JP5349577B2 - Ball joint and manufacturing method thereof - Google Patents

Description

  The present invention relates to a ball joint used for a link mechanism such as a stabilizer connecting rod or a mission control unit of an automobile, and a manufacturing method thereof.

  As this type of ball joint, one disclosed in Japanese Patent Laid-Open No. 9-189322 (Patent Document 1) is known. The ball joint disclosed in this document includes a ball stud having a ball serving as a swing center of a link mechanism at the tip of a shaft member, and a holder that slidably contacts the spherical surface of the ball covering the maximum diameter portion of the ball stud And is composed of.

  The holder is formed by casting using the ball as a core, and by using a steel ball for bearing having a high sphericity as the ball, the sphericity with the spherical surface of the ball transferred to the holder A high metal sliding contact surface is formed. The ball stud is formed by electrical resistance welding of a shaft member to the ball after casting of the holder. For this electric resistance welding, it is necessary to pass a welding current between the ball and the shaft member. However, since the holder cast with the ball as the core is in close contact with the ball, The electrode is not brought into direct contact with the holder, but the electrode is brought into contact with a holder that is in close contact with the ball, whereby a welding current is passed between the ball and the shaft member.

  In addition, the holder molded as described above is in close contact with the ball due to the crimping that occurs after casting, and the ball stud cannot be swung with respect to the holder. For this reason, in the ball joint disclosed in Patent Document 1, the ball stud is hit in the axial direction, and the metal sliding contact surface of the holder formed by casting is rolled by the spherical surface of the ball, so that the holder and the ball A gap is formed between the ball stud and the ball stud relative to the holder.

  On the other hand, Japanese Patent Application Laid-Open No. 2004-316771 (Patent Document 2) discloses a ball joint in which a ball and a holder cast as a core are separated by a resin sliding contact member. The resin sliding contact member covers the maximum diameter portion of the ball stud and is in sliding contact with the spherical surface of the ball, and the holder covers the periphery of the resin sliding contact member and holds the resin sliding contact member. The holder is formed by casting using a ball covered with the resin sliding contact member as a core, and the resin sliding contact member is fixed to the holder with a resin sliding contact surface that follows the spherical surface of the ball. Thus, a smooth movement of the ball stud with respect to the holder is ensured.

  The ball stud is formed by electric resistance welding of a shaft member to the ball after casting of the holder, as in the above-mentioned Patent Document 1. However, since a resin sliding contact member exists between the ball and the holder, it is impossible to apply a welding current to the ball using the holder as in Patent Document 1. For this reason, the resin sliding contact member and the holder are provided with a power supply opening, and the power supply electrode is brought into direct contact with the ball through the power supply opening.

  Furthermore, in the ball joint of Patent Document 2, by applying heat again to the resin sliding contact member after completion of casting of the holder, the force with which the resin sliding contact member clamps the ball is reduced, and the holder It manages the movement of the ball stud with respect to. That is, in the ball joint of Patent Document 2, there is no need to positively form a gap between the ball and the holder by plastically deforming the holder as in Patent Document 1, and the smooth movement of the ball stud relative to the holder is prevented. It was possible to realize.

JP-A-9-189322 Japanese Patent Application Laid-Open No. 2004-316771

  Thus, in the ball joint of Patent Document 2, the resin sliding contact member and the ball are in sliding contact with almost no gap, and the ball stud can move smoothly. In order to prevent foreign matter from entering from the outside, it is necessary to close the power supply opening with a closing cap after the ball stud is completed. The closing cap is fixed to the holder by caulking the peripheral edge of the power supply opening. However, since the other member is fixed to the opening of the holder, the work is fully performed. Even if expected, there was a possibility that the sealing performance between the closing cap and the holder would be insufficient due to unforeseen reasons. If such a situation occurs, lubricating oil may leak from the inside of the holder sealed with the closing cap, or foreign matter may enter the inside from the outside of the holder. Exercise may be impaired.

  The present invention has been made in view of such a problem, and an object of the present invention is to provide electric resistance welding of a shaft member to the ball without providing a power supply opening for a holder cast with the ball as a core. Another object of the present invention is to provide a ball joint capable of ensuring the smooth operation of the ball stud with respect to the holder without any special treatment, and a method for manufacturing the same.

  The ball joint of the present invention that achieves the above object includes a first opening that has a sliding contact surface between the ball and the ball, covers the maximum diameter portion of the ball, and exposes the spherical surface of the ball in opposite directions. A resin sliding contact member having a portion and a second opening, a body portion formed by casting with the ball and the resin sliding contact member placed thereon as a core, and covering the periphery of the resin sliding contact member; A spherical portion of the ball that is integrally formed with a blocking portion that covers the spherical surface of the ball protruding from the second opening portion of the resin sliding contact member and contacts the ball, and that is exposed from the first opening portion of the resin sliding contact member. And a non-contact holder, and a shaft member which forms a ball stud integrally with the ball by electric resistance welding after casting of the holder.

  Further, the ball joint manufacturing method of the present invention that achieves the above-described object has a sliding contact surface with the ball to cover the maximum diameter portion of the ball, and the spherical surface of the ball is exposed in opposite directions. A body portion that covers the periphery of the resin sliding contact member by molding a resin sliding contact member having an opening and a second opening, and casting with the ball and the resin sliding contact member placed on the ball as a core And a spherical surface of the ball that covers the spherical surface of the ball protruding from the second opening of the resin sliding contact member and contacts the ball, and is exposed from the first opening of the resin sliding contact member Forming a non-contact holder, and contacting the shaft while abutting the shaft member against the ball exposed from the first opening of the resin sliding contact member and contacting the electrode with the shaft member, Occlusion The contacting of the electrodes, and a, and forming a ball stud joined by electric resistance welding the ball and the shaft portion.

  Since the holder is integrally provided with a closing portion that covers the spherical surface of the ball protruding from the second opening of the resin sliding contact member and contacts the ball, the shaft member is electrically resistance welded to the ball. In this case, if a power feeding electrode is brought into contact with the holder, a welding current can be supplied to the ball from the closed portion. That is, since it is not necessary to provide a power supply opening for the holder, there is no need for a closing cap that closes the power supply opening after completion of the ball stud welding, thereby reducing the number of parts and simplifying the production process. This can be realized and the production cost can be reduced.

  In addition, the closed portion cast integrally with the holder is in contact with the ball, but when the shaft member is welded to the ball after casting of the holder, the resin sliding contact member is It has a shape that expands more in the vicinity of the first opening where the shaft member is welded to the ball than in the vicinity of the second opening that is covered by the blocking portion, and the ball after welding is slightly smaller in the direction of lifting from the blocking portion. Will be displaced. As a result, the contact surface pressure between the closed portion of the holder and the ball is weakened, and it is possible to ensure the smooth operation of the ball stud with respect to the holder without any special treatment being performed on the holder after casting.

It is front sectional drawing which shows an example of embodiment of the ball joint to which this invention was applied. FIG. 2 is a front view showing a state where a resin sliding contact member is covered on a ball in the ball joint manufacturing method shown in FIG. 1. FIG. 2 is a cross-sectional view showing a state in which a holder is cast using a ball and a resin sliding contact member as a core in the ball joint manufacturing method shown in FIG. 1. FIG. 2 is a front sectional view showing a cast holder in the method for manufacturing the ball joint shown in FIG. 1. FIG. 2 is a front cross-sectional view showing a state in which a shaft member is welded to a ball held by a holder in the ball joint manufacturing method shown in FIG. 1. FIG. 2 is a front sectional view showing a state after a shaft member is welded to a ball in the ball joint manufacturing method shown in FIG. 1. It is the schematic diagram which showed a mode that the ball expanded the resin sliding contact member, when the shaft member was electrically resistance-welded with respect to the ball | bowl.

  Hereinafter, a ball joint and a manufacturing method thereof according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows an example of an embodiment of a ball joint to which the present invention is applied. The ball joint includes a ball stud 1 having a ball 10 at the tip of a shaft member 11, a resin sliding contact member 3 that is covered with the ball 10 and that is in sliding contact with the ball 10, and around the resin sliding contact member 3. A holder 2 is molded and the resin sliding contact member 3 is fixed thereto, and the ball stud 1 is pivotably connected to the holder 2 around the ball.

  The ball stud 1 is formed by electric resistance welding of a rod-shaped shaft member 11 to a steel ball for a bearing having a high sphericity that becomes a ball 10. The shaft member 11 is formed with a flange 12 having a seating surface for fixing a body to be attached such as a link, and a male screw 13 is formed on the opposite side of the ball 10 with the flange 12 interposed therebetween. ing. Moreover, the said collar part 12 is formed in the shape of a hexagon nut, and it is possible to fasten the external thread 13 of the said ball stud 1 to to-be-attached bodies, such as a link, using a spanner wrench.

  The resin sliding contact member 3 has a first opening 31 and a second opening 32 through which the spherical surface of the ball 10 is exposed in opposite directions, and is formed in an annular shape, and substantially matches the spherical surface of the ball 10 on the inside. The concave spherical resin sliding contact surface 30 is provided. The shaft member 11 of the ball stud 1 is joined to the spherical surface of the ball 10 exposed from the first opening 31. The resin sliding contact member 3 covers the maximum diameter portion of the ball 10 and covers approximately 2/3 of the spherical surface of the ball 10.

  On the other hand, the holder 2 includes a main body 20 provided around the resin sliding contact member, a fixing portion 21 for coupling the main body 20 to the link, and the resin sliding contact member. The main body part 20, the fixing part 21 and the closing part 23 are integrally formed by die casting of an aluminum alloy or a zinc alloy. Although not shown in FIG. 1, the fixing portion 21 is formed with a female screw so that, for example, a male screw formed at the tip of a rod or the like constituting the link can be coupled. Further, the main body 20 can be directly fixed to the mounted body without providing the fixing portion 21.

  The main body portion 20 is formed in an annular shape outside the resin sliding contact member 3, and the resin sliding contact member 3 is fixed to the main body portion 20. Further, the main body 20 is provided with a holder opening 22 corresponding to the first opening 31 of the resin sliding contact member 3, and the first opening of the resin sliding contact member 3 is provided from the holder opening 22. The peripheral edge of the opening 31 is slightly exposed. That is, the main body 20 of the holder 2 is not in contact with the spherical surface of the ball 10 exposed from the first opening.

  Further, the closing portion 23 of the holder 2 is formed integrally with the main body portion 20 by the above-described casting, covers the second opening portion 32 of the resin sliding contact member 3, and protrudes from the second opening portion 32. The ball 10 is in contact with the convex spherical surface. That is, a metal slidable contact surface 23 a to which the convex spherical surface of the ball 10 is transferred is formed in the closing portion 23, and the metal slidable contact surface 23 a and the convex spherical surface of the ball 10 protruding from the second opening 32. In contact. The metal slidable contact surface 23a is continuous with the resin slidable contact surface 30 of the resin slidable contact member 3 without a step, and the metal slidable contact surface 23a and the resin slidable contact surface 30 come into contact with the ball 10 without a gap. A concave spherical surface is formed.

  Further, a boot seal 4 is attached between the outer peripheral edge of the main body portion 20 of the holder 2 and the shaft member 11 of the ball stud 1, and a gap between the ball 10 of the ball stud 1 and the main body portion 20 of the holder 2. In addition to preventing dust and dirt from entering the seal pocket 40, a seal pocket 40 for accommodating a lubricant such as grease is formed. Here, the end 41 on the ball stud 1 side of the boot seal 4 is in close contact with the shaft member 11 due to its elasticity, while the end 42 on the holder 2 side is sandwiched between the outer peripheral edge of the holder 2 by a locking ring. Therefore, the ball stud 1 does not come off even when the ball stud 1 swings or rotates.

  Next, a specific method for manufacturing the ball joint of this embodiment will be described.

  In the first step, the resin sliding contact member 3 is formed and mounted on a bearing steel ball that becomes the ball 10. As an example of the material of the resin sliding contact member 3, polyether ether ketone (manufactured by Victorex / trade name: PEEK) is used, and the thickness thereof is set to about 1.0 mm, for example. FIG. 2 is a front view showing a state where the resin sliding contact member 3 is mounted on the ball 10. The resin sliding contact member 3 is formed in an annular shape having an inner diameter that matches the outer diameter of the ball 10, and has the first opening 31 and the second opening 32 where the spherical surface of the ball 10 is exposed in opposite directions as described above. Have. The inner diameter D2 of the second opening 32 is set to be smaller than the inner diameter D1 of the first opening 31, and the distance H from the center O of the ball 10 to the first opening 31 and the center O of the ball 10 are set. When the distance h from the second opening 32 is compared, H <h. Therefore, the contact area between the resin sliding contact member 3 and the spherical surface of the ball 10 is smaller on the first opening 31 side than the center O of the ball 10 and larger on the second opening 32 side. .

  As an example of covering the resin sliding contact member 3 with the ball 10, the resin sliding contact member 3 is injection-molded using the ball 10 as a core, and the molding of the resin sliding contact member 3 and the mounting to the ball 10 are performed as one. It is possible to carry out in one process. When the resin sliding contact member 3 is molded using the ball 10 itself as a core in this way, the mounting effort to the ball 10 is omitted, and the spherical surface of the ball 10 is the resin sliding contact surface 30 of the resin sliding contact member 3. Therefore, the resin sliding contact member 3 and the ball 10 are in surface contact with no gap, and the sliding contact state between them can be improved.

  Note that only the resin sliding contact member 3 is formed without using the ball 10 as a core, and the ball 10 is introduced into the resin sliding contact member 3 from the first opening 31 of the molded resin sliding contact member 3. The resin sliding contact member 3 may be attached to the ball 10 by pushing it in.

  Next, the holder 2 is die-cast. In this die casting, as shown in FIG. 3, a ball 10 and a resin sliding contact member 3 attached to the ball 10 are inserted into a core in a pair of upper and lower casting molds 5 and 6. In this state, a molten aluminum alloy or zinc alloy is press-fitted into the cavity 7 in the mold. At this time, the ball 10 is fitted to a concave spherical support seat 60 formed on the mold 6 with the spherical surface exposed from the first opening 31 of the resin sliding contact member 3, and the support seat 60 has a peripheral edge. It contacts the periphery of the first opening 31 of the resin sliding contact member 3. In order to securely fix the ball 10 to the support seat 60, a magnetic attractive force may be applied to the ball 10 from the support seat 60.

  Thereby, as shown in FIG. 4, the holder 2 in which the ball 10 and the resin sliding contact member 3 are wrapped with the alloy is cast. In the cast holder 2, the holder opening 22 is formed at a portion corresponding to the support seat 60 of the mold 6, and the ball 10 is exposed only from the holder opening 22. The holder 2 is not in contact with the ball 10 in the first opening 31 of the resin sliding contact member 3, but the second opening 32 is covered with a closing portion 23 formed integrally with the main body 20. A metal sliding contact surface 23 a that contacts the spherical surface of the ball 10 protruding from the second opening 32 is formed in the closing portion 23. When the holder 2 is cast, the resin sliding contact member 3 attached to the ball 10 is embedded in the main body 20 of the cast holder 2, and the resin sliding contact with the ball 10 is made. The resin slidable contact surface 30 of the contact member 3 and the metal slidable contact surface 23a of the closing portion 23 are formed as one concave spherical surface that is continuous without a step. The concave spherical surface is in contact with the spherical surface of the ball 10 without a gap.

  Next, the shaft member 11 is welded to the ball 10. For such welding, projection welding which is a kind of electric resistance welding is used. Specifically, as shown in FIG. 5, the end surface of the shaft member 11 is pressed with a predetermined force F against the spherical surface of the ball 10 exposed from the holder opening 22, while the closing portion 23 of the holder 2 and The electrodes 14 and 15 are brought into contact with the shaft member 11, respectively, and a welding current is supplied to the closing portion 23 and the shaft member 11. A mounting surface 24 for contacting the electrode 14 is formed on the outside of the closing portion 23, and the mounting surface 24 has a circular shape centering on the axial center line of the ball stud 1. The electrode 15 is formed in an annular shape and abuts against the flange 12 of the shaft member 1.

  Since the holder 2 is cast using the ball 10 and the resin sliding contact member 3 as a core, the metal sliding contact surface 23a to which the spherical surface of the ball 10 is transferred is formed in the closing portion 23 of the holder 2 as already described. The metal sliding contact surface 23a is in contact with the spherical surface of the ball 10 without a gap. For this reason, by bringing the electrode 14 into contact with the closed portion 23, a welding current can be passed from the closed portion 23 to the ball 10, and the ball 10 and the shaft member 11 can be electrically resistance welded. It becomes.

  When the electric resistance welding is completed in this way, as shown in FIG. 6, the tip surface of the shaft member 11 is joined to the ball 10, and the ball 10 is connected to the main body of the holder 2 via the resin sliding contact member 3. The ball stud 1 held by the part is completed.

  At the stage after the casting of the holder 2 and before the shaft member 11 is welded to the ball 10, the main body portion 20 of the holder 2 moves outside the resin sliding contact member 3 due to the shrinkage of the holder 2 that proceeds after casting. Therefore, a large resistance acts on the rotation of the ball 10 relative to the resin sliding contact member 3 as it is. Further, since the metal sliding contact surface 23a formed on the closing portion 23 of the holder 2 by the casting is in close contact with the ball 10, the free rotation of the ball 10 is also prevented in this respect. .

  However, when the shaft member 11 is electrically resistance-welded to the ball 10 after the holder 10 is cast, the periphery of the joint between the ball 10 and the shaft member 11 becomes a heat source S as shown in FIG. The ball 10 is heated, and the heat is transmitted to the resin sliding contact member 3 that fastens the ball 10. Since the ball 10 and the resin sliding contact member 3 have a difference in coefficient of thermal expansion and also have a difference in contraction speed at the time of cooling, the resin sliding contact member 3 once spread by heating is not at the time of cooling. It is not possible to completely return to the original shape at the contraction stage, and it is possible to loosen the resin sliding contact member 3 with respect to the ball 10.

  At this time, the ball 10 itself undergoes a slight thermal expansion at a lower temperature than normal temperature, and the resin sliding contact member 3 is pushed and expanded. However, since the heat source S is a joint portion between the ball 10 and the shaft member 11, 7, the amount of expansion of the ball 10 increases in the vicinity of the first opening 31, and in the vicinity of the second opening 32 away from the heat source S than in the vicinity of the first opening 31. However, the amount of expansion becomes small. That is, the amount by which the resin sliding contact member 3 is expanded by the thermal expansion of the ball 10 is larger in the vicinity of the first opening 31 than in the vicinity of the second opening 32.

  The main body 20 of the holder 2 is not in contact with the ball exposed from the first opening, while the ball 10 passes through the second opening 32 of the resin sliding contact member 3 and the metal of the closing part 23. Since the ball 10 expands due to heat during electric resistance welding because it is in contact with the sliding contact surface 23a, the center of the ball 10 is directed toward the first opening 31 by a reaction force that presses the metal sliding contact surface 23a. It will be displaced slightly. For this reason, when the ball 10 is thermally expanded, the resin sliding contact member 3 is greatly expanded near the first opening 31 than near the second opening 32.

  As described above, when the shaft member 11 is welded to the ball 10, the resin sliding contact member 3 is temporarily moved closer to the first opening portion 31 than to the second opening portion 32 in a state where the ball is heated. The ball 10 and the shaft member 11 are completely joined to each other, and when the ball is cooled, the ball is lifted from the closing portion 23 (the direction indicated by the white arrow in FIG. 7). Will be slightly displaced. For this reason, although the ball 10 is in contact with the metal sliding contact surface 23a of the closing portion 23, the contact surface pressure between them is reduced.

  That is, in the ball joint of this embodiment, the closing portion 23 that covers the second opening portion 32 of the resin sliding contact member 3 is provided integrally with the holder 2, and the second opening portion 32 with respect to the closing portion 23 is provided. When the electric resistance welding of the shaft member 11 to the ball 10 is completed as a result of contacting the spherical surface of the ball 10 protruding from the ball 10, the clamping force of the resin sliding contact member 3 to the ball 10 is reduced, and the ball 10 and the blockage are further closed. The contact surface pressure with the metal sliding contact surface 23a of the part 23 is reduced, and the ball stud 1 completed by the welding can be moved lightly with respect to the holder 2 without performing any special treatment.

  In particular, in the above-described embodiment, the inner diameter D2 of the second opening 32 of the resin sliding contact member 3 is smaller than the inner diameter D1 of the first opening 31, and the ball 10 is formed from the center of the closing portion 23. More spherical surfaces are in contact with the resin sliding contact member 3 on the side. For this reason, when the fastening force of the resin sliding contact member 3 is reduced by welding the shaft member 11 to the ball 10, the first opening 31 and the second opening 32 are formed to have the same inner diameter. In comparison with the ball 10, the degree of freedom in the direction in which the ball 10 floats from the closing portion 23 is likely to increase. Therefore, in the ball joint of this embodiment, the contact surface pressure between the metal sliding contact surface 23a of the closing portion 23 and the ball 10 can be further reduced, and the contact state between the ball 10 and the closing portion 23 is maintained. The stud 1 can be moved lightly with respect to the holder 2.

  The inner diameter of the first opening 31 of the resin sliding contact member 3 is determined from the relationship with the movable range of the ball stud 1 relative to the holder 2. However, in consideration of the case where a radial load in a direction perpendicular to the axial direction acts on the ball stud 1, it is preferable that the contact area between the resin sliding contact member 3 and the ball 10 is large. In particular, the inner diameter of the second opening 32 of the resin sliding contact member 3 is preferably set as small as possible. As described above, the inner diameter D2 of the second opening is set smaller than the inner diameter D1 of the first opening. Is preferred.

  On the other hand, in order to perform electric resistance welding between the ball 10 and the shaft member 11, it is necessary that the energization resistance between the blocking portion 23 and the ball 10 is smaller than the energization resistance between them. . If the current-carrying resistance between the blocking portion 23 and the ball 10 is greater than that between the ball 10 and the shaft member 11, the boundary surface between the blocking portion 23 and the ball 10 generates heat, This is because the blocking portion 23 is fixed to the ball 10. For this reason, the contact area between the blocking portion 23 and the ball 10, that is, the area of the spherical surface of the ball 10 that is in contact with the metal sliding contact surface of the blocking portion through the second opening is the welded portion between the ball 10 and the shaft member 11. It needs to be set larger than the area. Here, the welded portion area is an area where the tip end surface of the shaft member 11 is joined to the ball 10, specifically, a circular area in the welded portion indicated by reference numeral 70 in FIG. 11 corresponds to a cross-sectional area of 11. More precisely, it is the surface area of the spherical surface of the ball 10 at the part where the shaft member 11 is joined to the ball 10.

  That is, the inner diameter D2 of the second opening portion 32 of the resin sliding contact member 3 is smaller than the inner diameter D1 of the first opening portion 31 and is in contact with the closing portion 23 of the holder 2 through the second opening portion 32. The area of the spherical surface of the ball 10 is set to be larger than the welded area of the shaft member 11.

  And according to such a ball joint of this invention, when carrying out the electrical resistance welding of the shaft member 11 with respect to the said ball | bowl 10, the opening part for electric power feeding with respect to the said holder 2 covering the circumference | surroundings of the said ball | bowl 10 is provided. There is no need to provide a closing cap that closes the power supply opening after the ball stud 1 is completely welded. Therefore, the number of parts can be reduced and the production process can be simplified accordingly. Can be reduced.

DESCRIPTION OF SYMBOLS 1 ... Ball stud, 2 ... Holder, 3 ... Resin sliding contact member, 10 ... Ball, 11 ... Shaft member, 20 ... Main-body part, 23 ... Closure part, 31 ... 1st opening part, 32 ... 2nd opening part

Claims (4)

With the ball,
A first contact portion having a sliding contact surface with the ball to cover the maximum diameter portion of the ball and exposing the spherical surface of the ball in opposite directions and an inner diameter smaller than the inner diameter of the first opening portion a resin sliding member having a second opening that is,
The ball, which is formed by casting with the resin and the resin sliding contact member placed on the core as a core, protrudes from a main body portion that covers the periphery of the resin sliding contact member and a second opening of the resin sliding contact member A holder that is integrally formed with a contact portion that touches the ball and that is in contact with the ball, and that is exposed from the first opening of the resin sliding contact member;
A shaft member that is joined to the spherical surface of the ball exposed from the first opening of the resin sliding contact member by electric resistance welding after casting of the holder and constitutes a ball stud ;
The inner diameter of the second opening of the resin sliding contact member is set so that the area of the spherical surface of the ball that contacts the closing portion of the holder through the second opening is larger than the area of the welded portion of the shaft member to the ball. Ball joint characterized by being . The step of forming a resin sliding contact member having a first opening and a second opening that have a sliding contact surface with the ball to cover the maximum diameter portion of the ball and expose the spherical surface of the ball in opposite directions When,
  The ball and the spherical surface of the ball protruding from the second opening of the resin sliding contact member by casting the ball and the resin sliding contact member placed on the ball as a core Forming a holder that has a closing portion that covers and touches the ball, and that is not in contact with the spherical surface of the ball exposed from the first opening of the resin sliding contact member;
  The shaft member is abutted against the ball exposed from the first opening of the resin sliding contact member, and the electrode is brought into contact with the shaft member, while the electrode is brought into contact with the closing portion of the holder in contact with the ball. And a step of joining the shaft portion by electric resistance welding to form a ball stud, and a method for manufacturing a ball joint. 3. The ball joint manufacturing method according to claim 2, wherein the resin sliding contact member covers a maximum diameter portion of the ball, and an inner diameter of the second opening is set smaller than an inner diameter of the first opening. Method. The resin sliding contact member has a second opening portion so that an area of a spherical surface of the ball that contacts the closing portion of the holder through the second opening portion is larger than a projected area of the tip surface of the shaft member with respect to the ball. The ball joint manufacturing method according to claim 3, wherein an inner diameter of the ball joint is set .

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