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Abstract

To provide a sealing device for a liquid pressure apparatus and a shock absorber which can improve assembly workability while restraining time delay of generation of damping force and thrust.SOLUTION: A sealing device S for a liquid pressure apparatus of this invention includes an annular main piston split body (outer member) 4, an auxiliary piston split body (inner member) 5 which is inserted into the main piston split body (outer member) 4, and a seal ring 12 which is stored in an annular groove 50 provided on an outer periphery of the auxiliary piston split body (inner member) 5 and is brought into contact with the main piston split body (outer member) 4 so as to restrain liquid from flowing between the main piston split body (outer member) 4 and the auxiliary piston split body (inner member) 5. The auxiliary piston split body (inner member) 5 has a recession for restricting axial movement of the seal ring 12 with respect to the annular groove 50 on a bottom 51 of the annular groove 50.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention , loose Regarding shock absorbers. [Background technology]

[0002] Seal devices for hydraulic equipment are used in hydraulic equipment such as shock absorbers that are placed between the body and wheels of a vehicle to exert a damping force and suppress vibrations between the body and wheels, and cylinder devices that drive the booms and arms of construction machinery.

[0003] The seal device applied to the shock absorber is, for example, a piston having two valve bodies, a main piston segment and a sub piston segment, which are held by a nut on the outer periphery of a rod. Sub-piston segment The device is provided with a seal ring that seals between the nozzle and the nozzle (see, for example, Patent Document 1).

[0004] The piston has a passage that connects the extension-side chamber and the compression-side chamber that are partitioned by the piston inside the cylinder, and two leaf valves that open and close the passage are attached to the corresponding main piston segment and sub-piston segment, respectively.

[0005] The seal ring is housed in an annular groove provided circumferentially on the outer periphery of the disk-shaped main piston segment, which is fitted into the cylindrical portion protruding from the secondary piston segment to close the inside of the cylindrical portion, and is in close contact with the inner periphery of the cylindrical portion to seal between the main piston segment and the secondary piston segment.

[0006] With this seal device configured in this manner, the seal ring can prevent hydraulic oil from bypassing the valve and passing between the main piston segment and the sub-piston segment, allowing the shock absorber to exert the damping force as designed. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-96453 Summary of the Invention [Problem to be solved by the invention]

[0008] In this way, in order to seal between the main piston segment and the sub-piston segment, the sealing device requires an annular groove to be formed on the outer periphery of the portion of the main piston segment that fits into the cylindrical portion of the sub-piston segment, and after a seal ring is placed in the annular groove, the main piston segment must be inserted into the cylindrical portion.

[0009] To prevent the seal ring from falling out of the annular groove, the inner diameter of the seal ring is set smaller than the outer diameter of the portion that fits into the cylindrical portion of the main piston segment, and the seal ring must be expanded in diameter to fit into the annular groove.

[0010] In order for the seal ring to properly seal between the main piston segment and the sub-piston segment, it must be pressed firmly against the cylindrical portion of the sub-piston segment, and the outer diameter of the seal ring is set larger than the inner diameter of the cylindrical portion, so that the seal ring is inserted into the cylindrical portion in a compressed state. Therefore, inserting the main piston segment with the seal ring attached into the cylindrical portion of the sub-piston segment involves compressing the seal ring.

[0011] The seal ring is made of, for example, vulcanized rubber, but in some cases, a hard material is used to prevent it from slipping out of the annular groove, ensure the pressing force against the cylindrical portion, and ensure durability. Therefore, the work of installing it in the annular groove and fitting it into the main piston segment inside the cylindrical portion places a heavy burden on the worker.

[0012] In order to reduce the burden on the worker and improve workability, attempts have been made to reduce the frictional force that occurs between the seal ring and the main piston segments or cylindrical portion by making the seal ring self-lubricating or by subjecting the seal ring to surface treatment.

[0013] However, when the frictional force generated between the seal ring and the main piston segments or the cylindrical portion is reduced by treating the seal ring in this manner, the seal ring becomes more likely to move axially within the annular groove, and the seal ring may move within the annular groove even when subjected to only a low pressure from the expansion-side chamber or the compression-side chamber.

[0014] Therefore, when the shock absorber starts to move at an extremely low speed, the seal ring moves within the annular groove, and the volume within the passage changes by the amount of the seal ring's movement, which creates the same effect as if the hydraulic oil corresponding to the change in volume had bypassed the leaf valve and passed between the main piston segment and the sub-piston segment.

[0015] This reduces the amount of hydraulic oil passing through the leaf valve when the shock absorber expands and contracts at extremely low speeds, preventing the shock absorber from exerting the intended damping force and resulting in a time delay in the generation of the damping force.

[0016] In addition, even if an annular groove is provided on the outer periphery of the piston and a seal ring that slides against the cylinder in which the piston slides is housed, when the seal ring moves it appears as if the hydraulic oil has bypassed the valve and passed between the cylinder and the piston. When an air chamber is provided with a free piston inside the cylinder and a seal ring that slides against the cylinder is housed on the outer periphery of the free piston, the amount of hydraulic oil that passes through the valve will also decrease due to the movement of the seal ring within the annular groove. Even in cylinder devices rather than shock absorbers, if the seal ring moves when pressurized oil is supplied into the cylinder, the hydraulic oil will not appear to be supplied into the cylinder in proportion to the movement of the seal ring, so a time delay in thrust will occur even in cylinder devices.

[0017] As described above, in the case of sealing devices in hydraulic equipment such as shock absorbers and cylinder devices, if the frictional force of the seal ring is reduced in order to improve the workability in assembling the seal ring and the hydraulic equipment, a time delay occurs in the generation of the damping force and thrust force of the hydraulic equipment, which is an inconvenience.

[0018] Therefore, the present invention , decreaseThe object of the present invention is to provide a shock absorber that can improve assembly workability while suppressing the time delay in the generation of damping force. [Means for solving the problem]

[0019] In order to solve the above-mentioned problems, buffer teeth, the piston has an annular outer member and an inner member inserted inside the outer member, and is inserted into the cylinder so as to be movable in the axial direction, the piston dividing the interior of the cylinder into an extension-side chamber and a compression-side chamber and having a passage connecting the extension-side chamber and the compression-side chamber; a rod inserted into the cylinder so as to be movable in the axial direction and connected to the piston; a seal ring housed in an annular groove provided in one of the outer member and the inner member and abutting against the other of the outer member and the inner member to prevent liquid from passing between the outer member and the inner member; and a valve for opening and closing the passage, one of the outer member and the inner member having a recess or unevenness at the bottom of the annular groove that restricts axial movement of the seal ring relative to the annular groove, and the valve has a main valve element and a sub-valve element provided in series in the passage, the main valve element is attached to the outer member and generates a damping force when the piston is in a medium to high speed range, and the sub-valve element is attached to the inner member and generates a damping force when the piston is in an extremely low speed range. This was configured buffer According to the present invention, since the axial movement of the seal ring in the annular groove can be restricted, it is possible to prevent the phenomenon of liquid apparently passing between the outer member and the inner member due to the movement of the seal ring in the annular groove. Furthermore, with a shock absorber configured in this manner, the flow rate passing through the valve does not decrease, and the damping force can be generated as designed from the start of movement, preventing any time delay in the generation of the damping force.

[0020] Also, buffer The seal ring in the above-described embodiment may have self-lubricating properties. buffer This facilitates both the operations of fitting the seal ring into the annular groove and fitting the inner member into the outer member.

[0021] moreover ,ring A recess at the bottom of the groove will be established case ,bottom The portion may have a bottom surface that is deepest in the center in the axial direction, and tapered or curved surfaces provided on both sides of the bottom surface. buffer According to this, the seal ring easily fits between the tapered surfaces or curved surfaces and the inner periphery of the seal ring is restrained by the bottom, so that axial positional deviation of the seal ring can be effectively suppressed. The annular groove may be a concave groove surrounded by a bottom and a pair of side walls extending from both axial ends of the bottom and facing each other, and when the seal ring is installed in the annular groove, it fits into the recess or the unevenness to be constrained from moving in the axial direction and may come into contact with the pair of side walls. The seal ring may also have a circular cross section. [Effects of the Invention]

[0023] From the above , Book According to the shock absorber of the present invention, it is possible to improve the assembly workability while suppressing the time delay in the generation of the damping force. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a longitudinal sectional view of a shock absorber to which a sealing device for hydraulic equipment according to an embodiment is applied; [Figure 2]1 is an enlarged cross-sectional view of a piston portion of a shock absorber to which a sealing device for hydraulic equipment according to an embodiment is applied; [Figure 3] 1 is a partially enlarged cross-sectional view of a piston of a shock absorber to which a sealing device for hydraulic equipment according to an embodiment is applied; [Figure 4] 1(a) is a partially enlarged longitudinal sectional view of an inner member in a sealing device for hydraulic equipment according to a first modified example of an embodiment; FIG. 1(b) is a partially enlarged longitudinal sectional view of an inner member in a sealing device for hydraulic equipment according to a second modified example of an embodiment; FIG. 1(c) is a partially enlarged longitudinal sectional view of an inner member in a sealing device for hydraulic equipment according to a third modified example of an embodiment; FIG. 1(d) is a partially enlarged longitudinal sectional view of an inner member in a sealing device for hydraulic equipment according to a fourth modified example of an embodiment; and FIG. 1(e) is a partially enlarged longitudinal sectional view of an inner member in a sealing device for hydraulic equipment according to a fifth modified example of an embodiment. [Figure 5] FIG. 10 is a vertical cross-sectional view of a shock absorber to which a sealing device according to a sixth modified example of the embodiment is applied. DETAILED DESCRIPTION OF THE INVENTION

[0025] The present invention will be described below based on the embodiments shown in the drawings. As shown in FIGS. 1 and 2, a sealing device S for hydraulic equipment in one embodiment is applied to a shock absorber D, which is a hydraulic equipment. The shock absorber D includes a cylinder 1, a piston 2 movably inserted into the cylinder 1 in the axial direction, which divides the cylinder 1 into two working chambers, an expansion-side chamber L1 and a compression-side chamber L2, and which has a passage P connecting the expansion-side chamber L1 and the compression-side chamber L2, a rod 3 movably inserted into the cylinder 1 in the axial direction, a valve V for opening and closing the passage P, and a sealing device S. The shock absorber D of this embodiment is installed between the body and axle of a vehicle (not shown) to suppress vibrations of the body and wheels. Note that the installation target of the shock absorber D equipped with the sealing device S according to the present invention is not limited to a vehicle, and can be changed as appropriate. The shock absorber D can also be installed upside down as shown in FIG. 1 depending on the installation target.

[0026] Next, the specific structures of the sealing device S and the shock absorber D to which the sealing device S is applied will be described. As shown in Fig. 1, the cylinder 1 is cylindrical with a bottom, and is fitted with an annular rod guide 10 on the inner periphery at the top end, into which the rod 3 is slidably inserted. Therefore, the interior of the cylinder 1 is an enclosed space.

[0027] A bracket (not shown) is provided at the upper end of the rod 3, and the rod 3 is connected to one of the vehicle body and the axle via the bracket. On the other hand, 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 axle via the bracket.

[0028] In this way, shock absorber D is interposed between the vehicle body and the axle. When the vehicle travels on an uneven road surface and the wheels vibrate up and down relative to the vehicle body, rod 3 moves in and out of cylinder 1, expanding and contracting shock absorber D, and piston 2 moves up and down (axially) within cylinder 1.

[0029] A free piston 11 is slidably inserted into the cylinder 1 on the opposite side of the piston 2 from the rod 3. The free piston 11 divides the interior of the cylinder 1 into a liquid chamber L filled with a liquid such as hydraulic oil and an air chamber G filled with a gas. The piston 2, inserted axially movably into the cylinder 1, divides the liquid chamber L into two working chambers: an expansion-side chamber L1 on the upper side in FIG. 1 and a compression-side chamber L2 on the lower side in FIG. 1. A compressed gas is sealed in the air chamber G. The liquid used in the shock absorber D can be other liquids besides hydraulic oil, such as water or an aqueous solution. The gas filled in the air chamber G is preferably an inert gas such as nitrogen gas, but other gases may also be used.

[0030] As shown in Figures 1 and 2, the rod 3 has a small-diameter portion 3a at its lower end, on whose outer diameter the piston 2 is attached, a threaded portion 3b provided on the outer periphery of the tip of the small-diameter portion 3a, and a step portion 3c formed at the boundary of the small-diameter portion 3a.The rod 3 is inserted into the cylinder 1 through the rod guide 10 so as to be movable in the axial direction.

[0031] When the shock absorber D extends, the rod 3 retracts from the cylinder 1, and the internal volume of the cylinder increases by the volume of the retracted rod 3, causing the free piston 11 to move upward within the cylinder 1 and expand the air chamber G. Conversely, when the shock absorber D contracts, the rod 3 enters the cylinder 1, and the internal volume of the cylinder decreases by the volume of the entered rod 3, causing the free piston 11 to move downward within the cylinder 1 and contract the air chamber G. In this way, the shock absorber D as a hydraulic device in this embodiment is configured as a single-rod, single-cylinder shock absorber, and the movement of the free piston 11 expands or contracts the air chamber G during extension and contraction, thereby compensating for the volume of the rod 3 moving in and out of the cylinder 1. Note that the partition between the liquid chamber L and the air chamber G may be formed by a bladder, bellows, or the like instead of the free piston 11.

[0032] Also, instead of providing the air chamber G by the free piston 11, an outer shell may be provided on the outer periphery of the cylinder 1 to form a reservoir filled with liquid and gas between the outer shell and the cylinder 1, and the reservoir may be used to compensate for the volume of the rod 3 moving in and out of the cylinder 1. Note that the reservoir may be provided by providing an outer shell on the outer periphery of the cylinder 1 or by providing a tank independent of the cylinder 1 that forms the reservoir. Also, rods may be provided on both sides of the piston to make the shock absorber D a double-rod type shock absorber.

[0033] The piston 2 is composed of a main piston segment 4 as an outer member held by a nut 30 on the outer periphery of the rod 3, and a sub-piston segment 5 as an inner member. Main valve bodies 6 and 7 are stacked on the main piston segment 4, and a sub-valve body 8 is attached to the sub-piston segment 5, and the main valve bodies 6 and 7 and the sub-valve body 8 together form a valve V.

[0034] 2, the main piston split body 4 includes an annular main body portion 4a and a cylindrical portion 4b that protrudes downward from the outer periphery of the lower end of the main body portion 4a, and constitutes an outer member of the sealing device S. The main body portion 4a is formed with an expansion-side passage 4c and a compression-side passage 4d that open to the inner periphery of the cylindrical portion 4b and axially penetrate the main body portion 4a. Furthermore, an expansion-side main valve element 6 that opens and closes the outlet of the expansion-side passage 4c is stacked on the lower side (compression-side chamber L2 side) of the main body portion 4a, and a compression-side main valve element 7 that opens and closes the outlet of the compression-side passage 4d is stacked on the upper side (compression-side chamber L1 side) of the main body portion 4a.

[0035] In this embodiment, the extension-side and compression-side main valve bodies 6, 7 of the shock absorber D are each formed as a laminated leaf valve in which a plurality of elastically deformable leaf valves are laminated. The number of laminated leaf valves in the main valve bodies 6, 7 can be changed as desired depending on the desired damping force.

[0036] The expansion-side main valve element 6 opens when the shock absorber D is expanding and the piston speed is in the medium-to-high speed range, and provides resistance to the flow of liquid through the expansion-side passage 4c from the expansion-side chamber L1 to the compression-side chamber L2. On the other hand, the compression-side main valve element 7 opens when the shock absorber D is contracting and the piston speed is in the medium-to-high speed range, and provides resistance to the flow of liquid through the compression-side passage 4d from the compression-side chamber L2 to the expansion-side chamber L1.

[0037] Of the multiple leaf valves constituting the extension-side and compression-side main valve bodies 6, 7, the first leaf valve located closest to the main piston segment 4 has a notch 6a, 7a formed on its outer periphery, respectively. When the piston speed is in the low-speed range and the extension-side and compression-side main valve bodies 6, 7 are closed, liquid flows between the extension-side chamber L1 and the compression-side chamber L2 through the orifice formed by the notch 6a, 7a. Resistance is applied to the flow of liquid by the orifice (notch 6a, 7a).

[0038] The orifice formed by the notches 6a, 7a allows bidirectional flow of liquid. Therefore, one of the notches 6a, 7a formed in the extension-side and compression-side main valve bodies 6, 7 may be omitted. The method of forming the orifice can be modified as appropriate. For example, an orifice may be formed by forming a stamp on the valve seat on which the extension-side or compression-side main valve body 6, 7 is seated or released. The orifice may also be replaced with a choke. Furthermore, the main valve bodies 6, 7 attached to the main piston segments 4 for generating a damping force in the medium- to high-speed range in the shock absorber D may be other than a laminated leaf valve, and may be, for example, a poppet valve.

[0039] 2, the sub-piston section 5 constitutes an inner member and includes an annular fitting portion 5a that fits onto the inner periphery of the cylindrical portion 4b of the main piston section 4, a cylindrical case portion 5b that protrudes downward from the outer periphery of the lower end of the fitting portion 5a, a communication passage 5c that passes axially through the fitting portion 5a and opens onto the inner periphery of the case portion 5b, and an annular groove 50 that is provided circumferentially on the outer periphery of the fitting portion 5a. A seal ring 12 is housed in the annular groove 50 on the outer periphery of the fitting portion 5a and abuts against the inner periphery of the cylindrical portion 4b of the main piston section 4, which is the outer member, to seal between the main piston section 4 and the sub-piston section 5.

[0040] As shown in Figure 3, the annular groove 50 in the secondary piston segment 5 is provided along the circumferential direction around the entire outer periphery of the fitting portion 5a, and is a concave groove surrounded by a bottom 51 and a pair of opposing side walls 52, 52 extending parallel to each other from both axial ends of the bottom 51.

[0041] As shown in FIG. 3, the bottom 51 has a bottom surface 51a in the center of FIG. 3 where the groove depth is greatest, and tapered surfaces 51b, 51b that are connected above and below the bottom surface 51a and whose depth gradually decreases toward the side wall 52, forming a single recess as a whole.

[0042] The annular groove 50 thus configured accommodates a seal ring 12, which is an O-ring. The seal ring 12 is made of rubber or the like blended with a lubricant and is self-lubricating. The seal ring 12 is also subjected to a surface treatment to smooth the surface, thereby reducing friction between the seal ring 12 and other components. As mentioned above, self-lubricating rubber is obtained by blending a lubricant into a base rubber. Any rubber suitable for sealing applications can be used as the base rubber, including, for example, fluororubber, ethylene-propylene-diene terpolymer rubber, acrylic rubber, acrylonitrile-butadiene rubber, and hydrogenated acrylonitrile-butadiene rubber. The lubricant blended into the base rubber can be any lubricant that bleeds from the base rubber and provides lubrication, including, for example, oils such as silicone oil and modified silicone oil, waxes such as paraffin wax, and fatty acids such as fatty acids, fatty acid salts, and fatty acid amides.

[0043] The seal ring 12 has an inner diameter smaller than the minimum outer diameter of the bottom 51 of the annular groove 50, is housed in the annular groove 50 in an expanded state, and attempts to contract due to its self-restoring force, thereby entering and closely contacting the bottom 51 whose inner periphery is concave. The outer diameter of the seal ring 12 is set to be larger than the outer diameter of the fitting portion 5a when housed in the annular groove 50.

[0044] When the fitting portion 5a of the sub-piston segment 5 is inserted into the cylindrical portion 4b of the main piston segment 4, the seal ring 12 is compressed by the cylindrical portion 4b, reducing its outer diameter. Therefore, the seal ring 12 presses against the inner peripheral surface of the cylindrical portion 4b by its self-restoring force and tightly contacts the inner periphery of the cylindrical portion 4b. Therefore, the inner periphery of the seal ring 12 enters the bottom portion 51 of the annular groove 50, tightening the bottom portion 51, while the outer periphery tightly contacts the cylindrical portion 4b, thereby sealing between the main piston segment 4 and the sub-piston segment 5. Furthermore, in the seal device S of this embodiment, a recess is formed in the bottom portion 51 of the annular groove 50, so that the inner periphery of the seal ring 12 fits into and is restrained by the bottom portion 51. Therefore, regardless of whether pressure acts on the seal ring 12 from above or below in FIG. 3 , the seal ring 12 remains positioned in the center of the annular groove 50, and displacement of the seal ring 12 in the vertical direction, which is the axial direction, is suppressed. Furthermore, since the bottom 51 has tapered surfaces 51b, 51b, the seal ring 12 can easily enter the recess by following the space between the tapered surfaces 51b, 51b, and the inner circumference of the seal ring 12 is restrained by the bottom 51, effectively suppressing axial positional displacement of the seal ring 12.

[0045] An annular opposing portion 5d protruding radially inward from the inner periphery of the case portion 5b is provided at the tip of the case portion 5b of the sub-piston split body 5. Two stopper members 9, 40 with different outer diameters are housed inside the case portion 5b. Furthermore, the sub-valve body 8 and stopper member 41 are stacked below the stopper member 40 in FIG. 2.

[0046] 2, the sub-valve element 8 of this embodiment is composed of three stacked leaf valves, with the outer diameter of the central leaf valve being larger than the outer diameters of the upper and lower leaf valves. Furthermore, spacers 20, 21 are interposed between the upper leaf valve and the stopper member 40 immediately above it, and between the lower leaf valve and the stopper member 41 immediately below it, respectively.

[0047] The stopper members 9, 40, spacer 20, sub-valve body 8, spacer 21, and stopper member 41 are assembled in this order to the outer periphery of the small diameter portion 3a of the rod 3, following the main valve body 7, main piston segment 4, main valve body 6, and sub-piston segment 5, and are fixed to the small diameter portion 3a of the rod 3 by being sandwiched together with the main valve body 7, main piston segment 4, main valve body 6, and sub-piston segment 5 by a nut 30 screwed onto the step portion 3c and the threaded portion 3b. The fitting portion 5a of the sub-piston segment 5 is inserted into the cylindrical portion 4b of the main piston segment 4, and the extension-side passage 4c and the compression-side passage 4d facing the extension-side chamber L1 are communicated with the compression-side chamber L2 via the communication passage 5c and the case portion 5b. Therefore, the passage P provided in the piston 2 is the extension-side passage 4c. 、 Pressure side passage 4d 、 The passage P is formed in the case portion 5b and the communication passage 5c. The seal ring 12 in the annular groove 50 is in close contact with the inner periphery of the cylindrical portion 4b, sealing the gap between the cylindrical portion 4b of the main piston segment 4 and the mating portion 5a of the sub-piston segment 5. Therefore, the seal device S prevents liquid from passing between the cylindrical portion 4b and the mating portion 5a through any route other than the passage P.

[0048] Next, each of the spacers 20, 21 is an annular plate whose outer diameter is smaller than that of each of the leaf valves that make up the sub-valve body 8. The sub-valve body 8 is fixed to the sub-piston divided body 5 with its inner periphery sandwiched between the spacers 20, 21. On the other hand, the part of the sub-valve body 8 that is outer than the spacers 20, 21 can move up and down (axially) with the outer peripheral edge of the contact point between the spacers 20, 21 and the sub-valve body 8 as a fulcrum.

[0049] As described above, in this embodiment, the inner periphery of the sub-valve element 8 attached to the sub-piston divided body 5 is a fixed end that does not move relative to the sub-piston divided body 5. Furthermore, the outer periphery of the sub-valve element 8 is a free end that can move up and down (on both sides in the axial direction) relative to the sub-piston divided body 5 when deflected. Furthermore, with the inner periphery of the sub-valve element 8 fixed to the sub-piston divided body 5, the central leaf valve having the largest outer diameter in the sub-valve element 8 has its inner periphery facing the facing portion 5d provided on the inner periphery of the case portion 5b of the sub-piston divided body 5 via a very short annular gap.

[0050] In an extremely low speed range where the piston speed is close to 0 (zero), such as when shock absorber D starts to move, sub-valve element 8 does not bend, and the free end of sub-valve element 8 faces opposing portion 5d with the annular gap therebetween. In this embodiment, the annular gap formed between opposing portions 5d and the free end of sub-valve element 8 is very narrow, and the flow path area in the annular gap is set to be smaller than the flow path area of ​​all orifices formed by notches 6a, 7a formed in main valve elements 6, 7 described above.

[0051] On the other hand, when the shock absorber D is extending or retracting and the piston speed is in the low speed range or the medium to high speed range, the sub-valve body 8 bends upward or downward, and the annular gap formed between the free end of the sub-valve body 8 that has shifted up or down and the opposing part 5d becomes larger, and the flow path area in the annular gap becomes larger than the flow path area of ​​the orifice formed by the notches 6a and 7a.

[0052] Furthermore, if the amount of bending of the sub-valve element 8 when it bends upward or downward becomes large, the radially middle portion of the sub-valve element 8 comes into contact with and is supported by the stopper member 40 or the stopper member 41. If the amount of bending of the sub-valve element 8 becomes even larger, the central leaf valve of the sub-valve element 8 comes into contact with the outer peripheral edge of the stopper member 9 or the nut 30, and further bending of the sub-valve element 8 is restricted.

[0053] In this way, as the deflection of the sub-valve element 8 progresses, the radial center is supported by the stopper member 40 or the stopper member 41, and the leaf valve at the center of the sub-valve element 8 abuts against the stopper member 9 or the nut 30, restricting further deflection of the sub-valve element 8. Therefore, when the sub-valve element 8 is deflected to the maximum, it bends in a smooth curve with the inclination gradually increasing toward the free end, thereby reducing the stress generated near the deflection fulcrum of the sub-valve element 8 and improving the durability of the sub-valve element 8.

[0054] Furthermore, in this embodiment, the diameter of the free end of the sub-valve element 8 in the initial installation state when it is not deflected is larger than the outer diameter of the outer-side stopper member 9 and the nut 30 on the sub-valve element 8 side. Therefore, when the sub-valve element 8 abuts against the stopper member 9 or the nut 30, the gap formed between the stopper member 9 or the nut 30 and the opposing portion 5d is smaller than the annular gap formed between the free end of the sub-valve element 8 and the opposing portion 5d, making it possible to prevent the gap from restricting the flow of liquid. Note that the sub-valve element 8 only needs to be configured with at least one leaf valve, and the leaf valve that each support portion abuts can also be changed as appropriate.

[0055] The operation of the shock absorber D equipped with the damping valve (valve) V according to this embodiment will be described below.

[0056] When the shock absorber D extends, the piston 2 moves upward in the cylinder 1, compressing the extension-side chamber L1, and the liquid in the extension-side chamber L1 passes through the passage P and moves to the compression-side chamber L2. Resistance is applied to the flow of the liquid by the extension-side main valve element 6, the orifices formed by the notches 6a and 7a of the main valve elements 6 and 7, or the sub-valve element 8, so the pressure in the extension-side chamber L1 rises, and the shock absorber D exerts an extension-side damping force that hinders the extension operation.

[0057] Conversely, when the shock absorber D contracts, the piston 2 moves downward within the cylinder 1, compressing the compression-side chamber L2, and the liquid in this compression-side chamber L2 moves to the expansion-side chamber L1 through the passage P. Resistance is applied to the flow of liquid by the orifices formed by the compression-side main valve element 7 and the notches 6a and 7a of the main valve elements 6 and 7, or the sub-valve element 8, so the pressure in the compression-side chamber L2 rises, and the shock absorber D exerts a compression-side damping force that prevents the contraction operation.

[0058] In this embodiment, the main valve bodies 6, 7 on the extension side and compression side open depending on the piston speed, and the outer periphery (the end on the free end side) of the sub-valve body 8 bends up and down, so that the shock absorber D can generate a speed-dependent damping force that depends on the piston speed.

[0059] More specifically, when the piston speed is in an extremely low speed range close to 0, the extension-side and compression-side main valve elements 6, 7 close, and the sub-valve element 8 does not bend, with its free end facing the facing portion 5d.

[0060] When the piston speed is in the extremely low speed range during extension of the shock absorber D, the liquid flows from the extension-side chamber L1 into the tubular portion 4b through the notches 6a, 7a of the extension-side and compression-side main valve bodies 6, 7, flows downward through the communicating passage 5c in FIG. 2, and flows out into the compression-side chamber L2 through the annular gap formed between the free end of the opposing sub-valve body 8 and the opposing portion 5d.

[0061] Conversely, when the piston speed is in the extremely low speed range during contraction of the shock absorber D, the liquid flows from the compression-side chamber L2 into the case portion 5b through the annular gap formed between the opposing portion 5d and the free end of the opposing sub-valve element 8, flows upward in FIG. 2 through the case portion 5b and the communicating passage 5c, and then flows out into the expansion-side chamber L1 through the notches 6a and 7a of the expansion-side and compression-side main valve elements 6 and 7.

[0062] As mentioned above, the opening area of ​​the annular gap formed between the free ends of the opposing sub-valve bodies 8 and the opposing portion 5d is very small, so when the piston speed is in the extremely low speed range, the shock absorber D exerts a damping force in the extremely low speed range due to the resistance when the liquid flows through the annular gap.

[0063] Here, when the shock absorber D expands and contracts at an extremely low speed, the amount of liquid passing through the passage P is extremely small. However, when the seal ring 12 that seals between the main piston segment 4 and the sub-piston segment 5 is displaced axially within the annular groove 50, the amount of liquid passing through the annular gap between the sub-valve element 8 and the opposing portion 5d is reduced by the amount of movement of the seal ring 12. In other words, although the gap between the main piston segment 4 and the sub-piston segment 5 is sealed by the seal ring 12, when the seal ring 12 moves axially within the annular groove 50, it appears as if liquid has passed between the main piston segment 4 and the sub-piston segment 5. A reduction in the amount of liquid passing through the annular gap means a reduction in the flow rate passing through the annular gap, which causes a corresponding delay in the generation of the damping force of the shock absorber D. However, in the seal device S in the shock absorber D of this embodiment, the shape of the bottom 51 of the annular groove 50 is concave to form a recess as a whole, and the seal ring 12 penetrates to the deepest part of the bottom 51 by its own tension force, and the inner periphery is constrained by the bottom 51, preventing it from moving axially relative to the annular groove 50. In this way, the inner periphery of the seal ring 12 is constrained and its axial movement within the annular groove 50 is restricted, so that even though the seal ring 12 is self-lubricating and has been surface-treated to reduce frictional force, it does not move axially within the annular groove 50, and no time delay occurs in the generation of the damping force of the shock absorber D.

[0064] Furthermore, when the piston speed increases and moves out of the extremely low speed range and into the low speed range, the extension-side and compression-side main valve bodies 6, 7 are closed, but the outer periphery of the sub-valve body 8 bends downward during extension and upward during contraction, causing a vertical displacement between the free end of the sub-valve body 8 and the opposing part 5d. The opening area of ​​the annular gap formed between them becomes larger than the opening area of ​​the orifice formed by the notches 6a, 7a.

[0065] For this reason, when the piston speed is in the low-speed range, the shock absorber D exerts a damping force in the low-speed range due to the resistance of the orifice formed by the notches 6a, 7a of the extension-side and compression-side main valve bodies 6, 7. When the piston speed shifts from the extremely low-speed range to this low-speed range, the damping coefficient of the shock absorber D decreases.

[0066] Furthermore, when the piston speed increases further and leaves the low speed range and enters the medium to high speed range, the outer periphery of the sub-valve element 8 not only bends upward or downward, but also the extension-side main valve element 6 opens during extension, and the compression-side main valve element 7 opens during contraction.

[0067] In this embodiment, when the extension-side main valve element 6 opens, the outer periphery of the main valve element 6 bends downward, allowing liquid to pass through the gap formed between the outer periphery and the main piston segments 4. Similarly, when the compression-side main valve element 7 opens, the outer periphery of the main valve element 7 bends upward, allowing liquid to pass through the gap formed between the outer periphery and the main piston segments 4.

[0068] For this reason, when the piston speed is in the medium to high speed range, shock absorber D exerts a damping force in the medium to high speed range due to the resistance of the gap created by the opening of the extension side or compression side main valve body 6, 7. When the piston speed shifts from the low speed range to this medium to high speed range, the damping coefficient of shock absorber D becomes smaller.

[0069] The amount of deflection of the extension-side and compression-side main valve bodies 6, 7 may be restricted midway through the medium-to-high speed range. In such a case, the damping coefficient increases again at the speed at which the amount of deflection of the extension-side and compression-side main valve bodies 6, 7 reaches a maximum.

[0070] As described above, the sealing device S for hydraulic equipment in this embodiment includes an annular main piston segment (outer member) 4, a secondary piston segment (inner member) 5 inserted inside the main piston segment (outer member) 4, and a seal ring 12 accommodated in an annular groove 50 provided on the outer periphery of the secondary piston segment (inner member) 5 and abutting against the main piston segment (outer member) 4 to prevent liquid from passing between the main piston segment (outer member) 4 and the secondary piston segment (inner member) 5, and the secondary piston segment (inner member) 5 has a recess at the bottom 51 of the annular groove 50 that restricts axial movement of the seal ring 12 relative to the annular groove 50. With the sealing device S configured in this manner, axial movement of the seal ring 12 within the annular groove 50 can be restricted, thereby preventing the phenomenon of liquid apparently passing between the main piston segment (outer member) 4 and the secondary piston segment (inner member) 5 due to movement of the seal ring 12 within the annular groove 50. Furthermore, the axial movement of the seal ring 12 within the annular groove 50 can be restricted even if the frictional force generated between the seal ring 12 and the main piston segment 4 and the sub-piston segment 5 is reduced by providing the seal ring 12 with self-lubricating properties or by performing a surface treatment on the seal ring 12. In other words, even if the frictional force of the seal ring 12 is reduced to improve the ease of assembly of the seal ring 12 to the main piston segment 4 and the sub-piston segment 5, the seal device S can restrict the axial movement of the seal ring 12 within the annular groove 50. Therefore, the seal device S of this embodiment can improve assembly workability while suppressing a time delay in the generation of a damping force in the shock absorber D to which it is applied. Note that, because the seal ring 12 can be restrained by the recess provided in the bottom 51 of the annular groove 50, the width of the side walls 52, 52 of the annular groove 50 may be longer than the axial width of the seal ring 12, and the seal device S may not contact the seal ring 12 when assembled. However, it is preferable that the side walls 52, 52 are in contact with the seal ring 12 when the seal device S is assembled so that the movement of the seal ring 12 can also be restricted by the side walls 52, 52. In addition, in the seal device S of this embodiment, the side walls 52, 52 are parallel and opposed to each other, but the opposed state can be arbitrarily changed in design.

[0071] The seal ring 12 in the seal device S for hydraulic equipment of this embodiment is self-lubricating. The seal ring 12 is configured to be in an expanded diameter state when housed in the annular groove 50. To fit the seal ring 12 into the annular groove 50, the seal ring 12 must be expanded in diameter and fitted onto the outer periphery of the fitting portion 5a so that it can slide along the circumferential surface of the fitting portion 5a. The seal ring 12, which presses tightly against the outer periphery of the fitting portion 5a, is subjected to resistance from frictional forces generated between the seal ring 12 and the sub-piston segment (inner member) 5. When fitted into the annular groove 50 of the sub-piston segment (inner member) 5, the outer periphery of the seal ring 12 protrudes from the fitting portion 5a when viewed in the axial direction, and the outer diameter of the seal ring 12 is larger than the inner diameter of the cylindrical portion 4b of the main piston segment (outer member) 4. Therefore, when the secondary piston segment (inner member) 5 with the seal ring 12 attached thereto is fitted into the cylindrical portion 4b of the main piston segment (outer member) 4, the seal ring 12 is pressed strongly against the cylindrical portion 4b, and the seal ring 12 is subjected to resistance from a frictional force generated between the seal ring 12 and the cylindrical portion 4b. In this way, frictional resistance is applied when the seal ring 12 is attached to the annular groove 50 of the secondary piston segment (inner member) 5 and when the secondary piston segment (inner member) 5 is fitted into the main piston segment (outer member) 4. However, in the seal device S of this embodiment, the seal ring 12 is self-lubricating, which reduces frictional force, and therefore resistance is reduced when the seal ring 12 is attached to the annular groove 50 of the secondary piston segment (inner member) 5 and when the secondary piston segment (inner member) 5 is fitted into the main piston segment (outer member) 4. Therefore, according to the sealing device S of this embodiment, it is easy to install the seal ring 12 in the annular groove 50 provided on the outer periphery of the fitting portion 5a of the secondary piston segment (inner member), and it is also easy to fit the secondary piston segment (inner member) 5 with the seal ring 12 installed into the cylindrical portion 4b of the main piston segment (outer member) 4. Note that in order to further improve the ease of installation of the seal ring 12 on the main piston segment (outer member) 4 and the secondary piston segment (inner member) 5, a surface treatment may be applied to smooth the surface of the self-lubricating seal ring 12.

[0072] Furthermore, in the seal device S for hydraulic equipment of this embodiment, the bottom 51 of the annular groove 50 of the secondary piston segment (inner member) 5 has a recessed portion, and the bottom 51 has a bottom surface 51a that is the deepest in the axial center and tapered surfaces 51b, 51b provided on both sides of the bottom surface 51a. According to the seal device S for hydraulic equipment configured in this manner, the seal ring 12 easily enters the recessed portion of the bottom 51 along the tapered surfaces 51b, 51b, and the inner periphery of the seal ring 12 is restrained by the bottom 51, thereby effectively suppressing axial positional displacement of the seal ring 12.

[0073] In addition to the shapes described above, the bottom 51 of the annular groove 50 may have a bottom surface 51a in the center of FIG. 4, where the groove depth is greatest, and curved surfaces 51c, 51c that are connected above and below the bottom surface 51a and gradually become shallower toward the side wall 52, as shown in FIG. 4(a), thereby forming a recess as a whole. Furthermore, the bottom 51 of the annular groove 50 may have a V-shaped recess or an arc-shaped recess without a bottom surface 51a, as shown in FIG. 4(b) or 4(c). Even when a recess is formed in the bottom 51 in this way, the inner periphery of the seal ring 12 can easily enter and fit into the recess formed by the bottom 51, thereby effectively restricting axial movement of the seal ring 12 within the annular groove 50.

[0074] Furthermore, in the seal device S of this embodiment, the bottom 51 forms one recess as a whole, but the bottom 51 of the annular groove 50 may have a recess 51d formed by deepening the groove depth by one step at the center in the vertical direction in FIG. 4, as shown in FIG. 4(d). Even if the recess 51d is formed in a part of the bottom 51 in this way, the inner periphery of the seal ring 12 is fitted into and restrained in the recess 51d formed in the bottom 51, and the axial movement of the seal ring 12 within the annular groove 50 can be restricted. In this way, the recess 51d of the seal ring 12 is partially fitted into a part of the axial portion of the bottom 51. Inside A recess 51d may be formed in the bottom portion 51 so that the inner periphery of the seal ring 12 is fitted therein, and the inner periphery of the seal ring 12 is restrained by the recess 51d in the bottom portion 51.

[0075] Furthermore, the bottom 51 of the annular groove 50 may have a shape in which recesses 51e and protrusions 51f are continuous in the axial direction, as shown in Fig. 4(e). When the bottom 51 has a shape with recesses and protrusions in this manner, the inner periphery of the seal ring 12 fits into and is restrained by the recesses and protrusions formed on the bottom 51, thereby restricting axial movement of the seal ring 12 within the annular groove 50. Note that the recesses and protrusions provided on the bottom 51 may be provided partially in the axial direction, which is the up-and-down direction in Fig. 4(e), as long as they are able to restrict axial movement of the seal ring 12 within the annular groove 50.

[0076] Moreover, a shock absorber D of this embodiment includes a cylinder 1, a piston 2 inserted axially movably into the cylinder 1, dividing the interior of the cylinder 1 into an expansion-side chamber L1 and a compression-side chamber L2, and having a passage P connecting the expansion-side chamber L1 and the compression-side chamber L2, a rod 3 inserted axially movably into the cylinder 1 and connected to the piston 2, a valve V that opens and closes the passage P, and a sealing device S, and the piston 2 includes a main piston segment (outer member) and a sub-piston segment (inner member) 5. With the shock absorber D configured in this manner, when the shock absorber D expands or contracts at an extremely low speed, the sealing device S can suppress a phenomenon in which liquid apparently bypasses the valve V in the passage P and passes between the main piston segment (outer member) and the sub-piston segment (inner member) 5. Therefore, with the shock absorber D of this embodiment, the flow rate passing through the valve V is not reduced, and damping force can be generated as designed from the start of movement, preventing a time delay in the generation of the damping force.

[0077] In the above description, the annular groove 50 is provided in the sub-piston segment 5, which is the inner member, and the seal ring 12 is attached to the sub-piston segment 5. However, the annular groove for accommodating the seal ring 12 may be provided in the portion of the main piston segment 4, which is the outer member, that fits into the sub-piston segment 5.

[0078] In addition, in this embodiment, seal ring 12 is an O-ring with a circular cross section, but it is sufficient that it fits into a recess in bottom 51 of annular groove 50 and restricts axial movement within annular groove 50. Therefore, the cross-sectional shape of seal ring 12 may be a shape other than circular, and the inner peripheral shape may be a shape that matches the recess in bottom 51 and fits into said recess. Note that when seal ring 12 is attached to an annular groove of an outer member, the outer peripheral shape of seal ring 12 may be a shape that matches the recess in the bottom of the annular groove of the outer member.

[0079] In the shock absorber D of this embodiment, an annular groove 11a is provided on the outer periphery of the free piston 11, and a seal ring 60 that slides against the inner periphery of the cylinder 1 is housed in the annular groove 11a. Therefore, the cylinder 1 may serve as an outer member, the free piston 11 as an inner member, and a sealing device S of a hydraulic device may be used to seal between the cylinder 1 and the free piston 11. Specifically, in the shock absorber D shown in FIG. 1 , the bottom 11b of the annular groove 11a of the free piston 11 has a structure similar to that of the annular groove 50, including a bottom surface 11c at the axial center and tapered surfaces 11d above and below the bottom surface 11c, thereby providing a recess and restricting the axial movement of the seal ring 60. When the shock absorber D expands or contracts at an extremely low speed, if the seal ring 60 moves in the axial direction within the annular groove 11a relative to the free piston 11, the flow rate of the liquid exchanged between the expansion-side chamber L1 and the compression-side chamber L2 decreases accordingly, resulting in a time delay in the generation of a damping force at the start of expansion or contraction. In contrast to this, in the shock absorber D of this embodiment, the axial movement of the seal ring 60 within the annular groove 11a is restricted, so that such a time delay in the generation of the damping force of the shock absorber D can be eliminated.

[0080] 5, the shock absorber D1 may include a cylinder 70, a rod 71 movably inserted into the cylinder 70 in the axial direction, a piston 72 as a partition body inserted into the cylinder 70 to divide the interior of the cylinder 70 into two working chambers, an expansion-side chamber L1 and a compression-side chamber L2, and having a passage 72a connecting the expansion-side chamber L1 and the compression-side chamber L2, and a sealing device S1. The sealing device S1 includes the cylinder 70 as an outer member and the piston 72 as an inner member, and includes a seal ring 80 housed in an annular groove 72c provided on the outer periphery of the piston 72 and in close contact with the inner periphery of the cylinder 70. The piston 72 includes a passage 72a connecting the expansion-side chamber L1 and the compression-side chamber L2, and a valve 72b provided in the passage 72a to provide resistance to the flow of liquid passing through the passage 72a.

[0081] Furthermore, the shock absorber D1 has an outer shell 73 that covers the outer periphery of the cylinder 70 and forms a reservoir L3 between the cylinder 70 and the outer shell 73, which is filled with liquid and gas, and the cylinder 70, rod 71, piston 72 and outer shell 73 form the shock absorber body.

[0082] A valve case 74 is provided at the lower end of the cylinder 70, dividing the shock absorber body into a compression-side chamber L2 and a reservoir L3. The valve case 74 includes a passage 74a that connects the compression-side chamber L2 and the reservoir L3, a valve 74b provided in the passage 74a, and a suction passage 74c equipped with a check valve 74d that allows only the flow of liquid from the reservoir L3 to the compression-side chamber L2. In this way, the shock absorber D1 is a so-called double-cylinder shock absorber in which the reservoir L3 is provided between the cylinder 70 and an outer shell 73 provided on the outer periphery of the cylinder 70.

[0083] In the shock absorber D1 of this embodiment, the bottom 72d of the annular groove 72c of the piston 72 has a structure including a bottom surface 72e in the axial center and tapered surfaces 72f, 72f above and below the bottom surface 72e, similar to the annular groove 50, to provide a recess, thereby restricting axial movement of the seal ring 80. Here, when the shock absorber D1 expands or contracts at an extremely low speed, if the seal ring 80 moves axially within the annular groove 72c relative to the piston 72, the flow rate of fluid exchanged between the expansion-side chamber L1 and the compression-side chamber L2 via the valve 72b of the passage 72a decreases accordingly, causing a time delay in the generation of a damping force at the start of expansion or contraction. In contrast, in the shock absorber D1 of this embodiment, the axial movement of the seal ring 80 within the annular groove 72c is restricted, thereby eliminating such a time delay in the generation of a damping force of the shock absorber D1.

[0084] In shock absorber D1, an annular groove 74e is provided on the outer periphery of the valve case 74, and a seal ring 90 that slides against the inner periphery of the cylinder 70 is housed in the annular groove 74e. Therefore, the cylinder 70 may be used as the outer member and the valve case 74 may be used as the inner member, and the sealing device S1 for hydraulic equipment may be used to seal between the cylinder 70 and the valve case 74. Specifically, in shock absorber D1 shown in Fig. 5, the structure of the bottom 74f of the annular groove 74e of the valve case 74 is the same as that of the annular groove 50, with a bottom surface 74g at the axial center and tapered surfaces 74h above and below the bottom surface 74g, and recesses are provided to restrict axial movement of the seal ring 90. Here, when the shock absorber D1 contracts at an extremely low speed, if the seal ring 90 moves in the axial direction within the annular groove 74e relative to the valve case 74, the flow rate of the liquid moving from the compression-side chamber L2 to the reservoir L3 via the valve 74b of the passage 74a decreases accordingly, causing a time delay in the generation of the damping force at the start of contraction. In contrast, in the shock absorber D1 of this embodiment, the axial movement of the seal ring 90 within the annular groove 74e is restricted, thereby eliminating such a time delay in the generation of the damping force of the shock absorber D1. In this way, the seal device S1 may be used in a twin-cylinder shock absorber D1, and can eliminate the time delay in the generation of the damping force of the shock absorber D1.

[0085] Furthermore, the sealing devices S, S1 can be applied to locations within shock absorbers D, D1 where liquid or gas pressure acts on a seal ring. Thus, for example, when the outer member is a rod guide 10 and the inner member is a rod 3, and a seal ring housed in an annular groove provided on the inner periphery of the rod guide 10 seals the space between the rod guide 10 and the rod 3, the sealing device S can be applied to this seal. Furthermore, in addition to shock absorbers D, D1, the sealing devices S, S1 can also be applied to hydraulic equipment such as cylinder devices that expand and contract by supplying and discharging liquid into the cylinder, and applying the sealing devices S, S1 to cylinder devices can suppress the apparent decrease in liquid volume due to the axial movement of the seal ring, eliminating the time delay in thrust generation at the start of the expansion and contraction operation.

[0086] The valves 72b and 74b may be any valve that provides resistance to the flow of liquid passing through the passages 72a and 74a, and may be a restriction such as an orifice or a choke, or may be a leaf valve or other valve.

[0087] Although the preferred embodiment of the present invention has been described in detail, modifications, variations and changes can be made thereto without departing from the scope of the appended claims. [Explanation of symbols]

[0088] 1····cylinder, 2···piston, 3···rod, 4···main piston segment (outer member), 5···sub-piston segment (inner member), 11a, 50, 72c, 74e···annular groove, 12, 60, 80, 90···seal ring, 11b, 51···bottom (recess), 51a···bottom surface, 51b···tapered surface, 51c···curved surface, 51d ···recess, 51e···recess constituting the recess and projection, 51f···recess convex portion constituting the recess and projection, 72···piston (partition body), 72a, 74a, P···passage, 72b, 74b, V···valve, D, D1···shock absorber (hydraulic equipment), L1···extension side chamber (operating chamber), L2···compression side chamber (operating chamber), L3···reservoir (operating chamber), S, S1···sealing device

Claims

1. A cylinder; a piston having an annular outer member and an inner member inserted inside the outer member, the piston being inserted into the cylinder so as to be axially movable, the piston dividing the interior of the cylinder into an expansion-side chamber and a compression-side chamber, and having a passage communicating between the expansion-side chamber and the compression-side chamber; a rod inserted into the cylinder so as to be axially movable and connected to the piston; a seal ring that is accommodated in an annular groove provided in one of the outer member and the inner member and abuts against the other of the outer member and the inner member to prevent passage of liquid between the outer member and the inner member; a valve for opening and closing the passage, one of the outer member and the inner member has a recess or a protrusion at a bottom of the annular groove that restricts axial movement of the seal ring relative to the annular groove; The valve has a main valve element and a sub-valve element that are provided in series in the passage, the main valve body is attached to the outer member and generates a damping force when the piston speed is in a medium to high speed range, The sub-valve body is attached to the inner member and generates a damping force in a very low piston speed range. A shock absorber characterized by:

2. The seal ring has self-lubricating properties.

2. The shock absorber according to claim 1.

3. A recess is provided in the bottom of the annular groove, and the bottom has a deepest bottom surface in the center in the axial direction and tapered or curved surfaces provided on both sides of the bottom surface.

3. The shock absorber according to claim 1 or 2.

4. the annular groove is a concave groove surrounded by a bottom portion and a pair of side walls extending from both axial ends of the bottom portion and facing each other, When the seal ring is installed in the annular groove, it fits into the recess or the concave / convex portion to restrict axial movement and contact the pair of side walls.

4. The shock absorber according to claim 1, wherein the shock absorber is a shock absorber having a first end and a second end.

5. The seal ring has a circular cross section.

5. The shock absorber according to claim 1, wherein the shock absorber is a shock absorber having a first end and a second end.

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