Valve device and shock absorber

Abstract

This valve device (V) comprises: a piston (valve seat member) (3) having a port (3b); a first valve (V1) that opens and closes the port (3b), allows bidirectional flow of a liquid toward one side and the other side of the port (3b), and applies resistance to the flow of the liquid; and a second valve (V2) that is provided in series with the first valve (V1) with respect to the port (3b), and that opens and closes the port (3b), allows bidirectional flow of the liquid passing through the port (3b), and applies resistance to the flow of the liquid.

Description

Valve device and shock absorber

[0001] The present invention relates to a valve device and a shock absorber.

[0002] The shock absorber is interposed between the vehicle body and the wheels in a vehicle, for example, for the purpose of improving the riding comfort of the vehicle, and suppresses the vibrations of the vehicle body and the wheels by the damping force exerted during expansion and contraction.

[0003] Such a shock absorber includes, for example, a cylinder, a piston rod movably inserted into the cylinder, a piston slidably inserted into the cylinder and partitioning the inside of the cylinder into an extension chamber and a compression chamber, a free piston slidably inserted into the cylinder and partitioning an air chamber below the compression chamber inside the cylinder, and a valve device provided between the extension chamber and the compression chamber and generating a damping force.

[0004] In recent years, for shock absorbers for vehicles, in order to improve the riding comfort of the vehicle, in the very low speed range where the expansion and contraction speed is lower than the low speed, the damping coefficient is increased to quickly raise the damping force with respect to the switching of the expansion and contraction stroke, in the low speed range, the damping coefficient is made smaller than in the very low speed range, and further, in the high speed range exceeding the low speed, a damping force characteristic that is proportional to the expansion and contraction speed but has a smaller damping coefficient than in the low speed range is required. For this purpose, the valve device includes, for example, a main valve that mainly generates a damping force when the expansion and contraction speed of the shock absorber is from low speed to high speed, an orifice arranged in parallel with the main valve and mainly generating a damping force when the expansion and contraction speed of the shock absorber is low speed, and a sub valve arranged in series with the main valve and the orifice and mainly generating a damping force when the expansion and contraction speed of the shock absorber is very low speed.

[0005] The main valve in the valve device consists of a bottomed cylindrical piston as the valve seat member, an extension leaf valve whose inner circumference is fixed to the piston rod and opens and closes the extension port provided at the bottom of the piston, and a compression leaf valve whose inner circumference is fixed to the piston rod and opens and closes the compression port provided on the piston. The extension leaf valve opens its extension port when the pressure in the extension chamber exceeds the pressure in the compression chamber and the difference between the two (differential pressure) reaches the opening pressure, thereby resisting the flow of hydraulic fluid from the extension chamber to the compression chamber. The compression main valve opens its compression port when the pressure in the compression chamber exceeds the pressure in the extension chamber and the difference between the two (differential pressure) reaches the opening pressure, thereby resisting the flow of hydraulic fluid from the compression chamber to the extension chamber. An orifice formed by a notch is provided on the outer circumference of the extension leaf valve or the compression leaf valve, and when the valve is closed, the compression chamber and the extension chamber are connected through the orifice.

[0006] Furthermore, the valve device includes a disc that fits into the cylindrical portion of the piston and has ports that communicate with the extension port and compression port of the piston, a cylindrical case portion that rises from the outer circumference of the disc while expanding in diameter toward the opposite side of the piston, and an annular opposing portion that protrudes from the inner circumference of the case portion toward the inner circumference. The sub-valve is an annular leaf valve in which the inner circumference is fixed to the piston rod and the outer circumference is allowed to bend, and the outer circumference is opposed to the inner circumference of the opposing portion, thereby providing resistance to the flow of hydraulic fluid moving between the extension chamber and the compression chamber that passes between the opposing portion and the sub-valve.

[0007] Furthermore, when the shock absorber's expansion and contraction speed is in the very low speed range, the sub-valve does not bend much, maintaining a small annular gap with the opposing part, so the damping force characteristics rise sharply in accordance with the expansion and contraction speed due to the sub-valve. When the shock absorber's expansion and contraction speed is in the low speed range, the sub-valve bends significantly, and the flow area in the annular gap becomes larger than the flow area of ​​the orifice, so the shock absorber generates damping force through the orifice. Moreover, when the shock absorber's expansion and contraction speed is in the high speed range, the extension-side or compression-side leaf valve in the main valve bends and opens the extension-side or compression-side port, so the damping coefficient in the shock absorber becomes smaller than the damping coefficient at very low speeds and low speeds. For example, the conventional valve device shown in JP2022-155723A achieves damping force characteristics suitable for vehicles.

[0008] JP2022-155723A

[0009] Conventional valve systems generate damping force using sub-valves, orifices, and main valves. While this allows for damping characteristics suitable for a vehicle when applied to a shock absorber, they require an extension main valve located in the extension port to generate extension damping force, a compression main valve located in the compression port to generate compression damping force, and a sub-valve case for the sub-valve. Thus, conventional valve systems have a large number of components, inevitably leading to higher costs.

[0010] However, if a sub-valve is not provided, the orifice must generate damping force when the shock absorber's expansion and contraction speed is in the very low speed range. Unless the flow area of ​​the orifice is made extremely small, the desired height of damping force cannot be achieved. If the flow area of ​​the orifice is made extremely small, the damping force when the shock absorber expands and contracts at low speeds becomes too high, compromising the ride comfort of the vehicle.

[0011] Therefore, the present invention aims to provide a valve device and a shock absorber that can improve ride comfort in a vehicle while reducing costs.

[0012] To solve the above problems, the valve device of the present invention comprises a valve seat member having a port, a first valve that opens and closes the port and allows bidirectional flow of liquid toward one side of the port and the other side of the port, and provides resistance to the flow of the liquid, and a second valve provided in series with the first valve with respect to the port that opens and closes the port and allows bidirectional flow of liquid through the port, and provides resistance to the flow of the liquid.

[0013] In this valve system configuration, the first valve and the second valve are both located in a common port. By setting the opening pressures of the first and second valves to be different, the characteristics of the first and second valves can be brought out according to the expansion and contraction speed of the shock absorber, thereby improving the ride comfort in the vehicle. Furthermore, by providing the first and second valves in a common port, the number of components can be significantly reduced compared to conventional valve systems that have two main valves located in different ports and a sub-valve that requires a sub-valve case.

[0014] Figure 1 is a longitudinal cross-sectional view of a shock absorber equipped with a valve device according to one embodiment of the present invention. Figure 2 is a partially enlarged cross-sectional view of a shock absorber equipped with a valve device according to one embodiment of the present invention. Figure 3 is a diagram showing the damping force characteristics of a shock absorber equipped with a valve device according to one embodiment of the present invention. Figure 4 is a cross-sectional view of a valve seat member fitted with a modified example of the second valve. Figure 5 is a partially enlarged cross-sectional view of a shock absorber equipped with a valve device according to a first modified example of one embodiment of the present invention. Figure 6 is a partially enlarged cross-sectional view of a shock absorber equipped with a valve device according to a second modified example of one embodiment of the present invention.

[0015] The present invention will now be described based on the embodiments shown in the figures. As shown in Figures 1 and 2, the valve device V in the first embodiment is applied to the shock absorber D. In the case of this shock absorber D, it is used interposed between the vehicle body and the wheels of a vehicle (not shown) to suppress vibrations of the vehicle body and wheels.

[0016] The valve device V and the shock absorber D will be described in detail below. As shown in Figure 1, the shock absorber D comprises a cylinder 1 as an outer shell, a piston rod 2 inserted into the cylinder 1 so as to be movable in the axial direction, a shock absorber body A having two working chambers, an extension chamber R1 and a compression chamber R2, provided inside the cylinder 1, and a valve device V provided between the extension chamber R1 and the compression chamber R2.

[0017] The upper end of cylinder 1 is closed by fitting an annular rod guide 11 through which the piston rod 2 is inserted on its inner circumference, and the lower end of cylinder 1 is closed by a bottom cap 12. Above the rod guide 11 in Figure 1, a sealing member 13 is provided to seal the outer circumference of the piston rod 2, making the inside of cylinder 1 liquid-tight. Inside cylinder 1, a free piston 10 and a piston 3 as a valve seat member are inserted so as to be movable in the axial direction. The free piston 10 divides the inside of cylinder 1 into a liquid chamber L filled with liquid on the upper side in Figure 1 and a gas chamber G filled with gas on the lower side in Figure 1, and expands and contracts the volume of the liquid chamber L and gas chamber G by moving axially inside cylinder 1. The piston 3 is connected to the tip of the piston rod 2 which is inserted so as to be movable in the axial direction inside cylinder 1, and divides the liquid chamber L into an extension chamber R1 above the piston 3 in Figure 1 and a compression chamber R2 below the piston 3 in Figure 1. Furthermore, the extension chamber R1 and compression chamber R2 within the cylinder 1 are filled with a liquid, such as hydraulic fluid. Note that, in addition to hydraulic fluid, water, aqueous solutions, etc., may also be used as the liquid.

[0018] As described above, the shock absorber body A of this embodiment is configured as a single-cylinder type shock absorber. When the shock absorber body A expands or contracts, the piston rod 2 enters the cylinder 1, and the volume displaced by the piston rod 2 within the cylinder 1 changes. However, the free piston 10 moves up and down within the cylinder 1 in Figure 1 in accordance with the volume of the piston rod 2 moving back and forth within the cylinder 1, thereby expanding and contracting the volume of the air chamber G and absorbing the volume during the expansion and contraction of the shock absorber body A.

[0019] In this embodiment, the buffer body A is a single-cylinder type buffer body in which an air chamber G is provided inside the cylinder 1 and the volume of the air chamber G is changed according to the volume of the piston rod 2 moving back and forth inside the cylinder 1. However, it may also be a double-cylinder type buffer body in which an outer cylinder or tank forming a reservoir is provided outside the cylinder 1 to form a reservoir, and liquid is supplied and discharged between the reservoir and the inside of the cylinder 1. Alternatively, the buffer body A may be configured as a double-rod type buffer body in which a piston 3 is mounted in the center of the piston rod 2 and the ends of the piston rod 2 protrude outside the cylinder 1 from both ends of the cylinder 1.

[0020] The piston rod 2 is cylindrical in shape, with a reduced outer diameter at the tip, and includes a piston fitting portion 2a with the smallest diameter at the tip, a larger diameter portion 2b which has a larger outer diameter than the piston fitting portion 2a and is located above the piston fitting portion 2a in Figure 2, a stepped portion 2c provided at the boundary between the piston fitting portion 2a and the larger diameter portion 2b, and a threaded portion 2d provided on the outer circumference of the tip of the piston fitting portion 2a.

[0021] A bracket (not shown) is provided at the base end of the piston rod 2, which is the upper end in Figure 1, and the piston rod 2 is connected to one of the vehicle body and the wheel via this bracket (not shown). A bracket (not shown) is also provided at the bottom cap 12 that closes the end of the cylinder 1, and the cylinder 1 is connected to the other of the vehicle body and the wheel via this bracket (not shown).

[0022] In this way, the shock absorber body A is interposed between the vehicle body and the wheels. When the vehicle travels on an uneven road surface, causing the wheels to vibrate vertically relative to the vehicle body, the piston rod 2 moves in and out of the cylinder 1, causing the shock absorber D to expand and contract, and the piston 3 moves vertically (axially) within the cylinder 1.

[0023] The valve device V includes a piston 3 as a valve seat member having a port 3b, a first valve V1 that opens and closes the port 3b and allows bidirectional flow of liquid toward the extension chamber side (one side of the port 3b) and the pressure chamber side (the other side of the port 3b), while also providing resistance to the liquid flow, and a second valve V2 that is provided in series with the first valve V1 with respect to the port 3b and opens and closes the port 3b and allows bidirectional flow of liquid passing through the port 3b toward the extension chamber side (one side of the port 3b) and the pressure chamber side (the other side of the port 3b), while also providing resistance to the liquid flow.

[0024] Specifically, the piston 3, which serves as the valve seat member, is annular in shape and fitted onto the outer circumference of the piston fitting portion 2a of the piston rod 2. It is fixed to the piston rod 2 by a piston nut 14 that is screwed onto the threaded portion 2d of the piston rod 2. More specifically, as shown in Figure 2, the piston 3 comprises an annular body portion 3a, a port 3b that penetrates the body portion 3a from one end which is the upper end in Figure 2 to the other end which is the lower end in Figure 2, an annular valve seat 3c that protrudes from one end of the body portion 3a and surrounds one end of the port 3b, and an annular projection 3d that rises from the other end of the body portion 3a and from the outer circumference side of the other end of the port 3b, and has an annular opposing portion 3e on its inner circumference. The piston 3 also includes a piston ring 3f that is mounted on the outer circumference of the body portion 3a and slides against the inner circumference of the cylinder 1.

[0025] The main body portion 3a is annular and is fitted onto the outer circumference of the piston fitting portion 2a of the piston rod 2 and fixed to the piston rod 2. Multiple ports 3b are provided arranged on the same circumference relative to the main body portion 3a, opening from one end which is the upper end of the main body portion 3a in Figure 2 and continuing to the other end which is the lower end of the main body portion 3a in Figure 2. Furthermore, the upper inner circumference portion 3g of the upper end of the main body portion 3a, which is inside the port 3b, protrudes axially toward the extension chamber side from the upper end of the port 3b, and an annular valve seat 3c is provided on the outer circumference of the upper end of the main body portion 3a, which protrudes axially toward the extension chamber side from the upper end of the port 3b and surrounds the opening end of the upper end of the port 3b. An orifice 3i formed by a notch is provided at the upper end of the annular valve seat 3c. The orifice 3i may be provided on the inner circumference support seat 5 or the annular valve body 6.

[0026] Furthermore, the lower end inner circumference portion 3h of the main body portion 3a, which is inside the port 3b, protrudes axially toward the compression chamber side from the lower end of the port 3b, and the lower end of the main body portion 3a, which is on the outer circumference side from the port 3b, is provided with an annular projection 3d that protrudes axially toward the compression chamber side from the lower end of the port 3b, surrounds the open end of the lower end of the port 3b, and has an annular opposing portion 3e on its inner circumference. The opposing portion 3e is an annular projection that protrudes toward the inner circumference side from the lower end of the annular projection 3d and has an annular inner surface.

[0027] In Figure 2, a guide ring 4 is stacked above the upper inner circumference 3g of the piston 3, with an outer diameter larger than the outer diameter of the upper inner circumference 3g. Above the guide ring 4, an inner circumference support seat 5 is stacked, with an outer diameter larger than the outer diameter of the guide ring 4. The guide ring 4 and the inner circumference support seat 5 are fixed together with the piston 3 to the outer circumference of the piston fitting portion 2a of the piston rod 2.

[0028] An annular valve body 6 is positioned on the outer circumference of the guide ring 4. The annular valve body 6 has an inner diameter slightly larger than the outer diameter of the guide ring 4, and an outer diameter larger than the inner diameter of the annular valve seat 3c. The inner circumference on the side opposite the piston is supported by the inner circumference support seat 5, and the outer circumference is seated on the upper end of the annular valve seat 3c in Figure 2. As viewed from the piston 3, the height of the lower end surface of the inner circumference support seat 5 on the piston 3 is lower than the height of the upper end surface of the annular valve seat 3c. The annular valve body 6 is initially deflected with its inner circumference seated on the inner circumference support seat 5 and its outer circumference seated on the annular valve seat 3c, and it presses against the inner circumference support seat 5 and the annular valve seat 3c with its own elastic force. The guide ring 4 is positioned on the inner circumference of the annular valve body 6 and aligns the annular valve body 6.

[0029] Thus, the first valve V1 is composed of an annular valve body 6 and an inner circumferential support seat 5 that supports the inner circumferential portion of the annular valve body 6 on the side opposite the piston, and the valve opening pressure is set by the initial amount of deflection applied to the annular valve body 6.

[0030] The first valve V1 remains closed by seating on the inner circumferential support seat 5 and the annular valve seat 3c until the differential pressure between the extension chamber R1 and the compression chamber R2 reaches the opening pressure, and communicates the port 3b to the extension chamber R1 only through the orifice 3i.

[0031] Furthermore, when the pressure in the extension chamber R1 becomes higher than the pressure in the compression chamber R2 and exceeds the valve opening pressure, the first valve V1 opens by bending the inner circumference of the annular valve body 6 downward in Figure 2 with the annular valve seat 3c as a fulcrum against the flow of liquid from the extension chamber R1 to the compression chamber R2 through port 3b, thereby separating the inner circumference of the annular valve body 6 from the inner support seat 5. The first valve V1 then provides resistance to the flow of liquid passing through port 3b from the extension chamber R1 to the compression chamber R2. Note that the upper inner circumference 3g and the annular valve seat 3c protrude upward from the main body 3a in Figure 2, so care has been taken to ensure that the inner circumference of the annular valve body 6 does not interfere with the main body 3a even when it bends toward the main body 3a.

[0032] On the other hand, when the pressure in the compression chamber R2 becomes higher than the opening pressure in the extension chamber R1, the first valve V1 opens by bending the outer circumference of the port 3b upward in Figure 2 with the inner circumference support seat 5 as a fulcrum against the flow of liquid from the compression chamber R2 to the extension chamber R1, thereby separating the outer circumference from the annular valve seat 3c. The first valve V1 then provides resistance to the flow of liquid passing through the port 3b from the compression chamber R2 to the extension chamber R1.

[0033] In this manner, the first valve V1 opens and closes port 3b, and is set to open both inward and outward, by bending the inner circumference of the annular valve body 6 to open the valve for liquid flow passing through port 3b from the extension chamber R1 to the compression chamber R2, and by bending the outer circumference to open the valve for liquid flow passing through port 3b from the compression chamber R2 to the extension chamber R1. This allows for bidirectional flow of liquid through port 3b, both toward one side and the other, and can also provide resistance to the flow of liquid passing through.

[0034] A second valve V2 is stacked on the lower part of the inner circumference 3h of the lower end of the piston 3 in Figure 2. The second valve V2 is a leaf valve made of multiple elastic annular plates stacked together and is mounted on the outer circumference of the piston fitting portion 2a of the piston rod 2.

[0035] In this embodiment, the second valve V2 is composed of three stacked annular plates. In Figure 2, the outer diameter of the central annular plate is larger than the outer diameter of the annular plates stacked above and below it. When mounted on the piston fitting portion 2a of the piston rod 2, the outer circumferential surface of the central annular plate faces the inner circumferential surface of the opposing portion 3e of the piston 3 through a predetermined small annular gap P.

[0036] Furthermore, as shown in Figure 2, the second valve V2 is annular in shape and is fixedly mounted on the outer circumference of the piston fitting portion 2a of the piston rod 2, with its inner circumference sandwiched by spacers 7 and 8. The inner circumference is the fixed end and the outer circumference is the free end, allowing for deflection of the free outer circumference.

[0037] The number of annular plates constituting the second valve V2 can be arbitrarily set according to the damping force to be obtained by the shock absorber D. Also, although spacers 7 and 8 are shown to be composed of one annular plate each, they may be composed of multiple annular plates. Furthermore, the axial position of the annular plate facing the inner circumferential surface of the opposing portion 3e of the second valve V2 can be adjusted by adjusting the number of stacked spacers 7 or the thickness of the spacers arranged on the piston side of the second valve V2.

[0038] The axial width of the inner circumferential surface of the opposing portion 3e is set to a width such that when the outer circumference of the annular plate facing the inner circumferential surface of the opposing portion 3e in the second valve V2 is deflected by a predetermined amount or more, it will no longer be in opposition to the outer circumferential surface of the annular plate. To that extent, it may be narrower or wider than the axial width of the outer circumferential surface of the annular plate. When the annular plate with the largest outer diameter that was facing the opposing portion 3e is deflected, the outer circumferential surface of the annular plate shifts axially from the opposing portion 3e, thereby increasing the annular gap between the opposing portion 3e and the annular plate and expanding the flow area.

[0039] In the second valve V2 configured in this way, when the outer surface of the annular plate with the largest outer diameter is brought directly toward the inner surface of the opposing portion 3e, it enters a closed state, forming a restricting flow path consisting of a very narrow annular gap P between the annular plate and the opposing portion 3e. In the closed state of the second valve V2, the flow path area of ​​the annular gap P is approximately zero, and the port 3b is connected to the pressure side chamber R2 via the annular gap P, providing resistance to the flow of liquid passing through the port 3b.

[0040] Furthermore, when the pressure in the extension chamber R1 of the second valve V2 becomes higher than the pressure in the compression chamber R2 and exceeds the opening pressure, the outer circumference of the annular plate with the largest outer diameter is deflected, causing the outer surface of the annular plate to shift downward in the axial direction relative to the inner surface of the opposing portion 3e, thereby opening the valve and increasing the annular gap P, which acts as a restricting flow path, thereby providing resistance to the flow of liquid from the extension chamber R1 to the compression chamber R2 at port 3b, but the resistance provided is smaller than when the valve is closed.

[0041] On the other hand, when the pressure in the pressure chamber R2 becomes higher than the opening pressure of the second valve V2 by the opening pressure or more than the pressure in the extension chamber R1, the outer peripheral side is deflected, and the outer peripheral surface of the annular plate having the maximum outer diameter is displaced upward in the axial direction with respect to the inner peripheral surface of the facing portion 3e to open the valve, increasing the annular gap P as the restricted flow path, and providing resistance to the flow of liquid from the pressure chamber R2 to the extension chamber R1 through the port 3b, but making the resistance provided smaller than that at the time of valve closing.

[0042] As described above, the second valve V2 opens and closes the port 3b, and allows the bidirectional flow of liquid, that is, the flow of liquid passing through the port 3b from the extension chamber R1 to the pressure chamber R2 and the flow of liquid passing through the port 3b from the pressure chamber R2 to the extension chamber R1, and can provide resistance to the flowing liquid passing through.

[0043] As described above, the first valve V1 and the second valve V2 allow both the flow of liquid from the extension chamber R1, which is one side, to the pressure chamber R2, which is the other side, through the port 3b and the flow of liquid from the pressure chamber R2, which is the other side, to the extension chamber R1, which is one side, through the port 3b. Therefore, they can be provided in the port 3b that is commonly used both when the shock absorber D extends and when it contracts. Further, the opening pressure of the first valve V1 is set to be higher than the opening pressure of the second valve V2.

[0044] The first valve V1, the piston 3 as the valve seat member, and the second valve V2 that constitute these valve devices V are assembled on the outer periphery of the piston fitting portion 2a of the piston rod 2, and then are sandwiched between the piston nut 14 screwed to the screw portion 2d of the piston fitting portion 2a and the step portion 2c and fixed to the piston rod 2. Thus, the first valve V1, the piston 3 as the valve seat member, and the second valve V2 that constitute the valve device V are easily assembled and integrated by being assembled to the piston rod 2.

[0045] The valve device V and the buffer D are configured as described above, and the operation of the valve device V and buffer D according to this embodiment will be described below. When the buffer D extends, the piston 3 moves upward in the cylinder 1 in Figure 1 and compresses the extension chamber R1. When the extension speed of the buffer D is in the very low speed range and close to 0, the pressure in the extension chamber R1 rises, but the pressure difference with the pressure in the compression chamber R2 does not reach the opening pressure of the first valve V1, so the first valve V1 seats on the inner circumferential support seat 5 and the annular valve seat 3c and closes the port 3b.

[0046] When the extension speed of buffer D is close to zero, the pressure in the extension chamber R1 rises, but the pressure difference between it and the pressure in the compression chamber R2 does not reach the opening pressure of the second valve V2. Therefore, the second valve V2 remains closed, maintaining a state where the outer surface of the annular plate with the largest outer diameter faces the inner surface of the opposing part 3e in the radial direction, and the flow area of ​​the annular gap P becomes approximately zero. Furthermore, as the extension speed of buffer D increases and moves from the very low speed range to the low speed range, the pressure difference between the pressure in the extension chamber R1 and the pressure in the compression chamber R2 exceeds the opening pressure of the second valve V2. Therefore, the second valve V2 bends its outer circumference downward in Figure 2, shifting the outer surface of the annular plate with the largest outer diameter axially away from the inner surface of the opposing part 3e, and opens, thereby increasing the flow area of ​​the annular gap P. The first valve V1 remains closed without opening when the extension speed of buffer D is in the very low speed range.

[0047] Therefore, the liquid moves from the extension chamber R1 to the compression chamber R2 by passing through the orifice 3i, port 3b, and the annular gap P between the second valve V2 and the opposing part 3e. The liquid passes through the second valve V2 and the orifice 3i in this way, but the flow area of ​​the annular gap P between the second valve V2 and the opposing part 3e in the open state in the very low speed range is smaller than the flow area of ​​the orifice 3i. Therefore, when the extension speed of the buffer D is in the very low speed range, the buffer D generates a damping force that hinders extension mainly due to the resistance that the second valve V2 imparts to the liquid flow.

[0048] Therefore, when the extension speed of the shock absorber D is in the very low speed range, the damping force characteristics on the extension side of the shock absorber D (the damping force characteristics of the shock absorber D with respect to the extension speed) are as shown in Figure 3, with a characteristic in which the damping coefficient rises very high when the extension speed is near zero.

[0049] Next, when the extension speed of the shock absorber D is in the low-speed range exceeding the very low-speed range, although the pressure in the extension chamber R1 increases, the differential pressure with the pressure in the pressure chamber R2 does not reach the valve opening pressure of the first valve V1. Therefore, the first valve V1 remains closed without opening and keeps the port 3b blocked. When the extension speed of the shock absorber D is in the low-speed range, the differential pressure between the pressure in the extension chamber R1 and the pressure in the pressure chamber R2 greatly exceeds the valve opening pressure of the second valve V2. Thus, the second valve V2 deflects greatly to make the flow passage area of the annular gap P larger than the flow passage area of the orifice 3i. Therefore, also in this case, the liquid moves from the extension chamber R1 to the pressure chamber R2 through the orifice 3i, the port 3b, and the annular gap P. However, the resistance exerted by the orifice 3i on the flow of the liquid is larger than the resistance exerted by the second valve V2 on the flow of the liquid. Therefore, when the extension speed of the shock absorber D is in the low-speed range, the shock absorber D mainly generates a damping force that hinders extension due to the resistance exerted by the orifice 3i on the flow of the liquid. Therefore, as shown in FIG. 3, the damping force characteristic on the extension side of the shock absorber D when the extension speed of the shock absorber D is in the low-speed range is a characteristic proportional to the square of the extension speed of the shock absorber D specific to the orifice. However, compared with the case where the extension speed is in the very low-speed range, the damping coefficient becomes smaller.

[0050] Furthermore, when the extension speed of the buffer D exceeds the low-speed range and enters the high-speed range, the pressure difference between the pressure in the extension chamber R1 and the pressure in the compression chamber R2 reaches the opening pressure of the first valve V1, causing the annular valve body 6 to bend and separate from the inner circumferential support seat 5, and the first valve V1 opens, opening port 3b. When the extension speed of the buffer D is in the high-speed range, the pressure difference between the pressure in the extension chamber R1 and the pressure in the compression chamber R2 becomes even larger, causing the second valve V2 to open even wider and further increasing the flow area of ​​the annular gap P. When the extension speed of the buffer D is in the high-speed range, the flow rate of liquid moving from the extension chamber R1 to the compression chamber R2 increases, and the flow area between the first valve V1 and the annular valve seat 3c becomes smaller than the annular gap P between the second valve V2 and the opposing part 3e. Therefore, when the extension speed of the buffer D is in the high-speed range, the buffer D generates a damping force that hinders its extension, mainly due to the resistance that the first valve V1 imposes on the liquid flow. Consequently, when the extension speed of the buffer D is in the high-speed range, the damping force characteristics on the extension side of the buffer D are proportional to the specific extension speed of the buffer D of the first valve V1, as shown in Figure 3, but the damping coefficient becomes even smaller compared to when the extension speed is in the low-speed range.

[0051] Next, when the shock absorber D contracts, the piston 3 moves downward in the cylinder 1 in Figure 1, compressing the compression chamber R2. When the contraction speed of the shock absorber D is in the very low speed range and close to zero, the pressure in the compression chamber R2 rises, but the pressure difference with the pressure in the extension chamber R1 does not reach the opening pressure of the first valve V1. Therefore, the first valve V1 seats on the inner circumferential support seat 5 and the annular valve seat 3c, closing the port 3b.

[0052] When the contraction speed of the buffer D is close to zero, the pressure in the compression chamber R2 rises, but the pressure difference between it and the pressure in the extension chamber R1 does not reach the opening pressure of the second valve V2. Therefore, the second valve V2 remains closed, maintaining a state where the outer surface of the annular plate with the largest outer diameter faces the inner surface of the opposing part 3e in the radial direction, and the flow area of ​​the annular gap P becomes approximately zero. Furthermore, as the contraction speed of the buffer D increases and moves from the very low speed range to the low speed range, the pressure difference between the pressure in the compression chamber R2 and the pressure in the extension chamber R1 exceeds the opening pressure of the second valve V2. Therefore, the second valve V2 bends its outer circumference upward in Figure 2, shifting the outer surface of the annular plate with the largest outer diameter axially away from the inner surface of the opposing part 3e, and opens, thereby increasing the flow area of ​​the annular gap P. The first valve V1 remains closed without opening when the extension speed of the buffer D is in the very low speed range.

[0053] Therefore, the liquid moves from the compression chamber R2 to the extension chamber R1 by passing through the orifice 3i, the port 3b, and the annular gap P between the second valve V2 and the opposing part 3e. The liquid passes through the second valve V2 and the orifice 3i in this way, but the flow area of ​​the annular gap P between the second valve V2 and the opposing part 3e in the open state in the very low speed range is smaller than the flow area of ​​the orifice 3i. Therefore, when the contraction speed of the buffer D is in the very low speed range, the buffer D generates a damping force that hinders contraction mainly due to the resistance that the second valve V2 imparts to the liquid flow.

[0054] Therefore, when the contraction speed of the shock absorber D is in the very low speed range, the damping force characteristics on the compression side of the shock absorber D (the damping force characteristics with respect to the extension speed of the shock absorber D) are as shown in Figure 3, with a characteristic in which the damping coefficient rises very high when the contraction speed is near zero.

[0055] Next, if the contraction speed of buffer D is in the low speed range beyond the very low speed range, the pressure in the compression chamber R2 rises, but the pressure difference between it and the pressure in the extension chamber R1 does not reach the opening pressure of the first valve V1. Therefore, the first valve V1 remains closed and port 3b is kept closed. When the contraction speed of buffer D is in the low speed range, the pressure difference between the pressure in the compression chamber R2 and the pressure in the extension chamber R1 greatly exceeds the opening pressure of the second valve V2. As a result, the second valve V2 bends significantly, making the flow area of ​​the annular gap P larger than the flow area of ​​the orifice 3i. Therefore, in this case as well, the liquid moves from the compression chamber R2 to the extension chamber R1 by passing through the orifice 3i, port 3b, and annular gap P. However, the resistance exerted by the orifice 3i on the flow of liquid is greater than the resistance exerted by the second valve V2 on the flow of liquid. Therefore, when the contraction speed of the buffer D is in the low-speed range, the buffer D generates a damping force that hinders contraction mainly due to the resistance that the orifice 3i imposes on the liquid flow. Consequently, when the contraction speed of the buffer D is in the low-speed range, the damping force characteristics on the compression side of the buffer D are proportional to the square of the contraction speed of the buffer D, which is characteristic of orifices, as shown in Figure 3, but the damping coefficient is smaller compared to when the contraction speed is in the very low-speed range.

[0056] Furthermore, when the contraction speed of the buffer D exceeds the low-speed range and is in the high-speed range, the pressure difference between the pressure in the compression chamber R2 and the pressure in the extension chamber R1 reaches the opening pressure of the first valve V1, causing the annular valve body 6 to bend and separate from the annular valve seat 3c, and the first valve V1 opens, opening port 3b. When the contraction speed of the buffer D is in the high-speed range, the pressure difference between the pressure in the compression chamber R2 and the pressure in the extension chamber R1 becomes even larger, causing the second valve V2 to open even wider and further increasing the flow area of ​​the annular gap P. When the contraction speed of the buffer D is in the high-speed range, the flow rate of liquid moving from the compression chamber R2 to the extension chamber R1 increases, and the flow area between the first valve V1 and the annular valve seat 3c becomes smaller than the annular gap P between the second valve V2 and the opposing part 3e. Therefore, when the contraction speed of the buffer D is in the high-speed range, the buffer D generates a damping force that hinders contraction mainly due to the resistance that the first valve V1 exerts on the liquid flow. Therefore, when the contraction speed of the shock absorber D is in the high-speed range, the damping force characteristics on the compression side of the shock absorber D are proportional to the specific contraction speed of the shock absorber D of the first valve V1, as shown in Figure 3. However, the damping coefficient becomes even smaller compared to when the contraction speed is in the low-speed range.

[0057] Therefore, as shown in Figure 3, the damping force characteristics of the valve device in this embodiment are such that, in response to an increase in the extension or contraction speed of the shock absorber D, the damping force characteristics of the second valve V2 appear first, followed by the damping force characteristics of the orifice 3i, and finally the damping force characteristics of the first valve V1. Furthermore, as described above, the operation of the valve device V and shock absorber D is explained by dividing the extension and contraction speed of the shock absorber D into a very low speed range, a low speed range, and a high speed range, but each of these ranges can be arbitrarily set.

[0058] The valve device V and buffer D of this embodiment operate as described above. The valve device V of this embodiment includes a piston (valve seat member) 3 having a port 3b, a first valve V1 that opens and closes the port 3b, allows bidirectional flow of liquid toward one side of the port 3b and the other, and provides resistance to the liquid flow, and a second valve V2 that is provided in series with the first valve V1 with respect to the port 3b, opens and closes the port 3b, allows bidirectional flow of liquid through the port 3b, and provides resistance to the liquid flow.

[0059] In the valve device V configured in this way, the first valve V1 and the second valve V2 are both provided in a common port 3b. By setting the opening pressures of the first valve V1 and the second valve V2 to be different, the characteristics of the first valve V1 and the second valve V2 can be expressed according to the expansion and contraction speed of the shock absorber D, thereby improving the ride comfort in the vehicle. Furthermore, by providing the first valve V1 and the second valve V2 in a common port 3b, the number of components can be significantly reduced compared to a conventional valve device that has two main valves provided in different ports and a sub-valve that requires a sub-valve case. Therefore, according to the valve device V of this embodiment, the number of components can be reduced and costs can be lowered while improving the ride comfort in the vehicle. In addition, since a sub-valve that requires a sub-valve case is not required, the valve device V can be made smaller.

[0060] Furthermore, in the valve device V of this embodiment, the piston (valve seat member) 3 comprises a main body portion 3a, a port 3b that penetrates from one end of the main body portion 3a to the other end, an annular valve seat 3c that protrudes from one end of the main body portion 3a and surrounds one end of the port 3b, and an annular projection 3d that rises from the other end of the main body portion 3a on the outer circumference side than the other end of the port 3b and has an annular opposing portion 3e on its inner circumference. The first valve V1 is annular and has an annular valve body 6 whose outer circumference can seat and detach from the annular valve seat 3c, and an inner circumference support seat 5 that supports the inner circumference of the annular valve body 6 on the side opposite the valve seat member, and is set to open both inward and outward. The second valve V2 is annular and has an inner circumference that is fixed, while the outer circumference is allowed to deflect in the axial direction on both sides, and the outer circumference surface faces the inner circumference surface of the opposing portion 3e to form a restricted flow path.

[0061] With the valve device V configured in this way, it can be easily assembled by stacking a first valve V1 on one end of a piston (valve seat member) 3 and a second valve V2 on the other end of the piston (valve seat member) 3, and it can improve the ride comfort in a vehicle, while not increasing the overall length of the valve device V, so it can be easily applied to various shock absorbers D.

[0062] Furthermore, the shock absorber D of this embodiment comprises a cylinder 1 as an outer shell, a piston rod 2 inserted into the cylinder 1 so as to be movable in the axial direction, a shock absorber body A having two working chambers provided in the cylinder 1, an extension chamber R1 and a compression chamber R2, and a valve device V provided between the extension chamber R1 and the compression chamber R2.

[0063] The shock absorber D, configured in this way, generates damping force by the second valve V2 when expanding and contracting at very low speeds, and by the first valve V1 when expanding and contracting at high speeds, thereby generating appropriate damping force in each speed range. This improves ride comfort in vehicles and reduces costs by using inexpensive valve devices. Furthermore, with the shock absorber D configured in this way, the valve device V can be made smaller compared to conventional valve devices, making it easier to secure the stroke length and avoiding an increase in the basic length, thus improving ease of installation in vehicles.

[0064] In this embodiment, the buffer D is configured as a single-cylinder type buffer, with a cylinder 1 as the outer shell and a free piston 10 that forms a liquid chamber and an air chamber inside the cylinder 1, and the piston 3 dividing the liquid chamber into two working chambers. However, as mentioned above, it may also be configured as a double-cylinder type buffer with an outer cylinder that forms a reservoir on the outer circumference of the cylinder 1 or a tank that forms a reservoir separately from the cylinder 1. In that case, the valve device V may be provided not only between the extension chamber and the compression chamber, but also between the compression chamber and the reservoir.

[0065] Furthermore, in this embodiment, the opening pressure of the first valve V1 is set higher than the opening pressure of the second valve V2 so that when expanding and contracting at very low speeds, the second valve V2 generates a damping force, and when expanding and contracting at high speeds, the first valve V1 generates a damping force, thereby generating an appropriate damping force in each speed range. However, the opening pressure of the second valve V2 may be set higher than the opening pressure of the first valve V1 so that when expanding and contracting at very low speeds, the first valve V1 generates a damping force, and when expanding and contracting at high speeds, the second valve V2 generates a damping force. In addition, the valve device V of this embodiment is equipped with an orifice 3i, but a choke may be provided instead of the orifice 3i. In this embodiment, the first valve V1 is positioned on the extension side chamber, which is one end of the piston 3 as a valve seat member, and the second valve V2 is positioned on the compression side chamber, which is the other end of the piston 3. However, the first valve V1 may be positioned on the compression side chamber, which is the other end of the piston 3, and the second valve V2 may be positioned on the extension side chamber, which is one end of the piston 3.

[0066] In this configuration, the second valve V2 is set to open outwards, with its inner circumference fixed and its outer circumference allowed to flex, forming a restricted flow path with its outer circumference facing the opposing portion 3e. However, as shown in Figure 4, it may also be set to open inwards, with its outer circumference fixed and its inner circumference allowed to flex on both axial directions, forming a restricted flow path with its inner circumference facing the opposing portion 3j. Specifically, a retaining cylinder 3k is provided at the lower end of the piston 3, rising downward from the outer circumference side of the port 3b and holding the outer circumference of the second valve V2. An opposing portion 3j is provided on the outer circumference of an annular projection 3m that rises downward from the inner circumference side of the piston 3, with its port 3b being the outer circumference side. An annular gap P1 is formed between the inner circumference of the second valve V2 and the opposing portion 3j, and the lower end of the port 3b is opened and closed by the second valve V2. If the axial position of the second valve V2 relative to the retaining cylinder 3k can be adjusted, the axial alignment of the opposing portion 3j and the second valve V2 becomes easier. Alternatively, instead of providing the opposing portion 3j on the annular projection 3m of the piston 3, it may be formed by stacking annular plates on the lower inner circumference of the main body portion 3a of the piston 3 via spacers or multiple spacers. In this case, the axial position of the opposing portion 3j relative to the retaining cylinder 3k may not be adjusted, and the axial position of the opposing portion 3j may be adjusted using spacers or spacers to face the inner circumference of the second valve V2 directly.

[0067] Furthermore, as described above, the first valve V1 has an annular valve body 6 and an inner circumferential support seat 5 that supports the inner circumference of the annular valve body 6 on the side opposite the valve seat member, and is set to open both inward and outward. The second valve V2 is annular, with one of its inner or outer circumference fixed and allowing deflection of the inner or outer circumference, and its outer surface facing the inner surface of the opposing portion 3e to form a restricted flow path. However, as shown in the valve device Va in the first modified example in Figure 5, the second valve V3 may be a valve that has a second annular valve body 20 and a second inner circumferential support seat 21 that supports the inner circumference of the second annular valve body 20 on the side opposite the valve seat member, and is set to open both inward and outward.

[0068] Specifically, as shown in Figure 5, the valve device Va includes a piston 30 as a valve seat member, a first valve V1, and a second valve V3. Specifically, the piston 30 as a valve seat member is annular and fitted to the outer circumference of the piston fitting portion 2a of the piston rod 2, and is fixed to the piston rod 2 by a piston nut 14 that is screwed onto a threaded portion of the piston rod 2 (not shown). More specifically, as shown in Figure 5, the piston 30 is configured to include an annular body portion 30a, a port 30b that penetrates from one end of the body portion 30a, which is the upper end in Figure 5, to the other end, which is the lower end in Figure 5, an annular valve seat 30c that protrudes from one end of the body portion 30a and surrounds one end of the port 30b, and an annular valve seat 30d that is at the other end of the body portion 30a and surrounds the other end of the port 30b. The piston 30 also includes a piston ring 30e that is mounted on the outer circumference of the body portion 30a and slides against the inner circumference of the cylinder 1.

[0069] The main body portion 30a is annular and is fitted onto the outer circumference of the piston fitting portion 2a of the piston rod 2 and fixed to the piston rod 2. Multiple ports 30b are provided arranged on the same circumference relative to the main body portion 30a, opening from one end which is the upper end in Figure 5 of the main body portion 30a and continuing to the other end which is the lower end in Figure 5 of the main body portion 30a. Furthermore, the upper inner circumference portion 30f of the upper end of the main body portion 30a, which is inside the ports 30b, protrudes axially toward the extension chamber side from the upper end of the ports 30b, and an annular valve seat 30c is provided on the outer circumference of the upper end of the main body portion 30a, which protrudes axially toward the extension chamber side from the upper end of the ports 30b and surrounds the opening end of the upper end of the ports 30b. An orifice 30h formed by a notch is provided at the upper end of the annular valve seat 30c. Furthermore, the lower end inner circumference portion 30g of the main body portion 30a, which is inside the port 30b, protrudes axially toward the pressure side chamber side from the lower end of the port 30b, and the other end annular valve seat 30d is provided at the lower end of the main body portion 30a, which is on the outer circumference side from the port 30b, protruding axially toward the pressure side chamber side from the upper end of the port 30b and surrounding the open end of the lower end of the port 30b.

[0070] The first valve V1 is configured with an annular valve body 6 as a first annular valve body whose outer circumference can seat and disseat from the annular valve seat 30c at one end, and an inner circumferential support seat 5 as a first inner circumferential support seat which is stacked on the upper part of the inner circumferential portion 30f of the upper end of the piston 30 via a guide ring 4 in Figure 5 and supports the inner circumference of the annular valve body 6 on the side opposite the piston.

[0071] Furthermore, the second valve V3 is configured with a second annular valve body 20 whose outer circumference is movable toward and away from the annular valve seat 30d at the other end, and a second inner circumferential support seat 21 which is stacked on the lower inner circumferential portion 30g of the lower end of the piston 30 via a guide ring 22 in Figure 5 and supports the inner circumference of the second annular valve body 20 on the side opposite to the piston. The outer diameter of the guide ring 22 is larger than the outer diameter of the lower inner circumferential portion 30g, and the outer diameter of the second inner circumferential support seat 21 is larger than the inner diameter of the guide ring 22. The inner diameter of the second annular valve body 20 is slightly larger than the outer diameter of the guide ring 22, and it is positioned on the outer circumference side of the guide ring 22 and is radially centered by the guide ring 22. In this way, the second valve V3 is configured with the second annular valve body 20 and the second inner circumferential support seat 21 which supports the inner circumferential portion of the second annular valve body 20 on the side opposite to the piston, and the valve opening pressure is set by the initial amount of deflection given to the second annular valve body 20. Furthermore, the second valve V3 is set to open both inward and outward, similar to the first valve V1, and its opening pressure is lower than that of the first valve V1.

[0072] The second valve V3 allows the flow of liquid from the extension chamber R1 to the compression chamber R2 by flexing the outer circumference of the port 30b and separating it from the annular valve seat 30d at the other end, thereby allowing the flow of liquid while providing resistance to it. On the other hand, the second valve V3 allows the flow of liquid from the compression chamber R2 to the extension chamber R1 by flexing the inner circumference of the port 30b and separating it from the second inner circumference support seat 21, thereby allowing the flow of liquid while providing resistance to it.

[0073] In the valve device Va configured in this way, when the buffer D extends in the very low-speed range, the first valve V1 does not open and only the second valve V3 opens. However, the flow area between the second annular valve body 20 and the annular valve seat 30d at the other end of the second valve V3 is smaller than the flow area of ​​the orifice 30h, so the damping force characteristics of the valve device Va are such that the damping force from the second valve V3 rises quickly. Also, when the buffer D extends in the low-speed range, the first valve V1 does not open and only the second valve V3 opens. However, the flow area between the second annular valve body 20 and the annular valve seat 30d at the other end of the second valve V3 is larger than the flow area of ​​the orifice 30h, so the damping force characteristics of the valve device Va are such that they are proportional to the square of the extension speed of the buffer D by the orifice 30h. Furthermore, when the shock absorber D extends in the high-speed range, the first valve V1 opens, and the second annular valve body 20 in the second valve V3 bends significantly, making the flow area between the second annular valve body 20 and the annular valve seat 30d on the other end larger than the flow area of ​​the first valve V1. As a result, the damping force characteristics of the valve device Va become those of the first valve V1.

[0074] On the other hand, in valve device Va, when the shock absorber D contracts in the very low-speed range, the first valve V1 does not open and only the second valve V3 opens. However, the flow area between the second annular valve body 20 and the second inner circumferential support seat 21 in the second valve V3 is smaller than the flow area of ​​the orifice 30h, so the damping force characteristics of valve device Va are such that the damping force from the second valve V3 rises quickly. Also, when the shock absorber D contracts in the low-speed range, the first valve V1 does not open and only the second valve V3 opens. However, the flow area between the second annular valve body 20 and the second inner circumferential support seat 21 in the second valve V3 is larger than the flow area of ​​the orifice 30h, so the damping force characteristics of valve device Va are such that they are proportional to the square of the contraction speed of the shock absorber D by the orifice 30h. Furthermore, when the shock absorber D contracts at high speed, the first valve V1 opens, and the second annular valve body 20 in the second valve V3 bends significantly, making the flow area between the second annular valve body 20 and the second inner circumferential support seat 21 larger than the flow area of ​​the first valve V1. Therefore, the damping force characteristics of the valve device Va become those of the first valve V1. By setting the opening pressure of the first valve V1, which seats away from the annular valve seat 30c on one end where the orifice 30h is provided, higher than the opening pressure of the second valve V3, the damping force characteristics can be set as described above according to the expansion and contraction speed of the shock absorber D. Therefore, when the orifice 30h is provided on the annular valve seat 30d on the other end, it is sufficient to set the opening pressure of the second valve V3 higher than the opening pressure of the first valve V1. Furthermore, the orifice 30h may be provided on the inner support seat 5 as the first inner support seat, the annular valve body 6 as the first annular valve body, the second inner support seat 21, or the second annular valve body 20.

[0075] Therefore, according to the valve device Va in which both the first valve V1 and the second valve V3 are composed of annular valve bodies 6, 20 and inner circumferential support seats 5, 21, the first valve V1 and the second valve V3 are both provided in a common port 30b, and by making the opening pressures of the first valve V1 and the second valve V3 different, the characteristics of the first valve V1 and the second valve V3 can be expressed according to the expansion and contraction speed of the shock absorber D, thereby improving the ride comfort in the vehicle. Furthermore, by providing the first valve V1 and the second valve V3 in a common port 30b, the number of components can be significantly reduced compared to a conventional valve device that has two main valves provided in different ports and a sub-valve that requires a sub-valve case. Therefore, according to the valve device Va of this embodiment, the number of components can be reduced and costs can be lowered while improving the ride comfort in the vehicle. In addition, since a sub-valve that requires a sub-valve case is not required, the valve device Va can be made smaller.

[0076] Furthermore, the valve device Va of this embodiment comprises a piston (valve seat member) 30 comprising a main body portion 30a, a port 30b extending from one end to the other end of the main body portion 30a, a one-end annular valve seat 30c protruding from one end of the main body portion 30a and surrounding one end of the port 30b, and a other-end annular valve seat 30d at the other end of the main body portion 30a and surrounding the other end of the port 30b, and the first valve V1 is annular, with the outer circumference being the one-end annular valve seat 30c The first valve has an annular valve body (first annular valve body) 6 that can be seated and detached from the annular valve body (first annular valve body) 6 and an inner circumference support seat (first inner circumference support seat) 5 that supports the inner circumference of the annular valve body (first annular valve body) 6 on the side opposite to the valve seat member, and is set to open both inward and outward. The second valve V2 is annular and has a second annular valve body 20 whose outer circumference can be seated and detached from the annular valve seat 30d on the other end side, and a second inner circumference support seat 21 that supports the inner circumference of the second annular valve body 20 on the side opposite to the valve seat member, and is set to open both inward and outward.

[0077] With the valve device Va configured in this way, it can be easily assembled by stacking the first valve V1 on one end of a piston (valve seat member) 3 and the second valve V3 on the other end of the piston (valve seat member) 3, and it can improve the ride comfort in a vehicle, while not causing an increase in the overall length of the valve device Va, so it can be easily applied to various shock absorbers D.

[0078] Furthermore, as mentioned above, the first valve V1 has an annular valve body 6 and an inner circumferential support seat 5 that supports the inner circumference of the annular valve body 6 on the side opposite the valve seat member, and is set to open both inward and outward. The second valve V2 is annular, with either the inner or outer circumference fixed and allowing deflection of either the inner or outer circumference, and the outer surface facing the inner surface of the opposing portion 3e to form a restricted flow path. However, as shown in the valve device Vb in the second modified example in Figure 6, the first valve V4 may have its inner circumference fixed and allow deflection of the outer circumference in the axial direction on both sides, and the outer circumference may face the first opposing portion 40d provided on the first annular projection 40c provided on the piston 40 which serves as the valve seat member to form a restricted flow path.

[0079] Specifically, as shown in Figure 6, the valve device Vb comprises a piston 40 as a valve seat member, a first valve V4, and a second valve V2. Specifically, the piston 40 as a valve seat member is annular in shape and fitted onto the outer circumference of the piston fitting portion 2a of the piston rod 2, and is fixed to the piston rod 2 by a piston nut 14 that is screwed onto a threaded portion of the piston rod 2 (not shown). More specifically, as shown in Figure 6, the piston 40 is configured to include an annular body portion 40a, a port 40b that penetrates the body portion 40a from one end which is the upper end in Figure 6 to the other end which is the lower end in Figure 6, a first annular projection 40c that rises from the outer circumference of the body portion 40a at the upper end in Figure 6 and has an annular first opposing portion 40d on its inner circumference, and a second annular projection 40e that rises from the outer circumference of the body portion 40a at the other end which is the lower end in Figure 6 and has an annular second opposing portion 40f on its inner circumference. The piston 40 also includes a piston ring 40g that is mounted on the outer circumference of the body portion 40a and slides against the inner circumference of the cylinder 1.

[0080] The main body portion 40a is annular in shape and is fitted onto the outer circumference of the piston fitting portion 2a of the piston rod 2, thereby fixing it to the piston rod 2. Multiple ports 40b are provided on the same circumference relative to the main body portion 40a, opening from one end which is the upper end in Figure 6 of the main body portion 40a and connecting to the other end which is the lower end in Figure 6 of the main body portion 40a.

[0081] Furthermore, the upper end inner circumference portion 40h of the main body portion 40a, which is inside the port 40b, protrudes axially toward the extension chamber side from the upper end of the port 40b, and the upper end of the main body portion 40a, which is on the outer circumference side from the port 40b, is provided with a first annular projection 40c that protrudes axially toward the extension chamber side from the upper end of the port 40b, surrounds the opening end of the upper end of the port 40b, and has an annular first opposing portion 40d on its inner circumference. The first opposing portion 40d is an annular projection that protrudes toward the inner circumference side from the lower end of the first annular projection 40c and has an annular inner surface.

[0082] Furthermore, the lower end inner circumference portion 40i of the main body portion 40a, which is inside the port 40b, protrudes axially toward the compression chamber side from the lower end of the port 40b, and the lower end of the main body portion 40a, which is on the outer circumference side from the port 40b, is provided with a second annular projection 40e that protrudes axially toward the compression chamber side from the lower end of the port 40b, surrounds the opening end of the lower end of the port 40b, and has an annular second opposing portion 40f on its inner circumference. The second opposing portion 40f is an annular projection that protrudes toward the inner circumference side from the lower end of the second annular projection 40e, and has an annular inner surface.

[0083] A first valve V4 is stacked on the upper part of the inner circumference 40h of the upper end of the piston 40 in Figure 6. The first valve V4 is a leaf valve made of multiple elastic annular plates stacked together and is mounted on the outer circumference of the piston fitting portion 2a of the piston rod 2.

[0084] In this embodiment, the first valve V4 is composed of three stacked annular plates. In Figure 6, the outer diameter of the central annular plate is larger than the outer diameter of the annular plates stacked above and below it. When mounted on the piston fitting portion 2a of the piston rod 2, the outer circumferential surface of the central annular plate faces the inner circumferential surface of the first opposing portion 40d of the piston 40 through a predetermined small annular gap P1.

[0085] Furthermore, as shown in Figure 6, the first valve V4 is annular in shape and is fixedly mounted on the outer circumference of the piston fitting portion 2a of the piston rod 2, with its inner circumference sandwiched by spacers 25 and 26. The inner circumference is the fixed end and the outer circumference is the free end, allowing for deflection of the free outer circumference, and forming a restricted flow path with an annular gap P1 between it and the first opposing portion 40d.

[0086] The number of annular plates constituting the first valve V4 can be arbitrarily set according to the damping force to be obtained by the shock absorber D. Also, although spacers 25 and 26 are shown as being composed of one annular plate each, they may be composed of multiple annular plates. Furthermore, the axial position of the annular plate facing the inner circumferential surface of the first opposing portion 40d of the first valve V4 can be adjusted by adjusting the number of stacked spacers 25 or the thickness of the spacers arranged on the piston side of the first valve V4.

[0087] Furthermore, as shown in Figure 6, the second valve V2 is composed of three annular plates whose inner circumferences are fixed to the outer circumference of the piston fitting portion 2a of the piston rod 2, sandwiched between spacers 7 and 8 stacked below the inner circumference 40i of the lower end of the piston 40. The outer surface of the central annular plate, which has the largest outer diameter, faces directly opposite the inner surface of the annular second opposing portion 40f provided on the inner circumference of the second annular projection 40e of the piston 40, forming a restricting flow path with an annular gap P2 between it and the second opposing portion 40f.

[0088] In the configuration described above, when the outer circumferential surface of the annular plate with the largest outer diameter is directly facing the inner circumferential surfaces of the corresponding first opposing portion 40d and second opposing portion 40f, the flow area of ​​the annular gaps P1 and P2 becomes approximately zero, and the port 40b is connected to the pressure side chamber R2 via the annular gaps P1 and P2, thereby providing resistance to the flow of liquid passing through the port 40b.

[0089] Furthermore, the first valve V4 and the second valve V2, when the difference between the pressure in the extension chamber R1 and the pressure in the compression chamber R2 becomes higher than the valve opening pressure, will bend the outer circumference of the second valve V2 to open it, thereby increasing the annular gaps P1 and P2 which act as restricting passages and providing resistance to the flow of liquid passing through port 40b, but the resistance provided will be less than when the valve is closed.

[0090] In this manner, the first valve V4 and the second valve V2 open and close the port 40b, and allow bidirectional liquid flow through the port 40b, from the extension chamber R1 to the compression chamber R2 and from the compression chamber R2 to the extension chamber R1, while also providing resistance to the liquid flow. The opening pressure of the first valve V4 is set to be higher than the opening pressure of the second valve V2. Furthermore, the flow area of ​​the annular gap P1 when the first valve V4 is closed is set to be larger than the flow area of ​​the annular gap P2 when the second valve V2 is closed.

[0091] In the valve device Vb configured in this way, when the buffer D extends in the very low speed range, the first valve V4 does not open and only the second valve V2 opens. However, the flow area in the annular gap P2 between the second valve V2 and the second opposing part 40f is smaller than the flow area in the annular gap P1 between the first valve V4 and the first opposing part 40d, so the damping force characteristics of the valve device Vb are such that the damping force from the second valve V2 rises quickly. Also, when the buffer D extends in the low speed range, the first valve V4 does not open and only the second valve V2 opens. However, the second valve V2 bends significantly and the flow area in the annular gap P2 becomes larger than the flow area in the annular gap P1 of the first valve V4 in the closed state. Therefore, the damping force characteristics of the valve device Vb are such that they are proportional to the square of the extension speed of the buffer D due to the resistance when the liquid passes through the annular gap P1 of the first valve V4 in the closed state. Furthermore, when the shock absorber D extends at high speed, the first valve V4 opens, making the flow area of ​​the annular gap P2 in the second valve V2 larger than the flow area of ​​the first valve V4. As a result, the damping force characteristics of the valve device Vb become those of the first valve V4.

[0092] On the other hand, in valve device Vb, when the buffer D contracts in the very low-speed range, the first valve V4 does not open and only the second valve V2 opens. However, the flow area in the annular gap P2 between the second valve V2 and the second opposing part 40f is smaller than the flow area in the annular gap P1 between the first valve V4 and the first opposing part 40d. As a result, the damping force characteristics of valve device Vb are such that the damping force from the second valve V2 rises quickly. Furthermore, when the buffer D contracts in the low-speed range, the first valve V4 does not open and only the second valve V2 opens. However, the second valve V2 bends significantly, and the flow area in the annular gap P2 becomes larger than the flow area in the annular gap P1 of the first valve V4 in the closed state. Therefore, the damping force characteristics of valve device Vb are such that they are proportional to the square of the contraction speed of the buffer D due to the resistance when the liquid passes through the annular gap P1 of the first valve V4 in the closed state. Furthermore, when the shock absorber D contracts at high speed, the first valve V4 opens, making the flow area of ​​the annular gap P2 in the second valve V2 larger than the flow area of ​​the first valve V4. As a result, the damping force characteristics of the valve device Vb become those of the first valve V4.

[0093] Therefore, according to the valve device Vb in which both the first valve V4 and the second valve V2 are valves that form a restricting flow path between the corresponding first opposing portion 40d and second opposing portion 40f, the first valve V4 and the second valve V2 are both provided in a common port 40b, and by making the opening pressures of the first valve V4 and the second valve V2 different, the characteristics of the first valve V4 and the second valve V2 can be expressed according to the expansion and contraction speed of the shock absorber D, thereby improving the ride comfort in the vehicle. Furthermore, by providing the first valve V4 and the second valve V2 in a common port 40b, the number of components can be significantly reduced compared to a conventional valve device that has two main valves provided in different ports and a sub-valve that requires a sub-valve case. Therefore, according to the valve device Vb of this embodiment, the number of components can be reduced and costs can be reduced while improving the ride comfort in the vehicle. In addition, since a sub-valve that requires a sub-valve case is not required, the valve device Vb can be made smaller.

[0094] Furthermore, in this embodiment, the valve device Vb has a piston (valve seat member) 40 which has a main body portion 40a, a port 40b that penetrates the main body portion 40a from one end to the other, a first annular projection 40c that rises from one end of the main body portion 40a and has an annular first opposing portion 40d on its inner circumference, and a second annular projection 40e that rises from the other end of the main body portion 40a and has an annular second opposing portion 40f on its inner circumference. The first valve V4 is annular with a fixed inner circumference and is allowed to deflect on both sides of the outer circumference in the axial direction, so that the outer circumference faces the first opposing portion 40d to form a restricted flow path. The second valve V2 is annular with a fixed inner circumference and is allowed to deflect on both sides of the outer circumference in the axial direction, so that the outer circumference faces the second opposing portion 40f to form a restricted flow path.

[0095] With the valve device Vb configured in this way, it can be easily assembled by stacking the first valve V4 on one end of a piston (valve seat member) 40 and the second valve V2 on the other end of the piston (valve seat member) 40, and it can improve the ride comfort in a vehicle, while not causing an increase in the overall length of the valve device Vb, so it can be easily applied to various shock absorbers D. Note that the first valve V4 and the second valve V2 may be set to open inward, as shown in Figure 4, with the outer circumference fixed and the inner circumference deflection permitted.

[0096] Furthermore, the shock absorber D of this embodiment may also include a cylinder 1 as an outer shell, a piston rod 2 inserted into the cylinder 1 so as to be movable in the axial direction, a shock absorber body A having an extension chamber R1 and a compression chamber R2 as two working chambers provided in the cylinder 1, and a valve device Va or valve device Vb provided between the extension chamber R1 and the compression chamber R2.

[0097] The shock absorber D, configured in this way, generates damping force using the second valve when expanding and contracting at very low speeds, and damping force using the first valve when expanding and contracting at high speeds, thereby generating appropriate damping force in each speed range. This improves ride comfort in the vehicle and reduces costs by using inexpensive valve devices. Furthermore, with the shock absorber D configured in this way, the valve devices Va and Vb can be made smaller compared to conventional valve devices, making it easier to secure the stroke length and avoiding an increase in the basic length, thus improving the ease of installation in vehicles.

[0098] Although preferred embodiments of the present invention have been described in detail above, modifications, alterations, and changes are permitted as long as they do not deviate from the scope of the claims.

[0099] 1...Cylinder (outer shell), 2...Piston rod, 3, 30, 40...Piston (valve seat member), 3a, 30a, 40a...Main body, 3b, 30b, 40b...Port, 3d, 3m...Annular projection, 3e...Opposite part, 5...Inner circumferential support seat (first inner circumferential support seat), 6...Annular valve body (first annular valve body), 20...Second annular valve body, 21...Second inner circumferential support seat, 30c...One-end annular valve seat, 30d...Other-end annular valve seat, 40c...First annular projection, 40d...First opposite part, 40e...Second annular projection, 40f...Second opposite part, A...Buffer body, D...Buffer, V, Va, Vb...Valve device, V1, V4...First valve, V2, V3...Second valve

Claims

1. A valve device comprising: a valve seat member having a port; a first valve that opens and closes the port and allows bidirectional flow of liquid toward one and the other of the port, and provides resistance to the flow of the liquid; and a second valve provided in series with the first valve with respect to the port, which opens and closes the port and allows bidirectional flow of liquid through the port, and provides resistance to the flow of the liquid.

2. A valve device according to claim 1, wherein the valve seat member comprises a main body, a port extending from one end to the other end of the main body, a one-end annular valve seat protruding from one end of the main body and surrounding one end of the port, and a other-end annular valve seat protruding from the other end of the main body and surrounding the other end of the port, the first valve having an annular first annular valve body whose outer circumference is repositionable on and off the one-end annular valve seat, and a first inner circumferential support seat supporting the inner circumference of the first annular valve body on the side opposite the valve seat member, and is set to open both inward and outward, and the second valve having an annular second annular valve body whose outer circumference is repositionable on and off the other-end annular valve seat, and a second inner circumferential support seat supporting the inner circumference of the second annular valve body on the side opposite the valve seat member, and is set to open both inward and outward.

3. A valve device according to claim 1, wherein the valve seat member comprises: a main body; a port extending from one end of the main body to the other; a first annular projection rising from one end of the main body and having an annular first opposing portion on either the inner or outer circumference; and a second annular projection rising from the other end of the main body and having an annular second opposing portion on either the inner or outer circumference, wherein the first valve is annular, with one of its inner or outer circumferences fixed and the other being allowed to flex in the axial direction on both sides of the inner or outer circumference, so that the other being faces the first opposing portion to form a restricted flow path; and the second valve is annular, with one of its inner or outer circumferences fixed and the other being allowed to flex in the axial direction on either side of the inner or outer circumference, so that the other being faces the second opposing portion to form a restricted flow path.

4. A valve device according to claim 1, wherein the valve seat member comprises a main body, a port extending from one end of the main body to the other, an annular valve seat protruding from one end of the main body and surrounding one end of the port, and an annular projection rising from the other end of the main body and having an annular opposing portion on either its inner or outer circumference, the first valve comprises an annular annular valve body whose outer circumference is movable toward and toward the annular valve seat, and an inner circumferential support seat supporting the inner circumference of the annular valve body on the side opposite the valve seat member, and is set to open both inward and outward, the second valve comprises an annular valve device in which either the inner or outer circumference is fixed and the other of the inner or outer circumference is allowed to bend, and the other of the inner or outer circumference faces the opposing portion to form a restricted flow path.

5. A valve device according to claim 1, wherein the opening pressure of the first valve and the opening pressure of the second valve are different.

6. A shock absorber comprising a shock absorber body having an outer shell, a piston rod inserted into the outer shell so as to be movable in the axial direction, and two working chambers provided in the outer shell, and a valve device according to claim 1 provided between the two working chambers.

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