Shock absorber and method for manufacturing shock absorber

Abstract

This shock absorber comprises: a head cap that has a head cap bottom part having a head cap hole into which a piston rod can be inserted, and a head cap cylindrical part covering the radial outer periphery of the piston rod; and a bumper cap that is fixed to an axial end part of a cylinder, and that has a bumper cap bottom part having a bumper cap hole into which the piston rod can be inserted, and a bumper cap cylindrical part covering the radial outer periphery of the cylinder. The bumper cap has a radial protrusion that protrudes radially outward on the bumper-cap-bottom-part side of the bumper cap cylindrical part, and the outer diameter of the radial protrusion is formed to be larger than the inner diameter of the head cap cylindrical part.

Description

Shock Absorber and Method for Manufacturing the Same

[0001] The present disclosure relates to a shock absorber and a method for manufacturing the shock absorber.

[0002] Patent Document 1 discloses a shock absorber including a cylinder from one end of which a piston rod extends, a cap member provided at an end on one end side of the cylinder and having a recess formed in an outer peripheral surface thereof, and a cover member provided at a tip end side of the piston rod and having a protrusion formed on an inner peripheral surface thereof and locked to the recess. The shock absorber is held in a contracted state by locking the protrusion of the cover member to the recess of the cap member.

[0003] [[ID=J9]] Japanese Unexamined Patent Application Publication No. 2016-80023

[0004] By the way, in a shock absorber, it is desired to easily perform an assembly operation.

[0005] Therefore, an object of the present disclosure is to provide a shock absorber and a method for manufacturing the shock absorber capable of easily performing an assembly operation

[0006] To achieve the above object, a first aspect of the shock absorber of the present disclosure includes a cylinder in which a working fluid is enclosed, a piston rod protruding from an axial end portion of the cylinder, a head cap having a head cap bottom portion provided in a range where the piston rod protrudes from the cylinder and having a head cap hole through which the piston rod can be inserted, and a head cap cylindrical portion covering a radially outer periphery of the piston rod, and a bumper cap fixed to an axial end portion of the cylinder and having a bumper cap bottom portion having a bumper cap hole through which the piston rod can be inserted and a bumper cap cylindrical portion covering a radially outer periphery of the cylinder. The bumper cap has a radially protruding portion protruding radially outward on a side of the bumper cap cylindrical portion on the bumper cap bottom portion side, and an outer diameter of the radially protruding portion is formed to be larger than an inner diameter of the head cap cylindrical portion.

[0007] A second embodiment of the shock absorber of the present disclosure comprises: a cylinder in which a working fluid is sealed; a piston rod protruding from the axial end of the cylinder; a head cap provided in the portion of the piston rod protruding from the cylinder and having a head cap hole through which the piston rod can be inserted; and a bumper cap fixed to the axial end of the cylinder and having a bumper cap bottom portion having a bumper cap hole through which the piston rod can be inserted and a bumper cap cylindrical portion covering the radial outer circumference of the cylinder, wherein the bumper cap has an axial projection protruding from the outer circumference of the axial end face of the bumper cap bottom portion toward the head cap side, and the outer diameter of the head cap is formed to be larger than the inner diameter of the axial projection portion.

[0008] An embodiment of the method for manufacturing a shock absorber according to the present disclosure comprises: a cylinder in which a working fluid is sealed; a piston rod protruding from the axial end of the cylinder; a head cap provided in the portion of the piston rod that protrudes from the cylinder and having a head cap hole through which the piston rod can be inserted; and a bumper cap provided at the axial end of the cylinder and having a bumper cap bottom portion having a bumper cap hole through which the piston rod can be inserted and a bumper cap cylindrical portion covering the radial outer circumference of the cylinder, the method for manufacturing a shock absorber comprising: holding the bumper cap on the head cap; fixing the head cap to the piston rod; inserting the piston rod into the cylinder; and fixing the bumper cap to the cylinder.

[0009] According to this disclosure, assembly work can be easily performed.

[0010] This is a cross-sectional view showing a shock absorber of the first embodiment according to the present disclosure. This is a partial cross-sectional view showing the main part of the shock absorber. This is a plan view showing the bumper cap of the shock absorber. This is a cross-sectional view of the bumper cap of the shock absorber taken along the line IV-IV in Figure 3. This is a cross-sectional view showing the cylinder sub-assembly of the shock absorber. This is a plan view showing the head cap of the shock absorber. This is a cross-sectional view taken along the line VII-VII in Figure 6 showing the state in which the bumper cap is held on the head cap of the shock absorber. This is a cross-sectional view showing the piston rod sub-assembly of the shock absorber. This is a cross-sectional view for explaining the manufacturing method of the shock absorber. This is a cross-sectional view for explaining the manufacturing method of the shock absorber. This is a plan view showing the state in which the bumper cap is held on the head cap of the shock absorber of the second embodiment according to the present disclosure. This is a cross-sectional view taken along the line XII-XII in Figure 11 showing the state in which the bumper cap is held on the head cap of the shock absorber. This is a plan view showing the state in which the bumper cap is held on the head cap in the manufacturing method of the shock absorber of the third embodiment according to the present disclosure. This is a cross-sectional view taken along the line XIV-XIV in Figure 13, showing the state in which the bumper cap is held on the head cap in the manufacturing method of the shock absorber. This is a plan view showing the state in which the bumper cap is held on the head cap in the manufacturing method of the fourth embodiment of the shock absorber according to the present disclosure. This is a cross-sectional view taken along the line XVI-XVI in Figure 15, showing the state in which the bumper cap is held on the head cap in the manufacturing method of the shock absorber.

[0011] [First Embodiment] The buffer and method for manufacturing the buffer according to the first embodiment of the present disclosure will be described with reference to Figures 1 to 10.

[0012] Figure 1 shows a shock absorber 11 of the first embodiment. This shock absorber 11 is used in the suspension system of vehicles such as automobiles and railway vehicles. Specifically, the shock absorber 11 is used in the suspension system of an automobile. The shock absorber 11 is a double-cylinder type shock absorber equipped with a cylinder 17 having an inner cylinder 15 and an outer cylinder 16. The inner cylinder 15 is made of metal and is cylindrical. The outer cylinder 16 is made of metal and is a bottomed cylinder with a larger diameter than the inner cylinder 15. The outer cylinder 16 is provided coaxially with the inner cylinder 15, radially outward from the inner cylinder 15. A reservoir chamber 18 is located between the outer cylinder 16 and the inner cylinder 15.

[0013] 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 to one axial end of the body member 20 and fixed by welding. The fitted portion of the bottom member 21 with the body member 20 and the body member 20 together constitute the cylindrical body portion 22 of the outer cylinder 16. The portion of the bottom member 21 radially inward from the fitted portion with the body member 20 constitutes the 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 to the bottom portion 23 is 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 has an open end in the axial direction and a closed end in the axial direction.

[0014] The shock absorber 11 comprises a valve body 27 and a rod guide 28. 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 has a stepped outer circumference. The valve body 27 is placed on the bottom 23 of the outer cylinder 16. At this time, the valve body 27 is positioned radially relative to the outer cylinder 16 at the large diameter portion of its outer circumference.

[0015] As shown in Figure 2, the rod guide 28 comprises a rod guide body 32, a collar 33, and a sliding member 34. The rod guide body 32 is made of metal and is annular in shape. The rod guide body 32 has a large diameter portion 35 and a small diameter portion 36 on its outer circumference. The outer diameter of the large diameter portion 35 is larger than the outer diameter of the small diameter portion 36. Therefore, the outer circumference of the rod guide body 32 is stepped. The large diameter portion 35 of the rod guide body 32 is located on the opening 24 side of the outer cylinder 16 than the small diameter portion 36. The rod guide body 32 fits into the inner circumference of the body portion 22 of the outer cylinder 16 on the opening 24 side at the large diameter portion 35. The rod guide body 32 has a passage hole 37 that penetrates axially in the portion radially outward from the small diameter portion 36.

[0016] The collar 33 is cylindrical. The collar 33 is made by covering the inner surface of a metal cylinder with a highly sliding material. The collar 33 is fitted and fixed to the inner circumference of the rod guide body 32. The sliding member 34 is annular and is fitted and fixed to the inner circumference of the rod guide body 32 on the larger diameter side 35 in the axial direction than the collar 33.

[0017] As shown in Figure 1, one axial end of the inner cylinder 15 is fitted into the small-diameter portion of the outer circumference of the valve body 27. The other axial end of the inner cylinder 15 engages with the bottom 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 body 32. The other end of the inner cylinder 15 engages with the body 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. Here, the space between the valve body 27 and the bottom 23 is connected to the space between the inner cylinder 15 and the outer cylinder 16 via a passage groove 40 formed in the valve body 27. The space between the valve body 27 and the bottom 23 constitutes a reservoir chamber 18, similar to the space between the inner cylinder 15 and the outer cylinder 16.

[0018] The shock absorber 11 is equipped with an annular rod seal 41. The rod seal 41 is provided on the side opposite to the bottom 23 of the rod guide 28. This rod seal 41 is fitted to the inner circumference of the body 22, similar to the rod guide 28. A locking portion 43 is formed at the end of the body 22 opposite to the bottom 23. The locking portion 43 is formed by plastically deforming the opening 24 side of the body member 20 radially inward by crimping, such as curling. The rod seal 41 is sandwiched between this locking portion 43 and the rod guide 28. At that time, the rod seal 41 is pressed against the inner circumferential surface of the body 22 by the rod guide 28. As a result, the rod seal 41 closes 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 end open and the other end closed, and close this end. Specifically, the rod seal 41 is an oil seal.

[0019] The shock absorber 11 is equipped with a piston 45. The piston 45 is slidably inserted into the inner cylinder 15 of the cylinder 17. The piston 45 divides the inner cylinder 15 into two chambers: a first chamber 48 and a second chamber 49. The first chamber 48 is located between the piston 45 and the rod guide 28 in the inner cylinder 15. The second chamber 49 is located between the piston 45 and the valve body 27 in the inner cylinder 15. The second chamber 49 is separated from the reservoir chamber 18 by the valve body 27. The cylinder 17 is filled with oil liquid L as a working fluid in the first chamber 48 and the second chamber 49. The cylinder 17 is filled with oil liquid L as a working fluid and gas G in the reservoir chamber 18.

[0020] The shock absorber 11 is equipped with a piston rod 51. The first end of the piston rod 51, which is one end in the axial direction, is inserted into the inside of the cylinder 17. This first end of the piston rod 51 is connected to the piston 45. The second end of the piston rod 51, which is the other end in the axial direction, protrudes outward from the axial end 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.

[0021] The piston rod 51 has a main shaft portion 52, a mounting shaft portion 53, an annular groove 54, and a small-diameter shaft portion 55. The outer surface of the main shaft portion 52 is cylindrical. The main shaft portion 52 has the largest outer diameter among the piston rod 51.

[0022] The mounting shaft portion 53 extends from one end of the main shaft portion 52 in the axial direction. The mounting shaft portion 53 is coaxial with the main shaft portion 52, and its outer diameter is smaller than that of the main shaft portion 52.

[0023] The annular groove 54 is formed at an intermediate position in the axial direction of the main shaft portion 52 and is recessed radially inward from the outer circumferential surface of the main shaft portion 52. The annular groove 54 is an annular shape coaxial with the main shaft portion 52.

[0024] The small-diameter shaft portion 55 protrudes from the opposite side of the axial mounting shaft portion 53 of the main shaft portion 52. The small-diameter shaft portion 55 is coaxial with the main shaft portion 52, and its outer diameter is smaller than the outer diameter of the main shaft portion 52.

[0025] The piston rod 51 is inserted into the cylinder 17 at the mounting shaft portion 53. A piston 45 is connected to the mounting shaft portion 53 of the piston rod 51 by a nut 57. The piston rod 51 extends out of the cylinder 17 at the main shaft portion 52, passing through the collar 33 and sliding member 34 of the rod guide 28 and the rod seal 41. The rod guide 28 and rod seal 41 are provided on the side of the cylinder 17 from which the piston rod 51 extends.

[0026] The rod guide 28 has a collar 33 that slidably supports the piston rod 51. The piston rod 51 is guided by the collar 33 of the rod guide 28 on the outer circumferential surface of the main shaft portion 52. The rod guide 28 has a sliding member 34 that slides against the main shaft portion 52 of the piston rod 51, providing frictional resistance to the axial movement of the main shaft portion 52.

[0027] The piston rod 51 moves axially in conjunction with the piston 45 relative to the cylinder 17. During the extension stroke of the shock absorber 11, when the piston rod 51 increases the amount it protrudes from the cylinder 17, the piston 45 moves toward the first chamber 48. During the contraction stroke of the shock absorber 11, when the piston rod 51 decreases the amount it protrudes from the cylinder 17, the piston 45 moves toward the second chamber 49.

[0028] As shown in Figure 2, the rod seal 41 is a single molded product in which a perforated disc-shaped annular member 62 made of metal is embedded in a sealing material 61 made of synthetic rubber. The annular member 62 is for maintaining the shape of the sealing material 61 and gives the rod seal 41 the strength to fix it to the target area. The rod seal 41 is supported on one end side of the cylinder 17 by the position of the radial annular member 62 being sandwiched between the rod guide body 32 of the rod guide 28 and the locking portion 43 of the outer cylinder 16.

[0029] The sealing material 61 has a dust lip portion 71, an oil lip portion 72, a sealing ring portion 73, and a check lip portion 74.

[0030] The dust lip portion 71 extends in a cylindrical shape from the inner circumferential surface side of the annular member 62 to one side in the axial direction. The oil lip portion 72 extends in a cylindrical shape from the inner circumferential surface side of the annular member 62 to the other side in the axial direction. The rod seal 41 slides the main shaft portion 52 of the piston rod 51 inside these oil lip portion 72 and dust lip portion 71, and these dust lip portion 71 and oil lip portion 72 seal the gap between the main shaft portion 52 of the piston rod 51 and the rod seal 41.

[0031] The seal ring portion 73 protrudes in an annular shape from the outer circumferential surface side of the annular member 62, on the same side as the axial oil lip portion 72. The seal ring portion 73 contacts the rod guide body 32 and the body portion 22 of the outer cylinder 16 simultaneously, sealing the gap between the outer cylinder 16 and the rod guide 28.

[0032] The check lip portion 74 protrudes in an annular cylindrical shape from the radial midpoint of the annular member 62 on the same side as the axial oil lip portion 72. The check lip portion 74 opens and closes by moving away from and contacting the rod guide 28, and allows the oil liquid L that has entered from the first chamber 48 towards the rod seal 41 through the gap between the piston rod 51 and the rod guide 28 to flow into the reservoir chamber 18 through the passage hole 37 of the rod guide 28.

[0033] The rod seal 41 has a dust lip portion 71 that protrudes outward from the outer cylinder 16, that is, outward from the cylinder 17, through the opening 24 of the outer cylinder 16.

[0034] A spring 81 is provided on the outer circumference of the dust lip portion 71. The spring 81 is a metal, annular garter spring that presses the dust lip portion 71 against the main shaft portion 52 of the piston rod 51.

[0035] A spring 82 is provided on the outer circumference of the oil lip portion 72. The spring 82 is a metal, annular garter spring that presses the oil lip portion 72 against the main shaft portion 52 of the piston rod 51.

[0036] The rod seal 41 is provided on the side from which the piston rod 51 of the cylinder 17 extends, that is, on the side of the opening 24 of the outer cylinder 16. Together with the rod guide 28, the rod seal 41 seals the space between the body 22 of the outer cylinder 16 and the main shaft portion 52 of the piston rod 51, thereby preventing the oil liquid L in the inner cylinder 15 and the gas G and oil liquid L in the reservoir chamber 18 from leaking to the outside.

[0037] As shown in Figure 1, the piston 45 has passages 85 and 86 formed within it. Both passages 85 and 86 penetrate the piston 45 in the axial direction. Passages 85 and 86 can connect the first chamber 48 and the second chamber 49.

[0038] The shock absorber 11 includes a disc valve 87 and a disc valve 88. The disc valve 87 is located on the side of the piston 45 opposite the bottom 23 in the axial direction. The disc valve 87 is annular in shape and closes the passage 85 by contacting the piston 45. The disc valve 88 is located on the side of the piston 45 opposite the bottom 23 in the axial direction. The disc valve 88 is annular in shape and closes the passage 86 by contacting the piston 45. The disc valves 87 and 88 are attached to the piston rod 51 together with the piston 45.

[0039] When the piston rod 51 moves in a compression direction, increasing the amount it enters the inner cylinder 15 and outer cylinder 16, 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 first chamber 48 by a predetermined value or more. Then, the disc valve 87 opens the passage 85 and allows the oil L from the second chamber 49 to flow into the first chamber 48. At that time, the disc valve 87 generates a damping force.

[0040] As the piston rod 51 moves in the extension direction, increasing its protrusion from the inner cylinder 15 and outer cylinder 16, the piston 45 moves in a direction that narrows the first chamber 48, causing the pressure in the first chamber 48 to become higher than the pressure in the second chamber 49 by a predetermined value or more. This causes the disc valve 88 to open the passage 86, allowing the oil L from the first chamber 48 to flow into the second chamber 49. At this time, the disc valve 88 generates a damping force.

[0041] At least one of the piston 45 and the disk valve 87 is formed with a fixed orifice (not shown). This fixed orifice allows the first chamber 48 and the second chamber 49 to communicate with each other through the passage 85 even when the disk valve 87 closes the passage 85 most tightly.

[0042] Also, at least one of the piston 45 and the disk valve 88 is formed with a fixed orifice (not shown). This fixed orifice allows the first chamber 48 and the second chamber 49 to communicate with each other through the passage 86 even when the disk valve 88 closes the passage 86 most tightly.

[0043] The valve body 27 is formed with a liquid passage 91 and a liquid passage 92. Both the liquid passage 91 and the liquid passage 92 penetrate the valve body 27 in the axial direction. Both the liquid passages 91 and 92 can communicate the second chamber 49 and the reservoir chamber 18 with each other.

[0044] The base valve 30 includes a disk valve 95 and a disk valve 96. The disk valve 95 is provided on the bottom 23 side in the axial direction of the valve body 27. The disk valve 95 closes the liquid passage 91 by abutting against the valve body 27. The disk valve 96 is provided on the side opposite to the bottom 23 in the axial direction of the valve body 27. The disk valve 96 closes the liquid passage 92 by abutting against the valve body 27. The base valve 30 has a pin 98. This pin 98 attaches the disk valves 95 and 96 to the valve body 27. The valve body 27, the disk valves 95 and 96, the pin 98, etc. constitute the base valve ३०.

[0045] When the piston rod 51 moves toward the retracted side and the piston 45 moves in a direction to narrow 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, the base valve 30 causes the disk valve 95 to open the liquid passage 91, and the hydraulic fluid L in the second chamber 49 flows into the reservoir chamber 18. At that time, the disk valve 95 generates a damping force. When the piston rod 51 moves toward the extended side and the piston 45 moves toward the first chamber 48 side, the pressure in the second chamber 49 drops below the pressure in the reservoir chamber 18. Then, the base valve 30 causes the disk valve 96 to open the liquid passage 92, and the hydraulic fluid L in the reservoir chamber 18 flows into the second chamber 49. The disk valve 96 is a suction valve that allows the hydraulic fluid L to flow from the reservoir chamber 18 into the second chamber 49 without substantially generating a damping force at that time.

[0046] The shock absorber 11 includes a stopper member 101 and a cushion member 102. The stopper member 101 is made of metal and is annular. The stopper member 101 is fixed to the piston rod 51 by being engaged with an annular groove 54 while the main shaft portion 52 of the piston rod 51 is inserted radially inward.

[0047] The cushion member 102 is an annular elastic member and is provided between the stopper member 101 and the rod guide 28 with the main shaft portion 52 inserted radially inward. The cushion member 102 abuts against the rod guide 28 when the piston rod 51 extends fully to relieve the impact.

[0048] The shock absorber 11 includes a cylinder-side mounting eye 111 and a rod-side mounting eye 112. The cylinder-side mounting eye 111 has a cylinder-side mounting eye body 121 and a cylinder-side rubber bush 122. The cylinder-side mounting eye body 121 is cylindrical and made of metal.

[0049] The cylinder-side rubber bush 122 has a cylinder-side rubber portion 125 and a cylinder-side bush portion 126. The cylinder-side rubber portion 125 is made of an elastic material such as rubber and is annular in shape. The cylinder-side bush portion 126 is made of metal and is cylindrical in shape. The cylinder-side bush portion 126 is provided radially inward of the cylinder-side rubber portion 125.

[0050] The cylinder-side rubber bush 122 is formed by fixing the cylinder-side rubber portion 125 to the outer circumferential surface of the cylinder-side bush portion 126, thereby integrating the two components. The cylinder-side rubber bush 122 is fitted and fixed within the cylinder-side mounting eye body 121 at the cylinder-side rubber portion 125.

[0051] The cylinder-side mounting eye 111 is fixed by welding to the side opposite the opening 24 at the bottom 23 of the outer cylinder 16, with the cylinder-side mounting eye body 121 having its central axis perpendicular to the central axis of the outer cylinder 16. The cylinder-side bush portion 126 of the cylinder-side mounting eye 111 is connected to the vehicle's wheel side.

[0052] The rod-side mounting eye 112 has a rod-side mounting eye body 131 and a rod-side rubber bushing 132. The rod-side mounting eye body 131 is cylindrical and made of metal.

[0053] The rod-side rubber bush 132 has a rod-side rubber portion 135 and a rod-side bush portion 136. The rod-side rubber portion 135 is made of an elastic material such as rubber and is annular in shape. The rod-side bush portion 136 is made of metal and is cylindrical in shape. The rod-side bush portion 136 is provided radially inward of the rod-side rubber portion 135.

[0054] The rod-side rubber bush 132 is formed by fixing the rod-side rubber portion 135 to the outer circumferential surface of the rod-side bush portion 136, thereby integrating the two components. The rod-side rubber bush 132 is fitted and fixed within the rod-side mounting eye body 131 at the rod-side rubber portion 135.

[0055] The rod-side mounting eye 112 is fixed by welding to the small-diameter shaft portion 55, which is the tip of the portion of the piston rod 51 that extends from the cylinder 17, with the rod-side mounting eye body 131 having its central axis perpendicular to the central axis of the piston rod 51. The outer diameter of the rod-side mounting eye 112 is larger than the outer diameter of the main shaft portion 52 of the piston rod 51. The rod-side bush portion 136 of the rod-side mounting eye 112 is connected to the vehicle body.

[0056] The shock absorber 11 is equipped with a head cap 141. The head cap 141 is made of metal and has a head cap bottom portion 143 and a head cap cylindrical portion 144. The head cap 141 is formed by press molding from a single flat plate material, and is therefore integrally molded without seams.

[0057] As shown in Figure 2, the head cap bottom 143 has a tapered cylindrical tapered portion 146 and a flat disc portion 147. The tapered portion 146 has a head cap hole 149 that penetrates axially from the radially inward side. The disc portion 147 extends radially outward from the outer peripheral edge of the tapered portion 146.

[0058] The head cap cylindrical portion 144 is provided radially outward from the outer peripheral edge of the disc portion 147, which is the outer peripheral edge of the head cap bottom portion 143, and extends from the head cap bottom portion 143 to one side in the axial direction of the head cap bottom portion 143. The head cap cylindrical portion 144 extends from the disc portion 147 to the side opposite to the tapered portion 146 in the axial direction of the disc portion 147. The head cap cylindrical portion 144 is cylindrical in shape. The head cap bottom portion 143 widens radially inward from one end of the head cap cylindrical portion 144 in the axial direction.

[0059] The head cap 141 has a small-diameter shaft portion 55 of the piston rod 51 inserted through the head cap hole 149. The inner circumference of the tapered portion 146 of the head cap 141 is welded to the small-diameter shaft portion 55 of the piston rod 51 together with the rod-side mounting eye body 131 of the rod-side mounting eye 112. In this configuration, the head cap 141 is oriented such that, in the axial direction of the piston rod 51, the head cap cylindrical portion 144 extends from the head cap bottom portion 143 toward the opposite side from the rod-side mounting eye 112.

[0060] The head cap 141 is provided in the portion of the piston rod 51 that protrudes from the cylinder 17 and has a head cap bottom portion 143 with a head cap hole 149 through which the piston rod 51 can be inserted, and a head cap cylindrical portion 144 that covers the radial outer circumference of the piston rod 51.

[0061] The shock absorber 11 is equipped with a cover member 151. The cover member 151 is cylindrical, and one end in the axial direction is fitted and fixed to the outer circumferential surface of the head cap cylindrical portion 144 of the head cap 141. The cover member 151 extends from the head cap cylindrical portion 144 of the head cap 141 in the direction opposite to the rod-side mounting eye 112, and covers the opening 24 side of the body portion 22 of the outer cylinder 16 of the cylinder 17 radially outward. The cover member 151 is made of synthetic resin or metal.

[0062] The shock absorber 11 is equipped with a bumper cap 161. The bumper cap 161 is fitted and fixed to a fitting portion 25 at the end of the body portion 22 of the cylinder 17 on the side of the axial opening 24. The bumper cap 161 comprises a bumper cap bottom portion 163, a bumper cap cylindrical portion 164, and a radial projection portion 165. The bumper cap 161 is made of, for example, synthetic resin and is integrally molded without seams.

[0063] As shown in Figure 3, the bottom portion 163 of the bumper cap is disc-shaped, and a bumper cap hole 168 is formed radially inward, penetrating axially. As shown in Figure 2, the inner diameter of the bumper cap hole 168 is larger than the outer diameter of the dust lip portion 71 of the rod seal 41 and the spring 81 attached to the dust lip portion 71. The main shaft portion 52 of the piston rod 51, the dust lip portion 71 of the rod seal 41, and the spring 81 are arranged within this bumper cap hole 168.

[0064] As shown in Figure 4, the bottom portion 163 of the bumper cap has a base portion 171, a tapered projection 172, and an inner projection 173. The base portion 171 is flat, and a part of the bumper cap hole 168 is formed on its radially inner side.

[0065] The tapered projection 172 protrudes from the inner circumference side of the base plate 171 to one axial side of the base plate 171. The tapered projection 172 has a tapered shape, with its outer diameter decreasing as it moves away from the base plate 171 in the axial direction. The remaining portion of the bumper cap hole 168 is formed on the radially inner side of the tapered projection 172.

[0066] The inner projection 173 protrudes from the outer circumference of the base plate portion 171 on the opposite side from the axially tapered projection 172. Multiple inner projections 173 are formed on the bottom portion 163 of the bumper cap 161 at equal intervals in the circumferential direction of the bumper cap 161.

[0067] The bumper cap cylindrical portion 164 has a cylindrical body portion 177 and a fitting projection portion 178. The cylindrical body portion 177 is provided radially outward from the outer peripheral edge of the base portion 171, which is the outer peripheral edge of the bumper cap bottom portion 163, and extends from the base portion 171 to one side in the axial direction of the base portion 171. The cylindrical body portion 177 extends from the base portion 171 to the side opposite to the tapered projection portion 172 in the axial direction of the base portion 171. The cylindrical body portion 177 is cylindrical in shape. The bumper cap bottom portion 163 widens radially inward from one end of the bumper cap cylindrical portion 164 in the axial direction. Multiple inner projection portions 173 of the bumper cap bottom portion 163 are continuous with the cylindrical body portion 177, with the radial outer ends of the base portion 171 merging with it.

[0068] The fitting projection 178 protrudes radially inward from the cylindrical body 177. The fitting projection 178 extends axially from the cylindrical body 177. Multiple fitting projections 178 are formed on the bumper cap cylindrical portion 164 at equal intervals in the circumferential direction of the bumper cap 161. The number of fitting projections 178 on the bumper cap cylindrical portion 164 is the same as the number of inner projections 173 on the bumper cap bottom portion 163. Each of the multiple fitting projections 178 is in phase with one of the multiple inner projections 173 on the bumper cap bottom portion 163 in the circumferential direction of the bumper cap 161.

[0069] The radial projection 165 protrudes radially outward from the outer circumferential surface of the axial end of the bumper cap cylindrical portion 164 on the bumper cap bottom portion 163 side. In other words, the bumper cap 161 has radial projections 165 that protrude radially outward on the bumper cap bottom portion 163 side of the bumper cap cylindrical portion 164. As shown in Figure 3, the bumper cap 161 has multiple radial projections 165 formed at equal intervals in the circumferential direction of the bumper cap 161 (specifically, six locations). These radial projections 165 are arranged on the same cylindrical surface on the radial outer surface of the bumper cap 161. The bumper cap 161 has the same number of radial projections 165 as the fitting projections 178 of the bumper cap cylindrical portion 164. Each of the multiple radial projections 165 is in phase with one of the multiple fitting projections 178 of the bumper cap cylindrical portion 164 in the circumferential direction of the bumper cap 161, and is in phase with one of the multiple inner projections 173 of the bumper cap bottom portion 163.

[0070] The radial projection 165 is formed so that the axial length of the bumper cap 161 is shorter than the combined length of the thickness of the base portion 171 (which is the thickness of the bottom portion 163 of the bumper cap) and the thickness of the inner projection 173.

[0071] The bumper cap 161 is fitted and fixed to the fitting portion 25 of the outer cylinder 16 of the cylinder 17 by its multiple fitting protrusions 178, as shown in Figure 2. At that time, the piston rod 51 is inserted through the bumper cap hole 168 of the bumper cap 161. Therefore, the bumper cap 161 is fixed to the outer circumferential surface of the fitting portion 25 at the axial end of the cylinder 17, and has a bumper cap bottom portion 163 having a bumper cap hole 168 through which the piston rod 51 can be inserted, and a bumper cap cylindrical portion 164 that covers the radial outer circumference of the cylinder 17. Before fitting the bumper cap 161 to the cylinder 17, the diameter of the inscribed circles of the multiple fitting protrusions 178 is smaller than the outer diameter of the fitting portion 25 of the outer cylinder 16 of the cylinder 17 that will be fitted later.

[0072] The bumper cap 161 is formed such that the diameter of the circumscribed circles of the multiple radial projections 165, which is the outer diameter of the radial projections 165, is larger than the inner diameter of the head cap cylindrical portion 144 of the head cap 141. Furthermore, the bumper cap 161 is formed so that the radial projections 165 and the head cap cylindrical portion 144 of the head cap 141 can be fitted together.

[0073] Here, the relationship between the multiple radial projections 165 of the bumper cap 161 and the head cap cylindrical portion 144 of the head cap 141 to which they are fitted, and the relationship between the multiple fitting projections 178 of the bumper cap 161 and the fitting portion 25 of the outer cylinder 16 of the cylinder 17 to which they are fitted, is set such that the fitting force when the radial projections 165 of the bumper cap 161 and the head cap cylindrical portion 144 of the head cap 141 are fitted together is weaker than the fixing force that secures the bumper cap 161 and the cylinder 17.

[0074] Next, the manufacturing method of the shock absorber 11 of the first embodiment will be described. As shown in Figure 5, the manufacturing method of the shock absorber 11 includes a cylinder sub-assembly forming step in which the base valve 30 and the inner cylinder 15 are placed inside the outer cylinder 16 to which the cylinder-side mounting eye body 121 is fixed by welding, and the cylinder-side rubber bush 122 is assembled to the cylinder-side mounting eye body 121 to form a cylinder sub-assembly 181.

[0075] The manufacturing method of the shock absorber 11 includes a head cap fixing step, as shown in Figure 2, in which the head cap 141 is fixed to the piston rod 51. In the head cap fixing step, the head cap 141 is fixed to the small diameter shaft portion 55 of the piston rod 51. In the head cap fixing step, the small diameter shaft portion 55 of the piston rod 51 is inserted from the head cap cylindrical portion 144 side into the head cap hole 149 formed in the head cap bottom portion 143 of the head cap 141, and the rod side mounting eye body 131 is brought into contact with the end face of the small diameter shaft portion 55 opposite to the axial main shaft portion 52, thereby fixing the head cap 141 and the rod side mounting eye body 131 to the small diameter shaft portion 55 by welding. As a result, the head cap cylindrical portion 144 of the head cap 141 covers the main shaft portion 52 of the piston rod 51 radially outward.

[0076] Furthermore, as shown in Figures 6 and 7, the manufacturing method of the shock absorber 11 includes a holding step in which the bumper cap 161 is held in the head cap 141. In the holding step, the piston rod 51, with the head cap 141 fixed in the head cap fixing step, is inserted from the mounting shaft portion 53 side into the bumper cap hole 168 formed in the bumper cap bottom portion 163 of the bumper cap 161, from the side opposite to the bumper cap cylindrical portion 164. Then, the bumper cap 161 is inserted into the head cap cylindrical portion 144 of the head cap 141 from the side opposite to the head cap bottom portion 143, with the bumper cap bottom portion 163 leading, and the multiple radial projections 165 are press-fitted into the inner circumference of the head cap cylindrical portion 144 of the head cap 141. As a result, the head cap 141 and the bumper cap 161 are integrated. Furthermore, the head cap cylindrical portion 144 of the head cap 141 and the bumper cap cylindrical portion 164 of the bumper cap 161 held by it cover the main shaft portion 52 of the piston rod 51 radially outward. Also, the main shaft portion 52 of the piston rod 51 is inserted through the bumper cap hole 168 of the bumper cap 161.

[0077] The manufacturing method for the shock absorber 11 includes a rod seal fitting step in which, after the head cap 141 is fixed in the head cap fixing step and the bumper cap 161 is held in place by the head cap 141 in the holding step, a rod seal 41 with springs 81 and 82 attached is fitted onto the main shaft portion 52 of the piston rod 51 from the mounting shaft portion 53 side.

[0078] The manufacturing method for the shock absorber 11 includes a rod guide fitting step in which the rod guide 28 is fitted from the mounting shaft portion 53 side onto the main shaft portion 52 of the piston rod 51, which is in a state where the rod seal 41 has been fitted in the rod seal fitting step.

[0079] The manufacturing method for the shock absorber 11 includes a cushion member fitting step in which the cushion member 102 is fitted from the mounting shaft portion 53 side onto the main shaft portion 52 of the piston rod 51, which has the rod guide 28 fitted in the rod guide fitting step. In the cushion member fitting step, the cushion member 102 is fitted up to the smaller diameter shaft portion 55 side of the annular groove 54. As a result, the rod seal 41, rod guide 28, and cushion member 102 are positioned on the smaller diameter shaft portion 55 side of the annular groove 54 of the main shaft portion 52.

[0080] The manufacturing method for the shock absorber 11 includes a stopper member fixing step in which, after fitting the stopper member 101 from the mounting shaft portion 53 side to the position of the annular groove 54 on the main shaft portion 52 of the piston rod 51 in which the cushion member 102 has been fitted in the cushion member fitting step, the stopper member 101 is crimped into the annular groove 54 to fix it in place.

[0081] The manufacturing method for the shock absorber 11 includes a piston mounting step in which the piston 45 and disc valves 87, 88, etc. are fastened with nuts 57 to the mounting shaft portion 53 of the piston rod 51, which is in a state where the stopper member 101 has been fixed in the stopper member fixing step.

[0082] Through the above head cap fixing process, holding process, rod seal fitting process, rod guide fitting process, cushion member fitting process, stopper member fixing process, and piston mounting process, as shown in Figure 8, the rod side mounting eye body 131, the head cap 141 holding the bumper cap 161, the rod seal 41 with springs 81 and 82 attached, the rod guide 28, cushion member 102, stopper member 101, piston 45, disc valves 87 and 88, and nut 57 are assembled to the piston rod 51. Furthermore, the rod side rubber bush 132 is assembled to the rod side mounting eye body 131 to form the piston rod sub-assembly 182.

[0083] The manufacturing method for the shock absorber 11 includes a piston rod insertion step in which the piston rod 51 constituting the piston rod sub-assembly 182 is inserted into the inner cylinder 15 of the cylinder 17 of the cylinder sub-assembly 181, as shown in Figure 9. In the piston rod insertion step, by inserting the piston rod 51 into the inner cylinder 15 of the cylinder sub-assembly 181 into which the oil liquid L has been injected, the piston 45 is fitted into the inner cylinder 15 in the initial stage of insertion of the piston rod 51 into the inner cylinder 15. Subsequently, as the insertion of the piston rod 51 into the inner cylinder 15 progresses, the stopper member 101 and the cushion member 102 are inserted into the inner cylinder 15.

[0084] The manufacturing method for the shock absorber 11 includes a piston rod insertion step in which the small diameter portion 36 of the rod guide 28 is press-fitted into the inner cylinder 15 in which the piston 45, stopper member 101, and cushion member 102 are inserted, and a rod guide placement step in which the large diameter portion 35 of the rod guide 28 is inserted into the body portion 22 of the outer cylinder 16 before the locking portion 43 is formed, and a rod seal placement step in which the rod seal 41 is inserted into the body portion 22 of the outer cylinder 16 before the locking portion 43 is formed.

[0085] The manufacturing method for the shock absorber 11 includes a rod guide placement step and a rod seal placement step, followed by a locking portion forming step in which a locking portion 43 is formed on the opening 24 side of the body portion 22 of the outer cylinder 16 by crimping, such as curling. The locking portion forming step is performed under pressurized conditions inside the cylinder 17, and after the locking portion forming step, the inside of the cylinder 17 is sealed at a pressure higher than atmospheric pressure.

[0086] The manufacturing method for the shock absorber 11 includes a bumper cap fixing step in which the bumper cap 161, held by the head cap 141, is fixed to the fitting portion 25 of the cylinder 17 after the locking portion forming step.

[0087] This bumper cap fixing process includes a bumper cap mounting process in which the piston rod 51 is moved to its minimum length, as shown by the white arrow in Figure 9, to fit and attach the bumper cap 161 to the fitting portion 25 of the outer cylinder 16 of the cylinder 17. In the bumper cap mounting process, with the piston rod 51 protruding to its maximum length from the cylinder 17, the assembly device grips the outer circumference of the rod-side mounting eye body 131 of the rod-side mounting eye 112 on one side and the outer circumference of the rod-side mounting eye body 131 of the rod-side mounting eye 112 on the other side, and presses the rod-side mounting eye body 131 toward the bottom portion 23 of the outer cylinder 16. As a result, the multiple fitting protrusions 178 of the bumper cap 161, which are held by the head cap 141 that moves integrally with the rod-side mounting eye body 131 and the piston rod 51, are press-fitted into the fitting portion 25 of the outer cylinder 16 of the cylinder 17. At this time, the bumper cap 161 is fitted onto the outer cylinder 16 until the multiple inner protrusions 173 contact the locking portion 43 of the outer cylinder 16. Here, this bumper cap mounting process is performed by load control by the assembly device. That is, when the assembly device detects the load generated when the multiple inner protrusions 173 of the bumper cap 161 contact the locking portion 43 of the outer cylinder 16, it stops pressing the rod-side mounting eye body 131. In addition to pressing the rod-side mounting eye body 131 toward the bottom portion 23 of the outer cylinder 16, the assembly device may also press the head cap 141 toward the bottom portion 23 of the outer cylinder 16. Here, the shock absorber 11 is dimensionally such that even when the multiple inner protrusions 173 of the bumper cap 161 contact the locking portion 43 of the outer cylinder 16 during the bumper cap mounting process, the piston rod 51 does not come into contact with the base valve 30.

[0088] The bumper cap fixing process includes a separation process in which, after the bumper cap 161 is fitted onto the cylinder 17 in the bumper cap mounting process, the piston rod 51 is moved to its maximum length side, as shown by the white arrow in Figure 10, thereby separating the fitting between the head cap 141 and the bumper cap 161. In the separation process, the assembly device pulls the rod-side mounting eye body 131 of the rod-side mounting eye 112 away from the cylinder 17. Here, as described above, the fitting force when the radial projection 165 of the bumper cap 161 and the head cap cylindrical portion 144 of the head cap 141 are fitted together is weaker than the fixing force that secures the bumper cap 161 to the cylinder 17. Therefore, in the separation process, when the assembly device pulls the rod-side mounting eye body 131 of the rod-side mounting eye 112 away from the cylinder 17, the piston rod 51 and head cap 141 move together with the rod-side mounting eye body 131, while the bumper cap 161 remains fitted into the fitting portion 25 of the outer cylinder 16 of the cylinder 17, with its inner projection 173 in contact with the locking portion 43, thus maintaining its attachment to the cylinder 17. In this way, the head cap 141 can be separated from the bumper cap 161 fitted to the cylinder 17. This separation process is performed by displacement control by the assembly device.

[0089] The bumper cap attachment and detachment processes, which constitute the bumper cap fixing process, can be automated because they can be performed in a series of operations by a single assembly device. Therefore, the number of manual labor steps can be reduced.

[0090] The manufacturing method for the shock absorber 11 includes a cover member attachment step, after the cutting step, in which the cover member 151 shown in Figure 1 is attached to the head cap 141. In the cover member attachment step, the cover member 151 is fixed to the head cap 141 by, for example, fitting one axial end of the cover member 151 to the outer circumference of the head cap cylindrical portion 144 of the head cap 141.

[0091] Patent Document 1, mentioned above, discloses a shock absorber comprising a cylinder from which a piston rod extends from one end, a cap member provided at the end of the cylinder on the one-end side and having a recess formed on its outer circumference, and a cover member provided on the tip side of the piston rod and having a protrusion formed on its inner circumference that engages with the recess, wherein the cover member is held in a contracted state when the protrusion of the cover member engages with the recess of the cap member. However, it is desirable to make the assembly of the shock absorber easy.

[0092] The shock absorber 11 of the first embodiment includes a head cap 141 provided in the range of the piston rod 51 protruding from the cylinder 17, having a head cap bottom portion 143 with a head cap hole 149 through which the piston rod 51 can be inserted and a head cap cylindrical portion 144 that covers the radial outer circumference of the piston rod 51, and a bumper cap 161 fixed to the fitting portion 25 at the axial end of the cylinder 17, having a bumper cap bottom portion 163 with a bumper cap hole 168 through which the piston rod 51 can be inserted and a bumper cap cylindrical portion 164 that covers the radial outer circumference of the cylinder 17. Furthermore, the shock absorber 11 has a radial projection 165 that protrudes radially outward on the bumper cap bottom portion 163 side of the bumper cap cylindrical portion 164, and the outer diameter of the radial projection 165 is formed to be larger than the inner diameter of the head cap cylindrical portion 144 of the head cap 141. As a result, the shock absorber 11 can press-fit the radial projection 165 of the bumper cap 161 into the head cap cylindrical portion 144 of the head cap 141, thereby holding the bumper cap 161 on the head cap 141. Therefore, the shock absorber 11 can perform subsequent assembly work with the bumper cap 161 held on the head cap 141. Consequently, after the shock absorber 11 has held the bumper cap 161 on the head cap 141, the bumper cap 161 is less likely to interfere with the work, making subsequent assembly work easier. For example, with the bumper cap 161 held in place by the head cap 141 fixed to the piston rod 51, assembly work including assembling parts such as the rod seal 41, rod guide 28, cushion member 102, stopper member 101, piston 45, disc valves 87, 88 and nut 57 to the piston rod 51, as well as assembling the rod guide 28 and rod seal 41 assembled to the piston rod 51 to the cylinder 17, and further, forming a locking portion 43 on the cylinder 17 with the rod guide 28 and rod seal 41 assembled to seal the cylinder 17, can be easily performed.

[0093] Furthermore, the shock absorber 11 allows the bumper cap 161 to be attached to the cylinder 17 by having the head cap 141, which is fixed to the piston rod 51, hold the bumper cap 161, and by moving the piston rod 51 to its minimum length. Therefore, the shock absorber 11 can be assembled even more easily.

[0094] Furthermore, since the shock absorber 11 can be fitted with a bumper cap 161 on the cylinder 17, dust can be prevented from entering the cylinder 17. Also, because the bumper cap 161 is interposed between the cylinder 17 and the cover member 151, rust and abnormal noise caused by direct contact between the cylinder 17 and the cover member 151 can be prevented.

[0095] Furthermore, since the shock absorber 11 allows the bumper cap 161 to be attached to the cylinder 17 in the manner described above, even if the structure involves fixing a rod-side mounting eye body 131, which has a larger outer diameter than the piston rod 51, to the piston rod 51, and it becomes difficult to position the bumper cap 161 on the piston rod 51 when the rod-side mounting eye body 131 is fixed, the bumper cap 161 can still be attached to the cylinder 17. In addition, since the bumper cap 161 does not need to be divided, it is advantageous in terms of strength, and the process of attaching it to the cylinder 17 is not complicated.

[0096] Furthermore, since the shock absorber 11 is formed so that the radial projection 165 of the bumper cap 161 and the head cap cylindrical portion 144 of the head cap 141 can be fitted together, it is easy to hold the bumper cap 161 on the head cap 141. In addition, it is possible to suppress the bumper cap 161 from falling off the head cap 141 when it is held, thus suppressing a decrease in assembly efficiency. Specifically, for example, when performing a locking portion formation process in which a locking portion 43 is formed on the outer cylinder 16 by crimping such as curling, it is possible to suppress the bumper cap 161 from falling off the head cap 141, so that the bumper cap 161 is less likely to interfere with the work, and the workability of the locking portion formation process can be improved.

[0097] Furthermore, since the shock absorber 11 is formed such that the axial length of the radial projection 165 of the bumper cap 161 is shorter than the thickness of the bottom portion 163 of the bumper cap, it is possible to improve the rigidity of the bumper cap 161 and enhance the durability of the bumper cap 161 itself (in other words, reduce stress) while ensuring the press-fitting force necessary for the press-fitting of the bumper cap 161 with the head cap 141.

[0098] Furthermore, the shock absorber 11 is fitted with a force weaker than the fixing force that secures the bumper cap 161 to the cylinder 17, when the radial projection 165 of the bumper cap 161 and the head cap cylindrical portion 144 of the head cap 141 are fitted together. Therefore, even if the piston rod 51 moves to its minimum length during use and the head cap 141 and bumper cap 161 are fitted together, the shock absorber 11 can prevent the bumper cap 161 from coming off the cylinder 17 even if the piston rod 51 subsequently moves to its maximum length.

[0099] Furthermore, since the shock absorber 11 has multiple radial projections 165 of the bumper cap 161 formed at intervals in the circumferential direction, the radial projections 165 of the bumper cap 161 can be easily fitted into and detached from the head cap cylindrical portion 144 of the head cap 141.

[0100] The manufacturing method for the shock absorber 11 includes a head cap fixing step of fixing the head cap 141 to the piston rod 51, a holding step of holding the bumper cap 161 on the head cap 141, a piston rod insertion step of inserting the piston rod 51 into the cylinder 17, and a bumper cap fixing step of fixing the bumper cap 161 to the cylinder 17. Therefore, in this manufacturing method, the bumper cap 161 can be held on the head cap 141 in the holding step, so the assembly work of the shock absorber 11 after the holding step can be easily performed as the bumper cap 161 does not get in the way. Furthermore, in this manufacturing method, for example, the head cap 141 is fixed to the piston rod 51 in the head cap fixing step, the bumper cap 161 is held in the head cap 141 fixed to the piston rod 51 in the holding step, the piston rod 51 on which the head cap 141 and bumper cap 161 are attached is inserted into the cylinder 17 in the piston rod insertion step, and the bumper cap 161 held in the head cap 141 is fixed to the cylinder 17 in the bumper cap fixing step. As a result, the bumper cap 161 can be attached to the cylinder 17 while being held in the head cap 141 fixed to the piston rod 51. Therefore, the manufacturing method of the shock absorber 11 makes it possible to easily attach the bumper cap 161 to the cylinder 17, and further makes the assembly work easier.

[0101] Furthermore, in the manufacturing method of the shock absorber 11, the holding step of holding the bumper cap 161 on the head cap 141 involves fitting the radial projection 165 of the bumper cap 161 onto the inner circumference of the head cap cylindrical portion 144 of the head cap 141, thus facilitating the holding of the bumper cap 161 on the head cap 141.

[0102] Furthermore, the manufacturing method of the shock absorber 11 includes a bumper cap fixing step in which the bumper cap 161 is fixed to the cylinder 17, a bumper cap mounting step in which the piston rod 51 is moved to the minimum length side to fit the bumper cap 161 fitted to the head cap 141 onto the cylinder 17, and a separation step in which, after the bumper cap 161 is fitted onto the cylinder 17, the piston rod 51 is moved to the maximum length side to separate the fitting between the head cap 141 and the bumper cap 161. Since the fitting force when the radial projection 165 of the bumper cap 161 and the head cap cylindrical portion 144 of the head cap 141 are fitted together is weaker than the fixing force that fixes the bumper cap 161 and the cylinder 17, the head cap 141 can be separated from the bumper cap 161 by the separation step without removing the bumper cap 161 from the cylinder 17. For example, by adjusting the fitting force between the head cap 141 and the bumper cap 161 to be sufficient to support the weight of the bumper cap 161, it becomes possible to fix the bumper cap 161 to the cylinder 17 and detach the bumper cap 161 from the head cap 141 simply by changing the axial length of the piston rod 51. In this way, the bumper cap fixing process only involves the axial movement of the piston rod 51, which simplifies the structure of the assembly device and reduces equipment costs.

[0103] In addition, in the shock absorber 11 of the first embodiment, the outer surfaces of the multiple radial projections 165 of the bumper cap 161 in the radial direction of the bumper cap 161 may be formed to be arranged on the same tapered surface. This tapered surface is narrowed so that the outer diameter becomes smaller towards the tip of the bumper cap 161 in the direction of fitting into the head cap cylindrical portion 144. This makes it possible to fit the radial projections 165 of the bumper cap 161 into the head cap cylindrical portion 144 of the head cap 141 with a constant load, regardless of manufacturing errors.

[0104] [Second Embodiment] The buffer and method for manufacturing the buffer according to the second embodiment of the present disclosure will be described mainly with reference to Figures 11 and 12. Here, the differences from the first embodiment will be described. For parts common to the first embodiment, the same designations and reference numerals will be used, and redundant explanations will be omitted.

[0105] The shock absorber 11A of the second embodiment is equipped with a head cap 141A, which is partially different from the head cap 141, in place of the head cap 141. The head cap 141A is made of metal and is formed by press molding from a single flat plate. Therefore, the head cap 141A is integrally molded without seams.

[0106] The head cap 141A has a tapered portion 146A with an outer diameter different from that of the tapered portion 146, and a flat disc portion 147A with an inner and outer diameter different from that of the disc portion 147. A head cap hole 149 is formed radially inward of the tapered portion 146A. The head cap 141A does not have a head cap cylindrical portion 144.

[0107] The head cap 141A has ribs 200 that are recessed from the axial tapered portion 146A side of the disc portion 147A toward the tapered portion 146A, and protrude from the axial tapered portion 147A toward the tapered portion 146A, toward the opposite side of the tapered portion 146A. The head cap 141A has multiple (specifically eight) ribs 200 at equal intervals in its circumferential direction. The multiple ribs 200 are for increasing the strength of the outer circumference of the disc portion 147A.

[0108] The head cap 141A has a small-diameter shaft portion 55 of the piston rod 51 inserted into the head cap hole 149. The inner circumference of the tapered portion 146A of the head cap 141A is welded to the small-diameter shaft portion 55 of the piston rod 51 together with the rod-side mounting eye body 131 of the rod-side mounting eye 112. At this time, the head cap 141A is oriented such that the tapered portion 146A is positioned closer to the rod-side mounting eye body 131 than the disc portion 147A in the axial direction of the piston rod 51.

[0109] The head cap 141A is provided in the portion of the piston rod 51 that protrudes from the cylinder 17, and has a head cap hole 149 through which the piston rod 51 can be inserted.

[0110] The shock absorber 11A of the second embodiment is equipped with a bumper cap 161A which is partially different from the bumper cap 161, replacing the bumper cap 161. The bumper cap 161A is equipped with a bumper cap bottom 163A which is partially different from the bumper cap bottom 163, replacing the bumper cap bottom 163. The bumper cap bottom 163A has a base portion 171 and an inner projection 173, while a tapered projection 172 is not formed. A bumper cap hole 168A with the same diameter as the bumper cap hole 168 is formed radially inside the base portion 171, penetrating the base portion 171 in the axial direction.

[0111] The bumper cap 161A differs from the bumper cap 161 in that it has a bumper cap cylindrical portion 164A which is radially thicker than the cylindrical body portion 177. The bumper cap 161A does not have a radial projection 165.

[0112] The bumper cap 161A includes a bumper cap bottom portion 163A and a bumper cap cylindrical portion 164A, as well as an axial projection 201 that protrudes from the outer peripheral edge of the bumper cap bottom portion 163A in the axial direction of the bumper cap bottom portion 163A, on the opposite side from the bumper cap cylindrical portion 164A. The axial projection 201 protrudes from the outer peripheral axial end face of the bumper cap bottom portion 163A toward the head cap 141A. The bumper cap 161A is made of, for example, synthetic resin and is integrally molded without seams.

[0113] The axial projection 201 is cylindrical. Near the boundary with the bottom of the bumper cap 163A, the axial projection 201 has a communication passage 202 which is a hole that penetrates the axial projection 201 radially, allowing the inside and outside of the axial projection 201 to communicate.

[0114] Here, the outer diameter of the head cap 141A is smaller than the outer diameter of the bumper cap 161A.

[0115] The bumper cap 161A is fitted and fixed to the outer circumferential surface of the fitting portion 25 at the axial end of the outer cylinder 16 of the cylinder 17 at the fitting projection 178 of the bumper cap cylindrical portion 164A. At that time, the piston rod 51 is inserted through the bumper cap hole 168A of the bumper cap 161A. Thus, the bumper cap 161A is fixed to the fitting portion 25 at the axial end of the cylinder 17 and has a bumper cap bottom portion 163A having a bumper cap hole 168A through which the piston rod 51 can be inserted, and a bumper cap cylindrical portion 164A that covers the radial outer circumference of the cylinder 17.

[0116] The bumper cap 161A is formed such that the inner diameter of the axial projection 201 is smaller than the outer diameter of the head cap 141A. In other words, the outer diameter of the head cap 141A is formed to be larger than the inner diameter of the axial projection 201. Furthermore, the bumper cap 161A is formed so that the axial projection 201 and the head cap 141A can be fitted together.

[0117] Here, the relationship between the axial projection 201 of the bumper cap 161A and the head cap 141A to which it is fitted, and the axial projection 201 of the bumper cap 161A and the head cap 141A to which it is fitted, is set such that the fitting force when the axial projection 201 of the bumper cap 161A and the head cap 141A are fitted together is weaker than the fixing force that secures the bumper cap 161A and the cylinder 17.

[0118] Next, the manufacturing method of the shock absorber 11A of the second embodiment will be described. The manufacturing method of the shock absorber 11A includes a cylinder sub-assembly forming step similar to that of the manufacturing method of the shock absorber 11 of the first embodiment.

[0119] Furthermore, the manufacturing method of the shock absorber 11A includes a head cap fixing step in which the head cap 141A is fixed to the piston rod 51. In the head cap fixing step, the head cap 141A is fixed to the small diameter shaft portion 55 of the piston rod 51. In the head cap fixing step, the small diameter shaft portion 55 of the piston rod 51 is inserted into the head cap hole 149 of the head cap 141A from the disc portion 147A side, and the rod-side mounting eye body 131 is brought into contact with the end face of the small diameter shaft portion 55 opposite to the axial main shaft portion 52, thereby fixing the head cap 141A and the rod-side mounting eye body 131 to the small diameter shaft portion 55 by welding.

[0120] Furthermore, as shown in Figures 11 and 12, the manufacturing method of the shock absorber 11A includes a holding step in which the bumper cap 161A is held in the head cap 141A. In this holding step, the piston rod 51, with the head cap 141A fixed in the head cap fixing step, is inserted from the mounting shaft portion 53 side into the bumper cap hole 168A formed in the bumper cap bottom portion 163A of the bumper cap 161A, from the opposite side from the bumper cap cylindrical portion 164A. Then, with the disc portion 147A leading, the head cap 141A is inserted into the axial projection portion 201 of the bumper cap 161A from the opposite side from the bumper cap cylindrical portion 164A, and the disc portion 147A is press-fitted into the inner circumference of the axial projection portion 201. As a result, the head cap 141A and the bumper cap 161A are integrated. Furthermore, the bumper cap cylindrical portion 164A of the bumper cap 161A, which is held by the head cap 141A, covers the main shaft portion 52 of the piston rod 51 radially outward. Also, the main shaft portion 52 of the piston rod 51 is inserted through the bumper cap hole 168A of the bumper cap 161A.

[0121] The manufacturing method for the shock absorber 11A involves, after the head cap fixing and holding steps, a rod seal fitting step, a rod guide fitting step, a cushion member fitting step, a stopper member fixing step, and a piston mounting step, similar to the manufacturing method for the shock absorber 11 of the first embodiment. As a result, the rod side mounting eye body 131, the head cap 141A holding the bumper cap 161A, the rod seal 41 with springs 81 and 82 attached, the rod guide 28, the cushion member 102, the stopper member 101, the piston 45, the disc valves 87 and 88, and the nut 57 are assembled onto the piston rod 51. Furthermore, the rod side rubber bush 132 is assembled onto the rod side mounting eye body 131 to form the piston rod sub-assembly.

[0122] The manufacturing method for the shock absorber 11A involves inserting the piston rod 51 of the piston rod subassembly into the inner cylinder 15 of the cylinder 17 of the cylinder subassembly 181 and assembling the piston rod subassembly into the cylinder subassembly 181, and sequentially performing the piston rod insertion step, rod guide placement step, rod seal placement step, and locking portion formation step, all of which are the same as the manufacturing method for the shock absorber 11 of the first embodiment.

[0123] The manufacturing method for the shock absorber 11A includes a bumper cap fixing step in which the bumper cap 161A, held by the head cap 141A, is fixed to the fitting portion 25 of the cylinder 17 after the locking portion forming step.

[0124] This bumper cap fixing process includes a bumper cap mounting process in which the bumper cap 161A, held by the head cap 141A, is fitted into the fitting portion 25 of the outer cylinder 16 of the cylinder 17 by moving the piston rod 51 to the minimum length side, and a separation process in which, after the bumper cap 161A has been fitted into the cylinder 17 in the bumper cap mounting process, the piston rod 51 is moved to the maximum length side to separate the fitting between the head cap 141A and the bumper cap 161A.

[0125] In the shock absorber 11A, as described above, the fitting force when the axial projection 201 of the bumper cap 161A and the head cap 141A are fitted together is weaker than the fixing force that secures the bumper cap 161A to the cylinder 17. Therefore, in the detachment process, when the assembly device pulls the rod-side mounting eye body 131 of the rod-side mounting eye 112 away from the cylinder 17, the piston rod 51 and the head cap 141A move together with the rod-side mounting eye body 131, while the bumper cap 161A remains fitted into the fitting portion 25 of the outer cylinder 16 of the cylinder 17, with its inner projection 173 in contact with the locking portion 43, thus maintaining its state of being attached to the cylinder 17. In this way, the fitting of the head cap 141A with the bumper cap 161A fitted to the cylinder 17 can be detached.

[0126] In the shock absorber 11A, the bumper cap attachment process and the detachment process, which constitute the bumper cap fixing process, can be performed in a series of operations by a single assembly device, thus enabling automation and reducing the number of manual work steps.

[0127] The manufacturing method for the shock absorber 11A includes a cover member attachment step, in which a cover member (not shown) is attached to the head cap 141A after the cutting step.

[0128] The shock absorber 11A of the second embodiment includes a head cap 141A provided in the portion of the piston rod 51 that protrudes from the cylinder 17 and having a head cap hole 149 through which the piston rod 51 can be inserted, and a bumper cap 161A fixed to the axial end of the cylinder 17 and having a bumper cap bottom 163A having a bumper cap hole 168A through which the piston rod 51 can be inserted, and a bumper cap cylindrical portion 164A that covers the radial outer circumference of the cylinder 17. The shock absorber 11A has an axial projection 201 that protrudes from the outer circumference of the axial end face of the bumper cap bottom 163A toward the head cap 141A, and the outer diameter of the head cap 141A is formed to be larger than the inner diameter of the axial projection 201. As a result, the shock absorber 11A can hold the bumper cap 161A in the head cap 141A by press-fitting the head cap 141A into the axial projection 201 of the bumper cap 161A. Therefore, the shock absorber 11A can perform subsequent assembly work while holding the bumper cap 161A on the head cap 141A. Consequently, after the shock absorber 11A holds the bumper cap 161A on the head cap 141A, the bumper cap 161A is less likely to interfere with the work, making the assembly work easier. Furthermore, the shock absorber 11A can, for example, fix the head cap 141A to the piston rod 51, and while holding the bumper cap 161A on the head cap 141A, move the piston rod 51 to its minimum length side, thereby attaching the bumper cap 161A held on the head cap 141A to the cylinder 17. Consequently, the shock absorber 11A can easily attach the bumper cap 161 to the cylinder 17, making the assembly work even easier.

[0129] Furthermore, since the shock absorber 11A is formed so that the axial projection 201 of the bumper cap 161A and the head cap 141A can be fitted together, it is easy to retain the bumper cap 161A on the head cap 141A, and it is also possible to prevent the bumper cap 161A from falling off the head cap 141A while it is retained.

[0130] Furthermore, the shock absorber 11A is fitted with a force weaker than the fixing force that secures the bumper cap 161A to the cylinder 17, when the axial projection 201 of the bumper cap 161A is fitted to the head cap 141A. Therefore, even if the head cap 141A and the bumper cap 161A are fitted together during use, the shock absorber 11A can prevent the bumper cap 161A from coming off the cylinder 17 even if the piston rod 51 subsequently moves to its maximum length.

[0131] Furthermore, since the buffer 11A is provided with a communication passage 202 that allows the inside and outside of the axial projection 201 to communicate, rainwater and the like that that accumulates inside the axial projection 201 can be discharged through the communication passage 202. Note that the communication passage 202 is not limited to a hole, but may also be a notch that allows the inside and outside of the axial projection 201 to communicate.

[0132] The manufacturing method for the shock absorber 11A includes a head cap fixing step of fixing the head cap 141A to the piston rod 51, a holding step of holding the bumper cap 161A in the head cap 141A, a piston rod insertion step of inserting the piston rod 51 into the cylinder 17, and a bumper cap fixing step of fixing the bumper cap 161A to the cylinder 17. Therefore, with this manufacturing method for the shock absorber 11A, the subsequent assembly work of the shock absorber 11A can be performed with the bumper cap 161A held in the head cap 141A. Consequently, with this manufacturing method, after the holding step, the bumper cap 161 is less likely to interfere with the work, and the assembly work of the shock absorber 11A can be easily performed. Furthermore, in this manufacturing method, for example, the head cap 141A is fixed to the piston rod 51 in the head cap fixing step, the bumper cap 161A is held in the head cap 141A fixed to the piston rod 51 in the holding step, the piston rod 51 on which the head cap 141A and bumper cap 161A are attached is inserted into the cylinder 17 in the piston rod insertion step, and the bumper cap 161A held in the head cap 141A is fixed to the cylinder 17 in the bumper cap fixing step. As a result, the bumper cap 161A can be attached to the cylinder 17 while being held in the head cap 141A fixed to the piston rod 51. Therefore, this manufacturing method makes it possible to further simplify the assembly work of the shock absorber 11A.

[0133] Furthermore, in the manufacturing method of the shock absorber 11A, the holding step of holding the bumper cap 161A on the head cap 141A involves fitting the head cap 141A onto the inner circumference of the axial projection 201 of the bumper cap 161A, thus facilitating the holding of the bumper cap 161A on the head cap 141A.

[0134] Furthermore, the manufacturing method of the shock absorber 11A includes a bumper cap fixing step in which the bumper cap 161A is fixed to the cylinder 17, a bumper cap mounting step in which the bumper cap 161A fitted to the head cap 141A is fitted to the cylinder 17 by moving the piston rod 51 to the minimum length side, and a separation step in which, after the bumper cap 161A is fitted to the cylinder 17, the piston rod 51 is moved to the maximum length side to separate the fitting between the head cap 141A and the bumper cap 161A. Since the fitting force when the axial projection 201 of the bumper cap 161A and the head cap 141A are fitted together is weaker than the fixing force that fixes the bumper cap 161A and the cylinder 17, the head cap 141A can be separated from the bumper cap 161A by the separation step without removing the bumper cap 161A from the cylinder 17. Thus, since the bumper cap fixing process only involves the axial movement of the piston rod 51, the structure of the assembly device can be simplified, and equipment costs can be reduced.

[0135] [Third Embodiment] The buffer and method for manufacturing the buffer according to the third embodiment of the present disclosure will be described mainly with reference to Figures 13 and 14. Here, the differences from the first and second embodiments will be described. Note that the same designations and reference numerals will be used for parts common to the first and second embodiments, and redundant explanations will be omitted.

[0136] The shock absorber 11B of the third embodiment has a head cap 141A similar to the shock absorber 11A of the second embodiment. The shock absorber 11B has a bumper cap 161B which is slightly different from the bumper cap 161A, and replaces the bumper cap 161A with the bumper cap 161B. The bumper cap 161B differs from the bumper cap 161A in that it does not have an axial projection 201. The outer diameter of the head cap 141A is smaller than the outer diameter of the bumper cap 161B.

[0137] Next, the manufacturing method of the buffer 11B of the third embodiment will be described. The manufacturing method of the buffer 11B of the third embodiment includes a cylinder sub-assembly forming step similar to the manufacturing methods of the buffers 11 and 11A of the first and second embodiments.

[0138] Furthermore, the manufacturing method of the shock absorber 11B of the third embodiment includes a head cap fixing step in which the head cap 141A is fixed to the piston rod 51 in the same manner as the manufacturing method of the shock absorber 11A of the second embodiment.

[0139] Furthermore, the manufacturing method of the shock absorber 11B of the third embodiment includes a holding step of holding the bumper cap 161B on the head cap 141A using a jig 211, as shown in Figures 13 and 14.

[0140] The jig 211 is made of metal and has a jig base 212 and a jig cylinder 213. The jig base 212 is a circular flat plate and has a jig hole 221 that penetrates it in the axial direction. The jig hole 221 has a central hole 222 and a pair of enlarged holes 223.

[0141] The central hole 222 is a circular part with a larger diameter than the outer diameter of the tapered portion 146A of the head cap 141A, and is formed in the radial center of the jig bottom portion 212.

[0142] The pair of enlarged holes 223 extend outward from the central hole 222 along the radial direction of the central hole 222. The pair of enlarged holes 223 are positioned 180 degrees apart from the central hole 222 and thus extend in opposite directions from the central hole 222.

[0143] Here, the inner diameter of the central hole 222 is larger than the maximum length of the rod-side rubber bushing 132 of the rod-side mounting eye 112. Also, the width of each of the pair of enlarged holes 223 is wider than the axial length of the rod-side mounting eye body 131, and the length between their furthest apart parts is larger than the outer diameter of the rod-side mounting eye body 131. As a result, the jig hole 221 is large enough for the rod-side mounting eye 112 to pass through.

[0144] The jig cylinder portion 213 extends from the outer peripheral edge of the jig base portion 212 to one side in the axial direction of the jig base portion 212. The jig cylinder portion 213 is cylindrical in shape.

[0145] The jig 211 is formed such that the inner diameter of the jig cylinder portion 213 is smaller than the outer diameter of the bumper cap 161B. Furthermore, the jig 211 is formed such that the jig cylinder portion 213 can be fitted onto the bumper cap 161B.

[0146] Here, the relationship between the tightening allowance of the jig cylinder portion 213 of the jig 211 and the bumper cap 161B to which it is fitted, and the tightening allowance of the multiple fitting protrusions 178 of the bumper cap 161B and the fitting portion 25 of the outer cylinder 16 of the cylinder 17 to which it is fitted, is set such that the fitting force when the jig cylinder portion 213 of the jig 211 and the bumper cap 161B are fitted together is weaker than the fixing force that secures the bumper cap 161B and the cylinder 17.

[0147] In the holding process, for example, first, the piston rod 51, with the rod-side mounting eye body 131 and head cap 141A fixed in the head cap fixing process, is inserted from the mounting shaft portion 53 side into the bumper cap hole 168A formed in the bumper cap bottom portion 163A of the bumper cap 161B, from the opposite side from the bumper cap cylindrical portion 164A, so that the rib 200 of the head cap 141A comes into contact with the bumper cap bottom portion 163A. Next, the rod-side mounting eye body 131 fixed to the piston rod 51 is inserted from the jig cylindrical portion 213 side into the jig hole 221 formed in the jig bottom portion 212 of the jig 211. Then, the jig cylindrical portion 213 of the jig 211 is fitted onto the bumper cap 161B by press-fitting. As a result, the jig bottom 212 of the jig 211 and the base portion 171 of the bumper cap 161B clamp the disc portion 147A of the head cap 141A and the multiple ribs 200. This causes the bumper cap 161B to be held on the head cap 141A by the jig 211. In addition, the bumper cap cylindrical portion 164A of the bumper cap 161B, which is held on the head cap 141A by the jig 211, covers the main shaft portion 52 of the piston rod 51 radially outward. Furthermore, the main shaft portion 52 of the piston rod 51 is inserted through the bumper cap hole 168A of the bumper cap 161B.

[0148] The manufacturing method for the shock absorber 11B of the third embodiment involves, after the head cap fixing and holding steps, a rod seal fitting step, a rod guide fitting step, a cushion member fitting step, a stopper member fixing step, and a piston mounting step, similar to the manufacturing methods for the shock absorber 11 of the first and second embodiments. As a result, the rod-side mounting eye body 131, the head cap 141A with the bumper cap 161B held by the jig 211, the rod seal 41 with springs 81 and 82 attached, the rod guide 28, the cushion member 102, the stopper member 101, the piston 45, the disc valves 87 and 88, and the nut 57 are assembled onto the piston rod 51. Furthermore, the rod-side rubber bush 132 is assembled onto the rod-side mounting eye body 131 to form the piston rod sub-assembly.

[0149] The manufacturing method for the shock absorber 11B of the third embodiment involves inserting the piston rod 51 of the piston rod subassembly into the inner cylinder 15 of the cylinder 17 of the cylinder subassembly 181 and assembling the piston rod subassembly into the cylinder subassembly 181. The piston rod insertion step, rod guide placement step, rod seal placement step, and locking portion formation step are performed in order, similar to the manufacturing methods for the shock absorbers 11 and 11A of the first and second embodiments.

[0150] The manufacturing method of the shock absorber 11B of the third embodiment includes a bumper cap fixing step in which the bumper cap 161B, which is held on the head cap 141A by a jig 211, is fixed to the fitting portion 25 of the cylinder 17 after the locking portion forming step.

[0151] This bumper cap fixing process includes a bumper cap mounting process in which the bumper cap 161B, held on the head cap 141A by the jig 211, is fitted into the fitting portion 25 of the outer cylinder 16 of the cylinder 17 by moving the piston rod 51 to the minimum length side, and a separation process in which, after the bumper cap 161B has been fitted into the cylinder 17 in the bumper cap mounting process, the piston rod 51 is moved to the maximum length side to separate the fitting between the jig 211 and the bumper cap 161B.

[0152] In the manufacturing method of the shock absorber 11B of the third embodiment, as described above, the fitting force when the jig cylinder portion 213 of the jig 211 and the bumper cap 161B are fitted together is weaker than the fixing force that fixes the bumper cap 161B to the cylinder 17. Therefore, in the detachment process, when the assembly device pulls the rod-side mounting eye body 131 of the rod-side mounting eye 112 away from the cylinder 17, the piston rod 51, jig 211 and head cap 141A move together with the rod-side mounting eye body 131, while the bumper cap 161B remains fitted into the fitting portion 25 of the outer cylinder 16 of the cylinder 17, with its inner projection 173 in contact with the locking portion 43, thus maintaining its state of being attached to the cylinder 17. In this way, the fitting of the jig 211 with the bumper cap 161 fitted to the cylinder 17 can be detached.

[0153] In the manufacturing method of the shock absorber 11B of the third embodiment, the bumper cap attachment process and the detachment process, which constitute the bumper cap fixing process, can be performed in a series of operations by a single assembly device, and thus can be automated, thereby reducing the number of manual work steps.

[0154] The manufacturing method of the shock absorber 11B of the third embodiment includes a jig removal step in which, after the bumper cap fixing step, the jig 211 is removed from the piston rod 51 side by passing the rod-side mounting eye 112 into the jig hole 221.

[0155] The manufacturing method of the shock absorber 11B of the third embodiment includes a cover member attachment step, after the jig removal step, attaching a cover member (not shown) to the head cap 141A.

[0156] The manufacturing method for the shock absorber 11B of the third embodiment includes a head cap fixing step of fixing the head cap 141A to the piston rod 51, a holding step of holding the bumper cap 161B on the head cap 141A using a jig 211, a piston rod insertion step of inserting the piston rod 51 into the cylinder 17, and a bumper cap fixing step of fixing the bumper cap 161B to the cylinder 17. Therefore, with this manufacturing method, the assembly work of the shock absorber 11B can be performed after the bumper cap 161B has been held on the head cap 141A by the jig 211. Thus, with this manufacturing method, after the bumper cap 161B has been held on the head cap 141A by the jig 211, the bumper cap 161B is less likely to interfere with the work, and the assembly work of the shock absorber 11B can be performed easily. Furthermore, in this manufacturing method, for example, the head cap 141A is fixed to the piston rod 51 in the head cap fixing step, the bumper cap 161A is held by a jig 211 in the holding step on the head cap 141A fixed to the piston rod 51, the piston rod 51 on which the head cap 141 and bumper cap 161 are provided is inserted into the cylinder 17 in the piston rod insertion step, and the bumper cap 161 held by the jig 211 on the head cap 141 is fixed to the cylinder 17 in the bumper cap fixing step. As a result, the bumper cap 161 can be attached to the cylinder 17 while being held by the jig 211 on the head cap 141 fixed to the piston rod 51. Therefore, this manufacturing method makes the assembly work of the shock absorber 11B even easier.

[0157] Furthermore, in the manufacturing method of the shock absorber 11B of the third embodiment, the holding step of holding the bumper cap 161B on the head cap 141A includes the work of fitting the bumper cap 161B to the inner circumference of the jig cylinder portion 213 of the jig 211 so that the head cap 141A is sandwiched between the jig 211 and the bumper cap 161B, thus making it easier to hold the bumper cap 161B on the head cap 141A.

[0158] Furthermore, the manufacturing method of the shock absorber 11B of the third embodiment includes a bumper cap fixing step for fixing the bumper cap 161B to the cylinder 17, which involves a bumper cap mounting step in which the bumper cap 161B, held by the jig 211 on the head cap 141A, is fitted onto the cylinder 17 by moving the piston rod 51 to the minimum length side, and a separation step in which, after the bumper cap 161B is fitted onto the cylinder 17, the fitting between the jig 211 and the bumper cap 161B is separated by moving the piston rod 51 to the maximum length side. Since the fitting force when the jig cylinder portion 213 of the jig 211 and the bumper cap 161B are fitted together is weaker than the fixing force that fixes the bumper cap 161B and the cylinder 17, the jig 211 and the head cap 141A can be separated from the bumper cap 161B by the separation step without removing the bumper cap 161B from the cylinder 17. Thus, since the bumper cap fixing process only involves the axial movement of the piston rod 51, the structure of the assembly device can be simplified, and equipment costs can be reduced.

[0159] [Fourth Embodiment] The method for manufacturing a buffer according to the fourth embodiment of the present disclosure will be described mainly with reference to Figures 15 and 16. Here, the differences from the first to third embodiments will be described. For parts common to the first to third embodiments, the same designations and reference numerals will be used, and redundant explanations will be omitted.

[0160] The fourth embodiment is a manufacturing method for producing a buffer 11B similar to that of the third embodiment. The manufacturing method for the buffer 11B of the fourth embodiment includes a cylinder sub-assembly forming step similar to that of the manufacturing methods for the buffers 11, 11A, and 11B of the first to third embodiments.

[0161] Furthermore, the manufacturing method of the shock absorber 11B of the fourth embodiment includes a head cap fixing step in which the head cap 141A is fixed to the piston rod 51 in the same manner as the manufacturing method of the shock absorber 11A of the second embodiment.

[0162] Furthermore, the manufacturing method of the shock absorber 11B of the fourth embodiment includes a holding step of holding the bumper cap 161B on the head cap 141A using magnets 241, as shown in Figures 15 and 16. Here, for example, multiple magnets 241 are used. Multiple magnets 241 are arranged inside the bumper cap cylindrical portion 164A of the bumper cap 161B and are capable of attracting the head cap 141A which is located on the opposite side of the bumper cap bottom portion 163. In the holding step, for example, first, the piston rod 51, which has the head cap 141A fixed in the head cap fixing step, is inserted from the mounting shaft portion 53 side into the bumper cap hole 168A formed in the bumper cap bottom portion 163A of the bumper cap 161B, from the side opposite to the bumper cap cylindrical portion 164A, and the head cap 141A is brought into contact with the bumper cap bottom portion 163A. Next, multiple magnets 241 are inserted into the bumper cap cylindrical portion 164A of the bumper cap 161B, and the head cap 141A, which is located on the opposite side of the magnet 241 at the bottom portion 163A of the bumper cap, is attracted to the multiple magnets 241. As a result, the bumper cap 161B is held by the multiple magnets 241 on the head cap 141A. In addition, the bumper cap cylindrical portion 164A of the bumper cap 161B, which is held by the multiple magnets 241 on the head cap 141A, covers the main shaft portion 52 of the piston rod 51 radially outward. Furthermore, the main shaft portion 52 of the piston rod 51 is inserted through the bumper cap hole 168A of the bumper cap 161B.

[0163] The manufacturing method for the shock absorber 11B of the fourth embodiment involves, after the head cap fixing and holding steps, a rod seal fitting step, a rod guide fitting step, a cushion member fitting step, a stopper member fixing step, and a piston mounting step, similar to the manufacturing methods for the shock absorbers 11, 11A, and 11B of the first to third embodiments. As a result, the rod-side mounting eye body 131, the head cap 141A holding the bumper cap 161B by the magnet 241, the rod seal 41 with springs 81 and 82 attached, the rod guide 28, the cushion member 102, the stopper member 101, the piston 45, the disc valves 87 and 88, and the nut 57 are assembled to the piston rod 51. Furthermore, the rod-side rubber bush 132 is assembled to the rod-side mounting eye body 131 to form the piston rod sub-assembly.

[0164] The manufacturing method for the shock absorber 11B of the fourth embodiment involves inserting the piston rod 51 of the piston rod subassembly into the inner cylinder 15 of the cylinder 17 of the cylinder subassembly 181 and assembling the piston rod subassembly into the cylinder subassembly 181. The piston rod subassembly is then assembled into the cylinder subassembly 181, and the piston rod insertion step, rod guide placement step, rod seal placement step, and locking portion formation step are performed in order, similar to the manufacturing methods for the shock absorbers 11, 11A, and 11B of the first to third embodiments.

[0165] The manufacturing method of the shock absorber 11B of the fourth embodiment includes, after the locking portion forming step, a plurality of magnets 241 to release the holding of the bumper cap 161B by the head cap 141A, and then a bumper cap fixing step in which the bumper cap 161B is fixed to the fitting portion 25 of the cylinder 17.

[0166] This bumper cap fixing process includes a bumper cap mounting process in which the piston rod 51 is moved to the minimum length side, thereby fitting the bumper cap 161 to the outer circumference of the fitting portion 25 of the outer cylinder 16 of the cylinder 17. In this bumper cap mounting process, the piston rod 51 is inserted into the cylinder 17 in the same manner as in the bumper cap mounting process of the first to third embodiments, which causes the bumper cap 161B to press against the head cap 141A, thereby press-fitting the multiple fitting protrusions 178 of the bumper cap 161 into the fitting portion 25 of the outer cylinder 16 of the cylinder 17.

[0167] The bumper cap fixing process includes a separation step in which, after the bumper cap 161B is fitted onto the cylinder 17 in the bumper cap mounting process, the piston rod 51 is moved to its maximum length side, thereby separating the head cap 141A from the bumper cap 161B. As a result, the bumper cap 161B remains fitted onto the fitting portion 25 of the outer cylinder 16 of the cylinder 17, and its state of being attached to the cylinder 17 is maintained. On the other hand, the head cap 141A moves away from the bumper cap 161B and the cylinder 17.

[0168] The manufacturing method of the shock absorber 11B of the fourth embodiment includes a cover member attachment step, after the bumper cap fixing step, attaching a cover member (not shown) to the head cap 141A.

[0169] The manufacturing method for the shock absorber 11B of the fourth embodiment includes a head cap fixing step of fixing the head cap 141A to the piston rod 51, a holding step of holding the bumper cap 161B to the head cap 141A using a magnet 241, a piston rod insertion step of inserting the piston rod 51 into the cylinder 17, and a bumper cap fixing step of fixing the bumper cap 161B to the cylinder 17. Therefore, in this manufacturing method, the bumper cap 161B can be held to the head cap 141A by the magnet 241 in the holding step. Therefore, in this manufacturing method, the assembly work of the shock absorber 11B can be performed after the bumper cap 161B has been held to the head cap 141A by the magnet 241. Therefore, in this manufacturing method, after the bumper cap 161B has been held to the head cap 141A by the magnet 241, the bumper cap 161B is less likely to interfere with the work, and the assembly work of the shock absorber 11B can be performed easily.

[0170] Furthermore, in the manufacturing method of the shock absorber 11B of the fourth embodiment, the holding step of holding the bumper cap 161B on the head cap 141A is performed by attraction of the magnet 241, making it easier to hold the bumper cap 161B on the head cap 141A.

[0171] [Fifth Embodiment] The manufacturing method of the buffer according to the fifth embodiment of the present disclosure will be described. Here, the differences from the first to third embodiments will be described. For parts common to the first to third embodiments, the same designations and reference numerals will be used, and redundant explanations will be omitted.

[0172] The fifth embodiment is a manufacturing method for producing a shock absorber 11B similar to that of the third embodiment. The manufacturing method for the shock absorber 11B of the fifth embodiment includes a head cap fixing step in which the head cap 141A is fixed to the piston rod 51 in the same manner as the manufacturing method for the shock absorber 11A of the second embodiment.

[0173] Furthermore, the manufacturing method of the shock absorber 11B of the fifth embodiment includes a holding step of holding the bumper cap 161B to the head cap 141A with double-sided tape (not shown). The double-sided tape has adhesive layers on both sides of a strip-shaped base material. In the holding step, for example, the double-sided tape is attached to the side of the bumper cap bottom 163A of the bumper cap 161B opposite to the bumper cap cylindrical portion 164A, using the adhesive layer on one side. Then, the piston rod 51, with the head cap 141A fixed in the head cap fixing step, is inserted from the mounting shaft portion 53 side into the bumper cap hole 168A formed in the bumper cap bottom 163A of the bumper cap 161B, from the side opposite to the bumper cap cylindrical portion 164A. Then, the multiple ribs 200 of the head cap 141A are attached to the adhesive layer on the other side of the double-sided tape attached to the bumper cap bottom 163A of the bumper cap 161B. As a result, the bumper cap 161B is held to the head cap 141A by double-sided tape. The bumper cap cylindrical portion 164A of the bumper cap 161B, which is held to the head cap 141A by double-sided tape, covers the main shaft portion 52 of the piston rod 51 radially outward. The main shaft portion 52 of the piston rod 51 is inserted through the bumper cap hole 168A of the bumper cap 161B.

[0174] Here, the adhesive force of the double-sided tape is set such that the adhesive force when the bumper cap 161B and the head cap 141A are attached is weaker than the fixing force when the bumper cap 161B and the cylinder 17 are fixed together.

[0175] The manufacturing method for the shock absorber 11B of the fifth embodiment involves, after the head cap fixing and holding steps, a rod seal fitting step, a rod guide fitting step, a cushion member fitting step, a stopper member fixing step, and a piston mounting step, similar to the manufacturing methods for the shock absorbers 11, 11A, and 11B of the first to fourth embodiments. As a result, the rod-side mounting eye body 131, the head cap 141A with the bumper cap 161B held in place by double-sided tape, the rod seal 41 with springs 81 and 82 attached, the rod guide 28, the cushion member 102, the stopper member 101, the piston 45, the disc valves 87 and 88, and the nut 57 are assembled onto the piston rod 51. Furthermore, the rod-side rubber bush 132 is assembled onto the rod-side mounting eye body 131 to form the piston rod sub-assembly.

[0176] The manufacturing method for the shock absorber 11B of the fifth embodiment involves inserting the piston rod 51 of the piston rod subassembly into the inner cylinder 15 of the cylinder 17 of the cylinder subassembly 181 and assembling the piston rod subassembly into the cylinder subassembly 181. The piston rod subassembly is then assembled into the cylinder subassembly 181, and the piston rod insertion step, rod guide placement step, rod seal placement step, and locking portion formation step are performed in order, all of which are the same as the manufacturing methods for the shock absorbers 11, 11A, and 11B of the first to fourth embodiments.

[0177] The manufacturing method of the shock absorber 11B of the fifth embodiment includes a bumper cap fixing step in which the bumper cap 161B, which is held on the head cap 141A by double-sided tape, is fixed to the fitting portion 25 of the cylinder 17 after the locking portion forming step.

[0178] This bumper cap fixing process includes a bumper cap installation process in which the bumper cap 161B, which is held on the head cap 141A with double-sided tape, is fitted into the fitting portion 25 of the outer cylinder 16 of the cylinder 17 by moving the piston rod 51 to the minimum length side, and a separation process in which, after the bumper cap 161B has been fitted into the cylinder 17 in the bumper cap installation process, the piston rod 51 is moved to the maximum length side to separate the adhesion between the head cap 141A and the bumper cap 161B by double-sided tape.

[0179] In the manufacturing method of the shock absorber 11B of the fifth embodiment, as described above, the adhesive force of the double-sided tape is set such that the adhesive force when the bumper cap 161B and the head cap 141A are attached is weaker than the fixing force that fixes the bumper cap 161B to the cylinder 17. For this reason, in the separation process, when the assembly device pulls the rod-side mounting eye body 131 of the rod-side mounting eye 112 away from the cylinder 17, the piston rod 51 and the head cap 141A move together with the rod-side mounting eye body 131, while the bumper cap 161 remains fitted into the fitting portion 25 of the outer cylinder 16 of the cylinder 17, with the inner protrusion 173 in contact with the locking portion 43, thus maintaining its state of being attached to the cylinder 17. In this way, the attachment of the head cap 141A to the bumper cap 161 fitted to the cylinder 17 by double-sided tape can be separated.

[0180] In the manufacturing method of the shock absorber 11B of the fifth embodiment, the bumper cap attachment process and the detachment process, which constitute the bumper cap fixing process, can be performed in a series of operations by a single assembly device, and thus can be automated, thereby reducing the number of manual work steps.

[0181] In the manufacturing method of the shock absorber 11B of the fifth embodiment, after the bumper cap fixing step, a double-sided tape removal step is included in which the double-sided tape is peeled off and removed from the head cap 141A or the bumper cap 161B.

[0182] The manufacturing method of the shock absorber 11B of the fifth embodiment includes a cover member attachment step, after the double-sided tape removal step, attaching a cover member (not shown) to the head cap 141A.

[0183] The manufacturing method for the shock absorber 11B of the fifth embodiment includes a head cap fixing step of fixing the head cap 141A to the piston rod 51, a holding step of holding the bumper cap 161B to the head cap 141A using double-sided tape, a piston rod insertion step of inserting the piston rod 51 into the cylinder 17, and a bumper cap fixing step of fixing the bumper cap 161B to the cylinder 17. Therefore, in this manufacturing method, the assembly work of the shock absorber 11B can be performed after the bumper cap 161B has been held to the head cap 141A with double-sided tape in the holding step. Thus, in this manufacturing method, after the bumper cap 161B has been held to the head cap 141A with double-sided tape, the bumper cap 161B is less likely to interfere with the work, and the assembly work of the shock absorber 11B can be performed easily. Furthermore, in this manufacturing method, for example, in the head cap fixing step the head cap 141A is fixed to the piston rod 51, and in the holding step the bumper cap 161B is held to the head cap 141A with double-sided tape. Then, the piston rod 51 is inserted into the cylinder 17 in the piston rod insertion step, and the bumper cap 161B, which is held by the head cap 141A, is fixed to the cylinder 17 in the bumper cap fixing step. This allows the bumper cap 161B to be attached to the cylinder 17 while it is held by double-sided tape to the head cap 141A which is fixed to the piston rod 51. Therefore, this manufacturing method makes it possible to easily attach the bumper cap 161B to the cylinder 17, and further simplifies the assembly work of the shock absorber 11B.

[0184] Furthermore, in the manufacturing method of the shock absorber 11B of the fifth embodiment, the holding step of holding the bumper cap 161B to the head cap 141A is performed using double-sided tape, making it easier to hold the bumper cap 161B to the head cap 141A.

[0185] Furthermore, the manufacturing method of the shock absorber 11B of the fifth embodiment includes a bumper cap fixing step in which the bumper cap 161B is fixed to the cylinder 17, and a bumper cap mounting step in which the piston rod 51 is moved to the minimum length side to fit the bumper cap 161B, which is attached to the head cap 141A with double-sided tape, into the cylinder 17, and a separation step in which, after the bumper cap 161B is fitted into the cylinder 17, the piston rod 51 is moved to the maximum length side to separate the attachment between the head cap 141A and the bumper cap 161B by double-sided tape.The adhesive force of the double-sided tape is set so that the adhesive force when the bumper cap 161B and the head cap 141A are attached is weaker than the fixing force that fixes the bumper cap 161B and the cylinder 17, so that the head cap 141A can be separated from the bumper cap 161B without removing the bumper cap 161B from the cylinder 17 by the separation step. Thus, since the bumper cap fixing process only involves the axial movement of the piston rod 51, the structure of the assembly device can be simplified, and equipment costs can be reduced.

[0186] In addition to using double-sided tape having adhesive layers on both sides of a strip-shaped base material, a tape having an adhesive layer on only one side of a strip-shaped base material may also be used to hold the bumper cap 161B to the head cap 141A during the holding process.

[0187] The manufacturing method of the shock absorber 11B in the third embodiment described above uses a jig 211, the manufacturing method of the shock absorber 11B in the fourth embodiment uses a magnet 241, and the manufacturing method of the shock absorber 11B in the fifth embodiment uses double-sided tape, but the manufacturing method of the shock absorber of this disclosure is not limited to these. The manufacturing method of the shock absorber of this disclosure can use various means as long as the bumper cap can be held on the head cap. For example, it is also possible to use a jig that holds the bumper cap and the head cap by sandwiching them from both sides.

[0188] According to the buffer and method for manufacturing the buffer in the above-described embodiment of this disclosure, assembly work can be easily performed.

[0189] 11, 11A, 11B... shock absorber, 17... cylinder, 51... piston rod, 141, 141A... head cap, 143... head cap bottom, 144... head cap cylindrical part, 149... head cap hole, 161, 161A, 161B... bumper cap, 163, 163A... bumper cap bottom, 164, 164A... bumper cap cylindrical part, 165... radial projection, 168, 168A... bumper cap hole, 201... axial projection, 202... communication passage, L... oil (working fluid).

Claims

1. A shock absorber comprising: a cylinder in which a working fluid is sealed; a piston rod protruding from the axial end of the cylinder; a head cap provided in the portion of the piston rod that protrudes from the cylinder and having a head cap bottom portion with a head cap hole through which the piston rod can be inserted and a head cap cylindrical portion that covers the radial outer circumference of the piston rod; and a bumper cap fixed to the axial end of the cylinder and having a bumper cap bottom portion with a bumper cap hole through which the piston rod can be inserted and a bumper cap cylindrical portion that covers the radial outer circumference of the cylinder, wherein the bumper cap has a radial projection that protrudes radially outward on the bumper cap bottom side of the bumper cap cylindrical portion, and the outer diameter of the radial projection is formed to be larger than the inner diameter of the head cap cylindrical portion.

2. The shock absorber according to claim 1, wherein the bumper cap is formed such that the radial projection and the head cap cylindrical portion of the head cap can be fitted together.

3. The shock absorber according to claim 1, wherein the bumper cap is formed such that the axial length of the radial projection is shorter than the thickness of the bottom of the bumper cap.

4. A shock absorber according to claim 2, wherein the fitting force when the radial projection of the bumper cap and the head cap cylindrical portion of the head cap are fitted together is weaker than the fixing force that secures the bumper cap and the cylinder.

5. A shock absorber according to any one of claims 1 to 4, wherein the radial projections are formed in a plurality at intervals in the circumferential direction.

6. A shock absorber comprising: a cylinder containing a working fluid; a piston rod protruding from the axial end of the cylinder; a head cap provided in the portion of the piston rod protruding from the cylinder and having a head cap hole through which the piston rod can be inserted; and a bumper cap fixed to the axial end of the cylinder and having a bumper cap bottom portion having a bumper cap hole through which the piston rod can be inserted and a bumper cap cylindrical portion covering the radial outer circumference of the cylinder, wherein the bumper cap has an axial projection protruding from the outer circumference of the axial end face of the bumper cap bottom portion toward the head cap side, and the outer diameter of the head cap is formed to be larger than the inner diameter of the axial projection portion.

7. A shock absorber according to claim 6, wherein the axial projection is provided with a communication passage that allows the inside and outside of the axial projection to communicate.

8. A method for manufacturing a shock absorber comprising: a cylinder in which a working fluid is sealed; a piston rod protruding from the axial end of the cylinder; a head cap provided in the portion of the piston rod that protrudes from the cylinder and having a head cap hole through which the piston rod can be inserted; and a bumper cap provided at the axial end of the cylinder and having a bumper cap bottom portion having a bumper cap hole through which the piston rod can be inserted and a bumper cap cylindrical portion covering the radial outer circumference of the cylinder, the method comprising: holding the bumper cap on the head cap; fixing the head cap to the piston rod; inserting the piston rod into the cylinder; and fixing the bumper cap to the cylinder.

9. A method for manufacturing a shock absorber according to claim 8, wherein the head cap has a head cap bottom portion having the head cap hole and a head cap cylindrical portion covering the radial outer circumference of the piston rod, the bumper cap has a radial projection portion of the bumper cap cylindrical portion that protrudes radially outward on the bumper cap bottom portion side, and the step of holding the bumper cap on the head cap is a method for manufacturing a shock absorber in which the radial projection portion of the bumper cap is fitted onto the inner circumference of the head cap cylindrical portion of the head cap.

10. A method for manufacturing a shock absorber according to claim 9, wherein the fitting force when the radial projection of the bumper cap and the head cap cylindrical portion of the head cap are fitted together is weaker than the fixing force that fixes the bumper cap and the cylinder, and the step of fixing the bumper cap to the cylinder includes the steps of: fitting the bumper cap to the cylinder by moving the piston rod to the minimum length side; and after fitting the bumper cap to the cylinder, moving the piston rod to the maximum length side to disengage the fitting between the head cap and the bumper cap.

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