Shock absorber

Abstract

This shock absorber comprises a first damping force generation mechanism that is provided in a first passage and adjusts the flow of a working fluid moving within the first passage, and a second damping force generation mechanism that is provided in a second passage and adjusts the flow of the working fluid moving within the second passage, the second damping force generation mechanism being provided with: a case member in which a portion of the second passage is formed; a valve member that is disposed within the case member and adjusts the flow of the working fluid within the second passage; and a partition member that is disposed at a position where the valve member and the flow of the working fluid are in series, partitions the second passage within the case member to form a variable-volume chamber capable of storing the working fluid, and is operated by the working fluid flowing due to the movement of a piston to enable the volume of the variable-volume chamber to vary.

Description

Shock absorber

[0001] The present invention relates to a shock absorber. The present application claims priority based on Japanese Patent Application No. 2025-049321 filed in Japan on March 25, 2025, the content of which is incorporated herein by reference.

[0002] Some shock absorbers are provided with a variable volume chamber, so that the damping force can be varied in response to the piston frequency, which is the frequency of axial movement of the piston (see, for example, Patent Document 1 below).

[0003] Japanese Unexamined Patent Publication No. 2023-4730

[0004] In shock absorbers, there is a demand for miniaturization of damping force generating mechanisms.

[0005] Accordingly, an object of the present invention is to provide a shock absorber that enables miniaturization of a damping force generating mechanism.

[0006] In order to achieve the above object, the present invention adopts the following aspects. The shock absorber according to the first aspect of the present invention comprises: a cylinder in which a working fluid is sealed; a piston movably provided in the cylinder and partitioning the inside of the cylinder into a first chamber and a second chamber; a piston rod connected to the piston and extending to the outside of the cylinder; a first damping force generating mechanism provided in a first passage through which the working fluid flows due to movement of the piston, and configured to adjust a flow of the working fluid moving in the first passage; a second damping force generating mechanism provided in a second passage arranged in parallel with the first passage through which the working fluid flows due to movement of the piston, and configured to adjust a flow of the working fluid moving in the second passage; and the second damping force generating mechanism comprises: a case member in which a part of the second passage is formed; a valve member arranged in the case member and configured to adjust a flow of the working fluid in the second passage; a partition member arranged at a position where the valve member and the flow of the working fluid are in series, partitioning the second passage in the case member to form a variable volume chamber capable of storing the working fluid, and operable by the working fluid flowing due to movement of the piston to change the volume of the variable volume chamber.

[0007] A second embodiment of the shock absorber according to the present invention comprises: a cylinder in which a working fluid is sealed; a piston movably provided within the cylinder and dividing the inside of the cylinder into a first chamber and a second chamber; a piston rod connected to the piston and extending outside the cylinder; a first damping force generating mechanism provided in a first passage through which the working fluid flows as a result of the movement of the piston, and for adjusting the flow of the working fluid moving within the first passage; a second damping force generating mechanism provided in a second passage arranged in parallel with the first passage through which the working fluid flows as a result of the movement of the piston, and for adjusting the flow of the working fluid moving within the second passage, wherein the second damping force generating mechanism comprises: a case member fixed to the piston rod and forming a part of the second passage; a first valve positioned in contact with one axial side of the case member and for adjusting the flow of the working fluid in the second passage; and a second valve positioned in contact with the other axial side of the case member and for adjusting the flow of the working fluid in the second passage. The device includes a variable valve provided between the case member and the second valve, which contacts the second valve to form a variable volume chamber between them, and which opens and closes according to the flow of the working fluid.

[0008] According to each of the above embodiments of the present invention, it is possible to provide a shock absorber that can miniaturize the damping force generation mechanism.

[0009] This figure shows a shock absorber according to one embodiment of the present invention, and is a longitudinal cross-sectional view taken in a section including the central axis CL of the shock absorber. This is a partial cross-sectional view showing the area around the piston of the shock absorber, and is a partially enlarged cross-sectional view of part A in Figure 1. This is a partial cross-sectional view of one side showing the area around the damping force generation mechanism on the extension side of the shock absorber, and is a partially enlarged cross-sectional view of part B in Figure 2. This is a hydraulic circuit diagram of the main part of the shock absorber according to one embodiment of the present invention.

[0010] An embodiment of the present invention will be described below with reference to the drawings. For the sake of convenience in the following description, the upper side in Figures 1 to 3 will be referred to as "top" and the lower side in Figures 1 to 3 will be referred to as "bottom". Also, the reference numeral CL in Figures 1 and 2 indicates the central axis of the buffer.

[0011] The shock absorber 1 of this embodiment is a so-called twin-cylinder type hydraulic shock absorber, as shown in Figure 1. The shock absorber 1 includes a cylinder 2 in which an oil liquid L and a gas G are sealed as working fluids. The cylinder 2 has a cylindrical inner cylinder 3 and a bottomed cylindrical outer cylinder 4. The outer cylinder 4 has a larger diameter than the inner cylinder 3 and is provided concentrically with the inner cylinder 3 so as to cover the inner cylinder 3 on its radially outer side. The space between the inner cylinder 3 and the outer cylinder 4 is a reservoir chamber 6. The cylinder 2 has the oil liquid L sealed inside the inner cylinder 3, and the oil liquid L and gas G sealed in the reservoir chamber 6.

[0012] The outer cylinder 4 has a cylindrical body portion 11 and a cylinder bottom portion 12 that closes the lower part of the body portion 11. An attachment eye 13 is fixed to the cylinder bottom portion 12 on the side opposite to the body portion 11.

[0013] The shock absorber 1 includes a piston 18 that is movably fitted inside the inner cylinder 3 of the cylinder 2. This piston 18 divides the inside of the inner cylinder 3 into two chambers: an upper chamber 19 (first chamber) and a lower chamber 20 (second chamber).

[0014] The shock absorber 1 includes a piston rod 21, one end of which is positioned inside the inner cylinder 3 of the cylinder 2 and connected to the piston 18, and the other end of which extends outside the cylinder 2. The piston 18 and the piston rod 21 move together as a single unit. In the extension stroke of the shock absorber 1, when the piston rod 21 increases the amount it protrudes from the cylinder 2, the piston 18 moves toward the upper chamber 19. In the contraction stroke of the shock absorber 1, when the piston rod 21 decreases the amount it protrudes from the cylinder 2, the piston 18 moves toward the lower chamber 20.

[0015] Rod guides 22 are fitted to the upper openings of the inner cylinder 3 and the outer cylinder 4. A sealing member 23 is fitted to the outer cylinder 4 on the upper side, which is outside the cylinder 2, relative to the rod guides 22. Both the rod guides 22 and the sealing member 23 are annular in shape. The piston rod 21 is slidably inserted inside the respective rod guides 22 and sealing member 23 and extends from the inside to the outside of the cylinder 2.

[0016] The rod guide 22 supports the piston rod 21 so that it can move axially while restricting its radial movement, and guides the movement of the piston rod 21. The sealing member 23 is in close contact with the outer cylinder 4 at its outer circumference and slides against the outer circumference of the axially moving piston rod 21 at its inner circumference, preventing the oil liquid L in the inner cylinder 3 and the high-pressure gas G and oil liquid L in the reservoir chamber 6 from leaking to the outside.

[0017] The rod guide 22 has a stepped outer circumference, with the upper part being larger in diameter than the lower part. The rod guide 22 fits into the inner circumference of the upper end of the inner cylinder 3 at its smaller diameter lower section, and into the inner circumference of the upper part of the outer cylinder 4 at its larger diameter upper section. A base valve 25 is installed on the cylinder bottom 12 of the outer cylinder 4, defining the lower chamber 20 and the reservoir chamber 6. The inner circumference of the lower end of the inner cylinder 3 is fitted into this base valve 25. The upper end of the outer cylinder 4 is crimped radially inward, and this crimped portion and the rod guide 22 sandwich the sealing member 23.

[0018] The piston rod 21 has a main shaft portion 27 and a mounting shaft portion 28 with a smaller diameter. The mounting shaft portion 28 is positioned inside the cylinder 2 and the piston 18 and the like are attached to it. The end of the main shaft portion 27 on the mounting shaft portion 28 side is a shaft step portion 29 that widens in a direction perpendicular to the axis. A groove 26 extending in the axial direction is formed on the outer circumference of the mounting shaft portion 28 at an intermediate position in the axial direction. The groove 26 forms an intermediate chamber 30 in the piston rod 21. A male thread 31 is formed on the outer circumference of the mounting shaft portion 28 on the side opposite to the main shaft portion 27 from the axial groove 26.

[0019] In the shock absorber 1, for example, the portion of the piston rod 21 protruding from the cylinder 2 is positioned at the top and supported by the vehicle body, while the mounting eye 13 on the cylinder 2 side is positioned at the bottom and connected to the wheel side. If the shock absorber is of the single-tube type, the opposite may be true: the cylinder 2 side may be supported by the vehicle body and the piston rod 21 may be connected to the wheel side. When the wheel vibrates as the vehicle moves, the relative positions of the cylinder 2 and the piston rod 21 change with the vibration, but this change is suppressed by the fluid resistance of the flow path formed in at least one of the piston 18 and the piston rod 21. As will be described in detail below, the fluid resistance of the flow path formed in at least one of the piston 18 and the piston rod 21 is designed to differ depending on the speed and amplitude of the vibration, and by suppressing the vibration, the ride comfort is improved. In addition to the vibration generated by the wheel, inertial force and centrifugal force generated in the vehicle body as the vehicle moves also act between the cylinder 2 and the piston rod 21. For example, when the direction of travel changes due to steering, centrifugal force is generated in the vehicle body, and a force based on this centrifugal force acts between the cylinder 2 and the piston rod 21. As will be explained below, the shock absorber 1 has good characteristics against vibrations caused by forces generated in the vehicle body as the vehicle moves, and high stability is obtained during vehicle operation.

[0020] As shown in Figure 2, the piston 18 is composed of a metal piston body 35 supported by the mounting shaft portion 28 of the piston rod 21, and an annular synthetic resin sliding member 36 integrally mounted on the outer circumferential surface of the piston body 35. The piston body 35 consists of two disc-shaped piston components 32 and piston components 33. The piston components 32 and 33 are connected by engaging portions 34 with interlocking grooves and protrusions formed on their mating surfaces, aligning their circumferential phases, and in this state the sliding member 36 is mounted on the outer circumferential side. As a result, the piston components 32, 33, and sliding member 36 are integrated to form the piston 18. The piston 18 slides inside the inner cylinder 3 while the sliding member 36 contacts the inner cylinder 3. In the piston 18, the piston component 32 is positioned on the upper chamber 19 side, and the piston component 33 is positioned on the lower chamber 20 side.

[0021] The piston body 35 is provided with a piston passage section 37 that connects the upper chamber 19 and the lower chamber 20, and a piston passage section 39 that connects the upper chamber 19 and the lower chamber 20 separately from the piston passage section 37. The piston passage section 37 is formed from a plurality of passage holes opening into the upper chamber 19 and an annular passage groove connecting the lower chamber 20 side of these passage holes. The piston passage section 39 is formed from a plurality of passage holes opening into the lower chamber 20 and an annular passage groove connecting the upper chamber 19 side of these passage holes. The passage holes of the piston passage section 37 and the passage holes of the piston passage section 39 are arranged alternately in the circumferential direction of the piston body 35. The piston passage section 37 opens radially outward on the upper chamber 19 side and radially inward on the lower chamber 20 side. The piston passage section 39 opens radially outward on the lower chamber 20 side and radially inward on the upper chamber 19 side.

[0022] A first damping force generating mechanism 40 is provided in the piston passage 37, which generates damping force by opening and closing the piston passage 37. The first damping force generating mechanism 40 is located on the lower chamber 20 side, which is one end of the piston 18 in the axial direction, and is attached to the piston rod 21. Because the first damping force generating mechanism 40 is located on the lower chamber 20 side, the piston passage 37 becomes a passage through which oil L flows from one upper chamber 19 to the other lower chamber 20 during the movement of the piston 18 toward the upper chamber 19 side, i.e., the extension stroke. The first damping force generating mechanism 40 provided in relation to the piston passage 37 is an extension-side damping force generating mechanism that generates damping force by suppressing the flow of oil L in the extension-side piston passage 37.

[0023] A first damping force generating mechanism 42 is provided in the piston passage 39, which generates damping force by opening and closing the piston passage 39. The first damping force generating mechanism 42 is located on the upper chamber 19 side, which is the other axial end of the piston 18, and is attached to the piston rod 21. Because the first damping force generating mechanism 42 is located on the upper chamber 19 side, the piston passage 39 becomes a passage through which oil liquid L flows from one lower chamber 20 to the other upper chamber 19 during the movement of the piston 18 toward the lower chamber 20 side, that is, during the compression stroke. The first damping force generating mechanism 42 provided in relation to the piston passage 39 is a compression-side damping force generating mechanism that generates damping force by suppressing the flow of oil liquid L in the compression-side piston passage 39.

[0024] In the shock absorber 1, the piston passage section 37 and the piston passage section 39 are connected so that the working fluid, oil L, flows between the upper chamber 19 and the lower chamber 20 as the piston 18 moves. The oil L passes through the piston passage section 37 when the piston rod 21 and piston 18 move in the extension direction (upper side in Figure 2). The oil L passes through the piston passage section 39 when the piston rod 21 and piston 18 move in the compression direction (lower side in Figure 2).

[0025] The piston body 35 has a roughly disc shape, and a fitting hole 44 is formed in the center of its radial direction, penetrating axially for fitting the mounting shaft portion 28 of the piston rod 21. The piston body 35 has a groove 45 formed on the end face of the piston component 33 on the piston component 32 side, which opens to the piston passage portion 37 and the fitting hole 44. The groove 45 is an orifice 46. The orifice 46 keeps the piston passage portion 37 in constant communication with the intermediate chamber 30 of the mounting shaft portion 28.

[0026] At the axial end of the piston body 35 on the lower chamber 20 side, an annular valve seat portion 47, which is part of the first damping force generating mechanism 40, is formed radially outward from the opening of the piston passage portion 37 on the lower chamber 20 side. Also, at the axial end of the piston body 35 on the upper chamber 19 side, an annular valve seat portion 49, which is part of the first damping force generating mechanism 42, is formed radially outward from the opening of the piston passage portion 39 on the upper chamber 19 side.

[0027] In the piston body 35, the opening on the lower chamber 20 side of the compression piston passage 39 is located on the opposite side of the fitting hole 44 of the valve seat portion 47. In the piston body 35, the opening on the upper chamber 19 side of the extension piston passage 37 is located on the opposite side of the fitting hole 44 of the valve seat portion 49.

[0028] On the upper chamber 19 side of the piston 18, in order from the axial piston 18 side, one retainer 51, multiple (specifically six) valve discs 52, one retainer 53, multiple (specifically two) retainers 54, and one washer 55 are stacked. The retainers 51, 53, 54, valve discs 52, and washers 55 are all made of metal and are perforated circular flat plates of a certain thickness that can accommodate the mounting shaft portion 28 of the piston rod 21 on the inside. The multiple valve discs 52 are provided to be flexible.

[0029] The retainer 51 has an outer diameter smaller than the inner diameter of the valve seat portion 49 of the piston 18.

[0030] The valve disc 52 closest to the piston 18 has a larger outer diameter than the valve seat portion 49 of the piston 18. This valve disc 52 closest to the piston 18 is in contact with the valve seat portion 49, and opens and closes the opening of the piston passage portion 39 formed in the piston 18 by separating from and contacting the valve seat portion 49. The outer diameter of each of the valve discs 52 is equal to or smaller than the outer diameter of the adjacent valve disc 52 on the piston 18 side.

[0031] The retainer 53 has an outer diameter smaller than the outer diameter of the valve disc 52 that is furthest away from the piston 18.

[0032] The multiple retainers 54 have the same outer diameter, and their outer diameter is larger than that of retainer 53.

[0033] The washer 55 has an outer diameter that is larger than the outer diameter of the retainer 53 and smaller than the outer diameter of the retainer 54. The washer 55 is thicker and more rigid than the multiple valve discs 52. The washer 55 has an outer diameter that is larger than the outer diameter of the shaft step portion 29 of the piston rod 21 and is in contact with the shaft step portion 29.

[0034] Multiple valve discs 52 constitute the piston main valve 58. The piston main valve 58 can seat in and out of the valve seat portion 49, and by seating away from the valve seat portion 49, it opens the piston passage portion 39 to the upper chamber 19. The piston main valve 58 generates a damping force by suppressing the flow of oil L from the lower chamber 20 to the upper chamber 19 caused by the sliding of the piston 18 toward the compression side, i.e., toward the lower chamber 20 side. The piston main valve 58 is provided on the upper chamber 19 side of the cylinder 2. The piston main valve 58 and the valve seat portion 49 constitute the compression side first damping force generating mechanism 42. The piston passage portion 39 and the passage between the piston main valve 58 and the valve seat portion 49 when the valve is open constitute the compression side first passage 60 through which the working fluid, oil L, flows from one lower chamber 20 to the other upper chamber 19 as the piston 18 moves toward the compression side. The first damping force generating mechanism 42 is provided in the first passage 60 and adjusts the flow of the oil liquid L moving within the first passage 60.

[0035] As shown in Figure 3, on the lower chamber 20 side of the piston 18, in order from the axial piston 18 side, one retainer 71, one valve disc 72, multiple (specifically two) valve discs 73, one pilot valve 74, one retainer 75, one retainer 76, multiple (specifically two) retainers 77, one communicating disc 78, one regulating member 79, multiple (specifically two) seat discs 81, one sub-valve 82 (valve member, first valve), one retainer 83, and one pilot case 84 (case member) are stacked.

[0036] Furthermore, on the side of the pilot case 84 opposite to the piston 18, the following are stacked in order from the axial pilot case 84 side: one retainer 91, one variable valve 92 (partition member), one retainer 93, one retainer 94, one retainer 95, one valve disc 96, one valve disc 97, multiple (specifically eight) valve discs 98, one retainer 99, one retainer 100, and one washer 101.

[0037] The retainers 71, 75-77, 83, 91, 93-95, 99, 100, valve discs 72, 73, 96, 97, 98, communication disc 78, regulating member 79, seat disc 81, sub-valve 82, pilot case 84, variable valve 92, and washer 101 are all made of metal. The retainers 71, 75-77, 83, 91, 93-95, 99, 100, valve discs 72, 73, 96, 97, 98, communication disc 78, and washer 101 are all perforated flat plates of a certain thickness that can accommodate the mounting shaft portion 28 of the piston rod 21 on the inside. The sub-valve 82 is a perforated flat plate of a certain thickness that can accommodate the mounting shaft portion 28 of the piston rod 21 on the inside. The valve discs 72, 73, 96, 97, 98 and the sub-valve 82 are provided to be flexible. The pilot valve 74, regulating member 79, pilot case 84 and variable valve 92 all have annular shapes on the inside, into which the mounting shaft portion 28 of the piston rod 21 can be fitted.

[0038] The components from washer 55 to washer 101 shown in Figure 2, including the pilot case 84, are installed with the mounting shaft portion 28 of the piston rod 21 inserted through the inside. A nut 105 is screwed onto a male thread 31 provided on the portion of the mounting shaft portion 28 that protrudes from washer 101 and tightened. As a result, the components from washer 55 to washer 101, with the exception of the sub-valve 82, are clamped at least on their inner circumference by the shaft step portion 29 of the piston rod 21 and the nut 105, and are fixed to the piston rod 21.

[0039] As shown in Figure 3, the retainer 71 has an outer diameter smaller than the inner diameter of the valve seat portion 47 of the piston 18. The valve disc 72 has an outer diameter equivalent to the outer diameter of the valve seat portion 47 of the piston 18. The valve disc 72 is in contact with the valve seat portion 47 and opens and closes the opening of the piston passage portion 37 formed in the piston 18 by separating from and contacting the valve seat portion 47. The valve disc 72 has a notch 131 formed on the outer peripheral edge of the radial outer circumference, which penetrates axially, extends radially, and exits radially outward. Multiple notches 131 are formed on the valve disc 72 at equal intervals in the circumferential direction of the valve disc 72. The passages within these notches 131 serve as fixed orifices 132 that connect the piston passage portion 37 to the lower chamber 20 even when the valve disc 72 is in contact with the valve seat portion 47. Multiple valve discs 73 have the same outer diameter and are equivalent to the outer diameter of the valve disc 72.

[0040] The pilot valve 74 consists of a metal disc 135 and a rubber sealing member 136 fixed to the outer circumference of the disc 135. The disc 135 is a perforated circular flat plate of a certain thickness, into which the mounting shaft portion 28 of the piston rod 21 can be fitted, and is flexible. The outer diameter of the disc 135 is larger than the outer diameter of the valve disc 73. The sealing member 136 is fixed to the outer circumference of the side of the disc 135 opposite to the piston 18, and is an annular shape coaxial with the disc 135.

[0041] The valve discs 72, 73 and the pilot valve 74 constitute the piston main valve 138. The piston main valve 138 can seat and disseat from the valve seat portion 47, and by disseat from the valve seat portion 47, it opens the piston passage portion 37 to the lower chamber 20. The piston main valve 138 generates a damping force by suppressing the flow of oil L from the upper chamber 19 to the lower chamber 20 caused by the sliding of the piston 18 toward the extension side, i.e., toward the upper chamber 19 side. The piston main valve 138 is provided on the lower chamber 20 side of the cylinder 2. The piston main valve 138 and the valve seat portion 47 constitute the extension side first damping force generating mechanism 40. The piston passage portion 37 and the passage between the piston main valve 138 and the valve seat portion 47 when the valve is open constitute the extension side first passage 140 through which the working fluid, oil L, flows from one upper chamber 19 to the other lower chamber 20 as the piston 18 moves toward the extension side. The first damping force generating mechanism 40 is provided in the first passage 140 and adjusts the flow of the oil liquid L moving within the first passage 140.

[0042] The outer diameter of retainer 75 is smaller than the inner diameter of the sealing member 136 of the pilot valve 74. The outer diameter of retainer 76 is larger than the outer diameter of retainer 75, but smaller than the inner diameter of the sealing member 136 of the pilot valve 74. Retainer 76 is thicker and more rigid than the disc 135 of the pilot valve 74. Multiple retainers 77 have the same outer diameter as each other, but are smaller than the outer diameter of retainer 76 and larger than the outer diameter of retainer 75.

[0043] The communication disc 78 has an outer diameter larger than that of the retainer 77. The communication disc 78 has a notch 141 that extends radially outward from the inner peripheral edge that fits onto the mounting shaft portion 28 of the piston rod 21, and extends beyond the retainer 77. Multiple notches 141 are formed on the communication disc 78 at equal intervals in the circumferential direction of the communication disc 78. The passages within these notches 141 form a communication orifice 142 that is in constant communication with the intermediate chamber 30 of the piston rod 21.

[0044] The regulating member 79 includes a perforated disc-shaped main body portion 145 (outer peripheral valve portion regulating portion), and a protruding portion 146 protruding from an inner peripheral side of the main body portion 145 to one side in the axial direction of the main body portion 145. The outer diameter of the protruding portion 146 is equal to the outer diameter of the retainer 77. The outer diameter of the main body portion 145 is larger than the outer diameter of the communication disc 78. The regulating member 79 abuts against the communication disc 78 at the protruding portion 146. The plurality of sheet discs 81 have the same outer diameter, which is smaller than the outer diameter of the main body portion 145 of the regulating member 79 and larger than the outer diameter of the protruding portion 146 of the regulating member 79. The outer diameter of the retainer 83 is smaller than the outer diameter of the sheet disc 81.

[0045] The pilot case 84 is integrally formed without seams. The pilot case 84 includes a perforated disc-shaped bottom portion 151, an annular valve seat portion 152 protruding from an outer peripheral side of the bottom portion 151 to one side along the axial direction of the bottom portion 151, and a cylindrical outer cylindrical portion 153 protruding further than the valve seat portion 152 to the same side as the valve seat portion 152 along the axial direction of the bottom portion 151 from an outer peripheral edge portion radially outward of the valve seat portion 152 of the bottom portion 151. The outer cylindrical portion 153 is open on the side opposite to the bottom portion 151 in the axial direction. The pilot case 84 further includes an annular inner seat portion 155 protruding from an inner peripheral side of the bottom portion 151 to the side opposite to the outer cylindrical portion 153 along the axial direction of the bottom portion 151, and an annular valve seat portion 156 protruding further than the inner seat portion 155 to the same side as the inner seat portion 155 along the axial direction of the bottom portion 151 from an outer peripheral edge portion radially outward of the inner seat portion 155 of the bottom portion 151. The bottom portion 151, the valve seat portion 152, the outer cylindrical portion 153, the inner seat portion 155, and the valve seat portion 156 are formed coaxially.

[0046] In the pilot case 84, the outer cylindrical portion 153 is oriented to project from the bottom portion 151 toward the piston 18 side, and abuts against the retainer 83 at the bottom portion 151. The outer cylindrical portion 153 has the seal member 136 of the pilot valve 74 fitted to the inner side thereof. The seal member 136 moves in the axial direction while maintaining a close contact state with the inner peripheral surface of the outer cylindrical portion 153 in accordance with the deflection of the disk 135 of the pilot valve 74. The outer cylindrical portion 153 of the pilot case 84 and the seal member 136 of the pilot valve 74 cover the retainers 75 to 77, 83, the communication disk 78, the regulating member 79, the seat disk 81, and the sub-valve 82 on the radially outer side.

[0047] In the bottom portion 151 of the pilot case 84, an axially penetrating passage hole 161 is formed between the valve seat portions 152, 156, the outer cylindrical portion 153, and the inner seat portion 155. A plurality of the passage holes 161 are formed in the bottom portion 151 at equal intervals in the circumferential direction thereof. The pilot case 84 has, between two circumferentially adjacent passage holes 161 and passage hole 161 in the bottom portion 151, a projecting portion 162 (inner valve portion regulating portion) that projects from the bottom portion 151 toward the valve seat portion 152 side along the axial direction of the bottom portion 151 and projects lower than the valve seat portion 152. The pilot case 84 has a plurality of the projecting portions 162 spaced apart in the circumferential direction of the bottom portion 151. A plurality of the projecting portions 162 are respectively disposed at all positions between two circumferentially adjacent passage holes 161 and passage hole 161 in the bottom portion 151. On the inner periphery of the pilot case 84, a fitting hole 163 for fitting the mounting shaft portion 28 of the piston rod 21 is formed so as to axially penetrate the bottom portion 151 and the inner seat portion 155.

[0048] In the pilot case 84, the side of the bottom portion 151 opposite to the inner seat portion 155 in the axial direction abuts against the retainer 83. At this time, in the bottom portion 151, a radially inner portion of the bottom portion 151 relative to the plurality of passage holes 161 and the plurality of projecting portions 162 abuts against the retainer 83.

[0049] The sub-valve 82 has an outer diameter smaller than the inner diameter of the outer cylindrical portion 153 of the pilot case 84, and a larger diameter than the outer diameter of the valve seat portion 152 of the pilot case 84. The sub-valve 82 has an inner diameter smaller than the outer diameter of the seat disc 81, and a larger diameter than the outer diameter of the retainer 83. The outer annular outer valve portion 166 of the sub-valve 82 abuts against the valve seat portion 152 of the pilot case 84, and the inner annular inner valve portion 167 abuts against the seat disc 81. Before assembly, the sub-valve 82 is flat, and when assembled and in contact with the valve seat portion 152 and the seat disc 81, it elastically deforms into a substantially tapered shape in the axial direction so that the outer valve portion 166 is positioned closer to the piston 18 than the inner valve portion 167. As a result, the sub-valve 82 presses against the valve seat portion 152 and the seat disc 81. The main body 145 of the regulating member 79 described above is thicker and more rigid than the sub-valve 82.

[0050] The portion enclosed by the outer cylindrical portion 153 and valve seat portion 152 of the pilot case 84, the pilot valve 74, retainers 75-77, the communicating disc 78, the regulating member 79, the seat disc 81, and the sub-valve 82 forms the back pressure chamber 170. The back pressure chamber 170 communicates with the upper chamber 19 via the communicating orifice 142 of the communicating disc 78, the intermediate chamber 30 of the piston rod 21, and the orifice 46 and piston passage portion 37 of the piston 18 shown in Figure 2. The back pressure chamber 170 shown in Figure 3 applies the pressure from the upper chamber 19, introduced via the communicating orifice 142, to the pilot valve 74, i.e., the piston main valve 138, in the direction of the piston 18, i.e., in the valve closing direction.

[0051] The retainer 91 has an outer diameter smaller than the outer diameter of the inner seat portion 155 of the pilot case 84. The variable valve 92 has a disc spring shape and has a radially inner base portion 175 and a radially outer tapered plate portion 176. The base portion 175 is a perforated flat plate of a certain thickness that can accommodate the mounting shaft portion 28 of the piston rod 21 on its inner side. The tapered plate portion 176 widens radially outward from the outer peripheral edge of the base portion 175 and has a tapered cylindrical shape that moves further axially away from the base portion 175 the radially outward. The variable valve 92 has an outer diameter of the base portion 175 that is larger than the outer diameter of the retainer 91, and an outer diameter of the tapered plate portion 176 that is smaller than the inner diameter of the valve seat portion 156 of the pilot case 84. In the axial direction, the variable valve 92 is oriented such that the tapered plate portion 176 is positioned opposite to the bottom portion 151 of the pilot case 84 relative to the base portion 175.

[0052] The outer diameter of retainer 93 is smaller than the outer diameter of the base portion 175 of the variable valve 92 and is the same as the outer diameter of retainer 91. The outer diameter of retainer 94 is larger than the outer diameter of retainer 93 and smaller than the outer diameter of the base portion 175 of the variable valve 92.

[0053] The retainer 95 has an outer diameter that is larger than the outer diameter of the retainer 94, larger than the outer diameter of the base portion 175 of the variable valve 92, and smaller than the outer diameter of the tapered plate portion 176 of the variable valve 92. The retainer 95 has a notch 181 formed on the outer peripheral edge of its radial circumference, which penetrates in the thickness direction, extends radially, and exits radially outward. Multiple notches 181 are formed on the retainer 95 at equal intervals in the circumferential direction of the retainer 95. The inner end position of the notch 181 in the radial direction of the retainer 95 coincides with the outer end position in the radial direction of the retainer 94. The retainer 95 has at least three notches 181 formed therein. The variable valve 92 is provided spaced apart from the retainers 93 to 95 such that the tapered plate portion 176 on the outer circumference covers the outer circumference of the retainers 93 to 95, with the outer diameter increasing as it moves away from the base portion 175.

[0054] The valve disc 96 has an outer diameter equivalent to the outer diameter of the valve seat portion 156 of the pilot case 84. The valve disc 96 is able to be separated from and in contact with the valve seat portion 156. The valve disc 96 has a passage hole 185 that penetrates it in the axial direction. The passage hole 185 is in the shape of an arc extending in the circumferential direction of the valve disc 96. The passage hole 185 is located outside the outer peripheral edge of the retainer 95 and inside the outer peripheral edge of the tapered plate portion 176 of the variable valve 92. The portion of the valve disc 96 that is radially outside the passage hole 185 comes into contact with the outer peripheral edge of the tapered plate portion 176 of the variable valve 92 over its entire circumference. At that time, the variable valve 92 presses against the valve disc 96 over its entire circumference because the tapered plate portion 176 undergoes elastic deformation.

[0055] The portion enclosed by the sub-valve 82, the valve seat portion 152 and bottom portion 151 of the pilot case 84, the seat disc 81, and the retainer 83, the portion enclosed by the valve seat portion 156, bottom portion 151, and inner seat portion 155 of the pilot case 84, the retainer 91, the variable valve 92, and the valve disc 96, and the passages within the multiple passage holes 161 of the pilot case 84 constitute the variable volume chamber 191. Furthermore, the portion enclosed by the variable valve 92, the retainers 93 to 95, and the valve disc 96 also constitutes the variable volume chamber 192.

[0056] When the pressure in the back pressure chamber 170 of the sub-valve 82 becomes higher than the pressure in the variable volume chamber 191, the inner circumferential valve portion 167 of the sub-valve 82 separates from the seat disc 81, allowing the oil L from the back pressure chamber 170 to flow into the variable volume chamber 191. The inner circumferential valve portion 167 of the sub-valve 82 and the seat disc 81 constitute a sub-valve mechanism 201 that controls the communication and blocking of the back pressure chamber 170 and the variable volume chamber 191 by opening and closing. The sub-valve mechanism 201 generates a damping force when it opens to allow the oil L from the back pressure chamber 170 to flow into the variable volume chamber 191. Multiple protrusions 162 of the pilot case 84 limit the amount of opening by contacting the portion of the sub-valve 82 on the inner circumferential valve portion 167 side when the sub-valve mechanism 201 is opened. Furthermore, the multiple protrusions 162 suppress contact between the inner circumferential valve portion 167 side of the sub-valve 82 and the bottom 151 when the sub-valve mechanism 201 is opened, thereby preventing the inner circumferential valve portion 167 side of the sub-valve 82 from sticking to the bottom 151.

[0057] When the pressure on the volume variable chamber 191 side of the sub-valve 82 becomes higher than the pressure in the back pressure chamber 170, the outer peripheral valve portion 166 of the sub-valve 82 separates from the valve seat portion 152 of the pilot case 84, allowing the oil L from the volume variable chamber 191 to flow into the back pressure chamber 170. The outer peripheral valve portion 166 and the valve seat portion 152 of the sub-valve 82 open and close to form a sub-valve mechanism 202 that controls the communication and blocking of the volume variable chamber 191 and the back pressure chamber 170. The sub-valve mechanism 202 generates a damping force when it opens to allow the oil L from the volume variable chamber 191 side to flow into the back pressure chamber 170. The main body portion 145 of the regulating member 79 abuts against the portion of the sub-valve 82 on the outer peripheral valve portion 166 side when the sub-valve mechanism 202 opens, thereby suppressing further deformation of the sub-valve 82 and limiting the amount of opening. The sub-valve 82 is annular in shape and has an outer circumferential valve portion 166 that allows one flow of the oil liquid L and an inner circumferential valve portion 167 that allows the other flow of the oil liquid L.

[0058] The volume of the variable volume chambers 191 and 192 changes when the variable valve 92 deforms. When the pressure in the variable volume chamber 191 becomes higher than the pressure in the variable volume chamber 192, the variable valve 92 elastically deforms to move closer to the valve disc 96, increasing the volume of the variable volume chamber 191 while decreasing the volume of the variable volume chamber 192. When the pressure in the variable volume chamber 192 becomes higher than the pressure in the variable volume chamber 191, the variable valve 92 elastically deforms to move away from the valve disc 96, increasing the volume of the variable volume chamber 192 while decreasing the volume of the variable volume chamber 191. The pilot case 84, sub-valve 82, seat disc 81, retainer 83, retainer 91, variable valve 92, retainers 93-95 and valve disc 96, which form the variable volume chambers 191 and 192, together constitute a variable damping force mechanism 193 that varies the damping force according to the piston frequency, which is the frequency of the axial movement of the piston 18.

[0059] Here, when the pressure in the variable volume chamber 191 becomes higher than the pressure in the variable volume chamber 192 by a predetermined value or more, the variable valve 92 undergoes a large elastic deformation to approach the valve disc 96 and comes into contact with the outer peripheral edge of the retainer 95 at the tapered plate portion 176. As a result, the variable volume chamber 192 is divided into a first variable volume chamber 194 located radially inward from the portion of the variable valve 92 that contacts the retainer 95, and a second variable volume chamber 195 located radially outward from the portion of the variable valve 92 that contacts the retainer 95. In this state, the first variable volume chamber 194 and the second variable volume chamber 195 are in communication through a passage in the notch 181 formed on the outer peripheral edge of the retainer 95.

[0060] The valve disc 97 has an outer diameter equal to that of the valve disc 96. The valve disc 97 has a notch 197 formed on its radially outward side that penetrates axially and exits radially outward. The passage within the notch 197 is in constant communication with the passage within the passage hole 185 of the valve disc 96. The passage within the notch 197 and the passage within the passage hole 185 of the valve disc 96 connect the variable volume chamber 192 and the lower chamber 20.

[0061] When the pressure in the variable-volume chamber 192 becomes higher than the pressure in the variable-volume chamber 191 by a predetermined value or more, the variable valve 92 elastically deforms so as to move away from the valve disc 96, and the outer peripheral edge of the tapered plate portion 176 separates from the valve disc 96. Then, the variable-volume chamber 192 communicates with the variable-volume chamber 191, and the oil liquid L flows from the variable-volume chamber 192 to the variable-volume chamber 191. The outer peripheral edge of the tapered plate portion 176 of the variable valve 92 and the valve disc 96 open and close to form a valve mechanism 205 that controls the communication and blockage between the variable-volume chamber 192 and the variable-volume chamber 191. The valve mechanism 205 allows the flow of oil liquid L from the variable-volume chamber 192 to the variable-volume chamber 191 and generates a damping force when it opens to allow the oil liquid L to flow from the variable-volume chamber 192 to the variable-volume chamber 191.

[0062] The back pressure chamber 170 in the pilot case 84, due to the pressure from the upper chamber 19 introduced through the communicating orifice 142, opens the sub-valve mechanism 201, deforming the variable valve 92 in such a way that it increases the volume of the variable volume chamber 191 and decreases the volume of the variable volume chamber 192.

[0063] The valve disc 98 closest to the pilot case 84 has an outer diameter equivalent to that of valve disc 97. The outer diameter of each valve disc 98 is equivalent to or smaller than that of an adjacent valve disc 98 on the pilot case 84 side.

[0064] The outer diameter of the retainer 99 is smaller than that of the valve disc 98 that is furthest away from the pilot case 84. The outer diameter of the retainer 100 is larger than that of the retainer 99.

[0065] The washer 101 has an outer diameter that is larger than the outer diameter of the retainer 99 and smaller than the outer diameter of the retainer 100. The washer 101 is thicker and more rigid than the multiple valve discs 96-98.

[0066] Multiple valve discs 96 to 98 constitute a hard valve 211 (partition member, second valve). The hard valve 211 is repositionable on and off the valve seat portion 156, and by repositioning from the valve seat portion 156, it connects the variable volume chamber 191 to the lower chamber 20. The hard valve 211 generates a damping force by allowing and suppressing the flow of oil liquid L from the upper chamber 19, which is created by the sliding of the piston 18 toward the extension side, i.e., toward the upper chamber 19, to the lower chamber 20 via the piston passage portion 37 and orifice 46 of the piston 18, the intermediate chamber 30 of the piston rod 21, the communication orifice 142 of the communication disc 78, the back pressure chamber 170, the passage between the inner circumferential valve portion 167 of the sub-valve 82 and the seat disc 81, which is created when the sub-valve mechanism 201 is opened, and the variable volume chamber 191 when the valve is opened. The hard valve 211 is provided on the lower chamber 20 side of the cylinder 2. The hard valve 211 and the valve seat portion 156 of the pilot case 84 constitute the extension-side hard valve mechanism 212. The hard valve 211 is positioned to be in contact with the valve seat portion 156 of the pilot case 84 and opens away from the valve seat portion 156. A sub-valve 82 is provided on one axial side of the pilot case 84, and the hard valve 211 is provided on the other axial side of the pilot case 84. A variable valve 92 and retainers 93-95 are provided between the pilot case 84 and the hard valve 211.

[0067] The piston passage 37 and orifice 46 of the piston 18, the intermediate chamber 30 of the piston rod 21, the communication orifice 142 of the communication disk 78, the back pressure chamber 170, the passage between the inner circumferential valve portion 167 of the sub-valve 82 and the seat disk 81 that is created when the sub-valve mechanism 201 opens, the variable volume chamber 191, and the passage between the hard valve 211 and the valve seat portion 156 that is created when the hard valve mechanism 212 opens, all constitute the extension-side second passage 215 through which the working fluid, oil liquid L, flows from one upper chamber 19 to the other lower chamber 20 as the piston 18 moves toward the extension side. The hard valve 211 operates to allow one-way flow of oil liquid L from the upper chamber 19 to the lower chamber 20 through the second passage 215. The variable volume chamber 192, the passage in the passage hole 185 of the valve disk 96, and the passage in the notch 197 of the valve disk 97 also constitute the second passage 215. The second passage 215 runs parallel to the first passage 140, which is also on the extension side, except for a portion on the upper chamber 19 side of the orifice 46 of the piston passage 37, and connects the upper chamber 19 and the lower chamber 20. The sub-valve mechanism 201 restricts the flow of oil L from the upper chamber 19 to the lower chamber 20 through the second passage 215 when the piston 18 starts to move in the extension stroke.

[0068] The second passage 215 is provided with an orifice 46, a communication orifice 142, a back pressure chamber 170, a sub-valve mechanism 201, a damping force variable mechanism 193, and a hard valve mechanism 212. The sub-valve mechanism 201, the damping force variable mechanism 193, and the hard valve mechanism 212 are positioned in the second passage 215 so that the flow of the oil liquid L is in series, and constitute a second damping force generating mechanism 216 that adjusts the flow of the oil liquid L moving within the second passage 215.

[0069] The passage in the notch 197 of the valve disc 97, the passage in the passage hole 185 of the valve disc 96, the variable volume chamber 192, the passage between the variable valve 92 and the valve disc 96 that is created when the valve mechanism 205 is opened, the variable volume chamber 191, the passage between the outer peripheral valve portion 166 and the valve seat portion 152 of the sub-valve 82 that is created when the sub-valve mechanism 202 is opened, the back pressure chamber 170, the communication orifice 142 of the communication disc 78, the intermediate chamber 30 of the piston rod 21, and the orifice 46 and piston passage portion 37 of the piston 18 constitute the second passage 220 on the compression side, through which the working fluid, oil liquid L, flows from one lower chamber 20 to the other upper chamber 19 as the piston 18 moves toward the compression side. The second passage 220 is parallel to the first passage 60 on the compression side and connects the lower chamber 20 and the upper chamber 19. The second passage 220 is provided with a damping force variable mechanism 193, a sub-valve mechanism 202, a back pressure chamber 170, a communication orifice 142, and an orifice 46. The second damping force generating mechanism 216 is configured such that the damping force variable mechanism 193 and the sub-valve mechanism 202 are positioned in the second passage 220 so that the flow of the oil liquid L is in series, thereby adjusting the flow of the oil liquid L in the second passage 220.

[0070] The second damping force generating mechanism 216 includes a main body portion 145 of a restricting member 79 that restricts the amount of opening when the outer peripheral valve portion 166 of the sub-valve 82 of the sub-valve mechanism 202 opens, and a protruding portion 162 of a pilot case 84 that restricts the amount of opening when the inner peripheral valve portion 167 opens. The sub-valve mechanism 202 restricts the flow of oil liquid L from the lower chamber 20 to the upper chamber 19 via the second passage 220 when the piston 18 starts moving in the compression stroke.

[0071] As described above, the shock absorber 1 includes a first damping force generating mechanism 40 provided in the first passage 140 to adjust the flow of oil liquid L moving within the first passage 140, a first damping force generating mechanism 42 provided in the first passage 60 to adjust the flow of oil liquid L moving within the first passage 60, and a second damping force generating mechanism 216 provided in the second passages 215 and 220 arranged in parallel with the first passages 140 and 60 to adjust the flow of oil liquid L moving within the second passages 215 and 220. The second damping force generating mechanism 216 includes a pilot case 84 in which a part of the second passages 215 and 220 is formed, a sub-valve 82 arranged inside the pilot case 84 to adjust the flow of oil liquid L in the second passages 215 and 220, and a variable valve 92 positioned in a location where the sub-valve 82 and the flow of oil liquid L are in series. The variable valve 92 partitions the second passages 215 and 220 in the pilot case 84 to form variable-volume chambers 191 and 192 capable of storing oil liquid L. The variable valve 92 is also operated by the oil liquid L flowing due to the movement of the piston 18, and the volume of the variable-volume chambers 191 and 192 can be varied. The sub-valve 82 is annular and has an inner circumferential valve portion 167 that allows one flow of oil liquid L from the upper chamber 19 to the lower chamber 20 via the second passage 215, and an outer circumferential valve portion 166 that allows the other flow of oil liquid L from the lower chamber 20 to the upper chamber 19 via the second passage 220. The second damping force generating mechanism 216 is provided with a main body portion 145 of a regulating member 79 that regulates the amount of opening when the outer circumferential valve portion 166 of the sub-valve 82 is open, and a protruding portion 162 of the pilot case 84 that regulates the amount of opening when the inner circumferential valve portion 167 of the sub-valve 82 is open. The second damping force generating mechanism 216 includes a hard valve 211 that is positioned to contact the pilot case 84 and operates to allow one flow of oil L from the upper chamber 19 to the lower chamber 20 via the second passage 215, and a variable valve 92 positioned inside the pilot case 84 and operating to allow the other flow of oil L from the lower chamber 20 to the upper chamber 19 via the second passage 220, and which contacts the hard valve 211 to form a variable volume chamber 192 between itself and the hard valve 211. The hard valve 211 operates to move away from the pilot case 84 and open in the flow of oil L from the upper chamber 19 to the lower chamber 20 via the second passage 215.The variable valve 92 operates to separate from the hard valve 211 and open in the other flow of the oil liquid L from the lower chamber 20 to the upper chamber 19 via the second passage 220.

[0072] The second damping force generating mechanism 216 includes a pilot case 84 fixed to the piston rod 21 and forming part of the second passages 215 and 220; a sub-valve 82 positioned in contact with one axial side of the pilot case 84 and adjusting the flow of oil L in the second passages 215 and 220; a hard valve 211 positioned in contact with the other axial side of the pilot case 84 and adjusting the flow of oil L in the second passages 215 and 220; and a variable valve 92 provided between the pilot case 84 and the hard valve 211, which contacts the hard valve 211 to form a variable volume chamber 192 between itself and the hard valve 211. The variable valve 92 opens and closes in accordance with the flow of oil L.

[0073] The shock absorber 1 includes a first damping force generating mechanism 40 provided in the first passage 140 to adjust the flow of oil liquid L moving within the first passage 140, a first damping force generating mechanism 42 provided in the first passage 60 to adjust the flow of oil liquid L moving within the first passage 60, and a second damping force generating mechanism 216 provided in the second passages 215 and 220 to adjust the flow of oil liquid L moving within the second passages 215 and 220. The second damping force generating mechanism 216 includes a hard valve 211 that operates to allow one flow of oil liquid L from the upper chamber 19 to the lower chamber 20 via the second passage 215, and a variable valve 92 that operates to allow the other flow of oil liquid L from the lower chamber 20 to the upper chamber 19 via the second passage 220. The variable valve 92 contacts the hard valve 211 to form a variable volume chamber 192 between them, and operates so that the volume of the variable volume chamber 192 changes as it deforms due to the flow of the oil liquid L. Retainers 93 to 95 are provided between the hard valve 211 and the variable valve 92. Note that it is sufficient to provide at least one retainer between the hard valve 211 and the variable valve 92. Of the retainers 93 to 95, retainer 95 has a radially extending notch 181 on its radially outer circumference. The variable valve 92 deforms due to the flow of oil liquid L from the upper chamber 19 to the lower chamber 20 via the second passage 215, and by contacting the retainer 95, divides the variable volume chamber 192 into a first variable volume chamber 194 and a second variable volume chamber 195. The notch 181 in the retainer 95 is provided to allow communication between the first volume variable chamber 194 and the second volume variable chamber 195. The variable valve 92 has a disc spring shape in which the tapered plate portion 176 on the outer circumference is inclined toward the hard valve 211 so as to cover the outer circumference of the retainers 93 to 95.

[0074] The shock absorber 1 includes a first damping force generating mechanism 40 provided in the first passage 140 to adjust the flow of oil liquid L moving within the first passage 140, a first damping force generating mechanism 42 provided in the first passage 60 to adjust the flow of oil liquid L moving within the first passage 60, and a second damping force generating mechanism 216 provided in the second passages 215 and 220 to adjust the flow of oil liquid L moving within the second passages 215 and 220. The second damping force generating mechanism 216 includes a pilot case 84 fixed to the piston rod 21, a hard valve 211 provided so as to be in contact with the pilot case 84 and which separates from the pilot case 84 and opens with one flow of oil liquid L from the upper chamber 19 to the lower chamber 20 via the second passage 215, and a variable valve 92 provided between the pilot case 84 and the hard valve 211 and which forms a variable volume chamber 192 between itself and the hard valve 211 by contacting the hard valve 211. The variable valve 92 opens when the other flow of oil liquid L from the lower chamber 20 to the upper chamber 19 via the second passage 220.

[0075] The configuration described above is shown in the hydraulic circuit diagram in Figure 4. As shown in Figure 4, a first passage 140 is provided connecting the upper chamber 19 and the lower chamber 20. A first damping force generating mechanism 40 is provided in the first passage 140, and a fixed orifice 132 is provided in parallel with the first damping force generating mechanism 40. Also, second passages 215 and 220 are provided in parallel with the first passage 140, connecting the upper chamber 19 and the lower chamber 20. Common to the second passages 215 and 220, in order from the upper chamber 19 side, are an orifice 46, an intermediate chamber 30, a communication orifice 142, and a back pressure chamber 170. The back pressure chamber 170 controls the opening of the valve of the first damping force generating mechanism 40 with its pressure. On the side of the back pressure chamber 170 opposite the communication orifice 142, the second passage 215 and the second passage 220 are separated, with a sub-valve mechanism 201 provided in the second passage 215 and a sub-valve mechanism 202 provided in the second passage 220. On the lower chamber 20 side of the sub-valve mechanisms 201 and 202, a volume variable chamber 191 of the damping force variable mechanism 193 is provided, common to the second passages 215 and 220. The second passage 215 has a flow path that connects the volume variable chamber 192 of the damping force variable mechanism 193 to the lower chamber 20, and a flow path that connects the volume variable chamber 191 to the lower chamber 20 via a hard valve mechanism 212. The second passage 220 has a flow path that connects the volume variable chamber 192 to the lower chamber 20, which is common to the second passage 215, and has a flow path that allows oil liquid L to flow from the lower chamber 20 to the volume variable chamber 191 via a valve mechanism 205. Furthermore, a first passage 60 is provided connecting the lower chamber 20 and the upper chamber 19, and a first damping force generating mechanism 42 is provided in the first passage 60.

[0076] As shown in Figure 1, the base valve 25 described above is provided between the cylinder bottom 12 of the outer cylinder 4 and the inner cylinder 3. This base valve 25 has a base valve member 301 that separates the lower chamber 20 and the reservoir chamber 6, a disc 302 provided on the lower side of the base valve member 301, i.e., the reservoir chamber 6 side, a disc 303 provided on the upper side of the base valve member 301, i.e., the lower chamber 20 side, and mounting pins 304 for attaching the discs 302 and 303 to the base valve member 301.

[0077] The base valve member 301 has an annular shape through which a mounting pin 304 is inserted in the radial center. The base valve member 301 has a plurality of passage holes 305 for circulating oil L between the lower chamber 20 and the reservoir chamber 6, and a plurality of passage holes 306 for circulating oil L between the lower chamber 20 and the reservoir chamber 6, located radially outside these passage holes 305. The disk 302 on the reservoir chamber 6 side allows the flow of oil L from the lower chamber 20 to the reservoir chamber 6 through the passage holes 305, while suppressing the flow of oil L from the reservoir chamber 6 to the lower chamber 20 through the passage holes 305. The disk 303 allows the flow of oil L from the reservoir chamber 6 to the lower chamber 20 through the passage holes 306, while suppressing the flow of oil L from the lower chamber 20 to the reservoir chamber 6 through the passage holes 306.

[0078] Disc 302, together with the base valve member 301, constitutes a compression-side damping valve 307 that opens during the compression stroke of the shock absorber 1 to allow oil L to flow from the lower chamber 20 to the reservoir chamber 6 and generate damping force. Disc 303, together with the base valve member 301, constitutes a suction valve 308 that opens during the extension stroke of the shock absorber 1 to allow oil L to flow from the reservoir chamber 6 into the lower chamber 20. The suction valve 308 primarily functions to compensate for the lack of fluid caused by the extension of the piston rod 21 from the cylinder 2 by allowing fluid to flow from the reservoir chamber 6 to the lower chamber 20 without substantially generating damping force.

[0079] Next, the operation of the piston 18 and other components attached to the piston rod 21 of the shock absorber 1 will be explained.

[0080] First, let's assume that there is no variable damping force mechanism 193. In the extension stroke, when the piston rod 21 moves in the extension direction, in the very low speed range where the piston speed, which is the axial movement speed of the piston 18, is between 0 and less than the first speed v1 (greater than 0), the oil L from the upper chamber 19 flows from the piston passage 37 to the lower chamber 20 via the fixed orifice 132. Therefore, a damping force with orifice characteristics (where the damping force is approximately proportional to the square of the piston speed) is generated. As a result, the damping force characteristics with respect to piston speed in the very low speed range of the extension stroke are relatively hard, with a high rate of increase in damping force as the piston speed increases.

[0081] When the piston speed increases to a low speed range that is above the first speed v1 but below the second speed v2 (which is faster than the first speed v1), the oil L from the upper chamber 19 flows from the piston passage 37 to the lower chamber 20 through the first passage 140, which includes the gap between the piston main valve 138 and the valve seat portion 47 of the piston 18, while opening the piston main valve 138 of the first damping force generating mechanism 40. As a result, a damping force with valve characteristics (where the damping force is approximately proportional to the piston speed) is generated. Consequently, the damping force characteristics with respect to piston speed in the low speed range of the extension stroke become softer, as the rate of increase in damping force with increasing piston speed is lower than in the very low speed range of the extension stroke.

[0082] When the piston speed is in the medium speed range, which is above the second speed v2 but below the third speed v3 (faster than the second speed v2), the oil L from the upper chamber 19 flows to the lower chamber 20 via the first passage 140, which includes the gap between the separated piston main valve 138 and valve seat portion 47 of the first damping force generating mechanism 40. In addition, it flows to the back pressure chamber 170 via the piston passage portion 37 and orifice 46 of the piston 18, the intermediate chamber 30 of the piston rod 21, and the communication orifice 142 of the communication disc 78. This opens the sub-valve mechanism 201, allowing the oil to flow through the passage between the seat disc 81 and the inner circumferential valve portion 167 of the sub-valve 82, and opens the hard valve mechanism 212, allowing the oil to flow through the passage between the hard valve 211 and the valve seat portion 156 of the pilot case 84 to the lower chamber 20. Therefore, the damping force characteristics with respect to piston speed in the mid-speed range of the extension stroke are such that the rate of increase in damping force with respect to piston speed is lower than in the low-speed range of the extension stroke, resulting in an even softer characteristic.

[0083] When the piston speed reaches a high speed range of the third speed v3 or higher, the relationship between the force (hydraulic pressure) acting on the pilot valve 74 is such that the opening force applied from the piston passage 37 becomes greater than the closing force applied from the back pressure chamber 170. Therefore, in this high-speed range, as the piston speed increases, the piston main valve 138 of the first damping force generating mechanism 40 opens further away from the valve seat portion 47 of the piston 18 than in the low-speed and medium-speed ranges. Consequently, in addition to the flow of oil L from the upper chamber 19 to the lower chamber 20 through the second passage 215, which includes the piston passage 37, orifice 46, intermediate chamber 30, communicating orifice 142, back pressure chamber 170, open sub-valve mechanism 201, and open hard valve mechanism 212, more oil L flows to the lower chamber 20 through the first passage 140, which includes the passage between the pilot valve 74 and the valve seat portion 47 of the piston 18. Therefore, the damping force characteristics with respect to piston speed in the high-speed range of the extension stroke are such that the rate of increase in damping force with respect to piston speed is lower than in the mid-speed range of the extension stroke, resulting in an even softer characteristic.

[0084] During the compression stroke, when the piston rod 21 moves in the compression direction, in the very low speed range where the axial movement speed of the piston 18 is between 0 and a fourth speed v4 greater than 0, the oil L from the lower chamber 20 flows from the fixed orifice 132 through the piston passage 37 to the upper chamber 19, generating a damping force with orifice characteristics. For this reason, the damping force characteristics with respect to piston speed in the very low speed range of the compression stroke are relatively hard, with a high rate of increase in damping force as the piston speed increases.

[0085] As the piston speed increases to the low, medium, and high speed range of the fourth speed v4 or higher, the oil L introduced from the lower chamber 20 into the passage section 39 of the compression piston passage basically flows through the space between the piston main valve 58 and the valve seat section 49 to the upper chamber 19 while opening the piston main valve 58 of the first damping force generating mechanism 42, thereby generating a damping force according to the valve characteristics. As a result, the damping force characteristics with respect to piston speed in the low, medium, and high speed range of the compression stroke are softer, with the rate of increase in damping force decreasing with increasing piston speed compared to the very low speed range of the compression stroke.

[0086] The above describes the operation assuming the variable damping force mechanism 193 is absent. However, in this embodiment, the variable damping force mechanism 193 varies the damping force according to the piston frequency, even when the piston speed is the same.

[0087] During the extension stroke, the pressure in the upper chamber 19 increases, causing the oil L in the upper chamber 19 to flow into the back pressure chamber 170 through the piston passage 37 and orifice 46 of the piston 18 shown in Figure 2, the intermediate chamber 30 of the piston rod 21, and the communication orifice 142 of the communication disc 78 shown in Figure 3. This opens the sub-valve mechanism 201, and the oil L flows through the passage between the inner circumferential valve portion 167 of the sub-valve 82 and the seat disc 81, and is introduced into the volume variable chamber 191 of the damping force variable mechanism 193. As a result, the variable valve 92 of the damping force variable mechanism 193 elastically deforms in a direction toward the hard valve 211 due to the oil L introduced into the volume variable chamber 191, expanding the volume of the volume variable chamber 191 while decreasing the volume of the volume variable chamber 192. At that time, the oil liquid L in the variable volume chamber 192 is discharged to the lower chamber 20 through the passage in the passage hole 185 of the valve disc 96 and the passage in the notch 197 of the valve disc 97.

[0088] During the extension stroke at high piston frequencies, the amplitude of the piston 18 is small, and the amount of oil L introduced from the upper chamber 19 to the variable volume chamber 191 is small. Therefore, with each extension stroke, the variable valve 92 deforms as described above, introducing oil L from the upper chamber 19 to the variable volume chamber 191. As a result, the flow rate of oil L flowing from the upper chamber 19 to the lower chamber 20 via the first passage 140 while opening the first damping force generating mechanism 40 is reduced. In addition, by introducing oil L from the upper chamber 19 to the variable volume chamber 191, the pressure rise in the back pressure chamber 170 is suppressed compared to when there is no variable volume chamber 191, making it easier for the first damping force generating mechanism 40 to open. These factors result in a softer damping force on the extension side. At this time, the hard valve mechanism 212 does not open.

[0089] On the other hand, when the piston frequency is low, the amplitude of the piston 18 is large, and the amount of oil L introduced from the upper chamber 19 to the variable volume chamber 191 is also large. For this reason, in the initial stage of the extension stroke, oil L flows from the upper chamber 19 to the variable volume chamber 191, as described above, but thereafter the variable valve 92 comes into contact with the retainers 94 and 95 and stops, and oil L stops flowing from the upper chamber 19 to the variable volume chamber 191. As oil L stops flowing from the upper chamber 19 to the variable volume chamber 191, the pressure in the variable volume chamber 191 rises, and the pressure in the back pressure chamber 170 between the variable volume chamber 191 and the upper chamber 19 also rises, creating a state that suppresses the opening of the piston main valve 138 of the first damping force generating mechanism 40. In other words, the first damping force generating mechanism 40 makes it difficult for the piston main valve 138 to open, and the oil liquid L flows mainly from the upper chamber 19 to the lower chamber 20 via the fixed orifice 132, resulting in a harder damping force on the extension side.

[0090] As the pressure in the back pressure chamber 170 rises further, the oil liquid L opens the hard valve mechanism 212 and flows into the lower chamber 20 through the second passage 215, which includes the gap between the hard valve 211 and the valve seat portion 156. As the pressure in the back pressure chamber 170 rises further, in addition to flowing through the second passage 215, the oil liquid L opens the piston main valve 138 of the first damping force generating mechanism 40 and flows into the lower chamber 20 from the first passage 140.

[0091] As a result, the rebound damping force at low piston frequencies is higher than the rebound damping force at high piston frequencies, resulting in a harder characteristic.

[0092] Here, in the compression stroke, the damping force variable mechanism 193 increases the pressure in the lower chamber 20, causing the pressure in the volume variable chamber 192 to be higher than the pressure in the volume variable chamber 191. As a result, the valve mechanism 205 opens, and the oil L from the lower chamber 20 is introduced into the volume variable chamber 191 via the passage in the notch 197 of the valve disc 97, the passage in the passage hole 185 of the valve disc 96, the volume variable chamber 192, and the passage between the tapered plate portion 176 of the variable valve 92 and the hard valve 211. Furthermore, the sub-valve mechanism 202 opens, and the oil flows through the passage between the outer peripheral valve portion 166 and the valve seat portion 152 of the sub-valve 82, and flows into the upper chamber 19 via the back pressure chamber 170, the communication orifice 142 of the communication disc 78, the intermediate chamber 30 of the piston rod 21, and the orifice 46 and piston passage portion 37 of the piston 18.

[0093] Patent Document 1, mentioned above, discloses a shock absorber in which the damping force is variable in response to the piston frequency by having a variable-volume chamber. However, there is a demand for miniaturizing the damping force generation mechanism in shock absorbers. For example, the shock absorber disclosed in Patent Document 1 has a configuration in which the component forming the variable-volume chamber is press-fitted into the case member, which results in a large damping force generation mechanism.

[0094] The shock absorber 1 of this embodiment includes a second damping force generating mechanism 216 comprising: a pilot case 84 in which a portion of the second passages 215 and 220 are formed; a sub-valve 82 disposed within the pilot case 84 to adjust the flow of oil liquid L in the second passages 215 and 220; and a variable valve 92 positioned in a location where the sub-valve 82 and the flow of oil liquid L are in series, forming variable volume chambers 191 and 192 that partition the second passages 215 and 220 within the pilot case 84 and can store oil liquid L. The variable valve 92 is operated by the oil liquid L flowing due to the movement of the piston 18, and can change the volume of the variable volume chambers 191 and 192. In this way, the shock absorber 1 has a second damping force generating mechanism 216 that includes a sub-valve 82 and a variable valve 92 within the pilot case 84, making it possible to miniaturize the second damping force generating mechanism 216. Furthermore, since the shock absorber 1 has a sub-valve 82 positioned in series with the flow of oil liquid L to the variable valve 92 that partitions the second passages 215 and 220 to form variable volume chambers 191 and 192 capable of storing oil liquid L, the flow of oil liquid L at the start of piston 18 movement can be restricted by the sub-valve 82. Thus, the shock absorber 1 can improve ride comfort by reducing the transmission of unpleasant high-frequency vibrations to the vehicle body with the variable valve 92, while the sub-valve 82 can suppress the sluggishness at the start of vehicle roll and pitch movements, as well as the decrease in initial steering responsiveness. In this way, the shock absorber 1 can generate damping force more effectively.

[0095] Furthermore, the shock absorber 1 has an annular sub-valve 82 which has an inner circumferential valve portion 167 that allows one flow of oil liquid L from the upper chamber 19 to the lower chamber 20 via the second passage 215, and an outer circumferential valve portion 166 that allows the other flow of oil liquid L from the lower chamber 20 to the upper chamber 19 via the second passage 220. As a result, the shock absorber 1 has a sub-valve 82 that allows bidirectional flow, and a single sub-valve 82 can constitute both the extension and compression check valves. Therefore, the shock absorber 1 can shorten its axial length compared to a configuration in which the extension and compression sides are controlled by separate discs, and the second damping force generating mechanism 216 can be further miniaturized.

[0096] Furthermore, the shock absorber 1 is provided with a second damping force generating mechanism 216 that includes a main body 145 of a restricting member 79 that restricts the amount of opening when the outer peripheral valve portion 166 of the sub-valve 82 opens, and a protruding portion 162 of a pilot case 84 that restricts the amount of opening when the inner peripheral valve portion 167 of the sub-valve 82 opens. As a result, the shock absorber 1 can suppress excessive deformation of the sub-valve 82 and improve the durability of the sub-valve 82.

[0097] Furthermore, the shock absorber 1 includes a second damping force generating mechanism 216 which comprises a hard valve 211 positioned to contact the pilot case 84 and operating to allow one flow of oil L from the upper chamber 19 to the lower chamber 20 via the second passage 215, and a variable valve 92 positioned inside the pilot case 84 and operating to allow the other flow of oil L from the lower chamber 20 to the upper chamber 19 via the second passage 220. The variable valve 92 contacts the hard valve 211, thereby forming a variable volume chamber 192 between them. In this way, the shock absorber 1 forms a variable volume chamber 192 with the hard valve 211 that contacts the pilot case 84 and the variable valve 92 positioned inside the pilot case 84 and contacting the hard valve 211, making it possible to miniaturize the second damping force generating mechanism 216.

[0098] Furthermore, the buffer 1 is configured such that the hard valve 211 opens to separate from the pilot case 84 during one flow of oil liquid L from the upper chamber 19 to the lower chamber 20 via the second passage 215, and the variable valve 92 opens to separate from the hard valve 211 during the other flow of oil liquid L from the lower chamber 20 to the upper chamber 19 via the second passage 220. This allows for one flow from the upper chamber 19 to the lower chamber 20 and the other flow from the lower chamber 20 to the upper chamber 19.

[0099] Furthermore, the shock absorber 1 includes a pilot case 84 in which a second damping force generating mechanism 216 is fixed to the piston rod 21 and a part of the second passages 215 and 220 is formed; a sub-valve 82 positioned in contact with one axial side of the pilot case 84 to adjust the flow of oil liquid L in the second passages 215 and 220; a hard valve 211 positioned in contact with the other axial side of the pilot case 84 to adjust the flow of oil liquid L in the second passages 215 and 220; and a variable valve 92 provided between the pilot case 84 and the hard valve 211, which contacts the hard valve 211 to form a variable volume chamber 192 between itself and the hard valve 211. The variable valve 92 opens and closes in accordance with the flow of oil liquid L. As described above, the shock absorber 1 has a second damping force generating mechanism 216 that has a sub-valve 82 on one side of the pilot case 84, a hard valve 211 on the other side of the pilot case 84, and a variable valve 92 between the pilot case 84 and the hard valve 211, making it possible to miniaturize the second damping force generating mechanism 216. Furthermore, the shock absorber 1 is equipped with a sub-valve 82 that adjusts the flow of oil L in the second passages 215 and 220, and a variable valve 92 that contacts the hard valve 211 to form a variable volume chamber 192 between itself and the hard valve 211. Therefore, the flow of oil L at the start of piston 18 movement can be restricted by the sub-valve 82. Thus, the shock absorber 1 can improve ride comfort by reducing the transmission of unpleasant high-frequency vibrations to the vehicle body with the variable valve 92, while the sub-valve 82 can suppress the sluggishness at the start of vehicle roll and pitch movements and the decrease in initial steering responsiveness. In this way, the shock absorber 1 can generate damping force more effectively.

[0100] Furthermore, the shock absorber 1 includes a second damping force generating mechanism 216 which includes a hard valve 211 that operates to allow one flow of oil liquid L from the upper chamber 19 to the lower chamber 20 via the second passage 215, and a variable valve 92 that operates to allow the other flow of oil liquid L from the lower chamber 20 to the upper chamber 19 via the second passage 220. The variable valve 92 contacts the hard valve 211 to form a variable volume chamber 192 between them, and operates so that the volume of the variable volume chamber 192 changes as it deforms due to the flow of oil liquid L. In this way, the shock absorber 1 forms the variable volume chamber 192 by contacting the hard valve 211 with the variable valve 92, making it possible to miniaturize the second damping force generating mechanism 216.

[0101] Furthermore, the shock absorber 1 has retainers 93 to 95 between the hard valve 211 and the variable valve 92. The retainers 94 and 95 come into contact with the variable valve 92 when the variable valve 92 bends and deforms toward the hard valve 211, and function as stoppers to suppress the deformation of the variable valve 92. As a result, the shock absorber 1 can suppress excessive stress on the variable valve 92 and improve the durability of the variable valve 92. In addition, because the shock absorber 1 has retainers 93 to 95 between the hard valve 211 and the variable valve 92, the volume of the variable volume chamber 192 can be sufficiently secured. As a result, the shock absorber 1 can reduce the damping force generated in response to high-frequency vibration input to the wheels (e.g., 3 Hz or higher) that occupants find uncomfortable, and expand the variable range. Therefore, the reduction of the transmission of high-frequency vibrations to the wheels that occupants find uncomfortable can be further enhanced, and a further improvement in ride comfort can be achieved.

[0102] Furthermore, in the shock absorber 1, retainer 95, one of the retainers 93 to 95, has a radially extending notch 181 on its radially outer circumference. This prevents the shock absorber 1 from becoming tightly sealed even when the variable valve 92 bends and deforms toward the hard valve 211 and comes into contact with the radially outer circumference of the retainer 95. Thus, the area surrounded by the variable valve 92, retainer 95, and hard valve 211 is sealed, preventing the variable valve 92 from becoming hydraulically locked. Consequently, the shock absorber 1 can improve durability and suppress waveform defects in the damping force waveform.

[0103] Furthermore, in the shock absorber 1, the variable valve 92 deforms due to the one-way flow of oil L from the upper chamber 19 to the lower chamber 20 via the second passage 215, and comes into contact with the retainer 95, thereby dividing the volume variable chamber 192 into a first volume variable chamber 194 and a second volume variable chamber 195. Even in this state, the notch 181 in the retainer 95 allows the first volume variable chamber 194 and the second volume variable chamber 195 to communicate. As a result, the shock absorber 1 can prevent the variable valve 92 from becoming tightly sealed even when it comes into contact with the radial outer circumference of the retainer 95 when it bends and deforms toward the hard valve 211. Therefore, the portion surrounded by the variable valve 92, the retainer 95, and the hard valve 211 is sealed, preventing the variable valve 92 from becoming hydraulically locked. Consequently, the shock absorber 1 can improve durability and suppress waveform defects in the damping force waveform.

[0104] Furthermore, the shock absorber 1 has a disc spring shape in which the variable valve 92 has a tapered plate portion 176 on its outer circumference that is inclined toward the hard valve 211 side so as to cover the outer circumference of the retainers 93 to 95. Because the variable valve 92 of the shock absorber 1 is formed in a disc spring shape in this way, a volume variable chamber 192 can be formed with a simple configuration and a frequency-sensitive function can be exhibited.

[0105] Furthermore, the shock absorber 1 includes a second damping force generating mechanism 216 comprising: a pilot case 84 fixed to the piston rod 21; a hard valve 211 provided so as to be in contact with the pilot case 84 and opening when one flow of oil L from the upper chamber 19 to the lower chamber 20 via the second passage 215 separates it from the pilot case 84; and a variable valve 92 provided between the pilot case 84 and the hard valve 211, forming a variable volume chamber 192 between itself and the hard valve 211 by contacting it. The variable valve 92 opens when the other flow of oil L from the lower chamber 20 to the upper chamber 19 via the second passage 220. In this way, the shock absorber 1 forms the variable volume chamber 192 by bringing the variable valve 92 into contact with the hard valve 211, making it possible to miniaturize the second damping force generating mechanism 216. Furthermore, since the shock absorber 1 has a variable valve 92 that forms a variable volume chamber 192 between itself and the hard valve 211, and this variable valve 92 is provided between the pilot case 84 and the hard valve 211, the second damping force generating mechanism 216 can be made even smaller.

[0106] According to the above-described aspect of the present invention, it is possible to provide a shock absorber that can miniaturize the damping force generation mechanism.

[0107] 1... Shock absorber 2... Cylinder 18... Piston 19... Upper chamber (first chamber) 20... Lower chamber (second chamber) 21... Piston rod 40, 42... First damping force generating mechanism 60, 140... First passage 82... Sub-valve (valve member, first valve) 84... Pilot case (case member) 92... Variable valve (compartment member) 145... Main body (outer circumference valve regulating part) 162... Protrusion (inner circumference valve regulating part) 166... ​​Outer circumference valve part 167... Inner circumference valve part 191, 192... Volume variable chamber 211... Hard valve (compartment member, second valve) 215, 220... Second passage 216... Second damping force generating mechanism 194... First volume variable chamber 195... Second volume variable chamber L... Oil (working fluid).

Claims

1. A shock absorber comprising: a cylinder in which a working fluid is sealed; a piston movably provided within the cylinder and dividing the inside of the cylinder into a first chamber and a second chamber; a piston rod connected to the piston and extending to the outside of the cylinder; a first damping force generating mechanism provided in a first passage through which the working fluid flows as the piston moves and for adjusting the flow of the working fluid moving within the first passage; a second damping force generating mechanism provided in a second passage arranged in parallel with the first passage through which the working fluid flows as the piston moves and for adjusting the flow of the working fluid moving within the second passage, wherein the second damping force generating mechanism comprises: a case member in which a part of the second passage is formed; a valve member disposed within the case member and for adjusting the flow of the working fluid in the second passage; and a partitioning member positioned in a series with the valve member and the flow of the working fluid, partitioning the second passage within the case member to form a variable-volume chamber capable of storing the working fluid, and operating in accordance with the working fluid flowing as the piston moves to vary the volume of the variable-volume chamber.

2. The buffer according to claim 1, wherein the valve member is an annular first valve and comprises an inner circumferential valve portion that allows one flow of the working fluid and an outer circumferential valve portion that allows the other flow of the working fluid.

3. The shock absorber according to claim 2, wherein the second damping force generating mechanism is provided with an outer circumferential valve portion restricting the amount of valve opening when the first valve is opened and an inner circumferential valve portion restricting the amount of valve opening.

4. The buffer according to any one of claims 1 to 3, wherein the partition member comprises a second valve disposed so as to be in contact with the case member and operating to allow one flow of the working fluid, and a variable valve disposed within the case member and operating to allow the other flow of the working fluid, and in contact with the second valve to form the variable volume chamber between itself and the second valve.

5. The buffer according to claim 4, wherein the second valve operates to open in one flow of the working fluid by moving away from the case member, and the variable valve operates to open in the other flow of the working fluid by moving away from the second valve.

6. A cylinder in which a working fluid is sealed; a piston movably provided within the cylinder and dividing the inside of the cylinder into a first chamber and a second chamber; a piston rod connected to the piston and extending to the outside of the cylinder; a first damping force generating mechanism provided in a first passage through which the working fluid flows as the piston moves and for adjusting the flow of the working fluid moving within the first passage; a second damping force generating mechanism provided in a second passage arranged in parallel with the first passage through which the working fluid flows as the piston moves and for adjusting the flow of the working fluid moving within the second passage; wherein the second damping force generating mechanism comprises: a case member fixed to the piston rod and forming a part of the second passage; a first valve positioned in contact with one axial side of the case member and for adjusting the flow of the working fluid in the second passage; and a second valve positioned in contact with the other axial side of the case member and for adjusting the flow of the working fluid in the second passage. A buffer comprising: a variable valve provided between the case member and the second valve, which contacts the second valve to form a variable volume chamber between itself and the second valve, and which opens and closes according to the flow of the working fluid.

Images