Damper

Abstract

To provide a damper capable of increasing the degree of freedom in adjusting characteristics for mitigating impact when in a fully extended state.SOLUTION: Provided is a damper comprising: a piston slidably inserted into a cylinder 17 to divide the interior of the cylinder 17 into two chambers; a piston rod 51 having a first end connected to the piston and a second end extending outside the cylinder 17; a closure member 28 provided at an end of the cylinder 17 to close the cylinder 17; a stopper member 71 disposed between the closure member 28 and the piston; a cushion member 72 disposed between the stopper member 71 and the closure member 28; a cover member 73 arranged radially outside the cushion member 72 and covering at least a portion of the radially outer side of the cushion member 72; and a plurality of ribs 102 projecting radially outward from the cover member 73.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Some shock absorbers deform an elastic member when fully extended to absorb impact, and then bring a stopper member into contact with a blocking member to suppress excessive load on the elastic member and improve durability (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-4732 Summary of the Invention [Problem to be solved by the invention]

[0004] In shock absorbers, there is a demand for improved flexibility in adjusting the characteristics when absorbing impact when fully extended.

[0005] Therefore, an object of the present invention is to provide a shock absorber that allows for improved flexibility in adjusting characteristics when absorbing impact when fully extended. [Means for solving the problem]

[0006] In order to achieve the above object, a first aspect of the present invention is configured to include a cylinder filled with a working fluid, a piston slidably inserted into the cylinder and dividing the interior of the cylinder into two chambers, a piston rod having a first end connected to the piston and a second end extending to the outside of the cylinder, a closing member provided at an end of the cylinder and closing the cylinder, a stopper member provided between the closing member and the piston, a cushion member provided between the stopper member and the closing member, a cover member disposed radially outside the cushion member and covering at least a portion of the radially outer side of the cushion member, and a plurality of ribs provided and protruding radially outward from the cover member.

[0007] A second aspect of the present invention is configured to include a cylinder in which a working fluid is sealed, a piston slidably inserted into the cylinder and dividing the interior of the cylinder into two chambers, a piston rod having a first end connected to the piston and a second end extending to the outside of the cylinder, a closing member provided at an end of the cylinder and closing the cylinder, a stopper member provided between the closing member and the piston, a cushion member provided between the stopper member and the closing member, a cover member disposed radially outside the cushion member and covering at least a portion of the radially outside of the cushion member, and a protrusion protruding radially inward from the cover member and inserted into the cushion member.

[0008] A third aspect of the present invention is configured to include a cylinder in which a working fluid is sealed, a piston slidably inserted into the cylinder and dividing the interior of the cylinder into two chambers, a piston rod having a first end connected to the piston and a second end extending to the outside of the cylinder, a closing member provided at an end of the cylinder and closing the cylinder, a stopper member provided between the closing member and the piston, a cushion member provided between the stopper member and the closing member, a cover member disposed radially inside the cushion member and covering at least a portion of the radially inside of the cushion member, and a protrusion protruding radially outward from the cover member and inserted into the cushion member. [Effects of the Invention]

[0009] According to the present invention, it is possible to improve the degree of freedom in adjusting the characteristics when absorbing impact at full extension. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view showing a shock absorber according to a first embodiment of the present invention. [Figure 2] 1 is a cross-sectional view of a main part of a shock absorber according to a first embodiment of the present invention, showing a state in which a shock absorbing mechanism is not in operation. [Figure 3] 1 is a cross-sectional view showing a piston rod, a cushion member, and a cover member in a non-operating state of a shock absorber according to a first embodiment of the present invention. [Figure 4] 1 is a cross-sectional view of a main part of a shock absorber according to a first embodiment of the present invention, showing a state in which a shock absorbing mechanism is in operation. [Figure 5] 1 is a cross-sectional view showing a piston rod, a cushion member, and a cover member in an actuated state, illustrating a shock absorber according to a first embodiment of the present invention. [Figure 6] FIG. 10 is a cross-sectional view of a main part of a shock absorber according to a second embodiment of the present invention, showing a state in which the shock absorbing mechanism is not in operation. [Figure 7]FIG. 10 is a cross-sectional view of a main part of a shock absorber according to a second embodiment of the present invention, showing a state in which the shock absorbing mechanism is in operation. [Figure 8] FIG. 10 is a cross-sectional view of a main part of a shock absorber according to a third embodiment of the present invention, showing a state in which the shock absorbing mechanism is not in operation. [Figure 9] FIG. 10 is a cross-sectional view of a main part of a shock absorber according to a third embodiment of the present invention, showing a state in which the shock absorbing mechanism is in operation. [Figure 10] FIG. 10 is a cross-sectional view of a main part of a shock absorber according to a fourth embodiment of the present invention, showing a state in which the shock absorbing mechanism is not in operation. [Figure 11] FIG. 10 is a cross-sectional view of a main part of a shock absorber according to a fourth embodiment of the present invention, showing a state in which the shock absorbing mechanism is in operation. DETAILED DESCRIPTION OF THE INVENTION

[0011] [First embodiment] The shock absorber of the first embodiment will be described below with reference to FIGS. FIG. 1 shows a shock absorber 11 of a first embodiment. This shock absorber 11 is a shock absorber used in a suspension system of a vehicle such as an automobile or a railway vehicle. Specifically, the shock absorber 11 is a shock absorber used in a suspension system of an automobile. The shock absorber 11 is a double-tube shock absorber equipped with a cylinder 17 having an inner tube 15 and an outer tube 16. The inner tube 15 is cylindrical. The outer tube 16 is cylindrical with a bottom and has a larger diameter than the inner tube 15. The outer tube 16 is disposed radially outside the inner tube 15 and coaxially with the inner tube 15. A reservoir chamber 18 is formed between the outer tube 16 and the inner tube 15.

[0012] The outer cylinder 16 has a body member 20 and a bottom member 21. The body member 20 is cylindrical. The bottom member 21 is fitted onto one axial end of the body member 20 and fixed by welding. The body member 20 and the portion of the bottom member 21 that fits with the body member 20 form a cylindrical body portion 22 of the outer cylinder 16. A portion of the bottom member 21 that is radially inward from the portion that fits with the body member 20 forms a bottom portion 23 of the outer cylinder 16. The bottom portion 23 closes one axial end of the body portion 22. The side of the body portion 22 opposite the bottom portion 23 forms an opening 24. The opening 24 of the outer cylinder 16 is also provided at one axial end of the cylinder 17. The bottom portion 23 of the outer cylinder 16 is also provided at the other axial end of the cylinder 17. In other words, the cylinder 17 is open at one axial end and closed at the other axial end. A mounting eye 25 is fixed to the bottom 23 on the opposite side of the opening 24. The mounting eye 25 is connected to the wheel side of the vehicle. The inner cylinder 15 is a cylindrical, one-piece molded product made of a single piece of metal. The inner peripheral surface 15a of the inner cylinder 15 is cylindrical.

[0013] The shock absorber 11 includes a valve body 27 and a rod guide 28 (blocking member). The valve body 27 is annular and is provided at one axial end of the inner cylinder 15 and the outer cylinder 16. The rod guide 28 is annular and is provided at the other axial end of the inner cylinder 15 and the outer cylinder 16. The valve body 27 constitutes the base valve 30, and its outer periphery is stepped. The valve body 27 is placed on the bottom 23. At that time, the valve body 27 is positioned radially relative to the outer cylinder 16 at the large-diameter portion of its outer periphery.

[0014] As shown in FIG. 2 , the rod guide 28 includes a rod guide main body 32 and a collar 33. The rod guide main body 32 is made of metal and has an annular shape. The rod guide main body 32 has a large-diameter portion 35 and a small-diameter portion 36 on its outer periphery. The outer diameter of the large-diameter portion 35 is larger than the outer diameter of the small-diameter portion 36. Therefore, the rod guide main body 32 has a stepped outer periphery. The collar 33 is cylindrical. The collar 33 is formed by coating the inner periphery of a metal cylinder with a highly slidable material. The collar 33 is fitted and fixed to the inner periphery of the rod guide main body 32. The large-diameter portion 35 of the rod guide 28 fits into the inner periphery of the barrel portion 22 of the outer tube 16 on the opening 24 side. The rod guide 28 has an end face 28a at the end opposite the large-diameter portion 35 in the axial direction, which is flat and extends perpendicular to the central axis of the rod guide 28. The end surface 28 a is formed on the rod guide body 32 and the collar 33 .

[0015] As shown in FIG. 1 , one axial end of the inner cylinder 15 is fitted into the small-diameter portion of the outer periphery of the valve body 27 until it axially abuts against the large-diameter portion of the valve body 27. One axial end of the inner cylinder 15 engages with the bottom portion 23 of the outer cylinder 16 via the valve body 27. The other axial end of the inner cylinder 15 is fitted into the small-diameter portion 36 of the rod guide main body 32 until it axially abuts against the large-diameter portion 35. This other end of the inner cylinder 15 engages with the barrel portion 22 of the outer cylinder 16 via the rod guide 28. In this state, the inner cylinder 15 is positioned axially and radially relative to the outer cylinder 16. The valve body 27 and the bottom portion 23 communicate with each other via a passage groove 40 formed in the valve body 27. The space between the valve body 27 and the bottom portion 23, like the space between the inner cylinder 15 and the outer cylinder 16, defines a reservoir chamber 18.

[0016] The shock absorber 11 includes an annular rod seal 41 (blocking member). The rod seal 41 is provided on the side of the rod guide 28 opposite the bottom 23. Like the rod guide 28, the rod seal 41 is fitted to the inner periphery of the body 22. A locking portion 43 is formed on the end of the body 22 opposite the bottom 23. The locking portion 43 is formed by plastically deforming the body member 20 radially inward by a crimping process such as a curling process. The rod seal 41 is sandwiched between the locking portion 43 and the rod guide 28. At this time, the rod seal 41 is pressed against the inner periphery of the body 22 by the rod guide 28. As a result, the rod seal 41 blocks the opening 24 of the outer cylinder 16. In other words, the rod guide 28 and the rod seal 41 are provided at one end of the cylinder 17, which has one open end and the other closed end, and close this end. Specifically, the rod seal 41 is an oil seal.

[0017] The shock absorber 11 is equipped with a piston 45. The piston 45 is slidably inserted into the inner tube 15 of the cylinder 17. The piston 45 divides the inner tube 15 into two chambers: a first chamber 48 and a second chamber 49. The first chamber 48 is provided between the piston 45 and the rod guide 28 in the inner tube 15. The second chamber 49 is provided between the piston 45 and the valve body 27 in the inner tube 15. The second chamber 49 is separated from the reservoir chamber 18 by the valve body 27. In the cylinder 17, oil L is sealed in the first chamber 48 and the second chamber 49 as a working fluid. In the cylinder 17, oil L and gas G are sealed in the reservoir chamber 18 as working fluids.

[0018] The shock absorber 11 is equipped with a piston rod 51. A first end portion of the piston rod 51 is inserted into the cylinder 17. The first end portion of the piston rod 51 is connected to the piston 45. A second end portion of the piston rod 51 is the other axial end portion and extends to the outside of the cylinder 17 through the opening 24 of the outer cylinder 16. The piston rod 51 is made of metal, and passes through the first chamber 48. The piston rod 51 does not pass through the second chamber 49. Therefore, the first chamber 48 is a rod-side chamber through which the piston rod 51 passes. The second chamber 49 is a bottom-side chamber on the bottom 23 side of the cylinder 17. The portion of the piston rod 51 that extends to the outside from the cylinder 17 is connected to the vehicle body.

[0019] The piston rod 51 has a main shaft portion 52 and a mounting shaft portion 53. The outer diameter of the mounting shaft portion 53 is smaller than the outer diameter of the main shaft portion 52. The outer peripheral surface 52a of the main shaft portion 52 is cylindrical. The mounting shaft portion 53 side of the piston rod 51 is inserted into the cylinder 17. A piston 45 is connected to the mounting shaft portion 53 of the piston rod 51 with a nut 54. The piston rod 51 extends from the cylinder 17 to the outside via the rod guide 28 and the rod seal 41 at the main shaft portion 52. The rod guide 28 and the rod seal 41 are provided on the side of the cylinder 17 from which the piston rod 51 extends. The rod guide 28 slidably supports the piston rod 51. The piston rod 51 is guided by the rod guide 28 at the outer peripheral surface 52a of the main shaft portion 52. The end face 28a of the rod guide 28 extends perpendicular to the central axis of the piston rod 51. The piston rod 51 moves axially together with the piston 45 relative to the cylinder 17. During the extension stroke of the shock absorber 11, in which the piston rod 51 increases the amount of protrusion from the cylinder 17, the piston 45 moves toward the first chamber 48. During the compression stroke of the shock absorber 11, in which the piston rod 51 decreases the amount of protrusion from the cylinder 17, the piston 45 moves toward the second chamber 49.

[0020] The rod seal 41 is provided on the side from which the piston rod 51 of the cylinder 17 extends, i.e., on the side of the opening 24 of the outer cylinder 16. The rod seal 41, together with the rod guide 28, seals the gap between the body 22 of the outer cylinder 16 and the main shaft portion 52 of the piston rod 51, thereby restricting the oil L in the inner cylinder 15 and the gas G and oil L in the reservoir chamber 18 from leaking to the outside.

[0021] A passage 55 and a passage 56 are formed in the piston 45. Both the passage 55 and the passage 56 pass through the piston 45 in the axial direction. The passages 55, 56 can communicate between the first chamber 48 and the second chamber 49. The shock absorber 11 is equipped with a disc valve 57 and a disc valve 58. The disc valve 57 is provided on the side of the piston 45 opposite the bottom 23 in the axial direction. The disc valve 57 is annular and closes the passage 55 by abutting against the piston 45. The disc valve 58 is provided on the bottom 23 side of the piston 45 in the axial direction. The disc valve 58 is annular and closes the passage 56 by abutting against the piston 45. The disc valves 57, 58 are attached to the piston rod 51 together with the piston 45.

[0022] When the piston rod 51 moves toward the compression side, increasing the amount of penetration into the inner tube 15 and the outer tube 16, and the piston 45 moves in a direction narrowing the second chamber 49, the pressure in the second chamber 49 becomes higher than the pressure in the first chamber 48 by a predetermined value or more. This causes the disc valve 57 to open the passage 55, allowing the oil L in the second chamber 49 to flow into the first chamber 48. At this time, the disc valve 57 generates a damping force. When the piston rod 51 moves toward the extension side, increasing the amount of protrusion from the inner tube 15 and the outer tube 16, and the piston 45 moves in a direction narrowing the first chamber 48, the pressure in the first chamber 48 becomes higher than the pressure in the second chamber 49 by a predetermined value or more. This causes the disc valve 58 to open the passage 56, allowing the oil L in the first chamber 48 to flow into the second chamber 49. At this time, the disc valve 58 generates a damping force.

[0023] A fixed orifice (not shown) is formed in at least one of the piston 45 and the disc valve 57. This fixed orifice allows communication between the first chamber 48 and the second chamber 49 via the passage 55 even when the disc valve 57 is in a state where the passage 55 is most closed by the disc valve 57. In addition, a fixed orifice (not shown) is also formed in at least one of the piston 45 and the disc valve 58. This fixed orifice allows communication between the first chamber 48 and the second chamber 49 via the passage 56 even when the disc valve 58 is in a state where the passage 56 is most closed by the disc valve 58.

[0024] The valve body 27 is formed with a fluid passage 61 and a fluid passage 62. Both the fluid passage 61 and the fluid passage 62 axially penetrate the valve body 27. Both the fluid passages 61 and 62 can communicate between the second chamber 49 and the reservoir chamber 18. The base valve 30 includes a disc valve 65 and a disc valve 66. The disc valve 65 is provided on the bottom 23 side of the valve body 27 in the axial direction. The disc valve 65 closes the fluid passage 61 by abutting against the valve body 27. The disc valve 66 is provided on the opposite side of the valve body 27 from the bottom 23 in the axial direction. The disc valve 66 closes the fluid passage 62 by abutting against the valve body 27. The base valve 30 includes a pin 68. The pin 68 attaches the disc valves 65 and 66 to the valve body 27. The valve body 27, the disc valves 65 and 66, the pin 68, and the like constitute the base valve 30.

[0025] When the piston rod 51 moves toward the compression side and the piston 45 moves in a direction that narrows the second chamber 49, the pressure in the second chamber 49 becomes higher than the pressure in the reservoir chamber 18 by a predetermined value or more. Then, in the base valve 30, the disc valve 65 opens the fluid passage 61, allowing the hydraulic fluid L in the second chamber 49 to flow into the reservoir chamber 18. At this time, the disc valve 65 generates a damping force. When the piston rod 51 moves toward the extension side and the piston 45 moves toward the first chamber 48, the pressure in the second chamber 49 becomes lower than the pressure in the reservoir chamber 18. Then, in the base valve 30, the disc valve 66 opens the fluid passage 62, allowing the hydraulic fluid L in the reservoir chamber 18 to flow into the second chamber 49. The disc valve 66 is a suction valve that allows the hydraulic fluid L to flow from the reservoir chamber 18 into the second chamber 49 without generating any substantial damping force.

[0026] The shock absorber 11 includes an impact absorbing mechanism 75 having a stopper member 71, a cushion member 72, and a cover member 73, which are separate members.

[0027] An engagement groove 78 is formed in the main shaft portion 52 of the piston rod 51. The engagement groove 78 is recessed radially inward from the outer peripheral surface 52a of the main shaft portion 52. The engagement groove 78 has an annular shape that is coaxial with the outer peripheral surface 52a of the main shaft portion 52. The engagement groove 78 is formed in a portion of the main shaft portion 52 that is disposed inside the inner cylinder 15 and is disposed between the piston 45 and the rod guide 28.

[0028] The stopper member 71 is made of metal and has a circular ring shape that is formed integrally without joints. As shown in FIG.

[0029] The bottom portion 81 is annular and has a flat plate shape that extends perpendicular to its axial direction. The bottom portion 81 has, on one axial side thereof, an annular outer bottom surface 81a on the radially outer side and an annular inner bottom surface 81b on the radially inner side. The outer bottom surface 81a is flat and extends perpendicular to the axial direction of the bottom portion 81. The inner bottom surface 81b has a tapered surface shape that is inclined radially inward so that it is located closer to the interior of the bottom portion 81 (towards the tubular portion 82) than the outer bottom surface 81a.

[0030] The cylindrical portion 82 extends from the inner peripheral edge of the bottom portion 81 to the side opposite the outer bottom surface 81a and the inner bottom surface 81b in the axial direction of the bottom portion 81. The cylindrical portion 82 is cylindrical. The outer diameter of the cylindrical portion 82 is smaller than the outer diameter of the bottom portion 81.

[0031] As shown in FIG. 1 , the stopper member 71 is disposed between the piston 45 of the main shaft portion 52 of the piston rod 51 and the rod guide 28. As shown in FIG. 2 , the stopper member 71 is fitted and fixed to the engagement groove 78 of the piston rod 51 at the cylindrical portion 82, with the bottom portion 81 positioned closer to the rod guide 28 than the cylindrical portion 82. The cylindrical portion 82 is fitted and fixed to the engagement groove 78 by being crimped radially inward and plastically deforming. When fixed to the piston rod 51 in this manner, the outer bottom surface 81a of the bottom portion 81 of the stopper member 71 extends radially outward from the piston rod 51, perpendicular to the axial direction of the piston rod 51. The inner bottom surface 81b of the bottom portion 81 tapers radially inward from the inner peripheral edge of the outer bottom surface 81a so as to move away from the rod guide 28 in the axial direction as it becomes radially inward.

[0032] The cushion member 72 is made of synthetic rubber such as NBR (nitrile rubber) and has a seamless, integrally formed circular ring shape. The cushion member 72 is mirror-symmetrical in the axial direction. The cushion member 72 has a main body 91, a pair of outer protrusions 92, an annular recess 93, and an inner protrusion 94.

[0033] The main body portion 91 is cylindrical. An outer diameter surface 91a on the radially outer side of the main body portion 91 is a cylindrical surface that is discontinuous in the axial direction, and an inner diameter surface 91b on the radially inner side of the main body portion 91 is a cylindrical surface that is discontinuous in the axial direction. When the cushion member 72 is cut along a plane including the central axis of the cushion member 72, the cross-section of the main body portion 91 has an outwardly convex semicircular shape in the axial direction of the cushion member 72.

[0034] The pair of outer protrusions 92 are both annular. The pair of outer protrusions 92 are disposed at intermediate positions in the axial direction of the outer diameter surface 91a of the main body portion 91, spaced apart from each other in the axial direction of the outer diameter surface 91a, and protrude outward from the outer diameter surface 91a in the radial direction of the main body portion 91. The surfaces 92a of the pair of outer protrusions 92 have a cross-sectional shape that is convex outward in the radial direction of the cushion member 72 when the cushion member 72 is cut along a plane including the central axis of the cushion member 72, and are arc-shaped.

[0035] The annular recess 93 is provided at the axial center of the main body portion 91 and between the pair of outer protruding portions 92. The annular recess 93 is annular in shape and is recessed inward in the radial direction of the cushion member 72 relative to an outer diameter surface 91a of the main body portion 91. The annular recess 93 has a concave surface 93a, which is its surface, and the cross-sectional shape of the cushion member 72 when the cushion member 72 is cut along a plane including the central axis of the cushion member 72 is an arc-like shape recessed inward in the radial direction of the cushion member 72.

[0036] The inner protrusion 94 is annular and is disposed at the center of the inner diameter surface 91b of the main body 91 in the axial direction, and protrudes inward from the inner diameter surface 91b in the radial direction of the main body 91. The inner protrusion 94 has a cylindrical inner diameter surface 94a at the axial middle and radially inner side, and end surfaces 94b on both axial sides have tapered surfaces that move away from the inner diameter surface 94a in the axial direction toward the radially outer side.

[0037] The cover member 73 is made of a hard resin such as nylon and has a seamless, integrally formed circular shape. The cover member 73 is mirror-symmetrical in the axial direction. The cover member 73 has a base portion 101, a plurality of ribs 102, and a protrusion 103.

[0038] The base portion 101 is cylindrical. As shown in FIG. 3, the outer diameter surface 101a of the base portion 101 on the radially outer side is a cylindrical surface that is discontinuous in the circumferential direction, and as shown in FIG. 2, the inner diameter surface 101b on the radially inner side is a cylindrical surface that is discontinuous in the axial direction. The end faces 101c on both sides of the axial direction of the base portion 101 are flat surfaces that extend in a direction perpendicular to the axis of the base portion 101. The end faces 101c on both sides of the base portion 101 are located at both axial end portions of the cover member 73.

[0039] As shown in FIG. 3, a plurality of ribs 102 are provided at equal intervals in the circumferential direction of the base portion 101, and protrude radially outward from the outer diameter surface 101a of the base portion 101. Thus, the cover member 73 is provided with a plurality of ribs 102 that protrude radially outward. The plurality of ribs 102 have the same shape. As shown in FIG. 2, the ribs 102 extend from one end face 101c of the base portion 101 to the other end face 101c. Thus, the ribs 102 are formed from one axial end to the other end of the cover member 73.

[0040] As shown in Fig. 3, the rib 102 has side surfaces 102a on both sides in the circumferential direction of the base portion 101 that are parallel to each other and are planar along the axial direction of the base portion 101, parallel to a radial line of the base portion 101 that passes through the center between the side surfaces. As shown in Fig. 2, the rib 102 has a surface 102b on the radial outer side of the base portion 101, which is located at the radially outermost position at the axial center of the base portion 101, and the further away from the axial center of the base portion 101, the more inward the surface 102b of the rib 102 is located. The surface 102b of the rib 102 is located at the radially outer end of the cover member 73. Therefore, the radially outer side of the cover member 73 is formed so that the outer diameter increases from the axial end face 101c toward the axial center. An outer surface 102b of the rib 102 in the radial direction of the cover member 73 forms a curved "L" shape when the cover member 73 is viewed in a direction perpendicular to the axis. The cross section of the surface 102b of the rib 102 when the cover member 73 is cut along a plane extending in a direction perpendicular to the axis of the cover member 73 forms an arc shape coaxial with the outer diameter surface 101a of the base portion 101.

[0041] The protrusion 103 is annular, and protrudes inward in the radial direction of the base portion 101 from a central position in the axial direction of the inner diameter surface 101b of the base portion 101. The axial thickness of the protrusion 103 at a root portion on the outer side in the radial direction of the base portion 101 is narrower than the axial thickness of a tip portion on the inner side in the radial direction of the base portion 101. The tip surface 103a of the radially inner end of the protrusion 103 has a cross-sectional shape that is an arc convex inward in the radial direction of the cover member 73 when the cover member 73 is cut along a plane including the central axis of the cover member 73. The tip surface 103a of the protrusion 103 is a curved surface that is convex inward in the radial direction of the cover member 73, in the same shape as the concave surface 93a of the annular recess 93 of the cushion member 72.

[0042] The cushion member 72 is provided between the rod guide 28 and the stopper member 71, with the main shaft portion 52 of the piston rod 51 inserted radially inside the inner protrusion 94 of the cushion member 72. The cover member 73 is disposed radially outside the cushion member 72, with the protrusion 103 protruding radially inward being inserted into and fitted into the annular recess 93 on the radial outside of the cushion member 72, and the tip surface 103a of the protrusion 103 abutting in surface contact against the recessed surface 93a of the annular recess 93. In this state, the inner diameter surface 101b of the base portion 101 of the cover member 73 abuts against the surfaces 92a of the pair of outer protrusions 92 of the cushion member 72.

[0043] The axial length of the cushion member 72 is longer than the axial length of the cover member 73. Therefore, the cover member 73 covers the axial center portion, which is a part of the radially outer side of the cushion member 72. In other words, the cushion member 72 protrudes evenly from the cover member 73 on both sides in the axial direction. The cover member 73 has a plurality of ribs 102 that protrude radially outward. The outer diameter of the cover member 73 is smaller than the inner diameter of the inner tube 15. Therefore, the entire cover member 73 is spaced radially inward from the inner circumferential surface 15a of the inner tube 15. The cover member 73 has a protrusion 103 that protrudes radially inward and is inserted into the cushion member 72.

[0044] The cushion member 72 is fitted onto the main shaft portion 52 of the piston rod 51, to which the stopper member 71 has been fixed in advance, on the side that is fitted into the rod guide 28 relative to the stopper member 71. In this state, the cover member 73 is placed over the radially outer side of the cushion member 72, which is made of an elastic material, while elastically deforming the cushion member 72 radially inward as appropriate, and the protrusion 103 is fitted into the annular recess 93. By fitting the protrusion 103 of the cover member 73 into the annular recess 93 of the cushion member 72 in this way, the cushion member 72 and the cover member 73 are positioned axially and radially and integrated. Before assembling the cushion member 72 to the piston rod 51, the cushion member 72 made of an elastic material may be inserted into the cover member 73 while being elastically deformed radially inward as needed, and the annular recess 93 may be fitted into the protrusion 103 of the cover member 73 to integrate the cushion member 72 and the cover member 73. In this state, the cushion member 72 may be fitted into the main shaft portion 52 of the piston rod 51, to which the stopper member 71 has been fixed in advance, on the side that is fitted into the rod guide 28 rather than the stopper member 71.

[0045] An impact absorbing mechanism 75 having a stopper member 71, a cushion member 72, and a cover member 73, which are separate members, applies resistance to the piston rod 51 when the piston rod 51 moves to a predetermined position on the fully extended side relative to the cylinder 17, thereby absorbing the impact that occurs when the piston rod 51 stops. At that time, the cushion member 72 reduces the moving speed of the piston rod 51 to absorb the impact, and the cover member 73, which is more rigid than the cushion member 72, restricts the piston rod 51 from moving further beyond the fully extended position. The impact absorbing mechanism 75 is a so-called rebound stopper. The cushion member 72 is a so-called rebound cushion that absorbs the impact when restricting the piston rod 51 from moving further beyond the fully extended position.

[0046] When an axial tensile load is applied to the shock absorber 11, the piston rod 51 moves axially relative to the cylinder 17 in the extension direction, which increases the overall length of the shock absorber 11. When the piston rod 51 moves to a predetermined position relative to the cylinder 17, the cushion member 72 of the shock absorber 11 abuts against the end surface 28a of the rod guide 28 at the main body portion 91 of the shock absorber 75. When the piston rod 51 moves further in the extension direction relative to the cylinder 17, the main body portion 91 of the cushion member 72 is sandwiched axially between the rod guide 28 and the stopper member 71 and elastically deforms in the compression direction. This provides resistance to the movement of the piston rod 51. At this time, the cushion member 72 also expands radially inward and outward. As a result, the cushion member 72 is pressed against the inner diameter surface 101b of the base portion 101 of the cover member 73 and against the outer circumferential surface 52a of the main shaft portion 52. This also allows the cushion member 72 to provide resistance to the movement of the piston rod 51.

[0047] When the piston rod 51 further extends relative to the cylinder 17, as shown in FIG. 4 , the impact-absorbing mechanism 75 causes the cover member 73 to abut against the end surface 28a of the rod guide 28 at one end surface 101c of the base portion 101 and the outer bottom surface 81a of the bottom portion 81 of the stopper member 71 at the other end surface 101c of the base portion 101, restricting further movement of the stopper member 71 toward the rod guide 28. Thus, the piston rod 51 reaches a fully extended state in which further movement toward the cylinder 17 is restricted. When the piston rod 51 reaches the fully extended state, the cover member 73 restricts further deformation of the cushion member 72. In this state, the cushion member 72 elastically deforms within the area surrounded by the piston rod 51, the rod guide 28, the stopper member 71, and the cover member 73, as shown in FIGS. 4 and 5 . However, the volume within this range is larger than the volume of the cushion member 72 that is deformed within this range, and the cushion member 72 does not completely fill this range.

[0048] The above-mentioned Patent Document 1 discloses a shock absorber that, when fully extended, deforms an elastic member to absorb impact, and then brings a metal stopper member into contact with a blocking member, thereby suppressing excessive load on the elastic member and improving durability. In this shock absorber, adjusting the characteristics of absorbing impact when fully extended requires changing the shape of the stopper member, but considering the assembly process and height management of the stopper member, there are limitations on the height (axial length) of the stopper material that can be applied and the volume of the cushion, which creates an issue with the degree of freedom in adjusting the characteristics.

[0049] In contrast, the shock absorber 11 of the first embodiment has a cushion member 72 provided between the stopper member 71 and the rod guide 28, and a cover member 73 disposed radially outward of the cushion member 72 and covering a portion of the radially outer side of the cushion member 72. Therefore, during the extension process, the cushion member 72 first comes into contact with the stopper member 71 and the rod guide 28 and undergoes compressive deformation, causing the cushion member 72 to receive a compressive load. After that, the cushion member 72 deforms to a certain extent, and the cover member 73 comes into contact with the stopper member 71 and the rod guide 28, causing the cover member 73 to receive a compressive load, thereby suppressing noise and preventing excessive load from being applied to the cushion member 72. Because the shock absorber 11 has the cover member 73 provided separately from the stopper member 71, the shock absorber 11 can adjust the characteristics of absorbing impact during full extension by changing the shape of the cover member 73, eliminating the need to change the shape of the stopper member 71, thereby improving the flexibility of characteristic adjustment.

[0050] Furthermore, the shock absorber 11 includes a plurality of ribs 102 that protrude radially outward from the cover member 73, thereby suppressing deformation of the cover member 73 in the radially outward direction. That is, when the cushion member 72 is crushed by the rod guide 28 and the stopper member 71, it deforms toward the cover member 73, generating a force that deforms the cover member 73 radially outward. At that time, the ribs 102 can suppress deformation of the cover member 73. Even if the cover member 73 deforms and comes into contact with the inner circumferential surface 15a of the inner cylinder 15, the flow paths between the ribs 102 can suppress hydraulic locking caused by the impact absorbing mechanism 75.

[0051] Furthermore, in the shock absorber 11, the ribs 102 are formed from one axial end to the other axial end of the cover member 73, so that deformation of the cover member 73 can be further suppressed.

[0052] Furthermore, shock absorber 11 has protrusion 103 that protrudes radially inward from cover member 73 and is inserted into cushion member 72, thereby enabling the cushion member 72 and cover member 73 to be positioned. This facilitates the assembly work of assembling cushion member 72 and cover member 73 to piston rod 51.

[0053] Furthermore, by using a hard resin for the cover member 73 of the shock absorber 11, it is possible to expect measures against abnormal noise caused by metal contact, improved durability, and weight reduction.

[0054] Furthermore, the shock absorber 11 is formed so that the outer diameter of the radially outer side of the cover member 73, i.e., the outer side of the rib 102 in the radial direction of the cover member 73, increases from the axial end face 101c to the axial center. Therefore, when the cover member 73 is expanded in diameter by the radial load received from the cushion member 72 in addition to receiving the axial compressive load, it can come into contact with the inner circumferential surface 15a of the inner tube 15 of the cylinder 17, and deformation of the cover member 73 can be suppressed by the cylinder 17. This makes it possible to improve the durability of the cover member 73. In this case, the radially outer side of the cushion member 72 is not limited to being curved in a "L" shape, but may also be bent in a "L" shape.

[0055] Here, shock absorber 11 may be formed so that rib 102 of cover member 73 is in constant sliding contact with inner circumferential surface 15a of inner tube 15 of cylinder 17. With this configuration, compared to when there is a radial gap between rib 102 and inner tube 15, it is possible to suppress the generation of abnormal noise when cover member 73 deforms and abuts against inner tube 15, and to suppress variations in performance of cushion member 72 due to radial variations.

[0056] Furthermore, in the shock absorber 11, the cover member 73 is positioned radially outside the cushion member 72 and covers a portion of the radial outside of the cushion member 72, but if the end face 28a of the rod guide 28 is stepped and comes into contact with the cover member 73 after the cushion member 72 is compressed and deformed, the entire radial outside of the cushion member 72 may be covered.

[0057] [Second embodiment] Next, the second embodiment will be described, focusing on the differences from the first embodiment, mainly with reference to Figures 6 and 7. Note that parts common to the first embodiment will be designated by the same names and symbols.

[0058] 6, shock absorber 11A of the second embodiment is provided with shock absorber 75A that is partially different from shock absorber 75 instead of shock absorber 75. Shock absorber 75A has a cushion member 72A that is partially different from cushion member 72 instead of cushion member 72, and has a cover member 73A that is partially different from cover member 73 instead of cover member 73.

[0059] The cushion member 72A is made of synthetic rubber such as NBR (nitrile rubber) and has a seamless, integrally formed circular shape. The cushion member 72A has a main body portion 91A and an outer protruding portion 92A.

[0060] The main body portion 91A is annular. The main body portion 91A has an outer diameter surface 91Aa on the radially outer side that is cylindrical, and an inner diameter surface 91Ab on the radially inner side that is cylindrical. The main body portion 91A has an end face 91Ac on one axial side that has a cross-sectional shape, when the cushion member 72A is cut along a plane including the central axis of the cushion member 72A, that is a semicircular shape that convex outward in the axial direction of the cushion member 72A. The main body portion 91A has an end face 91Ad on the other axial side that is flat and extends perpendicular to the axial direction of the cushion member 72A. The end face 91Ad extends to the outer protrusion 92A and forms the end face of the cushion member 72A.

[0061] The outer protrusion 92A is annular. The outer protrusion 92A is disposed on the axial end face 91Ad side of the outer diameter surface 91Aa of the main body portion 91A, and protrudes radially outward from the outer diameter surface 91Aa of the main body portion 91A. The axial thickness of the outer protrusion 92A increases radially inward. The outer diameter surface 92Aa of the outer protrusion 92A on the radially outer side is cylindrical. One axial side of the outer protrusion 92A is the end face 91Ad, and an end face 92Ab opposite the axial end face 91Ad is tapered inward in the axial direction, becoming more distant from the end face 91Ad in the axial direction.

[0062] The cover member 73A is made of a hard resin such as nylon and has a circular shape that is formed seamlessly as a single piece. The cover member 73A has a bottom portion 111A, a base portion 101A, and a plurality of ribs 102A.

[0063] The bottom 111A is a circular, flat plate with holes. The bottom 111A has an outer diameter surface 111Aa that is a circumferentially discontinuous cylindrical surface, and an inner diameter surface 111Ab that is a cylindrical surface. The bottom 111A has a bottom surface 111Ac on one axial side and an end surface 111Ad on the other axial side that are both flat and extend in a direction perpendicular to the axis of the bottom 111A. The end surface 111Ad of the bottom 111A is located at the end of one axial side of the cover member 73A, and is flat and extends in a direction perpendicular to the axis of the cover member 73A.

[0064] The base portion 101A is cylindrical. The base portion 101A extends from the outside of the bottom surface 111Ac in the radial direction of the bottom portion 111A to the opposite side of the end surface 111Ad of the bottom portion 111A in the axial direction. The outer diameter surface 111Aa of the bottom portion 111A extends to the base portion 101A and also forms the outer diameter surface of the base portion 101A. The inner diameter surface 101Ab of the base portion 101A is cylindrical. The end surface 101Ac of the base portion 101A opposite the bottom portion 111A in the axial direction is flat and extends in a direction perpendicular to the axis of the cover member 73A. The end surface 101Ac of the base portion 101A is at the end on the other axial side of the cover member 73A.

[0065] The ribs 102A are provided at equal intervals around the circumferential direction of the bottom portion 111A and the base portion 101A, and protrude outward in the radial direction of the bottom portion 111A and the base portion 101A from the outer diameter surfaces 111Aa of the bottom portion 111A and the base portion 101A. Thus, the cover member 73A is provided with a plurality of ribs 102A that protrude outward in the radial direction. The plurality of ribs 102A have the same shape. The ribs 102A extend from an end surface 111Ad of the bottom portion 111A to an end surface 101Ac of the base portion 101A. Thus, the ribs 102A are formed from one axial end to the other axial end of the cover member 73A.

[0066] The rib 102A has side surfaces (not shown) on both sides in the circumferential direction of the bottom 111A and the base 101A that are parallel to each other and are planar along the axial direction of the bottom 111A and the base 101A, parallel to a radial line of the bottom 111A and the base 101A that passes through the center between them. The rib 102A has a radially outer surface 102Ab of the bottom 111A and the base 101A such that the center in the axial direction of the bottom 111A and the base 101A is located at the outermost position in the radial direction of the bottom 111A and the base 101A, and the further away from the axial center of the bottom 111A and the base 101A in the axial direction of the bottom 111A and the base 101A, the more inward the surface 102Ab is located in the radial direction of the bottom 111A and the base 101A. The surface 102Ab of the rib 102A is located at the radially outer end of the cover member 73A. Therefore, the radially outer side of the cover member 73A is formed so that the outer diameter increases from the axial end faces 101Ac, 111Ad toward the axial center. The surface 102Ab of the rib 102A on the radially outer side of the cover member 73A forms a curved "L" shape when the cover member 73A is viewed perpendicular to the axis. The cross section of the surface 102Ab of the rib 102A when the cover member 73A is cut along a plane extending perpendicular to the axis of the cover member 73A forms an arc shape coaxial with the bottom portion 111A and the outer diameter surface 111Aa of the base portion 101A.

[0067] The cover member 73A is provided between the rod guide 28 and the stopper member 71, with the main shaft portion 52 of the piston rod 51 inserted into the radially inner side of the bottom portion 111A. In this case, the cover member 73A is oriented so that the bottom portion 111A is on the stopper member 71 side in the axial direction, and the base portion 101A is on the rod guide 28 side in the axial direction.

[0068] The cushion member 72A is provided between the rod guide 28 and the bottom portion 111A of the cover member 73A, with the main shaft portion 52 of the piston rod 51 inserted radially inside the main body portion 91A. The cushion member 72A is oriented so that the outer protrusion 92A faces the bottom portion 111A of the cover member 73A in the axial direction, and is disposed radially inside the base portion 101A of the cover member 73A. An end surface 91Ad of the cushion member 72A abuts in surface contact against a bottom surface 111Ac of the bottom portion 111A of the cover member 73A.

[0069] The axial length of the cushion member 72A is longer than the axial length of the base portion 101A of the cover member 73A. Therefore, the cover member 73A covers the axial outward protruding portion 92A side, which is a radially outer portion of the cushion member 72A. In other words, the cushion member 72A protrudes from the cover member 73A on the side opposite the bottom portion 111A in the axial direction. The cover member 73A has a plurality of ribs 102A that protrude radially outward. The outer diameter of the cover member 73A is smaller than the inner diameter of the inner tube 15. Therefore, the entire cover member 73A is spaced radially inward from the inner circumferential surface 15a of the inner tube 15.

[0070] Impact absorbing mechanism 75A, which has separate members: stopper member 71, cushion member 72A, and cover member 73A, applies resistance to piston rod 51 when piston rod 51 moves to a predetermined position on the fully extended side relative to cylinder 17, thereby absorbing the impact that occurs when piston rod 51 stops. At that time, cushion member 72A reduces the moving speed of piston rod 51 to absorb the impact, and cover member 73A, which is more rigid than cushion member 72A, restricts movement of piston rod 51 toward the extended side beyond the fully extended position.

[0071] An axial tensile load is applied to shock absorber 11A, causing piston rod 51 to move axially relative to cylinder 17 in the extension direction, increasing the overall length of shock absorber 11A. When piston rod 51 moves to a predetermined position relative to cylinder 17, shock absorber 11A causes cushion member 72A to abut against end surface 28a of rod guide 28 at main body portion 91A of shock absorber mechanism 75A. When piston rod 51 moves further in the extension direction relative to cylinder 17, main body portion 91A of cushion member 72A is sandwiched axially between rod guide 28 and bottom portion 111A of cover member 73A and elastically deforms in the compression direction. This provides resistance to the movement of piston rod 51. At the same time, cushion member 72A expands radially inward and outward. As a result, cushion member 72A is pressed against inner diameter surface 101Ab of base portion 101A of cover member 73A and against outer diameter surface 52a of main shaft portion 52. This also allows the cushion member 72A to provide resistance to the movement of the piston rod 51.

[0072] When the piston rod 51 further extends relative to the cylinder 17, as shown in FIG. 7 , the cover member 73A of the impact-absorbing mechanism 75A abuts against the end surface 28a of the rod guide 28 at the end surface 101Ac of the base portion 101A. At this time, the cover member 73A abuts against the outer bottom surface 81a of the bottom portion 81 of the stopper member 71 at the end surface 111Ad of the bottom portion 111A, thereby restricting further movement of the stopper member 71 toward the rod guide 28. Thus, the piston rod 51 reaches a fully extended state in which further movement toward the extension side relative to the cylinder 17 is restricted. When the piston rod 51 reaches the fully extended state, the cover member 73A prevents further deformation of the cushion member 72A. In this state, the cushion member 72A elastically deforms within the area surrounded by the piston rod 51, the rod guide 28, and the cover member 73A. However, the volume within this range is larger than the volume of the cushion member 72A that is deformed within this range, and the cushion member 72A does not completely fill this range.

[0073] The shock absorber 11A of the second embodiment includes a cushion member 72A provided between the stopper member 71 and the rod guide 28, and a cover member 73A disposed radially outward of the cushion member 72A and covering a portion of the radially outer side of the cushion member 72A. Thus, during the extension process, the cushion member 72A first contacts the rod guide 28 and undergoes compressive deformation, causing the cushion member 72A to be subjected to a compressive load. The cushion member 72A then deforms to a certain extent, and the cover member 73A contacts the rod guide 28 and the stopper member 71, causing the cover member 73A to be subjected to a compressive load. This suppresses noise and prevents excessive loads on the cushion member 72A. Because the shock absorber 11A includes the cover member 73A separate from the stopper member 71, shock absorption characteristics during full extension can be adjusted by changing the shape of the cover member 73A. This eliminates the need to change the shape of the stopper member 71, improving the flexibility of characteristic adjustment.

[0074] Furthermore, shock absorber 11A includes multiple ribs 102A that protrude radially outward from cover member 73A, thereby suppressing deformation of cover member 73A in the radially outward direction. Specifically, when cushion member 72A is crushed by rod guide 28 and bottom portion 111A of cover member 73A, it deforms toward base portion 101A of cover member 73A, generating a force that deforms base portion 101A radially outward. At this time, ribs 102A can suppress deformation of base portion 101A of cover member 73A. Even if cover member 73A deforms and contacts inner circumferential surface 15a of inner cylinder 15, hydraulic locking due to impact absorbing mechanism 75A can be suppressed by the flow paths between ribs 102A.

[0075] Furthermore, in the shock absorber 11A, the rib 102A is formed from one axial end to the other axial end of the cover member 73A, so that deformation of the cover member 73A can be further suppressed.

[0076] Furthermore, by using a hard resin for the cover member 73A of the shock absorber 11A, it is possible to expect measures against abnormal noise caused by metal contact, improved durability, and weight reduction.

[0077] Furthermore, the shock absorber 11A is formed such that the outer diameter of the radially outer side of the cover member 73A, i.e., the outer side of the rib 102A in the radial direction of the cover member 73A, increases from the axial end faces 101Ac, 111Ad toward the axial center. Therefore, when the cover member 73A is expanded in diameter due to the radial load received from the cushion member 72A in addition to receiving the axial compressive load, it can come into contact with the inner circumferential surface 15a of the inner tube 15 of the cylinder 17, and deformation of the cover member 73A can be suppressed by the cylinder 17. This improves the durability of the cover member 73A. In this case, the radially outer side of the cushion member 72A is not limited to a curved "L" shape, but may also be a bent "L" shape.

[0078] Here, shock absorber 11A may be formed so that rib 102A of cover member 73A is in constant sliding contact with inner circumferential surface 15a of inner tube 15 of cylinder 17. With this configuration, compared to when there is a radial gap between rib 102A and inner tube 15, it is possible to suppress the generation of abnormal noise when cover member 73A deforms and abuts against inner tube 15, and to suppress variations in performance of cushion member 72A due to radial variations.

[0079] Furthermore, in shock absorber 11A, cover member 73A is positioned radially outside cushion member 72A and covers a portion of the radial outside of cushion member 72A, but if end face 28a of rod guide 28 is stepped and abuts against cover member 73A after cushion member 72A is compressed and deformed, it may be configured to cover the entire radial outside of cushion member 72A.

[0080] [Third embodiment] Next, the third embodiment will be described, focusing on the differences from the first embodiment, mainly with reference to Figures 8 and 9. Note that parts common to the first embodiment will be designated by the same names and symbols.

[0081] 8, in shock absorber 11B of the third embodiment, a shock absorbing mechanism 75B that is partially different from shock absorbing mechanism 75 is provided instead of shock absorbing mechanism 75. Shock absorbing mechanism 75B has a cushion member 72B that is partially different from cushion member 72 instead of cushion member 72, and has a cover member 73B that is partially different from cover member 73 instead of cover member 73.

[0082] The cushion member 72B is made of synthetic rubber such as NBR (nitrile rubber) and has a seamless, integrally formed circular shape. The cushion member 72B has a main body portion 91B, an outer protruding portion 92B, and an annular recessed portion 93B.

[0083] The main body portion 91B is cylindrical. An outer diameter surface 91Ba on the radially outer side of the main body portion 91B is a discontinuous cylindrical surface in the axial direction, and an inner diameter surface 91Bb on the radially inner side of the main body portion 91B is a continuous cylindrical surface in the axial direction. When the cushion member 72B is cut along a plane including the central axis of the cushion member 72B, the cross-section of the main body portion 91B has an outwardly convex semicircular shape in the axial direction of the cushion member 72B.

[0084] The outer protrusion 92B is annular. The outer protrusion 92B protrudes radially outward from the main body 91B from an axially intermediate position of an outer diameter surface 91Ba of the main body 91B. The axial thickness of the outer protrusion 92B decreases as the outer protrusion 92B moves radially outward from the main body 91B. An end face 92Ba on one axial side of the outer protrusion 92B is flat and extends in a direction perpendicular to the axis of the cushion member 72B. An end face 92Bb on the other axial side of the outer protrusion 92B is a curved surface that slopes entirely toward the end face 92Ba in the axial direction of the cushion member 72B as it moves radially outward. A tip end face 92Bc of the radially outer end of the outer protrusion 92B has a cross-sectional shape that is convex outward in the radial direction of the cushion member 72B when the cushion member 72B is cut along a plane including the central axis of the cushion member 72B.

[0085] The annular recess 93B is provided at an axially intermediate position of the main body portion 91B, adjacent to an end face 92Ba of the outer protrusion 92B. The annular recess 93B is annular and recessed radially inward of the cushion member 72B relative to the outer diameter surface 91Ba of the main body portion 91B. The annular recess 93B has a radially inner concave surface 93Ba and an inclined surface 93Bb at an end opposite the end face 92Ba of the concave surface 93Ba. The cross section of the concave surface 93Ba when the cushion member 72B is cut along a plane including the central axis of the cushion member 72B has an arc-shaped cross section that is concave inward in the radial direction of the cushion member 72B. The end face 92Bb is inclined so that it moves away from the end face 92Ba in the axial direction as it moves radially outward.

[0086] The cover member 73B is made of a hard resin such as nylon and has a circular shape that is formed seamlessly as a single piece. The cover member 73B has a protrusion 103B that is partially different from the protrusion 103 in place of the protrusion 103.

[0087] The protrusion 103B is annular and protrudes radially inward from an axially intermediate position of the inner diameter surface 101b of the base portion 101. The axial thickness of the protrusion 103B decreases as the protrusion 103B moves radially inward from the base portion 101. The protrusion 103B has an end face 103Ba on one axial side that is flat and extends in a direction perpendicular to the axis of the cover member 73B. The protrusion 103B has an end face 103Bb on the other axial side that is curved and inclined so as to approach the end face 103Ba in the axial direction of the cover member 73B as it approaches the radially inner side. The radially inner portion of the end face 103Bb is inclined in the same manner as the inclined surface 93Bb of the cushion member 72B. The protrusion 103B has a tip surface 103Bc at its radially inner end, and the cross section of the cover member 73B cut along a plane including the central axis of the cover member 73B has an arc-like shape that convexly faces inward in the radial direction of the cover member 73B. The tip surface 103Bc of the protrusion 103B is a curved surface that is convex inward in the shape similar to the concave surface 93Ba of the annular recess 93B of the cushion member 72B.

[0088] The cushion member 72B is provided between the rod guide 28 and the stopper member 71 with the main shaft portion 52 of the piston rod 51 inserted radially inside the main body portion 91B of the cushion member 72B. In this state, the cushion member 72B is oriented in the axial direction so that the annular recessed portion 93B is located closer to the stopper member 71 than the outer protruding portion 92B. The cover member 73B is disposed radially outside the cushion member 72B, with the protruding portion 103B protruding radially inward being inserted into and fitted into the annular recessed portion 93B of the cushion member 72B. As a result, the end face 103Ba of the protrusion 103B comes into surface contact with the end face 92Ba of the outer protrusion 92B of the cushion member 72B, the tip face 103Bc of the protrusion 103B comes into surface contact with the concave surface 93Ba of the annular recess 93B of the cushion member 72B, the end face 103Bb of the protrusion 103B comes into surface contact with the inclined surface 93Bb of the annular recess 93B of the cushion member 72B, and the inner diameter surface 101b of the base portion 101 comes into surface contact with the tip face 92Bc of the outer protrusion 92B of the cushion member 72B.

[0089] The axial length of the cushion member 72B is longer than the axial length of the cover member 73B. The cover member 73B covers a radially outer portion of the cushion member 72B, which is a central portion in the axial direction. In other words, the cushion member 72B protrudes from the cover member 73B on both sides in the axial direction. The cover member 73B has a plurality of ribs 102 that protrude radially outward. The outer diameter of the cover member 73B is smaller than the inner diameter of the inner tube 15. Therefore, the entire cover member 73B is spaced radially inward from the inner circumferential surface 15a of the inner tube 15. The cover member 73B has a protrusion 103B that protrudes radially inward and is inserted into the cushion member 72B. The protrusion 103B is formed so that one axial end face 103Bb is inclined with respect to a plane that extends in a direction perpendicular to the axis of the cover member 73B.

[0090] The cushion member 72B is fitted to the main shaft portion 52 of the piston rod 51, with the stopper member 71 fixed in advance, on the side that is fitted to the rod guide 28 relative to the stopper member 71. In this state, the cover member 73B is placed over the radially outer side of the cushion member 72B, which is made of an elastic material, while elastically deforming the cushion member 72B radially inward. At this time, the inclined end surface 103Bb of the protrusion 103B of the cover member 73B contacts the inclined end surface 92Bb of the outer protrusion 92B of the cushion member 72B, elastically deforming the outer protrusion 92B radially inward. The protrusion 103B then fits into the annular recess 93B. By fitting the protrusion 103B of the cover member 73B into the annular recess 93B of the cushion member 72B in this manner, the cushion member 72B and the cover member 73B are positioned axially and radially and integrated. Before assembling the cushion member 72B to the piston rod 51, the cushion member 72B made of an elastic material may be inserted into the cover member 73B while being elastically deformed radially inward as needed, and the annular recess 93B may be fitted into the protrusion 103B of the cover member 73B to integrate the cushion member 72B and the cover member 73B. In this state, the cushion member 72B may be fitted into the main shaft portion 52 of the piston rod 51, to which the stopper member 71 has been fixed in advance, on the side that is fitted into the rod guide 28 rather than the stopper member 71.

[0091] Impact absorbing mechanism 75B, which has separate members: stopper member 71, cushion member 72B, and cover member 73B, applies resistance to piston rod 51 when piston rod 51 moves to a predetermined position on the fully extended side relative to cylinder 17, thereby absorbing the impact that occurs when piston rod 51 stops. At that time, cushion member 72B reduces the moving speed of piston rod 51 to absorb the impact, and cover member 73B, which is more rigid than cushion member 72B, restricts movement of piston rod 51 toward the extended side beyond the fully extended position.

[0092] An axial tensile load is applied to shock absorber 11B, causing piston rod 51 to move axially relative to cylinder 17 in the extension direction, increasing the overall length of shock absorber 11B. When piston rod 51 moves to a predetermined position relative to cylinder 17, cushion member 72B of shock absorber 11B abuts against end surface 28a of rod guide 28 at main body portion 91B. When piston rod 51 moves further in the extension direction relative to cylinder 17, main body portion 91B of cushion member 72B is sandwiched axially between rod guide 28 and stopper member 71 and elastically deforms in the compression direction. This provides resistance to the movement of piston rod 51. At the same time, cushion member 72B expands radially inward and outward. As a result, cushion member 72B is pressed against inner diameter surface 101b of base portion 101 of cover member 73B and against outer diameter surface 52a of main shaft portion 52. This also allows the cushion member 72B to provide resistance to the movement of the piston rod 51.

[0093] As the piston rod 51 moves further toward the extension side relative to the cylinder 17, as shown in FIG. 9 , the impact-absorbing mechanism 75B causes the cover member 73B to abut against the end surface 28a of the rod guide 28 at one end surface 101c of the base portion 101 and against the outer bottom surface 81a of the bottom portion 81 of the stopper member 71 at the other end surface 101c of the base portion 101, restricting further movement of the stopper member 71 toward the rod guide 28. Thus, the piston rod 51 reaches a fully extended state in which further movement toward the extension side relative to the cylinder 17 is restricted. When the piston rod 51 reaches the fully extended state, the cover member 73B prevents further deformation of the cushion member 72B. In this state, the cushion member 72B elastically deforms within the area surrounded by the piston rod 51, the rod guide 28, the stopper member 71, and the cover member 73B. However, the volume within this range is larger than the volume of the cushion member 72B that is deformed within this range, and the cushion member 72B does not completely fill this range.

[0094] The shock absorber 11B of the third embodiment includes a cushion member 72B disposed between the stopper member 71 and the rod guide 28, and a cover member 73B disposed radially outward of the cushion member 72B and covering a portion of the radially outer side of the cushion member 72B. Thus, during the extension process, the cushion member 72B first contacts the stopper member 71 and the rod guide 28 and elastically deforms, causing the cushion member 72B to receive a compressive load. The cushion member 72B then deforms to a certain extent, and the cover member 73B contacts the stopper member 71 and the rod guide 28, causing the cover member 73B to receive a compressive load. This suppresses noise and prevents excessive loads on the cushion member 72B. Because the shock absorber 11B includes the cover member 73B separately from the stopper member 71, the shock absorber can adjust its shock absorption characteristics during full extension by simply changing the shape of the cover member 73B. This eliminates the need to change the shape of the stopper member 71, improving the flexibility of the characteristic adjustment.

[0095] Furthermore, shock absorber 11B includes a plurality of ribs 102 that protrude radially outward from cover member 73B, thereby suppressing deformation of cover member 73B in the radially outward direction. That is, when cushion member 72B is crushed by rod guide 28 and stopper member 71, it deforms toward cover member 73B, generating a force that deforms cover member 73B radially outward. At that time, ribs 102 can suppress deformation of cover member 73B. Even if cover member 73B deforms and contacts inner circumferential surface 15a of inner cylinder 15, hydraulic locking caused by impact absorbing mechanism 75B can be suppressed by the flow paths between ribs 102.

[0096] Furthermore, in the shock absorber 11B, the rib 102 is formed from one axial end to the other axial end of the cover member 73B, so that deformation of the cover member 73B can be further suppressed.

[0097] Furthermore, shock absorber 11B has protrusion 103B that protrudes radially inward from cover member 73B and is inserted into cushion member 72B, thereby enabling cushion member 72B and cover member 73B to be positioned. This facilitates the assembly work of assembling cushion member 72B and cover member 73B to piston rod 51.

[0098] Furthermore, by using a hard resin for the cover member 73B of the shock absorber 11B, it is possible to expect measures against abnormal noise caused by metal contact, improved durability, and weight reduction.

[0099] Furthermore, shock absorber 11B is formed so that the outer diameter of the radially outer side of cover member 73B, i.e., the outer side of rib 102 in the radial direction of cover member 73B, increases from axial end face 101c to the axial center. Therefore, when cover member 73B is expanded in diameter by a radial load received from cushion member 72B in addition to receiving an axial compressive load, cover member 73B can come into contact with inner circumferential surface 15a of inner tube 15 of cylinder 17, and deformation thereof can be suppressed by cylinder 17. This makes it possible to improve the durability of cover member 73B.

[0100] Furthermore, in the shock absorber 11B, one axial end face 103Bb of the protruding portion 103B is formed so as to be inclined, which can improve the strength of the protruding portion 103B and also improve the workability when assembling the cover member 73B to the cushion member 72B. Note that the other axial end face of the protruding portion 103B may be formed so as to be inclined.

[0101] Furthermore, in the shock absorber 11B, one axial end face 92Bb of the outer protruding portion 92B is formed to be inclined, which can improve the strength of the outer protruding portion 92B and also improve the workability when assembling the cover member 73B to the cushion member 72B. Note that the other axial end face of the outer protruding portion 92B may be formed to be inclined.

[0102] Here, shock absorber 11B may be formed so that rib 102 of cover member 73B is in constant sliding contact with inner circumferential surface 15a of inner tube 15 of cylinder 17. With this configuration, compared to when there is a radial gap between rib 102 and inner tube 15, it is possible to suppress the generation of abnormal noise when cover member 73B deforms and abuts against inner tube 15, and to suppress variations in performance of cushion member 72B due to radial variations.

[0103] Furthermore, in shock absorber 11B, cover member 73B is positioned radially outside cushion member 72B and covers a portion of the radial outside of cushion member 72B, but if end face 28a of rod guide 28 is stepped and comes into contact with cover member 73B after cushion member 72B is compressed and deformed, it may be possible to cover the entire radial outside of cushion member 72B.

[0104] [Fourth embodiment] Next, the fourth embodiment will be described, focusing on the differences from the first embodiment, mainly with reference to Figures 10 and 11. Note that parts common to the first embodiment will be designated by the same names and symbols.

[0105] 10, in a shock absorber 11C of the fourth embodiment, an impact absorbing mechanism 75C that is partially different from impact absorbing mechanism 75 is provided instead of impact absorbing mechanism 75. Impact absorbing mechanism 75C has a cushion member 72C that is partially different from cushion member 72 instead of cushion member 72, and has a cover member 73C that is partially different from cover member 73 instead of cover member 73.

[0106] The cushion member 72C is made of synthetic rubber such as NBR (nitrile rubber) and has a seamless, integrally formed circular shape. The cushion member 72C is mirror-symmetrical in the axial direction. The cushion member 72C has a main body portion 91C, an outer protrusion 94C, and an annular recess 93C.

[0107] The main body portion 91C is cylindrical. An outer diameter surface 91Ca on the radially outer side of the main body portion 91C is a cylindrical surface that is discontinuous in the axial direction, and an inner diameter surface 91Cb on the radially inner side of the main body portion 91C is a cylindrical surface that is discontinuous in the axial direction. When the cushion member 72C is cut along a plane including the central axis of the cushion member 72C, the cross-section of the main body portion 91C has an outwardly convex semicircular shape in the axial direction of the cushion member 72C.

[0108] The outer protrusion 94C is annular and is disposed at the center of the outer diameter surface 91Ca of the main body 91C in the axial direction, and protrudes from the outer diameter surface 91Ca outward in the radial direction of the main body 91C. The outer protrusion 94C has a cylindrical outer surface 94Ca on the radially outer side, and end surfaces 94Cb on both axial sides are tapered surfaces that become increasingly farther away from the outer surface 94Ca in the axial direction as they extend radially inward.

[0109] The annular recess 93C is provided in the axial center of the main body portion 91C. The annular recess 93C is annular and recessed radially outward of the cushion member 72C relative to an inner diameter surface 91Cb of the main body portion 91C. The annular recess 93C has end surfaces 93Ca on both axial sides that are flat and extend in a direction perpendicular to the axis of the cushion member 72C. When the cushion member 72C is cut along a plane including the central axis of the cushion member 72C, the cross-section of the recessed surface 93Cb at the radial outer end of the annular recess 93C has an arc-like shape recessed radially outward of the cushion member 72C.

[0110] The cover member 73C is made of a hard resin such as nylon and has a seamless, integrally formed circular shape. The cover member 73C is mirror-symmetrical in the axial direction. The cover member 73C has a base portion 101C and a protrusion 103C.

[0111] The base portion 101C is cylindrical. The outer diameter surface 101Ca of the base portion 101C is a cylindrical surface that is discontinuous in the axial direction, and the inner diameter surface 101Cb of the base portion 101C is a cylindrical surface that is continuous in the axial direction. The end faces 101Cc on both sides of the axial direction of the base portion 101C are flat surfaces that extend in a direction perpendicular to the axis of the base portion 101C. The end faces 101Cc on both sides of the base portion 101C are located at both axial end portions of the cover member 73C.

[0112] The protrusion 103C is annular and protrudes radially outward from the axial center of the outer diameter surface 101Ca of the base portion 101C. Both axial end surfaces 103Ca of the protrusion 103C are flat and extend in a direction perpendicular to the axis of the cover member 73C. The distal end surface 103Cb of the protrusion 103C at its radially outer end has a cross-sectional shape that is convex outward in the radial direction of the cover member 73C when the cover member 73C is cut along a plane including the central axis of the cover member 73C. The distal end surface 103Cb of the protrusion 103C is a convex curved surface with a shape similar to the concave surface 93Cb of the annular recess 93C of the cushion member 72C.

[0113] The cover member 73C is disposed between the rod guide 28 and the stopper member 71, with the main shaft portion 52 of the piston rod 51 inserted radially inside the base portion 101C. The cover member 73C is disposed radially inside the cushion member 72C, with a protruding portion 103C protruding radially outwardly inserted into and fitted into the annular recessed portion 93C of the cushion member 72C, such that a tip end surface 103Cb of the protruding portion 103C abuts in surface contact against the recessed surface 93Cb of the annular recessed portion 93C, and one end surface 103Ca abuts in surface contact against one end surface 93Ca of the annular recessed portion 93C, and the other end surface 103Ca abuts in surface contact against the other end surface 93Ca of the annular recessed portion 93C. In this state, the outer diameter surface 101Ca of the base portion 101C of the cover member 73C abuts in surface contact against the inner diameter surface 91Cb of the main body portion 91C of the cushion member 72C.

[0114] The axial length of the cushion member 72C is longer than the axial length of the cover member 73C. Therefore, the cover member 73C covers the axial center portion, which is a part of the radially inner side of the cushion member 72C. In other words, the cushion member 72C protrudes evenly on both sides in the axial direction from the cover member 73C. The outer diameter of the cushion member 72C is smaller than the inner diameter of the inner tube 15. Therefore, the entire cushion member 72C is spaced radially inward from the inner circumferential surface 15a of the inner tube 15. The cover member 73C has a protrusion 103C that protrudes radially outward and is inserted into the cushion member 72C.

[0115] The cover member 73C is fitted to the main shaft portion 52 of the piston rod 51, to which the stopper member 71 is fixed in advance, on the side that is fitted to the rod guide 28 relative to the stopper member 71. In this state, the cushion member 72C made of an elastic material is elastically deformed radially outward as appropriate to cover the radially outer side of the cover member 73C, and the protrusion 103C is fitted into the annular recess 93C. By fitting the protrusion 103C of the cover member 73C into the annular recess 93C of the cushion member 72C in this way, the cushion member 72C and the cover member 73C are positioned axially and radially and integrated. Before assembling the cushion member 72C made of an elastic material to the piston rod 51, the cushion member 72C may be elastically deformed radially outward to cover the cover member 73C, and the annular recess 93C may be fitted into the protrusion 103C of the cover member 73C to integrate the cushion member 72C and the cover member 73C. In this state, the cover member 73C may be fitted into the main shaft portion 52 of the piston rod 51, to which the stopper member 71 has been fixed, on the side that is fitted into the rod guide 28 rather than the stopper member 71.

[0116] Impact absorbing mechanism 75C, which has separate members: stopper member 71, cushion member 72C, and cover member 73C, applies resistance to piston rod 51 when piston rod 51 moves to a predetermined position on the fully extended side relative to cylinder 17, thereby absorbing the impact that occurs when piston rod 51 stops. At that time, cushion member 72C reduces the moving speed of piston rod 51 to absorb the impact, and cover member 73C, which is more rigid than cushion member 72C, restricts movement of piston rod 51 toward the extended side beyond the fully extended position.

[0117] An axial tensile load is applied to shock absorber 11C, causing piston rod 51 to move axially relative to cylinder 17 in the extension direction, which increases the overall length of shock absorber 11C. When piston rod 51 moves to a predetermined position relative to cylinder 17, cushion member 72C of impact absorbing mechanism 75C abuts against end surface 28a of rod guide 28 at main body portion 91C. When piston rod 51 moves further in the extension direction relative to cylinder 17, main body portion 91C of cushion member 72C is sandwiched axially between rod guide 28 and stopper member 71 and elastically deforms in the compression direction. This provides resistance to the movement of piston rod 51. At that time, cushion member 72C expands radially outward.

[0118] 11, when the piston rod 51 moves further toward the extension side relative to the cylinder 17, the cover member 73C of the impact absorbing mechanism 75C abuts against the end surface 28a of the rod guide 28 at one end surface 101Cc of the base portion 101C, and abuts against the inner bottom surface 81b of the bottom portion 81 of the stopper member 71 at the other end surface 101Cc of the base portion 101C, restricting further movement of the stopper member 71 toward the rod guide 28. Thus, the piston rod 51 reaches a fully extended state in which further movement toward the extension side relative to the cylinder 17 is restricted. When the piston rod 51 reaches the fully extended state, the cover member 73C restricts further deformation of the cushion member 72C.

[0119] The shock absorber 11C of the fourth embodiment includes a cushion member 72C disposed between the stopper member 71 and the rod guide 28, and a cover member 73C disposed radially inside the cushion member 72C and covering a portion of the radially inside of the cushion member 72C. Thus, during the extension process, the cushion member 72C first contacts the stopper member 71 and the rod guide 28 and undergoes compressive deformation, resulting in the cushion member 72C being subjected to a compressive load. The cushion member 72C then deforms to a certain extent, and the cover member 73C contacts the stopper member 71 and the rod guide 28, resulting in the cover member 73C being subjected to a compressive load. This suppresses noise and prevents excessive loads on the cushion member 72C. Because the shock absorber 11C includes the cover member 73C separate from the stopper member 71, the shock absorber can adjust its shock absorption characteristics during full extension by simply changing the shape of the cover member 73C, eliminating the need to change the shape of the stopper member 71, thereby improving the flexibility of characteristic adjustment.

[0120] Furthermore, shock absorber 11C has protrusion 103C that protrudes radially outward from cover member 73C and is inserted into cushion member 72C, thereby enabling cushion member 72C and cover member 73C to be positioned, thereby facilitating the assembly work of assembling cushion member 72C and cover member 73C to piston rod 51.

[0121] Furthermore, by using a hard resin for the cover member 73C of the shock absorber 11C, it is possible to expect measures against abnormal noise caused by metal contact, improved durability, and weight reduction.

[0122] Here, in shock absorber 11C, cover member 73C is positioned radially inside cushion member 72C and covers a portion of the radial inside of cushion member 72C, but if end face 28a of rod guide 28 is stepped and abuts against cover member 73C after cushion member 72C is compressed and deformed, it may be configured to cover the entire radial inside of cushion member 72C.

[0123] In addition, in shock absorber 11C, one or both of end faces 103Ca of protrusion 103C may be inclined in its entirety so that the radially outward end faces approach end face 101Cc of base portion 101C, which faces in the same axial direction. This improves the strength of protrusion 103C and improves the ease of attachment of cushion member 72C to cover member 73C. In this case, the corresponding end face 93Ca of annular recess 93C of cushion member 72C is also inclined in the same manner. [Explanation of symbols]

[0124] 11, 11A to 11C... shock absorber, 17... cylinder, 28... rod guide (blocking member), 41... rod seal (blocking member), 45... piston, 48... first chamber (chamber), 49... second chamber (chamber), 51... piston rod, 71... stopper member, 72, 72A to 72C... cushion member, 73, 73A to 73C... cover member, 102, 102A... rib, 103, 103B, 103C... protrusion, 103Bb... end surface, L... oil (working fluid).

Claims

1. a cylinder in which a working fluid is sealed; a piston slidably inserted into the cylinder to divide the interior of the cylinder into two chambers; a piston rod having a first end connected to the piston and a second end extending outside the cylinder; a closing member provided at an end of the cylinder and closing the cylinder; a stopper member provided between the closing member and the piston; a cushion member provided between the stopper member and the closing member; a cover member disposed radially outward of the cushion member and covering at least a portion of the radially outward side of the cushion member; a plurality of ribs protruding radially outward from the cover member; A buffer comprising:

2. a cylinder in which a working fluid is sealed; a piston slidably inserted into the cylinder to divide the interior of the cylinder into two chambers; a piston rod having a first end connected to the piston and a second end extending outside the cylinder; a closing member provided at an end of the cylinder and closing the cylinder; a stopper member provided between the closing member and the piston; a cushion member provided between the stopper member and the closing member; a cover member disposed radially outward of the cushion member and covering at least a portion of the radially outward side of the cushion member; a protrusion protruding radially inward from the cover member and inserted into the cushion member; A buffer comprising:

3. The shock absorber according to claim 2, The cover member is provided with a plurality of ribs that protrude radially outward.

4. The shock absorber according to claim 1 or 3, The rib is formed from one axial end to the other axial end of the cover member.

5. The shock absorber according to claim 2 or 3, The protruding portion is a shock absorber in which one or the other of the axial end faces is formed to be inclined.

6. The shock absorber according to claim 1 or 3, The rib is formed so as to be in constant sliding contact with the cylinder.

7. The shock absorber according to claim 1 or 2, A shock absorber in which the outer diameter of the radially outer side of the cover member increases from the axial end face toward the axial center.

8. a cylinder in which a working fluid is sealed; a piston slidably inserted into the cylinder to divide the interior of the cylinder into two chambers; a piston rod having a first end connected to the piston and a second end extending outside the cylinder; a closing member provided at an end of the cylinder and closing the cylinder; a stopper member provided between the closing member and the piston; a cushion member provided between the stopper member and the closing member; a cover member disposed radially inside the cushion member and covering at least a portion of the radially inside of the cushion member; a protrusion protruding radially outward from the cover member and inserted into the cushion member; A buffer comprising:

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