Shock absorber

Abstract

To provide a shock absorber which enables assembly to be performed reliably and easily.SOLUTION: In a shock absorber 1, a first passage 132 and a second passage 152 in which a working fluid flows from a chamber at the upstream side to a chamber at the downstream side are provided in a piston 21 configured to move in a cylinder 4. A first damping force generation mechanism DF1 is provided in the first chamber 132 and a second damping force generation mechanism DF2, a valve seat member 166, and a cap member 178 are provided at a second passage 152 side. A first sub valve 321 and a second sub valve 301 are provided at the second damping force generation mechanism side. A working fluid passage hole 195 is provided at the cap member 178 and relief mechanisms 335, 336 are provided at the second passage 152 side. The valve seat member 166 is fitted in the cap member by placing an outer peripheral surface thereof in contact with an inner surface of a peripheral wall part of the cap member and press-fitting the outer peripheral surface in the cap member. A part of the outer peripheral surface of the valve seat member 166 has an introduction part 166b having a diameter smaller than an inner diameter of a peripheral wall of the cap member.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

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

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-186977 Summary of the Invention [Problem to be solved by the invention]

[0004] The shock absorber described above has an on-off valve provided on each of the piston and the valve seat member, and can open one valve when the piston speed is high during the same stroke and open the other valve when the piston speed is low. In the case of such a shock absorber, the valve seat member is housed in a cap member, and the on-off valve is incorporated into the cap member. When assembling the valve seat member inside the cap member, it is necessary to press-fit the valve seat member into the cap member via a seal member to ensure liquid-tightness. However, when the valve seat member is press-fitted into the cap member, if the resistance to pressing is large, there is a risk that the cap member will be deformed.

[0005] An object of the present invention is to provide a shock absorber having a structure in which a valve seat member is press-fitted into the inside of a cap member while preventing deformation of the cap member. [Means for solving the problem]

[0006] In order to achieve the above object, a first aspect of the shock absorber according to the present invention includes a cylinder in which a working fluid is sealed, a piston slidably provided within the cylinder and dividing the interior of the cylinder into one side chamber and another side chamber, a piston rod connected to the piston and extending to the outside of the cylinder, a first passage and a second passage through which the working fluid flows from an upstream chamber to a downstream chamber within the cylinder as the piston moves, a first damping force generating mechanism provided in the first passage provided in the piston and generating a damping force, and a second damping force generating mechanism provided in the second passage provided in an annular valve seat member arranged in the other side chamber and parallel to the first passage, generating a damping force, the valve seat member is provided within the cap member, the first sub-valve is provided in the other-side chamber, and the second sub-valve is provided in a cap chamber between a bottom of the cap member and the valve seat member; the second passage has an orifice disposed upstream or downstream of a flow at which the first sub-valve opens, and a relief mechanism is provided that opens a second damping force generating mechanism in a low piston speed region; the valve seat member has an outer circumferential surface in contact with an inner surface of a peripheral wall of the cap member and is press-fitted into the cap member, and a part of the outer circumferential surface of the valve seat member has an introduction portion whose diameter is smaller than the inner diameter of the peripheral wall of the cap member. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a shock absorber configured so that a valve seat member can be press-fitted into a cap member while preventing deformation of the cap member. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing a shock absorber according to a first embodiment of the present invention. [Figure 2] 1 is a partial front view showing a main portion of a piston rod in a shock absorber according to a first embodiment of the present invention. FIG. [Figure 3] 1 is a partial cross-sectional view showing a piston, a valve seat member, a cap member, etc. in a shock absorber according to a first embodiment of the present invention. [Figure 4] 1 is a partial cross-sectional view showing a valve seat member, a cap member, etc. in a shock absorber according to a first embodiment of the present invention. [Figure 5] 1 is a plan view showing a valve seat member in a shock absorber according to a first embodiment of the present invention. FIG. [Figure 6] FIG. 2 is a bottom view showing a valve seat member in the shock absorber of the first embodiment according to the present invention. [Figure 7] 2 is an exploded perspective view of the lower surface side showing a cap member, a support member, etc. in the shock absorber of the first embodiment according to the present invention. FIG. [Figure 8] FIG. 6 is a partial cross-sectional view showing a piston, a valve seat member, a cap member, etc. in a shock absorber according to a second embodiment of the present invention. [Figure 9] FIG. 6 is a partial cross-sectional view showing a valve seat member, a cap member, etc. in a shock absorber according to a second embodiment of the present invention. [Figure 10] FIG. 10 is an exploded perspective view of the lower surface side showing a cap member, a support member, etc. in a shock absorber according to a second embodiment of the present invention. [Figure 11] FIG. 10 is a partial cross-sectional view showing a valve seat member, a cap member, etc. in a shock absorber according to a third embodiment of the present invention. [Figure 12] FIG. 10 is a partial cross-sectional view showing a valve seat member, a cap member, etc. in a shock absorber according to a fourth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] [First embodiment] The shock absorber of the first embodiment will be described below with reference to FIGS. The shock absorber 1 of the first embodiment is a shock absorber used in suspension devices 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 devices for four-wheeled automobiles. As shown in FIG. 1, the shock absorber 1 is a double-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.

[0010] 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 axial side of the bottom portion 9 opposite the tubular portion 8.

[0011] 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.

[0012] 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 is engaged 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 is engaged 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.

[0013] 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 peripheral portion 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 processing such as curling. The seal member 18 is sandwiched between this 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.

[0014] The shock absorber 1 includes a piston 21. The piston 21 is slidably provided in a cylinder 4. The piston 21 is slidably provided in 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 provided between the piston 21 and the rod guide 13 in the inner tube 2. The second chamber 23 is provided between the piston 21 and the valve body 12 in the inner tube 2. The second chamber 23 is defined as a reservoir chamber 5 by the valve body 12. In the cylinder 4, a working fluid (oil) L, which is a fluid, is sealed in the first chamber 22 and the second chamber 23. In the cylinder 4, a gas G and the working fluid L, which are fluids, are sealed in the reservoir chamber 5. Therefore, the shock absorber 1 is a hydraulic shock absorber that uses a working fluid L, which is a fluid.

[0015] The shock absorber 1 is equipped with a piston rod 31 (shaft member) which 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 to the outside of 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.

[0016] 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.

[0017] 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.

[0018] The rod guide 13 supports the piston rod 31 relative to the cylinder 4 so that it can move in the axial direction 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 out to the outside.

[0019] 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.

[0020] 2, 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.

[0021] 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 continues around the entire circumferential direction of the base-end side cylindrical portion 41.

[0022] The tip-side cylindrical portion 43 is a cylindrical portion and is provided on the opposite side of the base-side cylindrical portion 41 from the main shaft portion 32 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 with and has the same diameter as the outer peripheral surface 41a of the base-side cylindrical portion 41.

[0023] 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-side circumferential groove 51 (second circumferential groove), a pair of axial grooves 52, and a tip-end-side circumferential groove 53 (first circumferential groove).

[0024] The pair of outer end surfaces 42a each have the shape of a part of a cylindrical surface that is coaxial with and has the same diameter as the outer peripheral surface 41a of the base-end side cylindrical portion 41 and the outer peripheral 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 peripheral surface 41a of the base-end side cylindrical portion 41 and the outer peripheral 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.

[0025] The base-end circumferential groove 51 is provided at the end of the intermediate shaft 42 on the base-end cylindrical portion 41 side in the axial direction. The base-end circumferential groove 51 is recessed inward in the radial direction of the base-end circumferential groove 51 and the intermediate shaft 42 from the outer circumferential surface 41 a of the base-end cylindrical portion 41 and the pair of outer end surfaces 42 a of the intermediate shaft 42. The base-end circumferential groove 51 has an annular shape that continues around the entire circumferential direction of the intermediate shaft 42.

[0026] The tip-side circumferential groove 53 is provided at the 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 43a of the tip-side cylindrical portion 43 and the pair of outer end faces 42a 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.

[0027] The pair of axial grooves 52 are recessed radially inward from the pair of outer end surfaces 42a of the intermediate shaft portion 42. The pair of axial grooves 52 have the same shape, and the inner bottom surface in the radial direction of the intermediate shaft portion 42 is a flat surface 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 42a 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.

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] 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 other.

[0033] The passages in the multiple 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 can communicate between the first chamber 22 and the second chamber 23. The passages in the multiple 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 can communicate between the first chamber 22 and the second chamber 23.

[0034] 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, that is, 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, thereby generating a damping force.

[0035] 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, that is, 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.

[0036] The piston passage 82 is provided as a part of a first passage 132, which will be described later, and a valve mechanism 86 is provided in the first passage 132, thereby forming a first damping force generating mechanism DF1. The piston passage 81 is provided as part of a second passage 152, which will be described later, and a valve mechanism 85 is provided in the second passage 152, thereby forming a second damping force generating mechanism DF2.

[0037] As a result, the piston passage 81 and the piston passage 82 communicate with each other so that oil L, which is a fluid, flows between the first chamber 22 and the second chamber 23 as the piston 21 moves. As a result, the oil L passes through the piston passage 81 when the piston rod 31 and the piston 21 move toward the extension side, and the oil L passes through the piston passage 82 when the piston rod 31 and the piston 21 move toward the compression side.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] 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 a 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.

[0042] The first piston body 91 is formed with an engagement 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 engagement protrusion 108 is provided partially in the circumferential direction of the first piston body 91.

[0043] 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.

[0044] 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 portion 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 portion 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.

[0045] 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.

[0046] 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 in which 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.

[0047] 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 addition, 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.

[0048] The fixing hole 111 of the piston 21 is fitted onto the outer peripheral surface 41a (shown in FIG. 2) of the base-side cylindrical portion 41 of the piston rod 31, and the fixing hole 101 (shown in FIG. 3) is fitted onto a pair of outer end surfaces 42a (shown in FIG. 2) 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 circumferentially aligning the piston 21 with the piston rod 31.

[0049] 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 disc 121 and multiple discs 122. On the axial side of the multiple discs 122 opposite to disc 121, in order from the multiple discs 122 side, there are provided one disc 123, one disc 124, and one annular member 125. The discs 121 to 124 and the annular member 125 are all circular flat plates with holes, and the outer peripheral surface 41a (shown in FIG. 2) of the base-end cylindrical portion 41 of the mounting shaft portion 33 is fitted into the inside of each of them.

[0050] 3, the disc 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 disc 121 is in constant contact with the inner seat portion 116.

[0051] Of the multiple discs 122, the disc 122 closest to 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 disc 121 in the axial direction is capable of being seated on the valve seat portion 115.

[0052] The disc 123 has an outer diameter smaller than the outer diameter of the plurality of discs 122 and slightly smaller than the outer diameter of the inner seat portion 116 of the piston 21 . The disk 124 has an outer diameter larger than that of the disk 123 .

[0053] The annular member 125 has an outer diameter smaller than that of the disk 124 and larger than that of the end of the main shaft portion 32 of the piston rod 31 on the mounting shaft portion 33 side in the axial direction. The annular member 125 is thicker and more rigid than the discs 121 to 124, and abuts against the end of the main shaft portion 32 on the attachment shaft portion 33 side in the axial direction.

[0054] 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 is lifted from 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 abuts against the valve member 131 using the discs 124, thereby suppressing deformation of the valve member 131 in the opening direction beyond a specified limit.

[0055] 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 passage (first flow path) 132. The first passage 132 is provided in the piston 21. The first passage 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 passage 132. The first passage 132 is provided in the piston 21 that includes the valve seat portion 115, and oil L passes through the first passage 132 when the piston rod 31 and the piston 21 move toward the compression side.

[0056] 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 passage 132 is not a passage that constantly connects the first chamber 22 and the second chamber 23. The first passage 132 and the valve mechanism 86 are provided in the piston 21 to form a first damping force generating mechanism DF1.

[0057] 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 disc 141 and multiple discs 142. On the axially opposite side of the multiple discs 142 from disc 141, in order from the multiple discs 142 side, one disc 143 and multiple discs 144 are provided. The discs 141 to 144 are all circular flat plates with holes, and each has a pair of outer end surfaces 42a (shown in FIG. 2) of the intermediate shaft portion 42 of the mounting shaft portion 33 fitted into its inner side.

[0058] 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.

[0059] Of the multiple discs 142, the disc 142 closest to 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 disc 141 in the axial direction is capable of being seated on the valve seat portion 105.

[0060] 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 . The plurality of disks 144 have an outer diameter larger than that of the disk 143.

[0061] 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 lifted 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 it and the valve seat portion 105, 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.

[0062] 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 part of a second passage 152 (second flow path). The second passage 152 is formed in the piston 21. The second passage 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 second passage 152. The second passage 152 is provided in the piston 21 that includes the valve seat portion 105, and oil L passes through the second passage 152 when the piston rod 31 and the piston 21 move toward the extension side.

[0063] 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 against it, even when the valve seat portion 105 and the valve member 151 are in contact with each other. Therefore, the second passage 152 is not a flow path that constantly communicates between the first chamber 22 and the second chamber 23. The second passage 152 and the valve mechanism 85 provided in the piston 21 constitute part of the second damping force generating mechanism DF2. The second damping force generating mechanism DF2 also includes a first sub-valve 321, a second sub-valve 301, and relief mechanisms 335 and 336, which will be described later.

[0064] 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 in-piston flow path 103 and a 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 constitute a first-chamber-side flow path 156 (second flow path). The in-piston flow path 103, which is at least a part of the first-chamber-side flow path 156, is provided in parallel to the second passage 152.

[0065] 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 second passage 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 second passage 152, and a first-chamber-side passage 156 in which at least a portion of the in-piston passage 103 is arranged parallel to the second passage 152.

[0066] 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 valve seat member 166 having an O-ring (seal member) 165 provided on its outer periphery. Also, on the axial side of valve seat member 166 opposite valve member 163, there are provided, in order from the valve 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. Furthermore, 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 cap member 178 (partition member), and one annular member 182.

[0067] The mounting shaft portion 33 of the piston rod 31 is fitted inside the disks 160, 162, 168, 170, 172, 173, 174, 176, 181, spring members 161, 169, valve members 163, 167, valve seat member 166, disc spring 177, cap member 178, and annular member 182. At this time, the disk 160, spring member 161, disk 162, valve member 163, and valve seat member 166 are fitted inside the pair of outer end surfaces 42a (shown in FIG. 2) of the intermediate shaft portion 42 of the mounting shaft portion 33. As shown in FIG. 4, the valve 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 cap member 178, and the annular member 182 each have the outer circumferential surface 43a (shown in FIG. 2) of the tip-side cylindrical portion 43 of the mounting shaft portion 33 fitted into their respective interiors.

[0068] 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 screwed onto the male threads 57 on the outer periphery of the threaded shaft portion 44. The retainer 185 abuts against the disc 181.

[0069] The disks 160, 162, 168, 170, 172, 173, 174, 176, 181, spring members 161, 169, valve members 163, 167, valve seat member 166, disc spring 177, cap member 178, and annular member 182 shown in FIG. 4 are each clamped in the axial direction at least on their radially inner sides by the main shaft portion 32 of the piston rod 31 shown in FIG. 3 and a retainer 185.

[0070] The disks 160, 162, 168, 170, 172, 173, and 176 and the valve members 163 and 167 shown in FIG. 4 are all circular flat plates with holes.

[0071] The cap member 178 is a cylindrical, bottomed, one-piece molded product made of resin. The cap member 178 has a bottom portion 191, an intermediate tapered portion 192, and a peripheral wall portion 193. As shown in FIG. 3, the maximum outer diameter of the cap member 178 is approximately the same as the outer diameter of the piston 21.

[0072] As shown in FIG. 4, the bottom portion 191 is in the shape of a flat disk with holes. 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.

[0073] The peripheral wall portion 193 extends in the axial direction of the intermediate tapered portion 192 from an edge portion of the intermediate tapered portion 192 opposite the bottom portion 191, in the opposite direction from the bottom portion 191. The peripheral wall portion 193 is funnel-shaped, and the inner diameter of the peripheral wall portion 193 on the opposite side (the side closer to the piston 21) is larger than the inner diameter on the bottom portion 191 side. The thickness of the peripheral wall portion 193 is approximately the same as the thickness of the bottom 191. The peripheral wall portion 193 is a tapered wall in which the inner diameter on the side closer to the bottom 191 is larger than the inner diameter on the opposite side. Therefore, a tapered surface 193a is formed on the inner surface of the peripheral wall portion 193, in which the inner diameter on the side closer to the bottom 191 is larger than the inner diameter on the opposite side. The peripheral wall portion 193 has the largest outer diameter on the side closest to the piston 21, and this outer diameter is slightly smaller than the outer diameter of the piston 21.

[0074] The cap member 178 is fitted onto the inner peripheral portion of the bottom 191 of the piston rod 31 at the outer peripheral surface 43a shown in FIG. 2. As shown in FIGS. 4 and 7, the bottom 191 is formed with a plurality of working fluid passage holes 195. The plurality of working fluid passage holes 195 penetrate the bottom 191 in the axial direction of the bottom 191. The plurality of working fluid 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 cap member 178 is oriented so that the bottom 191 is located on the opposite side of the disk 144 from the peripheral wall portion 193 in the axial direction.

[0075] Arranged radially inside the cap member 178 are the valve seat member 166, the valve members 163 and 167, the discs 168, 170, 172, 173, 174 and 176, the spring member 169 and the disc spring 177.

[0076] The disc spring 177 has flexibility. The disc spring 177 has an inner annular portion 201 and an outer tapered portion 202.

[0077] 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. The outer tapered portion 202 has a conical cylindrical shape that spreads outward in the radial direction from the outer peripheral edge of the inner annular portion 201 and toward one side in the axial direction.

[0078] The inner annular portion 201 of the disc spring 177 abuts against the bottom portion 191 of the cap member 178, and the outer tapered portion 202 moves away from the bottom portion 191 in the axial direction of the bottom portion 191 as it moves radially outward. When the inner annular portion 201 of the disc spring 177 abuts against the bottom portion 191 of the cap member 178 , the passage hole 205 of the inner annular portion 201 communicates with the working fluid passage hole 195 of the cap member 178 .

[0079] The outer diameter of the disk 176 is smaller than the outer diameter of the inner annular portion 201 of the disc spring 177 . The disc 174 is flexible. The outer diameter of the disc 174 is larger than the outer diameter of the disc spring 177, i.e., the outer diameter of the outer tapered portion 202. The disc spring 177 has a circular outer peripheral edge portion on the radially outer side of the outer tapered portion 202 that is in pressure contact with the outer peripheral edge of the disc 174 over the entire circumference.

[0080] 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.

[0081] The disc 173 is flexible. The outer diameter of the disc 173 is smaller than the outer diameter of the disc 174. The outer diameter of the disc 173 is large enough to close the communication hole 211 of the disc 174. The disc 173 abuts against the disc 174 over the entire circumference. As a result, the disc 173 closes the communication hole 211 of the disc 174. When the disc 174 elastically deforms toward the bottom 191 of the cap member 178 while elastically deforming the outer tapered portion 202 of the disc spring 177, the disc 173 opens the communication hole 211 of the disc 174.

[0082] 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 . The disk 170 is flexible. The outer diameter of the disk 170 is larger than the outer diameter of the disk 173 and slightly smaller than the outer diameter of the disk 174.

[0083] The spring member 169 has flexibility. The spring member 169 has a substrate portion 221 and a plurality of spring plate portions 222.

[0084] The base plate portion 221 is a circular flat plate with holes. The mounting shaft portion 33 is fitted onto the inner periphery of the base plate portion 221.

[0085] 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.

[0086] 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.

[0087] The outer diameter of the disk 168 is smaller than the outer diameter of the base plate portion 221 of the spring member 169 and is larger than the outer diameter of the disk 172. The disk 168 abuts against the base plate portion 221 of the spring member 169.

[0088] The valve member 167 is flexible and has an outer diameter larger than the maximum outer diameter of the spring member 169.

[0089] 5 and 6, the valve seat member 166 is in the shape of a perforated disk. The cap member 178 is press-fitted onto the inside of a peripheral wall portion 193 of the cap member 178. The outer diameter of the valve seat member 166 is smaller on the side of the bottom portion 191 of the cap member 178 and is larger on the opposite side (the side closer to the piston 21). The entire valve seat member 166 has an inverted truncated cone shape. Therefore, a tapered surface 166a is formed on the outer peripheral surface of the valve seat member 166, with the diameter being smaller on the bottom 191 side of the cap member 178 and larger on the opposite side (the side closer to the piston 21). The valve seat member 166 is press-fitted into the inside of the cap member 178 by pressing the tapered surface 166a of its outer peripheral surface against a tapered surface 193a provided on a peripheral wall portion 193 of the cap member 178. The tapered surface 166a of the valve seat member 166 serves as an introduction portion when the valve seat member 166 is fitted into the cap member 178. In this embodiment, the portion of the valve seat member 166 where the tapered surface 166a is formed serves as a small-diameter introduction portion 166b that is smaller than the inner diameter of the cap member 178. Note that, since the peripheral wall portion 193 of the cap member 178 has the tapered surface 193a, the inner diameter of the cap member 178 varies depending on the position. The outer peripheral surface of the valve seat member 166 also has a tapered surface 166a, and the outer diameter varies depending on the position. As shown in Figures 3 and 4, at the portion where the valve seat member 166 is fitted into the cap member 178, when the outer peripheral portion of the valve seat member 166 is compared with the inner peripheral portion of the cap member 178 along a direction perpendicular to the intermediate shaft portion 42, the outer peripheral portion of the valve seat member 166 is smaller. For this reason, the tapered surface 166a of the valve seat member 166 can be described as an introduction portion 166b whose diameter is smaller than the inner diameter of the peripheral wall of the cap member 178.

[0090] The valve seat member 166 has a central hole 231 formed in its radial center, penetrating in the axial direction of the valve seat member 166. In other words, the central hole 231 extends in the axial direction of the valve seat member 166 and penetrates the valve seat member 166 in the axial direction. As shown in Fig. 4, the mounting shaft portion 33 of the piston rod 31 is inserted into the central hole 231 of the valve seat member 166.

[0091] As shown in FIGS. 5 and 6, the central hole 231 has a first inner circumferential wall 232 (first inner circumferential wall) and a second inner circumferential wall 233 (second inner circumferential wall).

[0092] The first inner circumferential wall 232 has a cylindrical inner circumferential surface. As shown in Fig. 4, the first inner circumferential wall 232 penetrates the valve seat member 166 in the axial direction.

[0093] As shown in FIGS. 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 FIG. 4, the second inner circumferential wall 233 extends linearly along the axial direction of the valve seat member 166 and penetrates the valve seat member 166 in the axial direction. The central hole 231 has one or more second inner circumferential walls 233. Here, as shown in FIGS. 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.

[0094] 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 valve 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 valve seat member 166 has a plurality of expansion portions 235 that are equally spaced around the circumferential direction of the insertion hole 234. As shown in FIG. 4 , the insertion hole 234 and the expansion portion 235 both extend from one end face to the other end face of the valve seat member 166 in the axial direction, penetrating the valve seat member 166.

[0095] The mounting shaft portion 33 of the piston rod 31 is fitted into the first inner circumferential wall 232 of the center hole 231 at a pair of outer end surfaces 42a of the intermediate shaft portion 42 shown in FIG. 2 and the outer circumferential surface 43a of the tip-side cylindrical portion 43. 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 valve 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 passage 54. The center hole 231 overlaps with the tip-side circumferential groove 53 of the piston rod 31 in the axial direction of the piston rod 31. Therefore, the center hole 231 communicates directly or indirectly with the tip-side circumferential groove 53 of the piston rod 31; in this case, the center hole 231 communicates directly with it. An intermediate chamber 237 is formed by the second inner circumferential wall 233 of the valve 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 valve seat member 166 with the piston rod 31.

[0096] As shown in Fig. 4, the valve 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.

[0097] As shown in Fig. 4, the valve 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.

[0098] 4, the valve 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 disk-like shape with holes.

[0099] The inner seat portion 241 protrudes from an 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 on the same side as the inner seat portion 241, radially outward from the inner seat portion 241, along the axial direction of the main body portion 247. The valve seat member 166 has the aforementioned tapered surface 166a formed on the outer peripheral surface of the main body 247, and the valve seat member 166 is press-fitted into the cap member 178 so that the tapered surface 166a is pressed against the tapered surface 193a of the cap member 178.

[0100] 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 valve seat member 166 and are arranged on the same plane.

[0101] 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, radially outward of the inner seat portion 244, along the axial direction of the main body portion 247.

[0102] 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 side tip surfaces of the inner seat portion 244 and the protruding side tip surfaces of the valve seat portion 245 extend in a direction perpendicular to the axis of the valve seat member 166 and are arranged on the same plane.

[0103] As shown in FIG. 5, the inner seat portion 241 has an annular portion 251 and a plurality of protrusions 252. The annular portion 251 is annular and is provided to surround the central hole 231 .

[0104] 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 in the circumferential direction of the annular portion 251 at intervals.

[0105] The inner seat portion 241 has a radial communicating groove 253 that penetrates 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 groove 253 is recessed in the axial direction of the valve seat member 166 from the tip end surface of the inner seat portion 241 on the side opposite to the main body portion 247.

[0106] 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 inside of this corresponding second inner circumferential wall 233. Each of the plurality of radial communicating grooves 253 is provided between adjacent protruding portions 252 in the circumferential direction of the annular portion 251.

[0107] The valve seat portion 242 is a non-circular, petal-shaped irregular seat. The valve seat portion 242 has a plurality of valve seat constituent portions 255. These valve seat constituent portions 255 have the same shape and are arranged at equal intervals around the circumferential direction of the valve seat member 166. Note that these valve seat constituent portions 255 do not need to have the same shape, and may have two or more different shapes or may have mutually different shapes. Furthermore, they may be arranged at unequal intervals around the circumferential direction of the valve 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.

[0108] The valve seat constituent portion 255 has a pair of extending portions 256 and a connecting portion 257. The pair of extending portions 256 each extend outward in the radial direction of the annular portion 251 from the outer peripheral edge portion of the annular portion 251 of the inner seat portion 241. The pair of extending portions 256 are arranged at an interval in the circumferential direction of the annular portion 251.

[0109] The connecting portion 257 connects the outer ends of the pair of extending 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 valve seat member 166.

[0110] Here, a pair of protrusions 252 adjacent to each other in the circumferential direction of the inner seat portion 241 are arranged on the inner side of the valve seat member 166 of the valve seat constituent portion 255 in the circumferential direction, and a radial communicating groove 253 is arranged between this pair of protrusions 252. Therefore, a pair of protrusions 252 and one radial communicating groove 253 are arranged on the inner side of the valve seat member 166 of each of the multiple valve seat constituent portions 255 in the circumferential direction.

[0111] A passage recess 258 is formed between each of the plurality of valve seat constituent portions 255 and the inner seat portion 241 on the inner side thereof. The passage recess 258 is formed by being surrounded by a part 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 valve 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.

[0112] A passage hole 259 is formed in the center of the passage recess 258 in the circumferential direction of the valve 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 valve seat member 166. As shown in FIG. 4 , the passage hole 259 axially penetrates the main body 247, and thereby penetrates the valve seat member 166 in the axial direction. The passage hole 259 is a linear hole parallel to the central axis of the valve seat member 166. As shown in FIG. 5, a passage hole 259 is formed in the bottom surface of every passage recess 258 .

[0113] As shown in FIG. 6, the inner seat portion 244 has an annular portion 261 and a plurality of protrusions 262. The annular portion 261 is annular and is provided to surround the central hole 231 .

[0114] 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.

[0115] The inner seat portion 244 is formed with a plurality of communicating grooves 263 that traverse the annular portion 261 in the radial direction of the annular portion 261 and are equally spaced apart in the circumferential direction of the annular portion 261. As shown in Fig. 4, the communicating grooves 263 are formed so as to be recessed in the axial direction of the valve seat member 166 from the tip surface of the inner seat portion 244 on the side opposite to the main body portion 247.

[0116] 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 inside of this 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.

[0117] The valve seat portion 245 is a non-circular, petal-shaped irregular seat. The valve seat portion 245 has a plurality of valve seat constituent portions 265. These valve seat constituent portions 265 have the same shape and are arranged at equal intervals around the circumferential direction of the valve seat member 166. Note that these valve seat portions 245 do not need to have the same shape, and may have two or more different shapes or may have mutually different shapes. Furthermore, they may be arranged at unequal intervals around the circumferential direction of the valve 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.

[0118] In the annular portion 261 of the inner seat portion 244, a communication groove 263 is arranged between two valve seat constituent portions 265 adjacent to each other in the circumferential direction of the valve seat member 166. Therefore, the communication groove 263 is formed in a portion of the inner seat portion 244 that is arranged outside the valve seat portion 245.

[0119] The valve seat forming portion 265 has a pair of extending portions 266 and a connecting portion 267 . 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.

[0120] The connecting portion 267 connects the outer ends of the pair of extending 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 valve seat member 166.

[0121] Here, a pair of protrusions 262 adjacent to each other in the circumferential direction of the inner seat portion 244 are arranged on the inner side in the circumferential direction of the valve seat member 166 of the valve seat constituent portion 265. Therefore, a pair of protrusions 262 is arranged on the inner side in the circumferential direction of the valve seat member 166 of each of the multiple valve seat constituent portions 265.

[0122] 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.

[0123] As shown in Fig. 4, the passage recess 268 is recessed in the axial direction of the valve seat member 166 from the tip end surface on the protruding side of the inner seat portion 244 and the tip end surface on the protruding side 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.

[0124] A passage hole 269 is formed in the center of the passage recess 268 in the circumferential direction of the valve 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 valve seat member 166. As shown in FIG. 4, the passage hole 269 axially penetrates the main body 247 and therefore the valve seat member 166. The passage hole 269 is a linear hole parallel to the central axis of the valve 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.

[0125] 5 is arranged at the same pitch in the circumferential direction of the valve seat member 166 as the pitch in the circumferential direction of the valve seat member 166. The valve seat constituent portions 255 and 265 are out of phase with each other in the circumferential direction of the valve seat member 166 by half the pitch.

[0126] 5, the passage hole 269 is disposed between adjacent valve seat constituent portions 255 in the circumferential direction of the valve seat member 166. Therefore, the passage hole 269 is disposed outside the range of the valve seat portion 242.

[0127] 6, the passage hole 259 is disposed between adjacent valve seat constituent portions 265 in the circumferential direction of the valve seat member 166. Therefore, the passage hole 259 is disposed outside the range of the valve seat portion 245.

[0128] 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 section 281 (third flow path, axial flow path) provided in the valve seat member 166. The valve seat member 166 is provided with a plurality of passage sections 281 at equal intervals in the circumferential direction of the valve seat member 166. The passage sections 281 communicate with the passage in the radial communicating groove 253 and the passage in the communicating groove 263.

[0129] The passage hole 269 and the passage in the passage recess 268 into which the passage hole 269 opens constitute a passage portion 282 provided in the valve seat member 166. The valve seat member 166 is provided with a plurality of passage portions 282 at equal intervals in the circumferential direction of the valve seat member 166.

[0130] The valve seat member 166 has a peripheral groove (seal groove) 271 formed in the axial center of the outer periphery of the main body portion 247. The peripheral groove 271 is annular and recessed radially inward from the outer periphery of the main body portion 247. An O-ring (seal member) 165 is disposed in this peripheral groove 271. The O-ring 165 is housed in the peripheral groove 271 so that a portion of the O-ring 165 protrudes outward from the peripheral groove 271.

[0131] The valve seat member 166 is fitted into the peripheral wall portion 193 of the cap member 178 with the inner seat portion 241 and the valve seat portion 242 facing away from the bottom portion 191 of the cap member 178. In this state, the outer periphery of the O-ring 165 is pressed against the peripheral wall portion 193 of the cap member 178, and the O-ring 165 seals the gap between the peripheral wall portion 193 of the cap member 178 and the valve seat member 166.

[0132] The cap member 178, O-ring 165, and valve seat member 166 form a cap chamber 285 inside the cap member 178. The cap chamber 285 is provided between the bottom 191 of the cap member 178 and the valve seat member 166. The valve member 167, discs 168, 170, 172, 173, 174, 176, spring member 169, and disc spring 177 are provided within this cap chamber 285. The valve seat member 166 has a valve seat portion 245 disposed on the cap chamber 285 side.

[0133] A first chamber communication chamber 286 (storage chamber) that stores oil L is formed within the cap chamber 285. The first chamber communication chamber 286 is surrounded by the cap member 178, the disc spring 177, the disc 174, the disc 173, the disc 172, the disc 170, the spring member 169, the disc 168, the valve member 167, and the valve seat member 166.

[0134] A second-chamber communication chamber 287 that stores oil L is formed within the cap chamber 285. The second-chamber communication chamber 287 is surrounded by the disc 173, the disc 174, the disc spring 177, and the disc 176. The first-chamber communication chamber 286 is the portion of the cap 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 working fluid passage holes 195 in the bottom portion 191 of the cap member 178.

[0135] 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 .

[0136] As shown in Fig. 3, the annular valve seat member 166 and the bottomed cylindrical cap 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 valve seat member 166 is disposed on the second chamber 23 side. As shown in Fig. 4, the passage within the working fluid passage hole 195 of the cap member 178 is constantly in communication with the second chamber 23. Therefore, the second-chamber communication chamber 287 communicates with the second chamber 23 using the working fluid passage hole 195 as an orifice.

[0137] 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 valve 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.

[0138] As the disc 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 disc 174 is prevented from being hindered by the oil liquid L in the first chamber communication chamber 286 and the second chamber communication chamber 287.

[0139] As shown in FIG. 3, the plurality of passages 282 of the valve seat member 166 are provided facing the second chamber 23 and are constantly in communication with the second chamber 23.

[0140] 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 valve 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.

[0141] The spring member 169 biases the valve member 167 so that it abuts against the valve seat portion 245 of the valve 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 moves away from the valve seat portion 245, thereby opening the passage portion 282.

[0142] 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 valve 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 FIG. 3. At this time, the valve member 167 shown in FIG. 4 suppresses the flow of oil liquid L between it and the valve seat portion 245, thereby generating a damping force.

[0143] The valve member 167 is an inflow valve that opens when oil 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 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 valve seat member 166. Therefore, the passages 281 are always in communication with the first-chamber communication chamber 286 regardless of the valve member 167 seated on the valve seat portion 245.

[0144] The second passage 291 is composed of the multiple 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 passage 288 in the communication groove 263, the intermediate chamber 237, the axial passage 54, the in-piston passage 103 shown in FIG. 3, and the piston passage 81. The second passage 291 is opened and closed by the valve member 167 shown in FIG. 4. The second passage 291 allows the oil L to flow from the second chamber 23, which is on the upstream side within the cylinder 4, to the first chamber 22, which is on the downstream side, as the piston 21 moves toward the second chamber 23. The second passage 291 serves as a compression-side passage through which the oil L flows from the second chamber 23, which is on the upstream side, to the first chamber 22, which is on the downstream side, as the piston 21 moves toward the second chamber 23, i.e., during the compression stroke. At least a portion of the second compression passage 291, in this case the entirety thereof, is provided in parallel with the first compression passage 132 shown in Figure 3. The second passage 291 includes the first chamber side flow path 156.

[0145] 4, the passage in the working fluid 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 compression-side second passage 291. The second-chamber communication flow path 292 is provided in parallel to the second passage 291.

[0146] The valve member 167, the valve 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: second sub-valve). The valve mechanism 301 is provided in a second passage 291 on the compression side. The valve mechanism 301 opens and closes this second passage 291, and suppresses the flow of oil L from this second passage 291 to the first chamber 22, thereby generating a damping force. The valve mechanism 301 is a compression side valve mechanism.

[0147] Valve mechanism 301 includes valve seat portion 245, which is a valve seat, and valve member 167, which is a flexible valve body, and is a check valve mechanism that allows flow in the direction from second chamber 23, which is the upstream region, to first chamber 22, which is the downstream region, in second passage 291 during the compression stroke, while restricting flow from first chamber 22, which is the upstream region, to second chamber 23, which is the downstream region, in the extension stroke. In other words, valve mechanism 301 only allows flow in the direction from second chamber 23, which is the upstream region, to first chamber 22, which is the downstream region, in second passage 291 during the compression stroke.

[0148] The valve mechanism 301 has a valve seat portion 245 provided on the valve seat member 166. The valve mechanism 301 is disposed separately from the valve mechanism 86 which generates a damping force in the same compression stroke. The valve member 167 constituting the compression side valve mechanism 301 is a compression side sub-valve.

[0149] In the compression-side valve mechanism 301, neither the valve seat portion 245 nor the valve member 167 abutting thereon has a fixed orifice 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 passage 291 does not have a fixed orifice that constantly connects the first chamber 22 and the second chamber 23. The second passage 291 is not a passage that constantly connects the first chamber 22 and the second chamber 23.

[0150] The second compression passage 291, which allows communication between the first chamber 22 and the second chamber 23, is arranged in parallel with the first passage 132, which is also a compression passage that allows communication between the first chamber 22 and the second chamber 23. A valve mechanism 86 is provided in the first passage 132. A valve mechanism 301 is provided in the second passage 291. Thus, the compression valve mechanism 86 and the valve mechanism 301 are arranged in parallel.

[0151] 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 valve seat member 166. The valve member 163 is always in contact with the inner seat portion 241 and is able to be seated on and removed from the valve seat portion 242. When the valve member 163 is seated on 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.

[0152] The disc 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 . The spring member 161 has flexibility. The spring member 161 includes a substrate portion 311 and a plurality of spring plate portions 312.

[0153] The base plate portion 311 is in the shape of a circular flat plate with holes. The mounting shaft portion 33 is fitted into the inner periphery of the base plate portion 311. The outer diameter of the base plate portion 311 is slightly larger than the outer diameter of the disk 162. The base plate portion 311 abuts against the disk 162.

[0154] The plurality of spring plate portions 312 extend radially from the outer peripheral edge 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.

[0155] 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 tips of the extending sides 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 urge the outer periphery of the valve member 163 so that it abuts against the valve seat portion 242 of the valve seat member 166. The urging 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 urging force of the spring member 161 and separates from the valve seat portion 242, thereby opening the passage portion 281.

[0156] The valve member 163 is provided in the second chamber 23. When the valve member 163 is lifted off 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 valve seat member 166. At this time, the valve member 163 suppresses the flow of oil liquid L between the valve member 163 and the valve seat portion 242, 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 inflow 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 member 166 and the valve seat portion 242. Therefore, the passage portion 282 always communicates with the second chamber 23 regardless of whether the valve member 163 is seated on the valve seat portion 242 .

[0157] The radial communicating groove 253 formed in the inner seat portion 241 of the valve seat member 166 serves as a radial flow path 317 (fourth flow path). The radial flow path 317 is provided at a position facing the axial flow path 54 in the radial direction of the valve seat member 166, and communicates with the intermediate chamber 237.

[0158] As shown in FIG. 3, the second passage 315 is composed of the first-chamber-side passage 156 consisting of the piston passage 81 and the intra-piston passage 103, the axial passage 54 of the piston rod 31, the intermediate chamber 237 and the passage 288 in the second inner circumferential wall 233 of the valve seat member 166, the first-chamber communication chamber 286, the passage portion 281, the radial passage 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 opened.

[0159] The second passage 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 hydraulic oil L flows through the second passage 315 from the first chamber 22 (on the upstream side) in the cylinder 4 to the second chamber 23 (on the downstream side). The second passage 315 serves as an extension-side passage through which the hydraulic 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 passage 315 is provided separately from the extension-side second passage 152. The second passage 315 is at least partially, in this case, partially parallel to the second passage 152. The second passage 315 is parallel to the second passage 152 except for a portion of the piston passage 81 closer to the first chamber 22 than the in-piston flow path 103.

[0160] 4 connects the intermediate chamber 237 of the second passage 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 paths 317 connect the intermediate chamber 237 to the valve seat portion 242. In other words, the radial flow paths 317 connect the central hole 231 to the valve mechanism 321 including the valve seat portion 242.

[0161] 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.

[0162] 4, the disk 160 has an outer diameter equal to the outer diameter of the valve member 163. The disk 160 is flexible.

[0163] The valve member 163, the valve 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: first sub-valve). The valve mechanism 321 is provided in the extension-side second passage 315 and opens and closes this second passage 315. The valve mechanism 321 generates a damping force by suppressing the flow of hydraulic fluid L from this second passage 315 to the second chamber 23. The valve mechanism 321 is an extension-side second damping force generating mechanism. The valve mechanism 321 is arranged separately from the valve mechanism 85 that generates a damping force in the same extension stroke. The valve member 163 that constitutes the extension-side valve mechanism 321 is an extension-side sub-valve. The valve mechanism 321 includes a radial flow path 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.

[0164] Valve mechanism 321 includes valve seat portion 242 serving as a valve seat and valve member 163 serving as a flexible valve body, and is a check valve mechanism that allows flow from first chamber 22, which is the upstream region, toward second chamber 23, which is the downstream region, during the extension stroke of second passage 315 including first chamber-side flow path 156, while restricting flow from second chamber 23, which is the upstream region, toward first chamber 22, which is the downstream region, during the compression stroke. In other words, valve mechanism 321 only allows flow from first chamber 22, which is the upstream region, toward second chamber 23, which is the downstream region, during the extension stroke of second passage 315 including first chamber-side flow path 156.

[0165] The second chamber communication chamber 287 and the disc 174, disc 173, disc spring 177 and disc 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.

[0166] The second-chamber volume variable mechanism 325 deforms and moves the disc 174 and the disc 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 so as to increase it. At that time, if the disc 174 remains in contact with the disc spring 177 over the entire circumference, the space between the disc 174 and the outer tapered portion 202 of the disc spring 177 is blocked. In other words, if the disc 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.

[0167] Furthermore, the second chamber volume variable mechanism 325 deforms and moves the disc 174 and the disc 173 together so that they approach the bottom 191. Then, the second chamber volume variable mechanism 325 changes the volume of the second chamber communication chamber 287 to decrease it. At that time, the disc 174 is kept in contact with the disc spring 177 as a whole, and the space between the disc 174 and the outer tapered portion 202 of the disc spring 177 is blocked.

[0168] The first chamber communication chamber 286, which communicates with the first chamber 22, constitutes a part of the extension-side second passage 315. The first chamber communication chamber 286, and the valve 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 cap 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.

[0169] The first-chamber volume variable mechanism 326 deforms and moves the disc 174 and the disc 173 together so as to separate from the disc 170. Then, the first-chamber volume variable mechanism 326 changes the volume of the first-chamber communication chamber 286 so as to increase it. At that time, if the disc 173 is maintained in a state in which it is entirely in contact with the disc 174, it closes the passage in the communication hole 211 of the disc 174. In other words, the state in which the second-chamber communication chamber 287 and the first-chamber communication chamber 286 are blocked is maintained.

[0170] Additionally, first chamber volume variable mechanism 326 deforms and moves disc 174 and disc 173 so that they approach disc 170. As a result, first chamber volume variable mechanism 326 changes the volume of first chamber communication chamber 286 to decrease it. At this time, disc 173 is maintained in a state where it is entirely in contact with disc 174, and closes the passage in communication hole 211 of disc 174.

[0171] 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 passage 315 does not have a fixed orifice that constantly communicates between the first chamber 22 and the second chamber 23. The second passage 315 is not a passage that constantly communicates between the first chamber 22 and the second chamber 23.

[0172] The spring member 161, the disc 162, the valve member 163, the O-ring 165, the valve seat member 166, the valve member 167, the disc 168, the spring member 169, the disc 170, the disc 172, the disc 173, the disc 174, the disc 176, the disc spring 177, and the cap member 178 constitute a second structural member 331 (second structural member).

[0173] 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 cap 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 hydraulic fluid 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 hydraulic fluid 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 opposite 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 cap 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.

[0174] 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.

[0175] As described above, the first-chamber volume variable mechanism 326 shown in FIG. 4 changes the volume of the first-chamber communication chamber 286 so as to increase it 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. When this occurs, 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. When this occurs, 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.

[0176] The disc 174 and the disc 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.

[0177] 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 so that it approaches the disc 170. At that time, with the valve mechanism 301 in an open state, 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 away from the outer periphery of the disc spring 177 in the axial direction. 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.

[0178] The disc 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.

[0179] 1, the base valve 15 has a valve mechanism 351 on the axial side of the bottom 9 of the valve body 12. The base valve 15 also has a valve mechanism 352 on the axial side of the valve body 12 opposite to the bottom 9.

[0180] When the piston rod 31 moves toward the contraction side and the piston 21 moves in the 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, allowing the oil L in the second chamber 23 to flow into the reservoir chamber 5. At this time, the valve mechanism 351 generates a damping force.

[0181] 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 that 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.

[0182] "About the operation of shock absorbers" Next, the operation of the shock absorber 1 will be described. 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 and generates a damping force when the piston speed is slower than that of the valve mechanism 85, generating a damping force. 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 when the piston speed is in the extremely low-speed region.

[0183] 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 valve 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 toward the bottom 191 at a portion radially inward of the contact position of the disc 174's coned disc spring 177 with the outer tapered portion 202. As a result, disc 174 increases the capacity of first-chamber communication chamber 286. As a result, first-chamber volume variable mechanism 326 suppresses an increase in pressure in first-chamber communication chamber 286. At this time, disc 173 deforms following disc 174, maintaining the closed state of the passage in communication hole 211. Also, at this time, disc 174 bends and moves toward bottom 191, causing second-chamber volume variable mechanism 325 to reduce the volume of second-chamber communication chamber 287.

[0184] 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 into 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 passage 315 increases until the valve mechanism 321 opens.

[0185] At this time, neither valve mechanisms 85, 86 nor valve mechanisms 301, 321 have a fixed orifice that constantly connects first chamber 22 and second chamber 23. For this reason, the damping force rises abruptly during the extension stroke when the piston speed is less than the first predetermined value at which valve mechanism 321 opens. Furthermore, in a region where the piston speed is higher than the first predetermined value and in an extremely low speed region that is higher than the first predetermined value but lower than a second predetermined value, valve mechanism 321 opens while valve mechanism 85 remains closed.

[0186] That is, the valve member 163 deforms against the biasing force of the spring member 161 and lifts off the valve seat portion 242. This causes the first chamber 22 and the second chamber 23 to communicate with each other through the extension-side second passage 315. Therefore, the oil L in the first chamber 22 flows to the second chamber 23 via the first-chamber-side passage 156 of the piston 21, the axial passage 54 of the piston rod 31, the intermediate chamber 237, passage 288, and passage portion 281 of the valve 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 passage 156, the axial passage 54, the intermediate chamber 237 and radial passages 317 of the valve 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.

[0187] 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 communicating chamber 286 increases while the piston speed is 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, causing the hydraulic fluid L in the first-chamber communicating chamber 286 to flow into the second chamber 23 via the second-chamber communicating chamber 287 and the second-chamber communicating 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 separates from 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 second passage 315 on the extension side. Thereafter, with the valve mechanism 321 remaining open, the relief mechanism 335 opens, allowing the hydraulic fluid L to flow from the first chamber 22 to the second chamber 23 through 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 through the extension-side second passage 152. Therefore, the hydraulic fluid L in the first chamber 22 flows to the second chamber 23 through the second passage 152, which is made up of the piston passage 81 and the passage between the valve member 151 and the valve seat 105.

[0188] As a result, even in the normal speed range 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 in response to an increase in piston speed in the normal speed range is lower than the rate of increase in the extension damping force in response to an increase in piston speed in the extremely low speed range.

[0189] As described above, during the extension stroke, when the piston speed is in the normal speed range where it 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 second passage 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 freedom.

[0190] During the extension stroke when a high-frequency input (small-amplitude vibration) occurs, in which a higher frequency than that during 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. As a result, 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. As a result, the pressure rise in the first-chamber communication chamber 286 is small. As a result, 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., it is possible to achieve a state similar to that in a structure without the valve mechanism 321.

[0191] 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, which includes the disc 174, limits 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 disc 174.

[0192] 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 and generates 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 and generates a damping force when the piston speed is in the extremely low speed region.

[0193] 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 the increase in pressure in the second-chamber communication chamber 287. At this time, disc 173 deforms following disc 174, maintaining the closed state of the passage in communication hole 211. Also, at this time, disc 174 bends and moves toward disc 170, so that first chamber volume variable mechanism 326 reduces the volume of first chamber communication chamber 286.

[0194] 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 side 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 passage 291 increases until the valve mechanism 301 opens.

[0195] At this time, neither valve mechanisms 85, 86 nor valve mechanisms 301, 321 have a fixed orifice that constantly communicates between second chamber 23 and first chamber 22. For this reason, the damping force rises abruptly during the compression stroke when the piston speed is less than the third predetermined value at which 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, valve mechanism 301 opens while valve mechanism 86 remains closed.

[0196] 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 passage 291. Therefore, the oil L in the second chamber 23 flows into the first chamber 22 via the passage portion 282 in the valve seat member 166, the passage between the valve member 167 and the valve seat portion 245, the first-chamber communication chamber 286, the passage 288 and the intermediate chamber 237 of the valve seat member 166, the axial passage 54 of the piston rod 31, the first-chamber-side passage 156 of the piston 21, and the piston passage 81 of 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 region where the piston speed is lower than the fourth predetermined value.

[0197] Furthermore, a relief mechanism 336 is provided that opens after the valve mechanism 301 opens during the compression stroke. Therefore, when the piston speed is in a normal speed region where the piston speed is equal to or greater than a fourth predetermined value, if the pressure in the second-chamber communicating chamber 287 increases, the relief mechanism 336 opens while the valve mechanism 301 remains open, allowing the hydraulic fluid L from the second chamber 23 and the second-chamber communicating chamber 287 to flow to the first chamber 22 via the first-chamber communicating chamber 286. Thereafter, 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 portion 245 as described above, the hydraulic fluid L flows from the second chamber 23 to the first chamber 22 through the compression-side second passage 291. Thereafter, the relief mechanism 336 opens while the valve mechanism 301 remains open, allowing the hydraulic fluid 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 passage 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 lifts off the valve seat portion 115, causing hydraulic fluid L to flow from the second chamber 23 to the first chamber 22 in the compression-side first passage 132. 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 portion 115.

[0198] 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 in response to an increase in piston speed in the normal speed region is lower than the rate of increase in the compression damping force in response to an increase in piston speed in the extremely low speed region.

[0199] As described above, during the compression stroke, when the piston speed is in the normal speed range 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 passage 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 relative to an increase in 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.

[0200] During the compression stroke when a high frequency input (small amplitude vibration) occurs in which a higher frequency than that during 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 rising, the same state as when the disc 174 is not present is achieved. In other words, when the extremely low-speed damping force is rising, the second-chamber communication chamber 287 can be constantly connected to the first-chamber communication chamber 286, i.e., the same state as when the valve mechanism 301 is not present.

[0201] 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, which includes the disc 174, limits 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 disc 174.

[0202] The aforementioned Patent Document 1 discloses a shock absorber in which a piston and a valve seat member separate from the piston are mounted 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 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.

[0203] 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.

[0204] The first structural member 155 has circular fixing holes 101, 111 that penetrate in the axial direction, a second passage 152 that can connect the first chamber 22 and the second chamber 23, a flexible valve member 151 that can close the second passage 152, and a first chamber side flow path 156 that is at least partially arranged parallel to the second passage 152.

[0205] The piston rod 31 is rod-shaped and includes 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 closer to the second chamber 23 than the tip-end circumferential groove 53.

[0206] 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 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 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.

[0207] As a result, the shock absorber 1 has the axial flow path 54, which is in communication with the first chamber-side flow path 156, at least a portion of which is provided parallel to the second passage 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 a large-diameter hole portion as a circumferential groove is not formed in the inner seat portion 241, which is the portion of the second structural member 331 on which the valve member 163 is stacked. Therefore, the shock absorber 1 does not require a highly rigid part that can enable high fastening pressure when fastening the valve member 163, thereby ensuring design freedom. Furthermore, the shock absorber 1 does not require circumferential phase alignment between the second structural member 331 and the piston rod 31.

[0208] Furthermore, in the shock absorber 1, the second structural member 331 extends across the axial flow path 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 path 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 path 317 that is provided at a position opposite the axial flow path 54 and communicates with the valve mechanism 321. Therefore, the shock absorber 1 can change the damping force characteristics in more detail.

[0209] Furthermore, the shock absorber 1 further includes one or more extension 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 cap member 178 communicating with the extension 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 and the valve mechanism 321. Therefore, the shock absorber 1 can change the damping force characteristics in more detail.

[0210] Furthermore, the shock absorber 1 further has a valve mechanism 301 in which the second structural member 331 includes a valve seat portion 245 which is a valve seat, and a valve member 167 which is a flexible valve body disposed in the tip-end cylindrical portion 43, and which allows the oil liquid L to flow only in a direction from the second chamber 23 to the first chamber 22. Therefore, the shock absorber 1 can change the damping force characteristics in more detail.

[0211] Furthermore, in the shock absorber 1, the second structural member 331 further includes a cap member 178 that communicates with an intermediate chamber 237 formed by the second inner circumferential wall 233 and the piston rod 31 and forms a first-chamber communication chamber 286 that stores hydraulic fluid 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 hydraulic fluid 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 changes the volume of the first-chamber communication chamber 286.

[0212] 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.

[0213] Furthermore, the shock absorber 1 has the second structural member 331 positioned opposite the axial flow path 54 and having the radial flow path 317 communicating with the valve mechanism 321, so that the damping force characteristics can be changed in more detail.

[0214] 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 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.

[0215] In the shock absorber 1 of the first embodiment, the valve seat member 166 is press-fitted into the cap member 178 with the tapered surface 166a of its outer peripheral wall in contact with the inner surface of the peripheral wall portion 193 of the cap member 178. Furthermore, with this structure, the valve seat member 166 presses the O-ring 165 against the inner peripheral surface of the cap member 178, sealing the gap between the valve seat member 166 and the cap member 178.

[0216] According to the structure of the first embodiment, the valve seat member 166 has a tapered surface 166a, and the peripheral wall portion 193 of the cap member 178 also has a tapered surface 193a, so when fitting the valve seat member 166 to the cap member 178, the front and back sides cannot be reversed. If the peripheral wall portion 193 of the cap member 178 were cylindrical and not tapered, the valve seat member 166 fitted inside it would also be disc-shaped and not tapered. In this case, when fitting the valve seat member inside the cylindrical cap member, there is a possibility that the valve seat member will be fitted upside down. As shown in Figures 5 and 6, the front and back sides of the valve seat member 166 have different shapes, but they are highly similar in shape. For this reason, assembling the valve seat member 166 upside down could result in a defective shock absorber 1. The fit between the tapered surface 166a of the valve seat member 166 and the tapered surface 193a of the cap member 178 prevents the valve seat member 166 from being fitted in the wrong direction. Therefore, by adopting a fitting structure via the tapered surfaces 166a and 193a, the shock absorber 1 can be assembled accurately and easily.

[0217] In the first embodiment, since both the valve seat member 166 and the cap member 178 are made of resin, a seal structure is formed in which the O-ring 165 is provided between the resin products, and therefore, there is no deterioration in sealing performance. If the peripheral wall 193 of the cap member 178 were cylindrical and not tapered, the valve seat member 166 fitted inside it would also be disc-shaped and not tapered. In this case, to ensure a reliable sealing force with the O-ring 165, the disc-shaped valve seat member would need to be press-fitted deep into the cylindrical cap member by the entire thickness of the disc-shaped valve seat member. This press-fitting operation could result in the valve seat member deforming the cylindrical, resin cap member.

[0218] In contrast, if the valve seat member 166 having the tapered surface 166a is fitted with the cap member 178 having the tapered surface 193a, the resistance when inserting the small-diameter side of the valve seat member 166 into the large-diameter side of the cap member 178 can be reduced. Also, to ensure the sealing force of the O-ring 165, the valve seat member 166 is press-fitted into the cap member 178 up to the side close to the bottom 191, and the load applied to the cap member 178 during this fitting can be smaller than the load applied when fitting a cylindrical cap member. Therefore, according to the structure of the first embodiment, the shock absorber 1 can be assembled while preventing deformation of the cap member 178. As a result, the performance that the cap member 178 should originally have can be reliably obtained. Furthermore, in order to prevent deformation when fitting the valve seat member 166, it was necessary to form the cap member 178 using a high-strength, expensive resin. However, because deformation of the cap member 178 can be suppressed as described above, the resin forming the cap member 178 can be switched to a low-strength, inexpensive resin. This widens the range of resins that can be used for the cap member 178, enabling cost reductions and improving the ease of manufacturing the cap member 178.

[0219] [Second embodiment] Next, the second embodiment will be described, focusing on differences from the first embodiment, mainly with reference to Figures 8 to 10. Note that parts common to the configuration of the first embodiment will be designated by the same names and symbols. The shock absorber 1A of the second embodiment is characterized in that a valve seat member 366 and a cap member 378 shown in FIGS. 8 to 10 are provided instead of the valve seat member 166 and the cap member 178 of the first embodiment.

[0220] As explained in the first embodiment with reference to Figures 5 and 6, the valve seat member 366 has the same structure as the first embodiment, in that it has a central hole 231 and is provided with a first inner circumferential wall 232, a second inner circumferential wall 233, passage holes 259, 269, valve seat portions 242, 245, valve seat constituent portions 255, 265, etc. In the valve seat member 366, a circumferential step portion 368 is formed on an outer circumferential wall 367, and an O-ring (seal member) 165 is disposed in the circumferential step portion 368. In the outer circumferential wall 367, a press-fit portion 369 is formed above the circumferential step portion 368 (on the side closer to the piston 21). In the outer circumferential wall 367, an introduction portion 370 is formed below the circumferential step portion 368 (on the side closer to the annular member 182). In the cap member 378, the shapes of the bottom portion 191 and the intermediate tapered portion 192 are similar to the configuration of the cap member 178 of the first embodiment. In the cap member 378, a peripheral step portion 394 is formed on the height direction center side of a peripheral wall portion 393, an upper wall 395 is formed above the peripheral step portion 394 (the side closer to the piston 21), and a lower wall 396 is formed below the peripheral step portion 394 (the side closer to the bottom portion 191). Both the upper wall 395 and the lower wall 396 are cylindrical, and the inner diameter of the upper wall 395 is formed slightly larger than the inner diameter of the lower wall 396.

[0221] The valve seat member 366 is press-fitted into the inside of the cap member 378, and the press-fit portion 369 of the valve seat member 366 is press-fitted into the inside of the upper wall 395 of the cap member 378. The outer peripheral surface of the press-fit portion 369 is not tapered and is tightly fitted into the inner peripheral surface of the cylindrical upper wall 395. The O-ring 165 attached to the outer periphery of the valve seat member 366 is sandwiched between the circumferential step 368 of the valve seat member 366 and the circumferential step 394 of the cap member 378. The O-ring 165 closes the gap between the outer peripheral surface of the valve seat member 366 and the inner peripheral surface of the cap member 378, sealing this gap liquid-tight. The outer diameter of the introduction portion 370 of the valve seat member 366 is slightly smaller than the inner diameter of the lower wall 396 of the cap member 378. Therefore, the introduction portion 370 is loosely inserted into the cylindrical lower wall 396.

[0222] The shock absorber 1A of the second embodiment also provides the same effects as the shock absorber 1 of the first embodiment. That is, since the shock absorber 1A has the first damping force generating mechanism DF1 and the second damping force generating mechanism DF2, it is possible to obtain the required damping force characteristics as the piston 21 and the piston rod 31 move toward the extension side and toward the compression side. In addition, since it has the first sub-valve 321 and the second sub-valve 301, and relief mechanisms 335 and 336, it is possible to obtain the required damping force characteristics in various regions, such as the extremely low speed region where the moving speed of the piston 21 is bounded by a first predetermined value or a second predetermined value.

[0223] In the shock absorber 1A of the second embodiment, the press-fit portion 369 of the valve seat member 366 is press-fitted into the inside of the upper wall 395 of the cap member 378, while the introduction portion 370 of the valve seat member 366 is loosely inserted into the inside of the lower wall 396 of the cap member 378. The valve seat member 366 applies a load to the upper wall 395 of the cap member 378 due to the fitting of the press-fit portion 369, but applies almost no load to the lower wall 396 of the cap member 378. For this reason, in the structure of the second embodiment, as in the structure of the first embodiment, the proportion of load applied to the cap member 378 is small. For this reason, the shock absorber 1A can be assembled without causing deformation of the cap member 378. Furthermore, since the valve seat member 366 is provided with the peripheral step 368, the valve seat member 366 cannot be mounted upside down when it is fitted into the cap member 378. Therefore, similar to the first embodiment, the shock absorber 1A can be assembled accurately and easily.

[0224] In the structure of the second embodiment, the O-ring 165 is interposed between the valve seat member 366 and the cap member 378, which makes it possible to effectively seal the gap between the valve seat member 366 and the cap member 378. In addition, since deformation of the cap member 378 can be prevented when the valve seat member 366 is fitted, the flexibility in selecting the constituent material of the cap member 378 is improved.

[0225] [Third embodiment] Next, the third embodiment will be described, focusing on the differences from the first embodiment, with reference to Fig. 11. Note that parts common to the configuration of the first embodiment will be designated by the same names and symbols. The shock absorber 1B of the third embodiment is characterized in that a valve seat member 466 and a cap member 478 shown in Fig. 11 are provided instead of the valve seat member 166 and the cap member 178 of the first embodiment. The other configurations are the same as those of the first embodiment. The valve seat member 466 used in the third embodiment is press-fitted into the inner side of the peripheral wall portion 193 of the cap member 478, similar to the valve seat member 166 of the first embodiment. The outer diameter of the valve seat member 466 is smaller on the bottom portion 191 side of the cap member 478 and larger on the opposite side. The valve seat member 466 as a whole has an inverted truncated cone shape. A peripheral groove 467 is formed on the outer peripheral surface of the valve seat member 466 at a position approximately halfway in the height direction, and an O-ring (seal member) 165 is housed in the peripheral groove 467.

[0226] 11, an insertion portion 468 is formed on the upper side (the side closer to the opening of the cap member 478), and a press-fit portion (introduction portion) 469 is formed on the lower side (the side closer to the bottom 191 of the cap member 478) of the peripheral groove 467. In the state shown in FIG. 11, a slight gap is formed between an outer peripheral surface 468a of the insertion portion 468 and an inner peripheral surface of the peripheral wall portion 193 of the cap member 478. In the state shown in FIG. 11, an outer peripheral surface 469a of the press-fit portion 469 of the valve seat member 466 is press-fitted with no gap between it and the inner peripheral surface of the peripheral wall portion 193 of the cap member 478. In the third embodiment, the valve seat member 466 is fitted by pushing and press-fitting the press-fit portion 469 into the inside of the peripheral wall portion 193 of the cap member 478. In other words, the valve seat member 466 is fitted by pressing and fitting the press-fit portion 469, which is provided below the peripheral groove 467 in which the O-ring (seal member) 165 is disposed, into the inside of the peripheral wall portion 193 of the cap member 478. The outer diameter of the press-fit portion 469 of the valve seat member 466 is clearly smaller than the inner diameter of the opening of the peripheral wall portion 193 of the cap member 478. Therefore, at the stage of inserting the press-fit portion 469 into the opening of the cap member 478 to fit the valve seat member 466 to the cap member 478, the press-fit portion 469 serves as a lead-in portion that can easily pass through the opening. For this reason, the press-fit portion 469 of the valve seat member 466 can also be referred to as a lead-in portion.

[0227] In the structure of the third embodiment, the entire outer circumferential surface of the valve seat member 466 is not press-fitted and fitted into the cap member 478, but only a portion of the outer circumferential surface of the valve seat member 466 is press-fitted and fitted into the cap member 478. Therefore, when the valve seat member 466 is press-fitted into the cap member 478, deformation of the cap member 478 can be further suppressed than in the first embodiment.

[0228] [Fourth embodiment] Next, the fourth embodiment will be described, focusing on the differences from the first embodiment, with reference to Fig. 12. Note that parts common to the configuration of the first embodiment will be designated by the same names and symbols. A shock absorber 1C of the fourth embodiment is characterized in that a cap member 578 shown in Fig. 12 is provided instead of the cap member 178 of the first embodiment. The other configurations are the same as those of the first embodiment.

[0229] The cap member 578 applied to the fourth embodiment has a bottom portion 191 and an intermediate tapered portion 192 similar to the cap member 178 of the first embodiment, but the shape of the peripheral wall portion 593 formed on the outside of the intermediate tapered portion 192 is different. Circumferential wall portion 593 has a cross-sectional shape that is thick on the bottom side and becomes thinner toward the top. A tapered inner circumferential surface 594 is formed on the inner surface of peripheral wall portion 593, with the inner diameter being small on the side closer to bottom portion 191 and gradually increasing toward the top. Outer circumferential surface 593a of peripheral wall portion 593 is an outer circumferential surface with a uniform outer diameter that does not have a taper or the like. The valve seat member 166 can be press-fitted into the cap member 578 having such a tapered inner peripheral surface 594 to fit it.

[0230] The structure of the fourth embodiment can also achieve the same effects as those of the structure of the first embodiment. That is, when fitting the valve seat member 166 to the cap member 578, the tapered surface 166a of the valve seat member 166 can be press-fitted into the tapered inner circumferential surface 594 while suppressing deformation of the cap member 578. In addition, the structure of the fourth embodiment can also obtain the same rod-shaped bath effect as the structure of the first embodiment. [Explanation of symbols]

[0231] 1... shock absorber, 4... cylinder, 22... one side chamber (first chamber), 23... other side chamber (second chamber), 21...piston, 31...piston rod, 81, 82...piston passage, 132...first passage, 152...second passage, 165...O-ring (sealing member), 166... ​​valve seat member, 166a... tapered surface, 166b... introduction portion, 178... cap member, 182... annular member, 185... retainer, 191... bottom portion, 193... peripheral wall portion (tapered wall), 195... working fluid passage hole, 271... peripheral groove (seal groove), 285... cap chamber, 291... second passage, 301... valve mechanism (second check valve mechanism: second sub-valve), 321... Valve mechanism (first check valve mechanism: first sub-valve), 315...second passage, 335...relief mechanism, 336...relief mechanism, 366... ​​valve seat member, 368... peripheral step portion, 370... introduction portion, 378... cap member, 394...peripheral step portion, 396...lower wall, 466...valve seat member, 467...peripheral groove, 478...cap member, 469...press-fitting portion (introduction portion), 578...cap member, 593...peripheral wall portion, 594...tapered inner peripheral surface, DF1...first damping force generating mechanism, DF2...second damping force generating mechanism, L...working fluid.

Claims

1. a cylinder in which a working fluid is sealed; a piston slidably provided in the cylinder and dividing the interior of the cylinder into one side chamber and another side chamber; a piston rod connected to the piston and extending to the outside of the cylinder; a first passage and a second passage through which working fluid flows from an upstream chamber to a downstream chamber in the cylinder as the piston moves; a first damping force generating mechanism that is provided in the first passage provided in the piston and generates a damping force; and a second damping force generating mechanism that is provided in the second passage that is provided in an annular valve seat member arranged in the other side chamber and is parallel to the first passage and generates a damping force, The second damping force generating mechanism includes: a first sub-valve provided on one side of the second passage provided in the valve seat member and a second sub-valve provided on the other side; a bottomed cylindrical cap member provided on the valve seat member, the valve seat member is provided within the cap member, the first sub-valve is provided in the other-side chamber, and the second sub-valve is provided within a cap chamber between a bottom of the cap member and the valve seat member; the second passage is provided with an orifice located upstream or downstream of a flow at which the first sub-valve opens, and a relief mechanism is provided in which a second damping force generating mechanism opens in a region where the piston speed is low; the valve seat member has an outer peripheral surface that contacts the inner surface of the peripheral wall of the cap member and is press-fitted into the cap member, and a part of the outer peripheral surface of the valve seat member has an introduction portion with a diameter smaller than the inner diameter of the peripheral wall of the cap member.

2. a seal member between the valve seat member and the cap member; The shock absorber according to claim 1 .

3. a peripheral groove is formed in the outer peripheral wall of the valve seat member, and the seal member is provided in the peripheral groove; The shock absorber according to claim 2 .

4. a press-fit portion on the side of the valve seat member closer to the bottom of the cap member than the position where the seal member is provided; The shock absorber according to claim 2 or 3.

5. The valve seat member has a peripheral step on the outer circumferential surface thereof, and a seal member is provided along the peripheral step. The shock absorber according to claim 2 or 3.

6. The peripheral wall of the cap member is a tapered wall having a small inner diameter on the bottom side of the cap member and an inner diameter that increases as the distance from the bottom increases, a tapered surface that fits inside the tapered wall is formed on the outer peripheral wall of the valve seat member; The shock absorber according to claim 2 or 3.

7. The cap member has an inner surface with a tapered inner circumferential surface, the inner diameter of which is small at the bottom of the cap member and increases with increasing distance from the bottom, the valve seat member has an outer peripheral surface that has a tapered surface that fits into the tapered inner peripheral surface when the valve seat member is housed in the cap member; The shock absorber according to claim 2 or 3.

Images