JP2003103307A - Method for bending closed cross section member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for bending a closed cross section member capable of easily being implemented and capable of making a good appearance tube after bending. SOLUTION: After a slit 12 or window holes 13, 14, 15 are continuously shaped on a closed cross section member, for example, predetermined surfaces for bending (vertical surfaces) 11a, 11b of a rectangular tube 11 and right-angled surfaces (side surfaces) 11c, 11d and then, with respect to the method for bending the closed cross section member to bend the predetermined surfaces for bending 11a, 11b, a fine showing closed bending which causes no cross section deformation without using cores is easily executed. The slit width or the size of window holes to be opened on the predetermined surface of the bending and the right- angled surface can be changed so that the cross section dimension and the shape of the closed cross section member after bending can be changed to correspond with a variety of products. Further, when the slit or the window hole is shaped, bending is more easily executed and the bending die or jig requires no complicated construction, which enables less investment.

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 member having a closed cross section, for example, a rectangular hollow tube (square tube) without a core.

[0002]

2. Description of the Related Art When the square tube is bent as shown in 1 of FIG. 14 and a core is not used, the cross section after bending is shown in FIG. 16 regardless of whether a bender or a press is used. It is well known that such deformation causes a bad appearance.

When bending, as shown in FIG. 15, on the surface (side surface) of the rectangular tube which is perpendicular to the bending surfaces 1a and 1b, the side surface shrinkage portion is centered on the bending neutral axis X and on the bending surface 1a side. On the other hand, on the side of the curved surface 1b, an extension phenomenon that becomes a side surface extension portion is generated, which is the curved surface 1a,
This is because the concave portions 2, 2'are generated on the curved surfaces 1a, 1b as shown in FIG.

Therefore, if a core having a cross section conforming to the inner diameter is inserted into the rectangular tube 1 before bending and bent in this state by a bender or a press machine, a concave portion 2 as shown in FIG.
It can be bent without generating 2 '.

However, when the core is inserted and bent,
Considering the removal of the core, it cannot be applied to a pipe that is to be bent with a small curvature, and it is not applicable to a pipe that requires a complicated bend.

Therefore, in a hollow tube requiring a small curvature or a complicated bending, for example, as shown in FIG. 17, a rectangular tube 3 is divided into upper and lower parts, and a lower member 3b and an upper member for covering the lower member 3b. 3a is manufactured by a press machine or the like, and both members 3a, 3
b is fitted and welded like 3c.

However, the method for manufacturing the rectangular tube 3 shown in FIG. 17 can be applied to a small curvature or complicated bending, but naturally, a mold for manufacturing the upper and lower members 3a and 3b is required. The cost will be very high.

As a means for preventing the formation of the concave portions 2 and 2'when a rectangular tube or the like is bent as shown in FIG. 16, for example, in the one disclosed in Japanese Patent Application Laid-Open No. 7-60365, a rectangular hollow section is used. In the case where the wide side of the square tube P to be held is the upper and lower sides and the narrow side is the side, and the side is bent, the following concave portion is formed on the outside of the bent side, that is, on the tension side bent surface. 24, that is, a concave portion whose central portion 21 has a curvature in the longitudinal direction smaller than the width-direction both-sided portions 26,
The inside of the side surface that bends, that is, the compression-side bending surface Pa
In addition, the following concave portion 20, that is, a concave portion having a central portion 21 whose curvature in the longitudinal direction is larger than that of the widthwise both corner portions 22 is formed (the reference numeral is the one described in the above publication).

With the above structure, when the side surface of the rectangular tube P is bent with the tension side bent surface facing outward,
As described above, the force that causes dents or cracks in the wide surface (upper and lower surfaces) is released to the recesses 20 and 24 to obtain a rectangular tube having an excellent appearance.

However, in order to carry out the technical contents disclosed in Japanese Patent Laid-Open Publication No. Hei 10 (1999) -29242, a special bender (bending device) equipped with a roller capable of forming the recesses 20 and 24 is required, and it cannot be carried out easily.

[0011]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for bending a member having a closed cross section, which is easy to implement and has a good appearance of the pipe after bending.

[0012]

A method for bending a closed cross-section member according to the present invention for solving the above-mentioned problems is obtained by continuously forming a slit or a window on a surface orthogonal to a planned bending surface of the closed cross-section member. The surface to be bent is bent.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION
1 to 9, a method of bending a closed cross-section member according to the present invention includes a closed cross-section member, for example, a surface (width wide surface, upper and lower surfaces) 11a, 11b perpendicular to the bending surface (width) of the rectangular tube 11. The slits 12 or the window holes 13, 14, and 15 are continuously formed on the narrow surfaces (side surfaces and side surfaces) 11c and 11d, and then the planned bending surfaces 11a and 11b are bent.

The embodiment shown in FIGS. 1 to 13 will be described in more detail. In the embodiment shown in FIG. 1, side surfaces 11c and 11d of the rectangular tube 11 which are perpendicular to the planned bending surfaces 11a and 11b.
A slit 12 having a predetermined length is formed symmetrically in the left and right, and the position where the slit 12 is formed is the planned bending surface 1
The bent portions 1a and 11b are formed at predetermined positions, and are formed over the planned bending length.

The slit 12 may be replaced by window holes 13, 14, 15 as shown in FIGS. That is, FIG.
The window hole 13 shown in Fig. 3 continuously forms a rectangular window hole, the window hole 14 shown in Fig. 3 continuously forms a diamond shaped window hole, and the window hole 15 shown in Fig. 4 is , And those in which arrow-shaped window holes are continuously formed are shown.

Similarly to the slit 12, the window holes 13 to 15 are formed continuously as a whole and are formed symmetrically on the side surfaces 11c and 11d of the rectangular tube 11, and their positions are as follows.
The surfaces to be bent 11a and 11b are set to positions to be bent, and are formed over the length to be bent.

The widths (heights) of the slits 12 and the window holes 13 to 15 and the shapes of the window holes are determined by experiments and the like, and the side surface widths of the side surfaces 11c and 11d of the rectangular tube 11 are changed depending on the heights. . That is, for example, when the width (height) of the slit 12 is as small as S1 as shown in FIG. 10, the side surface width of the square tube 11 ′ after bending is H1, but the width of the slit 12 is S2 as shown in FIG. When it is large, the square tube 11 'after bending
The side width of H2 becomes as small as H2. In addition, the slit 1
2. The window holes 13 to 15 are formed by laser processing or punching with a press. 12 'indicates a slit or window hole after bending.

Next, as described above, the side surfaces 11c and 11 are formed.
d symmetrically with the slit 12 or the window holes 13 to 15
The rectangular tube 11 having the above-mentioned shape is positioned and placed on the bending die 16 under the press shown in FIG. 5, and is bent by pressing it with the upper bending die 17.

At this time, on the side surfaces 11c and 11d of the rectangular tube 11, as shown in FIG. 6, there are bending neutral axes Y and Z on both sides of the slit 12, respectively.
On each of the two sides, a relatively small contraction phenomenon, which is a side surface contraction portion, occurs on the bent surface 1a side, and on the contrary, a relatively small extension phenomenon, which is a side surface extension portion, occurs on the bent surface 1b side. The internal stress generated on the side surfaces 11c and 11d due to such a relatively small contraction and extension phenomenon, that is, the side surfaces 11c and 1d.
1d itself and / or via the side surfaces 11c, 11d, the concave portions 2 are formed in the planned bending surfaces (upper and lower surfaces) 11a, 11b.
The internal stress that tends to generate 2'becomes small, and the concave portions 2 and 2'which are unsightly as shown in FIG.
It can be avoided to generate in a and 11b.

A bent tube 11 'according to the present invention bent by a press or the like as described above is shown in FIGS. 7 and 8.
In FIG. 7, the slit 12 is completely crushed into a single linear 12 'by pressing or the like, but in FIG. 8, the window hole 13 is bent only by being deformed.

If it is desired to add strength to the bent pipe, the slit 12 'which is substantially linear as shown in FIG. Also, the side surfaces 11c, 1
When the window holes 13 to 15 are opened in 1d, a reinforcing plate 19 for closing the window holes 13 to 15 is applied as shown in FIG.
It may be welded like 0.

The bending method of the present invention can be applied not only to bending having a predetermined curvature in opposite directions, so-called S-shaped bending, as shown in FIGS. 7 and 8, but also to only one of them as shown in FIG. It can also be applied to bending with curvature, and 11 ″ is the bending tube obtained in this way.

[0023]

According to the method for bending a member having a closed cross section of the present invention, a slit or a window hole is continuously formed on a surface perpendicular to a surface to be bent of the member having a closed cross section, and then the surface to be bent is bent. Therefore, it is possible to easily bend a good-looking closed cross-section member with little cross-section deformation without using a core. Further, by changing the width of the slit or the size of the window hole formed in the surface perpendicular to the planned bending surface, the cross-sectional size and shape of the closed cross-section member after bending can be changed, and various products can be supported. Further, since the bending can be easily performed by forming the slits or the window holes, the bending die or the jig does not require a complicated structure, and therefore, there is an effect that the investment is small.

[Brief description of drawings]

FIG. 1 is a perspective view of a closed cross-section member having slits before bending according to the present invention.

FIG. 2 is a view showing an example of a window hole formed in the closed cross section member according to the present invention.

FIG. 3 is a view showing another example of the window hole formed in the closed cross-section member according to the present invention.

FIG. 4 is a view showing still another example of the window hole formed in the closed cross-section member according to the present invention.

FIG. 5 is a perspective view illustrating bending means of a closed cross-section member according to the present invention.

FIG. 6 is a diagram showing an internal stress generation state when the closed cross-section member according to the present invention is bent.

FIG. 7 is a perspective view of a closed cross-section member having slits according to the present invention after bending in an S shape.

FIG. 8 shows S of a closed cross-section member having a window hole according to the present invention.
Perspective view after bending

FIG. 9 is a perspective view after bending to only one of the closed cross-section members having a window hole according to the present invention.

FIG. 10 is a view showing cross sections before and after bending of a closed cross-section member having a small slit width according to the present invention.

FIG. 11 is a view showing cross sections before and after bending of a closed cross-section member having a large slit width according to the present invention.

FIG. 12 is a cross-sectional view showing an example of reinforcement of a closed cross-section member according to the present invention.

FIG. 13 is a cross-sectional view showing another example of reinforcement of the closed cross-section member according to the present invention.

FIG. 14 is a perspective view of a conventional closed cross-section member after bending.

FIG. 15 is an enlarged partial view of a portion A in FIG. 13, which is a state diagram of internal stress generation at the time of bending of a conventional closed cross-section member.

16 is a cross-sectional view taken along the line BB of FIG.

FIG. 17 is a cross-sectional view showing a conventional means for forming a closed cross-section member having a complicated bend.

[Explanation of symbols]

1,3,11 Square tube 1a, 1b, 11a, 11b
Bending surface 11c, 11d Side surface 11 'Bending tube 2, 2'
Recess 12 Slit 12 'Slit after bending, window holes 13, 14, 15 Window hole 16 Lower bending type 17
Upper bending type 18, 20 Welding 19 Reinforcing plate.

Claims (2)

[Claims] 1. A method for bending a member having a closed cross section, which comprises forming a slit or a window hole continuously on a surface of the member having a closed cross section, the surface being perpendicular to the surface to be bent, and then bending the surface to be bent. 2. The method for bending a member having a closed cross section according to claim 1, wherein the slit or the window hole is provided over a predetermined bending length.