperative braking.

According to a characteristic of the invention, the central braking block and the individual braking blocks are of the hydraulic or pneumatic type. Such types of braking are inexpensive and simple to install.

According to the previous paragraph, the central brake unit includes

- a master cylinder actuated by the brake pedal and coupled to a return means;

- a first solenoid valve, located downstream of the master cylinder, and reversibly movable between two positions:

- a rest position in which the central braking block is connected to the individual braking blocks by a hydraulic or pneumatic connection;

- an actuation position in which the hydraulic or pneumatic connection between the central brake block and the individual brake blocks is interrupted.

Thus, the central braking block replaces the individual braking block to brake the wheel in the event of failure of the individual braking block. In other words, the central braking block is an emergency braking means which makes it possible to further secure the braking system, especially in the event of a failure of one of the individual braking blocks. The braking system with at least one of the individual brake blocks faulty operates in degraded mode.

According to another characteristic of the invention, the central braking block comprises a braking simulator disposed downstream of the first solenoid valve. Thus, the simulator gives the driver a feeling of braking while depressing it on the brake pedal.

According to a characteristic of the invention, each individual braking block comprises:

- a supply duct connected to a wheel brake;

- a pressure relief device;

- an individual pressure sensor connected to the supply duct; and

- A second solenoid valve reversibly movable between a closed position and an open position in which the pressure relief device is connected to the supply duct hydraulically or pneumatically.

Thus, in the event of a wheel lock and poor grip of the tire for example, the pressure relief device and the second solenoid valve reduces the pressure therein, which makes it possible to unlock the wheel in order to find wheel grip (wheel anti-lock function).

According to another characteristic of the invention, each individual braking block comprises a supply duct connected to a brake on the wheel, a spare duct connecting the central braking block to the supply duct. Thus, the emergency conduit is a second path allowing the brake fluid to reach the wheel brake.

According to a characteristic of the invention, each individual braking block cooperates with a regenerative braking member by providing the hydraulic torque complementary to the regenerative torque to reach the target conjugate braking torque.

According to another characteristic of the invention, the electronic control system comprises a single central control unit.

Alternatively, the electronic control system comprises a central control unit and secondary control units respectively driving the individual brake blocks. Thus, in the event of a failure of one of the secondary units, the central control unit can cause the defective secondary unit to be replaced by another secondary unit. The central control unit can replace the faulty secondary unit itself because they are all interconnected on the same communication network as well as with all the other sensors in the vehicle chassis system.

In another embodiment of the invention, the electronic control system can comprise a central control unit and a secondary control unit per axle. In this case, the secondary control unit controls the individual brake blocks of the axle with which it is associated.

The invention also relates to a motor vehicle comprising a braking system produced according to at least one of the preceding characteristics.

The invention also relates to a method of operating the braking system comprising at least one of the preceding characteristics. Each of the individual brake blocks of the brake system includes an actuator for acting on an axle wheel.

According to the invention, in normal operating mode of the braking system, said method comprises the following steps:

- detection of the brake pedal movement by the brake pedal position sensor;

- sending a signal Pi from the brake pedal position sensor to the electronic control system;

- in each individual braking block, detection of the speed of the wheel by the speed sensor and sending of a signal P ₂ from the speed sensor to the electronic control system;

- activation by the electronic control system of the actuator of each individual braking block according to the signals Pi and P ₂ .

The invention further relates to a method of operating the braking system in degraded mode comprising a central braking block. Said method comprises the following steps:

- the first solenoid valve remaining or returning to the rest position;

- pressure increase in the central brake block and in the individual brake blocks by means of the master cylinder;

- supply of air or brake fluid to the supply duct of each individual brake unit by the hydraulic or pneumatic connection between the central brake unit and the individual brake units.

The invention also relates to a method of operating the braking system in the event of a wheel locking and of loss of grip of said wheel, said method comprises the following steps:

- detection of blockage by the speed sensor;

- sending of a blocking signal P3 by the speed sensor to the electronic control system;

- activation of the second solenoid valve by the electronic control system, putting the pressure relief device in hydraulic or pneumatic communication with the supply duct;

- release of the pressure in the brake block by means of the pressure relief device.

When a wheel is locked, the tire slips and the grip of this wheel as well as the braking and control capacity are reduced. For this reason, it is necessary to quickly unload the individual braking block to allow the wheel to turn and therefore improve its grip. Then, the pressure is restored in the individual brake block and if the wheel is still locked, the process starts again so as to allow the wheel to regain grip.

The operating method of the preceding paragraph may include a step of retracting a piston of the actuator to empty the brake fluid from the pressure relief device in the case where it is of the hydraulic type.

For example, the pressure relief device is a low pressure accumulator.

Detailed description of the figures

Other characteristics and innovative advantages will emerge from the description below, provided for information and in no way limitative, with reference to the appended drawings, in which:

- Figure 1 shows, schematically, a vehicle comprising a braking system produced according to a first embodiment of the invention with a multitude of computers;

- Figure 2 shows, schematically, a vehicle comprising a braking system produced according to a second embodiment of the invention with a single central computer;

- Figure 3 shows, schematically, a part of the braking system according to Figure 1 or according to Figure 2 in the inactive state;

- Figure 4 shows, schematically, the same view as Figure 3 and illustrates the braking system normally operating in active state;

- Figure 5 shows, schematically, the same view as Figure 4, and illustrates the operation of the braking system when it cooperates with a regenerative braking means, without the need for hydraulic braking;

- Figure 6 shows, schematically, the same view as Figure 3, and illustrates the operation of the braking system, in degraded mode, in a first case of failure of one of its constituent elements;

- Figures 7 to 10 show, schematically, the same view as Figure 3, and illustrate the operation of the braking system, in degraded mode, in a second case of failure of one of its constituent elements;

- Figures 11 to 13 show, schematically, the same view as Figure 3 and illustrate the operation of the braking system when a vehicle wheel is blocked following a degraded grip of said wheel;

- Figure 14 shows, schematically, a part of the braking system produced according to the first embodiment of the invention and installed in an electric vehicle or hybrid electric vehicle.

Referring to Figures 1 and 2, there is illustrated a braking system 1 produced respectively according to a first and a second embodiment of the invention.

In the first embodiment or in the second embodiment, the braking system 1 comprises a central braking block 2 and four individual braking blocks 3, hereinafter referred to as shortcut central block 2 and individual block 3. Each of the blocks individual 3 is associated with a wheel 4 of the vehicle. More precisely, each individual block 3 is connected to a brake 41. The brake 41 here comprises a caliper 42 comprising a piston 45 acting on two plates 44 arranged on either side of a disc 43 of the wheel 4.

From a global view, the central block 2 is connected to each of the individual blocks 3 by a fluidic path A and communicates with each of them by a telecommunication path B. In fact, the central block 2 is connected to each of the individual blocks by a first fluid conduit 20. According to the invention and in the first and second embodiments, the piston 45 of the caliper 42 on each wheel 4 is actuated by brake fluid. Thus, the first fluid conduit 20 is used to conduct brake fluid from the central block 2 to the individual blocks 3, hence its second, more precise name, first hydraulic conduit 20. The first hydraulic conduit 20 will be called hereinafter as a shortcut first conduit 20.

Telecommunication channel B is provided between a central electronic control unit 21 and electronic and electromechanical components of the braking system 1.

The electronic control unit is an on-board computer which is capable of driving electronic components. The electronic control unit is hereinafter called by its acronym UCE.

The main difference between the first and the second embodiment lies in the manner of communication between the central ECU 21 and the individual blocks 3. According to the first embodiment, each individual block 3 is equipped with its own electronic control unit 31 , otherwise called individual ECU 31. The communication between the central ECU 21 and each individual ECU 31 is carried out for example by means of a multiplexing network 10 also called the CAN bus (control Area Network in English). Each individual ECU 31 controls the electronic components present in the individual block 3 with which it is associated.

As for the second embodiment, it has a single central ECU 21 for all the brake blocks. Thus, the single central ECU 21 controls all the electronic components, both of the central block 2 and of the individual blocks 3. In this case, the central ECU 21 receives on the one hand the signals emitted by these components and on the other hand transmits the control and piloting signals to these components.

Furthermore, in these two embodiments, the central ECU 21 communicates with other sensors, such as a yaw sensor 5 and a steering wheel angle sensor 6 via the multiplex network 10.

Despite the difference concerning the number of ECUs present in the braking system, the operation thereof according to the first mode and according to the second mode remains identical.

The constituent elements of the central block 2 and of the individual blocks 3 as well as the interaction between these blocks of the second embodiment will be described below. Since the individual blocks 3 are identical, only one individual block 3 will be described and its description applies in the same way for the other individual blocks.

Referring to Figure 3, there is shown the central block 2 and the individual block 3 during the inactive state of the braking system, for example during normal running of the vehicle without braking or when the vehicle is parked.

Description of the central block

The central block 2 comprises a master cylinder 22 with a single pressure chamber 221. A piston 222 slides in the master cylinder 22 to vary the volume of the compression chamber 221. The master cylinder 22 is in its initial position of rest on figure 3.

The master cylinder 22 is also connected with a return means 24 allowing the piston 222 to return to its initial position when there is no longer any pressure exerted on the brake pedal 29. According to the invention and in this example, the return means 24 is a spring extending along the compression chamber 221 until contact with the piston 222.

The compression chamber 221 is filled with brake fluid via a hydraulic passage 231 connected to a reservoir 23 of brake fluid. The compression chamber 221 further comprises an orifice 223 opening towards the first hydraulic conduit 20.

A first solenoid valve 25 is disposed after the master cylinder 22. The first solenoid valve 25 is reversibly movable between a rest position and an actuation position. The first solenoid valve 25 is connected to a first return means 251 allowing it to return to the rest position.

The braking system 1 being inactive, the first solenoid valve 25 is in the rest position as illustrated in FIG. 3. In the rest position, the first solenoid valve 25 makes it possible to establish a hydraulic connection between the central block 2 and the individual block 3. In this example, the hydraulic connection is here the first conduit 20.

On the other hand, the first solenoid valve 25 in the actuation position cuts the hydraulic connection between the central block 2 and individual blocks 3. In other words, the central block 2 is structurally decoupled from the individual blocks

3.

A braking simulator 26, here of hydraulic type, is installed downstream of the first solenoid valve 25. In this document, the terms “downstream” and “upstream”, or “before” and “after” are defined relative the direction of brake fluid circulation in the brake system. The braking simulator 26 comprises a chamber in which a simulation piston 261 slides. The simulation piston 261 is pushed on one side by brake fluid arriving from the first solenoid valve 25 and on the other side by a deformation element elastic 262. The position of the simulation piston 261 depends on the brake fluid pressure and the restoring force of the elastic deformation element 262. Thanks to the braking simulator 26, the brake pedal 29 receives a force which s opposes the actuation of said pedal 26 and which thus simulates the braking force. Thus, the driver has a feeling similar to that which would be obtained if the braking of the wheel was carried out directly by the pressure of the liquid in the master cylinder of the central block 3.

The elastic deformation element 262 is for example an elastomer (rubber) which deforms and provides resistance to crushing. This type of elastomer is used rather than a mechanical spring because the force of a compressed elastomer is not linear and is close to that of a crushed brake pedal, i.e. it at the start there is an immediate jump or sinking, then a flat effort which quickly becomes exponential and stiff at the end. The shape and material of the elastomer depends on the desired pedal feel and can be calibrated.

In an exemplary embodiment of the invention, a second braking simulator can be installed which gives a feeling to the pedal different from that provided by the first simulator to offer two modes of touching the pedal. For example, a hard setting of the braking simulator is appreciated in a sports vehicle while a less hard setting gives the feeling of a hyper sensitive and assisted pedal.

A first non-return valve 27 is installed in parallel with the first solenoid valve 25 so as to allow the circulation of the brake fluid from the braking simulator 26 upstream of the first solenoid valve 25.

Thus, the first solenoid valve 25, the braking simulator 26 and the first non-return valve 27 form a loop 12 for circulating the brake fluid located after the master cylinder.

The piston 222 of the master cylinder 22 is connected to a manual brake control member 29, here a brake pedal 29, in a manner known to a person skilled in the art. A brake pedal position sensor 28 is provided in order to detect the displacement of the brake pedal 29.

Description of the individual block

The individual block 3 comprises an actuator 32 designed to act on the brake 41 of the wheel 4 with which it is associated. The actuator 32 is of the hydraulic and electric actuator type 320, hereinafter called actuator 320. This actuator 320 receives brake fluid from the master cylinder 22 through the first conduit 20. The latter opens into a pressure chamber 321 of the jack 320 via a light 322. The pressure chamber 321 of jack 320 is filled with brake fluid.

The jack 320 comprising a piston 323 is in its initial rest position in FIG. 3. The jack 320 is connected to a return means 324 having the function of returning the piston 323 to its initial position at the end of braking. For example, the return means 324 can be a spring installed in the pressure chamber 321 or a high angle worm screw system.

The jack 320 is controlled by an electronic control member 33 comprising an electronic power circuit 332 controlling a control element 331. There is provided, at the level of the electronic control member 33, a stroke sensor (not illustrated) of the cylinder 320.

The brake fluid in the pressure chamber 321 can flow to the caliper 42 via a supply conduit 30.

The individual block 3 further comprises a hydraulic emergency conduit 34, or in shortcut emergency conduit 34, installed in parallel with the jack 320. Specifically, the emergency conduit 34 is connected to the central block 2 by being connected to the first conduit 20 to a node 341 located upstream of the light

322 of cylinder 320.

The emergency conduit 34 joins the supply conduit 30 to a node 342 located after the junction between the actuator 320 and the supply conduit 30. It further comprises an emergency non-return valve 343 with low calibration installed so to allow the circulation of brake fluid from the first conduit 20 to the supply conduit 30.

Thus, the emergency conduit 343 makes it possible to supply brake fluid in the supply conduit 30 in the event of failure of the jack during which the light 322 is closed by the piston 323 in its advanced position.

Furthermore, the individual unit 3 comprises a pressure relief device 36 in the supply duct 30 in the event of a wheel lock. This pressure relief device 36 is here a hydraulic accumulator 36. The latter is connected to a second solenoid valve 35 connected to the supply conduit 30.

The second solenoid valve 35 is reversibly movable between a closed position and an open position. It is connected to a second return means 351 allowing it to return to the closed position.

The hydraulic accumulator 36 is also connected to a second non-return valve 37 so as to allow a return of brake fluid in the direction of the accumulator 36 towards the supply conduit 30.

In normal operation, i.e. when the brake fluid pressure in the supply line 30 is below a limit threshold, the second solenoid valve 35 is in the closed position and prevents the fluid connection between the line supply 30 and the hydraulic accumulator 36. Conversely, when the pressure in the supply line 30 exceeds the limit threshold, the second solenoid valve 35 is in the open position, which allows a circulation of brake fluid from the line supply 30 to the hydraulic accumulator 36. In order to measure the pressure in real time in the supply duct 30, a pressure sensor 38 is provided.

Telecommunication channel B and the central ECU 21 are not illustrated either in FIG. 3 or in the following figures, but it is understood that the electronic components present in the central block 2 and the individual block 3 communicate with the central ECU 21 and act according to the order given by the central ECU 21.

The operation of the braking system 1, in active state, will be described below based on FIGS. 4 to 13. The braking system 1 is active when there is braking of at least one wheel 4 of the vehicle .

Normal brake system operation

Figures 4 and 5 illustrate the system in normal operating mode.

Without regenerative braking! Decoupled

The driver, by pressing the brake pedal 29, defines a stroke of the piston 222 which reaches a percentage X% of its maximum stroke. The movement of the pedal 29 causes the piston 222 to move in the direction in which it compresses the brake fluid present in the pressure chamber 221 of the master cylinder 22. The brake fluid pressure present in the pressure chamber 221 thus that in the loop 12 of the central block 2 increases, for example up to about 10 bars.

The pedal position sensor 28 detects the movement of the pedal. This sensor 28 sends a signal Pi to the electronic control system, here the central ECU 21 (see FIG. 2). In parallel, the speed sensor 39 of the individual block detects the speed of the wheel 4 and sends a signal P2 to the central ECU 21 (see FIG. 2). The latter then causes several actions to be carried out, approximately simultaneously, in the central block 2 and in the individual block 3.

The first action is to put the first solenoid valve in the actuation position. In the actuating position, the first solenoid valve 25 prevents the brake fluid from circulating in the first conduit 20 and directs it to the braking simulator 26. The simulator 26 is thus filled with brake fluid and the element with elastic deformation 262 is distorted.

The second action, carried out almost at the same time as the first action, consists in actuating the jack 320 of the individual block 3 by means of the electronic control member 33. The jack 320 compresses completely to increase the pressure of the brake fluid in the compression chamber 321 of the jack 320, in the supply conduit 30 and in a portion of the emergency conduit 34 situated after the emergency non-return valve 343, for example up to 120 bars. Thus, the pressurized brake fluid arrives in the caliper 42 and pushes the piston 45 of the caliper 42 in the direction where the brake pads 44 tighten the disc 43 of the wheel 4 to stop it.

Thus, the normal braking of the wheel is carried out directly by the individual block 3 following the actuation of the brake pedal 29 connected to the central block 3.

After the driver no longer acts on the brake pedal 29, the pressure of the brake fluid in the central block 2 decreases. The elastic deformation element 262 of the simulator returns to its initial position and returns brake fluid upstream of the first solenoid valve 25 via the first non-return valve 27. At the same time, the first solenoid valve 25 returns to the rest position thanks at the first return means 251. Likewise, the piston 222 returns to its initial position and raises the brake pedal 29.

During this time, in the individual block 2, the electronic control member 33 no longer acts on the jack 320. The return means 324 of the jack 320 returns the piston 323 to its initial position. The brake fluid pressure in the individual block 3 also decreases.

The braking system 1 therefore returns to its inactive state at the end of braking.

With decoupled regenerative braking

When the driver presses the brake pedal 29, the central unit 3 behaves similarly to the braking system described above. The pressure of the brake fluid in the central block 2 reaches for example 10 bars.

However, in the individual block 3, the jack 320 is not activated by the control member 33. The braking of the wheel 4 is ensured by a decoupled regenerative braking system (not illustrated).

The individual block 3 remains inactive as long as the regenerative braking of the motor covers the drive request. In this case, the brake fluid pressure in the individual block 3 is zero.

The individual block 3 can be activated in the event that additional braking to the braking of the regenerative system is necessary.

The advantage of this system for decoupled regenerative braking is that it is able to dose the additional hydraulic braking required wheel by wheel and therefore manage strong regenerative braking and balance any braking torque difference between the left wheel and the right wheel without having to deactivate the regenerative braking system.

Braking system operation during the first failure of the individual brake unit

FIG. 6 illustrates the operation of the system during a first case of failure of the individual block. The braking system thus operates in degraded mode.

A power failure occurs while the electronic control member 33 is acting on the jack 320. The peculiarity of this first case is that at this time of failure, the piston 323 of the jack 320 does not exceed again the light 322. The power failure can also occur before the control member 33 causes the piston 323 to move. In this case, the light 322 is also not blocked.

In this case of failure, the first solenoid valve 25 remains in the rest position. Thus, the brake fluid of the master cylinder 22 can flow towards the first conduit 20 and towards the individual block 3. The master cylinder 22, under the action of the brake pedal 29, increases the pressure of the brake fluid in the block central 2 and in the individual block 3 enough to brake the wheel 4, for example about 65 bars. In this example, the master cylinder 22 achieves 100% of its stroke causing the brake fluid pressure to increase to 65 bars.

The pressurized brake fluid in the central block 2 flows to the individual block 3 via the first conduit 20. The pressurized brake fluid passes through the lumen 322 and passes through the pressure chamber 321 of the jack 320 to join the conduit d 'supply 30. Thus, the caliper 42 is supplied with brake fluid with sufficient pressure to brake the wheel 4.

It should be noted that a portion of the brake fluid under pressure also passes through the emergency conduit 34 to also join the supply conduit 30.

The master cylinder 22 is designed to allow the maximum stroke to be achieved with 50 daN of force on the pedal of the main brake 29. This thus optimizes the potential pressure build-up until reaching an optimal deceleration if the degraded braking is on all 4 wheels, that is to say when the four individual blocks all suffer a failure. This optimal deceleration is much higher than a deceleration obtained via a traditional master cylinder (for example, greater than a value of 0.25 G without assistance at 50 DaN at the brake pedal). The performance of the braking system in degraded mode is all the more important as the number of individual blocks in failure decreases, which constitutes an advantage in performance compared to the current system which has only one actuator.

In all cases, it is necessary to send an alert to the driver to warn him of the breakdown and that he can immobilize the vehicle immediately.

Brake system operation during a second failure of the individual brake unit

Figures 7 to 10 illustrate the operation of the braking system during a second failure of the individual unit. In this case, the braking system also operates in degraded mode.

In this second failure case, the braking system is in a more advanced operating state than that of the first failure case when a power failure occurs.

The advanced operating state is shown in the figure

7. The first solenoid valve 25 is in the actuating position in which the brake fluid coming from the master cylinder fills the braking simulator 26. The pressure of the brake fluid in the loop of the central block 2 has a non-zero value of X bars. In parallel, in the individual block 3, the jack 320, actuated by the control member 33, increases the pressure of the brake fluid in the individual block 3 to a value of Y bars, greater than the pressure of the brake fluid. in central block 2 (Y> X bars). At this stage, the piston 323 of the jack 320 is in an advanced position in which the light 322 is closed.

Referring to Figure 8, the power failure occurs in the individual block 3. The cylinder 320 is blocked in the advanced position described above. In the central block 2, the first solenoid valve 25 returns to the rest position thanks to its first return means 251. Thus, brake fluid from the central block, under a pressure of X bars, can circulate in the first conduit 20. However, it cannot yet enter the individual block 3 because the pressure of the brake fluid in the individual block 3 still remains higher than that of the central block, namely Y bars.

In Figure 9, the master cylinder 22 is further compressed. The pressure of the brake fluid in the central block 2 and in the first conduit 20 is thus increased to a value of Z bars greater than that of the individual block Y bars. The pressurized brake fluid can now enter the individual block 3 via the emergency conduit 34 to arrive at the supply conduit 30 connected to the caliper 42. The emergency non-return valve 341 opens to allow circulate brake fluid.

This is the only path available to reach the stirrup 42 because the light 322 of the jack 320 is closed. The piston 45 of the caliper 42, under the action of the pressurized brake fluid, acts on the pads 44 so that they grip the disc 43 and thus brake the wheel 4.

At the end of braking, illustrated in FIG. 10, the brake pedal 29 is released. The brake fluid pressure in the central block 2 and in the individual block 3 decreases. The master cylinder 22 and the cylinder 320, thanks to their respective return means, returns to their initial position.

In the central block 2, the first non-return valve 27 opens under the action of the braking simulator 26, which makes it possible to reduce the pressure accumulated in said simulator.

In the individual block 3, the light 322 of the jack 320 is released. The emergency non-return valve 343 is no longer required and it closes.

The braking system 1 returns to a state similar to that of the first failure case because the power failure persists. An alarm must be set up to warn the driver of the failure.

Brake system operation during wheel lock-up and loss of grip

Figures 11 to 13 illustrate the operation of the braking system when the wheel 4 is blocked because of a loss of grip of the wheel. In this case, it is necessary to relieve the hydraulic pressure at the level of the calipers as illustrated in FIG. 11.

After detecting the blocking, the speed sensor 39 of the wheel 4 sends a blocking signal P3 to the central ECU 21 (see FIG. 2). The latter involves the pressure relief device 36 of the individual block 3, here the hydraulic accumulator 36.

In FIGS. 12 and 13, the central ECU 21 activates the second solenoid valve 35. This passed rapidly from the closed position to the open position allowing the circulation of the brake fluid from the supply conduit 30 to the hydraulic accumulator 36 at low pressure. At the same time or just after the opening of the second solenoid valve 35, the electronic control member 33 no longer acts on the jack 320, the latter returning to its initial position. Thus, the pressure of the brake fluid in the individual block 3 drops rapidly, therefore the pressure exerted on the piston 45 of the caliper 42. The pads 44 gradually release the wheel 4.

At the end of the operation, the wheel 4 is again free to rotate. The second solenoid valve 35 closes and the hydraulic accumulator 36 is emptied via the second non-return valve 37. This makes it possible to prepare the accumulator 36 for a new pressure release operation in the supply conduit 30 in the event of wheel lock.

Note that during the pressure evacuation operation in the individual block 3, the first solenoid valve 25 is maintained in the actuation position, the central block 2 remaining isolated from the individual block 3.

The braking system provides an anti-lock function like known anti-lock systems, otherwise called ABS systems.

Example of the invention in an electric or hybrid electric vehicle

FIG. 14 represents the braking system 1 produced according to the first embodiment and installed in an electric or hybrid electric vehicle. The braking system 1 thus comprises a central ECU 21 and the individual ECUs 31, here a single individual ECU 31 is illustrated.

Each wheel 4 is connected to an individual traction control unit 7. Furthermore, the vehicle is also equipped with a steering wheel management unit 8, a trajectory management unit 9 and a management unit shock absorbers, braking aerodynamics 10. Each of these blocks is controlled by an ECU.

All the ECUs are connected to a general ECU 11 which cooperatively manages the braking and traction of each of the wheels. This management concerns just as much the braking and traction torque, the steering angle, the shock absorber, the attitude and the aerodynamics, and this for each of the vehicle's wheels.

Claims (15)

1. Braking system (1) for a motor vehicle comprising: - an electronic control system (21, 31); - a position sensor (28) of a brake pedal (29); said braking system (1) being characterized in that it comprises two individual braking blocks (3) for at least one axle, each of said blocks (3) being intended to act on a wheel (4) of the axle under the order of the electronic control system (21, 31) when a movement of the brake pedal (29) is detected and each of said blocks (3) comprising a speed sensor (39) connected to the wheel (4). 2. Braking system (1) according to claim 1 characterized in that it comprises a central braking block (21) connected to each of the individual braking blocks (3). 3. Braking system (1) according to claim 2 characterized in that the central brake block (21) being structurally decoupled from each of the individual brake blocks (3) when a movement of the brake pedal (29) is detected. 4. Braking system (1) according to claim 2 or according to claim 3 characterized in that the central braking block (2) and the individual braking blocks (3) are of hydraulic or pneumatic type. 5. Braking system (1) according to claim 4 characterized in that the central braking block (2) comprises - a master cylinder (22) actuated by the brake pedal (29) and coupled to a return means (24); - a first solenoid valve (25), located downstream of the master cylinder (22), and reversibly movable between two positions: - a rest position in which the central braking block (2) is connected to the individual braking blocks (3) by a hydraulic (20) or pneumatic connection; - An actuating position in which the hydraulic (20) or pneumatic connection between the central braking block (2) and the individual braking blocks (3) is interrupted. 6. Braking system (1) according to claim 5 characterized in that the central braking block (2) comprises a braking simulator (26) disposed downstream of the first solenoid valve (25). 7. Braking system (1) according to one of claims 4 to 6 characterized in that each individual braking block (3) comprises - a supply duct (30) connected to a brake (41) of the wheel (4); - a pressure relief device (36); - an individual pressure sensor (38) connected to the supply duct (30); and - A second solenoid valve (35) reversibly movable between a closed position and an open position in which the pressure relief device (36) is connected to the supply conduit (30) hydraulically or pneumatically. 8. Braking system (1) according to one of claims 4 to 7 characterized in that each individual braking block (3) comprises a supply duct (30) connected to a brake (41) of the wheel (4 ), an emergency conduit (34) connecting the central braking block (2) to the supply conduit (30). 9. Braking system (1) according to one of the preceding claims, characterized in that each individual braking block (3) cooperates with a regenerative braking member. 10. Braking system (1) according to one of claims 1 to 9 characterized in that the electronic control system comprises a single central control unit (21). 11. Braking system (1) according to one of claims 1 to 9 characterized in that the electronic control system comprises a central control unit (21) and secondary control units (31) respectively controlling the brake blocks individual (3). 12. Vehicle characterized in that it comprises a braking system (1) according to one of the preceding claims. 13. A method of operating a braking system (1) according to one of claims 1 to 11, each of the individual braking blocks (3) of the braking system comprising an actuator (32) intended to act on a wheel ( 4) the axle; said method being characterized in that in normal operating mode of the braking system (1), said method comprises the following steps: - detection of the movement of the brake pedal (29) by the position sensor (28) of the brake pedal; - sending of a signal Pi from the position sensor (28) of the brake pedal to the electronic control system (21); - in each individual braking block (3), detection of the speed of the wheel (4) by the speed sensor (39) and sending of a signal P ₂ from the speed sensor (39) to the electronic control system ( 21); - activation by the electronic control system (21) of the actuator (32) of each individual braking block (3) according to the signals Pi and P ₂ . 14. A method of operating the braking system (1), according to one of claims 5 to 11 when claims 7 to 11 depend on claim 5, said method characterized in that in degraded mode of the braking system (1 ), said method comprises the following steps: - holding or returning the first solenoid valve (25) to the rest position; - pressure increase in the central brake block (2) and in the individual brake blocks (3) by means of the master cylinder (22); - supply of air or brake fluid to the supply duct (3) of each individual brake unit (3) by the hydraulic (20) or pneumatic connection between the central brake unit (2) and the individual brake units (3). 15. A method of operating the braking system (1) according to one of claims 7 to 11 when claims 8 to 11 depend on claim 7, characterized in that in the event of a wheel lock (4) and loss of grip of said wheel, said method comprises the following steps: - detection of blockage by the speed sensor (39); - sending of a blocking signal P3 by the speed sensor (39) to the electronic control system (21); - Activation of the second solenoid valve (35) by the electronic control system (21), putting the pressure relief device (36) in hydraulic or pneumatic communication with the supply conduit (30); - evacuation of the pressure in the individual brake unit (3) by means of the pressure relief device (36). 1/7 31 41 4 31 41 4