DE102014215030A1 - Hydraulic brake device with high-pressure switching valve - Google Patents

Abstract

The invention relates to a hydraulic braking device (200) for a vehicle having at least one brake circuit (201) which has an actuating device (202) which is set up to generate a brake pressure when actuated in a main brake line (203) filled with a hydraulic fluid an electrically controllable inlet valve (204), which is the input side connected to the main brake line (203) and adapted to conduct a brake pressure on the output side in a Radbremsleitung (205) having a wheel brake (206) with a hydraulic brake cylinder (207), the is connected to the wheel brake line (205) and arranged to brake a wheel of the vehicle in dependence on the brake pressure in the wheel brake line (205), which further comprises an electrically controllable outlet valve (208) which is adapted to dispense hydraulic fluid from the wheel brake line (205 ) in a storage chamber (209) to guide and which is a elektrisc h controllable high-pressure switching valve (211), which is arranged to pass through a before the high-pressure switching valve (211) arranged check valve (212) through hydraulic fluid from the storage chamber (209) back into the main brake line (203) According to the invention it is provided that the high-pressure switching valve ( 211) is designed as a high pressure-resistant switching valve with an electrically switchable blocking position, which is in the idle state in an open position in which a return of hydraulic fluid from the storage chamber (209) back into the main brake line (203) can be achieved. The invention further relates to a method for emptying a storage chamber (209) of a hydraulic braking device (200) of a vehicle.

Description

The invention relates to a hydraulic braking device for a vehicle.

State of the art

Modern hydraulic brake devices for vehicles, in particular motor vehicles, usually have control devices such as anti-lock braking systems (ABS), traction control systems (ASR) or vehicle dynamics controls (ESP, Electronic Stability Program). Typically, these control devices require a storage chamber as a buffer for receiving hydraulic fluid. Upon activation of one of the control devices, i. a rule event, the storage chamber is filled. The subsequent emptying of the storage chamber is usually associated with a perceptible by a driver of the vehicle noise.

1 shows an example of a braking device 100 According to the state of the art. For safety reasons, the braking device 100 two separate, substantially symmetrical trained, containing a hydraulic fluid hydraulic brake circuits 101 on. Depending on the vehicle manufacturer brakes a brake circuit 101 typically each one wheel on the front axle and a wheel diagonally opposite to it on the rear axle (X-division), or the one brake circuit 101 Brakes the wheels of the front axle and the other the wheels of the rear axle (II-division).

The braking device 100 includes one for both brake circuits 101 common actuator 102 (eg foot pedal) with a brake booster 118 and a surge tank 120 , as well as each brake circuit 101 a master cylinder 119 with several valves for setting a wheel-specific brake pressure. Unless otherwise stated, the following description applies to both brake circuits 101 alike.

Upon actuation of the braking device 100 is in a main brake line 103 generates a brake pressure via a switching valve 115 and one inlet valve each 104 per wheel on the brake cylinder 107 the wheel brakes 106 acts. In the case of full braking, the brake cylinder can 107 the wheel brakes 106 acting brake pressure by a targeted, intermittent opening and closing of the intake valve 104 and a corresponding exhaust valve 108 be reduced by, for example, the control of an anti-lock braking system (ABS).

The case over the exhaust valves 108 from the main brake line 103 Escaping hydraulic fluid is stored in a storage chamber 109 buffered and during the duration of an ABS control via a return conveyor, usually a motor-pump unit 117 and the switching valve connected in the reverse pressure direction 115 into the main brake line 103 conveyed back. In addition, with the hydraulic fluid in the storage chamber 109 via the motor-pump unit 117 in the main brake line 103 a brake pressure may be generated which exceeds the brake pressure desired by a driver, for example to trigger or amplify braking by means of a Brake Assist (BAS) or Vehicle Dynamics Controller (VDC). To determine the aforementioned, desired by the driver brake pressure points one of the two brake circuits 101 a brake sensor 116 on.

Emptying the storage chamber 109 Outside of an ABS control is via an acoustically perceptible by the driver wake of the motor-pump unit 117 or alternatively via high pressure switching valves 110 possible. The high pressure switching valves 110 are designed according to the prior art as high-pressure resistant switching valves with an electromagnetically switchable passage position. Provided by the brake sensor 116 no desired by the driver brake pressure can be determined, the high pressure switching valves 110 to return the hydraulic fluid in the main brake line 103 open. At standstill or in low ambient noise is the switching noise of the high pressure switching valves 110 also audible by the driver. Thus, the aforementioned options for emptying the storage chamber 109 both connected to noises that are perceivable by the driver and can lead to its irritation.

Disclosure of the invention

Object of the present invention is to provide a simple hydraulic braking device, in which an emptying of a buffer for hydraulic fluid from the driver is acoustically imperceptible.

The object is achieved by the features of the independent claims. Advantageous embodiments of the invention are specified in the subclaims.

According to the invention, a hydraulic brake device is provided for a vehicle having at least one brake circuit which has an actuating device which is set up to generate a brake pressure when actuated in a main brake line filled with a hydraulic fluid, which has an electrically controllable inlet valve which is connected on the input side to the main brake line and is set up, one To pass brake pressure on the output side in a Radbremsleitung having a wheel brake with a hydraulic brake cylinder which is connected to the Radbremsleitung and adapted to brake a wheel of the vehicle in response to the brake pressure in the Radbremsleitung, which further comprises an electrically controllable exhaust valve, which is arranged to direct hydraulic fluid from the Radbremsleitung in a storage chamber, which further comprises an electrically controllable high-pressure switching valve which is arranged to pass through a arranged before the high-pressure switching valve check valve hydraulic fluid from the storage chamber back into the main brake line, wherein the high-pressure switching valve as a high pressure-resistant switching valve with an electrically switchable blocking position is executed and is in the idle state in an open position in which a return of hydraulic fluid from the storage chamber back into the Ha Uptbremsleitung is achievable.

According to the prior art, high-pressure switching valves (HSV) are actuated by means of magnetic switches whose switching noises are acoustically perceptible. So that hydraulic fluid can flow from the storage chamber back into the main brake line, an opening of the HSV is required. The invention exploits the effect that the switching requirements for the magnetic switches of the HSV correlate with the operating situation of the vehicle. A return of the hydraulic fluid from the storage chamber in the main brake line is usually in quiet operating situations, such as slow driving or a stop of the vehicle. In quiet operating situations there are no or only low ambient noise, so that a switching of a magnetic switch for opening an HSV, as in a braking device according to the prior art, is clearly perceptible. In contrast, the HSV of the braking device according to the invention is in its rest position in an open position, so that in quiet operating situations for opening the HSV no actuation of a magnetic switch is required. Advantageously, the operation of the braking device according to the invention is less clearly perceived by a driver.

Furthermore, the braking device advantageously has a return device for conveying hydraulic fluid from the storage chamber back into the main brake line, wherein the return conveyor device comprises a motor-pump unit and a change-over valve. The switching valve is arranged in the main brake line between the actuator and the at least one inlet valve, that it is divided into two sections, wherein the switching valve for hydraulic fluid in a rest state in the direction of the at least one inlet valve continuously and in a reverse state in the direction of the actuator through is. The engine-pump unit is configured to pump hydraulic fluid from the storage chamber into the portion of the main brake line between the changeover valve and the intake valve, and the brake device is configured such that during pumping of the engine-pump unit, the changeover valve reverses and the high-pressure switching valve Has locked state.

When the high-pressure switching valve is closed, such a braking device designed by means of the motor-pump unit enables the generation of a brake pressure which exceeds the brake pressure desired by a driver.

Advantageously, the braking device further comprises a control device, wherein the electrically controllable inlet valve, the electrically controllable outlet valve, the electrically controllable changeover valve and the motor-pump unit of the control device during a control process, in particular an ABS control, are controllable, and wherein the Braking device is set up such that the high-pressure switching valve is closed during a control process.

In this case, such a braking device has the advantage that no sensor system is required for emptying the storage chamber, which determines possible periods of emptying by the exclusion of a braking request. Rather, the state of HSV depends on the execution of a control process. The control of the HSV can thus be included in the control process. Since no sensor system is required for detecting the driver's braking request, a complexity reduction, in particular with regard to memory deflation algorithms, can be achieved by the braking device according to the invention. Due to lower complexity, the braking device according to the invention is relatively robust compared to the prior art.

A further advantage of the braking device according to the invention is that a permissible duration of a drive slip control is no longer limited by maximum drive times of an HSV. Since the HSV are open in the idle state, no thermal load takes place by the control, which influences the maximum permissible duration of a drive slip control. By way of example, in a comparison with a braking device according to the prior art with identical driving maneuvers, the sum of the driving times of the HSV is advantageously reduced.

Advantageously, the braking device is set up such that the high-pressure switching valve is open immediately after a control process. A Such an embodiment has the advantage that an immediate backflow of the hydraulic fluid is made possible, a switching of solenoid valves in the direct connection to a control process, however, due to the associated driving situation by a driver is barely perceptible.

Advantageously, the braking device is further configured such that the high-pressure switching valve is open at a recoverable by the actuator, but not sufficient for triggering a control braking pressure and a backflow of the hydraulic fluid from the main brake line in the storage chamber through the check valve can be prevented.

Such a configuration offers the advantage that during partial braking with superimposed pressure buildup requirements (for example by a VDC), the space between HSV, check valve and motor-pump unit is automatically pre-filled. Thus, without the need for control with complex provisioning algorithms, hydraulic fluid is automatically ready for potential rapid pressure build-up.

Also provided according to the invention is a method for emptying a storage chamber of a hydraulic brake device of a vehicle, wherein the brake device has an actuating device that is set up to generate a brake pressure when actuated in a main brake line filled with a hydraulic fluid, which has an electrically controllable inlet valve which has an input side connected to the main brake line and arranged to direct a brake pressure on the output side in a Radbremsleitung having a wheel brake with a hydraulic brake cylinder which is connected to the Radbremsleitung and adapted to brake a wheel of the vehicle in response to the brake pressure in the Radbremsleitung, which further comprises an electrically controllable outlet valve, which is arranged to direct hydraulic fluid from the wheel brake line into a storage chamber, and which is an electrically controllable high-pressure switch valve, which is arranged to empty hydraulic fluid from the storage chamber back into the main brake line through a check valve arranged upstream of the high-pressure switching valve, the high-pressure switching valve being designed as a high-pressure-resistant switching valve with an electrically switchable blocking position and emptying the storage chamber into the main brake line in an open rest position he follows.

An advantage of this method is that a return of the hydraulic fluid from the storage chamber into the main brake line is barely perceptible even in quiet operating situations, for example during slow driving or a stop of the vehicle by the driver. In quiet operating situations there are no or only low ambient noise, so that a switching of a magnetic switch for opening an HSV, as in a braking device according to the prior art, is clearly perceptible. In contrast, the HSV of the braking device according to the invention is in its rest position in an open position, so that in quiet operating situations for opening the HSV no actuation of a magnetic switch is required. Advantageously, the method according to the invention is perceived by a driver to be quieter.

Advantageously, the method is carried out with a braking device having a motor-pump unit and a switching valve, wherein the switching valve in the main brake line and this dividing between the actuator and the at least one inlet valve is arranged, and wherein the motor-pump unit established is to pump hydraulic fluid from the storage chamber in the part of the main brake line between the changeover valve and the inlet valve, and wherein the high-pressure switching valve closes for the duration of a pumping operation of the motor-pump unit.

By closing the high-pressure switching valve, such an embodiment of the method by means of the motor-pump unit enables the generation of a brake pressure which exceeds the brake pressure desired by a driver.

Advantageously, the method is carried out in such a way that the high-pressure switching valve is open outside a pumping operation and a pre-filling of a connecting space between the high-pressure switching valve, check valve and motor-pump unit with hydraulic fluid takes place through the opened high-pressure switching valve.

Such an implementation of the method offers the advantage that during partial braking with superimposed pressure buildup requirements (for example by a VDC), the space between HSV, check valve and pump is automatically pre-filled. Thus, without the need for control with complex deployment algorithms, hydraulic fluid is automatically ready for potential rapid pressure build-up so that pressure build-up requests can be responded quickly.

Advantageously, the method is carried out such that the electrically controllable inlet valve, the electrically controllable outlet valve, the electrically controllable changeover valve and the motor-pump unit are controlled by an electrical control device for performing a control operation, the high-pressure switching valve closed for the duration of this control process becomes.

Such a method has the advantage that no sensor system is required for emptying the storage chamber, which determines possible periods of emptying by the exclusion of a braking request. Rather, the state of HSV depends on the execution of a control process. The control of the HSV can thus be included in the control process. Since no sensor system is required for detecting the driver's braking request, a reduction in complexity, in particular with regard to memory emptying algorithms, can be achieved in comparison with methods according to the prior art.

Another advantage of this embodiment of the method according to the invention is that an allowable duration of a drive slip control is no longer limited by maximum drive times of an HSV. Since the HSV is open in the idle state, no thermal load takes place by the control, which influences the maximum permissible duration of a drive slip control. By way of example, in a comparison with prior art methods with identical driving maneuvers, the sum of the drive times of the HSV is advantageously reduced.

Advantageously, an implementation of the method is further carried out such that the high-pressure switching valve is closed exclusively for the duration of a control process, so that the storage chamber otherwise emptied via the high-pressure switching valve.

This embodiment of the method has the advantage that a switching of the magnetic switch takes place exclusively during such driving situations, which require a corresponding control process and thereby correlate the noise caused by the magnetic switch directly with the driving situation. The switching noise of the magnetic switch are usually acoustically covered by the ambient noise, especially the brake noise. If they are even perceptible by the driver, the driver can assign them to the control process, so that an irritation of the driver is not expected by the switching noise of the magnetic switch.

drawings

The invention will be explained in more detail with reference to the accompanying drawings with reference to preferred embodiments.

Show it

1 a hydraulic braking device according to the prior art

2 an embodiment of a braking device according to the invention

1 shows an example of a braking device 100 According to the state of the art. For safety reasons, the braking device 100 two separate, substantially symmetrical trained, containing a hydraulic fluid hydraulic brake circuits 101 on.

The braking device 100 includes one for both brake circuits 101 common actuator 102 (Foot pedal) with a brake booster 118 and a surge tank 120 , as well as each brake circuit 101 a master cylinder 119 with several valves for setting a wheel-specific brake pressure. Unless otherwise stated, the following description applies to both brake circuits 101 alike.

Upon actuation of the braking device 100 gets in the main brake line 103 generates a brake pressure via a switching valve 115 and one inlet valve each 104 per wheel on the wheel brake lines 105 is forwarded and there on the brake cylinder 107 the wheel brakes 106 acts. In the case of full braking, the brake cylinder can 107 a wheel brake 106 acting brake pressure in wheel brake line 105 by a targeted, intermittent opening and closing of the inlet valve 104 and a corresponding exhaust valve 108 be reduced by, for example, the control of an ABS.

The case over the exhaust valves 108 from the wheel brake lines 105 Escaping hydraulic fluid is stored in a storage chamber 109 buffered and during the duration of a control process via a return conveyor, consisting of a motor-pump unit 117 and the switching valve connected in the reverse pressure direction 115 into the main brake line 103 conveyed back. In addition, with the hydraulic fluid in the storage chamber 109 via the motor-pump unit 117 in the main brake line 103 a brake pressure may be generated which exceeds the brake pressure desired by a driver, for example to trigger or amplify braking by means of a Brake Assist (BAS) or Vehicle Dynamics Controller (VDC). To determine the aforementioned, desired by the driver brake pressure points one of the two brake circuits 101 a brake sensor 116 on.

Emptying the storage chamber 109 Outside of a control process is via an acoustically perceptible by the driver wake of the motor-pump unit 117 or alternatively via high pressure switching valves 110 possible. The high pressure switching valves 110 are known in the art as high-pressure-resistant switching valves with an electromagnetically switchable passage position. Provided by the brake sensor 116 no desired by the driver brake pressure can be determined, the high pressure switching valves 110 for returning the hydraulic fluid from the storage chamber 109 through the check valve 112 in the main brake line 103 open.

As a safety device to limit the pressure, the switching valve 115 and the inlet valve 104 each arranged parallel to them pressure relief valves 113 . 114 on.

2 shows a preferred embodiment of a braking device according to the invention 200 , How out 2 can be seen, the braking device 200 a high pressure switching valve 211 on, which is made open in its rest position. By not only inverted, but modified control of the high-pressure switching valve, the embodiment differs not only structurally but also functionally from the prior art.

2 shows a hydraulic braking device 200 for a vehicle with two brake circuits 201 , one for both brake circuits 201 common actuator 202 (Foot pedal) with a brake booster 218 and a surge tank 220 as well as each brake circuit 201 a master cylinder 219 , By an actuation of the actuator 202 can in a filled with a hydraulic fluid main brake line 203 a brake pressure can be generated. The main brake line 203 is with the input of an electrically controllable inlet valve 204 connected.

The inlet valve 204 is set up, a brake pressure on the output side in a Radbremsleitung 205 to conduct a wheel brake 206 with a hydraulic brake cylinder 207 having, with the wheel brake line 205 is connected and arranged, a wheel of the vehicle in response to the brake pressure in the Radbremsleitung 205 to break.

Furthermore, the exemplary embodiment has an electrically controllable outlet valve 208 on which is set, hydraulic fluid from the wheel brake line 205 in a storage chamber 209 to lead.

Further shows 2 an electrically controllable high pressure switching valve, which is arranged via a front of the high pressure switching valve 211 arranged check valve 212 through hydraulic fluid from the storage chamber 209 back to main brake line 203 to conduct, with the high pressure switching valve 211 is designed as a high-pressure-resistant switching valve with an electrically switchable blocking position and is in the idle state in an open position in which a return of hydraulic fluid from the storage chamber 209 back to the main brake line 203 is possible.

Further shows 2 Advantageously, a return conveyor for conveying hydraulic fluid from the storage chamber 209 back to the main brake line 203 wherein the return conveyor means comprises a motor-pump unit 217 and a changeover valve 215 includes and the switching valve 215 such in the main brake line 203 between the actuator 202 and the at least one inlet valve 204 is arranged that this is divided into two sections.

Here is the switching valve 215 for hydraulic fluid in an idle state in the direction of the at least one inlet valve 204 continuously and in a reversed state towards the actuator 202 continuously.

The motor-pump unit 217 is set up, hydraulic fluid from the storage chamber 209 in the section of the main brake line 203 between changeover valve 215 and inlet valve 204 to pump, and the braking device 200 is configured such that during pumping the motor-pump unit 217 the changeover valve 215 the reverse state and the high pressure switching valve 211 has the lock state.

With high-pressure switching valve closed 211 allows such a running braking device 200 by means of the motor-pump unit 217 the generation of a brake pressure that exceeds the brake pressure desired by a driver.

Not shown, the braking device 200 Furthermore, a control device, wherein the electrically controllable inlet valve 204 , the electrically controlled exhaust valve 208 , the electrically controllable diverter valve 215 and the motor-pump unit 217 be controlled by the control device during a control process, in particular an ABS control, and wherein the braking device 200 is set up such that the high-pressure switching valve 211 is closed during a regulation process.

The braking device 200 is further configured such that the high pressure switching valve 211 immediately after a control process is open, so that the brake fluid instantly into the main brake line 203 can flow back. Furthermore, allows an open high-pressure switching valve 211 a pre-filling of the space between high-pressure switching valve 211 , the check valve 212 and the motor-pump unit 217 to quickly meet pressure buildup requirements.

If the brake pressure is insufficient to trigger a control action, the check valve prevents it 212 in that hydraulic fluid from the main brake line 203 through the open high-pressure switching valve 211 in the storage chamber 209 flows.

As a safety device to limit the pressure, the switching valve 215 and the inlet valve 204 Pressure relief valves arranged parallel to them 213 . 214 on.

Claims (10)

Hydraulic brake device ( 200 ) for a vehicle having at least one brake circuit ( 201 ), which an actuating device ( 202 ), which is arranged, when actuated in a filled with a hydraulic fluid main brake line ( 203 ) to generate a brake pressure which is an electrically controllable inlet valve ( 204 ), which on the input side with the main brake line ( 203 ) is connected and set up, a brake pressure on the output side in a Radbremsleitung ( 205 ), which is a wheel brake ( 206 ) with a hydraulic brake cylinder ( 207 ), which is connected to the Radbremsleitung ( 205 ) is connected and arranged, a wheel of the vehicle in dependence on the brake pressure in the Radbremsleitung ( 205 ), which further comprises an electrically controllable outlet valve ( 208 ), which is arranged, hydraulic fluid from the Radbremsleitung ( 205 ) in a storage chamber ( 209 ), and which an electrically controllable high-pressure switching valve ( 211 ), which is arranged via a front of the high-pressure switching valve ( 211 ) arranged check valve ( 212 ) through hydraulic fluid from the storage chamber ( 209 ) back into main brake line ( 203 ), characterized in that the high pressure switching valve ( 211 ) is designed as a high-pressure-resistant switching valve with an electrically switchable blocking position and is in the idle state in an open position in which a return of hydraulic fluid from the storage chamber ( 209 ) back into the main brake line ( 203 ) is achievable. Hydraulic brake device ( 200 ) according to claim 1, characterized in that the braking device ( 200 ) a return conveyor for conveying hydraulic fluid from the storage chamber ( 209 ) back into the main brake line ( 203 ), wherein the return conveyor device comprises a motor-pump unit ( 217 ) and a switching valve ( 215 ), the changeover valve ( 215 ) in the main brake line ( 203 ) between the actuator ( 202 ) and the at least one inlet valve ( 204 ) is arranged, that this is divided into two sections, wherein the switching valve ( 215 ) for hydraulic fluid in an idle state in the direction of at least one inlet valve ( 204 ) continuously and in a reversed state in the direction of the actuating device ( 202 ) is continuous, and wherein the motor-pump unit ( 217 ) is arranged, hydraulic fluid from the storage chamber ( 209 ) into the section of the main brake line ( 203 ) between changeover valve ( 215 ) and inlet valve ( 204 ) and the braking device ( 200 ) is arranged such that during pumping the motor-pump unit ( 217 ) the changeover valve ( 215 ) the reverse state and the high pressure switching valve ( 211 ) has the lock state. Hydraulic brake device ( 200 ) according to claim 2, characterized in that the braking device ( 200 ) has a control device, and that the electrically controllable inlet valve ( 204 ), the electrically controllable outlet valve ( 208 ), the electrically controllable changeover valve ( 215 ) and the motor-pump unit ( 217 ) by the control device during a control process, in particular an ABS control, are controllable, and the braking device ( 200 ) is arranged such that the high-pressure switching valve ( 211 ) is closed during a control process. Hydraulic brake device ( 200 ) according to claim 3, characterized in that the braking device ( 200 ) is arranged such that the high-pressure switching valve ( 211 ) is open immediately after a control process. Hydraulic brake device ( 200 ) according to claim 4, characterized in that the braking device ( 200 ) is arranged such that the high-pressure switching valve ( 211 ) at one by the actuator ( 202 ) achievable, but not enough to trigger a control operation sufficient brake pressure is open and a return flow of the hydraulic fluid from the main brake line ( 203 ) in the storage chamber ( 209 ) through the check valve ( 212 ) is preventable. Method for emptying a storage chamber ( 209 ) a hydraulic braking device ( 200 ) of a vehicle, wherein the braking device ( 200 ) an actuating device ( 202 ), which is arranged, when actuated in a filled with a hydraulic fluid main brake line ( 203 ) to generate a brake pressure which is an electrically controllable inlet valve ( 204 ), which on the input side with the main brake line ( 203 ) is connected and set up, a brake pressure on the output side in a Radbremsleitung ( 205 ), which is a wheel brake ( 206 ) with a hydraulic brake cylinder ( 207 ), which is connected to the Radbremsleitung ( 205 ) is connected and arranged, a wheel of the vehicle in dependence on the brake pressure in the Radbremsleitung ( 205 ), which is further an electric controllable outlet valve ( 208 ), which is arranged, hydraulic fluid from the Radbremsleitung ( 205 ) in a storage chamber ( 209 ), and which an electrically controllable high-pressure switching valve ( 211 ), which is set up by a front of the high-pressure switching valve ( 211 ) arranged check valve ( 212 ) through hydraulic fluid from the storage chamber ( 209 ) back into main brake line ( 203 ), characterized in that the high pressure switching valve ( 211 ) is designed as a high-pressure-resistant switching valve with an electrically switchable blocking position and in an open rest position emptying the storage chamber ( 209 ) in the main brake line ( 203 ) he follows. Method according to claim 6, wherein the braking device ( 200 ) a motor-pump unit ( 217 ) and a switching valve ( 215 ), the switching valve ( 215 ) in the main brake line ( 203 ) and dividing them between the actuator ( 202 ) and the at least one inlet valve ( 204 ), and wherein the motor-pump unit ( 217 ) is arranged, hydraulic fluid from the storage chamber ( 209 ) in the part of the main brake line ( 203 ) between changeover valve ( 215 ) and inlet valve ( 204 ), characterized in that the high-pressure switching valve ( 211 ) for the duration of a pumping operation of the motor-pump unit ( 217 ) closes. Method according to claim 7, characterized in that the high-pressure switching valve ( 211 ) is open outside a pumping operation and by the open high-pressure switching valve ( 211 ) a pre-filling of a connecting space between high-pressure switching valve ( 211 ), Check valve ( 212 ) and motor-pump unit ( 217 ) with hydraulic fluid. A method according to claim 6, characterized in that the electrically controllable inlet valve ( 204 ), the electrically controllable outlet valve ( 208 ), the electrically controllable changeover valve ( 215 ) and the motor-pump unit ( 217 ) are controlled by an electrical control device for performing a control operation, wherein the high-pressure switching valve ( 211 ) is closed for the duration of this control process. Method according to claim 9, characterized in that the high-pressure switching valve ( 211 ) is closed exclusively for the duration of a control process, so that the storage chamber ( 209 ) otherwise via the high-pressure switching valve ( 211 ) emptied.

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