JPS6325859B2 - - Google Patents

Description

Detailed Description of the Invention (Technical Field) The present invention relates to a cylindrical body having an inner surface and an outer surface, and a molded article (hereinafter referred to as , referred to as a molded product with different internal diameters). In this case, the molded product with different inner diameters may be, for example, a tripod type constant velocity universal joint,
This applies to so-called tulips.

(Background Art) Molded products with different inner diameters, such as tulips, are in sliding contact with the rollers associated with the spider on their inner surfaces. Very high dimensional accuracy is required. A method for forming such a molded product with different inner diameters is a method based on plastic working, which consists of a forging process in which the inner surface is roughly formed, and an ironing process that improves the dimensional accuracy of the inner surface by squeezing the outer surface. There is.

(Technical Problem) By the way, in this type of forming method, the forging process causes the formed product to have a different distance in the inner radial direction at each part in the circumferential direction, but on the other hand, The radial distance from the axis to the outer surface (hereinafter referred to as the outer surface radial distance) is the same at each location in the circumferential direction, and therefore the thickness is different at each location in the circumferential direction. It becomes ivy. This is due to the fact that the outer surface does not need to have the aforementioned functions like the inner surface.

Therefore, in order to increase the dimensional accuracy of the inner surface throughout the circumferential direction through the subsequent ironing process,
The ironing rate must be higher for areas that are relatively thicker than for areas that are relatively thinner, and due to the difference in ironing rate, the molded product is There was a problem in that "cracking" occurred.

In addition, in order to avoid this problem, it is possible to use a material with high strength (for example, case-hardened steel) that can withstand the difference in ironing rate as a material for forming the molded product with different inner diameters. In this case, the degree of freedom in material selection is necessarily small (for example,
Carbon steel with a carbon content of about 0.45% cannot be used).

(Objective of the Invention) The object of the present invention is to solve such technical problems (ie, the occurrence of cracks and the low degree of freedom in selecting materials).

(Summary of the Invention) The present invention allows the outer surface radial distance to be varied at each circumferential portion of the molded product in correspondence with the inner radial distance in the forging process, and the molded product to be subjected to the ironing process to be subjected to an ironing process. It is characterized in that the thickness is made uniform over the entire circumferential direction.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

Figures 1 A, B to 4 show the procedure for forming a constant velocity universal joint tube (here, the one with an integrated shaft). In each figure, 1 is a tulip (Fig. 4),
2 and 2' are dice and 3 and 3' are mandrels. Regarding molded products, so-called workpieces,
The product before the forging process is shown as 1A, and the product after the forging process and before the ironing process is shown as 1B.

First, as shown in FIG.
As shown in FIG. 2, a workpiece 1A is placed in the die 2.
The workpiece 1A is forged by aligning the axes of the die 2 and the die 2, and then lowering the mandrel 3 located above the die 2.

As shown in FIG. 3, the workpiece 1B thus obtained has a cylindrical recess 1a, and three cylindrical recesses 1a protruding radially outward at 120° intervals in the circumferential direction of the recess 1a.
roller sliding contact recesses 1b, and the distance in the radial direction of the inner surface of the workpiece 1B is the roller sliding contact recess 1b.
It is different between the site where b is present and the site where it is not present, and each site within the site where b is present. Moreover, the outer surface shape of the workpiece 1B is not just a cylindrical outer shape, but also has a recess 1b for roller sliding contact.
The area corresponding to the non-existing area is depressed radially inward, and the outer radial distance at the area corresponding to the existing area of the roller sliding contact recess 1b is defined as the inner radial distance at the existing area. It is changed to resemble the change in . Therefore, work 1B
The thickness of the workpiece 1B is approximately uniform throughout the circumferential direction of the workpiece 1B.

(Aspects in the forging process) In the forging process, the inner surface forming and the outer surface forming do not necessarily need to be performed at the same time. That is, both moldings may be performed at a time interval.

Next, as shown in FIG. 4, the mandrel 3' is inserted into the workpiece 1B, and while maintaining this inserted state, the entire outer surface of the workpiece 1B is covered with a die (the inner shape is slightly larger than the outer shape of the workpiece 1B). ) 2', thereby improving the dimensional accuracy of the inner surface of the workpiece 1B, and obtaining the tulip 1 as a product as shown in FIG.

(Aspects in the ironing process) When the mandrel 3' is initially inserted into the workpiece 1B (before the ironing process is performed), a certain gap is created along the axial direction between the mandrel 3' and the workpiece 1B. It is good to have it present (Figure 4). For example, it is preferable to provide a gap of 0.1 to 2 mm in the area corresponding to the area where the roller sliding contact recess 1b exists, and a gap of 0.5 to 3 mm in the area corresponding to the area where the roller sliding contact recess 1b does not exist. By squeezing while bringing the tubes closer together in this manner, the dimensional accuracy of the inner surface of the tube 1 can be improved at an even smaller straining rate.

The straining rate may be slightly different at each location in the circumferential direction of the workpiece 1B.

For ease of comparison, the workpiece 1B according to the conventional method is shown in FIG. 6, and the tulip 1 is shown in FIG. 7.

(Modification) In the embodiment, an example of a tube lip was described, but as long as the molded product has a different inner diameter, the shape of the inner surface does not matter. In other words, it is not limited to the unique shape of the tube, that is, the shape in which the roller sliding contact recesses 1b are arranged at three intervals of 120 degrees in the circumferential direction.

(Effects of the Invention) As described above, according to the present invention, the above-mentioned technical problem is solved, and at the same time,
It has the following additional effects.

1 Molded product to be subjected to ironing process (work 1B)
However, since the wall is thin as a whole, the radially inward load due to the ironing of the outer surface of the molded product is sufficiently applied to the inner surface. Therefore, at a small ironing rate (for example, 3%) The dimensional accuracy of the inner surface of the molded product with different diameters can be improved.

2 Molded product to be subjected to ironing process (work 1B)
Because the thickness of
(above) can also be set.

3. The molded product with different inner diameters has a thinner wall overall, which contributes to the weight reduction of the product.

[Brief explanation of the drawing]

Figures 1A and 1B are views showing a workpiece 1A in an embodiment of the present invention, in which Figure 1A is a side view, Figure 1B is a plan view, and Figure 2 shows the forging process in the above example. FIG. 3 is a plan view showing the workpiece 1B in the above example, FIG. 4 is a side sectional view for explaining the ironing process in the above example, and FIG. 5 is a side sectional view for explaining the ironing process in the above example. A plan view showing a molded product with different inner diameters (tulip 1), and FIGS. 6 and 7 are related to the conventional method. FIG. 6 is similar to the above-mentioned FIG. 3, and FIG. The diagrams respectively correspond to the diagrams. 1...Tulip (molded product with different inner diameter), 2,
2'...Dice, 3,3'...Mandrel, 1A...
...Work before forging process, 1B...Work before ironing process.

Claims (1)

[Claims] 1. In a method for molding a molded product having different inner diameters, which is a cylindrical body having an inner surface and an outer surface, and in which the radial distance from the axis to the inner surface is different at each part in the circumferential direction, (a) the inner surface and the outer surface are It is roughly formed into a shape, and the radial distance from the axis to the outer surface is varied at each location in the circumferential direction in correspondence with the radial distance to the inner surface, making the thickness uniform throughout the circumferential direction. (b) Next, a mandrel is inserted into the cylindrical body of the formed product and the outer surface of the cylindrical body is squeezed to improve the dimensional accuracy of the inner surface. How to form things.