DE102011085986A1 - Brake assembly for motor car, has hydraulic chamber limited by cylinder piston and acted upon with pressure delivered by pressure provision device such that force effect is produced on cylinder piston in operation direction - Google Patents

Abstract

The assembly has a cylinder piston arrangement (5) whose piston (55) is coupled with brake pedals. A hydraulic space (14) of the piston arrangement is connected with a hydraulic simulation device (8). A master brake cylinder (10) comprises a pressure chamber (13) and a master brake cylinder piston (6), where a wheel brake circuit (I, II) is attached to the cylinder. A hydraulic chamber (12) is limited by the cylinder piston and acted upon with pressure delivered by a pressure provision device (9) such that force effect is produced on the cylinder piston in an operation direction. The master brake cylinder piston is designed as a differential piston.

Description

The invention relates to a brake system for motor vehicles with an electrically controllable pressure supply device, which is formed in particular by a cylinder-piston arrangement whose piston can be actuated by an electromechanical drive device.

From the DE 10 2009 033 499 A1 a brake system with a master cylinder and an integrated Pedalentkopplungs- and simulation unit with a retaining piston and a compression spring is known, wherein the retaining piston receives an axial extension of the master cylinder piston hydraulically sealed and wherein in a fallback by the extension of a master cylinder can be mechanically operated.

The present invention has for its object to provide a brake system with a high system availability, especially in the fallback level, with the simplest possible structure.

This object is achieved by providing a first cylinder-piston arrangement is provided, the piston is coupled to a brake pedal and the hydraulic space is connected to a hydraulic simulation device, and by a master cylinder is provided which has at least one pressure chamber and a master cylinder piston and to which wheel brake circuits are connected, wherein the master brake cylinder piston defines a hydraulic chamber which is acted upon by the pressure supplied from the pressure supply device, wherein pressurization of the chamber causes a force on the master brake cylinder piston in the actuation direction.

Advantageous embodiments of the invention are the subject of the dependent claims.

The invention is based on the consideration that a brake system with a pressure supply device, which allows a normal mode in the manner of a "brake-by-wire" mode of operation and an operation in a fallback level, should have the most robust and error-insensitive construction possible. In addition, the overall length should be as low as possible due to the space available in modern vehicles. Too long an expansion of a component group also poses safety risks to passengers in the event of a crash in which this unit can slide into the driver's compartment and cause serious injury to passengers.

As has now been recognized, a short overall length can be achieved if the pedal feel sensing device and the pressure delivery device are physically separate from the master cylinder. For this purpose, the hydraulic space of the first cylinder-piston arrangement is hydraulically connected to the hydraulic simulation device. Because of this hydraulic connection, the simulation device can be installed in a lateral direction to the master cylinder and does not have to be arranged in the axial direction with the (tandem) master cylinder and / or with the first cylinder-piston arrangement. The Fremdkraftaktuator or the pressure supply device can be arranged in the lateral direction of the master cylinder due to the hydraulic operation of the brake system. This results in a compact design of the brake system and flexible arrangement options for their components.

In a preferred embodiment, a further hydraulic chamber is arranged hydraulically between the first cylinder-piston arrangement and the master cylinder, which is connected via a lockable hydraulic connection with a pressure medium container or a line with low pressure, in particular a pressurized medium reservoir under atmospheric pressure. Such a further chamber makes the brake system capable of being used on demand, in particular in a fallback mode, hydraulic power transmission between the piston of the first cylinder-piston arrangement and the master brake cylinder or its master brake cylinder piston. This further hydraulic chamber is arranged in the sense of a hydraulic circuit diagram between the first cylinder-piston assembly and the master cylinder; this does not necessarily relate to the geometric or spatial-structural arrangement.

Advantageously, the further hydraulic chamber, the piston of the first cylinder-piston assembly and the master brake cylinder piston are designed and arranged such that upon actuation of the brake pedal and shut-off hydraulic chamber takes place a hydraulic power transmission from the piston to the master brake cylinder piston. In a normal operation of the brake system, the further hydraulic chamber is preferably not shut off, so that it is hydraulically connected to the pressure medium tank. During a movement of the piston of the first cylinder-piston assembly into this chamber while pressure fluid flows from, so that the piston (hydraulic) resistance is opposed. The construction of wheel brake pressure is effected by the pressure supply device which actuates the master brake cylinder piston.

In a hydraulic fallback level, in which no more brake pressure can be built up in the wheel brakes by the pressure supply device, the further hydraulic chamber is separated from the hydraulic pressure tank, so that hydraulic pressure can be built up in this chamber. In this way, when the piston of the first cylinder-piston arrangement is displaced into this chamber, the master brake cylinder piston can be hydraulically actuated. This design eliminates an idle path, as occurs for example in many mechanical solutions, since during a movement of the piston of the first cylinder-piston arrangement hydraulically pressure is transmitted directly to the master brake cylinder piston and this is actuated without delay.

Due to the immediate operation of such a hydraulically designed push rod does not exist in a mechanical solution requirement that in normal operation, the path of the primary piston of the master cylinder must be at least as large as the path of the driver piston or the piston of the first cylinder-piston assembly (If this were not the case, the driver would suddenly experience a strong change in the brake feel during mechanical contact). This requirement means in practice a volume limitation of the chambers of the (tandem) master cylinder, so that a reduced volume for braking pressure modulation is available.

The master brake cylinder piston is preferably designed as a stepped piston whose piston part projects with the smaller diameter into the further hydraulic chamber. Advantageously, the piston of the first cylinder-piston arrangement is designed as a stepped piston whose piston part protrudes with the smaller diameter into the further hydraulic chamber or is adjustable. In the event that both the master brake cylinder piston and the piston of the first cylinder-piston arrangement with their respective smaller diameter protrude into the further hydraulic chamber, a hydraulic ratio can be realized, which corresponds to the ratio of the two corresponding smaller cross-sectional areas.

Advantageously, when the brake pedal is actuated, the piston part with the smaller diameter is displaced or pushed into the further hydraulic chamber, so that when the hydraulic chamber is shut off, a hydraulic power transmission takes place on the master brake cylinder piston.

The further hydraulic chamber is advantageously connectable via a lockable hydraulic connection with the pressure supply device or the simulation device.

Advantageously, in particular in the event of a leak in the hydraulic chamber in the event of a malfunction of the brake system, the piston of the first cylinder-piston arrangement and the master brake cylinder piston are designed and arranged such that they can be brought into a mechanical force-transmitting connection after a predetermined movement distance of the piston. As a result, a second, mechanical fallback level is effectively implemented, whereby the brake system meets high safety criteria. In this second fallback mode, the driver can mechanically shift the master brake cylinder piston to build up pressure in the wheel brakes in this manner. The pistons and the further hydraulic chamber are preferably designed and dimensioned such that the mechanical contact neither in the normal operating state nor in the hydraulic fallback mode in which the master brake cylinder piston is hydraulically actuated, otherwise the driver would experience a sudden change in the pedal feel.

Such a force-transmitting connection, for example, directly by contact of the two pistons arise, d. h., The driver piston presses after overcoming a free travel in the other hydraulic chamber directly against the primary piston and moves it to build up pressure in the corresponding pressure chamber.

Alternatively, such a force-transmitting connection can also be achieved via an axial projection fixedly connected to the master brake cylinder piston or primary piston, which protrudes into the further hydraulic chamber. After covering an idle travel of the driver piston, this then enters into mechanical contact with the extension and actuates or shifts in this way the primary piston.

The hydraulic space of the first cylinder-piston arrangement is advantageously connected via a lockable hydraulic connection, which can be shut off in particular by a normally open or NO valve, with a pressure medium container, in particular a pressure medium reservoir under atmospheric pressure.

The wheel brake circuits are advantageously via a means of an electrically controllable valve, in particular a normally closed (SG) or NC (Normally Closed) -Ventils, releasable hydraulic connection with at least one pressure fluid reservoir, in particular low-pressure accumulator, or in each case a pressure fluid reservoir or a pressure medium reservoir under atmospheric pressure connectable.

The pressure supply device or the hydraulic chamber is advantageously connected to the hydraulic connection between the first cylinder-piston arrangement and the simulation device via a hydraulic connection which can be shut off, in particular with a normally open (SO) or NO (normally-open) valve or connectable.

Each wheel brake is advantageously connected via an electrically controllable, normally open valve to the master cylinder, so that, if necessary, by shutting off the valve - for example, during a multiplex process - the wheel brake pressure in the wheel can be maintained. In addition, a shut-off of all wheel brakes can be performed by the master cylinder even during a diagnosis of the brake system. In this way pressure can be built up and taken down in the brake system without the vehicle being decelerated.

For use as required filling space of the hydraulic chamber of the first cylinder-piston assembly is advantageously via a hydraulic connection with at least one of the brake circuits in connection, in particular a check valve is arranged in this connection, which the return of pressure medium from the corresponding brake circuit in the Filling space prevented. This can be provided in an urgent situation - essentially after failure of the pressure supply device or even in the occurrence of heavy fading - additional pressure medium in the corresponding brake circuit.

The advantages of the invention are, in particular, the simple disconnectability of the hydraulic simulator. Another advantage is the hydraulic fallback, in which due to the realization of a hydraulic pressure rod by a hydraulic chamber, in which carry both the driver piston and the primary piston, a direct hydraulic actuation of the primary piston is made possible, with no mechanical free travel occurs in the currentless fault , By a mechanical force-transmitting connection into which the appropriately designed primary piston and driver piston can be brought, a mechanical fallback level can be realized in addition to the hydraulic fallback level.

Two preferred embodiments of the brake system will be explained in more detail with reference to a drawing. In it show in a highly schematic representation:

1 a first embodiment of a brake system, and

2 A second embodiment of a brake system.

Identical parts are provided in both figures with the same reference numerals.

In 1 a first embodiment of a brake system according to the invention is shown schematically. The brake system includes a master cylinder 10 , For example, a tandem master cylinder, with an in the direction of displacement 32 displaceable guided master cylinder piston or primary piston 6 , To the two pressure chambers 13 of the (tandem) master cylinder 10 are each one of two wheel brake circuits I, II connected, which in each case two wheel brakes 30 assigned. The primary piston or skin brake cylinder piston 6 limited to the master cylinder 10 on the pressure room 13 opposite side a hydraulic chamber 12 , The hydraulic chamber 12 is via a hydraulic connection line with an electrically controllable pressure supply device 9 connected. When chamber is pressurized 12 with a pressure through the pressure supply device 9 the primary piston is actuated, ie brake pressure is built up in the brake circuits.

In the hydraulic connections between the wheel brakes 30 and the master cylinder 10 are electrically controllable normally open valves 3 arranged. By a suitable circuit of the valves 3 can be a brake pressure control of the individual wheel brakes 30 be performed.

The electrically controllable pressure supply device 9 is, for example, designed as a cylinder-piston assembly whose piston 21 is actuated by an electromechanical actuator. The actuator is z. B. drivable in accordance with a brake pedal operation or on the request by a driver assistance system. The actuator may, for. B. include an electric motor with a gear and ensures a translational movement of the piston 21 the hydraulic cylinder-piston arrangement. A force applied by the actuator foreign force F _act leads to a pressure build-up in a pressure chamber 11 , what about the chamber 12 to an actuation of the master cylinder 10 leads ("brake-by-wire" mode).

One from the driver, z. B. via a brake pedal, not shown, exerted force F _Driver is on the piston of a cylinder-piston assembly 5 transfer. The hydraulic room 14 the cylinder-piston arrangement 5 is with a simulation device 8th connected. The simulation device 8th includes an elastic element and is intended to give the driver a pleasant brake pedal feel. The pedal feel simulator or the simulation device 8th is hydraulically designed and includes a cylinder-piston assembly, which limits a hydraulic space.

The hydraulic connection between the hydraulic room 14 the cylinder-piston arrangement 5 and the simulation device 8th is via an electrically controllable valve, for. B. a normally open valve 1 (NO: Normally Open, or SO: normally open), connected to a pressure medium tank. In the pressure fluid container, it may be z. B. to act under atmospheric pressure fluid reservoir of the brake system. According to the example, the pressure medium container is the same pressure medium reservoir, with which the master cylinder 10 is connectable. However, it can also be different pressure medium container.

Furthermore, the hydraulic room 14 the cylinder-piston arrangement 5 via a hydraulic connection (with a normally open valve 2 ) with the chamber 12 or with the hydraulic connection between pressure supply device 9 and chamber 12 connected.

Preferably, the brake system includes a, z. B. redundant, displacement sensor 40 for detecting the driver's braking request. In addition, the brake system can be a, z. B. redundant, pressure sensor, about with the chamber 14 The first cylinder-piston assembly may be connected, for detecting the driver's brake request include.

To detect the pressure reached, the brake system advantageously comprises another, z. B. redundant, pressure sensor 41 , which in one or both brake circuits, z. B. in the hydraulic connections to the wheel brakes 30 , is arranged.

Alternatively or additionally, the brake system preferably comprises a, z. B. redundant, displacement sensor 42 which shows the position of the piston 21 the pressure supply device 9 detected. Based on the displacement sensor signal, the pressure achieved can be determined by means of a predetermined volume intake characteristic. Alternatively or in combination with this, an angle sensor can also be used to detect the angular position of an electric motor that is actuated to increase or decrease the pressure. The actuator or the pressure supply device is preferred 9 controlled via an electronic control unit ECU (not shown).

According to the embodiment of 1 are the wheel brakes 30 the brake system each via a normally open valve 3 (NO valve) to the master cylinder 10 connected. A brake pressure modulation (pressure build-up and pressure reduction) is preferably carried out by means of the valves 3 and the rapidly reversing actuator or the pressure supply device 9 in the so-called multiplex process. Additionally, the brake system can exhaust valves per wheel brake 30 include.

In principle, to realize a fallback level, when there is no electrical energy available, it is conceivable to use a mechanical fallback level in which the driver force is mechanically controlled by the piston of the cylinder-piston arrangement 5 on the primary piston or master cylinder piston 6 of the master cylinder 10 is transmitted. This mechanical fallback level is realized in the illustrated brake system as follows: In the unactuated state of the brake system is the piston of the cylinder-piston assembly 5 spaced by a free travel of the primary piston and upon actuation of the piston by the driver, this can be brought into a force-transmitting (mechanical) connection with the primary piston, so that the primary piston is mechanically actuated.

However, to provide, at least under certain conditions, a brake system with a fallback level without additional free travel in the case of a currentless operation, but is preferably a hydraulic connection between the piston of the cylinder-piston assembly 5 (Driver piston 55 ) and the primary piston or master cylinder piston 6 of the master cylinder 10 provide, a so-called hydraulic pressure rod, which in the brake system of 1 is realized. This hydraulic push rod is used to represent a hydraulic (first) fallback level, in which, in the event of a system failure (eg due to a power failure or an internal fault), the driver piston 55 the master brake cylinder piston 6 hydraulically powered.

Between the cylinder-piston arrangement 5 and the master cylinder 10 is another hydraulic chamber 16 arranged. The further hydraulic chamber 16 is from the chambers 12 and 14 the master cylinder and the cylinder-piston assembly separated and sealed. The chamber 16 is a lockable hydraulic connection, z. B. with a normally closed valve 17 (NC: Normally Closed, or SG: normally closed), with a lower pressure level, such as a pressure medium tank or a line with low pressure, in particular a pressure medium reservoir under atmospheric pressure connected. The further hydraulic chamber 16 can continue via a lockable hydraulic connection, z. B. with a normally closed test valve 18 , with the pressure delivery device 9 or the simulation device 8th get connected.

The hydraulic chamber 16 , a piston 55 the cylinder-piston arrangement 5 and the master brake cylinder piston 6 are designed and arranged such that upon actuation of the brake pedal and shut off the hydraulic chamber 16 a hydraulic power transmission from the piston 55 on the master brake cylinder piston 6 takes place. Preferably drives the driver piston 55 the primary piston in the event of system failure (due to power failure or due to an internal fault, fallback level), ie in the fallback mode. In the "Brake by Wire" normal mode, the master brake cylinder piston becomes pressurized 9 actuated.

Preferably, primary piston is designed as a stepped piston, wherein the piston / piston part sealed with the smaller diameter in the chamber 16 protrudes.

The driver piston is preferred 55 executed as a stepped piston whose piston / piston part with the smaller diameter already with unconfirmed brake pedal in the hydraulic chamber 16 protrudes or upon actuation of the brake pedal in the chamber 16 dips.

Due to the desired effect as a hydraulic pressure rod arise requirements for the geometric design of the piston 6 . 55 , The pressure acting on the push rod force hydraulic surface is the large cross-sectional area of the stepped piston 6 multiplied by the ratio of the small cross-sectional areas of the stepped piston 55 and 6 , The effective area shall not be too large to ensure an adequate balance between pedal force and deceleration in this unreinforced mode. The stroke of the master cylinder piston (s) 6 . 7 must be so low that the driver the master cylinder 10 can occur almost to the stop to ensure a residual braking effect in case of circuit failure. This results in a limitation of the master cylinder volume.

In case of leakage in the hydraulic pressure rod, z. B. in the normally closed valve 17 , becomes after passing over the (mechanical) gap between the driver piston 55 and the primary piston, ie force transmitting mechanical connection between the pistons 55 . 6 , Brake pressure built up. This corresponds to a further (mechanical) fallback, whereby the brake system shown meets particularly high safety requirements.

In normal operation ("brake-by-wire" mode), the normally open valves 1 and 2 and the valve 17 energized at the beginning of the operation of the brake pedal, ie the valves 1 and 2 be closed and the valve 17 will be opened. As a result, the driver from chamber 14 displaced brake fluid volume into the simulator 8th moved, the driver gets through simulator 8th a familiar pedal feel. That by the piston 55 out of the chamber 16 displaced brake fluid volume is discharged into a container. The gap between the driver piston 55 and the primary piston or master cylinder piston 6 corresponds to the maximum Druckstangenweg in normal operation, so that the pedal characteristics except for dynamic pressure effects by the simulator 8th is produced. The brake pressure is due to the external drive on the piston 21 the pressure supply device 9 provided. Optionally, the valve 1 also be switched a little late after brake pedal operation to produce the jumper in the pedal characteristic, ie, until the valve is closed 1 the driver experiences a low pedal resistance, whereby a pedal feel is realized, which corresponds to a pedal feel of a hydraulic brake system with a vacuum brake booster.

The modulation of the wheel pressure is preferably done via the four normally open valves 3 according to the multiplex principle. Alternatively, exhaust valves may be added. If the master brake cylinder volume can not be large enough for all applications, especially for the increased brake pressure during fading, can each brake circuit I, II, a normally closed valve 4a . 4b be added, which connects the brake circuit I, II with a pressure medium container. By the wheel valves 3 closed and the foreign drive pressure by means of the piston 21 the pressure supply device 9 can be broken down, through the valves 4a . 4b additional volume to be promoted in the braking system. The volume supply (pressure medium tank) can be realized by one or two low-pressure accumulator which is / are filled at initialization of the system, or as in 1 represented by an under atmospheric pressure pressure fluid reservoir of the brake system. If that from the master cylinder 10 displaced brake fluid volume should not be used to build up pressure on the wheel brakes (about low friction or recuperation), the brake fluid volume through the two normally closed valves 4a . 4b be drained. In the embodiment shown here but this is not required due to the dimensioning of the brake system.

In the brake system, a comprehensive self-diagnosis can be performed, for. B. during an acceleration phase of the vehicle. Such a diagnosis may, for example, proceed in the following order. The normally open Valve 2 and the wheel valves 3 are energized (closed), and on the piston 21 an external force is initiated. When the valves 2 . 3 and at least one of the valves 17 and 18 are tight, the piston moves 21 the pressure supply device 9 only according to the Schnüffelloch-Leerweg. Next are the normally closed valves 17 and 18 energized together. When both open, the piston of the pressure supply device moves 9 , Then the valves 17 and 18 individually energized to check that they are tight. Now the SG valves 17 and 18 and the SO valve 2 off. When the SO valves 1 and 2 are continuous, the piston moves. Now the SO valve is 1 energized. When it actually closes, the pressure and thus the motor current increase. If the piston continues to move, the simulator is 8th not jammed.

The SG check valve 18 can also connect the simulator to the hydraulic push rod.

Due to the limited Hauptzylinderhubs leads as small as possible cross-section but that only a significantly limited volume of pressure medium is available. This volume can be in the de-energized fallback levels through the use of the driver's piston 5 be extended as a level of filling in the sense of a substantially additional force-free additional function as it were. This is the hydraulic space 14 the cylinder-piston arrangement 5 via a hydraulic connection 26 connected to the brake circuit I (or II). In the connection 26 is a towards the room 14 closing check valve 25 arranged. Furthermore, this connection is through the valve 1 shut off. This design of the brake system can, if necessary, brake fluid from the hydraulic space 14 for pressure build-up in one (as shown) or both brake circuits I, II are promoted.

A springy check valve 27 is between the connection 26 and a lower pressure level (for example, a pressure medium reservoir), wherein the check valve 27 is set so that it releases the connection to the lower pressure level when a predetermined pressure is exceeded. By inserting the three check valves 25 . 27 . 28 as in the in 2 shown second embodiment of a brake system, the brake system can thus be extended so that a filling stage for the currentless operation arises in which a brake circuit, z. B. brake circuit I, with brake pedal actuation via chamber 14 is additionally filled.

LIST OF REFERENCE NUMBERS

1

normally open valve

2

normally open valve

3

normally open valve

4a, 4b

normally closed valve

5

Cylinder-piston arrangement

6

Master cylinder piston

7

piston

8th

simulation device

9

Pressure supply device

10

Master Cylinder

11

pressure chamber

12

hydraulic chamber

13

pressure chamber

14

hydraulic room

16

another hydraulic chamber

17

normally closed valve

18

check valve

21

piston

25

check valve

26

hydraulic connection

27

check valve

28

check valve

30

wheel brake

31

hydraulic connection line

32

displacement direction

40

displacement sensor

41

pressure sensor

42

displacement sensor

55

piston

I, II

wheel brake

F _act

foreign power

F _driver

force

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102009033499 A1 [0002]

Claims (13)

Brake system for motor vehicles with • an electrically controllable pressure supply device ( 9 ), which is formed in particular by a cylinder-piston arrangement, whose piston can be actuated by an electromechanical drive device, • a first cylinder-piston arrangement ( 5 ), whose pistons ( 55 ) is coupled to a brake pedal and whose hydraulic space ( 14 ) with a hydraulic simulation device ( 8th ), a master cylinder ( 10 ), which has at least one pressure chamber ( 13 ) and a master brake cylinder piston ( 6 ) and to which wheel brake circuits (I, II) are connected, wherein the master brake cylinder piston ( 6 ) a hydraulic chamber ( 12 ), which depends on that of the pressure supply device ( 9 ) pressure can be acted upon, wherein a pressurization of the chamber ( 12 ) a force acting on the master brake cylinder piston ( 6 ) in the actuation direction. Brake system according to claim 1, characterized in that a further hydraulic chamber ( 16 ) hydraulically between the first cylinder-piston assembly ( 5 ) and the master cylinder ( 10 ) is arranged, which via a lockable hydraulic connection ( 17 ) is connected to a pressure medium container or a line with low pressure, in particular a pressurized medium reservoir, which is under atmospheric pressure. Brake system according to claim 2, characterized in that the further hydraulic chamber ( 16 ), The piston ( 55 ) of the first cylinder-piston arrangement ( 5 ) and the master brake cylinder piston ( 6 ) are designed and arranged such that when the brake pedal is actuated and the hydraulic chamber is shut off ( 16 ) a hydraulic power transmission from the piston ( 55 ) on the master brake cylinder piston ( 6 ) takes place. Brake system according to claim 2 or 3, characterized in that the master brake cylinder piston ( 6 ) is designed as a stepped piston whose piston part with the smaller diameter in the further hydraulic chamber ( 16 protrudes. Brake system according to one of claims 2 to 4, characterized in that the piston ( 55 ) of the first cylinder-piston arrangement ( 5 ) is designed as a stepped piston whose piston part with the smaller diameter in the further hydraulic chamber ( 16 ) protrudes or is adjustable. Brake system according to claim 5, characterized in that the piston part with the smaller diameter upon actuation of the brake pedal in the further hydraulic chamber ( 16 ) is adjusted so that when the hydraulic chamber is shut off a hydraulic power transmission to the master brake cylinder piston ( 6 ) takes place. Brake system according to one of claims 2 to 6, characterized in that the further hydraulic chamber ( 16 ) via a lockable hydraulic connection (18) with the pressure supply device ( 9 ) or the simulation device ( 8th ) is connectable. Brake system according to one of claims 2 to 7, characterized in that, in particular in the case of a leakage of the hydraulic chamber ( 16 ) in case of failure of the brake system, the piston ( 55 ) of the first cylinder-piston arrangement ( 5 ) and the master brake cylinder piston ( 6 ) are designed and arranged such that, after a predetermined movement distance of the piston ( 55 ) can be brought into a mechanical force-transmitting connection. Brake system according to one of claims 1 to 8, characterized in that the hydraulic space ( 14 ) of the first cylinder-piston arrangement ( 5 ) via a lockable hydraulic connection (NO valve 1 ) is in communication with a pressure medium container, in particular a pressurized medium reservoir under atmospheric pressure. Brake system according to one of claims 1 to 9, characterized in that the wheel brake circuits (I, II) via a means of an electrically controllable valve (NC valve 4 ) releasable hydraulic connection with at least one pressure medium reservoir, in particular low-pressure accumulator, or in each case a pressure medium accumulator or a pressurized medium storage container are connected under atmospheric pressure. Brake system according to one of claims 1 to 10, characterized in that the pressure supply device ( 9 ) or the hydraulic chamber ( 12 ) via a lockable hydraulic connection (NO valve 2 ) with the hydraulic connection between the first cylinder-piston arrangement ( 5 ) and the simulation device ( 8th ) is connected or connectable. Brake system according to one of claims 1 to 11, characterized in that each wheel brake ( 30 ) via an electrically controllable, normally open valve ( 3 ) with the master cylinder ( 10 ) connected is. Brake system according to one of claims 1 to 12, characterized in that the hydraulic space ( 14 ) of the first cylinder-piston arrangement ( 5 ) via a hydraulic connection ( 26 ) with at least one of the brake circuits (I, II) in In particular, a check valve ( 25 ) is arranged in the connection.

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