JPH0688066B2 - Hollow stabilizer manufacturing method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a hollow stabilizer provided in a suspension mechanism portion of a vehicle.

[Conventional technology]

The vehicle stabilizer has a torsion portion along the width direction of the vehicle and arm portions located at both ends of the torsion portion, and the torsion portion is mainly twisted and the arm portion is bent. Further, there is a curved portion between the torsion portion and the arm portion, and bending and twisting act on this curved portion.

Recently, the stabilizer tends to be hollow for the purpose of reducing the weight of vehicle parts. Conventionally, steel pipes such as electric resistance welded pipes and seamless pipes have been used as pipe materials for hollow stabilizers, but these have the same outer diameter and constant wall thickness over the entire length.

[Problems to be solved by the invention]

Since the hollow stabilizer using such a steel pipe has the highest load stress in the curved portion, the outer diameter and the wall thickness of the entire stabilizer are designed according to the curved portion. Therefore, in terms of stress, there is a margin in places other than the curved portion. In other words, the material is used in addition to the curved portion, which is not optimal in terms of weight reduction.

Therefore, it is desired to thicken only a portion having a high load stress such as the curved portion, but in the conventional manufacturing method, it is appropriate to thicken only a part in the longitudinal direction of the electric resistance welded pipe or the seamless pipe. There was no means.

For example, hot upsetting (upset processing) is known as a method of locally increasing the wall thickness of a pipe. In upsetting, the part to be thickened is heated locally by high-frequency heating or a burner, and after being inserted into the mold, a load is applied from the end face direction of the pipe to compress the heated part in the axial direction of the pipe. It is a method of thickening.

However, in upsetting, the wall thickness distribution after processing is determined by the temperature distribution in the tube axis direction during heating, so if there is temperature unevenness, the wall thickness of the thickened part will be uneven in the axial or circumferential direction. It is easy to become. Therefore, it is difficult to control the heating temperature distribution to obtain the target thickness profile. Moreover, decarburization or coarsening of crystal grains may occur in the heated portion, which not only causes a decrease in fatigue strength, but also easily causes scratches when taking out from the mold due to oxide scale accompanying heating, and This method is not suitable because buckling occurs when the thickened portion is long.

Further, according to the study by the present inventors, in the curved portion of the hollow stabilizer, the principal stress at each position on the circumference of the pipe material is about ± from the line segment connecting the bending center and the center of the pipe material.
The 60 ° part is the largest. Therefore, merely increasing the thickness of the curved portion is not optimal in terms of weight reduction.

[Means for solving problems]

The present invention performs a contraction process by drawing a straight tubular metal pipe material from a die and forms a thin wall portion and a thick wall portion in the axial direction of the pipe material and then bends the pipe material. A method for manufacturing a stabilizer, wherein a plug having a large-diameter portion having a circular radial cross section and a substantially elliptical different-diameter portion having a short diameter smaller than the large-diameter portion is provided inside the pipe material. Insert and roll the pipe material between the large diameter portion of the plug and the die when molding the thin portion,
Further, when forming the thick portion, by rolling the pipe material between the different diameter portion of the plug and the die to form a thick portion having a substantially elliptical inner surface in the radial direction, the pipe material When bending, the curved portion is formed by bending the pipe material in the thick portion so that the major axis of the elliptical inner surface of the thick portion faces the inside and the outside of the bend.

[Action]

The cross-sectional shape of the different diameter portion of the plug is, for example, an elliptical shape,
By passing the pipe material through the die while adjusting the relative position of the plug to the die, each part of the pipe material is rolled between the die and the plug to obtain a desired thickness distribution. Thus, the inner surface shape of the thick portion in the radial direction becomes a non-circular shape such as an ellipse. After performing the above processing, the pipe material is bent at the position of the thick portion so as to have a predetermined stabilizer shape.

It should be noted that the shape of the plug may be selected so that the principal stress of each part is substantially uniform according to the shape of the stabilizer. For example, by making the front part tapered and adjusting the relative positional relationship between the plug and the die, the thickening distribution of the pipe material can be variously changed in the axial direction.

〔Example〕

As shown in FIG. 1, while the plug 11 is inserted inside the straight pipe-shaped metal pipe material 10 made of, for example, a steel pipe or the like, the tip portion 10a of the pipe material 10 is gripped by a chuck and the pipe material 10 is diced. Pull out from 12.

As shown in FIGS. 2 to 4, the plug 11 has a large diameter portion 11a having a circular radial cross section and a different diameter portion 11b having an elliptical radial cross section. Further, a taper portion 11c is provided between the large diameter portion 11a and the different diameter portion 11b. This plug 11 is attached to the tip of a rod 13 inserted from the open end 10b side of the pipe material 10. This rod 13
It can be moved in the axial direction (the left-right direction in FIG. 1) by a hydraulic drive mechanism (not shown). Therefore plug
11 can change the relative position with respect to the die 12 in the axial direction.

The outer diameter of the large-diameter portion 11a of the plug 11 is smaller than the inner diameter of the die 12, and the thin-walled portion of the pipe material 10 'after contraction processing is performed.
Corresponds to an inner diameter of 15. On the other hand, the cross-sectional shape of the different diameter portion 11b is
The shape is made to correspond to the inner surface shape of the thick portion 16 of the pipe material 10 'after the contraction processing. That is, the radial inner surface shape of the thick portion 16 is substantially elliptical, and the diameter (major axis) in the major axis direction thereof is equal to or slightly smaller than the inner diameter of the thin portion 15. The diameter (minor diameter) of the thick portion 16 in the minor axis direction is smaller than the inner diameter of the thin portion 15 by several mm (for example, 2 mm on each side, about 4 mm in total).

When the pipe material 10 is pulled out from the die 12, when forming the thin portion 15, the rod 13 is advanced so that the large diameter portion 11a of the plug 11 is located inside the die 12, and the large diameter portion 11a The pipe material 10 is rolled between it and the die 12. Therefore thin part
The wall thickness of 15 is determined by the dimension between the large diameter portion 11a and the die 12. The thin-walled portion 15 has a circular cross-sectional shape in the radial direction.

When molding the thick portion 16, the different diameter portion 11b of the plug 11
The rod 13 is retracted so that the inside of the die 12 is located at. Then, by rolling the pipe material 10 between the different diameter portion 11b and the die 12, the thick portion 16 having an elliptical inner surface is obtained according to the cross-sectional shape of the different diameter portion 11b. Since the thick portion 16 is a portion that will be the curved portion 21 of the stabilizer as will be described later, it is provided in at least two places depending on the position of the curved portion 21.

Through the above process, the thin wall portion 15 and the thick wall portion are provided at predetermined positions in the axial direction.
After molding 16, the pipe material 10 'is bent at the thick portion 16 so as to have a desired stabilizer shape (fifth portion).
See figure). In this case, as shown in FIG.
The elliptical inner surface of 16 is bent so that the major axis o-o faces the inside and the outside of the bend. The bent portion becomes the curved portion 21 of the stabilizer 20. The curved portion 21 is located between the torsion portion 22 and the arm portion 23. In other words, the curved portion 21 is composed of the thick wall portion 16, while the torsion portion 22 and the arm portion 23 are mainly composed of the thin wall portion 15.

The inner surface shape of the thick portion 16 is not limited to an elliptical shape, but the main stress of each portion of the curved portion 21 in the circumferential direction during use is
Approximately ± 60 from the line connecting the bending center of the bending part 21 and the center of the pipe
Since the range .theta. Of .degree. (See FIG. 6) is the largest, at least this range should be thickened. The outer diameter of the thick portion 16 may be larger than the outer diameter of the thin portion 15.

After the above-described bending and forming, heat treatment is performed as necessary, and the tip of the arm portion 23 is processed to form the terminal attachment portion 24.

The hollow stabilizer manufactured by the above method has an elliptical inner surface so that the wall thickness of the curved portion 21 is large, and that the wall thickness of the maximum principal stress portion of each portion in the circumferential direction is large in the curved portion 21. Therefore, in the stabilizer 20, the stress in each part in the axial direction and the circumferential direction is equalized as compared with the conventional one,
A lighter hollow stabilizer is obtained.

As an example, the hollow stabilizer according to the method of the present invention (the outer diameter of the curved portion is 26.5 mm and the wall thickness on the major diameter side of its inner surface is 2.
The thickness was 6 mm, the thickness on the minor axis side was 4.7 mm, and the weight of the outer diameter was 26.5 mm and the thickness was 2.6 mm except for the curved portion, and the weight was 2.6 kg. On the other hand, the weight of the conventional product (outer diameter 25.4 mm, wall thickness 3.5 mm) with constant outer diameter and wall thickness over the entire length was about 3.0 kg. That is, the product of the present invention having the spring constant and the fatigue strength equivalent to those of the conventional product is about 16% lighter than the conventional product. Moreover, since the cold processing is performed by the die 12 while controlling the wall thickness distribution from the inner surface side of the pipe material 10 using the plug 11, the thick wall portion having the accurate inner surface shape is located at the accurate position in the axial direction of the pipe material 10. 16 can be formed. Further, since local heating such as hot swaging is not required, accurate thickness distribution can be obtained without decarburization, coarsening of crystal grains, generation of oxide scale, buckling and scratches. .

〔The invention's effect〕

According to the present invention, it is possible to form a pipe material in a preferable wall thickness distribution in order to equalize stress, further reduce the weight of the hollow stabilizer, and obtain a thick wall portion having an accurate inner surface shape at an accurate position. Therefore, a high quality hollow stabilizer can be manufactured. That is, by using a thick portion for the curved portion and mainly applying a thin portion other than the curved portion, it is possible to reduce variations in the stress in the axial direction of the hollow stabilizer, and in the present invention, the circle in the curved portion can be reduced. By making the inner surface of the curved part of a substantially elliptical shape that increases the wall thickness of the part where the maximum principal stress occurs in each part in the circumferential direction, the stress of the part where the maximum principal stress occurs is reduced. The stress at each of the above positions is closer to equalization than the conventional one, resulting in a lighter weight hollow stabilizer.

[Brief description of drawings]

The drawings show one embodiment of the present invention. FIG. 1 is a sectional view for explaining the contraction process, FIG. 2 is a side view of a plug, and FIG.
FIG. 4 is a sectional view taken along line III-III in the figure, and FIG. 4 is IV in FIG.
-IV is a sectional view taken along line IV, Fig. 5 is a sectional view of the hollow stabilizer, Fig. 6 is a sectional view taken along line VI-VI in Fig. 5, and Fig. 7 is taken along line VII-VII in Fig. 5. FIG. 10 …… Pipe material, 11 …… Plug, 11a …… Large diameter part, 11b…
… Different diameter part, 12 …… Die, 15 …… Thin part, 16 …… Thick part, 20 …… Hollow stabilizer, 21 …… Bending part, 22 …… Torsion part, 23 …… Arm part.

Claims (1)

[Claims] Claim: What is claimed is: 1. A straight pipe-shaped metal pipe material is drawn out from a die to perform a contraction process, a thin wall portion and a thick wall portion are formed in an axial direction of the pipe material, and then the pipe material is bent to produce torsion. A method for manufacturing a hollow stabilizer comprising a curved portion and an arm portion connected to the curved portion, wherein a large diameter portion having a circular cross section in a radial direction and a short diameter smaller than the large diameter portion are provided inside the pipe material. A plug having a substantially elliptical different diameter portion having a diameter is inserted, and when forming the thin portion, the pipe material is rolled between the large diameter portion of the plug and the die, and the thick portion is also formed. At the time of molding, after molding the thick wall portion having a substantially elliptical inner surface shape in the radial direction by rolling the pipe material between the different diameter portion of the plug and the die, when bending the pipe material, The major axis of the elliptical inner surface of the thick part is A method for manufacturing a hollow stabilizer, characterized in that the curved portion is formed by bending a pipe material in the thick portion so as to face the inside and the outside.