The present invention relates to a ball joint mainly used as a coupling device of a link mechanism for a vehicle and particularly relates to a ball joint in which the sealing characteristic of a dust cover is not reduced.
Conventionally, for example, the one described in Patent Literature 1 has been known as a ball joint which is used in a suspension mechanism or a steering mechanism of a vehicle. This ball joint has a structure in which a small-diameter side end part of a dust cover composed of an elastic material such as rubber is provided with a lip part (annular projection) which is in close contact by elasticity with the entire periphery of the outer peripheral surface of a flange part of a ball stud, and the small-diameter side end part is brought into close contact with the flange-part end surface of the ball stud by the urging force generated by the elasticity of the dust cover.
However, the elastic force of the dust cover is reduced due to time-dependent change such as thermal deterioration; and, in a low-temperature environment, the elastic material such as rubber is hardened, and the elastic force is significantly reduced compared with that in a normal temperature environment. Therefore, in the conventional ball joint as described above, the urging force of the small-diameter side end part with respect to the flange-part end surface is reduced along with reduction in the elastic force of the dust cover, and the close contact between the small-diameter side end part and the flange part cannot be maintained.
Particularly when the ball stud swings in a low-temperature environment, the side in which the film part (bellows part) of the dust cover is stretched, in other words, in the side in which the distance between the socket outer peripheral surface to which the dust cover is attached and the flange part of the ball stud is increased, the small-diameter side end part of the dust cover is strained to the socket-side direction by the hardened film part. Therefore, an appropriate assembly state with respect to the ball stud cannot be maintained, and the sealing characteristic of the dust cover is reduced. Therefore, the structure of the ball joint described in Patent Literature 1 has a problem that the dust cover cannot exhibit a good sealing characteristic in all the environments in which the ball joint is used. The urging force of the dust cover is the force that is generated by the elastic force of the film part that works to restore deformation when the dust cover is assembled with the socket and the ball stud. Therefore, the shape of the film part such as a film thickness and a film length affects the magnitude of the obtained urging force. The larger the swing angle of the ball stud with respect to the socket, the larger the film length of the dust cover has to be in order to follow the swinging actuation thereof. However, the larger the film length, the less the film part of the dust cover undergoes buckling, partial extreme bending, etc. in the state assembled with the socket and the ball stud, and it is difficult to generate predetermined urging force. Therefore, in the case in which a comparatively large swing angle is needed, there is a problem that the urging force that is necessary for bringing the small-diameter side end part into close contact with the flange-part end surface of the ball stud cannot be obtained by the structure of the ball joint described in Patent Literature 1. Furthermore, in the case in which a comparatively large swing angle is required, a function of generating predetermined urging force in the shape of the film part is added. Therefore, compared with the case without the addition of the function, management of a complex film shape and highly-precise film shape in consideration of thick film thickness or the state of elastic deformation is required, and the cost of the dust cover is increased. It is an object of the present invention to provide at low cost a ball joint capable of maintaining a good sealing characteristic even when the film part of the dust cover is strained and capable of improving the assembly characteristic of the dust cover.
The present invention is configured in the below manner in order to achieve this object. First, the present invention is a ball joint having: a ball stud provided with a spherical head part at one end of a stud part; a socket turnably housing the spherical head part, the socket having one side provided with an opening from which the stud part projects; and a dust cover provided with a small-diameter opening attached to the stud part and a large-diameter opening attached to the socket, the dust cover having elasticity; wherein the stud part of the ball stud is provided with a first flange part, an intermediate shaft part, and a second flange part sequentially from the side of the spherical head part; the small-diameter opening of the dust cover is provided with an inner peripheral part sandwiched between the first flange part and the second flange part and fits the intermediate shaft part by elasticity, a lip part being in close contact with an outer peripheral surface of the second flange part by elasticity, and a protruding part positioned between the inner peripheral part and the lip part, having at least a gap at one location, and abutting a spherical-head-part side end surface of the second flange part.
The protruding part of the dust cover is composed of an annular protrusion provided with one or a plurality of cut-away part or is composed of a plurality of protrusions of any one species of or a combination of two or more species of a circular-cone protrusion, a hemispherical protrusion, a circular-cylindrical protrusion, a pyramidal protrusion, and a prism protrusion disposed in a circumferential direction.
The second flange part of the ball stud is inclined toward the inside of a radial direction so that the spherical-head-part side end surface is close to the spherical head part side; and the intermediate shaft part of the ball stud is inclined so that the diameter of the outer peripheral surface thereof is reduced toward the spherical head part side.
Furthermore, the inner peripheral part of the dust cover has an end part of the first flange part side having a diameter larger than the diameter of an end part of the second flange part side and is provided with a groove in a circumferential direction which retains a lubricant agent.
According to the present invention, the small-diameter opening of the dust cover can be reliably retained with the ball stud since the ball stud is provided with the first flange part and the second flange part. Therefore, the close contact of the dust cover with respect to the ball stud can be maintained even when the elastic force of the dust cover is changed depending on a used environment, and the film is not required to have an increased thickness or have a complex shape in order to ensure the urging force of the dust cover toward the ball stud in that process. Therefore, a ball joint capable of maintaining a good sealing characteristic can be provided at low cost. According to the present invention, the dust cover is provided with the protruding part having a gap at least at one location and abutting the spherical-head-part side end surface of the second flange part of the ball stud. Therefore, the inner peripheral part of the dust cover can be reliably positioned between the first flange part and the second flange part of the ball stud. Therefore, a good sealing characteristic can be ensured. Moreover, the protruding part is provided with the location not abutting the spherical-head-part side end surface of the second flange part of the ball stud. As a result, the deformation rigidity of the protruding part can be reduced. Therefore, upon assembly of the dust cover, stoppage in the state in which the protruding part is spread over the outer peripheral surface of the second flange part is not caused, and the dust cover can be easily assembled at a predetermined position. Furthermore, in the state in which the ball joint is used, the protruding part is provided with a part that is not in contact with the ball stud when the ball stud actuates to slide about the axial line thereof with respect to the socket. Therefore, joined-turning of the dust cover and the ball stud can be prevented, and the sealing characteristic can be improved. According to the present invention, the spherical-head-part side end surface of the second flange part of the ball stud is inclined toward the inside of the radial direction so as to be close to the spherical head part side. As a result, upon assembly of the dust cover, the resistance generated upon introduction of the protruding part to the predetermined position can be reduced, and the assembly characteristic of the dust cover can be therefore improved. According to the present invention, the outer peripheral surface of the intermediate shaft part of the ball stud is tapered so that the diameter thereof is reduced toward the spherical head part side. As a result, in the process in which the inner peripheral part of the small-diameter opening is seated upon assembly of the dust cover, the contact resistance of the inner peripheral part and the outer peripheral surface of the intermediate shaft part is reduced to facilitate movement, and the inner peripheral part and the protruding part can be smoothly introduced to the predetermined position. Therefore, the assembly characteristic of the dust cover can be improved. According to the present invention, the inner peripheral part of the small-diameter opening of the dust cover is configured so that the diameter of the first-flange-part side end part is larger than the diameter of the second-flange-part side end part.
As a result, in the process in which the inner peripheral part of the small-diameter opening is seated upon assembly of the dust cover, the contact resistance of the inner peripheral part and the outer peripheral surface of the intermediate shaft part is reduced to facilitate movement, and the inner peripheral part and the protruding part can be smoothly introduced to the predetermined position.
Therefore, the assembly characteristic of the dust cover can be improved.
Also, the shape of the film part 38 is not limited to the shape shown in
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Furthermore, except the part of the gap 48, the protruding part 46 is abutting a spherical-head-part side end surface 24b of the second flange part 24.
The protruding part 46 of the dust cover 36 is provided in order to position the inner peripheral part 44 in the axial direction between the first flange part 20 and the second flange part 24 of the ball stud 12. In other words, the inner peripheral part 44 is positioned when the distal end 46a of the protruding part 46 and the jaw part 42 are compressed and sandwiched by the first flange part 20 and the second flange part 24. In this manner, in addition to bringing the inner peripheral part 44 of the dust cover 36 into close contact with the intermediate shaft part 22 of the ball stud 12 by elasticity, the inner peripheral part 44 is sandwiched between the first flange part 20 and the second flange part 24 so as to reliably fit the intermediate shaft part 22. As a result, the small-diameter opening 40 of the dust cover 36 can be firmly retained by the ball stud 12. Therefore, a good sealing characteristic can be maintained. Upon assembly of the dust cover 36, the spherical head part 16 of the ball stud 12 is housed in the ball seat 30 in the socket 32, and the large-diameter opening 52 and the small-diameter opening 40 of the dust cover 36 are subjected to insertion from the handle part 28 side of the ball stud 12. In the process in which the inner peripheral part 44 of the dust cover 36 is assembled at a predetermined position, the inner peripheral part 44 sequentially passes the jaw part 42 to the second flange part 24 when the inner peripheral part 44 is to pass through the second flange part 24. Therefore, the part of the inner peripheral part 44 after passing through the second flange part has an inner diameter smaller than the outer shape of the second flange part 24 because of the restoring force of elastic deformation. As a result, the inner peripheral part 44 and the peripheral part thereof receive the force in the direction that lifts up the protruding part 46 side to the outside of the radial direction. Also, the reaction force of the lip part 50 against the tension force to the second flange part 24 works in the direction that increases the force in the direction that lifts up the protruding part 46 side to the outside of the radial direction. If the protruding part 46 is not provided with the gap 48, in other words, if the protruding part 46 has high deformation rigidity, upon assembly of the dust cover 36, the protruding part 46 easily stops in the state in which the protruding part is spread over the outer peripheral surface 24a of the second flange part 24 due to the force in the direction of lift-up to the outside of the radial direction. However, this can be prevented by cutting away part of the protruding part 46 to provide the gap 48 and reduce the deformation rigidity, and the assembly characteristic of the dust cover 36 is improved.
If the inner peripheral part 44 of the dust cover 36 is seated on the intermediate shaft part 22 in the state in which it is inclined with respect to the axial line direction of the ball stud 12, defective assembly (the state in which not assembled at the predetermined position) such as stoppage in the state in which the protruding part 46 is spread over the outer peripheral part 24a of the second flange part 24 easily occurs.
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The number of the groove 60 is one in the present embodiment. However, a plurality of grooves narrower than that may be provided, and the groove (s) may be provided in the embodiment shown in
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When the spherical-head-part side end surface 62b is inclined in this manner, upon assembly of the dust cover 36, the resistance generated upon introduction of the protruding part 46 to the predetermined position, in other words, the resistance generated when the protruding part 46 is moved from the outer peripheral surface 62a of the second flange part 62 to the spherical-head-part side end surface 62b over a corner part 62c can be reduced. Therefore, the assembly characteristic of the dust cover 36 can be improved.
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The present invention can be applied not only to a ball joint used as a coupling device of a link mechanism for a vehicle, but also to any ball joint provided with a dust cover; and the present invention is not limited to the above described embodiments and includes arbitrary modifications that do not impair the object and advantages thereof.
Number | Date | Country | Kind |
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2009-243353 | Oct 2009 | JP | national |
Number | Date | Country | |
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Parent | PCT/JP2010/068134 | Oct 2010 | US |
Child | 13400956 | US |