EP3036135A1

EP3036135A1 - Brake system for motor vehicles

Info

Publication number: EP3036135A1
Application number: EP14750212.4A
Authority: EP
Inventors: Hans-Jörg Feigel
Original assignee: Continental Teves AG and Co OHG
Current assignee: Continental Teves AG and Co OHG
Priority date: 2013-08-20
Filing date: 2014-08-08
Publication date: 2016-06-29
Also published as: CN105473396A; US20160200307A1; KR20160045778A; WO2015024795A1; DE102013216477A1

Abstract

Brake system for motor vehicles, which brake system can be driven both by the vehicle driver and also independently of the vehicle driver in a "brake-by-wire" mode, having a main brake cylinder (1) which has at least a first and a second main brake cylinder piston (2, 3), which pistons delimit a first and a second pressure space (4; 5) and to which pistons in each case one braking circuit (I; II) with wheel brakes (6a, 6b; 6c, 6d) is connected, wherein the first main brake cylinder piston (2) is coupled to a brake pedal (21), having a pressure medium storage container (9), a hydraulically operable simulation device (11) which provides the vehicle driver with a pleasant brake pedal sensation in the "brake-by-wire" mode, a simulator valve (16) for turning on and turning off the effect of the simulation device (11), an electrically controllable pressure-providing device (18), and a pressure control valve arrangement which is hydraulically connected to the main brake cylinder (1), the pressure-providing device (18) and the wheel brakes (6a-6d) and has a first wheel valve (7a-7d), which can be electrically driven and is open when no current is applied, for each wheel brake, wherein the first main brake cylinder piston (2) is in the form of a differential piston, the annular surface (23) of said differential piston delimiting a hydraulic chamber (22), wherein the hydraulic chamber (22) is hydraulically connected to the simulator chamber (12).

Description

Brake system for motor vehicles

The present invention relates to a brake system for

Motor vehicles according to the preamble of claim 1.

Such a brake system for motor vehicles is known for example from DE 102011081463 AI. The known brake system comprises an actuatable by means of a brake pedal main ^¬ brake cylinder with two pressure chambers, wheel brakes, an electrically controllable pressure supply device, a pressure control valve assembly with two valves per wheel brake, two more valves per brake circuit, of which the two isolation valves for decoupling the master cylinder pressure chambers of the wheel ^¬; mode brakes in the 'brake-by-wire "are needed, and a simulation device, which is connected to the pressure chambers of the master brake cylinder and which supplied via a simulator release valve and can be switched off. to maintain high availability of the braking system, even in the fallback mode of operation to achieve the brake system comprises a total of thirteen valves and the simulator release valve must be made de-energized closed, so that in case of failure of the electrical power supply of the brake system in the fallback mode, a shutdown of Simulationseinrichtun g and the possibility of a hydraulic pressure build-up on the wheel brakes is ensured by the driver. A disadvantage of the use of a normally closed simulator release valve is that in the case of contamination of the valve, this may no longer completely closes, so that a hyd ^¬ raulischer penetration of the driver on the wheel brakes in the fallback mode would be no longer or to a limited extent , Furthermore, the large number of valves leads to high production costs for the brake system. Object of the present invention is therefore to provide a brake system, which has a further improved availability and at the same time is inexpensive to produce.

This object is achieved by a brake system according to claim 1.

The invention is based on the idea that the brake master cylinder coupled to the first master cylinder piston is designed as a stepped piston whose annular surface bounds a hy ^¬ cal chamber, which is connected to the simulator chamber of the hydraulically actuated simulation device.

An advantage of the invention is that a normally open simulator valve can be used and that separating valves for decoupling the master cylinder pressure chambers from the wheel brakes can be dispensed with. This is achieved in that the simulation device is not connected to one of the pressure chambers of the master cylinder, so it can be hydraulically separated from the pressure chambers of the master cylinder, but is still coupled directly to the movement of the first master cylinder piston.

The first master cylinder piston is thus formed as a stepped piston with at least one circular surface and an annular surface ^¬ forms, the circular area of the first pressure chamber and the annular surface bounds the hydraulic chamber, wherein a

Pressure effect in the chamber corresponds to a force acting on the first master cylinder piston against the actuation direction.

Preferably, a hydraulic connection between the first pressure chamber and the pressure medium reservoir is provided, in which an electrically actuated drain valve is arranged. As a result, particularly in an actuated state of the first master cylinder piston, the first pressure chamber can be kept pressureless in the "brake-by-wire" mode, whereby the brake pedal characteristic in the response region is not influenced by the movement of the second master cylinder piston The drain valve also offers the advantage that in the event that a transition to the fallback mode takes place during a brake pedal operation, closing the drain valve results in a brake pedal travel loss-free, direct closing pressing the wheel ^¬ brake by the driver is possible. the simulator valve is preferably carried out normally open so that soiling or incomplete closing of the simulator valve does not affect the functionality of the Rückfallb According to a preferred embodiment of the brake system, a hydraulic connection is provided between the chamber and the first pressure chamber, in which an electrically operable prefill valve is arranged. The pre-fill valve allows a brake pedal travel shortening in a second fallback mode.

Preferably, a hydraulic connection between the chamber and the pressure medium reservoir is provided, in which the simulator valve is arranged. Particularly preferably, the simulator valve is connected in parallel with a non-return valve opening in the direction of the chamber.

Each first wheel valve is preferably arranged in the connection between the wheel brake and the associated pressure chamber, with no further valve in the connection between the first wheel valve and pressure chamber is arranged, ie that in each of the respective pressure chamber with a wheel brake connecting hydraulic line is arranged as a single valve, the first wheel valve.

According to one embodiment of the invention, a hydraulic connection between the second pressure chamber and the chamber, or between the second pressure chamber and the simulator chamber is provided, in which an electrically actuated separating valve is arranged, which is particularly preferably without current open from ^¬ out, so that the wheel brakes, which are connected to the second pressure chamber, communicate with the pressure fluid reservoir. This is advantageous to allow a continu ^¬ ous pressure compensation. This connection is advantageously shut off by an actuation of the second main ^¬ brake cylinder piston.

According to a preferred embodiment of the brake system according to the invention at least one radial bore is arranged in the second master cylinder piston such that the second pressure chamber in the unactuated position of the second master cylinder piston via the radial bore and a container connection with the pressure fluid reservoir is in communication, the connection through an operation of the second master cylinder piston is shut off, and between the container port and the chamber, a hydraulic connection is provided, in which the separating valve is arranged. This allows a compact design.

The first pressure chamber and the hydraulic chamber are preferably hydraulically sealed against each other at least in an actuated state of the first master brake ^¬ cylinder piston. Preferably, the first pressure chamber and the hydraulic chamber in the "brake-by-wire" mode are not hydraulically connected to each other upon actuation of the brake pedal.

In the first master cylinder piston preferably at least one radial bore is arranged such that the first pressure chamber is in the unactuated position of the first master cylinder piston via the radial bore in communication with the chamber, wherein the connection is shut off by an actuation of the first master cylinder piston. This is advantageous ^¬ to bring the wheel brakes connected to the first pressure chamber with the pressure fluid reservoir for the purpose of pressure equalization in combination.

In order to apply in the 'brake-by-wire "mode, the wheel brakes of the second brake circuit by means of the pressure supply device with pressure, a hydraulic Ver ^¬ connection between the pressure supply device and the second pressure chamber is preferably provided. This compound is particularly preferably by actuating the In the "brake-by-wire" mode, the wheel brakes associated with the second pressure chamber are therefore pressurized via the connection between the pressure supply device and the second pressure chamber and the first wheel valves.

According to one development of the invention, at least one radial bore is arranged in the second master brake cylinder piston in such a way that the second pressure chamber communicates with the pressure supply device via the radial bore in the unactuated position of the second master brake cylinder piston, the connection being shut off by actuation of the second master cylinder piston ,

At least the wheel brakes of the first pressure chamber assigned .

b

Brake circuit is preferably a second, electrically

controllable wheel valve associated with the pressure control valve assembly, which is arranged in a hydraulic connection between the pressure supply device and the wheel brake. Particularly preferred is the wheel brakes of both brake circuits depending on a second, electrically controllable wheel valve

Pressure control valve assembly associated, which is arranged in a hydraulic connection between the pressure supply device and the wheel brake.

According to a preferred embodiment of the brake system according to the invention, the second wheel valves associated with the wheel brakes are designed to be normally closed and no further valve is arranged in the connection between the pressure supply device and the second wheel valve. This is particularly preferred for the second wheel valves of the first pressure chamber.

According to another preferred embodiment of the brake system according to the invention, the second wheel valves assigned to the wheel brakes of the first pressure chamber are designed to be normally open and there is a normally closed circular valve in the connection between the second wheel valves and the pressure supply device.

Furthermore, according to one embodiment, it is preferable for the wheel brakes of the brake circuit associated with the second pressure chamber to each have a second, electrically actuatable, normally closed wheel valve associated with the pressure control valve arrangement, which is arranged in a hydraulic connection between the wheel brake and the pressure medium reservoir. In this case, no further valve is arranged in the connection between the second wheel valve and the pressure medium reservoir. The brake system preferably comprises at least one electronic control and regulating unit for controlling the simulator valve, the pressure supply device and the pressure regulating valve arrangement and possibly further valves of the brake system, in particular the drain valve and / or the separating valve.

Another advantage of the invention is that less electrically operable valves are required than in the known from the prior art brake system. The brake system according to the invention is thus smaller, cheaper and lighter. Furthermore, the invention offers the advantage that no extension of the brake pedal travel occurs at a transition to the fallback mode. It is also advantageous that a rapid pressure build-up by means of the Druckbereitstellungsein- direction is possible, since only the first wheel valve is arranged between the pressure provisioning ^¬ means and a wheel brake to ^¬ arranged so that the hydraulic resistance of a further valve does not occur. Further preferred embodiments of the invention will become apparent from the subclaims and the following description with reference to figures.

It show schematically

1 shows a first embodiment of a erfindungsge ^¬ MAESSEN brake system,

2 shows a second embodiment of a brake system according to the invention,

3 third embodiment of a fiction, contemporary brake system, 4 shows a fourth embodiment of a fiction, ^¬ brake system,

5 shows a fifth embodiment of a fiction, ^¬ brake system,

6 shows a sixth embodiment of a fiction, ^¬ brake system,

Fig. 7 shows a seventh embodiment of a brake system of modern fiction, ^¬,

8 is an eighth embodiment of a erfindungsge ^¬ MAESSEN brake system,

Fig. 9, a ninth embodiment of a brake system according to Inventive ^¬,

Fig. 10 shows a twelfth embodiment of a brake system of modern fiction, ^¬,

Fig. 11 shows a fifteenth embodiment of a brake system according OF INVENTION ^¬ dung, and

Fig. 12 shows a seventeenth embodiment of an OF INVENTION ^¬ to the invention the brake system.

The brake system according to the first off ^¬ operation example shown in FIG. 1 consists essentially of an operable by an actuating or brake pedal hydraulic master cylinder 1, a co-operating the master cylinder 1, hydraulically operable simulation device 11, a master brake cylinder 1 associated pressure fluid reservoir 9 , an electrically controllable _

y

Pressure supply device 18, hydraulically actuated wheel brakes 6a-6d, an electrically controllable pressure control valve assembly 30 for controlling and / or controlling the wheel brakes applied to the wheel brakes and an electronic control unit (not shown).

The master cylinder 1 has, in a housing 10, two successively arranged hydraulic master cylinder piston 2, 3 (primary piston 2, the secondary piston 3), the hydraulic to the housing 10 pressure chambers 4, 5 (primary pressure space 4, seconding ^¬ därdruckraum 5) limit. The pressure chambers 4, 5 are on the one hand via trained in the master cylinder piston 2, 3 radial bores and corresponding pressure equalization lines 26a, 26b with the pressure fluid reservoir 9 in connection, which can be shut off by a relative movement of the piston 2, 3 in the housing 10, and on the other hand by means of hydraulic Lines 27a, 27b with the pressure control valve assembly 30 in connection. The hydraulic lines 27a, 27b each belong to a brake circuit, which is provided with the reference symbols I and II. Each wheel brake 6a-6d is, for example, a normally open, analogized or analog controlled first wheel valve 7a-7d the pressure ^¬ control valve assembly 30 associated, which is arranged in the hydraulic connection between the pressure chamber 4, 5 and the wheel 6a-6d. In the hydraulic connection between the pressure chamber 4, 5 and wheel brake 6a-6d is arranged according to another example no valve. According to the example, the first brake circuit I, which is connected to the pressure chamber 4, the wheel brakes front left 6a (FL) and rear right 6b (RR), the second brake circuit II, the front right 6c (FR) and rear left 6d (RL) assigned. The first wheel valves 7a, 7c of the wheel brakes 6a, 6c of the front axle are each connected in parallel with a non-return valve 43a, 43c opening in the direction of the wheel brake. ₁

Furthermore, the first pressure chamber 4 is connected by means of a hydraulic connection 33 with a, advantageously currentless closed ^¬ drain valve 25 to the pressure medium reservoir 9 separable. Thus, the pressure chamber 4 can be switched in the actuated state of the piston 2 "depressurized" by

Pressure chamber 4 is connected by opening the drain valve 25 to the pressure medium reservoir 9.

The mechanically coupled to the brake pedal, first main ^¬ cylinder piston (primary piston) 2 is formed as a stepped piston with a circular area 24 and an annular surface 23, the circular surface 24 of the first pressure chamber 4 and the annular surface of a hydraulic chamber 22 limits the 23rd In this case, a pressure effect in the chamber 22 corresponds to a force acting on the first master cylinder piston 2 against the actuation direction. According to the example, a return spring 28 is arranged in the chamber 22, which holds the primary piston 2 in the unactuated state at a brake pedal side stop. The first pressure chamber 4 and the hydraulic chamber 22 are hydraulic against each other, for example, by a housing 10 or on the piston 2 arranged sealing element, sealed.

The pressure chambers 4, 5 take on unspecified ^¬ return springs, which move the pistons 2, 3 in the non-actuated main brake cylinder 1 in a starting position. The

Return spring for the primary piston 2 is supported, for example, on the piston 3 from. Alternatively, a return spring for the primary piston 2 can be used, which is supported on the housing 10. The secondary chamber return spring is advantageously tied up and fixed to the housing 10 and the secondary piston 3.

A push rod 20 couples the pivotal movement of the brake pedal (not shown) to the translational motion of the first (master cylinder) piston 2 due to a pedaling action. whose actuation is detected by a redundant preferably from ^¬ guided displacement sensor 32nd As a result, the corresponding piston travel signal is a measure of the Bremspedalbetäti ^¬ supply angle. It represents a braking request of a vehicle driver.

The simulation device 11, which is intended to give the driver a pleasant brake pedal feel in the "brake-by-wire" mode, essentially comprises a hydraulic simulator chamber 12, a simulator spring chamber 14 with an elastic element 13 and a partition separating the two chambers 12, 14 Simulator piston 15 The simulator chamber 12 is connected via a hydraulic connection 29a to the chamber 22 of the master cylinder 1 and connected via a hydraulic connection 29b with a normally open, eg analog or analog controlled, simulator valve 16 separable connected to the pressure medium reservoir 9. Der Simulatorventil 16 ist a check valve 17 opening in the direction of the chamber 22 is connected in parallel.

When presetting a brake pedal force and activated (closed ^¬ sen) simulator valve 16 pressure fluid flows from the chamber 22 of the master cylinder 1 in the simulator chamber 12, wherein the generated thereby pedal feeling depends on the built-up by the elastic element 13 back pressure. A connected to the chamber 22 and the simulator chamber 12 pressure sensor 31 detects the pressure built up in the chamber 22 by a displacement of the primary piston 2. The electrically controllable pressure supply device 18 is formed, for example, as a hydraulic Zylin ^¬ the piston assembly or a single-circuit electrohydraulic actuator, the piston 34 of a schematically indicated electric motor 35 with the interposition of a likewise rotati- ons translation gear shown schematically operable. One of the detection of the rotor position of the electric motor 35 serving, only schematically indicated rotor position sensor is designated by the reference numeral 36. In addition, a temperature sensor 37 for detecting the temperature of the motor winding may also be used. The piston 34 defines a pressure chamber 38. A pressure medium connection 39 which is connected to the pressure fluid reservoir 9, via an opening in this flow-through check valve 40 to the pressure chamber 38 of the Druckbe ^¬ riding provision device 18. The pressure chamber 38 is connected via a line 41 derived from the the electrically controllable pressure supply device 18 dispensed system pressure, with example according to all wheel brakes 6a-6d separably connected. Each wheel brake 6a-6d is associated with an electrically controllable, advantageously normally closed, second wheel valve 8a-8d of the pressure regulating valve arrangement, which is arranged in the hydraulic connection between the pressure chamber 38 and the wheel brake 6a-6d. In the hydraulic connection between the pressure chamber 38 and the respective wheel brake 6a-6d example, no further valve is arranged on ^¬ . To the line 41, a preferably redundant executed pressure sensor 42 is connected, which detects the system pressure.

In a normal braking in the normal mode of the

Brake system ("brake-by-wire" mode) is actuated at a Be ^¬ actuation of the brake pedal by the driver of the primary piston 2, wherein the piston movement is detected by means of the displacement sensor 32. By means of the electronic control unit, the simulator valve 16 are closed and the discharge valve 25 is opened in the (annular piston) chamber 22 of the primary piston 2, according to the simulator characteristic of the simulation device 11, a pressure builds up with the Pressure sensor 31 is measured and can be used to the driver request detection. Since due to the open drain valve 25 no pressure build-up in the (primary) pressure chamber 4 is possible, the only static counterforce is the

Simulator pressure force. A hydraulic damping effect can be achieved by the opening characteristic of the drain valve 25. Thus, primary piston travel-dependent damping values can also be implemented (hydraulically / mechanically and / or electronically). Due to the non-pressurized primary chamber 4 and the secondary chamber 5 is depressurized or almost free of pressure (depending on the spring concept of the return springs of the master cylinder). The currentless open, first wheel valves 7a-7d are closed and the normally closed wheel valves 8a-8d are opened, this being advantageously carried out slowly to reduce noise. By means of the pressure supply device 18 is constructed by moving the piston 34 by means of the Elect ^¬ romotors 35 a system pressure, which in open wheel valves 8a-8d via line 41 to a Raddruckaufbau at the wheel brakes 6a-6d. The system pressure or wheel pressure is measured by pressure sensor 42.

Upon release of the brake pedal by the vehicle driver, the correspondingly lower deceleration request is detected by means of displacement sensor 32 and retracted correspondingly to the pistons 34 of the pressure supply device 18, whereby the (system) pressure and thus the wheel brake pressures are reduced. The primary pressure chamber 4 fills via the drain valve 25 from the pressure fluid reservoir 9 with pressure medium and via the sealing collars, possibly via a non-illustrated check valve in the relief valve 25th

To carry out a wheel-specific brake control (eg ABS or ESC control (antilock brake system or vehicle dynamics control system)), a pressure reduction takes place on a wheel brake 6a-6d Opening the associated, normally open wheel valve 7a-7d causes. Alternatively or simultaneously, a pressure reduction in the multiplex mode by retraction of the piston 34 Druckbe ^¬ provision device 18 can be achieved. The latter reduces the volume consumption or the Nachsaugbedarf and allows a smaller volume of the pressure chamber 38. A pressure ^¬ rebuild is done by opening the wheel valve 8a-8d and possibly advancing the piston 34. In this case, a Volu ^¬ mensteuerung on the analog controlled wheel valves 8a-8d quiet and accurate. In addition, there is the possibility in the multiplex method by means of the pressure sensor 42 to measure the pressure in each wheel brake.

Active brake pedal feedback and even brake pedal reset is possible by driving the bleed valve 25 and the outflowing volume.

The brake system offers the advantage of being single-handed in brake-by-wire mode, in particular for use in assisted comfort functions or in hybrid blending, so that any desired wheel brake pressure (eg only front axle, rear axle, left wheels, right wheels) remains quiet Pressure control loop can be controlled without ^{Sekundärkol ¬} ben-pressure friction pressure difference.

A particularly rapid pressure build-up, such as e.g. is required by a collision mitigation or prevention function (Collision Mitigation by Braking) is particularly favorable represented by the brake system according to the invention, since the hydraulic resistance is formed on the path to the wheel valves only by one wheel valve per wheel brake.

In a fallback mode of the brake system (fallback level), the simulator valve 16 remains open and the drain valve 25 closed. The normally open wheel valves 7a-7d remain open. Upon actuation of the brake pedal by the vehicle driver, pressure medium is moved out of the chamber 22 via the opened simulator valve 16 into the pressure medium reservoir 9. Due to the fact that the simulation device of the

Pressure chambers 4, 5 of the master cylinder 1 is hydraulically separated, can be built by the driver pressure in the pressure chambers 4, 5, so that a pressure build-up in the wheel brakes 6a-6d via the lines 27a, 27b by the driver. An emergency EBV (EBV: Electronic Brake Force Distribution) on the rear axle is possible by e.g. the wheel valves 7a and 7b are prematurely closed before a blockage tendency.

In a transition to the fallback level, the brake system provides by closing the discharge valve 25, a Gap-free, ie Bremspedalwegverlustfreie, direct actuation of the wheel brakes, as displaced by the vehicle pressure fluid volume is dissipated only in the wheel brakes. Via the non-return valves 43a, 43c, in a fallback ^{mode of} operation, pressure medium can be pressed directly into the wheel circuits 6a, 6c, even with the wheel valves 7a, 7c closed.

2, a second embodiment of an inventive brake system is shown. The second Ausfüh ^¬ tion example corresponds to the first embodiment, in addition, a hydraulic connection between the chamber 22 and the pressure chamber 4 can be produced. For this purpose, a line 29c is present, in which an electrically actuated, normally closed pre-fill valve 44 is arranged.

The pre-fill valve 44 allows for an intermediate fallback level, up to a certain pressure from the (annular piston) chamber 22 pressure fluid volume is fed into the primary pressure chamber 4. For this purpose, the pre-fill valve 44 is opened and the simulator valve 16 is closed. The pedal travel is shortened in this intermediate fallback level.

The pre-fill valve 44 also improves the failure ^{mode ¬} and influence analysis of the brake system, as is available through the line 29c with pre-filling valve 44, a redundant hydraulic path at a drained to drain valve 25 or simulator valve 16.

As an alternative to the pressure supply device 18 shown in FIGS. 1 and 2 in the form of a single-circuit electrohydraulic actuator (linear actuator), the brake system according to the invention can also comprise a unidirectional, advantageously pulsation-free, feed pump, which is driven by an electric motor, as pressure supply device (not shown in a figure). , In this case, the pressure connection of the pump to the line 41 and the suction connection to the check valve 40 is connected. Such Mo ^¬ tor-pump unit has the advantage that no high re versierfähigkeit the motor-pump unit and no ^¬ After sucking pressure medium are required. Furthermore, a compact design is possible.

A pressure build-up takes place with the pump stopped and the wheel valves 8a-8d open in the pressure-compensated pressure control circuit 41 (shown with pressure sensor 42) via the analog-controlled wheel valves 7a-7d.

The pressure sensor 42 of the pressure supply device can be dispensed with if a sufficiently accurate current measurement of the brushless electric motor of the pressure supply device is performed and it is concluded on the system pressure. On the basis of, for example, in the brake system itself, calibrated wheel valves 7, 8 a sufficiently accurate pressure position on the wheel brakes is possible. Furthermore, the Raddrehzahlinforma- tions of the wheel brakes associated wheels for

Plausibility of a pressure model for the system pressure are used.

Correspondingly, FIG. 3 shows a third exemplary embodiment of a brake system according to the invention, which does not include a pressure sensor in the line 41 of the pressure supply device 118. The pressure sensor has been replaced by a current measurement of the brushless electric motor 35 of the pressure ^supply device 118 by means of the current sensor 45. The hydraulic structure of the third embodiment basically corresponds to the first embodiment, which is why in the following only the differences from the first embodiment will be discussed. The pressure providing device 118 is as a bidirectional, by means of a

Electric motor driven, advantageously pulsation-free, pump designed by means of which a pressure build-up and a pressure reduction at the wheel brakes 6a-6d is directly feasible. For this purpose, the pump 118 is connected with its two connections to the line 41 to the wheel brakes and the line 39 (without check valve 40 of FIG. 1) to the pressure fluid reservoir 9. Pressure supply device 118 has the advantage that no suction of pressure medium is required and a compact design is possible. Furthermore, the exemplary brake system includes no

Pressure sensor in the line 29b of the simulation device 11. For determining the pressure of the simulation device, a double-displacement sensor 32, 46 is applicable, in which a displacement sensor, a movement of the piston 2 and another displacement sensor movement the piston rod 20 detected. By the interposition of a spring element 47 can be closed from the differential path and the stiffness of the spring element on the actuation force. At the same time, the two displacement sensors monitor themselves (double-path sensor). As a result, the cost of the brake system can be reduced. However, this also makes it possible to sense a non-desired opposing force via a pressure effect in the primary pressure chamber 4 (eg in the case of an undesired closed drain valve 25).

4, a fourth embodiment of an inventive brake system ^{¬ is} shown. The fourth exporting ^¬ approximately example corresponds to the third embodiment, the pressure supply device is designed differently. Pressure supply device 218 is designed as a two-circuit unidirectional, driven by a common electric motor 35, advantageously pulsation-free, feed pump. In this case, both suction ports of the pump via the check valve 40 to the pressure fluid reservoir 9, which is a pressure port of the pump via the line 41a with the second wheel valves 8a, 8b of the wheel brakes 6a, 6b of the first brake circuit I and the other pressure port of the pump is over the line 41b is connected to the second wheel valves 8c, 8d of the wheel brakes 6c, 6d of the second brake circuit II. Such a motor-pump unit has the advantage that a clear circuit separation is present. Again, there are no high reversibility of the motor-pump unit and no

After suction of pressure medium required. Furthermore, a compact design is possible.

A pressure build-up takes place with the pump stopped and the wheel valves 8a-8d open in the pressure-balanced pressure control circuit 41 (a pressure sensor can advantageously be used for this purpose) per line 41a, 41b be present) via an analog controlled, first wheel valves 7a-7d per wheel brake.

5 shows a fifth exemplary embodiment of a brake system according to the invention, which essentially comprises a hydraulic master cylinder 1 which can be actuated by means of an actuating or brake pedal 21, a hydraulically actuatable simulation device 11 cooperating with the master brake cylinder 1, a pressure medium reservoir assigned to the master brake cylinder 1 9, an electrically controllable pressure supply device 18, hydraulically actuated wheel brakes 6a-6d, an electrically controllable pressure control valve assembly 130 for controlling and / or controlling the wheel brakes applied to the wheel brakes and an electronic control unit (not shown).

The master cylinder 1 has, in a housing 10, two hydraulic master cylinder pistons 2, 3 arranged one behind the other, which delimit hydraulic pressure chambers 4, 5 with the housing 10. The coupled via a push rod 20 to the brake pedal 21, the first master cylinder piston (primary piston) 2 is a stepped piston with a circular surface 24 and a

Ring surface 23 is formed, wherein the circular surface 24 the first pressure chamber 4 and the annular surface 23 defines a hydraulic chamber 22. In this case, a pressure effect in the chamber 22 corresponds to a force acting on the first master cylinder piston 2 against the actuation direction. By way of example, a return spring 128 is operatively arranged between the housing 10 and the brake pedal 21, which positions the brake pedal 21 and thus the primary piston 2 in an initial position when the brake pedal is ^de- energized. The pressure chamber 5 receives an unspecified return spring, which position the piston 3 with unoperated master cylinder 1 in a starting position. The return spring is advantageously fixed to the housing 10. The actuating travel of the master brake cylinder piston 2 is detected by a preferably redundantly designed displacement sensor 32 and represents the braking request of the vehicle driver. The pressure chambers 4, 5 are connected by means of hydraulic lines 27a, 27b with the pressure control valve assembly 130 in connection.

Pressure control valve arrangement 130 comprises for each wheel brake 6a-6d, for example, a normally open, first wheel valve 7a-7d and for the primary pressure chamber 4 associated wheel brakes 6a, 6b each a normally closed, second wheel valve 8a, 8b. The

Wheel valves 7a and 7b are, for example, analogized or analog controlled. Wheel valves 7a-7d are arranged in the per ^¬ weiligen hydraulic connection between the pressure space 4, 5 and the wheel brake 6a-6d, where, for example in accordance with no further valve is arranged in this connection. In ^¬ game are the first brake circuit I, which is connected to the pressure chamber 4, the rear wheel brakes (6a: rear left (RL), 6b: rear right (RR)) and the second brake circuit II, the front wheel brakes (6c: front left (FL), 6d: front right (FR)) assigned.

In each of the master brake cylinder piston 2, 3 radial bores are formed. In the unactuated state of the master cylinder piston 3, the pressure chamber 5 via the radial bores and a connection 141 to the pressure chamber 38 of the pressure supply device 18 and the radial bores, the container port 48 and a line 26 b with a return ^¬ check valve 40 to the pressure medium reservoir 9 is connected. The check valve is arranged opening in the direction of the pressure fluid reservoir 9 to the pressure chamber 5, so that pressure medium from the pressure medium reservoir 9 via the connection 26 b, the pressure chamber 5 and the connection 141 can be sucked into the pressure supply device 18. In the unactuated state of the master cylinder piston 2 is the Pressure chamber 4 connected via the radial bore with the chamber 22. The connection via the radial bores is shut off by an actuation (a displacement) of the piston 2 or 3 in the housing 10. The first pressure chamber 4 and the hydraulic chamber 22 are thus hydraulically sealed against each other in an actuated state of the first main ^¬ brake cylinder piston.

Furthermore, the first pressure chamber 4 is separably connected to the pressure medium reservoir 9 by means of a hydraulic connection 33 with a drain valve 25, which is advantageously closed normally. Thus, the pressure chamber 4 may also be in the actuated state of the piston 2 are switched "pressureless" by the pressure chamber 4 is connected by opening the drain valve 25 with the pressure fluid supply reservoir. 9 Furthermore, the excess pressure fluid volume which is composed at a Bremsre ^¬ gelung (for example spin) the wheel brakes 6a, 6b must be discharged into the pressure medium reservoir 9, be discharged via the drain valve 25 in the pressure fluid reservoir.

The simulation device 11 essentially corresponds to the simulation device explained in detail with reference to FIG. 1. The simulator chamber 12 is connected via a hydraulic connection 29 a with the chamber 22 of the master cylinder 1. The chamber 22 is connected via a hydraulic connection 129 with a normally open simulator valve 16 separable connected to the pressure medium ^¬ reservoir 9. The simulator valve 16 has a check valve 17 which opens in the direction of the chamber 22 in parallel. By the simulator valve 16, the effect of the simulation device 11 can be switched on and off.

According to the example, the container port 48 of the secondary pressure chamber 4 is connected via a hydraulic connection to the chamber 22 and thus to the simulator chamber 12, wherein the connection through a second, advantageously normally open, isolation valve 49 is separable. Separating valve 49 is arranged, for example, in a line section 131 which connects the line 26b to the line section between chamber 22 and simulator valve 16 (connection 129).

When presetting a brake pedal force and closed

Simulator valve 16 and closed container-separating valve 49 flows pressure medium from the chamber 22 of the master cylinder 1 in the simulator chamber 12, wherein the case generated pedal feeling is essentially determined by the elastic member 13.

The electrically controllable pressure supply device 18 is designed as a single-circuit electrohydraulic actuator and essentially corresponds to the pressure supply device explained in detail with reference to FIG. 1. The pressure chamber 38 of the pressure supply device 18 is connected via a line 41 to the wheel brakes 6a, 6b of the first brake circuit I via a normally closed, second wheel valve 8a, 8b of the pressure control valve assembly 130. In the hydraulic connection between the pressure chamber 38 and the respective wheel brake 6a, 6b, no further valve is arranged according to the example. On the other hand, the pressure chamber 38 is connected at the non-operated secondary piston 3 via the hydraulic connection 141 to the pressure chamber 5, so that in the 'brake-by-wire "mode, a pressure is restored ^¬ suppression of the wheel brakes 6a, 6b can be effected by the pressure supply device 18th

In addition to the distance sensor 32 for detecting brake demand and the sensor 36 for detecting a position of the pressure supply device 18, the exemplary brake system comprises a preferably redundantly designed pressure sensor 42, by means of which the system pressure of the pressure supply device 18 is detected in the "brake-by-wire" mode. Optionally (indicated by the dashed line section 50), a separable hydraulic connection between the connection 27b and the pressure fluid reservoir 9, bypassing the check valve 40, is provided. According to the example, for this purpose, a line section 50 with a normally closed Zuschaltventil 51 between the lines 27b and 26b (between the container port 48 and check valve 40) is arranged.

Alternatively, the normally closed make-up valve 51 may be disposed in parallel with the check valve 40 (i.e., in a passage bypassing the check valve) similarly as shown in the seventh embodiment explained below. As a result, the pressure reduction at the wheel brakes 6c and 6d can take place very quickly and the demands on the reversing dynamics of the pressure supply device 18 can be reduced.

The exemplary brake system has the advantage that it has only nine or ten valves.

In a normal braking in the normal mode of the

Braking system ("brake-by-wire" mode) is actuated by the driver of the primary piston 2 at a Be ^¬ actuation of the brake pedal 21, wherein the piston movement is detected by means of the displacement sensor 32. By means of the electronic control unit, the simulator valve 16 and the

Isolation valve 49 is closed and the drain valve 25 is opened. In the chamber 22 of the primary piston 2, a pressure builds up according to the simulator characteristic of the simulation device 11. Since no pressure build-up in the (primary) pressure chamber 4 is possible due to the opened drain valve 25, the only static reaction force is the simulator pressure force. A hydraulic Dämp ^¬ vaporization effect is, as already described by reference to Fig. 1, made possible by the opening characteristic of the discharge valve 25. Due to the non-pressurized primary chamber 4 and the secondary chamber 5 is depressurized or almost depressurized. The normally open wheel valves 7c, 7d of the brake circuit II remain open, whereas the normally open wheel valves 7a, 7b of the brake circuit I are closed. The normally closed wheel valves 8a, 8b of the

Brake circuit I are opened. By means of the Druckbereitstel ^¬ lling device 18, a system pressure is built up by moving the piston 34 by means of the electric motor 35, which leads via the line 41 and the hydraulic connection 141, 4, 27b to a wheel pressure at the wheel brakes 6a-6d. The system pressure or wheel pressure is measured by pressure sensor 42.

Upon release of the brake pedal by the driver, the correspondingly lower deceleration request is detected by means of displacement sensor 32 and correspondingly the piston 34 of Druckbereitstel ^¬ ment device 18 is reduced, whereby on the (open) multiplex wheel valves 7c, 7d in the brake circuit II (according to the Vorderach circle) and the open, second wheel valves 8a, 8b in the brake circuit I (according to Hinterach circle) degradation of the wheel brake pressures.

The example modern brake system offers a number of Diag ^¬ nose-options, which are explained below. A leakage at the wheel valves 7a-7d, the wheel valves 8a, 8b, the outer cuff of the simulation device and the simulator (outer) cuff can be detected by the first wheel valves 7a-7d and the simulator valve 16 is closed and a pressure build-up with then keeping constant the pressure by means of the pressure supply device 18 is performed. By means of the pressure sensor 42 may be a possible

Pressure drop due to leakage can be detected.

An air entry in the spaces 4, 5, 22 of the master cylinder or the simulator chamber 12 can be detected by the first Wheel valves 7a-7d and the simulator valve 16 are closed and a slow pressure build-up means of Druckbereitstel ^¬ ment device 18 is performed. The Volu ^¬ men-pressure characteristic curve by means of sensor 36 (actuator pathway) and pressure sensor 42 is measured and specified with a

Target simulator characteristic compared.

A leakage at the first wheel valves 7a-7d, the isolation valve, the seal of the secondary pressure chamber 5 or the cuff of the pressure supply device 18 can be detected by the wheel valves 7a-7d and the isolation valve 49 closed and a pressure build-up followed by keeping the pressure constant by means of the pressure supply device 18 is performed.

By means of the pressure sensor 42, a possible pressure drop due to leakage can be detected.

The movement capability of the piston 3 can be checked by closing the valves 7a-7d and the simulator valve 16 and performing a pressure build-up (by means of pressure-providing device 18) and biasing of the simulation device 11. Then, the isolation valve 49 is closed and carried out a pressure reduction by means of pressure supply device 18. As proof of the movement of the piston 3 is the observation of the simulator pressure at the pressure sensor 42, since the pressurized simulator 11 after the pressure reduction, the piston 3 will move when the system is intact, which again leads to a pressure build-up in the space 5.

A leakage detection at the seal of the primary pressure chamber 4 and a corresponding feedback to the driver (OK / NOK) is possible with each driver operation, since this seal acts on both sides. In Fig. 6, a sixth embodiment of an inventive brake system ^{¬ is} shown schematically. In contrast to the exemplary embodiment explained with reference to FIG. 5, the brake system additionally comprises a second pressure-delivery device 60 and a further electronic control and regulation unit 61. These additional components enable autonomous driving.

The second pressure supply device 60 is advantageously designed as an independent module. In ^¬ spielsgemäß the pressure supply device 60 is formed by a motor-pump unit, wherein the suction side of the pump is connected to the pressure medium reservoir 9 and the pressure side of the pump is connected to the hydraulic connection 129.

The control unit 61 is designed to control the second pressure supply device 60 and the simulator valve 16 (schematically indicated drive lines 62 in FIG. 6) in order to be able to carry out a pressure buildup in the chamber 22 independently of an actuation of the brake pedal 21 by the driver. In order to enable autonomous driving, the control unit 61, for example, at least one desired longitudinal acceleration a _so n and a

Actual longitudinal acceleration ai _St supplied. Furthermore stands the

Control unit 61 to the control unit 19 of the brake system for the exchange of information in connection. For example, the target pressure P _{S 0} n for the Druckbereitstel ^¬ luling device 18 is transmitted from the control unit 61 to the control unit 19 and the control and

Control unit 19 transmits a status signal S (for example about its functionality) to the control and regulation unit 61. In addition, the control unit 61 exchanges with one another according to the example a drive motor or its control and regulation unit information, which is indicated in Fig. 6 by the arrows 63.

According to the illustrated in Fig. 7, seventh embodiment, which corresponds to the fifth embodiment except for the differences explained below, the brake system comprises a pressure supply device 218 in the form of a unidirectional, driven by an electric motor 35 feed pump whose pressure side with the lines 41st and 141 is connected via a check valve 240 opening in the direction of the lines 41, 141, and whose suction side is hydraulically connected to the pressure medium reservoir 9. In addition, the brake system includes, for example according to a normally closed Zus ^¬ chaltventil 51, which is arranged parallel to the check valve 40.

The illustrated in Fig. 8, the eighth embodiment of a brake system according to the invention corresponds to the fifth embodiment except for the differently designed electrically controllable pressure supply device and their connection. Pressure supply device 318 is, for example, designed as a hydraulic cylinder-piston arrangement whose piston 334 driven by the electric motor 35 is designed as a stepped piston. The stepped piston 334 and the cylinder of the cylinder-piston assembly are formed such that after a predetermined actuation of the piston 334, the pressure chamber 38 of the pressure supply device 318 is divided into a first chamber 320 and a second chamber 321, the second chamber 321 a Ring chamber is. The first chamber 320 and the second chamber 321 are then sealed against each other by a second sealing element 322, wherein the second chamber 321 is sealed by an unspecified sealing element against atmospheric pressure (as in the embodiments of FIGS. 1, 2, 5, 6 ). In the area of the first chamber 320 is the pressure chamber 38 as in the fifth embodiment via a line 41 with the normally closed wheel valves 8a, 8b of the brake circuit II and connected via a line 141 to the pressure chamber 5. In addition, the pressure chamber 38 in the region of the second chamber 321 is connected via a line section 341 to a ^normally closed valve 342 with the line 27a. In this way; mode, the second chamber may be in the 'brake-by-wire "opened from ^¬ outlet valve 25 are 321 connected to a pressure medium ^¬ reservoir. 9 This allows for the further pressure build-up of engine 35, only the pressure effect on the small effective area This means that motor 35 can be designed to be smaller and therefore weight and cost-saving for the same dynamics, as opposed to electrically operated valve 342, which can not be replaced by one here shown hydraulic switching valve, in which the switching takes place in that the pressure in the space 38, the valve body against the container pressure effect (atmospheric pressure) and the force of a spring whose bias determines the switching pressure (eg 120 bar), so that the Chamber 321 is connected to the container pressure .In the case that the Dichteleme nt, which seals the second chamber 238 against atmospheric pressure, is leaking, after overcoming the predetermined actuation path of the piston 334, the first chamber 320 is sealed by the then coming into effect sealing element 322, so that nevertheless a pressure build-up on the wheel brakes 6a-6d by means of Druckbe ^¬ provision device 318 is possible. This is particularly important for a use of the brake system for the functions of highly automated driving, since the occurrence of a single error, such as the failure of the sealing sleeve, no To ^¬ talausfall the brake system may be the result, because the driver is practically not available in this case, to perform the braking by means of hydraulic fallback. In the following, various advantageous execution ^¬ examples are described in terms of the pressure control valve arrangement and / or the brake circuit distribution. The exemplary embodiments are in the context of a brake system, which with respect to the components master cylinder 1, simulation device 11, pressure supply device 18, valves 16, 25, 49 and their hydraulic connections substantially corresponds to the fifth embodiment. However, the described Druckre ^¬ gelventilanordnungen and / or the brake circuit divisions can also be used in combination with one of the other embodiments already described (in particular of Figs. 6 to 8).

The ninth embodiment shown in FIG. 9 as well as the twelfth embodiment of a brake system according to the invention shown in FIG. 10 have a black-and-white circular layout like the fifth embodiment, i. the wheel brakes of a vehicle axle 6a, 6b (RL, RR) and 6c, 6d (FL, FR) are assigned to a brake circuit I and II, respectively.

According to the ninth embodiment of FIG. 9, the pressure control valve arrangement 230 for the front axle (brake circuit II) per wheel brake 6c, 6d comprises a normally open, analogized or analog controllable (first) wheel valve 7c, 7d, wherein the wheel valves 7c, 7d respectively in the direction the wheel brake 6c, 6d closing check valve 143c, 143d is connected in parallel, and a normally closed (second) wheel valve 8c, 8d. The first wheel valves 7c, 7d are arranged in the respective hydraulic connection between the pressure chamber 5 and the wheel brake 6c, 6d. Each wheel brake 6c, 6d can be connected to the pressure medium reservoir 9 via the second wheel valves 8c, 8d

(Return line 231). For the rear axle (brake circuit I), the pressure regulating valve arrangement 230 per wheel brake 6a, 6b comprises a normally open, analog or analog controllable (First) wheel valve 7a, 7b, via which the pressure chamber 4 is separably connected to the respective wheel brake 6a, 6b, and a normally open, analogized or analog controllable (second) wheel valve 8a, 8b, via which the pressure chamber 38 of Druckbereitstellseirichtung 18 with the respective wheel brake 6a, 6b is separably connected, wherein in the connection (line 41) still another, normally closed circular valve 208 is arranged. The valve configuration shown in Fig. 9 is particularly advantageous in that the pressure build-up can take place very softly each individual wheel and the pressure reduction is very fast on each individual wheel displayed, thus also the on ^¬ requirements are reduced at the Reversierdynamik of the engine.

According to a tenth, not shown embodiment, the pressure control valve assembly advantageously for the front axle a valve assembly as shown in Fig. 9 for the front axle (normally open, analog or analog controllable wheel valves 7c, 7d with check valves 143c, 143d and normally closed wheel valves 8c, 8d) and for the rear axle, a valve assembly as in Fig. 5 for the

Rear axle shown (normally open, analogized or analog controllable wheel valves 7a, 7b and normally closed wheel valves 8a, 8b). According to an eleventh, not shown embodiment, the pressure control valve assembly advantageously for the rear axle, a valve assembly as shown in Fig. 5 for the rear axle (normally open, analogized or analog controllable wheel valves 7a, 7b and normally closed wheel valves 8a, 8b). For the front axle, the Druckre ^¬ gelventilanordnung comprises a valve arrangement similar to the arrangement shown in Fig. 9 for the front axle with normally open wheel valves 7c, 7d and normally closed wheel valves 8c, 8d, but the valves 7c, 7d not analogized or analog are executed controllable and no parallel check valves are present. However, this pressure regulating valve arrangement thus corresponds to the pressure regulating valve arrangement 130 of FIG. 5 with additional, normally closed wheel valves 8c, 8d for the front wheels.

According to the twelfth embodiment of FIG. 10, the pressure control valve arrangement 330 for the rear axle comprises a valve arrangement as shown in FIG. 9 for the rear axle (normally open, analogized or analog controllable wheel valves 7a, 7b, 8a, 8b and a normally closed circular valve 208). For the front axle, the Druckre ^¬ gelventilanordnung 330 includes a valve assembly according to the above-described eleventh embodiment with normally open, digital wheel valves 7c, 7d and normally closed wheel valves 8c, 8d, which the wheel brakes 6c, 6d if necessary via return line 231 with the pressure medium reservoir. 9 connect . According to a thirteenth, not shown embodiment, the pressure control valve assembly advantageously for the front axle a valve assembly as shown in Fig. 5 for the front axle (normally open wheel valves 7c, 7d) and for the rear axle a valve assembly as shown in Fig. 9 for the rear axle (de-energized open, analogized or analog controllable wheel valves 7a, 7b, 8a, 8b and a normally closed circular valve 208).

According to a fourteenth, not shown embodiment, the pressure control valve assembly advantageously for the front axle a valve assembly as shown in Fig. 5 for the front axle (normally open wheel valves 7c, 7d) and for the rear axle a valve assembly similar to that shown in Fig. 9 for the rear axle Valve arrangement with de-energized open, analogized or analog controllable, first wheel valves 7a, 7b, but the normally open second wheel valves 8a, 8b digitally and the normally closed

Circular valve 208 analogized or analog controllable executed.

According to the illustrated in Fig. 11, fifteenth embodiment of a brake system according to the invention, the wheel brakes 6a and 6b of the brake circuit I right side of the vehicle (right front FR and right rear wheel RR) and the wheel brakes 6c, 6d of the brake circuit II left side of the vehicle (left Front wheel FL and left rear wheel RL) assigned. The Druckregelven ^¬ tilanordnung 430 includes for each wheel 6a-6d a normally open, analog or analog controlled first wheel valve 7a-7d, which is arranged in the hydraulic connection between the pressure chamber 4, 5 and the wheel 6a-6d. Here, the wheel valves 7c, 7d each in the direction of the wheel brake 6c, 6d closing check valve 143c, 143d connected in parallel. Further comprising the Druckregelventil- assembly 430 for each wheel brake 6a-6d a normally ge ^¬ connected, analogized or analog is operated, second wheel valve 8a-8d, wherein the wheel valves 8a, 8b in the hydraulic connection between the pressure chamber 38 of the pressure supply device 18 and the respective Wheel brake 6a, 6b and the wheel valves 8c, 8d are each arranged in the hydraulic connection between the wheel brake 6c, 6d and pressure fluid reservoir 9.

According to a sixteenth, not shown Ausführungsbei- play the pressure control valve assembly advantageously comprises a brake circuit split and a valve assembly as shown in Fig. 11, but only two of the eight wheel valves 7a-7d, 8a-8d, for example, the wheel valves 7d and 8b, analogized or analog controllable, and the remaining of the eight valves digital are executed.

Fig. 12 shows a seventeenth embodiment of a ^{¬ he} inventive braking system, which with respect to the components of actuatable by means of a brake pedal 21 Hauptbremszy ^¬ Linders 1, the simulation device 11, the pressure medium reservoir 9, the pressure supply device 18, the valves 16, 25, 49 and 40 and of the sensor 32 substantially corresponds to the fifth embodiment (FIG. 5). By way of example, the pressure sensor 42 is arranged on the line section 141, that is to say near the pressure chamber 38 of the pressure supply device 18. The components mentioned are arranged in the housing 10. Furthermore, the brake system comprises a per se known hydraulic control unit 530, as it is known from conventional brake systems with vehicle dynamics control (standard ESC brake systems), and which a two-circuit motor-pump unit 501 with a low-pressure accumulator 502 per brake circuit I. , II, a normally open wheel valve 7a-7d and normally closed wheel valve 8a-8d per wheel brake 6a-6d and a normally open isolation valve 503 and a normally closed ^¬ closed change-over valve 504 per brake circuit I, II includes. The wheel brakes 6a-6d are connected to the hydraulic control unit 530 and assigned to the brake circuits I, II on the vehicle side. The pressure supply device 18 is connected by means of the line 41 to the first terminal of the hydraulic control unit 530 for the brake circuit I, the secondary pressure chamber 5 of the master cylinder 1 is connected by means of the line 27b to the second terminal of the hydraulic control unit 530 for the brake circuit II. The primary pressure chamber 4 of the main brake cylinder 1 is separably connected by means of the line 27 a with the Lei ^¬ processing section 141 between the pressure chamber 38 and the pressure chamber 5, wherein the separation is electrically possible by a normally open isolation valve 510.

Claims

Brake system for motor vehicles, which can be controlled in a "brake-by-wire" operating mode both by the driver and independently of the driver

• a master brake cylinder (1), which has at least a first and a second master brake cylinder piston (2, 3), which are arranged one behind the other and delimit a first and a second pressure chamber (4; 5), each of which has a brake circuit (I; II) is connected to wheel brakes (6a, 6b; 6c, 6d), the first ^main brake cylinder piston (2) being coupled to a brake pedal (21) via a push rod (20) which transmits actuating forces,

• a pressure medium storage container (9) assigned to the pressure chambers (4, 5) and under atmospheric pressure,

• a hydraulically actuated simulation device (11) with a hydraulic simulator chamber (12) and an elastic element (13), which in the "brake-by-wire" operating mode gives the vehicle driver a ^pleasant brake pedal feel,

• one, in particular electrically actuated,

Simulator valve (16) for switching the effect of the simulation device (11) on and off,

• an electrically controllable pressure supply device (18) for actuating the wheel brakes, and

• a pressure control valve arrangement hydraulically connected to the master brake cylinder (1), the pressure supply device (18) and the wheel brakes (6a-6d) for regulating and/or controlling a wheel brake pressure controlled at a wheel brake, each wheel brake having a first, electrically controllable, normally open wheel valve (7a-7d) is assigned to the ^pressure control valve arrangement,

characterized in that the first master brake cylinder piston (2) is designed as a stepped piston, the annular surface (23) of which delimits a hydraulic chamber (22), the hydraulic chamber (22) being hydraulically connected to the simulator chamber (12).

Brake system according to claim 1, characterized in that a hydraulic connection (33) is provided between the first pressure chamber (4) and the pressure medium reservoir (9), in which an electrically actuable, in particular normally closed, drain valve (25) is arranged.

Brake system according to claim 1 or 2, characterized in that the simulator valve (16) is designed to be open when de-energized.

Brake system according to one of claims 1 to 3, characterized in that a hydraulic connection (29a, 29b; 129) is provided between the chamber (22) and the pressure medium reservoir (9), in which the

Simulator valve (16) is arranged.

Brake system according to one of claims 1 to 4, characterized in that each first wheel valve (7a-7d) is arranged in the connection (27a, 27b) between the wheel brake (6a-6d) and the associated pressure chamber (4, 5), whereby no further valve is arranged in the connection between the first wheel valve and the pressure chamber.

Brake system according to one of claims 1 to 5, characterized in that a hydraulic connection (26b, 131)

• between the second pressure chamber (5) and the chamber (22), or

• between the second pressure chamber (5) and the

Simulator chamber (12)

is provided, in which an electrically actuated, in particular normally open, isolation valve (49) is arranged.

Brake system according to claim 6, characterized in that the connection (26b, 131) is shut off by actuation of the second master brake cylinder piston (3).

Brake system according to one of claims 1 to 7, characterized in that in the first master cylinder piston

(2) at least one radial bore is arranged such that the first pressure chamber (4) is connected to the chamber (22) via the radial bore in the unactuated position of the first master brake cylinder piston, the connection being shut off by actuation of the first master brake cylinder piston .

Brake system according to one of claims 1 to 8, characterized in that a hydraulic connection (141) is provided between the pressure supply device (18) and the second pressure chamber (5), which is achieved in particular by actuating the second master brake cylinder piston

(3) is blocked off.

Brake system according to one of claims 1 to 9, characterized in that at least the wheel brakes (6a, 6b) of the brake circuit (I) assigned to the first pressure chamber (4) are each assigned a second, electrically controllable wheel valve (8a, 8b) of the pressure control valve arrangement, which is located in a hydraulic connection (41) between the pressure supply device (18) and the wheel brake (6a, 6b). is ordered.

Brake system according to claim 10, characterized in that the wheel brakes (6a-6d), in particular the first

Pressure chamber (4), assigned, second wheel valves (8a-8d) are designed to be normally closed and that no further valve is arranged in the connection between the pressure supply device (18) and the second wheel valve.

Brake system according to claim 10, characterized in that the second wheel valves (8a, 8b) assigned to the wheel brakes (6a, 6b) of the first pressure chamber (4) are designed to be normally open and that in the connection (41) between the second wheel valves and the A normally closed circuit valve (208) is arranged in the pressure supply device (18).

Brake system according to one of claims 1 to 10, characterized in that the wheel brakes (6c, 6d) of the brake circuit (II) assigned to the second pressure chamber (5) are each assigned a second, electrically controllable, normally closed wheel valve (8c, 8d) of the pressure control valve arrangement is, which is arranged in a hydraulic connection (231) between the wheel brake (6c, 6d) and the pressure medium reservoir (9), with no further valve being arranged in the connection between the second wheel valve and the pressure medium reservoir.