JPH04313442A - Inner spline having tooth chamfering - Google Patents

Abstract

PURPOSE:To stably execute the forming extending over a long period without generating damage by forming a mandrel of this invention with a split structure and using cemented carbide whose strength is large and die steel for a spline forming part and a chamfering shape forming part which necessitate strength, and a mandrel main body part which necessitates toughness, respectively. CONSTITUTION:In a mandrel 10 of a cold forging die for forming simultaneously an inner spline and tooth chamfering, a spline forming part 2b and a chamfering shape forming part 2c are formed by a ring-like split structure, consist of a structure in which the mandrel main body part 10 is fitted, and the spline forming part 2b and chamfering shape forming part 2c, and the mandrel main body part 10 are constituted of cemented carbide and die steel, respectively.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cold forging mold for forming sharp tooth chamfers on the end faces of internal splines simultaneously with internal splines.

0002

[Prior Art] As a prior art related to the present invention, there is
There is a publication of No.-11241.

[0003] This is a cold forging method in which sharp ridge teeth are formed on one end face of the internal spline at the same time as the internal spline, and a chamfered part is provided following the spline at the position where the spline forming of the spline extrusion die ends. This is a simultaneous cold forging method that chamfers the teeth of an internal spline in which a knockout sleeve is placed at a position where the extruded material hits the upper surface while remaining concentric with the spline extrusion die.

0004

[Problems to be Solved by the Invention] The problem to be solved is that the mandrel for the cold forging die is an integral type using die steel (SKD11) or high speed steel (SKH55), or a mandrel that is unstable in terms of strength. If die steel or high speed steel is used, it will not be able to withstand the pressure applied during spline forming or tooth chamfer shape forming, and parts 12 and 13 shown in Fig. 7, that is, splines. Cracks occur at the introduction part or the part where the chamfered shape is formed, which tends to lead to early breakage of the mandrel.Also, when carbide is used, there is no problem in terms of strength, but its toughness is low, so it may be repeatedly damaged during molding or when taking out the molded product. Unable to withstand such compressive tension and bending stress, the
This is the point where fatigue failure occurs from the 14th part shown in Figure 14, that is, near the center of the mandrel, leading to early failure and sudden failure.

[0005]

[Means for Solving the Problems] In a cold forging type mandrel that simultaneously forms internal splines and tooth chamfers, the mandrel body must have toughness that can withstand repeated compression, tension, and bending stress. For this purpose, the spline molded part and the chamfered molded part are made into a ring shape so that the spline molded part and the chamfered molded part can withstand the enormous pressure generated by the sealed state, and the split structure is such that the main body part is fitted into the ring shape. Carbide is used for the spline molded part and chamfered shape molded part, which require strength during molding, and die steel is used for the main body part, which requires toughness.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a cold forging die configuration for simultaneously forming internal splines and tooth chamfers.

1 is a blank processed into a cylindrical shape by a method such as cold forging, and 2 is a mandrel having a cylindrical portion 2a at the top that serves as a guide for the blank, a spline forming portion 2b and a chamfered forming portion 2c at the center. 3 is a die, 4 is a knockout sleeve arranged to fit with the mandrel 2, and 5 has an inner diameter and an outer diameter that are slidable with the upper outer diameter of the mandrel 2 and the upper inner diameter of the die 3, not shown. This is a punch that is attached to the press ram and can be moved up and down.

Numerals 6, 7, and 8 are spacers that support the mandrel 2 and die 3 while keeping them concentric, and 9 is a knockout pin for taking out the product through the knockout sleeve 4.

[0009] A method for simultaneously forming internal splines and tooth chamfers using 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 part 2b of the mandrel 2, thereby forming the gap in the mandrel 2 shown in FIG. Material flows into the portion 2b and is extruded into the cross-sectional shape shown in FIG. 3 to form an internal spline.

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

After completing the forming in this way, punch 5
, and raise the knockout pin 9 to remove the molded product 1.
The molding is completed by taking out.

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

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

[0015] Furthermore, since the spline forming part 2b of the mandrel is always in contact with the material during molding and when taking out the molded product, compressive, tensile or bending stress is repeatedly applied to the mandrel body, so that it is difficult to withstand this stress. Toughness is required.

For this purpose, the mandrel 2 has a ring-shaped spline molded portion 2b and a chamfered shape 2c, as shown in FIG. Carbide is used for the spline molded part 2b and the chamfered shape molded part 2c, which require strength during molding, and die steel (SK) is used for the main body part, which requires toughness.
D61), the life of the mandrel can be extended by making the mandrel into a divided structure using materials suitable for the forces applied to each part.

[0017]

Effects of the Invention As explained above, the internal spline cold forging mold of the present invention is a one-piece type using conventional die steel (SKD11) or high speed steel (SKH55), or
With an integrated type mandrel made of carbide, as explained in the prior art section, cracks may occur at the spline introduction part or the chamfered shape forming part due to lack of strength, and fatigue fracture may occur near the center due to lack of toughness, which can cause the mandrel to fail. This can lead to sudden breakage and early breakage.

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

[Brief explanation of the drawing]

FIG. 1 shows a cold forging mold for an internal spline having a partially fractured surface according to the present invention.

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

FIG. 3 is a cross-sectional view of the blank, in which (a) is a cross-sectional view during molding, and (b) is a cross-sectional view from A to A' in (a).

[Figure 4] Mandrel (a) is a side view, (b) is (a)
It is a sectional view taken along B-B'.

FIG. 5 is a diagram of the blank; (a) is a cross-sectional view after completion of molding;
(b) is a plan view of (a).

FIG. 6 is an explanatory cross-sectional view of the mandrel.

FIG. 7 is a diagram of a conventional mandrel; (a) is a side view; (a) is a side view;
b) is a spline molded part, and both are enlarged views of the chamfered shape molding diagrams.

[Explanation of symbols]

1 Zrank 1b Chamfered part with sharp ridgeline 2 Spline part 2 Mandrel 2a Cylindrical part 2b of mandrel Spline molded part 2c of mandrel Chamfered shape molding diagram of mandrel 3 Die 4 Knockout sleeve 10 Mandrel body 11 Tightening screw

Claims (2)

[Claims] Claim 1: In a mandrel for a cold forging die that simultaneously forms an internal spline and a tooth chamfer, the spline forming part and the chamfer shape forming part have a ring-shaped divided structure,
A cold forging mold into which the mandrel body is fitted. 2. The cold forging mold according to claim 1, wherein the spline forming part and the chamfer forming part are made of super steel, and the mandrel main body part is made of die steel.