JPH0452040A - Formation of cross roll - Google Patents

Abstract

PURPOSE:To securely prevent a flaw caused by a piping defect from remaining at a shaft end part of a forging product by forming a dead boss part having partially large outer diameters at the end part in the direction of a shaft line of a cross roll forming stock. CONSTITUTION:The forging stock 6 is pressed and elongated from the central part toward both end parts in the direction of a rotary shaft line to be formed into a shape having a comparatively fine bar-like shaft end part 6a and an outer diameter changing part 6b. In cross roll forming, a dead boss 6c having partially large outer diameters is formed by a groove 7b in the circumferential direction of a roll die 7. Since the reduction ratio of cross-sectional area of the forging stock 6 is lowered in the dead boss part 6c, the extension ratio of the outside wall part is reduced at the end in the direction of a shaft line and the piping defect 6d generated in the central part is shallowed drastically. Further, the piping defect 6d stops at the dead boss part 6c and does not reach the central part of the shaft end part 6a at the inner part of the boss part.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to cross roll forming in which a pair of dies sandwich a material and the surfaces of the dies are moved in opposite directions to extend the material axially. In particular, the present invention relates to a cross-roll forming method that does not leave any flaws in the axial end portions of the forged product even when forging is performed using a forged material that has been preformed into a shaft shape by cross-roll forming.

(Prior art) An example of a method for cross-roll forming is shown in Figure 6 (
As shown in a) and (b), the forged material I is sandwiched between a pair of roll dies 2 having circumferential protrusions 2a that gradually become wider as they rotate, and the roll dies 2 are rotated in opposite directions. By moving the outer circumferential surfaces having the circumferential protrusions 2a in mutually opposite directions, the central portion of the forged material 1 is rotated without being translated in parallel under the guidance of the pair of guides 3. Some products are formed into a shaft by stretching the material from the beginning toward both ends in the direction of the rotational axis.

By the way, by the above-mentioned cross roll forming, the forging material 1 for forging a crankshaft, for example, is formed into a relatively thin rod-shaped shaft end portion 1a that will become a crank pulley shaft portion and an outer diameter changing portion 1b that will become a journal portion or a counterweight portion. When preforming is performed to distribute the volume in an axial manner, conventionally, as shown in FIGS. Only 1a was formed.

(Problem to be solved by the invention) However, in such a conventional method, the shaft end 1a
Since the reduction rate of the cross-sectional area of the forged material 1 is high at the axial end portion where the axial end portion 1a is formed, only the outer peripheral portion of the end portion is particularly elongated and the forged material 1 is forged as shown in FIG. Material 1
A relatively deep sink hole IC remains at the center of the shaft end 1a, and the depth of the sink hole 1c varies.

For this reason, a crankshaft 4 as shown in FIG. 9 is manufactured by performing die forging on the forged material l preformed by the above-mentioned conventional method, and the burrs around it are removed as shown in FIG.
Even if the burr 5 is removed, all parts of the sink hole IC cannot be included in the burr 5 to be removed, and as shown in FIG. There was a problem in that a flaw 4b caused by the sink hole IC may remain in the center portion.

The present invention provides a cross-roll forming method that advantageously solves these problems.

(Means for Solving the Problems) The cross roll forming method of the present invention involves cross roll forming in which a pair of dies sandwich the material and the surfaces of the dies are moved in opposite directions to extend the material into an axial shape. When carrying out this method, a discarded boss portion having a partially large outer diameter is formed at the axial end portion of the material.

(Function) According to this method, when forming the material into a shaft shape, at the discarded boss portion at the end in the axial direction, the outer diameter is partially large.
The reduction rate of the cross-sectional area is low (because the rate of elongation of the outer circumference at the axial end is reduced, the sink hole that occurs in the center becomes extremely shallow, and moreover, it stops at the sink hole or its waste hole). It won't reach any deeper than that.

Therefore, if preforming is performed using this cross-roll forming method and the forged material is formed into a axial shape, even if the forged material is forged to produce a product, there will remain some residue on the axial end of the forged material. The sink hole in the forged product is extremely shallow and always stops at the waste boss, so all parts of the sink hole can be easily included in the debris to be removed around the product. It is possible to reliably prevent flaws caused by sinkholes from remaining in the center portion.

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

FIGS. 1(a) to (C) are cross-sectional views showing the sequential steps in an embodiment of the cross-roll forming method of the present invention, and 6 in the figure is a cross-sectional view for die forging a crankshaft as a product. The forged material 7 indicates a roll die having approximately the same shape as the conventional roll die 2.

Here, each of the pair of roll dies 7 has, in particular, a circumferential groove 7b at one end in the axial direction (in the left-right direction in the figure) of the circumferential protrusion 7a on its outer peripheral surface.

In the method of this embodiment, the forged material 6 is sandwiched between the roll dies 7, and the roll dies 7 are rotated in mutually opposite directions to move their outer circumferential surfaces having circumferential protrusions 7a in mutually opposite directions. By doing so, the forging material 6 is not rotated without being translated in parallel under the guidance of a pair of guides (not shown) similar to the conventional guide 3.
As shown in Figures (a) to (C), the material is stretched from the center to both ends in the direction of the rotational axis, and as shown in Figure 2, the material becomes the crank pulley shaft. Preforming is performed to distribute the volume into a shaft having a thin rod-shaped shaft end 6a and an outer diameter changing portion 6b that becomes a journal portion or a counterweight portion.

During this cross roll forming, one end of the forged material 6 in the axial direction is formed by the circumferential groove 7b of the roll die 7.
As shown in FIGS. 1 and 2, a discarded boss portion 6C having a partially larger outer diameter is formed at a position further toward the end than the shaft end portion 6a, and in this discarded boss portion 6C, the forging material 6 is Since the reduction rate of the cross-sectional area is lower, the rate of elongation of the outer peripheral portion at the axial end portion is reduced, and the sink hole 6d formed in the center portion becomes extremely shallow, and moreover, the sink hole 6d stops at the discarded boss portion 6C. The shaft end 6a further back than that
It will not reach the center of the area.

Therefore, the forged material 6, which has been preformed using this cross-roll forming method and made into a shaft shape as shown in FIG. 2, is die-forged to produce the crankshaft 8 as shown in FIG. As shown in Fig. 4, the forged material 6 that has been preformed is
The sink hole 6d remaining at the axial end of is extremely shallow.
Moreover, since it always stops at the discarded boss part 6C, all parts of the sink hole 6d can be easily included in the hole 9 to be removed. It is possible to reliably prevent the flaw 4b caused by the sink hole 6d from remaining in the central portion of the crank pulley shaft portion 8a.

Although the present invention has been described above based on the illustrated examples, the present invention is not limited to the above-mentioned examples. You can go.

Further, the present invention can be applied to forged products other than the crankshaft in the above example, such as preforming of a forged material during forging such as a camshaft.

(Effects of the Invention) Thus, the warpage caused by the cross roll forming method of the present invention is caused by the sink hole remaining at the axial end of the forged material that has been preformed into a shaft shape, or by the extremely shallow sink hole, and also by the waste boss part. Therefore, even if a product is manufactured by forging the forged material, 1. Since all parts of the sink hole can be easily included in the area to be removed around the product, it is possible to reliably prevent any flaws caused by the sink hole from remaining in the center of the shaft end of the forged product. I can do something.

[Brief explanation of drawings]

Figures 1 (a) to (C) are cross-sectional views showing the sequential steps in an embodiment of the cross-roll forming method of the present invention, and Figure 2 is a partial cross-section of a forged material formed by the method of the above embodiment. FIG. 3 is a front view showing the crankshaft die-forged from the forged material formed by the method of the above embodiment with a burr attached, and FIG. 4 is a front view showing the crankshaft with the burr removed. , FIG. 5 is a perspective view partially showing the crankshaft in cross section, FIGS. 6(a) and (b) are a side view and a perspective view showing a roll die in the conventional cross roll forming method, and FIG. 7(a) ) to (c) are cross-sectional views showing the sequential steps in the above conventional method, Fig. 8 is a perspective view partially showing a cross section of the forged material formed by the above conventional method, and Fig. 9 is a cross-sectional view showing the forged material formed by the above conventional method. FIG. 10 is a front view showing the crankshaft die-forged from a forged material with a burr, FIG. 10 is a front view of the crankshaft with the burr removed, and FIG. 11 is a perspective view showing a partial cross section of the crank shirt I. It is a diagram. 6-Forged material 6a-・Shaft end 6cm-11 Discarded boss portion 6d-・Sink hole 7-Roll die
7b--... Circumferential grooves Fig. 1 Fig. 2 Fig. 6 & Fig. 6 (a) (b) Fig. 4 Fig. 5 Fig. 7 Fig. 8 Fig. 1 - Fig. 1O Fig. 11

Claims (1)

[Claims] 1. When performing cross roll forming in which the material is sandwiched between a pair of dies and the surfaces of the dies are moved in opposite directions to extend the material axially, the axial end portion of the material is A cross roll forming method characterized by forming a discarded boss portion having a partially large outer diameter.