Bumper Caps and Shock Absorbers

Abstract

This bumper cap is used in a shock absorber. The shock absorber comprises a cylinder, a piston provided inside the cylinder, and a piston rod having a first end portion linked to the piston and a second end portion that extends from the cylinder. The bumper cap comprises: a lid portion which is provided on an end portion of the cylinder on the side from which the piston rod extends, the lid portion being formed by diecasting or injection molding, abutting an axial-direction end surface of the cylinder, and having a through-hole through which the piston rod is inserted; a cylindrical tubular portion which is provided further toward a radially outer side than the through-hole, and which covers at least a portion of an outer circumferential surface of the cylinder; and communicating holes which are provided in the tubular portion to provide communication between an inner circumferential surface and an outer circumferential surface of the tubular portion. An edge of the communicating hole is narrower in a first end portion positioned on a downstream side in a direction in which material flows during molding, than in a second end portion positioned on an upstream side.

Description

[Technical Field]

[0001] The present invention relates to a bumper cap and a shock absorber. This application claims priority based on Japanese Patent Application No. 2022-110369, filed on July 8, 2022, the contents of which are incorporated herein by reference. [Background technology]

[0002] In some shock absorbers, the side of the cylinder from which the rod protrudes is covered with a bumper cap (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2016-061425 Summary of the Invention [Problem to be solved by the invention]

[0004] In shock absorbers, it is desirable to improve the durability of bumper caps.

[0005] Therefore, an object of the present invention is to provide a bumper cap and a shock absorber that can improve durability. [Means for solving the problem]

[0006] In order to achieve the above object, one aspect of the present invention is a bumper cap for use in a shock absorber, the shock absorber comprising a cylinder, a piston provided within the cylinder, and a piston rod having a first end connected to the piston and a second end extending from the cylinder, the bumper cap comprising: a cover portion provided at the end of the cylinder from which the piston rod extends, molded by die casting or injection molding, which abuts against the axial end face of the cylinder and has a through hole through which the piston rod is inserted; a cylindrical tube portion provided radially outward from the through hole and covering at least a portion of the outer peripheral surface of the cylinder; and a communication hole provided in the tube portion that communicates between the inner and outer peripheral surfaces of the tube portion, the edge of the communication hole being narrower at the first end located downstream than at the second end located upstream where material flows in during molding.

[0007] Another aspect of the present invention is a bumper cap for a shock absorber comprising a cylinder, a piston provided within the cylinder, and a piston rod having one end connected to the piston and the other end extending from the cylinder, the bumper cap being provided at the end of the cylinder from which the piston rod extends, wherein the bumper cap comprises a lid portion that abuts the axial end face of the cylinder and has a through hole through which the piston rod is inserted, a cylindrical tube portion that is provided radially outward from the through hole and covers at least a portion of the outer peripheral surface of the cylinder, and a communication hole that is provided in the tube portion and communicates between the inner peripheral surface and the outer peripheral surface of the tube portion, the edge of the communication hole having a circumferential edge portion extending in the circumferential direction of the tube portion and an axial edge portion extending in the axial direction of the tube portion, and at least a portion of the circumferential edge portion is formed so as to be inclined with respect to the axial direction of the tube portion, and the rim of the communication hole comprises an inclined portion that is the end side of the axial end of the tube portion in the axial direction.

[0008] Yet another aspect of the present invention employs a shock absorber comprising: a cylinder; a piston provided within the cylinder; a piston rod having one end connected to the piston and the other end extending from the cylinder; and a bumper cap, wherein the bumper cap has a lid portion that abuts the axial end face of the cylinder and has a through hole through which the piston rod is inserted; a cylindrical tube portion provided at the radially outer end of the lid portion and covering at least a portion of the outer peripheral surface of the cylinder; and a communication hole provided in the tube portion that communicates between the inner and outer peripheral surfaces of the tube portion, wherein the communication hole is narrower at a first end located downstream than at a second end located upstream where material flows in during molding. [Effects of the Invention]

[0009] According to the above aspects of the present invention, the durability of the bumper cap can be improved. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a front view, partly in section, showing a shock absorber including a bumper cap according to a first embodiment of the present invention. [Figure 2] FIG. 2 is an enlarged perspective view showing a main part of the shock absorber including the bumper cap of the first embodiment. [Figure 3] FIG. 3 is a development view showing a communication hole of a bumper cap of the shock absorber of the first embodiment. [Figure 4] 4 is a developed cross-sectional view showing a mold portion that forms a communication hole of a mold that forms the bumper cap of the shock absorber of the first embodiment. FIG. [Figure 5] FIG. 10 is a development view showing a communication hole of a bumper cap of a shock absorber according to a second embodiment of the present invention. [Figure 6] FIG. 10 is a development view showing a communication hole of a bumper cap of a shock absorber according to a third embodiment of the present invention. [Figure 7] FIG. 10 is a development view showing a communication hole of a bumper cap of a shock absorber according to a fourth embodiment of the present invention. [Figure 8] FIG. 10 is a development view showing a communication hole of a bumper cap of a shock absorber according to a fifth embodiment of the present invention. [Figure 9] FIG. 13 is a development view showing a communication hole of a bumper cap of a shock absorber according to a sixth embodiment of the present invention. [Figure 10] FIG. 13 is a development view showing a communication hole of a bumper cap of a shock absorber according to a seventh embodiment of the present invention. [Figure 11] FIG. 13 is a development view showing a communication hole of a bumper cap of a shock absorber according to an eighth embodiment of the present invention. [Figure 12] FIG. 13 is a development view showing a communication hole of a bumper cap of a shock absorber according to a ninth embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0011] [First embodiment] A first embodiment of the present invention will be described below with reference to FIGS.

[0012] FIG. 1 shows a shock absorber according to a first embodiment. The shock absorber 11 according to the first embodiment is a twin-tube hydraulic shock absorber. The shock absorber 11 is used in a vehicle, specifically, a strut-type suspension device for an automobile. The shock absorber 11 has a shock absorber body 12 and a bumper cap 13.

[0013] The shock absorber body 12 includes a cylinder 21, a main bracket 22, a spring seat 23, and a sub-bracket 24.

[0014] The cylinder 21 has an inner cylinder 31 and an outer cylinder 32, both of which are made of metal. The inner cylinder 31 is cylindrical. The outer cylinder 32 is cylindrical and has a bottom. The inner cylinder 31 is disposed radially inside the outer cylinder 32. A reservoir chamber 33 is formed between the inner cylinder 31 and the outer cylinder 32. In the cylinder 21, oil L as a working fluid is sealed in the inner cylinder 31, and oil L and gas G as working fluids are sealed in the reservoir chamber 33.

[0015] The outer cylinder 32 has a cylindrical body 36 and a bottom 37 that closes one axial end of the body 36. The outer cylinder 32 has an opening at the end of the body 36 opposite the bottom 37 in the axial direction.

[0016] The main bracket 22 is made of metal and is fitted to the body 36 on the bottom 37 side of the axial center position of the outer cylinder 32 and fixed by welding. The main bracket 22 is connected to the wheel (not shown) side of the vehicle with fasteners (not shown) inserted into a plurality of mounting holes 39.

[0017] The spring seat 23 is made of metal and is fitted into the body portion 36 on the opposite side of the bottom portion 37 from the center position in the axial direction of the outer cylinder 32 and fixed by welding. The spring seat 23 supports the lower end of a vehicle body support spring (not shown), which is a coil spring that supports the vehicle body (not shown).

[0018] The sub-bracket 24 is made of metal and is fixed by welding to the outer periphery of the main bracket 22. The sub-bracket 24 supports harnesses, hoses, etc. that are routed around the shock absorber 11.

[0019] The shock absorber body 12 has a piston 40 provided in the cylinder 21. The piston 40 is slidably fitted in the inner tube 31 of the cylinder 21. The piston 40 defines a first chamber 41 and a second chamber 42 within the inner tube 31. The first chamber 41 is provided on the opposite side of the piston 40 from the bottom 37 in the axial direction of the inner tube 31. The second chamber 42 is provided on the bottom 37 side of the piston 40 in the axial direction of the inner tube 31.

[0020] The shock absorber main body 12 includes a piston rod 50. A first end, which is one end of the piston rod 50 in the axial direction, is disposed inside the inner tube 31 of the cylinder 21. The first end of the piston rod 50 is connected to the piston 40. A second end, which is the other end of the piston rod 50 opposite the first end in the axial direction, extends from the cylinder 21 to the outside of the cylinder 21.

[0021] The piston rod 50 has a main shaft portion 51 and a mounting shaft portion 52. The main shaft portion 51 and the mounting shaft portion 52 are both rod-shaped. The outer diameter of the mounting shaft portion 52 is smaller than the outer diameter of the main shaft portion 51. The mounting shaft portion 52 is disposed within the inner cylinder 31. The piston 40 of the piston rod 50 is attached to the mounting shaft portion 52. The piston 40 moves integrally with the piston rod 50.

[0022] A passage 54 and a passage 55 are formed through the piston 40 in the axial direction. Both the passage 54 and the passage 55 are capable of connecting the first chamber 41 and the second chamber 42 to each other.

[0023] The shock absorber body 12 includes a disc valve 56 and a disc valve 57 . The disc valve 56 is provided on the opposite side of the piston 40 from the bottom portion 37 in the axial direction. The disc valve 56 is capable of closing the passage 54 by coming into contact with the piston 40.

[0024] The disc valve 57 is provided on the bottom 37 side of the piston 40 in the axial direction. The disc valve 57 is able to close the passage 55 by abutting against the piston 40. The disc valves 56 and 57, together with the piston 40, are attached to the mounting shaft portion 52 of the piston rod 50 with nuts 59.

[0025] When the piston rod 50 moves toward the compression side, increasing the amount of entry into the cylinder 21, and the piston 40 moves in a direction narrowing the second chamber 42, causing the pressure in the second chamber 42 to exceed the pressure in the first chamber 41 by a predetermined value or more, the disc valve 56 opens the passage 54 to allow the flow of hydraulic fluid L. At that time, the disc valve 56 generates a damping force. At least one of the piston 40 and the disc valve 56 is provided with a fixed orifice (not shown) that communicates between the first chamber 41 and the second chamber 42 via the passage 54 even when the disc valve 56 is in a state where the passage 54 is most closed.

[0026] When the piston rod 50 moves toward the extension side, increasing the amount of protrusion from the cylinder 21, and the piston 40 moves in a direction narrowing the first chamber 41, causing the pressure in the first chamber 41 to exceed the pressure in the second chamber 42 by a predetermined value or more, the disc valve 57 opens the passage 55 to allow the flow of hydraulic fluid L. At that time, the disc valve 57 generates a damping force. At least one of the piston 40 and the disc valve 57 is provided with a fixed orifice (not shown) that allows communication between the first chamber 41 and the second chamber 42 via the passage 55 even when the disc valve 57 is in a state where the passage 55 is most closed.

[0027] The bumper cap 13 is provided at the end of the cylinder 21 on the side from which the piston rod 50 extends, so as to cover this end. Here, the shock absorber body 12 has a seal member (not shown) at the outer end of the cylinder 21 on the side from which the piston rod 50 projects, which seals the gap between the cylinder 21 and the piston rod 50. The bumper cap 13 covers and protects this seal member.

[0028] When the shock absorber 11 is mounted on a vehicle, a bump rubber (not shown) is provided on the piston rod 50 at a portion that protrudes outward in the axial direction beyond the seal member. This bump rubber is made of a cylindrical elastic material, and the piston rod 50 is inserted inside it. When the cylinder 21 of the shock absorber main body 12 shortens the distance between itself and the vehicle body (not shown), this bump rubber comes into contact with the vehicle body and the bumper cap 13, elastically deforming to absorb the impact. The bumper cap 13 prevents the bump rubber from colliding with the seal member (not shown) at that time. The bumper cap 13 also prevents dust and other foreign particles from adhering to the seal member (not shown) from the outside.

[0029] The bumper cap 13 used in the shock absorber 11 has a cylindrical shape with a lid. As shown in Fig. 2, the bumper cap 13 includes a lid portion 70, an axial protruding portion 71, a cylindrical portion 72, a flange portion 73, and a radial protruding portion 74.

[0030] The lid portion 70 is a perforated disk-like member having a through-hole 81 penetrating the axial direction at its radial center. The through-hole 81 is a circular hole. In other words, the inner peripheral edge 82 of the through-hole 81 of the lid portion 70 is circular.

[0031] The axial protruding portion 71 protrudes from the lid portion 70 to one side in the axial direction of the lid portion 70. The axial protruding portion 71 is provided partially in the circumferential direction of the lid portion 70. The axial protruding portion 71 extends linearly outward from the inner peripheral edge portion 82 of the lid portion 70 along the radial direction of the lid portion 70. The bumper cap 13 is provided with multiple axial protruding portions 71 of the same shape on the same side of the lid portion 70 in the axial direction, at equal intervals in the circumferential direction of the lid portion 70, specifically three locations.

[0032] The tubular portion 72 is cylindrical and extends coaxially from the entire outer peripheral edge of the lid portion 70 to the opposite side of the axial protruding portion 71 in the axial direction of the lid portion 70. In other words, the tubular portion 72 is provided at the radially outer end of the lid portion 70. The tubular portion 72 is provided radially outward of a through-hole 81 provided in the radial center of the lid portion 70. A recessed portion 83 is formed in the tubular portion 72 at the end opposite the lid portion 70 in the axial direction, recessed in the axial direction from the end face opposite the lid portion 70 in the axial direction. The recessed portion 83 penetrates the tubular portion 72 in the radial direction. The tubular portion 72 has multiple recessed portions 83 of the same shape, specifically three recessed portions 83, provided at predetermined equal intervals in the circumferential direction of the tubular portion 72. Each of these recessed portions 83 is aligned with one of the axial protruding portions 71 in the circumferential direction of the tubular portion 72. The cylindrical portion 72 has an opening 85 on the axially opposite side to the lid portion 70. The opening 85 includes a plurality of recessed portions 83. The bumper cap 13 has the opening 85 at one axial end, and the axial protruding portion 71, the lid portion 70, and a through-hole 81 penetrating the lid portion 70 at the other axial end.

[0033] Here, the central axis of the through hole 81, the lid portion 70, and the cylindrical portion 72, which are arranged coaxially, is set to be the central axis of the bumper cap 13. Therefore, the through hole 81, the lid portion 70, the cylindrical portion 72, and the bumper cap 13 are aligned in the axial direction, the circumferential direction, and the radial direction.

[0034] The flange portion 73 protrudes radially outward from the edge of the cylindrical portion 72 on the opposite side of the axial direction from the lid portion 70. The flange portion 73 is provided partially in the circumferential direction of the cylindrical portion 72. The flange portion 73 is formed between adjacent recessed portions 83 on the edge of the cylindrical portion 72 on the opposite side of the axial direction from the lid portion 70. The bumper cap 13 has multiple flange portions 73 of the same shape provided at equal intervals in the circumferential direction of the cylindrical portion 72, specifically at three locations. These flange portions 73 are aligned in the axial direction of the cylindrical portion 72.

[0035] The radial protrusions 74 protrude radially outward from between the cover portion 70 and the flange portion 73 in the axial direction of the cylindrical portion 72. The radial protrusions 74 are partially provided in the circumferential direction of the cylindrical portion 72. The radial protrusions 74 are provided at the position of the recessed portion 83 in the edge portion of the cylindrical portion 72 opposite the cover portion 70 in the axial direction. The bumper cap 13 has multiple radial protrusions 74 of the same shape provided at equal intervals in the circumferential direction of the cylindrical portion 72, specifically three locations. These radial protrusions 74 are aligned with each other in the axial direction of the cylindrical portion 72. Each of these radial protrusions 74 is aligned with one of the axial protrusions 71 in the circumferential direction of the cover portion 70. The radial protrusions 74 are positioned differently from the flange portion 73 in the circumferential direction of the cylindrical portion 72. The radial protrusions 74 and the flanges 73 are alternately arranged at equal intervals in the circumferential direction of the cylindrical portion 72 .

[0036] The cylindrical portion 72 has a communication hole 91 formed therein, which penetrates the cylindrical portion 72 in the radial direction of the cylindrical portion 72, at a position between the radial protruding portion 74 and the cover portion 70 in the axial direction of the cylindrical portion 72. In other words, the communication hole 91 is provided in the cylindrical portion 72 and communicates between the inner circumferential surface 72a and the outer circumferential surface 72b of the cylindrical portion 72 shown in FIG. 1 . The communication hole 91 is a horizontal hole that penetrates the cylindrical portion 72 in the radial direction of the bumper cap 13. The bumper cap 13 has a plurality of communication holes 91 of the same shape, specifically, three communication holes 91, formed at equal intervals in the circumferential direction of the cylindrical portion 72. These communication holes 91 are aligned in the axial direction of the cylindrical portion 72. Each of these communication holes 91 is aligned in phase with one of the radial protruding portions 74 in the circumferential direction of the cylindrical portion 72.

[0037] The edge 101 of the communication hole 91 is in the form of a closed loop. As shown in FIG. 2 , the edge 101 has a first axial edge portion 102 and a second axial edge portion 103 as axial edge portions extending in the axial direction of the tubular portion 72. The first axial edge portion 102 and the second axial edge portion 103 are aligned in the axial direction of the tubular portion 72, spaced apart in the circumferential direction of the tubular portion 72, and are mirror-symmetrical. Here, in the bumper cap 13, the side of the tubular portion 72 opposite the lid portion 70 in the axial direction is referred to as a first end side, and the side of the tubular portion 72 facing the lid portion 70 in the axial direction is referred to as a second end side. In addition, in the communication hole 91, the end of the tubular portion 72 opposite the lid portion 70 in the axial direction is referred to as a first end side, and the end of the tubular portion 72 facing the lid portion 70 in the axial direction is referred to as a second end side.

[0038] As shown in FIG. 3, the first axial edge 102 has a first linear portion 111 , a first chamfered portion 112 , and a second chamfered portion 113 .

[0039] The first linear portion 111 extends linearly in the axial direction of the tubular portion 72, including an inner surface 111a facing the space within the communicating hole 91. The inner surface 111a of the first linear portion 111 also extends radially of the tubular portion 72 and is flat.

[0040] The first chamfered portion 112 extends from an end of the first linear portion 111 closer to the first end in the axial direction of the cylindrical portion 72 toward the first end. The first chamfered portion 112 has an inner surface 112a facing the space within the communicating hole 91 extending from an end of the inner surface 111a of the first linear portion 111 closer to the first end in the axial direction of the cylindrical portion 72 toward the first end. The first chamfered portion 112, including the inner surface 112a, has an arc shape with its center closer to the second axial edge portion 103 in the circumferential direction of the cylindrical portion 72 than the inner surface 112a. The first chamfered portion 112 is round-chamfered. The closer the first chamfered portion 112, including the inner surface 112a, is to the first end in the axial direction of the cylindrical portion 72, the closer it is to the second axial edge portion 103 in the circumferential direction of the cylindrical portion 72. An inner surface 112a of the first chamfered portion 112 is also aligned in the radial direction of the tubular portion 72 and has a cylindrical surface shape.

[0041] The second chamfered portion 113 extends from an end of the first linear portion 111 closer to the second end in the axial direction of the tubular portion 72 toward the second end. The second chamfered portion 113 has an inner surface 113a that faces the space within the communicating hole 91 extending from an end of the inner surface 111a of the first linear portion 111 closer to the second end in the axial direction of the tubular portion 72 toward the second end. The second chamfered portion 113, including the inner surface 113a, has an arc shape with its center closer to the second axial edge portion 103 in the circumferential direction of the tubular portion 72 than the inner surface 113a. The second chamfered portion 113 is R-chamfered. The closer the second chamfered portion 113, including the inner surface 113a, is to the second end in the axial direction of the tubular portion 72, the closer it is to the second axial edge portion 103 in the circumferential direction of the tubular portion 72. An inner surface 113a of the second chamfered portion 113 is also aligned in the radial direction of the tubular portion 72 and has a cylindrical surface shape.

[0042] The second axial edge portion 103 has a second linear portion 121 , a third chamfered portion 122 and a fourth chamfered portion 123 .

[0043] The second linear portion 121 extends linearly in the axial direction of the tubular portion 72, including an inner surface 121a facing the space within the communicating hole 91. The inner surface 121a of the second linear portion 121 is flat and also extends along the radial direction of the tubular portion 72. The second linear portion 121 is aligned with the first linear portion 111 in the axial direction of the tubular portion 72 and is spaced apart in the circumferential direction of the tubular portion 72, forming a mirror image.

[0044] The third chamfered portion 122 extends from an end of the second straight portion 121 closer to the first end in the axial direction of the tubular portion 72 toward the first end. The third chamfered portion 122 has an inner surface 122a that faces the space within the communicating hole 91 extending from an end of the inner surface 121a of the second straight portion 121 closer to the first end in the axial direction of the tubular portion 72 toward the first end. The third chamfered portion 122, including the inner surface 122a, has an arc shape with its center closer to the first axial edge portion 102 in the circumferential direction of the tubular portion 72 than the inner surface 122a. The third chamfered portion 122 is R-chamfered. The closer the third chamfered portion 122, including the inner surface 122a, is to the first end in the axial direction of the tubular portion 72, the closer it is to the first axial edge portion 102 in the circumferential direction of the tubular portion 72. The inner surface 122a of the third chamfered portion 122 is cylindrical and extends radially of the tubular portion 72. The third chamfered portion 122 is aligned with the first chamfered portion 112 in the axial direction of the tubular portion 72 and is spaced apart circumferentially of the tubular portion 72, forming a mirror image.

[0045] The fourth chamfered portion 123 extends from an end of the second straight portion 121 closer to the second end in the axial direction of the tubular portion 72 toward the second end. The fourth chamfered portion 123 has an inner surface 123a that faces the space within the communicating hole 91 extending from an end of the inner surface 121a of the second straight portion 121 closer to the second end in the axial direction of the tubular portion 72 toward the second end. The fourth chamfered portion 123, including the inner surface 123a, has an arc shape with its center closer to the first axial edge portion 102 in the circumferential direction of the tubular portion 72 than the inner surface 123a. The fourth chamfered portion 123 is R-chamfered. The closer the fourth chamfered portion 123, including the inner surface 123a, is to the second end in the axial direction of the tubular portion 72, the closer it is to the first axial edge portion 102 in the circumferential direction of the tubular portion 72. The inner surface 123a of the fourth chamfered portion 123 is cylindrical and extends radially of the tubular portion 72. The fourth chamfered portion 123 is aligned with the second chamfered portion 113 in the axial direction of the tubular portion 72 and is spaced apart circumferentially of the tubular portion 72, forming a mirror image.

[0046] The edge 101 has a first circumferential edge portion 131 and a second circumferential edge portion 132 as circumferential edge portions extending in the circumferential direction of the tubular portion 72. The edge 101 has the first circumferential edge portion 131 at an end portion on the first end side in the axial direction of the tubular portion 72. The edge 101 has the second circumferential edge portion 132 at an end portion on the second end side in the axial direction of the tubular portion 72.

[0047] The first circumferential edge 131 is mirror-symmetric and has a first inclined portion 141 , a second inclined portion 142 and a fifth chamfered portion 143 .

[0048] The first inclined portion 141 is formed to extend from one end of the first axial edge portion 102 on the first end side in the axial direction of the cylindrical portion 72 at an angle with respect to the first linear portion 111 of the first axial edge portion 102. The first inclined portion 141 is linear, including an inner surface 141a that faces the space within the communicating hole 91. The inner surface 141a of the first inclined portion 141 is also aligned in the radial direction of the cylindrical portion 72 and is flat.

[0049] The first inclined portion 141 extends from one end of the first chamfered portion 112 that is closer to the first end in the axial direction of the tubular portion 72 to the first end in the axial direction of the tubular portion 72. Moreover, the closer the first inclined portion 141 is to the first end in the axial direction of the tubular portion 72, the closer it is to the second straight portion 121 in the circumferential direction of the tubular portion 72. The inner surface 141a of the first inclined portion 141 extends from one end of the inner surface 112a of the first chamfered portion 112 that is closer to the first end in the axial direction of the tubular portion 72 to the first end in the axial direction of the tubular portion 72. Moreover, the closer the inner surface 141a of the first inclined portion 141 is to the first end in the axial direction of the tubular portion 72, the closer it is to the second straight portion 121 in the circumferential direction of the tubular portion 72.

[0050] The second inclined portion 142 is formed to extend from one end of the second axial edge portion 103 on the first end side in the axial direction of the cylindrical portion 72 at an angle with respect to the second linear portion 121 of the second axial edge portion 103. The second inclined portion 142 is linear, including an inner surface 142a that faces the space within the communicating hole 91. The inner surface 142a of the second inclined portion 142 is also aligned in the radial direction of the cylindrical portion 72 and is flat.

[0051] The second inclined portion 142 extends from one end of the third chamfered portion 122 that is closer to the first end in the axial direction of the cylindrical portion 72 toward the first end in the axial direction of the cylindrical portion 72. Moreover, the closer the second inclined portion 142 is to the first end in the axial direction of the cylindrical portion 72, the closer it is to the first straight portion 111 in the circumferential direction of the cylindrical portion 72. The inner surface 142a of the second inclined portion 142 extends from one end of the inner surface 122a of the third chamfered portion 122 that is closer to the first end in the axial direction of the cylindrical portion 72 toward the first end in the axial direction of the cylindrical portion 72. Moreover, the closer the inner surface 142a of the second inclined portion 142 is to the first end in the axial direction of the cylindrical portion 72, the closer it is to the first straight portion 111 in the circumferential direction of the cylindrical portion 72. The second inclined portion 142 is aligned with the first inclined portion 141 in the axial direction of the cylindrical portion 72 and is spaced apart in the circumferential direction of the cylindrical portion 72, forming a mirror image of the first inclined portion 141. An angle formed between an inner surface 142a of the second inclined portion 142 and an inner surface 141a of the first inclined portion 141 is an acute angle.

[0052] The fifth chamfered portion 143 connects one end of the first inclined portion 141 on the first end side in the axial direction of the cylindrical portion 72 to one end of the second inclined portion 142 on the first end side in the axial direction of the cylindrical portion 72. The fifth chamfered portion 143 has an inner surface 143a facing the space within the communicating hole 91, which connects one end of the inner surface 141a of the first inclined portion 141 on the first end side in the axial direction of the cylindrical portion 72 to one end of the inner surface 142a of the second inclined portion 142 on the first end side in the axial direction of the cylindrical portion 72.

[0053] The fifth chamfered portion 143, including the inner surface 143a, has an arc shape with its center closer to the second end of the tubular portion 72 in the axial direction than the inner surface 143a. The fifth chamfered portion 143 is a rounded chamfer. The closer the fifth chamfered portion 143 is to the first inclined portion 141 in the circumferential direction of the tubular portion 72, the closer it is to the second end of the tubular portion 72 in the axial direction, including the inner surface 143a. The closer the fifth chamfered portion 143 is to the second end of the tubular portion 72 in the axial direction, including the inner surface 143a, the closer it is to the second inclined portion 142 in the circumferential direction of the tubular portion 72, the closer it is to the second end of the tubular portion 72 in the axial direction, including the inner surface 143a.

[0054] The second circumferential edge 132 extends in the circumferential direction of the tubular portion 72, including an inner surface 132a facing the space within the communicating hole 91. The inner surface 132a of the second circumferential edge 132 is flat and extends along the radial direction of the tubular portion 72. The inner surface 132a is flat and extends perpendicular to the central axis of the tubular portion 72. The second circumferential edge 132 connects the end of the second chamfered portion 113 opposite to the first straight portion 111 and the end of the fourth chamfered portion 123 opposite to the second straight portion 121. The inner surface 132a of the second circumferential edge portion 132 connects the end of the inner surface 113a of the second chamfered portion 113 opposite the inner surface 111a of the first straight portion 111 to the end of the inner surface 123a of the fourth chamfered portion 123 opposite the inner surface 121a of the second straight portion 121.

[0055] As described above, the first circumferential edge portion 131 is provided with the first inclined portion 141 and the second inclined portion 142 as a partial inclined portion formed to be inclined with respect to the axial direction of the tubular portion 72 and located on the first end side of the edge 101 in the axial direction of the tubular portion 72. Note that it is sufficient for the first circumferential edge portion 131 to have at least a partial inclined portion formed to be inclined with respect to the axial direction of the tubular portion 72 and located on the first end side of the edge 101 in the axial direction of the tubular portion 72. The first inclined portion 141 and the second inclined portion 142 are provided on the first end side of the edge 101 in the axial direction of the tubular portion 72. The fifth chamfered portion 143 is provided on the first end of the edge 101 in the axial direction of the tubular portion 72.

[0056] The edge 101 of the communication hole 91 is formed so that a first end in the axial direction of the cylindrical portion 72 is thinner than a second end in the axial direction of the cylindrical portion 72.

[0057] Each corner of the communication hole 91 is rounded to form a first chamfered portion 112, a second chamfered portion 113, a third chamfered portion 122, a fourth chamfered portion 123, and a fifth chamfered portion 143.

[0058] The bumper cap 13 having the above-described shape is made of synthetic resin or metal. When the bumper cap 13 is made of synthetic resin, it is formed by injection molding. When the bumper cap 13 is made of metal, for example, aluminum alloy, it is formed by die casting.

[0059] In both injection molding and die casting, bumper cap 13 is formed by pouring molten material under pressure into a mold cavity having a cavity in the shape of bumper cap 13. In both injection molding and die casting, the portion of the cavity that forms through-hole 81 of lid portion 70 of bumper cap 13 shown in FIG. 2 is used as the material inlet. For example, when injection molding bumper cap 13, a plurality of inlets (e.g., six) are provided at equal intervals in the circumferential direction in the portion that forms inner periphery 82 of through-hole 81 of lid portion 70. When material is poured into the cavity from these inlets, the material flows through the space that forms lid portion 70 of the cavity so as to expand radially outward of lid portion 70, and then flows through the space that forms cylindrical portion 72 of the cavity in the axial direction of cylindrical portion 72, away from the space that forms lid portion 70.

[0060] Here, the mold has a mold portion 200 shown in FIG. 4 for forming the communicating hole 91. This mold portion 200 has a shape similar to the space within the communicating hole 91 shown in FIG. 3. As shown in FIG. 4, the mold portion 200 has an edge-forming surface portion 201 for forming the edge 101 of the communicating hole 91 shown in FIG. 3. The edge-forming surface portion 201 has a first linear portion-forming surface portion 211, a first chamfered portion-forming surface portion 212, a second chamfered portion-forming surface portion 213, a second linear portion-forming surface portion 221, a third chamfered portion-forming surface portion 222, and a fourth chamfered portion-forming surface portion 223. The edge-forming surface portion 201 also has a second circumferential edge-forming surface portion 232, a first inclined portion-forming surface portion 241, a second inclined portion-forming surface portion 242, and a fifth chamfered portion-forming surface portion 243.

[0061] The first linear portion forming surface 211 forms the inner surface 111a of the first linear portion 111 shown in FIG. 3. The first chamfered portion forming surface 212 forms the inner surface 112a of the first chamfered portion 112 shown in FIG. 3. The second chamfered portion forming surface 213 forms the inner surface 113a of the second chamfered portion 113 shown in FIG. 3. The second linear portion forming surface 221 forms the inner surface 121a of the second linear portion 121 shown in FIG. 3. The third chamfered portion forming surface 222 forms the inner surface 122a of the third chamfered portion 122 shown in FIG. 3. The fourth chamfered portion forming surface 223 forms the inner surface 123a of the fourth chamfered portion 123 shown in FIG. 3. The second circumferential edge forming surface 232 forms the inner surface 132a of the second circumferential edge 132 shown in FIG. 3. The first inclined portion-forming surface 241 forms the inner surface 141a of the first inclined portion 141 shown in Fig. 3. The second inclined portion-forming surface 242 forms the inner surface 142a of the second inclined portion 142 shown in Fig. 3. The fifth chamfered portion-forming surface 243 forms the inner surface 143a of the fifth chamfered portion 143 shown in Fig. 3. The angle formed between the first inclined portion-forming surface 241 and the second inclined portion-forming surface 242 is an acute angle.

[0062] In both injection molding and die casting, as described above, the material flows through the space that forms the cylindrical portion 72 of the cavity in the axial direction of the cylindrical portion 72, in a direction away from the space that forms the lid portion 70 (see FIG. 2). That is, the material flows through the space that forms the cylindrical portion 72 of the cavity in the axial direction of the cylindrical portion 72 from the second end side toward the first end side. Therefore, around the periphery of the mold portion 200, as shown by the two-dot chain arrow in FIG. 4, the material flows from the side of the second circumferential edge forming surface 232 opposite the fifth chamfered portion forming surface 243 to the side of the fifth chamfered portion forming surface 243 opposite the second circumferential edge forming surface 232. Then, part of the material is guided in this order to flow along the second chamfered-portion-forming surface 213, the first straight-portion-forming surface 211, the first chamfered-portion-forming surface 212, the first inclined-portion-forming surface 241, and a portion of the fifth chamfered-portion-forming surface 243 on the first inclined-portion-forming surface 241 side. Also, part of the material is guided in this order to flow along the fourth chamfered-portion-forming surface 223, the second straight-portion-forming surface 221, the third chamfered-portion-forming surface 222, the second inclined-portion-forming surface 242, and a portion of the fifth chamfered-portion-forming surface 243 on the second inclined-portion-forming surface 242 side.

[0063] At this time, the distance between the first inclined portion-forming surface 241 and the second inclined portion-forming surface 242 is narrower on the downstream side than on the upstream side along the direction of material flow. As a result, the meeting angle between the material flowing along the first inclined portion-forming surface 241 and the material flowing along the second inclined portion-forming surface 242 becomes larger, allowing them to merge smoothly.

[0064] The edge 101 of the communicating hole 91 shown in FIG. 3 is formed so that the portion of the first circumferential edge 131 constituting the first end located downstream is narrower than the portion of the second circumferential edge 132 constituting the second end located upstream of the flow of material during molding. In other words, the communicating hole 91 of the bumper cap 13 is formed so that the first end located downstream is narrower than the second end located upstream of the flow of material during molding. Furthermore, the edge 101 of the communicating hole 91 of the bumper cap 13 is formed so that the second circumferential edge 132, which is the upstream end of the flow of material during molding, is approximately perpendicular to the flow of material. The communicating hole 91 of the bumper cap 13 has a tapered shape such that the first end located downstream in the direction of flow of material during molding becomes narrower toward the downstream side.

[0065] 2, the bumper cap 13 is attached to the cylinder 21 by covering the end of the barrel 36 of the outer tube 32 of the cylinder 21 from which the piston rod 50 extends in the axial direction of the barrel 36. At this time, the piston rod 50 is inserted into the through-hole 81 of the lid portion 70.

[0066] 1, when the bumper cap 13 is attached to the cylinder 21, the tubular portion 72 radially covers part of the outer circumferential surface 32a of the outer cylinder 32, which is the outer circumferential surface of the cylinder 21. In this state, the lid portion 70 of the bumper cap 13 abuts against the axial end surface 32b of the outer cylinder 32, which is the axial end surface of the cylinder 21 opposite the bottom portion 37 in the axial direction. In this state, the tubular portion 72 abuts against and fits into the outer circumferential surface 32a of the outer cylinder 32, and is fixed to the outer cylinder 32. The outer circumferential surface 32a of the outer cylinder 32 is the outer circumferential surface of the trunk portion 36.

[0067] Note that the bumper cap 13 may have the tubular portion 72 covering the entire outer peripheral surface 32a of the outer cylinder 32, which is the outer peripheral surface of the cylinder 21, on the radially outer side. That is, it is sufficient for the bumper cap 13 to have the tubular portion 72 covering at least a portion of the outer peripheral surface 32a of the outer cylinder 32, which is the outer peripheral surface of the cylinder 21, on the radially outer side.

[0068] When the shock absorber 11 is mounted on a vehicle, one end of a dust boot (not shown) that covers the portion of the piston rod 50 extending from the cylinder 21 is engaged with the flange 73 of the bumper cap 13. The communication hole 91 of the bumper cap 13 forms a flow path for air to flow from the gap between the outer cylinder 32 of the cylinder 21 and the bumper cap 13 to the outside of the bumper cap 13. As a result, dust that has entered the gap between the outer cylinder 32 and the bumper cap 13 from the through hole 81 shown in FIG. 2, for example, is discharged to the outside of the bumper cap 13 by the flow of air that passes from the through hole 81 through the gap between the outer cylinder 32 and the bumper cap 13 and through the communication hole 91 to the outside.

[0069] Patent Document 1 discloses a shock absorber in which the side of the cylinder from which the rod protrudes is covered with a bumper cap. In this shock absorber, the bumper cap has a cylindrical portion formed in a cylindrical shape and a top plate portion formed to close one end of the cylindrical portion, with an opening formed in the cylindrical portion. However, it is desirable to improve the durability of the bumper cap in shock absorbers. For example, when forming the opening during molding of the bumper cap using a mold, if there is a disturbance in the flow of material around the mold portion used to form the opening, surface defects are likely to occur on the surface around the opening. Such surface defects may reduce the strength and durability of the bumper cap.

[0070] In the shock absorber 11 of the first embodiment, the bumper cap 13, which is provided at the end of the cylinder 21 from which the piston rod 50 extends, is molded by die casting or injection molding. The bumper cap 13 has a connecting hole 91, which is provided in the cylindrical portion 72 and connects the inner circumferential surface 72a of the cylindrical portion 72 to the outer circumferential surface 72b of the cylindrical portion 72. The edge 101 of the connecting hole 91 is narrower at a first end located downstream of the connecting hole 91 than at a second end located upstream of the connecting hole 91, where the material flows during molding. This allows the bumper cap 13 to increase the meeting angle between the materials flowing on both sides of the mold portion 200 that forms the connecting hole 91 when they meet downstream, allowing the materials to meet smoothly. This prevents the bumper cap 13 from losing strength due to weld lines, which are surface defects that appear as grooves or patterns where the materials meet. This improves the durability of the bumper cap 13 and the shock absorber 11 that includes the bumper cap 13.

[0071] Furthermore, the shock absorber 11 is formed so that the second circumferential edge 132 of the edge 101 of the communication hole 91 of the bumper cap 13, which is the upstream end of the material that flows in during molding, is approximately perpendicular to the flow of the material. This makes it possible to suppress a decrease in strength of the bumper cap 13 due to the shape of the second circumferential edge 132. This makes it possible to further improve the durability of the bumper cap 13 and the shock absorber 11 that includes it.

[0072] Furthermore, in the shock absorber 11, the corners of the edge 101 of the communication hole 91 of the bumper cap 13 are chamfered to form a first chamfered portion 112, a second chamfered portion 113, a third chamfered portion 122, a fourth chamfered portion 123, and a fifth chamfered portion 143. This allows the material to flow smoothly around the mold portion 200 that forms the communication hole 91 of the bumper cap 13. This further improves the durability of the bumper cap 13 and the shock absorber 11 that includes it.

[0073] Furthermore, since the bumper cap 13 of the shock absorber 11 is made of metal or resin, the bumper cap 13 can be easily formed.

[0074] Furthermore, in the shock absorber 11, at least a portion of a first circumferential edge 131 extending in the circumferential direction of the tubular portion 72 of the edge 101 of the communication hole 91 of the bumper cap 13 is inclined relative to the axial direction of the tubular portion 72, and includes a first inclined portion 141 and a second inclined portion 142 at the end portions of the edge 101 in the axial direction of the tubular portion 72. Therefore, by flowing material along the axial direction of the tubular portion 72, the bumper cap 13 can increase the meeting angle when the material flowing from both sides of the mold portion 200 forming the communication hole 91 in the circumferential direction of the tubular portion 72 meets at the first circumferential edge 131, allowing the material to meet smoothly. Therefore, the bumper cap 13 can suppress a decrease in strength due to the occurrence of weld lines, which are surface defects that appear as grooves or patterns on the surface where the material meets. This improves the durability of the bumper cap 13 and the shock absorber 11 including it.

[0075] Furthermore, in the shock absorber 11, the bumper cap 13 has a first axial edge portion 102 and a second axial edge portion 103 as axial edge portions extending in the axial direction of the tubular portion 72. Furthermore, the bumper cap 13 has, as inclined portions formed to be inclined with respect to the axial direction of the tubular portion 72, a first inclined portion 141 formed to extend at an angle from one axial end of the first axial edge portion 102 and a second inclined portion 142 formed to extend at an angle from one axial end of the second axial edge portion 103. Therefore, the bumper cap 13 can reduce the angle difference between the angle formed by the first axial edge portion 102 and the first inclined portion 141 and the angle formed by the second axial edge portion 103 and the second inclined portion 142. Therefore, by flowing the material along the axial direction of the cylindrical portion 72, the bumper cap 13 can reduce the difference in flow speed between the material flowing on both sides in the circumferential direction of the cylindrical portion 72 of the mold portion 200 that forms the communication hole 91, allowing the material to merge more smoothly. This can further improve the durability of the bumper cap 13 and the shock absorber 11 that includes it.

[0076] Furthermore, the bumper cap 13 of the shock absorber 11 has the first inclined portion 141 and the second inclined portion 142 provided on the first end side in the axial direction of the tubular portion 72. Therefore, by flowing material along the axial direction of the tubular portion 72, the bumper cap 13 can increase the meeting angle when the material flowing toward the first end side on both sides in the circumferential direction of the tubular portion 72 of the mold portion 200 that forms the communication hole 91 join together, allowing the material to join together smoothly. This can improve the durability of the bumper cap 13 and the shock absorber 11 that includes it.

[0077] Furthermore, the bumper cap 13 of the shock absorber 11 is formed so that a first circumferential edge 131 at a first end in the axial direction of the tubular portion 72 is more acutely angled than a second circumferential edge 132 at a second end in the axial direction of the tubular portion 72. Therefore, the bumper cap 13 can suppress the occurrence of weld lines on the first end side while suppressing a decrease in strength due to the shape of the second end side.

[0078] Furthermore, at the edge 101 of the communicating hole 91 of the bumper cap 13, the portion on the second end side including the second circumferential edge portion 132 can also be made mirror-symmetrical to the portion on the first end side including the first circumferential edge portion 131.

[0079] [Second embodiment] A second embodiment of the present invention will be described, focusing on differences from the first embodiment, mainly with reference to Fig. 5. Note that parts common to the first embodiment will be designated by the same names and symbols.

[0080] 5, the second embodiment uses a bumper cap 13A that is partially different from the bumper cap 13 of the first embodiment. The bumper cap 13A has a cylindrical portion 72A that is partially different from the cylindrical portion 72 instead of the cylindrical portion 72. The cylindrical portion 72A has a communicating hole 91A that is partially different from the communicating hole 91 instead of the communicating hole 91. The communicating hole 91A communicates between an outer peripheral surface 72Ab of the cylindrical portion 72A and an inner peripheral surface (not shown).

[0081] The edge 101A of the communicating hole 91A has a first axial edge 102A that is partially different from the first axial edge 102, instead of the first axial edge 102. The edge 101A has a second axial edge 103A that is partially different from the second axial edge 103, instead of the second axial edge 103. Here, in the bumper cap 13A as well, the side of the tubular portion 72A opposite the lid portion 70 (see FIG. 2) in the axial direction is referred to as a first end side, and the side of the tubular portion 72A facing the lid portion 70 in the axial direction is referred to as a second end side. In addition, in the communicating hole 91A, the end of the tubular portion 72A opposite the lid portion 70 in the axial direction is referred to as a first end side, and the end of the tubular portion 72A facing the lid portion 70 in the axial direction is referred to as a second end side.

[0082] The first axial edge 102A has a first chamfered portion 112A instead of the first chamfered portion 112, and has a second chamfered portion 113A instead of the second chamfered portion 113.

[0083] The first chamfered portion 112A extends from an end of the first linear portion 111 closer to the first end in the axial direction of the cylindrical portion 72A toward the first end. The first chamfered portion 112A has an inner surface 112Aa facing the space within the communicating hole 91A extending from an end of the inner surface 111a of the first linear portion 111 closer to the first end in the axial direction of the cylindrical portion 72A toward the first end. The first chamfered portion 112A is a flat chamfer (chamfered) such that the inner surface 112Aa is flat. The closer the first chamfered portion 112A, including the inner surface 112Aa, is to the first end in the axial direction of the cylindrical portion 72A, the closer it is to the second axial edge portion 103A in the circumferential direction of the cylindrical portion 72A. The inner surface 112Aa of the first chamfered portion 112A also extends radially of the cylindrical portion 72A. The angle formed between the inner surface 112Aa and the inner surface 111a is an obtuse angle.

[0084] The second chamfered portion 113A extends from an end of the first linear portion 111 closer to the second end in the axial direction of the cylindrical portion 72A toward the second end. The second chamfered portion 113A has an inner surface 113Aa facing the space within the communicating hole 91A extending from an end of the inner surface 111a of the first linear portion 111 closer to the second end in the axial direction of the cylindrical portion 72A toward the second end. The second chamfered portion 113A is a flat chamfer with the inner surface 113Aa being flat. The closer the second chamfered portion 113A, including the inner surface 113Aa, is to the second end in the axial direction of the cylindrical portion 72A, the closer it is to the second axial edge portion 103A in the circumferential direction of the cylindrical portion 72A. The inner surface 113Aa of the second chamfered portion 113A also extends radially of the cylindrical portion 72A. The angle between the inner surface 113Aa and the inner surface 111a is an obtuse angle and is smaller than the angle between the inner surface 112Aa and the inner surface 111a. The angle between the inner surface 113Aa and the inner surface 111a is equal to the angle between the inner surface 113Aa and the inner surface 132a of the second circumferential edge portion 132.

[0085] The second axial edge 103A has a third chamfered portion 122A instead of the third chamfered portion 122, and has a fourth chamfered portion 123A instead of the fourth chamfered portion 123.

[0086] The third chamfered portion 122A extends from an end of the second straight portion 121 closer to the first end in the axial direction of the tubular portion 72A toward the first end. The third chamfered portion 122A has an inner surface 122Aa that faces the space within the communicating hole 91A extending from an end of the inner surface 121a of the second straight portion 121 closer to the first end in the axial direction of the tubular portion 72A toward the first end. The third chamfered portion 122A is a flat chamfer in which the inner surface 122Aa is flat. The closer the third chamfered portion 122A, including the inner surface 122Aa, is to the first end in the axial direction of the tubular portion 72A, the closer it is to the first axial edge portion 102A in the circumferential direction of the tubular portion 72A. The inner surface 122Aa of the third chamfered portion 122A also extends radially of the tubular portion 72A. The third chamfered portion 122A is aligned with the first chamfered portion 112A in the axial direction of the cylindrical portion 72A and is spaced apart in the circumferential direction of the cylindrical portion 72A, forming a mirror image thereof.

[0087] The fourth chamfered portion 123A extends from an end of the second straight portion 121 closer to the second end in the axial direction of the tubular portion 72A toward the second end. The fourth chamfered portion 123A has an inner surface 123Aa facing the space within the communicating hole 91A extending from an end of the inner surface 121a of the second straight portion 121 closer to the second end in the axial direction of the tubular portion 72A toward the second end. The fourth chamfered portion 123A is a flat chamfer with the inner surface 123Aa being flat. The closer the fourth chamfered portion 123A, including the inner surface 123Aa, is to the second end in the axial direction of the tubular portion 72A, the closer it is to the first axial edge portion 102A in the circumferential direction of the tubular portion 72A. The inner surface 123Aa of the fourth chamfered portion 123A also extends radially of the tubular portion 72A. The angle between the inner surface 123Aa and the inner surface 121a is an obtuse angle and is smaller than the angle between the inner surface 122Aa and the inner surface 121a. The angle between the inner surface 123Aa and the inner surface 121a is equal to the angle between the inner surface 123Aa and the inner surface 132a of the second circumferential edge 132. The fourth chamfered portion 123A is aligned with the second chamfered portion 113A in the axial direction of the tubular portion 72A and is spaced apart circumferentially of the tubular portion 72A, forming a mirror image thereof.

[0088] The edge 101A has a first circumferential edge 131A instead of the first circumferential edge 131. The first circumferential edge 131A is a mirror image and has a fifth chamfer 143A instead of the fifth chamfer 143.

[0089] The fifth chamfered portion 143A connects one end of the first inclined portion 141 that is closer to the first end in the axial direction of the cylindrical portion 72A to one end of the second inclined portion 142 that is closer to the first end in the axial direction of the cylindrical portion 72A. The fifth chamfered portion 143A has an inner surface 143Aa that faces the space within the communicating hole 91A and connects one end of the inner surface 141a of the first inclined portion 141 that is closer to the first end in the axial direction of the cylindrical portion 72A to one end of the inner surface 142a of the second inclined portion 142 that is closer to the first end in the axial direction of the cylindrical portion 72A.

[0090] The fifth chamfered portion 143A is a flat chamfer with a flat inner surface 143Aa. The angle between the inner surface 143Aa of the fifth chamfered portion 143A and the inner surface 141a of the first inclined portion 141 is equal to the angle between the inner surface 142a of the second inclined portion 142. The angle between the inner surface 112Aa and the inner surface 141a is equal to the angle between the inner surface 112Aa and the inner surface 111a. The angle between the inner surface 122Aa and the inner surface 142a is equal to the angle between the inner surface 122Aa and the inner surface 121a.

[0091] As described above, the first circumferential edge 131A is formed to be inclined with respect to the axial direction of the tubular portion 72A and includes a first inclined portion 141 and a second inclined portion 142 as a portion of the edge 101A that is on the first end side in the axial direction of the tubular portion 72A. The fifth chamfered portion 143A is provided at the first end side in the axial direction of the tubular portion 72A of the edge 101A.

[0092] An edge 101A of the communication hole 91A is formed so that a first end in the axial direction of the cylindrical portion 72A is thinner than a second end in the axial direction of the cylindrical portion 72A.

[0093] Each corner of the communication hole 91A is chamfered to form a first chamfered portion 112A, a second chamfered portion 113A, a third chamfered portion 122A, a fourth chamfered portion 123A, and a fifth chamfered portion 143A.

[0094] Like bumper cap 13, bumper cap 13A having the shape described above is formed by injection molding of a synthetic resin material or die-casting of an aluminum alloy material. In both injection molding and die-casting, like bumper cap 13, the portion of the cavity that forms through-hole 81 (see FIG. 2) of lid portion 70 of bumper cap 13A (see FIG. 2) serves as the material inlet. When the material is poured into the cavity from the inlet, the material flows through the space that forms lid portion 70 of the cavity so as to expand radially outward of lid portion 70, and then flows through the space that forms tubular portion 72A of the cavity in the axial direction of tubular portion 72A, away from the space that forms lid portion 70. That is, the material flows through the space that forms tubular portion 72A of the cavity in the axial direction of tubular portion 72A, from the second end side to the first end side.

[0095] The edge 101A of the communicating hole 91A is formed so that the portion of the first circumferential edge 131A, which constitutes the first end located downstream, is narrower than the portion of the second circumferential edge 132, which constitutes the second end located upstream in the direction of material flow during molding. In other words, the communicating hole 91A of the bumper cap 13A is formed so that the first end located downstream is narrower than the second end located upstream in the direction of material flow during molding. Furthermore, the edge 101A of the communicating hole 91A of the bumper cap 13A is formed so that the second circumferential edge 132, which is the upstream end of the material flowing during molding, is approximately perpendicular to the flow of the material. The communicating hole 91A of the bumper cap 13A has a tapered shape such that the first end located downstream in the direction of material flow during molding becomes narrower toward the downstream side.

[0096] In the second embodiment, the bumper cap 13A has a tubular portion 72A with a connecting hole 91A. The rim 101A is narrower at its downstream end than at its upstream end, where the material flows during molding. This allows the bumper cap 13A to increase the meeting angle between the materials flowing on both sides of the mold portion forming the connecting hole 91A when they meet downstream, ensuring a smooth merger. This prevents the bumper cap 13A from losing strength due to weld lines, which are surface defects that appear as grooves or patterns on the surface where the materials meet. This improves the durability of the bumper cap 13A.

[0097] Additionally, the corners of the edge 101A of the communication hole 91A of the bumper cap 13A are chamfered to form a first chamfered portion 112A, a second chamfered portion 113A, a third chamfered portion 122A, a fourth chamfered portion 123A, and a fifth chamfered portion 143A. This allows the material to flow smoothly around the mold portion that forms the communication hole 91A of the bumper cap 13A. This further improves the durability of the bumper cap 13A.

[0098] In addition, at the edge 101A of the communicating hole 91A of the bumper cap 13A, the portion on the second end side including the second circumferential edge portion 132 can also be made mirror-symmetrical to the portion on the first end side including the first circumferential edge portion 131A.

[0099] [Third embodiment] A third embodiment of the present invention will be described, focusing on differences from the first embodiment, mainly with reference to Fig. 6. Note that parts common to the first embodiment will be designated by the same names and symbols.

[0100] In the third embodiment, as shown in Fig. 6, a bumper cap 13B that is partially different from the bumper cap 13 of the first embodiment is used. The bumper cap 13B has a cylindrical portion 72B that is partially different from the cylindrical portion 72 instead of the cylindrical portion 72. The cylindrical portion 72B has a communicating hole 91B that is partially different from the communicating hole 91 instead of the communicating hole 91. The communicating hole 91B communicates between an outer peripheral surface 72Bb of the cylindrical portion 72B and an inner peripheral surface (not shown).

[0101] The edge 101B of the communicating hole 91B has a first axial edge 102B that is partially different from the first axial edge 102, instead of the first axial edge 102. The edge 101B has a second axial edge 103B that is partially different from the second axial edge 103, instead of the second axial edge 103. Here, in the bumper cap 13B as well, the side of the tubular portion 72B opposite the lid portion 70 (see FIG. 2) in the axial direction is referred to as the first end side, and the side of the tubular portion 72B facing the lid portion 70 in the axial direction is referred to as the second end side. In addition, in the communicating hole 91B, the end of the tubular portion 72B opposite the lid portion 70 in the axial direction is referred to as the first end, and the end of the tubular portion 72B facing the lid portion 70 in the axial direction is referred to as the second end.

[0102] The first axial edge portion 102B does not have the first chamfered portion 112 or the second chamfered portion 113. The first axial edge portion 102B has a shape in which the first linear portion 111 is simply elongated in the axial direction of the tubular portion 72B by the amount corresponding to the absence of the first chamfered portion 112 or the second chamfered portion 113. The first axial edge portion 102B has an inner surface 102Ba which is simply elongated in the axial direction of the tubular portion 72B from the inner surface 111a of the first linear portion 111.

[0103] The second axial edge portion 103B does not have the third chamfered portion 122 or the fourth chamfered portion 123. The second axial edge portion 103B has a shape in which the second straight portion 121 is simply elongated in the axial direction of the tubular portion 72B by the amount corresponding to the absence of the third chamfered portion 122 and the fourth chamfered portion 123. The second axial edge portion 103B has an inner surface 103Ba which is simply elongated in the axial direction of the tubular portion 72B from the inner surface 121a of the second straight portion 121.

[0104] The edge 101B has a first circumferential edge portion 131B instead of the first circumferential edge portion 131. The first circumferential edge portion 131B has a first inclined portion 141B instead of the first inclined portion 141, and a second inclined portion 142B instead of the second inclined portion 142. The first circumferential edge portion 131B does not have the fifth chamfered portion 143.

[0105] The first inclined portion 141B has a shape that is the same as the first inclined portion 141 but longer in the axial and circumferential directions of the cylindrical portion 72B by the amount where the fifth chamfered portion 143 is not provided and the amount where the first chamfered portion 112 is not provided on the first axial edge portion 102B. The first inclined portion 141B has an inner surface 141Ba that is the same as the inner surface 141a of the first inclined portion 141 but longer in the axial and circumferential directions of the cylindrical portion 72B.

[0106] The second inclined portion 142B has a shape that is the same as the second inclined portion 142 but longer in the axial and circumferential directions of the tubular portion 72B due to the absence of the fifth chamfered portion 143 and the absence of the third chamfered portion 122 on the second axial edge portion 103B. The second inclined portion 142B has an inner surface 142Ba that is the same as the inner surface 142a of the second inclined portion 142 but longer in the axial and circumferential directions of the tubular portion 72B. The end of the first inclined portion 141B on the first end side in the axial direction of the tubular portion 72B is connected to the end of the second inclined portion 142B on the first end side in the axial direction of the tubular portion 72B. The end of the inner surface 141Ba on the first end side in the axial direction of the tubular portion 72B is connected to the end of the inner surface 142Ba on the first end side in the axial direction of the tubular portion 72B.

[0107] The edge 101B has a second circumferential edge 132B instead of the second circumferential edge 132. The second circumferential edge 132B has a shape that is the same as the second circumferential edge 132 but longer in the circumferential direction of the tubular portion 72B by the amount corresponding to the first axial edge 102B where the second chamfered portion 113 is not provided and the second axial edge 103B where the fourth chamfered portion 123 is not provided. The second circumferential edge 132B has an inner surface 132Ba that is the same as the inner surface 132a of the second circumferential edge 132 but longer in the circumferential direction of the tubular portion 72B.

[0108] As a result of the above, the first circumferential edge portion 131B has a first inclined portion 141B and a second inclined portion 142B as inclined portions formed to be inclined with respect to the axial direction of the tubular portion 72B and which form the first end portion of the edge 101B in the axial direction of the tubular portion 72B.

[0109] An edge 101B of the communication hole 91B is formed so that a first end in the axial direction of the cylindrical portion 72B is narrower than a second end in the axial direction of the cylindrical portion 72B.

[0110] Like bumper cap 13, bumper cap 13B having the shape described above is formed by injection molding of a synthetic resin material or die-casting of an aluminum alloy material. In both injection molding and die-casting, like bumper cap 13, the portion of the cavity that forms through-hole 81 (see FIG. 2) of lid portion 70 of bumper cap 13B (see FIG. 2) serves as the material inlet. When the material is poured into the cavity from the inlet, the material flows through the space that forms lid portion 70 of the cavity so as to expand radially outward of lid portion 70, and then flows through the space that forms tubular portion 72B of the cavity in the axial direction of tubular portion 72B, away from the space that forms lid portion 70. That is, the material flows through the space that forms tubular portion 72B of the cavity in the axial direction of tubular portion 72B from the second end side toward the first end side.

[0111] The edge 101B of the communicating hole 91B is formed so that the portion on the side of the first circumferential edge 131B constituting the first end located downstream is narrower than the portion on the side of the second circumferential edge 132B constituting the second end located upstream in the direction of material flow during molding. In other words, the communicating hole 91B of the bumper cap 13B is formed so that the first end located downstream in the direction of material flow during molding is narrower than the second end located upstream in the direction of material flow during molding. Furthermore, the edge 101B of the communicating hole 91B of the bumper cap 13B is formed so that the second circumferential edge 132B, which is the upstream end of the material flowing during molding, is approximately perpendicular to the flow of material. The communicating hole 91B of the bumper cap 13B has a tapered shape such that the first end located downstream in the direction of material flow during molding becomes narrower toward the downstream side.

[0112] In the third embodiment, the bumper cap 13B has a tubular portion 72B with a connecting hole 91B. The rim 101B is narrower at its first end, located downstream, than at its second end, located upstream, where the material flows during molding. This allows the bumper cap 13B to increase the meeting angle between the materials flowing on both sides of the mold portion forming the connecting hole 91B when they meet downstream, ensuring a smooth merger. This prevents the bumper cap 13B from losing strength due to weld lines, which are surface defects that appear as grooves or patterns on the surface where the materials meet. This improves the durability of the bumper cap 13B.

[0113] In addition, at the edge 101B of the communicating hole 91B of the bumper cap 13B, the portion on the second end side including the second circumferential edge portion 132B can be made mirror-symmetrical to the portion on the first end side including the first circumferential edge portion 131B.

[0114] [Fourth embodiment] A fourth embodiment of the present invention will be described, focusing on differences from the third embodiment, mainly with reference to Fig. 7. Note that parts common to the third embodiment will be designated by the same names and symbols.

[0115] In the fourth embodiment, as shown in FIG. 7, a bumper cap 13C that is partially different from the bumper cap 13B of the third embodiment is used. The bumper cap 13C has a cylindrical portion 72C that is partially different from the cylindrical portion 72B instead of the cylindrical portion 72B. The cylindrical portion 72C has a communicating hole 91C that is partially different from the communicating hole 91B instead of the communicating hole 91B. The communicating hole 91C communicates between the outer peripheral surface 72Cb of the cylindrical portion 72C and an inner peripheral surface (not shown). Here, in the bumper cap 13C, the side of the cylindrical portion 72C opposite the lid portion 70 (see FIG. 2) in the axial direction is referred to as a first end side, and the side of the cylindrical portion 72C facing the lid portion 70 in the axial direction is referred to as a second end side. In addition, in the communication hole 91C, the end of the cylindrical portion 72C opposite the lid portion 70 in the axial direction is defined as a first end, and the end of the cylindrical portion 72C on the lid portion 70 side in the axial direction is defined as a second end.

[0116] The edge 101C of the communication hole 91C has a first circumferential edge portion 131C instead of the first circumferential edge portion 131B. The first circumferential edge portion 131C has a first inclined portion 141C instead of the first inclined portion 141B, and has a second inclined portion 142C instead of the second inclined portion 142B.

[0117] The first inclined portion 141C is formed to extend at an angle relative to the first axial edge portion 102B from one end of the first axial edge portion 102B that is closer to the first end in the axial direction of the cylindrical portion 72C. The first inclined portion 141C is arc-shaped, including an inner surface 141Ca that faces the space within the communication hole 91C. The first inclined portion 141C is arc-shaped, including the inner surface 141Ca, with its center located closer to the second end of the cylindrical portion 72C in the axial direction than the inner surface 141Ca. The inner surface 141Ca of the first inclined portion 141C is cylindrical and extends radially of the cylindrical portion 72C.

[0118] The first inclined portion 141C extends from one end of the first axial edge portion 102B on the first end side in the axial direction of the tubular portion 72C toward the first end in the axial direction of the tubular portion 72C. Moreover, the closer the first inclined portion 141C is to the first end side in the axial direction of the tubular portion 72C, the closer it is to the second axial edge portion 103B in the circumferential direction of the tubular portion 72C. The inner surface 141Ca of the first inclined portion 141C extends from one end of the inner surface 102Ba of the first axial edge portion 102B on the first end side in the axial direction of the tubular portion 72C toward the first end in the axial direction of the tubular portion 72C. Moreover, the closer the inner surface 141Ca of the first inclined portion 141C is to the first end side in the axial direction of the tubular portion 72C, the closer it is to the second axial edge portion 103B in the circumferential direction of the tubular portion 72C.

[0119] The second inclined portion 142C is formed to extend at an angle relative to the second axial edge portion 103B from one end of the second axial edge portion 103B that is closer to the first end in the axial direction of the cylindrical portion 72C. The second inclined portion 142C is arc-shaped, including an inner surface 142Ca that faces the space within the communicating hole 91C. The second inclined portion 142C is arc-shaped, including the inner surface 142Ca, with its center located closer to the second end in the axial direction of the cylindrical portion 72C than the inner surface 142Ca. The inner surface 142Ca of the second inclined portion 142C is cylindrical and extends radially of the cylindrical portion 72C.

[0120] The second inclined portion 142C extends from one end of the second axial edge portion 103B on the first end side in the axial direction of the tubular portion 72C toward the first end side in the axial direction of the tubular portion 72C. Moreover, the closer the second inclined portion 142C is to the first end side in the axial direction of the tubular portion 72C, the closer it is to the first axial edge portion 102B in the circumferential direction of the tubular portion 72C. The inner surface 142Ca of the second inclined portion 142C extends from one end of the inner surface 103Ba of the second axial edge portion 103B on the first end side in the axial direction of the tubular portion 72C toward the first end side in the axial direction of the tubular portion 72C. Moreover, the closer the inner surface 142Ca of the second inclined portion 142C is to the first axial edge portion 102B in the circumferential direction of the tubular portion 72C, the closer it is to the first end side in the axial direction of the tubular portion 72C. The second inclined portion 142C is mirror-symmetrical to the first inclined portion 141C, with the second inclined portion 142C positioned in the axial direction of the cylindrical portion 72C. An inner surface 141Ca of the first inclined portion 141C and an inner surface 142Ca of the second inclined portion 142C are the same continuous cylindrical surface.

[0121] As a result of the above, the first circumferential edge portion 131C has a first inclined portion 141C and a second inclined portion 142C as inclined portions formed to be inclined with respect to the axial direction of the tubular portion 72C and which form the first end portion of the edge 101C in the axial direction of the tubular portion 72C.

[0122] An edge 101C of the communication hole 91C is formed so that a first end in the axial direction of the cylindrical portion 72C is thinner than a second end in the axial direction of the cylindrical portion 72C.

[0123] Like the bumper cap 13, the bumper cap 13C having the above-described shape is formed by injection molding of a synthetic resin material or die-casting of an aluminum alloy material. In both injection molding and die-casting, like the bumper cap 13, the portion of the cavity that forms the through-hole 81 (see FIG. 2) of the lid portion 70 of the bumper cap 13C (see FIG. 2) serves as the material inlet. When the material is poured into the cavity from the inlet, the material flows through the space that forms the lid portion 70 of the cavity so as to expand radially outward of the lid portion 70, and then flows through the space that forms the tubular portion 72C of the cavity in the axial direction of the tubular portion 72C, away from the space that forms the lid portion 70. That is, the material flows through the space that forms the tubular portion 72C of the cavity in the axial direction of the tubular portion 72C, from the second end side toward the first end side.

[0124] The edge 101C of the communication hole 91C is formed so that the first circumferential edge 131C, which constitutes the first end located downstream, is narrower than the portion on the side of the second circumferential edge 132B, which constitutes the second end located upstream in the direction of material flow during molding. In other words, the communication hole 91C of the bumper cap 13C is formed so that the first end located downstream is narrower than the second end located upstream in the direction of material flow during molding. Furthermore, the edge 101C of the communication hole 91C of the bumper cap 13C is formed so that the second circumferential edge 132B, which is the upstream end of the material flowing during molding, is approximately perpendicular to the flow of the material. The communication hole 91C of the bumper cap 13C has a tapered shape such that the first end located downstream in the direction of material flow during molding becomes narrower toward the downstream side.

[0125] In the fourth embodiment, the bumper cap 13C has a tubular portion 72C with a connecting hole 91C. The rim 101C is narrower at its downstream end than at its upstream end, where the material flows during molding. This allows the bumper cap 13C to increase the meeting angle between the materials flowing on both sides of the mold portion forming the connecting hole 91C when they meet downstream, ensuring a smooth merger. This prevents the bumper cap 13C from losing strength due to weld lines, which are surface defects that appear as grooves or patterns at the material merging points. This improves the durability of the bumper cap 13C.

[0126] Furthermore, at the edge 101C of the communicating hole 91C of the bumper cap 13C, the portion on the second end side including the second circumferential edge portion 132B can be made mirror-symmetrical to the portion on the first end side including the first circumferential edge portion 131C.

[0127] [Fifth embodiment] The fifth embodiment of the present invention will be described, focusing on the differences from the first embodiment, mainly with reference to Fig. 8. Note that parts common to the first embodiment will be designated by the same names and symbols.

[0128] In the fifth embodiment, as shown in FIG. 8, a bumper cap 13D that is partially different from the bumper cap 13 of the first embodiment is used instead of the bumper cap 13 of the first embodiment. The bumper cap 13D has a tubular portion 72D that is partially different from the tubular portion 72 instead of the tubular portion 72. The tubular portion 72D has a communicating hole 91D that is partially different from the communicating hole 91 instead of the communicating hole 91. The communicating hole 91D communicates between the outer peripheral surface 72Db of the tubular portion 72D and an inner peripheral surface (not shown). Here, in the bumper cap 13D, the side of the tubular portion 72D opposite the lid portion 70 (see FIG. 2) in the axial direction is referred to as a first end side, and the side of the tubular portion 72D facing the lid portion 70 in the axial direction is referred to as a second end side. Furthermore, in the communicating hole 91D, the end of the tubular portion 72D opposite the lid portion 70 in the axial direction is referred to as a first end side, and the end of the tubular portion 72D facing the lid portion 70 in the axial direction is referred to as a second end side.

[0129] The edge 101D of the communication hole 91D is in the shape of a closed loop. The edge 101D has a first axial edge portion 102D and a second axial edge portion 103D as axial edge portions extending in the axial direction of the cylindrical portion 72D. The first axial edge portion 102D and the second axial edge portion 103D are aligned in the axial direction of the cylindrical portion 72D, spaced apart in the circumferential direction of the cylindrical portion 72D, and are mirror-symmetrical.

[0130] The first axial edge portion 102D extends in the axial direction of the tubular portion 72D, including an inner surface 102Da that faces the space within the communicating hole 91D. The first axial edge portion 102D, including the inner surface 102Da, is curved with the center of curvature on the second axial edge portion 103D side in the circumferential direction of the tubular portion 72D. The inner surface 102Da of the first axial edge portion 102D also extends radially of the tubular portion 72D and is curved.

[0131] The second axial edge portion 103D extends in the axial direction of the tubular portion 72D, including an inner surface 103Da facing the space within the communicating hole 91D. The second axial edge portion 103D, including the inner surface 103Da, is curved with the center of curvature on the first axial edge portion 102D side in the circumferential direction of the tubular portion 72D. The inner surface 103Da of the second axial edge portion 103D is also curved along the radial direction of the tubular portion 72D. The second axial edge portion 103D is aligned with the first axial edge portion 102D in the axial direction of the tubular portion 72D and is spaced apart in the circumferential direction of the tubular portion 72D, forming a mirror image.

[0132] The edge 101D has a first circumferential edge portion 131D and a second circumferential edge portion 132D as circumferential edge portions extending in the circumferential direction of the tubular portion 72D. The edge 101D has the first circumferential edge portion 131D at an end portion on the first end side in the axial direction of the tubular portion 72D. The edge 101D has the second circumferential edge portion 132D at an end portion on the second end side in the axial direction of the tubular portion 72D. The first circumferential edge portion 131D and the second circumferential edge portion 132D are mirror symmetrical.

[0133] The first circumferential edge 131D is mirror-symmetric and has a first inclined portion 141D and a second inclined portion 142D.

[0134] The first inclined portion 141D is formed to extend from one end of the first axial edge portion 102D on the first end side in the axial direction of the cylindrical portion 72D at an angle relative to the first axial edge portion 102D of the first axial edge portion 102D. The first inclined portion 141D, including an inner surface 141Da facing the space within the communication hole 91D, is curved with the center of curvature on the second axial edge portion 103D side in the circumferential direction of the cylindrical portion 72D. The inner surface 141Da of the first inclined portion 141D also extends radially of the cylindrical portion 72D and is curved.

[0135] The first inclined portion 141D extends from one end of the first axial edge portion 102D on the first end side in the axial direction of the tubular portion 72D toward the first end in the axial direction of the tubular portion 72D. Moreover, the closer the first inclined portion 141D is to the first end side in the axial direction of the tubular portion 72D, the closer it is to the second axial edge portion 103D in the circumferential direction of the tubular portion 72D. The inner surface 141Da of the first inclined portion 141D extends from one end of the inner surface 102Da of the first axial edge portion 102D on the first end side in the axial direction of the tubular portion 72D toward the first end in the axial direction of the tubular portion 72D. Moreover, the closer the inner surface 141Da of the first inclined portion 141D is to the first end side in the axial direction of the tubular portion 72D, the closer it is to the second axial edge portion 103D in the circumferential direction of the tubular portion 72D.

[0136] The second inclined portion 142D is formed to extend from one end of the second axial edge portion 103D on the first end side in the axial direction of the cylindrical portion 72D at an angle relative to the second axial edge portion 103D. The second inclined portion 142D, including an inner surface 142Da facing the space within the communication hole 91D, is curved with the center of curvature on the first axial edge portion 102D side in the circumferential direction of the cylindrical portion 72D. The inner surface 142Da of the second inclined portion 142D also extends radially of the cylindrical portion 72D and is curved.

[0137] The second inclined portion 142D extends from one end of the second axial edge portion 103D on the first end side in the axial direction of the tubular portion 72D toward the first end side in the axial direction of the tubular portion 72D. Moreover, the closer the second inclined portion 142D is to the first end side in the axial direction of the tubular portion 72D, the closer it is to the first axial edge portion 102D in the circumferential direction of the tubular portion 72D. The inner surface 142Da of the second inclined portion 142D extends from one end of the inner surface 103Da of the second axial edge portion 103D on the first end side in the axial direction of the tubular portion 72D toward the first end side in the axial direction of the tubular portion 72D. Moreover, the closer the inner surface 142Da of the second inclined portion 142D is to the first axial edge portion 102D in the circumferential direction of the tubular portion 72D, the closer it is to the first end side in the axial direction of the tubular portion 72D. The second inclined portion 142D is mirror-symmetrical to the first inclined portion 141D, with the second inclined portion 142D positioned in the axial direction of the cylindrical portion 72D.

[0138] The second circumferential edge 132D is mirror-symmetric and has a third inclined portion 151D and a fourth inclined portion 152D.

[0139] The third inclined portion 151D is formed to extend at an angle relative to the first axial edge portion 102D from one end of the first axial edge portion 102D that is closer to the second end in the axial direction of the cylindrical portion 72D. The third inclined portion 151D, including an inner surface 151Da that faces the space within the communication hole 91D, is curved with the center of curvature on the second axial edge portion 103D side in the circumferential direction of the cylindrical portion 72D. The inner surface 151Da of the third inclined portion 151D also extends radially of the cylindrical portion 72D and is curved.

[0140] The third inclined portion 151D extends from one end of the first axial edge portion 102D on the second end side in the axial direction of the tubular portion 72D toward the second end side in the axial direction of the tubular portion 72D. Moreover, the closer the third inclined portion 151D is to the second axial edge portion 103D in the circumferential direction of the tubular portion 72D, the closer it is to the second axial edge portion 103D in the circumferential direction of the tubular portion 72D. The inner surface 151Da of the third inclined portion 151D extends from one end of the inner surface 102Da of the first axial edge portion 102D on the second end side in the axial direction of the tubular portion 72D toward the second end side in the axial direction of the tubular portion 72D. Moreover, the closer the inner surface 151Da of the third inclined portion 151D is to the second axial edge portion 103D in the circumferential direction of the tubular portion 72D, the closer it ... end side in the axial direction of the tubular portion 72D.

[0141] The fourth inclined portion 152D is formed to extend at an angle relative to the second axial edge portion 103D from one end of the second axial edge portion 103D that is closer to the second end in the axial direction of the cylindrical portion 72D. The fourth inclined portion 152D, including an inner surface 152Da that faces the space within the communication hole 91D, is curved with the center of curvature on the first axial edge portion 102D side in the circumferential direction of the cylindrical portion 72D. The inner surface 152Da of the fourth inclined portion 152D also extends radially of the cylindrical portion 72D and is curved.

[0142] The fourth inclined portion 152D extends from one end of the second axial edge portion 103D on the second end side in the axial direction of the tubular portion 72D toward the second end side in the axial direction of the tubular portion 72D. Moreover, the closer the fourth inclined portion 152D is to the second end side in the axial direction of the tubular portion 72D, the closer it is to the first axial edge portion 102D in the circumferential direction of the tubular portion 72D. The inner surface 152Da of the fourth inclined portion 152D extends from one end of the inner surface 103Da of the second axial edge portion 103D on the second end side in the axial direction of the tubular portion 72D toward the second end side in the axial direction of the tubular portion 72D. Moreover, the closer the inner surface 152Da of the fourth inclined portion 152D is to the second end side in the axial direction of the tubular portion 72D, the closer it is to the first axial edge portion 102D in the circumferential direction of the tubular portion 72D. The fourth inclined portion 152D is mirror-symmetrical to the third inclined portion 151D, with the fourth inclined portion 152D being positioned in the axial direction of the cylindrical portion 72D.

[0143] The first axial edge portion 102D, the second axial edge portion 103D, the first inclined portion 141D, the second inclined portion 142D, the third inclined portion 151D, and the fourth inclined portion 152D have the same continuous elliptical shape. The inner surfaces 102Da, 103Da, 141Da, 142Da, 151Da, and 152Da have the same continuous elliptical shape.

[0144] As described above, the first circumferential edge 131D includes a first inclined portion 141D and a second inclined portion 142D as inclined portions formed to be inclined with respect to the axial direction of the tubular portion 72D and serving as a first end portion of the edge 101D in the axial direction of the tubular portion 72D. The second circumferential edge 132D includes a third inclined portion 151D and a fourth inclined portion 152D as inclined portions formed to be inclined with respect to the axial direction of the tubular portion 72D and serving as a second end portion of the edge 101D in the axial direction of the tubular portion 72D.

[0145] Like the bumper cap 13, the bumper cap 13D having the above-described shape is formed by injection molding of a synthetic resin material or die-casting of an aluminum alloy material. In both injection molding and die-casting, like the bumper cap 13, the portion of the cavity that forms the through-hole 81 (see FIG. 2) of the lid portion 70 of the bumper cap 13D (see FIG. 2) serves as the material inlet. When the material is poured into the cavity from the inlet, the material flows through the space that forms the lid portion 70 of the cavity so as to expand radially outward of the lid portion 70, and then flows through the space that forms the tubular portion 72D of the cavity in the axial direction of the tubular portion 72D, away from the space that forms the lid portion 70. That is, the material flows through the space that forms the tubular portion 72D of the cavity in the axial direction of the tubular portion 72D from the second end side toward the first end side.

[0146] In the fifth embodiment, the bumper cap 13D includes a first circumferential edge 131D extending circumferentially around the cylindrical portion 72D of the edge 101D of the communication hole 91D. The first sloping edge 131D is inclined relative to the axial direction of the cylindrical portion 72D, and includes a first inclined portion 141D and a second inclined portion 142D, which are the axial ends of the edge 101D. Therefore, by flowing material along the axial direction of the cylindrical portion 72D, the bumper cap 13D can increase the meeting angle when the material flows from both circumferential sides of the cylindrical portion 72D of the mold part forming the communication hole 91D meet at the first circumferential edge 131D, allowing the material to meet smoothly. Therefore, the bumper cap 13D can suppress a decrease in strength due to the occurrence of weld lines, which are surface defects that appear as grooves or patterns at the material meeting points. This improves the durability of the bumper cap 13D.

[0147] The bumper cap 13D also has a first axial edge portion 102D and a second axial edge portion 103D as axial edge portions extending in the axial direction of the tubular portion 72D. The bumper cap 13D also has, as inclined portions formed to be inclined with respect to the axial direction of the tubular portion 72D, a first inclined portion 141D formed to extend at an angle from one axial end of the first axial edge portion 102D and a second inclined portion 142D formed to extend at an angle from one axial end of the second axial edge portion 103D. Therefore, the bumper cap 13D can reduce the angle difference between the angle formed between the first axial edge portion 102D and the first inclined portion 141D and the angle formed between the second axial edge portion 103D and the second inclined portion 142D. Therefore, by flowing the material along the axial direction of the cylindrical portion 72D, the bumper cap 13D can reduce the difference in flow speed between the material flowing on both sides in the circumferential direction of the cylindrical portion 72D of the mold portion that forms the communication hole 91D, allowing the material to merge more smoothly, thereby further improving the durability of the bumper cap 13D.

[0148] Furthermore, bumper cap 13D has first inclined portion 141D and second inclined portion 142D provided at a first axial end of tubular portion 72D. Therefore, by flowing material along the axial direction of tubular portion 72D, bumper cap 13D can increase the meeting angle when the material flowing toward the first end on both circumferential sides of tubular portion 72D of the mold portion that forms communication hole 91D meets, allowing the material to meet smoothly. This improves the durability of bumper cap 13D.

[0149] Furthermore, in the bumper cap 13D, the first inclined portion 141D and the second inclined portion 142D are provided on the first axial end side of the tubular portion 72D, and the third inclined portion 151D and the fourth inclined portion 152D are provided on the second axial end side of the tubular portion 72D. Furthermore, in the bumper cap 13D, the first inclined portion 141D and the second inclined portion 142D and the third inclined portion 151D and the fourth inclined portion 152D are formed symmetrically. This allows the material to flow smoothly around the mold portion that forms the communication hole 91D. This improves the durability of the bumper cap 13D.

[0150] [Sixth embodiment] The sixth embodiment of the present invention will be described mainly with reference to Fig. 9, focusing on the differences from the third embodiment. Note that parts common to the third embodiment will be designated by the same names and symbols.

[0151] In the sixth embodiment, as shown in FIG. 9, a bumper cap 13E that is partially different from the bumper cap 13B of the third embodiment is used. The bumper cap 13E has a cylindrical portion 72E that is partially different from the cylindrical portion 72B instead of the cylindrical portion 72B. The cylindrical portion 72E has a communicating hole 91E that is partially different from the communicating hole 91B instead of the communicating hole 91B. The communicating hole 91E communicates between the outer peripheral surface 72Eb of the cylindrical portion 72E and an inner peripheral surface (not shown). Here, in the bumper cap 13E, the side of the cylindrical portion 72E opposite the lid portion 70 (see FIG. 2) in the axial direction is referred to as a first end side, and the side of the cylindrical portion 72E facing the lid portion 70 in the axial direction is referred to as a second end side. In addition, in the communication hole 91E, the end of the cylindrical portion 72E opposite the lid portion 70 in the axial direction is defined as a first end, and the end of the cylindrical portion 72E on the lid portion 70 side in the axial direction is defined as a second end.

[0152] An edge 101E of the communicating hole 91E has a first axial edge portion 102E that is partially different from the first axial edge portion 102B. The first axial edge portion 102E differs from the first axial edge portion 102B in that the axial length of the tubular portion 72E is longer than the first axial edge portion 102B. An inner surface 102Ea of the first axial edge portion 102E that faces the space within the communicating hole 91E also differs from an inner surface 102Ba of the first axial edge portion 102B in that the axial length of the tubular portion 72E is longer than the inner surface 102Ba.

[0153] The edge 101E of the communicating hole 91E has a first circumferential edge 131E (inclined portion) instead of the first circumferential edge 131B. The first circumferential edge 131E is formed to extend from one end of the second axial edge 103B on the first end side in the axial direction of the cylindrical portion 72E at an angle relative to the second axial edge 103B. The end of the first circumferential edge 131E opposite the second axial edge 103B is connected to one end of the first axial edge 102E on the first end side in the axial direction of the cylindrical portion 72E. The first circumferential edge 131E is linear, including an inner surface 131Ea facing the space within the communicating hole 91E. The inner surface 131Ea is flat and extends radially along the cylindrical portion 72E.

[0154] The first circumferential edge 131E extends from one end of the second axial edge 103B on the first end side in the axial direction of the tubular portion 72E toward the first end in the axial direction of the tubular portion 72E. Moreover, the closer the first circumferential edge 131E is to the first axial edge 102E in the circumferential direction of the tubular portion 72E, the closer it is to the first end in the axial direction of the tubular portion 72E. The inner surface 131Ea of the first circumferential edge 131E extends from one end of the inner surface 103Ba of the second axial edge 103B on the first end side in the axial direction of the tubular portion 72E toward the first end in the axial direction of the tubular portion 72E. Moreover, the closer the inner surface 131Ea of the first circumferential edge 131E is to the first axial edge 102E in the circumferential direction of the tubular portion 72E, the closer it is to the first end side in the axial direction of the tubular portion 72E, and the closer it is to the first axial edge 102E in the circumferential direction of the tubular portion 72E, and the closer it is to the first end side in the axial direction of the tubular portion 72E, the closer it is to the first axial edge 102E in the circumferential direction of the tubular portion 72E, and the closer it is to the inner surface 102Ea.

[0155] As a result, the first circumferential edge 131E is formed so as to be inclined with respect to the axial direction of the cylindrical portion 72E, and serves as an inclined portion on the first end side of the edge 101E in the axial direction of the cylindrical portion 72E.

[0156] An edge 101E of the communication hole 91E is formed so that a first end in the axial direction of the cylindrical portion 72E is narrower than a second end in the axial direction of the cylindrical portion 72E.

[0157] Like the bumper cap 13, the bumper cap 13E having the shape described above is formed by injection molding of a synthetic resin material or die-casting of an aluminum alloy material. In both injection molding and die-casting, like the bumper cap 13, the portion of the cavity that forms the through-hole 81 (see FIG. 2) of the lid portion 70 of the bumper cap 13E (see FIG. 2) serves as the material inlet. When the material is poured into the cavity from the inlet, the material flows through the space that forms the lid portion 70 of the cavity so as to expand radially outward of the lid portion 70, and then flows through the space that forms the tubular portion 72E of the cavity in the axial direction of the tubular portion 72E, away from the space that forms the lid portion 70. That is, the material flows through the space that forms the tubular portion 72E of the cavity in the axial direction of the tubular portion 72E, from the second end side toward the first end side.

[0158] The edge 101E of the communication hole 91E is formed so that the portion on the side of the first circumferential edge 131E constituting the first end located downstream is narrower than the portion on the side of the second circumferential edge 132B constituting the second end located upstream in the direction of material flow during molding. In other words, the communication hole 91E of the bumper cap 13E is formed so that the first end located downstream in the direction of material flow during molding is narrower than the second end located upstream in the direction of material flow during molding. Furthermore, the edge 101E of the communication hole 91E of the bumper cap 13E is formed so that the second circumferential edge 132B, which is the upstream end of the material flowing during molding, is approximately perpendicular to the flow of material. The communication hole 91E of the bumper cap 13E has a tapered shape such that the first end located downstream in the direction of material flow during molding becomes narrower toward the downstream side.

[0159] In the sixth embodiment, the bumper cap 13E has a tubular portion 72E. The edge 101E of the communication hole 91E is narrower at its downstream end than at its upstream end, where the material flows during molding. This allows the bumper cap 13E to increase the meeting angle between the materials flowing on both sides of the mold portion forming the communication hole 91E when they meet downstream, allowing the materials to meet smoothly. This reduces the reduction in strength of the bumper cap 13E due to the occurrence of weld lines, which are surface defects that appear as grooves or patterns on the surface where the materials meet. This improves the durability of the bumper cap 13E.

[0160] Furthermore, at the edge 101E of the communicating hole 91E of the bumper cap 13E, the portion on the second end side including the second circumferential edge portion 132B can be made mirror-symmetric or point-symmetric with the portion on the first end side including the first circumferential edge portion 131E.

[0161] [Seventh embodiment] The seventh embodiment of the present invention will be described mainly with reference to Fig. 10, focusing on the differences from the sixth embodiment. Note that parts common to the sixth embodiment will be designated by the same names and symbols.

[0162] In the seventh embodiment, as shown in Fig. 10, a bumper cap 13F that is partially different from the bumper cap 13E of the sixth embodiment is used. The bumper cap 13F has a cylindrical portion 72F that is partially different from the cylindrical portion 72E instead of the cylindrical portion 72E. The cylindrical portion 72F has a communicating hole 91F that is partially different from the communicating hole 91E instead of the communicating hole 91E. The communicating hole 91F communicates between the outer peripheral surface 72Fb of the cylindrical portion 72F and an inner peripheral surface (not shown). Here, in the bumper cap 13F, the side of the cylindrical portion 72F opposite the lid portion 70 (see Fig. 2) in the axial direction is referred to as a first end side, and the side of the cylindrical portion 72F facing the lid portion 70 in the axial direction is referred to as a second end side. In addition, in the communication hole 91F, the end of the cylindrical portion 72F opposite the lid portion 70 in the axial direction is defined as a first end, and the end of the cylindrical portion 72F on the lid portion 70 side in the axial direction is defined as a second end.

[0163] The edge 101F of the communicating hole 91F has a first circumferential edge 131F (inclined portion) instead of the first circumferential edge 131E. The first circumferential edge 131F is formed to extend from one end of the second axial edge 103B on the first end side in the axial direction of the cylindrical portion 72E at an angle with respect to the second axial edge 103B. The end of the first circumferential edge 131F opposite the second axial edge 103B is connected to one end of the first axial edge 102E on the first end side in the axial direction of the cylindrical portion 72F. The first circumferential edge 131F is arc-shaped, including an inner surface 131Fa facing the space within the communicating hole 91F. The inner surface 131Fa is cylindrical and extends radially along the cylindrical portion 72F.

[0164] The first circumferential edge 131F extends from one end of the second axial edge 103B on the first end side in the axial direction of the tubular portion 72F toward the first end in the axial direction of the tubular portion 72F. Moreover, the closer the first circumferential edge 131F is to the first axial edge 102E in the circumferential direction of the tubular portion 72F, the closer it is to the first end in the axial direction of the tubular portion 72F. The inner surface 131Fa of the first circumferential edge 131F extends from one end of the inner surface 103Ba of the second axial edge 103B on the first end side in the axial direction of the tubular portion 72F toward the first end in the axial direction of the tubular portion 72F. Moreover, the closer the inner surface 131Fa of the first circumferential edge 131F is to the first axial edge 102E in the circumferential direction of the tubular portion 72F, the closer it is to the first end side in the axial direction of the tubular portion 72F, and the closer it is to the first axial edge 102E in the circumferential direction of the tubular portion 72F, and the closer it is to the first end side in the axial direction of the tubular portion 72F, the closer it is to the first axial edge 102E in the circumferential direction of the tubular portion 72F, and the closer it is to the inner surface 102Ea.

[0165] As a result, the first circumferential edge 131F is formed so as to be inclined with respect to the axial direction of the cylindrical portion 72F, and serves as an inclined portion on the first end side of the edge 101F in the axial direction of the cylindrical portion 72F.

[0166] An edge 101F of the communication hole 91F is formed so that a first end in the axial direction of the cylindrical portion 72F is narrower than a second end in the axial direction of the cylindrical portion 72F.

[0167] Like the bumper cap 13, the bumper cap 13F having the shape described above is formed by injection molding of a synthetic resin material or die-casting of an aluminum alloy material. In both injection molding and die-casting, like the bumper cap 13, the portion of the cavity that forms the through-hole 81 (see FIG. 2) of the lid portion 70 of the bumper cap 13F (see FIG. 2) serves as the material inlet. When the material is poured into the cavity from the inlet, the material flows through the space that forms the lid portion 70 of the cavity so as to expand radially outward of the lid portion 70, and then flows through the space that forms the tubular portion 72E of the cavity in the axial direction of the tubular portion 72F, away from the space that forms the lid portion 70. That is, the material flows through the space that forms the tubular portion 72F of the cavity in the axial direction of the tubular portion 72F, from the second end side to the first end side.

[0168] The edge 101F of the communicating hole 91F is formed so that the portion on the side of the first circumferential edge 131F constituting the first end located downstream is narrower than the portion on the side of the second circumferential edge 132B constituting the second end located upstream in the direction of material flow during molding. In other words, the communicating hole 91F of the bumper cap 13F is formed so that the first end located downstream is narrower than the second end located upstream in the direction of material flow during molding. Furthermore, the edge 101F of the communicating hole 91F of the bumper cap 13F is formed so that the second circumferential edge 132B, which is the upstream end of the material flowing during molding, is approximately perpendicular to the flow of the material. The communicating hole 91F of the bumper cap 13F has a tapered shape such that the first end located downstream in the direction of material flow during molding becomes narrower toward the downstream side.

[0169] In the seventh embodiment, the bumper cap 13F has a tubular portion 72F with a connecting hole 91F. The edge 101F is narrower at its downstream end than at its upstream end, where the material flows during molding. This allows the bumper cap 13F to increase the meeting angle between the materials flowing on both sides of the mold portion forming the connecting hole 91F when they meet downstream, allowing the materials to meet smoothly. This prevents the bumper cap 13F from losing strength due to weld lines, which are surface defects that appear as grooves or patterns on the surface where the materials meet. This improves the durability of the bumper cap 13F.

[0170] Furthermore, at the edge 101F of the communicating hole 91F of the bumper cap 13F, the portion on the second end side including the second circumferential edge portion 132B can be made mirror-symmetric or point-symmetric with the portion on the first end side including the first circumferential edge portion 131F.

[0171] [Eighth embodiment] An eighth embodiment of the present invention will be described, focusing on differences from the first embodiment, mainly with reference to Fig. 11. Note that parts common to the first embodiment will be designated by the same names and symbols.

[0172] 11, the eighth embodiment uses a bumper cap 13G that is partially different from the bumper cap 13 of the first embodiment. The bumper cap 13G has a cylindrical portion 72G that is partially different from the cylindrical portion 72 instead of the cylindrical portion 72. The cylindrical portion 72G has a communicating hole 91G that is partially different from the communicating hole 91 instead of the communicating hole 91. The communicating hole 91G communicates between an outer peripheral surface 72Gb of the cylindrical portion 72G and an inner peripheral surface (not shown).

[0173] The edge 101G of the communicating hole 91G has a first axial edge 102G that is partially different from the first axial edge 102, instead of the first axial edge 102. The edge 101G has a second axial edge 103G that is partially different from the second axial edge 103, instead of the second axial edge 103. Here, in the bumper cap 13G as well, the side of the tubular portion 72G opposite the lid portion 70 (see FIG. 2) in the axial direction is referred to as the first end side, and the side of the tubular portion 72G facing the lid portion 70 in the axial direction is referred to as the second end side. Furthermore, in the communicating hole 91G, the end of the tubular portion 72G opposite the lid portion 70 in the axial direction is referred to as the first end, and the end of the tubular portion 72G facing the lid portion 70 in the axial direction is referred to as the second end.

[0174] The first axial edge 102G does not have the first chamfered portion 112. The second axial edge 103G does not have the third chamfered portion 122.

[0175] The edge 101B has a first circumferential edge 131G instead of the first circumferential edge 131. The first circumferential edge 131G has a first inclined portion 141G instead of the first inclined portion 141, and a second inclined portion 142G instead of the second inclined portion 142. The first circumferential edge 131G does not have the fifth chamfered portion 143.

[0176] The first inclined portion 141G is formed to extend from one end of the first axial edge portion 102G on the first end side in the axial direction of the cylindrical portion 72G at an angle with respect to the first linear portion 111 of the first axial edge portion 102G. The first inclined portion 141G is arc-shaped, including an inner surface 141Ga facing the space within the communicating hole 91G. The first inclined portion 141G is arc-shaped, including the inner surface 141Ga, with its center located closer to the second end side in the axial direction of the cylindrical portion 72G than the inner surface 141Ga. The inner surface 141Ga of the first inclined portion 141G also extends radially of the cylindrical portion 72G and is cylindrical.

[0177] The first inclined portion 141G extends from one end of the first axial edge portion 102G on the first end side in the axial direction of the tubular portion 72G toward the first end in the axial direction of the tubular portion 72G. Moreover, the closer the first inclined portion 141G is to the first end side in the axial direction of the tubular portion 72G, the closer it is to the second axial edge portion 103G in the circumferential direction of the tubular portion 72G. The inner surface 141Ga of the first inclined portion 141G extends from one end of the inner surface 111a of the first linear portion 111 on the first end side in the axial direction of the tubular portion 72G toward the first end in the axial direction of the tubular portion 72G. Moreover, the closer the inner surface 141Ga of the first inclined portion 141G is to the first end side in the axial direction of the tubular portion 72G, the closer it is to the second axial edge portion 103G in the circumferential direction of the tubular portion 72G.

[0178] The second inclined portion 142G is formed to extend from one end of the second axial edge portion 103G on the first end side in the axial direction of the cylindrical portion 72G at an angle with respect to the second linear portion 121 of the second axial edge portion 103G. The second inclined portion 142G is arc-shaped, including an inner surface 142Ga facing the space within the communicating hole 91G. The second inclined portion 142G is arc-shaped, including the inner surface 142Ga, with its center located closer to the second end side in the axial direction of the cylindrical portion 72G than the inner surface 142Ga. The inner surface 142Ga of the second inclined portion 142G also extends radially of the cylindrical portion 72G and is cylindrical.

[0179] The second inclined portion 142G extends from one end of the second axial edge portion 103G on the first end side in the axial direction of the tubular portion 72G toward the first end in the axial direction of the tubular portion 72G. Moreover, the closer the second inclined portion 142G is to the first end side in the axial direction of the tubular portion 72G, the closer it is to the first axial edge portion 102G in the circumferential direction of the tubular portion 72G. The inner surface 142Ga of the second inclined portion 142G extends from one end of the inner surface 121a of the second linear portion 121 of the second axial edge portion 103G on the first end side in the axial direction of the tubular portion 72G toward the first end in the axial direction of the tubular portion 72G. Moreover, the closer the inner surface 142Ga of the second inclined portion 142G is to the first axial edge portion 102G in the circumferential direction of the tubular portion 72G, the closer it is to the first end side in the axial direction of the tubular portion 72G. The second inclined portion 142G is mirror-symmetrical to the first inclined portion 141G, with the second inclined portion 142G positioned in the axial direction of the cylindrical portion 72G. An inner surface 141Ga of the first inclined portion 141G and an inner surface 142Ga of the second inclined portion 142G are the same continuous cylindrical surface.

[0180] As a result of the above, the first circumferential edge portion 131G has a first inclined portion 141G and a second inclined portion 142G as inclined portions formed to be inclined with respect to the axial direction of the tubular portion 72G and which form the first end portion of the edge 101G in the axial direction of the tubular portion 72G.

[0181] An edge 101G of the communication hole 91G is formed so that a first end in the axial direction of the cylindrical portion 72G is thinner than a second end in the axial direction of the cylindrical portion 72G.

[0182] Like the bumper cap 13, the bumper cap 13G having the shape described above is formed by injection molding of a synthetic resin material or die-casting of an aluminum alloy material. In both injection molding and die-casting, like the bumper cap 13, the portion of the cavity that forms the through-hole 81 (see FIG. 2) of the lid portion 70 of the bumper cap 13G (see FIG. 2) serves as the material inlet. When the material is poured into the cavity from the inlet, the material flows through the space that forms the lid portion 70 of the cavity so as to expand radially outward of the lid portion 70, and then flows through the space that forms the tubular portion 72G of the cavity in the axial direction of the tubular portion 72G, away from the space that forms the lid portion 70. That is, the material flows through the space that forms the tubular portion 72G of the cavity in the axial direction of the tubular portion 72G, from the second end side toward the first end side.

[0183] The edge 101G of the communication hole 91G is formed so that the first circumferential edge 131G, which constitutes the first end located downstream, is narrower than the portion on the side of the second circumferential edge 132G, which constitutes the second end located upstream in the direction of material flow during molding. In other words, the communication hole 91G of the bumper cap 13G is formed so that the first end located downstream is narrower than the second end located upstream in the direction of material flow during molding. Furthermore, the edge 101G of the communication hole 91G of the bumper cap 13G is formed so that the second circumferential edge 132, which is the upstream end of the material flowing during molding, is approximately perpendicular to the flow of the material. The communication hole 91G of the bumper cap 13G has a tapered shape such that the first end located downstream in the direction of material flow during molding becomes narrower toward the downstream side.

[0184] In the bumper cap 13G of the eighth embodiment, the edge 101G of the communication hole 91G formed in the tubular portion 72G is narrower at its first end located downstream of the flow of material during molding than at its second end located upstream. This allows the bumper cap 13G to increase the meeting angle between the materials flowing on both sides of the mold portion forming the communication hole 91G when they meet downstream, allowing the materials to meet smoothly. This reduces the reduction in strength of the bumper cap 13G due to the occurrence of weld lines, which are surface defects that appear as grooves or patterns on the surface where the materials meet. This improves the durability of the bumper cap 13G.

[0185] Furthermore, at the edge 101G of the communicating hole 91G of the bumper cap 13G, the portion on the second end side including the second circumferential edge portion 132 can be made mirror-symmetrical to the portion on the first end side including the first circumferential edge portion 131G.

[0186] [Ninth embodiment] The ninth embodiment of the present invention will be described mainly with reference to Fig. 12, focusing on the differences from the third embodiment. Note that parts common to the third embodiment will be designated by the same names and symbols.

[0187] In the ninth embodiment, as shown in FIG. 12, a bumper cap 13H that is partially different from the bumper cap 13B of the third embodiment is used. The bumper cap 13H has a cylindrical portion 72H that is partially different from the cylindrical portion 72B instead of the cylindrical portion 72B. The cylindrical portion 72H has a communicating hole 91H that is partially different from the communicating hole 91B instead of the communicating hole 91B. The communicating hole 91H communicates between the outer peripheral surface 72Hb of the cylindrical portion 72H and an inner peripheral surface (not shown). Here, in the bumper cap 13H, the side of the cylindrical portion 72H opposite the lid portion 70 (see FIG. 2) in the axial direction is referred to as a first end side, and the side of the cylindrical portion 72H facing the lid portion 70 in the axial direction is referred to as a second end side. In the communication hole 91H, the end of the cylindrical portion 72H opposite the lid portion 70 in the axial direction is defined as a first end, and the end of the cylindrical portion 72H on the lid portion 70 side in the axial direction is defined as a second end.

[0188] The edge 101H of the communication hole 91H does not have the first axial edge portion 102B or the second axial edge portion 103B. The edge 101H has a first circumferential edge portion 131H instead of the first circumferential edge portion 131B. The first circumferential edge portion 131H has a first inclined portion 141H instead of the first inclined portion 141B and a second inclined portion 142H instead of the second inclined portion 142B.

[0189] The first inclined portion 141H extends from one end of the second circumferential edge 132B in the circumferential direction of the cylindrical portion 72H. The first inclined portion 141H is linear, including an inner surface 141Ha that faces the space within the communication hole 91H. The inner surface 141Ha of the first inclined portion 141H is flat and extends radially along the cylindrical portion 72H.

[0190] The first inclined portion 141H extends from one end of the second circumferential edge portion 132B in the circumferential direction of the tubular portion 72H toward a first end in the axial direction of the tubular portion 72H. Moreover, the closer the first inclined portion 141H is to the first end in the axial direction of the tubular portion 72H, the closer it is to the other end of the second circumferential edge portion 132B in the circumferential direction of the tubular portion 72H. The inner surface 141Ha of the first inclined portion 141H extends from one end of the inner surface 132Ba of the second circumferential edge portion 132B in the circumferential direction of the tubular portion 72H toward the first end in the axial direction of the tubular portion 72H. Moreover, the closer the inner surface 141Ha of the first inclined portion 141H is to the first end in the axial direction of the tubular portion 72H, the closer it is to the other end of the inner surface 132Ba in the circumferential direction of the tubular portion 72H.

[0191] The second inclined portion 142H extends from the other circumferential end of the cylindrical portion 72H of the second circumferential edge 132B. The second inclined portion 142H is linear, including an inner surface 142Ha that faces the space within the communication hole 91H. The inner surface 142Ha of the second inclined portion 142H is flat and extends radially along the cylindrical portion 72H.

[0192] The second inclined portion 142H extends from the other circumferential end of the second circumferential edge 132B of the tubular portion 72H toward a first end in the axial direction of the tubular portion 72H. Moreover, the closer the second inclined portion 142H is to the first end in the axial direction of the tubular portion 72H, the closer it is to one circumferential end of the second circumferential edge 132B of the tubular portion 72H in the circumferential direction of the tubular portion 72H. The inner surface 142Ha of the second inclined portion 142H extends from the other circumferential end of the tubular portion 72H of the inner surface 132Ba of the second circumferential edge 132B toward the first end in the axial direction of the tubular portion 72H. Moreover, the inner surface 142Ha of the second inclined portion 142H approaches the first end in the axial direction of the cylindrical portion 72H, and thus connects to the inner surface 141Ha of the first inclined portion 141H, approaching one end of the inner surface 132Ba in the circumferential direction of the cylindrical portion 72H. The second inclined portion 142H is positioned axially of the cylindrical portion 72H and is mirror-symmetrical to the first inclined portion 141H. The angle formed between the inner surface 141Ha of the first inclined portion 141H and the inner surface 142Ha of the second inclined portion 142H is an acute angle.

[0193] As a result of the above, the first circumferential edge portion 131H has a first inclined portion 141H and a second inclined portion 142H as inclined portions formed to be inclined with respect to the axial direction of the tubular portion 72H and extending over the entire axial direction of the tubular portion 72H of the edge 101H.

[0194] An edge 101H of the communication hole 91H is formed so that a first end in the axial direction of the cylindrical portion 72H is narrower than a second end in the axial direction of the cylindrical portion 72H.

[0195] Like the bumper cap 13, the bumper cap 13H having the above-described shape is formed by injection molding of a synthetic resin material or die-casting of an aluminum alloy material. In both injection molding and die-casting, like the bumper cap 13, the portion of the cavity that forms the through-hole 81 (see FIG. 2) of the lid portion 70 of the bumper cap 13H (see FIG. 2) serves as the material inlet. When the material is poured into the cavity from the inlet, the material flows through the space that forms the lid portion 70 of the cavity so as to expand outward in the radial direction of the lid portion 70, and then flows through the space that forms the cylindrical portion 72H of the cavity in the axial direction of the cylindrical portion 72H, in a direction away from the space that forms the lid portion 70. That is, the material flows through the space that forms the cylindrical portion 72H of the cavity in the axial direction of the cylindrical portion 72H, from the second end side toward the first end side.

[0196] The edge 101H of the communicating hole 91H is formed so that the first circumferential edge 131H, which constitutes the first end located downstream, is narrower than the portion on the side of the second circumferential edge 132H, which constitutes the second end located upstream in the direction of material flow during molding. In other words, the communicating hole 91H of the bumper cap 13H is formed so that the first end located downstream is narrower than the second end located upstream in the direction of material flow during molding. Furthermore, the edge 101H of the communicating hole 91H of the bumper cap 13H is formed so that the second circumferential edge 132B, which is the upstream end of the material flowing during molding, is approximately perpendicular to the flow of the material. The communicating hole 91H of the bumper cap 13H has a tapered shape that narrows toward the downstream side in the direction of material flow during molding.

[0197] In the ninth embodiment, the bumper cap 13H has a connecting hole 91H formed in its cylindrical portion 72H. The edge 101H is narrower at its first end, located downstream, than at its second end, located upstream, where the material flows during molding. This allows the bumper cap 13H to increase the meeting angle between the materials flowing on both sides of the mold portion forming the connecting hole 91H when they meet downstream, allowing the materials to meet smoothly. This prevents the bumper cap 13H from losing strength due to weld lines, which are surface defects that appear as grooves or patterns on the surface where the materials meet. This improves the durability of the bumper cap 13H.

[0198] It is also possible to make the second circumferential edge 132B mirror-symmetrical to the first circumferential edge 131H at the edge 101H of the communication hole 91H of the bumper cap 13H. [Industrial Applicability]

[0199] According to the above aspects of the present invention, it is possible to provide a bumper cap and a shock absorber that can improve durability, and thus the industrial applicability is great. [Explanation of symbols]

[0200] 11... shock absorber, 13, 13A to 13H... bumper cap, 21... cylinder, 32b... axial end surface, 40... piston, 50... piston rod, 70... lid portion, 72, 72A to 72E... cylindrical portion, 72a... inner peripheral surface, 72b, 72Ab to 72Hb... outer peripheral surface, 81... through hole, 91, 91A to 91H... communicating hole, 101, 101A to 101H... edge, 102, 102A, 102B, 102D, 102E, 102F, 102G, 102H, 102H 02E...first axial edge portion, 103, 103A, 103B, 103D...second axial edge portion, 112, 112A...first chamfered portion, 113, 113A...second chamfered portion, 122, 122A...third chamfered portion, 123, 123A...fourth chamfered portion, 131, 131A to 131H...first circumferential edge portion, 141, 141D...first inclined portion, 142, 142D...second inclined portion, 143, 143A...fifth chamfered portion.

Claims

1. A bumper cap used in a shock absorber, The buffer comprises: A cylinder; a piston provided in the cylinder; a piston rod having a first end connected to the piston and a second end extending from the cylinder; Equipped with The bumper cap is The piston rod is provided at an end of the cylinder from which the piston rod extends, and is molded by die casting or injection molding, a cover portion that abuts against an axial end surface of the cylinder and has a through hole through which the piston rod is inserted; a cylindrical portion provided radially outward of the through hole and covering at least a portion of an outer peripheral surface of the cylinder; a communication hole provided in the cylindrical portion, the communication hole connecting an inner peripheral surface and an outer peripheral surface of the cylindrical portion; and an edge of the communication hole has a circumferential edge portion extending in a circumferential direction of the cylindrical portion and an axial edge portion extending in an axial direction of the cylindrical portion, The circumferential edge portion is formed so that the first end portion located downstream has a more acute angle than the second end portion located upstream of the material flowing in during molding. Bumper cap.

2. 2. The bumper cap according to claim 1, wherein the edge of the communication hole is formed so that the upstream end of the material flowing in during molding is oriented substantially perpendicular to the flow of the material.

3. The corners of the communication hole are chamfered. The bumper cap according to claim 1 or 2.

4. Made of metal or resin The bumper cap according to claim 1 or 2.

5. A cylinder; a piston provided in the cylinder; a piston rod having one end connected to the piston and the other end extending from the cylinder; a bumper cap for a shock absorber, the bumper cap being provided at an end of the cylinder from which the piston rod extends, The bumper cap is a cover portion that abuts against an axial end surface of the cylinder and has a through hole through which the piston rod is inserted; a cylindrical portion provided radially outward of the through hole and covering at least a portion of an outer peripheral surface of the cylinder; a communication hole provided in the cylindrical portion, the communication hole connecting an inner peripheral surface and an outer peripheral surface of the cylindrical portion; and The edge of the communication hole is a circumferential edge portion extending in the circumferential direction of the cylindrical portion; an axial edge portion extending in the axial direction of the cylindrical portion; and At least a part of the circumferential edge portion is formed to be inclined with respect to the axial direction of the cylindrical portion, and includes an inclined portion which is an end side of the edge of the communication hole in the axial direction of the cylindrical portion, The circumferential edge portion is formed such that a first end portion in the axial direction of the cylindrical portion has an acuter angle than a second end portion in the axial direction of the cylindrical portion. Bumper cap.

6. The axial edge portion has a first axial edge portion and a second axial edge portion, The inclined portion includes a first inclined portion formed to extend obliquely from one axial end of the first axial edge portion, and a second inclined portion formed to extend obliquely from one axial end of the second axial edge portion. The bumper cap of claim 5 , comprising:

7. The inclined portion is provided on a first end side of the cylindrical portion in the axial direction. The bumper cap of claim 6.

8. the inclined portions are provided on a first end side in the axial direction of the cylindrical portion and a second end side in the axial direction of the cylindrical portion, and are formed symmetrically with each other; The bumper cap of claim 7.

9. Made of metal or resin, The bumper cap according to any one of claims 5 to 8.

10. A cylinder; a piston provided in the cylinder; a piston rod having one end connected to the piston and the other end extending from the cylinder; Bumper caps and Equipped with The bumper cap is a cover portion that abuts against an axial end surface of the cylinder and has a through hole through which the piston rod is inserted; a cylindrical portion provided at a radially outer end of the lid portion and covering at least a portion of an outer peripheral surface of the cylinder; a communication hole provided in the cylindrical portion, the communication hole connecting an inner peripheral surface and an outer peripheral surface of the cylindrical portion; and an edge of the communication hole has a circumferential edge portion extending in a circumferential direction of the cylindrical portion and an axial edge portion extending in an axial direction of the cylindrical portion, The circumferential edge is formed such that a first end portion located downstream of the second end portion located upstream of the flow of material during molding has a more acute angle than a second end portion located upstream of the flow of material during molding. buffer.

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