EP3700786A1

EP3700786A1 - Brake system and two methods for operating such a brake system

Info

Publication number: EP3700786A1
Application number: EP18800486.5A
Authority: EP
Inventors: Jochen Zimmermann; Robert Grimm
Original assignee: Continental Teves AG and Co OHG
Current assignee: Continental Automotive Technologies GmbH
Priority date: 2017-10-24
Filing date: 2018-10-22
Publication date: 2020-09-02
Also published as: CN111278695B; CN111278695A; WO2019081414A1; KR102352643B1; DE102017219000A1; US20210188237A1; US11414062B2; KR20200055092A

Abstract

The invention relates to a motor vehicle having at least four hydraulically controllable wheel brakes (8a-8d), comprising, for each of the wheel brakes (8a-8d), an electrically controllable, currentless open first wheel valve (6a-6d) and an electrically controllable, currentless closed second wheel valve (7a-7d), a first electrically controllable pressure source (5), which is connected to the first wheel valves (6a-6d) by a first brake supply line (13), wherein an electrically controllable circuit breaker valve (9) is arranged in the first brake supply line (13), by means of which two of the first wheel valves (6c, 6d) can be hydraulically separated from the first pressure source (5), a second electrically controllable pressure source (2) and a pressure medium reservoir (4), which is in particular under atmospheric pressure, wherein the circuit breaker valve (9) is designed to be currentless open and the second electrically controllable pressure source (2) is connected to the second wheel valves (7a-7d) via a second brake supply line (33). The invention further relates to methods for the operation thereof.

Description

BRAKING SYSTEM AND TWO METHODS FOR OPERATING SUCH A BRAKING SYSTEM

The invention relates to a brake system according to the preamble of claim 1 and a method for operating such a brake system.

From DE 10 2013217 954 AI a generic brake system with two electrically controllable pressure sources for a motor vehicle with four hydraulically actuated wheel brakes is known. The wheel brakes are to operate in different

Operating modes connected to the two electrically controllable pressure sources as well as with a brake master cylinder brake master cylinder. The brake system comprises wheel-individual inlet valves, wheel-individual exhaust valves which connect the wheel brakes with the pressure medium reservoir, a normally closed circular valve and a total of four isolation valves for separating the master cylinder and the electrically controllable pressure sources from the inlet valves. The Kreistrennventil basically separates the brake circuits, so that in the first brake circuit exclusively from the first

Pressure source and in the second brake circuit is constructed solely by the second pressure source brake pressure. A compound of the brake circuits through the Kreistrennventil is only made if one of the two pressure sources is severely impaired in function or fails. Furthermore, the brake system of 10 2013 217 954 AI includes a central control unit, a first pressure source associated with the first control unit and a second pressure source associated second control unit. The first and second control and regulating units are each used to control the corresponding pressure source. By means of the central control and regulating unit, the Kreistrennventil is actuated. In future brake systems, which should also be suitable for highly automated driving, should be on a return ^¬ fallebene, in which the driver can be operated by muscle power wheel brakes omitted. For this and also for highly automated driving to the braking devices must have a suffi ^¬-reaching availability and "fail-operational" out ^¬ leads his This applies to a hydraulic failure, such as a leak or an electrical fault such as a failure of an electrical. Power source or a failure of an electronic drive device.

It is an object of the present invention to provide a brake system with two electrically actuated pressure sources and a method for operating such a brake system, which is suitable for highly automated or autonomously driving vehicles and has a correspondingly sufficient availability. In this case, the brake system should be inexpensive to produce. This object is achieved by a brake system according to claim 1 and a method for operating according to claim 13 or 15.

The invention is based on the idea that for each of the wheel brakes an electrically actuated, normally open open executed first wheel valve and an electrically operable, normally closed executed second wheel valve is provided and that the first electrically actuatable pressure source via a first brake supply line to the first, normally open executed wheel valves is connected and the second electrically actuated pressure source via a second

Brake supply line is connected to the second, normally closed closed wheel valves, wherein in the first brake supply line an electrically actuated, de-energized arranged open Kreistrennventil is arranged, by means of which two of the first wheel valves can be hydraulically separated from the first pressure source. The Kreistrennventil allows a need for division into two brake circuits, each with at least two wheel brakes and so a diaphragm between the brake circuits. In principle, in particular in the de-energized state of the brake system, the first electrically actuable pressure source, however, is connected to actuate the wheel brakes with each of the wheel brakes via the respective first, normally open, open wheel valve. The second electrically betae ^¬ tigbare pressure source is connected to actuate the wheel brakes to each of the second wheel valves. An advantage of the invention is that - despite high availability in hydraulic or electrical errors - compared to known brake systems with two electrically controllable pressure sources less electrically actuated valves are needed, especially can be dispensed between the pressure sources and the wheel valves separating valves.

Preferably, no electrically operable valve is arranged between the first pressure source and the other first wheel valves. Particularly preferably, no valve, that is to say no check valve, is arranged between the first pressure source and the other first wheel valves. This means that an isolation valve between the first pressure source and the (all) first wheel valves, as e.g. is known from DE 10 2013 217 954 AI, is omitted, thereby reducing manufacturing costs.

Preferably, in the second brake supply line, ie in the hydraulic connection between the second electrically actuable pressure source and the second wheel valves, no arranged electrically actuated valve. This saves costs and avoids unnecessary flow resistance between the pressure source and wheel valves. Particularly preferably, no valve, that is to say no check valve, is arranged in the second brake supply line. In other words, the second electrically actuable pressure source is preferably connected directly to each of the second wheel valves. This means, on the one hand, that only one of the two brake supply lines (namely the first brake supply line) has an electrically actuated circular selector valve, by means of which a part of the corresponding (namely the first) wheel valves are hydraulically separated from the corresponding pressure source (namely the first pressure source) can. In the second brake supply lines no Kreistrennventil is arranged. However, this also means that no separating valve between the second pressure source and the (all) second wheel valves is provided.

The two first wheel valves, which can be hydraulically separated from the first pressure source, are preferably assigned to the wheels of a first vehicle axle, while the other first wheel valves are assigned to the wheels of another vehicle axle. Advantageously, the first vehicle axle is the front axle and the other vehicle axle is the rear axle. According to a preferred embodiment of the invention, the brake system comprises a first electronic device, by means of which the first pressure source is actuated, and a second electronic device, by means of which the second pressure ^¬ source is actuated. In this case, the second electronic device is electrically independent of the first electronic device, so that an electrical or electronic fault in one of the electronic devices does not lead to failure of both electronic devices. _π

5

The two electronic devices are electrically independent of each other in the sense that failure of the first electronic device does not cause failure of the second electronic device, and vice versa, i. the two electronic devices are galvanically isolated.

Preferably, the first electronic device is powered by a first electrical energy source and the second electronic device is powered by a second electrical energy source, wherein the first electrical energy source is independent of the second electrical energy source. Alternatively, it is preferred that the first electronic device comprises a first electrical energy source and the second electronic device comprises a second electrical energy source, wherein the first electrical energy source is independent of the second electrical energy source.

The two electronic devices may be housed in a common housing or on a common circuit board, e.g. in a common electronic control unit (ECU), be arranged. Alternatively, the two electronic devices may be housed in two separate housings or on two separate circuit boards, e.g. in two electronic control units (ECU1, ECU2), be arranged.

The first electronic device is designed for actuating or activating the first pressure source. The first pressure source is preferably also supplied with electrical energy by the first electronic device. Accordingly, by means of the second electronic device, the second

Pressure source operated or controlled. Preferably, the second pressure source is also supplied by the second electronic device with electrical energy. .

b

The first and the second wheel valves are preferably actuated by means of the second electronic device. Thus, an actuation of the wheel brakes is possible even in the event of a failure of the first electronic device or of the first energy source, by controlling the second pressure source, closing the first wheel valves and opening the second wheel valves by means of the second electronic device. The first and second wheel valves are particularly preferably actuated exclusively by means of the second electronic device so as not to have to provide any more costly, double-controllable valves.

Depending wheel brakes a wheel speed sensor is preferably provided, wherein the signals of the wheel speed sensors of the second electronic device are supplied for evaluation. Thus, in the event of failure of the first electronic device, a wheel-specific brake pressure control (e.g., slip control) may be performed by the second electronic device. Particularly preferably, the wheel speed sensors are supplied with electrical energy by the second electronic device.

The circular selector valve is preferably actuated by means of the first electronic device. Thus, in the case of a failure of the second electronic device or the second energy source, and thus the controllability of the wheel valves, a pressure supply by means of the first pressure source and at least one circular or axial blending performed or circular or axle different brake pressures a be put. The circular selector valve is particularly preferably actuated exclusively by means of the first electronic device. Preferably, a driving dynamics sensor is provided, wherein the signals of the vehicle dynamics sensors of the first electronic device are supplied to the evaluation, since the first electronic device associated with the first pressure source is designed for pressure delivery with the highest comfort and dynamics. Particularly preferably, the driving dynamics sensor system is supplied with electrical energy by the first electronic device. Preferably, a redundant executed pressure sensor is provided in each brake circuit to allow control of the pressure in the brake circuit. The pressure sensor particularly preferably measures the wheel brake pressure of a wheel brake of the brake circuit. Preferably, for two of the wheel brakes arranged between the first and the second wheel valve of the wheel, redundantly executed pressure sensor is provided.

Preferably, at least the first pressure source is designed as a cylinder-piston arrangement with a pressure chamber which is delimited by a piston, which by means of an electric motor and a rotational-translation gear for a pressure build-up in an operating direction and for a pressure reduction in the operating direction opposite direction is displaced. Such pressure sources can adjust as needed with high precision temporal brake pressure curves.

Preferably, the cylinder-piston arrangement is designed such that the pressure chamber is connected in an unactuated state of the piston via at least one Schnüffelloch with the pressure medium reservoir, wherein this connection is interrupted upon actuation of the piston. Preferably, in the pressure chamber of the cylinder-piston arrangement, a reset element is provided which positions the piston in the unconfirmed state in de-energized electric motor ^¬. Advantageously, the rotation-translation gear is not designed to be self-locking. Thus, in case of failure of the first pressure source or the first electronic device, the piston is positioned in the unactuated state, whereby the connection from the pressure chamber to the pressure medium reservoir is open. By means of this connection, in the case of an anti-skid control, pressure medium can then flow away via one of the first valves and the pressure chamber of the first pressure source to the pressure medium reservoir in order to carry out a pressure reduction at the associated wheel brake. In the case of a currentless electric motor, the return element particularly preferably positions the piston against a stop against the actuation direction.

According to a preferred embodiment of the invention, the second pressure source is designed as a piston pump whose suction side with the pressure medium reservoir and the

Pressure side is connected to the second brake supply line, wherein the piston pump is an electrically operable

Isolating valve is connected in parallel hydraulically. This means that between the second brake supply line and the pressure medium reservoir, a hydraulic connection is present, in which the isolation valve is arranged. About this connection pressure medium can be discharged from one of the wheel brakes on the corresponding second wheel valve in the pressure fluid reservoir, for example, at a pressure supply by means of the first pressure source to perform a pressure reduction at the corresponding wheel brake (eg for a wheel-individual pressure control). The parallel ge ^¬ switched divider allows for pressure supply by the piston pump pressure control by overflow. The isolation valve is particularly preferably closed normally executed in order to prevent inadvertent flow of pressure medium into the pressure medium reservoir.

The brake system preferably comprises a simulation device which can be actuated by means of a brake pedal, wherein no mechanical and / or hydraulic operative connection is provided between the brake pedal and the wheel brakes.

The invention also relates to a method for operating a brake system with two electrically actuated pressure sources.

Preferably, in the event of failure of the first pressure source or first electronic device by means of the second electronic device, the first wheel valves are closed and the second wheel valves are opened and the second pressure source is actuated to build up a pressure. This is particularly preferably carried out during normal braking.

In the event of a failure of the first pressure source or first electronic device, a wheel-specific brake pressure control is preferably carried out by means of the second electronic device, wherein a pressure reduction is performed on one of the wheel brakes by opening the corresponding first wheel valve, wherein pressure medium via the Kreistrennventil and the first pressure source to drains off the pressure medium reservoir.

The first pressure source for establishing a braking pressure circuit and the isolating valve are preferably actuated for adjusting brake pressures of individual circular ^¬ upon failure of the second pressure source or second electronic device by the first electronic device.

In a normal operating mode, a normal mode of operation is preferred. only the first pressure source to build up a pressure for actuating the wheel brakes driven. In this case, none of the valves (ie no first wheel valve, no second wheel valve, no Kreistrennventil) is actuated.

A normal braking is understood to mean a braking initiated by a driver or an autopilot function in which all wheel brakes are subjected to the same brake pressure and no wheel-specific brake pressure regulation takes place.

In the normal operating mode, a wheel-specific slip control is preferably carried out by activating the first wheel valves and the second wheel valves, a pressure reduction being carried out on one of the wheel brakes by opening the corresponding second wheel valve and the separating valve.

Further preferred embodiments of the invention will become apparent from the dependent claims and the following description with reference to a figure.

It shows schematically

Fig. 1 shows an embodiment of an inventive

Brake system.

In Fig. 1, an embodiment of a brake system according to the invention for a motor vehicle with four hydraulically betä ^¬ tigbaren wheel brakes 8a-8d is shown schematically. The

Brake system comprises a first electrically controllable pressure source 5, a second electrically controllable pressure source 2, a pressurized medium reservoir 4 under atmospheric pressure and a first electrically operable wheel valve 6a-6d (also called intake valve) per wheel brake 8a-8d and a second electrically actuated wheel valve 7a-7d (also called outlet valve). The first wheel valves 6a-6d are designed to be normally open, the second wheel valves 7a-7d are designed to be normally closed. The first wheel valves 6a-6d are advantageously carried out analogized or analog controlled to allow an exact Druckein- position at the wheel brakes 8a-8d.

For actuating the wheel brakes 8a-8d, both the first electrically actuable pressure source 5 and the second electrically actuatable pressure source 2 are connected to each of the wheel brakes 8a-8d in a hydraulically separable manner. This is the first one

Pressure source 5 via a first brake supply line 13 to the first wheel valves 6a-6d, the second pressure source 2 is connected via a second brake supply line 33 to the second wheel valves 7a-7d.

Each of the wheel brakes 8a-8d is thus assigned a normally open, first wheel valve 6a-6d and a normally closed, second wheel valve 7a-7d. In this case, the first electrically actuable pressure source 5 is connected to the wheel brakes 8a-8d via the first wheel valves 6a-6d (or the first pressure source is connected to each of the wheel brakes via the respective first wheel valve) and the second electrically actuatable pressure source 2 is via the second wheel valves 7a-7d connected to the wheel brakes 8a-8d (or the second pressure source is connected to each of the wheel brakes via the respective second wheel valve). The brake system does not include any other (wheel) valves associated with the individual wheel brakes 8a-8d.

For each wheel brake 8a, 8b, 8c, 8d, an output port of the first wheel valve 6a, 6b, 6c, 6d and an output port of the second wheel valve 7a, 7b, 7c, 7d are interconnected and connected to the wheel brake. The input terminals of the second wheel valves 7a-7d are directly hydraulically connected via the second brake supply line 33 to the second pressure source 2 or the pressure space thereof. "Directly hydraulically connected" is to be understood here in the sense that no electrically operable valve or even no valve (eg check valve) is arranged in the second brake supply line 33. Thus, it is neither a circular valve for separating the second pressure source from a part of the wheel brakes nor provided a separating valve for separating the second pressure source of all wheel brakes.

In the first brake supply line 13, an electrically actuated, normally open open circular valve 9 is arranged. By the Kreistrennventil 9 two of the first wheel valves, namely the wheel valves 6c and 6d, are hydraulically separated from the first pressure source 5. In other words, the recirculation valve 9 is arranged in the first Bremsversor ^¬ supply line 13, that when closing the Kreistrennventils the brake supply line 13 is hydraulically separated into a first line section 13a and a second line section 13b, wherein the first line section 13a with the first wheel valves 6a and 6b and the second Lei ^¬ processing section 13b with the other first wheel valves 6c and 6d is connected. The first line section 13a connects the first pressure source 5 with the first wheel valves 6a and 6b and the circular valve 9 and the second line section 13b ver ^¬ binds the Kreistrennventil 9 with the first wheel valves 6c and 6d. In this sense, the brake system is in a first brake circuit I for the wheel brakes 8a and 8b and a second brake circuit II for the wheel brakes 8c and 8d separated with a closed circuit valve 9.

The input terminals of the first wheel valves 6a-6d are connected to the first pressure source 5 via the first brake supply line 13 or whose pressure chamber is hydraulically connected, wherein the input terminals of the first wheel valves 6a and 6b (the first brake circuit I) are hydraulically connected directly to the first pressure source 5 and the pressure chamber and the input terminals of the first wheel valves 6c and 6d (the second brake circuit II) via the circular valve 9 with the first pressure source 5 and the pressure chamber are hydraulically connected.

Each brake circuit I, II is a redundant executed pressure sensor available. Between wheel valve 6a and 7a, the redundantly executed pressure sensor 12a is connected, which measures the pressure in the wheel brake 8a. Connected between the wheel valve 6d and 7d is the redundantly designed pressure sensor 12b, which measures the pressure in the wheel brake 8d.

The exemplary brake system comprises per wheel brake 8a-8d a wheel speed sensor 10a-10d or is connected to such.

Furthermore, a driving dynamics sensor 60 is provided by means of which at least one, preferably all, of the following variables is detected: longitudinal vehicle acceleration, vehicle lateral acceleration, vehicle yaw rate and steering angle.

The brake system comprises or is connected to two redundant electrical energy sources (for example, electrical systems), which are referred to below as the first electrical energy source and the second electrical energy source.

The brake system comprises a first electronic device A and a second electronic device B, wherein the second electronic device B is electrically independent of the first electronic device A. The electronic devices A, B are galvanically isolated. In case of an error in the first electronic device A, for example by a electrical defect, the second electronic device remains fully functional.

The electronic device A comprises electrical and / or electronic components for controlling and actuating the first pressure source 5 (indicated by the arrow with A in FIG. 1). Device A may e.g. be executed as a first electronic control unit or as a first part of an electronic control unit.

The electronic device A, the first electrical energy source, through which 5 is supplied with energy, the apparatus A itself and the source of pressure include, or pre ^¬ direction A with the first source of electrical energy (eg, the first vehicle electrical network).

The first pressure source 5 can be supplied directly from the first source of electrical energy with energy, or from pre ^¬ direction A (that is, indirectly, by the first electrical energy source).

The electronic device B comprises electrical and / or electronic components for controlling and actuating the second pressure source 2 (indicated by the arrow with B in FIG. 1). Device B may e.g. be designed as a second electronic control unit or as a second part of an electronic control unit.

The electronic device B, the second source of electrical energy, by which the device B itself and the pressure source 2 is supplied with energy, include or Above ^¬ direction B is connected to the second electrical power source (the second vehicle electrical system, for example). In any case, it is advantageous for a sufficient availability of the brake system that the second electrical energy source is independent of the first energy source.

The second pressure source 2 can be supplied directly from the second electrical energy source with energy, or from pre ^¬ direction B (ie indirectly by the second electrical energy source).

The first wheel valves 6a-6d as well as the second wheel valves 7a-7d are actuated by the second electronic device B (indicated by arrows with B in FIG. 1). By way of example, the wheel valves are not operable by the first electronic device A, i. the second wheel valves are operated exclusively by means of the second electronic device B.

The circular valve 9 is actuated by the first electronic device A (indicated by the arrow with A in Fig. 1). By way of example, the circular valve is not operable by the electronic device B, i. the

Circular valve is actuated exclusively by means of the first electronic device A.

The signals of the wheel speed sensors 10a-10d are supplied to the second electronic device B for evaluation (indicated by arrows with B in FIG. 1). The wheel speed sensors 10a-10d can be supplied with electrical power from the second electronic device B. The signals of the driving dynamics sensor 60 are supplied to the first electronic device A for evaluation (indicated by the arrow with A in FIG. 1). The vehicle dynamics sensor system 60 can be supplied with electrical energy by the first electronic device A. Example According to the first pressure source 5 by a so-called ^¬ linear actuator (cylinder-piston assembly) is formed. For this purpose, the pressure source 5 to an electric motor 22, the rotational movement is converted by means of a schematically indicated rotation-translation gear 23 in a translational movement of a piston 21, for a

Pressure buildup is moved in an operating direction 24 in a hydraulic pressure chamber 20. For a pressure reduction, the piston 21 is displaced in the direction opposite to the direction of actuation 24.

The pressure chamber 20 of the first pressure source 5 is, regardless of the operating state of the piston 21, hydraulically connected to the first Bremsver ^¬ sorgungsleitung 13.

The pressure chamber 20 is also connected in an unactuated state of the piston 21 via one or more sniffer holes and a return line 26 to the pressure medium reservoir 4. The connection between the pressure chamber 20 and return line 26 (and thus pressure fluid reservoir 4) is at a

(sufficient) actuation of the piston 21 in the direction of actuation 24 separately.

Thus, in a de-energized state of the electric motor 22, a hydraulic connection between the pressure chamber 20 and Druckmit ^¬ telvorratsbehälter 4 is in the pressure chamber 20, a return element 25, for example a compression spring, is provided, which in electroless electric motor 22, the piston 21 in the unactuated state, eg at a stop against the operating direction, positioned. In order to make this possible, the rotation-translation gear 23 is not designed to be self-locking.

Thus, when the electric motor 22 (and de-energized first wheel valves 6a-6d) are not energized, the wheel brakes 8a-8d are in contact with the pressure medium reservoir 4 connected in the sense of pressure equalization. For example, brake pressure in the wheel brakes 8a-8d can be reduced. According to the example, the second pressure source 2 is designed as a piston pump (eg radial piston pump). The suction side 40 of the piston pump is connected via a suction line 46 with the Druckmit ^¬ telvorratsbehälter 4. The pressure side 42 of the piston pump is connected to the second brake supply line 33, and thus the second wheel valves 7a-7d. On or before the suction port of the plunger pump in a closing direction of the pressure medium supply container 4 ^¬ check valve before ^¬ is seen. At or before the pressure connection of the piston pump, a check valve opening in the direction of the brake supply line 33 is provided. The said check valves are usually part of the piston pump.

Advantageously, the piston pump, a normally closed ^¬ closed isolation valve 3 is connected in parallel hydraulically, which is used to control the pressure of the piston pump by over ^¬ flow. According to the example, a hydraulic connection 47 is provided between brake supply line 33 and intake line 46, in which the separating valve 3 is arranged.

The piston pump and the separating valve 3 are operated, for example, exclusively by means of the second electronic device B. Instead of the unit of piston pump with separating valve 3 and the use of a second linear actuator as the second

Pressure source possible. The brake system of the example according to Fig. 1 comprises ^¬ advantageous way enough, a total of only ten solenoids 6a-6d, 7a-7d, 3, 9.

By way of example, the wheel brakes 8a and 8b are one of the vehicle axles (e.g., the rear axle HA) and the wheel brakes 8c and 8d of the other vehicle axle (e.g., the front axle)

VA) assigned.

The invention provides a redundant braking system, which is particularly suitable for future vehicles for the realization of high automation ^¬ terraced driving functions. The play-date at ^¬ brake system is able to implement autonomous Bremsan ^¬ requirements. Even after serious errors, such as a primary electrical system power failure, the exemplary brake system is able to realize the following important ^¬ most residual braking functions (primary functions) of a brake system autonomous or controlled by an autopilot:

Build up delay,

- Adhere to the blocking order of the axles to avoid breaking the vehicle's rear even when cornering, maintain steerability to allow the (auto) pilot also braked evasive maneuvers. Example According to a hydraulic brake system is pre ^¬ propose that contains two electrically actuatable pressure sources, a Raddruckmodulationsgruppe of first and second wheel valves and at least one additional interconnection for ^¬ not manoeuvrable and useful valve. The brake system includes no hydraulic auxiliary level, but the driver a DAU ^¬ manent hydraulic isolation (the brake pedal 1). The exemplary brake system comprises a first (primary) pressure source 5, which is designed as a linear actuator (cylinder-piston Anord ^¬ tion), and a second (secondary) pressure source 2, which includes a radial piston pump, and eight

Wheel (s) 6a-6d, 7a-7d. The radial piston pump is a normally closed separating valve 3 as overflow valve to ^¬ ordered, by the control of a pressure relief and pressure reduction can be realized. The exemplary brake system has the advantage that can be dispensed for the first pressure source on a separating valve (also called Zuschaltventil), since the second pressure source is connected via the normally closed second wheel valves with the wheel brakes.

The first pressure source 5 is the high-performance pressure plate, which realizes standard brakes in the highest possible comfort and dynamics in the error-free system. During a normal braking in the "by-wire operation" (especially in error-free system operation) no valves are switched and the wheel brakes 8a-8d are "single-circuit" via the first valves 6a-6d (and the normally open circular valve 9) hydraulically to the first Pressure source 5 coupled. By driving over the Schnüffellochs with the piston 21, the pressure build-up in the pressure chamber 20th

Methods for operating the exemplary brake systems are described below.

If one of the two pressure sources 2, 5 fails due to an error (for example due to an energy supply failure), then the respective other pressure sources 5, 2 can still actuate all the wheel brakes 8a-8d. The following control strategies are performed for a residual brake function after an error.

In case of failure of the first energy source or the first electronic device:

The second electronic device B (or the second electrical energy source) of the second pressure source 2, the wheel valves 6a-6d, 7a-7d are assigned, ie they are operated by the device B and the second power source supplied. Likewise, the wheel speed sensors or their signal detections are assigned to the second electronic device B (or the second electrical energy source). The second electronic device B can now perform as such known anti-lock regulations or wheel-specific rule ^¬ functions and together with the possibility

Build brake pressure (by pressure source 2), all

Realize residual braking functions. In wheel-individual control, the second (normally closed) wheel valves 7a-7d are operated as intake valves and the first (normally open) wheel valves 6a-6d are operated as exhaust valves. In case of failure of the second power source or the second electronic device:

The first electronic device A (or the first electrical energy source) is associated with the first pressure source 5 and the circular selector valve 9, as well as the entire vehicle dynamics sensor system 60 (eg for detecting longitudinal acceleration, lateral acceleration, yaw rate and steering angle signal). Pressure source 5 can now control the pressure in addition to the pressure still central with very high dynamics and accuracy. The Kreistrennventil 9 (or the ability to operate this) even allows that brake circuits or axles under ^¬ different pressures can be adjusted. This is done by an axis-multiplexing method. The performance of this control strategy is not at the level of the faultless system in terms of braking performance. However, it is sufficient to be signed ^¬ case of failure to ensure the residual brake functions.

Claims

claims

1. brake system for a motor vehicle with at least four

hydraulically actuatable wheel brakes (8a-8d), comprising · for each of the wheel brakes (8a-8d) an electrically actuated, normally open open first wheel valve (6a-6d) and an electrically actuated, normally closed closed second wheel valve (7a-7d),

A first electrically actuable pressure source (5) which is connected via a first brake supply line (13) to the first wheel valves (6a-6d), wherein in the first brake supply line (13) an electrically operable Kreistrennventil (9) is arranged, by means of which two of the first wheel valves (6c, 6d) can be hydraulically separated from the first pressure source (5),

• a second electrically operated pressure source (2), and

A pressure medium reservoir (4), in particular under atmospheric pressure,

characterized in that

the recirculation valve (9) is designed to be normally open and the second electrically actuable pressure source (2) is connected to the second wheel valves (7a-7d) via a second brake supply line (33).

2. Brake system according to claim 1, characterized in that in the second brake supply line (33) between the second pressure source (2) and second wheel valves (7a-7d) no electrically operable valve, in particular no valve, is arranged. Brake system according to claim 1 or 2, characterized in that no valve is arranged between the first pressure source (5) and the other first wheel valves (6a, 6b).

Brake system according to one of the preceding claims, characterized in that it has a first electronic Vor ^¬ direction (A), by means of which the first pressure source (5) is actuated, and a second electronic device

(B), by means of which the second pressure source (2) is actuated, wherein the second electronic device

(B) is electrically independent of the first electronic device (A).

Brake system according to claim 4, characterized in that the first and the second wheel valves (6a-6d, 7a-7d), in particular exclusively, by means of the second elekt ^¬ ronic device (B) are actuated.

Brake system according to claim 4 or 5, characterized in that per wheel brake, a wheel speed sensor (10a-10d) is provided, the signals of the wheel speed sensors of the second electronic device (B) are supplied for evaluation, and in particular the wheel speed sensors of the second electronic device ( B) are supplied with electrical energy.

Brake system according to one of claims 4 to 6, characterized in that the circular selector valve (9), in particular exclusively, by means of the first electronic device (A) is actuated.

Brake system according to one of claims 4 to 7, characterized in that a driving dynamics sensor (60) is seen before ^¬ , wherein the signals of the driving dynamics sensor of the first electronic device (A) are supplied for evaluation, and in particular the driving dynamics sensor of the first electronic device (A) with

electrical energy is supplied.

Brake system according to one of the preceding claims, characterized in that at least the first pressure source (5) is designed as a cylinder-piston arrangement with a pressure chamber (20) which is bounded by a piston (21) by means of an electric motor (22 ) and a rotational translational gear (23) for pressure build-up in an actuating direction (24) and for a pressure reduction in the direction opposite to the direction of actuation is displaceable.

Brake system according to claim 9, characterized in that the pressure chamber (20) in an unactuated state of the piston (21) via at least one Schnüffelloch with the pressure fluid reservoir (4) is connected, said connection being interrupted upon actuation of the piston (21).

Brake system according to claim 9 or 10, characterized in that in the pressure chamber (20) is provided a return element (25) which, when the electric motor (22) is de-energized, positions the piston (21) in the unactuated state.

Brake system according to one of the preceding claims, characterized in that it comprises a by means of a brake pedal (1) operable simulation device (30), wherein no mechanical and / or hydraulic operative connection between the brake pedal (1) and the wheel brakes (8a-8d) is provided ,

Method for operating a brake system according to one of Claims 1 to 12, characterized in that in case of failure of the first pressure source (5) or first electronic ^¬ African device (A) by means of the second electronic device (B), the first wheel valves (6a-6d) closed and the second wheel valves (7a -7d) are opened and the second pressure source (2) is actuated to build up a pressure.

14. The method according to claim 13, characterized in that in case of failure of the first pressure source (5) or first electronic device (A) a wheel-individual

Brake pressure control by means of the second electronic device (B) is performed, wherein a pressure reduction is performed on one of the wheel brakes by opening the corresponding first Radventils (6a-6d), said pressure means via the Kreistrennventil (9) and the first pressure source (5) to the Pressure medium reservoir (4) flows off.

15. A method for operating a brake system according to one of claims 1 to 12, in particular according to one of claims 13 or 14, characterized in that in case of failure of the second pressure source (2) or second electronic device (B) by means of the first electronic device ( A) the first pressure source (5) for building up a brake pressure and the Kreistrennventil (9) for adjusting kreisindivi ^¬ dueller brake pressures is actuated.