Buffer

Abstract

To provide a shock absorber which can improve a riding comfort of a vehicle.SOLUTION: A shock absorber comprises: a passage 43 which is formed at a piston 18, and in which a working fluid circulates from one chamber 19 to the other chamber 20; a housing member 131 attached to one end of a piston rod 21; a deflective plate-shaped valve member 171 disposed in the housing member 131, regulated in movement in a direction along an axis of the piston rod 21 at an internal periphery, and forming a variable chamber 191 which communicates with the passage 43 between the housing member 131 and itself; a movement regulation member 185 for limiting the movement of the valve member 171; and a support member 181 disposed between the valve member 171 and the movement regulation member 185, supported to the piston rod 21 at an internal peripheral side, abutting on the valve member 171 by a deflection of the valve member 171, and deformable by a pressing force from the valve member 171.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a shock absorber. This application claims priority based on Japanese Patent Application No. 2021-145916 filed in Japan on September 8, 2021, and incorporates its content herein by reference.

Background Art

[0002] Some shock absorbers are provided with a valve member having a simple support structure that is supported without being clamped in a passage through which a working fluid flows due to the movement of a piston (see, for example, Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a shock absorber, it is required to improve the ride comfort of a vehicle.

[0005] Therefore, an object of the present invention is to provide a shock absorber that can improve the ride comfort of a vehicle.

Means for Solving the Problems

[0006] To achieve the above object, the present invention adopts the following aspects. That is, a shock absorber according to one aspect of the present invention includes a cylinder in which a working fluid is enclosed, a piston slidably fitted in the cylinder and partitioning the inside of the cylinder into two chambers, a piston rod having the piston attached to one end and the other end extending outside the cylinder through one of the two chambers of the cylinder, a passage formed in the piston through which the working fluid flows from the one chamber to the other of the two chambers of the cylinder, a housing member attached to the one end of the piston rod, a flexible plate-like valve member provided in the housing member and restricting movement in a direction along the axis of the piston rod at the inner periphery to form a variable chamber communicating with the passage between the housing member, a movement restricting member for restricting the movement of the valve member, and a support member provided between the valve member and the movement restricting member, supported by the piston rod on the inner peripheral side, contacting the valve member when the valve member flexes, and deformable by the pressing force from the valve member.

Advantages of the Invention

[0007] According to the above aspect, the riding comfort of the vehicle can be improved.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0009] [First Embodiment] A shock absorber including a damping force generation mechanism according to the first embodiment will be described below with reference to FIGS. 1 to 6. In the following description, for convenience of explanation, the upper side in FIGS. 1 to 3 is referred to as "upper", and the lower side in FIGS. 1 to 3 is referred to as "lower".

[0010] As shown in FIG. 1, the shock absorber 1 of the first embodiment is a double-tube type hydraulic shock absorber. The shock absorber 1 is used for a vehicle suspension device. The shock absorber 1 includes a cylinder 2 in which a hydraulic fluid (not shown) as a working fluid is enclosed. The cylinder 2 has an inner cylinder 3 and an outer cylinder 4. The inner cylinder 3 is cylindrical. The outer cylinder 4 is a bottomed cylinder. The inner diameter of the outer cylinder 4 is larger than the outer diameter of the inner cylinder 3. The inner cylinder 3 is disposed inside the outer cylinder 4 in the radial direction. The central axis of the inner cylinder 3 coincides with the central axis of the outer cylinder 4. A reservoir chamber 6 is formed between the inner cylinder 3 and the outer cylinder 4. The shock absorber 1 has a cover 5. The cover 5 covers the upper opening side of the outer cylinder 4.

[0011] The outer cylinder 4 has a body member 11 and a bottom member 12. The body member 11 is cylindrical. The bottom member 12 is a bottomed cylinder. The bottom member 12 is fitted to the lower side of the body member 11 and fixed by welding. The bottom member 12 closes the lower part of the body member 11. A mounting eye 13 is fixed to the outer side of the bottom member 12 in the axial direction opposite to the body member 11. The cover 5 is fixed to the outer peripheral surface of the body member 11 while covering the upper end opening of the body member 11.

[0012] The shock absorber 1 is provided with a piston 18. The piston 18 is slidably fitted into the inner cylinder 3 of the cylinder 2. The piston 18 divides the inside of the inner cylinder 3 into two chambers, an upper chamber 19 and a lower chamber 20. In the axial direction of the cylinder 2, the upper chamber 19 is on the side opposite to the bottom member 12 with respect to the piston 18. In the axial direction of the cylinder 2, the lower chamber 20 is on the side of the bottom member 12 with respect to the piston 18. Oil, which is a working fluid, is enclosed in the upper chamber 19 and the lower chamber 20 inside the inner cylinder 3. Oil and gas, which are working fluids, are enclosed in the reservoir chamber 6 between the inner cylinder 3 and the outer cylinder 4.

[0013] The shock absorber 1 is provided with a piston rod 21. One end side of the piston rod 21 in its axial direction is disposed inside the inner cylinder 3 of the cylinder 2. The piston rod 21 is connected to the piston 18 at this one end portion. The other end side of the piston rod 21 in its axial direction, which is opposite to this one end portion, extends from the cylinder 2 to the outside of the cylinder 2. The piston 18 is fixed to the piston rod 21. For this reason, the piston 18 and the piston rod 21 move integrally. In the shock absorber 1, the stroke in which the piston rod 21 moves in the direction of increasing the protruding amount from the cylinder 2 is the extending stroke in which the overall length extends. In the shock absorber 1, the stroke in which the piston rod 21 moves in the direction of decreasing the protruding amount from the cylinder 2 is the contracting stroke in which the overall length contracts. The shock absorber 1 has the piston 18 move toward the upper chamber 19 side during the extending stroke. The shock absorber 1 has the piston 18 move toward the lower chamber 20 side during the contracting stroke.

[0014] A rod guide 22 is fitted to the upper end opening side of the inner cylinder 3 and the upper end opening side of the outer cylinder 4. A seal member 23 is fitted to the outer cylinder 4 above the rod guide 22. A friction member 24 is provided between the rod guide 22 and the seal member 23. The rod guide 22, the seal member 23, and the friction member 24 are all annular. The piston rod 21 slides along the axial directions of these with respect to the rod guide 22, the friction member 24, and the seal member 23 respectively. The piston rod 21 extends from inside the cylinder 2 to the outside of the cylinder 2 beyond the seal member 23.

[0015] The rod guide 22 restricts the piston rod 21 from moving radially with respect to the inner cylinder 3 and the outer cylinder 4 of the cylinder 2. The piston rod 21 is fitted to the rod guide 22 and the piston 18 is fitted inside the inner cylinder 3. Thereby, the central axis of the piston rod 21 coincides with the central axis of the cylinder 2. The rod guide 22 supports the piston rod 21 so as to be movable in the axial direction of the piston rod 21. The outer peripheral portion of the seal member 23 is in close contact with the outer cylinder 4. The inner peripheral portion of the seal member 23 is in close contact with the outer peripheral portion of the piston rod 21. The piston rod 21 moves in the axial direction of the seal member 23 with respect to the seal member 23. The seal member 23 suppresses the leakage of the oil in the inner cylinder 3 and the high-pressure gas and oil in the reservoir chamber 6 to the outside. The inner peripheral portion of the friction member 24 contacts the outer peripheral portion of the piston rod 21. The piston rod 21 moves in the axial direction of the friction member 24 with respect to the friction member 24. The friction member 24 generates frictional resistance against the piston rod 21.

[0016] The rod guide 22 has a larger outer diameter at the upper part than at the lower part on its outer periphery. The rod guide 22 is fitted to the inner peripheral part of the upper end of the inner cylinder 3 at its lower part with a smaller diameter. The rod guide 22 is fitted to the inner peripheral part of the upper part of the outer cylinder 4 at its upper part with a larger diameter. A base valve 25 is installed on the bottom member 12 of the outer cylinder 4. The base valve 25 is positioned radially with respect to the outer cylinder 4. The base valve 25 partitions the lower chamber 20 and the reservoir chamber 6. The inner peripheral part of the lower end of the inner cylinder 3 is fitted to the base valve 25. The upper end part of the outer cylinder 4 is not shown in the figure, but a part of it is caulked inward in the radial direction of the outer cylinder 4. The seal member 23 is fixed to the cylinder 2 by being sandwiched between this caulked part and the rod guide 22.

[0017] The piston rod 21 has a main shaft part 27 and a mounting shaft part 28. The outer diameter of the mounting shaft part 28 is smaller than the outer diameter of the main shaft part 27. The mounting shaft part 28 is disposed inside the cylinder 2. A piston 18 is attached to the mounting shaft part 28. The main shaft part 27 has a shaft step part 29. The shaft step part 29 is provided at the end of the main shaft part 27 on the side of the mounting shaft part 28. The shaft step part 29 extends in a direction orthogonal to the central axis of the piston rod 21. A passage groove 30 is formed on the outer periphery of the mounting shaft part 28 of the piston rod 21. The passage groove 30 extends in the axial direction of the mounting shaft part 28. A plurality of passage grooves 30 are formed at intervals in the circumferential direction of the mounting shaft part 28. A male thread 31 is formed on the outer periphery of the end of the mounting shaft part 28 on the side opposite to the main shaft part 27 with respect to the passage groove 30 in the axial direction of the mounting shaft part 28.

[0018] An annular stopper member 32 and an annular buffer member 33 are provided on the piston rod 21. Both the stopper member 32 and the buffer member 33 are provided in the part between the piston 18 and the rod guide 22 of the main shaft part 27. The piston rod 21 is inserted into the inner peripheral side of the stopper member 32 and the buffer member 33. The stopper member 32 is caulked and fixed to the main shaft part 27. The buffer member 33 is disposed between the stopper member 32 and the rod guide 22.

[0019] The shock absorber 1 is connected to the vehicle body with, for example, the portion of the piston rod 21 protruding from the cylinder 2 disposed at the upper part. In this case, the shock absorber 1 is connected to the wheel side of the vehicle with the mounting eye 13 provided on the cylinder 2 side disposed at the lower part. Conversely, the shock absorber 1 may be connected to the vehicle body with the cylinder 2 side. In this case, the piston rod 21 of the shock absorber 1 is connected to the wheel side.

[0020] In a vehicle, as the vehicle travels, the wheels vibrate with respect to the vehicle body. Then, in the shock absorber 1, the relative positions of the cylinder 2 and the piston rod 21 change with this vibration. This change is suppressed by the fluid resistance of the flow path provided in the shock absorber 1. As will be described below, the fluid resistance of the flow path provided in the shock absorber 1 varies depending on the speed and amplitude of the above-described vibration. By suppressing the vibration by the shock absorber 1, the riding comfort of the vehicle is improved.

[0021] Also, in a vehicle, in addition to the vibration generated by the wheels with respect to the vehicle body between the cylinder 2 and the piston rod 21, inertial forces and centrifugal forces generated in the vehicle body as the vehicle travels also act. For example, when the traveling direction changes due to a steering operation, a centrifugal force is generated in the vehicle body. Then, a force based on this centrifugal force acts between the cylinder 2 and the piston rod 21. As will be described below, the shock absorber 1 has good characteristics with respect to the vibration based on the force generated in the vehicle body as the vehicle travels. High running stability is obtained for the vehicle by the shock absorber 1.

[0022] As shown in FIG. 2, the piston 18 has a piston body 35 and a sliding member 36. The piston body 35 is made of metal and is annular. The piston 18 has the piston body 35 fitted to the piston rod 21. The sliding member 36 is made of synthetic resin and is annular. The sliding member 36 is integrally attached to the outer peripheral surface of the piston body 35. The piston 18 slides with respect to the inner cylinder 3 with the sliding member 36 in contact with the inner cylinder 3.

[0023] The piston body 35 is provided with a passage hole 37, a passage groove 38, a passage hole 39, and a passage groove 40. The passage hole 37 penetrates the piston body 35 in the axial direction of the piston body 35. The passage hole 37 is formed in the piston body 35 at a plurality of positions spaced apart in the circumferential direction of the piston body 35 (only one position is shown in FIG. 2 due to the sectional view). The passage hole 39 penetrates the piston body 35 in the axial direction of the piston body 35. The passage hole 39 is formed in the piston body 35 at a plurality of positions spaced apart in the circumferential direction of the piston body 35 (only one position is shown in FIG. 2 due to the sectional view). In the circumferential direction of the piston body 35, the passage hole 37 and the passage hole 39 are alternately formed at equal pitches at one position each.

[0024] The passage groove 38 is formed in the piston body 35 in an annular shape in the circumferential direction of the piston body 35. The passage groove 38 is formed at one end portion in the axial direction of the piston body 35. All the passage holes 37 open into the passage groove 38 at this one end portion side in the axial direction of the piston body 35. The passage groove 40 is formed in the piston body 35 in an annular shape in the circumferential direction of the piston body 35. The passage groove 40 is formed at the other end portion in the axial direction of the piston body 35, which is opposite to the passage groove 38. All the passage holes 39 open into the passage groove 40 at the end portion on the side opposite to the passage groove 38 in the axial direction of the piston body 35. The end portions of the plurality of passage holes 37 on the side opposite to the passage groove 38 in the axial direction of the piston body 35 open outside the passage groove 40 in the radial direction of the piston body 35. The end portions of the plurality of passage holes 39 on the side opposite to the passage groove 40 in the axial direction of the piston body 35 open outside the passage groove 38 in the radial direction of the piston body 35. In the piston 18, the inside of the plurality of passage holes 37 and the inside of the passage groove 38 form a first passage portion 43. In the piston 18, the inside of the plurality of passage holes 39 and the inside of the passage groove 40 form a first passage portion 44.

[0025] The first passage portion 43 is provided with a first damping force generating mechanism 41. The first damping force generating mechanism 41 opens and closes the first passage portion 43 to generate a damping force. The first damping force generating mechanism 41 is disposed on the lower chamber 20 side which is one end side in the axial direction of the piston 18 and is attached to the piston rod 21. Thereby, the first passage portion 43 becomes a passage through which the oil as the working fluid flows out from the upper chamber 19 toward the lower chamber 20 by the movement of the piston 18 toward the upper chamber 19 side. That is, the first passage portion 43 is a passage through which the oil as the working fluid flows out from the upper chamber 19 toward the lower chamber 20 during the extension stroke. The first damping force generating mechanism 41 is an extension-side damping force generating mechanism that suppresses the flow of the oil from the first passage portion 43 to the lower chamber 20 generated during the extension stroke to generate a damping force.

[0026] The first passage portion 44 is provided with a first damping force generating mechanism 42. The first damping force generating mechanism 42 opens and closes the first passage portion 44 to generate a damping force. The first damping force generating mechanism 42 is disposed on the upper chamber 19 side which is the other end side in the axial direction of the piston 18 and is attached to the piston rod 21. Thereby, the first passage portion 44 becomes a passage through which the oil flows out from the lower chamber 20 toward the upper chamber 19 by the movement of the piston 18 toward the lower chamber 20 side. That is, the first passage portion 44 is a passage through which the oil flows out from the lower chamber 20 toward the upper chamber 19 during the compression stroke. The first damping force generating mechanism 42 is a compression-side damping force generating mechanism that suppresses the flow of the oil from the first passage portion 44 to the upper chamber 19 generated during the compression stroke to generate a damping force.

[0027] The piston body 35 has an insertion hole 45 formed to penetrate in the axial direction of the piston body 35 at the center in the radial direction thereof. The insertion hole 45 allows the mounting shaft portion 28 of the piston rod 21 to pass through. The insertion hole 45 has a small-diameter hole portion 46 and a large-diameter hole portion 47. The large-diameter hole portion 47 has a larger diameter than the small-diameter hole portion 46. The mounting shaft portion 28 of the piston rod 21 is fitted into the small-diameter hole portion 46 of the piston body 35. In the axial direction of the insertion hole 45, the large-diameter hole portion 47 is on the lower chamber 20 side than the small-diameter hole portion 46.

[0028] At the end of the piston body 35 on the lower chamber 20 side in the axial direction, a valve seat portion 48 is formed. The valve seat portion 48 is annular. The valve seat portion 48 is disposed outside in the radial direction of the piston body 35 than the opening on the lower chamber 20 side of the passage groove 38. The valve seat portion 48 constitutes a part of the first damping force generating mechanism 41. At the end of the piston body 35 on the upper chamber 19 side in the axial direction, a valve seat portion 49 is formed. The valve seat portion 49 is annular. The valve seat portion 49 is disposed outside in the radial direction of the piston body 35 than the opening on the upper chamber 19 side of the passage groove 40. The valve seat portion 49 constitutes a part of the first damping force generating mechanism 42. In the piston body 35, on the side opposite to the passage groove 38 of the valve seat portion 48 in the radial direction of the piston body 35, the openings on the lower chamber 20 side in all the passage holes 39 are arranged. In the piston body 35, on the side opposite to the passage groove 40 of the valve seat portion 49 in the radial direction of the piston body 35, the openings on the upper chamber 19 side in all the passage holes 37 are arranged.

[0029] As shown in FIG. 3, on the valve seat portion 48 side in the axial direction of the piston 18, in the axial direction of the piston 18, in order from the piston 18 side, one disk 51, one damping valve 52, one disk 53, one disk 54, one pilot case 55, one disk 56, one disk 57, a plurality of (specifically, three) disks 58, one disk 59, and one disk 60 are provided. The disks 51, 53, 54, 56 to 60 and the pilot case 55 are all made of metal. The disks 51, 53, 54, 56 to 60 are all perforated circular flat plates with a certain thickness. The disks 51, 53, 54, 56 to 60 all have the mounting shaft portion 28 of the piston rod 21 fitted inside. The damping valve 52 and the pilot case 55 are both annular. The damping valve 52 and the pilot case 55 both have the mounting shaft portion 28 of the piston rod 21 fitted inside.

[0030] The pilot case 55 is a bottomed cylindrical shape. A through hole 70 is formed in the center in the radial direction of the pilot case 55. The through hole 70 penetrates the pilot case 55 in its axial direction. The pilot case 55 has a bottom portion 71, an inner cylindrical portion 72, an outer cylindrical portion 73, an inner sheet portion 74, and a valve sheet portion 75.

[0031] The through hole 70 has a large-diameter hole portion 76 and a small-diameter hole portion 77. The large-diameter hole portion 76 has a larger diameter than the small-diameter hole portion 77. The large-diameter hole portion 76 is disposed on the piston 18 side in the axial direction of the through hole 70. The small-diameter hole portion 77 is disposed on the side opposite to the piston 18 from the large-diameter hole portion 76 in the axial direction of the through hole 70. The bottom portion 71 is a perforated disk shape. A passage hole 78 that penetrates the bottom portion 71 in the axial direction of the bottom portion 71 is formed on the radially outer side of the through hole 70 in the bottom portion 71. The inner cylindrical portion 72 is cylindrical and protrudes from the inner peripheral edge portion of the bottom portion 71 along the axial direction of the bottom portion 71 toward the piston 18 side. The inner cylindrical portion 72 is provided on the inner side of the passage hole 78 in the radial direction of the bottom portion 71. The outer cylindrical portion 73 is cylindrical and protrudes from the outer peripheral edge portion of the bottom portion 71 along the axial direction of the bottom portion 71 to the same side as the inner cylindrical portion 72. The outer cylindrical portion 73 is provided on the outer side of the passage hole 78 in the radial direction of the bottom portion 71. The passage hole 78 is disposed between the inner cylindrical portion 72 and the outer cylindrical portion 73 in the radial direction of the bottom portion 71.

[0032] The inner sheet portion 74 is annular and protrudes from the inner peripheral edge portion of the bottom portion 71 to the side opposite to the inner cylindrical portion 72 in the axial direction. The valve sheet portion 75 is annular with a larger diameter than the inner sheet portion 74. The valve sheet portion 75 protrudes from the bottom portion 71 along the axial direction of the bottom portion 71 to the same side as the inner sheet portion 74 on the radially outer side of the inner sheet portion 74. The passage hole 78 is disposed between the inner sheet portion 74 and the valve sheet portion 75 in the radial direction of the bottom portion 71.

[0033] The disk 51 has an outer diameter smaller than the inner diameter of the front end surface of the valve seat portion 48. A notch 81 is formed in the disk 51. The notch 81 extends radially outward from the inner peripheral edge portion that fits onto the mounting shaft portion 28 of the disk 51 up to within the passage groove 38. The inside of the notch 81 forms a throttle 82. The throttle 82 is constantly in communication with the first passage portion 43 of the piston 18. The passage within the large-diameter hole portion 47 of the piston 18 and the passage within the passage groove 30 of the piston rod 21 are constantly in communication. The passage within the large-diameter hole portion 47 and the passage within the passage groove 30 constitute a rod chamber 83. The throttle 82 within the notch 81 of the disk 51 is constantly in communication with the rod chamber 83. The throttle 82 constantly connects the first passage portion 43 and the rod chamber 83.

[0034] The damping valve 52 is composed of a disk 85 and a seal member 86. The disk 85 is made of metal and is a perforated circular flat plate. The disk 85 has an outer diameter larger than the outer diameter of the front end surface of the valve seat portion 48. The mounting shaft portion 28 of the piston rod 21 is fitted inside the disk 85. The disk 85 abuts against the valve seat portion 48 of the piston 18 and opens and closes the opening of the first passage portion 43 formed in the piston 18 by moving away from and abutting against the valve seat portion 48. The seal member 86 is made of rubber and is adhered to the disk 85. The seal member 86 is fixed to the outer peripheral side of the disk 85 and forms an annular shape. The seal member 86 is liquid-tightly fitted over the entire circumference to the inner peripheral portion of the outer cylindrical portion 73 of the pilot case 55. The seal member 86 is axially slidable with respect to the inner peripheral portion of the outer cylindrical portion 73. The seal member 86 constantly seals the gap between the damping valve 52 and the outer cylindrical portion 73.

[0035] The outer diameter of disk 53 is smaller than the minimum inner diameter of seal member 86. The outer diameter of disk 54 is larger than the outer diameter of disk 53 and smaller than the minimum inner diameter of seal member 86. A notch 91 is formed in disk 54. Notch 91 extends radially outward from the inner peripheral edge that fits onto the mounting shaft portion 28 of disk 54 to the outside of disk 53. The inside of notch 91 forms a throttle 92. Throttle 92 is constantly in communication with the passage in passage groove 30 of piston rod 21 and the passage in the large-diameter hole portion 76 of pilot case 55.

[0036] Disk 56 has an outer diameter smaller than the inner diameter of the tip surface of valve seat portion 75 of pilot case 55. Disk 57 has an outer diameter larger than the outer diameter of the tip surface of valve seat portion 75. Disk 57 is capable of seating on valve seat portion 75. A notch 93 is formed on the outer peripheral side of disk 57. Notch 93 traverses valve seat portion 75 in the radial direction. Disk 58 has the same outer diameter as disk 57. Disk 59 has an outer diameter smaller than the outer diameter of disk 58. Disk 60 has an outer diameter larger than the outer diameter of disk 59 and smaller than the outer diameter of disk 58. Disks 57 and 58 constitute disk valve 99. Disk valve 99 is capable of separating from and seating on valve seat portion 75.

[0037] Between the bottom 71, the inner cylindrical portion 72, and the outer cylindrical portion 73 of the pilot case 55, and the damping valve 52 and the disks 53, 54, and between the bottom 71, the inner sheet portion 74, and the valve seat portion 75 of the pilot case 55, and the disk 56 and the disk valve 99, and inside the passage hole 78 of the pilot case 55, there is formed a back pressure chamber 100. The back pressure chamber 100 applies pressure to the damping valve 52 in the direction of the piston 18. In other words, the back pressure chamber 100 applies internal pressure to the damping valve 52 in the closing valve direction of seating on the valve seat portion 48. The damping valve 52 is a pilot type damping valve having the back pressure chamber 100. These damping valve 52 and the back pressure chamber 100 constitute a part of the first damping force generating mechanism 41. The back pressure chamber 100 is constantly in communication with the rod chamber 83 through the throttle 92 in the notch 91 of the disk 54. The passage in the large diameter hole portion 76 of the pilot case 55 is constantly in communication with the passage in the passage groove 30 of the piston rod 21. The passage in the large diameter hole portion 76 of the pilot case 55 also constitutes the rod chamber 83.

[0038] The throttle 82 in the notch 81 of the disk 51, the rod chamber 83, and the throttle 92 in the notch 91 of the disk 54 form a second passage portion 102 that constantly communicates the first passage portion 43 of the piston 18 with the back pressure chamber 100 to introduce hydraulic fluid from the first passage portion 43 into the back pressure chamber 100. When the disk 85 of the damping valve 52 separates from the valve seat portion 48 of the piston 18 and opens, the damping valve 52 allows the hydraulic fluid from the first passage portion 43 to flow into the lower chamber 20 through the space between the piston 18 and the outer cylindrical portion 73 of the pilot case 55. At that time, the damping valve 52 suppresses the flow of the hydraulic fluid between itself and the valve seat portion 48. The first damping force generating mechanism 41 on the extension side introduces a part of the flow of the hydraulic fluid into the back pressure chamber 100 through the second passage portion 102, and controls the opening of the damping valve 52 by the pressure in the back pressure chamber 100.

[0039] The disk valve 99 communicates the back pressure chamber 100 with the lower chamber 20 by separating from the valve seat portion 75. At this time, the disk valve 99 suppresses the flow of the oil fluid between it and the valve seat portion 75. The passage in the notch 93 of the disk valve 99 constitutes a fixed orifice 105 that communicates the back pressure chamber 100 with the lower chamber 20 even when the disk valve 99 is in contact with the valve seat portion 75. The disk 60 abuts against the disk valve 99 when the disk valve 99 deforms in the opening direction, suppressing deformation of the disk valve 99 beyond the specified amount.

[0040] The disk valve 99 and the valve seat portion 75 constitute a second damping force generating mechanism 110. When the disk valve 99 separates from the valve seat portion 75, the second damping force generating mechanism 110 communicates the back pressure chamber 100 with the lower chamber 20. At this time, the second damping force generating mechanism 110 suppresses the flow of the oil fluid between the back pressure chamber 100 and the lower chamber 20 to generate a damping force. The second damping force generating mechanism 110 is provided between the back pressure chamber 100 and the lower chamber 20 and generates a damping force by the flow of the oil fluid. In the extension stroke, the second damping force generating mechanism 110 causes the oil fluid to flow from the upper chamber 19 to the lower chamber 20 through the first passage portion 43, the second passage portion 102, and the back pressure chamber 100. The second damping force generating mechanism 110 is an extension-side damping force generating mechanism that suppresses the flow of the oil fluid from the back pressure chamber 100 to the lower chamber 20 occurring in the extension stroke to generate a damping force.

[0041] As shown in FIG. 2, on the valve seat portion 49 side in the axial direction of the piston 18, in the axial direction of the piston 18, in order from the piston 18 side, there are provided one disk 111, one disk 112, a plurality of disks (specifically 3) 113, a plurality of disks (specifically 2) 114, one disk 115, one disk 116, and one annular member 117. The disks 111 to 116 and the annular member 117 are all made of metal. The disks 111 to 116 and the annular member 117 are all circular flat plates with holes and a certain thickness. The disks 111 to 116 and the annular member 117 all fit the mounting shaft portion 28 of the piston rod 21 on the inner side.

[0042] The disk 111 has an outer diameter smaller than the inner diameter of the tip surface of the valve seat portion 49 of the piston 18. The disk 112 has an outer diameter slightly larger than the outer diameter of the tip surface of the valve seat portion 49 of the piston 18. The disk 112 can be seated on the valve seat portion 49. A notch 121 is formed on the outer peripheral side of the disk 112. The notch 121 traverses the valve seat portion 49 in the radial direction.

[0043] The plurality of disks 113 have an outer diameter equal to the outer diameter of the disk 112. The plurality of disks 114 have an outer diameter smaller than the outer diameter of the disk 113. The disk 115 has an outer diameter smaller than the outer diameter of the disk 114. The disk 116 has an outer diameter larger than the outer diameter of the disk 114 and smaller than the outer diameter of the disk 113. The annular member 117 has an outer diameter smaller than the outer diameter of the disk 116 and larger than the outer diameter of the disk 114. The annular member 117 is thicker and has higher rigidity than the disks 111 - 116. This annular member 117 is in contact with the shaft step portion 29 of the piston rod 21.

[0044] The disks 112 - 114 constitute the disk valve 122. The disk valve 122 can be seated on and separated from the valve seat portion 49. The disk valve 122 can open the first passage portion 44 to the upper chamber 19 by separating from the valve seat portion 49. At that time, the disk valve 122 suppresses the flow of the oil fluid from the lower chamber 20 to the upper chamber 19 through the first passage portion 44. The disk valve 122 and the valve seat portion 49 constitute the first damping force generating mechanism 42 on the contraction side. The notch 121 of the disk 112 constitutes the fixed orifice 123. The fixed orifice 123 communicates the lower chamber 20 and the upper chamber 19 even when the disk 112 is in contact with the valve seat portion 49. The fixed orifice 123 also constitutes the first damping force generating mechanism 42. The disk 116 contacts the disk valve 122 when the disk valve 122 deforms in the opening direction and suppresses deformation of the disk valve 122 beyond the specified amount in the opening direction.

[0045] As shown in FIG. 3, a frequency-sensitive mechanism 130 is provided on the side opposite to the disk 59 in the axial direction of the disk 60. The frequency-sensitive mechanism 130 makes the damping force variable according to the frequency of the axial movement of the piston 18 (hereinafter referred to as the piston frequency). The frequency-sensitive mechanism 130 includes, in order from the disk 60 side in the axial direction, a single housing body 131, a single disk 132, a single disk 133, a single disk 134, and a single partition disk 135. As shown in FIG. 4, on the side opposite to the disk 132 of the disk 134 and the partition disk 135 in the axial direction, the frequency-sensitive mechanism 130 includes, in order from the disk 134 and partition disk 135 sides, a single disk 136 (plate-like member), a single disk 137 (plate-like member), a single disk 138 (plate-like member), a single disk 139 (plate-like member), a single disk 140 (plate-like member), a plurality of (specifically, two) disks 141 (plate-like members), and a plurality of (specifically, three) disks 142. A plurality of disks 143 are provided on the side opposite to the disk 141 in the axial direction of the plurality of disks 142. An annular member 144 is provided on the side opposite to the disk 142 in the axial direction of the plurality of disks 143.

[0046] The housing body 131, disks 132 to 134, 136 to 143, and the annular member 144 are all made of metal. The disks 132 to 134, 136 to 143, and the annular member 144 are all perforated circular flat plates with a certain thickness. The disks 132 to 134, 136 to 143, the housing body 131, and the annular member 144 all fit the mounting shaft portion 28 of the piston rod 21 inside. The partition disk 135 allows the mounting shaft portion 28 of the piston rod 21 to pass through the inner peripheral side. The disks 132 to 134, 136 to 142, and the housing body 131 constitute the housing 145 of the frequency-sensitive mechanism 130.

[0047] As shown in FIG. 3, the housing body 131 is a bottomed cylindrical shape. The housing body 131 has a through hole 155 formed at its central position in the radial direction, which penetrates the housing body 131 in its axial direction. The through hole 155 has a large-diameter hole portion 156 and a small-diameter hole portion 157. The large-diameter hole portion 156 has a larger diameter than the small-diameter hole portion 157. The large-diameter hole portion 156 is arranged on the side opposite to the disk 60 in the axial direction of the through hole 155. The small-diameter hole portion 157 is arranged on the side closer to the disk 60 than the large-diameter hole portion 156 in the axial direction of the through hole 155. The passage in the large-diameter hole portion 156 of the housing body 131 is always in communication with the passage in the passage groove 30 of the piston rod 21. The passage in the large-diameter hole portion 156 of the housing body 131 also constitutes the rod chamber 83.

[0048] The housing body 131 has a bottom portion 150, a one-side protruding portion 151, an other-side protruding portion 152, a cylindrical portion 153, and a sheet portion 154. The bottom portion 150 is a perforated disk shape. The one-side protruding portion 151 is an annular shape. The one-side protruding portion 151 protrudes from the inner peripheral edge portion of the bottom portion 150 along the axial direction of the bottom portion 150 to the side opposite to the disk 60. The other-side protruding portion 152 is an annular shape. The other-side protruding portion 152 protrudes from the inner peripheral edge portion of the bottom portion 150 along the axial direction of the bottom portion 150 to the side opposite to the one-side protruding portion 151. The cylindrical portion 153 is a cylindrical shape. The cylindrical portion 153 extends from the outer peripheral edge portion of the bottom portion 150 along the axial direction of the bottom portion 150 to the same side as the one-side protruding portion 151. The sheet portion 154 is an annular shape. The sheet portion 154 protrudes from the position between the one-side protruding portion 151 and the cylindrical portion 153 in the radial direction of the bottom portion 150 along the axial direction of the bottom portion 150 to the same side as the one-side protruding portion 151 and the cylindrical portion 153. A notch 158 that penetrates the sheet portion 154 in the radial direction is formed at the end portion on the protruding tip side of the sheet portion 154.

[0049] As shown in FIG. 4, the disk 132 has an outer diameter that is larger than the outer diameter of the tip surface of the one-side protrusion 151 and smaller than the inner diameter of the tip surface of the sheet portion 154. A notch 161 is formed in the disk 132. The notch 161 extends radially outward from the inner peripheral edge portion that fits onto the mounting shaft portion 28 of the disk 132 to beyond the tip surface of the one-side protrusion 151. Inside the notch 161 is a throttle 162. The throttle 162 is constantly in communication with the passage in the large-diameter hole portion 156 of the housing body 131. Therefore, the throttle 162 is constantly in communication with the rod chamber 83. The disk 133 has an outer diameter that is smaller than the outer diameter of the disk 132. The notch 161 of the disk 132 extends radially outward beyond the disk 133 in the radial direction of the disk 132. The disk 133 is thicker than the disk 132. The disk 134 has an outer diameter that is smaller than the outer diameter of the disk 133. The disk 134 is thinner than the disk 133.

[0050] The partition disk 135 is composed of a valve disk 171 (valve member) and an elastic seal member 172 (elastic member, seal member). The partition disk 135 is disposed inside the cylindrical portion 153 of the housing body 131. The partition disk 135 is disposed in the radial space between the cylindrical portion 153 and the disks 133 and 134.

[0051] The valve disk 171 is made of metal. The valve disk 171 is a perforated circular flat plate with a certain thickness. The valve disk 171 is in an annular shape with a constant radial width. The mounting shaft portion 28 of the piston rod 21 is inserted through the inner peripheral side of the valve disk 171. The valve disk 171 is arranged in the cylindrical portion 153 of the housing body 131. The valve disk 171 is elastically deformable, that is, bendable. The inner diameter of the valve disk 171 is larger than the outer diameter of the disk 133. The valve disk 171 has an inner diameter that allows the disks 133 and 134 to be arranged with a radial gap on the inner side. The thickness of the valve disk 171 is thinner than the combined thickness of the two disks 133 and 134. The outer diameter of the valve disk 171 is larger than the outer diameter of the tip surface of the seat portion 154 of the housing body 131.

[0052] The elastic seal member 172 is made of rubber and is annular. The elastic seal member 172 is adhered to the outer peripheral side of the valve disk 171. The elastic seal member 172 is baked onto the valve disk 171 and provided integrally with the valve disk 171. The elastic seal member 172 has a seal portion 175 and a plurality of contact portions 176. The seal portion 175 is annular and is fixed to the outer peripheral side of the valve disk 171 over the entire circumference. The seal portion 175 projects from the valve disk 171 toward the bottom portion 150 of the housing body 131 in the axial direction of the partition disk 135. The plurality of contact portions 176 are fixed to the outer peripheral side of the valve disk 171. The plurality of contact portions 176 are arranged at equal intervals in the circumferential direction of the valve disk 171. The plurality of contact portions 176 project from the valve disk 171 to the side opposite to the bottom portion 150 in the axial direction of the partition disk 135.

[0053] An annular gap is provided between the valve disk 171 and the cylindrical portion 153 of the housing body 131. The elastic seal member 172 fixes the seal portion 175 and the plurality of contact portions 176 to both surfaces of the valve disk 171 through this gap. With such a configuration, the fixing of the seal portion 175 and the plurality of contact portions 176 to the valve disk 171 is facilitated.

[0054] The elastic seal member 172 has its seal portion 175 fitting in a liquid-tight manner over the entire circumference to the inner peripheral portion of the cylindrical portion 153 of the housing body 131. The seal portion 175 is slidable in the axial direction of the cylindrical portion 153 with respect to the cylindrical portion 153. The elastic seal member 172 has its seal portion 175 constantly sealing the gap between the partition disk 135 and the cylindrical portion 153. The minimum inner diameter of the seal portion 175 is larger than the outer diameter of the tip surface of the seat portion 154. The partition disk 135 enables the valve disk 171 to be seated on the seat portion 154 of the housing body 131.

[0055] The disk 136 has an outer diameter larger than the inner diameter of the valve disk 171. The disk 136 is thinner than the disk 134. The disk 136 is thinner than the valve disk 171. The disk 136 is in contact with the inner peripheral side of the valve disk 171 over the entire circumference. As a result, the gap between the disk 136 and the valve disk 171 is blocked. The partition disk 135 has its inner peripheral side of the valve disk 171 disposed between the disk 132 and the disk 136 and is supported in contact with the disk 136. The inner peripheral side of the partition disk 135 with respect to the valve disk 171 is movable within the axial length range of the two disks 133 and 134 between the disk 132 and the disk 136. The partition disk 135 is centered with respect to the housing 145 when the seal portion 175 contacts the cylindrical portion 153 over the entire circumference. The inner peripheral side of the partition disk 135 with respect to the valve disk 171 is supported only by the disk 136 on one side without being clamped from both sides. The radially outer side of the partition disk 135 with respect to the valve disk 171 and the disk 136 is supported only by the sheet portion 154 on one side without being clamped from both sides. Therefore, the partition disk 135 has a simple support structure in which one side of the valve disk 171 is supported by the disk 136 and the other side of the valve disk 171 is supported by the sheet portion 154. The partition disk 135 is annular as a whole and is elastically deformable, that is, bendable.

[0056] Disk 137 has an outer diameter that is larger than the outer diameter of disk 136 and smaller than the minimum inner diameter of the contact portion 176. Disk 137 is thinner than disk 136. Disk 138 has an outer diameter that is smaller than the outer diameter of disk 137. Disk 138 is thicker than disk 137. Disk 139 has an outer diameter that is smaller than the outer diameter of disk 138. Disk 139 is thicker than disk 138. Disk 140 has an outer diameter that is smaller than the outer diameter of disk 139. Disk 140 is thicker than disk 139. Disk 141 has an outer diameter that is smaller than the outer diameter of disk 140 and larger than the outer diameter of disk 136. Disk 141 is thicker than disk 140.

[0057] Disks 136 to 141, all of which are plate-like members, are laminated to form the support member 181. The support member 181 includes the contact portion 176 of the partition disk 135. Among disks 136 to 141, disks 137 to 141 have a smaller outer diameter on the side opposite to the valve disk 171 in the axial direction than on the side of the valve disk 171 in the axial direction. Disks 137 to 141 are thicker on the side opposite to the valve disk 171 in the axial direction than on the side of the valve disk 171 in the axial direction. The support member 181 supports the inner peripheral side of the valve disk 171 of the partition disk 135. The valve disk 171 of the partition disk 135 is supported by the support member 181 only on one side in the axial direction without being clamped from both sides in the axial direction on the inner peripheral side.

[0058] The plurality of disks 142 have an outer diameter that is larger than the outer diameter of the disk 141 and smaller than the inner diameter of the cylindrical portion 153. The disks 142 are thicker than the disk 141. The plurality of disks 142 are constantly in contact with the contact portion 176 of the partition disk 135. The plurality of disks 142 constitute the stopper member 182. The stopper member 182 restricts the movement of the valve disk 171 in the axial direction of the housing body 131 opposite to the seat portion 154 by the contact portion 176 of the elastic seal member 172. The inner peripheral side of the stopper member 182 is fixed to the piston rod 21. The inner peripheral side of the stopper member 182 is immovable with respect to the housing body 131. The elastic seal member 172 is such that its contact portion 176 is stretchable and contractible in the axial direction of the housing body 131 with respect to the housing body 131. The end portion of the contact portion 176 of the elastic seal member 172 on the side of the stopper member 182 is movable with respect to the piston rod 21 and the housing body 131. Since the elastic seal member 172 is adhered to the valve disk 171, it is constantly in contact with the valve disk 171. The contact portion 176 of the elastic seal member 172 and the stopper member 182 are constantly in contact. The contact portion 176 of the elastic seal member 172 and the stopper member 182 constitute a movement restricting member 185 that restricts the movement of the valve disk 171.

[0059] The outer diameters of the disks 137 to 141 of the support member 181 on the side of the movement restricting member 185 in the axial direction of the support member 181 are smaller than the outer diameters of those on the valve disk 171 side in the axial direction of the support member 181. The thicknesses of the disks 137 to 141 on the side of the movement restricting member 185 in the axial direction of the support member 181 are larger than the thicknesses of those on the valve disk 171 side in the axial direction of the support member 181. The radial space between the disk 142 and the cylindrical portion 153 forms the communication passage 195. The communication passage 195 is constantly in communication with the lower chamber 20. The communication passage 195 is arranged radially outside the contact portion 176 of the elastic seal member 172 that contacts the disk 142.

[0060] The seal portion 175 of the partition disk 135 is in contact with the inner peripheral surface of the cylindrical portion 153 of the housing body 131 over the entire circumference. Thereby, the seal portion 175 seals the gap between the partition disk 135 and the cylindrical portion 153. That is, the partition disk 135 is a packing valve. Even when the seal portion 175 deforms within the range allowed for the partition disk 135 within the housing 145, the seal portion 175 always seals the gap between the partition disk 135 and the cylindrical portion 153. The partition disk 135 is centered with respect to the housing 145 as described above by the seal portion 175 being in contact with the cylindrical portion 153 over the entire circumference. The partition disk 135 closes the gap with the disk 136 by the valve disk 171 being in contact with the disk 136 over the entire circumference.

[0061] The seat portion 154 of the housing body 131 supports the valve disk 171 of the partition disk 135 from one axial side. The support member 181 supports the disk 136 from the other axial side on the inner peripheral side of the seat portion 154 of the valve disk 171. The shortest axial distance between the seat portion 154 and the disk 136 is smaller than the axial thickness of the valve disk 171. Therefore, the valve disk 171 is press - contacted with the seat portion 154 and the disk 136 over the entire circumference by its own elastic force in a slightly elastically deformed state.

[0062] The partition disk 135 divides the inside of the housing 145 into a variable chamber 191 and a variable chamber 192. The variable chamber 191 is located between the bottom 150 side of the housing main body 131 and the partition disk 135. The variable chamber 192 is located between the partition disk 135 and the disk 142. Both the variable chamber 191 and the variable chamber 192 have variable volumes, and the volumes change due to the deformation of the partition disk 135. In other words, the two variable chambers 191 and 192 are defined by the partition disk 135 and provided inside the housing 145. The variable chamber 191 is always in communication with the rod chamber 83 through the throttle 162 in the notch 161 of the disk 132. Therefore, the variable chamber 191 is always in communication with the upper chamber 19 through the throttle 162 in the disk 132, the rod chamber 83, the throttle 82 in the disk 51 shown in FIG. 3, and the first passage portion 43. Also, the variable chamber 191 is always in communication with the back pressure chamber 100 through the throttle 162 in the disk 132, the rod chamber 83, and the throttle 92 in the disk 54. The variable chamber 192 is always in communication with the lower chamber 20 through the communication passage 195. The variable chamber 191 and the variable chamber 192 constitute an inner chamber 198 of the housing provided inside the housing 145. The partition disk 135 is provided in the inner chamber 198 of the housing.

[0063] A plurality of contact portions 176 shown in FIG. 4 are arranged at intervals in the circumferential direction on the partition disk 135. As a result, the inner and outer sides of the variable chamber 192 in its radial direction are always in communication. Also, a notch 158 is provided in the seat portion 154 of the housing main body 131. As a result, the inner and outer sides of the variable chamber 191 in its radial direction are always in communication. By these means, the pressure receiving areas on the side where the seal portion 175 of the valve disk 171 is provided and the side where the contact portion 176 of the valve disk 171 is provided become approximately the same.

[0064] In the extension stroke, the hydraulic fluid from the upper chamber 19 shown in FIG. 3 is introduced into the variable chamber 191 through the first passage portion 43, the throttle 82 in the disk 51, the rod chamber 83, and the throttle 162 in the disk 132. Then, the valve disk 171 of the partition disk 135 is deformed in a tapered shape such that the outer peripheral side moves away from the seat portion 154 in the axial direction of the seat portion 154 with the contact point of the support member 181 with the disk 136 shown in FIG. 4 as a fulcrum. In other words, the valve disk 171 moves while deforming toward the movement restricting member 185 side. At that time, the valve disk 171 compresses and deforms the contact portion 176 of the elastic seal member 172 that abuts against the stopper member 182. In other words, the valve disk 171 deforms so as to move the outer peripheral side in the direction of the stopper member 182 and the contact portion 176. Due to this deformed movement of the valve disk 171, the volume of the variable chamber 191 will increase.

[0065] At that time, the support member 181 including the contact portion 176 that supports the valve disk 171 applies a resistance force to this deformed movement of the valve disk 171. In other words, the support member 181 restricts the lift of the valve disk 171. Here, when the valve disk 171 undergoes this deformed movement, the volume of the variable chamber 192 will decrease. At that time, the hydraulic fluid in the variable chamber 192 flows into the lower chamber 20 through the communication passage 195.

[0066] In the initial stage of the deformed movement of the valve disk 171 toward the movement restricting member 185 side, the valve disk 171 itself deforms and moves, and compresses and deforms the contact portion 176 of the elastic seal member 172 that abuts against the stopper member 182. The movement range during this deformed movement of the valve disk 171 is defined as the first movement range. In this first movement range, the spring constant of the support member 181 is the spring constant of the contact portion 176. This spring constant is defined as the first spring constant.

[0067] When the deformation movement of the valve disk 171 toward the movement restricting member 185 further progresses, the valve disk 171 deforms and moves more than its first movement range and compresses and deforms the contact portion 176 of the elastic seal member 172 more than the first movement range. At the same time, the valve disk 171 abuts against the outer peripheral side of the disk 137 of the support member 181 and deforms and moves the outer peripheral side of the disk 137 in a tapered shape toward the movement restricting member 185 side. The movement range during the deformation movement of the valve disk 171 at this time is defined as the second movement range. The spring constant of the support member 181 in this second movement range is defined as the second spring constant. Then, the second spring constant becomes the spring constant obtained by combining the spring constant of the contact portion 176 and the spring constant of the disk 137, and is larger than the first spring constant. In other words, the support member 181 has a higher rigidity when the valve disk 171 is in the second movement range than when the valve disk 171 is in the first movement range.

[0068] When the deformation movement of the valve disk 171 toward the movement restricting member 185 further progresses, the valve disk 171 deforms and moves more than its second movement range and compresses and deforms the contact portion 176 of the elastic seal member 172 more than the second movement range. At the same time, the valve disk 171 deforms and moves the outer peripheral side of the disk 137 of the support member 181 in a tapered shape toward the movement restricting member 185 side more than the second movement range. At the same time, the valve disk 171 deforms and moves the outer peripheral side of the disk 138 in a tapered shape toward the movement restricting member 185 side via the disk 137. The movement range during the deformation movement of the valve disk 171 toward the movement restricting member 185 following the second movement range is defined as the third movement range. The spring constant of the support member 181 in this third movement range is defined as the third spring constant. Then, the third spring constant becomes the spring constant obtained by combining the spring constant of the contact portion 176, the spring constant of the disk 137, and the spring constant of the disk 138, and is larger than the second spring constant. In other words, the support member 181 has a higher rigidity when the valve disk 171 is in the third movement range than when the valve disk 171 is in the second movement range.

[0069] When the deformation movement of the valve disk 171 toward the movement restricting member 185 further progresses, the valve disk 171 deforms and moves more than its third movement range and compresses and deforms the contact portion 176 of the elastic seal member 172 more than the third movement range. At the same time, the valve disk 171 deforms and moves the outer peripheral side of the disk 137 of the support member 181 in a tapered manner toward the movement restricting member 185 more than the third movement range. At the same time, the valve disk 171 deforms and moves the outer peripheral side of the disk 138 in a tapered manner toward the movement restricting member 185 more than the third movement range via the disk 137. At the same time, the valve disk 171 deforms and moves the outer peripheral side of the disk 139 in a tapered manner toward the movement restricting member 185 via the disk 138. The movement range during the deformation movement of the valve disk 171 toward the movement restricting member 185 following the third movement range is defined as the fourth movement range. The spring constant of the support member 181 in this fourth movement range is defined as the fourth spring constant. Then, the fourth spring constant becomes the spring constant obtained by adding the spring constant of the contact portion 176, the spring constant of the disk 137, the spring constant of the disk 138, and the spring constant of the disk 139, and becomes larger than the third spring constant. In other words, the support member 181 has a higher rigidity when the valve disk 171 is in the fourth movement range than when the valve disk 171 is in the third movement range.

[0070] When the deformation movement of the valve disk 171 toward the movement restricting member 185 further progresses, as shown in FIG. 5, the valve disk 171 is deformed and moved more than the fourth movement range and compresses and deforms the contact portion 176 of the elastic seal member 172 more than the fourth movement range. At the same time, the valve disk 171 deforms and moves the outer peripheral side of the disk 137 of the support member 181 in a tapered shape toward the movement restricting member 185 more than the fourth movement range. At the same time, the valve disk 171 deforms and moves the outer peripheral side of the disk 138 in a tapered shape toward the movement restricting member 185 more than the fourth movement range via the disk 137. At the same time, the valve disk 171 deforms and moves the outer peripheral side of the disk 139 in a tapered shape toward the movement restricting member 185 more than the fourth movement range via the disk 138. At the same time, the valve disk 171 deforms and moves the outer peripheral side of the disk 140 in a tapered shape toward the movement restricting member 185 via the disk 139. The movement range during the deformation movement of the valve disk 171 toward the movement restricting member 185 following the fourth movement range is defined as the fifth movement range. The spring constant of the support member 181 in this fifth movement range is defined as the fifth spring constant. Then, the fifth spring constant is the sum of the spring constants of the contact portion 176, the disk 137, the disk 138, the disk 139, and the disk 140, and is larger than the fourth spring constant. In other words, the support member 181 has a higher rigidity when the valve disk 171 is in the fifth movement range than when the valve disk 171 is in the fourth movement range.

[0071] The disk 143 has an outer diameter smaller than the outer diameter of the disk 142. The annular member 144 has an outer diameter larger than the outer diameter of the disk 143 and smaller than the outer diameter of the disk 142.

[0072] The first passage portion 43 shown in FIG. 3, the throttle 82, the rod chamber 83, the throttle 162, the housing inner chamber 198, and the communication passage 195 constitute a passage 201. The passage 201 enables communication between the upper chamber 19 and the lower chamber 20. In the passage 201, the first passage portion 43, the throttle 82, the rod chamber 83, the throttle 162, and the variable chamber 191 are always in communication with the upper chamber 19. In the passage 201, the variable chamber 192 and the communication passage 195 are always in communication with the lower chamber 20. In the passage 201, when the piston 18 moves in the extending stroke, the oil, which is the working fluid, flows out from the upper chamber 19, which is one of the chambers in the cylinder 2, through the first passage portion 43, the throttle 82, the rod chamber 83, the throttle 162, and the variable chamber 191. In the passage 201, when the piston 18 moves in the retracting stroke, the oil, which is the working fluid, flows out from the lower chamber 20, which is one of the chambers in the cylinder 2, through the communication passage 195 and the variable chamber 192. The partition disk 135 including the valve disk 171 is provided in this passage 201.

[0073] The inner peripheral side of the valve disk 171 of the partition disk 135 is movable between the disk 132 and the disk 136. When the inner peripheral side of the valve disk 171 of the partition disk 135 is in contact with the disk 136 over the entire circumference, the partition disk 135 blocks the flow of oil between the variable chambers 191 and 192. Further, when the inner peripheral side of the valve disk 171 of the partition disk 135 is separated from the disk 136, the partition disk 135 allows the flow of oil between the variable chamber 192 and the variable chamber 191. The inner peripheral side of the valve disk 171 and the disk 136 constitute a check valve 205. The check valve 205 is provided in the passage 201. The check valve 205 regulates the flow of oil from the variable chamber 191 to the variable chamber 192 while allowing the flow of oil from the variable chamber 192 to the variable chamber 191. In the extending stroke where the pressure in the upper chamber 19 is higher than the pressure in the lower chamber 20, the check valve 205 blocks the passage 201 that enables communication between the upper chamber 19 and the lower chamber 20. In the retracting stroke where the pressure in the lower chamber 20 is higher than the pressure in the upper chamber 19, the check valve 205 puts the entire passage 201 in a communicating state.

[0074] The check valve 205 is a free valve in which the entire partition disk 135, which is its valve body, can move without being axially clamped. Note that the partition disk 135 may be set so as to always keep the entire inner circumference of its valve disk 171 in contact with the disk 136 regardless of the pressure states of the variable chambers 191 and 192. That is, the flow between the variable chambers 191 and 192 may be constantly blocked. That is, the valve disk 171 of the partition disk 135 only needs to block the flow of the hydraulic fluid in at least one direction of the passage 201.

[0075] With the mounting shaft portions 28 inserted into the inside of the piston rod 21, the annular member 117, disk 116, disk 115, a plurality of disks 114, a plurality of disks 113, disk 112, disk 111, piston 18, disk 51, damping valve 52, disk 53, disk 54, pilot case 55, disk 56, disk 57, a plurality of disks 58, disk 59, disk 60, housing body 131, disk 132, disk 133, and disk 134 shown in FIG. 3 are stacked on the shaft step portion 29 in this order. At this time, the pilot case 55 fits the seal member 86 of the damping valve 52 to the outer cylindrical portion 73.

[0076] Also, as shown in FIG. 4, with the mounting shaft portions 28 and the disks 133 and 134 inserted into the inside, the partition disk 135 is stacked on the seat portion 154 of the housing body 131. At this time, the elastic seal member 172 of the partition disk 135 is fitted to the cylindrical portion 153 of the housing body 131. Further, with the mounting shaft portions 28 inserted into the inside, the disk 136, disk 137, disk 138, disk 139, disk 140, disk 141, disk 142, disk 143, and annular member 144 are stacked on the disk 134 and the valve disk 171 of the partition disk 135 in this order.

[0077] With the components from the annular member 117 to the annular member 144 thus arranged on the piston rod 21, a nut 211 is screwed onto the male thread 31 shown in FIG. 3 of the mounting shaft portion 28 that protrudes beyond the annular member 144. As a result, the annular member 117, the disk 116, the disk 115, the plurality of disks 114, the plurality of disks 113, the disk 112, the disk 111, the piston 18, the disk 51, the damping valve 52, the disk 53, the disk 54, the pilot case 55, the disk 56, the disk 57, the plurality of disks 58, the disk 59, the disk 60, the housing body 131, the disk 132, the disk 133, the disk 134, the disk 136, the disk 137, the disk 138, the disk 139, the disk 140, the disk 141, the disk 142, the disk 143, and the annular member 144 are each clamped axially between the shaft step portion 29 of the piston rod 21 and the nut 211. At that time, the partition disk 135 is not axially clamped on the inner peripheral side. In this state, the partition disk 135 has the valve disk 171 abutting against the seat portion 154 of the housing body 131 and the disk 136 of the support member 181. Also, in this state, the partition disk 135 has the contact portion 176 of the elastic seal member 172 abutting against the disk 142 with a clamping allowance.

[0078] As shown in FIG. 1, the above-described base valve 25 is provided between the inner cylinder 3 and the bottom member 12 of the outer cylinder 4. This base valve 25 has a base valve member 221, a disk valve 222, a disk valve 223, and a mounting pin 224. The base valve 25 is placed on the bottom member 12 at the base valve member 221 and is fitted into the inner cylinder 3 at the base valve member 221. The base valve member 221 partitions the lower chamber 20 and the reservoir chamber 6. The disk valve 222 is provided on the lower side of the base valve member 221, that is, on the reservoir chamber 6 side. The disk valve 223 is provided on the upper side of the base valve member 221, that is, on the lower chamber 20 side. The mounting pin 224 attaches the disk valve 222 and the disk valve 223 to the base valve member 221.

[0079] The base valve member 221 is annular, and a mounting pin 224 is inserted through the center in the radial direction. A plurality of passage holes 225 and a plurality of passage holes 226 are formed in the base valve member 221. The plurality of passage holes 225 allow the oil to flow between the lower chamber 20 and the reservoir chamber 6. The plurality of passage holes 226 are arranged outside the plurality of passage holes 225 in the radial direction of the base valve member 221. The plurality of passage holes 226 allow the oil to flow between the lower chamber 20 and the reservoir chamber 6. The disk valve 222 on the reservoir chamber 6 side allows the flow of oil from the lower chamber 20 to the reservoir chamber 6 through the passage hole 225. On the other hand, the disk valve 222 suppresses the flow of oil from the reservoir chamber 6 to the lower chamber 20 through the passage hole 225. The disk valve 223 allows the flow of oil from the reservoir chamber 6 to the lower chamber 20 through the passage hole 226. On the other hand, the disk valve 223 suppresses the flow of oil from the lower chamber 20 to the reservoir chamber 6 through the passage hole 226.

[0080] The disk valve 222 constitutes a damping valve mechanism 227 by the base valve member 221. The damping valve mechanism 227 opens during the compression stroke of the shock absorber 1 to allow the oil to flow from the lower chamber 20 to the reservoir chamber 6 and generates a damping force. The disk valve 223 constitutes a suction valve mechanism 228 by the base valve member 221. The suction valve mechanism 228 opens during the extension stroke of the shock absorber 1 to allow the oil to flow from the reservoir chamber 6 into the lower chamber 20. The suction valve mechanism 228 mainly functions to supply the oil from the reservoir chamber 6 to the lower chamber 20 to compensate for the shortage of the liquid caused by the extension of the piston rod 21 from the cylinder 2 without substantially generating a damping force.

[0081] Next, the main operation of the shock absorber 1 will be described.

[0082] "When it is assumed that in the extension stroke, the frequency-sensitive mechanism 130 does not act and only the first damping force generating mechanism 41 and the second damping force generating mechanism 110 on the extension side act" In this case, when the moving speed of the piston 18 (hereinafter referred to as the piston speed) is slower than the first predetermined value, the oil fluid from the upper chamber 19 flows into the lower chamber 20 through the first passage portion 43, throttle 82, rod chamber 83, throttle 92, back pressure chamber 100, and fixed orifice 105 shown in FIG. 3. Therefore, a damping force with an orifice characteristic (the damping force is approximately proportional to the square of the piston speed) is generated. For this reason, the characteristic of the damping force with respect to the piston speed when the piston speed is slower than the first predetermined value is such that the rising rate of the damping force with respect to the rising of the piston speed becomes relatively high.

[0083] When the piston speed is equal to or greater than the first predetermined value and less than the second predetermined value, the oil fluid from the upper chamber 19 passes through the first passage portion 43, throttle 82, rod chamber 83, throttle 92, back pressure chamber 100, and while opening the disk valve 99, flows into the lower chamber 20 through the space between the disk valve 99 and the valve seat portion 75. Therefore, a damping force with a valve characteristic (the damping force is approximately proportional to the piston speed) is generated. For this reason, the characteristic of the damping force with respect to the piston speed when the piston speed is equal to or greater than the first predetermined value and less than the second predetermined value is such that the rising rate of the damping force with respect to the rising of the piston speed will be lower than when the piston speed is less than the first predetermined value.

[0084] When the piston speed becomes faster than the second predetermined value, the relationship of the force (hydraulic pressure) acting on the damping valve 52 is such that the opening-direction force applied from the first passage portion 43 is greater than the closing-direction force applied from the back pressure chamber 100. Therefore, in this region, as the piston speed increases, the damping valve 52 will move away from the valve seat portion 48 of the piston 18 and open. Therefore, the oil fluid from the upper chamber 19 passes through the first passage portion 43, throttle 82, rod chamber 83, throttle 92, back pressure chamber 100, and in addition to the flow into the lower chamber 20 through the space between the disk valve 99 and the valve seat portion 75, also flows into the lower chamber 20 through the space between the damping valve 52 and the valve seat portion 48 from the first passage portion 43. For this reason, the rising rate of the damping force with respect to the rising of the piston speed when the piston speed is equal to or greater than the second predetermined value is lower than when the piston speed is equal to or greater than the first predetermined value and less than the second predetermined value.

[0085] "When it is assumed that in the compression stroke, the frequency-sensitive mechanism 130 does not act and only the first damping force generating mechanism 42 on the compression side acts" In this case, when the piston speed is slower than the third predetermined value, the oil from the lower chamber 20 flows into the upper chamber 19 through the first passage portion 44 shown in FIG. 2 and the fixed orifice 123 of the disk valve 122. As a result, a damping force with orifice characteristics is generated. Therefore, the characteristic of the damping force with respect to the piston speed when the piston speed is slower than the third predetermined value is such that the rising rate of the damping force with respect to the rising of the piston speed is relatively high.

[0086] When the piston speed becomes faster than the third predetermined value, the oil introduced from the lower chamber 20 into the first passage portion 44 flows into the upper chamber 19 through between the disk valve 122 and the valve seat portion 49 while opening the disk valve 122. As a result, a damping force with valve characteristics is generated. Therefore, the characteristic of the damping force with respect to the piston speed when the piston speed is equal to or higher than the third predetermined value is such that the rising rate of the damping force with respect to the rising of the piston speed is lower than when the piston speed is less than the third predetermined value.

[0087] "When the frequency-sensitive mechanism 130 acts in the extension stroke" In the first embodiment, the frequency-sensitive mechanism 130 makes the damping force variable according to the piston frequency even when the piston speed is the same.

[0088] In the extension stroke, oil is introduced from the upper chamber 19 into the variable chamber 191 of the frequency-sensitive mechanism 130 through the first passage portion 43, the throttle 82, the rod chamber 83, and the throttle 162 shown in FIG. 4. Therefore, the valve disk 171 of the partition disk 135 that was in contact with the seat portion 154 and the disk 136 of the support member 181 is deformed and moved in a tapered shape in a direction in which the outer peripheral side moves away from the seat portion 154 with the contact point with the disk 136 as a fulcrum. At that time, the partition disk 135 compresses and deforms the contact portion 176 of the elastic seal member 172 that contacts the stopper member 182. Also, at that time, the partition disk 135 discharges oil from the variable chamber 192 of the frequency-sensitive mechanism 130 into the lower chamber 20 through the communication passage 195. Here, during the extension stroke when the piston frequency is high, the stroke of the piston 18 is small. Therefore, the amount of oil introduced from the upper chamber 19 into the variable chamber 191 through the first passage portion 43, the throttle 82, the rod chamber 83, and the throttle 162 is small. Thus, although the valve disk 171 of the partition disk 135 deforms as described above, it does not deform close to the limit.

[0089] Therefore, during the extension stroke when the piston frequency is high, each time the extension stroke occurs, the valve disk 171 of the partition disk 135 of the frequency sensing mechanism 130 deforms as described above, and oil is introduced from the upper chamber 19 into the variable chamber 191. Then, the flow rate of the oil flowing from the upper chamber 19 through the first passage portion 43, the throttle 82, the rod chamber 83, the throttle 92, and the back pressure chamber 100 and opening the second damping force generating mechanism 110 to the lower chamber 20 decreases. In addition to this, the flow rate of the oil flowing from the first passage portion 43 and opening the first damping force generating mechanism 41 to the lower chamber 20 also decreases. In addition, by introducing oil from the upper chamber 19 into the variable chamber 191, the pressure rise in the back pressure chamber 100 is suppressed compared to the case where there is no variable chamber 191, and the damping valve 52 of the first damping force generating mechanism 41 is more likely to open. As a result, the damping force on the extension side becomes soft. Here, the inner peripheral side of the partition disk 135 is separated from the disk 132 and is supported by the disk 136 only from one side. Therefore, the partition disk 135 is likely to deform so that the inner peripheral side approaches the disk 132. Thus, the contact portion 176 on the outer peripheral side of the partition disk 135 easily undergoes compressive deformation.

[0090] Here, during the extension stroke, the valve disk 171 of the partition disk 135 deforms and moves taperedly toward the movement restricting member 185 with the contact point with the disk 136 of the support member 181 as a fulcrum as described above. At the initial stage of this deformation and movement, the valve disk 171 deforms and moves itself and compresses and deforms the contact portion 176 of the elastic seal member 172 that contacts the stopper member 182. Furthermore, as the deformation movement of the valve disk 171 toward the movement restricting member 185 progresses, the valve disk 171 further deforms and moves itself, and further compresses and deforms the contact portion 176 of the elastic seal member 172. At the same time, the valve disk 171 abuts against the outer peripheral side of the disk 137 of the support member 181, and deforms and moves the outer peripheral side of the disk 137 in a tapered shape toward the movement restricting member 185 side.

[0091] Furthermore, as the deformation movement of the valve disk 171 toward the movement restricting member 185 progresses, the valve disk 171 further deforms and moves itself, and further compresses and deforms the contact portion 176 of the elastic seal member 172. At the same time, the valve disk 171 deforms and moves the outer peripheral sides of the disk 137 and the disk 138 of the support member 181 in a tapered shape toward the movement restricting member 185 side.

[0092] Furthermore, as the deformation movement of the valve disk 171 toward the movement restricting member 185 progresses, the valve disk 171 further deforms and moves itself, and further compresses and deforms the contact portion 176 of the elastic seal member 172. At the same time, the valve disk 171 deforms and moves the outer peripheral sides of the disk 137, the disk 138, and the disk 139 of the support member 181 in a tapered shape toward the movement restricting member 185 side.

[0093] Furthermore, as the deformation movement of the valve disk 171 toward the movement restricting member 185 progresses, as shown in FIG. 5, the valve disk 171 further deforms and moves itself, and further compresses and deforms the contact portion 176 of the elastic seal member 172. At the same time, the valve disk 171 deforms and moves the outer peripheral sides of the disk 137, the disk 138, the disk 139, and the disk 140 of the support member 181 in a tapered shape toward the movement restricting member 185 side.

[0094] The support member 181 is such that the plurality of stacked disks 137 to 140 have a smaller diameter toward the movement restricting member 185 side and a greater thickness toward the movement restricting member 185 side. For this reason, the relationship between the deflection of the valve disk 171 and the differential pressure becomes as shown by the thick solid line X1 in FIG. 6. That is, in the initial stage of the deformation movement where the differential pressure between the variable chamber 191 and the variable chamber 192 is small, the valve disk 171 is easily deflected with a large deflection amount with respect to the increase in the differential pressure. Also, the valve disk 171 suppresses excessive deflection even when the differential pressure increases.

[0095] On the other hand, in the extension stroke when the piston frequency is low, the stroke of the piston 18 is large. For this reason, a large amount of oil is introduced from the upper chamber 19 into the variable chamber 191 through the first passage portion 43, the throttle 82, the rod chamber 83, and the throttle 162. Thus, at the initial stage of the stroke of the piston 18, oil flows from the upper chamber 19 into the variable chamber 191, but thereafter, the valve disk 171 of the partition disk 135 is deformed to near the limit and no longer deforms. As a result, oil no longer flows from the upper chamber 19 into the variable chamber 191. Thereby, the flow rate of the oil flowing from the upper chamber 19 through the first passage portion 43, the throttle 82, the rod chamber 83, the throttle 92, and the back pressure chamber 100 and opening the second damping force generating mechanism 110 to the lower chamber 20 does not decrease. In addition to this, the flow rate of the oil flowing from the first passage portion 43 through the first damping force generating mechanism 41 and opening to the lower chamber 20 also does not decrease. In addition, since oil is not introduced from the upper chamber 19 into the variable chamber 191, the pressure in the back pressure chamber 100 increases, and it becomes difficult for the damping valve 52 of the first damping force generating mechanism 41 to open. As a result, the damping force on the extension side becomes harder than when the piston frequency is high. Even in the extension stroke when the piston frequency is low, the valve disk 171 deforms while deforming the support member 181 in the same manner as when the piston frequency is high.

[0096] During the compression stroke, the pressure in the lower chamber 20 increases. However, the valve disk 171 of the partition disk 135 of the frequency-sensitive mechanism 130 abuts against the seat portion 154 of the housing body 131 to suppress the expansion of the variable chamber 192. Therefore, the amount of oil introduced from the lower chamber 20 into the variable chamber 192 through the communication passage 195 is suppressed. As a result, the flow rate of the oil flowing from the lower chamber 20 into the first passage portion 44, passing through the first damping force generating mechanism 42, and flowing into the upper chamber 19 does not decrease. Thus, the damping force becomes hard. During the compression stroke, when the piston speed increases and the pressure in the variable chamber 192 becomes higher than a predetermined value or more than the pressure in the variable chamber 191, the inner peripheral side of the valve disk 171 of the partition disk 135 separates from the disk 136. In other words, the check valve 205 opens. As a result, oil flows from the lower chamber 20 into the upper chamber 19 through the communication passage 195, the variable chamber 192, the variable chamber 191, the throttle 162, the rod chamber 83, the throttle 82, and the first passage portion 43. In this way, when the check valve 205 opens, the differential pressure between the variable chamber 192 side and the variable chamber 191 side of the valve disk 171 of the partition disk 135 is suppressed. Therefore, excessive deflection of the valve disk 171 is suppressed.

[0097] Patent Documents 1 and 2 mentioned above describe a shock absorber provided with a valve member having a simple support structure that is supported without being clamped in a passage through which a working fluid flows due to the movement of a piston. In such a structure, there is a desire to suppress the excessive deflection of the valve member when the differential pressure generated in the valve member becomes large. For this reason, for example, a regulating member is provided that abuts against the radially intermediate position of the valve member during the deformation movement of the valve member to regulate the deformation movement of one side portion in the radial direction of the valve member. Then, before and after the valve member and the regulating member come into contact, the amount of change in the deflection of the valve member with respect to the increase in the differential pressure suddenly changes. Then, the damping force becomes transient, and the ride comfort of the vehicle using this shock absorber deteriorates. Also, in this structure, the stress generated in the valve member also increases, and there is a possibility that the durability deteriorates. Further, for example, in order to suppress the increase in the amount of deflection of the valve member due to the increase in the differential pressure, a movement restricting member that constantly abuts against the valve member to restrict the lift is provided and its rigidity is increased. Then, it becomes difficult for the valve member to move. As a result, the initial timing of the movement of the valve member is delayed, so the ride comfort of the vehicle using this shock absorber deteriorates.

[0098] In the shock absorber 1 of the first embodiment, a valve disk 171 is provided in a passage 201 through which hydraulic fluid flows out from one upper chamber 19 in the cylinder 2 due to the movement of the piston 18 in the extension stroke. The inner peripheral side of this valve disk 171 is supported only by a support member 181 on one side without being clamped from both sides. The support member 181 has a second spring constant in a second movement range where the valve disk 171 moves to the side of the movement restricting member 185 beyond the first movement range and deforms and moves the outer peripheral side of the disk 137, which is larger than the first spring constant in the first movement range where the valve disk 171 deforms and moves the contact portion 176. Further, the support member 181 has a third spring constant in a third movement range where the valve disk 171 moves to the side of the movement restricting member 185 beyond the second movement range and deforms and moves the outer peripheral sides of the contact portion 176 and the disks 137 and 138, which is larger than the second spring constant in the second movement range where the valve disk 171 deforms and moves the contact portion 176 and the outer peripheral side of the disk 137. Also, the support member 181 has a fourth spring constant in a fourth movement range where the valve disk 171 moves to the side of the movement restricting member 185 beyond the third movement range and deforms and moves the outer peripheral sides of the contact portion 176 and the disks 137 to 139, which is larger than the third spring constant in the third movement range. Furthermore, the support member 181 has a fifth spring constant in a fifth movement range where the valve disk 171 moves to the side of the movement restricting member 185 beyond the fourth movement range and deforms and moves the outer peripheral sides of the contact portion 176 and the disks 137 to 140, which is larger than the fourth spring constant in the fourth movement range. The shock absorber 1 has the spring constant of the support member 181 increasing stepwise in this way. Therefore, the shock absorber 1 can suppress a sudden transient change in the deflection with respect to an increase in the differential pressure of the valve disk 171.

[0099] That is, as shown by the thick solid line X1 in FIG. 6, the valve disk 171 has a characteristic in which the change in the amount of deflection with respect to an increase in the differential pressure is small and smooth. Therefore, the shock absorber 1 can suppress the damping force from becoming transient, and can improve the ride comfort of a vehicle in which this shock absorber 1 is used. Also, in the initial stage of the deformation movement where the differential pressure between the variable chamber 191 and the variable chamber 192 is small, the valve disk 171 is easily deflected as the change in the amount of deflection is large with respect to the increase in the differential pressure. In other words, the low rigidity at the initial deflection of the valve disk 171 can be maintained. Therefore, the initial timing of the movement of the valve disk 171 is not delayed. This also improves the riding comfort of the vehicle using this shock absorber 1. Also, the variable width of the valve disk 171 is not reduced. This also improves the riding comfort of the vehicle using this shock absorber 1. Also, since the support member 181 can suppress excessive deflection of the valve disk 171, the stress generated in the valve disk 171 is also reduced, and its durability can be improved. Therefore, the shock absorber 1 can obtain high reliability while ensuring performance.

[0100] Here, the characteristic X2 shown by the broken line in FIG. 6 is the case where, for the shock absorber 1 of the first embodiment, the deflection regulation of the valve disk 171 by the support member is not performed. In this case, when the differential pressure of the valve disk 171 increases, the deflection of the valve disk 171 becomes larger than that of the shock absorber 1 of the first embodiment, and the generated stress also becomes larger. Therefore, the durability of the valve disk 171 will be reduced compared to the shock absorber 1 of the first embodiment.

[0101] Also, the characteristic X3 shown by the thin solid line in FIG. 6 is the case where, for the shock absorber 1 of the first embodiment, the deflection regulation of the valve disk 171 is performed by a support member with a constant and high spring constant without changing the spring constant like the support member 181. In this case, before and after the valve disk 171 abuts against the support member, the change in the amount of deflection with respect to the increase in the differential pressure becomes larger than that of the shock absorber 1 of the first embodiment. Then, the riding comfort of the vehicle will be reduced compared to the shock absorber 1 of the first embodiment.

[0102] Further, characteristic X4 shown by the dashed-dotted line in FIG. 6 is a case where, with respect to the shock absorber 1 of the first embodiment, the tightening margin on the side of the movement restricting member 185 is increased to restrict bending without restricting the bending of the valve disk 171 by the support member. In this case, at the initial stage of the deformation movement where the differential pressure of the valve disk 171 is small, the bending amount is small even with the same differential pressure, and it is difficult to bend. Therefore, the initial timing of the movement of the valve disk 171 is delayed compared to the shock absorber 1 of the first embodiment. Then, the riding comfort of the vehicle is deteriorated compared to the shock absorber 1 of the first embodiment.

[0103] In the shock absorber 1 of the first embodiment, the movement restricting member 185 and the valve disk 171 are always in contact. For this reason, in the shock absorber 1, the valve disk 171 and the movement restricting member 185 do not change from the separated state to the contacting state. Therefore, the change in characteristics before and after this contact can be suppressed.

[0104] In the shock absorber 1 of the first embodiment, the movement restricting member 185 is composed of the stopper member 182 and the contact portion 176 of the elastic seal member 172 that is movable or stretchable. For this reason, in the shock absorber 1, when the valve disk 171 is deformed, the contact portion 176 moves or expands and contracts to suppress the deformation of the valve disk 171.

[0105] In the shock absorber 1 of the first embodiment, the elastic seal member 172 is provided integrally with the valve disk 171. Thereby, the shock absorber 1 can reduce the number of parts and improve productivity.

[0106] In the shock absorber 1 of the first embodiment, the support member 181 is formed by laminating a plurality of disks 136 to 141. For this reason, the shock absorber 1 can easily adjust the bending characteristics of the valve disk 171 by changing the individual specifications of the disks 136 to 141.

[0107] In the shock absorber 1 of the first embodiment, the outer diameters of the plurality of disks 137 to 140 are smaller on the side of the movement restricting member 185 than on the side of the valve disk 171. For this reason, it is easy for the shock absorber 1 to have the characteristic that the rigidity of the support member 181 is low at the initial deflection of the valve disk 171 and becomes high according to the deflection amount (lift amount) of the valve disk 171.

[0108] In the shock absorber 1 of the first embodiment, the plate thicknesses of the plurality of disks 137 to 140 are larger on the side of the movement restricting member 185 than on the side of the valve disk 171. For this reason, the shock absorber 1 can have the characteristic that the rigidity of the support member 181 is low at the initial deflection of the valve disk 171 and becomes high according to the deflection amount (lift amount) of the valve disk 171.

[0109] In the shock absorber 1 of the first embodiment, the piston rod 21 is inserted through the inner peripheral side of the valve disk 171 and is disposed in the cylindrical portion 153 of the housing 145, and a seal portion 175 of an elastic seal member 172 that slidably contacts the cylindrical portion 153 while closing the gap with the cylindrical portion 153 is provided on the outer peripheral side of the valve disk 171. Thereby, it is easy for the shock absorber 1 to variably change the damping force in response to the piston frequency by the valve disk 171 and the elastic seal member 172.

[0110] [Second Embodiment] Next, the second embodiment will be mainly described focusing on the differences from the first embodiment based on FIG. 7. Note that the parts common to the first embodiment are denoted by the same names and the same reference numerals.

[0111] As shown in FIG. 7, the shock absorber 1A of the second embodiment has a frequency sensing mechanism 130A that is partially different from the frequency sensing mechanism 130 in place of the frequency sensing mechanism 130. The frequency sensing mechanism 130A has a partition disk 135A that is partially different from the partition disk 135 in place of the partition disk 135. The partition disk 135A has an elastic seal member 172A that is partially different from the elastic seal member 172 in place of the elastic seal member 172.

[0112] The elastic seal member 172A has a connecting portion 251 and a protruding portion 252 in addition to the seal portion 175 and the abutting portion 176. The connecting portion 251 and the protruding portion 252 are also adhered to the valve disk 171 in the same manner as the seal portion 175 and the abutting portion 176. The seal portion 175, the abutting portion 176, the connecting portion 251, and the protruding portion 252 are integrally formed without seams and baked onto the valve disk 171.

[0113] The connecting portion 251 extends from the inner peripheral portion on the valve disk 171 side in the axial direction of the abutting portion 176 to the inside in the radial direction of the valve disk 171. The height of the connecting portion 251 from the valve disk 171 in the axial direction of the valve disk 171 is lower than that of the abutting portion 176. The protruding portion 252 is provided on the inside in the radial direction of the valve disk 171 from the inner peripheral portion of the connecting portion 251. The protruding portion 252 is annular. The height of the protruding portion 252 from the valve disk 171 in the axial direction of the valve disk 171 is lower than that of the abutting portion 176 and higher than that of the connecting portion 251. Note that the protruding portion 252 may be provided intermittently in the circumferential direction of the valve disk 171 instead of being annular.

[0114] The frequency sensing mechanism 130A has a support member 181A that is partially different from the support member 181. The support member 181A has a plurality of (specifically, three) disks 136A and a plurality of (specifically, two) disks 255 instead of the disks 136 to 141.

[0115] The disk 136A is made of metal and is a perforated circular flat plate with a certain thickness. The disk 136A has the mounting shaft portion 28 of the piston rod 21 fitted inside. The disk 136A has the same outer diameter as the outer diameter of the disk 136. The disk 136A is thicker than the disk 136. The disk 255 is made of metal and is a perforated circular flat plate with a certain thickness. The disk 255 has a mounting shaft portion 28 of the piston rod 21 fitted therein on the inner side. The outer diameter of the disk 255 is larger than the outer diameter of the disk 136A and larger than the outer diameter of the tip surface of the protruding portion 252. A plurality (specifically, three) of disks 136A are laminated on the disk 142 side in the axial direction of the valve disk 171, and a plurality (specifically, two) of disks 255 are laminated on the disk 142 side. At this time, the disk 136A abuts against the disk 134 and the valve disk 171, and the disk 255 abuts against the disk 142. The disks 132 - 134, 136A, 255, 142 and the housing body 131 constitute the housing 145A of the frequency sensing mechanism 130A.

[0116] The inner diameter of the tip surface of the protruding portion 252 of the partition disk 135A on the side opposite to the valve disk 171 in the axial direction is larger than the outer diameter of the disk 136A. The outer diameter of the tip surface of the protruding portion 252 is smaller than the outer diameter of the disk 255. The height of the protruding portion 252 from the valve disk 171 in the axial direction is lower than the total height of the three disks 136A. When the variable chambers 191 and 192 are at the same pressure in the buffer 1A, the protruding portion 252 faces the disk 255 with a gap in the axial direction of the disk 255. The disks 136A, 255, the contact portion 176 and the protruding portion 252 constitute the support member 181A.

[0117] In the buffer 1A, at the initial stage of the deformation movement of the valve disk 171 toward the movement restricting member 185 side, the valve disk 171 itself deforms and moves, and compresses and deforms the contact portion 176 that abuts against the stopper member 182. The movement range during the deformation movement of the valve disk 171 is defined as the sixth movement range. The spring constant of the support member 181A in this sixth movement range is the spring constant of the contact portion 176. This spring constant is defined as the sixth spring constant.

[0118] When the deformation movement of the valve disk 171 toward the movement restricting member 185 further progresses, the valve disk 171 deforms and moves more than its sixth movement range and compresses and deforms the contact portion 176 of the elastic seal member 172 more than the sixth movement range. At the same time, the valve disk 171 abuts the protruding portion 252 of the support member 181A against the disk 255 of the support member 181A and compresses and deforms it. The movement range during the deformation movement of the valve disk 171 is defined as the seventh movement range. The spring constant of the support member 181A in this seventh movement range is defined as the seventh spring constant. Then, the seventh spring constant is the spring constant obtained by combining the spring constant of the contact portion 176 and the spring constant of the protruding portion 252, and becomes larger than the sixth spring constant. In other words, the support member 181A has a higher rigidity when the valve disk 171 is in the seventh movement range than when the valve disk 171 is in the sixth movement range.

[0119] Also in the shock absorber 1A of the second embodiment, the spring constant of the support member 181A in the seventh movement range where the valve disk 171 moves toward the movement restricting member 185 side beyond the sixth movement range and deforms and moves the protruding portion 252 is larger than the sixth spring constant in the sixth movement range where the valve disk 171 deforms and moves the contact portion 176. Also in the shock absorber 1A, the spring constant of the support member 181A thus increases stepwise. Therefore, the shock absorber 1A can also suppress a transient rapid change in the deflection with respect to the increase in the differential pressure of the valve disk 171. Therefore, the shock absorber 1A can also improve the ride comfort of the vehicle in which it is used.

[0120] In addition, since the shock absorber 1A can maintain the low rigidity at the initial deflection of the valve disk 171, the initial timing of the movement of the valve disk 171 is not delayed. Also by this, the ride comfort of the vehicle in which this shock absorber 1A is used can be improved. In addition, since the shock absorber 1A does not reduce the variable width of the valve disk 171, the ride comfort of the vehicle in which this shock absorber 1A is used can also be improved by this. In addition, since the support member 181A can suppress excessive deflection of the valve disk 171, the durability of the valve disk 171 can be improved.

[0121] [Third Embodiment] Next, the third embodiment will be described mainly based on FIG. 8, centering on the differences from the first and second embodiments. For parts common to the first and second embodiments, the same names and the same reference numerals are used.

[0122] As shown in FIG. 8, the shock absorber 1B of the third embodiment has a frequency-sensitive mechanism 130B that is partially different from the frequency-sensitive mechanism 130 in place of the frequency-sensitive mechanism 130. The frequency-sensitive mechanism 130B has a support member 181B that is partially different from the support member 181 in place of the support member 181. The support member 181B has, in place of the disks 136 to 141, a plurality (specifically, three) of disks 136A similar to those of the second embodiment, one disk 261, and one disk 262.

[0123] Both the disks 261 and 262 are made of metal. Both the disks 261 and 262 are perforated disk-shaped. Both the disks 261 and 262 have the mounting shaft portion 28 of the piston rod 21 fitted inside.

[0124] The disk 261 has a substrate portion 271 and a protruding plate portion 272. The substrate portion 271 is a perforated circular flat plate shape with a certain thickness. The disk 261 has the mounting shaft portion 28 of the piston rod 21 fitted inside the substrate portion 271. The protruding plate portion 272 extends outward in the radial direction of the substrate portion 271 from the outer peripheral edge portion of the substrate portion 271. The protruding plate portion 272 is farther from the substrate portion 271 toward the one axial side of the substrate portion 271 as it is farther from the substrate portion 271 in the radial direction. The protruding plate portion 272 extends while expanding in diameter from the outer peripheral edge portion of the substrate portion 271 toward one axial side of the substrate portion 271. The protruding plate portion 272 is tapered and annular. Note that the protruding plate portion 272 may be provided intermittently in the circumferential direction of the substrate portion 271 instead of being annular. The outer diameter of the protruding plate portion 272 is smaller than the minimum inner diameter of the contact portion 176 of the partition disk 135. The inner diameter of the protruding plate portion 272 is larger than the outer diameter of the disk 136A.

[0125] The disk 262 has an inner substrate portion 281, a contact plate portion 282, and an outer substrate portion 283. The inner substrate portion 281 is a perforated circular flat plate with a constant thickness. The disk 262 has the mounting shaft portion 28 of the piston rod 21 fitted inside the inner substrate portion 281. The contact plate portion 282 has an inner plate portion 291 and an outer plate portion 292. The inner plate portion 291 extends from the outer peripheral edge portion of the inner substrate portion 281 to the outside in the radial direction of the inner substrate portion 281. The inner plate portion 291 is farther from the inner substrate portion 281 toward the outside in the radial direction of the inner substrate portion 281 on one side in the axial direction of the inner substrate portion 281. The inner plate portion 291 extends while expanding in diameter from the outer peripheral edge portion of the inner substrate portion 281 to one side in the axial direction of the inner substrate portion 281. The inner plate portion 291 is tapered and annular. The outer plate portion 292 extends from the outer peripheral edge portion of the inner plate portion 291 to the outside in the radial direction of the inner plate portion 291. The outer plate portion 292 is located closer to the inner substrate portion 281 side in the axial direction of the inner plate portion 291 toward the outside in the radial direction of the inner plate portion 291. The outer plate portion 292 extends while expanding in diameter from the outer peripheral edge portion of the inner plate portion 291 to the inner substrate portion 281 side in the axial direction of the inner plate portion 291. The outer plate portion 292 is tapered and annular.

[0126] The outer substrate portion 283 extends from the outer peripheral edge portion of the outer plate portion 292 to the outside in the radial direction of the outer plate portion 292. The outer substrate portion 283 is a circular flat plate with a constant thickness. The outer substrate portion 283 is arranged in the same plane as the inner substrate portion 281. The contact plate portion 282 protrudes from the inner substrate portion 281 and the outer substrate portion 283 to one side in their axial directions. The outer diameter of the outer substrate portion 283 is smaller than the minimum inner diameter of the contact portion 176 of the partition disk 135. The outer diameter of the outer substrate portion 283 is larger than the outer diameter of the protruding plate portion 272. The contact plate portion 282 is such that the diameter of the tip end portion, which is the farthest from the inner substrate portion 281 and the outer substrate portion 283 in their axial directions, is smaller than the outer diameter of the substrate portion 271. The contact plate portion 282 is such that the inner diameter of its inner plate portion 291 is larger than the outer diameter of the disk 136A.

[0127] A plurality (specifically, two) of disks 136A are laminated on the disk 142 side in the axial direction of the valve disk 171 and the disk 134. At this time, the disk 136A abuts against the valve disk 171 and the disk 134. Further, on the disk 142 side in the axial direction of these disks 136A, the disk 261 is disposed in contact with the disk 136A at the substrate portion 271. At this time, the protruding plate portion 272 of the disk 261 from the substrate portion 271 protrudes toward the valve disk 171 side in the axial direction of the substrate portion 271.

[0128] On the side opposite to the valve disk 171 in the axial direction of the substrate portion 271 of the disk 261, one disk 136A is disposed in contact with the substrate portion 271. Further, on the side opposite to the valve disk 171 in the axial direction of this disk 136A, the disk 262 is disposed in contact with the disk 136A at the inner substrate portion 281. At this time, the disk 262 is oriented such that the contact plate portion 282 protrudes toward the valve disk 171 side in the axial directions of the inner substrate portion 281 and the outer substrate portion 283. The disk 262 is such that the inner substrate portion 281 and the outer substrate portion 283 abut against the disk 142. The disks 132 to 134, 136A, 261, 262, 142 and the housing body 131 constitute the housing 145B of the frequency sensing mechanism 130B.

[0129] The disks 136A, 261, 262 and the contact portion 176 constitute the support member 181B.

[0130] In the buffer 1B, in the initial stage of the deformation movement of the valve disk 171 toward the movement restricting member 185, the valve disk 171 itself deforms and moves, and compresses and deforms the contact portion 176 of the elastic seal member 172 that contacts the stopper member 182. The movement range of the valve disk 171 during the deformation movement is defined as the eighth movement range. The spring constant of the contact portion 176 of the support member 181B in this eighth movement range is defined as the eighth spring constant.

[0131] When the deformation movement of the valve disk 171 toward the movement restricting member 185 further progresses, the valve disk 171 deforms and moves more than the eighth movement range and compresses and deforms the contact portion 176 of the elastic seal member 172 more than the eighth movement range. At the same time, the valve disk 171 contacts the protruding plate portion 272 of the disk 261 of the support member 181B, and deforms the substrate portion 271 of the disk 261 into a tapered shape. The movement range of the valve disk 171 during the deformation movement is defined as the ninth movement range. The spring constant of the support member 181B in this ninth movement range is defined as the ninth spring constant. Then, the ninth spring constant becomes the spring constant obtained by combining the spring constant of the contact portion 176 and the spring constant of the substrate portion 271, and is larger than the eighth spring constant. In other words, the support member 181B has a higher rigidity when the valve disk 171 is in the ninth movement range than when the valve disk 171 is in the eighth movement range.

[0132] When the deformation movement of the valve disk 171 toward the movement restricting member 185 further progresses, the valve disk 171 moves by deforming more than the ninth movement range and compresses and deforms the contact portion 176 of the elastic seal member 172 more than the ninth movement range. At the same time, the valve disk 171 brings the substrate portion 271 of the disk 261 of the support member 181B into contact with the contact plate portion 282 of the disk 262, and then deforms the protruding plate portion 272 of the disk 261 so that the taper becomes larger. The movement range during the deformation movement of the valve disk 171 is defined as the tenth movement range. The spring constant of the support member 181B in this tenth movement range is defined as the tenth spring constant. Then, the tenth spring constant becomes the spring constant obtained by combining the spring constant of the contact portion 176 and the spring constant of the protruding plate portion 272, and becomes larger than the ninth spring constant. In other words, the support member 181B has a higher rigidity when the valve disk 171 is in the tenth movement range than when the valve disk 171 is in the ninth movement range.

[0133] Also in the shock absorber 1B of the third embodiment, the support member 181B has a larger ninth spring constant in the ninth movement range in which the valve disk 171 moves the substrate portion 271 of the disk 261 by moving toward the movement restricting member 185 more than the eighth movement range than the eighth spring constant in the eighth movement range in which the valve disk 171 deforms and moves the contact portion 176. Further, the support member 181B has a larger tenth spring constant in the tenth movement range in which the valve disk 171 moves the protruding plate portion 272 of the disk 261 by moving toward the movement restricting member 185 more than the ninth movement range than the ninth spring constant in the ninth movement range in which the valve disk 171 deforms and moves the substrate portion 271 of the disk 261. Also in the shock absorber 1B, the spring constant of the support member 181B increases step by step in this way. Therefore, the shock absorber 1B can also suppress a transient rapid change in the deflection with respect to the increase in the differential pressure of the valve disk 171. Therefore, the shock absorber 1B can also improve the ride comfort of the vehicle in which it is used.

[0134] Also, since the shock absorber 1B can maintain the low rigidity during the initial deflection of the valve disk 171, the initial timing of the movement of the valve disk 171 will not be delayed. Also by this, the riding comfort of the vehicle using this shock absorber 1B can be improved. Also, since the shock absorber 1B does not reduce the variable width of the valve disk 171, the riding comfort of the vehicle using this shock absorber 1B can be improved also by this. Also, since the support member 181B can suppress excessive deflection of the valve disk 171, the durability of the valve disk 171 can be improved.

[0135] Note that the support member 181B uses the disk 261 having non-linear spring characteristics, but it is also possible to use a plurality of coil springs or a coil spring having non-linear spring characteristics instead of the disks 261 and 262.

[0136] In the above first to third embodiments, the case where the movement restricting member 185 integrally provides the contact portion 176, which is an elastic member, on the stopper member 182 side of the valve disk 171 has been described as an example. However, it is not limited to this, and the contact portion 176, which is an elastic member, may be integrally provided on the valve disk 171 side of the stopper member 182 without providing it on the valve disk 171.

[0137] In the above first to third embodiments, an example of applying the present invention to a double-tube hydraulic shock absorber has been shown, but it is not limited to this. The present invention may be applied to a monotube hydraulic shock absorber without an outer cylinder. In a monotube hydraulic shock absorber, a slidable partition body is provided on the side opposite to the upper chamber of the lower chamber in the cylinder. And the side opposite to the lower chamber of the partition body in the cylinder is made into a gas chamber.

[0138] Further, in the first to third embodiments, the present invention is applied to the frequency sensing mechanisms 130, 130A, and 130B, but the present invention may also be applied to the first damping force generating mechanism 41. The first damping force generating mechanism 41 is provided with a back pressure chamber 100 into which oil is introduced from the upper chamber 19 on the upstream side in the extended fixed state and the internal pressure is applied to the damping valve 52 in the valve closing direction. When the present invention is applied to this first damping force generating mechanism 41, the valve member becomes a damping valve 52 that gives resistance to the flow of oil from the upper chamber 19 on the upstream side of the first passage portion 43 in the extended fixed state to the lower chamber 20 on the downstream side. And, regarding the support member that supports the damping valve 52, the spring constant of the second movement range that moves to the bottom 71 side rather than this first movement range is made larger than the spring constant of the first movement range in which the damping valve 52 moves to the bottom 71 side of the pilot case 55 that becomes the movement restricting member.

[0139] Also, it is possible to provide the frequency sensing mechanisms 130, 130A, and 130B so as to operate in the same manner as in the above-described operation in the extension stroke in the contraction stroke. In this case, the variable chamber 191 is always in communication with the lower chamber 20, and the variable chamber 192 is always in communication with the upper chamber 19. Also, it is possible to apply the present invention to the base valve 25 described above. Also, when an oil passage communicating with the inside of the cylinder 2 is provided outside the cylinder 2 and a damping force generating mechanism is provided in this oil passage, it is possible to apply the present invention to the valve member and the like of this damping force generating mechanism. Also, in the above-described first to third embodiments, a hydraulic shock absorber is taken as an example, but water or air can also be used as the fluid.

Industrial Applicability

[0140] According to each of the above aspects of the present invention, it is possible to provide a shock absorber that can improve the ride comfort of a vehicle. Therefore, the industrial applicability is great.

Explanation of Reference Numerals

[0141] 1, 1A, 1B... buffers, 2... cylinder, 18... piston, 19... upper chamber, 20... lower chamber, 21... piston rod (shaft member), 52... damping valve, 100... back pressure chamber, 136 - 141... disk (plate-like member), 153... cylindrical part, 171... valve disk (valve member), 172... elastic seal member (elastic member, seal member), 181, 181A, 181B... support members, 182... stopper member, 185... movement restricting member, 201... passageway.

Claims

1. A cylinder in which a working fluid is sealed; a piston slidably fitted within the cylinder to divide the interior of the cylinder into two chambers; a piston rod having one end to which the piston is attached and the other end extending to the outside of the cylinder through one of the two chambers of the cylinder; a passage formed in the piston through which the working fluid flows from the one chamber to the other of the two chambers of the cylinder; a housing member attached to the one end of the piston rod; a flexible plate-like valve member provided within the housing member, the movement of which in a direction along the axis of the piston rod is restricted by an inner periphery thereof, and which forms a variable chamber between the housing member and the valve member and which communicates with the passage; a movement limiting member for limiting movement of the valve member; a support member provided between the valve member and the movement limiting member, the support member having an inner circumferential side supported by the piston rod, the support member coming into contact with the valve member as the valve member bends, and the support member being deformable by a pressing force from the valve member; A shock absorber equipped with

2. 2. The shock absorber according to claim 1, wherein the support member is configured to have a plurality of disks having different outer diameters.

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