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Abstract

To provide a damper which can suppress the instability of a behavior of a vehicle.SOLUTION: A damper comprises: a first passage 43 and a second passage 175 in which working fluids flow out of one chamber in a cylinder by the movement of a piston 18; a first attenuation force generation mechanism 161 which is arranged at the first passage 43, and generates an attenuation force, and on which a compression force of rubber acts at an operation; pressure chambers 170, 280 arranged in the middle of the second passage 175; a second attenuation force generation mechanism 176 arranged at a passage port 177 for making the pressure chambers 170, 280 communicate with the other chamber 20 in the cylinder; and a third attenuation force generation mechanism 181 which is valve-opened in a region in which its piston speed is lower than those of the first attenuation force generation mechanism 161 and the second attenuation force generation mechanism 176 at upstream sides of the first attenuation force generation mechanism 161 and the second attenuation force generation mechanism 176.SELECTED DRAWING: Figure 3

Description

[Technical Field]

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

[0002] Some shock absorbers have a damping force generating mechanism provided in each of parallel flow paths through which working fluid flows from one chamber to the other chamber as a result of piston movement (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2012-137167 Summary of the Invention [Problem to be solved by the invention]

[0004] It is desirable to use shock absorbers to prevent the vehicle's behavior from becoming unstable.

[0005] Therefore, an object of the present invention is to provide a shock absorber that can prevent the behavior of a vehicle from becoming unstable. [Means for solving the problem]

[0006] In order to achieve the above object, one embodiment of the present invention is configured to include a cylinder filled with working fluid, 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 outside the cylinder, a first passage and a second passage through which working fluid flows from one chamber within the cylinder as the piston moves, a first damping force generating mechanism provided in the first passage to generate a damping force and on which rubber compression force acts when the mechanism is in operation, a pressure chamber provided midway through the second passage, a second damping force generating mechanism provided at a passage opening that connects the pressure chamber to the other chamber within the cylinder, and a third damping force generating mechanism provided upstream of the first damping force generating mechanism and the second damping force generating mechanism, which opens in a range where the piston speed is lower than that of the first damping force generating mechanism and the second damping force generating mechanism. [Effects of the Invention]

[0007] According to the present invention, it is possible to prevent the behavior of the vehicle from becoming unstable. [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 cross-sectional view showing a main part of a shock absorber according to a first embodiment of the present invention. [Figure 3] 1 is a cross-sectional view showing a main part of a shock absorber according to a first embodiment of the present invention. [Figure 4] 1 is a perspective view showing a valve seat member of a shock absorber according to a first embodiment of the present invention. FIG. [Figure 5] FIG. 4 is a cross-sectional view showing a main part of a shock absorber according to a second embodiment of the present invention. [Figure 6] FIG. 2 is a cross-sectional view showing a main part of the shock absorber. 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 4. For ease of explanation, the upper side in Figures 1, 2, 5, and 6 will be referred to as "upper", and the lower side in Figures 1, 2, 5, and 6 will be referred to as "lower".

[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 suspension device for a vehicle, specifically an automobile. The shock absorber 1 is equipped with a cylinder 2. 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.

[0011] The outer cylinder 4 has a body 11 and a bottom 12. The body 11 and the bottom 12 are formed seamlessly as a single unit. The body 11 is cylindrical. The bottom 12 closes the lower part of the body 11.

[0012] The shock absorber 1 is equipped with a piston 18. The piston 18 is inserted into the inner tube 3 of the cylinder 2. The piston 18 is slidably fitted inside the inner tube 3 of the cylinder 2. The piston 18 divides the inner tube 3 into two chambers: a cylinder chamber 19 on one side and a cylinder chamber 20 on the other side. In the axial direction of the cylinder 2, the cylinder chamber 19 is located on the opposite side of the piston 18 from the bottom 12. In the axial direction of the cylinder 2, the cylinder chamber 20 is located closer to the bottom 12 than the piston 18. In the cylinder 2, oil liquid L is sealed in the cylinder chamber 19 and cylinder chamber 20 inside the inner tube 3 as a working fluid. In the cylinder 2, oil liquid L and gas G are sealed in a reservoir chamber 6 between the inner tube 3 and the outer tube 4.

[0013] The shock absorber 1 is equipped with a piston rod 21. One axial end of the piston rod 21 is disposed inside the inner tube 3 of the cylinder 2 and connected to the piston 18. The other axial end of the piston rod 21 extends from the cylinder 2 to the outside of the cylinder 2.

[0014] 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 the direction of increasing the amount of protrusion from the cylinder 2 is the extension stroke, in which the overall length increases. In the shock absorber 1, the stroke in which the piston rod 21 moves in the direction of decreasing the amount of protrusion from the cylinder 2 is the compression stroke, in which the overall length shortens. In the shock absorber 1, the piston 18 moves towards the cylinder chamber 19 during the extension stroke. In the shock absorber 1, the piston 18 moves towards the cylinder chamber 20 during the compression stroke.

[0015] 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. Both the rod guide 22 and the seal member 23 are annular. The piston rod 21 is inserted radially inside the rod guide 22 and the seal member 23. The piston rod 21 slides along the axial direction of each of the rod guide 22 and the seal member 23. The piston rod 21 extends from inside the cylinder 2 to the outside of the cylinder 2 beyond the seal member 23.

[0016] 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. When the piston rod 21 is fitted into the rod guide 22, the piston 18 is fitted into the inner cylinder 3. This causes the central axis of the piston rod 21 to coincide with the central axis of the cylinder 2. The rod guide 22 supports the piston rod 21 so that it can move in the axial direction of the piston rod 21. The outer periphery of the seal member 23 is in close contact with the outer periphery of the piston rod 21. The piston rod 21 moves in the axial direction of the seal member 23 relative to the seal member 23. The seal member 23 prevents the oil liquid L in the inner cylinder 3 and the high-pressure gas G and oil liquid L in the reservoir chamber 6 from leaking to the outside.

[0017] 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 member 26 of the base valve 25 is installed on the bottom 12 of the outer cylinder 4. The base member 26 is positioned radially relative to the outer cylinder 4. The base member 26 has an outer periphery with a smaller diameter at its upper part than at its lower part. The base member 26 fits into the inner periphery of the lower end of the inner cylinder 3 at its smaller diameter upper part. The base member 26 separates the cylinder chamber 20 from the reservoir chamber 6. 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.

[0018] The piston rod 21 has a main shaft portion 27 and an attachment shaft portion 28. The main shaft portion 27 and the attachment shaft portion 28 are both rod-shaped. 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 inside the cylinder 2. The piston 18 is attached to the mounting shaft portion 28. The main shaft portion 27 has a shaft step portion 29. The shaft step 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 shaft step portion 29 widens in a direction perpendicular to the central axis of the piston rod 21.

[0019] A groove 30 is formed on the outer periphery of the mounting shaft portion 28 of the piston rod 21. The groove 30 extends in the axial direction of the mounting shaft portion 28. The groove 30 is formed by cutting out the outer periphery of the mounting shaft portion 28 in a plane parallel to the central axis of the mounting shaft portion 28. The grooves 30 are formed in two locations equidistantly spaced apart in the circumferential direction of the mounting shaft portion 28. A threaded portion 31 is formed on the outer periphery of the mounting shaft portion 28 at an end on the opposite side of the groove 30 from the main shaft portion 27 in the axial direction of the mounting shaft portion 28.

[0020] The shock absorber 1 is connected to the vehicle body with the portion of the piston rod 21 that protrudes from the cylinder 2 located at the top. At the same time, the shock absorber 1 is connected to the wheel side of the vehicle with the mounting bracket 32 ​​fixed to the body portion 11 of the outer cylinder 4 located at the bottom. If the shock absorber 1 is a single-cylinder type, it is also possible to connect the cylinder 2 side to the vehicle body and the piston rod 21 to the wheel side.

[0021] 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 sliding member 36 is made of synthetic resin and has an annular band shape. The sliding member 36 is integrally attached to the outer circumferential surface of the piston body 35. The piston 18 has the piston body 35 fitted onto the mounting shaft portion 28 of the piston rod 21. The piston 18 slides relative to the inner cylinder 3 with the sliding member 36 in contact with the inner cylinder 3.

[0022] 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 extends in the axial direction of the piston body 35. A plurality of the passage holes 37 are formed in the piston body 35 at intervals in the circumferential direction of the piston body 35. The passage hole 39 extends in the axial direction of the piston body 35. A plurality of the passage holes 39 are formed in the piston body 35 at intervals in the circumferential direction of the piston body 35. The piston body 35 is formed with one passage hole 37 and one passage hole 39 alternately at equal pitches in the circumferential direction of the piston body 35.

[0023] 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 the end of the piston body 35 on the cylinder chamber 20 side in the axial direction. All of the passage holes 37 open to the passage groove 38 at their axial end sides 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 end of the piston body 35 on the cylinder chamber 19 side in the axial direction. All of the passage holes 39 open to the passage groove 40 at their axial end sides opposite the passage groove 38.

[0024] In the piston 18, the insides of the plurality of passage holes 37 and the insides of the passage grooves 38 form first passages 43. The first passages 43 pass through the piston 18 in the axial direction of the piston 18. In the piston 18, the insides of the plurality of passage holes 39 and the insides of the passage grooves 40 form first passages 44. The first passages 44 pass through the piston 18 in the axial direction of the piston 18. Both the first passages 43 and the first passages 44 are provided in the piston 18.

[0025] An inner seat portion 46 and an outer seat portion 48 are formed at the axial end of the piston body 35 on the cylinder chamber 20 side. Both the inner seat portion 46 and the outer seat portion 48 are annular. The inner seat portion 46 is disposed on the inner side of the passage groove 38 in the radial direction of the piston body 35. The outer seat portion 48 is disposed on the outer side of the passage groove 38 in the radial direction of the piston body 35.

[0026] An inner seat portion 47 and a valve seat portion 49 are formed at the axial end of the piston body 35 on the cylinder chamber 19 side. Both the inner seat portion 47 and the valve seat portion 49 are annular. The inner seat portion 47 is located radially inward of the piston body 35 relative to the passage groove 40. The valve seat portion 49 is located radially outward of the passage groove 40. The valve seat portion 49 is provided on the outer periphery of the first passage 44.

[0027] In the piston body 35, the openings of all the passage holes 39 facing the cylinder chamber 20 are arranged on the radially opposite side of the piston body 35 from the passage groove 38 of the outer seat portion 48. In the piston body 35, the openings of all the passage holes 37 facing the cylinder chamber 19 are arranged on the radially opposite side of the piston body 35 from the passage groove 40 of the valve seat portion 49.

[0028] 3, on the side of the inner seat portion 46 in the axial direction of the piston 18, there are provided, in order from the piston 18 side in the axial direction of the piston 18, a plurality of (specifically, four) discs 51, a disc valve 52, a valve seat member 53, a disc valve 54, a plurality of (specifically, four) discs 55, a valve disc 56, a valve disc 57, a pilot valve 70, a disc 71, a pilot case 72, a disc 73, a plurality of (specifically, eleven) discs 74, a disc 75, and a disc 76. The number of discs shown here is one embodiment and can be adjusted as appropriate according to the desired damping force characteristics.

[0029] The discs 51, 55, 71, 73-76, disc valves 52, 54, valve seat member 53, valve discs 56, 57, and pilot case 72 are all made of metal. The discs 51, 55, 71, 73-76, disc valves 52, 54, and valve discs 56, 57 are all circular flat plates with holes and a uniform thickness. The valve seat member 53, pilot valve 70, and pilot case 72 are all annular. The mounting shaft portion 28 of the piston rod 21 is fitted inside the discs 51, 55, 71, 73-76, disc valves 52, 54, valve seat member 53, valve discs 56, 57, pilot valve 70, and pilot case 72.

[0030] The disc 51 has an outer diameter equal to the outer diameter of the inner seat portion 46 of the piston 18 . The disc valve 52 has an outer diameter larger than that of the disc 51.

[0031] The valve seat member 53 has an inner seat portion 82, a valve seat portion 83, and an outer seat portion 84 at its end axially opposite to the piston 18. As shown in Fig. 4, the inner seat portion 82 is formed in an annular shape on the inner peripheral edge of the valve seat member 53. The valve seat portion 83 extends radially outward from the inner seat portion 82. The outer seat portion 84 is formed in an annular shape on the outer peripheral edge of the valve seat member 53.

[0032] As shown in Fig. 3, the valve seat member 53 has an inner seat portion 86, a valve seat portion 87, and an outer seat portion 88 at its axial end on the piston 18 side. The inner seat portion 86 is formed in an annular shape on the inner peripheral edge of the valve seat member 53. The valve seat portion 87 extends radially outward from the inner seat portion 86. The outer seat portion 88 is formed in an annular shape on the outer peripheral edge of the valve seat member 53.

[0033] The valve seat member 53 has a main body 90 between the inner seat portion 82, the valve seat portion 83, and the outer seat portion 84 in the axial direction and the inner seat portion 86, the valve seat portion 87, and the outer seat portion 88. The main body 90 is a perforated disk.

[0034] The inner seat portion 82 protrudes from the inner peripheral edge of the end of the main body portion 90 opposite the piston 18 in the axial direction, along the axial direction of the main body portion 90, toward the opposite side from the piston 18. The valve seat portion 83 protrudes radially outward from the inner seat portion 82, along the axial direction of the main body portion 90, from the main body portion 90 on the same side as the inner seat portion 82. The inner seat portion 82 has a flat tip end surface on the protruding side, i.e., the tip end surface on the opposite side from the main body portion 90. The valve seat portion 83 has a flat tip end surface on the protruding side, i.e., the tip end surface on the opposite side from the main body portion 90. The protruding tip end surfaces of the inner seat portion 82 and the protruding tip end surfaces of the valve seat portion 83 extend in a direction perpendicular to the axis of the valve seat member 53 and are arranged on the same plane.

[0035] The outer seat portion 84 protrudes from the outer peripheral edge of the end of the main body portion 90 opposite the piston 18 in the axial direction, along the axial direction of the main body portion 90, toward the opposite side from the piston 18. The outer seat portion 84 protrudes from the main body portion 90 by a larger amount than the inner seat portion 82 and the valve seat portion 83.

[0036] The inner seat portion 86 protrudes from the inner peripheral edge of the end of the main body portion 90 that is on the piston 18 side in the axial direction of the main body portion 90 toward the piston 18 along the axial direction of the main body portion 90. The valve seat portion 87 protrudes from the main body portion 90 along the axial direction of the main body portion 90 radially outward of the inner seat portion 86, on the same side as the inner seat portion 86. The inner seat portion 86 has a flat tip end surface on the protruding side, i.e., the tip end surface opposite the main body portion 90. The valve seat portion 87 has a flat tip end surface on the protruding side, i.e., the tip end surface opposite the main body portion 90. The protruding tip end surfaces of the inner seat portion 86 and the protruding tip end surfaces of the valve seat portion 87 extend in a direction perpendicular to the axis of the valve seat member 53 and are arranged on the same plane.

[0037] The outer seat portion 88 protrudes from the outer peripheral edge of the end of the main body portion 90 that is on the piston 18 side in the axial direction toward the piston 18 along the axial direction of the main body portion 90. The outer seat portion 88 protrudes from the main body portion 90 by a larger amount than the inner seat portion 86 and the valve seat portion 87.

[0038] As shown in FIG. 4, the valve seat portion 83 is a non-circular, petal-shaped irregular seat. The valve seat portion 83 has multiple, specifically five, valve seat constituent portions 91. These valve seat constituent portions 91 have the same shape and are arranged at equal intervals around the circumferential direction of the valve seat member 53. The inner seat portion 82 is annular in shape, centered on the central axis of the valve seat member 53. Multiple valve seat constituent portions 101 extend radially from the inner seat portion 82. Note that, although the present embodiment has been described with five valve seat constituent portions 91, the number may be more or less than five. Furthermore, although the valve seat constituent portions 91 have the same shape, they may have different shapes or be arranged at uneven intervals.

[0039] A passage recess 92 is formed between each valve seat constituent portion 91 and the inner seat portion 82 on the inner side. The passage recess 92 is surrounded by a part of the inner seat portion 82 and the valve seat constituent portion 91. The passage recess 92 is recessed along the axial direction of the valve seat member 53 from the tip end surface on the protruding side of the inner seat portion 82 and the tip end surface on the protruding side of the valve seat constituent portion 91. The bottom surface of the passage recess 92 is formed by the main body portion 90. A passage recess 92 is formed on the inner side of all of the valve seat constituent portions 91.

[0040] A passage hole 93 is formed in the center of the passage recess 92 in the circumferential direction of the valve seat member 53. The passage hole 93 axially penetrates the main body 90, and thereby the valve seat member 53. The passage hole 93 is a linear hole parallel to the central axis of the valve seat member 53. The passage hole 93 is formed in the bottom surface of all of the passage recesses 92.

[0041] The valve seat member 53 has a passage groove 96 in the inner seat portion 82. The passage groove 96 is recessed along the axial direction of the valve seat member 53 from the tip face of the inner seat portion 82 on the side opposite to the main body portion 90 in the axial direction. The passage groove 96 traverses the inner seat portion 82 in the radial direction of the inner seat portion 82. A passage in the passage groove 96 extends in the radial direction of the valve seat member 53 and opens between adjacent valve seat constituent portions 91 in the circumferential direction of the valve seat member 53.

[0042] The valve seat portion 87 shown in FIG. 3 is also a non-circular, petal-shaped irregular seat. The valve seat portion 87 has multiple, specifically five, valve seat constituent portions 101. These valve seat constituent portions 101 have the same shape and are arranged at equal intervals around the circumferential direction of the valve seat member 53. The inner seat portion 86 has an annular shape centered on the central axis of the valve seat member 53. The multiple valve seat constituent portions 101 extend radially from the inner seat portion 86. The valve seat constituent portions 101 have the same shape as the valve seat constituent portions 91. Note that, in this embodiment, five valve seat constituent portions 91 are described, but the number may be more or less than five. Furthermore, although the valve seat constituent portions 91 have the same shape, they may have different shapes or be arranged at uneven intervals.

[0043] A passage recess 102 is formed between each valve seat constituent portion 101 and the inner seat portion 86 on the inner side. The passage recess 102 is surrounded by a part of the inner seat portion 86 and the valve seat constituent portion 101. The passage recess 102 is recessed along the axial direction of the valve seat member 53 from the tip end surface on the protruding side of the inner seat portion 86 and the tip end surface on the protruding side of the valve seat constituent portion 101. The bottom surface of the passage recess 102 is formed by the main body portion 90. A passage recess 102 is formed on the inner side of all of the valve seat constituent portions 101.

[0044] A passage hole 103 is formed in the center of the passage recess 102 in the circumferential direction of the valve seat member 53. The passage hole 103 axially penetrates the main body 90, and thereby the valve seat member 53. The passage hole 103 is a linear hole parallel to the central axis of the valve seat member 53. The passage hole 103 is formed in the bottom surface of all of the passage recesses 102.

[0045] Here, the arrangement pitch of the multiple valve seat constituent portions 91 in the circumferential direction of the valve seat member 53 is the same as the arrangement pitch of the multiple valve seat constituent portions 101 in the circumferential direction of the valve seat member 53. The valve seat constituent portions 91 and 101 are offset from each other in the circumferential direction of the valve seat member 53 by half the arrangement pitch. The passage hole 93 is disposed between the valve seat constituent portions 101 that are adjacent to each other in the circumferential direction of the valve seat member 53. Therefore, the passage hole 93 is disposed outside the range of the valve seat portion 87. The passage hole 103 is disposed between the valve seat constituent portions 91 and 91 that are adjacent to each other in the circumferential direction of the valve seat member 53, as shown in FIG. 4 . Therefore, the passage hole 103 is disposed outside the range of the valve seat portion 83.

[0046] As shown in FIG. 3, the outer seat portion 88 abuts against the outer seat portion 48 of the piston 18 over its entire circumference. The disc 51 has an outer diameter equal to the outer diameter of the inner seat portion 86 . The disc valve 52 has an outer diameter larger than that of the disc 51, larger than that of the valve seat portion 87, and smaller than the inner diameter of the outer seat portion 88. The disc valve 52 opens and closes the passages in the multiple passage holes 103 and the passage recess 102.

[0047] The disc valve 54 has an outer diameter larger than the outer diameter of the valve seat portion 83 and smaller than the inner diameter of the outer seat portion 84. The disc valve 54 opens and closes the passages in the multiple passage holes 93 and the passage recess 92. The disc 55 has an outer diameter smaller than that of the disc valve 54 and equal to that of the inner seat portion 82 .

[0048] The pilot case 72 has a cylindrical shape with a bottom and includes a bottom portion 131, an inner cylindrical portion 132, an outer cylindrical portion 133, an inner seat portion 134, and a valve seat portion 135. The bottom portion 131 is formed with passage holes 138 that penetrate the bottom portion 131 in the axial direction of the bottom portion 131. A plurality of passage holes 138 are provided at equal intervals in the circumferential direction of the bottom portion 131.

[0049] The inner cylindrical portion 132 is cylindrical and protrudes from the inner peripheral edge of the bottom portion 131 along the axial direction of the bottom portion 131 toward the piston 18 . The outer cylindrical portion 133 is cylindrical and protrudes from the outer peripheral edge of the bottom portion 131 along the axial direction of the bottom portion 131 on the same side as the inner cylindrical portion 132 . The passage hole 138 is disposed between the inner cylindrical portion 132 and the outer cylindrical portion 133 in the radial direction of the bottom portion 131 .

[0050] The inner seat portion 134 is annular, and protrudes slightly from the inner peripheral edge of the bottom portion 131 in the axial direction opposite to the inner cylindrical portion 132. A passage groove 139 is formed in the inner seat portion 134, penetrating the inner seat portion 134 in the radial direction. The valve seat portion 135 is annular and has a larger diameter than the inner seat portion 134. The valve seat portion 135 protrudes from the bottom portion 131 along the axial direction of the bottom portion 131 to the same side as the inner seat portion 134, radially outward of the inner seat portion 134. The height position of the end of the valve seat portion 135 opposite the bottom portion 131 in the axial direction of the pilot case 72 is slightly higher than the height position of the end of the inner seat portion 134 opposite the bottom portion 131.

[0051] The passage hole 138 is disposed between the inner seat portion 134 and the valve seat portion 135 in the radial direction of the bottom portion 131. The passage in the passage groove 139 of the inner seat portion 134 is always in communication with the passage in the groove portion 30 of the piston rod 21 and the passage in the passage hole 138.

[0052] The outer diameter of the valve disc 56 is larger than the outer diameter of the outer seat portion 84 of the valve seat member 53. The outer peripheral side of the valve disc 56 abuts against the outer seat portion 84 of the valve seat member 53. The valve disc 56 is movable away from the outer seat portion 84 of the valve seat member 53. The outer diameter of the valve disc 57 is equal to the outer diameter of the valve disc 56 .

[0053] The first passage 43 described above is a flow path through which oil L flows from the cylinder chamber 19 to the cylinder chamber 20 shown in Fig. 2 during the extension stroke. In addition to the passages inside the plurality of passage holes 37 and the passage groove 38 of the piston 18, the first passage 43 also includes, as shown in Fig. 3, a chamber 141 between the valve seat member 53 and the piston 18, passages inside the plurality of passage holes 93 and the passage recess 92 of the valve seat member 53, a passage between the disc valve 54 and the valve seat portion 83 when the valve is open, a chamber 142 between the valve discs 56, 57 and the valve seat member 53, and a passage between the valve discs 56, 57 and the outer seat portion 84 when the valve is open.

[0054] The valve disc 56 opens and closes the first passage 43 by moving away from and into contact with the outer seat portion 84. A notched fixed orifice 143 is formed on the outer periphery of the valve disc 56. The fixed orifice 143 is formed to cross the outer seat portion 84 in the radial direction of the outer seat portion 84. The fixed orifice 143 maintains communication between the inside and outside of the outer seat portion 84 in the radial direction, even when the valve disc 56 is in contact with the outer seat portion 84. The fixed orifice 143 constitutes the first passage 43.

[0055] The fixed orifice 143, the chamber 142, the passages in the multiple passage holes 103 and the passage recess 102, the passage between the disc valve 52 and the valve seat portion 87 when the valve is open, the chamber 141, the passage in the passage groove 38, and the passages in the multiple passage holes 37 form a compression-side passage 144 through which oil L flows from the cylinder chamber 20 toward the cylinder chamber 19 shown in FIG. 2 during the compression stroke.

[0056] As shown in FIG. 3, the pilot valve 70 is made up of a pilot disk 145 and a seal member 146 . The pilot disc 145 is made of metal and has a circular flat plate shape with holes. The mounting shaft portion 28 of the piston rod 21 is fitted inside the pilot disc 145. The outer diameter of the pilot disc 145 is larger than the outer diameter of the valve disc 57.

[0057] The seal member 146 is made of rubber and is bonded to the pilot disc 145 on the axially opposite side from the valve disc 57. The seal member 146 is fixed to the outer peripheral side of the pilot disc 145 and has an annular shape. The seal member 146 is fitted liquid-tightly around the entire inner peripheral portion of the outer cylindrical portion 133 of the pilot case 72. The seal member 146 is axially slidable relative to the inner peripheral portion of the outer cylindrical portion 133. The seal member 146 is axially movable while constantly sealing the gap between the pilot valve 70 and the outer cylindrical portion 133.

[0058] The valve disc 56, the valve disc 57, and the pilot valve 70 constitute a damping valve 151. A chamber 142 of the first passage 43 is formed between the damping valve 151 and the valve seat member 53. When the damping valve 151 leaves the outer seat portion 84 of the valve seat member 53 and opens, it opens the first passage 43 and allows hydraulic fluid L to flow from the first passage 43 to the cylinder chamber 20. At that time, the damping valve 151 restricts the flow of hydraulic fluid L between the damping valve 151 and the outer seat portion 84 of the valve seat member 53.

[0059] The disk 71 has an outer diameter equal to that of the disk 55 and slightly smaller than that of the inner cylindrical portion 132 of the pilot case 72 .

[0060] The damping valve 151 and the outer seat portion 84 of the valve seat member 53 constitute a first damping force generation mechanism 161. The damping valve 151 has a fixed orifice 143 formed in the valve disc 56, which communicates the first passage 43 with the cylinder chamber 20 even when the damping valve 151 is in contact with the outer seat portion 84 of the valve seat member 53. The fixed orifice 143 constitutes the first passage 43, and also constitutes the first damping force generation mechanism 161.

[0061] The first damping force generating mechanism 161 is provided in the first passage 43. The first damping force generating mechanism 161 opens and closes the first passage 43 to generate a damping force. As shown in FIG. 2 , the first passage 43 is a passage through which oil L flows from the cylinder chamber 19, which is on the upstream side, to the cylinder chamber 20, which is on the downstream side, as the piston 18 moves during the extension stroke of the cylinder chambers 19 and 20. The first damping force generating mechanism 161 is an extension-side damping force generating mechanism that generates a damping force by suppressing the flow of oil L from the first passage 43 to the cylinder chamber 20, which occurs during the extension stroke.

[0062] As shown in FIG. 3, the disk 73 has an outer diameter that is larger than the outer diameter of the inner seat portion 134 of the pilot case 72 and smaller than the inner diameter of the valve seat portion 135.

[0063] Of the multiple discs 74, the disc 74 on the disc 73 side in the axial direction can be seated on the valve seat portion 135. The multiple discs 74 constitute a disc valve 165. The disc valve 165 can be seated on and removed from the valve seat portion 135. The outer diameter of the disc valve 165 decreases as it moves away from the valve seat portion 135 in the axial direction.

[0064] The outer diameter of the disc 75 is smaller than the minimum outer diameter of the disc valve 165 . The disk 76 has an outer diameter larger than that of the disk 75 .

[0065] A pressure chamber 170 is formed between the bottom 131, inner cylindrical portion 132, and outer cylindrical portion 133 of the pilot case 72, the pilot valve 70, and the disc 71, between the bottom 131, inner seat portion 134, and valve seat portion 135 of the pilot case 72, the disc 73, and the disc valve 165, and within the passage hole 138 of the pilot case 72. The pressure chamber 170 applies pressure to the valve discs 56 and 57 in the direction of the piston 18 via the pilot valve 70. In other words, the pressure chamber 170 applies internal pressure to the damping valve 151 of the first damping force generating mechanism 161 in the valve closing direction so that the damping valve 151 seats on the outer seat portion 84. The pressure chamber 170 is constantly in communication with the passage in the groove portion 30 of the piston rod 21 via a passage in the passage groove 139 of the pilot case 72.

[0066] The disc valve 165 is released from the valve seat portion 135 to communicate between the pressure chamber 170 and the cylinder chamber 20. At this time, the disc valve 165 restricts the flow of the oil L between the disc valve 165 and the valve seat portion 135.

[0067] The passages in the multiple passage holes 37 and passage groove 38 of the piston 18, the chamber 141, the passages in the multiple passage holes 93 and passage recess 92 of the valve seat member 53, the passage between the disc valve 54 and the valve seat 83 when the valve is open, the chamber 142, the passage in the passage groove 96 of the valve seat member 53, the passage in the groove 30 of the piston rod 21, the passage in the passage groove 139 of the pilot case 72, the pressure chamber 170, and the passage between the disc valve 165 and the valve seat 135 when the valve is open constitute a second passage 175. The pressure chamber 170 is provided midway through the second passage 175.

[0068] The disc valve 165 and the valve seat portion 135 constitute a second damping force generating mechanism 176. The second damping force generating mechanism 176 is provided in the second passage 175. When the disc valve 165 is released from the valve seat portion 135, the second damping force generating mechanism 176 connects the cylinder chamber 19 and the cylinder chamber 20 shown in FIG. 2 via the second passage 175. At that time, the second damping force generating mechanism 176 generates a damping force by suppressing the flow of hydraulic fluid L in the second passage 175. In other words, the second damping force generating mechanism 176 is an extension-side damping force generating mechanism that generates a damping force by suppressing the flow of hydraulic fluid L when hydraulic fluid L flows from the cylinder chamber 19 to the cylinder chamber 20 via the second passage 175 during the extension stroke. The second passage 175 is a passage through which oil L flows from the upstream cylinder chamber 19 to the downstream cylinder chamber 20 as the piston 18 moves during the extension stroke of the cylinder chambers 19 and 20. The second damping force generating mechanism 176 does not have a fixed orifice that constantly connects the pressure chamber 170 and the cylinder chamber 20.

[0069] 3, a passage port 177 that connects the pressure chamber 170 to the cylinder chamber 20 in the cylinder 2 is provided between the disc valve 165 and the valve seat portion 135. A second damping force generating mechanism 176 is provided in this passage port 177.

[0070] The second passage 175 is common with the first passage 43 in that it includes the passages within the multiple passage holes 37 and the passage groove 38 of the piston 18, the chamber 141, the passages within the multiple passage holes 93 and the passage recess 92 of the valve seat member 53, the passage between the disc valve 54 and the valve seat portion 83 when the valve is open, and the chamber 142.

[0071] The second passage 175 includes a passage in the passage groove 96 of the valve seat member 53, a passage in the groove portion 30 of the piston rod 21, a passage in the passage groove 139 of the pilot case 72, the pressure chamber 170, and a passage between the disc valve 165 and the valve seat portion 135 when the valve is open, and is arranged in parallel with the passage in the first passage 43 between the damping valve 151 and the outer seat portion 84.

[0072] In the extension-side first damping force generating mechanism 161, the opening of the damping valve 151 is controlled by the pressure of the oil L introduced into the pressure chamber 170 of the second passage 175. The pressure chamber 170 of the second passage 175 pressurizes the damping valve 151 of the first damping force generating mechanism 161 in the valve closing direction.

[0073] The disc valve 54 and the valve seat 83 provided in the first passage 43 constitute a third damping force generating mechanism 181. When the disc valve 54 leaves the valve seat 83, the third damping force generating mechanism 181 causes oil L to flow from the chamber 141 of the first passage 43 to the chamber 142 through the passages in the multiple passage holes 93 and the passage recess 92. At that time, the third damping force generating mechanism 181 suppresses the flow of oil L to generate a damping force. The third damping force generating mechanism 181 restricts the flow of oil L from the chamber 142 to the chamber 141 through the passages in the multiple passage holes 93 and the passage recess 92. The third damping force generating mechanism 181 is a check valve. The third damping force generating mechanism 181 is an extension-side damping force generating mechanism that suppresses the flow of oil L that occurs during the extension stroke to generate a damping force.

[0074] The third damping force generating mechanism 181 is provided upstream of the first damping force generating mechanism 161 and the second damping force generating mechanism 176 in the flow direction of the oil L during the extension stroke. The third damping force generating mechanism 181 has lower rigidity and a lower valve opening pressure than the first damping force generating mechanism 161 and the second damping force generating mechanism 176. Therefore, the third damping force generating mechanism 181 opens in a region where the moving speed of the piston 18 (hereinafter referred to as piston speed) is lower than those of the first damping force generating mechanism 161 and the second damping force generating mechanism 176.

[0075] The disc valve 52 and the valve seat 87 constitute a third damping force generating mechanism 182. When the disc valve 52 leaves the valve seat 87, the third damping force generating mechanism 182 causes oil L to flow from the chamber 142 to the chamber 141 through the passages in the multiple passage holes 103 and the passage recess 102. At that time, the third damping force generating mechanism 182 suppresses the flow of oil L to generate a damping force. The third damping force generating mechanism 182 restricts the flow of oil L from the chamber 141 to the chamber 142 through the passages in the multiple passage holes 103 and the passage recess 102. The third damping force generating mechanism 182 is a check valve. The third damping force generating mechanism 182 is provided in the compression-side passage 144 and serves as a compression-side damping force generating mechanism that suppresses the flow of oil L that occurs during the compression stroke and generates a damping force.

[0076] The valve opening pressures can be set individually for the extension-side third damping force generating mechanism 181 and the compression-side third damping force generating mechanism 182. That is, the third damping force generating mechanism 181 can set the valve opening pressure by appropriately selecting and setting the disc valve 54, and separately, the third damping force generating mechanism 182 can set the valve opening pressure by appropriately selecting and setting the disc valve 52.

[0077] As shown in Fig. 2, on the inner seat portion 47 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 disc 191, a plurality of (specifically, nine) discs 192, one disc 193, one disc 194, and one circular ring member 195. The discs 191 to 194 and the circular ring member 195 are all made of metal. The discs 191 to 194 and the circular ring member 195 are all in the shape of a circular flat plate with holes and a constant thickness. The mounting shaft portion 28 of the piston rod 21 is fitted inside the discs 191 to 194 and the circular ring member 195.

[0078] The disc 191 has an outer diameter that is equal to the outer diameter of the inner seat 47 of the piston 18 . Of the multiple discs 192, the disc 192 closest to the piston 18 in the axial direction abuts against the valve seat portion 49 of the piston 18. The multiple discs 192 open and close the opening of the first passage 44 formed in the piston 18 by moving away from and abutting against the valve seat portion 49.

[0079] The multiple discs 192 constitute a disc valve 201. The disc valve 201 is removably seated on the valve seat portion 49. The outer diameter of the disc valve 201 decreases as it moves away from the piston 18 in the axial direction. A first passage 44 is formed between the disc valve 201 and the valve seat portion 49 of the piston 18. When the disc valve 201 moves away from the valve seat portion 49, it opens the first passage 44 and exposes the first passage 44 to the cylinder chamber 19. When the disc valve 201 moves away from the valve seat portion 49 of the piston 18 and opens, it allows oil L from the first passage 44 to flow into the cylinder chamber 19. At that time, the disc valve 201 restricts the flow of oil L between the disc valve 201 and the valve seat portion 49. Therefore, the disc valve 201 restricts the flow of oil L from the cylinder chamber 20 to the cylinder chamber 19 via the first passage 44.

[0080] The disc valve 201 and the valve seat portion 49 constitute a first damping force generating mechanism 202. The first damping force generating mechanism 202 is provided in the first passage 44. The first damping force generating mechanism 202 opens and closes the first passage 44 to generate a damping force. The first damping force generating mechanism 202 is disposed on the cylinder chamber 19 side of the piston 18 and attached to the piston rod 21. As a result, the first passage 44 serves as a passage through which oil L moves from the cylinder chamber 20 toward the cylinder chamber 19 as the piston 18 moves toward the cylinder chamber 20. In other words, the first passage 44 is a passage through which oil L flows from the cylinder chamber 20, which is upstream of the cylinder chambers 19, 20, toward the cylinder chamber 19, which is downstream, as the piston 18 moves during the compression stroke. The first damping force generating mechanism 202 is a compression-side damping force generating mechanism that generates a damping force by suppressing the flow of oil L from the first passage 44 to the cylinder chamber 19 during the compression stroke. The first damping force generating mechanism 202 is not provided with a fixed orifice that constantly connects the first passage 44 and the cylinder chamber 19 .

[0081] The disc 193 has an outer diameter smaller than the minimum outer diameter of the disc valve 201 . The outer diameter of the disk 194 is larger than the outer diameter of the disk 193 . The outer diameter of the annular member 195 is larger than the outer diameter of the disk 193 and smaller than the outer diameter of the disk 194 .

[0082] The disc 194 and the circular member 195 come into contact with the disc valve 201 when the disc valve 201 deforms in the opening direction, preventing the disc valve 201 from deforming in the opening direction more than a specified amount. The circular member 195 comes into contact with the shaft step portion 29 of the piston rod 21.

[0083] A frequency sensitive mechanism 230 is provided on the axial side of the disc 76 opposite to the piston 18. The frequency sensitive mechanism 230 varies the damping force according to the frequency of the axial movement of the piston 18 (hereinafter referred to as the piston frequency).

[0084] 3, frequency sensitive mechanism 230 has one case member 231 on the side of disc 76 in the axial direction. Frequency sensitive mechanism 230 has a plurality of discs 232 (specifically, two discs) and one partition member 233 on the opposite side of case member 231 from disc 76 in the axial direction. Frequency sensitive mechanism 230 has, in order from the disc 232 and partition member 233 side, one support disc 235, one disc 236, and one stopper member 237 on the opposite side of disc 76 in the axial direction from discs 232 and partition member 233.

[0085] The case member 231, the disks 232 and 236, the support disk 235, and the stopper member 237 are all made of metal. The disks 232 and 236, and the support disk 235 are all perforated circular flat plates of a uniform thickness. The partition member 233, the case member 231, and the stopper member 237 are all annular. The mounting shaft portion 28 of the piston rod 21 is fitted into the inside of the case member 231, the disks 232 and 236, the support disk 235, and the stopper member 237. The mounting shaft portion 28 of the piston rod 21 and the multiple disks 232 are inserted into the inner periphery of the partition member 233 with radial gaps between them.

[0086] The case member 231 is cylindrical and has a bottom. The case member 231 has a bottom portion 250 , an inner sheet portion 251 , a cylindrical portion 253 , and an outer sheet portion 254 . The bottom portion 250 has an annular shape. The mounting shaft portion 28 of the piston rod 21 is fitted into the inner periphery of the bottom portion 250.

[0087] The inner seat portion 251 is annular. The inner seat portion 251 protrudes from the inner peripheral edge of the bottom portion 250 in the axial direction of the bottom portion 250 toward the opposite side from the disc 76. A passage groove 258 is formed in the inner seat portion 251, penetrating the inner seat portion 251 in the radial direction. The passage in the passage groove 258 communicates with the passage in the groove portion 30 of the piston rod 21.

[0088] The tubular portion 253 is cylindrical with an inner diameter larger than the outer diameter of the inner seat portion 251. The tubular portion 253 extends from the outer peripheral edge of the bottom portion 250 on the same side as the inner seat portion 251 along the axial direction of the bottom portion 250. The height position of the end of the tubular portion 253 opposite the bottom portion 250 in the axial direction of the case member 231 is higher than the height position of the end of the inner seat portion 251 opposite the bottom portion 250.

[0089] The outer seat portion 254 is annular. The outer seat portion 254 protrudes from between the inner seat portion 251 and the cylindrical portion 253 in the radial direction of the bottom portion 250 on the same side as the inner seat portion 251 and the cylindrical portion 253 along the axial direction of the bottom portion 250. A notch 259 is formed in the outer seat portion 254, penetrating the outer seat portion 254 in the radial direction. A plurality of the notches 259 are formed in the outer seat portion 254 at intervals in the circumferential direction of the outer seat portion 254. The height position of the outer seat portion 254 at the end opposite the bottom portion 250 in the axial direction of the case member 231 is slightly higher than the height position of the end of the inner seat portion 251 opposite the bottom portion 250.

[0090] The disc 232 has an outer diameter smaller than the outer diameter of the inner seat portion 251 . The support disk 235 has an outer diameter equal to the outer diameter of the inner seat portion 251 . The disk 236 has an outer diameter larger than the outer diameter of the support disk 235 .

[0091] The stopper member 237 has a base portion 261 and a flange portion 262 . The base portion 261 is cylindrical, and the mounting shaft portion 28 of the piston rod 21 is fitted into the radially inner side thereof.

[0092] The flange portion 262 is disk-shaped and has a thinner axial thickness than the base portion 261. The flange portion 262 extends from an axially intermediate portion of the base portion 261 to an outer side in the radial direction of the substrate portion 241. A passage groove 263 is formed on the outer periphery of the flange portion 262, penetrating the flange portion 262 in the axial direction.

[0093] The partition member 233 is made up of a valve disc 271 and a seal member 272. The partition member 233 is disposed between the cylindrical portion 253 of the case member 231 and the plurality of discs 232 in the radial direction.

[0094] The valve disc 271 is made of metal. The valve disc 271 is a circular flat plate with holes and a uniform thickness. The mounting shaft portion 28 of the piston rod 21 and the multiple discs 232 are inserted into the inner periphery of the valve disc 271. The valve disc 271 has an inner diameter that allows the multiple discs 232 to be arranged inside with radial gaps between them. The thickness of the valve disc 271 is thinner than the combined thickness of all the discs 232.

[0095] The seal member 272 is made of rubber and has an annular shape. The seal member 272 is baked and bonded to the outer periphery of the valve disc 271. The seal member 272 has a seal portion 273 and a contact portion 274. The seal portion 273 is cylindrical and is fixed over the entire outer periphery of the valve disc 271. The seal portion 273 protrudes from the valve disc 271 toward the bottom 250 of the case member 231 in the axial direction of the partition member 233.

[0096] The abutment portion 274 is fixed to the outer periphery of the separator 233. The abutment portion 274 protrudes from the valve disc 271 on the opposite side to the bottom portion 250 in the axial direction of the separator 233. The seal member 272 has a plurality of abutment portions 274 spaced equally apart circumferentially around the valve disc 271. The abutment portions 274 are connected to the seal portion 273 on the outer periphery of the valve disc 271. The abutment portion 274 has an outer diameter that decreases and an inner diameter that increases with increasing axial distance from the valve disc 271. As a result, the cross-section of the abutment portion 274, taken along a plane including the central axis, has a tapered mountain-like shape that becomes thinner with increasing axial distance from the valve disc 271.

[0097] As described above, there is a radial gap between the partition member 233 and the plurality of discs 232. The partition member 233 is fitted into the cylindrical portion 253 of the case member 231 at its seal portion 273. The seal portion 273 then comes into close contact with the cylindrical portion 253 over the entire circumference. This fitting causes the partition member 233 to be coaxially centered with respect to the case member 231, the plurality of discs 232, the support disc 235, and the piston rod 21. At this time, the seal portion 273 of the partition member 233 abuts against the cylindrical portion 253 over the entire circumference with a radial interference. The seal portion 273 is able to slide relative to the cylindrical portion 253 in the axial direction of the cylindrical portion 253 while maintaining close contact with the cylindrical portion 253 over the entire circumference. The valve disc 271 of the partition member 233 is seated on the outer seat portion 254.

[0098] The outer diameter of the support disk 235 is larger than the inner diameter of the partition member 233, i.e., the inner diameter of the valve disk 271. The support disk 235 is disposed on the opposite side of the valve disk 271 from the bottom portion 250 in the axial direction, and is pressed against the inner peripheral side of the valve disk 271 over the entire periphery. This closes the gap between the support disk 235 and the valve disk 271, i.e., the partition member 233.

[0099] The partition member 233 has a radially intermediate portion of its valve disc 271 abutting against and supported by the outer seat portion 254 on the axial side of the bottom portion 250. Therefore, the partition member 233 has a simply supported structure in which the inner peripheral side of the valve disc 271 is supported by the support disc 235, and the outer peripheral side of the valve disc 271 beyond the support disc 235 is supported by the outer seat portion 254. In other words, the valve disc 271 is not clamped in the axial direction.

[0100] The outer seat portion 254 of the case member 231 supports a radially intermediate portion of the valve disc 271 of the partition member 233 from one axial side. The support disc 235 supports a portion of the valve disc 271 that is more inward than the outer seat portion 254 from the other axial side. The shortest axial distance between the outer seat portion 254 and the support disc 235 is slightly smaller than the axial thickness of the valve disc 271. Therefore, the valve disc 271 presses against both the outer seat portion 254 and the support disc 235 by its own elastic force while being slightly elastically deformed.

[0101] The partition member 233 has a plurality of abutting portions 274 arranged on the opposite side of the partition member 233 from the bottom portion 250 in the axial direction. The plurality of abutting portions 274 abut against the flange portion 262 of the stopper member 237.

[0102] The partition member 233 is elastically deformable, i.e., flexible, as a whole. The partition member 233 flexes and moves so that the outer circumferential side of the valve disc 271 moves axially away from the outer seat portion 254, while the inner circumferential side of the valve disc 271 remains in contact with the support disc 235.

[0103] The area surrounded by the case member 231, the disks 232 and 236, the support disk 235, and the stopper member 237 forms a pressure chamber 280. The partition member 233 is provided within the pressure chamber 280 and divides the pressure chamber 280 into a first chamber 281 and a second chamber 282. The first chamber 281 is located between the bottom 250 and the partition member 233 in the axial direction of the case member 231. The second chamber 282 is located between the partition member 233 and the stopper member 237 in the axial direction of the case member 231. The partition member 233 is provided movably within the pressure chamber 280.

[0104] The volumes of both the first chamber 281 and the second chamber 282 change due to deformation of the partition member 233. The first chamber 281 is constantly connected to the passage in the groove portion 30 of the piston rod 21 via a passage in the passage groove 258 of the case member 231. The first chamber 281 is constantly connected to the pressure chamber 170 via the passage in the passage groove 258, the passage in the groove portion 30, and the passage in the passage groove 139. The second chamber 282 is constantly connected to the cylinder chamber 20 via the passage in the passage groove 263 of the stopper member 237. A passage port 177 between the disc valve 165 and the valve seat portion 135 connects the first chamber 281 of the pressure chamber 280 to the cylinder chamber 20, which is outside the first chamber 281.

[0105] During the extension stroke, oil L from the cylinder chamber 19 shown in FIG. 2 is introduced into the first chamber 281 via the passages in the passage holes 37 and the passage groove 38, the chamber 141, the passages in the passage holes 93 and the passage recess 92, the third damping force generating mechanism 181 (which opens), the chamber 142, the passage in the passage groove 96 of the valve seat member 53, the passage in the groove portion 30 of the piston rod 21, and the passage in the passage groove 258 of the case member 231. As a result, the valve disc 271 of the partition member 233 bends in a tapered shape, with the contact point with the support disc 235 as a fulcrum, moving away from the bottom portion 250 in the axial direction of the case member 231 as it approaches the outer periphery. At this time, the valve disc 271 compresses and deforms the abutment portion 274 that abuts against the stopper member 237. Due to this deformation, the partition member 233 increases the volume of the first chamber 281. Here, when the valve disc 271 is deformed in this manner, the volume of the second chamber 282 decreases. At this time, the oil L in the second chamber 282 flows into the cylinder chamber 20 via the passage in the passage groove 263 of the stopper member 237.

[0106] The second passage 175 includes a flow path from the passages in the passage holes 37 to the cylinder chamber 20 via the passage in the groove 30 and the pressure chamber 170, as well as a passage in the passage groove 258 that communicates with the passage in the groove 30, a first chamber 281, a second chamber 282, and a passage in the passage groove 263 of the stopper member 237. In the second passage 175, the passage in the passage groove 263 of the stopper member 237 and the second chamber 282 are constantly in communication with the cylinder chamber 20. A pressure chamber 280 including the first chamber 281 and the second chamber 282 is located midway through the second passage 175. A partition member 233 located within the pressure chamber 280 partitions the second passage 175 into two regions: a region on the cylinder chamber 19 side and a region on the cylinder chamber 20 side. When the partition member 233 operates, a compressive force from a rubber abutment portion 274 acts on the partition member 233.

[0107] The passage in passage groove 263 of stopper member 237, second chamber 282, first chamber 281, the passage in passage groove 258, the passage in groove portion 30, the passage in passage groove 96, chamber 142, the passage between disc valve 52 and valve seat portion 87 when the valve is open, chamber 141, and the passages in passage groove 38 and the plurality of passage holes 37 form a compression-side passage 292 through which oil L flows from cylinder chamber 20, which is upstream, to cylinder chamber 19, which is downstream, during the compression stroke.

[0108] When the inner circumferential side of the valve disc 271 is in contact with the support disc 235 along the entire circumference, the partition member 233 blocks the flow of oil liquid L between the first chamber 281 and the second chamber 282. When the inner circumferential side of the valve disc 271 is separated from the support disc 235 in the axial direction, the partition member 233 allows the flow of oil liquid L between the second chamber 282 and the first chamber 281. The inner circumferential side of the valve disc 271 and the support disc 235 form a check valve 293.

[0109] The check valve 293 restricts the flow of hydraulic fluid L from the first chamber 281 to the second chamber 282 via the second passage 175, while allowing the flow of hydraulic fluid L from the second chamber 282 to the first chamber 281 via the compression-side passage 292. During the extension stroke when the pressure in the cylinder chamber 19 becomes higher than the pressure in the cylinder chamber 20, the check valve 293 blocks communication between the cylinder chamber 19 and the cylinder chamber 20 via the second passage 175. During the compression stroke when the pressure in the cylinder chamber 20 becomes higher than the pressure in the cylinder chamber 19, the check valve 293 opens appropriately to allow the hydraulic fluid L to flow from the cylinder chamber 20 to the cylinder chamber 19 via the compression-side passage 292. The compression-side passage 292 is in parallel with the first passage 44 and connects the cylinder chamber 20 and the cylinder chamber 19.

[0110] Here, during the compression stroke, when oil L flows from the cylinder chamber 20 toward the cylinder chamber 19 via this compression-side passage 292, and when oil L flows from the cylinder chamber 20 toward the cylinder chamber 19 via the compression-side passage 144, the third damping force generating mechanism 182 opens to generate a damping force. The third damping force generating mechanism 182 is provided in parallel with the first damping force generating mechanism 202. The third damping force generating mechanism 182 has lower rigidity and a lower valve-opening pressure than the first damping force generating mechanism 202. Therefore, the third damping force generating mechanism 182 opens in a range where the piston speed is lower than that of the first damping force generating mechanism 202.

[0111] 2, the piston rod 21 has the components from the annular member 195 to the stopper member 237 stacked in this order on the stepped shaft portion 29 with the mounting shaft portion 28 inserted through the inside of each component. In this state, a nut 295 is screwed onto the threaded portion 31 of the mounting shaft portion 28 that protrudes beyond the stopper member 237. As a result, the inner circumferential sides or the entirety of the components from the annular member 195 to the stopper member 237, excluding the partition member 233, are sandwiched between the stepped shaft portion 29 of the piston rod 21 and the nut 295 and clamped in the axial direction. At this time, the partition member 233, including its inner circumferential side, is not clamped in the axial direction. In this state, as shown in FIG. 4, the inner peripheral side of the valve disc 271 of the partition member 233 abuts against the support disc 235, and the outer peripheral side abuts against the outer seat portion 254 of the case member 231, and the abutment portion 274 of the seal member 272 abuts against the flange portion 262 of the stopper member 237.

[0112] As shown in FIG. 1 , the base member 26 of the base valve 25 described above is provided between the bottom 12 of the outer cylinder 4 and the inner cylinder 3. In addition to the base member 26, the base valve 25 has a disc valve 312, a disc valve 313, and a mounting pin 314. The disc valve 312 is provided on the lower side of the base member 26, i.e., on the reservoir chamber 6 side. The disc valve 313 is provided on the upper side of the base member 26, i.e., on the cylinder chamber 20 side. The mounting pin 314 attaches the disc valve 312 and the disc valve 313 to the base member 26.

[0113] The base member 26 has an annular shape, and a mounting pin 314 is inserted through its radial center. The base member 26 is formed with a plurality of passage holes 315 and a plurality of passage holes 316. The plurality of passage holes 315 allow the hydraulic fluid L to flow between the cylinder chamber 20 and the reservoir chamber 6. The plurality of passage holes 316 are arranged outside the plurality of passage holes 315 in the radial direction of the base member 26. The plurality of passage holes 316 allow the hydraulic fluid L to flow between the cylinder chamber 20 and the reservoir chamber 6. The disc valve 312 on the reservoir chamber 6 side allows the hydraulic fluid L to flow from the cylinder chamber 20 to the reservoir chamber 6 via the passage hole 315. On the other hand, the disc valve 312 restricts the flow of the hydraulic fluid L from the reservoir chamber 6 to the cylinder chamber 20 via the passage hole 315. The disc valve 313 allows the hydraulic fluid L to flow from the reservoir chamber 6 to the cylinder chamber 20 via the passage hole 316. On the other hand, the disc valve 313 restricts the flow of the oil L from the cylinder chamber 20 to the reservoir chamber 6 through the passage hole 316 .

[0114] The disc valve 312 and the base member 26 form a damping valve mechanism 317. The damping valve mechanism 317 opens during the compression stroke of the shock absorber 1 to allow hydraulic fluid L to flow from the cylinder chamber 20 to the reservoir chamber 6, generating a damping force. The disc valve 313 and the base member 26 form a suction valve mechanism 318. The suction valve mechanism 318 opens during the extension stroke of the shock absorber 1 to allow hydraulic fluid L to flow from the reservoir chamber 6 into the cylinder chamber 20. The suction valve mechanism 318 mainly functions to allow hydraulic fluid L to flow from the reservoir chamber 6 to the cylinder chamber 20 without generating any damping force, so as to make up for a shortage of hydraulic fluid caused by the extension of the piston rod 21 from the cylinder 2.

[0115] Next, the main operation of the shock absorber 1 will be described. "When it is assumed that the frequency sensitive mechanism 230 does not operate during the extension stroke, and only the first damping force generating mechanism 161 and the second damping force generating mechanism 176 on the extension side operate"

[0116] In this case, in the extremely low speed region where the piston speed is slower than the first predetermined value, the oil L from the cylinder chamber 19 is introduced into the chamber 141 through the passages in the multiple passage holes 37 and the passage groove 38. The oil L introduced into the chamber 141 then passes through the passages in the multiple passage holes 93 and the passage recess 92, opens the third damping force generation mechanism 181, and is introduced into the chamber 142. The oil L introduced into the chamber 142 in this manner flows into the cylinder chamber 20 through the fixed orifice 143 of the first damping force generation mechanism 161. That is, in the extremely low speed region, the oil L from the cylinder chamber 19 flows into the cylinder chamber 20 through the first passage 43. Because no fixed orifice is provided in the first passage 44, the entire flow of the oil L from the cylinder chamber 19 passes through the third damping force generation mechanism 181, opening the valve. When the third damping force generation mechanism 181 is opened, the pressure in the cylinder chamber 19 increases. Therefore, even in the extremely low speed region, the third damping force generating mechanism 181 opens and the damping force rises immediately, generating a damping force with valve characteristics (the damping force is approximately proportional to the piston speed).

[0117] In the extremely low speed region where the piston speed is equal to or greater than a first predetermined value and less than a second predetermined value, a damping force having the orifice characteristics (where the damping force is approximately proportional to the square of the piston speed) defined by the fixed orifice 143 is generated when the oil L flows through the first passage 43. Therefore, the characteristic of the damping force relative to the piston speed in the extremely low speed region is such that the rate of increase of the damping force relative to an increase in the piston speed is higher than in the extremely low speed region.

[0118] In the low-speed region where the piston speed is equal to or greater than the second predetermined value and less than the third predetermined value, oil L from the cylinder chamber 19 passes through the second passage 175 while the third damping force generating mechanism 181 is open, and while opening the disc valve 165 of the second damping force generating mechanism 176, passes between the disc valve 165 and the valve seat portion 135 and flows into the cylinder chamber 20. This generates a damping force with valve characteristics (the damping force is approximately proportional to the piston speed). Therefore, the characteristic of the damping force relative to the piston speed in the low-speed region is such that the rate of increase of the damping force relative to an increase in piston speed is lower than in the very low-speed region.

[0119] In the medium to high speed range where the piston speed becomes faster than the third predetermined value, the relationship of the forces (hydraulic pressure) acting on the damping valve 151 of the first damping force generation mechanism 161 is such that the force in the opening direction applied from the chamber 142 is greater than the force in the closing direction applied from the pressure chamber 170. Therefore, in this medium to high speed range, as the piston speed increases, the damping valve 151 of the first damping force generation mechanism 161 opens by moving away from the outer seat portion 84 of the valve seat member 53. Therefore, in addition to flowing from the cylinder chamber 19 to the cylinder chamber 20 through the second passage 175 while opening the disc valve 165 as described above, the hydraulic fluid L also flows to the cylinder chamber 20 through the first passage 43 while opening the damping valve 151 of the first damping force generation mechanism 161. For this reason, the rate of increase in damping force in response to an increase in piston speed in the medium to high speed range is lower than in the low speed range.

[0120] "When it is assumed that the frequency sensitive mechanism 230 does not operate during the compression stroke, and only the first damping force generating mechanism 202 on the compression side operates"

[0121] In this case, in the extremely low speed region where the piston speed is slower than the fourth predetermined value, the first damping force generation mechanism 202 does not have a fixed orifice, so the entire flow rate of oil L from the cylinder chamber 20 flows from the fixed orifice 143 of the first damping force generation mechanism 161 to the chamber 142, opens the third damping force generation mechanism 182, and flows from the passages in the multiple passage holes 103 and the passage recess 102 to the chamber 141 and the passages in the passage groove 38 and the multiple passage holes 37 to the cylinder chamber 19. In other words, the oil flows to the cylinder chamber 19 through the compression-side passage 144. Therefore, even if the piston speed is in the extremely low speed region, a damping force is immediately generated by the third damping force generation mechanism 182, and a damping force with a valve characteristic (damping force is approximately proportional to the piston speed) is generated.

[0122] In the extremely low speed region where the piston speed is equal to or greater than a fourth predetermined value and less than a fifth predetermined value, when oil L flows through the compression-side passage 144, a damping force with the orifice characteristics (the damping force is approximately proportional to the square of the piston speed) defined by the fixed orifice 143 is generated. This results in the generation of a damping force with the orifice characteristics. Therefore, the characteristic of the damping force relative to the piston speed in the extremely low speed region is such that the rate of increase of the damping force relative to an increase in piston speed is higher than in the extremely low speed region.

[0123] When the piston speed becomes faster than the fifth predetermined value, the oil L introduced from the cylinder chamber 20 into the first passage 44 opens the disc valve 201 of the first damping force generating mechanism 202 and flows between the disc valve 201 and the valve seat portion 49 into the cylinder chamber 19. This generates a damping force with valve characteristics (damping force is approximately proportional to piston speed). Therefore, when the piston speed is greater than the fifth predetermined value, the damping force characteristic with respect to piston speed is such that the rate of increase in damping force relative to an increase in piston speed is lower than in the extremely low speed region.

[0124] "When the frequency sensitive mechanism 230 operates during the extension stroke" In the first embodiment, the frequency sensitive mechanism 230 varies the damping force according to the piston frequency even when the piston speed is the same.

[0125] During the extension stroke, hydraulic oil L is introduced from the cylinder chamber 19 into the first chamber 281 of the frequency sensitive mechanism 230 via the second passage 175. Then, the valve disc 271 of the partition member 233, which had been in contact with the support disc 235, the outer seat portion 254, and the stopper member 237, bends in a tapered shape, with the contact point with the support disc 235 as a fulcrum, such that the outer circumferential side moves away from the bottom portion 250 in the axial direction of the case member 231. At the same time, the contact portion 274 of the partition member 233 is compressively deformed. In this way, the partition member 233 expands the volume of the first chamber 281, introducing hydraulic oil L into the first chamber 281. At the same time, the partition member 233 discharges hydraulic oil L from the second chamber 282 to the cylinder chamber 20 via the passage in the passage groove 263 of the stopper member 237.

[0126] Here, during the extension stroke when the piston frequency is high, the stroke of the piston 18 is small. Therefore, the amount of oil L introduced from the cylinder chamber 19 to the first chamber 281 via the second passage 175 is small. Therefore, although the partition member 233 deforms as described above, it does not deform to near its limit.

[0127] Therefore, during the extension stroke when the piston frequency is high, the partition member 233 of the frequency sensitive mechanism 230 flexes and moves as described above, thereby introducing hydraulic fluid L from the cylinder chamber 19 into the first chamber 281. This reduces the flow rate of hydraulic fluid L flowing from the cylinder chamber 19 through the first passage 43 and the first damping force generating mechanism 161 to the cylinder chamber 20, and the flow rate of hydraulic fluid L flowing through the second passage 175 and the second damping force generating mechanism 176 to the cylinder chamber 20. Furthermore, by introducing hydraulic fluid L from the cylinder chamber 19 into the first chamber 281, the pressure increase in the pressure chamber 170 is suppressed compared to when the first chamber 281 is not present, and the damping valve 151 of the first damping force generating mechanism 161 is more likely to open. As a result, the damping force on the extension side is softened.

[0128] 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 L is introduced from the cylinder chamber 19 to the first chamber 281 via the second passage 175. Therefore, although hydraulic fluid L flows from the cylinder chamber 19 to the first chamber 281 at the beginning of the stroke of the piston 18, the partition member 233 thereafter deforms to near its limit and further deformation is suppressed. As a result, hydraulic fluid L does not flow from the cylinder chamber 19 to the first chamber 281. This prevents a decrease in the flow rate of hydraulic fluid L flowing from the cylinder chamber 19 through the first passage 43 to the cylinder chamber 20 via the first damping force generating mechanism 161 and the flow rate of hydraulic fluid L flowing through the second passage 175 to the cylinder chamber 20 via the second damping force generating mechanism 176. Furthermore, since the oil L is not introduced into the first chamber 281 from the cylinder chamber 19, the pressure in the pressure chamber 170 increases, making it difficult for the damping valve 151 of the first damping force generating mechanism 161 to open. As a result, when the piston frequency is low, the damping force during the extension stroke is stronger than when the piston frequency is high.

[0129] Here, during the extension stroke, when the first damping force generating mechanism 161 performs an opening operation, the rubber seal member 146 of the pilot valve 70 provided in the pressure chamber 170 is compressed and deformed radially outward by the pressure of the oil liquid L introduced into the second passage 175. Also, during the extension stroke, when the first damping force generating mechanism 161 performs an opening operation, the seal portion 273 of the rubber seal member 272 of the partition member 233 provided in the pressure chamber 280 is compressed and deformed radially outward, and the abutment portion 274 is compressed and deformed axially. Therefore, when the first damping force generating mechanism 161 provided in the first passage 43 and generating a damping force operates, the compressive force of the seal members 146, 272 acts on the first damping force generating mechanism 161 via the oil liquid L.

[0130] During the compression stroke, the pressure in the cylinder chamber 20 increases, but the valve disc 271 of the partition member 233 of the frequency sensitive mechanism 230 abuts against the outer seat portion 254 of the case member 231, suppressing the expansion of the second chamber 282. This suppresses the amount of oil L introduced from the cylinder chamber 20 into the second chamber 282 via the passage in the passage groove 263 of the stopper member 237. As a result, the flow rate of oil L flowing from the cylinder chamber 20 to the cylinder chamber 19 via the compression-side passage 144 and the flow rate of oil L flowing from the cylinder chamber 20 to the cylinder chamber 19 via the first passage 44 do not decrease. This results in a hard damping force.

[0131] During the compression stroke, when the piston speed increases and the pressure in the second chamber 282 becomes higher than the pressure in the first chamber 281 by a predetermined value or more, the inner peripheral side of the partition member 233 moves away from the support disc 235. In other words, the check valve 293 opens. This allows the oil L to flow from the cylinder chamber 20 to the cylinder chamber 19 via the compression-side passage 292. In this way, opening the check valve 293 suppresses the pressure difference between the second chamber 282 side and the first chamber 281 side of the partition member 233. This prevents the partition member 233 from bending excessively.

[0132] The aforementioned Patent Document 1 discloses a shock absorber in which a damping force generating mechanism is provided in each of parallel flow paths through which working fluid flows from one chamber to the other as the piston moves. In a shock absorber provided in a vehicle, if a compressive force acts on the rubber when the damping force generating mechanism operates, the increase in cylinder pressure may be delayed in the extremely slow piston speed range, potentially causing instability in the vehicle's behavior. For this reason, it is desirable for the shock absorber to suppress instability in the vehicle's behavior.

[0133] The shock absorber 1 of the first embodiment has a first passage 43 and a second passage 175 through which oil L, which is a working fluid, flows out from one cylinder chamber 19 in the cylinder 2 as the piston 18 moves. The shock absorber 1 also has a first damping force generation mechanism 161 that is provided in the first passage 43 to generate a damping force and that, when in operation, is subjected to a compressive force of rubber sealing members 146, 272. The shock absorber 1 also has pressure chambers 170, 280 provided in the second passage 175. The shock absorber 1 also has a second damping force generation mechanism 176 that is provided in a passage port 177 that connects the pressure chambers 170, 280 to the cylinder chamber 20.

[0134] In the shock absorber 1 configured as described above, a third damping force generating mechanism 181 is provided upstream of the first damping force generating mechanism 161 and the second damping force generating mechanism 176, and opens in a region where the piston speed is lower than that of the first damping force generating mechanism 161 and the second damping force generating mechanism 176. Therefore, in the shock absorber 1, the third damping force generating mechanism 181 opens and generates a damping force even at piston speeds (extremely low speed regions) where the first damping force generating mechanism 161 and the second damping force generating mechanism 176 do not open, and a delay in the rise in internal pressure of the cylinder chamber 19 can be suppressed.

[0135] That is, assuming that the third damping force generating mechanism 181 is not included in the above structure, the oil L introduced into the second passage 175 would compress and deform the seal member 146 of the damping valve 151 provided in the pressure chamber 170 and the seal member 272 of the partition member 233 provided in the pressure chamber 280 at a piston speed at which the first damping force generating mechanism 161 and the second damping force generating mechanism 176 do not open. As a result, there is a possibility that the increase in the internal pressure of the cylinder chamber 19 would be delayed. In contrast, the shock absorber 1 can suppress the delay in the increase in the internal pressure of the cylinder chamber 19 because the third damping force generating mechanism 181 generates a damping force. Therefore, the shock absorber 1 can suppress the vehicle's behavior from becoming unstable.

[0136] In the shock absorber 1, the third damping force generating mechanism 181 is provided upstream of the first damping force generating mechanism 161 and the second damping force generating mechanism 176, so that the third damping force generating mechanism 181 can be provided in a position that is less susceptible to the effects of compression of the rubber parts. Therefore, the shock absorber 1 can effectively prevent the behavior of the vehicle from becoming unstable.

[0137] In the shock absorber 1, the third damping force generating mechanism 181 is provided upstream of the first damping force generating mechanism 161 and the second damping force generating mechanism 176, and therefore the third damping force generating mechanism 181 can be assembled to the piston rod 21 together with the first damping force generating mechanism 161 and the second damping force generating mechanism 176. Therefore, it is possible to suppress an increase in the number of assembly steps due to the provision of the third damping force generating mechanism 181.

[0138] The shock absorber 1 has a partition member 233 that is movably provided within the pressure chamber 280 of the second passage 175 to partition the second passage 175 into two regions, and on which a rubber compressive force acts when the shock absorber 1 is in operation. Therefore, assuming that the third damping force generation mechanism 181 is not provided, the oil liquid L introduced into the second passage 175 would compress and deform the rubber seal member 272 of the partition member 233 at a piston speed at which the first damping force generation mechanism 161 and the second damping force generation mechanism 176 do not open. Therefore, the shock absorber 1 can reliably obtain the effect of the third damping force generation mechanism 181 generating a damping force.

[0139] [Second embodiment] Next, the second embodiment will be described, focusing on the differences from the first embodiment, mainly with reference to Fig. 5. Note that parts common to the first embodiment will be designated by the same names and symbols. The shock absorber 1A of the second embodiment does not include the pilot case 72, discs 73 to 76, case member 231, disc 232, partition member 233, support disc 235, disc 236 and stopper member 237 of the shock absorber 1 of the first embodiment.

[0140] In shock absorber 1A, one case member 331 and one seat member 332 are stacked in this order from the disk 71 side on the opposite side of the piston 18 in the axial direction of disk 71. A partition member 233A is provided between case member 331 and seat member 332. The case member 331 and seat member 332 constitute a pilot case 72A. The partition member 233A is provided inside pilot case 72A.

[0141] On the opposite side of the seat member 332 from the case member 331 in the axial direction of the seat member 332, there are stacked, in order from the seat member 332 side, one disk 341, multiple disks, specifically seven disks 342, one disk 343, one disk 344, and one annular member 345, and they are fastened together with a nut 295.

[0142] The discs 341 to 344, the case member 331, the seat member 332, and the annular member 345 are all made of metal. The case member 331 is integrally formed by sintering. The seat member 332 is integrally formed by sintering. At least one of the case member 331 and the seat member 332 may be formed by machining. The discs 341 to 344 and the annular member 345 are all circular flat plates with holes and a constant thickness. The case member 331 and the seat member 332 are all annular. The mounting shaft portion 28 of the piston rod 21 is fitted onto the inner periphery of each of the discs 341 to 344, the case member 331, the seat member 332, and the annular member 345.

[0143] The case member 331 has a member main body 351 and a protruding portion 352. The member main body 351 is annular. The protruding portion 352 is also annular. The protruding portion 352 is provided on the inner peripheral side of the member main body 351. The protruding portion 352 protrudes from the end face of the member main body 351 on the piston 18 side in the axial direction toward the piston 18 along the axial direction of the case member 331.

[0144] The case member 331 is formed with a seat member side annular groove 362, a piston side annular groove 363, a seat member side radial groove 364, and a piston side radial groove 365.

[0145] The seat member side annular groove 362 is recessed from the end face of the member main body 351 opposite to the piston 18 in the axial direction toward the piston 18 along the axial direction of the member main body 351. The seat member side annular groove 362 is annular in shape.

[0146] The piston-side annular groove 363 is recessed from the end face of the member body 351 on the piston 18 side in the axial direction toward the opposite side from the piston 18 along the axial direction of the member body 351. The piston-side annular groove 363 is disposed further outward than the seat member-side annular groove 362 in the radial direction of the member body 351. The piston-side annular groove 363 is annular.

[0147] The seat member-side radial groove 364 is recessed from the end face of the member body 351 opposite the piston 18 in the axial direction toward the piston 18 along the axial direction of the member body 351. The seat member-side radial groove 364 has a depth from the end face of the member body 351 opposite the piston 18 in the axial direction shallower than the seat member-side annular groove 362. The seat member-side radial groove 364 crosses the seat member-side annular groove 362 in the radial direction of the case member 331. The seat member-side radial groove 364 has an inner groove portion 371 and an outer groove portion 372. The inner groove portion 371 extends from the inner circumferential surface of the member body 351 to the seat member-side annular groove 362. The outer groove portion 372 extends from the seat member-side annular groove 362 to the outer circumferential surface of the member body 351. A passage in the inner groove portion 371 communicates with a passage in the groove portion 30 of the piston rod 21. The passage in the outer groove portion 372 communicates with the cylinder chamber 20 .

[0148] The piston-side radial groove 365 crosses the protrusion 352 in the radial direction of the protrusion 352. The passage in the piston-side radial groove 365 communicates with the passage in the groove 30 of the piston rod 21.

[0149] The seat member 332 has a member main body 381, a protruding portion 382, ​​and a valve seat portion 383. The member main body 381 is annular. The protruding portion 382 is also annular. The valve seat portion 383 is also annular. The protruding portion 382 is provided on the inner circumferential side of the member main body 381. The valve seat portion 383 is provided on the member main body 381 outside the protruding portion 382 in the radial direction of the seat member 332.

[0150] The protrusion 382 protrudes from the end face of the member main body 381 on the opposite side to the piston 18 in the axial direction of the seat member 332, toward the opposite side to the piston 18 along the axial direction of the seat member 332. The valve seat portion 383 protrudes from the end face of the member main body 381 on the side opposite to the piston 18 along the axial direction of the seat member 332 toward the side opposite to the piston 18 .

[0151] A radial groove 386 is formed in the seat member 332. The radial groove 386 traverses the protrusion 382 in the radial direction. The passage in the radial groove 386 communicates with the passage in the groove portion 30 of the piston rod 21.

[0152] The end face of the seat member 332 on the piston 18 side in the axial direction overlaps and comes into surface contact with the end face of the case member 331 on the opposite side of the axial direction from the piston 18. As a result, the case member 331 and the seat member 332 form a pressure chamber 280A in the seat member-side annular groove 362. The pressure chamber 280A has an annular shape.

[0153] The passage in the inner groove 371 communicates with the pressure chamber 280A and the passage in the groove 30 of the piston rod 21. The passage in the outer groove portion 372 communicates with the pressure chamber 280A and the cylinder chamber 20.

[0154] The defining member 233A is annular. The defining member 233A is an O-ring having a circular cross section in a plane including its central axis. The defining member 233A is an elastic member with rubber elasticity. The defining member 233A is housed in the pressure chamber 280A. The defining member 233A simultaneously contacts the bottom surface of the seat member-side annular groove 362 and the end surface of the seat member 332 on the piston 18 side in the axial direction. At that time, the defining member 233A elastically deforms in the axial direction of the defining member 233A. The defining member 233A moves in the radial direction of the defining member 233A within the pressure chamber 280A. The defining member 233A elastically deforms in the radial direction of the defining member 233A within the pressure chamber 280A.

[0155] The partition member 233A divides the pressure chamber 280A into a first chamber 281A located radially inward from the partition member 233A and a second chamber 282A located radially outward from the partition member 233A. The first chamber 281A communicates with a passage in the groove 30 of the piston rod 21 via a passage in the inner groove 371. The second chamber 282A communicates with the cylinder chamber 20 via a passage in the outer groove 372.

[0156] Pilot case 72A, which includes pressure chamber 280A, the passage in inner groove 371, and the passage in outer groove 372, and partition member 233A constitute frequency sensitive mechanism 230A that varies the damping force in response to the frequency of the reciprocating motion of piston 18. Frequency sensitive mechanism 230A is provided in pilot case 72A. In frequency sensitive mechanism 230A, pressure chamber 280A, the passage in inner groove 371, and the passage in outer groove 372 are formed by two members, case member 331 and seat member 332.

[0157] In the damping valve 151, the seal member 146 of the pilot valve 70 is slidably and liquid-tightly fitted around the entire circumference to the radially outer wall surface of the piston-side annular groove 363 of the case member 331. The seal member 146 constantly seals between itself and the radially outer wall surface of the piston-side annular groove 363. The damping valve 151, the case member 331, and the disc 71 form a pressure chamber 170A. The pressure chamber 170A applies pressure to the damping valve 151 in the direction of the outer seat portion 84 of the valve seat member 53. The pressure chamber 170A is in communication with a passage in the groove portion 30 of the piston rod 21 via a passage in the piston-side radial groove 365 of the case member 331.

[0158] The disk 341 has an outer diameter that is smaller than the inner diameter of the valve seat portion 383 of the seat member 332 and larger than the outer diameter of the protrusion 382 . The plurality of discs 342 are configured so that the disc 342 on the disc 341 side in the axial direction can be seated on the valve seat portion 383 . The plurality of discs 342 constitute a disc valve 165A. The disc valve 165A is removably seated on a valve seat portion 383. The outer diameter of the disc valve 165A decreases as it moves away from the valve seat portion 383 in the axial direction.

[0159] The disc 343 has an outer diameter smaller than the minimum outer diameter of the disc valve 165A. The disc 344 has an outer diameter that is larger than the minimum outer diameter of the disc valve 165A and smaller than the maximum outer diameter of the disc valve 165A. The outer diameter of the annular member 345 is larger than the outer diameter of the disc 343 and smaller than the outer diameter of the disc 344. The annular member 345 is thicker than the discs 341 to 344. The annular member 345 has higher rigidity than the discs 341 to 344.

[0160] The disc valve 165A, which is made up of multiple discs 342, is removably seated on the valve seat portion 383. Between the disc valve 165A and the seat member 332, a radial passage 401 is formed between the valve seat portion 383 and the protrusion 382. The radial passage 401 communicates with a passage in the groove portion 30 of the piston rod 21 via a passage in a radial groove 386 of the seat member 332. When the disc valve 165A is removed from the valve seat portion 383, the radial passage 401 communicates with the cylinder chamber 20.

[0161] The second passage 175A is composed of the passages in the multiple passage holes 37 and the passage groove 38 of the piston 18, the chamber 141, the passages in the multiple passage holes 93 and the passage recess 92 of the valve seat member 53, the passage between the disc valve 54 and the valve seat 83 when the valve is open, the chamber 142, the passage in the passage groove 96 of the valve seat member 53, the passage in the groove 30 of the piston rod 21, the passage in the piston-side radial groove 365 of the pilot case 72A, the pressure chamber 170A, the passage in the inner groove 371 of the pilot case 72A, the first chamber 281A of the pressure chamber 280A, the passage in the radial groove 386 of the pilot case 72A, the radial passage 401, and the passage between the disc valve 165A and the valve seat 383 when the valve is open. The pressure chambers 170A and 280A are provided midway through the second passage 175A.

[0162] The disc valve 165A and the valve seat portion 383 constitute a second damping force generating mechanism 176A. The second damping force generating mechanism 176A is provided in the second passage 175A. When the disc valve 165A is released from the valve seat portion 383, the second damping force generating mechanism 176A connects the cylinder chamber 19 and the cylinder chamber 20 via the second passage 175A. At that time, the second damping force generating mechanism 176A generates a damping force by suppressing the flow of hydraulic fluid L in the second passage 175A. In other words, the second damping force generating mechanism 176A is an extension-side damping force generating mechanism that generates a damping force by suppressing the flow of hydraulic fluid L when hydraulic fluid L flows from the cylinder chamber 19 to the cylinder chamber 20 via the second passage 175A during the extension stroke. The second passage 175A is a passage through which oil L flows from the upstream cylinder chamber 19 to the downstream cylinder chamber 20 as the piston 18 moves during the extension stroke of the cylinder chambers 19 and 20. The second damping force generating mechanism 176A does not have a fixed orifice that constantly connects the radial passage 401 and the cylinder chamber 20.

[0163] The disc 344 and the annular member 345 come into contact with the disc valve 165A when the disc valve 165A is deformed in the opening direction, thereby preventing the disc valve 165A from deforming beyond a specified limit.

[0164] Between the disc valve 165A and the valve seat portion 383 is a passage opening 177A that connects the pressure chamber 170A to the cylinder chamber 20 outside the pressure chamber 170A and connects the first chamber 281A of the pressure chamber 280A to the cylinder chamber 20. A second damping force generating mechanism 176A is provided in this passage opening 177A.

[0165] The second passage 175A includes a passage within the passage groove 96 of the valve seat member 53, a passage within the groove portion 30 of the piston rod 21, a passage within the piston-side radial groove 365 of the case member 331, the pressure chamber 170A, a passage within the inner groove portion 371 of the case member 331, the first chamber 281A of the pressure chamber 280A, a passage within the radial groove 386 of the seat member 332, the radial passage 401, and a passage between the disc valve 165A and the valve seat portion 383 when the valve is open, and is arranged in parallel with the passage between the damping valve 151 and the outer seat portion 84 of the first passage 43.

[0166] The third damping force generating mechanism 181 is provided upstream of the first damping force generating mechanism 161 and the second damping force generating mechanism 176A in the flow direction of the oil L during the extension stroke. The third damping force generating mechanism 181 has lower rigidity and a lower valve opening pressure than the first damping force generating mechanism 161 and the second damping force generating mechanism 176A. Therefore, the third damping force generating mechanism 181 opens in a region where the piston speed is lower than those of the first damping force generating mechanism 161 and the second damping force generating mechanism 176A.

[0167] Next, the main operation of the shock absorber 1A will be described. "When it is assumed that the frequency sensitive mechanism 230A does not act during the extension stroke, and only the first damping force generating mechanism 161 and the second damping force generating mechanism 176A on the extension side act"

[0168] In this case, the shock absorber 1A operates in the same manner as the shock absorber 1 in the extremely low speed region where the piston speed is slower than the first predetermined value, and in the extremely low speed region where the piston speed is equal to or greater than the first predetermined value and less than the second predetermined value.

[0169] In shock absorber 1A, in the low-speed region where the piston speed is equal to or greater than the second predetermined value and less than the third predetermined value, oil L from cylinder chamber 19 passes through second passage 175A while keeping third damping force generation mechanism 181 open, and while opening disc valve 165A of second damping force generation mechanism 176A, passes between disc valve 165A and valve seat portion 383 and flows into cylinder chamber 20. As a result, a damping force with valve characteristics (damping force is approximately proportional to piston speed) is generated. For this reason, the characteristic of damping force relative to piston speed in the low-speed region is such that the rate of increase of damping force relative to an increase in piston speed is lower than in the extremely low-speed region.

[0170] In the medium-to-high speed range where the piston speed becomes faster than the third predetermined value, the relationship of the forces (hydraulic pressure) acting on the damping valve 151 of the first damping force generation mechanism 161 is such that the opening force applied from the chamber 142 is greater than the closing force applied from the pressure chamber 170A. Therefore, in this medium-to-high speed range, as the piston speed increases, the damping valve 151 of the first damping force generation mechanism 161 opens by moving away from the outer seat portion 84 of the valve seat member 53. Therefore, in addition to flowing from the cylinder chamber 19 to the cylinder chamber 20 through the second passage 175A while opening the disc valve 165A, the hydraulic fluid L also flows to the cylinder chamber 20 through the first passage 43 while opening the damping valve 151 of the first damping force generation mechanism 161. Therefore, the rate of increase in damping force relative to an increase in piston speed in the medium-to-high speed range is lower than in the low speed range.

[0171] In the compression stroke, the operation of the shock absorber 1A is the same as that of the shock absorber 1, assuming that the frequency sensitive mechanism 230A does not operate and only the first damping force generating mechanism 202 on the compression side operates.

[0172] "When the frequency sensitive mechanism 230A acts during the extension stroke" During the extension stroke, hydraulic oil L is introduced from the cylinder chamber 19 into the first chamber 281A of the frequency sensitive mechanism 230A via the second passage 175A. The partition member 233A then moves radially outward while elastically deforming. In this manner, the partition member 233A expands the volume of the first chamber 281A, introducing hydraulic oil L into the first chamber 281A. At the same time, the partition member 233A discharges hydraulic oil L from the second chamber 282A into the cylinder chamber 20 via the passage in the outer groove portion 372.

[0173] Here, during the extension stroke when the piston frequency is high, the stroke of the piston 18 is small. Therefore, the amount of oil L introduced from the cylinder chamber 19 to the first chamber 281A via the second passage 175A is small. Therefore, although the partition member 233A deforms as described above, it does not deform to near its limit.

[0174] Therefore, during the extension stroke when the piston frequency is high, the partition member 233A of the frequency sensitive mechanism 230A deforms and moves as described above, thereby introducing hydraulic fluid L from the cylinder chamber 19 into the first chamber 281A. This reduces the flow rate of hydraulic fluid L flowing from the cylinder chamber 19 through the first passage 43 and the first damping force generating mechanism 161 to the cylinder chamber 20, and the flow rate of hydraulic fluid L flowing through the second passage 175A and the second damping force generating mechanism 176A to the cylinder chamber 20. Furthermore, by introducing hydraulic fluid L from the cylinder chamber 19 into the first chamber 281A, the pressure increase in the pressure chamber 170A is suppressed compared to when the first chamber 281A is not present, making it easier for the damping valve 151 of the first damping force generating mechanism 161 to open. As a result, the damping force on the extension side is softened.

[0175] 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 L is introduced from the cylinder chamber 19 to the first chamber 281A via the second passage 175A. Therefore, although hydraulic fluid L flows from the cylinder chamber 19 to the first chamber 281A at the beginning of the stroke of the piston 18, the partition member 233A subsequently deforms and moves to near its limit, and further deformation and movement are suppressed. As a result, hydraulic fluid L does not flow from the cylinder chamber 19 to the first chamber 281A. This prevents a decrease in the flow rate of hydraulic fluid L flowing from the cylinder chamber 19 through the first passage 43 to the cylinder chamber 20 via the first damping force generating mechanism 161 and the flow rate of hydraulic fluid L flowing through the second passage 175A to the cylinder chamber 20 via the second damping force generating mechanism 176A. Furthermore, since oil L is not introduced into the first chamber 281A from the cylinder chamber 19, the pressure in the pressure chamber 170A increases, making it difficult for the damping valve 151 of the first damping force generating mechanism 161 to open. As a result, when the piston frequency is low, the damping force during the extension stroke is stronger than when the piston frequency is high.

[0176] During the extension stroke, when the first damping force generating mechanism 161 opens, the rubber seal member 146 of the pilot valve 70 provided in the pressure chamber 170A is compressed radially outward by the pressure of the oil L introduced into the second passage 175A. Furthermore, during the extension stroke, when the first damping force generating mechanism 161 opens, the rubber partition member 233A provided in the pressure chamber 280A is compressed radially outward. Therefore, when the first damping force generating mechanism 161 provided in the first passage 43 operates to generate a damping force, the compressive forces of the seal member 146 and the partition member 233A act on the first damping force generating mechanism 161 via the oil L.

[0177] "When the frequency sensitive mechanism 230A operates during the retraction stroke" During the compression stroke, oil L is introduced from the cylinder chamber 20 into the second chamber 282A of the frequency sensitive mechanism 230A through the passage in the outer groove portion 372. The partition member 233A then moves radially inward while elastically deforming. In this manner, the partition member 233A expands the volume of the second chamber 282A, introducing oil L into the second chamber 282A. At the same time, the partition member 233A discharges oil L from the first chamber 281A to the cylinder chamber 19 through the second passage 175A.

[0178] Here, during the compression stroke when the piston frequency is high, the stroke of the piston 18 is small. Therefore, the amount of oil L introduced from the cylinder chamber 20 into the second chamber 282A through the passage in the outer groove portion 372 is small. Therefore, although the partition member 233A deforms as described above, it does not deform to near its limit.

[0179] Therefore, during the compression stroke when the piston frequency is high, the partition member 233A of the frequency sensitive mechanism 230A deforms and moves as described above, causing the oil L to be introduced from the cylinder chamber 20 into the second chamber 282A. This reduces the flow rate of the oil L flowing from the cylinder chamber 20 to the cylinder chamber 19 through the compression-side passage 144 including the fixed orifice 143, and the flow rate of the oil L flowing through the first passage 44 to the cylinder chamber 19 via the first damping force generating mechanism 202. This reduces the damping force on the compression side.

[0180] On the other hand, during the extension stroke when the piston frequency is low, the stroke of the piston 18 is long. Therefore, a large amount of hydraulic fluid L is introduced from the cylinder chamber 19 to the second chamber 282A through the passage in the outer groove portion 372. Therefore, although hydraulic fluid L flows from the cylinder chamber 20 to the second chamber 282A at the beginning of the stroke of the piston 18, the partition member 233A subsequently deforms and moves to near its limit, suppressing further deformation and movement. As a result, hydraulic fluid L does not flow from the cylinder chamber 20 to the second chamber 282A. This prevents a decrease in the flow rate of hydraulic fluid L flowing from the cylinder chamber 20 to the cylinder chamber 19 through the compression-side passage 144 including the fixed orifice 143, and the flow rate of hydraulic fluid L flowing through the first passage 44 to the cylinder chamber 19 via the first damping force generating mechanism 202. Therefore, during the compression stroke when the piston frequency is low, the damping force is stronger than when the piston frequency is high.

[0181] The shock absorber 1A of the second embodiment has a first passage 43 and a second passage 175A through which hydraulic fluid L flows from one cylinder chamber 19 in the cylinder 2 (see FIG. 2) as the piston 18 moves. The shock absorber 1A also has a first damping force generation mechanism 161 that is provided in the first passage 43 to generate a damping force and that, when in operation, is subjected to compressive forces of a sealing member 146 and a partition member 233A, both of which are made of rubber. The shock absorber 1A also has pressure chambers 170A and 280A provided in the second passage 175A. The shock absorber 1A also has a second damping force generation mechanism 176A that is provided in a passage opening 177A that connects the pressure chambers 170A and 280A to the cylinder chamber 20.

[0182] In the shock absorber 1A configured as described above, a third damping force generating mechanism 181 is provided upstream of the first damping force generating mechanism 161 and the second damping force generating mechanism 176A, and the third damping force generating mechanism 181 opens in a region where the piston speed is lower than that of the first damping force generating mechanism 161 and the second damping force generating mechanism 176A. Therefore, in the shock absorber 1A, the third damping force generating mechanism 181 opens and generates a damping force even at a piston speed (extremely low speed region) where the first damping force generating mechanism 161 and the second damping force generating mechanism 176A do not open, and a delay in the rise in internal pressure of the cylinder chamber 19 can be suppressed. Therefore, like the shock absorber 1, the shock absorber 1A can suppress instability in the behavior of the vehicle.

[0183] In shock absorber 1A, third damping force generating mechanism 181 is provided upstream of first damping force generating mechanism 161 and second damping force generating mechanism 176A, so that third damping force generating mechanism 181 can be provided in a position that is less susceptible to the effects of compression of rubber parts. Therefore, shock absorber 1A can effectively prevent the behavior of the vehicle from becoming unstable.

[0184] In the shock absorber 1A, the third damping force generating mechanism 181 is provided upstream of the first damping force generating mechanism 161 and the second damping force generating mechanism 176A, and therefore the third damping force generating mechanism 181 can be assembled to the piston rod 21 together with the first damping force generating mechanism 161 and the second damping force generating mechanism 176A. Therefore, it is possible to suppress an increase in the number of assembly steps due to the provision of the third damping force generating mechanism 181.

[0185] The shock absorber 1A has a partition member 233A that is movably provided within the pressure chamber 280A of the second passage 175A to partition the second passage 175A into two regions, and on which a rubber compressive force acts when the shock absorber 1A is in operation. Therefore, assuming that the third damping force generation mechanism 181 is not provided, the oil L introduced into the second passage 175A would deform the rubber partition member 233A at a piston speed at which the first damping force generation mechanism 161 and the second damping force generation mechanism 176 do not open. Therefore, the shock absorber 1A can reliably obtain the effect of the damping force generated by the third damping force generation mechanism 181.

[0186] The shock absorber 1A can also be modified to a shock absorber 1B shown in FIG. Shock absorber 1B is configured such that shock absorber 1A does not have valve disc 57, pilot valve 70, disc 71, frequency sensitive mechanism 230A, and disc 341, but instead has discs 342 to 344 and annular member 345 stacked on valve disc 56 and fastened with nut 295. Furthermore, shock absorber 1B does not have groove portion 30 in piston rod 21, and does not have passage groove 96 in valve seat member 53.

[0187] In the shock absorber 1B, the valve disc 56 and the disc 342 form a disc valve 165B, and the disc valve 165B and the outer seat portion 84 form a first damping force generating mechanism 161B.

[0188] The main operation of the shock absorber 1B will now be described. "Extension stroke" During the extension stroke, in the extremely low speed region where the piston speed is slower than the first predetermined value, the oil L from the cylinder chamber 19 is introduced into the chamber 141 through the passages in the passage holes 37 and the passage groove 38. The oil L introduced into the chamber 141 then passes through the passages in the passage holes 93 and the passage recess 92, opening the third damping force generating mechanism 181 and being introduced into the chamber 142. The oil L introduced into the chamber 142 in this manner flows into the cylinder chamber 20 through the fixed orifice 143 of the first damping force generating mechanism 161B. That is, in the extremely low speed region, the oil L from the cylinder chamber 19 flows into the cylinder chamber 20 through the first passage 43. Because no fixed orifice is provided in the first passage 44, the entire flow of the oil L from the cylinder chamber 19 passes through the third damping force generating mechanism 181, opening the valve. When the third damping force generating mechanism 181 is opened, the pressure in the cylinder chamber 19 increases. Therefore, even in the extremely low speed region, the third damping force generating mechanism 181 opens and the damping force rises immediately, generating a damping force with valve characteristics (the damping force is approximately proportional to the piston speed).

[0189] In the extremely low speed region where the piston speed is equal to or greater than a first predetermined value and less than a second predetermined value, a damping force having the orifice characteristics (where the damping force is approximately proportional to the square of the piston speed) defined by the fixed orifice 143 is generated when the oil L flows through the first passage 43. Therefore, the characteristic of the damping force relative to the piston speed in the extremely low speed region is such that the rate of increase of the damping force relative to an increase in the piston speed is higher than in the extremely low speed region.

[0190] In the region where the piston speed is equal to or greater than the second predetermined value, oil L from the cylinder chamber 19 flows from the chamber 142 to the cylinder chamber 20 through between the disc valve 165B and the outer seat portion 84 while opening the disc valve 165B of the first damping force generating mechanism 161B, while keeping the third damping force generating mechanism 181 open. This generates a damping force with valve characteristics (the damping force is approximately proportional to the piston speed). Therefore, in the region where the piston speed is equal to or greater than the second predetermined value, the rate of increase of the damping force relative to an increase in piston speed is lower than in the extremely low speed region.

[0191] "Retraction process"

[0192] During the compression stroke, in the extremely low speed region where the piston speed is slower than the fourth predetermined value, the first damping force generation mechanism 202 does not have a fixed orifice, so the entire flow of oil L from the cylinder chamber 20 flows from the fixed orifice 143 of the first damping force generation mechanism 161B to the chamber 142, opens the third damping force generation mechanism 182, and flows from the passages in the multiple passage holes 103 and the passage recess 102 to the chamber 141 and the passages in the passage groove 38 and the multiple passage holes 37 to the cylinder chamber 19. In other words, the oil flows to the cylinder chamber 19 through the compression-side passage 144. Therefore, even if the piston speed is in the extremely low speed region, a damping force is immediately generated by the third damping force generation mechanism 182, and a damping force with a valve characteristic (damping force is approximately proportional to the piston speed) is generated.

[0193] In the extremely low speed region where the piston speed is equal to or greater than a fourth predetermined value and less than a fifth predetermined value, when oil L flows through the compression-side passage 144, a damping force with the orifice characteristics (the damping force is approximately proportional to the square of the piston speed) defined by the fixed orifice 143 is generated. This results in the generation of a damping force with the orifice characteristics. Therefore, the characteristic of the damping force relative to the piston speed in the extremely low speed region is such that the rate of increase of the damping force relative to an increase in piston speed is higher than in the extremely low speed region.

[0194] When the piston speed becomes faster than the fifth predetermined value, the oil L introduced from the cylinder chamber 20 into the first passage 44 opens the disc valve 201 of the first damping force generating mechanism 202 and flows between the disc valve 201 and the valve seat portion 49 into the cylinder chamber 19. This generates a damping force with valve characteristics (damping force is approximately proportional to piston speed). Therefore, when the piston speed is greater than the fifth predetermined value, the damping force characteristic with respect to piston speed is such that the rate of increase in damping force relative to an increase in piston speed is lower than in the extremely low speed region.

[0195] Although hydraulic shock absorbers have been shown as examples of shock absorbers 1, 1A, and 1B, the above structure can also be applied to shock absorbers that use water or air as the working fluid. [Explanation of symbols]

[0196] 1,1A... shock absorber, 2... cylinder, 18... piston, 19,20... cylinder chamber, 21... piston rod, 43... first passage, 161... first damping force generating mechanism, 170,170A, 280,280A... pressure chamber, 175,175A... second passage, 176,176A... second damping force generating mechanism, 177,177A... passage opening, 181... third damping force generating mechanism, 233,233A... partition member.

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 and a second passage through which working fluid flows from one chamber in the cylinder as the piston moves; a first damping force generating mechanism that is provided in the first passage and generates a damping force, and that exerts a compressive force of rubber when it is in operation; a pressure chamber provided midway through the second passage; a second damping force generating mechanism provided at a passage port that connects the pressure chamber to another chamber in the cylinder; A shock absorber comprising a third damping force generating mechanism located upstream of the first damping force generating mechanism and the second damping force generating mechanism, the third damping force generating mechanism opening in a region where the piston speed is lower than that of the first damping force generating mechanism and the second damping force generating mechanism.

2. 2. The shock absorber according to claim 1, further comprising a dividing member movably disposed within said pressure chamber to divide said second passage into two regions, said dividing member being operable to exert a compressive force on said rubber.

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