DE102008008556A1 - Method for generating dynamic pressure in hydraulic wheel brake, involves closing inlet valve when outlet valve is opened, where hydraulic wheel brake is connected on brake circuit filled with pressurized medium - Google Patents

Abstract

The method involves closing an inlet valve (12) when the outlet valve (13) is opened. A hydraulic wheel brake (4) is connected on a brake circuit (2,3) filled with pressurized medium by the inlet valve and the outlet valve. A pressurized medium pump (17) and an operating unit (5) are connected over an isolating valve (11) of an operating unit before the inlet valve of the high pressure area of a pressurized medium pump. An independent claim is also included for a control for generating a dynamic pressure in a hydraulic wheel brake.

Description

The The invention relates to a method and a control for generation a dynamic pressure in a hydraulic brake, independent compensate for an actual braking action airguns and Orders such as water, salt or the like on the brake disc to eliminate. In particular, a back pressure in a hydraulic operated by pressure medium wheel brake of a motor vehicle be generated, which via a preferably non-actuated Condition open inlet valve and a preferably non-actuated Condition closed outlet valve to one with the pressure medium filled hydraulic brake circuit is connected. Before the Inlet valve are connected to the brake circuit of the high pressure area Pressure medium pump and a separating valve, an actuating unit, in particular a pedal-operated master cylinder with pressure medium container, connected. Furthermore, in the brake circuit, the exhaust valve via a pressure holding valve with the low pressure region of the pressure medium pump connected. Further, to the brake circuit between the pressure holding valve and the low pressure region of the pressure medium pump which is a pressure medium reservoir having associated actuation unit via a suction valve. In the brake circuit is between the actuator unit and the separating valve arranged a pressure sensor. To build up a dynamic pressure in a wheel brake connected to the brake circuit are the Separating valve with an opening function at an adjustable Pressure upper limit closed as a pressure relief valve, the intake valve opened and the pressure medium pump switched on. Then it will be the outlet valve is time-controlled.

Such brake systems are for example from the DE 197 01 070 A1 or the DE 10 2004 014 171 A1 known. In the latter, a vehicle brake system is described with a device for controlling the brake and traction and the vehicle dynamics control, which has a brake device with a pneumatic brake booster and a master cylinder, the pressure chambers connected via brake lines with paired within the brake circuits wheel brakes and by means of electromagnetically actuated isolation valves are separable from the wheel brakes. A designed as a pressure medium pump with a motor conveyor can supply pressure medium in a high-pressure accumulator, which is arranged on the pressure side of the conveyor. The wheel brakes are connected via inlet and outlet valves to the brake circuit, the wheel brakes are connected on the outlet side with a low pressure accumulator, which is connected to a suction or low pressure side of the conveyor.

Between the master cylinder and the isolation valve is the braking intervention the driver indicating pressure increase detected and to a control unit the brake circuit reported.

at such brake systems are increasingly realized functions which almost imperceptibly support the driver and safety to increase the motor vehicles. These functions are used in usually to put the wheel brake in a defined state. It should be compensated if necessary built air games or Orders on the brake disc by water, salt, oil or other contaminants are eliminated. This is known Brake systems usually by a pump running at an open Release valve and an open intake valve dissolved. By the switching on of the pressure medium pump is dependent on the pump speed a certain, compared to a real one Braking generates low back pressure, which makes it easy to attach Brake pads on the brake discs causes and the brake, for example put in readiness for brakes or orders on the Brake disc eliminated.

In Such an open hydraulic system with an open Isolation valve and an open intake valve can be Dynamic pressure can only be generated by a permanent volume flow, which is achieved by the operation of the pressure medium pump. Therefore the pressure-based pressure generation is particularly demanding on the durability of the engine and pump units, since relatively high Pump speeds are required to maintain the dynamic pressure (dynamic) to create. In addition, varies in these systems turned on Back pressure, as it depends heavily on the temperature in the brake system and the pump speed depends.

Next the high loads for the engine and the pressure medium pump The required high speed level also poses a noise problem represents.

Around To get around this, it is possible instead of dynamic generated back pressure a quasi static back pressure with the help of the pressure holding valve between the exhaust valve and the suction valve or to produce the suction of the pressure medium pump, wherein the Dynamic pressure is maintained even after switching off the pressure medium pump. When setting such a static pressure arises by opening valves in the brake circuit for a short time a hydraulic short that causes the braking the driver through the operating unit and the between the actuator and the isolation valve provided sensor can not be reliably detected.

The object of the invention is therefore to provide a reliable and secure generation of a dynamic pressure while avoiding the aforementioned Sicherheitspro to allow trouble.

These The object is achieved by a method having the features of the claim 1 and a controller with the features of claim 9 solved. In this case, the invention essentially provides that the inlet valve is closed while the outlet valve is open to build up the dynamic pressure in the wheel brake. In this circuit, therefore, the pressure holding valve for generating of the dynamic pressure is set, whereby a security problem by a short-term hydraulic short circuit in the brake line system is avoided by closing the inlet valve. Due to the static pressure build-up the load of the Engine and / or the pressure medium pump to maintain the dynamic pressure be kept low because the pressure medium pump after construction the dynamic pressure in the wheel brake while maintaining the static Dynamic pressure can be switched off.

According to one preferred embodiment of the invention can the exhaust valve and the intake valve in time between their switching states, d. H. opened and closed, to be switched. there must be the ratio of closed inlet valve and open exhaust valve not be symmetrical, but can be varied to increase the dynamic dynamic pressure ratio or lower.

The already mentioned opening function with an adjustable Pressure upper limit of the isolation valve, which the isolation valve to a pressure relief valve makes and avoiding excessive system pressure in the overall system serves, can advantageously by an analogized isolation valve be reached, the switching threshold by a current application can be adjusted. This feature is used while the predetermined by a controller function, for example Elimination of air games or orders on the brake disc to avoid a significant braking effect. Within typical Motor vehicle brake systems can this a switching threshold from about 5 or 10 to 130 bar in question. According to one further, possibly also with the clocked control of Inlet and exhaust valves combinable embodiment of the proposed Method, also as an inlet valve, an analogized valve be used, its closing force by a switching current is adjustable.

If according to a particularly preferred embodiment both isolation valve and the inlet valve as analogized Valves are formed, it is advantageous if the isolation valve an opening function at about 5 to 25 times realized higher pressure upper limit than the inlet valve. At a pressure upper limit for the isolation valve of about 100 bar, the inlet valve according to a particular preferred embodiment, a pressure upper limit between 5 to 10 bar. As a result, the intake valve at a low system pressure flows between the inlet valve and the isolation valve, and pressure medium is conveyed in the direction of the wheel brake, because the highly energized isolation valve with a pressure upper limit clearly above the Pressure level of the inlet valve not the pressure limiting function represents, but the inlet valve. If in this constellation a braking of the driver takes place, this is due to a pressure value in the range of 5 to 10 bar according to the energization of the inlet valve detected.

For to be effected by the back pressure according to the invention Functions of the wheel brake, in particular the degradation built up Air games or the removal of orders on the brake disc, should preferably a back pressure in the wheel in the range of 1 to 9 bar, in particular in the range of 3 to 7 bar, are generated. This statically realized dynamic pressure is in the inventive Circuit of the valves involved by the opening characteristic of the pressure retention valve.

To the Static holding the generated dynamic pressure can after the structure of the dynamic pressure, d. H. after opening the exhaust valve and the closing of the intake valve or the clocked Switching of exhaust and intake valves, for a given or adjustable dynamic pressure holding time the intake valve closed and the pressure medium pump are turned off, wherein the inlet valve open, the outlet valve and the isolation valve be kept closed. The separating valve may optionally in the state with an opening function at an adjustable Pressure limit to be held as a pressure relief valve.

The Releasing the dynamic pressure after the dynamic pressure holding time can according to the invention by opening the Disconnect valve done, the above-described state of the rest Valves is maintained. Then the plant is in the normal Operating state in which the actuator immediate Has access to the wheel brake. After opening the isolation valve is an inventive cycle for building the Dynamic pressure in the wheel brake completed.

In a constructed from two or more hydraulic brake circuits brake system according to the invention in each case a wheel brake of a brake circuit simultaneously a back pressure can be generated. Preferably, each brake circuit, the same, above-described valves with a common or separate pressure medium pumps with corresponding conveyors on. In diagonal brake circuit split a two-brake circuit brake system, for example, the valves of both wheel brakes of the rear axle switch simultaneously; in a so-called black / white division, the valves of the left and right two brakes of the front and rear axles can switch simultaneously. However, the proposal according to the invention is not limited to brake systems with two hydraulic brake circuits nor to the above-described division of wheel brakes in the respective brake circuits. Other versions can be realized in the context of expert action.

Further The present invention relates to a controller, in particular a control unit for generating a dynamic pressure in one hydraulically operated by means of pressure medium wheel brake a Motor vehicle, which according to the already described Configuration via an inlet valve and an outlet valve connected to a filled with a pressure medium brake circuit is at which in front of the inlet valve of the high pressure area of a Pressure medium pump and a separating valve, an operating unit are connected. In the brake circuit, the exhaust valve is over a pressure holding valve with the rear pressure range of the pressure medium pump connected. Furthermore, the actuating unit between the Pressure retention valve and the low pressure region of the pressure medium pump via a suction valve connected to the brake circuit, in which between the actuating unit and the isolation valve further includes a pressure sensor is arranged. According to the features of claim 9, the Control a processor, in particular a microprocessor, and Signal connections for building up the dynamic pressure in one or multiple wheel brakes, with the processor configured to by means of the signal connections Control signals the isolation valve, preferably with an opening function at an adjustable upper pressure limit, close to open the intake valve and turn on the pressure medium pump and then time-open the exhaust valve. Further the processor is set up to close the inlet valve, while the exhaust valve is open.

Preferably For example, the processor may perform any or all of the above Procedural steps to be set up. In particular, the controller through the processor and appropriate signal connections for Control of all valves of the brake system be set up independently whether it has one, two or more hydraulic brake circuits.

Therefore it is particularly advantageous, the inventive Control to generate a dynamic pressure in an already existing Integrate control of a brake system and the inventive Implement the procedure as a special function.

Further Features, advantages and applications of the present Invention will become apparent from the following description of a Embodiment and the drawing. All form described and / or pictured Lich illustrated features for itself or in any combination the subject matter of the present Invention, also independent of its summary in the claims or their remittances.

It demonstrate:

1 a brake system with two brake circuits, in which the invention can be realized;

2 a diagram with switching times and generated back pressures according to a first embodiment of the invention and

3 a diagram with switching times and generated back pressures according to a second embodiment of the invention.

In 1 is a hydraulically dual-circuit brake system 1 for conventional, driver-initiated service braking described the two hydraulically separated brake circuits 2 . 3 having. To a brake circuit 2 . 3 are each two wheel brakes 4 connected by the brake system 1 be operated. For example, the brake circuit 2 the wheel brakes 4 a vehicle rear axle and the brake circuit 3 the wheel brakes 4 Press a vehicle front axle. However, there are other assignments of wheel brakes according to the invention 4 and brake circuits 2 . 3 possible.

By the driver of a motor vehicle, a braking by means of a pedal-operated actuator 5 be released, which is a master cylinder 6 with two pressure chambers 7 that has over brake lines 8th with the first and second brake circuit 2 . 3 are connected. Because the breakdown of the brake system 1 in two brake circuits 2 . 3 is not essential to the present invention are for the respective components of the two brake circuits 2 . 3 simply the same reference numerals used.

In the pressure chambers 7 and brake lines 8th there is a pressure medium, which in one to the master cylinder 6 connected pressure medium tank 9 is stored. To amplify the pedal action is the master cylinder 6 a pneumatic brake booster 10 upstream.

A pressure chamber 7 of the master cylinder 6 is by means of the brake lines 8th via a separating valve 11 and an inlet valve 12 with a wheel brake 4 connected. In the open position of isolation valve 11 and inlet valve 12 becomes one through the operating unit 5 generated pressure directly on the wheel brake 4 transmit and unfold there a braking effect corresponding to the applied pressure.

With open exhaust valve 13 the pressure generating fluid flows out of the wheel brake 4 into a low-pressure reservoir 14 having low pressure region of the brake circuit 2 . 3 from. The wheel brake 4 relaxed. Via a pressure retention valve 15 and as an electric switching valve (EUV short) designed intake valve 16 is this low pressure area with the pressure chamber 7 of the master cylinder 6 connected.

In the brake circuits 2 . 3 is an example. For slip control systems provided pressure medium pump 17 with a motor 18 and one in each brake circuit 2 . 3 arranged conveyor 19 arranged together or for each brake circuit 2 . 3 can be operated separately from each other. This pressure medium pump 17 with conveyor 19 can now also for additional functions, such as bringing the wheel brake 4 in a standby state, the initiation of emergency braking, the application of the brake shoes with a low or low dynamic pressure for eliminating orders such as water, salt or other contaminants on the brake disc or to eliminate air games used.

By conveying the pressure medium, the conveyor 19 in the direction of the inlet valve 12 one the wheel brakes 4 deliverable (ie dynamically generated) back pressure, including the conveyor 19 the pressure medium pump 17 at its intake or low pressure port via the pressure retention valve 15 with the low-pressure accumulator 14 and over the open intake valve 16 with the master cylinder 6 and the pressure fluid container 9 connected to the suction of the conveyed pressure medium.

The brake system 1 is replaced by an in 1 not shown control (control unit) driven, which the pressure medium pump 17 drives and controls the valves described above by control signals and switches. In the brake line 8th between the pressure chamber 7 and the isolation valve 11 is a pressure sensor 20 provided, the pressure of the pressure medium in the brake circuit 3 measures. This pressure value is also reported to the controller.

In 1 the valves are shown in their non-activated or not switched rest position. In this rest position are the isolation valve 11 and the inlet valve 12 opened and the exhaust valve 13 closed. Further, the suction valve 16 closed. In the rest position causes by the operating unit 5 generated pressure increase in the brake circuit 2 . 3 directly a braking effect of the wheel brakes 4 as already described. If, for example, by a driver assistance system, a readiness for braking or an emergency braking independently of an actuation of the operating unit 5 is to be triggered by the driver, first the isolation valve 11 closed, reducing the return flow to the actuator unit 5 from the brake circuit 2 . 3 is prevented. The pressure required to initiate the braking is now through the conveyor 19 the pressure medium pump 17 generates, which required for the promotion pressure medium with open intake valve 16 from the master cylinder 6 or the pressure medium container 9 the operating unit 5 sucks. Once in the brake circuit 2 . 3 enough pressure medium is available, the intake valve 16 preferably closed again.

Due to the closed isolation valve performs an actuation of the actuator 5 by the driver directly to a significant pressure increase in the pressure sensor 20 , so that the control of the brake system 1 the operation of the brake by the driver is displayed very quickly and reliably. In this case, a function exercised by a driver assistance system or other control system can be stopped immediately and the braking effect can be realized according to the driver's request. Further, the driver in this case, the brake on a check valve shown in the drawing on the separating valve 11 actuate.

at the exercise of an invention only low, no appreciable braking effect deploying dynamic pressure in the wheel brake, for example, to compensate for air games or eliminating orders on the brake disc is against proposed following control of the valves.

To be in front of the inlet valve 12 in the brake circuit to avoid too high pressure, the analogized isolation valve 11 controlled by a current which causes the separating valve to open from an applied pressure above a pressure upper limit. Thus, the isolation valve acts as a pressure relief valve that opens at a pressure above the upper pressure limit and pressure medium on the lying in the idle state in the low pressure range master cylinder 6 in the pressure medium tank 9 transferred. The upper pressure limit can be adjusted, for example, so that a strong braking effect is reliably avoided. At an applied pressure of 100 bar is typically obtained a very strong braking effect with a delay of more than 1 G. Even at 5 or 10 bar in the wheel brake a noticeable braking effect is achieved.

At the same time, the intake valve 16 and the pressure medium pump 17 or their conveyor 19 activated. This causes pressure fluid from the pressure fluid container 9 and / or the pressure chamber 7 through the pressure medium pump 17 is sucked. The pressure retention valve 15 intended to prevent the brake pistons are sucked back when braking with the use of an anti-lock braking system, when the low-pressure accumulator 14 is empty and the intake valve 16 is open.

The wheel brake 4 is filled with pressure medium. This closes existing air games and it is built a low wheel pressure, which leads to a simple concern of the brake shoes on the brake disc, without developing a high braking effect. As a result, orders can be eliminated on the brake disc.

Time-controlled now switches an exhaust valve in the open state, so that in the wheel brake 4 sets a back pressure that depends on the opening characteristic of the pressure holding valve 15 is determined. With two brake circuits 2 . 3 Timed two outlet valves can also switch in the open position, for example, the valves at the rear left and rear right with diagonal brake force distribution or the valves front left and rear left in the so-called "black and white division". This defined by the opening characteristic of the pressure-holding valve back pressure is also held static when then the pressure medium pump 17 is turned off and the isolation valve 11 remains closed. The intake valve 16 will be closed as well. In this switching arrangement of the valves, the pressure holding valve 15 used as a pressure relief valve.

During the period in which the exhaust valve 13 to build up the dynamic pressure in front of the pressure retention valve 15 is open, however, the hydraulic system is hydraulically shorted so far, as an increase in pressure in the actuator unit 5 due to the opening of the check valve from the isolation valve 11 at a pressure which is greater than the generated back pressure is passed through the entire system and in the pressure sensor 20 may not be significantly detectable. The pressure value of this pressure sensor 20 However, it serves to determine the operation intervention by the driver and, if necessary, cancel measures to eliminate an air clearance or order of dirt on the brake disc. If the driver were to apply the brake in this condition, he would only have to overcome the pre-established dynamic pressure. This would mean that deceleration could possibly not be detected.

In order to avoid the short period of a hydraulic short circuit, the valves of the brake circuit 2 a wheel brake 4 now switched so that the inlet valve 12 is closed while the exhaust valve 13 is open. Because the inlet valve 12 opened in a de-energized state and the exhaust valve 13 is closed in a de-energized state, the inlet valve 12 and the exhaust valve 13 be switched simultaneously by the controller.

This switching can be performed clocked, wherein a plurality of switching operations are carried out successively. When applying the switching signal thus closes the normally open inlet valve and the normally closed exhaust valve opens. In the manner already described, the back pressure then arises via the pressure retention valve 15 , A possible braking of the driver in this switching state is against the closed inlet valve 12 quickly generate a pressure increase caused by the pressure sensor 20 is reliably detected. The cycle for generating the dynamic pressure is then terminated prematurely.

In the next cycle, in which the inlet valve 12 and the exhaust valve 13 are not switched, so change their switching states: the inlet valve 12 opens and the exhaust valve closes. This results in a short pressure build-up in the Radverbraucher, since the isolation valve 11 still closed, the intake valve 16 still open and the pressure medium pump 17 still in operation. In this cycle, the driver has an immediate hydraulic grip on the wheel brake 4 according to the normal operating position.

The Ratio of cycle times of closed inlet and open outlet to open inlet and closed Outlet does not have to be symmetrical (1: 1), but can also be varied to increase the dynamic dynamic pressure share or lower.

Since the driver has immediate access to the braking system in this cycle, the braking of the driver due to the by the operating unit 5 reached pressure increase in the sensor 20 safely detected, so that the Zyk lus for building the dynamic pressure according to the invention can be terminated prematurely.

Likewise, in this cycle, the liquid or pressure medium volume, which may have accumulated in the previous cycle in the low-pressure accumulator degraded. Thereafter, the switching states of the intake and exhaust valves change 12 . 13 again in the previously described cycle.

Timed switching of intake valves 12 and the exhaust valves 13 can be the upper half of the 2 remove. There are among each other the switching states of the isolation valve 11 , the intake valve 12 , the pressure medium pump 17 , the exhaust valve 13 and the intake valve 12 over time in arbitrary units for one cycle to generate the back pressure on a wheel brake 4 shown.

The cycle is accomplished by simultaneously switching the isolation valve 11 , the intake valve 16 and the pressure medium pump 17 initiated. This closes the analogized isolation valve 11 , wherein by the applied current, an opening pressure is set according to the upper pressure limit. At the same time, the intake valve opens 16 , The inlet valve not switched at this time 12 and exhaust valve 13 lead in the wheel brake 4 to build up an increased pressure (back pressure).

After a time clock, the inlet valve 12 and the exhaust valve 13 switched, causing the inlet valve 12 closes and the exhaust valve 13 opens. This builds up a through the pressure retention valve 15 limited traffic jam pressure. This clocked circuit is maintained for a period of time until the desired back pressure via the pressure retention valve 15 typically built. Then the intake valve 16 closed by stopping the control and the pressure medium pump 17 switched off. Also the inlet valve 12 and the exhaust valve 13 find themselves in a non-switched state where the inlet valve 12 opened and the exhaust valve 13 are closed. In this state, the static back pressure is maintained, via the pressure retention valve 15 was set because the isolation valve 11 remains closed. By opening the isolation valve 11 After the end of the cycle to generate the dynamic pressure, the back pressure builds up in the wheel brakes 4 again. The chronological course of the dynamic pressure in the four wheel brakes 4 the in 1 illustrated brake circuits 2 . 3 is in the lower half of the 2 shown.

For hydraulic brake systems with analogized intake valves 12 The method can also be carried out in a slightly different embodiment. Also in this method, the inventively provided back pressure on the pressure retention valve 15 between the outlet valve 13 and the intake valve 16 generated according to the timing protocol according to 3 first the isolation valve 11 For this purpose, in turn, a current is selected, which corresponds to an opening pressure according to the selected pressure upper limit, in front of the inlet valve 12 avoid too high system pressure. At the same time, the intake valve 16 opened by switching on and the pressure medium pump 17 switched on. This will fill the wheel brakes 4 which, for example, leads to closing of existing air games. It is built a low wheel pressure.

Instead of a clocked circuit then switch simultaneously one or more exhaust valves 13 and inlet valves 12 , whereby the inlet valve 12 closed and the exhaust valve 13 is opened. In the wheel brake 4 adjusts the desired dynamic pressure, which depends on the opening characteristics of the pressure retention valve 15 is determined. This pressure is kept static when the pressure medium pump 17 is turned off as long as the isolation valve 11 remains closed. By simultaneously actuating inlet valve 12 and exhaust valve 13 becomes the hydraulic short circuit in the brake circuit 2 . 3 avoided, which can lead to a hazardous situation, since at this time a braking intervention of the driver can not be reliably detected.

In this variant, the inlet valve 12 but with a current proportional to an opening pressure of 5 to 10 bar connected. This turns the inlet valve 12 at a lower system pressure between the inlet valve 12 and the isolation valve 11 overflows, and it becomes brake fluid in the direction of the wheel brake 4 promoted, as the higher energized isolation valve 11 with an opening pressure of about 100 bar so far no pressure limiting function, but the inlet valve 12 ,

A possible braking of the driver generated by the energization of the inlet valve in the pressure sensor 20 a pressure in the range of 5 to 10 bar, which is via the pressure sensor 20 is reliably detected. As a result, the cycle is terminated and it can come to no hydraulic short circuit. The above-described switching behavior is associated with the back pressures in the wheel brakes 4 in 3 shown similar 2 is constructed so that can be dispensed with a detailed description.

As a clear difference you can see that the inlet valve 12 and the exhaust valve 13 not switched clocked. After switching off the pressure medium pump 15 and closing the intake valve 16 is the back pressure in the system (with the inlet valve open 12 and closed exhaust valve 13 ) still held until the isolation valve 11 is opened. Then the dynamic pressure of the wheel brakes falls 4 to zero.

Another advantage of the proposed method and the set up for performing this method control device is the relative temperature independence, since the pressure is not adjusted by a flow as back pressure, but by a correspondingly adjusted pressure retention valve 15 , which is used as a pressure relief valve.

1

braking system

2, 3

brake circuit

4

wheel brakes

5

operating unit

6

master cylinder

7

pressure chamber

8th

brake line

9

Pressure fluid reservoir

10

Brake booster

11

isolation valve

12

intake valve

13

outlet valve

14

Low-pressure accumulator

15

pressure-retaining valve

16

intake valve

17

Hydraulic pump

18

engine

19

Conveyor

20

pressure sensor

QUOTES INCLUDE IN THE DESCRIPTION

This list The documents listed by the applicant have been automated generated and is solely for better information recorded by the reader. The list is not part of the German Patent or utility model application. The DPMA takes over no liability for any errors or omissions.

Cited patent literature

• - DE 19701070 A1 [0002]
• DE 102004014171 A1 [0002]

Claims (10)

Method for generating a dynamic pressure in a hydraulically operated by means of pressure medium wheel brake ( 4 ) of a motor vehicle, which via an inlet valve ( 12 ) and an outlet valve ( 13 ) to a filled with the pressure medium brake circuit ( 2 . 3 ), at which in front of the inlet valve ( 12 ) the high pressure area of a pressure medium pump ( 17 ) and via a separating valve ( 11 ) an actuating unit ( 5 ) and in which the exhaust valve ( 13 ) via a pressure retention valve ( 15 ) with the low-pressure region of the pressure medium pump ( 17 ) is connected to which between the pressure retention valve ( 15 ) and the low-pressure region of the pressure medium pump ( 17 ) the actuating unit ( 5 ) via an intake valve ( 16 ) and in which between the operating unit ( 5 ) and the isolation valve ( 11 ) a pressure sensor ( 20 ) is arranged, wherein to build up a back pressure, the isolation valve ( 11 ), preferably with an opening function at an adjustable upper pressure limit, closed, the intake valve ( 16 ) and the pressure medium pump ( 17 ) and then the exhaust valve ( 13 ) is timed, characterized in that the inlet valve ( 12 ) is closed while the exhaust valve ( 13 ) is open. Method according to claim 1, characterized in that the outlet valve ( 13 ) and the inlet valve ( 12 ) are switched in the clock between their switching states. A method according to claim 1 or 2, characterized in that as a separating valve ( 11 ) and / or as an inlet valve ( 12 ) analogized valves are used. Method according to claim 3, characterized in that the separating valve ( 11 ) an opening function at a 5- to 25-fold higher pressure upper limit than the inlet valve ( 12 ) realized. Method according to one of the preceding claims, characterized in that a dynamic pressure in the range of 1 to 9 bar is generated. Method according to one of the preceding claims, characterized in that after the build-up of the back pressure for a dynamic pressure holding time, the intake valve ( 16 ) and the pressure medium pump ( 17 ), the inlet valve ( 12 ), the outlet valve ( 13 ) and the isolation valve ( 11 ) are kept closed. A method according to claim 6, characterized in that after the dynamic pressure holding time, the separating valve ( 11 ) is opened. Method according to one of the preceding claims, characterized in that in one of two hydraulic brake circuits ( 2 . 3 ) constructed brake system ( 1 ) in each case a wheel brake ( 4 ) of a brake circuit ( 2 . 3 ) at the same time a dynamic pressure is generated. Control for generating a dynamic pressure in a hydraulically operated by means of pressure medium wheel brake ( 4 ) of a motor vehicle, which via an inlet valve ( 12 ) and an outlet valve ( 13 ) to a filled with the pressure medium brake circuit ( 2 . 3 ), at which in front of the inlet valve ( 12 ) the high pressure area of a pressure medium pump ( 17 ) and via a separating valve ( 11 ) an actuating unit ( 5 ) and in which the exhaust valve ( 13 ) via a pressure retention valve ( 16 ) with the low-pressure region of the pressure medium pump ( 17 ) to which the operating unit ( 5 ) between the pressure retention valve ( 16 ) and the low-pressure region of the pressure medium pump ( 17 ) via an intake valve ( 16 ) and in which between the operating unit ( 5 ) and the isolation valve ( 11 ) a pressure sensor ( 20 ), wherein the controller comprises a processor and signal terminals for establishing the back pressure, wherein the processor is adapted to the control valve via control signals output via the signal terminals ( 11 ), preferably with an opening function at an adjustable upper pressure limit, to close the intake valve ( 16 ) and the pressure medium pump ( 17 ) and then the exhaust valve ( 13 ) is timed, characterized in that the processor is further adapted to control the inlet valve ( 12 ) while the exhaust valve ( 13 ) is open. Control according to claim 9, characterized in that the control for generating a dynamic pressure in a control of a brake system ( 1 ) is integrated.