Shock absorber

Abstract

To provide a shock absorber capable of stabilizing performance.SOLUTION: A shock absorber 1 includes: a first damping force generation mechanism which is provided in a first passage and generates damping force; a second damping force generation mechanism 301, 321 which is provided in a second passage 291, 315 and generates the damping force; and a variable volume mechanism 325, 326 which is provided in parallel with the second passage 291, 315, is operated prior to the second damping force generation mechanism 301, 321 due to a pressure difference between a first chamber and a second chamber 23, and changes the volume of a volume chamber 286, 287. The variable volume mechanism 325, 326 includes a variable volume member 177 which is supported at both ends in an axial direction on an inner side in a radial direction by a bendable member 175, 178 provided on a piston rod 31, and which constitutes at least a part of the volume chamber 286, 287.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] Some shock absorbers have two damping force variable mechanisms that open valves in the same stroke and a volume variable mechanism (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, there is a desire to stabilize the performance of shock absorbers.

[0005] An object of the present invention is to provide a shock absorber capable of stabilizing performance.

Means for Solving the Problems

[0006] In order to achieve the above object, one aspect of the shock absorber according to the present invention includes a cylinder in which a working fluid is enclosed, a piston slidably provided in the cylinder and partitioning the inside of the cylinder into a first chamber and a second chamber, a piston rod connected to the piston and extending outside the cylinder, a first passage through which the working fluid flows out due to the movement of the piston, a second passage provided in parallel with the first passage, a first damping force generating mechanism provided in the first passage and generating a damping force, a second damping force generating mechanism provided in the second passage and generating a damping force, and a variable volume mechanism provided in parallel with the second passage and operating prior to the second damping force generating mechanism due to the pressure difference between the first chamber and the second chamber and having a variable volume of a volume chamber. The variable volume mechanism is configured to include a flexible member provided on the piston rod, with both axial ends on the radially inner side supported, and a variable volume member constituting at least a part of the volume chamber.

Advantages of the Invention

[0007] According to the present invention, it is possible to achieve performance stabilization.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0009] [First Embodiment] The first embodiment will be described with reference to FIGS. 1 to 3.

[0010] The shock absorber 1 of the first embodiment is a shock absorber used in a suspension device of a railway vehicle or an automobile such as a two-wheeled or four-wheeled vehicle. Specifically, the shock absorber 1 is a shock absorber used in a suspension device of a four-wheeled vehicle. As shown in FIG. 1, the shock absorber 1 is a double-tube shock absorber including a cylinder 4 having an inner tube 2 and an outer tube 3. The inner tube 2 is cylindrical. The outer tube 3 is a bottomed tube having a larger diameter than the inner tube 2. The outer tube 3 is provided coaxially with the inner tube 2 on the radially outer side of the inner tube 2. The space between the outer tube 3 and the inner tube 2 forms a reservoir chamber 5.

[0011] The outer tube 3 has a tube portion 8 and a bottom portion 9. The tube portion 8 is cylindrical. The bottom portion 9 closes one axial end portion of the tube portion 8. The side opposite to the bottom portion 9 of the tube portion 8 is an opening. A mounting eye 10 is fixed to the side of the bottom portion 9 opposite to the tube portion 8 in the axial direction.

[0012] 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 portion 9 side in the axial direction of the inner tube 2 and the outer tube 3. The rod guide 13 is annular and is provided on the side opposite to the bottom portion 9 in the axial direction of the inner tube 2 and the outer tube 3. The valve body 12 constitutes a base valve 15. The outer peripheral portion of the valve body 12 has a stepped shape, and it is placed on the bottom portion 9 in a state of being positioned radially with respect to the tube portion 8 at its large-diameter portion. The outer peripheral portion of the rod guide 13 also has a stepped shape, and its large-diameter portion is radially positioned and fitted into the tube portion 8.

[0013] The inner cylinder 2 has one axial end fitted to the small-diameter portion of the outer peripheral portion 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 this valve body 12. Also, the other axial end of the inner cylinder 2 is fitted to the small-diameter portion of the outer peripheral portion 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 this rod guide 13. In this state, the inner cylinder 2 is positioned radially with respect to the outer cylinder 3. Here, the space between the valve body 12 and the bottom 9 communicates with the space between the inner cylinder 2 and the outer cylinder 3. Therefore, the space between the valve body 12 and the bottom 9 forms a reservoir chamber 5, similar to the space between the inner cylinder 2 and the outer cylinder 3.

[0014] The shock absorber 1 includes a seal member 18. The seal member 18 is provided on the side opposite to the bottom 9 of the rod guide 13. This seal member 18 is also fitted to the inner peripheral portion of the cylindrical portion 8, similar to the rod guide 13. A locking portion 19 is formed at the end of the cylindrical portion 8 in the axial direction opposite to the bottom 9. The locking portion 19 is formed by plastically deforming the cylindrical portion 8 radially inward by caulking or the like. 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.

[0015] The shock absorber 1 includes a piston 21. The piston 21 is slidably provided in the cylinder 4. The piston 21 is slidably provided in the inner cylinder 2 of the cylinder 4. The piston 21 divides the inside of the inner cylinder 2 into a first chamber 22 and a second chamber 23. The first chamber 22 is provided between the piston 21 and the rod guide 13 inside the inner cylinder 2. The second chamber 23 is provided between the piston 21 and the valve body 12 inside the inner cylinder 2. The second chamber 23 is defined by the valve body 12 and the reservoir chamber 5. In the cylinder 4, hydraulic fluid, i.e., oil L, is enclosed in the first chamber 22 and the second chamber 23. In the cylinder 4, gas G and oil L, which are the working fluids, are enclosed in the reservoir chamber 5. Therefore, the shock absorber 1 is a hydraulic shock absorber that uses the fluid oil L.

[0016] The shock absorber 1 includes a metal rod-shaped piston rod 31. One end portion in the axial direction of the piston rod 31 is disposed inside the cylinder 4 and is connected and fixed to the piston 21. The other end portion in the axial direction of the piston rod 31 extends outside the cylinder 4. The piston rod 31 penetrates through the first chamber 22. The piston rod 31 does not penetrate through the second chamber 23. Therefore, the first chamber 22 is a rod-side chamber through which the piston rod 31 penetrates. The second chamber 23 is a bottom-side chamber on the bottom 9 side of the cylinder 4.

[0017] The piston 21 and the piston rod 31 move integrally. In the extension stroke of the shock absorber 1 in which the protruding amount of the piston rod 31 from the cylinder 4 increases, the piston 21 moves toward the first chamber 22 side. In the contraction stroke of the shock absorber 1 in which the protruding amount of the piston rod 31 from the cylinder 4 decreases, the piston 21 moves toward the second chamber 23 side.

[0018] Both the rod guide 13 and the seal member 18 are annular. The piston rod 31 is slidably inserted inside each of these rod guide 13 and seal member 18 and extends from the inside of the cylinder 4 to the outside. One end portion in the axial direction of the piston rod 31 is fixed to the piston 21 inside the cylinder 4. The other end portion in the axial direction of the piston rod 31 extends outside the cylinder 4 via the rod guide 13 and the seal member 18.

[0019] The rod guide 13 supports the piston rod 31 with respect to the cylinder 4 so as to be movable in the axial direction while restricting its radial movement. The outer peripheral portion of the seal member 18 is in close contact with the outer cylinder 3 of the cylinder 4. The inner peripheral portion of the seal member 18 is in sliding contact with the outer peripheral portion of the piston rod 31 that moves in the axial direction. Thereby, the seal member 18 prevents the oil fluid L and the gas G inside the cylinder 4 from leaking to the outside.

[0020] The piston rod 31 has a main shaft portion 32, a mounting shaft portion 33, and a threaded shaft portion 34. The mounting shaft portion 33 has an outer diameter smaller than that of the main shaft portion 32 and extends along the axial direction of the main shaft portion 32 from one axial end of the main shaft portion 32. The threaded shaft portion 34 has an outer diameter slightly smaller than that of the mounting shaft portion 33 and extends along the axial direction of the mounting shaft portion 33 from the end portion on the opposite side of the main shaft portion 32 in the axial direction of the mounting shaft portion 33. For the piston rod 31, the main shaft portion 32 is slidably fitted to the rod guide 13 and the seal member 18. For the piston rod 31, the mounting shaft portion 33 is disposed in the cylinder 4 and connected to the piston 21 and the like. The end portion of the main shaft portion 32 on the mounting shaft portion 33 side extends in the direction orthogonal to the axis.

[0021] As shown in Fig. 2, on the mounting shaft portion 33, a base-end-side circumferential groove 51, a pair of axial grooves 52, and a tip-end-side circumferential groove 53 are formed on the outer side in the radial direction.

[0022] The base-end-side circumferential groove 51 is provided at an intermediate position on the main shaft portion 32 side in the axial direction of the mounting shaft portion 33. The base-end-side circumferential groove 51 is recessed inward in the radial direction of the mounting shaft portion 33 from the outer peripheral surface of the mounting shaft portion 33. The base-end-side circumferential groove 51 is an annular shape continuous over the entire circumference in the circumferential direction of the mounting shaft portion 33.

[0023] The tip-end-side circumferential groove 53 is provided at an intermediate position on the opposite side of the main shaft portion 32 from the base-end-side circumferential groove 51 in the axial direction of the mounting shaft portion 33. The tip-end-side circumferential groove 53 is recessed inward in the radial direction of the mounting shaft portion 33 from the outer peripheral surface of the mounting shaft portion 33. The tip-end-side circumferential groove 53 is an annular shape continuous over the entire circumference in the circumferential direction of the mounting shaft portion 33.

[0024] The pair of axial grooves 52 are recessed inward in the radial direction of the mounting shaft portion 33 from the outer peripheral surface of the mounting shaft portion 33. The pair of axial grooves 52 have the same shape, and the inner bottom surface in the radial direction of the mounting shaft portion 33 is in a planar shape that extends perpendicular to the radial direction of the mounting shaft portion 33. The pair of axial grooves 52 extend in the axial direction of the piston rod 31. The pair of axial grooves 52 are provided with a 180-degree phase difference in the circumferential direction of the mounting shaft portion 33 and extend parallel to each other. One end of the pair of axial grooves 52 in the axial direction of the mounting shaft portion 33 opens into the base-end side circumferential groove 51, and the other end in the axial direction of the mounting shaft portion 33 opens into the tip-end side circumferential groove 53.

[0025] The passage in the base-end side circumferential groove 51, the passage in the pair of axial grooves 52, and the passage in the tip-end side circumferential groove 53 constitute an axial passage 54 formed to extend in the axial direction of the piston rod 31 in the piston rod 31.

[0026] The threaded shaft portion 34 is provided on the side opposite to the main shaft portion 32 in the axial direction of the mounting shaft portion 33. A male thread 57 is formed on the threaded shaft portion 34 on the radially outer side.

[0027] The shock absorber 1 is supported by the vehicle body with, for example, the protruding portion shown in FIG. 1 of the piston rod 31 from the cylinder 4 disposed at the upper part in the vertical direction. At this time, the shock absorber 1 has the mounting eye 10 fixed to the bottom portion 9 of the cylinder 4 disposed at the lower part in the vertical direction and connected to the wheel side. In the case of a single-tube type shock absorber 1, conversely, it is also possible to configure the shock absorber 1 such that the cylinder 4 side is supported by the vehicle body and the piston rod 31 is connected to the wheel side.

[0028] As shown in FIG. 2, 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 peripheral surface of the piston body 61 and sliding inside the inner cylinder 2.

[0029] The piston body 61 is formed with a plurality of passage holes 71 (only one is shown in FIG. 2 due to the sectional view relationship) and an annular passage groove 72 that communicates with the ends of these passage holes 71 on the side opposite to the first chamber 22. Further, the piston body 61 is formed with a plurality of passage holes 75 (only one is shown in FIG. 2 due to the sectional view relationship) and an annular passage groove 76 that communicates with 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 a passage hole 75 interposed therebetween at each interval.

[0030] The passages in the plurality of passage holes 71 and the passages in the passage groove 72 constitute a piston passage 81 that penetrates the piston 21 in the axial direction of the piston 21 and enables communication between the first chamber 22 and the second chamber 23. The passages in the plurality of passage holes 75 and the passages in the passage groove 76 constitute a piston passage 82 that penetrates the piston 21 in the axial direction of the piston 21 and enables communication between the first chamber 22 and the second chamber 23.

[0031] The piston passage 81 is provided with a first damping force generating mechanism 85 that opens and closes the piston passage 81 to generate a damping force. The first damping force generating mechanism 85 is disposed on the second chamber 23 side in the axial direction of the piston 21 and is attached to the piston rod 31. By disposing the first damping force generating mechanism 85 on the second chamber 23 side, in the movement of the piston 21 toward the first chamber 22 side, that is, in the extending stroke, the oil fluid L flowing out from the first chamber 22 flows toward the second chamber 23. The first damping force generating mechanism 85 provided for the piston passage 81 serves as a damping force generating mechanism on the extending side that suppresses the flow of the oil fluid L from the piston passage 81 on the extending side to the second chamber 23 and generates a damping force.

[0032] The piston passage 82 is provided with a first damping force generating mechanism 86 that opens and closes the piston passage 82 to generate a damping force. The first damping force generating mechanism 86 is disposed on the first chamber 22 side in the axial direction of the piston 21 and is attached to the piston rod 31. By disposing the first damping force generating mechanism 86 on the first chamber 22 side, in the movement of the piston 21 toward the second chamber 23 side, that is, in the compression stroke, the hydraulic fluid L flowing out from the second chamber 23 flows toward the first chamber 22. The first damping force generating mechanism 86 provided for the piston passage 82 serves as a compression-side damping force generating mechanism that suppresses the flow of the hydraulic fluid L from the compression-side piston passage 82 to the first chamber 22 to generate a damping force.

[0033] The piston body 61 is composed of two members, a first piston body 91 and a second piston body 92. The first piston body 91 constitutes the portion on the second chamber 23 side in the axial direction of the piston body 61, and the second piston body 92 constitutes the portion on the first chamber 22 side in the axial direction of the piston body 61.

[0034] The first piston body 91 has a substantially disc shape. A circular fixing hole 101 is formed in the center of the first piston body 91 in the radial direction, penetrating the first piston body 91 in the axial direction thereof. The mounting shaft portion 33 of the piston rod 31 is fitted into the fixing hole 101 in the first piston body 91.

[0035] On the end face of the first piston body 91 on the second piston body 92 side in the axial direction, a passage groove 102 extending in the radial direction of the first piston body 91 is formed. The passage in the passage groove 102 forms a piston internal passage 103 that communicates with the piston passage 81.

[0036] The above-described passage groove 72 is formed at the end portion on the second chamber 23 side in the axial direction of the first piston body 91. An annular valve seat portion 105 that forms part of the first damping force generating mechanism 85 is formed on the end portion on the second chamber 23 side in the axial direction of the first piston body 91, radially outside the opening of the passage groove 72 on the second chamber 23 side. Further, an annular inner seat portion 106 is formed on the end portion on the second chamber 23 side in the axial direction of the piston main body 61, radially inside the opening of the passage groove 72 on the second chamber 23 side.

[0037] On the first piston body 91, an engaging convex portion 108 that protrudes outward along the axial direction of the first piston body 91 is formed from the end face on the second piston body 92 side in the axial direction of the first piston body 91. The engaging convex portion 108 is provided partially in the circumferential direction of the first piston body 91.

[0038] The second piston body 92 has a substantially disc shape. A circular fixing hole 111 is formed at the center in the radial direction of the second piston body 92, penetrating the second piston body 92 in the axial direction of the second piston body 92. The mounting shaft portion 33 of the piston rod 31 is fitted into the fixing hole 111 of the second piston body 92.

[0039] The above-described passage groove 76 is formed at the end portion on the first chamber 22 side in the axial direction of the second piston body 92. An annular valve seat portion 115 that forms part of the first damping force generating mechanism 86 is formed on the end portion on the first chamber 22 side in the axial direction of the second piston body 92, radially outside the opening of the passage groove 76 on the first chamber 22 side. Further, an annular inner seat portion 116 is formed on the end portion on the first chamber 22 side in the axial direction of the piston main body 61, radially inside the opening of the passage groove 76 on the first chamber 22 side.

[0040] On the second piston body 92, an engaging concave portion 118 that is recessed inward along the axial direction of the second piston body 92 is formed from the end face on the first piston body 91 side in the axial direction of the second piston body 92. The engaging concave portion 118 is provided partially in the circumferential direction of the second piston body 92.

[0041] The first piston body 91 and the second piston body 92 are connected by engaging the engaging convex portion 108 of the first piston body 91 with the engaging concave portion 118 of the second piston body 92. Thereby, the first piston body 91 and the second piston body 92 are connected in a state of being circumferentially positioned so as to form the piston passage 81 and the piston passage 82. In this state, the friction member 62 is covered on the radially outer sides of the first piston body 91 and the second piston body 92. Thereby, the first piston body 91 and the second piston body 92 are integrated into the piston main body 61, and the first piston body 91, the second piston body 92, and the friction member 62 are integrated into the piston 21.

[0042] In the first piston body 91, an opening on the second chamber 23 side of the piston passage 82 on the shrinking side is disposed outside the valve seat portion 105 in the radial direction. Further, in the second piston body 92, an opening on the first chamber 22 side of the piston passage 81 on the extending side is disposed outside the valve seat portion 115 in the radial direction.

[0043] For the piston 21, the fixing holes 101 and 111 are fitted to the mounting shaft portion 33 of the piston rod 31. In the axial direction of the piston rod 31, the piston inner passage 103 of the piston 21 is arranged so as to overlap the circumferential groove 51 on the proximal end side of the piston rod 31 in position. Thereby, even without performing circumferential phase alignment of the piston 21 with respect to the piston rod 31, the piston inner passage 103 can be communicated with the axial passage 54 of the piston rod 31.

[0044] The first damping force generating mechanism 86 on the shrinking side includes the valve seat portion 115 of the piston 21. Between the main shaft portion 32 of the piston rod 31 and the piston 21, in order from the piston 21 side in the axial direction, a single disk 121, a plurality of disks 122 constituting the first damping force generating mechanism 86, a single disk 123, a single disk 124, and a single annular member 125 are provided. The disks 121 to 124 and the annular member 125 are all perforated circular flat plates made of metal, and all of them have the mounting shaft portion 33 fitted to the inside.

[0045] The disk 121 has an outer diameter that is larger than the outer diameter of the inner seat portion 116 of the piston 21 and smaller than the inner diameter of the valve seat portion 115. The disk 121 is constantly in contact with the inner seat portion 116.

[0046] Among the plurality of disks 122, the disk 122 closest to the disk 121 in the axial direction has an outer diameter equal to the outer diameter of the valve seat portion 115 of the piston 21. Among the plurality of disks 122, the disk 122 closest to the disk 121 in the axial direction can be seated and separated from the valve seat portion 115.

[0047] The disk 123 has an outer diameter smaller than the outer diameter of any of the plurality of disks 122 and slightly smaller than the outer diameter of the inner seat portion 116 of the piston 21.

[0048] The disk 124 has an outer diameter larger than the outer diameter of the disk 123.

[0049] The annular member 125 has an outer diameter smaller than the outer diameter of the disk 124 and larger than the outer diameter of the end portion on the mounting shaft portion 33 side in the axial direction of the main shaft portion 32 of the piston rod 31. The annular member 125 is thicker and has higher rigidity than the disks 121 to 124, and is in contact with the end portion on the mounting shaft portion 33 side in the axial direction of the main shaft portion 32.

[0050] A plurality of disks 122 constitute a valve member 131 on the contracting side that can be seated on and separated from the valve seat portion 115. The valve member 131 constitutes a first damping force generating mechanism 86. The valve member 131 is flexible and, by separating from the valve seat portion 115, communicates the piston passage 82 with the first chamber 22. At that time, the valve member 131 suppresses the flow of the hydraulic fluid L between itself and the valve seat portion 115 to generate a damping force. The valve member 131 blocks the communication between the piston passage 82 and the first chamber 22 by seating on the valve seat portion 115. The annular member 125, together with the disk 124, abuts against the valve member 131 to suppress deformation of the valve member 131 in the opening direction beyond a specified amount.

[0051] The piston passage 82 and the passage between the valve member 131 and the valve seat portion 115 that appears when the valve opens constitute a first passage 132. The first passage 132 is provided in the piston 21. The first passage 132 is a contracting-side passage through which the hydraulic fluid L flows out from the second chamber 23, which becomes the upstream side in the cylinder 4, to the first chamber 22, which becomes the downstream side, due to the movement of the piston 21 toward the second chamber 23 side. The contracting-side first damping force generating mechanism 86 that generates a damping force includes the valve member 131 and the valve seat portion 115. The first damping force generating mechanism 86 is provided in the first passage 132. The first damping force generating mechanism 86 opens and closes this first passage 132 and suppresses the flow of the hydraulic fluid L from this first passage 132 to the first chamber 22 to generate a damping force. The first passage 132 is provided in the piston 21 including the valve seat portion 115, and the hydraulic fluid L flows out to the first chamber 22 due to the movement of the piston rod 31 and the piston 21 toward the contracting side.

[0052] Here, neither the valve seat portion 115 nor the valve member 131 that abuts against it in the contracting-side first damping force generating mechanism 86 is provided with a fixed orifice that communicates the first chamber 22 and the second chamber 23 even when the valve seat portion 115 and the valve member 131 are in contact. Therefore, the first passage 132 is not a passage that constantly communicates the first chamber 22 and the second chamber 23.

[0053] The extension-side first damping force generating mechanism 85 includes the valve seat portion 105 of the piston 21. On the side opposite to the main shaft portion 32 in the axial direction of the piston 21, in order from the piston 21 side in the axial direction, there are provided a single disk 141, a plurality of disks 142 constituting the first damping force generating mechanism 85, a single disk 143, and a plurality of disks 144. The disks 141 to 144 are all perforated circular flat plates made of metal, and all have the mounting shaft portion 33 fitted inside them.

[0054] 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 always in contact with the inner seat portion 106.

[0055] Among the plurality of disks 142, the disk 142 closest to the disk 141 in the axial direction has an outer diameter equal to the outer diameter of the valve seat portion 105 of the piston 21. Among the plurality of disks 142, the disk 142 closest to the disk 141 in the axial direction can be seated on and separated from the valve seat portion 105.

[0056] 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.

[0057] The plurality of disks 144 have an outer diameter larger than the outer diameter of the disk 143.

[0058] The plurality of disks 142 constitute the extension-side valve member 151 that can be seated on and separated from the valve seat portion 105. The valve member 151 constitutes the first damping force generating mechanism 85. The valve member 151 is flexible, and by separating from the valve seat portion 105, it communicates the piston passage 81 with the second chamber 23. At that time, the valve member 151 suppresses the flow of the hydraulic fluid L between it and the valve seat portion 105 to generate a damping force. The valve member 151 blocks the communication between the piston passage 81 and the second chamber 23 by seating on the valve seat portion 105.

[0059] The piston passage 81 and the passage between the valve member 151 and the valve seat portion 105 that appears when the valve is opened constitute the first passage 152. The first passage 152 is formed in the piston 21. The first passage 152 is a passage on the extending side through which the hydraulic fluid L flows from the first chamber 22, which becomes the upstream side in the cylinder 4, to the second chamber 23, which becomes the downstream side, due to the movement of the piston 21 toward the first chamber 22 side. The first damping force generating mechanism 85 on the extending side, which generates a damping force, includes the valve member 151 and the valve seat portion 105. The first damping force generating mechanism 85 is provided in this first passage 152. The first damping force generating mechanism 85 opens and closes this first passage 152 and suppresses the flow of the hydraulic fluid L from this first passage 152 to the second chamber 23 to generate a damping force. The first passage 152 is provided in the piston 21 including the valve seat portion 105, and the hydraulic fluid L flows out to the second chamber 23 due to the movement of the piston rod 31 and the piston 21 toward the extending side.

[0060] In the first damping force generating mechanism 85 on the extending side, neither the valve seat portion 105 nor the valve member 151 that abuts against it has a fixed orifice that connects the first chamber 22 and the second chamber 23 even when the valve seat portion 105 and the valve member 151 are in contact. Therefore, the first passage 152 is not a passage that constantly connects the first chamber 22 and the second chamber 23.

[0061] The piston inner passage 103 provided in the piston 21 communicates with the first chamber 22 through a part of the piston inner passage 103 of the piston passage 81 on the first chamber 22 side. The piston inner passage 103 and the shaft passage 54 are provided in parallel with respect to the first passage 152.

[0062] As shown in FIG. 3, on the side opposite to the disk 143 in the axial direction of the disk 144, in order from the disk 144 side, there are provided a single disk 160, a single spring member 161, a plurality of disks 162, a single valve member 163, and a single sheet member 166 provided with one O-ring 165 on the outer peripheral side. Further, on the side opposite to the valve member 163 in the axial direction of the sheet member 166, in order from the sheet member 166 side, there are provided a single valve member 167, a plurality of disks 168, a single spring member 169, and a single disk 170. Further, on the side opposite to the spring member 169 in the axial direction of the disk 170, in order from the disk 170 side, there are provided a plurality of disks 172, a single biasing member 173, and a plurality of disks 174. Further, on the side opposite to the biasing member 173 in the axial direction of the disk 174, in order from the disk 174 side, there are provided a single first bending member 175 (bending member), a single inner disk 176 and a single volume variable member 177, a single second bending member 178 (bending member), a single disk 179, a single case member 180, a single disk 181, and a single annular member 182.

[0063] The disks 160, 162, 168, 170, 172, 174, 179, 181, the spring members 161, 169, the valve members 163, 167, the sheet member 166, the biasing member 173, the first bending member 175, the inner disk 176, the volume variable member 177, the second bending member 178, the case member 180, and the annular member 182 are all made of metal.

[0064] The disks 160, 162, 168, 170, 172, 174, 179, 181, the spring members 161, 169, the valve members 163, 167, the sheet member 166, the biasing member 173, the first bending member 175, the inner disk 176, the second bending member 178, the case member 180, and the annular member 182 are all annular, and the mounting shaft portion 33 of the piston rod 31 is fitted inside each of them.

[0065] Here, the mounting shaft portions 33 of the piston rods 31 are respectively fitted inside, and an annular member 125, a disk 124, a disk 123, a disk 122, a disk 121, a piston 21, a disk 141, a disk 142, a disk 143, a disk 144, a disk 160 shown in FIG. 3, a spring member 161, a disk 162, a valve member 163, a seat member 166, a valve member 167, a disk 168, a spring member 169, a disk 170, a disk 172, a biasing member 173, a disk 174, a first flexure member 175, an inner disk 176, a second flexure member 178, a disk 179, a case member 180, a disk 181, and an annular member 182 are stacked in this order on the main shaft portion 32 shown in FIG. 2. In this state, a nut member 185 is screwed onto the male thread 57 on the outer periphery of the threaded shaft portion 34 shown in FIG. 2 that protrudes from the annular member 182 of the piston rod 31. As a result, these components from the annular member 125 to the annular member 182 are each axially clamped at least on the radially inner peripheral side by the main shaft portion 32 of the piston rod 31 and the nut member 185. At that time, the volume variable member 177 is sandwiched between the first flexure member 175 and the second flexure member 178.

[0066] The disks 160, 162, 168, 170, 172, 174, 179, 181, the valve members 163, 167, the biasing member 173, the first flexure member 175, the inner disk 176, the volume variable member 177, and the second flexure member 178 are all in the form of perforated circular flat plates at least in the state before being assembled to the piston rod 31.

[0067] The case member 180 is an integrally formed product having a bottomed cylindrical shape. The case member 180 has a bottom portion 191 and a cylindrical portion 192. As shown in FIG. 2, the outer diameter of the case member 180 is smaller than the outer diameter of the piston 21.

[0068] As shown in FIG. 3, the bottom portion 191 has an inner peripheral side plate portion 193, an intermediate plate portion 194, and an outer peripheral side plate portion 195.

[0069] The inner peripheral side plate portion 193 is in the form of a perforated circular flat plate.

[0070] The intermediate plate portion 194 extends outward from the outer peripheral edge of the inner peripheral side plate portion 193 in the radial direction of the inner peripheral side plate portion 193. The intermediate plate portion 194 is tapered so as to be axially separated from the inner peripheral side plate portion 193 more toward the outer side in the radial direction.

[0071] The outer peripheral side plate portion 195 extends outward from the outer peripheral edge of the intermediate plate portion 194 in the radial direction of the intermediate plate portion 194. The outer peripheral side plate portion 195 is annular and flat, and extends parallel to the inner peripheral side plate portion 193. The convex corner portion at the boundary between the intermediate plate portion 194 and the outer peripheral side plate portion 195 is the member contact portion 196, and the member contact portion 196 forms an annulus.

[0072] A plurality of (only one is shown in FIG. 3 due to the sectional view relationship) passage holes 197 are formed in the bottom portion 191. The plurality of passage holes 197 penetrate the intermediate plate portion 194 in the thickness direction of the intermediate plate portion 194. The plurality of passage holes 197 are provided at equal intervals in the circumferential direction of the intermediate plate portion 194 at an intermediate position in the radial direction of the intermediate plate portion 194.

[0073] The cylindrical portion 192 is cylindrical, curves to one axial side of the bottom portion 191 from the outer peripheral edge of the outer peripheral side plate portion 195 which is the outer peripheral edge of the bottom portion 191, and then extends along the axial direction of the bottom portion 191. In other words, the bottom portion 191 has a shape that curves radially inward and constricts from the end of the cylindrical cylindrical portion 192. In its axial direction, the outer peripheral side plate portion 195 is closer to the cylindrical portion 192 than the inner peripheral side plate portion 193. The intermediate plate portion 194 approaches the cylindrical portion 192 in the axial direction more toward the outer side in the radial direction.

[0074] The case member 180 has the mounting shaft portion 33 of the piston rod 31 fitted to the inner peripheral portion of the inner peripheral side plate portion 193. The case member 180 is oriented such that in its axial direction, the bottom portion 191 is located on the side opposite to the piston 21 shown in FIG. 2 from the cylindrical portion 192. In the case member 180 shown in FIG. 3, the inner peripheral side plate portion 193 of the bottom portion 191 abuts against the disk 181.

[0075] The outer diameter of the disk 181 is sized such that it does not block the passage hole 197 of the case member 180.

[0076] The outer diameter of the annular member 182 is larger than the outer diameter of the disk 181.

[0077] Inside the case member 180, there are arranged the disks 162, 168, 170, 172, 174, 179, the valve members 163, 167, the sheet member 166 provided with the O-ring 165, the spring member 169, the biasing member 173, the first flexure member 175, the inner disk 176, the volume variable member 177, and the second flexure member 178.

[0078] The outer diameter of the disk 179 is smaller than the outer diameter of the inner peripheral side plate portion 193 of the bottom portion 191 of the case member 180 and abuts against the inner peripheral side plate portion 193.

[0079] The second flexure member 178 is flexible. The outer diameter of the second flexure member 178 is larger than the outer diameter of the disk 179 and slightly smaller than the outer diameter of the inner peripheral side plate portion 193 of the case member 180.

[0080] The outer diameter of the inner disk 176 is smaller than the outer diameter of the second flexure member 178 and is equal to the outer diameter of the disk 179.

[0081] The inner diameter of the volume variable member 177 is larger than the outer diameter of the inner disk 176 and smaller than the outer diameter of the second flexure member 178. The outer diameter of the volume variable member 177 is larger than the outer diameter of the second flexure member 178 and is equal to the inner diameter of the cylindrical portion 192 of the case member 180.

[0082] The volume variable member 177 is fitted into the cylindrical portion 192 of the case member 180, whereby it is centered with respect to the case member 180. The volume variable member 177 is edge-cut with respect to the inner disk 176, and thus has a degree of freedom of axial movement on the inner peripheral side while being centered by the cylindrical portion 192.

[0083] The first flexure member 175 is flexible, and its outer diameter is larger than the outer diameter of the inner disk 176 and larger than the inner diameter of the variable volume member 177. Here, the outer diameter of the first flexure member 175 is equal to the outer diameter of the second flexure member 178. The first flexure member 175 is provided on one axial end side of the variable volume member 177, and the second flexure member 178 is provided on the other axial end side of the variable volume member 177.

[0084] The disk 174 has an outer diameter smaller than the outer diameter of the first flexure member 175 and equal to the outer diameter of the disk 179.

[0085] The biasing member 173 is flexible. The outer diameter of the biasing member 173 is larger than the inner diameter of the variable volume member 177 and smaller than the outer diameter of the variable volume member 177. The outer diameter of the biasing member 173 is equal to the diameter of the member contact portion 196 of the bottom portion 191 of the case member 180.

[0086] A plurality of (only one is shown in the cross-sectional view in FIG. 3) passage holes 211 are formed in the biasing member 173. The plurality of passage holes 211 penetrate the biasing member 173 in the axial direction of the biasing member 173. The plurality of passage holes 211 are provided at equal intervals in the circumferential direction of the biasing member 173 at an intermediate position in the radial direction of the biasing member 173. The plurality of passage holes 211 are entirely arranged outside the disk 174 in the radial direction of the biasing member 173 and outside the first flexure member 175.

[0087] The disk 172 has an outer diameter smaller than the outer diameter of the biasing member 173 and equal to the outer diameter of the disk 174. The plurality of passage holes 211 of the biasing member 173 are entirely arranged outside the disk 172 in the radial direction of the biasing member 173.

[0088] The disk 170 is flexible. The outer diameter of the disk 170 is larger than the outer diameter of the biasing member 173 and smaller than the outer diameter of the variable volume member 177.

[0089] The spring member 169 is flexible. The spring member 169 has a substrate portion 221 and a plurality of spring plate portions 222.

[0090] The substrate portion 221 is a perforated circular flat plate. A mounting shaft portion 33 fits inside the substrate portion 221.

[0091] The plurality of spring plate portions 222 extend radially from the outer peripheral edge of the substrate portion 221. The plurality of spring plate portions 222 are farther from the substrate portion 221 in the axial direction of the substrate portion 221 as they are farther from the center in the radial direction of the substrate portion 221.

[0092] The spring member 169 abuts on the disk 170 at the substrate portion 221. The plurality of spring plate portions 222 are farther from the disk 170 in the axial direction of the substrate portion 221 as they are farther from the center in the radial direction of the substrate portion 221.

[0093] The outer diameter of the disk 168 is smaller than the outer diameter of the substrate portion 221 of the spring member 169 and is equal to the outer diameter of the disk 172. The disk 168 abuts on the substrate portion 221 of the spring member 169.

[0094] The valve member 167 is flexible. The outer diameter of the valve member 167 is larger than the maximum outer diameter of the spring member 169.

[0095] Here, the biasing member 173 has a thickness greater than the respective thicknesses of the valve member 167, the spring member 169, the disk 170, the first flexible member 175, the volume variable member 177, and the second flexible member 178, and is more rigid than these. The case member 180 has a thickness greater than the respective thicknesses of the valve member 167, the spring member 169, the disk 170, the biasing member 173, the first flexible member 175, the volume variable member 177, and the second flexible member 178, and is more rigid than these from its shape.

[0096] The sheet member 166 is in the shape of a perforated disc. A central hole 231 that penetrates the sheet member 166 in the axial direction with its center in the radial direction is formed in the sheet member 166. In other words, the central hole 231 extends in the axial direction of the sheet member 166 and penetrates the sheet member 166 in the axial direction. The mounting shaft portion 33 of the piston rod 31 is inserted into the central hole 231 of the sheet member 166.

[0097] The central hole 231 has a fitting hole 234 with a cylindrical inner peripheral surface and a passage groove 235 that is recessed radially outward of the fitting hole 234 with respect to the radius of the fitting hole 234. Both the fitting hole 234 and the passage groove 235 penetrate the sheet member 166 in the axial direction. The central hole 231 has a plurality (only one location is shown in the sectional view in FIG. 3) of passage grooves 235. The plurality of passage grooves 235 are arranged at equal intervals in the circumferential direction of the fitting hole 234.

[0098] The mounting shaft portion 33 of the piston rod 31 fits into the fitting hole 234 of the central hole 231. In the central hole 231, the passage groove 235 extends radially outward of the fitting hole 234. In the axial direction of the piston rod 31, the central hole 231 is aligned with the circumferential groove 53 on the tip side of the piston rod 31. Even without circumferentially aligning the sheet member 166 with respect to the piston rod 31 by the circumferential groove 53 on the tip side of the piston rod 31, the passage in the passage groove 235 can be communicated with the axial passage 54.

[0099] The sheet member 166 has an inner sheet portion 241 and a valve sheet portion 242 at one end in the axial direction. The inner sheet portion 241 forms an annular shape surrounding the central hole 231. The valve sheet portion 242 extends outward from the inner sheet portion 241 in the radial direction of the inner sheet portion 241.

[0100] The sheet member 166 has an inner sheet portion 244 and a valve sheet portion 245 at the other end in the axial direction. The inner sheet portion 244 forms an annular shape surrounding the central hole 231. The valve sheet portion 245 extends outward from the inner sheet portion 244 in the radial direction of the inner sheet portion 244.

[0101] The sheet member 166 has a main body portion 247 between its axially inner sheet portion 241 and valve sheet portion 242 and its inner sheet portion 244 and valve sheet portion 245. The main body portion 247 is a perforated disc shape.

[0102] The inner sheet portion 241 projects from the inner peripheral edge portion on one axial side of the main body portion 247 along the axial direction of the main body portion 247 to one side. The valve sheet portion 242 projects from the main body portion 247 on the same side as the inner sheet portion 241 along the axial direction of the main body portion 247 outside the inner sheet portion 241 in the radial direction.

[0103] The inner sheet portion 244 projects from the inner peripheral edge portion on the side opposite to the inner sheet portion 241 in the axial direction of the main body portion 247 along the axial direction of the main body portion 247 to the side opposite to the inner sheet portion 241. The valve sheet portion 245 projects from the main body portion 247 on the same side as the inner sheet portion 244 along the axial direction of the main body portion 247 outside the inner sheet portion 244 in the radial direction.

[0104] A radial communication groove 253 that penetrates the inner sheet portion 241 in the radial direction of the inner sheet portion 241 is formed in the inner sheet portion 241. A plurality of radial communication grooves 253 (only one is shown in FIG. 3 in terms of cross-section) are formed at equal intervals in the circumferential direction of the inner sheet portion 241. The radial communication groove 253 is formed to be recessed in the axial direction of the sheet member 166 from the tip surface of the inner sheet portion 241 on the side opposite to the main body portion 247.

[0105] The valve sheet portion 242 is a petal-shaped non-circular irregular sheet. The valve sheet portion 242 has a plurality of valve sheet components 255. These valve sheet components 255 have the same shape and are arranged at equal intervals in the circumferential direction of the sheet member 166.

[0106] In the valve seat component 255, a passage recess 258 is formed on each inner side. The passage recess 258 is formed surrounded by a part of the inner seat portion 241 and the valve seat component 255. The passage recess 258 is recessed in the axial direction of the seat member 166 from the tip surface on the protruding side of the inner seat portion 241 and the tip surface on the protruding side of the valve seat component 255. The bottom surface of the passage recess 258 is formed by the main body portion 247. The passage recess 258 is formed on the inner side of all the valve seat components 255.

[0107] A passage hole 259 is formed at the central position of the passage recess 258 in the circumferential direction of the seat member 166. The passage hole 259 penetrates the seat member 166 in the axial direction by penetrating the main body portion 247 in the axial direction. The passage hole 259 is a linear hole parallel to the central axis of the seat member 166. The passage hole 259 is formed on the bottom surface of all the passage recesses 258 in the seat member 166. The passage in the radial communication groove 253 communicates with the inside of the passage recess 258, and communicates the passage in the passage recess 258 with the passage in the passage groove 235.

[0108] In the inner seat portion 244, a plurality of communication grooves 263 (only one is shown in FIG. 3 in the sectional view for the sake of illustration) are formed at equal intervals in the circumferential direction of the inner seat portion 244, which cross the inner seat portion 244 in the radial direction of the inner seat portion 244. The communication groove 263 is recessed in the axial direction of the seat member 166 from the tip surface on the side opposite to the main body portion 247 of the inner seat portion 244.

[0109] The valve seat portion 245 is a non-circular petal-shaped irregular sheet. The valve seat portion 245 has a plurality of valve seat components 265. These valve seat components 265 have the same shape and are arranged at equal intervals in the circumferential direction of the seat member 166.

[0110] In the inner sheet portion 244, a communication groove 263 is disposed between the valve sheet component portions 265 adjacent to each other in the circumferential direction of the sheet member 166. Therefore, the communication groove 263 is formed in a portion disposed outside the valve sheet portion 245 in the inner sheet portion 244.

[0111] In each of the plurality of valve sheet component portions 265, a passage recess 268 is formed inside. The passage recess 268 is formed surrounded by a part of the inner sheet portion 244 and the valve sheet component portion 265. The passage recess 268 is recessed in the axial direction of the sheet member 166 from the tip surface on the protruding side of the inner sheet portion 244 and the tip surface on the protruding side of the valve sheet component portion 265. The bottom surface of the passage recess 268 is formed by the main body portion 247. The passage recess 268 is formed inside all of the valve sheet component portions 265.

[0112] At the central position of the passage recess 268 in the circumferential direction of the sheet member 166, a passage hole 269 is formed. The passage hole 269 penetrates the sheet member 166 in the axial direction by penetrating the main body portion 247 in the axial direction. The passage hole 269 is a linear hole parallel to the central axis of the sheet member 166. The passage hole 269 is formed on the bottom surface of all of the passage recesses 268.

[0113] Here, the arrangement pitch in the circumferential direction of the sheet member 166 of the plurality of valve sheet component portions 255 is the same as the arrangement pitch in the circumferential direction of the sheet member 166 of the plurality of valve sheet component portions 265. And the valve sheet component portion 255 and the valve sheet component portion 265 are shifted by about half a phase of the arrangement pitch from each other in the circumferential direction of the sheet member 166.

[0114] And the passage hole 269 is disposed between the valve sheet component portions 255 adjacent to each other in the circumferential direction of the sheet member 166. Therefore, the passage hole 269 opens outside the range of the valve sheet portion 242.

[0115] Further, the passage hole 259 is disposed between adjacent valve seat constituent parts 265 in the circumferential direction of the seat member 166. Therefore, the passage hole 259 opens outside the range of the valve seat portion 245.

[0116] A seal groove 271 is formed at the axial center position of the outer peripheral portion of the main body portion 247 in the seat member 166. The seal groove 271 is annular and recessed radially inward from the outer peripheral surface of the main body portion 247. An O-ring 165 is disposed in the seal groove 271.

[0117] The passage in the passage hole 259 and the passage in the passage recess 258 where the passage hole 259 opens constitute a passage portion 281 provided in the seat member 166. A plurality of passage portions 281 are provided at equal intervals in the circumferential direction of the seat member 166. The passage portion 281 communicates with the passage in the radial communication groove 253 and the passage in the communication groove 263.

[0118] The passage hole 269 and the passage in the passage recess 268 where the passage hole 269 opens constitute a passage portion 282 provided in the seat member 166. A plurality of passage portions 282 are provided at equal intervals in the circumferential direction of the seat member 166.

[0119] The seat member 166 is fitted to the cylindrical portion 192 of the case member 180 at the outer peripheral portion with the inner seat portion 241 and the valve seat portion 242 facing away from the bottom portion 191 of the case member 180. In this state, the O-ring 165 seals the gap between the cylindrical portion 192 of the case member 180 and the seat member 166.

[0120] With the inner disk 176 attached to the piston rod 31, the inner disk 176 is axially clamped by the first flexure member 175 and the second flexure member 178 as a whole. Also, in this state, the volume variable member 177 is axially clamped by the first flexure member 175 and the second flexure member 178 over the entire inner peripheral side. Further, in this state, on the outer peripheral side of one side in the axial direction of the volume variable member 177, the case member contact portion 205 contacts the member contact portion 196 at the boundary corner between the intermediate plate portion 194 and the outer peripheral side plate portion 195 of the case member 180 over the entire circumference. At that time, the inner peripheral portion of the volume variable member 177 is clamped by the first flexure member 175 and the second flexure member 178, so that it spreads parallel to the first flexure member 175 and the second flexure member 178, and the portion that spreads radially outside the first flexure member 175 and the second flexure member 178 is elastically deformed in a curved shape so as to approach the sheet member 166 in the axial direction toward the outer peripheral side and closely adheres to the member contact portion 196. Also, in this state, on the outer peripheral side of the other side in the axial direction of the volume variable member 177, it contacts the outer peripheral edge portion of the biasing member 173 over the entire circumference.

[0121] In this state, the outer peripheral side of the biasing member 173 is elastically deformed in a curved shape so as to approach the sheet member 166 in the axial direction toward the outer peripheral end side. As a result, the biasing member 173 closely adheres to the volume variable member 177 over the entire circumference, and presses the case member contact portion 205 of the volume variable member 177 against the member contact portion 196 of the case member 180 over the entire circumference. In this state, the outer diameter of the biasing member 173 is substantially equal to the outer diameter of the member contact portion 196.

[0122] The volume variable member 177 has a case member contact portion 205 on the outer radial side that contacts the case member 180 in the axial direction, and is biased toward the member contact portion 196 side of the case member 180 by the biasing member 173 provided on the side opposite to the case member contact portion 205 in the axial direction.

[0123] The case member 180, the O-ring 165, and the sheet member 166 form a case chamber 285 inside the case member 180. The case chamber 285 is provided between the bottom portion 191 of the case member 180 and the sheet member 166. The valve member 167, the disks 168, 170, 172, 174, 179, the spring member 169, the biasing member 173, the first flexing member 175, the inner disk 176, the volume variable member 177, and the second flexing member 178 are provided inside this case chamber 285. The sheet member 166 has the valve seat portion 245 disposed on the case chamber 285 side.

[0124] Inside the case chamber 285, a first chamber communicating volume chamber 286 (volume chamber) for storing the hydraulic fluid L is formed. The first chamber communicating volume chamber 286 is formed and surrounded by the cylindrical portion 192 of the case member 180, the sheet member 166, the valve member 167, the disks 168, 170, 172, 174, the spring member 169, the biasing member 173, the first flexing member 175, and the volume variable member 177. Thus, the case member 180 covers at least a part of the first chamber communicating volume chamber 286.

[0125] Inside the case chamber 285, a second chamber communicating volume chamber 287 (volume chamber) for storing the hydraulic fluid L is formed. The second chamber communicating volume chamber 287 is formed and surrounded by the bottom portion 191 of the case member 180, the disk 179, the second flexing member 178, and the volume variable member 177. Thus, the case member 180 covers at least a part of the second chamber communicating volume chamber 287. The second chamber communicating volume chamber 287 includes the passage inside the passage hole 197 of the bottom portion 191 of the case member 180. The first chamber communicating volume chamber 286 is the portion of the case chamber 285 excluding the second chamber communicating volume chamber 287.

[0126] The communication between the first chamber communicating volume chamber 286 and the second chamber communicating volume chamber 287 is blocked by the first flexing member 175, the volume variable member 177, and the second flexing member 178.

[0127] The annular sheet member 166 and the bottomed cylindrical case member 180 are arranged in the second chamber 23, which is one of the first chamber 22 and the second chamber 23, as shown in FIG. 2. At that time, as shown in FIG. 3, the sheet member 166 is arranged at a position where the valve sheet portion 242 faces the second chamber 23. The passage in the passage hole 197 of the case member 180 is always in communication with the second chamber 23. Therefore, the second chamber communicating volume chamber 287 including the passage in the passage hole 197 communicates with the second chamber 23.

[0128] The first chamber communicating volume chamber 286 is always in communication with the first chamber 22 through the passage in the communication groove 263 of the sheet member 166, the passage in the passage groove 235, the axial passage 54 of the piston rod 31, the piston internal passage 103 and the piston passage 81 provided in the piston 21 shown in FIG. 2.

[0129] When the volume variable member 177 shown in FIG. 3 bends axially while being centered by the cylindrical portion 192 of the case member 180, the volumes of the first chamber communicating volume chamber 286 and the second chamber communicating volume chamber 287 change. The second chamber communicating volume chamber 287 decreases in volume to absorb the increase in the volume of the first chamber communicating volume chamber 286 and discharges the hydraulic fluid L from the passage in the passage hole 197 to the second chamber 23. The second chamber communicating volume chamber 287 increases in volume to absorb the decrease in the volume of the first chamber communicating volume chamber 286 and allows the hydraulic fluid L in the second chamber 23 to flow in from the passage in the passage hole 197.

[0130] The first chamber communicating volume chamber 286 decreases in volume to absorb the increase in the volume of the second chamber communicating volume chamber 287 and discharges the hydraulic fluid L to the first chamber 22 side. The first chamber communicating volume chamber 286 increases in volume to absorb the decrease in the volume of the second chamber communicating volume chamber 287 and allows the hydraulic fluid L to flow in from the first chamber 22 side.

[0131] As described above, the deformation of the first flexure member 175, the volume variable member 177, and the second flexure member 178 is suppressed from being inhibited by the hydraulic fluid L in the first chamber communicating volume chamber 286 and the second chamber communicating volume chamber 287.

[0132] The plurality of passage portions 282 of the sheet member 166 are provided facing the second chamber 23 and are always in communication with the second chamber 23.

[0133] The valve member 167 is flexible. The valve member 167 has an outer diameter equivalent to the outer diameter of the valve seat portion 245 of the sheet member 166. The valve member 167 is always in contact with the inner sheet portion 244 and can be seated on and disengaged from the valve seat portion 245. The valve member 167 closes all the passage portions 282 by seating on the entire valve seat portion 245. Also, the valve member 167 opens the passage portion 282 inside the valve seat component 265 from which it has disengaged by disengaging from any one of the valve seat components 265 of the valve seat portion 245.

[0134] The spring member 169 biases the valve member 167 to abut against the valve seat portion 245 of the sheet member 166. The valve member 167 seats on the valve seat portion 245 by the biasing force of the spring member 169 to close the passage portion 282. The valve member 167 opens the passage portion 282 by deforming against the biasing force of the spring member 169 and disengaging from the valve seat portion 245. The disk 170 and the biasing member 173 suppress excessive deformation of the valve member 167 when the valve is opened. That is, when the valve opening amount of the valve member 167 increases, it abuts against the disk 170 and deflects the disk 170 toward the biasing member 173 side. When this disk 170 abuts, the biasing member 173 suppresses further deflection of the disk 170 and the valve member 167.

[0135] When the valve member 167 disengages from the valve seat portion 245, it communicates the plurality of passage portions 282 with the first chamber communicating volume 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 communicating volume chamber 286, the passages in the communication groove 263 of the sheet member 166 and the passages in the passage groove 235, the axial passage 54 of the piston rod 31, and the piston inner passage 103 and the piston passage 81 provided in the piston 21 shown in FIG. 2. At this time, the valve member 167 shown in FIG. 3 suppresses the flow of the hydraulic fluid L between it and the valve seat portion 245 to generate a damping force.

[0136] The valve member 167 is an inflow valve that opens when allowing the hydraulic fluid L to flow into the first chamber communicating volume chamber 286 from the second chamber 23 through a plurality of passage portions 282. The valve member 167 is a check valve that restricts the outflow of the hydraulic fluid L through the passage portion 282 from the first chamber communicating volume chamber 286 to the second chamber 23. Here, the passage portion 281 opens outside the range of the valve seat portion 245 in the sheet member 166. For this reason, the passage portion 281 is always in communication with the first chamber communicating volume chamber 286 regardless of the valve member 167 seated on the valve seat portion 245.

[0137] The plurality of passage portions 282, the passage between the valve member 167 and the valve seat portion 245 that appears when the valve opens, the first chamber communicating volume chamber 286, the passage in the communication groove 263, the passage in the passage groove 235, the axial passage 54, the piston internal passage 103 shown in FIG. 2, and the piston passage 81 constitute the second passage 291. The second passage 291 is opened and closed by the valve member 167 shown in FIG. 3. The second passage 291 allows the hydraulic fluid L to flow out from the second chamber 23, which becomes the upstream side in the cylinder 4, to the first chamber 22, which becomes the downstream side, due to the movement of the piston 21 shown in FIG. 2 toward the second chamber 23 side. The second passage 291 is a passage on the contraction side where the hydraulic fluid L flows out from the second chamber 23, which becomes the upstream side, toward the first chamber 22, which becomes the downstream side, during the movement of the piston 21 toward the second chamber 23 side, that is, during the contraction stroke. The second passage 291 on the contraction side is provided in parallel with the first passage 132 on the contraction side.

[0138] The valve member 167 shown in FIG. 3, the sheet member 166 including the valve seat portion 245, the disk 168, and the spring member 169 constitute the second damping force generating mechanism 301. The second damping force generating mechanism 301 is provided in the second passage 291 on the contraction side. The second damping force generating mechanism 301 opens and closes this second passage 291 and suppresses the flow of the hydraulic fluid L from this second passage 291 to the first chamber 22 shown in FIG. 2 to generate a damping force. The second damping force generating mechanism 301 is a damping force generating mechanism on the contraction side. The second damping force generating mechanism 301 is provided inside the case member 180. In other words, the case member 180 covers the second damping force generating mechanism 301.

[0139] The second damping force generating mechanism 301 includes a valve seat portion 245 which is a valve seat shown in FIG. 3 and a valve member 167 which is a deflectable valve body, and allows the flow in the second passage 291 from the second chamber 23 on the upstream side in the compression stroke to the first chamber 22 shown in FIG. 2 on the downstream side, while serving as a check valve mechanism that restricts the flow in the direction from the first chamber 22 on the upstream side to the second chamber 23 on the downstream side in the expansion stroke. In other words, the second damping force generating mechanism 301 allows only the flow in the second passage 291 from the second chamber 23 on the upstream side to the first chamber 22 on the downstream side in the compression stroke.

[0140] The second damping force generating mechanism 301 is arranged separately from the first damping force generating mechanism 86 that generates a damping force in the same compression stroke. The valve member 167 that constitutes the second damping force generating mechanism 301 on the compression side is a sub-valve on the compression side.

[0141] Neither the valve seat portion 245 shown in FIG. 3 nor the valve member 167 that abuts against it in the second damping force generating mechanism 301 on the compression side has a fixed orifice that allows the first chamber 22 and the second chamber 23 to communicate even when the valve seat portion 245 and the valve member 167 are in contact. In other words, the second passage 291 is not provided with a fixed orifice that constantly communicates the first chamber 22 and the second chamber 23 shown in FIG. 2. The second passage 291 is not a passage that constantly communicates the first chamber 22 and the second chamber 23.

[0142] The second passage 291 on the compression side that allows the first chamber 22 and the second chamber 23 to communicate is parallel to the first passage 132 which is also a passage on the compression side that allows the first chamber 22 and the second chamber 23 to communicate. The first damping force generating mechanism 86 is provided in the first passage 132. The second damping force generating mechanism 301 is provided in the second passage 291. Therefore, both the first damping force generating mechanism 86 and the second damping force generating mechanism 301 on the compression side are arranged in parallel.

[0143] The valve member 163 shown in FIG. 3 is flexible. The valve member 163 has an outer diameter equivalent to the outer diameter of the valve seat portion 242 of the seat member 166. The valve member 163 is constantly in contact with the inner seat portion 241 and can be seated on and disengaged from the valve seat portion 242. When the valve member 163 seats on the entire valve seat portion 242, all the passage portions 281 are blocked. Also, when the valve member 163 disengages from any one of the valve seat components 255 of the valve seat portion 242, the passage portion 281 inside the disengaged valve seat component 255 is opened.

[0144] The disk 162 has an outer diameter smaller than that of the valve member 163 and smaller than that of the inner seat portion 241.

[0145] The spring member 161 is flexible. The spring member 161 has a substrate portion 311 and a plurality of spring plate portions 312.

[0146] The substrate portion 311 is a perforated circular flat plate. The substrate portion 311 fits the mounting shaft portion 33 to its inner peripheral portion. The substrate portion 311 has an outer diameter slightly larger than that of the disk 162. The substrate portion 311 abuts on the disk 162.

[0147] The plurality of spring plate portions 312 extend radially from the outer peripheral edge portion of the substrate portion 311. The plurality of spring plate portions 312 are farther from the substrate portion 311 in the axial direction of the substrate portion 311 as they are farther outward in the radial direction of the substrate portion 311.

[0148] The spring member 161 has a maximum outer diameter smaller than the outer diameter of the valve member 163. The spring member 161 is configured such that a plurality of spring plate portions 312 extend from the substrate portion 311 toward the valve member 163 in the axial direction of the substrate portion 311. The spring member 161 is such that the tip portions on the extending side of the plurality of spring plate portions 312 are in pressure contact with the outer peripheral side of the valve member 163. As a result, the spring member 161 biases the plurality of spring plate portions 312 to abut the outer peripheral side of the valve member 163 against the valve seat portion 242 of the seat member 166. The valve member 163 seats on the valve seat portion 242 by the biasing force of the spring member 161 to close the passage portion 281. The valve member 163 deforms against the biasing force of the spring member 161 to separate from the valve seat portion 242 and open the passage portion 281.

[0149] The valve member 163 is provided facing the second chamber 23. When the valve member 163 separates from the valve seat portion 242, the first chamber communicating volume chamber 286 and the second chamber 23 are communicated via a plurality of passage portions 281 of the seat member 166. At this time, the valve member 163 suppresses the flow of the hydraulic fluid L between itself and the valve seat portion 242 to generate a damping force. The valve member 163 is a discharge valve that opens when discharging the hydraulic fluid L from the inside of the first chamber communicating volume chamber 286 to the second chamber 23 via a plurality of passage portions 281. The valve member 163 is a check valve that restricts the inflow of the hydraulic fluid L from the second chamber 23 into the first chamber communicating volume chamber 286 via the passage portion 281. Here, the passage portion 282 opens outside the range of the valve seat portion 242 in the seat member 166. For this reason, the passage portion 282 is always in communication with the second chamber 23 regardless of the valve member 163 that seats on the valve seat portion 242.

[0150] The passage in the radial communication groove 253 formed in the inner seat portion 241 of the seat member 166 is the radial passage 317. The radial passage 317 is provided at a position facing the axial passage 54 in the radial direction of the seat member 166 and communicates with the passage in the passage groove 235. The radial passage 317 communicates the passage in the passage groove 235 with the passage in the passage recess 258.

[0151] As shown in FIG. 2, a part of the first chamber 22 side of the piston passage 81, the piston internal passage 103, the axial passage 54 of the piston rod 31, the passages in the passage groove 235 and the communication groove 263 of the seat member 166 shown in FIG. 3, the first chamber communicating volume chamber 286, the passage portion 281, the radial passage 317, and the passage between the valve member 163 and the valve seat portion 242 that appears when the valve is opened constitute the second passage 315.

[0152] The second passage 315 is opened and closed by the valve member 163. When the piston 21 shown in FIG. 2 moves toward the first chamber 22 side, the hydraulic fluid L flows out from the first chamber 22, which becomes the upstream side in the cylinder 4, to the second chamber 23, which becomes the downstream side, through the second passage 315. The second passage 315 serves as a passage for the hydraulic fluid L to flow out from the first chamber 22, which becomes the upstream side, to the second chamber 23, which becomes the downstream side, during the movement of the piston 21 toward the first chamber 22 side, that is, during the extending stroke. The second passage 315 on the extending side is partially provided separately from the first passage 152 on the extending side. The second passage 315 is partially provided in parallel with the first passage 152. The second passage 315 is provided in parallel with the first passage 152, excluding a part on the first chamber 22 side of the piston internal passage 103 of the piston passage 81.

[0153] The radial passage 317 shown in FIG. 3 communicates the passage in the passage groove 235 of the second passage 315 and the passage portion 281 without passing through the passage in the communication groove 263 and the first chamber communicating volume chamber 286.

[0154] The disk 160 has an outer diameter equal to the outer diameter of the valve member 163. The disk 160 is flexible. The disk 160 and the disk 144 suppress excessive deformation of the valve member 163 when the valve is opened. That is, when the opening amount of the valve member 163 increases, it abuts against the disk 160 and deflects the disk 160 toward the disk 144 side. The disk 144 suppresses the deflection of this disk 160 and suppresses further deflection of the valve member 163.

[0155] The valve member 163, the seat member 166 including the valve seat portion 242, the disk 162, and the spring member 161 constitute the second damping force generating mechanism 321. The second damping force generating mechanism 321 is provided in the second passage 315 on the extension side and opens and closes this second passage 315. The second damping force generating mechanism 321 suppresses the flow of the hydraulic fluid L from this second passage 315 to the second chamber 23 to generate a damping force. The second damping force generating mechanism 321 is a second damping force generating mechanism on the extension side. The second damping force generating mechanism 321 is arranged separately from the first damping force generating mechanism 85 shown in FIG. 2 that generates a damping force during the same extension stroke. The valve member 163 shown in FIG. 3 that constitutes the second damping force generating mechanism 321 on the extension side is a sub-valve on the extension side. The second damping force generating mechanism 321 includes a radial passage 317. In the extension stroke, when the valve member 163 opens the valve in the second damping force generating mechanism 321, the hydraulic fluid L on the first chamber 22 side upstream shown in FIG. 2 flows from a part of the piston passage 81 on the first chamber 22 side and the piston inner passage 103 through the shaft passage 54, the passage in the passage groove 235 shown in FIG. 3, and the radial passage 317 to the second chamber 23 on the downstream side. In other words, in the extension stroke, in the second damping force generating mechanism 321, when the valve member 163 opens the valve, the hydraulic fluid L in the first chamber 22 upstream flows from a part of the piston passage 81 on the first chamber 22 side and the piston inner passage 103 shown in FIG. 2 through the shaft passage 54, the central hole 231 and the radial passage 317 shown in FIG. 3 to the second chamber 23 which is on the downstream side.

[0156] The second damping force generating mechanism 321 includes a valve seat portion 242 which is a valve seat and a valve member 163 which is a deflectable valve body, and allows the flow in the direction from the first chamber 22 which becomes the upstream side to the second chamber 23 which becomes the downstream side in the extension stroke of the second passage 315 including a part of the piston passage 81 on the first chamber 22 side and the piston inner passage 103, while serving as a check valve mechanism that restricts the flow in the direction from the second chamber 23 which becomes the upstream side to the first chamber 22 which becomes the downstream side in the compression stroke. In other words, the second damping force generating mechanism 321 allows only the flow in the direction from the first chamber 22 which becomes the upstream side to the second chamber 23 which becomes the downstream side in the extension stroke of the second passage 315 including a part of the piston passage 81 on the first chamber 22 side and the piston inner passage 103.

[0157] As shown in FIG. 3, the second chamber communication volume chamber 287, the bottom portion 191 of the case member 180 forming the same, the biasing member 173, the first flexing member 175, the inner disk 176, the volume variable member 177, the second flexing member 178, and the disk 179 constitute a second chamber volume variable mechanism 325 (volume variable mechanism) capable of changing the volume of the second chamber communication volume chamber 287.

[0158] The second chamber volume variable mechanism 325 is provided in parallel with the second passage 291. The second chamber volume variable mechanism 325 operates prior to the second damping force generating mechanism 301 due to the pressure difference between the second chamber 23 and the first chamber 22 shown in FIG. 2, and the volume of the second chamber communication volume chamber 287 changes. As shown in FIG. 3, the second chamber volume variable mechanism 325 has a volume variable member 177. The volume variable member 177 is supported at both axial ends in the radial inner side by the flexible first flexing member 175 and the second flexing member 178 provided on the piston rod 31, and constitutes at least a part of the second chamber communication volume chamber 287. The second chamber volume variable mechanism 325 has a biasing member 173 that biases the volume variable member 177 in the valve closing direction of contacting the member contact portion 196 of the case member 180.

[0159] In the second chamber volume variable mechanism 325, the volume variable member 177 is centered by the cylindrical portion 192 of the case member 180, and while the case member contact portion 205 is in contact with the member contact portion 196 of the case member 180, it flexes so as to separate its inner peripheral side from the bottom portion 191. At that time, the volume variable member 177 flexes so as to bring the outer peripheral side of the first flexing member 175 closer to the biasing member 173. Then, the second chamber volume variable mechanism 325 changes so as to increase the volume of the second chamber communication volume chamber 287 while keeping the second chamber communication volume chamber 287 partitioned from the first chamber communication volume chamber 286.

[0160] Further, in the second chamber volume variable mechanism 325, the volume variable member 177 is centered by the cylindrical portion 192 of the case member 180, and while the case member contact portion 205 is in contact with the member contact portion 196 of the case member 180, it bends so that its inner peripheral side approaches the bottom portion 191. At this time, the volume variable member 177 bends so that the outer peripheral side of the second bending member 178 approaches the bottom portion 191 of the case member 180. Then, the second chamber volume variable mechanism 325 changes so as to reduce the volume of the second chamber communicating volume chamber 287 while keeping the second chamber communicating volume chamber 287 partitioned from the first chamber communicating volume chamber 286.

[0161] The first chamber communicating volume chamber 286 communicating with the first chamber 22 constitutes a part of the second passage 315 on the extending side. The first chamber communicating volume chamber 286, the cylindrical portion 192 of the case member 180 forming the same, the sheet member 166, the valve member 167, the disk 168, the spring member 169, the disk 170, the disk 172, the biasing member 173, the disk 174, the first bending member 175, the inner disk 176, the volume variable member 177, and the second bending member 178 constitute a first chamber volume variable mechanism 326 (volume variable mechanism) capable of changing the volume of the first chamber communicating volume chamber 286.

[0162] The first chamber volume variable mechanism 326 is provided in parallel with a part of the second passage 315. The first chamber volume variable mechanism 326 operates prior to the second damping force generation mechanism 321 due to the pressure difference between the first chamber 22 and the second chamber 23 shown in FIG. 2, and the volume of the first chamber communicating volume chamber 286 changes. The first chamber volume variable mechanism 326 shown in FIG. 3 has a volume variable member 177. The volume variable member 177 is supported at both axial ends in the radial inner side by the bendable first bending member 175 and the second bending member 178 provided on the piston rod 31, and constitutes at least a part of the first chamber communicating volume chamber 286. The first chamber volume variable mechanism 326 has a biasing member 173 that biases the volume variable member 177 in the valve closing direction of contacting the member contact portion 196 of the case member 180.

[0163] The first chamber volume variable mechanism 326 causes the volume variable member 177 to be centered by the cylindrical portion 192 of the case member 180, and while the case member contact portion 205 is in contact with the member contact portion 196 of the case member 180, the inner peripheral side thereof is bent so as to approach the bottom portion 191. At this time, the volume variable member 177 bends the outer peripheral side of the second bending member 178 so as to approach the bottom portion 191 of the case member 180. Then, the first chamber volume variable mechanism 326 changes so as to increase the volume of the first chamber communicating volume chamber 286 while keeping the first chamber communicating volume chamber 286 partitioned from the second chamber communicating volume chamber 287.

[0164] Further, the first chamber volume variable mechanism 326 causes the volume variable member 177 to be centered by the cylindrical portion 192 of the case member 180, and while the case member contact portion 205 is in contact with the member contact portion 196 of the case member 180, the inner peripheral side thereof is bent so as to move away from the bottom portion 191. At this time, the volume variable member 177 bends the outer peripheral side of the first bending member 175 so as to approach the biasing member 173. Then, the first chamber volume variable mechanism 326 changes so as to decrease the volume of the first chamber communicating volume chamber 286 while keeping the first chamber communicating volume chamber 286 partitioned from the second chamber communicating volume chamber 287.

[0165] Neither the valve seat portion 242 nor the valve member 163 in contact therewith of the extending side second damping force generating mechanism 321 has a fixed orifice for communicating the first chamber 22 and the second chamber 23 even when the valve seat portion 242 and the valve member 163 are in contact. That is, the extending side second damping force generating mechanism 321 does not communicate the first chamber 22 and the second chamber 23 if the valve seat portion 242 and the valve member 163 are in contact. In other words, the second passage 315 is not provided with a fixed orifice for constantly communicating the first chamber 22 and the second chamber 23. The second passage 315 is not a passage for constantly communicating the first chamber 22 and the second chamber 23.

[0166] As shown in FIG. 1, the base valve 15 has a valve mechanism 351 on the bottom portion 9 side in the axial direction of the valve body 12. Further, the base valve 15 has a valve mechanism 352 on the side opposite to the bottom portion 9 in the axial direction of the valve body 12.

[0167] When the piston rod 31 moves toward the retraction side and the piston 21 moves in a direction to narrow the second chamber 23, and the pressure in the second chamber 23 becomes higher than a predetermined value than the pressure in the reservoir chamber 5, the base valve 15 causes the valve mechanism 351 to open and the hydraulic fluid L in the second chamber 23 to flow into the reservoir chamber 5. The valve mechanism 351 generates a damping force at that time.

[0168] When the piston rod 31 moves toward the extension side and the piston 21 moves toward the first chamber 22 side, and the pressure in the second chamber 23 drops below the pressure in the reservoir chamber 5, the base valve 15 causes the valve mechanism 352 to open and the hydraulic fluid L in the reservoir chamber 5 to flow into the second chamber 23. The valve mechanism 352 generates a damping force at that time. The valve mechanism 352 may be a suction valve that allows the hydraulic fluid L to flow without substantially generating a damping force from the reservoir chamber 5 into the second chamber 23.

[0169] Next, the main operation of the shock absorber 1 will be described.

[0170] Among the first damping force generating mechanism 85 and the second damping force generating mechanism 321, both on the extension side shown in FIG. 2, the valve member 151 of the first damping force generating mechanism 85 has higher rigidity and a higher valve opening pressure than the valve member 163 shown in FIG. 3 of the second damping force generating mechanism 321. Therefore, in the extension stroke, in the extremely low speed region where the piston speed is lower than a predetermined value, the first damping force generating mechanism 85 shown in FIG. 2 closes and the second damping force generating mechanism 321 opens. In other words, the second damping force generating mechanism 321 opens and generates a damping force at a lower piston speed than the first damping force generating mechanism 85. Also, in the normal speed region where the piston speed is equal to or higher than this predetermined value, both the first damping force generating mechanism 85 and the second damping force generating mechanism 321 open. The valve member 163 shown in FIG. 3 is an extremely low speed valve that deforms against the biasing force of the spring member 161 and opens to generate a damping force in the region where the piston speed is extremely low.

[0171] That is, in the extension stroke, as the piston 21 shown in FIG. 2 moves toward the first chamber 22 side, the pressure in the first chamber 22 increases and the pressure in the second chamber 23 decreases. Here, neither the first damping force generating mechanisms 85 and 86 nor the second damping force generating mechanisms 301 and 321 have a fixed orifice that constantly connects the first chamber 22 and the second chamber 23. Therefore, the hydraulic fluid L in the first chamber 22 flows into the first chamber communicating volume chamber 286 through a part of the piston passage 81 on the first chamber 22 side of the piston 21, the piston internal passage 103, the axial passage 54 of the piston rod 31, and the passages in the passage groove 235 and the communication groove 263 of the seat member 166. As a result, the pressure in the first chamber communicating volume chamber 286 increases.

[0172] For this reason, before the second damping force generating mechanism 321 opens the valve, the volume variable member 177 shown in FIG. 3 of the first chamber volume variable mechanism 326 deflects so that its inner peripheral side moves toward the bottom 191 side. At that time, the volume variable member 177 deflects the outer peripheral side of the second deflecting member 178 toward the bottom 191 side. Then, the volume variable member 177 increases the capacity of the first chamber communicating volume chamber 286. As a result, the first chamber volume variable mechanism 326 suppresses the increase in the pressure of the first chamber communicating volume chamber 286. At this time, since the inner peripheral side of the volume variable member 177 moves toward the bottom 191 side, the second chamber volume variable mechanism 325 reduces the volume of the second chamber communicating volume chamber 287.

[0173] Here, in the extension stroke during low-frequency input (large-amplitude excitation) of the shock absorber 1, the inflow amount of the hydraulic fluid L from the first chamber 22 to the first chamber communicating volume chamber 286 is large as described above. For this reason, the volume variable member 177 deflects so that its inner peripheral side moves largely toward the bottom 191 side while elastically deforming the second deflecting member 178. When the moving amount of the inner peripheral side of the volume variable member 177 increases, it comes into surface contact with the intermediate plate portion 194 of the bottom 191 and the movement is restricted. As a result, the pressure in the first chamber communicating volume chamber 286 increases. As a result, the second passage 315 is pressurized until the second damping force generating mechanism 321 opens the valve. In other words, the bottom 191 of the case member 180 is formed to be a stopper that comes into contact when the volume variable member 177 and the second deflecting member 178 deflect.

[0174] At this time, neither the first damping force generating mechanisms 85 and 86 nor the second damping force generating mechanisms 301 and 321 have a fixed orifice that constantly connects the first chamber 22 and the second chamber 23. For this reason, when the piston speed is in the extension stroke at or below a first predetermined value at which the second damping force generating mechanism 321 opens the valve, the damping force rapidly rises. Also, in a region where the piston speed is higher than the first predetermined value and in an extremely low speed region that is lower than a second predetermined value higher than the first predetermined value, the first damping force generating mechanism 85 is in a closed valve state while the second damping force generating mechanism 321 opens the valve.

[0175] That is, the valve member 163 deforms against the biasing force of the spring member 161 and separates from the valve seat portion 242. Then, the first chamber 22 and the second chamber 23 communicate with each other through the second passage 315 on the extension side. Thus, the hydraulic fluid L in the first chamber 22 flows into the second chamber 23 through a part of the piston passage 81 on the first chamber 22 side and the piston internal passage 103 of the piston 21, the axial passage 54 of the piston rod 31, the passage in the passage groove 235 of the seat member 166, the passage in the communication groove 263, the passage portion 281, and the passage between the valve member 163 and the valve seat portion 242. Also, at this time, the hydraulic fluid L in the first chamber 22 flows into the second chamber 23 through a part of the piston passage 81 on the first chamber 22 side and the piston internal passage 103, the axial passage 54, the passage in the passage groove 235 of the seat member 166, and the radial passage 317, 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 lower than the second predetermined value, a damping force with valve characteristics (characteristics in which the damping force is substantially proportional to the piston speed) can be obtained.

[0176] Also, in the extension stroke during low-frequency input to the shock absorber 1, in the normal speed region where the piston speed is equal to or higher than the second predetermined value, when the pressure in the first chamber communicating volume chamber 286 increases, in addition to the flow through the extension-side second passage 315 due to the valve opening of the second damping force generating mechanism 321, the valve member 151 of the first damping force generating mechanism 85 separates from the valve seat portion 105, and the hydraulic fluid L flows from the first chamber 22 to the second chamber 23 through the extension-side first passage 152. Therefore, the hydraulic fluid L in the first chamber 22 flows into the second chamber 23 through the first passage 152 composed of the piston passage 81 and the passage between the valve member 151 and the valve seat portion 105.

[0177] As a result, even in the normal speed region where the piston speed is equal to or higher than the second predetermined value, a damping force with valve characteristics (the damping force is substantially proportional to the piston speed) can be obtained. The increase rate of the extension-side damping force with respect to the increase in the piston speed in the normal speed region is lower than the increase rate of the extension-side damping force with respect to the increase in the piston speed in the extremely low speed region.

[0178] In the extension stroke during high-frequency input (during small-amplitude excitation) when a frequency higher than that during the above-mentioned low-frequency input is input to the shock absorber 1, the inflow amount of the hydraulic fluid L from the first chamber 22 to the first chamber communicating volume chamber 286 is small. For this reason, the amount of movement toward the bottom portion 191 side while elastically deforming the second flexing member 178 on the inner peripheral side of the volume variable member 177 is small, and the first chamber volume variable mechanism 326 can absorb the volume of the inflow of the hydraulic fluid L into the first chamber communicating volume chamber 286 with the amount of flexure of the volume variable member 177 and the second flexing member 178. Therefore, the pressure increase in the first chamber communicating volume chamber 286 is reduced. For this reason, at the start of the extremely low speed damping force, it becomes a state similar to the case where there is no volume variable member 177. In other words, at the start of the extremely low speed damping force, it is possible to make the state similar to the state where the first chamber communicating volume chamber 286 is always in communication with the second chamber 23. Therefore, in the extension stroke during high-frequency input, the rise of the extremely low speed damping force becomes gentle with respect to the damping force characteristics during low-frequency input.

[0179] Among the first damping force generating mechanism 86 and the second damping force generating mechanism 301 on the compression side, the valve member 131 of the first damping force generating mechanism 86 has higher rigidity and a higher valve opening pressure than the valve member 167 of the second damping force generating mechanism 301. Therefore, in the compression stroke, in the extremely low speed region where the piston speed is lower than a predetermined value, the first damping force generating mechanism 86 is in a closed valve state and the second damping force generating mechanism 301 opens the valve. In other words, the second damping force generating mechanism 301 generates a damping force by opening the valve at a lower piston speed than the first damping force generating mechanism 86. In the normal speed region where the piston speed is equal to or higher than this predetermined value, both the first damping force generating mechanism 86 and the second damping force generating mechanism 301 open the valve. The valve member 167 is an extremely low speed valve that opens the valve and generates a damping force in the region where the piston speed is extremely low.

[0180] That is, in the compression stroke, when the piston 21 moves toward the second chamber 23 side, the pressure in the second chamber 23 increases and the pressure in the first chamber 22 decreases. Here, none of the first damping force generating mechanisms 85, 86 and the second damping force generating mechanisms 301, 321 have a fixed orifice that always communicates the second chamber 23 and the first chamber 22. For this reason, the hydraulic fluid L in the second chamber 23 flows into the second chamber communicating volume chamber 287. As a result, the pressure in the second chamber communicating volume chamber 287 increases.

[0181] For this reason, before the second damping force generating mechanism 301 opens the valve, the second chamber volume variable mechanism 325 moves the inner peripheral side of the volume variable member 177 toward the biasing member 173 side while elastically deforming the first flexing member 175. As a result, the volume variable member 177 increases the capacity of the second chamber communicating volume chamber 287. As a result, the second chamber volume variable mechanism 325 suppresses the increase in pressure in the second chamber communicating volume chamber 287. At this time, since the inner peripheral side of the volume variable member 177 moves toward the biasing member 173 side, the first chamber volume variable mechanism 326 decreases the volume of the first chamber communicating volume chamber 286.

[0182] Here, during the compression stroke of the shock absorber 1 at low-frequency input (large-amplitude excitation), the inflow rate of the hydraulic fluid L from the second chamber 23 to the second chamber communicating volume chamber 287 becomes large as described above. For this reason, the inner peripheral side of the volume variable member 177 moves greatly toward the biasing member 173 side while elastically deforming the first flexing member 175. When the movement amount of the inner peripheral side of the volume variable member 177 becomes large, the volume variable member 177 comes into surface contact with the biasing member 173 and the movement amount is restricted. As a result, the second chamber communicating volume chamber 287 is pressurized. As a result, the second passage 291 is pressurized until the second damping force generating mechanism 301 is in an open valve state.

[0183] At this time, none of the first damping force generating mechanisms 85, 86 and the second damping force generating mechanisms 301, 321 have a fixed orifice that constantly communicates the second chamber 23 and the first chamber 22. From this, when the piston speed is in the compression stroke at or below the third predetermined value at which the second damping force generating mechanism 301 opens the valve, the damping force rises rapidly. Also, in the region where the piston speed is higher than the third predetermined value and in the extremely low speed region lower than the fourth predetermined value which is higher than the third predetermined value, the second damping force generating mechanism 301 opens the valve while the first damping force generating mechanism 86 is in a closed valve state.

[0184] That is, when the valve member 167 deforms against the biasing force of the spring member 169 and separates from the valve seat portion 245, the second chamber 23 and the first chamber 22 are communicated in the second passage 291 on the compression side. Therefore, the hydraulic fluid L in the second chamber 23 flows into the first chamber 22 through the passage portion 282 in the seat member 166, the passage between the valve member 167 and the valve seat portion 245, the first chamber communicating volume chamber 286, the passage in the communication groove 263 of the seat member 166 and the passage in the passage groove 235, the axial passage 54 of the piston rod 31, a part of the first chamber 22 side of the piston passage 81 of the piston 21 and the piston inner passage 103, and the piston passage 81 of the piston 21. Thereby, even in the extremely low speed region where the piston speed is lower than the fourth predetermined value, a damping force with valve characteristics (characteristics in which the damping force is substantially proportional to the piston speed) can be obtained.

[0185] Also, in the compression stroke during low-frequency input to the shock absorber 1, in the normal speed range where the piston speed is equal to or higher than the fourth predetermined value, when the pressure in the second chamber communication volume chamber 287 increases, the first damping force generating mechanism 86 opens while the second damping force generating mechanism 301 remains open. That is, the valve member 131 of the first damping force generating mechanism 86 separates from the valve seat portion 115, and the hydraulic fluid L flows from the second chamber 23 to the first chamber 22 through the first passage 132 on the compression side. Therefore, the hydraulic fluid L in the second chamber 23 flows into the first chamber 22 through the piston passage 82 and the passage between the valve member 131 and the valve seat portion 115.

[0186] As a result, even in the normal speed range where the piston speed is equal to or higher than the fourth predetermined value, a damping force with valve characteristics (the damping force is substantially proportional to the piston speed) can be obtained. The increase rate of the compression-side damping force with respect to the increase in the piston speed in the normal speed range is lower than the increase rate of the compression-side damping force with respect to the increase in the piston speed in the extremely low speed range.

[0187] In the compression stroke during high-frequency input (during small-amplitude excitation) when a frequency higher than the above-mentioned low-frequency input is input to the shock absorber 1, the inflow amount of the hydraulic fluid L from the second chamber 23 to the second chamber communication volume chamber 287 is small. For this reason, the amount of movement toward the biasing member 173 side while elastically deforming the first flexing member 175 on the inner peripheral side of the volume variable member 177 is small. As a result, the second chamber volume variable mechanism 325 can absorb the volume of the inflow of the hydraulic fluid L into the second chamber communication volume chamber 287 with the amount of movement on the inner peripheral side of the volume variable member 177. Therefore, the pressure increase in the second chamber communication volume chamber 287 becomes small. For this reason, at the start of the extremely low speed damping force, it becomes the same state as if there were no volume variable member 177. In other words, at the start of the extremely low speed damping force, it is possible to make the state similar to the state where the second chamber communication volume chamber 287 is always in communication with the first chamber communication volume chamber 286. Therefore, in the compression stroke during high-frequency input, the rise of the extremely low speed damping force becomes gentle with respect to the damping force characteristics during low-frequency input.

[0188] Patent Document 1 described above discloses a shock absorber having two damping force variable mechanisms that open valves in the same stroke and a volume variable mechanism. By the way, there is a desire to stabilize the performance of the shock absorber. For example, in the shock absorber of Patent Document 1, since the volume variable member is flexible and has a shape that requires plastic deformation by bending, there is room for improvement in terms of performance stabilization.

[0189] In the shock absorber 1 of the first embodiment, a volume variable member 177 that constitutes at least a part of the first chamber communication volume chamber 286 of the first chamber volume variable mechanism 326 and at least a part of the second chamber communication volume chamber 287 of the second chamber volume variable mechanism 325 is provided on the piston rod 31. It is supported at both axial ends on the radially inner side by the flexible first flexural member 175 and second flexural member 178. Therefore, although the volume variable member 177 is flexible, it can be formed into a shape that does not require plastic deformation by bending, so that it is possible to stabilize the performance.

[0190] Further, in the shock absorber 1, since the volume variable member 177 is supported at both axial ends on the radially inner side by the flexible first flexural member 175 and second flexural member 178 provided on the piston rod 31, compared with the case where the inner peripheral side of the volume variable member is axially clamped and fixed to the piston rod 31, the stress on the inner peripheral side of the volume variable member 177 can be relaxed, and the durability of the volume variable member 177 can be improved.

[0191] Further, the shock absorber 1 has a case member contact portion 205 on the radially outer side where the volume variable member 177 contacts a case member 180 that covers at least a part of the second damping force generation mechanism 301, the first chamber communication volume chamber 286, and the second chamber communication volume chamber 287 in the axial direction. It is biased toward the member contact portion 196 side of the case member 180 by a biasing member 173 provided on the side opposite to the case member contact portion 205 in the axial direction. Therefore, the shock absorber 1 can suppress the movement of the volume variable member 177 on the radially outer side, so that the stress on the inner peripheral side of the volume variable member 177 can be further relaxed, and the durability of the volume variable member 177 can be further improved.

[0192] Further, the shock absorber 1 is formed such that the case member 180 serves as a stopper that contacts when the volume variable member 177 and the second bending member 178 bend. Therefore, the shock absorber 1 can suppress the radial outward movement of the volume variable member 177, further relieve the stress on the inner peripheral side of the volume variable member 177, and further improve the durability of the volume variable member 177.

[0193] In addition, since the volume variable member 177 in the state before being incorporated is flat, the shock absorber 1 has a low rigidity and a simple configuration compared to the case of using a volume variable member that undergoes plastic deformation due to bending. That is, the shock absorber in Patent Document 1 uses a volume variable member that undergoes plastic deformation due to bending, so it has a complicated configuration to reduce the rigidity of this volume variable member. However, the shock absorber 1 of the first embodiment can use the flat volume variable member 177, so it has a low rigidity and a simple configuration. Further, since bending is not required for the volume variable member 177, preload management becomes easy and the manufacturing cost can also be reduced.

[0194] In addition, the shock absorber 1 has a structure in which the volume variable member 177 is brought into contact with the member contact portion 196, which is the bending portion of the case member 180, and seals the space therebetween. Therefore, the shock absorber 1 facilitates leak control and improves reliability.

[0195] Here, in the shock absorber 1 of the first embodiment, it is possible to form the first bending member 175 and the second bending member 178 so that their bending amounts are different. With this configuration, the movement of the volume variable member 177 can be changed between the extension stroke and the compression stroke.

[0196] In that case, for example, the first bending member 175 and the second bending member 178 are formed such that their thicknesses in the axial direction are different. Thereby, tuning can be easily performed with a simple structure.

[0197] Further, for example, the first flexural member 175 and the second flexural member 178 are formed such that their outer diameters in the radial direction are different. Thereby, tuning can be easily performed with a simple structure. The first flexural member 175 and the second flexural member 178 may be formed such that their thicknesses in the axial direction are different and, in addition, their outer diameters in the radial direction are different.

[0198] In the shock absorber 1 of the first embodiment, the outer diameter of the biasing member 173 can be formed to be larger or smaller than the case member contact portion 205. Thereby, tuning can be easily performed with a simple structure.

[0199] [Second Embodiment] Next, the second embodiment will be mainly described focusing on the differences from the first embodiment with reference to FIGS. 4 and 5. Note that the parts common to the first embodiment are denoted by the same reference numerals and the same names.

[0200] As shown in FIG. 4, in the shock absorber 1A of the second embodiment, instead of the biasing member 173, the disk 174, the first flexural member 175, the inner disk 176, the volume variable member 177, the second flexural member 178, the disk 179, the case member 180, and the disk 181 shown in FIG. 3, a movement restricting member 401, a disk 402, a first flexural member 175A (flexural member), a disk 404, a volume variable member 177A, a second flexural member 178A (flexural member), a disk 407, and a movement restricting member 408 are provided.

[0201] On the side opposite to the disk 170 in the axial direction of the disk 172, in order from the disk 172 side, one movement restricting member 401, a plurality of disks 402, one first flexural member 175A, a plurality of disks 404 and one volume variable member 177A (volume variable member), one second flexural member 178A, a plurality of disks 407, and one movement restricting member 408 are provided.

[0202] The movement restraining members 401 and 408, the disks 402, 404, and 407, the first flexural member 175A, the volume variable member 177A, and the second flexural member 178A are all made of metal and are all annular.

[0203] The movement restraining members 401 and 408, the disks 402, 404, and 407, the first flexural member 175A, and the second flexural member 178A fit the mounting shaft portion 33 of the piston rod 31 inside them respectively.

[0204] By fitting the mounting shaft portion 33 of the piston rod 31 inside them respectively, the movement restraining member 401, the disk 402, the first flexural member 175A, the disk 404, the second flexural member 178A, the disk 407, the movement restraining member 408, and the annular member 182 are stacked on the disk 172 in this order. In this state, a nut member 185 (see FIG. 2) is screwed onto the male thread 57 (see FIG. 2) on the outer periphery of the threaded shaft portion 34 (see FIG. 2) of the piston rod 31 that protrudes from the annular member 182. Thereby, these components from the annular member 125 (see FIG. 2) to the annular member 182 are axially clamped by at least the radially inner peripheral side by the main shaft portion 32 (see FIG. 2) of the piston rod 31 and the nut member 185 (see FIG. 2). At that time, the volume variable member 177A is axially sandwiched by the first flexural member 175A and the second flexural member 178A.

[0205] The movement restraining members 401 and 408, the disks 402, 404, and 407, and the second flexural member 178A are all in the shape of perforated circular flat plates.

[0206] The volume variable member 177A is an integrally molded product. The volume variable member 177A has a cylindrical portion 192 similar to the case member 180 and a throttle portion 411. The outer diameter of the volume variable member 177A is smaller than the outer diameter of the piston 21 (see FIG. 2).

[0207] The throttle 411 has an inner peripheral side plate portion 412 and an outer peripheral side plate portion 413.

[0208] The inner peripheral side plate portion 412 is a perforated disc-shaped flat plate.

[0209] The outer peripheral side plate portion 413 extends outward in the radial direction of the inner peripheral side plate portion 412 from the outer peripheral edge portion of the inner peripheral side plate portion 412. The outer peripheral side plate portion 413 is tapered so that it is axially separated from the inner peripheral side plate portion 412 as it extends radially outward.

[0210] The cylindrical portion 192 curves from the outer peripheral edge portion of the outer peripheral side plate portion 413, which is the outer peripheral edge portion of the throttle 411, to the side opposite to the inner peripheral side plate portion 412 in the axial direction of the throttle 411, and then extends in the direction opposite to the inner peripheral side plate portion 412 along the axial direction of the throttle 411. In other words, the throttle 411 has a shape that curves radially inward from the end of the cylindrical cylindrical portion 192 and is throttled. The outer peripheral side plate portion 413 is axially separated from the inner peripheral side plate portion 412 and approaches the cylindrical portion 192 as it extends radially outward. The inner peripheral side plate portion 412 is a flat plate that extends perpendicular to the central axis of the cylindrical portion 192.

[0211] The volume variable member 177A is oriented such that the throttle portion 411 is located on the side opposite to the disc 144 from the cylindrical portion 192 in its axial direction and fits into the sheet member 166 and the O-ring 165 in the cylindrical portion 192.

[0212] The movement restraining member 401 has an outer diameter that is larger than the outer diameter of the disc 172 and smaller than the outer diameter of the disc 170. The movement restraining member 401 is thicker and has higher rigidity than the valve member 167. The disc 170 and the movement restraining member 401 suppress excessive deformation of the valve member 167 when the valve is opened. That is, when the valve opening amount of the valve member 167 increases, it abuts against the disc 170 and deflects the disc 170 toward the movement restraining member 401. When this disc 170 abuts, the movement restraining member 401 suppresses further deflection of the disc 170 and the valve member 167.

[0213] The disc 402 has an outer diameter that is smaller than the outer diameter of the movement restraining member 401 and is equivalent to the outer diameter of the disc 172.

[0214] The first flexure member 175A is flexible and has a main plate portion 421 and a plurality of locking plate portions 422 as shown in FIG. 5.

[0215] The main plate portion 421 is a perforated circular flat plate. As shown in FIG. 4, a mounting shaft portion 33 is fitted inside the main plate portion 421.

[0216] As shown in FIG. 5, the locking plate portion 422 extends outward in the radial direction of the main plate portion 421 from the outer peripheral edge portion of the main plate portion 421. The locking plate portion 422 is inclined with respect to the main plate portion 421 so as to be farther from the main plate portion 421 in the axial direction of the main plate portion 421 toward the extending tip side. The locking plate portions 422 are formed at three equally spaced positions in the circumferential direction of the main plate portion 421.

[0217] As shown in FIG. 4, the outer diameter of the main plate portion 421 of the first flexure member 175A is larger than the inner diameter of the inner peripheral side plate portion 412 of the throttle portion 411 of the volume variable member 177A and smaller than the outer diameter of the inner peripheral side plate portion 412. The outer peripheral side of the main plate portion 421 of the first flexure member 175A abuts against the inner peripheral side plate portion 412 of the volume variable member 177A. The locking plate portion 422 of the first flexure member 175A extends in a direction away from the main plate portion 421 and axially away from the inner peripheral side plate portion 412. The outer diameter of the first flexure member 175A, that is, the diameter of the circumscribed circle of the plurality of locking plate portions 422, is slightly smaller than the inner diameter of the cylindrical portion 192 of the volume variable member 177A.

[0218] The movement restraining member 401 is thicker and has higher rigidity than the first flexure member 175A. The movement restraining member 401 suppresses excessive deformation of the first flexure member 175A. That is, when the first flexure member 175A flexes in the direction of the movement restraining member 401 and the amount of its flexure increases, it abuts against the movement restraining member 401. Then, the movement restraining member 401 suppresses further flexure of the first flexure member 175A.

[0219] The outer diameter of the disk 404 is smaller than the inner diameter of the volume variable member 177A, that is, the inner diameter of the inner peripheral side plate portion 412, and is equivalent to the outer diameter of the disk 402. The overall thickness of the plurality of disks 404 is equivalent to the thickness of the inner peripheral side plate portion 412 of the volume variable member 177A.

[0220] The second flexure member 178A is flexible and has a perforated circular flat plate shape. The outer diameter of the second flexure member 178A is larger than the inner diameter of the inner peripheral side plate portion 412 of the throttle portion 411 of the volume variable member 177A and smaller than the outer diameter of the inner peripheral side plate portion 412. The outer peripheral side of the second flexure member 178A abuts on the inner peripheral side plate portion 412 of the volume variable member 177A.

[0221] The outer diameter of the disk 407 is smaller than the outer diameter of the second flexure member 178A and is equivalent to the outer diameter of the disk 404.

[0222] The outer diameter of the movement suppression member 408 is larger than the outer diameter of the disk 407 and is equivalent to the outer diameter of the movement suppression member 401. The movement suppression member 408 is thicker and has higher rigidity than the second flexure member 178A. The movement suppression member 408 suppresses excessive deformation of the second flexure member 178A. That is, when the second flexure member 178A flexes in the direction of the movement suppression member 408 and the amount of its flexure increases, it abuts on the movement suppression member 408. Then, the movement suppression member 408 suppresses further flexure of the second flexure member 178A.

[0223] The volume variable member 177A is positioned in the radial direction by the sheet member 166 and the O-ring 165, and the inner peripheral side plate portion 412 of the throttle portion 411 is clamped in the axial direction by the outer peripheral side of the main plate portion 421 of the first flexure member 175A and the outer peripheral side of the second flexure member 178. Thereby, the volume variable member 177A is slidable in the axial direction with respect to the sheet member 166 and the O-ring 165 while being positioned in the radial direction by the sheet member 166 and the O-ring 165.

[0224] The volume variable member 177A moves in a direction approaching the sheet member 166 while the throttle portion 411 elastically deforms the first flexure member 175A. At this time, when the movement suppression member 401 abuts against the first flexure member 175A, further movement of the volume variable member 177A in the direction approaching the sheet member 166 is suppressed. In other words, when the volume variable member 177A moves axially so that the throttle portion 411 approaches the movement suppression member 401, and the first flexure member 175A that is pressed and deformed by this throttle portion 411 abuts, further flexure of the first flexure member 175A is suppressed, and thus, further movement of the volume variable member 177A is suppressed.

[0225] The volume variable member 177A moves in a direction away from the sheet member 166 while the throttle portion 411 elastically deforms the second flexure member 178A. At this time, when the movement suppression member 408 abuts against the second flexure member 178A, further movement of the volume variable member 177A in the direction away from the sheet member 166 is suppressed. In other words, when the volume variable member 177A moves axially so that the throttle portion 411 approaches the movement suppression member 408, and the second flexure member 178A that is pressed and deformed by this throttle portion 411 abuts, further flexure of the second flexure member 178A is suppressed, and thus, further movement of the volume variable member 177A is suppressed. The movement suppression member 408 defines the movement range of the volume variable member 177A so as to maintain the sealing state between the volume variable member 177A and the sheet member 166 by the O-ring 165.

[0226] Inside the volume variable member 177A, the sheet member 166, the valve member 167, the disks 168, 170, 172, 402, 404, the spring member 169, the first flexure member 175A, and the movement suppression member 401 are arranged. The second flexure member 178A, the disk 407, and the movement suppression member 408 are arranged outside the volume variable member 177A.

[0227] Inside the variable volume member 177A, instead of the first chamber communicating volume chamber 286 shown in FIG. 3 of the shock absorber 1 of the first embodiment, a first chamber communicating volume chamber 286A (volume chamber), which is partially different from this, is formed. The first chamber communicating volume chamber 286A is surrounded and formed by the cylindrical portion 192 of the variable volume member 177A, the sheet member 166, the valve member 167, the disks 168, 170, 172, 402, the spring member 169, the first bending member 175A, and the movement restricting member 401. Therefore, the variable volume member 177A constitutes at least a part of the first chamber communicating volume chamber 286A. The sheet member 166 has the valve sheet portion 245 disposed on the side of the first chamber communicating volume chamber 286A.

[0228] The communication between the first chamber communicating volume chamber 286A and the second chamber 23 is blocked by the first bending member 175A, the variable volume member 177A, and the second bending member 178A.

[0229] The first chamber communicating volume chamber 286A is constantly in communication with the first chamber 22 (see FIG. 2) via the passage in the communication groove 263 of the sheet member 166 and the passage in the passage groove 235, the axial passage 54 of the piston rod 31, and the piston inner passage 103 (see FIG. 2) and the piston passage 81 (see FIG. 2) provided in the piston 21 (see FIG. 2).

[0230] When the variable volume member 177A moves axially while being centered by the O-ring 165 and the sheet member 166, the volume of the first chamber communicating volume chamber 286A and the volume of the second chamber 23 change. When the first bending member 175A bends in a direction away from the sheet member 166 and moves the variable volume member 177A in a direction in which the throttle portion 411 moves away from the sheet member 166, the volume of the first chamber communicating volume chamber 286A expands, and accordingly, the volume of the second chamber 23 shrinks. When the second bending member 178A bends in a direction approaching the sheet member 166 and moves the variable volume member 177A in a direction in which the throttle portion 411 approaches the sheet member 166, the volume of the first chamber communicating volume chamber 286A shrinks, and accordingly, the volume of the second chamber 23 expands.

[0231] In the buffer 1A, a first chamber communicating volume chamber 286A, which replaces the first chamber communicating volume chamber 286, forms a part of the second passage 291 on the contraction side and a part of the second passage 315 on the expansion side, similar to the first chamber communicating volume chamber 286.

[0232] The first chamber communicating volume chamber 286A, the volume variable member 177A forming the same, the sheet member 166, the valve member 167, the disk 168, the spring member 169, the disk 170, the disk 172, the movement restricting member 401, the disk 402, the first flexural member 175A, the disk 404, and the second flexural member 178A constitute a first chamber volume variable mechanism 326A capable of changing the volume of the first chamber communicating volume chamber 286A. The first chamber volume variable mechanism 326A can also change the volume of the second chamber 23.

[0233] The first chamber volume variable mechanism 326A is provided in parallel with a part of the second passage 315. The first chamber volume variable mechanism 326A is provided in parallel with a part of the second passage 291. The first chamber volume variable mechanism 326A operates prior to the second damping force generating mechanism 321 due to the pressure difference between the first chamber 22 (see FIG. 2) and the second chamber 23, and the volume of the first chamber communicating volume chamber 286A changes. The first chamber volume variable mechanism 326A operates prior to the second damping force generating mechanism 301 due to the pressure difference between the first chamber 22 (see FIG. 2) and the second chamber 23, and the volume of the first chamber communicating volume chamber 286A changes. The first chamber volume variable mechanism 326A has a volume variable member 177A. The volume variable member 177A is supported at both axial ends on the radially inner side by the flexible first flexural member 175A and the second flexural member 178A provided on the piston rod 31, and constitutes at least a part of the first chamber communicating volume chamber 286A.

[0234] The first chamber volume variable mechanism 326A bends the outer peripheral side away from the sheet member 166 while the first bending member 175A remains in contact with the throttle portion 411 of the volume variable member 177A centered by the O-ring 165 and the sheet member 166. At this time, the first bending member 175A presses and moves the throttle portion 411 of the volume variable member 177A away from the sheet member 166. Then, the first chamber volume variable mechanism 326A changes to increase the volume of the first chamber communicating volume chamber 286A and decrease the volume of the second chamber 23 while partitioning the first chamber communicating volume chamber 286A from the second chamber 23.

[0235] Also, the first chamber volume variable mechanism 326A bends the outer peripheral side closer to the sheet member 166 while the second bending member 178A remains in contact with the throttle portion 411 of the volume variable member 177A centered by the O-ring 165 and the sheet member 166. At this time, the second bending member 178A presses and moves the throttle portion 411 of the volume variable member 177A closer to the sheet member 166. Then, the first chamber volume variable mechanism 326A changes to decrease the volume of the first chamber communicating volume chamber 286A and increase the volume of the second chamber 23 while partitioning the first chamber communicating volume chamber 286A from the second chamber 23.

[0236] Next, the main operation of the shock absorber 1A will be described.

[0237] Both the first damping force generating mechanism 85 (see FIG. 2) and the second damping force generating mechanism 321 on the extension side are the same as those of the shock absorber 1 of the first embodiment. Therefore, in the extension stroke, in the extremely low speed region where the piston speed is lower than a predetermined value, the first damping force generating mechanism 85 (see FIG. 2) is in a closed valve state and the second damping force generating mechanism 321 is in an open valve state. Also, in the normal speed region where the piston speed is equal to or higher than this predetermined value, both the first damping force generating mechanism 85 and the second damping force generating mechanism 321 are in an open valve state.

[0238] That is, in the extension stroke, as the piston 21 (see FIG. 2) moves toward the first chamber 22 (see FIG. 2), the pressure in the first chamber 22 (see FIG. 2) increases and the pressure in the second chamber 23 decreases. Here, neither the first damping force generating mechanisms 85, 86 (see FIG. 2) nor the second damping force generating mechanisms 301, 321 have a fixed orifice that constantly connects the first chamber 22 (see FIG. 2) and the second chamber 23. Therefore, the hydraulic fluid L in the first chamber 22 (see FIG. 2) flows into the first chamber communicating volume chamber 286A through a part of the first chamber 22 (see FIG. 2) side of the piston passage 81 (see FIG. 2) of the piston 21 (see FIG. 2), the piston internal passage 103 (see FIG. 2), the axial passage 54 of the piston rod 31, and the passages in the passage groove 235 and the communication groove 263 of the seat member 166. As a result, the pressure in the first chamber communicating volume chamber 286A increases.

[0239] For this reason, before the second damping force generating mechanism 321 opens the valve, the first volume variable mechanism 326A elastically deforms so that the first flexing member 175A approaches the movement suppressing member 408 on the outer peripheral side, and while maintaining the sealing state with the volume variable member 177A, moves the volume variable member 177A in the direction in which the throttle portion 411 on its inner peripheral side approaches the movement suppressing member 408. Then, the first flexing member 175A and the volume variable member 177A increase the capacity of the first chamber communicating volume chamber 286A. As a result, the first volume variable mechanism 326A suppresses the increase in the pressure in the first chamber communicating volume chamber 286A. At that time, the volume variable member 177A deforms so as to bring the outer peripheral side of the second flexing member 178A closer to the movement suppressing member 408. At this time, the first volume variable mechanism 326A decreases the volume of the second chamber 23.

[0240] Here, during the extension stroke at low-frequency input (large-amplitude excitation) of the shock absorber 1A, the inflow rate of the hydraulic fluid L from the first chamber 22 (see FIG. 2) to the first chamber communicating volume chamber 286A becomes large as described above. For this reason, the first flexure member 175A is greatly elastically deformed so as to bring the outer peripheral side closer to the movement restricting member 408, and the volume variable member 177A is greatly moved in a direction in which the throttle portion 411 on its inner peripheral side approaches the movement restricting member 408. When the movement amount of the throttle portion 411 increases, the volume variable member 177A increases the amount of flexure of the second flexure member 178A, and causes the second flexure member 178A to contact the movement restricting member 408. Then, the movement of the volume variable member 177A is restricted. As a result, the pressure in the first chamber communicating volume chamber 286A increases. As a result, the second passage 315 is pressurized until the second damping force generating mechanism 321 opens the valve.

[0241] Therefore, during the extension stroke at low-frequency input, the shock absorber 1A, similar to the shock absorber 1 of the first embodiment, has a piston speed that is at a first predetermined value at which the second damping force generating mechanism 321 opens the valve or lower, and the damping force rapidly rises during the extension stroke. Further, in the extremely low-speed region where the piston speed is in a region higher than the first predetermined value and lower than a second predetermined value higher than the first predetermined value, the first damping force generating mechanism 85 is closed and the second damping force generating mechanism 321 opens the valve, and the hydraulic fluid L flows from the first chamber 22 (see FIG. 2) to the second chamber 23 in the second passage 315 on the extension side.

[0242] Also, during the extension stroke at low-frequency input, when the piston speed is in the normal speed region of the second predetermined value or higher, when the pressure in the first chamber communicating volume chamber 286A increases, the first damping force generating mechanism 85 (see FIG. 2) opens the valve while the second damping force generating mechanism 321 remains open, and the hydraulic fluid L flows from the first chamber 22 (see FIG. 2) to the second chamber 23 in the first passage 152 on the extension side (see FIG. 2).

[0243] During the extension stroke at high-frequency input (small-amplitude excitation) when a frequency higher than that during low-frequency input is applied to the shock absorber 1, the inflow rate of the hydraulic fluid L from the first chamber 22 (see FIG. 2) to the first chamber communicating volume chamber 286A is small. Therefore, the amount of movement when the first flexure member 175A moves the volume variable member 177A toward the movement suppression member 408 while elastically deforming is small, and the first chamber volume variable mechanism 326A can absorb the volume of the inflow of the hydraulic fluid L into the first chamber communicating volume chamber 286A based on the amount of flexure of the first flexure member 175A and the amount of movement of the volume variable member 177A. Thus, the pressure increase in the first chamber communicating volume chamber 286A is reduced. Therefore, during the extension stroke at high-frequency input, the rise of the extremely low-speed damping force becomes gentle with respect to the damping force characteristics during low-frequency input.

[0244] All of the compression-side first damping force generation mechanisms 86 (see FIG. 2) and second damping force generation mechanisms 301 are the same as those of the shock absorber 1 of the first embodiment. Therefore, during the compression stroke, in the extremely low-speed region where the piston speed is lower than a predetermined value, the first damping force generation mechanism 86 (see FIG. 2) closes the valve and the second damping force generation mechanism 301 opens the valve. Also, in the normal speed region where the piston speed is equal to or higher than this predetermined value, both the first damping force generation mechanism 86 (see FIG. 2) and the second damping force generation mechanism 301 open the valve.

[0245] That is, in the compression stroke, as the piston 21 (see FIG. 2) moves toward the second chamber 23 side, the pressure in the second chamber 23 increases and the pressure in the first chamber 22 (see FIG. 2) decreases. Here, neither the first damping force generating mechanisms 85, 86 (see FIG. 2) nor the second damping force generating mechanisms 301, 321 have a fixed orifice that constantly connects the second chamber 23 and the first chamber 22 (see FIG. 2). Therefore, before the second damping force generating mechanism 301 opens its valve, the first chamber volume variable mechanism 326A elastically deforms so that the second flexure member 178A approaches the movement suppressing member 401 on the outer peripheral side, and while maintaining the sealing state with the volume variable member 177A, moves the volume variable member 177A so that the throttle portion 411 on its inner peripheral side approaches the movement suppressing member 401. Then, the volume variable member 177A reduces the capacity of the first chamber communicating volume chamber 286A and increases the capacity of the second chamber 23. As a result, the first chamber volume variable mechanism 326A suppresses the increase in the pressure of the second chamber 23. At that time, the volume variable member 177A deforms so that the outer peripheral side of the first flexure member 175A approaches the movement suppressing member 401.

[0246] Here, in the compression stroke during low-frequency input (large-amplitude excitation) of the shock absorber 1, the pressure difference between the second chamber 23 and the first chamber communicating volume chamber 286A becomes large as described above. Therefore, the second flexure member 178A elastically deforms greatly so that the outer peripheral side approaches the movement suppressing member 401, and moves the volume variable member 177A greatly so that the throttle portion 411 on its inner peripheral side approaches the movement suppressing member 401. When the movement amount of the throttle portion 411 increases, the volume variable member 177A increases the flexure amount of the first flexure member 175A, and causes the main plate portion 421 of the first flexure member 175A to contact the movement suppressing member 401. Then, the movement of the volume variable member 177A is restricted. As a result, the pressure in the second chamber 23 increases. As a result, the pressure in the second passage 291 increases until the second damping force generating mechanism 301 opens its valve.

[0247] Therefore, during the compression stroke at low-frequency input, similar to the shock absorber 1 in the first embodiment, the piston speed of the shock absorber 1A is such that in the compression stroke where it is below the third predetermined value at which the second damping force generating mechanism 301 opens the valve, the damping force rises rapidly. Also, in the extremely low-speed region where the piston speed is in a region higher than the third predetermined value and lower than the fourth predetermined value which is higher than the third predetermined value, the first damping force generating mechanism 86 (see FIG. 2) is in a closed valve state while the second damping force generating mechanism 301 opens the valve, and the hydraulic fluid L flows from the second chamber 23 to the first chamber 22 (see FIG. 2) through the second passage 291 on the compression side.

[0248] Further, during the compression stroke in the normal speed region where the piston speed of the shock absorber 1A is equal to or higher than the fourth predetermined value during the compression stroke at low-frequency input, when the pressure in the second chamber 23 increases, while the second damping force generating mechanism 301 remains in an open valve state, the first damping force generating mechanism 86 (see FIG. 2) opens the valve, and the hydraulic fluid L flows from the second chamber 23 to the first chamber 22 (see FIG. 2) through the first passage 132 (see FIG. 2) on the compression side.

[0249] During the compression stroke at high-frequency input (during small-amplitude excitation) when a frequency higher than the above-mentioned low-frequency input is input to the shock absorber 1A, the discharge amount of the hydraulic fluid L in the first chamber communicating volume chamber 286A is small. For this reason, when the second flexural member 178A moves the throttle portion 411 of the volume variable member 177A toward the movement restraining member 401 while elastically deforming, the movement amount is small, and the first chamber volume variable mechanism 326A can absorb the volume reduction of the second chamber 23 with the flexure amount of the second flexural member 178A and the movement amount of the volume variable member 177A. Therefore, the pressure increase in the second chamber 23 becomes small. Thus, during the compression stroke at high-frequency input, the rise of the extremely low-speed damping force becomes gentle compared to the damping force characteristics at low-frequency input.

[0250] In the shock absorber 1A of the second embodiment, at least a part of the volume variable member 177A that constitutes the first chamber communicating volume chamber 286A of the first chamber volume variable mechanism 326A is supported at both axial ends on the radially inner side by the flexible first flexural member 175A and the second flexural member 178A provided on the piston rod 31. Therefore, since the volume variable member 177A does not need to be flexible, it becomes possible to stabilize the performance.

[0251] Further, in the shock absorber 1A, the variable-volume member 177A has a cylindrical tubular portion 192 and a throttle portion 411 that curves radially inward from the end of the tubular portion 192. Since the throttle portion 411 is supported by the flexible first flexural member 175A and the second flexural member 178A provided on the piston rod 31, the stress on the inner peripheral side of the variable-volume member can be relaxed compared to the case where the inner peripheral side of the variable-volume member is clamped in the axial direction and fixed to the piston rod, and the durability of the variable-volume member 177A can be improved. In addition, since the first chamber communicating volume chamber 286A can be formed by the variable-volume member 177A, the structure can be simplified.

[0252] Further, in the shock absorber 1A, since the variable-volume member 177A does not need to be flexible, it is not necessary to reduce the rigidity of the variable-volume member 177A, and the structure is simple. In addition, the management of the preload becomes easy, and the manufacturing cost can be reduced.

[0253] Here, in the shock absorber 1A of the second embodiment, it is possible to form the first flexural member 175A and the second flexural member 178A so that their amounts of deflection are different. With this configuration, the movement of the variable-volume member 177A can be changed between the extension stroke and the compression stroke.

[0254] In that case, for example, the first flexural member 175A and the second flexural member 178A are formed so that their thicknesses in the axial direction are different. Thereby, tuning can be easily performed with a simple structure.

[0255] Also, for example, the first flexural member 175A and the second flexural member 178A are formed so that their outer diameters in the radial direction are different. Thereby, tuning can be easily performed with a simple structure. The first flexural member 175A and the second flexural member 178A may be formed so that their thicknesses in the axial direction are different and, in addition, their outer diameters in the radial direction are different.

Description of Reference Numerals

[0256] 1,1A... buffer, 4... cylinder, 21... piston, 22... first chamber, 23... second chamber, 31... piston rod, 85, 86... first damping force generating mechanism, 132, 152... first passage, 173... biasing member, 175, 175A... first flexural member (flexural member), 177, 177A... volume variable member, 178, 178A... second flexural member (flexural member), 180... case member, 192... cylindrical portion, 205... case member abutting portion, 286, 286A... first chamber communicating volume chamber (volume chamber), 287... second chamber communicating volume chamber (volume chamber), 291, 315... second passage, 301, 321... second damping force generating mechanism, 325... second chamber volume variable mechanism (volume variable mechanism), 326, 326A... first chamber volume variable mechanism (volume variable mechanism), 411... throttle portion.

Claims

1. A cylinder in which a working fluid is enclosed, A piston slidably provided in the cylinder and partitioning the inside of the cylinder into a first chamber and a second chamber, A piston rod connected to the piston and extending outside the cylinder, A first passage through which the working fluid flows out due to the movement of the piston, A second passage provided in parallel with the first passage, A first damping force generating mechanism provided in the first passage and generating a damping force, A second damping force generating mechanism provided in the second passage and generating a damping force, A variable volume mechanism provided in parallel with the second passage, operating prior to the second damping force generating mechanism due to the pressure difference between the first chamber and the second chamber, and having a variable volume portion whose volume changes, and having The variable volume mechanism is supported at both axial ends on the radially inner side by a flexible member provided on the piston rod, and includes a variable volume member that constitutes at least a part of the volume chamber A shock absorber.

2. The shock absorber according to claim 1, and having a case member covering at least a part of the second damping force generating mechanism and the volume chamber, and having The variable volume member has a radially outer case member contact portion that contacts the case member in the axial direction, A shock absorber biased by a biasing member provided on the side opposite to the case member contact portion in the axial direction.

3. The shock absorber according to claim 1, The variable volume member has a cylindrical tubular portion and a throttle portion that curves radially inward from an end of the tubular portion, A shock absorber in which the throttle portion is supported by the flexible member.

4. The shock absorber according to claim 1, The volume variable mechanism is a shock absorber having a biasing member that biases the volume variable member in the valve closing direction.

5. The shock absorber according to claim 1, The flexing member has a first flexing member on one axial end side of the volume variable member and a second flexing member on the other axial end side of the volume variable member, The shock absorber is formed such that the amount of flexing is different between the first flexing member and the second flexing member.

6. The shock absorber according to claim 5, The shock absorber is formed such that the first flexing member and the second flexing member have different thicknesses in the axial direction.

7. The shock absorber according to claim 5, The shock absorber is formed such that the first flexing member and the second flexing member have different outer diameters in the radial direction.

8. The shock absorber according to claim 2, The case member is formed to be a stopper that contacts when the volume variable member and the flexing member flex.

9. The shock absorber according to claim 2, The outer diameter of the biasing member is formed to be larger or smaller than the case member contact portion.

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