buffer

Abstract

To provide a shock absorber which can suppress a variation of a valve-opening characteristic.SOLUTION: A shock absorber comprises: first attenuation force generation mechanisms 41, 42 arranged at first passages 72, 92, and generating attenuation forces: second passages 172, 182 which are arranged separately from the first passages 72, 92; second attenuation force generation mechanisms 173, 183 arranged at the second passages 172, 182, valve-opened at lower piston speeds lower than those of the first attenuation force generation mechanisms 41, 42, and generating attenuation forces; third passages 511, 512 which are arranged separately from the second passages 172, 182; and volume variable mechanisms 185, 186 arranged at the third passages 511, 512. The second attenuation force generation mechanisms 173, 183 have passage forming members 109 at which the second passages 172, 182 are formed, first valves 107, 110 placed on the passage forming members 109, and opening and closing the second passages 172, 182, and first energizing members 106, 111 for energizing external peripheral sides of the first valves 107, 110.SELECTED DRAWING: Figure 2

Description

Technical Field

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

Background Art

[0002] Some shock absorbers have a valve that opens in a region where the piston speed is extremely low (see, for example, Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, a valve that opens in a region where the piston speed is extremely low is likely to have variations in opening characteristics because it opens with a minute differential pressure. Therefore, it is required to suppress variations in the opening characteristics.

[0005] An object of the present invention is to provide a shock absorber capable of suppressing variations in opening characteristics.

Means for Solving the Problems

[0006] To achieve the above objective, a first aspect of the present invention comprises a cylinder in which a working fluid is sealed; a piston slidably provided within the cylinder and dividing the cylinder into two chambers; a piston rod connected to the piston and extending to the outside of the cylinder; a first passage through which the working fluid flows from the upstream chamber to the downstream chamber as the piston moves; a first damping force generating mechanism provided in the first passage and generating a damping force; a second passage provided separately from the first passage; a second damping force generating mechanism provided in the second passage and opening at a piston speed lower than that of the first damping force generating mechanism to generate a damping force; a third passage provided separately from the second passage; and a volume variable mechanism provided in the third passage, wherein the second damping force generating mechanism comprises a passage forming member in which the second passage is formed; a first valve mounted on the passage forming member and opening and closing the second passage; and a first biasing member that biases the outer circumference of the first valve.

[0007] A second aspect of the present invention comprises a cylinder in which a working fluid is sealed; a piston slidably provided within the cylinder and dividing the cylinder into two chambers; a piston rod connected to the piston and extending to the outside of the cylinder; a first passage through which the working fluid flows from the upstream chamber to the downstream chamber as the piston moves; a first damping force generating mechanism provided in the first passage and generating a damping force; a second passage provided separately from the first passage; and a second damping force generating mechanism provided in the second passage and opening at a piston speed lower than that of the first damping force generating mechanism to generate a damping force, wherein the second damping force generating mechanism comprises a passage forming member in which the second passage is formed; a first valve mounted on the passage forming member and opening and closing the second passage; and a first biasing member that biases the outer circumference of the first valve. [Effects of the Invention]

[0008] According to the present invention, it is possible to suppress variations in valve opening characteristics. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view showing a buffer according to a first embodiment of the present invention. [Figure 2] This is a partial cross-sectional view showing the area around the piston of a buffer according to a first embodiment of the present invention. [Figure 3] This is a partial cross-sectional view showing the main part of a buffer according to the first embodiment of the present invention. [Figure 4] This is a plan view showing the spring member of a shock absorber according to the first embodiment of the present invention. [Figure 5] This is a partial cross-sectional view showing the main part of a buffer according to a second embodiment of the present invention. [Figure 6] This is a partial cross-sectional view showing the main part of a buffer according to a third embodiment of the present invention. [Modes for carrying out the invention]

[0010] [First Embodiment] The first embodiment will be described based on Figures 1 to 3. For the sake of explanation, in the following description, the upper side in Figures 1 to 3, 5 and 6 will be referred to as "top," and the lower side in Figures 1 to 3, 5 and 6 will be referred to as "bottom."

[0011] <Structure> The shock absorber 1 of the first embodiment is a shock absorber used in the suspension systems of railway vehicles and automobiles such as two-wheeled and four-wheeled vehicles. Specifically, the shock absorber 1 is a shock absorber used in the suspension system of a four-wheeled automobile. As shown in Figure 1, the shock absorber 1 is a double-cylinder type shock absorber equipped with a cylinder 4 having an inner cylinder 2 and an outer cylinder 3. The inner cylinder 2 is cylindrical. The outer cylinder 3 is a bottomed cylinder with a larger diameter than the inner cylinder 2. The outer cylinder 3 is provided coaxially with the inner cylinder 2, radially outward from the inner cylinder 2. A reservoir chamber 5 is located between the outer cylinder 3 and the inner cylinder 2.

[0012] The outer cylinder 3 has a body member 8 and a bottom member 9. The body member 8 is a stepped cylindrical shape with smaller diameters at both axial ends than at the axial middle section. The bottom member 9 closes one axial end of the body member 8. The side of the body member 8 opposite the bottom member 9 is an opening.

[0013] The shock absorber 1 comprises a valve body 12 and a rod guide 13. The valve body 12 is annular and is provided at one axial end of the inner cylinder 2. The rod guide 13 is annular and is provided at the other axial end of the inner cylinder 2 and the outer cylinder 3. The valve body 12 constitutes the base valve 15 and has a stepped outer circumference. The rod guide 13 also has a stepped outer circumference, and its large diameter portion is positioned radially on the body member 8.

[0014] One end of the inner cylinder 2 is fitted into the small-diameter portion of the outer circumference of the valve body 12. The other end of the inner cylinder 2 is fitted into the small-diameter portion of the outer circumference of the rod guide 13. The other end of the inner cylinder 2 is engaged with the body member 8 of the outer cylinder 3 via the rod guide 13. In this state, the inner cylinder 2 is positioned radially relative to the outer cylinder 3. Here, the space between the valve body 12 and the bottom member 9 is connected to the space between the inner cylinder 2 and the outer cylinder 3 via a passage groove 16 formed in the valve body 12. The space between the valve body 12 and the bottom member 9 constitutes a reservoir chamber 5, similar to the space between the inner cylinder 2 and the outer cylinder 3.

[0015] The shock absorber 1 is equipped with a sealing member 18. The sealing member 18 is located on the side of the rod guide 13 opposite to the bottom member 9. This sealing member 18, like the rod guide 13, is fitted to the inner circumference of the body member 8. A locking portion 19 is formed at the end of the body member 8 opposite to the bottom member 9. The locking portion 19 is formed by plastically deforming the body member 8 radially inward through crimping, such as curling. The sealing member 18 is sandwiched between this locking portion 19 and the rod guide 13. The sealing member 18 closes the opening of the outer cylinder 3 and is specifically an oil seal.

[0016] The shock absorber 1 includes a piston 21. The piston 21 is provided slidably within a cylinder 4. The piston 21 is provided slidably within the inner cylinder 2 of the cylinder 4. The piston 21 divides the inside of the inner cylinder 2 into two chambers, an upper chamber 22 and a lower chamber 23. The upper chamber 22 is provided between the piston 21 and the rod guide 13 within the inner cylinder 2. The lower chamber 23 is provided between the piston 21 and the valve body 12 within the inner cylinder 2. The lower chamber 23 is defined by the valve body 12 and the reservoir chamber 5. Oil L as a working fluid is enclosed within the upper chamber 22 and the lower chamber 23 in the cylinder 4. Gas G and oil L as working fluids are enclosed within the reservoir chamber 5 in the cylinder 4.

[0017] The shock absorber 1 includes a piston rod 25. One axial end portion of the piston rod 25 is disposed inside the cylinder 4 and is connected and fixed to the piston 21. The other end portion of the piston rod 25 extends outside the cylinder 4 together with it. The piston rod 25 is made of metal and penetrates through the upper chamber 22. The piston rod 25 does not penetrate through the lower chamber 23. Therefore, the upper chamber 22 is a rod side chamber through which the piston rod 25 penetrates. The lower chamber 23 is a bottom side chamber on the side of the bottom member 9 of the cylinder 4.

[0018] The piston 21 and the piston rod 25 move integrally. In the extension stroke of the shock absorber 1 in which the protruding amount of the piston rod 25 from the cylinder 4 increases, the piston 21 moves toward the upper chamber 22 side. In the compression stroke of the shock absorber 1 in which the protruding amount of the piston rod 25 from the cylinder 4 decreases, the piston 21 moves toward the lower chamber 23 side.

[0019] The rod guide 13 and the seal member 18 are both annular. The piston rod 25 is slidably inserted inside each of these rod guide 13 and seal member 18 and extends from the inside to the outside of the cylinder 4. One end portion in the axial direction of the piston rod 25 is fixed to the piston 21 inside the cylinder 4. The other end portion in the axial direction of the piston rod 25 extends outside the cylinder 4 through the rod guide 13 and the seal member 18.

[0020] The rod guide 13 supports the piston rod 25 with respect to the cylinder 4 so as to be movable in the axial direction while restricting its radial movement. The rod guide 13 guides the axial movement of the piston rod 25. The outer peripheral portion of the seal member 18 is in close contact with the outer cylinder 3 of the cylinder 4. The inner peripheral portion of the seal member 18 is in sliding contact with the outer peripheral portion of the piston rod 25 that moves in the axial direction. Thereby, the seal member 18 prevents the oil fluid L and the gas G inside the cylinder 4 from leaking to the outside.

[0021] The piston rod 25 has a main shaft portion 27 and a mounting shaft portion 28. The mounting shaft portion 28 has a smaller diameter than the main shaft portion 27. For the piston rod 25, the main shaft portion 27 is slidably fitted to the rod guide 13 and the seal member 18. For the piston rod 25, the mounting shaft portion 28 is disposed inside the cylinder 4 and connected to the piston 21 and the like. The end portion of the main shaft portion 27 on the side of the mounting shaft portion 28 is an axial step portion 29 that extends in the direction orthogonal to the axis.

[0022] A passage notch portion 30 is formed on the outer peripheral portion of the mounting shaft portion 28. The passage notch portion 30 is formed at an intermediate position in the axial direction of the mounting shaft portion 28 and extends in the axial direction of the mounting shaft portion 28. A male thread 31 is formed at the tip position on the side opposite to the main shaft portion 27 in the axial direction on the outer peripheral portion of the mounting shaft portion 28. The passage notch portion 30 is formed, for example, by planar cutting of the outer peripheral portion of the mounting shaft portion 28 with a plane parallel to the central axis of the mounting shaft portion 28. The passage notch portion 30 can be formed in a so-called double-sided width shape at two positions 180 degrees different in the circumferential direction of the mounting shaft portion 28.

[0023] In the shock absorber 1, for example, the portion of the piston rod 25 protruding from the cylinder 4 is positioned vertically at the top and supported by the vehicle body. In this case, the bottom member 9 of the cylinder 4 is positioned vertically at the bottom and connected to the wheel side. Conversely, the cylinder 4 side may be supported by the vehicle body and the piston rod 25 may be connected to the wheel side.

[0024] As shown in Figure 2, the piston 21 has a metal piston body 36 and a synthetic resin sliding member 37. The piston body 36 is in contact with and connected to the piston rod 25. The sliding member 37 is integrally mounted on the outer circumferential surface of the piston body 36. The piston 21 slides inside the inner cylinder 2 of the cylinder 4 with the sliding member 37 in contact with the inner cylinder 2.

[0025] The piston body 36 is provided with multiple passage holes 38 and multiple passage holes 39. Both the multiple passage holes 38 and the multiple passage holes 39 can connect the upper chamber 22 and the lower chamber 23.

[0026] Multiple passage holes 38 are arranged at equal pitches in the circumferential direction of the piston body 36. Each of the multiple passage holes 38 is arranged in the circumferential direction of the piston body 36 with one passage hole 39 in between. The multiple passage holes 38 constitute half of the total number of passage holes 38,39. Each of the multiple passage holes 38 has a crank shape with two bending points. In each of the multiple passage holes 38, the end on the lower chamber 23 side in the axial direction of the piston 21 opens radially inward from the end on the upper chamber 22 side of the piston 21. An annular groove 55 is formed in the piston body 36 on the lower chamber 23 side in the axial direction. The annular groove 55 connects the multiple passage holes 38.

[0027] A first damping force generating mechanism 41 is provided on the lower chamber 23 side of the annular groove 55. The first damping force generating mechanism 41 generates damping force by opening and closing passages within the multiple passage holes 38 and the annular groove 55. By positioning the first damping force generating mechanism 41 on the lower chamber 23 side, the passages within the multiple passage holes 38 and the annular groove 55 become passages through which the oil liquid L flows from the upper chamber 22, which is the upstream side, to the lower chamber 23, which is the downstream side, during the movement of the piston 21 toward the upper chamber 22. The passages within the multiple passage holes 38 and the annular groove 55 become extension-side passages through which the oil liquid L flows from the upper chamber 22, which is the upstream side, to the lower chamber 23, which is the downstream side, during the extension stroke of the shock absorber 1. The first damping force generating mechanism 41 is provided for the extension-side passages within the multiple passage holes 38 and the annular groove 55. The first damping force generating mechanism 41 is an extension-side damping force generating mechanism that generates damping force by suppressing the flow of oil liquid L from the passages in the multiple extension-side passage holes 38 and the annular groove 55 to the lower chamber 23.

[0028] The remaining half of the total number of passage holes 38, 39, consisting of multiple passage holes 39, are arranged at equal pitches in the circumferential direction of the piston body 36. Each of the multiple passage holes 39 is arranged with one passage hole 38 in between. Each of the multiple passage holes 39 has a crank shape with two bending points. In each of the multiple passage holes 39, the end on the upper chamber 22 side in the axial direction of the piston 21 opens radially inward from the end on the lower chamber 23 side. An annular groove 56 is formed in the piston body 36 on the upper chamber 22 side in the axial direction. The annular groove 56 connects the multiple passage holes 39.

[0029] A first damping force generating mechanism 42 is provided on the upper chamber 22 side of the annular groove 56. The first damping force generating mechanism 42 generates damping force by opening and closing passages within the multiple passage holes 39 and the annular groove 56. By positioning the first damping force generating mechanism 42 on the upper chamber 22 side, the passages within the multiple passage holes 39 and the annular groove 56 become passages through which the oil liquid L flows from the upper chamber 22, which is the upstream side, to the upper chamber 22, which is the downstream side, during the movement of the piston 21 toward the lower chamber 23. The passages within the multiple passage holes 39 and the annular groove 56 become the compression-side passages through which the oil liquid L flows from the upper chamber 22, which is the downstream side, during the compression stroke of the shock absorber 1. The first damping force generating mechanism 42 is provided for the passages within the multiple passage holes 39 and the annular groove 56 on the compression side. The first damping force generating mechanism 42 is a compression-side damping force generating mechanism that generates damping force by suppressing the flow of oil liquid L from the passages in the multiple passage holes 39 and the annular groove 56 on the compression side to the upper chamber 22.

[0030] The piston body 36 is roughly disc-shaped, with an insertion hole 44 formed in its radial center. The insertion hole 44 penetrates the piston body 36 in its axial direction. The mounting shaft portion 28 of the piston rod 25 is inserted into the insertion hole 44. The insertion hole 44 has a small diameter hole portion 45 and a large diameter hole portion 46. The small diameter hole portion 45 is located on one side from the axial center of the insertion hole 44. The large diameter hole portion 46 is located on the other side of the axial direction of the insertion hole 44. The large diameter hole portion 46 is larger in diameter than the small diameter hole portion 45. In the piston body 36, the small diameter hole portion 45 is provided on the axial side of the upper chamber 22, and the large diameter hole portion 46 is provided on the axial side of the lower chamber 23. The piston 21 has the mounting shaft portion 28 of the piston rod 25 fitted into its small diameter hole portion 45. This positions the piston 21 radially relative to the piston rod 25.

[0031] An inner seat portion 47 and a valve seat portion 48 are formed at the axial end of the piston body 36 on the lower chamber 23 side. The inner seat portion 47 is positioned radially inward of the piston body 36 relative to the opening of the annular groove 55 on the lower chamber 23 side. The inner seat portion 47 is annular. The valve seat portion 48 is positioned radially outward of the piston body 36 relative to the opening of the annular groove 55 on the lower chamber 23 side. The valve seat portion 48 is annular. The valve seat portion 48 constitutes part of the first damping force generating mechanism 41.

[0032] An inner seat portion 49 and a valve seat portion 50 are formed at the axial end of the piston body 36 on the upper chamber 22 side. The inner seat portion 49 is positioned radially inward of the piston body 36 relative to the opening of the annular groove 56 on the upper chamber 22 side. The inner seat portion 49 is annular. The valve seat portion 50 is positioned radially outward of the piston body 36 relative to the opening of the annular groove 56 on the upper chamber 22 side. The valve seat portion 50 is annular. The valve seat portion 50 constitutes part of the first damping force generating mechanism 42.

[0033] The insertion hole 44 of the piston body 36 has a large-diameter hole portion 46 located axially closer to the inner seat portion 47 than the small-diameter hole portion 45. The passage within the large-diameter hole portion 46 of the piston body 36 is aligned axially with the piston rod passage portion 51 within the passage notch portion 30 of the piston rod 25. The passage within the large-diameter hole portion 46 is in constant communication with the piston rod passage portion 51.

[0034] In the piston body 36, the radially outer portion of the piston body 36 is stepped, with a lower axial height than the valve seat portion 48. The opening of the compression passage hole 39 on the lower chamber 23 side is located in this stepped portion of the piston body 36. Similarly, in the piston body 36, the radially outer portion of the piston body 36 is stepped, with a lower axial height than the valve seat portion 50. The opening of the extension passage hole 38 on the upper chamber 22 side is located in this stepped portion of the piston body 36.

[0035] The compression-side first damping force generating mechanism 42 includes the valve seat portion 50 of the piston 21. The first damping force generating mechanism 42 has, in order from the axial piston 21 side, one disc 63, multiple (specifically two) discs 64, multiple (specifically three) discs 65, multiple (specifically two) discs 66, one disc 67, one disc 68, and one annular member 69. The multiple discs 64 have the same outer diameter. The multiple discs 65 have the same outer diameter. The multiple discs 66 have the same outer diameter. The discs 63-68 and the annular member 69 are all made of metal and are perforated circular flat plates with a constant thickness and a constant radial width around their entire circumference. The discs 63-68 and the annular member 69 are all positioned radially relative to the piston rod 25 by fitting a mounting shaft portion 28 inside them. The discs 63-68 are plain discs. A plain disk is a flat disk without any protrusions that extend in the axial direction.

[0036] Disc 63 has an outer diameter larger than the outer diameter of the inner seat portion 49 of the piston 21 and smaller than the inner diameter of the valve seat portion 50. Disc 63 is in constant contact with the inner seat portion 49. Multiple discs 64 have an outer diameter equivalent to the outer diameter of the valve seat portion 50 of the piston 21. Of the multiple discs 64, the disc 64 closest to disc 63 can seat on the valve seat portion 50. Multiple discs 65 have an outer diameter smaller than the outer diameter of disc 64. Multiple discs 66 have an outer diameter smaller than the outer diameter of disc 65. Disc 67 has an outer diameter smaller than the outer diameter of disc 66 and equivalent to the outer diameter of the inner seat portion 49 of the piston 21. Disc 68 has an outer diameter equivalent to the outer diameter of disc 65. The annular member 69 has an outer diameter smaller than the outer diameter of disc 68 and larger than the outer diameter of the axial step portion 29 of the piston rod 25. The annular member 69 is thicker and more rigid than the discs 63-68 and is in contact with the shaft step portion 29.

[0037] Multiple discs 64, 65, and 66 constitute a compression-side main valve 71 that can seat and detach from the valve seat portion 50. By separating from the valve seat portion 50, the main valve 71 connects the passages within the multiple passage holes 39 and the annular groove 56 to the upper chamber 22. At that time, the main valve 71 suppresses the flow of oil L between itself and the valve seat portion 50, thereby generating a damping force. The annular member 69, together with the disc 68, restricts deformation of the main valve 71 in the opening direction beyond a specified limit by contacting the main valve 71.

[0038] The passages within the multiple passage holes 39 and the annular groove 56, and the passage between the main valve 71 and the valve seat portion 50 that appears when the valve is opened, constitute the first passage 72. The first passage 72 is provided in the piston 21. As the piston 21 moves toward the lower chamber 23, the oil liquid L flows out of the first passage 72 from the lower chamber 23, which is the upstream side of the cylinder 4, to the upper chamber 22, which is the downstream side. The first passage 72 is a compression-side passage. The compression-side first damping force generating mechanism 42, which generates damping force, includes the main valve 71 and the valve seat portion 50. Therefore, the first damping force generating mechanism 42 is provided in this first passage 72. The first passage 72 is provided in the piston 21 including the valve seat portion 50, and the oil liquid L passes through it when the piston rod 25 and the piston 21 move toward the compression side.

[0039] Here, in the compression-side first damping force generating mechanism 42, no fixed orifice is formed in either the valve seat portion 50 or the main valve 71 that abuts against it. A fixed orifice connects the upper chamber 22 and the lower chamber 23 even when the valve seat portion 50 and the main valve 71 are in contact. In other words, the compression-side first damping force generating mechanism 42 does not connect the upper chamber 22 and the lower chamber 23 if the valve seat portion 50 and the main valve 71 are in contact around their entire circumference. To put it another way, the first passage 72 is not provided with a fixed orifice that constantly connects the upper chamber 22 and the lower chamber 23. The first passage 72 is not a passage that constantly connects the upper chamber 22 and the lower chamber 23.

[0040] The extension-side first damping force generating mechanism 41 includes the valve seat portion 48 of the piston 21. The first damping force generating mechanism 41 has, in order from the axial piston 21 side, one disc 82, one disc 83, multiple (specifically four) discs 84, one disc 85, multiple (specifically three) discs 86, and one disc 87. The multiple discs 84 have the same outer diameter. The multiple discs 86 have the same outer diameter. Discs 82 to 87 are made of metal and are annular in shape. Discs 83 to 87 are all plain discs that are perforated circular flat plates with a constant thickness and a constant radial width around their entire circumference. Discs 82 to 87 are all positioned radially relative to the piston rod 25 by fitting a mounting shaft portion 28 inside them.

[0041] The disc 82 has an outer diameter larger than the outer diameter of the inner seat portion 47 of the piston 21 and smaller than the inner diameter of the valve seat portion 48. The disc 82 is in constant contact with the inner seat portion 47. A notch 90 is formed in the disc 82, extending from an intermediate position outside the radially outer inner seat portion 47 to the inner peripheral edge. The notch 90 allows the passages within the annular groove 55 and the multiple passage holes 38 to be constantly connected to the passage within the large-diameter hole portion 46 of the piston 21 and the piston rod passage portion 51 of the piston rod 25. The notch 90 is formed during the press molding of the disc 82. The disc 83 has the same outer diameter as the disc 82 and does not have a notch like the disc 82. Multiple discs 84 have an outer diameter equivalent to the outer diameter of the valve seat portion 48 of the piston 21. Of the multiple discs 84, the disc 84 closest to disc 83 is capable of seating on the valve seat portion 48. Disc 85 has a smaller outer diameter than disc 84. Multiple discs 86 have smaller outer diameters than disc 85. Disc 87 has a smaller outer diameter than disc 86 and a slightly larger outer diameter than the inner seat portion 47 of piston 21.

[0042] Multiple discs 84, one disc 85, and multiple discs 86 constitute the extension-side main valve 91, which can seat and detach from the valve seat portion 48. When the main valve 91 detaches from the valve seat portion 48, it connects the passages within the annular groove 55 and the multiple passage holes 38 to the lower chamber 23. At that time, the main valve 91 suppresses the flow of oil L between itself and the valve seat portion 48, thereby generating a damping force.

[0043] The passages within the multiple passage holes 38 and the annular groove 55, and the passage between the main valve 91 and the valve seat portion 48 that appears when the valve is opened, constitute the first passage 92. The first passage 92 is formed in the piston 21. As the piston 21 moves toward the upper chamber 22, the oil liquid L flows out of the first passage 92 from the upper chamber 22, which is the upstream side of the cylinder 4, to the lower chamber 23, which is the downstream side. The first passage 92 is an extension-side passage. The extension-side first damping force generating mechanism 41, which generates damping force, includes the main valve 91 and the valve seat portion 48. Therefore, the first damping force generating mechanism 41 is provided in this first passage 92. The first passage 92 is provided in the piston 21 including the valve seat portion 48, and the oil liquid L passes through it when the piston rod 25 and the piston 21 move toward the extension side.

[0044] In the extension-side first damping force generating mechanism 41, no fixed orifice is formed in either the valve seat portion 48 or the main valve 91 that abuts against it. A fixed orifice would connect the upper chamber 22 and the lower chamber 23 even when the valve seat portion 48 and the main valve 91 are in contact. In other words, the extension-side first damping force generating mechanism 41 does not connect the upper chamber 22 and the lower chamber 23 when the valve seat portion 48 and the main valve 91 are in contact around their entire circumference. To put it another way, the first passage 92 is not provided with a fixed orifice that would normally connect the upper chamber 22 and the lower chamber 23. The first passage 92 is not a passage that normally connects the upper chamber 22 and the lower chamber 23.

[0045] As shown in Figure 3, on the side of the extension-side first damping force generating mechanism 41 opposite the piston 21, in order from the first damping force generating mechanism 41 side, there is a case member 95, a disc spring 116, a disc 97, and a disc valve 100. On the side of the disc valve 100 opposite the disc 97, in order from the disc valve 100 side, there is a valve seat disc 101, a disc 102, and a disc 104. On the side of disc 104 opposite disc 102, in order from the disc 104 side, there is a disc 105, a spring member 106 (first biasing member), a sub-valve 107 (first valve), and a passage forming member 109 with an O-ring 108 on its outer circumference. Furthermore, on the side of the passage forming member 109 opposite to the sub-valve 107, in order from the passage forming member 109 side, one sub-valve 110 (first valve), one spring member 111 (first biasing member), one disc 112, one disc 113, and one annular member 114 are provided. The case member 95, disc spring 116, discs 97, 102, 104, 105, 112, 113, disc valve 100, valve seat disc 101, spring members 106, 111, sub-valves 107, 110, passage forming member 109, and annular member 114 have the mounting shaft portion 28 of the piston rod 25 fitted inside each of them. By fitting the mounting shaft portion 28 inside each of them, the case member 95, disc spring 116, discs 97, 102, 104, 105, 112, 113, disc valve 100, valve seat disc 101, spring members 106, 111, sub-valves 107, 110, passage forming member 109, and annular member 114 are positioned radially with respect to the piston rod 25.

[0046] As shown in Figure 2, a male thread 31 is formed on the mounting shaft portion 28 of the piston rod 25 in a part that protrudes beyond the annular member 114. A nut 119 is screwed onto this male thread 31. The nut 119 is in contact with the annular member 114.

[0047] As shown in Figure 2, the annular member 69, discs 63-68, 82-87, piston 21, case member 95, disc spring 116 shown in Figure 3, discs 97, 102, 104, 105, 112, 113, disc valve 100, valve seat disc 101, spring members 106, 111, sub-valves 107, 110, passage forming member 109 and annular member 114 are axially clamped by the axial step portion 29 of the piston rod 25 and the nut 119, at least on the radially inner circumference side of each. These annular members 69, discs 63-68, 82-87, piston 21, case member 95, disc spring 116 shown in Figure 3, discs 97, 102, 104, 105, 112, 113, disc valve 100, valve seat disc 101, spring members 106, 111, sub-valves 107, 110, passage forming member 109, and annular member 114 are each fixed to the piston rod 25 at least on their radially inner circumference. In this state, discs 97, 102, 104, 105, 112, 113, disc valve 100, valve seat disc 101, spring members 106, 111, sub-valves 107, 110, passage forming member 109, and disc spring 116 are arranged inside the case member 95.

[0048] The case member 95, discs 97, 102, 104, 105, 112, 113, disc valve 100, valve seat disc 101, spring members 106, 111, sub-valves 107, 110, passage forming member 109, annular member 114, and disc spring 116 are all made of metal. The discs 97, 102, 104, 105, 112, 113, disc valve 100, valve seat disc 101, sub-valves 107, 110, and annular member 114 are all plain discs that are perforated circular flat plates with a constant thickness and a constant radial width around their entire circumference. The case member 95, passage forming member 109, spring members 106, 111, and disc spring 116 are all annular with a constant radial width around their entire circumference.

[0049] The case member 95 is a bottomed cylindrical integrally molded product, formed, for example, by plastic deformation or cutting of a metal plate. The case member 95 has a bottom portion 122, an intermediate tapered portion 123, and a cylindrical portion 124. The bottom portion 122 is a perforated disc of a certain thickness. The intermediate tapered portion 123 extends from the outer peripheral edge of the bottom portion 122 in one axial direction of the bottom portion 122, expanding in diameter. The intermediate tapered portion 123 is annular. The cylindrical portion 124 extends in the axial direction of the intermediate tapered portion 123 from the edge of the intermediate tapered portion 123 opposite to the bottom portion 122, in the opposite direction to the bottom portion 122. The cylindrical portion 124 is cylindrical.

[0050] The bottom portion 122 is a perforated circular plate with a constant radial width around its entire circumference. The mounting shaft portion 28 of the piston rod 25 is fitted into the inner circumference of the bottom portion 122. As a result, the case member 95 is positioned radially with respect to the piston rod 25 and arranged coaxially. Multiple passage holes 126 are formed in the bottom portion 122. The multiple passage holes 126 are located between the inner and outer circumferences of the bottom portion 122 and penetrate the bottom portion 122 in the axial direction. The multiple passage holes 126 are arranged at equal intervals in the circumferential direction of the bottom portion 122 at equidistant positions from the center of the bottom portion 122. The case member 95 is positioned in its axial direction such that the bottom portion 122 is on the piston 21 side of the cylindrical portion 124 and is in contact with the disk 87. The outer diameter of the disk 87 is smaller than twice the shortest distance connecting the radial center of the case member 95 and the passage holes 126.

[0051] The intermediate tapered section 123 is tapered in the same axis as the bottom section 122. The intermediate tapered section 123 is tapered in the axial direction, with its diameter increasing as it moves away from the bottom section 122. The cylindrical section 124 is also coaxial with the bottom section 122 and the intermediate tapered section 123.

[0052] The bottom portion 122 has a flat bottom surface 122a on the side of the cylindrical portion 124 in the axial direction. The intermediate tapered portion 123 has a tapered inner surface 123a on the side of the cylindrical portion 124 in the axial direction. The inner surface 123a is tapered, becoming larger in diameter as it moves away from the bottom surface 122a in the axial direction. The inner circumferential surface 124a on the radially inner side of the cylindrical portion 124 is cylindrical. The bottom surface 122a of the bottom portion 122 and the inner surface 123a of the intermediate tapered portion 123 are continuous. The inner surface 123a of the intermediate tapered portion 123 and the inner circumferential surface 124a of the cylindrical portion 124 are continuous.

[0053] The case member 95 is thicker than one of the discs 84-86 and, combined with its closed-bottom cylindrical shape, has higher rigidity than the discs 84-86. Therefore, the case member 95 restricts deformation of the main valve 91, which is composed of multiple discs 84-86, in the opening direction beyond a specified limit by contacting the main valve 91.

[0054] The disc spring 116 is a perforated circular plate made of metal and is flexible. The disc spring 116 is formed from a single sheet of metal by press forming, punching, and press forming. The disc spring 116 has an inner annular portion 401, an intermediate annular portion 402, an outer tapered portion 403, and a support portion 404. The inner annular portion 401 is a perforated circular flat plate. The intermediate annular portion 402 is a perforated circular flat plate having an inner diameter larger than the outer diameter of the inner annular portion 401. The support portion 404 is provided between the inner annular portion 401 and the intermediate annular portion 402, connecting them. The inner annular portion 401, the intermediate annular portion 402, and the support portion 404 are flat plates arranged on the same plane. The outer tapered portion 403 is a conical cylinder that extends radially outward and axially in one direction from the outer peripheral edge of the intermediate annular portion 402. The outer diameter side of the disc spring 116 is the outer tapered portion 403. The outer tapered portion 403 has a constant radial width throughout its entire circumference. The outer tapered portion 403 has a constant axial length throughout its entire circumference.

[0055] The disc spring 116 has an inner flat plate portion 414 on its inner diameter side, which has an inner annular portion 401, an intermediate annular portion 402, and a support portion 404. The inner flat plate portion 414 has a constant radial width throughout its entire circumference. The inner annular portion 401, the intermediate annular portion 402, and the support portion 404 of the inner flat plate portion 414 are arranged on the same plane. The outer tapered portion 403 has an outer tapered end on the outer side of the disc spring 116, opposite to the inner flat plate portion 414 in the axial direction of the disc spring 116. The outer tapered end of the outer tapered portion 403 is the outer tapered end of the disc spring 116. The outer tapered end of the disc spring 116 is a contact portion 416 that abuts against the disc valve 100. The contact portion 416 is annular. The disc spring 116 has an inner flat plate portion 414 on the opposite end to the contact portion 416 at one end in its axial direction. The portion of the disc spring 116 on the inner circumference side of the contact portion 416 is the main body portion 417. The main body portion 417 consists of the inner flat plate portion 414 and the portion of the outer tapered portion 403 excluding the contact portion 416.

[0056] The disc spring 116 has an outer diameter of the outer tapered portion 403, i.e., the outer diameter of the disc spring 116 is slightly smaller than the inner diameter of the cylindrical portion 124 of the case member 95. The inner flat plate portion 414 of the disc spring 116, which has an inner annular portion 401, an intermediate annular portion 402, and a support portion 404, abuts against the bottom surface 122a of the bottom portion 122 of the case member 95. In this state, the outer tapered portion 403 of the disc spring 116 extends axially on the same side as the cylindrical portion 124. In this state, the disc spring 116 is positioned radially relative to the piston rod 25 by fitting the mounting shaft portion 28 to the inner circumference side of the inner annular portion 401. The disc spring 116 is formed so that its inner circumferential end abuts against the piston rod 25. The cylindrical portion 124 of the case member 95 is positioned radially outward of the disc spring 116. The disc spring 116 has a contact portion 416 that faces the inner surface 123a of the intermediate tapered portion 123 of the case member 95 in the axial direction.

[0057] Here, the intermediate tapered portion 123 of the case member 95 has a minimum diameter of its inner surface 123a that is smaller than the outer diameter of the outer tapered portion 403 of the disc spring 116, and larger than the outer diameter of the inner flat portion 414. The intermediate tapered portion 123 has a maximum diameter of its inner surface 123a that is larger than the outer diameter of the outer tapered portion 403 of the disc spring 116. In other words, the intermediate tapered portion 123 has a minimum diameter of its inner surface 123a that is smaller than the outer diameter of the contact portion 416, and a maximum diameter of its inner surface 123a that is larger than the outer diameter of the contact portion 416. The intermediate tapered portion 123 has an inner surface 123a that is deformed in its axial direction on the side where the disc spring 116 is positioned, relative to the bottom surface 122a of the bottom portion 122. Moreover, the inner surface 123a of the intermediate tapered portion 123 extends in its axial direction beyond the inner flat plate portion 414 of the disc spring 116 to the opposite side from the bottom portion 122. In other words, the inner surface 123a of the intermediate tapered portion 123 is located in its axial direction beyond the bottom surface 122a of the bottom portion 122 to the side where the disc spring 116 is positioned. To put it another way, the inner surface 123a of the intermediate tapered portion 123 is formed by deforming in the axial direction toward the contact portion 416 than the end of the main body portion 417 which is on the inner circumference side of the contact portion 416 on one axial end of the disc spring 116. The inner surface 123a of the intermediate tapered portion 123 suppresses the displacement of the contact portion 416 on one axial end of the disc spring 116 toward the other end in the axial direction of the disc spring 116, compared to the main body portion 417 which is on the inner circumference side of the contact portion 416. The case member 95 suppresses this displacement of the disc spring 116 by contacting the disc spring 116 with the inner surface 123a of the intermediate tapered portion 123 that faces the contact portion 416.

[0058] The inner annular portion 401, the intermediate annular portion 402, and the outer tapered portion 403 all have a constant radial width around their entire circumference. The radial width of the outer tapered portion 403 is wider than that of the inner annular portion 401. The radial width of the inner annular portion 401 is wider than that of the intermediate annular portion 402. The inner annular portion 401, the intermediate annular portion 402, and the outer tapered portion 403 are arranged coaxially. The support portion 404 connects the inner annular portion 401, the intermediate annular portion 402, and the outer tapered portion 403 in a coaxial manner. The support portion 404 extends in the circumferential direction of the inner annular portion 401 and the intermediate annular portion 402, connecting the outer peripheral edge of the inner annular portion 401 and the inner peripheral edge of the intermediate annular portion 402.

[0059] The disc spring 116 has a hole 415 formed by being surrounded by an inner annular portion 401, an intermediate annular portion 402, and a support portion 404. The hole 415 penetrates the disc spring 116 in the thickness direction (axial direction). The hole 415 is provided between the inner annular portion 401 and the intermediate annular portion 402. Therefore, the disc spring 116 has a hole 415 between the inner end and the outer end. The hole 415 is provided in the inner flat plate portion 414.

[0060] In the disc spring 116, the inner diameter of the intermediate annular portion 402 is smaller than twice the longest distance connecting the radial center of the case member 95 and the passage hole 126. The inner diameter of the intermediate annular portion 402 is larger than twice the shortest distance connecting the radial center of the case member 95 and the passage hole 126. Therefore, in the disc spring 116, the passage in the hole portion 415 is always in communication with the passage in the passage hole 126 of the bottom portion 122. Also, in the disc spring 116, the outer diameter of the intermediate annular portion 402, i.e., the inner diameter of the outer tapered portion 403, is larger than twice the longest distance connecting the radial center of the case member 95 and the passage hole 126. In the disc spring 116, the intermediate annular portion 402 abuts over the entire circumference of the bottom surface 122a of the bottom portion 122 of the case member 95 at a position radially outward from all the passage holes 126.

[0061] The outer diameter of the disc 97 is smaller than the outer diameter of the inner ring portion 401 of the disc spring 116. The inner annular portion 401 of the disc spring 116 is clamped axially by the bottom portion 122 of the case member 95 and the disc 97. As a result, the inner annular portion 401 of the disc spring 116 is fixed to the piston rod 25. The support portion 404 and the intermediate annular portion 402 contact the bottom surface 122a of the case member 95, but do not contact the disc 97, and therefore are not clamped axially.

[0062] The disc valve 100 is flexible. The inner circumferential end of the disc valve 100 abuts against the piston rod 25. The outer diameter of the disc valve 100 is larger than the outer diameter of the disc spring 116 and slightly smaller than the inner diameter of the cylindrical portion 124 of the case member 95. The disc valve 100 has a thickness equivalent to the plate thickness of the disc spring 116. The circular contact portion 416 of the disc spring 116 abuts against the outer circumferential edge of the disc valve 100 around its entire circumference.

[0063] The disc valve 100 is formed from a single sheet of material by press forming and punching. In its natural state before being assembled to the piston rod 25, the disc valve 100 is flat. Multiple communication holes 501 are formed in the disc valve 100 at intermediate radial positions. All communication holes 501 are round holes of the same diameter and penetrate the disc valve 100 in its thickness direction (axial direction). All communication holes 501 are formed at equidistant positions from the center of the disc valve 100. All communication holes 501 are formed at equal intervals in the circumferential direction of the disc valve 100. The communication holes 501 of the disc valve 100 are formed in positions that are not blocked by the disc 97.

[0064] The valve seat disc 101 is flat in its natural state before being assembled to the piston rod 25. The outer diameter of the valve seat disc 101 is smaller than the outer diameter of the disc valve 100. The outer diameter of the valve seat disc 101 is larger than twice the maximum distance between the center of the disc valve 100 and the communication hole 501. The valve seat disc 101 makes surface contact with the disc valve 100 around its entire circumference. As a result, the valve seat disc 101 closes all of the communication holes 501 of the disc valve 100.

[0065] The outer diameter of disc 102 is smaller than the outer diameter of the valve seat disc 101. Disc 102 is a common part with the same shape as disc 97. Disc 102, together with disc 97, axially clamps the inner circumference of the disc valve 100 and the valve seat disc 101. The outer diameter of disc 104 is larger than that of valve seat disc 101, and slightly smaller than that of disc valve 100. Disc 104 is thicker and more rigid than both disc valve 100 and valve seat disc 101.

[0066] The outer diameter of disc 105 is smaller than the outer diameter of disc 104.

[0067] The spring member 106 has a main body member 331 and a protruding member 332. The main body member 331 is a perforated circular flat plate with a constant radial width around its entire circumference. The mounting shaft portion 28 is fitted into the inner circumference of the main body member 331. A passage hole 333 is formed in the main body member 331. The passage hole 333 penetrates the main body member 331 in the axial direction. As shown in Figure 4, the passage hole 333 is an elongated arc-shaped hole that is long in the circumferential direction of the main body member 331. Multiple passage holes 333 of the same shape are formed in the main body member 331 at equal intervals in the circumferential direction of the main body member 331, at positions equidistant from its center. The main body member 331 is made more flexible due to the formation of multiple arc-shaped passage holes 333.

[0068] The protruding member 332 is a perforated circular plate with a constant radial width around its entire circumference. The protruding member 332 has an outer diameter equal to the outer diameter of the main body member 331, but larger than the inner diameter of the main body member 331. The protruding member 332 is coaxial with the main body member 331 and is welded to one side of the main body member 331 in the axial direction. Multiple welded joints 334 are formed on the protruding member 332 and the main body member 331 at equal intervals in their circumferential direction, specifically at two locations. The inner diameter of the protruding member 332 is set such that its entirety is located radially outside the multiple passage holes 333 of the main body member 331.

[0069] As shown in Figure 3, the spring member 106 is oriented such that the protruding member 332 is positioned on the sub-valve 107 side in the axial direction of the main body member 331 rather than on the outer circumference side of the main body member 331. The spring member 106 has one axial side on the inner circumference of the main body member 331 in contact with the disc 105, and the other axial side on the inner circumference of the main body member 331 in contact with the inner circumference of the sub-valve 107. The spring member 106 has the protruding member 332 in contact with the outer circumference of the sub-valve 107. In this state, the spring member 106 elastically deforms in a tapered shape so that the radially intermediate portion of the main body member 331 moves further away from the sub-valve 107 in the axial direction as it moves radially outward.

[0070] As a result, the spring member 106 is integrally provided with a main body member 331 that rests on the sub-valve 107 and a protruding member 332 that is provided on the outer circumference of the main body member 331 and protrudes toward the sub-valve 107. The spring member 106 biases the outer circumference of the sub-valve 107 via the protruding member 332 through the main body member 331. The spring member 106 applies a set load, or preload, to the sub-valve 107, which is adjusted by the thickness of the protruding member 332. The multiple passage holes 333 of the main body member 331 are located radially outward from the outer circumference of the disc 105.

[0071] As shown in Figure 2, the passage forming member 109 is a perforated disc. A through hole 131 is formed in the radial center of the passage forming member 109. The through hole 131 extends in the axial direction of the passage forming member 109 and penetrates the passage forming member 109 in the thickness direction. The mounting shaft portion 28 of the piston rod 25 is inserted into the through hole 131. The through hole 131 has a small diameter hole portion 132 and a large diameter hole portion 133. The large diameter hole portion 133 is larger in diameter than the small diameter hole portion 132. The small diameter hole portion 132 is located on one side of the through hole 131 in the axial direction. The large diameter hole portion 133 is located on the other side of the through hole 131 in the axial direction from the center. The mounting shaft portion 28 of the piston rod 25 is fitted into the small diameter hole portion 132.

[0072] The passage forming member 109 has an inner seat portion 134 and a valve seat portion 135 at the end on the axial side of the large diameter hole portion 133. The inner seat portion 134 is annular in shape so as to surround the large diameter hole portion 133. The valve seat portion 135 extends radially outward from this inner seat portion 134. The passage forming member 109 also has an inner seat portion 138 and a valve seat portion 139 at the end on the opposite axial side of the small diameter hole portion 132. The inner seat portion 138 is annular in shape so as to surround the small diameter hole portion 132. The valve seat portion 139 extends radially outward from this inner seat portion 138. The passage forming member 109 has a main body portion 140 between the axial inner seat portion 134 and valve seat portion 135 and the inner seat portion 138 and valve seat portion 139. The main body portion 140 is perforated disc-shaped.

[0073] The inner seat portion 134 protrudes to one side along the axial direction of the main body portion 140 from the inner peripheral edge on the axial side of the large diameter hole portion 133 of the main body portion 140. The valve seat portion 135 protrudes from the main body portion 140 on the same side as the inner seat portion 134, radially outward from the inner seat portion 134, along the axial direction of the main body portion 140. The protruding end surface of the inner seat portion 134, i.e., the end surface opposite to the main body portion 140, is a flat surface. The protruding end surface of the valve seat portion 135, i.e., the end surface opposite to the main body portion 140, is a flat surface. The protruding end surfaces of the inner seat portion 134 and the protruding end surfaces of the valve seat portion 135 are arranged on the same plane, spreading out in a direction perpendicular to the axis of the passage forming member 109.

[0074] The inner seat portion 138 protrudes from the inner peripheral edge of the main body portion 140 on the side of the axially small diameter hole portion 132, along the axial direction of the main body portion 140, on the side opposite to the inner seat portion 134. The valve seat portion 139 protrudes radially outward from the inner seat portion 138, along the axial direction of the main body portion 140, on the same side as the inner seat portion 138. The protruding end surface of the inner seat portion 138, i.e., the end surface opposite to the main body portion 140, is a flat surface. The protruding end surface of the valve seat portion 139, i.e., the end surface opposite to the main body portion 140, is a flat surface. The protruding end surfaces of the inner seat portion 138 and the protruding end surfaces of the valve seat portion 139 are arranged on the same plane, spreading out in a direction perpendicular to the axis of the passage forming member 109.

[0075] The valve seat portion 135 is a non-circular, petal-shaped irregular seat. The valve seat portion 135 has multiple valve seat components 201. These valve seat components 201 are identical in shape and are arranged at equal intervals in the circumferential direction of the passage forming member 109. The inner seat portion 134 forms an annular shape with the central axis of the passage forming member 109 as its center. The multiple valve seat components 201 extend radially from the inner seat portion 134.

[0076] A passage recess 205 is formed inside each valve seat component 201. The passage recess 205 is formed by being surrounded by a part of the inner seat portion 134 and the valve seat component 201. The passage recess 205 is recessed in the axial direction of the passage forming member 109 from the protruding end surface of the inner seat portion 134 and the protruding end surface of the valve seat component 201. The bottom surface of the passage recess 205 is formed by the main body portion 140. A passage recess 205 is formed inside all valve seat components 201.

[0077] A passage hole 206 is formed at the center of the passage recess 205 in the circumferential direction of the passage forming member 109. The passage hole 206 penetrates the passage forming member 109 axially by passing through the main body portion 140 in the axial direction. The passage hole 206 is a straight hole parallel to the central axis of the passage forming member 109. A passage hole 206 is formed on the bottom surface of all passage recesses 205.

[0078] The valve seat portion 139 is also a non-circular, petal-shaped irregular seat. The valve seat portion 139 has multiple valve seat components 211. These valve seat components 211 are identical in shape and are arranged at equal intervals in the circumferential direction of the passage forming member 109. The inner seat portion 138 forms an annular shape centered on the central axis of the passage forming member 109. Multiple valve seat components 201 extend radially from the inner seat portion 134. The valve seat components 211 are identical in shape to the valve seat components 201.

[0079] A passage recess 215 is formed inside each valve seat component 211. The passage recess 215 is formed by being surrounded by a part of the inner seat portion 138 and the valve seat component 211. The passage recess 215 is recessed in the axial direction of the passage forming member 109 from the protruding end surface of the inner seat portion 138 and the protruding end surface of the valve seat component 211. The bottom surface of the passage recess 215 is formed by the main body portion 140. A passage recess 215 is formed inside all valve seat components 211.

[0080] A passage hole 216 is formed at the center of the passage recess 215 in the circumferential direction of the passage forming member 109. The passage hole 216 penetrates the passage forming member 109 axially by passing through the main body portion 140 in the axial direction. The passage hole 216 is a straight hole parallel to the central axis of the passage forming member 109. A passage hole 216 is formed on the bottom surface of all passage recesses 215.

[0081] Here, the circumferential arrangement pitch of the passage forming members 109 of the multiple valve seat components 201 is the same as the circumferential arrangement pitch of the passage forming members 109 of the multiple valve seat components 211. The valve seat components 201 and 211 are offset from each other by half an arrangement pitch in the circumferential direction of the passage forming member 109. The passage hole 206 is located between adjacent valve seat components 211 in the circumferential direction of the passage forming member 109. Therefore, the passage hole 206 is located outside the range of the valve seat portion 139. The passage hole 216 is located between adjacent valve seat components 201 in the circumferential direction of the passage forming member 109. Therefore, the passage hole 216 is located outside the range of the valve seat portion 135.

[0082] The passage forming member 109 has a passage groove 221 on the axial side of the large-diameter hole portion 133. The passage groove 221 is formed in the inner seat portion 134, traversing the inner seat portion 134 radially. The passage groove 221 is formed as a recess in the axial direction of the passage forming member 109 from the end face of the inner seat portion 134 opposite to the main body portion 140. The passage groove 221 also includes the space between adjacent valve seat components 201 in the circumferential direction of the passage forming member 109. The passage hole 216 opens to the bottom surface of the passage groove 221. The passage in the passage groove 221 connects the passage in the passage hole 216 and the passage in the large-diameter hole portion 133.

[0083] The passage within the passage hole 216 and the passage within the passage recess 215 into which the passage hole 216 opens constitute the passage portion 161 provided on the passage forming member 109. Multiple passage portions 161 are provided on the passage forming member 109 at equal intervals in the circumferential direction of the passage forming member 109. The passage groove 221 forms a radial passage 222 that extends radially toward the passage portion 161. Multiple radial passages 222 are provided on the passage forming member 109 at equal intervals in the circumferential direction of the passage forming member 109. The passage portion 161 and the radial passage 222 are in communication with each other.

[0084] The passage forming member 109 has a passage groove 225 between adjacent valve seat components 211 in the circumferential direction of the passage forming member 109. The passage hole 206 opens to the bottom surface of the passage groove 225. Therefore, the passage within the passage groove 225 communicates with the passage within the passage hole 206.

[0085] The passage hole 206 and the passage recess 205 into which the passage hole 206 opens form a passage portion 162 provided on the passage forming member 109. Multiple passage portions 162 are provided on the passage forming member 109 at equal intervals in the circumferential direction of the passage forming member 109. Multiple passage sections 161 and multiple passage sections 162 are provided in the passage forming member 109 to constitute a member passage 160 through which the oil liquid L flows.

[0086] The passage forming member 109 has a seal groove 141 formed at the axial center of the outer circumference of the main body portion 140. The seal groove 141 is annular and recessed radially inward from the outer surface of the main body portion 140. An O-ring 108 is placed inside this seal groove 141. The passage forming member 109 is fitted to the cylindrical portion 124 of the case member 95 at its outer circumference, with the inner seat portion 138 and the valve seat portion 139 facing away from the bottom portion 122. In this state, the O-ring 108 seals the gap between the cylindrical portion 124 of the case member 95 and the passage forming member 109.

[0087] The case member 95, O-ring 108, and passage forming member 109 form a case chamber 146 inside the case member 95. The case chamber 146 is located between the bottom 122 of the case member 95 and the passage forming member 109. As shown in Figure 3, the discs 97, 102, 104, 105, disc valve 100, valve seat disc 101, spring member 106, sub-valve 107, and disc spring 116 are located within this case chamber 146.

[0088] A lower chamber communication chamber 149 is formed within the case chamber 146. The lower chamber communication chamber 149 is surrounded by the disc valve 100, the valve seat disc 101, the disc spring 116, the disc 97, and the bottom 122 of the case member 95. This lower chamber communication chamber 149 is in constant communication with the passages in the multiple holes 415 of the disc spring 116. This lower chamber communication chamber 149 is in constant communication with the passages in the multiple passage holes 126 of the bottom 122 of the case member 95.

[0089] An upper chamber communication chamber 147 is formed within the case chamber 146. The upper chamber communication chamber 147 is surrounded by a case member 95, a disc spring 116, a disc valve 100, a valve seat disc 101, discs 102, 104, and 105, a spring member 106, a sub-valve 107, and a passage forming member 109. Communication between the lower chamber communication chamber 149 and the upper chamber communication chamber 147 is blocked by the disc spring 116, the disc valve 100 which contacts the contact portion 416 of the disc spring 116, and the valve seat disc 101 which contacts the disc valve 100.

[0090] As shown in Figure 2, the annular passage-forming member 109 and the bottomed cylindrical case member 95 are arranged in the lower chamber 23, which is one of the upper chamber 22 and the lower chamber 23. In this arrangement, the valve seat portion 135 of the passage-forming member 109 is positioned on the case chamber 146 side. Also, the valve seat portion 139 of the passage-forming member 109 is positioned on the lower chamber 23 side. As shown in Figure 3, the passage within the passage hole 126 of the case member 95 is constantly in communication with the lower chamber 23.

[0091] The upper chamber communication chamber 147 is in constant communication with the upper chamber 22 shown in Figure 2 via the passage between the cylindrical portion 124 of the case member 95 and the sub-valve 107, the radial passage 222 in the passage groove 221 of the passage forming member 109, the passage in the large-diameter hole portion 133 of the passage forming member 109, the passage in the piston rod passage portion 51 of the piston rod 25 and the passage in the large-diameter hole portion 46 of the piston 21, the passage in the notch 90 of the disc 82, and the passages in the annular groove 55 and the multiple passage holes 38 of the piston 21.

[0092] As the disc valve 100 shown in Figure 3 flexes axially, the volumes of the lower chamber communication chamber 149 and the upper chamber communication chamber 147 change. That is, the flexing of the disc valve 100 gives the lower chamber communication chamber 149 and the upper chamber communication chamber 147 the function of an accumulator. The lower chamber communication chamber 149 decreases in volume to absorb the increase in volume of the upper chamber communication chamber 147 and discharges the oil liquid L into the lower chamber 23. The lower chamber communication chamber 149 increases in volume to absorb the decrease in volume of the upper chamber communication chamber 147 and allows the oil liquid L to flow in from the lower chamber 23. Conversely, the upper chamber communication chamber 147 decreases in volume to absorb the increase in volume of the lower chamber communication chamber 149 and discharges the oil liquid L to the upper chamber 22 side. The upper chamber communication chamber 147 increases in volume to absorb the decrease in volume of the lower chamber communication chamber 149 and allows the oil liquid L to flow in from the upper chamber 22 side. As described above, the deformation of the disc valve 100 is suppressed from being hindered by the oil liquid L in the upper chamber communication chamber 147 and the lower chamber communication chamber 149.

[0093] As shown in Figure 2, the multiple passage grooves 225 of the passage forming member 109 are provided facing the lower chamber 23. The multiple passage sections 162 are constantly in communication with the lower chamber 23 via the passages within the multiple passage grooves 225. As shown in Figure 3, the passages within the holes 415 formed in the disc spring 116 and the passages within the passage holes 126 formed in the bottom 122 of the case member 95 are constantly in communication with the lower chamber 23, which is one of the upper chamber 22 and the lower chamber 23.

[0094] The radial passage 222 within the passage groove 221 that opens into the passage portion 161 of the passage forming member 109 is in constant communication with the upper chamber communication chamber 147. The radial passage 222 is in constant communication with the upper chamber communication chamber 147, the passage within the large-diameter hole portion 133 of the passage forming member 109, and the piston rod passage portion 51 of the piston rod 25.

[0095] As shown in Figure 2, the sub-valve 107 is disc-shaped and has an outer diameter equivalent to the outer diameter of the valve seat portion 135 of the passage forming member 109. The sub-valve 107 is constantly in contact with the inner seat portion 134 and can seat and detach from the valve seat portion 135. In other words, the sub-valve 107 is placed on the valve seat portion 135 of the passage forming member 109. By seating the entire valve seat portion 135, the sub-valve 107 closes all passage portions 162. Also, by seating the entire valve seat component 201 of the valve seat portion 135, the sub-valve 107 closes the passage portion 162 inside that valve seat component 201. The spring member 106 brings the sub-valve 107 into contact with the valve seat portion 135 of the passage forming member 109. The sub-valve 107 seats on the valve seat portion 135 due to the biasing force of the spring member 106, thereby closing the passage portion 162. The sub-valve 107 opens the passage portion 162 by deforming against the biasing force of the spring member 106.

[0096] A sub-valve 107, which can seat and detach from the valve seat portion 135, is provided in the case chamber 146. The sub-valve 107 separates from the valve seat portion 135 within the case chamber 146. When this happens, the sub-valve 107 connects the multiple passage portions 162 to the upper chamber communication chamber 147. As a result, the lower chamber 23 communicates with the upper chamber 22. At this time, the sub-valve 107 suppresses the flow of oil liquid L between itself and the valve seat portion 135, generating a damping force. The sub-valve 107 is an inflow valve that opens when oil liquid L flows from the lower chamber 23 to the upper chamber communication chamber 147 side via the multiple passage portions 162. The sub-valve 107 is a check valve that restricts the outflow of oil liquid L from the upper chamber communication chamber 147 to the lower chamber 23 via the passage portion 162. Here, the passage hole 216 constituting the passage portion 161 opens outward from the range of the valve seat portion 135 in the passage forming member 109. Therefore, the passage hole 216 is always in communication with the upper chamber communication chamber 147, independently of the sub-valve 107 seated on the valve seat portion 135.

[0097] The passages within the multiple passage grooves 225, the multiple passage sections 162, the passage between the sub-valve 107 and the valve seat section 135 that appear when the valve is opened, the upper chamber communication chamber 147, the radial passage 222 within the passage groove 221 of the passage forming member 109, the passage within the large-diameter hole section 133 of the passage forming member 109, the passage within the piston rod passage section 51 of the piston rod 25 and the large-diameter hole section 46 of the piston 21, the passage within the notch 90 of the disc 82, and the passages within the annular groove 55 and multiple passage holes 38 of the piston 21 constitute the second passage 172. The second passage 172 is opened and closed by the sub-valve 107. As the piston 21 moves toward the lower chamber 23, the oil liquid L flows out of the second passage 172 from the lower chamber 23, which is the upstream side of the cylinder 4, to the upper chamber 22, which is the downstream side. The second passage 172 allows the oil liquid L to flow from the lower chamber 23, which is upstream during the piston 21's movement toward the lower chamber 23, that is, during the compression stroke, toward the upper chamber 22, which is downstream. The second passage 172 is the compression-side passage. The compression-side second passage 172 is provided separately from the first passage 72, which is also on the compression side. The second passage 172 is in parallel with the first passage 72. A portion of the second passage 172 is formed in the passage-forming member 109.

[0098] The passage within the passage hole 126 shown in Figure 3, the passage within the hole 415, and the lower chamber communication chamber 149 constitute the third passage 511 on the contraction side. The third passage 511 is always in communication with the lower chamber 23. The third passage 511 on the contraction side is provided separately from the second passage 172 shown in Figure 2, which is also on the contraction side. The third passage 511 is arranged in parallel with the second passage 172.

[0099] As shown in Figure 3, the disc 104 is thicker and more rigid than the sub-valve 107. When the sub-valve 107 deforms, the disc 104 comes into contact with the sub-valve 107, suppressing further deformation of the sub-valve 107. When the disc valve 100 deforms, the disc 104 comes into contact with the disc valve 100, suppressing further deformation of the disc valve 100.

[0100] The sub-valve 107 shown in Figure 2, the passage forming member 109 including the valve seat portion 135, the discs 104 and 105, and the spring member 106 constitute the second damping force generating mechanism 173. The second damping force generating mechanism 173 is provided on the piston rod 25. The second damping force generating mechanism 173 is provided in the compression-side second passage 172. The second damping force generating mechanism 173 opens and closes this second passage 172, suppressing the flow of oil L from this second passage 172 to the upper chamber 22 and generating damping force. The second damping force generating mechanism 173 is the compression-side second damping force generating mechanism. The compression-side third passage 511 is provided separately from the compression-side second damping force generating mechanism 173. The compression-side third passage 511 is provided in parallel with the compression-side second damping force generating mechanism 173.

[0101] The second damping force generating mechanism 173 has its valve seat portion 135 provided in the passage forming member 109. The second damping force generating mechanism 173 is arranged separately from the first damping force generating mechanism 42, which generates damping force in the same compression stroke. The sub-valve 107 that constitutes the compression-side second damping force generating mechanism 173 is a compression-side sub-valve.

[0102] As shown in Figure 3, a passage within the passage hole 126 is formed in the bottom portion 122 of the case member 95. The passage within the passage hole 126 connects the inside and outside of the case member 95. The disc spring 116 is provided so that one end face in the axial direction abuts against the outer circumference of the passage within the passage hole 126 of the case member 95. The flexible disc valve 100 is provided so as to abut against the other end face in the axial direction of the disc spring 116.

[0103] As shown in Figure 2, in the second passage 172, the passage within the notch 90 of the disc 82 becomes the orifice 175. The orifice 175 is located downstream of the sub-valve 107 in the flow of the oil liquid L when the sub-valve 107 opens and the oil liquid L flows through the second passage 172. Alternatively, the orifice 175 may be located upstream of the sub-valve 107 in the flow of the oil liquid L when the sub-valve 107 opens and the oil liquid L flows through the second passage 172. The orifice 175 is formed by cutting a notch in the disc 82 that contacts the piston 21 in the first damping force generating mechanism 41.

[0104] The compression-side second damping force generating mechanism 173 does not have a fixed orifice formed in either the valve seat portion 135 or the sub-valve 107 that abuts against it. A fixed orifice would connect the upper chamber 22 and the lower chamber 23 even when the valve seat portion 135 and the sub-valve 107 are in contact. In other words, the compression-side second damping force generating mechanism 173 does not connect the upper chamber 22 and the lower chamber 23 when the valve seat portion 135 and the sub-valve 107 are in contact. To put it another way, the second passage 172 does not have a fixed orifice formed to constantly connect the upper chamber 22 and the lower chamber 23. The second passage 172 is not a passage that constantly connects the upper chamber 22 and the lower chamber 23.

[0105] The second compression-side passage 172, which connects the upper chamber 22 and the lower chamber 23, is in parallel with the first compression-side passage 72, which also connects the upper chamber 22 and the lower chamber 23. The first damping force generating mechanism 42 is provided in the first passage 72. The second damping force generating mechanism 173 is provided in the second passage 172. Therefore, both the first damping force generating mechanism 42 and the second damping force generating mechanism 173, which are on the compression side, are arranged in parallel.

[0106] As shown in Figure 3, the sub-valve 110 is disc-shaped and has an outer diameter equivalent to the outer diameter of the valve seat portion 139 of the passage forming member 109. The sub-valve 110 is in constant contact with the inner seat portion 138 and can seat and detach from the valve seat portion 139. In other words, the sub-valve 110 is placed on the valve seat portion 139 of the passage forming member 109. The sub-valve 110 seats over the entire valve seat portion 139. In this case, the sub-valve 110 closes all of the passage portions 161. Alternatively, the sub-valve 110 seats over the entire valve seat component 211 of the valve seat portion 139. In this case, the sub-valve 110 closes the passage portion 161 inside this valve seat component 211. The sub-valve 110 can be a common part with the same shape as the sub-valve 107.

[0107] The spring member 111 has a main body member 341 and a protruding member 342. The main body member 341 is a perforated circular flat plate with a constant radial width around its entire circumference. The mounting shaft portion 28 is fitted into the inner circumference of the main body member 341. The main body member 341 has passage holes 343 formed therein. The passage holes 343 penetrate the main body member 341 in the axial direction of the main body member 341. The passage holes 343 are elongated, arc-shaped holes that are long in the circumferential direction of the main body member 341. Multiple passage holes 343 of the same shape are formed on the main body member 341 at equal intervals in the circumferential direction of the main body member 341, at positions equidistant from its center. The main body member 341 is made more flexible due to the formation of multiple arc-shaped passage holes 343.

[0108] The protruding member 342 is a perforated circular plate with a constant radial width around its entire circumference. The protruding member 342 has an outer diameter equal to the outer diameter of the main body member 341, but larger than the inner diameter of the main body member 341. The protruding member 342 is joined to one side of the main body member 341 in the axial direction by welding, in a coaxial manner with the main body member 341. Multiple welded joints, specifically two, are formed on the protruding member 342 and the main body member 341 at equal intervals in their circumferential direction. The inner diameter of the protruding member 342 is set such that its entirety is located radially outside the multiple passage holes 343 of the main body member 341.

[0109] The main body member 341 may be a common part with the same shape as the main body member 331. Similarly, the protruding member 342 may be a common part with the same shape as the protruding member 332. Alternatively, the main body member 341 may be a common part with the same shape as the main body member 331, the protruding member 342 may be a common part with the same shape as the protruding member 332, and the spring member 111 may be a common part with the same shape as the spring member 106.

[0110] The outer diameter of disc 112 is the same as that of disc 105. Disc 112 is a common part with the same shape as disc 105.

[0111] The spring member 111 is oriented such that the protruding member 342 is positioned closer to the sub-valve 110 in the axial direction of the main body member 341 than to the outer circumference of the main body member 341. The spring member 111 has one axial side of the inner circumference of the main body member 341 in contact with the disc 112, and the other axial side of the inner circumference of the main body member 341 in contact with the inner circumference of the sub-valve 110. The spring member 111 has the protruding member 342 in contact with the outer circumference of the sub-valve 110. In this state, the spring member 111 elastically deforms in a tapered shape so that the radially intermediate portion of the main body member 341 moves further away from the sub-valve 110 in the axial direction as it moves radially outward.

[0112] As a result, the spring member 111 is integrally provided with a main body member 341 that rests on the sub-valve 110 and a protruding member 342 that is provided on the outer circumference of the main body member 341 and protrudes toward the sub-valve 110. The spring member 111 biases the outer circumference of the sub-valve 110 via the protruding member 342 through the main body member 341. The spring member 111 applies a set load, or preload, to the sub-valve 110, which is adjusted by the thickness of the protruding member 342. The spring member 111 causes the sub-valve 110 to come into contact with the valve seat portion 139 of the passage forming member 109. The sub-valve 110 seats on the valve seat portion 139 due to the biasing force of the spring member 111 and closes the passage portion 161. The sub-valve 110 deforms against the biasing force of the spring member 111 and separates from the valve seat portion 139, opening the passage portion 161. The multiple passage holes 343 of the main body member 341 are positioned further outward in the radial direction of the disk 112 than the outer peripheral surface of the disk 112.

[0113] The sub-valve 110 is located within the lower chamber 23. By moving away from the valve seat portion 139, the sub-valve 110 connects the upper chamber 22 and the upper chamber communication chamber 147 with the lower chamber 23. At this time, the sub-valve 110 suppresses the flow of oil L between itself and the valve seat portion 139, thereby generating a damping force. The sub-valve 110 is a discharge valve that opens when the oil L is discharged from the upper chamber 22 and the upper chamber communication chamber 147 into the lower chamber 23 via the multiple passage portions 161 of the passage forming member 109. The sub-valve 110 is a check valve that restricts the inflow of oil L from the lower chamber 23 into the upper chamber 22 and the upper chamber communication chamber 147 via the passage portions 161. Here, as shown in Figure 2, the passage holes 206 constituting the passage portion 162 open outward from the range of the valve seat portion 139 in the passage forming member 109. Therefore, the passage hole 206 is always in communication with the lower chamber 23, independently of the sub-valve 110 seated on the valve seat portion 139.

[0114] The passages within the multiple passage holes 38 and annular groove 55 of the piston 21, the passage within the notch 90 of the disc 82, the passage within the large diameter hole 46 of the piston 21, the passage within the piston rod passage 51 of the piston rod 25 and the passage within the large diameter hole 133 of the passage forming member 109, the radial passage 222 of the passage forming member 109, the multiple passages 161 of the passage forming member 109, and the passage between the sub-valve 110 and the valve seat 139 that appears when the valve is opened constitute the second passage 182. The second passage 182 is opened and closed by the sub-valve 110. As the piston 21 moves toward the upper chamber 22, the oil liquid L flows out of the second passage 182 from the upper chamber 22, which is the upstream side of the cylinder 4, to the lower chamber 23, which is the downstream side. The second passage 182 is an extension-side passage through which the oil liquid L flows from the upper chamber 22, which is upstream, to the lower chamber 23, which is downstream, during the movement of the piston 21 toward the upper chamber 22, i.e., the extension stroke. The extension-side second passage 182 is provided separately from the extension-side first passage 92. The second passage 182 is in parallel with the first passage 92. A portion of the second passage 182 is formed in the passage-forming member 109.

[0115] The second extension passage 182, which connects the upper chamber 22 and the lower chamber 23, runs parallel to the first extension passage 92, which also connects the upper chamber 22 and the lower chamber 23, except for the passages within the annular groove 55 on the upper chamber 22 side and the passages within the multiple passage holes 38. The parallel sections of the first passage 92 and the second passage 182 are provided separately from each other.

[0116] The upper chamber communication chamber 147, along with the passage between the cylindrical portion 124 of the case member 95 and the sub-valve 107, constitutes the extension-side third passage 512. The extension-side third passage 512 branches off from the extension-side second passage 182 and is provided separately from the second passage 182.

[0117] The outer diameter of the disc 113 is the same as the outer diameter of the sub-valve 110. The disc 113 is thicker and more rigid than the sub-valve 110. When the sub-valve 110 deforms, the disc 113 comes into contact with the sub-valve 110, suppressing further deformation of the sub-valve 110. The annular member 114 has a smaller outer diameter than the outer diameter of the disc 113. The annular member 114 is a common part with the same shape as the annular member 69.

[0118] The sub-valve 110, the passage forming member 109 including the valve seat portion 139, the discs 112 and 113, and the spring member 111 constitute the second damping force generating mechanism 183. The second damping force generating mechanism 183 is provided in the extension-side second passage 182 and opens and closes this second passage 182. The second damping force generating mechanism 183 generates damping force by suppressing the flow of oil L from the second passage 182 to the lower chamber 23. The second damping force generating mechanism 183 is the extension-side second damping force generating mechanism. This second damping force generating mechanism 183 is provided on the piston rod 25, and its valve seat portion 139 is provided on the passage forming member 109. The second damping force generating mechanism 183 is arranged separately from the first damping force generating mechanism 41, which generates damping force in the same extension stroke. The sub-valve 110 that constitutes the extension-side second damping force generating mechanism 183 is the extension-side sub-valve. The third passage 512 is provided in parallel with the extension-side second damping force generating mechanism 183.

[0119] As shown in Figure 3, the disc valve 100, the valve seat disc 101, the disc spring 116, the disc 97, the bottom 122 of the case member 95, and the lower chamber communication chamber 149 constitute a lower chamber volume variable mechanism 185 (volume variable mechanism) that can change the volume of the lower chamber communication chamber 149. The lower chamber volume variable mechanism 185 is provided in the contraction-side third passage 511 which includes the lower chamber communication chamber 149. In the flow path, the lower chamber communication chamber 149 is provided between the disc valve 100 and the sub-valve 110 via the lower chamber 23, the passage in the passage hole 126, and the passage in the hole 415.

[0120] The lower chamber volume variable mechanism 185 deforms and moves the disc valve 100 and valve seat disc 101 together so that they move away from the bottom 122. As a result, the lower chamber volume variable mechanism 185 changes its configuration to increase the volume of the lower chamber communication chamber 149. At this time, if the disc valve 100 maintains contact with the disc spring 116 around its entire circumference, the space between it and the outer tapered portion 403 of the disc spring 116 is closed. In other words, as the disc valve 100 deforms to move away from the bottom 122, if it maintains contact with the disc spring 116 around its entire circumference, the closed state between the lower chamber communication chamber 149 and the upper chamber communication chamber 147 is maintained.

[0121] Furthermore, the lower chamber volume variable mechanism 185 deforms and moves as a whole so that the disc valve 100 and the valve seat disc 101 move closer to the bottom 122. As a result, the lower chamber volume variable mechanism 185 changes its configuration to reduce the volume of the lower chamber communication chamber 149. At this time, the disc valve 100 maintains a state in which it is in contact with the disc spring 116 as a whole, and the space between it and the outer tapered portion 403 of the disc spring 116 is closed.

[0122] As shown in Figure 2, the extension-side third passage 512, which includes the upper chamber communication chamber 147 communicating with the upper chamber 22, branches off from the extension-side second passage 182. The third passage 512 is provided separately from the second passage 182. As shown in Figure 3, the disc valve 100, the valve seat disc 101, the disc spring 116, the discs 102, 104, 105, the spring member 106, the sub-valve 107, the case member 95, and the upper chamber communication chamber 147 constitute the upper chamber volume variable mechanism 186 (volume variable mechanism). The upper chamber volume variable mechanism 186 can change the volume of the upper chamber communication chamber 147. The upper chamber volume variable mechanism 186 is provided in the extension-side third passage 512, which includes the upper chamber communication chamber 147. In the flow path, the upper chamber communication chamber 147 is provided between the disc valve 100 and the sub-valve 107.

[0123] The upper chamber volume variable mechanism 186 deforms and moves the disc valve 100 and valve seat disc 101 as a single unit so that they move away from the disc 104. As a result, the upper chamber volume variable mechanism 186 changes its configuration to increase the volume of the upper chamber communication chamber 147. At this time, if the valve seat disc 101 maintains a state in which it is in contact with the disc valve 100 as a whole, it closes the passage in the communication hole 501 of the disc valve 100. In other words, it maintains a state of isolation between the lower chamber communication chamber 149 and the upper chamber communication chamber 147.

[0124] Furthermore, the upper chamber volume variable mechanism 186 deforms and moves so that the disc valve 100 and the valve seat disc 101 move closer to the disc 104. As a result, the upper chamber volume variable mechanism 186 changes its configuration to reduce the volume of the upper chamber communication chamber 147. At this time, the valve seat disc 101 maintains a state in which it is in contact with the disc valve 100 as a whole, thereby blocking the passage in the communication hole 501 of the disc valve 100.

[0125] The disc valve 100, valve seat disc 101, and disc spring 116 are shared between the lower chamber volume variable mechanism 185 and the upper chamber volume variable mechanism 186. The lower chamber volume variable mechanism 185, which includes the lower chamber communication chamber 149, and the upper chamber volume variable mechanism 186, which includes the upper chamber communication chamber 147, constitute an accumulator 190 that stores oil liquid as the working fluid. The accumulator 190 has a disc valve 100, a disc spring 116, and a case member 95. The accumulator 190 is provided on the piston rod 25. The accumulator 190 is located inside the shock absorber 1, separately from the second damping force generating mechanisms 173 and 183. The disc valve 100 of the accumulator 190 deforms before the second damping force generating mechanism 183 opens during the extension stroke, and deforms before the second damping force generating mechanism 173 opens during the compression stroke. The accumulator 190 is located in the compression-side third passage 511. The accumulator 190 is also located in the extension-side third passage 512. The disc valve 100 that constitutes the accumulator 190 is also located in the third passages 511 and 512.

[0126] In the second passage 182, the passage within the notch 90 of the disk 82 becomes the orifice 175. The orifice 175 is common to both the second passages 172 and 182. The orifice 175 is located upstream of the sub-valve 110 in the flow of the oil liquid L when the sub-valve 110 opens and the oil liquid L flows through the second passage 182. Alternatively, the orifice 175 may be located downstream of the sub-valve 110 in the flow of the oil liquid L when the sub-valve 110 opens and the oil liquid L flows through the second passage 182. The sub-valve 110 and the sub-valve 107 described above open and close independently.

[0127] The extension-side second damping force generating mechanism 183 does not have a fixed orifice formed in either the valve seat portion 139 or the sub-valve 110 that abuts against it. A fixed orifice would connect the upper chamber 22 and the lower chamber 23 even when the valve seat portion 139 and the sub-valve 110 are in contact. In other words, the extension-side second damping force generating mechanism 183 does not connect the upper chamber 22 and the lower chamber 23 when the valve seat portion 139 and the sub-valve 110 are in contact. To put it another way, the second passage 182 does not have a fixed orifice formed to constantly connect the upper chamber 22 and the lower chamber 23. The second passage 182 is not a passage that constantly connects the upper chamber 22 and the lower chamber 23. The annular member 114, together with the disc 113, restricts deformation of the sub-valve 110 in the opening direction beyond a specified limit.

[0128] In the shock absorber 1, the flow of the oil liquid L passing through the upper chamber 22 and the lower chamber 23 is only possible via the first damping force generating mechanisms 41, 42, the second damping force generating mechanisms 173, 183 and the accumulator 190, in order to allow the oil liquid L to pass through axially at least within the range of the piston 21. The shock absorber 1 does not have a fixed orifice in the passage of the oil liquid L that would keep the upper chamber 22 and the lower chamber 23 in constant communication.

[0129] As described above, the second passage 182 and the first passage 92 are parallel to each other, except for the passages within the annular groove 55 and the passages within the multiple passage holes 38. In the parallel sections of the second passage 182 and the first passage 92, the first damping force generating mechanism 41 is provided in the first passage 92, and the second damping force generating mechanism 183 is provided in the second passage 182. Therefore, the extension-side first damping force generating mechanism 41 and the second damping force generating mechanism 183 are arranged in parallel.

[0130] The second damping force generating mechanism 173,183 comprises a passage forming member 109, a sub-valve 110 provided on one side of the member passage 160 and a sub-valve 107 provided on the other side of the member passage 160, and a case member 95. The member passage 160 is the portion of the second passages 172,182 provided on the passage forming member 109. The case member 95 is a bottomed cylindrical shape and is provided between the piston 21 and the passage forming member 109 in the second passages 172,182. The passage forming member 109 is provided inside the case member 95. The sub-valve 110 is provided on the lower chamber 23 side of the passage forming member 109. The sub-valve 107 is provided in the case chamber 146 between the bottom 122 of the case member 95 and the passage forming member 109.

[0131] As described above, the upper chamber volume variable mechanism 186 changes the volume of the upper chamber communication chamber 147 by deforming and moving the disc valve 100 so that it moves away from the disc 104. At that time, with the second damping force generating mechanism 183 open, the pressure difference between the upper chamber communication chamber 147 and the lower chamber communication chamber 149 may exceed a predetermined value. In that case, the upper chamber volume variable mechanism 186 causes the disc valve 100 to deform towards the bottom 122 while elastically deforming the outer tapered portion 403 of the disc spring 116 towards the bottom 122. As a result, the disc valve 100 moves axially away from the valve seat disc 101. Then, the disc valve 100 connects the upper chamber communication chamber 147 and the lower chamber communication chamber 149 through the passage in the communication hole 501. The passage within the communication hole 501 and the passage between the disc valve 100 and the valve seat disc 101 constitute the fourth passage 521. The fourth passage 521 connects the upper chamber communication chamber 147 and the lower chamber communication chamber 149 during the extension stroke. The fourth passage 521 is the extension-side passage. The fourth passage 521 is provided separately from the third passage 512, which includes the upper chamber communication chamber 147. When open, the fourth passage 521 communicates in series with the third passage 512. The upper chamber volume variable mechanism 186, which consists of the disc valve 100, the valve seat disc 101, the disc spring 116, discs 102, 104, 105, spring member 106, sub-valve 107, case member 95, and the upper chamber communication chamber 147, is provided in the third passage 512.

[0132] The disc valve 100 and the valve seat disc 101 constitute the relief mechanism 522. The relief mechanism 522 flows oil liquid L from the upper chamber communication chamber 147 to the lower chamber communication chamber 149 via the fourth passage 521. In other words, the relief mechanism 522 flows oil liquid L from the upper chamber 22 to the lower chamber 23. The relief mechanism 522 is an extension-side relief mechanism. The relief mechanism 522 is provided in the extension-side fourth passage 521. The relief mechanism 522 is set to open after the extension-side second damping force generating mechanism 183 opens.

[0133] The upper chamber volume variable mechanism 186 includes a disc valve 100 and a disc spring 116. The disc valve 100 is flexible and deforms before the second damping force generating mechanism 183 opens. The disc valve 100 has a communication hole 501 connecting the upstream and downstream sides between its inner and outer circumferences. The disc spring 116 contacts the end face of the disc valve 100 and biases it. The relief mechanism 522 is provided to open and close the communication hole 501 of the disc valve 100 depending on the amount of deflection of the disc valve 100.

[0134] The lower chamber volume variable mechanism 185 modifies the disc valve 100 so that it deforms and moves closer to the disc 104, thereby increasing the volume of the lower chamber communication chamber 149. At that time, with the second damping force generating mechanism 173 open, the pressure difference between the upper chamber communication chamber 147 and the lower chamber communication chamber 149 may exceed a predetermined value. In this case, the lower chamber volume variable mechanism 185 increases the amount of deformation on the outer circumference side of the disc valve 100. As a result, the disc valve 100 moves axially away from the contact portion 416 of the disc spring 116. Then, the disc valve 100 connects the lower chamber communication chamber 149 and the upper chamber communication chamber 147 through the disc spring 116. In other words, the contact portion 416 of the disc spring 116 that abuts against the end face of the disc valve 100 moves at least partially away from the end face of the disc valve 100 due to the amount of deflection of the disc valve 100. The passage between the disc valve 100 and the disc spring 116 is the fourth passage 531. The fourth passage 531 connects the lower chamber communication chamber 149 and the upper chamber communication chamber 147 during the compression stroke. The fourth passage 531 is the compression-side passage. The fourth passage 531 is provided separately from the third passage 511, which includes the lower chamber communication chamber 149. When open, the fourth passage 531 communicates in series with the third passage 511. The lower chamber volume variable mechanism 185, which consists of the disc valve 100, the valve seat disc 101, the disc spring 116, the disc 97, the bottom 122 of the case member 95, and the lower chamber communication chamber 149, is provided in the third passage 511.

[0135] The disc valve 100 and the disc spring 116 constitute the relief mechanism 532. The relief mechanism 532 flows oil liquid L from the lower chamber communication chamber 149 to the upper chamber communication chamber 147 via the fourth passage 531. In other words, the relief mechanism 532 flows oil liquid L from the lower chamber 23 to the upper chamber 22. The relief mechanism 532 is a compression-side relief mechanism. The relief mechanism 532 is provided in the compression-side fourth passage 531. The relief mechanism 532 is set to open after the compression-side second damping force generating mechanism 173 opens.

[0136] As shown in Figure 2, when assembled to the piston rod 25, the main valve 71 is clamped on its inner circumference by discs 63 and 67. At the same time, the outer circumference of the main valve 71 abuts against the valve seat portion 50 of the piston 21 over its entire circumference. Also in this state, the main valve 91 is clamped on its inner circumference by discs 83 and 87. At the same time, the outer circumference of the main valve 91 abuts against the valve seat portion 48 of the piston 21 over its entire circumference.

[0137] In this state, the inner circumference of the sub-valve 107 is clamped between the inner seat portion 134 of the passage forming member 109 and the disc 105. At the same time, the sub-valve 107 abuts against the valve seat portion 135 of the passage forming member 109 all around. In this state, the inner circumference of the sub-valve 110 is clamped between the inner seat portion 138 of the passage forming member 109 and the disc 112. At the same time, the sub-valve 110 abuts against the valve seat portion 139 of the passage forming member 109 all around.

[0138] Furthermore, in this state, as shown in Figure 3, the inner circumference of the disc valve 100 is clamped by the disc 97 and disc 102 together with the valve seat disc 101. At the same time, the outer circumference of the disc valve 100 contacts the contact portion 416 of the disc spring 116 over its entire circumference. At this time, the disc valve 100 elastically deforms in a tapered shape so that the portion radially outside the disc 97 moves further axially away from the bottom 122 as it moves radially outward. At this time, the disc spring 116's outer tapered portion 403 elastically deforms and contacts the disc valve 100 over its entire circumference at the contact portion 416. Also in this state, the valve seat disc 101 also elastically deforms in a tapered shape so that the portion radially outside the disc 102 moves further axially away from the bottom 122 as it moves radially outward, following the shape of the disc valve 100.

[0139] As shown in Figure 1, the valve body 12 has fluid passages 251 and 252 that penetrate in the axial direction. Fluid passages 251 and 252 can communicate the lower chamber 23 and the reservoir chamber 5. The base valve 15 has a damping force generating mechanism 255 on the axial bottom member 9 side of the valve body 12. The damping force generating mechanism 255 can open and close the fluid passage 251. The damping force generating mechanism 255 is a compression-side damping force generating mechanism. The base valve 15 also has a damping force generating mechanism 256 on the opposite side of the axial bottom member 9 of the valve body 12. The damping force generating mechanism 256 can open and close the fluid passage 252. The damping force generating mechanism 256 is an extension-side damping force generating mechanism.

[0140] When the piston rod 25 moves in the compression direction and the piston 21 moves in a direction that narrows the lower chamber 23, the pressure in the lower chamber 23 may become higher than a predetermined value than the pressure in the reservoir chamber 5. In this case, the base valve 15 causes the damping force generating mechanism 255 to open the fluid passage 251, allowing the oil L in the lower chamber 23 to flow into the reservoir chamber 5. The damping force generating mechanism 255 generates damping force at this time. In other words, when the piston rod 25 moves in the compression direction and moves the piston 21, the oil L flows out of the fluid passage 251 into the reservoir chamber 5. The damping force generating mechanism 255 is a damping force generating mechanism on the compression side. This damping force generating mechanism 255 does not obstruct the flow of oil L in the fluid passage 252.

[0141] When the piston rod 25 moves in the extension direction and the piston 21 moves towards the upper chamber 22, the pressure in the lower chamber 23 drops below the pressure in the reservoir chamber 5. Then, the base valve 15 causes the damping force generating mechanism 256 to open the fluid passage 252, allowing the oil L from the reservoir chamber 5 to flow into the lower chamber 23. At this time, the damping force generating mechanism 256 generates a damping force. In other words, when the piston rod 25 moves in the extension direction and moves the piston 21, the oil L flows out of the fluid passage 252 into the lower chamber 23. The damping force generating mechanism 256 is an extension-side damping force generating mechanism. This damping force generating mechanism 256 does not obstruct the flow of oil L in the fluid passage 251. The damping force generating mechanism 256 may also function as a suction valve that flows oil L from the reservoir chamber 5 into the lower chamber 23 without substantially generating a damping force.

[0142] <Operation> As shown in Figure 2, of the first damping force generating mechanism 41 and the second damping force generating mechanism 183 on the extension side, the main valve 91 of the first damping force generating mechanism 41 has higher rigidity and a higher opening pressure than the sub-valve 110 of the second damping force generating mechanism 183. Therefore, in the extension stroke, in the extremely low-speed region where the piston speed is lower than a predetermined value, the first damping force generating mechanism 41 remains closed while the second damping force generating mechanism 183 is open. In other words, the second damping force generating mechanism 183 opens and generates damping force when the piston speed is lower than that of the first damping force generating mechanism 41. Furthermore, in the normal speed region where the piston speed is above this predetermined value, both the first damping force generating mechanism 41 and the second damping force generating mechanism 183 are open. The sub-valve 110 is an extremely low-speed valve that deforms against the biasing force of the spring member 111 in the region of extremely low piston speed, opening and generating a damping force.

[0143] In other words, during the extension stroke, the piston 21 moves toward the upper chamber 22, increasing the pressure in the upper chamber 22 and decreasing the pressure in the lower chamber 23. Here, neither the first damping force generating mechanisms 41, 42 nor the second damping force generating mechanisms 173, 183 have a fixed orifice that keeps the upper chamber 22 and the lower chamber 23 in constant communication. Therefore, the oil L in the upper chamber 22 flows into the upper chamber communication chamber 147 via the passages in the multiple passage holes 38 and annular groove 55 of the piston 21, the orifice 175, the passage in the large-diameter hole portion 46 of the piston 21, the piston rod passage portion 51 of the piston rod 25 and the passage in the large-diameter hole portion 133 of the passage forming member 109, the radial passage 222 of the passage forming member 109, and the third passage 512. As a result, the upper chamber communication chamber 147 is pressurized. Therefore, before the second damping force generating mechanism 183 opens, the upper chamber volume variable mechanism 186 bends radially inward from the contact position of the disc spring 116 of the disc valve 100 with the outer tapered portion 403 toward the bottom 122. As a result, the disc valve 100 increases the volume of the upper chamber communication chamber 147. This allows the upper chamber volume variable mechanism 186 to suppress the rise in pressure in the upper chamber communication chamber 147. At this time, the valve seat disc 101 deforms in accordance with the disc valve 100 and maintains the closed state of the fourth passage 521. Also, at this time, as the disc valve 100 bends and moves toward the bottom 122, the lower chamber volume variable mechanism 185 reduces the volume of the lower chamber communication chamber 149.

[0144] Here, during the extension stroke when the shock absorber 1 is subjected to low-frequency input (large-amplitude excitation), the amount of oil L flowing from the upper chamber 22 to the upper chamber communication chamber 147 becomes large. As a result, the disc valve 100 deforms significantly. When the amount of deformation of the disc valve 100 becomes large, the reaction force due to the support rigidity of the clamped inner circumference side becomes large, limiting the amount of deformation. This causes the upper chamber communication chamber 147 to become pressurized. As a result, the second passage 182 becomes pressurized to the point where the second damping force generating mechanism 183 opens.

[0145] In this case, neither the first damping force generating mechanisms 41, 42 nor the second damping force generating mechanisms 173, 183 have a fixed orifice that keeps the upper chamber 22 and the lower chamber 23 in constant communication. As a result, in the extension stroke when the piston speed is below the first predetermined value at which the second damping force generating mechanism 183 opens, the damping force rises rapidly. Furthermore, in the region where the piston speed is faster than the first predetermined value but slower than the second predetermined value, the first damping force generating mechanism 41 remains closed while the second damping force generating mechanism 183 opens.

[0146] In other words, when the sub-valve 110 deforms against the biasing force of the spring member 111 and separates from the valve seat portion 139, the extension-side second passage 182 connects the upper chamber 22 and the lower chamber 23. As a result, the oil L in the upper chamber 22 flows into the lower chamber 23 through the passages in the multiple passage holes 38 and annular groove 55 of the piston 21, the orifice 175, the passage in the large-diameter hole portion 46 of the piston 21, the piston rod passage portion 51 of the piston rod 25 and the passage in the large-diameter hole portion 133 of the passage forming member 109, the radial passage 222 of the passage forming member 109, the passage portion 161 within the passage forming member 109, and the passage between the sub-valve 110 and the valve seat portion 139. This allows the damping force of the valve characteristics (a characteristic in which the damping force is approximately proportional to the piston speed) to be obtained even in the extremely low-speed region where the piston speed is lower than the second predetermined value.

[0147] Furthermore, a relief mechanism 522 is provided that opens after the second damping force generating mechanism 183 opens during the extension stroke. Therefore, in the normal speed range where the piston speed is above a second predetermined value, when the pressure in the upper chamber communication chamber 147 increases, the relief mechanism 522 opens the fourth passage 521 while the second damping force generating mechanism 183 remains open, allowing the oil liquid L from the upper chamber communication chamber 147 to flow into the lower chamber 23. Subsequently, with the second damping force generating mechanism 183 and the relief mechanism 522 still open, the first damping force generating mechanism 41 opens. In other words, as described above, when the sub-valve 110 deforms against the biasing force of the spring member 111 and separates from the valve seat portion 139, the oil liquid L flows from the upper chamber 22 to the lower chamber 23 through the extension-side second passage 182. Subsequently, with the second damping force generating mechanism 183 remaining open, the relief mechanism 522 opens the fourth passage 521, allowing the oil liquid L to flow from the upper chamber 22 to the lower chamber 23 through the fourth passage 521. At this time, the flow of the oil liquid L is restricted by the orifice 175 located downstream of the main valve 91 in the second passage 182. As a result, the pressure applied to the main valve 91 increases, the differential pressure rises, the main valve 91 separates from the valve seat portion 48, and the oil liquid L flows from the upper chamber 22 to the lower chamber 23 through the extension-side first passage 92. Thus, the oil liquid L in the upper chamber 22 flows to the lower chamber 23 through the passages in the multiple passage holes 38 and the annular groove 55, and the passage between the main valve 91 and the valve seat portion 48.

[0148] This allows for the acquisition of valve-like damping force (damping force is approximately proportional to piston speed) even in the normal speed range where the piston speed is above a second predetermined value. The rate of increase in extension damping force with respect to piston speed in the normal speed range is lower than the rate of increase in extension damping force with respect to piston speed in the extremely low speed range. In other words, the slope of the rate of increase in extension damping force with respect to piston speed in the normal speed range can be made flatter than in the extremely low speed range.

[0149] Here, when the disc valve 100 constituting the accumulator 190 and the relief mechanism 522 deforms significantly toward the bottom 122 side of the case member 95, the outer tapered portion 403 of the disc spring 116 deforms to increase its taper and follow suit. At this time, the outer tapered portion 403 abuts against the inner surface 123a of the intermediate tapered portion 123 of the case member 95, suppressing deformation that would increase the taper further. As a result, the inner surface 123a of the intermediate tapered portion 123 of the case member 95 prevents the abutting portion 416 of the disc spring 116 from being displaced toward the bottom surface 122a of the bottom 122 than the main body portion 417. Therefore, it is possible to suppress the deformation of the outer tapered portion 403 of the disc spring 116 so that its outer circumference is located toward the bottom 122 side than its inner circumference. In other words, it is possible to suppress the outer tapered portion 403 of the disc spring 116 from becoming axially reversed compared to its normal shape.

[0150] During the extension stroke, in the normal speed range where the piston speed is above the second predetermined value, the differential pressure between the upper chamber 22 and the lower chamber 23 is greater than in the low-speed range where it is above the first predetermined value but below the second predetermined value. The first passage 92 does not have an orifice for throttling. Therefore, when the main valve 91 opens, the oil liquid L can flow through the first passage 92 at a large flow rate. By throttling the second passage 182 with the orifice 175, and by the relief mechanism 522 opening the fourth passage 521 to allow the oil liquid L from the upper chamber communication chamber 147 to flow into the lower chamber 23, deformation of the sub-valve 110 can be suppressed.

[0151] Furthermore, in this state, the closed sub-valve 107 is subjected to opposing pressures from the lower chamber 23 and the upper chamber communication chamber 147. An orifice 175 is formed upstream of the sub-valve 107 in the second passage 182. Therefore, even if the pressure difference between the upper chamber 22 and the lower chamber 23 becomes large, the pressure rise in the upper chamber communication chamber 147 is slower than the pressure rise in the upper chamber 22. Combined with the relief mechanism 522 opening the fourth passage 521 and allowing the oil liquid L from the upper chamber communication chamber 147 to flow into the lower chamber 23, this suppresses an increase in the pressure difference between the upper chamber communication chamber 147 and the lower chamber 23. Thus, it is possible to suppress an increase in the pressure difference between the upper chamber communication chamber 147 and the lower chamber 23 that the closed sub-valve 107 experiences. As a result, it is possible to suppress a large back pressure being applied to the sub-valve 107 from the upper chamber communication chamber 147 side towards the lower chamber 23 side.

[0152] The buffer 1 has a flow path for the oil liquid L to flow from the upper chamber 22 to the lower chamber 23 during the extension stroke, with the first passage 92 and the second passage 182 arranged in parallel. The buffer 1 also has a main valve 91 and a sub-valve 110 arranged in parallel, which operate during the extension stroke. The orifice 175 is connected in series with the sub-valve 110.

[0153] As described above, in the extension stroke, in the normal speed range where the piston speed is above the second predetermined value, the main valve 91 opens, allowing the oil liquid L to flow at a large flow rate through the first passage 92. This reduces the flow rate through the passage between the sub-valve 110 and the valve seat portion 139. Therefore, for example, it is possible to reduce the rate of increase of the damping force with respect to the increase in piston speed in the normal speed range (above the second predetermined value). In other words, the slope of the rate of increase of the extension damping force with respect to the increase in piston speed in the normal speed range (above the second predetermined value) can be made flatter than in the extremely low speed range (below the second predetermined value). This expands the degree of design freedom.

[0154] During the extension stroke when a higher frequency is input to the buffer 1 than during the low-frequency input described above (during small-amplitude excitation), the amount of oil L flowing from the upper chamber 22 to the upper chamber communication chamber 147 is small. Therefore, the deformation of the disc valve 100 is small, and the upper chamber volume variable mechanism 186 can absorb the volume of oil L flowing into the upper chamber communication chamber 147 with the amount of deflection of the disc valve 100. Thus, the pressure increase in the upper chamber communication chamber 147 is small. Therefore, when the extremely low-speed damping force is generated, the condition is the same as if the disc valve 100 were not present. In other words, when the extremely low-speed damping force is generated, the upper chamber communication chamber 147 is in constant communication with the lower chamber 23 through the passage in the hole 415 of the disc spring 116 and the passage in the passage hole 126 of the case member 95, that is, the same as a structure without the second damping force generating mechanism 183.

[0155] Therefore, during the extension stroke at high-frequency input, the rise of the extremely low-speed damping force becomes gentler compared to low-frequency input or conventional damping force characteristics. In other words, during the extension stroke, when the frequency of the piston 21 exceeds a predetermined frequency, the upper chamber volume variable mechanism 186, including the disc valve 100, limits the flow rate of the oil liquid L to the sub-valve 110 of the second damping force generating mechanism 183. Furthermore, the change in damping force until the valve of the second damping force generating mechanism 183 opens (the slope of the damping force with respect to piston speed) can be adjusted by changing the rigidity (plate thickness, etc.) of the disc valve 100.

[0156] In this case, during the extension stroke, the damping force characteristics are combined with those of the damping force generation mechanism 256.

[0157] In both cases, of the first damping force generating mechanism 42 and the second damping force generating mechanism 173 on the compression side, the main valve 71 of the first damping force generating mechanism 42 has higher rigidity and a higher opening pressure than the sub-valve 107 of the second damping force generating mechanism 173. Therefore, in the compression stroke, in the extremely low-speed region where the piston speed is lower than a predetermined value, the first damping force generating mechanism 42 remains closed while the second damping force generating mechanism 173 is open. In other words, the second damping force generating mechanism 173 opens and generates damping force when the piston speed is lower than that of the first damping force generating mechanism 42. In the normal speed region where the piston speed is above this predetermined value, both the first damping force generating mechanism 42 and the second damping force generating mechanism 173 are open. The sub-valve 107 is an extremely low-speed valve that opens and generates damping force in the extremely low-speed region of the piston speed.

[0158] In other words, during the compression stroke, the piston 21 moves towards the lower chamber 23, increasing the pressure in the lower chamber 23 and decreasing the pressure in the upper chamber 22. Here, neither the first damping force generating mechanisms 41, 42 nor the second damping force generating mechanisms 173, 183 have a fixed orifice that keeps the lower chamber 23 and the upper chamber 22 in constant communication. As a result, the oil L in the lower chamber 23 flows into the lower chamber communication chamber 149 through the passage in the passage hole 126 of the case member 95 and the passage in the hole 415 of the disc spring 116. This causes the lower chamber communication chamber 149 to become pressurized. As a result, the disc valve 100 of the lower chamber volume variable mechanism 185 flexes towards the disc 104 before the second damping force generating mechanism 173 opens. This causes the disc valve 100 to increase the volume of the lower chamber communication chamber 149. As a result, the lower chamber volume variable mechanism 185 suppresses the pressure rise in the lower chamber communication chamber 149. At this time, the valve seat disc 101 deforms in accordance with the disc valve 100, maintaining the closed state of the fourth passage 521. Also, at this time, as the disc valve 100 bends and moves toward the disc 104, the upper chamber volume variable mechanism 186 reduces the volume of the upper chamber communication chamber 147.

[0159] Here, during the compression stroke when the shock absorber 1 is subjected to low-frequency input (large-amplitude excitation), the amount of oil L flowing from the lower chamber 23 to the lower chamber communication chamber 149 becomes large. As a result, the disc valve 100 deforms significantly. When the amount of deformation of the disc valve 100 becomes large, the reaction force due to the support rigidity of the clamped inner circumference side becomes large, limiting the amount of deformation. This causes the lower chamber communication chamber 149 to become pressurized. As a result, the second passage 172 becomes pressurized to the point where the second damping force generating mechanism 173 opens.

[0160] In this case, neither the first damping force generating mechanisms 41, 42 nor the second damping force generating mechanisms 173, 183 have a fixed orifice that keeps the lower chamber 23 and the upper chamber 22 in constant communication. As a result, in the compression stroke when the piston speed is below the third predetermined value at which the second damping force generating mechanism 173 opens, the damping force rises rapidly. Furthermore, in the region where the piston speed is faster than the third predetermined value but slower than the fourth predetermined value, the first damping force generating mechanism 42 remains closed while the second damping force generating mechanism 173 opens.

[0161] In other words, when the sub-valve 107 deforms against the biasing force of the spring member 106 and separates from the valve seat portion 135, the second passage 172 on the compression side connects the lower chamber 23 and the upper chamber 22. As a result, the oil L in the lower chamber 23 flows into the upper chamber 22 via the passage portion 162 in the passage forming member 109, the passage between the sub-valve 107 and the valve seat portion 135, the upper chamber connecting chamber 147, the radial passage 222 of the passage forming member 109, the passage in the large-diameter hole portion 133 of the passage forming member 109, the piston rod passage portion 51 of the piston rod 25, the passage in the large-diameter hole portion 46 of the piston 21, the orifice 175, and the passages in the multiple passage holes 38 and annular groove 55 of the piston 21. This allows the damping force of the valve characteristics (a characteristic in which the damping force is approximately proportional to the piston speed) to be obtained even in the extremely low-speed region where the piston speed is lower than the fourth predetermined value.

[0162] Furthermore, a relief mechanism 532 is provided that opens after the second damping force generating mechanism 173 opens during the compression stroke. Therefore, in the normal speed range where the piston speed is above the fourth predetermined value, when the pressure in the lower chamber communication chamber 149 increases, the relief mechanism 532 opens the fourth passage 531 while the second damping force generating mechanism 173 remains open, allowing the oil L from the lower chamber 23 and the lower chamber communication chamber 149 to flow to the upper chamber 22 via the upper chamber communication chamber 147. Subsequently, the first damping force generating mechanism 42 opens while the second damping force generating mechanism 173 and the relief mechanism 532 remain open. In other words, as described above, when the sub-valve 107 separates from the valve seat portion 135, the oil L flows from the lower chamber 23 to the upper chamber 22 through the second passage 172 on the compression side. Subsequently, with the second damping force generating mechanism 173 still open, the relief mechanism 532 opens the fourth passage 531, allowing the oil liquid L to flow from the lower chamber 23 to the upper chamber 22 through the fourth passage 531. At this time, the flow of the oil liquid L is restricted in the second passage 172 by the sub-valve 107 and the orifice 175 located downstream of the relief mechanism 532. This increases the pressure applied to the main valve 71, increasing the differential pressure. As a result, the main valve 71 separates from the valve seat portion 50, allowing the oil liquid L to flow from the lower chamber 23 to the upper chamber 22 through the compression-side first passage 72. Therefore, the oil liquid L in the lower chamber 23 flows to the upper chamber 22 through the passages within the multiple passage holes 39 and the annular groove 56, and the passage between the main valve 71 and the valve seat portion 50.

[0163] This allows for the acquisition of valve-like damping force (damping force is approximately proportional to piston speed) even in the normal speed range where the piston speed is above the fourth predetermined value. The rate of increase in compression damping force with respect to piston speed in the normal speed range is lower than the rate of increase in compression damping force with respect to piston speed in the extremely low speed range. In other words, the slope of the rate of increase in extension damping force with respect to piston speed in the normal speed range can be made flatter than in the extremely low speed range.

[0164] Here, during the compression stroke, in the normal speed range where the piston speed is above the fourth predetermined value, the differential pressure between the lower chamber 23 and the upper chamber 22 is greater than in the low-speed range where it is above the third predetermined value and below the fourth predetermined value. At this time, there is no orifice throttling in the first passage 72. Therefore, when the main valve 71 opens, the oil liquid L can flow through the first passage 72 at a large flow rate. By doing this, throttling the second passage 172 with the orifice 175, and having the relief mechanism 532 open the fourth passage 531 to allow the oil liquid L from the lower chamber 23 and the lower chamber communication chamber 149 to flow into the upper chamber communication chamber 147, deformation of the sub-valve 107 can be suppressed.

[0165] Furthermore, in this state, the closed sub-valve 110 is subjected to opposing pressures from the lower chamber 23 and the upper chamber communication chamber 147. Even if the pressure difference between the lower chamber 23 and the upper chamber 22 becomes large, the formation of the orifice 175 downstream of the sub-valve 110 in the second passage 172, and the relief mechanism 532 opening the fourth passage 531 to allow the oil liquid L from the lower chamber 23 and the lower chamber communication chamber 149 to flow into the upper chamber communication chamber 147, suppress the increase in the pressure difference between the lower chamber 23 and the upper chamber communication chamber 147. Therefore, it is possible to suppress the increase in the pressure difference between the lower chamber 23 and the upper chamber communication chamber 147 that the closed sub-valve 110 experiences. As a result, it is possible to suppress the application of a large back pressure to the sub-valve 110 from the lower chamber 23 side to the upper chamber communication chamber 147 side.

[0166] The shock absorber 1 has a flow path for the oil liquid L to flow from the lower chamber 23 to the upper chamber 22 during the compression stroke, with the first passage 72 and the second passage 172 arranged in parallel. The shock absorber 1 has a main valve 71 and a sub-valve 107 arranged in parallel, which operate during the compression stroke. The orifice 175 is connected in series with the sub-valve 107.

[0167] As described above, in the compression stroke, in the normal speed range where the piston speed is above the fourth predetermined value, the main valve 71 opens, allowing the oil liquid L to flow at a large flow rate through the first passage 72. This reduces the flow rate through the passage between the sub-valve 107 and the valve seat portion 135. Therefore, for example, it is possible to reduce the rate of increase of the damping force with respect to the increase in piston speed in the normal speed range (above the fourth predetermined value). In other words, the slope of the rate of increase of the compression-side damping force with respect to the increase in piston speed in the normal speed range (above the fourth predetermined value) can be made flatter than in the extremely low speed range (below the fourth predetermined value). This expands the degree of design freedom.

[0168] During the compression stroke when a higher frequency is input to the buffer 1 than during the low-frequency input described above (during small-amplitude excitation), the amount of oil L flowing from the lower chamber 23 to the lower chamber communication chamber 149 is small. Therefore, the deformation of the disc valve 100 is small. As a result, the lower chamber volume variable mechanism 185 can absorb the volume of oil L flowing into the lower chamber communication chamber 149 with the amount of deflection of the disc valve 100. Therefore, the pressure increase in the lower chamber communication chamber 149 is small. As a result, when the extremely low-speed damping force is rising, it is as if the disc valve 100 were not present. In other words, when the extremely low-speed damping force is rising, it is possible to create a state in which the lower chamber communication chamber 149 is constantly in communication with the upper chamber communication chamber 147, that is, a state as if the second damping force generation mechanism 173 were not present.

[0169] Therefore, during the compression stroke at high frequency input, the rise of the extremely low-speed damping force becomes gentler compared to low-frequency input or conventional damping force characteristics. In other words, when the frequency of the piston 21 exceeds a predetermined frequency, the lower chamber volume variable mechanism 185, including the disc valve 100, limits the flow rate of the oil liquid L to the sub-valve 107 of the second damping force generating mechanism 173. Furthermore, the change in damping force until the valve of the second damping force generating mechanism 173 opens (the slope of the damping force with respect to piston speed) can be adjusted by the difference in rigidity (plate thickness, etc.) of the disc valve 100.

[0170] In this case, during the compression stroke, the damping force characteristics are combined with those of the damping force generation mechanism 255.

[0171] Patent Document 1, mentioned above, discloses a buffer having a valve that opens in the region of extremely low piston speed. As such, valves that open in the region of extremely low piston speed open with a small differential pressure, making them prone to variations in opening characteristics. Therefore, there is a need to suppress variations in opening characteristics.

[0172] The shock absorber 1 of the first embodiment includes a first passage 72 through which working fluid flows from the lower chamber 23, which is upstream, to the upper chamber 22, which is downstream, as the piston 21 moves toward the compression side; a first damping force generating mechanism 42 provided in the first passage 72 for generating damping force; a second passage 172 provided separately from the first passage 72; a second damping force generating mechanism 173 provided in the second passage 172 for generating damping force by opening at a piston speed lower than that of the first damping force generating mechanism 42; a third passage 511 provided separately from the second passage 172; and a lower chamber volume variable mechanism 185 provided in the third passage 511. The second damping force generating mechanism 173 includes a passage forming member 109 in which the second passage 172 is formed; a sub-valve 107 placed on the passage forming member 109 for opening and closing the second passage 172; and a spring member 106 for biasing the outer circumference of the sub-valve 107. Thus, in the first embodiment, the shock absorber 1 biases the outer circumference of the sub-valve 107 that opens and closes the second passage 172 with a spring member 106. Therefore, even if the sub-valve 107 is opened by a small differential pressure during the compression stroke, variations in the valve opening characteristics can be suppressed. As a result, the shock absorber 1 of the first embodiment can generate a stable damping force even in the extremely low piston speed range during the compression stroke.

[0173] Furthermore, the shock absorber 1 of the first embodiment includes a first passage 92 through which working fluid flows from the upper chamber 22, which is upstream, to the lower chamber 23, which is downstream, as the piston 21 moves toward the extension side; a first damping force generating mechanism 41 provided in the first passage 92 for generating damping force; a second passage 182 provided separately from the first passage 92; a second damping force generating mechanism 183 provided in the second passage 182 for generating damping force by opening at a piston speed lower than that of the first damping force generating mechanism 41; a third passage 512 provided separately from the second passage 182; and an upper chamber volume variable mechanism 186 provided in the third passage 512. The second damping force generating mechanism 183 includes a passage forming member 109 in which the second passage 182 is formed; a sub-valve 110 placed on the passage forming member 109 for opening and closing the second passage 182; and a spring member 111 for biasing the outer circumference of the sub-valve 110. Thus, in the first embodiment, the shock absorber 1 biases the outer circumference of the sub-valve 110 that opens and closes the second passage 172 with a spring member 111. Therefore, even if the sub-valve 110 is opened by a small differential pressure during the extension stroke, variations in the valve opening characteristics can be suppressed. As a result, the shock absorber 1 of the first embodiment can generate a stable damping force even in the extremely low piston speed range during the extension stroke.

[0174] If a leaf spring made of a single press-formed product has a circular flat mounting portion on its inner circumference and multiple spring plate portions extending radially from the mounting portion in an oblique direction relative to the mounting portion, the biasing force tends to be unstable and difficult to adjust. In contrast, the shock absorber 1 of the first embodiment is formed by integrally providing a spring member 106 with a main body member 331 that is placed on the sub-valve 107 and a protruding member 332 that is provided on the outer circumference of the main body member 331 and protrudes toward the sub-valve 107. Furthermore, the shock absorber 1 is formed by integrally providing a spring member 111 with a main body member 341 that is placed on the sub-valve 110 and a protruding member 342 that is provided on the outer circumference of the main body member 341 and protrudes toward the sub-valve 110. Therefore, compared to a leaf spring that is entirely formed by press molding, the shock absorber 1 can generate a stable biasing force with spring members 106 and 111. Furthermore, since the quality of the spring members 106 and 111 can be controlled by managing the plate thickness of the main body members 331 and 341 and the protruding members 332 and 342, quality control becomes easier. Therefore, the shock absorber 1 can generate an even more stable damping force. Also, by appropriately setting the thickness of the main body member 331 and the protruding member 332, the biasing force of the spring member 106 can be easily and precisely adjusted. Similarly, by setting the thickness of the main body member 341 and the protruding member 342, the biasing force of the spring member 111 can be easily and precisely adjusted. Therefore, the degree of freedom in adjusting the biasing force of the spring members 106 and 111 is increased.

[0175] Furthermore, in spring member 106, both the main body member 331 and the protruding member 332 are circular flat plates, and in spring member 111, both the main body member 341 and the protruding member 342 are circular flat plates. Therefore, spring members 106 and 111 can generate a more stable biasing force.

[0176] [Second Embodiment] Next, the second embodiment will be described, primarily based on Figure 5, focusing on the differences from the first embodiment. Parts common to both the first and second embodiments will be represented by the same designations and reference numerals.

[0177] As shown in Figure 5, the shock absorber 1A of the second embodiment has a spring member 106A that is partially different from the spring member 106, replacing the spring member 106. The spring member 106A has a protruding member 332A that has a different thickness from the protruding member 332, replacing the protruding member 332. Specifically, the protruding member 332A is thicker than the protruding member 332.

[0178] Furthermore, in the shock absorber 1A of the second embodiment, a retainer 551 is provided between the main body member 331 of the spring member 106A and the sub-valve 107. The retainer 551 is made of metal and is a perforated circular flat plate with a constant thickness and a constant radial width around its entire circumference. The retainer 551 is positioned radially relative to the piston rod 25 by fitting a mounting shaft portion 28 inside it. The outer diameter of the retainer 551 is the same as the outer diameter of the disc 105. The outer diameter of the retainer 551 is positioned inside the passage hole 333 in the radial direction of the main body member 331.

[0179] Furthermore, in the shock absorber 1A of the second embodiment, a spring member 111A, which is partially different from the spring member 111, is provided in place of the spring member 111. The spring member 111A provides a protruding member 342A, which has a different thickness from the protruding member 342, in place of the protruding member 342. Specifically, the protruding member 342A is thicker than the protruding member 342. The protruding member 342A may be a common part with the same shape as the protruding member 332A.

[0180] Furthermore, in the shock absorber 1A of the second embodiment, a retainer 552 is provided between the main body member 341 of the spring member 111A and the sub-valve 110. The retainer 552 is made of metal and is a perforated circular flat plate with a constant thickness and a constant radial width around its entire circumference. The retainer 552 is positioned radially relative to the piston rod 25 by fitting a mounting shaft portion 28 inside it. The outer diameter of the retainer 552 is the same as the outer diameter of the disc 112. The outer diameter of the retainer 552 is positioned inside the passage hole 343 in the radial direction of the main body member 341. The retainer 552 may be a common part with the same shape as the retainer 551.

[0181] In the shock absorber 1A of the second embodiment, a retainer 551 is provided between the inner circumference of the main body member 331 of the spring member 106A and the sub-valve 107, and a retainer 552 is provided between the inner circumference of the main body member 331 of the spring member 111A and the sub-valve 110. Therefore, by appropriately setting the thickness of the retainer 551 in addition to the thickness of the main body member 331 and the thickness of the protruding member 332A, the biasing force of the spring member 106A can be adjusted in more detail. Similarly, by appropriately setting the thickness of the retainer 552 in addition to the thickness of the main body member 341 and the thickness of the protruding member 342A, the biasing force of the spring member 111A can be adjusted in more detail. Therefore, the degree of freedom in adjusting the biasing force of the spring members 106A and 111A is further increased.

[0182] In addition, in the shock absorber 1 of the first embodiment, the configuration of the spring member 111 side of the spring members 106 and 111 may be kept as is, and only the spring member 106 may be replaced with the spring member 106A, and only the retainer 551 of the retainers 551 and 552 may be provided. Alternatively, in the shock absorber 1 of the first embodiment, the configuration of the spring member 106 side of the spring members 106 and 111 may be kept as is, and only the spring member 111 may be replaced with the spring member 111A, and only the retainer 552 of the retainers 551 and 552 may be provided.

[0183] [Third Embodiment] Next, the third embodiment will be described, primarily based on Figure 6, focusing on the differences from the first embodiment. Parts common to both the first and third embodiments will be represented by the same designations and reference numerals.

[0184] As shown in Figure 6, in the buffer 1B of the third embodiment, multiple stacked discs 561 (second biasing member) and stacked disc 562 (second biasing member) are provided between the disc 105 and the spring member 106. Both stacked discs 561 and 562 are made of metal and are perforated circular flat plates with a constant thickness and a constant radial width around their entire circumference. Both stacked discs 561 and 562 are positioned radially relative to the piston rod 25 by fitting a mounting shaft portion 28 to the inside.

[0185] Of the stacked disks 561 and 562, the stacked disk 561 on the disk 105 side has an outer diameter that is larger than the outer diameter of disk 105 and smaller than the inner diameter of the protruding member 332 of the spring member 106. Of the stacked disks 561 and 562, the stacked disk 562 on the spring member 106 side has an outer diameter equal to the outer diameter of the main body member 331 and the protruding member 332 of the spring member 106.

[0186] With the inner circumference of the main body member 331 sandwiched between the disc 105 and the sub-valve 107, the spring member 106 causes the main body member 331 to deform into a tapered shape as described above. The stacked discs 561 and 562, along with the main body member 331, have their inner circumferences sandwiched between the disc 105 and the sub-valve 107. As a result, the portions of the stacked discs 561 and 562 that overlap with the tapered portion of the main body member 331 deform into a tapered shape in accordance with this. This causes the stacked discs 561 and 562 to bias the spring member 106 toward the sub-valve 107.

[0187] Furthermore, in the buffer 1B of the third embodiment, multiple stacked discs 571 (second biasing member) and stacked disc 572 (second biasing member) are provided between the disc 112 and the spring member 111. Both stacked discs 571 and 572 are made of metal and are perforated circular flat plates with a constant thickness and a constant radial width around their entire circumference. Both stacked discs 571 and 572 are positioned radially relative to the piston rod 25 by fitting a mounting shaft portion 28 to the inside.

[0188] Of the stacked disks 571 and 572, the stacked disk 571 on the disk 112 side has an outer diameter that is larger than the outer diameter of disk 112 and smaller than the inner diameter of the protruding member 342 of the spring member 111. The stacked disk 571 may also be a common part with the same shape as the stacked disk 561. Of the stacked disks 571 and 572, the stacked disk 572 on the spring member 111 side has an outer diameter equal to the outer diameter of the main body member 341 and the protruding member 342 of the spring member 111. The stacked disk 572 may also be a common part with the same shape as the stacked disk 562.

[0189] With the inner circumference of the main body member 341 sandwiched between the disc 112 and the sub-valve 110, the spring member 111 deforms into a tapered shape as described above. The stacked discs 571 and 572 are also sandwiched into the disc 112 and the sub-valve 110 together with the main body member 341 on their respective inner circumferences. As a result, the portions of the stacked discs 571 and 572 that overlap with the tapered portion of the main body member 341 deform into a tapered shape in accordance with this. This causes the stacked discs 571 and 572 to bias the spring member 111 toward the sub-valve 110.

[0190] The shock absorber 1B of the third embodiment is provided with stacked discs 561 and 562 that bias the spring member 106 toward the sub-valve 107. Therefore, in addition to the thickness of the main body member 331 and the thickness of the protruding member 332, the biasing force of the spring member 106 can be adjusted in more detail by setting the number of stacked discs 561 and 562 (one is also acceptable), the respective thicknesses of the stacked discs 561 and 562, and the respective outer diameters of the stacked discs 561 and 562. Furthermore, the shock absorber 1B is provided with stacked discs 571 and 572 that bias the spring member 111 toward the sub-valve 110. Therefore, in the shock absorber 1B, in addition to the thickness of the main body member 341 and the thickness of the protruding member 342, the biasing force of the spring member 111 can be adjusted in more detail by setting the number of stacked discs 571 and 572 (one is also acceptable), the respective thicknesses of the stacked discs 571 and 572, and the respective outer diameters of the stacked discs 571 and 572. Therefore, the shock absorber 1B offers even greater freedom in adjusting the biasing force of the spring members 106 and 111.

[0191] In addition, in the shock absorber 1 of the first embodiment, the configuration of the spring member 111 side of the spring members 106, 111 may be kept as is, and stacked discs 561, 562 may be provided only between the spring member 106 and the disc 105. Alternatively, in the shock absorber 1 of the first embodiment, the configuration of the spring member 106 side of the spring members 106, 111 may be kept as is, and stacked discs 571, 572 may be provided only between the spring member 111 and the disc 112.

[0192] Furthermore, in the shock absorber 1A of the second embodiment, stacked discs 561 and 562 may be provided between the spring member 106A and the disk 105, and stacked discs 571 and 572 may be provided between the spring member 111A and the disk 112. Alternatively, in the shock absorber 1A of the second embodiment, the configuration of the spring member 111A may be kept as is, and stacked discs 561 and 562 may be provided only between the spring member 106A and the disk 105. Alternatively, in the shock absorber 1A of the second embodiment, the configuration of the spring member 106A may be kept as is, and stacked discs 571 and 572 may be provided only between the spring member 111A and the disk 112.

[0193] (Note 1) The shock absorber of the embodiment comprises a cylinder in which a working fluid is sealed, a piston slidably provided within the cylinder and dividing the inside of the cylinder into two chambers, a piston rod connected to the piston and extending outside the cylinder, a first passage through which the working fluid flows from the upstream chamber to the downstream chamber as the piston moves, a first damping force generating mechanism provided in the first passage and generating damping force, a second passage provided separately from the first passage, a second damping force generating mechanism provided in the second passage and opening at a piston speed lower than that of the first damping force generating mechanism to generate damping force, a third passage provided separately from the second passage, and a volume variable mechanism provided in the third passage, wherein the second damping force generating mechanism comprises a passage forming member in which the second passage is formed, a first valve mounted on the passage forming member and opening and closing the second passage, and a first biasing member that biases the outer circumference of the first valve.

[0194] (Note 2) In the above appendix 1, the first biasing member may be integrally provided with a main body member that is placed on the first valve and a protruding member that is provided on the outer circumference of the main body member and protrudes toward the first valve.

[0195] (Note 3) In the above appendix 1 or appendix 2, a retainer may be provided on the inner circumference between the first valve and the first biasing member.

[0196] (Note 4) In any one of the above appendices 1 to 3, a second biasing member may be provided that biases the first biasing member toward the first valve.

[0197] (Note 5) The shock absorber of the embodiment comprises a cylinder in which a working fluid is sealed, a piston slidably provided within the cylinder and dividing the inside of the cylinder into two chambers, a piston rod connected to the piston and extending to the outside of the cylinder, a first passage through which the working fluid flows from the upstream chamber to the downstream chamber as the piston moves, a first damping force generating mechanism provided in the first passage and generating damping force, a second passage provided separately from the first passage, and a second damping force generating mechanism provided in the second passage and opening when the piston speed is lower than that of the first damping force generating mechanism to generate damping force, wherein the second damping force generating mechanism comprises a passage forming member in which the second passage is formed, a first valve placed on the passage forming member and opening and closing the second passage, and a first biasing member that biases the outer circumference of the first valve. [Explanation of Symbols]

[0198] 1,1A,1B... Shock absorber, 4... Cylinder, 21... Piston, 22... Upper chamber, 23... Lower chamber, 25... Piston rod, 41,42... First damping force generating mechanism, 72,92... First passage, 172,182... Second passage, 173,183... Second damping force generating mechanism, 106,106A,111,111A... Spring member (first biasing member), 107,110... Sub-bar Lube (first valve), 109...passage forming member, 185...lower chamber volume variable mechanism (volume variable mechanism), 186...upper chamber volume variable mechanism (volume variable mechanism), 331, 341...main body member, 332, 332A, 342, 342A...protruding member, 511, 512...third passage, 551, 552...retainer, 561, 562, 571, 572...laminated disc (second biasing member).

Claims

1. A cylinder in which the working fluid is sealed, A piston is slidably mounted within the cylinder, dividing the cylinder into two chambers, A piston rod connected to the piston and extending to the outside of the cylinder, A first passage through which working fluid flows from the upstream chamber to the downstream chamber due to the movement of the piston, A first damping force generating mechanism is provided in the first passage and generates a damping force, A second passage is provided separately from the first passage, A second damping force generating mechanism is provided in the second passage and opens at a piston speed lower than that of the first damping force generating mechanism to generate damping force, A third passage is provided separately from the second passage, A volume variable mechanism provided in the third passage, Equipped with, The second damping force generating mechanism includes a passage forming member in which the second passage is formed, A first valve is placed on the passage forming member and opens and closes the second passage, A first biasing member that biases the outer circumference of the first valve, It has, A second biasing member is provided that biases the first biasing member toward the first valve. buffer.

2. The shock absorber according to claim 1, wherein the first biasing member is integrally provided with a main body member that is placed on the first valve and a protruding member that is provided on the outer circumference of the main body member and protrudes toward the first valve.

3. The shock absorber according to claim 1, wherein a retainer is provided on the inner circumference between the first valve and the first biasing member.

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