JP2868319B2 - Internal spline with tooth chamfer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold forging die for forming a sharp tooth chamfer on an end face of an inner spline simultaneously with an inner spline.

[0002]

2. Description of the Related Art Japanese Patent Laid-Open No.
There is a publication of -11241.

This is a cold forging method in which a sharp ridge is formed on one end face of the inner spline at the same time as the inner spline. In the cold forging method, a chamfer forming section is provided following the spline at a position where the spline forming of the spline extrusion die is completed. This is a simultaneous cold forging method in which an inner spline in which a knockout sleeve is arranged at a position where the extruded material hits the upper surface while maintaining concentricity with a spline extrusion die is tooth chamfered.

[0004]

The problem to be solved is that the mandrel of the cold forging die is an integral type using die steel (SKD11) or high-speed steel (SKH55), or has a problem in strength. In the case, it is manufactured as a one-piece carbide, and when using die steel or high-speed steel,
It cannot withstand the pressure applied during the spline molding or the tooth chamfering shape molding, and cracks are generated in the portions 12 and 13 shown in FIG. 7, that is, the spline introduction portion or the chamfering shape molding portion, which easily leads to early damage of the mandrel,
In the case where carbide is used, there is no problem in strength, but the toughness is small, so that the portion 14 shown in FIG. Fatigue failure occurs near the center of the mandrel, leading to early damage and sudden damage.

[0005]

SUMMARY OF THE INVENTION In a cold forging die mandrel for simultaneously forming an inner spline and a tooth chamfer, the mandrel body must have toughness to withstand repeated compression, tension and bending stress. For this purpose, the spline forming section and the chamfering shape forming section are formed into a ring shape so that the spline forming section and the chamfering shape forming section can withstand the strong pressure generated by the closed state, and the divided structure is fitted therein with the main body. The spline forming portion and the chamfered shape forming portion which require strength at the time of forming use carbide, and the main body portion which requires toughness uses die steel.

[0006]

FIG. 1 shows a configuration of a cold forging die for simultaneously forming an inner spline and a tooth chamfer.

Reference numeral 1 denotes a blank processed into a cylindrical shape by a method such as cold forging, etc., 2 denotes a mandrel having a cylindrical portion 2a at the upper portion serving as a guide for the blank, a spline forming portion 2b and a chamfered forming portion 2c at the center. Numeral 3 is a die, numeral 4 is a knockout sleeve arranged by fitting the mandrel 2, numeral 5 is an inner diameter and an outer diameter slidable with the upper outer diameter of the mandrel 2 and the upper inner diameter of the die 3, not shown. A punch attached to the press ram and movable up and down.

Reference numerals 6, 7, and 8 denote spacers for supporting the mandrel 2 and the die 3 while keeping them concentric, and reference numeral 9 denotes a knockout pin for taking out the product via the knockout sleeve 4.

A method of simultaneously forming the inner spline and the tooth chamfer in the cold forging die will be described.

The blank 1 shown in FIG. 2 is inserted into the gap between the die 2 and the mandrel 3, and the punch 5 is lowered to press the blank 1 against the spline forming section 2b of the mandrel 2, thereby forming the gap of the mandrel 2 shown in FIG. The material flows into the portion 2b and is extruded into the cross-sectional shape shown in FIG. 3 to form an inner spline.

By lowering the punch 5 further,
It flows along the chamfered molded portion 2c arranged so as to coincide with the center of the gap 2d of the mandrel 2, and a chamfered shape is formed at the tip of the spline.

After the molding is completed in this manner, the punch 5
Is retracted, the knockout pin 9 is raised, and the molded article 1
The molding is completed by removing the.

Through the above steps, a molded product 1 having a spline 1b and a chamfer 1a having a sharp ridge as shown in FIG. 5 is obtained.

In the above-mentioned forming step, in order to form a chamfer with a sharp ridge line at the tip of the spline, the axial flow is suppressed at the tip of the knockout sleeve 4, and the spline molding of the mandrel, FIG. 3 and molding in a sealed state, especially the spline molding 2
b, because a strong pressure acts on the chamfered shape forming part 2c,
Strength is required to withstand this.

Also, since the mandrel spline forming part 2b is always in contact with the material during molding and at the time of taking out the molded product, the mandrel main body is repeatedly subjected to compressive, tensile or bending stress, so that it can withstand this. Toughness is required.

For this purpose, as shown in FIG. 6, the mandrel 2 has a spline molding portion 2b and a chamfered shape 2c formed in a ring shape, in which a main body portion 10 is fitted and fixed with screws 11. Carbide is used for the spline forming portion 2b and the chamfered shape forming portion 2c which require strength at the time of forming, and die steel (SK) is used for the main body which requires toughness.
By using D61) and making the mandrel a divided structure using a material suitable for the force applied to each portion, the life of the mandrel can be extended.

[0017]

As described above, the mold for cold forging of the inner spline according to the present invention is an integrated type using conventional die steel (SKD11) or high-speed steel (SKH55), or
In the case of the integral type mandrel using carbide, as described in the prior art, cracks occur in the spline introduction part or the chamfered shape forming part due to insufficient strength, and fatigue failure occurs near the center due to insufficient toughness, which causes mandrel Sudden damage and early damage.

However, according to the mandrel of the present invention, the spline forming section, the chamfering forming section and the main body have a divided structure, and the former which requires strength is made of carbide, and the latter which requires toughness is made of die steel. By using (SKD61), it was possible to stably mold over a long period of time.

[Brief description of the drawings]

FIG. 1 is a mold for cold forging of an inner spline having a partially broken surface according to the present invention.

FIG. 2 is a cross-sectional view of a blank before molding.

3A is a cross-sectional view of the blank, and FIG. 3A is a cross-sectional view in the middle of molding, and FIG. 3B is a cross-sectional view of FIG.

FIG. 4 (a) is a side view of the mandrel, and (b) is (a)
It is BB 'sectional drawing of.

5 (a) is a cross-sectional view after completion of molding, and FIG.
(B) is a plan view of (a).

FIG. 6 is an explanatory sectional view of a mandrel.

7A is a side view of a conventional mandrel. FIG.
(B) is an enlarged view of a chamfered shape forming diagram, all of which are spline forming portions.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Slunk 1b Chamfered part of sharp ridgeline 2 Spline part 2 Mandrel 2a Cylindrical part of mandrel 2b Spline molding part of mandrel 2c Chamfering molding of mandrel 3 Die 4 Knockout sleeve 10 Mandrel body 11 Tightening screw

Claims (2)

(57) [Claims] 1. A cold forging die mandrel for simultaneously forming an inner spline and tooth chamfering, wherein a spline forming portion and a chamfering shape forming portion have a ring-shaped divided structure, and a mandrel body portion is fitted therein. Mold for forging. 2. The cold forging die according to claim 1, wherein the spline forming portion and the chamfered shape forming portion are formed of a super-steel material, and the mandrel body is formed of a die steel material.