JP3407148B2 - Cold forging method of spline shaft - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a forging method for cold forging a spline shaft widely used for transmission parts of automobiles. 2. Description of the Related Art At present, as a method of manufacturing a spline shaft widely used for a transmission part of an automobile, etc.,
Cold forging has been widely applied for the purpose of saving materials and reducing the number of processing steps. Therefore, as shown in FIG. 1, a first small-diameter portion 1 having a tooth profile portion 102 having a gear substantially at the center in the axial direction and having a first spline 105 at one end in the axial direction of the tooth profile portion 102 is provided.
03, in the completed spline shaft 110 provided with the second small-diameter portion 104 having the second spline 106 at the other end, as shown in FIG. 5, the splines 105 and 106 were formed by cold forging. That is, the rod-shaped material 12
In the first step of cold forging, a large-diameter portion 112 having a large diameter is formed substantially at the center in the axial direction, and preliminary center holes 117 and 118 are formed at both end surfaces in the axial direction.
Both ends of the first preforming portion 113 and the second preforming portion 114
The spline 105, 106 is formed in the center hole 107, 1
08, and then the large-diameter portion 1
The gear was molded into 12, and the details were finished by a cutting process in another process. A cold forging method for forming the spline shaft 101 as described above is disclosed in Japanese Patent Application Laid-Open No. Sho 62-168626.
There are many publications. A cold forging method for simultaneously processing the splines 105 and 106 and the center holes 107 and 108 is disclosed in Japanese Patent Publication No. 58-8931. [0005] As described above, when the spline shaft 101 is formed by cold forging, great merit such as a reduction in the number of processing steps is generated. However, here, the gear of the tooth profile portion 102 substantially at the center in the axial direction is cold forged,
It is formed by gear cutting.
Productivity may decrease. Further, splines 105 and 10 are formed by cold forging.
6 and the center holes 107 and 108, the splines 105,
Although the center of the center hole 107 coincides with the center of the center hole 107, 108, the gear of the tooth profile portion 102 performs the gear cutting by chucking the center hole 107, 108. The centers of the gears and the center holes 107 and 108 may not coincide. Therefore, it is conceivable that the gear of the tooth profile portion 102 is formed by cold forging, like the splines 105 and 106 and the center holes 107 and 108. As a result, the gears, splines 105 and 106, and
Since 07 and 108 can be processed at the same time, the processing time can be shortened, and the centers can be matched. However, if the gears of the tooth profile are formed by cold forging, burrs are generated on the outside when the gears are pushed out, and the precision of the gears is remarkably reduced. Accordingly, the present invention solves the above-mentioned problems,
An object of the present invention is to provide a cold forging method for a spline shaft that has high productivity and obtains stable and high accuracy. [0009] The means of the present invention are as follows. In the first step, a large diameter portion having a large diameter is formed substantially at the center in the axial direction of the rod-shaped material, and preliminary center holes are formed in both end surfaces in the axial direction. In the second step, both ends of the large diameter portion are first preformed. A spline is formed in the portion and the second preforming portion, a gear is formed while leaving a marginal portion at one axial end of the large diameter portion, and a preparatory center hole is formed into a desired center hole. An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a completed spline shaft 10 having a toothed portion 2 having a gear at substantially the center in the axial direction, and a first small diameter portion 3 having a first spline 5 extending axially at one axial end of the toothed portion 2. And a second small-diameter portion 4 having a second spline 6 extending in the axial direction at the other axial end of the tooth profile portion 2. In addition, center holes 7, 8 are recessed on the inner side at the center of both end faces in the axial direction. The cold forging process, which is the process of forming the completed spline shaft 10, will be described with reference to FIGS. First, a rod-shaped material 2 as shown in FIG.
1 is a first step of cold forging, and includes a large diameter portion 12 having a large diameter substantially at the center in the axial direction as shown in FIG. 2A, a first preformed portion 13 and a second large diameter portion 12 at both ends of the large diameter portion 12. A preformed part 1 having a preformed part 14 and preliminary center holes 17 and 18 at both end surfaces.
Mold 1. This step will be described with reference to FIG. First, the forging apparatus 30 shown in the figure will be described in order. An upper die 31 has an upper forming surface 32a which defines the outer diameter of the second preforming portion 14 of the preform 11 at the lower portion of the inner periphery. The upper die 32, an upper collar 33 located above the upper die 32, an upper holder 34 that integrally supports the upper die 32 and the upper collar 33, and a holding ring 37 that holds the upper holder 34. . And upper die 32 and upper collar 3
A punch 35 having an upper convex portion 36 protruding from the lower end surface is inserted into the inner periphery of the punch 3. Also, 41 is a lower mold,
A lower die 42 having a lower forming surface 42a defining an outer diameter of the large-diameter portion 12 of the preformed product 11 and the first preformed portion 13 in an upper portion of the inner periphery, and a lower die positioned below the lower die 42. The lower collar 43 supports the lower die 42 and the lower holder 44 that integrally supports the lower die 42 and the lower collar 43. A lower convex portion 46 protruding from the upper end surface is provided on the inner periphery of the lower collar 43.
Is inserted. The forging device 30 as described above is used to
The first step of molding the preform 11 into the preform 11 will be described. First, as shown in the left half of FIG. 3, the bar-shaped material 21 is inserted into the lower forming surface 42a of the lower die 42 from the die-forming space 47 formed on the upper surface of the lower die 41. Subsequently, as shown in the right half of FIG.
Then, the bar-shaped material 21 is pressed by the punch 35 and the lower die 42 is pressed.
The large diameter portion 12 is projected in the intermediate space 42b, and the first preformed portion 13 and the second preformed portion 14 are formed at both ends of the large diameter portion 12, and the upper convex portion 36 and the knockout punch 45 of the punch 35 are formed. Preliminarily formed holes 11 and 18 are provided at both end surfaces by the lower convex portion 46 to form the preformed product 11. Thereafter, the upper mold 31 is retracted upward, and the knockout punch 45 projects upward, and the preform 11 is removed from the lower mold 41. Next, the step of forming the preformed article 11 into a spline shaft 1 as shown in FIG. 2C in the second step of cold forging will be described with reference to FIG. First, the forging device 50 shown in the figure will be described sequentially. Reference numeral 51 denotes an upper die, a cylindrical spacer 58, a backup ring 59 located on the outer peripheral side of the spacer 58, and an upper part of the spacer 58 and the backup ring 59. , An upper die 52 having a first spline tooth profile 52c for molding the first spline 5 on the inner periphery, an upper collar 53 located above the upper die 52, a backup ring 59, an upper die 52, and an upper collar 53 , And a holding ring 57 for holding the upper holder 54. A punch 55 having an upper convex portion 56 protruding from the lower end surface is provided on the inner periphery of the upper die 52 and the upper collar 53.
Is inserted. Reference numeral 61 denotes a lower die, and a lower die 62 provided with a gear tooth mold 62c for forming the tooth profile 2 at the lower portion of the inner periphery.
A lower collar 63 provided below the lower die 62 and having a second spline tooth profile 63c for forming the second spline 6 on an inner peripheral upper portion; and a lower holder integrally supporting the lower die 62 and the lower collar 63. 64. And lower color 6
A knockout punch 65 having a lower protruding portion 66 protruding from the upper end surface is inserted into a lower portion of the inner periphery of 3. With the forging device 50 as described above, the preform 1
The second step of forming the first shaft 1 into the spline shaft 1 will be described. First, as shown in the left half of FIG. 4, the preforming is performed from the engraving space 67 formed on the upper surface of the lower die 61 into the lower forming surface 62 a of the lower die 62 and the tip forming surface 63 a of the lower collar 63. The product 11 is inserted from the second preforming portion 14 side. At this time, the preform 11 is arranged such that the tip of the second preform 14 abuts on the second spline tooth 63 c of the lower collar 63. Subsequently, as shown in the right half of FIG. 4, the upper die 51 is lowered from above and the second die spline 63 c of the lower collar 63 is pressed while pressing the preform 11 with the upper die 52.
At the same time, the second spline 6 is formed in the second preforming section 14 of the preform 11, and at the same time, the first spline 5 is formed in the first preforming section 13 of the preform 11 by the first spline tooth profile 52 c of the upper die 52. I do. Further, while continuously backing up the large diameter portion 12 of the preformed product 11 with the spacer 58 of the upper die 51, the gear is formed while leaving the excess thickness 9 on the upper die 51 side of the large diameter portion 12, and the first spline is formed. Finish the center hole 7 on the 5 side end face. Thereafter, the upper die 51 is retracted upward, and the knockout punch 65 projects upward, and the center hole 8 on the end surface of the preformed product 11 on the second spline 6 side is finished by the lower convex portion 66 projecting from the upper end surface thereof.
The spline shaft 1 is removed from the lower mold 61, and the cold forging is completed. The spline shaft 1 which has been cold forged as described above is subjected to a finishing process as shown in FIG. The spline shaft 10 is formed. Therefore, in the spline shaft 1 formed by cold forging, it is possible to form the toothed portion 2 having a gear by forming the surplus portion 9 together with the splines 5, 6 and the center holes 7, 8. Become. Further, since the splines 5 and 6, the center holes 7 and 8 and the tooth profile 2 are simultaneously formed by cold forging, the concentricity of each can be accurately obtained. As described above, according to the present invention, in the first step, a large-diameter portion having a large diameter is formed substantially at the center of the rod-shaped material in the axial direction, and preliminary center holes are formed at both end surfaces in the axial direction. And the second
In the process, splines are formed at the first and second preformed portions at both ends of the large diameter portion, and while forming a gear while leaving a marginal portion at one axial end of the large diameter portion, a preliminary center hole is desired. Since it is formed in the center hole, it is possible to form the toothed part having the gear by forming the excess part together with the spline and the center hole. Can be increased. Further, since the spline, the center hole, and the tooth profile are simultaneously formed by cold forging, the concentricity of each can be accurately obtained, so that a stable and high-precision spline shaft can be formed.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a completed spline shaft. FIG. 2 is a cross-sectional plan view showing a process from a rod-shaped material to a spline shaft according to an embodiment of the present invention. FIG. 3 is a partial cross-sectional plan view illustrating a first step of cold forging according to an embodiment of the present invention, in which a left half portion is before molding and a right half portion is after molding. FIG. 4 is a partial cross-sectional plan view illustrating a second step of the cold forging according to the embodiment of the present invention, in which a left half portion is before forming and a right half portion is after forming. FIG. 5 is a cross-sectional plan view showing a process from a conventional rod-shaped material to a spline shaft. [Description of Signs] 2 Toothed portion 3 First small diameter portion 4 Second small diameter portion 5 First spline 6 Second spline 7 Center hole 8 Center hole 9 Extra thickness portion 12 Large diameter portion 13 First preformed portion 14 Second preliminary Molding part 17 Spare center hole 18 Spare center hole 21 Bar-shaped material

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int. Cl. ⁷ , DB name) B21J 1/00-13/14 B21J 17/00-19/04 B21K 1/00-31/00

Claims (1)

(1) A toothed portion (2) having a gear at substantially the center in the axial direction, and a first spline (5) at one axial end of the toothed portion (2). In the cold forging method of a spline shaft provided with one small diameter portion (3) and provided with a second small diameter portion (4) having a second spline (6) at the other axial end of the tooth profile portion (2), A large-diameter portion (12) having a large diameter is formed substantially at the center in the axial direction of the rod-shaped material (21), and preliminary center holes (17) and (18) are formed at both end surfaces in the axial direction. Splines (5) and (6) are formed on the first and second preformed portions (13) and (14) at both ends of the large diameter portion (12), and an extra end in the axial direction of the large diameter portion (12) is formed. The gear is formed while leaving the meat portion (9), and the spare center holes (17) and (18) are formed in the desired positions. Tha hole (7), cold forging method of the spline shaft, characterized in that the molding (8).