JPS6033847A - Production of driving shaft having high torsional strength - Google Patents

Abstract

PURPOSE:To enable production of a driving shaft having high torsional strength in the stage of producing the driving shaft for an automobile from a blank material which is a steel pipe by drawing the end of the steel pipe to reduce the diameter thereof then hot working said end to form a solid part and forming solidly a serrated part and a neck part thereof into one body. CONSTITUTION:A driving shaft such as a driving shaft for a front drive car is produced of a blank material which is a hollow steel pipe for the purpose of reducing the weight of the automobile. The end of the steel pipe which is the blank material is quickly heated and while a cooling die is used for the non- heated part to prevent said part from receiving thermal influence, the heated end is drawn to reduce the diameter and is then hot worked to form a solid part 3, by which a serrated (gear part 1 as a power transmission part of the driving shaft and a serrated neck part 2 are formed solidly to one body. Since the other part is hollow, the driving shaft which is lightweight and has high torsional strength is produced.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a method of manufacturing a drive shaft with excellent torsional strength, and in particular to manufacturing a drive shaft such as a drive shaft for a heavy-duty front wheel drive vehicle using a small diameter steel pipe. It's about how to do it.

(Prior Art) Recently, efforts have been made to reduce the weight and improve the reliability of automobile parts, and one of these efforts is to make parts conventionally made of steel bars hollow, that is, to make them into steel pipes.

Among these parts, drive shafts such as drive shafts for front-wheel drive vehicles are manufactured using steel pipes.

After cold drawing, the tube end is hot upset.

Apply serrations (gear) processing etc. to the relevant part.

It may be used as a driving force transmission part. Conventionally, such an integrally drawn drive shaft is made of a seamless steel pipe, and as shown in FIG. A drive shaft with a large outer diameter part (diameter processing part) was used. However, one way to improve the performance of front-wheel drive vehicles is to reduce the minimum turning radius. For this purpose, it has been desired to reduce the outer diameter of the serration neck 2 to prevent contact with the housing and increase the steering angle. Furthermore, with the aim of reducing the cost of materials, it has become desirable to use electric resistance welded pipes. In view of this, various attempts have been made, but none of them have been able to solve the problem.

For example, FIG. 2(a) shows a drive shaft formed by integral drawing, in which the outer diameter of the serration neck portion 2 is smaller than the root diameter of the serration portion 1. However, as shown in Figure (b), if the range of the solid part 3 is approximately equal to the range of the serration part 1, the cross-sectional shape of the selenium neck part 2 will be the same when a seamless steel pipe is used. Figure (C)
As shown in d), when wrinkles are formed on the inner surface of the tube and torsional force is applied to the drive shaft, cracks will form and grow from the wrinkles, significantly reducing the strength of the drive shaft. .

FIG. 3(a) shows the axial cross-sectional shape when the hot working range is expanded and the thickness increase rate of the serration neck 2 is increased. However, in this case, as in the case of Fig. 2, the cross-sectional shape of the serration neck 2 is as shown in Fig. 2(b) i
When using the seamless steel pipe shown here, and when using the electric resistance welded pipe shown in the same figure (C), wrinkles occur on the inner surface of the pipe, which reduces the strength of the drive shaft. .

(Objective and Structure of the Invention) In view of the above-mentioned circumstances, the present invention makes it possible to manufacture a drive shaft with excellent torsional strength, and its gist is to shrink the end of a steel pipe by drawing. The drive shaft is characterized in that the serration part and the neck part of the serrations are integrally formed into a solid part when the drive shaft is manufactured by hot working after diametralizing the diameter.The drive shaft has excellent torsional strength. It is in the manufacturing method.

The present invention will be explained in detail below.

FIG. 4(a) shows an embodiment of the method of the present invention, and as shown in the figure, the range of the solid part 3 includes all of the serration part 1 and the serration neck part 2f, or more than (as shown in the figure)
This is what is molded. Heating methods include furnace door hot flame, high frequency induction heating, etc., and are not particularly limited, but rapid heating is used.

Alternatively, the heating range is limited to the area where the solid part is formed by preventing the heat-affected zone from reaching the ground using a non-heated part (cooling mold, etc.). As shown in Figure (b), the outer periphery is restrained by the dies 6 and 7, and the plunger 8 applies a sufficient absorbing force to the heated part. 2 is solid, and the tip 5 of the upset portion is approximately perpendicular to the tube axis.

(Effect of the invention) In the drive shaft material formed and processed in this way,
There is almost no occurrence of cracks on the inner surface of the drawn part, which has a larger outer diameter than the serration neck 2, and on the tip 5 of the upset part, and in the subsequent hardening process, the hardness and hardening depth required from the strength calculation are achieved. Moreover, since wrinkles, which become the core of crack generation, are hardly generated, it is possible to manufacture a drive shaft having extremely superior torsional strength.

(Example) Hereinafter, the effects of the present invention will be illustrated more specifically by examples.

Using a material equivalent to 540C, use a φ40.0Xt4.5 electric resistance welded pipe, set the number of drawing stages to 3, and make the serration neck φ2.
2.0Xt6.8. As shown in Figure 2 (b), when the area of 40 trenches including the serrations was heated by high frequency heating to make it solid, the cross-sectional shape of the serration neck was observed.

A crack with a maximum length of 0.05 m was observed on the inner surface near the weld. Therefore, the surface hardness is HV=650. Hardening depth 5
Briefly, when quenching was performed using induction heat treatment 1 and a torsional fatigue test was performed, an S-N relationship as shown in FIG. 5 II was obtained. Here, the source of fatigue cracks is cracks caused by wrinkles near the welds on the inner surface.

On the other hand, with the same material and shape, the heating range due to high frequency heating ζ has been expanded, as shown in Fig. 4.

The serration part was made solid with 80 ml at the serration neck. In this case, heating and forging can each be performed in one cycle, and the difference in manufacturing cost is small. Quenched with surface hardness Hv = 650 and hardening depth of 6 mm.
The results of the torsional fatigue test are shown in Figure 5.

It is clear that the torsional fatigue life is increased by about 5 times, and that cracks are generated only by minute defects on the surface and are sufficiently durable for practical use.

[Brief explanation of the drawing]

FIG. 1 is an external view of a conventional integrally drawn drive shaft. Figure 2 (a) is an external view of a drive shaft with a small outer diameter of the serration neck, Figure 2 (b) is a longitudinal cross-sectional view thereof, and Figure 2 (a) is a cross-sectional view of the serration neck when seamless steel pipe is used. , FIG. 3(d) is a cross-sectional view of the serration neck when an electric resistance welded pipe is used. FIG. 3(a) is a vertical cross-sectional view when the heating range is expanded, and FIG. Cross-sectional view of serration neck when seamless steel pipe is used,
4(a) is a cross-sectional view of the serration neck when each electric resistance welded pipe is used. FIG. 4(a) is a vertical cross-sectional view of the drive shaft according to the present invention, and FIG. FIG. 5 is a diagram showing an S-N curve. 1°...Serration part, 2... Serration neck part. 3... Solid part, 4... Electric resistance welding part. , 5...Tip of the upset part, 6, 7...Dice, 8...Plunger. Patent applicant Representative Patent Attorney Tomoyuki Yabuki (and 1 other person)

Claims (1)

[Claims] After reducing the diameter of the end of the steel pipe by drawing, a solid part is formed by a hot processing vessel to manufacture the drive shaft, and the serration part and the neck part of the serration are integrally formed into a solid part. do. A method for manufacturing a drive shaft with excellent torsional strength.