buffer

Abstract

To provide a damper capable of improving durability of a valve member.SOLUTION: A damper includes: a second passage 201 disposed so as to allow at least one of working fluids in two chambers to flow in due to movement of a piston; and a second attenuation force mechanism 130 for generating attenuation force, disposed in the second passage 201 to partition the second passage 201, and having a valve member 171 capable of discharging at least one of working fluids in the second passage 201 into a cylinder via a cutout part 178 formed in an elastic body 172 when performing first displacement by a working fluid flowing in due to movement of the piston, and a restriction part 188 for forming a pressure chamber 196 closed between the second passage 201 and the valve member 171 due to that the cutout part 178 is closed when the valve member 171 performs second displacement, and restricting movement of a working fluid in the pressure chamber 196.SELECTED DRAWING: Figure 4

Description

[Technical Field]

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

[0002] Some shock absorbers are provided with a partition disk that has a disk as a valve member and partitions a passage (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-16288 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, an aspect of the present invention includes 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 piston rod connected to the piston and extending to the outside of the cylinder, a first passage that communicates the two chambers so that the working fluid can flow between them as the piston moves, a second passage that is provided in parallel to the first passage and into which the working fluid of at least one of the two chambers can flow as the piston moves, and a first damping mechanism that is provided in the first passage and generates a damping force. a valve member that is provided in the second passage and that partitions the second passage, and that is capable of discharging at least a portion of the working fluid in the second passage into the cylinder through a notch formed in an elastic body when a first displacement is caused by the working fluid that flows in due to movement of the piston, and a limiting portion that, when the valve member is displaced a second time, closes the notch to form a closed pressure chamber between the second passage and the valve member, thereby limiting the movement of the working fluid in the pressure chamber, and a second damping force mechanism that generates a damping force. [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 a first 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 a first embodiment of the present invention. [Figure 3] 1 is a half-side cross-sectional view showing a piston, a damping force mechanism, a frequency sensitive mechanism, etc. of a shock absorber according to a first embodiment of the present invention. [Figure 4] 1 is a partially enlarged cross-sectional view showing a frequency sensitive mechanism of a shock absorber according to a first embodiment of the present invention. [Figure 5] FIG. 2 is a plan view showing a partition member of the shock absorber according to the first embodiment of the present invention. [Figure 6]6 is a partially enlarged side view of the partition member of the shock absorber according to the first embodiment of the present invention, as viewed from the direction VI in FIG. 5. [Figure 7] 1 is a partially enlarged cross-sectional view showing a frequency sensitive mechanism of a shock absorber according to a first embodiment of the present invention. [Figure 8] FIG. 10 is a partially enlarged side view showing a partition member of a shock absorber according to a second embodiment of the present invention. [Figure 9] FIG. 10 is a partially enlarged side view showing a partition member of a shock absorber according to a third embodiment of the present invention. [Figure 10] FIG. 10 is a partially enlarged side view showing a partition member of a shock absorber according to a fourth embodiment of the present invention. [Figure 11] FIG. 10 is a partially enlarged side view showing a partition member of a shock absorber according to a fifth embodiment of the present invention. [Figure 12] FIG. 10 is a partially enlarged side view showing a partition member of a shock absorber according to a sixth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] [First embodiment] A shock absorber according to a first embodiment will be described below with reference to Figures 1 to 7. For ease of explanation, the upper side in Figures 1 to 3 will be referred to as "top" and the lower side in Figures 1 to 3 will be referred to as "bottom."

[0010] As shown in FIG. 1, the shock absorber 1 of the first 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 fitted onto the outer periphery 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 of the cylinder 2 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, serving 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, serving 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 is inserted through the rod guide 22, the friction member 24, and the seal member 23. The piston rod 21 slides along the axial direction of the rod guide 22, the friction member 24, and the seal member 23, respectively. The piston rod 21 extends from the inside of 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 inner periphery of the body member 11 of 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 contacts the outer periphery of the piston rod 21. The piston rod 21 moves relative to the friction member 24 in the axial direction of the friction member 24. The friction member 24 generates frictional 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 passage 43 (first passage). In the piston 18, the insides of the plurality of passage holes 39 and the passage groove 40 form a passage 44.

[0025] A damping force mechanism 41 (first damping force mechanism) is provided in the passage 43. The damping force mechanism 41 opens and closes the passage 43 to generate a damping force. The damping force 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 passage 43 serves as a passage through which oil flows from the upper chamber 19 to the lower chamber 20 as the piston 18 moves toward the upper chamber 19. In other words, the passage 43 communicates between the upper chamber 19 and the lower chamber 20 as the piston 18 moves, allowing oil as a working fluid to flow between them. The passage 43 is an extension-side passage through which oil as a working fluid flows from the upper chamber 19 to the lower chamber 20 during the extension stroke. The damping force mechanism 41 is an extension-side damping force mechanism that generates a damping force by suppressing the flow of oil from the passage 43 to the lower chamber 20 during the extension stroke.

[0026] A damping force mechanism 42 is provided in the passage 44. The damping force mechanism 42 opens and closes the passage 44 to generate a damping force. The damping force mechanism 42 is disposed on the upper chamber 19 side, which is the other end of the piston 18 in the axial direction, and is attached to the piston rod 21. As a result, the passage 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 passage 44 communicates between the lower chamber 20 and the upper chamber 19 as the piston 18 moves, allowing oil as a working fluid to flow between them. The passage 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 damping force mechanism 42 is a compression-side damping force mechanism that generates a damping force by suppressing the flow of oil from the passage 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 damping force 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 located 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 damping force 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 passage 43 of the piston 18. The passage within the large diameter hole 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 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 passage 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 passage 43 formed in the piston 18 by moving away from and abutting against the valve seat portion 48. The passage between the spaced-apart disc 85 and the valve seat portion 48 also constitutes the passage 43. 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 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 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 part of the damping force 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 passage 102 that constantly connects the passage 43 of the piston 18 with the back pressure chamber 100 and introduces hydraulic fluid from the passage 43 to the back pressure chamber 100. When the disc 85 lifts off from the valve seat portion 48 of the piston 18 and opens, the damping valve 52 allows hydraulic fluid from the passage 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 restricts the flow of hydraulic fluid between the valve seat portion 48. The extension-side damping force mechanism 41 introduces a portion of the hydraulic fluid flow into the back pressure chamber 100 via the passage 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 portion 75 constitute a damping force mechanism 110. When the disc valve 99 is released from the valve seat portion 75, the damping force mechanism 110 connects the back pressure chamber 100 and the lower chamber 20. At that time, the damping force 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 damping force 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 damping force mechanism 110 causes hydraulic fluid to flow from the upper chamber 19 to the lower chamber 20 via the passage 43, the passage 102, and the back pressure chamber 100. The damping force mechanism 110 is an extension-side damping force 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. When the disc valve 122 is releasable from the valve seat portion 49, it can open the passage 44 to the upper chamber 19. At that time, the disc valve 122 suppresses the flow of oil from the lower chamber 20 to the upper chamber 19 via the passage 44. The disc valve 122 and the valve seat portion 49 constitute a compression-side damping force mechanism 42. 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 damping force 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 (second damping force mechanism) is provided on the axial side of disc 60 opposite to disc 59. Frequency sensitive mechanism 130 varies the damping force according to the frequency of the axial movement of piston 18 (hereinafter referred to as piston frequency). The frequency sensitive mechanism 130 has one housing main body 131 closest to the disk 60 in the axial direction. The frequency sensitive mechanism 130 also has, in order from the housing main body 131 side, one disk 132, one disk 133, and one disk 134 on the inner circumferential side of the housing main body 131 opposite the disk 60 in the axial direction. The frequency sensitive mechanism 130 also has one partition member 135 radially outward of the disks 133 and 134, which are on the opposite side of the housing main body 131 from the disk 60 in the axial direction. As shown in FIG. 4 , the frequency sensitive mechanism 130 also has, in order from the disk 134 and partition member 135 side, one disk 136, one disk 137, one disk 138, one disk 139, and one disk 140, a plurality of disks, specifically three disks 141, on the axial opposite side of the disk 134 and partition member 135 from the disk 132. An annular member 144 is provided on the opposite side of the disk 141 from the disk 140 in the axial direction.

[0046] The housing main body 131, discs 132-134, 136-141, 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 discs 132-134, 136-141 are all formed by punching out from a single thin plate. The mounting shaft 28 of the piston rod 21 is fitted inside the discs 132-134, 136-141, housing main body 131, and annular member 144. The mounting shaft 28 of the piston rod 21 and the discs 133 and 134 are inserted into the inner periphery of the partition member 135. The disks 132 to 134 and 136 to 141 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 partitioning member 135 is made up of a valve disc 171 (valve member) and an elastic body 172. The partitioning member 135 is disposed inside the cylindrical portion 153 of the housing main body 131. The partitioning 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] Elastic body 172 is made of a rubber material and has an annular shape. Elastic body 172 is adhered to the outer periphery of valve disc 171. Elastic body 172 is baked onto valve disc 171 and is provided integrally with valve disc 171. Elastic body 172 has a seal portion 175 and a contact portion 176.

[0053] The seal portion 175 is annular and is fixed over the entire outer periphery of the valve disc 171. The seal portion 175 protrudes from the valve disc 171 toward the bottom 150 of the housing main body 131 in the axial direction of the partition member 135. The seal portion 175 has an annular protrusion 177 that protrudes radially outward from the outer periphery at a midpoint in the axial direction.

[0054] The abutment portion 176 is provided on the opposite side of the seal portion 175 of the valve disc 171 in the axial direction of the partitioning member 135. As shown in Figure 5, the abutment portion 176 is annular, and is fixed to the outer periphery of the valve disc 171 over its entire circumference. As shown in Figure 4, the abutment portion 176 protrudes from the valve disc 171 on the opposite side of the bottom portion 150 in the axial direction of the partitioning member 135. The abutment portion 176 of the elastic body 172 is expandable and contractible in the axial direction of the partitioning member 135.

[0055] A notch 178 is formed in the tip of the abutting portion 176 on the side opposite the valve disc 171 in the axial direction of the partitioning member 135. The notch 178 is groove-shaped and recessed towards the valve disc 171 from the tip of the abutting portion 176 on the side opposite the valve disc 171 in the axial direction of the partitioning member 135. The notch 178 penetrates the abutting portion 176 in the radial direction of the abutting portion 176. The abutting portion 176 is provided with a plurality of notches 178 of the same shape, specifically three notches 178, spaced equally apart around the circumferential direction of the abutting portion 176, as shown in FIG.

[0056] 6, the cutout portion 178 has a bottom surface portion 179 and a pair of wall surface portions 180. The bottom surface portion 179 is flat and extends perpendicular to the axial direction of the partitioning member 135. The pair of wall surface portions 180 are inclined at the same angle relative to the bottom surface portion 179. The distance between the pair of wall surface portions 180 in the circumferential direction of the partitioning member 135 increases as the wall surface portions 180 become farther apart from the bottom surface portion 179 in the axial direction of the partitioning member 135.

[0057] As shown in FIG. 4, the abutment portion 176 has a main body portion 181 that is adhered to the valve disc 171 by forming a notch portion 178, and a protrusion portion 182 that protrudes from the main body portion 181 to the opposite side of the valve disc 171 in the axial direction of the partition member 135. The main body 181 is annular. The bottom surface 179 of the notch 178 is formed in the main body 181.

[0058] As shown in Fig. 5, the protrusions 182 are formed between adjacent notches 178 in the circumferential direction of the partition member 135. The abutting portion 176 is provided with the same number of protrusions 182 as the notches 178, and the protrusions 182 have the same shape and are equally spaced apart in the circumferential direction of the partition member 135. The protrusions 182 are arc-shaped when viewed in the axial direction of the partition member 135. The length of the protrusions 182 in the circumferential direction of the partition member 135 is longer than the length of the notches 178 in the circumferential direction of the partition member 135. As shown in Fig. 6, the wall surface portions 180 of the notches 178 are formed in the protrusions 182.

[0059] 4, an annular gap is provided between the valve disc 171 and the cylindrical portion 153 of the housing main body 131. The elastic body 172 has a seal portion 175 and an abutment portion 176 fixed to both sides of the valve disc 171 via this gap.

[0060] The annular protrusion 177 of the seal portion 175 of the elastic body 172 is fitted liquid-tightly 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 body 172 constantly seals the gap between the partition 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 disc 171 of the partition member 135 is capable of being seated on the seat portion 154 of the housing main body 131.

[0061] 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 partitioning member 135 is positioned axially between the discs 132 and 136 and abuts against the disc 136 for support. The inner periphery of the valve disc 171 of the partitioning member 135 is movable between the discs 132 and 136 within the axial lengths of the two discs 133, 134. The partitioning member 135 is centered relative to the housing 145 by the seal portion 175 contacting the cylindrical portion 153 over the entire circumference. The inner circumferential side of the partitioning member 135, that is, the inner circumferential side of the valve disc 171, is not clamped from either side, but is supported on only one side by the disc 136. The radially outer side of the valve disc 171 of the partitioning member 135 than the disc 136 is not clamped from either side, but is supported on only one side by the seat portion 154. Therefore, the partitioning 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 partitioning member 135 is annular in shape as a whole, and is elastically deformable, that is, flexible.

[0062] The disc 137 has an outer diameter that is larger than the outer diameter of the disc 136 and smaller than the minimum inner diameter of the abutting portion 176. The disc 137 has a smaller axial thickness than the disc 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.

[0063] 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. The outer diameter of disc 141 is larger than the outer diameter of disc 140. Disc 141 has a greater axial thickness than each of discs 136 to 138. The outer diameter of disc 141 is smaller than the inner diameter of cylindrical portion 153. Of the multiple discs 141, the disc 141 closest to disc 140 always abuts against protruding portion 182 of abutting portion 176 of partition member 135.

[0064] The support member 185 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 on the valve disc 171 side. 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 on the valve disc 171 side. The support member 185 supports the inner peripheral side of the valve disc 171 of the partition member 135. The inner peripheral side of the valve disc 171 of the partition member 135 is not clamped from both axial sides, and only one axial side is supported by disc 136 of the support member 185.

[0065] A plurality of discs 141 are stacked to form a stopper member 188 (limiting portion). The stopper member 188 limits movement of the partition member 135 in the opposite direction to the seat portion 154 in the axial direction of the housing main body 131.

[0066] Here, when the valve disc 171 is displaced axially toward the stopper member 188, the partitioning member 135 elastically deforms the abutting portion 176 of the elastic body 172. Even when a pressure load is generated, in the partitioning member 135, when the valve disc 171 is displaced toward the stopper member 188 by a first displacement amount equal to or less than a predetermined value, mainly the protruding portion 182 of the abutting portion 176 elastically deforms, but the notch 178 is not blocked by the stopper member 188. On the other hand, when the pressure load increases and the valve disc 171 is displaced toward the stopper member 188 by a second displacement amount exceeding the predetermined value, mainly the protruding portion 182 of the abutting portion 176 elastically deforms, and the notch 178 is blocked by the stopper member 188, as shown in FIG. 7 . In other words, stopper member 188 does not close notch 178 when valve disc 171 is displaced toward stopper member 188 by a first displacement amount equal to or less than a predetermined value. On the other hand, stopper member 188 closes notch 178 of abutting portion 176 when valve disc 171 is displaced toward stopper member 188 by a second displacement amount exceeding the predetermined value. Abutting portion 176 of elastic body 172 and disc 141 of stopper member 188 are always in contact with each other.

[0067] 4, 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 contact portion 176 of the elastic body 172 that contacts the stopper member 188.

[0068] The annular protrusion 177 of the seal portion 175 of the partitioning member 135 contacts 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 partitioning member 135 and the cylindrical portion 153. In other words, the partitioning member 135 is a packing valve. The seal portion 175 constantly seals the gap between the partitioning member 135 and the cylindrical portion 153, even if the partitioning member 135 deforms within the allowable range within the housing 145. The seal portion 175 contacts the cylindrical portion 153 over the entire circumference, so that the partitioning member 135 is centered relative to the housing 145. The valve disc 171 of the partitioning member 135 contacts the disc 136 over the entire circumference, so that the gap between the disc 136 and the seal portion 175 is closed.

[0069] The seat portion 154 of the housing main body 131 supports the valve disc 171 of the partition member 135 from one axial side. The support member 185 supports the valve disc 171 from the other axial side, with the disc 136 supporting the valve disc 171 on the inner 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.

[0070] The partitioning 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 partitioning member 135. The variable chamber 192 is located between the partitioning member 135 and the stopper member 188. The volumes of the variable chambers 191 and 192 are both variable, and the volumes change depending on the deformation of the partitioning member 135. The variable chambers 191 and 192 form a housing internal chamber 198 that is provided within the housing 145. The partitioning member 135 is provided in the housing internal chamber 198.

[0071] The variable chamber 191 is constantly in communication with the rod chamber 83 via the throttle 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 throttle 162 in the disk 132, the rod chamber 83, the throttle 82 in the disk 51 shown in FIG. 3, and the passage 43. In addition, the variable chamber 191 is constantly in communication with the back pressure chamber 100 via the throttle 162 in the disk 132, the rod chamber 83, and the throttle 92 in the disk 54.

[0072] A notch 158 is provided in the seat portion 154 of the housing 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.

[0073] The variable chamber 192 has an inner chamber 196 (pressure chamber) located radially inward of the contact portion 176, and an outer chamber 197 located radially outward of the contact portion 176. The outer chamber 197 is constantly in communication with the lower chamber 20 via a communication passage 195.

[0074] As described above, the partitioning member 135 has a plurality of cutouts 178 arranged at intervals in the circumferential direction in the abutment portion 176. This allows the inner chamber 196 and the outer chamber 197 of the variable chamber 192 to communicate with each other via the passages in the cutouts 178. When the displacement of the valve disc 171 of the partitioning member 135 is the first displacement described above, the inner chamber 196 and the outer chamber 197 can communicate with each other via the passages in the cutouts 178. On the other hand, when the displacement of the valve disc 171 of the partitioning member 135 is the second displacement described above that is larger than the first displacement, the passages in the cutouts 178 are closed, and communication between the inner chamber 196 and the outer chamber 197 is blocked. In other words, when the valve disc 171 is in the second displacement state, the partitioning member 135 is in a hydraulically locked state in which the inner chamber 196 on one side is closed and further displacement toward the inner chamber 196 is suppressed.

[0075] During the extension stroke, hydraulic fluid from the upper chamber 19 shown in FIG. 3 is introduced into the variable chamber 191 via the passage 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 partitioning member 135 deforms in a tapered shape, with the point of contact between the support member 185 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, mainly the protruding portion 182, of the abutting portion 176 that abuts against the stopper member 188 of the partitioning member 135. This deformation of the valve disc 171 increases the volume of the variable chamber 191.

[0076] At this time, the support member 185 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 manner, the volume of the variable chamber 192 decreases. If the notch 178 is not blocked at this time, the oil in the variable chamber 192 flows into the lower chamber 20 via the communication passage 195.

[0077] In the initial stage of deformation toward the stopper member 188, the valve disc 171 itself deforms, and compresses and deforms mainly the protruding portion 182 of the abutting portion 176 that abuts against the disc 141 of the stopper member 188. As the deformation of the valve disc 171 toward the stopper member 188 progresses further, the valve disc 171 itself deforms further and further compresses and deforms, mainly the protruding portion 182 of the abutment portion 176. At the same time, the valve disc 171 abuts against the outer periphery of the disc 137 of the support member 185, elastically deforming the outer periphery of the disc 137 in a tapered shape toward the stopper member 188.

[0078] As the deformation of the valve disc 171 toward the stopper member 188 progresses further, the valve disc 171 itself deforms further and further compresses and deforms mainly the protruding portion 182 of the abutment portion 176. At the same time, the valve disc 171 further deforms the outer circumferential side of the disc 137 of the support member 185 in a tapered shape toward the stopper member 188. At the same time, the valve disc 171 elastically deforms the outer circumferential side of the disc 138, via the disc 137, in a tapered shape toward the stopper member 188.

[0079] 3, the passage 43, the throttle 82, the rod chamber 83, the throttle 162, the housing inner chamber 198, and the communicating passage 195 constitute a passage 201 (second passage). A portion of the passage 201 is provided in parallel with the passage 43. The entire passage 201 is provided in parallel with the passage 44. A flexible plate-shaped partition member 135 including a valve disc 171 is provided in the passage 201 to partition the passage 201. The passage 201 can communicate between the upper chamber 19 and the lower chamber 20. The passage 201 constantly communicates the passage 43, the throttle 82, the rod chamber 83, the throttle 162, and the variable chamber 191 with the upper chamber 19. The passage 201 constantly communicates the outer chamber 197 of the variable chamber 192 and the communicating passage 195 with the lower chamber 20. The passage 201 allows the inner chamber 196 of the variable chamber 192 to communicate with the lower chamber 20 .

[0080] Passage 201 is provided so that oil can flow into passage 43, throttle 82, rod chamber 83, throttle 162, and variable chamber 191 from upper chamber 19, which is one of upper chamber 19 and lower chamber 20 in cylinder 2, as piston 18 moves during the extension stroke. Passage 201 is provided so that oil can flow into communication passage 195 and variable chamber 192 from lower chamber 20, which is one of upper chamber 19 and lower chamber 20 in cylinder 2, as piston 18 moves during the compression stroke. Here, passage 201 may be provided so that oil can flow into only upper chamber 19, which is one of upper chamber 19 and lower chamber 20. In other words, passage 201 only needs to be provided so that oil can flow into it from at least one of upper chamber 19 and lower chamber 20.

[0081] The inner circumferential side of the valve disc 171 of the partitioning 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 partitioning 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 partitioning 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.

[0082] The check valve 205 is a free valve in which the entire partitioning member 135, which is its valve body, is movable in the axial direction without being clamped. Note that the partitioning 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 partitioning member 135 may be configured to always block communication between the variable chambers 191, 192. In other words, it is sufficient that the valve disc 171 of the partitioning member 135 blocks communication of oil in at least one direction through the passage 201.

[0083] Frequency sensitive mechanism 130 is provided in passage 201 and generates a damping force during the extension stroke. Frequency sensitive mechanism 130 has a partition member 135 that partitions passage 201. When valve disc 171 of partition member 135 undergoes a first displacement due to oil flowing into variable chamber 191 as piston 18 moves toward the extension side, it can discharge oil from an inner chamber 196, which is at least a part of passage 201, to lower chamber 20 in cylinder 2 via notch 178 formed in elastic body 172, outer chamber 197, and communicating passage 195. Furthermore, when valve disc 171 undergoes this first displacement, it can discharge oil from outer chamber 197, which is at least a part of passage 201, to lower chamber 20 in cylinder 2 via communicating passage 195.

[0084] The frequency sensitive mechanism 130 also has a stopper member 188. When the valve disc 171 undergoes a second displacement greater than the first displacement, the stopper member 188 closes the notch 178 of the elastic body 172, thereby forming a closed inner chamber 196 between the inside of the passage 201 and the valve disc 171, as shown in FIG. 7. In this state, the stopper member 188 restricts the outward movement of oil in the inner chamber 196. When the valve disc 171 undergoes the second displacement, the partition member 135 closes the inner chamber 196 on one side, resulting in a hydraulic lock state in which further displacement toward the stopper member 188 is restricted.

[0085] 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.

[0086] 4, with the mounting shaft portion 28 and the discs 133 and 134 inserted inside, the partition member 135 is placed on the seat portion 154 of the housing main body 131. At this time, the elastic body 172 of the partition 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, the disc 136, disc 137, disc 138, disc 139, disc 140, the plurality of discs 141, and the annular member 144 are placed on the disc 134 and the valve disc 171 of the partition member 135 in this order.

[0087] With the components from the annular member 117 to the annular member 144 arranged on the piston rod 21 in this manner, a nut 211 is threaded 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 inner circumferential sides or the entirety of the annular member 117, the disc 116, the disc 115, the plurality of discs 114, the plurality of discs 113, the disc 112, the disc 111, the piston 18, the disc 51, the damping valve 52, the disc 53, the disc 54, the pilot case 55, the disc 56, the disc 57, the plurality of discs 58, the disc 59, the disc 60, the housing main body 131, the disc 132, the disc 133, the disc 134, the disc 136, the disc 137, the disc 138, the disc 139, the disc 140, the plurality of discs 141, and the annular member 144 are sandwiched between the shaft step portion 29 of the piston rod 21 and the nut 211 and clamped in the axial direction. At this time, the inner peripheral side of the partitioning member 135 is not clamped in the axial direction. In this state, the valve disc 171 of the partitioning member 135 abuts against the seat portion 154 of the housing main body 131 and the disc 136 of the support member 185. Also, in this state, the protruding portion 182 of the abutting portion 176 of the partitioning member 135 abuts against the disc 141 of the stopper member 188 with an interference fit.

[0088] 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.

[0089] 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 .

[0090] 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.

[0091] Next, the main operation of the shock absorber 1 will be described.

[0092] "When it is assumed that the frequency sensitive mechanism 130 does not act during the extension stroke, and only the extension side damping force mechanism 41 and the damping force mechanism 110 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 from the upper chamber 19 flows into the lower chamber 20 via the passage 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.

[0093] 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 passage 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 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 the piston speed is lower than when the piston speed is less than the first predetermined value.

[0094] 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 passage 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 passage 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 passage 43 through between the damping valve 52 and the valve seat portion 48 to the lower chamber 20. Therefore, when the piston speed is 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 greater than the first predetermined value and less than the second predetermined value.

[0095] "Assuming that the frequency sensitive mechanism 130 does not operate during the compression stroke and only the compression side damping force mechanism 42 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 passage 44 shown in FIG. 2 and the fixed orifice 123 of the disc valve 122. 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.

[0096] When the piston speed becomes faster than the third predetermined value, the oil introduced from the lower chamber 20 into the passage 44 opens the disc valve 122 and flows between the disc valve 122 and the valve seat 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 in response to an increase in the piston speed is lower than when the piston speed is less than the third predetermined value.

[0097] "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.

[0098] 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 passage 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 partitioning member 135, which has been in contact with the seat portion 154 and the disc 136 of the support member 185, is deformed by the pressure load in a tapered shape with its outer periphery tapered away from the seat portion 154, with the contact point with the disc 136 serving as a fulcrum. At this time, the partitioning member 135 compresses and deforms mainly the protruding portion 182 of the contact portion 176 that is in contact with the stopper member 188.

[0099] Here, during the extension stroke when the piston frequency is high, the stroke of piston 18 is small. As a result, the amount of oil introduced from upper chamber 19 into variable chamber 191 via passage 43, orifice 82, rod chamber 83, and orifice 162 is small. Therefore, although valve disc 171 of partition member 135 deforms as described above due to the pressure load, it does not deform to near its limit.

[0100] Therefore, during the extension stroke when the piston frequency is high, the valve disc 171 of the partition 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 flowing from the upper chamber 19 through the 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 damping force mechanism 110. Additionally, the flow rate of hydraulic fluid flowing from the passage 43 to the lower chamber 20, opening the damping force 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 damping force mechanism 41 to open. These factors result in a softer damping force on the extension side. Here, the inner circumferential side of the partitioning member 135 is separated from the disk 132 and is supported only on one side by the disk 136. For this reason, the partitioning member 135 is likely to deform so that the inner circumferential side approaches the disk 132. Therefore, the partitioning member 135 is easily compressed and deformed, mainly at the protruding portion 182 of the abutting portion 176 on the outer circumferential side.

[0101] During the extension stroke, as described above, the valve disc 171 of the partition 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 185 serving as the fulcrum. In the initial stage of this deformation, the valve disc 171 itself deforms, and compresses and deforms mainly the protruding portion 182 of the abutting portion 176 that abuts against the disc 141 of the stopper member 188.

[0102] As the deformation of the valve disc 171 toward the stopper member 188 progresses, the valve disc 171 itself deforms further and further compresses and deforms, mainly the protruding portion 182 of the abutment portion 176. At the same time, the valve disc 171 abuts against the outer periphery of the disc 137 of the support member 185, deforming the outer periphery of the disc 137 in a tapered shape toward the stopper member 188.

[0103] As the deformation of valve disc 171 toward stopper member 188 progresses, valve disc 171 itself deforms further and further compresses and deforms mainly protruding portion 182 of abutment portion 176. At the same time, valve disc 171 deforms the outer periphery of disc 137 and the outer periphery of disc 138 of support member 185 in a tapered shape toward stopper member 188.

[0104] However, during the extension stroke when the piston frequency is high, the pressure difference between variable chamber 191 and variable chamber 192 of valve disc 171 is small in partition member 135. Therefore, the displacement of valve disc 171 toward stopper member 188 becomes a first displacement, where the displacement amount is equal to or less than a predetermined value, and notch 178 of abutment portion 176 is not blocked by stopper member 188. Therefore, partition member 135 discharges oil from inner chamber 196 of variable chamber 192 of frequency sensitive mechanism 130 to outer chamber 197 via the passage in notch 178, and discharges oil from outer chamber 197 to lower chamber 20 via communicating passage 195.

[0105] 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 passage 43, the throttle 82, the rod chamber 83, and the throttle 162. Therefore, although hydraulic fluid flows from the upper chamber 19 into the variable chamber 191 at the beginning of the stroke of the piston 18, the valve disc 171 of the partition 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 into the variable chamber 191. This prevents a decrease in the flow rate of hydraulic fluid flowing from the upper chamber 19 through the passage 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 damping force mechanism 110. In addition, the flow rate of hydraulic fluid flowing from the passage 43 to the lower chamber 20 while opening the damping force 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 damping force mechanism 41 to open. As a result, the damping force on the extension stroke 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 185, just as when the piston frequency is high.

[0106] However, at the beginning of the extension stroke when the piston frequency is low and the displacement of the valve disc 171 toward the stopper member 188 is a first displacement where the displacement amount is equal to or less than a predetermined value, the cutout 178 of the abutment portion 176 is not blocked by the stopper member 188. In this state, the partition member 135 discharges oil from the inner chamber 196 of the variable chamber 192 to the outer chamber 197 through the passage in the cutout 178, and also discharges oil from the outer chamber 197 to the lower chamber 20 through the communicating passage 195.

[0107] On the other hand, after the initial stage of the extension stroke when the piston frequency is low, the pressure difference between variable chamber 191 and variable chamber 192 increases, increasing the pressure load on valve disc 171. This causes the valve disc 171 to displace toward stopper member 188, resulting in a second displacement exceeding a predetermined value. As a result, the notch 178 of the abutment portion 176 is closed by stopper member 188, as shown in FIG. 7 . In this state, partition member 135 prevents oil from the inner chamber 196 of variable chamber 192 from discharging to the outer chamber 197 through the passage in notch 178. With inner chamber 196 closed in this manner, the pressure in inner chamber 196 increases in conjunction with the increase in pressure in variable chamber 191. This prevents the pressure difference between the variable chamber 191 side and the variable chamber 192 side of the valve disc 171 from increasing. This particularly prevents the inner peripheral side of the valve disc 171 from deforming too much and increasing stress on the inner peripheral side.

[0108] During the compression stroke, the pressure in the lower chamber 20 increases, but the valve disc 171 of the partitioning 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 passage 44, passing through the damping force 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 a predetermined value or more, the inner peripheral side of the valve disc 171 of the partitioning 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, the variable chamber 192, the variable chamber 191, the throttle 162, the rod chamber 83, the throttle 82, and the passage 43. In this way, by opening the check valve 205, the pressure difference between the variable chamber 192 side and the variable chamber 191 side of the valve disc 171 of the partitioning member 135 is suppressed. Therefore, excessive bending of the valve disc 171 is suppressed.

[0109] The aforementioned Patent Document 1 discloses a shock absorber equipped with a partition disk that partitions a passage. The partition disk of this shock absorber includes a flexible, circular, flat, perforated disk made of a metal material with a constant thickness, and an elastic member made of a rubber material fixed to the outer periphery of the disk. The partition disk has stopper portions of the elastic member intermittently formed in the circumferential direction of the disk, which serves as a valve member. In other words, the grooves between adjacent stopper portions in the circumferential direction of the partition disk have the disk, which serves as the valve member, at their bottoms. With this structure, the pressure difference between both sides of the valve member increases, which may reduce the durability of the valve member.

[0110] In the shock absorber 1 of the first embodiment, a frequency sensitive mechanism 130 that is provided in a passage 201 and generates a damping force has a valve disc 171 that is a valve member. When the valve disc 171 undergoes a first displacement due to oil flowing in as the piston 18 moves toward the extension side, the oil in an inner chamber 196 in the passage 201 can be discharged to the lower chamber 20 in the cylinder 2 via a notch 178 formed in the elastic body 172, an outer chamber 197, and a communication passage 195. The frequency sensitive mechanism 130 also has a stopper member 188. When the valve disc 171 undergoes a second displacement that is larger than the first displacement, the stopper member 188 closes the notch 178 of the elastic body 172, thereby forming a closed inner chamber 196 between the passage 201 and the valve disc 171. In this state, the stopper member 188 restricts the movement of oil in the inner chamber 196. In this way, by restricting the movement of oil inside the inner chamber 196 when the valve disc 171 undergoes a second displacement that is larger than the first displacement, when the pressure in the variable chamber 191 on the opposite side of the valve disc 171 from the inner chamber 196 increases, the pressure inside the inner chamber 196 can be increased accordingly. This makes it possible to prevent the pressure difference between both sides of the valve disc 171 from becoming too large. Therefore, the shock absorber 1 can improve the durability of the valve disc 171, which is the valve member.

[0111] Furthermore, in the shock absorber 1, the elastic body 172 is provided integrally with the valve disc 171, which is the valve member, and therefore an increase in the number of parts can be suppressed.

[0112] [Second embodiment] Next, the second embodiment will be described, focusing on the differences from the first embodiment, mainly with reference to Fig. 8. Note that parts common to the first embodiment will be designated by the same names and symbols.

[0113] 8, in the second embodiment, a partitioning member 135A that is partially different from the partitioning member 135 is provided in place of the partitioning member 135. The partitioning member 135A has an elastic body 172A that is partially different from the elastic body 172 in place of the elastic body 172. The elastic body 172A has an abutting portion 176A that is partially different from the abutting portion 176 in place of the abutting portion 176. The abutting portion 176A has a notch 178A that is partially different from the notch 178 in place of the notch 178. The elastic body 172A has a protrusion 182A that is partially different from the protrusion 182 in place of the protrusion 182.

[0114] The notch 178A is groove-shaped and recessed from the tip of the abutting portion 176A on the opposite side from the seal portion 175 toward the seal portion 175 in the axial direction of the partitioning member 135A. The notch 178A penetrates the abutting portion 176A in the radial direction of the abutting portion 176A. The abutting portion 176A has a plurality of notches 178A of the same shape provided at equal intervals in the circumferential direction of the partitioning member 135A. The bottom of the notch 178A on the seal portion 175 side in the axial direction of the partitioning member 135A is curved in an arc shape when viewed in the radial direction of the partitioning member 135A.

[0115] The protrusion 182A protrudes from the main body portion 181 toward the opposite side to the seal portion 175 in the axial direction of the partitioning member 135A. The protrusion 182A is formed between adjacent notches 178A in the circumferential direction of the partitioning member 135A. The abutting portion 176A is provided with the same number of protrusions 182A of the same shape as the notches 178A, spaced equally apart in the circumferential direction of the partitioning member 135A. The protrusions 182A are convex and protrude from the main body portion 181 toward the opposite side to the seal portion 175 in the axial direction of the partitioning member 135A. The tip of the protrusion 182A, which is on the opposite side to the seal portion 175 in the axial direction of the partitioning member 135A, is curved in an arc shape when viewed in the radial direction of the partitioning member 135A. The length of the protrusion 182A in the circumferential direction of the partition member 135A is equal to the length of the cutout 178A in the circumferential direction of the partition member 135A. The abutting portion 176A is provided with a plurality of cutouts 178A that are smoothly continuous in the circumferential direction.

[0116] Here, when a pressure load is generated in partitioning member 135A due to the pressure difference between variable chamber 191 (see FIG. 4) and variable chamber 192 (see FIG. 4) and valve disc 171 (see FIG. 4) is displaced toward stopper member 188 (see FIG. 4), mainly protruding portion 182A of abutting portion 176A of elastic body 172A that abuts against stopper member 188 (see FIG. 4) is elastically deformed. In partitioning member 135A, when the pressure difference between variable chamber 191 (see FIG. 4) and variable chamber 192 (see FIG. 4) is small and the displacement of valve disc 171 (see FIG. 4) toward stopper member 188 (see FIG. 4) is a first displacement in which the displacement amount is equal to or less than a predetermined value, mainly protruding portion 182A of abutting portion 176A is elastically deformed, but notch 178A is not blocked by stopper member 188 (see FIG. 4).

[0117] On the other hand, in partition member 135A, the pressure difference between variable chamber 191 (see FIG. 4) and variable chamber 192 (see FIG. 4) increases, the pressure load increases, and the valve disc 171 (see FIG. 4) is displaced toward stopper member 188 (see FIG. 4) in a second displacement where the displacement amount exceeds a predetermined value, and mainly protrusion 182A of abutment portion 176A undergoes large elastic deformation, and notch 178A is blocked by stopper member 188 (see FIG. 4).

[0118] In other words, stopper member 188 (see FIG. 4) does not close notch 178A of contact portion 176A when valve disc 171 (see FIG. 4) is displaced toward stopper member 188 (see FIG. 4) by a first displacement amount equal to or less than a predetermined value. On the other hand, stopper member 188 (see FIG. 4) closes notch 178A of contact portion 176A when valve disc 171 (see FIG. 4) is displaced toward stopper member 188 (see FIG. 4) by a second displacement amount equal to or greater than a predetermined value.

[0119] During the extension stroke when the piston frequency is high and during the early stage of the extension stroke when the piston frequency is low, when the displacement of the valve disc 171 (see FIG. 4) toward the stopper member 188 (see FIG. 4) is a first displacement in which the displacement amount is equal to or less than a predetermined value, the partitioning member 135A does not block the notch 178A of the abutting portion 176A with the stopper member 188 (see FIG. 4). In this state, the partitioning member 135A discharges oil from the inner chamber 196 (see FIG. 4) of the variable chamber 192 (see FIG. 4) to the outer chamber 197 (see FIG. 4) through the passage in the notch 178A, and also discharges oil from the outer chamber 197 (see FIG. 4) to the lower chamber 20 (see FIG. 4) through the communication passage 195 (see FIG. 4). This causes the valve disc 171 (see FIG. 4) to deform immediately, instantly expanding the variable chamber 191.

[0120] On the other hand, after the above-mentioned initial stage of the extension stroke when the piston frequency is low, the displacement of the partitioning member 135A toward the stopper member 188 (see FIG. 4) of the valve disc 171 (see FIG. 4) reaches a second displacement where the displacement amount exceeds a predetermined value. Then, mainly the protruding portion 182A of the abutting portion 176A undergoes large elastic deformation, and the notch 178A is closed by the stopper member 188. In this state, the partitioning member 135A does not allow the oil in the inner chamber 196 (see FIG. 4) of the variable chamber 192 (see FIG. 4) to be discharged into the outer chamber 197 (see FIG. 4). In this state where inner chamber 196 (see FIG. 4) is closed, the pressure in inner chamber 196 (see FIG. 4) increases as the pressure in variable chamber 191 (see FIG. 4) increases, and therefore, valve disc 171 (see FIG. 4) prevents the pressure difference between variable chamber 191 (see FIG. 4) and variable chamber 192 (see FIG. 4) from increasing. Therefore, in the second embodiment as well, the durability of valve disc 171 (see FIG. 4) can be improved.

[0121] [Third embodiment] Next, the third embodiment will be described, focusing on the differences from the first embodiment, mainly with reference to Fig. 9. Note that parts common to the first embodiment will be designated by the same names and symbols.

[0122] 9, the third embodiment has a partitioning member 135B that is partially different from the partitioning member 135 in place of the partitioning member 135. The partitioning member 135B has an elastic body 172B that is partially different from the elastic body 172 in place of the elastic body 172. The elastic body 172B has an abutting portion 176B that is partially different from the abutting portion 176 in place of the abutting portion 176. The abutting portion 176B has a notch 178B that is partially different from the notch 178 in place of the notch 178. The elastic body 172B has a protrusion 182B that is partially different from the protrusion 182 in place of the protrusion 182.

[0123] The notch 178B is a groove-like recess that extends from the tip of the abutting portion 176B on the opposite side from the seal portion 175 toward the seal portion 175 in the axial direction of the partitioning member 135B. The notch 178B penetrates the abutting portion 176B in the radial direction of the abutting portion 176B. The abutting portion 176B is provided with a plurality of the same shaped notches 178B at equal intervals in the circumferential direction of the partitioning member 135B.

[0124] The cutout portion 178B has a bottom surface portion 179B and a pair of wall surface portions 180B. The bottom surface portion 179B is flat and extends perpendicular to the axial direction of the partitioning member 135B. The bottom surface portion 179B of the cutout portion 178B is formed in the main body portion 181. The pair of wall surface portions 180B are inclined at the same angle relative to the bottom surface portion 179B. The distance between the pair of wall surface portions 180B in the circumferential direction of the partitioning member 135B increases as the distance between the pair of wall surface portions 180B increases from the bottom surface portion 179B in the axial direction of the partitioning member 135B.

[0125] The protruding portion 182B protrudes from the main body portion 181 on the opposite side to the seal portion 175 in the axial direction of the partition member 135B. The protrusions 182B are formed between adjacent notches 178B in the circumferential direction of the partitioning member 135B. The abutting portion 176B is provided with the same number of protrusions 182B as the notches 178B, and are equally spaced apart in the circumferential direction of the partitioning member 135B.

[0126] The length of the cutout portion 178B in the circumferential direction of the partition member 135B is longer than the length of the protrusion 182B in the circumferential direction of the partition member 135B. The cutout portion 178B is arc-shaped when viewed in the axial direction of the partition member 135B. A wall surface portion 180B of the cutout portion 178B is formed on the protrusion 182B. The wall surface portion 180B and the wall surface portion 180B that are adjacent to each other and continuous in the circumferential direction of the partition member 135B are formed on the protrusion 182B.

[0127] Here, when a pressure load is generated in partitioning member 135B due to the pressure difference between variable chamber 191 (see FIG. 4) and variable chamber 192 (see FIG. 4) and valve disc 171 (see FIG. 4) is displaced toward stopper member 188 (see FIG. 4), mainly protruding portion 182B of abutting portion 176B of elastic body 172B that abuts against stopper member 188 (see FIG. 4) is elastically deformed. In partitioning member 135B, when the pressure difference between variable chamber 191 (see FIG. 4) and variable chamber 192 (see FIG. 4) is small and the displacement of valve disc 171 (see FIG. 4) toward stopper member 188 (see FIG. 4) is a first displacement in which the displacement amount is equal to or less than a predetermined value, mainly protruding portion 182B of abutting portion 176B is elastically deformed, but notch 178B is not blocked by stopper member 188 (see FIG. 4).

[0128] On the other hand, in partition member 135B, the pressure difference between variable chamber 191 (see FIG. 4) and variable chamber 192 (see FIG. 4) increases, the pressure load increases, and the valve disc 171 (see FIG. 4) is displaced toward stopper member 188 (see FIG. 4) in a second displacement where the displacement amount exceeds a predetermined value, and mainly protrusion 182B of abutment portion 176B undergoes large elastic deformation, and notch 178B is blocked by stopper member 188 (see FIG. 4).

[0129] In other words, stopper member 188 (see FIG. 4) does not close notch 178B of contact portion 176B when valve disc 171 (see FIG. 4) is displaced toward stopper member 188 (see FIG. 4) by a first displacement amount equal to or less than a predetermined value. On the other hand, stopper member 188 (see FIG. 4) closes notch 178B of contact portion 176B when valve disc 171 (see FIG. 4) is displaced toward stopper member 188 (see FIG. 4) by a second displacement amount equal to or greater than a predetermined value.

[0130] During the extension stroke when the piston frequency is high and during the early stage of the extension stroke when the piston frequency is low, when the displacement of the valve disc 171 (see FIG. 4) toward the stopper member 188 (see FIG. 4) is a first displacement in which the displacement amount is equal to or less than a predetermined value, the partitioning member 135B does not block the notch 178B of the abutting portion 176B with the stopper member 188 (see FIG. 4). In this state, the partitioning member 135B discharges oil from the inner chamber 196 (see FIG. 4) of the variable chamber 192 (see FIG. 4) to the outer chamber 197 (see FIG. 4) through the passage in the notch 178B, and also discharges oil from the outer chamber 197 (see FIG. 4) to the lower chamber 20 (see FIG. 4) through the communication passage 195 (see FIG. 4). This causes the valve disc 171 (see FIG. 4) to deform immediately, instantly expanding the variable chamber 191.

[0131] On the other hand, after the initial stage of the extension stroke when the piston frequency is low, the displacement of the partitioning member 135B toward the stopper member 188 (see FIG. 4) of the valve disc 171 (see FIG. 4) reaches a second displacement where the displacement amount exceeds a predetermined value. As a result, mainly the protruding portion 182B of the abutting portion 176B undergoes large elastic deformation, and the cutout portion 178B is closed by the stopper member 188. In this state, the partitioning member 135B does not allow the oil in the inner chamber 196 (see FIG. 4) of the variable chamber 192 (see FIG. 4) to be discharged into the outer chamber 197 (see FIG. 4). In this state where inner chamber 196 (see FIG. 4) is closed, the pressure in inner chamber 196 (see FIG. 4) increases as the pressure in variable chamber 191 (see FIG. 4) increases, and therefore, valve disc 171 (see FIG. 4) prevents the pressure difference between variable chamber 191 (see FIG. 4) and variable chamber 192 (see FIG. 4) from increasing. Therefore, in the third embodiment as well, the durability of valve disc 171 (see FIG. 4) can be improved.

[0132] [Fourth embodiment] Next, the fourth embodiment will be described, focusing on the differences from the first embodiment, mainly with reference to Fig. 10. Note that parts common to the first embodiment will be designated by the same names and symbols.

[0133] 10, the fourth embodiment has a partitioning member 135C that is partially different from the partitioning member 135 in place of the partitioning member 135. The partitioning member 135C has an elastic body 172C that is partially different from the elastic body 172 in place of the elastic body 172. The elastic body 172C has an abutting portion 176C that is partially different from the abutting portion 176 in place of the abutting portion 176. The abutting portion 176C has a notch 178C that is partially different from the notch 178 in place of the notch 178. The elastic body 172C has a protruding portion 182C that is partially different from the protruding portion 182 in place of the protruding portion 182.

[0134] The notch 178C is a groove-shaped recess that extends from the tip of the abutting portion 176C on the opposite side from the seal portion 175 toward the seal portion 175 in the axial direction of the partitioning member 135C. The notch 178C penetrates the abutting portion 176C in the radial direction of the abutting portion 176C. The abutting portion 176C has a plurality of notches 178C of the same shape that are equally spaced apart in the circumferential direction of the partitioning member 135C. When viewed in the radial direction of the partitioning member 135C, the entire notch 178C is curved in an arc shape.

[0135] The protruding portion 182C protrudes from the main body portion 181 on the opposite side to the seal portion 175 in the axial direction of the partition member 135C. The protrusions 182C are formed between adjacent notches 178C in the circumferential direction of the partitioning member 135C. The abutting portion 176C is provided with the same number of protrusions 182C of the same shape as the notches 178C, spaced equally apart in the circumferential direction of the partitioning member 135C. The length of the protrusions 182C in the circumferential direction of the partitioning member 135C is longer than the length of the notches 178C in the circumferential direction of the partitioning member 135C.

[0136] Here, when a pressure load is generated in partitioning member 135C due to the pressure difference between variable chamber 191 (see FIG. 4) and variable chamber 192 (see FIG. 4) and valve disc 171 (see FIG. 4) is displaced toward stopper member 188 (see FIG. 4), mainly protruding portion 182C of abutting portion 176C of elastic body 172C that abuts against stopper member 188 (see FIG. 4) is elastically deformed. In partitioning member 135C, when the pressure difference between variable chamber 191 (see FIG. 4) and variable chamber 192 (see FIG. 4) is small and the displacement of valve disc 171 (see FIG. 4) toward stopper member 188 (see FIG. 4) is a first displacement in which the displacement amount is equal to or less than a predetermined value, mainly protruding portion 182C of abutting portion 176C is elastically deformed, but notch 178C is not blocked by stopper member 188 (see FIG. 4).

[0137] On the other hand, in partition member 135C, the pressure difference between variable chamber 191 (see FIG. 4) and variable chamber 192 (see FIG. 4) increases, the pressure load increases, and the valve disc 171 (see FIG. 4) is displaced toward stopper member 188 (see FIG. 4) in a second displacement where the displacement amount exceeds a predetermined value, and mainly protrusion 182C of abutment portion 176C undergoes large elastic deformation, and cutout portion 178C is blocked by stopper member 188 (see FIG. 4).

[0138] In other words, stopper member 188 (see FIG. 4) does not close notch 178C of contact portion 176C when valve disc 171 (see FIG. 4) is displaced toward stopper member 188 (see FIG. 4) by a first displacement amount equal to or less than a predetermined value. On the other hand, stopper member 188 (see FIG. 4) closes notch 178C of contact portion 176C when valve disc 171 (see FIG. 4) is displaced toward stopper member 188 (see FIG. 4) by a second displacement amount equal to or greater than a predetermined value.

[0139] During the extension stroke when the piston frequency is high and during the early stage of the extension stroke when the piston frequency is low, when the displacement of the valve disc 171 (see FIG. 4) toward the stopper member 188 (see FIG. 4) is a first displacement in which the displacement amount is equal to or less than a predetermined value, the partitioning member 135C does not block the notch 178C of the abutting portion 176C with the stopper member 188 (see FIG. 4). In this state, the partitioning member 135C discharges oil from the inner chamber 196 (see FIG. 4) of the variable chamber 192 (see FIG. 4) to the outer chamber 197 (see FIG. 4) through the passage in the notch 178C, and also discharges oil from the outer chamber 197 (see FIG. 4) to the lower chamber 20 (see FIG. 4) through the communication passage 195 (see FIG. 4). This causes the valve disc 171 (see FIG. 4) to deform immediately, instantly expanding the variable chamber 191.

[0140] On the other hand, after the initial stage of the extension stroke when the piston frequency is low, the displacement of the partitioning member 135C toward the stopper member 188 (see FIG. 4) of the valve disc 171 (see FIG. 4) reaches a second displacement where the displacement amount exceeds a predetermined value. As a result, mainly the protruding portion 182C of the abutting portion 176C undergoes large elastic deformation, and the cutout portion 178C is closed by the stopper member 188. In this state, the partitioning member 135C does not allow the oil in the inner chamber 196 (see FIG. 4) of the variable chamber 192 (see FIG. 4) to be discharged into the outer chamber 197 (see FIG. 4). In this state where inner chamber 196 (see FIG. 4) is closed, the pressure in inner chamber 196 (see FIG. 4) increases as the pressure in variable chamber 191 (see FIG. 4) increases, and therefore, valve disc 171 (see FIG. 4) prevents the pressure difference between variable chamber 191 (see FIG. 4) and variable chamber 192 (see FIG. 4) from increasing. Therefore, in the fourth embodiment as well, the durability of valve disc 171 (see FIG. 4) can be improved.

[0141] [Fifth embodiment] Next, the fifth embodiment will be described, focusing on the differences from the first embodiment, mainly with reference to Fig. 11. Note that parts common to the first embodiment will be designated by the same names and symbols.

[0142] 11 , the fifth embodiment has a partitioning member 135D that is partially different from the partitioning member 135, instead of the partitioning member 135. The partitioning member 135D has an elastic body 172D that is partially different from the elastic body 172, instead of the elastic body 172. The elastic body 172D has an abutting portion 176D that is partially different from the abutting portion 176, instead of the abutting portion 176. The abutting portion 176D has a notch 178D that is partially different from the notch 178, instead of the notch 178. The elastic body 172D has a protrusion 182D that is partially different from the protrusion 182, instead of the protrusion 182.

[0143] The protrusion 182D protrudes from the main body portion 181 on the opposite side of the seal portion 175 in the axial direction of the partition member 135D. A plurality of protrusions 182D of the same shape are provided on the abutting portion 176D at equal intervals in the circumferential direction of the partition member 135D. When viewed in the radial direction of the partition member 135D, the entire protrusion 182D is curved in an arc shape.

[0144] The notch 178D is a groove-like recess that extends from the tip of the abutting portion 176D on the side opposite the seal portion 175 toward the seal portion 175 in the axial direction of the partitioning member 135D. The notch 178D penetrates the abutting portion 176D in the radial direction of the abutting portion 176D. The abutting portion 176D has the same shape as the protrusions 182D, and the same number of notches 178D are provided at equal intervals in the circumferential direction of the partitioning member 135D.

[0145] The cutout portion 178D has a bottom surface portion 179D and a pair of wall surface portions 180D. The bottom surface portion 179D is flat and extends perpendicular to the axial direction of the partitioning member 135D. The bottom surface portion 179D of the cutout portion 178D is formed in the main body portion 181. The wall surface portions 180D adjacent to each other in the circumferential direction of the partitioning member 135D are continuously formed into a single protrusion portion 182D. The length of the cutout portion 178D in the circumferential direction of the partitioning member 135D is longer than that of the protrusion portions 182D.

[0146] Here, when a pressure load is generated in partitioning member 135D due to the pressure difference between variable chamber 191 (see FIG. 4) and variable chamber 192 (see FIG. 4) and valve disc 171 (see FIG. 4) is displaced toward stopper member 188 (see FIG. 4), mainly protruding portion 182D of abutting portion 176D that abuts against stopper member 188 (see FIG. 4) of elastic body 172D elastically deforms. In partitioning member 135D, when the pressure difference between variable chamber 191 (see FIG. 4) and variable chamber 192 (see FIG. 4) is small and the displacement of valve disc 171 (see FIG. 4) toward stopper member 188 (see FIG. 4) is a first displacement in which the displacement amount is equal to or less than a predetermined value, mainly protruding portion 182D of abutting portion 176D elastically deforms, but notch 178D is not blocked by stopper member 188 (see FIG. 4).

[0147] On the other hand, in partition member 135D, the pressure difference between variable chamber 191 (see FIG. 4) and variable chamber 192 (see FIG. 4) increases, the pressure load increases, and the valve disc 171 (see FIG. 4) is displaced toward stopper member 188 (see FIG. 4) in a second displacement where the displacement amount exceeds a predetermined value, and mainly protrusion 182D of abutment portion 176D undergoes large elastic deformation, and notch 178D is blocked by stopper member 188 (see FIG. 4).

[0148] In other words, stopper member 188 (see FIG. 4) does not close notch 178D of contact portion 176D when valve disc 171 (see FIG. 4) is displaced toward stopper member 188 (see FIG. 4) by a first displacement amount equal to or less than a predetermined value. On the other hand, stopper member 188 (see FIG. 4) closes notch 178D of contact portion 176D when valve disc 171 (see FIG. 4) is displaced toward stopper member 188 (see FIG. 4) by a second displacement amount equal to or greater than a predetermined value.

[0149] During the extension stroke when the piston frequency is high and during the early stage of the extension stroke when the piston frequency is low, when the displacement of the valve disc 171 (see FIG. 4) toward the stopper member 188 (see FIG. 4) is a first displacement in which the displacement amount is equal to or less than a predetermined value, the partitioning member 135D does not block the notch 178D of the abutting portion 176D with the stopper member 188 (see FIG. 4). In this state, the partitioning member 135D discharges oil from the inner chamber 196 (see FIG. 4) of the variable chamber 192 (see FIG. 4) to the outer chamber 197 (see FIG. 4) through the passage in the notch 178D, and also discharges oil from the outer chamber 197 (see FIG. 4) to the lower chamber 20 (see FIG. 4) through the communication passage 195 (see FIG. 4). This causes the valve disc 171 (see FIG. 4) to deform immediately, instantly expanding the variable chamber 191.

[0150] On the other hand, after the initial stage of the extension stroke when the piston frequency is low, the displacement of the partitioning member 135D toward the stopper member 188 (see FIG. 4) of the valve disc 171 (see FIG. 4) reaches a second displacement where the displacement amount exceeds a predetermined value. As a result, mainly the protruding portion 182D of the abutting portion 176D undergoes large elastic deformation, and the cutout portion 178D is closed by the stopper member 188. In this state, the partitioning member 135D does not allow the oil in the inner chamber 196 (see FIG. 4) of the variable chamber 192 (see FIG. 4) to be discharged into the outer chamber 197 (see FIG. 4). In this state where inner chamber 196 (see FIG. 4) is closed, the pressure in inner chamber 196 (see FIG. 4) increases as the pressure in variable chamber 191 (see FIG. 4) increases, and therefore, valve disc 171 (see FIG. 4) prevents the pressure difference between variable chamber 191 (see FIG. 4) and variable chamber 192 (see FIG. 4) from increasing. Therefore, in the fifth embodiment as well, the durability of valve disc 171 (see FIG. 4) can be improved.

[0151] [Sixth embodiment] Next, the sixth embodiment will be described, focusing on the differences from the first embodiment, mainly with reference to Fig. 12. Note that parts common to the first embodiment will be designated by the same names and symbols.

[0152] 12, the sixth embodiment has a partitioning member 135E that is partially different from the partitioning member 135, instead of the partitioning member 135. The partitioning member 135E has an elastic body 172E that is partially different from the elastic body 172, instead of the elastic body 172. The elastic body 172E has an abutting portion 176E that is partially different from the abutting portion 176, instead of the abutting portion 176. The abutting portion 176E has a notch 178E that is partially different from the notch 178, instead of the notch 178. The elastic body 172E has a protruding portion 182E that is partially different from the protruding portion 182, instead of the protruding portion 182.

[0153] The notch 178E is a groove-like recess that extends from the tip of the abutting portion 176E on the side opposite the seal portion 175 toward the seal portion 175 in the axial direction of the partitioning member 135E. The notch 178E penetrates the abutting portion 176E in the radial direction of the abutting portion 176E. The abutting portion 176E is provided with a plurality of the same shaped notches 178E at equal intervals in the circumferential direction of the partitioning member 135E.

[0154] The cutout portion 178E has a bottom surface portion 179E and a pair of wall surface portions 180E. The bottom surface portion 179E is flat and extends perpendicular to the axial direction of the partitioning member 135E. The bottom surface portion 179E of the cutout portion 178E is formed in the main body portion 181. The pair of wall surface portions 180E are inclined at the same angle with respect to the bottom surface portion 179E. The pair of wall surface portions 180E are spaced apart from each other in the circumferential direction of the partitioning member 135E as they move away from the bottom surface portion 179E in the axial direction of the partitioning member 135E.

[0155] The protruding portion 182E protrudes from the main body portion 181 on the opposite side to the seal portion 175 in the axial direction of the partition member 135E. The protrusions 182E are formed between adjacent notches 178E in the circumferential direction of the partitioning member 135E. The abutting portion 176E is provided with the same number of protrusions 182E of the same shape as the notches 178E, spaced equally apart in the circumferential direction of the partitioning member 135E. The protrusions 182E are provided with wall surface portions 180E on both sides in the circumferential direction of the partitioning member 135E, spaced apart in the circumferential direction of the partitioning member 135E.

[0156] The length of the notch 178E in the circumferential direction of the partition member 135E is longer than the length of the protrusion 182E in the circumferential direction of the partition member 135E. The notch 178E has an arc shape when viewed in the axial direction of the partition member 135E.

[0157] Here, when a pressure load is generated in partitioning member 135E due to the pressure difference between variable chamber 191 (see FIG. 4) and variable chamber 192 (see FIG. 4) and valve disc 171 (see FIG. 4) is displaced toward stopper member 188 (see FIG. 4), mainly protruding portion 182E of abutting portion 176E that abuts against stopper member 188 (see FIG. 4) of elastic body 172E elastically deforms. In partitioning member 135E, when the pressure difference between variable chamber 191 (see FIG. 4) and variable chamber 192 (see FIG. 4) is small and the displacement of valve disc 171 (see FIG. 4) toward stopper member 188 (see FIG. 4) is a first displacement in which the displacement amount is equal to or less than a predetermined value, mainly protruding portion 182E of abutting portion 176E elastically deforms, but notch 178E is not blocked by stopper member 188 (see FIG. 4).

[0158] On the other hand, in partition member 135E, the pressure difference between variable chamber 191 (see FIG. 4) and variable chamber 192 (see FIG. 4) increases, the pressure load increases, and the valve disc 171 (see FIG. 4) is displaced toward stopper member 188 (see FIG. 4) in a second displacement where the displacement amount exceeds a predetermined value, and mainly protrusion 182E of abutment portion 176E undergoes large elastic deformation, and notch 178E is blocked by stopper member 188 (see FIG. 4).

[0159] In other words, stopper member 188 (see FIG. 4) does not close notch 178E of contact portion 176E when valve disc 171 (see FIG. 4) is displaced toward stopper member 188 (see FIG. 4) by a first displacement amount equal to or less than a predetermined value. On the other hand, stopper member 188 (see FIG. 4) closes notch 178E of contact portion 176E when valve disc 171 is displaced toward stopper member 188 (see FIG. 4) by a second displacement amount equal to or greater than the predetermined value.

[0160] During the extension stroke when the piston frequency is high and during the early stage of the extension stroke when the piston frequency is low, when the displacement of the valve disc 171 (see FIG. 4) toward the stopper member 188 (see FIG. 4) is a first displacement in which the displacement amount is equal to or less than a predetermined value, the partitioning member 135E does not block the notch 178E of the abutting portion 176E with the stopper member 188 (see FIG. 4). In this state, the partitioning member 135E discharges oil from the inner chamber 196 (see FIG. 4) of the variable chamber 192 (see FIG. 4) to the outer chamber 197 (see FIG. 4) through the passage in the notch 178E, and discharges oil from the outer chamber 197 (see FIG. 4) to the lower chamber 20 (see FIG. 4) through the communication passage 195 (see FIG. 4). This causes the valve disc 171 (see FIG. 4) to deform immediately, instantly expanding the variable chamber 191.

[0161] On the other hand, after the above-mentioned initial stage of the extension stroke when the piston frequency is low, the displacement of the partitioning member 135E toward the stopper member 188 (see FIG. 4) of the valve disc 171 (see FIG. 4) reaches a second displacement where the displacement amount exceeds a predetermined value. As a result, mainly the protruding portion 182E of the abutting portion 176E undergoes large elastic deformation, and the notch 178E is closed by the stopper member 188. In this state, the partitioning member 135E does not allow the oil in the inner chamber 196 (see FIG. 4) of the variable chamber 192 (see FIG. 4) to be discharged into the outer chamber 197 (see FIG. 4). In this state where inner chamber 196 (see FIG. 4) is closed, the pressure in inner chamber 196 (see FIG. 4) increases as the pressure in variable chamber 191 (see FIG. 4) increases, and therefore, valve disc 171 (see FIG. 4) prevents the pressure difference between variable chamber 191 (see FIG. 4) and variable chamber 192 (see FIG. 4) from increasing. Therefore, in the sixth embodiment as well, the durability of valve disc 171 (see FIG. 4) can be improved.

[0162] In the first to sixth embodiments, the abutment portions 176, 176A-176E of the elastic bodies 172, 172A-172E are provided integrally with the valve disc 171. However, this is not limiting. For example, the abutment portions 176, 176A-176E may not be provided on the valve disc 171, but may be provided integrally with the disc 141 that is closest to the valve disc 171 and faces the valve disc 171 among the multiple discs 141 that make up the stopper member 188. In this case, the abutment portions 176, 176A-176E, which are elastic bodies, are provided on the valve disc 171 side of this disc 141, with the main body portion 181 provided on the disc 141 side and the cutout portions 178, 178A-178E and the protrusions 182, 182A-182E provided on the side that abuts against the valve disc 171.

[0163] 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]

[0164] 1... shock absorber, 2... cylinder, 18... piston, 19... upper chamber (chamber), 20... lower chamber (chamber), 21... piston rod, 41... damping force mechanism (first damping force mechanism), 43... passage (first passage), 130... frequency sensitive mechanism (second damping force mechanism), 171... valve disc (valve member), 172, 172A to 172E... elastic body, 178, 178A to 178E... notch portion, 188... stopper member (restriction portion), 196... inner chamber (pressure chamber), 201... passage (second passage).

Claims

1. a cylinder in which a working fluid is sealed; a piston slidably fitted in the cylinder and dividing the interior of the cylinder into two chambers; a piston rod connected to the piston and extending to the outside of the cylinder; a first passage that communicates the two chambers by movement of the piston so that the working fluid can flow between them; a second passage provided in parallel with the first passage and configured to allow the working fluid of at least one of the two chambers to flow therein by movement of the piston; a first damping force mechanism provided in the first passage and configured to generate a damping force; a valve member that is provided in the second passage, partitioning the second passage, and that is capable of discharging at least a portion of the working fluid in the second passage into the cylinder through a notch formed in an elastic body when the working fluid flows in due to movement of the piston, and a limiting portion that forms a closed pressure chamber between the second passage and the valve member by closing the notch when the valve member undergoes a second displacement, thereby limiting the movement of the working fluid in the pressure chamber; and a second damping force mechanism that generates a damping force, the second damping force mechanism having: a valve member that is provided in the second passage, partitioning the second passage, and that is capable of discharging at least a portion of the working fluid in the second passage into the cylinder through a notch formed in an elastic body when the working fluid flows in due to movement of the piston, and a limiting portion that forms a closed pressure chamber between the second passage and the valve member by closing the notch when the valve member undergoes a second displacement, thereby limiting the movement of the working fluid in the pressure chamber; A buffer comprising:

2. The shock absorber according to claim 1, wherein the elastic body is provided integrally with the valve member.

3. The shock absorber according to claim 1, wherein the elastic body is provided on a member facing the valve member.

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