Cylinder, manufacturing method of cylinder and shock absorber

Abstract

To provide a cylinder which can suppress a cost, a manufacturing method of the cylinder, and a shock absorber.SOLUTION: In a cylinder 10 having a cylindrical cylinder part 51 and a lateral hole 58 formed at the cylinder part 51, the lateral hole 58 is formed of a first circular part 131 which is formed so that a length of the cylinder 10 in a circumferential direction becomes longer than at least a length of the cylinder 10 in an axial direction, and a second circular part 132 in which the length of the cylinder 10 in the axial direction becomes longer than at least a length of the cylinder 10 in the circumferential direction, and whose circular-arc length is longer than that of the first circular part 131.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a cylinder, a method for manufacturing a cylinder, and a shock absorber. [Background technology]

[0002] There is a technique for forming a side hole in the cylindrical portion of a cylinder (see, for example, Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] DE 102012207076 [Patent Document 2] China Utility Model No. 214601360 Specification Summary of the Invention [Problem to be solved by the invention]

[0004] It is desirable to reduce costs in cylinders with side holes.

[0005] Therefore, an object of the present invention is to provide a cylinder, a manufacturing method for a cylinder, and a shock absorber that make it possible to reduce costs. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, one embodiment of the cylinder of the present invention is a cylinder having a cylindrical tubular portion and a lateral hole provided in the tubular portion, wherein the lateral hole is formed by a first arc-shaped portion formed so that its length in the circumferential direction of the cylinder is longer than its length in the axial direction of the cylinder, and a second arc-shaped portion whose length in the axial direction of the cylinder is longer than its length in the circumferential direction of the cylinder and whose arc length is longer than that of the first arc-shaped portion.

[0007] One aspect of the manufacturing method of the cylinder according to the present invention is a manufacturing method of a cylinder having a cylindrical tubular portion and a lateral hole provided in the tubular portion, and includes a fixing step of fixing the cylinder, a first arc-shaped portion machining step of forming a first arc-shaped portion which is at least a part of the lateral hole and is formed so that its length in the circumferential direction of the cylinder is longer than its length in the axial direction of the cylinder, and a second arc-shaped portion machining step of machining from a position different from that of the first arc-shaped portion machining step, and which is formed so that its length in the axial direction of the cylinder is longer than its length in the circumferential direction of the cylinder and has a longer arc length than the first arc-shaped portion.

[0008] One aspect of the shock absorber of the present invention comprises a cylinder in which a working fluid is sealed, a piston that divides the cylinder into two chambers, and a piston rod having a first end fixed to the piston and a second end protruding from the cylinder, wherein the cylinder has a cylindrical tubular portion and a lateral hole provided in the tubular portion, the lateral hole being formed by a first arc-shaped portion formed so that its length in the circumferential direction of the cylinder is longer than its length in the axial direction of the cylinder, and a second arc-shaped portion whose length in the axial direction of the cylinder is longer than its length in the circumferential direction of the cylinder and whose arc length is longer than that of the first arc-shaped portion. Effect of the Invention

[0009] According to the present invention, it is possible to reduce costs. [Brief description of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view showing a shock absorber including a cylinder according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is a partial side view showing the cylinder of the first embodiment according to the present invention. [Diagram 3] 3 is a cross-sectional view taken along line III-III in FIG. 2, showing the cylinder of the first embodiment according to the present invention. FIG. [Figure 4]FIG. 2 is a partial side view showing a state after a first hole forming step in the manufacturing method of the cylinder according to the first embodiment of the present invention. [Diagram 5] 2 is a side view, partially in cross section, showing a first set mold and a cylindrical portion, illustrating a first fixing step of a first hole forming step in a manufacturing method of a cylinder according to a first embodiment of the present invention. FIG. [Figure 6] 11 is a side view, partially in cross section, showing a second set mold and a cylindrical portion, illustrating a second fixing step of a second hole forming step in the manufacturing method of the cylinder of the first embodiment according to the present invention. FIG. [Figure 7] 10 is a partial plan view showing a second set mold and a cylindrical portion for explaining a second fixing step of a second hole forming step in the manufacturing method of the cylinder of the first embodiment according to the present invention. FIG. [Figure 8] 10 is a partial plan view showing a second set die and a cylindrical portion for explaining a second arc-shaped portion machining step in a second hole forming step in the manufacturing method of the cylinder of the first embodiment according to the present invention. FIG. [Figure 9] 13 is a partial side view showing a second set mold and a cylindrical portion, illustrating a second fixing step of a second hole forming step in a manufacturing method of a cylinder according to a second embodiment of the present invention. FIG. [Figure 10] 10 is a plan view showing a notch used in a manufacturing method of a cylinder according to a second embodiment of the present invention. FIG. [Figure 11] 11 is a side view taken in a direction XI in FIG. 10, showing a notch used in a manufacturing method of a cylinder according to a second embodiment of the present invention. FIG. [Figure 12] 12 is a side view taken from the direction XII in FIG. 10, showing a notch used in a manufacturing method of a cylinder according to a second embodiment of the present invention. FIG. [Figure 13] 11 is a side view taken in a direction XIII in FIG. 10, showing a notch used in a manufacturing method of a cylinder according to a second embodiment of the present invention. FIG. [Figure 14] FIG. 11 is a perspective view showing a notch used in a manufacturing method of a cylinder according to a second embodiment of the present invention. [Figure 15]13 is a partial plan view showing a second set die and a cylindrical portion for explaining a second arc-shaped portion machining step in a second hole forming step in a manufacturing method for a cylinder according to a second embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

[0012] [First embodiment] 1 shows a shock absorber 11 including a cylinder 10 according to a first embodiment. The shock absorber 11 is a twin-cylinder hydraulic shock absorber. The shock absorber 11 is used in a suspension device for a vehicle, specifically, an automobile.

[0013] The cylinder 10 has an inner tube 21, a separator tube 22, and an outer shell 23. The inner tube 21 and the separator tube 22 are cylindrical. The outer shell 23 is cylindrical and has a bottom.

[0014] The cylinder 10 has a first fixed member 31, a first seal member 32, a first locking member 33, a second fixed member 34, a second seal member 35, and a second locking member 36. The first fixed member 31, the first seal member 32, the first locking member 33, the second fixed member 34, the second seal member 35, and the second locking member 36 are all annular.

[0015] The inner tube 21 is made of metal. The inner tube 21 is disposed coaxially with the outer shell 23 and disposed radially inside the outer shell 23.

[0016] The separator tube 22 is made of metal. The axial length of the separator tube 22 is shorter than the axial length of the inner tube 21. The separator tube 22 is disposed coaxially with the inner tube 21 and the outer shell 23 and is provided between the inner tube 21 and the outer shell 23 in the radial direction.

[0017] The separator tube 22 is supported on the outer peripheral surface of the inner tube 21 at a predetermined intermediate position in the axial direction via a first fixing member 31, a first sealing member 32, a first locking member 33, a second fixing member 34, a second sealing member 35 and a second locking member 36.

[0018] One axial end of the separator tube 22 is fixed to the outer circumferential surface of the inner tube 21 via a first fixing member 31 arranged radially inside the separator tube 22. The other axial end of the separator tube 22 is fixed to the outer circumferential surface of the inner tube 21 via a second fixing member 34 arranged radially inside the separator tube 22.

[0019] A first seal member 32 is provided between the separator tube 22 and the inner tube 21 adjacent to the first fixing member 31 on the side facing the second fixing member 34, and a first locking member 33 is provided adjacent to the first seal member 32 on the side opposite to the first fixing member 31. The first seal member 32 seals between one axial end of the separator tube 22 and the inner tube 21. The first locking member 33 restricts movement of the first seal member 32 in a direction away from the first fixing member 31.

[0020] A second seal member 35 is provided between the separator tube 22 and the inner tube 21 adjacent to the second fixing member 34 on the side facing the first fixing member 31, and a second locking member 36 is provided adjacent to the second seal member 35 on the side opposite to the second fixing member 34. The second seal member 35 seals between the other axial end of the separator tube 22 and the inner tube 21. The second locking member 36 restricts movement of the second seal member 35 in a direction away from the second fixing member 34.

[0021] Between the separator tube 22 and the inner tube 21, an intermediate chamber 41 is formed between the first locking member 33 and the second locking member 36. The intermediate chamber 41 is defined between the separator tube 22 and the inner tube 21 by the first fixing member 31, the first sealing member 32, the first locking member 33, the second fixing member 34, the second sealing member 35 and the second locking member 36.

[0022] A communication hole 42 that penetrates the inner tube 21 in the radial direction of the inner tube 21 is formed in the inner tube 21 at a position near the first locking member 33 between the first locking member 33 and the second locking member 36. The communication hole 42 opens into the intermediate chamber 41.

[0023] Separator tube 22 has a mounting hole 45 formed in a position adjacent to second locking member 36 between first locking member 33 and second locking member 36, the mounting hole 45 penetrating separator tube 22 in the radial direction of separator tube 22.

[0024] The outer shell 23 is made of metal and has a cylindrical portion 51, an extension portion 52, and a bottom portion 53.

[0025] The tubular portion 51 is cylindrical. A horizontal hole 58 is formed on one axial end of the tubular portion 51, penetrating the tubular portion 51 in the radial direction so as to open to an outer peripheral surface 55 on the radial outside of the tubular portion 51 and an inner peripheral surface 56 on the radial inside of the tubular portion 51. In other words, the cylinder 10 has the cylindrical tubular portion 51 and the horizontal hole 58 provided in the tubular portion 51. The horizontal hole 58 is aligned with the mounting hole 45 of the separator tube 22 in the axial direction of the cylinder 10 and in the circumferential direction of the cylinder 10.

[0026] The extension portion 52 is cylindrical and is fitted into an end portion of the outer circumferential surface 55 of the tubular portion 51 opposite the horizontal hole 58 in the axial direction. The extension portion 52 extends outward from the tubular portion 51 in the axial direction of the tubular portion 51. The extension portion 52 is fixed to the outer circumferential portion of the tubular portion 51 by welding.

[0027] The bottom portion 53 fits into the inner periphery of the end portion of the cylindrical portion 51 opposite the extension portion 52 in the axial direction. The bottom portion 53 closes the opening of the end portion of the cylindrical portion 51 opposite the extension portion 52 in the axial direction. The lateral hole 58 of the cylindrical portion 51 is disposed on the bottom portion 53 side of the cylindrical portion 51 in the axial direction.

[0028] The shock absorber 11 has a base member 61 , a cover member 62 , a seal member 63 , a rod guide 64 , and a piston seal 65 . The base member 61 is placed on the bottom portion 53 within the outer shell 23 .

[0029] The cover member 62 has a cylindrical portion 71 and a lid portion 72 that extends radially inward from one axial end of the cylindrical portion 71. The cover member 62 is screwed onto the inner periphery of the end of the extension portion 52 of the outer shell 23 opposite the bottom portion 53 in the axial direction, with the lid portion 72 oriented to be disposed on the opposite side to the bottom portion 53 in the axial direction of the outer shell 23 than the cylindrical portion 71.

[0030] The seal member 63 is disposed between the cylindrical portion 71 of the cover member 62 and the extension portion 52 of the outer shell 23 to provide a seal therebetween.

[0031] The rod guide 64 is fitted into the inner periphery of the cylindrical portion 71 of the cover member 62 . The piston seal 65 is disposed inside the cylindrical portion 71 of the cover member 62 , and is disposed between the cover portion 72 of the cover member 62 and the rod guide 64 .

[0032] One axial end of the inner tube 21 is supported by the base member 61, and the other axial end is supported by the rod guide 64. As a result, the inner tube 21 and the separator tube 22 are arranged coaxially with respect to the outer shell 23. At this time, the inner tube 21 has the communication hole 42 arranged on the rod guide 64 side in the axial direction. At this time, the separator tube 22 has the mounting hole 45 arranged on the base member 61 side in the axial direction. At this time, the first fixing member 31, the first sealing member 32, and the first locking member 33 are arranged on the rod guide 64 side of the inner tube 21 in the axial direction. At this time, the second fixing member 34, the second sealing member 35, and the second locking member 36 are arranged on the base member 61 side of the inner tube 21 in the axial direction.

[0033] A reservoir chamber 75 is formed between the inner tube 21 and the separator tube 22 and the outer shell 23. The reservoir chamber 75 extends to between the bottom 53 of the outer shell 23 and the base member 61 by a communication groove 78 formed in the base member 61.

[0034] The shock absorber 11 includes a piston 80 inserted into the cylinder 10. The piston 80 is slidably fitted into the inner tube 21 of the cylinder 10. The piston 80 defines a first chamber 81 and a second chamber 82 in the inner tube 21. In other words, the piston 80 divides the cylinder 10 into two chambers, the first chamber 81 and the second chamber 82. The first chamber 81 is provided between the piston 80 and the rod guide 64 in the axial direction of the inner tube 21. The first chamber 81 communicates with the intermediate chamber 41 via a communication hole 42 formed in the inner tube 21. The second chamber 82 is provided between the piston 80 and the base member 61 in the axial direction of the inner tube 21. The second chamber 82 is divided from the reservoir chamber 75 by the base member 61.

[0035] In the cylinder 10, oil L as a working fluid is sealed in the first chamber 81 and the second chamber 82 in the inner tube 21 and the intermediate chamber 41 in the separator tube 22. In the cylinder 10, oil L and gas G as a working fluid are sealed in the reservoir chamber 75.

[0036] The shock absorber 11 includes a piston rod 90. A first end, which is one end of the piston rod 90 in the axial direction, is disposed within the inner tube 21 of the cylinder 10. The first end of the piston rod 90 is fixed to the piston 80. A second end, which is the other end of the piston rod 90 opposite to the first end in the axial direction, protrudes from the cylinder 10 to the outside of the cylinder 10.

[0037] The piston rod 90 has a main shaft portion 91 and a mounting shaft portion 92. The mounting shaft portion 92 has an outer diameter smaller than that of the main shaft portion 91. The mounting shaft portion 92 is provided at a first end portion of the piston rod 90, and is disposed within the inner tube 21. The main shaft portion 91 of the piston rod 90 passes through a piston seal 65. The piston seal 65 seals between the main shaft portion 91 and the cylindrical portion 71 of the cover member 62. The piston rod 90 has a piston 80 attached to the mounting shaft portion 92. The piston 80 moves integrally with the piston rod 90.

[0038] The piston 80 is formed with a passage 101 and a passage 102 that axially penetrate the piston 80. Both the passage 101 and the passage 102 are capable of connecting the first chamber 81 and the second chamber 82 to each other.

[0039] The shock absorber 11 includes a disc valve 103 and a disc valve 104 . The disk valve 103 is provided on the opposite side of the piston 80 from the bottom portion 53 in the axial direction. The disk valve 103 is capable of closing the passage 101 by abutting against the piston 80.

[0040] The disc valve 104 is provided on the bottom portion 53 side in the axial direction of the piston 80. The disc valve 104 is capable of closing the passage 102 by abutting against the piston 80. The disc valves 103 and 104 are attached to the mounting shaft portion 92 of the piston rod 90 together with the piston 80 by a nut 105.

[0041] When the piston rod 90 moves toward the compression side to increase the amount of entry into the cylinder 10 and the piston 80 moves in the direction narrowing the second chamber 82, causing the pressure in the second chamber 82 to be higher than the pressure in the first chamber 81 by a predetermined value or more, the disc valve 103 opens the passage 101 to allow the oil L to flow from the second chamber 82 to the first chamber 81. At that time, the disc valve 103 generates a damping force. At least one of the piston 80 and the disc valve 103 is provided with a fixed orifice (not shown) that communicates between the first chamber 81 and the second chamber 82 via the passage 101 even when the disc valve 103 is in the most blocked state of the passage 101.

[0042] When the piston rod 90 moves to the extension side to increase the amount of protrusion from the cylinder 10 and the piston 80 moves in a direction narrowing the first chamber 81, and the pressure in the first chamber 81 becomes higher than the pressure in the second chamber 82 by a predetermined value or more, the disc valve 104 opens the passage 102 to allow the oil L to flow from the first chamber 81 to the second chamber 82. At that time, the disc valve 104 generates a damping force. At least one of the piston 80 and the disc valve 104 is provided with a fixed orifice (not shown) that communicates between the first chamber 81 and the second chamber 82 via the passage 102 even when the disc valve 104 is in a state where the passage 102 is most blocked.

[0043] The shock absorber 11 includes a base valve 110 including the base member 61 described above. A passage 111 and a passage 112 are formed penetrating the base member 61 in the axial direction. The passage 111 and the passage 112 are both capable of connecting the second chamber 82 and the reservoir chamber 75 to each other.

[0044] The base valve 110 has an annular disk valve 113 that can close the passage 111 by abutting against the base member 61 on the side of the base member 61 opposite the second chamber 82 in the axial direction. The base valve 110 also has an annular disk valve 114 that can close the passage 112 by abutting against the base member 61 on the second chamber 82 side of the base member 61 in the axial direction. The base valve 110 has a fastening member 115, and the disk valves 113, 114 are attached to the base member 61 by this fastening member 115. The base valve 110 is composed of the base member 61, the disk valves 113, 114, the fastening member 115, etc.

[0045] When the piston rod 90 moves toward the contraction side and the piston 80 moves in a direction narrowing the second chamber 82, and the pressure in the second chamber 82 becomes higher than the pressure in the reservoir chamber 75 by a predetermined value or more, the disk valve 113 opens the passage 111 to allow the oil L to flow from the second chamber 82 to the reservoir chamber 75. At that time, the disk valve 113 generates a damping force. When the piston rod 90 moves toward the extension side and the piston 80 moves toward the first chamber 81, and the pressure in the second chamber 82 becomes lower than the pressure in the reservoir chamber 75, the disk valve 114 opens the passage 112 to allow the oil L to flow from the reservoir chamber 75 to the second chamber 82. At that time, the disk valve 114 is a suction valve that allows the oil L to flow from the reservoir chamber 75 to the second chamber 82 without generating a damping force.

[0046] The shock absorber 11 has a damping force adjustment mechanism 121 and a mounting member 122 . The mounting member 122 is annular, and is fitted into and fixed to the mounting hole 45 of the separator tube 22 .

[0047] The damping force adjustment mechanism 121 is attached to the outside of the tubular portion 51 of the outer shell 23 so as to surround the lateral hole 58. The damping force adjustment mechanism 121 protrudes outward from the outer shell 23 along the radial direction of the outer shell 23. The damping force adjustment mechanism 121 closes the lateral hole 58 of the tubular portion 51 by being attached to the tubular portion 51. The damping force adjustment mechanism 121 has a cylindrical inner communication port 125 that passes through the lateral hole 58 of the outer shell 23, protrudes into the tubular portion 51, and fits into the mounting member 122. The damping force adjustment mechanism 121 has an outer communication port 126 that is located radially outward from the inner communication port 125 and opens outward from the inner communication port 125 in the lateral hole 58 of the outer shell 23.

[0048] The damping force adjustment mechanism 121 has an inner communication port 125 that communicates with the first chamber 81 through the intermediate chamber 41 in the separator tube 22 and a passage in the communication hole 42 formed in the inner tube 21. The damping force adjustment mechanism 121 has an outer communication port 126 that communicates with the reservoir chamber 75. The damping force adjustment mechanism 121 is controlled by an electric signal transmitted through a wiring 127 to adjust the amount of communication between the inner communication port 125 and the outer communication port 126. As a result, the damping force adjustment mechanism 121 adjusts the amount of communication between the intermediate chamber 41 in the separator tube 22, the passage in the communication hole 42 of the inner tube 21, and the first chamber 81 and the reservoir chamber 75. That is, the damping force adjustment mechanism 121 is electrically driven to adjust the amount of communication between the first chamber 81 and the reservoir chamber 75, thereby adjusting the damping force generated by the shock absorber 11.

[0049] In the shock absorber 11, the bottom 53 of the outer shell 23 of the cylinder 10 is disposed at the lower part and connected to the wheel (not shown) side of the vehicle, and the part of the piston rod 90 extending from the cylinder 10 is disposed at the upper part and connected to the vehicle body side. In this way, the shock absorber 11 damps the relative vibration between the wheel and the vehicle body.

[0050] 2, the inner peripheral edge of the lateral hole 58 provided in the tubular portion 51 of the outer shell 23 of the cylinder 10 is formed by a pair of first arc-shaped portions 131 and first arc-shaped portions 131 and a pair of second arc-shaped portions 132 and second arc-shaped portions 132. The inner peripheral edge of the lateral hole 58 is arranged in the circumferential direction in the order of the first arc-shaped portion 131, the second arc-shaped portion 132, the first arc-shaped portion 131, and the second arc-shaped portion 132.

[0051] The pair of first arc-shaped portions 131 and first arc-shaped portions 131 are both arc-shaped and are disposed on both sides of the horizontal hole 58 in the axial direction of the cylinder 10, i.e., the axial direction of the tubular portion 51. The pair of first arc-shaped portions 131 and first arc-shaped portions 131 have the same shape and are mirror-symmetrical to each other in the axial direction of the cylinder 10. The pair of first arc-shaped portions 131 and first arc-shaped portions 131 have the same shape as the first inner surface 141 that forms the horizontal hole 58 of one first arc-shaped portion 131 and the first inner surface 141 that forms the horizontal hole 58 of the other first arc-shaped portion 131, and are mirror-symmetrical to each other in the axial direction of the cylinder 10. The pair of first inner surfaces 141 and first inner surfaces 141 each have a mirror-symmetric shape, and each is a curved surface that is concave in a direction away from the central axis O2, which is a line that passes through the center of the horizontal hole 58 and is perpendicular to the central axis O1 of the cylinder 10. The pair of first inner surfaces 141 and first inner surfaces 141 each extend parallel to the central axis O2 of the horizontal hole 58.

[0052] The first inner surface 141 of the first arc-shaped portion 131 has a first outer boundary portion 141a at the boundary with the outer peripheral surface 55 of the cylindrical portion 51 and a first inner boundary portion 141b at the boundary with the inner peripheral surface 56 of the cylindrical portion 51, as shown in FIG. 3. As shown in FIG. 2, the first inner surface 141 is a curved surface and is formed so that the length in the circumferential direction of the cylinder 10 is longer than the length in the axial direction of the cylinder 10, i.e., the direction in which the central axis O1 of the cylinder 10 extends. Thus, the first arc-shaped portion 131 is also formed so that the length in the circumferential direction of the cylinder 10 is longer than the length in the axial direction of the cylinder 10. When the first inner surface 141 is viewed along the direction of the central axis O2 of the horizontal hole 58 as shown in FIG. 2, the first outer boundary portion 141a and the first inner boundary portion 141b shown in FIG. 3 overlap each other.

[0053] 2, the first inner surface 141 of the first arc-shaped portion 131 has an intermediate surface portion 142 and a pair of end side surfaces 143. The intermediate surface portion 142 is formed in a mirror-symmetric shape at an intermediate portion of the first inner surface 141 in the circumferential direction of the horizontal hole 58. The pair of end side surfaces 143 are formed in a mirror-symmetric shape at both end portions of the first inner surface 141 in the circumferential direction of the horizontal hole 58.

[0054] The intermediate surface portion 142 is arc-shaped with a center of curvature within the lateral hole 58. The pair of end side surfaces 143 and the end side surface portion 143 each have a center of curvature within the lateral hole 58, and each is arc-shaped with a smaller radius of curvature than the intermediate surface portion 142. The first inner surface 141 of the first arc-shaped portion 131, including the intermediate surface portion 142 and the pair of end side surfaces 143 and the end side surface portion 143, all extend parallel to the central axis O2 of the lateral hole 58 that is aligned in the radial direction of the cylinder 10.

[0055] At least a portion of the first inner surface 141 of the first arc-shaped portion 131, specifically the central position in the circumferential direction of the cylinder 10, i.e., the central position of the intermediate surface portion 142 in the circumferential direction of the cylinder 10, is formed in the thickness direction of the tubular portion 51. In other words, the first inner surface 141 of the first arc-shaped portion 131 has a line segment at the central position in the circumferential direction of the cylinder 10 that extends in the thickness direction of the tubular portion 51.

[0056] The pair of second arc-shaped portions 132 and second arc-shaped portions 132 are both arc-shaped and are disposed on both sides of the horizontal hole 58 in the circumferential direction of the cylinder 10, i.e., the circumferential direction of the tubular portion 51. The pair of second arc-shaped portions 132 and second arc-shaped portions 132 have the same shape and are mirror-symmetrical to each other in the circumferential direction of the cylinder 10. The pair of second arc-shaped portions 132 and second arc-shaped portions 132 have the same shape as the second inner surface 146 that forms the horizontal hole 58 of one second arc-shaped portion 132 and the second inner surface 146 that forms the horizontal hole 58 of the other second arc-shaped portion 132, and are mirror-symmetrical to each other in the circumferential direction of the cylinder 10. The pair of second inner surfaces 146 and 146 each have a mirror symmetrical shape, and each is a curved surface that is concave in a direction away from the central axis O2 of the lateral hole 58.

[0057] The second arc-shaped portion 132 has a second inner surface 146 which is a curved surface having a second outer boundary portion 146a at the boundary with the outer peripheral surface 55 of the cylindrical portion 51 and a second inner boundary portion 146b at the boundary with the inner peripheral surface 56 of the cylindrical portion 51. The second inner surface 146 is formed so that the length in the axial direction of the cylinder 10 is longer than the length in the circumferential direction of the cylinder 10. Thus, the second arc-shaped portion 132 is formed so that the length in the axial direction of the cylinder 10 is longer than the length in the circumferential direction of the cylinder 10.

[0058] 3, the second inner surface 146 of the second arc-shaped portion 132 is inclined with respect to the central axis O2 of the lateral hole 58 such that the distance from the central axis O2 of the lateral hole 58 becomes shorter the further inward in the radial direction of the cylinder 10. In other words, the second inner surface 146 of the second arc-shaped portion 132 spreads out along a line connecting the second arc-shaped portion 132 and the central axis O1 side of the tubular portion 51 relative to the inner circumferential surface 56 of the tubular portion 51.

[0059] At least a portion of the second inner surface 146 of the second arc-shaped portion 132, specifically a central position in the axial direction of the cylinder 10, is formed in the thickness direction of the tubular portion 51. In other words, the second inner surface 146 of the second arc-shaped portion 132 has a line segment at a central position in the direction of the central axis O1 of the cylinder 10 that extends in the thickness direction of the tubular portion 51. In further other words, an extension line of the line segment at a central position of the second inner surface 146 in the direction of the central axis O1 of the cylinder 10 passes through the central axis O1 of the tubular portion 51.

[0060] 3, the line segment at the center of the second inner surface 146 in the direction of the central axis O1 of the cylinder 10 does not necessarily have to extend in the thickness direction of the tubular portion 51. In other words, the extension line of the line segment at the center of the second inner surface 146 in the direction of the central axis O1 of the cylinder 10 does not have to pass through the central axis O1 of the tubular portion 51. For example, the extension line of the line segment at the center of the second inner surface 146 in the direction of the central axis O1 of the cylinder 10 may pass through a point on the central axis O2 of the lateral hole 58 and on the opposite side of the central axis O1 of the tubular portion 51 from the lateral hole 58.

[0061] Here, an example of the dimensional relationship of the horizontal hole 58 is shown. For example, as shown in FIG. 2, the distance between the intersection of the inner boundary 146b of one second arc-shaped portion 132 with the end side surface portion 143 of one first arc-shaped portion 131 and the intersection of this inner boundary 146b with the end side surface portion 143 of the other first arc-shaped portion 131 is defined as A. Also, the distance between the intersection of one end side surface portion 143 of one first arc-shaped portion 131 with the inner boundary 146b of one second arc-shaped portion 132 and the intersection of the other end side surface portion 143 of this one first arc-shaped portion 131 with the inner boundary 146b of the other second arc-shaped portion 132 is defined as B. Also, the diameter of the inner boundary 146b of the second arc-shaped portion 132 is defined as φC. Also, the diameter of the intermediate surface portion 142 of the first arcuate portion 131 is φD. As shown in Fig. 3, the angle between a line perpendicular to the central axis O1 of the cylinder 10 and perpendicular to the central axis O2 of the lateral hole 58 and a line segment at the center of the second inner surface 146 in the direction of the central axis O1 of the cylinder 10 is E. Then, when E = 55°, the lateral hole 58 is formed so that A:B = 1.25:1 and C:D = 1:1.1.

[0062] When the lateral hole 58 is viewed from the radial outside of the cylinder 10 along the central axis O2 of the lateral hole 58 as shown in FIG. 2, the second outer boundary 146a is positioned radially outward of the lateral hole 58 than the second inner boundary 146b, i.e., on the opposite side of the central axis O2 of the lateral hole 58.

[0063] The second arc-shaped portion 132 protrudes toward the central axis O2 of the horizontal hole 58 further than the first arc-shaped portion 131 and the first arc-shaped portion 131 adjacent to each other in the circumferential direction of the horizontal hole 58. The second inner surface 146 of the second arc-shaped portion 132 has a longer arc length than the first inner surface 141 of the first arc-shaped portion 131. Thus, the second arc-shaped portion 132 has a longer arc length than the first arc-shaped portion 131. The first inner surface 141 of the first arc-shaped portion 131 is formed in an arc shape with a smaller radius of curvature than the second inner surface 146 of the second arc-shaped portion 132.

[0064] A protrusion 151 that protrudes toward the inner diameter side of the lateral hole 58 is formed at an end where the first outer boundary 141a of the first arc-shaped portion 131 and the second outer boundary 146a of the second arc-shaped portion 132 that are adjacent in the circumferential direction of the lateral hole 58 are connected. Since the lateral hole 58 has four ends where the first outer boundary 141a and the second outer boundary 146a are connected, a total of four protrusions 151 are formed.

[0065] Next, a description will be given of a manufacturing method of the tubular portion 51, which is one part of the manufacturing method of the cylinder 10. The manufacturing method of the tubular portion 51 is a processing method in which the lateral hole 58 is formed in the tubular portion 51.

[0066] In this manufacturing method, first, as shown in Fig. 4, a first hole forming step is performed to form a pair of first holes 161 and first holes 161 having the same substantially elliptical shape in the tubular portion 51. The pair of first holes 161 and first holes 161 include the pair of first arc-shaped portions 131 and first arc-shaped portions 131 of the lateral hole 58 shown in Fig. 2. In the first hole forming step, as shown in Fig. 5, a pair of first punches 165 and a first male mold 166 integrally having the first punch 165 are used for press molding to form the pair of first holes 161 and first holes 161 shown in Fig. 4 in the tubular portion 51.

[0067] In the first hole forming step, as shown in FIG. 5, a first fixing step is performed in which the tubular portion 51 before the horizontal hole 58 is formed is fixed to a first set mold 174 having a first support wall portion 171 and a cylindrical first core 173 extending perpendicularly from a planar first base surface 172 of the first support wall portion 171 to the first base surface 172. In the first fixing step, the first core 173 is fitted inside the tubular portion 51, and the axial end portion is abutted against the first base surface 172 of the first support wall portion 171 by pushing the tubular portion 51 in the axial direction with a first pusher 175. As a result, the tubular portion 51 is fixed to the first set mold 174 in a state where it is positioned in the axial and radial directions. As a result, the tubular portion 51 is also positioned with respect to the first male mold 166 shown in FIG. 3.

[0068] In the first hole forming step, after the first fixing step, a first arc-shaped portion processing step is performed, which is a press process in which the cylindrical portion 51 is punched from its radial outside by a pair of first punches 165 and 165 of a first male die 166. In the first arc-shaped portion processing step, the pair of first punches 165 and 165 of the first male die 166 move linearly toward the central axis O1 of the cylindrical portion 51 along the central axis O2 of the horizontal hole 58 along the radial direction of the cylindrical portion 51. Then, one first punch 165 punches out one first hole portion 161 including one first arc-shaped portion 131 while forming the first inner surface 141 of the first arc-shaped portion 131. At the same time, the other first punch 165 punches out the other first hole 161 including the other first arc-shaped portion 131 while forming the first inner surface 141 of the first arc-shaped portion 131. As a result, the pair of first holes 161 and the inner portions of each of the first holes 161 are cut off as punched pieces from the tubular portion 51. Note that the first core 173 has a clearance for allowing the punched pieces of the pair of first holes 161 and the inner portions of each of the first holes 161 to escape in the first arc-shaped portion processing step.

[0069] The pair of first hole portions 161 and first hole portions 161 formed in the tubular portion 51 by the first arc-shaped portion machining step have the same shape, are aligned in the circumferential direction of the tubular portion 51, and are spaced a predetermined distance apart in the axial direction of the tubular portion 51. The first arc-shaped portion machining step is a process of forming the pair of first arc-shaped portions 131 and first arc-shaped portions 131 that are at least a part of the lateral hole 58.

[0070] Next, a second hole forming process is performed to form the pair of second arc-shaped portions 132 and 132 of the horizontal hole 58 shown in Fig. 2 in the cylindrical portion 51. In the second hole forming process, the pair of second arc-shaped portions 132 and 132 are formed in the cylindrical portion 51 by press molding using a pair of second male dies 177 and 177 shown in Fig. 3. Of the pair of second male dies 177 and 177, one second male die 177 has one second punch 178, and the other second male die 177 has the other second punch 178, respectively.

[0071] In the second hole forming process, as shown in FIG. 6, a second fixing process is performed in which the pair of first holes 161 and the tubular portion 51 with the first hole 161 formed therein are set in a second set mold 184 having a second support wall portion 181 and a cylindrical second core 183 extending perpendicularly from a planar second base surface 182 of the second support wall portion 181 to the second base surface 182.

[0072] Here, second core 183 has a cylindrical core body 191, a pair of identically shaped notches 192 and a reciprocating mechanism (not shown) for advancing and reciprocating each of the pair of notches 192.

[0073] Of the pair of notches 192 and notches 192, one notch 192 is slidably fitted into one arrangement hole 195 that is recessed from the outer circumferential surface 194 of core body 191 along the radial direction of core body 191. Of the pair of notches 192 and notches 192, the other notch 192 is slidably fitted into the other arrangement hole 195 that is recessed from the outer circumferential surface 194 of core body 191 along the radial direction of core body 191.

[0074] The pair of arrangement holes 195 and arrangement holes 195 have the same shape, and when core body 191 is viewed from the outside along its radial direction, they form an ellipse having a major axis in the circumferential direction of core body 191 as shown in Fig. 7. The pair of arrangement holes 195 and arrangement holes 195 are aligned in the circumferential direction of core body 191 and arranged at a predetermined interval in the axial direction of core body 191. Of the pair of arrangement holes 195 and arrangement holes 195, the arrangement hole 195 farther from second base surface 182 shown in Fig. 6 is referred to as the first arrangement hole 195, and the arrangement hole 195 closer to second base surface 182 is referred to as the second arrangement hole 195.

[0075] As shown in FIG. 7, the pair of notches 192 and the pair of notches 192 have the same shape. The notch 192 has a flat outer placement surface 202, an elliptical cylindrical side surface 203, and a chamfer 204 provided between the outer placement surface 202 and the side surface 203. The side surface 203 is perpendicular to the outer placement surface 202.

[0076] One of the pair of notches 192 and notches 192 is fitted into one of the arrangement holes 195 of the core body 191, and the other of the pair of notches 192 is fitted into the other arrangement hole 195 of the core body 191, at the respective side surfaces 203. As a result, the pair of notches 192 and notches 192 are both attached to the core body 191 such that the major axes of the side surfaces 203 are aligned along the circumferential direction of the core body 191. Also, as shown in Fig. 6, the pair of notches 192 and notches 192 are both supported by the core body 191 so as to be movable along the radial direction of the core body 191. The pair of notches 192 and notches 192 are arranged at a predetermined interval in the axial direction of the core body 191 with their positions aligned in the circumferential direction of the core body 191, as shown in Fig. 7. Here, of the pair of notches 192 and notches 192, the one that fits into the first arrangement hole 195, i.e., the one farther from the second base surface 182 shown in Figure 6, is referred to as the first notch 192, and the one that fits into the second arrangement hole 195, i.e., the one closer to the second base surface 182, is referred to as the second notch 192.

[0077] The advancing / retreating mechanism (not shown) is driven by hydraulic pressure or the like to move the pair of notches 192 and 192 between an advanced state and a retreated state. In the advanced state, the outer arrangement surfaces 202 and side surfaces 203 of the pair of notches 192 and 192 protrude outward from the outer circumferential surface 194 of the core body 191. In the retreated state, the outer arrangement surfaces 202 and side surfaces 203 of the pair of notches 192 and 192 are located radially inward from the outer circumferential surface 194 of the core body 191. The retreated state is the standby state for the pair of notches 192 and 192.

[0078] In the second hole forming step, a second fixing step is performed in which the tubular portion 51 in which the pair of first holes 161 and the first hole 161 are formed is fixed to the above-mentioned second set mold 184. When the second fixing step is performed, the second core 183 is fitted inside the tubular portion 51 in a state in which the phase of the pair of first holes 161 and the first hole 161 matches the phase of the first notch 192 and the second notch 192.

[0079] Then, in the axial direction of the second core 183, as shown in FIG. 7, when the position of the first hole portion 161 on the opposite side of the second base surface 182 of the pair of first hole portions 161 and first hole portion 161 aligns with the first notch 192 and the position of the first hole portion 161 on the second base surface 182 aligns with the second notch 192, the advancing / retracting mechanism (not shown) moves the first notch 192 and the second notch 192 forward as shown in FIG. 6 to protrude from the outer peripheral surface 194 of the core body 191.

[0080] Then, a portion of the side surface 203 of the first notch 192 opposite to the second base surface 182 abuts against the first arc-shaped portion 131 of the first hole portion 161 on the opposite side of the second base surface 182 of the pair of first holes 161 and first holes 161. At the same time, a portion of the side surface 203 of the second notch 192 on the second base surface 182 abuts against the first arc-shaped portion 131 of the first hole portion 161 on the second base surface 182 side of the pair of first holes 161 and first holes 161. As a result, the pair of first holes 161 and first holes 161 of the cylindrical portion 51 are positioned in the axial and circumferential directions of the second core 183. In this state, the cylindrical portion 51 is fixed to the second set mold 184. As a result, the pair of first holes 161 and first holes 161 of the tubular portion 51 are also positioned with respect to the pair of second male dies 177 and second male dies 177 shown in FIG.

[0081] In the second hole forming step, after the above-mentioned second fixing step, a second arc-shaped portion processing step is performed, which is a press working in which the tubular portion 51 is punched from its radially outer side by a pair of second male dies 177 and a second punch 178 of one of the second male dies 177 and a second punch 178 of the other second male dies 177. In the second arc-shaped portion processing step, the one of the pair of second male dies 177 and the second male dies 177 punches out the tubular portion 51 from its radially outer side by the second punch 178 to form one second hole portion 168 including one of the pair of second arc-shaped portions 132 and one of the second arc-shaped portions 132, as shown in FIG. 8, while forming the second inner surface 146 of the second arc-shaped portion 132. At the same time, in the second arc-shaped portion processing step, the other of the pair of second male dies 177 and second male dies 177 shown in Figure 3 uses its second punch 178 to punch out the tubular portion 51 from the radial outside, as shown in Figure 8, to form the other second hole portion 168 including the other of the pair of second arc-shaped portions 132 and second arc-shaped portions 132, while forming the second inner surface 146 of the second arc-shaped portion 132.

[0082] Here, in all combinations of adjacent first hole portions 161 and second hole portions 168, the first hole portions 161 and the second hole portions 168 overlap in part (the hatched portion shown in FIG. 8), whereby the inner piece 197 of the portion surrounded by the first hole portion 161, the second hole portion 168, and the first hole portion 161 and the second hole portion 168 is separated from the tubular portion 51.

[0083] As a result of the second arc-shaped portion machining step, a pair of second arc-shaped portions 132 and 132 are formed in the tubular portion 51, and as a result, a lateral hole 58 having a pair of first arc-shaped portions 131 and 131 formed in the first arc-shaped portion machining step performed prior to the second arc-shaped portion machining step and a pair of second arc-shaped portions 132 and 132 is formed as shown in Fig. 2. Note that the second core 183 shown in Fig. 6 has reliefs (not shown) formed to allow the punched edges of the inner portions of the pair of second hole portions 168 and 168 of the tubular portion 51 removed by punching to escape.

[0084] Here, in the second arc-shaped portion processing step, the pair of second male dies 177 and second male dies 177 move along linear tracks that are symmetrical at equal angles to the central axis O2 of the horizontal hole 58 and approach each other closer to the cylindrical portion 51 side, on a plane perpendicular to the central axis O1 of the cylindrical portion 51 and including the central axis O2 of the horizontal hole 58, as shown in FIG. 3, when punching out the cylindrical portion 51. Therefore, in the second arc-shaped portion processing step, the cylindrical portion 51 is processed from a position different from that in the first arc-shaped portion processing step. Moreover, in the second arc-shaped portion processing step, press processing is performed from two or more, specifically, from two different directions. Therefore, in the cylindrical portion 51, the first arc-shaped portion 131 and the second arc-shaped portion 132 are formed from different angles. The size and dimensional relationship of the pair of notches 192 and notches 192 shown in FIG. 8 are set so that they do not interfere with the pair of second male molds 177 and the pair of second punches 178 and second punches 178 of the second male molds 177 shown in FIG. 3 during the second arc-shaped portion processing step.

[0085] After the second arc-shaped portion machining step is performed to form the horizontal hole 58, the advancing / retracting mechanism (not shown) moves the first notch 192 and the second notch 192 to a retracted state. Then, the outer arrangement surface 202 and the side surface 203 of the first notch 192 and the second notch 192 move radially inward from the outer circumferential surface 194 of the core body 191 shown in FIG. 6. In this state, a removal step is performed in which the tubular portion 51 is moved in a direction away from the second base surface 182 to be removed from the second core 183. In this way, by making the first notch 192 and the second notch 192 advancing and retracting relative to the core body 191 along the radial direction of the core body 191, the tubular portion 51 can be easily attached to and detached from the second set mold 184.

[0086] Patent Documents 1 and 2 disclose techniques for forming a side hole in the cylindrical portion of a cylinder. The technique disclosed in Patent Document 1 rotates the cylinder, which is the workpiece, to form a side hole of a desired shape in the cylinder by pressing. The technique disclosed in Patent Document 2 has a horizontally moving support wall that works in conjunction with a punching top to firmly fix the cylinder, which is the workpiece, and forms a side hole in the cylinder by pressing.

[0087] In these techniques, the cylinder to be pressed must be rotated to form the hole, and a support wall structure that works in conjunction with the punching block to prevent the cylinder from shifting is required, which makes the structure complicated and increases costs. On the other hand, when trying to obtain a side hole of a desired press shape in one punch, the larger the punching diameter of the side hole becomes, the more deformation of the cylinder base material and distortion such as burrs and sagging will occur, resulting in a decrease in formability. It is desirable to reduce costs in cylinders with side holes. In particular, it is desirable to reduce costs while suppressing the decrease in formability in cylinders with large diameter side holes.

[0088] In the first embodiment, the cylinder 10 has a horizontal hole 58 provided in the cylindrical tubular portion 51, and is formed by a first arc-shaped portion 131 formed so that the length in the circumferential direction of the cylinder 10 is longer than the length in the axial direction of the cylinder 10, and a second arc-shaped portion 132 whose length in the axial direction of the cylinder 10 is longer than the length in the circumferential direction of the cylinder 10 and whose arc length is longer than the first arc-shaped portion 131.

[0089] As a result, the cylinder 10 can form one of the first arc-shaped portion 131 and the second arc-shaped portion 132 in the tubular portion 51 by press molding, position the tubular portion 51 using the one, and form the other of the first arc-shaped portion 131 and the second arc-shaped portion 132 by press molding to form the lateral hole 58. Therefore, the cylinder 10 can form the lateral hole 58 in the tubular portion 51 without rotating, which makes it possible to prevent the structure of the manufacturing device from becoming complicated and reduce costs.

[0090] Also, the cylinder 10 does not press a large range in one go, but presses each small range in several separate steps. The cylinder 10 uses the previous press hole to position the tubular portion 51 and fix it in place, making it possible to prevent the tubular portion 51 from shifting position in subsequent presses. Also, by dividing the press into several steps, the cylinder 10 can suppress deformation of the base material of the tubular portion 51. As a result, the cylinder 10 can suppress costs by extending the life of the press tool, and can suppress costs by achieving stable molding and high mass productivity.

[0091] In the cylinder 10, the first arc-shaped portion 131 and the second arc-shaped portion 132 are formed at different angles. Therefore, the cylinder 10 can be pressed multiple times at angles close to the plate thickness direction of the tubular portion 51. This allows the cylinder 10 to further reduce costs by further extending the life of the press tool, and to further reduce costs by achieving higher mass productivity with stable molding.

[0092] In the cylinder 10, at least a portion of the first arc-shaped portion 131 or the second arc-shaped portion 132 is formed in the plate thickness direction of the tubular portion 51. Therefore, in the cylinder 10, the press working of the first arc-shaped portion 131 or the second arc-shaped portion 132 can be performed at an angle close to the plate thickness direction of the tubular portion 51. As a result, the cylinder 10 can further reduce costs by further extending the life of the press tool, and can further reduce costs by achieving higher mass productivity with stable molding.

[0093] In the cylinder 10, the first arc-shaped portion 131 is formed as an arc having a smaller diameter than the second arc-shaped portion 132. Therefore, in the cylinder 10, deformation such as burrs and sagging occurring when the first arc-shaped portion 131 is formed by press working can be suppressed more than deformation occurring when the second arc-shaped portion 132 is formed. Therefore, if the cylinder 10 is positioned using the first arc-shaped portion 131, the positioning accuracy can be improved.

[0094] The cylinder 10 has a protrusion 151 that protrudes toward the inner diameter side of the horizontal hole 58 at the end where the first arc-shaped portion 131 and the second arc-shaped portion 132 are connected. By leaving the protrusion 151 in this manner, the cylinder 10 can easily suppress interference between the positioning notch 192 and the press tool. The size of the protrusion 151 can be minimized by adjusting the dimensional relationship of the punching.

[0095] Since the shock absorber 11 of the first embodiment includes the cylinder 10, the cost of the cylinder 10 can be reduced, and therefore the cost of the shock absorber 11 can be reduced.

[0096] In the manufacturing method of the cylinder 10 of the first embodiment, the cylinder 10 is fixed by a fixing step. In addition, in the manufacturing method of the cylinder 10, a first arc-shaped portion 131 is formed in the cylinder 10, which is at least a part of the lateral hole 58, and is formed so that the length in the circumferential direction of the cylinder 10 is longer than the length in the axial direction of the cylinder 10. In addition, in the manufacturing method of the cylinder 10, a second arc-shaped portion 132 is formed in the cylinder 10 by processing from a position different from the first arc-shaped portion processing step, and the second arc-shaped portion 132 is formed in the cylinder 10, which is longer in the axial direction of the cylinder 10 than the length in the circumferential direction of the cylinder 10 and has a longer arc length than the first arc-shaped portion 131. In this way, the manufacturing method of the cylinder 10 can form the lateral hole 58 in the tubular portion 51 without rotating, so that the manufacturing device can be prevented from becoming complicated in structure and the cost can be reduced.

[0097] In the manufacturing method of the cylinder 10, the first arc-shaped portion processing step and the second arc-shaped portion processing step are press processing, and the second arc-shaped portion processing step is a step of pressing from two or more different directions. Therefore, in the manufacturing method of the cylinder 10, a large range is not pressed in one go, but each small range is pressed in multiple steps, and the cylinder portion 51 is fixed in a positioned state using the previous press hole, so that it is possible to prevent the cylinder portion 51 from shifting in position with respect to the subsequent press. In addition, in the manufacturing method of the cylinder 10, by dividing the press into multiple steps, it is possible to suppress deformation of the base material of the cylinder portion 51. As a result, the manufacturing method of the cylinder 10 can suppress costs by extending the life of the press tool and by obtaining high mass productivity with stable molding.

[0098] Furthermore, in the manufacturing method of the cylinder 10, the first arc-shaped portion 131 and the second arc-shaped portion 132 are formed at different angles. Therefore, in the manufacturing method of the cylinder 10, it is possible to perform multiple press processes at angles close to the plate thickness direction of the tubular portion 51. As a result, in the manufacturing method of the cylinder 10, it is possible to further reduce costs by further extending the life of the press tool, and to further reduce costs by achieving higher mass productivity with stable molding.

[0099] Moreover, in the manufacturing method of the cylinder 10, a first arc-shaped portion machining step of forming a first arc-shaped portion 131 formed so that the length in the circumferential direction of the cylinder 10 is longer than the length in the axial direction of the cylinder 10 is performed before a second arc-shaped portion machining step of forming a second arc-shaped portion 132 whose length in the axial direction of the cylinder 10 is longer than the length in the circumferential direction of the cylinder 10 and whose arc length is longer than the first arc-shaped portion 131. Therefore, in the manufacturing method of the cylinder 10, the tubular portion 51 can be fixed in a positioned state by utilizing the first arc-shaped portion 131, and it is possible to suppress positional deviation of the tubular portion 51 in the subsequent second arc-shaped portion machining step.

[0100] [Second embodiment] Next, the second embodiment will be described with a focus on differences from the first embodiment, mainly with reference to Figures 9 to 15. Note that parts common to the first embodiment will be designated by the same names and reference numerals.

[0101] In the second embodiment, the second fixing step of the second hole forming step is partially different from that of the first embodiment. In the second embodiment, in the second fixing step of the second hole forming step, a second set mold 184A shown in FIG. 9, which is partially different from the second set mold 184, is used instead of the second set mold 184. In the second set mold 184A, a second core 183A, which is partially different from the second core 183, is provided instead of the second core 183. In the second core 183A, a core body 191A, which is partially different from the core body 191, is provided instead of the core body 191. In the second core 183A, a notch 192A, which is partially different from the notch 192, is provided instead of the notch 192. The second core 183A has only one notch 192A. Second core 183A is provided with a biasing member 193A instead of a reciprocating mechanism (not shown).

[0102] Core body 191A is provided with only one arrangement hole 195A recessed from outer circumferential surface 194A along the radial direction of core body 191A, and one notch 192A is slidably fitted into this arrangement hole 195A.

[0103] The notch 192A has a shape shown in Figures 10 to 14. The notch 192A has a planar inner arrangement surface 201A shown in Figures 11 to 13, an outer arrangement surface 202A shown in Figures 10 to 14 facing away from the inner arrangement surface 201A, an elliptical cylindrical side surface 203A extending from the outer peripheral edge of the inner arrangement surface 201A shown in Figures 11 to 13 toward the outer peripheral edge of the outer arrangement surface 202A shown in Figures 10 to 14, and a chamfer 204A provided between the outer arrangement surface 202A and the side surface 203A. The side surface 203A is perpendicular to the inner arrangement surface 201A shown in Figures 11 to 13.

[0104] The outer arrangement surface 202A has a planar tip surface portion 211, a planar bottom surface portion 212 that is closer to the inner arrangement surface 201A than the tip surface portion 211, and an inclined surface portion 213 that connects the tip surface portion 211 and the bottom surface portion 212. The tip surface portion 211 and the bottom surface portion 212 extend parallel to the inner arrangement surface 201A. The closer the inclined surface portion 213 is to the tip surface portion 211, the longer the distance from the inner arrangement surface 201A.

[0105] 10, the tip surface portion 211 is disposed on a first side in the short axis direction and a first side in the long axis direction of the elliptical side surface 203A, and the bottom surface portion 212 is disposed on a second side in the short axis direction and a second side in the long axis direction of the side surface 203A. When viewed in a direction perpendicular to the tip surface portion 211 and the bottom surface portion 212, the inclined surface portion 213 forms a straight line extending from the second side in the short axis direction and the first side in the long axis direction of the side surface 203A to the first side in the short axis direction and the second side in the long axis direction.

[0106] Notch 192A is slidably fitted into arrangement hole 195A of core body 191A such that the major axis of side surface 203A is along the circumferential direction of core body 191A, with tip surface portion 211 oriented so as to be positioned closer to second base surface 182 of second support wall portion 181 than inclined surface portion 213, as shown in Fig. 15, in the axial direction of core body 191A shown in Fig. 9. Thereby, notch 192A is supported by core body 191A so as to be movable along the radial direction of core body 191A, as shown in Fig. 9.

[0107] The biasing member 193A biases the notch 192A so that the tip surface portion 211 and the inclined surface portion 213 protrude outward from the outer peripheral surface 194A of the core body 191A. At that time, the notch 192A positions the bottom surface portion 212 radially inward from the outer peripheral surface 194A of the core body 191A. In this state, the notch 192A is in a standby state. The notch 192A is capable of moving in the radial direction of the core body 191A against the biasing force of the biasing member 193A to retract the tip surface portion 211 and the inclined surface portion 213 from the outer peripheral surface 194 of the core body 191A.

[0108] In the second hole forming step, a second fixing step is performed in which the tubular portion 51 in which the pair of first holes 161 and the first hole 161 are formed is fixed to the second set mold 184A. At this time, a part of the tip side of the second core 183A is fitted inside the tubular portion 51 in a state in which the phase of the pair of first holes 161 and the first hole 161 matches the phase of the notch 192A. In this state, the tubular portion 51 is moved in the direction of the second base surface 182 of the second support wall portion 181 by the second pusher 221.

[0109] Then, notch 192A in the standby state first comes into contact with the end portion of cylindrical portion 51 on the second base surface 182 side, and is pressed by this end portion. Then, a component force toward the inside in the radial direction of core body 191A is generated by the inclination of this inclined surface portion 213, and notch 192A moves toward the inside in the radial direction of core body 191A against the biasing force of biasing member 193A. As a result, notch 192A slips into the radial inside of a portion between the end portion of cylindrical portion 51 on the second base surface 182 side in the axial direction and the first hole 161 on the second base surface 182 side of the pair of first hole portions 161 and first hole portion 161.

[0110] Next, notch 192A is aligned with the pair of first holes 161 of tubular portion 51 and the first hole 161 of the first hole 161 that is on the second base surface 182 side. As a result, notch 192A returns to a standby state in which it protrudes from outer circumferential surface 194A of core main body 191A by the biasing force of biasing member 193A, and enters this first hole 161. At the same time, tubular portion 51 being pressed by second pusher 221 abuts against second base surface 182 at its end portion on the second base surface 182 side in the axial direction.

[0111] As a result, as shown in FIG. 15, the portion of the side surface 203A of the notch 192A on the second base surface 182 side abuts against the first arc-shaped portion 131 of the pair of first holes 161 and the first holes 161 on the second base surface 182 side. At the same time, the end portion of the tubular portion 51 on the second base surface 182 side abuts against the second base surface 182. As a result, the tubular portion 51 is fixed to the second set mold 184A as shown in FIG. 9 in a state in which the pair of first holes 161 and the first holes 161 are positioned in the axial and circumferential directions of the second core 183A. As a result, the pair of first holes 161 and the first holes 161 of the tubular portion 51 are also positioned with respect to the pair of second male molds 177 and the second male molds 177 shown in FIG.

[0112] In the second hole forming step of the second embodiment, after the above-mentioned second fixing step is performed, the second arc-shaped portion processing step similar to that of the first embodiment is performed. As a result, the pair of second arc-shaped portions 132 and 132 is formed in the tubular portion 51, similar to that of the first embodiment. As a result, the tubular portion 51 is formed with the pair of first arc-shaped portions 131 and 131 formed in the first arc-shaped portion processing step performed prior to the second arc-shaped portion processing step, and the horizontal hole 58 having the pair of second arc-shaped portions 132 and 132 is formed. Note that the second core 183A also has an escape (not shown) for escaping the punched pieces of the inner portions of the pair of second hole portions 168 and 168 of the tubular portion 51 removed by punching.

[0113] In the second embodiment, after the second arc-shaped portion machining step is performed to form the lateral hole 58 in the tubular portion 51, the pressure of the second pusher 221 on the tubular portion 51 is released, and a rotation step is performed to rotate the tubular portion 51 in the circumferential direction relative to the second core 183A. At that time, the tubular portion 51 is rotated in a direction in which the inner peripheral edge of the lateral hole 58 of the tubular portion 51 overlaps with the bottom surface portion 212 of the notch 192A and then comes into contact with the inclined surface portion 213 of the notch 192A. Then, the inclined surface portion 213 of the notch 192A comes into contact with the inner peripheral edge of the lateral hole 58 of the tubular portion 51, and then the inclined surface portion 213 is pressed against the inner peripheral edge of the lateral hole 58 of the tubular portion 51. As a result, a component of force acting radially inwardly of core body 191A is generated by the inclination of inclined surface portion 213, and notch 192A moves radially inwardly of core body 191A against the biasing force of biasing member 193A. This causes notch 192A to enter radially inward of a portion of tubular portion 51 that is outer than horizontal hole 58 in the circumferential direction. In this state, a pulling-out process is performed in which tubular portion 51 is moved in a direction away from second base surface 182 to be pulled out from second core 183A.

[0114] When the cylindrical portion 51 is pulled out from the second core 183A, the notches 192A are no longer restricted by the cylindrical portion 51 from the radially outward movement of the core body 191A, and return to the standby state by the biasing force of the biasing member 193A.

[0115] According to the manufacturing method of the cylinder 10 of the second embodiment, a forward / backward mechanism using hydraulics or the like to drive the notch 192A is not required, so the equipment costs can be reduced more than in the first embodiment, and therefore the manufacturing costs of the cylinder 10 can be further reduced more than in the first embodiment.

[0116] In the above embodiment, the first arc-shaped portion machining step for forming the first arc-shaped portion 131, which is formed so that the length in the circumferential direction of the cylinder 10 is longer than the length in the axial direction of the cylinder 10, is performed before the second arc-shaped portion machining step for forming the second arc-shaped portion 132, which is formed so that the length in the axial direction of the cylinder 10 is longer than the length in the circumferential direction of the cylinder 10 and has a longer arc length than the first arc-shaped portion 131, to form the side hole 58. However, the first arc-shaped portion machining step may be performed after the second arc-shaped portion machining step to form the side hole 58. With such a manufacturing method for the cylinder 10, the cylindrical portion 51 can be fixed in a positioned state using the second arc-shaped portion 132, and it is possible to suppress the positional deviation of the cylindrical portion 51 with respect to the subsequent first arc-shaped portion machining step.

[0117] In addition, in the above first embodiment, an example has been described in which the lateral hole 58 is formed by a two-stage punching process consisting of a first arc-shaped portion machining process and a second arc-shaped portion machining process, but the lateral hole 58 may be formed by a multiple-stage punching process consisting of three or more stages. [Explanation of symbols]

[0118] 10...cylinder, 11...shock absorber, 51...tubular portion, 58...lateral hole, 80...piston, 81...first chamber, 82...second chamber, 90...piston rod, 131...first arc-shaped portion, 132...second arc-shaped portion, 151...protruding portion.

Claims

1. A cylinder having a cylindrical portion and a lateral hole provided in the cylindrical portion, The side hole is a first arc-shaped portion formed so that a length in a circumferential direction of the cylinder is longer than a length in an axial direction of the cylinder; a second arc-shaped portion having a length in an axial direction of the cylinder that is longer than a length in a circumferential direction of the cylinder and having a longer arc length than the first arc-shaped portion; A cylinder formed by

2. 2. The cylinder according to claim 1, A cylinder in which the first arcuate portion and the second arcuate portion are formed at different angles.

3. 2. The cylinder according to claim 1, A cylinder, at least a portion of which is formed in a thickness direction of the tubular portion, the first arc-shaped portion or the second arc-shaped portion.

4. 2. The cylinder according to claim 1, The first arcuate portion is a cylinder having a smaller diameter than the second arcuate portion.

5. 2. The cylinder according to claim 1, A cylinder, wherein a protrusion that protrudes toward the inner diameter side of the lateral hole is formed at an end where the first arc-shaped portion and the second arc-shaped portion are connected.

6. A method for manufacturing a cylinder having a cylindrical tube portion and a lateral hole provided in the tube portion, a fixing step of fixing the cylinder; a first arc-shaped portion machining step of forming a first arc-shaped portion which is at least a part of the lateral hole and is formed so that a length in a circumferential direction of the cylinder is longer than a length in an axial direction of the cylinder; a second arc-shaped portion machining step of machining from a position different from that of the first arc-shaped portion machining step, to form a second arc-shaped portion having a length in the axial direction of the cylinder longer than a length in the circumferential direction of the cylinder and a longer arc length than the first arc-shaped portion; A method for manufacturing a cylinder comprising:

7. A method for manufacturing a cylinder according to claim 6, the first arc-shaped portion machining step and the second arc-shaped portion machining step are press working; A method for manufacturing a cylinder, in which the second arc-shaped portion processing step is a step of pressing from two or more different directions.

8. A method for manufacturing a cylinder according to claim 6 or 7, A method for manufacturing a cylinder, wherein the first arc-shaped portion machining step is performed prior to the second arc-shaped portion machining step.

9. A method for manufacturing a cylinder according to claim 6 or 7, A method for manufacturing a cylinder, wherein the first arc-shaped portion machining step is performed after the second arc-shaped portion machining step.

10. A cylinder in which a working fluid is sealed; A piston that divides the cylinder into two chambers; a piston rod having a first end fixed to the piston and a second end protruding from the cylinder; Equipped with The cylinder has a cylindrical portion and a lateral hole provided in the cylindrical portion, The side hole is a first arc-shaped portion formed so that a length in a circumferential direction of the cylinder is longer than a length in an axial direction of the cylinder; a second arc-shaped portion whose length in the axial direction of the cylinder is longer than the length in the circumferential direction of the cylinder and whose arc length is longer than that of the first arc-shaped portion.

Images