JPH09150225A - Production of l-shaped pipe product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a low producing cost and also, the satisfy the strength by bending a pipe to almost L-shape, loading axial force from both ends and bulging an excess thickness developed in the inner surface to the inward recessed parts of a bulging die to form outer ribs. SOLUTION: Oil is filled up in a preform 2 incorporated into a cavity C and pressurize-closed jigs 4, 5 are inserted into both end opening parts 2c, 2d and the forming pressures F are applied. The axial force is applied to the perform 2 and the excess thickness is developed by the shifting of the material onto the inner curved surface 2a of the preform 2. This excess thickness is bulged into gap parts C1 of the inward recessed 3e, 3f of the bulging die 3 to form the outer ribs. The outer curved surface 2b of the preform 2b is bulged to the outer curved wall surface 3b of the bulging die 3 to form the outer curved surface of the bending part of a formed product. Thereafter, the obtd. formed product is pressed into a slightly flat state to form a pressed product. A hollow L-shaped suspension arm is obtd. by applying boring, trimming and burring.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for manufacturing an L-shaped pipe product. This manufacturing method is suitable for use in, for example, a method for manufacturing an L-shaped suspension arm.

[0002]

2. Description of the Related Art Recently, for the purpose of weight reduction, FIG.
The hollow L-shaped suspension arm shown in is being adopted in vehicles. This suspension arm is shown in FIG.
As shown in (B), after punching each steel plate into a substantially L shape, it is pressed into a U-shaped cross section to obtain an upper member 90 and a lower member 91, and thereafter, the upper member 90 and the lower member. It was manufactured by joining the upper member 90 and the lower member 91 by forming the bead 93 by arc welding in the joining part 92 with 91.

[0003]

However, when manufacturing the above-mentioned conventional suspension arm, it is necessary to prepare two members, an upper member 90 and a lower member 91, and the number of parts is large. Further, in this case, the joint portion 92 of the entire circumference of the upper member 90 and the lower member 91 must be arc-welded, and since the precision of the joint portion 92 must be strictly controlled, the number of processes is large and the yield is low, and The welding length is also long. Therefore, when the suspension arm is manufactured, the manufacturing cost is increased.

In this respect, the pipe is bent into a substantially L-shape to obtain a crude product, and the crude product is pressed into a flat shape and then punched, trimmed and burred to give a hollow L-shaped suspension arm. If it is to manufacture, since the welding process can be omitted, it is possible to reduce the manufacturing cost. However, if a pipe is used, the curvature of the inner curved surface and the outer curved surface of the rough product bent in a substantially L shape is different, so that the bent portion 94 of the suspension arm is different.
However, the cross-sectional modulus cannot be secured without being formed into a desired shape, and the strength becomes unsatisfactory.

Such a problem is not limited to the hollow L-shaped suspension arm as described above, but also exists in other L-shaped pipe products. The present invention has been made in view of the above problems, and an object of the present invention is to provide a method for manufacturing an L-shaped pipe product capable of simultaneously achieving reduction in manufacturing cost and satisfactory strength.

[0006]

According to a first aspect of the present invention, there is provided a method of manufacturing an L-shaped pipe product, which comprises a bending step of bending a pipe into a substantially L-shape to obtain a crude product, and an inner surface facing an inner curved surface of the crude product. A storage step of preparing a bulge mold in which a cavity having a concave portion on a curved wall surface is prepared, and storing the crude product in the cavity with the inner curved surface of the crude product facing the inner curved wall surface, By subjecting the crude product housed in the cavity to bulging and applying an axial force from both ends, the crude product is molded into a desired shape, and the surplus generated on the inner curved surface of the crude product is formed into the recess. And a forming step of making the outer rib bulge.

In the manufacturing method of the first aspect, since the pipe is used, the welding process can be omitted when manufacturing the L-shaped pipe product, and the manufacturing cost can be reduced. Then, after the storing step, the crude product obtained in the bending step is subjected to a forming step in order to form a desired shape capable of ensuring a section modulus. At this time, an axial force is applied to the crude product housed in the cavity, and at this time, since the inner curved surface and the outer curved surface of the crude product have different curvatures, extra material is generated on the inner curved surface of the crude product due to material movement. . Due to the bulging process, this extra thickness is not buckled to the inner side of the crude product, but bulges into the bulge-shaped recess to become the outer rib. Therefore, in the molded product thus obtained, the outer rib formed of the extra thickness is formed in the bent portion, a desired section modulus is secured, and the strength becomes satisfactory.

[0008]

DETAILED DESCRIPTION OF THE INVENTION Embodiments 1 to 3 will be described below with reference to the drawings. In these Embodiments 1 to 3, Claim 1
The present invention is embodied in a method of manufacturing an L-shaped suspension arm. (Embodiment 1) "Bending process" First, as shown in Fig. 1 (A), a steel pipe 1 is prepared.

Then, as shown in FIG. 1B, the pipe 1 is bent into a substantially L shape to obtain a crude product 2. At this time, an inner curved surface 2a and an outer curved surface 2b are formed on the crude product 2. [Storing Step] Next, the bulge mold 3 shown in FIG. 2 is prepared. A substantially L-shaped cavity C is formed in the bulge die 3, and the cavity C has an inner curved wall surface 3a facing the inner curved surface 2a of the rough product 2 and an outer curved surface 3b facing the outer curved surface 2b of the rough product 2. It has a curved wall surface 3b. Two inner recesses 3e and 3f for securing two voids C _I and C _I between the inner curved wall surface 3a and the inner curved surface 2a of the rough product 2 are provided on both sides of the outer curved wall surface 3a. 3b is recessed to ensure a gap C _O between the outer curved surface 2b of the crude 2.

The inner curved surface 2a of the crude product 2 is faced to the inner curved wall surface 3a, and the outer curved surface 2b of the crude product 2 is opposed to the outer curved wall surface 3b.
The crude product 2 is housed in the cavity C while facing each other. [Molding Step] The crude product 2 housed in the cavity C is filled with oil, and the pressure sealing jigs 4 and 5 are inserted into the openings 2c and 2d at both ends thereof. These pressurizing and sealing jigs 4, 5 are provided on the outer periphery of the shaft portions 4a, 5a inserted into the both end openings 2c, 2d and the shaft portions 4a, 5a and can seal the both end openings 2c, 2d. It is composed of seals 4b and 5b, and flanges 4c and 5c which are integrally formed on the outer sides of the shaft portions 4a and 5a and which can abut perpendicularly to the end portions of the both end openings 2c and 2d.

Then, by applying the molding pressures F, F shown in the drawing to the pressure sealing jigs 4, 5, the bulging process is performed on the rough product 2 and the axial force is applied from both ends. That is, FIG.
As shown in (A), since the flanges 4c and 5c of the pressure sealing jigs 4 and 5 gradually push in the end portions 2c and 2d of the crude product 2 from the start of molding to the end of pushing,
The pushing amount S gradually increases. Also, seal 4
Since b and 5b are moved to the inside of the crude product 2 in the axial direction, the internal pressure P is applied at a substantially constant value while leaking the remaining air from the seals 4b and 5b to the outside. After this, if the flanges 4c, 5c of the pressure sealing jigs 4, 5 cannot be pushed in, the pushing amount S becomes constant. Further, the internal pressure P rapidly increases. Thus, the molding is completed, and a molded product 6 molded into a desired shape is obtained as shown in FIGS. 1 (C), 4 and 5.

During this time, as shown in FIG. 3B, an axial force is applied to the crude product 2 housed in the cavity C, and at this time, the curvature of the inner curved surface 2a and the outer curved surface 2b of the crude product 2 is changed. Because of the difference, the inner curved surface 2a of the crude product 2 has a surplus due to the material movement in the direction shown by the arrow in the figure. This extra meat is
Due to the internal pressure P of the bulge process, it is not buckled to the inside of the crude product 2 and the voids C _I , C _I of the inner recesses 3e, 3f of the bulge die 3
It bulges inward and becomes the outer rib 6a. Here, in order for the outer rib 6a of the molded product 6 to be in close contact with the inner recesses 3e, 3f of the bulge die 3, the inclination angle α on the upstream side of material movement in the inner recesses 3e, 3f is 0 ° <α. <30 ° was suitable.
Further, in order that the outer rib 6a of the molded product 6 is less likely to be deformed thereafter due to the compressive stress, the inclination angle β on the downstream side of the material movement in the inner recesses 3e, 3f is 45 ° <β <70.
° was appropriate.

During this time, the outer curved surface 2b of the crude product 2 shown in FIG. 2 is bulged to the outer curved wall surface 3b of the bulge die 3 by the internal pressure P of the bulge processing, and as shown in FIG. It becomes the outer curved surface 6d of the bent portion 6c. After that, the obtained molded product 6 is pressed into a flat shape to obtain a pressed product 7 as shown in FIG. And FIG. 1 (E) and (F)
As shown in, a hollow L-shaped suspension arm 8 is manufactured by punching, trimming and burring the pressed product 7.

In this way, according to this manufacturing method, since the hollow L-shaped suspension arm 8 is manufactured from the pipe 1, the conventional welding process can be omitted and the manufacturing cost can be reduced. Further, in the hollow L-shaped suspension arm 8 thus obtained, the bent portion 6c of the molded product 6 having the outer rib 6a and the outer curved surface 6d formed of the extra thickness is deformed to become the bent portion 8a, and therefore, at the bent portion 8a. The desired section modulus is secured and the strength can be satisfied. (Embodiment 2) In Embodiment 2, as shown in FIG. 6, a bulge type 9 different from that of Embodiment 1 is adopted. The inner curved wall surface 9a of the bulge die 9 that faces the inner curved surface 2a of the crude product 2 is continuous to both openings 9c and 9d, and has a single space C _I between the inner curved surface 2a of the crude product 2 and the inner curved surface 2a. A substantially L-shaped inner concave portion 9g to be secured is provided. Other steps and configurations are similar to those of the first embodiment.

Molded product 6 obtained by using this bulge mold 9
The outer rib 6e is continuously formed as shown in FIG. Therefore, the hollow L-shaped suspension arm thus obtained is more satisfactory in strength. If a plurality of inner concave portions 9g are provided in parallel, a molded product 6 having a plurality of continuous outer ribs 6f can be obtained as shown in FIG. The hollow L-shaped suspension arm obtained in this way is more satisfactory in terms of strength. (Embodiment 3) In Embodiment 3, as shown in FIG. 9, pressure sealing jigs 10 and 11 different from those of Embodiment 1 are adopted. These pressurizing and sealing jigs 10 and 11 include shaft portions 10a and 11a inserted into openings 2c and 2d at both ends of the crude product 2,
Both end openings 2c are provided on the outer periphery of the shaft portions 10a, 11a,
Seals 10b and 11b capable of sealing the inside of 2d, and the shaft portion 10
a, 11a are integrally formed on the outer sides of both ends 2a, 2c, and
Flange 1 whose bottom surface is inclined by a length h in the axial direction so that the end portion of d and the inner curved surface 2a side contact before the outer curved surface 2b side
It consists of 0c and 11c. Other steps and configurations are similar to those of the first embodiment.

When these pressure sealing jigs 10 and 11 are used, the inner curved surface 2a of the crude product 2 has an inner curved surface 2a and an outer curved surface 2.
Since the material is supplied more than the difference in curvature from b, the outer rib of the molded product can be formed larger. Therefore, the hollow L-shaped suspension arm thus obtained has an optimum section modulus and is more satisfactory in strength.

[Brief description of the drawings]

1A to 1E are perspective views showing a method of manufacturing an L-shaped suspension arm, and FIG. 1F is a schematic sectional view taken along line ff of FIG.

FIG. 2 is a schematic cross-sectional view of a bulge type or the like according to the first embodiment.

FIG. 3 is a graph showing a relationship between time and an internal pressure and an indentation amount according to the first embodiment, and (B) is an enlarged schematic cross-sectional view of an inner curved surface of a crude product for each time.

FIG. 4 is a schematic cross-sectional view of a molded product according to the first embodiment.

FIG. 5 shows a molded product according to the first embodiment, and is taken along line VV of FIG.
FIG.

FIG. 6 is a schematic cross-sectional view of a bulge type or the like according to the second embodiment.

FIG. 7 is a schematic cross-sectional view similar to FIG. 5, showing the molded product according to the second embodiment.

8 shows a molded product according to a modified example of Embodiment 2, and FIG.
It is a schematic cross section similar to FIG.

FIG. 9 is a schematic sectional view of a bulge type or the like according to a third embodiment.

10A is a perspective view of a conventional L-type suspension arm, and FIG. 10B is a schematic cross-sectional view taken along the line bb of FIG.

[Explanation of symbols]

 1 ... Pipe 2 ... Crude product 2a ... Inner curved surface 3, 9 ... Bulge type 3a, 9a ... Inner curved wall surface 3e, 3f, 9g ... Inner recessed part C ... Cavities 6a, 6e, 6f ... Outer rib

Claims (1)

[Claims] 1. A bending step of bending a pipe into a substantially L shape to obtain a crude product, and a bulge mold having a cavity having a concave portion formed on an inner curved wall surface facing the inner curved surface of the crude product are prepared. An accommodating step of accommodating the crude product in the cavity in a state where the inner curved surface of the crude product faces the inwardly curved wall surface, and bulging is performed on the crude product accommodated in the cavity and a shaft is applied from both ends. A step of molding the crude product into a desired shape by applying force, and bulging the surplus generated on the inner curved surface of the crude product into the recess to form an outer rib. And a method for manufacturing an L-shaped pipe product.