Cylinder Device

Abstract

To provide a cylinder device which can inhibit rapid change in an amount of deflection of a rebound cushion against a load.SOLUTION: A cylinder device includes: a piston rod which is connected at one end side to a piston and inserted through a rod guide to extend to the outside of a cylinder at the other end side; and a rebound cushion 81 which is provided between the piston and the rod guide and comes into contact with the rod guide when the piston rod moves in a direction in which the piston rod extends from the cylinder. In the rebound cushion 81, multiple protruding parts 122 are provided arranged in a circumferential direction on a surface 145 facing the rod guide and multiple planar parts 111 are provided arranged in the circumferential direction at the outer periphery side facing the cylinder.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a cylinder device. [Background technology]

[0002] BACKGROUND ART In some cylinder devices, a rebound cushion is provided between a piston connected to a piston rod and a rod guide that guides the piston rod (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-092169 Summary of the Invention [Problem to be solved by the invention]

[0004] When the piston rod reaches a predetermined position on the fully extended side, the rebound cushion is pressed against the rod guide and deforms to absorb the impact of the fully extended state. In a cylinder device, there is a demand for suppressing a sudden change in the amount of deflection of the rebound cushion in response to a load.

[0005] SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a cylinder device that can suppress a sudden change in the amount of deflection of a rebound cushion in response to a load. [Means for solving the problem]

[0006] In order to achieve the above object, one aspect of the present invention comprises a cylinder in which a working fluid is sealed, a piston slidably fitted within the cylinder to divide the interior of the cylinder into two chambers, a rod guide provided on the opening side of the cylinder, a piston rod having one end connected to the piston and passing through the rod guide with the other end extending out of the cylinder, and a rebound cushion provided between the piston and the rod guide and abutting against the rod guide when the piston rod moves in a direction extending from the cylinder, wherein the rebound cushion has a plurality of convex portions arranged circumferentially on a surface facing the rod guide, and a plurality of flat portions arranged circumferentially on an outer periphery side facing the cylinder. [Effects of the Invention]

[0007] According to the present invention, it is possible to suppress a sudden change in the amount of deflection of the rebound cushion in response to a load. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing a cylinder device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view showing a rebound cushion of the cylinder device according to the embodiment of the present invention. [Figure 3] 2 is a cross-sectional view showing a rebound cushion, an inner cylinder, and a piston rod of the cylinder device according to the embodiment of the present invention. FIG. [Figure 4] 2 is a cross-sectional view showing a rebound cushion, an inner cylinder, a piston rod, a stopper member, and a rod guide of the cylinder device according to the embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

[0010] FIG. 1 shows a cylinder device 11 according to an embodiment. This cylinder device 11 is a shock absorber used in a suspension device for a vehicle such as an automobile or a railway vehicle. Specifically, the cylinder device 11 is a hydraulic shock absorber used in an automobile suspension device. The cylinder device 11 is a twin-cylinder shock absorber equipped with a cylinder 17 having an inner cylinder 15 and an outer cylinder 16. The inner cylinder 15 is cylindrical. The outer cylinder 16 is cylindrical with a bottom and has a larger diameter than the inner cylinder 15. The outer cylinder 16 is disposed radially outside the inner cylinder 15 and coaxially with the inner cylinder 15. A reservoir chamber 18 is formed between the outer cylinder 16 and the inner cylinder 15.

[0011] The outer cylinder 16 has a body 20 and a bottom 21. The body 20 is cylindrical. The bottom 21 closes one axial end of the body 20. The side of the body 20 opposite the bottom 21 forms an opening 22. The opening 22 of the outer cylinder 16 is also provided at one axial end of the cylinder 17. The bottom 21 of the outer cylinder 16 is also provided at the other axial end of the cylinder 17. In other words, one axial end of the cylinder 17 is open as the opening 22, and the other axial end is closed.

[0012] The inner cylinder 15 is a cylindrical, one-piece molded product made of a single piece of metal. The inner circumferential surface 15a of the inner cylinder 15 is cylindrical.

[0013] The cylinder device 11 includes a valve body 25 and a rod guide 26 . The valve body 25 is annular and is provided at one axial end of the inner cylinder 15 and the outer cylinder 16. The valve body 25 constitutes the base valve 30, and its outer periphery is stepped. The valve body 25 is placed on the bottom 21. At this time, the large-diameter portion of the outer periphery of the valve body 25 is positioned radially relative to the outer cylinder 16.

[0014] The rod guide 26 is annular, and is provided at the other axial end of the inner cylinder 15 and the outer cylinder 16. The rod guide 26 is provided on the opening 22 side of the cylinder 17. The rod guide 26 has a rod guide body 32 and a collar 33.

[0015] The rod guide body 32 is made of metal and has a circular ring shape. The rod guide 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 body 32 has a stepped outer periphery.

[0016] The collar 33 is cylindrical. The collar 33 is made of a metal cylinder whose inner circumferential surface is coated with a material having high slidability. The collar 33 is fitted and fixed to the inner circumferential portion of the rod guide main body 32.

[0017] The rod guide 26 is fitted into the inner periphery of the opening 22 side of the barrel 20 of the outer cylinder 16 at the large diameter portion 35 of the rod guide main body 32. The rod guide 26 has an end face 26a 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 26. The end face 26a is formed on the rod guide main body 32 and the collar 33.

[0018] One axial end of the inner cylinder 15 is fitted into the small-diameter portion of the outer periphery of the valve body 25 until it axially abuts against the large-diameter portion of the valve body 25. One axial end of the inner cylinder 15 is placed on the bottom 21 of the outer cylinder 16 via the valve body 25. 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 is fitted into the barrel 20 of the outer cylinder 16 via the rod guide 26. In this state, the inner cylinder 15 is positioned axially and radially relative to the outer cylinder 16. Here, the valve body 25 and the bottom 21 communicate with each other via a passage groove 40 formed in the valve body 25. The space between the valve body 25 and the bottom 21, like the space between the inner cylinder 15 and the outer cylinder 16, defines a reservoir chamber 18.

[0019] The cylinder device 11 is equipped with an annular rod seal 41. The rod seal 41 is provided on the opposite side of the rod guide 26 from the bottom 21 in the axial direction of the cylinder 17. Like the rod guide 26, this rod seal 41 is fitted to the inner periphery of the barrel 20. The outer cylinder 16 has a locking portion 43 formed at the end opposite the bottom 21 of the barrel 20. The locking portion 43 is formed by plastically deforming the barrel 20 radially inward by crimping, such as curling. The rod seal 41 is sandwiched between the locking portion 43 and the rod guide 26. At this time, the rod seal 41 is pressed against the inner periphery of the barrel 20 by the rod guide 26. As a result, the rod seal 41 closes the opening 22 of the outer cylinder 16. Specifically, the rod seal 41 is an oil seal.

[0020] The cylinder device 11 includes a piston 45. The piston 45 is slidably fitted in 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 26 in the inner tube 15. The second chamber 49 is provided between the piston 45 and the valve body 25 in the inner tube 15. The second chamber 49 is separated from the reservoir chamber 18 by the valve body 25. In the cylinder 17, oil L as a working fluid is sealed in the first chamber 48 and the second chamber 49. In the cylinder 17, gas G and oil L as working fluids are sealed in the reservoir chamber 18.

[0021] The cylinder device 11 is equipped with a piston rod 50. One axial end portion of the piston rod 50 is inserted inside the cylinder 17. The one end portion of the piston rod 50 is connected to the piston 45. An intermediate portion of the piston rod 50 in the axial direction passes through a rod guide 26 and a rod seal 41. The other axial end portion of the piston rod 50 extends outside the cylinder 17. The piston rod 50 is made of metal and passes through a first chamber 48. The piston rod 50 does not pass through a second chamber 49. Therefore, the first chamber 48 is a rod-side chamber through which the piston rod 50 passes. The second chamber 49 is a bottom-side chamber on the bottom 21 side of the cylinder 17. The portion of the piston rod 50 extending outside from the cylinder 17 is connected to the vehicle body.

[0022] The piston rod 50 has a main shaft portion 51 and a mounting shaft portion 52 . The outer diameter of the mounting shaft portion 52 is smaller than the outer diameter of the main shaft portion 51. The mounting shaft portion 52 side of the piston rod 50 is inserted into the cylinder 17.

[0023] The outer peripheral surface 51a of the main shaft portion 51 is cylindrical. The main shaft portion 51 of the piston rod 50 passes through the rod guide 26 and the rod seal 41. An engagement groove 53 is formed in the main shaft portion 51 of the piston rod 50. The engagement groove 53 is recessed radially inward from the outer peripheral surface 51a of the main shaft portion 51. The engagement groove 53 is annular and coaxial with the outer peripheral surface 51a of the main shaft portion 51. The engagement groove 53 is formed in a portion of the main shaft portion 51 that is disposed inside the inner cylinder 15 and that is disposed between the piston 45 and the rod guide 26.

[0024] The rod guide 26 and rod seal 41 are provided on the portion of the cylinder 17 from which the piston rod 50 extends. The rod guide 26 slidably supports the piston rod 50. The piston rod 50 is guided by the rod guide 26 at the outer peripheral surface 51a of the main shaft portion 51. The end surface 26a of the rod guide 26 extends perpendicular to the central axis of the piston rod 50. The piston rod 50 moves axially together with the piston 45 relative to the cylinder 17. During the extension stroke of the cylinder device 11, in which the piston rod 50 increases its protrusion from the cylinder 17, the piston 45 moves toward the first chamber 48. During the retraction stroke of the cylinder device 11, in which the piston rod 50 decreases its protrusion from the cylinder 17, the piston 45 moves toward the second chamber 49.

[0025] The rod seal 41 is provided on the side of the cylinder 17 from which the piston rod 50 extends, i.e., on the side of the opening 22 of the outer cylinder 16. The rod seal 41, together with the rod guide 26, seals the gap between the body 20 of the outer cylinder 16 and the main shaft portion 51 of the piston rod 50, 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.

[0026] A passage 55 and a passage 56 are formed in the piston 45. Both the passage 55 and the passage 56 axially penetrate the piston 45. The passages 55, 56 can communicate between the first chamber 48 and the second chamber 49. The cylinder device 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 21 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 21 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 50 together with the piston 45.

[0027] When the piston rod 50 moves toward the compression side, increasing the amount of penetration into the inner cylinder 15 and the outer cylinder 16, and the piston 45 moves in the direction narrowing the second chamber 49, the pressure in the second chamber 49 becomes higher than the pressure in the first chamber 48. Then, the disc valve 57 opens the passage 55, allowing the oil L in the second chamber 49 to flow into the first chamber 48. At that time, the disc valve 57 generates a damping force.

[0028] When the piston rod 50 moves toward the extension side, increasing the amount of protrusion from the inner cylinder 15 and the outer cylinder 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. 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 that time, the disc valve 58 generates a damping force.

[0029] 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 the most closed state of the passage 55.

[0030] A fixed orifice (not shown) is 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 the most closed state of the passage 56.

[0031] A fluid passage 61 and a fluid passage 62 are formed in the valve body 25. Both the fluid passage 61 and the fluid passage 62 axially pass through the valve body 25. Both the fluid passages 61 and 62 can communicate between the second chamber 49 and the reservoir chamber 18.

[0032] The base valve 30 includes a disc valve 65 and a disc valve 66. The disc valve 65 is provided on the bottom 21 side of the valve body 25 in the axial direction. The disc valve 65 closes the liquid passage 61 by abutting against the valve body 25. The disc valve 66 is provided on the opposite side of the valve body 25 from the bottom 21 in the axial direction. The disc valve 66 closes the liquid passage 62 by abutting against the valve body 25. The base valve 30 has a pin 68. This pin 68 attaches the disc valves 65, 66 to the valve body 25. The valve body 25, the disc valves 65, 66, the pin 68, etc. constitute the base valve 30.

[0033] When the piston rod 50 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. 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 50 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.

[0034] The cylinder device 11 includes a stopper member 80 and a rebound cushion 81. The stopper member 80 is made of metal and has an annular shape. The stopper member 80 has a support portion 91 and a fixing portion 92.

[0035] The support portion 91 is in the shape of a circular flat plate. The support portion 91 has a support surface 91a on one axial side thereof that is annular and has a flat surface that extends perpendicular to the axial direction of the support portion 91. The outer diameter of the support portion 91 is smaller than the inner diameter of the inner cylinder 15, i.e., the diameter of the inner circumferential surface 15a.

[0036] The fixing portion 92 protrudes from the inner peripheral edge of the support portion 91 on the opposite side to the support surface 91a in the axial direction of the support portion 91. The fixing portion 92 is cylindrical. The outer diameter of the fixing portion 92 is smaller than the outer diameter of the support portion 91.

[0037] Before being attached to the piston rod 50, the stopper member 80 has a cylindrical fixing portion 92. In this state, the stopper member 80 is fitted onto the main shaft portion 51 of the piston rod 50 with the fixing portion 92 projecting from the support portion 91 toward the piston 45. The fixing portion 92 is then crimped radially inward with its position aligned with the engagement groove 53 of the piston rod 50. As a result, the fixing portion 92 is plastically deformed and enters the engagement groove 53, and the stopper member 80 is fixed to the piston rod 50. In this state, the support surface 91a of the support portion 91 extends perpendicular to the central axis of the piston rod 50.

[0038] The rebound cushion 81 is an integrally molded product made of, for example, a thermoplastic resin material such as polyphenylene sulfide (PPS). Although PPS is used as an example of the material for the rebound cushion 81, other elastic materials may also be used.

[0039] 2 and 3, the rebound cushion 81 is cylindrical. The rebound cushion 81 has an outer peripheral surface 101 that is polygonal, specifically, a substantially regular hexagonal shape. The rebound cushion 81 also has an inner peripheral surface 102 that is cylindrical.

[0040] Here, the central axis of the inner peripheral surface 102 is the central axis of the rebound cushion 81, the direction along this central axis is the axial direction of the rebound cushion 81, the direction perpendicular to this central axis is the radial direction of the rebound cushion 81, and the circumferential direction of the inner peripheral surface 102 is the circumferential direction of the rebound cushion 81.

[0041] The outer peripheral surface 101 has a plurality of planar portions 111, specifically six planar portions 111, of the same shape. In other words, the rebound cushion 81 has a plurality of planar portions 111 formed on the outer peripheral side and arranged in the circumferential direction. All of these planar portions 111 have a flat shape that extends perpendicular to the radial direction of the rebound cushion 81. All of these planar portions 111 are arranged at equal distances from the central axis of the rebound cushion 81. These planar portions 111 are arranged at equal intervals in the circumferential direction of the rebound cushion 81.

[0042] The outer peripheral surface 101 has a plurality of, specifically six, chamfered portions 112 of the same shape. These chamfered portions 112 are all disposed at positions equidistant from the central axis of the rebound cushion 81. These chamfered portions 112 are arranged at equal intervals in the circumferential direction of the rebound cushion 81. Each of these chamfered portions 112 smoothly connects adjacent flat portions 111 in the circumferential direction of the rebound cushion 81. On the outer peripheral surface 101, the flat portions 111 and the chamfered portions 112 are alternately disposed in the circumferential direction of the rebound cushion 81.

[0043] As shown in FIG. 2, the rebound cushion 81 has a main body 121 and a plurality of, specifically six, protrusions 122 of the same shape.

[0044] The main body portion 121 is annular and has a constant length in the axial direction of the rebound cushion 81. The main body portion 121 is formed from a middle portion to one end portion in the axial direction of the inner circumferential surface 102 of the rebound cushion 81. The main body portion 121 has an end face 125 formed at one end in the axial direction of the rebound cushion 81. The end face 125 is flat and extends perpendicular to the central axis of the rebound cushion 81.

[0045] The main body portion 121 is formed from the middle portion to one end portion in the axial direction of the rebound cushion 81 on the outer peripheral surface 101. The main body portion 121 is formed with the entire chamfered portion 112 and the flat portion 111 from the middle portion to one end portion in the axial direction of the rebound cushion 81.

[0046] Each of the plurality of protrusions 122 protrudes from the main body 121 in the opposite direction to an end face 125 in the axial direction of the rebound cushion 81. The plurality of protrusions 122 are formed with a portion on the other end side of the inner circumferential surface 102 of the rebound cushion 81, opposite to the end face 125 in the axial direction.

[0047] Each of the plurality of protruding portions 122 has a portion formed on the other end side opposite to the end face 125 of the outer peripheral surface 101 of the rebound cushion 81 in the axial direction. Each of the plurality of protruding portions 122 has a portion formed on the other end side opposite to the end face 125 of the flat portion 111 in the axial direction of the rebound cushion 81. In other words, each of the plurality of protruding portions 122 is provided at the position of the corresponding flat portion 111 in the circumferential direction of the rebound cushion 81, and forms a part of this flat portion 111. In other words, in the rebound cushion 81, the protruding portions 122 and the flat portion 111 are aligned in phase with each other in the circumferential direction of the rebound cushion 81.

[0048] Since the plurality of protrusions 122 have the same shape, one of the protrusions 122 will be further described.

[0049] The protrusion 122 has a tapered shape such that the width in the circumferential direction of the rebound cushion 81 becomes narrower as the protrusion height from the main body 121 increases. The protrusion 122 has a protruding surface 130 on the opposite side to the end surface 125 in the axial direction of the rebound cushion 81, the protruding surface 130 having a tip surface portion 131, a pair of middle surface portions 132, and a pair of base end side surface portions 133.

[0050] The tip surface portion 131 is provided at the center of the protruding surface 130 in the circumferential direction of the rebound cushion 81. On the protruding surface 130, the tip surface portion 131 is located at the end opposite the end surface 125 in the axial direction of the rebound cushion 81. The tip surface portion 131 is also located at the end of the rebound cushion 81 opposite the end surface 125 in the axial direction of the rebound cushion 81. The tip surface portion 131 is flat and extends perpendicular to the central axis of the rebound cushion 81.

[0051] The pair of intermediate surface portions 132 are provided contiguous with the tip surface portion 131, on both sides of the tip surface portion 131 in the circumferential direction of the rebound cushion 81. The further each of the pair of intermediate surface portions 132 is from the tip surface portion 131 in the circumferential direction of the rebound cushion 81, the closer each of the pair of intermediate surface portions 132 is to the end face 125 in the axial direction of the rebound cushion 81. Each of the pair of intermediate surface portions 132 is arc-shaped with its center within the convex portion 122. The pair of intermediate surface portions 132 are mirror-symmetrical in the circumferential direction of the rebound cushion 81.

[0052] One of the pair of base end side surfaces 133 is provided contiguously with one of the pair of intermediate surfaces 132 on the opposite side of the tip surface 131 in the circumferential direction of the rebound cushion 81 from the intermediate surface 132. The other of the pair of base end side surfaces 133 is provided contiguously with the other of the pair of intermediate surfaces 132 on the opposite side of the tip surface 131 in the circumferential direction of the rebound cushion 81 from the intermediate surface 132. The further each of the pair of base end side surfaces 133 is from the tip surface 131 in the circumferential direction of the rebound cushion 81, the closer each of the pair of base end side surfaces 133 is to the end surface 125 in the axial direction of the rebound cushion 81. Each of the pair of base end side surfaces 133 has an arc shape with its center outside the convex portion 122. The pair of base end side surfaces 133 are mirror-symmetrical in the circumferential direction of the rebound cushion 81. The protrusions 122 are mirror-symmetrical in the circumferential direction of the rebound cushion 81 .

[0053] Such protrusions 122 are provided on the rebound cushion 81 and aligned in the circumferential direction. Between the protrusions 122 and the base end side surface portions 133 adjacent to the protrusions 122 in the circumferential direction of the rebound cushion 81, an end surface 141 is formed on the opposite side to the end surface 125 of the main body portion 121. The end surface 141 is flat and extends parallel to the end surface 125. The multiple protrusions 122 protrude from this end surface 141 of the main body portion 121 in the direction opposite to the end surface 125. In the rebound cushion 81, the end surface 141 and the multiple protruding surfaces 130 form an opposing surface 145 (surface) opposite to the end surface 125. In the rebound cushion 81, the multiple protrusions 122 are provided on this opposing surface 145 and aligned in the circumferential direction.

[0054] As shown in FIG. 1, the rebound cushion 81 configured as described above is disposed between the rod guide 26 and the piston 45, and between the rod guide 26 and the stopper member 80, with the main shaft portion 51 of the piston rod 50 inserted into the inner peripheral side. In this state, the rebound cushion 81 is oriented such that the protrusion 122 faces the end face 26a of the rod guide 26 and the end face 125 abuts against the support surface 91a of the support portion 91 of the stopper member 80. Therefore, the opposing surface 145 of the rebound cushion 81 faces the end face 26a of the rod guide 26. The rebound cushion 81 is also disposed within the inner tube 15 of the cylinder 17 together with the stopper member 80. As shown in FIG. 3, the outer peripheral surface 101 of the rebound cushion 81, including the plurality of flat portions 111, has a smaller diameter than the inner peripheral surface 15a of the inner tube 15 and faces the inner peripheral surface 15a.

[0055] Therefore, the rebound cushion 81 has a plurality of convex portions 122 arranged circumferentially on the opposing surface 145 facing the rod guide 26, and a plurality of flat portions 111 arranged circumferentially on the outer circumferential side facing the cylinder 17.

[0056] When the piston rod 50 moves in the direction extending from the cylinder 17 and reaches a predetermined position on the fully extended side, the rebound cushion 81 abuts against the rod guide 26 at the multiple protrusions 122. As the piston rod 50 moves further toward the fully extended side, the rebound cushion 81 is pressed against the rod guide 26 by the stopper member 80 and undergoes compressive deformation in the axial direction, as shown in FIG. 4, and applies resistance to the piston rod 50 via the stopper member 80, stopping the piston rod 50 at the fully extended position. In this way, the rebound cushion 81 absorbs the impact generated when the piston rod 50 is stopped relative to the cylinder 17 at the fully extended position. At this time, the rebound cushion 81 first undergoes compressive deformation in the axial direction, mainly at the multiple protrusions 122 shown in FIG. 2, and then the main body portion 121 undergoes compressive deformation in the axial direction.

[0057] Patent Document 1 discloses a cylinder device having a rebound cushion between a piston connected to a piston rod and a rod guide that guides the piston rod. The rebound cushion of this cylinder device has a cylindrical inner circumferential surface and a cylindrical outer circumferential surface. When this rebound cushion undergoes axial compression deformation, its cross section along the central axis deforms into a C-shape, bulging radially outward and pressing against the inner circumferential surface of the cylinder, increasing its resistance. This results in a rapid change in the rebound cushion's deflection characteristics relative to the applied load. Furthermore, this rebound cushion has multiple axially protruding protrusions on both axial sides, each circumferentially aligned. This results in the rebound cushion's C-shaped cross section, bulging radially outward at the portion where the multiple protrusions are located, strongly pressing against the inner circumferential surface of the cylinder, increasing its resistance. This results in a more rapid change in the rebound cushion's deflection characteristics relative to the applied load. That is, when the load is light, the amount of deflection of this rebound cushion increases almost linearly with an increase in the load, but when the load becomes heavy, the increase in the amount of deflection with respect to the increase in the load suddenly decreases. In other words, this rebound cushion becomes difficult to deflect suddenly under heavy load. There is a demand for a cylinder device that suppresses a sudden change in the amount of deflection of the rebound cushion with respect to the load.

[0058] In contrast, the cylinder device 11 of this embodiment has a plurality of planar portions 111 arranged circumferentially on the outer circumferential side of the rebound cushion 81, facing the inner tube 15 of the cylinder 17. This allows for a radial clearance between the rebound cushion 81 and the inner tube 15 of the cylinder 17. Furthermore, when a load is applied and the rebound cushion 81 is compressed and deformed in the axial direction, the shape of the planar portions 111 prevents the rebound cushion 81 from deforming into a C-shaped cross section that bulges outward in the radial direction, as shown in FIG. 4, and also deforms so as to be pressed radially inward. This prevents the rebound cushion 81 from pressing against the inner circumferential surface 15a of the inner tube 15 of the cylinder 17. This prevents a sudden change in the amount of deflection of the rebound cushion 81 in response to a load, allowing for a more linear load-deflection characteristic.

[0059] Furthermore, in the cylinder device 11 of this embodiment, the rebound cushion 81 has the convex portions 122 arranged circumferentially on the opposing surface 145 that faces the rod guide 26, and the planar portion 111 is aligned in phase with each other. In this way, the planar portion 111 is the portion of the rebound cushion 81 that is prone to deformation that bulges outward in the radial direction and forms a C-shaped cross section due to the presence of the convex portions 122. This further reduces the rebound cushion 81's pressure contact with the inner circumferential surface 15a of the inner cylinder 15 when it undergoes compressive deformation in the axial direction. This further reduces abrupt changes in the amount of deflection of the rebound cushion 81 in response to a load, allowing for a more linear load-deflection characteristic. [Explanation of symbols]

[0060] 11...cylinder device, 17...cylinder, 26...rod guide, 45...piston, 48...first chamber, 49...second chamber, 50...piston rod, 81...rebound cushion, 111...flat portion, 122...convex portion.

Claims

[Claim 1] a cylinder in which a working fluid is sealed; a piston slidably fitted in the cylinder to divide the interior of the cylinder into two chambers; a rod guide provided on an opening side of the cylinder; a piston rod having one end connected to the piston and the other end extending outside the cylinder through the rod guide; a rebound cushion that is provided between the piston and the rod guide and spaced apart from the piston, and that comes into contact with the rod guide when the piston rod moves in a direction extending from the cylinder, The rebound cushion is A surface facing the rod guide is provided with a plurality of convex portions of the same shape arranged in a circumferential direction, a plurality of flat portions of the same shape arranged at equal intervals in the circumferential direction on an outer circumferential side facing the cylinder; the convex portion and the flat portion are in phase with each other, an obtuse angle is formed between the planar portions adjacent to each other in the circumferential direction on the radially inner side; a chamfered portion is provided between the planar portions adjacent to each other in the circumferential direction, the chamfered portion smoothly connecting the planar portions; a concave portion extending across the radial direction is provided between the convex portions adjacent to each other in the circumferential direction; Cylinder device.

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