WO2020098998A1

WO2020098998A1 - Brake system and method for operating a brake system

Info

Publication number: WO2020098998A1
Application number: PCT/EP2019/074958
Authority: WO
Inventors: Andre Bollwerk; Willi Nagel
Original assignee: Robert Bosch Gmbh
Priority date: 2018-11-15
Filing date: 2019-09-18
Publication date: 2020-05-22
Also published as: DE102018219516A1; JP7360461B2; JP2022507326A

Abstract

The invention relates to a brake system (100) for a vehicle, comprising a master cylinder (1) with a primary piston (11), which can be moved in a cylinder chamber (10) with a primary outlet (10A) by means of a spindle drive (7), and with an inlet plunger (6), which can be moved coaxially in the primary piston (11) and which protrudes into the cylinder chamber (10); a wheel brake circuit (2) with a wheel brake cylinder (20); a pressure modulating device (3) with a pump motor (30) and a pump device (31), which is driven by the pump motor (30) and is coupled to the wheel brakes cylinder (20); a switchover valve (4), which separates the primary outlet (10A) of the master cylinder (1) from the wheel brake circuit (2) in a closed state and couples the primary outlet (10A) of the master cylinder (1) to the wheel brake circuit (2) in an open state; and a controller (5), which is designed to close the switchover valve (4) in a first operating mode and operate the pump motor (30) such that the wheel brake cylinder (20) is actuated so as to adjust a brake pressure according to an actuation signal which represents an axial movement of the inlet plunger (6) and to operate the spindle drive (7) of the master cylinder (1) such that a path-dependent reaction force is counteracted by the axial movement of the inlet plunger (6) as a result of an axial movement of the primary piston (11) according to a specified characteristic. The invention additionally relates to a method for operating the brake system (100).

Description

description

title

Brake system and method for operating a brake system

State of the art

Brake systems for vehicles, in particular for motor vehicles, such as cars or trucks, are usually implemented as electro-hydraulic brake systems.

Typically, such brake systems have a master brake cylinder with an actuator piston. This can either be operated directly manually or by means of a brake booster. In the latter case, the master brake cylinder is typically operated in accordance with an actuation signal that represents an axial displacement of a manually actuated input piston. The hydraulic pressure generated in the master brake cylinder is transmitted to wheel brakes to build up a brake pressure. In such

Brake systems are often integrated pressure modulation circuits, which are coupled to the wheel brakes via inlet and outlet valves

Have pressure generating device to be able to modulate the brake pressure independently of the master cylinder. Such a system will

described for example in EP 0 281 769 A2.

So-called brake-by-wire systems are also increasingly being used. Such a system is described for example in DE 10 2011 079 454 A1.

In this brake system, hydraulic pressure is generated in a simulator device by actuating a master brake cylinder. The pressure generated by the master brake cylinder is recorded and a setpoint brake pressure is determined on the basis of the recorded pressure

Pressure generating device, which has an electric motor and a displacement piston which can be moved by means of the electric motor, is set in an active circuit for actuating the wheel brakes. Disclosure of the invention

According to a first aspect of the invention, a brake system for a vehicle is provided. The brake system comprises a master brake cylinder with a primary piston, which is axially displaceable in a cylinder space having a primary output, one coaxially in the primary piston

Slidable input plunger, which protrudes into the cylinder space and is provided for coupling to a brake pedal, and a spindle drive coupled to the primary piston for the axial actuation of the primary piston. Through an axial displacement of the primary piston, a volume of

Cylinder space can be varied. In addition, a variation of the

Cylinder volume through the input plunger. The brake system further comprises a wheel brake circuit with at least one wheel brake cylinder and a pressure modulation device with a pump motor and a pump driven by the pump motor, which pump is coupled to the wheel brake cylinder. The brake system has a changeover valve which separates the primary output of the master brake cylinder from the wheel brake circuit in a closed state and couples the primary output of the master brake cylinder to the wheel brake circuit in an open state. According to the invention, a control device is also provided which is set up to close the changeover valve in a first operating mode and the

To operate the pump motor in such a way that the wheel brake cylinder is actuated to set a brake pressure as a function of an actuation signal which represents an axial displacement of the input plunger, and the

Operate the spindle drive of the master brake cylinder such that the axial displacement of the input plunger by an axial movement of the

Primary piston a path-dependent reaction force is opposed according to a predetermined characteristic.

One idea on which the invention is based is that of

Master brake cylinder hydraulically by means of a changeover valve

To separate the wheel brake cylinder, to use the master brake cylinder as a brake feel simulator and to generate a brake pressure in the wheel brake cylinder by means of the pressure modulation device. To operate the When the input plunger is displaced, the master brake cylinder as the brake feel simulator is adjusted by the spindle drive in such a way that a reaction force acts on the input plunger, the reaction force according to one of the adjustment path or the distance of the axial displacement of the

Input plunger dependent predetermined course is set. The predetermined course or the predetermined characteristic can be, for example, a linear, a parabolic or a course according to a higher degree polynomial. The distance of the axial displacement of the input plunger can be detected for example by means of a displacement sensor, wherein a value detected by the displacement sensor can form the actuation signal. Through the

Adjustment of the primary piston can completely or partially compensate for a change in volume of the cylinder space which occurs as a result of the actuation of the input plunger, so that a path simulation is realized.

Using the master brake cylinder as a brake feel simulator offers the advantage that different characteristics of the reaction force can be set in a flexible manner. In particular, however, the master brake cylinder can be used to generate the brake pressure in the event of an operating failure of the pressure modulation device by opening the changeover valve. This allows the braking system to be in a safety mode without any noticeable

Performance losses continue to be operated. This improves the system's reliability.

According to one embodiment of the brake system, it is provided that an output of the pump device is coupled to the wheel brake cylinder via a wheel inlet valve and an input of the pump device via a wheel outlet valve, an intermediate store being connected to the wheel brake valve

Wheel brake circuit is coupled. The intermediate store can be implemented, for example, as an isolated pressure store or as a reservoir which is under ambient pressure and is hydraulically coupled to the cylinder space via sniffer bores.

According to one embodiment, the control device is set up in the first operating mode when the primary piston is in a

Stop position is in which the volume of the cylinder space through the Primary piston can no longer be enlarged, the changeover valve and that

To open the wheel outlet valve and to operate the spindle drive in such a way that the primary piston is moved out of the stop position so that one of the

Input plunger and / or the volume displaced by the primary piston

Buffer is fed. It is therefore ensured that the

Cylinder space is not completely filled by moving the primary piston away from the stop position and thereby reducing the volume of the cylinder space or pushing hydraulic fluid out of the cylinder space. The

ejected volume is pushed into the wheel brake circuit via the changeover valve and from there through the wheel drain valve into a buffer.

According to a further embodiment, the control device is set up to open the changeover valve in a second operating mode, to operate the spindle drive and / or the pump motor in accordance with a vehicle control signal in such a way that the wheel brake cylinder for adjusting a

Brake pressure is actuated depending on a vehicle control signal, the control signal being provided for coupling to the vehicle

Vehicle interface of the control device is provided. The brake pressure is generated by the primary piston and / or by the pressure modulation device when the changeover valve is open. This is preferably carried out jointly by the primary piston and the pressure modulation device, because the spindle drive and the pump device are each subjected to lower loads. This protects the components or they can be designed for lower loads. The control signal can in particular by an on-board computer based on route data in an autonomous

Ferry operation of the vehicle are generated and represents one

Brake request.

According to a further embodiment, the control device is set up to operate the spindle drive in the second operating mode in such a way that a change in volume of the cylinder space caused by an axial displacement of the input plunger is compensated for by an opposite axial displacement of the primary piston. Accordingly, one

Operation of the input plunger by a driver or one by the Actuation of the input plunger neutralizes the change in volume of the cylinder space. This means that the primary piston is shifted back by a distance corresponding to the volume change through the input plunger. As a result, the input plunger can be functionally decoupled from the wheel brake circuit in a simple manner without additional components. In particular, this does not change the brake pressure as a result of actuation of the input plunger.

According to a further embodiment, the control device is set up in the second operating mode when the primary piston is in a stop position in which the volume of the cylinder space can no longer be increased by the primary piston, the changeover valve and

Input plunger and / or the volume displaced by the primary piston

Buffer is fed. This actuation of the primary piston by the spindle drive takes place analogously to that for the first operating mode

described actuation when the primary piston is in the

Stop position.

According to a further embodiment it is provided that the

Input plunger is displaceable by an input rod, the input plunger being biased against the input rod by means of a first spring. In this way, the input plunger against the

Input rod pressed so that when the input rod is moved in a reverse direction, the input plunger is placed against the input rod. However, the input plunger can be moved against the force of the first spring in a forward direction regardless of the input rod. This may prevent the input rod from being carried along, e.g. in the second operating mode. The first spring can be supported on the primary piston, for example.

According to a further embodiment, it is provided that the spindle drive has a drive device, a spindle which can be axially displaced by the latter and a support plate connected to the spindle. The support plate forms one Driver for the primary piston or the primary piston rests on the support plate. Optionally, the primary clamp is against the by means of a second spring

Support plate is biased or pressed against the support plate by the second spring. This ensures a tight fit between the support plate and

Primary piston ensured.

According to a further embodiment it is provided that the support plate is prestressed by means of a return spring which is located on one of the

Supporting cylinder-defining housing. The return spring can rest on the housing with a first end and on the support plate with a second end. Alternatively, the return spring or with a first end on the housing and with a second end on a radial shoulder of the

Apply primary piston and thereby press the primary piston against the support plate.

According to a further embodiment, it is provided that the master cylinder is designed as a tandem cylinder and, in addition to the primary piston, has a secondary piston which is located axially in an area of the cylinder space located between the primary outlet and a secondary outlet

is movable. A further wheel brake circuit can be coupled to the primary output via a further changeover valve, and the wheel brake cylinder of the further wheel brake circuit can be actuated via a further pump, which is driven by the pump motor of the pressure modulation device, as was described above.

According to a further aspect of the invention is a method for operating a brake system according to one of the preceding embodiments

intended. According to the invention there is an axial displacement of the

Input plunger, the axial being in a first operating mode

Shift of the input plunger representing actuating signal is generated. In further steps, the switching valve is closed, the pump motor is operated in such a way that the wheel brake cylinder is actuated as a function of the actuation signal, and the spindle drive of the master brake cylinder is operated in such a way that the axial displacement of the

Input plunger by an axial movement of the primary piston path-dependent reaction force is opposed according to a predetermined characteristic.

The present invention is explained in more detail below with reference to the exemplary embodiments given in the schematic figures of the drawings. It shows:

Fig. 1 is a schematic representation of a brake system according to a

Embodiment of the present invention;

2 shows a master brake cylinder of a brake system according to a further exemplary embodiment of the present invention; and

3 shows a master brake cylinder of a brake system according to a further exemplary embodiment of the present invention.

In the figures of the drawing, elements, features and components which are the same, have the same function and have the same effect - unless otherwise stated - are each provided with the same reference symbols.

1 shows an example of a brake system 100 for a vehicle. The

Brake system 100 has a master brake cylinder 1, at least one

Wheel brake circuit 2, a pressure modulation device 3, a changeover valve 4 per wheel brake circuit 2, a control device 5 and an optional one

High pressure switching valve 9 per wheel brake circuit 2. The brake system 100 shown by way of example in FIG. 1 has a first wheel brake circuit 2A and a second wheel brake circuit 2B.

The master brake cylinder 1 shown by way of example in FIG. 1 has a housing 15 which defines a cylinder space 10 which extends in an axial direction. The master brake cylinder 1 shown by way of example in FIG. 1 is designed as a tandem cylinder with a primary piston 11 and a secondary piston 12. The primary piston 11 and the optional secondary piston are axially displaceably mounted in the cylinder space 10. The housing 15 has a primary output 10A and a secondary output 10B. The primary output 10A is arranged between a first axial end 15A and a second axial end 15B of the cylinder space 10 lying opposite thereto. The secondary outlet 10B is located between the primary outlet 10A and the second axial end 15B of the cylinder space 10. The primary piston 11 is axially displaceable in a first region of the cylinder space 10, which extends between a first axial end and the primary outlet 10A. The secondary piston 12 is axially displaceable in a second region, which extends between the primary outlet 10A and the secondary outlet 10B. The primary piston 11 and the secondary piston 12 each define, together with the housing 15, a working volume of the cylinder space 10, which can be varied by the axial positioning of the pistons 11, 12.

As shown by way of example in FIG. 1, the master brake cylinder 1 also has an input plunger 6. The input plunger 6 is coaxial with that

Primary piston 11 arranged and guided axially displaceably in an axial bore 14 of the primary piston 11. As exemplified in Fig. 1, the protrudes

Input plunger 6 into the cylinder space 10. The input plunger 6 can, in particular, be cylindrical in shape, as shown in FIG. 1 by way of example. The input plunger has an optional shoulder 61 on an inner end section projecting into the cylinder space 10. Preferably, the

Input plunger 6 is axially displaceable by means of an input rod 65, which acts against an outer end section of the input plunger 6 opposite the inner end section. The input rod 65 serves to couple the input plunger 6 to a brake pedal or one

Brake lever of the vehicle (not shown). The input plunger 6 can be countered by a first spring 81 along the axial direction

Input rod 65 may be biased. The first spring 81 can be

support, for example, on the secondary piston 12, as is shown by way of example in FIG. 1. The secondary piston 12 can also by means of a spring 84, which is arranged on a side of the secondary piston 12 facing away from the primary piston 11 and is attached to an end wall of the

Housing 15 supports.

The master brake cylinder 1 has a spindle drive 7 for the axial displacement of the primary piston 11. As exemplified in Fig. 1, the Spindle drive 7 in particular have a drive device 71, for example in the form of an electric motor, a spindle 73 axially displaceable by the drive device 71 and a support plate 74 connected to the spindle 73. The drive device 71 can be coupled to the spindle 73 in particular via a spindle nut 72. The drive device 71 and the spindle nut 72 are arranged stationary with respect to the housing 15. The spindle 73 has an external thread 73A. The spindle nut 72 has an internal thread 72A which corresponds to the external thread 73A of the spindle 73 and engages with it, so that rotation of the spindle nut 72 by the drive device 71 brings about an axial displacement of the spindle 73. The spindle 73 is preferably arranged coaxially with the primary piston 11.

In particular, the input rod 65 can extend coaxially through an inner bore 73B of the spindle 73, as is shown by way of example in FIG. 1. Optionally, the drive device 71 is also arranged coaxially with the spindle nut 72, as is shown by way of example in FIG. 1.

The support plate 74 is disposed at an axial end of the spindle 73 and extends in a radial direction transverse to the spindle 73. Optionally, the support plate 74 is in an outer region with respect to the radial direction by one or more extending in the axial direction Tie rods 75 are guided, as is shown by way of example in FIG. 1. Optionally, the

Support plate 74 has a central recess through which the

Input rod 65 projects through. The support plate 74 can also be biased by a return spring 83 along the axial against the spindle 73.

The return spring 83 can, for example, as shown in FIG. 1, be supported on the housing 15 and on the support plate 74 itself.

As shown in Fig. 1 by way of example and schematically, the

Support plate 74, in particular on a shoulder projecting from this in the axial direction, a differential travel sensor 86 can be arranged, which is set up to detect a change in a position of the input rod 65 relative to the support plate 74. The differential travel sensor 86 can

For example, be implemented as an inductive sensor and a magnetic element 86A can be arranged on the input rod 65, so that the Differential path sensor 86 detects a change in the magnetic field as a result of an axial displacement of the input rod 65.

In a manual mode of operation of the brake system 100, a driver, e.g. by operating a brake pedal or lever (not shown) that

Axially shift input rod 65. This shift is detected by the differential travel sensor 86, which generates a corresponding actuation signal. The drive device 71 is then in accordance with the

Actuation signal operated, e.g. through the control device 5 so that the spindle 73 supports the support plate 74 and thus the support plate 74

Primary piston 11 moves. This will increase the work volume of the

Reduced cylinder space 10 and a hydraulic fluid (not shown) can be pushed out of the cylinder space through the primary outlet 10A. The optional secondary piston 12 is also axially displaced by the incompressible hydraulic fluid displaced by the primary piston 11 and also delivers hydraulic fluid from the secondary outlet 10B.

Each wheel brake circuit 2A, 2B has at least one wheel brake cylinder 20. 1 shows that each of the wheel brake circuits 2A, 2B has two wheel brake cylinders 20. The wheel brake cylinders 20 are only shown symbolically in FIG. 1. The wheel brake cylinders 20 can be actuated by a hydraulic fluid and are set up in dependence on a pressure of the

Hydraulic fluids to exert a force on a friction surface. The pressure of the hydraulic fluid is called the brake pressure.

As is also shown schematically in FIG. 1, the primary output 10A and the optional secondary output 10B are each connected to a wheel brake circuit 2A, 2B via a changeover valve 4. The changeover valve 4 is preferably designed as a normally open solenoid valve. In a closed state, the respective changeover valve 4 separates the primary output 10A and, if appropriate, the secondary output 10B of the master brake cylinder 1 from the respective wheel brake circuit 2A, 2B, thus blocking a hydraulic one

Connection off. In an open state, which is shown by way of example in FIG. 1, the respective changeover valve 4 couples the primary output 10A and, if appropriate, the secondary output 10B of the master brake cylinder 1 the wheel brake circuit 2, so that hydraulic fluid can be conveyed from the cylinder space 10 to build up a brake pressure into the wheel brake circuit 2A, 2B.

1 also shows schematically the pressure modulation device 3

Pressure modulation device 3 has a pump device 31 with one or more pumps for each wheel brake circuit 2. The pressure modulation device 3 further comprises a pump motor 30 which drives the pump devices 31. The pump device 31 is set up to increase the pressure of one of these hydraulic fluids supplied at an inlet and the hydraulic fluid at an outlet with an increased pressure compared to the inlet

to provide.

As shown schematically in FIG. 1, the output of the pump device 31 is coupled to the wheel brake cylinder or cylinders 20 of the respective wheel brake circuit 2, preferably via a wheel inlet valve 34. In particular that is

The wheel inlet valve 34 is arranged in a hydraulic path 40 extending between the changeover valve 4 and the wheel brake cylinder 20. The input of the pump device 31 is also coupled to the wheel brake cylinder 20, preferably via a wheel outlet valve 35, as shown in FIG. 1. The wheel outlet valve 35 is in particular located between the wheel brake cylinder 20 and the input of the pump device 31

extending hydraulic path 41 arranged.

The wheel inlet valve 34 and the wheel outlet valve 35 can in particular each be implemented as solenoid valves. The wheel inlet valve 34 is

preferably implemented as a normally open solenoid valve. The

Wheel outlet valve 35 is preferably closed as a de-energized

Solenoid valve realized. 1 shows the wheel inlet valve 34 in an open state and the wheel outlet valve 35 in a closed state.

As is further shown by way of example in FIG. 1, an optional

Buffer 36 can be coupled to the wheel brake circuit 2 via the wheel outlet valve 35. 1 shows an example of a pressure accumulator connected to the hydraulic path 41 as an intermediate accumulator 36. As shown symbolically in Fig. 1, the pressure accumulator has a spring biased piston, which conveys a hydraulic fluid located in the intermediate store 36 back from the intermediate store 36 into the hydraulic path 41 when the pressure in the hydraulic path 41 becomes less than a limit value predetermined by the spring constant of the spring. As an alternative to this, the intermediate store 36 can be designed as a reservoir (not shown) in which ambient pressure prevails. The reservoir is preferably fluidically connected to the cylinder chamber 10 via an inlet 16, sniffing bores 16A being formed in an axial end region of the primary piston 11 opposite the spindle drive 7, which open the inlet 16 in a stop position of the primary piston 11, so that hydraulic fluid between them the reservoir and the cylinder chamber 10 can be replaced. Such a reservoir can also be provided in addition to the pressure accumulator.

A high-pressure switching valve 9 is also provided for each wheel brake circuit 2, which can be designed in particular as a normally closed solenoid valve. In Fig. 1, the high pressure switching valves 9 are symbolic in one

shown closed state. In a closed state, the respective high-pressure switching valve 9 separates the primary output 10A and, if applicable, the secondary output 10B of the master brake cylinder 1 from the respective wheel brake circuit 2. In a closed state, the respective high-pressure switching valve 9 couples the primary output 10A and, if appropriate, the secondary output 10B of the master brake cylinder 1 with the respective

Wheel brake circuit 2.

The control device 5 shown symbolically in FIG. 1 is functional with the spindle drive 7, in particular with the drive device 71 of the

Spindle drive 7, the pump motor 30 and the changeover valves 4, the wheel inlet valves 34, the wheel outlet valves 35, and the optional

High-pressure switching valves 9 of the brake system 100 connected. A functional connection is understood to mean in particular a connection set up for transmitting information, e.g. a wired or wireless data connection. The control device 5 has in particular one

Control interface 50 for transmitting and receiving data or signals from and to the components of the brake system 100. Optionally can a vehicle interface 51 can also be provided, at which data or signals from a vehicle (not shown) can be received and transmitted to the vehicle. The control device 5 is in particular set up to provide output signals on the basis of received input signals. For this purpose, the control device 5 can in particular have a processor (not shown) and a non-volatile data memory (not shown).

In the manual operating mode already briefly described above, the control device 5 keeps the high-pressure switching valves 9 closed and the switching valves 4 open. The wheel inlet valves 34 are kept open. The wheel outlet valves 35 are kept closed. By moving the input plunger 6, e.g. an input signal is generated by input rod 65 following operator actuation, e.g. through the

Differential travel sensor 86. The actuation signal thus represents an axial displacement of the input plunger 6. The control device 5 operates the spindle drive 7, in particular the drive device 71 of the spindle drive 7, and optionally additionally the pump motor 30 in such a way that the wheel brake cylinder 20 for setting a brake pressure as a function of an actuation signal is operated. That is, to increase the brake pressure, the primary piston 11 and the optional secondary piston 12 are axially displaced by the spindle drive 7 in the direction of the respective outlet 10A, 10B, whereby fluid is conveyed into the respective wheel brake circuit 2 and the brake pressure is thereby increased. In addition, brake pressure can be built up by means of the pump device 31.

In a first operating mode, the control device 5 closes the

Switching valves 4 and operates the pump motor 30 such that the

Wheel brake cylinder 20 is actuated to set a brake pressure depending on an actuation signal which is an axial displacement of the

Input plunger 6 represents. The actuation signal can e.g. by the differential travel sensor 86 or another sensor, e.g. one

Absolute travel sensor (not shown) can be provided, which is set up to provide a signal representing an axial displacement of the input plunger 6. Consequently, when the driver enters the input bar 65 and thereby shifts the input plunger 6, generates an actuation signal that represents the driver's braking request. The control device 5 determines an actuating signal from the actuation signal, for example by means of a calculation rule stored as software in the memory, and transmits this to the pump motor 30, which operates the pump device 31 accordingly, in order to set the desired brake pressure in the wheel brake cylinder 20.

In the first operating mode, the control device 5 operates the

Operate the spindle drive 7 or the drive device 71 such that the axial displacement of the input plunger 6 by an axial movement of the

Primary piston 11 a path-dependent reaction force according to a

predetermined characteristic is opposed. In particular, the axial movement of the primary piston 11 simulates a reaction force that would be generated by the wheel brake cylinders 20 in the manual operating mode. The predetermined characteristic is generally determined by a curve which is dependent on the distance of the axial displacement of the input plunger 6

Represented reaction force, which acts on the input plunger 6. This reaction force can be adjusted by the axial displacement of the primary piston 11 since the changeover valves 4 are closed. The

Control device 5 determines an actuating signal from the actuation signal, e.g. by means of a calculation rule stored as software in the memory, and transmits this to the spindle drive 7 in order to produce a predetermined pressure in the cylinder space 10 for generating the reaction force.

In Fig. 1, the primary piston 11 is shown as an example in a stop position. In this position, the primary piston 11 bears on the support plate 74 and the support plate 74 abuts the spindle nut 72. The

Primary piston 11 is therefore at a maximum distance from the

Primary outlet 10A. Thus, the volume of the cylinder space 10 can no longer be increased by the primary piston 11. Consequently, the pressure in the

Cylinder chamber 10 can no longer be reduced by axial displacement of the primary piston 11. In order to be able to flexibly set a desired characteristic of the reaction force, one of the

Control device 5 generated signal opened at least one switch valve 4 and the wheel outlet valve 35 on the respective wheel brake circuit 2. The Control device 5 also operates the spindle drive 7 such that the support plate 74 is removed from the spindle nut 72 and the primary piston 11 is thus moved out of the stop position. A volume of hydraulic fluid that is displaced from the cylinder space by the movement of the primary piston 11 is thereby supplied to the intermediate store 36 via the wheel outlet valve 35. In this way, the requested brake pressure can be kept constant and the desired pedal feel can still be simulated for the driver.

In a second operating mode, the changeover valve 4 is switched on

Corresponding signal of the control device is opened and the spindle drive 7 and / or the pump motor 30 are operated by means of the control device 5 in accordance with a vehicle control signal such that the

Wheel brake cylinder 20 is actuated to set a brake pressure depending on a vehicle control signal. The control signal is the

Control device 5 provided here by the vehicle interface 51 provided. In the second operating mode, a signal characterizing the braking request is therefore not activated by actuating the

Input plunger 6 provided by the driver, but from an external signal generator, e.g. from an on-board computer (not shown) of the vehicle, which generates the control signal based on route data in an autonomous driving operation of the vehicle. The control device 5 controls the spindle drive 7 and the pump motor 30 in the manner described above with reference to the manual operating mode.

Optionally, it can be provided that the control device 5 in the second operating mode operates the spindle drive 7 in such a way that a change in volume of the cylinder space 10 caused by an axial displacement of the input plunger 6 is compensated for by an opposite axial displacement of the primary piston 11. If the driver axially displaces the input plunger 6, for example by actuating the input rod, which can be detected, for example, with the differential travel sensor 86 or another sensor, even though the brake system 100 is in the second operating mode, the primary piston 11 is moved in such a way that Working volume of the Cylinder chamber 10 remains constant. This prevents the driver from inadvertently changing the brake pressure.

If the primary piston 11 is in the stop position during the operation of the brake system 100 in the second operating mode, the

Control device 5 at least one switch valve 4 and that

Wheel outlet valve 35 of the corresponding brake circuit, and operates the spindle drive 7 in such a way that the primary piston 11 is moved out of the stop position, so that a volume displaced by the input plunger 6 and / or the primary piston 11 is fed to the intermediate store 36.

Another master brake cylinder 1 is shown by way of example in FIG. 2. This differs from the master brake cylinder 1 shown in FIG. 1 in particular in that the first spring 81, which prestresses the input plunger 6 along the axial direction against the input rod 65, is supported on the primary piston 11. As shown by way of example in FIG. 2, the input plunger 6 can have a stop 62 projecting in the radial direction at the outer end section opposite the inner end section with optional shoulder 61, against which the first spring 81 presses. The stop 62 can in particular be hat-shaped or sleeve-shaped, as is shown by way of example in FIG. 2.

Optionally, a second spring 82 is also provided in FIG. 2, which biases the primary piston 11 against the support plate 74 along the axial direction. The second spring 82 is arranged on the side of the primary piston 11 facing away from the support plate 74. In particular, the second spring 82 can be arranged between the primary piston 11 and the secondary piston 12 and can be supported against the secondary piston 12, as is shown by way of example in FIG. 2.

FIG. 3 shows a further master brake cylinder 1 by way of example. This is constructed similarly to the master brake cylinder 1 shown in FIG

differs from this in particular in that the return spring 83 does not press directly against the support plate 74 but against a radial shoulder 13 of the primary piston 11. As can be seen in Fig. 3, the radial extends Shoulder 13 of the primary piston 11 from this in the radial direction and is preferably located in one facing the support plate 74

End portion of the primary piston 11 is arranged. Although the present invention is described above with reference to

Exemplary embodiments has been explained by way of example, it is not limited to them, but can be modified in a variety of ways. In particular, combinations of the above exemplary embodiments are also conceivable.

Claims

Expectations

1. Brake system (100) for a vehicle, with:

a master brake cylinder (1) with a primary piston (11) which is axially displaceable in a cylinder space (10) having a primary outlet (10A), an input plunger (6) which is displaceable coaxially in the primary piston (11) and which flows into the cylinder space (10) protrudes and is provided for coupling to a brake pedal, and a spindle drive (7) coupled to the primary piston (11) for the axial actuation of the primary piston (11);

a wheel brake circuit (2) with at least one wheel brake cylinder (20);

a pressure modulation device (3) with a pump motor (30) and a pump device (31) driven by the pump motor (30), which is coupled to the wheel brake cylinder (20);

a changeover valve (4), which in a closed state

Primary output (10A) of the master brake cylinder (1) from the wheel brake circuit (2) separates and in an open state, the primary output (10A) of the

Master brake cylinder (1) couples to the wheel brake circuit (2); and

a control device (5) which is set up to

in a first operating mode to close the changeover valve (4) and to operate the pump motor (30) in such a way that the wheel brake cylinder (20) is actuated to set a brake pressure as a function of an actuation signal which represents an axial displacement of the input plunger (6), and

to operate the spindle drive (7) of the master brake cylinder (1) in such a way that the axial displacement of the input plunger (6) by an axial movement of the primary piston (11) results in a path-dependent reaction force according to a

predetermined characteristic is opposed.

2. Brake system (100) according to claim 1, wherein an output of the

Pump device (31) via a wheel inlet valve (34) and an input of the pump device (31) via a wheel outlet valve (35) to the wheel brake cylinder (20) is coupled, a buffer (36) being coupled to the wheel brake circuit (2) via the wheel outlet valve (35), and wherein the

Control device (5) is set up to switch the changeover valve (4) in the first operating mode when the primary piston (11) is in a stop position in which the volume of the cylinder space (10) can no longer be increased by the primary piston (11). and to open the wheel outlet valve (35) and to operate the spindle drive (7) in such a way that the primary piston (11) is moved out of the stop position, so that a volume displaced by the input plunger (6) and / or the primary piston (11) displaces the intermediate store (36) is supplied.

3. Brake system (100) according to claim 1 or 2, wherein the

Control device (5) is set up to

open the changeover valve (4) in a second operating mode,

the spindle drive (7) and / or the pump motor (30) according to one

To operate the vehicle control signal such that the wheel brake cylinder (20) is actuated to set a brake pressure as a function of a vehicle control signal, the control signal being provided by a vehicle interface (51) of the control device (5) provided for coupling to the vehicle.

4. Brake system (100) according to one of the preceding claims, wherein the control device (5) is set up to operate the spindle drive (7) in the second operating mode such that a volume change of the cylinder space caused by an axial displacement of the input plunger (6) (10) is compensated for by an opposite axial displacement of the primary piston (11).

5. Brake system (100) according to claim 3 or 4, wherein the

Control device (5) is set up in the second operating mode when the primary piston (11) is in a stop position in which the volume of the cylinder space (10) can no longer be increased by the primary piston (11), the changeover valve (4) and to open the wheel outlet valve (35) and to operate the spindle drive (7) in such a way that the primary piston (11) is moved out of the stop position, so that one of the input plungers (6) and / or volume displaced to the primary piston (11) is fed to the intermediate store (36).

6. Brake system (100) according to one of the preceding claims, wherein the input plunger (6) is displaceable by an input rod (65), and wherein the input plunger (6) by means of a first spring (81), which is preferably on the primary piston (11 ) is biased against the input rod (65).

7. Brake system (100) according to one of the preceding claims, wherein the spindle drive (7) has a drive device (71), a spindle (73) axially displaceable by this and one connected to the spindle (73)

Support plate (74), wherein the primary block (11) is preferably biased against the support plate by means of a second spring (82).

8. Brake system (100) according to claim 7, wherein the support plate (74) is biased by a return spring (83) which is supported on a housing (15) defining the cylinder space (10), and wherein the

Return spring (83) is also supported on the support plate (74) or on a radial shoulder (13) of the primary piston (11).

9. Brake system (100) according to one of the preceding claims, wherein the master cylinder (1) is designed as a tandem cylinder and in addition to the primary piston (11) has a secondary piston (12) which is axially in a between the primary output (10A) and a secondary output (10B) located area of the cylinder space (10) is displaceable.

10. A method for operating a brake system (100) according to one of the preceding claims, comprising the following steps:

axial displacement of the input plunger (6), in a first

Operating mode, an actuation signal representing the axial displacement of the input plunger (6) is generated;

Closing the changeover valve (4);

Operating the pump motor (30) in such a way that the wheel brake cylinder (20) is actuated as a function of the actuation signal; Operating the spindle drive (7) of the master brake cylinder in such a way that the axial displacement of the input plunger (6) by an axial movement of the primary piston (11) results in a path-dependent reaction force according to a

predetermined characteristic is opposed.