JP2000233257A - Forming die for outer helical gear - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a forming die by which an outer helical gear excellent in the precision of a tooth profile can be stably formed. SOLUTION: In a die 2 equipping with a tooth profile forming part 7 constituted by providing lands 5 for tooth profile forming and land relief 6 successively, which relieves the lands 5 in the outside direction of a radius, a side surface land part 5c inclined upward to the stock push-in direction is extended in the extruding direction of a material inclined in the axial direction. By fluidizing the material which has passed through the lands 5 along this extended part 10, by controlling the spring back of the material, and especially by preventing the deformations of tooth traces on both sides of the tooth profile, the precision of the tooth profile is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a mold for cold extrusion of an outer helical gear.

[0002]

2. Description of the Related Art Generally, as shown in FIGS. 3 and 4, a molding die of an outer helical gear includes a die 2 reinforced by a reinforcing ring 1 on a lower die (not shown) and an upper die (not shown). ), And a punch 3 whose tip is concentrically fitted into the die 2 when the upper die is lowered. Die 2
A cylindrical hole 4 having a diameter slightly larger than that of the material (not shown) is connected to an upper portion thereof, and a tooth forming land 5 and a land relief 6 for releasing the land 5 in a radially outward direction are connected to a lower portion thereof. A plurality of tooth forming portions 7 are provided, and between the cylindrical hole portion 4 and the tooth forming portion 7, a conical surface 8 inclined downward at a predetermined angle (introduction angle) toward the axis. Connected by

[0003] Each tooth forming section 7 is extended at a predetermined inclination angle (torsion angle) around the axis of the die 2, and a material not shown is inserted into the cylindrical hole section 4 of the die 2. Thereafter, when the punch 3 is lowered integrally with the upper die and the material is pressed into the die 2, the leading end of the material flows into the conical surface 8, enters the tooth forming portion 7, and the tooth forming portion 7. , Thereby forming an outer helical gear having helical teeth on the outer periphery.

[0004]

By the way, the land 5 of the tooth forming portion 7 includes a large-diameter land portion 5a for forming the gear tooth tip surface, a small-diameter land portion 5b for forming the gear tooth bottom surface, and a gear. And a side surface land portion 5c for forming the tooth surface of the second member. In this case, since the tooth forming shape part 7 is inclined with respect to the axis of the die 2, as shown in FIG.
a of the pair of side land portions 5c located on both sides of the punch 3a, one side land portion 5c 'is inclined upward in the moving direction A of the punch 3 (the direction in which the material is pushed), and the other side land portion 5c.
c ″ is arranged so as to be inclined downward in the moving direction A of the punch 3. Therefore, the material pushed into the lands 5 of the tooth forming shape portion 7 passes through the lands 5 and becomes as shown in FIG. As indicated by the broken line, it returns to the one side land portion 5c 'and tries to flow along that surface. As a result, the tooth traces S ₁ and S _{2 on} both sides of the tooth profile change into a waveform, and the tooth profile accuracy increases. There was a problem that it became worse.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object the following:
An object of the present invention is to provide a molding die capable of stably molding an outer helical gear having excellent tooth profile accuracy.

[0006]

SUMMARY OF THE INVENTION To achieve the above object, the present invention provides a tooth forming shape portion formed by connecting a tooth forming shape land and a land relief for releasing the land in a radially outward direction. In a die for an outer helical gear provided with a die provided and a punch that moves on the axis of the die and pushes a material into the tooth forming part, of the lands of the tooth forming part of the die, with respect to the punch moving direction. The side land portion inclined upwardly is extended in the material extrusion direction.

[0007] In the outer helical gear forming die thus configured, the extended portion of the side land portion extending in the material extrusion direction serves to regulate the return of the material passing through the land, and the deformation of the tooth traces is reduced. Is suppressed.

In the present invention, if the length of the extended portion of the side land portion is too short, the effect of restricting the return of the material is small. Therefore, it is preferable to set the length to 0.5 times or more the diameter of the tip cylinder. .

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

FIGS. 1 and 2 show a main structure of a molding die for an outer helical gear according to the present invention. Since the basic structure of this molding die is the same as that shown in FIGS. 3 and 4 above, the same reference numerals are given to the same parts here, and
Duplicate description will be omitted. In the present embodiment, the land 5 of the tooth forming portion 7 of the die 2 forms a tooth surface with a large-diameter land portion 5a for forming a tooth tip surface and a small-diameter land portion 5b for forming a tooth bottom surface as in the related art. Side land 5
c. Thus, the large-diameter land portion 5a
One of the side land portions 5c '(FIG. 2), which is inclined upward in the moving direction A of the punch 3 (the direction in which the material is pushed), of the pair of side land portions 5c located on both sides of It is extended by a predetermined length L. The length L of the extension portion 10 is set to be 0.5 times or more the diameter of the tip cylinder.

The procedure of the extrusion molding of the helical gear by the molding die having the above-mentioned structure has no difference from the conventional one, and a material (not shown) is inserted into the cylindrical hole 4 of the die 2 shown in FIG. Thereafter, the punch 3 is lowered integrally with the upper die, and the material is pushed into the die 2. Then, the leading end of the material flows on the conical surface 8 and enters the tooth forming part 7, and is extruded along the tooth forming part 7, whereby an outer helical gear having helical teeth on the outer periphery is formed. You. in this case,
Since the one side land portion 5c 'that is inclined upward in the moving direction A of the punch 3 is extended, the material that has passed through the land 5 of the tooth forming shape portion 7, as shown by the broken hatching in FIG. The return is regulated by the extension portion 10 of the side land portion 5c ', and flows along the surface of the extension portion 10 as it is. As a result, even if the extension portion 10 is interrupted, the material is extruded without bending to the side of the land relief 6, thereby preventing deformation of the tooth traces S ₁ and S _{2 on} both sides of the tooth profile of the formed outer helical gear. As a result, the tooth profile accuracy is significantly improved.

[0012]

As described above, according to the mold for a helical gear according to the present invention, the simple improvement that the side land portion inclined upward with respect to the punch moving direction is extended in the material extrusion direction can be obtained. Extrusion molding of a helical gear with excellent tooth profile accuracy is possible, and its utility value is large.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a main structure of a molding die of a helical gear according to the present invention.

FIG. 2 is a cross-sectional view schematically showing a form of material flow by a main mold.

FIG. 3 is a cross-sectional view showing a general structure of a molding die of a helical gear.

FIG. 4 is an enlarged perspective view showing a main part of a conventional molding die.

FIG. 5 is a cross-sectional view schematically showing a form of material flow by a conventional molding die.

[Explanation of symbols]

 Reference Signs List 2 Die 3 Punch 5 Land 5a Large diameter land 5b Small diameter land 5c Side land 6 Land relief 7 Tooth forming part 10 Extension part of side land

Claims (2)

[Claims] 1. A die provided with a tooth forming shape portion formed by connecting a tooth forming shape land and a land relief for releasing the land in a radially outward direction, and a die provided on the axis. In a molding die for an outer helical gear having a punch pressed into the tooth forming part, a side land part of the land of the tooth forming part of the die, which is inclined upward with respect to a punch moving direction, is extended in a material pushing direction. A molding die for an outer helical gear, characterized in that: 2. The outer helical gear forming die according to claim 1, wherein the length of the extended portion of the side land portion is set to be at least 0.5 times the diameter of the tooth tip cylinder.