JPH10180360A - Bending press die device for square pipe and bent square pipe manufactured with this die device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To bend a square pipe formed so as not to become a drum type in cross section as well as wrinkles and cracks without working a recessed groove and a bellow previously in the tensile side bending surface and the compressing side bending surface of the square pipe. SOLUTION: A lower die 1 is provided with a recessed bend forming surface 1a formed a holding side wall holding the opposite side surface of the square pipe 3, and an upper die 2 is provided with a projecting bend forming surface formed plural numbers of punch projections 6 in the central part toward the longitudinal direction. In this case, a bending load is applied to form while holding both lateral side surfaces between holding side walls 4, 5 and also holding both compressing side and tensile side bent surfaces of the bent square pipe between the recessed bend forming surface 1a and the projected bend forming surface 2a. At this moment, a plastic deforming recessed part is formed in the central part of the compressing side bent surface side of the bent square pipe with punch projections 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a square pipe bending press forming die apparatus used for forming a bent square pipe such as a bumper beam of an automobile, and a bent square pipe manufactured by the forming die apparatus.

[0002]

2. Description of the Related Art Recently, as a measure for strengthening a vehicle body in the event of an automobile collision, a bumper beam made of high-tensile material is provided behind a plastic bumper installed on the front of the automobile. The beam is intended to prevent the bumper from directly contacting the side member by transmitting the impact force to the side member, which is the reinforcement of the vehicle body, in the event of a vehicle collision. The bumper beam is usually formed by bending a rectangular pipe having a rectangular cross section so as to conform to the front shape of the vehicle body.

[0003] As a method of bending the square pipe, there are roughly a method using a winding bending apparatus and a method using a press machine.

In the case of using a winding bending apparatus (bender), a sheet material is formed into a rectangular pipe having a rectangular cross section in advance by using a roll forming machine (often incorporated in the bender), and the following steps are performed. This square pipe is wound around a winding drum and bent, and the welded ends of the bent square pipes are spot-welded with a gap therebetween to complete the bent square pipe.

[0005] In the case of using a press machine, a plate material is previously formed into a rectangular cross section, and joint ends are welded over the entire surface, and a square pipe is used, and both ends of the square pipe are set in a lower mold. By pressing the central portion of the square pipe with the upper die, the pipe is bent to complete a bent square pipe.

[0006] Therefore, when the bent rectangular pipes completed by both devices are compared, the one using a pressing machine in which the joining ends of the rectangular pipes are welded over the entire length has high rigidity, and is used as a high-tensile bumper beam. Is preferred,
Further, in the case of a winding apparatus, it is normal to put a core in a square pipe and form the core, which requires a man-hour for attaching and detaching the core.

[0007]

The case of bending a high-tensile material square pipe E using a press machine with reference to the schematic diagram shown in FIG. 8 will now be described. After fixedly supported by the lower mold F, the upper mold G
Thus, a bending load is applied to the center of the square pipe E to be bent.

[0008] Therefore, when the square pipe E is bent by the press machine, one of the upper and lower side walls facing each other among the four side walls constituting the square pipe E becomes a compression side bent surface, and the other becomes a tension side bent surface.

The tension-side bent surface may be elongated and cracked. On the other hand, the compression side is compressed and wrinkles are generated. The wrinkles extend from the corner of the square pipe to both side walls. And, when an impact is applied, this wrinkle becomes a bending line,
The result was a reduction in rigidity.

When the square pipe is bent, a force (see arrows) as shown in FIG. 9 is generated, and the upper and lower side walls B and B are pulled inward around the neutral axis A. The side walls C, C bulged outward and were formed in a drum-shaped cross section, affecting the strength of the square pipe E.

Therefore, if the bending load is reduced in order to minimize the occurrence of wrinkles and cracks as described above, cracks in the bending surface on the tensile side can be reduced, but after the bending load is removed, a springback is performed. Therefore, a desired bent shape cannot be obtained, and it cannot be used as a bumper beam. In addition, if the spring is bent until the springback disappears, plastic deformation is reached, and the occurrence of cracks and wrinkles becomes extreme, which may cause the square pipe itself to break.

[0012] In view of this point, an example of the above-mentioned winding apparatus is, for example, a case in which the tension side of a square pipe is formed in a bellows shape, or disclosed in Japanese Patent Application Laid-Open No.
As described in Japanese Patent No. 60365, a groove is formed in the longitudinal direction in advance on the tension side and the compression side bending surface side of the square pipe before bending by winding, and the groove on the tension side bending surface side is formed. A method has been adopted in which a cross-section opening type is used, and a concave groove on the compression side bending surface side is tapered to suppress wrinkles and cracks.

However, when such a bent-angle pipe is used as a bumper beam of an automobile, the collision between the vehicles is not limited to a complete head-on collision, but if it is assumed that a so-called offset collision will occur, a bellows or a concave groove may occur. The presence can result in a weakened bumper beam.

In view of the above-mentioned conventional problems, the present invention provides a bumper beam manufactured by bending a square pipe in such a manner that a concave groove or a bellows is previously formed on the tension-side bending surface or the compression-side bending surface side. It is another object of the present invention to provide a bumper beam which is formed so as not to be wrinkled or cracked and not to have a drum-shaped cross section.

[0015]

SUMMARY OF THE INVENTION In order to solve the above-mentioned conventional problems, according to the present invention, a bending press for a square pipe having an upper die and a lower die and having a rectangular cross section is provided. In a molding die for performing molding, the lower mold has a concave curved molding surface having a width dimension substantially equal to the width dimension of the square pipe, and the curved molding surface has two longitudinal side walls facing each other. The upper mold has a convex curved molding surface having a width dimension substantially equal to the dimension between the retaining mold side walls of the lower mold. Having, and in the longitudinal direction at the center of the convex curved molding surface,
A plurality of punch projections are arranged side by side, and after placing the square pipe facing the concave curved forming surface of the lower mold, the upper mold is lowered with respect to the lower mold, and the side of the square pipe is While holding the side surface between the holding side walls of the lower mold, a square pipe is bent and formed between the convex curved forming surface of the upper die and the concave curved forming surface of the lower die, and the plurality of punch protrusions are used. The present invention is characterized in that the square pipe is bent and formed while forming a plastically deformed concave portion at the center of the concave curved forming surface side of the square pipe.

As a result, the preformed square pipe is placed on the lower mold, a bending load is applied by the upper mold, and the pipe is bent. In this case, the compression side bending formed by the upper mold is performed. The surface is bent and supported at multiple points by a plurality of punch protrusions of the convex curved molding surface, and the tension-side bending surface side is
It is convexly bent by the concave curved molding surface of the lower mold.

At this time, both longitudinal side surfaces of the square pipe facing each other are held by the holding side walls erected on the lower mold, and both lateral sides are formed to bulge outward. It will be corrected to become a drum-shaped cross section.

Further, as for the punch protrusions of the convex curved forming surface, plastic deformation recesses are formed on the compression side bent surface of the square pipe by the number of the punch protrusions, and the plastic deformation recesses prevent wrinkles from occurring. The bent pipe works so as not to cause springback of the bent pipe, thereby forming a bent pipe having a desired shape, that is, a bent pipe having substantially the same cross-sectional shape as the square pipe before bending.

Further, since the punch protrusion is disposed at the center of the surface on the side of the convex curved forming surface and does not reach the edge, the bent angle pipe has a plastically deformed concave portion only at the center of the bent surface on the compression side. Although formed, the surrounding area is formed by a straight plane substantially equivalent to the rectangular shape of the square pipe before bending, and there are conventional wrinkles and concave grooves such as when each bent pipe is used as a bumper beam of an automobile. As compared with the case, the rigidity is greatly increased even with respect to the offset collision of the vehicle.

According to the second aspect of the present invention, the bent angle pipe according to the present invention is a square pipe having a rectangular cross section, and one of both longitudinal side surfaces facing each other is formed into a convex curved surface, and the other is formed. Is formed on a concave curved surface, and a plurality of plastically deformed concave portions are formed at the center of the concave curved surface. Although plastic deformation recesses are formed,
The four surroundings are formed by straight planes substantially equivalent to the rectangular shape of the square pipe before bending, and exhibit high rigidity against impacts from various angles.

[0021]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a front view of an apparatus for bending and forming a square pipe according to an embodiment of the present invention, wherein 1 is a lower die, 2 is an upper die, and the upper and lower dies 2, 1 form a forming die. Make up.

The lower mold 1 is provided with a concave curved molding surface 1a having a width substantially equal to the width of the square pipe 3 before bending and extending in the longitudinal direction (see FIG. 2 for details). reference),
Opposite side surfaces 1 of the concave curved molding surface 1a facing each other
The holding side walls 4 and 5 for holding the side surfaces which are the opposite side surfaces of the square pipe 3 are provided upright at b and 1c. At both ends of the concave curved forming surface 1a, mounting surfaces 1d and 1e of the square pipe 3 are formed so as to be located on a horizontal plane.

The upper mold 2 is formed with a convex curved molding surface 2a having a width dimension substantially equal to the dimension between the holding side walls 4 and 5 of the lower mold 1 and extending in the longitudinal direction. Convex curved molding surface 1
A plurality of punch protrusions 6, 6,... are arranged side by side in the longitudinal direction at the center portion of a (see FIG. 3 for details).

The tips of the punch projections 6, 6,... Are formed in a truncated pyramid shape as shown in more detail in FIG. 4, and are implanted in the upper mold 2 from the convex curved molding surface 1a. .

Next, a case in which the preformed square pipe 3 is formed into a bent square pipe will be described. First, both ends of the square pipe 3 are placed on the mounting surfaces 1d and 1e of the concave curved forming surface 1a of the lower die 1. Place and set. At this time, square pipe 3
Are held by the holding side walls 4, 5.

From this state, when the upper die 2 is lowered by a cylinder device or the like (not shown), the lateral side of the square pipe 3 is held between the holding side walls 4 and 5 of the lower die 1 while the upper die 2 is held. Between the convex curved molding surface 2a of the lower mold 1 and the concave curved molding surface 1a of the lower mold 1.
A bending load is applied to the square pipe 3 to be bent and formed.
The bent angle pipe 31 as shown in FIG. Therefore, the square pipe 3 is bent and formed so that the entire surrounding area is surrounded by the upper and lower dies 2 and 1.

At this time, the punch projections 6, 6 provided on the upper die 2
, The square pipe 3 is bent and formed while forming the plastic deformation concave portion 7 at the center of the compression-side bent surface side of the square pipe 3.

The plastically deformed concave portion 7 has a bent angle pipe 31.
Has a truncated pyramid shape located only at the center of the compression-side bent surface 31a, and as shown in FIGS. 6 and 7, the width-direction dimension of the compression-side bent surface 31a is longer than the width in the longitudinal direction. It is formed.

The bent pipe 31 formed as described above
Are the side surfaces 31 facing each other in the bending process.
6 is held by the holding side walls 4 and 5 of the lower mold 1, and the compression-side bending surface 31a and the tension-side bending surface 31b are held by the concave and convex curved forming surfaces 1a and 1b. As shown in the figure, both lateral side walls bulge outward, and the compression-side bending surface 31a and the tension-side bending surface 31b do not form a drum-shaped cross-section formed by bulging inward. Since it is formed in a plane, the strength of the bent angle pipe is increased.

Further, the punch projections 6, 6,... Of the convex curved forming surface 2a are formed on the compression side bending surface 31a of the bending angle pipe 31a.
Are formed as many as the number of the punch protrusions 6, 6,..., And the plastic deformation recesses 7 prevent wrinkles on the compression-side bending surface 31a due to bending stress. Further, since the plastic deformation causes no springback of the bent-angle pipe 31, the bent-angle pipe 31 having a desired shape is formed.

The punch projections 6, 6,... Are arranged at the center of the surface on the side of the convex curved forming surface 2a, and do not reach the edge. The plastically deformed concave portion 7 is formed, the edge of the compression-side bending surface 31a of the bending angle pipe 31 and the lateral side surface 31c are straight, and the conventional bending is used when the bending angle pipe 31 is used as a bumper beam of an automobile. As compared with the case where wrinkles or concave grooves such as a square pipe are present, the rigidity is greatly increased even with respect to the offset collision of the vehicle.

[0033]

According to the first aspect of the present invention, there is provided a molding die apparatus comprising an upper die and a lower die for bending a square pipe having a rectangular cross section, wherein the lower die has a width of the square pipe. A concave side wall having a width dimension substantially equal to the dimension is provided, and holding side walls for holding the longitudinal side surfaces of the square pipe are erected on opposite longitudinal side walls of the concave curved side surface. The upper mold has a convex curved molding surface having a width dimension substantially equal to the dimension between the holding sidewalls of the lower mold, and a central portion of the convex curved molding surface extends in the longitudinal direction. A plurality of punch protrusions are arranged side by side, and after placing the square pipe facing the concave curved forming surface of the lower mold, the upper mold is lowered with respect to the lower mold to form the square pipe. While holding the both side surfaces between the holding walls of the upper mold, the angle between the convex curved molding surface of the upper mold and the concave curved molding surface of the lower mold is reduced. The square pipe is bent and formed while forming a plastically deformed concave portion at the center of the compression-side bent surface side of the square pipe by the plurality of punch protrusions. Place the preformed square pipe on the lower mold, apply bending load by the upper mold,
In this case, the compression side bending surface formed by the upper mold is supported at multiple points by a plurality of punch projections of the convex curved forming surface and bent, and the tension side bending surface side is bent. It is convexly bent by the concave curved forming surface of the lower mold.

At this time, the side surfaces of the square pipe facing each other are held by the holding side walls standing upright on the lower mold, and both side walls are formed to bulge outward. It will be forced to become a state.

Further, as for the punch projections on the convex curved forming surface, plastic deformation recesses are formed on the compression side bending surface of the square pipe by the number of the punch projections, and the plastic deformation recesses prevent wrinkles from occurring. Thus, the springback of the bent square pipe is not caused, and the bent pipe having a desired shape is formed.

Further, the punch projection is arranged at the center of the surface on the side of the convex curved forming surface and does not reach the edge. As a result, the four corners of the bent angle pipe are plastically deformed only at the center of the compression side bent surface. Although it is formed, it is composed of a straight plane substantially equivalent to the rectangular shape of the square pipe before bending, and when the bent angle pipe is used as a bumper beam of an automobile,
As compared with the case where the conventional wrinkles or concave grooves exist, the rigidity is greatly increased even with respect to the offset collision of the vehicle.

The bent angle pipe according to the present invention is a square pipe having a rectangular cross section, and one of longitudinal side surfaces facing each other is formed into a convex curved surface,
Since the other is formed in a concave curved surface and a plurality of plastically deformed concave portions are formed in the central portion of the concave curved surface, the bent angle pipe is formed only in the central portion of the compression side bent surface. A plastically deformed concave portion is formed in the compression-formed portion, and the edges of the compression-side bent surface and both lateral side surfaces are straight, and exhibit high rigidity against impacts from various angles.

[Brief description of the drawings]

FIG. 1 is a front view of an apparatus for bending and forming a square pipe according to an embodiment of the present invention.

FIG. 2 is a perspective view of a lower mold in FIG. 1;

FIG. 3 is a perspective view of an upper mold in FIG. 1;

FIG. 4 is a perspective view of an upper mold showing a part of FIG. 3 in an enlarged manner.

FIG. 5 is a perspective view of a bent pipe manufactured by the bending apparatus for bending a square pipe in the embodiment.

FIG. 6 is a sectional view taken along line XX of FIG. 5;

FIG. 7 is a vertical sectional view taken along the line YY of FIG. 5;

FIG. 8 is a schematic view of an apparatus for bending and forming a square pipe when using a conventional press machine.

FIG. 9 is a side view of a square pipe bent and formed by the press of FIG. 8;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Lower mold 1a Concave curved molding surface 1b, 1c Opposite side surface 1d, 1e Mounting surface 2 Upper mold 2a Convex curved molding surface 3 Square pipe 4,5 Holding side wall 6 Punch projection 7 Plastic deformation concave part 31 Bent pipe 31a Compression side bend Surface 31b Bending surface on tension side 31c Side surface

Claims (2)

[Claims] 1. A forming die, comprising an upper die and a lower die, for performing bending press forming of a square pipe having a rectangular cross section, wherein the lower die has a width substantially equal to a width of the square pipe. It has a concave curved forming surface, and a holding side wall for holding both longitudinal side surfaces of the square pipe is erected on both longitudinal side walls facing each other of the curved forming surface, and the upper die is A convex curved molding surface having a width dimension substantially equal to the dimension between the holding side walls of the lower mold, and a plurality of punch projections arranged in the longitudinal direction at the center of the convex curved molding surface. After the square pipe is placed facing the concave curved molding surface of the lower mold, the upper mold is lowered with respect to the lower mold, and the side surface of the square pipe is held by the lower mold. While holding between the side walls, bend the square pipe between the convex curved forming surface of the upper mold and the concave curved forming surface of the lower mold, and Wherein the square pipe is bent and formed while forming a plastically deformed concave portion at the center of the concave curved forming surface side of the square pipe by the plurality of punch projections. Mold equipment. 2. A rectangular pipe having a rectangular cross section, wherein one of two longitudinal side surfaces facing each other is formed as a convex curved surface, the other is formed as a concave curved surface, and a central portion of the concave curved surface is formed. A bent angle pipe characterized in that a plurality of plastically deformed concave portions are formed in the pipe.