DE102006050277A1 - Brake system has first piston element adjustable via spindle and rotor drive directly or via gearing, and second piston element is adjustable directly or via gearing of brake operating pedal - Google Patents

Abstract

The brake system, which comprises a piston and cylinder system, has a first (10) and a second (8) piston element, wherein the first piston element is adjustable via a spindle and rotor drive (9,11) directly or via a gearing, and the second piston element is adjustable directly or via a gearing of the brake operating pedal (1). The drive adjusts the first piston element for pressure build-up in the working chamber (I,II) of the piston and cylinder system along with the second piston element.

Description

Subject of the invention

The The present invention relates to a brake system with a piston-cylinder system for generating pressure in at least one working space of the piston-cylinder system and a drive for adjusting the piston of the piston-cylinder system, wherein a mechanical adjustment of the piston of the piston-cylinder system via a Brake actuator, such as. a brake pedal possible is

State of the art

Both in the PCT / EP2006 / 003647 as well as in the PCT / EP2003 / 007406 Electromotive brake booster are described. The brake booster described there have a so-called displacement simulator, in which the pedal reaction is determined by the spring and not by the master cylinder piston. As a result, a poorly ventilated brake system is not recognized as usual on the longer pedal travel. Farther on, a critical situation can occur in the described electromotive drive when the motor or the spindle is blocked, resulting in a total failure of the braking effect. As a possible solution to this problem will be in the PCT / EP2006 / 003647 discloses a coupling between the spindle nut and rotor. However, this solution is disadvantageous consuming. If this error occurs during braking, the brake pressure can not be further reduced, which can be hazardous to accidents.

at Failure of the engine, the pedal forces should be as low as possible, ideal is when the pedal force path to normal operation is minimal different. In today's braking systems occurs in case of failure of the vacuum amplifier a very high pedal force, which the normally experienced driver very much strongly irritated and known to cause accidents.

One Another problem in the electric motor drive the operating force which consists of the cogging torque of the engine and the efficiency of the Spindle drive result. In addition, return springs necessary to return the pistons of the master cylinder. In case of failure of the engine, the actuating forces, return spring forces and frictional forces of the master cylinder and give a high initial pedal force, which irritates the driver very much, since normally these forces through the electromotive reinforcement are not effective.

Object of the invention

Of the Invention is based on the object, a fail-safe braking system provide, in the event of failure of the electric motor or hydraulically or pneumatically driven piston of the piston-cylinder system a braking by means of the mechanical on the piston of the Koblen-cylinder system with low forces possible is.

These Task is advantageous with a brake system with the features of claim 1. Advantageous developments of the brake system according to claim 1 result from the features of the subclaims.

The Invention provides, the primary piston of the Piston-cylinder system to divide into a first piston member and a second piston member. Of course it is It is also within the meaning of the invention, the primary piston in more than two piston elements splitting, which are relative to each other displaceable in and / or are stored in the cylinder of the piston-cylinder system. The first Piston element is mechanically coupled to the drive and adjustable. On a second piston element, the brake actuator, such as. the brake pedal act mechanically, with the second Piston element independent from the first piston element to increase pressure in the cylinder load. This advantageously ensures that a pressure build-up in the piston-cylinder system even with blocked drive and / or Spindle and thus firmly seated first piston element is possible. Thus stands the driver advantageous even when failure of the brake booster only slightly reduced full braking effect available.

The axial length the two piston elements is advantageous to choose such that in each position of the piston elements relative to each other a sufficient guide the piston elements is guaranteed.

The Cross-sectional shape of the two piston elements is freely selectable. A Particularly simple production of the piston elements results when the first piston element designed as an annular piston in the form of a sleeve is and the second piston element is designed as an inner piston, which is mounted displaceably in the first piston element.

In normal operation, when the brake booster or the braking operation is carried out by the drive of the piston-cylinder system and not via the brake actuator, the first piston member takes the second piston member to build up pressure. For this purpose, at least one driver element should be provided at a suitable location. This can in the simplest case a particular collar be shaped projection extending radially. The collar can be arranged both on the first and on the second piston element. Of course, it is also possible to arrange the driver element outside of the piston-cylinder system. However, this usually requires a higher design effort.

The second piston element is over adjusted separate spring elements in its original position. These can advantageously smaller dimensions than those for the provision of the first piston member or the drive required return spring elements. hereby results advantageous that the braking force by means of the Adjustment of the second piston element only small pedal forces required are similar to the pedal force curve in normal operation and can be advantageously adapted by suitable spring elements.

Around To obtain a highly dynamic system, where there is no vibration due to the existing spring elements for the return of the piston and piston elements comes to the starting position, a lock can be provided be the first and second piston element in normal operation connects with each other. This ensures that the second Piston element the first piston element even with faster reset followed by the drive of the first piston element. The lock can be advantageously designed so that they automatically fail the drive or when blocking the drive is released, such that the second piston element is independent of the first piston element by means of the brake actuator, is adjustable in particular for pressure build-up.

By the provision of suitable valves, in particular the use of a controlled sniffer valve If the drive is locked, a pressure reduction can be achieved by opening the poppet valve respectively.

By the brake system according to the invention can In addition, advantageously a diagnosis of the ventilation state at the start of the journey be made.

In a vehicle advantageously a brake system according to the invention can be provided, wherein in each case a piston-cylinder system can be used for at least two wheel brakes. By means of the piston-cylinder system driven according to the invention, a pressure regulation in the wheel brakes can be carried out simultaneously and / or successively, as it were a multiplex operation. The corresponding regulation is the patent applications PCT / EP2006 / 003647 and PCT / EP2003 / 007406 to be taken, this application makes the full disclosure of its own.

Accordingly Is it possible, that two piston-cylinder systems are operated in parallel, wherein the brake actuator via a Rocker can act on the respective second piston element.

Also Is it possible, the piston-cylinder system with another piston, a so-called Equip tandem pistons, making this the two working spaces from each other separates, from each of which pressure lines lead to wheel brakes. there It is within the meaning of the invention, when the coupling of the second piston element with the other piston, which is also commonly called a floating piston is called, over a spring element takes place. By adjusting the second piston element is thus over the spring and the one formed by the second piston member and the floating piston Working space built pressure of the floating piston adjusted and builds in turn, a pressure in the second working space.

Of the Floating piston can also from a driver element, which on the second piston element is arranged, back to the starting position be adjusted. In this case, the driver element is designed such that it is only at a maximum distance from the floating piston and second piston element a restoring force on the floating piston exercises.

In a further advantageous embodiment of the brake system according to the invention the floating piston is adjustable by means of an additional drive. This can provide a faster reset respectively. The further drive causes the provision alone or for support the reset elements.

• – Generelle Vermeidung oder zeitlich begrenzte Entstehung von Unterdruck im Hauptzylinder in den beiden Bremskreisen sowie
• – Vermeidung des Nachschnüffelns bei der Druckmodulation der Kolben aus dem Vorratsbehälter durch schaltbares Schnüffelventil;
• – Hoher Druckabbaugradient bei Eis durch möglichen Antrieb des Schwimmkolbens;
• – Vermeidung der Kolbenbewegung des Schwimmkolbens bei Druckabbau im angrenzenden Bremskreis I bei kleinen Drücken, wenn der Schwimmkolben eine Rückstellfeder besitzt.

Further advantages listed below only in the form of a dot result from the brake system according to the invention:

• - General prevention or temporary emergence of negative pressure in the master cylinder in the two brake circuits as well
• - Avoid Nachschnüffelns in the pressure modulation of the piston from the reservoir through switchable sniffer valve;
• - high pressure reduction gradient in ice due to possible drive of the floating piston;
• - Avoidance of the piston movement of the floating piston at pressure reduction in the adjacent brake circuit I at low pressures when the floating piston has a return spring.

In addition, brake fluid can be nachgefördert when steam is formed when the brake is heated, what a skilled driver done by pumping on the brake pedal. This is done in the brake system according to the invention characterized in that a kurzeitiger negative pressure in the or each working space or spaces is generated by resetting the piston, which then briefly the sniffer valve is opened.

The brake system according to the invention therefore advantageously has a comprehensive functionality and is easy and inexpensive in their construction. Furthermore, it is characterized by a low weight and a small installation volume.

Description of the figures

following become possible based on drawings embodiments the brake system according to the invention explained in more detail.

It demonstrate:

1 A first possible embodiment with tandem piston and sniffer supply in the first piston element;

2 : second possible embodiment with controlled sniffer valve;

2a : Pressure volume characteristic;

3 third possible embodiment with separate switchable sniffer valves for both working spaces of the tandem piston system;

3a : Detail of the 3 ;

4 fourth possible embodiment with driven floating piston.

The 1 shows the basic arrangement of 4 out PCT / EP2006 / 003647 with some extensions. The pedal 1 acts on the fork piece 2 and transmits the force to a transmission link 3 , its guide rod 4 in the case 5 is stored. This housing contains all elements of 3 out PCT / EP2006 / 003647 like path simulator 5a and displacement sensor 5b and path simulator locking 6 , It is therefore dispensed with a separate description. Upon actuation the brake pedal is above the sensor 5b the electric motor is activated and moved via the rotor with spindle nut 11 the spindle 9 and the coupled piston 10 ,

Instead of the motor circuit via the travel simulator 5a can also have a force proportional amplifier switching device 3a the engine is adjusting a pneumatic or hydraulic cylinder for brake booster. This ultimately causes as in the known vacuum brake booster dependent on the pedal force gain, which may be linear or non-linear. If the gain can not be further increased due to the maximum boost force, the foot force on the inner piston causes a further pressure increase. The boosting force acts on the so-called spindle piston, which is combined with a spindle in the electric drive. The amplification factor should be variable eg for the hybrid vehicles for recuperation.

According to the pressure volume pressure path characteristic as in the PCT / EP2006 / 003647 described, a certain pressure is controlled. At the corresponding displacement of the spindle piston 10 As in a tandem master cylinder, it is initially moved via the return spring 21 the floating piston 23 adjusted. After further piston movement, the spindle piston rushes 10 the floating piston 23 ahead and builds pressure in the brake circuit I, which transmits via the floating piston in a known manner in the circle II. This corresponds to the structure as in the patent application PCT / EP2006 / 003647 and the PCT / EP2003 / 007406 is described. The pistons have Schnuffelfloch holes according to the prior art 15 and 16 , The torque of the spindle 9 is about a lever 17 on the guide pin 18 supported. The same support is advantageously offset by an additional 180 °, which is not shown. The return spring 19 moves the spindle 9 with pistons 10 each in the starting position and must be such that the friction of the seal 14 and 14a of the spindle piston and the cogging torque of the motor is overcome. These forces are considerable. The first embodiment according to 1 differs in terms of the structure of the primary piston of the PCT / EP2006 / 003647 and the PCT / EP2003 / 007406 Primary piston. The primary piston has a first piston element, the outer spindle piston 10 and a second piston element, the inner piston 8th on. Both are not connected. If a failure of the motor or spindle drive now occurs, the transmission element acts 3 on the push rod 7 with the inner bulb 8th connected is. This in turn shifts over the spring 21 the floating piston 23 and upon further movement arises, as just described, in the two brake circuits I and II pressure. The inner piston 8th is about the seals 13 . 13a and 13b against the inner wall of the outer ring piston 10 sealed. The inner piston 8th also has a Schnüffellochbohrung 16 in the spindle piston 10 , Because of the piston 8th only needed in emergency mode, it can be smaller in diameter than the spindle piston 10 be interpreted, resulting in significantly smaller pedal forces. He can of course not the large volume of the spindle piston 10 displace. However, this disadvantage does not come to fruition because brake booster failure due to the high piston forces and the limited pedal force only limited pressure can be built up, which with egg is connected to a smaller volume. For this emergency, legislators only demand 30% of the deceleration with a foot force of 500 N. With reinforcement, the full deceleration = 100% is achieved in normal operation with about 200 N. This shows the large increase by more than 400%, in case of failure of the gain to the same deceleration ie the corresponding pressure to achieve. By the separation of the pistons 8th and 10 act the return springs 19 of the piston 10 with spindle not on the pedal 1 so that the on the pedal 1 retroactive piston return spring 7 only the piston friction of the seals 13 . 13a . 13b . 25 and 25a must take into account. This is less than the known vacuum to brake booster (BKV), the return spring must also be overcome in an emergency of the pedal force.

According to the regulations, the seals must 13 . 13a and 13b be moved in normal operation. That's why between inner pistons 8th and spindle piston 10 a plate spring 12 used, which is compressed at each braking, which is a relative movement of the piston 8th and 10 entails.

By the corresponding design are smaller with this concept Restoring forces and smaller pedal forces in case of failure of the gain possible.

Basically, this arrangement could also be realized with the vacuum or hydraulic brake booster by the spindle piston 10 connected to the diaphragm or the booster piston.

A further advantage is that the floating piston 23 has no return springs, as the stopper bolt connected to the inner piston 22 the with the floating piston 23 connected sleeve 23a retracts to the piston drive. During forward movement to build up pressure, the return spring moves 21 the floating piston until the pressure component of the circle I outweighs. Preferably have floating piston 23 and inner pistons 8th similar diameter.

The floating piston 23 and the spindle piston 10 are in the case 24 stored and have, as well known from the prior art, a piston inside Schnüffellochbohrung 15 and 26 , With the housing is the reservoir 27 sealed and has a level sensor 28 ,

The same arrangement is also in a twin arrangement according to the 2 and 10 of the PCT / EP2006 / 003647 possible, both spindle pistons 10 with a drive and the internal pistons 8th connected to the pedal.

The actuator can accordingly DE 102 005 059 be extended with a pedal lock, so that a reaction of the pressure modulation on the pedal does not take place.

In addition, the inner piston 8th with the spindle piston 10 be connected via a lock, not shown. Thus, it can be prevented that the inner piston 8th At high dynamic return speed of the spindle piston or under negative pressure in the brake circuit oscillates relative to the spindle piston. This lock is unlocked when an emergency occurs and the pedal force over the push rod 7 on the inner piston 8th acts.

The 2 shows a further possible embodiment of the brake system according to the invention, wherein additionally the valve block 42 is shown for pressure modulation. The sniffer hole for the inner piston 8th here is replaced by an alternative. This consists of a path-controlled ball seat valve 29 with return spring 30 which directly with the brake circuit I through the connecting channel 31 connected is. This valve closes the brake circuit with a small pedal movement. The valve is through an anchor 32 with plunger to the ball valve by the magnetic forces of the magnet system consisting of pole plate 35 and pole plate 33 actuated. These poles are equipped with a permanent magnet 34 connected, whose magnetic flux across the poles 33 and 35 and through the container wall 37 a force on the anchor 32 which unfolds the ball valve 29 against the return spring 30 pushes in the open position. Instead of the magnetic actuation, a mechanical actuation, not shown, with a seal to the container can also be selected.

The anchor 32 has an additional permanent magnet 29a which causes by reversing the magnetic circuit 47 and 48 the anchor 32 can also be switched without actuation of the pedal in the closed position of the valve. By closing the sniffer valve, brake pressure in the brake circuit I can thus be established, for example in the case of an ESP intervention.

The magnetic solution has advantages particularly in the extension described later. The pole plate 35 is with a driver 33a connected with a collar bolt 38 connected is. The brake pedal movement is over in the sleeve 39 mounted compression spring 40 on the collar bolt 38 transfer. As well as the driver 33a on the stop 41 meets with further pedal movement, the compression spring 40 compressed and there is no further adjustment of the permanent magnet 34 ,

The anchor 32 has on its upper side even more poles, which together with one above the housing wall 47 arranged second magnetic circuit 48 the via an excitation coil 47 is activated cooperate, such that the ball valve or sniffer valve can be opened at any time. This is especially necessary for two cases. Should block in a first case at higher pressure in the brake circuits of the motor drive, it can be reduced by opening the valve pressure and thus the critical case of the locked brake can be avoided. The second case relates to the pumping of brake fluid, for example, in vapor formation in the brake circuit I or II. Here, for example, the spindle piston 8th over the engine with closed solenoid valves 44 For example, be returned in the brake circuit II. Due to the negative pressure in circuit I is over the seal 14 Brake fluid sucked, causing an opening of the ball valve 29 over the magnetic circuit 48 / 47 necessary. Should be promoted in the brake circuit II due to vapor bubbles, so remains during the piston return movement of the piston 8th , which piston 23 take the valve 29 opened and closed during forward movement. Thus, with this valve actuation two important safety functions are solved very easily. This eliminates the in 1 illustrated elaborate Schnüffellochbohrung in the spindle piston and the use of the three seals 13 . 13a and 13b in the inner bulb, passing through the one seal 13 can be replaced. Again, the floating piston 23 on the inner piston 8th coupled. Both outputs of the brake circuits I and II are each via two 2/2-solenoid valves 43 and 44 connected to wheel brakes, not shown. The pressure modulation in the multiplex method (MUX) is in the PCT / EP2006 / 003648 described in detail. Reference is made in full to this application in this regard.

In both brake circuits are before the solenoid valves pressure transducer 45 and 46 arranged. With these, an automatic diagnosis of the bleeding state of the brake can be made at the start of the journey. In this case, the motor is activated and via the rotary encoder 49 the piston travel detected. Here the pressure volume characteristic V = piston area × travel in relation to the measured pressure can be recorded. If the tolerance limit is exceeded, the error message is sent to the driver.

The individual pressure volume curves can be recorded individually by testing for e.g. three solenoid valves are closed and the Wheel brake to be tested through an open solenoid valve with the appropriate Piston is connected. This is necessary for the control functions, since the Pressure control for ABS / ESP primarily over the Position control of the piston takes place. The pressure measurement can not in the dynamic case, as the pressure in the wheel varies to the measured pressure in front of the solenoid valve. The pressure in the wheel can however over the drawn pressure transducer are detected when the transient process after approx. 30 ms at unchanged Piston position is completed. This is necessary for longer control times in multiplex mode to normalize the stored characteristics.

If the system does not permit this due to degassing of the brake fluid under reduced pressure, the pressure reduction in both brake circuits is regulated to eg 0-0.5 bar via the pressure transmitters. The distance measurement of the spindle piston via the sensor 49 determines the set pressure level for the controller via the pressure volume characteristic.

For the multiplex operation, it is of great importance that a high pressure reduction speed ṗ _ab takes place at low brake pressures. As a rule, the blocking pressure at μ = 1.0 is 100 bar and at μ = 0.1, for example, on ice at 10 bar. As is known, the pressure reduction characteristic is after 2a at low pressure p0.1 very flat ie the volume flow rate is higher at low pressures. Therefore, ṗ _{ab decreases} disproportionately at low pressures.

today Braking systems are usually designed in the pressure level that the blocking pressure at μ = 1.0 at 100 bar. At possible high pedal forces and additional Pressure peaks caused by the ABS / ESP pump thus more than 200bar, Accordingly, the brake system must actually be oversized.

At the Proposed system, however, the pedal is decoupled from the spindle. In normal mode, the driver enters the path simulator and the Motor determines the maximum pressure which is about 30% higher than the blocking pressure. Thus, it can be prevented that at high pedal forces unnecessary high pressure arises. In case of failure of the motor decoupling falls between activity and spindle into a mechanical fallback level and the pedal force acts directly on the inner piston or the second piston element. Because of the smaller diameter it has a smaller maximum volume repressed, it can be ensured that no excessive pressures arise.

The brake system according to the invention can therefore be better dimensioned. Due to smaller pistons in the Brake caliper and master cylinder can increase the blocking pressure by 50% be, e.g. from 100 to 150 bar. This results in the aforementioned reserve of 30% the same maximum pressure.

The pressure volume characteristic is in 2a shown for low and high design. Due to the fact that the low pressure level at μ = 0.1 increases from p0.1 to p0.1 ', the higher pressure level makes considerably higher pressure gradients possible when controlled on ice. At the same time significant weight savings are possible by smaller piston diameter by about 20% in the caliper.

The arrangement of the Schnüffellochbohrung has regarding the failure consideration another advantage. If this is not arranged in the region of the piston outlet position but in the region of the end position, no loss path for bridging the bore is lost. Thus, no additional displacement volume is lost. Consequently, even in the most unfavorable case, "Failure brake booster and brake circuit II" the maximum displaceable volume and thus the achievable brake pressure is high.This effect is further enhanced even if the Schnipphole hole with solenoid valve in the piston end position is arranged on the floating piston 2 not shown.

In the 3 embodiment shown corresponds essentially to that of 2 with the difference that for the brake circuit II, an electromagnetic sniffer valve is used, which consists of ball valve 50 with return spring 50a , Anchor 51 , Magnetic valve 52 , Excitation coil 53 and armature return spring 54 consists. This valve is already in PCT / EP2006 / 003647 described. In contrast to embodiment according to the 2 this valve is necessary if for the pressure modulation briefly negative pressure in the master cylinder should be possible. For this, the sniffer valve must be closed. It opens at the in 2 Nachförderung described.

The 3a shows a piston stroke sensor 55 with Target as an alternative to the pressure transducer. Here is only a pressure transducer 45 necessary.

The 4 shows another possible embodiment in which the floating piston 23 not coupled to the inner piston. Accordingly, the spring sleeve lies 58 with return spring 22 on the floating piston, this has a separate return spring 60 with spring sleeve 61 , The ball valve 30 is over a channel 57 with the sniffer hole 15 connected. Here no pressure reduction can be realized with blocked motor. In this system, the floating piston 23 with a linear actuator, consisting of stator 63 with excitation coil 64 and ring magnet 65 added to the piston. The magnetic circuit acts through a thin non-magnetic wall of the housing 62 , The actuator can deploy force in both directions. At low pressures, the compressive force to return the piston in circuit II is small for high ṗ _ab values. The magnetic force supports the pressure force for a higher piston speed. For the demand for avoidance of negative pressure, this magnetic force on the pressure transducer 46 regulated. If pressure is reduced in circuit I for pressure modulation, the solenoid valves in circuit II are closed. Here would be at low pressures the return spring 60 move the floating piston. To avoid this effect then counteracts the magnetic force of the spring and prevents piston movement.

1

pedal

2

forked piece

3

transmission member

3a

Proportional force Amplifier switching device

4

guide rod

5

casing

5a

travel simulator

5b

displacement sensor

6

Wegsimulatorarretierung

7

pushrod

8th

Inner piston - second piston element

9

spindle

10

Spindle piston - first piston element

11

rotor with spindle nut

12

Belleville spring

13

poetry internal piston

13a

poetry internal piston

13b

poetry internal piston

14

poetry spindle piston

14a

poetry spindle piston

15

breather hole spindle piston

16

breather hole internal piston

17

lever for support spindle

18

guide pins

19

Return spring spindle

20

Return spring internal piston

21

Return spring floating piston

22

stop pin

23

floating piston

23a

Sleeve piston drive

24

piston housing

25

Floating piston seal

26

breather hole floating piston

27

Brake fluid reservoir

28

level sensor

29

ball valve

29a

Permanent magnet - armature

30

Return spring

31

connecting channel in the brake circuit

32

anchor with pestle

33

pole plate 1

33a

takeaway for pole plate

34

permanent magnet

35

pole plate 2

36

storage

37

housing

38

threaded stud

39

shell

40

compression spring

41

storage and stop

42

manifold

43

2.2 Solenoid valve brake circuit I

44

2.2 Solenoid valve brake circuit II

45

pressure sensor I

46

pressure sensor II

47

magnetic circuit

48

excitation coil

49

Rotation angle sensor or Weggeber

50

Ball seat valve II

50a

Ball seat valve return spring

51

armature

52

magnetic circuit

53

excitation coil

54

Armature return spring

55

displacement sensor

56

target for displacement sensor

57

sniffing channel

58

spring sleeve

59

stop pin

60

Return spring

61

Spring sleeve floating piston

62

casing

63

drive

64

stator

65

excitation coil

66

ring magnet

Claims (58)

Brake system with a piston-cylinder system for generating pressure in at least one working space (I, II) of the piston-cylinder system and a drive for adjusting the piston of the piston-cylinder system, wherein a mechanical adjustment of the piston of the piston-cylinder System via a brake actuator ( 1 ), such as a brake pedal is possible, characterized in that the piston of the piston-cylinder system, a first piston element ( 10 ) and a second piston element ( 8th ), wherein the first piston element ( 10 ) from the drive ( 9 . 11 ) is adjustable directly or via a transmission, and a second piston element ( 8th ) directly or via a transmission of the brake actuator ( 1 ) is adjustable. Brake system according to claim 1, characterized in that the drive ( 9 . 11 ) the first piston element ( 10 ) for pressure build-up in the working space (I, II) of the piston-cylinder system together with the second piston element ( 8th ) adjusted. Brake system according to claim 1 or 2, characterized in that the first or second piston element ( 8th . 10 ) has a driver element, whereby the first piston member entrains or adjusts the second piston member in its adjustment to the pressure build-up. Brake system according to one of claims 1 to 3, characterized in that between the first and the second piston element ( 8th . 10 ) a spring element ( 12 ), in particular a disc spring, is arranged. Brake system according to one of claims 1 to 4, characterized in that the first and second piston element ( 8th . 10 ) are mounted displaceably relative to each other in the piston stroke direction. Brake system according to one of the preceding claims, characterized in that the first piston element ( 10 ) is sleeve-shaped, wherein in the first piston element ( 10 ) the second piston element ( 8th ) is slidably mounted. Brake system according to claim 6, characterized in that between the outer wall of the sleeve-shaped first piston element ( 10 ) and the inner wall of the cylinder ( 24 ) of the piston-cylinder system at least one circumferential seal ( 14 . 14a ) is arranged. Brake system according to claim 6 or 7, characterized in that between the inner wall of the sleeve-shaped first piston member ( 10 ) and the outer wall of the second piston element ( 8th ) at least one seal ( 13 . 13a . 13b ) is arranged. Brake system according to one of claims 6 to 8, characterized in that the first piston element ( 10 ) is an annular piston or spindle piston, in which the second piston element ( 8th ) is arranged as an inner piston. Brake system according to one of claims 6 to 9, characterized in that the first and / or second piston element has a radially directed one Collar has a driver element and / or stop. Brake system according to one of the preceding claims, characterized in that feedback mechanisms ( 19 . 20 ) the first and second piston elements ( 8th . 10 ) reset separately to the initial position. Brake system according to one of the preceding claims, characterized in that a spring element ( 19 ) acts on the drive or the first piston element, such that the spring force acts in the piston stroke direction, in which a pressure reduction takes place by adjusting the piston element. Brake system according to one of the preceding claims, characterized in that a further spring element ( 20 ) for resetting and for depressurizing the second piston element ( 8th ). Brake system according to claim 13, characterized in that the spring element ( 8th ) on the first piston element ( 10 ), the housing ( 5 ) or a part arranged thereon. Brake system according to claim 13, characterized in that the spring element ( 20 ) on the housing ( 24 ) of the piston-cylinder system or the drive is supported. Brake system according to one of the preceding claims, characterized in that the drive of the first piston is an electric motor, in particular as a spindle drive ( 9 . 11 ) is trained. Brake system according to one of the preceding claims, characterized characterized in that the drive is a pneumatic or hydraulic acting drive is. Brake system according to claim 17, characterized that the adjustment of the first and second piston member by a pneumatically or hydraulically operating booster piston he follows. Brake system according to one of the preceding claims, characterized characterized in that a drive of a brake booster device adjusted the first piston element. Brake system according to one of the preceding claims, characterized in that the second piston part ( 8th ) with another piston ( 23 ), in particular tandem pistons, is coupled, which is displaceably mounted in the cylinder of the piston-cylinder system. Brake system according to claim 20, characterized in that the further piston is a floating piston which sealingly against the inner wall of the cylinder ( 24 ) is present. Brake system according to claim 20 or 21, characterized in that a spring ( 21 ) between the second piston element ( 8th ) and the further piston ( 23 ) is arranged, which the second piston element ( 8th ) and the other piston ( 23 ) presses apart. Brake system according to one of claims 20 to 22, characterized in that the further piston ( 23 ) two work spaces (I, II) separated from each other. Brake system according to one of claims 20 to 23, characterized in that in or on the second piston part ( 8th ) an axial guide for the further piston is arranged, wherein the guide an end stop ( 22 ), such that the further piston ( 23 ) only by a maximum distance from the second piston element ( 8th ), which is used to return the floating piston to the initial position. Brake system according to one of claims 20 to 24, characterized in that the spring ( 21 ) with its one end on the second piston part ( 8th ), in particular at the bottom of a blind hole, supported and at its other end to the further piston or a part arranged or fixed thereto ( 23a ), in particular guide part, supported. Brake system according to one of claims 24 or 25, characterized in that the spring ( 21 ) is a coil spring which coaxially surrounds the guide. Brake system according to one of claims 20 to 26, characterized that first working space through the first and second piston element and the further piston is formed, and that a second working space through the bottom wall of the cylinder and the other piston in Axial direction is limited, wherein a spring element in the second Working space is arranged, which is attached to the bottom wall and the supports another piston with its ends and tries the other Adjust piston to an initial position, with another Spring element is arranged in the first working space, which is with one end to the other piston and with his other End supported on the second piston element and tries the second piston element to adjust to an initial position. Brake system according to claim 27, characterized that in each case a mechanical limitation, in particular in the form of a End stop, the spring travel of arranged in the work spaces spring elements limited. Brake system according to one of claims 20 to 28, characterized in that a drive ( 63 . 64 . 65 . 66 ) the further piston ( 23 ) adjusted in the cylinder. Brake system according to claim 29, characterized in that the drive ( 63 ) on the outside and / or around the cylinder ( 24 ) of the piston-cylinder system in the region of the further piston ( 23 ) is arranged and the drive ( 63 ) adjusts the other piston by means of a generatable magnetic field. Brake system according to claim 30 or 31, characterized that the drive is a linear actuator is. Brake system according to one of the preceding claims, characterized in that a sensor ( 5b ) the position of the actuator ( 1 ), in particular of the brake pedal, and a control activates the drive (s) as a function of the sensor signal. Brake system according to one of the preceding claims, characterized in that a travel simulator ( 5a ) exerts a restoring force with predefinable, presettable or by means of drive einregelbarer restoring force on the brake actuator. Brake system according to claim 33, characterized in that a Wegsimulatorarretierung ( 6 ) is provided, wherein in emergency operation, in which the drive of the brake system is not ready to build up pressure, the lock releases the travel simulator, such that reduces the applicatable via the brake actuator force. Brake system according to one of the preceding claims, characterized characterized in that the control means of a rotary encoder or a displacement sensor the position of the piston, consisting of the first and second piston element determined. Brake system according to claim 35, characterized that the control by means of at least one pressure transducer in the primary circuit as well of the rotary encoder or the displacement sensor, the pressure-displacement curve or pressure-volume curve of the piston-cylinder system determined. Brake system according to claim 36, characterized that by means of the control on the basis of the determined pressure-displacement curve or pressure-volume characteristic the piston-cylinder system is a position control of the piston. Brake system according to claim 36 or 37, characterized that the controller based on the determined pressure-displacement curve or pressure-volume curve, the ventilation state of the Brake system determined. Brake system according to one of the preceding claims, characterized in that a subsequent delivery of hydraulic medium via sniffer valves ( 29 . 50 ) into the or the workrooms (I, II) takes place. Brake system according to claim 39, characterized in that the first piston element ( 10 ) at least one channel ( 15 ) has, over which the brake system sniffing hydraulic medium in the working space (I) with zückgestelltem second piston element. Brake system according to claim 39 or 40, characterized in that at least one sniffer valve ( 29 ) mechanically via the brake actuator and / or by means of its own drive ( 47 . 48 ), in particular magnetic, is switchable. Brake system according to one of the preceding claims, characterized characterized in that after evaluation of the determined pressure-volume characteristic a sniff by adjusting the piston and possibly required additional Control of at least one controlled sniffer valve takes place. Brake system according to one of Claims 39 to 42, characterized in that the drive has an electromagnet and an armature ( 32 ), wherein the armature ( 32 ) with the valve actuator ( 29 ) of the sniffer valve is connected. Brake system according to one of claims 39 to 43, characterized in that the drive is a permanent magnet ( 34 ) and a drivable by this anchor ( 32 ), wherein the armature ( 32 ) with the valve actuator ( 29 ) of the sniffer valve is connected. Brake system according to claim 44, characterized in that the permanent magnet ( 34 ) and displaceably mounted by means of the brake actuator ( 1 ) is adjustable at least by a certain distance and / or angle range. Brake system according to one of claims 43 to 45, characterized in that the armature ( 32 ) of both the permanent magnet ( 34 ) as well as the controlled electromagnet ( 48 ) is adjustable, wherein by means of the electromagnet ( 48 ) greater adjustment forces on the anchor ( 32 ) are generated than that of the permanent magnet ( 34 ) on the anchor ( 32 ) acting forces, such that by means of a controller and controlled by the control tion electromagnets ( 48 ) the anchor ( 32 ) with arbitrarily adjusted permanent magnet ( 34 ) is adjustable, in particular such that the sniffer valve is adjustable by the energized electromagnet in its closed or open position. Brake system according to one of claims 39 to 46, characterized in that a spring element ( 30 ) the valve actuator ( 29 ) is force-urged in the direction of the valve seat, wherein its force is smaller than the magnetic force of the electromagnet ( 48 ) and the permanent magnet ( 34 ), provided that the latter at least in its not from the brake actuator ( 1 ) is in the misadjusted position. Brake system according to one of claims 39 to 47, characterized in that by means of the electromagnetic drive ( 48 ) the sniffer valve is closable, in particular in piston actuation by driving the first piston element (eg ESP operation). Brake system according to one of claims 39 to 48, characterized in that the controller opens the sniffer valve for pressure reduction, provided that blocked the piston drive during braking. Brake system according to one of claims 39 to 49, characterized that the sniffer valve for snooping and request by means of the permanent magnet or the electromagnet open is. Brake system according to one of the preceding claims, characterized in that the first piston element ( 10 ) with a spindle ( 9 ) connected by a spindle drive ( 11 ) is adjustable, the spindle ( 9 ) in the axial direction of an over tragungsglied ( 7 ), in particular a push rod is passed through which the power transmission from the brake actuator ( 1 ) on the second piston element ( 8th ) he follows. Brake system according to claim 51, characterized in that that the transmission link connected to the second piston element, in particular its end face is. Brake system according to claim 5143 or 52, characterized in that a helical spring ( 20 ) coaxially the transmission member ( 7 ), and is supported at one end to an abutment disposed on the transfer member and at the other end to the spindle or the second piston member or a part arranged thereon. Brake system according to one of the preceding claims, characterized characterized in that the brake system comprises two piston-cylinder systems has, which are arranged in particular parallel to each other and each over your own or together over a common drive for each have the first piston elements. Brake system according to one of the preceding claims, characterized characterized in that each working space (I, II) via at least one pressure line with at least one cylinder of a wheel brake is in communication, wherein in each case a valve, in particular a 2/2-way valve, is associated with a wheel brake, and the one or more drives of the piston-and-cylinder system (s) together with the valves the pressure in the wheel brakes at the same time and / or dismantled and / or set up in multiplex operation. Brake system according to claim 55, characterized that four 2/2-way solenoid valves arranged in a valve block are, each associated with a valve of a wheel brake. Brake system according to one of the preceding claims, characterized characterized in that by means of a locking the first and the second piston element are connectable, such that they are relative to each other are no longer movable. Brake system according to claim 57, characterized that a drive drives the locking, in particular in the undisturbed operating state of Brake system holds in a locked position or in case of failure of Brake system from a locking position out into a not adjusted locking position.