FR2861037A1 - Electrohydraulic braking device for motor vehicle, has simulator for sensing braking and being connected hydraulically with master cylinder in normal operation condition, and having cartridge integrated inside cylinder - Google Patents

Abstract

The device has a master cylinder (10) connected to a brake pedal. Safety solenoid valves allow separation and connection of the cylinder and a wheel brake when a service braking system and an emergency braking system function, respectively. A simulator for sensing braking is connected hydraulically with the cylinder in normal operation condition. The simulator has a cartridge (16) integrated inside the cylinder.

Description

Electrohydraulic braking device with vehicle simulator

automobile.

  The present invention relates to an electrohydraulic braking device with a simulator for a motor vehicle. It aims to integrate a simulator into an electrohydraulic braking system. More precisely, it aims to mount such a simulator with respect to a master cylinder.

  The invention aims to reduce the volume of an electrohydraulic braking system as a whole in an engine compartment. The invention also aims to reduce the size of a simulator.

  Currently, there are several motor vehicle braking systems. In particular, one of the oldest is a muscular energy braking system. It is generally equipped with a servomotor comprising a housing and a master cylinder. During braking, a foot controller actuates the servomotor. The control member may be a brake pedal ... The servomotor multiplies the value of the force exerted on the control member. This multiplied effort will be transmitted to the master cylinder. The master cylinder then transforms this effort into hydraulic pressure. A brake fluid contained in the master cylinder is sent to wheel brakes.

  More recently, an external energy braking system has been developed. It is very often associated with a muscular energy braking system. The muscular energy braking system then acts as a backup braking system when the external energy braking system fails. When the external energy braking system operates, the braking energy is entirely provided by a power source and not much of it by the driver. The connection between the brakes and the brake pedal is then essentially provided by a wired electrical connection.

  In such an external energy system, an electro-hydraulic brake detects the braking command given by a driver via the manual control member. Sensors quantify the force with which the controller was depressed as well as the speed at which the controller was depressed. A computer indicates to electronic actuators the braking force to be applied. This braking force is then distributed individually to wheel braking units.

  Such a braking device allows a braking whose intensity is not limited by the physical strength of the driver.

  However the driver has a psychological need to have the feeling of braking. So we put in place means to rebuild a resistance similar to that oppose a traditional braking system with muscular effort. This means or simulator allows the driver to have the sensation of dosing his braking effort.

  Such an external energy system no longer requires the presence of a servomotor. Despite the elimination of an already bulky servomotor part, the space required for such a braking device in the engine block remains important. Indeed, it is more prudent to associate with a braking system with external energy a mechanical braking system with muscular energy. This mechanical braking system only serves as an emergency braking system when the external energy braking system fails.

  A complete electrohydraulic braking device therefore generally comprises an external energy braking system, a muscular energy back-up braking system, a foot control member, a master cylinder connected to the brake pedal, and a sensation simulator. braking. Such a device is also provided with a safety valve. The brake pedal maintains a normal operating stroke, allowing the driver to feel mechanically braking, thanks to the simulator.

  When the external energy braking system operates, the master cylinder of the muscular brake system is isolated from the wheel brakes by the safety valve. When the external energy braking system fails, the safety valve connects the master cylinder to the wheel brake. The master cylinder then functions as a conventional master cylinder, that is to say a master cylinder of a mechanical braking device. Such a master cylinder is generally provided with a primary piston and a secondary piston. A primary chamber is formed between the primary piston and the secondary piston. A secondary chamber is formed between the secondary piston and a bottom of the master cylinder. Both chambers communicate with a brake fluid reservoir. Both chambers are filled with brake fluid.

  During muscular energy braking, the foot control actuates the primary piston by means of a push rod. The push rod pushes the primary piston inside the primary chamber. The primary piston pushes the secondary piston inside the secondary chamber. The advance of the primary and secondary pistons in their rooms, respectively primary and secondary, leads to a flow of hydraulic fluid to the wheel brakes.

  The simulator of the braking sensation is for example fixed to the master cylinder. The simulator may consist of a removable cartridge screwed to the master cylinder. The simulator generally includes a piston and a spring located between the piston and a bottom of the cartridge. When braking with the external energy brake system, the hydraulic fluid in the chambers of the master cylinder is injected into the cartridge. It pushes the piston of the cartridge toward the bottom of the cartridge. The spring is compressed. The spring action of the cartridge forms the simulation force.

  Such a simulator has a large footprint. The size of the simulator is added to the size of the master cylinder to which it is attached. It is therefore necessary to spare space accordingly in the engine compartment to accommodate this master cylinder-simulator device. In addition, there are also means for operating the external energy braking system.

  The engine block of a vehicle also has a large volume. The problem of space in the engine compartment requires the manufacture of vehicles whose body can contain such engine blocks. In the age of miniaturization, the congestion of the simulator is a real handicap for the automotive industry. The electrohydraulic braking system is a technological advance whose interest is minimized by the problems it generates.

  In the invention, it is sought to solve this problem of space in the engine compartment by reducing the size of the master cylinder and the braking sensation simulator. To do this we reduce the size of the simulator, and we integrate the simulator in the master cylinder.

  The subject of the invention is therefore an electrohydraulic braking device for a motor vehicle comprising: an external energy service braking system; - a muscular energy backup braking system; - a foot controller actuating the service braking system, and the emergency braking system when the service braking system is not operating; a master cylinder connected to the foot control member; - a safety solenoid valve for isolating the master cylinder of a wheel brake when the service braking system is operating, and for connecting the master cylinder to a wheel brake when the emergency braking system operates; a braking sensation simulator hydraulically connected to the master cylinder in normal operation, characterized in that the simulator comprises an integrated cartridge inside the master cylinder; The invention will be better understood on reading the description which follows and on examining the figures which accompany it. These are presented only as an indication and in no way limitative of the invention. The figures show: FIG. 1: a partial schematic representation of a vehicle braking installation according to the invention; 2: a general representation of a master cylinder incorporating a cartridge according to the invention, and where the master cylinder is at rest, FIG. 3: a general representation of a master cylinder incorporating a cartridge according to FIG. invention, and wherein the master cylinder is actuated; - Figure 4: an enlargement of a cartridge according to a particular embodiment of the invention.

  In Figure 1 there is shown a braking system for a vehicle according to the invention. Such a braking installation comprises an external energy braking system 1 and a muscular energy braking system 2.

  The muscular energy braking system 2 is an emergency braking system that operates when the external energy braking system 1 fails.

  The braking system 1 is for example a hydraulic system. It could be all electric. When it is hydraulic, the braking system 1 is fed with pressurized liquid via a pump 3, driven by a motor 4. The liquid supplying the pump 3 comes from a reservoir 5 of liquid out of pressure. The pressurized liquid is sent by the pump 3 into a supply pipe 6 which is connected in parallel by branches 6a, 6b, 6c and 6d to wheel brakes (not shown). The branches 6a to 6d are each provided with a solenoid valve (not shown) for the supply of pressurized wheel brakes. The solenoid valves are controlled by a calculator 7.

  The brake fluid then returns to the tank 5 via a pipe 8.

  The device comprises a foot control member 9, such as a brake pedal. The control member 9 is connected to a master cylinder 10 by means of a push rod 11 bearing against a primary piston 12 of the master cylinder 10. During braking, the driver actuates the brake pedal 9 which, via the push rod 11, actuates the primary piston 12. The primary piston 12 moves towards a secondary piston 13. A primary chamber 14 is formed between the primary piston 12 and the secondary piston 13 and a secondary chamber 15 is formed between the secondary piston 13 and a bottom 26 of the master cylinder 10.

  Figure 2, a simulator according to the invention is located inside the master cylinder 10. The simulator is mounted on the secondary piston 13. A front portion 28 of the simulator is located in the primary chamber 14. A rear portion 29 is located in the secondary chamber 15. The simulator is, in this example, in an intermediate position between the two chambers of the master cylinder 10. In this embodiment, the simulator forms the secondary piston. In another embodiment, it can form the primary piston or the bottom of the master cylinder. This simulator preferably comprises a cartridge 16.

  An electrical contact 17 is provided in the braking system. The contact 17 is sensitive to the actuation of the brake pedal 9. The contact 17, which in particular lights stop lights, is connected to the computer 7.

  The computer 7 controls the actuation of the external energy braking system 1, notably as a function of a signal supplied by the contact 17.

  A sensor 18 is also sensitive to the movement of the brake pedal 9. The sensor 18 is connected to the computer 7 and sends an electrical signal representative of the amplitude of movement of the pedal 9 and the speed with which the pedal 9 has been moved. The computer 7 calculates the result of a braking algorithm taking into account the signals provided respectively by the contact 17 and the sensor 18.

  The master cylinder primary chamber 14 is connected to at least one brake via a pipe 20, a solenoid valve 19 interrupting the passage in normal operation. Similarly, the secondary chamber 15 is connected to at least one brake via a pipe 22, a solenoid valve 21 interrupting the passage in normal operation. The computer 7 controls the closing of the solenoid valves 19 and 21 when the external energy braking system 1 operates. The brake fluid contained in the master cylinder 10 can not then move towards the wheel brakes.

  The computer 7 is informed of the pressure in the master cylinder 10 via a pressure sensor 23 connected for example to the pipe 22. The pressure sensor 23 sends an electric signal proportional to the existing pressure in the master cylinder 10 to the computer 7. This parameter is also taken into account in the braking algorithm.

  When the external energy braking system 1 fails, the sensor 7 controls the opening of the solenoid valves 21 and 19. The sensor 7 simultaneously controls the closing of a solenoid valve 30. The hydraulic liquid can not then go up to the reservoir 5 by the pipe 8. The liquid is directed through the pipe 8 and branches 8a, 8b, 8c and 8d each provided with a solenoid valve (not shown) to the respective wheel brakes.

  When the external energy braking system 1 is not faulty (situation shown in FIG. 1), the master cylinder 10 is isolated from the wheel brakes. The liquid in the master cylinder can not flow back to the brakes. The simulator allows a transfer of the brake fluid. The driver thus has the sensation of braking mechanically.

  In Figure 2 is shown a master cylinder according to the invention. A cartridge 16 is integrated in the master cylinder 10 in an intermediate position between the primary chamber 14 and the secondary chamber 15. The primary piston 12 bears against a push rod 11 (not shown in FIG. 2). A primary spring 24 is in abutment between the primary piston 12 and the secondary piston 13. A secondary spring 25 bears between the secondary piston 13 and a bottom 26 of the master cylinder 10. The primary springs 24 and secondary 25 allow in particular the return in the rest position of the respective pistons 12 and 13 during the release of the control member 9.

  The simulator comprises a cartridge 16 hermetically sealed on the side of the primary chamber 14 and secondary 15, for example. The liquid contained in the secondary chamber 15 can not enter the cartridge 16. On the other hand, a pipe device 34 communicates the primary chamber 14 and the inside of the cartridge 16. The liquid contained in the primary chamber 14 can penetrate partially in the cartridge 16 by the device 34. The cartridge 16 plays the role of secondary piston (or single piston if the master cylinder is a single chamber). The cartridge 16 can also be sealed on the side of the primary chamber 14 and communicate with the secondary chamber 15. The cartridge 16 then plays the role of primary piston.

  The cartridge 16 is wrapped in a rigid envelope 27. This envelope 27 has a volume slightly greater than the volume of the cartridge 16. A layer of air is interposed between the cartridge 16, elastically deformable, and the rigid envelope 27, in a space 33 (Figure 4).

  At rest, that is to say when the master cylinder is not actuated, the primary chamber 14 is filled with brake fluid from the reservoir 5. The secondary chamber 15 is filled with brake fluid also coming from the reservoir 5 The cartridge 16 is filled with brake fluid from the primary chamber 14.

  When a driver presses on the brake pedal 9, the primary piston 12 is pushed, via the thrust rod 11, inside the primary chamber 12. The pressure in the primary chamber 14, filled with brake fluid, increases. As the cartridge 16 communicates with the primary chamber by the channeling device 34, the pressure in the cartridge 16 also increases. The air layer interposed between the cartridge 16 and the envelope 27 is compressed. This compression simulates a reaction of a conventional braking system. Thus, for example, in FIG. 4, the cartridge 16 is provided with splines 32 providing space 33 filled with air between the rigid envelope 27 and the rubber cartridge 16. The volume inside the cartridge 16 increases as a function of the pressure exerted on the cartridge 16. The cartridge 16 is deformed, within the limits of what is authorized by the rigid envelope 27 and the space 33. The space 33 is reduced, the air is compressed. The compression of the air gives the driver the sensation of mechanically braking the vehicle.

  In another example, the cartridge 16 is of the same type as the conventional cartridges. It has a piston and an arc spring propped against the bottom of the cartridge and the rear of the piston. The piston is pushed towards the bottom of the cartridge by the liquid passing, for example, by the primary chamber towards the inside of the cartridge. The advance of the piston in the cartridge compresses the spring. The compression of the spring of the cartridge, or its resistance to compression, gives the driver the sensation of braking mechanically.

  In normal operation, the external energy braking system 1 operates. The secondary piston 13 advances very little. The sensor 7 controls the closing of the solenoid valves 19 and 21 so that the brake fluid contained in the primary chamber 14 and secondary 15 can not go to the wheel brakes.

  When the external energy braking system 1 is faulty, the muscular energy braking system 2 takes over. As shown in Figure 3, the master cylinder 10 then functions as a conventional master cylinder. The cartridge 16 then plays the role of and moves as the secondary piston 13 (or primary 12 if the cartridge 16 is mounted on the primary piston 12). The computer 7 controls the opening of the solenoid valves 19 and 21. The brake fluid contained in the master cylinder 10 can then move towards the wheel brakes. Also, when the driver presses on the brake pedal 9, the primary piston 12 is pushed inside the primary chamber 14 by the push rod 11. The primary piston 12 pushes the secondary piston 13. The advance of the piston secondary 13 closes a communication between the secondary chamber 15 and the tank 5. The pressure in the secondary chamber 15 increases. A communication between the primary chamber 14 and the tank 5 is in turn closed by the advance of the primary piston 12 inside the primary chamber 14. The pressure in the primary chamber 14 increases. As solenoid valves 19 and 21 are open, the brake fluid is sent into line 8.

  The liquid is then directed to the wheel brakes via branches 8a, 8b, 8c and 8d.

  It is also possible to use a master cylinder comprising a single pressure chamber. The cartridge then forms the piston or the bottom of the master cylinder.

  In the exemplary embodiment as shown in FIGS. 2 and 3, the cartridge is integrated in an intermediate position between the primary chamber and the secondary chamber of the master cylinder. The cartridge may, however, have another position. For example the cartridge can be fully integrated into the bottom of the secondary chamber.

  It is possible to provide a device for purging the cartridge. On the other hand, in order to reduce the volume of liquid to be purged, it is possible, for example, to dispose a core in the cartridge 16. The core, for example made of plastic, has dimensions slightly smaller than the internal dimensions of the cartridge 16. A defined volume between the core and an inner wall of the cartridge 16 is reduced. This volume being the one accommodating the brake fluid, the amount of liquid contained in the cartridge 16 is reduced. The amount of brake fluid to be purged in case of purging is also.

Claims (11)

  An electrohydraulic braking device for a motor vehicle comprising: an external energy service braking system (1); a muscular energy rescue brake system (2); - a foot controller (9) operating the service braking system, and the emergency braking system when the service braking system does not work; - a master cylinder (10) connected to the foot control member; - a safety solenoid valve (19, 21) for isolating the master cylinder of a wheel brake when the service braking system is operating, and for connecting the master cylinder to a wheel brake when the braking system of rescue works; - A braking sensation simulator, hydraulically connected to the master cylinder in normal operation, characterized in that the simulator comprises a cartridge (16) integrated within the master cylinder.   2- Device according to claim 1, characterized in that the master cylinder is provided with a primary piston (12) and a secondary piston (13), the primary piston bearing on the secondary piston via a primary spring (24) and delimiting a variable volume primary chamber (14), the secondary piston being supported on a bottom (26) of the master cylinder via a secondary spring (25) and delimiting a secondary chamber ( 15), the primary and secondary chambers being connected to a hydraulic reservoir (5), the cartridge forming one of the piston or the bottom of the master cylinder.   3- Device according to one of claims 1 and 2, characterized in that the cartridge is located in an intermediate position between the primary chamber and the secondary chamber of the master cylinder.   4- Device according to one of claims 1 and 2, characterized in that the cartridge is integrated in the secondary piston master cylinder.   5. Device according to claim 1, characterized in that the master cylinder is provided with a single piston delimiting, with a bottom of the master cylinder, a pressure chamber.   6. Device according to claim 5, characterized in that the cartridge is mounted on the piston of the master cylinder.   7. Device according to claim 5, characterized in that the cartridge forms a bottom of the master cylinder.   8- Device according to one of claims 1 to 7, characterized in that the cartridge is made of rubber, and is wrapped in a rigid envelope (27) volume slightly greater than a volume of the cartridge.   9- Device according to one of claims 1 to 8, characterized in that the cartridge is provided with grooves (32) defining a space (33) between the rigid casing and the cartridge.   10- Device according to one of claims 1 to 9, characterized in that the cartridge communicates only with a chamber of the master cylinder by a device (34) of pipe.   11- Device according to one of claims 1 to 10, characterized in that the cartridge comprises, in an interior volume, a core whose dimensions are slightly smaller than internal dimensions of the cartridge.