ELECTROHYDRAULIC BRAKE OF A VEHICLE

Description

[0001] The invention relates to an electrohydraulic brake of a vehicle according to claim 1.

[0002] Electro-hydraulic brakes are brakes in which the driver's braking request is detected on a pedal by means of a sensor in a brake value transmitter, whereupon a control unit controlled by the sensor generates a pressure via a pressure transmitter in a hydraulic brake system, based on which the brakes carry out a braking intervention corresponding to the driver's braking request.

[0003] JP 2014 079789 A discloses a hydraulic brake for a press with a bidirectional pump. WO 2017 / 030476 A1 describes a braking system for vehicles with a pressure accumulator and a bidirectional pump, and DE 43 40 467 A1 describes a braking system for vehicles with a pressure accumulator. A hydraulic brake of this type is known from EP 2 674 638 A2.

[0004] The object of the invention is to provide an energy-saving electrohydraulic brake for a vehicle with an expanded range of functions. Furthermore, a vehicle with such an electrohydraulic brake is to be provided.

[0005] This object is achieved according to the invention by the features of claims 1 and 17. Disclosure of the invention

[0006] The invention is based on an electro-hydraulic brake of a vehicle, which has at least the following: a) an electronic control system with an implemented control system, which is carried out during a braking operation as needed in at least one control cycle, wherein during the control cycle at least one brake pressure reduction and at least one brake pressure build-up occurs in at least one hydraulic brake actuator, b) the at least one hydraulic brake actuator, which generates a braking force depending on the applied brake pressure, c) a hydraulic fluid reservoir for storing hydraulic fluid, d) a pump and a drive motor for the pump, e) at least one pressure accumulator for storing hydraulic fluid originating from the hydraulic fluid reservoir, f) flow connections between the at least one brake actuator, the hydraulic fluid reservoir, the pump, and the pressure accumulator, wherein g) a valve device that can be controlled at least partially by the electronic control system is arranged in at least one flow connection,which controls a flow of hydraulic fluid in the at least one flow connection. According to the invention, h) the electronic control unit controls at least the drive motor for the pump and / or the valve device such that, during the at least one control cycle, hydraulic fluid flows back and forth or is pumped back and forth between the at least one brake actuator and the pressure accumulator.

[0007] The electrohydraulic brake can, in particular, comprise a brake request device, which, in order to control the braking process, feeds signals for the start and end of the braking process, as well as for the degree of brake application, into the electronic control system. Depending on these signals, the electronic control system then controls at least the drive motor for the pump and / or the valve device.

[0008] The invention achieves a power transmission from the drive motor to the hydraulic actuator, for example, a hydraulic brake cylinder, via the hydraulic system. The hydraulic power transmission is easily scalable, allowing drive motors of different power levels to be used. Hydraulic fluid then flows back and forth between the at least one brake actuator and the pressure accumulator during at least one control cycle, or is pumped back and forth, in particular, by the pump. Consequently, during control, hydraulic energy in the form of pressurized hydraulic fluid is temporarily stored in the pressure accumulator and withdrawn from the pressure accumulator during the control cycles, before being returned to the pressure accumulator. Control processes can then be executed with high dynamics.

[0009] The pressure accumulator is preferably a high-pressure accumulator in which a first pressure prevails, which, in particular, at least after a brake pressure reduction during the at least one control cycle, is greater than a second pressure prevailing in the hydraulic fluid reservoir, because, for example, the pressure accumulator is pressurized from the at least one brake actuator during the brake pressure reduction. The pressure accumulator therefore preferably represents an intermediate reservoir for the hydraulic fluid, in which it is temporarily stored under pressure.

[0010] In particular, exclusively or also during the at least one control cycle, hydraulic fluid flows back and forth between the at least one brake actuator and the pressure accumulator or is pumped back and forth.

[0011] Due to the higher pressure level in the accumulator, a drive unit for the pump, such as a relatively low-power electric motor, is sufficient. Furthermore, this also results in advantageously low energy consumption during control, and the control system offers high dynamics. Last but not least, the pressure in the accumulator can support the buildup of brake pressure in at least one brake actuator, particularly during longer braking operations that last longer than a minimum duration.

[0012] Advantageous further developments of the invention are specified in the subclaims.

[0013] Preferably, the electronic control is designed such that it controls the drive motor of the pump and / or the valve device at least during the at least one control cycle a) controls the brake pressure reduction in such a way that hydraulic fluid flows or is delivered from the at least one brake actuator into the pressure accumulator, and b) controls the brake pressure build-up in such a way that hydraulic fluid flows or is delivered from the pressure accumulator into the at least one brake actuator.

[0014] The control can also be designed such that at least during the at least one control cycle, at least one brake pressure holding is carried out following a brake pressure build-up or a brake pressure reduction, in which the electronic control unit controls the drive motor of the pump and / or the valve device in such a way that hydraulic fluid is held in the at least one brake actuator.

[0015] According to a further development, the electronic control can control at least the drive motor for the pump and / or the valve device in such a way that, in particular even when the control is inactive, ie, in particular when the control is not carried out or activated, a) for a brake pressure build-up, e.g. at the start of or during a braking operation in the at least one brake actuator, hydraulic fluid flows or is conveyed from the hydraulic fluid reservoir and / or from the pressure accumulator into the at least one brake actuator, and / or b) for a brake pressure reduction, e.g. at the end of a braking operation, hydraulic fluid flows or is conveyed from the at least one brake actuator into the hydraulic fluid reservoir and / or into the pressure accumulator.

[0016] The brake pressure build-up and / or the brake pressure reduction then takes place in the manner described, without the control being activated or coming into effect, for example because its execution is not necessary or desired. In other words, the pressure in the pressure accumulator can be used to support a brake pressure build-up or as the exclusive pressure for brake pressure build-up in the at least one brake actuator, even if the control is not or not yet active. Likewise, the pressure prevailing in the at least one brake actuator can be used during a brake pressure reduction in the at least one brake actuator in order to pressurize the pressure accumulator and / or the hydraulic fluid supply. When the pressure accumulator is pressurized, the then higher pressure level in the pressure accumulator can in turn be used to build up brake pressure.

[0017] The electro-hydraulic brake can in particular comprise a brake request device which, in order to control the braking process, feeds signals for the start and end of the braking process as well as for the degree of brake application into the electronic control system, and which a) a brake signal transmitter operable by a driver of the vehicle, and / or b) a driver assistance system and / or an autopilot.

[0018] Consequently, the brake signal sensor, and / or the driver assistance system and / or the autopilot can then generate a brake request signal to request the braking process.

[0019] In the electrohydraulic brake, the pump can be a unidirectionally operable pump with a single delivery direction, in which case the electronic control can control the drive motor of the unidirectionally operable pump such that the unidirectionally operable pump delivers hydraulic fluid in the single delivery direction. Preferably, the unidirectionally operable pump can be operated in the single delivery direction to build up brake pressure, in particular during the at least one control cycle. Alternatively, the unidirectionally operable pump can also be operated in the single delivery direction to reduce brake pressure, in particular during the at least one control cycle.

[0020] According to an alternative embodiment, the pump can also be designed as a bidirectionally operable pump, wherein the electronic control unit controls the drive motor of the pump in such a way that the bidirectionally operable pump a) in a first conveying direction, hydraulic fluid is conveyed from the hydraulic fluid reservoir and / or from the pressure accumulator into the at least one brake actuator, and b) in a second conveying direction opposite to the first conveying direction, hydraulic fluid is conveyed from the at least one brake actuator into the pressure accumulator and / or into the hydraulic fluid reservoir.

[0021] In particular, the operation of the bidirectionally operable pump can be carried out during at least one control cycle a) in the first delivery direction to build up brake pressure, and b) in the second delivery direction to reduce brake pressure.

[0022] The electronic control unit can also control the drive motor of the pump at least during the at least one control cycle in such a way that the pump is operated alternately between the first delivery direction and the second delivery direction for reducing the brake pressure and for building up the brake pressure, in particular during the at least one control cycle.

[0023] In the case of the electro-hydraulic brake, the control can comprise a wheel-individual (wheel-selective) or axle-individual (axle-selective) control, in particular a brake slip control (ABS), a traction control (ASR) and / or an electronic stability program (ESP), which, depending on the vehicle situation, carries out a wheel-selective braking intervention if such is necessary to prevent the vehicle from skidding.

[0024] The electronic control unit can also be configured to control the pump's drive motor and, if necessary, the valve device during a filling phase in order to pump hydraulic fluid into the pressure accumulator until the pressure prevailing in the pressure accumulator is greater than a minimum pressure. Alternatively or additionally, the electronic control unit can be configured to control the pump's drive motor and, if necessary, the valve device during a filling phase in order to pump hydraulic fluid into the pressure accumulator during at least one brake pressure reduction, in particular during at least one control cycle, until the pressure prevailing in the pressure accumulator is greater than the minimum pressure.

[0025] The minimum pressure can preferably be in a range between 50 and 100 bar. The pressure accumulator is therefore preferably a high-pressure accumulator. In contrast, the hydraulic fluid reservoir, for example, is a low-pressure accumulator with a pressure prevailing therein of approximately ambient pressure.

[0026] The valve device can also comprise at least one solenoid valve controlled by the electronic control system and have a switching position in which the valve device creates a flow connection between the at least one brake actuator and the pressure accumulator and / or the hydraulic fluid reservoir. In this case, the at least one solenoid valve can be spring-biased in particular into this one switching position and can assume this one switching position without current (normally open). The at least one solenoid valve can then preferably serve to quickly reduce force and, in the event of a fault (e.g., power loss due to a power supply failure or a fault in the control system), connects the at least one hydraulic brake actuator to the pressure accumulator and / or to the hydraulic fluid reservoir, thereby providing a fail-silent functionality.

[0027] Preferably, the valve device may comprise at least the following: a) a check valve, b) a 2 / 2-way solenoid valve, c) a 3 / 2-way solenoid valve, d) a 4 / 2-way solenoid valve.

[0028] The invention also relates to a vehicle having at least one electrohydraulic brake as described above. drawing

[0029] Exemplary embodiments of the invention are illustrated in the drawings below and explained in more detail in the following description. In the drawing, Fig.1 shows a schematic circuit diagram of an electro-hydraulic brake according to a preferred embodiment of the invention; Fig.2 shows the electro-hydraulic brake of Fig. 1 during braking force build-up at the beginning and during a braking process without active control; Fig. 3 the electrohydraulic brake of Fig. 1 when reducing the brake force to terminate the braking process without active control; Fig. 4the electrohydraulic brake of Fig. 1 during braking force reduction with active control; Fig. 5the electrohydraulic brake of Fig. 1 during braking force build-up with active control; Fig. 6the electrohydraulic brake of Fig. 1 during a filling phase of a pressure accumulator; Fig. 7 shows a schematic circuit diagram of an electrohydraulic brake according to a further embodiment of the invention; Description of the embodiments

[0030] Fig. 1 shows a schematic circuit diagram of an electro-hydraulic brake 100 according to a preferred embodiment of the invention.

[0031] The electrohydraulic brake 100 comprises an electronic controller 1 with an implemented control system, which is activated and executed as needed during a braking operation in at least one control cycle. During a control cycle, at least one brake pressure reduction and at least one brake pressure buildup occur in at least one hydraulic brake actuator 2. The control system here includes, for example, a brake slip control (ABS), in which the brake slip is controlled, in particular, on an individual wheel basis. The electronic controller 1 thus represents a brake control unit of the electrohydraulic brake 100.

[0032] Furthermore, the electrohydraulic brake 100 comprises a plurality of brake actuators, of which only one brake actuator 2 is shown here as a representative of the other brake actuators. The brake actuator 2 is formed here, for example, by a hydraulic disc brake with a hydraulic brake cylinder that can be loaded with hydraulic fluid and released from hydraulic fluid. The hydraulic brake actuator 2 generates a braking force at the respective wheel depending on the brake pressure applied to it. Preferably, each wheel of the vehicle is assigned such a brake actuator 2 so that the wheels can be braked individually.

[0033] In addition, the electro-hydraulic brake 100 comprises a hydraulic fluid reservoir 3 for preferably pressureless storage of hydraulic fluid, for example, under ambient pressure, as well as a pump 4, here for example a bidirectional pump, which is driven by a drive unit 5, for example, an electric motor, and can be operated in two opposite pumping directions depending on the direction of rotation of the drive unit. This means that in a first pumping direction, the suction side of the pump corresponds to the pressure side of the pump when the pump is operated in the opposite second pumping direction, and vice versa. The pump 4 therefore has a first connection 6, which, depending on the pumping direction, then points to the suction side or the pressure side of the pump 4. The same applies to a second connection 7 of the pump 4.

[0034] Furthermore, the electro-hydraulic brake comprises a pressure accumulator 8 for, in particular, high-pressure storage of hydraulic fluid as well as flow connections between the at least one brake actuator 2, the hydraulic fluid reservoir 3, the pump 4 and the pressure accumulator 8.

[0035] Last but not least, the electro-hydraulic brake 100 comprises a valve device 9, which here provides, for example, a 3 / 2-way solenoid valve 10 and a first check valve 11 as well as a second check valve 12.

[0036] The flow connections include a first flow connection 13 between the hydraulic fluid supply 3, the first connection 6 of the pump 4, a first connection 14 of the 3 / 2-way solenoid valve 10 and the at least one brake actuator 2, a second flow connection 15 between the hydraulic fluid supply 3, the second connection 7 of the pump 4, a second connection 16 of the 3 / 2-way solenoid valve 10 and the pressure accumulator 8, and a third flow connection 17 between the hydraulic fluid supply 3 and a third connection 18 of the 3 / 2-way solenoid valve 10.

[0037] In the first flow connection 13, the first check valve 11 is arranged such that it allows a flow from the hydraulic fluid reservoir 3 to the at least one brake actuator 2, to the first port 6 of the pump 4 and to the first port 14 of the 3 / 2-way solenoid valve 10, but prevents a flow in the opposite direction, namely from the at least one brake actuator 2 and / or from the first port 6 of the pump and / or from the first port 14 of the 3 / 2-way solenoid valve 10 into the hydraulic fluid reservoir 3.

[0038] In an analogous manner, in the second flow connection 15, the second check valve 12 is arranged such that it permits a flow from the hydraulic fluid reservoir 3 to the second port 7 of the pump 4, to the pressure accumulator 8 and to the second port 16 of the 3 / 2-way solenoid valve 10, but prevents a flow in the opposite direction, namely from the pressure accumulator 8 and / or from the second port 7 of the pump 4 and / or from the second port 16 of the 3 / 2-way solenoid valve 10 into the hydraulic fluid reservoir 3.

[0039] The 3 / 2-way solenoid valve 10 has a Fig. 1 shown through-flow position, in which the first connection 14, the second connection 16 and the third connection 18 are connected to each other, as well as a blocking position, in which there is no flow connection between any of the first, second and third connections 14, 16, 18. In the Fig.1 In the open position shown, the at least one brake actuator 2 is directly connected to the hydraulic fluid reservoir 3 and the pressure accumulator 8. In the closed position, these connections are interrupted. The 3 / 2-way solenoid valve 10 is preferably a "normally open" valve, whereby it is spring-loaded into the open position and then assumes this position without power. However, if it is energized by the electronic control unit 1, it switches to the closed position.

[0040] The 3 / 2-way solenoid valve 10 and the drive motor 5 of the pump 4 are controlled in a coordinated manner by an electronic control unit 1 to circulate hydraulic fluid in the flow connections. For this purpose, the electronic control unit 1 is also connected to an electric brake signal transmitter 19 of the electrohydraulic brake 100 via a signal line 20. This transmitter can be actuated by a driver, for example, via a brake pedal 21, to feed actuation-dependent brake request signals into the electronic control unit 1.It is provided here that brake request signals are generated not only by the driver-operated brake value sensor 19, but additionally or alternatively by a driver assistance system such as an adaptive cruise control (ACC) or an emergency brake assistant and / or by an autopilot and are then fed into the electronic control 1 by a corresponding control unit 22 in order to trigger, control and terminate braking operations.

[0041] The following describes various situations or stages of braking processes, illustrated in the figures. Flows under relatively low pressure are indicated by dotted arrows, and flows under relatively high pressure are indicated by dashed arrows.

[0042] Fig. 2 shows the electro-hydraulic brake 100 from Fig. 1 when braking force is built up at the beginning and during a braking operation without active ABS control, i.e., the wheels assigned to the brake actuators 2 do not slip excessively at the beginning and during the braking operation. The electronic control unit 1 controls the drive motor 5 of the pump 4 to drive it in a first pumping direction, symbolized here by the arrow, in which the pump 4 pumps hydraulic fluid from the hydraulic fluid reservoir 3 via the second flow connection 15 and then into the at least one brake actuator 2 via the first flow connection 13. The first check valve 11 prevents hydraulic fluid from the first flow connection 13 from being pumped back into the hydraulic fluid reservoir 3.Since the 3 / 2-way solenoid valve 10 is energized by the electronic control 1 and is thereby switched to the blocking position, the direct flow connection between the at least one brake actuator 2 and the pressure accumulator 8 as well as the hydraulic fluid reservoir 3 is blocked.

[0043] The first flow connection 13 is therefore located on the pressure side of the pump 4, whereby the pressure in the first flow connection 13 is higher than on the suction-side second flow connection 15, whereby a braking pressure is built up in the at least one brake actuator 2 and thus braking force is built up there.

[0044] If the braking force is to be kept constant over a certain period of time, for example, which results from a corresponding actuation of the brake pedal 21 and a resulting braking request signal, the 3 / 2-way solenoid valve 10 remains in its blocking position, but the drive motor 5 can continue to drive the pump 4, but with reduced power or speed in the first pumping direction, for example to compensate for leakage losses.

[0045] If the brake is released at the end of the braking process, the Fig. 3 The situation shown is that the 3 / 2-way solenoid valve 10 is switched from the blocking position to the through position by the electronic control unit 1. Hydraulic fluid then flows from the at least one brake actuator 2 through the opened 3 / 2-way solenoid valve 10 via the third flow connection 17 back into the hydraulic fluid reservoir 3. The drive motor 5 of the pump 4 is switched off.

[0046] If an unacceptably high brake slip occurs on at least one wheel of the vehicle during the described braking process, the braking force on the affected wheel is reduced, maintained, and rebuilt in control cycles by the ABS control implemented in the electronic control system 1. A control cycle, here, for example, an ABS control cycle, therefore includes a brake pressure reduction, a brake pressure maintenance, and a brake pressure buildup at the relevant brake actuator 2.

[0047] The brake pressure reduction within the ABS control cycle is in Fig. 4 shown. The electronic control unit 1 controls or maintains the 3 / 2-way solenoid valve 10 in the blocking position and drives the drive motor 5 such that the pump 4 is driven in the second pumping direction, symbolized by the arrow. This ensures that hydraulic fluid is pumped from the at least one brake actuator 2 via the first flow connection 13 into the pressure accumulator 8, in which the pressure subsequently increases.

[0048] If subsequent pressure maintenance is part of the ABS control cycle, the drive motor 5 is stopped, for example, by the electronic control 1.

[0049] For a subsequent brake pressure build-up within the ABS control cycle, the direction of rotation of the drive motor 5 of the pump 4 is now reversed, so that the pump 4 now rotates in the direction indicated by the arrow in Fig. 5 symbolized opposite direction rotating drive motor 5 and the pump 4 then pumps the hydraulic fluid from the pressure accumulator 8 and the hydraulic fluid reservoir 3 into the at least one brake actuator 2 in the first pumping direction. The pressure previously increased in the pressure accumulator 8 during the brake pressure reduction is then preferably used for the subsequent brake pressure buildup.

[0050] Consequently, during control, with each change from a brake pressure reduction to a brake pressure buildup and vice versa, hydraulic fluid is pumped back and forth into the pressure accumulator 8, increasing the pressure there, and out of the pressure accumulator 8, decreasing the pressure there, by changing the drive direction of the bidirectionally operating pump 4. Consequently, hydraulic fluid flows back and forth between the at least one brake actuator 2 and the pressure accumulator 8 in the manner of an energy swing and is pumped back and forth by the pump 4, particularly in the embodiment described here.

[0051] In Fig. 6 a filling phase of the pressure accumulator 8 is shown, as it can be carried out, for example, before a control cycle by the electronic control 1. For this purpose, the 3 / 2-way solenoid valve 10 is again controlled into the blocking position and the drive motor 5 is driven in such a way that the pump 4 is driven in the second pumping direction symbolized by the arrow, so that hydraulic fluid is pumped from the hydraulic fluid reservoir 3 into the pressure accumulator 8, so that a relatively high pressure of, for example, 50 to 100 bar can build up there, which can then be used, for example, to build up the brake pressure within a (particularly upcoming or later) control cycle or to support a general brake pressure build-up without active control, such as Fig. 2 can be used as described.

[0052] If a malfunction occurs in the electrical system, for example, due to a power outage, the 3 / 2-way solenoid valve 10 is de-energized and then switches to its open position, spring-loaded. Consequently, hydraulic fluid then flows from the at least one brake actuator 2 through the open 3 / 2-way solenoid valve 10 via the third flow connection 17 into the hydraulic fluid reservoir 3, thereby de-energizing the at least one brake actuator 2 and thus providing a fail-silent function.

[0053] Fig. 7 shows a schematic circuit diagram of an electrohydraulic brake 100 according to another embodiment of the invention. In contrast to the embodiment of Fig. 1 There is a pump 4 that can only be operated unidirectionally.

[0054] Furthermore, instead of a 3 / 2-way solenoid valve, three 2 / 2-way solenoid valves are provided, namely a first 2 / 2-way solenoid valve 23 in a first flow connection 24, to which the hydraulic fluid reservoir 3, the pump 4, and the at least one brake actuator 2 are connected; a second 2 / 2-way solenoid valve 25 in a second flow connection 26 between the hydraulic fluid reservoir 3 and the at least one brake actuator 2; and a third 2 / 2-way solenoid valve 27 in a third flow connection 28, to which the pressure accumulator 8 and the at least one brake actuator 2 are connected. The three flow connections 24, 26, and 28 are interconnected on the brake actuator 2 side.The three 2 / 2-way solenoid valves 23, 25 and 27 each have a blocking position and a flow position and, for example, as "Normally Open" valves, are spring-loaded into the non-energized flow position, while they assume their blocking position when energized.

[0055] The remaining elements of the electro-hydraulic brake 100 such as the electronic control 1, the brake value transmitter 19 and the control unit 22 of the driver assistance system or the autopilot are in Fig. 7 Although not shown, they are still present and interact with each other as described above.

[0056] To build up brake pressure or to apply the brake without ABS control, the drive motor 5 of the pump 4 is controlled by the electronic control 1 such that the pump 4, in its only pumping direction, pumps hydraulic fluid from the hydraulic fluid reservoir 3 via the first flow connection 24 into the brake actuator 2. The first 2 / 2-way solenoid valve 23 is switched to the pass-through position by the electronic control 1, while the second 2 / 2-way solenoid valve 25 and the third 2 / 2-way solenoid valve 27 are switched to their blocking positions.

[0057] To release the brake, the drive motor 5 of the pump 4 is deactivated, i.e., it does not rotate, and the second 2 / 2-way solenoid valve 25 is switched to its open position, while the first 2 / 2-way solenoid valve 23 and the third 2 / 2-way solenoid valve 27 are each switched to the closed position. As a result, hydraulic fluid flows through the open second 2 / 2-way solenoid valve 25 and the second flow connection 26 back into the hydraulic fluid reservoir 3.

[0058] For a brake pressure reduction within the scope of an ABS control cycle, the electronic control 1 controls the first and second 2 / 2-way solenoid valves 23, 25 each into the blocking position, but the third 2 / 2-way solenoid valve 27 into the pass-through position, so that hydraulic fluid flows from the at least one brake actuator 2 into the pressure accumulator 8 via the open third 2 / 2-way solenoid valve 27 and the third flow connection 28 in order to increase the pressure there.

[0059] If a subsequent pressure maintenance is part of the ABS control cycle, the third 2 / 2-way solenoid valve 27 is switched, for example, from the open position to the closed position, in which the first and second 2 / 2-way solenoid valves 23, 25 then also continue to be located.

[0060] For a subsequent brake pressure build-up within the ABS control cycle, the drive motor 5 of the pump 4 is now again controlled such that the pump 4, in its only pumping direction, pumps hydraulic fluid from the hydraulic fluid reservoir 3 via the first flow connection 24 into the at least one brake actuator 2. For this purpose, the first 2 / 2-way solenoid valve 23 is switched from the blocking position to the through position. Furthermore, the third 2 / 2-way solenoid valve 27 is switched to the through position so that hydraulic fluid previously pumped into the pressure accumulator 8 during brake pressure reduction and increasing the pressure there can flow back into the at least one brake actuator 2. The pressure in the pressure accumulator 8 then acts in addition to the pressure in the at least one brake actuator 2, which is built up by the pump 4.

[0061] Consequently, in the embodiment of Fig. 7 with each change from a brake pressure reduction to a brake pressure build-up and vice versa, hydraulic fluid flows back and forth into the pressure accumulator 8 with an increase in pressure there and out of the pressure accumulator 8 with a reduction in pressure there.

[0062] If a malfunction occurs in the electrical system, for example, due to a power outage, the three 2 / 2-way solenoid valves 23, 25, and 27 are de-energized and then switch to their open position, spring-loaded. Consequently, hydraulic fluid flows from the at least one brake actuator 2 through the open second 2 / 2-way solenoid valve 25 via the second flow connection 26 into the hydraulic fluid reservoir 3, thereby de-energizing the at least one brake actuator 2 and thus providing a fail-silent function.

[0063] In the exemplary embodiments described above, a wheel-specific brake pressure buildup and brake pressure reduction were described. However, it is clear that the brake pressure buildup and brake pressure reduction can also be carried out axle-by-axle, ie, for all brake actuators 2 on an axle. Bezugszeichenliste

[0064] 1Control 2Brake actuator 3Hydraulic fluid reservoir 4Pump 5Drive motor 6First connection 7Second connection 8Accumulator 9Valve assembly 103 / 2-way solenoid valve 11First check valve 12Second check valve 13First flow connection 14First connection 15Second flow connection 16Second connection 17Third flow connection 18Third connection 19Brake value sensor 20Signal line 21Brake pedal 22Control unit 23First 2 / 2-way solenoid valve 24First flow connection 25Second 2 / 2-way solenoid valve 26Second flow connection 27Third 2 / 2-way solenoid valve 28Third flow connection 100Electrohydraulic brake

Claims

1. Electrohydraulic brake (100) of a vehicle, which has at least the following: a) an electronic control unit (1) with an implemented control, which is performed during a braking process, as required, in at least one control cycle, wherein at least one brake pressure reduction and at least one brake pressure build-up takes place in at least one hydraulic brake actuator (2) during the control cycle, b) the at least one hydraulic brake actuator (2), which generates a braking force depending on the braking pressure applied, c) a hydraulic fluid reservoir (3) for the unpressurized storage of hydraulic fluid, d) a pump (4) and a prime mover (5) for the pump (4), e) at least one pressure accumulator (8) for the pressure accumulation of hydraulic fluid which originates from the hydraulic fluid reservoir (3), f) flow connections(13, 15, 17; 24, 26, 28) between the at least one brake actuator (2), the hydraulic fluid reservoir (3), the pump (4) and the pressure accumulator (8), wherein g) in at least one flow connection (13, 15, 17; 24, 26, 28) a valve apparatus (10; 23, 25, 27) is arranged which can be controlled at least partly by the electronic control unit (1) and which controls a flow of hydraulic fluid in the at least one flow connection (13, 15, 17; 24, 26, 28), characterized in that h) the electronic control unit (1) controls at least the prime mover (5) for the pump (4) and / or the valve apparatus (10; 23, 25, 27) such that during the at least one control cycle hydraulic fluid flows back and forth or is conveyed between the at least one brake actuator (2) and the pressure accumulator (8).

2. Electrohydraulic brake according to claim 1, characterized in that the electronic control unit (1) is configured such that, at least during the at least one control cycle, it activates the prime mover (5) of the pump (4) and / or the valve apparatus (10; 23, 25, 27) a) for reducing the brake pressure such that hydraulic fluid flows or is conveyed from the at least one brake actuator (2) into the pressure accumulator (8), and b) for building up the brake pressure such that hydraulic fluid flows or is conveyed from the pressure accumulator (8) into the at least one brake actuator (2).

3. Electrohydraulic brake according to claim 1 or 2, characterized in that the control is configured such that, at least during the at least one control cycle, at least one brake pressure hold is performed following a brake pressure build-up or a brake pressure reduction, in which the electronic control unit (1) controls the prime mover (5) of the pump (4) and / or the valve apparatus (10; 23, 25, 27) such that hydraulic fluid is held in the at least one brake actuator (2).

4. Electrohydraulic brake according to any one of the preceding claims, characterized in that the electronic control unit (1) controls at least the prime mover (5) of the pump (4) and / or the valve apparatus (10; 23, 25, 27) such that, when the control is inactive, a) for a brake pressure build-up in the at least one brake actuator (2), hydraulic fluid flows or is conveyed from the hydraulic fluid reservoir (3) and / or from the pressure accumulator (8) into the at least one brake actuator (2), and b) for a brake pressure reduction hydraulic fluid flows or is conveyed from the at least one brake actuator (2) into the hydraulic fluid reservoir (3).

5. Electrohydraulic brake according to any one of the preceding claims, characterized in that it comprises a brake request apparatus which, in order to control the braking process, delivers signals for the start and end of the braking process and for the degree of brake application of the brake into the electronic control unit (1), and which comprises a) a brake value transmitter (19) which can be actuated by a driver of the vehicle, and / or b) a driver assistance system (22) and / or an autopilot.

6. Electrohydraulic brake according to any one of the preceding claims, characterized in that the pump (4) is a unidirectionally operable pump with a single delivery direction, wherein the electronic control unit (1) controls the prime mover (5) of the unidirectionally operable pump (4) such that the unidirectionally operable pump (4) delivers hydraulic fluid in the single delivery direction.

7. Electrohydraulic brake according to claim 6, characterized in that the unidirectionally operable pump (4) is operated in the single delivery direction to build up the brake pressure.

8. Electrohydraulic brake according to any one of claims 1 to 5, characterized in that the pump (4) is a bidirectionally operable pump, wherein the electronic control unit (1) controls the prime mover (5) of the pump (4) such that the bidirectionally operable pump a) delivers hydraulic fluid from the hydraulic fluid reservoir (3) and / or from the pressure accumulator (8) into the at least one brake actuator (2) in a first delivery direction, and b) delivers hydraulic fluid from the at least one brake actuator (2) into the pressure accumulator (8) and / or into the hydraulic fluid reservoir (3) in a second delivery direction opposite the first delivery direction.

9. Electrohydraulic brake according to claim 8, characterized in that the operation of the bidirectionally operable pump (4) a) is in the first delivery direction to build up brake pressure, and b) is in the second delivery direction to reduce brake pressure.

10. Electrohydraulic brake according to claim 9, characterized in that the electronic control unit (1) controls the prime mover (5) of the pump (4) at least during the at least one control cycle in such a way that the pump (4) is operated alternately between the first delivery direction and the second delivery direction for brake pressure reduction and for brake pressure build-up.

11. Electrohydraulic brake according to any one of the preceding claims, characterized in that the control comprises a wheel-individual or axle-individual brake slip or traction slip control and / or a driving dynamics control.

12. Electrohydraulic brake according to any one of the preceding claims, characterized in that the electronic control unit (1) is configured to control the prime mover (5) of the pump (4) and the valve apparatus (10; 23, 25, 27) during a filling phase in order to deliver hydraulic fluid into the pressure accumulator (8) until the pressure in the pressure accumulator (8) is greater than a minimum pressure.

13. Electrohydraulic brake according to claim 12, characterized in that the minimum pressure is in a range of between 50 and 100 bar.

14. Electrohydraulic brake according to any one of the preceding claims, characterized in that the valve apparatus (10; 23, 25, 27) comprises at least one solenoid valve controlled by the electronic control unit and the valve apparatus (10; 23, 25, 27) has at least one switching position, in which the valve apparatus (10; 23, 25, 27) creates a flow connection between the at least one brake actuator (2) and the pressure accumulator (8) and / or the hydraulic fluid reservoir (3).

15. Electrohydraulic brake according to claim 14, characterized in that the solenoid valve is spring-biased into the one switching position and adopts the one switching position when unpowered.

16. Electrohydraulic brake according to any one of claims 13 to 15, characterized in that the valve apparatus (10; 23, 25, 27) comprises at least the following: a)anon-return valve,b)a2 / 2-way solenoid valve,c)a3 / 2-way solenoid valve,d)a4 / 2-way solenoid valve.

17. Vehicle with an electrohydraulic brake according to any one of the preceding claims.