JP3594485B2 - Molding method of hollow ball stud - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a method for forming a hollow ball stud having a spherical ball head and a shaft protruding from the ball head.
[0002]
[Prior art]
2. Description of the Related Art A ball joint used for a suspension system of an automobile or the like has a configuration as shown in FIG. This ball joint 171 is a double shaft type ball joint 171. W105 is a ball stud comprising a spherical ball head 108 and two shaft portions 107, 107 coaxially protruding from the ball head 108. The ball stud W105 has a hollow shape. Further, a cylindrical bearing 73 made of synthetic resin is disposed on the outer peripheral side of the ball head 108 of the ball stud W105, and a metallic cylindrical housing 72 is disposed on the outer peripheral side of the bearing 73. . The inner circumference end of the housing 72, directly or indirectly one end of the boot 74 is attached, the other end edge portion of the boot 74 to the shaft portion 107, 107 the outer periphery of the ball stud W105 It is installed.
[0003]
A method of forming the ball stud W105 used for the ball joint 171 will be described with reference to FIGS.
[0004]
FIG. 6 shows a forming step of forming the ball stud W105 from the material W100. First, a steel wire rod is cut in the direction perpendicular to the axis line to form a cylindrical raw material W100 (FIG. 6A). Next, a spare material W101 (FIG. 6 (a)) is formed by molding a slightly recessed portion 102a at one end of the raw material W100. Subsequently, the recess 102a is further extended to the other end and a spare hole 103 is formed. By molding, a single-opening material W102 ((c) in FIG. 6) having a bottom 104 formed at the other end is formed. Thereafter, a cylindrical pipe member W103 (FIG. 6D) in which the bottom portion 104 is punched to form the through hole 105 is formed, and then the central portion in the axial direction of the pipe member W103 is bulged outwardly. An intermediate material W104 ((e) in FIG. 6) composed of a spherical ball head 108 and shaft portions 107, 107 projecting coaxially from the ball head 108 is formed, and finally the ball head 108 is rolled. Thus, the ball stud W105 (FIG. 6 (f)) was formed.
[0005]
The step of forming the intermediate member W104 from the pipe member W103 in the molding step of the ball stud W105 will be described with reference to FIGS.
[0006]
FIG. 7 shows a state before forging and FIG. 8 shows a state after forging. First, the configuration of the forging device 110 will be described with reference to FIG. This forging device 110 has a substantially lower hemispherical static engraving space 134 with the same curvature as the ball head 108 of the ball stud W105 at the top, and a knockout ring 135 that can slide back and forth with respect to the static engraving space 134. A static mold 131 having a static fixing pin 137 disposed on the inner periphery of the knockout ring 135, and a dynamic engraving space 114 having a substantially upper hemispherical shape with the same curvature as the ball head 108 of the ball stud W105 is provided below. The moving die 111 includes a ring punch 115 slidable back and forth with respect to the dynamic engraving space 114 and a dynamic fixing pin 117 arranged on the inner periphery of the ring punch 115. Here, in the static mold 131, a lower shaft holding space 134a is formed continuously with the static engraving space 134 with the knockout ring 135 retracted downward. Further, in the moving die 111, an upper shaft holding space 114a is formed continuously with the moving die engraving space 114 with the ring punch 115 retracted upward.
[0007]
In the case of forging with this forging device 110, a pipe material W103 formed in a cylindrical shape in advance is put into the lower shaft holding space 134a of the static engraving space 134, and is supported on the upper surface of the knockout ring 135. Subsequently, the moving die 111 is moved forward to bring the ring punch 115 into contact with the pipe material W103, and the moving die 111 is moved forward to accommodate the ring punch 115 inside the moving die 111. Thereafter, the moving die 111 further moves forward to fit the pipe member W103 into the upper shaft holding space 114a, and the ring punch 115 applies a load to the pipe member W103, as shown in FIG. 8, near the axial center of the pipe member W103. Is bulged to the outer peripheral side along the engraving spaces 114 and 134 to form the intermediate material W104.
[0008]
[Problems to be solved by the invention]
After the cylindrical pipe member W103 is formed in advance as described above, the intermediate member W104 is formed by expanding the vicinity of the center in the axial direction to the outer peripheral side, and swelling to the outer peripheral side as shown in FIG. The excess meat 199 may overhang. In this case, the bulge on the outer peripheral side is reduced by the amount of extra thickness 199 that protrudes toward the inner peripheral side, and the underfill is generated on the outer periphery of the ball head. Therefore, the ball head 108 cannot be corrected by the subsequent rolling process, and the accuracy of the ball head 108 may be reduced.
[0009]
Accordingly, an object of the present invention is to solve the above-described problems and to provide a method of forming a hollow ball stud with a high precision of a ball head.
[0010]
[Means for Solving the Problems]
The present invention is as follows.
[0011]
A pipe forming step of forming a cylindrical pipe material having substantially the same outer diameter as the ball head outer diameter of a desired ball stud; forming a shaft by reducing the diameter of the end of the pipe material; A squeeze forming process in which a straight portion having the same outer diameter as the pipe material is left on the outer periphery in the center of the direction, and a squeeze forming process, in which the preliminary convex portion is pressed and formed into a spherical shape without increasing the outer diameter of the preliminary convex portion Finishing process.
[0012]
【Example】
An embodiment of the present invention will be described below with reference to FIGS.
[0013]
FIG. 3 shows a ball joint 71 using a ball stud W5 formed according to an embodiment of the present invention. The ball stud W5 is a hollow metal having a spherical ball head 8 and two shaft portions 7, 7 projecting coaxially from the ball head 8. Reference numeral 73 denotes a cylindrical bearing made of synthetic resin, which is disposed on the outer peripheral side of the ball head 8 of the ball stud W5. The bearing 73 has openings at both ends for projecting the shaft portions 7, 7 of the ball stud W5. The bearing 73 has an inner spherical surface 73a having substantially the same curvature as the ball head 8 of the ball stud W5 on the inner side. The ball head 8 is swingably held. Reference numeral 72 denotes a substantially cylindrical housing having openings at both ends. A retaining ring 75 having a substantially cylindrical and inwardly extending flange shape is fixed to the inner peripheral side of one end, and the bearing 73 moves in the axial direction. Is regulated. Reference numeral 74 denotes a substantially cylindrical boot made of a rubber elastic body, both ends of which are opened, and a metal annular collar 76 having an L-shaped cross section is embedded in the large opening. The boots 74, 74 are located between the inner periphery of the retaining ring 75 and the outer periphery of the one shaft 7 of the ball stud W5, and between the inner periphery of one end of the housing 72 and the outer periphery of the other shaft 7 of the ball stud W5. Are arranged respectively.
[0014]
The forming process of the ball stud W5 used for the ball joint 71 will be described with reference to FIG.
[0015]
FIG. 1 shows a forming step of forming a ball stud W5 from a raw material W0. First, a steel wire rod having substantially the same outer diameter as the outer diameter of the ball head 8 of the desired ball stud W5 is cut in the direction perpendicular to the axis to form a columnar material W0 ((A) in FIG. 1). Thus, a spare material W1 (FIG. 1A) in which a slightly concave portion 2a is formed at one end of the material W0 is formed. Next, a one-sided recessed portion 2a of the spare material W1 is extended to the other end portion side to form a spare hole 3, and a cup-shaped single-opening material W2 having a bottom portion 4 formed with a recessed portion 2b at the other end ((c in FIG. 1). )), The bottom portion 4 of the one-sided opening material W2 is punched out by a punch (not shown), and a cylindrical pipe material W3 having an outer diameter D1 substantially the same as the outer diameter D3 of the ball head 8 of the desired ball stud W5 (see FIG. 1 (d)) is formed. Thereafter, the diameters of both ends of the pipe material W3 are reduced to form the shaft portions 7, 7, and the vicinity of the center of the unformed portion is left as a straight portion 6a, and the connecting portion 6b connecting the straight portion 6a and the shaft portion 7 is formed into an arc. An intermediate material W4 ((e) in FIG. 1) to be formed into a shape is formed.
[0016]
Here, a process of forming the intermediate material W4 from the pipe W3 will be described with reference to FIGS.
[0017]
FIG. 4 shows a state before forging, and FIG. 5 shows a state after forging. First, the configuration of the forging device 10 will be described with reference to FIG. The forging device 10 includes a stationary mold 31 fixed and a moving mold 11 provided to be able to advance and retreat with respect to the static mold 31.
[0018]
The static mold 31 has a lower guide portion 42 having the same diameter as the outer diameter of the pipe member W3 at the upper portion, and an arc-shaped lower portion continuous with the lower guide portion 42 and having a curvature larger than the curvature of the ball head 8 of the ball stud W5. The die 32 is provided with a downwardly squeezed portion 43 having a gradually decreasing diameter toward the bottom, and the lower guide portion 42 and the downwardly squeezed portion 43 define a static engraving space 34. Further, a lower shaft holding space 34a which is continuous with the static engraving space 34 and has the same diameter as the outer diameter of the shaft portion 7 of the ball stud W5 is formed, and the knockout hole 33 is continuously formed. In the knockout hole 33, a knockout ring 35 and a collar 36 which are slidable back and forth with respect to the static engraving space 34 are disposed, and a static fixing pin 37 fixed by a static pin guide 38 is inserted into the inner periphery thereof. It is fitted. Further, the static pin guide 38 is integrally fixed with a bolt 40 to a static cover 39 that closes the knockout hole 33, and the static pin guide 38 and the static cover 39 that are fixed penetrate the inside thereof and abut against the collar 36. The pin 41 is inserted.
[0019]
In addition, the dynamic mold 11 has an upper guide portion 22 having a diameter substantially equal to the outer diameter of the pipe material W3 at a lower portion, and an arc shape having a curvature larger than the curvature of the ball head 8 of the ball stud W5 continuous with the upper guide portion 22. An upper squeezing portion 23 having a gradually decreasing diameter is formed upward. The upper guide portion 22 and the upper squeezing portion 23 define the static engraving space 14 and include the punch guide 12. The punch guide 12 is provided with a punch hole 13 that passes through the inside of the punching space 14 in the axial direction continuously from the dynamic engraving space 14. A ring punch 15 and a collar 16 slidable back and forth with respect to the dynamic engraving space 14 are provided in the punch hole 13, and a dynamic fixing pin 17 fixed by a dynamic pin guide 18 is inserted in the inner periphery thereof. It is fitted. Further, the moving pin guide 18 is integrally fixed to a moving cover 19 that closes the punch hole 13 with bolts 20, and the fixed moving pin guide 18 and the moving cover 19 pass through the inside of the moving pin guide 18 and abut on the collar 16. The pin 21 is inserted. Note that the ring punch 15 protrudes from the end face of the punch guide 12 before molding, and the collar 16 and the moving pin guide 18 also move toward the moving engraving space 14 following the ring punch 15.
[0020]
When performing forging by the forging device 10, first, the pipe material W <b> 3 is put into the static engraving space 34 from the lower guide portion 42 of the static mold 31. Subsequently, the moving die 11 is moved forward to bring the ring punch 15 into contact with the pipe material W3, and the moving die 11 is moved forward to accommodate the ring punch 15 inside the moving die 11. Then, after the upper end of the pipe member W3 is inserted into the upper guide portion 22 of the moving die 11, squeezing is performed along the lower squeezed portion 43 and the upper squeezed portion 23, and as shown in FIG. Shaft portions 7, 7 are formed in the shaft holding space 14a, and a straight portion 6a is formed on the outer periphery of the center in the axial direction, and a preliminary convex portion 6 composed of an arc-shaped connecting portion 6b connecting the straight portion 6a and the shaft portion is formed. The material W4 is formed. Thereafter, the moving die 11 is retracted, the knockout ring 35 is protruded toward the static die engraving space 34 by the static support pin 41, and the intermediate material W4 is taken out of the static die 31, and the molding in this step is completed.
[0021]
Finally, as shown in FIG. 1, the outer diameter (D2) of the preliminary convex portion 6 formed of the straight portion 6a and the connecting portion 6b of the intermediate material W4 is finished to a spherical shape without expanding, and the ball stud W5 (see FIG. 1 (f)) is formed.
[0022]
Therefore, since the shaft portion 7 is formed by the squeezing process, the underfill does not occur in the preliminary convex portion 6 of the intermediate material W4. Further, after the preliminary convex portion 6 including the straight portion 6a and the connecting portion 6b is once formed from the pipe material W3, and further the ball head 8 is formed as shown in FIG. 2, the spherical portion can be formed without difficulty. Here, when the volume of the preliminary convex portion 6 of the intermediate material W4 is formed to be the same as the volume of the ball head 8 of the ball stud W5, the finish forming becomes easier.
[0023]
In the above embodiment, the molding method has been described taking the double-shaft type ball stud W5 as an example, but the present invention is not limited to such a double-shaft type ball stud W5. Studs are fine.
[0024]
【The invention's effect】
As described above, according to the present invention, a pipe forming step of forming a cylindrical pipe material having substantially the same outer diameter as the ball head outer diameter of a desired ball stud, and reducing the diameter of the end of the pipe material to form a shaft Squeezing forming step of forming a pre-projection part that forms a part and leaving a straight part with the same outer diameter as the pipe material at the center outer periphery of the unformed part in the axial direction, and pressing the pre-projection part , the outer diameter of the pre-projection part And a finishing step of forming the ball into a spherical shape without expanding the diameter, so that the preliminary convex portion can be easily finished without underfilling, and can be formed into a spherical shape without difficulty. Can be formed with high precision.
[Brief description of the drawings]
FIG. 1 is a cross-sectional plan view illustrating a forming process of a ball stud according to an embodiment of the present invention.
FIG. 2 is an enlarged view of a portion A for explaining a state of a portion A of FIG. 1;
FIG. 3 is a sectional plan view of a ball joint using a ball stud formed by a forming method according to an embodiment of the present invention.
FIG. 4 is a cross-sectional plan view illustrating a state before an intermediate member is formed from a pipe member according to an embodiment of the present invention.
FIG. 5 is a cross-sectional plan view illustrating a state after an intermediate member is formed from a pipe member according to an embodiment of the present invention.
FIG. 6 is a cross-sectional plan view illustrating a conventional ball stud forming process.
FIG. 7 is a cross-sectional plan view showing a state before a ball stud is formed from a conventional intermediate material.
FIG. 8 is a sectional plan view showing a state after a ball stud is formed from a conventional intermediate material.
FIG. 9 is an enlarged view of a main part of FIG. 8;
[Explanation of symbols]
5 Through Hole 6 Preliminary Convex Portion 6a Straight Portion 6b Connecting Portion 7 Shaft Portion 8 Ball Head W3 Pipe Material W5 Ball Stud D1 Outer Diameter D2 of Pipe Material Straight Outer Diameter D3 of Intermediate Material Ball Head Outer Diameter of Ball Stud

Claims (2)

A method of forming a hollow ball stud having a spherical ball head (8) and a shaft portion (7) protruding from the ball head (8) and having a through hole (5) penetrating in the axial direction, A pipe forming step of forming a cylindrical pipe member (W3) having an outer diameter (D1) substantially equal to the outer diameter (D3) of the desired ball head (8) of the ball stud (W5); The shaft portion (7) is formed by reducing the diameter of the end portion, and the preliminary convex portion (6a) having the same outer diameter (D2) as the pipe material (W3) is left around the center of the unformed portion in the axial direction. 6) and a finishing step of pressing the preliminary convex portion (6) and forming a spherical shape without expanding the outer diameter (D2) of the preliminary convex portion (6). Characteristic hollow ball stud forming method. 2. The method of forming a hollow ball stud according to claim 1, wherein the volume of the preliminary projection is formed to be the same as the volume of the ball head of the ball stud.

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