buffer

Abstract

To provide a shock absorber capable of improving durability of a valve member.SOLUTION: A shock absorber comprises: a piston slidably fitted into a cylinder, and partitioning the inside of the cylinder into two compartments; a passage 201 into which working fluid flows out from one compartment in the cylinder by movement of the piston; a flexible plate-like valve member 135 disposed in the passage 201, whose inner peripheral side is supported by a support member 181 only on one surface side without being clamped from both surface sides; and a movement restriction member 142 which restricts movement of the valve member 135. The movement restriction member 142 is formed by sintering or forging, and a plate-like member 141 is disposed on the side of the valve member 135 in an axial direction of the movement restriction member 142.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] Some shock absorbers have a partitioned disk structured so that the inner circumferential side is not clamped and only one side is supported, in a passage through which working fluid flows as a piston moves (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6722683 Summary of the Invention [Problem to be solved by the invention]

[0004] In shock absorbers, there is a demand for improving the durability of valve members.

[0005] Therefore, an object of the present invention is to provide a shock absorber that can improve the durability of the valve member. [Means for solving the problem]

[0006] In order to achieve the above object, the present invention provides a cylinder in which a working fluid is sealed, a piston slidably fitted within the cylinder and dividing the interior of the cylinder into two chambers, a passage through which the working fluid flows from one chamber within the cylinder as the piston moves, a flexible plate-like valve member provided in the passage and supported on only one side by a support member without being clamped on either side, and a movement limiting member that limits the movement of the valve member, the movement limiting member being formed by sintering or forging, and a plate-like member being disposed on the axial side of the movement limiting member toward the valve member. [Effects of the Invention]

[0007] According to the present invention, the durability of the valve member can be improved. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing a shock absorber according to an embodiment of the present invention. [Figure 2] 1 is a partial cross-sectional view showing the periphery of a piston of a shock absorber according to an embodiment of the present invention. [Figure 3] 1 is a half-side cross-sectional view showing a piston, a first damping force generating mechanism, a second damping force generating mechanism, and a frequency varying mechanism of a shock absorber according to an embodiment of the present invention. [Figure 4] FIG. 2 is a partially enlarged cross-sectional view showing a frequency variable mechanism of the shock absorber according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] A shock absorber according to an embodiment will be described below with reference to the drawings. For ease of explanation, the upper side in Figures 1 to 3 will be referred to as "upper", and the lower side in Figures 1 to 3 will be referred to as "lower".

[0010] As shown in Figure 1, the shock absorber 1 of this embodiment is a twin-cylinder hydraulic shock absorber. The shock absorber 1 is used in a vehicle suspension device. The shock absorber 1 has a cylinder 2 in which oil (not shown) is sealed as a working fluid. The cylinder 2 has an inner cylinder 3 and an outer cylinder 4. The inner cylinder 3 is cylindrical. The outer cylinder 4 is cylindrical with a bottom. 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 radially inside the outer cylinder 4. The central axis of the inner cylinder 3 and the central axis of the outer cylinder 4 coincide. 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 cylindrical with a bottom. The bottom member 12 is fitted onto the lower side of the body member 11 and fixed to the body member 11 by welding. The bottom member 12 closes the lower part of the body member 11. A mounting eye 13 is fixed to the outside of the bottom member 12, opposite the body member 11 in the axial direction. The cover 5 is fixed to the outer peripheral surface of the body member 11, covering the upper end opening of the body member 11.

[0012] The shock absorber 1 is equipped with a piston 18. The piston 18 is slidably fitted within the inner tube 3 of the cylinder 2. The piston 18 divides the inner tube 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 located on the opposite side of the piston 18 from the bottom member 12. In the axial direction of the cylinder 2, the lower chamber 20 is located on the bottom member 12 side of the piston 18. Oil liquid is sealed within the upper chamber 19 and the lower chamber 20 of the inner tube 3 as a working fluid. Oil liquid and gas are sealed within a reservoir chamber 6 between the inner tube 3 and the outer tube 4 as a working fluid.

[0013] The shock absorber 1 is equipped with a piston rod 21. One axial end of the piston rod 21 is disposed within the inner tube 3 of the cylinder 2. One end of the piston rod 21 is connected to the piston 18. The other axial end of the piston rod 21, opposite to the one end, extends from the cylinder 2 to the outside of the cylinder 2. The piston 18 is fixed to the piston rod 21. Therefore, the piston 18 and the piston rod 21 move together. In the shock absorber 1, the stroke in which the piston rod 21 moves in a direction to increase the amount of protrusion from the cylinder 2 is the extension stroke, in which the overall length is extended. In the shock absorber 1, the stroke in which the piston rod 21 moves in a direction to decrease the amount of protrusion from the cylinder 2 is the compression stroke, in which the overall length is shortened. In the shock absorber 1, the piston 18 moves toward the upper chamber 19 during the extension stroke. In the shock absorber 1, the piston 18 moves toward the lower chamber 20 during the compression stroke.

[0014] Rod guides 22 are fitted to the upper openings of the inner cylinder 3 and 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 relative to the rod guide 22, the friction member 24, and the seal member 23 along their axial directions. 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 radial movement of the piston rod 21 relative to the inner cylinder 3 and outer cylinder 4 of the cylinder 2. The piston rod 21 is fitted into the rod guide 22, and the piston 18 is fitted into the inner cylinder 3. This causes the central axis of the piston rod 21 to coincide with the central axis of the cylinder 2. The rod guide 22 supports the piston rod 21 so that it can move in the axial direction of the piston rod 21. The outer periphery of the seal member 23 is in close contact with the outer cylinder 4. The inner periphery of the seal member 23 is in close contact with the outer periphery of the piston rod 21. The piston rod 21 moves in the axial direction of the seal member 23 while maintaining close contact with the seal member 23. The seal member 23 prevents the oil in the inner cylinder 3 and the high-pressure gas and oil in the reservoir chamber 6 from leaking to the outside. The inner periphery of the friction member 24 is in contact with the outer periphery of the piston rod 21. The piston rod 21 moves in the axial direction of the friction member 24 relative to the friction member 24. The friction member 24 generates friction resistance against the piston rod 21 .

[0016] The rod guide 22 has an outer periphery with a larger diameter at its upper part than at its lower part. The rod guide 22 fits into the inner periphery of the upper end of the inner cylinder 3 at its smaller diameter lower part. The rod guide 22 fits into the inner periphery of the upper part of the outer cylinder 4 at its larger diameter upper part. A base valve 25 is installed on the bottom member 12 of the outer cylinder 4. The base valve 25 is positioned radially relative to the outer cylinder 4. The base valve 25 separates the lower chamber 20 and the reservoir chamber 6. The inner periphery of the lower end of the inner cylinder 3 is fitted into the base valve 25. Although not shown, a portion of the upper end of the outer cylinder 4 is crimped radially inward of the outer cylinder 4. The seal member 23 is fixed to the cylinder 2 by being sandwiched between this crimped portion and the rod guide 22.

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

[0018] Piston rod 21 is provided with an annular stopper member 32 and an annular buffer body 33. Stopper member 32 and buffer body 33 are both provided in a portion of main shaft portion 27 between piston 18 and rod guide 22. Piston rod 21 is inserted into the inner peripheral sides of stopper member 32 and buffer body 33. Stopper member 32 is fixed to main shaft portion 27 by crimping. Buffer body 33 is disposed between stopper member 32 and rod guide 22.

[0019] The shock absorber 1 is connected to the vehicle body with, for example, the portion of the piston rod 21 that protrudes from the cylinder 2 located at the top. In this case, the shock absorber 1 is connected to the vehicle wheel side with the mounting eye 13 provided on the cylinder 2 side located at the bottom. The shock absorber 1 may also be connected to the vehicle body with the cylinder 2 side connected to the vehicle body. In this case, the piston rod 21 of the shock absorber 1 is connected to the wheel side.

[0020] When a vehicle travels, the wheels vibrate relative to the vehicle body. This vibration causes the relative positions of the cylinder 2 and the piston rod 21 of the shock absorber 1 to change. This change is suppressed by the fluid resistance of the flow paths provided in the shock absorber 1. As will be explained below, the fluid resistance of the flow paths provided in the shock absorber 1 is designed to vary depending on the speed and amplitude of the vibration. The shock absorber 1 suppresses vibration, thereby improving the ride comfort of the vehicle.

[0021] Furthermore, in a vehicle, in addition to vibrations generated by the wheels relative to the vehicle body, inertial forces and centrifugal forces generated in the vehicle body as the vehicle travels also act between the cylinder 2 and the piston rod 21. For example, centrifugal forces are generated in the vehicle body when the direction of travel is changed by operating the steering wheel. Then, a force based on this centrifugal force acts between the cylinder 2 and the piston rod 21. As will be explained below, the shock absorber 1 has good characteristics against vibrations based on forces generated in the vehicle body as the vehicle travels. The shock absorber 1 provides the vehicle with high driving stability.

[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 has an annular shape. The piston 18 has the piston body 35 fitted onto the piston rod 21. The sliding member 36 is made of synthetic resin and has an annular shape. The sliding member 36 is integrally attached to the outer circumferential surface of the piston body 35. The piston 18 slides relative 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. A plurality of passage holes 37 are formed in the piston body 35 at intervals in the circumferential direction of the piston body 35 (only one is shown in FIG. 2 because it is a cross-section). The passage hole 39 penetrates the piston body 35 in the axial direction of the piston body 35. A plurality of passage holes 39 are formed in the piston body 35 at intervals in the circumferential direction of the piston body 35 (only one is shown in FIG. 2 because it is a cross-section). The piston body 35 is formed with one passage hole 37 and one passage hole 39 alternately at equal intervals in the circumferential direction of the piston body 35.

[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 of the piston body 35 in the axial direction. All of the passage holes 37 open to the passage groove 38 at this one end 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 of the piston body 35 opposite the passage groove 38 in the axial direction. All of the passage holes 39 open to the passage groove 40 at the end opposite the passage groove 38 in the axial direction of the piston body 35. The ends of the multiple passage holes 37 opposite the passage groove 38 in the axial direction of the piston body 35 open outward from the passage groove 40 in the radial direction of the piston body 35. The ends of the plurality of passage holes 39 opposite the passage groove 40 in the axial direction of the piston body 35 open outward from the passage groove 38 in the radial direction of the piston body 35. In the piston 18, the insides of the plurality of passage holes 37 and the passage groove 38 form a first passage portion 43. In the piston 18, the insides of the plurality of passage holes 39 and the passage groove 40 form a first passage portion 44.

[0025] A first damping force generating mechanism 41 is provided in the first passage portion 43. 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 of the piston 18 in the axial direction, and is attached to the piston rod 21. As a result, the first passage portion 43 serves as a passage through which oil as a working fluid flows from the upper chamber 19 toward the lower chamber 20 as the piston 18 moves toward the upper chamber 19. In other words, the first passage portion 43 is an extension-side passage through which oil as a working fluid flows 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 generates a damping force by suppressing the flow of oil from the first passage portion 43 to the lower chamber 20 during the extension stroke.

[0026] A first damping force generating mechanism 42 is provided in the first passage portion 44. 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 of the piston 18 in the axial direction, and is attached to the piston rod 21. As a result, the first passage portion 44 serves as a passage through which oil flows from the lower chamber 20 toward the upper chamber 19 as the piston 18 moves toward the lower chamber 20. In other words, the first passage portion 44 is a compression-side passage through which oil flows 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 generates a damping force by suppressing the flow of oil from the first passage portion 44 to the upper chamber 19 during the compression stroke.

[0027] The piston body 35 has an insertion hole 45 formed in its radial center, penetrating the piston body 35 in the axial direction. The mounting shaft portion 28 of the piston rod 21 is inserted into the insertion hole 45. 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 located closer to the lower chamber 20 than the small diameter hole portion 46.

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

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

[0030] The pilot case 55 is cylindrical and has a bottom. A through-hole 70 is formed in the center of the pilot case 55 in the radial direction. The through-hole 70 passes through the pilot case 55 in the axial direction. The pilot case 55 has a bottom 71, an inner cylindrical portion 72, an outer cylindrical portion 73, an inner seat portion 74, and a valve seat 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 of the through hole 70 in the axial direction. The small diameter hole portion 77 is disposed on the opposite side of 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 disk-shaped portion having holes. A passage hole 78 is formed in the bottom portion 71 radially outward of the through-hole 70, penetrating the bottom portion 71 in the axial direction of the bottom portion 71. The inner cylindrical portion 72 is cylindrical and protrudes from the inner peripheral edge of the bottom portion 71 toward the piston 18 along the axial direction of the bottom portion 71. The inner cylindrical portion 72 is located radially inward of the passage hole 78 of the bottom portion 71. The outer cylindrical portion 73 is cylindrical and protrudes from the outer peripheral edge of the bottom portion 71 along the axial direction of the bottom portion 71 on the same side as the inner cylindrical portion 72. The outer cylindrical portion 73 is provided outward 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 seat portion 74 is annular and protrudes from the inner peripheral edge of the bottom portion 71 in the axial direction opposite to the inner cylindrical portion 72 . The valve seat portion 75 is annular and has a larger diameter than the inner seat portion 74. The valve seat portion 75 protrudes radially outward from the inner seat portion 74 along the axial direction of the bottom portion 71 from the bottom portion 71 on the same side as the inner seat portion 74. The passage hole 78 is disposed between the inner seat portion 74 and the valve seat portion 75 in the radial direction of the bottom portion 71.

[0033] The disc 51 has an outer diameter smaller than the inner diameter of the tip surface of the valve seat portion 48. A notch 81 is formed in the disc 51. The notch 81 extends radially outward from the inner peripheral edge of the disc 51 that fits onto the mounting shaft portion 28, and into the passage groove 38. A throttle 82 is formed within the notch 81. The throttle 82 is constantly connected to 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 connected. The passage within the large diameter hole portion 47 and the passage within the passage groove 30 form a rod chamber 83. The throttle 82 within the notch 81 of the disc 51 is constantly connected to the rod chamber 83. The throttle 82 constantly connects the first passage portion 43 and the rod chamber 83.

[0034] The damping valve 52 comprises a disk 85 and a seal member 86 . The disc 85 is made of metal and has a circular, flat plate shape with holes. The disc 85 has an outer diameter larger than the outer diameter of the tip end surface of the valve seat portion 48. The mounting shaft portion 28 of the piston rod 21 is fitted inside the disc 85. The disc 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 bonded to the disc 85. The seal member 86 is fixed to the outer periphery of the disc 85 and has an annular shape. The seal member 86 is fitted liquid-tightly around the entire inner periphery of the outer cylindrical portion 73 of the pilot case 55. The seal member 86 is axially slidable relative to the inner periphery 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 the disc 53 is smaller than the minimum inner diameter of the seal member 86. The outer diameter of the disc 54 is larger than the outer diameter of the disc 53 and smaller than the minimum inner diameter of the seal member 86. A notch 91 is formed in the disc 54. The notch 91 extends radially outward from the inner peripheral edge of the disc 54 that fits onto the mounting shaft portion 28, to a position outside the disc 53. A restrictor 92 is formed within the notch 91. The restrictor 92 is constantly in communication with the passage in the passage groove 30 of the piston rod 21 and the passage in the large diameter hole portion 76 of the pilot case 55.

[0036] The disc 56 has an outer diameter smaller than the inner diameter of the tip surface of the valve seat portion 75 of the pilot case 55. The disc 57 has an outer diameter larger than the outer diameter of the tip surface of the valve seat portion 75. The disc 57 is able to seat on the valve seat portion 75. A notch 93 is formed on the outer periphery of the disc 57. The notch 93 extends radially across the valve seat portion 75. The disc 58 has an outer diameter equal to the outer diameter of the disc 57. The disc 59 has an outer diameter smaller than the outer diameter of the disc 58. The disc 60 has an outer diameter larger than the outer diameter of the disc 59 but smaller than the outer diameter of the disc 58. The discs 57 and 58 constitute a disc valve 99. The disc valve 99 is able to seat on and separate from the valve seat portion 75.

[0037] A back pressure chamber 100 is formed between the bottom 71, inner cylindrical portion 72, and outer cylindrical portion 73 of the pilot case 55, the damping valve 52 and the discs 53 and 54, between the bottom 71, inner seat portion 74, and valve seat portion 75 of the pilot case 55, the disc 56 and the disc valve 99, and within the passage hole 78 of the pilot case 55. 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 valve closing direction so that the damping valve 52 seats on the valve seat portion 48. The damping valve 52 is a pilot-type damping valve having the back pressure chamber 100. The 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 via a restrictor 92 in a notch 91 of the disc 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 a rod chamber 83.

[0038] The orifice 82 in the notch 81 of the disc 51, the rod chamber 83, and the orifice 92 in the notch 91 of the disc 54 form a second passage portion 102 that constantly connects the first passage portion 43 of the piston 18 and the back pressure chamber 100 and introduces hydraulic fluid from the first passage portion 43 to the back pressure chamber 100. When the disc 85 is released from the valve seat portion 48 of the piston 18 and opens, the damping valve 52 allows hydraulic fluid from the first passage portion 43 to flow into the lower chamber 20 through the gap 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 hydraulic fluid between the valve seat portion 48. The extension-side first damping force generation mechanism 41 introduces a portion of the hydraulic fluid flow into the back pressure chamber 100 via the second passage portion 102, and controls the opening of the damping valve 52 using the pressure in the back pressure chamber 100.

[0039] The disc valve 99 communicates between the back pressure chamber 100 and the lower chamber 20 by lifting off the valve seat 75. At that time, the disc valve 99 suppresses the flow of oil between it and the valve seat 75. The passage within the notch 93 of the disc valve 99 forms a fixed orifice 105 that allows the back pressure chamber 100 to communicate with the lower chamber 20 even when the disc valve 99 is in contact with the valve seat 75. The disc 60 abuts against the disc valve 99 when the disc valve 99 deforms in the opening direction, suppressing deformation of the disc valve 99 beyond a specified limit.

[0040] The disc valve 99 and the valve seat 75 constitute a second damping force generating mechanism 110. When the disc valve 99 is released from the valve seat 75, the second damping force generating mechanism 110 connects the back pressure chamber 100 and the lower chamber 20. At this time, the second damping force generating mechanism 110 generates a damping force by suppressing the flow of hydraulic fluid between the back pressure chamber 100 and the lower chamber 20. 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 hydraulic fluid. During the extension stroke, the second damping force generating mechanism 110 causes hydraulic fluid to flow from the upper chamber 19 to the lower chamber 20 via the first passage 43, the second passage 102, and the back pressure chamber 100. The second damping force generating mechanism 110 is an extension-side damping force generating mechanism that generates a damping force by suppressing the flow of hydraulic fluid from the back pressure chamber 100 to the lower chamber 20 during the extension stroke.

[0041] As shown in FIG. 2, on the valve seat portion 49 side of the piston 18 in the axial direction, there are provided, in order from the piston 18 side in the axial direction of the piston 18, one disk 111, one disk 112, a plurality of (specifically, three) disks 113, a plurality of (specifically, two) disks 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 in the shape of a circular flat plate with holes and a uniform thickness. The mounting shaft portion 28 of the piston rod 21 is fitted inside the disks 111 to 116 and the annular member 117.

[0042] The disc 111 has an outer diameter smaller than the inner diameter of the leading end surface of the valve seat portion 49 of the piston 18. The disc 112 has an outer diameter slightly larger than the outer diameter of the leading end surface of the valve seat portion 49 of the piston 18. The disc 112 is capable of being seated on the valve seat portion 49. A notch 121 is formed on the outer periphery of the disc 112. The notch 121 traverses the valve seat portion 49 in the radial direction.

[0043] The plurality of discs 113 have an outer diameter equal to that of discs 112. The plurality of discs 114 have an outer diameter smaller than that of discs 113. Disc 115 has an outer diameter smaller than that of disc 114. Disc 116 has an outer diameter larger than that of disc 114 and smaller than that of disc 113. Annular member 117 has an outer diameter smaller than that of disc 116 and larger than that of disc 114. Annular member 117 is thicker than discs 111 to 116 and has high rigidity. This annular member 117 abuts against shaft step portion 29 of piston rod 21.

[0044] The discs 112 to 114 constitute a disc valve 122. The disc valve 122 is releasable from the valve seat portion 49. The disc valve 122 can open the first passage portion 44 to the upper chamber 19 by releas- ing from the valve seat portion 49. At that time, the disc valve 122 suppresses the flow of oil from the lower chamber 20 to the upper chamber 19 via the first passage portion 44. The disc valve 122 and the valve seat portion 49 constitute a first damping force generating mechanism 42 on the compression side. The notch 121 of the disc 112 constitutes a fixed orifice 123. The fixed orifice 123 communicates between the lower chamber 20 and the upper chamber 19 even when the disc 112 is in contact with the valve seat portion 49. The fixed orifice 123 also constitutes the first damping force generating mechanism 42. When the disc valve 122 deforms in the opening direction, the disc 116 abuts against the disc valve 122 to prevent the disc valve 122 from deforming in the opening direction beyond a specified limit.

[0045] 3, a frequency sensitive mechanism 130 is provided on the axial side of the disc 60 opposite to the disc 59. The frequency sensitive mechanism 130 varies the damping force according to the frequency of the axial movement of the piston 18 (hereinafter referred to as the piston frequency). The frequency sensitive mechanism 130 has one housing main body 131 closest to the disc 60 in the axial direction. The frequency sensitive mechanism 130 also has, in order from the housing main body 131 side, one disc 132, one disc 133, and one disc 134 on the inner peripheral side of the housing main body 131 opposite the disc 60 in the axial direction. The frequency sensitive mechanism 130 also has one valve member 135 radially outward of the discs 133 and 134 on the inner peripheral side of the housing main body 131 opposite the disc 60 in the axial direction. As shown in FIG. 4, frequency sensitive mechanism 130 has, on the opposite side of disk 132 in the axial direction of disk 134 and valve member 135, in order from the disk 134 and valve member 135 side, one disk 136, one disk 137, one disk 138, one disk 139, one disk 140, one disk 141 (plate-shaped member), and one movement limiting member 142. An annular member 144 is provided on the opposite side of the movement restricting member 142 from the disk 141 in the axial direction.

[0046] The housing main body 131, discs 132-134, 136-141, movement limiting member 142, and annular member 144 are all made of metal. The discs 132-134, 136-141, and annular member 144 are all perforated circular flat plates of a uniform thickness. The discs 133, 134, 136-141, and annular member 144 have a uniform radial width over the entire circumference. The movement limiting member 142 is also perforated circular flat plate of a uniform radial width over the entire circumference. The discs 132-134, 136-141 are all formed by punching out from a single thin plate. The movement limiting member 142 is formed by sintering. The mounting shaft portion 28 of the piston rod 21 is fitted inside the discs 132-134, 136-141, movement limiting member 142, housing main body 131, and annular member 144. The mounting shaft portion 28 of the piston rod 21 and the discs 133 and 134 are inserted into the inner periphery of the valve member 135. The discs 132 to 134 and 136 to 141, the movement limiting member 142, and the housing main body 131 form a housing 145 of the frequency sensitive mechanism 130.

[0047] As shown in FIG. 3, the housing body 131 is cylindrical and has a bottom. A through hole 155 is formed in the radial center of the housing body 131, penetrating the housing body 131 in the 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 located on the opposite side of the through hole 155 from the disc 60 in the axial direction. The small diameter hole portion 157 is located closer to the disc 60 than the large diameter hole portion 156 in the axial direction of the through hole 155. The passage within the large diameter hole portion 156 of the housing body 131 is constantly in communication with the passage within the passage groove 30 of the piston rod 21. The passage within 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 protruding portion 151 on one side, a protruding portion 152 on the other side, a cylindrical portion 153 , and a seat portion 154 . The bottom 150 is a perforated disk. The one-side protrusion 151 is annular in shape and protrudes from the inner peripheral edge of the bottom portion 150 in the axial direction of the bottom portion 150 to the side opposite to the disk 60. The other-side protrusion 152 is annular and protrudes from the inner peripheral edge of the bottom 150 in the axial direction of the bottom 150 to the opposite side to the one-side protrusion 151. The cylindrical portion 153 is cylindrical and extends from the outer peripheral edge 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 seat portion 154 is annular. The seat portion 154 protrudes from a 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 seat portion 154 in the radial direction is formed at the end of the seat portion 154 on the protruding tip side.

[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 seat portion 154. A notch 161 is formed in the disk 132. The notch 161 extends radially outward from the inner peripheral edge of the disk 132 that fits onto the mounting shaft portion 28, to a position outside the tip surface of the one-side protrusion 151. A throttle 162 is formed within the notch 161. The throttle 162 is constantly in communication with a passage within the large-diameter hole portion 156 of the housing main body 131. Therefore, the throttle 162 is constantly in communication with the rod chamber 83. The outer diameter of the disk 133 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 has a greater axial thickness than the disk 132. The disk 134 has an outer diameter smaller than that of the disk 133. The disk 134 has a smaller axial thickness than the disk 133.

[0050] The valve member 135 is made up of a valve disc 171 and an elastic seal member 172. The valve member 135 is disposed within the cylindrical portion 153 of the housing body 131. The valve member 135 is disposed radially between the cylindrical portion 153 and the discs 133 and 134.

[0051] The valve disc 171 is made of metal. The valve disc 171 is a circular, flat plate with holes and a constant thickness. The valve disc 171 is annular with a constant radial width. The mounting shaft portion 28 of the piston rod 21 is inserted into the inner periphery of the valve disc 171. The valve disc 171 is disposed within the cylindrical portion 153 of the housing main body 131. The valve disc 171 is elastically deformable, i.e., flexible. The inner diameter of the valve disc 171 is larger than the outer diameter of the disc 133. The valve disc 171 has an inner diameter that allows the discs 133 and 134 to be disposed therein with a radial gap. The axial thickness of the valve disc 171 is thinner than the axial thickness of two of the discs 133 and 134. The outer diameter of the valve disc 171 is larger than the outer diameter of the tip surface of the seat portion 154 of the housing main body 131.

[0052] The elastic seal member 172 is made of rubber and has an annular shape. The elastic seal member 172 is bonded to the outer periphery of the valve disc 171. The elastic seal member 172 is baked onto the valve disc 171 and is provided integrally with the valve disc 171. The elastic seal member 172 has a seal portion 175 and multiple abutment portions 176 (only one is shown in FIG. 4 because it is a cross-section). The seal portion 175 is annular and is fixed around the entire outer periphery of the valve disc 171. The seal portion 175 protrudes from the valve disc 171 towards the bottom 150 of the housing main body 131 in the axial direction of the valve member 135. The multiple abutment portions 176 are fixed to the outer periphery of the valve disc 171. The multiple abutment portions 176 are arranged at equal intervals around the circumferential direction of the valve disc 171. The plurality of abutment portions 176 protrude from the valve disc 171 on the opposite side to the bottom portion 150 in the axial direction of the valve member 135 .

[0053] An annular gap is provided between the valve disc 171 and the cylindrical portion 153 of the housing main body 131. The elastic seal member 172 has a seal portion 175 and a plurality of abutment portions 176 fixed to both sides of the valve disc 171 through this gap. This configuration makes it easy to fix the seal portion 175 and the plurality of abutment portions 176 to the valve disc 171.

[0054] The elastic seal member 172 has a seal portion 175 that is liquid-tightly fitted around the entire inner periphery of the cylindrical portion 153 of the housing main body 131. The seal portion 175 is slidable relative to the cylindrical portion 153 in the axial direction of the cylindrical portion 153. The seal portion 175 of the elastic seal member 172 constantly seals the gap between the valve member 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 valve member 135 has a valve disc 171 that is seatable on the seat portion 154 of the housing main body 131.

[0055] The disc 136 has an outer diameter larger than the inner diameter of the valve disc 171. The disc 136 has a thinner axial thickness than the disc 134. The disc 136 has a thinner axial thickness than the valve disc 171. The disc 136 abuts against the inner periphery of the valve disc 171 over the entire circumference, thereby closing the gap between the disc 136 and the valve disc 171. The inner periphery of the valve disc 171 of the valve member 135 is positioned axially between the discs 132 and 136 and is supported by abutting against the disc 136. The inner periphery of the valve disc 171 of the valve member 135 is movable between the discs 132 and 136 within the axial length range of the two discs 133, 134. The valve member 135 is centered with respect to the housing 145 by the seal portion 175 contacting the cylindrical portion 153 over the entire circumference. The valve member 135 is supported on only one side by the disc 136 at the inner circumferential side of the valve disc 171, without being clamped from either side. The valve member 135 is supported on only one side by the seat portion 154 at the radially outer side of the valve disc 171 than the disc 136, without being clamped from either side. Therefore, the valve member 135 is not clamped in the axial direction, and has a simply supported structure in which one side of the valve disc 171 is supported by the disc 136 and the other side of the valve disc 171 is supported by the seat portion 154. The valve member 135 is annular overall, and is elastically deformable, that is, flexible.

[0056] The disk 137 has an outer diameter that is larger than the outer diameter of the disk 136 and smaller than the smallest inner diameter of the plurality of abutment portions 176. The disk 137 has a smaller axial thickness than the disk 136. The disk 138 has an outer diameter smaller than that of the disk 137. The disk 138 has a greater axial thickness than the disk 137.

[0057] The outer diameter of the disk 139 is smaller than the outer diameter of the disk 138. The disk 139 is thicker in the axial direction than each of the disks 136 to 138. The disk 139 can be formed by punching out from a single thin plate, or by cutting out. The outer diameter of disk 140 is larger than the outer diameter of disk 139 and is equal to the outer diameter of disk 137. Disk 140 has a greater axial thickness than disk 139. Disk 140 can be formed by punching out from a single thin plate, or by cutting out.

[0058] The outer diameter of the disc 141 is larger than the outer diameter of the disc 140. The disc 141 has a thinner axial thickness than the disc 140. The disc 141 has a thicker axial thickness than each of the discs 136 to 138. The disc 141 can be formed by punching out from a single thin plate, or by machining. The outer diameter of the disc 141 is smaller than the inner diameter of the cylindrical portion 153. The disc 141 is constantly in contact with a plurality of contact portions 176 of the valve member 135.

[0059] The support member 181 is formed by stacking discs 136-138, which are all plate-shaped members. Of the discs 136-138, discs 137 and 138 have a smaller outer diameter on the axial side opposite valve disc 171 than on the axial side of disc 137. Of the discs 137 and 138, disc 138 on the axial side opposite valve disc 171 has a greater thickness than on the axial side of disc 137. The support member 181 supports the inner peripheral side of the valve disc 171 of the valve member 135. The inner peripheral side of the valve disc 171 of the valve member 135 is not clamped from both axial sides, and only one axial side is supported by disc 136 of the support member 181.

[0060] The outer diameter of the movement limiting member 142 is equal to the outer diameter of the disk 141. The movement limiting member 142 has a greater overall thickness than any of the disks 132-134 and 136-141. The movement limiting member 142 is integrally molded by sintering. Step-shaped notches 183 are formed on both axial ends of the outer periphery of the movement limiting member 142 during molding by sintering. These notches 183 are chips created at the corners of the movement limiting member 142 by a sintering mold when sintering the movement limiting member 142. As a result, the movement limiting member 142 has a thick-walled portion 184 extending from its middle portion to its inner periphery in the radial direction, and a thin-walled portion 185 extending to its outer periphery in the radial direction. The thick-walled portion 184 is a perforated disk-like portion, and the thin-walled portion 185 is annular. The thick-walled portion 184 has a constant thickness, and the thin-walled portion 185 is thinner in the axial direction than the thick-walled portion 184. The radial width of the thin portion 185 is smaller than the radial width of the thick portion 184 .

[0061] Besides sintering, the movement-limiting member 142 can also be formed by forging. When the movement-limiting member 142 is formed by forging, the movement-limiting member 142 has substantially the same shape as described above because the notches 183 are formed on both axial ends of the outer periphery during molding. The outer diameter of the movement limiting member 142 may be smaller than the outer diameter of the disk 141. In other words, the disk 141 has the same diameter as the movement limiting member 142 or a larger diameter than the movement limiting member 142. Note that the disk 141 may have chamfers or the like on both axial ends of its outer periphery, but the radial size of the chamfers is smaller than the radial size of the notch 183 of the movement limiting member 142. The outer diameter of the annular member 144 is smaller than the outer diameter of the thick portion 184 of the movement restricting member 142 .

[0062] The movement limiting member 142 and the disc 141 disposed adjacent to the movement limiting member 142 on the axial side of the valve member 135 constitute a stopper member 188. The stopper member 188 limits movement of the valve member 135 in the opposite direction to the seat portion 154 in the axial direction of the housing main body 131. In other words, the movement limiting member 142, together with the disc 141, limits movement of the valve member 135 in the opposite direction to the seat portion 154 in the axial direction of the housing main body 131. The inner circumferential side of the stopper member 188 is fixed to the piston rod 21. The inner circumferential side of the stopper member 188 is immovable relative to the housing main body 131. The elastic seal member 172 has a plurality of abutment portions 176 that are expandable and contractible in the axial direction of the housing main body 131. The plurality of abutment portions 176 of the elastic seal member 172 and the disk 141 of the stopper member 188 are always in contact with each other. A communication passage 195 is formed radially between the stopper member 188 and the cylindrical portion 153 of the housing main body 131. The communication passage 195 is constantly in communication with the lower chamber 20. The communication passage 195 is disposed radially outward of the multiple abutment portions 176 of the elastic seal member 172 that abut against the stopper member 188.

[0063] The seal portion 175 of the valve member 135 is in contact with the inner circumferential surface of the cylindrical portion 153 of the housing main body 131 over the entire circumference. As a result, the seal portion 175 seals the gap between the valve member 135 and the cylindrical portion 153. In other words, the valve member 135 is a packing valve. The seal portion 175 constantly seals the gap between the valve member 135 and the cylindrical portion 153, even if the valve member 135 deforms within the allowable range within the housing 145. The valve member 135 is centered relative to the housing 145 as the seal portion 175 contacts the cylindrical portion 153 over the entire circumference. The valve member 135 closes the gap with the disk 136 as the valve disk 171 contacts the disk 136 over the entire circumference.

[0064] The seat portion 154 of the housing main body 131 supports the valve disc 171 of the valve member 135 from one axial side. The support member 181 supports the valve disc 171 from the other axial side, with the disc 136 supporting the valve disc 171 on the inner circumferential side of the seat portion 154. The shortest axial distance between the seat portion 154 and the disc 136 is smaller than the axial thickness of the valve disc 171. Therefore, the valve disc 171 is pressed against the seat portion 154 and the disc 136 over its entire periphery by its own elastic force while being elastically deformed in a slightly tapered shape.

[0065] The valve member 135 divides the interior 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 valve member 135. The variable chamber 192 is located between the valve member 135 and the stopper member 188. The volumes of both the variable chamber 191 and the variable chamber 192 are variable, and their volumes change with deformation of the valve member 135. In other words, the two variable chambers 191, 192 are defined by the valve member 135 and are provided within the housing 145. The variable chamber 191 is constantly in communication with the rod chamber 83 via the orifice 162 in the notch 161 of the disk 132. Therefore, the variable chamber 191 is constantly in communication with the upper chamber 19 via the orifice 162 in the disk 132, the rod chamber 83, the orifice 82 in the disk 51 shown in FIG. 3, and the first passage portion 43. Furthermore, the variable chamber 191 is constantly in communication with the back pressure chamber 100 via the throttle 162 in the disc 132, the rod chamber 83, and the throttle 92 in the disc 54. The variable chamber 191 and the variable chamber 192 form a housing internal chamber 198 provided in the housing 145. The valve member 135 is provided in the housing internal chamber 198.

[0066] The valve member 135 has a plurality of abutment portions 176 shown in FIG. 4 arranged at intervals in the circumferential direction. As a result, the inside and outside of the variable chamber 192 relative to the abutment portions 176 in the radial direction are always in communication with each other. In addition, a notch 158 is formed in the seat portion 154 of the housing main body 131. As a result, the inside and outside of the variable chamber 191 relative to the seat portion 154 in the radial direction are always in communication with each other. As a result, the pressure-receiving area of ​​the side of the valve disc 171 where the seal portion 175 is provided is approximately the same as the pressure-receiving area of ​​the side of the valve disc 171 where the abutment portions 176 are provided. The variable chamber 192 is always in communication with the lower chamber 20 via a communication passage 195.

[0067] During the extension stroke, hydraulic fluid from the upper chamber 19 shown in FIG. 3 is introduced into the variable chamber 191 via the first passage portion 43, the orifice 82 in the disc 51, the rod chamber 83, and the orifice 162 in the disc 132. As a result, the valve disc 171 of the valve member 135 deforms in a tapered shape, with the point of contact between the support member 181 and the disc 136 shown in FIG. 4 acting as a fulcrum, such that the outer periphery moves away from the seat portion 154 in the axial direction of the seat portion 154. At this time, the valve disc 171 compresses and deforms the abutment portion 176 of the elastic seal member 172 of the valve member 135, which abuts against the disc 141 of the stopper member 188. This deformation of the valve disc 171 increases the volume of the variable chamber 191.

[0068] At this time, the support member 181 that supports the valve disc 171 applies resistance to this deformation of the valve disc 171. Here, when the valve disc 171 deforms in this way, the volume of the variable chamber 192 decreases. At that time, the oil in the variable chamber 192 flows into the lower chamber 20 via the communication passage 195.

[0069] In the initial stage of deformation toward the stopper member 188, the valve disc 171 itself deforms, and also compresses and deforms the abutting portion 176 of the elastic seal member 172 that abuts against the disc 141 of the stopper member 188. As the deformation of valve disc 171 toward stopper member 188 progresses further, valve disc 171 itself deforms further and further compresses and deforms contact portion 176 of elastic seal member 172. At the same time, valve disc 171 abuts against the outer periphery of disc 137 of support member 181, elastically deforming the outer periphery of disc 137 in a tapered shape toward stopper member 188. As the deformation of valve disc 171 toward stopper member 188 progresses further, valve disc 171 itself deforms further and further compresses and deforms contact portion 176 of elastic seal member 172. At the same time, valve disc 171 further deforms the outer periphery of disc 137 of support member 181 in a tapered shape toward stopper member 188. At the same time, valve disc 171 elastically deforms the outer periphery of disc 138 in a tapered shape toward stopper member 188 via disc 137.

[0070] 3, the first passage portion 43, 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 can communicate between the upper chamber 19 and the lower chamber 20. The passage 201 constantly connects the first passage portion 43, the throttle 82, the rod chamber 83, the throttle 162, and the variable chamber 191 to the upper chamber 19. The passage 201 constantly connects the variable chamber 192 and the communication passage 195 to the lower chamber 20. The passage 201 connects the first passage portion 43, the throttle 82, the rod chamber 83, the throttle 162, and the variable chamber 191, and allows oil, which is a working fluid, to flow out from the upper chamber 19, which is one of the chambers in the cylinder 2, as the piston 18 moves during the extension stroke. When the piston 18 moves during the compression stroke, the oil, which is the working fluid, flows out of the lower chamber 20, which is one of the chambers in the cylinder 2, through the passage 201, connecting the communication passage 195 and the variable chamber 192. A flexible plate-shaped valve member 135 including a valve disc 171 is provided in this passage 201.

[0071] The inner circumferential side of the valve disc 171 of the valve member 135 is movable between the disc 132 and the disc 136. When the inner circumferential side of the valve disc 171 is in contact with the disc 136 over the entire circumference, the valve member 135 blocks the flow of oil between the variable chambers 191, 192. When the inner circumferential side of the valve disc 171 is separated from the disc 136, the valve member 135 allows the flow of oil between the variable chambers 192 and 191. The inner circumferential side of the valve disc 171 and the disc 136 form a check valve 205. The check valve 205 is provided in the passage 201. The check valve 205 restricts 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. The check valve 205 blocks communication of the passage 201 during the extension stroke when the pressure in the upper chamber 19 becomes higher than the pressure in the lower chamber 20. The check valve 205 opens the passage 201 during the compression stroke when the pressure in the lower chamber 20 becomes higher than the pressure in the upper chamber 19.

[0072] The check valve 205 is a free valve in which the entire valve member 135, which is its valve body, is movable in the axial direction without being clamped. Note that the valve member 135 may be configured so that the entire inner periphery of its valve disc 171 is always in contact with the disc 136, regardless of the pressure states of the variable chambers 191, 192. In other words, the valve disc 171 of the valve member 135 may always block communication between the variable chambers 191, 192. In other words, it is sufficient that the valve disc 171 of the valve member 135 blocks communication of oil in at least one direction through the passage 201.

[0073] 3 are placed on the piston rod 21 in this order on the shaft step portion 29, with the mounting shaft portion 28 inserted inside each of them. At this time, the pilot case 55 fits the seal member 86 of the damping valve 52 into the outer cylindrical portion 73.

[0074] 4, with the mounting shaft portion 28 and the discs 133 and 134 inserted inside, the valve member 135 is placed on the seat portion 154 of the housing main body 131. At this time, the elastic seal member 172 of the valve member 135 is fitted into the cylindrical portion 153 of the housing main body 131. Furthermore, with the mounting shaft portion 28 inserted inside each of them, the disc 136, disc 137, disc 138, disc 139, disc 140, disc 141, movement limiting member 142, and annular member 144 are placed on the disc 134 and the valve disc 171 of the valve member 135, in this order.

[0075] 3 of the mounting shaft portion 28 that protrudes beyond the annular member 144. As a result, the inner circumferential sides or the entirety of the annular member 117, disc 116, disc 115, the plurality of discs 114, the plurality of discs 113, disc 112, disc 111, piston 18, disc 51, damping valve 52, disc 53, disc 54, pilot case 55, disc 56, disc 57, the plurality of discs 58, disc 59, disc 60, housing main body 131, disc 132, disc 133, disc 134, disc 136, disc 137, disc 138, disc 139, disc 140, disc 141, movement limiting member 142, and annular member 144 are sandwiched between the shaft step portion 29 of the piston rod 21 and the nut 211, and are clamped in the axial direction. At this time, the inner peripheral side of the valve member 135 is not clamped in the axial direction. In this state, the valve disc 171 of the valve member 135 abuts against the seat portion 154 of the housing main body 131 and the disc 136 of the support member 181. Also, in this state, the abutment portion 176 of the elastic seal member 172 of the valve member 135 abuts against the disc 141 of the stopper member 188 with an interference fit.

[0076] As shown in FIG. 1 , the above-mentioned base valve 25 is provided between the inner tube 3 and the bottom member 12 of the outer tube 4. This base valve 25 has a base valve member 221, a disc valve 222, a disc 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 to the inner tube 3 at the base valve member 221. The base valve member 221 separates the lower chamber 20 from the reservoir chamber 6. The disc valve 222 is provided below the base valve member 221, i.e., on the reservoir chamber 6 side. The disc valve 223 is provided above the base valve member 221, i.e., on the lower chamber 20 side. The mounting pin 224 attaches the disc valves 222 and 223 to the base valve member 221.

[0077] The base valve member 221 has an annular shape, and a mounting pin 224 is inserted through its radial center. The base valve member 221 is formed with a plurality of passage holes 225 and a plurality of passage holes 226. The plurality of passage holes 225 allow hydraulic fluid 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 hydraulic fluid to flow between the lower chamber 20 and the reservoir chamber 6. The disk valve 222 on the reservoir chamber 6 side allows hydraulic fluid to flow from the lower chamber 20 to the reservoir chamber 6 via the passage hole 225. On the other hand, the disk valve 222 restricts hydraulic fluid to flow from the reservoir chamber 6 to the lower chamber 20 via the passage hole 225. The disk valve 223 allows hydraulic fluid to flow from the reservoir chamber 6 to the lower chamber 20 via the passage hole 226. On the other hand, the disc valve 223 restricts the flow of oil from the lower chamber 20 to the reservoir chamber 6 through the passage hole 226 .

[0078] The disc valve 222 and the base valve member 221 form a damping valve mechanism 227. The damping valve mechanism 227 opens during the compression stroke of the shock absorber 1 to allow hydraulic fluid to flow from the lower chamber 20 to the reservoir chamber 6 and generate a damping force. The disc valve 223 and the base valve member 221 form a suction valve mechanism 228. The suction valve mechanism 228 opens during the extension stroke of the shock absorber 1 to allow hydraulic fluid to flow from the reservoir chamber 6 into the lower chamber 20. The suction valve mechanism 228 mainly functions to allow hydraulic fluid to flow from the reservoir chamber 6 to the lower chamber 20 without generating any damping force, so as to compensate for a shortage of hydraulic fluid caused by the extension of the piston rod 21 from the cylinder 2.

[0079] Next, the main operation of the shock absorber 1 will be described.

[0080] "When it is assumed that the frequency sensitive mechanism 130 does not operate during the extension stroke, and only the first damping force generating mechanism 41 and the second damping force generating mechanism 110 on the extension side operate" 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 from the upper chamber 19 flows into the lower chamber 20 via the first passage portion 43, the throttle 82, the rod chamber 83, the throttle 92, the back pressure chamber 100, and the fixed orifice 105 shown in FIG. 3. This generates a damping force with orifice characteristics (the damping force is approximately proportional to the square of the piston speed). Therefore, when the piston speed is slower than the first predetermined value, the damping force increases at a relatively high rate as the piston speed increases.

[0081] When the piston speed is equal to or greater than the first predetermined value and less than the second predetermined value, oil from the upper chamber 19 passes through the first passage portion 43, the throttle 82, the rod chamber 83, the throttle 92, the back pressure chamber 100, and flows between the disc valve 99 and the valve seat portion 75 into the lower chamber 20 while opening the disc valve 99. This generates a damping force with valve characteristics (the damping force is approximately proportional to the piston speed). Therefore, when the piston speed is equal to or greater than the first predetermined value and less than the second predetermined value, the damping force characteristic with respect to the piston speed is such that the rate of increase of the damping force in response to an increase in piston speed is lower than when the piston speed is less than the first predetermined value.

[0082] When the piston speed becomes faster than the second predetermined value, the relationship of the forces (hydraulic pressure) acting on the damping valve 52 becomes such that the force in the opening direction applied from the first passage portion 43 becomes greater than the force in the closing direction applied from the back pressure chamber 100. Therefore, in this region, as the piston speed increases, the damping valve 52 moves away from the valve seat portion 48 of the piston 18 and opens. Therefore, in addition to flowing from the upper chamber 19 through the first passage portion 43, the throttle 82, the rod chamber 83, the throttle 92, the back pressure chamber 100, and between the disc valve 99 and the valve seat portion 75 to the lower chamber 20, the hydraulic fluid also flows from the first passage portion 43 through between the damping valve 52 and the valve seat portion 48 to the lower chamber 20. Therefore, when the piston speed is equal to or greater than the second predetermined value, the rate of increase in the damping force in response to an increase in the piston speed is lower than when the piston speed is equal to or greater than the first predetermined value but less than the second predetermined value.

[0083] "When it is assumed that the frequency sensitive mechanism 130 does not operate during the compression stroke, and only the first damping force generating mechanism 42 on the compression side operates" 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 via the first passage portion 44 and the fixed orifice 123 of the disc valve 122 shown in FIG. 2. This generates a damping force with orifice characteristics. Therefore, when the piston speed is slower than the third predetermined value, the damping force increases at a relatively high rate as the piston speed increases.

[0084] 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 opens the disc valve 122 and flows between the disc valve 122 and the valve seat portion 49 into the upper chamber 19. This generates a damping force with valve characteristics. Therefore, when the piston speed is equal to or greater than the third predetermined value, the damping force characteristic with respect to the piston speed is such that the rate of increase of the damping force relative to an increase in piston speed is lower than when the piston speed is less than the third predetermined value.

[0085] "When the frequency sensitive mechanism 130 acts during the extension stroke" In this embodiment, the frequency sensitive mechanism 130 varies the damping force depending on the piston frequency even when the piston speed is the same.

[0086] During the extension stroke, oil is introduced from the upper chamber 19 into the variable chamber 191 of the frequency sensitive mechanism 130 via the first passage portion 43, the throttle 82, the rod chamber 83, and the throttle 162 shown in FIG. 4. As a result, the valve disc 171 of the valve member 135, which has been in contact with the seat portion 154 and the disc 136 of the support member 181, deforms in a tapered shape with its outer periphery moving away from the seat portion 154, with the contact point with the disc 136 serving as a fulcrum. At this time, the valve member 135 compresses and deforms the abutment portion 176 of the elastic seal member 172, which is in contact with the disc 141 of the stopper member 188. At this time, the valve member 135 also discharges oil from the variable chamber 192 of the frequency sensitive mechanism 130 to the lower chamber 20 via the communicating 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 via the first passage portion 43, the throttle 82, the rod chamber 83, and the throttle 162 is small. Therefore, although the valve disc 171 of the valve member 135 deforms as described above, it does not deform to near its limit.

[0087] Therefore, during the extension stroke when the piston frequency is high, the valve disc 171 of the valve member 135 of the frequency sensitive mechanism 130 deforms as described above, introducing hydraulic fluid from the upper chamber 19 into the variable chamber 191. This reduces the flow rate of hydraulic fluid from the upper chamber 19 through the first passage 43, the throttle 82, the rod chamber 83, the throttle 92, and the back pressure chamber 100 to the lower chamber 20, opening the second damping force generating mechanism 110. Furthermore, the flow rate of hydraulic fluid from the first passage 43 to the lower chamber 20, opening the first damping force generating mechanism 41, also reduces. Furthermore, introducing hydraulic fluid from the upper chamber 19 into the variable chamber 191 suppresses the pressure increase in the back pressure chamber 100 compared to when the variable chamber 191 is not present, making it easier for the damping valve 52 of the first damping force generating mechanism 41 to open. These factors result in a softer damping force on the extension side. Here, the inner circumferential side of the valve member 135 is spaced apart from the disk 132 and is supported on only one side by the disk 136. For this reason, the inner circumferential side of the valve member 135 is likely to deform so as to approach the disk 132. Therefore, the abutment portion 176 on the outer circumferential side of the valve member 135 is easily compressively deformed.

[0088] During the extension stroke, as described above, the valve disc 171 of the valve member 135 deforms in a tapered shape toward the stopper member 188, with the point of contact between the valve disc 171 and the disc 136 of the support member 181 as the fulcrum. In the early stages of this deformation, the valve disc 171 itself deforms and compresses and deforms the abutment portion 176 of the elastic seal member 172 that abuts against the disc 141 of the stopper member 188. As the deformation of valve disc 171 toward stopper member 188 progresses, valve disc 171 itself deforms further and further compresses and deforms contact portion 176 of elastic seal member 172. At the same time, valve disc 171 abuts against the outer periphery of disc 137 of support member 181, deforming the outer periphery of disc 137 in a tapered shape toward stopper member 188. As the deformation of valve disc 171 toward stopper member 188 progresses, valve disc 171 itself deforms further and further compresses and deforms contact portion 176 of elastic seal member 172. At the same time, valve disc 171 deforms the outer periphery of disc 137 and the outer periphery of disc 138 of support member 181 in a tapered shape toward stopper member 188.

[0089] On the other hand, during the extension stroke when the piston frequency is low, the stroke of the piston 18 is large. Therefore, a large amount of hydraulic fluid is introduced from the upper chamber 19 into the variable chamber 191 via the first passage portion 43, the throttle 82, the rod chamber 83, and the throttle 162. Therefore, although hydraulic fluid flows from the upper chamber 19 to the variable chamber 191 at the beginning of the stroke of the piston 18, the valve disc 171 of the valve member 135 subsequently deforms to near its limit and no longer deforms. As a result, hydraulic fluid no longer flows from the upper chamber 19 to the variable chamber 191. This prevents a decrease in the flow rate of hydraulic fluid 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 to the lower chamber 20 while opening the second damping force generating mechanism 110. In addition, the flow rate of hydraulic fluid from the first passage portion 43 to the lower chamber 20 while opening the first damping force generating mechanism 41 also does not decrease. In addition, because oil is not introduced into the variable chamber 191 from the upper chamber 19, the pressure in the back pressure chamber 100 increases, making it 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 stronger than at high frequencies. Even during the extension stroke when the piston frequency is low, the valve disc 171 deforms while deforming the support member 181, just as when the piston frequency is high.

[0090] During the compression stroke, the pressure in the lower chamber 20 increases, but the valve disc 171 of the valve member 135 of the frequency sensitive mechanism 130 abuts against the seat portion 154 of the housing main body 131, suppressing the expansion of the variable chamber 192. This suppresses the amount of hydraulic fluid introduced from the lower chamber 20 into the variable chamber 192 via the communication passage 195. As a result, the flow rate of hydraulic fluid introduced 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 remains almost constant. This increases the damping force. During the compression stroke, if the piston speed increases and the pressure in the variable chamber 192 exceeds the pressure in the variable chamber 191 by more than a predetermined value, the inner peripheral side of the valve disc 171 of the valve member 135 moves away from the disc 136. In other words, the check valve 205 opens. As a result, oil flows from the lower chamber 20 to the upper chamber 19 via the communicating passage 195, variable chamber 192, variable chamber 191, throttle 162, rod chamber 83, throttle 82, and first passage portion 43. In this way, opening of the check valve 205 suppresses the differential pressure between the variable chamber 192 side and the variable chamber 191 side of the valve disc 171 of the valve member 135. Therefore, excessive bending of the valve disc 171 is suppressed.

[0091] The aforementioned Patent Document 1 discloses a shock absorber in which a partitioned disc with a simple support structure, in which the inner circumferential side is not clamped but only one side is supported, is provided in a passage through which working fluid flows as a piston moves. This shock absorber is provided with a cover member, i.e., a movement limiting member, that limits deformation of the partitioned disc, i.e., the valve member. If the movement limiting member has low rigidity, there is a possibility that the movement limiting member will also deform when the valve member deforms under high load. This may result in the valve member not achieving the desired characteristics.

[0092] For this reason, we considered forming the movement limiting member by sintering or forging to increase rigidity while suppressing cost increases. However, when forming the movement limiting member by sintering or forging, chips are likely to form at the corners of the movement limiting member due to the manufacturing process of the mold used during molding. When the valve member abuts against the movement limiting member, these chips may affect the durability of the valve member. In particular, in a structure such as shock absorber 1 in which valve member 135 has a contact portion 176 made of a rubber elastic material, the rubber contact portion 176 abuts against movement limiting member 142. When valve member 135 deforms, if contact portion 176 abuts against notched portion 183 of movement limiting member 142, excessive stress may be concentrated at contact portion 176, potentially affecting the durability of contact portion 176, especially when a high load is applied to valve member 135.

[0093] In the shock absorber 1 of this embodiment, the disk 141 is disposed on the valve member 135 side of the movement-limiting member 142, which is formed by sintering or forging. This allows the valve member 135 to abut against the disk 141. Specifically, this allows the abutting portion 176 of the valve member 135 to abut against the disk 141. This prevents the abutting portion 176 of the valve member 135 from abutting against the notched portion 183 of the movement-limiting member 142. This prevents stress concentration at the abutting portion 176, which occurs when the abutting portion 176 abuts against the notched portion 183 of the movement-limiting member 142. This improves the durability of the abutting portion 176 and, ultimately, the durability of the valve member 135. Furthermore, because the valve member 135 can withstand high loads, the frequency sensitive mechanism 130, including the valve member 135, becomes a mechanism capable of supporting high damping force.

[0094] Furthermore, in the shock absorber 1 of this embodiment, the disk 141 has the same diameter as the movement limiting member 142 or a larger diameter than the movement limiting member 142. Therefore, the abutting portion 176 of the valve member 135 reliably abuts against the disk 141 and does not abut against the notched portion 183 of the movement limiting member 142. This eliminates stress concentration at the abutting portion 176 that would occur if the abutting portion 176 abutted against the notched portion 183 of the movement limiting member 142. This ensures that the durability of the abutting portion 176, and therefore the durability of the valve member 135, can be improved.

[0095] In the above embodiment, a hydraulic shock absorber is used as an example, but water or air can also be used as the working fluid. [Explanation of symbols]

[0096] 1... shock absorber, 2... cylinder, 18... piston, 19... upper chamber (chamber), 20... lower chamber (chamber), 135... valve member, 141... disc (plate-shaped member), 142... movement limiting member, 201... passage.

Claims

[Claim 1] a cylinder in which a working fluid is sealed; a piston slidably fitted in the cylinder to divide the interior of the cylinder into two chambers; a passage through which working fluid flows out from one chamber in the cylinder as the piston moves; a flexible plate-shaped valve member provided in the passage, the inner circumferential side of which is supported by a support member on only one side without being clamped from both sides; a movement limiting member that limits movement of the valve member; Equipped with the movement limiting member is formed by sintering or forging, a plate-shaped member is disposed on the valve member side of the movement limiting member in the axial direction, The plate-shaped member has a diameter equal to or larger than that of the movement limiting member.

Images