DE102016206453A1 - Brake system for motor vehicles - Google Patents

Abstract

Brake system (1) for motor vehicles, comprising • hydraulically actuated wheel brakes (8, 9, 10, 11); • at least one electrically actuated wheel valve (6a-6d, 7a-7d) per wheel brake for setting wheel-specific brake pressures; • a pressure medium reservoir (4) under atmospheric pressure; • a system pressure line (64) in which pressure is built up as needed; wherein between the system pressure line (64) and the pressure fluid reservoir (4) hydraulically a venting device (60) is connected, which during operation of the brake system (1) with changing system pressures automatic separation of in the system pressure line (64) possibly present air to the pressure medium reservoir (4 ) causes.

Description

The invention relates to a brake system for motor vehicles, comprising hydraulically actuated wheel brakes, at least one electrically operable wheel valve per wheel to set wheel individual brake pressures and a pressure medium reservoir under atmospheric pressure, and a system pressure line, is built up in the pressure as needed.

Hydraulic brake-by-wire brake systems are becoming increasingly widespread in automotive engineering. Such brake systems often comprise, in addition to an actuatable by the driver master cylinder an electrically ("by-wire") controllable pressure supply device by means of which in the operating mode "brake-by-wire" takes place a pressurization of the wheel brakes.

In these modern braking systems, in particular electro-hydraulic brake systems, the driver is decoupled from the direct access to the brakes. This function is used in a "brake-by-wire" mode. Upon actuation of the pedal, the driver's braking request is detected and a pedal decoupling unit and a simulator are activated. The hydraulic volume displaced from the master cylinder by the driver by means of its pedal actuation flows into the simulator, which serves to give the driver as familiar and comfortable a brake pedal feel as possible. The braking request detected with the aid of sensors leads to the determination of a desired braking effect, from which a target brake pressure for the brakes is then determined. The corresponding actual brake pressure in the wheel brakes is then actively provided by a pressure supply device.

The actual braking thus takes place by active pressure build-up in the brake circuits by means of a pressure supply device, which is controlled by a control and regulation unit. As a result of the hydraulic decoupling of the brake pedal actuation from the pressure build-up, many functionalities such as ABS, ESC, TCS, hill-start assist etc. can be realized in a brake system which is technically efficient and particularly comfortable for the driver due to the pedal decoupling.

In such brake systems, there is usually provided a hydraulic fallback level by which the driver can decelerate or stop the vehicle by muscular force upon actuation of the brake pedal when the "by-wire" mode fails or is disturbed. While in normal operation by a pedal decoupling unit, the above-described hydraulic decoupling between brake pedal operation and brake pressure build-up, this decoupling is not activated in the fallback so that the driver can directly move pressure medium in the brake circuits. In the fallback level is switched when with the help of the pressure supply device no pressure build-up is possible. This is i.a. then the case when the check valve, which connects the pressure supply device with the reservoir, no longer reliably locks, so that a pressure build-up is no longer possible reliably.

The pressure supply device in brake systems described above is also referred to as an actuator or electro-hydraulic actuator. For example, an electro-hydraulic actuator is formed by an electromechanical linear actuator, which displaces a piston axially into a hydraulic pressure chamber for pressure build-up. The electromechanical linear actuator is usually formed by the combination of an electric motor with a rotational-translation gear.

From the DE 10 2013 204 778 A1 is a "brake-by-wire" -Bremsanlage known for motor vehicles, which is a brake pedal operable tandem master cylinder, the pressure chambers are connected via an electrically actuated release valve separable with a brake circuit with two wheel brakes, one with the master cylinder hydraulically connected, and deactivatable simulation device, and an electrically controllable pressure supply device, which is formed by a cylinder-piston arrangement with a hydraulic pressure chamber, the piston is displaceable by an electromechanical linear actuator comprises, wherein the pressure supply device is connected via two electrically actuated Zuschaltventile with the intake valves of the wheel brakes ,

The function of hydraulic brake systems is based on the very low compressibility of the fluids used as pressure fluid compared to gases. Functional requirement for such brake systems is therefore that the hydraulic pressure medium contains no or only very small gaseous impurities. When pressure fluid is sucked from a reservoir, however, air in the form of air bubbles can be sucked with. In addition, the pressure medium in the container over a large area in contact with air, so that it can be assumed that there is air in dissolved form in the pressure medium supply of the container. When sucking so unwanted air enters the pressure chambers of the hydraulic system. During repeated suction from the reservoir, a critical amount of air can accumulate in the hydraulic system, which then exists as an air bubble.

In brake technology, manually operated vent valves are known for venting the hydraulic system. In some known brake systems, it is possible to periodically flush the hydraulic system in phases when system pressure is not needed. For this purpose, valves must first be switched, so that a hydraulic path from the actuator to the container is created. Then with the actuator, a volume flow is generated which is so large that it entrains possible air bubbles on the way to the container. Thereafter, the missing volume is supplemented by vacuuming.

Such a method has the following disadvantages. The valve circuits and the volume flow generation cause noise. During the flushing process, the operational readiness of the brake system is limited. The container is flushed through systematically, whereby the contact of the liquid is intensified with the air in the container, so that the next time you suck in further air can get into the hydraulic system.

The invention is therefore based on the object to improve the venting properties of a brake system.

This object is achieved in that hydraulically a venting device is connected between the system pressure line and the pressure medium reservoir, which causes an automatic separation of possibly present in the system pressure line air to the pressure fluid supply reservoir during operation of the brake system with changing system pressures.

Advantageous embodiments of the invention are the subject of the dependent claims.

The invention is based on the consideration that the known means and methods for venting a brake system meet modern requirements for the safety and reliability of the brake system only insufficient. In particular, a non-availability of the brake system during a flushing process can lead to dangerous and unpredictable consequences in critical driving dynamics situations. The bleeding of the brake system should therefore be carried out regularly and without its significant functional impairment. In addition, passive means instead of actively controllable components are to be preferred in order to minimize the susceptibility to errors.

As has now been recognized, these requirements can be met with a venting device in which at each pressure buildup air bubbles, if any, are removed from the hydraulic circuit and transferred to the pressure fluid reservoir. The pressure medium itself is supplied to the hydraulic circuit or recycled after the air bubbles have been removed, so that no permanent pressure medium loss occurs. The brake system does not go through phases in which it is not immediately ready to brake.

The venting device preferably has a system pressure connection which is connected to the system pressure line and is arranged to collect air at a lower area of the venting device, as well as an air discharge connection arranged in an upper area of the venting device, preferably either directly or through an opening into another Pressure medium reservoir connection, is connected to the pressure medium reservoir.

The venting device is arranged substantially vertically in the vehicle with an upper portion and a lower portion such that accumulated air can escape upward from its lower portion facing the system pressure line into the pressure medium reservoir.

The venting device preferably comprises a sealed in a housing, in particular in a bore of a hydraulic block of the brake system, guided valve body which is acted upon by the system pressure in the lower region of the venting device. The housing is thus preferably a hydraulic block of the brake system, wherein the valve body is preferably arranged movably in a bore in this hydraulic block at least in one direction.

The valve body preferably enables the collection of air in a region facing the system pressure connection and is preferably configured such that it transfers the air in a region facing the pressure fluid reservoir when the pressure builds up, and connects to the pressure fluid reservoir when pressure is reduced in the system pressure line Produces area to the pressure medium reservoir, whereby the air escapes into the pressure medium reservoir.

The valve body preferably cooperates with a valve seat formed in an upper region of the housing, in particular in a bore of the hydraulic block, in order to control the escape of the collected air to the pressure medium reservoir.

The valve body advantageously defines in the housing a working space, the application of which, at a pressure which is higher than the system pressure, causes a lifting of the valve body from the valve seat down to allow escape of air from the working space.

The working space is preferably designed as an annular space around a region of the valve body which tapers at least partially in the direction of the pressure medium reservoir. In this annulus, the air entering through the flow passage in the valve body collects before it can escape at a system pressure reduction in the pressure fluid reservoir.

In a preferred embodiment, the valve body has a flow-through channel, which leads from the lower region of the venting device to the working space, wherein a first check valve is inserted or hydraulically connected in the flow-through channel, which allows a flow through the flow-through channel only in the direction of the working space. The flow-through channel preferably runs at least partially within the valve body.

The venting device advantageously comprises a hydraulic compliance arranged in the housing, which is connected to the working space via a second non-return valve opening in the direction of hydraulic compliance and to the system pressure connection or the system pressure line permanently connected to the system pressure connection via a third non-return valve opening in the direction of the system pressure connection. The hydraulic compliance is in a sense a buffer for pressure medium, which is conveyed during a pressure build-up from the second working space before it is conveyed back to the system pressure connection at a pressure reduction. It allows for a limited fluid displacement from the working space according to the dimensioning of the compliance.

The hydraulic compliance is preferably designed as a hydraulic pressure accumulator, which has a loaded by a compression spring hydraulic piston which separates a pressure accumulator working space of a pressure accumulator spring space. It can be dimensioned comparatively low according to the pressure medium volume to be displaced. In particular, it can be designed as a hydraulic low-pressure accumulator.

The accumulator spring chamber is preferably hydraulically connected to the air discharge port. Then the spring or compression spring is "wet" and protected by the wetting against corrosion. Alternatively, a "dry" spring may be used, in which case an atmosphere port is needed.

A connection bore of the second check valve is preferably formed on the working space in a lower region of the working space to discharge pressure medium with the lowest possible proportion of air.

The opening formed in the valve body of the flow passage in the working space is preferably arranged above a connection bore of the second check valve to the working space and below the valve seat.

The respective check valve, ie the first and / or the second and / or the third check valve, is preferably designed as a spring-loaded ball-seat valve.

In a preferred embodiment of the brake system, an electrically controllable pressure supply device for actuating the wheel brakes is provided, which is formed by a cylinder-piston arrangement with a hydraulic pressure chamber whose pressure piston is displaceable by an electromechanical drive, wherein the pressure chamber with the pressure fluid reservoir via a hydraulic Nachsaugleitung is connected to the suction of pressure medium.

The bleeding of the brake system is preferably as follows. In a pressure build-up by the electrically controllable pressure supply means pressure fluid flows together with possibly accumulated in the lower part of the venting air through the flow channel into the working space, where the majority of the air remains and pressure medium continues to flow without or with little air in the hydraulic compliance.

When pressure is reduced by the electrically controllable pressure supply device, pressure medium preferably flows out of the hydraulic compliance via the third check valve to the system pressure line. If air is present in the working space, this expands, whereby the valve body is displaced downwards, whereby the valve seat opens and the air escapes in the direction of pressure fluid reservoir into the air discharge port.

The advantages of the invention are in particular that can be done by the venting device described a removal of air at each pressure build-up and pressure reduction cycle, without the brake system is impaired in its function. The venting is achieved in a passive manner with a valve body, a hydraulic compliance and check valves, so that no actively controllable and thus error-prone components are used, so that the ventilation device works very reliable. In addition, only gas contaminated with fluid is temporarily deposited. If there is no contamination, no pressure medium is lost.

An embodiment of the invention will be explained in more detail with reference to a drawing. In it show in highly schematized

Presentation:

1 A preferred embodiment of a brake system according to the invention; and

2 a ventilation device of the brake system according to 1 ,

Identical parts are provided in both figures with the same reference numerals.

In 1 is an embodiment of a brake system according to the invention 1 shown. The brake system 1 includes one by means of an actuating or brake pedal 1a actuated master cylinder 2 , one with the master cylinder 2 cooperating simulation device 3 , a pressurized medium reservoir under atmospheric pressure 4 , an electrically controllable pressure supply device 5 , which by a cylinder-piston arrangement with a hydraulic pressure space 37 is formed, whose pistons 36 is displaceable by an electromechanical drive, an electrically controllable pressure modulation device for setting wheel-individual brake pressures and an electronic control unit 12 ,

An unspecified pressure modulation device comprises according to the example per hydraulically actuated wheel brakes 8th . 9 . 10 . 11 and each operable wheel brake 8th . 9 . 10 . 11 a motor vehicle, not shown, an inlet valve 6a - 6d and an exhaust valve 7a - 7d , the hydraulically interconnected in pairs via center ports and to the wheel brakes 8th . 9 . 10 . 11 are connected. The inlet connections of the inlet valves 6a - 6d be by means of brake circuit supply lines 13a . 13b With

Pressed, which are derived in a "brake-by-wire" mode from a system pressure in one to the pressure chamber 37 the pressure supply device 5 connected system pressure line 38 is present.

The inlet valves 6a - 6d is one to each of the brake circuit supply lines 13a . 13b opening check valve 50a - 50d connected in parallel. In a fallback mode, the brake circuit supply lines become 13a . 13b via hydraulic lines 22a . 22b with the pressures of the pressure chambers 17 . 18 of the master cylinder 2 applied. The outlet connections of the outlet valves 7a - 7d are via a return line 14b with the pressure medium reservoir 4 connected.

The master cylinder 2 points in a housing 21 two pistons arranged one behind the other 15 . 16 on top of the hydraulic pressure chambers 17 . 18 limit. The pressure chambers 17 . 18 on the one hand over into the piston 15 . 16 formed radial bores and corresponding pressure equalization lines 41a . 41b with the pressure medium reservoir 4 in conjunction, wherein the connections by a relative movement of the pistons 17 . 18 in the case 21 can be shut off. The pressure chambers 17 . 18 On the other hand, in the in 1 illustrated powerless fallback mode by means of the hydraulic lines 22a . 22b via isolation valves 23a . 23b with the already mentioned brake circuit supply lines 13a . 13b in connection.

The pressure compensation line 41a is by means of an inserted normally open valve 28 shut off. The pressure chambers 17 . 18 take unspecified return springs on which the pistons 15 . 16 with unoperated master cylinder 2 position in a starting position. A piston rod 24 couples the pivoting movement of the brake pedal 1 due to a pedal operation with the translational movement of the first master cylinder piston 15 , whose actuation path of a, preferably redundantly running, displacement sensor 25 is detected. As a result, the corresponding piston travel signal is a measure of the brake pedal actuation angle. It represents a braking request of the driver.

In the to the pressure chambers 17 . 18 connected line sections 22a . 22b is ever a separating valve 23a . 23b arranged, which is designed as an electrically actuated, preferably normally open, 2/2-way valve. Through the isolation valves 23a . 23b can the hydraulic connection between the pressure chambers 17 . 18 the master cylinder and the brake circuit supply lines 13a . 13b be shut off. One to the line section 22b connected pressure sensor 20 detects the in the pressure room 18 by a displacement of the second piston 16 built up pressure.

The simulation device 3 is hydraulic to the master cylinder 2 can be coupled and essentially consists, for example, of a simulator chamber 29 , a simulator spring chamber 30 as well as one the two chambers 29 . 30 mutually separating simulator piston 31 , The simulator piston 31 is supported by a in the simulator spring chamber 30 arranged elastic element (eg., A spring), which is advantageously biased on the housing 21 from. The simulator chamber 29 is by means of an electrically operated simulator valve 32 with the first pressure chamber 17 of the master cylinder 2 connectable. When setting a pedal force and open simulator valve 32 flows pressure medium from the master cylinder pressure chamber 17 into the simulator chamber 29 , A hydraulically antiparallel to the simulator valve 32 arranged check valve 34 allows independent of the switching state of the simulator valve 32 a largely unhindered backflow of the pressure medium from the simulator chamber 29 to the master cylinder pressure chamber 17 , Other designs and connections of the simulation device to the master cylinder 2 are conceivable.

The electrically controllable pressure supply device 5 is designed as a hydraulic cylinder-piston arrangement or a single-circuit electrohydraulic actuator whose / whose pressure piston 36 which the pressure room 37 limited, by a schematically indicated electric motor 35 can be actuated with the interposition of a rotation-translation gear also shown schematically. Electric motor and rotational translational gear form the drive of the actuator. One of the detection of the rotor position of the electric motor 35 serving, only schematically indicated rotor position sensor is denoted by the reference numeral 44 designated. In addition, a temperature sensor for detecting the temperature of the motor winding may also be used.

The by the force effect of the piston 36 on the in the pressure room 37 enclosed pressure fluid generated actuator pressure is in the system pressure line 38 fed and with a preferably redundant pressure sensor 19 detected. With open connection valves 26a . 26b the pressure medium enters the wheel brakes 8th . 9 . 10 . 11 for their operation. By pushing back and forth the piston 36 takes place with open connection valves 26a . 26b in a normal braking in the "brake-by-wire" mode a Radbremsdruckaufbau and degradation for all wheel brakes 8th . 9 . 10 . 11 , During pressure reduction, this flows from the pressure chamber before 37 in the wheel brakes 8th . 9 . 10 . 11 shifted pressure medium on the same way back into the pressure chamber 37 back. On the other hand, when braking with different individual wheel flows, with the help of the intake and exhaust valves 6a - 6d . 7a - 7d controlled wheel brake pressures (eg in the case of anti-lock control (ABS control)) via the exhaust valves 7a - 7d drained pressure medium content in the pressure fluid reservoir 4 and thus initially stands the pressure supply device 5 for actuating the wheel brakes 8th . 9 . 10 . 11 no longer available. A suction of pressure medium in the pressure chamber 37 is by a return of the piston 36 with closed connection valves 26a . 26b possible.

By the operation of the brake system 1 may be due to the repeated pressure build-up and pressure reduction, in which pressure medium is displaced in particular in hydraulic lines, pressure chambers and brake piston and the associated suction from the pressure fluid reservoir 4 Air bubbles form in the pressure medium, which can lead to a deterioration of the braking behavior due to their compressibility.

The present invention eliminates such accumulations of air bubbles by means of a venting device 60 which automatically removes a gas contaminated and thus compressible portion of the pressurized fluid at each pressurization of the hydraulic system. The thereby released volume is dependent on the amount of polluting air, so that the discharged fluid volume goes to zero, if no gas is present.

The in the 1 and 2 illustrated venting device 60 is hydraulically connected to the actuator pressurized system pressure line 64 (please refer 1 ) with a system pressure connection 66 connected to a point where gas bubbles can collect when the liquid is at rest. This may in particular be a recess in the hydraulic block, which is constructed so that the flow cross-section compared to the remaining portions of the system pressure line 38 is extended. This achieves a local reduction in the flow rate, which gives small air bubbles the opportunity to collect, combine to form larger air bubbles, and to move, by virtue of their buoyancy force, to the upper end of that line section. Furthermore, this section is preferably designed such that the mentioned other line sections of the system pressure line 38 With a smaller flow cross-section open at different angles, which forces a change in direction of the fluid particle velocity at a flow through which locally an air separation is favored. With a container connection 72 is the venting device 60 to the pressure fluid reservoir 4 hydraulically connected.

The vertically arranged ventilation device 60 has a valve body 76 up, by a spring 78 in a container port 72 or pressure fluid reservoir 4 facing and upper area 80 against the container connection 72 is pressed and in this way the departure to the pressure fluid reservoir 4 closes. The valve body 76 is at his pen 78 facing end or in a system pressure connection 66 facing and lower area 74 concave shaped and allows air to bubble under him in the cocoon space formed by the concave end portion 108 to collect.

In the valve body 76 the venting device 60 is a flow channel 82 . 94 formed in which a first check valve 84 is arranged, which consists of a ball 86 and a spring 88 is formed. The ball 86 is from the spring 88 against that System pressure connection 66 facing the end of the flow channel 82 pressed. The check valve 84 locks the flow direction of the flow channel 82 to the system pressure connection 66 and opens in the opposite direction when the hydraulic pressure difference is also on the ball 86 acting force of the spring 88 exceeds.

The flow channel 82 . 94 is with a hydraulic working space 98 connected in a container connection 72 facing region of the valve body 76 an annulus around the valve body 76 forms. The workroom 98 is above the flow channel 82 . 94 arranged. The valve body 76 it tapers upwards in the direction of the container connection and hydraulically closes the connection between the working space in a closed position 98 and container connection 72 , Due to the connection between flow channel 82 and workspace 98 becomes air flowing through it, which is lighter than the pressure medium, always from the flow channel 82 . 94 in the workroom 98 transported and collected there. The ventilation device 60 As described, it is arranged vertically in the brake system, essentially as shown.

At rest, the brake system, so if not pressure using the pressure supply device 5 is constructed, the valve body closes 76 the departure to the pressure medium reservoir 4 , in that the valve body 76 through the spring 78 up against an opening 104 of the container connection 72 is pressed. The air collects in particular during these periods of rest as a bubble 108 under the valve body 76 ,

In a system pressure buildup, a liquid-gas mixture, ie a mixture of pressure medium and air, through the first check valve 84 in the flow channel 82 . 94 and continue the workspace 98 postponed. This fluid displacement is made possible by having a second check valve 110 Pressure medium volume from the second working space 98 , flows into a hydraulic compliance, in the present embodiment as a pressure accumulator 116 , in particular as a hydraulic low-pressure accumulator, is executed. The accumulator 116 In this case, it is preferably dimensioned to be low in such a way that, in the case of a typical system pressure build-up of light braking, it takes up a volume of the order of magnitude of approximately one percent of that of the pressure supply device 5 has ejected amount of pressure medium. This means that with the filling of the pressure accumulator 116 Connected volume loss for the operation of the wheel brakes is negligible.

For this purpose, a hydraulic line connects 120 the second working space and a hydraulic valve space 126 of the second check valve 110 , The check valve 110 allows the inflow of pressure medium from the working space 98 in the valve room 126 and blocks the return flow from the valve chamber 126 in the second work dream 98 , A hydraulic pipe 132 hydraulically connects the valve chamber 126 with the accumulator 126 , If in the second work dream 98 an air portion is present, is correspondingly more volume on the first check valve 84 postponed.

At a system pressure reduction flows into the pressure accumulator 116 arrived small fluid or pressure medium quantity via a third check valve 140 back to the system pressure connection 66 , In the illustrated arrangement, the pressure medium initially flows via the hydraulic line 132 in the valve room 126 , From there it flows via a hydraulic line 146 in a hydraulic valve room 152 , As well could the hydraulic line 146 the accumulator 116 directly with the valve chamber 152 connect. From there it flows via a hydraulic line 156 back to the system pressure connection 66 , Alternatively, the hydraulic connection could be in the system pressure line permanently hydraulically connected to the system pressure port 38 For example, in the system pressure line section 64 open out.

If at the time of system pressure reduction in the work space 98 an air fraction is contained, this expands and pushes the valve body 76 from his seat at the opening 104 downwards or in the direction of the system pressure connection 66 , whereby gas-contaminated fluid through the vacant opening 104 and the tank connection 72 to the pressure medium reservoir 4 escapes.

As soon as the air has escaped after a sufficient number of Systemdruckaufbauzyklen, remain because of the incompressibility of the remaining air-free pressure medium, the fluid volumes in the flow channel 82 . 94 and workspace 98 constant. The valve body 76 then remains at rest during further system pressure reduction cycles. The spring of the second check valve 110 is designed so that its opening pressure is sufficient to move the valve body down.

The tank connection 72 is hydraulically via a hydraulic line 162 with a hydraulic chamber or accumulator spring chamber 106 of the accumulator 116 connected.

As already mentioned, the accumulator spring chamber 106 preferably via a hydraulic connection 162 connected to the air discharge port. Then the spring or compression spring is "wet" and protected by the wetting against corrosion. Alternatively, a "dry" spring can be used, in which case instead of the hydraulic connection 162 an atmospheric connection is needed to equalize the pressure in the pressure accumulator spring space 106 to allow with the atmosphere.

Although the embodiment relates to a brake system of the "brake-by-wire" type, the invention also encompasses conventional brake systems in which brake pressure is built up in the brake circuits and the brakes associated with the brake circuits by muscle power and optionally by means of a brake booster.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• DE 102013204778 A1 [0007]

Claims (13)

Brake system ( 1 ) for motor vehicles, comprising • hydraulically actuated wheel brakes ( 8th . 9 . 10 . 11 ); At least one electrically actuated wheel valve ( 6a - 6d . 7a - 7d ) per wheel brake for setting wheel-specific brake pressures; A pressurized medium reservoir (under atmospheric pressure) 4 ); • a system pressure line ( 38 . 64 ), is built up in the required pressure; characterized in that between the system pressure line ( 38 . 64 ) and the pressure fluid reservoir ( 4 ) hydraulically a venting device ( 60 ), which during operation of the brake system ( 1 ) with changing system pressures an automatic separation of in the system pressure line ( 38 . 64 ) possibly present air to the pressure fluid reservoir ( 4 ) causes. Brake system ( 1 ) according to claim 1, wherein the venting device ( 60 ) one to the system pressure line ( 64 ) connected system pressure port ( 66 ), which is adapted to air at a lower portion of the venting device ( 60 ), and one in an upper area of the ventilation device ( 60 ) arranged air discharge port ( 72 ) connected to the pressure fluid reservoir ( 4 ) is connected. Brake system ( 1 ) according to claim 1 or 2, wherein the venting device ( 60 ) one in a housing ( 21 ), in particular in a bore of a hydraulic block of the brake system ( 1 ), sealed guided valve body ( 76 ), which in the lower part of the ventilation device ( 60 ) is acted upon by the system pressure. Brake system ( 1 ) according to claim 3, wherein the valve body ( 76 ) with one in an upper area of the housing ( 21 ), in particular in a bore of the hydraulic block, formed valve seat ( 80 ) cooperates to prevent the escape of the collected air to the pressure fluid reservoir ( 4 ) to control. Brake system ( 1 ) according to claim 3 or 4, wherein the valve body ( 76 ) in the housing ( 21 ) a work space ( 98 ), the application of which, at a pressure which is higher than the system pressure, a lifting of the valve body ( 76 ) from the valve seat ( 80 ) down to escape of air from the working space ( 98 ). Brake system ( 1 ) according to one of claims 3 to 5, wherein the valve body ( 76 ) a flow channel ( 82 . 94 ) from the lower area ( 74 ) of the venting device ( 60 ) to the workroom ( 98 ), wherein in the flow channel ( 82 . 94 ) a first check valve ( 84 ; 86 . 88 ) is inserted, which is a flow through the flow channel ( 82 . 84 ) only in the direction of the working room ( 98 ) allows. Brake system ( 1 ) according to one of claims 1 to 6, wherein the venting device ( 60 ) one in the housing ( 21 ) arranged hydraulic compliance ( 116 ), which are in the direction of hydraulic compliance ( 116 ) opening second check valve ( 126 ) to the working room ( 98 ) and a third non-return valve opening towards the system pressure port ( 152 ) to the system pressure port ( 66 ) or with the system pressure port ( 66 ) permanently connected system pressure line ( 38 . 64 ) connected. Brake system ( 1 ) according to claim 7, wherein the hydraulic compliance ( 116 ) is designed as a hydraulic pressure accumulator, which has a loaded by a compression spring hydraulic piston which separates a pressure accumulator working space of a pressure accumulator spring space. Brake system ( 1 ) according to claim 8, wherein the accumulator spring chamber to the air discharge port ( 72 ) is hydraulically connected. Brake system ( 1 ) according to one of claims 7 to 9, wherein the connection bore of the second check valve ( 126 ) to the working room ( 98 ) in a lower area of the working space ( 98 ) is designed to discharge pressure medium with the lowest possible proportion of air. Brake system ( 1 ) according to one of claims 6 to 10, wherein the in the valve body ( 76 ) formed mouth of the flow channel ( 94 ) in the working space ( 98 ) above the connection bore of the second check valve ( 126 ) to the working room ( 98 ) and below the valve seat ( 80 ) is arranged. Brake system ( 1 ) according to one of claims 6 to 11, wherein the respective non-return valve ( 86 . 88 ; 126 ; 152 ) is designed as a spring-loaded ball seat valve. Brake system ( 1 ) according to one of claims 1 to 12, wherein an electrically controllable pressure supply device ( 5 ) for actuating the wheel brakes ( 8th . 9 . 10 . 11 ) is provided, which by a cylinder-piston arrangement with a hydraulic pressure chamber ( 37 ) is formed, the pressure piston ( 36 ) is displaceable by an electromechanical drive, wherein the pressure chamber ( 37 ) with the pressure fluid reservoir ( 4 ) via a hydraulic Nachsaugleitung ( 14a ) is connected to the suction of pressure medium.

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