Brake system for a vehicle and method for regulating brake pressure

Abstract

The invention relates to a brake system for a vehicle, comprising a hydraulic electronic sub-brake system and an electromechanical brake pedal for transmitting a braking force request to the brake system. The hydraulic electronic sub-brake system comprises at least one hydraulic brake, a pressure providing device and a brake fluid container. For this purpose, the hydraulic electronic sub-brake system comprises a continuously adjustable pressure relief valve arranged upstream of the brake fluid reservoir, which pressure relief valve provides the atmospheric pressure of the brake fluid reservoir for the brake pressure regulation of the hydraulic brake. The hydraulic electronic sub-brake system comprises a continuously adjustable isolation valve arranged between one side of the at least one hydraulic brake and one side of the pressure providing device and the brake fluid container, said isolation valve being configured so that the pressure providing device can be continuously adjusted when the pressure providing device is in the suction process. The established brake pressure is maintained on the at least one hydraulic brake. The invention also relates to a method for controlling the brake pressure in such a brake system.

Description

[0001] The present invention relates to a braking system for a vehicle, the braking system comprising a hydraulic electronic sub-braking system and an electromechanical brake pedal, the electromechanical brake pedal being used to transmit a user's braking force requirement to the braking system, wherein the hydraulic electronic sub-braking system comprises at least one hydraulic brake, at least one pressure supply device and at least one brake fluid container. The present invention also relates to a method for performing brake pressure regulation in such a braking system.

[0002] Such a brake-by-wire system is known from WO 2023 138 720 A1, which has an electromechanical brake pedal. The brake system described therein proposes, in particular, that in order to increase the safety in a brake system without a hydraulic fallback stage (Rückfallebene) implemented by means of a hydraulic electronic brake pedal, redundant control units and their respectively assigned shut-off valves are additionally arranged in series upstream of the brake fluid reservoir. The pressure switching valves in front of the pressure supply device can also be arranged redundantly in parallel. This greatly reduces the risk of a total system failure due to a single component failure.

[0003] Although these solutions increase the safety of wire-controlled brake systems with electromechanical brake pedals, they also lead to greater complexity and costs due to the greater number of components. It is conceivable that such a brake system usually includes at least one electromechanical sub-brake system and usually also a regenerative brake system (in which the electric motor can be operated as a generator). These non-hydraulic sub-brake systems are usually used in preference to hydraulic brakes because they are more efficient and more wear-resistant, so that hydraulic-electronic sub-brake systems are only used for high braking force requirements. Therefore, depending on the design of the rest of the brake system, it may be desirable that the hydraulic-electronic sub-brake system be designed to be less complex, wherein sufficient redundancy should still be provided in the overall system for a variety of single faults. However, at the same time, full adjustability of the hydraulic brakes should be ensured in order to provide the usual safety functions.

[0004] It is therefore an object of the present invention to provide a brake system of the type mentioned in the introduction which meets as many of these requirements as possible.

[0005] According to the invention, this object is achieved by a brake system according to claim 1. Due to the continuously adjustable pressure reducing valve and the continuously adjustable isolating valve, all basic safety functions can be provided together with the inlet valve and the outlet valve of each hydraulic brake, and at the same time the total number of valves and hydraulic lines and / or connections can be reduced, for example in comparison with WO 2023138 720A1.

[0006] Preferably, the isolation valve and the pressure reducing valve are normally open (open without power supply) valves. It is thus ensured that even in the event of a failure of one of these valves, at least limited functionality of the hydraulic-electronic sub-brake system can still be ensured.

[0007] In one embodiment, at least one hydraulic brake is supplied with hydraulic fluid via a normally open inlet valve and is connected to a brake fluid reservoir via a normally closed outlet valve, the inlet valve being continuously adjustable and the outlet valve being a two-position valve. Together with a continuously adjustable pressure reducing valve and a continuously adjustable isolating valve, this hydraulic arrangement allows full adjustability of the hydraulic brake(s), but wherein a significantly simpler two-position valve is used as the outlet valve for the hydraulic brake(s). In the prior art, the outlet valve is usually a continuously adjustable valve which is used for a plurality of regulating functions.

[0008] Preferably, the hydraulic-electronic brake subsystem comprises exactly two hydraulic brakes, which are in particular for the same axle. For example, the solution according to the invention is particularly advantageous in "semi-dry" brake systems, since other (in particular electromechanical and regenerative) brake subsystems of the brake system can be supplemented particularly well in terms of system safety and the hydraulic-electronic brake subsystem can be simplified.

[0009] Preferably, the brake system is configured such that the pressure reducing valve is fully or partially opened during brake pressure regulation in order to reduce the brake pressure. The inlet valve and the outlet valve can also be used for brake pressure regulation as is conventional. In this case, the continuously adjustable pressure reducing valve replaces part of the previous function of the outlet valve, which can no longer be partially opened but has only an open and a closed position.

[0010] Preferably, the brake system comprises exactly one hydraulic control unit, wherein the hydraulic control unit is configured to control the hydraulic-electronic brake sub-system and to perform brake pressure regulation for the hydraulic brake. Thus, a single hydraulic control unit is provided for the entire hydraulic-electronic brake sub-system (only the pressure supply device can optionally also include a separate electromechanical control unit). In the past, brake-by-wire systems usually had separate control units, for example a control unit for the actuator section (in particular the pressure supply device and the brake fluid reservoir) and a control unit for the regulator section (in particular the hydraulic brake and the associated regulating valves), in order to provide sufficient reliability. However, especially when electromechanical brake sub-systems and / or regenerative brake sub-systems are present, such an additional redundancy level is not always necessary, so that the electronics of the hydraulic-electronic brake sub-system can be simplified.

[0011] In one embodiment, the brake system further comprises an electromechanical sub-brake system, wherein the electromechanical sub-brake system comprises at least one electromechanical brake, which is assigned to different axles of the vehicle than the hydraulic brake of the hydraulic electronic sub-brake system. For such a brake system, the embodiment according to the invention of the hydraulic electronic sub-brake system is particularly advantageous, since the electromechanical sub-brake system provides an additional fallback level in the event of a partial failure of the hydraulic electronic sub-brake system.

[0012] Preferably, each electromechanical brake comprises its own brake control unit, which is configured to regulate the braking force or the braking torque provided by the electromechanical brake. This embodiment is particularly advantageous because each electromechanical brake provides an additional fallback step, for example in the event of a failure of the control unit of the brake system, which no longer has to be provided separately by the hydraulic electronic sub-brake system.

[0013] Preferably, the brake system also comprises a regenerative sub-brake system, wherein the electric machine of the vehicle can be operated as a generator in order to provide a braking force for the vehicle. In particular, in the presence of an electromechanical sub-brake system and a regenerative sub-brake system, the solution according to the invention of a hydraulic electronic sub-brake system is particularly advantageous. A high reliability is achieved by means of a plurality of sub-brake systems, which allows the complexity of the hydraulic electronic sub-brake system to be reduced.

[0014] Preferably, the hydraulic electronic sub-brake system comprises a suction valve, which is connected to the brake fluid container through its own connector in parallel with the pressure reducing valve, wherein the suction valve is designed as a check valve, and when the pressure supply device generates negative pressure on the side of the suction valve facing away from the brake fluid container during the suction process, the check valve opens, wherein the hydraulic lines of the suction valve and the pressure reducing valve respectively converge at a first node facing away from the brake fluid container, and the main line starts at the first node. Through this design, the hydraulic connector with the pressure supply device can be saved, and the sealing of the pressure supply device can be simplified.

[0015] Preferably, the hydraulic line of the isolation valve and the hydraulic line of the pressure supply device meet at a second node, which is located on the main line from the brake fluid container to the at least one hydraulic brake, wherein no valve is arranged in the hydraulic line from the pressure supply device to the second node. Therefore, a dedicated shut-off valve upstream of the pressure supply device is omitted, which reduces the complexity of the brake system.

[0016] In one embodiment, only one hydraulic line is led from the pressure supply device to the hydraulic circuit leading to at least one hydraulic brake hydraulic circuit and the brake fluid container. Through this design, hydraulic connections with the pressure supply device can be saved and the sealing of the pressure supply device can be simplified.

[0017] The object according to the invention is also achieved by a method according to claim 12. Thus, the brake pressure applied to the hydraulic brake is also adjusted by partially opening and closing the pressure reducing valve again. In addition, in order to provide different brake pressures for the hydraulic brake, the opening degree of the associated inlet valve can be varied and the outlet valve can be opened in stages.

[0018] Preferably, the brake system comprises a pressure sensor configured for measuring a brake pressure applied to the hydraulic brake, wherein the step of regulating the brake pressure utilizes the brake pressure measured by the pressure sensor. Preferably, the brake system comprises exactly one pressure sensor, which is sufficient for the relevant regulating function, in particular due to the reduced number of valves.

[0019] The following is a detailed explanation of the embodiments of the present invention with the aid of the accompanying drawings. In the accompanying drawings:

[0020] Figure 1 shows a hydraulic circuit diagram of a brake system according to the present invention,

[0021] Figure 2 A flow chart of a method according to the invention is shown.

[0022] Figure 1 An embodiment of a brake system 1 according to the invention is shown, which comprises a hydraulic electronic sub-brake system 2 and an electromechanical brake pedal 3 for transmitting a user's braking force request to the brake system 1. The hydraulic electronic sub-brake system 2 comprises at least one (here two, for example for the front axle of a motor vehicle) hydraulic brake 4, 5, a pressure supply device 6 and a brake fluid container 7.

[0023] The hydraulic electronic sub-brake system 2 also has a continuously adjustable pressure reducing valve 8 (magnetic valve) arranged upstream of the brake fluid reservoir 7. The pressure reducing valve 8 is configured to provide the atmospheric pressure of the brake fluid reservoir 7 for regulating the brake pressure of the hydraulic brakes 4,5.

[0024] Furthermore, the hydraulic electronic sub-brake system 2 comprises a continuously adjustable isolating valve 9 (solenoid valve) arranged between the hydraulic brakes 4, 5 on the one hand and the pressure supply device 6 and the brake fluid reservoir 7 on the other hand. The isolating valve 9 is configured to maintain the built-up brake pressure on at least one hydraulic brake 4, 5 when the pressure supply device 6 is in the process of sucking brake fluid from the brake fluid reservoir 7.

[0025] Each hydraulic brake 4, 5 is supplied with hydraulic fluid via a normally open inlet valve 10, 11 (solenoid valve) and is connected to the brake fluid reservoir 7 via a normally closed outlet valve 12, 13. The inlet valves 10, 11 are continuously adjustable, while the outlet valves 12, 13 are simple two-position valves. Together with the continuously adjustable pressure reducing valve 8 and the continuously adjustable isolating valve 9, this hydraulic arrangement allows full adjustability of the hydraulic brakes 4, 5, but wherein significantly simpler two-position valves can be used as outlet valves 12, 13 for the hydraulic brakes 4, 5, as is usually the case in the prior art.

[0026] The brake system 1 comprises a hydraulic control unit 14 which is configured for controlling the hydraulic-electronic sub-brake system 2 and for performing brake pressure regulation for the hydraulic brakes 4 , 5 .

[0027] The brake system 1 further comprises an electromechanical sub-brake system 15, wherein the electromechanical sub-brake system 15 comprises at least one (here two) electromechanical brakes 16, 17. The electromechanical brakes 16, 17 and the hydraulic brakes 4, 5 (for example, assigned to the front axle) of the hydraulic electronic sub-brake system 2 are assigned to different axles (for example, the rear axle) of the vehicle. The electromechanical brakes 16, 17 are preferably electromechanical drum brakes. Each electromechanical brake 16, 17 comprises its own brake control unit 18, 19, which are respectively configured to adjust the braking force or the braking torque provided by the assigned electromechanical brake 16, 17.

[0028] Furthermore, the brake system 1 has a regenerative brake subsystem 20 , in which an electric machine of the vehicle can be operated as a generator in order to provide a braking force for the vehicle.

[0029] The hydraulic electronic sub-brake system 2 additionally comprises a suction valve 21, which is connected to the brake fluid container 7 via its own connection 22 when connected in parallel with the pressure reducing valve 8. The pressure reducing valve 8 is connected to the brake fluid container 7 via another connection 23. The suction valve 21 is designed as a non-return valve, which opens when the pressure supply device 6 generates a negative pressure on the side of the suction valve 21 facing away from the brake fluid container 7 during the suction process. The hydraulic lines of the suction valve 21 and the pressure reducing valve 8 are respectively connected at a first node 24 facing away from the brake fluid container 7, and the main line starts at the first node.

[0030] The hydraulic line of the isolation valve 9 and the hydraulic line of the pressure supply device 6 meet at a second node 25, which is located on the main line from the brake fluid reservoir 7 to the hydraulic brakes 4, 5. No valve is located in the hydraulic line from the pressure supply device 6 to the second node 25. Exactly one hydraulic line leads from the pressure supply device 6 to the hydraulic circuit leading to the hydraulic brakes 4, 5 and the brake fluid reservoir 7.

[0031] The brake system 1 further comprises a pressure sensor 26 which is configured to measure the brake pressure applied to the hydraulic brakes 4 , 5 .

[0032] Figure 2 A flow chart of a method according to the invention is shown. The method for brake pressure regulation first comprises the step of closing 100 the pressure reducing valve 8 and the discharge valves 12, 13 when a brake pressure demand for the hydraulic electronic sub-brake system 2 is detected. Subsequently, in a further step, the isolation valve 9 and the inlet valves 10, 11 are opened 110, if they are not already opened. Then, a brake pressure is established 120 at the hydraulic brakes 4, 5 by the pressure supply device 6. The brake pressure applied to the hydraulic brakes 4, 5 (which may be different from each other) is also adjusted 130 by partially opening and closing the pressure reducing valve 8 again. Adjusting 130 the brake pressure can include opening the two-position discharge valves 12, 13 in stages, and optionally partially opening and closing the inlet valves 10, 11. At the end of the brake pressure demand, a pressure reduction 140 occurs at the hydraulic brakes 4, 5 by opening the discharge valves 12, 13.

Claims

1. A braking system (1) for a vehicle, the braking system comprising a hydraulic electronic sub-braking system (2) and an electromechanical brake pedal (3), the electromechanical brake pedal being used to transmit a user's braking force requirement to the braking system (1), The hydraulic electronic sub-brake system (2) comprises at least one hydraulic brake (4, 5), a pressure supply device (6) and a brake fluid container (7). It is characterized in that The hydraulic electronic sub-brake system (2) has a continuously adjustable pressure reducing valve (8) arranged upstream of the brake fluid container (7), the pressure reducing valve being configured to provide the atmospheric pressure of the brake fluid container (7) for brake pressure regulation of the hydraulic brakes (4, 5). The hydraulic electronic sub-brake system (2) comprises a continuously adjustable isolating valve (9) which is arranged between the at least one hydraulic brake (4, 5) on the one hand and the pressure supply device (6) and the brake fluid container (7) on the other hand, and the isolating valve is configured to maintain the brake pressure built up on the at least one hydraulic brake (4, 5) when the pressure supply device (6) is in the process of sucking brake fluid from the brake fluid container (7).

2. The brake system (1) according to claim 1, characterized in that The isolation valve (9) and the pressure reducing valve (8) are normally open valves.

3. The brake system (1) according to any one of the preceding claims, characterized in that The at least one hydraulic brake (4, 5) is supplied with hydraulic fluid via a normally open inlet valve (10, 11) and is connected to a brake fluid container (7) via a normally closed outlet valve (12, 13), wherein the inlet valve (10, 11) is continuously adjustable and the outlet valve (12, 13) is a two-position valve.

4. Braking system (1) according to any one of the preceding claims, characterized in that The brake system (1) is configured to fully or partially open the pressure reducing valve (8) during brake pressure regulation in order to reduce the brake pressure.

5. Braking system (1) according to any one of the preceding claims, characterized in that The hydraulic electronic sub-brake system (2) comprises exactly one hydraulic control unit (14), which is configured to control the hydraulic electronic sub-brake system (2) and to perform brake pressure regulation on the hydraulic brakes (4, 5).

6. Braking system (1) according to any one of the preceding claims, characterized in that The brake system (1) also includes an electromechanical sub-brake system (15), which includes at least one electromechanical brake (16, 17), and the at least one electromechanical brake and the hydraulic brake (4, 5) of the hydraulic electronic sub-brake system (2) are assigned to different axles of the vehicle.

7. The brake system (1) according to claim 6, characterized in that Each electromechanical brake (16, 17) comprises its own brake control unit (18, 19), which is configured to regulate the braking force or the braking torque provided by the electromechanical brake (16, 17).

8. Braking system (1) according to any one of the preceding claims, characterized in that The braking system (1) also includes a regenerative braking sub-system (20), and the vehicle's electric machine can operate as a generator to provide braking force for the vehicle.

9. Braking system (1) according to any one of the preceding claims, characterized in that The hydraulic electronic sub-brake system (2) comprises a suction valve (21), which is connected to the brake fluid container (7) via its own connector (22) in parallel with the pressure reducing valve (8). The suction valve (21) is designed as a non-return valve. When the pressure supply device (6) generates negative pressure on the side of the suction valve (21) facing away from the brake fluid container (7) during the suction process, the non-return valve opens. The hydraulic circuit of the suction valve (21) and the hydraulic circuit of the pressure reducing valve (8) are respectively joined at a first node (24) on the side facing away from the brake fluid container (7), and the main circuit starts at the first node.

10. Braking system (1) according to any one of the preceding claims, characterized in that The hydraulic line of the isolation valve (9) and the hydraulic line of the pressure supply device (6) merge at a second node (25), which is located on the main line from the brake fluid container (7) to the at least one hydraulic brake (4, 5), and no valve is provided in the hydraulic line from the pressure supply device (6) to the second node (25).

11. Braking system (1) according to any one of the preceding claims, characterized in that Exactly one hydraulic line leads from the pressure supply device (6) to the hydraulic circuit leading to the at least one hydraulic brake (4, 5) and to the brake fluid reservoir (7).

12. A method for brake pressure regulation in a brake system (1) according to any one of claims 3 to 11, the method comprising the following steps: - Close the pressure reducing valve (8) and the discharge valves (12, 13) (100), - Open the isolation valve (9) and the inlet valves (10, 11) (110), - building up a brake pressure (120) at the hydraulic brake (4, 5) via a pressure supply device (6), - regulating (130) the brake pressure applied to the hydraulic brakes (4, 5), wherein regulating (130) the brake pressure comprises partially opening and again closing the pressure reducing valve (8).

13. The method according to claim 12, characterized in that The brake system (1) comprises a pressure sensor (26) configured to measure a brake pressure applied to a hydraulic brake (4, 5). The step of regulating (130) the brake pressure utilizes the brake pressure measured by the pressure sensor (26).

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