JP2004330838A - Suspension member and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a lightweight parallel cross-shaped suspension member having sufficient strength against torsion, and its manufacturing method. <P>SOLUTION: The suspension member is connected with four members of a pair of cross members 11, 12 and a pair of side rails 13, 14 in a parallel cross-shaped way. A part of the two opposed members or all are projected from the other vertical members relative to these two members by hydraulic forming. The bifurcation of the cross member with the side rail having applied stress is integrally formed thereby. In the manufacturing method, the hydraulic forming is executed while moving the die mold toward the projection part to obtain the sufficient projection amount and strength. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a girder-shaped suspension member that is a structural member for an automobile and a method for manufacturing the same.
[0002]
[Prior art]
[Patent Document 1] Japanese Patent Application Laid-Open No. 2002-154454
2. Description of the Related Art As shown in FIG. 6, a suspension member for a vehicle is known in which a pair of cross members 1 and 2 and a pair of side rails 3 and 4 are joined in a grid pattern.
[0004]
In such a girder-shaped suspension member, both ends of the cross members 1 and 2 are welded to the side surfaces of the side rails 3 and 4 at a position W. However, these positions W are positions where a large force acts when the suspension member is twisted. In addition, the variation in strength of the welded portion tends to be large due to the heat effect at the time of welding and the shape of the weld bead. As described above, in the conventional suspension member, since the welded portion having a large variation in strength is located at the position W of the branch where a large force is applied, measures such as increasing the thickness of the entire suspension member and joining the reinforcing plate are taken. Is needed. As a result, the weight reduction of the suspension member has been hindered.
[0005]
In order to reduce the weight of the suspension member, it has been proposed to form the cross member and the side rail by hydraulic forming as shown in Patent Document 1. However, the suspension member of Patent Document 1 is also welded at the end position of the cross member, and it has not been possible to realize sufficient weight reduction.
[0006]
[Problems to be solved by the invention]
The present invention solves the above-mentioned conventional problems, and can reduce the weight by eliminating the need to increase the overall plate thickness or to join a reinforcing plate, and has sufficient strength against torsion. The present invention has been made to provide a double-girder-shaped suspension member having the above structure and a method for manufacturing the same.
[0007]
[Means for Solving the Problems]
A suspension member of the present invention made to solve the above-mentioned problem is a suspension member in which four members, a pair of cross members and a pair of side rails, are connected in a cross-girder shape, and a part of two opposing members or The whole is characterized by being extended by hydraulic forming from the other member perpendicular to these two members. The opposite ends of the two members are extended by hydraulic molding, and the central portion may be formed by joining separate members. In addition, welding can be performed with the end face of the overhanging portion kept closed. In addition, two members having the same shape and having an overhanging portion can be manufactured by hydraulic molding, and they can be directly or indirectly joined to form a double-girder shape. Further, it is preferable that the overhang height is 10 times or more the thickness of the blank tube.
[0008]
On the other hand, a method for manufacturing a suspension member according to the present invention is a method for manufacturing a suspension member as described above, wherein a part or the entirety of two opposing members is overmolded by hydraulic molding from the other member. The hydraulic forming is performed while moving the fin toward the overhang.
[0009]
In the suspension member of the present invention, a part or the whole of the two opposing members is extended from the other member perpendicular to the two members by hydraulic forming, so that the joint portion by welding is twisted. It can be removed from the position of the branch where a large force acts when it is released. For this reason, it is not necessary to increase the wall thickness and the reinforcing member as in the related art, and the weight can be reduced.
[0010]
In addition, a large overhang is required to manufacture such a suspension member, and it is difficult to form the suspension member by ordinary hydraulic forming. However, in the present invention, the overhang height equal to or larger than the diameter of the base tube can be obtained by adopting a method of performing the hydraulic forming while moving the mold toward the overhang portion.
[0011]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described.
FIG. 1 shows a first embodiment, and shows a suspension member in which four members of a pair of cross members 11 and 12 and a pair of side rails 13 and 14 are connected in a cross-girder shape. The side rails 13 and 14 of this embodiment are entirely extended from the cross members 11 and 12 by hydraulic forming, and two members having the same shape are manufactured using the same hydraulic forming die. They are joined by direct welding at central welded portions 15 and 16 to form a girder. Since the suspension member does not have a welded portion at a location where stress is applied, it is not necessary to consider welding softening and welding defects, and thus the weight can be reduced.
[0012]
FIG. 2 and FIG. 3 are views for explaining a method of overhang-forming the side rails 13 and 14 having such large overhangs by hydraulic molding. Inside the split mold 20, a bent cavity 21 and cavities 22, 22 for forming an overhang are formed, and movable dies 23, 23 which can move toward these cavities 22, 22 are formed. Is provided.
[0013]
The material of the raw tube is not particularly limited, and any metal such as steel and aluminum alloy can be used. Here, a JIS standard (G3445) STKM13B raw tube (diameter: 76.3 mm, plate thickness: 2.0 mm) was used. For example, a high-strength steel pipe having a strength of 590 MPa or more may be used. Such a raw tube is bent in accordance with the shape of the cavity 21, press-molded as necessary, and housed in the cavity 21. Do.
[0014]
As a result, the raw tube is expanded so that the cross section thereof has a predetermined shape along the shape of the cavity 21, and the cavities 22, 22 are overhang-formed. At this time, if the flow of the material is promoted by moving the movable dies 23, 23 toward the cavities 22, 22, as shown in FIG. Can be. In addition, the strength of the branch portion can be increased by work hardening and thickening.
[0015]
In this embodiment, after a molding pressure was set to 40 MPa and axial pressing was performed by 150 mm, the molding pressure was finally increased to 140 MPa, and the cross-sectional shape of the cross member and the side rail was made predetermined. The cross-sectional shape of the cross member or the side rail is not limited to a square, and is not particularly limited, such as a polygon, a D-shape, or an ellipse. Thereafter, the molded product is taken out from the inside of the mold 20, the tip of the overhang is cut, expanded, press-formed, etc., processed into a shape that can be easily joined, and the same shape is welded to form a cross over the overhang. As shown in FIG. 1, the suspension members in the form of a girder having the members 11 and 12 can be manufactured.
[0016]
In this case, it is preferable to use a method of joining two members having the same shape because the same mold and molding apparatus can be used. In addition, if the overhang height is set to 10 times or more of the tube thickness, the burring step for forming the welding flange becomes unnecessary, and the cost can be reduced. If the overhang height is lower than this, it is necessary to finish the branch portion by burring such as plugging.
[0017]
In addition, as shown in FIG. 5, it is also possible to carry out the welding by keeping the end face 17 of at least one overhanging portion in a closed section. As a result, the end face 17 remains as a partition at the joint, and the rigidity of the side rails 13 and 14 can be increased. In addition, it is possible to omit a step of separately welding the partition wall for improving rigidity.
[0018]
In the embodiment described above, the whole of the cross members 11 and 12 is constituted by the projecting portions from the side rails 13 and 14. However, in the second embodiment shown in FIG. 4, both ends of the cross members 11 and 12 are extended by hydraulic molding, but a separate member 18 is joined at the center. Also in this case, similarly to the first embodiment, the tip of the overhang portion is processed into a shape that can be easily joined by cutting, expanding, pressing, or the like, and then welded to a separate member 18. In addition, welding may be performed with the end face 17 of the overhanging portion kept closed. The member 18 may be a member obtained by integrally molding a tubular member, a member having a hat-shaped cross section, a member having a U-shaped cross section, and a member having a closed cross section, or a member having an open cross section.
[0019]
The suspension member shown in FIG. 4 is suitable for a case where the cross members 11 and 12 need to be sufficiently long. In addition, the use of the separate member 18 increases the degree of freedom in the cross-sectional shape of the cross members 11 and 12, and allows the thickness to be freely set, thereby facilitating weight reduction. Also in this case, if the amount of overhang becomes small, the welded portion approaches that of the conventional type, so that the overhang height is preferably equal to or greater than the diameter of the raw tube.
[0020]
In each of the above embodiments, the side rails 13 and 14 are extended from the cross members 11 and 12, but the cross members 11 and 12 can be extended from the side rails 13 and 14.
[0021]
【The invention's effect】
As described above, according to the first aspect of the present invention, since the branch portion between the cross member and the side rail to which a large stress is applied can be integrally formed, the thickness is increased in consideration of welding softening and welding defects at the welding portion. It is not necessary to take measures such as mounting of a reinforcing member or the like, and the weight can be reduced. According to the second aspect of the present invention, the degree of freedom in designing and manufacturing is increased, and it is possible to further reduce the weight. According to the third aspect of the invention, the rigidity can be improved. According to the fourth aspect of the present invention, it is possible to greatly reduce equipment costs and die costs. According to the fifth aspect of the present invention, since the flange can be easily set up, the load of the welding process can be greatly reduced, and the welding workability is enhanced.
[0022]
According to the method of the sixth aspect, the strength of the branch portion can be increased by work hardening and thickening while stably performing hydraulic forming. In addition, a sufficient overhang height can be obtained.
[Brief description of the drawings]
FIG. 1 is a plan view showing a first embodiment.
FIG. 2 is a sectional view showing a state at the start of a hydroforming step.
FIG. 3 is a cross-sectional view showing a state at the end of the hydroforming step.
FIG. 4 is an exploded plan view showing a modification of the first embodiment.
FIG. 5 is a plan view showing a second embodiment.
FIG. 6 is a plan view showing a conventional double-girder suspension member.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Conventional cross member 2 Conventional cross member 3 Conventional side rail 4 Conventional side rail 11 Cross member 12 Cross member 13 Side rail 14 Side rail 15 Welding part 16 Welding part 17 End face 18 Separate member 20 Mold 21 Cavity 22 Cavity 23 Moving mold 24 Shaft fitting

Claims (6)

A suspension member in which four members, a pair of cross members and a pair of side rails, are connected in a girder shape, and a part or all of the two opposing members are fluidized from the other member perpendicular to the two members. A suspension member characterized by being overhanged by pressing. 2. The suspension member according to claim 1, wherein the opposite ends of the two members are extended by hydraulic molding, and the center portion is formed by joining separate members. The suspension member according to claim 1 or 2, wherein the end portion of the overhang portion is welded and joined while keeping the end surface closed. The suspension member according to any one of claims 1 to 3, wherein two members having the same shape and having an overhang portion are manufactured by hydraulic forming, and they are directly or indirectly joined to form a double-girder shape. The suspension member according to any one of claims 1 to 4, wherein the overhang height is 10 times or more the thickness of the shell tube. The method for manufacturing a suspension member according to any one of claims 1 to 5, wherein when a part or the entirety of two opposing members is overhang-molded from the other member by hydraulic molding, an overhang portion of a mold is provided. A method of manufacturing a suspension member, comprising performing hydraulic forming while moving the member toward the suspension member.

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