Damping device, hydraulic control unit, and brake system

Abstract

The present invention dampens pressure pulsations in a hydraulic control unit. This damping device is provided in a hydraulic control unit for controlling a braking force generated in a wheel, has an inlet port and an outlet port, and dampens pressure pulsations. The damping device comprises a first fluid chamber, a second fluid chamber, and a third cover that can communicate with the first fluid chamber and the second fluid chamber via a plurality of communicating passages, that internally fits together with at least a first piston, a second piston, and a housing to constitute the second fluid chamber, and that includes a connecting hole permitting a flow of hydraulic fluid from the first fluid chamber to the second fluid chamber. The first piston has a through passage formed in the axial direction thereof. The passage area of the through passage is formed to be the largest among the passage areas of flow paths arranged from a first opening to a second opening, and the third cover opens in response to the hydraulic fluid flowing via the through passage when the hydraulic fluid flows into the first fluid chamber, thus allowing the hydraulic fluid to flow through the second opening and out to the outlet port.

Description

[0001] [Document name] Statement

[0002] [Title of invention] Damping device, hydraulic control unit and brake system

[0003] [Technical Field]

[0004] [. 001] The present invention relates to a damping device, a hydraulic control unit, and a brake system.

[0005] [Background technology]

[0006] [. 0 0 2] Conventional vehicles are provided with a hydraulic control unit to control the braking force applied to the wheels. For example, as disclosed in Patent Document 1, a plurality of valves and a pump are provided in the flow paths within the hydraulic control unit. In such a hydraulic control unit, for example, in anti-lock brake control or anti-skid control, the open / closed states of each valve are set to specific states and the pump is driven.

[0007] [Prior art documents]

[0008] [Patent documents]

[0009]

〇 0 0 3

[0010] [Patent Document 1] Japanese Patent Application Laid-Open No. 2010-052519

[0011] Summary of the Invention

[0012] [Problem to be solved by the invention]

[0013] [0 0 0 4] In hydraulic control units, a reciprocating plunger pump is mainly used as the pump. Therefore, the pump intermittently pumps brake fluid. Therefore, when the pump is driven, pressure pulsation occurs, which is a phenomenon in which the hydraulic pressure of the brake fluid pulsates in the flow path within the hydraulic control unit. The sound generated by such pressure pulsation may be perceived as noise by vehicle occupants and may be a factor in reducing comfort. Therefore, from the perspective of improving comfort, it is desirable to appropriately damp the pressure pulsation of the hydraulic control unit.

[0014]

[0005] The applicant has filed Japanese Patent Application No. 2023-067975 for a damping device that appropriately damps pressure pulsations in the above-mentioned hydraulic control unit. However, in order to reduce vibrations during operation, this damping device is configured so that pressurized liquid flows through several restrictors and valve mechanisms formed between the input port and the output port, and through holes formed in the piston. Therefore, it may be difficult to quickly increase pressure, which is considered to be a factor that hinders improved responsiveness when attempting to ensure high pressure and flow rate.

[0015]

[0006] In view of these problems, the present invention aims to provide a damping device, a hydraulic control unit, and a brake system that are capable of damping pressure pulsations in a hydraulic control unit.

[0016] [Means for solving the problem]

[0017]

[0007] In order to solve the above problem, a damping device is provided in a hydraulic control unit that controls braking force generated on a wheel, and has an inlet port connected to a discharge side of a pump and an outlet port that communicates with the inlet port, and is a damping device that damps pressure pulsation, wherein the damping device comprises: a first fluid chamber that communicates with the inlet port via a first opening; a second fluid chamber that communicates with the outlet port via a second opening; the first fluid chamber and the second fluid chamber can communicate with each other via a plurality of communication passages, and the damping device comprises at least a first piston that slides within a housing, a second piston that is disposed within the first piston and can slide in response to pressure fluid flowing into the first fluid chamber, and a third fluid chamber that fits within the housing and constitutes the second fluid chamber, and includes a communication hole that allows pressure fluid to flow from the first fluid chamber to the second fluid chamber. and a third cover, wherein the first piston has a through passage formed in the axial direction, the through passage having the largest passage area among the passage areas of the flow paths arranged from the first opening to the second opening, and the third cover has a valve that opens in response to the pressure liquid when the pressure liquid flows into the first fluid chamber through the through passage, so that the pressure liquid can flow out to the outlet port through the second opening.

[0018]

[0008] To solve the above problem, the hydraulic control unit is provided with the above damping device.

[0019]

[0009] To solve the above problem, the brake system is provided with the above hydraulic control unit.

[0020] [Effects of the invention]

[0021]

[0010] According to the present invention, it is possible to improve responsiveness in ensuring high pressure and flow rate while damping pressure pulsation of the hydraulic control unit.

[0022] [Brief description of the drawing]

[0023] [ 0 0 1 1 ]

[0024] FIG. 1 is a schematic diagram showing the general configuration of a brake system according to an embodiment of the present invention.

[0025] [Figure 2] A cross-sectional view showing the schematic configuration of a damping device according to an embodiment of the present invention, showing the damping device in an inoperative state.

[0026] FIG. 3 is a cross-sectional view showing a schematic configuration of a damping device according to an embodiment of the present invention, illustrating the damping start state of the damping device.

[0027] FIG. 4 is a cross-sectional view showing a schematic configuration of a damping device according to an embodiment of the present invention, illustrating the damping end state of the damping device.

[0028] FIG. 5 is a cross-sectional view showing a schematic configuration of a damping device according to an embodiment of the present invention, illustrating an active pressure-increasing state.

[0029] [Mode for Carrying Out the Invention]

[0030]

[0012] Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. The dimensions, materials, and other specific values ​​shown in the embodiments are merely examples for facilitating understanding of the invention, and do not limit the present invention unless otherwise specified. In this specification and drawings, elements having substantially the same functions and configurations are designated by the same reference numerals to avoid redundant explanation, and elements not directly related to the present invention are not shown.

[0031] 〇

[0032]

[0013] In this embodiment, a vehicle having four wheels 17 will be described as an example. However, the vehicle to which the present invention is applied is not limited to a vehicle having four wheels 17. For example, the vehicle may have one, two, or three wheels 17, or may have five or more wheels 17.

[0033] [ 0 0 1 4 ]

[0034] <Configuration of Brake System> The configuration of a brake system 1 according to an embodiment of the present invention will be described with reference to FIG. 1.

[0035]

[0015] Fig. 1 is a schematic diagram showing the overall configuration of a brake system 1. The brake system 1 is installed in a vehicle and is a system for controlling the braking force generated in the vehicle. As shown in Fig. 1, the brake system 1 includes a brake pedal 11, a brake multiplier 12, a master cylinder 13, a reservoir 14, a hydraulic control unit 15, a brake device 16, and wheels 1?.

[0036]

[0016] The brake system 1 is mounted on a vehicle having four wheels 17, and each wheel 17 is braked by a brake device 16 provided on each wheel 17. The braking force acting on each wheel 17 is controlled by a hydraulic control unit 15. To facilitate understanding, FIG. 1 shows only a portion of the brake system 1 related to one of the front wheels and the rear wheels, and does not show a portion related to the other of the front wheels and the rear wheels.

[0037]

[0017] The number of wheels 17 whose braking force is controlled by the hydraulic control unit according to the present invention may be other than four. For example, the number of wheels 17 whose braking force is controlled by the hydraulic control unit 15 may be two. In this case, the brake system 1 may be installed on a vehicle having two wheels 17.

[0038]

[0018] The brake pedal 11 is used by the driver to apply the brakes. When applying the brakes, the driver presses the brake pedal 11. The brake booster 12 is connected to the brake pedal 11 and amplifies the force applied to the brake pedal 11. The master cylinder 13 is connected to the brake booster 12 and contains a piston that reciprocates in conjunction with the brake pedal 11, generating hydraulic pressure according to the amount of braking. The reservoir 14 is attached to the master cylinder 13 and stores brake fluid.

[0039]

[0019] The hydraulic control unit 15 has a base 15a in which a flow path for brake fluid is formed. The master cylinder 13 and each brake device 16 are connected to the base 15a of the hydraulic control unit 15. The flow path for brake fluid in the base 15a of the hydraulic control unit 15 is connected to the wheel cylinder of the brake device 16. A braking force corresponding to the hydraulic pressure of the brake fluid in the wheel cylinder of the brake device 16 is generated on the wheel 17.

[0040]

[0020] A main flow path 21, a sub-flow path 22, and a supply flow path 23 are formed in a base body 15a of the hydraulic control unit 15 as flow paths for brake fluid. The main flow path 21 circulates brake fluid in the master cylinder 13 to the wheel cylinders of the braking device 16. The sub-flow path 22 releases brake fluid from the wheel cylinders of the braking device 16. The supply flow path 23 supplies brake fluid from the master cylinder 13 to the sub-flow path 22.

[0041]

[0021] The base 15a of the hydraulic control unit 15 is provided with components for controlling the braking force acting on each wheel 17, including an on valve (EV) 31, a release valve (AV) 32, a first valve (USV) 33, a second valve (HSV) 34, an accumulator 35, a pump 36, and a motor 37.

[0042]

[0022] The configuration of the hydraulic control unit according to the present invention may be different from the configuration of hydraulic control unit 15 shown in Fig. 1 as long as it has pump 36. For example, a hydraulic control unit according to the present invention may include a hydraulic control unit obtained by omitting supply flow path 23, first valve 33, and second valve 34 from hydraulic control unit 15 shown in Fig. 1.

[0043]

[0023] The main flow path 21 connects the master cylinder 13 and the wheel cylinders of the braking devices 16. The main flow path 21 includes a first main flow path 21a and two second main flow paths 21b. The first main flow path 21a is connected to the master cylinder 13. The two second main flow paths 21 branch off from the first main flow path 21a and are connected to the respective braking devices 16. A first valve 33 is provided in the first main flow path 21a. An inlet valve 31 is provided in the second main flow path 21b.

[0044]

[0024] The sub-flow path 22 communicates the brake device 16 side of the main flow path 21 via the inlet valve 31 with the master cylinder 13 side of the main flow path 21 via the inlet valve 31, and also communicates with the brake device 16 side via the first valve 33. The sub-flow path 22 includes two first sub-flow paths 22a and a second sub-flow path 22b. Each of the first sub-flow paths 22a is connected to the brake device 16 side of the main flow path 21 via the inlet valve 31. The second sub-path 22b connects the junction of the two first sub-paths 22a to the master cylinder 13 side of the main path 21 via the inlet valve 31 and to the brake device 16 side via the first valve 33. A release valve 32 is provided in the first sub-path 22a. An accumulator 35 and a pump 36 are provided in the second sub-path 22b, in this order from the first sub-path 22a side.

[0025] The pump 36 is driven by a motor 37 and sucks brake fluid from the first sub-path 22a side and discharges it to the main path 21 side. The pump 36 is a reciprocating plunger pump. Specifically, the plunger of the pump 36 reciprocates by being intermittently pressed by an eccentric cam provided on the output shaft of the motor 37. This causes the pump 36 to pump brake fluid.

[0045]

[0026] The supply flow path 23 communicates the master cylinder 13 side of the main flow path 21 with the suction side of the pump 36 in the sub-flow path 22 via the first valve 33. A second valve 34 is provided in the supply flow path 23.

[0046]

[0027] The inlet valve 31 is, for example, a solenoid valve that is open when de-energized and closed when energized. The release valve 32 is, for example, a solenoid valve that is closed when de-energized and open when energized. The first valve 33 is, for example, a solenoid valve that is open when de-energized and closed when energized. The second valve 34 is, for example, a solenoid valve that is closed when de-energized and open when energized. By controlling the operation of these valves and the motor 37, the braking force acting on each wheel 17 is controlled.

[0047] For example, under normal circumstances when antilock brake control or anti-skid control (described later) is not being performed, the inlet valve 31 is open, the release valve 32 is closed, the first valve 33 is open, and the second valve 34 is closed. This allows brake fluid to flow from the master cylinder 13 to the wheel cylinder of the brake device 16 only through the main flow path 21, without passing through the sub-flow path 22 and the supply flow path 23. When the brake pedal 11 is depressed in this state, the piston of the master cylinder 13 is pressed, increasing the hydraulic pressure of the brake fluid in the wheel cylinder, and applying braking force to the wheel 17.

[0048] Antilock brake control is a control for preventing the wheels 17 from locking. For example, when antilock brake control is executed, first, the inlet valve 31 is closed, the release valve 32 is opened, the first valve 33 is opened, and the second valve 34 is closed. This stops the flow of brake fluid between the main flow path 21 and the wheel cylinder of the brake device 16, allowing the brake fluid to flow from the wheel cylinder to the secondary flow path 22. Therefore, brake fluid flows from the wheel cylinder to the accumulator 35, the hydraulic pressure of the brake fluid in the wheel cylinder decreases, and the braking force applied to the wheel 17 decreases. The brake fluid that has flowed into the accumulator 35 is returned to the main flow path 21 via the secondary flow path 22 by driving the pump 36.

[0049]

[0030] Then, from the above state, when both the inlet valve 31 and the release valve 32 are closed, the flow of brake fluid between the main flow path 21 and the sub-flow path 22 and the wheel cylinders is stopped, the hydraulic pressure of the brake fluid in the wheel cylinders is maintained, and the braking force applied to the wheels 17 is maintained. After that, when the inlet valve 31 is opened and the release valve 32 is closed, the flow of brake fluid between the main flow path 21 and the wheel cylinders is resumed, the hydraulic pressure of the brake fluid in the wheel cylinders is increased, and the braking force applied to the wheels 17 is increased.

[0050]

[0031] Anti-skid control is a control for stabilizing vehicle behavior. In anti-skid control, the driving force and braking force of the vehicle are appropriately controlled. For example, when anti-skid control is being performed and the vehicle is to be braked without brake operation, the inlet valve 31 is opened, the release valve 32 is closed, the first valve 33 is closed, and the second valve 34 is opened. This causes brake fluid to flow from the master cylinder 13 to the wheel cylinder of the brake device 16 via the supply flow path 23 and the sub-flow path 22. In this state, when the pump 36 is driven, the hydraulic pressure of the brake fluid in the wheel cylinder increases, generating a braking force that brakes the wheel 17.

[0051]

[0032] As described above, the hydraulic control unit 15 controls the operation of the pump 36. When the pump 36 is operated, pressure pulsation occurs, which is a phenomenon in which the hydraulic pressure of the brake fluid pulsates in the flow path within the hydraulic control unit 15. The sound generated by such pressure pulsation may be perceived as noise by vehicle occupants and may be a factor in reducing comfort. Therefore, the hydraulic control unit 15 is provided with a damping device 100 that damps the pressure pulsation.

[0052]

[0033] The damping device 100 is provided in the secondary flow path 22 (specifically, the second secondary flow path 22b) downstream of the pump 36. The damping device 100 has an inlet port P1 and an outlet port P2. The inlet port P1 is connected to the discharge side of the pump 36. The inlet port P1 and the outlet port P2 are connected to each other. Therefore, the brake fluid discharged from the pump 36 flows into the damping device 100 through the inlet port P!, passes through the damping device 100, and then flows out of the damping device 100 through the outlet port P2.

[0053] [ 0 0 3 4 ]

[0054] <Configuration of the damping device> With reference to Figure 2, the configuration of the damping device 100 according to an embodiment of the present invention will be described.

[0055]

[0035] Fig. 2 is a cross-sectional view showing a schematic configuration of the damping device 100. However, the damping device 100 shown in Fig. 2 is merely one example of a damping device according to the present invention, and as will be described later, damping devices according to the present invention also include those obtained by adding various modifications to the example of Fig. 2.

[0056]

[0036] In Fig. 2 and Figs. 3 to 5 described below, the damping device 100 is shown so that the axial direction of the housing 101 is the left-right direction, the first opening PO1 connected to the inlet port PO1 is located on the left side in the axial direction, and the second opening PO2 connected to the outlet port PO2 is located on the right side in the axial direction. Hereinafter, the left-right direction, which is the axial direction of the housing 101, will also be simply referred to as the axial direction. The first opening PO1 side means the side facing the first opening PO1 in the axial direction with the second opening PO2 as the reference (the left side in Figs. 2 to 5), or the upstream side in the flow direction of brake fluid from the first opening PO1 to the second opening PO2. The second opening PO2 side means the side facing the second opening PO2 in the axial direction relative to the first opening PO1 (the right side in Figures 2 to 5), or the downstream side in the flow direction of brake fluid from the first opening PO1 to the second opening PO2.

[0057]

[0037] As shown in Figure 2, the damping device 1 has a first damping area A1 on the first opening PO1 side and a second damping area A2 on the second opening PO2 side. The damping device 100 includes a housing 101, a first cover 111, a second cover 112, a third cover 113, a fourth cover 114, a first piston 121, a second piston 122, a first seal member 131, a second seal member 132, a first biasing member 141, a second biasing member 142, a third biasing member 143, a fourth biasing member 144, a first valve body 151, a second valve body 152, and a protrusion member 161.

[0058]

[0038] The housing 101 is formed, for example, in a cylindrical shape with a hollow space inside. The axial direction of the housing 101 is the left-right direction. An internal space is formed in the housing 101 so as to penetrate from the left end face to the right end face. The internal space of the housing 101 includes a first hole 101a, a second hole 101b, and a third hole 101c. Each of the first hole 101a, the second hole 101b, and the third hole 101c has a cylindrical shape and is arranged coaxially with the central axis of the housing 101. The first hole 101a, the second hole 101b, and the third hole 101c are continuous in this order from the left side. The diameters of the holes are such that the third hole 101c is smaller than the second hole 101b and the first hole 101a is smaller.

[0059]

[0039] A first cover 111 is fitted into the first hole 101a and the second hole 101b. The first cover 111 has a generally circular plate shape. The left end of the outer circumferential surface of the first cover 111 expands radially outward. The portion of the first cover 111 that expands radially outward is fitted into the first hole 101a, and the portion of the first cover 111 that does not expand radially outward is fitted into the second hole 101b. The first cover 111 is also provided with one or more slits 111a, which communicate with the first opening PO1.

[0060]

[0040] A third cover 113 is fitted into the third hole portion 101c. The third cover 113 has a substantially cylindrical shape. The third cover 113 has a first cylindrical portion 113a and a second cylindrical portion 113e. The first cylindrical portion 113a and the second cylindrical portion 113e have a cylindrical shape and are arranged coaxially with each other. The first cylindrical portion 113a and the second cylindrical portion 113e are continuous in this order from the right side. The outer diameter of the second cylindrical portion 113e is smaller than the outer diameter of the first cylindrical portion 113a. The first cylindrical portion 113a is fitted into the right end portion of the third hole portion 101c. The outer peripheral surface of the second cylindrical portion 113e is radially spaced apart from the inner peripheral surface of the second hole portion 101b.

[0061]

[0041] A first opening PO1 is formed in the peripheral wall portion of the housing 10!, between the first cover 111 and the third cover 113. The first opening PO1 communicates with the second hole portion 101b. A first liquid chamber s! is defined by the right surface of the first cover 111, the left surface of the third cover 113, and the inner peripheral surface of the second hole portion ioib of the housing 10!. In other words, the first cover 111 covers the first liquid chamber S1 from the left side. In other words, the right surface of the first cover 111 forms the left wall surface of the first liquid chamber S1. The third cover 113 covers the first fluid chamber S1 from the right side. In other words, the left surface of the third cover 113 forms the right wall surface of the first fluid chamber S1. The first fluid chamber S1 has a generally cylindrical shape. The first fluid chamber S1 communicates with the inlet port P! via the first opening PO1.

[0062]

[0042] A second liquid chamber S2 is defined by the inner circumferential surface of the third cover 113. The left end of the inner circumferential surface of the third cover 113 narrows radially inward. This forms a communication hole 113c in the center of the left end of the third cover 113. The second liquid chamber S2 communicates with the first liquid chamber S! via the communication hole 113c.

[0063]

[0043] The second cover 112 is fitted to the right end of the inner circumferential surface of the third cover 113. The second cover 112 is formed in a generally circular disk shape and has a second opening PO2. The second opening PO2 is arranged radially outward from the center of the second cover 112. In the example of FIG. 2, there are multiple second openings PO2. However, the number of second openings PO2 may be one. The second opening PO2 is connected to an outlet port P2 that connects to the first main flow path 21a.

[0064]

[0044] The right end of the inner circumferential surface of the third cover 113 has an expanded diameter. The second cover 112 is fitted to the expanded diameter portion of the inner circumferential surface of the third cover 113. As a result, the second liquid chamber S2 is defined by the left surface of the second cover 112. In other words, the second cover 112 covers the second liquid chamber S2 from the right side. In other words, the left surface of the second cover 112 forms the right wall surface of the second liquid chamber S2. The second liquid chamber S2 communicates with the outlet port P2 via the second opening PO2.

[0065]

[0045] In the example of FIG. 2, a plurality of third valve devices V3 are embedded in the first cylindrical portion 113 a of the third cover. The number of third valve devices V3 may be one. The structure of the third valve device V3 will be described later.

[0066]

[0046] The first piston 121 is housed in the second hole portion 101b. The first piston 121 has a substantially cylindrical shape. The first piston 121 is disposed coaxially with the central axis of the second hole portion 101b. The first piston 121 has a cylindrical portion 121a, and the cylindrical portion 121a has a cylindrical shape.

[0047] The outer peripheral surface of the cylindrical portion 121a is slidable against the inner peripheral surface of the second hole portion 101b. Therefore, the first piston 121 is provided in the first liquid chamber S1 so as to be slidable in the axial direction. The first liquid chamber S1 is connected to the first opening PO1 via gaps among the slit 111a, the left outer peripheral surface of the first piston 121, and the second hole portion 101b.

[0067]

[0048] An annular groove 121c is formed in the outer peripheral surface of the cylindrical portion 121a. The annular groove 121c extends in the circumferential direction of the first piston 121. A first seal member 131 is fitted in the annular groove 121c. The first seal member 131 is, for example, a circular ring made of an elastic member. The first seal member 131 is pressed against the inner peripheral surface of the second hole portion 101b. This creates a liquid-tight seal between the outer peripheral surface of the second cylindrical portion 121b and the inner peripheral surface of the second hole portion 101b. In the example of FIG. 2, two annular grooves 121c are arranged at an interval in the axial direction, and a first seal member 131 is fitted into each annular groove 121c. However, the number of annular grooves 121c may be one or may be three or more. Furthermore, a through passage 121b that communicates between the first liquid chamber S1 and the second liquid chamber S2 is formed in the cylindrical portion 121a. This is to prevent sudden sliding of the first piston 121 and any resulting damage if high-pressure liquid temporarily flows into the first liquid chamber S1. Note that one or more through passages 121b may be formed.

[0068]

[0049] The opening area of ​​this through passage 121b is larger than that of the other holes. As a result, when high-pressure liquid temporarily flows into the first liquid chamber S1, the liquid is more likely to flow to the right through the through passage 121b, which is expected to improve responsiveness.

[0069]

[0050] The first piston 121 is urged to the left by the first urging member 141. The first urging member 141 is, for example, an elastic member such as a spring. The first urging member 141 is disposed between the first piston 121 and the third cover 113. One end (the left end in FIG. 2) of the first urging member 141 abuts against the right end surface of the first piston 121. The other end (the right end in FIG. 2) of the first urging member 141 abuts against the left surface of the first cylindrical portion 113a of the third cover 113. The first urging member 141 expands and contracts in the left-right direction. The first biasing member 141 is in a contracted state relative to its natural length.

[0070]

[0051] A hole 121e is formed on the right side of the first piston 121. The hole 121e is a portion of the first piston 121 that is recessed from the right side to the left side. The hole 121e is recessed from the right end face of the first piston 121 to the left side. The hole 121e has a cylindrical shape and is arranged coaxially with the central axis of the housing 101. However, the hole 121e does not have to be arranged coaxially with the central axis of the housing 101.

[0071]

[0052] The hole portion 121e penetrates the first piston 121 from left to right. The hole portions 121e are continuous in this order from the left side and are arranged coaxially with one another.

[0072]

[0053] The second piston 122 is housed in the hole 121e. The second piston 122 has a substantially cylindrical shape. The second piston 122 is arranged coaxially with the central axis of the hole 121e. The outer peripheral surface of the second piston 122 is slidable relative to the inner peripheral surface of the hole 121e. Therefore, the second piston 122 is provided axially slidable in the hole 121e.

[0073] An annular groove 122a is formed in the outer peripheral surface of the second piston 122. The annular groove 122a extends in the circumferential direction of the second piston 122. A second seal member 132 is fitted into the annular groove 122a. The second seal member 132 is, for example, a circular ring made of an elastic member. The second seal member 132 is pressed against the inner peripheral surface of the hole 121e. This creates a liquid-tight seal between the outer peripheral surface of the second piston 122 and the inner peripheral surface of the hole 121e.

[0074]

[0055] The second piston 122 is urged to the left by the second urging member 142. The second urging member 142 is, for example, an elastic member such as a spring. As will be described later, a protrusion member 161 is fitted into the right end portion of the inner circumferential surface of the hole portion 121e. The second urging member 142 is disposed between the second piston 122 and the protrusion member 161. One end of the second urging member 142 (the left end in FIG. 2 ) abuts against the right surface of the second piston 122. The other end (the right end in FIG. 2) of the second biasing member 142 abuts against a recess 161g formed in a tip end 161f of a protrusion member 161 (described later). The second biasing member 142 expands and contracts in the left-right direction. The second biasing member 142 is in a contracted state relative to its natural length.

[0075] A hole 122b is formed on the left side of the second piston 122, and when the damping device 100 is in a non-operating state, the left end of the second piston 122 abuts against a stopper 121d that is integrally formed with the left end of the first piston 121 and has a predetermined length on the inner diameter side, thereby determining the non-operating position of the second piston 122 when the damping device 100 is in a non-operating state. The hole 122b is a portion of the second piston 122 that is recessed from the left to the right. The hole 122b is recessed from the left end face of the second piston 122 to the right. The hole 122b has a substantially cylindrical shape and is arranged coaxially with the central axis of the hole 121e. However, the hole 122b does not have to be arranged coaxially with the central axis of the hole 121e.

[0076]

[0057] A fourth cover 114 is fitted into the left end of the inner circumferential surface of the hole 122b. The fourth cover 114 is formed in a circular plate shape with a through hole 114a in its center. The through hole 114a penetrates the fourth cover 114 from left to right. The left end of the inner circumferential surface of the hole 122b has an expanded diameter. The fourth cover 114 is fitted into the expanded diameter part of the inner circumferential surface of the hole 122b. The space in the first fluid chamber S! to the left of the second piston 122 and the hole 122b communicate via the through hole 114a in the fourth cover 114.

[0077]

[0058] The second piston 122 is provided with a first through hole 122c that penetrates from the bottom of the hole 122b (the right part in FIG. 2) to the right end face of the second piston 122. The first through hole 122c penetrates the second piston 122 from left to right. The hole 122b and the first through hole 122c are continuous in this order from the left side and are arranged coaxially with each other. The inner diameter of the first through hole 122c is smaller than the inner diameter of the hole 122b.

[0078]

[0059] The first valve body 151 is provided in the hole portion 122b and can open and close the left side of the first through hole 122c. In an open state in which the first valve body 151 does not block the first through hole 122c, brake fluid can flow through the first through hole 122c. This state corresponds to the open state of the first valve body 151 and the open state of the first through hole 122c. In a closed state in which the first valve body 151 blocks the first through hole 122c, brake fluid cannot flow through the first through hole 122c. This state corresponds to the closed state of the first valve body 151 and the closed state of the first through hole 122c.

[0079]

[0060] The first valve body 151 has, for example, a spherical shape. However, the shape of the first valve body 151 may be a shape other than a spherical shape. The third biasing member 143 is, for example, an elastic member such as a spring. The third biasing member 143 is disposed between the fourth cover 114 and the first valve body 151. The third biasing member 143 expands and contracts in the left-right direction. The third biasing member 143 is in a contracted state relative to its natural length. Therefore, the first valve body 151 is biased to the right by the third biasing member 143.

[0080]

[0061] The first valve device V! is composed of the first valve body 151, the third biasing member 143, and a valve seat (no reference numeral) on which the first valve body 151 is seated and released. A protrusion 161c (described later) comes into contact with the first valve body 151 to establish an open valve state, and the first valve body 151 is seated on the valve seat to establish a closed valve state.

[0081]

[0062] The protrusion member 161 is provided to open and close the first valve body 151. The protrusion member 161 is attached to the first piston 121 and moves integrally with the first piston 121. The protrusion member 161 is provided on the right side of the first piston 121 relative to the second piston 122. Specifically, the protrusion member 161 is fitted into the right end portion of the inner circumferential surface of the hole portion 121e.

[0082]

[0063] The protruding member 161 has a first cylindrical portion 161a, a second cylindrical portion 161b, a protruding portion 161c, and a tip portion 161f. The first cylindrical portion 161a, the second cylindrical portion 161b, the protruding portion 161c, and the tip portion 161f have a substantially cylindrical shape and are arranged coaxially with one another. The first cylindrical portion 161a, the second cylindrical portion 161b, the protruding portion 161c, and the tip portion 161f are continuous in this order from the right side. The outer diameters of the first cylindrical portion 161a, the second cylindrical portion 161b, the protrusion 161c, and the tip portion 161f are substantially the same and smaller than that of the second cylindrical portion 161b. The tip portion 161f has the smallest diameter. The first cylindrical portion 161a is fitted into the right end of the inner circumferential surface of the hole 121e. The outer circumferential surface of the second cylindrical portion 161b is engaged radially with the inner circumferential surface of the hole 121e. The protrusion 161c protrudes to the left from the recess 161g.

[0083]

[0064] The protrusion 161c is disposed coaxially with the first through hole 122c of the second piston 122. When the second piston 122 moves to the right relatively to the first piston 121 from the position shown in FIG. 2, the protrusion 161c is inserted into the first through hole 122c, and the tip of the protrusion 161c can come into contact with the first valve body 151. When the tip of the protrusion 161c comes into contact with the first valve body 151, the relative position of the first valve body 151 with respect to the first piston 121 is maintained. In this state, the second piston 122 further moves to the right relative to the first piston 121, thereby opening the first valve body 151. In this manner, the protrusion 161c can be inserted into the first through-hole 122c and can come into contact with the first valve body 151.

[0084]

[0065] A plurality of second through holes 161e are formed in the protruding member 161. The second through holes 161e penetrate the protruding member 161 from left to right. The inner diameter of the second through holes 161e is, for example, approximately 0.4 mm to 0.5 mm. In the example of FIG. 2, the second through holes 161e extend in the axial direction. However, the path of the second through holes 161e is not particularly limited. For example, the second through holes 161e may extend in a direction inclined relative to the axial direction, or may be curved or bent.

[0085]

[0066] The second through holes 161e are arranged at equal intervals in the circumferential direction of the protruding member 161. However, the arrangement of the second through holes 161e is not limited to this example. For example, the second through holes 161e may be arranged at uneven intervals in the circumferential direction. The number of second through holes 161e may also be one. Brake fluid can flow from the left side to the right side of the protruding member 161 through the second through hole 161e. The second through hole 161e is provided to enhance the effect of reducing pressure pulsation. The function of the second through hole 161e will be described later.

[0086]

[0067] The third piston 123 is formed inside the third cover 113, and is fitted so that its left side is connected to the through hole 113c and its right side is connected to the second opening PO2. A fourth biasing member 144 is fitted into the third piston 123 and constantly presses the third piston 123 to the left. The third piston 123 is provided with a recess 123a that opens to the second opening PO2, and a communicating hole 123b that connects to the communicating hole 113c is formed in the bottom surface of the recess 123a. The second valve body 152 is fitted into the recess 123a, and a fifth biasing member 145 is disposed in the recess 123a to constantly press the second valve body 152 to the left. In addition, a plate 145 having a through-hole 152c at its center is disposed in the left end portion of the third piston 123.

[0087] 52d is fitted and contacts the fifth biasing member 145.

[0088]

[0068] The second valve body 152 is provided in the second fluid chamber S2 and can open and close the right side of the communication hole 113c. When the second valve body 152 is in an open state where it does not block the communication hole 113c, brake fluid can flow through the communication hole 113c. This state corresponds to the open state of the second valve body 152 and the open state of the communication hole 113c. When the second valve body 152 is in a closed state where it blocks the communication hole 113c, brake fluid cannot flow through the communication hole 113c. This state corresponds to the closed state of the second valve body 152 and the closed state of the communication hole 113c.

[0089]

[0069] The second valve body 152 has, for example, a spherical shape, similar to the first valve body 15!. However, the shape of the second valve body 152 may be a shape other than a spherical shape. The fifth biasing member 145 is, for example, an elastic member such as a spring. The fifth biasing member 145 is disposed between the second valve body 152 and the plate 152d. The second valve body 152 has a substantially spherical shape, and is able to open and close the communication hole 113c by being seated on a valve seat formed on the third piston 123.

[0090]

[0070] The fourth biasing member 144 is an elastic member such as a spring. The fourth biasing member 144 is disposed between the second cover 112 and the second valve body 152. The fourth biasing member 144 expands and contracts in the left-right direction. The fourth biasing member 144 is in a contracted state relative to its natural length. Therefore, the second valve body 152 is biased to the left by the fourth biasing member 144. The second valve device V2 is composed of the second valve element 152, the fourth biasing member 144, and a valve seat (no reference numeral) on which the second valve element 151 is seated or released. The second valve element 152 releases from the valve seat in response to the inflow of pressurized liquid to establish a valve open state, and the second valve element 152 seats on the valve seat to establish a valve closed state.

[0091]

[0071] The third valve device V3, which is disposed in the first cylindrical portion 113a of the third cover, has a small-diameter hole 402 on its left side and a large-diameter portion 403 on its right side that is larger than the small-diameter hole 402, with the third valve element 401 disposed between them. A valve spring 404 applies spring force to the right side of the third valve element 401, and when the third valve device V3 is in an inoperative state, the third valve element 401 is seated on a valve seat (no reference numeral) formed between the small-diameter hole 402 and the large-diameter portion 404. The third valve element 401 is released from the valve seat in response to pressurized fluid flowing into the small-diameter hole 402, and the third valve device V3 is in an open valve state. The left end of the valve spring 404 engages with a plate 405 that fits onto the left end surface of the third cover 113, and this plate 405 has a communication hole 406 that can communicate with the second opening PO2.

[0092] [ 0 0 7 2 ]

[0093] <Operation of the damping device> With reference to Figures 2 to 4, the operation of the damping device 100 according to the embodiment of the present invention will be described.

[0094]

[0073] FIG. 2 above shows the damping device 100 in the hydraulic control unit 15 under normal conditions when the pump 36 is not driven. In this case, the first piston 121 is urged to the left by the first urging member 141 and is located at the leftmost position within its range of motion. The second piston 122 is urged to the left by the second urging member 142 and is located at the leftmost position within its range of motion. The left end face of the first piston 121 abuts against the first cover 111. The left end face of the second piston 122 abuts against the stopper 121d. The second valve device V2 is also biased to the left by the fifth biasing member 145, and the second valve device V2 is also in a closed state. However, the timing at which the first piston 121 starts to move and the timing at which the second piston 122 starts to move relative to the first piston 121 may be simultaneous, or the first piston 121 may start to move after the second piston 122 starts to move relative to the first piston 121.

[0095]

[0076] Fig. 3 is a diagram showing a state in which the first piston 121 in the damping device 100 has moved to the right compared to the state in Fig. 2. In the state in Fig. 3, pressure is accumulated in the space to the left of the first piston 121 in the first fluid chamber S1. The first piston 121 is pressed to the right by the pressure in the space to the left of the first piston 121 in the first fluid chamber S1, and the first piston 121 has moved to the right compared to the state in Fig. 2. When the first piston 121 moves to the right, the first biasing member 141 expands and contracts, and as a result, it contracts. As a result, the force acting on the first piston 121 is absorbed by the first biasing member 141. In this way, the first biasing member 141 expands and contracts as the first piston 121 moves, thereby attenuating the pressure pulsation.

[0096]

[0077] In the state shown in FIG. 3, the brake fluid in the first fluid chamber S1 can flow into the second fluid chamber S2 through the through passage 121b. At this time, by setting the opening area of ​​the through passage 121b wider than the opening areas of the through hole 114a and the second through hole 161e, the pressurized fluid also flows into the through passage 121b, preventing damage to the damping device 100 due to a sudden increase in pressure in the first fluid chamber S1. Furthermore, depending on the setting of the opening area of ​​the through passage 121b, a certain degree of resistance is applied to the inflowing brake fluid. Therefore, the desired damping of pressure pulsation can be expected by the brake fluid flowing through the through passage 121b.

[0097]

[0078] In the state shown in Fig. 3, the first valve element 151 does not separate from the valve seat, so the first valve device V1 remains closed, and the brake fluid in the first fluid chamber S1 does not flow into the protruding member 161. If the state shown in Fig. 3 continues, the fluid pressure in the first fluid chamber S1 increases further, causing the first piston 121 to move to the right, and the second piston 122 to also move to the right. As a result, the first valve element 151 comes into contact with the protruding portion 161c, and the first valve device V1 enters the open state, as shown in Fig. 4.

[0098] 4 shows the state in which the second piston 122 moves to the right compared to the state in FIG. 3, the first valve device V1 is in an open state, and the second valve element 152 also leaves the valve seat, causing the second valve device V2 to also be in an open state. In the figure, the second piston 122 is pressed to the right by the pressure in the space to the left of the second piston 122 in the first fluid chamber S!, causing it to move to the right relative to the first piston 121. When the second piston 122 moves to the right relative to the first piston 121, the second biasing member 142 expands and contracts, and as a result, it contracts. As a result, the force acting on the second piston 122 is absorbed by the second biasing member 142. In this way, the second biasing member 142 expands and contracts as the second piston 122 moves, thereby attenuating the pressure pulsation. Note that when the second piston 122 moves to the right relative to the first piston 121, the first piston 121 also actually moves to the right. Therefore, the pressure pulsation is attenuated not only by the absorption of force by the second biasing member 142, but also by the absorption of force by the first biasing member 141.

[0099] When the first valve device V1 is in an open state, pressurized liquid from the first liquid chamber S1 can flow into the second liquid chamber S2 via the second through-hole 161e and the communication hole 113c. As a result of the increased pressure in the communication hole 113c, the third piston 123 moves to the right while compressing the fourth biasing member 144. At this time, the volume of the left side of the third piston 123 increases, and it is expected that pressure pulsation will also be attenuated by the absorption of force in this portion. Note that when the third piston 123 moves to the left, it moves to the left with the second valve body 152. Then, as the pressure on the left side of the third piston 123 increases, the second valve body 152 is released from the valve seat while elastically deforming the fifth biasing member 145 through the communication hole 123b in the third piston 123, thereby opening the second valve device V2. Brake fluid then flows from the left side to the right side through the communication hole 113c, and the brake fluid that has passed through the communication hole 113c flows out from the second fluid chamber S2 through the second opening PO2.

[0100]

[0081] As described above, when brake fluid flows out from the second fluid chamber S2 through the second opening PO2, the pressure inside the damping device 100 decreases. As a result, the first piston 121, which is located on the right side inside the damping device 100, moves to the left and returns to the state shown in Figure 2. Thereafter, brake fluid flows into the damping device 100 through the first opening PO!, and the operations described with reference to Figures 2 to 4 are repeated.

[0101]

[0082] Fig. 5 illustrates the flow of hydraulic fluid when active pressure boosting is required. In Fig. 5, the pump 36 is driven, causing an increase in the amount of pressurized fluid flowing into the first fluid chamber S1. At this time, the first fluid chamber S1 attempts to suddenly become high-pressure, but a portion of the pressurized fluid that flows into the first fluid chamber S1 passes through the through passage 121b formed in the first piston 121. Note that this portion of the pressurized fluid changes depending on the opening area of ​​the through passage 121b and the shaping of the through passage 121b. The remainder of the pressurized fluid flows from the through hole 113c through the second valve device V2, is attenuated, and then flows out to the second opening PO2.

[0102]

[0083] Therefore, when active pressure boosting is required, the first valve mechanism V1 and the second valve mechanism V2 are bypassed, thereby forming a configuration that prevents damage to or malfunction of the first piston. Furthermore, when active pressure boosting is required, it is possible to temporarily ensure the amount of hydraulic fluid.

[0103] [ 0 0 8 4 ]

[0104] <Effects of the Damping Device> The effects of the damping device 1 XX according to the embodiment of the present invention will be described.

[0105] When the pump 36 is driven, pressure first accumulates in the space of the first fluid chamber S! to the left of the first piston 121. During this time, the first biasing member 141 gradually contracts as the first piston 121 moves, thereby absorbing the energy of the pressure rise. Furthermore, the second biasing member 142 gradually contracts as the second piston 122 moves relative to the first piston 121, thereby absorbing the energy of the pressure rise. As a result, the rate of increase in pressure on the second opening PO2 side of the first piston 121 is slower than the rate of increase in pressure on the first opening PO! side of the first piston 121.

[0106] When the pressure on the first opening PO1 side decreases and the first piston 121 moves toward the first opening PO1 side, the first biasing member 141 and the second biasing member 142 gradually expand, and the rate at which the pressure decreases on the second opening PO2 side of the first piston 121 becomes slower than the rate at which the pressure decreases on the first opening PO1 side of the first piston 121. This makes it possible to attenuate the pressure pulsation on the second opening PO2 side relative to the pressure pulsation on the first opening PO1 side.

[0107] Furthermore, in the process in which the first piston 121 and the second piston 122 move toward the second opening PO2, the protrusion 161c of the protrusion member 161 can open the first valve body 151. Therefore, brake fluid can be appropriately sent from the first piston 121 to the second opening PO2. Therefore, by increasing the pressure in the communication hole 113c, the second valve body 152 can be opened, and brake fluid can be appropriately discharged from the second fluid chamber S2 through the second opening PO2. In this way, the damping device 100 can damp pressure pulsation in the hydraulic control unit 15.

[0108]

[0088] In addition, in the damping device 100, the protruding member 161 is formed with at least one second through hole 161e that penetrates from the first opening PO1 side to the second opening PO2 side. This allows the brake fluid to flow through the second through hole 161e, thereby damping pressure pulsation.

[0109]

[0089] Furthermore, when the pump 36 is driven, for example, when the viscosity of the brake fluid is high or when the brake fluid is resisted between the inlet port P1 and the outlet port P2 of the damping device 100, the necessary brake fluid is not supplied to the main flow path 21, etc., and brake failure does not occur. In order to prevent this, when active pressure increase is required, the first valve mechanism V1 and the second valve mechanism V2 are bypassed, and the amount of brake fluid can be temporarily secured.

[0110]

[0090] Although not disclosed in the damping device 100 shown in Figs. 2 to 4, when a plurality of through holes (unnumbered) are formed in the protruding member 161, the plurality of through holes (unnumbered) are arranged at equal intervals in the circumferential direction of the protruding member 161, thereby making the flow field of the brake fluid uniform in the circumferential direction around the protruding member 161. Therefore, the brake fluid can flow smoothly within the damping device 100.

[0111]

[0091] Furthermore, although not disclosed in the damping device 100 shown in FIGS. 2 to 4, if a through hole (no symbol) is formed in the second piston 122 so as to bypass the first valve body 151, the pressure pulsation can also be damped by flowing through this through hole (no symbol).

[0112] Furthermore, although not disclosed in the damping device 100 shown in Figs. 2 to 4, when through holes (unnumbered) are arranged at equal intervals in the circumferential direction of the second piston 122 so as to bypass the first valve body 151, the flow field of the brake fluid is made uniform in the circumferential direction around the second piston 122. Therefore, the brake fluid can flow smoothly within the damping device 100.

[0113]

[0093] Furthermore, the damping device 100 includes a first cover 111 that covers the first fluid chamber S! from the first opening PO1 side. If a buffer member (no reference symbol) that can come into contact with the first cover 111 is provided on the first opening PO! side of the first piston 121, the impact when the first piston 121 collides with the first cover 111 can be mitigated.

[0114] Furthermore, in the damping device 100, the second valve body 152 slides on the inner circumferential surface of the third cover 113, which can guide the sliding of the second valve body 152 and stabilize the posture of the second valve body 152 when opening or closing. This can smooth the opening and closing operation of the second valve body 152.

[0115]

[0095] Although the preferred embodiments of the present invention have been described above with reference to the accompanying drawings, it goes without saying that the present invention is not limited to the above-described embodiments, and that various modifications and alterations within the scope of the claims also fall within the technical scope of the present invention.

[0116]

[0096] The configuration of the damping device 100 has been described above with reference to Fig. 2. However, various modifications to the example of Fig. 2 may also be included in the damping device according to the present invention.

[0117] For example, the sliding direction of the first piston 121 and the second piston 122 may be different from the axial direction of the housing 101. For example, if the central axis of the first fluid chamber S1 is not arranged coaxially with the housing 101, the sliding direction of the first piston 121 and the second piston 122 will be different from the axial direction of the housing 101.

[0118] Furthermore, for example, the cross-sectional shape perpendicular to the sliding direction of the first liquid chamber S1, the first piston 121, and the second piston 122 does not have to be circular. The cross-sectional shape may be, for example, an ellipse or a polygon. Even in this case, the circumferential direction of each of the first piston 121 and the second piston 122 is a direction along the outer circumferential edge of each of the first piston 121 and the second piston 122, and is a direction around the central axis of each of the first piston 121 and the second piston 122.

[0119] Furthermore, for example, the cross-sectional shape of the protrusion member 161 perpendicular to the axial direction does not have to be circular. The cross-sectional shape may be, for example, an ellipse or a polygon. Even in this case, the circumferential direction of the protrusion member 161 is the direction along the outer periphery of the protrusion member 161, and is the direction around the central axis of the protrusion member 161.

[0120]

[0100] Furthermore, for example, in the example of Figure 2, the shape of the second valve body 152 does not have to be spherical, as long as it has a shape that functions as an on-off valve.

[0121]

[0101] Furthermore, for example, the example of FIG. 2 may be modified so that the first opening PO1 is provided in the first cover 111 rather than in the peripheral wall portion of the housing 10!.

[0122] [Explanation of symbols]

[0123] [ 0 1 0 2 ]

[0124] 1. Brake system

[0125] 1 5 Hydraulic control unit

[0126] 1 7 wheels

[0127] 3 6 Pump

[0128] ! 〇〇 damping device

[0129] 1 0 1 Housing

[0130] 1 1 3 3rd cover

[0131] 1 1 3 c Communication hole

[0132] 1 2 1 First piston

[0133] 1 2 1 b Passageway

[0134] 1 2 1 d stopper

[0135] 1 2 2 Second piston

[0136] 1 4 1 First biasing member

[0137] 1 4 2 Second biasing member

[0138] 1 4 3 Third biasing member

[0139] 1 4 4 Fourth biasing member

[0140] 1 4 5 Fifth biasing member

[0141] 1 5 1 First valve body

[0142] 1 5 2 Second valve body

[0143] 152c Plate 152d Through hole 161 Projection member 4 〇 ! Third valve body

[0144] 4 0 2 Small diameter hole

[0145] 4 0 3 Large diameter hole

[0146] 4 04 Valve spring

[0147] 4 0 5 plate

[0148] 4. 6 Communication hole

[0149] P 1 Inlet port P 2 Outlet port P 〇 1 First opening P 〇 2 Second opening S 1 First fluid chamber

[0150] 5 2 Second fluid chamber V 1 First valve device

[0151] V2 Second valve device

[0152] V3 3rd valve gear

Claims

[Document name] Scope of claims

1. A damping device 100 for damping pressure pulsation, the damping device 100 being provided in a hydraulic control unit 15 that controls the braking force generated on a wheel 17, and having an inlet port P! connected to the discharge side of a pump 36 and an outlet port P2 communicating with said inlet port P1, wherein said damping device 100 comprises a first fluid chamber S1 communicating with said inlet port P1 via a first opening PO!, a second fluid chamber S2 communicating with said outlet port P2 via a second opening PO2, and said first fluid chamber S1 and said second fluid chamber S2 being capable of communicating with each other via a plurality of communication passages, and wherein said damping device 100 comprises at least a first piston 121 sliding within a housing 101 and a second piston 122 a second piston 122 disposed within the housing 101 and slidable in response to the pressurized liquid flowing into the first liquid chamber S!; and a third cover 113 fitted into the housing 101 to define the second liquid chamber S2 and including a communication hole 113c that allows the pressurized liquid to flow from the first liquid chamber S! to the second liquid chamber S2, wherein the first piston 121 is formed with a through passage 121b extending in the axial direction, and the passage area of ​​this through passage 121b is formed to be the largest among the passage areas of the flow passages arranged from the first opening PO1 to the second opening PO2, and the third cover 113 is formed with a through passage 121b extending in the axial direction. The damping device 100 is characterized in that it opens in response to the pressurized liquid flowing in through the first opening PO2, and allows the pressurized liquid to flow out to the outlet port P2 through the second opening PO2.

2. The damping device 100 according to claim 1, characterized in that the through passage 121b is formed at one or more locations on the first piston 121, and when more pressurized liquid than desired flows into the first liquid chamber S1, part of the pressurized liquid passes through the through passage 121b, and the remainder acts on the second piston.

3. The damping device 100 according to claim 1 or 2, characterized in that it comprises: a first biasing member 141 having one end engaged with the first piston 121 and the other end engaged with the third cover 113, thereby biasing the first piston 121 toward the first fluid chamber S1; a second biasing member 142 having one end engaged with the second piston 122 and the other end engaged with a protrusion member 161 fitted within the first piston 121, thereby biasing the second piston 122 toward the first fluid chamber S2; and a third valve device V3 provided on the third cover 113, which allows only the flow of pressure fluid from the upstream side to the downstream side.

4. The damping device according to claim 1, wherein the third valve device V3 includes: a third valve element 401 that receives pressurized fluid flowing into the first fluid chamber S!; a valve spring 404 that is arranged in a large-diameter hole 403 through which the third valve element 401 is movable; a small-diameter hole 402 that is arranged opposite the large-diameter hole 403 and communicates with the first fluid chamber S1; and a plate 405 that has one end that engages with the third valve element 401 and the other end that fits into the third cover 113,

5. A hydraulic control unit equipped with the damping device 100 according to any one of claims 1 to 4.

6. A brake system comprising the hydraulic control unit 15 according to claim 5.

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