FR2931766A1 - Hydraulic control braking system e.g. electronic stability program system, for motor vehicle, has braking fluid accumulator permitting generation of brake pressure independent of actions of driver on control device - Google Patents

Abstract

The system has a brake managing circuit (1) controlled by a driver of a motor vehicle from a brake pedal (100) installed in an interior of a passenger compartment, and another brake managing circuit (2) electronically controlled by an electronic control unit. The managing circuit (2) has a high pressure braking fluid accumulator (10) connected to a reversible or brake gear motor (21) by a mechanical connection constituted of a cable (22) and a coupling unit (23). The accumulator permits generation of the brake pressure independent of actions of the driver on control device. An independent claim is also included for a method for implementing a hydraulic control braking system.

Description

BACKGROUND OF THE INVENTION The invention relates to a hydraulically-controlled braking system for a motor vehicle, in particular making it possible to perform the stability control and trajectory control functions of the vehicle. vehicle with relatively inexpensive means. This system can be implemented on a vehicle equipped with at least two motorized brake elements. The invention also relates to a method implemented by this system. The invention has applications in the field of the automobile and, in particular, in the field of braking of motor vehicles. State of the art A vehicle generally comprises two braking control devices whose operation is independent of one another. Thus, for example, most vehicles include a mechanical control device for the secondary brake, or hand brake, and a hydraulic control device for the main brake. A conventional hydraulic control braking system comprises the following elements: an amplification element increasing the force exerted on the brake pedal by the driver, this force being called a pedal force; a tandem master cylinder which consists of a piston pump used to transform the pedal force into hydraulic pressure; for this purpose, the tandem master cylinder is in communication with a reservoir of brake fluid, receivers situated at the level of the wheels and intended to transform the hydraulic pressure into a braking torque of the wheel, for example by means of an effort pressure between the brake pads and the disc, in the case of disc brakes. These braking systems, while effective in stopping the wheels themselves, do not solve the problems of loss of control, stability and trajectory that can occur when a vehicle is traveling in a vehicle. certain special conditions, for example on a damaged, slippery or icy road, or at a speed that is too high, or when the driver has to brake or change direction suddenly. In order to solve these problems, the car manufacturers have designed different braking force control systems. A first type of braking force control system is an anti-lock system, which aims to prevent wheel lock when a driver brakes suddenly, in order to maintain a good grip of the wheels on the roadway in all circumstances. The principle of such systems, in particular so-called ABS (AntiBlockieren System) systems, is to use solenoid valves and hydraulic pumps to reduce the brake pressure applied to a wheel, since a risk of blockage of this wheel is detected. . Such a system comprises, for example, a speed sensor installed on each wheel, and two solenoid valves per wheel, to enable this pressure control. Electronic stability and trajectory control systems are also known, in particular so-called ESP systems (Electronic Stability Program), whose objective is to increase or generate a braking torque applied to a wheel as soon as a unit of electronic control, in conjunction with the engine control, in charge of the system control detects that a driver setpoint, transmitted via an action on the brake pedal, is non-existent or insufficient in view of a situation of stability of the vehicle, this situation being determined from measurements made by different sensors installed in the vehicle. In order to be able to carry out this increase or generation of braking torque without action of the driver on the pedal, it is necessary to have a power supply device, installed in the braking system, and independent of any effort of the driver. on the brake pedal. The implementation of such a power supply device is controlled, if necessary, by the electronic control unit. Braking systems are known in which the energy supply device consists of a hydraulic pump controlled by an electronic control unit installed in the vehicle.

Generally, a braking system provided with a stability and trajectory control also allows the implementation of an anti-lock system, because the elements used to increase the braking pressure on each wheel can be used, conversely, to decrease this pressure, and thus allow the unlocking of a wheel. The operation of such a system will now be described in relation to FIG. 1. This figure represents a braking configuration according to a single circuit of the vehicle, ie only for two wheels, the second circuit being identical for both other wheels.

As a simplification of the figure, the electronic control unit, which controls the various modulations of braking forces according to data provided by different sensors of the vehicle, has not been shown. The braking system shown in Figure 1 comprises all the elements of a conventional hydraulic braking system, as described above. Such a braking system comprises a first brake management circuit 1, controlled by the driver of the vehicle from the brake pedal 100, and a second brake management circuit 2, controlled by the electronic control unit. More precisely, the first braking management circuit 1 comprises the following elements: a brake pedal 100, intended to transmit and amplify the force exerted by the driver of the vehicle when he wishes to brake, a booster 101, to amplify the braking force of the driver, - a tandem master cylinder 102, connected to a brake fluid reservoir 115 and making it possible to transform the force amplified by the booster and the pedal into hydraulic pressure, and - a sensor of pressure 113. It also comprises, for each wheel or set of two wheels, a brake fluid intake and exhaust system.

The intake and exhaust circuits and the brake management circuits each comprise one or more solenoid valves and a set of hydraulic pipes, not referenced, for channeling the fluid, namely the brake fluid, between the different elements of the system.

In the description, solenoid valve is called an electrically controlled valve. It is specified here that, unless otherwise indicated, the solenoid valves used may be of all-or-nothing or proportional type. An all-or-nothing solenoid valve has two positions, a rest position, called normal position, in which it is located when it is not activated, and an activation position. In the normal position, a solenoid valve can be opened, circulating the fluid, or closed, preventing the flow of fluid. Thus, a normally open solenoid valve allows the fluid to pass when it is not activated and, on the contrary, blocks the passage of the fluid when it is electrically activated. A proportional solenoid valve can take an infinite number of positions between the open position and the closed position, which allows a progressive opening or closing of the solenoid valve to control the flow of brake fluid. It may also be solenoid valve flow, that is to say, to control a flow, or pressure solenoid valve, that is to say, to control the pressure difference applied to this solenoid valve. The first braking circuit 1 comprises in particular a control electrovalve 105, normally open. The second brake management circuit comprises in particular a suction electrovalve 106, normally closed. It further comprises a hydraulic pump 107. The first and second brake management circuits also each comprise a valve, respectively 108, 109, allowing to allow the passage of the fluid in one direction. The intake and exhaust circuit 3 comprises: a low-pressure accumulator 110, intended to temporarily store fluid during certain operating phases of the system; at each brake caliper, a circuit comprising two solenoid valves; one being a normally open intake solenoid valve (111a, 111b), and the other a normally closed exhaust solenoid valve (112a, 112b), as well as a check valve (114a, 114b), and - receivers 103a and 103b (or stirrups), associated with the brake discs 104a and 104b, for converting the hydraulic pressure into a braking torque of each of the wheels. During a conventional braking, in which the stability and trajectory control is not used, all the solenoid valves are deactivated, that is to say that they are in their normal position. The operation is then as follows: when the driver presses the pedal 100, as previously described, a pressurized fluid is emitted at the output of the tandem master cylinder 102, this fluid passes through, on the one hand, the solenoid valve 105 and, on the other hand, the valve 108, the fluid is then directed, via the network of hydraulic lines, towards the receivers 103a and 103b, via the solenoid valves 111a and 111b, the fluid under pressure is thus introduced into the stirrups 103a and 103b, which ensures the braking of each of the wheels. During a conventional brake release, that is to say when the driver reduces the force on the brake pedal 100, the pressurized fluid contained in the stirrups 103a and 103b is redirected to the tandem master cylinder 102, via the solenoid valves 111a and 111b and the valves 114a and 114b. When a risk of blockage of a wheel is detected, for example of the wheel bearing the caliper 103a, it is advisable to reduce the pressure in this caliper, in order to proceed with the release of this wheel. Such a blocking generally follows a too great braking action with respect to the conditions of adhesion. To effect this reduction in pressure, the electronic control unit controls the normally closed, normally open, and normally closed exhaust valves 111a to become closed and open respectively.

As a result, the pressurized fluid contained in the lug 103a flows via the solenoid valve 112a to the low pressure accumulator 110. This low pressure accumulator 110 temporarily stores the fluid evacuated by the exhaust solenoid valves 112a and 112b of the calipers 103a and 103b. The valve 109 installed between the accumulator 110 and the suction pump 107, and allowing the flow of the brake fluid in the accumulator => pump direction allows the pump 107 to empty and thus reduce the pressure of the pump. accumulator 110 when needed. In the opposite case, where the driver does not exert any force on the brake pedal or that he exerts an insufficient force on the brake pedal with respect to the situation of the vehicle, the electronic control unit detects that the pressure in The output of the master cylinder, measured by the sensor 113, is less than the pressure required to maintain good vehicle stability. It then controls the activation of the control solenoid valve 105, which closes, which has the effect of isolating the master cylinder 102 of the braking circuit. The suction solenoid valve 106, placed between the master cylinder 102 and the suction of the hydraulic pump 107, is also activated and is then in the open state. The pump 107 is thus connected to the master cylinder 102 and can take (aspirate) fluid directly at the master cylinder 102 or its reservoir 115. The electronic control unit then controls an operation of the hydraulic pump 107 , in order to send fluid under pressure to the inlet solenoid valve lila or 111b corresponding to the wheel on which it is necessary to apply a larger braking pressure. A system of this type is relatively effective in remedying the loss of stability and trajectory that can occur with a vehicle. However, with such a system, the maximum pressure is obtained, in the brake elements, with a delay time compared to the command issued by the electronic control unit. In addition, the system described above is composed of relatively expensive elements, which, at present, make it difficult to install serially on all vehicles produced by car manufacturers.

SUMMARY OF THE INVENTION The object of the invention is precisely to overcome the drawbacks of the techniques described above. To this end, the invention proposes a braking system with stability control and trajectory, also called ESP (Electronic Stability Program), made without pump, which reduces the cost of the basic elements of said system, while allowing a relatively simple installation. For this purpose, the invention proposes a braking system in which the second braking management circuit comprises, in place of the hydraulic pump, an organ in which potential energy is stored and restored during the phases requiring a pressure of braking independent of the action of the driver. In the invention, the pressure increase of the brake fluid is obtained, by this member, for two brake elements mounted on two wheels of the vehicle. The other wheels of the vehicle are each equipped with a motorized brake element capable of regulating the braking action (decrease, increase, creation) independently of a driver action on the brake pedal, while maintaining a hydraulic type braking. According to the invention, the unit replacing the pump is in the form of a high pressure accumulator associated with a geared motor traction system. Such a member provides a maximum pressure in the system, almost immediately, which allows to consider additional functions for the braking system. More specifically, the invention relates to a hydraulic control braking system for a motor vehicle comprising: a first circuit for admitting and exhausting the brake fluid into at least one mechanical brake element mounted on a first wheel; of the vehicle - a first braking management circuit, controlled by a driver of the vehicle from a control device installed inside the passenger compartment, and - a second braking management circuit, electronically controlled by a electronic control unit, - the first and second braking management circuits being connected to the brake fluid intake and exhaust circuit, characterized in that - the system comprises at least one motorized brake element mounted on a second wheel of the vehicle, and in that - the second braking management circuit comprises a brake fluid accumulator 35 connected via a connection m mechanical, to a geared motor, the accumulator being adapted to supply pressurized brake fluid and for generating a brake pressure independently of the actions of the driver on the control device installed inside the passenger compartment.

The invention may also comprise one or more of the following features: the second brake management circuit comprises a solenoid valve, normally closed, placed at the outlet of the high pressure accumulator, the first brake management circuit comprising a master cylinder and a solenoid valve, normally open, placed at the output of said master cylinder. the system comprises a solenoid valve with 3 orifices, of all or nothing type, placed at the same time at the output of the high pressure accumulator and at the output of the master cylinder. the high-pressure accumulator comprises at least one piston associated with a spring and connected to the gearmotor via the mechanical link so that the gearmotor, by moving the piston, ensures the compression of the spring as well as the circulation of the liquid of brake inside an enclosure of the accumulator. the high pressure accumulator comprises a force sensor able to determine a level of pressure potentially available in the accumulator. - The system includes a torque limiter built into the gearmotor or mechanical connection to control the compression force of the spring and therefore the pressure potentially available in the accumulator. the mechanical connection comprises, for example, a cable connecting the piston of the accumulator to the geared motor. the geared motor is of the braked or irreversible type. In the case of an irreversible geared motor, the system comprises a coupling means for separating the geared motor traction system. - The geared motor is reversible type and the piston is equipped with a mechanical locking means. the system comprises a pressure sensor placed upstream of the intake and exhaust circuit for determining the hydraulic pressure transmitted to the brake elements. the second brake management circuit comprises a hydraulic amplifier. the intake and exhaust circuit comprises at least a first pipe network ensuring the admission and the escape of the brake fluid into the mechanical stirrup, this first network comprising a plurality of solenoid valves and, at its exit a low pressure accumulator adapted to temporarily store escaped brake fluid from the mechanical brake element and to restore it to the first braking management circuit. the intake and exhaust circuit comprises at least one second pipe network ensuring the admission and the escape of the brake fluid into the motorized caliper, this second network comprising an isolation solenoid valve and a valve allowing the passage of the brake fluid only from the motorized brake element to the first brake management circuit. - The valve of the second pipe network is mounted in parallel with the solenoid valve. the motorized brake element comprises a body integral with a brake pad and at least one chamber filled with hydraulic fluid, a hollow hydraulic piston being installed inside this chamber, an electric piston system being installed in the chamber; inside the hollow of the piston, the electric piston system comprising a piston associated with an electric motor, one end of the piston of the electrical system being positioned facing a second plate, the two plates being positioned on either side of a disc associated with a wheel of the vehicle. the brake element comprises a body having at least two chambers formed on either side of a disc associated with a wheel of the vehicle, a hydraulic piston being installed in one of the chambers filled with hydraulic fluid, one end of this hydraulic piston being positioned facing a first plate, an electric piston system comprising an electric piston associated with an electric motor being installed inside the other chamber, one end of the electric piston being positioned opposite a second plate, the two plates being positioned on either side of the disk. the brake element comprises a body integral with a first plate, this body having at least one chamber filled with hydraulic fluid inside which is disposed a hollow hydraulic piston, this hydraulic piston having an end positioned facing the a second wafer, an electric piston system being installed inside the hollow of the piston, this electric piston system comprising a nut cooperating with a helical shaft driven in rotation by an electric motor, the nut being able to move away or approach the hydraulic piston of the disk disposed between the plates. - The first braking management circuit comprising a master cylinder associated with a brake fluid reservoir, the outlet of the intake and exhaust circuit is connected directly to the brake fluid reservoir. the normally open piloting solenoid valve is interposed between the master cylinder and valves of the intake circuit so as to form a braking circuit distinct from the braking circuit. the system comprising a second brake fluid intake and exhaust circuit, also connected to a second brake management circuit, the second brake management circuit connected to the second intake and exhaust circuit comprises a high pressure brake fluid accumulator connected to the geared motor - the high pressure accumulators of each of the second brake management circuits are connected to a single lifter, said lifter being connected by a mechanical connection to the geared motor. The invention also relates to a method for implementing the system described above, characterized in that it comprises the following operations: a pressure potentially available in the accumulator is compared with a predetermined threshold value, when the potentially available pressure is below the threshold value, the gearmotor is activated, - under the action of the geared motor, the piston of the high pressure accumulator moves, sucking brake fluid into the high pressure accumulator, - as soon as the pressure potentially available has reached the threshold value, the gearmotor is deactivated, - the piston is held in position as long as the control unit does not require pressure independently of the action of the driver on the control device installed inside the interior, the potentially available pressure is thus preserved even if the hydraulic pressure of the accumulator can decrease. The method of the invention may also include one or more of the following features - when a pressure greater than the pressure measured by the pressure sensor placed upstream of the intake and exhaust circuit is required, the solenoid valve of isolation of motorized calipers is activated and the braking force of these calipers is obtained directly by activating the actuator motorizing these calipers; such a method makes it possible to use a high-pressure accumulator of smaller size; - when the system comprises a valve in parallel with the normally closed solenoid valve 106, said solenoid valve may not be activated when the geared motor is activated - when the system does not include a valve in parallel with the normally closed solenoid valve, said solenoid valve must be activated before the gearmotor is activated. - when the system does not include a normally closed valve or solenoid valve, the gearmotor is activated directly. the method comprises a preliminary operation for determining the pressure potentially available in the accumulator from a measurement of a traction force of the piston, carried out by means of a force sensor, and a measurement of a pressure of the master cylinder, performed by means of a pressure sensor. the method comprises a preliminary operation for determining a potentially available pressure in the accumulator from a maximum torque transmissible by a torque limiter.

The invention further relates to a motor vehicle characterized in that it comprises the system described above.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1, already described, represents a braking circuit with stability control and a conventional trajectory.

FIG. 2 represents an example of a hydraulically controlled braking system according to the invention. FIGS. 3A to 3D show the braking system of FIG. 2, on which is indicated the direction of circulation of the brake fluid during different phases of operation. Figures 4 to 9 show various embodiments and variants of the invention. Figs. 10A to 10C show various examples of motorized brake elements used in the braking system of the invention. DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION An example of a braking system according to the invention is shown in FIG. 2. As in the prior art, the braking system of the invention comprises at least one circuit of FIG. intake and exhaust of the brake fluid. In the embodiment of Figures 2 and 3 described below, the intake and exhaust circuit 3 is associated with two brake elements, that is to say two wheels of the vehicle. It is associated, in particular, with a mechanical brake element 103, or mechanical caliper, and a motorized brake element 203, or motorized caliper. As will be seen more precisely later, the braking system of the invention may also include a first intake and exhaust circuit associated with two mechanical brake elements and a second intake and exhaust system. exhaust associated with two motorized brake elements. It will be recalled for all intents and purposes that a conventional brake element, hereinafter referred to as a mechanical brake element, is an element of the braking system installed at a wheel of the vehicle for the purpose of pressure transformation. hydraulic braking torque of the wheel. In the invention, the braking system comprises two mechanical brake elements and two motorized brake elements. A motorized brake element comprises, in addition to the mechanical brake element, electrical means for acting on the braking torque independently of the support on the brake pedal by the driver.

Various examples of motorized brake element are shown in FIGS. 10A to 10C. For each of these different examples, the brake element 305.1 makes it possible to generate a braking torque at the wheel by pressing brake pads 316.1, 316.2 against a brake disk 324, these plates being arranged on both sides. Other disk 324. The brake element 305.1 comprises a body 315 integral with a brake pad 316.1. This body 315 comprises at least one hydraulic chamber 317 filled with hydraulic fluid. The volume of the chamber 317 may vary following the movement of a piston 319 delimiting this chamber.

The sealing of the chamber 317 is ensured by means of a seal 320 which can be mounted in a groove in the inner wall of the chamber 317 and clamped on the piston 319 or on the contrary mounted in a groove on the surface of the piston 319 and clamped against the inner wall of the chamber 317.

To enable braking and ensure wear compensation platelets 316.1, 316.2, there is a relative movement between the body 315 of the brake element 305.1 and the brake disc 324. To do this, the brake disc can be in sliding connection with the axis of rotation of the wheel (floating disk type) or the body 315 may be slidably connected relative to the rest of the vehicle by means of a yoke not shown in the figures (floating caliper type). As shown in FIG. 10A, the hydraulic piston 319 is hollow and comprises an electric piston system 322. This system is composed of a piston 322.1, one end of which is in contact with a brake pad 316.2 and an electric motor 322.2 . A system for blocking the rotational movement of the electric piston 322.1 around the axis of the electric motor 322.2, for example consisting of a key 322.3 mounted in the electric piston 322.1 and slidable in a groove formed in the hydraulic piston 319 allows allow only a translation movement of the electric piston 322.1 relative to the hydraulic piston 319 when the electric motor 322.2 is activated, the electric piston 322.1 being locked in its position when the motor 322.2 is not actuated (irreversibility of a screw / nut system, use of a braked motor 322.2, etc.).

The rotation of the piston 319 about the axis of the motor 322.2 is prevented by the friction torque generated by the seal 320 or by a similar blocking device not shown. Thus, when the pressure in the hydraulic circuit is established, the hydraulic piston 319 presses, via the electric piston 322.1, the plate 316.2 on the disc 324. As it moves, the hydraulic piston 319 deforms the seal 320. Furthermore, to the reaction force due to the pressure, the caliper body 315 or the disk 324 moves in translation so as to press the plate 316.1 against the disk 324. During brake release, when the hydraulic pressure decreases in the hydraulic circuit , the seal 320, returning to its original shape, remembers the piston 319 in its initial position. The wear of the pads is compensated by a sliding of the piston 319 vis-à-vis the seal 320, the piston 319 does not return exactly to its initial position in this case.

The braking torque can be modulated by the joint action of the electric piston system 322 and the solenoid isolation valve 307.1 independently of the pressure generated in the hydraulic circuit. Indeed, once the chamber 317 isolated, the braking torque can be increased when the piston 322.1 is pressed against the plate 316.2 in order to reduce the volume of the chamber 317 (hence an increase in the pressure and therefore the clamping force), or decreased when the piston 322.1 is away from the plate 316.2 to increase the volume of the chamber 317 (hence a decrease in pressure and therefore the clamping force). In the variant of the figure OB, the brake element 305.1 comprises a body 315 having two chambers 317.1, 317.2 formed on either side of a disc 324 associated with a wheel of the vehicle, the chamber 317.1 being identical to the chamber 317 described above. In this variant, the hydraulic piston 319 is full and an electric piston system 322 identical to that described above is located in the chamber 317.2. Thus, when the pressure in the hydraulic circuit is established, the hydraulic piston 319 presses the plate 316.2 on the disk 324. Furthermore, following the reaction force due to the pressure, the caliper body 315 or the disk 324 moves in translation so as to press the plate 316.1 against the disk 324 via the electric piston system 322. As it moves, the piston 319 deforms the seal 320. During the brake release, when the hydraulic pressure decreases, the seal 320, returning to its original shape, recalls the piston 319 in its initial position. The wear of the pads is compensated by a sliding of the piston 319 vis-à-vis the seal 320, the piston 319 does not return exactly to its initial position in this case. As for the embodiment of FIG. 10A, the braking torque can be modulated thanks to the joint action of the electric piston system 322 and the isolation solenoid valve 307.1 independently of the pressure generated in the hydraulic circuit. Indeed, once the chamber 317 isolated, the braking torque can be increased by approaching the piston 322.1 against the plate 316.1 in order to reduce the volume of the chamber 317, or decreased by moving the piston 322.1 from the plate 316.1 in order to to increase the volume of the chamber 317. FIG. 10C shows a schematic representation of a motorized brake element 305.1 used with a braking system according to the invention comprising a non-return valve 309.1 connected in parallel with each isolating solenoid valve. 307.1. In this embodiment, the piston 319 is hollow and the electric motor 327.3 of an electric piston system 327 is outside the body 315 of the brake element 305.1. A seal 327.4 completes the sealing of the chamber 317. This electric piston system 327 comprises a nut 327.1 located inside the hollow piston 319. A locking system of the rotational movement of the nut 327.1, not shown on FIG. the figure, allows only a translational movement of the nut 327.1 when the 327.2 helical rod is rotated by the motor 327.3. The electric piston system 327 is of the irreversible type. This irreversibility can be achieved through the use of a braked motor or a 327.2 screw / nut 327.3 irreversible. Furthermore, a removable element 327.5 which can be a circlip is installed in a groove made inside the piston 319. This element 327.5 allows for a shoulder 329.1. A second shoulder 329.2 is formed directly inside the piston 319 on the side of the plate 316.2. The element 327.5 is removable in order to be able to mount the nut 327.1 between the two shoulders 329.1, 329.2, this nut 327.1 being intended to abut against these two shoulders 329.1, 329.2. The games j1 and j2 between the nut 327.1 and the shoulders 329.1, 329.2 are defined to allow operation without the electrical system 327 interfering with the purely hydraulic operation of the braking system. Thus, the clearance j1 between the nut 327.1 and the shoulder 329.1 corresponds to the maximum stroke of the piston 319 hydraulic braking without electrical action. The clearance j2 between the nut 327.1 and the shoulder 329.2 guarantees that there will be no residual braking force following the creation or the increase of a braking torque thanks to the electrical system (use of the electric parking brake function for example). Thus, when the pressure in the hydraulic circuit is established, the hydraulic piston 319 moves in translation relative to the piston 327 towards the disk 324 and presses the plate 316.2 on the disk 324. Furthermore, following the reaction force due at the pressure, the body of the stirrup 315 or the disc 324 moves in translation so as to press the plate 316.1 against the disc 324. On moving, the hydraulic piston 319 deforms the seal 320. When the hydraulic pressure decreases in the hydraulic circuit, the seal 320, returning to its original shape, remembers the piston 319 in its initial position. The wear of the pads is compensated by a sliding of the piston 319 vis-à-vis the seal 320, the piston 319 does not return exactly to its initial position in this case. The braking torque can be modulated by the joint action of the 327 electric piston system and the solenoid isolation valve 307.1 independently of the pressure generated in the hydraulic circuit. Indeed, the braking torque can be increased when the nut 327.1 is pressed by the motor against the shoulder 329.2 so as to increase the pressing force of the piston 319 against the plate 316.2 or decreased when the nut 327.1 is pressed against the shoulder 329.1 so as to reduce the pressing force of the piston 319 against the plate 316.2. In the example of FIG. 2, which will now be described, the motorized brake element 203 is associated with an intake solenoid valve 211 and a nonreturn valve 214. In this embodiment, the valve 214 is mounted in parallel with the intake solenoid valve 211.

In this example of FIG. 2, the intake and exhaust circuit 3 is connected, on the one hand, to a first braking management circuit 1 and, on the other hand, to a second circuit 2 for managing the braking management circuit. braking. The first braking management circuit 1, also called a pedal braking device, is controlled by the driver of the vehicle from a control device installed in the passenger compartment of the vehicle. This control device may be a brake pedal or a manual actuator, mechanical or electrical or electromechanical. The second braking management circuit 2, also called stability and trajectory control device, is controlled electronically by an electronic control unit. In the invention, the first braking management circuit 1 comprises, as previously described, a booster 101, a master cylinder 102 associated with a brake fluid reservoir 115 and a solenoid valve 105.

As explained in more detail below, the first brake management circuit also comprises a pressure sensor 113. This pressure sensor 113 is placed upstream of the intake and exhaust circuit 3 to determine the hydraulic pressure transmitted to the valves. brake elements. It can be placed, for example, at the output of the master cylinder 102 or at the outlet of the solenoid valve 105, as shown in FIG. 2. In the invention, the second braking management circuit 2 is made with relatively simple elements. to install on the vehicle and relatively inexpensive compared to the price of a hydraulic pump. This second brake management circuit comprises a brake fluid accumulator 10. A high pressure accumulator is an accumulator for delivering fluid at pressures of the order of 100 to 150 bar, as opposed to the low pressure accumulator 110 whose hydraulic pressure is of the order of 0 to 15 bar. The high pressure accumulator is calibrated at a pressure of 100 to 150 bar, that is to say that the preload force of the spring or springs on the piston provides a pressure of 100 to 150 bar. The high pressure accumulator 10 of the invention comprises a chamber 14 provided with an orifice 16 through which the brake fluid can enter the accumulator or exit said accumulator; it comprises, in addition, at least one piston 11 inserted inside the chamber 14. The piston 11 is a movable member with a rectilinear movement inside the chamber 14. The piston 11 has a a shape that can be substantially T-shaped; it comprises a piston head 11b and a piston rod 11a. In the invention, the piston is associated with a spring 12. This spring 12 can be mounted around a piston rod 11a, between the piston head 11b and a stop 15 formed inside the piston. pregnant. When the spring is compressed between the piston head 11b and the stop 15, brake fluid can enter the accumulator 10. As long as the spring 12 is in its compressed position, the brake fluid is stored in the reservoir. accumulator. The compression of the spring 12 makes it possible to store energy in potential form in the accumulator 10. It is this potential energy which ensures the pressurization of the fluid in the said accumulator 10. When the spring 12 expands, the piston 11 is pushed towards the port 16 of the accumulator, discharging the brake fluid towards said orifice 16. The brake fluid, stored until now in the accumulator 10, is then discharged from said accumulator through the orifice 16, with a pressure sufficient to allow it to reach the brake elements 103 and 203. The compressed and relaxed positions of the spring 12 are obtained in the invention by means of a traction system 20. This traction system 20 comprises a geared motor 21 connected to the high pressure accumulator 10 via a mechanical connection 22/23. This mechanical connection 22/23 is fixed on the piston rod 11a. The geared motor 21 is a rotary motor for driving, via the mechanical connection 22/23, the piston 11 of the high pressure accumulator. When the gearmotor is activated, that is to say in motion, it drives the connection 22/23, and consequently the piston 11 which compresses the spring 12. As explained above, the fact of moving the piston 11 towards the stop 15 allows to release the orifice 16 and to introduce brake fluid into the chamber of the accumulator 10. As will be seen later, the geared motor is preferably irreversible; thus when the gearmotor 21 is deactivated, the spring 12 remains compressed. On the other hand, when the gearmotor is released, the spring 12 expands, driving the piston head 11b towards the orifice 16, which has the effect of driving the brake fluid towards the hydraulic lines external to the accumulator 10. with a pressure which depends, in particular, on the compressive force experienced by the spring 12. In a preferred variant of the invention, the geared motor 21 is connected to the high-pressure accumulator 10 via a cable 22 associated with a coupling means 23. This coupling means allows to separate the traction system of the geared motor, when the gear motor is irreversible type. The cable 22 and the coupling means 23 form the mechanical connection 22/23. The traction system may comprise a pulley or a set of pulleys arranged so as to increase the reduction ratio of the traction system while decreasing the stress on the cable. According to a variant of the invention, the pistons constituting the high pressure accumulator of each of the two circuits are interconnected by a spreader, which is itself connected to the gearmotor 21 by the cable 22 and thus by the coupling means 23. variant makes it possible to have only one traction element for all the braking systems of the vehicle. In a preferred embodiment of the invention, the high pressure accumulator 10 also comprises a force sensor 13. This force sensor 13 can be placed between the piston 11 and the traction system 20, for example between the cable 22 of the mechanical connection and the piston rod 11a. The force sensor 13 makes it possible to estimate the pressure that is potentially available in the accumulator 10 when the spring 12 is released. Indeed, the information provided by the force sensor 13 relates to the displacement of the piston 11 inside the enclosure 14, this displacement making it possible to estimate the pressure force with which the brake fluid will be evacuated. enclosure 14. An alternative embodiment with a displacement sensor of the piston or the traction system is also possible. In other words, the force sensor 13 makes it possible to know if, at a given moment, the pressure potentially available thanks to the high pressure accumulator 10 is sufficient to allow the realization of the functions requiring a braking pressure independently of the action of the driver on the brake pedal 100 or, conversely, if it is insufficient. This information is necessary, in particular, at the start of the vehicle or after braking controlled by the electronic control unit.

In such an embodiment, this information can be used to indicate to the driver, by means of a bulletin board (light (s), message (s) ...), if the stability control device and trajectory is in an optimal operating state or not. In an alternative embodiment, this information is transmitted to a safety device which prevents the engine from starting as long as the pressure potentially available thanks to the high pressure accumulator 10 necessary for the safety of the vehicle and its occupants has not been reached. The force sensor 13 may also make it possible to diagnose a rupture of a cable and / or springs. The rupture of a cable does not involve unwanted braking since the chamber of the high pressure accumulator 10 is isolated from the braking circuit by the solenoid valve 106 and the valve 116. Thus, with such a braking system, the braking process is as follows: - when the driver of the vehicle wishes to brake, it exerts a force 200 on the brake pedal 100; this force is amplified by the brake pedal 100 as well as the booster 101 and then transmitted to the master cylinder 102. The master cylinder 102 generates a hydraulic pressure depending on the effort received. The brake fluid under pressure is transmitted through a set of hydraulic lines to the intake and exhaust circuit 3. More specifically, the brake fluid under pressure is transmitted to the circuit 3 via a valve 108 and a solenoid valve 105. In its normal state, the solenoid valve 105 is open allowing the passage of the fluid of the master cylinder 102 to the circuit 3. The hydraulic pressure is thus transmitted to the brake elements 103 and 203. The circulation of the brake fluid from the master cylinder 102 to the brake elements 103 and 203, in the event of braking by the driver, is represented by an arrow in FIG. 3A. during a brake release, that is to say when the driver reduces or stops exerting a force on the brake pedal, the brake fluid contained under pressure in the brake elements 103, 203, returns to the master cylinder 102, as shown in Figure 3B. The return of the brake fluid takes place through the valves 114, 214 and the solenoid valves 111, 211, normally open, of the circuit 3. It then passes through the solenoid valve 105 to reach the master cylinder 102. - the braking of the vehicle, when controlled by the electronic control unit, will now be described through Figures 3C and 3D. FIG. 3C represents the braking system of the invention during the energy storage phase in the high pressure accumulator 10. In this FIG. 3C, the circulation of the brake fluid between the reservoir 115 and the high pressure accumulator 10 is represented by an arrow. As explained above, the force sensor 13 of the high pressure accumulator 10 makes it possible to determine whether the level of force exerted by the spring 12 on the piston 11 is sufficient or not to allow the performance of the stability control functions and trajectory, or more generally requiring a braking pressure independent of the action of the driver on the brake pedal 100. The level of effort may be insufficient, for example, at the time of starting the vehicle or after using the system to make a correction of the vehicle trajectory. In such a case, when the level of effort is insufficient, the solenoid valve 106 and the gear motor 21 are activated. The geared motor then exerts a traction force on the piston 11 via the mechanical link 22/23. On moving, the piston 11 compresses the spring 12. In parallel, the movement of the piston has the effect of sucking brake fluid into the accumulator 10. This brake fluid comes from the reservoir 115, through the solenoid valves 105 and 106 and the valves 108 and 116. When the force sensor 13 measures that the level of force exerted by the spring 12 on the piston 11 is sufficient, the solenoid valve 106 and the gear motor 21 are deactivated. As explained above, when the geared motor is deactivated, the traction force established by the geared motor on the piston is retained. The energy supplied by the geared motor 21 to the traction system is thus transformed and stored in potential form in the spring 12 of the high pressure accumulator 10. This potential energy will make it possible to generate the pressure required to provide a trajectory control for example. since the piston 11 will be released. Thus, the braking system of the invention implements the following method: the pressure potentially available thanks to the accumulator 10 is compared with a predetermined threshold value, when the potentially available pressure is below the threshold value, The operation may be slightly different depending on the variant embodiments: • If the system comprises a valve 116, the solenoid valve 106 may not be activated but the gearmotor 21 is activated. • If the system does not include a valve 116, the solenoid valve 106 must be activated then the gear motor 21 is activated. • If there is no valve 116 or solenoid valve 106, the gear motor 21 is directly activated. under the action of the gearmotor 21, the piston 11 of the high-pressure accumulator 10 moves, sucking brake fluid into the high-pressure accumulator, - as soon as the potentially available pressure has reached the threshold value, the geared motor 21 is deactivated as well as the solenoid valve 106 if it was previously active, - the piston 11 is held in position as the control system does not require pressure independently of the action of the driver on the pedal 100. The potentially available pressure is therefore preserved even if the hydraulic pressure of the accumulator can be reduced (under the effect of the leaks of the solenoid valve 106 and / or the valve 116). This method comprises a preliminary operation for determining the pressure potentially available in the accumulator. This determination can be made from a measurement of a pulling force of the piston, carried out by means of the force sensor 13, and a measurement of a pressure of the master cylinder, carried out by means of the pressure sensor. 113. It can also be performed from a maximum torque transmissible by a torque limiter. In a preferred embodiment of the invention, the geared motor 21 is of irreversible type, or braked. In this case, it maintains the traction force on the piston 11 and therefore the compression force of the spring 12 until it is released. In another embodiment of the invention, the geared motor 21 is of the reversible type. In this case, the tensile force of the piston 11 is maintained by a mechanical locking system of the piston 11 of the accumulator 10. This mechanical locking system may, for example, consist of a rack and pinion assembly with freewheel associated with a brake. When the electronic control unit issues an activation command of the second brake management circuit 2, the piston 11 is released.

The spring 12 can then relax by exerting a force on the piston 11 which consequently generates a hydraulic pressure. This pressure can be controlled by means of the solenoid valve 106 or the inlet solenoid valves 111 and 211. The fluid flow caused by the displacement of the piston 11 in the chamber 14 of the accumulator 10 is represented by the arrows on Figure 3D. The pressurized brake fluid passes through the solenoid valve 106 and the hydraulic lines to the intake and exhaust circuit 3, then passes through said circuit 3 to the brake elements 103 and / or 203. During this entire phase of operation and to be able to generate a hydraulic pressure in the braking circuit, the normally open solenoid valve 105 is activated (closed). If during this phase of operation the driver presses on the brake pedal 100, the pressure resulting from this action can be transmitted to the brake elements, if it is greater than the pressure modulated by the solenoid valve 106 or by the solenoid valves 111. and 211, through the flap 116.

Alternatively, the solenoid valve 211 can be activated, the braking torque then being directly created by the actuator motorizing the caliper 203. It should be noted that when the stability control device is actuated, it has the effect of modify the hydraulic pressure in some brake elements by increasing or decreasing it. The four brake elements of the vehicle can then have a different hydraulic pressure. In the example of FIG. 3D, there is shown the case where the hydraulic pressure is increased in the two brake elements 103 and 203, it being understood that the hydraulic pressure in one or both element (s) brake could be kept constant or diminished.

When it is necessary to reduce the pressure in the mechanical brake element 103, the normally open intake solenoid valve 111 and the normally closed exhaust solenoid valve 112 associated with the brake element concerned , are activated, simultaneously or not. In one embodiment of the invention, the brake fluid then flows via the valve 117 to a low pressure accumulator 110. This accumulator 110 is called a low pressure accumulator, as opposed to the high pressure accumulator. 10 because its internal pressure is much lower than that of the high pressure accumulator. This low pressure accumulator 110 is connected by a valve 109 to the inlet of the intake and exhaust circuit 3. It can also be connected, by said valve 109, to the output of the master cylinder 102, as shown in Figure 7A. The valve 109 allowing flow in only one direction, namely from the low pressure accumulator 110 to the braking management circuits 1 and 2, the pressure of the low pressure accumulator 110 may be lower than the pressure the master cylinder 102. The low pressure accumulator 110 is dimensioned in volume and stiffness so that it can store the entire volume of brake fluid discharged from the brake elements by the solenoid valves 112 during the regulation, while having a relatively low pressure rise.

The low pressure accumulator 110 is then emptied, via the valve 109, when, during release, the pressure of the master cylinder 102 becomes lower than the pressure of the low pressure accumulator 110. When it is necessary to to reduce the clamping force at the motorized brake element 203, the inlet solenoid valve 211 is activated.

The pressure of the insulated wheel is kept constant as long as solenoid valve 211 is not deactivated. If the pressure is still too high, the motorized piston of the brake element 203 is activated. According to the variant chosen for motorizing the brake element 203, the actuator of said brake element 203 pushes the hydraulic piston and delivers the brake fluid to the master cylinder 102 through the valve 214, or the electric piston moves. , causing an increase in the volume of the hydraulic chamber, therefore a decrease in pressure and, consequently, in the clamping force. There is therefore no circulation of the brake fluid. In another embodiment of the invention, when it is necessary to lower the pressure in a mechanical brake element, the surplus brake fluid flows through the exhaust solenoid valve 112 and then directly to the reservoir 115 of the master cylinder 102. Indeed, in this embodiment, shown in Figure 8, the output of the intake and exhaust circuit 3, that is to say the valve 117, is connected directly, by a hydraulic line, to the reservoir 115 of brake fluid. There is no low pressure accumulator to store the brake fluid while waiting for the next brake release. Thus, in this embodiment, the brake fluid returns directly to the reservoir 115 of the master cylinder instead of being stored in a low pressure accumulator and then discharged to the reservoir 115. This embodiment avoids the constraints relating to the volume of the low pressure accumulator. It also simplifies the operation and control of the braking system. The return line between the valve 117 and the reservoir 115 may be specific to each of the intake and exhaust circuits (each corresponding to two wheels of the vehicle) or share by the two circuits. There is only one return line for all 4 wheels. It should be noted that the various variants of the invention described above, relating for example to the traction system, can be implemented regardless of the embodiment of the circuit 3 intake and exhaust. Other variants of the invention, which will be described below, may also be considered, regardless of the embodiment of the circuit 3 intake and exhaust. Alternatively, the traction system 23 of the invention may be a winch, as shown in Figures 2 and 3. This traction system 23 may also be formed of a pinion and rack assembly, as shown in Figure 4 In this case, the traction system can be directly connected to the piston of the high pressure accumulator 10. The traction system 23 can also be realized by means of a worm, as shown in FIG.

In a variant of the invention, the force sensor 13 previously described can be replaced by an integrated torque limiter, either to the geared motor 21 or to the traction system 23. In this variant, the traction force is not controlled electronically, thanks to the information provided by the force sensor, but by the limitation of the torque.

In another variant, the force sensor 13 is replaced by a linear displacement sensor or an angular displacement sensor. According to a variant of the invention, a hydraulic amplifier 18 is inserted on the hydraulic line connecting the high pressure accumulator 10 to the intake and exhaust circuit 3. This hydraulic amplifier 18 has the role of increasing the pressure at the outlet of the high pressure accumulator.

This hydraulic amplifier 18 can be installed either between the solenoid valve 106 and the high pressure accumulator 10, as shown in FIG. 6A, or between the solenoid valve 106 and the hydraulic line joining the intake and exhaust circuit 3, as shown in Figure 6B.

In the above description, the solenoid valves of the braking management circuits 1 and 2, namely the solenoid valves 105 and 106, are two-port solenoid valves. These solenoid valves 105 and 106 may be replaced by a single three-hole solenoid valve 118, as shown in FIG. 7B. This solenoid valve 118 is all-or-nothing type. The control of the pressure in the stirrups is then effected by the intake solenoid valves 111 and 211. The solenoid valve 118 makes it possible to connect the intake and exhaust circuit 3 either with the accumulator 10 or with the master. cylinder 102. In this case, it is possible to move the valve 116, as shown in Figure 7C, see delete it. It is also possible to directly connect the valve 109 to the master cylinder 102, as shown in Figure 7D. It is also possible to directly connect the valve 109 to the master cylinder 102 and remove the valve 116, as shown in Figure 7E. In the embodiments described above, the valve 214 associated with the motorized brake element 203 is connected in parallel with the solenoid valve 211. In other variants, the valve 214 may be mounted differently. For example, in certain variants, the valves 114 and 214 may be connected to the solenoid valve 105 without connection with the valve 108. Thus, the normally open piloting solenoid valve 105 is interposed between the master cylinder 102 and the valves 114. 214 of the intake circuit. These configurations make it possible to obtain a specific braking circuit distinct from the braking circuit. Figure 7F illustrates an embodiment of this type having in addition the valve 109 directly connected to the master cylinder 102. In the embodiment of Figure 7F, the valve 116 and the solenoid valve 106 can also be removed. The valve 109 may also be connected to the solenoid valve 105 instead of the master cylinder 102. The valve 116 and the solenoid valve 106 may also be omitted. Figure 7G corresponds to this embodiment but retaining a solenoid valve 106.

In another variant of the invention, one or more restrictions may be added at different points in the hydraulic circuit. The restriction is a section change of the hydraulic line. A restriction may be added, for example, between the high pressure accumulator 10 and the point A located at the outlet of the solenoid valve 106, as shown in FIG. 7A. According to this variant, the valve 116 may be in series or in parallel with this restriction. If one chooses a design of the motorized brake elements in which there is no valve (as in FIGS. 10A and 10B, for example) then the valve 214 can be conserved and placed upstream of the solenoid valve 211, as represented in Figure 9A. In the braking system of the invention, the motorized brake elements may be installed on the rear wheels or the front wheels of the vehicle, the mechanical brake elements being placed opposite said motorized brake elements. The mechanical brake elements and the motorized brake elements can also be mounted diagonally, for example a motorized element at the front right and a rear left of the vehicle. In the example of Figure 9C, the mechanical brake elements, that is to say, conventional, are installed on the front wheels of the vehicle, while the motorized brake elements are installed on the rear wheels, or conversely, in an architecture called L. The second brake management circuit 2 is then connected to the mechanical brake elements via a first intake and exhaust circuit 403. This intake and exhaust circuit 403 comprises, for each of the two mechanical brake elements, a solenoid valve 111, a valve 114, a solenoid valve 112 and a valve 117, which each have the same function as that explained for a single element. in this variant, the brake system comprises a second intake and exhaust circuit 503, associated with the motorized brake elements 203, and which comprises only a solenoid valve 211 and a valve 214 , for each motorized brake element. This second intake and exhaust circuit 503 is connected to a first braking management circuit 1.

In a variant of this L-shaped architecture, a high pressure accumulator 10 associated with a solenoid valve 106 is kept and connected to the second intake and exhaust circuit 203 to manage the pressure in the motorized brake elements.

The brake elements can also be mounted according to an architecture called X or H, as shown in Figure 9B. In this case, a first hydraulic circuit as described above manages the pressure in two brake elements, namely a mechanical brake element 103 and a motorized brake element 203 and a second hydraulic circuit, identical, manages the hydraulic pressure in the two other brake elements of said vehicle. In other words, the braking system of the invention then comprises two intake and exhaust circuits 3 and two second braking management circuits 2. Each intake and exhaust circuit 3 is connected to a first circuit brake management 1.

In another embodiment of the invention, it is possible to use, for the two hydraulic circuits, a single traction system. In other words, each hydraulic circuit has its own high pressure accumulator but the pistons of these two high pressure accumulators are connected by the same mechanical connection to the same geared motor. For this, the pistons of the two accumulators can be connected to a rudder, itself connected to the mechanical connection.

Claims (30)

CLAIMS1 - Hydraulically controlled braking system for a motor vehicle comprising: a first circuit (3) for the intake and exhaust of a brake fluid into at least one mechanical brake element (103) mounted on a first wheel of the vehicle, - a first braking management circuit (1), controlled by a driver of the vehicle from a control device (100) installed inside the passenger compartment, and - a second circuit (2) of braking management, electronically controlled by an electronic control unit, - the first and second braking management circuits being connected to the brake fluid intake and exhaust circuit, characterized in that - the system comprises at least a motorized brake element mounted on a second wheel of the vehicle, and in that - the second brake management circuit (2) comprises a brake fluid accumulator (10) connected via a mechanical link e (22/23), to a geared motor (21), the accumulator for generating a brake pressure independently of the actions of the driver on the control device (100) installed inside the passenger compartment. 2 - System according to claim 1, characterized in that the second brake management circuit comprises a solenoid valve (106), normally closed, placed at the output of the high pressure accumulator, the first brake management circuit comprising a master cylinder (102) and a solenoid valve (105), normally open, placed at the output of said master cylinder. 3 - System according to claim 1, characterized in that it comprises a solenoid valve (118) with 3 orifices, all-or-nothing type, placed both at the output of the high pressure accumulator (10) and at the output of the master cylinder (102). 4 - System according to any one of claims 1 to 3, characterized in that the high pressure accumulator (10) comprises at least one piston (11) associated with a spring (12) and connected to the geared motor via the mechanical connection so that the geared motor, by moving the piston, ensures the compression of the spring (12) and the circulation of the brake fluid inside a chamber (14) of the accumulator. 5 - System according to any one of claims 1 to 4, characterized in that the high pressure accumulator (10) comprises a force sensor (13) adapted to determine a pressure level in the accumulator. 6 - System according to any one of claims 1 to 4, characterized in that it comprises a torque limiter integrated gear motor or the mechanical connection. 7 - System according to any one of claims 4 to 6, characterized in that the mechanical connection (22/23) comprises a cable (22) connecting the piston (11) of the accumulator to the geared motor (21). 8 - System according to any one of claims 1 to 7, characterized in that the geared motor is braked or irreversible type. 9 - System according to claim 8, characterized in that it comprises a coupling means allowing, when the geared motor is irreversible type, to separate the mechanical connection of the geared motor. 10 - System according to any one of claims 1 to 9, characterized in that the geared motor is reversible type and the piston is equipped with a mechanical locking means. 11 - System according to any one of claims 1 to 10, characterized in that it comprises a pressure sensor (113) placed enamont of the intake and exhaust circuit to determine the hydraulic pressure transmitted to the brake elements. 12 - System according to any one of claims 1 to 11, characterized in that the second brake management circuit comprises a hydraulic amplifier (18). 13 - System according to any one of claims 1 to 12, characterized in that the intake and exhaust circuit comprises at least a first pipe network ensuring the admission and escape of the brake fluid in the mechanical stirrup, this first network comprising a plurality of solenoid valves and, at its output, a low pressure accumulator (110) capable of temporarily storing escaped brake fluid from the mechanical brake element and returning it to the first circuit brake management. 14 - System according to any one of claims 1 to 13, characterized in that the intake and exhaust circuit comprises at least a second pipe network ensuring the admission and escape of the brake fluid in the motorized caliper, the second network comprising an isolating solenoid valve and a valve allowing the passage of the brake fluid only from the motorized brake element to the first brake management circuit. 15 - System according to claim 14, characterized in that the valve of the second pipe network is connected in parallel with the solenoid valve. 16 - A braking system according to any one of claims 1 to 15, characterized in that the motorized brake element comprises a body (315) integral with a brake pad (316.1) and at least one chamber (317). filled with hydraulic fluid, a hollow hydraulic piston (319) being installed inside this chamber, an electric piston system (322) being installed inside the hollow of the piston, this electric piston system comprising a piston ( 322.1) associated with an electric motor (322.2), an end of the piston of the electrical system being positioned facing a second plate, the two plates being positioned on either side of a disk (324) associated with a wheel of the vehicle. 17 - A braking system according to any one of claims 1 to 15, characterized in that the brake element comprises a body having at least two chambers (317.1 - 317.2) formed on either side of a disc 324 ) associated with a wheel of the vehicle, a hydraulic piston (319) being installed in one of the chambers (317.1) filled with hydraulic fluid, one end of this hydraulic piston being positioned facing a first plate (316.2), a system with electric piston comprising an electric piston associated with an electric motor being installed inside the other chamber (317.2), one end of the electric piston being positioned facing a second plate, the two plates being positioned on the other side and other of the disc. 18 - A braking system according to any one of claims 1 to 15, characterized in that the brake element comprises a body integral with a first plate, this body having at least one chamber filled with hydraulic fluid inside of which is disposed a hollow hydraulic piston, this hydraulic piston having an end positioned opposite a second plate, an electric piston system being installed inside the hollow of the piston, this electric piston system (327) comprising a nut (327.1) cooperating with a helical pin (327.2) driven in rotation by an electric motor (327.3), the nut being adapted to move away or approach the hydraulic piston of the disk (324) disposed between the plates (316). 19 - System according to any one of claims 1 to 18, wherein the first braking management circuit comprises a master cylinder (102) associated with a brake fluid reservoir (115), characterized in that the output of the circuit intake and exhaust is connected directly to the brake fluid reservoir. 20 - System according to any one of claims 2 to 19, characterized in that the normally open control solenoid valve (105) is interposed between the master cylinder (102) and valves (114, 214) of the circuit of intake to form a brake release circuit separate from the braking circuit. 21 - A hydraulic drive brake system for a motor vehicle according to any one of the preceding claims, further comprising a second brake fluid intake and exhaust circuit, also connected to a second braking management circuit, characterized in that the second braking management circuit connected to the second intake and exhaust circuit comprises a high pressure brake fluid accumulator connected to the geared motor. 22 - System according to claim 21, characterized in that the high pressure accumulators of each of the second brake management circuits are connected to a single lifter, said lifter being connected by a mechanical connection to the geared motor. 23 - A method of implementing the system according to any one of claims 2 to 22, characterized in that it comprises the following operations: - a potentially available pressure in the accumulator (10) is compared to a predetermined threshold value - when the potentially available pressure is below the threshold value, the gearmotor is activated, - under the action of the geared motor (21), the piston (11) of the high pressure accumulator moves, sucking brake fluid in the high-pressure accumulator, - as soon as the potentially available pressure has reached the threshold value, the gearmotor (21) is deactivated, - the piston (11) is held in position as long as the control unit does not require pressure independently of the action of the driver on the control device (100) installed inside the passenger compartment, the potentially available pressure being thus preserved even if the hydraulic pressure of the battery emulator may decrease. 24 - Method according to claim 23, characterized in that, when the system comprises a valve (116) in parallel with the solenoid valve (106) normally closed, said solenoid valve (106) may not be activated when the geared motor (21) is activated 25 - Method according to claim 23, characterized in that, when the system does not include a valve (116) in parallel with the solenoid valve (106) normally closed, said solenoid valve (106) must be activated before the geared motor (21). ) is enabled. 26 - Process according to claim 23, characterized in that, when the system comprises neither valve (116) nor electrovalve (106) normally closed, the geared motor (21) is activated directly. 27 - Process according to any one of claims 23 to 26, characterized in that it comprises a preliminary operation for determining the pressure potentially available in the accumulator from a measurement of a tractive force of the piston, performed by means of a force sensor (13), and a measurement of a pressure of the master cylinder, performed by means of a pressure sensor (113). 28 - Process according to any one of claims 23 to 26, characterized in that it comprises a preliminary operation for determining a potentially available pressure in the accumulator from a maximum torque transmissible by a torque limiter. 29 - Process according to any one of claims 23 to 28, characterized in that when a pressure greater than the pressure measured by the pressure sensor (113) placed upstream of the intake and exhaust circuit is required, the solenoid isolation valve motorized calipers is activated and the braking force of these calipers is obtained directly by activating the actuator motorizing these calipers. 30 - Motor vehicle characterized in that it comprises a system according to any one of claims 1 to 22.