Valve device and shock absorber

Abstract

A valve device (Ve) according to the present invention includes: a first passage (3c); a valve seat (3e) which surrounds an outlet end of the first passage (3c); an annular seat part (3g) which has an annular groove (3g1) installed at a location not surrounded by the valve seat (3e); a second passage (3i) which opens to the annular groove (3g1); a main valve (4) which is seated on and separated from the valve seat (3e) and opens and closes the outlet end of the first passage (3c); and a sub-valve (7) which is annular, has elasticity, is attached to the annular groove (3g1), closes the second passage (3i), and can open the second passage (3i) when the diameter of the sub-valve (7) is increased. The valve opening pressure of the sub-valve (7) is set to be lower than the valve opening pressure of the main valve (4).

Description

Valve device and shock absorber

[0005]

[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 in the vehicle, and suppresses the vibrations of the vehicle body and the wheels with 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 in the vehicle, the damping coefficient is increased in the very low speed range where the expansion and contraction speed is lower than the low speed, and the damping force is quickly raised with respect to the switching of the expansion and contraction stroke. In the low speed range, the damping coefficient is made smaller than that in the very low speed range. Further, in the high speed range exceeding the low speed, it is desired to exhibit 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. 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, as mentioned above, generate damping force through a sub-valve, orifice, and main valve. When applied to a shock absorber, they can achieve damping characteristics suitable for the vehicle. However, a sub-valve case is required for the installation of the sub-valve, and the gap between the sub-valve and the opposing part on the inner circumference of the sub-valve case must be made extremely narrow. This requires highly precise dimensional control of the gap, which inevitably increases 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 first passage, a valve seat surrounding the outlet end of the first passage, an annular seat portion having an annular groove installed in a location not surrounded by the valve seat, a second passage opening into the annular groove, a main valve that opens and closes the outlet end of the first passage by seating toward and away from the valve seat, and a sub-valve that is annular and elastic, and is fitted into the annular groove in the annular seat portion to close the second passage, and can open the second passage when its diameter is expanded, wherein the opening pressure of the sub-valve is set lower than the opening pressure of the main valve.

[0013] With this valve device configuration, the second passage is opened and closed by a sub-valve with a lower opening pressure than the main valve. Therefore, when the buffer expands and contracts at a very low speed, the sub-valve generates a damping force; when the buffer expands and contracts at a low speed, the second passage generates a damping force; and when the buffer expands and contracts at a high speed, the main valve opens and generates a damping force. Furthermore, with this valve device, there is no need to generate a damping force using an orifice when the buffer's expansion and contraction speed is in the very low speed range, as the sub-valve can generate a damping force when the buffer expands and contracts at a very low speed.

[0014] Therefore, with the valve device, when the shock absorber expands and contracts at very low speeds, the damping force does not become too high or too low, and an appropriate damping force can be generated according to the expansion and contraction speed of the shock absorber. Furthermore, since the sub-valve is installed in an annular groove that is annular and elastic and not surrounded by a valve seat, and opens and closes the second passage, unlike conventional valve devices, high-level dimensional control of the gap between the sub-valve and the opposing part of the sub-valve case is not required.

[0015] 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 sub-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.

[0016] 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 in the first embodiment is applied to the shock absorber D as an extension valve device Ve that generates damping force when the shock absorber D is extended, and a compression valve device Vc that generates damping force when the shock absorber D is contracted. 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.

[0017] The extension valve device Ve and compression valve device Vc, which function as valve devices, and the various parts of the shock absorber D will be described in detail below. As shown in Figure 1, the shock absorber D comprises an outer cylinder 10 as an outer shell, a piston rod 2 inserted into the outer cylinder 10 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 outer cylinder 10, and an extension valve device Ve and a compression valve device Vc, which function as valve devices provided between the extension chamber R1 and the compression chamber R2.

[0018] The shock absorber body A includes a cylinder 1 housed within an outer cylinder 10. The piston rod 2 is inserted into the cylinder 1 so as to be movable in the axial direction, and can move in and out of the cylinder 1 together with the outer cylinder 10.

[0019] Cylinder 1 is cylindrical in shape, and a piston 3, which serves as a valve seat member, is inserted inside so as to be movable in the axial direction. The inside of cylinder 1 is divided by the piston 3 into an extension chamber R1 above the piston 3 in Figure 1 and a compression chamber R2 below the piston 3 in Figure 1. The extension chamber R1 and the compression chamber R2 inside cylinder 1 are filled with a liquid, such as hydraulic fluid. In addition to hydraulic fluid, water, aqueous solution, etc., may also be used as the liquid.

[0020] The shock absorber body A of this embodiment is equipped with a bottomed cylindrical outer cylinder 10 that covers the outer circumference of the cylinder 1 on the outer circumference side of the cylinder 1. An annular gap is provided between the outer cylinder 10 and the cylinder 1, and a reservoir R is formed by this annular gap. Thus, the shock absorber body A of this embodiment is configured as a double-cylinder type shock absorber. The reservoir R is filled with the same liquid as the liquid filled in the cylinder 1, as well as a gas. When the shock absorber body A expands and contracts, the piston rod 2 enters the cylinder 1, and the volume displaced by the piston rod 2 within the cylinder 1 changes. This volume fluctuation is compensated for when the shock absorber body A expands and contracts by supplying and discharging liquid from the reservoir R into the cylinder 1. If the liquid filled in the reservoir R is hydraulic fluid, it is preferable to use an inert gas such as nitrogen as the gas to prevent deterioration of the hydraulic fluid.

[0021] In this embodiment, the shock absorber body A includes an outer cylinder 10 and a reservoir R between the cylinder 1 and the outer cylinder 10. However, instead of the outer cylinder 10, a separate tank may be provided, and the reservoir R may be formed in the tank. Furthermore, the shock absorber body A may be a single-cylinder type shock absorber body that does not include an outer cylinder 10 and a valve case 13, but is inserted into the cylinder 1 so as to be movable in the axial direction and has a free piston that partitions an air chamber within the cylinder 1. In this way, the shock absorber body A with an air chamber inside the cylinder 1 compensates for volume during expansion and contraction by changing the volume of the air chamber as the free piston moves inside the cylinder 1 in response to the volume fluctuation displaced by the piston rod 2 during expansion and contraction. Alternatively, the shock absorber body A may be configured as a double-rod type shock absorber 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.

[0022] Next, a valve case 13 is fitted to the lower end of the cylinder 1 in Figure 1, which is placed on the bottom of the outer cylinder 10 and separates the pressure chamber R2 inside the cylinder 1 from the reservoir R between the cylinder 1 and the outer cylinder 10. Furthermore, a rod guide 11 is fitted to the upper end of the cylinder 1 in Figure 1, which slidably supports the piston rod 2. This rod guide 11 is fitted to the inner circumference of the outer cylinder 10 and fixed to the outer cylinder 10 by crimping the upper end of the outer cylinder 10, along with a sealing member 12 which is stacked above the rod guide 11 in Figure 1 and seals the space between the outer cylinder 10, the cylinder 1 and the piston rod 2. Once the rod guide 11 is fixed to the outer cylinder 10 in this way, the cylinder 1 is held in place within the outer cylinder 10 by being sandwiched between the crimped upper end and the bottom of the outer cylinder 10, along with the sealing member 12, the rod guide 11 and the valve case 13. Alternatively, instead of crimping the upper opening of the outer cylinder 10, a cap may be screwed onto the upper opening, and the sealing member 12, rod guide 11, cylinder 1, and valve case 13 may be sandwiched between this cap and the bottom of the outer cylinder 10, thereby fixing these components inside the outer cylinder 10.

[0023] 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.

[0024] 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 of the outer cylinder 10, and the outer cylinder 10 is connected to the other of the vehicle body and the wheel via this bracket (not shown).

[0025] 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 up and down relative to the vehicle body, the piston rod 2 moves in and out of the outer cylinder 10, causing the shock absorber D to expand and contract, and the piston 3 moves up and down (axially) inside the cylinder 1.

[0026] Next, the piston 3, which serves as the valve seat member, is annular in shape and is 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 15 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 cylindrical portion 3b provided on the outer circumference of the lower end of the body portion 3a in Figure 2, a plurality of extension ports 3c passing through the body portion 3a in the axial direction, a plurality of compression ports 3d passing through the body portion 3a in the axial direction, an extension annular projection 3e surrounding the lower end in Figure 2 which is the outlet end of the extension port 3c, a compression annular projection 3f surrounding the upper end in Figure 2 which is the outlet end of the compression port 3d, an extension annular seat portion 3g provided on the outer circumference of the extension annular projection 3e, a compression annular seat portion 3h provided on the outer circumference of the compression annular projection 3f, a hole 3i opening from the extension port 3c to the extension annular seat portion 3g, and a hole 3j opening from the compression port 3d to the compression annular seat portion 3h.

[0027] As described above, the piston 3 is a bottomed cylindrical shape comprising a main body portion 3a and a cylindrical portion 3b, and a piston ring 3k is mounted on its outer circumference, which slides against the inner circumference of the cylinder 1, allowing it to move axially relative to the cylinder 1. Furthermore, as shown in Figure 2, the upper and lower ends of the inner circumference of the main body portion 3a protrude upward and downward, respectively, forming an inner circumferential seat portion on which the inner circumferences of the annular extension main valve 4 and the annular compression main valve 7, which serve as the main valves, are seated.

[0028] Multiple extension ports 3c are provided on the same circumference, located on the outer circumference side of the inner circumferential seat portion of the main body 3a, and penetrate the main body 3a in the axial direction, connecting the extension chamber R1 and the compression chamber R2, which serve as working chambers.

[0029] The compression ports 3d are located on the outer circumference of the main body 3a, further outward than the extension ports 3c, and are arranged in a row on the same circumference. They penetrate the main body 3a in the axial direction, connecting the extension chamber R1 and the compression chamber R2, which serve as working chambers.

[0030] The extension port 3c forms a first passage in the extension valve device Ve, which functions as a valve device, and the compression port 3d forms a first passage in the compression valve device Vc, which functions as a valve device.

[0031] The extension-side annular projection 3e is annular in shape and protrudes downward in Figure 2 from between the extension-side port 3c and the compression-side port 3d at the lower end of the main body portion 3a in Figure 2, surrounding the lower end in Figure 2 which is the outlet end of the extension-side port 3c. On the other hand, the compression-side annular projection 3f is annular in shape and protrudes upward in Figure 2 from the outer circumference of the compression-side port 3d at the upper end of the main body portion 3a in Figure 2, surrounding the upper end in Figure 2 which is the outlet end of the compression-side port 3d.

[0032] The extension-side annular projection 3e forms a valve seat surrounding the outlet end of the first passage in the extension-side valve device Ve, which functions as a valve device, and the compression-side annular projection 3f forms a valve seat surrounding the outlet end of the first passage in the compression-side valve device Vc, which functions as a valve device.

[0033] In this embodiment, the extension-side annular seat portion 3g includes an annular groove 3g1 formed circumferentially on the outer circumference of the extension-side annular projection 3e, and is formed by the outer circumference of the extension-side annular projection 3e, and is integrated with the extension-side annular projection 3e. Since the extension-side annular seat portion 3g is the outer circumference of the extension-side annular projection 3e, the annular groove 3g1 provided in the extension-side annular seat portion 3g is located in a position not surrounded by the extension-side annular projection 3e surrounding the extension-side port 3c.

[0034] Furthermore, the compression-side annular seat portion 3h includes an annular groove 3h1 formed circumferentially on the outer circumference of the compression-side annular projection 3f, and is formed by the outer circumference of the compression-side annular projection 3f, and is integrated with the compression-side annular projection 3f. Since the compression-side annular seat portion 3h is the outer circumference of the compression-side annular projection 3f in this way, the annular groove 3h1 provided in the compression-side annular seat portion 3h is located in a position that is not surrounded by the compression-side annular projection 3f surrounding the compression-side port 3d.

[0035] Thus, the extension-side annular seat portion 3g forms the annular seat portion of the extension-side valve device Ve as a valve device, and the compression-side annular seat portion 3h forms the annular seat portion of the compression-side valve device Vc as a valve device.

[0036] Hole 3i opens from the extension port 3c and leads to the bottom of the annular groove 3g1 in the extension annular seat portion 3g. Therefore, hole 3i branches off from the extension port 3c and runs parallel to the extension port 3c, connecting the extension chamber R1 and the compression chamber R2. Hole 3j opens from the compression port 3d and leads to the bottom of the annular groove 3h1 in the compression annular seat portion 3h. Therefore, hole 3j branches off from the compression port 3d and runs parallel to the compression port 3d, connecting the compression chamber R2 and the extension chamber R1.

[0037] Hole 3i opens into an annular groove 3g1 formed in a position not surrounded by the extension-side annular projection 3e acting as a valve seat, and functions as an orifice to provide throttling resistance to the flow of liquid passing through it, forming a second passage in the extension-side valve device Ve, which functions as a valve device. Hole 3j opens into an annular groove 3h1 formed in a position not surrounded by the compression-side annular projection 3f acting as a valve seat, and functions as an orifice to provide throttling resistance to the flow of liquid passing through it, forming a second passage in the compression-side valve device Vc, which functions as a valve device. Multiple holes 3i and 3j may be provided depending on the desired damping force characteristics, and the cross-sectional areas of holes 3i and 3j can also be arbitrarily changed according to the desired damping force characteristics.

[0038] Furthermore, the second passage does not necessarily have to branch off from the first passage; therefore, it may be provided independently of the first passage, rather than being formed by a hole 3i branching off from the extension port 3c or a hole 3j branching off from the compression port 3d. Also, the second passage only needs to be configured as a passage that provides resistance to the flow of the liquid passing through it, so it may function as a choke in addition to an orifice. Thus, although holes 3i and 3j are configured to function as orifices in this embodiment, they may also function as chokes.

[0039] Next, in the lower part of the main body 3a of the piston 3, which serves as a valve seat member, in Figure 2, there is an annular shim 5, an extension main valve 4 which is a laminated leaf valve whose inner circumference is fixed to the piston fitting portion 2a of the piston rod 2 and which seats away from the extension annular projection 3e that serves as a valve seat to open and close the extension port 3c, and an annular spacer 6 which has a smaller outer diameter than the extension main valve 4 and sets the position of the pivot point for the deflection of the extension main valve 4.

[0040] The extension main valve 4 is a laminated leaf valve constructed by stacking multiple annular plates, with its inner circumference fixed to the piston fitting portion 2a and superimposed on the compression chamber side, which is the lower side of the piston 3 in Figure 1. On the side of the extension main valve 4 opposite the piston, a spacer 6, having an outer diameter smaller than the outer diameter of the annular plates constituting the extension main valve 4, is fixed and laminated to the outer circumference of the piston fitting portion 2a. Therefore, the outer circumference of the extension main valve 4 can bend downward in Figure 2, with the outer edge of the spacer 6 acting as a fulcrum.

[0041] Thus, the extension-side main valve 4 is allowed to flex on its outer circumference. When it contacts the extension-side annular projection 3e, it completely closes the extension-side port 3c, and when it flexes on its outer circumference and moves away from the extension-side annular projection 3e, it opens the extension-side port 3c. Therefore, the extension-side main valve 4 can open and close the outlet end of the extension-side port 3c.

[0042] An annular shim 5, formed by stacking multiple annular plates, is interposed between the extension main valve 4 and the inner circumferential seat portion, which is the inner circumference of the lower end of the main body portion 3a of the piston 3 in Figure 2. The shim 5 is mounted on the outer circumference of the piston fitting portion 2a of the piston rod 2, and the axial position of the inner circumference portion of the extension main valve 4 relative to the piston 3 can be adjusted by adjusting the number of stacked annular plates that make up the shim 5.

[0043] The lower end surface of the shim 5 in FIG. 2 is lower than the lower end surface of the extension-side annular protrusion 3e as a valve seat when viewed from the piston 3, and the lower end of the extension-side annular protrusion 3e protrudes downward in FIG. 2 from the lower end of the shim 5, and a height difference is provided between the shim 5 and the extension-side annular protrusion 3e. Therefore, when the extension-side main valve 4 is overlapped on the shim 5 and the extension-side annular protrusion 3e, the extension-side main valve 4 presses against the extension-side annular protrusion 3e with the elastic force generated by bending its outer periphery. From the above, by adjusting the number of laminated annular plates constituting the shim 5, the degree of bending of the extension-side main valve 4 can be adjusted, and the opening pressure when the extension-side main valve 4 separates from the extension-side annular protrusion 3e and opens the valve can be adjusted.

[0044] The shim 5 is composed of a plurality of laminated annular plates, but it may also be composed of a single annular plate. In the case of being composed of a single annular plate, the opening pressure of the extension-side main valve 4 can be adjusted by changing to a shim with a different thickness. Also, if the shim 5 is not required, the inner periphery of the extension-side main valve 4 may be directly overlapped on the inner peripheral sheet portion of the inner periphery of the main body portion 3a of the piston 3.

[0045] Also, above the piston 3 as a valve seat member in FIG. 2, a pressure-side main valve 7 which is a laminated leaf valve whose inner periphery is fixed to the piston fitting portion 2a of the piston rod 2 and opens and closes the pressure-side port 3d, and an annular seat 8 which sets the position of the fulcrum of the bending of the pressure-side main valve 7 and has a smaller outer diameter than the pressure-side main valve 7 and an annular valve stopper 9 are overlapped.

[0046] The pressure-side main valve 7 is a laminated leaf valve composed of a plurality of laminated annular plates, and its inner periphery is fixed to the piston fitting portion 2a and is overlapped on the extension-side chamber side which is the upper side of the piston 3 in FIG. 2. On the anti-piston side of the pressure-side main valve 7, a seat 8 having an outer diameter smaller than the outer diameter of the annular plate constituting the pressure-side main valve 7 is fixed to the outer periphery of the piston fitting portion 2a and laminated. Therefore, the outer periphery of the pressure-side main valve 7 can be bent upward in FIG. 2 with the outer peripheral edge of the seat 8 as a fulcrum. The pressure-side main valve 7 may also be composed of a single annular plate.

[0047] Thus, the pressure-side main valve 7 allows for deflection of its outer periphery. When it abuts against the pressure-side annular projection 3f, it completely blocks the pressure-side port 3d. When it deflects its outer periphery and separates from the pressure-side annular projection 3f, it opens the pressure-side port 3d. Therefore, the pressure-side main valve 7 can open and close the outlet end of the pressure-side port 3d.

[0048] Holes are provided in the annular plates constituting the pressure-side main valve 7. When the annular plates are stacked, the holes of the respective annular plates are connected to form a passage 7a that connects the inlet end of the extension-side port 3c to the extension-side chamber R1. Therefore, even when the pressure-side main valve 7 is stacked above the main body portion 3a of the piston 3, the extension-side port 3c is communicated with the extension-side chamber R1 without being blocked by the pressure-side main valve 7.

[0049] As viewed from the piston 3, the upper end surface of the inner peripheral seat portion, which is the inner peripheral portion at the upper end in FIG. 2 of the main body portion 3a of the piston 3 where the inner peripheral side of the pressure-side main valve 7 seats, is lower than the upper end surface in FIG. 2 of the pressure-side annular projection 3f serving as the valve seat where the inner peripheral side of the pressure-side main valve 7 seats. Therefore, when the pressure-side main valve 7 seats its inner periphery on the inner peripheral seat portion and its outer periphery on the pressure-side annular projection 3f, its outer periphery deflects and it is pressed against the pressure-side annular projection 3f by the elastic force generated by itself, and the opening pressure when it separates from the pressure-side annular projection 3f and opens the valve is set.

[0050] The valve stopper 9 is laminated on the anti-piston side of the pressure-side main valve 7 via the spacer 8. Its outer diameter is larger than the outer diameter of the spacer 8, its inner periphery is fitted to the piston fitting portion 2a, and when the outer periphery of the pressure-side main valve 7 deflects by a predetermined amount or more, it abuts against the outer periphery of the pressure-side main valve 7 to restrict further deflection of the pressure-side main valve 7 and protect the pressure-side main valve 7.

[0051] Then, these valve stopper 9, spacer 8, pressure-side main valve 7, piston 3 as the valve seat member, shim 5, extension-side main valve 4, and spacer 6 are sequentially assembled to the outer periphery of the piston fitting portion 2a of the piston rod 2, and then are sandwiched between the piston nut 15 screwed to the screw portion 2d at the tip of the piston rod 2 and the stepped portion 2c of the piston rod 2 and fixed to the piston rod 2.

[0052] Next, an extension sub-valve 16, made of an elastic material that is annular in shape, is mounted in the annular groove 3g1 of the extension annular seat portion 3g on the outer circumference of the extension annular projection 3e of the piston 3. In this embodiment, the extension sub-valve 16 is a rubber O-ring and is mounted in the annular groove 3g1 in a slightly expanded state, opening and closing the outlet end of the hole 3i which serves as the second passage. Specifically, when the extension sub-valve 16 is in close contact with the bottom of the annular groove 3g1, it closes the outlet end of the hole 3i. When it expands in diameter due to the pressure from the extension chamber R1 through the hole 3i and rises away from the outlet end of the hole 3i, it opens the hole 3i which serves as the second passage, allowing liquid to flow from the extension chamber R1 to the pressure chamber R2 while providing resistance to the liquid flow. Note that when the extension sub-valve 16 is closed, it may not completely block the hole 3i, but may allow a liquid flow to leak through the hole 3i.

[0053] Furthermore, the valve opening pressure when the extension sub-valve 16 moves away from the outlet end of hole 3i and opens the second passage is lower than the valve opening pressure when the extension main valve 4 moves away from the extension annular projection 3e and opens the first passage. When the piston speed of the buffer D extends in the very low speed range, which is lower than low speed, the valve opens, and the extension chamber R1 communicates with the compression chamber R2 via the second passage.

[0054] The extension sub-valve 16 is elastic and only needs to be able to open and close the second passage by expanding in diameter due to the pressure acting through the hole 3i which serves as the second passage. Therefore, in addition to an O-ring, it may also be an annular elastic body made of rubber or synthetic resin.

[0055] Furthermore, a compression-side sub-valve 17, made of an elastic material that is annular in shape, is fitted into the annular groove 3h1 of the compression-side annular seat portion 3h on the outer circumference of the compression-side annular projection 3f of the piston 3. In this embodiment, the compression-side sub-valve 17 is a rubber O-ring and is fitted into the annular groove 3h1 in a slightly expanded state, opening and closing the outlet end of the hole 3j which serves as the second passage. Specifically, when the compression-side sub-valve 17 is in close contact with the bottom of the annular groove 3h1, it closes the outlet end of the hole 3j. When it expands in diameter due to the pressure from the compression-side chamber R2 through the hole 3j and rises away from the outlet end of the hole 3j, it opens the hole 3j which serves as the second passage, allowing the flow of liquid from the compression-side chamber R2 to the expansion-side chamber R1 while providing resistance to the liquid flow. Note that when the compression-side sub-valve 17 is closed, it may not completely block the hole 3j, but may allow a liquid flow to leak through the hole 3j.

[0056] Furthermore, the valve opening pressure when the compression-side sub-valve 17 moves away from the outlet end of hole 3j and opens the second passage is lower than the valve opening pressure when the compression-side main valve 7 moves away from the extension-side annular projection 3e and opens the first passage. When the piston speed of the buffer D contracts in the very low speed range, which is lower than low speed, the valve opens, and the compression-side chamber R2 communicates with the extension-side chamber R1 via the second passage.

[0057] The pressure-side sub-valve 17 is elastic and only needs to be able to open and close the second passage by expanding in diameter due to the pressure acting through the hole 3j which serves as the second passage. Therefore, in addition to an O-ring, it may also be an annular elastic body made of rubber or synthetic resin.

[0058] Furthermore, since the extension sub-valve 16 and compression sub-valve 17 open and close the corresponding holes 3i and 3j by expanding and contracting, if the axial width is narrower than the axial width of the corresponding annular grooves 3h1 and 3g1, and the side walls of the annular grooves 3h1 and 3g1 are curved or inclined surfaces with a wider width on the opening side and a narrower width on the bottom side, then when the diameter is reduced, the bottom of the annular grooves 3h1 and 3g1 will easily return to its original position, and the holes 3i and 3j will be more easily and stably blocked even when expansion and contraction are repeated.

[0059] Furthermore, in order to tightly seal the corresponding holes 3i and 3j by the extension sub-valve 16 and the compression sub-valve 17, the cross-sectional shapes of the extension sub-valve 16 and the compression sub-valve 17 are circular, and the bottom surfaces of the annular grooves 3h1 and 3g1 are curved. In order to tightly seal the corresponding holes 3i and 3j by the extension sub-valve 16 and the compression sub-valve 17, the cross-sectional shape of the inner circumference portion of the extension sub-valve 16 and the compression sub-valve 17 facing the outlet ends of the holes 3i and 3j should correspond to the shape of the bottom surface of the annular grooves 3h1 and 3g1 at the portion where the holes 3i and 3j open. However, the cross-sectional shapes of the inner circumference of the extension sub-valve 16 and the compression sub-valve 17 and the corresponding annular grooves 3h1 and 3g1 may differ as long as the corresponding holes 3i and 3j can be opened and closed by the extension sub-valve 16 and the compression sub-valve 17.

[0060] In this embodiment, the extension valve device Ve, as a valve device, is configured to include a piston 3 as a valve seat member, an extension main valve 4 and an extension sub-valve 16 arranged in parallel between the extension chamber R1 and the compression chamber R2, and the compression valve device Vc, as a valve device, is configured to include a piston 3 as a valve seat member, a compression main valve 7 and a compression sub-valve 17 arranged in parallel between the compression chamber R2 and the extension chamber R1. Furthermore, the first passage in the extension valve device Ve is the extension port 3c of the piston 3, and the second passage in the extension valve device Ve is a hole 3i branching off from the extension port 3c of the piston 3. In addition, the first passage in the compression valve device Vc is the compression port 3d of the piston 3, and the second passage in the compression valve device Vc is a hole 3j branching off from the compression port 3d of the piston 3.

[0061] Next, the valve case 13 is provided with a discharge passage EP and a suction passage SP that connect the pressure chamber R2 and the reservoir R. The discharge passage EP is provided with a pressure damping valve DV that allows only the flow of liquid from the pressure chamber R2 to the reservoir R and provides resistance to the flow of liquid passing through it, and the suction passage SP is provided with a suction check valve SV that allows only the flow of liquid from the reservoir R to the pressure chamber R2 and provides almost no resistance to the flow of liquid passing through it.

[0062] The extension valve device Ve, the compression valve device Vc, and the buffer D, which function as a valve system, are configured as described above. The operation of the extension valve device Ve, the compression valve device Vc, and the buffer D according to this embodiment will be described below. When the buffer D extends, the piston 3 moves upward inside the cylinder 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 extension main valve 4, so the extension main valve 4 does not open and maintains the extension port 3c closed. The compression main valve 7 receives the pressure of the extension chamber R1 from the rear side and closes the compression port 3d. When the extension speed of the buffer D is 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 extension sub-valve 16. Furthermore, as the extension speed of the buffer D increases and reaches the low speed range from the very 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 extension sub-valve 16. As a result, the extension sub-valve 16 receives the pressure of the extension chamber R1 acting through the extension port 3c and hole 3i on its inner surface, expands in diameter, moves away from the outlet end of hole 3i, and opens. Note that the extension main valve 4 does not open when the extension speed of the buffer D is in the very low speed range.

[0063] Therefore, the liquid moves from the extension chamber R1 to the compression chamber R2 by passing through the extension port 3c, hole 3i, and annular groove 3g1. As the liquid passes through the second passage in this manner, it passes through hole 3i, but the flow area between the extension sub-valve 16 in the open state at very low speeds and the outlet end of hole 3i is smaller than the flow area of ​​hole 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 extension sub-valve 16 imparts to the liquid flow.

[0064] 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 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 extension speed is near zero. When the shock absorber D extends, the piston rod 2 retracts from inside the cylinder 1, so the suction check valve SV provided in the valve case 13 opens, and liquid equivalent to the volume of the piston rod 2 retracting from inside the cylinder 1 is supplied from the reservoir R to the cylinder 1 via the suction passage SP, thereby compensating for the volume of the piston rod 2 retracting from inside the cylinder 1.

[0065] Next, when the extension speed of buffer D is in the low speed range beyond the very low speed range, 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 extension main valve 4. Therefore, the extension main valve 4 does not open and maintains the extension port 3c closed. The compression main valve 7 receives the pressure from the extension chamber R1 from the rear side and closes the compression port 3d. When the extension speed of buffer D is in 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 extension sub-valve 16. Therefore, the extension sub-valve 16 expands significantly due to the pressure in the extension chamber R1, increasing the flow area between it and the outlet end of hole 3i. Therefore, in this case as well, the liquid moves from the extension chamber R1 to the compression chamber R2 by passing through the extension port 3c, hole 3i, and annular groove 3g1, but the flow area between the extension sub-valve 16 and the outlet end of hole 3i becomes larger than the flow area of ​​hole 3i. Therefore, hole 3i functions as an orifice, and the resistance it imparts to the liquid flow is greater than the resistance that the extension sub-valve 16 imparts to the liquid flow. Thus, when the extension speed of the buffer D is in the low-speed range, the buffer D mainly relies on hole 3i functioning as an orifice, generating a damping force that hinders extension due to the resistance that hole 3i imparts to the liquid flow. Consequently, when the extension speed of the buffer D is in the low-speed range, the damping force characteristics on the extension side of the buffer D are proportional to the square of the extension speed of the buffer D, which is characteristic of an orifice, as shown in Figure 3, but the damping coefficient is smaller compared to when the extension speed is in the very low-speed range.

[0066] Furthermore, when the extension speed of buffer D exceeds the low-speed range and is in the high-speed range, the pressure difference between the pressure in the extension-side chamber R1 and the pressure in the compression-side chamber R2 reaches the opening pressure of the extension-side main valve 4, causing the extension-side main valve 4 to bend and open, opening the extension-side port 3c. The compression-side main valve 7 receives the pressure of the extension-side chamber R1 from the rear side and closes the compression-side port 3d. When the extension speed of buffer D is in the high-speed range, the pressure difference between the pressure in the extension-side chamber R1 and the pressure in the compression-side chamber R2 exceeds the opening pressure of the extension-side sub-valve 16, so the extension-side sub-valve 16 opens, and the flow area between the extension-side sub-valve 16 and the outlet end of the hole 3i becomes even larger. The liquid moves from the extension-side chamber R1 to the compression-side chamber R2 by passing through the extension-side port 3c, the space between the extension-side main valve 4 and the extension-side annular projection 3e acting as a valve seat, as well as through the hole 3i and the annular groove 3g1. 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. As a result, the flow area in the gap between the extension main valve 4 and the extension annular projection 3e becomes larger than the flow area between the extension sub-valve 16 and the outlet end of the hole 3i, and the flow area in the hole 3i. Furthermore, because the flow rate of liquid moving from the extension chamber R1 to the compression chamber R2 increases, the liquid has difficulty passing through the hole 3i, which has a small flow area. Therefore, when the extension speed of the buffer D is in the high-speed range, the buffer D generates a damping force that hinders extension mainly due to the resistance that the extension main valve 4 imparts to the liquid. Consequently, the damping force characteristics on the extension side of the buffer D when the extension speed of the buffer D is in the high-speed range are proportional to the extension speed of the buffer D, which is specific to the extension main valve 4, as shown in Figure 3. However, the damping coefficient becomes even smaller compared to when the extension speed is in the low-speed range. In this embodiment, the extension-side main valve 4 can also be set to open before the hole 3i, which serves as the second passage, begins to exert resistance as a throttling force on the flow of liquid passing through the hole 3i. In this case, when the extension speed of the buffer D changes from a very low speed range to a high speed range, the characteristics of the hole 3i, which serves as the second passage, do not appear in the damping force characteristics, and the damping force characteristics of the buffer D transition from the characteristics of the extension-side sub-valve 16 to the characteristics of the extension-side main valve 4.

[0067] Next, when the buffer D contracts, the piston 3 moves downward inside the cylinder 1, compressing the pressure chamber R2. As the buffer D contracts, the piston rod 2 enters the cylinder 1, so the pressure damping valve DV provided in the valve case 13 opens, and liquid equivalent to the volume of the piston rod 2 entering the cylinder 1 is discharged from the pressure chamber R2 to the reservoir R via the discharge passage EP. This compensates for the volume of the piston rod 2 entering the cylinder 1, and the pressure inside the cylinder 1 increases.

[0068] When the contraction speed of buffer D is in the very low speed range and 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 compression main valve 7, so the compression main valve 7 does not open and maintains the closure of the compression port 3d. The extension main valve 4 receives the pressure in the compression chamber R2 from the rear side and closes the extension port 3c. When the contraction speed of 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 compression sub-valve 17. Furthermore, as the contraction speed of the buffer D increases and reaches the low speed range from the very 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 compression sub-valve 17. As a result, the compression sub-valve 17 receives the pressure of the compression chamber R2 acting through the compression port 3d and hole 3j on its inner surface, expands in diameter, moves away from the outlet end of hole 3j, and opens. Note that the compression main valve 7 does not open when the contraction speed of the buffer D is in the very low speed range.

[0069] Therefore, the liquid moves from the pressure-side chamber R2 to the extension-side chamber R1 by passing through the pressure-side port 3d, hole 3j, and annular groove 3h1. As the liquid passes through the second passage in this manner, it passes through hole 3j, but the flow area between the pressure-side sub-valve 17 in the open state at very low speeds and the outlet end of hole 3j is smaller than the flow area of ​​hole 3j. Therefore, when the contraction speed of the buffer D is in the very low speed range, the buffer D generates a damping force that prevents contraction due to the resistance that the pressure-side sub-valve 17 and the pressure-side damping valve DV exert on the liquid flow.

[0070] 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 of the shock absorber D with respect to the contraction speed) are as shown in Figure 3, with a characteristic in which the damping coefficient rises very high when the contraction speed is near zero.

[0071] Next, if the contraction speed of the 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 compression main valve 7. Therefore, the compression main valve 7 does not open and maintains the closure of the compression port 3d. The extension main valve 4 receives the pressure from the back side of the compression chamber R2 and closes the extension port 3c. If the contraction speed of the 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 exceeds the opening pressure of the compression sub-valve 17. Therefore, the compression sub-valve 17 expands significantly due to the pressure in the compression chamber R2, increasing the flow area between it and the outlet end of hole 3j. Therefore, in this case as well, the liquid moves from the pressure-side chamber R2 to the extension-side chamber R1 by passing through the pressure-side port 3d, hole 3j, and annular groove 3h1, but the flow area between the pressure-side sub-valve 17 and the outlet end of hole 3j becomes larger than the flow area of ​​hole 3j. Therefore, hole 3j functions as an orifice, and the resistance it imparts to the liquid flow is greater than the resistance that the pressure-side sub-valve 17 imparts to the liquid flow. Thus, when the contraction speed of the buffer D is in the low-speed range, the buffer D mainly relies on hole 3j functioning as an orifice, generating a damping force that hinders contraction due to the resistance that hole 3j imparts to the liquid flow. Consequently, when the contraction speed of the buffer D is in the low-speed range, the damping force characteristics on the pressure side of the buffer D exhibit the characteristic of being proportional to the square of the contraction speed of the buffer D, which is characteristic of an orifice, as shown in Figure 3, but the damping coefficient becomes smaller compared to when the contraction speed is in the very low-speed range.

[0072] 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 compression main valve 7, causing the compression main valve 7 to bend and open, opening the compression port 3d. The extension main valve 4 receives the pressure from the back side of the compression chamber R2 and closes the extension port 3c. 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 exceeds the opening pressure of the compression sub-valve 17, causing the compression sub-valve 17 to open and further increasing the flow area between the compression sub-valve 17 and the outlet end of hole 3j. The liquid moves from the compression chamber R2 to the extension chamber R1 through the pressure port 3d, the space between the compression main valve 7 and the compression annular projection 3f acting as a valve seat, as well as through hole 3j and the annular groove 3h1. When the compression 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. As a result, the flow area in the gap between the compression main valve 7 and the compression annular projection 3f becomes larger than the flow area between the compression sub-valve 17 and the outlet end of hole 3j, and the flow area in hole 3j. Furthermore, because the flow rate of liquid moving from the compression chamber R2 to the extension chamber R1 increases, the liquid has difficulty passing through the hole 3j, which has a small flow area. Therefore, when the compression speed of the buffer D is in the high-speed range, the buffer D generates a damping force that hinders its contraction due to the resistance that the compression main valve 7 and the compression damping valve DV impart to the liquid. Consequently, when the compression speed of the buffer D is in the high-speed range, the damping force characteristics on the compression side of the buffer D, as shown in Figure 3, exhibit characteristics that are proportional to the compression speed of the buffer D, which is specific to the compression main valve 7. However, the damping coefficient becomes even smaller compared to when the compression speed is in the low-speed range.

[0073] Therefore, as shown in Figure 3, the damping force characteristics of the valve device are such that, in response to an increase in the extension or contraction speed of the buffer D, the damping force characteristics of the sub-valve appear first, followed by the damping force characteristics of the second passage, and finally the damping force characteristics of the main valve. Furthermore, as described above, the operation of the valve device and buffer D is explained by dividing the extension and contraction speed of the buffer 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. In this embodiment, it is also possible to set the pressure-side main valve 7 to open before the hole 3j, which serves as the second passage, begins to exert resistance as a throttling against the flow of liquid passing through the hole 3j. In this case, when the contraction speed of the buffer D changes from the very low speed range to the high speed range, the characteristics of the hole 3j, which serves as the second passage, do not appear in the damping force characteristics, and the damping force characteristics of the buffer D become such that they transition from the characteristics of the pressure-side sub-valve 17 to the characteristics of the pressure-side main valve 7.

[0074] The valve device and buffer D of this embodiment operate as described above. Furthermore, the extension valve device Ve, which generates damping force when the shock absorber D is extended, comprises an extension port (first passage) 3c, an extension annular projection (valve seat) 3e surrounding the outlet end of the extension port (first passage) 3c, an extension annular seat portion 3g having an annular groove 3g1 installed in a location not surrounded by the extension annular projection (valve seat) 3e, a hole (second passage) 3i opening into the annular groove 3g1, an extension main valve 4 that opens and closes the outlet end of the extension port (first passage) 3c by seating away from the extension annular projection (valve seat) 3e, and an extension sub-valve 16 that is annular and elastic, is mounted in the annular groove 3g1 of the extension annular seat portion 3g, closes the hole (second passage) 3i, and can open the hole (second passage) 3i when its diameter expands, and the opening pressure of the extension sub-valve 16 is set lower than the opening pressure of the extension main valve 4.

[0075] Furthermore, the compression valve device Vc, which generates damping force when the shock absorber D contracts, comprises a compression port (first passage) 3d, a compression annular projection (valve seat) 3f surrounding the outlet end of the compression port (first passage) 3d, a compression annular seat portion 3h having an annular groove 3h1 installed in a location not surrounded by the compression annular projection (valve seat) 3f, a hole (second passage) 3j opening into the annular groove 3h1, a compression main valve 7 that opens and closes the outlet end of the compression port (first passage) 3d by seating away from the compression annular projection (valve seat) 3f, and a compression sub-valve 17 that is annular and elastic, fitted into the annular groove 3h1 in the compression annular seat portion 3h, closes the hole (second passage) 3j, and can open the hole (second passage) 3j when its diameter expands, and the opening pressure of the compression sub-valve 17 is set lower than the opening pressure of the compression main valve 7.

[0076] In valve devices configured in this way, the extension valve device Ve and the compression valve device Vc, the second passage is opened and closed by a sub-valve with a lower opening pressure than the main valve. Therefore, when the buffer D expands and contracts at a very low speed, the sub-valve generates a damping force; when the buffer D expands and contracts at a low speed, the second passage generates a damping force; and when the buffer D expands and contracts at a high speed, the main valve opens and generates a damping force. Thus, with a valve device configured in this way, there is no need to generate a damping force using an orifice when the expansion and contraction speed of the buffer D is in the very low speed range, and the sub-valve can generate a damping force when the buffer D expands and contracts at a very low speed. Therefore, with a valve device, when the buffer D expands and contracts at a very low speed, the damping force does not become too high or too low, and an appropriate damping force can be generated according to the expansion and contraction speed of the buffer D.

[0077] Furthermore, since the sub-valve is annular and elastic, and is installed in an annular groove that is not surrounded by a valve seat, thereby opening and closing the second passage, unlike conventional valve devices, high-level dimensional control of the gap between the sub-valve and the opposing part of the sub-valve case is not required.

[0078] Therefore, according to the valve device of this embodiment, when applied to the shock absorber D, damping characteristics suitable for the vehicle can be achieved according to the expansion and contraction speed of the shock absorber D, improving the ride comfort in the vehicle, and reducing costs because it does not require sophisticated dimensional control.

[0079] Furthermore, the extension valve device Ve of this embodiment includes an extension port (port) 3c that opens from one end to the other, an extension annular projection 3e that protrudes from the other end and surrounds the outer circumference of the extension port (port) 3c, an annular groove 3g1 formed on the outer circumference of the extension annular projection 3e, and a hole 3i that opens from the extension port (port) 3c and leads to the annular groove 3g1. The first passage is formed by the extension port (port) 3c, the valve seat is formed by the extension annular projection 3e, the extension annular seat portion 3g is formed by the outer circumference of the extension annular projection 3e, and the second passage is formed by the hole 3i. Furthermore, the pressure-side valve device Vc as a valve device of this embodiment includes a piston (valve seat member) 3 having a pressure-side port (port) 3d that opens from one end to the other, a pressure-side annular projection 3f that protrudes from the other end and surrounds the outer circumference of the pressure-side port (port) 3d, an annular groove 3h1 formed on the outer circumference of the pressure-side annular projection 3f, and a hole 3j that opens from the pressure-side port (port) 3d and leads to the annular groove 3h1. The first passage is formed by the pressure-side port (port) 3d, the valve seat is formed by the pressure-side annular projection 3f, the pressure-side annular seat portion 3h is formed by the outer circumference of the pressure-side annular projection 3f, and the second passage is formed by the hole 3j.

[0080] In this valve device configuration, the piston (valve seat member) 3 has a port forming a first passage, an annular projection forming a valve seat, an annular seat portion, an annular groove, and a hole forming a second passage all integrated together. The piston 3 can be used as the valve seat member for both the main valve and the sub-valve, and there is no need to provide a separate valve seat member for the sub-valve. As a result, the valve device can be miniaturized and the number of parts can be reduced, further lowering costs. Furthermore, in this valve device configuration, the outer circumference of the annular projection that protrudes from the valve seat member and forms the valve seat is the annular seat portion. Therefore, there is no need to secure a separate annular seat portion elsewhere for installing the sub-valve on the valve seat member. This prevents the valve seat member from becoming larger even when a sub-valve is installed on the valve seat member, and when applied to a buffer D, the stroke length of the buffer D can be secured without increasing the basic length of the buffer D.

[0081] Furthermore, since the extension sub-valve 16 and compression sub-valve 17 in the valve device of this embodiment are rubber rings fitted into annular grooves 3h1 and 3g1, the outlet end of the second passage can be easily and tightly blocked without requiring high-level dimensional control, and the valve opening pressure can be easily set by setting the inner diameter and Young's modulus. Even if the extension sub-valve 16 and compression sub-valve 17 are formed from rings made of synthetic resin, the outlet end of the second passage can be easily and tightly blocked without requiring high-level dimensional control, and the valve opening pressure can be easily set by setting the inner diameter and Young's modulus.

[0082] Furthermore, the compression sub-valve 171 may be a C-ring fitted into the annular groove 3h1, as shown in Figure 4. When the compression sub-valve 171 is a C-ring, it becomes easier to fit the compression sub-valve 171 into the annular groove 3h1, and because it is made of metal and has excellent durability, it can generate a stable damping force over a long period of time.

[0083] When the compression-side sub-valve 171 is a C-ring, it may be configured as follows, for example. Specifically, the compression-side sub-valve 171 comprises a C-shaped body 171a and a claw 171b extending inward from one end of the body 171a, and a fitting hole 3h2 into which the claw 171b is inserted is provided in an annular groove 3h1 provided in the compression-side annular seat portion 3h which is the outer circumference of the compression-side annular projection 3f of the piston 3.

[0084] The compression sub-valve 171 is fitted into the annular groove 3h1 by housing its body 171a within the annular groove 3h1 and inserting its claws 171b into the fitting holes 3h2. The inner diameter of the body 171a of the compression sub-valve 171 is smaller than the diameter at the bottom of the annular groove 3h1. When the compression sub-valve 171 is fitted into the annular groove 3h1, the body 171a expands in diameter, causing its inner circumferential surface to tightly adhere to the annular groove 3h1 and block the hole 3j. Furthermore, since the claws 171b are fitted into the fitting holes 3h2, the compression sub-valve 171 is positioned circumferentially with respect to the annular groove 3h1 and fitted into the annular groove 3h1. The shape of the claws 171b can be arbitrarily changed, and positioning structures other than the claws 171b and fitting holes 3h2 may be used for the circumferential positioning of the compression sub-valve 17 with respect to the annular groove 3h1. Since the compression-side sub-valve 171 is positioned circumferentially with respect to the annular groove 3h1 in this manner, even if the compression-side sub-valve 171 repeatedly expands and contracts within the annular groove 3h1, its rotation in the circumferential direction is restricted. Therefore, even if it is formed in a C shape, it will always return to a position where it can block the hole 3j, and the second passage can be blocked when the valve is closed.

[0085] Furthermore, as shown in Figure 4, hole 3j opens near fitting hole 3h2 in the annular groove 3h1. Therefore, when the compression sub-valve 171 is installed in the annular groove 3h1, the inner circumference of the other end of the main body 171a faces hole 3j and closes hole 3j.

[0086] In this way, one end of the compression-side sub-valve 171 is fixed to the compression-side annular seat portion 3h, and the inner circumference of the other end opens and closes the hole 3j. Therefore, when the buffer D contracts, the pressure of the compression-side chamber R2 causes the main body 171a to bend along its entire length and move away from the hole 3j. In this way, the amount of deflection of the compression-side sub-valve 171 from the closed state to the open state can be reduced, so the opening pressure of the compression-side sub-valve 171 can be set low, and the stress acting on the compression-side sub-valve 171 when it opens can be reduced, thus suppressing fatigue of the compression-side sub-valve 171. Even when suppressing fatigue of the compression-side sub-valve 171, multiple holes 3j may be provided in positions that can be closed by the inner circumference of the other end of the compression-side sub-valve 171.

[0087] Furthermore, when opening and closing the hole 3j on the inner circumference of the other end of the compression sub-valve 171, the opening pressure of the compression sub-valve 171 can be adjusted by changing the opening position of the hole 3j in the circumferential direction of the annular groove 3h1 relative to the fixed position of one end of the compression sub-valve 171. The configuration of the compression sub-valve 171 can also be used as is for the extension sub-valve 16 in the extension valve device Ve.

[0088] Furthermore, the shock absorber D of this embodiment comprises an outer cylinder 10 as an outer shell, a piston rod 2 inserted into the outer cylinder 10 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 outer cylinder 10, and an extension valve device Ve and a compression valve device Vc as valve devices provided between the extension chamber R1 and the compression chamber R2.

[0089] The shock absorber D, configured in this way, generates damping force through a sub-valve when expanding and contracting at very low speeds, through a second passage when expanding and contracting at low speeds, and through a main valve when expanding and contracting at high speeds. This allows for the generation of appropriate damping force in each speed range, improving ride comfort in the vehicle and reducing costs through the use of inexpensive valve devices.

[0090] In this embodiment, the shock absorber D is configured as a double-cylinder type shock absorber, with an outer cylinder 10 as the outer shell, a cylinder 1 housed inside the outer cylinder 10, and a reservoir R between the outer cylinder 10 and the cylinder 1. However, it may also be configured as a single-cylinder type shock absorber without the outer cylinder 10, with the cylinder 1 as the outer shell, a partition member forming a liquid chamber and an air chamber inside the cylinder 1, and a piston 3 dividing the liquid chamber into two working chambers. In a shock absorber D configured in this way, a valve device can be provided between the two working chambers inside the cylinder 1, the extension chamber R1 and the compression chamber R2. Furthermore, in this embodiment, an extension valve device Ve and a compression valve device Vc are provided to generate damping force by the valve device both during extension and contraction of the shock absorber D. However, it is also possible to apply only one of the extension valve device Ve or the compression valve device Vc to the damping valve of the shock absorber D.

[0091] Furthermore, in the case of a buffer equipped with a reservoir R, such as buffer D in this embodiment, the pressure side chamber R2 and the reservoir R may be used as the operating chamber, and a valve device may be provided between the pressure side chamber R2 and the reservoir R. In that case, as shown in the valve device of the first modified example in Figure 5, the valve case 13 may be used as a valve seat member, and a main valve and a sub-valve may be provided in the valve case 13.

[0092] A more detailed explanation will be given regarding the case where a main valve and a sub-valve are provided in the valve case 13. The valve case 13 is configured to include an annular main body portion 13a that fits onto the inner circumference of the lower end of the cylinder 1, a cylindrical leg portion 13b that extends downward in Figure 5 from the outer circumference of the lower end of the main body portion 13a, a plurality of discharge ports 13c that penetrate the main body portion 13a in the axial direction, a plurality of suction ports 13d that penetrate the main body portion 13a in the axial direction, an annular discharge projection 13e that surrounds the lower end in Figure 5 which is the outlet end of the discharge port 13c, an annular suction projection 13f that surrounds the upper end in Figure 5 which is the outlet end of the suction port 13d, an annular discharge seat portion 13g provided on the outer circumference of the annular discharge projection 13e, an annular suction seat portion 13h provided on the outer circumference of the annular discharge projection 13f, a hole 13i that opens from the discharge port 13c to the annular discharge seat portion 13g, and a hole 13j that opens from the suction port 13d to the annular suction seat portion 13h.

[0093] The discharge port 13c penetrates the main body 3a and connects the pressure-side chamber R2, which serves as the working chamber, to the reservoir R. The suction port 13d is provided on the outer circumference of the discharge port 13c of the main body 3a and penetrates the main body 3a and connects the pressure-side chamber R2, which serves as the working chamber, to the reservoir R. The discharge port 13c forms the first passage in the pressure-side valve device Vc1, which serves as the valve device, and the suction port 13d forms the first passage in the extension-side valve device Ve1, which serves as the valve device.

[0094] The discharge-side annular projection 13e is annular in shape and protrudes downward in Figure 5 from between the discharge port 13c and the suction port 13d at the lower end of the main body portion 13a in Figure 5, surrounding the lower end in Figure 5 which is the outlet end of the discharge port 13c. On the other hand, the suction-side annular projection 13f is annular in shape and protrudes upward in Figure 5 from the outer circumference of the suction port 13d at the upper end of the main body portion 3a in Figure 5, surrounding the upper end in Figure 5 which is the outlet end of the suction port 13d. The discharge-side annular projection 13e forms a valve seat surrounding the outlet end of the first passage in the extension-side valve device Ve1, which is a valve device, and the suction-side annular projection 13f forms a valve seat surrounding the outlet end of the first passage in the compression-side valve device Vc1, which is a valve device.

[0095] The discharge-side annular seat portion 13g is formed by the outer periphery of the discharge-side annular projection 13e, including an annular groove 13g1 formed along the circumferential direction on the outer periphery of the discharge-side annular projection 13e. The annular groove 13g1 is provided in a position not surrounded by the discharge-side annular projection 13e surrounding the discharge port 13c.

[0096] Furthermore, the suction-side annular seat portion 13h includes an annular groove 13h1 formed circumferentially on the outer circumference of the suction-side annular projection 13f, and is formed by the outer circumference of the suction-side annular projection 13f. The annular groove 13h1 is provided in a position not surrounded by the suction-side annular projection 13f surrounding the suction port 13d.

[0097] Thus, the discharge-side annular seat portion 13g forms the annular seat portion of the extension-side valve device Ve1 as a valve device, and the suction-side annular seat portion 13h forms the annular seat portion of the compression-side valve device Vc1 as a valve device.

[0098] Hole 13i opens from the discharge port 13c and leads to the bottom of the annular groove 13g1 of the discharge-side annular seat portion 13g. Hole 13i also branches off from the discharge port 13c and runs parallel to the discharge port 13c, connecting the pressure-side chamber R2 and the reservoir R. Hole 3j opens from the suction port 13d and leads to the bottom of the annular groove 13h1 in the suction-side annular seat portion 13h. Therefore, hole 13j branches off from the suction port 13d and runs parallel to the suction port 13d, connecting the reservoir R and the pressure-side chamber R2. Holes 13i and 13j both function as orifices, providing throttling resistance to the flow of liquid passing through them, and form second passages in the extension-side valve device Ve1 and the compression-side valve device Vc1, which are valve devices.

[0099] In the lower part of the main body 13a of the valve case 13, which serves as a valve seat member, in Figure 5, there is a discharge-side main valve 22 which is an annular stacked leaf valve that seats away from and onto the discharge-side annular projection 13e, which serves as a valve seat, to open and close the discharge port 13c, and a spacer 23 which is an annular and has a smaller outer diameter than the discharge-side main valve 22, which sets the position of the pivot point for the deflection of the discharge-side main valve 22. The discharge-side main valve 22 functions as the main valve in the pressure-side valve device Vc1.

[0100] Furthermore, in the upper part of the main body portion 13a of the valve case 13, which serves as a valve seat member, in Figure 5, there is a suction-side main valve 24, which is an annular stacked leaf valve that seats away from and onto the suction-side annular projection 13f, which serves as a valve seat, to open and close the suction port 13d, and a spacer 25, which is an annular spacer with a smaller outer diameter than the suction-side main valve 24, which sets the position of the pivot point for the deflection of the suction-side main valve 24. The suction-side main valve 24 functions as the main valve in the extension valve device Ve1. The discharge-side main valve 22, spacer 23, valve case 13, suction-side main valve 24, and spacer 25 are assembled to the outer circumference of a center rod 20, which has a flange on its lower outer circumference, and then fixed to the center rod 20 by a nut 21 that is screwed to the tip of the center rod 20.

[0101] Next, an O-ring made of an elastic material that is annular in shape is fitted into the annular groove 13g1 of the annular seat portion 13g on the outer circumference of the annular projection 13e of the valve case 13. The O-ring is made of an elastic material that is annular in shape. When the O-ring is in close contact with the bottom of the annular groove 13g1, it closes the outlet end of the hole 13i. When the diameter expands due to the pressure of the pressure chamber R2 acting through the hole 13i, it opens and opens the outlet end of the hole 13i, which serves as a second passage.

[0102] Furthermore, a suction-side sub-valve 27, which is an O-ring made of an elastic material that is annular in shape, is fitted into the annular groove 13h1 of the suction-side annular seat portion 13h on the outer circumference of the suction-side annular projection 13f of the valve case 13. When the suction-side sub-valve 27 is in close contact with the bottom of the annular groove 13h1, it closes the outlet end of the hole 13j, and when it expands in diameter due to the pressure of the reservoir R acting through the hole 13j, it opens up and opens the outlet end of the hole 13j as a second passage.

[0103] Furthermore, the discharge-side sub-valve 26 and the suction-side sub-valve 27 are elastic and only need to be able to open and close the second passage by expanding in diameter due to the pressure acting through the holes 13i and 13j which serve as the second passage. Therefore, in addition to O-rings, they may also be annular elastic bodies made of rubber or synthetic resin. The discharge-side sub-valve 26 functions as a sub-valve in the pressure-side valve device Vc1, and the suction-side sub-valve 27 functions as a sub-valve in the extension-side valve device Ve1.

[0104] In the buffer D equipped with the valve device configured in this way, when extended, liquid equivalent to the volume by which the piston rod 2 exits the cylinder 1 moves from the reservoir R to the pressure chamber R2, and when retracted, liquid equivalent to the volume by which the piston rod 2 enters the cylinder 1 moves from the pressure chamber R2 to the reservoir R.

[0105] Therefore, the compression valve device Vc1 generates a damping force that hinders the contraction of the buffer D by the discharge sub-valve 26 when the buffer D contracts at a very low speed, by the hole 13j which serves as a second passage when the buffer D contracts at a low speed, and by the discharge main valve 22 when the buffer D contracts at a high speed. In addition, the extension valve device Ve1 generates a damping force that hinders the extension of the buffer D by the suction sub-valve 27 when the buffer D extends at a very low speed, by the hole 13i which serves as a second passage when the buffer D extends at a low speed, and by the suction main valve 24 when the buffer D extends at a high speed.

[0106] Therefore, even if the valve device is installed between the compression chamber R2 and the reservoir R, with the working chamber being the compression chamber R2 and the reservoir R, there is no need to generate damping force by orifice when the expansion and contraction speed of the shock absorber D is in the very low speed range, and the sub-valve can generate damping force when the shock absorber D expands and contracts at a very low speed. Thus, with the valve device, even if installed between the compression chamber R2 and the reservoir R, the damping force will not be too high or too low when the shock absorber D expands and contracts at a very low speed, and an appropriate damping force can be generated according to the expansion and contraction speed of the shock absorber D.

[0107] Furthermore, since the sub-valve is annular and elastic, and is installed in an annular groove that is not surrounded by a valve seat, thereby opening and closing the second passage, a high degree of dimensional control regarding the gap between the sub-valve and the opposing part of the sub-valve case is not required, as is the case with conventional valve devices.

[0108] Therefore, according to the valve device of this embodiment, when applied to the shock absorber D, damping characteristics suitable for the vehicle can be achieved according to the expansion and contraction speed of the shock absorber D, improving the ride comfort in the vehicle, and reducing costs because it does not require sophisticated dimensional control. Furthermore, even when the valve seat member is the valve case 13, the valve case 13 can integrate the port that forms the first passage, the annular projection that forms the valve seat, the annular seat portion, the annular groove, and the hole that forms the second passage. As a result, the valve case 13 can be used as the valve seat member for both the main valve and the sub-valve, and there is no need to provide a separate valve seat member for the sub-valve. This allows for miniaturization of the valve device and a reduction in the number of parts, further reducing costs.

[0109] In the above description, the valve seat member is equipped with a first passage, a valve seat, a second passage, and an annular seat portion having an annular groove. However, as shown in the second modified valve device in Figure 6, the valve seat member may be provided with a port as the first passage and a valve seat surrounding the port, and the annular member provided in addition to the valve seat member may be the annular seat portion.

[0110] More specifically, in the valve device of the second modification, a piston 30 that divides the inside of the cylinder 1 into an extension chamber R1 and a compression chamber R2 is used as a valve seat member, and in addition to the piston 30, an extension annular member 31 and a compression annular member 32 are provided as annular members, thereby constituting an extension valve device Ve2 and a compression valve device Vc2 as a valve device.

[0111] The piston 30 has an annular main body 30a into which the piston fitting portion 2a of the piston rod 2 is inserted, multiple extension ports 30b provided on the same circumference of the main body 30a and passing through the main body 30a to connect the extension chamber R1 and the compression chamber R2 as first passages, compression ports 30c provided on the same circumference of the main body 30a and between the extension ports 30b, 30b and passing through the main body 30a to connect the compression chamber R2 and the extension chamber R1 as first passages, and the lower end of the main body 30a in Figure 6 The device includes an extension valve seat 30d that protrudes toward the direction and surrounds only the outer circumference of the extension port 30b while avoiding the compression port 30c, a compression valve seat 30e that protrudes upward from the upper end of the main body 30a in Figure 6 and surrounds only the outer circumference of the compression port 30c while avoiding the extension port 30b, an extension communication passage 30f provided at the lower end of the main body 30a in Figure 6 and connecting the extension port 30b to the inner circumference of the main body 30a, and a compression communication passage 30g provided at the upper end of the main body 30a in Figure 6 and connecting the compression port 30c to the inner circumference of the main body 30a.

[0112] In this embodiment, the extension valve seat 30d is a petal-shaped valve seat that protrudes downward from the lower end of the main body portion 30a in Figure 6, and surrounds only the lower end in Figure 6, which is the outlet end of the extension port 30b. Furthermore, an extension connecting passage 30f is provided, which connects the extension port 30b and the inner circumference of the main body portion 30a, formed by a groove provided at the lower end of the main body portion 30a in Figure 6.

[0113] In this embodiment, the pressure-side valve seat 30e is a petal-shaped valve seat that protrudes upward from the upper end of the main body portion 30a in Figure 6, and surrounds only the upper end in Figure 6, which is the outlet end of the pressure-side port 30c. The pressure-side communication passage 30g is formed by a groove provided at the upper end of the main body portion 30a in Figure 6, and connects the pressure-side port 30c to the inner circumference of the main body portion 30a.

[0114] In the valve device of the second modified example, the piston 30 has extension ports 30b and compression ports 30c arranged alternately on the same circumference. Therefore, the extension valve seat 30d and the compression valve seat 30e are petal-shaped valve seats that surround only one of the corresponding ports, the extension port 30b and the compression port 30c, and not the other. In contrast, when one of the extension port 30b and the compression port 30c is located on the inner circumference of the main body 30a, and the other is located on the outer circumference of the main body 30a, the extension valve seat 30d and the compression valve seat 30e provided on the piston 30 may be annular valve seats, similar to the extension annular projection 3e and the compression annular projection 3f provided on the piston 3 described above.

[0115] The extension main valve 33 is a laminated leaf valve formed by stacking multiple annular plates. When it is placed on the lower end of the main body portion 30a of the piston 30 in Figure 6, its inner circumference is fixed to the piston fitting portion 2a and it seats on the extension valve seat 30d. The extension main valve 33 is allowed to flex on its outer circumference. When it seats on the extension valve seat 30d, it closes only the extension port 30b, and when it flexes and separates from the extension valve seat 30d, it opens and opens the extension port 30b. Even when the extension main valve 33 is placed on the main body portion 30a of the piston 30 and its outer circumference seats on the extension valve seat 30d, the communication between the extension port 30b and the inner circumference of the main body portion 30a is not severed by the extension communication passage 30f.

[0116] An annular extension-side annular member 31 is superimposed on the lower part of the extension-side main valve 33 in Figure 6. The extension-side annular member 31 has an annular groove 31b formed along the circumferential direction on its outer circumference and a through hole 31c that opens from the annular groove 31b and leads to the inner circumference, forming an extension-side annular seat portion 31a on its outer circumference.

[0117] The compression-side main valve 34 is a laminated leaf valve formed by stacking multiple annular plates. When it is placed on the upper end of the main body portion 30a of the piston 30 in Figure 6, its inner circumference is fixed to the piston fitting portion 2a and it seats on the compression-side valve seat 30e. The compression-side main valve 34 is allowed to flex on its outer circumference. When it seats on the compression-side valve seat 30e, it closes only the compression-side port 30c, and when its outer circumference flexes and moves away from the compression-side valve seat 30e, it opens and releases the compression-side port 30c. Even when the compression-side main valve 34 is placed on the main body portion 30a of the piston 30, the communication between the compression-side port 30c and the inner circumference of the main body portion 30a is not severed by the compression-side communication passage 30g.

[0118] An annular compression-side annular member 32 is superimposed on the compression-side main valve 34 in Figure 6. The compression-side annular member 32 has an annular groove 32b formed along the circumferential direction on its outer circumference and a through hole 32c that opens from the annular groove 32b and leads to the inner circumference, forming a compression-side annular seat portion 32a on its outer circumference.

[0119] As described above, when the piston 30 is fitted together with the extension main valve 33, the compression main valve 34, the extension annular member 31, and the compression annular member 32 onto the outer circumference of the piston fitting portion 2a, which serves as a shaft member, and fixed with the piston nut 15, the extension connecting passage 30f faces the extension connecting groove 2e provided axially on the outer circumference of the piston fitting portion 2a, and the compression connecting passage 30g faces the compression connecting groove 2f provided axially on the outer circumference of the piston fitting portion 2a.

[0120] The extension-side connecting groove 2e extends from the portion of the piston 30 in the piston fitting portion 2a facing the extension-side connecting passage 30f of the piston 30 downward from the lower end of the extension-side main valve 33 in Figure 6, and faces the through hole 31c of the extension-side annular member 31, thus connecting the extension-side connecting passage 30f and the through hole 31c. Therefore, the extension-side connecting passage 30f, the extension-side connecting groove 2e, and the through hole 31c connect the extension-side port 30b to the annular groove 31b, and function as a second passage in the extension-side valve device Ve2. Part or all of the extension-side connecting passage 30f, the extension-side connecting groove 2e, and the through hole 31c that form the second passage may form a throttling passage that provides resistance to the flow of liquid through which it passes.

[0121] Furthermore, the pressure-side communication groove 2f extends from the portion of the piston 30 in the piston fitting portion 2a facing the pressure-side communication passage 30g of the piston 30 upward from the upper end of the pressure-side main valve 34 in Figure 6, and faces the through-hole 32c of the pressure-side annular member 32, thus connecting the pressure-side communication passage 30g and the through-hole 32c. Therefore, the pressure-side communication passage 30g, the pressure-side communication groove 2f, and the through-hole 32c connect the pressure-side port 30c to the annular groove 32b, and function as a second passage in the pressure-side valve device Vc2. Part or all of the pressure-side communication passage 30g, the pressure-side communication groove 2f, and the through-hole 32c that form the second passage may form a throttling passage that provides resistance to the flow of the liquid through which it passes.

[0122] Next, an extension sub-valve 35, made of an elastic material that is annular in shape, is mounted in the annular groove 31b of the extension annular seat portion 31a on the outer circumference of the extension annular member 31. The extension sub-valve 35 is mounted in the annular groove 31b in a slightly enlarged state and opens and closes the outlet end of the through hole 31c, which is the outlet end of the second passage in the extension valve device Ve2. In addition, a compression sub-valve 36, made of an elastic material that is annular in shape, is mounted in the annular groove 32b of the compression annular seat portion 32a on the outer circumference of the compression annular member 32. The compression sub-valve 36 is mounted in the annular groove 32b in a slightly enlarged state and opens and closes the outlet end of the through hole 32c, which is the outlet end of the second passage in the compression valve device Vc2.

[0123] The extension valve device Ve2 and compression valve device Vc2 configured in this way differ from the extension valve device Ve and compression valve device Vc shown in Figure 2 in that the configuration of the second passage is different, and instead of a piston 30 as a valve seat member, an annular seat portion is provided on the extension annular member 31 and the compression annular member 32. However, they operate in the same way as the extension valve device Ve and compression valve device Vc shown in Figure 2.

[0124] Therefore, according to the valve device in the second modified example, when applied to the shock absorber D, it is possible to achieve damping characteristics suitable for the vehicle according to the expansion and contraction speed of the shock absorber D, thereby improving the ride comfort in the vehicle, and also reducing costs because it does not require sophisticated dimensional control.

[0125] The extension valve device Ve2, which is a valve device in a second modified example that generates damping force when the shock absorber D is extended, has an annular piston (valve seat member) 30 having an extension port (port) 30b that opens from one end to the other, an extension valve seat 30d that protrudes from the other end and surrounds the outer circumference of the extension port (port) 30b, and an extension connecting passage 30f that communicates the extension port (port) 30b with the inner circumference, and a piston rod that is fitted to the inner circumference of the piston (valve seat member) 30 and has an extension connecting groove 2e on its outer circumference that communicates with the extension connecting passage 30f. The device comprises a fitting portion (shaft member) 2a and an extendable annular member 31 which is fitted onto the outer circumference of the piston rod fitting portion (shaft member) 2a and has an annular groove 31b formed along the circumferential direction on the outer circumference and a through hole 31c that opens from the annular groove 31b and leads to the inner circumference and communicates with an extendable connecting groove 2e. The first passage is formed by an extendable port (port) 30b, the extendable annular seat portion 31a is formed by the outer circumference of the extendable annular member 31, and the second passage is formed including an extendable connecting path 30f, an extendable connecting groove 2e and a through hole 31c.

[0126] Furthermore, the compression valve device Vc2, which is a valve device in the second modified example that generates damping force when the shock absorber D contracts, has an annular piston (valve seat member) 30 having a compression port (port) 30c that opens from one end to the other, a compression valve seat 30e that protrudes from the other end and surrounds the outer circumference of the compression port (port) 30c, and a compression communication passage 30g that communicates the compression port (port) 30c with the inner circumference, and a piston rod that is fitted to the inner circumference of the piston (valve seat member) 30 and has a compression communication groove 2f on its outer circumference that communicates with the compression communication passage 30g. The device comprises a piston rod fitting portion (shaft member) 2a, a pressure-side annular member 32 which is fitted to the outer circumference of the piston rod fitting portion (shaft member) 2a and has an annular groove 32b formed along the circumferential direction on the outer circumference, and a through hole 32c that opens from the annular groove 32b and leads to the inner circumference and communicates with the pressure-side communication groove 2f, wherein the first passage is formed by the pressure-side port (port) 30c, the pressure-side annular seat portion 32a is formed by the outer circumference of the pressure-side annular member 32, and the second passage is formed including the pressure-side communication path 30g, the pressure-side communication groove 2f, and the through hole 32c.

[0127] With this valve device configuration, a sub-valve can be mounted on an annular member provided separately from the valve seat member. Compared to a structure in which the annular seat portion is concentrated on the valve seat member and the sub-valve is mounted there, the shape of the valve seat of the valve seat member is not restricted by the sub-valve, thus improving the design freedom of the valve seat member. Furthermore, since a connecting groove is provided on the shaft member, a second passage that communicates with the annular groove on the outer circumference of the annular member can be easily provided.

[0128] Furthermore, in the second modified valve device, the sub-valve is mounted in an annular groove on the outer circumference of an annular member that is independent of the valve seat member. Compared to the case where the annular groove is provided on the valve seat member, the dimensions of the annular groove and the sub-valve can be set independently of the valve seat member, improving the design freedom for the opening pressure and damping force characteristics of the sub-valve.

[0129] Furthermore, the second passage in the extension valve device Ve2 may be formed to open from the side of the piston rod 2 facing the extension chamber R1 and communicate with the through hole 31c of the extension annular member 31, without branching from the extension port 30b of the piston 30. Similarly, the second passage in the compression valve device Vc2 may be formed to open from the tip of the piston rod 2 facing the pressure chamber R2 and communicate with the through hole 32c of the pressure annular member 32, without branching from the pressure port 30c of the piston 30. Moreover, the valve device of the second modification may be provided between the pressure chamber R2 and the reservoir R.

[0130] 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.

[0131] 2... Piston rod, 2a... Piston rod fitting part (shaft member), 2e... Extension side connecting groove (connecting groove), 2f... Compression side connecting groove (connecting groove), 3, 30... Piston (valve seat member), 3c, 30b... Extension side port (first passage, port), 3d, 30c... Compression side port (first passage, port), 3e... Extension side annular projection (valve seat), 3f... Compression side annular projection (valve seat), 3g, 31a... Extension side annular seat part (annular seat part), 3g1, 3h1, 31b, 32b... Annular groove, 3h, 32a... Compression side annular seat (annular seat), 3i, 3j... Hole (second passage), 4, 33... Extension side main valve (main valve), 7, 34... Compression side main valve (main valve), 10... Outer cylinder (outer shell), 13... Valve case (valve seat member), 13c... Discharge side port (first passage, port), 13d... Suction side port (first passage, port), 13e... Discharge side annular projection (valve seat), 13f... Suction side annular projection (valve seat), 13f... Discharge side annular seat portion (annular seat portion), 13h1, 13g1... Annular groove, 13g... Suction side annular seat portion (annular seat portion), 13i, 13j... Hole (second passage), 16, 35... Extension side sub-valve (sub-valve), 17, 36, 171... Compression side sub-valve (sub-valve), 30d... Extension side valve seat (valve seat), 30e... Compression side valve seat (valve seat), 30f... Extension Side connecting passage (connecting passage), 30g... Compression side connecting passage (connecting passage), 31... Expansion side annular member (annular member), 31c, 32c... Through hole, 32... Compression side annular member (annular member), A... Buffer body, D... Buffer, R1... Expansion side chamber (operating chamber), R2... Compression side chamber (operating chamber), R... Reservoir (operating chamber), Vc, Vc1, Vc2... Compression side valve device (valve device), Ve, Ve1, Ve2... Expansion side valve device (valve device)

Claims

1. A valve device comprising: a first passage; a valve seat surrounding the outlet end of the first passage; an annular seat portion having an annular groove installed in a location not surrounded by the valve seat; a second passage opening into the annular groove; a main valve that seats away from the valve seat to open and close the outlet end of the first passage; and a sub-valve that is annular and elastic, fitted into the annular groove in the annular seat portion to close the second passage, and which can open the second passage when expanded, wherein the opening pressure of the sub-valve is set lower than the opening pressure of the main valve.

2. A valve device according to claim 1, comprising a valve seat member having a port opening from one end to the other, an annular projection protruding from the other end and surrounding the outer circumference of the port, an annular groove formed on the outer circumference of the annular projection, and a hole opening from the port and leading to the annular groove, wherein the first passage is formed by the port, the valve seat is formed by the annular projection, the annular seat portion is formed by the outer circumference of the annular projection, and the second passage is formed by the hole.

3. A valve device according to claim 1, comprising: an annular valve seat member having a port opening from one end to the other, a valve seat protruding from the other end and surrounding the outer circumference of the port, and a communication passage communicating the port to its inner circumference; a shaft member fitted to the inner circumference of the valve seat member and having a communication groove on its outer circumference that communicates to the communication passage; and an annular member fitted to the outer circumference of the shaft member and having an annular groove formed on its outer circumference along the circumferential direction, and a through hole opening from the annular groove and communicating to the inner circumference and the communication groove, wherein the first passage is formed by the port, the annular seat portion is formed by the outer circumference of the annular member, and the second passage is formed including the communication passage, the communication groove, and the through hole.

4. A valve device according to claim 1, wherein the sub-valve is a ring made of rubber or synthetic resin that is fitted into the annular groove.

5. A valve device according to claim 1, wherein the sub-valve is a C-ring fitted in the annular groove.

6. A valve device according to claim 5, wherein the sub-valve is positioned at one end on the annular seat and opens and closes the outlet end of the second passage at the inner circumference of the other end.

7. 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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