JP3061505B2 - Torsion bar and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a torsion bar mainly used for a suspension system of an automobile or a cab tilt system of a truck.

[0002]

2. Description of the Related Art A torsion bar used for a suspension device or a cab tilt device is usually formed by stamping and forging both ends of a solid round bar and forming a joint such as serration by slightly processing the ends. It has become. Then, the connecting part at one end is attached to the vehicle body fixed side, and the connecting part at the other end is attached to the suspension arm or cab tilt arm, respectively. ) Exerts a spring action by the torsional deformation of the

[0003]

However, recently, the torsion bar itself is becoming multifunctional, and a torsion bar body having a complicated shape is designed. If the shape becomes complicated, stamping forging may not be possible. In such a case, the conventional technology requires a total cutting process from a large material as shown in FIG. 5, resulting in extremely low cost, manufacturing capability and quality. There are many problems.

An object of the present invention is to provide a method of manufacturing a torsion bar that can be easily manufactured even in a complicated shape under such circumstances, is low in cost, and is excellent in quality of the obtained product. It is the purpose.

[0005]

As a result of intensive studies, the present inventor has solved the above-mentioned problems by applying friction welding to a spring steel which has conventionally been considered to be very poor in weldability and difficult to weld. The inventors have found that it can be solved, and have reached the present invention.

That is, the present invention relates to a method for manufacturing a torsion bar made of spring steel and comprising an effective portion of a torsion bar and an end portion which is continuous with the effective portion. The gist of the present invention is a method of manufacturing a torsion bar in which the end portion and the effective portion separately manufactured are integrally joined by friction welding.

As described above, in manufacturing the torsion bar in the present invention, it is important to frictionally weld the effective portion and the end of the torsion bar. As described above, in the case of spring steel, the weldability including pressure welding is extremely poor, and the joints are liable to cause burning cracks and the like, and welding has been considered to be more difficult than before. However, the present inventor was able to overcome this problem by studying friction welding. That is,
In the case where the torsion bar is formed by friction welding, the occurrence of burning cracks at the joint is prevented by simply keeping the upset pressure (P ₂ ) and the offset allowance (U) among the friction conditions in a certain relationship. I found what I could do. FIG. 6 is a graph showing whether or not cracking occurs in the welded portion when the torsion bar is manufactured using friction welding.
_It shows the relationship between ₂ and U. FIG. 6 shows that the friction welding conditions in the present invention

[0008]

(Equation 2)

It can be seen that the above can prevent the occurrence of burning cracks at the joint. Since the torsion bar according to the present invention manufactured as described above is a friction-welded product, there is a possibility that the torsion bar is temporarily durable and has poor settability. Therefore, in order to confirm this point, as shown in FIG. 2, an attempt was made to compare a torsion bar manufactured by friction welding at the center of the effective portion of a normal torsion bar with a normal product without friction welding.

FIGS. 3 and 4 show the results of comparative tests on durability and sag resistance. As is clear from FIGS. 3 and 4, the torsion bar manufactured by friction welding according to the present invention has performance equal to or higher than that of a conventional product, and there is no quality concern due to the use of the friction welding means. It was confirmed that. In addition, this test was performed at a high stress portion, that is, at the center of the effective portion, where the friction welding was performed. Is possible.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described with reference to FIG. A part called a normally effective part (a part that is mainly twisted at the time of a spring action) is made of a spring bar steel φd material, and both ends are formed into a predetermined shape φD × l by stamping and forging to produce an effective member A. (FIG. 1a). At the same time, in another step, both end members B and C which are frictionally pressed against the member A are prepared (FIG. 1b), and these members are rotated at a rotation speed N of 1500 rpm.
Friction pressure P ₁ , 6 kg / mm ² , friction time t, 10 s, upset pressure P ₂ , 10 kg / mm ² , offset U, 13 m
The friction welding is performed under the condition of m (FIG. 1c). Then, a portion other than the effective portion is machine-finished (final finished) into a predetermined shape (FIG. 1D). Thereafter, it is subjected to a conventional torsion bar production process.

The torsion bar manufactured by the method of the present invention manufactured as described above can maintain the high quality because the effective portion, which is the most important part in quality, can be manufactured by the same stamping forging as the conventional one, unlike the whole cut product. Since the other part of the torsion bar (the end part which is continuous with the effective part) can be finished by machining separately, it is possible to sufficiently cope with the tendency of the shape becoming complicated. In addition, the manufacturing cost can be significantly reduced as compared with the total cutting method.

[0013]

As described above, according to the manufacturing method of the present invention, it is possible to sufficiently cope with the complicated shape of the torsion bar, and the quality of the manufactured torsion bar is high and the cost is low. .

[Brief description of the drawings]

FIG. 1 is an explanatory view of a process of the present invention,

FIG. 2 is an explanatory view of a friction welding portion of a torsion bar manufactured for comparison with a normal product by stamping forging,

FIG. 3 is a graph showing the relationship between the stress of the torsion bar according to the present invention and the normal product—the SN of the torsion bar (vertical shaft torsional stress, number of horizontal axis breakage);

FIG. 4 is a graph showing the relationship between the creep strain of the torsion bar according to the present invention and a normal product and the creep of the torsion bar.

FIG. 5 is an explanatory view of manufacturing a torsion bar by a total cutting process according to a conventional technique.

FIG. 6 is a diagram for explaining the relationship between the presence or absence of occurrence of sintering cracks at the joint in the production of the torsion bar by friction welding, the upset pressure (P ₂ ), and the allowance (U).

Claims (1)

(57) [Claims] 1. A method for producing a torsion bar comprising an effective portion of a torsion bar made of spring steel and an end portion continuous with the torsion bar, wherein the effective portion is manufactured by stamping forging with or without dividing. The end (U) of the separately manufactured end and the effective part is given by A method for manufacturing a torsion bar, comprising joining by friction welding as described above.