Cylinder Device

Abstract

To provide a cylinder device that can improve strength.SOLUTION: A cylinder device comprises: a cylinder 17 comprising a cylindrical member 21, and a bottom member 22 closing one end side of the cylindrical member 21; a piston 41 movably provided in the cylinder 17; and a piston rod 46 of which one end side is connected to the piston 41, and of which the other end side extends to the outside from the cylinder 17. In the bottom member 22, a closing part 81 closing one end side of the cylindrical member 21, an annular eye part 83, and a connection part 82 connecting the closing part 81 and the eye part 83 are integrally formed.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Some cylinder devices have a rod-shaped member connected at one end to an outer tube and an annular mounting eye joined to the other end of the rod-shaped member (see, for example, Patent Document 1). In this cylinder device, the rod-shaped member and the mounting eye are joined by welding. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5013255 Summary of the Invention [Problem to be solved by the invention]

[0004] There is a demand for improved strength in cylinder devices.

[0005] Therefore, an object of the present invention is to provide a cylinder device that can improve strength. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, a first aspect of the present invention comprises a cylinder having a cylindrical member and a bottom member that closes one end of the cylindrical member, a piston that is movably arranged within the cylinder, and a piston rod that has one end connected to the piston and the other end extending out from the cylinder, wherein the bottom member is integrally molded with a closing portion that closes one end of the cylindrical member, a ring-shaped eye portion, and a connecting portion that connects the closing portion and the eye portion. [Effects of the Invention]

[0007] According to the present invention, it is possible to improve the strength. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a cross-sectional view showing a cylinder device according to an embodiment of the present invention. [Figure 2] FIG. 2 is a front view showing a bottom member of the cylinder device according to the embodiment of the present invention. [Figure 3] FIG. 2 is a side view showing a bottom member of the cylinder device according to the embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0009] A cylinder device according to an embodiment will be described below with reference to the drawings. FIG. 1 shows a cylinder device 11 according to an embodiment. This cylinder device 11 is a shock absorber used in a suspension device for a vehicle such as an automobile or a railway vehicle. Specifically, the cylinder device 11 is a hydraulic shock absorber used in an automobile suspension device. The cylinder device 11 is a twin-cylinder hydraulic shock absorber equipped with a cylinder 17 having an inner cylinder 15 and an outer cylinder 16. The inner cylinder 15 is cylindrical. The outer cylinder 16 is cylindrical with a bottom. The inner diameter of the outer cylinder 16 is larger than the outer diameter of the inner cylinder 15. The outer cylinder 16 is disposed radially outside the inner cylinder 15 and coaxially with the inner cylinder 15. A reservoir chamber 18 is formed between the outer cylinder 16 and the inner cylinder 15.

[0010] The outer cylinder 16 has a cylindrical member 21 and a bottom member 22. The cylindrical member 21 is a one-piece molded product made of a single piece of metal and has a stepped cylindrical shape. The bottom member 22 is a one-piece molded product made of a single piece of metal and is fitted onto one axial end of the cylindrical member 21 and fixed to the cylindrical member 21 by welding. As a result, the bottom member 22 closes one axial end side of the cylindrical member 21. The cylindrical member 21 has an opening 23 on the side opposite the bottom member 22 in the axial direction. A spring seat 27 is attached to the outer periphery of the cylindrical member 21 at a midpoint in the axial direction. The spring seat 27 receives the lower end of a spring (not shown) that supports the vehicle body. The inner cylinder 15 is a cylindrical, one-piece molded product made of a single piece of metal.

[0011] The cylinder device 11 includes a valve body 25 and a rod guide 26. The valve body 25 is annular and is provided at one axial end of the inner cylinder 15 and the outer cylinder 16. The rod guide 26 is annular and is provided at the other axial end of the inner cylinder 15 and the outer cylinder 16.

[0012] The valve body 25 has a stepped outer periphery with a large diameter portion and a smaller diameter portion. The valve body 25 is placed on the bottom member 22. At this time, the large diameter portion of the outer periphery of the valve body 25 is positioned radially relative to the bottom member 22, i.e., the outer cylinder 16.

[0013] The rod guide 26 has a stepped outer periphery with a large diameter portion and an even smaller diameter portion. The large diameter portion of the outer periphery of the rod guide 26 fits into the inner periphery of the outer cylinder 16 on the opening 23 side of the tubular member 21. As a result, the rod guide 26 is positioned radially relative to the tubular member 21, i.e., the outer cylinder 16, at the large diameter portion of the outer periphery.

[0014] One axial end of the inner cylinder 15 is fitted into a small-diameter portion of the outer periphery of the valve body 25. One axial end of the inner cylinder 15 is placed on the bottom member 22 of the outer cylinder 16 via the valve body 25. The other axial end of the inner cylinder 15 is fitted into a small-diameter portion of the outer periphery of a rod guide 26. This rod guide 26 is fitted into the tubular member 21 of the outer cylinder 16. As a result, the inner cylinder 15 is positioned radially relative to the outer cylinder 16 via the valve body 25 and the rod guide 26. The axial space between the valve body 25 and the bottom member 22 communicates with the outer cylinder 16 via a passage groove 31 formed in the valve body 25. The axial space between the valve body 25 and the bottom member 22, like the space between the inner cylinder 15 and the outer cylinder 16, defines a reservoir chamber 18.

[0015] The cylinder device 11 is provided with a seal member 38. The seal member 38 is provided on the opposite side of the rod guide 26 from the bottom member 22 in the axial direction. This seal member 38 is annular, and is fitted to the inner periphery of the tubular member 21, similar to the rod guide 26. A locking portion 39 is formed on the end of the tubular member 21 opposite the bottom member 22 in the axial direction. The locking portion 39 is formed by plastically deforming the tubular member 21 radially inward by crimping, such as curling. The seal member 38 is sandwiched between the locking portion 39 and the rod guide 26. The opening 23 is located radially inward of the locking portion 39 of the outer cylinder 16.

[0016] The cylinder device 11 includes a piston 41. The piston 41 is provided within the inner tube 15 of the cylinder 17 so as to be slidable along the axial direction of the inner tube 15. Thus, the piston 41 is provided within the cylinder 17 so as to be movable along the axial direction of the cylinder 17. The piston 41 divides the inner tube 15 into two chambers: a first chamber 42 and a second chamber 43. The first chamber 42 is provided between the piston 41 and the rod guide 26 within the inner tube 15. The second chamber 43 is provided between the piston 41 and the valve body 25 within the inner tube 15. The second chamber 43 is divided from a reservoir chamber 18 by the valve body 25. Within the cylinder 17, oil is sealed in the first chamber 42 and the second chamber 43 as a working fluid. Within the cylinder 17, oil and gas are sealed in the reservoir chamber 18 as working fluids.

[0017] The cylinder device 11 is equipped with a piston rod 46. One axial end of the piston rod 46 is inserted into the inner cylinder 15. This one end of the piston rod 46 is connected to the piston 41. The other axial end of the piston rod 46 is inserted through the rod guide 26 and the seal member 38 and extends from the cylinder 17 to the outside through the opening 23.

[0018] Piston rod 46 has a main shaft portion 47 and a mounting shaft portion 48. Mounting shaft portion 48 extends from one axial end of main shaft portion 47 along the axial direction of main shaft portion 47. The outer diameter of mounting shaft portion 48 is smaller than the outer diameter of main shaft portion 47. The mounting shaft portion 48 side of piston rod 46 is inserted into cylinder 17. A piston 41 is fixed to mounting shaft portion 48 of piston rod 46 with a nut 51. Main shaft portion 47 of piston rod 46 passes through rod guide 26 and seal member 38 and extends to the outside from cylinder 17.

[0019] The rod guide 26 positions the piston rod 46 in the radial direction and supports it axially slidably. The piston rod 46 is guided by sliding contact with the rod guide 26 at the main shaft portion 47. The piston rod 46 moves axially together with the piston 41 relative to the cylinder 17. During the extension stroke, in which the piston rod 46 increases the amount of protrusion from the cylinder 17, the piston 41 moves toward the first chamber 42. During the compression stroke, in which the piston rod 46 decreases the amount of protrusion from the cylinder 17, the piston 41 moves toward the second chamber 43.

[0020] The main shaft portion 47 of the piston rod 46 is in sliding contact with the inner periphery of the seal member 38. At that time, the seal member 38 closes the gap between the piston rod 46. The seal member 38 seals between the cylindrical member 21 of the outer cylinder 16 and the main shaft portion 47 of the piston rod 46, and prevents the oil in the inner cylinder 15 and the gas and oil in the reservoir chamber 18 from leaking to the outside.

[0021] A passage 55 and a passage 56 are formed in the piston 41. Both the passage 55 and the passage 56 pass through the piston 41 in the axial direction. Both the passages 55, 56 can communicate between the first chamber 42 and the second chamber 43. The cylinder device 11 is equipped with a disc valve 57 and a disc valve 58. The disc valve 57 is provided on the side of the piston 41 opposite the bottom member 22 in the axial direction. The disc valve 57 is annular and closes the passage 55 by abutting against the piston 41. The disc valve 58 is provided on the bottom member 22 side of the piston 41 in the axial direction. The disc valve 58 is annular and closes the passage 56 by abutting against the piston 41. The disc valves 57, 58 are attached to the piston rod 46 together with the piston 41.

[0022] When the piston rod 46 moves toward the compression side, increasing the amount of penetration into the inner cylinder 15 and the outer cylinder 16, and the piston 41 moves in a direction narrowing the second chamber 43, the pressure in the second chamber 43 becomes higher than the pressure in the first chamber 42. When the pressure in the second chamber 43 becomes higher than the pressure in the first chamber 42 by a predetermined value or more, the disc valve 57 opens the passage 55, allowing the oil in the second chamber 43 to flow through the passage 55 to the first chamber 42. At this time, the disc valve 57 generates a damping force. When the piston rod 46 moves toward the extension side, increasing the amount of protrusion from the inner cylinder 15 and the outer cylinder 16, and the piston 41 moves in a direction narrowing the first chamber 42, the pressure in the first chamber 42 becomes higher than the pressure in the second chamber 43. When the pressure in the first chamber 42 becomes higher than the pressure in the second chamber 43 by a predetermined value or more, the disc valve 58 opens the passage 56, allowing the oil in the first chamber 42 to flow through the passage 56 to the second chamber 43. At this time, the disc valve 58 generates a damping force.

[0023] A fixed orifice (not shown) is formed in at least one of the piston 41 and the disc valve 57. This fixed orifice allows communication between the first chamber 42 and the second chamber 43 via the passage 55 even when the disc valve 57 is in a state where the passage 55 is most closed by the disc valve 57. In addition, a fixed orifice (not shown) is formed in at least one of the piston 41 and the disc valve 58. This fixed orifice allows communication between the first chamber 42 and the second chamber 43 via the passage 56 even when the disc valve 58 is in a state where the passage 56 is most closed by the disc valve 58.

[0024] A passage 61 and a passage 62 are formed in the valve body 25. Both the passage 61 and the passage 62 axially penetrate the valve body 25. Both the passages 61 and 62 can communicate between the second chamber 43 and the reservoir chamber 18. The cylinder device 11 is equipped with a disc valve 65 and a disc valve 66. The disc valve 65 is provided on the opposite side of the valve body 25 from the piston 41 in the axial direction. The disc valve 65 closes the passage 61 by abutting against the valve body 25. The disc valve 66 is provided on the piston 41 side of the valve body 25 in the axial direction. The disc valve 66 closes the passage 62 by abutting against the valve body 25.

[0025] When the piston rod 46 moves toward the compression side and the piston 41 moves in a direction that narrows the second chamber 43, the pressure in the second chamber 43 becomes higher than the pressure in the reservoir chamber 18. When the pressure in the second chamber 43 becomes higher than the pressure in the reservoir chamber 18 by a predetermined value or more, the disc valve 65 opens the passage 61, allowing the hydraulic fluid in the second chamber 43 to flow through the passage 61 into the reservoir chamber 18. At this time, the disc valve 65 generates a damping force. When the piston rod 46 moves toward the extension side and the piston 41 moves toward the first chamber 42, the pressure in the second chamber 43 becomes lower than the pressure in the reservoir chamber 18. Then, the disc valve 66 opens the passage 62, allowing the hydraulic fluid in the reservoir chamber 18 to flow through the passage 62 into the second chamber 43. The disc valve 66 is a suction valve that allows the hydraulic fluid to flow from the reservoir chamber 18 into the second chamber 43 without generating any substantial damping force.

[0026] The cylinder device 11 includes a covered cylindrical cover 71. The cover 71 is fixed to a portion of the main shaft portion 47 of the piston rod 46 that protrudes outward beyond the seal member 38. The cover 71 covers the portion of the piston rod 46 in the axial direction between the portion to which the cover 71 is fixed and the seal member 38, the seal member 38, and the portion of the outer cylinder 16 on the opening 23 side in the axial direction. The cylinder device 11 is connected to the vehicle body at a portion of the piston rod 46 opposite the piston 41 from the cover 71 in the axial direction, and the bottom member 22 is connected to the wheel side of the vehicle. This allows the cylinder device 11 to damp relative vibration between the vehicle body side and the wheel side.

[0027] The bottom member 22 has a closing portion 81 , a connecting portion 82 , and an eye portion 83 .

[0028] The closing portion 81 has a tubular portion 91 and a plate-like portion 92. The tubular portion 91 is cylindrical. The plate-like portion 92 is disk-shaped and closes one axial end of the tubular portion 91. Therefore, the closing portion 81 is cylindrical with a bottom.

[0029] The connecting portion 82 extends from an end of the plate-shaped portion 92 opposite the cylindrical portion 91 in the axial direction of the blocking portion 81, in the opposite direction from the cylindrical portion 91 in the axial direction of the blocking portion 81. The connecting portion 82 extends from a range radially inward of the plate-shaped portion 92. The connecting portion 82 has a neck portion 101 and an extending portion 102. The connecting portion 82 is connected to the plate-shaped portion 92 with the neck portion 101 located closer to the blocking portion 81 than the extending portion 102 in the axial direction of the blocking portion 81.

[0030] 2 and 3, the neck portion 101 has a tapered shape that becomes narrower the further away from the blocking portion 81 in the axial direction of the blocking portion 81. As shown in FIG. 2, the neck portion 101 becomes narrower in width in a first direction (left-right direction in FIG. 2; the same applies hereinafter) perpendicular to the central axis of the blocking portion 81 the further away from the blocking portion 81 in the axial direction of the blocking portion 81. Furthermore, as shown in FIG. 3, the neck portion 101 also becomes narrower in width in a second direction (left-right direction in FIG. 3; the same applies hereinafter) perpendicular to the central axis of the blocking portion 81 and perpendicular to the first direction the further away from the blocking portion 81 in the axial direction of the blocking portion 81.

[0031] The extending portion 102 extends in the opposite direction to the blocking portion 81 from the end of the neck portion 101 opposite to the blocking portion 81 in the axial direction of the blocking portion 81. As shown in Fig. 2, the extending portion 102 becomes wider in a first direction as it moves away from the blocking portion 81 in the axial direction of the blocking portion 81. Furthermore, as shown in Fig. 3, the extending portion 102 also becomes wider in a second direction as it moves away from the blocking portion 81 in the axial direction of the blocking portion 81.

[0032] As shown in FIG. 2 , the extending portion 102 has a lightening portion 105 in an inner range in the extension direction and an inner range in the width direction. The lightening portion 105 has a thickness in the second direction smaller than that of a portion of the extending portion 102 surrounding the lightening portion 105. Specifically, the lightening portion 105 is a through-hole that penetrates the extending portion 102 in the second direction. In other words, the lightening portion 105 is a portion of the extending portion 102 that has no thickness in the second direction. The lightening portion 105 has a triangular shape whose width in the first direction increases as it moves away from the closing portion 81 in the axial direction of the closing portion 81. The lightening portion 105 has an isosceles triangular shape with its apex on the closing portion 81 side in the axial direction of the closing portion 81. In other words, the lightening portion 105 is an irregular-shaped hole that is not a circular hole.

[0033] The eye portion 83 extends in the opposite direction to the occluding portion 81 from the end of the extending portion 102 opposite to the occluding portion 81 in the axial direction of the occluding portion 81. In other words, the connecting portion 82 connects the occluding portion 81 and the eye portion 83. A through hole 111 is formed in the eye portion 83, penetrating the eye portion 83 in a direction perpendicular to the central axis of the occluding portion 81. The through hole 111 is a circular hole, and penetrates the eye portion 83 in the second direction, the same as the lightening portion 105. In other words, the lightening portion 105 and the through hole 111 penetrate the bottom member 22 parallel to each other. The eye portion 83 has an annular shape due to the formation of the through hole 111.

[0034] The eye portion 83 has an eye base end 112 and an eye tip end 113 . The eye base end 112 extends in the opposite direction to the occluding portion 81 from the end of the extending portion 102 opposite to the occluding portion 81 in the axial direction of the occluding portion 81. The eye base end 112 has an outer width in the first direction that increases as it moves away from the connecting portion 82 in the axial direction of the occluding portion 81. The eye base end 112 has a half of the through hole 111 formed on the occluding portion 81 side in the axial direction of the occluding portion 81.

[0035] The eye tip portion 113 extends in the opposite direction to the occluding portion 81 from the end of the eye base end portion 112 opposite the occluding portion 81 in the axial direction of the occluding portion 81. The outer width of the eye tip portion 113 in the first direction narrows as it moves away from the eye base end portion 112 in the axial direction of the occluding portion 81. The eye tip portion 113 is semicircular. The half of the through hole 111 opposite the occluding portion 81 in the axial direction of the occluding portion 81 is formed in the eye tip portion 113.

[0036] In the eye portion 83, the outer diameter portion of the boundary between the eye tip portion 113 and the eye base portion 112 is a maximum width portion 115 where the width in the first direction is maximum in the eye portion 83. In other words, the maximum width portion 115 is the portion in the eye portion 83 where the width in the direction perpendicular to the central axis of the closure portion 81 and perpendicular to the central axis of the through hole 111 is the maximum.

[0037] A straight line X1 connecting one end of maximum width portion 115 in the first direction to the other end of the outer periphery of closing portion 81 in the first direction intersects with a straight line X2 connecting the other end of maximum width portion 115 in the first direction to one end of the outer periphery of closing portion 81 in the first direction. The above-mentioned cutout portion 105 is provided at the position of intersection Z of the two straight lines X1 and X2. That is, the above-mentioned cutout portion 105 is provided at the position of intersection Z of the two straight lines X1 and X2 that intersect and connect maximum width portion 115 to the outer periphery of closing portion 81.

[0038] A plane that includes the central axis of the closing portion 81 and extends perpendicular to the first direction is defined as a first reference plane. The bottom member 22 is then mirror-symmetrical with respect to the first reference plane. Furthermore, a plane that includes the central axis of the closing portion 81 and extends perpendicular to the second direction is defined as a second reference plane. The bottom member 22 is then mirror-symmetrical with respect to the second reference plane.

[0039] As shown in FIG. 3, the bottom member 22 has a pair of base end side surfaces 121 on both ends in the second direction. The pair of base end side surfaces 121 face opposite each other in the second direction. Each of the pair of base end side surfaces 121 is a curved surface, and both extend entirely perpendicular to the first reference plane. As shown in FIG. 2, each of the pair of base end side surfaces 121 surrounds the entire circumference of the lightening portion 105. Each of the pair of base end side surfaces 121 is provided on the connecting portion 82. Each of the pair of base end side surfaces 121 extends from the end of the neck portion 101 on the closing portion 81 side to the extending portion 102 in the axial direction of the closing portion 81.

[0040] 3, the distance between the pair of base end side surface portions 121 in the second direction decreases as the portions of the pair of base end side surface portions 121 in the neck portion 101 move away from the blocking portion 81 in the axial direction of the blocking portion 81. The distance between the pair of base end side surface portions 121 in the second direction increases as the portions of the pair of base end side surface portions 121 in the extension portion 102 move away from the blocking portion 81 in the axial direction of the blocking portion 81. The pair of base end side surface portions 121 are both mirror symmetrical with respect to a first reference plane. The pair of base end side surface portions 121 are both mirror symmetrical with respect to a second reference plane. The pair of base end side surface portions 121 are both entirely continuous curved surfaces without bending.

[0041] The bottom member 22 has a pair of intermediate surface portions 122 on both sides in the second direction. The pair of intermediate surface portions 122 are both planar and face opposite each other in the second direction. The pair of intermediate surface portions 122 extend in the opposite direction from the closure portion 81 in the axial direction of the closure portion 81 from the edge portions of the pair of base end side portions 121 opposite the closure portion 81. Both of the pair of intermediate surface portions 122 are provided at the end portions of the extension portion 102 opposite the neck portion 101 in the axial direction of the closure portion 81. Both of the pair of intermediate surface portions 122 extend entirely perpendicular to the first reference plane.

[0042] The distance between the pair of intermediate surface portions 122 in the second direction increases as the distance from the closing portion 81 increases in the axial direction of the closing portion 81. The pair of intermediate surfaces 122 are both mirror-symmetric with respect to a first reference plane. The pair of intermediate surfaces 122 are both mirror-symmetric with respect to a second reference plane. Each of the pair of intermediate surface portions 122 is a continuous flat surface without bending.

[0043] The bottom member 22 has a pair of tip side surfaces 123 on both sides in the second direction. The pair of tip side surfaces 123 are both flat and extend in the opposite direction from the closing portion 81 in the axial direction of the closing portion 81 from the edge portions of the pair of intermediate surfaces 122 opposite the closing portion 81. The pair of tip side surfaces 123 face opposite each other in the second direction. The pair of tip side surfaces 123 both extend entirely perpendicular to the first reference plane. The pair of tip side surfaces 123 both extend perpendicular to the central axis of the through hole 111. In other words, the pair of tip side surfaces 123 both extend perpendicular to the second direction. In other words, the pair of tip side surfaces 123 both extend parallel to the second reference plane.

[0044] 2, each of the pair of tip side surface portions 123 surrounds the entire periphery of the through hole 111. Each of the pair of tip side surface portions 123 is provided on the eye portion 83. The pair of tip side surface portions 123 are both mirror-symmetrical with respect to a first reference plane. The pair of tip side surface portions 123 are both mirror-symmetrical with respect to a second reference plane. The pair of tip side surface portions 123 are each entirely formed as a continuous flat surface without bending.

[0045] The bottom member 22 has an outer surface portion 131 at its peripheral portion in the direction in which the second reference plane extends. The outer surface portion 131 is a curved surface. The outer surface portion 131 is the end of the neck portion 101 on the closing portion 81 side in the axial direction of the closing portion 81, and extends from one end position in the first direction through the neck portion 101 and the extending portion 102, around the eye portion 83, and again through the extending portion 102 and the neck portion 101 to the other end position in the first direction of the end of the neck portion 101 on the closing portion 81 side. The entire outer surface portion 131 extends perpendicular to the second reference plane. The entire outer surface portion 131 is a continuous curved surface without bending.

[0046] The outer surface portions 131 are spaced apart in the first direction narrower at the portions at the neck portion 101 as they move away from the occluding portion 81 in the axial direction of the occluding portion 81. The outer surface portions 131 are spaced apart in the first direction wider at the portions at the extension portion 102 as they move away from the occluding portion 81 in the axial direction of the occluding portion 81. The outer surface portions 131 are spaced apart in the first direction wider at the portions at the eye base end 112 as they move away from the occluding portion 81 in the axial direction of the occluding portion 81. The outer surface portions 131 are spaced apart in the first direction narrower at the portions at the eye tip end 113 as they move away from the occluding portion 81 in the axial direction of the occluding portion 81. The portion of the outer surface portion 131 at the eye tip end 113 is semi-cylindrical.

[0047] The outer surface portion 131 is mirror-symmetrical with respect to a first reference plane. The outer surface portion 131 is mirror-symmetrical with respect to a second reference plane. The above-mentioned maximum width portion 115 is provided on this outer surface portion 131 .

[0048] The bottom member 22 has a base end chamfer 141 that connects adjacent edge portions of the base end side surface portion 121 and the outer surface portion 131 in the circumferential direction of the closure portion 81. The base end chamfer 141 is an outwardly convex R-chamfer that connects, in a curved surface, the base end side surface portion 121 adjacent to the base end chamfer 141 on one side and a portion of the outer surface portion 131 adjacent to the base end chamfer 141 on the other side. The bottom member 22 has four base end chamfers 141 spaced apart in the circumferential direction of the closure portion 81. All four base end chamfers 141 extend from the end of the neck portion 101 on the closure portion 81 side to the extension portion 102 in the axial direction of the closure portion 81.

[0049] The two base end chamfers 141 connected to the same base end side surface portion 121 are mirror symmetrical to each other with respect to the first reference plane. The two base end chamfers 141 connected to another same base end side surface portion 121 are mirror symmetrical to each other with respect to the first reference plane. The two base end chamfers 141 connected to the same base end side surface portion 121 and the two base end chamfers 141 connected to another same base end side surface portion 121 are mirror symmetrical to each other with respect to the second reference plane.

[0050] The bottom member 22 has a tip chamfer 142 that connects adjacent edges of the tip side surface 123, the intermediate surface 122, and the outer surface 131. The tip chamfer 142 is an R-chamfer that connects the tip side surface 123 and the intermediate surface 122 adjacent to the tip chamfer 142 on one side to a portion of the outer surface 131 adjacent to the tip chamfer 142 on the other side in a convex curved surface. The bottom member 22 has a pair of tip chamfers 142 spaced apart in the second direction. Each of the pair of tip chamfers 142 extends from the portion of the extension portion 102 on the eye portion 83 side to the eye portion 83 in the axial direction of the closure portion 81. The pair of tip chamfers 142 are mirror-symmetrical with respect to a first reference plane. The pair of tip chamfers 142 are mirror-symmetrical with respect to a second reference plane.

[0051] In the bottom member 22, the closing portion 81, the connecting portion 82, and the eye portion 83 are integrally molded without any seams. In other words, the entire bottom member 22 is integrally molded without any seams. In yet other words, the closing portion 81, the connecting portion 82, and the eye portion 83 of the bottom member 22 are integrally formed without welding. In the bottom member 22, the closing portion 81, the connecting portion 82, and the eye portion 83 are integrally molded by forging. In the bottom member 22, the pair of base end side surface portions 121, the pair of middle surface portions 122, the pair of tip end side surface portions 123, the outer surface portion 131, the four base end side chamfers 141, the pair of tip end side chamfers 142, and the lightening portion 105 are all formed during forging. In other words, the bottom member 22 has a pair of base end side surfaces 121, a pair of intermediate surfaces 122, a pair of tip end side surfaces 123, an outer surface 131, four base end side chamfers 141, and a pair of tip end side chamfers 142, all of which are forged surfaces. The inner peripheral surface of the lightening portion 105 also has a forged surface. A pilot hole for the through hole 111 is formed in the bottom member 22 during forging, and then the pilot hole is machined to form the through hole 111.

[0052] As shown in FIG. 1 , the tubular portion 91 of the closing portion 81 of the bottom member 22 is fitted into the inner periphery of the tubular member 21 on the side opposite the opening 23 in the axial direction. At this time, the connecting portion 82 and the eye portion 83 of the bottom member 22 extend beyond the tubular member 21 on the side opposite the opening 23 in the axial direction of the tubular member 21. In this state, the bottom member 22 is welded to the tubular member 21 around the entire circumference of the closing portion 81. As a result, the closing portion 81 of the bottom member 22 closes one end side of the tubular member 21 opposite the opening 23 in the axial direction.

[0053] In this manner, when the bottom member 22 is fixed to the tubular member 21 by welding, the central axis of the closing portion 81 coincides with the central axis of the tubular member 21. In this state, the first and second directions of the bottom member 22 extend in the radial direction of the tubular member 21. In this state, the first and second reference planes of the bottom member 22 both include the central axis of the tubular member 21. In this state, the bottom member 22 is hollowed out in the radial direction of the tubular member 21 by the hollowed-out portion 105. In this state, the hollowed-out portion 105 penetrates the bottom member 22 in the radial direction of the tubular member 21. In this state, the through-hole 111 penetrates the bottom member 22 in the radial direction of the tubular member 21. In this state, the bottom member 22 has a hollowed-out portion 105 located at the intersection Z of two straight lines X1 and X2 that intersect and connect the widest portion 115 of the eye portion 83 in the radial direction of the tubular member 21 and the outer periphery of the blocking portion 81.

[0054] Although not shown, a rubber bushing is fitted into the through hole 111 and fixed to the bottom member 22. The rubber bushing has a cylindrical bushing made of metal and a cylindrical rubber portion made of rubber that is adhered to the outer periphery of the bushing. The rubber portion of the rubber bushing is fitted into the through hole 111 of the bottom member 22. The rubber bushing is connected to the wheel side of the vehicle by a fastener inserted into the bushing. In this way, the bottom member 22 is connected to the wheel side of the vehicle.

[0055] The aforementioned Patent Document 1 discloses a cylinder device having a rod-shaped member connected at one end to an outer tube and an annular mounting eye joined to the other end of the rod-shaped member. In this cylinder device, the rod-shaped member and the mounting eye are separate and are joined by welding. With this structure, when a bending load is applied to a member formed by joining the rod-shaped member and the mounting eye, the welded portion can become a stress concentration point, potentially reducing the member's strength. Furthermore, the strength of the member formed by joining the rod-shaped member and the mounting eye can vary depending on the welding conditions and quality.

[0056] In contrast, the cylinder device 11 of the embodiment has a bottom member 22 integrally formed with a closing portion 81 that closes one end of the tubular member 21 of the cylinder 17, an annular eye portion 83, and a connecting portion 82 that connects the closing portion 81 and the eye portion 83. Because the closing portion 81, the eye portion 83, and the connecting portion 82 are integrally formed in the bottom member 22, there are no welds that could become stress concentration points when, for example, a bending load is applied. This improves the strength of the bottom member 22, thereby improving the strength of the cylinder device 11. This allows the cylinder device 11 to accommodate increased inputs to the cylinder device 11 due to increased vehicle weight. Furthermore, because the bottom member 22 has no welds, its strength is not affected by welding conditions or welding quality. This stabilizes the strength of the bottom member 22, thereby stabilizing the strength of the cylinder device 11.

[0057] Furthermore, the cylinder device 11 has a lightening portion 105 provided at the connecting portion 82 of the bottom member 22. This allows the weight of the bottom member 22 to be reduced, and therefore the weight of the cylinder device 11 to be reduced.

[0058] Furthermore, in the cylinder device 11, the hollowed-out portion 105 of the bottom member 22 is provided at the position of the intersection Z of two straight lines X1, X2 that intersect and connect the widest portion 115 of the eye portion 83 in the radial direction of the tubular member 21 and the outer periphery of the closing portion 81. Therefore, the weight of the bottom member 22 can be effectively reduced while suppressing a decrease in the strength of the bottom member 22, and ultimately the weight of the cylinder device 11 can be effectively reduced.

[0059] Furthermore, in the cylinder device 11, the lightening portion 105 is a through hole that penetrates the bottom member 22. This allows the bottom member 22 to be further lightened, and ultimately the cylinder device 11 to be further lightened. The lightening portion 105 does not have to penetrate the bottom member 22. In other words, the lightening portion 105 only needs to remove light from the bottom member 22, and may be, for example, concave. The lightening portion 105 can be provided in multiple locations per bottom member 22, rather than just one location.

[0060] Furthermore, in the cylinder device 11, the lightening direction of the lightening portion 105 coincides with the penetration direction of the through hole 111 of the eye portion 83. This allows the weight of the bottom member 22 to be effectively reduced while suppressing a decrease in strength of the bottom member 22, thereby effectively reducing the weight of the cylinder device 11. Furthermore, a molding die for integrally forging the bottom member 22 can be easily manufactured, thereby reducing manufacturing costs. Note that it is also possible to make the lightening direction of the lightening portion 105 and the penetration direction of the through hole 111 different from each other, for example, by shifting the lightening direction of the lightening portion 105 from the penetration direction of the through hole 111 by 90 degrees. Furthermore, the bottom member 22 can also be integrally formed by casting rather than forging.

[0061] Furthermore, in the cylinder device 11, the outer surface portion 131 of the bottom member 22 has a curved surface shape that is continuous and not bent overall. Therefore, there are no bent portions that could become stress concentration points when a bending load is applied, for example. This further improves the strength of the bottom member 22, and ultimately the strength of the cylinder device 11. [Explanation of symbols]

[0062] 11...cylinder device, 17...cylinder, 21...cylindrical member, 22...bottom member, 41...piston, 46...piston rod, 81...closure portion, 82...connecting portion, 83...eye portion, 105...thinned portion, 115...maximum width portion, X1, X2...straight line, Z...intersection point.

Claims

[Claim 1] a cylinder having a cylindrical member and a bottom member closing one end of the cylindrical member; a piston movably provided within the cylinder; a piston rod having one end connected to the piston and the other end extending from the cylinder to the outside; and The bottom member is a closing portion that closes one end side of the cylindrical member; an annular eye portion having a through hole into which a rubber bushing is fitted and fixed; a connecting portion that connects the blocking portion and the eye portion is integrally molded, the closing portion has a cylindrical tubular portion that is fitted into the tubular member, and a plate-like portion that closes one end of the tubular portion in the axial direction, The connecting portion has a neck portion connected to the plate-shaped portion and an extension portion extending from the neck portion to an opposite side to the blocking portion, The neck portion has a width that is narrower in the axial direction of the through hole and in a direction perpendicular to the axis of the through hole as the neck portion is spaced apart from the blocking portion, The extension portion has a width in the axial direction of the through hole and in a direction perpendicular to the axis of the through hole that increases as the extension portion moves away from the blocking portion, The connecting portion is provided with a triangular hollow portion formed in an inner area of ​​the extending portion in parallel to the through hole, the hollow portion having a width that increases in a direction perpendicular to the axis of the through hole as it moves away from the closing portion in the axial direction of the closing portion, The hollowed portion is A cylinder device characterized in that it is located at the intersection of two straight lines that intersect and connect the widest part of the eye portion in the radial direction of the cylindrical member and the outer periphery of the closure portion.

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