DE102022202832A1 - Braking system and method of operating same - Google Patents

Abstract

Brake system (1) for a motor vehicle for at least four hydraulically actuated wheel brakes (8a-8d) with a pressure medium reservoir (40) under atmospheric pressure, with a first brake control unit (100) comprising at least four output connections (4a-4d) for connection to one of the hydraulically actuated wheel brakes (8a-8d), an electrically actuated inlet valve (6a-6d) per wheel brake, an electrically actuated outlet valve (7a-7d) per wheel brake, by means of which the assigned output connection can be connected to the pressure medium reservoir (40), and a first electrically controllable hydraulic pressure source (5), which comprises a cylinder-piston arrangement with a pressure chamber (30), the piston (31) of which can be pushed back and forth by an electromechanical actuator (32, 33), the pressure chamber (30) also a brake line section (60) to which the at least four inlet valves (6a-6d) are connected, and to a second brake control unit (200), which is hydraulically connected between two of the output connections (4a, 4b) of the first brake control unit (100) and two the wheel brakes (8a, 8b) is switched, and which comprises a second electrically controllable hydraulic pressure source (2), the pressure chamber (30) being connected to the brake line section (60) and at least one of the inlet valves via an electrically actuated pressure switching valve (9). (6a-6d) a check valve closing in the direction of the assigned output connection (4a-4d) is connected in parallel, as well as methods for their operation.

Description

The invention relates to a braking system for a motor vehicle according to the preamble of claim 1 and a method for operating it.

From the DE 10 2017 211 953 A1 is a brake system known with a primary brake control unit comprising a first electrically actuated pressure source as well as inlet and outlet valves for four hydraulically actuated wheel brakes, an additional module with a second electrically actuated pressure source, which is hydraulically connected between the primary brake control unit and two of the wheel brakes, and a hydraulic Simulation unit, which is connected to the pressure medium reservoir of the primary brake control unit. The pressure chamber of the first pressure source is connected to the inlet valves via a check valve that closes in the direction of the pressure chamber, so that a backflow of brake fluid from the direction of the wheel brakes via the inlet valves into the pressure chamber is prevented.

It is the object of the present invention to provide an alternative braking system for a motor vehicle that is suitable for highly automated driving, which can dispense with a mechanical and/or hydraulic fallback level and yet still has a high level of availability and thus ensures sufficient safety for highly automated driving or a Autopilot function offers.

This object is achieved according to the invention by a brake system according to claim 1 and a method for operating it according to claim 14.

The invention is based on the idea that the brake system comprises a pressure medium reservoir under atmospheric pressure, a first brake control unit and a second brake control unit. The first brake control unit comprises at least four output connections for connection to one of the hydraulically actuated wheel brakes, an electrically actuated inlet valve for each wheel brake, an electrically actuated outlet valve for each wheel brake, by means of which the assigned output port can be connected to the pressure medium reservoir, and a first electrically controllable hydraulic pressure source, which comprises a cylinder-piston arrangement with a pressure chamber, the piston of which can be pushed back and forth by an electromechanical actuator, the pressure chamber being connected to a brake line section to which the at least four inlet valves are connected. The second brake control unit is connected hydraulically between two of the output connections of the first brake control unit and two of the wheel brakes and includes a second electrically controllable hydraulic pressure source. The pressure chamber of the first pressure source is connected to the brake line section via an electrically actuated pressure switching valve and at least one of the inlet valves is connected in parallel with a check valve that closes in the direction of the assigned output port. This allows pressure medium to flow from the output port towards the pressure chamber. When the pressure switching valve is open, a backflow of pressure medium from at least one of the output connections or wheel brakes into the pressure chamber is possible, even regardless of the switching state of the inlet valves.

Preferably, each of the inlet valves is connected in parallel with a check valve that closes in the direction of the associated output port. This makes it possible to equalize the pressure more quickly.

In the case of wheel brakes connected to the brake system, at least two of the wheel brakes are preferably hydraulically connected to the corresponding output connections of the first brake control unit via the second brake control unit, while the other wheel brakes are hydraulically connected directly, without the interposition of further valves, to the corresponding output connections of the first brake control unit.

In particular, the wheel brakes of the front axle of the motor vehicle are hydraulically connected to the first brake control unit via the second brake control unit and the wheel brakes of the rear axle of the motor vehicle are hydraulically connected directly to the first brake control unit.

The braking system preferably has a first on-board electrical system and a second on-board electrical system, the first brake control unit being supplied with electrical energy by the first on-board electrical system and the second brake control unit being supplied with electrical energy by the second on-board electrical system. Even if one of the on-board electrical systems fails, an electrically controlled pressure build-up for at least two of the wheel brakes is possible using one of the two electrically actuated pressure sources.

Advantageously, the first brake control unit and the second brake control unit are designed as structurally separate components. This means they can be arranged separately in the motor vehicle.

The brake system is advantageously designed entirely for by-wire operation, so that no master brake cylinder that can be actuated using the brake pedal is provided.

The first brake control unit preferably includes a first electronic control and regulation unit unit, which actuates the inlet and outlet valves, the first electrically controllable hydraulic pressure source and the pressure switching valve. Particularly preferably, the inlet and outlet valves, the first electrically controllable hydraulic pressure source and the pressure switching valve are actuated exclusively by means of the first electronic control and regulation unit.

In addition to the inlet and outlet valves and the pressure switching valve, the first brake control unit preferably does not include any other electrically actuated valve.

The outlet valves are preferably connected to a first connection of the pressure medium storage container and the pressure chamber is connected to a second connection of the pressure medium storage container via a suction valve. The re-suction valve is particularly preferably designed as a check valve that opens in the direction of the pressure chamber.

Preferably, the second brake control unit comprises a separation valve for each of the two associated wheel brakes, which is arranged hydraulically between the corresponding output port of the first brake control unit and the corresponding wheel brake. To build up pressure using the second pressure source, the isolating valves are closed.

The second brake control unit preferably comprises a second electronic control and regulation unit, which actuates the second electrically controllable hydraulic pressure source. The isolating valves are particularly preferably operated exclusively by means of the second electronic control and regulation unit.

The first electronic control and regulation unit and the second electronic control and regulation unit are preferably connected to one another via a communication bus.

The isolating valves are also preferably operated, particularly preferably exclusively, by means of the second electronic control and regulation unit.

Preferably, the second brake control unit comprises at least one pressure medium reservoir arranged in the second brake control unit and under atmospheric pressure for providing pressure medium for the second pressure source. The pressure medium reservoir is particularly preferably connected to a third connection of the pressure medium reservoir.

The second pressure source preferably comprises at least one pump which is driven by an electric motor and whose suction side is hydraulically connected to the pressure medium reservoir.

According to a preferred embodiment of the brake system, the pressure switching valve is designed to be normally closed, the inlet valves are designed to be normally open and the outlet valves are designed to be normally closed. By opening one of the outlet valves, pressure can be equalized with the pressure medium reservoir, for example. B. to prevent unwanted wheel braking torque and thus over-braking or damage to the braking system.

According to a preferred embodiment of the brake system, the pressure switching valve is designed to be normally closed, the inlet valves are designed to be normally open and at least one of the outlet valves is designed to be normally open, while the remaining exhaust valves are designed to be normally closed. Particularly preferably, an outlet valve, which is connected to the wheel brake without the interposition of the second brake control unit, is designed to be open without current. Particularly preferably, an outlet valve of a rear wheel brake is designed to be open when de-energized. In non-energized operation, the wheel brakes are connected to the pressure medium reservoir through the normally open outlet valve and the pressure can be equalized to the atmosphere.

According to a preferred alternative embodiment of the brake system, the pressure switching valve is designed to be normally open. The first electrically controllable hydraulic pressure source has at least one sniffer hole, via which the pressure chamber of the first pressure source is connected to the pressure medium reservoir when the piston is not actuated. Particularly preferably, the pressure chamber is connected to the second connection of the pressure medium reservoir via the sniffer hole. When the brake system / the first pressure source is not actuated, the wheel brakes are connected to the pressure medium reservoir via the sniffing hole and the pressure can be equalized to the atmosphere. Particularly preferably, the suction valve and the sniffer hole are connected to the same connection of the pressure medium reservoir.

Preferably, the two wheel brakes assigned to the second brake control unit are assigned to the front axle of the motor vehicle and the other wheel brakes are assigned to the rear axle of the motor vehicle.

The brake system preferably includes no further hydraulic pressure source, in particular no further electrically controllable hydraulic one Pressure source and no brake pedal actuated master brake cylinder.

The brake system can preferably be controlled by means of an electronic brake pedal, which is not hydraulically connected to the brake system. In particular, the electronic brake pedal or its brake pedal feel simulation device is not hydraulically connected to the pressure medium reservoir. The electronic brake pedal is preferably only electrically connected to the brake system.

The electronic brake pedal preferably comprises a first braking request detection sensor and a second braking request detection sensor, wherein the signal of the first braking request detection sensor of the first brake control unit, in particular the first electronic control and regulation unit, and the signal of the second braking request detection sensor of the second brake control unit, in particular of the second electronic control and regulation unit , is supplied.

A pressure sensor is preferably provided between the pressure switching valve and inlet valves to determine and regulate the pressure provided by the first pressure source.

The invention also relates to a method for operating a brake system according to the invention. Here, a thermal load on the brake system is monitored before the brake system is switched off. The braking system is only switched off when the thermal load has fallen below a specified limit.

This method is preferably carried out in a brake system with a normally closed pressure switching valve, in which all inlet valves are designed to be normally open and all outlet valves are designed to be normally closed.

Preferably, at least one of the outlet valves is opened at least temporarily during monitoring. This creates a pressure equalization of the wheel brakes with atmospheric pressure.

The method according to the invention can ensure a necessary pressure equalization to the atmosphere in the unconfirmed state of the brake system, especially in the case of thermal effects such as a “hot brake”.

Further preferred embodiments of the invention emerge from the subclaims and the following description based on figures.

• 1 ein erstes Ausführungsbeispiel eines erfindungsgemäßen Bremssystems,
• 2 ein zweites Ausführungsbeispiel eines erfindungsgemäßen Bremssystems, und
• 3 ein drittes Ausführungsbeispiel eines erfindungsgemäßen Bremssystems.

Show it schematically

• 1 a first exemplary embodiment of a brake system according to the invention,
• 2 a second embodiment of a brake system according to the invention, and
• 3 a third embodiment of a braking system according to the invention.

In 1 a first exemplary embodiment of a brake system 1 according to the invention for a motor vehicle is shown schematically.

According to the example, the brake system is designed to actuate four hydraulically actuated wheel brakes 8a-8d; an extension to more wheel brakes is easily possible. According to the example, the wheel brakes 8a, 8b are assigned to the front axle (8a: front left FL, 8b: front right FR) and the wheel brakes 8c, 8d to the rear axle (8c: rear right RR, 8b: rear left RL) of the vehicle.

The brake system comprises a pressure medium reservoir 40 under atmospheric pressure, a first brake control unit 100 and a second brake control unit 200. Pressure medium reservoir 40 is advantageously arranged on the first brake control unit 100. Pressure medium storage container 40 comprises, for example, three chambers, each with its own connection 40a, 40b, 40c.

Pressure medium storage container 40 preferably has a pressure medium warning switch or pressure medium warning sensor 401, which determines or indicates the pressure medium level in the pressure medium storage container 40 when the pressure medium level falls below a critical level.

Brake control unit 100 is, for example, designed as a first electro-hydraulic brake control device with a valve block HCU1 and a first electronic control and regulation unit 101 (ECU1). Likewise, brake control unit 200 is designed, for example, as a second electrohydraulic brake control device with a valve block HCU2 and a second electronic control and regulation unit 201 (ECU2).

Brake control unit 100 includes four output ports 4a-4d for connection to one of the hydraulically actuated wheel brakes 8a-8d, an electrically actuated inlet valve 6a-6d per output port 4a-4d or wheel brake, an electrically actuated outlet valve 7a-7d per output port 4a-4d or Wheel brake and an electrically controllable hydraulic pressure source 5, which comprises a cylinder-piston arrangement with a pressure chamber 30, the piston 31 of which is actuated by an electromechanical actuator 32, 33 can be pushed back and forth. Pressure chamber 30 is connected via an electrically actuated pressure switching valve 9 to a brake line section 60, to which the inlet valves 6a-6d are connected. The inlet valves 6a-6d are connected directly to the pressure switching valve 9, in the sense that no further valve is hydraulically arranged between the inlet valves and the pressure switching valve. Each inlet valve 6a-6d is connected in parallel with a check valve 16a-16d that closes in the direction of the associated output port 4a-4d.

The outlet valves 7a-7d are connected to the first connection 40a of the pressure medium reservoir 40 by means of a common return line 70. The associated output port 4a-4d can be connected to the pressure medium reservoir 40 by means of the outlet valve 7a-7d. So can e.g. B. Pressure medium can be drained from the corresponding wheel brake 8a-8d.

The inlet and outlet valves represent a pressure modulation device for the wheel brakes, with the electrically actuated inlet valve 6a-6d being arranged between the wheel brake 8a-8d (or the output connection 4a-4d) and the brake line section 60 for each wheel brake 8a-8d and for each wheel brake 8a-8d, the electrically actuated outlet valve 7a-7d is arranged between the wheel brake 8a-8d (or the output connection 4a-4d) and the return line 70.

According to the example, each wheel brake 8a-8d is assigned a normally open inlet valve 6a-6d and a normally closed outlet valve 7a-7d. The pressure switching valve 9 is designed to be normally closed.

The electrically controllable pressure source 5 comprises a hydraulic cylinder-piston arrangement, the piston 31 of which can be actuated by an electromechanical actuator, which is formed, for example, by a schematically indicated electric motor 32 and a rotation-translation gear 33, which is also shown schematically. The rotation-translation gear 33 is preferably formed by a ball screw drive (KGT).

The piston 31 delimits a pressure chamber 30 with the valve block. The pressure source 5 is designed as a single circuit, ie the pressure source 5 or its pressure chamber 30 is connected or can be connected to all hydraulically actuated wheel brakes 8a-8d of the motor vehicle. By moving the piston 31 in the actuation direction (to the right in 1 ) pressure medium can be displaced from the pressure chamber 30 via the pressure switching valve 9, the brake line section 60 and the inlet valves 6a-6d to the wheel brakes 8a-8d. The pressure chamber 30 is connected via a resuction line 51 to the second connection 40b of the pressure medium storage container 40, into which a resuction valve 52, for example in the form of a check valve closing in the direction of the pressure medium storage container 4, is connected. It is possible to suck in pressure medium into the pressure chamber 30 via line 51 by retracting the piston 31.

A pressure sensor 19 for detecting the pressure of the pressure source 5 is arranged, for example, in the area of the brake line section 60.

Regardless of the actuation state of the piston 31, the pressure chamber 30 is sealed against atmospheric pressure via a sealing element arranged, for example, on the piston 31, ie, for example, even in the unactuated state of the piston 31 (as in 1 shown). The first pressure source 5 does not include any sniffer holes in this exemplary embodiment.

To detect a variable that is characteristic of the position/location of the piston 31 of the pressure source 5, a sensor 59 is present, which, for example, is designed as a rotor position sensor used to detect the rotor position of the electric motor 32. Other sensors are also conceivable, e.g. B. a displacement sensor for detecting the position/position of the piston 31. Based on the size characteristic of the position/position of the piston 31, a determination of the volume of pressure medium released or received by the pressure source 5 is possible.

The second brake control unit 200 is arranged hydraulically between the output connections 4a, 4b of the first brake control unit 100 and the wheel brakes 8a, 8b. Brake control unit 200 includes a second electrically controllable hydraulic pressure source 2. The pressure side of the pressure source 2 is connected to the output connections 204a, 204b of the second brake control unit 200 in order, for example. B. in the event of failure of the first pressure source 5, to be able to build up pressure to actuate the wheel brakes 8a, 8b connected to the output connections 201a, 201b. Brake control unit 200 includes two input connections 214a, 214b, with input connection 214a being connected to output connection 4a of the first brake control unit 100 and input connection 214b being connected to output connection 4b of the first brake control unit 100.

Brake control unit 200 further advantageously comprises a separation valve 240a, 240b for each of the assigned wheel brakes 8a, 8b, which is in a hydraulic connection 241a, 241b between the corresponding input port 214a, 214b of the second brake control unit 200 (or output connection 4a, 4b of the first brake control unit 100) and the corresponding output connection 204a, 204b of the second brake control unit 200 (or the corresponding wheel brake 8a, 8b).

The hydraulic layout of the brake control unit 200 basically corresponds to the layout of the DE 10 2016 203 119 A1 well-known additional module.

Pressure source 2 includes an electric motor 90, which, if necessary, drives two pumps 91a, 91b. The pump 91a is connected on the pressure side to the output connection 204a or the wheel brake 8a via a hydraulic line or wheel brake supply line. The pump 91b is connected on the pressure side via a line or wheel brake supply line to the output connection 204b or the wheel brake 8b.

In this way, pressure can be actively built up in the front wheel brakes 8a, 8b with the help of the brake control unit 200. Brake control unit 200 is designed to be able to reliably take over a braking function if necessary. For this purpose, two pressure medium reservoirs 95a, 95b under atmospheric pressure are provided, which are integrated into the brake control unit 200. The pressure medium reservoir 95a is hydraulically connected to the suction side of the pump 91a via a hydraulic line, into which a normally closed reservoir valve 96a is connected. The pressure medium reservoir 95b is hydraulically connected to the pump 91b on the suction side via a hydraulic line into which a normally closed reservoir valve 96b is connected.

To reduce pressure or release pressure medium from the wheel brakes 8a, 8b, a normally closed drain valve 97a, 97b is provided for each wheel brake, through which the output connection 204a, 204b or the wheel brake 8a, 8b can be hydraulically connected to the pressure medium reservoir 95a, 95b.

The two pressure medium reservoirs 95a, 96b are connected to the pressure medium reservoir 4 by means of a common compensation line 290. For this purpose, the compensation line 290 is connected to a compensation connection 295 of the brake control unit 200, which in turn is connected to the third connection 40c of the pressure medium reservoir 40.

A check valve 242a, 242b closing in the direction of the first brake control unit 100 is connected in parallel with the respective isolating valve 240a, 240b.

The first electronic control and regulation unit 101 advantageously serves to control all electrically actuable components of the first brake control unit 100, in particular the inlet and outlet valves 6a-6d, 7a-7d, the first electrically controllable hydraulic pressure source 5 and the pressure switching valve 9.

The second electronic control and regulation unit 201 advantageously serves to control all electrically actuable components of the second brake control unit 200, in particular the second electrically controllable hydraulic pressure source 2 and the valves 240a, 240b, 96a, 96b, 97a, 97b.

An electronic brake pedal (not shown) is advantageously provided in the motor vehicle for controlling the braking system by a driver. The electronic brake pedal advantageously comprises a first braking request detection sensor 120 and a second braking request detection sensor 220, wherein the signal of the first braking request detection sensor 120 of the first brake control unit 100, in particular the first electronic control and regulation unit 101, and the signal of the second braking request detection sensor 220 of the second brake control unit 200, in particular the second electronic control and regulation unit 201, is supplied (by arrows 105, 205 in 1 indicated).

To exchange information, the first electronic control and regulation unit 101 and the second electronic control and regulation unit 201 are connected to one another via a communication bus 300.

The braking system 1 is preferably supplied with electrical energy by two on-board electrical systems, a first on-board electrical system 110 and a second on-board electrical system 210. The first vehicle electrical system 110 supplies the first brake control unit 100 or its electronic control and regulation unit 101 as well as the first braking request detection sensor 120 (arrows 111). The second vehicle electrical system 210 supplies the second brake control unit 200 or its electronic control and regulation unit 201 as well as the second braking request detection sensor 220 (arrows 211).

The braking system does not include a master brake cylinder that can be actuated by means of a brake actuating element and is connected to the wheel brakes. It is a “brake-by-wire” brake system in which the vehicle driver has no possibility of direct mechanical-hydraulic actuation of the wheel brakes. There is therefore no mechanical or hydraulic fallback level for the driver to directly access the wheel brakes. A request to brake The driver's information is transmitted or implemented exclusively electrically (“by-wire”).

During normal operation of the brake system, brake pressure can be actively built up in all four wheel brakes 8a-8d by means of the first brake control unit 100. The second brake control unit 200 can still actively build up brake pressure on the front axle if the brake control unit 100 fails.

According to the first exemplary embodiment 1 (as well as the second exemplary embodiment 2 ), the pressure switching valve 9 is designed to be normally closed. This is intended to counteract an unlikely but possible leakage error. In such an error case (e.g. marten bite in the wheel brake hose), if the pressure switching valve 9 is open without current, the pressure medium supply from the pressure medium reservoir 40 in the non-activated brake system 1 could be lost. When the brake system 1 is subsequently activated, it is not guaranteed that the leak, e.g. B. in an active leak test, could be localized and separated by switching/closing the inlet valve of the affected wheel brake circuit. As a result, if a critical level of the pressure medium warning switch 401 were triggered, it would no longer be possible to continue driving. By selecting the pressure switching valve 9 as closed when de-energized, this problem is avoided and limited continued travel can normally be made possible by locating and separating the affected wheel brake circuit.

The braking system of the 1 however, has the following disadvantage. Thermal effects can result in residual brake pressures in at least one wheel brake circuit/wheel brake when the pressure switching valve 9 is closed, which can further increase over time. This could lead to significant unwanted wheel braking torque and thus over-braking, or damage to the braking system. To avoid this, a thermal load on the brake system is monitored before the brake system is switched off, and the brake system is only switched off when the thermal load has fallen below a predetermined limit value. During monitoring, at least one of the outlet valves 7a-7d is opened at least temporarily in order to reduce the residual brake pressures.

When the brake system is energized, the residual pressure, e.g. B. via the pressure sensor 19, can be easily measured and reduced into the unpressurized pressure medium reservoir 40 by controlling one or more wheel-selective outlet valves 7a-7d.

Before the brake system is shut down, it is checked that none of the measurement or model variables used indicate any suspicion of thermal stress (“hot brake”). If there is suspicion, an electronic control and regulation unit, in particular the first electronic control and regulation unit 101, goes into a controlled overrun in order to be able to reduce any residual pressure that may arise until a non-critical situation has arisen (e.g. the brake has cooled down sufficiently when the vehicle is stationary). During operation and after-run, pressure relief can occur via regular or controlled activation of one or more outlet valves.

In 2 a second exemplary embodiment of a brake system 1 according to the invention for a motor vehicle is shown schematically. In contrast to the exemplary embodiment 1 At least one of the outlet valves, for example the outlet valve 7d for a rear axle wheel brake, is designed to be open when de-energized.

In the second exemplary embodiment, the thermal effect described can be controlled by the at least one normally open outlet valve even without overrun under thermal load, since there is a reduction in residual pressure in the depressurized pressure medium reservoir 40 even when the brake system is de-energized (switched off).

As soon as the brake system is ready for operation, the normally open outlet valve(s) (7d) are energized and thus closed. During operation, the same function is achieved as in the braking system 1 reached. When the brake system is not being energized, the wheel brakes 8a-8d are connected to the pressure medium reservoir 40 through the normally open outlet valve(s) (7d) and the pressure can be equalized to the atmosphere. During operation of the brake system, pressure relief can take place via regular or controlled activation of one or more exhaust valves 7a-7d.

In 3 a third exemplary embodiment of a brake system 1 according to the invention for a motor vehicle is shown schematically. In contrast to the exemplary embodiment 1 (and 2 ), the pressure switching valve 9 is designed to be normally open and the cylinder-piston arrangement of the first pressure source 5 includes at least one sniffer hole 50, via which the pressure chamber 30 of the first pressure source 5 is connected to the pressure medium reservoir 40 when the piston 31 is not actuated.

According to the example, the pressure chamber 30 is connected to the second connection 40b of the pressure medium storage container 40 via the sniffer hole 50. For this purpose, the sniffer hole is connected to the suction line 51 to the second connection 40b.

In the unactuated state of the first pressure source 5 (i.e. when the piston 31 is in the zero position, is not actuated), the wheel brakes 8a-8d are connected to the pressure medium reservoir 40 via the pressure chamber 30, the sniffer hole 50 and the suction line 51 and pressure compensation can be achieved to the atmosphere. In this way, excess system pressure (e.g. from thermal effects) can be reduced even when the first brake control unit 100 is not energized. During operation, pressure relief can take place via regular or controlled activation of one or more outlet valves 7a-7d.

The brake systems according to the example meet the requirement for a brake-by-wire braking system including wheel-selective implementation of a brake request and brake control, e.g. B. ABS slip control.

Basic function of the redundant braking system: The braking torque request is usually transmitted by an external electrical system (e.g. an electronic brake pedal or a virtual driver (virtual driver signals). The braking request is then usually transmitted in the redundant braking system by the first brake control unit 100 implemented by means of the first pressure source 5. If the pressure position is not available from the first brake control unit 100, the pressure position is taken over by the second brake control unit 200.

QUOTES INCLUDED IN THE DESCRIPTION

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

Cited patent literature

• DE 102017211953 A1 [0002]
• DE 102016203119 A1 [0051]

Claims (15)

Brake system (1) for a motor vehicle for at least four hydraulically actuated wheel brakes (8a-8d) with a pressure medium reservoir (40) under atmospheric pressure, with a first brake control unit (100) comprising at least four output connections (4a-4d) for connection to one each the hydraulically actuated wheel brakes (8a-8d), • an electrically actuated inlet valve (6a-6d) for each wheel brake, • an electrically actuated outlet valve (7a-7d) for each wheel brake, by means of which the assigned output connection can be connected to the pressure medium reservoir (40), and • a first electrically controllable hydraulic pressure source (5), which comprises a cylinder-piston arrangement with a pressure chamber (30), the piston (31) of which can be pushed back and forth by an electromechanical actuator (32, 33), the pressure chamber (30) is connected to a brake line section (60) to which the at least four inlet valves (6a-6d) are connected, and to a second brake control unit (200), which is hydraulically connected between two of the output connections (4a, 4b) of the first brake control unit ( 100) and two of the wheel brakes (8a, 8b) are connected, and which comprises a second electrically controllable hydraulic pressure source (2), characterized in that the pressure chamber (30) is connected to the brake line section (60) via an electrically actuated pressure switching valve (9). is connected and at least one of the inlet valves (6a-6d) is connected in parallel with a check valve (16a-16d) which closes in the direction of the associated output port (4a-4d). Brake system (1). Claim 1 , characterized in that the first brake control unit (100) comprises a first electronic control and regulation unit (101), which controls the inlet and outlet valves (6a-6d, 7a-7d), the first electrically controllable hydraulic pressure source (5) and that Pressure switching valve (9) is actuated. Brake system (1). Claim 1 or 2 , characterized in that the outlet valves (7a-7d) are connected to a first connection (40a) of the pressure medium storage container (40) and the pressure chamber (30) via a suction valve (52), in particular a check valve opening in the direction of the pressure chamber (30). (52), is connected to a second connection (40b) of the pressure medium storage container (40). Brake system (1) according to one of the Claims 1 until 3 , characterized in that the pressure switching valve (9) is designed to be normally closed. Brake system (1) according to one of the Claims 1 until 3 , characterized in that the pressure switching valve (9) is designed to be normally open and the first electrically controllable hydraulic pressure source (5) has at least one sniffing hole (50) through which the pressure chamber (30) of the first electrically controllable hydraulic pressure source (5) is unactuated Piston (31) is connected to the pressure medium storage container (40), in particular a second connection (40b) of the pressure medium storage container (40). Brake system (1). Claim 4 or 5 , characterized in that the inlet valves (6a-6d) are designed to be normally open and the outlet valves (7a-7d) are designed to be normally closed. Brake system (1). Claim 4 or 5 , characterized in that the inlet valves (6a-6d) are designed to be normally open and that at least one of the outlet valves (7d) is designed to be normally open, while the remaining outlet valves (7a-7c) are designed to be normally closed. Braking system (1) according to one of the preceding claims, characterized in that the two wheel brakes (8a, 8b) assigned to the second brake control unit (200) are assigned to the front axle of the motor vehicle and that the other wheel brakes (8c, 8d) are assigned to the rear axle of the motor vehicle are. Brake system (1) according to one of the preceding claims, characterized in that it does not include any further hydraulic pressure source, in particular no further electrically controllable hydraulic pressure source and no brake pedal-operable master brake cylinder. Brake system (1) according to one of the preceding claims, characterized in that the second brake control unit (200) comprises a isolating valve (240a, 240b) for each of the two associated wheel brakes (8a, 8b), which is hydraulically connected between the corresponding output port (4a, 4b ) the first brake control unit (100) and the corresponding wheel brake (8a, 8b) is arranged. Brake system (1) according to one of the preceding claims, characterized in that the second brake control unit (200) comprises a second electronic control and regulation unit (201), which controls the second electrically controllable hydraulic pressure source (2), and in particular the isolating valves (240a, 240b), operated. Brake system (1) according to one of the preceding claims, characterized in that it can be controlled by means of an electronic brake pedal which is not hydraulically connected to the brake system, in particular its pressure medium reservoir (40). Brake system (1). Claim 12 , when referenced back to Claim 2 and 11 , characterized in that the electronic brake pedal comprises a first brake request detection sensor (120) and a second brake request detection sensor (220), the signal of the first brake request detection sensor (120) of the first brake control unit (100) and the signal of the second brake request detection sensor (220) of the second brake control unit (200) is supplied. Method for operating a brake system (1). Claim 6 , when referenced back to Claim 4 , characterized in that a thermal load on the brake system is monitored before the brake system is switched off, and that the brake system is only switched off when the thermal load has fallen below a predetermined limit value. Procedure according to Claim 14 , characterized in that at least one of the outlet valves (7a-7d) is opened at least temporarily during monitoring.

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