Shock absorber

Abstract

This shock absorber comprises a housing, a first structural member, a shaft member, and a second structural member. The second structural member is smaller in diameter than the first structural member and extends along a first circumferential groove and a second cylinder part. The second structural member has a first check valve mechanism that: has a first inner peripheral wall which penetrates the center in the axial direction, and through which the shaft member is inserted, and a second inner peripheral wall which is separated from the shaft member in the radial direction more than the first inner peripheral wall; includes a center hole which is directly or indirectly in communication with the first circumferential groove, a first check valve seat which is a valve seat, and a first check valve body which is a flexible valve body; and allows flow in the second flow path only in a direction from an upstream region to a downstream region.

Description

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[0001] This application claims priority from Japanese Patent Application No. 2023-165947, filed on September 27, 2023, the contents of which are incorporated herein by reference.

[0002] Some shock absorbers have a piston and a valve seat member that is separate from the piston, which are provided on a piston rod (see, for example, Patent Document 1).

[0003] International Publication No. 2020 / 261683

[0004] Incidentally, there is a demand for greater freedom in design of shock absorbers.

[0005] An object of the present invention is to provide a shock absorber that allows for ensuring a degree of freedom in design.

[0006] In order to achieve the above object, the present invention employs the following aspects. That is, a first aspect of the present invention is a fluid-using shock absorber, comprising: a bottomed cylindrical housing having a cylindrical portion and a bottom; a first structural member dividing the housing into an upstream region on an upstream side and a downstream region on a downstream side; a rod-shaped shaft member; and a second structural member, wherein the first structural member has: a circular fixing hole penetrating in the axial direction; a first flow path that can communicate between the upstream region and the downstream region; a flexible first valve member that can close the first flow path; and a second flow path at least a portion of which is provided parallel to the first flow path, and the shaft member has: a first cylindrical portion that is a cylindrical portion inserted into the fixing hole; an axial flow path that is a flow path that is connected to the second flow path and leads toward the downstream region; a first circumferential groove that is a circumferential groove provided at an end of the axial flow path on the downstream region side; and a second cylindrical portion that is a cylindrical portion provided closer to the downstream region than the first circumferential groove, the second structural member has a smaller diameter than the first structural member and extends over the first circumferential groove and the second cylindrical portion, and has a first inner circumferential wall penetrating the center in the axial direction and through which the shaft member is inserted, and a second inner circumferential wall that is radially spaced further from the shaft member than the first inner circumferential wall, a central hole that directly or indirectly communicates with the first circumferential groove, and a first check valve mechanism that includes a first check valve seat that is a valve seat, and a first check valve element that is a flexible valve element, and that allows flow through the second flow path only in a direction from the upstream region to the downstream region.

[0007] a first structural member dividing the housing into an upstream region on an upstream side and a downstream region on a downstream side; a rod-shaped shaft member; and a second structural member, wherein the first structural member has: a circular fixing hole penetrating in the axial direction; a first flow path that can communicate the upstream region and the downstream region; a flexible first valve member that can close the first flow path; and a second flow path at least a portion of which is provided parallel to the first flow path; and the shaft member has: a first cylindrical portion that is a cylindrical portion inserted into the fixing hole; an axial flow path that is a flow path that is connected to the second flow path and leads toward the downstream region; and a second cylindrical portion that is a cylindrical portion provided closer to the downstream region than the axial flow path; and the second structural member has a smaller diameter than the first structural member and extends across the axial flow path and the second cylindrical portion, a central hole including a first inner circumferential wall that penetrates the center in the axial direction and through which the axial member is inserted, a first circumferential groove that is an annular space that is provided inside the thickness direction of the second structural member and through which the axial flow path communicates, and one or more second inner circumferential walls that communicate with the first circumferential groove and extend radially beyond the first inner circumferential wall, and a first check valve mechanism that includes a first check valve seat that is a valve seat, and a first check valve element that is flexible and is disposed in the axial flow path, and that allows the fluid to flow only in a direction from the downstream region to the upstream region.

[0008] Furthermore, a third aspect of the present invention is a fluid shock absorber comprising: a bottomed cylindrical housing having a cylindrical portion and a bottom; a first structural member dividing the housing into an upstream region on an upstream side and a downstream region on a downstream side; a rod-shaped shaft member; and a second structural member, wherein the first structural member has: a circular fixing hole penetrating in the axial direction; a first flow path that can communicate between the upstream region and the downstream region; a flexible first valve member that can close the first flow path; and a second flow path at least a portion of which is provided parallel to the first flow path; and the shaft member has: a first cylindrical portion that is a cylindrical portion inserted into the fixing hole; an axial flow path that is a flow path that is connected to the second flow path and leads toward the downstream region; and a second cylindrical portion that is a cylindrical portion provided closer to the downstream region than the axial flow path; and the second structural member has a diameter smaller than that of the first structural member and extends across the axial flow path and the second cylindrical portion, the first check valve mechanism including a first check valve seat serving as a valve seat and a first check valve element serving as a flexible valve element disposed in the axial flow path, and allowing the fluid to flow only in a direction from the upstream region toward the downstream region; and a radial flow path provided at a position opposite the axial flow path and communicating with the first check valve mechanism.

[0009] Furthermore, a fourth aspect of the present invention is a fluid shock absorber comprising: a bottomed cylindrical housing having a cylindrical portion and a bottom; a first structural member dividing the housing into an upstream region on an upstream side and a downstream region on a downstream side; a rod-shaped shaft member; and a second structural member, wherein the first structural member has: a circular fixing hole penetrating in the axial direction; a first flow path that can communicate between the upstream region and the downstream region; a flexible first valve member that can close the first flow path; and a second flow path at least a portion of which is provided parallel to the first flow path; and the shaft member has: a first cylindrical portion that is a cylindrical portion inserted into the fixing hole; an axial flow path that is a flow path that is connected to the second flow path and leads toward the downstream region; and a second cylindrical portion that is a cylindrical portion provided closer to the downstream region than the axial flow path; and the second structural member has a diameter smaller than that of the first structural member and extends across the axial flow path and the second cylindrical portion, a central hole that penetrates the center in the axial direction and includes a first inner circumferential wall through which the axial member is inserted, and one or more second inner circumferential walls that communicate with the axial flow path and extend radially beyond the first inner circumferential wall; and a first check valve mechanism that includes a first check valve seat that is a valve seat, and a first check valve element that is flexible and is disposed in the axial flow path, and that allows the fluid to flow only in a direction from the upstream region to the downstream region.

[0010] According to the above aspects of the present invention, a shock absorber that can ensure a degree of freedom in design can be provided.

[0011] FIG. 1 is a view showing a shock absorber according to a first embodiment of the present invention, and is a cross-sectional view taken along a cross section including the central axis line CL thereof; FIG. 2 is a partial side view showing a main portion of a piston rod of the shock absorber according to the embodiment; FIG. 3 is a partial side view showing a main portion of the piston rod of the shock absorber according to the embodiment, as viewed from another direction; FIG. 4 is a partial cross-sectional view showing a first structural member and a second structural member of the shock absorber according to the embodiment; FIG. 5 is a partial cross-sectional view showing a main portion of the second structural member of the shock absorber according to the embodiment; FIG. 6 is a plan view showing a seat member of the shock absorber according to the embodiment; FIG. 7 is a bottom view showing a seat member of the shock absorber according to the embodiment; FIG. 8 is a partial cross-sectional view showing a main portion of the second structural member of the shock absorber according to the embodiment; FIG. 9 is a plan view showing a seat member of the shock absorber according to the embodiment; Fig. 10 is a partial cross-sectional view showing a first structural member, a second structural member, etc. of a shock absorber according to a fifth embodiment of the present invention; Fig. 11 is a bottom view showing a case member of the shock absorber according to the same embodiment; Fig. 12 is a partial cross-sectional view showing a first structural member, a second structural member, etc. of a shock absorber according to a sixth embodiment of the present invention; Fig. 13 is a bottom view showing a pilot case of the shock absorber according to the same embodiment;

[0012] [First embodiment] A first embodiment of the present invention will be described with reference to Figures 1 to 6. In each figure, the central axis of the shock absorber is indicated by the symbol CL.

[0013] The shock absorber 1 of the first embodiment is a shock absorber used in suspension systems for railway vehicles and automobiles such as two-wheeled and four-wheeled vehicles. Specifically, the shock absorber 1 is a shock absorber used in suspension systems for four-wheeled automobiles. As shown in FIG. 1 , the shock absorber 1 is a twin-tube shock absorber equipped with a cylinder 4 (housing) having an inner tube 2 and an outer tube 3. The inner tube 2 is cylindrical. The outer tube 3 is cylindrical with a bottom and has a larger diameter than the inner tube 2. The outer tube 3 is disposed radially outside the inner tube 2 and coaxially with the inner tube 2. A reservoir chamber 5 is formed between the outer tube 3 and the inner tube 2.

[0014] The outer cylinder 3 has a tubular portion 8 and a bottom portion 9. The tubular portion 8 is cylindrical. The bottom portion 9 closes one axial end of the tubular portion 8. The tubular portion 8 has an opening on the side opposite the bottom portion 9. A mounting eye 10 is fixed to the bottom portion 9 on the side opposite the tubular portion 8 in the axial direction.

[0015] The shock absorber 1 includes a valve body 12 and a rod guide 13. The valve body 12 is annular and is provided on the bottom 9 side of the inner cylinder 2 and the outer cylinder 3 in the axial direction. The rod guide 13 is annular and is provided on the opposite side of the inner cylinder 2 and the outer cylinder 3 from the bottom 9 in the axial direction. The valve body 12 constitutes a base valve 15. The valve body 12 has a stepped outer periphery, and is placed on the bottom 9 with its large diameter portion positioned radially relative to the cylindrical portion 8. The rod guide 13 also has a stepped outer periphery, and its large diameter portion is positioned radially relative to the cylindrical portion 8 and fitted thereto.

[0016] One axial end of the inner cylinder 2 is fitted into a small-diameter portion of the outer periphery of the valve body 12. One axial end of the inner cylinder 2 engages with the bottom 9 of the outer cylinder 3 via the valve body 12. The other axial end of the inner cylinder 2 is fitted into a small-diameter portion of the outer periphery of the rod guide 13. The other axial end of the inner cylinder 2 engages with the cylindrical portion 8 of the outer cylinder 3 via the rod guide 13. In this state, the inner cylinder 2 is positioned radially relative to the outer cylinder 3. Here, the space between the valve body 12 and the bottom 9 is in communication with the inner cylinder 2 and the outer cylinder 3. Therefore, the space between the valve body 12 and the bottom 9, like the space between the inner cylinder 2 and the outer cylinder 3, forms a reservoir chamber 5.

[0017] The shock absorber 1 is provided with a seal member 18. The seal member 18 is provided on the opposite side of the rod guide 13 from the bottom 9. This seal member 18 is also fitted into the inner periphery of the tubular portion 8, similar to the rod guide 13. A locking portion 19 is formed on the end of the tubular portion 8 opposite the bottom 9. The locking portion 19 is formed by plastically deforming the tubular portion 8 radially inward by crimping, such as curling. The seal member 18 is sandwiched between the locking portion 19 and the rod guide 13. The seal member 18 closes the opening of the outer cylinder 3, and is specifically an oil seal.

[0018] The shock absorber 1 includes a piston 21. The piston 21 is slidably disposed within a cylinder 4. The piston 21 is slidably disposed within an inner tube 2 of the cylinder 4. The piston 21 divides the inner tube 2 into two chambers: a first chamber 22 (upstream region) and a second chamber 23 (downstream region). The first chamber 22 is disposed between the piston 21 and the rod guide 13 within the inner tube 2. The second chamber 23 is disposed between the piston 21 and the valve body 12 within the inner tube 2. The second chamber 23 is separated from a reservoir chamber 5 by the valve body 12. Within the cylinder 4, oil L, which is a fluid, is sealed in the first chamber 22 and the second chamber 23. Within the cylinder 4, gas G and oil L, which are fluids, are sealed in the reservoir chamber 5. Thus, the shock absorber 1 is a hydraulic shock absorber that uses oil L, which is a fluid.

[0019] The shock absorber 1 includes a piston rod 31 (shaft member) that is a rod-shaped shaft member. One axial end portion of the piston rod 31 is disposed inside the cylinder 4 and is connected and fixed to the piston 21. The other axial end portion of the piston rod 31 extends outside the cylinder 4. The piston rod 31 is made of metal and passes through the first chamber 22. The piston rod 31 does not pass through the second chamber 23. Therefore, the first chamber 22 is a rod-side chamber through which the piston rod 31 passes. The second chamber 23 is a bottom-side chamber on the bottom 9 side of the cylinder 4.

[0020] The piston 21 and the piston rod 31 move together. During the extension stroke of the shock absorber 1, in which the piston rod 31 increases the amount of protrusion from the cylinder 4, the piston 21 moves toward the first chamber 22. During the compression stroke of the shock absorber 1, in which the piston rod 31 decreases the amount of protrusion from the cylinder 4, the piston 21 moves toward the second chamber 23.

[0021] Both the rod guide 13 and the seal member 18 are annular. The piston rod 31 is slidably inserted through the rod guide 13 and the seal member 18 and extends from the inside to the outside of the cylinder 4. One axial end of the piston rod 31 is fixed to the piston 21 inside the cylinder 4. The other axial end of the piston rod 31 extends outside the cylinder 4 via the rod guide 13 and the seal member 18.

[0022] The rod guide 13 supports the piston rod 31 relative to the cylinder 4 so that it can move axially while restricting its movement in the radial direction. The rod guide 13 guides the axial movement of the piston rod 31. The outer periphery of the seal member 18 is in close contact with the outer tube 3 of the cylinder 4. The inner periphery of the seal member 18 is in sliding contact with the outer periphery of the piston rod 31 that moves in the axial direction. In this way, the seal member 18 prevents the oil L and gas G in the cylinder 4 from leaking to the outside.

[0023] The piston rod 31 has a main shaft portion 32 and an attachment shaft portion 33. The attachment shaft portion 33 has a smaller diameter than the main shaft portion 32. The main shaft portion 32 of the piston rod 31 is slidably fitted into the rod guide 13 and the seal member 18. The attachment shaft portion 33 of the piston rod 31 is disposed in the cylinder 4 and is connected to the piston 21 and the like. The end of the main shaft portion 32 on the attachment shaft portion 33 side widens in a direction perpendicular to the axis.

[0024] 2A and 2B, the mounting shaft portion 33 has a base end side cylindrical portion 41 (first cylindrical portion), an intermediate shaft portion 42, a tip end side cylindrical portion 43 (second cylindrical portion), and a threaded shank portion 44 (second cylindrical portion). The mounting shaft portion 33 is provided with the base end side cylindrical portion 41, the intermediate shaft portion 42, the tip end side cylindrical portion 43, and the threaded shank portion 44 in this order from the main shaft portion 32 side in the axial direction.

[0025] The base-end side cylindrical portion 41 is a cylindrical portion, and is provided on the main shaft portion 32 side, i.e., the base end side, in the axial direction of the mounting shaft portion 33. The base-end side cylindrical portion 41 has an outer peripheral surface 41a on the radially outer side that is a cylindrical surface that is continuous around the entire circumferential direction of the base-end side cylindrical portion 41.

[0026] The tip-side cylindrical portion 43 is a cylindrical portion and is provided on the opposite side of the main shaft portion 32 from the base-side cylindrical portion 41 in the axial direction of the mounting shaft portion 33, i.e., on the tip side. The outer peripheral surface 43a of the tip-side cylindrical portion 43 on the radially outer side is a cylindrical surface that is continuous around the entire circumferential direction of the tip-side cylindrical portion 43. The outer peripheral surface 43a of the tip-side cylindrical portion 43 is coaxial and has the same diameter as the outer peripheral surface 41a of the base-side cylindrical portion 41.

[0027] The intermediate shaft portion 42 is provided at an axially intermediate position of the mounting shaft portion 33. The intermediate shaft portion 42 has, on its radially outer side, a pair of outer end surfaces 42a, a base-end circumferential groove 51 (second circumferential groove), a pair of axial grooves 52, and a tip-end circumferential groove 53 (first circumferential groove).

[0028] Each of the pair of outer end surfaces 42a has the shape of a part of a cylindrical surface that is coaxial and has the same diameter as the outer circumferential surface 41a of the base-end side cylindrical portion 41 and the outer circumferential surface 43a of the tip-end side cylindrical portion 43. In other words, the pair of outer end surfaces 42a are arranged on the same cylindrical surface as the outer circumferential surface 41a of the base-end side cylindrical portion 41 and the outer circumferential surface 43a of the tip-end side cylindrical portion 43. The pair of outer end surfaces 42a are 180 degrees out of phase with each other in the circumferential direction of the intermediate shaft portion 42.

[0029] The base-side circumferential groove 51 is provided at the end of the intermediate shaft 42 on the base-side cylindrical portion 41 side in the axial direction. The base-side circumferential groove 51 is recessed inward in the radial direction of the base-side circumferential groove 51 and the intermediate shaft 42 from the outer circumferential surface 41 a of the base-side cylindrical portion 41 and the pair of outer end surfaces 42 a of the intermediate shaft 42. The base-side circumferential groove 51 has an annular shape that continues around the entire circumferential direction of the intermediate shaft 42.

[0030] The tip side circumferential groove 53 is provided at an end of the intermediate shaft portion 42 on the tip side cylindrical portion 43 side in the axial direction. The tip side circumferential groove 53 is recessed inward in the radial direction of the tip side cylindrical portion 43 and the intermediate shaft portion 42 from the outer circumferential surface 43 a of the tip side cylindrical portion 43 and the pair of outer end surfaces 42 a of the intermediate shaft portion 42. The tip side circumferential groove 53 has an annular shape that continues around the entire circumferential direction of the intermediate shaft portion 42.

[0031] The pair of axial grooves 52 are recessed radially inward from the pair of outer end surfaces 42 a of the intermediate shaft portion 42. The pair of axial grooves 52 have the same shape, and the inner bottom surfaces of the radially inner sides of the intermediate shaft portion 42 form flat surfaces extending perpendicular to the radial direction of the intermediate shaft portion 42. The pair of axial grooves 52 extend in the axial direction of the piston rod 31. The pair of axial grooves 52 are provided 180 degrees out of phase with each other in the circumferential direction of the intermediate shaft portion 42 and extend parallel to each other. The outer end surfaces 42 a and the axial grooves 52 are alternately arranged in the circumferential direction of the intermediate shaft portion 42. One axial end of the pair of axial grooves 52 of the intermediate shaft portion 42 opens into the base-side circumferential groove 51, and the other axial end of the pair of axial grooves 52 of the intermediate shaft portion 42 opens into the tip-side circumferential groove 53.

[0032] As shown in FIG. 3 , the passage in the base-end circumferential groove 51, the passages in the pair of axial grooves 52, and the passage in the tip-end circumferential groove 53 constitute an axial flow path 54 formed in the piston rod 31 and extending in the axial direction of the piston rod 31.

[0033] The threaded shaft portion 44 is provided on the axial side of the mounting shaft portion 33 opposite to the main shaft portion 32, i.e., on the tip end side. The threaded shaft portion 44 is cylindrical, and has a male thread 57 formed on the radially outer side.

[0034] The shock absorber 1 is supported by the vehicle body, for example, with the portion of the piston rod 31 protruding from the cylinder 4 as shown in Figure 1 positioned at the top in the vertical direction. In this case, the shock absorber 1 is connected to the wheel side with the mounting eye 10 fixed to the bottom 9 of the cylinder 4 positioned at the bottom in the vertical direction. If the shock absorber 1 is a single-tube type, it can also be configured in the opposite way, with the cylinder 4 side supported by the vehicle body and the piston rod 31 connected to the wheel side.

[0035] As shown in FIG. 3 , the piston 21 is composed of a metal piston body 61 supported by the piston rod 31, and an annular friction member 62 integrally attached to the outer circumferential surface of the piston body 61 and sliding within the inner cylinder 2.

[0036] The piston body 61 is formed with a plurality of passage holes 71 (only one is shown in FIG. 3 because it is a cross-section) and an annular passage groove 72 that connects the ends of these passage holes 71 opposite the first chamber 22. The piston body 61 is also formed with a plurality of passage holes 75 (only one is shown in FIG. 3 because it is a cross-section) and an annular passage groove 76 that connects the ends of these passage holes 75 on the first chamber 22 side. The plurality of passage holes 71 are formed in the circumferential direction of the piston body 61 with one passage hole 75 sandwiched between each adjacent pair of passage holes 71.

[0037] The passages in the plurality of passage holes 71 and the passage in the passage groove 72 constitute a piston passage 81 that penetrates the piston 21 in the axial direction of the piston 21 and allows communication between the first chamber 22 and the second chamber 23. The passages in the plurality of passage holes 75 and the passage in the passage groove 76 constitute a piston passage 82 that penetrates the piston 21 in the axial direction of the piston 21 and allows communication between the first chamber 22 and the second chamber 23.

[0038] The piston passage 81 is provided with a valve mechanism 85, which is a valve that opens and closes the piston passage 81 to generate a damping force. The valve mechanism 85 is arranged on the second chamber 23 side, which is one axial end side of the piston 21, and is attached to the piston rod 31. By arranging the valve mechanism 85 on the second chamber 23 side, the oil L that flows out from the first chamber 22 flows toward the second chamber 23 in the piston passage 81 when the piston 21 moves toward the first chamber 22, i.e., during the extension stroke. The valve mechanism 85 provided for the piston passage 81 serves as an extension-side valve mechanism that suppresses the flow of oil L from the extension-side piston passage 81 to the second chamber 23 to generate a damping force.

[0039] The piston passage 82 is provided with a valve mechanism 86, which is a valve that opens and closes the piston passage 82 to generate a damping force. The valve mechanism 86 is arranged on the first chamber 22 side, which is the other axial end side of the piston 21, and is attached to the piston rod 31. By arranging the valve mechanism 86 on the first chamber 22 side, the oil L that flows out from the second chamber 23 flows toward the first chamber 22 in the piston passage 82 when the piston 21 moves toward the second chamber 23, i.e., during the compression stroke. The valve mechanism 86 provided for the piston passage 82 is a compression-side valve mechanism that suppresses the flow of oil L from the compression-side piston passage 82 to the first chamber 22 to generate a damping force.

[0040] As a result of the above, the piston passage 81 and the piston passage 82 are connected so that the oil liquid L, which is a fluid, flows between the first chamber 22 and the second chamber 23 as the piston 21 moves. The oil liquid L passes through the piston passage 81 when the piston rod 31 and the piston 21 move toward the extension side, and the oil liquid L passes through the piston passage 82 when the piston rod 31 and the piston 21 move toward the contraction side.

[0041] The piston body 61 is made up of two members: a first piston body 91 and a second piston body 92. The first piston body 91 constitutes the portion of the piston body 61 on the second chamber 23 side in the axial direction, and the second piston body 92 constitutes the portion of the piston body 61 on the first chamber 22 side in the axial direction.

[0042] The first piston body 91 has a generally circular disk shape. A circular fixing hole 101 is formed in the radial center of the first piston body 91, penetrating the first piston body 91 in the axial direction of the first piston body 91. The fixing hole 101 is a portion of the first piston body 91 into which the mounting shaft portion 33 of the piston rod 31 is fitted.

[0043] A passage groove 102 extending in the radial direction of the first piston body 91 is formed on the end face of the first piston body 91 on the second piston body 92 side in the axial direction. The passage in the passage groove 102 forms an in-piston flow path 103 that communicates with the piston passage 81.

[0044] The above-mentioned passage groove 72 is formed at the axial end of the first piston body 91 on the second chamber 23 side. An annular valve seat 105 constituting part of the valve mechanism 85 is formed at the axial end of the first piston body 91 on the second chamber 23 side, radially outward from the opening of the passage groove 72 on the second chamber 23 side. Furthermore, an inner seat 106 is formed at the axial end of the piston main body 61 on the second chamber 23 side, radially inward from the opening of the passage groove 72 on the second chamber 23 side.

[0045] The first piston body 91 is formed with an engaging protrusion 108 that protrudes outward along the axial direction of the first piston body 91 from an end face of the first piston body 91 that faces the second piston body 92 in the axial direction. The engaging protrusion 108 is provided partially in the circumferential direction of the first piston body 91.

[0046] The second piston body 92 has a generally circular disk shape. A circular fixing hole 111 is formed in the radial center of the second piston body 92, penetrating the second piston body 92 in the axial direction of the second piston body 92. The fixing hole 111 is a portion of the second piston body 92 into which the mounting shaft portion 33 of the piston rod 31 is fitted.

[0047] The above-mentioned passage groove 76 is formed at the axial end of the second piston body 92 on the first chamber 22 side. An annular valve seat 115 constituting a part of the valve mechanism 86 is formed at the axial end of the second piston body 92 on the first chamber 22 side, radially outward from the opening of the passage groove 76 on the first chamber 22 side. Furthermore, an inner seat 116 is formed at the axial end of the piston main body 61 on the first chamber 22 side, radially inward from the opening of the passage groove 76 on the first chamber 22 side.

[0048] The second piston body 92 is formed with an engagement recess 118 that is recessed inward along the axial direction of the second piston body 92 from the end face of the second piston body 92 that faces the first piston body 91 in the axial direction. The engagement recess 118 is provided partially in the circumferential direction of the second piston body 92.

[0049] The first piston body 91 and the second piston body 92 are connected by engaging the engaging protrusion 108 of the first piston body 91 with the engaging recess 118 of the second piston body 92. As a result, the first piston body 91 and the second piston body 92 are connected in a state where they are positioned circumferentially so as to form piston passages 81 and 82. In this state, the friction member 62 is placed over the radially outer sides of the first piston body 91 and the second piston body 92. As a result, the first piston body 91 and the second piston body 92 are integrated to form the piston main body 61, and the first piston body 91, the second piston body 92, and the friction member 62 are integrated to form the piston 21.

[0050] In the first piston body 91, the opening of the compression-side piston passage 82 on the second chamber 23 side is disposed radially outward of the valve seat portion 105. In the second piston body 92, the opening of the extension-side piston passage 81 on the first chamber 22 side is disposed radially outward of the valve seat portion 115.

[0051] 2A and 2B of the base-side cylindrical portion 41 of the piston rod 31, and the fixing hole 101 shown in FIG. 3 is fitted to a pair of outer end surfaces 42a shown in FIGS. 2A and 2B of the intermediate shaft portion 42 of the piston rod 31. In other words, the piston rod 31 has the base-side cylindrical portion 41, which is a cylindrical portion that is inserted into the fixing hole 111 shown in FIG. 3. The piston 21 is disposed such that the intra-piston flow path 103 overlaps the base-side circumferential groove 51 of the piston rod 31 in the axial direction of the piston rod 31. This allows the intra-piston flow path 103 to communicate with the axial flow path 54 of the piston rod 31 without circumferential phase alignment of the piston 21 with respect to the piston rod 31.

[0052] The compression-side valve mechanism 86 includes a valve seat portion 115 of the piston 21. The valve mechanism 86 has, in order from the piston 21 side in the axial direction, one disk 121 and multiple disks 122. On the axial side of the multiple disks 122 opposite to disk 121, in order from the multiple disks 122 side, are provided one disk 123, one disk 124, and one annular member 125. The disks 121 to 124 and the annular member 125 are all circular flat plates with holes, and the outer peripheral surface 41 a of the base-end cylindrical portion 41 of the mounting shaft portion 33, shown in FIGS. 2A and 2B , is fitted into the inside of each.

[0053] 3, the disk 121 has an outer diameter that is larger than the outer diameter of the inner seat portion 116 of the piston 21 and smaller than the inner diameter of the valve seat portion 115. The disk 121 is in constant contact with the inner seat portion 116.

[0054] Of the multiple discs 122, the disc 122 closest to the disc 121 in the axial direction has an outer diameter equal to the outer diameter of the valve seat portion 115 of the piston 21. Of the multiple discs 122, the disc 122 closest to the disc 121 in the axial direction is capable of being seated on the valve seat portion 115.

[0055] The disk 123 has an outer diameter smaller than the outer diameter of the plurality of disks 122 and slightly smaller than the outer diameter of the inner seat portion 116 of the piston 21 .

[0056] The disk 124 has an outer diameter larger than that of the disk 123 .

[0057] The annular member 125 has an outer diameter smaller than that of the disks 124 and larger than that of the end of the main shaft portion 32 of the piston rod 31 on the side of the mounting shaft portion 33 in the axial direction. The annular member 125 is thicker and more rigid than the disks 121 to 124, and abuts against the end of the main shaft portion 32 on the side of the mounting shaft portion 33 in the axial direction.

[0058] A plurality of discs 122 constitute a compression-side valve member 131 that can be seated on and removed from the valve seat portion 115. The valve member 131 is flexible, and when it leaves the valve seat portion 115, it connects the piston passage 82 to the first chamber 22. At that time, the valve member 131 suppresses the flow of oil liquid L between it and the valve seat portion 115, generating a damping force. When the valve member 131 is seated on the valve seat portion 115, it blocks communication between the piston passage 82 and the first chamber 22. The annular member 125, together with the discs 124, abuts against the valve member 131 to suppress deformation of the valve member 131 in the opening direction beyond a specified limit.

[0059] The piston passage 82 and a passage between the valve member 131 and the valve seat portion 115 that appears when the valve is open constitute a first flow path 132. The first flow path 132 is provided in the piston 21. The first flow path 132 is a compression-side passage through which oil L flows from the second chamber 23, which is the upstream region within the cylinder 4, to the first chamber 22, which is the downstream region, as the piston 21 moves toward the second chamber 23. A compression-side valve mechanism 86 that generates a damping force includes the valve member 131 and the valve seat portion 115. The valve mechanism 86 is provided in the first flow path 132. The first flow path 132 is provided in the piston 21 including the valve seat portion 115, and oil L passes through the first flow path 132 when the piston rod 31 and the piston 21 move toward the compression side.

[0060] Here, in the compression-side valve mechanism 86, neither the valve seat portion 115 nor the valve member 131 abutting thereon is provided with a fixed orifice that connects the first chamber 22 and the second chamber 23 even when the valve seat portion 115 and the valve member 131 are in contact with each other. Therefore, the first flow path 132 is not a passage that constantly connects the first chamber 22 and the second chamber 23.

[0061] The extension-side valve mechanism 85 includes a valve seat portion 105 of the piston 21. The valve mechanism 85 has, in order from the piston 21 side in the axial direction, one disk 141 and multiple disks 142. On the axially opposite side of the multiple disks 142 from disk 141, in order from the multiple disks 142 side, one disk 143 and multiple disks 144 are provided. The disks 141 to 144 are all circular flat plates with holes, and each has a pair of outer end surfaces 42a of the intermediate shaft portion 42 of the mounting shaft portion 33, shown in Figures 2A and 2B, fitted into its inner side.

[0062] The disk 141 has an outer diameter that is larger than the outer diameter of the inner seat portion 106 of the piston 21 and smaller than the inner diameter of the valve seat portion 105. The disk 141 is in constant contact with the inner seat portion 106.

[0063] Of the multiple discs 142, the disc 142 closest to the disc 141 in the axial direction has an outer diameter equal to the outer diameter of the valve seat portion 105 of the piston 21. Of the multiple discs 142, the disc 142 closest to the disc 141 in the axial direction is capable of being seated on the valve seat portion 105.

[0064] The disk 143 has an outer diameter smaller than the outer diameter of any of the plurality of disks 142 and equal to the outer diameter of the inner seat portion 106 of the piston 21 .

[0065] The plurality of disks 144 have an outer diameter larger than that of the disk 143 .

[0066] A plurality of discs 142 constitute an extension-side valve member 151 (first valve member) that can be seated on and removed from the valve seat portion 105. The valve member 151 is flexible, and when it is removed from the valve seat portion 105, it connects the piston passage 81 to the second chamber 23. At that time, the valve member 151 suppresses the flow of oil liquid L between the valve seat portion 105 and the valve member 151, thereby generating a damping force. When the valve member 151 is seated on the valve seat portion 105, it blocks communication between the piston passage 81 and the second chamber 23.

[0067] The piston passage 81 and the passage between the valve member 151 and the valve seat portion 105 that appears when the valve is open constitute a first flow path 152 (first flow path). The first flow path 152 is formed in the piston 21. The first flow path 152 is an extension-side flow path through which oil L flows from the first chamber 22, which is the upstream region within the cylinder 4, to the second chamber 23, which is the downstream region, as the piston 21 moves toward the first chamber 22. An extension-side valve mechanism 85 that generates a damping force includes the valve member 151 and the valve seat portion 105. The valve mechanism 85 is provided in this first flow path 152. The first flow path 152 is provided in the piston 21 including the valve seat portion 105, and oil L passes through the first flow path 152 when the piston rod 31 and the piston 21 move toward the extension side.

[0068] In the extension-side valve mechanism 85, a fixed orifice that communicates between the first chamber 22 and the second chamber 23 is not formed in either the valve seat portion 105 or the valve member 151 that abuts thereon. Therefore, the first flow path 152 is not a flow path that constantly communicates between the first chamber 22 and the second chamber 23.

[0069] The in-piston flow path 103 provided in the piston 21 communicates with the first chamber 22 via a part of the piston passage 81 that is closer to the first chamber 22 than the in-piston flow path 103. The part of the piston passage 81 provided in the piston 21 that is closer to the first chamber 22 than the in-piston flow path 103 and the in-piston flow path 103 form a first-chamber-side flow path 156 (second flow path). At least a part of the first-chamber-side flow path 156, the in-piston flow path 103, is provided in parallel to the first flow path 152.

[0070] The piston 21, the disk 121, the valve member 131, the disk 141, and the valve member 151 constitute a first structural member 155 (first structural member) that divides the interior of the inner tube 2 of the cylinder 4 into a first chamber 22 and a second chamber 23. The first structural member 155 divides the interior of the inner tube 2 of the cylinder 4 into the first chamber 22, which is an upstream region during the extension stroke, and the second chamber 23, which is a downstream region during the extension stroke. The first structural member 155 has circular fixing holes 101, 111 that penetrate the first structural member 155 in the axial direction, a first flow path 152 that can communicate between the first chamber 22, which is the upstream region during the extension stroke, and the second chamber 23, which is the downstream region during the extension stroke, a flexible valve member 151 that can close the first flow path 152, and a first-chamber-side flow path 156 in which at least a portion of the in-piston flow path 103 is arranged parallel to the first flow path 152.

[0071] 4 , on the axial side of disk 144 opposite disk 143, there are provided, in order from the disk 144 side, one disk 160, one spring member 161, multiple disks 162, one valve member 163 (first check valve element), and one seat member 166 having an O-ring 165 provided on its outer periphery. Also, on the axial side of seat member 166 opposite valve member 163, there are provided, in order from the seat member 166 side, one valve member 167 (second check valve element), multiple disks 168, one spring member 169, and one disk 170. Also, on the axial side of disk 170 opposite spring member 169, there are provided, in order from the disk 170 side, one disk 172, one disk 173, and one disk 174. In addition, on the axial side of disk 174 opposite disk 173, there are provided, in order from the disk 174 side, one disk 176, one disc spring 177, one case member 178 (partition member), one disk 181, and one annular member 182.

[0072] The mounting shaft portion 33 of the piston rod 31 is fitted inside the disks 160, 162, 168, 170, 172, 173, 174, 176, and 181, the spring members 161 and 169, the valve members 163 and 167, the seat member 166, the disc spring 177, the case member 178, and the annular member 182. At this time, the disks 160, the spring member 161, the disk 162, the valve member 163, and the seat member 166 are fitted inside the pair of outer end surfaces 42a (shown in Figures 2A and 2B) of the intermediate shaft portion 42 of the mounting shaft portion 33. As shown in FIG. 4, the seat member 166, the valve member 167, the disk 168, the spring member 169, the disk 170, the disk 172, the disk 173, the disk 174, the disk 176, the disc spring 177, the case member 178, the disk 181, and the annular member 182 each have the outer circumferential surface 43 a of the tip-end cylindrical portion 43 of the mounting shaft portion 33, shown in FIGS. 2A and 2B , fitted into their respective interiors.

[0073] 3, the mounting shaft portion 33 of the piston rod 31 has a threaded shaft portion 44 disposed at a portion that protrudes beyond the annular member 182. A retainer 185 is threadedly engaged with the male threads 57 on the outer periphery of the threaded shaft portion 44. The retainer 185 abuts against the annular member 182.

[0074] At least the radially inner circumferential sides of the disks 160, 162, 168, 170, 172, 173, 174, 176, and 181, the spring members 161 and 169, the valve members 163 and 167, the seat member 166, the disc spring 177, the case member 178, and the annular member 182 shown in FIG. 4 are clamped in the axial direction by the main shaft portion 32 of the piston rod 31 shown in FIG. 3 and a retainer 185.

[0075] As shown in FIG. 4, the disks 160, 162, 168, 170, 172, 173, 176, and 181, the valve members 163 and 167, and the annular member 182 are all in the form of circular flat plates having holes.

[0076] The case member 178 is a cylindrical, bottomed, one-piece molded product. The case member 178 has a bottom portion 191, an intermediate tapered portion 192, and a cylindrical portion 193. As shown in FIG. 3 , the outer diameter of the case member 178 is smaller than the outer diameter of the piston 21.

[0077] As shown in FIG. 4, the bottom portion 191 is in the form of a circular flat plate with holes.

[0078] The intermediate tapered portion 192 extends from the outer peripheral edge of the bottom portion 191 toward one axial side of the bottom portion 191 while expanding in diameter. The intermediate tapered portion 192 is annular.

[0079] The tubular portion 193 extends in the axial direction of the intermediate tapered portion 192 from an edge portion of the intermediate tapered portion 192 opposite to the bottom portion 191 in the opposite direction to the bottom portion 191. The tubular portion 193 is cylindrical.

[0080] The case member 178 has a bottom 191 into which the tip-side cylindrical portion 43 of the mounting shaft portion 33 of the piston rod 31 is fitted at the outer peripheral surface 43a shown in FIGS. 2A and 2B . As shown in FIG. 4 , the bottom 191 is formed with a plurality of passage holes 195. The plurality of passage holes 195 penetrate the bottom 191 in the axial direction of the bottom 191. The plurality of passage holes 195 are arranged at equal intervals in the circumferential direction of the bottom 191 at positions equidistant from the center of the bottom 191. The case member 178 is oriented such that the bottom 191 is located on the opposite side of the disk 144 from the cylindrical portion 193 in the axial direction. The bottom 191 of the case member 178 abuts against the disk 181. The outer diameter of the disk 181 is large enough not to block the passage holes 195 of the case member 178.

[0081] The seat member 166, the valve members 163, 167, the disks 168, 170, 172, 173, 174, 176, the spring member 169, and the disc spring 177 are arranged radially inside the case member 178.

[0082] The disc spring 177 has flexibility and includes an inner annular portion 201 and an outer tapered portion 202.

[0083] The inner annular portion 201 is a circular flat plate with holes. A passage hole 205 is formed in the inner annular portion 201, penetrating the inner annular portion 201 in the axial direction of the inner annular portion 201. The passage hole 205 has an arc shape extending in the circumferential direction of the inner annular portion 201.

[0084] The outer tapered portion 202 has a conical cylindrical shape that expands radially outward from the outer peripheral edge of the inner annular portion 201 and to one side in the axial direction.

[0085] The inner annular portion 201 of the disc spring 177 abuts against the bottom 191 of the case member 178, and the outer tapered portion 202 moves radially outward and away from the bottom 191 in the axial direction of the bottom 191. When the inner annular portion 201 of the disc spring 177 abuts against the bottom 191 of the case member 178, the disc spring 177 connects a passage hole 205 of the inner annular portion 201 to a passage hole 195 of the case member 178.

[0086] The outer diameter of the disk 176 is smaller than the outer diameter of the inner annular portion 201 of the disc spring 177 .

[0087] The disk 174 is flexible. The outer diameter of the disk 174 is larger than the outer diameter of the disc spring 177, i.e., the outer diameter of the outer tapered portion 202. The circular outer peripheral edge of the disc spring 177 on the radially outer side of the outer tapered portion 202 is in pressure contact with the outer peripheral edge of the disk 174 over the entire circumference.

[0088] The disk 174 is formed with a communication hole 211 that passes through the disk 174 in the axial direction of the disk 174. The communication hole 211 is formed in the disk 174 at a position that will not be blocked by the disk 176.

[0089] The disk 173 is flexible. The outer diameter of the disk 173 is smaller than the outer diameter of the disk 174. The outer diameter of the disk 173 is large enough to close the communication hole 211 of the disk 174. The disk 173 abuts against the disk 174 over the entire circumference. As a result, the disk 173 closes the communication hole 211 of the disk 174. When the disk 174 elastically deforms toward the bottom 191 of the case member 178 while elastically deforming the outer tapered portion 202 of the disc spring 177, the disk 173 opens the communication hole 211 of the disk 174.

[0090] The outer diameter of the disk 172 is smaller than the outer diameter of the disk 173 and smaller than the outer diameter of the disk 176 .

[0091] The disk 170 is flexible and has an outer diameter that is larger than the outer diameter of the disk 173 and slightly smaller than the outer diameter of the disk 174.

[0092] The spring member 169 has flexibility and includes a substrate portion 221 and a plurality of spring plate portions 222.

[0093] The base plate 221 is a circular flat plate with holes. The mounting shaft 33 is fitted onto the inner periphery of the base plate 221.

[0094] The plurality of spring plate portions 222 extend radially from the outer peripheral edge of the base plate portion 221. The plurality of spring plate portions 222 are spaced farther from the base plate portion 221 in the axial direction of the base plate portion 221 as they move radially outward from the base plate portion 221.

[0095] The spring member 169 abuts against the disk 170 at the base plate portion 221. The more the spring plate portions 222 are positioned radially outward of the base plate portion 221, the further away they are from the disk 170 in the axial direction of the base plate portion 221.

[0096] The disk 168 has an outer diameter smaller than that of the base plate portion 221 of the spring member 169 and larger than that of the disk 172. The disk 168 abuts against the base plate portion 221 of the spring member 169.

[0097] The valve member 167 is flexible and has an outer diameter larger than the maximum outer diameter of the spring member 169.

[0098] As shown in Figures 5 and 6, the seat member 166 is a perforated disk. A central hole 231 is formed in the seat member 166, penetrating its radial center in the axial direction. In other words, the central hole 231 extends in the axial direction of the seat member 166 and penetrates the seat member 166 in the axial direction. As shown in Figure 4, the mounting shaft portion 33 of the piston rod 31 is inserted into the central hole 231 of the seat member 166.

[0099] As shown in FIGS. 5 and 6, the central hole 231 has a first inner peripheral wall 232 (first inner peripheral wall) and a second inner peripheral wall 233 (second inner peripheral wall).

[0100] The first inner peripheral wall 232 has a cylindrical inner peripheral surface. As shown in Fig. 4, the first inner peripheral wall 232 penetrates the seat member 166 in the axial direction.

[0101] As shown in Figures 5 and 6, the second inner circumferential wall 233 is recessed radially outward from the inner circumferential surface of the first inner circumferential wall 232. The inner circumferential surface of the second inner circumferential wall 233 is semi-cylindrical. As shown in Figure 4, the second inner circumferential wall 233 extends linearly along the axial direction of the seat member 166 and penetrates the seat member 166 in the axial direction. The central hole 231 has one or more second inner circumferential walls 233. Here, as shown in Figures 5 and 6, the central hole 231 has a plurality of second inner circumferential walls 233 spaced equally apart in the circumferential direction of the first inner circumferential wall 232.

[0102] As shown in FIG. 4 , the inside of the first inner circumferential wall 232 of the central hole 231 forms an insertion hole 234 through which the mounting shaft portion 33 of the piston rod 31 is inserted, and the inside of the second inner circumferential wall 233 forms an expansion portion 235 that expands radially outward from the insertion hole 234. The seat member 166 has the insertion hole 234 and one or more expansion portions 235 extending radially from the insertion hole 234. Here, as shown in FIGS. 5 and 6 , the seat member 166 has a plurality of expansion portions 235 that are equally spaced circumferentially around the insertion hole 234. As shown in FIG. 4 , the insertion hole 234 and the expansion portion 235 each extend from one end face to the other end face of the seat member 166 in the axial direction, penetrating the seat member 166.

[0103] The mounting shaft portion 33 of the piston rod 31 is fitted into the first inner circumferential wall 232 of the central hole 231 at a pair of outer end surfaces 42a of the intermediate shaft portion 42 and the outer circumferential surface 43a of the tip-side cylindrical portion 43, as shown in FIGS. 2A and 2B . Then, as shown in FIG. 4 , the second inner circumferential wall 233 is radially spaced apart from the mounting shaft portion 33 of the piston rod 31. The expansion portion 235 is formed from the surface of the seat member 166 opposite to the surface facing the first structural member 155 shown in FIG. 3 to a position communicating with the axial flow path 54. The central hole 231 overlaps with the tip-side circumferential groove 53 of the piston rod 31 in the axial direction of the piston rod 31. Thus, the central hole 231 communicates directly or indirectly with the tip-side circumferential groove 53 of the piston rod 31; here, the central hole 231 communicates directly with it. An intermediate chamber 237 is formed by the second inner circumferential wall 233 of the seat member 166 and the mounting shaft portion 33 of the piston rod 31. The distal end circumferential groove 53 of the piston rod 31 allows the intermediate chamber 237 to communicate with the axial flow path 54 without circumferentially aligning the seat member 166 with the piston rod 31.

[0104] As shown in Fig. 4, the seat member 166 has an inner seat portion 241 and a valve seat portion 242 (first check valve seat) at one axial end. As shown in Fig. 5, the inner seat portion 241 has an annular shape surrounding the central hole 231. The valve seat portion 242 extends outward from the inner seat portion 241 in the radial direction of the inner seat portion 241.

[0105] As shown in Fig. 4, the seat member 166 has an inner seat portion 244 and a valve seat portion 245 (second check valve seat) at the other axial end. As shown in Fig. 6, the inner seat portion 244 has an annular shape surrounding the central hole 231. The valve seat portion 245 extends outward from the inner seat portion 244 in the radial direction of the inner seat portion 244.

[0106] 4, the seat member 166 has a main body 247 between the inner seat portion 241 and the valve seat portion 242 and between the inner seat portion 244 and the valve seat portion 245 in the axial direction. The main body 247 is a perforated disk-like shape.

[0107] The inner seat portion 241 protrudes from the inner peripheral edge portion on one axial side of the main body portion 247 along the axial direction of the main body portion 247 to one side. The valve seat portion 242 protrudes from the main body portion 247 along the axial direction of the main body portion 247 radially outside the inner seat portion 241 to the same side as the inner seat portion 241.

[0108] The inner seat portion 241 has a flat tip surface on the protruding side, i.e., the tip surface opposite the main body portion 247. The valve seat portion 242 has a flat tip surface on the protruding side, i.e., the tip surface opposite the main body portion 247. The protruding side tip surfaces of the inner seat portion 241 and the protruding side tip surfaces of the valve seat portion 242 extend in a direction perpendicular to the axis of the seat member 166 and are arranged on the same plane.

[0109] The inner seat portion 244 protrudes from an inner peripheral edge portion of the main body portion 247 on the opposite side of the inner seat portion 241 in the axial direction, along the axial direction of the main body portion 247, toward the opposite side of the inner seat portion 241. The valve seat portion 245 protrudes from the main body portion 247 on the same side as the inner seat portion 244, along the axial direction of the main body portion 247, radially outside the inner seat portion 244.

[0110] The inner seat portion 244 has a flat tip surface on the protruding side, i.e., the tip surface opposite the main body portion 247. The valve seat portion 245 has a flat tip surface on the protruding side, i.e., the tip surface opposite the main body portion 247. The protruding tip surfaces of the inner seat portion 244 and the protruding tip surfaces of the valve seat portion 245 extend in a direction perpendicular to the axis of the seat member 166 and are arranged on the same plane.

[0111] As shown in FIG. 5 , the inner seat portion 241 has an annular portion 251 and a plurality of protrusions 252 .

[0112] The annular portion 251 is annular and is provided to surround the central hole 231 .

[0113] The protrusions 252 extend outward in the radial direction of the annular portion 251 from the outer peripheral edge of the annular portion 251. The multiple protrusions 252 are arranged at intervals in the circumferential direction of the annular portion 251.

[0114] The inner seat portion 241 has radial communicating grooves 253 that penetrate the annular portion 251 in the radial direction of the annular portion 251. A plurality of radial communicating grooves 253 are formed at equal intervals in the circumferential direction of the annular portion 251. As shown in FIG. 4 , the radial communicating grooves 253 are recessed in the axial direction of the seat member 166 from the tip end surface of the inner seat portion 241 on the side opposite to the main body portion 247.

[0115] 5 , each of the radial communicating grooves 253 is aligned in phase with a corresponding one of the plurality of second inner circumferential walls 233 of the central hole 231 in the circumferential direction of the annular portion 251, and communicates with the corresponding second inner circumferential wall 233. Each of the plurality of radial communicating grooves 253 is provided between adjacent protrusions 252 in the circumferential direction of the annular portion 251.

[0116] The valve seat portion 242 is a non-circular, irregularly shaped seat in the shape of a petal. The valve seat portion 242 has a plurality of valve seat constituent portions 255. These valve seat constituent portions 255 are of the same shape and are arranged at equal intervals around the circumferential direction of the seat member 166. Note that these valve seat constituent portions 255 do not need to be of the same shape; they may have two or more different shapes or may have mutually different shapes. They may also be arranged at unequal intervals around the circumferential direction of the seat member 166. With this configuration, the valve-opening pressure applied to the valve member 163 (described later) is made uneven in the circumferential direction, which makes it possible to vary the valve-opening timing and smoothly change the damping force characteristics.

[0117] The valve seat forming portion 255 has a pair of extension portions 256 and a connecting portion 257 .

[0118] The pair of extension portions 256 each extend outward in the radial direction of the annular portion 251 from the outer peripheral edge of the annular portion 251 of the inner seat portion 241. The pair of extension portions 256 are arranged at an interval in the circumferential direction of the annular portion 251.

[0119] The connecting portion 257 connects the outer ends of the pair of extension portions 256 in the radial direction of the annular portion 251. The connecting portion 257 extends in the circumferential direction of the annular portion 251. The connecting portion 257 has an arc shape centered on the central axis of the seat member 166.

[0120] Here, a pair of protrusions 252 adjacent to each other in the circumferential direction of the inner seat portion 241 are arranged on the circumferential inside of the seat member 166 of the valve seat constituent portion 255, and a radial communicating groove 253 is arranged between this pair of protrusions 252. Thus, a pair of protrusions 252 and one radial communicating groove 253 are arranged on the circumferential inside of each seat member 166 of the multiple valve seat constituent portions 255.

[0121] A passage recess 258 is formed between each of the multiple valve seat constituent portions 255 and the inner seat portion 241 on the inner side. The passage recess 258 is surrounded by a portion of the inner seat portion 241 and the valve seat constituent portion 255. As shown in FIG. 4 , the passage recess 258 is recessed in the axial direction of the seat member 166 from the tip surface on the protruding side of the inner seat portion 241 and the tip surface on the protruding side of the valve seat constituent portion 255. The bottom surface of the passage recess 258 is formed by the main body portion 247. As shown in FIG. 5 , a passage recess 258 is formed on the inner side of all of the valve seat constituent portions 255.

[0122] A passage hole 259 is formed in the circumferential center of the passage recess 258 of the seat member 166. The passage hole 259 is disposed between a pair of protrusions 262 in the passage recess 258 in which the passage hole 259 is formed, in the circumferential direction of the seat member 166. As shown in FIG. 4 , the passage hole 259 axially penetrates the main body 247, and thereby also penetrates the seat member 166 in the axial direction. The passage hole 259 is a linear hole parallel to the central axis of the seat member 166. As shown in FIG. 5 , the passage hole 259 is formed in the bottom surface of all of the passage recesses 258.

[0123] As shown in FIG. 6 , the inner seat portion 244 has an annular portion 261 and a plurality of protrusions 262 .

[0124] The annular portion 261 is annular and is provided to surround the central hole 231 .

[0125] The protrusions 262 extend outward in the radial direction of the annular portion 261 from the outer circumferential edge of the annular portion 261. The multiple protrusions 262 are arranged at intervals in the circumferential direction of the annular portion 261.

[0126] The inner seat portion 244 is formed with a plurality of communication grooves 263 that traverse the annular portion 261 in the radial direction and are equally spaced apart in the circumferential direction of the annular portion 261. As shown in FIG. 4 , the communication grooves 263 are recessed in the axial direction of the seat member 166 from the tip end surface of the inner seat portion 244 on the side opposite to the main body portion 247.

[0127] 6 , each of the plurality of communicating grooves 263 is aligned in phase with a corresponding one of the plurality of second inner circumferential walls 233 of the central hole 231 in the circumferential direction of the annular portion 261, and communicates with the corresponding second inner circumferential wall 233. Each of the plurality of communicating grooves 263 is provided between adjacent protrusions 262 in the circumferential direction of the annular portion 251.

[0128] The valve seat portion 245 is a non-circular, irregularly shaped seat in the shape of a petal. The valve seat portion 245 has a plurality of valve seat constituent portions 265. These valve seat constituent portions 265 are of the same shape and are arranged at equal intervals around the circumferential direction of the seat member 166. Note that these valve seat portions 245 do not need to be of the same shape; they may have two or more different shapes or may have mutually different shapes. They may also be arranged at unequal intervals around the circumferential direction of the seat member 166. With this configuration, the valve-opening pressure applied to the valve member 167 (described later) is made uneven in the circumferential direction, which makes it possible to vary the valve-opening timing and smoothly change the damping force characteristics.

[0129] A communication groove 263 is arranged in the annular portion 261 of the inner seat portion 244 between two valve seat constituent portions 265 adjacent to each other in the circumferential direction of the seat member 166. Thus, the communication groove 263 is formed in a portion of the inner seat portion 244 that is arranged outside the valve seat portion 245.

[0130] The valve seat forming portion 265 has a pair of extension portions 266 and a connecting portion 267 .

[0131] The pair of extending portions 266 each extend outward in the radial direction of the annular portion 261 from the outer peripheral edge of the annular portion 261 of the inner seat portion 244. The pair of extending portions 266 are arranged at an interval in the circumferential direction of the annular portion 261.

[0132] The connecting portion 267 connects the outer ends of the pair of extension portions 266 in the radial direction of the annular portion 261. The connecting portion 267 extends in the circumferential direction of the annular portion 261. The connecting portion 267 has an arc shape centered on the central axis of the seat member 166.

[0133] Here, a pair of protrusions 262 adjacent to each other in the circumferential direction of the inner seat portion 244 are arranged on the circumferentially inner side of the seat member 166 of the valve seat constituent portion 265. Therefore, a pair of protrusions 262 is arranged on the circumferentially inner side of the seat member 166 of each of the multiple valve seat constituent portions 265.

[0134] A passage recess 268 is formed between each of the plurality of valve seat constituent portions 265 and the inner seat portion 244. The passage recess 268 is formed by being surrounded by a part of the inner seat portion 244 and the valve seat constituent portion 265.

[0135] As shown in Fig. 4, the passage recess 268 is recessed in the axial direction of the seat member 166 from the protruding tip end surface of the inner seat portion 244 and the protruding tip end surface of the valve seat constituent portion 265. The bottom surface of the passage recess 268 is formed by the main body portion 247. As shown in Fig. 6, the passage recess 268 is formed inside all of the valve seat constituent portions 265.

[0136] A passage hole 269 is formed in the circumferential center of the passage recess 268 of the seat member 166. The passage hole 269 is disposed between the pair of protrusions 262 in the passage recess 268 in which the passage hole 269 is formed, in the circumferential direction of the seat member 166. As shown in FIG. 4 , the passage hole 269 axially penetrates the main body 247, thereby penetrating the seat member 166 in the axial direction. The passage hole 269 is a linear hole parallel to the central axis of the seat member 166. As shown in FIG. 6 , the passage hole 269 is formed in the bottom surface of all of the passage recesses 268.

[0137] 5 is arranged at the same pitch in the circumferential direction of the seat member 166 as the pitch in the circumferential direction of the seat member 166. The valve seat constituents 255 and 265 are arranged at a phase shift of half the pitch in the circumferential direction of the seat member 166.

[0138] 5, the passage hole 269 is disposed between adjacent valve seat constituent portions 255 in the circumferential direction of the seat member 166. Therefore, the passage hole 269 is disposed outside the range of the valve seat portion 242.

[0139] 6, the passage hole 259 is disposed between adjacent valve seat constituent portions 265 in the circumferential direction of the seat member 166. Therefore, the passage hole 259 is disposed outside the range of the valve seat portion 245.

[0140] 4 , the passage in the passage hole 259 and the passage in the passage recess 258 into which the passage hole 259 opens constitute a passage portion 281 (third flow path, axial flow path) provided in the seat member 166. The seat member 166 is provided with a plurality of passage portions 281 at equal intervals in the circumferential direction of the seat member 166. The passage portions 281 communicate with the passage in the radial communicating groove 253 and the passage in the communicating groove 263.

[0141] The passage hole 269 and the passage in the passage recess 268 into which this passage hole 269 opens constitute a passage portion 282 provided in the seat member 166. A plurality of passage portions 282 are provided in the seat member 166 at equal intervals in the circumferential direction of the seat member 166.

[0142] A seal groove 271 is formed in the seat member 166 at the axial center of the outer periphery of the main body 247. The seal groove 271 is annular and recessed radially inward from the outer periphery of the main body 247. An O-ring 165 is disposed in this seal groove 271.

[0143] The seat member 166 is fitted at its outer periphery into the cylindrical portion 193 of the case member 178 with the inner seat portion 241 and the valve seat portion 242 facing away from the bottom portion 191 of the case member 178. In this state, the O-ring 165 seals the gap between the cylindrical portion 193 of the case member 178 and the seat member 166.

[0144] The case member 178, O-ring 165, and seat member 166 form a case chamber 285 inside the case member 178. The case chamber 285 is provided between the bottom 191 of the case member 178 and the seat member 166. The valve member 167, discs 168, 170, 172, 173, 174, 176, spring member 169, and disc spring 177 are provided inside this case chamber 285. The seat member 166 is arranged with the valve seat portion 245 facing the case chamber 285.

[0145] A first chamber communication chamber 286 (storage chamber) that stores oil L is formed within the case chamber 285. The first chamber communication chamber 286 is surrounded by the case member 178, the disc spring 177, the disk 174, the disk 173, the disk 172, the disk 170, the spring member 169, the disk 168, the valve member 167, and the seat member 166.

[0146] A second-chamber communication chamber 287 that stores oil L is formed within the case chamber 285. The second-chamber communication chamber 287 is surrounded by the disk 173, the disk 174, the disc spring 177, and the disk 176. The first-chamber communication chamber 286 is the portion of the case chamber 285 excluding the second-chamber communication chamber 287. The second-chamber communication chamber 287 communicates with a passage within the passage hole 205 of the disc spring 177, and the passage within the passage hole 205 communicates with passages within the multiple passage holes 195 in the bottom 191 of the case member 178.

[0147] The first chamber communication chamber 286 and the second chamber communication chamber 287 are blocked from communication by the disc spring 177 , the disc 174 that abuts against the outer periphery of the disc spring 177 , and the disc 173 that abuts against the disc 174 .

[0148] As shown in Fig. 3, the annular seat member 166 and the bottomed cylindrical case member 178 are disposed in the second chamber 23, which is one of the first chamber 22 and the second chamber 23. In this case, the valve seat portion 242 of the seat member 166 is disposed on the second chamber 23 side. As shown in Fig. 4, the passage within the passage hole 195 of the case member 178 is constantly in communication with the second chamber 23. Therefore, the second-chamber communication chamber 287 is in communication with the second chamber 23.

[0149] The first chamber communication chamber 286 is constantly connected to the first chamber 22 via a flow path 288 in the communication groove 263 of the seat member 166, the intermediate chamber 237 in the second inner circumferential wall 233, the axial flow path 54 of the piston rod 31, and the piston internal flow path 103 and piston passage 81 provided in the piston 21 shown in Figure 3.

[0150] As the disk 174 shown in FIG. 4 bends in the axial direction, the volumes of the first-chamber communication chamber 286 and the second-chamber communication chamber 287 change. The second-chamber communication chamber 287 decreases in volume to absorb the increase in the volume of the first-chamber communication chamber 286, thereby discharging the oil L to the second chamber 23. The second-chamber communication chamber 287 increases in volume to absorb the decrease in the volume of the first-chamber communication chamber 286, thereby allowing the oil L to flow in from the second chamber 23. Conversely, the first-chamber communication chamber 286 decreases in volume to absorb the increase in the volume of the second-chamber communication chamber 287, thereby discharging the oil L to the first chamber 22 side shown in FIG. 3. The first-chamber communication chamber 286 increases in volume to absorb the decrease in the volume of the second-chamber communication chamber 287, thereby allowing the oil L to flow in from the first chamber 22 side. In this way, the deformation of the disk 174 is prevented from being hindered by the oil L in the first chamber communication chamber 286 and the second chamber communication chamber 287 .

[0151] As shown in FIG. 3, the plurality of passages 282 of the seat member 166 are provided facing the second chamber 23 and are constantly in communication with the second chamber 23 .

[0152] The valve member 167 shown in Figure 4 is flexible. The valve member 167 has an outer diameter equal to the outer diameter of the valve seat portion 245 of the seat member 166. The valve member 167 is always in contact with the inner seat portion 244 and is able to be seated on and removed from the valve seat portion 245. When the valve member 167 is seated on the entire valve seat portion 245, it closes all of the passage portions 282. When the valve member 167 is lifted from one of the valve seat constituent portions 265 of the valve seat portion 245, it opens the passage portion 282 inside the valve seat constituent portion 265 that is lifted.

[0153] The spring member 169 biases the valve member 167 so that it abuts against the valve seat portion 245 of the seat member 166. The biasing force of the spring member 169 causes the valve member 167 to seat on the valve seat portion 245 and close the passage portion 282. The valve member 167 deforms against the biasing force of the spring member 169 and disengages from the valve seat portion 245, thereby opening the passage portion 282.

[0154] When the valve member 167 leaves the valve seat portion 245, it communicates between the plurality of passage portions 282 and the first-chamber communication chamber 286. As a result, the second chamber 23 communicates with the first chamber 22 via the plurality of passage portions 282, the first-chamber communication chamber 286, the flow path 288 in the communication groove 263 of the seat member 166, the intermediate chamber 237 in the second inner circumferential wall 233, the axial flow path 54 of the piston rod 31, and the intra-piston flow path 103 and piston passage 81 provided in the piston 21 shown in Figure 3. At this time, the valve member 167 shown in Figure 4 suppresses the flow of oil liquid L between the valve seat portion 245 and the first chamber 22, thereby generating a damping force.

[0155] The valve member 167 is an inflow valve that opens when oil liquid L is allowed to flow from the second chamber 23 to the first-chamber communication chamber 286 via the plurality of passages 282. The valve member 167 is a check valve that restricts the outflow of oil liquid L from the first-chamber communication chamber 286 to the second chamber 23 via the passages 282. Here, the passages 281 open outside the range of the valve seat portion 245 of the seat member 166. Therefore, the passages 281 are always in communication with the first-chamber communication chamber 286 regardless of whether the valve member 167 is seated on the valve seat portion 245.

[0156] A second flow path 291 is formed by the plurality of passage portions 282, the passage between the valve member 167 and the valve seat portion 245 that appears when the valve is open, the first-chamber communication chamber 286, the flow path 288 in the communication groove 263, the intermediate chamber 237, the axial flow path 54, the in-piston flow path 103 shown in FIG. 3 , and the piston passage 81. The second flow path 291 is opened and closed by the valve member 167 shown in FIG. 4 . When the piston 21 moves toward the second chamber 23, the oil L flows from the second chamber 23, which is the upstream side in the cylinder 4, to the first chamber 22, which is the downstream side. The second flow path 291 serves as a compression-side passage through which the oil L flows from the second chamber 23, which is the upstream side, to the first chamber 22, which is the downstream side, during movement of the piston 21 toward the second chamber 23, i.e., during the compression stroke. At least a portion (in this example, the entirety) of the second compression flow path 291 is arranged in parallel with the first compression flow path 132 shown in Figures 2A and 2B. The second flow path 291 includes the first chamber-side flow path 156.

[0157] As shown in Figure 4, the passage in the passage hole 195, the passage in the passage hole 205, and the second-chamber communication chamber 287 constitute a second-chamber communication flow path 292. The second-chamber communication flow path 292 is a compression-side flow path that is always connected to the second chamber 23. The compression-side second-chamber communication flow path 292 is provided separately from the second flow path 291, which is also on the compression side. The second-chamber communication flow path 292 is provided in parallel to the second flow path 291.

[0158] The valve member 167, the seat member 166 including the valve seat portion 245, the disc 168, and the spring member 169 constitute a valve mechanism 301 (second check valve mechanism). The valve mechanism 301 is provided in the second flow path 291 on the compression side. The valve mechanism 301 opens and closes this second flow path 291, suppressing the flow of oil L from this second flow path 291 to the first chamber 22 and generating a damping force. The valve mechanism 301 is a compression side valve mechanism.

[0159] The valve mechanism 301 includes a valve seat portion 245 serving as a valve seat and a valve member 167 serving as a flexible valve body, and serves as a check valve mechanism that allows flow in the second flow path 291 from the second chamber 23, which is the upstream region, toward the first chamber 22, which is the downstream region, during the compression stroke, while restricting flow from the first chamber 22, which is the upstream region, toward the second chamber 23, which is the downstream region, during the extension stroke. In other words, the valve mechanism 301 only allows flow in the second flow path 291 from the second chamber 23, which is the upstream region, toward the first chamber 22, which is the downstream region, during the compression stroke.

[0160] The valve mechanism 301 has a valve seat portion 245 provided on the seat member 166. The valve mechanism 301 is disposed separately from the valve mechanism 86 that generates a damping force during the same compression stroke. The valve member 167 that constitutes the compression-side valve mechanism 301 is a compression-side sub-valve.

[0161] In the compression-side valve mechanism 301, neither the valve seat portion 245 nor the valve member 167 abutting thereon has a fixed orifice formed therein that connects the first chamber 22 and the second chamber 23 even when the valve seat portion 245 and the valve member 167 are in contact with each other. In other words, the second flow path 291 does not have a fixed orifice that constantly connects the first chamber 22 and the second chamber 23. The second flow path 291 is not a passage that constantly connects the first chamber 22 and the second chamber 23.

[0162] The second flow path 291 on the compression side, which allows communication between the first chamber 22 and the second chamber 23, is arranged in parallel with the first flow path 132, which is also a compression side passage that allows communication between the first chamber 22 and the second chamber 23. A valve mechanism 86 is provided in the first flow path 132. A valve mechanism 301 is provided in the second flow path 291. Thus, the valve mechanism 86 and the valve mechanism 301 on the compression side are arranged in parallel.

[0163] The valve member 163 is flexible. The valve member 163 has an outer diameter equal to the outer diameter of the valve seat portion 242 of the seat member 166. The valve member 163 is constantly in contact with the inner seat portion 241 and is capable of reseating from the valve seat portion 242. When the valve member 163 is seated over the entire valve seat portion 242, it closes all of the passage portions 281. Furthermore, when the valve member 163 is released from one of the valve seat constituent portions 255 of the valve seat portion 242, it opens the passage portion 281 inside the valve seat constituent portion 255 that has been released.

[0164] The disk 162 has an outer diameter that is smaller than the outer diameter of the valve member 163 and smaller than the outer diameter of the inner seat portion 241 .

[0165] The spring member 161 has flexibility and includes a substrate portion 311 and a plurality of spring plate portions 312.

[0166] The base plate 311 is a circular flat plate with holes. The mounting shaft 33 is fitted into the inner periphery of the base plate 311. The outer diameter of the base plate 311 is slightly larger than the outer diameter of the disk 162. The base plate 311 abuts against the disk 162.

[0167] The plurality of spring plate portions 312 extend radially from the outer periphery of the base plate portion 311. The plurality of spring plate portions 312 are spaced farther from the base plate portion 311 in the axial direction of the base plate portion 311 as they move radially outward from the base plate portion 311.

[0168] The maximum outer diameter of the spring member 161 is smaller than the outer diameter of the valve member 163. The spring member 161 has multiple spring plate portions 312 oriented to extend from the base plate portion 311 toward the valve member 163 in the axial direction of the base plate portion 311. The extending ends of the multiple spring plate portions 312 of the spring member 161 are in pressure contact with the outer periphery of the valve member 163. As a result, the multiple spring plate portions 312 of the spring member 161 bias the outer periphery of the valve member 163 so that it abuts against the valve seat portion 242 of the seat member 166. The biasing force of the spring member 161 causes the valve member 163 to seat on the valve seat portion 242 and close the passage portion 281. The valve member 163 deforms against the biasing force of the spring member 161 and lifts off the valve seat portion 242, opening the passage portion 281.

[0169] The valve member 163 is provided in the second chamber 23. When the valve member 163 is lifted from the valve seat portion 242, the first-chamber communication chamber 286 and the second chamber 23 communicate with each other via the plurality of passage portions 281 of the seat member 166. At this time, the valve member 163 suppresses the flow of oil liquid L between the valve seat portion 242 and the valve member 163, thereby generating a damping force. The valve member 163 is a discharge valve that opens when oil liquid L is discharged from the first-chamber communication chamber 286 to the second chamber 23 via the plurality of passage portions 281. The valve member 163 is a check valve that restricts the flow of oil liquid L from the second chamber 23 into the first-chamber communication chamber 286 via the passage portions 281. Here, the passage portions 282 open outside the range of the valve seat portion 242 in the seat member 166. Therefore, the passage portion 282 is always in communication with the second chamber 23 regardless of whether the valve member 163 is seated on the valve seat portion 242 .

[0170] The radial communication groove 253 formed in the inner seat portion 241 of the seat member 166 serves as a radial flow passage 317 (fourth flow passage). The radial flow passage 317 is provided at a position facing the axial flow passage 54 in the radial direction of the seat member 166, and is connected to the intermediate chamber 237.

[0171] As shown in FIG. 3 , the second flow path 315 is made up of the first-chamber-side flow path 156 consisting of the piston passage 81 and the intra-piston flow path 103, the axial flow path 54 of the piston rod 31, the intermediate chamber 237 and flow path 288 in the second inner circumferential wall 233 of the seat member 166, the first-chamber communication chamber 286, the passage portion 281, the radial flow path 317 shown in FIG. 4 , and the passage between the valve member 163 and the valve seat portion 242 that appears when the valve is open.

[0172] The second flow path 315 is opened and closed by a valve member 163. When the piston 21 moves toward the first chamber 22 (shown in FIG. 3 ), the oil L flows from the first chamber 22 (on the upstream side) in the cylinder 4 to the second chamber 23 (on the downstream side). The second flow path 315 serves as an extension-side passage through which the oil L flows from the first chamber 22 (on the upstream side) to the second chamber 23 (on the downstream side) as the piston 21 moves toward the first chamber 22, i.e., during the extension stroke. The extension-side second flow path 315 is provided separately from the extension-side first flow path 152. At least a portion (in this example, a portion) of the second flow path 315 is arranged parallel to the first flow path 152. The second flow path 315 is parallel to the first flow path 152 except for a portion of the piston passage 81 closer to the first chamber 22 than the in-piston flow path 103.

[0173] 4 connects the intermediate chamber 237 of the second flow path 315 to the passage portion 281 without passing through the flow path 288 in the communication groove 263 or the first-chamber communication chamber 286. The radial flow path 317 connects the intermediate chamber 237 to the valve seat portion 242. In other words, the radial flow path 317 connects the central hole 231 to the valve mechanism 321 including the valve seat portion 242.

[0174] As shown in FIG. 3 , the piston rod 31 is formed with an axial flow path 54 which is a flow path that communicates with the first-chamber-side flow path 156 and leads to the second chamber 23 which is the downstream region during the extension stroke, a tip-side circumferential groove 53 which is a circumferential groove provided at the end of the axial flow path 54 on the second chamber 23 side which is the downstream region during the extension stroke, and a tip-side cylindrical portion 43 which is a cylindrical portion provided on the second chamber 23 side of the tip-side circumferential groove 53.

[0175] 4, the outer diameter of the disk 160 is equal to the outer diameter of the valve member 163. The disk 160 is flexible.

[0176] The valve member 163, the seat member 166 including the valve seat portion 242, the disc 162, and the spring member 161 constitute a valve mechanism 321 (first check valve mechanism). The valve mechanism 321 is provided in the extension-side second flow path 315 and opens and closes the second flow path 315. The valve mechanism 321 generates a damping force by suppressing the flow of hydraulic fluid L from the second flow path 315 to the second chamber 23. The valve mechanism 321 is a second extension-side damping force generating mechanism. The valve mechanism 321 is arranged separately from the valve mechanism 85, which generates a damping force during the same extension stroke. The valve member 163 constituting the extension-side valve mechanism 321 is an extension-side sub-valve. The valve mechanism 321 includes radial flow paths 317. In the valve mechanism 321, during the extension stroke, the oil L flows from the first chamber-side flow path 156 shown in Fig. 3 to the second chamber 23, which is the downstream region, even after passing through the axial flow path 54 including the tip-side circumferential groove 53, the intermediate chamber 237, and the radial flow paths 317 shown in Fig. 4. In other words, in the valve mechanism 321, during the extension stroke, the oil L flows from the first chamber-side flow path 156 to the second chamber 23, which is the downstream region, even after passing through the axial flow path 54 including the tip-side circumferential groove 53, the central hole 231, and the radial flow paths 317.

[0177] The valve mechanism 321 includes a valve seat portion 242 serving as a valve seat and a valve member 163 serving as a flexible valve body, and serves as a check valve mechanism that allows flow from the first chamber 22, which is the upstream region, toward the second chamber 23, which is the downstream region, during the extension stroke of the second flow path 315 including the first chamber-side flow path 156, while restricting flow from the second chamber 23, which is the upstream region, toward the first chamber 22, which is the downstream region, during the compression stroke. In other words, the valve mechanism 321 only allows flow from the first chamber 22, which is the upstream region, toward the second chamber 23, which is the downstream region, during the extension stroke of the second flow path 315 including the first chamber-side flow path 156.

[0178] The second chamber communication chamber 287 and the disk 174, disk 173, disc spring 177 and disk 176 that form the second chamber communication chamber 287 constitute a second chamber volume variable mechanism 325 that can change the volume of the second chamber communication chamber 287.

[0179] The second-chamber volume variable mechanism 325 deforms and moves the disks 174 and 173 together so as to move away from the bottom 191. As a result, the second-chamber volume variable mechanism 325 changes the volume of the second-chamber communication chamber 287 to increase it. At that time, if the disk 174 remains in contact with the disc spring 177 over the entire circumference, the space between the disk 174 and the outer tapered portion 202 of the disc spring 177 is blocked. In other words, if the disk 174 remains in contact with the disc spring 177 over the entire circumference when it deforms so as to move away from the bottom 191, the second-chamber communication chamber 287 and the first-chamber communication chamber 286 are kept blocked.

[0180] Furthermore, the second chamber volume variable mechanism 325 deforms and moves the disks 174 and 173 together so that they approach the bottom 191. As a result, the second chamber volume variable mechanism 325 changes the volume of the second chamber communication chamber 287 to decrease it. At this time, the disk 174 is maintained in a state where it is entirely in contact with the disc spring 177, and the gap between the disk 174 and the outer tapered portion 202 of the disc spring 177 is closed.

[0181] The first chamber communication chamber 286, which is in communication with the first chamber 22, constitutes a part of the extension-side second flow path 315. The first chamber communication chamber 286, and the seat member 166, valve member 167, disk 168, spring member 169, disk 170, disk 172, disk 173, disk 174, disk 176, disc spring 177, and case member 178 that form the first chamber communication chamber 286, constitute a first chamber volume variable mechanism 326 that can change the volume of the first chamber communication chamber 286.

[0182] The first chamber volume variable mechanism 326 deforms and moves the disc 174 and the disc 173 together so that they move away from the disc 170. As a result, the first chamber volume variable mechanism 326 changes the volume of the first chamber communication chamber 286 to increase it. At this time, if the disc 173 remains in full contact with the disc 174, it closes the passage inside the communication hole 211 of the disc 174. In other words, the second chamber communication chamber 287 and the first chamber communication chamber 286 are kept blocked from each other.

[0183] Furthermore, the first chamber volume variable mechanism 326 deforms and moves the disks 174 and 173 so that they approach the disk 170. As a result, the first chamber volume variable mechanism 326 changes the volume of the first chamber communication chamber 286 to decrease it. At this time, the disk 173 is maintained in overall contact with the disk 174, blocking the passage in the communication hole 211 of the disk 174.

[0184] In the extension-side valve mechanism 321, neither the valve seat portion 242 nor the valve member 163 abutting thereon has a fixed orifice that communicates between the first chamber 22 and the second chamber 23, even when the valve seat portion 242 and the valve member 163 are in contact with each other. In other words, the extension-side valve mechanism 321 does not communicate between the first chamber 22 and the second chamber 23 when the valve seat portion 242 and the valve member 163 are in contact with each other. In other words, the second flow path 315 does not have a fixed orifice that constantly communicates between the first chamber 22 and the second chamber 23. The second flow path 315 is not a passage that constantly communicates between the first chamber 22 and the second chamber 23.

[0185] Spring member 161, disc 162, valve member 163, O-ring 165, seat member 166, valve member 167, disc 168, spring member 169, disc 170, disc 172, disc 173, disc 174, disc 176, disc spring 177, and case member 178 constitute a second structural member 331 (second structural member).

[0186] Therefore, the second structural member 331 has a first inner circumferential wall 232 that axially penetrates its center and through which the piston rod 31 is inserted, and a second inner circumferential wall 233 that is radially spaced further from the piston rod 31 than the first inner circumferential wall 232, and has a central hole 231 that directly or indirectly communicates with the tip-side circumferential groove 53 of the piston rod 31. The second structural member 331 also has a valve mechanism 321 that includes a valve seat portion 242 that serves as a valve seat, and a valve member 163 that is a flexible valve body, and that allows flow through the first-chamber-side flow path 156 only in the direction from the first chamber 22 to the second chamber 23. The second structural member 331 also has a valve mechanism 301 and a valve mechanism 321. The second structural member 331 also has a case member 178 that communicates with an intermediate chamber 237 defined by the second inner circumferential wall 233 and the piston rod 31 and that defines a first-chamber communication chamber 286 that stores oil liquid L. The second structural member 331 also has a valve mechanism 321 that includes a central hole 231 that penetrates the center in the axial direction and through which the piston rod 31 is inserted, a valve seat portion 242 that serves as a valve seat, and a valve member 163 that is a flexible valve body disposed in the axial flow path 54, and that allows oil liquid L to flow only in a direction from the first chamber 22 to the second chamber 23. The second structural member 331 also has a radial flow path 317 that is provided at a position facing the axial flow path 54 and that communicates with the valve mechanism 321. The second structural member 331 also has one or more extension sections 235 extending radially from the insertion hole 234 and formed from the surface opposite to the surface facing the first structural member 155 to a position communicating with the axial flow path 54, a case member 178 communicating with the extension section 235 and forming a first chamber communication chamber 286 for storing oil liquid L, and a passage section 281 connecting the first chamber communication chamber 286 and the valve mechanism 321.

[0187] 3, the outer diameter of the second structural member 331 is smaller than the outer diameter of the first structural member 155. There is a radial gap between the second structural member 331 and the inner cylinder 2. The second structural member 331 extends over the tip-side circumferential groove 53 and the tip-side cylindrical portion 43 of the piston rod 31.

[0188] As described above, the first chamber volume variable mechanism 326 shown in FIG. 4 changes the volume of the first chamber communication chamber 286 by deforming and moving the disc 174 away from the disc 170. At this time, with the valve mechanism 321 open, the pressure difference between the first chamber communication chamber 286 and the second chamber communication chamber 287 may exceed a predetermined value. Then, the first chamber volume variable mechanism 326 causes the disc 174 to elastically deform the outer tapered portion 202 of the disc spring 177 toward the bottom 191, while deforming the outer periphery toward the bottom 191. As a result, the disc 174 moves away from the disc 170 in the axial direction. Then, the disc 174 communicates between the first chamber communication chamber 286 and the second chamber communication chamber 287 via the passage in the communication hole 211.

[0189] The disks 174 and 173 constitute a relief mechanism 335. When the relief mechanism 335 is open, it causes the oil L to flow from the first-chamber communication chamber 286 to the second-chamber communication chamber 287. In other words, the relief mechanism 335 causes the oil L to flow from the first chamber 22 to the second chamber 23. The relief mechanism 335 is an extension-side relief mechanism. The relief mechanism 335 is set to open after the extension-side valve mechanism 321 opens.

[0190] The second-chamber volume variable mechanism 325 changes the volume of the second-chamber communication chamber 287 so that it increases by deforming and moving the disc 174 toward the disc 170. At this time, with the valve mechanism 301 open, the pressure difference between the first-chamber communication chamber 286 and the second-chamber communication chamber 287 may exceed a predetermined value. In this case, the second-chamber volume variable mechanism 325 increases the amount of deformation on the outer periphery of the disc 174. As a result, the disc 174 moves axially away from the outer periphery of the disc spring 177. In this case, the disc 174 communicates with the second-chamber communication chamber 287 and the first-chamber communication chamber 286 via the disc 174 and the disc spring 177.

[0191] The disk 174 and the disc spring 177 constitute a relief mechanism 336. When the relief mechanism 336 is open, it causes oil L to flow from the second-chamber communication chamber 287 to the first-chamber communication chamber 286. In other words, the relief mechanism 336 causes oil L to flow from the second chamber 23 to the first chamber 22. The relief mechanism 336 is a compression-side relief mechanism. The relief mechanism 336 is set to open after the compression-side valve mechanism 301 opens.

[0192] 1, the base valve 15 has a valve mechanism 351 on the bottom 9 side of the valve body 12 in the axial direction. The base valve 15 also has a valve mechanism 352 on the opposite side of the valve body 12 from the bottom 9 in the axial direction.

[0193] When the piston rod 31 moves toward the compression side and the piston 21 moves in a direction narrowing the second chamber 23, and the pressure in the second chamber 23 becomes higher than the pressure in the reservoir chamber 5 by a predetermined value or more, the valve mechanism 351 of the base valve 15 opens, causing the oil L in the second chamber 23 to flow into the reservoir chamber 5. At that time, the valve mechanism 351 generates a damping force.

[0194] When the piston rod 31 moves in the extension direction and the piston 21 moves toward the first chamber 22, causing the pressure in the second chamber 23 to drop below the pressure in the reservoir chamber 5, the valve mechanism 352 of the base valve 15 opens, allowing the oil L in the reservoir chamber 5 to flow into the second chamber 23. At this time, the valve mechanism 352 generates a damping force. The valve mechanism 352 may be a suction valve that allows the oil L to flow from the reservoir chamber 5 into the second chamber 23 without generating any substantial damping force.

[0195] Next, the operation of the shock absorber 1 will be described.

[0196] Of the extension-side valve mechanism 85 and valve mechanism 321 shown in FIG. 3 , the valve member 151 of the valve mechanism 85 is more rigid than the valve member 163 of the valve mechanism 321 shown in FIG. 4 and has a higher valve opening pressure than the valve member 163. Therefore, during the extension stroke, in the extremely low-speed region where the piston speed is slower than a predetermined value, the valve mechanism 85 shown in FIG. 3 remains closed while the valve mechanism 321 opens. In other words, the valve mechanism 321 opens to generate a damping force when the piston speed is slower than that of the valve mechanism 85. Furthermore, in the normal speed region where the piston speed is equal to or greater than the predetermined value, both the valve mechanism 85 and the valve mechanism 321 open. The valve member 163 shown in FIG. 4 is an extremely low-speed valve that deforms against the biasing force of the spring member 161 to open and generate a damping force in the extremely low-speed region.

[0197] That is, during the extension stroke, the piston 21 shown in FIG. 3 moves toward the first chamber 22, increasing the pressure in the first chamber 22 and decreasing the pressure in the second chamber 23. Here, neither the valve mechanisms 85, 86 nor the valve mechanisms 301, 321 have a fixed orifice that constantly connects the first chamber 22 and the second chamber 23. Therefore, the oil L in the first chamber 22 flows into the first-chamber-communicating chamber 286 via the first-chamber-side flow path 156 of the piston 21, the axial flow path 54 of the piston rod 31, and the intermediate chamber 237 and flow path 288 of the seat member 166. This increases the pressure in the first-chamber-communicating chamber 286. Therefore, before the valve mechanism 321 opens, the first-chamber volume variable mechanism 326 bends a portion of the disc 174 radially inward from the contact position of the disc spring 177 with the outer tapered portion 202 toward the bottom 191. As a result, the disk 174 increases the capacity of the first-chamber communication chamber 286. As a result, the first-chamber volume variable mechanism 326 suppresses an increase in pressure in the first-chamber communication chamber 286. At this time, the disk 173 deforms following the shape of the disk 174, maintaining the closed state of the passage in the communication hole 211. Also, at this time, the disk 174 bends and moves toward the bottom 191, causing the second-chamber volume variable mechanism 325 to reduce the volume of the second-chamber communication chamber 287.

[0198] Here, during the extension stroke when the shock absorber 1 is subjected to low-frequency input (large-amplitude vibration), the amount of oil L flowing from the first chamber 22 to the first-chamber communication chamber 286 increases. This causes the disc 174 to deform significantly. As the amount of deformation of the disc 174 increases, the reaction force due to the support rigidity of the clamped inner periphery side increases, limiting the amount of deformation. This causes the first-chamber communication chamber 286 to increase in pressure. As a result, the pressure in the second flow path 315 increases to the point where the valve mechanism 321 opens.

[0199] At this time, neither the valve mechanisms 85, 86 nor the valve mechanisms 301, 321 have a fixed orifice that constantly communicates between the first chamber 22 and the second chamber 23. As a result, the damping force rises abruptly during the extension stroke when the piston speed is less than the first predetermined value at which the valve mechanism 321 opens. Furthermore, in a region where the piston speed is higher than the first predetermined value but is in an extremely low speed region that is higher than the first predetermined value but lower than a second predetermined value, the valve mechanism 321 opens while the valve mechanism 85 remains closed.

[0200] That is, the valve member 163 deforms against the biasing force of the spring member 161 and lifts off the valve seat portion 242. As a result, the first chamber 22 and the second chamber 23 are connected to each other through the extension-side second flow path 315. Therefore, the oil L in the first chamber 22 flows to the second chamber 23 via the first-chamber-side flow path 156 of the piston 21, the axial flow path 54 of the piston rod 31, the intermediate chamber 237, flow path 288, and passage portion 281 of the seat member 166, and the passage between the valve member 163 and the valve seat portion 242. At this time, the oil L in the first chamber 22 also flows to the second chamber 23 via the first-chamber-side flow path 156, the axial flow path 54, the intermediate chamber 237 and radial flow paths 317 of the seat member 166, and the passage between the valve member 163 and the valve seat portion 242. As a result, even in an extremely low speed region where the piston speed is slower than the second predetermined value, a damping force with a valve characteristic (a characteristic in which the damping force is approximately proportional to the piston speed) can be obtained.

[0201] Furthermore, a relief mechanism 335 is provided that opens after the valve mechanism 321 opens during the extension stroke. Therefore, when the pressure in the first-chamber communication chamber 286 increases in a normal speed region where the piston speed is equal to or greater than a second predetermined value, the relief mechanism 335 opens while the valve mechanism 321 remains open, allowing the hydraulic fluid L in the first-chamber communication chamber 286 to flow to the second chamber 23 via the second-chamber communication chamber 287 and the second-chamber communication flow path 292. Thereafter, the valve mechanism 85 opens while the valve mechanism 321 and the relief mechanism 335 remain open. That is, when the valve member 163 deforms against the biasing force of the spring member 161 and lifts off the valve seat portion 242 as described above, the hydraulic fluid L flows from the first chamber 22 to the second chamber 23 through the extension-side second flow path 315. Thereafter, while the valve mechanism 321 remains open, the relief mechanism 335 opens, allowing the hydraulic fluid L to flow from the first chamber 22 to the second chamber 23 via the second-chamber communication chamber 287 and the second-chamber communication passage 292. At this time, the flow of the hydraulic fluid L is throttled in the first-chamber-side passage 156 provided in the second passage 315. This increases the pressure applied to the valve member 151, increasing the pressure difference, causing the valve member 151 to separate from the valve seat 105, and allowing the hydraulic fluid L to flow from the first chamber 22 to the second chamber 23 via the extension-side first passage 152. Therefore, the hydraulic fluid L in the first chamber 22 flows to the second chamber 23 via the first passage 152, which is made up of the piston passage 81 and the passage between the valve member 151 and the valve seat 105.

[0202] As a result, even in the normal speed region where the piston speed is equal to or greater than the second predetermined value, a damping force with valve characteristics (where the damping force is approximately proportional to the piston speed) can be obtained. The rate of increase in the extension damping force relative to an increase in piston speed in the normal speed region is lower than the rate of increase in the extension damping force relative to an increase in piston speed in the extremely low speed region.

[0203] As described above, during the extension stroke, when the piston speed is in the normal speed range where the piston speed is equal to or greater than the second predetermined value, the valve member 151 opens, allowing the oil L to flow at a large flow rate through the first flow path 152. This reduces the flow rate through the passage between the valve member 163 and the valve seat portion 242. Therefore, for example, it is possible to reduce the rate of increase in the damping force relative to an increase in the piston speed when the piston speed is in the normal speed range (equal to or greater than the second predetermined value). This allows for greater design flexibility.

[0204] During the extension stroke when a high-frequency input (small-amplitude vibration) occurs, in which a higher frequency than the low-frequency input described above is input to the shock absorber 1, the amount of oil L flowing from the first chamber 22 into the first-chamber communication chamber 286 is small. Therefore, the deformation of the disc 174 is small, and the first-chamber volume variable mechanism 326 can absorb the volume of oil L flowing into the first-chamber communication chamber 286 by the amount of deflection of the disc 174. This reduces the pressure rise in the first-chamber communication chamber 286. Therefore, when the extremely low-speed damping force is building up, the same state as if the disc 174 were not present can be achieved. In other words, when the extremely low-speed damping force is building up, the first-chamber communication chamber 286 is constantly connected to the second chamber 23 via the second-chamber communication flow path 292, i.e., the same state as if the valve mechanism 321 were not present.

[0205] Therefore, during the extension stroke when a high frequency is input, the rise of the extremely low-speed damping force is gradual compared to when a low frequency is input or compared to conventional damping force characteristics. In other words, when the frequency of the piston 21 exceeds a predetermined frequency during the extension stroke, the first chamber volume variable mechanism 326 including the disk 174 restricts the flow rate of the hydraulic fluid L to the valve member 163 of the valve mechanism 321. Note that the change in damping force (the slope of the damping force relative to the piston speed) until the valve mechanism 321 opens can be adjusted by varying the rigidity (plate thickness, etc.) of the disk 174.

[0206] Of the compression-side valve mechanism 86 and valve mechanism 301, the valve member 131 of valve mechanism 86 has greater rigidity and a higher valve opening pressure than the valve member 167 of valve mechanism 301. Therefore, during the compression stroke, in the extremely low-speed region where the piston speed is slower than a predetermined value, the valve mechanism 86 remains closed while the valve mechanism 301 opens. In other words, the valve mechanism 301 opens to generate a damping force when the piston speed is slower than that of the valve mechanism 86. In the normal speed region where the piston speed is equal to or greater than this predetermined value, both the valve mechanism 86 and the valve mechanism 301 open. The valve member 167 is an extremely low-speed valve that opens to generate a damping force when the piston speed is in the extremely low-speed region.

[0207] That is, during the compression stroke, the piston 21 moves toward the second chamber 23, increasing the pressure in the second chamber 23 and decreasing the pressure in the first chamber 22. Here, neither the valve mechanisms 85, 86 nor the valve mechanisms 301, 321 have a fixed orifice that constantly connects the second chamber 23 and the first chamber 22. Therefore, the oil L in the second chamber 23 flows into the second-chamber communication chamber 287 via the second-chamber communication flow path 292. This increases the pressure in the second-chamber communication chamber 287. Therefore, in the second-chamber volume variable mechanism 325, the disc 174 bends toward the disc 170 before the valve mechanism 301 opens. This causes the disc 174 to increase the volume of the second-chamber communication chamber 287. As a result, the second-chamber volume variable mechanism 325 suppresses an increase in pressure in the second-chamber communication chamber 287. At this time, the disc 173 deforms following the shape of the disc 174, maintaining the closed state of the passage in the communication hole 211. Also, at this time, the disc 174 bends and moves toward the disc 170, causing the first chamber volume variable mechanism 326 to reduce the volume of the first chamber communication chamber 286.

[0208] Here, during the compression stroke when the shock absorber 1 is subjected to low-frequency input (large-amplitude vibration), the amount of oil L flowing from the second chamber 23 to the second-chamber communication chamber 287 increases. This causes the disc 174 to deform significantly. As the amount of deformation of the disc 174 increases, the reaction force due to the support rigidity of the clamped inner periphery increases, limiting the amount of deformation. This causes the pressure in the second-chamber communication chamber 287 to increase. As a result, the pressure in the second flow path 291 increases until the valve mechanism 301 opens.

[0209] At this time, neither the valve mechanisms 85, 86 nor the valve mechanisms 301, 321 have a fixed orifice that constantly communicates between the second chamber 23 and the first chamber 22. As a result, the damping force rises abruptly during the compression stroke when the piston speed is less than the third predetermined value at which the valve mechanism 301 opens. Furthermore, in a region where the piston speed is higher than the third predetermined value but in an extremely low speed region that is higher than the third predetermined value but lower than a fourth predetermined value, the valve mechanism 301 opens while the valve mechanism 86 remains closed.

[0210] That is, when the valve member 167 deforms against the biasing force of the spring member 169 and leaves the valve seat portion 245, the second chamber 23 and the first chamber 22 are connected to each other through the compression-side second flow path 291. Therefore, the oil L in the second chamber 23 flows to the first chamber 22 via the passage portion 282 in the seat member 166, the passage between the valve member 167 and the valve seat portion 245, the first-chamber communication chamber 286, the flow path 288 and the intermediate chamber 237 in the seat member 166, the axial flow path 54 in the piston rod 31, the first-chamber-side flow path 156 in the piston 21, and the piston passage 81 in the piston 21. As a result, a damping force with a valve characteristic (a characteristic in which the damping force is approximately proportional to the piston speed) can be obtained even in an extremely low speed range where the piston speed is lower than the fourth predetermined value.

[0211] Furthermore, a relief mechanism 336 is provided that opens after the valve mechanism 301 opens during the compression stroke. Therefore, in the normal speed region where the piston speed is equal to or greater than a fourth predetermined value, when the pressure in the second-chamber communication chamber 287 increases, the relief mechanism 336 opens while the valve mechanism 301 remains open, allowing the oil L from the second chamber 23 and the second-chamber communication chamber 287 to flow to the first chamber 22 via the first-chamber communication chamber 286. Subsequently, the valve mechanism 86 opens while the valve mechanism 301 and the relief mechanism 336 remain open. That is, when the valve member 167 leaves the valve seat 245 as described above, the oil L flows from the second chamber 23 to the first chamber 22 through the second flow path 291 on the compression side. Subsequently, the relief mechanism 336 opens while the valve mechanism 301 remains open, allowing the oil L to flow from the second chamber 23 to the first chamber 22. At this time, the flow of hydraulic fluid L is throttled in the in-piston flow path 103, which is provided in the second flow path 291 downstream of the valve member 167 and the relief mechanism 336. This increases the pressure applied to the valve member 131, increasing the pressure difference. As a result, the valve member 131 is lifted off the valve seat 115, causing hydraulic fluid L to flow from the second chamber 23 to the first chamber 22 through the first flow path 132 on the compression side. Therefore, the hydraulic fluid L in the second chamber 23 flows into the first chamber 22 via the piston passage 82 and the passage between the valve member 131 and the valve seat 115.

[0212] As a result, even in the normal speed region where the piston speed is equal to or greater than the fourth predetermined value, a damping force with valve characteristics (where the damping force is approximately proportional to the piston speed) can be obtained. The rate of increase in the compression damping force with respect to an increase in piston speed in the normal speed region is lower than the rate of increase in the compression damping force with respect to an increase in piston speed in the extremely low speed region.

[0213] As described above, during the compression stroke, when the piston speed is in the normal speed range where the piston speed is equal to or greater than the fourth predetermined value, the valve member 131 opens, allowing the oil L to flow at a large flow rate through the first flow path 132. This reduces the flow rate through the passage between the valve member 167 and the valve seat portion 245. Therefore, for example, it is possible to reduce the rate of increase in the damping force in response to an increase in the piston speed when the piston speed is in the normal speed range (equal to or greater than the fourth predetermined value). This allows for greater design flexibility.

[0214] During the compression stroke when a high-frequency input (small-amplitude vibration) occurs, in which a higher frequency than the low-frequency input described above is input to the shock absorber 1, the amount of oil L flowing from the second chamber 23 into the second-chamber communication chamber 287 is small. Therefore, the deformation of the disc 174 is small. As a result, the second-chamber volume variable mechanism 325 can absorb the volume of oil L flowing into the second-chamber communication chamber 287 by the amount of deflection of the disc 174. Therefore, the pressure increase in the second-chamber communication chamber 287 is small. Therefore, when the extremely low-speed damping force is building up, the same state as when the disc 174 is not present is achieved. In other words, when the extremely low-speed damping force is building up, the second-chamber communication chamber 287 is constantly connected to the first-chamber communication chamber 286, i.e., the same state as when the valve mechanism 301 is not present.

[0215] Therefore, during the compression stroke when a high frequency is input, the rise of the extremely low-speed damping force is gradual compared to when a low frequency is input or compared to conventional damping force characteristics. In other words, when the frequency of the piston 21 exceeds a predetermined frequency, the second chamber volume variable mechanism 325 including the disk 174 restricts the flow rate of the oil L to the valve member 167 of the valve mechanism 301. Note that the change in damping force (the slope of the damping force relative to the piston speed) until the valve mechanism 301 opens can be adjusted by varying the rigidity (plate thickness, etc.) of the disk 174.

[0216] The aforementioned Patent Document 1 discloses a shock absorber in which a piston and a valve seat member separate from the piston are provided on a piston rod. The shock absorber described in Patent Document 1 utilizes a piston rod passage and a passage groove in the valve seat member, which corresponds to the second structural member, to introduce working fluid to the sub-valve and valve seat, which correspond to the first check valve mechanism. However, because there is a circumferential phase difference between these, a large-diameter hole is provided as a circumferential groove to accommodate this misalignment. This structure limits design flexibility, as the contact area with the stacked sub-valve in the circumferentially open area is reduced accordingly, necessitating the need for highly rigid components capable of achieving high tightening pressure. Furthermore, because the valve member is centered on the piston rod, it is virtually impossible to provide a circumferential groove corresponding to a large-diameter hole in either of these components.

[0217] The shock absorber 1 of the first embodiment has a first structural member 155 that divides the inner tube 2 of the cylinder 4 into a first chamber 22 and a second chamber, a piston rod 31 , and a second structural member 331 .

[0218] The first structural member 155 has circular fixing holes 101, 111 that penetrate in the axial direction, a first flow path 152 that can connect the first chamber 22 and the second chamber 23, a flexible valve member 151 that can block the first flow path 152, and a first chamber side flow path 156 that is at least partially arranged parallel to the first flow path 152.

[0219] The piston rod 31 is rod-shaped and is formed with a base-end cylindrical portion 41 which is a cylindrical portion inserted into the fixing hole 111, an axial flow path 54 which is a flow path connected to the first chamber side flow path 156 and directed toward the second chamber 23, a tip-end circumferential groove 53 which is a circumferential groove provided at the end of the axial flow path 54 on the second chamber 23 side, and a tip-end cylindrical portion 43 which is a cylindrical portion provided on the second chamber 23 side of the tip-end circumferential groove 53.

[0220] The second structural member 331 has a smaller diameter than the first structural member 155 and extends across the tip-side circumferential groove 53 and the tip-side cylindrical portion 43. The second structural member 331 has a first inner circumferential wall 232 that axially penetrates its center and through which the piston rod 31 passes, and a second inner circumferential wall 233 that is radially spaced further from the piston rod 31 than the first inner circumferential wall 232, and has a central hole 231 that directly or indirectly communicates with the tip-side circumferential groove 53. The second structural member 331 has a valve mechanism 321 that includes a valve seat portion 242 that serves as a valve seat, and a valve member 163 that is a flexible valve body, and that allows flow through the axial flow path 54 only in the direction from the first chamber 22 to the second chamber 23.

[0221] As described above, the shock absorber 1 has the axial flow path 54 communicating with the first chamber-side flow path 156, at least a portion of which is parallel to the first flow path 152 that can be closed by the valve member 151, and the tip-side circumferential groove 53, which is a circumferential groove, formed in the piston rod 31. This makes it possible for the shock absorber 1 to have a structure in which the inner seat portion 241, where the valve member 163 is stacked in the second structural member 331, does not have a large-diameter hole portion as a circumferential groove. Therefore, the shock absorber 1 does not require a highly rigid component that enables high tightening pressure when tightening the valve member 163, thereby ensuring design flexibility. Furthermore, the shock absorber 1 does not require circumferential phase alignment between the second structural member 331 and the piston rod 31.

[0222] Furthermore, in the shock absorber 1, the second structural member 331 extends across the axial flow passage 54 and the tip-side cylindrical portion 43. The second structural member 331 has a central hole 231 that penetrates through the center in the axial direction and through which the piston rod 31 is inserted, a valve seat portion 242 that serves as a valve seat, and a valve member 163 that is a flexible valve body that is disposed in the axial flow passage 54. The second structural member 331 also has a valve mechanism 321 that allows the oil L to flow only in a direction from the first chamber 22 to the second chamber 23, and a radial flow passage 317 that is provided at a position opposite the axial flow passage 54 and communicates with the valve mechanism 321. Therefore, the shock absorber 1 can change the damping force characteristics in more detail.

[0223] Furthermore, the shock absorber 1 further includes one or more expansion sections 235 formed in the second structural member 331 extending radially from the insertion hole 234 and extending from the surface opposite to the surface facing the first structural member 155 to a position communicating with the axial flow path 54, a case member 178 communicating with the expansion section 235 and forming a first chamber communication chamber 286 that stores oil L, and a passage section 281 connecting the first chamber communication chamber 286 with the valve mechanism 321. Therefore, the shock absorber 1 can change the damping force characteristics in more detail.

[0224] Furthermore, the shock absorber 1 further has a valve mechanism 301 in which the second structural member 331 includes a valve seat portion 245 that is a valve seat, and a valve member 167 that is a flexible valve body that is disposed in the tip-end cylindrical portion 43, and that allows the oil liquid L to flow only in a direction from the second chamber 23 toward the first chamber 22. Therefore, the shock absorber 1 can change the damping force characteristics in more detail.

[0225] Furthermore, the shock absorber 1 further includes a case member 178 in which the second structural member 331 communicates with an intermediate chamber 237 defined by the second inner circumferential wall 233 and the piston rod 31 and forms a first-chamber communication chamber 286 that stores oil L. In the shock absorber 1, the valve mechanism 321 further includes a passage portion 281 that communicates from the first-chamber communication chamber 286 to the valve seat portion 242. The oil L flows from the first-chamber-side flow path 156 to the second chamber 23 via the axial flow path 54, the intermediate chamber 237, the first-chamber communication chamber 286, and the passage portion 281. This makes it possible to provide a first-chamber volume variable mechanism 326 that varies the volume of the first-chamber communication chamber 286.

[0226] Furthermore, in the shock absorber 1, the valve mechanism 321 further has a radial flow passage 317 that communicates from the central hole 231 to the valve seat portion 242, and the oil L flows from the first chamber-side flow passage 156 to the second chamber 23 via the axial flow passage 54, the central hole 231, and the radial flow passage 317. Therefore, the shock absorber 1 can change the damping force characteristics in more detail.

[0227] In addition, since the second structural member 331 of the shock absorber 1 is positioned opposite the axial flow path 54 and has a radial flow path 317 that communicates with the valve mechanism 321, the damping force characteristics can be changed in more detail.

[0228] Furthermore, in the shock absorber 1, the second structural member 331 has one or more extension portions 235 that extend radially from the insertion hole 234 through which the piston rod 31 is inserted, and that are formed from the surface opposite to the surface facing the first structural member 155 to a position that communicates with the axial flow path 54. Therefore, in the shock absorber 1, the axial flow path 54 can communicate with the surface side facing the first structural member 155.

[0229] [Second Embodiment] Next, a second embodiment will be described with reference to Figures 7 and 8, focusing on differences from the first embodiment. The same names and symbols are used for parts common to the first embodiment. In each figure, the central axis of the shock absorber is indicated by the symbol CL.

[0230] 7, the shock absorber 1A of the second embodiment has a second structural member 331A that is partially different from the second structural member 331 of the first embodiment, instead of the second structural member 331. The second structural member 331A has a sheet member 166A that is partially different from the sheet member 166 of the first embodiment, instead of the sheet member 166.

[0231] 8, the seat member 166A has an inner seat portion 241A instead of the inner seat portion 241 of the first embodiment, which differs from the inner seat portion 241 of the first embodiment in that it does not have a protrusion 252. The inner seat portion 241A has a shape similar to the annular portion 251 of the inner seat portion 241 of the first embodiment. Therefore, since the inner seat portion 241A of the seat member 166A does not have a protrusion 252, the shape of the passage recess 258A is different from the passage recess 258 of the first embodiment.

[0232] Furthermore, the seat member 166A does not have the passage hole 269 of the first embodiment. Furthermore, the seat member 166A does not have the radial communicating grooves 253 provided in the entire second inner circumferential wall 233 of the central hole 231. Specifically, the radial communicating grooves 253 are provided in two of the three locations on the second inner circumferential wall 233 of the central hole 231.

[0233] 7, the portion of seat member 166A facing axially to valve member 163 has the shape shown in FIG. 8, but the portion facing axially away from valve member 163 may have the same shape as the portion facing axially to valve member 163. In this case, the valve seat constituent portion 255 facing axially to valve member 163 and the valve seat constituent portion 255 to be provided on the side facing axially away from valve member 163 may be provided so that their phases in the circumferential direction of seat member 166B are aligned.

[0234] As described above, the seat member 166A does not have the passage hole 269 of the first embodiment, and therefore the second structural member 331A does not have the passage portion 282, second flow path 291, and compression side valve mechanism 301 of the first embodiment.

[0235] In the shock absorber 1A of the second embodiment having such a configuration, when the valve mechanism 321 opens during the extension stroke, the oil liquid L in the first chamber 22 (see FIG. 3 ) flows into the second chamber 23 via the first chamber side flow path 156 (see FIG. 3 ), the axial flow path 54, the intermediate chamber 237, the flow path 288, and the flow path between the passage portion 281 and the valve member 163 and the valve seat portion 242, just like the shock absorber 1 of the first embodiment, and also flows from the intermediate chamber 237 into the second chamber 23 via the radial flow path 317 and the flow path between the valve member 163 and the valve seat portion 242. Furthermore, in the shock absorber 1A, when the valve mechanism 85 (see FIG. 3) opens during the extension stroke, the oil L in the first chamber 22 (see FIG. 3) flows into the second chamber 23 via the piston passage 81 (see FIG. 3) and the flow path between the valve member 151 (see FIG. 3) and the valve seat portion 105 (see FIG. 3), in addition to the flow via the valve mechanism 321 described above.

[0236] The shock absorber 1A of the second embodiment does not have a compression-side valve mechanism 301, and therefore, during the compression stroke, the valve mechanism 86 (see FIG. 3) opens, causing the oil L in the second chamber 23 to flow into the first chamber 22 (see FIG. 3) via the piston passage 82 (see FIG. 3) and the first flow path 132 (see FIG. 3) between the valve member 131 (see FIG. 3) and the valve seat portion 115 (see FIG. 3).

[0237] The second structural member 331A has a smaller diameter than the first structural member 155 and extends across the tip-side circumferential groove 53 and the tip-side cylindrical portion 43. The second structural member 331A has a first inner circumferential wall 232 that axially penetrates its center and through which the piston rod 31 is inserted, and a second inner circumferential wall 233 that is radially spaced further from the piston rod 31 than the first inner circumferential wall 232, and has a central hole 231 that directly or indirectly communicates with the tip-side circumferential groove 53. The second structural member 331A has a valve mechanism 321 that includes a valve seat portion 242 that serves as a valve seat and a valve member 163 that is a flexible valve body, and that allows flow through the axial flow path 54 only in the direction from the first chamber 22 to the second chamber 23.

[0238] The shock absorber 1A of the second embodiment has substantially the same effects as the shock absorber 1 of the first embodiment.

[0239] [Third Embodiment] Next, a third embodiment will be described with reference to Figures 9 to 11, focusing on differences from the first embodiment. The same parts as those in the first embodiment are designated by the same names and symbols. In each figure, the central axis of the shock absorber is designated by the symbol CL.

[0240] 9, the third embodiment has a piston rod 31B (shaft member) that is partially different from the piston rod 31 of the first embodiment, instead of the piston rod 31. The piston rod 31B has a mounting shaft portion 33B that is partially different from the mounting shaft portion 33 of the first embodiment, instead of the mounting shaft portion 33.

[0241] The mounting shaft portion 33B has an intermediate shaft portion 42B, which is partially different from the intermediate shaft portion 42 of the first embodiment, between a base end side cylindrical portion 41 and a tip end side cylindrical portion 43 similar to those of the first embodiment, instead of the intermediate shaft portion 42. The base end side circumferential groove 51 and the tip end side circumferential groove 53 of the first embodiment are not formed in the intermediate shaft portion 42B. Note that the base end side circumferential groove 51 similar to that of the first embodiment may be formed in the intermediate shaft portion 42B.

[0242] The intermediate shaft portion 42B has a pair of outer end surfaces 42Ba, a pair of axial grooves 52B shown in FIG.

[0243] 9 each have the shape of a part of a cylindrical surface that is coaxial with and has the same diameter as the outer circumferential surface 41 a of the base-side cylindrical portion 41 and the outer circumferential surface 43 a of the tip-side cylindrical portion 43. The pair of outer end surfaces 42Ba are continuous with the outer circumferential surface 41 a of the base-side cylindrical portion 41 and the outer circumferential surface 41 a of the tip-side cylindrical portion 43.

[0244] The pair of axial grooves 52B shown in FIG. 10 are recessed radially inward from the pair of outer end surfaces 42Ba of the intermediate shaft portion 42B. The pair of axial grooves 52B have the same shape, and the inner bottom surface of the intermediate shaft portion 42B in the radial direction is a flat surface extending perpendicular to the radial direction of the intermediate shaft portion 42B. The pair of axial grooves 52B extend in the axial direction of the piston rod 31B. The pair of axial grooves 52B are provided 120 degrees out of phase with each other in the circumferential direction of the intermediate shaft portion 42B. The outer end surfaces 42Ba and the axial grooves 52B are alternately arranged in the circumferential direction of the intermediate shaft portion 42B. One axial end of the pair of axial grooves 52B extends to the base-side cylindrical portion 41, and the other axial end of the pair of axial grooves 52B extends to the tip-side cylindrical portion 43.

[0245] The radial protrusion 371 is provided on the bottom surface of one of the pair of axial grooves 52B, at the center in the circumferential direction of the piston rod 31B, at the end of the piston rod 31B on the side of the tip-side cylindrical portion 43 in the axial direction. The radial protrusion 371 extends along the axial direction of the piston rod 31B.

[0246] The passage in one of the pair of axial grooves 52B, which is provided with the radial protrusion 371, forms an axial flow path 54B in the piston rod 31B, extending in the axial direction of the piston rod 31B. The passage in the other of the pair of axial grooves 52B, which is not provided with the radial protrusion 371, forms an axial flow path 55B in the piston rod 31B, extending in the axial direction of the piston rod 31B. The circumferential phase of the piston 21 is aligned with the piston rod 31B so that the axial flow paths 54B, 55B of the piston rod 31B communicate with the first chamber-side flow path 156 (see FIG. 3) of the piston 21 (see FIG. 3). Note that the intermediate shaft portion 42B may be formed with a base-end circumferential groove 51 similar to that in the first embodiment, thereby eliminating the need for this phase alignment.

[0247] The shock absorber 1B of the third embodiment has a second structural member 331B that is partially different from the second structural member 331 of the first embodiment, instead of the second structural member 331. The second structural member 331B has a sheet member 166B that is partially different from the sheet member 166 of the first embodiment, instead of the sheet member 166. The second structural member 331B does not have the case member 178 of the first embodiment.

[0248] As shown in Fig. 11, the seat member 166B is a perforated disk. A center hole 231B is formed in the seat member 166B, penetrating the seat member 166B in the axial direction through its radial center. In other words, the center hole 231B extends in the axial direction of the seat member 166B and penetrates the seat member 166B in the axial direction. As shown in Fig. 10, the mounting shaft portion 33B of the piston rod 31B is inserted into the center hole 231B of the seat member 166B.

[0249] As shown in FIG. 11, the central hole 231B has a first inner peripheral wall 232B (first inner peripheral wall) and a second inner peripheral wall 233B (second inner peripheral wall).

[0250] The first inner peripheral wall 232B has a cylindrical inner peripheral surface, and as shown in Fig. 10, the first inner peripheral wall 232B axially penetrates the seat member 166B.

[0251] As shown in FIG. 11 , the second inner circumferential wall 233B is recessed radially outward from the inner circumferential surface of the first inner circumferential wall 232B. The second inner circumferential wall 233B has a rectangular cross section in a plane perpendicular to the axial direction of the seat member 166B. As shown in FIG. 10 , the second inner circumferential wall 233B extends linearly along the axial direction of the seat member 166B and penetrates the seat member 166B in the axial direction. The center hole 231B has one or more second inner circumferential walls 233B. Here, as shown in FIG. 12 , the center hole 231B has one second inner circumferential wall 233B.

[0252] The central hole 231B has an insertion hole 234B, through which the mounting shaft 33B is inserted, on the inside of the first inner circumferential wall 232B, and an expansion portion 235B, which expands radially outward from the insertion hole 234B, on the inside of the second inner circumferential wall 233B. Both the insertion hole 234B and the expansion portion 235B extend from one end face to the other end face of the seat member 166B in the axial direction of the seat member 166B, penetrating the seat member 166B. The seat member 166B has the insertion hole 234B and one or more expansion portions 235B extending radially from the insertion hole 234B.

[0253] As shown in FIG. 10 , the mounting shaft portion 33B of the piston rod 31B is fitted to the first inner circumferential wall 232B of the central hole 231B at the intermediate shaft portion 42B and the tip-side cylindrical portion 43. At this time, the radial protrusion 371 of the piston rod 31B is fitted to the second inner circumferential wall 233B, i.e., the expansion portion 235B. The seat member 166B is then positioned circumferentially relative to the piston rod 31B. As a result, the expansion portion 235B is aligned with the axial flow passage 54B of the piston rod 31B in the circumferential direction of the seat member 166B. The expansion portion 235B is formed from the surface of the seat member 166B opposite the surface facing the first structural member 155 (see FIG. 3 ) to a position communicating with the axial flow passage 54B. When fitted into the expansion portion 235B, the entire radial protrusion 371 is positioned radially inward of the bottom surface of the second inner circumferential wall 233B of the seat member 166B. Therefore, the expansion portion 235B is radially spaced apart from the mounting shaft 33B of the piston rod 31B. The second inner circumferential wall 233B of the seat member 166B and the mounting shaft 33B of the piston rod 31B form an intermediate chamber 237B.

[0254] As shown in FIG. 11 , the seat member 166B has an inner seat portion 241B that does not have the protrusion 252 of the first embodiment, instead of the inner seat portion 241 of the first embodiment. The inner seat portion 241B has an annular shape surrounding the central hole 231B. The inner seat portion 241B has a shape substantially similar to the annular portion 251 of the inner seat portion 241 of the first embodiment. Since the seat member 166B does not have the protrusion 252, the shape of the passage recess 258B is different from the passage recess 258 of the first embodiment. The seat member 166B does not have the passage holes 259 and 269 of the first embodiment.

[0255] The seat member 166B has one radial communicating groove 253B instead of the one radial communicating groove 253 of the first embodiment. The radial communicating groove 253B radially penetrates a portion of the inner seat portion 241B that is in phase with the one passage recess 258B and the extension portion 235B in the circumferential direction of the seat member 166B. When the seat member 166B is attached to the piston rod 31B with the extension portion 235B fitted into the radial protrusion 371, the radial communicating groove 253B communicates between the axial flow path 54B of the piston rod 31B and the intermediate chamber 237B and the one passage recess 258B in the extension portion 235B of the seat member 166B.

[0256] The seat member 166B has a radial communicating groove 254B instead of the other radial communicating groove 253 of the first embodiment. The radial communicating groove 254B penetrates the inner seat portion 241B in the radial direction through a portion of the inner seat portion 241B that is in phase with the other passage recess 258B in the circumferential direction of the seat member 166B. The radial communicating groove 254B is out of phase with the radial communicating groove 253B by 120 degrees. When the seat member 166B is attached to the piston rod 31B with the extension portion 235B fitted into the radial protrusion 371, the radial communicating groove 254B communicates between the axial flow passage 55B of the piston rod 31B and the other passage recess 258B.

[0257] 11, the portion of seat member 166B on the axial side of valve member 163 shown in Fig. 10 may have the same shape as the portion on the axial side of valve member 163. In this case, the valve seat constituent portion 255 on the axial side of valve member 163 and the valve seat constituent portion 255 to be provided on the axial side opposite valve member 163 may be provided so that their phases in the circumferential direction of seat member 166B are aligned.

[0258] As described above, the passage hole 269 of the first embodiment is not formed in the seat member 166B, and therefore the passage portion 282, second flow path 291, and compression side valve mechanism 301 of the first embodiment are not provided in the second structural member 331B shown in FIG. 10.

[0259] The passage in the radial communicating groove 253B formed in the inner seat portion 241B of the seat member 166B serves as a radial flow passage 317B (fourth flow passage). The radial flow passage 317B is located opposite the axial flow passage 54B in the radial direction of the seat member 166B and communicates with the intermediate chamber 237B. The radial flow passage 317B communicates the axial flow passage 54B and the intermediate chamber 237B with one of the passage recesses 258B.

[0260] 11 , the passage in the radial communicating groove 254B formed in the inner seat portion 241B of the seat member 166B serves as a radial flow passage 318B (fourth flow passage). The radial flow passage 318B is located opposite the axial flow passage 55B in the radial direction of the seat member 166B. The radial flow passage 318B connects the axial flow passage 55B with another passage recess 258B.

[0261] The second flow path 315B is composed of the first chamber-side flow path 156 (see FIG. 3) consisting of the piston passage 81 (see FIG. 3) and the intra-piston flow path 103 (see FIG. 3), the axial flow path 54B of the piston rod 31B shown in FIG. 10, the intermediate chamber 237B and the flow path 288 in the second inner circumferential wall 233B of the seat member 166B, the radial flow paths 317B, the axial flow paths 55B, the radial flow paths 318B shown in FIG. 11, and the passage between the valve member 163 and the valve seat portion 242 shown in FIG. 10 that appears when the valve is open.

[0262] A portion of the oil liquid L flowing through the second flow passage 315B from the first chamber 22 (see FIG. 3) toward the second chamber 23 flows from the axial flow passages 54B, 55B to the second chamber 23 via the radial flow passages 317B, 318B shown in FIG. 11 and the passage between the valve member 163 and the valve seat portion 242 shown in FIG. 10 that appears when the valve is open. The remaining portion of the oil liquid L flowing through the second flow passage 315B from the first chamber 22 (see FIG. 3) toward the second chamber 23 flows from the axial flow passage 54B to the second chamber 23 via the intermediate chamber 237B and the flow passage 288.

[0263] The second flow path 315B allows the oil L to flow from the first chamber 22 (see FIG. 3), which is the upstream side in the cylinder 4 (see FIG. 3), to the second chamber 23, which is the downstream side, when the piston 21 (see FIG. 3) moves toward the first chamber 22 (see FIG. 3). The second flow path 315B serves as an extension-side passage through which the oil L flows from the first chamber 22 (see FIG. 3), which is the upstream side, to the second chamber 23, which is the downstream side, when the piston 21 (see FIG. 3) moves toward the first chamber 22 (see FIG. 3), i.e., during the extension stroke. The extension-side second flow path 315B is provided separately from the extension-side first flow path 152 (see FIG. 3). At least a portion (in this example, a portion) of the second flow path 315B is provided in parallel with the first flow path 152 (see FIG. 3). The second flow path 315B is parallel to the first flow path 152 (see FIG. 3) except for a portion of the piston passage 81 (see FIG. 3) closer to the first chamber 22 than the in-piston flow path 103 (see FIG. 3).

[0264] In the shock absorber 1B of the third embodiment having such a configuration, when the valve mechanism 321 opens during the extension stroke, part of the oil liquid L in the first chamber 22 (see FIG. 3) is caused to flow into the second chamber 23 via the second flow path 315B, which has the first-chamber-side flow path 156 (see FIG. 3), the axial flow paths 54B and 55B, the radial flow paths 317B and 318B, and a flow path between the valve member 163 and the valve seat portion 242, and another part of the oil liquid L in the first chamber 22 (see FIG. 3) is caused to flow from the axial flow path 54B to the second chamber 23 via the intermediate chamber 237B and the flow path 288. Furthermore, in the shock absorber 1B, when the valve mechanism 85 (see FIG. 3) opens during the extension stroke, the oil L in the first chamber 22 (see FIG. 3) flows into the second chamber 23 via the piston passage 81 (see FIG. 3) and the passage between the valve member 151 (see FIG. 3) and the valve seat portion 105 (see FIG. 3), in addition to flowing via the second flow passage 315B described above.

[0265] The shock absorber 1B of the third embodiment does not have a compression-side valve mechanism 301, and therefore during the compression stroke, the oil L in the second chamber 23 flows into the first chamber 22 (see FIG. 3) through the second flow path 315B, the intermediate chamber 237B, the axial flow path 54B, and the first-chamber-side flow path 156 (see FIG. 3), and when the valve mechanism 86 (see FIG. 3) opens, in addition to flowing through the second flow path 315B, the oil L also flows into the first chamber 22 (see FIG. 3) through the piston passage 82 (see FIG. 3) and the flow path between the valve member 131 (see FIG. 3) and the valve seat portion 115 (see FIG. 3).

[0266] In the shock absorber 1B of the third embodiment, a base end cylindrical portion 41, which is a cylindrical portion that is inserted into the fixing holes 101, 111 (see FIG. 3) of the piston 21 (see FIG. 3), axial flow paths 54B, 55B that are flow paths that communicate with the first chamber side flow path 156 (see FIG. 3) and lead toward the second chamber 23, and a tip end cylindrical portion 43, which is a cylindrical portion that is provided on the second chamber 23 side of the axial flow paths 54B, 55B, are formed on the piston rod 31B.

[0267] The shock absorber 1B also has a second structural member 331B that has a smaller diameter than the first structural member 155 (see FIG. 3 ) and extends across the axial flow passages 54B, 55B and the tip-side cylindrical portion 43. The second structural member 331B has a central hole 231B that penetrates the center in the axial direction and includes a first inner circumferential wall 232B through which the piston rod 31B passes, and one or more second inner circumferential walls 233B that communicate with the axial flow passage 54B and extend radially beyond the first inner circumferential wall 232B. The second structural member 331B has a valve mechanism 321 that includes a valve seat portion 242 that serves as a valve seat, and a valve member 163 that is flexible and disposed in the axial flow passages 54B, 55B, and that allows the oil L to flow only in a direction from the first chamber 22 (see FIG. 3 ) to the second chamber 23. In the second structural member 331B, the valve mechanism 321 discharges to the second chamber 23 only the oil L that has passed through the radial flow paths 317B and 318B from the first chamber 22 (see FIG. 3).

[0268] The shock absorber 1B has substantially the same effects as the shock absorber 1 of the first embodiment.

[0269] [Fourth Embodiment] Next, the fourth embodiment will be described mainly with reference to Figures 12 to 14, focusing on differences from the first to third embodiments. Note that parts common to the first to third embodiments will be designated by the same names and symbols. In each figure, the central axis of the shock absorber is designated by the symbol CL.

[0270] 12, the fourth embodiment has a piston rod 31C (shaft member) that is partially different from the piston rod 31B of the third embodiment instead of the piston rod 31B. The piston rod 31C has a mounting shaft portion 33C that is partially different from the mounting shaft portion 33B of the third embodiment instead of the mounting shaft portion 33B.

[0271] The mounting shaft portion 33C has an intermediate shaft portion 42C, which is partially different from the intermediate shaft portion 42B of the third embodiment, between the base end side cylindrical portion 41 and the tip end side cylindrical portion 43, similar to those of the first to third embodiments, instead of the intermediate shaft portion 42B. The intermediate shaft portion 42C does not have a radial protrusion 371 in any of the multiple axial grooves 52B. Note that the intermediate shaft portion 42C has a pair of axial grooves 52B that are 180 degrees out of phase with each other in the circumferential direction of the intermediate shaft portion 42C. The base end side circumferential groove 51, similar to that of the first embodiment, may be formed in the intermediate shaft portion 42C.

[0272] As shown in Fig. 13, the inner passages of the multiple axial grooves 52B constitute axial flow paths 54B formed in the piston rod 31B and extending in the axial direction of the piston rod 31B. The circumferential phase of the piston 21 is aligned with the piston rod 31C so that the axial flow path 54B of the piston rod 31C communicates with the first-chamber-side flow path 156 (see Fig. 3) of the piston 21 (see Fig. 3). Note that the intermediate shaft portion 42C may be formed with a base-end circumferential groove 51 similar to that in the first embodiment, thereby making this phase alignment unnecessary.

[0273] The shock absorber 1C of the fourth embodiment has a second structural member 331C that is partially different from the second structural member 331 of the first embodiment, instead of the second structural member 331. The second structural member 331C has a sheet member 166C that is partially different from the sheet member 166 of the first embodiment, instead of the sheet member 166.

[0274] As shown in Fig. 14, the seat member 166C is a circular plate with a hole. The seat member 166C has a central hole 231C that is partially different from the central hole 231 of the first embodiment, formed in place of the central hole 231. As shown in Fig. 13, in the seat member 166C as well, the mounting shaft portion 33C of the piston rod 31C is inserted into a first inner circumferential wall 232 of the central hole 231C.

[0275] The central hole 231C has an internal circumferential groove 381 (first circumferential groove) recessed radially outward from the first inner circumferential wall 232 of the seat member 166C. The internal circumferential groove 381 is formed inside the thickness direction of the seat member 166C, in other words, at the middle position in the axial direction of the seat member 166C. The internal circumferential groove 381 is provided around the entire circumference of the seat member 166C. The internal circumferential groove 381 connects all of the multiple second inner circumferential walls 233 shown in FIG. 14 . In other words, the internal circumferential groove 381 connects all of the multiple extension portions 235 of the central hole 231C.

[0276] As shown in FIG. 13 , the mounting shaft portion 33C of the piston rod 31C is fitted to the first inner circumferential wall 232 of the central hole 231C at the intermediate shaft portion 42C and the tip-side cylindrical portion 43. The second inner circumferential wall 233 and the internal circumferential groove 381 of the seat member 166C, along with the mounting shaft portion 33C of the piston rod 31C, form an intermediate chamber 237C. The internal circumferential groove 381 of the seat member 166C is aligned with the intermediate shaft portion 42C of the piston rod 31C in the axial direction. Therefore, the intermediate chamber 237C communicates with the multiple axial flow paths 54B through the internal circumferential groove 381. The seat member 166C can communicate the intermediate chamber 237C with the axial flow path 54B without circumferentially aligning the seat member 166C with the piston rod 31C.

[0277] As shown in FIG. 14 , the seat member 166C has an inner seat portion 241C that does not have the protrusion 252 and radial communicating groove 253 of the first embodiment, instead of the inner seat portion 241 of the first embodiment. The inner seat portion 241C is annular and surrounds the central hole 231C. Since the seat member 166C does not have the protrusion 252, it has a passage recess 258A similar to that of the second embodiment. The seat member 166C does not have the passage hole 269 of the first embodiment. Furthermore, the second inner circumferential wall 233 of the seat member 166C is out of phase with the valve seat constituent portion 255 in the circumferential direction of the seat member 166C.

[0278] 14, the portion of seat member 166C on the axial side of valve member 163 shown in Fig. 13 may have the same shape as the portion on the axial side of valve member 163. In this case, the valve seat constituent portion 255 on the axial side of valve member 163 and the valve seat constituent portion 255 to be provided on the axial side opposite valve member 163 may be provided in phase with each other in the circumferential direction of seat member 166B.

[0279] As described above, the seat member 166C does not have the passage hole 269 of the first embodiment, and therefore the second structural member 331C shown in FIG. 13 does not have the passage portion 282, second flow path 291, and compression side valve mechanism 301 of the first embodiment.

[0280] The second flow path 315C is composed of the first chamber-side flow path 156 (see FIG. 3) consisting of the piston passage 81 (see FIG. 3) and the in-piston flow path 103 (see FIG. 3), the axial flow path 54B of the piston rod 31C shown in FIG. 13, the second inner circumferential wall 233 of the seat member 166C and the intermediate chamber 237C and flow path 288 in the internal circumferential groove 381, the passage portion 281 of the seat member 166C, and the passage between the valve member 163 and the valve seat portion 242 that appears when the valve is opened. The oil L flowing through the second flow path 315C from the first chamber 22 (see FIG. 3) toward the second chamber 23 flows into the second chamber 23 while opening the valve mechanism 321.

[0281] The second flow path 315C allows the oil L to flow from the first chamber 22 (see FIG. 3), which is the upstream side in the cylinder 4 (see FIG. 3), to the second chamber 23, which is the downstream side, when the piston 21 (see FIG. 3) moves toward the first chamber 22 (see FIG. 3). The second flow path 315C serves as an extension-side passage through which the oil L flows from the first chamber 22 (see FIG. 3), which is the upstream side, to the second chamber 23, which is the downstream side, when the piston 21 (see FIG. 3) moves toward the first chamber 22 (see FIG. 3), i.e., during the extension stroke. The extension-side second flow path 315C is provided separately from the extension-side first flow path 152 (see FIG. 3). At least a portion (in this example, a portion) of the second flow path 315C is provided in parallel with the first flow path 152 (see FIG. 3). The second flow path 315C is parallel to the first flow path 152 (see FIG. 3) except for a portion of the piston passage 81 (see FIG. 3) closer to the first chamber 22 than the in-piston flow path 103 (see FIG. 3).

[0282] In the shock absorber 1C of the fourth embodiment having such a configuration, when the valve mechanism 321 opens during the extension stroke, the oil L in the first chamber 22 (see FIG. 3) flows to the second chamber 23 via the first-chamber-side flow path 156 (see FIG. 3), the axial flow path 54B, the intermediate chamber 237B, the flow path 288 and the passage portion 281 of the seat member 166C, and the second flow path 315C that has the passage between the valve member 163 and the valve seat portion 242 that appears when the valve is opened. Also, in the shock absorber 1B, when the valve mechanism 85 (see FIG. 3) opens during the extension stroke, the oil L in the first chamber 22 (see FIG. 3) flows to the second chamber 23 via the piston passage 81 (see FIG. 3) and the first flow path 152 (see FIG. 3) between the valve member 151 (see FIG. 3) and the valve seat portion 105 (see FIG. 3), in addition to the flow via the second flow path 315C.

[0283] The shock absorber 1C of the fourth embodiment does not have a valve mechanism 301 on the compression side, and therefore, during the compression stroke, the valve mechanism 86 (see FIG. 3) opens, causing the oil L in the second chamber 23 to flow into the first chamber 22 (see FIG. 3) via the piston passage 82 (see FIG. 3) and a first flow path 132 (see FIG. 3) that has a flow path between the valve member 131 (see FIG. 3) and the valve seat portion 115 (see FIG. 3).

[0284] In the shock absorber 1C of the fourth embodiment, a base end cylindrical portion 41, which is a cylindrical portion that is inserted into the fixing holes 101, 111 (see FIG. 3) of the piston 21 (see FIG. 3), an axial flow path 54B, which is a flow path that communicates with the first chamber side flow path 156 (see FIG. 3) and leads toward the second chamber 23, and a tip end cylindrical portion 43, which is a cylindrical portion that is provided on the second chamber 23 side of the axial flow path 54B, are formed on the piston rod 31C.

[0285] The shock absorber 1C also has a second structural member 331C that has a smaller diameter than the first structural member 155 (see FIG. 3 ) and extends across the axial flow passage 54B and the tip-side cylindrical portion 43. The second structural member 331C has a central hole 231C that penetrates the center in the axial direction and includes a first inner circumferential wall 232 through which the piston rod 31C passes, and one or more second inner circumferential walls 233 that communicate with the axial flow passage 54B and extend radially beyond the first inner circumferential wall 232. The second structural member 331C has a valve mechanism 321 that includes a valve seat portion 242 that serves as a valve seat, and a valve member 163 that is flexible and disposed in the axial flow passage 54B, and that allows the oil L to flow only in a direction from the first chamber 22 (see FIG. 3 ) to the second chamber 23. The second structural member 331C has a central hole 231C that is provided inside the second structural member 331C in the thickness direction and that includes an internal circumferential groove 381 that is an annular space with which the axial flow path 54B communicates. In the second structural member 331C, the valve mechanism 321 discharges only the oil liquid L that has passed through the passage portion 281 out of the oil liquid L in the first chamber 22 (see FIG. 3 ) into the second chamber 23. The shock absorber 1C achieves substantially the same effects as the shock absorber 1 of the first embodiment.

[0286] Fifth Embodiment Next, a fifth embodiment will be described with reference to Figures 15 and 16, focusing on differences from the first embodiment. The same parts as those in the first embodiment are designated by the same names and reference numerals. In each figure, the central axis of the shock absorber is designated by the reference numeral CL.

[0287] 15 , a shock absorber 1D of the fifth embodiment has a piston rod 31D (shaft member) that is partially different from the piston rod 31 of the first embodiment, instead of the piston rod 31. The piston rod 31D has a mounting shaft portion 33D that is partially different from the mounting shaft portion 33 of the first embodiment, instead of the mounting shaft portion 33.

[0288] Similar to the first embodiment, an axial groove 52D extending in the axial direction of the mounting shaft portion 33D is formed on the outer periphery of the mounting shaft portion 33D between the main shaft portion 32 and the threaded shaft portion 44. The inner bottom surface of the axial groove 52D in the radial direction of the mounting shaft portion 33D is a flat surface that extends perpendicular to the radial direction of the mounting shaft portion 33D.

[0289] The mounting shaft portion 33D has a base-end side cylindrical portion 41D (first cylindrical portion) that differs from the base-end side cylindrical portion 41 of the first embodiment in that a portion of the axial groove 52D is formed therein, an intermediate shaft portion 42D that differs from the intermediate shaft portion 42 of the first embodiment in that a portion of the axial groove 52D is formed therein, and a threaded shaft portion 44 (second cylindrical portion) that is similar to that of the first embodiment. The intermediate shaft portion 42D has a base-end side circumferential groove 51D (second circumferential groove) that differs from the base-end side circumferential groove 51 of the first embodiment in that a portion of the axial groove 52D is formed therein, and a tip-end side circumferential groove 53D (first circumferential groove) that differs from the tip-end side circumferential groove 53 of the first embodiment in that a portion of the axial groove 52D is formed therein.

[0290] The outer end surface 41Da of the base end cylindrical portion 41D excluding the axial groove 52D and the outer end surface 42Da of the intermediate shaft portion 42D excluding the axial groove 52D, the base end circumferential groove 51D and the tip end circumferential groove 53D are arranged on the same cylindrical surface.

[0291] The passage in the axial groove 52D, the passage in the base end circumferential groove 51D, and the passage in the tip end circumferential groove 53D form an axial flow path 54D formed in the piston rod 31D and extending in the axial direction of the piston rod 31D.

[0292] The shock absorber 1D includes a piston 21D instead of the piston 21 of the first embodiment.

[0293] The piston 21D is composed of a piston body 61D supported by a piston rod 31D, and an annular friction member 62D that is integrally attached to the outer circumferential surface of the piston body 61D and slides inside the inner cylinder 2.

[0294] The piston body 61D has a perforated, disc-shaped base plate portion 401 and a cylindrical tubular portion 402 extending from the outer periphery of the base plate portion 401 to one axial side of the base plate portion 401. The base plate portion 401 of the piston body 61D is formed with a plurality of passage holes 71D (only one is shown in FIG. 15 because it is a cross-section). The passage holes 71D are located radially inward of the base plate portion 401, closer to the tubular portion 402 in the axial direction of the base plate portion 401. The piston body 61D also has a plurality of passage holes 75D (only one is shown in FIG. 15 because it is a cross-section) and an annular passage groove 76D that connects the ends of the passage holes 75D on the first chamber 22 side. The passage holes 75D extend along the axial direction of the base plate portion 401. The plurality of passage holes 71D are formed circumferentially around the piston body 61D, with one passage hole 75D sandwiched between each of them. The passage holes 71D and 75D have ends on the cylindrical portion 402 side in the axial direction of the base portion 401 that open radially inward of the cylindrical portion 402 .

[0295] The passages in the plurality of passage holes 71D penetrate the piston 21D in the axial direction of the piston 21D to form a piston passage 81D that can communicate between the first chamber 22 and the second chamber 23. The passages in the plurality of passage holes 75D and the passage in the passage groove 76D penetrate the piston 21D in the axial direction of the piston 21D to form a piston passage 82D that can communicate between the first chamber 22 and the second chamber 23.

[0296] The piston passage 81D is provided with a valve mechanism 85D, which is a valve that opens and closes the piston passage 81D to generate a damping force. The valve mechanism 85D is arranged on the second chamber 23 side, which is one axial end side of the piston 21D, and is attached to the piston rod 31D. By arranging the valve mechanism 85D on the second chamber 23 side, the oil L that flows out from the first chamber 22 flows toward the second chamber 23 through the piston passage 81D when the piston 21D moves toward the first chamber 22, i.e., during the extension stroke. The valve mechanism 85D provided for the piston passage 81D serves as an extension-side valve mechanism that suppresses the flow of oil L from the extension-side piston passage 81D to the second chamber 23 to generate a damping force.

[0297] The piston passage 82D is provided with a valve mechanism 86D, which is a valve that opens and closes the piston passage 82D to generate a damping force. The valve mechanism 86D is located on the first chamber 22 side, which is the other axial end side of the piston 21D, and is attached to the piston rod 31D. By locating the valve mechanism 86D on the first chamber 22 side, oil L that flows out from the second chamber 23 flows toward the first chamber 22 through the piston passage 82D when the piston 21D moves toward the second chamber 23, i.e., during the compression stroke. The valve mechanism 86D provided for the piston passage 82D serves as a compression-side valve mechanism that suppresses the flow of oil L from the compression-side piston passage 82D to the first chamber 22 to generate a damping force.

[0298] As a result of the above, the piston passage 81D and the piston passage 82D are connected so that the oil liquid L, which is a fluid, flows between the first chamber 22 and the second chamber 23 as the piston 21D moves. The oil liquid L passes through the piston passage 81D when the piston rod 31D and the piston 21D move toward the extension side, and the oil liquid L passes through the piston passage 82D when the piston rod 31D and the piston 21D move toward the compression side.

[0299] A circular fixing hole 101D is formed in the radial center of the piston body 61D, penetrating the piston body 61D in the axial direction and adapted to fit the mounting shaft portion 33D of the piston rod 31D. The base end side cylindrical portion 41D of the mounting shaft portion 33D is fitted into the fixing hole 101D at the outer end surface 41Da.

[0300] The above-mentioned multiple passage holes 71D open at the axial end of the base plate portion 401 of the piston body 61D on the second chamber 23 side. An annular valve seat portion 105D constituting part of the valve mechanism 85D is formed at the axial end of the base plate portion 401 of the piston body 61D on the second chamber 23 side, radially outward from the opening of the passage hole 71D on the second chamber 23 side. Furthermore, an inner seat portion 106D is formed at the axial end of the piston body 61D on the second chamber 23 side, radially inward from the opening of the passage hole 71D on the second chamber 23 side.

[0301] The above-mentioned passage groove 76D is formed at the axial end of the base plate portion 401 of the piston body 61D on the first chamber 22 side. An annular valve seat portion 115D constituting part of the valve mechanism 86D is formed at the axial end of the piston body 61D on the first chamber 22 side, radially outward from the opening of the passage groove 76D on the first chamber 22 side. Furthermore, an inner seat portion 116D is formed at the axial end of the piston body 61D on the first chamber 22 side, radially inward from the opening of the passage groove 76D on the first chamber 22 side.

[0302] In the base plate portion 401 of the piston body 61D, the opening of the compression-side piston passage 82D on the second chamber 23 side is disposed radially outward of the valve seat portion 105D. In addition, in the base plate portion 401 of the piston body 61D, the opening of the extension-side piston passage 81D on the first chamber 22 side is disposed radially outward of the valve seat portion 115D.

[0303] The fixing hole 101D of the piston 21D is fitted into the base end side cylindrical portion 41D of the piston rod 31D. In other words, the piston rod 31D has the base end side cylindrical portion 41D which is a cylindrical portion inserted into the fixing hole 101D.

[0304] The compression-side valve mechanism 86D includes a valve seat portion 115D of the piston 21D. The valve mechanism 86D has, in axial order from the piston 21D side, multiple disks 122D and an annular member 125D. The disks 122D and the annular member 125D are both circular flat plates with holes, and the base-end columnar portion 41D of the mounting shaft 33D is fitted into the inside of each of them at the outer end surface 41Da.

[0305] Of the plurality of discs 122D, the disc 122D closest to the piston 21D in the axial direction has an outer diameter equal to the outer diameter of the valve seat portion 115D of the piston 21D. Of the plurality of discs 122D, the disc 122D closest to the piston 21D in the axial direction is capable of being seated on the valve seat portion 115D.

[0306] The annular member 125D has the smallest diameter of the plurality of discs 122D, smaller than the outer diameter of the disc 112D that is located furthest from the piston 21D, and has an outer diameter equivalent to the outer diameter of the end of the piston rod 31D on the mounting shaft 33D side in the axial direction of the main shaft 32. The annular member 125D is thicker and more rigid than the discs 122D, and abuts against the end of the main shaft 32 on the mounting shaft 33D side in the axial direction.

[0307] A passage groove 102D penetrating the annular member 125D in the radial direction is formed on the end surface of the annular member 125D that faces the main shaft portion 32 in the axial direction. The annular member 125D is attached to the piston rod 31D with the phase of the passage groove 102D in the circumferential direction aligned with the axial groove 52D of the piston rod 31D. This establishes communication between the first chamber-side flow path 156D (second flow path) in the passage groove 102D of the annular member 125D and the axial flow path 54D of the piston rod 31D. A circumferential groove may be provided on the end of the mounting shaft portion 33D of the piston rod 31D that faces the main shaft portion 32 in the axial direction, thereby making this phase alignment unnecessary.

[0308] A plurality of discs 122D constitute a compression-side valve member 131D that can be seated on and removed from the valve seat portion 115D. The valve member 131D is flexible, and when it is removed from the valve seat portion 115D, it connects the piston passage 82D to the first chamber 22. At that time, the valve member 131D suppresses the flow of oil L between the valve seat portion 115D and the valve member 131D, thereby generating a damping force. When the valve member 131D is seated on the valve seat portion 115D, it blocks communication between the piston passage 82D and the first chamber 22.

[0309] The piston passage 82D and the passage between the valve member 131D and the valve seat 115D that appears when the valve is open constitute a first flow path 132D. The first flow path 132D is provided in the piston 21D. The first flow path 132D is a compression-side passage through which oil L flows from the second chamber 23, which is the upstream region within the cylinder 4, to the first chamber 22, which is the downstream region, as the piston 21D moves toward the second chamber 23. A compression-side valve mechanism 86D that generates a damping force includes the valve member 131D and the valve seat 115D. The valve mechanism 86D is provided in the first flow path 132D. The first flow path 132D is provided in the piston 21D, including the valve seat 115D, and oil L passes through the first flow path 132D when the piston rod 31D and the piston 21D move toward the compression side.

[0310] Here, in the compression-side valve mechanism 86D, neither the valve seat portion 115D nor the valve member 131D abutting therewith is provided with a fixed orifice that communicates between the first chamber 22 and the second chamber 23 even when the valve seat portion 115D and the valve member 131D are in contact with each other. Therefore, the first flow path 132D is not a passage that constantly communicates between the first chamber 22 and the second chamber 23.

[0311] The extension-side valve mechanism 85D includes a valve seat portion 105D of the piston 21D. The valve mechanism 85D has, in order from the piston 21D side in the axial direction, a valve member 151D (first valve member) consisting of a single disk and a single disk 143D. The valve member 151D and the disk 143D are both circular flat plates with holes, and the base-end cylindrical portion 41D of the mounting shaft 33D is fitted into the inside of each of them at the outer end surface 41Da.

[0312] The valve member 151D has an outer diameter larger than the inner diameter of the valve seat portion 105D of the piston 21D. The valve member 151D is constantly in contact with the inner seat portion 106D. The valve member 151D is releasable from the valve seat portion 105D. The valve member 151D is flexible, and when it is releasable from the valve seat portion 105D, it connects the piston passage 81D to the second chamber 23. At that time, the valve member 151D suppresses the flow of oil L between the valve seat portion 105D and the valve member 151D, thereby generating a damping force. When the valve member 151D is seated on the valve seat portion 105D, it blocks communication between the piston passage 81D and the second chamber 23.

[0313] The piston passage 81D and the passage between the valve member 151D and the valve seat 105D that appears when the valve is open constitute a first flow path 152D (first flow path). The first flow path 152D is formed in the piston 21D. The first flow path 152D is an extension-side flow path through which oil L flows from the first chamber 22, which is the upstream region within the cylinder 4, to the second chamber 23, which is the downstream region, as the piston 21D moves toward the first chamber 22. The extension-side valve mechanism 85D that generates a damping force includes the valve member 151D and the valve seat 105D. The valve mechanism 85D is provided in this first flow path 152D. The first flow path 152D is provided in the piston 21D, including the valve seat 105D, and oil L passes through the first flow path 152D when the piston rod 31D and the piston 21D move toward the extension side.

[0314] In the extension-side valve mechanism 85D, neither the valve seat portion 105D nor the valve member 151D abutting thereon has a fixed orifice formed therein that connects the first chamber 22 and the second chamber 23 even when the valve seat portion 105D and the valve member 151D are in contact with each other. Therefore, the first flow path 152D is not a flow path that constantly connects the first chamber 22 and the second chamber 23.

[0315] The first chamber-side flow path 156D provided in the annular member 125D is in communication with the first chamber 22. At least a portion, specifically the entirety, of the first chamber-side flow path 156D provided in the annular member 125D is arranged parallel to the first flow path 152D.

[0316] The piston 21D, the annular member 125D, the valve member 131D, and the valve member 151D constitute a first structural member 155D (first structural member) that divides the interior of the inner tube 2 of the cylinder 4 into a first chamber 22 and a second chamber 23. The first structural member 155D divides the interior of the inner tube 2 of the cylinder 4 into the first chamber 22, which serves as an upstream region on the upstream side during the extension stroke, and the second chamber 23, which serves as a downstream region on the downstream side during the extension stroke. The first structural member 155D has a circular fixing hole 101D that penetrates it in the axial direction, a first flow path 152D that can communicate between the first chamber 22, which serves as the upstream region, and the second chamber 23, which serves as the downstream region, during the extension stroke, a flexible valve member 151D that can close the first flow path 152D, and a first-chamber-side flow path 156D that is at least partially parallel to the first flow path 152D.

[0317] On the axially opposite side of the disk 143D from the valve member 151D, there are provided, in order from the disk 143D side, a seat member 166D and a valve member 163D made up of multiple disks 412. On the axially opposite side of the valve member 163D from the seat member 166D, there is provided a case member 416 (partition member) having an O-ring 415 on its outer periphery so as to abut against the inner periphery of the valve member 163D. The mounting shaft portion 33D of the piston rod 31D is inserted through the seat member 166D, the valve member 163D, and the case member 416.

[0318] The seat member 166D has a circular fitting hole 421 formed in the radial center thereof, penetrating in the axial direction, into which the mounting shaft portion 33D of the piston rod 31D is fitted.

[0319] The seat member 166D has a tubular portion 422 and an annular portion 423. The tubular portion 422 has a cylindrical shape with a fitting hole 421 formed on the radially inner side. The annular portion 423 has a ring shape with a fitting hole 421 formed on the radially inner side. The outer diameter of the annular portion 423 is larger than the outer diameter of the tubular portion 422.

[0320] An inner seat portion 431 and a valve seat portion 242D (first check valve seat) are provided in the annular portion 423 on the axially opposite side to the cylindrical portion 422. The valve seat portion 242D is provided on the outer circumferential side of the annular portion 423, and the inner seat portion 431 is provided radially inward of the annular portion 423 relative to the valve seat portion 242D.

[0321] A passage recess 433 is formed in the annular portion 423 radially inward of the valve seat portion 242D. The passage recess 433 is recessed toward the cylindrical portion 422 from an end face of the annular portion 423 opposite to the inner seat portion 431 and the cylindrical portion 422 of the valve seat portion 242D in the axial direction.

[0322] A passage groove 435 is formed in the annular portion 423, extending linearly from the inner circumferential surface radially outward of the annular portion 423 and communicating with the passage recess 433. In the radial direction of the annular portion 423, the passage groove 435 is located more inward than the valve seat portion 242D. The passage groove 435 is recessed from the inner seat portion 431 and the end face of the valve seat portion 242D opposite the cylindrical portion 422 in the axial direction of the annular portion 423 to the cylindrical portion 422 side beyond the bottom surface of the passage recess 433. At least one passage groove 435 is formed in the annular portion 423. The passage groove 435 and the passage recess 433 communicate with each other to form a radial flow path 317D.

[0323] The seat member 166D is fitted onto the mounting shaft portion 33D of the piston rod 31D with the cylindrical portion 422 facing the disk 143D in the axial direction and the annular portion 423 facing away from the disk 143D. The cylindrical portion 422 of the seat member 166D abuts against the disk 143D at an end face opposite the annular portion 423 in the axial direction.

[0324] The cylindrical portion 422 of the seat member 166D is fitted to the outer end surface 41Da of the base-side cylindrical portion 41D of the mounting shaft portion 33D, and the annular portion 423 is fitted to the outer end surface 41Da of the base-side cylindrical portion 41D of the mounting shaft portion 33D and the outer end surface 42Da of the intermediate shaft portion 42D. At this time, the passage groove 435 of the seat member 166D is positioned to overlap the base-side circumferential groove 51D of the piston rod 31D in the axial direction of the piston rod 31D. This allows the radial flow passage 317D formed by the passage recess 433 and the passage groove 435 to communicate with the passage in the base-side circumferential groove 51D of the axial flow passage 54D. The base-side circumferential groove 51D of the piston rod 31D allows the radial flow passage 317D to communicate with the axial flow passage 54D without circumferentially aligning the seat member 166D with the piston rod 31D.

[0325] The valve member 163D is made up of a plurality of disks 412 each having a perforated circular flat plate shape. Of the plurality of disks 412 constituting the valve member 163D, the disk 412 axially closest to the seat member 166D has an outer diameter equal to the outer diameter of the valve seat portion 242D of the seat member 166D. The valve member 163D is removably seated on the valve seat portion 242D.

[0326] The case member 416 has a perforated circular bottom plate portion 441, a cylindrical small-diameter tubular portion 442 extending from the inner peripheral edge of the bottom plate portion 441 to one side in the axial direction of the bottom plate portion 441, and a cylindrical large-diameter tubular portion 443 extending from the outer peripheral edge of the bottom plate portion 441 to the opposite side of the small-diameter tubular portion 442 in the axial direction of the bottom plate portion 441.

[0327] A plurality of passage holes 451 are formed in the bottom plate portion 441 between the small diameter cylindrical portion 442 and the large diameter cylindrical portion 443 in the radial direction. An O-ring 415 is fitted onto the outer periphery of the bottom plate portion 441.

[0328] The small-diameter cylindrical portion 442 has an outer diameter on the bottom plate portion 441 side in the axial direction that is larger than the outer diameter on the opposite side of the bottom plate portion 441. As a result, a step portion 455 having an annular cutout shape is formed on the outer periphery of the small-diameter cylindrical portion 442 on the opposite side of the bottom plate portion 441 in the axial direction.

[0329] The outer circumferential surface of the large diameter cylindrical portion 443 is arranged on the same cylindrical surface as the outer circumferential surface of the bottom plate portion 441 and is continuous with it.

[0330] A central hole 231D is formed in the radial center of the bottom plate portion 441 and the small-diameter cylindrical portion 442 of the case member 416, penetrating the axial direction of the case member 416. In other words, the central hole 231D extends in the axial direction of the case member 416 and penetrates the case member 416 in the axial direction. In the seat member 166D, the mounting shaft portion 33D of the piston rod 31D is inserted into the central hole 231D.

[0331] The central hole 231D has a first inner peripheral wall 232D (first inner peripheral wall) and a second inner peripheral wall 233D (second inner peripheral wall).

[0332] The first inner circumferential wall 232D penetrates the case member 416 in the axial direction of the case member 416. The first inner circumferential wall 232D has a cylindrical wall portion 456 whose inner circumferential surface is a cylindrical surface, and an internal thread portion 457. The cylindrical wall portion 456 is formed on the radially inner side of the small-diameter cylindrical portion 442, and the internal thread portion 457 is formed on the radially inner side of the bottom plate portion 441. In other words, the first inner circumferential wall 232D has the internal thread portion 457 on the axial side facing the large-diameter cylindrical portion 443, and the cylindrical wall portion 456 on the opposite side from the large-diameter cylindrical portion 443.

[0333] As shown in FIG. 16 , the second inner circumferential wall 233D is recessed radially outward from the inner circumferential surface of the first inner circumferential wall 232D, i.e., the inner circumferential surfaces of the cylindrical wall portion 456 and the female thread portion 457. As shown in FIG. 15 , the second inner circumferential wall 233D extends linearly along the axial direction of the case member 416. The second inner circumferential wall 233D is formed from the end face of the bottom plate portion 441 opposite the small-diameter cylindrical portion 442 to a middle position on the bottom plate portion 441 side in the axial direction of the case member 416. The second inner circumferential wall 233D is formed on the entire axial direction of the female thread portion 457 and on a portion of the axial direction of the cylindrical wall portion 456 on the female thread portion 457 side. The central hole 231D has one or more second inner circumferential walls 233D. Specifically, as shown in FIG. 16, the central hole 231D has a plurality of second inner circumferential walls 233D arranged at equal intervals in the circumferential direction of a first inner circumferential wall 232D.

[0334] The central hole 231D has an insertion hole 234D, through which the mounting shaft 33D is inserted, on the inside of the first inner circumferential wall 232D, and an expansion portion 235D, which expands radially outward from the insertion hole 234D, on the inside of the second inner circumferential wall 233D. The case member 416 has the insertion hole 234D and one or more expansion portions 235D extending radially outward from the insertion hole 234D. As shown in FIG. 15 , the insertion hole 234D extends from one end face of the case member 416 in the axial direction to the other end face, penetrating the case member 416. The expansion portion 235D extends from the end face of the case member 416 opposite the small-diameter cylindrical portion 442 of the guide main body to a midpoint on the bottom plate portion 441 side of the small-diameter cylindrical portion 442.

[0335] As shown in FIG. 15 , the mounting shaft 33D of the piston rod 31D is threadedly engaged with the threaded portion 44 of the first inner circumferential wall 232D in the central hole 231D. This causes the second inner circumferential wall 233D to move radially away from the mounting shaft 33D of the piston rod 31D. The expansion portion 235D is formed from the surface of the case member 416 opposite the surface facing the first structural member 155D to a position communicating with the axial flow path 54D. The expansion portion 235D of the central hole 231D overlaps with the distal circumferential groove 53D of the piston rod 31D in the axial direction of the piston rod 31D. Therefore, the central hole 231D communicates directly or indirectly with the distal circumferential groove 53D of the piston rod 31D; in this case, it communicates directly. An intermediate chamber 237D is formed by the second inner circumferential wall 233D of the case member 416 and the mounting shaft portion 33D of the piston rod 31D. The distal end circumferential groove 53D of the piston rod 31D allows the intermediate chamber 237D to communicate with the axial flow path 54D without circumferentially aligning the case member 416 with the piston rod 31D.

[0336] When the case member 416 is screwed onto the threaded shaft portion 44 of the piston rod 31D, the annular member 125D, the valve member 131D, the piston 21D, the valve member 151D, the disc 143D, the seat member 166D and the valve member 163D are each clamped axially at least on their radially inner sides by the main shaft portion 32 of the piston rod 31D and the small diameter cylindrical portion 442 of the case member 416.

[0337] A cover member 461 is fixed to the inner periphery of the large-diameter cylindrical portion 443 of the case member 416 at the end opposite the bottom plate portion 441 in the axial direction. The cover member 461 is disk-shaped and closes the radially inner side of the large-diameter cylindrical portion 443.

[0338] A recessed portion 462 is formed in the cover member 461 on the axial side facing the bottom plate portion 441. The recessed portion 462 has a shape of a part of a sphere. The recessed portion 462 is curved so that it moves away from the bottom plate portion 441 in the axial direction of the cover member 461 as it approaches the center in the radial direction of the cover member 461.

[0339] A filter 470 for filtering the oil L is fitted and fixed to the cover member 461 on the axial side opposite to the bottom plate portion 441 .

[0340] The cover member 461 has a plurality of passage holes 467 formed at the attachment position of the filter 470. The passage holes 467 pass through the cover member 461 in the axial direction.

[0341] A partition disk 471 and a spring member 472 are provided radially inside the large-diameter cylindrical portion 443 of the case member 416, between the bottom plate portion 441 and the cover member 461 in the axial direction of the case member 416.

[0342] The partition disk 471 is a circular, flat plate. The partition disk 471 abuts against the outer peripheral edge of the recessed portion 462 of the lid member 461 over the entire circumference, thereby forming a first chamber communication chamber 286D (storage chamber) between the bottom plate portion 441 of the case member 416 and the partition disk 471, and forming a second chamber communication chamber 287D between the partition disk 471 and the recessed portion 462.

[0343] The spring member 472 is provided between the bottom plate portion 441 of the case member 416 and the partition disk 471. The spring member 472 biases the partition disk 471 so that the entire periphery of the partition disk 471 abuts against the outer peripheral edge portion of the recessed portion 462.

[0344] A sliding member 481 (partition member) is provided on the outer periphery of the bottom plate portion 441 of the case member 416. The sliding member 481 has a cylindrical sliding tubular portion 482 and an inner flange portion 483 that extends radially inward from one axial end of the sliding tubular portion 482. The outer diameter of the sliding member 481 is smaller than the outer diameter of the piston 21D.

[0345] The sliding member 481 has an inner flange portion 483 provided between the valve member 163D and the bottom plate portion 441 of the case member 416, and in this state, the sliding cylindrical portion 482 is slidably fitted onto the outer periphery of the bottom plate portion 441. At this time, an O-ring 415 provided on the outer periphery of the bottom plate portion 441 seals between the sliding cylindrical portion 482 and the bottom plate portion 441. The sliding member 481 slides in the axial direction relative to the case member 416 while maintaining a state in which the gap between the sliding member 481 and the bottom plate portion 441 is sealed by the O-ring 415.

[0346] A perforated, disc-shaped leaf spring 486 is provided between the inner flange portion 483 of the sliding member 481 and the stepped portion 455 of the case member 416. The outer peripheral edge of the leaf spring 486 abuts on the side of the inner flange portion 483 opposite to the valve member 163D in the axial direction, and the inner peripheral edge abuts on the valve member 163D side of the stepped portion 455 in the axial direction. The leaf spring 486 urges the inner flange portion 483 in the direction of abutting against the valve member 163D, thereby urging the valve member 163D in the direction of abutting against the valve seat portion 242D.

[0347] A pressure chamber 491 (storage chamber) is formed surrounded by the case member 416, the sliding member 481, and the O-ring 415. The pressure chamber 491 communicates with the first-chamber communication chamber 286D via a passage in the passage hole 451 of the case member 416. The first-chamber communication chamber 286D communicates with the first chamber 22 via the intermediate chamber 237D, the axial passage 54D, and the first-chamber-side passage 156D of the annular member 125D. The axial passage 54D communicates with a radial passage 317D formed by the passage groove 435 and the passage recess 433 of the seat member 166D.

[0348] The valve member 163D, the case member 416, the partition disk 471, and the sliding member 481 communicate with the intermediate chamber 237D and form a first chamber communication chamber 286D and a pressure chamber 491 that store oil L. The sliding member 481 applies a force to the valve member 163D in the valve closing direction according to the pressures in the first chamber communication chamber 286D and the pressure chamber 491.

[0349] The second chamber communication chamber 287D communicates with the second chamber 23 via a passage in the passage hole 467 of the cover member 461 and a filter 470 .

[0350] The partition disc 471 bends toward the second-chamber communication chamber 287D, thereby expanding the volume of the first-chamber communication chamber 286D. The volume of the second-chamber communication chamber 287D decreases to absorb the expansion of the volume of the first-chamber communication chamber 286D, and the oil L is discharged into the second chamber 23.

[0351] When the valve member 163D is lifted off the valve seat portion 242D, the valve member 163D communicates between the first chamber 22 and the second chamber 23 via the first-chamber-side flow path 156D of the annular member 125D, the axial flow path 54D of the piston rod 31D, and the radial flow path 317D of the seat member 166D. At this time, the valve member 163D suppresses the flow of oil L between the valve member 163D and the valve seat portion 242D, thereby generating a damping force.

[0352] The valve member 163D opens when the oil L is discharged from the first chamber 22 to the second chamber 23 via the first-chamber-side flow path 156D, the axial flow path 54D, and the radial flow path 317D. The valve member 163D is a check valve that regulates the inflow of the oil L from the second chamber 23 to the first chamber 22 via the radial flow path 317D, the axial flow path 54D, and the first-chamber-side flow path 156D.

[0353] The first-chamber-side flow path 156D, the axial flow path 54D, the radial flow paths 317D, and the passage between the valve member 163D and the valve seat 242D that appears when the valve is open constitute a second flow path 315D. The second flow path 315D communicates with the pressure chamber 491 via the intermediate chamber 237D, the first-chamber communication chamber 286D, and a passage in the passage hole 451.

[0354] The second flow path 315D is opened and closed by a valve member 163D. When the piston 21D moves toward the first chamber 22, the oil L flows from the first chamber 22, which is the upstream side of the cylinder 4, to the second chamber 23, which is the downstream side. The second flow path 315D serves as an extension-side passage through which the oil L flows from the first chamber 22, which is the upstream side, to the second chamber 23, which is the downstream side, when the piston 21D moves toward the first chamber 22, i.e., during the extension stroke. The extension-side second flow path 315D is provided separately from the extension-side first flow path 152D. At least a portion (in this example, the entirety) of the second flow path 315D is provided in parallel with the first flow path 152D.

[0355] The valve member 163D and the seat member 166D including the valve seat portion 242D constitute a valve mechanism 321D (first check valve mechanism). The valve mechanism 321D is provided in the second flow path 315D on the extension side and opens and closes the second flow path 315D. The second flow path 315D has a radial flow path 317D that communicates with the valve mechanism 321D. The valve mechanism 321D generates a damping force by suppressing the flow of hydraulic fluid L from the second flow path 315D to the second chamber 23. The valve mechanism 321D generates a damping force during the extension stroke. The valve mechanism 321D is arranged separately from the valve mechanism 85D, which also generates a damping force during the extension stroke. In the valve mechanism 321D, during the extension stroke, the oil L in the first chamber 22 flows from the first chamber side flow path 156D to the second chamber 23 via the axial flow path 54D including the base end side circumferential groove 51D, the radial flow path 317D, and the passage between the valve member 163D and the valve seat portion 242D that appears when the valve is opened.

[0356] The valve mechanism 321D includes a valve seat portion 242D serving as a valve seat and a valve member 163D serving as a flexible valve body, and serves as a check valve mechanism that allows flow from the first chamber 22, which is the upstream region, toward the second chamber 23, which is the downstream region, during the extension stroke of the second flow path 315D including the first chamber-side flow path 156D, while restricting flow from the second chamber 23, which is the upstream region, toward the first chamber 22, which is the downstream region, during the compression stroke. In other words, the valve mechanism 321D only allows flow from the first chamber 22, which is the upstream region, toward the second chamber 23, which is the downstream region, during the extension stroke of the second flow path 315D including the first chamber-side flow path 156D.

[0357] The first-chamber communication chamber 286D, which is in communication with the first chamber 22, is in communication with the second flow path 315D on the extension side. The first-chamber communication chamber 286D and the second-chamber communication chamber 287D, and the case member 416, cover member 461, partition disk 471, and spring member 472 that form these chambers, constitute a frequency-sensitive mechanism 495 that changes the damping force in accordance with the frequency of the piston 21D.

[0358] When the partitioning disk 471 deforms to enter the recessed portion 462, the frequency sensitive mechanism 495 changes the volume of the first-chamber communication chamber 286D to increase it. At that time, the frequency sensitive mechanism 495 discharges the oil L from the second-chamber communication chamber 287D through the passage hole 467 of the lid member 461 and the filter 470 to the second chamber 23. When the partitioning disk 471 moves away from the outer peripheral edge of the recessed portion 462, it connects the second-chamber communication chamber 287D and the first-chamber communication chamber 286D. The partitioning disk 471 and the recessed portion 462 constitute the frequency sensitive mechanism 495 and also constitute a check valve mechanism 496 that restricts the flow of oil L from the first-chamber communication chamber 286D to the second-chamber communication chamber 287D and allows the flow of oil L from the second-chamber communication chamber 287D to the first-chamber communication chamber 286D.

[0359] The seat member 166D, the valve member 163D, the O-ring 415, the case member 416, the cover member 461, the partition disk 471, the spring member 472, the sliding member 481, and the leaf spring 486 constitute the second structural member 331D (second structural member).

[0360] Therefore, the second structural member 331D has a first inner circumferential wall 232D that axially penetrates its center and through which the piston rod 31D is inserted, and a second inner circumferential wall 233D that is radially spaced further from the piston rod 31D than the first inner circumferential wall 232D, and has a central hole 231D that directly or indirectly communicates with the tip-side circumferential groove 53 of the piston rod 31D. The second structural member 331D also has a valve mechanism 321D that includes a valve seat portion 242D that serves as a valve seat, and a valve member 163D that is a flexible valve body, and that allows flow through the first-chamber-side flow path 156 only in the direction from the first chamber 22 to the second chamber 23. The second structural member 331D has a case member 416 and a sliding member 481 that communicate with an intermediate chamber 237D defined by the second inner circumferential wall 233D and the piston rod 31D and that define a first-chamber communication chamber 286D and a pressure chamber 491 that store oil liquid L. The second structural member 331D also has a central hole 231D that penetrates the center in the axial direction and through which the piston rod 31D is inserted. The second structural member 331D also has a valve mechanism 321D that includes a valve seat portion 242D that serves as a valve seat, and a valve member 163D that is a flexible valve body disposed in the axial flow path 54D, and that allows oil liquid L to flow only in a direction from the first chamber 22 to the second chamber 23.

[0361] The second structural member 331D has an outer diameter smaller than that of the first structural member 155D. The second structural member 331D extends over the tip-side circumferential groove 53 and the threaded shaft portion 44 of the piston rod 31D.

[0362] The piston rod 31D is provided with a base end circumferential groove 51D, which is a circumferential groove, at a predetermined position of the axial flow passage 54D, and the base end circumferential groove 51D communicates with a valve seat portion 242D.

[0363] The second structural member 331D is in communication with the intermediate chamber 237D formed by the second inner circumferential wall 233D and the piston rod 31D, and has a case member 416, a cover member 461, and a sliding member 481 that form a first chamber communication chamber 286D and a pressure chamber 491 that store oil L. The sliding member 481 applies a force to the valve member 163D in the valve closing direction in accordance with the pressure in the first chamber communication chamber 286D and the pressure chamber 491.

[0364] Next, the operation of the shock absorber 1D will be described.

[0365] It is assumed that the partition disc 471 of the frequency sensitive mechanism 495 does not operate during the extension stroke in which the piston rod 31D moves toward the extension side. Then, when the piston speed is slow, the oil L from the first chamber 22 flows from the first chamber-side flow path 156D of the annular member 125D to the axial flow path 54D of the piston rod 31D, and then flows through the radial flow paths 317D of the seat member 166D to open the valve member 163D of the valve mechanism 321D, and then flows into the second chamber 23 through the second flow path 315D that includes the gap between the valve member 163D and the valve seat portion 242D of the seat member 166D, generating a damping force with valve characteristics (the damping force is approximately proportional to the piston speed).

[0366] When the piston speed becomes even faster, the oil L from the first chamber 22 flows into the second chamber 23 via the second flow path 315D, which includes the gap between the valve mechanism 321D and the valve seat portion 242D, and also flows from the first flow path 152D to the second chamber 23 through the gap between the valve member 151D and the valve seat portion 105D while opening the valve member 151D of the valve mechanism 85D, thereby suppressing an increase in the damping force. Therefore, the characteristic of the damping force relative to the piston speed is such that the rate of increase in the damping force decreases as the piston speed increases.

[0367] As the piston speed increases, the flow rate of hydraulic fluid L branching from the second flow path 315D and flowing from the intermediate chamber 237D to the pressure chamber 491 via the first-chamber communication chamber 286D and the passage hole 467 is throttled, and the force (hydraulic pressure) acting on the valve member 163D becomes greater in the direction of the second flow path 315D than in the direction of the pressure chamber 491. Therefore, in this region, as the piston speed increases, the valve member 163D of the valve mechanism 321D opens farther away from the valve seat portion 242D of the seat member 166D than described above. As a result, the increase in damping force is further suppressed. Therefore, the damping force versus piston speed characteristic further decreases in the rate of increase in damping force relative to an increase in piston speed.

[0368] During the compression stroke in which the piston rod 31D moves toward the compression side, the oil L introduced from the second chamber 23 into the compression-side piston passage 82D flows into the first chamber 22 through between the valve member 131D and the valve seat portion 115D while opening the valve member 131D of the valve mechanism 86D, generating a damping force with valve characteristics (the damping force is approximately proportional to the piston speed).

[0369] The above is the case assuming that the partition disc 471 does not operate. In contrast, when the partition disc 471 operates, the amplitude of the piston 21D is small when the piston frequency is equal to or higher than a predetermined value, and during the extension stroke when the piston frequency is high in this manner, the pressure in the first chamber 22 increases, causing the oil liquid L to be introduced from the first chamber 22 into the first-chamber-communicating chamber 286D via the first-chamber-side flow path 156D, the axial flow path 54D, and the intermediate chamber 237D. In response to this, the partition disc 471, which had previously been flat, elastically deforms to enter the recessed portion 462 while blocking communication between the first-chamber-communicating chamber 286D and the second-chamber-communicating chamber 287D, thereby expanding the volume of the first-chamber-communicating chamber 286D and discharging the oil liquid L from the second-chamber-communicating chamber 287D to the second chamber 23 via the passage in the passage hole 467 and the filter 470.

[0370] As the partition disc 471 is deformed in this manner, hydraulic fluid L is introduced from the first chamber 22 into the first chamber communication chamber 286D, thereby suppressing the pressure increase in the pressure chamber 491. This makes it easier for the valve member 163D of the valve mechanism 321D to open. This softens the damping force on the extension side. At this time, the valve mechanism 85D, which is a hard valve, does not open.

[0371] Here, when the piston frequency is equal to or higher than a predetermined value, the amount of oil L introduced from the first chamber 22 to the first-chamber-communication chamber 286D via the first-chamber-side flow path 156D, the axial flow path 54D, and the intermediate chamber 237D is small, so the deformation of the partition disc 471 is small and the partition disc 471 does not come into full contact with the recessed portion 462, thereby preventing the deformation from being restricted. Therefore, the damping force becomes softer with each extension stroke.

[0372] On the other hand, when the piston frequency is lower than a predetermined value, the amplitude of the piston 21D is large. During the extension stroke when the piston frequency is low, hydraulic fluid L flows from the first chamber 22 to the first-chamber-communicating chamber 286D via the first-chamber-side flow path 156D, the axial flow path 54D, and the intermediate chamber 237D in the same manner as described above. However, the amount of hydraulic fluid L flowing into the first-chamber-communicating chamber 286D is large, resulting in significant deformation of the partition disc 471. Therefore, the partition disc 471 then comes into full contact with the recessed portion 462, restricting further deformation, and hydraulic fluid L no longer flows from the first chamber 22 to the first-chamber-communicating chamber 286D. Since hydraulic fluid L no longer flows from the first chamber 22 to the first-chamber-communicating chamber 286D, the pressure in the pressure chamber 491 increases, suppressing the opening of the valve member 163D of the valve mechanism 321D. This results in a hard damping force on the extension side. When the pressure in the first chamber communication chamber 286D further increases, the oil L opens the valve member 151D of the valve mechanism 85D, which is a hard valve, and flows into the second chamber 23 through the first flow path 152D, which includes the gap between the valve member 151D and the valve seat portion 115D.

[0373] During the compression stroke, when the piston speed is slow and the pressure in the second chamber 23 increases, the pressure in the second-chamber-communicating chamber 287D becomes higher than the pressure in the first-chamber-communicating chamber 286D. As a result, the partition disc 471 moves away from the outer circumferential edge of the recessed portion 462 against the biasing force of the spring member 472. In other words, the check valve mechanism 496 opens. Then, the oil L in the second chamber 23 flows into the first chamber 22 via the filter 470, the passage in the passage hole 467, the second-chamber-communicating chamber 287D, the first-chamber-communicating chamber 286D, the intermediate chamber 237D, the axial passage 54D, and the first-chamber-side passage 156D.

[0374] During the compression stroke, when the piston speed increases, in addition to the above flow, the valve member 131D of the valve mechanism 86D is lifted off the valve seat portion 115D and oil L flows from the second chamber 23 to the first chamber 22 via the first flow path 132D.

[0375] When switching from the compression stroke to the extension stroke, if the pressure in the second chamber 23 drops, the partition disc 471 is instantly seated on the outer periphery of the recessed portion 462 by the biasing force of the spring member 472. In other words, the check valve mechanism 496 is instantly closed. This prevents the oil L on the first chamber 22 side from flowing to the second chamber 23 side via the check valve mechanism 496 when switching from the compression stroke to the extension stroke, thereby suppressing a delay in the rise of the damping force at the initial stage of the extension stroke.

[0376] The shock absorber 1D of the fifth embodiment has a first structural member 155D that divides the inner tube 2 of the cylinder 4 into a first chamber 22 and a second chamber, a piston rod 31D, and a second structural member 331D.

[0377] The first structural member 155D has a circular fixing hole 101D that penetrates in the axial direction, a first flow path 152D that can connect the first chamber 22 and the second chamber 23, a flexible valve member 151D that can close the first flow path 152D, and a first chamber side flow path 156D that is at least partially arranged parallel to the first flow path 152D.

[0378] The piston rod 31D is rod-shaped and is formed with a base-end cylindrical portion 41D, which is a cylindrical portion that is inserted into the fixing hole 101D, an axial flow path 54D, which is a flow path that is connected to the first chamber-side flow path 156D and leads toward the second chamber 23, a tip-end circumferential groove 53D, which is a circumferential groove provided at the end of the axial flow path 54D on the second chamber 23 side, and a screw shaft portion 44, which is a cylindrical portion that is provided on the second chamber 23 side of the tip-end circumferential groove 53D.

[0379] The second structural member 331D has a smaller diameter than the first structural member 155D and extends across the tip-side circumferential groove 53D and the threaded shank 44. The second structural member 331D has a first inner circumferential wall 232D that axially penetrates its center and through which the piston rod 31D passes, and a second inner circumferential wall 233D that is radially spaced further from the piston rod 31D than the first inner circumferential wall 232D, and has a central hole 231D that directly or indirectly communicates with the tip-side circumferential groove 53. The second structural member 331D also has a valve mechanism 321D that includes a valve seat portion 242D that serves as a valve seat and a valve member 163D that is a flexible valve body, and that allows flow through the axial flow path 54D only in the direction from the first chamber 22 to the second chamber 23.

[0380] As a result of the above, the shock absorber 1D can achieve substantially the same effects as the shock absorber 1 of the first embodiment.

[0381] Furthermore, in shock absorber 1D, second structural member 331D communicates with intermediate chamber 237D formed by second inner circumferential wall 233D and piston rod 31D, and includes case member 416, cover member 461, and sliding member 481 that form first chamber communication chamber 286D and pressure chamber 491 that store oil L. Furthermore, in second structural member 331D, sliding member 481 applies force to valve member 163D in the valve closing direction in accordance with the pressure in first chamber communication chamber 286D and pressure chamber 491. This allows shock absorber 1D to control the damping force more precisely.

[0382] [Sixth Embodiment] Next, a sixth embodiment will be described with reference to Figures 17 and 18, focusing on differences from the first embodiment. The same names and symbols are used for parts common to the first embodiment. In each figure, the central axis of the shock absorber is indicated by the symbol CL.

[0383] 17 , a shock absorber 1E of the sixth embodiment has a first structural member 155E (first structural member) that is partially different from the first structural member 155 of the first embodiment, instead of the first structural member 155. The first structural member 155E has a valve mechanism 86E that is partially different from the valve mechanism 86 of the first embodiment, instead of the valve mechanism 86. The valve mechanism 86E has a valve member 131E that is partially different from the valve member 131 of the first embodiment, instead of the valve member 131.

[0384] The valve member 131E has a single disk 511 with a notch 510 formed in its outer periphery, and multiple disks 122. The disk 511 is the part of the valve member 131E that is closest to the piston 21 and abuts against the valve seat portion 115 of the piston 21. The inside of the notch 510 is an orifice 512 that connects the piston passage 81 to the first chamber 22 even when the valve member 131E is in contact with the valve seat portion 115. Therefore, the shock absorber 1E of the sixth embodiment has a first flow path 132E that differs from the first flow path 132 of the first embodiment in that it has an orifice 512.

[0385] In the shock absorber 1E of the sixth embodiment, the configuration between the piston 21 and the annular member 182 is different from that of the shock absorber 1 of the first embodiment.

[0386] On the valve seat portion 105 and inner seat portion 106 sides of the piston 21, in order from the piston 21 side in the axial direction, there are provided one disk 551, one valve disk 552, one pilot valve 553, one pilot case 556 (partition member), multiple valve disks 557, one disk 558, one valve disk 559, multiple valve disks 560, one disk 561, and one disk 562, with the mounting shaft portion 33 of the piston rod 31 fitted inside each of them. The disks 551, 558, 561, 562 and the valve disks 552, 557, 559, 560 are all perforated circular flat plates of a constant thickness, into which the mounting shaft portion 33 of the piston rod 31 can be fitted. The pilot valve 553 and the pilot case 556 are both annular in shape, and the mounting shaft portion 33 of the piston rod 31 can be fitted therein.

[0387] Pilot case 556 is a cylindrical shape with a bottom, and a central hole 231E that passes through pilot case 556 in the axial direction of pilot case 556 is formed in its radial center. Pilot case 556 has a perforated disk-shaped bottom 571, a cylindrical outer cylindrical portion 572 that protrudes to one side from the outer peripheral edge of bottom 571 along the axial direction of bottom 571, and a cylindrical inner cylindrical portion 573 that protrudes to the same side as outer cylindrical portion 572 from the inner peripheral edge of bottom 571 along the axial direction of bottom 571.

[0388] The pilot case 556 also has an inner seat portion 574 that protrudes from the inner peripheral edge of the bottom 571 along the axial direction of the bottom 571 to the side opposite the inner cylindrical portion 573, an intermediate valve seat portion 575 that protrudes from outside the inner seat portion 574 in the radial direction of the bottom 571 to the same side as the inner seat portion 574 along the axial direction of the bottom 571, and an outer valve seat portion 242E (first check valve seat) that protrudes from outside the intermediate valve seat portion 575 in the radial direction of the bottom 571 to the same side as the inner seat portion 574 along the axial direction of the bottom 571.

[0389] The mounting shaft portion 33 of the piston rod 31 is fitted into the central hole 231E of the pilot case 556. In this case, the pilot case 556 is oriented such that the outer cylindrical portion 572 and the inner cylindrical portion 573 extend from the bottom portion 571 toward the piston 21 in the axial direction of the piston rod 31. In addition, in this case, the pilot case 556 is provided with an inner seat portion 574, an intermediate valve seat portion 575, and an outer valve seat portion 242E on the surface of the bottom portion 571 facing the second chamber 23 in the axial direction of the piston rod 31.

[0390] The bottom portion 571 is formed with a seat portion 580 and a recess 582 on the axial side of the bottom portion 571, closer to the outer cylindrical portion 572 and the inner cylindrical portion 573. The seat portion 580 and the recess 582 are formed at a position between the outer cylindrical portion 572 and the inner cylindrical portion 573 in the radial direction of the bottom portion 571.

[0391] The seat portion 580 is annular, and the seat surface is on the side of the outer cylindrical portion 572 and the inner cylindrical portion 573 in the axial direction of the bottom portion 571. This seat surface is flat and extends perpendicular to the central axis of the bottom portion 571.

[0392] The recess 582 is annular and is provided at a radially intermediate position of the seat portion 580. The recess 582 is recessed from the seat surface of the seat portion 580 in the axial direction of the bottom portion 571. The recess 582 has a shape in which the width in the radial direction of the bottom portion 571 becomes narrower as the depth increases. The recess 582 is provided in an annular shape, but does not have to be annular. In other words, it is sufficient that the recess 582 is provided on at least a portion of the seat portion 580.

[0393] An outer through-hole 587 is formed in the bottom 571, passing through the position of the recess 582 in the axial direction of the bottom 571. The outer through-hole 587 is inclined with respect to the central axis of the bottom 571 so that the farther away from the recess 582 in the axial direction of the bottom 571 the outer through-hole 587 is, the more outwardly positioned the outer through-hole 587 is in the radial direction of the bottom 571. As shown in FIG. 18 , a plurality of outer through-holes 587 are formed in the bottom 571 at equal intervals in the circumferential direction of the bottom 571. It is sufficient that at least one outer through-hole 587 is provided in the bottom 571.

[0394] The bottom portion 571 is formed with an inner through-hole 588 that penetrates along the axial direction of the bottom portion 571. The bottom portion 571 is formed with a plurality of inner through-holes 588 that are equally spaced apart in the circumferential direction of the bottom portion 571. It is sufficient that at least one inner through-hole 588 is provided in the bottom portion 571. The outer through-hole 587 is provided outward of the inner through-hole 588 in the radial direction of the pilot case 556, i.e., in the radial direction of the bottom portion 571.

[0395] The inner seat portion 574 is annular in shape. A passage groove 590 is formed in the inner seat portion 574, penetrating the inner seat portion 574 in the radial direction of the inner seat portion 574. A plurality of passage grooves 590 are formed in the inner seat portion 574 at equal intervals in the circumferential direction of the inner seat portion 574.

[0396] 17 , the intermediate valve seat portion 575 protrudes from the bottom portion 571 on the same side as the inner seat portion 574 along the axial direction of the bottom portion 571. The height of the intermediate valve seat portion 575 protruding from the bottom portion 571 in the axial direction of the bottom portion 571 is slightly greater than the height of the inner seat portion 574 protruding from the bottom portion 571.

[0397] 18 , the intermediate valve seat portion 575 has a plurality of valve seat constituent portions 591 spaced equally apart around the circumference of the pilot case 556. The plurality of valve seat constituent portions 591 have the same shape and all extend radially outward from the inner seat portion 574. In the present embodiment, the intermediate valve seat portions 575 are provided in a plurality of sector shapes along the circumference of the bottom portion 571, but the shape is not limited to this and may be, for example, an annular shape.

[0398] The valve seat constituent portion 591 has a passage groove 594 that penetrates the radial direction of the bottom portion 571 of the valve seat constituent portion 591 at a radially outer portion of the bottom portion 571 .

[0399] As shown in Fig. 17 , the outer valve seat portion 242E protrudes from the bottom portion 571 in the axial direction of the bottom portion 571 on the same side as the intermediate valve seat portion 575. The height by which the outer valve seat portion 242E protrudes from the bottom portion 571 in the axial direction of the bottom portion 571 is greater than the height by which the intermediate valve seat portion 575 protrudes from the bottom portion 571. As shown in Fig. 18 , the outer valve seat portion 242E is annular.

[0400] An inner passage recess 595 is formed between each of the multiple valve seat forming portions 591 of the intermediate valve seat portion 575 and the inner seat portion 574. In other words, the inner passage recess 595 is formed by being surrounded by each of the multiple valve seat forming portions 591 of the intermediate valve seat portion 575 and the inner seat portion 574. The multiple inner passage recesses 595 are arranged at equal intervals in the circumferential direction of the pilot case 556. As shown in FIG. 17 , each of the multiple inner passage recesses 595 is recessed along the axial direction of the pilot case 556 from the leading end surface on the protruding side of the inner seat portion 574 and the leading end surface on the protruding side of the intermediate valve seat portion 575. The bottom surface of the inner passage recess 595 is formed by the bottom portion 571.

[0401] 18 , a passage groove 594 formed in a valve seat constituent portion 591 opens into an inner passage recess 595. The inner through-hole 588 is formed in the bottom surface of the inner passage recess 595 and opens into the inner passage recess 595.

[0402] An outer passage recess 596 is formed between the outer valve seat portion 242E and the inner seat portion 574 and intermediate valve seat portion 575. The outer passage recess 596 is continuous around the entire circumference of the pilot case 556. As shown in FIG. 17 , the outer passage recess 596 is recessed in the axial direction of the pilot case 556 from the protruding-side tip surface of the inner seat portion 574, the protruding-side tip surface of the intermediate valve seat portion 575, and the protruding-side tip surface of the outer valve seat portion 242E. The bottom surface of the outer passage recess 596 is formed by the bottom portion 571.

[0403] A passage groove 590 formed in the inner seat portion 574 opens into an outer passage recess 596 .

[0404] The outer through-hole 587 has an end portion on the outer valve seat 242E side in the axial direction of the bottom portion 571 that opens outward from the outer valve seat 242E in the radial direction of the pilot case 556. The outer through-hole 587 opens into the second chamber 23. As shown in FIG. 18 , the outer through-hole 587 does not open into the inner passage recess 595 or the outer passage recess 596. The inner through-hole 588 opens into the inner passage recess 595 but does not open into the outer passage recess 596.

[0405] The central hole 231E has a first inner peripheral wall 232E (first inner peripheral wall) that is provided on the central axis of the pilot case 556, and a second inner peripheral wall 233E (second inner peripheral wall) that is recessed radially outward from the first inner peripheral wall 232E of the pilot case 556.

[0406] The first inner peripheral wall 232E has a cylindrical inner peripheral surface and penetrates the pilot case 556 in the axial direction.

[0407] The second inner circumferential wall 233E is recessed radially outward from the inner circumferential surface of the first inner circumferential wall 232E. The inner circumferential surface of the second inner circumferential wall 233E is semi-cylindrical. The second inner circumferential wall 233E extends linearly along the axial direction of the pilot case 556. As shown in FIG. 17 , the second inner circumferential wall 233E extends linearly from the end face of the inner seat portion 574 opposite the inner cylindrical portion 573 to a middle position of the inner cylindrical portion 573 in the axial direction of the pilot case 556. The center hole 231E has one or more second inner circumferential walls 233E. Here, as shown in FIG. 18 , the center hole 231E has multiple second inner circumferential walls 233E spaced equally apart in the circumferential direction of the first inner circumferential wall 232E. In the circumferential direction of the pilot case 556, the multiple second inner circumferential walls 233E are aligned in phase with the corresponding passage grooves 590.

[0408] 17, the mounting shaft portion 33 of the piston rod 31 is fitted to the first inner circumferential wall 232E of the central hole 231E. In the axial direction of the piston rod 31, the second inner circumferential wall 233E is positioned to overlap the tip-side circumferential groove 53 and the tip-side cylindrical portion 43.

[0409] In the pilot case 556, an intermediate chamber 237E formed by the second inner circumferential wall 233E and the piston rod 31 communicates with the passage in the tip-side circumferential groove 53 of the piston rod 31 and with the passage in the passage groove 590 of the pilot case 556. The intermediate chamber 237E in the second inner circumferential wall 233E communicates with the axial passage 54 of the piston rod 31. The axial passage 54 of the piston rod 31 communicates with the passage in the outer passage recess 596 via the intermediate chamber 237E in the second inner circumferential wall 233E of the pilot case 556 and the passage in the passage groove 590.

[0410] As shown in FIG. 18 , the central hole 231E has an insertion hole 234E, through which the mounting shaft 33 of the piston rod 31 is inserted, on the inside of the first inner circumferential wall 232E, and an expansion portion 235E, which expands radially outward from the insertion hole 234E, on the inside of the second inner circumferential wall 233E. The pilot case 556 has the insertion hole 234E and one or more expansion portions 235E extending radially from the insertion hole 234E. Here, the pilot case 556 has multiple expansion portions 235E spaced equally spaced circumferentially around the insertion hole 234E. The insertion hole 234E extends from one axial end face of the seat member 166 to the other end face, penetrating the seat member 166. The expansion portion 235 extends from one axial end face of the seat member 166 to the position of the axial flow passage 54 and is in communication with the axial flow passage 54.

[0411] As shown in FIG. 17 , a free valve 611 is disposed within the pilot case 556, axially facing the bottom portion 571. The free valve 611 is a flexible, plate-like member. The outer diameter of the free valve 611 is larger than the outer diameter of the recessed portion 582 in the radial direction of the bottom portion 571. The inner diameter of the free valve 611 is smaller than the inner diameter of the recessed portion 582 in the radial direction of the bottom portion 571. The inner cylindrical portion 573 of the pilot case 556 and the mounting shaft portion 33 of the piston rod 31 penetrate radially inward through the free valve 611.

[0412] As described above, the bottom 571 of the pilot case 556 has a recess 582 covered by the free valve 611 and a seat portion 580 that abuts against the free valve 611, and has an outer through-hole 587 that passes through the bottom 571 at the position of the recess 582. The pilot case 556 has an inner through-hole 588 in the seat portion 580 that passes through the bottom 571 and is located more inward in the radial direction of the pilot case 556 than the outer through-hole 587.

[0413] The outer through-hole 587 formed in the recess 582 of the bottom 571 has an end on the recess 582 side that is radially overlapping and axially opposed to the free valve 611. The free valve 611 closes the outer through-hole 587 by coming into surface contact with the seat portion 580, and opens the outer through-hole 587 by moving away from the seat portion 580. The free valve 611 is also elastically deformable to enter the recess 582, and even in this case, the free valve 611 abuts against the peripheral boundary of the recess 582 with the seat portion 580 or the entire surface of the recess 582, thereby maintaining the closed state of the outer through-hole 587.

[0414] The disk 551 has an outer diameter that is smaller than the inner diameter of the valve seat portion 105 of the piston 21 and larger than the outer diameter of the inner seat portion 106 .

[0415] The valve disc 552 has an outer diameter slightly larger than the outer diameter of the valve seat portion 105 of the piston 21. The valve disc 552 abuts against the valve seat portion 105, and opens and closes the opening of the piston passage 81 by moving away from and abutting against the valve seat portion 105.

[0416] The pilot valve 553 is made up of a metal valve disc 641 and an elastic fastening member 642 that is fastened to the valve disc 641. For example, the fastening member 642 may be made of rubber and fastened to the valve disc 641 by vulcanization adhesion.

[0417] The valve disc 641 is a circular flat plate with holes and a constant thickness, into which the mounting shaft portion 33 of the piston rod 31 can be fitted. The outer diameter of the valve disc 641 is slightly larger than the outer diameter of the valve disc 552. The pilot valve 553 fits onto the intermediate shaft portion 42 of the mounting shaft portion 33 in the valve disc 641, and abuts against the valve disc 552 and the inner cylindrical portion 573 of the pilot case 556.

[0418] The fixing member 642 is fixed to the outer circumferential side of the valve disc 641, which is opposite the piston 21 in the axial direction. The fixing member 642 has a seal portion 645 and a support portion 646. The seal portion 645 and the support portion 646 are both fixed to the outer circumferential side of the valve disc 641, which is opposite the piston 21 in the axial direction.

[0419] The seal portion 645 has an annular shape and is fixed to the outer peripheral edge of the valve disc 641. The seal portion 645 extends from the valve disc 641 in the axial direction of the valve disc 641 to the side opposite to the piston 21.

[0420] The support portion 646 has an annular shape. The support portion 646 is formed contiguous with the seal portion 645, inside the seal portion 645 in the radial direction of the valve disc 641. Like the seal portion 645, the support portion 646 extends from the valve disc 641 in the axial direction of the valve disc 641 to the side opposite the piston 21.

[0421] The support portion 646 has at least one passage groove 648 formed therein, penetrating the support portion 646 in the radial direction thereof. This passage groove 648 may be a hole formed in the support portion 646, or a notch that cuts from the tip of the support portion 646 (the portion that contacts the free valve 611, described below) toward the seal portion 645. The support portion 646 has a base end that is located closer to the valve disc 641 than the passage groove 648 and is connected to the valve disc 641, and is connected to the base end of the seal portion 645 that is connected to the valve disc 641. The seal portion 645 and the support portion 646 of the fixing member 642 are made of the same material and are formed seamlessly and integrally.

[0422] As described above, the seal portion 645 is integrally connected to the valve disc 641. The support portion 646 is made of the same material as the seal portion 645 and, like the seal portion 645, is integrally connected to the valve disc 641. The support portion 646 is connected to the inner portion of the seal portion 645 in the radial direction of the valve disc 641. The support portion 646 also extends from the inner side of the seal portion 645 in the radial direction of the valve disc 641.

[0423] The seal portion 645 is slidably and liquid-tightly fitted over the entire inner circumferential surface of the outer cylindrical portion 572 of the pilot case 556, and constantly seals the gap between the pilot valve 553 and the outer cylindrical portion 572. In other words, the pilot valve 553 slidably and liquid-tightly fits the seal portion 645 to the outer cylindrical portion 572 of the pilot case 556. At this time, the valve disc 641 covers the opening of the outer cylindrical portion 572 on the opposite side of the bottom portion 571 in the axial direction of the pilot case 556.

[0424] The tip side of the support portion 646 abuts against the free valve 611. The support portion 646 presses the free valve 611 against the seat portion 580. One end of the support portion 646 is connected to the valve disc 641, and the other end abuts against the free valve 611, directly applying a biasing force to the valve disc 641 and the free valve 611 in the direction separating them.

[0425] The support portion 646 abuts against the free valve 611 opposite a portion of the free valve 611 that seats on the seat portion 580. In other words, the portion of the support portion 646 that comes into contact with the free valve 611 overlaps the position of the portion of the free valve 611 that seats on the seat portion 580 in the radial direction of the free valve 611. Specifically, the portion of the support portion 646 that comes into contact with the free valve 611 overlaps the position of the portion of the free valve 611 that seats on a portion of the free valve 611 that is more inward than the recessed portion 582 of the seat portion 580 in the radial direction of the bottom portion 571 in the radial direction of the free valve 611.

[0426] With free valve 611 closing outer through-hole 587, the space between pilot valve 553, pilot case 556, and free valve 611 forms pressure chamber 651 (storage chamber), and the space between recess 582 of pilot case 556 and free valve 611 forms variable chamber 652. Thus, pressure chamber 651 and variable chamber 652 are defined by free valve 611 within pilot case 556. Pressure chamber 651 and variable chamber 652 are formed by pilot case 556, which is a cylindrical pilot case with a bottom, having a bottom 571 and an outer cylindrical portion 572.

[0427] Free valve 611 blocks the flow of oil L between pressure chamber 651 and variable chamber 652 in the following states: when both its outer and inner peripheral sides are in contact with seat portion 580 over the entire circumference; when both its outer and inner peripheral sides are in contact with both boundary edges of recess 582 between seat portion 580 and free valve 611 over the entire circumference; and when free valve 611 is in contact with recess 582 over the entire circumference. Free valve 611 also allows the flow of oil L between pressure chamber 651 and variable chamber 652 when free valve 611 is spaced apart from seat portion 580 of bottom portion 571. Variable chamber 652 communicates with second chamber 23 via a passage in outer through-hole 587.

[0428] The support portion 646 of the fixing member 642 of the pilot valve 553 biases the free valve 611 so that it abuts against the seat portion 580. When the differential pressure between the pressure chamber 651 and the variable chamber 652 (the variable chamber 652 is higher) reaches a predetermined level, the free valve 611 moves against the biasing force of the support portion 646 and separates from the seat portion 580. At this time, the free valve 611 separates from the seat surface radially outward from the recessed portion 582, which is not biased by the support portion 646, and may not separate from the seat surface radially inward from the recessed portion 582, depending on the differential pressure. The support portion 646 of the pilot valve 553, the free valve 611, and the seat portion 580 and recess 582 of the bottom portion 571 of the pilot case 556 constitute a check valve 655 that restricts the flow of oil liquid L from the pressure chamber 651 side to the variable chamber 652 side, i.e., the second chamber 23 side, while allowing the flow of oil liquid L from the variable chamber 652 side, i.e., the second chamber 23 side, to the pressure chamber 651 side.

[0429] The free valve 611, which is the valve element of the check valve 655, is not clamped in its entirety in the axial direction and is not fixed to any component. In other words, the free valve 611 can come into contact with and move away from the support portion 646 of the pilot valve 553 and the bottom portion 571 of the pilot case 556, with which it abuts. The free valve 611 is a floating-type free valve that can move in its entirety in the axial direction. The free valve 611 is biased by only the support portion 646 of the pilot valve 553, other than by hydraulic pressure, to move toward and away from the seat portion 580.

[0430] In addition, the biasing force of the support portion 646 of the pilot valve 553 may be set so that the free valve 611 always blocks the flow of oil liquid L between the pressure chamber 651 and the variable chamber 652 regardless of the pressure state of the pressure chamber 651 and the variable chamber 652.

[0431] Because recess 582 is formed in bottom 571, free valve 611 can bend due to the pressure of hydraulic oil L in pilot case 556. When the pressure in pressure chamber 651 becomes higher than the pressure in variable chamber 652, free valve 611 bends to enter recess 582 as described above, expanding the volume of pressure chamber 651 and deforming to reduce the volume of variable chamber 652 while continuing to block communication between pressure chamber 651 and variable chamber 652. Furthermore, from this state, when the pressure difference between the pressure in pressure chamber 651 and the pressure in variable chamber 652 becomes smaller, free valve 611 decreases its entry into recess 582, increasing the volume of variable chamber 652 and deforming (restoring) to reduce the volume of pressure chamber 651 while continuing to block communication between pressure chamber 651 and variable chamber 652.

[0432] The bottom 571 of the pilot case 556 has an outer through-hole 587 that can communicate with the pressure chamber 651 on a surface of the bottom 571 that is radially outer than the outer valve seat portion 242E and faces the second chamber 23. The pilot case 556 is provided with a free valve 611 that closes the outer through-hole 587 from the inside of the pressure chamber 651 and can change the volume of the pressure chamber 651 using the pressure within the pressure chamber 651.

[0433] As described above, the valve disc 552 can be seated on the valve seat portion 105 of the piston 21. The valve disc 641 of the pilot valve 553 abuts against the valve disc 552. The valve disc 641 of the pilot valve 553 and the valve disc 552 constitute a valve member 151E (first valve member) that seats and separates from the valve seat portion 105.

[0434] A valve member 151E made up of the valve disc 552 and the valve disc 641 constitutes a valve mechanism 85E together with a valve seat portion 105 of the piston 21. There is no orifice between the valve member 151E and the valve seat portion 105 of the piston 21.

[0435] When the valve disc 552 of the valve member 151E is lifted off the valve seat 105 and opens, the oil liquid L in the first chamber 22 flows into the second chamber 23 via the piston passage 81 and a passage between the valve member 151E and the valve seat 105. The piston passage 81 and the passage between the valve member 151E and the valve seat 105 form a first flow path 152E. In other words, the piston passage 81 and the space between the separated valve member 151E and the valve seat 105 form the first flow path 152E through which the oil liquid L flows as a fluid flowing out of the first chamber 22, which is one of the first chamber 22 and the second chamber 23. The first flow path 152E is a flow path that communicates from the first chamber 22 to the second chamber 23, and is a flow path that runs from the first chamber 22 toward the valve mechanism 85E and passes through the valve mechanism 85E.

[0436] This first flow path 152E serves as an extension-side flow path through which oil L flows as a fluid from the first chamber 22 to the second chamber 23 when the piston 21 moves toward the first chamber 22, i.e., during the extension stroke. The extension-side valve mechanism 85E, which is made up of the valve seat portion 105 and the valve member 151E, is a valve provided in the first flow path 152E, and the valve member 151E acts in a direction to reduce the cross-sectional area of ​​this first flow path 152E, thereby suppressing the flow of oil L and generating a damping force.

[0437] The multiple valve discs 557 have the same outer diameter, which allows them to seat on an intermediate valve seat portion 575 of the pilot case 556. The multiple valve discs 557 constitute a valve member 671 that can be seated on and removed from the intermediate valve seat portion 575. The valve member 671 closes the passage within the inner passage recess 595 between the inner seat portion 574 and the intermediate valve seat portion 575 when it abuts against the intermediate valve seat portion 575. When the valve member 671 moves away from the intermediate valve seat portion 575, it opens the passage within the inner passage recess 595, connecting it to the passage within the outer passage recess 596 between the intermediate valve seat portion 575 and the outer valve seat portion 242E.

[0438] The intermediate valve seat portion 575 of the pilot case 556 and the valve member 671 constitute a valve mechanism 672. The passage in the passage groove 594 of the intermediate valve seat portion 575 serves as an orifice 673 that connects the passage in the inner passage recess 595 to the outer passage recess 596, even when the valve member 671 is in contact with the intermediate valve seat portion 575. In other words, the orifice 673 constantly connects the passage in the inner passage recess 595 with the passage in the outer passage recess 596. The orifice 673 is provided in the valve mechanism 672, but functions as a throttle that reduces pressure by narrowing the flow path between the passage in the inner passage recess 595 and the passage in the outer passage recess 596 only when the valve mechanism 672 is closed, and does not function as a throttle when the valve mechanism 672 is open. Therefore, the orifice 673 is parallel to the valve mechanism 672 in terms of the hydraulic circuit. The orifice 673 has a flow passage cross-sectional area S2 that is smaller than the flow passage cross-sectional area S1 of the in-piston flow passage 103.

[0439] During the compression stroke, the check valve 655 opens, introducing hydraulic fluid L from the second chamber 23 into the pressure chamber 651. When the pressure in the pressure chamber 651 exceeds a predetermined value, the valve member 671 is lifted off the intermediate valve seat 575. The valve mechanism 672 then causes the hydraulic fluid L from the second chamber 23 to flow into the first chamber 22 via the passage in the outer through-hole 587, the pressure chamber 651, the passage in the inner through-hole 588, the passage in the inner passage recess 595, the passage in the outer passage recess 596, the passage in the passage groove 590, the intermediate chamber 237E in the second inner circumferential wall 233E, the axial passage 54, the in-piston passage 103, and the piston passage 81.

[0440] The disk 558 has an outer diameter that is smaller than the outer diameter of the valve member 671 and approximately the same as the outer diameter of the inner seat portion 574 of the pilot case 556 .

[0441] The valve disc 559 has an outer diameter slightly larger than the outer diameter of the outer valve seat portion 242E of the pilot case 556. The valve disc 559 abuts against the outer valve seat portion 242E and opens and closes the passage in the outer passage recess 596 by moving away from and abutting against the outer valve seat portion 242E. When the valve disc 559 moves away from the outer valve seat portion 242E, the passage in the outer passage recess 596 communicates with the second chamber 23. A notch 675 is formed on the outer peripheral side of the valve disc 559, and the notch 675 traverses the outer valve seat portion 242E in the radial direction.

[0442] The multiple valve discs 560 have the same outer diameter, which is equal to the outer diameter of the valve disc 559. The valve disc 559 and the multiple valve discs 560 constitute a valve member 163E (first check valve element) that is removably seated on the outer valve seat 242E. The valve member 163E abuts against the outer valve seat 242E to close the passage in the outer passage recess 596 between the inner seat 574 and the intermediate valve seat 575 and the outer valve seat 242E. The valve member 671 opens the passage in the outer passage recess 596 to the second chamber 23 by moving away from the outer valve seat 242E.

[0443] When the valve member 163E is in contact with the outer valve seat 242E, the inside of the notch 675 of the valve disc 559 forms an orifice 677 that connects the passage in the outer passage recess 596 to the second chamber 23. In other words, the orifice 677 always connects the passage in the outer passage recess 596 to the second chamber 23.

[0444] The outer valve seat portion 242E of the pilot case 556 and the valve member 163E constitute a valve mechanism 321E (first check valve mechanism). The valve mechanism 321E is a check valve that allows the flow of oil liquid L from the second chamber 23 to the passage in the outer passage recess 596, and that constantly restricts the flow of oil liquid L from the passage in the outer passage recess 596 to the second chamber 23.

[0445] The orifice 677 is provided in the valve mechanism 321E, and functions as a throttle that reduces the pressure by narrowing the flow path between the passage in the outer passage recess 596 and the second chamber 23 only when the valve mechanism 321E is closed, and does not function as a throttle when the valve mechanism 321E is open. Therefore, the orifice 677 is parallel to the valve mechanism 321E in terms of the hydraulic circuit. The flow path cross-sectional area S3 of the orifice 677 is smaller than the flow path cross-sectional area S1 of the in-piston flow path 103 and larger than the flow path cross-sectional area S2 of the orifice 673. In other words, the flow path cross-sectional area S1 of the in-piston flow path 103 > the flow path cross-sectional area S3 of the orifice 677 > the flow path cross-sectional area S2 of the orifice 673 are satisfied.

[0446] Between the first chamber 22 and the second chamber 23, the oil liquid L flows through the first chamber side flow path 156, the axial flow path 54, the intermediate chamber 237E, the passage in the passage groove 590, the passage in the outer passage recess 596, and the orifice 677 or the passage between the open valve member 163E and the outer valve seat portion 242E.

[0447] The first chamber-side flow path 156, the axial flow path 54, the intermediate chamber 237E, the passage in the passage groove 590, the passage in the outer passage recess 596, and the orifice 677 or the passage between the open valve member 163E and the outer valve seat portion 242E constitute a second flow path 315E that is partially parallel to the first flow path 152E and allows the oil liquid L to flow from the first chamber 22 to the second chamber 23. In other words, the second flow path 315E is a flow path that runs from the first chamber 22 toward the valve mechanism 321E and passes through the orifice 677 or the open valve mechanism 321E.

[0448] Here, the entire second flow path 315E leading from the first chamber 22 to the valve mechanism 321E may be parallel to the first flow path 152E. That is, it is sufficient that at least a portion of the second flow path 315E is parallel to the first flow path 152E. The second flow path 315E has an axial flow path 54 provided on the surface of the piston rod 31. Therefore, a portion of the second flow path 315E is provided on the surface of the piston rod 31.

[0449] The in-piston flow path 103 provided in the piston 21 receives the oil L from the first chamber 22 and reduces the pressure of the oil L passing through it with a first strength. The in-piston flow path 103 is provided in parallel to the first flow path 152E.

[0450] The orifice 673 provided in the valve mechanism 672 receives the oil liquid L from the first chamber 22 and reduces the pressure of the oil liquid L passing through it at a second strength that is stronger than the first strength. The orifice 673 is provided in parallel to the first flow path 152E. The orifice 673 branches off from a passage in the outer passage recess 596 of the second flow path 315E. The orifice 673 has a flow path cross-sectional area S2 that is smaller than the flow path cross-sectional area S1 of the in-piston flow path 103. The orifice 673 communicates with the pressure chamber 651 between the pilot valve 553, the pilot case 556, and the free valve 611 via a passage in the inner passage recess 595 and a passage in the inner through-hole 588. Therefore, the first chamber 22 communicates with the pressure chamber 651 via the first chamber-side flow path 156, the axial flow path 54, the intermediate chamber 237E, the passage in the passage groove 590, the passage in the outer passage recess 596, the orifice 673, the passage in the inner passage recess 595, and the passage in the inner through-hole 588. The orifice 673, the passage in the inner passage recess 595, and the passage in the inner through-hole 588 form a communication path 682 that branches off from the second flow path 315E and communicates with the pressure chamber 651.

[0451] Free valve 611 is provided in pressure chamber 651 to which hydraulic oil L is introduced from first chamber 22 via second flow path 315E and communication passage 682, and deforms in response to the internal pressure of pressure chamber 651. Free valve 611 and recess 582 of pilot case 556, which allows its deformation, constitute frequency sensitive mechanism 685 that varies the damping force in response to the piston frequency by changing the volume of pressure chamber 651. In other words, frequency sensitive mechanism 685 has free valve 611 provided in pressure chamber 651 that deforms in response to the internal pressure of pressure chamber 651, thereby changing the volume of pressure chamber 651.

[0452] The pressure chamber 651 applies internal pressure to the valve member 151E in the direction of the piston 21, i.e., in the valve closing direction to seat the valve disc 552 of the valve member 151E on the valve seat portion 105. The opening of the valve member 151E is adjusted by the pressure of this pressure chamber 651. That is, the opening of the valve mechanism 85E including the valve member 151E is adjusted by the pressure of the pressure chamber 651. The pressure chamber 651 is located downstream of the orifice 673 through which the oil liquid L flows from the first chamber 22 to the second chamber 23, and is capable of applying pressure to the valve member 151E in the valve closing direction by the oil liquid L.

[0453] The orifice 677 receives the oil L from the first chamber 22 and reduces the pressure of the oil L passing through it. The orifice 677 is provided in parallel to the first flow path 152E. The orifice 677 is provided in parallel to the orifice 673. The orifice 677 has a flow path cross-sectional area S3 that is smaller than the flow path cross-sectional area S1 of the in-piston flow path 103 and larger than the flow path cross-sectional area S2 of the orifice 673.

[0454] The valve mechanism 321E is provided in parallel with the orifice 677 in terms of hydraulic circuitry on the downstream side of the in-piston flow path 103 when the oil liquid L flows into the valve mechanism 321E from the first chamber 22. The valve mechanism 321E can allow the oil liquid L to flow into the second chamber 23, which is downstream when the oil liquid L flows into the valve mechanism 321E from the first chamber 22.

[0455] The valve mechanism 85E is provided in parallel to the in-piston flow path 103. The orifice 673 is provided downstream of the in-piston flow path 103 and in series with the in-piston flow path 103.

[0456] The pilot case 556, the pilot valve 553, and the free valve 611 constitute a valve opening control mechanism 686 that has a pressure chamber 651 and applies back pressure to the valve member 151E including the valve disc 641 of the pilot valve 553 to control the opening of the valve member 151E.

[0457] The disk 561 has an outer diameter that is smaller than the outer diameter of the valve member 163E and approximately equal to the outer diameter of the inner seat portion 574 of the pilot case 556.

[0458] Disk 562 has an outer diameter that is larger than the outer diameter of disk 558 .

[0459] The outer diameter of the annular member 182 is larger than the outer diameter of the disk 562 but smaller than the outer diameter of the valve member 163E. The annular member 182 has higher rigidity than the valve member 163E. The disk 562 and the annular member 182 abut against the valve member 163E when the valve member 163E deforms in the opening direction, thereby preventing the valve member 163E from deforming in the opening direction beyond a specified limit.

[0460] The check valve 655, which is composed of the support portion 646 of the pilot valve 553, the free valve 611, and the bottom portion 571 of the pilot case 556, is provided between the pressure chamber 651 and the passages in the variable chamber 652 and the outer through-hole 587, and restricts the flow of oil liquid L from the pressure chamber 651 to the second chamber 23 via the variable chamber 652 and the passages in the outer through-hole 587, while allowing the flow of oil liquid L from the second chamber 23 to the pressure chamber 651 via the passages in the outer through-hole 587 and the variable chamber 652.

[0461] The valve member 671 leaves the intermediate valve seat portion 575 when the pressure in the pressure chamber 651 reaches a predetermined pressure. As described above, the valve member 671, together with the intermediate valve seat portion 575, constitutes the valve mechanism 672 that opens and generates a damping force when the pressure in the pressure chamber 651 reaches a predetermined pressure. The valve mechanism 672 is provided outside the pilot case 556, and the valve member 671 is disposed opposite the bottom 571. An inner through-hole 588 is provided in the bottom 571 of the pilot case 556, facing the valve member 671 of the valve mechanism 672.

[0462] As described above, the valve member 163E, together with the outer valve seat portion 242E, constitutes the valve mechanism 321E. The valve mechanism 321E is provided in a portion of the second flow path 315E that is parallel to the first flow path 152E. The valve mechanism 321E is provided outside the pilot case 556, and the valve member 163E is disposed facing the bottom portion 571. The bottom portion 571 of the pilot case 556 has an outer through-hole 587 radially outward of the valve mechanism 321E. When the valve member 163E is released from the outer valve seat portion 242E and opens, it allows the oil L from the first chamber 22 to flow through the second flow path 315E to the second chamber 23. When the valve member 163E is seated on the outer valve seat portion 242E and closed, it prevents communication between the second chamber 23 and the second flow path 315E. The pilot case 556 is provided between the outer valve seat portion 242E and the valve member 163E and has an intermediate valve seat portion 575 of a valve mechanism 672 having an orifice 673 that restricts the communication of the oil liquid L more than at least the orifice 677.

[0463] A valve opening control mechanism 686 consisting of a pilot case 556, a pilot valve 553, and a free valve 611 includes a check valve 655 and a frequency sensitive mechanism 685. In the valve opening control mechanism 686, the free valve 611 deforms in accordance with the frequency of the reciprocating motion of the piston 21, thereby changing the capacity of a pressure chamber 651 that is always in communication with the first chamber 22 and the capacity of a variable chamber 652 that is always in communication with the second chamber 23.

[0464] The mounting shaft portions 33 are fitted inside the piston rod 31, and the annular member 125, disc 124, disc 123, multiple discs 122, disc 511, disc 121, piston 21, disc 551, valve disc 552, pilot valve 553, pilot case 556, multiple valve discs 557, disc 558, valve disc 559, multiple valve discs 560, disc 561, disc 562, and annular member 182 are stacked in this order on the end of the main shaft portion 32 on the mounting shaft portion 33 side. At this time, the pilot case 556 fits the seal portion 645 of the pilot valve 553 into the outer cylindrical portion 572. At this time, the free valve 611 is disposed between the bottom portion 571 of the pilot case 556 and the support portion 646 of the pilot valve 553.

[0465] With the parts arranged in this manner, a retainer 185 is coupled to the male threads 57 of the threaded shaft portion 44 that protrudes beyond the annular member 182. As a result, the inner circumferential sides or the entirety of the stacked parts from the annular member 125 to the annular member 182 are sandwiched between the end of the main shaft portion 32 of the piston rod 31 on the mounting shaft portion 33 side and the retainer 185, and are clamped in the axial direction. At this time, the valve disc 641 of the pilot valve 553, on the side opposite to the piston 21, abuts against the inner cylindrical portion 573 of the pilot case 556. At this time, the free valve 611 is not clamped in the axial direction, but is sandwiched between the support portion 646 of the pilot valve 553 and the pilot case 556.

[0466] The piston 21, the disk 121, the valve member 131E, the disk 551, and the valve member 151E constitute a first structural member 155E that divides the interior of the inner tube 2 of the cylinder 4 into a first chamber 22 and a second chamber 23. The first structural member 155E divides the interior of the inner tube 2 of the cylinder 4 into the first chamber 22, which serves as an upstream region on the upstream side during the extension stroke, and the second chamber 23, which serves as a downstream region on the downstream side during the extension stroke. The first structural member 155E has circular fixing holes 101, 111 that penetrate the first structural member 155E in the axial direction, a first flow path 152E that can communicate between the first chamber 22, which serves as the upstream region, and the second chamber 23, which serves as the downstream region, during the extension stroke, a flexible valve member 151E that can close the first flow path 152E, and a first-chamber-side flow path 156 in which at least a portion of the in-piston flow path 103 is arranged parallel to the first flow path 152E.

[0467] The pilot valve 553, pilot case 556, free valve 611, valve member 671, disk 558, and valve member 163E constitute a second structural member 331E (second structural member). The second structural member 331E has a first inner circumferential wall 232E that axially penetrates its center and through which the piston rod 31 is inserted, and a second inner circumferential wall 233E that is radially spaced further from the piston rod 31 than the first inner circumferential wall 232E, and has a central hole 231E that directly or indirectly communicates with the tip-side circumferential groove 53 of the piston rod 31. The second structural member 331E also has a valve mechanism 321E that includes an outer valve seat portion 242E that serves as a valve seat, and a valve member 163E that serves as a flexible valve body, and that allows flow through the first-chamber-side flow path 156 only in the direction from the first chamber 22 to the second chamber 23.

[0468] The second structural member 331E has an outer diameter smaller than that of the first structural member 155E. The second structural member 331E extends over the tip-side circumferential groove 53 and the tip-side cylindrical portion 43 of the piston rod 31.

[0469] The second structural member 331E has a pilot case 556 that communicates with the intermediate chamber 237E formed by the second inner wall 233E and the piston rod 31 and forms a pressure chamber 651 that stores oil liquid L, and applies a force in the closing direction to the valve member 151E depending on the pressure in the pressure chamber 651.

[0470] Next, the operation of the shock absorber 1E will be described.

[0471] During the extension stroke in which the piston rod 31 moves toward the extension side, when the piston speed is in the extremely low speed region X1 which is slower than the first predetermined speed and a low frequency is input in which the piston frequency is lower than the predetermined frequency, the oil liquid L from the first chamber 22 flows through the second flow path 315E which has the first chamber side flow path 156, the axial flow path 54, the intermediate chamber 237E, a passage in the passage groove 590, and a passage in the outer passage recess 596, and through the communicating passage 682 which has the orifice 673, the passage in the inner passage recess 595, and a passage in the inner through-hole 588, to the pressure chamber 651.

[0472] During the extension stroke of the low-frequency input in the extremely low speed range X1, the amplitude of the piston 21 is large. Therefore, a large amount of hydraulic fluid L flows into the pressure chamber 651, resulting in significant deformation of the free valve 611. Therefore, at the beginning of the extension stroke, the deformed free valve 611 immediately abuts against the recess 582, restricting further deformation, and preventing hydraulic fluid L from flowing from the first chamber 22 to the pressure chamber 651. At this time, the variable chamber 652 discharges hydraulic fluid L to the second chamber 23 through the passage in the outer through-hole 587. During the extension stroke of the low-frequency input in the extremely low speed range X1, when the free valve 611 abuts against the recess 582 and restricts further deformation, the volume of the pressure chamber 651 does not increase. This increases the pressure in the pressure chamber 651, restricting the opening of the valve member 151E of the valve mechanism 85E. In other words, the valve member 151E of the valve mechanism 85E does not open.

[0473] Therefore, during the extension stroke when a low frequency is input in the extremely low speed range X1, the oil L from the first chamber 22 flows through the second flow passage 315E, which has the first chamber-side flow passage 156, the axial flow passage 54, the intermediate chamber 237E, a passage in the passage groove 590, a passage in the outer passage recess 596, and the orifice 677, and then flows from the orifice 677 at the end of the second flow passage 315E to the second chamber 23. At this time, the oil L from the first chamber 22 is throttled by the in-piston flow passage 103 of the first chamber-side flow passage 156, and then further throttled by the orifice 677, which has a flow passage cross-sectional area smaller than that of the in-piston flow passage 103, before flowing into the second chamber 23. The oil L from the first chamber 22 also flows into the second chamber 23 through the first flow passage 132E, which includes the orifice 512. Therefore, during the low frequency is input in the extremely low speed range X1, a damping force with an orifice characteristic (the damping force is approximately proportional to the square of the piston speed) is generated. Therefore, in the extension stroke when a low frequency is input in the extremely low speed region X1, the damping force characteristic with respect to the piston speed is such that the rate of increase of the damping force becomes relatively high as the piston speed increases.

[0474] During the extension stroke, when the piston speed is in the very low speed region X1 which is slower than the first predetermined speed and the piston frequency is a high frequency input which is equal to or higher than a predetermined frequency, the oil liquid L from the first chamber 22 flows into the pressure chamber 651 through the second flow path 315E which includes the piston internal flow path 103 and the connecting passage 682 which branches off from the middle of the second flow path 315E and includes the orifice 673, just as when a low frequency is input in the very low speed region X1.

[0475] During the extension stroke when high-frequency input occurs in the extremely low speed range X1, the amplitude of the piston 21 is small. Therefore, the amount of oil L flowing into the pressure chamber 651 is small, and the deformation of the free valve 611 is small. Therefore, when oil L from the first chamber 22 is introduced into the pressure chamber 651 from the second flow path 315E via the communication passage 682, the free valve 611, which had previously been in a flat plate shape and abutting against the seat portion 580, elastically deforms to enter the recess 582 while blocking communication between the pressure chamber 651 and the variable chamber 652, thereby expanding the volume of the pressure chamber 651 and discharging oil L from the variable chamber 652 to the second chamber 23 via the passage in the outer through-hole 587.

[0476] While the free valve 611 is deformed in this manner, oil liquid L is introduced from the first chamber 22 into the pressure chamber 651, but because the amount of oil liquid L introduced from the first chamber 22 into the pressure chamber 651 is small, the deformation of the free valve 611 is small and the free valve 611 does not come into contact with the recess 582 and is not restricted in deformation as occurs during low-frequency input. In this manner, the bending of the free valve 611 suppresses the pressure rise in the pressure chamber 651, making it easier for the valve member 151E to open.

[0477] Therefore, during the extension stroke when a high frequency is input in the extremely low speed range X1, the oil L from the first chamber 22 flows through the second flow path 315E, including the in-piston flow path 103, and into the second chamber 23 from the orifice 677 at the end thereof. In addition, the oil L also flows into the second chamber 23 from the first flow path 152E, opening the valve mechanism 85E, i.e., by lifting the valve member 151E off the valve seat 105. Therefore, during the extension stroke when a high frequency is input in the extremely low speed range X1, a damping force with a valve characteristic (damping force approximately proportional to piston speed) is generated. During the extension stroke when a high frequency is input in the extremely low speed range X1, the damping force is lower than during the extension stroke when a low frequency is input. In other words, during the extension stroke when a high frequency is input in the extremely low speed range X1, the damping force characteristic is softer than during the extension stroke when a low frequency is input in the extremely low speed range X1. Furthermore, during the extension stroke when high frequency input is made in the very low speed region X1, the damping force characteristics relative to piston speed are such that the rate of increase in damping force relative to an increase in piston speed is lower than during the extension stroke when low frequency input is made in the very low speed region X1.

[0478] During the extension stroke, when the piston speed is equal to or greater than a first predetermined speed and is in a low-speed region X2 that is faster than a second predetermined speed that is faster than the first predetermined speed, and when a low-frequency input is made in which the piston frequency is lower than a predetermined frequency, oil liquid L from the first chamber 22 flows from the second flow path 315E that includes the piston internal flow path 103 to the pressure chamber 651 via the connecting passage 682 that includes the orifice 673, just as when a low-frequency input is made in the very low-speed region X1.

[0479] During the extension stroke of such a low-frequency input in the low-speed range X2, the amplitude of the piston 21 is large, similar to the low-frequency input in the very-low-speed range X1. Therefore, a large amount of hydraulic fluid L flows into the pressure chamber 651, resulting in significant deformation of the free valve 611. Therefore, at the beginning of the extension stroke, the deformed free valve 611 immediately abuts against the recess 582, restricting further deformation and preventing an increase in the volume of the pressure chamber 651. During the extension stroke of this low-frequency input in the low-speed range X2, the volume of the pressure chamber 651 does not increase, so the pressure in the pressure chamber 651 increases, inhibiting the opening of the valve member 151E of the valve mechanism 85E. That is, even during the extension stroke of the low-frequency input in the low-speed range X2, the valve member 151E of the valve mechanism 85E does not open.

[0480] During the extension stroke when a low-frequency input is made in the low-speed range X2, the flow rate of hydraulic oil L flowing from the first chamber 22 to the second flow path 315E is greater than during the extension stroke when a low-frequency input is made in the very-low speed range X1. Therefore, hydraulic oil L flows from the first chamber 22 to the second chamber 23 in the second flow path 315E while opening the valve mechanism 321E, i.e., while lifting the valve member 163E off the outer valve seat 242E. This generates a damping force with valve characteristics. Therefore, during the extension stroke when a low-frequency input is made in the low-speed range X2, the rate of increase in the damping force relative to an increase in piston speed is lower than during the extension stroke when a low-frequency input is made in the very-low speed range X1.

[0481] During the extension stroke, when the piston speed is equal to or greater than the first predetermined speed and is in the low-speed region X2 slower than the second predetermined speed, and when a high-frequency input is applied with a piston frequency equal to or greater than a predetermined frequency, the oil liquid L from the first chamber 22 flows into the pressure chamber 651 via the second flow path 315E including the piston internal flow path 103 and the connecting passage 682 including the orifice 673, just as when a high-frequency input is applied in the very low-speed region X1.

[0482] During the extension stroke when high-frequency input is performed in the low-speed range X2, the amplitude of the piston 21 is small, just as during high-frequency input in the very-low-speed range X1. Therefore, the amount of oil L flowing into the pressure chamber 651 is small, and the deformation of the free valve 611 is small. Therefore, the bending of the free valve 611 can suppress the pressure increase in the pressure chamber 651, making it easier for the valve member 151E to open.

[0483] Therefore, during the extension stroke when a high frequency input is made in the low speed range X2, the oil L from the first chamber 22 flows into the second chamber 23 in the second flow path 315E, opening the valve mechanism 321E, i.e., causing the valve member 163E to separate from the outer valve seat 242E. At the same time, the oil L from the first chamber 22 flows into the second chamber 23 in the first flow path 152E, opening the valve mechanism 85E, i.e., causing the valve member 151E to separate from the valve seat 105. Therefore, during the extension stroke when a high frequency input is made in the low speed range X2, the damping force is lower than during the low frequency input in the low speed range X2. Furthermore, during the extension stroke when a high frequency input is made in the low speed range X2, the damping force characteristic relative to the piston speed is such that the rate of increase in the damping force relative to an increase in piston speed is lower than during the low frequency input in the low speed range X2. Here, in the extension stroke when a high frequency is input in the low speed region X2, the characteristic of the damping force relative to the piston speed is such that the rate of increase of the damping force relative to the increase in piston speed is the same as in the extension stroke when a high frequency is input in the very low speed region X1.

[0484] During the extension stroke, when the piston speed is in the medium-high speed range X3 that is equal to or greater than a second predetermined speed and the piston frequency is a low frequency input that is lower than the predetermined frequency, the oil liquid L from the first chamber 22 flows into the pressure chamber 651 through the second flow path 315E that includes the piston internal flow path 103 and the connecting passage 682 that includes the orifice 673, just as during the extension stroke when a low frequency is input in the low speed range X2.

[0485] During the extension stroke of such a low-frequency input in the medium-to-high speed range X3, the amplitude of the piston 21 is large, similar to the low-frequency input in the low-speed range X2. Therefore, a large amount of hydraulic fluid L flows into the pressure chamber 651, resulting in significant deformation of the free valve 611. Therefore, at the beginning of the extension stroke, the deformed free valve 611 immediately abuts against the recess 582, restricting further deformation and preventing an increase in the volume of the pressure chamber 651. During the extension stroke of this low-frequency input in the medium-to-high speed range X3, the volume of the pressure chamber 651 does not increase, so the pressure in the pressure chamber 651 increases. However, the relationship of the forces (hydraulic pressure) acting on the valve member 151E is such that the opening force applied from the piston passage 81, which directly communicates with the first chamber 22, is greater than the closing force applied from the pressure chamber 651. Therefore, during this low-frequency input in the medium-to-high speed range X3, the valve mechanism 85E opens. That is, the valve member 151E opens away from the valve seat portion 105 of the piston 21. As a result, in addition to the flow to the second chamber 23 through the second flow path 315E by opening the valve mechanism 321E, a larger amount of hydraulic fluid L flows into the second chamber 23 through the first flow path 152E, which includes the passage between the valve member 151E and the valve seat portion 105, further suppressing the increase in damping force. Therefore, in the extension stroke of a low-frequency input in the medium to high speed range X3, the characteristic of the damping force relative to the piston speed is such that the rate of increase in damping force relative to an increase in piston speed is lower than that in the extension stroke of a low-frequency input in the low speed range X2.

[0486] During the extension stroke, when the piston speed is in the medium-high speed range X3 above a second predetermined speed and the piston frequency is a high-frequency input above a predetermined frequency, the oil liquid L from the first chamber 22 flows through the second flow path 315E including the piston internal flow path 103, as in the case of a high-frequency input in the low-speed range X2, and flows into the pressure chamber 651 via the connecting passage 682 including the orifice 673.

[0487] During the extension stroke when high frequency input is made in the medium to high speed range X3, the amplitude of the piston 21 is small, similar to the extension stroke when high frequency input is made in the low speed range X2. Therefore, the amount of oil L flowing into the pressure chamber 651 is small, and the deformation of the free valve 611 is small. Therefore, by bending the free valve 611, the pressure rise in the pressure chamber 651 can be suppressed, and the valve member 151E can be easily opened.

[0488] Therefore, during the extension stroke when a high frequency is input in the medium-to-high speed range X3, the oil L from the first chamber 22 flows into the second chamber 23 through the second flow path 315E, opening the valve mechanism 321E, i.e., separating the valve member 163E from the outer valve seat 242E. At the same time, the oil L from the first chamber 22 flows into the second chamber 23 through the first flow path 152E, opening the valve mechanism 85E, i.e., separating the valve member 151E from the valve seat 105. Therefore, during the extension stroke when a high frequency is input in the medium-to-high speed range X3, the damping force is lower than during the low frequency input in the medium-to-high speed range X3. Here, during the extension stroke when a high frequency is input in the medium-to-high speed range X3, the damping force characteristics relative to piston speed are such that the rate of increase in damping force relative to an increase in piston speed is similar to that during the extension stroke when a high frequency is input in the low speed range X2.

[0489] During the compression stroke in which the piston rod 31 moves toward the compression side, in the extremely low speed region X4 where the piston speed is slower than the fourth predetermined speed, the hydraulic oil L from the second chamber 23 flows into the first chamber 22 via the compression-side piston passage 82 and the orifice 512 of the valve member 131E of the valve mechanism 86E. At the same time, the hydraulic oil L from the second chamber 23 flows into the second flow path 315E through the orifice 677 and into the first chamber 22 via the second flow path 315E including the in-piston flow path 103. At the same time, the hydraulic oil L from the second chamber 23 passes through the passage in the outer through-hole 587 and the variable chamber 652, opens the check valve 655, and flows from the pressure chamber 651 and the communicating passage 682 through the orifice 673 to the first chamber 22 via the second flow path 315E including the in-piston flow path 103. Therefore, during the compression stroke in the extremely low speed region X4, a damping force with orifice characteristics is generated. Therefore, in the compression stroke in the extremely low speed region X4, the damping force characteristic with respect to the piston speed is such that the rate of increase of the damping force becomes relatively high as the piston speed increases.

[0490] During the compression stroke in the low-speed region X5, where the piston speed is equal to or greater than the fourth predetermined speed and slower than the fifth predetermined speed, oil L flows from the second chamber 23 through the passage in the outer through-hole 587 and the variable chamber 652, and flows through the pressure chamber 651 and the communicating passage 682 while opening the check valve 655. This causes the valve mechanism 672 at the end of the communicating passage 682 to open, i.e., the valve member 671 to separate from the intermediate valve seat 575, and then flows into the first chamber 22 via the second flow path 315E including the in-piston flow path 103. Therefore, during the compression stroke in the low-speed region X5, a damping force with a valve characteristic is generated. Therefore, during the compression stroke in the low-speed region X5, the rate of increase in the damping force relative to an increase in piston speed is lower than during the compression stroke in the very-low-speed region X4.

[0491] During the compression stroke in the medium to high speed range X6, where the piston speed is equal to or higher than the fifth predetermined speed, the oil L flows from the second chamber 23 to the first chamber 22 via the second flow path 315E including the in-piston flow path 103, while opening the valve mechanism 672, as in the compression stroke in the low speed range X5. During the compression stroke in the medium to high speed range X6, the oil L is also introduced from the second chamber 23 into the compression-side piston passage 82, opening the valve mechanism 86E, i.e., while separating the valve member 131E from the valve seat portion 115, and flows into the first chamber 22. For this reason, during the compression stroke in the medium to high speed range X6, the characteristic of the damping force relative to the piston speed is such that the rate of increase of the damping force relative to an increase in piston speed is lower than during the compression stroke in the low speed range X5.

[0492] The shock absorber 1E of the sixth embodiment has a first structural member 155E that divides the inner tube 2 of the cylinder 4 into a first chamber 22 and a second chamber, a piston rod 31, and a second structural member 331E.

[0493] The first structural member 155E has circular fixing holes 101, 111 that penetrate in the axial direction, a first flow path 152E that can connect the first chamber 22 and the second chamber 23, a flexible valve member 151E that can close the first flow path 152E, and a first chamber side flow path 156 that is at least partially arranged parallel to the first flow path 152E.

[0494] The second structural member 331E has a smaller diameter than the first structural member 155E and extends across the tip-side circumferential groove 53 and the tip-side cylindrical portion 43. The second structural member 331E has a first inner circumferential wall 232E that axially penetrates its center and through which the piston rod 31 is inserted, and a second inner circumferential wall 233E that is radially spaced further from the piston rod 31 than the first inner circumferential wall 232E, and has a central hole 231E that directly or indirectly communicates with the tip-side circumferential groove 53, an outer valve seat portion 242E that serves as a valve seat, and a valve member 163E that is a flexible valve body, and a valve mechanism 321E that allows flow through the axial flow path 54 only in the direction from the first chamber 22 to the second chamber 23.

[0495] As described above, the shock absorber 1E has an axial flow path 54 that communicates with the first chamber-side flow path 156, at least a portion of which is parallel to the first flow path 152E that can be closed by the valve member 151E, and a tip-side circumferential groove 53, which is a circumferential groove, formed in the piston rod 31. This allows the shock absorber 1E to have a structure in which a large-diameter hole portion as a circumferential groove is not formed in the inner seat portion 574, where the valve member 671 is stacked in the second structural member 331E. Therefore, the shock absorber 1E does not require a highly rigid component that allows for high tightening pressure when tightening the valve member 671, thereby ensuring design flexibility. Furthermore, the shock absorber 1E does not require circumferential phase alignment between the second structural member 331E and the piston rod 31.

[0496] In the shock absorber 1E, the second structural member 331E has a pilot case 556 that communicates with an intermediate chamber 237E formed by the second inner circumferential wall 233E and the piston rod 31, and forms a pressure chamber 651 that stores hydraulic fluid L, and applies a force to the valve member 151E in the valve closing direction according to the pressure in the pressure chamber 651. This makes it possible to control the damping force characteristics of the valve member 151E in detail.

[0497] According to the above-described aspects of the present invention, it is possible to provide a shock absorber that can ensure a degree of freedom in design, and thus the industrial applicability is great.

[0498] DESCRIPTION OF SYMBOLS 1, 1A to 1E... shock absorber, 4... cylinder (housing), 22... first chamber (upstream region), 23... second chamber (downstream region), 31, 31B to 31D... piston rod (shaft member), 41, 41D... base end side cylindrical portion (first cylindrical portion), 43... tip end side cylindrical portion (second cylindrical portion), 44... threaded shaft portion (second cylindrical portion), 51, 51D... base end side circumferential groove (second circumferential groove), 53, 53D... tip end side circumferential groove (first circumferential groove), 54, 54B, 54D... axial flow path, 101, 101D, 111... Fixing hole, 151, 151D, 151E... valve member (first valve member), 152, 152D, 152E... first flow path (first flow path), 155, 155A, 155D, 155E... first structural member (first structural member), 156, 156D... first chamber side flow path (second flow path), 163, 163D, 163E... valve member (first check valve body), 167... valve member (second check valve body), 178, 416... case member (partition wall member), 231, 231B to 231E... center hole, 23 2, 232D, 232E...first inner circumferential wall (first inner circumferential wall), 233, 233D, 233E...second inner circumferential wall (second inner circumferential wall), 234, 234D, 234E...insertion hole, 235, 235B, 235D, 235E...extension portion, 237, 237B to 237E...intermediate chamber, 242, 242D...valve seat portion (first check valve seat), 242E...outer valve seat portion (first check valve seat), 245...valve seat portion (second check valve seat), 281...passage portion (third flow path, axial flow path), 2 86, 286D...first chamber communication chamber (storage chamber), 301...valve mechanism (second check valve mechanism), 317, 317B, 318B...radial flow path (fourth flow path), 321, 321D, 321E...valve mechanism (first check valve mechanism), 331, 331A, 331D, 331E...second structural member (second structural member), 381...internal circumferential groove (first circumferential groove), 481...sliding member (partition member), 491...pressure chamber (storage chamber), 556...pilot case (partition member), 651...pressure chamber (storage chamber).

Claims

1. A shock absorber that uses a fluid, comprising: a bottomed cylindrical housing having a cylindrical portion and a bottom; a first structural member dividing the housing into an upstream region on an upstream side and a downstream region on a downstream side; a rod-shaped shaft member; and a second structural member, wherein the first structural member has: a circular fixing hole penetrating in the axial direction; a first flow path that can communicate between the upstream region and the downstream region; a first valve member that is flexible and can close the first flow path; and a second flow path at least a portion of which is provided parallel to the first flow path, and the shaft member has: a first cylindrical portion that is a cylindrical portion that is inserted into the fixing hole; an axial flow path that is a flow path to which the second flow path is connected and leads toward the downstream region; a first circumferential groove that is a circumferential groove provided at the end of the axial flow path on the downstream region side; and a second cylindrical portion that is a cylindrical portion provided on the downstream region side of the first circumferential groove, and a central hole having a diameter smaller than that of the first structural member and extending over the first circumferential groove and the second cylindrical portion, the central hole having a first inner circumferential wall penetrating the center in the axial direction and through which the shaft member is inserted, and a second inner circumferential wall that is radially further away from the shaft member than the first inner circumferential wall, the central hole directly or indirectly communicating with the first circumferential groove, and a first check valve mechanism including a first check valve seat which is a valve seat, and a first check valve body which is a flexible valve body, the first check valve mechanism allowing flow through the second flow path only in a direction from the upstream region to the downstream region.

2. A shock absorber as described in claim 1, wherein the second structural member further comprises: a second check valve seat which is a valve seat; and a second check valve body which is a flexible valve body arranged in the second cylindrical portion, and which allows the fluid to flow only in a direction from the downstream region to the upstream region.

3. A shock absorber as described in claim 2, wherein the second structural member further has a partition member that communicates with an intermediate chamber formed by the second inner wall and the axial member and forms a storage chamber for storing the fluid, the first check valve mechanism further has a third flow path that communicates from the storage chamber to the first check valve seat, and the fluid flows from the second flow path through the axial flow path, the intermediate chamber, the storage chamber, and the third flow path to the downstream region.

4. A shock absorber as described in claim 2, wherein the first check valve mechanism further has a fourth flow passage communicating from the central hole to the first check valve seat, and the fluid flows from the second flow passage through the axial flow passage, the central hole, and the fourth flow passage to the downstream region.

5. A shock absorber as described in claim 1, wherein the shaft member is further provided with a second circumferential groove which is a circumferential groove at a predetermined location of the axial flow path, the second circumferential groove being connected to the first check valve seat, and the second structural member further comprises: a partition member which is connected to an intermediate chamber formed by the second inner wall and the shaft member and forms a storage chamber for storing the fluid, and a sliding member which applies a force in a valve closing direction to the first check valve body in accordance with the pressure in the storage chamber.

6. A shock absorber as described in claim 1, wherein the second structural member further has a partition member that communicates with an intermediate chamber formed by the second inner wall and the shaft member and forms a storage chamber for storing the fluid, and applies a force in a valve closing direction to the first valve member according to the pressure in the storage chamber.

7. A shock absorber using a fluid, comprising: a bottomed cylindrical housing having a cylindrical portion and a bottom; a first structural member dividing the housing into an upstream region on an upstream side and a downstream region on a downstream side; a rod-shaped shaft member; and a second structural member, wherein the first structural member has: a circular fixing hole penetrating in the axial direction; a first flow path capable of communicating the upstream region and the downstream region; a first valve member that is flexible and capable of closing the first flow path; and a second flow path at least a portion of which is provided parallel to the first flow path, wherein the shaft member has: a first cylindrical portion that is a cylindrical portion inserted into the fixing hole; an axial flow path that is a flow path to which the second flow path is connected and which leads toward the downstream region; and a second cylindrical portion that is a cylindrical portion provided on the downstream region side of the axial flow path, wherein the second structural member has a smaller diameter than the first structural member and extends across the axial flow path and the second cylindrical portion, a central hole including a first inner circumferential wall penetrating through a center in the axial direction and through which the shaft member is inserted, a first circumferential groove provided inside the thickness direction of the second structural member and which is an annular space with which the axial flow passage is communicated, and one or more second inner circumferential walls which communicate with the first circumferential groove and extend radially beyond the first inner circumferential wall, and a first check valve mechanism including a first check valve seat which is a valve seat, and a first check valve element which is a flexible valve element disposed in the axial flow passage, and which allows the fluid to flow only in a direction from the downstream region to the upstream region.

8. A shock absorber using a fluid, comprising: a bottomed cylindrical housing having a cylindrical portion and a bottom; a first structural member dividing the housing into an upstream region on an upstream side and a downstream region on a downstream side; a rod-shaped shaft member; and a second structural member, wherein the first structural member has: a circular fixing hole penetrating in the axial direction; a first flow path capable of communicating the upstream region and the downstream region; a first valve member that is flexible and capable of closing the first flow path; and a second flow path at least a portion of which is provided parallel to the first flow path, wherein the shaft member has: a first cylindrical portion that is a cylindrical portion inserted into the fixing hole; an axial flow path that is a flow path to which the second flow path is connected and which leads toward the downstream region; and a second cylindrical portion that is a cylindrical portion provided on the downstream region side of the axial flow path, wherein the second structural member has a smaller diameter than the first structural member and extends across the axial flow path and the second cylindrical portion, a first check valve mechanism that allows the fluid to flow only in a direction from the upstream region to the downstream region; and a radial flow path that is provided opposite the axial flow path and communicates with the first check valve mechanism.

9. A shock absorber as described in claim 8, wherein the second structural member further has one or more extension portions extending radially from the insertion hole and formed from a surface opposite to the surface facing the first structural member to a position communicating with the axial flow path, a partition member communicating with the extension portions and forming a storage chamber for storing the fluid, and an axial flow path connecting the storage chamber and the first check valve mechanism.

10. A shock absorber using a fluid, comprising: a bottomed cylindrical housing having a cylindrical portion and a bottom; a first structural member dividing the housing into an upstream region on an upstream side and a downstream region on a downstream side; a rod-shaped shaft member; and a second structural member, wherein the first structural member has: a circular fixing hole penetrating in the axial direction; a first flow path capable of communicating the upstream region and the downstream region; a first valve member that is flexible and capable of closing the first flow path; and a second flow path at least a portion of which is provided parallel to the first flow path, wherein the shaft member has: a first cylindrical portion that is a cylindrical portion inserted into the fixing hole; an axial flow path that is a flow path to which the second flow path is connected and which leads toward the downstream region; and a second cylindrical portion that is a cylindrical portion provided on the downstream region side of the axial flow path, wherein the second structural member has a smaller diameter than the first structural member and extends across the axial flow path and the second cylindrical portion, a central hole including a first inner circumferential wall penetrating through a center in the axial direction and through which the shaft member is inserted, and one or more second inner circumferential walls which are connected to the axial flow passage and extend radially beyond the first inner circumferential wall, and a first check valve mechanism which includes a first check valve seat which is a valve seat, and a first check valve element which is flexible and is disposed in the axial flow passage, and which only allows the fluid to flow in a direction from the upstream region to the downstream region.

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