Damping valve and buffer

Abstract

To provide a damping valve capable of functioning as a check valve while suppressing fatigue of a leaf valve, and a buffer which can improve riding quality.SOLUTION: A damping valve EV, CV includes: an annular valve body 21, 27 having a fixed end and a free end; and a valve seat member 20, 26 having an annular opposing seat part 20b, 26b opposing to a peripheral surface in a side of the free end of the valve body 21, 27, a port 20c, 26d provided closer to the fixed end of the valve body 21, 27 than the opposing seat part 20b, 26b, and an annular valve seat 20e, 26f which can sit on / leave the valve body 21, 27 while facing the valve body 21, 27 in an axial direction. The valve body 21,27 includes an annular leaf valve 21a, 27a, and an annular backup valve 21b, 27b which is overlapped with a side of the leaf valve 21a, 27a closer to the valve seat member, and restrains bending of a free end of the leaf valve 21a, 27a toward the valve seat member.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a damping valve and a shock absorber. [Background technology]

[0002] A shock absorber is used, for example, by being interposed between the body and wheels of a vehicle for the purpose of improving the ride comfort of the vehicle, and suppresses vibration of the body and wheels by the damping force that it exerts when expanding and contracting.

[0003] Such a shock absorber includes, for example, a cylinder, a rod that is movably inserted into the cylinder, a piston that is slidably inserted into the cylinder and divides the inside of the cylinder into an expansion side chamber and a compression side chamber, a free piston that is slidably inserted into the cylinder and divides an air chamber below the compression side chamber in the cylinder, a damping passage provided in the piston that connects the expansion side chamber and the compression side chamber, and a damping valve provided in the damping passage.

[0004] In recent years, in order to improve ride comfort in vehicles, there has been a demand for vehicle shock absorbers to exhibit damping force characteristics in which the damping coefficient is high in the very low speed range where the extension / retraction speed is lower than low speed, so that the damping force is quickly increased in response to the change in the extension / retraction stroke, and the damping coefficient is smaller in the low speed range than in the very low speed range, and further, in the medium to high speed range above low speed, the damping coefficient is proportional to the extension / retraction speed but smaller than in the low speed range.

[0005] In order to meet such demands, the damping valve is equipped with an annular leaf valve that is fixed on the inner circumference and allows deflection on the outer circumference, and a valve seat member that is annular and has an annular opposing seat portion that faces the outer circumference of the leaf valve but does not contact the outer circumference, and has a port on the inner circumference of the opposing seat portion, and provides resistance to the flow of hydraulic oil between the extension side chamber and the compression side chamber.

[0006] In a damping valve configured in this manner, when the shock absorber's expansion / contraction speed is in the very low speed range, the leaf valve does not bend significantly and the flow path area between the opposing seat is restricted to an extremely small value, resulting in a damping force characteristic that rises sharply in accordance with the expansion / contraction speed, thereby achieving damping force characteristics suitable for the vehicle (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2019-183918 A Summary of the Invention [Problem to be solved by the invention]

[0008] Conventional damping valves are equipped with a leaf valve and an opposing seat portion, which can improve the damping force characteristics when the shock absorber expands and contracts at very low speeds. However, because the leaf valve bends and opens both when the shock absorber is extended and when it is contracted, it is not possible to obtain different damping force characteristics during extension and contraction.

[0009] In response to this, it is conceivable to provide a valve seat that comes into contact with the leaf valve and closes the port when the leaf valve bends toward the valve seat member relative to the valve seat member, so that the damping valve opens only when hydraulic oil flows through the port in only one direction, thereby configuring the damping valve to also function as a check valve. In this way, when the leaf valve sits on the valve seat and closes the port, the portion of the leaf valve between the fixed end and the valve seat is subjected to back pressure and bends significantly toward the port side, which raises the concern that the leaf valve will become fatigued, and it is difficult to make the damping valve function as a check valve simply by providing a valve seat.

[0010] Therefore, an object of the present invention is to provide a damping valve that can function as a check valve while suppressing fatigue of the leaf valve, and a shock absorber that can improve the ride comfort of a vehicle by incorporating a damping valve. [Means for solving the problem]

[0011] In order to solve the above problems, the damping valve of the present invention comprises an annular valve body having one of its inner circumference or outer circumference as a fixed end and the other of its inner circumference or outer circumference as a free end allowing the free end to deflect relative to the fixed end, and a valve seat member having an annular opposing seat portion facing at least a part of the circumferential surface of the free end side of the valve body, a port provided radially on the fixed end side of the valve body relative to the opposing seat portion, and an annular valve seat provided between the opposing seat portion and the port and axially facing the valve body so that the valve body can be seated and separated therefrom, and the valve body comprises an annular leaf valve and a backup valve which is annular and overlaps the valve seat member side of the leaf valve to suppress deflection of the free end of the leaf valve towards the valve seat member side.

[0012] With the damping valve configured in this manner, when the valve disc receives pressure from the port side, it bends to open the port and provide resistance to the flow of liquid passing through the port, and when it receives pressure pressing the valve disc toward the valve seat member, it seats on the annular valve seat and closes the port, so that it functions as a damping valve for the flow of liquid attempting to pass through the port to one side and functions as a check valve for the flow of liquid attempting to pass through the port to the other side. And, with the damping valve, when the valve disc receives pressure pressing toward the valve seat member while seated on the annular valve seat, the backup valve abuts against the valve seat member side of the leaf valve to support the leaf valve and suppress bending of the middle part of the leaf valve, so that the stress acting on the leaf valve is reduced and fatigue of the leaf valve can be suppressed.

[0013] Moreover, the valve seat member in the damping valve is provided with a restricting portion that is provided radially closer to the fixed end of the valve disc than the annular valve seat, faces the valve disc in the axial direction, and abuts against the valve disc to restrict the deflection of the valve disc when the free end of the valve disc bends toward the valve seat member by a predetermined amount or more. According to the damping valve configured in this manner, in addition to the support by the backup valve, when the middle portion of the valve disc is pressed toward the valve seat member and bends to abut against the restricting portion, the middle portion of the valve disc is supported by the restricting portion to prevent the valve disc from deflecting further, so that even if an excessive pressure acts on the valve disc, the stress on the leaf valve can be reduced and fatigue of the leaf valve can be further suppressed.

[0014] Furthermore, the backup valve in the damping valve may have a notch penetrating the wall thickness in the axial direction. According to the damping valve configured in this manner, the valve body can bend smoothly at the beginning of bending, and a sudden change in the damping force characteristics can be prevented.

[0015] Furthermore, the backup valve in the damping valve may have a notch that penetrates the wall thickness in the axial direction in the range where it abuts against the restricting portion. With a damping valve configured in this way, the valve body 27 can bend smoothly when it starts to bend, preventing a sudden change in the damping force characteristics, and also allowing the valve body to return quickly when it returns in a direction away from the valve seat member from a state where the backup valve abuts against the restricting portion, preventing a delay in opening the port.

[0016] Furthermore, the shock absorber of the present invention includes an outer tube, a rod inserted into the outer tube so as to be axially movable, a shock absorber body having at least two working chambers through which liquid flows by the movement of the rod relative to the outer tube, and a damping valve provided between the working chambers. In the shock absorber configured in this manner, the damping valve can also function as a check valve, so that the damping force characteristics can be set independently according to the expansion or contraction of the shock absorber, and the damping coefficient can be increased in the extremely low speed range of the expansion / contraction speed to quickly raise the damping force in response to the switching of the expansion / contraction stroke, and the damping coefficient can be made smaller in the low speed range than in the extremely low speed range, so that damping force characteristics suitable for suppressing vibration of the vehicle body can be realized, and the ride comfort of the vehicle can be improved. Effect of the Invention

[0017] According to the damping valve of the present invention, it is possible to function as a check valve while suppressing fatigue of the leaf valve, and according to the shock absorber of the present invention, it is possible to improve the ride comfort in the vehicle. [Brief description of the drawings]

[0018] [Figure 1] 1 is a vertical sectional view of a shock absorber to which a damping valve according to an embodiment of the present invention is applied; [Diagram 2] 1 is a partially enlarged cross-sectional view of a shock absorber to which a damping valve according to an embodiment of the present invention is applied; [Diagram 3] 4 is a diagram showing the damping force characteristics of a shock absorber to which the damping valve according to the embodiment of the present invention is applied. FIG. [Figure 4] FIG. 4 is a partially enlarged cross-sectional view of a damping valve in a first modified example of one embodiment of the present invention. [Diagram 5] FIG. 11 is a partially enlarged cross-sectional view of a damping valve in a second modified example of the embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] The present invention will be described below based on the embodiment shown in the drawings. As shown in Fig. 1 and Fig. 2, a shock absorber D in one embodiment includes a shock absorber body A that is expandable and contractible and has a cylinder 1 as an outer tube and a rod 2 movably inserted into the cylinder 1, and an expansion-side sub-valve EV and a compression-side sub-valve CV as damping valves provided between an expansion-side chamber R1 and a compression-side chamber R2 as two working chambers provided in the shock absorber body A. This shock absorber D is used by being interposed between the body and wheels of a vehicle (not shown) to suppress vibration of the body and wheels.

[0020] Hereinafter, each part of the shock absorber D will be described in detail. As shown in Fig. 1, the shock absorber main body A includes a cylindrical cylinder 1 with a bottom as an outer tube, a rod 2 movably inserted into the cylinder 1, and a piston 3 connected to the rod 2, movably inserted into the cylinder 1, and partitioning the inside of the cylinder 1 into an expansion-side chamber R1 and a compression-side chamber R2 as working chambers.

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

[0022] In this way, shock absorber D is interposed between the vehicle body and the wheels. When the vehicle runs on an uneven road surface and the wheels vibrate up and down relative to the vehicle body, the rod 2 moves in and out of the cylinder 1, the shock absorber D expands and contracts, and the piston 3 moves up and down (axially) within the cylinder 1.

[0023] The shock absorber body A also includes an annular rod guide 10 that closes the upper end of the cylinder 1 and through which the rod 2 is slidably inserted around its inner periphery. Thus, the inside of the cylinder 1 is an enclosed space. A free piston 11 is slidably inserted into the cylinder 1 on the opposite side of the piston 3 from the rod 2.

[0024] A liquid chamber L is formed above the free piston 11 in the cylinder 1, and an air chamber G is formed below it. The liquid chamber L is further divided by the piston 3 into an extension side chamber R1 on the rod 2 side and a compression side chamber R2 on the piston 3 side, and the extension side chamber R1 and the compression side chamber R2 are each filled with liquid. The liquid filled in the shock absorber body A may be hydraulic oil, water, an aqueous solution, or other liquid. On the other hand, the air chamber G is filled with compressed air or a gas such as nitrogen gas.

[0025] When the rod 2 retreats from the cylinder 1 during the extension operation of the shock absorber D and the internal volume of the cylinder increases by the volume of the retreated rod 2, the free piston 11 moves upward within the cylinder 1 to expand the air chamber G. Conversely, when the rod 2 advances into the cylinder 1 during the contraction operation of the shock absorber D and the internal volume of the cylinder decreases by the volume of the advanced rod 2, the free piston 11 moves downward within the cylinder 1 to reduce the air chamber G.

[0026] Incidentally, instead of the free piston 11, a bladder, a bellows or the like may be used to separate the liquid chamber L and the air chamber G, and the configuration of the movable partition that serves as this partition can be appropriately changed.

[0027] Furthermore, in this embodiment, the shock absorber D is a single-rod, single-cylinder shock absorber, and when the shock absorber D expands or contracts, the free piston 11 expands or contracts the air chamber G to compensate for the volume of the rod 2 moving in and out of the cylinder 1. However, the configuration for this volume compensation can also be changed as appropriate.

[0028] For example, in the case where the free piston 11 and the air chamber G are eliminated and an outer tube is provided around the outer periphery of the cylinder 1, and a reservoir for storing liquid is formed between the cylinder 1 and the outer tube to make the shock absorber a twin-cylinder type shock absorber, the reservoir may be used to compensate for the volume of the rod 2 moving in and out of the cylinder 1. The reservoir may be formed in a tank that is separate from the cylinder 1. The shock absorber D may also be configured as a double-rod type shock absorber in which the piston 3 is attached to the center of the rod 2 and the ends of the rod 2 protrude outside the cylinder 1 from both ends of the cylinder 1.

[0029] The rod 2 is cylindrical and has a reduced outer diameter at the tip side. The rod 2 is equipped with a small diameter section 2a having the smallest diameter at the tip side, a large diameter section 2b having an outer diameter larger than that of the small diameter section 2a and provided above the small diameter section 2a in Figure 2, a step section 2c provided at the boundary between the small diameter section 2a and the large diameter section 2b, a screw section 2d provided on the outer periphery of the tip of the small diameter section 2a, and four through holes 2e, 2f, 2g, 2h provided at positions shifted from each other upward in Figure 2 from the screw section 2d of the small diameter section 2a and communicating between the inside and the outside of the small diameter section 2a.

[0030] A valve seat member 20, a valve disc 21, a spacer 22, and a valve stopper 23 of the extension side sub-valve EV, a spacer 24, a partition member 25, a valve seat member 26, a valve disc 27, a spacer 28, and a valve stopper 29 of the compression side sub-valve CV, a main valve stopper 6, a compression side main valve 5, a piston 3, and an extension side main valve 4 are assembled in this order to the small diameter portion 2a of the rod 2, and fixed by a piston nut 33 screwed into the threaded portion 2d at the tip of the small diameter portion 2a.

[0031] 1 and 2, the piston 3 is annular and fixed to the outer periphery of the small diameter portion 2a of the rod 2, and is in sliding contact with the inner periphery of the cylinder 1, dividing the inside of the cylinder 1 into an expansion-side chamber R1 on the upper side in Fig. 1 and a compression-side chamber R2 on the lower side in Fig. 1. The piston 3 is provided with an expansion-side passage 3a and a compression-side passage 3b that communicate the expansion-side chamber R1 and the compression-side chamber R2.

[0032] The expansion-side main valve 4 is laminated at the lower end of the piston 3 in FIG. 2. The expansion-side main valve 4 is annular and fitted to the outer periphery of the small diameter portion 2a of the rod 2 to open and close the expansion-side passage 3a. The expansion-side main valve 4 is a laminated leaf valve formed by laminating a plurality of annular plates, and the inner periphery side is fixed to the small diameter portion 2a of the rod 2 to allow bending on the outer periphery side. When the expansion-side main valve 4 is seated on the lower end of the piston 3, it closes the outlet end of the lower end of the expansion-side passage 3a, and when the outer periphery side is bent and separated from the piston 3, it opens the expansion-side passage 3a and provides resistance to the flow of liquid from the expansion-side chamber R1 to the compression-side chamber R2 through the expansion-side passage 3a. The expansion-side main valve 4 is seated on the piston 3 to close the expansion-side passage 3a against the flow of liquid from the compression-side chamber R2 to the expansion-side chamber R1.

[0033] At the upper end of the piston 3 in FIG. 2, a contraction-side main valve 5 is laminated, which is annular and fitted to the outer periphery of the small diameter portion 2a of the rod 2 to open and close the contraction-side passage 3b. The contraction-side main valve 5 is a laminated leaf valve formed by laminating a plurality of annular plates, and the inner periphery side is fixed to the small diameter portion 2a of the rod 2 to allow bending on the outer periphery side. When the contraction-side main valve 5 is seated on the upper end of the piston 3, it closes the outlet end of the upper end of the contraction-side passage 3b, and when the outer periphery side is bent and separated from the piston 3, it opens the contraction-side passage 3b and provides resistance to the flow of liquid from the contraction-side chamber R2 to the expansion-side chamber R1 through the contraction-side passage 3b. The contraction-side main valve 5 is seated on the piston 3 to close the contraction-side passage 3b against the flow of liquid from the expansion-side chamber R1 to the contraction-side chamber R2. A main valve stopper 6 is laminated above the contraction-side main valve 5 in FIG. 2. When the compression side main valve 5 is deflected significantly, the main valve stopper 6 comes into contact with the side of the compression side main valve 5 opposite the piston to support the compression side main valve 5 and prevent excessive stress from acting on the compression side main valve 5, thereby protecting the compression side main valve 5.

[0034] In this embodiment, the expansion-side sub-valve EV serving as a damping valve includes a valve seat member 20, a valve body 21, a spacer 22, and a valve stopper 23, as shown in FIG. The valve seat member 20 is annular and comprises a perforated disk-shaped partition body 20a that fits onto the outer periphery of the small diameter portion 2a, an annular opposing seat portion 20b that protrudes downward from the outer periphery of the lower end of the partition body 20a in FIG. 2, a plurality of ports 20c that are provided on the same circumference and on the inner side of the opposing seat portion 20b at the lower end of the partition body 20a in FIG. 2, a window 20d that is annular recessed portion that is provided at the lower end of the partition body 20a in FIG. 2 and communicates with the outlet ends of each port 20c, an annular valve seat 20e that is provided at the lower end of the partition body 20a in FIG. 2 and protrudes downward from between the opposing seat portion 20b and the port 20c, and an annular inner seat portion 20f that is provided on the inner circumference of the window 20d.

[0035] The facing seat 20b surrounds the outer periphery of the annular valve seat 20e with a gap from the partition body 20a, and protrudes downward from the lower end of the annular valve seat 20e. That is, the height of the facing seat 20b is higher than the annular valve seat 20e when viewed from the partition body 20a, and the height difference between the facing seat 20b and the annular valve seat 20e is at least higher than the axial thickness of the valve body 21 described later. In addition, in the case of this embodiment, the inner circumference of the valve body 21 is a fixed end and the outer circumference is a free end, so that the annular valve seat 20e is provided on the inner circumference side of the facing seat 20b in the valve seat member 20, which is the fixed end side of the valve body 21 in the radial direction. In addition, the height of the seat surface of the inner circumference seat 20f, which is the lower end surface in FIG. 2, is higher than the height of the seat surface of the annular valve seat 20e, which is the lower end surface in FIG. 2, and is lower than the facing seat 20b.

[0036] In this embodiment, the opposing seat 20b and the annular valve seat 20e protrude axially relative to the partition body 20a, and an annular recess is formed between the opposing seat 20b and the annular valve seat 20e. However, when the inner circumference of the valve body 21 is a fixed end, the annular valve seat 20e is provided on the inner circumference of the opposing seat 20b, and as long as the height of the opposing seat 20b is higher than that of the annular valve seat 20e as described above, the opposing seat 20b and the annular valve seat 20e may be integrally arranged to protrude axially from the partition body 20a without having an annular recess between them.

[0037] As shown in FIG. 2, the valve body 21 is configured to include a leaf valve 21a made of a plurality of annular plates, the inner periphery of which is fixed to the small diameter portion 2a as a fixed end and the outer periphery of which is allowed to flex as a free end, and a backup valve 21b stacked on the valve seat member side of the leaf valve 21a, and is stacked on the lower end of the partition body 20a of the valve seat member 20 in FIG. 2 and fixed to the outer periphery of the small diameter portion 2a.

[0038] The leaf valve 21a is composed of three elastic annular plates 21a1, 21a2, and 21a3, each of which has an inner diameter set to a diameter that can fit around the outer periphery of the small diameter portion 2a. More specifically, the leaf valve 21a includes an elastic annular plate 21a1 that is located at the top in Fig. 2 and has the largest outer diameter, an annular plate 21a2 that has an outer diameter smaller than that of the annular plate 21a1 and is stacked on the side opposite the valve seat member of the annular plate 21a1, and an annular plate 21a3 that has an outer diameter smaller than that of the annular plate 21a2 and is stacked on the side opposite the valve seat member of the annular plate 21a2. The number of annular plates constituting the leaf valve 21a can be appropriately changed according to the desired damping force characteristics, and may be one.

[0039] The backup valve 21b is stacked on the valve seat member side, which is the upper side in Fig. 2, of the annular plate 21a1 having the maximum outer diameter of the leaf valve 21a, and is an annular plate whose outer diameter is smaller than that of the annular plate 21a1 and whose inner diameter is equal to that of the annular plate 21a1. In this case, the outer diameter of the backup valve 21b is larger than the inner diameter of the seating surface at the lower end of the annular valve seat 20e.

[0040] When the valve body 21 thus configured is placed on the inner peripheral seat 20f of the partition body 20a of the valve seat member 20, the inner peripheral seat 20f is higher than the annular valve seat 20e, so that the valve body 21 faces the annular valve seat 20e in the axial direction, and a gap is formed between the backup valve 21b and the annular valve seat 20e in the axial direction, and the outer peripheral surface of the free end of the annular plate 21a1 having the maximum outer diameter in the leaf valve 21a faces the inner peripheral surface of the opposing seat 20b of the valve seat member 20 in the radial direction via a small gap. When the leaf valve 21a faces the opposing seat 20b directly, the gap between the leaf valve 21a and the opposing seat 20b is extremely small, making it difficult for liquid to pass through the gap, and this state is defined as a state in which the extension-side sub-valve EV is closed. In addition, since the extension side sub-valve EV can open and close the port 20c as long as at least a portion of the outer peripheral surface on the free end side of the valve body 21 faces radially against the opposing seat portion 20b, it is not necessary for the entire outer peripheral surface of the annular plate 21a1 to face radially against the entire inner peripheral surface of the opposing seat portion 20b.

[0041] The spacer 22 stacked on the valve body 21 on the side opposite the valve seat member has an outer diameter smaller than that of the annular plate 21a3 arranged on the leaf valve 21a on the side closest to the valve seat member, and is fixed immovably to the small diameter portion 2a. The spacer 22 is composed of one annular plate, but may be composed of multiple annular plates. Therefore, when the leaf valve 21a and the backup valve 21b of the valve body 21 receive pressure from the upper side of the valve seat member 20 in FIG. 2, which is passing through the port 20c downward, the outer periphery of the spacer 22 is deflected downward in FIG. 2 with the outer periphery of the spacer 22 as a fulcrum. Then, the outer periphery of the leaf valve 21a is no longer directly opposite the inner periphery of the opposing seat portion 20b in the radial direction, and is shifted downward with respect to the opposing seat portion 20b, and the area of ​​the flow path formed by the gap between the leaf valve 21a and the opposing seat portion 20b is increased according to the amount of deflection of the leaf valve 21a. When the leaf valve 21a and the opposing seat portion 20b are misaligned in this manner and no longer face each other directly, the expansion-side sub-valve EV opens, and the expansion-side sub-valve EV provides resistance to the flow of liquid while allowing the liquid to flow through the gap via the valve body 21.

[0042] When the leaf valve 21a and the backup valve 21b of the valve element 21 receive pressure from the lower side of the valve seat member 20 in FIG. 2, the leaf valve 21a and the backup valve 21b bend the outer periphery upward in FIG. 2 with the inner periphery of the inner periphery seat portion 20f of the valve seat member 20 as a fulcrum. When the valve element 21 bends by a preset amount or more, the backup valve 21b seats on the annular valve seat 20e and closes the port 20c. In this way, when the liquid flows from the upper side to the lower side in FIG. 2, the extension-side sub-valve EV as a damping valve allows the liquid to flow by bending the free end of the valve element 21 toward the opposite side to the valve seat member to open the valve, and conversely, when the liquid flows from the lower side to the upper side in FIG. 2, the free end of the valve element 21 bends toward the valve seat member to seat on the annular valve seat 20e and block the liquid flow. In this way, the expansion-side sub-valve EV functions as a damping valve that opens to allow the flow of liquid through the port 20c in one direction while providing resistance to the flow, and also functions as a check valve that closes to prevent the flow of liquid through the port 20c in the other direction. The backup valve 21b overlaps the valve seat member side of the leaf valve 21a, and when the valve body 21 is seated on the annular valve seat 20e, it abuts against the valve seat side surface of the leaf valve 21a to support the leaf valve 21a, and restricts the portion of the leaf valve 21a between the annular valve seat 20e and the inner peripheral seat portion 20f from bending upward toward the valve seat member side due to pressure from below. In this way, the backup valve 21b supports the leaf valve 21a and suppresses the leaf valve 21a from bending significantly toward the valve seat member side when the valve body 21 is seated on the annular valve seat 20e, thereby preventing excessive stress from acting on the leaf valve 21a and protecting the leaf valve 21a.

[0043] The expansion-side sub-valve EV allows the liquid to flow from the lower side to the upper side through the port 20c until the valve element 21 bends toward the valve seat member and seats on the annular valve seat 20e. The amount of bending of the valve element 21 until it abuts on the annular valve seat 20e when it functions as a check valve can be adjusted by setting the height of the seating surfaces of the inner circumferential seat portion 20f and the annular valve seat 20e, but the amount of bending may also be adjusted by interposing a spacer between the inner circumferential seat portion 20f and the valve element 21. When a spacer is used, the height of the seating surface of the inner circumferential seat portion 20f may be made lower than the height of the seating surface of the annular valve seat 20e, and the amount of bending may be adjusted by the number of stacked spacers.

[0044] The valve stopper 23 is laminated on the side of the spacer 22 opposite the valve seat member, and when the valve body 21 bends significantly, it comes into contact with at least one of the annular plates 21a1, 21a2, 21a3 of the valve body 21 to support the valve body 21 and prevent excessive stress from acting on the valve body 21, thereby protecting the valve body 21.

[0045] A spacer 24 is stacked below the valve stopper 23 in Fig. 2. The spacer 24 is formed in a bottomed cylindrical shape, and a hole 24a is provided at the bottom to allow the small diameter portion 2a of the rod 2 to pass through. A notch 24c is provided in the cylindrical portion 24b to communicate the inside and outside, and the spacer 24 is fixed to the outer periphery of the small diameter portion 2a of the rod 2 with the opening side facing downward in Fig. 2. The cylindrical portion 24b faces the through holes 2e and 2f provided in the small diameter portion 2a in the radial direction, and the inside of the cylindrical portion 24b is connected to the inside of the rod 2. Since the spacer 24 is disposed on the side opposite the valve seat member of the valve body 21, the upper end of the spacer 24 may be used as a valve stopper, and the valve stopper 23 may be eliminated.

[0046] The partition member 25 is a bottomed cylinder, and has a hole 25a at the bottom that allows the small diameter portion 2a of the rod 2 to pass through. The partition member 25 is placed on the lower end of the spacer 24 in FIG. 2 with the opening facing upward, and is fixed to the outer periphery of the small diameter portion 2a of the rod 2 by fitting the cylindrical portion to the outer periphery of the valve seat member 20. The partition member 25 has an outer diameter smaller than the inner diameter of the cylinder 1, and forms an annular gap between the partition member 25 and the cylinder 1. The partition member 25 separates the space R3 into the contraction side chamber R2 together with the valve seat member 20. The space R3 is connected to the expansion side chamber R1 through a port 20c provided in the valve seat member 20, and is connected to the contraction side chamber R2 through the notch 24c of the spacer 24, the through holes 2e and 2f of the small diameter portion 2a, and the inside of the rod 2. The port 20c, the space R3, the through holes 2e, 2f, and the rod 2 form an expansion-side sub-passage EP as a damping passage that connects the expansion-side chamber R1 and the compression-side chamber R2. The expansion-side sub-passage EP thus configured connects the expansion-side chamber R1 and the compression-side chamber R2 in parallel with the expansion-side passage 3a provided in the piston 3. Therefore, the expansion-side sub-valve EV is provided in the expansion-side sub-passage EP that bypasses the expansion-side passage 3a and connects the expansion-side chamber R1 and the compression-side chamber R2.

[0047] In this embodiment, the compression side sub-valve CV as a damping valve is disposed between a partition member 25 and the compression side main valve 5 and is attached to the outer periphery of the small diameter portion 2a, as shown in Fig. 2. In detail, the compression side sub-valve CV includes a valve seat member 26, a valve body 27, a spacer 28, and a valve stopper 29.

[0048] The valve seat member 26 is annular and includes a partition body 26a in the shape of a disk with a hole that fits onto the outer periphery of the small diameter portion 2a, an annular opposing seat portion 26b that protrudes downward from the outer periphery of the lower end of the partition body 26a in FIG. 2, an annular groove 26c provided on the inner periphery of the partition body 26a, a plurality of ports 26d that open from the inner periphery side of the opposing seat portion 26b at the lower end of the partition body 26a in FIG. 2 and communicate with the annular groove 26c, and 2, an annular valve seat 26f provided at the lower end of partition body 26a in FIG. 2 so as to protrude downward from between opposing seat portion 26b and port 26d, an annular inner seat portion 26g provided on the inner circumference of window 26e, and a plurality of regulating portions 26h protruding in the axial direction from within window 26e of partition body 26a.

[0049] The facing seat 26b surrounds the outer periphery of the annular valve seat 26f and protrudes downward from the lower end of the annular valve seat 26f. That is, the height of the facing seat 26b is higher than the annular valve seat 26f when viewed from the partition body 26a, and the height difference between the facing seat 26b and the annular valve seat 26f is at least higher than the axial thickness of the valve body 27 described later. In addition, in the case of this embodiment, the inner circumference of the valve body 27 is a fixed end and the outer circumference is a free end, so that the annular valve seat 26f is provided on the inner circumference side of the facing seat 26b in the valve seat member 26 that is the fixed end side of the valve body 27 in the radial direction. In addition, the height of the seat surface of the inner circumference seat 26g, which is the lower end surface in FIG. 2, is higher than the height of the seat surface of the annular valve seat 26f, which is the lower end surface in FIG. 2, and is lower than the facing seat 26b.

[0050] In this embodiment, the opposing seat 26b and the annular valve seat 26f protrude axially as one unit with respect to the partition body 26a, and the annular valve seat 26f is provided adjacent to the inside of the opposing seat 26b. However, if the inner circumference side of the valve body 27 is a fixed end, the annular valve seat 26f may be spaced apart from the opposing seat 26b and protrude from the partition body 26a on the inner circumference side of the opposing seat 26b.

[0051] In addition, in the contraction side sub-valve CV, the valve seat member 26 is provided with a plurality of restricting portions 26h that protrude in the axial direction from the inner circumferential side, which is the lower end of the partition body 26a and is closer to the fixed end of the valve body 27 than the annular valve seat 26f in the radial direction. In this embodiment, the restricting portions 26h are provided between the annular valve seat 26f and the inner circumferential seat portion 26g and between the ports 26d, 26d in the window 26e in the circumferential direction of the partition body 26a, but the installation position of the restricting portions 26h can be arbitrarily changed in design as long as they are between the annular valve seat 26f and the inner circumferential seat portion 26g and do not interfere with the port 26d. In addition, the shape of the restricting portions 26h when the valve seat member 26 is viewed in the axial direction may be an arc shape or a circle, and can be arbitrarily changed in design. The restricting portion 26h is provided between the ports 26d, 26d, in order to avoid the port 26d, but it is preferable that the restricting portion 26h is provided at equal intervals on the same circumference in order to uniformly support the valve element 27 in the circumferential direction when the valve element 27 is deflected toward the valve seat member, but it does not necessarily have to be provided at equal intervals on the same circumference as long as it can support the valve element 27. The height of the seating surface of the restricting portion 26h is the same as the seating surface of the annular valve seat 26f, but it may be lower than the annular valve seat 26f as long as the valve element 27 can be supported by being in contact with the backup valve 27b when seated on the annular valve seat 26f.

[0052] As shown in FIG. 2, the valve body 27 is configured to include a leaf valve 27a made up of a plurality of annular plates, the inner periphery of which is fixed to the small diameter portion 2a as a fixed end and the outer periphery of which is allowed to flex as a free end, and a backup valve 27b stacked on the valve seat member side of the leaf valve 27a, and is stacked on the lower end of the partition body 26a of the valve seat member 26 in FIG. 2 and fixed to the outer periphery of the small diameter portion 2a.

[0053] The leaf valve 27a is composed of three elastic annular plates 27a1, 27a2, 27a3, each of which has an inner diameter set to a diameter that can fit around the outer periphery of the small diameter portion 2a. More specifically, the leaf valve 27a is equipped with an elastic annular plate 27a1 which is located at the top in FIG. 2 and has the largest outer diameter, an annular plate 27a2 which has an outer diameter smaller than that of the annular plate 27a1 and is stacked on the anti-valve seat member side of the annular plate 27a1, and annular plate 27a3 which has an outer diameter smaller than that of the annular plate 27a2 and is stacked on the anti-valve seat member side of the annular plate 27a2.

[0054] 2 of the annular plate 27a1 having the maximum outer diameter of the leaf valve 27a, and is an annular plate whose outer diameter is smaller than that of the annular plate 27a1 and the annular valve seat 26f and whose inner diameter is equal to that of the annular plate 27a1. Note that, in this case, the outer diameter of the backup valve 27b is smaller than the inner diameter of the seating surface at the lower end of the annular valve seat 26f, so that even if the valve body 27 is deflected toward the valve seat member, it is the annular plate 27a1 of the leaf valve 27a that seats on the annular valve seat 26f.

[0055] When the valve element 27 thus configured is placed on the inner circumferential seat portion 26g of the partition body 26a of the valve seat member 26, the inner circumferential seat portion 26g is higher than the annular valve seat 26f, so that the valve element 27 faces the annular valve seat 26f in the axial direction, and a gap is formed between the backup valve 27b and the annular valve seat 26f in the axial direction, and the outer peripheral surface of the free end of the annular plate 27a1 having the maximum outer diameter in the leaf valve 27a faces directly in the radial direction, via a small gap, the inner circumferential surface of the opposing seat portion 26b of the valve seat member 26. When the leaf valve 27a faces directly the opposing seat portion 26b, the gap between the leaf valve 27a and the opposing seat portion 26b is extremely small, making it difficult for liquid to pass through the gap, and this state is defined as a state in which the compression-side sub-valve CV is closed. Furthermore, as long as at least a portion of the outer peripheral surface on the free end side of the valve body 27 faces radially against the opposing seat portion 26b, the compression side sub-valve CV can open and close the port 26d, so it is not necessary for the entire outer peripheral surface of the annular plate 27a1 to face radially against the entire inner peripheral surface of the opposing seat portion 26b.

[0056] The spacer 28 stacked on the valve body 27 on the side opposite the valve seat member has an outer diameter smaller than that of the annular plate 27a3 arranged on the leaf valve 27a on the side closest to the valve seat member and is fixed immovably to the small diameter portion 2a. The spacer 28 is composed of one annular plate, but may be composed of multiple annular plates. Therefore, when the leaf valve 27a and the backup valve 27b of the valve body 27 receive pressure from the upper side of the valve seat member 26 in FIG. 2, which is passing through the port 26d downward, the outer periphery of the spacer 28 is deflected downward in FIG. 2 with the outer periphery of the spacer 28 as a fulcrum. Then, the outer periphery of the leaf valve 27a is no longer directly opposite the inner periphery of the facing seat portion 26b in the radial direction, and is shifted downward with respect to the facing seat portion 26b, and the area of ​​the flow path formed by the gap between the leaf valve 27a and the facing seat portion 26b is increased according to the amount of deflection of the leaf valve 27a. When the leaf valve 27a and the opposing seat 26b are misaligned in this manner and no longer face each other directly, the compression side sub-valve CV opens, and the compression side sub-valve CV provides resistance to the flow of liquid while allowing the liquid to flow through the gap via the valve body 27.

[0057] When the leaf valve 27a and the backup valve 27b of the valve element 27 receive pressure from the lower side of the valve seat member 26 in FIG. 2, the leaf valve 27a and the backup valve 27b bend the outer periphery upward in FIG. 2 with the inner periphery of the inner periphery seat portion 26g of the valve seat member 26 as a fulcrum. When the valve element 27 bends by a preset amount or more, the annular plate 27a1 of the leaf valve 27a seats on the annular valve seat 26f to close the port 26d. In this way, when the liquid flows from the upper side to the lower side in FIG. 2, the contraction side sub-valve CV as a damping valve allows the liquid to flow by bending the free end of the valve element 27 toward the opposite side to the valve seat member to open the valve, and conversely, when the liquid flows from the lower side to the upper side in FIG. 2, the free end of the valve element 27 bends toward the valve seat member to seat on the annular valve seat 26f to block the liquid flow. In this way, the contraction side sub-valve CV functions as a damping valve that opens to allow the flow of liquid through the port 26d in one direction while providing resistance to the flow, and conversely, functions as a check valve that closes to prevent the flow of liquid through the port 26d in the other direction. The backup valve 27b overlaps the leaf valve 27a on the valve seat member side, and when the leaf valve 27a sits on the annular valve seat 26f, it abuts against the valve seat side surface of the leaf valve 27a to support the leaf valve 27a, and restricts the portion of the leaf valve 27a between the annular valve seat 26f and the inner peripheral seat portion 26g from bending upward toward the valve seat member side due to pressure from below. In this way, the backup valve 27b supports the leaf valve 27a and suppresses the leaf valve 27a from bending significantly toward the valve seat member side when the valve body 27 sits on the annular valve seat 26f, thereby preventing excessive stress from acting on the leaf valve 27a and protecting the leaf valve 27a. In addition to the configuration of the expansion side sub-valve EV, the valve seat member 26 in the compression side sub-valve CV is provided with a regulating portion 26h that axially faces the valve body 27 on the inner side of the annular valve seat 26f and abuts against the backup valve 27b when an intermediate portion between the portion of the valve body 27 abutting against the annular valve seat 26f and the portion abutting against the inner seat portion 26g bends by a predetermined amount or more, thereby supporting the valve seat member from the valve seat member side and regulating the bending between the annular valve seat 26f of the valve body 27 and the fixed end.Therefore, in the compression side sub-valve CV, the bending of the middle part of the leaf valve 27a can be suppressed not only by the backup valve 27b but also by the restricting portion 26h, so that the fatigue of the leaf valve 27a can be further reduced. Note that the height between the restricting portion 26h and the annular valve seat 26f may be set so that the restricting portion 26h does not interfere with the valve element 27's seating on and removal from the annular valve seat 26f, and to that extent, a predetermined amount that is the amount of bending when the valve element 27 abuts against the restricting portion 26h may be set arbitrarily, but the predetermined amount may be set so that the valve element 27 can be supported by the restricting portion 26h before the stress on the valve element 27 becomes excessive.

[0058] The compression side sub-valve CV allows liquid to flow from the lower side to the upper side through the port 26d until the valve element 27 bends toward the valve seat member and seats on the annular valve seat 26f. The amount of deflection, which is the amount of deflection until the valve element 27 abuts on the annular valve seat 26f when functioning as a check valve, can be adjusted by setting the height of the seating surfaces of the inner circumferential seat portion 26g and the annular valve seat 26f, but the amount of deflection may also be adjusted by interposing a spacer between the inner circumferential seat portion 26g and the valve element 27. When a spacer is used, the height of the seating surface of the inner circumferential seat portion 26g may be made lower than the height of the seating surface of the annular valve seat 26f, and the amount of deflection may be adjusted by the number of stacked spacers.

[0059] The valve stopper 29 is laminated on the side of the spacer 28 opposite the valve seat member, and when the valve body 27 bends significantly, it comes into contact with at least one of the annular plates 27a1, 27a2, 27a3 of the valve body 27 to support the valve body 27 and prevent excessive stress from acting on the valve body 27, thereby protecting the valve body 27.

[0060] When the compression side sub-valve CV configured in this manner is stacked on the outer periphery of the small diameter portion 2a and below the spacer 24, the annular groove 26c formed on the inner periphery of the valve seat member 26 faces the through holes 2g and 2h provided in the small diameter portion 2a in the radial direction, so that the port 26d is communicated with the inside of the rod 2. Therefore, the expansion side chamber R1 is communicated with the compression side chamber R2 through the port 26d, the through holes 2g and 2h, and the inside of the rod 2. The port 26d, the through holes 2g and 2h, and the inside of the rod 2 form a compression side sub-passage CP as a damping passage that communicates the expansion side chamber R1 and the compression side chamber R2. The compression side sub-passage CP configured in this manner is parallel to the compression side passage 3b provided in the piston 3 and communicates the expansion side chamber R1 and the compression side chamber R2. Therefore, the compression side sub-valve CV is provided in the compression side sub-passage CP that bypasses the compression side passage 3b and communicates the expansion side chamber R1 and the compression side chamber R2.

[0061] Next, a cylindrical rotary valve 12 is housed within the rod 2, with its outer circumferential surface in sliding contact with the inner circumferential surface of the rod 2, and is allowed to rotate in the circumferential direction within the rod 2. The rotary valve 12 has holes 12a, 12b, 12c, and 12d that communicate with the inside and outside at positions that can face the through holes 2e, 2f, 2g, and 2h, respectively, and when rotated by a control rod 13 inserted within the rod 2, the degree of communication between the through hole 2e and the hole 12a, the through hole 2f and the hole 12b, the through hole 2g and the hole 12c, and the through hole 2h and the hole 12d can be changed, and the through holes 2e, 2f, 2g, and 2h can be blocked without facing the holes 12a, 12b, 12c, and 12d. In other words, the rotary valve 12 can adjust the areas of the four flow passages consisting of the through hole 2e and the hole 12a, the through hole 2f and the hole 12b, the through hole 2g and the hole 12c, and the through hole 2h and the hole 12d depending on the circumferential rotation position relative to the rod 2, and can adjust the resistance to the flow of hydraulic oil passing through the flow passages. In this embodiment, the control rod 13 is driven by a rotary actuator (not shown) such as a stepping motor attached to the tip of the rod 2, but the rotary actuator may be housed within the rod 2.

[0062] When the rotary valve 12 communicates the corresponding holes 12a, 12b with the through holes 2e, 2f, the expansion-side chamber R1 communicates with the compression-side chamber R2 through the expansion-side sub-passage EP. When the rotary valve 12 communicates the corresponding holes 12c, 12d with the through holes 2g, 2h, the expansion-side chamber R1 communicates with the compression-side chamber R2 through the compression-side sub-passage CP. In this way, the rotary valve 12 is provided in the middle of the expansion-side sub-passage EP and the compression-side sub-passage CP, and when rotated by the control rod 13, the degree of communication (flow path area) between the holes 12a, 12b, 12c, 12d and the corresponding through holes 2e, 2f, 2g, 2h can be changed to change the resistance to the flow of the liquid passing through the expansion-side sub-passage EP and the compression-side sub-passage CP. The rotary valve 12 has two holes 12a, 12b for adjusting the flow area of ​​the expansion-side sub-passage EP and two holes 12c, 12d for adjusting the flow area of ​​the compression-side sub-passage CP, but the number of holes can be changed as desired according to the setting of the maximum flow area. The number of through holes in the rod 2 may be set in accordance with the number of holes in the rotary valve 12. Furthermore, the holes 12a, 12b, 12c, and 12d in the rotary valve 12 may be offset in the circumferential direction, and the through holes 2e, 2f, 2g, and 2h in the rod 2 may be positioned appropriately in accordance with the holes 12a, 12b, 12c, and 12d. In addition, depending on the damping force characteristics desired for the shock absorber D, the hole 12b and the through hole 2f may be made to communicate with each other when the hole 12a and the through hole 2e provided in the middle of the extension side sub-passage EP face each other and communicate with each other, or the hole 12b and the through hole 2f may be set to face each other at a timing different from the timing at which the hole 12a and the through hole 2e face each other, and the same applies to the relationship between the holes 12c, 12d and the through holes 2g, 2h provided in the middle of the compression side sub-passage CP.

[0063] The expansion side sub-valve EV and the compression side sub-valve CV, which serve as damping valves, and the shock absorber D are configured as described above. Below, the operation of the expansion side sub-valve EV and the compression side sub-valve CV, which serve as damping valves, and the shock absorber D will be described.

[0064] First, when the shock absorber D expands, the piston 3 moves upward in the cylinder 1 in FIG. 1 to compress the expansion-side chamber R1. When the expansion-side sub-passage EP and the compression-side sub-passage CP are in communication with each other through the rotary valve 12, the liquid in the expansion-side chamber R1 compressed by the upward movement of the piston 3 tries to move to the expanding compression-side chamber R2 through the expansion-side sub-passage EP together with the expansion-side passage 3a provided in the piston 3. Here, when the expansion speed of the shock absorber D is in the extremely low speed range and close to 0, the pressure in the expansion-side chamber R1 increases, but the differential pressure between the pressure in the expansion-side chamber R1 and the pressure in the compression-side chamber R2 does not reach the opening pressure of the expansion-side main valve 4, so the expansion-side main valve 4 does not open and keeps the expansion-side passage 3a closed. The compression-side main valve 5 receives the pressure in the expansion-side chamber R1 from the back side and closes the compression-side passage 3b.

[0065] When the piston speed during the extension operation of the shock absorber D is close to 0, the pressure in the extension side chamber R1 rises, but the pressure difference between the pressure in the compression side chamber R2 does not reach the valve opening pressure of the valve body 21 in the extension side sub-valve EV. Therefore, even if the valve body 21 bends, the outer surface of the annular plate 21a1 in the leaf valve 21a faces the axial width range of the inner circumference of the opposing seat portion 20b, thereby closing the valve and maintaining the flow path area in the annular gap between the valve body 21 and the opposing seat portion 20b to an extremely small value.

[0066] On the other hand, when the extension speed of the shock absorber D is in the extremely low speed range and close to 0, the pressure in the expansion-side chamber R1 rises, but the pressure difference between the pressure in the expansion-side chamber R1 and the pressure in the contraction-side chamber R2 is small, so the valve element 27 in the compression-side sub-valve CV does not bend toward the valve seat member until it seats on the annular valve seat 26f. In this way, when the extension speed of the shock absorber D is in the extremely low speed range and close to 0, the valve element 27 remains closed by opposing the outer circumferential surface of the annular plate 27a1 of the leaf valve 27a within the axial width range of the inner periphery of the opposing seat portion 26b, and the flow path area in the annular gap between the valve element 27 and the opposing seat portion 26b is kept extremely small.

[0067] Therefore, when the extension speed of the shock absorber D is in the very low speed range and close to 0, the liquid in the extension-side chamber R1 has difficulty passing through the extension-side sub-passage EP and the compression-side sub-passage CP because the extension-side sub-valve EV and the compression-side sub-valve CV remain closed. Also, the extension-side main valve 4 keeps the extension-side passage 3a closed. Therefore, when the extension speed of the shock absorber D is in the very low speed range and close to 0, the characteristic of the damping force generated with respect to the piston speed of the shock absorber D (damping force characteristic) becomes a characteristic that rises sharply as shown in FIG. 3.

[0068] Furthermore, when the piston speed during the expansion operation of the shock absorber D increases and changes from the very low speed region to the low speed region, the pressure difference between the pressure in the expansion-side chamber R1 and the pressure in the contraction-side chamber R2 exceeds the valve opening pressure of the valve body 21, so that the valve body 21 bends and opens by shifting its outer periphery downward in FIG. 2 from the range of the axial width of the inner periphery of the opposing seat portion 20b, and increases the flow passage area of ​​the annular gap between the valve body 21 and the opposing seat portion 20b. Then, the liquid passes through the expansion-side sub-valve EV and passes through the expansion-side sub-passage EP to move from the expansion-side chamber R1 to the contraction-side chamber R2. On the other hand, when the piston speed during the expansion operation of the shock absorber D increases and changes from the very low speed region to the low speed region, the valve body 27 of the contraction-side sub-valve CV bends under the pressure in the expansion-side chamber R1 and seats on the annular valve seat 26f of the valve seat member 26, closing the port 26d and preventing the liquid from passing through the contraction-side sub-passage CP.

[0069] Therefore, when the piston speed during the extension operation of the shock absorber D increases and changes from the very low speed range to the low speed range, the flow path area of ​​the extension side sub-valve EV increases in accordance with the increase in the piston speed, so that the damping force characteristics of the shock absorber D become smaller in slope than the damping force characteristic line in the very low speed range, as shown in FIG. 3.

[0070] Furthermore, when the piston speed during the extension operation of the shock absorber D increases and exceeds the low-speed range, the valve body 21 is largely deflected and abuts against the valve stopper 23, maximizing the flow passage area in the annular gap between the opposing seat portion 20b, while the extension-side main valve 4 is deflected and separated from the piston 3 to open the extension-side passage 3a. Then, the liquid moves from the extension-side chamber R1 to the compression-side chamber R2 through the gap between the extension-side main valve 4 and the piston 3, and the deflection amount of the extension-side main valve 4 increases due to the increase in the piston speed, and the flow passage area in the gap between the extension-side main valve 4 and the piston 3 becomes larger than the flow passage area in the annular gap between the valve body 21 and the opposing seat portion 20b in the extension-side sub-valve EV. Therefore, the shock absorber D generates a damping force mainly by the resistance that the extension-side main valve 4 provides to the flow of the liquid. Therefore, when the piston speed during the extension operation of the shock absorber D increases and exceeds the low-speed range, the damping force characteristic of the shock absorber D becomes a characteristic that generates a damping force with a substantially constant slope with respect to the increase in the piston speed as shown in FIG. 3. Since the resistance to the flow of liquid passing through the extension-side sub-passage EP can be adjusted by rotating the rotary valve 12, the damping force of the shock absorber D of this embodiment can be adjusted to a high or low level. During extension of the shock absorber D, the rod 2 retreats from the cylinder 1, but the free piston 11 moves upward in FIG. 2 within the cylinder 1 to expand the air chamber G and compensate for the volume of the rod 2 retreated from the cylinder 1.

[0071] As described above, when the piston speed during the expansion operation of the shock absorber D increases and exceeds the low-speed range, the pressure in the expansion-side chamber R1 largely exceeds the pressure in the contraction-side chamber R2, and the difference between the pressure in the expansion-side chamber R1 acting on the valve body 27 from below in Fig. 2 and the pressure in the contraction-side chamber R2 acting from above in Fig. 2 via the port 26d becomes large. Then, the leaf valve 27a in the valve body 27 in the contraction-side sub-valve CV is pressed upward by the pressure in the expansion-side chamber R1, but since the outer circumferential side is supported by the annular valve seat 26f and the inner circumferential side is supported by the inner circumferential seat portion 26g, the intermediate portion between the portion of the leaf valve 27a that abuts against the annular valve seat 26f and the portion that abuts against the inner circumferential seat portion 26g bends so as to be convex toward the upper side in Fig. 2. The backup valve 27b abuts against the valve seat member side of the leaf valve 27a to support the leaf valve 27a, and suppresses the bending of the middle portion of the leaf valve 27a, thereby suppressing the bending deformation of the middle portion of the leaf valve 27a to be convex upward, reducing the stress acting on the leaf valve 27a and suppressing fatigue of the leaf valve 27a. When the valve body 27 is pressed by the pressure in the expansion-side chamber R1 and the backup valve 27b abuts against the restricting portion 26h of the valve seat member 26, the leaf valve 27a is supported by the restricting portion 26h and the bending of the middle portion of the leaf valve 27a is prevented from becoming larger, and the stress of the leaf valve 27a does not increase any more, thereby further suppressing fatigue of the leaf valve 27a.

[0072] Next, when the shock absorber D contracts, the piston 3 moves downward in FIG. 1 inside the cylinder 1 to compress the compression side chamber R2. When the expansion side sub-passage EP and the compression side sub-passage CP are in communication with each other through the rotary valve 12, the liquid in the compression side chamber R2 compressed by the downward movement of the piston 3 tries to move to the expanding expansion side chamber R1 through the compression side sub-passage CP together with the compression side passage 3b provided in the piston 3. Here, when the contraction speed of the shock absorber D is in the extremely low speed range and close to 0, the pressure in the compression side chamber R2 rises, but the pressure difference between the pressure in the compression side chamber R2 and the pressure in the expansion side chamber R1 does not reach the opening pressure of the compression side main valve 5, so the compression side main valve 5 does not open and keeps the compression side passage 3b closed. The expansion side main valve 4 receives the pressure of the compression side chamber R2 from the back side and closes the expansion side passage 3a.

[0073] When the piston speed during the contraction operation of the shock absorber D is close to 0, the pressure in the compression side chamber R2 rises, but the pressure difference with the pressure in the expansion side chamber R1 does not reach the valve opening pressure of the valve body 27 in the compression side sub-valve CV, so even if the valve body 27 bends, the outer surface of the annular plate 27a1 in the leaf valve 27a faces the axial width range of the inner circumference of the opposing seat 26b, thereby entering a closed state, and the flow path area in the annular gap between the valve body 27 and the opposing seat 26b is kept extremely small.

[0074] On the other hand, when the contraction speed of the shock absorber D is in the extremely low speed range and close to 0, the pressure in the compression side chamber R2 rises, but the pressure difference between the pressure in the compression side chamber R2 and the pressure in the expansion side chamber R1 is small, so the valve element 21 in the expansion side sub-valve EV does not bend toward the valve seat member until it is seated on the annular valve seat 20e. In this way, when the contraction speed of the shock absorber D is in the extremely low speed range and close to 0, the valve element 21 remains closed by opposing the outer circumferential surface of the annular plate 21a1 of the leaf valve 21a within the axial width range of the inner periphery of the opposing seat portion 20b, and the flow path area in the annular gap between the valve element 21 and the opposing seat portion 20b is kept extremely small.

[0075] Therefore, when the contraction speed of the shock absorber D is in the very low speed range and close to 0, the expansion side sub-valve EV and the compression side sub-valve CV remain closed, so that the liquid in the compression side chamber R2 has difficulty passing through the expansion side sub-passage EP and the compression side sub-passage CP. In addition, the compression side main valve 5 also keeps the compression side passage 3b closed. Therefore, when the contraction speed of the shock absorber D is in the very low speed range and close to 0, the characteristic of the damping force generated with respect to the piston speed of the shock absorber D (damping force characteristic) becomes a characteristic that rises sharply as shown in FIG. 3.

[0076] Furthermore, when the piston speed during the contraction operation of the shock absorber D increases and changes from the very low speed region to the low speed region, the pressure difference between the pressure in the compression side chamber R2 and the pressure in the expansion side chamber R1 exceeds the valve opening pressure of the valve body 27, so that the valve body 27 bends and opens by shifting its outer periphery downward in FIG. 2 from the range of the axial width of the inner periphery of the opposing seat portion 26b, and increases the flow path area of ​​the annular gap between the valve body 27 and the opposing seat portion 26b. Then, the liquid passes through the compression side sub-valve CV and passes through the compression side sub-passage CP to move from the compression side chamber R2 to the expansion side chamber R1. On the other hand, when the piston speed during the contraction operation of the shock absorber D increases and changes from the very low speed region to the low speed region, the valve body 21 in the expansion side sub-valve EV bends under the pressure in the compression side chamber R2 and seats on the annular valve seat 20e of the valve seat member 20, closing the port 20c and preventing the liquid from passing through the expansion side sub-passage EP.

[0077] Therefore, when the piston speed during the contraction operation of shock absorber D increases and changes from the very low speed range to the low speed range, the flow path area of ​​the compression side sub-valve CV increases in accordance with the increase in piston speed, and the damping force characteristics of shock absorber D become characteristics with a smaller slope than the damping force characteristic line in the very low speed range, as shown in FIG. 3.

[0078] Furthermore, when the piston speed during the contraction operation of the shock absorber D increases and exceeds the low-speed range, the valve body 27 is largely deflected and abuts against the valve stopper 29, maximizing the flow path area in the annular gap between the opposing seat portion 26b, while the contraction-side main valve 5 is deflected and separated from the piston 3 to open the contraction-side passage 3b. Then, the liquid moves from the contraction-side chamber R2 to the extension-side chamber R1 through the gap between the contraction-side main valve 5 and the piston 3, and the deflection amount of the contraction-side main valve 5 increases due to the increase in the piston speed, so that the flow path area in the gap between the contraction-side main valve 5 and the piston 3 becomes larger than the flow path area in the annular gap between the valve body 27 and the opposing seat portion 26b in the contraction-side sub-valve CV. Therefore, the shock absorber D generates a damping force mainly due to the resistance that the contraction-side main valve 5 provides to the flow of the liquid. Therefore, when the piston speed during the contraction operation of the shock absorber D increases and exceeds the low-speed range, the damping force characteristic of the shock absorber D becomes a characteristic that generates a damping force with a substantially constant slope with respect to the increase in the piston speed as shown in FIG. 3. Since the resistance to the flow of liquid passing through the compression side sub-passage CP can be adjusted by rotating the rotary valve 12, the damping force of the shock absorber D in this embodiment can be adjusted to a high or low level. When the shock absorber D is contracting, the rod 2 enters the cylinder 1, and the free piston 11 moves downward in FIG. 2 within the cylinder 1 to reduce the air chamber G and compensate for the volume of the rod 2 that has entered the cylinder 1.

[0079] As described above, when the piston speed during the contraction operation of the shock absorber D increases and exceeds the low speed range, the pressure in the compression side chamber R2 largely exceeds the pressure in the expansion side chamber R1, and the difference between the pressure in the compression side chamber R2 acting on the valve body 21 from below in Fig. 2 and the pressure in the expansion side chamber R1 acting from above in Fig. 2 via the port 20c becomes large. Then, the leaf valve 21a in the valve body 21 of the expansion side sub-valve EV is pressed upward by the pressure in the compression side chamber R2, but since the outer circumferential side is supported by the annular valve seat 20e and the inner circumferential side is supported by the inner circumferential seat portion 20f, the intermediate portion between the portion of the leaf valve 21a that abuts against the annular valve seat 20e and the portion that abuts against the inner circumferential seat portion 20f bends so as to be convex toward the upper side in Fig. 2. The backup valve 21b abuts against the valve seat member side of the leaf valve 21a to support the leaf valve 21a, and suppresses bending of the middle portion of the leaf valve 21a. This suppresses bending deformation of the middle portion of the leaf valve 21a such that the leaf valve 21a is convex upward, thereby reducing the stress acting on the leaf valve 21a and suppressing fatigue of the leaf valve 21a.

[0080] As described above, the expansion side sub-valve EV and the compression side sub-valve CV as damping valves in this embodiment include the annular valve element 21, 27 having an inner periphery as a fixed end and an outer periphery as a free end that is allowed to bend relative to the fixed end, the annular opposing seats 20b, 26b that are annular and face at least a part of the peripheral surface on the free end side of the valve element 21, 27, the ports 20c, 26d that are provided on the fixed end side of the valve element 21, 27 relative to the opposing seats 20b, 26b in the radial direction, and and a valve seat member 20, 26 having an annular valve seat 20e, 26f that is provided between the ports 20c, 26d and 26b and faces the valve body 21, 27 in the axial direction, and on which the valve body 21, 27 can be seated and separated. The valve body 21, 27 is provided with an annular leaf valve 21a, 27a and a backup valve 21b, 27b that is annular and is superimposed on the valve seat member side of the leaf valve 21a, 27a to suppress bending of the free end of the leaf valve 21a, 27a towards the valve seat member side.

[0081] According to the extension side sub-valve EV and the compression side sub-valve CV configured as described above as damping valves, when the valve elements 21, 27 receive pressure from the ports 20c, 26d, the valve elements 21, 27 bend to open the ports 20c, 26d and provide resistance to the flow of liquid passing through the ports 20c, 26d. When the valve elements 21, 27 receive pressure pressing toward the valve seat members 20, 26, the valve elements 21, 27 seat on the annular valve seats 20e, 26f to block the ports 20c, 26d. Therefore, the valve elements 21, 27 function as damping valves for the flow of liquid attempting to pass through the ports 20c, 26d in one direction and function as check valves for the flow of liquid attempting to pass through the ports 20c, 26d in the other direction. According to the extension side sub-valve EV and the compression side sub-valve CV as the damping valves, when the valve bodies 21, 27 are seated on the annular valve seats 20e, 26f and receive pressure pressing them toward the valve seat members 20, 26, the backup valves 21b, 27b come into contact with the valve seat member side of the leaf valves 21a, 27a to support the leaf valves 21a, 27a and suppress bending of the middle portions of the leaf valves 21a, 27a, thereby reducing the stress acting on the leaf valves 21a, 27a and suppressing fatigue of the leaf valves 21a, 27a. As described above, according to the extension side sub-valve EV and the compression side sub-valve CV as the damping valves of this embodiment, fatigue of the leaf valves 21a, 27a is suppressed while functioning as a check valve.

[0082] In addition, when the leaf valves 21a, 27a bend in a direction away from the valve seat members 20, 26 to open the ports 20c, 26d and then return to their original positions with their outer peripheries facing the opposing seats 20b, 26b, the backup valves 21b, 27b reduce the momentum of the leaf valves 21a, 27a as they return to their original positions, preventing the leaf valves 21a, 27a from colliding forcefully with the annular valve seats 20e, 26f, thereby suppressing the generation of abnormal noise. Furthermore, when the leaf valve 21a bends toward the valve seat member 20 due to pressure from the back side, the leaf valve 21a is supported by the backup valve 21b, reducing the amount of bending, and bending toward the valve seat member 20 can suppress a sudden pressure fluctuation in the compression side chamber R2. In addition, when the leaf valve 27a bends toward the valve seat member 26 due to pressure from the back side, the leaf valve 27a is supported by the backup valve 27b, so the amount of bending is reduced. At the same time, the leaf valve 27a bends toward the valve seat member 26, thereby suppressing abrupt pressure fluctuations in the expansion-side chamber R1.

[0083] In the above, the inner circumferential side of the valve body 21, 27 is a fixed end, the outer circumferential side is a free end, and the outer circumferential surface of the valve body 21, 27 is opposed to the inner circumferential surface of the opposed seat portion 20b, 26b to form the extension side sub-valve EV and the compression side sub-valve CV as the damping valve, but the outer circumferential side of the valve body may be a fixed end, the inner circumferential side is a free end, an opposed seat portion is provided on the inner circumferential side of the valve body, and the inner circumferential surface of the valve body may be opposed to the outer circumferential surface of the opposed seat portion to form a damping valve. In the above, when the valve body 21, 27 is deflected toward the valve seat member side and seated on the annular valve seat 20e, 26f, the ports 20c, 26d are completely blocked, but the annular valve seat 20e, 26f may be provided with a groove communicating from the inner circumferential side to the outer circumferential side to form an orifice, and when the valve body 21, 27 is deflected toward the valve seat member side and seated on the annular valve seat 20e, 26f, the liquid may be allowed to flow only through the orifice.

[0084] In addition, the valve seat member 26 in the compression side sub-valve CV as a damping valve in this embodiment is provided with a regulating portion 26h that is provided radially closer to the fixed end of the valve body 27 than the annular valve seat 26f, faces the valve body 27 in the axial direction, and abuts against the valve body 27 to regulate the deflection of the valve body 27 when the free end of the valve body 27 deflects toward the valve seat member by more than a predetermined amount.

[0085] According to the compression side sub-valve CV configured in this manner as a damping valve, in addition to being supported by the backup valve 27b, when the middle portion of the valve body 27 is pressed toward the valve seat member and bent to abut against the regulating portion 26h, the middle portion of the valve body 27 is supported by the regulating portion 26h and the valve body 27 is prevented from bending further. Therefore, even if excessive pressure is applied to the valve body 27, stress on the leaf valve 27a can be reduced and fatigue of the leaf valve 27a can be further suppressed.

[0086] In the compression side sub-valve CV, the outer diameter of the backup valve 27b is smaller than the inner diameter of the annular valve seat 26f, and only the leaf valve 27a is able to seat and separate from the annular valve seat 26f in the axial direction, and the backup valve 27b cannot abut against the annular valve seat 26f. However, the outer diameter of the backup valve 27b may be made larger so that when the valve body 27 bends towards the valve seat member, the backup valve 27b seats on the annular valve seat 26f and closes the port 26d. In the extension-side sub-valve EV, the outer diameter of the backup valve 21b is larger than the inner diameter of the annular valve seat 20e, and both the backup valve 21b and the leaf valve 21a face the annular valve seat 20e in the axial direction. When the valve body 21 bends toward the valve seat member, the backup valve 21b seats on the annular valve seat 20e to close the port 20c. However, the outer diameter of the backup valve 21b may be smaller than the inner diameter of the annular valve seat 20e to allow the leaf valve 21a to seat on and off the annular valve seat 20e.

[0087] In addition, when the backup valve 21b has a notch 21b1 that penetrates the wall thickness in the axial direction and faces the leaf valve 21a as shown in Fig. 4, liquid can easily enter between the leaf valve 21a and the backup valve 21b through the notch 21b1, and sticking between the leaf valve 21a and the backup valve 21b can be suppressed. Therefore, according to the extension-side sub-valve EV as a damping valve configured in this manner, the valve body 21 can bend smoothly at the beginning of bending of the valve body 21, and a sudden change in the damping force characteristics can be prevented. Note that the notch 21b1 may be provided in any shape and in any number as long as it is provided in a manner that can prevent the passage of liquid when the valve body 21 abuts against the annular valve seat 20e.

[0088] Furthermore, as shown in FIG. 5, when backup valve 27b has notch 27b1 that axially penetrates the wall thickness and faces leaf valve 27a in the range where it abuts against restricting portion 26h, notch 27b1 is provided even when backup valve 27b abuts against restricting portion 26h, and liquid can easily enter between leaf valve 27a and backup valve 27b and between restricting portion 26h and backup valve 27b through notch 27b1, thereby preventing sticking between leaf valve 27a and backup valve 27b and between restricting portion 26h and backup valve 27b. Therefore, according to the compression side sub-valve CV configured as above as a damping valve, the valve element 27 can bend smoothly at the beginning of bending, preventing a sudden change in the damping force characteristics, and can quickly return when the valve element 27 returns in a direction away from the valve seat member 26 from a state in which the backup valve 27b abuts against the restricting portion 26h, thereby preventing a delay in opening the port 26d. Note that the notch 27b1 may be provided in a manner that can prevent the passage of liquid when the valve element 27 abuts against the annular valve seat 26f, but is preferably provided so as not to be closed by the restricting portion 26h when the backup valve 27b abuts against the restricting portion 26h. If the notch 27b1 is not closed by the regulating portion 26h, when the backup valve 27b abuts against the regulating portion 26h, liquid will easily enter between the regulating portion 26h and the backup valve 27b through the notch 27b1, thereby further preventing the regulating portion 26h and the backup valve 27b from sticking to each other.

[0089] In addition, the shock absorber D of this embodiment includes a cylinder (outer tube) 1, a rod 2 inserted into the cylinder (outer tube) 1 so as to be axially movably, a shock absorber body A having at least an extension side chamber (working chamber) R1 and a compression side chamber (working chamber) R2 through which liquid flows as the rod 2 moves relative to the cylinder (outer tube) 1, and an extension side sub-valve EV and a compression side sub-valve CV as damping valves provided between the extension side chamber (working chamber) R1 and the compression side chamber (working chamber) R2. In the shock absorber D configured as described above, the expansion-side sub-valve EV generates a damping force when the liquid flows from the expansion-side chamber R1 to the compression-side chamber R2, and closes the expansion-side sub-passage EP when the liquid flows from the compression-side chamber R2 to the expansion-side chamber R1, so that the damping force characteristics on the expansion side of the shock absorber D can be set independently, and the compression-side sub-valve CV generates a damping force when the liquid flows from the compression-side chamber R2 to the expansion-side chamber R1, and closes the compression-side sub-passage CP when the liquid flows from the expansion-side chamber R1 to the compression-side chamber R2, so that the damping force characteristics on the compression side of the shock absorber D can be set independently. The expansion-side sub-valve EV and the compression-side sub-valve CV as damping valves increase the damping coefficient in the extremely low speed range of the expansion / contraction speed to quickly raise the damping force in response to the switching of the expansion / contraction stroke, and can reduce the damping coefficient in the low speed range compared to the extremely low speed range, so that the damping force characteristics suitable for suppressing vibration of the vehicle body can be realized, and the ride comfort of the vehicle can be improved.

[0090] In the shock absorber D of this embodiment, the extension side sub-valve EV and the compression side sub-valve CV as damping valves are provided in the extension side sub-passage EP and the compression side sub-passage CP that bypass the extension side passage 3a and the compression side passage 3b in the piston 3, and the damping valves are arranged in parallel with the extension side main valve 4 and the compression side main valve 5 in the piston 3, but the damping valves may be used as the extension side main valve or the compression side main valve. Also, in the shock absorber D of this embodiment, the extension side sub-valve EV and the compression side sub-valve CV as damping valves are provided in the extension side sub-passage EP and the compression side sub-passage CP that bypass the extension side passage 3a and the compression side passage 3b in the piston 3, but the shock absorber D may be provided with only the extension side sub-valve EV or only the compression side sub-valve CV.

[0091] In addition, in the example shown in Fig. 1, the two working chambers are the expansion-side chamber R1 and the compression-side chamber R2, but in the case where the shock absorber D is a double-tube shock absorber having an outer shell as an outer tube on the outer periphery of the cylinder and a reservoir between the cylinder and the outer shell, a damping valve DV may be provided between the compression-side chamber and the reservoir. Therefore, the port in the damping valve may communicate between the expansion-side chamber R1 and the compression-side chamber R2, or may communicate between the compression-side chamber and the reservoir.

[0092] In the shock absorber D of this embodiment, the speed range in which damping force is generated mainly by the extension side sub-valve EV and the compression side sub-valve CV as damping valves is set to the low speed range. However, the speeds that divide the extremely low speed, the low speed, and the high speed that exceeds the low speed can be arbitrarily set by the designer.

[0093] Although the preferred embodiment of the present invention has been described in detail above, modifications, variations and changes can be made without departing from the scope of the appended claims. [Explanation of symbols]

[0094] 1···Cylinder (outer tube), 2···Rod, 20, 26···Valve seat member, 20b, 26b···Opposite seat portion, 20c, 26d···Port, 20e, 26f···Annular valve seat, 26h···Restriction portion, 21, 27···Valve body, 21a, 27a···Leaf valve, 21b, 27b···Back-up valve, 21b1, 27b1···Notch, A···Shock absorber body, CV···Compression side sub-valve (damping valve) D···Shock absorber, EV···Extension side sub-valve (damping valve), R1···Extension side chamber (operating chamber), R2···Compression side chamber (operating chamber)

Claims

1. an annular valve body having one of its inner periphery and outer periphery as a fixed end and the other of its inner periphery and outer periphery as a free end, the free end being allowed to bend relative to the fixed end; a valve seat member having an annular opposing seat portion opposing at least a portion of a peripheral surface of the valve body on the free end side, a port provided radially closer to the fixed end side of the valve body than the opposing seat portion, and an annular valve seat provided between the opposing seat portion and the port, opposing the valve body in the axial direction, and on which the valve body can be seated and separated, the valve element includes an annular leaf valve and an annular backup valve that is superimposed on a valve seat member side of the leaf valve to suppress bending of the free end of the leaf valve toward the valve seat member side, A gap is provided between the valve body and the annular valve seat. A damping valve characterized by:

2. The valve seat member has a restricting portion that is provided radially closer to the fixed end of the valve body than the annular valve seat, faces the valve body in the axial direction, and abuts against the valve body when the free end of the valve body bends toward the valve seat member by a predetermined amount or more to restrict bending of the free end of the valve body.

2. The damping valve of claim 1.

3. The backup valve has a notch that penetrates the wall in the axial direction.

2. The damping valve of claim 1.

4. The backup valve has a notch that penetrates the wall in the axial direction in a region where it abuts against the restricting portion.

3. The damping valve according to claim 2.

5. The gap formed between the peripheral surface of the free end side of the valve body and the opposing seat portion is narrower than the gap between the valve body and the annular valve seat.

2. The damping valve of claim 1.

6. a shock absorber body having an outer tube, a rod inserted into the outer tube so as to be movable in an axial direction, and at least two working chambers through which liquid flows as the rod moves relative to the outer tube; and a damping valve according to any one of claims 1 to 5, which is provided between the operating chambers. A shock absorber characterized by:

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