JP2001047140A - Bending method of hollow profile, manufacturing method of seat back frame and seat back frame structure - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To be able to bend a hollow profile with a small bending radius without generating harmful cracks, dents, wrinkles, etc. in a curved portion, and to be troublesome in processing, and to generate heat influence by welding. The present invention proposes a method of bending a hollow material having no hollow, and a method of manufacturing a seat back frame and a structure of a seat back frame using the method of bending a hollow material. SOLUTION: A side wall (inside a curved portion of the side wall 13 and a center portion of the side wall 15) of the hollow profile 10 parallel to the bending radial direction is formed.
At least in a portion of the hollow profile 10 where bending is to be performed, a valley-fold deformed portion T that is deformed inward in the hollow portion (second hollow portion 10B) along the longitudinal direction of the hollow profile 10 is formed. And a method of bending the hollow material, wherein the hollow material is then bent.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of bending a hollow profile, and more particularly to a method of bending a hollow profile which is effective when bending a hollow extruded aluminum alloy with a small bending radius. Further, the present invention relates to a method for manufacturing a seat back frame using the method for bending a hollow material and a structure of the seat back frame.

[0002]

2. Description of the Related Art FIG. 5 is a perspective view showing an automobile seat back frame. This seat back frame 2
0 'is a front-row / rear-row seat of an automobile, a walk-through type front-row seat, a middle-row seat such as an RV car, or a seat having a configuration that independently maintains strength (hereinafter, simply referred to as a "seat").
And a right seat back frame 21 'for one person and a left seat back frame 22' for two people. The right seat back frame 21 'is configured by combining a horizontal upper frame material 21a', a horizontal lower frame material 21b ', a vertical outer frame material 21c', and a vertical inner frame material 21d '. 22 ′ is the upper frame member 22
a ', horizontal lower frame member 22b', vertical outer frame member 2
2c ', a vertical center frame member 22d', and a vertical inner frame member 22e '.

As each of these frame members, a hollow cross-section member formed by extrusion-molding an aluminum alloy may be used in order to secure strength not to be broken at the time of collision of a vehicle, while responding to recent demands for weight reduction of the vehicle. It is considered. As a method of joining such frame members, there are a vertical frame member (for example, vertical outer frame members 21c 'and 22c') and a horizontal frame member (for example, horizontal upper frame members 21a 'and 22a'). Were generally joined by welding or bolts (for bolt joining, see, for example, Japanese Patent Application No. 11-196888).

[0004] Here, the joining method by welding has a drawback that the material strength of the frame material is reduced by the influence of heat, and the joining method by bolts has the disadvantage of increasing the number of processing and assembling steps. Alternatively, it is desirable to reduce the number of joints by bolts as much as possible. Further, when the end face of one frame member is simply joined to the side surface of the other frame member by welding or bolts, the outer shape of the joint corner cannot be rounded, and thus, for example, the seat back frames 21 ′ and 22 ′. The thickness n of the corner portion of the seat back cushion 23 to be put on the vehicle is insufficient.

[0005] Therefore, the joints by welding or bolts are reduced as much as possible, and the seat back cushion 23
In order to secure the thickness n of the corner portion of the seat back frame, instead of manufacturing the seat back frame by welding or bolting all the frame members, for example, one straight tubular frame member may be L-shaped or It is bent into a character shape, and this is part of the seat back frame (for example, in the case of an L shape, the vertical outer frame material 21c ′ and the horizontal upper frame material 21c).
a ', or in the case of a U-shape, a vertical outer frame member 21c', a horizontal upper frame member 21a ', and a vertical inner frame member 21d' may be used.

[0006]

However, when a hollow frame material having a large cross-sectional profile is bent with a small bending radius by an ordinary method, a crack K may be generated on the outer surface of the curved portion (see FIG. 6A). ), Dents H occur on the outer surface of the curved portion (see FIG. 6B), and wrinkles S approach the inner surface of the curved portion (see FIG. 6C). On the other hand, when bending is performed with a large bending radius that does not cause such a problem, a member to be fixed to the flat surface of the frame material must be fixed to the curved surface of the frame material generated by the bending process. (For example, a bracket fixing pipe 25 for attaching the headrest bracket 24 in FIG. 7), which is not preferable in terms of processing or structure.

As a measure for avoiding such an adverse effect, for example, a notch 26 is provided in one frame member (see FIG. 8A), and the notch 26 is positioned inside the curved portion. Bend the frame material and cut out 2
6 may be welded to each other (see FIG. 8B). However, according to this measure, although it is possible to bend the frame material with a small bending radius without generating cracks, dents, wrinkles, etc. in the curved portion, it takes extra processing time to form the notch 26, There is also the problem of thermal effects from welding.

The above problem applies not only to a hollow frame material formed by extrusion of an aluminum alloy used for an automobile seat back frame, but also to a general hollow material regardless of its use and material.

SUMMARY OF THE INVENTION In view of the above problems, the present invention can bend a hollow profile with a small bending radius without causing harmful cracks, dents, wrinkles, etc. in a curved portion, and does not require troublesome processing. It is an object of the present invention to propose a method of bending a hollow profile which does not cause thermal effects due to welding, and further propose a seat back frame manufacturing method and a seat back frame structure using the method of bending a hollow profile. Also aim.

[0010]

That is, according to the first aspect of the present invention, at least a portion of a side wall parallel to a bending radius direction of a hollow section is to be subjected to bending processing of the hollow section. A method of bending a hollow shape, characterized in that the hollow shape is deformed inward in the hollow portion along the longitudinal direction, and then the hollow shape is bent.

The "portion where the hollow section is to be bent" is defined as a section of the hollow section (hereinafter referred to as a "curved portion") in which the axis of the section is not a straight line but a curve after the bending.
Also called. ). Further, "in the portion where the hollow section is to be bent" is limited to deforming the side wall in exactly the same section as the section of the hollow section in which the material axis becomes curved after the bending. Instead, it is intended to include deforming the side wall of a section slightly longer than the section or a section slightly shorter than the section. Furthermore, the expression “at least” means that the side wall is deformed over the entire length of the hollow profile.
Further, “along the longitudinal direction of the hollow profile” means that, for example, when the side wall is deformed by valley folding, the direction of the valley bottom line is parallel to the axial direction of the hollow profile.

As described above, according to the first aspect of the present invention, when the hollow profile is bent, the side wall parallel to the bending radius direction is formed along the longitudinal direction at least at the portion where the hollow profile is to be bent. By deforming the hollow section inward, the deformation of the hollow section caused by the bending process is concentrated on the side wall. That is, by making a part of the hollow profile easy to deform, the deformation caused by the bending process is concentrated on the relevant part, and harmful cracks, dents, wrinkles, etc. are generated in other parts. The feature is that it is avoided. According to such a measure, the hollow profile can be bent with a small bending radius, and troublesome processing such as providing a notch at the time of the bending is unnecessary, and the hollow profile after the bending is welded to the hollow profile. No thermal effects occur. Although the cross-sectional profile of the hollow section in the bent and deformed section after the bending is smaller than before the bending, the cross-sectional area of the hollow section does not necessarily decrease, so the final hollow section is not formed. The breaking strength does not decrease.

According to a second aspect of the present invention, when the hollow profile is extruded, the side wall parallel to the bending radius direction of the hollow profile is formed in the hollow portion over the entire length thereof along the longitudinal direction of the hollow profile. This method is characterized in that the hollow shape is bent in the direction, and then the hollow shape is bent.

This method of bending a hollow profile employs substantially the same means as the first aspect of the present invention.
It is characterized in that the side walls are deformed over the entire length of the hollow profile when the hollow profile is extruded, that is, simultaneously with the production of the hollow profile. Therefore, the process of deforming the side wall during the period from the production of the hollow profile to before the bending can be omitted, and the cost can be reduced.

According to a third aspect of the present invention, in the method for bending a hollow section according to the first or second aspect, the hollow section is provided with a rib or a partition wall perpendicular to the bending radius direction in the hollow portion. It is characterized by having.

That is, even in the case of a hollow section having a cross section in which the hollow portion is divided into a plurality of chambers continuous in the bending radial direction, the side wall parallel to the bending radial direction is formed in the hollow portion inward over a predetermined section in the longitudinal direction. By deforming, it is possible to concentrate the deformation of the hollow profile caused by the bending process on the side wall.

Further, the invention according to claim 4 is the invention according to claim 1.
A hollow extruded aluminum alloy material bent into an L-shape or a U-shape by the method for bending a hollow shape material according to any one of claims 3 to 3, is used as a part of the seat back frame. The invention according to claim 5 is an aluminum bent into an L-shape or a U-shape by the hollow shape bending method according to any one of claims 1 to 3. A seat back frame structure characterized by partially using a hollow extruded shape member of an alloy.

In the seat back frame manufacturing method and the seat back frame structure, since a bent frame material bent into an L-shape or a U-shape is used as a part of the seat back frame, welding and bolts are used as compared with the conventional seat back frame. Therefore, the number of joints can be reduced, and the number of processing steps can be significantly reduced. Moreover, since the bending is performed using the hollow shape bending method according to any one of claims 1 to 3, the same strength as that of the conventional seat back frame can be secured.

[0019]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. In the description, the same elements will be denoted by the same reference symbols, without redundant description.

FIG. 1 is an explanatory view of one embodiment of a method for bending a hollow profile according to the present invention. As shown in FIG. 1A, the hollow profile 10 to be bent is a first hollow portion 10A.
And the second hollow portion 10B, and the first hollow portion 10A
Is surrounded by an upper wall 11, side walls 12, 13 and a partition wall 14, and a second hollow portion 10B is partitioned by a partition wall 14, side walls 13, 15 and a lower wall 1.
It is surrounded by 6. Then, the hollow profile 10 is bent so that the upper wall 11 is the outer surface of the curved portion and the lower wall 16 is the inner surface of the curved portion.

As shown in FIG. 2, the inside of the curved portion of the side wall 13 and the center of the side wall 15 of the side walls 12, 13, 15 parallel to the bending radial direction are directed toward the inside of the second hollow portion 10B. The valley fold is deformed (hereinafter, a valley fold deformed portion is indicated by a symbol T in the drawing). Here, the direction of the valley fold deformation portion T is parallel to the material axis direction of the hollow profile 10 as shown in FIG. The length m of the valley-fold deformed portion T is the same as or slightly longer than the section length m ′ (see FIG. 1B) where the material axis becomes a curve when the hollow profile 10 is bent. It may be slightly shorter than this.
Further, the valley-fold deformed portion T may be formed over the entire length L of the hollow profile 10, and in this case, the valley-fold deformed portion T can be formed when the hollow profile 10 is extruded. Further, the depth of the valley fold deformation portion T is determined by the side walls 13 and 1.
It is sufficient that a slight broken line is added to 5. The reason why the valley fold deformation is used instead of the mountain fold deformation is that if the mountain fold deformation is performed, the cross-sectional profile of the curved portion expands after the bending of the hollow shape member 10, which causes inconvenience in connection with other members. On the other hand, in the case of valley-fold deformation, such inconvenience does not occur, and deformation processing is easy.

As described above, the side walls 13 and 15 are connected to the second hollow portion 1.
After the valley fold is deformed inward in the direction 0B, as shown in FIG. 1B, the hollow profile 10 is bent so that the upper wall 11 is on the outer surface of the curved portion and the lower wall 16 is on the inner surface of the curved portion. I do. Then, the valley-folding deformed portions T of the side walls 13 and 15 further bite inward in the second hollow portion 10B, and the second hollow portion 10B is squashed in the curved portion, but portions other than the curved portion are completely sound. A good cross-sectional shape is maintained. Also in the curved portion, the upper wall 11, the side wall 12, the outside of the curved portion of the side wall 13,
No harmful cracks, dents, wrinkles or the like are generated on the partition wall 14 and the lower wall 16, and the first hollow portion 10 </ b> A maintains a perfectly sound cross-sectional shape. In this manner, the predetermined sections of the side walls 13 and 15 are made easy to deform, and the deformation of the hollow profile 10 due to the bending process is concentrated on the sections of the side walls 13 and 15 so that the cross section of the other part is obtained. It is possible to keep the shape sound.

Therefore, no harmful cracks, dents, wrinkles, etc. are generated in the hollow profile 10 even when the bending is performed with a small bending radius, and troublesome processing such as providing a notch at the time of bending is not required. Hollow profile 10 after bending
There is no thermal effect due to welding. Although the cross-sectional profile of the hollow profile 10 at the curved portion after the bending process is smaller than before the bending process, the cross-sectional area of the hollow profile 10 does not necessarily decrease. The breaking strength does not decrease.

Next, the embodiment described with reference to FIG. 1 will be described more specifically. FIG. 2 shows a rotary bending machine 30.
It is explanatory drawing showing the method of bending the hollow shape material 10 using. The rotary bending machine 30 includes a carrier (not shown), a guide 31, a bending mold 32, a clamp 33,
It consists of a wiper 34. Here, the transfer table is a device that fixes the hollow profile 10 and transfers it in the right direction in the figure. The guide 31 and the wiper 34 are respectively provided on the upper wall 11 and the lower wall 1 of the hollow profile 10 transported by the transport table.
6 and the hollow profile 10 immediately before reaching the bending mold 32.
Is a device for holding the device from above and below in the figure so that it can slide freely in the left and right directions in the figure. And bending mold 3
Reference numeral 2 denotes a cylindrical body having a mold groove portion 32a for receiving the lower wall 16 serving as the inner surface of the curved portion of the hollow shape member 10. The cylindrical body has a hollow shape formed by a rotation driving device (not shown) connected to the rotation shaft 32b. It rotates in the direction (clockwise in the figure) coinciding with the transport direction of the material 10. Clamp 33
The rotating shaft 32 of the bending mold 32 is
b and rotates together with the bending mold 32 in the same direction. The clamp 33 has a clamp groove 33a for receiving the upper wall 11 which is the outer surface of the curved portion of the hollow profile member 10. The clamp groove 33a and the mold groove 3
2a is sandwiched between the hollow shape member 10 and the base member 2a.

First, the side walls 13 and 15 of the hollow profile 10
Is valley-folded inward in the second hollow portion 10B over a predetermined section in the longitudinal direction to form a valley-fold deformed portion T (see FIG. 1A). After that, the hollow profile 10 is placed on the carriage of the rotary bending machine 30, and the core dies 36a, 36b fixed to the tip of the insertion rod 35 which can be freely inserted and removed from the opening at the rear end of the hollow profile 10 are inserted. Insert into the hollow interior. Then, the front end of the curved portion of the hollow shape member 10 is fixed between the mold groove 32a and the clamp groove 33a (see FIG. 2A). Here, the core mold 36a inserted into the first hollow portion 10A has a cross-sectional shape substantially similar to the cross-sectional shape of the first hollow portion 10A.
The core die 36b inserted into the inside of the second hollow portion 10B also has a cross-sectional shape substantially similar to the cross-sectional shape of the valley-fold deformation section of the second hollow portion 10B. (FIG. 2 (b) showing a II section of FIG. 2 (a).
reference).

Next, in this state, when the bending mold 32 and the clamp 33 are rotated clockwise in the figure together with the rotation shaft 32b as a center, the front end of the curved portion of the hollow profile 10 is shaped into the mold groove 32a. And the clamp groove 33a, the positions of the guide 31, the wiper 34 and the core dies 36a, 36b are fixed, so that the hollow material 10 is pulled out and bent into an L-shape. (Figure 2
(C)). At this time, in the curved portion of the hollow shape member 10, the side walls 13, 15 further bite into the inside of the second hollow portion 10B, and the cross-sectional shape of the second hollow portion 10B is crushed from both sides (FIG. 2). As shown in FIG. 2 (d) showing the II-II cross section of (c)), the portions other than the curved portion maintain a perfectly sound cross-sectional shape. Even in the curved part, the upper wall 11,
Outside of curved portion of side wall 12 and side wall 13, partition wall 14, lower wall 1
No harmful cracks, dents, wrinkles, etc. are generated in 6, and the first hollow portion 10A maintains a perfectly sound cross-sectional shape. In addition,
In the bending, the rotation angle of the rotation shaft 32b for rotating the bending mold 32 and the clamp 33 together becomes slightly larger than 90 ° in consideration of springback.

In the above description, a hollow cross section having a stepped irregular cross section having a first hollow portion 10A and a second hollow portion 10B has been described as an example. The cross-sectional shape of the hollow profile is not limited to this. For example, as shown in FIG.
0, ribs 17 are provided instead of the partition walls 14 (in FIG. 3, as in FIG. 1, the outer surface of the curved portion is assumed to be upward and the inner surface of the curved portion is assumed to be downward). 3B, and may have a stepless rectangular cross section having a partition wall 18 orthogonal to the bending radial direction as shown in FIG. 3 (b). It may have a simple rectangular cross section without ribs.

The portion to be deformed prior to the bending process is not limited to the inside of the curved portion of the side wall, but the outside of the curved portion of the side wall (for example, prior to the bending process of the hollow profile 10 shown in FIG. 1).
The central portion of the side wall 12 and the outside of the curved portion of the side wall 13 may be valley-folded toward the inside of the first hollow portion 10A. In addition, the length of the section to be deformed may be slightly longer or shorter than the portion to be bent, or may extend over the entire length of the hollow profile 10. The most preferable of these is a portion slightly longer than the portion to be bent, because the strength is not reduced in the portion where the bending is not performed, and the degree of deformation of the bent portion during the bending is only increased. This is because Further, when the hollow profile 10 is deformed over its entire length, there is an advantage that the side wall can be deformed when the hollow profile 10 is extruded.

Further, in FIG. 2, the method of bending a hollow profile using the rotary bending machine 30 has been described, but the method of bending a hollow profile according to the present invention is performed by using a rotary bending machine. It goes without saying that other bending machines (for example, press bending machines, roll bending machines, etc.) can be used.

Subsequently, a seat back frame structure or a method for manufacturing a seat back frame according to the present invention using the above-described method for bending a hollow profile will be described. FIG. 4 is a perspective view illustrating an embodiment of a seat back frame structure according to the present invention. The seat back frame 20 shown in FIG. 4 is a frame of a seat back like the conventional seat back frame 20 'shown in FIG. 5, and includes a right seat back frame 21 for one person and a left seat back frame for two people. It comprises a seat back frame 22. The right seat back frame 21 includes an upper frame material 21a bent in a U shape, a linear lower horizontal frame material 21b, a lower outer frame material 21c bent in an L shape, and a lower inner frame material 21d. The left seat back frame 22 includes an upper frame member 22a bent in a U-shape, a straight vertical center frame member 22b, a lower side frame member 22c, and a lower bent in an L shape. The outer frame member 22d and the lower inner frame member 22e are combined. In addition, each of the frame members is formed of a hollow cross-section formed by extruding an aluminum alloy in order to secure strength not to be broken at the time of a collision of a vehicle, while responding to recent demands for reducing the weight of the vehicle.

Here, the upper frame members 21a, L of the right seat back frame 21, which are bent into a U-shape, are formed.
The lower outer frame member 21c and the lower inner frame member 21d bent into a U shape, and the upper frame members 22a and L bent into a U shape in the left seat back frame 22 are formed.
The lower outer frame member 22d and the lower inner frame member 22e bent into a letter shape are bent using the hollow shape bending method described above. Therefore, FIG.
As compared with the conventional seat back frame 20 'shown in FIG. 1, the number of joints by welding or bolts is smaller, the number of processing and assembling steps can be reduced, and the reduction in the material strength of the frame material due to heat can be avoided as much as possible. . Further, since the bending frame material bent with a small bending radius is used, there is no inconvenience that the thickness n of the corner portion of the seat back cushion 23 to be put on the seat back frame 20 is insufficient. Further, it is possible to secure a strength substantially equal to that of the conventional seat back frame 20 '.

[0032]

As described above, the invention according to claim 1 is
When bending a hollow profile, the side wall parallel to the bending radius direction is deformed inward in the hollow portion along the longitudinal direction at least in the portion where the hollow profile is to be bent, so that the bending process can be performed. The accompanying deformation of the hollow profile is concentrated on the side wall, and harmful cracks, dents, wrinkles, and the like can be prevented from being generated in other portions. According to such a measure, the hollow profile can be bent with a small bending radius, and troublesome processing such as providing a notch at the time of the bending is unnecessary, and the hollow profile after the bending is welded to the hollow profile. No thermal effects occur. Although the cross-sectional profile of the hollow section in the bent and deformed section after the bending is smaller than before the bending, the cross-sectional area of the hollow section does not necessarily decrease, so the final hollow section is not formed. The breaking strength does not decrease.

Further, the invention according to claim 2 not only exhibits substantially the same operation and effect as the invention according to claim 1, but also deforms the side wall from after the hollow section is manufactured until before the bending. Processing time can be saved, and costs can be reduced.

According to the third aspect of the present invention, even if the hollow section is a hollow section having a transverse section divided into a plurality of chambers continuous in the bending radial direction, the side wall parallel to the bending radial direction is formed. By deforming in the hollow portion inward direction over a predetermined section in the longitudinal direction, the deformation of the hollow profile caused by the bending can be concentrated on the side wall.

Further, according to the fourth or fifth aspect of the present invention, a bent frame material bent into an L-shape or a U-shape is used as a part of the seat back frame, and is welded as compared with a conventional seat back frame. Since the number of joints by bolts and bolts is reduced, the number of processing steps can be significantly reduced. Moreover, since the bending is performed using the hollow shape bending method according to any one of claims 1 to 3, the same strength as that of the conventional seat back frame can be secured.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of one embodiment of a method for bending a hollow material according to the present invention.

FIG. 2 is an explanatory diagram illustrating a method of bending a hollow profile using a rotary bending machine.

FIG. 3 is a diagram showing a cross-sectional pattern of a hollow profile to which the method for bending a hollow profile according to the present invention is applied.

FIG. 4 is a perspective view illustrating an embodiment of a seat back frame structure according to the present invention.

FIG. 5 is a perspective view showing a seat back frame for an automobile.

FIG. 6 is a diagram illustrating a problem when a hollow frame material having a large cross-sectional outer shape is bent by a normal method with a small bending radius.

FIG. 7 is a diagram illustrating a problem when a hollow frame material having a large cross-sectional outer shape is bent with a large bending radius.

FIG. 8 is an explanatory view of a conventional measure for bending a hollow frame material having a large cross-sectional outer shape with a small bending radius.

[Description of Signs] 10 ... hollow shape member 10A ... first hollow portion 10B ... second hollow portion 11 ... upper wall 12, 13, 15 ... side wall 14, 18 ... partition wall 16 ... lower wall 17 ... rib 20, 20 ' ... seat back frame 21, 21 '... right seat back frame 21a ... upper frame material 21b ... lower horizontal frame material 21c ... lower outer frame material 21d ... lower inner frame material 21a' ... horizontal upper frame material 21b '... horizontal lower side Frame material 21c 'Vertical vertical frame material 21d' Vertical inner frame material 22, 22 'Left seat back frame 22a Upper frame material 22b Vertical center frame material 22c Horizontal lower frame material 22d Lower outer frame material 22e ... Lower inner frame member 22a '... Lateral upper frame member 22b' ... Lateral lower frame member 22c '... Vertical outer frame material 22d 'Vertical vertical frame material 22e' Vertical inner frame material 23 Seat back cushion 24 Headrest bracket 25 Bracket fixing pipe 26 Notch 30 Rotary bending machine 31 Guide 32 Bending metal Mold 32a: Mold groove 32b: Rotating shaft 33: Clamp 33a: Clamp groove 34: Wiper 35: Insertion rods 36a, 36b: Core mold H: Recess K: Crack S: Wrinkle

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Takashi Sasamoto 1-34-1 Kambara, Kambara-cho, Anbara-gun, Shizuoka Prefecture Within Nippon Light Metal Co., Ltd. Group Technology Center (72) Inventor Sakamoto Sakamoto Sakamoto Higashishinagawa, Shinagawa-ku, Tokyo No. 2-20 Japan Light Metal Co., Ltd. (72) Inventor Toshiro Matsuyama 2-chome 2-chome Higashishinagawa, Shinagawa-ku, Tokyo (72) Inventor Tomoyuki Ajiro 2-chome Higashishinagawa, Shinagawa-ku, Tokyo No. 20 Japan Light Metal Co., Ltd.

Claims (5)

[Claims] 1. A side wall parallel to a bending radius direction of a hollow profile is deformed inward in a hollow portion along a longitudinal direction of the hollow profile at least at a portion where the hollow profile is to be bent. And a method for bending the hollow shape, wherein the hollow shape is then bent. 2. During extrusion molding of a hollow profile, a side wall parallel to a bending radial direction of the hollow profile is deformed inward in a hollow portion over the entire length along the longitudinal direction of the hollow profile, and thereafter, A method for bending a hollow profile, comprising bending the hollow profile. 3. The method for bending a hollow profile according to claim 1, wherein the hollow profile includes a rib or a partition wall perpendicular to the bending radius direction in the hollow portion. . 4. A hollow extruded aluminum alloy material bent into an L-shape or a U-shape by the hollow shape bending method according to any one of claims 1 to 3, and A seat back frame manufacturing method characterized by being used as a part. 5. An aluminum alloy hollow extruded shape bent into an L-shape or a U-shape by the hollow shape bending method according to claim 1 is partially used. A seat back frame structure characterized by: