Shock absorber

Abstract

This shock absorber comprises: a cylinder; a divided member; a shaft-like member; a first flow path through which flows a fluid that has flowed out from one chamber among a first chamber and a second chamber; a second flow path, at least part of which is provided parallel to the first flow path; a first valve member which is provided to the first flow path and via which fluid in said one chamber can flow into the other chamber; a partition wall member which has a wall part and a bottom part, through which the shaft-like member passes, which is connected to the second flow path, and which forms a backpressure chamber that generates a force in the valve closing direction in the first valve member; a volume variation member which is disposed opposite from the bottom part and which, when deformed by the pressure of the fluid, can change the volume of the backpressure chamber; a seal member which forms a seal between said other chamber and the wall part; and a support member which directly or indirectly applies a biasing force to the first valve member and the volume variation member in the direction of separation.

Description

buffer

[0001] This application claims priority from Japanese Patent Application No. 2023-129402, filed on August 8, 2023, the contents of which are incorporated herein by reference.

[0002] Some shock absorbers have a variable damping force that is sensitive to frequency (see, for example, Patent Document 1).

[0003] Japanese Patent Application Publication No. 2021-55850

[0004] There is a demand for cost reduction in shock absorbers.

[0005] Therefore, an object of the present invention is to provide a shock absorber that can reduce costs.

[0006] a partition member having a wall portion and a bottom portion, the partition member being penetrated by the shaft-shaped member and connected to the second flow path to form a back pressure chamber that generates a force in a valve-closing direction on the first valve member; a volume variable member being disposed opposite the bottom portion and deformed by the pressure of the fluid to vary the volume of the back pressure chamber; a seal member being provided to seal between the other chamber and the wall portion; and a support member being provided to directly or indirectly apply a biasing force in a direction separating the first valve member and the volume variable member.

[0007] According to the above-described aspect, it is possible to provide a shock absorber that can reduce costs.

[0008] 2. FIG. 1 is a view showing a shock absorber according to a first embodiment of the present invention, and is a cross-sectional view taken along a line including a central axis line CL thereof. FIG. 2 is a view showing a configuration provided on a piston rod of the shock absorber according to the first embodiment, and is a partially enlarged cross-sectional view showing part A of FIG. 1. FIG. 3 is a view showing a main part of the shock absorber according to the first embodiment, and is a partially enlarged cross-sectional view showing part B of FIG. 2. FIG. 4 is a view showing a main part of a modified example of the shock absorber according to the first embodiment, and is a partially enlarged cross-sectional view showing a part corresponding to part B of FIG. 2. FIG. 5 is a view showing a main part of a modified example of the shock absorber according to the first embodiment, and is a partially enlarged cross-sectional view showing a part corresponding to part B of FIG. 2. FIG. 6 is a view showing a main part of a modified example of the shock absorber according to the first embodiment, and is a partially enlarged cross-sectional view showing a part corresponding to part B of FIG. 2. FIG. 7 is a view showing a main part of a modified example of the shock absorber according to the first embodiment, and is a partially enlarged cross-sectional view showing a part corresponding to part B of FIG. 2. FIG. 8 is a view showing a main part of a modified example of the shock absorber according to the first embodiment, and is a partially enlarged cross-sectional view showing a part corresponding to part B of FIG. 2. 16 is a view showing a main part of a shock absorber according to a third embodiment of the present invention, and is a partially enlarged sectional view showing a portion corresponding to portion B in FIG. 2 . FIG. 17 is a view showing a main part of a shock absorber according to a fourth embodiment of the present invention, and is a partially enlarged sectional view showing a portion corresponding to portion B in FIG. 2 . FIG. 18 is a view showing a configuration provided on a piston rod of a shock absorber according to a fifth embodiment of the present invention, and is a partially enlarged sectional view showing a portion corresponding to portion A in FIG. 1 . FIG. 19 is a view showing a main part of the shock absorber according to the fifth embodiment of the present invention, and is a partially enlarged sectional view showing portion C in FIG. 12 . FIG. 19 is a view showing a main part of a shock absorber according to a sixth embodiment of the present invention, and is a partially enlarged sectional view showing a portion corresponding to portion B in FIG. 2 . FIG. 20 is a view showing a main part of a shock absorber according to a seventh embodiment of the present invention, and is a partially enlarged sectional view showing a portion corresponding to portion B in FIG. 2 . FIG. 21 is a view showing a configuration provided on a piston rod of a shock absorber according to an eighth embodiment of the present invention, and is a partially enlarged sectional view showing a portion corresponding to FIG. 2 . FIG. 22 is a view showing a main part of the shock absorber according to the eighth embodiment of the present invention, and is a partially enlarged sectional view showing portion D in FIG. 16 . FIG. 23 is a hydraulic circuit diagram of a configuration provided on a piston rod of the shock absorber according to the eighth embodiment.

[0009] [First embodiment] A first embodiment of a shock absorber according to the present invention will be described with reference to Figures 1 to 8. For ease of explanation, the upper side of the drawings will be referred to as "top" and the lower side of the drawings will be referred to as "bottom." In addition, in the drawings, the central axis of the shock absorber may be indicated by the symbol CL. The same applies to the other embodiments.

[0010] As shown in Figure 1, the shock absorber 1 of the first embodiment is a so-called twin-cylinder hydraulic shock absorber, and includes a cylindrical cylinder 2 filled with oil L, which is a fluid. The cylinder 2 includes a cylindrical inner cylinder 3, a cylindrical outer cylinder 4 with a bottom that is larger in diameter than the inner cylinder 3 and is disposed concentrically with the inner cylinder 3 so as to cover the inner cylinder 3, and a cover 5 that is disposed to cover the upper opening side of the outer cylinder 4. A reservoir chamber 6 is formed between the inner cylinder 3 and the outer cylinder 4. As described above, the shock absorber 1 of the first embodiment is a twin-cylinder type, but the scope of the present invention is not limited to this and is applicable to other types such as a single-cylinder type and a triple-cylinder type.

[0011] The outer cylinder 4 is made up of a cylindrical body member 11 and a bottom member 12 that closes the lower part of the body member 11. The bottom member 12 is fitted onto the lower side of the body member 11 and welded to the body member 11 around its entire circumference. In this way, the bottom member 12 is fixed to the lower side of the body member 11. A mounting eye 13 is fixed to the outer side of the bottom member 12, opposite the body member 11.

[0012] The cover 5 has a cylindrical portion 15 and an inner flange portion 16 extending radially inward from the upper end side of the cylindrical portion 15. The cover 5 is placed on the body member 11 so that the upper end opening of the body member 11 is covered with the inner flange portion 16 and the outer peripheral surface of the body member 11 is covered with the cylindrical portion 15. In this state, a portion of the cylindrical portion 15 is crimped radially inward to be fixed to the body member 11.

[0013] The shock absorber 1 includes a piston 18 (dividing member). The piston 18 is slidably fitted within the inner tube 3 of the cylinder 2. The piston 18 divides the interior of the inner tube 3 of the cylinder 2 into a first chamber 19 (one chamber) and a second chamber 20 (the other chamber). Oil L as a fluid is sealed within the first chamber 19 and the second chamber 20 of the inner tube 3, and oil L and gas G as fluids are sealed within a reservoir chamber 6 between the inner tube 3 and the outer tube 4. There is no particular limitation on the fluid used.

[0014] The shock absorber 1 includes a piston rod 21 (shaft-shaped member). One end of the piston rod 21 is disposed within the inner tube 3 of the cylinder 2 and is inserted through the piston 18, while the other end extends to the outside of the cylinder 2. The piston 18 and the piston rod 21 move together. During the extension stroke, in which the piston rod 21 increases its protrusion from the cylinder 2, the piston 18 moves toward the first chamber 19. During the compression stroke, in which the piston rod 21 decreases its protrusion from the cylinder 2, the piston 18 moves toward the second chamber 20.

[0015] Rod guides 22 are fitted to the upper end openings of the inner cylinder 3 and the outer cylinder 4, and a seal member 23 is attached to the outer cylinder 4 above the rod guide 22, closer to the exterior of the cylinder 2. A friction member 24 is provided between the rod guide 22 and the seal member 23. The rod guide 22, the seal member 23, and the friction member 24 are all annular, and the piston rod 21 is slidably inserted through the rod guide 22, the friction member 24, and the seal member 23, respectively, and extends from the interior of the cylinder 2 to the exterior.

[0016] The rod guide 22 supports the piston rod 21 so as to be movable in the axial direction while restricting its radial movement, thereby guiding the movement of the piston rod 21. The seal member 23 has its outer periphery in close contact with the outer cylinder 4 and its inner periphery in sliding contact with the outer periphery of the piston rod 21 moving in the axial direction, preventing leakage of the oil L in the inner cylinder 3 and the gas G and oil L in the reservoir chamber 6 in the outer cylinder 4 to the outside. The friction member 24 has its inner periphery in sliding contact with the outer periphery of the piston rod 21, generating frictional resistance in the piston rod 21.

[0017] The rod guide 22 has a stepped outer periphery with a larger diameter at the top than at the bottom, with the smaller-diameter lower part fitting into the inner periphery of the upper end of the inner cylinder 3 and the larger-diameter upper part fitting into the inner periphery of the upper part of the outer cylinder 4. A base valve 25 that separates the second chamber 20 and the reservoir chamber 6 is installed on the bottom member 12 of the outer cylinder 4, and the inner periphery of the lower end of the inner cylinder 3 is fitted into this base valve 25. A portion (not shown) of the upper end of the outer cylinder 4 is crimped radially inward, and this crimped portion and the rod guide 22 hold the seal member 23 in place.

[0018] The piston rod 21 has a main shaft portion 27 and a mounting shaft portion 28 having an outer diameter smaller than that of the main shaft portion 27. The mounting shaft portion 28 is disposed within the cylinder 2, and the piston 18 and other components are attached to the mounting shaft portion 28. The end face of the main shaft portion 27 on the mounting shaft portion 28 side in the axial direction of the piston rod 21 widens in a direction perpendicular to the axis. A passage groove 30 extending in the axial direction is formed in the outer periphery of the mounting shaft portion 28 at a central position in the axial direction, and a male thread 31 is formed at the tip position on the opposite side of the axial direction from the main shaft portion 27. A plurality of passage grooves 30 are formed at intervals around the circumferential direction of the mounting shaft portion 28, and are formed so that the cross section of the piston rod 21 taken on a plane perpendicular to the central axis is rectangular, square, or D-shaped. The passage groove 30 may be formed by making the interior of the piston rod 21 hollow.

[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, and the mounting eye 13 on the cylinder 2 side is positioned at the bottom and connected to the wheel. Alternatively, the cylinder 2 may be supported by the vehicle body and the piston rod 21 may be connected to the wheel. When the wheel vibrates as the vehicle moves, the relative positions of the cylinder 2 and the piston rod 21 change with the vibration. However, this change is suppressed by the fluid resistance of the flow passages formed in at least one of the piston 18 and the piston rod 21. As described in detail below, the fluid resistance of the flow passages formed in at least one of the piston 18 and the piston rod 21 is designed to vary depending on the speed and amplitude of the vibration. By suppressing the vibration, ride comfort is improved. In addition to vibrations generated by the wheels, inertial forces and centrifugal forces generated on the vehicle body as the vehicle moves act between the cylinder 2 and the piston rod 21. For example, centrifugal forces are generated on the vehicle body when the direction of travel is changed by steering, and a force based on this centrifugal force acts between the cylinder 2 and the piston rod 21. As will be described below, the shock absorber 1 has good characteristics against vibrations caused by forces generated in the vehicle body as the vehicle travels, and high stability can be obtained when the vehicle travels.

[0020] As shown in FIG. 2, the piston 18 is composed of a metal piston body 33 supported by the piston rod 21, and an annular sliding member 34 integrally attached to the outer circumferential surface of the piston body 33 and sliding within the inner cylinder 3.

[0021] The piston body 33 is formed with a plurality of passage holes 35 (only one is shown in FIG. 2 because it is a cross-section) and an annular passage groove 36 that connects the ends of these passage holes 35 opposite the first chamber 19. The piston body 33 is also formed with a plurality of passage holes 37 (only one is shown in FIG. 2 because it is a cross-section) and an annular passage groove 38 that connects the ends of these passage holes 37 on the first chamber 19 side. The plurality of passage holes 35 are formed in the circumferential direction of the piston body 33 with one passage hole 37 sandwiched between each of them.

[0022] The passages in the plurality of passage holes 35 and the passage in the passage groove 36 constitute a piston passage 39 that penetrates the piston 18 in the axial direction of the piston 18 and can communicate between the first chamber 19 and the second chamber 20. The passages in the plurality of passage holes 37 and the passage in the passage groove 38 constitute a piston passage 40 that penetrates the piston 18 in the axial direction of the piston 18 and can communicate between the first chamber 19 and the second chamber 20.

[0023] The piston passage 39 is provided with a damping force generating mechanism 41 that opens and closes the piston passage 39 to generate a damping force. The damping force generating mechanism 41 is arranged on the second chamber 20 side, which is one axial end side of the piston 18, and is attached to the piston rod 21. By arranging the damping force generating mechanism 41 on the second chamber 20 side, the oil L that flows out of the first chamber 19 flows toward the second chamber 20 in the piston passage 39 when the piston 18 moves toward the first chamber 19, i.e., during the extension stroke. The damping force generating mechanism 41 provided for the piston passage 39 serves as an extension-side damping force generating mechanism that generates a damping force by suppressing the flow of oil L from the extension-side piston passage 39 to the second chamber 20.

[0024] The piston passage 40 is provided with a damping force generating mechanism 42 that opens and closes the piston passage 40 to generate a damping force. The damping force generating mechanism 42 is arranged on the first chamber 19 side, which is the other axial end side of the piston 18, and is attached to the piston rod 21. By arranging the damping force generating mechanism 42 on the first chamber 19 side, oil L that flows out from the second chamber 20 flows toward the first chamber 19 in the piston passage 40 when the piston 18 moves toward the second chamber 20, i.e., during the compression stroke. The damping force generating mechanism 42 provided for the piston passage 40 serves as a compression-side damping force generating mechanism that generates a damping force by suppressing the flow of oil L from the compression-side piston passage 40 to the first chamber 19.

[0025] As a result of the above, the piston passage 39 and the piston passage 40 are connected so that the oil liquid L, which is a fluid, flows between the first chamber 19 and the second chamber 20 as the piston 18 moves. The oil liquid L passes through the piston passage 39 when the piston rod 21 and the piston 18 move toward the extension side, and the oil liquid L passes through the piston passage 40 when the piston rod 21 and the piston 18 move toward the compression side.

[0026] The piston body 33 has a generally circular disk shape, and an insertion hole 44 is formed in its radial center, penetrating in the axial direction, for inserting the mounting shaft portion 28 of the piston rod 21. The insertion hole 44 has a small diameter hole portion 45 on one axial side into which the mounting shaft portion 28 of the piston rod 21 is fitted, and a large diameter hole portion 46 on the other axial side, the small diameter hole portion 45 having an inner diameter larger than that of the small diameter hole portion 45.

[0027] An annular valve seat portion 47 constituting part of the damping force generating mechanism 41 is formed at the axial end of the piston body 33 on the second chamber 20 side, radially outward from the opening of the passage groove 36 on the second chamber 20 side. Furthermore, an inner seat portion 48 is formed at the axial end of the piston body 33 on the second chamber 20 side, radially inward from the opening of the passage groove 36 on the second chamber 20 side. The insertion hole 44 has the large diameter hole portion 46 located closer to the valve seat portion 47 and inner seat portion 48 than the small diameter hole portion 45 in the axial direction of the piston body 33.

[0028] An annular valve seat portion 49 constituting part of the damping force generating mechanism 42 is formed at the axial end of the piston body 33 on the first chamber 19 side, radially outward from the opening of the passage groove 38 on the first chamber 19 side. An inner seat portion 50 is formed at the axial end of the piston body 33 on the first chamber 19 side, radially inward from the opening of the passage groove 38 on the first chamber 19 side.

[0029] In the piston body 33, the radially opposite side of the valve seat portion 47 from the insertion hole 44 forms a step that is lower in axial height than the valve seat portion 47, and the opening of the compression-side piston passage 40 on the second chamber 20 side is located in this step-like portion. Similarly, in the piston body 33, the radially opposite side of the valve seat portion 49 from the insertion hole 44 forms a step that is lower in axial height than the valve seat portion 49, and the opening of the piston passage 39 in the extension-side passage hole 35 on the first chamber 19 side is located in this step-like portion.

[0030] As shown in Figure 3, on the valve seat portion 47 and inner seat portion 48 sides of the piston 18, in order from the piston 18 in the axial direction, there are provided one disk 51, one valve disk 52, one pilot valve 53, one pilot case 56 (partition member), multiple disks 57, one disk 58, one disk 59, and an annular member 60, with the mounting shaft portion 28 of the piston rod 21 fitted inside each of them. The disks 51, 57 to 59, the valve disk 52, and the annular member 60 are all perforated circular flat plates of a constant thickness, into which the mounting shaft portion 28 of the piston rod 21 can be fitted. The pilot valve 53 and the pilot case 56 are all annular, into which the mounting shaft portion 28 of the piston rod 21 can be fitted.

[0031] The pilot case 56 is a cylindrical bottomed member having a rod insertion hole 70 formed in its radial center, the rod insertion hole 70 passing through the pilot case 56 in the axial direction of the pilot case 56. The pilot case 56 has a perforated disk-shaped bottom 71, a cylindrical wall portion 72 protruding to one side from the outer peripheral edge of the bottom 71 along the axial direction of the bottom 71, and a cylindrical inner cylindrical portion 73 protruding from the inner peripheral edge of the bottom 71 along the axial direction of the bottom 71 on the same side as the wall portion 72. The pilot case 56 also has an inner seat portion 74 protruding from the inner peripheral edge of the bottom 71 to the opposite side from the inner cylindrical portion 73 along the axial direction of the bottom 71, and a valve seat portion 75 (valve seat) protruding from outside the inner seat portion 74 in the radial direction of the bottom 71 to the same side as the inner seat portion 74 along the axial direction of the bottom 71.

[0032] The pilot case 56 has the mounting shaft portion 28 of the piston rod 21 fitted into the rod insertion hole 70. At this time, the pilot case 56 is oriented in such a way that the wall portion 72 and the inner cylindrical portion 73 extend from the bottom portion 71 toward the piston 18 in the axial direction of the piston rod 21.

[0033] The bottom portion 71 is formed with a seat portion 80 and a recess 82 on the side of the wall portion 72 and the inner cylindrical portion 73 in the axial direction of the bottom portion 71. The seat portion 80 and the recess 82 are formed at a position between the wall portion 72 and the inner cylindrical portion 73 in the radial direction of the bottom portion 71.

[0034] The seat portion 80 is annular and has a seat surface 84 and a seat surface 85 that is disposed radially inward of the seat surface 84 of the bottom portion 71. The seat surfaces 84 and 85 are both flat annular surfaces that extend perpendicular to the central axis of the bottom portion 71 and are disposed on the same plane.

[0035] The recess 82 is formed between the seat surfaces 84, 85. The recess 82 has a stopper surface 86 recessed from the seat surfaces 84, 85 in the axial direction of the bottom portion 71. The recess 82 has a shape in which the width in the radial direction of the bottom portion 71 becomes narrower as the depth increases. Although the recess 82 is provided in an annular shape in FIG. 3 , it does not have to be annular. In other words, it is sufficient that the recess 82 is provided on at least a portion of the seat portion 80.

[0036] As shown in Fig. 2, the bottom portion 71 is formed with an outer through-hole 87 (first through-hole) that penetrates the bottom portion 71 in the axial direction. The bottom portion 71 is formed with a plurality of outer through-holes 87 spaced apart in the circumferential direction of the bottom portion 71 (only one is shown in Fig. 2 because it is a cross-section). It is sufficient that at least one outer through-hole 87 is provided in the bottom portion 71.

[0037] As shown in FIG. 3 , the bottom portion 71 is provided with an inner through-hole 88 (second through-hole) that penetrates the bottom portion 71 along the axial direction of the bottom portion 71, the inner through-hole 88 being located inside the seat portion 80 in the radial direction of the bottom portion 71 and outside the inner cylindrical portion 73 and the inner seat portion 74 in the radial direction of the bottom portion 71. The bottom portion 71 is provided with a plurality of inner through-holes 88 spaced apart in the circumferential direction of the bottom portion 71 (only one is shown in FIG. 3 because it is a cross-section). It is sufficient that at least one inner through-hole 88 is provided in the bottom portion 71. As shown in FIG. 2 , the outer through-hole 87 is provided outside the inner through-hole 88 in the radial direction of the pilot case 56, i.e., in the radial direction of the bottom portion 71.

[0038] The inner seat portion 74 is annular. The valve seat portion 75 is annular and radially outer than the inner seat portion 74. The valve seat portion 75 protrudes from the bottom portion 71 in the axial direction of the bottom portion 71 on the same side as the inner seat portion 74. In this embodiment, the valve seat portions 75 are fan-shaped and provided in multiple positions along the circumferential direction of the bottom portion 71, but the present invention is not limited to this and may be annular, for example. The valve seat portion 75 has multiple valve seat constituent portions 91 (only one is shown in FIG. 2 due to the cross-sectional view) and multiple valve seat constituent portions 92 (only one is shown in FIG. 2 due to the cross-sectional view).

[0039] The plurality of valve seat constituent portions 91 are identically shaped like arcs. The plurality of valve seat constituent portions 91 are located outward of the inner seat portion 74 in the radial direction of the pilot case 56, and are arranged intermittently at equal intervals on the same circle coaxial with the inner seat portion 74.

[0040] The multiple valve seat constituent portions 92 are identical in shape and convex outward in the radial direction of the pilot case 56. Each of the multiple valve seat constituent portions 92 connects between valve seat constituent portions 91 adjacent to each other in the circumferential direction of the pilot case 56 and convex outward in the radial direction of the pilot case 56. The outer surface of the valve seat constituent portion 92 facing outward in the circumferential and radial directions of the pilot case 56 is convex outward in the radial direction of the pilot case 56. The inner surface of the valve seat constituent portion 92 facing inward in the circumferential and radial directions of the pilot case 56 is also concave outward in the radial direction of the pilot case 56. The multiple valve seat constituent portions 92 protrude radially outward in the radial direction of the pilot case 56 from broken portions of the valve seat constituent portions 91 that are arranged discontinuously.

[0041] A passage recess 93 is formed between the inner seat portion 74 and the valve seat portion 75. The passage recess 93 is surrounded by the inner seat portion 74 and the valve seat portion 75. The passage recess 93 is continuous around the entire circumference of the pilot case 56. The passage recess 93 is recessed in the axial direction of the pilot case 56 from the tip surface on the protruding side of the inner seat portion 74 and the tip surface on the protruding side of the valve seat portion 75. The bottom surface of the passage recess 93 is formed by the bottom portion 71.

[0042] A passage groove 95 is formed in the inner seat portion 74, penetrating the inner seat portion 74 in the radial direction thereof. The passage groove 95 opens into the passage recess 93. The inner through-hole 88 is formed in the bottom surface of the passage recess 93. The outer through-hole 87 is located between adjacent valve seat components 92 in the circumferential direction of the bottom portion 71 and outward of the valve seat components 91 in the radial direction of the bottom portion 71. Therefore, the outer through-hole 87 does not open into the passage recess 93. Note that when the valve seat portion 75 is annular, as shown in FIG. 4, the outer through-hole 87 is provided radially outward of the valve seat portion 75. Alternatively, as shown in FIG. 5, the passage in the large-diameter hole portion 101 may communicate with the passage in the passage groove 30 of the piston rod 21 and communicate with the back pressure chamber 151 via a passage in a notch 253 of a disk 252 instead of the passage groove 95.

[0043] The rod insertion hole 70 has a large diameter hole portion 101 and a small diameter hole portion 102. The large diameter hole portion 101 has a larger diameter than the small diameter hole portion 102. The small diameter hole portion 102 is formed in the inner cylindrical portion 73 and a portion of the bottom portion 71 on the inner cylindrical portion 73 side in the axial direction. The large diameter hole portion 101 is formed in the inner seat portion 74 and a portion of the bottom portion 71 on the inner seat portion 74 side in the axial direction. In the rod insertion hole 70, the mounting shaft portion 28 of the piston rod 21 is fitted into the small diameter hole portion 102. In the axial direction of the piston rod 21, the large diameter hole portion 101 is positioned overlapping the passage groove 30 of the piston rod 21.

[0044] The passage in the large diameter hole 101 of the pilot case 56 communicates with the passage in the passage groove 30 of the piston rod 21 and with the passage in the passage groove 95 of the pilot case 56. A portion of the mounting shaft portion 28 of the piston rod 21 is disposed within the pilot case 56. The passage in the large diameter hole 46 of the piston 18, the passage in the passage groove 30 of the piston rod 21, and the passage in the large diameter hole 101 of the pilot case 56 form a rod-side chamber 105.

[0045] As shown in FIG. 3 , a free valve 111 (volume variable member) is disposed within the pilot case 56, facing the wall portion 72 side of the bottom portion 71 in the axial direction. The free valve 111 is a flexible plate-like member. The outer diameter of the free valve 111 is larger than the outer diameter of the stopper surface 86. The inner diameter of the free valve 111 is smaller than the outer diameter of the seat surface 85 of the seat portion 80. The mounting shaft portion 28 of the piston rod 21 passes through the free valve 111 radially inward.

[0046] 2, the bottom 71 of the pilot case 56 has a recess 82 covered by the free valve 111 and a seat portion 80 that abuts against the free valve 111, and has an outer through-hole 87 that penetrates the bottom 71 at the position of the recess 82. The pilot case 56 has an inner through-hole 88 in the seat portion 80 that penetrates the bottom 71 and is located more inward in the radial direction of the pilot case 56 than the outer through-hole 87.

[0047] The outer through-hole 87, formed at the deepest position of the recess 82 in the bottom 71, is radially overlapping and axially opposed to the free valve 111. As shown in FIG. 3 , the free valve 111 closes the outer through-hole 87 (shown by an imaginary line (two-dot chain line) in FIG. 3 ; see FIG. 2 ) by coming into surface contact with the seat surfaces 84 and 85, and opens the outer through-hole 87 by moving away from the seat surface 84. The free valve 111 is elastically deformable so as to enter the recess 82, and even in this case, it maintains the closed state of the outer through-hole 87 by abutting against the boundary periphery between the seat surfaces 84 and 85 on both radial sides of the stopper surface 86 or against the entire surface of the stopper surface 86.

[0048] The disk 51 has an outer diameter that is smaller than the inner diameter of the valve seat portion 47 and larger than the outer diameter of the inner seat portion 48. The disk 51 is formed with a notch 121 that extends radially outward from the inner peripheral edge that fits onto the mounting shaft portion 28 of the piston rod 21 to the outside of the inner seat portion 48. The passage within the notch 121 is constantly in communication with the piston passage 39 of the piston 18, and the piston passage 39 is constantly in communication with the passage within the large diameter bore 46 of the piston 18, the passage within the passage groove 30 of the piston rod 21, and the passage within the large diameter bore 101 of the pilot case 56 via the passage within the notch 121.

[0049] The valve disc 52 has an outer diameter larger than the outer diameter of the valve seat portion 47 of the piston 18. The valve disc 52 abuts against the valve seat portion 47 and opens and closes the opening of the piston passage 39 by moving away from and abutting against the valve seat portion 47. A cutout portion 131 is formed on the outer periphery of the valve disc 52, and the cutout portion 131 crosses the valve seat portion 47 in the radial direction. Therefore, the inside of the cutout portion 131 forms a fixed orifice 132 that constantly connects the piston passage 39 to the second chamber 20.

[0050] The pilot valve 53 is made up of a metal valve disc 141 and an elastic fastening member 142 that is fastened to the valve disc 141. For example, the fastening member 142 may be made of rubber and fastened to the valve disc 141 by vulcanization adhesion.

[0051] The valve disc 141 is a circular flat plate with holes and a constant thickness, inside which the mounting shaft portion 28 of the piston rod 21 can be fitted. The outer diameter of the valve disc 141 is slightly larger than the outer diameter of the valve disc 52. The pilot valve 53 abuts against the valve disc 52 at the valve disc 141.

[0052] The fixing member 142 is fixed to the outer circumferential side of the valve disc 141, which is opposite the piston 18 in the axial direction. The fixing member 142 has a seal portion 145 (seal member) and a support portion 146 (support member). Both the seal portion 145 and the support portion 146 are fixed to the outer circumferential side of the valve disc 141, which is opposite the piston 18 in the axial direction.

[0053] The seal portion 145 has an annular shape. The seal portion 145 is fixed to the outer peripheral edge of the valve disc 141. The seal portion 145 extends from the valve disc 141 along the axial direction of the valve disc 141 toward the opposite side from the piston 18. The seal portion 145 has an expanding diameter shape, with both the inner and outer diameters increasing toward the extending tip. As shown in FIG. 6 , the outer diameter of the seal portion 145 (on the pilot case 56 side) may be shaped so that it initially decreases and then increases from the part where the seal portion 145 is fixed to the valve disc 141 toward the extending tip. This makes the seal portion 145 more likely to deform at the smallest outer diameter portion, reducing the effect of friction on the valve disc 141 and thereby reducing rigidity and the minimum damping force.

[0054] The support portion 146 has an annular shape and is formed contiguous with the seal portion 145, inside the seal portion 145 in the radial direction of the valve disc 141. Like the seal portion 145, the support portion 146 extends from the valve disc 141 in the axial direction of the valve disc 141 to the side opposite the piston 18.

[0055] The support portion 146 has at least one passage groove 148 formed therein, penetrating the support portion 146 in the radial direction thereof. This passage groove 148 may be a hole formed in the support portion 146, or a notch that cuts from the tip of the support portion 146 (the portion that comes into contact with the free valve 111, described below) toward the seal portion 145. The support portion 146 has a base end that is located closer to the valve disc 141 than the passage groove 148 and is connected to the valve disc 141, and is connected to the base end of the seal portion 145 that is connected to the valve disc 141. The seal portion 145 and the support portion 146 of the fixing member 142 are made of the same material and are formed seamlessly and integrally.

[0056] As described above, the seal portion 145 is integrally connected to the valve disc 141. The support portion 146 is made of the same material as the seal portion 145 and, like the seal portion 145, is integrally connected to the valve disc 141. The support portion 146 is connected to the inner portion of the seal portion 145 in the radial direction of the valve disc 141. The support portion 146 also extends from the inner side of the seal portion 145 in the radial direction of the valve disc 141.

[0057] The seal portion 145 is slidably and liquid-tightly fitted to the inner circumferential surface of the wall portion 72 of the pilot case 56 over the entire circumference, and constantly seals the gap between the pilot valve 53 and the wall portion 72. In other words, the pilot valve 53 has the seal portion 145 slidably and liquid-tightly fitted to the wall portion 72 of the pilot case 56. At this time, the valve disc 141 covers the opening of the wall portion 72 on the opposite side of the bottom portion 71 in the axial direction of the pilot case 56.

[0058] The tip side of the support portion 146 abuts against the free valve 111. The support portion 146 presses the free valve 111 against the seat surfaces 84, 85 of the seat portion 80. One end of the support portion 146 is connected to the valve disc 141, and the other end abuts against the free valve 111, directly applying a biasing force to the valve disc 141 and the free valve 111 in the direction separating them.

[0059] The support portion 146 abuts against the free valve 111 opposite to a portion of the free valve 111 that seats on the seat portion 80. In other words, the portion of the support portion 146 that comes into contact with the free valve 111 overlaps the position of the portion of the free valve 111 that seats on the seat portion 80 in the radial direction of the free valve 111. Specifically, the portion of the support portion 146 that comes into contact with the free valve 111 overlaps the position of the portion of the free valve 111 that seats on the seat surface 85 of the free valve 111 in the radial direction of the free valve 111.

[0060] With the free valve 111 closing the outer through-hole 87, the space between the pilot valve 53, the pilot case 56, and the free valve 111 forms a back pressure chamber 151, and the space between the bottom 71 of the pilot case 56 and the free valve 111 forms a variable chamber 152. Thus, these two chambers, the back pressure chamber 151 and the variable chamber 152, are defined by the free valve 111 within the pilot case 56.

[0061] 2 via a passage in the inner through-hole 88 of the pilot case 56, a passage in the passage recess 93, a passage in the passage groove 95, a passage in the large diameter hole 101, a passage in the passage groove 30 of the piston rod 21, a passage in the large diameter hole 46 of the piston 18, a passage in the notch 121 of the disk 51, and the piston passage 39. The variable chamber 152 is constantly in communication with the second chamber 20 via a passage in the outer through-hole 87.

[0062] 3 , the free valve 111 blocks the flow of oil L between the back pressure chamber 151 and the variable chamber 152 in the following states: when both its outer circumferential side and its inner circumferential side are in contact with the seat surfaces 84, 85 of the seat portion 80 over the entire circumference; when both its outer circumferential side and its inner circumferential side are in contact with the boundary edges on both sides of the seat surfaces 84, 85 and the stopper surface 86 over the entire circumference; and when the free valve 111 is in contact with the stopper surface 86 over the entire circumference. Furthermore, when the free valve 111 is separated from the seat surfaces 84, 85 of the bottom portion 71, the free valve 111 allows the flow of oil L between the back pressure chamber 151 and the variable chamber 152.

[0063] The support portion 146 of the fixing member 142 of the pilot valve 53 biases the free valve 111 so that it abuts against the seat surfaces 84, 85. When the differential pressure between the back pressure chamber 151 and the variable pressure chamber 152 (the variable pressure chamber 152 is higher) reaches or exceeds a predetermined value, the free valve 111 moves against the biasing force of the support portion 146 and separates from the seat surfaces 84, 85. At this time, the seat surface 84, which is not biased by the support portion 146, separates, and depending on the differential pressure, the seat surface 85 may not separate. The support portion 146 of the pilot valve 53, the free valve 111, and the seat portion 80 and recess 82 of the bottom portion 71 of the pilot case 56 constitute a check valve 155 that restricts the flow of oil liquid L from the back pressure chamber 151 side to the variable chamber 152 side, i.e., the second chamber 20 side, while allowing the flow of oil liquid L from the variable chamber 152 side, i.e., the second chamber 20 side, to the back pressure chamber 151 side.

[0064] The free valve 111, which is the valve element of the check valve 155, is not clamped in its entirety in the axial direction and is not fixed to any component. In other words, the free valve 111 can come into contact with and move away from the support portion 146 of the pilot valve 53 and the bottom portion 71 of the pilot case 56, against which it abuts. The free valve 111 is a floating-type free valve that can move in its entirety in the axial direction. The free valve 111 is biased by only the support portion 146 of the pilot valve 53, other than by hydraulic pressure, and moves toward and away from the seat surfaces 84, 85.

[0065] In addition, the biasing force of the support portion 146 of the pilot valve 53 may be set so that the free valve 111 always blocks the flow of oil liquid L between the back pressure chamber 151 and the variable chamber 152 regardless of the pressure state of the back pressure chamber 151 and the variable chamber 152.

[0066] Because the recess 82 is formed in the bottom 71, the free valve 111 can bend due to the oil liquid L in the pilot case 56. When the pressure in the back pressure chamber 151 becomes higher than the pressure in the variable chamber 152, the free valve 111 bends to enter the recess 82 as described above, expanding the volume of the back pressure chamber 151 and deforming to reduce the volume of the variable chamber 152 while continuing to block communication between the back pressure chamber 151 and the variable chamber 152. Furthermore, from this state, when the pressure difference between the pressure in the back pressure chamber 151 and the pressure in the variable chamber 152 becomes smaller, the free valve 111 reduces its entry into the recess 82, increasing the volume of the variable chamber 152 and deforming (restoring) to reduce the volume of the back pressure chamber 151 while continuing to block communication between the back pressure chamber 151 and the variable chamber 152.

[0067] As described above, the valve disc 52 is capable of being seated on the valve seat portion 47 of the piston 18. The valve disc 141 of the pilot valve 53 abuts against the valve disc 52. The valve disc 141 of the pilot valve 53 and the valve disc 52 together form a valve member 161 (first valve member). The valve disc 52 and the valve disc 141, i.e., the valve member 161, together with the valve seat portion 47 of the piston 18, form a fixed orifice 132 in the cutout portion 131 of the valve disc 52.

[0068] The valve member 161, together with the valve seat portion 47 of the piston 18, constitutes the damping force generating mechanism 41. When the valve disc 52 of the valve member 161 is lifted off the valve seat portion 47 and opens, the valve member 161 causes oil L in the first chamber 19 shown in FIG. 2 to flow into the second chamber 20 via the piston passage 39 and a passage between the valve member 161 and the valve seat portion 47. The piston passage 39 formed inside the multiple passage holes 35 and the passage groove 36, and the passage between the valve member 161 and the valve seat portion 47 constitute a flow path 162 (first flow path). In other words, the piston passage 39, the fixed orifice 132 shown in FIG. 3, and the space between the valve member 161 and the valve seat portion 47, which are spaced apart, form the flow path 162 through which oil L flows as a fluid flowing out of the first chamber 19, which is one of the first chamber 19 and the second chamber 20 shown in FIG. 2. The fixed orifice 132 allows communication between the first chamber 19 and the second chamber 20 via the flow path 162, even when the valve disc 52 is in contact with the valve seat portion 47. The valve member 161, which is made up of the valve disc 52 and the valve disc 141, closes the opening of the flow path 162 on the second chamber 20 side.

[0069] This flow path 162 serves as an extension-side flow path through which oil L flows as a fluid from the first chamber 19 to the second chamber 20 when the piston 18 moves toward the first chamber 19, i.e., during the extension stroke. The extension-side damping force generating mechanism 41, which is made up of the valve seat portion 47 and the valve member 161, is provided in the flow path 162, and the valve member 161 acts in a direction to reduce the cross-sectional area of ​​this flow path 162, thereby suppressing the flow of oil L and generating a damping force. In other words, the valve member 161 is provided in the flow path 162 and suppresses the flow of oil L caused by the sliding of the piston 18 toward the extension side, thereby generating a damping force.

[0070] 3 , the plurality of discs 57 have an outer diameter that allows them to be seated on the valve seat portion 75. The plurality of discs 57 constitute a valve member 171 (second valve member) that can be seated on and removed from the valve seat portion 75. The valve member 171 abuts against the valve seat portion 75 to close the passage in the passage recess 93 between the inner seat portion 74 and the valve seat portion 75. The valve member 171 moves away from the valve seat portion 75 to connect the passage in the passage recess 93 between the inner seat portion 74 and the valve seat portion 75 to the second chamber 20.

[0071] The piston passage 39 of the piston 18, the passage in the notch 121 of the disc 51, the passage in the large-diameter hole 46 of the piston 18, the passage in the passage groove 30 of the piston rod 21, the passage in the large-diameter hole 101 of the pilot case 56, the passage in the passage groove 95 of the pilot case 56, and the passage in the passage recess 93 of the pilot case 56 constitute a passage 172 (second passage) at least partially arranged in parallel with the passage 162. In this embodiment, the piston passage 39 on the first chamber 19 side shown in FIG. 2 is common to the passage 162, and the remaining portion of the passage 172 is arranged in parallel with the passage 162. Alternatively, the passage groove 30 of the piston rod 21 may be directly connected to the first chamber 19, so that the passage 162 and the passage 172 are completely parallel. As described above, the passage in the large diameter hole portion 46 of the piston 18, the passage in the passage groove 30 of the piston rod 21, and the passage in the large diameter hole portion 101 of the pilot case 56 constitute the rod side chamber 105. Therefore, the rod side chamber 105 is a part of the flow path 172.

[0072] The valve member 171 is provided on the second chamber 20 side of the flow path 172 and opens and closes the flow path 172. An inner through-hole 88 is arranged inside the valve seat portion 75 of the pilot case 56. An outer through-hole 87 is arranged between valve seat constituent portions 92 that are adjacent to each other in the circumferential direction of the pilot case 56, and outside the valve seat constituent portion 91 shown in FIG. 2 in the radial direction of the pilot case 56. As a result, the valve member 171 closes the inner through-hole 88 without closing the outer through-hole 87.

[0073] As described above, the pilot case 56, which has the bottom 71 and the wall 72 and is penetrated by the piston rod 21, has a passage in the inner through-hole 88 that serves as the connection passage 173 that connects to the flow passage 172 and the back pressure chamber 151. In other words, the pilot case 56 has the connection passage 173 that connects to the flow passage 172. The connection passage 173 is an orifice that narrows the flow passage from the flow passage 172 to the back pressure chamber 151. The flow passage 172 and the connection passage 173 introduce the oil L from the first chamber 19 into the back pressure chamber 151.

[0074] The flow path 172 has a passage in the cutout portion 121 of the disk 51 shown in FIG. 3 that serves as an inlet orifice 174 that narrows the flow path area. The pilot case 56 forms a back pressure chamber 151 that generates a force on the valve member 161 in the valve closing direction. The back pressure chamber 151 between the pilot valve 53, the pilot case 56, and the free valve 111 applies internal pressure to the valve member 161 in the direction of the piston 18, i.e., in the valve closing direction that seats the valve disk 52 on the valve seat portion 47. The opening of the valve member 161 is adjusted by the pressure in this back pressure chamber 151. In other words, the opening of the damping force generating mechanism 41 including the valve member 161 is adjusted by the pressure in the back pressure chamber 151.

[0075] The free valve 111 is disposed opposite the bottom 71 of the pilot case 56 and is a volume-variable member that deforms due to the pressure of the hydraulic fluid L to vary the volume of the back pressure chamber 151. The support portion 146 of the pilot valve 53 directly or indirectly applies a biasing force to the valve member 161 and the free valve 111 in the separating direction. A passage groove 148 formed in the support portion 146 of the pilot valve 53 forms a communication passage 175 that allows a portion of the back pressure chamber 151 that is radially inward from the support portion 146 to communicate with a portion that is radially outward from the support portion 146 to communicate with a portion that is radially in ...

[0076] The pilot case 56, the pilot valve 53, and the free valve 111 form a back pressure chamber 151, and constitute a valve opening control mechanism 182 that applies back pressure to a valve member 161 including a valve disc 141 of the pilot valve 53 in a direction that closes the flow path 162, thereby controlling the opening of the valve.

[0077] The annular member 60 has higher rigidity than the valve member 171. The disk 59 and the annular member 60 come into contact with the valve member 171 when the valve member 171 deforms in the opening direction, thereby preventing the valve member 171 from deforming in the opening direction beyond a specified limit.

[0078] The check valve 155, which is composed of the support portion 146 of the pilot valve 53, the free valve 111, and the bottom portion 71 of the pilot case 56, is provided between the back pressure chamber 151 and the variable chamber 152 and the passage in the outer through-hole 87, and restricts the flow of oil liquid L from the back pressure chamber 151 to the second chamber 20 via the variable chamber 152 and the passage in the outer through-hole 87, while allowing the flow of oil liquid L from the second chamber 20 to the back pressure chamber 151 via the passage in the outer through-hole 87 and the variable chamber 152.

[0079] The valve member 171 lifts off the valve seat 75 when the pressure in the back pressure chamber 151 reaches a predetermined pressure. The valve member 171, together with the valve seat 75, constitutes a damping force generating mechanism 183 that opens and generates a damping force when the pressure in the back pressure chamber 151 reaches a predetermined pressure. The damping force generating mechanism 183 is provided in a portion of the flow path 172 that is parallel to the flow path 162. The damping force generating mechanism 183 is provided outside the pilot case 56, with the valve member 171 disposed opposite the bottom 71. An inner through-hole 88 is provided in the bottom 71 of the pilot case 56, facing the valve member 171 of the damping force generating mechanism 183. When the valve member 171 lifts off the valve seat 75 and opens, it allows the oil L in the first chamber 19 to flow through the flow path 172 to the second chamber 20. When the valve member 171 is seated on the valve seat portion 75 and closed, it blocks communication between the flow path 172 and the second chamber 20. Note that, as shown in FIG. 7 , some of the multiple shims that make up the valve member 171 can be configured to include a preload disk 261.

[0080] 2, the compression-side damping force generating mechanism 42 has, in order from the piston 18 side in the axial direction, one disc 201, one disc 202, multiple discs 203, multiple discs 204, one disc 205, one disc 206, and one annular member 207. The discs 201 to 206 and the annular member 207 are all made of metal, and each is in the form of a perforated circular flat plate of a certain thickness, inside which the mounting shaft portion 28 of the piston rod 21 can be fitted.

[0081] The discs 203 and 204 constitute a valve member 212 that can be seated on and removed from the valve seat portion 49. When the valve member 212 is released from the valve seat portion 49, it connects the piston passage 40 in the passage hole 37 and the passage groove 38 to the first chamber 19 and suppresses the flow of oil L between them, thereby generating a damping force. The piston passage 40 and the space between the valve member 212 and the valve seat portion 49 constitute a flow path 210. The inside of the cutout portion 211 of the disc 202 forms a fixed orifice 213 that connects the first chamber 19 and the second chamber 20 via the flow path 210 even when the disc 202 is in contact with the valve seat portion 49. In other words, the space between the piston passage 40, the fixed orifice 213, and the spaced apart valve member 212 and valve seat portion 49 forms a flow path 210 through which oil liquid L flows as a fluid flowing out from the second chamber 20, which is one of the first chamber 19 and the second chamber 20.

[0082] This flow path 210 serves as a compression-side flow path through which oil L flows as a fluid from the second chamber 20 to the first chamber 19 when the piston 18 moves toward the second chamber 20, i.e., during the compression stroke. A compression-side damping force generating mechanism 42, consisting of a valve seat portion 49 and a valve member 212, is provided in the flow path 210, and generates a damping force by opening and closing the flow path 210 with the valve member 212 to suppress the flow of oil L. In other words, the valve member 212 is provided in the flow path 210 and generates a damping force by suppressing the flow of oil L caused by the sliding of the piston 18 toward the compression side. The disk 206 and the annular member 207 suppress deformation of the valve member 212 in the opening direction beyond a specified limit.

[0083] 3, the valve opening control mechanism 182, which is composed of the pilot case 56, the pilot valve 53, and the free valve 111, also constitutes a variable damping force mechanism that varies the damping force in response to the frequency of the reciprocating motion of the piston 18 (hereinafter referred to as the piston frequency). In the valve opening control mechanism 182, the free valve 111 deforms in response to the frequency of the reciprocating motion of the piston 18, thereby varying the volume of the back pressure chamber 151, which is always in communication with the first chamber 19, and the volume of the variable chamber 152, which is always in communication with the second chamber 20.

[0084] As shown in Fig. 2, the mounting shaft portions 28 are fitted inside the piston rod 21, and the annular member 207, disc 206, disc 205, multiple discs 204, multiple discs 203, disc 202, disc 201, piston 18, disc 51, valve disc 52, pilot valve 53, pilot case 56, multiple discs 57, disc 58, disc 59, and annular member 60 are stacked in this order on the end of the main shaft portion 27 on the mounting shaft portion 28 side. At this time, as shown in Fig. 3, the free valve 111 is disposed between the bottom portion 71 of the pilot case 56 and the support portion 146 of the pilot valve 53. At this time, the seal portion 145 of the pilot valve 53 is fitted into the wall portion 72 of the pilot case 56.

[0085] As shown in Figure 2, with the parts arranged in this manner, a retainer 221 is coupled to the mounting shaft portion 28 that protrudes beyond the annular member 60. As a result, the inner circumferential sides or the entirety of the stacked parts from the annular member 207 to the annular member 60 are sandwiched between the end of the main shaft portion 27 of the piston rod 21 on the mounting shaft portion 28 side and the retainer 221, and are clamped in the axial direction. At this time, as shown in Figure 3, the valve disc 141 of the pilot valve 53 has a side opposite to the piston 18 abutting against the inner cylindrical portion 73 of the pilot case 56. At this time, the free valve 111 is not clamped in the axial direction, but is sandwiched between the support portion 146 of the pilot valve 53 and the pilot case 56.

[0086] 1, the above-mentioned base valve 25 is provided between the bottom member 12 of the outer cylinder 4 and the inner cylinder 3. This base valve 25 has a base member 231 that separates the second chamber 20 from the reservoir chamber 6, a disk valve 232 provided on the lower side of this base member 231, i.e., on the reservoir chamber 6 side, a disk valve 233 provided on the upper side of the base member 231, i.e., on the second chamber 20 side, and a mounting pin 234 that attaches the disk valve 232 and the disk valve 233 to the base member 231.

[0087] The disc valve 232, together with the base member 231, constitutes a compression-side damping valve mechanism 237 that opens during the compression stroke of the shock absorber 1 to allow hydraulic fluid L to flow from the second chamber 20 to the reservoir chamber 6 and generate a damping force. The disc valve 233, together with the base member 231, constitutes a suction valve mechanism 238 that opens during the extension stroke of the shock absorber 1 to allow hydraulic fluid L to flow from the reservoir chamber 6 into the second chamber 20. The suction valve mechanism 238 mainly functions to allow hydraulic fluid to flow from the reservoir chamber 6 to the second chamber 20 without generating any damping force, so as to make up for a shortage of hydraulic fluid caused by the extension of the piston rod 21 from the cylinder 2.

[0088] FIG. 8 shows a hydraulic circuit diagram of the piston rod 21 in the shock absorber 1 having the above-described configuration. As shown in FIG. 8 , the shock absorber 1 is provided with a flow path 162 connecting the first chamber 19 and the second chamber 20. The flow path 162 is provided with a valve member 161 and a fixed orifice 132, both of which constitute the damping force generating mechanism 41, arranged in parallel. The first chamber 19 is also connected to the rod side chamber 105 via an inlet orifice 174. The inlet orifice 174 and the rod side chamber 105 form the flow path 172. A damping force generating mechanism 183 is provided on the second chamber 20 side of the flow path 172. The flow path 172 is connected to the back pressure chamber 151 from the rod side chamber 105 via a connecting path 173, which is an orifice. The pressure in the back pressure chamber 151 acts on the valve member 161. The back pressure chamber 151 is separated from the variable chamber 152 by a free valve 111. The variable chamber 152 is in communication with the second chamber 20. A check valve 155 is provided between the second chamber 20 and the back pressure chamber 151. A flow path 210 is provided connecting the second chamber 20 and the first chamber 19. A valve member 212 and a fixed orifice 213, both of which constitute the damping force generating mechanism 42, are provided in parallel in the flow path 210.

[0089] Next, the operation of the shock absorber 1 will be described.

[0090] It is assumed that the valve opening control mechanism 182 does not function as a damping force variable mechanism during the extension stroke when the piston rod 21 moves toward the extension side. Then, when the moving speed of the piston 18 (hereinafter referred to as the piston speed) is slow, the oil L from the first chamber 19 flows from the piston passage 39 of the piston 18 to the second chamber 20 via the fixed orifice 132 of the valve member 161 of the damping force generating mechanism 41, generating a damping force with orifice characteristics (the damping force is approximately proportional to the square of the piston speed). Therefore, the damping force characteristic with respect to the piston speed is such that the rate of increase in the damping force becomes relatively high as the piston speed increases.

[0091] When the piston speed increases, the oil L from the first chamber 19 flows from the piston passage 39 of the piston 18 to the second chamber 20 through a flow path 162 including a gap between the valve member 161 and the valve seat portion 47 of the piston 18 while opening the valve member 161, which is the main valve of the damping force generating mechanism 41, and a damping force with valve characteristics (damping force is approximately proportional to piston speed) is generated. Therefore, the characteristic of the damping force relative to the piston speed is such that the rate of increase of the damping force decreases as the piston speed increases.

[0092] When the piston speed becomes even faster, the oil L from the first chamber 19 flows into the second chamber 20 via the flow path 162, which includes the gap between the valve member 161 and the valve seat portion 47, which are separated from each other in the damping force generating mechanism 41. In addition, the oil L also flows into the second chamber 20 from the flow path 172, which opens the valve member 171 of the damping force generating mechanism 183, which is a hard valve, and passes through the gap between the valve member 171 and the valve seat portion 75, further suppressing the increase in damping force. Therefore, the characteristic of the damping force relative to the piston speed is such that the rate of increase in the damping force decreases further as the piston speed increases.

[0093] As the piston speed increases further, the relationship of the forces (hydraulic pressure) acting on the valve member 161 in the valve opening control mechanism 182 changes such that the opening force applied from the piston passage 39, which directly communicates with the first chamber 19, becomes greater than the closing force applied from the back pressure chamber 151, which communicates with the first chamber 19 via the flow path 172 and the connection path 173. Therefore, in this region, as the piston speed increases, the valve member 161 of the damping force generating mechanism 41 opens farther away from the valve seat portion 47 of the piston 18 than described above. As a result, in addition to the flow to the second chamber 20 through the flow path 172, which includes the gap between the valve member 171 and the valve seat portion 75 of the damping force generating mechanism 183, more hydraulic fluid L flows to the second chamber 20 through the flow path 162, which includes the passage between the valve member 161 and the valve seat portion 47, thereby further suppressing the increase in damping force. Therefore, the damping force vs. piston speed characteristic further decreases the rate of increase in damping force as the piston speed increases.

[0094] During the compression stroke in which the piston rod 21 moves toward the compression side, when the piston speed is slow, the oil L from the second chamber 20 flows into the first chamber 19 via the compression-side piston passage 40 and the fixed orifice 213 of the valve member 212 of the damping force generating mechanism 42, generating a damping force with orifice characteristics (the damping force is approximately proportional to the square of the piston speed). Therefore, the damping force characteristic relative to the piston speed is such that the rate of increase in the damping force becomes relatively high as the piston speed increases.

[0095] As the piston speed increases, the oil L introduced from the second chamber 20 into the compression-side piston passage 40 flows into the first chamber 19 through the gap between the valve member 212 and the valve seat portion 49 while opening the valve member 212 of the damping force generating mechanism 42, generating a damping force with valve characteristics (damping force is approximately proportional to piston speed). In other words, as the piston speed increases, the oil L from the second chamber 20 flows into the first chamber 19 while opening the valve member 212 in the compression-side flow passage 210. For this reason, the damping force characteristic relative to piston speed is such that the rate of increase in damping force decreases as the piston speed increases.

[0096] The above is the case assuming that the valve opening control mechanism 182 does not function as a damping force variable mechanism, but in the first embodiment, the valve opening control mechanism 182 functions as a damping force variable mechanism that varies the damping force according to the piston frequency even when the piston speed is the same.

[0097] When the piston frequency is equal to or higher than a predetermined value, the amplitude of the piston 18 is small, and during the extension stroke when the piston frequency is thus high, the pressure in the first chamber 19 increases, and oil liquid L is introduced from the first chamber 19 into the back pressure chamber 151 via the flow path 172 and the connecting path 173. In response to this, the free valve 111, which had previously been flat and in contact with the seat surfaces 84, 85, elastically deforms so as to enter the recess 82 while blocking communication between the back pressure chamber 151 and the variable chamber 152, expanding the volume of the back pressure chamber 151 and discharging oil liquid L from the variable chamber 152 to the second chamber 20 via the passage in the outer through-hole 87.

[0098] As the free valve 111 is deformed in this way, hydraulic fluid L is introduced from the first chamber 19 into the back pressure chamber 151. As a result, the flow rate of hydraulic fluid L flowing from the first chamber 19 through the flow path 162 to the second chamber 20 is reduced while opening the damping force generating mechanism 41. In addition, the expansion of the volume of the back pressure chamber 151 suppresses the increase in pressure in the back pressure chamber 151, making it easier for the valve member 161 of the damping force generating mechanism 41 to open. As a result, the damping force on the extension side becomes soft. At this time, the damping force generating mechanism 183, which is a hard valve, does not open.

[0099] Here, when the piston frequency is equal to or higher than a predetermined value, the amount of hydraulic fluid L introduced from the first chamber 19 into the back pressure chamber 151 via the flow path 172 and the connecting path 173 is small, so the deformation of the free valve 111 is small and it does not come into contact with the stopper surface 86 to restrict deformation. Therefore, the damping force is softened with each extension stroke. Note that although the pressure in the back pressure chamber 151 increases by the amount corresponding to the stiffness (spring reaction force) of the free valve 111, because the piston frequency is high and the deflection of the free valve 111 is small, the pressure increase in the back pressure chamber 151 can be suppressed, and the effect on the ease of opening of the valve member 161 can be suppressed.

[0100] On the other hand, when the piston frequency is lower than a predetermined value, the amplitude of the piston 18 is large. During the extension stroke when the piston frequency is low, hydraulic fluid L flows from the first chamber 19 to the back pressure chamber 151 via the flow path 172 and the connecting path 173 in the same manner as described above. However, the amount of hydraulic fluid L flowing into the back pressure chamber 151 is large, resulting in significant deformation of the free valve 111. Therefore, the free valve 111 subsequently abuts against the stopper surface 86, restricting further deformation, and hydraulic fluid L no longer flows from the first chamber 19 to the back pressure chamber 151. Since hydraulic fluid L no longer flows from the first chamber 19 to the back pressure chamber 151, the pressure in the back pressure chamber 151 increases, suppressing the opening of the valve member 161 of the damping force generating mechanism 41. In other words, the damping force generating mechanism 41 is in a state where the valve member 161 does not open and hydraulic fluid L flows from the first chamber 19 to the second chamber 20 via the fixed orifice 132, resulting in a hard damping force on the extension side. When the pressure in the back pressure chamber 151 increases further, the oil L opens the valve member 171 of the damping force generating mechanism 183, which is a hard valve, and flows into the second chamber 20 through a flow path 172 that includes the gap between the valve member 171 and the valve seat portion 75. When the pressure in the back pressure chamber 151 increases further, the oil L not only flows through the flow path 172, but also opens the valve member 161 of the damping force generating mechanism 41 and flows from the flow path 162 to the second chamber 20. As a result, the damping force on the extension side becomes hard.

[0101] During the compression stroke, the pressure in the second chamber 20 increases, causing the pressure in the variable chamber 152 of the valve opening control mechanism 182 to exceed the pressure in the back pressure chamber 151. As a result, the free valve 111 of the check valve 155 lifts off the seat surfaces 84 and 85 against the biasing force of the support portion 146 of the pilot valve 53. That is, the check valve 155 opens. Then, oil L in the second chamber 20 flows from the second chamber 20 toward the first chamber 19 through the passage in the outer through-hole 87, the variable chamber 152, the back pressure chamber 151, the connecting passage 173, and the flow passage 172. At this time, the free valve 111 moves away from the seat surfaces 84 and 85, eliminating the pressure difference and suppressing further movement. The biasing force of the support portion 146 of the pilot valve 53 need only be sufficient to cause the free valve 111 to abut against the seat surfaces 84 and 85 in the absence of load pressure.

[0102] When the pressure in the second chamber 20 drops during a switch from the compression stroke to the extension stroke, the free valve 111 is instantly seated on the seat surfaces 84, 85 due to the biasing force of the support portion 146 of the pilot valve 53. In other words, the check valve 155 is instantly closed. This prevents the oil L on the first chamber 19 side from flowing into the second chamber 20 through the check valve 155 during a switch from the compression stroke to the extension stroke, thereby suppressing a delay in the rise of the damping force at the initial stage of the extension stroke.

[0103] In the configuration described in the aforementioned Patent Document 1, the free valve, which bends due to the internal pressure of the back pressure chamber in order to respond to frequency, is supported by a spring disc fixed to the piston rod. To allow the free valve to easily open as a check valve, the spring disc's biasing force must be set weakly, and the height of the spring disc must be kept low. This requires stacking multiple discs between the spring disc and the pilot valve, which increases the number of parts and increases costs. Stacking multiple discs requires increasing the precision of the multiple discs to suppress cumulative tolerances, which also increases costs.

[0104] The shock absorber 1 of the first embodiment includes a valve member 161 provided in a flow path 162 to allow hydraulic fluid L from the first chamber 19 to flow into the second chamber 20; a pilot case 56 connected to a flow path 172, at least a portion of which is parallel to the flow path 162, to form a back pressure chamber 151 that generates a force in the valve closing direction on the valve member 161; a free valve 111 disposed opposite the bottom 71 of the pilot case 56 and deformed by the pressure of the hydraulic fluid L to vary the volume of the back pressure chamber 151; and a seal portion 145 that seals between the second chamber 20 and the wall portion 72. The shock absorber 1 also includes a support portion 146 that directly applies a biasing force in the separating direction to the valve member 161 and the free valve 111. This eliminates the need to stack multiple discs, as is the case when using a spring disc fixed to a piston rod. This allows the shock absorber 1 to have a reduced number of parts, thereby reducing costs.

[0105] In the shock absorber 1, the bottom 71 of the pilot case 56 has a recess 82 covered by the free valve 111 and a seat portion 80 that abuts against the free valve 111, and an outer through-hole 87 that passes through the bottom 71 at the position of the recess 82. Therefore, the shock absorber 1 can vary the volume of the back pressure chamber 151 with a simple configuration.

[0106] In the shock absorber 1, the pilot case 56 has an inner through-hole 88 in the seat portion 80, which penetrates the bottom portion 71 and is provided radially inward of the outer through-hole 87. The shock absorber 1 also has a valve member 171 that does not close the outer through-hole 87 but closes the inner through-hole 88. As a result, when the valve member 171 opens the inner through-hole 88, the oil L in the back pressure chamber 151 can escape to the second chamber 20.

[0107] In the shock absorber 1, the seal portion 145 and the support portion 146 are integrally connected to the valve disc 141 that constitutes the valve member 161. This allows the number of parts to be further reduced, thereby reducing costs, in the shock absorber 1. Moreover, because the seal portion 145 and the support portion 146 in the shock absorber 1 are made of the same material, it is easy to integrally connect the seal portion 145 and the support portion 146 to the valve disc 141, thereby further reducing costs.

[0108] In the shock absorber 1, the support portion 146 extends from the seal portion 145 radially inward of the valve disc 141 that constitutes the valve member 161. Therefore, in the shock absorber 1, it is possible to easily integrally connect the support portion 146 to the valve disc 141 together with the seal portion 145 that seals between the second chamber 20 and the wall portion 72, thereby reducing costs.

[0109] In the shock absorber 1, the flow path 172 has a downstream opening that communicates with the inside of the valve seat portion 75 on which the valve member 171 is seated. Then, the oil L flows into the back pressure chamber 151 via a connection path 173 in the inner through-hole 88. Therefore, in the shock absorber 1, the connection path 173 that introduces the oil L from the flow path 172 to the back pressure chamber 151 can be provided in the pilot case 56, and therefore a dedicated member for introducing the oil L from the flow path 172 to the back pressure chamber 151 is not required. Therefore, the shock absorber 1 can further reduce the number of parts and reduce costs.

[0110] In the shock absorber 1, the support portion 146 abuts against the free valve 111, facing the portion of the free valve 111 that seats on the seat portion 80. Therefore, the shock absorber 1 can seat the free valve 111 on the seat portion 80 without deforming the free valve 111. Therefore, the shock absorber 1 can ensure a variable range of the capacity of the back pressure chamber 151.

[0111] Second Embodiment Next, a second embodiment of a shock absorber according to the present invention will be described, focusing on differences from the first embodiment, mainly with reference to Fig. 9. Note that parts common to the first embodiment will be designated by the same names and symbols.

[0112] As shown in Fig. 9, the shock absorber 1D of the second embodiment has a valve opening control mechanism 182D, which is a partial modification of the valve opening control mechanism 182, instead of the valve opening control mechanism 182. The valve opening control mechanism 182D has a pilot case 56D (partition member), which is a partial modification of the pilot case 56, instead of the pilot case 56. The pilot case 56D is also made of metal and is a seamless, one-piece molded product. Like the pilot case 56, the pilot case 56D forms the back pressure chamber 151. The pilot case 56D has an inner cylindrical portion 73D, which is slightly shorter in axial length than the inner cylindrical portion 73, instead of the inner cylindrical portion 73.

[0113] The valve opening control mechanism 182D has a pilot valve 53D that is partially different from the pilot valve 53, instead of the pilot valve 53. The valve opening control mechanism 182D has a pressing member 272 that is separate from the pilot valve 53D.

[0114] The pilot valve 53D comprises a valve disc 141 similar to that of the pilot valve 53, and a rubber seal portion 145D fixed by vulcanization adhesion to the valve disc 141. The pilot valve 53D abuts on the valve disc 141 on the side opposite to the disc 51 of the valve disc 52.

[0115] The seal portion 145D is fixed to the valve disc 141 on the side opposite the piston 18 in the axial direction. The seal portion 145D is annular. The seal portion 145D is fixed to the outer peripheral edge portion of the valve disc 141. In other words, the seal portion 145D is integrally connected to the valve disc 141. The seal portion 145D extends from the valve disc 141 on the side opposite the piston 18 along the axial direction of the valve disc 141. The seal portion 145D has an expanding diameter shape in which both the inner diameter and the outer diameter become larger toward the extending tip. The seal portion 145D is slidably and liquid-tightly fitted around the entire inner circumferential surface of the wall portion 72 of the pilot case 56D, and constantly seals the gap between the pilot valve 53D and the wall portion 72.

[0116] The pressing member 272 is made up of a metal disk 275 and a rubber support portion 146D fixed to the disk 275 by vulcanization adhesion.

[0117] The disk 275 is a perforated, circular flat plate of a constant thickness, into which the mounting shaft portion 28 of the piston rod 21 can be fitted. The disk 275 has an outer diameter that is smaller than the minimum inner diameter of the seal portion 145D and larger than the outer diameter of the inner cylindrical portion 73D of the pilot case 56D. The pressing member 272 abuts on the disk 275 on the side of the valve disk 141 opposite to the valve disk 52. The axial length of the inner cylindrical portion 73D is shorter than that of the inner cylindrical portion 73D by the thickness of the disk 275.

[0118] The support portion 146D has an annular shape. The support portion 146D is fixed to the edge portion of the outer circumferential side of the disk 275, opposite the piston 18 in the axial direction. In other words, the support portion 146D is integrally connected to the disk 275. The support portion 146D extends from the disk 275 along the axial direction of the disk 275 to the side opposite the piston 18. The support portion 146D has a tapered shape in which both the inner diameter and the outer diameter become smaller toward the extending tip. The support portion 146D is disposed between the inner cylindrical portion 73D of the pilot case 56D and the seal portion 145D of the pilot valve 53D in the radial direction.

[0119] The support portion 146D is formed with a passage groove 148D that penetrates the support portion 146D in the radial direction of the support portion 146D. The passage groove 148D opens at the tip of the support portion 146D in the extension direction. The support portion 146D is formed with a plurality of passage grooves 148D at equal intervals in the circumferential direction of the support portion 146D.

[0120] The tip side of the support portion 146D abuts against the free valve 111. The support portion 146D presses the free valve 111 against the seat surfaces 84, 85 of the seat portion 80. One end of the support portion 146D is connected to the disk 275, and the other end abuts against the free valve 111, applying a biasing force in the direction separating the disk 275 and the free valve 111. At that time, the support portion 146D also applies a biasing force to the valve member 161 via the disk 275. In other words, the support portion 146D indirectly applies a biasing force in the direction separating the valve member 161 and the free valve 111.

[0121] The support portion 146D abuts against the free valve 111 opposite to a portion of the free valve 111 that seats on the seat portion 80. In other words, the portion of the support portion 146D that comes into contact with the free valve 111 overlaps the position of the portion of the free valve 111 that seats on the seat portion 80 in the radial direction of the free valve 111. Specifically, the portion of the support portion 146D that comes into contact with the free valve 111 overlaps the position of the portion of the free valve 111 that seats on the seat surface 85 of the free valve 111 in the radial direction of the free valve 111.

[0122] With the free valve 111 closing the outer through-hole 87, the back pressure chamber 151 is formed between the pilot valve 53D and the pilot case 56D and the free valve 111. A passage groove 148D formed in the support portion 146D of the pressing member 272 serves as a communication passage 175D that allows a portion of the back pressure chamber 151 that is radially inward from the support portion 146D to communicate with a portion that is radially outward from the support portion 146D and that allows a portion of the back pressure chamber 151 that is radially outward from the support portion 146D to communicate with a portion that is radially inward from the support portion 146D. In other words, the support portion 146D of the pilot valve 53D has the communication passage 175D that allows communication with the inside of the back pressure chamber 151.

[0123] The support portion 146D of the pressing member 272 of the pilot valve 53D biases the free valve 111 so that it abuts against the seat surfaces 84, 85. The free valve 111 moves against the biasing force of the support portion 146D and moves away from the seat surfaces 84, 85. The support portion 146D of the pressing member 272, the free valve 111, and the seat portion 80 and recess 82 of the bottom portion 71 of the pilot case 56D constitute a check valve 155D that restricts the flow of oil liquid L from the back pressure chamber 151 side to the variable chamber 152 side, i.e., the second chamber 20 side, while allowing the flow of oil liquid L from the variable chamber 152 side, i.e., the second chamber 20 side, to the back pressure chamber 151 side.

[0124] As described above, the valve disc 52 is capable of being seated on the valve seat portion 47 of the piston 18. The valve disc 141 of the pilot valve 53D abuts against the valve disc 52. The disc 275 of the pressing member 272 abuts against the valve disc 141 of the pilot valve 53D from the side opposite the valve disc 52. The back pressure chamber 151 generates a force in the valve closing direction on the valve member 161 made up of the valve disc 52 and the valve disc 141 of the pilot valve 53D.

[0125] The shock absorber 1D has a hydraulic circuit similar to that of the shock absorber 1 of the first embodiment.

[0126] As described above, the shock absorber 1D of the second embodiment has each of the modified configurations of the shock absorber 1 of the first embodiment functioning in substantially the same manner as the configurations of the shock absorber 1 before the modifications, and therefore, even though it has each modified configuration, it can achieve substantially the same effects as the shock absorber 1.

[0127] In the shock absorber 1D, the seal portion 145D is provided on the pilot valve 53D, and the support portion 146D is provided on a pressing member 272 that is separate from the pilot valve 53D. Therefore, in the shock absorber 1D, the seal portion 145D and the support portion 146D can each be formed with high precision.

[0128] Even if there is a change in the specifications of the pilot valve 53D, the shock absorber 1D can accommodate the change without changing the pressing member 272. Even if there is a change in the specifications of the free valve 111, the shock absorber 1D can accommodate the change by changing only the pressing member 272 while leaving the pilot valve 53D as is.

[0129] [Third Embodiment] Next, a third embodiment of the shock absorber according to the present invention will be described, focusing on differences from the first embodiment, mainly with reference to Fig. 10. Note that parts common to the first embodiment will be designated by the same names and symbols.

[0130] 10 , a shock absorber 1E of the third embodiment has a valve opening control mechanism 182E, which is a partial modification of the valve opening control mechanism 182, instead of the valve opening control mechanism 182. The valve opening control mechanism 182E has a pilot valve 53E, which is partially different from the pilot valve 53, instead of the pilot valve 53.

[0131] The pilot valve 53E comprises a valve disc 141 similar to that of the pilot valve 53, a rubber sealing portion 145E (sealing member) fixed to the valve disc 141 by vulcanization bonding, and a rubber support portion 146E (supporting member) fixed to the valve disc 141 by vulcanization bonding.

[0132] The seal portion 145E is fixed to the valve disc 141 on the axial side opposite the piston 18. The seal portion 145E is annular. The seal portion 145E is fixed to the outer peripheral edge portion of the valve disc 141. The seal portion 145E extends from the valve disc 141 on the side opposite the piston 18 along the axial direction of the valve disc 141. The seal portion 145E has an expanding diameter shape in which both the inner diameter and the outer diameter become larger toward the extending tip.

[0133] The support portion 146E is fixed to the valve disc 141 on the side opposite the piston 18 in the axial direction. The support portion 146E has an annular shape. The support portion 146E is formed inside the seal portion 145E in the radial direction of the valve disc 141 and spaced apart from the seal portion 145E. In other words, the support portion 146E is spaced a predetermined distance from the seal portion 145E inward in the radial direction of the valve member 161 and is integrally connected to the valve disc 141 of the valve member 161. Like the seal portion 145E, the support portion 146E extends from the valve disc 141 on the side opposite the piston 18 along the axial direction of the valve disc 141. The support portion 146E has a tapered shape in which both the inner and outer diameters become smaller toward the extending tip.

[0134] The support portion 146E is formed with a passage groove 148E that penetrates the support portion 146E in the radial direction of the support portion 146E. The passage groove 148E opens at the tip of the support portion 146E in the extension direction. The support portion 146E is formed with a plurality of passage grooves 148E at equal intervals in the circumferential direction of the support portion 146E. In the pilot valve 53E, the seal portion 145E and the support portion 146E are made of the same material.

[0135] As described above, the seal portion 145E is integrally connected to the valve disc 141. The support portion 146E is made of the same material as the seal portion 145E and, like the seal portion 145E, is integrally connected to the valve disc 141. The support portion 146E is spaced apart from the seal portion 145E in the radial direction of the valve disc 141. The support portion 146E also extends from a position more inward than the seal portion 145E in the radial direction of the valve disc 141. In other words, the support portion 146E is spaced apart a predetermined amount radially inward of the valve member 161 from the seal portion 145E and is integrally connected to the valve disc 141 of the valve member 161.

[0136] The seal portion 145E is slidably and liquid-tightly fitted over the entire periphery to the inner circumferential surface of the wall portion 72 of the pilot case 56, and constantly seals the gap between the pilot valve 53E and the wall portion 72.

[0137] The tip side of the support portion 146E abuts against the free valve 111. The support portion 146E presses the free valve 111 against the seat surfaces 84, 85 of the seat portion 80. One end of the support portion 146E is connected to the valve disc 141, and the other end abuts against the free valve 111, directly applying a biasing force to the valve disc 141 and the free valve 111 in the direction separating them.

[0138] The support portion 146E abuts against the free valve 111 opposite to a portion of the free valve 111 that seats on the seat portion 80. In other words, the portion of the support portion 146E that comes into contact with the free valve 111 overlaps the position of the portion of the free valve 111 that seats on the seat portion 80 in the radial direction of the free valve 111. Specifically, the portion of the support portion 146E that comes into contact with the free valve 111 overlaps the position of the portion of the free valve 111 that seats on the seat surface 85 of the free valve 111 in the radial direction of the free valve 111.

[0139] With the free valve 111 closing the outer through-hole 87, the space between the pilot valve 53E and the pilot case 56 and free valve 111 forms a back pressure chamber 151. A passage groove 148E formed in the support portion 146E of the pilot valve 53E serves as a communication passage 175E that allows a portion of the back pressure chamber 151 that is radially inward from the support portion 146E to communicate with a portion that is radially outward from the support portion 146E and that allows a portion of the back pressure chamber 151 that is radially outward from the support portion 146E to communicate with a portion that is radially inward from the support portion 146E. In other words, the support portion 146E of the pilot valve 53E has the communication passage 175E that allows communication with the inside of the back pressure chamber 151.

[0140] The support portion 146E of the pilot valve 53E biases the free valve 111 so that it abuts against the seat surfaces 84, 85. The free valve 111 moves against the biasing force of the support portion 146E and moves away from the seat surfaces 84, 85. The support portion 146E of the pilot valve 53E, the free valve 111, and the seat portion 80 and recess 82 of the bottom portion 71 of the pilot case 56 constitute a check valve 155E that restricts the flow of hydraulic oil L from the back pressure chamber 151 side to the variable chamber 152 side, i.e., the second chamber 20 side, while allowing the flow of hydraulic oil L from the variable chamber 152 side, i.e., the second chamber 20 side, to the back pressure chamber 151 side.

[0141] The shock absorber 1E has a hydraulic circuit similar to that of the shock absorber 1 of the first embodiment.

[0142] As described above, the shock absorber 1E of the third embodiment has each of the modified configurations of the shock absorber 1 of the first embodiment functioning in substantially the same manner as the configurations of the shock absorber 1 before the modifications, and therefore, even though it has each modified configuration, it can achieve substantially the same effects as the shock absorber 1.

[0143] In the shock absorber 1E, the seal portion 145E and the support portion 146E are integrally connected to the valve disc 141 that constitutes the valve member 161. Therefore, the number of parts in the shock absorber 1E can be further reduced, thereby reducing costs. Moreover, in the shock absorber 1E, the seal portion 145E and the support portion 146E are made of the same material, so it is easy to integrally connect the seal portion 145E and the support portion 146E to the valve disc 141, thereby further reducing costs.

[0144] In the shock absorber 1E, the support portion 146E is integrally connected to the valve disc 141 of the valve member 161 at a predetermined distance from the seal portion 145E radially inward of the valve member 161. Therefore, in the shock absorber 1E, when the support portion 146E and the seal portion 145E are vulcanization bonded to the valve disc 141, the position between the support portion 146E and the seal portion 145E of the valve disc 141 can be fixed to the device. Therefore, the shock absorber 1E can improve the manufacturability of the pilot valve 53E and stabilize the quality.

[0145] In the shock absorber 1E, the support portion 146E is spaced apart from the seal portion 145E radially inward of the valve member 161 and is integrally connected to the valve disc 141. Therefore, even if the shock absorber 1E is designed so that the radial distance between the seal portion 145E and the support portion 146E is large, an increase in the volume of the rubber material can be suppressed.

[0146] [Fourth embodiment] Next, a fourth embodiment of the shock absorber according to the present invention will be described, focusing on differences from the first embodiment, mainly with reference to Fig. 11. Note that parts common to the first embodiment will be designated by the same names and symbols.

[0147] 11 , the shock absorber 1G of the fourth embodiment has a valve opening control mechanism 182G, which is a partial modification of the valve opening control mechanism 182, instead of the valve opening control mechanism 182. The valve opening control mechanism 182G has a pilot valve 53G, which is partially different from the pilot valve 53, instead of the pilot valve 53.

[0148] The pilot valve 53G comprises a valve disc 141 similar to that of the shock absorber 1 of the first embodiment, and a rubber fixing member 142G fixed to the valve disc 141 by vulcanization adhesion.

[0149] The fixed member 142G is fixed to the valve disc 141 on the axially opposite side to the piston 18. The fixed member 142G has a seal portion 145G (seal member) and a support portion 146G (support member).

[0150] The seal portion 145G is fixed to the outer peripheral edge portion of the valve disc 141, opposite the piston 18 in the axial direction. The seal portion 145G is annular in shape. The seal portion 145G is fixed to the outer peripheral edge portion of the valve disc 141. The seal portion 145G extends from the valve disc 141 in the axial direction of the valve disc 141 to the side opposite the piston 18. The seal portion 145G has an expanding diameter shape in which both the inner diameter and the outer diameter become larger toward the extending tip.

[0151] The support portion 146G has an annular shape. The support portion 146G is provided at the end of the seal portion 145G on the opposite side of the valve disc 141 in the axial direction. The support portion 146G extends from the radially outer portion of the seal portion 145G along the axial direction of the seal portion 145G in the opposite direction to the valve disc 141. The support portion 146G is formed contiguous with the seal portion 145G. The support portion 146G has an annular shape coaxial with the seal portion 145G.

[0152] The support portion 146G is formed with a passage groove 148G that penetrates the support portion 146G in the radial direction of the support portion 146G. A plurality of passage grooves 148G are formed in the support portion 146G at equal intervals in the circumferential direction of the support portion 146G. In the fixing member 142G, the seal portion 145G and the support portion 146G are made of the same material and are formed seamlessly and integrally.

[0153] As described above, the seal portion 145G is integrally connected to the valve disc 141. Furthermore, the support portion 146G is made of the same material as the seal portion 145G, and is integrally connected to the seal portion 145G on the side opposite the valve disc 141. In other words, the support portion 146G extends from the end of the seal portion 145G in the thickness direction of the valve member 161 made up of the valve disc 52 and the valve disc 141. The support portion 146G extends from the radially outer portion of the seal portion 145G.

[0154] The seal portion 145G is slidably and liquid-tightly fitted over the entire periphery to the inner circumferential surface of the wall portion 72 of the pilot case 56, and constantly seals the gap between the pilot valve 53G and the wall portion 72.

[0155] The tip side of the support portion 146G abuts against the free valve 111. The support portion 146G presses the free valve 111 against the seat surfaces 84, 85 of the seat portion 80. One end of the support portion 146G in the axial direction of the valve disc 141 is connected to the seal portion 145G, and the other end abuts against the free valve 111, applying a biasing force in the separating direction to the seal portion 145G and the free valve 111. At that time, the support portion 146G applies a biasing force to the valve member 161 via the seal portion 145G. In other words, the support portion 146G indirectly applies a biasing force in the separating direction to the valve member 161 and the free valve 111.

[0156] The support portion 146G abuts against the free valve 111 opposite to a portion of the free valve 111 that seats on the seat portion 80. In other words, the portion of the support portion 146G that comes into contact with the free valve 111 overlaps the position of the portion of the free valve 111 that seats on the seat portion 80 in the radial direction of the free valve 111. Specifically, the portion of the support portion 146G that comes into contact with the free valve 111 overlaps the position of the portion of the free valve 111 that seats on the seat surface 84 of the free valve 111 in the radial direction of the free valve 111.

[0157] When the free valve 111 closes the outer through-hole 87 , a back pressure chamber 151 is formed between the pilot valve 53G and the pilot case 56 and the free valve 111 .

[0158] The support portion 146G of the fixing member 142G of the pilot valve 53G biases the free valve 111 so that it abuts against the seat surfaces 84, 85. The free valve 111 moves against the biasing force of the support portion 146G and moves away from the seat surfaces 84, 85. The support portion 146G of the pilot valve 53G, the free valve 111, and the seat portion 80 and recess 82 of the bottom 71 of the pilot case 56 constitute a check valve 155G that restricts the flow of hydraulic oil L from the back pressure chamber 151 side to the variable chamber 152 side, i.e., the second chamber 20 side, while allowing the flow of hydraulic oil L from the variable chamber 152 side, i.e., the second chamber 20 side, to the back pressure chamber 151 side. When the pressure in the variable chamber 152 becomes higher than the pressure in the back pressure chamber 151 by an amount greater than the biasing force of the support portion 146G of the pilot valve 53G, the free valve 111 lifts off the seat surfaces 84, 85 against the biasing force of the support portion 146G of the pilot valve 53G, thereby connecting the variable chamber 152 and the back pressure chamber 151.

[0159] The shock absorber 1G has a hydraulic circuit similar to that of the shock absorber 1 of the first embodiment.

[0160] In the shock absorber 1G of the fourth embodiment, a seal portion 145G and a support portion 146G are integrally connected to a valve disc 141 that constitutes a valve member 161G.

[0161] As described above, each of the configurations of the shock absorber 1G that have been modified relative to the shock absorber 1 of the first embodiment functions in substantially the same way as the configurations of the shock absorber 1 before the modifications, and therefore, even though it has each modified configuration, it can achieve substantially the same effects as the shock absorber 1.

[0162] Unlike the support portion 146, the support portion 146G of the shock absorber 1G does not divide the back pressure chamber in the radial direction, so the communication passage 175 is not necessary, which is advantageous in terms of cost.

[0163] [Fifth Embodiment] Next, a fifth embodiment of the shock absorber according to the present invention will be described, focusing on differences from the first embodiment, mainly with reference to Figures 12 and 13. Note that parts common to the first embodiment will be designated by the same names and symbols.

[0164] 12, a shock absorber 1H of the fifth embodiment has a valve opening control mechanism 182H, which is a partial modification of the valve opening control mechanism 182, instead of the valve opening control mechanism 182. Like the valve opening control mechanism 182, the valve opening control mechanism 182H has a valve member 161 (plate valve) made up of a valve disc 52 and a valve disc 141, which closes the opening of the flow path 162 on the side of the second chamber 20, as shown in FIG.

[0165] The valve opening control mechanism 182H has a pilot case 56H (partition member) that is partially different from the pilot case 56 instead of the pilot case 56.

[0166] The pilot case 56H has a seal groove 285 formed inward in the radial direction from the outer peripheral surface. The pilot case 56H has a bottom 71H instead of the bottom 71, which differs from the bottom 71 in that the seal groove 285 is formed.

[0167] The pilot case 56H has an inner cylindrical portion 73H that is partially different from the inner cylindrical portion 73, instead of the inner cylindrical portion 73. A step portion 281 is formed on the radially outer side of the inner cylindrical portion 73H. The end face of the step portion 281 opposite the bottom portion 71H in the axial direction is closer to the bottom 71H than the end face of the inner cylindrical portion 73H opposite the bottom 71H in the axial direction. An extension groove 282 is formed in the step portion 281 of the inner cylindrical portion 73H so as to extend the inner through-hole 88 of the bottom portion 71H in the axial direction of the inner cylindrical portion 73H.

[0168] Pilot case 56H has a wall portion 72H that is partially different from wall portion 72 in place of wall portion 72. The axial height of wall portion 72H from bottom portion 71H is lower than that of wall portion 72. Seal groove 285 is formed across bottom portion 71 and wall portion 72H.

[0169] The valve opening control mechanism 182H has a spool 291, a sealing member 145H which is an O-ring, and a pressing member 293.

[0170] The spool 291 has a tubular portion 301 and an inner flange portion 302. The tubular portion 301 is cylindrical. The inner flange portion 302 extends radially inward from one axial end of the tubular portion 301.

[0171] With the inner flange portion 302 disposed between the valve disc 141 and the wall portion 72H of the pilot case 56H, the spool 291 has the cylindrical portion 301 covering the radially outer side of the wall portion 72H. As a result, the spool 291 slides in the axial direction of the pilot case 56H relative to the pilot case 56H, with the cylindrical portion 301 guided by the wall portion 72H.

[0172] The seal member 145H is fitted into the seal groove 285. The seal member 145H seals the gap between the cylindrical portion 301 of the spool 291 and the wall portion 72H of the pilot case 56H. The seal member 145H seals the gap between the second chamber 20 and the wall portion 72H.

[0173] The valve disc 141 is disposed so as to cover an opening in the wall portion 72H of the pilot case 56H on the opposite side of the bottom portion 71H in the axial direction.

[0174] The pressing member 293 is made up of a metal disk 295 and a rubber support portion 146H fixed to the disk 295 by vulcanization adhesion.

[0175] Before being incorporated into the valve opening control mechanism 182H, the disk 295 is in the shape of a circular flat plate with holes and a constant thickness. The disk 295 has cutouts 296 formed on its outer periphery. The cutouts 296 penetrate the disk 295 in the axial direction of the disk 295. The cutouts 296 open radially outward from the disk 295. The disk 295 has a plurality of cutouts 296 formed at equal intervals around its periphery.

[0176] When the disk 295 is incorporated into the valve opening control mechanism 182H, it is deformed into a tapered shape and abuts against the end face of the stepped portion 281 of the pilot case 56H opposite the bottom portion 71H and the surface of the inner flange portion 302 of the spool 291 on the bottom portion 71H side. As a result, the disk 295 presses the inner flange portion 302 of the spool 291 against the valve disk 141.

[0177] The pressing member 293 has a support portion 146H that is annular. The support portion 146H is fixed to the disk 295 on the side opposite the piston 18 in the axial direction. In other words, the support portion 146H is integrally connected to the disk 295. The support portion 146H is fixed to a radially intermediate position of the disk 295. The support portion 146H extends from the disk 295 on the side opposite the piston 18 along the axial direction of the disk 295. The support portion 146H has a tapered shape in which both the inner and outer diameters decrease toward the extending tip. The support portion 146H is disposed between the stepped portion 281 and the wall portion 72H in the radial direction of the pilot case 56H. The notch 296 of the disk 295 is formed outward of the support portion 146H in the radial direction of the disk 295.

[0178] The support portion 146D is formed with a passage groove 148H that penetrates the support portion 146H in the radial direction of the support portion 146H. The support portion 146H is formed with a plurality of passage grooves 148H at equal intervals in the circumferential direction of the support portion 146H.

[0179] The tip side of the support portion 146H abuts against the free valve 111. The support portion 146H presses the free valve 111 against the seat surfaces 84, 85 of the seat portion 80. One end of the support portion 146H is connected to the disk 295, and the other end abuts against the free valve 111, applying a biasing force in the direction separating the disk 295 and the free valve 111. At that time, the support portion 146H applies a biasing force to the valve member 161 via the disk 295 and the spool 291. In other words, the support portion 146H indirectly applies a biasing force in the direction separating the valve member 161 and the free valve 111.

[0180] The support portion 146H abuts against the free valve 111 opposite to a portion of the free valve 111 that seats on the seat portion 80. In other words, the portion of the support portion 146H that comes into contact with the free valve 111 overlaps the position of the portion of the free valve 111 that seats on the seat portion 80 in the radial direction of the free valve 111. Specifically, the portion of the support portion 146H that comes into contact with the free valve 111 overlaps the position of the portion of the free valve 111 that seats on the seat surface 85 of the free valve 111 in the radial direction of the free valve 111.

[0181] With the free valve 111 closing the outer through-hole 87, the back pressure chamber 151 is formed between the valve disc 141, the spool 291, the pilot case 56H, and the free valve 111. A passage groove 148H formed in the support portion 146H of the pressing member 293 serves as a communication passage 175H that allows a portion of the back pressure chamber 151 that is radially inward from the support portion 146H to communicate with a portion that is radially outward from the support portion 146H and that allows a portion of the back pressure chamber 151 that is radially outward from the support portion 146H to communicate with a portion that is radially inward from the support portion 146H. In other words, the support portion 146H of the pressing member 293 has the communication passage 175H that allows communication with the inside of the back pressure chamber 151.

[0182] The support portion 146H of the pressing member 293 biases the free valve 111 so that it abuts against the seat surfaces 84, 85. The free valve 111 moves against the biasing force of the support portion 146H and moves away from the seat surfaces 84, 85. The support portion 146H of the pressing member 293, the free valve 111, and the seat portion 80 and recess 82 of the bottom portion 71H of the pilot case 56H constitute a check valve 155H that restricts the flow of oil liquid L from the back pressure chamber 151 side to the variable chamber 152 side, i.e., the second chamber 20 side, while allowing the flow of oil liquid L from the variable chamber 152 side, i.e., the second chamber 20 side, to the back pressure chamber 151 side.

[0183] As described above, the valve disc 52 can be seated on the valve seat portion 47 of the piston 18. The valve disc 141 abuts against the valve disc 52. The disc 295 of the pressing member 293 abuts against the spool 291 from the side opposite the valve disc 52. The back pressure chamber 151 generates a force in the valve closing direction on the valve member 161 made up of the valve disc 52 and the valve disc 141. The spool 291 receives pressure from the back pressure chamber 151 and transmits it to the valve disc 141. The support portion 146H generates a force between the spool 291 and free valve 111 in a direction separating them.

[0184] The shock absorber 1H has a hydraulic circuit similar to that of the shock absorber 1 of the first embodiment.

[0185] In the shock absorber 1H, during the extension stroke in which the piston rod 21 moves toward the extension side, the hydraulic oil L flowing from the first chamber 19 toward the back pressure chamber 151 reaches the back pressure chamber 151 via the flow path 172, the connecting path 173, and the passages in the extension groove 282. Then, in response to the pressure in the back pressure chamber 151 changing due to the flow of the hydraulic oil L, the damping force generating mechanism 41 operates in the same manner as the damping force generating mechanism 41 of the shock absorber 1 of the first embodiment. At that time, the free valve 111 operates in response to the piston frequency in the same manner as the free valve 111 of the shock absorber 1, and causes the opening of the valve member 161 of the damping force generating mechanism 41 to respond to the piston frequency. During the extension stroke, when the valve member 161 of the damping force generating mechanism 41 opens, the hydraulic oil L from the first chamber 19 flows into the second chamber 20 via the flow path 162.

[0186] During the compression stroke, the pressure in the second chamber 20 increases, and the pressure in the variable chamber 152 of the valve opening control mechanism 182H becomes higher than the pressure in the back pressure chamber 151. As a result, the free valve 111 of the check valve 155H lifts off the seat surfaces 84, 85 against the biasing force of the support portion 146H of the pressing member 293. In other words, the check valve 155H opens. Then, the oil L in the second chamber 20 flows into the first chamber 19 via the passage in the outer through-hole 87, the variable chamber 152, the back pressure chamber 151, the connecting passage 173, and the flow passage 172.

[0187] When the pressure in the second chamber 20 drops during a transition from the compression stroke to the extension stroke, the free valve 111 is instantly seated against the seat surfaces 84, 85 due to the biasing force of the support portion 146H of the pressing member 293. In other words, the check valve 155H is instantly closed. This prevents the oil L on the first chamber 19 side from flowing into the second chamber 20 through the check valve 155H during a transition from the compression stroke to the extension stroke, thereby suppressing a delay in the rise of the damping force at the initial stage of the extension stroke.

[0188] A shock absorber 1H of the fifth embodiment includes a valve member 161 that is provided in a flow path 162 and allows the oil liquid L in the first chamber 19 to flow into the second chamber 20, a pilot case 56H and a spool 291 that are connected to a flow path 172 that is at least partially parallel to the flow path 162 and that forms a back pressure chamber 151 that generates a force in the valve closing direction on the valve member 161, a free valve 111 that is disposed opposite a bottom 71H of the pilot case 56H and that deforms due to the pressure of the oil liquid L to vary the volume of the back pressure chamber 151, and a seal member 145H that seals between the second chamber 20 and a wall portion 72H. The shock absorber 1H also includes a support portion 146H that indirectly applies a biasing force in the separation direction to the valve member 161 and the free valve 111.

[0189] As described above, each of the configurations of the shock absorber 1H that have been changed compared to the shock absorber 1 of the first embodiment functions in almost the same way as the configurations of the shock absorber 1 before the changes, so even though it has each changed configuration, it can achieve almost the same effects as the shock absorber 1.

[0190] Furthermore, in the shock absorber 1H, a seal member 145H that seals the gap between the second chamber 20 and the wall portion 72H is provided separately from the valve member 161. Therefore, in the shock absorber 1H, the valve member 161 can open smoothly. Therefore, in the shock absorber 1H, the damping force generated by the valve member 161 can be reduced.

[0191] [Sixth embodiment] Next, a sixth embodiment of the shock absorber according to the present invention will be described, focusing on differences from the first and second embodiments, mainly based on Fig. 14. Note that parts common to the first and second embodiments will be designated by the same names and symbols.

[0192] 14, a shock absorber 1J of the sixth embodiment has a valve opening control mechanism 182J, which is a partial modification of the valve opening control mechanism 182, instead of the valve opening control mechanism 182. The valve opening control mechanism 182J has a pilot case 56 similar to that of the shock absorber 1 of the first embodiment, a pilot valve 53D similar to that of the shock absorber 1D of the second embodiment, and a support member 146J that is separate from the pilot valve 53D.

[0193] The pilot valve 53D has a seal portion 145D that is slidably and liquid-tightly fitted over the entire periphery to the inner circumferential surface of the wall portion 72 of the pilot case 56, and constantly seals the gap between the pilot valve 53D and the wall portion 72.

[0194] The support member 146J is a metal leaf spring, seamlessly formed by press molding from a flat plate of a constant thickness. The support member 146J is annular in shape and includes an inner plate portion 321, an intermediate plate portion 322, an outer plate portion 323, and an outer end plate portion 324. The inner plate portion 321, the intermediate plate portion 322, the outer plate portion 323, and the outer end plate portion 324 are all annular in shape and are all formed coaxially.

[0195] The inner plate portion 321 is tapered so that its diameter becomes larger toward one side in the axial direction. The intermediate plate portion 322 widens from the edge portion on the larger diameter side of the inner plate portion 321. The intermediate plate portion 322 is tapered so that its diameter becomes larger the further away it is from the inner plate portion 321 in the axial direction. The taper of the intermediate plate portion 322 is smaller than the taper of the inner plate portion 321. A passage hole 325 is formed in the intermediate plate portion 322, penetrating it in the thickness direction. A plurality of passage holes 325 are formed in the intermediate plate portion 322, at equal intervals around the circumferential direction of the intermediate plate portion 322.

[0196] The outer plate portion 323 spreads out from the edge portion of the intermediate plate portion 322 opposite to the inner plate portion 321. The outer plate portion 323 is tapered so that its diameter increases as it moves away from the intermediate plate portion 322 in the axial direction. The taper of the outer plate portion 323 is greater than the taper of the intermediate plate portion 322. The outer end plate portion 324 spreads outward in the radial direction from the edge portion of the outer plate portion 323 opposite to the intermediate plate portion 322. The outer end plate portion 324 is flat.

[0197] The support member 146J is disposed radially between the inner cylindrical portion 73 of the pilot case 56 and the seal portion 145D of the pilot valve 53D. The support member 146J is disposed axially between the valve disc 141 and the free valve 111 of the pilot case 56. The support member 146J abuts against the valve disc 141 at one axial end of the inner plate portion 321 opposite the intermediate plate portion 322. The support member 146J abuts against the free valve 111 at the other axial end, the outer end plate portion 324. As a result, the support member 146J presses the free valve 111 against the seat surfaces 84, 85 of the seat portion 80. One end of the support member 146J abuts against the valve disc 141 of the valve member 161, and the other end abuts against the free valve 111, applying a biasing force to the valve member 161 and the free valve 111 in the separating direction. In other words, the support member 146J directly applies a biasing force to the valve member 161 and the free valve 111 in the direction separating them.

[0198] The support member 146J abuts against the free valve 111 opposite the portion of the free valve 111 that seats on the seat portion 80. In other words, the portion of the support member 146J that comes into contact with the free valve 111 overlaps the position of the portion of the free valve 111 that seats on the seat portion 80 in the radial direction of the free valve 111. Specifically, the outer end plate portion 324 of the support member 146J, which is the portion that comes into contact with the free valve 111, overlaps the position of the portion that seats on the seat surface 84 of the free valve 111 in the radial direction of the free valve 111.

[0199] With the free valve 111 closing the outer through-hole 87, the space between the pilot valve 53D and the pilot case 56 and the free valve 111 forms a back pressure chamber 151. A passage hole 148J formed in the support member 146J serves as a communication passage 175J that allows a portion of the back pressure chamber 151 that is radially inward from the support member 146J to communicate with a portion that is radially outward from the support member 146J and that allows a portion of the back pressure chamber 151 that is radially outward from the support member 146J to communicate with a portion that is radially inward from the support member 146J. In other words, the support member 146J has a communication passage 175J that allows communication within the back pressure chamber 151.

[0200] The support member 146J biases the free valve 111 so that it abuts against the seat surfaces 84, 85. The free valve 111 moves against the biasing force of the support member 146J and moves away from the seat surfaces 84, 85. The support member 146J, the free valve 111, and the seat portion 80 and recess 82 of the bottom portion 71 of the pilot case 56 constitute a check valve 155J that restricts the flow of hydraulic oil L from the back pressure chamber 151 side to the variable chamber 152 side, i.e., the second chamber 20 side, while allowing the flow of hydraulic oil L from the variable chamber 152 side, i.e., the second chamber 20 side, to the back pressure chamber 151 side.

[0201] As described above, the valve disc 52 can be seated on the valve seat portion 47 of the piston 18. The valve disc 141 of the pilot valve 53D abuts against the valve disc 52. The back pressure chamber 151 generates a force in the valve closing direction on a valve member 161 made up of the valve disc 52 and the valve disc 141 of the pilot valve 53D.

[0202] The shock absorber 1J has a hydraulic circuit similar to that of the shock absorber 1 of the first embodiment.

[0203] As described above, the shock absorber 1J has modified configurations compared to the shock absorbers 1 and 1D of the first and second embodiments, and therefore functions in substantially the same manner as the configurations of the shock absorbers 1 and 1D before the modifications. Therefore, even though it has modified configurations, it can achieve substantially the same effects as the shock absorbers 1 and 1D.

[0204] Furthermore, even if the specifications of the pilot valve 53D of the shock absorber 1J are changed, the support member 146J can be adapted to the change without being changed.

[0205] [Seventh embodiment] Next, a seventh embodiment of the shock absorber according to the present invention will be described, focusing on differences from the first and sixth embodiments, mainly based on Fig. 15. Note that parts common to the first and sixth embodiments will be designated by the same names and symbols.

[0206] 15, the shock absorber 1K of the seventh embodiment has a valve opening control mechanism 182K, which is a partial modification of the valve opening control mechanism 182J, instead of the valve opening control mechanism 182J. The valve opening control mechanism 182J has a pilot case 56 and a pilot valve 53D, and a valve member 331, similar to those of the shock absorber 1J of the sixth embodiment.

[0207] The valve member 331 is a free valve 111 similar to the shock absorber 1J of the sixth embodiment, but with a support portion 146K provided thereto. The valve member 331 is formed by fastening the rubber support portion 146K to the free valve 111 by vulcanization adhesion.

[0208] The support portion 146K has an annular shape. The support portion 146K is fixed to the piston 18 side of the free valve 111 in the axial direction. The support portion 146K is fixed to the inner peripheral edge portion of the free valve 111 in the radial direction. In other words, the support portion 146K is integrally connected to the free valve 111. The support portion 146K extends from the free valve 111 toward the piston 18 along the axial direction of the free valve 111. The support portion 146K is disposed between the inner cylindrical portion 73 of the pilot case 56 and the seal portion 145D of the pilot valve 53D in the radial direction.

[0209] The support portion 146K is formed with a passage groove 148K that penetrates the support portion 146K in the radial direction of the support portion 146K. The passage groove 148K opens at the tip of the support portion 146K opposite the free valve 111. The support portion 146K is formed with a plurality of passage grooves 148K at equal intervals in the circumferential direction of the support portion 146K.

[0210] The tip side of the support portion 146K abuts against the valve disc 141 of the pilot valve 53D. The support portion 146K presses the free valve 111 against the seat surfaces 84, 85 of the seat portion 80 by the reaction force from the valve disc 141. One end of the support portion 146K is connected to the free valve 111, and the other end abuts against the valve disc 141 of the valve member 161, directly applying a biasing force in the separating direction to the valve member 161 and the free valve 111. The support portion 146K is connected to the free valve 111 opposite the portion of the free valve 111 that seats on the seat portion 80. In other words, the portion of the support portion 146K that is connected to the free valve 111 overlaps the portion of the free valve 111 that seats on the seat portion 80 in the radial direction of the free valve 111. Specifically, the support portion 146K has a connection portion with the free valve 111 that is positioned so that the portion that seats on the seat surface 85 of the free valve 111 overlaps the radial position of the free valve 111 .

[0211] When the valve member 331 closes the outer through-hole 87 with the free valve 111, a back pressure chamber 151 is formed between the pilot valve 53D and the pilot case 56 / free valve 111. A passage groove 148K formed in the support portion 146K of the valve member 331 defines a communication passage 175K that connects a portion of the back pressure chamber 151 that is radially inward from the support portion 146K to a portion that is radially outward from the support portion 146K and a portion of the back pressure chamber 151 that is radially outward from the support portion 146K to a portion that is radially inward from the support portion 146K. In other words, the support portion 146K of the valve member 331 has a communication passage 175K that connects the inside of the back pressure chamber 151. The back pressure chamber 151 generates a force in a valve closing direction on a valve member 161 that is composed of the valve disc 52 and the valve disc 141 of the pilot valve 53D.

[0212] The support portion 146K of the valve member 331 biases the free valve 111 so that it abuts against the seat surfaces 84, 85. The free valve 111 moves against the biasing force of the support portion 146K and moves away from the seat surfaces 84, 85. The support portion 146K and free valve 111 of the valve member 331, and the seat portion 80 and recess 82 of the bottom portion 71 of the pilot case 56 constitute a check valve 155K that restricts the flow of hydraulic oil L from the back pressure chamber 151 side to the variable chamber 152 side, i.e., the second chamber 20 side, while allowing the flow of hydraulic oil L from the variable chamber 152 side, i.e., the second chamber 20 side, to the back pressure chamber 151 side.

[0213] The shock absorber 1K has a hydraulic circuit similar to that of the shock absorber 1 of the first embodiment.

[0214] As described above, the shock absorber 1K has modified configurations compared to the shock absorbers 1 and 1J of the first and sixth embodiments, which function in substantially the same manner as the configurations of the shock absorbers 1 and 1J before the modifications. Therefore, even though it has modified configurations, it can achieve substantially the same effects as the shock absorbers 1 and 1J.

[0215] Furthermore, even if the specifications of the pilot valve 53D of the shock absorber 1K are changed, the valve member 331 can be adapted to the change.

[0216] [Eighth Embodiment] Next, an eighth embodiment of a shock absorber according to the present invention will be described, focusing on differences from the first embodiment, mainly with reference to Figures 16 to 18. Note that parts common to the first embodiment will be designated by the same names and symbols.

[0217] 16, a shock absorber 1L of the eighth embodiment has a piston rod 21L (shaft-shaped member) that is partially different from the piston rod 21, instead of the piston rod 21. The piston rod 21L has a passage hole 351 formed therein. The piston rod 21L has a main shaft portion 27L that is different from the main shaft portion 27 in that a portion of the passage hole 351 is formed therein, and a mounting shaft portion 28L that is different from the mounting shaft portion 28 in that the remaining portion of the passage hole 351 is formed therein.

[0218] The passage hole 351 has a radial hole portion 352 , an axial hole portion 353 , and a radial hole portion 354 .

[0219] The radial hole 352 penetrates the main shaft portion 27L in the radial direction of the main shaft portion 27L. The radial hole 352 is formed in a portion of the main shaft portion 27L on the mounting shaft portion 28L side in the axial direction. The radial hole 352 opens to the first chamber 19.

[0220] The axial hole portion 353 extends from the center of the radial hole portion 352 in the radial direction of the main shaft portion 27L along the axial direction of the piston rod 21L. The axial hole portion 353 extends from the radial hole portion 352 to the end face of the mounting shaft portion 28L on the axial side opposite to the main shaft portion 27L.

[0221] The radial hole 354 penetrates the mounting shaft portion 28L in the radial direction of the mounting shaft portion 28L. The radial hole 354 is formed in a portion of the mounting shaft portion 28L between the main shaft portion 27L and the male thread 31 in the axial direction. The radial hole 354 intersects with the axial hole 353.

[0222] The mounting shaft portion 28L is formed with an annular passage groove 30L that is recessed radially inward from the outer peripheral surface of the mounting shaft portion 28L. The passage groove 30L is formed in a portion of the mounting shaft portion 28L in the axial direction between the main shaft portion 27L and the male thread 31. A radial hole 354 opens into the radially inner bottom surface of the passage groove 30L.

[0223] The shock absorber 1L has a blocking member 361 that is fitted into an end of the axial hole portion 353 on the opposite side in the axial direction from the radial hole portion 532. The blocking member 361 is fitted into and fixed to a portion of the axial hole portion 353 that is on the opposite side in the axial direction from the radial hole portion 352 than the radial hole portion 354. The blocking member 361 blocks a portion of the axial hole portion 353 that is on the opposite side in the axial direction from the radial hole portion 352 than the radial hole portion 354.

[0224] The shock absorber 1L has a piston 18L (divided member) that is partially different from the piston 18, instead of the piston 18. The piston 18L has a piston body 33L that is partially different from the piston body 33, instead of the piston body 33. The piston body 33L has an insertion hole 44L that is partially different from the insertion hole 44, instead of the insertion hole 44. The insertion hole 44L has an inner diameter equal to the small diameter hole portion 45 of the insertion hole 44 over almost the entire axial length of the piston body 33L. In other words, the large diameter hole portion 46 of the insertion hole 44 is not formed in the insertion hole 44L. The piston body 33L has an inner seat portion 48L, instead of the inner seat portion 48, that differs from the inner seat portion 48 in that the inner diameter of the inner seat portion 48 is smaller than the inner diameter of the inner seat portion 48 due to the formation of the insertion hole 44L.

[0225] In the shock absorber 1L, the configuration between the piston 18L and the retainer 221 is different from the configuration between the piston 18 and the retainer 221 of the shock absorber 1 of the first embodiment.

[0226] 17, the shock absorber 1L has, on the valve seat portion 47 and inner seat portion 48L side of the piston 18L, in order from the piston 18L side in the axial direction, one disc 51L, a valve disc 52 similar to that of the shock absorber 1 of the first embodiment described above, multiple discs 373, multiple discs 374, one disc 375, and one disc 376. The discs 51L, 373 to 376 and the valve disc 52 are all made of metal, and each is in the form of a perforated circular flat plate of a certain thickness into which the mounting shaft portion 28L of the piston rod 21L can be fitted.

[0227] The disk 51L has an outer diameter that is smaller than the inner diameter of the valve seat portion 47 and larger than the outer diameter of the inner seat portion 48L.

[0228] The valve disc 52 and the discs 373, 374 constitute a valve member 161L that is removably seated on the valve seat portion 47. The valve member 161L, together with the valve seat portion 47 of the piston 18L, constitutes an extension-side damping force generating mechanism 41L.

[0229] The valve member 161L abuts against the valve seat portion 47 of the valve disc 52, and opens and closes the opening of the piston passage 39 by moving away from and abutting against the valve seat portion 47. A notch 131 formed in the valve disc 52 radially crosses the valve seat portion 47. Therefore, the inside of the notch 131 forms a fixed orifice 132L that constantly connects the piston passage 39 to the second chamber 20.

[0230] When the valve member 161L is released from the valve seat portion 47 and opens, it causes the oil liquid L in the first chamber 19 shown in FIG. 15 to flow into the second chamber 20 via the piston passage 39 and the passage between the valve member 161L and the valve seat portion 47. The piston passage 39 formed inside the plurality of passage holes 35 and the passage groove 36, and the space between the valve member 161L and the valve seat portion 47 form a flow path 162L. In other words, the piston passage 39, the fixed orifice 132L shown in FIG. 16, and the space between the spaced-apart valve member 161L and the valve seat portion 47 form the flow path 162L through which the oil liquid L flows as a fluid flowing out of the first chamber 19, which is one of the first chamber 19 and the second chamber 20 shown in FIG. 15. 16 communicates the first chamber 19 and the second chamber 20 shown in FIG. 15 through the flow path 162L even when the valve disc 52 of the valve member 161L is in contact with the valve seat portion 47. The valve member 161L, which is made up of the valve disc 52 and the discs 373 and 374, closes the opening of the flow path 162L on the second chamber 20 side.

[0231] 16 , on the axially opposite side of the disk 376 from the piston 18L, there are provided, in order from the disk 376 side, one pilot case 56L (partition member), one disk 391, one disk 392, one pilot valve 53 similar to that of the shock absorber 1 of the first embodiment, one seat member 395, one disk 396, and one annular member 60 similar to that of the shock absorber 1, with the mounting shaft portion 28L of the piston rod 21L fitted inside each of them. The disks 391, 392, 396, the pilot case 56L, and the seat member 395 can be made of metal, for example, but any material may be used. The disks 391, 392, 396 are each a perforated circular flat plate of a certain thickness, into which the mounting shaft portion 28L of the piston rod 21L can be fitted. The pilot valve 53, the pilot case 56L, and the seat member 395 are all formed in an annular shape, inside which the mounting shaft portion 28L of the piston rod 21L can be fitted.

[0232] The pilot case 56L is cylindrical and has a bottom, with a rod insertion hole 70L formed in its radial center, which passes through the pilot case 56L in the axial direction. The pilot case 56L has a perforated, disc-shaped bottom 71L, a wall 72 similar to that of the pilot case 56 and extending from the outer peripheral edge of the bottom 71L to one side along the axial direction of the bottom 71L, and a cylindrical inner cylindrical portion 73L extending from the inner peripheral edge of the bottom 71L to the same side as the wall 72 along the axial direction of the bottom 71L. The pilot case 56L is attached to the piston rod 21L so that the wall 72 and the inner cylindrical portion 73L extend from the bottom 71L in a direction opposite to the piston 18L.

[0233] The bottom 71L has a seat portion 74L formed on the radial center side opposite the wall portion 72 and the inner cylindrical portion 73L in the axial direction of the bottom 71L. The seat portion 74L protrudes further toward the opposite side of the wall portion 72 and the inner cylindrical portion 73L in the axial direction of the bottom 71L than the radial outer side. The pilot case 56L abuts against the disk 376.

[0234] The bottom portion 71L is formed with a seat portion 80 similar to the pilot case 56 and a recessed portion 82 similar to the pilot case 56 on the side of the wall portion 72 and the inner cylindrical portion 73L in the axial direction of the bottom portion 71L. The seat portion 80 and the recessed portion 82 are formed at a position between the wall portion 72 and the inner cylindrical portion 73L in the radial direction of the bottom portion 71L. Seat surfaces 84, 85 of the seat portion 80 are both flat, annular shapes that extend perpendicular to the central axis of the bottom portion 71L and are arranged on the same plane.

[0235] An outer through-hole 87 similar to that of the pilot case 56 is formed in the bottom portion 71L at the center of the width of the recess 82 in the radial direction of the bottom portion 71L, penetrating along the axial direction of the bottom portion 71L. A plurality of outer through-holes 87 are formed in the bottom portion 71L at intervals in the circumferential direction of the bottom portion 71L. It is sufficient that at least one outer through-hole 87 is provided in the bottom portion 71L. The outer through-hole 87 is formed outward of the seat portion 74L in the radial direction of the bottom portion 71L.

[0236] The rod insertion hole 70L has a large diameter hole portion 101L and a small diameter hole portion 102L. The large diameter hole portion 101L has a larger diameter than the small diameter hole portion 102L. The small diameter hole portion 102L is formed in the bottom portion 71L. The large diameter hole portion 101L is formed in the inner cylindrical portion 73L. In the rod insertion hole 70L, the mounting shaft portion 28L of the piston rod 21L is fitted into the small diameter hole portion 102L. In the axial direction of the piston rod 21L, the large diameter hole portion 101L is positioned overlapping the passage groove 30L of the piston rod 21L. As a result, the passage within the large diameter hole portion 101L of the pilot case 56L is connected to the passage within the passage groove 30L of the piston rod 21L. A portion of the mounting shaft portion 28L of the piston rod 21L is disposed within the pilot case 56L.

[0237] A free valve 111 similar to that of the shock absorber 1 of the first embodiment is disposed inside the pilot case 56L, facing the wall portion 72 side of the bottom portion 71L in the axial direction.

[0238] As a result of the above, the bottom 71L of the pilot case 56L has a recess 82 covered by the free valve 111 and a seat portion 80 that abuts against the free valve 111, and has an outer through hole 87 that penetrates the bottom 71L at the position of the recess 82.

[0239] The disk 391 has an outer diameter larger than that of the inner cylindrical portion 73L. The disk 391 is formed with a notch 401 that extends radially outward from the inner peripheral edge that fits onto the mounting shaft 28L of the piston rod 21L to a position outside the inner cylindrical portion 73L. The passage within the notch 401 is constantly in communication with the passage within the passage groove 30L of the piston rod 21L.

[0240] The disk 392 has an outer diameter smaller than that of the disk 391. A notch 401 formed in the disk 391 crosses the disk 392 in the radial direction.

[0241] The pilot valve 53 is similar to the shock absorber 1 of the first embodiment and includes a valve disc 141 (first valve member) and a fixed member 142. The pilot valve 53 is positioned such that the fixed member 142 faces the piston 18L in the axial direction of the piston rod 21L relative to the valve disc 141. The pilot valve 53 has a seal portion 145 of the fixed member 142 slidably and liquid-tightly fitted over the entire periphery to the inner circumferential surface of the wall portion 72 of the pilot case 56L, thereby constantly sealing the gap between the pilot valve 53 and the wall portion 72. In this case, the valve disc 141 covers the opening of the wall portion 72 on the opposite side of the bottom portion 71L in the axial direction of the pilot case 56L.

[0242] The seat member 395 is disk-shaped and has a through-hole 411 formed in its radial center, passing through the seat member 395 in the axial direction of the seat member 395. The seat member 395 has a bottom portion 412, an inner seat portion 413, and a valve seat portion 414.

[0243] The bottom portion 412 is a perforated disk. The inner seat portion 413 is annular and protrudes from the inner peripheral side of the bottom portion 412 to one side in the axial direction of the bottom portion 412. The valve seat portion 414 is annular and located radially outward of the inner seat portion 413. The valve seat portion 414 protrudes from the bottom portion 412 to the same side as the inner seat portion 413 along the axial direction of the bottom portion 412.

[0244] A passage recess 415 is formed between the inner seat portion 413 and the valve seat portion 414. The passage recess 415 is surrounded by the inner seat portion 413 and the valve seat portion 414. The passage recess 415 is continuous around the entire circumference of the seat member 395. The passage recess 415 is recessed in the axial direction of the seat member 395 from the tip surface on the protruding side of the inner seat portion 413 and the tip surface on the protruding side of the valve seat portion 414. The bottom surface of the passage recess 415 is formed by the bottom portion 412.

[0245] A passage groove 416 is formed in the inner seat portion 413 and in a portion of the bottom portion 412 on the inner seat portion 413 side in the axial direction, penetrating the inner seat portion 413 in the radial direction of the inner seat portion 413. The passage groove 416 overlaps with the passage recess 415 in the radial direction of the bottom portion 412 and opens into the passage recess 415. A plurality of passage grooves 416 are formed in the seat member 395 at intervals in the circumferential direction of the seat member 395. It is sufficient that at least one passage groove 416 is provided in the seat member 395.

[0246] The through hole 411 has a large diameter hole portion 421 and a small diameter hole portion 422. The large diameter hole portion 421 has a larger diameter than the small diameter hole portion 422. The small diameter hole portion 422 is formed in the bottom portion 412. The large diameter hole portion 421 is formed in the inner seat portion 413 and in a portion of the bottom portion 412 on the inner seat portion 413 side in the axial direction. In the seat member 395, the large diameter hole portion 421 is formed to a position deeper than the bottom surface of the passage groove 416. The mounting shaft portion 28L of the piston rod 21L is fitted into the small diameter hole portion 422 of the through hole 411 of the seat member 395. In the axial direction of the piston rod 21L, the large diameter hole portion 421 is positioned overlapping the passage groove 30L of the piston rod 21L. As a result, the passage in the large diameter hole portion 421 of the seat member 395 is connected to the passage in the passage groove 30 of the piston rod 21. A portion of the mounting shaft portion 28L of the piston rod 21L is disposed inside the pilot case 56L.

[0247] The passage in the passage hole 351 of the piston rod 21L, the passage in the passage groove 30, the passage in the large diameter hole portion 101L of the pilot case 56L, and the passage in the large diameter hole portion 421 of the seat member 395 form a rod side chamber 105L.

[0248] The pilot valve 53 has a valve disc 141 with an outer diameter larger than the outer diameter of a valve seat portion 414 of the seat member 395. The valve disc 141 abuts against the valve seat portion 414, and opens and closes the passage in the passage recess 415 by moving away from and abutting against the valve seat portion 414.

[0249] The tip end side of the support portion 146 of the pilot valve 53 abuts against the free valve 111. The support portion 146 presses the free valve 111 against the seat surfaces 84, 85 of the seat portion 80. One end of the support portion 146 is connected to the valve disc 141, and the other end abuts against the free valve 111, directly applying a biasing force to the valve disc 141 and the free valve 111 in the direction separating them.

[0250] The support portion 146 abuts against the free valve 111 opposite to a portion of the free valve 111 that seats on the seat portion 80. In other words, the portion of the support portion 146 that comes into contact with the free valve 111 overlaps the position of the portion of the free valve 111 that seats on the seat portion 80 in the radial direction of the free valve 111. Specifically, the portion of the support portion 146 that comes into contact with the free valve 111 overlaps the position of the portion of the free valve 111 that seats on the seat surface 85 of the free valve 111 in the radial direction of the free valve 111.

[0251] With the free valve 111 closing the outer through-hole 87, the space between the pilot valve 53, the pilot case 56L, and the free valve 111 forms a back pressure chamber 151, and the space between the bottom 71L of the pilot case 56L and the free valve 111 forms a variable chamber 152. Thus, these two chambers, the back pressure chamber 151 and the variable chamber 152, are defined by the free valve 111 within the pilot case 56L.

[0252] The passage in the cutout portion 401 of the disk 391 forms an orifice 431. The back pressure chamber 151 is constantly in communication with the first chamber 19 shown in Fig. 16 via the orifice 431, a passage in the large diameter hole portion 101L of the pilot case 56L, a passage in the passage groove 30L of the piston rod 21L, and a passage in the passage hole 351 of the piston rod 21L. As shown in Fig. 26, the variable chamber 152 is constantly in communication with the second chamber 20 via the passage in the outer through-hole 87.

[0253] The support portion 146 of the fixing member 142 of the pilot valve 53 biases the free valve 111 so that it abuts against the seat surfaces 84, 85. The free valve 111 moves against the biasing force of the support portion 146 and moves away from the seat surfaces 84, 85. The support portion 146 of the pilot valve 53, the free valve 111, and the seat portion 80 and recess 82 of the bottom 71L of the pilot case 56L constitute a check valve 155L that restricts the flow of hydraulic oil L from the back pressure chamber 151 side to the variable chamber 152 side, i.e., the second chamber 20 side, while allowing the flow of hydraulic oil L from the variable chamber 152 side, i.e., the second chamber 20 side, to the back pressure chamber 151 side.

[0254] The valve disc 141 of the pilot valve 53, together with the valve seat portion 414 of the seat member 395, constitutes a damping force generating mechanism 432. When the valve disc 141 is released from the valve seat portion 414 and opens, it causes the oil L in the first chamber 19 shown in Fig. 16 to flow into the second chamber 20 via the passage in the passage hole 351 of the piston rod 21L, the passage in the passage groove 30L of the piston rod 21L, the passage in the large diameter hole portion 421 of the seat member 395 shown in Fig. 17, the passage in the passage groove 416 of the seat member 395, the passage in the passage recess 415 of the seat member 395, and the passage between the valve disc 141 and the valve seat portion 414.

[0255] The passage in the passage hole 351 of the piston rod 21L, the passage in the passage groove 30L of the piston rod 21L, the passage in the large diameter hole portion 101L of the pilot case 56L, the passage in the large diameter hole portion 421 of the seat member 395, the passage in the passage groove 416 of the seat member 395, the passage in the passage recess 415 of the seat member 395, and the passage between the valve disc 141 and the valve seat portion 414 constitute a flow path 435 (first flow path) that communicates between the first chamber 19 and the second chamber 20 shown in FIG. 15 . In other words, the passage within the passage hole 351 of the piston rod 21L, the passage within the passage groove 30L of the piston rod 21L, the passage within the large-diameter hole portion 101L of the pilot case 56L, the passage within the large-diameter hole portion 421 of the seat member 395, the passage within the passage groove 416 of the seat member 395, the passage within the passage recess 415 of the seat member 395, and the passage between the valve disc 141 and the valve seat portion 414 form a flow path 435 through which oil flows as a fluid flowing out from the first chamber 19, which is one of the first chamber 19 and the second chamber 20 shown in FIG. 15 . The rod-side chamber 105L is a part of the flow path 435. The passage within the passage groove 416 of the seat member 395 forms an orifice 436 that throttles the flow path 435.

[0256] The flow path 435 serves as an extension-side flow path through which oil L flows as a fluid from the first chamber 19 to the second chamber 20 when the piston 18L moves toward the first chamber 19 shown in FIG. 15 , i.e., during the extension stroke. An extension-side damping force generating mechanism 432, consisting of the valve seat portion 414 and the valve disc 141, is provided in the flow path 435, and generates a damping force by opening and closing the flow path 435 with the valve disc 141 to suppress the flow of oil L. In other words, the valve disc 141 is provided in the flow path 435 and generates a damping force by suppressing the flow of oil L caused by the sliding of the piston 18L toward the extension side. In yet other words, the valve disc 141 allows oil from the first chamber 19, which is one of the first chamber 19 and the second chamber 20, to flow to the second chamber 20, which is the other chamber.

[0257] The back pressure chamber 151 is constantly in communication with the first chamber 19 shown in Fig. 16 via an orifice 431 shown in Fig. 17 , a passage in the large diameter hole 101L of the pilot case 56L, a passage in the passage groove 30L of the piston rod 21L, and a passage in the passage hole 351 of the piston rod 21L. As shown in Fig. 17 , the passage in the passage hole 351 of the piston rod 21L, the passage in the passage groove 30L of the piston rod 21L, the passage in the large diameter hole 101L of the pilot case 56L, the passage in the large diameter hole 421 of the seat member 395, and the orifice 431 form a flow path 438 (second flow path) that connects the first chamber 19 shown in Fig. 16 with the back pressure chamber 151. The orifice 431 shown in Fig. 17 narrows the flow path area of ​​the flow path 438.

[0258] The flow path 438 is at least partially parallel to the flow path 435. Specifically, the flow path 438 is shared with the flow path 435 by the passage hole 351 of the piston rod 21L, the passage groove 30L of the piston rod 21L, the passage large-diameter hole 101L of the pilot case 56L, and the passage large-diameter hole 421 of the seat member 395, and the orifice 431 is arranged in parallel with the orifice 436 of the flow path 435 and the passage recess 415. Here, as described above, the passage in the passage hole 351 of the piston rod 21L, the passage groove 30L of the piston rod 21L, the passage large-diameter hole 101L of the pilot case 56L, and the passage large-diameter hole 421 of the seat member 395 constitute the rod-side chamber 105L. Therefore, the rod-side chamber 105L is part of the flow path 435 and part of the flow path 438.

[0259] As a result of the above, the pilot case 56L, which has the bottom 71L and the wall 72 and is penetrated by the piston rod 21L, forms a back pressure chamber 151 that is connected to the flow path 438 and generates a force in the valve closing direction on the valve disc 141. The back pressure chamber 151 between the pilot valve 53, the pilot case 56L, and the free valve 111 applies internal pressure to the valve disc 141 of the pilot valve 53 in the direction of the seat member 395, i.e., the valve closing direction that seats the valve disc 141 on the valve seat portion 414. The valve opening pressure of the valve disc 141 (damping force generating mechanism 432) is adjusted by the pressure in this back pressure chamber 151.

[0260] The free valve 111 is disposed opposite the bottom 71L of the pilot case 56L and is a volume variable member that deforms due to the pressure of the hydraulic fluid L to vary the volume of the back pressure chamber 151. The seal portion 145 of the pilot valve 53 seals between the pilot valve 53 and the wall portion 72, blocking communication between the second chamber 20 and the back pressure chamber 151. The seal portion 145 of the pilot valve 53 seals between the second chamber 20 and the wall portion 72. The support portion 146 of the pilot valve 53 directly or indirectly applies a biasing force to the valve disc 141 and the free valve 111 in the separating direction. Specifically, the support portion 146 of the pilot valve 53 directly applies a biasing force to the valve disc 141 and the free valve 111 in the separating direction. A passage groove 148 formed in the support portion 146 of the pilot valve 53 serves as a communication passage 175 that allows a portion of the back pressure chamber 151 that is radially inward of the support portion 146 to communicate with a portion that is radially outward of the support portion 146 and that allows a portion of the back pressure chamber 151 that is radially outward of the support portion 146 to communicate with a portion that is radially inward of the support portion 146. In other words, the support portion 146 of the pilot valve 53 has the communication passage 175 that allows communication within the back pressure chamber 151.

[0261] The pilot case 56L, the pilot valve 53, and the free valve 111 constitute a valve opening control mechanism 182L which has a back pressure chamber 151 and applies back pressure to the valve disc 141 of the pilot valve 53 to control the opening of the valve.

[0262] The disk 396 has an outer diameter smaller than that of the annular member 60. The annular member 60 has an outer diameter smaller than that of the seat member 395.

[0263] The check valve 155L, which is composed of the support portion 146 of the pilot valve 53, the free valve 111, and the bottom portion 71L of the pilot case 56L, is provided between the back pressure chamber 151 and the variable chamber 152 and the passage in the outer through hole 87, and restricts the flow of oil liquid L from the back pressure chamber 151 to the second chamber 20 via the variable chamber 152 and the passage in the outer through hole 87, while allowing the flow of oil liquid L from the second chamber 20 to the back pressure chamber 151 via the passage in the outer through hole 87 and the variable chamber 152.

[0264] The valve disc 141 of the pilot valve 53 leaves the valve seat 414 when the pressure in the back pressure chamber 151 reaches a predetermined pressure. The valve disc 141, together with the valve seat 75, constitutes the damping force generation mechanism 432, which opens and generates a damping force when the pressure in the back pressure chamber 151 reaches a predetermined pressure. The damping force generation mechanism 432 is provided in a portion of the flow path 435 that is parallel to the flow path 438. The damping force generation mechanism 432 is provided outside the pilot case 56L. When the valve disc 141 leaves the valve seat 414 and opens, it allows the oil L in the first chamber 19 to flow through the flow path 435 to the second chamber 20. When the valve disc 141 seats on the valve seat 414 and closes, it blocks communication between the flow path 435 and the second chamber 20.

[0265] FIG. 18 shows a hydraulic circuit diagram of the configuration provided in the piston rod 21L of the shock absorber 1L configured as described above. As shown in FIG. 18, the shock absorber 1L is provided with flow paths 435, 438 that connect the first chamber 19 and the second chamber 20 and include the rod-side chamber 105L. The flow path 438, which includes the orifice 431, is connected to the back pressure chamber 151. A damping force generating mechanism 432 is provided on the second chamber 20 side of the flow path 435, which includes the orifice 436. The pressure in the back pressure chamber 151 acts on the valve disc 141 of the damping force generating mechanism 432. The back pressure chamber 151 is separated from the variable pressure chamber 152 by the free valve 111. The variable pressure chamber 152 is connected to the second chamber 20. A check valve 155L is provided between the second chamber 20 and the back pressure chamber 151. A flow path 162L and a flow path 210 are provided to connect the first chamber 19 and the second chamber 20. The flow path 162L is provided with a damping force generating mechanism 41L including a valve member 161L. The flow path 210 is provided with a damping force generating mechanism 42 including a valve member 212. The flow path 162L and the flow path 210 are provided with a fixed orifice 132L of the damping force generating mechanism 41L and a fixed orifice 213 of the damping force generating mechanism 42.

[0266] Next, the operation of the shock absorber 1L will be described.

[0267] Assuming that the valve opening control mechanism 182L does not function as a damping force variable mechanism during the extension stroke in which the piston rod 21L moves toward the extension side, when the piston speed is slow, the oil L from the first chamber 19 flows from the piston passage 39 of the piston 18L to the second chamber 20 via the fixed orifice 132L of the valve member 161L of the damping force generating mechanism 41L, generating a damping force with orifice characteristics (the damping force is approximately proportional to the square of the piston speed). Therefore, the damping force characteristic relative to the piston speed is such that the rate of increase in the damping force becomes relatively high as the piston speed increases.

[0268] When the piston speed increases, the oil L from the first chamber 19 opens the valve disc 141, which is the main valve of the damping force generating mechanism 432, and flows into the second chamber 20 via a flow path 435 that includes the gap between the valve disc 141 and the valve seat portion 414 of the seat member 395, generating a damping force with valve characteristics (the damping force is approximately proportional to the piston speed). Therefore, the characteristic of the damping force relative to the piston speed is such that the rate of increase of the damping force decreases as the piston speed increases.

[0269] When the piston speed becomes even faster, the oil L from the first chamber 19 flows into the second chamber 20 via the flow path 435, which includes the gap between the valve disc 141 and the valve seat 414, which are separated from each other in the damping force generating mechanism 432, and also flows from the flow path 162L to the second chamber 20 through the gap between the valve member 161L and the valve seat 47, while opening the valve member 161L of the damping force generating mechanism 41L, which is a hard valve, thereby further suppressing the increase in damping force. Therefore, the characteristic of the damping force relative to the piston speed is such that the rate of increase in the damping force decreases further as the piston speed increases.

[0270] As the piston speed increases, the relationship of the forces (hydraulic pressure) acting on the pilot valve 53 in the valve opening control mechanism 182L changes such that the opening force applied from the flow path 435 communicating with the first chamber 19 becomes greater than the closing force applied from the backpressure chamber 151 communicating with the first chamber 19 via the flow path 438. Therefore, in this region, as the piston speed increases, the valve disc 141 of the damping force generating mechanism 432 opens farther away from the valve seat portion 414 of the seat member 395 than described above. As a result, in addition to the flow from the flow path 162L to the second chamber 20 while opening the valve member 161L of the damping force generating mechanism 41L, more hydraulic fluid L flows into the second chamber 20 via the flow path 435, including the passage between the valve disc 141 and the valve seat portion 414. This further suppresses the increase in damping force. Therefore, the damping force vs. piston speed characteristic further decreases the rate of increase in damping force as the piston speed increases.

[0271] During the compression stroke in which the piston rod 21L moves toward the compression side, the shock absorber 1L operates in the same manner as the shock absorber 1 of the first embodiment.

[0272] The above is the case assuming that the valve opening control mechanism 182L does not function as a damping force variable mechanism, but in shock absorber 1L, the valve opening control mechanism 182L functions as a damping force variable mechanism that varies the damping force according to the piston frequency even when the piston speed is the same.

[0273] When the piston frequency is equal to or higher than a predetermined value, the amplitude of the piston 18L is small, and during the extension stroke when the piston frequency is thus high, the pressure in the first chamber 19 increases, and oil liquid L is introduced from the first chamber 19 into the back pressure chamber 151 via the flow path 438. In response to this, the free valve 111, which had previously been flat and in contact with the seat surfaces 84, 85, elastically deforms so as to enter the recess 82 while blocking communication between the back pressure chamber 151 and the variable chamber 152, thereby expanding the volume of the back pressure chamber 151 and discharging oil liquid L from the variable chamber 152 to the second chamber 20 via the passage in the outer through-hole 87.

[0274] As the free valve 111 is deformed in this manner, hydraulic fluid L is introduced from the first chamber 19 into the back pressure chamber 151 via the flow path 438. As a result, the flow rate of hydraulic fluid L from the first chamber 19 through the flow path 435 to the second chamber 20 is reduced while opening the damping force generating mechanism 432. In addition, the expansion of the volume of the back pressure chamber 151 suppresses the increase in pressure in the back pressure chamber 151, making it easier for the valve disc 141 of the damping force generating mechanism 432 to open. As a result, the damping force on the extension side becomes softer. At this time, the damping force generating mechanism 41L, which is a hard valve, does not open.

[0275] Here, when the piston frequency is equal to or higher than a predetermined value, the amount of hydraulic fluid L introduced from the first chamber 19 into the back pressure chamber 151 is small, so the deformation of the free valve 111 is small and it does not come into contact with the stopper surface 86 to restrict deformation. Therefore, the damping force is softened with each extension stroke. Note that although the pressure in the back pressure chamber 151 increases by an amount equivalent to the stiffness (spring reaction force) of the free valve 111, because the piston frequency is high and the deflection of the free valve 111 is small, the increase in pressure in the back pressure chamber 151 can be suppressed, and the effect on the ease of opening of the valve disc 141 can be suppressed.

[0276] On the other hand, when the piston frequency is lower than a predetermined value, the amplitude of the piston 18L is large, and during the extension stroke when the piston frequency is low in this manner, although the hydraulic oil L flows from the first chamber 19 to the back pressure chamber 151 via the flow path 438 in the same manner as described above at the beginning of the extension stroke, the amount of hydraulic oil L flowing into the back pressure chamber 151 is large, resulting in significant deformation of the free valve 111. Therefore, thereafter, the free valve 111 abuts against the stopper surface 86, restricting further deformation, and the hydraulic oil L no longer flows from the first chamber 19 to the back pressure chamber 151. Because the hydraulic oil L no longer flows from the first chamber 19 to the back pressure chamber 151, the pressure in the back pressure chamber 151 increases, and a state is created in which the valve disc 141 of the damping force generating mechanism 432 is inhibited from opening. That is, the damping force generating mechanism 432 is in a state where the valve disc 141 does not open and hydraulic fluid L flows from the first chamber 19 to the second chamber 20 via the fixed orifice 132L of the damping force generating mechanism 41L, making the damping force on the extension side hard. When the pressure in the back pressure chamber 151 further increases, the hydraulic fluid L opens the valve member 161L of the damping force generating mechanism 41L, which is a hard valve, and flows into the second chamber 20 through the flow path 162L, which includes the gap between the valve member 161L and the valve seat portion 47. When the pressure in the back pressure chamber 151 further increases, in addition to flowing through the flow path 162L, the hydraulic fluid L also opens the valve disc 141 of the damping force generating mechanism 432 and flows from the flow path 435 to the second chamber 20. As a result, the damping force on the extension side becomes hard.

[0277] During the compression stroke, the pressure in the second chamber 20 increases, and the pressure in the variable chamber 152 of the valve opening control mechanism 182L becomes higher than the pressure in the back pressure chamber 151. As a result, the free valve 111 of the check valve 155L moves away from the seat surfaces 84, 85 against the biasing force of the support portion 146 of the pilot valve 53. That is, the check valve 155L opens. Then, the oil L in the second chamber 20 flows from the second chamber 20 toward the first chamber 19 through the passage in the outer through-hole 87, the variable chamber 152, the back pressure chamber 151, and the flow path 438. At this time, the free valve 111 moves away from the seat surfaces 84, 85, eliminating the pressure difference and suppressing further movement.

[0278] When the pressure in the second chamber 20 drops during a transition from the compression stroke to the extension stroke, the free valve 111 is instantly seated against the seat surfaces 84, 85 due to the biasing force of the support portion 146 of the pilot valve 53. In other words, the check valve 155L immediately closes. This prevents the oil L on the first chamber 19 side from flowing into the second chamber 20 through the check valve 155L during a transition from the compression stroke to the extension stroke, thereby suppressing a delay in the rise of the damping force at the initial stage of the extension stroke.

[0279] The shock absorber 1L of the eighth embodiment has a valve disc 141 that is provided in the flow path 435 and allows the oil liquid L in the first chamber 19 to flow into the second chamber 20, a pilot case 56L that is connected to a flow path 438 that is at least partially parallel to the flow path 435 and forms a back pressure chamber 151 that generates a force in the valve closing direction on the valve disc 141, a free valve 111 that is disposed opposite a bottom 71L of the pilot case 56L and deforms due to the pressure of the oil liquid L to vary the volume of the back pressure chamber 151, and a seal portion 145 that seals between the second chamber 20 and the wall portion 72. The shock absorber 1L also has a support portion 146 that directly applies a biasing force in the separation direction to the valve disc 141 and the free valve 111.

[0280] As described above, each of the configurations of the shock absorber 1L that have been changed relative to the shock absorber 1 of the first embodiment has almost the same function as the configuration of the shock absorber 1 before the changes, so the shock absorber 1L can achieve almost the same effects as the shock absorber 1.

[0281] Each of the configurations provided on the piston rods 21, 21L of the shock absorbers 1 to 1H, 1J to 1L may be appropriately applied in place of the corresponding configuration of another shock absorber among the shock absorbers 1 to 1H, 1J to 1L.

[0282] Furthermore, the entire structure provided on the piston rods 21, 21L of the shock absorbers 1 to 1H and 1J to 1L may be provided on the piston rods 21, 21L with the extension side and the compression side reversed.

[0283] The above-mentioned configuration may also be provided inside a damping valve case (cylinder) that is provided outside the shock absorber either integrally or separately.

[0284] According to the above aspects of the present invention, it is possible to provide a shock absorber that can reduce costs, and therefore the industrial applicability is great.

[0285] 1 to 1H, 1J to 1L... shock absorber, 2... cylinder, 18, 18L... piston (divided member), 19... first chamber (one chamber), 20... second chamber (the other chamber), 21, 21B, 21L... piston rod (shaft-shaped member), 56, 56A, 56B, 56D, 56H, 56L... pilot case (partition member), 71, 71L... bottom, 72, 72H... wall portion, 75... valve seat portion (valve seat), 80... seat portion, 82... recess, 87... outer through-hole (first through-hole), 88... inner through-hole (second through-hole), 111... free valve (volume variable member), 141 ...valve disc (first valve member), 145, 145E to 145H...seal portion (seal member), 146, 146E to 146G...support portion (support member), 151...back pressure chamber, 161, 161F...valve member (first valve member, plate valve), 162, 435...flow path (first flow path), 171, 171A, 171C...valve member (second valve member), 172, 172A, 172B, 438...flow path (second flow path), 256...flow path portion (second flow path), 175, 175D to 175G, 175J, 175K...communicating passage, 291...spool.

Claims

1. A cylindrical cylinder filled with fluid, A dividing member that divides the inside of the cylinder into a first chamber and a second chamber, A shaft-shaped member inserted through the aforementioned divided member, A first flow path through which the fluid that has flowed out of one of the first chambers and the second chamber flows, A second flow path is provided in parallel with the first flow path, at least a portion of which is parallel. A first valve member provided in the first flow path, which allows the fluid in one chamber to flow into the other chamber, A partition member having a wall portion and a bottom portion, penetrating the axial member, connected to the second flow path, and forming a back pressure chamber that generates a force in the valve closing direction on the first valve member, A volume-variable member is positioned opposite the bottom and deforms due to the pressure of the fluid to vary the volume of the back pressure chamber, A sealing member that seals the space between the other chamber and the wall portion, A support member that directly or indirectly applies a biasing force in the separation direction to the first valve member and the variable volume member, It has, The sealing member, It is integrally connected to the first valve member; The support member, It is made of the same material as the sealing member and is integrally connected to the first valve member; buffer.

2. The support member, The back pressure chamber is divided into an inner chamber located radially inward and an outer chamber located radially outward, and has a connecting passage between the inner chamber and the outer chamber. The shock absorber according to claim 1.

3. The aforementioned volume-variable member, It has a free valve which is a flexible plate-shaped member; The bottom part is The recess covered by the free valve, It has a seat portion that contacts the free valve; At the position of the recess, It has a first through hole that penetrates the bottom; The shock absorber according to claim 1.

4. The partition wall member, The sheet portion further has a second through hole that penetrates the bottom portion and is provided radially inward from the first through hole; The present invention further comprises a second valve member that does not block the first through-hole but blocks the second through-hole; The shock absorber according to claim 3.

5. The support member, The sealing member is connected integrally with the first valve member at a predetermined distance from the first valve member radially inward from the first valve member, The shock absorber according to claim 1.

6. The support member, The sealing member extends from the radially inward side of the first valve member, The shock absorber according to claim 1.

7. The support member, The sealing member extends from the thickness-direction end of the first valve member, The shock absorber according to claim 1.

8. The first valve member is A plate-shaped plate valve that covers the opening of the partition member and closes the other chamber-side opening of the first flow path, It has a spool that receives the pressure of the back pressure chamber and transmits it to the plate valve; The aforementioned support member, A force is generated in the direction of separation between the spool and the volume-variable member; The shock absorber according to claim 1.

9. The aforementioned support member, The volume variable member is integrally connected to the above-mentioned variable volume member. The shock absorber according to claim 1.

10. The second flow path is The downstream opening communicates with the interior of the valve seat on which the second valve member sits; In the aforementioned back pressure chamber, The fluid flows in through the second through hole; The shock absorber according to claim 4.

11. The aforementioned support member, Opposite to the portion of the free valve that sits on the seat portion, and in contact with the free valve, The shock absorber according to claim 3.