Braking system for a motor vehicle

Abstract

Brake system (1) for a motor vehicle, which has a hydraulically actuatable wheel brake (8-11) for each wheel of the motor vehicle, wherein each wheel brake (8-11) is each provided with a hydraulic brake actuator (12-15) for actuating it, which has a hydraulic pump (P) and a drive motor (M) for the hydraulic pump (P). The invention provides that the brake system (1) has a main brake cylinder (6), which is hydraulically connected to the wheel brakes (8-11) for actuating the wheel brakes, wherein between the main brake cylinder (6) and each wheel brake (8-11) a first controllable separation valve (T8-T11) is connected.

Description

Technical Field

[0001] The present invention relates to a braking system for a motor vehicle, the braking system having hydraulically operable wheel brakes for multiple wheels of the motor vehicle, wherein each wheel brake is equipped with a hydraulic brake actuator for operating it, the hydraulic brake actuator having a hydraulic pump, particularly a piston pump, and a drive motor for the hydraulic pump. Background Technology

[0002] Braking systems of the type described at the beginning are known in the prior art. These systems increasingly employ hydraulic brake actuators, which act as individual actuators for a selected wheel of a motor vehicle, known as corner-Aktuators. These actuators each have a hydraulic pump and a controllable drive motor for the pump, thereby causing the pump to generate hydraulic pressure only for the assigned wheel brake by manipulating the drive motor. This reduces complexity, particularly with regard to the piping system with controllable valves for regulating the respective wheel brakes. Specifically, in this case, the braking pressure is provided directly by the hydraulic pump, eliminating the need for pressure regulation valves. Consequently, the overall software of the braking system can be simplified, and it can be programmed, for example, by the vehicle manufacturer.

[0003] This type of brake actuator is connected to the brake pedal via a controller. The brake pedal is not mechanically connected to the brake actuator but operates on the principle of a brake-by-wire device. Based on brake pedal operation detected by at least one sensor, the drive motor of the brake actuator is controlled to set the braking force for each wheel. Summary of the Invention

[0004] The advantage of the braking system according to claim 1 is that it provides a mechanical backup layer in a simple and cost-effective manner.

[0005] According to the invention, the braking system is provided to have a master brake cylinder, which is mechanically connected, in particular, to or can be mechanically connected to the brake pedal. This master brake cylinder is hydraulically connected to the wheel brakes to operate them, wherein operable release valves are inserted and connected between the master brake cylinder and each wheel brake. By integrating the master brake cylinder as a backup level, known components of the braking system are utilized. Standard components can be used, resulting in cost advantages. By advantageously attaching the master brake cylinder to the wheel brakes, a centralized backup level is provided, which acts on or can act on all wheel brakes, thereby reducing, for example, the number of brake lines and valves and saving installation space. In the event of a failure of one or more brake actuators, the driver can now also operate the master brake cylinder by means of the brake pedal, thereby mechanically generating hydraulic pressure at the wheel brakes.

[0006] According to a preferred embodiment of the invention, each release valve is configured to open when no power is supplied. This ensures that braking force can still be generated at the wheel brakes via the master brake cylinder in a deactivated state, for example, in the event of an intentional or unintentional interruption of the vehicle's electrical system. If power is interrupted, the release valve automatically, particularly by spring force, switches to the open state, thereby establishing a hydraulic connection between the master brake cylinder and the wheel brakes. This ensures that braking can be performed even in the event of a complete interruption of the vehicle's electrical system. Under normal circumstances, the release valve is energized and thus remains closed to hydraulically separate the master brake cylinder from the wheel brakes. This, for example, ensures that the hydraulic pressure generated by the brake actuator does not cause the brake fluid to move towards the master brake cylinder.

[0007] Furthermore, it is preferably specified that a second release valve is inserted and connected between each brake actuator and its associated wheel brake. The second release valve is preferably configured to close when no power is applied, so that when the motor vehicle's electrical or combustion system is interrupted, the second release valve closes, thereby preventing the brake fluid supplied by the master brake cylinder from flowing back towards the corresponding brake actuator or corresponding hydraulic pump, so that the hydraulic pressure supplied by the master brake cylinder can effectively act on the wheel brakes.

[0008] Furthermore, it is preferably specified that the master brake cylinder is equipped with a first reservoir for containing and supplying liquid brake fluid, and at least one of the brake actuators is equipped with a second reservoir containing liquid brake fluid. Preferably, each brake actuator is equipped with its own second reservoir for brake fluid. Thus, the master brake cylinder receives brake fluid supply through the first reservoir, and the brake actuators receive brake fluid supply through their respective reservoirs. This further improves the reliability of the braking system.

[0009] According to an alternative embodiment of the invention, the master brake cylinder and at least one of the brake actuators, and in particular all of the brake actuators, are equipped with a shared reservoir for storing and supplying brake fluid. Thus, the master brake cylinder and one or more, preferably all, of the brake actuators receive brake fluid from a single reservoir. This saves installation space and reduces the number of parts. Alternatively, every two brake actuators are equipped with a shared reservoir. This eliminates the need for a separate reservoir for each brake actuator, further reduces the number of parts, and improves reliability compared to an embodiment where only one reservoir is provided for all brake actuators.

[0010] According to a preferred embodiment of the invention, each brake actuator has a pressure balancer. This pressure balancer ensures advantageous compensation or balancing of undesirable overpressure or underpressure in the braking system. This advantageously overcomes pressure fluctuations, for example, due to leakage or temperature changes, and thereby protects the components of the braking system from damage.

[0011] According to a preferred embodiment of the invention, each hydraulic pump is configured as a piston pump, wherein each pressure balancer has a flow orifice in the piston pump, which connects the pressure chamber of the piston pump to a pressure relief passage leading to a reservoir, particularly at least when the piston of the piston pump is in an unloaded position. This flow orifice works in conjunction with the hydraulic piston of the piston pump such that the flow orifice is connected to the brake fluid in the piston pump only when the hydraulic piston is in a predetermined position, particularly an unloaded position. Thus, a connection is formed when the pump is not in operation, more precisely, when it is unloaded, through which excess pressure can be released to the rest of the braking system, particularly towards the reservoir. When the hydraulic piston moves to generate hydraulic pressure by the brake actuator, the hydraulic piston closes the flow orifice, and the balancing connection is severed and the pressure balancer is deactivated.

[0012] Furthermore, it is preferably specified that a controllable pressure balancing valve is connected downstream of each brake actuator. Here, each pressure balancing valve is preferably also connected to a corresponding reservoir, thereby purposefully relieving excess pressure by the volume flowing out of the corresponding reservoir. Unlike pressure relief channels with orifices, here the pressure is balanced by actively controlling the pressure balancing valve, thus allowing for purposeful pressure balancing during operation.

[0013] According to a preferred embodiment of the invention, the main brake cylinder is either a single-unit cylinder or a tandem cylinder. If the main brake cylinder is configured as a tandem cylinder, the different pressure chambers of the tandem cylinder are preferably equipped with different brake actuators, wherein, for example, one pressure chamber is provided for every two brake actuators.

[0014] Preferably, the master brake cylinder and the first brake actuator in the brake actuators form a first modular unit, and the remaining brake actuators each form an additional second modular unit. Thus, for example, in a four-wheel brake system, the braking system has four modular units: one first modular unit and three additional second modular units. The first modular unit is preferably mounted, or can be mounted, on the front bulkhead of the vehicle to ensure connection between the master brake cylinder and the vehicle's brake pedal. The remaining second modular units are mounted in other locations within the vehicle where the respective wheel brakes are technically advantageous for mounting space. The additional modular units are connected to the first modular unit, particularly to the master brake cylinder, especially via corresponding brake lines, more precisely, hydraulic lines. Optionally, each wheel brake and / or each brake actuator is connected to the master brake cylinder via two hydraulic lines or brake lines respectively to improve reliability.

[0015] According to a preferred embodiment, the first separation valve of each brake actuator is preferably arranged in the first module unit. Thus, the switching of the brake actuators is centrally performed in the first module unit. This allows the second module unit to be constructed to be smaller.

[0016] According to an alternative embodiment of the invention, the first separation valve of at least one of the brake actuators is arranged in the second module unit. This allows for direct switching at the respective brake actuator and enables a space-saving construction of the first module unit.

[0017] According to a preferred embodiment of the invention, the first module unit further includes a pedal feel simulator connected to the master brake cylinder. Thus, the pedal feel simulator is integrated into the first module unit, and the first module unit is designed to be both compact and powerful.

[0018] Preferably, at least one of the brake actuators is further equipped with a pressure sensor connected to the master brake cylinder. This pressure sensor can also detect the driver's braking intention by means of pressure changes in the master brake cylinder, and thus can be used as an additional backup level for detecting driver intention. Attached Figure Description

[0019] The invention will now be explained in more detail with reference to the accompanying drawings. Wherein:

[0020] Figure 1 A simplified circuit diagram of an advantageous braking system according to the first embodiment is shown.

[0021] Figure 2 A circuit diagram of the braking system according to the second embodiment is shown.

[0022] Figures 3A to 3DSimplified detailed diagrams of the braking system under different operating conditions are shown.

[0023] Figure 4 A simplified circuit diagram of the braking system according to the third embodiment is shown.

[0024] Figure 5 A simplified circuit diagram of the braking system according to the fourth embodiment is shown.

[0025] Figure 6 A simplified circuit diagram of the braking system according to the fifth embodiment is shown. Detailed Implementation

[0026] Figure 1 A simplified wiring diagram of an advantageous embodiment of a braking system 1 for a motor vehicle (not shown in detail in the figure) is illustrated. The braking system 1 has a first module unit 2 and three second module units 3, 4, and 5. Module units 2 to 5 are preferably operable as a single unit and are configured, for example, as hydraulic blocks.

[0027] The first module unit 2 has a master brake cylinder 6, which, according to the current embodiment, is configured as a tandem cylinder with two pressure chambers 6' and 6''. The master brake cylinder 6 is also connected to, or may be connected to, the brake pedal 7 of the motor vehicle 1.

[0028] The braking system 1 also includes multiple wheel brakes 8, 9, 10, and 11, each assigned to one wheel of the vehicle and configured as friction brakes. Each wheel brake 8 to 11 is equipped with a controllable hydraulic brake actuator 12, 13, 14, and 15. Each brake actuator 12 to 15 has a hydraulic pump P and an electric motor M for driving the hydraulic pump P. According to the present embodiment, these hydraulic pumps P are configured as piston pumps, which are coupled to the corresponding electric motor M via a transmission device not shown in the figure. Each hydraulic pump P has a hydraulic piston K that can move within a hydraulic cylinder Z. By moving the hydraulic piston K with the aid of the electric motor M, pressure is applied to the hydraulic fluid, particularly the brake fluid, located within the cylinder. The hydraulic cylinder Z, more specifically the pressure chamber of the hydraulic cylinder Z, is hydraulically connected to the associated wheel brakes 8 to 11 via connecting lines. According to the current embodiment, a separation valve TB is inserted into the connecting pipeline. The separation valve TB is configured to close when not energized, and is used to hydraulically separate the hydraulic cylinder Z, or more precisely the hydraulic pump P, from the wheel brake 8 in the unenergized state.

[0029] According to the current embodiment, each module unit 2 to 5 has a reservoir R2, R3, R4, and R5, which are configured to contain and supply brake fluid to the braking system 1. Each hydraulic pump P is connected to its respective reservoir R on the suction side via a hydraulic line or a brake line.

[0030] In module unit 2, reservoir R2 is also fluid-technically connected to master brake cylinder 6, specifically to two pressure chambers 6' and 6''.

[0031] The first module unit 2 is preferably fastened to the front bulkhead of the vehicle, and a coupling rod passes through the front bulkhead, connecting the brake pedal 7 to the master brake cylinder 6. Module units 3, 4, and 5 are arranged in other locations in the motor vehicle, for example, near the wheels to be braked, each equipped with a corresponding wheel brake 9, 10, or 11.

[0032] The master brake cylinder 6 is connected to the pedal feel simulator PFS on one side and to wheel brakes 8, 9, 10, and 11 on the other. In this configuration, pressure chamber 6' is connected to the pedal feel simulator PFS and to wheel brakes 8 and 9, while pressure chamber 6'' is connected to wheel brakes 10 and 11 via corresponding fluid lines. Controllable release valves T8, T9, T10, and T11 are respectively inserted and connected between the master brake cylinder 6 and each wheel brake 8, 9, 10, and 11. Release valves T8 to T11 are configured to open when de-energized, ensuring that the master brake cylinder 6 is always hydraulically connected to wheel brakes 8 to 11 when de-energized. When the driver of the vehicle operates the brake pedal 7, the driver can thus directly generate braking force mechanically / hydraulically at wheel brakes 8 to 11.

[0033] The brake pedal 7 is also equipped with a sensor S7 configured to monitor the pedal travel or pedal operation of the brake pedal 7. A controller (not shown) detects the signals generated by sensor S7 and, under normal conditions, operates brake actuators 12 to 15 based on these signals to set braking force for each wheel at wheel brakes 8 to 11. During normal operation, i.e., when electrical power is supplied, the release valve TB is open and the release valves T8 to T11 are closed, thus preventing the driver from mechanically / hydraulically operating the wheel brakes 8 to 11, allowing only purely electric or electro-hydraulic operation. This constitutes a brake-by-wire system.

[0034] In the event of a malfunction, particularly during partial or complete power outages, the braking system 1 automatically switches to a mechanical backup level via the release valves TB and T8 to T11. In this backup level, the driver can directly generate braking force at the wheel brakes 8 to 11 by operating the brake pedal 7 using the master brake cylinder 6. Here, the release valves T8 to T11 respectively connect to the master brake cylinder, while the release valve TB disconnects the connection between each wheel brake 8 to 11 and each brake actuator 12 to 15.

[0035] Figure 2 Another embodiment of the braking system 1 is shown, wherein, by Figure 1 Known components are labeled with the same reference numerals, and their descriptions can be found above. The following descriptions will primarily focus on the differences.

[0036] The difference from the previous embodiment is that, in Figure 2 In this embodiment, only one reservoir R is provided as a centralized reservoir, and all module units 2, 3, 4, and 5, more specifically all brake actuators 12, 13, 14, and 15, are hydraulically connected to this reservoir. For clarity, in Figure 2 Only two of these module units, 2 and 4, are shown. Other module units 3 and 5 are preferably constructed according to module unit 4. Optionally, the braking system 1 is constructed to have only these two module units. Alternatively, the braking system 1 may have three or more module units. The number of module units depends particularly on the number of wheels to be braked in the motor vehicle equipped with the braking system 1.

[0037] Preferably, the hydraulic pump P has a pressure balancer 17, as described in detail below with reference to FIG3.

[0038] Figures 3A to 3D Hydraulic pump P is shown in different operating states. Figure 3A The hydraulic pump P in its unloaded position is shown. In this case, the hydraulic piston K retracts to its maximum extent, and thus the volume of the pressure chamber formed between cylinder Z and piston K reaches its maximum. Cylinder Z has a flow orifice 18 as a pressure balancer 17, through which cylinder Z is hydraulically connected to reservoir R or a corresponding reservoir R via a pressure balance channel. In the unloaded position of piston K, the flow orifice 18 flows into the pressure chamber of cylinder Z, thereby creating pressure balance between the corresponding wheel brakes 8-11 on one side and / or the release valves T8-T11 connected upstream of each wheel brake 8-11 and the reservoir R on the other side.

[0039] If piston K moves due to electric motor M, the flow orifice 18 will close before pressure can be generated in the cavity of cylinder Z, such as... Figure 3B As shown. The stroke until this state is reached is also called the dead stroke. If piston K continues to move, pressure will build up in the cavity, as... Figure 3C As shown, this pressure is then applied to wheel brakes 8 to 11 when the release valves T8 to T11 open. To reduce the pressure at each wheel brake 8 to 11, the piston K is moved back to the unloaded position by the electric motor M, as shown. Figure 3D As shown.

[0040] Figure 4 Another embodiment of braking system 1 is shown, which is related to Figure 2The difference in the previous embodiment is that each brake actuator 12 to 15 is equipped with a controllable pressure balancing valve VP, through which the hydraulic pump P is connected on the pressure side to, or can be connected to, the reservoir R and / or the pedal feel simulator PFS. Each pressure balancing valve VP is preferably configured to close when not energized. In this case, the flow orifice 18 serving as a pressure balancer is preferably omitted, and the pressure balancing valve VP is operated instead as the pressure balancer when needed.

[0041] Figure 5 Another embodiment is shown, which differs from the previous embodiment in that, according to Figure 1 In the first embodiment, the separation valves T9 to T11, which were arranged together with the separation valve T8 in module unit 2, are now located in other module units 3 to 5. Therefore, separation valves T9, T10, and T11 are now located in module units 3, 4, and 5, so that the hydraulic connection between module units 3 to 5 and the first module unit 2 can be controlled within module units 3, 4, and 5 themselves. Figure 5 Only module units 2 and 4 are shown in the diagram. This results in compact module units 3, 4, and 5, which also allow module units 3, 4, and 5 to be hydraulically separated from module unit 2 when needed.

[0042] Preferably, each module unit 2 to 5 further includes pressure sensors P2, P3, P4, and P5, which monitor the hydraulic pressure between the corresponding release valves T8 to T11 and the master brake cylinder 6, thereby providing a backup level for detecting the driver's braking expectation in the event of a failure of sensor S7. At least, this allows verification of the braking request detected by sensor S7.

[0043] Furthermore, according to the current embodiment, the master brake cylinder 6 is configured as a simple master brake cylinder with only one pressure chamber, which is connected to or may be connected to two or all of the wheel brakes 8 to 11.

[0044] Figure 6 Another embodiment is shown, which is similar to Figure 4 The difference in the embodiment is that the master brake cylinder 6 is constructed as a simple master brake cylinder 6 with only one pressure chamber. Compared with... Figure 5 The difference in the embodiment is that the separation valves T8 to T11 are arranged in module unit 2.

[0045] Of course, the above embodiments can also be combined with each other.

Claims

1. A braking system (1) for a motor vehicle, said braking system having hydraulically operable wheel brakes (8-11) for each of the plurality of wheels of said motor vehicle, wherein, Each wheel brake (8-11) is equipped with a hydraulic brake actuator (12-15) for operating it, the brake actuator having a hydraulic pump (P) and a drive motor (M) for the hydraulic pump (P), characterized in that the braking system (1) has a master brake cylinder (6) hydraulically connected to the wheel brakes (8-11) to operate the wheel brakes, wherein a first controllable release valve (T8-T11) is inserted and connected between the master brake cylinder (6) and each wheel brake (8-11).

2. The braking system according to claim 1, characterized in that, Each of the first separation valves (T8-T11) is configured to be a separation valve (T8-T11) that is open when no power is applied.

3. The braking system according to any one of the preceding claims, characterized in that, A second controllable release valve (TB), particularly a release valve (TB) that is closed when not energized, is inserted between each brake actuator (12-15) and its associated wheel brake (8-11).

4. The braking system according to any one of the preceding claims, characterized in that, The main brake cylinder (6) is equipped with a first reservoir (R2) for containing and supplying liquid brake medium, and at least one of the brake actuators (12-15) is equipped with a second reservoir (R).

5. The braking system according to any one of the preceding claims, characterized in that, At least one of the main brake cylinder (6) and the brake actuators (12-15) is equipped with a common reservoir (R) for providing liquid brake medium.

6. The braking system according to any one of the preceding claims, characterized in that, Each brake actuator (12-15) has a pressure balancer (17).

7. The braking system according to any one of the preceding claims, characterized in that, Each hydraulic pump (P) is configured as a piston pump, and each pressure balancer (17) has a flow passage (18) in the piston pump (P).

8. The braking system according to any one of the preceding claims, characterized in that, Downstream of each brake actuator (12-15) is a controllable pressure balancing valve (VP).

9. The braking system according to any one of the preceding claims, characterized in that, The main brake cylinder (6) is a single cylinder or a tandem cylinder.

10. The braking system according to any one of the preceding claims, characterized in that, The main brake cylinder (6) and the first brake actuator (12) in the brake actuator form a first module unit (2), and the remaining brake actuators (13-15) respectively form other module units (3-5).

11. The braking system according to any one of the preceding claims, characterized in that, The first separation valves (T8-T11) of each brake actuator are arranged in the first module unit (2).

12. The braking system according to any one of the preceding claims, characterized in that, The first separation valve (T9-T11) of at least one of the brake actuators (13-15) is arranged in the corresponding second module unit (3-5).

13. The braking system according to any one of the preceding claims, characterized in that, At least one of the brake actuators (12-15) is equipped with a pressure sensor (P2-P5) connected to the main brake cylinder (6).

14. The braking system according to any one of the preceding claims, characterized in that, The first module unit (2) has a pedal feel simulator (PFS).

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