By-wire type vehicle hydraulic brake system and control method thereof

Abstract

The present invention provides a drive-by-wire type hydraulic brake system for vehicles and a control method thereof. The drive-by-wire type hydraulic brake system for vehicles includes a fluid reservoir (1), a pedal feel control oil passage and a pressure boosting brake control oil passage connected to the fluid reservoir (1), the pedal feel control oil passage being connected in parallel with the pressure boosting brake control oil passage via a decoupling isolation solenoid valve (4), and the pedal feel control oil passage including a single-chamber type master cylinder (2) and a pedal feel simulator (3) connected via the oil passage.

Description

Technical Field

[0001] The present invention relates to the technical field of automotive brake systems, and particularly to a by-wire type hydraulic brake system for vehicles and a control method thereof.

Background Art

[0002] With the development of intelligent driving and autonomous driving technologies in the automotive industry, the research on intelligent driving and autonomous driving by each automobile manufacturer is becoming increasingly in-depth. Under such a background, the by-wire type brake, as one of the important technologies for autonomous driving, has achieved rapid development.

[0003] The conventional by-wire type hydraulic brake system has the following problems. First, the master cylinder generally adopts output by a dual chamber. In the case of the same arrangement space, the stroke of the master cylinder is short, and since both chambers receive hydraulic pressure, when the master cylinder operates, it is necessary to straddle two empty strokes, resulting in fluctuations in the pedal feeling and a complicated structure of the entire brake system. Second, the conventional braking method performs pressure boosting braking by a pressure cylinder. However, when a failure occurs in the pressure boosting braking, an effective brake cannot be realized, and the safety of the brake is reduced. Third, when the brake is released, brake dragging occurs, affecting the restart, acceleration running, and coasting of the vehicle, making it difficult to use the vehicle normally.

Summary of the Invention

Problems to be Solved by the Invention

[0004] In order to solve the above technical problems, the present invention provides a by-wire type hydraulic brake system for vehicles and a control method thereof, which can reduce the complexity of the structure of the brake system, solve the problem of pedal feeling fluctuations, and realize highly reliable braking.

Means for Solving the Problems

[0005] To achieve the above objectives, the technical solution employed by the present invention is as follows: The by-wire type vehicle hydraulic brake system includes a fluid reservoir tank and a pedal feel control oil passage and a pressure boosting brake control oil passage connected to the fluid reservoir tank, wherein the pedal feel control oil passage is connected in parallel with the pressure boosting brake control oil passage via a decoupling isolation solenoid valve, and the pedal feel control oil passage includes a single-chamber type master cylinder and a pedal feel simulator connected via the oil passage.

[0006] The pressure-boosting brake control oil passage includes a brushless motor and a pressure cylinder scalably connected to the brushless motor, the port of the pressure cylinder being connected to a plurality of pressure-boosting oil passages via a pressure supply oil passage, the plurality of pressure-boosting oil passages being connected to the reservoir tank via corresponding pressure-reducing oil passages, and the outlets of the plurality of pressure-boosting oil passages being connected to corresponding wheel brakes.

[0007] A pressure supply solenoid valve is provided in the pressure supply oil passage, a pressure boosting solenoid valve is provided in the pressure boosting oil passage, and a pressure reducing solenoid valve is provided in the pressure reducing oil passage.

[0008] The port of the pressure cylinder is connected to the liquid storage tank via a liquid supply oil passage, a liquid supply electric control valve or check valve is provided in the liquid supply oil passage, and a first pressure sensor is attached to the port of the pressure cylinder.

[0009] A decoupling isolation oil passage is connected between the pedal sensation control oil passage and the pressure boosting brake control oil passage, a decoupling isolation solenoid valve is installed in the decoupling isolation oil passage, the decoupling isolation oil passage is connected in parallel with the pressure supply oil passage, and the decoupling isolation oil passage is connected in series with a plurality of pressure boosting oil passages.

[0010] A second pressure sensor is connected between the single-chamber master cylinder and the decoupling isolation solenoid valve, between the pedal feel simulator and the decoupling isolation solenoid valve, or between the single-chamber master cylinder and the pedal feel simulator.

[0011] One decoupling isolation oil passage is provided, and the outlet of the decoupling isolation oil passage is connected to the corresponding wheel brake via four pressure boosting oil passages.

[0012] Two decoupling isolation oil passages and two pressure supply oil passages are provided, and one decoupling isolation solenoid valve is installed in each decoupling isolation oil passage. Each decoupling isolation oil passage is connected in parallel to one pressure supply oil passage, and the outlet of each decoupling isolation oil passage is connected to two pressure boosting oil passages.

[0013] A simulator isolation solenoid valve is connected between the single-chamber type master cylinder and the pedal feel simulator.

[0014] A control method for a drive-by-wire vehicle hydraulic brake system includes control processes for the primary brake, mechanical backup brake, and brake release.

[0015] In the basic brake control process described above, when the brake pedal is pressed, brake fluid flows from the outlet port of the single-chamber master cylinder to the pedal feel simulator, generating a pedal feel. Simultaneously, the ECU controller sends a pressure boosting brake command to the pressure boosting brake control oil passage to brake the wheels, and controls the decoupling isolation solenoid valve to decouple and isolate the pedal feel generation process and the pressure boosting brake process.

[0016] In the control process for the mechanical backup brake, if a failure occurs in the pressure-boosting brake control oil passage, the decoupling isolation solenoid valve opens, and when the brake pedal is pressed, brake fluid is introduced from the single-chamber master cylinder through the decoupling isolation oil passage into the four pressure-boosting oil passages, thereby braking the wheels.

[0017] In the aforementioned brake release control process, when the brake pedal is released, the brake fluid in the pedal feel simulator is returned to the single-chamber master cylinder, and at the same time, the ECU controller returns the piston of the pressure cylinder of the pressure boosting brake control oil passage and closes the fluid supply oil passage of the pressure cylinder, thereby quickly returning the high-pressure brake fluid to the pressure cylinder. [Effects of the Invention]

[0018] The beneficial effects of this invention are as follows:

[0019] 1. The present invention employs a single-chamber type master cylinder having a single-circuit hydraulic output chamber. This single-chamber type master cylinder has a long stroke and only requires passing through one empty stroke during operation. Furthermore, by adjusting the overall structure of the by-wire hydraulic brake system, the complexity of the system is reduced, and the problems of stroke reduction and pedal feel fluctuations present in conventional dual-chamber type master cylinders can be solved. In addition, by directly connecting the single-chamber type master cylinder to a pedal feel simulator, the complexity of the system is effectively reduced, the pedal feel feedback time is shortened, and the problem of pedal feel feedback delay caused by flow blockage can be solved.

[0020] 2. When the boost brake fails, in the present invention, the energization of the decoupling isolation solenoid valve is cut off to put the decoupling isolation solenoid valve in an open state. By stepping on the brake pedal, the brake fluid in the single-chamber master cylinder enters the four wheel brakes respectively via the four boost oil circuits, realizing a mechanical backup brake and ensuring effective braking.

[0021] 3. In the process of brake release, the present invention controls the liquid supply electric control valve in the liquid supply oil circuit connected to the pressure cylinder to close, so that the brake fluid in the liquid storage tank is not replenished into the pressure cylinder in a timely manner, generating a negative pressure in the pressure cylinder, accelerating the backward movement of the brake wheel cylinder, and effectively reducing the brake drag.

Brief Description of the Drawings

[0022] Hereinafter, the display content of each drawing of the present invention and the drawing reference numerals will be briefly described. [Figure 1] It is a structural schematic diagram of Embodiment 1 of the two-wire type vehicle hydraulic brake system of the present invention. [Figure 2] It is a structural schematic diagram of Embodiment 2 of the two-wire type vehicle hydraulic brake system of the present invention. [Figure 3] It is a control principle diagram of the basic brake according to Embodiment 1 of the present invention. [Figure 4] It is a control principle diagram of the mechanical backup brake according to Embodiment 1 of the present invention.

Modes for Carrying Out the Invention

[0023] To make the purpose, technical means and advantages of the embodiments of the present invention clearer, while referring to the drawings in the embodiments of the present invention, the technical means in the embodiments will be clearly and completely described. The following embodiments are only for explaining the present invention and do not limit the protection scope of the present invention.

[0024] In the description of the present invention, as points to be explained, the directions or positional relationships indicated by terms such as "upper", "lower", "front", "rear", "left", "right", "vertical", "inner", and "outer" are the directions or positional relationships based on the illustration, and are only for the convenience of description and simplification of the description of the present invention, and do not explicitly or implicitly imply that the target device or member must have a specific direction and be configured and operated in a specific direction. Therefore, it should not be construed as limiting the present invention.

[0025] Also, in the description of the present invention, unless otherwise clearly defined and limited separately, terms such as "attach", "be continuous with", and "connect" should be construed in a broad sense. For example, it may be a fixed connection, a removable connection, or an integral connection. Also, it may be a mechanical connection or an electrical connection. And it may be a direct continuity or an indirect continuity through an intermediate medium. A person skilled in the art can interpret the specific meaning of the above terms in the present invention according to the specific situation.

[0026] The specific embodiments of the present invention will be described by the following examples. Example 1

[0027] As shown in Figure 1, the by-wire vehicle hydraulic brake system includes a fluid reservoir 1, a pedal feel control oil passage connected to the fluid reservoir 1, and a pressure boosting brake control oil passage. The pedal feel control oil passage is connected in parallel to the pressure boosting brake control oil passage via a decoupling isolation solenoid valve 4. The decoupling isolation solenoid valve 4 decouples and isolates the pedal feel control oil passage and the pressure boosting brake control oil passage, ensuring independence and operational stability of pedal feel generation and pressure boosting brake. The pedal feel control oil passage includes a single-chamber master cylinder 2 and a pedal feel simulator 3 connected via the oil passage. The single-chamber master cylinder 2 includes one chamber and two ports; one port is connected to the fluid reservoir 1, and the other port is connected to the pedal feel simulator 3 and the pressure boosting brake control oil passage. The single-chamber master cylinder 2 has a long stroke and only needs to pass through one empty stroke during operation, thus reducing system complexity and solving the problems of shortened stroke and pedal feel fluctuations present in dual-chamber master cylinders. Furthermore, by directly connecting the single-chamber master cylinder 2 to the pedal feel simulator 3, the complexity of the system can be effectively reduced, the pedal feel feedback time can be shortened, and the problem of pedal feel feedback delay caused by flow blockage can be solved.

[0028] Specifically, the pressure boosting brake control oil passage includes a brushless motor 5 and a pressure cylinder 6 that is movably connected to the brushless motor 5 via a reduction mechanism. The brushless motor 5 has a built-in position sensor that can detect the operating position of the brushless motor 5. The port of the pressure cylinder 6 is connected to a plurality of pressure boosting oil passages 8 via a pressure supply oil passage 7. There are four pressure boosting oil passages 8, and the four pressure boosting oil passages 8 are connected to the corresponding wheel brakes 10. The brushless motor 5 extends the piston rod of the pressure cylinder 6, causing the brake fluid in the pressure cylinder 6 to enter the plurality of pressure boosting oil passages 8 via the pressure supply oil passage 7 and further enter the corresponding wheel brakes 10, thereby enabling braking. The plurality of pressure boosting oil passages 8 are connected to a reservoir tank 1 via corresponding pressure reducing oil passages 9 and are used to adjust the hydraulic pressure in the pressure boosting brake control oil passage. A pressure supply solenoid valve 11 is provided in the pressure supply oil passage 7, a pressure boosting solenoid valve 12 is provided in the pressure boosting oil passage 8, and a pressure reducing solenoid valve 13 is provided in the pressure reducing oil passage 9. Furthermore, a first pressure sensor 17 is attached to the port of the pressure cylinder 6 to detect whether the hydraulic pressure in the pressure boosting brake control oil passage is within a set range. The first pressure sensor 17 is connected to the signal input terminal of the ECU controller 21, and the signal output terminal of the ECU controller 21 is connected to the brushless motor 5, the pressure supply solenoid valve 11, the pressure boosting solenoid valve 12, and the pressure reducing solenoid valve 13. If the hydraulic pressure in the pressure boosting brake control oil passage is too high or too low, the ECU controller 21 adjusts the magnitude of the hydraulic pressure by controlling the operating stroke of the brushless motor 5 or by controlling the opening and closing of the pressure reducing solenoid valve 13.

[0029] Specifically, the port of the pressure cylinder 6 is connected to the storage tank 1 via a fluid supply passage 14, and a fluid supply electric control valve 15 is provided within this fluid supply passage 14. When the brake is released, the brushless motor 5 rotates in reverse, causing the brake fluid in the wheel brake 10 to recirculate into the pressure cylinder 6, and the fluid supply electric control valve 15 is closed, thereby blocking the fluid supply passage 14 and preventing the brake fluid in the storage tank 1 from being replenished to the pressure cylinder 6 in a timely manner. This generates negative pressure within the pressure cylinder 6, accelerating the retraction of the brake wheel cylinder and effectively reducing brake drag.

[0030] Specifically, a decoupling isolation oil passage 18 is connected between the pedal feel control oil passage and the pressure boosting brake control oil passage, and a decoupling isolation solenoid valve 4 is installed inside the decoupling isolation oil passage 18. The decoupling isolation oil passage 18 is connected in parallel with the pressure supply oil passage 7, and the decoupling isolation oil passage 18 is connected in series with multiple pressure boosting oil passages 8. When the pressure boosting brake is applied, the decoupling isolation solenoid valve 4 is closed to decouple and isolate the brake pressure boosting process and the pedal feel generation process, thereby isolating the master cylinder circuit and the pressure cylinder 6 circuit, and ensuring the stability of the pedal feel and pressure boosting brake. If a failure occurs in the pressure boosting brake, the decoupling isolation solenoid valve 4 opens, and when the brake pedal is pressed, brake fluid is allowed to enter the four pressure boosting oil passages 8 from the single-chamber type master cylinder 2 via the decoupling isolation oil passage 18, ensuring reliable braking of the wheels.

[0031] Specifically, a second pressure sensor 19 for detecting the magnitude of the hydraulic pressure in the pedal sensation control oil passage is connected between the single-chamber master cylinder 2 and the decoupling isolation solenoid valve 4, between the pedal sensation simulator 3 and the decoupling isolation solenoid valve 4, or between the single-chamber master cylinder 2 and the pedal sensation simulator 3. The single-chamber master cylinder 2 is equipped with a stroke sensor for detecting its stroke, and the stroke sensor and the second pressure sensor 19 are connected to the single-chamber master cylinder 2, the pressure boosting solenoid valve 12, and the pressure reducing solenoid valve 13 via the ECU controller 21. When basic braking is performed (pedal sensation is generated and pressure boosting braking is normal), if the hydraulic pressure in the pedal sensation control oil passage is too high or too low, the ECU controller 21 adjusts the hydraulic pressure within a set range by controlling the movement of the piston rod of the single-chamber master cylinder 2. When a mechanical backup brake is in operation, if the hydraulic pressure in the pedal feel control oil passage is too high or too low, the ECU controller 21 adjusts the hydraulic pressure by controlling the movement of the piston rod of the single-chamber type master cylinder 2 or by controlling the opening and closing of the pressure reducing solenoid valve 13.

[0032] There are two decoupling isolation oil passages 18 and two pressure supply oil passages 7, and one decoupling isolation solenoid valve 4 is installed in each decoupling isolation oil passage 18. Each decoupling isolation oil passage 18 is connected in parallel to one pressure supply oil passage 7, and the outlet of each decoupling isolation oil passage 18 is connected to two pressure boosting oil passages 8. The outlet port of the single-chamber type master cylinder 2 is connected to two pressure boosting oil passages 8 via two decoupling isolation oil passages 18, and is connected in parallel to the port of the pressure cylinder 6 via two pressure supply oil passages 7 connected to the two decoupling isolation oil passages 18. In other words, pressure boosting brake fluid is supplied to the four pressure boosting oil passages 8 via the two pressure supply oil passages 7, improving braking efficiency.

[0033] Furthermore, one decoupling isolation oil passage 18 and one pressure supply oil passage 7 are provided, and the outlet of the decoupling isolation oil passage 18 may be connected to the corresponding wheel brake 10 via four pressure boosting oil passages 8. The system structure can be further simplified by providing pressurized brake fluid to the four pressure boosting oil passages 8 via one pressure supply oil passage 7.

[0034] The control method for the above-described drive-by-wire vehicle hydraulic brake system includes control processes for the primary brake, mechanical backup brake, and brake release.

[0035] As shown in Figure 3, in the basic brake control process, when the brake pedal 22 is pressed, brake fluid flows from the outlet port of the single-chamber master cylinder 2 to the pedal feel simulator, generating pedal sensation. Simultaneously, the ECU controller 21 sends a pressure boosting brake command to the pressure boosting brake control oil passage, and the brushless motor 5 operates the pressure cylinder 6, causing brake fluid to enter the four pressure boosting oil passages 8 simultaneously from the pressure supply oil passage 7, and further enter the corresponding wheel brake 10 via the pressure boosting oil passages 8, thereby braking the wheel. At the same time, the ECU controller 21 controls the decoupling isolation solenoid valve 4 to decouple and isolate the pedal sensation generation process and the pressure boosting brake process.

[0036] As shown in Figure 4, in the control process of the mechanical backup brake, if a failure occurs in the pressure-boosting brake control oil passage, the decoupling isolation solenoid valve 4 opens, and when the brake pedal is pressed, brake fluid is allowed to enter the four pressure-boosting oil passages 8 from the single-chamber type master cylinder 2 via the decoupling isolation oil passage 18, thereby braking the wheels.

[0037] In the brake release control process (opposite to the flow direction of brake fluid in the system in Figure 3), when the brake pedal 22 is released, the brake fluid in the pedal feel simulator 3 returns to the single-chamber master cylinder 2. At the same time, the ECU controller 21 returns the piston of the pressure cylinder 6 of the pressure-boosting brake control oil passage and closes the replenishment oil passage 14 of the pressure cylinder 6, thereby generating negative pressure in the pressure cylinder 6. This quickly returns high-pressure brake fluid to the pressure cylinder 6, accelerating the retraction of the brake wheel cylinder and effectively reducing brake drag. Example 2

[0038] As shown in Figure 2, the difference from Embodiment 1 is that a simulator isolation solenoid valve 20 is provided in the oil passage between the single-chamber master cylinder 2 and the pedal feel simulator 3. When mechanical backup braking is performed, the simulator isolation solenoid valve 20 blocks the brake fluid in the single-chamber master cylinder 2 from entering the pedal feel simulator 3, making mechanical backup braking faster. The fluid supply electric control valve 15 in the fluid supply oil passage 14 of the pressure cylinder 6 is changed to a check valve 16. The installation of the check valve 16 allows brake fluid to be replenished into the pressure cylinder 6 in a timely and active manner when the brakes are released, ensuring a stable return of the pressure cylinder 6. Example 3

[0039] The difference from Example 1 (not shown) is that a simulator isolation solenoid valve 20 is provided in the oil passage between the single-chamber type master cylinder 2 and the pedal feel simulator 3. When mechanical backup braking is performed, the simulator isolation solenoid valve 20 blocks the brake fluid in the single-chamber type master cylinder 2 from entering the pedal feel simulator 3, thereby making mechanical backup braking faster. Example 4

[0040] The difference from Example 1 (not shown) is that the fluid supply electric control valve 15 in the fluid supply oil passage 14 of the pressure cylinder 6 has been changed to a check valve 16. By installing the check valve 16, brake fluid can be replenished into the pressure cylinder 6 in a timely and active manner when the brake is released, and the stable return of the pressure cylinder 6 is ensured.

[0041] As described above, the present invention reduces the complexity of the brake system structure, solves the problem of pedal feel fluctuations, and achieves highly reliable braking.

[0042] Although the principles of the present invention have been illustrated above, this specification does not limit the present invention to the specific structures and scope of application illustrated and described. Accordingly, all available modifications and equivalents are covered within the scope of the present invention. [Explanation of Symbols]

[0043] 1. Liquid storage tank 2. Single-chamber master cylinder 3. Pedal feel simulator 4. Decoupling isolation solenoid valve 5. Brushless motor 6. Pressure cylinder 7. Pressure supply oil passage 8. Pressure boosting oil passage 9. Pressure reducing oil passage 10. Wheel brake 11. Pressure supply solenoid valve 12. Pressure boosting solenoid valve 13. Pressure reducing solenoid valve 14. Fluid supply oil passage 15. Fluid supply electric control valve 16. Check valve 17. First pressure sensor 18. Decoupling isolation oil passage 19. Second pressure sensor 20. Simulator isolation solenoid valve 21. ECU controller 22. Brake pedal

Claims

1. A by-wire type hydraulic brake system for vehicles, comprising a fluid storage tank, a pedal feel control oil passage and a pressure boosting brake control oil passage connected to the fluid storage tank, wherein the pedal feel control oil passage is connected in parallel with the pressure boosting brake control oil passage via a decoupling isolation solenoid valve, and the pedal feel control oil passage includes a single-chamber type master cylinder and a pedal feel simulator connected via the oil passage.

2. The by-wire vehicle hydraulic brake system according to claim 1, wherein the pressure-boosting brake control oil passage includes a brushless motor and a pressure cylinder scalably connected to the brushless motor, the port of the pressure cylinder is connected to a plurality of pressure-boosting oil passages via a pressure supply oil passage, the plurality of pressure-boosting oil passages are connected to the reservoir tank via corresponding pressure-reducing oil passages, and the outlets of the plurality of pressure-boosting oil passages are connected to corresponding wheel brakes.

3. The drive-by-wire type hydraulic brake system for vehicles according to claim 2, characterized in that a pressure supply solenoid valve is provided in the pressure supply oil passage, a pressure boosting solenoid valve is provided in the pressure boosting oil passage, and a pressure reducing solenoid valve is provided in the pressure reducing oil passage.

4. The drive-by-wire vehicle hydraulic brake system according to claim 2, characterized in that the port of the pressure cylinder is connected to the fluid storage tank via a fluid supply passage, a fluid supply electric control valve or check valve is provided in the fluid supply passage, and a first pressure sensor is attached to the port of the pressure cylinder.

5. The drive-by-wire type hydraulic brake system for vehicles according to claim 2, characterized in that a decoupling isolation oil passage is connected between the pedal sensation control oil passage and the pressure boosting brake control oil passage, a decoupling isolation solenoid valve is installed in the decoupling isolation oil passage, the decoupling isolation oil passage is connected in parallel with the pressure supply oil passage, and the decoupling isolation oil passage is connected in series with a plurality of pressure boosting oil passages.

6. The by-wire type hydraulic brake system for vehicles according to claim 5, characterized in that a second pressure sensor is connected between the single-chamber type master cylinder and the decoupling isolation solenoid valve, between the pedal feel simulator and the decoupling isolation solenoid valve, or between the single-chamber type master cylinder and the pedal feel simulator.

7. The drive-by-wire vehicle hydraulic brake system according to claim 5, characterized in that one decoupling isolation oil passage and one pressure supply oil passage are provided, and the outlet of the decoupling isolation oil passage is connected to the corresponding wheel brake via four pressure boosting oil passages.

8. The drive-by-wire type hydraulic brake system for vehicles according to claim 5, characterized in that two decoupling isolation oil passages and two pressure supply oil passages are provided, one decoupling isolation solenoid valve is installed in each decoupling isolation oil passage, each decoupling isolation oil passage is connected in parallel with one pressure supply oil passage, and the outlet of each decoupling isolation oil passage is connected to two pressure boosting oil passages.

9. The by-wire type hydraulic brake system for vehicles according to claim 5, characterized in that a simulator isolation solenoid valve is connected between the single-chamber type master cylinder and the pedal feel simulator.

10. The by-wire vehicle hydraulic brake system according to claim 1, characterized in that the single-chamber master cylinder includes one chamber and two ports, one of which is connected to the fluid reservoir and the other port is connected to the pedal feel simulator and the pressure boosting brake control fluid passage.

11. This includes a control process for the basic brake, mechanical backup brake, and brake release. In the basic brake control process described above, when the brake pedal is pressed, brake fluid flows from the outlet port of the single-chamber master cylinder to the pedal feel simulator, generating pedal sensation. Simultaneously, the ECU controller sends a pressure boosting brake command to the pressure boosting brake control oil passage to brake the wheels, and controls the decoupling isolation solenoid valve to decouple and isolate the pedal sensation generation process and the pressure boosting brake process. In the control process of the aforementioned mechanical backup brake, if a failure occurs in the pressure-boosting brake control oil passage, the decoupling isolation solenoid valve opens, and when the brake pedal is pressed, brake fluid enters the four pressure-boosting oil passages from the single-chamber type master cylinder via the decoupling isolation oil passage, thereby braking the wheels. The control process for brake release is characterized in that when the brake pedal is released, the brake fluid in the pedal feel simulator is returned to the single-chamber type master cylinder, and at the same time, the ECU controller returns the piston of the pressure cylinder of the pressure boosting brake control oil passage and closes the fluid supply oil passage of the pressure cylinder, thereby quickly returning the high-pressure brake fluid to the pressure cylinder, as described in any one of claims 1 to 10.

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