JPH0641704Y2 - Extrusion mold - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to an extrusion die, and more specifically, for example, an automobile having a hollow cup shape and an inner periphery having a track groove for rolling a roller bearing. The present invention relates to a die for extruding a preformed body for an outer ring of a constant velocity joint, which is capable of obtaining a good preformed body without galling or the like.

[Background of the Invention] For example, in a constant velocity joint outer ring that connects a differential device and a front wheel shaft in a wheel drive unit of an automobile, a cold forging step of forming a first preformed body by forging a billet,
Manufactured by an extrusion molding step of forming a second preformed body from the first preformed body using an extrusion die, and a sizing step of forming a final product having a final finished size from the second preformed body. Has been done.

Therefore, first, the cold forging step, which is the first step, will be described with reference to FIG. In this step, the billet 2a having a columnar shape is forged to form the billet 2b from the billet 2b, and finally the first preform 4 having the upset portion 4a at the end thereof.
To form. Next, in the extrusion molding step which is the second step, the second step is performed while the upsetting portion 4a is held by the lower mold 5.
Molded by the extrusion die 6 shown in the figure, a blank 8 which is a second preformed body is formed.

Here, the blank 8 formed by the extrusion die 6 is a preformed body of the outer ring of the constant velocity joint proposed by the present applicant (Japanese Patent Application No. 62-25098 (Japanese Patent Application Laid-Open No. 63-19542).
See 1)). That is, as shown in FIG. 3, the blank 8 which is the second preform has a cup shape having an opening 8a in which the driven shaft 10 is integrally formed at one end and the other end is open, as shown in FIG. In the interior of the blank 8, there are three recessed portions 12a to 12c extending in the axial direction to receive the trunnion (not shown), and between the recessed portions 12a to 12c, the hollow portions of the blank 8 project. Convex portions 14a to 14c of the strip
And are formed.

The concave portions 12a to 12c are the ceiling surfaces 16a to 16c and the ceiling surface, respectively.
There are track grooves 18a to 18f on both sides of 16a to 16c, on which slide rollers forming a trunnion roll. Further, the track grooves 18a to 18f and the convex portions 14a to 1
The protrusions 20a to 2c
0f, the protrusions 20a to 20f and the track groove 18a.
Through 18f, undercut portions 22a through 22f for restricting the lateral movement range of the slide roller rolling in the track grooves 18a through 18f and improving the performance of the constant velocity joint are formed, respectively. There is.

On the other hand, the extrusion die 6 for forming the blank 8 has an outer peripheral shape corresponding to the inner peripheral shape of the blank 8,
The lower end portion shown in FIG. 2 mainly reduces the sliding resistance with the blank 8 at the time of extrusion molding and facilitates the extrusion of the extrusion die 6 to the blank 8. A land portion 24 having a land surface 24a protruding outward from the site is provided.

By the way, in the blank 8 thus formed,
As described above, the undercut portions 22a to 22f are formed to improve the performance of the constant velocity joint. Therefore, the protrusions adjacent to the undercut portions 22a to 22f
20a to 20f are thin-walled with relatively low rigidity. here,
At the time of extrusion molding, the hollow portion of the blank 8 is extrusion-molded by the extrusion die 6 and the outer peripheral portion is ironed by the lower die 5. In this case, the protruding portions 20a to 20f after the land portion 24 has passed do not come into contact with the extrusion die 6, and their rigidity is lower than that of other portions because they are thin. , Easy to deform. Moreover, at the time of extrusion molding, the material of the central portion of the first preform 4 receives a force to move to the outer peripheral portion side by the extrusion die 6, but the outer peripheral portion is restrained by the lower die 5. ,
Eventually, it moves in the extrusion direction while receiving the force toward the outer peripheral portion side. Therefore, at the time of extrusion molding, as the material flows, the undercut portions 22a to 22f at which the protruding portions 20a to 20f are located closer to the outer peripheral portion than that are located.
Tends to tilt to the side. Then, the protrusions 20a to 2
With the inclination of 0f, the openings of the undercut portions 22a to 22f
The 8a side inclines toward the extrusion die 6 side as shown in FIG. This tendency becomes greater as the blank 8 formed by the extrusion die 6 has a longer axial length.

As a result, a situation occurs in which the undercut portions 22a to 22f come into contact with the extrusion die 6 during extrusion molding (see FIG. 2), whereby the undercut portions 22a to 22f come into contact with each other when the extrusion die 6 is pulled out from the blank 8. Gnawing occurs at the part. In this case, not only is it difficult to release the extrusion die 6 and the blank 8 from each other, but the land surface 24a protruding outwardly from the other parts of the extrusion die 6 has the opening 8a at the time of release. There is also a possibility that it may come into contact with the vicinity and cause damage. It has also been pointed out that the galling of the blank 8 with respect to the extrusion die 6 causes the lubricant film to disappear when the die is released, and the land surface 24a is seized, which shortens the life of the extrusion die 6.

On the other hand, it is possible to reduce the influence of the above-mentioned galling as much as possible by setting the protrusion amount of the land surface 24a of the extrusion die 6 as large as possible. However, in this case, the strength of the extrusion die 6 decreases. Therefore, it is not possible to set the protrusion amount so large, and the land surface 24a
It is difficult to completely eliminate the problem of galling, since galling still exists.

[Object of the Invention] The present invention has been made to overcome the above-mentioned inconvenience, and forms a molded body having a cup shape like an outer ring of a constant velocity joint and having an undercut portion in its hollow portion. In the extrusion die to be provided, a land portion having a land surface protruding outward is provided at the tip end portion of the columnar body having a long groove forming the undercut portion, and a relief portion from the land surface side along the long groove, By providing the taper surface and the stepped portion in which the protrusion amount is set to be larger than that of the land surface, it is possible to form a good molded body without galling of the molded product by the mold during extrusion molding, and An object of the present invention is to provide an extrusion die capable of promoting a long life of the die.

[Means for Achieving the Object] In order to achieve the above-mentioned object, the present invention forms a molded body (8) having an undercut portion (22a to 22f) in a portion that bulges with respect to a hollow portion. In the extrusion die (30), the columnar body (32a to 3c) defining a plurality of long grooves (34a to 34c) extending from the base along the axial direction is provided.
2c), and provided at the tip of the pillar (32a to 32c),
The column body (32a to 32c) in the direction orthogonal to the extending direction.
Land portion (4a) having a land surface (44a) protruding more than
4), the side portions (40a to 40f) of the columnar body (32a to 32c) adjacent to the long grooves (34a to 34c) are connected to the land portion (44), and the land surface (44a) From the column (32a to 32)
The extrusion die (30) is connected to the relief portions (43a to 43f) having a surface receding to the c) side and the relief portions (43a to 43f).
As it moves to the base side of the long grooves (34a to 34a).
The taper surfaces (42a to 42f) close to the c) side, and the stepped portions (41a to 41c) that are continuous with the taper surfaces (42a to 42f) and project toward the long grooves (34a to 34c) from the land surface (44a). 41f) is provided.

[Embodiment] Next, a preferred embodiment of the extrusion die according to the present invention will be given and described in detail below with reference to the accompanying drawings.

In FIGS. 4 and 6, reference numeral 30 indicates an extrusion die. In this case, the first preform 4 shown in FIG. 1 is used as the object of extrusion molding, and the blank which is the preform of the outer ring used for the constant velocity joint shown in FIG. 3 from the first preform 4 is used. 8 shall be formed.

The extrusion die 30 is formed so that its outer peripheral shape substantially corresponds to the inner peripheral shape of the blank 8. That is, three elongated prismatic portions are provided at the portions corresponding to the three concave portions 12a to 12c of the blank 8.
32a to 32c are formed to bulge, and each prismatic portion 32a to 32c is formed.
A long groove 34 corresponding to the convex portions 14a to 14c of the blank 8 is provided between them.
a to 34c are formed respectively.

The prismatic portions 32a to 32c are ceiling surfaces 16a to 1 of the concave portions 12a to 12c.
Flat portions 36a to 36c forming 6c, and the flat portions 36a to 3c
Side portions 38a to 38f on both sides of 6c which form the track grooves 18a to 18f, the long grooves 34a to 34c, and the side portions 38, respectively.
jaws 40a-40f that form undercuts 22a-22f between a-38f. Each jaw 40a-40f
Includes stepped portions 41a to 41f which are relatively wide from above in FIG.
Tapered surface 42a that gradually becomes narrower than the stepped portions 41a to 41f
To 42f and straight and narrow relief portions 43a to 43f are formed in this order in the downward direction, and a land portion 44 is formed at the lower end portion of the jaw portions 40a to 40f. In addition, the land portion 44 covers the entire circumference of the lower end portion of the extrusion die 30 shown in FIG. 4 and the rectangular column portions 32a to 32c and the long groove 34a.
It has a land surface 44a projecting in a direction substantially orthogonal to the through holes 34c.

The side end surfaces of the step portions 41a to 41f project by δ from the side end surfaces of the relief portions 43a to 43f, as shown in FIG. Also,
The land surface 44a projects by ε from the side end surfaces of the escape portions 43a to 43f. In this case, the protrusion amount δ of the step portions 41a to 41f is set to be larger than the protrusion amount ε of the land surface 44a.

The amount of protrusion ε of the land surface 44a from the escape portions 43a to 43f is
Is, for example, about 0.3 to 0.4 mm, and the step portion 41a
The projection amount δ of each of the clearances 41 to 41f from the escape portions 43a to 43f is set to be larger than the projection amount ε by, for example, about 0.3 to 0.5 mm.

The tapered surfaces 42a to 42f are used to form the opening 8a of the blank 8 when the land portion 44 forms the bottom surface of the hollow portion of the blank 8.
It is provided at a position near the undercut portions 22a to 22f.

The extrusion die 30 according to the present embodiment is basically configured as described above. Next, the first preform 4 is processed by using the extrusion die 30 to form the second preform. The case of forming the blank 8 will be described.

First, as shown in FIG. 1, the billet 2a is forged to form a first preform 4 having an upset portion 4a.
Next, the land portion 44 of the extrusion die 30 is brought into contact with the upsetting portion 4a of the first preform 4, and the lower die 5 holds the first preform 4 to move the extrusion die 30 to the first position. The extrusion molding process is started by displacing it in the direction of arrow A shown in FIGS. 4 and 5. The land portion 44 of the extrusion die 30 gradually defines a hollow portion with respect to the first preform 4, and finally the land portion 44 is formed.
Blank 8 having a hollow portion having a shape corresponding to the outer peripheral shape of
To form.

Here, when the extrusion die 30 is pushed into the upsetting portion 4a of the first preform 4 to form the blank 8 that is the second preform, the outer periphery of the blank 8 is ironed by the lower die 5. To be done. In this case, the material of the central portion of the first preform 4 is subjected to the force of moving to the outer peripheral side by the extrusion die 30, and in particular, the material forming the thin-walled protrusions 20a to 20f is , The relief portion 43a of the extrusion die 30 during molding
Since it is in a non-contact state with respect to 43f, the extrusion die 3
As 0 is pushed into the first preform 4, the force toward the outer peripheral portion tends to deform toward the undercut portions 22a to 22f, which are located closer to the outer peripheral portion than the protruding portions 20a to 20f. On the other hand, the tapered surfaces 42a to 42f and the step portions 41a to 41f formed on the jaw-like portions 40a to 40f of the extrusion die 30 are located on the opening 8a side of the protrusions 20a to 20f of the blank 8. It is extruded toward the convex portions 14a to 14c.

As a result, as the deformation of the protrusions 20a to 20f toward the escape portions 43a to 43f is restricted, the inclination of the undercut portions 22a to 22f toward the extrusion die 8 as shown in FIG. Suppressed. As a result, the highly accurate undercut portion 22a
It is possible to obtain a blank 8 having 22f. Further, since the protrusion amount δ of the stepped portions 41a to 41f with respect to the relief portions 43a to 43f is set to be larger than the protrusion amount ε of the land surface 44a with respect to the relief portions 43a to 43f, the undercut portion is formed.
22a to 22f are blanks in which not only the inclination toward the extrusion die 30 side in the vicinity of the opening 8a is suppressed but also the separation distance from the extrusion die 30 in the vicinity of the opening 8a is defined by the land surface 44a. It is set to be larger than the separation distance from the extrusion die 30 on the bottom surface of No. 8. Therefore, when the extrusion die 30 is pulled out from the blank 8 in the direction of the arrow B, the blank 8 does not seize not only on the escape grooves 43a to 43f of the extrusion die 30 but also on the land surface 44a, which is smooth. Can perform mold release work.

In addition, since there is no risk of the land surface 44a scraping off the vicinity of the opening 8a during the mold release, it is possible to obtain the blank 8 that is a very good second preform. further,
Since the blank 8 does not seize with respect to the extrusion die 30, the lubricating coating on the surface of the blank 8 is cut off and the base of the material is not exposed. Therefore, there is no risk of sticking to the extrusion die 30. The durability is also improved. Furthermore, it is not necessary to increase the protrusion amount ε of the land surface 44a so much in order to prevent galling, and therefore, in combination with the above effect, the durability of the extrusion die 30 is further improved.

[Advantages of the Invention] As described above, according to the present invention, when forming a molded body having an undercut portion in the hollow portion by using an extrusion die, the end portion of the undercut portion in the molded body is dealt with. A step portion having a tapered surface is provided at a portion of the extrusion die, and the undercut portion in the vicinity of the opening is widened by the step portion. Further, the step portion is made to project to the molded body side with respect to the land surface of the die tip portion. in this case,
It can be formed accurately without tilting the undercut part, and when the extrusion die press-fitted into the molded body is released from the molded body, the molded body does not stick to the extrusion die. The mold release work can be performed extremely smoothly. Therefore, at the time of releasing from the mold, there is no possibility that a part of the molded body is scraped off by the extrusion die, and an extremely good molded body can be obtained. Further, since the molded body does not stick to the extrusion die, there is an advantage that the life of the extrusion die is promoted.

Although the present invention has been described with reference to the preferred embodiment, the present invention is not limited to this embodiment.
It goes without saying that various improvements and design changes can be made without departing from the scope of the present invention.

[Brief description of drawings]

1A to 1D are explanatory views of a forging process for forming a first preformed body from a billet, FIG. 2 is an explanatory view of a state of extrusion molding according to a conventional technique in a cross section taken along line II-II shown in FIG. 3, 3 a and b are partially omitted vertical and horizontal cross-sectional views showing the structure of a blank which is an outer ring of a constant velocity joint, and FIG. 4 shows an extrusion die according to the present invention and a preform formed by the extrusion die. FIG. 5 is a perspective view of the structure, FIG. 5 is an explanatory view of the extrusion molding state of the extrusion die according to the present invention in the section taken along the line VV of FIG. 6, and FIG. 6 is a sectional view of the extrusion die shown in FIG. Is. 2a to 2c ... billet, 4 ... preform 8 ... blank, 12a to 12c ... concave section 14a to 14c ... convex section 18a to 18f ... track groove 20a to 20f ... projecting section 22a to 22f …… Undercut part 30 …… Extrusion die, 32a to 32c …… Square prism part 34a to 34c …… Long groove, 40a to 40f …… Jaw-shaped part 41a to 41f …… Step part, 42a to 42f …… Tapered surface 43a ~ 43f …… Escape part, 44 …… Land part 44a …… Land surface

Claims (1)

[Scope of utility model registration request] 1. An extrusion mold (30) for molding a molded body (8) having an undercut portion (22a to 22f) in a region that bulges with respect to a hollow portion, wherein the extrusion mold (30) is , Pillars (32a to 3) defining a plurality of long grooves (34a to 34c) extending from the base along the axial direction.
2c), and provided at the tip of the pillar (32a to 32c),
The column body (32a to 32c) in the direction orthogonal to the extending direction.
Land portion (4a) having a land surface (44a) protruding more than
4), the side portions (40a to 40f) of the columnar body (32a to 32c) adjacent to the long grooves (34a to 34c) are connected to the land portion (44), and the land surface (44a) From the column (32a to 32)
The extrusion die (30) is connected to the relief portions (43a to 43f) having a surface receding to the c) side and the relief portions (43a to 43f).
As it moves to the base side of the long grooves (34a to 34a).
The taper surfaces (42a to 42f) close to the c) side, and the stepped portions (41a to 41c) that are continuous with the taper surfaces (42a to 42f) and project toward the long grooves (34a to 34c) from the land surface (44a). 41f) and an extrusion die.