JP2004051066A - Aluminum alloy hollow structural angle for sub-frame and sub-frame - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aluminum alloy hollow structural angle for a sub-frame and the sub-frame preventing the occurrence of wrinkles during bending, and capable of improving jointing strength and jointing rigidity against a material to be jointed. <P>SOLUTION: This aluminum alloy hollow structural angle 1a includes a roughly rectangular sectional form which is composed of two long-side flanges 2, 3 and two short-side flanges 4, 5, and which serve as the sub-frames by being curved in the 3D direction by the bending from at least two directions which are the long-side flanges 2, 3 and the short-side flanges 4, 5. A step 6 extended in the longitudinal direction of the aluminum alloy hollow structural angle 1a is provided at the center of walls of the long-side flanges 2, 3 which form a bending inside during a bending process. The short-side flanges 4, 5 have circular arc forms which are overhung in the outward direction. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a hollow aluminum alloy material suitable for an automobile subframe on which an engine or the like is mounted and fixed to a vehicle body frame (body frame), and a subframe structure using the same.
[0002]
[Prior art]
The subframe of the vehicle is attached to the lower part of the body frame before and after the vehicle. For example, in the case of a front-wheel steering rear-wheel drive (FR) vehicle, the front subframe attached to the front of the vehicle body includes an engine and a front suspension. Is attached. In addition, a rear suspension and a differential gear are mounted on a rear subframe attached to the rear part of the vehicle body. A power train is constituted by the subframe on which the engine and the like are mounted, and a body frame is mounted on the power train and connected. Therefore, the sub-frame receives vibration from the road surface during traveling through the suspension, and a large load is applied to the sub-frame via the suspension. It is necessary to be able to endure.
[0003]
FIG. 7 is a perspective view showing the shape of a general front subframe. In this sub-frame, brackets 23 are provided at the four corners of the main body 20a to be joined to the body frame via collar members. A sub-frame is fixed to the body frame by inserting a rod-shaped fastening member such as a bolt into the body frame. The main body 20 is formed into a U-shaped frame by welding and joining a U-shaped main frame 21 made of a hollow material and a frame member of the cross member 22 to each other.
[0004]
FIG. 8 is a perspective view showing the shape of a general rear subframe. In this sub-frame, the main body 20b is formed by welding two main frames 21 and 21 made of a hollow material and four frame members of cross members 22 and 22 to each other to form a so-called cross-shaped frame. Is configured. Brackets 23 for joining to the body frame are provided at the four corners of the main body 20. For example, a rubber bush for buffering is press-fitted into the bracket 23, and a rod-shaped fastening member such as a bolt is inserted into the inside thereof. Then, the sub-frame is fixed to the body frame by this fastening member.
[0005]
On the other hand, in order to reduce the weight of an automobile, it has been proposed in Japanese Patent Application Laid-Open Nos. 2000-238657 and 2000-177621 to manufacture a subframe from an aluminum alloy material.
[0006]
When the sub-frame is made of an aluminum alloy material, the main frame must be curved in a so-called three-dimensional direction in the horizontal direction and the vertical direction as shown in FIGS. Becomes a problem. Another problem is that the cross-sectional shape of the main frame must be changed in the longitudinal direction of the frame in order to avoid interference with other components or to facilitate joining with other components.
[0007]
For this reason, in a subframe using an aluminum alloy material, a circular tube of an aluminum alloy is used as a material, which is bent to form a three-dimensional bent shape, and thereafter, the cross section is formed by press crushing and hydroforming. By changing the shape at each part, a main frame or a cross member is manufactured, and then the frame and other brackets are welded.
[0008]
However, the hydroforming process has a problem that a large die is required to cover the entire frame, so that the die cost is high, the processing equipment is expensive, and the processing time is long. Furthermore, complicated pre-processing such as pressing for inserting into a mold may be required, and there is a problem that processing cost is high. This cost problem has been a major factor that has hindered the adoption of aluminum alloys for subframes.
[0009]
In addition, when a small circular tube material that can avoid interference with other parts is used, wrinkles at the time of bending can be suppressed. Also, in joining with other parts, since the joining portion is formed in an arc shape, it is necessary to cut the end of the cross member to be joined into an arc shape, resulting in an increase in cost, and However, there is a problem that the joining strength and the rigidity are reduced by approaching wire joining or T-type butt welding.
[0010]
On the other hand, for example, if the hydroforming step can be omitted by using a profiled extruded section of an aluminum alloy that can avoid interference with other parts in advance, the processing cost is greatly reduced, and a circular tube material is used. In this case, the above problem can be solved.
[0011]
However, in the case of using the extruded section having the irregular cross-section, there is a major problem that wrinkles are easily generated during bending as compared with the conventional circular pipe. Such a shape defect cannot satisfy the required shape accuracy, and significantly impairs the characteristics and reliability of the subframe as a security component.
[0012]
The main frame of the sub-frame (21 in FIGS. 7 and 8) is curved in the three-dimensional direction as described above. Therefore, in the case where the material is formed by bending only using a straight aluminum alloy hollow extruded shape 8 as shown in FIG. 6A instead of the conventional circular pipe as shown in FIG. As shown by arrows F1 and F2 in (b) and (c), it is necessary to bend in at least two directions and bend in the three-dimensional directions of the left-right direction and the up-down direction in FIG. That is, the aluminum alloy hollow extruded shape member 8 has at least a left-right bending process F1 from the short-side flange sides 11 and 12 shown in FIG. 6B and a long-side flange portion 9 and 10 shown in FIG. Receiving the vertical bending process F2 from the side, it is bent in a three-dimensional direction.
[0013]
In the sub-frame, it is necessary to avoid interference with other components in a narrow area where various components are present in a complicated manner, and the bending radius itself at the time of the bending is required to be very small. For this reason, since the bending processing conditions become severe, wrinkles are likely to occur particularly on the flanges on the inside of the bend as shown by 13 and 14 in FIGS. 6B and 6C, respectively.
[0014]
On the other hand, the circular pipe currently used as a material of the sub-frame has a shape that is most difficult to buckle even when bent in any direction. Thereby, bending can be performed without generating wrinkles. Therefore, the problem of wrinkles can be said to be a unique problem when an extruded section having a modified cross section is used instead of the circular pipe as a material of the subframe.
[0015]
Conventionally, in order to suppress the occurrence of wrinkles, it has been practiced to improve the shape (bending) (conditions) of the profile to suppress the shape defect of the profile. A typical example is a method in which a mandrel, a core, or the like is inserted into a hollow portion inside a shape member during bending to bend while restraining deformation. Various methods have been proposed in, for example, JP-A-6-142805, JP-A-6-170449, JP-A-8-300052, JP-A-8-300053, and JP-A-10-300053. .
[0016]
[Problems to be solved by the invention]
However, in these methods of improving the bending side, shape defects such as wrinkles are liable to occur in a region not constrained by a mandrel or a core.
[0017]
In some cases, the design of the subframe itself is changed in order to suppress such a shape defect at the time of bending. Specifically, this design change is carried out by increasing or increasing the thickness or reinforcing wall of the hollow shape, sacrificing weight reduction, or changing the cross section or the overall shape itself. However, the necessity of these design changes is still a major factor that hinders the expansion of the use of aluminum alloys in subframes. For this reason, it is absolutely necessary to suppress wrinkles in the cross-sectional shape of the extruded profile material having an irregular cross-section.
[0018]
Since the sub-frame is generally a large-sized and thick-walled material, a press or drawbender having a relatively simple structure is often used to bend in two or more directions. In this case, in order to suppress the shape defect at the time of bending, it is necessary to rely on the improvement of the buckling limit stress of the profile itself by changing the cross-sectional shape or the deformation restraining effect by using the mandrel.
[0019]
In addition, as a processing method other than this, the application of a stretch bender or a multi-bender is also conceivable. However, the multi-bender has a problem that wrinkles are easily generated when compressive stress acts on the bent portion. Further, in order to suppress wrinkles by a stretch bender, it is necessary to apply a large tension, and therefore, there is a problem that the apparatus must be made larger than usual. In addition, since both stretch benders and multi-benders require high rigidity to bend large and thick sections such as subframes, the equipment originally increased in size from this point. This is not a practical processing method because expensive equipment is required.
[0020]
In the present invention, by omitting the hydroforming step, it is possible to reduce the cost, suppress the occurrence of wrinkles in bending as pre-processing, and improve the joining strength and joining rigidity with the material to be joined. An object of the present invention is to provide an aluminum alloy hollow section for a subframe having a cross-sectional shape and a subframe using the same, which can reduce the cost of processing the end portion of the extruded section as a joining material.
[0021]
[Means for Solving the Problems]
The gist of the aluminum alloy hollow profile for a subframe of the present invention for this purpose has a substantially rectangular cross-sectional shape composed of two long-side flanges and two short-side flanges. A hollow aluminum alloy material that is bent in a three-dimensional direction by a bending process from at least two directions from a short side flange side to be a subframe, and is a long side that is bent inside during the bending process. A step extending in the longitudinal direction of the hollow member is provided at the center of the flange wall, while the short-side flange has an arc-like shape projecting outward.
[0022]
The gist of the subframe of the present invention is a subframe made of the aluminum alloy hollow shape having the above structure.
[0023]
Long side flange (long side wall) to be bent inside at the time of bending process A step that is concave in the center of the hollow profile or bulges outward in the center of the hollow profile and extends in the longitudinal direction of the hollow profile in the center The wrinkles due to the buckling of the long-side flange wall, which is on the inside of the bend, can be prevented when bending from the long-side flange side, particularly when the long-side flange side is bent.
[0024]
Furthermore, the short-side flange (short-side wall), which is the inside and outside of the bend during bending, has an arc-shaped shape that protrudes outward, so that it can be used when bending from the short-side flange side. In particular, it is possible to prevent wrinkles due to buckling of the short side flange wall which is the inside of the bend.
[0025]
Therefore, due to these effects, even when the aluminum alloy hollow section is bent in at least two directions from the long side flange side and the short side flange side, it is bent in a three-dimensional direction to form a subframe. In addition, the occurrence of wrinkles in the aluminum alloy hollow profile can be prevented or suppressed.
[0026]
Japanese Patent Application Laid-Open No. 9-66317 according to the present applicant discloses that the same recess as the above-described step of the present invention is provided on the bent inner side wall portion of an aluminum alloy hollow profile having a substantially rectangular cross-sectional shape. It has been disclosed. However, according to the present invention, as in the present invention, the aluminum alloy hollow profile is bent in at least two directions from the long side flange side and the short side flange side to bend in a three-dimensional direction. Not intended, only two-dimensional bending in one direction.
[0027]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. FIG. 1 is a perspective view of an aluminum alloy hollow section 1a for a subframe according to the present invention. In FIG. 1, an aluminum alloy hollow profile 1 a is formed by substantially orthogonally intersecting two long side flanges 2, 3 substantially parallel to each other and two short side flanges 4, 5 substantially parallel to each other. It has a rectangular cross-sectional shape.
[0028]
Reference numeral 7 denotes a reinforcing middle rib for connecting the long side flanges 2 and 3 in the longitudinal direction. The middle rib itself is provided as necessary according to the required rigidity and strength of the subframe. In this regard, a cross-section having no ribs may be used. In addition, when the middle rib is provided, in addition to the cross-sectional shape in which one longitudinal middle rib is provided in FIG. Various methods are included, such as a cross section having a cross shape formed in a cross shape along with the middle ribs connected in the lateral direction.
[0029]
The characteristic point of the aluminum alloy hollow profile 1a according to the present invention is that, as shown in FIG. 2, at least the bending F1 (horizontal direction in FIG. 2) among the bending from at least two directions. The short side flanges 4 on the inside and outside of the bend have an arcuate curved shape that protrudes outward (in the horizontal direction in the drawing).
[0030]
By making the short-side flange arc-shaped (arch-shaped) in this way, the buckling limit stress of the short-side flange is greatly increased as compared with the straight flange, as compared under the same thickness condition. For example, the buckling limit stress of a straight flange is proportional to (t / b) ² using the flange width b and the plate thickness t, whereas t / r (r: arch Radius). It is clear from the comparison between the two that the arc-shaped flange is less likely to buckle.
[0031]
The arc shape (curved shape) of this short side flange is determined by the final shape to be designed of the subframe and the bending radius. (2) The amount or size is such that wrinkles due to bending buckling can be prevented. Therefore, the outward projection of the short side flange is not limited to a smooth arc as shown in FIG. 1, but also a plurality of continuous arcs or a substantially arc shape such as a partial arc. Is appropriately selected within a range that achieves the above effects. Even if both short-side flanges are not arc-shaped, depending on the bending direction and bending conditions, only one of the short-side flanges is formed into an arc shape (curved shape), and the other short-side flange is formed into a normal straight line. It may be a typical shape. By forming the other short side flange into a normal linear shape, there is also an advantage that joining with another vehicle body structural member is easy at this linear portion.
[0032]
Another characteristic point of the aluminum alloy hollow profile 1a according to the present invention is that, as shown in FIG. 3, when bending from at least two directions, bending F2 (vertical direction in the figure) A step 6 is provided at the center of the long side flange wall 2 which is on the inside of the bend during bending, and is recessed inwardly of the hollow profile and extended in the longitudinal direction of the hollow profile. The step 6 may be expanded outwardly of the hollow member as shown in FIG. 5 described later.
[0033]
With such a configuration, the long side flange wall 2 that is the inside of the bend is formed by independently bending the respective wall surfaces 6a, 6b, and 6c separated by the step 6 during the bending process F1. Will be. In this regard, the buckling limit stress of the bending inner side wall at the time of bending is determined by the wall width of each wall surface 6a, 6b, 6c generated by the step 6. Each of the wall surfaces 6a, 6b, and 6c has a smaller buckling width than the wall surface of the bent inner side wall 2 where no step is formed, and thus has a large buckling limit stress. Wrinkles due to buckling of the flange wall 2 can be prevented.
[0034]
The step 6 in the present invention is for forming the wall surfaces 6a, 6b, 6c which are the above-mentioned divided wall surfaces 6a, 6b, 6c which are independently bent. Therefore, as long as the divided wall surfaces 6a, 6b, 6c can be formed, the shape and size (width, etc.) of the recesses and protrusions forming the step 6 are appropriately selected. In other words, the shape and size of the step 6 provided on the long side flange wall 2 on the inside of the bend also correspond to the bending process F2 (vertical direction in the figure), which is determined by the final shape to be designed of the subframe and the bending radius. The amount or size is such that wrinkles due to buckling of the long side flange wall 2 which is the inside of the bend can be prevented.
[0035]
Note that the step provided on the long-side flange only needs to be present only in a portion affected by bending. In other words, this step 6 is divided not only into one piece as shown in FIG. 1 but also into a plurality of pieces in parallel with the longitudinal direction, as shown in FIG. And the like are appropriately selected within a range that achieves the above effects. Further, since this step is provided on the long-side flange wall which is on the inside of the bend, the long-side flange wall to be provided differs depending on the direction of the bending process F2.
[0036]
For example, as in the hollow profile shown in the perspective view in FIG. 4, when the bending process F2 is (from the bottom to the top in the drawing) out of the bending processes in at least two directions, the bottom of FIG. The long side flange wall 2 on the side is inside the bend during the bending process. Accordingly, in the case of FIG. 4, the step 6 is provided at the center of the long side flange wall 2. FIG. 4 also shows an embodiment of the aluminum alloy hollow profile 1b having a mouth-shaped cross section without a middle rib.
[0037]
Further, in the hollow profile shown in the perspective view in FIG. 5, instead of providing the recess as shown in FIGS. 1 and 4 to form the step 6, the hollow profile is formed so as to expand outwardly of the hollow profile 1c. An example in which a step 6 is provided (by providing a protruding portion that protrudes outward) is shown.
[0038]
Furthermore, in the present invention, it is preferable to provide a wall having a straight wall surface such as 3a of the flange 3 and 2a, 2b of the flange 2 on the long side flange. By providing such a wall surface with a straight wall, it is possible to join with the other plate-like parts such as the bracket 23 in a face-to-face manner, thereby increasing the joining rigidity and joining strength of the subframe. It becomes. In addition, when the short side flange corresponding to the outside of the bend is straight, joining is possible by cutting the end of the cross member to be joined in a straight line, thereby reducing the cost of cutting the end of the joined material. Is also possible.
[0039]
In the present invention, the above-described material aluminum alloy hollow profile is configured, and a bending process F1 (horizontal direction in the drawing) as shown in FIG. 2 and a bending process F2 (vertical direction in the drawing) as shown in FIG. ) Are combined in at least two directions, and are formed on the main frames 21 and 21 of the sub-frame shown in FIG. 6 which are curved in the three-dimensional direction while suppressing generation of wrinkles.
[0040]
As the bending method at this time, ordinary two-dimensional bending apparatuses having a relatively simple structure and low cost can be used in combination with each other as appropriate. The usual two-dimensional bending apparatus includes a press bender, a press bending shown in FIG. 9A, a compression bending shown in FIG. 9B, and a rotary drawing shown in FIG. 9C. There are bending, rotary bending, and other devices. As described above, in the present invention, there is a great advantage that bending can be performed while suppressing generation of wrinkles by using an inexpensive bending apparatus having a simple structure and a normal structure.
[0041]
In the present invention, since the generation of wrinkles is suppressed by the shape of the shape itself, if the aluminum alloy hollow shape for the subframe is small in diameter and thin, the above-mentioned stretch bender, multi-bender, etc. can also be used. It is. However, as described above, there is a problem that the size of the device is increased and an extremely expensive device is required as compared with a normal two-dimensional bending device.
[0042]
As the aluminum alloy used for the hollow profile of the present invention, aluminum alloys such as 3000 series, 5000 series, 6000 series, and 7000 series, which are generally used for this kind of structural material and specified in AA to JIS standards, can be used. It is. Then, among these aluminum alloys, an alloy type is appropriately selected, and heat treatment conditions such as solution heat treatment, quenching, and artificial aging hardening are appropriately selected to obtain desired proof stress and mechanical properties. Further, the aluminum alloy hollow shape itself of the present invention can be manufactured by a usual method such as a normal hot extrusion process, a forming process of a normal rolled plate, and welding.
[0043]
【The invention's effect】
As described above, according to the present invention, when manufacturing a subframe by bending, it is possible to provide an aluminum alloy hollow section for a subframe that prevents wrinkles from occurring during bending to be bent in a three-dimensional direction. . Therefore, a subframe can be manufactured at low cost by bending an aluminum alloy hollow profile. As a result, the use of the aluminum alloy for the subframe can be expanded.
[Brief description of the drawings]
FIG. 1 is a perspective view showing one embodiment of an aluminum alloy hollow extruded shape according to the present invention.
FIG. 2 is a perspective view showing a mode of bending of the profile of FIG. 1;
FIG. 3 is a perspective view showing another mode of bending the profile of FIG. 1;
FIG. 4 is a perspective view showing another embodiment of the aluminum alloy hollow extruded profile of the present invention.
FIG. 5 is a perspective view showing another embodiment of the aluminum alloy hollow extruded profile of the present invention.
FIG. 5 (a) is a perspective view showing a conventional aluminum alloy hollow extruded profile, and FIGS. 5 (b) and (c) are perspective views respectively showing the form of bending of the profile of FIG. 5 (a). FIG.
FIG. 7 is a perspective view showing a shape of a general front sub-frame.
FIG. 8 is a perspective view showing the shape of a general rear subframe.
FIG. 9
It is the schematic which shows the example of the normal bending apparatus, (a) shows a press bending, (b) shows a compression bending, (c) shows a rotary pull bending, respectively.
[Explanation of symbols]
1: Aluminum alloy hollow extruded profile, 2, 3: Long side flange,
4, 5: short side flange, 6: step, 7: middle rib

Claims (4)

It has a substantially rectangular cross-sectional shape composed of two long-side flanges and two short-side flanges, and is bent in at least 2 ° directions from the long-side flange side and the short-side flange side in the 3 -dimensional direction. An aluminum alloy hollow profile that is curved to be a subframe, and a step extending in the longitudinal direction of the hollow profile is provided at the center of the long side flange wall that is bent inside during the bending process. On the other hand, the aluminum alloy hollow shape for a subframe, wherein the short side flange has an arc shape protruding outward. The hollow aluminum alloy material for a subframe according to claim 1, wherein a middle rib for connecting the long side flanges is provided. The aluminum alloy hollow shape for a subframe according to claim 1 or 2, wherein the flange that hits the outside of the bend at the time of the bending is straight. A subframe made of the aluminum alloy hollow profile according to any one of claims 1 to 3.

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