Fluid power system and brake system

Abstract

To provide, as an example, a fluid power system that is able to reduce a load on a pressure source.SOLUTION: A fluid power system according to an embodiment includes a valve device having: a first check valve provided with a first flow passage connecting a first chamber connected to a pressure source and a second chamber connected to an actuating device, the first check valve being movable between a first open position and a first closed position and allowing a fluid to flow from the first chamber to the second chamber; and a movable component that is displaced relative to the first check valve in conjunction with actuation of the pressure source. The movable component is in a position to hold the first check valve in the first open position when the pressure source causes a pressure in the first chamber to be lower than a first pressure or while the pressure source is actuated to decrease the pressure in the first chamber, and the movable component is in a position to allow the first check valve to be placed in the first closed position when the pressure source causes the pressure in the first chamber to be higher than or equal to the first pressure or while the pressure source is actuated to increase the pressure in the first chamber.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present invention relate to fluid power systems and braking systems. [Background technology]

[0002] Conventionally, there is known a fluid power system in which a fluid is pressurized by an electric pressure source and an actuator is driven by the pressurized fluid. For example, in a brake system, an electric cylinder or pump pressurizes brake fluid to drive a wheel cylinder (Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] DE 102017214859 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the conventional configuration, the pressure source continues to pressurize the fluid to maintain the desired pressure while the actuator is continuously driven, which may result in a large load on the pressure source.

[0005] In view of the above, the present invention provides a fluid power system and a brake system that can reduce the load on the pressure source. [Means for solving the problem]

[0006] As an example, a fluid power system according to an embodiment of the present invention includes a pressure source configured to be driven electrically to pressurize or depressurize a fluid, an actuator connected to the pressure source and configured to be driven by the fluid pressurized by the pressure source, a first chamber connected to the pressure source, a second chamber connected to the actuator, and a first flow path connecting the first chamber and the second chamber, a first check valve movable between a first open position that opens the first flow path and a first closed position that closes the first flow path and allowing the fluid to flow from the first chamber to the second chamber through the first flow path, and and a valve device having a movable part configured to be displaced relative to the first check valve in response to actuation of the pressure source, the movable part being configured to be in a position to hold the first check valve in the first open position at least one of when the pressure source is lowering the pressure of the fluid in the first chamber below a first pressure and when actuated to depressurize the fluid in the first chamber, and to be in a position to allow the first check valve to be disposed in the first closed position at least one of when the pressure source is increasing the pressure of the fluid in the first chamber to equal to or greater than the first pressure and when actuated to pressurize the fluid in the first chamber. Thus, as an example, when the pressure source pressurizes the fluid in the first chamber, the fluid flows from the first chamber to the second chamber through a first flow path. When the pressure source reduces the pressure of the fluid in the first chamber from a state in which the pressure of the fluid in the first chamber and the second chamber is higher than the first pressure to a predetermined pressure equal to or higher than the first pressure, the first check valve is placed in a first closed position due to the pressure difference between the first chamber and the second chamber. The first check valve maintains the pressure difference between the first chamber and the second chamber by blocking the first flow path. That is, the fluid power system can reduce the pressure of the first chamber and the pressure source to a value close to the first pressure while maintaining the pressure of the second chamber and the actuator at the desired high pressure. This reduces the load on the pressure source while the second chamber is maintained at the desired high pressure. [Brief description of the drawings]

[0007] [Figure 1]FIG. 1 is a diagram illustrating a schematic configuration of a brake system according to a first embodiment. [Diagram 2] FIG. 2 is a cross-sectional view showing the valve device of the first embodiment. [Diagram 3] FIG. 3 is a cross-sectional view showing an example of the valve device according to the first embodiment, in which the valve element is in a valve-closed position. [Figure 4] FIG. 4 is a graph showing an example of pressure changes in the upstream chamber and the downstream chamber in the first embodiment. [Diagram 5] FIG. 5 is a cross-sectional view showing an example of the valve device according to the first embodiment when the pressure in the upstream chamber is equal to or higher than one boundary pressure. [Figure 6] FIG. 6 is a cross-sectional view showing an example of the valve device according to the first embodiment when the pressure in the upstream chamber is equal to or higher than another boundary pressure. [Figure 7] FIG. 7 is a cross-sectional view illustrating an example of the valve device during pressure adjustment according to the first embodiment. [Figure 8] FIG. 8 is a diagram showing a schematic configuration of a fluid power system according to the second embodiment. [Figure 9] FIG. 9 is a diagram showing a schematic configuration of a fluid power system according to the third embodiment. [Figure 10] FIG. 10 is a schematic diagram showing a cross section of the valve device and a front view of the transmission mechanism in a state where the movable part according to the fourth embodiment is in a position that "allows the valve element to be disposed in the valve closed position." [Figure 11] FIG. 11 is a schematic diagram showing a cross section of the valve device and a front view of the transmission mechanism in a fourth embodiment in which the movable part is in a position in which the valve element is held in the valve open position. [Figure 12] FIG. 12 is a graph showing an example of pressure changes in the upstream chamber and the downstream chamber of the fourth embodiment. [Figure 13] FIG. 13 is a schematic diagram showing a cross section of the valve gear and a front view of the transmission mechanism in a state where the second rotating body of the fourth embodiment has rotated through the boundary angle. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] (First embodiment) The first embodiment will be described below with reference to FIGS. 1 to 7. In this specification, the vertically upward direction is basically defined as the upward direction, and the vertically downward direction is basically defined as the downward direction. In this specification, the components according to the embodiment and the explanation of the components may be described in a plurality of ways. The components and their explanations are merely examples and are not limited by the expressions in this specification. The components may be specified by names different from those in this specification. The components may be described by expressions different from those in this specification.

[0009] In the following description, "suppress" is defined as, for example, preventing the occurrence of an event, action, or influence, or reducing the severity of an event, action, or influence. Also, in the following description, "restrict" is defined as, for example, preventing movement or rotation, or allowing movement or rotation within a predetermined range and preventing movement or rotation beyond the predetermined range.

[0010] 1 is a diagram illustrating a schematic configuration of a brake system 10 according to a first embodiment. The brake system 10 is mounted on a vehicle 1 such as a four-wheeled automobile. However, the brake system 10 is not limited to this example. The brake system 10 brakes the vehicle 1.

[0011] As shown in Fig. 1, a brake system 10 has a fluid power system 11. The fluid power system 11 is a drive system that uses a fluid as a pressure medium. In this embodiment, the fluid power system 11 is a hydraulic system that uses brake fluid as a pressure medium. However, the fluid power system 11 is not limited to this example. Brake fluid is an example of a fluid.

[0012] The fluid power system 11 includes four wheel cylinders 21FL, 21FR, 21RL, and 21RR, a plurality of brake pads 22, a brake pedal 23, and a brake control device 24. The wheel cylinders 21RL and 21RR are an example of an actuator and a wheel cylinder. The actuator may be another device that is driven by a pressurized fluid.

[0013] Each of the wheel cylinders 21FL, 21FR, 21RL, and 21RR is mounted, for example, on a caliper together with the corresponding brake pad 22. Each of the wheel cylinders 21FL, 21FR, 21RL, and 21RR presses the brake pad 22 in response to the pressure of the brake fluid.

[0014] The wheel cylinders 21FL, 21FR press the brake pads 22 against the rotor 5 which rotates integrally with the front wheels, generating a braking force for the front wheels. The wheel cylinders 21RL, 21RR press the brake pads 22 against the rotor 5 which rotates integrally with the rear wheels, generating a braking force for the rear wheels.

[0015] The brake pedal 23 is disposed inside the vehicle 1 and is operated by the driver by stepping on it. The brake control device 24 adjusts the pressure of the wheel cylinders 21FL, 21FR, 21RL, and 21RR based on the amount of operation of the brake pedal 23, thereby controlling the braking force of the vehicle 1.

[0016] The brake control device 24 includes an upstream unit 31, a downstream unit 32, and an electronic control unit (ECU) 33. The upstream unit 31 may also be referred to as a hydraulic pressure generating device. The downstream unit 32 may also be referred to as a brake actuator. The ECU 33 is an example of a control device.

[0017] The upstream unit 31 includes a reservoir tank 41, a master cylinder 42, a stroke simulator 43, a pressure source 44, a plurality of control valves 51, 52, 53, and 54, and a check valve (check valve) 55.

[0018] Brake fluid is stored in the reservoir tank 41. The reservoir tank 41 is, for example, open to the atmosphere. Therefore, the pressure of the brake fluid in the reservoir tank 41 is approximately equal to atmospheric pressure.

[0019] The master cylinder 42 has a main cylinder 61, a cover cylinder 62, a master piston 63, an input piston 64, a master spring 65, and an input spring 66. It should be noted that the master cylinder 42 is not limited to this example.

[0020] The main cylinder 61 has a bottom wall 61a, a first peripheral wall 61b, a second peripheral wall 61c, and a first annular wall 61d. The bottom wall 61a is provided at an end of the master cylinder 42 in the axial direction. The first peripheral wall 61b is formed in a substantially cylindrical shape extending in the axial direction from the bottom wall 61a. The second peripheral wall 61c is formed in a substantially cylindrical shape extending in the axial direction from the first peripheral wall 61b. The second peripheral wall 61c has a larger inner diameter than the first peripheral wall 61b. The first annular wall 61d protrudes from an end of the second peripheral wall 61c in the axial direction toward the central axis of the master cylinder 42.

[0021] The master piston 63 is attached to the main cylinder 61 so as to be slidable in the axial direction of the master cylinder 42. A portion of the master piston 63 is fitted inside the first annular wall 61d. A master chamber Rm is provided in the main cylinder 61. The master chamber Rm is defined by, for example, a bottom wall 61a, a first peripheral wall 61b, and the master piston 63.

[0022] Hereinafter, the direction of movement of the master piston 63 that decreases the volume of the master chamber Rm will be referred to as the "forward direction," and the direction of movement of the master piston 63 that increases the volume of the master chamber Rm will be referred to as the "rearward direction."

[0023] The main cylinder 61 is further provided with a first fluid chamber R1 and a servo chamber Rs. The first fluid chamber R1 is formed, for example, by a second peripheral wall 61c and a master piston 63. The first fluid chamber R1 is located behind the master chamber Rm. The servo chamber Rs is formed, for example, by the second peripheral wall 61c, a first annular wall 61d, and the master piston 63.

[0024] The servo chamber Rs is located behind the first liquid chamber R1. The master chamber Rm, the first liquid chamber R1, and the servo chamber Rs are separated from each other. The cross-sectional areas of the master chamber Rm and the servo chamber Rs are approximately equal to each other.

[0025] The cover cylinder 62 has a third peripheral wall 62a and a second annular wall 62b. The third peripheral wall 62a is formed in a cylindrical shape extending from the first annular wall 61d in the axial direction of the master cylinder 42. The second annular wall 62b protrudes from an end of the third peripheral wall 62a in the axial direction of the master cylinder 42 toward the central axis of the master cylinder 42.

[0026] The input piston 64 is attached to the cover cylinder 62 so as to be slidable in the axial direction of the master cylinder 42. A portion of the input piston 64 is fitted inside the second annular wall 62b.

[0027] A second liquid chamber R2 is provided in the cover cylinder 62. The second liquid chamber R2 is formed by, for example, a first annular wall 61d, a third peripheral wall 62a, and a second annular wall 62b. The second liquid chamber R2 is located behind the servo chamber Rs.

[0028] The rear end of the master piston 63 protrudes rearward from the first annular wall 61d and is located in the second liquid chamber R2. The area of ​​the master piston 63 disposed in the second liquid chamber R2 and the cross-sectional area of ​​the first liquid chamber R1 are approximately equal to each other.

[0029] A rear end of the input piston 64 protrudes rearward from the second annular wall 62b and is located outside the cover cylinder 62. Outside the cover cylinder 62, the input piston 64 is connected to the brake pedal 23. In response to the amount of operation of the brake pedal 23, the input piston 64 moves forward and approaches the master piston 63.

[0030] The master spring 65 is disposed in the master chamber Rm between the bottom wall 61a and the master piston 63. The master spring 65 pushes the master piston 63 rearward. The input spring 66 is disposed in the second fluid chamber R2 between the first annular wall 61d and the input piston 64. The input spring 66 pushes the input piston 64 rearward.

[0031] When the master piston 63 is disposed in the initial position, the master chamber Rm is connected to the reservoir tank 41. For example, the master chamber Rm is connected to the reservoir tank 41 through a port formed in the first peripheral wall 61b.

[0032] On the other hand, when the master piston 63 moves forward from the initial position, the master piston 63 blocks communication between the master chamber Rm and the reservoir tank 41. Therefore, the pressure in the master chamber Rm increases as the master piston 63 moves forward. For example, the master piston 63 is driven forward by the pressure in the servo chamber Rs.

[0033] The master chamber Rm is connected to the downstream unit 32 through a flow path C1. For example, the master chamber Rm is connected to the wheel cylinders 21FL, 21FR through the flow path C1. The first fluid chamber R1 is connected to the second fluid chamber R2 through a flow path C2. The flow path C2 is connected to the reservoir tank 41 through a flow path C3.

[0034] The control valve 51 is, for example, a normally closed solenoid valve, and is provided in the flow path C2 between the second liquid chamber R2 and the flow path C3. The control valve 52 is, for example, a normally open solenoid valve, and is provided in the flow path C3. While the ECU 33 is operating, the control valve 51 is opened and the control valve 52 is closed.

[0035] The stroke simulator 43 is provided in the flow path C2 between the first fluid chamber R1 and the control valve 51. The stroke simulator 43 generates a reaction force corresponding to the amount of operation of the brake pedal .

[0036] For example, the stroke simulator 43 has a piston pushed by a spring. When brake fluid is supplied to the stroke simulator 43, the spring pushes the piston, increasing the pressure of the brake fluid.

[0037] When the control valve 51 is open and the control valve 52 is closed, the input piston 64 moves forward by operating the brake pedal 23, and the volume of the second fluid chamber R2 decreases. As a result, brake fluid is supplied from the second fluid chamber R2 through the flow path C2 to the stroke simulator 43. As a result, the pressure in the stroke simulator 43 increases, and the pressures in the first fluid chamber R1 and the second fluid chamber R2 connected to the stroke simulator 43 also increase to the same value. Note that since the pressures in the first fluid chamber R1 and the second fluid chamber R2 are approximately the same, the master piston 63 is stationary.

[0038] The pressure source 44 is an electric device and is controlled, for example, by the ECU 33. The pressure source 44 can adjust the pressure of the wheel cylinders 21FL, 21FR, 21RL, and 21RR.

[0039] The pressure source 44 of the present embodiment includes, for example, an electric cylinder 70. However, the pressure source 44 is not limited to this example. The electric cylinder 70 includes a cylinder 71, a piston 72, a rotary-linear motion conversion mechanism 73, a motor 74, and a reduction mechanism 75.

[0040] The cylinder 71 has a bottom wall 71a and a peripheral wall 71b. The bottom wall 71a is provided at one end in the axial direction of the electric cylinder 70. The peripheral wall 71b is formed in a substantially cylindrical shape extending in the axial direction of the electric cylinder 70 from the bottom wall 71a.

[0041] The piston 72 is attached to the cylinder 71 so as to be slidable in the axial direction of the electric cylinder 70. A liquid chamber Re is provided in the cylinder 71. The liquid chamber Re is an example of a fluid chamber. The liquid chamber Re is formed by, for example, a bottom wall 71a, a peripheral wall 71b, and the piston 72. Therefore, the piston 72 changes the volume of the liquid chamber Re by moving.

[0042] Hereinafter, the moving direction of the piston 72 that decreases the volume of the fluid chamber Re is also referred to as "forward". In addition, the moving direction of the piston 72 that increases the volume of the fluid chamber Re is also referred to as "rearward". Note that "forward" and "rearward" in the electric cylinder 70 and "forward" and "rearward" in the master cylinder 42 may be different directions.

[0043] When the piston 72 is disposed at the initial position, the liquid chamber Re is connected to the reservoir tank 41 through the flow passage C4. For example, the liquid chamber Re is connected to the flow passage C4 through a port provided in the peripheral wall 71b. The flow passage C4 connects the port to the reservoir tank 41.

[0044] On the other hand, when the piston 72 moves forward, the piston 72 blocks communication between the liquid chamber Re and the reservoir tank 41. Therefore, as the piston 72 moves forward, the pressure in the liquid chamber Re increases.

[0045] The rotary / linear motion conversion mechanism 73 is, for example, a ball screw. The rotary / linear motion conversion mechanism 73 has, for example, a rotating member 73a, a linear motion member 73b, and a plurality of balls 73c. ​​The rotating member 73a may also be referred to as a screw shaft. The linear motion member 73b may also be referred to as a nut.

[0046] The rotating member 73a is formed in a cylindrical shape extending along the central axis of the electric cylinder 70. A male screw 73d is provided on the rotating member 73a. The male screw 73d is an example of a first screw thread.

[0047] The linear motion member 73b is formed in a substantially cylindrical shape extending in the axial direction of the electric cylinder 70. The linear motion member 73b is attached to a piston 72, or the piston 72 supporting the piston 72 is located between the bottom wall 71a and the linear motion member 73b.

[0048] The linear motion member 73b is provided with a female screw 73e. The female screw 73e is an example of a second screw thread. The linear motion member 73b may further be provided with a circulation path that connects both ends of the female screw 73e.

[0049] The balls 73c are, for example, held by a female screw 73e so as to be able to roll and rotate, and are fitted into a male screw 73d. Therefore, the female screw 73e is attached to the male screw 73d via the balls 73c.

[0050] The motor 74 is disposed outside the cylinder 71. The speed reduction mechanism 75 of this embodiment has, for example, a plurality of gears that mesh with each other. One gear of the speed reduction mechanism 75 is attached to the rotating member 73a, and the other gear is attached to the output shaft of the motor 74. The speed reduction mechanism 75 transmits the rotation of the motor 74 to the rotating member 73a.

[0051] The fluid chamber Re is connected to the downstream unit 32 through the flow path C5. For example, the fluid chamber Re is connected to the wheel cylinders 21RL, 21RR through the flow path C5. That is, the wheel cylinders 21RL, 21RR are connected to a pressure source 44. The pressure source 44 is provided between the flow path C4 and the flow path C5.

[0052] The servo chamber Rs is connected to the flow path C5 through the flow path C6. The control valve 53 and the check valve 55 are provided in the flow path C6. The control valve 53 is an electromagnetic valve that adjusts the differential pressure between a portion of the flow path C6 between the control valve 53 and the servo chamber Rs and a portion of the flow path C6 between the control valve 53 and the pressure source 44. The control valve 53 can adjust the amount of brake fluid supplied from the pressure source 44 to the servo chamber Rs.

[0053] The check valve 55 is provided in parallel with the control valve 53 in the flow path C6. The check valve 55 allows the flow of brake fluid from the servo chamber Rs to the flow path C5. On the other hand, the check valve 55 blocks the flow of brake fluid from the pressure source 44 and the flow path C5 to the servo chamber Rs.

[0054] The motor 74 of the electric cylinder 70 is driven by electricity. The motor 74 rotates the output shaft in one direction to rotate the rotating member 73a via the reduction mechanism 75. The linear moving member 73b moves forward in response to the rotation of the rotating member 73a. The linear moving member 73b pushes the piston 72 so that the volume of the fluid chamber Re decreases. As a result, the electric cylinder 70 pressurizes the brake fluid in the fluid chamber Re.

[0055] On the other hand, when the motor 74 rotates the output shaft in the reverse direction, the linear motion member 73b moves rearward in response to the rotation of the rotating member 73a. The piston 72 moves rearward in response to the movement of the linear motion member 73b. This causes the electric cylinder 70 to reduce the pressure of the brake fluid in the fluid chamber Re.

[0056] The flow path C4 is connected to the flow path C5 through a flow path C7. The flow path C7 is connected to the flow path C5 between the pressure source 44 and the flow path C6. The control valve 54 is a normally closed solenoid valve and is provided in the flow path C7.

[0057] The upstream unit 31 further includes a stroke sensor 81 and a plurality of pressure sensors 82, 83, and 84. The stroke sensor 81 detects the amount of operation of the brake pedal 23. The pressure sensor 82 is provided, for example, in the flow path C1 and detects the pressure of the master chamber Rm. The pressure sensor 83 is provided, for example, in the flow path C2 between the second fluid chamber R2 and the control valve 51 and detects the pressure of the second fluid chamber R2. The pressure sensor 83 is provided, for example, in the flow path C5 between the pressure source 44 and the flow path C6.

[0058] The downstream unit 32 can adjust the pressures of the wheel cylinders 21FL, 21FR, 21RL, and 21RR individually. The downstream unit 32 has a front wheel control unit 91 and a rear wheel control unit 92.

[0059] The front wheel control unit 91 adjusts the pressure in the wheel cylinders 21FL, 21FR to adjust the braking force on the front wheels, while the rear wheel control unit 92 adjusts the pressure in the wheel cylinders 21RL, 21RR to adjust the braking force on the rear wheels.

[0060] The ECU 33 includes, for example, a CPU and a memory. The memory stores a control program executed by the CPU. The ECU 33 controls, for example, the motor 74 of the pressure source 44 and the plurality of control valves 51, 52, 53, and 54 as a result of the CPU executing the control program. Furthermore, the ECU 33 acquires detection signals from a stroke sensor 81 and pressure sensors 82, 83, and 84.

[0061] The ECU 33 calculates a target braking force based on the operation amount of the brake pedal 23. The ECU 33 controls the motor 74 and the control valve 53 of the pressure source 44 based on the target braking force. For example, the ECU 33 causes the pressure source 44 to pressurize the brake fluid.

[0062] The pressure source 44 pressurizes the brake fluid in the fluid chamber Re to supply the brake fluid to the wheel cylinders 21RL, 21RR via the flow path C5. The wheel cylinders 21RL, 21RR are driven by the brake fluid pressurized by the pressure source 44, and press the brake pads 22 against the rotor 5 to generate a braking force on the rear wheels.

[0063] Furthermore, the ECU 33 adjusts the pressure in the servo chamber Rs by the control valve 53. The pressure in the servo chamber Rs drives the master piston 63 forward. This pressurizes the brake fluid in the master chamber Rm and supplies it to the wheel cylinders 21FL, 21RR via the flow path C1. The wheel cylinders 21FL, 21FR are driven by the brake fluid indirectly pressurized by the pressure source 44, and press the brake pads 22 against the rotor 5 to generate a braking force on the front wheels.

[0064] The upstream unit 31 further includes a valve device 100. The valve device 100 is provided in the flow path C5 between the pressure source 44 and the pressure sensor 84. That is, the valve device 100 is interposed between the pressure source 44 and the wheel cylinders 21RL, 21RR.

[0065] Fig. 2 is a cross-sectional view showing the valve device 100 of the first embodiment. As shown in Fig. 2, the upstream unit 31 further includes a housing 31a. The housing 31a is, for example, a metal block, and is provided with a flow path C5.

[0066] The housing 31a is further provided with a mounting hole Hf. The mounting hole Hf is a recess that is open to the outside of the housing 31a. The valve device 100 is attached to the housing 31a by being fitted into the mounting hole Hf.

[0067] The mounting hole Hf extends along the central axis Ax of the valve device 100 and has a substantially circular cross section. In the following description, the direction along the central axis Ax is defined as the axial direction, the direction perpendicular to the central axis Ax is defined as the radial direction, and the direction around the central axis Ax is defined as the circumferential direction.

[0068] The axial direction includes a first axial direction D1 and a second axial direction D2. The second axial direction D2 is opposite to the first axial direction D1. The mounting hole Hf is recessed from the surface of the housing 31a in the first axial direction D1.

[0069] The flow passage C5 has an upstream flow passage Cu and a downstream flow passage Cd. The upstream flow passage Cu is a portion of the flow passage C5 between the mounting hole Hf and the fluid chamber Re of the pressure source 44. The downstream flow passage Cd is a portion of the flow passage C5 between the mounting hole Hf and the wheel cylinders 21RL, 21RR. The upstream flow passage Cu communicates with the mounting hole Hf at a position spaced from the downstream flow passage Cd in the second axial direction D2.

[0070] The valve device 100 is provided with an upstream chamber Ru, a downstream chamber Rd, and an atmospheric chamber Ra. The upstream chamber Ru is an example of a first chamber. The downstream chamber Rd is an example of a second chamber. The upstream chamber Ru is connected to the fluid chamber Re of the pressure source 44 through an upstream flow passage Cu. The downstream chamber Rd is connected to the wheel cylinders 21RL, 21RR through a downstream flow passage Cd.

[0071] The atmospheric chamber Ra is connected to the reservoir tank 41 through, for example, a flow path C8. This allows the pressure in the atmospheric chamber Ra to be kept at atmospheric pressure. The atmospheric chamber Ra may be open to the outside of the housing 31a.

[0072] The valve device 100 includes a frame 101, a check valve 102, a movable part 103, springs 104 and 105, and a seal 106. The frame 101 includes a filter 111, a seat valve 112, a plug 113, and a stopper 114.

[0073] The filter 111 has an end wall 111a and a peripheral wall 111b. The end wall 111a is located at an end of the mounting hole Hf in the first axial direction D1. The peripheral wall 111b is formed in a substantially cylindrical shape extending from the end wall 111a in the second axial direction D2. The peripheral wall 111b covers the downstream flow passage Cd that opens into the mounting hole Hf.

[0074] For example, a mesh is provided on the peripheral wall 111b. The brake fluid can flow between the downstream chamber Rd and the downstream flow path Cd through the mesh of the filter 111. The mesh of the filter 111 collects foreign matter that gets mixed into the brake fluid.

[0075] The seat valve 112 is formed in a generally cylindrical shape extending along the central axis Ax. The seat valve 112 is located between the upstream flow passage Cu and the downstream flow passage Cd that open into the mounting hole Hf. The seat valve 112 is attached to the housing 31a and the peripheral wall 111b of the filter 111 by, for example, press fitting. The seat valve 112 has an inner surface 112a and a seat surface 112b.

[0076] The inner surface 112a is a generally cylindrical curved surface extending along the central axis Ax. The seating surface 112b is connected to an end of the inner surface 112a in the first axial direction D1. The seating surface 112b is a generally conical curved surface tapering toward the second axial direction D2.

[0077] The plug 113 is spaced apart in the second axial direction D2 from the seat valve 112. The plug 113 is attached to the housing 31a by, for example, crimping. As a result, the plug 113 liquid-tightly closes the mounting hole Hf.

[0078] The plug 113 has an end wall 113a and a peripheral wall 113b. The end wall 113a is located at an end of the mounting hole Hf in the second axial direction D2. The peripheral wall 113b is formed in a generally cylindrical shape extending from the end wall 113a in the first axial direction D1.

[0079] The stopper 114 is spaced apart from the seat valve 112 in the second axial direction D2 and is formed in a generally cylindrical shape extending along the central axis Ax. The stopper 114 is located between the seat valve 112 and the plug 113 and is attached to the peripheral wall 113b of the plug 113 by, for example, press fitting.

[0080] The stopper 114 has an inner surface 114a and a protrusion 114b. The inner surface 114a is a substantially cylindrical curved surface extending along the central axis Ax. The protrusion 114b protrudes from an end of the inner surface 114a in the first axial direction D1 toward the central axis Ax. The protrusion 114b is formed in a substantially annular shape.

[0081] The check valve 102 is disposed in the downstream chamber Rd so as to be movable in the axial direction. The check valve 102 has two valve bodies 121 and 122. The valve body 121 is an example of a second check valve. The valve body 122 is an example of a first check valve. The check valve 102 may have one valve body, or may have three or more valve bodies.

[0082] The valve body 121 is provided with a storage chamber Rh and two orifices O1 and O2. The orifice O2 is an example of a first flow path. The storage chamber Rh is provided inside the valve body 121. The orifice O1 communicates an end of the storage chamber Rh in the first axial direction D1 with the outside of the valve body 121. The orifice O2 communicates an end of the storage chamber Rh in the second axial direction D2 with the outside of the valve body 121. The diameters of the orifices O1 and O2 are smaller than the diameter of the storage chamber Rh. The storage chamber Rh and the orifice O1 are included in the downstream chamber Rd. The orifice O2 connects the upstream chamber Ru with the storage chamber Rh included in the downstream chamber Rd.

[0083] The valve element 121 is located between the end wall 111a of the filter 111 and the seat valve 112. The valve element 121 is supported, for example, by the peripheral wall 111b of the filter 111 so as to be axially slidable. The valve element 121 has a contact surface 121a and a seat surface 121b.

[0084] The contact surface 121a is formed in a substantially hemispherical shape and faces the seat surface 112b of the seat valve 112. The contact surface 121a can contact the seat surface 112b over the entire circumference in the circumferential direction. The seat surface 121b is located between the accommodation chamber Rh and the orifice O2. The seat surface 121b is a substantially conical curved surface tapering toward the second axial direction D2. The inner diameter of the seat surface 121b is smaller than the inner diameter of the seat surface 112b of the seat valve 112.

[0085] When the contact surface 121a is separated from the seat surface 112b of the seat valve 112, a substantially annular gap G is provided between the contact surface 121a and the seat surface 112b. The gap G is an example of a second flow path, and connects the upstream chamber Ru and the downstream chamber Rd.

[0086] The valve body 122 is, for example, a ball. However, the valve body 122 is not limited to this example. The valve body 122 is accommodated in the accommodation chamber Rh so as to be movable in the axial direction. The diameter of the valve body 122 is smaller than the diameter of the accommodation chamber Rh and larger than the diameters of the orifices O1 and O2. The valve body 122 can contact the seat surface 121b of the valve body 121 over the entire circumference in the circumferential direction.

[0087] Fig. 3 is a cross-sectional view showing an example of the valve device 100 in which the valve bodies 121, 122 of the first embodiment are in the valve closing positions Pcv, Pcb. The valve body 121 is movable between the valve opening position Pov shown in Fig. 2 and the valve closing position Pcv shown in Fig. 3. The valve opening position Pov is an example of a second valve opening position. The valve closing position Pcv is an example of a second valve closing position.

[0088] 2, at the valve open position Pov, the valve element 121 is spaced from the seat surface 112b of the seat valve 112 in the first axial direction D1. Therefore, the valve element 121 at the valve open position Pov opens the gap G. On the other hand, as shown in FIG. 3, at the valve closed position Pcv, the contact surface 121a of the valve element 121 contacts the seat surface 112b of the seat valve 112. Therefore, the valve element 121 at the valve closed position Pcv closes the gap G.

[0089] The valve element 122 is movable between an open position Pob shown in Fig. 2 and a closed position Pcb shown in Fig. 3. The open position Pob is an example of a first open position. The closed position Pcb is an example of a first closed position.

[0090] As shown in FIG. 2, in the valve open position Pob, the valve element 122 is spaced from the seating surface 121b of the valve element 121 in the first axial direction D1. Therefore, the valve element 122 in the valve open position Pob opens the orifice O2. The valve element 122 located in the valve open position Pob may be in partial contact with the seating surface 121b. On the other hand, as shown in FIG. 3, in the valve closed position Pcb, the valve element 122 is in contact with the seating surface 121b of the valve element 121. Therefore, the valve element 122 in the valve closed position Pcb blocks the orifice O2.

[0091] The diameter of the gap G is larger than the diameter of the orifice O2. Therefore, when the valve element 121 is in the valve open position Pov and the valve element 122 is in the valve open position Pob, the opening area of ​​the gap G is larger than the opening area (cross-sectional area) of the orifice O2. In addition, when the valve element 121 is in the valve closed position Pcv and the valve element 122 is in the valve closed position Pcb, the contact area between the contact surface 121a of the valve element 121 and the seat surface 112b of the seat valve 112 is larger than the contact area between the valve element 122 and the seat surface 121b of the valve element 121.

[0092] The movable part 103 is disposed in the upstream chamber Ru so as to be movable in the axial direction. The movable part 103 has a piston 131 and a shaft 132. Note that the movable part 103 is not limited to this example.

[0093] The piston 131 is located between the end wall 113a of the plug 113 and the projection 114b of the stopper 114. The piston 131 is formed in a generally cylindrical shape extending along the central axis Ax. The diameter of the piston 131 is smaller than the diameter of the inner surface 114a of the stopper 114 and larger than the diameter of the projection 114b. Therefore, the piston 131 can move in the axial direction between the end wall 113a and the projection 114b while being guided by the inner surface 114a.

[0094] The shaft 132 is axially movable and located between the check valve 102 and the piston 131. The shaft 132 has, for example, a contact portion 132a, a guide portion 132b, and two drive protrusions 132c and 132d.

[0095] The contact portion 132a extends along the central axis Ax and is in contact with the piston 131. The contact portion 132a may be fixed to the piston 131. The diameter of the contact portion 132a is smaller than the inner diameter of the projection 114b of the stopper 114.

[0096] The guide portion 132b is connected to an end of the contact portion 132a in the first axial direction D1 and is disposed inside the seat valve 112. The guide portion 132b has, for example, a cross-shaped cross section. Therefore, the brake fluid can flow through the space between the inner surface 112a of the seat valve 112 and the guide portion 132b.

[0097] The diameter of the guide portion 132b is smaller than the diameter of the inner surface 112a of the seat valve 112. When the shaft 132 moves in the axial direction, the guide portion 132b is guided by the inner surface 112a.

[0098] Each of the drive protrusions 132c and 132d protrudes in the first axial direction D1 from an end of the guide portion 132b in the first axial direction D1. In the axial direction, the drive protrusion 132c is longer than the drive protrusion 132d.

[0099] The cross-sectional area of ​​the drive protrusion 132c is smaller than the cross-sectional area of ​​the orifice O2. The drive protrusion 132c is at least partially received in the orifice O2. That is, the drive protrusion 132c protrudes from the guide portion 132b toward the valve body 122. The drive protrusion 132d is radially spaced from the drive protrusion 132c. The drive protrusion 132d protrudes from the guide portion 132b toward the contact surface 121a of the valve body 121.

[0100] The spring 104 is disposed in the downstream chamber Rd. The spring 104 is compressed in the axial direction between the end wall 111a of the filter 111 and the valve body 121. The spring 104 presses the valve body 121 in the second axial direction D2 toward the seat surface 112b of the seat valve 112. That is, the spring 104 can drive the valve body 121 to the valve closing position Pcv.

[0101] The spring 105 is located in the atmospheric chamber Ra. The spring 105 is axially compressed between the end wall 113a of the plug 113 and the piston 131. The spring 105 pushes the piston 131 in the first axial direction D1. That is, the spring 105 can drive the piston 131 toward the check valve 102. The protrusion 114b of the stopper 114 abuts against the piston 131 to restrict the piston 131 from moving further.

[0102] The seal 106 is provided between the peripheral wall 113b of the plug 113 and the piston 131. The seal 106 includes, for example, an O-ring and a seal shaft provided between the O-ring and the piston 131.

[0103] The piston 131 is located between the upstream chamber Ru and the atmospheric chamber Ra. The seal 106 air-tightly seals between the upstream chamber Ru and the atmospheric chamber Ra so that the piston 131 is axially slidable.

[0104] The piston 131 is exposed to the upstream chamber Ru. Therefore, the piston 131 is pushed in the second axial direction D2 by the pressure of the upstream chamber Ru. When the difference between the pressure of the upstream chamber Ru and the pressure (atmospheric pressure) of the atmospheric chamber Ra becomes larger than the force of the spring 105, the pressure of the upstream chamber Ru drives the piston 131 in the second axial direction D2.

[0105] When driven by the pressure of the upstream chamber Ru, the piston 131 is displaced in the second axial direction D2 relative to the check valve 102. Since the distance between the check valve 102 and the piston 131 increases, the shaft 132 is also displaced in the second axial direction D2 relative to the check valve 102, for example, by gravity. That is, the movable part 103 is driven by the pressure of the brake fluid in the upstream chamber Ru and displaced relative to the check valve 102 (valve bodies 121, 122). Hereinafter, the pressure of the brake fluid in the upstream chamber Ru will be referred to as the pressure of the upstream chamber Ru. Also, the pressure of the brake fluid in the downstream chamber Rd will be referred to as the pressure of the downstream chamber Rd.

[0106] 2, when the pressure in the upstream chamber Ru and the downstream chamber Rd is at a minimum (for example, atmospheric pressure), the piston 131 is pushed in the first axial direction D1 by the spring 105 and abuts against the protrusion 114b of the stopper 114. At this time, the piston 131 pushes the shaft 132 in the first axial direction D1.

[0107] The driving protrusion 132c of the shaft 132 pushes the valve body 122 in the first axial direction D1 through the orifice O2. This causes the valve body 122 to move to the valve open position Pob, and the orifice O2 opens. Furthermore, the driving protrusion 132d of the shaft 132 pushes the valve body 121 in the first axial direction D1. This causes the valve body 121 to move to the valve open position Pov, and the gap G opens. The upstream chamber Ru and the downstream chamber Rd are connected to each other by the orifice O2 and the gap G, respectively.

[0108] The above-described valve device 100 can maintain the pressure in the wheel cylinders 21RL, 21RR at a predetermined high pressure even if the pressure of the pressure source 44 drops after the pressure source 44 has increased the pressure in the wheel cylinders 21RL, 21RR to the predetermined high pressure. The operation of the valve device 100 will be described below.

[0109] Fig. 4 is a graph showing an example of pressure changes in the upstream chamber Ru and the downstream chamber Rd in the first embodiment. In Fig. 4, the pressure Pru in the upstream chamber Ru is shown by a two-dot chain line, and the pressure Prd in the downstream chamber Rd is shown by a solid line. In the following description, the pressure Pru in the upstream chamber Ru is substantially equal to the pressure in the fluid chamber Re of the pressure source 44, and the pressure Prd in the downstream chamber Rd is substantially equal to the pressure in the wheel cylinders 21RL, 21RR.

[0110] When the brake pedal 23 is operated at time T1 when the pressures Pru, Prd in the upstream chamber Ru and the downstream chamber Rd are at their minimums (e.g., atmospheric pressure), the ECU 33 calculates a target braking force and drives the pressure source 44. As a result, the pressure source 44 pressurizes the brake fluid, and the brake fluid is supplied from the upstream flow path Cu to the upstream chamber Ru.

[0111] At time T1, as shown in Fig. 2, the valve element 121 is in the valve open position Pov, and the valve element 122 is in the valve open position Pob. Therefore, the brake fluid in the upstream chamber Ru flows into the downstream chamber Rd through the orifice O2 and the gap G. The brake fluid in the downstream chamber Rd is supplied to the wheel cylinders 21RL and 21RR through the downstream flow path Cd. This increases the pressure in the pressure source 44, the upstream chamber Ru, the downstream chamber Rd, and the wheel cylinders 21RL and 21RR.

[0112] When the pressure Pru in the upstream chamber Ru rises, the piston 131 is displaced in the second axial direction D2 by the pressure Pru in the upstream chamber Ru. In response to the displacement of the piston 131, the shaft 132 is also displaced in the second axial direction D2. That is, the movable part 103 is displaced relative to the valve bodies 121 and 122 in conjunction with the driving of the pressure source 44.

[0113] FIG. 5 is a cross-sectional view showing an example of the valve device 100 when the pressure Pru of the upstream chamber Ru of the first embodiment is equal to or higher than the boundary pressure Ptl. As shown in FIG. 5, when the pressure Pru of the upstream chamber Ru is equal to or higher than the boundary pressure Ptl, the movable part 103 is in a position that allows the valve body 121 to be disposed in the valve-closed position Pcv. In other words, when the pressure source 44 makes the pressure Pru of the upstream chamber Ru equal to or higher than the boundary pressure Ptl, the movable part 103 is in a position that allows the valve body 121 to be disposed in the valve-closed position Pcv. At this time, the valve body 121 can also be disposed in the valve-opened position Pov and functions as a check valve. The boundary pressure Ptl is an example of a second pressure.

[0114] For example, when the contact surface 121a of the valve body 121 is in contact with the seat surface 112b of the seat valve 112, the drive protrusion 132d of the shaft 132 is separated from the valve body 121. Note that the drive protrusion 132d may simply be in contact with the valve body 121 without any load.

[0115] At time T2 when the pressure Pru in the upstream chamber Ru rises to the boundary pressure Ptl, the rising pressure Pru in the upstream chamber Ru drives the valve body 121 in the first axial direction D1 against the force of the spring 104. Therefore, at time T2, the valve body 121 is in the valve open position Pov. That is, the valve body 121 allows the brake fluid to flow from the upstream chamber Ru to the downstream chamber Rd through the gap G.

[0116] FIG. 6 is a cross-sectional view showing an example of the valve device 100 when the pressure Pru of the upstream chamber Ru of the first embodiment is equal to or higher than the boundary pressure Pth. As shown in FIG. 6, when the pressure Pru of the upstream chamber Ru is equal to or higher than the boundary pressure Pth, the movable part 103 is in a position that allows the valve body 122 to be disposed in the valve-closed position Pcb. In other words, when the pressure source 44 makes the pressure Pru of the upstream chamber Ru equal to or higher than the boundary pressure Pth, the movable part 103 is in a position that allows the valve body 122 to be disposed in the valve-closed position Pcb. At this time, the valve body 122 can also be disposed in the valve-opened position Pob and functions as a check valve. The boundary pressure Pth is an example of a first pressure. The boundary pressure Ptl is lower than the boundary pressure Pth.

[0117] For example, when the valve body 122 is in contact with the seat surface 121b of the valve body 121, the drive protrusion 132c of the shaft 132 is separated from the valve body 122. Note that the drive protrusion 132c may simply be in contact with the valve body 122 without any load.

[0118] At time T3 when the pressure Pru in the upstream chamber Ru rises to the boundary pressure Pth, the rising pressure Pru in the upstream chamber Ru drives the valve body 122 in the first axial direction D1. Therefore, at time T3, the valve body 122 is in the valve open position Pob. That is, the valve body 122 allows the brake fluid to flow from the upstream chamber Ru to the downstream chamber Rd through the orifice O2.

[0119] The pressure source 44 increases the pressure in the fluid chamber Re, the upstream chamber Ru, the downstream chamber Rd, and the wheel cylinders 21RL, 21RR to a target pressure Pm. When the pressure in the wheel cylinders 21RL, 21RR is at the target pressure Pm, the wheel cylinders 21RL, 21RR can generate a target braking force.

[0120] Between time T3 and time T4 when the pressure Pru in the upstream chamber Ru and the pressure Prd in the downstream chamber Rd rise to the target pressure Pm, the piston 72 moves to its maximum in the second axial direction D2 as shown in Fig. 3. At this time, the drive projections 132c and 132d of the movable part 103 are separated from the valve bodies 121 and 122.

[0121] From time T4, the pressure source 44 moves the piston 72 rearward to reduce the pressure in the liquid chamber Re and the pressure Pru in the upstream chamber Ru to the maintained pressure Pk. The ECU 33 detects that the pressure Prd in the downstream chamber Rd has reached the target pressure Pm, for example, based on a detection signal from the pressure sensor 84. The maintained pressure Pk is higher than the boundary pressure Pth but lower than the target pressure Pm. For example, the difference between the maintained pressure Pk and the boundary pressure Pth is smaller than the difference between the maintained pressure Pk and the target pressure Pm.

[0122] When the pressure Pru in the upstream chamber Ru drops from the target pressure Pm, the pressure Prd in the downstream chamber Rd becomes greater than the pressure Pru in the upstream chamber Ru, causing a pressure difference between the upstream chamber Ru and the downstream chamber Rd. Therefore, as shown in FIG. 3, the pressure Prd in the downstream chamber Rd and the spring 104 drive the valve body 121 in the second axial direction D2. As a result, the valve body 121 is placed in the valve closing position Pcv, and the gap G is closed. That is, the valve body 121 restricts the brake fluid in the downstream chamber Rd from flowing through the gap G to the upstream chamber Ru.

[0123] Furthermore, the pressure Prd in the downstream chamber Rd drives the valve body 122 in the second axial direction D2. As a result, the valve body 122 is disposed in the valve closing position Pcb and the orifice O2 is blocked. That is, the valve body 122 restricts the brake fluid in the downstream chamber Rd from flowing through the orifice O2 to the upstream chamber Ru.

[0124] Since the gap G and the orifice O2 are blocked, the brake fluid in the downstream chamber Rd does not flow to the upstream chamber Ru. That is, even if the pressure Pru in the upstream chamber Ru drops, the pressure Prd in the downstream chamber Rd is substantially maintained at the target pressure Pm.

[0125] At time T5 when the pressure Pru in the upstream chamber Ru drops to the holding pressure Pk, the pressure source 44 stops the movement of the piston 72. The ECU 33 detects, for example, based on the rotation of the output shaft of the motor 74, that the pressure Pru in the upstream chamber Ru has substantially reached the holding pressure Pk.

[0126] Because the holding pressure Pk is higher than the boundary pressure Pth, the movable part 103 allows the valve element 121 to be disposed in the valve closed position Pcv and allows the valve element 122 to be disposed in the valve closed position Pcb. Due to the pressure difference between the upstream chamber Ru and the downstream chamber Rd, the valve element 121 is disposed in the valve closed position Pcv and the valve element 122 is also disposed in the valve closed position Pcb. In other words, while the pressure Pru of the upstream chamber Ru is maintained at the holding pressure Pk, the pressure Prd of the downstream chamber Rd is maintained at the target pressure Pm.

[0127] For example, at time T6 when the operation of the brake pedal 23 is released, the ECU 33 sets the target braking force to zero. The pressure source 44 moves the piston 72 further rearward, and reduces the pressure in the fluid chamber Re and the pressure Pru in the upstream chamber Ru to the valve opening pressure Po. The valve opening pressure Po is an example of a third pressure. The valve opening pressure Po is lower than the boundary pressure Pth and higher than the boundary pressure Ptl. Note that the valve opening pressure Po may be lower than the boundary pressure Ptl.

[0128] When the pressure Pru in the upstream chamber Ru decreases, the spring 105 displaces the piston 131 in the first axial direction D1 against the pressure Pru in the upstream chamber Ru. As the piston 131 is displaced, the shaft 132 is also displaced in the first axial direction D1.

[0129] FIG. 7 is a cross-sectional view showing an example of the valve device 100 during pressure adjustment according to the first embodiment. As shown in FIG. 7, when the pressure in the upstream chamber Ru becomes lower than the boundary pressure Pth, the driving protrusion 132c of the shaft 132 pulls the valve body 122 away from the seat surface 121b of the valve body 121. In other words, the driving protrusion 132c moves the valve body 122 to the valve open position Pob. While the pressure Pru in the upstream chamber Ru is lower than the boundary pressure Pth, the movable part 103 is in a position to hold the valve body 122 in the valve open position Pob. In other words, when the pressure source 44 makes the pressure Pru in the upstream chamber Ru lower than the boundary pressure Pth, the movable part 103 is in a position to hold the valve body 122 in the valve open position Pob.

[0130] When the valve element 122 is placed in the valve open position Pob, the orifice O2 opens, causing the brake fluid in the wheel cylinders 21RL, 21RR and the downstream chamber Rd to flow through the orifice O2 to the upstream chamber Ru and the pressure source 44.

[0131] From time T7 when the pressure Pru in the upstream chamber Ru drops to the valve opening pressure Po, the brake fluid flows from the downstream chamber Rd to the upstream chamber Ru through the orifice O2, the pressure Pru in the upstream chamber Ru rises, and the pressure in the downstream chamber Rd drops. Even after time T7, the pressure source 44 continues to move the piston 72 backward. Therefore, the absolute value of the increase in the pressure Pru in the upstream chamber Ru per hour is smaller than the absolute value of the decrease in the pressure Prd in the downstream chamber Rd per hour.

[0132] The opening area of ​​the orifice O2 is smaller than the opening area of ​​the gap G. The orifice O2 functions as a throttle and adjusts the flow rate of the brake fluid flowing from the downstream chamber Rd to the upstream chamber Ru. That is, the orifice O2 suppresses a sudden increase in the pressure Pru of the upstream chamber Ru.

[0133] When the brake fluid flowing from the downstream chamber Rd to the upstream chamber Ru increases the pressure Pru in the upstream chamber Ru, the pressure Pru in the upstream chamber Ru drives the piston 131 in the second axial direction D2. This displaces the movable part 103 in the second axial direction D2, and the gap between the valve body 122 and the seat surface 121b of the valve body 121 becomes smaller. In other words, the opening area of ​​the orifice O2 becomes smaller.

[0134] When the gap between the valve body 122 and the seating surface 121b of the valve body 121 becomes smaller, the flow rate of the brake fluid flowing from the downstream chamber Rd to the upstream chamber Ru through the orifice O2 decreases. That is, the narrowed gap between the valve body 122 and the seating surface 121b functions as a throttle. The reduction in the flow rate of the brake fluid makes it difficult for the pressure Pru in the upstream chamber Ru to increase, and the pressure source 44 reduces the pressure Pru in the upstream chamber Ru.

[0135] When the pressure Pru in the upstream chamber Ru drops, the spring 105 displaces the piston 131 in the first axial direction D1 against the pressure Pru in the upstream chamber Ru. This displaces the movable part 103 in the first axial direction D1, and the gap between the valve body 122 and the seat surface 121b of the valve body 121 increases. That is, the opening area of ​​the orifice O2 increases.

[0136] When the gap between the valve body 122 and the seat surface 121b of the valve body 121 becomes large, the flow rate of the brake fluid flowing from the downstream chamber Rd to the upstream chamber Ru through the orifice O2 increases. The increase in the flow rate of the brake fluid increases the pressure in the upstream chamber Ru.

[0137] As described above, the movable part 103 varies the opening amount of the orifice O2 (the gap between the valve body 122 and the seat surface 121b of the valve body 121) according to the pressure Pru of the upstream chamber Ru. In this way, the movable part 103 adjusts the pressure Pru of the upstream chamber Ru and suppresses a sudden increase in the pressure Pru of the upstream chamber Ru.

[0138] While the movable part 103 adjusts the pressure Pru in the upstream chamber Ru, the pressure Pru in the upstream chamber Ru may temporarily rise to the boundary pressure Pth, and the valve body 122 may be placed in the valve closed position Pcb. At this time, the force Fu with which the drive protrusion 132c presses the valve body 122 is balanced with the force Fd with which the pressure Prd in the downstream chamber Rd presses the valve body 122 against the seat surface 121b of the valve body 121.

[0139] The force Fu is expressed by the following equation (1). Fu = Fs - Sp · Pru ... (Number 1) In formula 1, Fs is the force with which the spring 105 pushes the piston 131. Sp is the area of ​​the piston 131 that receives the pressure Pru of the upstream chamber Ru.

[0140] The force Fd is expressed by the following equation (2). Fd = Sb (Prd - Pru) ... (Equation 2) In formula (2), Sb is the inner contact area between the valve body 122 and the seat surface 121b of the valve body 121.

[0141] When the pressure Pru in the upstream chamber Ru temporarily rises to the boundary pressure Pth, the valve body 122 is placed in the valve closing position Pcb, and the inflow of brake fluid from the downstream chamber Rd to the upstream chamber Ru temporarily stops. However, the pressure source 44 continues to move the piston 72 backward, and the pressure in the upstream chamber Ru decreases. In other words, the movable part 103 prevents the pressure Pru in the upstream chamber Ru from becoming greater than the boundary pressure Pth.

[0142] When the pressure Prd in the downstream chamber Rd drops to the boundary pressure Pth, the pressure Pru in the upstream chamber Ru also becomes the boundary pressure Pth. From time T8 when the pressures Pru, Prd in the upstream chamber Ru and the downstream chamber Rd both become the boundary pressure Pth, the pressures Pru, Prd in the upstream chamber Ru and the downstream chamber Rd both drop.

[0143] When the pressure Pru in the upstream chamber Ru falls below the boundary pressure Pth, the movable part 103 moves the valve body 122 to the valve open position Pob. This opens the orifice O2, but because the pressure Prd in the downstream chamber Rd is lower than the boundary pressure Pth, the pressure Pru in the upstream chamber Ru does not rise to the boundary pressure Pth. Therefore, as shown in FIG. 5, the movable part 103 holds the valve body 122 in the valve open position Pob.

[0144] At time T9 when the pressures Pru, Prd in the upstream chamber Ru and the downstream chamber Rd both reach the boundary pressure Ptl, the movable part 103 moves the valve body 121 to the valve open position Pov. As shown in FIG. 2, while the pressure Pru in the upstream chamber Ru is lower than the boundary pressure Ptl, the movable part 103 is in a position to hold the valve body 121 in the valve open position Pov. In other words, when the pressure source 44 makes the pressure Pru in the upstream chamber Ru lower than the boundary pressure Ptl, the movable part 103 is in a position to hold the valve body 121 in the valve open position Pov. Therefore, the brake fluid in the downstream chamber Rd flows to the upstream chamber Ru not only through the orifice O2 but also through the gap G. The pressures Pru, Prd in the upstream chamber Ru and the downstream chamber Rd both eventually drop to their minimum values.

[0145] In the above valve device 100, after time T4 when the pressures Pru, Prd in the upstream chamber Ru and the downstream chamber Rd are set to the target pressure Pm that is higher than the boundary pressure Pth, the pressure Prd in the downstream chamber Rd is maintained at the target pressure Pm between time T5 and time T6 when the pressure Pru in the upstream chamber Ru is set to a maintained pressure Pk that is lower than the target pressure Pm and equal to or higher than the boundary pressure Pth. The valve device 100 can mechanically maintain the pressure Prd in the downstream chamber Rd and the pressures in the wheel cylinders 21RL, 21RR in this manner without relying on electrical control.

[0146] Since the pressure Prd in the downstream chamber Rd and the pressures in the wheel cylinders 21RL and 21RR are maintained at the target pressure Pm, the wheel cylinders 21RL and 21RR can maintain the target braking force. Meanwhile, the pressure source 44 maintains the pressure Pru in the upstream chamber Ru at a relatively low holding pressure Pk, not the high target pressure Pm. Therefore, the load on the motor 74 of the pressure source 44 is reduced compared to when the pressure source 44 maintains the pressure Pru in the upstream chamber Ru at the target pressure Pm. That is, the heat generation and power consumption of the motor 74 are reduced. Furthermore, damage to the motor 74 and ECU 33 due to heat generation by the motor 74, and damage to the ECU 33 due to heat generation by the elements of the ECU 33 are suppressed.

[0147] Furthermore, for example, if the power supply to the ECU 33 is lost, the power supply to the motor 74 is also lost. In this case, if the pressure Pru in the upstream chamber Ru is high, the pressure Pru in the upstream chamber Ru rapidly moves the piston 72 and the linearly moving member 73b of the electric cylinder 70 backward. For example, there is a risk that the linearly moving member 73b will collide with the gear of the reduction mechanism 75 and be damaged. However, since the pressure Pru in the upstream chamber Ru is maintained at a relatively low holding pressure Pk, the piston 72 and the linearly moving member 73b are maintained in the same position or move slightly due to sliding resistance (friction). In other words, damage to the pressure source 44 is suppressed.

[0148] The holding pressure Pk is set so as to prevent damage to the pressure source 44 when power supply to the motor 74 is lost. For example, the holding pressure Pk is set based on the sliding resistance of the piston 72 and the linearly moving member 73b.

[0149] Furthermore, in the above valve device 100, from time T7 when the pressure Prd in the downstream chamber Rd is greater than the boundary pressure Pth and the pressure Pru in the upstream chamber Ru, which was equal to or greater than the boundary pressure Pth, is reduced to the valve-opening pressure Po, to time T8 when the pressures Pru, Prd in the upstream chamber Ru and the downstream chamber Rd become the boundary pressure Pth, the pressure Pru in the upstream chamber Ru is maintained between the boundary pressure Pth and the valve-opening pressure Po. The valve device 100 can mechanically adjust the pressure Pru in the upstream chamber Ru in this way, without relying on electrical control. Note that the pressure Pru in the upstream chamber Ru between time T7 and time T8 in FIG. 4 is shown as a straight line, but it fluctuates as described above.

[0150] For example, when the power supply to the motor 74 is lost, the pressure Pru in the upstream chamber Ru drops, and the brake fluid flows from the downstream chamber Rd to the upstream chamber Ru. However, the valve device 100 keeps the pressure Pru in the upstream chamber Ru between the boundary pressure Pth and the valve opening pressure Po between time T7 and time T8, and therefore suppresses a sudden increase in the pressure Pru in the upstream chamber Ru and the pressure in the fluid chamber Re of the electric cylinder 70. In other words, a sudden movement of the piston 72 and the linear moving member 73b due to a rise in the pressure Pru in the upstream chamber Ru is suppressed, and thus damage to the pressure source 44 is suppressed.

[0151] In the brake system 10 according to the first embodiment described above, the pressure source 44 is configured to pressurize or depressurize the brake fluid by being driven electrically. The wheel cylinders 21RL, 21RR are connected to the pressure source 44 and configured to be driven by the brake fluid pressurized by the pressure source 44. The valve device 100 is provided with an upstream chamber Ru connected to the pressure source 44, a downstream chamber Rd connected to the wheel cylinders 21RL, 21RR, and an orifice O2 connecting the upstream chamber Ru and the downstream chamber Rd. The valve device 100 has a valve body 122 and a movable part 103. The valve body 122 is movable between an open position Pob that opens the orifice O2 and a closed position Pcb that closes the orifice O2, and allows the brake fluid to flow from the upstream chamber Ru to the downstream chamber Rd through the orifice O2. The movable part 103 is configured to be displaced relative to the valve body 122 in conjunction with the driving of the pressure source 44. The movable part 103 is in a position to hold the valve element 122 in the open position Pob when the pressure source 44 makes the pressure in the upstream chamber Ru lower than the boundary pressure Pth. The movable part 103 is in a position to allow the valve element 122 to be disposed in the closed position Pcb when the pressure source 44 makes the pressure Pru in the upstream chamber Ru equal to or higher than the boundary pressure Pth.

[0152] When the pressure source 44 pressurizes the brake fluid in the upstream chamber Ru, the brake fluid flows from the upstream chamber Ru to the downstream chamber Rd through the orifice O2. When the pressure source 44 reduces the pressure Pru in the upstream chamber Ru to a predetermined holding pressure Pk equal to or higher than the boundary pressure Pth from a state in which the pressures Pru and Prd in the upstream chamber Ru and downstream chamber Rd are higher than the boundary pressure Pth, the valve body 122 is placed in the valve closed position Pcb due to the pressure difference between the upstream chamber Ru and the downstream chamber Rd. The valve body 122 maintains the pressure difference between the upstream chamber Ru and the downstream chamber Rd by closing the orifice O2. That is, the fluid power system 11 can reduce the pressure in the upstream chamber Ru and the pressure source 44 to a holding pressure Pk close to the boundary pressure Pth while maintaining the pressure in the downstream chamber Rd and the wheel cylinders 21RL and 21RR at the desired target pressure Pm. This reduces the load on the pressure source 44 while the pressure Prd in the downstream chamber Rd is maintained at the target pressure Pm. For example, heat generation from the motor 74 is reduced, which prevents various devices such as the ECU 33 from being damaged by the heat generated by the motor 74, and also reduces power consumption. Furthermore, since the pressure Pru in the upstream chamber Ru can be kept low, for example, in the event of a loss of power supply to the pressure source 44, the pressure Pru in the upstream chamber Ru is prevented from damaging the pressure source 44. Note that the fluid power system 11 can reduce the pressure in the downstream chamber Rd and the wheel cylinders 21RL, 21RR by the pressure source 44 lowering the pressure Pru in the upstream chamber Ru below the boundary pressure Pth.

[0153] The valve device 100 is provided with a gap G connecting the upstream chamber Ru and the downstream chamber Rd. The valve device 100 has a valve body 121. The valve body 121 is movable between an open position Pov that opens the gap G and a closed position Pcv that closes the gap G, and allows brake fluid to flow from the upstream chamber Ru to the downstream chamber Rd through the gap G. The movable part 103 is displaced relative to the valve body 121 in conjunction with the driving of the pressure source 44. The movable part 103 is in a position that holds the valve body 121 in the open position Pov when the pressure source 44 makes the pressure Pru in the upstream chamber Ru lower than a boundary pressure Ptl that is lower than the boundary pressure Pth. The movable part 103 is in a position that allows the valve body 121 to be disposed in the closed position Pcv when the pressure source 44 makes the pressure Pru in the upstream chamber Ru higher than the boundary pressure Ptl.

[0154] When the pressure source 44 makes the pressure Pru in the upstream chamber Ru lower than the boundary pressure Ptl, the movable part 103 holds the valve element 122 in the valve open position Pob and holds the valve element 121 in the valve open position Pov. On the other hand, when the pressure source 44 makes the pressure Pru in the upstream chamber Ru between the boundary pressure Pth and the boundary pressure Ptl, the movable part 103 holds the valve element 122 in the valve open position Pob, but allows the valve element 121 to be disposed in the valve closed position Pcv. That is, the lower the pressure Pru in the upstream chamber Ru, the larger the opening area of ​​the flow path (the orifice O2 and the gap G) that opens between the upstream chamber Ru and the downstream chamber Rd can be. As a result, the fluid power system 11 can adjust the speed and flow rate of the brake fluid flow from the downstream chamber Rd to the upstream chamber Ru by adjusting the pressure Pru in the upstream chamber Ru. Furthermore, because the opening area of ​​the flow passage between the upstream chamber Ru and the downstream chamber Rd is automatically adjusted by the pressure Pru in the upstream chamber Ru, the fluid power system 11 can suppress undesired sudden changes in the pressures Pru, Prd in the upstream chamber Ru and the downstream chamber Rd. For example, the fluid power system 11 can suppress damage to the pressure source 44 caused by a sudden rise in the pressure Pru in the upstream chamber Ru.

[0155] The movable part 103 is driven by the pressure Pru in the upstream chamber Ru. When the pressure Pru in the upstream chamber Ru is lower than the boundary pressure Pth, the movable part 103 is in a position that holds the valve disc 122 in the open position Pob. On the other hand, when the pressure Pru in the upstream chamber Ru is equal to or higher than the boundary pressure Pth, the movable part 103 is in a position that allows the valve disc 122 to be disposed in the closed position Pcb. As a result, the movable part 103 and the valve disc 122 are automatically displaced according to the actual pressure Pru in the upstream chamber Ru, so that the fluid power system 11 can suppress undesired fluctuations in the pressures Pru, Prd in the upstream chamber Ru and the downstream chamber Rd.

[0156] The pressure Pru of the upstream chamber Ru is maintained between the boundary pressure Pth and the valve opening pressure Po from when the pressure Prd of the downstream chamber Rd is higher than the boundary pressure Pth and the pressure Pru of the upstream chamber Ru, which is equal to or higher than the boundary pressure Pth, is set to the valve opening pressure Po, which is lower than the boundary pressure Pth, until the pressures Pru, Prd of the upstream chamber Ru and the downstream chamber Rd become the boundary pressure Pth. For example, when the pressure Pru of the upstream chamber Ru becomes the valve opening pressure Po by the pressurization suppression or depressurization drive of the pressure source 44, the brake fluid of the downstream chamber Rd flows into the upstream chamber Ru through the orifice O2 (through both the orifice O2 and the gap G when the valve opening pressure Po is lower than the boundary pressure Ptl), and the pressure Pru of the upstream chamber Ru rises. However, when the pressure Pru of the upstream chamber Ru rises to the boundary pressure Pth, the valve body 122 is disposed in the valve closing position Pcb. Therefore, the inflow of the brake fluid from the downstream chamber Rd to the upstream chamber Ru is restricted, and the further increase of the pressure Pru of the upstream chamber Ru is stopped. That is, the pressure Pru in the upstream chamber Ru does not become higher than the boundary pressure Pth. This allows the fluid power system 11 to suppress undesired sudden changes in the pressures Pru, Prd in the upstream chamber Ru and the downstream chamber Rd. For example, the fluid power system 11 can suppress damage to the pressure source 44 caused by a sudden increase in the pressure Pru in the upstream chamber Ru.

[0157] The seating surface 121b contacts the valve body 122 located at the valve closing position Pcb. The seating surface 112b contacts the valve body 121 located at the valve closing position Pcv. The contact area between the valve body 122 and the seating surface 121b is smaller than the contact area between the valve body 121 and the seating surface 112b. Therefore, when the pressure Prd in the downstream chamber Rd is higher than the pressure Pru in the upstream chamber Ru, the force with which the valve body 122 presses the seating surface 121b is smaller. Therefore, the movable part 103 can easily move the valve body 122 from the valve closing position Pcb to the valve opening position Pob, the spring 105 that presses the movable part 103 can be made smaller, the valve bodies 121 and 122 can be smoothly displaced, and wear of the movable part 103 and the valve bodies 121 and 122 is reduced.

[0158] The diameter of the gap G is larger than the diameter of the orifice O2. That is, the opening area of ​​the gap G is larger than the opening area of ​​the orifice O2. As a result, for example, when the pressure source 44 pressurizes the brake fluid, the brake fluid can quickly flow from the upstream chamber Ru to the downstream chamber Rd through the gap G. This improves the time (response) from when the pressure source 44 pressurizes the brake fluid to when the wheel cylinders 21RL, 21RR are driven.

[0159] The pressure source 44 is provided with a fluid chamber Re connected to the upstream chamber Ru. The pressure source 44 has a piston 72, a rotating member 73a, a ball 73c, a linear motion member 73b, and a motor 74. The piston 72 is configured to change the volume of the fluid chamber Re by moving. The rotating member 73a is provided with a male screw 73d. The linear motion member 73b is provided with a female screw 73e that is attached to the male screw 73d via a ball 73c, and moves in response to the rotation of the rotating member 73a. The motor 74 rotates the rotating member 73a. The pressure source 44 pressurizes the brake fluid in the fluid chamber Re by the linear motion member 73b pushing the piston 72 so that the volume of the fluid chamber Re is reduced.

[0160] If the power supply to the motor 74 is lost, the pressure Pru in the upstream chamber Ru will push the piston 72 and the linearly moving member 73b in a direction that expands the volume of the liquid chamber Re, but as described above, the fluid power system 11 can reduce the pressure Pru in the upstream chamber Ru from the target pressure Pm to the retained pressure Pk. Therefore, the fluid power system 11 can suppress sudden movement of the piston 72 and the linearly moving member 73b, and therefore can suppress the piston 72 and the linearly moving member 73b from colliding with other members and damage to the piston 72 and the linearly moving member 73b due to the collision.

[0161] The brake system 10 includes the fluid power system 11. As described above, the fluid power system 11 can reduce the pressure in the upstream chamber Ru and the pressure source 44 to a value close to the boundary pressure Pth while maintaining the pressure in the downstream chamber Rd and the wheel cylinders 21RL, 21RR at a desired high pressure. This allows the brake system 10 to reduce the load on the pressure source 44 while maintaining braking by the wheel cylinders 21RL, 21RR.

[0162] Second Embodiment The second embodiment will be described below with reference to Fig. 8. In the following description of the embodiments, components having the same functions as components already described are given the same reference numerals as the components already described, and further description may be omitted. Also, components given the same reference numerals do not necessarily have all the same functions and properties, and may have different functions and properties according to each embodiment.

[0163] 8 is a diagram showing a schematic configuration of a fluid power system 200 according to a second embodiment. The brake system 10 of the second embodiment has the fluid power system 200 instead of the fluid power system 11. The fluid power system 200 is substantially the same as the fluid power system 11, except for the points described below.

[0164] The fluid power system 200 has a master cylinder 201 and control valves 202, 203, 204, and 205 instead of the downstream unit 32, the master cylinder 42, the control valves 51, 52, 53, and 54, and the check valve 55.

[0165] The master cylinder 201 has a cylinder 211 and a piston 212. The piston 212 is attached to the cylinder 211 so as to be slidable in the axial direction of the master cylinder 201. When the piston 212 moves forward, the volume of a master chamber Rm provided in the cylinder 211 is reduced. The piston 212 is connected to the brake pedal 23.

[0166] The control valve 202 is also called, for example, a master cut valve, and is a normally open solenoid valve. The control valve 202 is connected to the master chamber Rm through a flow path C21. The stroke simulator 43 is connected to the flow path C21 through a flow path C22. The control valve 203 is also called, for example, a simulator cut valve, and is a normally closed solenoid valve. The control valve 203 is provided in the flow path C22.

[0167] The wheel cylinder 21FL is connected to the control valve 202 through a flow path C23. The control valve 204 is, for example, a normally open solenoid valve, and is provided in the flow path C23. The wheel cylinder 21FR is connected to the control valve 202 through a flow path C24. The control valve 205 is, for example, a normally open solenoid valve, and is provided in the flow path C24.

[0168] The fluid power system 200 has two pressure sources 44 and two valve devices 100. One pressure source 44 is connected to a flow path C23 between the wheel cylinder 21FL and the control valve 204 through a flow path C25. One valve device 100 is provided in the flow path C25. The other pressure source 44 is connected to a flow path C24 between the wheel cylinder 21FR and the control valve 205 through a flow path C26. The other valve device 100 is provided in the flow path C26.

[0169] Each of the two pressure sources 44 pressurizes the brake fluid in the fluid chamber Re to individually drive the corresponding wheel cylinders 21FL, 21FR. As a result, the wheel cylinders 21FL, 21FR generate a braking force on the rear wheels. Meanwhile, the rear wheels are braked by, for example, an electromechanical brake (EMB).

[0170] (Third embodiment) The third embodiment will be described below with reference to Fig. 9. Fig. 9 is a diagram that illustrates a configuration of a fluid power system 300 according to the third embodiment. The brake system 10 of the third embodiment has the fluid power system 300 instead of the fluid power system 11. The fluid power system 300 is substantially the same as the fluid power system 11, except for the points described below.

[0171] The fluid power system 300 has a master cylinder 201 and control valves 202 , 203 , and 301 instead of the master cylinder 42 , the control valves 51 , 52 , 53 , and 54 , and the check valve 55 .

[0172] As in the second embodiment, the control valve 202 is connected to the master chamber Rm through a passage C21. The stroke simulator 43 is connected to the passage C21 through a passage C22. The control valve 203 is provided in the passage C22.

[0173] The control valve 202 is connected to the downstream unit 32 through parallel flow paths C31 and C32. For example, the control valve 202 is connected to the wheel cylinders 21FL and 21FR through the flow path C31. The control valve 202 is connected to the wheel cylinders 21RL and 21RR through the flow path C32. The control valve 301 is, for example, a normally open solenoid valve, and is provided in the flow path C32.

[0174] The pressure source 44 is connected through a flow path C33 to the flow path C32 between the downstream unit 32 and the control valve 301. The valve device 100 is provided in the flow path C33.

[0175] As shown in the above first to third embodiments, the valve device 100 can be mounted on a plurality of types of fluid power systems 11, 200, and 300. The valve device 100 is not limited to being mounted on the fluid power systems 11, 200, and 300, and may be mounted on other fluid power systems.

[0176] (Fourth embodiment) The fourth embodiment will be described below with reference to Fig. 10 to Fig. 13. Fig. 10 is a schematic diagram showing a cross section of a valve device 400 and a front view of a transmission mechanism 420 in a state where the movable part 103 according to the fourth embodiment is in a position that "allows the valve bodies 121, 122 to be disposed in the valve-closed positions Pcv, Pcb". Fig. 11 is a schematic diagram showing a cross section of a valve device 400 and a front view of a transmission mechanism 420 in a state where the movable part 103 according to the fourth embodiment is in a position that "holds the valve bodies 121, 122 in the valve-open positions Pov, Pob".

[0177] 10, the fluid power system 11 of the fourth embodiment has a valve arrangement 400 instead of the valve arrangement 100. The valve arrangement 400 is substantially the same as the valve arrangement 100, except as described below. Also, the fluid power system 200, the fluid power system 300, or other fluid power systems may have the valve arrangement 400.

[0178] The frame 101 of the valve device 400 has a plug 411 instead of the plug 113 and the stopper 114. The plug 411 is spaced apart from the seat valve 112 in the second axial direction D2. The plug 411 is attached to the housing 31a by, for example, crimping, and liquid-tightly closes the mounting hole Hf. In addition, the movable part 103 of the valve device 400 has a shaft 132 but does not have a piston 131.

[0179] The fluid power system 11 of the fourth embodiment further includes a transmission mechanism 420. The transmission mechanism 420 includes a first rotating body 421, a second rotating body 422, a connecting shaft 423, a cam 424, and a biasing member 425.

[0180] The first rotating body 421 is a gear attached to the output shaft 74a of the motor 74. The first rotating body 421 is rotated by the motor 74 around a central axis Axg1 of the output shaft 74a and the first rotating body 421. The central axis Axg1 is an example of the first central axis.

[0181] The first rotor 421 has a plurality of first teeth 421a. The first teeth 421a are provided over the entire circumference of the first rotor 421 around the central axis Axg1.

[0182] The first rotating body 421 is included in the speed reduction mechanism 75. The first teeth 421a mesh with one gear of the speed reduction mechanism 75 provided on the rotating member 73a of the rotary-linear motion conversion mechanism 73. This allows the speed reduction mechanism 75 to transmit the rotation of the output shaft 74a of the motor 74 to the rotating member 73a. The speed reduction mechanism 75 may further include at least one other gear provided between the rotating member 73a and the first rotating body 421.

[0183] When the motor 74 rotates the rotating member 73a in a first rotation direction Dr1 via the reduction gear mechanism 75, the linear motion member 73b reduces the volume of the fluid chamber Re. As a result, the pressure source 44 pressurizes the brake fluid in the upstream chamber Ru. The first rotation direction Dr1 is an example of a first direction.

[0184] On the other hand, when the motor 74 rotates the rotating member 73a in the second rotation direction Dr2 via the reduction gear mechanism 75, the linear moving member 73b expands the volume of the fluid chamber Re. As a result, the pressure source 44 reduces the pressure of the brake fluid in the upstream chamber Ru. The second rotation direction Dr2 is the opposite direction to the first rotation direction Dr1 and is an example of the second direction.

[0185] The second rotating body 422 and the cam 424 are attached to the connecting shaft 423. The second rotating body 422, the connecting shaft 423, and the cam 424 can rotate integrally around a central axis Axg2 of the second rotating body 422 and the connecting shaft 423. The central axis Axg2 is an example of the second central axis.

[0186] The second rotating body 422 is a gear and has a plurality of second teeth 422a. The second teeth 422a are provided only on a portion of the second rotating body 422 around the central axis Axg2. The portion of the second rotating body 422 where the second teeth 422a are not provided has an arc-shaped outer peripheral surface extending around the central axis Axg2. The diameter of the outer peripheral surface is equal to or smaller than the diameter of the bottom of the second teeth 422a.

[0187] When the second rotating body 422 rotates within a predetermined range Rr shown in Fig. 11, the second teeth 422a mesh with (are coupled to) the first teeth 421a. That is, the second rotating body 422 can receive rotation from the first rotating body 421. The range Rr is, for example, a range of approximately 180° around the central axis Axg2.

[0188] When the second rotating body 422 rotates beyond the range Rr, the second teeth 422a are separated from the first teeth 421a. In other words, when the second rotating body 422 rotates beyond the range Rr, the transmission of rotation between the first rotating body 421 and the second rotating body 422 is released.

[0189] The connecting shaft 423 extends between the upstream chamber Ru and the outside of the upstream chamber Ru. The second rotor 422 is attached to the connecting shaft 423 outside the upstream chamber Ru. The connecting shaft 423 is supported, for example, by the housing 31a of the upstream unit 31 so as to be rotatable around the central axis Axg2. The connecting shaft 423 may be supported by another component.

[0190] The cam 424 is attached to the connecting shaft 423 in the upstream chamber Ru. Therefore, the cam 424 is connected to the second rotating body 422 via the connecting shaft 423. Note that other parts may be provided between the second rotating body 422 and the cam 424. The cam 424 is, for example, a disk that is eccentric from the central axis Axg2. Note that the shape of the cam 424 is not limited to this example.

[0191] The cam 424 comes into contact with the contact portion 132a of the shaft 132. The cam 424 can displace the shaft 132 in the first axial direction D1 or the second axial direction D2 by rotating about the central axis Axg2.

[0192] When the motor 74 rotates the second rotor 422 via the output shaft 74a and the first rotor 421, the cam 424 displaces the shaft 132. That is, the transmission mechanism 420 displaces the movable part 103 relative to the valve body 122 in conjunction with the driving of the motor 74. In the transmission mechanism 420, the second rotor 422 is interposed between the first rotor 421 and the movable part 103.

[0193] The transmission mechanism 420 transmits the force (rotational force) generated by the motor 74 of the pressure source 44 to the movable part 103, thereby displacing the movable part 103 relative to the valve body 122 in conjunction with the driving of the motor 74. The force generated by the pressure source 44 may be the pressure of the liquid chamber Re as in the first embodiment, or may be another force.

[0194] The biasing member 425 is, for example, a tension spring. One end of the biasing member 425 is attached to the second rotating body 422 at, for example, approximately the center of the range Rr. The other end of the biasing member 425 is attached to the housing 31a of the upstream unit 31, for example.

[0195] When the second rotating body 422 rotates from the center of the range Rr, the biasing member 425 is stretched and pulls the second rotating body 422 by the restoring force from the elastic deformation. Therefore, the biasing member 425 biases the second rotating body 422 that has rotated beyond the range Rr toward the range Rr. By biasing the second rotating body 422, the biasing member 425 biases the multiple second teeth 422a that are spaced apart from the multiple first teeth 421a toward the first teeth 421a.

[0196] The biasing member 425 is not limited to a tension spring, but may be, for example, two compression springs that bias the second rotating body 422 toward the range Rr by pushing levers provided on the second rotating body 422 from opposite directions.

[0197] In the fourth embodiment, the atmospheric chamber Ra is provided in the housing 31a between the upstream chamber Ru and the second rotor 422. The connecting shaft 423 extends through the atmospheric chamber Ra. The valve device 400 of the fourth embodiment further includes seals 431, 432 and a spacer 433 disposed in the atmospheric chamber Ra.

[0198] The seals 431, 432 are provided between the housing 31a and the connecting shaft 423. The seals 431, 432 include, for example, an O-ring and a seal shaft provided between the O-ring and the connecting shaft 423. The seal 431 provides an airtight seal between the upstream chamber Ru and the atmospheric chamber Ra. The seal 432 provides an airtight seal between the atmospheric chamber Ra and the outside of the upstream chamber Ru. The spacer 433 is disposed between the two seals 431, 432 and supports the seals 431, 432.

[0199] The valve device 400 and the transmission mechanism 420 described above can maintain the pressure in the wheel cylinders 21RL, 21RR at a predetermined high pressure even if the pressure of the pressure source 44 drops after the pressure source 44 has increased the pressure in the wheel cylinders 21RL, 21RR to the predetermined high pressure. The operation of the valve device 400 and the transmission mechanism 420 will be described below.

[0200] 12 is a graph showing an example of pressure changes in the upstream chamber Ru and the downstream chamber Rd in the fourth embodiment. As shown in FIG. 12, when the brake pedal 23 is operated at a time T41 when the pressures Pru, Prd in the upstream chamber Ru and the downstream chamber Rd are at their minimums (e.g., atmospheric pressure), the ECU 33 calculates a target braking force and drives the motor 74.

[0201] The ECU 33 drives the motor 74 to rotate the rotating member 73a in the first rotation direction Dr1, whereby the pressure source 44 pressurizes the brake fluid, and the brake fluid is supplied from the upstream flow path Cu to the upstream chamber Ru.

[0202] By pushing the valve bodies 121, 122 to the open positions Pov, Pob, the brake fluid in the upstream chamber Ru flows into the downstream chamber Rd through the orifice O2 and the gap G. The brake fluid in the downstream chamber Rd is supplied to the wheel cylinders 21RL, 21RR through the downstream flow path Cd. This increases the pressure in the pressure source 44, the upstream chamber Ru, the downstream chamber Rd, and the wheel cylinders 21RL, 21RR.

[0203] The ECU 33 rotates the rotating member 73a in the first rotation direction Dr1 by the motor 74, thereby setting the pressures Pru, Prd in the upstream chamber Ru and the downstream chamber Rd to the target pressure Pm. This allows the wheel cylinders 21RL, 21RR to generate the target braking force. The target pressure Pm is an example of a fourth pressure, and is higher than the boundary pressure Pth.

[0204] As shown in FIG. 10, when the motor 74 rotates the rotating member 73a in the first rotational direction Dr1, the cam 424 rotates so that the distance between the outer peripheral surface of the cam 424 (the apex of the cam 424 in the first axial direction D1) and the downstream chamber Rd increases.

[0205] Between time T41 and time T42 when the pressures Pru, Prd in the upstream chamber Ru and the downstream chamber Rd rise to the target pressure Pm, the motor 74 rotates the rotating member 73a in the first rotation direction Dr1. Furthermore, the motor 74 rotates the second rotating body 422 beyond the range Rr.

[0206] When the second rotor 422 rotates beyond the range Rr, the distance between the outer circumferential surface of the cam 424 and the downstream chamber Rd becomes substantially maximum. At this time, the shaft 132 moves to the maximum in the second axial direction D2, and the drive projections 132c, 132d move away from the valve bodies 121, 122. That is, while the pressure source 44 is driven to pressurize the brake fluid in the upstream chamber Ru, the movable part 103 is in a position that allows the valve bodies 121, 122 to be disposed in the valve closing positions Pcv, Pcb.

[0207] When the second rotor 422 rotates beyond the range Rr, the second teeth 422a move away from the first teeth 421a. As a result, the first rotor 421 rotates freely relative to the second rotor 422, and the distance between the outer circumferential surface of the cam 424 and the downstream chamber Rd is maintained at approximately the maximum.

[0208] In this embodiment, the cam 424 supports the movable part 103 at a position that allows the valve bodies 121, 122 to be disposed at the valve-closed positions Pcv, Pcb when the motor 74 rotates the rotating member 73a in the first rotational direction Dr1 and the second rotating body 422 rotates beyond the range Rr. That is, the transmission mechanism 420 disposes the movable part 103 at a position that allows the valve bodies 121, 122 to be disposed at the valve-closed positions Pcv, Pcb while the motor 74 rotates the rotating member 73a in the first rotational direction Dr1.

[0209] When the second rotor 422 rotates beyond the range Rr, the second tooth 422a moves away from the first tooth 421a, but the biasing member 425 biases the second rotor 422 to the range Rr. Therefore, the second tooth 422a comes into contact with the first tooth 421a again. Since the first rotor 421 is rotating, the second tooth 422a is pushed by the first tooth 421a and moves away from the first tooth 421a. In this way, the second rotor 422 and the cam 424 rotate back and forth slightly, but the movable part 103 allows the valve bodies 121, 122 to be disposed at the valve closing positions Pcv, Pcb.

[0210] Between time T41 and time T42, the valve elements 121 and 122 can also be disposed in the open positions Pov and Pob and function as check valves, allowing the brake fluid to flow from the upstream chamber Ru to the downstream chamber Rd through the orifice O2 and the gap G.

[0211] 13 is a schematic diagram showing a cross section of the valve gear 400 and a front view of the transmission mechanism 420 in the fourth embodiment in which the second rotating body 422 has rotated through the boundary angle θ. From time T42, the ECU 33 controls the motor 74 to rotate the rotating member 73a slightly in the second rotation direction Dr2. As a result, the second rotating body 422 rotates less than the boundary angle θ. The boundary angle θ is, for example, less than half of the range Rr.

[0212] At time T42, the second rotating body 422 rotates in the first rotation direction Dr1 beyond the range Rr, and the second teeth 422a are separated from the first teeth 421a. However, the biasing member 425 biases the second rotating body 422 in the first rotation direction Dr1, thereby causing the second teeth 422a to come into contact with the first teeth 421a. Therefore, when the second rotating body 422 starts to rotate in the second rotation direction Dr2, the second teeth 422a mesh with the first teeth 421a.

[0213] When the rotating member 73a rotates in the second rotation direction Dr2, the pressure source 44 moves the piston 72 backward, and sets the pressure Pru in the upstream chamber Ru to a holding pressure Pk. The holding pressure Pk is an example of a fifth pressure, and is lower than the target pressure Pm and equal to or higher than the boundary pressure Pth. Note that the boundary pressure Pth in the fourth embodiment is the pressure Pru in the upstream chamber Ru when the second rotating body 422 rotates through the boundary angle θ.

[0214] When the motor 74 rotates the rotating member 73a in the second rotation direction Dr2, it rotates the cam 424 via the second rotating body 422 and the connecting shaft 423, thereby reducing the distance between the outer circumferential surface of the cam 424 and the downstream chamber Rd. As a result, the cam 424 pushes the shaft 132 in the first axial direction D1.

[0215] 13, when the second rotating body 422 rotates through the boundary angle θ, the driving protrusion 132c simply contacts the valve body 122 without any load. At this time, the driving protrusion 132d is separated from the valve body 121.

[0216] When the rotation angle of the second rotating body 422 is smaller than the boundary angle θ, the drive protrusions 132c, 132d of the shaft 132 are separated from the valve bodies 121, 122. In this manner, when the rotation of the second rotating body 422 is equal to or smaller than the boundary angle θ and the pressure source 44 makes the pressure in the upstream chamber Ru equal to or greater than the boundary pressure Pth, the movable part 103 is in a position that allows the valve bodies 121, 122 to be disposed in the valve closing positions Pcv, Pcb.

[0217] When the pressure Pru in the upstream chamber Ru drops from the target pressure Pm, the pressure Prd in the downstream chamber Rd becomes greater than the pressure Pru in the upstream chamber Ru, causing a pressure difference between the upstream chamber Ru and the downstream chamber Rd. As a result, the valve bodies 121 and 122 are placed in the valve-closed positions Pcv and Pcb, and the gap G and the orifice O2 are blocked. Because the gap G and the orifice O2 are blocked, the brake fluid in the downstream chamber Rd does not flow to the upstream chamber Ru. In other words, even if the pressure Pru in the upstream chamber Ru drops, the pressure Prd in the downstream chamber Rd is substantially maintained at the target pressure Pm.

[0218] At time T43 when the second rotor 422 rotates less than the boundary angle θ and the pressure Pru in the upstream chamber Ru drops to the holding pressure Pk, the ECU 33 stops the movement of the piston 72 and the rotation of the second rotor 422.

[0219] For example, between time T42 and time T43, the ECU 33 reduces the output of the electric signal (electricity) that drives the motor 74. As a result, the pressure in the liquid chamber Re pushes the piston 72 and the linearly moving member 73b, and the rotating member 73a rotates in the second rotation direction Dr2. Similarly, at time T43, the ECU 33 adjusts the output of the electric signal that drives the motor 74 to stop the rotation of the second rotating body 422. However, between time T42 and time T43, the ECU 33 applies to the motor 74 an electric signal (e.g., positive) that rotates the rotating member 73a in the first rotation direction Dr1.

[0220] Between time points T42 and T43, the ECU 33 may apply to the motor 74 an electric signal (e.g., negative) that rotates the rotating member 73a in the second rotation direction Dr2. Also, the ECU 33 may stop the supply of electric power to the motor 74 at time point T43.

[0221] Since the rotation angle of the second rotating body 422 is kept below the boundary angle θ, the movable part 103 allows the valve bodies 121, 122 to be disposed at the valve-closed positions Pcv, Pcb. Due to the pressure difference between the upstream chamber Ru and the downstream chamber Rd, the valve bodies 121, 122 are disposed at the valve-closed positions Pcv, Pcb. That is, the ECU 33 controls the motor 74 to keep the pressure Pru in the upstream chamber Ru at the holding pressure Pk and to keep the movable part 103 at a position that allows the valve bodies 121, 122 to be disposed at the valve-closed positions Pcv, Pcb. While the pressure Pru in the upstream chamber Ru is kept at the holding pressure Pk, the pressure Prd in the downstream chamber Rd is kept at the target pressure Pm.

[0222] For example, at time T44 when the operation of the brake pedal 23 is released, the ECU 33 sets the target braking force to zero. The ECU 33 controls the motor 74 to further rotate the rotating member 73a in the second rotation direction Dr2.

[0223] When the rotary member 73a rotates in the second rotation direction Dr2, the pressure source 44 moves the piston 72 rearward, and reduces the pressure Pru in the upstream chamber Ru to the valve-opening pressure Po. The valve-opening pressure Po is lower than the boundary pressure Pth.

[0224] Between time T44 and time T45 when the pressure Pru in the upstream chamber Ru drops to the valve-opening pressure Po, the second rotating body 422 rotates beyond the boundary angle θ. The cam 424 rotates so that the distance between the outer circumferential surface of the cam 424 and the downstream chamber Rd decreases, displacing the shaft 132 in the first axial direction D1.

[0225] When the second rotor 422 rotates beyond the boundary angle θ, the pressure in the upstream chamber Ru becomes lower than the boundary pressure Pth, and the drive protrusion 132c of the shaft 132 pulls the valve body 122 away from the seat surface 121b of the valve body 121. In other words, the drive protrusion 132c moves the valve body 122 to the valve open position Pob.

[0226] When the valve element 122 is placed in the valve open position Pob, the orifice O2 opens, causing the brake fluid in the wheel cylinders 21RL, 21RR and the downstream chamber Rd to flow through the orifice O2 to the upstream chamber Ru and the pressure source 44.

[0227] From time T45, the brake fluid flows from the downstream chamber Rd to the upstream chamber Ru through the orifice O2, the pressure Pru in the upstream chamber Ru increases, and the pressure in the downstream chamber Rd decreases. The opening area of ​​the orifice O2 is smaller than the opening area of ​​the gap G. The orifice O2 functions as a throttle and adjusts the flow rate of the brake fluid flowing from the downstream chamber Rd to the upstream chamber Ru. That is, the orifice O2 suppresses a sudden drop in the pressure Prd in the downstream chamber Rd and suppresses a sudden rise in the pressure Pru in the upstream chamber Ru.

[0228] Even after time T45, the pressure source 44 continues to move the piston 72 backward, so that the motor 74 continues to rotate the second rotor 422. As shown in Fig. 11, when the second rotor 422 rotates beyond the range Rr, the distance between the outer circumferential surface of the cam 424 and the downstream chamber Rd becomes minimum. Therefore, the shaft 132 is further displaced in the first axial direction D1, and the driving protrusion 132d of the shaft 132 separates the valve body 121 from the seat surface 112b of the seat valve 112. In other words, the driving protrusion 132d moves the valve body 121 to the valve open position Pov.

[0229] When the second rotor 422 rotates beyond the range Rr, the second tooth 422a separates from the first tooth 421a. Therefore, the first rotor 421 rotates idly relative to the second rotor 422, and the distance between the outer circumferential surface of the cam 424 and the downstream chamber Rd is kept at a minimum. That is, while the pressure source 44 is driven to reduce the pressure of the brake fluid in the upstream chamber Ru, the movable part 103 is in a position that holds the valve bodies 121, 122 at the valve open positions Pov, Pob.

[0230] In this embodiment, when the motor 74 rotates the rotating member 73a in the second rotation direction Dr2 and the second rotating body 422 rotates beyond the range Rr, the cam 424 supports the movable part 103 at a position that holds the valve bodies 121, 122 at the valve open positions Pov, Pob. That is, the transmission mechanism 420 places the movable part 103 at a position that holds the valve bodies 121, 122 at the valve open positions Pov, Pob while the motor 74 rotates the rotating member 73a in the second rotation direction Dr2.

[0231] The second rotor 422 and the cam 424 rotate back and forth slightly due to the tensile force of the biasing member 425 and the rotation of the first rotor 421. However, the movable part 103 holds the valve bodies 121 and 122 at the valve open positions Pov and Pob.

[0232] At time T46 when the second rotor 422 rotates beyond the range Rr, the brake fluid in the downstream chamber Rd flows into the upstream chamber Ru not only through the orifice O2 but also through the gap G. When the rising pressure Pru in the upstream chamber Ru and the falling pressure Prd in the downstream chamber Rd match, both pressures Pru and Prd decrease. Note that time T46 may be after time T47 when the pressures Pru and Prd match. The pressures Pru and Prd in the upstream chamber Ru and downstream chamber Rd both eventually decrease to their minimum values.

[0233] In the above valve device 400, after time T42 when the pressures Pru, Prd in the upstream chamber Ru and the downstream chamber Rd are set to the target pressure Pm that is higher than the boundary pressure Pth, the pressure Prd in the downstream chamber Rd is maintained at the target pressure Pm between time T43 and time T44 when the pressure Pru in the upstream chamber Ru is set to a maintained pressure Pk that is lower than the target pressure Pm and equal to or higher than the boundary pressure Pth. The valve device 400 can mechanically maintain the pressure Prd in the downstream chamber Rd and the pressures in the wheel cylinders 21RL, 21RR in this manner without relying on electrical control.

[0234] Since the pressure Prd in the downstream chamber Rd and the pressures in the wheel cylinders 21RL and 21RR are maintained at the target pressure Pm, the wheel cylinders 21RL and 21RR can maintain the target braking force. Meanwhile, the pressure source 44 maintains the pressure Pru in the upstream chamber Ru at a relatively low holding pressure Pk, not the high target pressure Pm. Therefore, the load on the motor 74 of the pressure source 44 is reduced compared to when the pressure source 44 maintains the pressure Pru in the upstream chamber Ru at the target pressure Pm. That is, the heat generation and power consumption of the motor 74 are reduced. Furthermore, damage to the motor 74 and ECU 33 due to heat generation by the motor 74, and damage to the ECU 33 due to heat generation by the elements of the ECU 33 are suppressed.

[0235] Furthermore, for example, if the power supply to the ECU 33 is lost, the power supply to the motor 74 is also lost. In this case, if the pressure Pru in the upstream chamber Ru is high, the pressure Pru in the upstream chamber Ru rapidly moves the piston 72 and the linearly moving member 73b of the electric cylinder 70 backward. For example, there is a risk that the linearly moving member 73b will collide with the gear of the reduction mechanism 75 and be damaged. However, since the pressure Pru in the upstream chamber Ru is maintained at a relatively low holding pressure Pk, the piston 72 and the linearly moving member 73b are maintained in the same position or move slightly due to sliding resistance (friction). In other words, damage to the pressure source 44 is suppressed.

[0236] In the brake system 10 according to the fourth embodiment described above, the movable part 103 is in a position that holds the valve body 122 in the valve open position Pob at least one of when the pressure source 44 makes the pressure Pru of the brake fluid in the upstream chamber Ru lower than the boundary pressure Pth and while the pressure source 44 is driven to reduce the brake fluid in the upstream chamber Ru. On the other hand, the movable part 103 is in a position that allows the valve body 122 to be disposed in the valve closed position Pcb at least one of when the pressure source 44 makes the pressure Pru of the brake fluid in the upstream chamber Ru equal to or higher than the boundary pressure Pth and while the pressure source 44 is driven to pressurize the brake fluid in the upstream chamber Ru.

[0237] When the pressure source 44 pressurizes the brake fluid in the upstream chamber Ru, the brake fluid flows from the upstream chamber Ru to the downstream chamber Rd through the orifice O2. When the pressure source 44 reduces the brake fluid in the upstream chamber Ru from a state in which the pressures Pru, Prd of the brake fluid in the upstream chamber Ru and the downstream chamber Rd are higher than the boundary pressure Pth to a predetermined pressure (holding pressure Pk) equal to or higher than the boundary pressure Pth, the valve body 122 is placed in the valve closed position Pcb due to the pressure difference between the upstream chamber Ru and the downstream chamber Rd. The valve body 122 maintains the pressure difference between the upstream chamber Ru and the downstream chamber Rd by closing the orifice O2. That is, the fluid power system 11 can reduce the pressure Pru of the upstream chamber Ru and the pressure source 44 to a value close to the boundary pressure Pth while maintaining the pressure of the downstream chamber Rd and the wheel cylinders 21RL, 21RR at the desired high pressure (target pressure Pm). This reduces the load on the pressure source 44 while the downstream chamber Rd is maintained at the desired high pressure. For example, heat generation from the pressure source 44 is reduced, which prevents various devices such as the ECU 33 from being damaged by the heat generated by the pressure source 44, and also reduces power consumption. Furthermore, since the pressure Pru in the upstream chamber Ru can be kept low, for example, when the power supply to the pressure source 44 is lost, the pressure Pru in the upstream chamber Ru is prevented from damaging the pressure source 44. Note that the fluid power system 11 can reduce the pressure Prd in the downstream chamber Rd and the wheel cylinders 21RL, 21RR by driving the pressure source 44 to lower the pressure Pru of the brake fluid in the upstream chamber Ru below the boundary pressure Pth or to reduce the pressure of the brake fluid in the upstream chamber Ru.

[0238] The transmission mechanism 420 is configured to displace the movable part 103 relative to the valve body 122 in cooperation with the driving of the motor 74. The pressure source 44 is configured to pressurize the brake fluid in the upstream chamber Ru when the motor 74 rotates the rotating member 73a in the first rotation direction Dr1, and to reduce the pressure of the brake fluid in the upstream chamber Ru when the motor 74 rotates the rotating member 73a in a second rotation direction Dr2 opposite to the first rotation direction Dr1. The transmission mechanism 420 is configured to place the movable part 103 in a position that allows the valve body 122 to be placed in the valve open position Pob while the motor 74 rotates the rotating member 73a in the first rotation direction Dr1, and to place the movable part 103 in a position that holds the valve body 122 in the valve open position Pob while the motor 74 rotates the rotating member 73a in the second rotation direction Dr2. This allows the transmission mechanism 420 to link the pressurization and depressurization of the brake fluid in the upstream chamber Ru by the pressure source 44 with the displacement of the movable part 103. Furthermore, the transmission mechanism 420 can keep the movable part 103 in a predetermined position while the rotating member 73a is being rotated by the motor 74. Therefore, when the movable part 103 is positioned in a predetermined position, the fluid power system 11 can release the link between the rotation of the rotating member 73a by the motor 74 and the displacement of the movable part 103, thereby suppressing undesired displacement of the movable part 103.

[0239] The transmission mechanism 420 has a first rotating body 421 and a second rotating body 422. The first rotating body 421 is rotated by the motor 74. The second rotating body 422 is interposed between the first rotating body 421 and the movable part 103, and can receive rotation from the first rotating body 421. The second rotating body 422 is configured to release the transmission of rotation between the first rotating body 421 and the second rotating body 422 when the second rotating body 422 rotates beyond a predetermined range Rr. This allows the transmission mechanism 420 to keep the movable part 103 in a predetermined position while the rotating member 73a and the first rotating body 421 are rotated by the motor 74. Therefore, when the movable part 103 is placed in a predetermined position, the fluid power system 11 can release the link between the rotation of the rotating member 73a and the first rotating body 421 by the motor 74 and the displacement of the movable part 103, thereby suppressing undesired displacement of the movable part 103.

[0240] The transmission mechanism 420 further includes a cam 424 connected to the second rotating body 422, and a biasing member 425 that biases the second rotating body 422 that has rotated beyond the range Rr toward the range Rr. The first rotating body 421 has a plurality of first teeth 421a provided around the central axis Axg1, and is rotated around the central axis Axg1 by the motor 74. The second rotating body 422 has a plurality of second teeth 422a provided only at a portion around the central axis Axg2, and rotates around the central axis Axg2. The second rotating body 422 is configured to couple the plurality of second teeth 422a and the plurality of first teeth 421a when rotating within the range Rr, and to separate the plurality of second teeth 422a from the plurality of first teeth 421a when rotating beyond the range Rr. The cam 424 supports the movable part 103 at a position that allows the valve body 122 to be disposed at the valve-closed position Pcb when the motor 74 rotates the rotating member 73a in the first rotation direction Dr1 and the second rotating body 422 rotates beyond the range Rr. On the other hand, the cam 424 supports the movable part 103 at a position that holds the valve body 122 at the valve-opened position Pob when the motor 74 rotates the rotating member 73a in the second rotation direction Dr2 and the second rotating body 422 rotates beyond the range Rr. This allows the transmission mechanism 420 to continue disposing the movable part 103 at a predetermined position during the rotation of the rotating member 73a and the first rotating body 421 by the motor 74. Furthermore, the biasing member 425 biases the second rotating body 422, so that the first teeth 421a and the second teeth 422a can be more reliably engaged with each other when the second rotating body 422 reverses its rotation.

[0241] The first rotating body 421 and the second rotating body 422 are not limited to gears. For example, the first rotating body 421 and the second rotating body 422 may be a friction clutch. In this case, the first rotating body 421 and the second rotating body 422 can release the transmission of rotation between them by sliding against each other.

[0242] The ECU 33 is configured to control the motor 74. The ECU 33 controls the motor 74 so that the pressure Pru of the brake fluid in the upstream chamber Ru is set to a target pressure Pm higher than the boundary pressure Pth by rotating the rotating member 73a in a first rotation direction Dr1, and the pressure of the brake fluid in the upstream chamber Ru is set to a holding pressure Pk lower than the target pressure Pm and equal to or higher than the boundary pressure Pth by rotating the rotating member 73a in a second rotation direction Dr2, so that the pressure Pru of the brake fluid in the upstream chamber Ru is kept at the holding pressure Pk and the movable part 103 is kept at a position that allows the valve body 122 to be placed in the valve closed position Pcb. As a result, the valve body 122 keeps the pressure Prd of the downstream chamber Rd at the target pressure Pm, while the pressure Pru of the upstream chamber Ru is reduced to the holding pressure Pk. That is, the fluid power system 11 can reduce the pressure Pru of the upstream chamber Ru and the pressure source 44 to a value close to the boundary pressure Pth while maintaining the pressure of the downstream chamber Rd and the wheel cylinders 21RL, 21RR at a desired high pressure. This reduces the load on the pressure source 44 while the downstream chamber Rd is maintained at the desired high pressure.

[0243] In the above embodiment, the pressure source 44 has the electric cylinder 70. However, the pressure source 44 may have another electric device capable of pressurizing the brake fluid, such as a positive displacement pump. For example, when the power supply to the ECU 33 is lost, the pressure Pru in the upstream chamber Ru may cause the rotor of the positive displacement pump to rotate rapidly, possibly resulting in damage. However, since the pressure Pru in the upstream chamber Ru is kept at a relatively low value Pk, the rotor of the positive displacement pump is kept in the same position or moves slightly due to sliding resistance (friction). In other words, damage to the pressure source 44 is suppressed.

[0244] At least one of the embodiments described above may, for example, include a fluid power system including a pressure source configured to be electrically driven to pressurize or depressurize a fluid, an actuator connected to the pressure source and configured to be driven by the fluid pressurized by the pressure source, a first chamber connected to the pressure source, a second chamber connected to the actuator, and a first flow path connecting the first chamber and the second chamber, the first chamber being movable between a first open position that opens the first flow path and a first closed position that blocks the first flow path and allowing the fluid to flow from the first chamber to the second chamber through the first flow path. and a valve device having a check valve and a movable part configured to be displaced relative to the first check valve in response to actuation of the pressure source, the movable part being configured to be in a position to hold the first check valve in the first open position at least one of when the pressure source makes the pressure of the fluid in the first chamber lower than a first pressure and when it is actuated to reduce the pressure of the fluid in the first chamber, and to be in a position to allow the first check valve to be disposed in the first closed position at least one of when the pressure source makes the pressure of the fluid in the first chamber equal to or higher than the first pressure and when it is actuated to pressurize the fluid in the first chamber. Thus, as an example, when the pressure source pressurizes the fluid in the first chamber, the fluid flows from the first chamber to the second chamber through a first flow path. When the pressure source reduces the pressure of the fluid in the first chamber from a state in which the pressure of the fluid in the first chamber and the second chamber is higher than the first pressure to a predetermined pressure equal to or higher than the first pressure, the first check valve is placed in a first closed position due to the pressure difference between the first chamber and the second chamber. The first check valve maintains the pressure difference between the first chamber and the second chamber by blocking the first flow path. That is, the fluid power system can reduce the pressure of the first chamber and the pressure source to a value close to the first pressure while maintaining the pressure of the second chamber and the actuator at a desired high pressure. This reduces the load on the pressure source while the second chamber is maintained at the desired high pressure. For example, heat generation from the pressure source is reduced, which suppresses damage to various devices such as a control device due to heat generated by the pressure source, and also reduces power consumption.Furthermore, the lower pressure in the first chamber reduces the pressure in the first chamber from damaging the pressure source, for example, if power to the pressure source is lost. The fluid power system can reduce pressure in the second chamber and the actuator by driving the pressure source to reduce the pressure of the fluid in the first chamber below the first pressure or to reduce the pressure of the fluid in the first chamber.

[0245] In the above-mentioned fluid power system, as an example, the valve device is provided with a second flow path connecting the first chamber and the second chamber, and has a second check valve movable between a second open position that opens the second flow path and a second closed position that blocks the second flow path and allows the fluid to flow from the first chamber to the second chamber through the second flow path, and the movable part is displaced relative to the second check valve in conjunction with driving of the pressure source, and is in a position to hold the second check valve in the second open position at least one of when the pressure source reduces the pressure of the fluid in the first chamber to a second pressure lower than the first pressure and while the pressure source is driven to reduce the pressure of the fluid in the first chamber, and is in a position to allow the second check valve to be disposed in the second closed position at least one of when the pressure source reduces the pressure of the fluid in the first chamber to be equal to or higher than the second pressure and while the pressure source is driven to pressurize the fluid in the first chamber. Thus, as an example, when the pressure source reduces the pressure of the fluid in the first chamber to a pressure lower than the second pressure, the movable part holds the first check valve in a first open position and the second check valve in a second open position. On the other hand, when the pressure source reduces the pressure of the fluid in the first chamber to a pressure between the first pressure and the second pressure, the movable part holds the first check valve in a first open position but allows the second check valve to be disposed in a second closed position. That is, the lower the pressure in the first chamber, the larger the cross-sectional area of ​​the flow paths (the first flow path and the second flow path) that open between the first chamber and the second chamber. This allows the fluid power system to adjust the speed and flow rate of the fluid flow from the second chamber to the first chamber by adjusting the pressure of the fluid in the first chamber. Furthermore, because the cross-sectional area of ​​the flow passage between the first and second chambers is automatically adjusted depending on the pressure in the first chamber, the fluid power system can prevent undesired sudden changes in the pressure of the fluid in the first and second chambers. For example, the fluid power system can prevent the pressure source from being damaged due to a sudden increase in the pressure of the fluid in the first chamber.

[0246] In the above fluid power system, as one example, the movable part is driven by the pressure of the fluid in the first chamber, and is in a position to hold the first check valve in the first open position when the pressure of the fluid in the first chamber is lower than the first pressure, and is in a position to allow the first check valve to be placed in the first closed position when the pressure of the fluid in the first chamber is equal to or higher than the first pressure. Thus, as one example, the movable part and the first check valve are automatically displaced according to the actual pressure of the fluid in the first chamber, and therefore the fluid power system can suppress undesired fluctuations in the pressure of the fluid in the first chamber and the second chamber.

[0247] In the above-mentioned fluid power system, as an example, the pressure of the fluid in the first chamber is maintained between the first pressure and the third pressure from when the pressure of the fluid in the second chamber, which is higher than the first pressure and is equal to or higher than the first pressure, is set to a third pressure lower than the first pressure until the pressures of the fluid in the first chamber and the second chamber become the first pressure. Thus, as an example, when the pressure of the fluid in the first chamber becomes the third pressure, the fluid in the second chamber flows into the first chamber, and the pressure of the fluid in the first chamber increases. However, when the pressure of the fluid in the first chamber increases to the first pressure, the first check valve is disposed in the first valve closing position. Therefore, the inflow of the fluid from the second chamber to the first chamber is restricted, and the further increase in the pressure of the fluid in the first chamber is stopped. That is, the pressure of the fluid in the first chamber is unlikely to become higher than the first pressure. This allows the fluid power system to prevent undesired sudden changes in the pressure of the fluid in the first chamber and the second chamber, for example, the fluid power system can prevent the pressure source from being damaged by a sudden increase in the pressure of the fluid in the first chamber.

[0248] In the above-mentioned fluid power system, as an example, the pressure source includes a piston having a fluid chamber connected to the first chamber and configured to change the volume of the fluid chamber by moving, a rotating member having a first screw thread, a ball, a linearly moving member having a second screw thread attached to the first screw thread via the ball and moving according to the rotation of the rotating member, and a motor for rotating the rotating member, and the linearly moving member pressurizes the fluid in the fluid chamber by pushing the piston so that the volume of the fluid chamber decreases. Therefore, as an example, when the power supply to the motor is lost, the pressure of the fluid in the first chamber pushes the piston and the linearly moving member in a direction to increase the volume of the fluid chamber, but as described above, the fluid power system can reduce the pressure of the fluid in the first chamber. Therefore, the fluid power system can suppress abrupt movement of the piston and the linearly moving member, and thus suppress the piston and the linearly moving member from colliding with other members and the piston and the linearly moving member from being damaged by the collision.

[0249] The fluid power system further includes, as an example, a transmission mechanism configured to displace the movable part relative to the first check valve in cooperation with the driving of the motor, the pressure source configured to pressurize the fluid in the first chamber when the motor rotates the rotating member in a first direction and to depressurize the fluid in the first chamber when the motor rotates the rotating member in a second direction opposite to the first direction, the transmission mechanism configured to place the movable part in a position that allows the first check valve to be placed in the first closed position while the motor rotates the rotating member in the first direction, and to place the movable part in a position that holds the first check valve in the first open position while the motor rotates the rotating member in the second direction. Thus, as an example, the transmission mechanism can link the pressurization and depressurization of the fluid in the first chamber by the pressure source with the displacement of the movable part. Also, the transmission mechanism can keep the movable part placed in a predetermined position while the rotating member is rotated by the motor. Therefore, when the movable part is placed in a predetermined position, the fluid power system can release the link between the rotation of the rotating member by the motor and the displacement of the movable part, thereby suppressing undesired displacement of the movable part.

[0250] In the above-mentioned fluid power system, as an example, the transmission mechanism has a first rotating body rotated by the motor, and a second rotating body interposed between the first rotating body and the movable part and capable of transmitting rotation from the first rotating body, and the second rotating body is configured to release the transmission of rotation between the first rotating body and the second rotating body when the second rotating body rotates beyond a predetermined range. Thus, as an example, while the rotating member and the first rotating body are rotated by the motor, the transmission mechanism can keep the movable part in a predetermined position. Therefore, when the movable part is placed in the predetermined position, the fluid power system can release the link between the rotation of the rotating member and the first rotating body by the motor and the displacement of the movable part, and thus can suppress undesired displacement of the movable part.

[0251] In the above-mentioned fluid power system, as an example, the transmission mechanism further includes a cam connected to the second rotating body, and a biasing member that biases the second rotating body, which has rotated beyond the range, toward the range, and the first rotating body has a plurality of first teeth provided around a first central axis and is configured to be rotated around the first central axis by the motor, and the second rotating body has a plurality of second teeth provided only at a portion around the second central axis, and rotates around the second central axis, connecting the plurality of second teeth and the plurality of first teeth when rotating within the range. , the plurality of second teeth are configured to move away from the plurality of first teeth when the second rotor rotates beyond the range, and the cam is configured to support the movable part at a position that allows the first check valve to be disposed in the first closed position when the motor rotates the rotating member in the first direction and the second rotor rotates beyond the range, and to support the movable part at a position that holds the first check valve in the first open position when the motor rotates the rotating member in the second direction and the second rotor rotates beyond the range. Thus, as an example, the transmission mechanism can continue to dispose the movable part in a predetermined position during the rotation of the rotating member and the first rotor by the motor. Furthermore, the biasing member biases the second rotor to more reliably mesh the first teeth with the second teeth when the second rotor reverses.

[0252] The fluid power system further includes, as an example, a control device configured to control the motor, the control device controlling the motor to rotate the rotating member in the first direction to bring the pressure of the fluid in the first chamber to a fourth pressure higher than the first pressure, rotate the rotating member in the second direction to bring the pressure of the fluid in the first chamber to a fifth pressure lower than the fourth pressure and equal to or higher than the first pressure, and to keep the moving parts in a position that keeps the pressure of the fluid in the first chamber at the fifth pressure and allows the first check valve to be placed in the first closed position. Thus, as an example, the first check valve keeps the pressure of the second chamber at the fourth pressure, while the pressure of the first chamber is reduced to the fifth pressure. That is, the fluid power system can reduce the pressure of the first chamber and the pressure source to a value close to the first pressure while keeping the pressure of the second chamber and the actuator at the desired high pressure. This reduces the load on the pressure source while the second chamber is kept at the desired high pressure.

[0253] The brake system according to at least one embodiment described above includes, as an example, the above-mentioned fluid power system, and the actuator is a wheel cylinder. Thus, as an example, as described above, the fluid power system can reduce the pressure in the first chamber and the pressure source to a value close to the first pressure while maintaining the pressure in the second chamber and the wheel cylinder at a desired high pressure. This allows the brake system to reduce the load on the pressure source while maintaining braking by the wheel cylinder.

[0254] Although the embodiments of the present invention have been illustrated above, the above-mentioned embodiments and modifications are merely examples and are not intended to limit the scope of the invention. The above-mentioned embodiments and modifications can be implemented in various other forms, and various omissions, substitutions, combinations, and modifications can be made without departing from the gist of the invention. In addition, the configurations and shapes of each embodiment and each modification can be partially replaced and implemented. [Explanation of symbols]

[0255] 10...Brake system, 11,200,300...Fluid power system, 21RL, 21RR...Wheel cylinder (actuating device), 44...Pressure source, 72...Piston, 73a...Rotating member, 73b...Linear member, 73c...Ball, 73d...Male screw (first thread), 73e...Female screw (second thread), 74...Motor, 100,400...Valve device, 103...Moving part, 121...Valve body (second check valve), 122...Valve body (first check valve), 420...Transmission mechanism, 421...First rotating body, 421a...First tooth, 422...Second rotating body, 422a...Second tooth, 424...Cam, 425...Biasing member, Ru...Upstream chamber (first chamber), Rd... Downstream chamber (second chamber), O2...orifice (first flow path), G...gap (second flow path), Pob...open position (first open position), Pcb...closed position (first closed position), Pov...open position (second open position), Pcv...closed position (second closed position), Pth...boundary pressure (first pressure), Ptl...boundary pressure (second pressure), Po...open pressure (third pressure), Pm...target pressure (fourth pressure), Pk...holding pressure (fifth pressure), Re...liquid chamber, Axg1...central axis (first central axis), Axg2...central axis (second central axis), Dr1...first rotation direction (first direction), Dr2...second rotation direction (second direction), Rr...range.

Claims

1. a pressure source configured to be electrically powered to pressurize or depressurize a fluid; an actuator connected to the pressure source and configured to be driven by the fluid pressurized by the pressure source; a valve device including a first chamber connected to the pressure source, a second chamber connected to the actuator, and a first flow path connecting the first chamber and the second chamber, a first check valve movable between a first open position that opens the first flow path and a first closed position that blocks the first flow path and allows the fluid to flow from the first chamber to the second chamber through the first flow path, and a movable part configured to be displaced relative to the first check valve in conjunction with the actuation of the pressure source; Equipped with the movable part is configured to be in a position to hold the first check valve in the first open position when the pressure source reduces the pressure of the fluid in the first chamber below a first pressure and at least one of the pressure source being driven to reduce the pressure of the fluid in the first chamber, and to be in a position to allow the first check valve to be disposed in the first closed position when the pressure source reduces the pressure of the fluid in the first chamber to or above the first pressure and at least one of the pressure source being driven to increase the pressure of the fluid in the first chamber. Fluid Power Systems.

2. the valve device is provided with a second flow passage connecting the first chamber and the second chamber, and has a second check valve movable between a second valve open position that opens the second flow passage and a second valve closed position that blocks the second flow passage and allows the fluid to flow from the first chamber to the second chamber through the second flow passage, the movable part is displaced relative to the second check valve in response to driving of the pressure source, and is in a position to hold the second check valve in the second open position at least one of when the pressure source reduces the pressure of the fluid in the first chamber to a second pressure lower than the first pressure and while the pressure source is driven to reduce the pressure of the fluid in the first chamber, and is in a position to allow the second check valve to be disposed in the second closed position at least one of when the pressure source reduces the pressure of the fluid in the first chamber to a second pressure or higher and while the pressure source is driven to pressurize the fluid in the first chamber.

10. The fluid power system of claim 1.

3. the movable part is driven by the pressure of the fluid in the first chamber, and is in a position to hold the first check valve in the first open position when the pressure of the fluid in the first chamber is lower than the first pressure, and is in a position to allow the first check valve to be disposed in the first closed position when the pressure of the fluid in the first chamber is equal to or higher than the first pressure.

10. The fluid power system of claim 1.

4. the pressure of the fluid in the second chamber is higher than the first pressure, and the pressure of the fluid in the first chamber, which is equal to or higher than the first pressure, is set to a third pressure lower than the first pressure, until the pressures of the fluid in the first chamber and the second chamber reach the first pressure, the pressure of the fluid in the first chamber is maintained between the first pressure and the third pressure.

4. The fluid power system of claim 3.

5. the pressure source includes a piston having a fluid chamber connected to the first chamber and configured to change the volume of the fluid chamber by moving, a rotating member having a first screw thread, a ball, a linear motion member having a second screw thread attached to the first screw thread via the ball and moving in response to the rotation of the rotating member, and a motor that rotates the rotating member, and the linear motion member pressurizes the fluid in the fluid chamber by pushing the piston so that the volume of the fluid chamber is reduced; 10. The fluid power system of claim 1.

6. a transmission mechanism configured to displace the movable part relative to the first check valve in cooperation with the driving of the motor; Further equipped with the pressure source is configured to pressurize the fluid in the first chamber when the motor rotates the rotating member in a first direction and to depressurize the fluid in the first chamber when the motor rotates the rotating member in a second direction opposite to the first direction; the transmission mechanism is configured to position the movable part in a position that allows the first check valve to be positioned in the first closed position while the motor rotates the rotating member in the first direction, and to position the movable part in a position that holds the first check valve in the first open position while the motor rotates the rotating member in the second direction.

6. The fluid power system of claim 5.

7. the transmission mechanism includes a first rotating body rotated by the motor, and a second rotating body interposed between the first rotating body and the movable part and capable of receiving rotation from the first rotating body; The second rotating body is configured to release the transmission of rotation between the first rotating body and the second rotating body when the second rotating body rotates beyond a predetermined range.

7. The fluid power system of claim 6.

8. the transmission mechanism further includes a cam connected to the second rotating body and a biasing member that biases the second rotating body, which has rotated beyond the range, toward the range; the first rotor has a plurality of first teeth arranged around a first central axis and is configured to be rotated around the first central axis by the motor; the second rotor has a plurality of second teeth provided only on a portion of a second central axis, rotates about the second central axis, and is configured to connect the plurality of second teeth to the plurality of first teeth when rotating within the range, and to separate the plurality of second teeth from the plurality of first teeth when rotating beyond the range; the cam is configured to support the movable part in a position that allows the first check valve to be disposed in the first closed position when the motor rotates the rotating member in the first direction and the second rotating body rotates beyond the range, and to support the movable part in a position that holds the first check valve in the first open position when the motor rotates the rotating member in the second direction and the second rotating body rotates beyond the range.

8. The fluid power system of claim 7.

9. a controller configured to control the motor; Further comprising: the control device controls the motor to rotate the rotating member in the first direction to bring the pressure of the fluid in the first chamber to a fourth pressure higher than the first pressure, and to rotate the rotating member in the second direction to bring the pressure of the fluid in the first chamber to a fifth pressure lower than the fourth pressure and equal to or higher than the first pressure, and to keep the moving parts in a position that maintains the pressure of the fluid in the first chamber at the fifth pressure and allows the first check valve to be disposed in the first closed position.

8. The fluid power system of claim 7.

10. 10. The fluid power system of claim 1 . Equipped with The actuator is a wheel cylinder. Brake system.

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