DE102009054985A1 - Braking system for motor vehicle, has piston led into housing and limiting hydraulic area, where pressure application of piston effects movement of another piston in operating direction - Google Patents

Abstract

The invention relates to a brake system for motor vehicles, which can be operated in a "brake-by-wire" mode both by the driver and independently of the driver. The brake system includes, inter alia, a first piston (25) coupled to a brake pedal (19) and defining a hydraulic space (26) for exerting an actuating force upon actuation of the brake system by the driver, and a housing (20). In this case, several components of the brake system are arranged in the housing (20), such as the first piston (25) downstream pedal decoupling unit (3) with a second piston (28), a Wegsimulationseinrichtung (33), an electrically controllable pressure supply device (2), and a Wheel brake pressure modulation unit (5).
In order to check the mobility of the second piston (28) during a test operation, the so-called "predrive check", it is proposed according to the invention that the first piston (25) is guided in the housing (20) and delimits a hydraulic space (26). the pressurization causes movement of the second piston (28) in the direction of actuation.

Description

Braking system for motor vehicles

• – einem Hauptzylinder, an den Radbremskreise angeschlossen sind,
• – einem ersten Kolben, der über eine Betätigungskräfte übertragende Druckstange mit einem Bremspedal gekoppelt ist,
• – einem zweiten Kolben, der vom ersten Kolben betätigbar ist, und der in eine kraftübertragende Verbindung mit einem Hauptzylinderkolben bringbar ist,
• – mit einer Simulationseinrichtung mit mindestens einem elastischen Element, die in der Betriebsart „brake-by-wire” dem Fahrzeugführer ein angenehmes Pedalgefühl vermittelt,
• – mit einem mit hydraulischem Druck beaufschlagbaren Zwischenraum zwischen dem zweiten und dem Hauptzylinderkolben, wobei eine Druckbeaufschlagung des Zwischenraums den zweiten und den Hauptzylinderkolben in entgegen gesetzter Richtung belastet,
• – mit einer vom zweiten Kolben begrenzten, hydraulischen Kammer, deren Druckbeaufschlagung eine Bewegung des zweiten Kolbens in Betätigungsrichtung verhindert,
• – mit einer elektrisch steuerbaren Druckbereitstellungseinrichtung, die den Druck im Zwischenraum steuert,
• – mit einem unter Atmosphärendruck stehenden Druckmittelvorratsbehälter, der mit dem Zwischenraum hydraulisch verbindbar ist, sowie
• – mit Mitteln zur elektrischen Regelung des Drucks im Zwischenraum,
• – sowie mit einem Gehäuse, das den ersten und den zweiten Kolben, die Kammer, den Zwischenraum, den Hauptbremszylinder, die Wegsimulationseinrichtung und die elektrisch steuerbaren Druckbereitstellungseinrichtung aufnimmt.

The invention relates to a brake system for motor vehicles, which is controllable in a so-called. "Brake-by-wire" mode by both the driver and independently of the driver, preferably in the "brake-by-wire" mode is operated and in at least one fallback mode can be operated, in which only the operation by the driver is possible, with

• A master cylinder to which wheel brake circuits are connected,
• A first piston, which is coupled to a brake pedal via an actuating force transmitting push rod,
• A second piston which is actuatable by the first piston and which can be brought into a force-transmitting connection with a master cylinder piston,
• With a simulation device with at least one elastic element which gives the driver a pleasant pedal feel in the "brake-by-wire" operating mode,
• With a pressure to be acted upon by hydraulic pressure between the second and the master cylinder piston, wherein a pressurization of the intermediate space loads the second and the master cylinder piston in the opposite direction,
• With a hydraulic chamber bounded by the second piston, the pressurization of which prevents a movement of the second piston in the actuating direction,
• With an electrically controllable pressure supply device which controls the pressure in the intermediate space,
• - With a pressure medium reservoir under atmospheric pressure, which is hydraulically connected to the intermediate space, and
• With means for electrical regulation of the pressure in the intermediate space,
• - And with a housing which receives the first and the second piston, the chamber, the intermediate space, the master cylinder, the Wegsimulationseinrichtung and the electrically controllable pressure supply device.

In Automotive technology find "brake-by-wire" brake systems an ever-increasing spread. In these braking systems the brake can on the one hand without active intervention of the driver due to electronic signals "foreign" -activated. These electronic signals can be, for example, from an electronic stability program ESC or a Distance control system ACC are issued. On the other hand, on an operation of the brake system completely or partially omitted if one of the driver about a Brake pedal operating force requested braking effect, for example by switching an electric vehicle drive into a generator mode is achieved. In both cases, the operating state corresponds the brake not the braking effect requested by the driver. This leads to conventional brake systems a reaction to the brake pedal. The brake pedal characteristic, d. H. the dependence of the brake pedal travel on the brake pedal force, is disturbed by the described reaction. This reaction effect on the brake pedal can for make the driver startling and uncomfortable, leaving the driver in a critical situation of road traffic the brake pedal not actuated in a situation adapted to this situation, because of the unpredictable reaction for him on the brake pedal is irritated.

A brake system of the type mentioned is from the international patent application of the applicant WO 2008/025797 A1 known. The braking system disclosed therein can be used inter alia in vehicles with a hybrid drive, in which so-called recuperation braking operations are performed. In order to be able to dispense with a complex and energetically unfavorable intermediate storage of hydraulic authority energy, it is proposed that the pressure medium required for the electrical regulation of the pressure introduced in the mentioned intermediate space be kept pressureless in the pressure supply device and, if necessary, placed under a higher pressure. It can be seen from the disclosure content of the above-mentioned document that during normal operation of the previously known brake system, which corresponds to the "brake-by-wire" mode, no movement of the second piston takes place. However, it is conceivable that the mobility of the second piston, in particular after a longer period of operation, may deteriorate, so that in a fallback level, in which a mechanical-hydraulic displacement of the second piston takes place, thereby caused actuation disturbances may occur. Indications of a possible check of the mobility of the second piston, the aforementioned publication can not be removed.

It is therefore an object of the present invention, a brake system of to improve the type mentioned in the introduction that a review the mobility is enabled, reducing operational safety the brake system is increased.

These The object is achieved according to the invention that the first piston is guided in the housing and a hydraulic space limited, its pressurization a movement of the second piston in the actuating direction causes.

to Concretization of the inventive concept is provided that the hydraulic space in the "brake-by-wire" mode by switching an electromagnetically actuated simulator release valve is connected to the atmospheric pressure.

at an advantageous development of the subject invention is the path simulation device is formed by a simulator spring, in the hydraulic space between the first and second pistons is arranged. By the measure mentioned becomes a more compact Structure of the actuator of the invention Brake system and the downstream of the actuator Pedalentkopplungseinheit reached.

One pleasant pedal feel is in a normal braking the Vehicle driver mediates that the simulator release valve throttling in the "brake-by-wire" mode of the hydraulic fluid flowing out of the hydraulic fluid volume allows.

A indirect sensing of the driver applying the brake pedal Operating force is in another advantageous embodiment of Invention characterized in that in the second piston a Pressure measuring chamber is formed, the one by means of a return spring preloaded third piston is limited and the detection a force acting on the brake pedal actuation force is used.

Further advantageous embodiments of the invention Brake system are listed in the subclaims 7 to 15.

The The present invention will become more apparent from an embodiment explained in more detail with reference to the accompanying schematic drawing, whose only figure is the structure of an embodiment a brake system according to the invention shows.

The electrohydraulic brake system according to the invention shown in the drawing consists essentially of an actuating device 1 , an electrically controllable pressure supply device 2 , a pedal decoupling unit 3 , one of the pedal decoupling unit 3 operatively connected master cylinder or tandem master cylinder 4 , one of brake circuits I, II of the master cylinder 4 connected Radbremsdruckmodulationseinrichtung 5 to the wheel brake pressure modulator 5 connected wheel brakes 6 . 7 . 8th . 9 , an electronic control unit 10 and a plurality of preferably electromagnetically operable valves whose function will be explained in more detail below. The unspecified pressure chambers of the master cylinder 4 are with under atmospheric pressure chambers of a pressure medium reservoir 11 connectable. The units form 1 to 5 independent assembly and testable assemblies, which are combined to form a testable overall system. Optionally (in restricted, available axial space), the master cylinder can be 4 constructive design in parallel design, which is referred to as twin master cylinder. Here are the two, not shown, master cylinder piston in the fallback level (in case of failure of the electrically controllable pressure supply device 2 ) mechanically actuated via a pressure bar. All the aforementioned components of the brake system according to the invention are arranged in a housing indicated only schematically, which is denoted by the reference numeral 20 is provided. The assignment of the wheel brakes 6 . 7 . 8th . 9 to the brake circuits I, II is for example made such that the connected to the first brake circuit I wheel brakes 6 . 7 are associated with the vehicle rear axle, while the wheel brakes connected to the second brake circuit II 8th . 9 serve the deceleration of the vehicle front axle. Indirect detection of in the wheel brakes 6 to 9 For example, when a pressure is applied during a braking operation, wheel speed sensors (not shown) can serve as an example.

The wheel brake pressure modulation device 5 comprises separating valves connected to the brake circuits I, II and designed as normally open (SO) 2/2-way valves 13a . 13b , at whose outputs the wheel brakes 6 - 9 associated intake valves 14a -D are connected, which in their normally open basic position, an assembly and disassembly of a hydraulic pressure in the wheel brakes 6 - 9 enable. An example of an anti-skid control required wheel-specific degradation of the wheel brakes 6 - 9 Injected pressure takes place via exhaust valves 15a -D, wherein the outputs of the brake circuits I, II associated exhaust valves 15a . 15b and 15c . 15d each with a shared line section 16a . 16b are connected. The pipe sections 16a . 16b lead to a safety outlet valve 17a . 17b , whose output connection via a respective pressure reduction line 18a . 18b in constant communication with the individual brake circuits I, II associated chambers 11a . 11b the pressure medium reservoir 11 stands.

As the drawing further shows, the actuator unit 1 a first piston 25 on top of a hydraulic room 26 limited and transmitted via an actuating forces push rod 27 with a brake pedal 19 is coupled. The actuating travel of the brake pedal 19 is by means of a preferably redundant displacement sensor 30 captured the path of the first col bens 25 senses and thus the driver request recognition or a setpoint generation in the electronic control unit 10 serves. The space 26 is with the pressure fluid reservoir 11 over in the first piston 25 formed radial bores and a first connecting line 31 connectable, in which a pressure-maintaining valve 32 is inserted. The pressure holding valve 32 is designed as a normally open (SO-) 2/2-way valve, which in the energized switching position, the function of a pressure medium reservoir 11 closing check valve met. The operating unit 1 Effectively downstream pedal decoupling unit 3 is essentially by a likewise in the housing 20 guided second piston 28 and one from the second piston 28 in the case 20 limited hydraulic chamber 29 formed by the pressurization of a movement of the second piston 28 is prevented in the direction of actuation. The second piston 28 represents a second boundary of the aforementioned hydraulic space 26 being between the two pistons 25 . 28 a simulator spring is arranged, with the reference numeral 33 is provided. In addition, the second piston 28 in a force-transmitting connection with a first or primary piston 34 of the master cylinder 11 bringable, being between the second piston 28 and the primary piston 34 a pressurizable gap with hydraulic pressure 35 is provided, the pressurization of the second piston 28 and the primary piston 34 loaded in opposite directions. It can be seen that when the first piston 25 by means of the brake pedal 19 is moved mechanically, the second piston 28 according to the area ratio between the first ( 25 ) and the second piston 28 (large piston area) sets in motion and the aforementioned master cylinder piston 34 operated, provided that in 1 shown in the current state of the brake system, in which the hydraulic chamber 29 with the container 11 is connected and the mentioned connection line 31 the only possible outflow path from the hydraulic space 26 represents. This is the brake pedal 19 initiated actuating force according to the area ratio hydraulically amplified.

To those in the operation of the brake system according to the invention on the brake pedal 19 acting actuating force is indirectly to the first piston 25 opposite end of an inner bore of the second piston 28 a pressure measuring room 36 formed by a third piston 37 is limited and a third piston 37 biasing plate spring 38 receives. The detection of the pressure measuring chamber 36 prevailing pressure is a pressure sensor 40 , At the third piston 37 relies on the above-mentioned simulator spring 33 from where the pressure measuring space 36 via a pressure compensation valve 39 to the pressure fluid reservoir 11 leading first connection line 31 connected. Also, connect to the first connection line 31 with the interposition of a shut-off valve 41 the chamber 29 and with the interposition of a simulator release valve 42 the hydraulic room 26 connected. The simulator release valve 42 is formed in the illustrated embodiment as a normally closed (SG) 2/2-way valve, which in the state shown, the function of a pressure medium reservoir 11 closing check valve met. In the energized state, in which the connection between the hydraulic space 26 and the pressure fluid reservoir 11 is made, there is a throttling of the out of the hydraulic space 26 outflowing pressure medium volume flow. It can be seen that the pedal characteristic imparted to the driver results from a static component caused by the compression of the previously mentioned simulator spring 33 is predetermined, and a dynamic proportion together, which is determined by the throttling.

The aforementioned electrohydraulic pressure supply device 2 consists essentially of a hydraulic cylinder-piston arrangement 43 and an electromechanical actuator 44 For example, which is formed by an electric motor with a reduction gear, the translational movement of a hydraulic piston 45 guaranteed, so in a pressure room 46 the hydraulic cylinder-piston arrangement 43 a hydraulic pressure is built up. The electromechanical actuator 44 is powered by an electrical energy storage with energy, with the reference numeral 47 is provided. The brake system optionally includes an electrical power supply with voltage transformer 60 , The movement of the piston 45 is indirectly by means of a rotation angle sensor 48 detects the rotor position of the electromechanical actuator 44 sensed. The pressure room 46 is by means of a second connection line 49 to the gap 35 connected, with a pressure sensor 50 detecting the pressure supply device 2 provided or in the space 35 prevailing pressure serves. Furthermore, it can be seen from the drawing that to the second connecting line 49 on the one hand with the interposition of a test valve 51 the hydraulic room 26 and on the other hand, the chamber 29 by means of a line section 52 are connected. One in the line section 52 inserted, normally open (SO) isolation valve 53 , in the flow direction of the pressure medium of the cylinder-piston assembly 43 to the chamber 29 a cylinder-piston arrangement 43 closing check valve 54 downstream, allows shut off the line section 52 against the flow direction of the pressure medium of the cylinder-piston assembly 43 to the chamber 29 ,

The Function of the brake system according to the invention both in the multiple-called "brake-by-wire" mode, which is considered as a normal braking mode, as well as in the mechanical-hydraulic Operating mode, which represents a fallback level, are the Experts known and need not in the present context to be explained in more detail.

In a review of the mobility of the second piston 28 become the test valve 51 in its open switching position and the isolation valve 53 in its closed switching position and the pressure-holding valve 32 switched to its closed switching position. In the closed switching position the separating valve fulfills 53 the function of one to the chamber 29 towards closing check valve, so that in a subsequent control of the electro-hydraulic actuator 43 an admission of the chamber 29 with the actuator 43 generated test pressure is prevented. In contrast, the opening of the test valve allows 51 together with the closing of the pressure relief valve 32 a foreign operation of the second piston 28 , This starts to move and actuates the master cylinder piston 34 , whereby a corresponding pressure build-up in the brake circuits I, II is generated. By volumetric balancing, pressure information of a pressure sensor connected to the first brake circuit I. 55 and a path information of the aforementioned angle sensor 48 in the electrohydraulic actuator 43 is integrated, in addition to determining the mobility of the second piston 28 detect a leak in the overall system.

By The present invention will be a simply constructed brake system achieved in an octopus-by-wire mode, as well as in recuperation braking the brake pedal characteristic not depends on the operating state of the rest of the brake system, whereby the pedal feel in a driver's braking neither by the simultaneous presence of a foreign braking through other control activities of the braking system such as anti-lock braking, Traction control or driving stability control disturbed can be.

The brake system according to the invention also has the Advantage that no complex hydraulic components as pump, hydraulic accumulator and slide valve are needed. As the only hydraulic components are compared to the straight mentioned components simple and inexpensive elastomer-sealed Pistons and cylinders, as well as the millions of times proven in brake technology 2/2 solenoid valves used. The invention allows the use of a mechatronic actuator, both from a electrical place energy storage as well as directly from an electrical Vehicle electrical system can be fed.

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - WO 2008/025797 A1 [0003]

Claims (15)

Brake system for motor vehicles, which can be controlled in a so-called "brake-by-wire" mode both by the driver and independently of the driver, preferably operated in the "brake-by-wire" mode and operated in at least one fallback mode in which only operation by the driver is possible, with a master cylinder ( 4 ), are connected to the wheel brake circuits (I, II), • a first piston ( 25 ), which via an actuating forces transmitting push rod ( 27 ) with a brake pedal ( 19 ), a second piston ( 28 ) from the first piston ( 25 ) is operable, and in a force-transmitting connection with a master cylinder piston ( 34 ) can be brought • with a simulation device with at least one elastic element ( 33 ), which gives the driver a pleasant pedal feel in the "brake-by-wire" operating mode, with a space which can be acted upon by hydraulic pressure ( 35 ) between the second ( 28 ) and the master cylinder piston ( 34 ), wherein a pressurization of the gap ( 35 ) the second ( 28 ) and the master cylinder piston ( 34 ) in the opposite direction, • with one of the second piston ( 28 ) limited, hydraulic chamber ( 29 ), the pressurization of which causes a movement of the second piston ( 28 ) in the actuating direction, • with an electrically controllable pressure supply device ( 2 ), the pressure in the space ( 35 ), with a pressurized medium storage tank (under atmospheric pressure) ( 11 ), with the space ( 35 ) is hydraulically connectable, and • means for electrically controlling the pressure in the intermediate space ( 35 ), As well as with a housing ( 20 ), which is the first ( 25 ) and the second piston ( 28 ), the chamber ( 29 ), the gap ( 35 ), the master cylinder ( 4 ), the path simulation device ( 33 ) and the electrically controllable pressure supply device ( 2 ), characterized in that the first piston ( 25 ) in the housing ( 20 ) and a hydraulic space ( 26 ), the pressurization of which causes movement of the second piston ( 28 ) causes in the direction of actuation. Braking system according to claim 1, characterized in that the travel simulation device is driven by a simulator spring ( 33 ) formed in the hydraulic space ( 26 ) between the first ( 25 ) and the second piston ( 28 ) is arranged. Brake system according to claim 1, characterized in that the hydraulic space ( 26 ) in the "brake-by-wire" mode by switching an electromagnetically actuated simulator release valve ( 42 ) is connected to the atmospheric pressure. Brake system according to claim 3, characterized in that the simulator release valve ( 42 ) in the "brake-by-wire" mode, a throttling of the hydraulic space ( 26 ) flowing out of the pressure medium volume flow allows. Brake system according to one of claims 1 to 4, characterized in that in the second piston ( 28 ) a pressure measuring chamber ( 36 ) is formed by a by means of a return spring, in particular plate spring ( 38 ), preloaded third piston ( 37 ) and the detection of a brake pedal ( 19 ) acting actuating force is used. Brake system according to claim 5, characterized in that a pressure compensation valve ( 39 ), which provides a connection between the pressure measuring chamber ( 36 ) and the pressure fluid reservoir ( 11 ). Braking system according to claim 2 and 5, characterized in that the simulator spring ( 33 ) between the first ( 26 ) and the third piston ( 37 ) is arranged. Brake system according to one of claims 1 to 6, characterized in that a shut-off valve ( 41 ) provided in a connection between the chamber ( 29 ) and the pressure fluid reservoir ( 11 ) is inserted and which allows a shut-off of the connection. Braking system according to one of claims 1 to 8, characterized in that the pressure supply device ( 2 ) by a cylinder-piston arrangement ( 43 ) is formed whose piston ( 45 ) by an electromechanical actuator ( 44 ) is operable. Brake system according to claim 9, characterized in that between a pressure chamber ( 46 ) of the cylinder-piston arrangement ( 43 ) and the hydraulic chamber ( 29 ) a line section ( 52 ) is provided, in which a separating valve ( 53 ) and a cylinder-piston arrangement ( 43 ) closing check valve ( 54 ) are inserted. Brake system according to claim 10, characterized in that between the pressure chamber ( 46 ) of the cylinder-piston arrangement ( 43 ) and the hydraulic space ( 26 ) a test valve ( 51 ) is arranged, the pressurization of the space ( 26 ) with that of the pressure supply device ( 2 ) provided pressure. Braking system according to one of claims 1 to 11, characterized in that between the hydraulic space ( 26 ) and the pressure fluid reservoir ( 11 ) a connection ( 31 ) is provided, in which a pressure-maintaining valve ( 32 ) is inserted. Braking system according to one of claims 1 to 12, characterized in that the master cylinder pressure chambers and the pressure chambers have limiting master cylinder pistons, which are arranged parallel to each other. Braking system according to one of claims 1 to 13, characterized in that an electrical energy store ( 47 ) is provided, the pressure supply device ( 2 ) is supplied with energy, as long as it is not fed directly from an electrical vehicle electrical system. Braking system according to claim 14, characterized in that the electrical energy store ( 47 ) is recharged from the electrical vehicle electrical system and its state of charge and its functionality by a brake control system associated electronic control unit ( 10 ) is monitored.

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