Brake system for motor vehicle

Abstract

The invention relates to a brake system (2) for a motor vehicle, comprising wheel brakes (16, 18; the invention relates to a brake system (2) comprising a main brake unit (6) having an actuator (64) and a pressure regulator (50) to which two hydraulic wheel brakes (14, 18) are hydraulically connected, a dry secondary brake unit (10) having two further wheel brakes (22, 26), a reservoir (48) for brake fluid, an actuator (64), a pressure regulator (50) to which two hydraulic wheel brakes (14, 18) are hydraulically connected, and a simulator (60), the brake system (2) comprising a main brake unit (6) having an actuator (64) and a pressure regulator (50) to which two further wheel brakes (22, 26) are hydraulically connected. A control and regulation unit (30) for actuating the main brake unit (6) is provided, said control and regulation unit (30) actuating both the main brake unit (6) and the secondary brake unit (10).

Description

[0001] The present invention relates to a braking system for a motor vehicle, the braking system having wheel brakes, a reservoir for brake fluid, an actuator, a pressure regulator and a simulator, wherein the braking system includes a main brake unit having an actuator and a pressure regulator / pressure modulator, two hydraulic wheel brakes being hydraulically connected to the pressure regulator, and wherein the braking system includes a dry auxiliary brake unit having two additional wheel brakes, and a control and adjustment unit being provided for operating the main brake unit.

[0002] Hydraulic brake systems act hydraulically on two circuits that are diagonally opposite or split in black and white. In brake-by-wire systems, the actuator takes over this pressure supply work / pressure application work (Druckstellung). The driver participates in the simulator and then generates a brake pressure request, which is then implemented by the actuator. In this case, the brake pressure is equal on the front and rear axles.

[0003] DE 10 2012 217 825 A1 discloses a combined brake system for a motor vehicle, which has wheel brakes assigned to the rear axle of the vehicle and which can be respectively actuated by an electromechanical actuator, and a hydraulic brake system for the front axle of the vehicle, which hydraulic brake system comprises a single-circuit master brake cylinder actuable by means of a brake pedal and hydraulically actuable wheel brakes connected to the master brake cylinder and assigned to the front axle. The hydraulic brake system for the front axle is designed as a brake-by-wire system with an electrically controllable pressure supply device.

[0004] A disadvantage of known brake systems is that the availability of the brake system depends primarily on whether the brake circuit is intact. Fault detection in the brake system requires complex functions to detect air and leaks and to isolate the defective circuit. Successful fault detection can lead to a reduction in the braking power caused by the fault. There is no redundancy to compensate for the defective circuit.

[0005] Hydraulic systems also have the disadvantage that the installation and filling of the lines during production are complicated. Therefore, for production, solutions are sought that avoid fluids and reduce processes and work steps. Braking with ideal brake force distribution and axle blending for regenerative braking cannot be achieved with current systems without losing efficiency or reducing comfort.

[0006] The object of the present invention is to provide a reliable and stable braking system. In particular, it is desirable to provide a high availability (in terms of first-time failure of the entire system) with a small proportion of hydraulic components and at the same time reduce the complexity of the hydraulic part of the system. In addition, it is desirable to combine the advantages of hydraulic systems with the advantages of electromechanical systems by means of a hybrid system.

[0007] According to the invention, this object is achieved in that the control and regulating unit actuates both the main brake unit and the auxiliary brake unit.

[0008] Advantageous embodiments of the invention are the subject matter of the dependent claims.

[0009] The invention is based on the consideration that the brake system should be designed to be as reliable and stable as possible and at the same time should be easy to integrate into the vehicle environment.

[0010] As is already known, these requirements can be met in that the brake-by-wire system (main brake unit or simulator brake unit) acts hydraulically on only one axle (preferably the front axle), but in this case the control and regulation unit of the brake-by-wire system also controls the auxiliary brake unit. Preferably, this subsystem includes a brake actuation unit (pedal & main brake cylinder), a hydraulic block with a control and regulation unit (ECU), a simulator and an actuator.

[0011] The brake-by-wire system is used as the main brake unit and as the master / host for controlling the auxiliary brake unit. The overall system is combined with the electric brake for the rear axle. As a result, the overall system is designed as a dual-circuit and redundant system.

[0012] “The control and regulation unit actuates both the primary brake unit and the secondary brake unit” means in particular that the control and regulation unit generates a braking torque request for the secondary brake unit. This also means in particular that the braking torque request is transmitted directly to the wheel brakes of the secondary brake unit or their actuators.

[0013] Preferably, the actuator of the main brake unit is an electrohydraulic actuator. Particularly preferably, the actuator of the main brake unit comprises an electrically controllable hydraulic pressure source.

[0014] Preferably, the main brake unit comprises a main brake cylinder which can be actuated by means of a brake pedal.

[0015] Preferably, the pressure regulator comprises for each of the coupled hydraulic wheel brakes at least one electrically actuatable inlet valve which is arranged hydraulically between an actuator of the main brake unit and the associated hydraulic wheel brake.

[0016] Preferably, the pressure regulator comprises for each of the coupled hydraulic wheel brakes at least one electrically actuatable inlet valve which is arranged hydraulically between an actuator and a master brake cylinder of the main brake unit on the one hand and the associated hydraulic wheel brake on the other hand.

[0017] In an advantageous embodiment, the main brake unit and the auxiliary brake unit are powered by a common energy source. Since the brake system forms an overall system with a common ECU, the subsystems for the two axles (main brake unit and auxiliary brake unit) do not have to have separate and / or mutually independent energy sources, which simplifies the structure and design.

[0018] In a preferred first embodiment, the simulator valve is not hydraulically connected between the simulator and the pressure regulating valve. In the event of a fault, sufficient deceleration can be achieved without having to disconnect the simulator. The conventional volume of the front axle caliper enables a greater volume absorption by the simulator while the force remains constant. This makes it possible to accept longer pedal strokes, since only the force is preset as a limit.

[0019] In an alternative preferred embodiment, a simulator valve is hydraulically connected between the simulator and the pressure regulator. The advantages of this variant are present, for example, in the event of a fault. If the actuator fails and the front axle can only be operated by the driver without hydraulic assistance, the simulator valve is closed. In this case, the driver can move volume directly into the wheel brakes without filling the simulator, which results in a shorter pedal stroke or better response performance in the event of a fault. More volume is available that can be moved into the wheel brakes. Another advantage is that the space between the master brake cylinder, the simulator and the corresponding wheel brakes can be better separated and thus better results can be achieved during the hydraulic inspection of the components (self-test; air / leakage).

[0020] Preferably, a pressure switching valve is connected between the actuator and the pressure regulator of the main brake unit. By means of this valve, the actuator can be connected to the pressure regulator or the wheel brake to form pressure as required.

[0021] Advantageously, a driver separation valve is connected between the master brake cylinder and the pressure regulator, by means of which the master brake cylinder can be hydraulically separated from the pressure regulator or the wheel brakes or connected thereto as required. In normal operating mode of the wire brake, the master brake cylinder is hydraulically separated from the pressure regulator so that the driver moves the brake fluid into the simulator. In the fallback stage, the driver separation valve is opened so that the driver can move the brake fluid into the wheel brakes by muscle force.

[0022] In a preferred embodiment of the brake system, two hydraulic wheel brakes are designed as front wheel brakes. Thus, the main hydraulic brake unit brakes on the front axle, thereby also being able to brake at the front in the case of a backup stage.

[0023] Advantageously, the pressure regulator comprises an inlet valve and an outlet valve for each connected hydraulic wheel brake. In this way, the brake pressure of each wheel can be adjusted in a known manner. Particularly preferably, the outlet valve is respectively arranged between the corresponding hydraulic wheel brake and the reservoir. Advantageously, the outlet valve is designed to be electrically actuatable.

[0024] Preferably, the wheel brakes of the auxiliary brake unit are designed as electromechanical wheel brakes. In a further preferred variant, the wheel brakes of the auxiliary brake unit are electric drum brakes, wheel hub motors or electric motors acting on the rear axle. The hydraulic main brake unit should be able to work flexibly with different dry units or be integrated in the system with these units.

[0025] Advantageously, the actuator is designed as a linear actuator having a motor and a rotational-translational transmission connected thereto. Advantageously, the rotational-translational transmission is designed as a ball screw transmission (KGT).

[0026] In another variant, the present invention relates to a braking system for a motor vehicle, the braking system having wheel brakes, a reservoir for brake fluid, an actuator, a pressure regulator and a simulator, wherein the braking system includes a main brake unit having an actuator and a pressure regulator, two hydraulic wheel brakes being hydraulically connected to the pressure regulator, the braking system including a dry secondary brake unit having two further wheel brakes, wherein a control and adjustment unit is provided for operating the main brake unit, wherein a simulator valve is not hydraulically connected between the simulator and the pressure regulator.

[0027] Advantageously, the control and regulating unit actuates both the main brake unit and the auxiliary brake unit.

[0028] Advantageously, the primary brake unit and the secondary brake unit are powered by a common energy source.

[0029] The advantages of the present invention are in particular that the valve required for the second brake circuit is omitted, which can reduce components, increase cycle time during production and reduce costs. Monitoring and testing processes can be simplified. By reducing the complexity of the brake system, costs can be reduced.

[0030] The brake system can be combined with different electric brake systems. Instead of a tandem master cylinder (THZ), only a master brake cylinder is required, and the simulator valve can be omitted if less space is available on the front axle.

[0031] The actuator can be designed to be smaller, since only one circuit has to be supplied. Axle-blended braking is possible for vehicles with regenerative capability. Braking with optimal brake force distribution is possible.

[0032] Diagnostic valves and also simulator valves are not necessary. The omission of these valves brings cost advantages. In addition, the complexity of the system is reduced, because the required monitoring and hydraulic maintenance and self-tests are simplified. In addition, the system consumes less power.

[0033] The braking system is redundant, as the front and rear axles can be controlled separately. During driving, braking with optimal brake force distribution provides maximum stability benefits.

[0034] Embodiments of the present invention are explained in detail with reference to the accompanying drawings. In the highly schematic drawings:

[0035] Figure 1 A brake system having a primary brake unit and a secondary brake unit in a preferred embodiment is shown;

[0036] Figure 2 showing a main brake unit in a first operating state;

[0037] Figure 3 showing the main brake unit in a second operating state;

[0038] Figure 4 Shows the main brake unit in a preferred embodiment;

[0039] Figure 5 A brake system having a primary brake unit and a secondary brake unit is shown in a preferred embodiment.

[0040] In all the figures, identical parts are provided with the same reference numerals.

[0041] exist Figure 1 The brake system 2 shown in FIG. 1 shows that the brake system comprises a main brake unit 6 (PBS) and a secondary brake unit 10 (SBS). The main brake unit 6 is designed as a hydraulic brake system with two hydraulic wheel brakes 14, 18. Here, the two wheel brakes 14, 18 are front wheel brakes. The secondary brake unit 10 is designed as a dry or electromechanical brake unit with two electromechanical wheel brakes 22, 26. The wheel brakes 22, 26 are designed as electromechanical wheel brakes (EMB).

[0042] The main brake unit 6 comprises a control and regulating unit 30 which, as a function of a braking demand or brake request 36, builds up pressure in the two hydraulic wheel brakes 14, 18 (for example by means of electrically actuatable hydraulic actuators) and transmits a braking torque request 40 or a deceleration request to the secondary brake unit 10. In this case, the main brake unit 6 directly actuates one or more brake actuators of the electromechanical wheel brakes 22, 26 of the secondary brake unit, so that the secondary brake unit 10 does not have an additional or separate control and regulating unit.

[0043] exist Figure 2 , shows a preferred first embodiment of the main brake unit 6 in the no-current state. The main brake unit 6 is designed as a hydraulic brake unit and in particular as a single-circuit simulated brake unit. The main brake unit comprises a pedal unit 44 with a brake pedal 46, a reservoir 48 for brake fluid and a hydraulic block 52. The hydraulic block 52 contains a main brake cylinder 56, a simulator 60 and a (linear) actuator 64. The main brake cylinder 56 has only one pressure chamber, because the main brake unit 6 comprises only one hydraulic circuit.

[0044] The actuator 64 has a motor 66, by means of which a pressure piston 68 is moved into a hydraulic pressure chamber 108, and a motor position sensor 80, which is designed in particular to be redundant and is designed in particular as a rotation angle sensor. The motor 66 is designed as an electric motor. In order to convert the rotational movement of the motor rotor into a translational movement of the pressure piston 68, a rotational-translational transmission 76 is provided, which is designed in particular as a ball screw transmission (KGT).

[0045] Furthermore, the hydraulic block 52 comprises a pressure regulator 50 having four wheel valves, namely an inlet valve 70, 74 and an outlet valve 78, 82 for each wheel brake 14, 18. In this case, the inlet valves 70, 74 are designed as valves that are open when no current is supplied, and the outlet valves 78, 82 are designed as valves that are closed when no current is supplied.

[0046] The master brake unit 6 also has an optional, in particular current-free closed simulator valve 86, which hydraulically separates the simulator 60 from the master brake cylinder 56, and a driver separation valve 90, in particular current-free open, which hydraulically separates the driver, i.e., the driver separation valve hydraulically separates the master brake cylinder 56 actuated by the driver from the wheel brakes 14, 18, and a pressure switching valve 94, which hydraulically separates the (linear) actuator 64 from the system, in particular the wheel brakes 14, 18. The system pressure is measured by means of a system pressure sensor 100, i.e., the pressure in the pressure chamber 108 of the actuator 64 or the master brake cylinder pressure. The pressure in the pressure chamber of the simulator 60 is measured by means of the simulator pressure sensor 104.

[0047] The pedal unit 44 has a pedal sensor 110, which is designed in particular to be redundant and is designed as a pedal travel sensor. With the aid of the signal of the pedal sensor 110 and / or the simulator pressure sensor 104, the control and regulation unit 30 determines the braking demand or brake request 36 and accordingly controls the actuator 64 with a set braking torque corresponding to the braking demand. The actuator 64 actively builds up pressure in the wheel brakes 14, 18 according to the braking demand.

[0048] In addition, the control and regulation unit 30 generates a braking demand or a braking request 36 based on the braking demand or the braking request 36. Figure 1 The braking torque request 40 is described within the scope of FIG.

[0049] exist Figure 3 The following table shows the power-on state. Figure 2 The control and regulation unit 30 is used to control the main brake unit 6 of the vehicle. If the driver actuates the brake pedal 46, the control and regulation unit 30 closes the driver separation valve 90. Through the opened simulator valve 86, the driver allows brake fluid to enter the simulator 60. The resulting pressure request is implemented by the actuator 64 in the following way: the volume is introduced into the corresponding wheel brake 14, 18 through the opened pressure switching valve 94. With the help of the signal of the pedal sensor 110 and / or the simulator pressure sensor 104, the control and regulation unit 30 determines the braking demand or braking request 36 and controls the actuator 64 accordingly with the set braking torque corresponding to the braking demand. The actuator 64 actively builds up pressure in the wheel brakes 14, 18 according to the braking demand.

[0050] exist Figure 4 Another preferred embodiment of the main brake unit 6 is shown in FIG. In this embodiment, the simulator valve (in Figure 2 and Figure 386 in the figure), because the volume of the master brake cylinder (HZ) 56 is sufficient for the front axle or the wheel brakes 14, 18 of the front axle. This is related to the hydraulic fallback stage (RFE). If a fault occurs that degrades the pressure actuator (LAC) or the actuator 64, the driver must hydraulically decelerate the vehicle via the pedal 46.

[0051] The front axle is not hydraulically assisted and must be designed structurally so that a pedal force of F = 500N can be used to achieve 2.44m / s 2 In the case of a hydraulic fallback stage, the fluid volume in the master cylinder 56 is sufficient to supply the simulator 60 and the wheel brakes 14 , 18 at the front axle with the volume required for a predetermined deceleration.

[0052] According to the system definition, the two brake circuits, more precisely the braked axles, more precisely the main brake unit 6 and the auxiliary brake unit 10, are independent of each other. This means that a failure of the actuator 64 will not affect the braking capacity or availability of the rear axle braked by the auxiliary brake unit 10. In addition, a deceleration request 40 can also be made and executed. This is Figure 5 It is shown in Figure 5 The brake system 2 is shown in a fallback stage in which the actuator 64 has failed and the driver performs hydraulic braking by depressing the pedal with muscle force, so that a hydraulic pressure buildup 114 takes place in the wheel brakes 14, 18 without the actuator 64. However, the functionality of the brake system 2 is also maintained in the fallback stage, i.e. the control and regulating unit 30 still actuates the secondary brake unit 10.

[0053] List of Reference Numerals

[0054] 2 Braking system

[0055] 6 Main brake unit

[0056] 10 Auxiliary brake unit

[0057] 14 Wheel brakes

[0058] 18 Wheel brakes

[0059] 22 Wheel brakes

[0060] 26 Wheel brakes

[0061] 30 Control and regulation unit

[0062] 36 Brake request

[0063] 40 Braking torque requirement

[0064] 44 Pedal Unit

[0065] 46 Brake pedal

[0066] 48 Storage

[0067] 50 Pressure regulator

[0068] 52 Hydraulic block

[0069] 56 Master brake cylinder

[0070] 60 Simulator

[0071] 64 Actuator

[0072] 66 Motor

[0073] 68 Pressure piston

[0074] 70 Inlet valve

[0075] 74 Inlet valve

[0076] 76 Rotation and translation transmission mechanism

[0077] 78 Outlet valve

[0078] 80 Motor position sensor

[0079] 82 Outlet valve

[0080] 86 Simulator Valve

[0081] 90 Driver separation valve

[0082] 94 Pressure switching valve

[0083] 100 System Pressure Sensor

[0084] 104 Simulator Pressure Sensor

[0085] 110 Pedal sensor

[0086] 114 Hydraulic pressure build-up

Claims

1. A braking system (2) for a motor vehicle, the braking system having wheel brakes (16, 18; 22, 26), a reservoir (48) for brake fluid, an actuator (64), a pressure regulator (50) and a simulator (60), The brake system (2) comprises a main brake unit (6) having an actuator (64) and a pressure regulator (50), to which two hydraulic wheel brakes (14, 18) are hydraulically connected. The brake system (2) comprises a dry auxiliary brake unit (10) having two further wheel brakes (22, 26). A control and adjustment unit (30) is provided for controlling the main brake unit (6). It is characterized in that The control and adjustment unit (30) controls both the main brake unit (6) and the auxiliary brake unit (10).

2. The brake system (2) according to claim 1, wherein the primary brake unit (6) and the secondary brake unit (10) are powered by a common energy source.

3. The brake system (2) according to claim 1 or 2, wherein no simulator valve (86) is hydraulically connected between the simulator (60) and the pressure regulator (30).

4. The brake system (2) according to claim 1 or 2, wherein a simulator valve (86) is hydraulically connected between the simulator (60) and the pressure regulator (30).

5. The brake system (2) as claimed in one of the preceding claims, wherein a pressure switching valve (94) is connected between the actuator (64) and the pressure regulator (30).

6. The brake system (2) according to claim 1, wherein a driver isolating valve (90) is connected between the master brake cylinder (56) and the pressure regulator (30).

7. The brake system (2) as claimed in one of the preceding claims, wherein the two hydraulic wheel brakes (14, 18) are designed as front wheel brakes.

8. The brake system (2) as claimed in one of the preceding claims, wherein the pressure regulator (30) comprises an inlet valve (70, 74) and an outlet valve (78, 82) for each connected hydraulic wheel brake (14, 18).

9. The brake system (2) as claimed in one of the preceding claims, wherein the wheel brakes (22, 26) of the auxiliary brake unit (10) are designed as electromechanical wheel brakes.

10. The brake system (2) according to claim 1, wherein the actuator (64) is designed as a linear actuator having a motor (66) and a rotational-translational transmission (76) connected to the motor.

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