JPH0647137B2 - Method for manufacturing torsion bar - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a torsion bar (hereinafter, simply referred to as a bar).
The present invention relates to a preferred manufacturing method of a torsion bar that applies torsion and utilizes its elasticity.

(B) Prior Art Bars are generally used as one of the components of suspensions, as seen in automobiles. That is,
As stipulated in JIS (Japanese Standard) B2705, the shape generally has grips at both ends, and the middle of the grips at both ends has a parallel part with a diameter smaller than the grip. It is manufactured in the shape of a rod with a circular cross section. Then, the grip portion is serrated or, in some cases, formed into a polygonal shape to easily apply a twisting force.

On the other hand, the bar is also called a torsion bar and is used as a power steering device in the case of automobiles and as a suspension device in automobiles and railway vehicles. One of the bars is attached to the suspension and the other is fixed to the vehicle body. When the suspension moves up and down, the bar is twisted, and the repulsive force exerts the function of the spring.
Therefore, a strong repeated torsional force is applied to the bar, and the repulsion resistance against the torsional force is an important requirement from the viewpoint of vehicle safety.

In the method for manufacturing the bar, a long, tempered steel bar having a constant thickness is cut into a constant length, and a grip portion and a taper portion are processed, and a parallel portion is cut or ground.
The grips of the bar are either swallowed or serrated. Further, the taper portion is left as it is, or is sometimes cut and finished.
Then, although heat treatment is performed to increase the hardness of the surface, shot peening may also be performed. The bar processed in this way performs setting, but in this case,
The residual strain due to setting is usually finished to be in the range of 1%. Furthermore, the surface of the bar must be free of harmful defects such as rough skin, scratches and decarburization. However, when a parallel portion having a small diameter is formed by cutting, a cut trace remains in the parallel portion, which may be broken or a crack may be generated from the trace when residual strain due to setting is removed. there were. By the way, even if the parallel portion is machined by cutting or grinding, it is difficult to machine the surface roughness Rmax of 1 micron or less, and it is not economically suitable for mass production.

(C) Problem to be Solved by the Invention As described above, the bar-shaped bar exerts a spring function by its repulsive force when a torsional force is applied,
Not only the grip portion, but also the parallel portion having a small diameter must sufficiently withstand the twisting force. However, as seen in the conventional example, in the bar processed by cutting, since the cut streak remains in the parallel portion which is the middle of the bar, the streak develops a crack against repeated twisting force. It also caused the bar to break as a result.

The present invention intends to improve the yield rate by forming the bar by press forming in order to prevent the generation of scratches or scratches on the parallel portion having a small diameter.

(D) Means for Solving the Problems The present invention has been made in view of the above-mentioned circumstances, and for example, as shown in FIG. 2, a polished steel bar having a constant thickness is used as a material,
At least the parallel portion (12) is forged to be thinner than the material, and the grip portions (11A) (11B) are provided at both ends of the parallel portion.
To form both ends of the grip part (15A)
(15B) is cut to have a length (L), and the outer peripheries (14) and (14) of both end surfaces are chamfered and then heat treated, which is a method of manufacturing a torsion bar.

(E) Action When manufacturing the bar, since the polished steel bar is used as the raw material, there is no scratch on the surface, especially when the parallel part (12) is press-pressed, even if there is a scratch, the material is pressed in parallel. The part (12) is stretched in the length (12) direction, and the scratches are made fine. That is, the formation of cracks is prevented without growing scratches. Furthermore, since the parallel portion (12) is subjected to a small diameter processing by press forging, a fiber structure is obtained in the longitudinal direction of the bar (10) and the fiber structure is densified, and as a result, the outer surface is The bright surface becomes and acts so as to exert a high yield strength against the twisting force.

(F) Example Hereinafter, a method of manufacturing the article shown in FIG. 2 will be described based on the process chart of FIG.

As a first step, a steel bar having a constant thickness is received, and in a second step 2, the grip portion 11A on the front side A (left side in FIG. 2), the parallel portion 12 and the taper portion, and the rear side B.
The grip portion 11B (on the left side in FIG. 2) and the parallel portion and the tapered portion 13 are press-pressed (here, swaging). In this swaging process, although not shown, the material is gripped and constrained by a gripping device at least on the rear side B from the scheduled rear end 15B. Since the gripping device can move in the front-rear direction while gripping the material, it can be moved as necessary to swage the gripping part 11A, the parallel part 12 and the taper part 13, or sometimes, Parallel part 12 and grip part 11B
And the tapered portion 13 is swaged.
Further, depending on the moving position, only the parallel portion 11 may be swaged during the repeated swaging. Therefore, depending on the required length of the parallel portion 11, at least first, the grip portion 11A and the parallel portion 12 and the taper portion 13 thereof, and the parallel portion 12 and the grip portion 11B.
The taper portion 13 and the taper portion 13 are simultaneously processed.
Then, as described above, the gripping device is moved according to the required length of the parallel portion 12, and the parallel portion 12, the grip portion 11B, and the taper portion 13 are swaged. After the swaging process, in particular, the parallel part 12 is processed to have the small diameter d, when the swaging mold is separated from the processed article, the front end 15A
Then, cut 3 at the length L of the rear end 15B. That is, two or more bars 10 are sequentially obtained from one long polished steel bar. Predetermined length L from front end 15A to rear end 15B
The material cut by 3 is cut at the front end 15
A, the material moves in the forward direction of the gripping device by the length L cut, and repeats the swaging process again, and while sequentially performing the swaging process, cuts at the length L from the front end 15A to the rear end 15B. Then, the bar 10 is continuously molded. Further, the polished steel bar is the same as the diameter D of the grip portion 11 or slightly thicker than that, and is swaged to a small diameter d of the parallel portion 12.

Next, in the fourth step, both end faces of the front end 15A and the rear end 15B are turned, and the outer peripheries 14, 14 thereof are chamfered. Further, in the fifth step 5, heat treatment is performed,
In this heat treatment process, when the bars 10 are stacked at random, the bar 10 is distorted more than expected during the heat treatment process. Therefore, the bar 10 should be put in an upright state in a furnace for quenching and tempering. ing. After the heat treatment, shot blasting 6 is performed by a sand blasting machine, and then a flaw is inspected by a magnetic flaw detector, selected, and a finished product is obtained.

In the above-mentioned embodiment, the reason why the polished steel bar is selected as a material is that the commercially available steel bar has black skin and rust on the surface, which shortens the service life of the die for press forging and This is because the accuracy of the finished product is not good due to the skin and rust, and the small scratches hidden by the black skin and rust are prevented from growing as a serious crack due to press forging during the processing step. The material has a thickness equal to or slightly larger than the diameter D of the grip portion 11, and is made of a polished steel bar having a diameter D that is slightly thicker than the diameter D. The parallel portion 11 is mainly swaged so as to have a small diameter d. ing.

Furthermore, instead of the polished steel bar, it is also possible to press forge while polishing the steel bar, but in that case, polishing a long steel bar,
Requires a large factory site for grinding. Further, the steel bar may be cut into a certain length and polished by a centerless lathe to be replaced with the polished steel bar, and the polished steel bar may be cut and press-pressed. In both of these, the bar 10 is formed into a predetermined shape. After that, since both ends are cut, the number of turning parts increases, which is inferior to the improvement of the yield rate, which is one of the objects of the present invention, and cannot be said to be a preferable manufacturing method.

For reference, in the press die of the present invention, in order to reduce the swaging pressure and increase the roundness of the bar 10 to be forged, the material is squeezed by a split die, that is, a die that is divided into three. . Further, in the heat treatment, in order to arrange the bars 10 in parallel in an upright state, a grid-like wire mesh is fixed slightly above the bottom of a heat treatment container, for example, a pallet, and the bars 10 are arranged one by one in the grid mesh. , Or insert a few of them to keep them upright.

(G) Effect of the Invention As described above, in the present invention, the steel bar is made of a polished steel bar having a constant thickness, at least the parallel part is forged to be thinner than the material, and the both ends of the parallel part are grasped. Since the grains are formed in parallel, the fibrous structure is densified so that the crystal grains in the parallel portion are elongated, and as a result of improving the structure like bundling thin threads, Exerts high resistance. Since the outer surface of the bar has no scratches, cracks develop and the cause of breakage is also eliminated, which contributes to the high proof strength against the twisting force and the safety of the vehicle. Further, since the bar is heat-treated in an upright state, the strain is small and there is no need for setting, so that the occurrence of defects due to the setting can be prevented, and a beneficial effect such as an improvement in the material yield rate can be obtained. Is.

[Brief description of drawings]

FIG. 1 is a manufacturing process diagram of the present invention, and FIG. 2 is an external side view of a torsion bar. 1 ... Material acceptance, 2 ... Press forging, 3 ... Cutting, 4 ... Chamfering, 5 ... Heat treatment, 6 ... Shot blasting, 7 ...
… Magnetic flaw detection, 8 …… Completed product 10 …… (torsion) bar 11 …… Grip part, 12 …… Parallel part 13 …… Tapered part, 14 …… Outer circumference 15A …… Front end, 15B …… Rear end L …… Length, D ... (grasping part) diameter d ... (parallel part) small diameter

Claims (1)

[Claims] 1. A method for manufacturing a rod-shaped torsion bar, wherein a bar is processed and a grip portion is provided at both ends and a middle portion of the grip portion is a parallel portion, wherein the steel bar is made of a polished steel bar having a constant thickness and at least the parallel portion. Is pressed to make it thinner than the thickness of the material, and the grip portions are formed at both ends of the parallel portion, and the outer circumferences of both end surfaces of the grip portion are chamfered, and then heat treated. Production method.