DE102015103859A1 - Hydraulic device, in particular braking device for motor vehicles - Google Patents

Abstract

The invention relates to a hydraulic device, in particular brake device for motor vehicles, with at least one piston-cylinder unit (10) which is connected via a hydraulic line with at least one consumer, in particular vehicle brake (brake circuit BK1, BK2), to supply pressure medium to the consumer and pressurized with a drive (4) for the piston-cylinder unit (10). It is provided that by means of at least one piston (10) of the piston-cylinder unit (20), in a hydraulic circuit (BK2 or BK1) and at the same time in the pressure chamber 22b of the piston-cylinder unit (10) via a hydraulic line regulated pressure medium can be supplied.

Description

description

The present invention relates to a hydraulic device or system, in particular a brake device or system for motor vehicles according to the preamble of claim 1.

State of the art

The demands on brake systems are increasing. This applies in particular with regard to failure safety and good fallback level as well as length and costs.

A system with very little effort was designed by the applicant in EP 1874602B1 shown. The system described in the application is based on the fact that a piston-cylinder system for the brake pressure build-up and brake pressure reduction for the brake booster and to realize the ABS and traction control, and the control device Druckauf- and pressure reduction in the wheel brakes based on the evaluation of a Pressure volume characteristic and a pressure transducer or current measurement of an electric motor controls.

In an advantageous simple embodiment of the above-mentioned system ( EP 1874602 = WO2006 / 111393 ), only one switching valve per wheel brake is provided and the pressure control takes place after controlling the pressure volume curve simultaneously or sequentially. This embodiment is referred to as "multiplex system" (MUX) in the literature.

In EP 1874602 is exemplified that the pressure generating a motor-gear unit acts on a master cylinder with pressure and floating piston, which is connected to the wheel brakes ( 4 . EP 1874602 B1 ).

Systems with control based on the pressure volume characteristic curve in brake booster operation are in DE 10 2011 082 492 addressed. In this embodiment, the pressure is generated via a piston-cylinder unit, which is driven by an electric motor. The pressure control takes place directly with the piston-cylinder unit and wheel brake valves. In addition, a master brake cylinder is provided with travel simulator, which ensures a parallel pressure supply, especially for the error case "failure of the piston-cylinder unit", or the drive of the piston-cylinder unit.

In DE 10 2011 085 273 another embodiment of a multiplex system is shown. In contrast to EP 1874602 B1 is a separate piston-cylinder unit with pressure chamber ( 3 , Reference number ("BZ") 11 ) intended. The pressure of the piston-cylinder unit is transmitted via a hydraulic line to the rear of a master cylinder ( 3 BZ. 12 ) guided. The master cylinder has a pressure piston (BZ. 6 ) and floating piston (BZ. 7 ). This embodiment is functionally equivalent to the engine-gear unit, allows a more flexible arrangement of the piston-cylinder unit and thus a shorter overall length, but a higher cost.

In addition to the function of brake systems, the failure safety and the good controllability by the driver in the event of a fault is a decisive criterion in the execution. In addition, brake systems require, especially when used in hybrid vehicles Wegsimulatoren, since repercussions on the pedal, especially in regenerative braking are undesirable. If the brake booster fails, it should be achieved at the internationally predetermined foot force of 500 N, a delay greater than 0.64 g, which compared to the minimum requirement of the legislature of 0.24 g significantly more means. In addition, short pedal travel should be ensured in case of failure and a progressive increase in pedal force.

In DE 10 2010 050 132 The applicant is described an advantageous construction of a Wegsimulatorsystems and an embodiment of the fallback level in case of failure of the system. In DE 2010050132 an auxiliary piston is provided which is filled with hydraulic fluid ( 3 , BZ 26 . 29 ). The hydraulic piston acts on a travel simulator ( 3 BZ 66 ) in normal operation. In case of failure of the travel simulator, the volume of the auxiliary piston via a Wegsimulatorabsperrventil (WA valve, BZ 64 ) are discharged into the reservoir, or via a feed valve (ESV valve, BZ 68 ) are directed into the wheel brakes. This is an ideal fallback without pedal diarrhea possible. If the volume is drained into the reservoir, the pedal acts on a plunger 38 on the master cylinder. This allows a mechanical penetration by the driver. In addition, volume of the auxiliary piston can be guided in the wheel cylinder. This has the advantage, in particular in brake systems with a large volume intake, that a higher pressure can be built up with a shorter pedal travel in the fallback level.

This fallback of the DE 2010050132 is also found in the DE 10 2011 085 273 , The system has as a fallback level a mechanical access to the master cylinder, an auxiliary piston with hydraulic fluid ( 3 , BZ 14 . 15 ) and a path simulator (BZ 8th ). In the event of a fault, the driver can intervene, so that the volume of the auxiliary piston can via a feed valve (BZ 21 ) and a hydraulic line (BZ 1 . 26 ) in the floating piston (BZ 13 ) or the wheel brake of a circle promoted be (BZ 3 . 30 ), or in the reservoir via a second valve (BZ 1 ) can be drained.

DE 10 2011 085 273 allows a flexible arrangement of the components / modules by the hydraulic supply of the pressure supply, in particular the piston-cylinder unit and the electric motor. A disadvantage is the great length due to the serial arrangement of the master cylinder and auxiliary piston.

This was in DE 10 2010 050 132 A1 the auxiliary piston arranged in parallel to reduce the length, partly to compensate for the electric motor.

Since it is undesirable that hydraulic fluid in the footwell, lead system with auxiliary piston and master cylinder in the embodiment as THZ (pressure piston and floating piston) with a serial arrangement of the auxiliary piston to a long, especially for crash situations unfavorable length from bulkhead.

Object of the invention

The invention has for its object to improve a device of the type mentioned in that complexity and complexity and length of a brake system can be reduced.

Solution of the task

The object of the invention is solved by the features of claim 1.

With the solution according to the invention results in a simple construction of the master cylinder with a short overall length and low complexity. In addition, there is a high level of error safety.

The pressure is supplied via a driven by an actuator piston-cylinder unit with pressure build-up and Druckabbauregelmöglichkeit, which has a separate pressure chamber which is connected via a hydraulic line to the floating piston of the master cylinder and a first brake circuit.

The pressure control, in particular in normal operation (brake boost, regenerative braking) is carried out in multiplex (MUX) in the closed brake circuit. The pressure control takes place in the known method according to the path control via a pressure volume model with use of a pressure transducer or evaluation of the phase current measurement of the electric motor.

In addition, the control mode (ABS, ESP) in the MUX method is an advantageous embodiment of the invention, but not mandatory. It is possible that in or for certain (s) consumer (s) additionally exhaust valves are provided and in addition there is a pressure control in the open brake circuit.

The master cylinder is greatly simplified in the inventive solution and has only a single piston, which has the form of a floating piston, which is pressurized and is returned via a spring. This eliminates the pressure piston, which is typically part of the tandem master cylinder in brake systems.

The master cylinder is connected via a simple partition with an auxiliary piston, which - as described in the art - as an operating unit for the travel simulator and in case of error additional volume via a feed valve ESV in the brake circuit supplies and in the master cylinder (rear of the floating piston) are performed can and has a plunger that allows a mechanical penetration in case of failure on the master cylinder.

Advantageous embodiments of the invention have two versions of path simulators.

In a first possible embodiment, a hydraulic travel simulator to the working or pressure chamber of the third cylinder-piston unit (auxiliary piston) is connected, which receives the volume of the auxiliary piston in normal operation and is switched off in case of failure via a valve. In addition, a free travel between a pedal actuation unit and a plunger is provided. In the event of system failure, the system has a two-stage fallback level. In a first stage, the displaced by the piston (auxiliary piston) of the third cylinder-piston unit volume is fed via a feed valve in the master cylinder and the hydraulic circuit of the wheel cylinder. In a second stage, the actuating unit abuts the plunger and acts directly on the floating piston of the second cylinder-piston unit (master cylinder). Through the combination of hydraulic and mechanical fallback a very simple structure can be implemented.

In a second embodiment, a ram displacement simulator is provided with a free travel in the second cylinder-piston unit (master cylinder) to the floating piston. The plunger in this case firmly coupled to the actuator unit. The pedal feel is generated by the piston-cylinder unit. The area of the ram travel simulator and the pressure in the master cylinder determines the force on the pedal, the pedal force being proportional to the pressure and providing a natural pedal feel comparable to standard vacuum booster solutions. About a shut-off valve WA is the Auxiliary piston connected to the reservoir. In the control of the travel simulator, the WA valve also has the function of closing the valve during pressure changes in the master brake cylinder, eg during normal operation, and thus preventing pressure pulsations.

Further, the system has a valve (I / O) to a reservoir, compared to the prior art of the multiplexer with tandem master brake cylinder, a valve is less required, since the Leerwegfreiischaltfunktion deleted. The valve (I / O) has the function in the system that volumes e.g. can be nachgefördert in the fading case from the reservoir or can be discharged again.

A valve (DAV) is used to equalize the pressure between the brake circuits. The valve (DAV) is open in ABS control mode and in the case of refilling. The valve (DAV) allows efficient pumping via the piston-cylinder unit in both brake circuits with high volume requirements (for example, air in the brake circuit or fading). In addition, a pressure equalization between the two brake circuit can be created in ABS operation, thus preventing that the piston (floating piston) of the second cylinder-piston unit migrates to the stop and no pressure build-up is possible without Nachfördern with loss of time. A displacement measurement of the floating piston is helpful here, but can also be replaced by an accurate hydraulic model.

As a pressure generating unit a Einfachhubkolben or alternatively a Doppelhubkolben is used. Both pistons allow Druckauf- and pressure reduction. When pumping back, the single piston has to be moved back, which is not necessary with the double-stroke piston.

The double-stroke piston has the advantage that it can be continuously conveyed in the forward and reverse strokes and, in addition, hydraulic surfaces can be switched over via a switching valve. This allows the drive motor to be downsized as the torque can be reduced. In addition, the Nachfördern the Doppelhubkolben done with little time interruption.

When using a double-stroke piston, the valve (I / O) must only be designed as an outlet valve. The mode of action of the Doppelhubkolbens is detailed in PCT / EP2014 / 069723 to which reference is made so far described.

figure description

Further embodiments or embodiments of the invention and their advantages are contained in the further claims and are described in more detail below with reference to the drawing.

Show it:

1 a first embodiment of a brake system with Kolbenwegsimulator and Einfachhubkolben pressure generator unit;

2 a second embodiment of a brake system with a ram travel simulator and single-stroke piston pressure generator unit;

3 a third embodiment of a brake system with a ram simulator and Doppelhubkolben pressure generator unit;

4 : a double-stroke piston pressure generator unit with valve circuit for continuous delivery as well as pressure and pressure build-up.

In the 1 shown brake system has a first cylinder-piston unit 2 on that with a drive 4 is provided, which is an electric motor 6 and a gearbox 8th having. The transmission not shown 8th may include a ball screw with nut and spindle, wherein one of these parts with the piston 10 the cylinder-piston unit 2 is connected in order to drive this in both directions of movement (forward stroke, return stroke). The piston 10 limits a working or pressure room 10a , The engine is also equipped with sensors, in particular a rotation angle sensor 6a and current sensor 6b as a replacement for pressure sender 26a provided, as described in more detail below.

Another cylinder-piston unit 20 has a (floating) piston 22 on, which is arranged sealed in the cylinder via seals and two working spaces or pressure chambers 22a . 22b forms and on one side of a spring 24 is charged. This piston-cylinder unit 20 corresponds to the master cylinder of the brake system. The piston-cylinder unit 20 is optionally provided with sensors, in particular a pressure sensor 26a at the pressure room 22b and a displacement sensor 26b on the floating piston 22 , The work or pressure room 22a is via a hydraulic line 28 in the one, in particular normally open, switching valve I / O, is connected, with a non-pressurized reservoir 29 connected. Another hydraulic line 28b connects the space between the piston seals with the reservoir 29 ,

For Nachfördern must the piston 22 to be moved back to suck. This results in no pressure build-up, ie an interruption of the pressure build-up. The valve I / O is necessary for pressure build-up if there is more pressure fluid volume in the brake circuit than the displacement of the piston 22 equivalent. The limitation of the interruption of the pressure build-up does not apply to the embodiment described below 4 , in which the valve I / A can be omitted or replaced by an exhaust valve.

The work or pressure room 10a the first cylinder-piston unit 10 is via a hydraulic line 12 in which a switching valve MV (in particular closed without power) is arranged, with the working space 22b that of the master cylinder 20 connected. Another hydraulic line 12b , in which a check valve is arranged leads to the reservoir 29 , Via this line can pressure medium volume in the working space 10a the first cylinder-piston unit 2 (Plunger) be promoted, if the volume in the master cylinder is not sufficient (eg fading).

A third cylinder-piston unit 30 has a piston 32 on ("auxiliary piston cylinder"), which is sealed in the cylinder and can be acted upon by an actuator, not shown, with the foot force Fp of the driver. The piston 32 limits a working or pressure room 32a , The third cylinder-piston unit 30 is in series with the second cylinder-piston unit 20 arranged and can be arranged structurally advantageous with this in a common housing. Between the master cylinder 20 and auxiliary piston cylinder 30 is a pestle 40 arranged, which is arranged here sealed in an intermediate wall between the cylinders displaceable. Between the rear end of the pestle 40 and the piston 32 an idle LW is provided whose function is described in more detail below. The work or pressure room 32a is via a hydraulic line 33 connected to a hydraulic travel simulator WS. The hydraulic pipe 33 is branched 33a . 33b , being in a branch line 33a a switching valve WA, esp. Normally closed, and in the other a check valve 38 is switched. Another hydraulic line 39 connects the pressure room 32a with the rear pressure chamber 22 of the master cylinder 20 , In this line a, in particular normally open, switching valve ESV is arranged.

The piston 32 has a recess in which another piston 32a slidably arranged. The piston 32b is about a spring 32b on the piston 32 supported. The way of the pistons 32 . 32a can via a sensor, in particular displacement sensors 35a . 35b measured and processed in the ECU.

Here, the brake system has two brake circuits BK1, BK2, wherein two hydraulic lines HL1, HL2 in which switching valves EV1, EV2, EV3, EV4 are arranged lead to two wheel brakes RB1, RB2, RB3 and RB4 as consumers. The lines HL1 and HL2 are connected to each other via a connecting line in which a switching valve DAV is arranged. In one of the lines HL2 is a pressure sensor 36 arranged.

An electronic control unit (ECU), not shown, is provided in all embodiments of the invention for carrying out the control or regulating operations.

The pressure control, in particular in normal operation (brake boost, regenerative braking) takes place in the multiplexed closed brake circuit. The pressure control takes place in the known method according to the path control via a pressure volume model with use of a pressure transducer or evaluation of the phase current of the electric motor. For this purpose, the pressure builds up the piston 10 moved forward by the drive and withdrawn to reduce pressure. In addition, the regular operation (ABS, ESP) in the MUX procedure is performed primarily. In special cases, pressure can also be reduced via the I / O valve. In this invention, the motor is arranged parallel or perpendicular to the master cylinder and differs in this arrangement from EP 1874602 , A decisive difference, however, is that the pressure piston is eliminated and the pressure generator here by the driven cylinder-piston unit (plunger) 2 is formed directly on the piston (floating piston) of the second cylinder-piston unit 20 acts.

Furthermore, the system has, in particular normally open, valve I / O to the reservoir 29 on which one in the pressure room 22a the second cylinder-piston unit 20 to the reservoir 29 leading hydraulic line 28 is arranged. Compared to the prior art of the multiplexer with tandem master brake cylinder one valve less is required, since the Leerwegfreiischaltfunktion deleted. The valve I / O has the function in the system that volume eg in the fading case from the reservoir 29 can be nachgefördert or can be drained again.

For pressure equalization between the brake circuits is optionally a switching valve (DAV) and a displacement measurement of the piston (floating piston) 22 intended. Valve DAV is open in ABS control mode and in the case of refilling. The valve DAV allows efficient pumping via the piston-cylinder unit in both brake circuits with high volume requirements, eg air in the brake circuit or fading. In addition, a pressure equalization between the brake circuits can be created in ABS operation, thus preventing the floating piston 22 moves to the stop on the left and no pressure build-up is possible without re-feeding with loss of time. The same applies to a hike to the right stop when pressure is reduced in brake circuit BK2. A distance measurement of the floating piston is helpful, can but also be replaced by an accurate hydraulic model.

The hydraulic travel simulator WS is designed in this embodiment as Kolbenwegsimulator and takes pressure fluid volume of the piston (auxiliary piston) of the third cylinder-piston unit 30 in normal operation. In case of error, the travel simulator WS is blocked via the valve WA and the actuator acts on the plunger 40 and generates a brake pressure in the second cylinder-piston unit (master cylinder) 20 , With a corresponding design of the master cylinder diameter to 19.05 mm 2, a deceleration of 0.64 g with a foot force in case of failure of the system can still be achieved. Since the path simulator WS is controlled in this case, there is no or negligible pedal diarrhea. The dimensioning of the idle travel LW depends on the system after the fallback level without engine assistance according to the volume of the brake circuit BK1. With diagonal brake force distribution this is approximately the same for BK1 and BK2 and thus the free travel is approximately 50% of the stroke of the piston 32 of the auxiliary piston cylinder. This is only the meeting of auxiliary piston 32 and floating piston 22 at the end of the stroke.

In the 2 illustrated embodiment corresponds in its structure largely the 1 , In contrast to the latter, another simulator device, namely a plunger simulator, is provided. For this purpose, the piston of the third cylinder-piston unit 30 at its front end a pestle 41 on, which may be fixedly connected to the piston, wherein a free path LW between the front end of the plunger 41 and the piston 22 the master cylinder 20 is provided. The pressure room 32a The third cylinder-piston unit is here via a hydraulic line 34 with the reservoir 29 connected. The line is branched executed, wherein in a first branch line 34a a switching valve WA, in a second 34b a throttle and into a third 34c a check valve is connected.

In this invention greatly simplified Wegsimulatoreinrichtung the pedal reaction to the main part by the pressure of the pedal plunger 41 , on which the brake pressure acts generated. This is a function of the pedal travel S _PS measured by the pedal travel sensors in an AC system 35a . 35b and regulated according to the pressure generation with the reciprocating piston or pressure transducer 26a , In this Wegsimulatoreinrichtung invention is in other words by means of pedal travel sensors 35a and 35b the pressure determined by means of the engine and the piston of the first cylinder-piston unit is determined. This pressure acts in the pressure chamber 22b , Thus, the pressure also acts on the piston surface of the plunger 40 and produces the desired pressure proportional reaction to the brake pedal.

In the auxiliary piston 32 is a strong spring 36 between this and an intermediate piston 32b arranged to the pedal. When pedaling arises here a force-dependent differential path, via the two pedal travel sensors 35a / 35b is measured. This arrangement is therefore referred to as force-displacement sensor KWS and is used in particular for fault diagnosis.

At the in 3 illustrated embodiment, which is largely the 2 corresponds, indicates the cylinder-piston unit 50 a two pressure chambers 54 . 60 forming piston 52 can be built with the pressure in two directions and an expanded valve assembly. In particular, in the hydraulic line 12 the pressure room 54 of the double-stroke piston with the brake circuit BK2 connects a switching valve PD1 (esp. Normally closed) arranged. In another of the pressure room 54 to the brake circuit BK2 leading line 12a is a check valve 58 arranged. From the front pressure chamber leads a hydraulic line 68 in which a check valve is arranged to the reservoir 29 , From the back pressure chamber 60 of the double-stroke piston carries a hydraulic line 12c in which a switching valve SV (in particular closed without power) is arranged to the brake circuit BK2. Furthermore, a hydraulic line leads 64 from the pressure room 60 to the reservoir 29 ; in this a switching valve PD2 is arranged (esp., normally closed).

In 4 is a driven (engine / transmission) cylinder-piston unit with a Doppelhubkolben and correspondingly two working or pressure chambers with two different sized effective areas A1 and A2 shown with associated valve assembly. The front pressure chamber 54 and the rear pressure chamber 60 are via hydraulic lines 12b respectively. 12d , are connected to the check valves CV1 and CV2, with the reservoir 29 connected. In this embodiment, the only one pressure chamber forming plunger 10 the versions acc. 1 and 2 by a double-stroke piston with two pressure chambers 54 . 60 replaced, which means of Vorhub- and return stroke continuously pressure medium volume can be promoted to build up pressure in the hydraulic circuit 2 or the hydraulic line HL2. The Doppelhubkolben acts here in other words as a 1-circuit pump. The valve arrangement has a line leading in the hydraulic power HL or brake circuit BK2 12 arranged switching valve PD1 on or in the outgoing from the rear pressure chamber hydraulic branch line 12c arranged another check valve CV3. The wires 12 and 12c are about one connecting line 12d connected, in which a switching valve SV is arranged.

The pressure reduction takes place as in 4 indicated by arrows via the valve MV and arranged in a line leading from the rear pressure chamber to the reservoir line switching valve PD2.

This pressure generator unit can in accordance with 1 - 3 be used. The pressure is built up in the normal range (eg <100bar) by pre-stroke of the double-stroke piston. The larger effective area A1 is advantageously used to build up the pressure faster (prefilling effect). This is especially advantageous in the initial range of low pressure with regard to a fast braking behavior.

The pressure reduction takes place in the closed brake circuit by return stroke with opened PD1 and PD2. In regulator operation> 100 bar and in fading, when more volume is required, the piston is operated in the return stroke, or again in the forward stroke, if the volume of the return stroke is insufficient. In the return stroke, the smaller cross-sectional area A2 acts and thus requires smaller forces and a lower torque. Thus, the engine or the transmission / spindle drive can be downgesized. Even in the pre-stroke can be reduced by opening the SV valve, the effective cross-sectional area. It affects the surface A1-A2 then advantageous to the linear force of the drive.

By using this double-stroke piston, the I / O valve can be omitted or reduced to an exhaust valve.

LIST OF REFERENCE NUMBERS

2

Cylinder-piston unit

4

Single stroke piston with drive

6

electric motor

6a

Rotation angle sensor

6b

Current measurement and pressure estimation

8th

transmission

10

Piston single stroke piston

10a

Work or pressure room

12, 12a-12d

 hydraulic line pressure generator unit

20

Master brake cylinder (second cylinder-piston unit)

22

Piston of master cylinder (floating piston)

22a

first working or pressure chamber master cylinder

22b

second working or pressure chamber master cylinder

23

piston

23a

Work or pressure room

24

Reset fields Piston master cylinder

26a

pressure sensor

26b

displacement sensor

29

reservoir

30

Auxiliary piston cylinder (third cylinder-piston unit)

32

auxiliary piston

32a

 Actuating piston with pedal coupling

32a

Working or pressure chamber auxiliary piston cylinder

35a, b

 Distance sensor Pedalhub

37

Return spring Actuator

40

Plunger for piston simulator

41

Pestle for plunger simulator

50

Doppelhubkolbenantrieb

57

Piston double-stroke piston

BK1

 Brake circuit 1

BK2

 Brake circuit 2

CV1 ... CV4:

 check valves

DAV

 switching valve

I / O

Intake / exhaust valve

ECU

 electronic control unit

ESV

 feed valve

EV1

 Intake valve wheel brake cylinder 1

EV2

 Intake valve wheel brake cylinder 1

EV3

 Intake valve wheel brake cylinder 1

EV4

 Intake valve wheel brake cylinder 1

HL1

hydraulic line brake circuit 1

HL2

hydraulic line brake circuit 2

LW

leerweg

MV

Switching valve pressure generator unit

RB1

 wheel brake

RB2

 wheel brake

RB3

 wheel brake

RB4

 wheel brake

PD1

 Solenoid valve 1 of the double-stroke piston for pressure reduction

PD2

 Solenoid valve 2 of the double-stroke piston for pressure reduction

SV

Reversing valve double lift piston

WA

Wegsimulatorabsperrventil

WS

travel simulator

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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

• EP 1874602 B1 [0003, 0005, 0007]
• EP 1874602 [0004, 0005, 0044]
• WO 2006/111393 [0004]
• DE 102011082492 [0006]
• DE 102011085273 [0007, 0010, 0011]
• DE 102010050132 [0009]
• DE 2010050132 [0009, 0010]
• DE 102010050132 A1 [0012]
• EP 2014/069723 [0029]

Claims (23)

Brake system with a cylinder-piston unit, in particular master cylinder ( 20 ) and with an adjustable pressure source ( 2 . 4 . 8th . 10 ; 50 ), characterized in that in the cylinder-piston unit only a single piston ( 22 ) is slidably mounted, wherein the piston ( 22 ) two workrooms ( 22a . 22b ) and the first working space ( 22a ) with a first brake circuit hydraulic line (HL1) and the second working space ( 22b ) is connected to a second brake circuit hydraulic line (HL2), and each brake circuit hydraulic line (HL1, HL2) is connected to at least one wheel brake (RB1, RB2, RB3, RB4) via at least one switchable valve (EV1, EV2, EV3, EV4) , and that the controllable pressure source ( 2 . 4 . 8th . 10 ; 50 ) Feeds hydraulic medium for pressure build-up in both brake hydraulic lines (HL1, HL2) into one of the two brake hydraulic lines (HL1, HL2), in particular into the second brake hydraulic lines (HL2). Brake system according to claim 1, characterized in that the piston ( 22 ) is reset by a spring. Braking system according to claim 1 or 2, characterized in that the controllable pressure source ( 2 . 4 . 8th . 10 ; 50 ) is a piston-cylinder system which has at least one working space ( 10a . 54 . 60 ) whose volume by adjusting the piston ( 10 ) changeable, in particular during the pressure build-up in one side of the master cylinder ( 22b ) or in one of the hydraulic circuit lines (HL2) acts. Brake system according to claim 3, characterized in that the at least one working space ( 10a . 10b ; 54 . 60 ) via a, in particular switchable valve (MV, SV, PD1, CV3) is connected to the one brake hydraulic line (HL2). Braking system according to claim 3 or 4, characterized in that the controllable pressure source ( 2 . 4 . 8th . 10 ) one via an actuator ( 4 ) driven single-stroke piston ( 10 ), which only in advance by reducing the size of a first working space ( 10a ) Hydraulic fluid to pressure builds in the one brake circuit hydraulic lines (HL2) promotes and degrades pressure in the return stroke. Braking system according to claim 3 or 4, characterized in that the controllable pressure source ( 2 . 4 . 8th . 10 ) one via an actuator ( 50 ) driven double reciprocating pistons ( 52 ), which both in advance by reducing the first working space ( 54 ) as well as in the return stroke by reducing the second working space ( 60 ) Hydraulic medium for pressure build-up in which a brake circuit hydraulic line (HL2) promotes and in the forward and return stroke different large effective areas (A1 and A2) and also in the return stroke via valves (PD1, PD2) can reduce pressure. Brake system according to claim 6, characterized in that also the Doppelhubkolben ( 52 ) can be switched in the forward stroke on an active surface (A1-A2) by opening the switching valve (SV). Brake system according to one of claims 1 to 7, characterized in that the brake system is operated in multiplex mode at least in normal brake booster operation (brake force gain to about 80-100 bar) and blending functions in the closed brake circuit. Brake system according to one of the preceding claims, characterized in that a third cylinder-piston unit ( 30 ) is provided, which is actuated by means of an actuating device, in particular by the driver and that one of the piston (auxiliary piston) ( 32 ) of the third cylinder-piston unit ( 30 ) limited work space or pressure room ( 32a ) is connected via a valve arrangement (ESV, DAV) with at least one brake circuit (BK1, BK2). Brake system according to claim 9, characterized in that the second and third cylinder-piston unit ( 20 . 30 ) are arranged in a common housing. Brake system according to one of the preceding claims, characterized in that between the pistons ( 22 . 32 ) of the second and third cylinder-piston devices ( 20 . 30 ) a mechanical transmission device, in particular a plunger ( 40 ) is arranged with the, in particular with the interposition of a free path (LW) a movement of the piston ( 32 ) on the piston ( 22 ) is transferable. Brake system according to one of claims 9 to 11, characterized in that the working or pressure chamber ( 32a ) of the third cylinder-piston unit ( 30 ) is connected via a valve arrangement (WA) with a hydraulic travel simulator (WS). Braking system according to one of claims 9 to 12, characterized in that the simulator by means of the transmission device, in particular the plunger ( 41 ), and a spring arrangement is formed (plunger simulator), wherein between the transmission device or the plunger and the piston ( 22 ) of the second cylinder-piston unit, a free travel (LW) is provided. (eg 2 ) Brake system according to claim 13, characterized in that the simulator (tamping simulator) works with pressure proportional reinforcement, in particular a compensation of the Pedal reaction by closing a arranged in a hydraulic line to the reservoir switching valve (WA) takes place. Brake system according to one of the preceding claims, characterized in that a stepped or combined hydraulically and mechanically effective operation is provided in the fallback level, wherein in particular in a first (hydraulic) stage by means of the piston (auxiliary piston) ( 32 ) of the third cylinder-piston unit ( 30 ) via a valve arrangement the pressure chamber ( 22b ) of the second cylinder-piston unit ( 20 ) and by means of the piston ( 22 ) of the second cylinder-piston unit ( 20 ) is fed to the brake circuits and in a second (mechanical) stage via a plunger ( 40 ) The piston ( 22 ) of the second cylinder-piston unit 20 ) mechanically by means of the piston ( 32 ) of the third cylinder-piston unit ( 30 ) via a pestle ( 40 ) is operable. Brake system according to one of the preceding claims, characterized in that the pressure chambers ( 22a . 22b ) of the second cylinder-piston unit ( 20 ) via a hydraulic line ( 28 ) with each other and with the reservoir ( 29 ), wherein in the line a switching valve (I / O) is arranged, in particular for Nachfördern of pressure medium and / or pressure reduction. Brake system according to one of the preceding claims, characterized in that the pressure chambers ( 22a . 22b ) of the second cylinder-piston unit ( 20 ) are connected to each other via a hydraulic line, wherein in the line, a switching valve (DAV) is arranged, in particular for pressure equalization and Nachfördern of pressure medium. Brake system according to one of the preceding claims, characterized in that the piston ( 22 ) of the second cylinder-piston unit ( 20 ) has a device for path measurement. Method for operating a hydraulic device, in particular a brake device for motor vehicles, having a cylinder-piston unit, in particular master cylinder ( 20 ) and with a controllable pressure source, in particular according to one of the preceding claims, characterized in that the controllable pressure source ( 2 . 4 . 8th . 10 ; 50 ) Feeds hydraulic medium for pressure build-up in both brake hydraulic lines (HL1, HL2) into one of the two brake hydraulic lines (HL1, HL2), in particular into the second brake hydraulic lines (HL2). Method according to claim 19, characterized in that the controllable pressure source ( 2 . 4 . 8th . 10 ) one via an actuator ( 4 ) driven single-stroke piston ( 10 ), which only in advance by reducing the size of a first working space ( 10a ) Hydraulic fluid to pressure builds in the one brake circuit hydraulic lines (HL2) promotes and degrades pressure in the return stroke. Method according to claim 19 or 20, characterized in that the controllable pressure source ( 2 . 4 . 8th . 10 ) one via an actuator ( 50 ) driven double reciprocating pistons ( 52 ), which both in advance by reducing the first working space ( 54 ) as well as in the return stroke by reducing the second working space ( 60 ) Hydraulic medium for pressure build-up in which a brake circuit hydraulic line (HL2) promotes and in the forward and return stroke different large effective areas (A1 and A2) and also in the return stroke via valves (PD1, PD2) pressure decreases. Method according to one of claims claim 19 to 21, characterized in that the brake system is operated in multiplex mode at least in normal brake booster operation (brake force boost to about 80-100 bar) and blending functions in the closed brake circuit. Method according to one of claims 19 to 22, characterized in that the actuation in the fallback level combined takes place hydraulically and mechanically.

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