Dust cover and joint mechanism

Abstract

A dust cover according to the present invention is to be fixed to a socket that supports a ball stud. The dust cover comprises a body part that surrounds the ball stud and an annular fixed part that is connected to the body part. The fixed part includes an inner circumferential surface that contacts an installation groove in the socket, an outer circumferential surface that is on the reverse side from the inner circumferential surface, an annular groove part that is formed at the outer circumferential surface and accommodates a fastening member that fastens the fixed part to the socket, and an extending outer surface that connects the outer circumferential surface and an outer surface of the body part. At a first bent part that is positioned further to the outside in the radial direction of the fixed part than a first virtual surface that is a continuous extension of the outer surface of the body part toward the groove part, the outer circumferential surface of the fixed part is bent relative to the extending outer surface and is positioned further to the outside in the radial direction than an outer circumferential part of the fastening member.

Description

Dust cover and joint mechanism

[0001] The present disclosure relates to a dust cover for use in a ball joint.

[0002] Dust covers are used in ball joints of mechanical devices such as vehicles. Patent Document 1 discloses a dust cover including a deformable rubber body and a fixed part installed at one end of the body. An annular groove is formed on the outer circumferential surface of the fixed part. The fixed part is fixed to the socket by being tightened by a fixing member such as a clamp or band attached to the annular groove.

[0003] JP 2019-60437 A

[0004] The body of the dust cover deforms in conjunction with the swinging of the ball stud that constitutes the ball joint. Stress accompanying the deformation of the body is generated in the body and the fixed part. Stress tends to concentrate around the corner of the mounting groove of the fixed part that is close to the body. Repeated stress concentration at the corner of the mounting groove over a long period of time may cause fatigue failure originating from the corner. In consideration of the above circumstances, one aspect of the present disclosure aims to improve the fatigue life of a dust cover.

[0005] A dust cover according to one aspect of the present disclosure is a dust cover that is fixed to a socket that supports a ball stud, and includes a body portion that surrounds the ball stud and an annular fixed portion connected to the body portion, the fixed portion including an inner circumferential surface that contacts the mounting groove of the socket, an outer circumferential surface opposite the inner circumferential surface, an annular groove portion formed in the outer circumferential surface that accommodates a fastening member that fastens the fixed portion to the socket, and an extended outer surface that connects the outer surface of the body portion to the outer circumferential surface, the outer circumferential surface bent relative to the extended outer surface at a first bend portion that is located radially outward of the fixed portion than a first imaginary plane that continuously extends the outer surface of the body portion toward the groove, and is located radially outward of the outer circumferential portion of the fastening member.

[0006] A dust cover according to another aspect of the present disclosure is a dust cover fixed to a socket that supports a ball stud, and includes a body portion that surrounds the ball stud and an annular fixed portion connected to the body portion, the fixed portion including an inner circumferential surface that contacts a mounting groove of the socket, an outer circumferential surface opposite the inner circumferential surface, an annular groove portion formed on the outer circumferential surface that receives a fastening member that fastens the fixed portion to the socket, and an extended outer surface that connects an outer surface of the body portion to the outer circumferential surface, and the outer circumferential surface connects the outer surface of the body portion to the groove. the groove includes a groove bottom extending circumferentially around the fixed part, a first groove wall protruding radially outward from an edge of the groove bottom that is closer to the body part, and a second groove wall protruding radially outward from an edge of the groove bottom that is farther from the body part; and when the ball stud swings within a range of 20° or less with respect to the central axis of the fixed part, the corner of the groove between the groove bottom and the first groove wall does not displace.

[0007] A dust cover according to another aspect of the present disclosure is a dust cover that is fixed to a socket that supports a ball stud, and includes a body portion that surrounds the ball stud and an annular fixed portion connected to the body portion, the fixed portion including an inner circumferential surface that contacts the mounting groove of the socket, an outer circumferential surface opposite the inner circumferential surface, an annular groove formed on the outer circumferential surface that accommodates a fastening member that fastens the fixed portion to the socket, and a curved surface connecting the inner surface of the body portion to the inner circumferential surface, the curved surface including a first surface that is continuous with the inner surface of the body portion and a second surface that connects the first surface to the inner circumferential surface, the second surface being bent radially inward of the fixed portion relative to the first surface at a second bend that is located outside a second imaginary plane that continuously extends the inner surface of the body portion toward the inner circumferential surface.

[0008] A joint mechanism according to one aspect of the present disclosure includes a socket having an attachment groove, a ball stud supported by the socket, a dust cover including a body portion surrounding the ball stud and an annular fastener portion connected to the body portion, and a fastener member for fastening the fastener portion to the socket, wherein the fastener portion includes an inner circumferential surface that contacts the attachment groove of the socket, an outer circumferential surface opposite the inner circumferential surface, an annular groove portion formed on the outer circumferential surface to accommodate the fastener portion, and an extended outer surface connecting the outer surface of the body portion and the outer circumferential surface, and the outer circumferential surface is bent relative to the extended outer surface at a first bend portion that is located radially outward of the fastener portion relative to a first imaginary plane that continuously extends the outer surface of the body portion toward the groove portion, and is located radially outward of the outer circumferential portion of the fastener member.

[0009] A joint mechanism according to another aspect of the present disclosure is a joint mechanism including: a socket having an attachment groove; a ball stud supported by the socket; a dust cover including a body portion surrounding the ball stud and an annular fixed portion connected to the body portion; and a fastening member for fastening the fixed portion to the socket, wherein the fixed portion includes an inner circumferential surface that contacts the attachment groove of the socket; an outer circumferential surface opposite to the inner circumferential surface; an annular groove portion formed on the outer circumferential surface that receives the fastening member; and an extended outer surface connecting an outer surface of the body portion to the outer circumferential surface, The ball stud is bent relative to the fixed portion at a first bending portion located radially outward of a first imaginary plane formed by continuously extending the outer surface of the body portion toward the groove portion, and the groove portion is bent relative to the extended outer surface, and includes a groove bottom that extends circumferentially of the fixed portion, a first groove wall that protrudes radially outward from an edge of the groove bottom that is closer to the body portion, and a second groove wall that protrudes radially outward from an edge of the groove bottom that is farther from the body portion, and when the ball stud swings within a range of 20° or less relative to the central axis of the fixed portion, the corner of the groove portion between the groove bottom and the first groove wall does not displace.

[0010] A joint mechanism according to another aspect of the present disclosure includes: a socket having an attachment groove; a ball stud supported by the socket; a dust cover including a body portion surrounding the ball stud and an annular fastener portion connected to the body portion; and a fastener member for fastening the fastener portion to the socket, wherein the fastener portion includes an inner circumferential surface that contacts the attachment groove of the socket; an outer circumferential surface opposite the inner circumferential surface; an annular groove portion formed on the outer circumferential surface to accommodate the fastener member; and a curved surface connecting the inner surface of the body portion to the inner circumferential surface, wherein the curved surface includes a first surface continuous with the inner surface of the body portion and a second surface connecting the first surface to the inner circumferential surface, and the second surface bends radially inward of the fastener portion relative to the first surface at a second bend portion located outside a second imaginary plane that continuously extends the inner surface of the body portion toward the inner circumferential surface.

[0011] Fig. 1 is a cross-sectional view of a joint mechanism according to the first embodiment; Fig. 2 is a partial perspective view of the joint mechanism according to the first embodiment; Fig. 3 is a perspective view of a fastening member according to the first embodiment; Fig. 4 is an enlarged cross-sectional view of the periphery of a fixed portion of a dust cover in a non-deformed state; Fig. 5 is an enlarged cross-sectional view of the periphery of a fixed portion of a dust cover according to a comparative embodiment; Fig. 6 is an enlarged cross-sectional view of the periphery of a fixed portion of a dust cover according to a second embodiment in a non-deformed state; Fig. 7 is an enlarged cross-sectional view of the periphery of a fixed portion of a dust cover according to a third embodiment in a non-deformed state; Fig. 8 is an enlarged cross-sectional view of the periphery of a fixed portion of a dust cover according to a modified example in a non-deformed state.

[0012] Specific embodiments for carrying out the present disclosure will be illustrated with reference to the drawings. Note that the dimensions and scale of each element in each drawing may differ from those of the actual product. The embodiment described below is an exemplary embodiment that may be envisioned when carrying out the present disclosure. Therefore, the scope of the present disclosure is not limited to the embodiment exemplified below.

[0013] A: First Embodiment Fig. 1 is a cross-sectional view of a joint mechanism 100 according to a first embodiment. Fig. 2 is a perspective view with a portion of the joint mechanism 100 cut away. The joint mechanism 100 of the first embodiment is used in various mechanisms, such as a suspension mechanism or a steering mechanism, in a mechanical device such as a vehicle. However, the mechanical device to which the present disclosure is applicable is not limited to a vehicle.

[0014] 1 and 2, the joint mechanism 100 includes a ball joint 10, a dust cover 20, and a fastening member 15. The dust cover 20 is fixed to the ball joint 10 by the fastening member 15. As shown in FIG. 1, the ball joint 10 includes a ball stud 11, a socket 12, a knuckle 13, and a nut 14.

[0015] The ball stud 11 is an elongated structure. Specifically, the ball stud 11 includes a shank 11a, a spherical portion 11b, and a threaded portion 11c. The shank 11a is a columnar portion with a circular cross section. The spherical portion 11b is a spherical portion located at one end of the shank 11a. The threaded portion 11c is a cylindrical portion located at the end of the shank 11a opposite the spherical portion 11b. A thread groove is formed on the outer peripheral surface of the threaded portion 11c.

[0016] The socket 12 is a structure that supports the ball stud 11. In the following description, the direction along the central axis C of the socket 12 will be referred to as the "axial direction." The axial direction is divided into a +Z direction and a -Z direction. The +Z direction is, for example, an upward vertical direction, and the -Z direction is, for example, a downward vertical direction. However, the direction in which the joint mechanism 100 is installed can be changed as desired. Therefore, the axial direction is not limited to the vertical direction.

[0017] Furthermore, the direction of the circumference of an imaginary circle of any diameter centered on the central axis C is referred to as the "circumferential direction," and the direction of the radius of the imaginary circle is referred to as the "radial direction." In the radial direction, the direction toward the central axis C may be referred to as the "inner side," and the direction away from the central axis C may be referred to as the "outer side."

[0018] As shown in Figure 1, the socket 12 has a bearing portion 12a and a support portion 12b. The bearing portion 12a is a portion formed with a concave spherical bearing surface that opens in the +Z direction. The spherical portion 11b of the ball stud 11 is inserted into the bearing portion 12a. Specifically, the ball stud 11 is supported by the bearing portion 12a with the spherical portion 11b in contact with the bearing surface of the bearing portion 12a. A lubricant such as grease is filled in the gap between the surface of the spherical portion 11b and the bearing surface of the bearing portion 12a.

[0019] As described above, the bearing portion 12a supports the ball stud 11 in a rotatable and swingable state. Rotation of the ball stud 11 refers to rotation of the ball stud 11 around the central axis of the shaft portion 11a. Pivoting of the ball stud 11 refers to rotation of the ball stud 11 around the spherical portion 11b such that the central axis of the ball stud 11 is inclined relative to the central axis C of the socket.

[0020] The support portion 12b is a portion that supports the bearing portion 12a and the dust cover 20. An attachment groove 12c is formed in the vicinity of the end portion of the support portion 12b in the +Z direction. The attachment groove 12c is a portion (attachment portion) to which the dust cover 20 is attached. Specifically, the attachment groove 12c is formed in an annular shape around the entire outer circumferential surface of the support portion 12b.

[0021] The knuckle 13 is an annular structure (connecting member) that is fixed to the shank 11a of the ball stud 11 on the side opposite the spherical portion 11b. The shank 11a is inserted into the knuckle 13. The threaded portion 11c of the ball stud 11 protrudes in the +Z direction from the end face of the knuckle 13 that faces the +Z direction. A nut 14 is attached to the threaded portion 11c, thereby fixing the knuckle 13 to the ball stud 11 as a single unit.

[0022] FIG. 3 is a perspective view of the fastening member 15. As illustrated in FIG. 3, the fastening member 15 is an annular clip formed by winding a metal wire in a spiral shape (e.g., a torsion spring shape). In the first embodiment, the fastening member 15 has two turns, but the number of turns may be changed as desired. The thickness of the wire constituting the fastening member 15 is set, for example, within a range of 0.8 mm to 1.5 mm. The wire thickness is the dimension of the wire in the direction of the central axis of the fastening member 15. As illustrated in FIG. 4, the fastening member 15 has an outer circumferential portion 15a. If the fastening member 15 is approximately cylindrical, the outer circumferential portion 15a corresponds to the outer circumferential surface of the cylinder. The fastening member 15 may have any structure. For example, an annular member such as a clamp, a band, or a retaining ring may be used as the fastening member 15. Note that the bearing portions 12a of the ball stud 11 and the socket 12 are not shown in FIG. 2.

[0023] 1 and 2, the fastening member 15 is attached to the dust cover 20. Specifically, the dust cover 20 is fixed to the socket 12 by being fastened by the fastening member 15.

[0024] [Dust cover 20] The dust cover 20 is installed on the ball joint 10 to prevent dust or moisture from adhering to the connecting portion between the ball stud 11 (spherical portion 11b) and the socket 12 (bearing portion 12a) and to prevent the lubricant filled in the connecting portion from leaking out.

[0025] 1 and 2 , the dust cover 20 of the first embodiment has a seal portion 22, a body portion 30, and a fixed portion 40. The seal portion 22, body portion 30, and fixed portion 40 are integrally formed. That is, the dust cover 20 is a molded product in which the seal portion 22, body portion 30, and fixed portion 40 are integrally molded using, for example, a molding die. The central axis C can also be expressed as the central axis of the dust cover 20 in its initial state (hereinafter referred to as the "undeformed state"), in which it is not elastically deformed. The undeformed state can also be expressed as a state in which the central axis of the ball stud 11 coincides with the central axis C of the socket 12.

[0026] The dust cover 20 is made of a deformable elastic material such as a rubber material (elastomer). The elastic material used as the base material of the dust cover 20 is, for example, vinyl methyl silicone rubber (VMQ) or ethylene propylene diene rubber (EPDM). However, various rubber materials such as chloroprene rubber (CR), silicone rubber (SR), acrylic rubber (ACM), urethane rubber (U), polyurethane rubber (PUR), or fluororubber (FKM) can also be used.

[0027] [Body portion 30] The body portion 30 is a cylindrical portion that surrounds the ball stud 11. Specifically, the body portion 30 is formed in a curved shape so that the central portion in the axial direction has a larger diameter than the two end portions, and is elastically deformable when subjected to an external force. The body portion 30 has an inner surface 32 that faces the ball stud 11 and an outer surface 34 opposite the inner surface 32. The body portion 30 also has a neck portion 36 that is the boundary with the seal portion 22. The neck portion 36 is the portion of the body portion 30 with the smallest diameter.

[0028] [Sealing portion 22] As illustrated in FIG. 1 , the sealing portion 22 constitutes the +Z direction end of the dust cover 20. Specifically, the sealing portion 22 is an annular portion connected to the +Z direction end of the body portion 30 (i.e., the neck portion 36). The sealing portion 22 contacts the outer peripheral surface of the shank 11a and the −Z direction surface of the knuckle 13. The sealing portion 22 swings together with the ball stud 11. The sealing portion 22 also slides against the outer peripheral surface of the shank 11a and the surface of the knuckle 13. In other words, with the outer peripheral surface of the shank 11a and the surface of the knuckle 13 in contact with the sealing portion 22, the ball stud 11 can rotate around the central axis of the shank 11a.

[0029] [Fixed portion 40] The fixed portion 40 constitutes the end portion of the dust cover 20 in the -Z direction. Specifically, the fixed portion 40 is an annular portion connected to the end portion of the body portion 30 in the -Z direction. Therefore, the body portion 30 is located between the seal portion 22 and the fixed portion 40. As illustrated in FIGS. 1 and 2, the fixed portion 40 is attached to the mounting groove 12c of the socket 12. The fixed portion 40 is fixed coaxially to the socket 12. Therefore, the central axis C can also be expressed as the central axis of the fixed portion 40.

[0030] 4 is an enlarged cross-sectional view of the vicinity of the fixed portion 40. As illustrated in FIG. 4, the fixed portion 40 has an inner circumferential surface 42, an outer circumferential surface 43, a groove portion 44, a boundary portion 46, and a constricted portion 50.

[0031] The inner circumferential surface 42 is a cylindrical surface (arcuate surface) facing radially inward in the fixed portion 40. The inner circumferential surface 42 contacts the bottom surface of the mounting groove 12c in the socket 12. The radius RI of the inner circumferential surface 42 (the inner diameter of the fixed portion 40) is uniform in the axial direction.

[0032] The outer peripheral surface 43 is the surface opposite to the inner peripheral surface 42. Specifically, the outer peripheral surface 43 is a cylindrical surface (arcuate surface) facing radially outward in the fixed portion 40. The radius of the outer peripheral surface 43 is uniform in the axial direction. As illustrated in FIG. 4 , the outer peripheral surface 43 includes an outer peripheral surface 43a and an outer peripheral surface 43b. The outer peripheral surface 43a is located in the +Z direction relative to the outer peripheral surface 43b.

[0033] The groove 44 is formed in the outer peripheral surface 43. That is, the groove 44 is a bottomed groove recessed radially inward relative to the outer peripheral surface 43. The groove 44 extends annularly in the circumferential direction around the entire circumference of the fixed portion 40. The groove 44 is located between the outer peripheral surface 43a and the outer peripheral surface 43b in the axial direction. The fastening member 15 is accommodated in the groove 44. Specifically, the fastening member 15 is attached to the groove 44 with the fixed portion 40 housed in the attachment groove 12c of the socket 12. The dust cover 20 is fixed to the socket 12 by fastening the fixed portion 40 with the fastening member 15.

[0034] 4, the groove 44 is formed to have a substantially U-shaped cross section. Specifically, the groove 44 includes a groove bottom 44a, a groove wall 44b, and a groove wall 44c. The groove bottom 44a is a bottom surface along the circumferential direction and is a surface of revolution about the central axis C.

[0035] The groove wall 44b is a side wall of the groove 44 located in the +Z direction. Specifically, the groove wall 44b protrudes radially outward from the edge of the groove bottom 44a in the +Z direction (i.e., the upper edge close to the body 30). The groove wall 44b is connected to the outer circumferential surface 43a. The groove wall 44c is a side wall of the groove 44 located in the -Z direction. Specifically, the groove wall 44c protrudes radially outward from the edge of the groove bottom 44a in the -Z direction (i.e., the lower edge far from the body 30). The groove wall 44c is connected to the outer circumferential surface 43b. The groove wall 44b and the groove wall 44c are planes perpendicular to the central axis C and face each other with a gap in the axial direction. The groove wall 44b is an example of a "first groove wall," and the groove wall 44c is an example of a "second groove wall."

[0036] Corner 44d in FIG. 4 is a corner portion of groove 44 located in the +Z direction. That is, corner 44d is the portion where groove bottom 44a and groove wall 44b intersect. Corner 44d is configured as an R-shaped curved surface (i.e., an arc surface) extending from groove bottom 44a to groove wall 44b. Corner 44e in FIG. 4 is a corner portion of groove 44 located in the -Z direction. That is, corner 44e is the portion where groove bottom 44a and groove wall 44c intersect. Corner 44e is configured as an R-shaped curved surface (i.e., an arc surface) extending from groove bottom 44a to groove wall 44c.

[0037] The groove 44 is capable of accommodating the fastening member 15. When accommodated in the groove 44, the fastening member 15 is sandwiched between the groove wall 44b and the groove wall 44c. When the fixed portion 40 is fastened by the fastening member 15, the groove bottom 44a of the groove 44 is pressed radially inward by the fastening member 15. Furthermore, the groove wall 44b is pressed in the +Z direction by the fastening member 15, and the groove wall 44c is pressed in the -Z direction by the fastening member 15. In other words, the fastening member 15 applies a fastening force (i.e., contact pressure) to the groove 44.

[0038] 4, the outer peripheral surface 43 (43a, 43b) of the fixed portion 40 is located radially outward from the outer peripheral portion 15a of the fastening member 15 housed in the groove portion 44. That is, the outer peripheral portion 15a of the fastening member 15 is located radially inward from the outer peripheral surface 43 (outer peripheral surfaces 43a and 43b). Note that the outer peripheral surface 43 and the outer peripheral portion 15a of the fastening member 15 may overlap each other when viewed in the direction along the central axis C. Furthermore, the outer peripheral portion 15a may be located radially outward from the outer peripheral surface 43 (outer peripheral surfaces 43a and 43b).

[0039] FIG. 4 illustrates the groove width WG of the groove portion 44. The groove width WG is the dimension of the groove portion 44 in the axial direction. That is, the distance between the groove wall 44b and the groove wall 44c of the groove portion 44 corresponds to the groove width WG. In an embodiment in which the thickness of the wire material constituting the fastening member 15 is in the range of 0.8 mm to 1.5 mm, as described above, the groove width WG is preferably in the range of 2.5 mm to 5.0 mm. In the first embodiment, the groove width WG is 3.0 mm. However, the groove width WG may be changed as desired.

[0040] The distance RC in FIG. 4 is the length from the edge of the groove bottom 44a in the +Z direction (i.e., corner 44d) to the central axis C. The distance RC can also be expressed as the radius of the corner 44d. The distance RD in FIG. 4 is the length from the edge of the groove bottom 44a in the −Z direction (i.e., corner 44e) to the central axis C. The distance RD can also be expressed as the radius of the corner 44e. As illustrated in FIG. 4, the distance RC is greater than the distance RD (RC>RD).

[0041] That is, the groove bottom 44a of the groove 44 is a surface of revolution inclined with respect to the central axis C so that the distance RC exceeds the distance RD. Specifically, the groove bottom 44a is a surface of revolution having a truncated cone shape (i.e., a tapered shape) that linearly expands in diameter in the +Z direction. As described above, the distance RC exceeds the distance RD, so the thickness TC from the corner 44d to the inner circumferential surface 42 is thicker than the thickness TD from the corner 44e to the inner circumferential surface 42 (TC > TD). In the first embodiment, the thickness TC is 2 mm, and the thickness TD is 1.4 mm. Note that the distance RC is an example of the "first distance," and the distance RD is an example of the "second distance."

[0042] 4, the distance GR is the difference between the distance RC and the distance RD. The groove bottom 44a is formed so that the distance GR is within a range of 15% to 60% of the groove width WG. In the first embodiment, the distance GR is 0.6 mm.

[0043] The boundary portion 46 shown in Fig. 4 is the boundary between the body portion 30 and the fixed portion 40. That is, the boundary portion 46 is the portion of the dust cover 20 that connects the body portion 30 and the fixed portion 40. As illustrated in Fig. 4, in the undeformed state of the dust cover 20, the boundary portion 46 is located a distance GB away from the groove wall 44b (corner portion 44d) in the +Z direction. The distance GB is 1.2 times the groove width WG of the groove portion 44.

[0044] 4 is an imaginary surface of revolution that continuously extends the outer surface 34 of the body 30 from the boundary portion 46 toward the groove portion 44 in the undeformed dust cover 20. In other words, the imaginary surface KS1 continuously extends from the boundary portion 46 toward the corner portion 44d along the outer surface 34. The imaginary surface KS1 is an example of a "first imaginary surface."

[0045] 4 is an imaginary plane of revolution that continuously extends the inner surface 32 of the body portion 30 from the boundary portion 46 toward the inner circumferential surface 42 of the fixed portion 40 in the undeformed state of the dust cover 20. That is, the imaginary plane KS2 continuously extends from the boundary portion 46 along the inner surface 32 toward the upper edge of the inner circumferential surface 42 (i.e., the edge in the +Z direction). The imaginary plane KS2 is an example of a "second imaginary plane."

[0046] 4 , the constricted portion 50 is a portion of the dust cover 20 that connects the portion between the groove portion 44 and the inner circumferential surface 42 and the boundary portion 46. The constricted portion 50 has a curved surface 52 and a curved surface 252. The constricted portion 50 further has a padded portion 60.

[0047] The curved surface 52 connects the outer surface 34 of the body portion 30 and the groove portion 44. Specifically, the curved surface 52 is a region of the radially outer surface of the fixed portion 40 that is located between the groove portion 44 and the boundary portion 46.

[0048] The curved surface 52 has an extended outer surface 54, an outer peripheral surface 43a, and a curved portion 52a. The extended outer surface 54 connects the outer surface 34 of the body portion 30 to the outer peripheral surface 43a. Specifically, the extended outer surface 54 is an outer wall surface of the fixed portion 40 that continues to the outer surface 34 of the body portion 30 at the boundary portion 46. As illustrated in FIG. 4 , the portion of the extended outer surface 54 that continues to the outer surface 34 of the body portion 30 coincides with a part of the imaginary surface KS1. Note that the extended outer surface 54 may be located radially outward from the imaginary surface KS1.

[0049] [Bent portion 52a] The bent portion 52a is a bent portion of the bent surface 52. Specifically, the bent portion 52a is located at the boundary between the outer peripheral surface 43a and the extended outer surface 54 of the bent surface 52. The bent portion 52a can also be expressed as a portion of the bent surface 52 that connects the outer peripheral surface 43a and the extended outer surface 54. The bent portion 52a is an example of a "first bent portion."

[0050] The outer peripheral surface 43a is bent at the bent portion 52a relative to the extended outer surface 54 and is formed into a shape that extends toward the groove wall 44b. That is, the bent surface 52 is bent at the bent portion 52a so that the outer peripheral surface 43a is located radially outward from the imaginary plane KS1. As described above, the bent portion 52a is bent at the bent portion 52a so that the thickness of the portion of the fixed portion 40 sandwiched between the boundary portion 46 and the groove portion 44 is increased.

[0051] As illustrated in Fig. 4, the position of the bent portion 52a and the position of the corner portion 44d differ in the axial direction. Specifically, the bent portion 52a is located further in the +Z direction than the corner portion 44d in the axial direction. Furthermore, the position of the bent portion 52a and the position of the corner portion 44d differ in the radial direction. Specifically, the bent portion 52a is located radially outward than the corner portion 44d. As described above, the bent portion 52a and the corner portion 44d are formed at positions spaced apart from each other in the axial and radial directions.

[0052] 4 , the padded portion 60 is a portion of the fixed portion 40 that is surrounded by the imaginary plane KS1, the outer circumferential surface 43a, and the groove wall 44b in a cross-sectional view. Within the range between the groove wall 44b and the boundary portion 46, the portion of the fixed portion 40 that overlaps with the padded portion 60 in the axial direction has a greater thickness than the region that does not overlap with the padded portion 60 in the axial direction. In other words, the bent surface 52 bends at the bent portion 52a so as to increase the thickness of the portion sandwiched between the boundary portion 46 and the groove portion 44.

[0053] The curved surface 252 connects the inner surface 32 of the body portion 30 and the inner circumferential surface 42 of the fixed portion 40. Specifically, the curved surface 252 is a region of the radially inner surface of the fixed portion 40 that is located between the inner circumferential surface 42 and the boundary portion 46.

[0054] The curved surface 252 has an extended inner surface 254, an extended surface 245, and a curved portion 252a. The extended inner surface 254 is a surface of revolution that is continuous with the inner surface 32 of the body portion 30. Specifically, the extended inner surface 254 is continuous with the inner surface 32 of the body portion 30 at the boundary portion 46, and is located radially outward of the imaginary surface KS2 (on the extended outer surface 54 side). The extended inner surface 254 is an example of a "first surface."

[0055] The extended surface 245 is a surface of revolution that connects the extended inner surface 254 and the inner circumferential surface 42. Specifically, the extended surface 245 bends radially outward from the edge of the inner circumferential surface 42 in the +Z direction, and is located radially outward of the imaginary surface KS2 (on the extended outer surface 54 side). The extended surface 245 is an example of a "second surface."

[0056] [Bent portion 252a] The bent portion 252a is a bent portion of the bent surface 252. Specifically, the bent portion 252a is located at the boundary between the extended inner surface 254 of the bent surface 252 and the extended surface 245. The bent portion 252a can also be expressed as a portion of the bent surface 252 that connects the extended inner surface 254 and the extended surface 245. The bent portion 252a is located radially outward of the imaginary surface KS2. The bent portion 252a is an example of a "second bent portion."

[0057] The extended surface 245 is formed into a shape that bends radially inward with respect to the extended inner surface 254 at the bent portion 252a and extends toward the inner circumferential surface 42. That is, the bent surface 252 is bent at the bent portion 252a so that both the extended inner surface 254 and the extended surface 245 are positioned radially outward with respect to the imaginary surface KS2. As described above, the bent surface 252 is bent at the bent portion 252a so as to be convex radially outward with respect to the imaginary surface KS2.

[0058] As illustrated in Fig. 4, the position of the bent portion 252a and the position of the corner portion 44d differ in the axial direction. Specifically, the bent portion 252a is located further in the +Z direction than the corner portion 44d in the axial direction. Furthermore, the position of the bent portion 252a and the position of the corner portion 44d differ in the radial direction. Specifically, the bent portion 252a is located radially outward than the corner portion 44d. As described above, the bent portion 252a and the corner portion 44d are formed at positions spaced apart from each other in the axial and radial directions.

[0059] As illustrated in Fig. 4, the position of the bent portion 52a and the position of the bent portion 252a differ in both the axial direction and the radial direction. The bent portion 52a and the bent portion 252a are shifted from each other in the radial direction. That is, the position of the bent portion 52a in the radial direction differs from the position of the bent portion 252a in the radial direction. Specifically, the bent portion 52a is located radially outward of the bent portion 252a.

[0060] Furthermore, the bent portion 52a and the bent portion 252a are positioned offset from each other in the axial direction. That is, the position of the bent portion 52a in the axial direction is different from the position of the bent portion 252a in the axial direction. Specifically, the bent portion 52a is positioned in the −Z direction of the bent portion 252a in the axial direction.

[0061] 4 illustrates a virtual normal line KN. The virtual normal line KN is a virtual line obtained by extending the normal line of the extended outer surface 54 of the bent portion 52a toward the virtual surface KS2. It is preferable that the bent portion 252a is configured so as not to overlap the virtual normal line KN related to the bent portion 52a. In other words, the bent portion 252a is positioned away from the virtual normal line KN in a cross-sectional view and is not located on the virtual normal line KN.

[0062] The portion of the constricted portion 50 of the fixed portion 40 that is located in the +Z direction from the bent portion 252a can be deformed integrally with the body portion 30. Furthermore, the portion of the constricted portion 50 of the fixed portion 40 that is located in the +Z direction from the bent portion 52a can be deformed integrally with the body portion 30.

[0063] [Effects of the First Embodiment] The operation and effect of the dust cover 20 in the first embodiment will be described. Figure 5 is a partial cross-sectional view of a dust cover 20H according to a configuration (hereinafter referred to as the "comparative configuration") that is compared to the dust cover 20 of the first embodiment. For convenience, the same reference numerals as in the first embodiment will be used for elements of the dust cover 20H according to the comparative configuration that are similar to those of the dust cover 20 of the first embodiment.

[0064] 5, the dust cover 20H of the comparative embodiment does not have the constricted portion 50 of the dust cover 20 of the first embodiment. That is, the dust cover 20H does not have the bent portion 52a and the bent portion 252a. Furthermore, the dust cover 20H does not have the padding portion 60 of the first embodiment. The dust cover 20H of the comparative embodiment has a groove 44H, an extended outer surface 54H, and an extended inner surface 254H, instead of the groove 44, the extended outer surface 54, and the extended inner surface 254 of the first embodiment.

[0065] The groove 44H has a groove bottom 44aH, a groove wall 44bH, and a corner 44dH instead of the groove bottom 44a, groove wall 44b, and corner 44d of the first embodiment. The groove bottom 44aH is a cylindrical surface parallel to the inner circumferential surface 42. The groove wall 44bH has a shorter radial dimension than the groove wall 44c. The distance from the corner 44dH to the central axis C is the same as the distance RD from the corner 44e to the central axis C.

[0066] The extended outer surface 54H is a curved surface that extends from the boundary portion 46 along the outer surface 34 of the body portion 30 and connects to the groove wall 44bH. The extended inner surface 254H is a surface that extends from the boundary portion 46 along the inner surface 32 of the body portion 30 and connects to the inner circumferential surface 42. The extended inner surface 254H coincides with the imaginary surface KS2 in the first embodiment. The outer circumferential portion 15a of the fastening member 15 is located radially outward from the groove wall 44bH. The configuration of the dust cover 20H of the comparative embodiment other than those explicitly described above is the same as that of the dust cover 20 of the first embodiment.

[0067] Dust cover 20H does not have bent portions 52a and 252a. Therefore, in dust cover 20H, stress caused by the rocking of ball stud 11 is concentrated around corners 44dH of grooves 44H in which fastening members 15 are attached. Repeated stress concentration at corners 44dH over a long period of time may cause fatigue failure of dust cover 20H, starting from corners 44dH.

[0068] In contrast to the comparative example, the dust cover 20 of the first embodiment has a bent portion 52a. The bent portion 52a is located away from the corner portion 44d. With the above configuration, stress caused by the rocking of the ball stud 11 is distributed between the corner portion 44d and the bent portion 52a. Therefore, according to the first embodiment, the fatigue life of the dust cover 20 can be improved compared to the comparative example.

[0069] As described above, in the first embodiment, stress concentration at the corners 44 d of the fixed portion 40 is suppressed, thereby reducing displacement of the corners 44 d compared to the comparative embodiment. Specifically, in the first embodiment, when the ball stud 11 pivots within a range of 20° or less (more preferably 30° or less) relative to the central axis C, the corners 44 d of the groove 44 do not displace. That is, in the first embodiment, one or both of the bent portions 52 a and 252 a are formed in the fixed portion 40 so that the corners 44 d of the groove 44 do not displace when the ball stud 11 pivots within a range of 20° or less relative to the central axis C. Note that the angle of the ball stud 11 with respect to the central axis C is the angle between the central axis of the ball stud 11 and the central axis C of the socket 12, as can be seen from FIG. 1 .

[0070] In the first embodiment, the outer peripheral surface 43 (43a, 43b) of the fixed portion 40 is located radially outward from the outer peripheral portion 15a of the fastening member 15. Therefore, the width of the groove wall 44b of the groove portion 44 exceeds the linear width of the fastening member 15. In the above configuration, the entire width of the fastening member 15 overlaps the groove wall 44b in the axial direction. That is, the contact area of ​​the groove wall 44b with the fastening member 15 is larger than the contact area of ​​the groove wall 44bH with the fastening member 15 in the comparative embodiment. Therefore, the contact pressure acting from the fastening member 15 on the groove wall 44b is smaller than the contact pressure acting from the fastening member 15 on the groove wall 44bH in the comparative embodiment. In the above configuration, stress generated at the corner 44d due to contact between the fastening member 15 and the groove wall 44b can be suppressed compared to the dust cover 20H of the comparative embodiment. Therefore, according to the first embodiment, the fatigue life of the fixed portion 40 can be improved compared to the comparative embodiment. In particular, in the first embodiment, the dust cover 20 has the padded portion 60, which further reduces the pressure acting on the groove wall 44b due to contact with the fastening member 15. Therefore, according to the first embodiment, the fatigue life of the fixed portion 40 can be more effectively improved.

[0071] In the first embodiment, the distance RC from the corner 44d to the center axis C is greater than the distance RD from the corner 44e to the center axis C. That is, the thickness TC from the corner 44d to the inner circumferential surface 42 is greater than the thickness TD from the corner 44e to the inner circumferential surface 42. In the above configuration, the stress generated at the corner 44d due to tightening by the fastening member 15 is smaller than that at the corner 44dH of the comparative embodiment. Therefore, according to the first embodiment, the stress generated at the corner 44d due to tightening by the fastening member 15 can be further reduced. In particular, in the first embodiment, the distance GR, which is the difference between the distance RD and the distance RC, is 15% to 60% of the groove width WG of the groove 44. Therefore, the stress generated at the corner 44d due to tightening by the fastening member 15 can be more effectively reduced.

[0072] In the first embodiment, the groove bottom 44a is inclined with respect to the central axis C. Specifically, the groove bottom 44a is inclined with respect to the central axis C so that the distance RC exceeds the distance RD. Therefore, stress caused by fastening by the fastening member 15 tends to act in a direction toward the corner 44e. That is, according to the first embodiment, stress concentration on the corner 44d can be more effectively suppressed than in a configuration in which the groove bottom 44a is parallel to the central axis C.

[0073] Furthermore, the dust cover 20 of the first embodiment has a bent portion 252a. The bent portion 252a is located away from the corner portion 44d. With the above configuration, stress caused by the rocking of the ball stud 11 is dispersed not only to the corner portion 44d and the bent portion 52a but also to the bent portion 252a. Therefore, according to the first embodiment, the fatigue life of the dust cover 20 can be improved compared to the comparative embodiment.

[0074] In the first embodiment, the position of the bent portion 52a in the radial direction is different from the position of the bent portion 252a in the radial direction. With the above configuration, it is possible to prevent the length of the imaginary line connecting the bent portion 52a and the bent portion 252a at the shortest distance from becoming the same as the minimum value of the thickness of the deformable portion of the dust cover 20. Therefore, the fatigue life of the fixed portion 40 can be effectively improved.

[0075] Furthermore, the position of the bent portion 52a in the axial direction is different from the position of the bent portion 252a in the axial direction. With the above configuration, it is possible to prevent the length of the imaginary line connecting the bent portion 52a and the bent portion 252a at the shortest distance from becoming the same as the minimum value of the thickness of the deformable portion of the dust cover 20. Therefore, the fatigue life of the fixed portion 40 can be effectively improved.

[0076] Furthermore, the bent portion 252a is offset from the virtual normal line KN of the bent portion 52a. This more effectively prevents the length of the virtual line connecting the bent portions 52a and 252a at the shortest distance from becoming the same as the minimum thickness of the deformable portion of the dust cover 20. This more effectively improves the fatigue life of the bent portion 52a and the vicinity of the bent portion 252a of the dust cover 20.

[0077] B: Second Embodiment A second embodiment will be described. Note that, for elements in the following exemplary aspects that have the same functions as those in the first embodiment, the same reference numerals as those in the first embodiment will be used, and detailed descriptions of each element will be omitted as appropriate.

[0078] FIG. 6 is a cross-sectional view illustrating the configuration of a dust cover 20 according to a second embodiment. In the first embodiment, the dust cover 20 in which the fixed portion 40 includes both the bent portion 52 a and the bent portion 252 a was exemplified. As illustrated in FIG. 6 , the dust cover 20 according to the second embodiment is similar to the first embodiment in that the fixed portion 40 includes the bent portion 52 a, but differs from the first embodiment in that the fixed portion 40 does not include the bent portion 252 a. That is, in the second embodiment, the extended inner surface 254 (or the extended surface 245) extends in a continuous curved shape from the boundary portion 46 to the inner circumferential surface 42. The extended inner surface 254 (or the extended surface 245) according to the second embodiment has the same shape as the imaginary surface KS2 according to the first embodiment.

[0079] Similar to the first embodiment, the bent surface 52 of the second embodiment has an extended outer surface 54, an outer peripheral surface 43a, and a bent portion 52a. That is, in the second embodiment, the bent portion 52a is formed at a position spaced apart from the corner portion 44d. With the above configuration, similar to the first embodiment, stress caused by pivoting of the ball stud 11 is dispersed to the corner portion 44d and the bent portion 52a. Therefore, similar to the first embodiment, the second embodiment can improve the fatigue life of the dust cover 20 compared to the comparative embodiment.

[0080] C: Third Embodiment FIG. 7 is a cross-sectional view illustrating the configuration of a dust cover 20 according to a third embodiment. In the first embodiment, the dust cover 20 in which the fixed portion 40 includes both the bent portion 52a and the bent portion 252a was exemplified. As illustrated in FIG. 7 , the dust cover 20 of the third embodiment is similar to the first embodiment in that the fixed portion 40 includes the bent portion 252a, but differs from the first embodiment in that the fixed portion 40 does not include the bent portion 52a. That is, in the third embodiment, the extended outer surface 54 (or the outer peripheral surface 43a) extends in a continuous curved shape from the boundary portion 46 to the groove portion 44. The extended outer surface 54 (or the outer peripheral surface 43a) of the third embodiment has a shape similar to the imaginary surface KS1 in the first embodiment.

[0081] Similar to the first embodiment, the bent surface 252 of the third embodiment has an extended inner surface 254, an extended surface 245, and a bent portion 252a. That is, in the third embodiment, the bent portion 252a is formed at a position spaced apart from the corner 44d. With the above configuration, similar to the first embodiment, stress caused by pivoting of the ball stud 11 is dispersed to the corner 44d and the bent portion 252a. Therefore, similar to the first embodiment, the fatigue life of the dust cover 20 can be improved in the third embodiment as well, compared to the comparative embodiment.

[0082] A comparative fatigue life test was conducted using numerical simulation with the finite element method between the dust cover 20 according to each embodiment of the present disclosure (FIGS. 4, 6, and 7) and the dust cover 20H of the comparative embodiment. The results of the comparative test showed that the fatigue life of each of the dust covers 20 according to each embodiment of the present disclosure was at least 1.5 times that of the dust cover 20H of the comparative embodiment. As described above, the comparative test using numerical simulation confirmed that the dust cover 20 according to the present disclosure has a longer fatigue life than the dust cover 20H of the comparative embodiment.

[0083] D: Modifications Specific modifications that can be added to the above-mentioned embodiments are exemplified below. Two or more embodiments arbitrarily selected from the following examples may be combined as appropriate within the scope of not mutually contradicting each other.

[0084] (1) In the above-described embodiments, the groove bottom 44a of the groove 44 in the fixed portion 40 is inclined with respect to the central axis C, but as illustrated in Fig. 8, the groove bottom 44a of the groove 44 may be a cylindrical surface with a uniform radius in the axial direction. Note that Fig. 8 illustrates a configuration in which the fixed portion 40 has both the bent portion 52a and the bent portion 252a, but in the second embodiment (Fig. 6) in which the bent portion 252a is omitted, or in the third embodiment (Fig. 7) in which the bent portion 52a is omitted, the groove bottom 44a of the groove 44 may be a cylindrical surface, as in Fig. 8.

[0085] (2) The term "nth" (n is a natural number) in this application is used only as a formal and convenient label to distinguish each element in the description and does not have any substantive meaning. Therefore, there is no room for restrictive interpretation of the position or order of each element based on the term "nth."

[0086] 100... joint mechanism, 10... ball joint, 11... ball stud, 11a... shaft portion, 11b... spherical portion, 11c... threaded portion, 12... socket, 12a... bearing portion, 12b... support portion, 12c... mounting groove, 13... knuckle, 14... nut, 15... fastening member, 15a... outer periphery, 20... dust cover, 22... seal portion, 30... body portion, 32... inner surface, 34... outer surface, 36... neck portion, 40... Fixed portion, 42...inner surface, 43 (43a, 43b)...outer surface, 44...groove portion, 44a...groove bottom, 44b...groove wall, 44c...groove wall, 44d...corner portion, 44e...corner portion, 46...boundary portion, 50...constricted portion, 52...bent surface, 52a...bent portion, 54...extended outer surface, 60...built-up portion, 245...extended surface, 252...bent surface, 252a...bent portion, 254...extended inner surface, C...central axis, KS1...imaginary surface, KS2...imaginary surface.

Claims

1. A dust cover fixed to a socket that supports a ball stud, comprising: a body portion surrounding the ball stud; and an annular fixed portion connected to the body portion, the fixed portion including an inner circumferential surface that contacts a mounting groove of the socket; an outer circumferential surface opposite the inner circumferential surface; an annular groove portion formed on the outer circumferential surface that accommodates a fastening member that fastens the fixed portion to the socket; and an extended outer surface connecting the outer surface of the body portion to the outer circumferential surface, the outer circumferential surface being bent relative to the extended outer surface at a first bend portion that is located radially outward of the fixed portion than a first imaginary plane that continuously extends the outer surface of the body portion toward the groove, and the dust cover being located radially outward of the outer circumferential portion of the fastening member.

2. The dust cover of claim 1, wherein the groove portion includes a groove bottom that follows the circumferential direction of the fixed portion, a first groove wall that protrudes radially outward from an edge of the groove bottom that is close to the body portion, and a second groove wall that protrudes radially outward from an edge of the groove bottom that is farther from the body portion.

3. A dust cover fixed to a socket supporting a ball stud, comprising: a body portion surrounding the ball stud; and an annular fixed portion connected to the body portion, wherein the fixed portion includes: an inner circumferential surface that contacts an attachment groove of the socket; an outer circumferential surface opposite the inner circumferential surface; an annular groove portion formed on the outer circumferential surface that receives a fastening member that fastens the fixed portion to the socket; and an extended outer surface connecting the outer surface of the body portion to the outer circumferential surface, wherein the outer circumferential surface is bent relative to the extended outer surface at a first bend portion that is located radially outward of the fixed portion relative to a first imaginary plane that continuously extends the outer surface of the body portion toward the groove portion, and the groove portion includes: a groove bottom that follows the circumferential direction of the fixed portion; a first groove wall that protrudes radially outward from an edge of the groove bottom that is close to the body portion; and a second groove wall that protrudes radially outward from an edge of the groove bottom that is farther from the body portion, When the ball stud swings within a range of 20° or less with respect to the central axis of the fixed portion, the corner of the groove between the groove bottom and the first groove wall does not displace.

4. A dust cover according to claim 2 or 3, wherein the first groove wall is a plane perpendicular to the central axis of the fixed portion.

5. A dust cover according to claim 2 or claim 3, wherein the extended outer surface is the region from a boundary located at a distance of 1.2 times the groove width of the groove portion in the direction of the central axis of the fixed portion from the first groove wall toward the body portion to the outer peripheral surface when the dust cover is in an undeformed state.

6. A dust cover according to claim 2 or claim 3, wherein a first distance from an edge of the groove bottom that is closer to the body portion to the central axis of the fixed portion is greater than a second distance from an edge of the groove bottom that is farther from the body portion to the central axis of the fixed portion.

7. The dust cover according to claim 6, wherein the difference between the first distance and the second distance is 15% to 60% of the groove width of the groove portion.

8. A dust cover according to claim 2 or claim 3, wherein the groove bottom is inclined with respect to the central axis of the fixed part so that a first distance from an edge of the groove bottom that is closer to the body part to the central axis of the fixed part exceeds a second distance from an edge of the groove bottom that is farther from the body part to the central axis of the fixed part.

9. A dust cover according to claim 1 or claim 3, wherein the fixed portion further includes a curved surface connecting the inner surface of the body portion and the inner circumferential surface, and the curved surface includes a first surface continuous with the inner surface of the body portion and a second surface connecting the first surface and the inner circumferential surface, and the second surface is curved radially inward of the fixed portion relative to the first surface at a second curved portion located outside a second imaginary plane that continuously extends the inner surface of the body portion toward the inner circumferential surface.

10. The dust cover according to claim 9, wherein the position of the first bent portion in the radial direction of the fixed portion is different from the position of the second bent portion in the radial direction.

11. The dust cover according to claim 9, wherein the position of the first bent portion in the direction of the central axis of the fixed portion is different from the position of the second bent portion in the direction of the central axis.

12. A dust cover fixed to a socket that supports a ball stud, comprising: a body portion surrounding the ball stud; and an annular fixed portion connected to the body portion, the fixed portion including: an inner circumferential surface that contacts an attachment groove of the socket; an outer circumferential surface opposite the inner circumferential surface; an annular groove formed on the outer circumferential surface that accommodates a fastening member that fastens the fixed portion to the socket; and a curved surface connecting the inner surface of the body portion to the inner circumferential surface, the curved surface including a first surface continuous with the inner surface of the body portion, and a second surface connecting the first surface to the inner circumferential surface, the second surface being bent radially inward of the fixed portion relative to the first surface at a second bend portion located outside a second imaginary plane that continuously extends the inner surface of the body portion toward the inner circumferential surface.

13. A joint mechanism comprising: a socket having an attachment groove; a ball stud supported by said socket; a dust cover including a body portion surrounding the ball stud and an annular fastened portion connected to the body portion; and a fastening member for fastening the fastened portion to the socket, wherein the fastened portion includes an inner circumferential surface that contacts the attachment groove of the socket; an outer circumferential surface opposite to the inner circumferential surface; an annular groove portion formed on the outer circumferential surface for accommodating the fastening member; and an extended outer surface connecting the outer surface of the body portion to the outer circumferential surface, wherein the outer circumferential surface is bent relative to the extended outer surface at a first bend portion that is located radially outward of the fastened portion relative to a first imaginary plane that continuously extends the outer surface of the body portion toward the groove portion, and is located radially outward of the outer circumferential portion of the fastening member.

14. A joint mechanism according to claim 13, wherein the groove portion includes a groove bottom that follows the circumferential direction of the fixed portion, a first groove wall that protrudes radially outward from an edge of the groove bottom that is close to the body portion, and a second groove wall that protrudes radially outward from an edge of the groove bottom that is farther from the body portion.

15. A joint mechanism comprising: a socket having an attachment groove; a ball stud supported by said socket; a dust cover including a body portion surrounding said ball stud and an annular fixed portion connected to said body portion; and a fastening member for fastening said fixed portion to said socket, wherein said fixed portion includes an inner circumferential surface contacting the attachment groove of said socket; an outer circumferential surface opposite to said inner circumferential surface; an annular groove portion formed on said outer circumferential surface for accommodating said fastening member; and an extended outer surface connecting an outer surface of said body portion to said outer circumferential surface, said outer circumferential surface being bent relative to said extended outer surface at a first bend portion located radially outward of said fixed portion relative to a first imaginary plane formed by continuously extending the outer surface of said body portion toward said groove portion, said groove portion comprising: a groove bottom along the circumferential direction of said fixed portion; and a first groove wall protruding radially outward from an edge portion of said groove bottom that is close to said body portion. a second groove wall protruding radially outward from an edge of the groove bottom farthest from the body portion, wherein a corner of the groove between the groove bottom and the first groove wall does not displace when the ball stud swings within a range of 20° or less with respect to the central axis of the fixed portion.

16. A joint mechanism according to claim 14 or 15, wherein the first groove wall is a plane perpendicular to the central axis of the fixed part.

17. A joint mechanism comprising: a socket having an attachment groove; a ball stud supported by said socket; a dust cover including a body portion surrounding the ball stud and an annular fastened portion connected to the body portion; and a fastening member for fastening the fastened portion to the socket, wherein the fastened portion includes an inner circumferential surface that contacts the attachment groove of the socket; an outer circumferential surface opposite to the inner circumferential surface; an annular groove portion formed on the outer circumferential surface for accommodating the fastening member; and a curved surface connecting the inner surface of the body portion to the inner circumferential surface, wherein the curved surface includes a first surface continuing with the inner surface of the body portion and a second surface connecting the first surface to the inner circumferential surface, and the second surface bends radially inward of the fastened portion relative to the first surface at a second bend portion located outside a second imaginary plane that continuously extends the inner surface of the body portion toward the inner circumferential surface.

Images