BRAKING SYSTEM FOR A MOTOR VEHICLE

Abstract

A brake system comprises a first electrohydraulic open-loop and closed-loop control unit. The first electrohydraulic control unit comprises a master brake cylinder actuatable by a brake pedal; a first electrically controllable pressure-providing device; and an electrically controllable pressure-modulating device sets wheel-specific brake pressures for the wheel brakes. The electrically controllable pressure-modulating device has at least one electrically actuatable inlet valve for each wheel brake. A first pressure-medium reservoir for supplying the first electrohydraulic control unit with pressure medium is arranged on the first electrohydraulic control unit. The brake system also comprises a second electrohydraulic open-loop and closed-loop control unit, which comprises a second electrically controllable pressure-providing device for actuating at least some of the wheel brakes and electrically actuatable valves. A second pressure-medium reservoir for supplying the second electrohydraulic control unit with pressure medium is provided, the second pressure-medium reservoir being arranged on the second electrohydraulic control unit.

Claims

1. A braking system for a motor vehicle for actuating hydraulically actuated wheel brakes comprising: a first electrohydraulic control and regulating unit which comprises; a master brake cylinder actuated by a brake pedal to actuate the wheel brakes in a fallback mode; a first electrically controlled pressure supply device to actuate the wheel brakes in a “brake-by-wire” mode; a simulator connected to the brake pedal; an electrically controlled pressure modulator which sets wheel-specific brake pressures for the wheel brakes, wherein the modulator has at least one electrically operated inlet valve for each wheel brake; a first pressure medium reservoir at atmospheric pressure, wherein the pressure medium is disposed on the first electrohydraulic control and regulating unit; a second electrohydraulic control and regulating unit which comprises: a second electrically controlled pressure supply device to actuate at least two of the wheel brakes; and electrically operated valves; and a second pressure medium reservoir at atmospheric pressure, wherein the pressure medium is disposed on the second electrohydraulic control and regulating unit.

2. The braking system of claim 1, wherein the first pressure medium reservoir and the second pressure medium reservoir are structurally separate from one another.

3. The braking system of claim 1, further comprising one of a level detector and a level alarm for each of the first pressure medium reservoir and the second pressure medium reservoir.

4. The braking system of claim 1, wherein the the second pressure medium reservoir acts as an air separator.

5. The braking system of claim 1, further comprising: a first electrical power supply unit; a second electrical power supply unit, which is independent of the first power supply unit; and wherein the first electrohydraulic control and regulating unit is supplied with electrical energy by the first power supply unit and the second electrohydraulic control and regulating unit is supplied with electrical energy by the second power supply unit.

6. The braking system of claim 1, wherein the first electrohydraulic control and regulating unit and the second electrohydraulic control and regulating unit are disposed spaced apart from one another in the motor vehicle.

7. The braking system of claim 1, wherein the the second pressure supply device further comprises at least two hydraulic pumps that are commonly driven by an electric motor, each defining an intake port and a pressure port, wherein each of the pressure ports is connected to one of the wheel brakes without the interposition of a valve.

8. The braking system of claim 7, wherein the second pressure medium reservoir comprises a single hydraulic port, wherein the intake ports of the second pressure supply device are connected to the port.

9. The braking system of claim 8, wherein the intake ports of the second pressure supply device are connected to the port via a respective non-return valve that opens towards the intake port.

10. The braking system of claim 7, wherein the second pressure medium reservoir comprises a first hydraulic port and a second hydraulic port, wherein the first port is connected to the intake port of one pump and the second port is connected to the intake port of the other pump,

11. The braking system of claim 10, wherein the first port is connected to the intake port of one pump and the second port is connected to the intake port of the other pump via a respective non-return valve that opens towards the intake port.

12. The braking system of claim 11, wherein a third pressure medium reservoir at atmospheric pressure, defines a filling opening and is connected to the first and the second pressure medium reservoirs for supplying the first and the second pressure medium reservoirs with pressure medium.

13. The braking system of claim 1, wherein the first pressure medium reservoir defines a filling opening and is connected to the second pressure medium reservoir for supplying the second pressure medium reservoir with pressure medium.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Further embodiments of the invention are revealed by the subordinate claims and the following description using figures wherein:

[0038] FIG. 1 shows schematically a first exemplary embodiment of a braking system according to the invention; and

[0039] FIG. 2 shows schematically a second exemplary embodiment of a braking system according to the invention.

DETAILED DESCRIPTION

[0040] In FIG. 1, a first exemplary embodiment of a braking system is represented schematically. The braking system essentially comprises a first electrohydraulic control and regulating unit 60 and a second electrohydraulic control and regulating unit 160. Said units are implemented as separate units or standalone assemblies.

[0041] The first electrohydraulic control and regulating unit 60 comprises a first electronic control and regulating unit 60a (ECU1) and a first hydraulic control and regulating unit 60b (HCU1). Essentially, a master brake cylinder 2 that can be operated by means of a brake pedal 1, a simulator 3 that works in conjunction with the master brake cylinder 2, a first electrically controlled pressure supply device 5 and an electrically controlled pressure modulator 61 for setting wheel-specific brake pressures are disposed in the first hydraulic control and regulating unit 60b.

[0042] A first pressure medium reservoir 4 at atmospheric pressure for supplying the first electrohydraulic control and regulating unit 60 with pressure medium is disposed on the first electrohydraulic control and regulating unit 60.

[0043] The second electrohydraulic control and regulating unit 160 comprises a second electronic control and regulating unit 160a (ECU2) and a second hydraulic control and regulating unit 160b (HCU2). Essentially, a second electrically controlled pressure supply device 105 and electrically operated valves 145a, 145b, 146a, 146b, 147a, 147b are disposed in the second hydraulic control and regulating unit 160b.

[0044] A second pressure medium reservoir 4 at atmospheric pressure for supplying the second electrohydraulic control and regulating unit 160 with pressure medium is disposed on the second electrohydraulic control and regulating unit 160.

[0045] For example, a third pressure medium reservoir 304 at atmospheric pressure is provided, which is connected to the first pressure medium reservoir 4 and the second pressure medium reservoir 104 and supplies said reservoirs with pressure medium as a type of primary container. The third pressure medium reservoir 304 comprises a filling opening for filling the braking system with pressure medium during maintenance processes.

[0046] Alternatively, the first pressure medium reservoir that is disposed on the first electrohydraulic control and regulating unit 60 can also be implemented as a primary container with a filling opening that supplies the second pressure medium reservoir 104 with pressure medium.

[0047] A respective level detector 9, 109 or level alarm is provided for the first pressure medium reservoir 4 and for the second pressure medium reservoir 104, by means of which in each case the level of pressure medium is detected or the level of pressure medium falling below a predetermined level of the respective pressure medium reservoir 4, 104 is detected. This enables the loss of pressure medium at the second electrohydraulic control and regulating unit 160 to be sensed separately from a loss of pressure medium at the first electrohydraulic control and regulating unit 60. Conversely, the loss of pressure medium at the first control and regulating unit 60 can also be detected by the level detector 9 of the pressure medium reservoir 4. Accordingly, the respective control and regulating units 60, 160 can thus sense such leakage defects separately from each other. In the case of a leak, the affected control and regulating unit can then be deactivated, whereas the other control and regulating unit continues to be ready to carry out braking.

[0048] If only one pressure medium reservoir were to be provided for both control and regulating units 60, 160, on detecting a leak at the pressure medium reservoir both control and regulating units 60, 160 would have to be deactivated. An externally actuated or electrically controlled build-up of brake pressure would then not be possible at all.

[0049] The pressure medium reservoir 104 of the second control and regulating units 160 is implemented such that the pressure medium reservoir 104 acts as an air separator, for example owing to the geometry thereof. That is, that air present in the intake line can settle in the pressure medium reservoir 104 when the pumps 142 are sucking. However, the air does not pass further to the pumps 142, at least not before the level detector 109 or level alarm indicates a low level.

[0050] The pressure modulator 61 comprises at least one electrically operated inlet valve 6a-6d for each wheel brake. For example, for each wheel brake 8a-8d of a motor vehicle that is not shown the pressure modulator 61 comprises an inlet valve 6a-6d and an outlet valve 7a-7d, which are connected together hydraulically in pairs via center ports and are connected to the wheel brakes 8a-8d. The input ports of the inlet valves 6a-6d are supplied via brake circuit sections 13a, 13b with pressures that are derived from a system pressure in a “brake-by-wire” operating mode, said system pressure being present in a system pressure line 38 that is connected to a pressure chamber 37 of the first electrically controlled pressure supply device 5.

[0051] A respective non-return valve that opens towards the brake circuit sections 13a, 13b is connected in parallel with each of the inlet valves 6a-6d and is not specified in detail. In a fallback mode, the brake circuit sections 13a, 13b can be supplied with a pressure of the master brake cylinder 2 via hydraulic lines 22a, 22b. The output ports of the outlet valves 7a-7d are connected to the first pressure medium reservoir 4 via a return line 14a. For detecting the pressure prevailing in the system pressure line 38, a redundantly implemented pressure sensor 19 is provided. For example, the wheel brakes 8a or 8b are associated with the left front wheel FL or the right rear wheel RR and the wheel brakes 8c or 8d are associated with the right front wheel FR or the left rear wheel RL (so-called diagonal split).

[0052] The master brake cylinder 2 has two pistons 15, 16 that are disposed one after the other in a housing 21 and that bound pressure chambers 17, 18. On the one hand, the pressure chambers 17, 18 are connected to the first pressure medium reservoir 4 via radial bores formed in the pistons 15, 16 and suitable pressure equalization lines 41a, 41b (the pressure equalization line 41a is shown partly combined with the return line 14a, but separate lines are also possible), wherein the connections can be shut off by a relative movement of the pistons 15, 16 in the housing 21.

[0053] On the other hand, the pressure chambers 17, 18 are connected to the aforementioned brake circuit sections 13a, 13b by means of the hydraulic lines 22a, 22b. A normally open (SO—) diagnostic valve 28 is disposed in the pressure equalization line 41a. The pressure chambers 17, 18 accommodate restoring springs that are not specified in detail and that position the pistons 15, 16 in an initial position when the master brake cylinder 2 is not being actuated. A piston rod 24 couples the pivoting motion of the brake pedal 1 resulting from pedal actuation to the translational motion of the first (master cylinder) piston 15, the operating displacement of which is detected by a preferably redundantly implemented displacement sensor 25. As a result, the corresponding piston displacement signal represents a measure of the brake pedal actuation angle. It represents a braking demand of a driver of the vehicle.

[0054] An isolating valve 23a, 23b, by means of which the pressure chambers 17, 18 can be hydraulically isolated from the brake circuit sections 13a, 13b, is disposed in each of the hydraulic connections 22a, 22b.

[0055] The hydraulic connection between the master brake cylinder 2 and the wheel brakes 8a-8d can also be shut off by the isolating valves 23a, 23b. The isolating valves 23a, 23b are implemented as electrically operated, normally open (SO—) 2/2-way valves. A pressure sensor 20 connected to the line section 22b detects the pressure built up in the pressure chamber 18 by a displacement of the second piston 16.

[0056] The simulator 3 is hydraulically coupled to the master brake cylinder 2 and consists essentially of a simulator chamber 29, a simulator spring chamber 30 and a simulator piston 31 isolating the two chambers 29, 30 from each other. The simulator piston 31 is supported on the housing 21 by an elastic element (for example a spring) that is disposed in the simulator spring chamber 30 and that is pretensioned. The simulator chamber 29 can be connected to the first pressure chamber 17 of the master brake cylinder 2, for example by means of an electrically operated simulator release valve 32. With a determined pedal force and the simulator release valve 32 activated, pressure medium flows from the master brake cylinder pressure chamber 17 into the simulator chamber 29. A non-return valve 34 that is disposed hydraulically antiparallel to the simulator release valve 32 enables a substantially unhindered return flow of the pressure medium from the simulator chamber 29 to the master brake cylinder pressure chamber 17 independently of the switch state of the simulator release valve 32.

[0057] The simulator 3 imparts a pleasant brake pedal feel to the driver of the vehicle in the “brake-by-wire” operating mode.

[0058] The first electrically controlled pressure supply device 5 is implemented as a hydraulic cylinder-piston arrangement or a single-circuit electrohydraulic actuator (linear actuator), the pistons 36 of which can be actuated by a schematically indicated electric motor 35 with the interposition of a likewise schematically represented rotations-translation gearbox. A rotor position sensor that is used for the detection of the rotor position of the electric motor 35 and that is only schematically indicated is denoted by the reference character 44.

[0059] In addition, a temperature sensor can also be used for detecting the temperature of the motor winding. The piston 36 bounds the pressure chamber 37. The actuator pressure produced by the force action of the piston 36 on the pressure medium enclosed within the pressure chamber 37 is fed into the system pressure line 38 and detected by the system pressure sensor 19. In the “brake-by-wire” operating mode, the system pressure line 38 is connected to the brake circuit sections 13a, 13b via the supply valves 26a, 26b. In this way, a build-up and reduction of brake pressure are carried out for all the wheel brakes 8a-8d during normal braking.

[0060] During the build-up of brake pressure, the pressure medium previously displaced from the pressure chamber 37 of the actuator 5 into the wheel brakes 8a-8d flows back into the pressure chamber 37 of the actuator 5 via the same paths. By contrast, during braking with different wheel-specific wheel brake pressures that are regulated using the pressure modulation valves 6a-6d, 7a-7d, the component of the pressure medium discharged via the outlet valves 7a-7d flows into the first pressure medium reservoir 4. It is possible to suck pressure medium back into the pressure chamber 37 by returning the piston 36 with the supply valves 26a, 26b closed, wherein pressure medium flows from the first reservoir 4 into the actuator pressure chamber 37 via a connecting line 46 with a suction valve 52 that is implemented as a non-return valve that opens in the flow direction to the actuator.

[0061] The output ports of the inlet valves 6a-6d of the first electrohydraulic control and regulating unit 60 are each connected to just one of the wheel brakes 8a-8d via a respective hydraulic connection 51a-51d. In this case, the second electrohydraulic control and regulating unit 160 is for example hydraulically disposed between the first electrohydraulic control and regulating unit 60 and the wheel brakes 8a and 8c. The inlet valves 6b, 6d are connected directly to the wheel brakes 8b and 8d via the hydraulic connections 51b, 51d, which for example run outside the unit 160. The second electrohydraulic control and regulating unit 160 is implemented for applying pressure or setting pressure at the wheel brakes 8a and 8c. In the case of a failure of the first pressure supply device 5, pressure medium volumes can be made available for the wheel brakes 8a and 8c by activating the second pressure supply device 105.

[0062] It is also possible that the second electrohydraulic control and regulating unit 160 is implemented for applying pressure or setting pressure at all wheel brakes 8a, 8b, 8c and 8d.

[0063] For each wheel brake respective normally open, analogue-activated control valves 145a, 145b with a parallel connected non-return valve that opens towards the wheel brake are disposed in the connections 51a and 51c, each of which connects the wheel brake 8a or 8c to the output-side port of the inlet valve 6a or 6c associated therewith or to the input-side port of the outlet valve 7a or 7c associated therewith.

[0064] For building up wheel brake pressure, furthermore an electrically operated, normally closed, discharge valve 147a, 147b is provided for each wheel brake 8a and 8c, by means of which the wheel brake can be connected to the second pressure medium reservoir 104.

[0065] The second electrohydraulic control and regulating unit 160 comprises for example two pumps 142 as the second electrically controlled pressure supply device 105, which are commonly driven by an electric motor that is not shown. The second pressure medium reservoir 104 comprises a hydraulic port 114 to which the intake ports of the pumps 142 are connected, wherein a respective non-return valve 148a, 148b that opens towards the intake port is disposed in a line section 150a, 150a between the intake port and the port 114. The intake ports of the pumps 142 can furthermore be connected to the associated connection section of the connection 51a or 51c between the inlet valve 6a or 6c and the control valve 145a or 145b via respective electrically operated, advantageously normally closed, pressure medium supply valves 146a, 146b. The pressure port of one pump 142 is connected to the wheel brake 8a and the pressure port of the other pump 142 is connected to the wheel brake 8c, in each case without the interposition of a valve.

[0066] The pressure supply device 105 thus sucks pressure medium from the second pressure medium reservoir 104 and supplies the pressure medium that it outputs into the wheel brakes 8a and 8c directly in each case (without interposed valves).

[0067] The pressure supply function of the second electrohydraulic control and regulating unit 160 operates by means of the valves 145a and 145b, each of which regulates the pressure of the pressure medium volume supplied by the pumps 142 by suitable electronic actuation. Excess pressure medium volume that overflows to the valves 145a, 145b can be directly made available to the corresponding pump 142 again by means of the valves 146a, 146b.

[0068] According to an exemplary embodiment that is not shown of the braking system according to the invention, the valves 146a, 146b and the connecting line thereof are not present. In said exemplary embodiment, the excess pressure medium volume flows to the pressure medium reservoir via the first control and regulating unit 60.

[0069] The second control and regulating unit 160 comprises for example a pressure sensor 120 for detection of the input pressure in the connection 51a and a respective pressure sensor 119 for detection of the wheel brake pressure in each wheel brake 8a and 8c.

[0070] The first pressure medium reservoir 4 is thus used for supplying the first electrohydraulic control and regulating unit 60, in particular of the master brake cylinder 2, and the first pressure supply device 5.

[0071] The second pressure medium reservoir 104 is used for supplying the second electrohydraulic control and regulating unit 160, in particular the second pressure supply device 105.

[0072] The first electronic control and regulating unit 60a (ECU1) is used for actuating the pressure supply device 5, the valves 23a, 23b, 26a, 26b, 32 for changing between the “brake-by-wire” operating mode and the fallback mode and the valves 6a-6d, 7a-7d of the pressure modulator 61. The signals of the displacement sensors 25, of the sensor 44 and the pressure sensors 19 and 20 are fed to the control and regulating unit 60a.

[0073] The second electronic control and regulating unit 160a (ECU2) is used for actuating the pressure supply device 105 and the valves 142a, 142b, 146a, 146b, 147a, 147b. The signals of the pressure sensors 119 and 120 are fed to the control and regulating unit 160a.

[0074] For performing the regulation task, signals are also exchanged via one or more buses, for example. Depending on the implementation, a direct connection between the first and the second electronic control and regulating units can also be provided. To safeguard the functions, the level display of the second level detector 9 is read in directly into the second electronic control and regulating unit 160a. Furthermore, depending on the implementation, wheel sensor signals are read in by the second electronic control and regulating unit 160a.

[0075] The signals of the level detector 9 are advantageously fed to the first electronic control and regulating unit 60a (ECU1) and the signals of the level detector 109 are fed to the second electronic control and regulating unit 160a (ECU2) and are processed there.

[0076] A first electrical power supply unit 70 and a second electrical power supply unit 170, which is independent of the first power supply unit, are provided. The first electrohydraulic control and regulating unit 60 is supplied with electrical energy by the first power supply unit 70, whereas the second electrohydraulic control and regulating unit 160 is supplied with electrical energy by the second power supply unit 170.

[0077] In a normal operating mode of the braking system, the wheel brakes 8a-8d are supplied with brake pressure by means of the first pressure supply device 5 of the first electrohydraulic control and regulating unit 60. In the event of a failure of the first pressure supply device 5 or the first electrohydraulic control and regulating unit 60, the wheel brakes 8a, 8c can be supplied with brake pressure by means of the second pressure supply device 105 of the second electrohydraulic control and regulating unit 160. Thus, redundant, externally actuated or electrically controlled brake pressure generation is highly reliably provided, for example for an autonomous driving function.

[0078] In FIG. 2 a second exemplary embodiment of a braking system is schematically represented. The braking system essentially corresponds to the braking system of the first exemplary embodiment and essentially comprises a first electrohydraulic control and regulating unit 60, on which a first pressure medium reservoir 4 is disposed, and a second electrohydraulic control and regulating unit 160, on which a second pressure medium reservoir 204 is disposed. The control and regulating units 60, 160 are implemented as separate units or standalone assemblies. Whereas the second pressure medium reservoir 104 of the first exemplary embodiment of FIG. 1 only comprises one hydraulic port 114, to which both pump intake sides are connected, the pressure medium reservoir 104 thus being implemented with one circuit in this sense, the second pressure medium reservoir 204 of the second exemplary embodiment of FIG. 2 is implemented with two circuits. The second pressure medium reservoir 204 comprises a first hydraulic port 214a and a second hydraulic port 214b, wherein each of the ports 214a, 214b is connected to just one of the intake ports of the pumps 142. The remaining components of the second exemplary embodiment correspond to those of the first exemplary embodiment.

[0079] According to the second exemplary embodiment a respective level detector 9, 109 or level alarm is also provided for the first pressure medium reservoir 4 and for the second pressure medium reservoir 104, by means of which in each case the level of pressure medium or a decrease of the level of pressure medium below a predetermined level of the respective pressure medium reservoir 4, 204 is detected.

[0080] The pressure medium reservoir 204 of the second control and regulating unit 160 is implemented such that the pressure medium reservoir 204 acts as an air separator.

[0081] The foregoing preferred embodiments have been shown and described for the purposes of illustrating the structural and functional principles of the present invention, as well as illustrating the methods of employing the preferred embodiments and are subject to change without departing from such principles. Therefore, this invention includes all modifications encompassed within the scope of the following claims.