BRAKE SYSTEM AND BRAKE CONTROL DEVICE

Abstract

A second electrohydraulic brake control device for a motor vehicle comprises a pressure control valve assembly, an controllable pressure source and a reservoir connection. For a group of wheel brakes, the second electrohydraulic brake control device is connected in series between the associated output pressure connections of a first or main brake control device and the vehicle wheel brakes.

Claims

1. A brake system for motor vehicles having at least four hydraulically actuable wheel brakes, a pressure-medium reservoir under atmospheric pressure, and a first electrohydraulic brake control device comprising a first pressure control valve assembly configured to set wheel-specific brake pressures, a first electrically controllable pressure source and, for each wheel brake, a wheel-specific outlet pressure connection, the brake system comprising: a second electrohydraulic brake control device comprising: a second pressure control valve assembly; a second electrically controllable pressure source; and a reservoir connection; wherein, the second electrohydraulic brake control device is connected in series between the associated outlet pressure connections of the first brake control device and the four, hydraulically actuable wheel brakes, and wherein the the second electrohydraulic brake control device is connected to the pressure-medium reservoir via the reservoir connection.

2. The brake system of claim 1, wherein two, hydraulically actuable wheel brakes are on a front axle of the motor vehicle.

3. The brake system of claim 1, wherein the second electrically controllable pressure source comprises a pump having a suction side connected to the pressure-medium reservoir.

4. The brake system of claim 1, wherein the second electrohydraulic brake control device comprises, a wheel-specific inlet pressure connection connected to the outlet pressure connection associated with a wheel brake of the first brake control device, and additionally comprises a wheel-specific outlet pressure connection connected to the same wheel brake.

5. The brake system of claim 1, wherein the first electrohydraulic brake control device is embodied as a first electronic open-loop and closed-loop control unit and a first hydraulic open-loop and closed-loop control unit, wherein the first electronic open-loop and closed-loop control unit is designed to control the first pressure control valve assembly and the first pressure source.

6. A brake control device for at least two hydraulically actuable wheel brakes of a motor vehicle brake system that comprises an electrically controllable pressure source, a wheel-specific outlet pressure connection for each of the wheel brakes and a pressure control valve assembly that sets wheel-specific brake pressures at the outlet pressure connections, the brake control device comprising: a reservoir connection to a pressure-medium reservoir at atmospheric pressure; and a wheel-specific inlet pressure connection for each of the wheel brakes.

7. The brake control device of claim 6, wherein the reservoir connection is connected to the electrically controllable pressure source.

8. The brake control device of claim 6, wherein the electrically controllable pressure source comprises a pump for each of the wheel brakes, wherein the pumps have a suction side connected to the reservoir connection.

9. The brake control device of claim 6, wherein the pressure control valve assembly comprises an electrically actuable outlet valve assembly for each outlet pressure connection, wherein the outlet pressure connection is connected to the reservoir connection via the outlet valve assembly.

10. The brake control device of claim 6, wherein the brake control device is an electronic open-loop and closed-loop control unit and a hydraulic open-loop and closed-loop control unit configured to control the pressure control valve assembly and the pressure source.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0036] Further preferred embodiments of the invention will become apparent from the dependent claims and from the following description with reference to figures which schematically show:

[0037] FIG. 1 a first illustrative embodiment of a brake control device according to the invention for a brake system according to the invention,

[0038] FIG. 2 a second illustrative embodiment of a brake control device according to the invention for a brake system according to the invention, and

[0039] FIG. 3 shows another illustrative embodiment of a brake system according to the invention.

DETAILED DESCRIPTION

[0040] A first illustrative embodiment of a brake control device 70 according to the invention is illustrated schematically in FIG. 1. According to the example, the brake control device 70 for four wheel brakes 50, 51, 52, 53 is illustrated, although a reduction to fewer wheel brakes and expansion to more wheel brakes are possible in a simple manner. According to the example, brake control device 70 is embodied as an independent structural unit or module, e.g. as a brake control unit having an electronic open-loop and closed-loop control unit (ECU) and a hydraulic open-loop and closed-loop control unit (HCU).

[0041] Connected to each of the wheel-specific inlet pressure connections 30, 31, 32, 33 of the brake control device 70 is a respective high-pressure-proof brake line, which in each case comes from one of the wheel-specific outlet pressure connections 20, 21, 22, 23 of a brake control device 60 (indicated purely schematically by dashed lines) of a main brake system. Connected to each of the wheel-specific outlet pressure connections 40, 41, 42, 43 of brake control device 70 is a respective high-pressure-proof brake line, which leads to one of the wheel brakes 50, 51, 52, 53. That is to say that brake control device 70 is arranged hydraulically in series between the brake control device 60 of the main brake system and the wheel brakes 50, 51, 52, 53.

[0042] The brake control device 70 furthermore comprises at least one reservoir connection 81 for connection to a pressure-medium reservoir 80 under atmospheric pressure.

[0043] In order to keep down the number of connections, the brake control device 70 advantageously comprises precisely one reservoir connection.

[0044] Brake control device 70 is thus arranged downstream of the brake control device 60 of the main brake system and offers the advantage that it can draw in pressure medium directly from the pressure-medium reservoir 80. Intake via brake control device 60 would lead to insufficient pressure-medium volume flows because of the flow resistances thereof.

[0045] Brake control device 70 comprises a pressure control valve assembly for setting wheel-specific brake pressures at the outlet pressure connections 40, 41, 42, 43, and an electrically controllable pressure source 1, and is thus suitable for the electrically controlled buildup of a system brake pressure and for wheel-specific brake pressure control.

[0046] For each outlet pressure connection 40, 41, 42, 43 or wheel brake 50, 51, 52, 53 (pressure control circuit), the pressure control valve assembly comprises an electrically actuable separating valve 3 and an electrically actuable outlet valve assembly, e.g. for brake pressure reduction during an antilock control operation (ABS).

[0047] In each pressure control circuit, the separating valve 3 is arranged in a hydraulic link between the inlet pressure connection 30, 31, 32, 33 and the associated outlet pressure connection 40, 41, 42, 43. It is advantageous if the separating valves 3 are embodied so as to be open when deenergized, so that, if brake control device 70 fails, the wheel-specific wheel brake pressures supplied by brake control device 60 are allowed through by brake control device 70 and are applied at the outlet pressure connections 40, 41, 42, 43. According to the example, the separating valves 3 are embodied in analogized fashion or in a manner which allows analog control.

[0048] According to the example, a check valve 8 opening in the direction of the wheel brake 50, 51, 52, 53 is arranged in parallel with each separating valve 3, ensuring that an inlet pressure at an inlet pressure connection 30, 31, 32, 33 which is greater than the associated wheel brake pressure is allowed through to the wheel brake, irrespective of the state of activation of the separating valve.

[0049] In each pressure control circuit, the outlet pressure connection 40, 41, 42, 43 and thus the wheel brake 50, 51, 52, 53 can be connected to the pressure-medium reservoir 80 by means of the outlet valve assembly. According to the example, the outlet valve assembly is formed by series connection of an outlet valve 6 that is closed when deenergized and a second valve 7, which is open when deenergized and can be controlled in analog fashion or is embodied in analogized fashion. According to the example, the outlet connections of the valves 7 are connected to the reservoir connection 81 by a common line segment 12.

[0050] According to the example, the electrically controllable pressure source 1 of brake control device 70 comprises a high-pressure pump 2 for each wheel brake 50, 51, 52, 53, said pumps being driven by a common electric motor M. The suction side of each pump 2 is connected to the pressure-medium reservoir 80 under atmospheric pressure. According to the example, the suction sides of the pumps 2 are connected to the reservoir connection 81 by a common intake line segment 11. The discharge side of each pump 2 is connected to the associated outlet pressure connection 40, 41, 42, 43 by means of a check valve 9 that opens in the direction of the associated wheel brake. In this case, the check valve can be formed by a discharge valve present in the pump, this generally being the case when a piston pump is used as the pump 2.

[0051] Each wheel brake 50, 51, 52, 53 to be supplied (in particular either the two wheel brakes on the front axle or the four front-axle and rear-axle wheel brakes according to the example) is thus assigned a “hydraulic module”, which consists of a pump 2 and hydraulic valves 3, 6, 7 of the pressure control valve assembly and is of identical construction for each wheel brake to be supplied. According to the example, brake control device 70 comprises four identical pressure control circuits (one pressure control circuit for each wheel brake), each having essentially the electrically controllable pressure source in the form of the pump 2, the electrically actuable separating valve 3 and the outlet valve assembly 6, 7, wherein the intake sides of the pumps 2 and the valves 7 are connected to the reservoir connection 81.

[0052] According to the example, a respective pressure sensor 5 for determining the pressure at the outlet pressure connections 40 and 43 is provided in brake control device 70 for each of wheel brakes 50 and 53. In addition, according to the example, brake control device 70 comprises a pressure sensor 15 for determining the pressure at the inlet pressure connection 33. By means of the signal of this sensor, a pedal-controlled brake pressure buildup can be detected when the first brake control device 60 is electrically inactive.

[0053] Normally, pressure-medium reservoirs of conventional hydraulic brake systems comprise two chambers, which are associated with the two pressure spaces of the brake master cylinder that can be actuated by the brake pedal. It is advantageous if the pressure-medium reservoir 80 comprises three chambers, wherein the additional third chamber is provided for connection to brake control device 70. The pressure-medium volume drawn in during the operation of brake control device 70 is supplied from the third chamber, and the excess pressure-medium volume is discharged into the third chamber, e.g. during an antilock control operation by means of brake control device 70.

[0054] According to the invention, brake control device 70 is provided to supplement a brake control device 60 of a main brake system, said control device 60 itself comprising an electrically controllable pressure source 63 and a pressure control valve assembly 62 for setting wheel-specific brake pressures, i.e. being designed for the electrically controlled buildup of a system brake pressure and for wheel-specific brake pressure control.

[0055] For example, brake control device 60 is embodied as an independent structural unit or module, e.g. as a brake control unit (HECU) having an electronic open-loop and closed-loop control unit (ECU) and a hydraulic open-loop and closed-loop control unit (HCU). Here, the electronic open-loop and closed-loop control unit is designed to control the pressure control valve assembly 62 and the pressure source 63.

[0056] According to the example, brake pressure control device 60 (regular main brake module) performs system pressure buildup in the normal braking mode, and brake control device 70 (backup module) stands ready for the case where the system pressure supply function of brake control device 60 fails. In this situation, brake control device 70 takes over the pressure buildup by means of the pressure source 1. Brake control device 70 can build up a pressure independent of the driver and can modulate the pressure for each wheel by means of the pressure control valve assembly. In a fallback operating mode, e.g. when there is no electric power available for the brake system, i.e. brake control devices 60 and 70, brake control device 70 allows a hydraulic pressure buildup input by the driver at any time.

[0057] According to the example, brake control devices 60 and 70 each comprise a separate electronic open-loop and closed-loop control unit (ECU) for controlling the respective pressure source and pressure control valve assembly. Brake control device 70 thus comprises the second electronic open-loop and closed-loop control unit required for redundancy of the brake system and comprises the second pressure source, and therefore there are two independent electronic open-loop and closed-loop control units and two independent electrically controllable pressure sources in the overall system.

[0058] Another advantage of the brake system according to the invention is that the brake pressures can be modulated in a wheel-specific manner with high availability, either by means of the pressure control valve assembly of brake control device 60 (main brake module) or by means of the pressure control valve assembly of brake control device 70 (backup module). Thus the lockup prevention function of the brake system can be maintained even when brake control device 60 is electrically inactive.

[0059] It is likewise advantageous that no further pressure line connections in addition to the already customary single pressure outlet connection for each wheel brake are required on brake control device 60. The brake control device 70 according to the invention can simply be connected to the wheel-specific pressure outlets of brake control device 60, of which there are usually four.

[0060] To further enhance availability, especially of the brake control function, it is advantageous if at least two independent electric power supplies are provided in the brake system. For example, brake control device 60 is supplied by a first electric power supply and brake control device 70 is supplied by a second electric power supply.

[0061] The brake system or main brake system preferably comprises further components known per se, e.g. a brake pedal or a brake master cylinder that can be actuated by the brake pedal. According to the example, brake control device 60 is connected to the pressure spaces of a brake master cylinder.

[0062] For example, brake control device 60 comprises a brake master cylinder that can be actuated by the brake pedal, a hydraulic brake-pedal feel simulator, a pressure source in the form of a hydraulic cylinder-piston assembly or of an electrohydraulic linear actuator, the piston of which can be actuated by an electric motor, e.g. via a rotation/translation mechanism, and a pressure control valve assembly.

[0063] As an alternative, the main brake system comprises a brake master cylinder that can be actuated by the brake pedal and can also be actuated by means of an electromechanical actuator (with an electric motor), for example.

[0064] As an alternative, the main brake system comprises a brake master cylinder with an upstream, electrically controllable vacuum brake booster, for example.

[0065] As an alternative or in addition, the main brake system or brake control device 60 comprises an ESP brake control unit known per se, which comprises a pressure control valve assembly having twelve valves for controlling the wheel brake pressures, a low-pressure reservoir for each brake circuit and a dual circuit recirculating pump.

[0066] A second illustrative embodiment of a brake control device 70 according to the invention is illustrated schematically in FIG. 2. In contrast to the first illustrative embodiment in FIG. 1, the outlet valve assembly of the pressure control valve assembly is formed by one outlet valve 16 per pressure control circuit, which outlet valve is closed when deenergized and can be controlled in analog fashion or is embodied in analogized fashion. That is to say that the outlet valve 6 and the valve 7 of the first illustrative embodiment are replaced by outlet valve 16.

[0067] The brake system according to the invention satisfies the functional requirements on a brake system resulting from highly automated driving.

[0068] Another illustrative embodiment of a brake system according to the invention is illustrated schematically in FIG. 3. The brake system comprises four hydraulically actuable wheel brakes 50, 51, 52, 53 and a first brake control device 60 (referred to as the main brake system), which comprises a wheel-specific outlet pressure connection 20, 21, 22, 23 for each of these wheel brakes 50, 51, 52, 53. Brake control device 60 furthermore comprises an electrically controllable pressure source 63 and a pressure control valve assembly 62 for setting wheel-specific brake pressures at the outlet pressure connection 20, 21, 22, 23.

[0069] It is advantageous if brake control device 60 is embodied as an independent structural unit or module, e.g. as a brake control unit (HECU) having an electronic open-loop and closed-loop control unit (ECU) and a hydraulic open-loop and closed-loop control unit (HCU). Here, the electronic open-loop and closed-loop control unit is designed to control the pressure control valve assembly 62 and the pressure source 63.

[0070] The brake system furthermore comprises a second brake control device 70, which is provided for actuating and controlling just some of the hydraulically actuable wheel brakes. According to the example, brake control device 70 is provided for the two wheel brakes 50 and 51, which are associated with the front axle of the motor vehicle, for example (VR: front right-hand wheel, VL: front left-hand wheel). In corresponding fashion, brake control device 70 comprises a wheel-specific inlet pressure connection 30, 31 and a wheel-specific outlet pressure connection 40, 41 for each of the two wheel brakes 50 and 51, wherein the inlet pressure connection 30, 31 is connected by a high-pressure-proof brake line to the corresponding outlet pressure connection 20, 21 of the first brake control device 60, and the outlet pressure connection 40, 41 is connected by a respective high-pressure-proof brake line to wheel brake 50, 51.

[0071] The outlet pressure connection 22, 23 of the first brake control device 60 is connected by a high-pressure-proof brake line directly to wheel brake 52, 53, which is associated with the rear left-hand wheel HL or the rear right-hand wheel HR. As illustrated in FIG. 3, the brake lines can extend outside brake control device 70. As an alternative, the brake lines can also extend through brake control device 70.

[0072] The second brake control device 70 is thus connected hydraulically in series between the first brake control device 60 or the outlet pressure connections 20, 21, associated with the wheel brakes 50, 51, of the first brake control device 60 and the wheel brakes 50, 51.

[0073] The second brake control device 70 furthermore comprises at least one reservoir connection 81 for connection to a pressure-medium reservoir 80 under atmospheric pressure.

[0074] Otherwise, the fundamental construction of brake control device 70 corresponds to the construction of the illustrative embodiment of the (second) brake control device 70 explained in detail with reference to FIG. 1, in particular in respect of the pumps 2 and the pressure control valve assembly (valves 3, 6, 7, 8, 9). As an alternative, brake control device 70 can also be embodied in a manner corresponding to the illustrative embodiment shown in FIG. 2 (especially valves 3, 16, 8, 9).

[0075] A second brake control device 70 as illustrated, for example, in FIG. 3, having two hydraulic channels for the wheel brakes 50, 51 on the front axle is preferably combined with “EPB combination brakes” (EPB: electric parking brake) on the rear axle of the vehicle. Apart from its hydraulic function of a pressure-control clamping force buildup, the EPB combination brake can additionally be actuated electromechanically. That is to say, wheel brakes 52 and 53 are preferably embodied in such a way that they can be actuated both hydraulically and electromechanically.

[0076] According to the example, the second brake control device 70 is embodied as a brake control unit having an electronic open-loop and closed-loop control unit (ECU) and a hydraulic open-loop and closed-loop control unit (HCU). Here, the electronic open-loop and closed-loop control unit is designed to control the second pressure control valve assembly (3, 6, 7) and the second pressure source 1. It is furthermore advantageous if the EPB combination brakes are connected electrically to the electronic open-loop and closed-loop control unit of the second brake control device 70 to ensure that, in the event of a possible failure of the electronic open-loop and closed-loop control unit of the first brake control device 60, the electronic open-loop and closed-loop control unit of the second brake control device 70 is capable of building up braking torques at all four wheel brakes 50, 51, 52, 53.