JP2005230897A - Method and device for manufacturing special shaped tube for car component - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and a device for manufacturing a special shaped tube having excellent bending strength and absorption energy characteristics. <P>SOLUTION: The manufacturing method comprises a first step of performing the roll forming of a steel tube welded by a high frequency welding method or the like in the section consisting of two kinds of large and small projecting curved surfaces by setting the radius and the angle of an arc so as to be substantially adapted to the circumferential length of a curved edge part and a bag part of a special trapezoidal tube and the circumferential length except a short side part of a trapezoidal part, a second step of performing the roll forming by abutting a disk-shaped roll 21 from a center surface of the surface of larger radius of curvature out of the two kinds of projecting curved surfaces, and recessing the surface of the larger radius of curvature inward of the tube, a third step of performing the roll forming with small outside diameter of the tube by abutting rolls 31 and 32 on both sides of the section with the center thereof curved in a recessed gutter-shape to narrow a gutter-shaped opening part, and a fourth step of manufacturing a special shaped tube by pressing right and left side parts from the side to the inner side by using right and left tapered rolls 41 and 42 while supporting an upper portion by an upper roll 43, pushing up a bottom side part by a lower roll 44, and roll-forming the bottom side and the diagonal side of the special shaped trapezoidal tube. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method and an apparatus for manufacturing a deformed pipe used as an automobile structural member having excellent bending strength and absorbed energy characteristics.

Conventionally, a steel structure with excellent absorbed energy characteristics as a door impact beam or pillar reinforcement, which is a door reinforcement member, in order to absorb the energy at the time of a side collision of an automobile and ensure the safety of the driver and passengers Members are widely used. A similar structural member is also used for the bumper. A steel plate that has been press-formed is also used, but a steel pipe cut to an appropriate length is often used.
In particular, for the door impact beam, an ultra-high strength steel pipe having a tensile strength of 1400 N / mm ² or more is used in order to ensure safety at the time of collision and to reduce the weight.

In order to reduce the weight of automobile structural members, it may be possible to use a thin material, reduce the cross-sectional area, or change to a lighter material, etc., but reduce the cross-sectional area, If the weight is reduced by changing to a lighter material, the absorbed energy characteristic is lowered. For this reason, in reality, at the design stage, material strength and thinning are simultaneously considered.
However, even if the material strength is increased and the thickness is reduced, the bending strength is reduced due to the reduction in thickness, so that local deformation and buckling are likely to occur, and the absorbed energy characteristics are not improved.

Therefore, in order to increase the bending strength and suppress the local deformation and buckling to further improve the absorbed energy characteristics, a structural member having an irregular shape instead of a circular cross-sectional shape has been proposed.
For example, in Patent Document 1, as shown in FIG. 1 (a), an inwardly curved edge portion facing a part of a substantially circular tube is formed, and a concave portion is formed in the tube by continuous integration with both the curved edge portions. There has been proposed a door reinforcing material having a cross-sectional shape (hereinafter referred to as a “turn-up shape”). Patent Document 2 proposes a structural member for an automobile having a vertically long elliptical shape (hereinafter referred to as “oval shape”) as shown in FIG.

Japanese Patent Laid-Open No. 11-278055 JP 2002-248941 A

On the other hand, in order to improve the fuel consumption of automobiles, automobile components are required to be lighter, and structural members for reinforcement are required to be thinner. When the wall thickness is reduced, the absorbed energy decreases as described above. Therefore, the conventional circular tube and the deformed tube having the cross-sectional shape proposed in the above-mentioned patent document simply absorbs the high-strength wall and absorbs energy characteristics. There was a limit to improving this.
The present invention has been devised to solve such a problem, and provides a simple and low-cost means for manufacturing a specially-shaped deformed tube capable of enhancing bending strength and absorbed energy characteristics. For the purpose.

  In order to achieve the object, the manufacturing method of the deformed pipe for automobile structural members of the present invention shows that the outer shape of the cross section is substantially trapezoidal from the circular pipe, and the inward curved edge is relative to the short side of the trapezoid. When the deformed tube formed in the trapezoidal shape and facing the long side is roll-formed, the circular tube is divided into two types of large and small. A first step of roll forming into a cross section formed of a convex curved surface, and a disk-shaped roll is applied from the center surface of the surface having a large curvature radius of the two types of convex curved surfaces to dent the surface having the large curvature radius inside the tube. The second step of roll forming, the third step of narrowing the saddle-shaped opening to reduce the outer diameter of the tube by applying the roll to both sides of the cross section curved in the shape of a bowl with a depression at the center, and the upper roll with the upper part Use left and right taper rolls while supporting the left and right sides from the side Characterized by comprising a base and the hypotenuse of the deformed trapezoidal tube pushes up the bottom part under the roll from the fourth step of roll forming with pushed into.

In the first step, the curved lengths of the two types of large and small convex curved surfaces are substantially matched to the circumferential length of the curved edge portion and bag portion of the deformed trapezoidal tube and the circumferential length excluding the short side portion of the trapezoidal portion. It is preferable to roll-form.
Before the fourth step, from the left and right rolls having a tapered portion and a curved portion, the lower roll having a curved portion having a curvature radius smaller than the radius of curvature of the lower roll used in the fourth step, and the upper roll used in the fourth step Alternatively, a step of roll forming with an upper roll having a wide flat width may be sandwiched.

  An apparatus for producing a deformed pipe for automobile structural members according to the present invention includes a concave upper roll having a concave portion having a large curvature radius and a concave lower roll having a concave portion having a small curvature radius, which are arranged in the circumferential direction of the raw pipe. A molding stand, a concave lower roll having a concave portion with a curvature radius smaller than or equal to the concave lower roll having a concave portion with a small curvature radius, and a radius of curvature at the end, which are also arranged in the circumferential direction of the blank tube A second molding stand composed of a small disk-shaped convex upper roll, and a third molding stand in which a pair of concave rolls having concave portions with a radius of curvature similar to that of the concave lower roll of the second molding stand are arranged on the left and right; And a fourth forming stand in which a taper roll having a larger high part diameter than a low part diameter is arranged on the left and right, and a flat upper roll and a concave lower roll having a large curvature radius are arranged on the upper and lower sides. This The features.

In addition to the left and right rolls, the third forming stand has a disk-shaped flat upper roll whose flat width is narrower than the convex upper roll width of the second forming stand and a smaller radius of curvature than the concave lower roll of the second forming stand. A concave lower roll having a concave portion may be arranged vertically.
In this case, the flat upper roll of the third forming stand is wider than the flat upper roll of the fourth forming stand, and the concave lower roll has a smaller radius of curvature than the concave lower roll of the fourth forming stand. .

  Between the third molding stand and the fourth molding stand, a roll having a tapered portion having a larger diameter than the central portion and a curved portion curved from the central portion to the bottom portion is disposed on the left and right, and the third A flat upper roll with a flat width that is narrower than the flat upper roll of the forming stand and wider than the flat upper roll of the fourth forming stand, and a fourth forming stand that is equal to or larger than the concave lower roll of the third forming stand. You may interpose the shaping | molding stand by which the concave lower roll which has a smaller curvature radius than this concave lower roll is arrange | positioned up and down.

According to the present invention, the outline of the cross section shows a substantially trapezoidal shape, inwardly curved edge portions are formed opposite to each other on the short side portion of the trapezoid, and the bag portion continuously extending from the curved edge portion is formed. A deformed tube having a cross-sectional shape formed in the trapezoid so as to face the long side portion and having excellent absorbed energy characteristics can be formed with a small number of steps by taking a large amount of forming per step.
Since the shock absorption energy becomes high, it is possible to reduce the thickness of the deformed pipe used as the structural member for the automobile, which greatly contributes to the weight reduction of the automobile.

The inventors of the present invention first studied various cross-sectional shapes having the highest bending strength and absorbed energy characteristics as structural members for automobiles.
As a result, as shown in FIG. 2A, the outline of the cross section is substantially trapezoidal, and inwardly curved edge portions c to c ′ and d to d ′ opposite to the short sides of the trapezoid are formed. In addition, the bag portion e continuously extending from the curved edge portions c to c ′ and d to d ′ is formed in the trapezoid so that the tip a thereof faces the long side portion b of the trapezoid. It has been found that when a deformed pipe having a cross-sectional shape is arranged so as to receive a load at the trapezoidal short sides c and d, the bending strength and the absorbed energy become the highest.

The reason why the deformed pipe having the above-described cross-sectional shape is superior to the conventional deformed pipe having the cross-sectional shape as described above is considered as follows.
When a bending load is locally applied in the direction shown in FIG. 2, the deformed pipe having the cross-sectional shape shown in FIG. 2 (a) is deformed into a cross-sectional shape as shown in FIG. 2 (b). First, since the received load is supported by the contact between the trapezoidal long side portion b shown in the figure and the tip end a of the bag portion e facing the trapezoidal long side portion b, the load is hardly deformed. Next, when the tips c ′ and d ′ of the curved edge contact each other, deformation of the deformed pipe due to the load is suppressed and twisting is suppressed. In addition, there is also an effect of suppressing torsion due to the bag portion e expanding under the load. Further, the trapezoidal long side portion a, the tip end b of the bag portion, and the tip ends c ′ and d ′ of the curved edge portion come into contact with each other to support each other, whereby the angle θ1, Deformation is performed so that θ2 becomes small, and the effect of increasing the strength and absorbed energy of the deformed tube against bending load, that is, the structural member for automobiles is exhibited.

On the other hand, bending strength and absorbed energy are not so high in a simple cross-sectional shape such as a circular or oval shape or a turn-up cross-sectional shape conventionally used as a structural member for automobiles such as a reinforcing member. . That is, in a simple shape such as a perfect circle shape or an oval shape, the trapezoidal long side portion b, the bag portion tip a and the curved edge portions c ′ and d ′ contact each other as in the present invention. Therefore, the strength is weak and the absorbed energy is low. In the turn-up shape, the strength improvement effect by a and b and c ′ and d ′ being in contact with each other can be expected to be the same as that of the present invention product. It is easy to flatten and cannot be expected to absorb enough energy.
As described above, the cross-sectional shape of the product of the present invention is a structure that supports the received load, so that the strength is high, and the amount of deformation is small, so the absorbed energy is large.

The smaller the angle between the bottom side and the oblique side, the weaker the force to support the load, and the more easily deformed, the lower the absorbed energy. Therefore, the angle between the bottom side and the oblique side is preferably 60 degrees or more.
A structural member made of a deformed pipe as obtained in the present invention has different bending deformation and absorbed energy characteristics depending on the direction of receiving a load. For this reason, it is necessary to arrange them with directivity so that the bending characteristics are maximized. In the automotive structural member using the deformed pipe obtained in the present invention, it is preferable that the structural member is arranged so as to receive a load on the short side of the trapezoidal cross section.

A deformed pipe for an automobile structural member is formed by continuously performing a plurality of molding processes as follows.
The process is schematically described with reference to FIG. 3. (A) First, a steel pipe welded by a high-frequency welding method or the like is prepared. (B) As a first step, a curved edge part and a bag part of a deformed trapezoidal pipe Are formed into a cross section composed of two types of large and small convex curved surfaces in which the radius and angle of the arc are set so as to substantially match the circumferential length of the trapezoidal portion and the circumferential length excluding the short side portion of the trapezoidal portion. (C) Thereafter, as a second step, roll forming is performed such that a disk-shaped roll is applied from the central surface of the two types of convex curved surfaces with a large radius of curvature so that the surface with the large radius of curvature is recessed inside the tube. To do. (D) After that, as a third step, a concave roll is applied to both sides of the cross-section of which the center is concave and curved to narrow the saddle-shaped opening to reduce the outer diameter of the tube, and (f) the fourth step The upper and lower sides of the deformed trapezoidal tube are formed by rolling the bottom and slant sides of the deformed trapezoidal tube by pushing the left and right sides inward from the side using the left and right taper rolls while supporting the upper part with the upper roll. To manufacture.
Before the fourth step, a step (e) of roll forming may be sandwiched between right and left rolls having a tapered portion and a curved portion, a flat upper roll, and a lower roll having a curved portion having a small curvature radius.

Regarding the forming stand used in each of the above processes, the roll shape and the like to be used will be described in detail with reference to FIGS.
In the first forming step, the raw tube M is passed through a forming stand comprising a concave upper roll 11 having a recess with a large curvature radius and a concave lower roll 12 having a smaller curvature radius.
Next, in the second molding step, the base tube M has an end portion with a concave lower roll 22 having a concave portion having a radius of curvature that is the same as or smaller than the concave lower roll 12 used in the first molding step. The disk-shaped convex upper roll 21 is pressed between the forming stands formed of the disk-shaped convex upper roll 21 having a small curvature radius at the center of the convex curved surface formed with the large curvature radius in the first molding step. Pass through. The cross section of the raw tube at this stage has a horizontally long cross section that is concave in the center and curved like a bowl.

Therefore, it is necessary to reduce the lateral width. In the third molding step, a pair of concave side rolls 31 and 32 having concave portions with the same radius of curvature as the concave roll used as the lower roll in the second step is passed between the molding stands, Narrow the opening to reduce the tube outer diameter.
At this time, a disk-shaped flat upper roll 33 having a flat width narrower than the convex upper roll width of the second molding stand and a concave lower roll 34 having a concave portion having a smaller radius of curvature than the concave lower roll 22 of the second molding stand. Is passed between the molding stands arranged vertically, the entire outer periphery of the raw tube is constrained by the left and right and upper and lower four rolls, and a deformed tube with excellent shape accuracy can be molded without generating cracks and excess material. .

  As the final fourth step, the taper rolls 41 and 42 having a larger part diameter than the lower part diameter are arranged on the left and right, and the flat width is narrower than the flat width of the flat upper roll 33 of the third molding stand. A flat upper roll 43 and a concave lower roll 44 having a larger radius of curvature than the concave lower roll 34 of the third molding stand are passed between the molding stands arranged vertically, and the left and right sides are pushed inwardly from the side. The bottom side is pushed up with the lower roll to form the base and the hypotenuse of the trapezoidal section. Since it is supported by the upper roll and pressed by the roll from the left and right and from the bottom, it is sequentially deformed into a substantially trapezoidal cross-sectional shape having a bag portion.

Between the third molding stand and the fourth molding stand, rolls 51 and 52 having a tapered portion having a larger diameter than the central portion and a curved portion curved from the central portion to the bottom portion are arranged on the left and right. The amount of deformation in the fourth step may be reduced between the molding stands.
Also in this case, like the third molding stand, the flat width is narrower than the flat width of the flat upper roll 33 of the third molding stand and wider than the flat width of the flat upper roll 43 of the fourth molding stand. When a roll 53 and a concave lower roll 54 having a radius of curvature smaller than that of the concave lower roll 44 of the fourth molding stand is equal to or larger than the concave lower roll 34 of the third molding stand are passed between the molding stands disposed above and below. The entire outer periphery of the raw tube is constrained by four rolls on the left and right and upper and lower sides, and a deformed tube having excellent shape accuracy can be formed without causing cracks or surpluses.

Thickness 1.00 mm, a circular tube of outer diameter 54.0mm and pipe formation by high frequency welding method yield point 900 N / mm ^2, a tensile strength of 980 N / mm ^2, a total elongation of 20% cold rolled material as a base, Rolled according to the continuous process of the present invention.
In the first step, the circumferential length of the upper portion is 70 mm, the curvature is substantially matched with the circumferential length of the curved edge portion and bag portion of the deformed trapezoidal tube and the circumferential length excluding the short side portion of the trapezoidal portion. Using a concave upper roll having a radius of 150 mm and a concave lower roll having a lower circumferential length of 99.4 mm and a curvature radius of 40 mm, a flat cross-sectional shape in which two circular arcs are connected vertically is formed.

In the second step, roll forming was performed using a convex upper roll having a curvature radius of 50 mm and a concave lower roll having a curvature radius of 150 mm so that the upper half of the cross section of the first process product had a concave shape.
In the third step, a flat roll having a flat width of 10 mm is used as an upper roll, a concave roll having a curvature radius of 30 mm and a width of 8 mm is used as a lower roll, and a concave roll having a curvature radius of 150 mm is used as a side roll. While supporting the process product up and down, the lower half of the cross section was pushed upward from the left and right, thereby forming the rough shape of the bag portion of the irregular trapezoid and the side portion of the irregular trapezoid.

Next, in the additional step, a flat roll having a flat width of 10 mm is used as the upper roll, a concave roll having a curvature radius of 30 mm and a width of 8 mm is used as the lower roll, and a concave roll having a curvature radius of 150 mm is used as the side roll. The sides of the irregular trapezoid were roughly molded.
Thereafter, as a fourth step, a taper roll having an upper end diameter of 145 mm, a lower end diameter of 120 mm and a height of 32 mm is used as a side roll, a flat roll having a flat width of 7 mm is used as an upper roll, and a curvature radius is 300 mm. A concave roll having a width of 40 mm was used as the lower roll, and the bottom part was pushed up while pressing the hypotenuse part of the deformed trapezoid inward to form a deformed trapezoidal section.

The final cross-sectional shape of the deformed trapezoidal tube roll-formed in the above steps is 31.8 mm at the bottom, 31.8 mm in height, and 166.5 mm in cross-sectional line length (the cross-sectional line of the bag portion inside the tube). The length was 63 mm, the cross-sectional line length of the trapezoidal portion outside the tube was 103.5 mm), and the angle between the base and the hypotenuse had 75 degrees.
This deformed trapezoidal tube was cut into a predetermined length and subjected to a bending evaluation characteristic test. As shown in FIG. 6, in the bending evaluation characteristic test, a test piece is placed between a fulcrum of a shoulder R of 10 mm and a span of 1000 mm with the short side portion of a deformed trapezoid facing upward, and a punch having a width of R 100 mm and a width of 40 mm is placed at the center in the longitudinal direction. Was evaluated by the amount of absorbed energy when 150 mm was pushed in at a constant speed of 30 mm / min.

For comparison, a conventional heat treated round heat-treated steel pipe having a tensile strength of 1470 N / mm ² , a cross-sectional line length of 94.2 mm and a wall thickness of 1.8 mm, and a square pipe and an oval pipe having a tensile strength of 980 N / mm ² are used. The same bending evaluation characteristic test was conducted for the turnup type tube. At this time, the cross-sectional line length and the wall thickness were selected so that all the tubes were the same as the conventional material or lighter than the conventional material.
Table 1 shows the results of the bending evaluation characteristic test.

In Table 1, test no. Based on the conventional material of No. 2, those that are superior to conventional materials in terms of product weight and absorbed energy are evaluated as ◎, and those that are inferior are evaluated as ×.
No. which is a comparative example. The thickness of the square, oval, and turn-up type tubes of 4, 5, and 6 are selected so that they have the same weight as that of the present invention and the conventional product. There is no. However, the absorbed energy characteristics are inferior to conventional products.
On the other hand, the deformed trapezoidal tube manufactured by the method of the present invention is lighter than the conventional product, but the absorbed energy is increased by about 10% compared to the conventional product.
As described above, by changing the roll shape and roll arrangement form when manufacturing the conventional turn-up type pipe, the modified pipe for automobile structural member that is lighter in weight and superior in absorbed energy characteristics than the conventional product It becomes possible to manufacture at low cost.

The figure explaining the cross-sectional shape of the conventional structural member for motor vehicles The figure explaining the structural member for motor vehicles of this invention, and the cross-sectional shape at the time of the bending deformation Diagram explaining the cross-sectional shape of the process of transforming a circular tube into a deformed trapezoidal tube The figure explaining the roll arrangement of the process of transforming a circular pipe into a deformed trapezoidal pipe Sectional drawing explaining the roll shape of each process which transforms a circular pipe into a deformed trapezoidal pipe The figure which shows the bending evaluation characteristic test method of the structural member for automobiles

Claims (6)

  From the circular tube, the outline of the cross section shows a substantially trapezoidal shape, inwardly curved edge portions are formed opposite to each other on the short side portion of the trapezoid, and a bag portion continuously extending from the curved edge portion is formed. When roll-forming a deformed pipe formed in the trapezoid so as to face the long side portion thereof, a first step of roll-forming a circular pipe into a cross section composed of two kinds of large and small convex curves, and the two kinds of convex curves A second step in which a disk-shaped roll is applied from the center surface of the surface having a large radius of curvature to roll-form the surface having the large radius of curvature to the inside of the tube, and both sides of the cross section in which the center is recessed and curved in a bowl shape Apply the concave roll to the third step to narrow the tube-shaped opening and reduce the outer diameter of the tube, and press the left and right sides inward from the side using the left and right taper rolls while supporting the upper part with the upper roll and lower Raise the bottom with a roll and bottom of the shaped trapezoidal tube Method for producing a motor vehicle structural member for a profiled pipe, characterized by comprising and a hypotenuse from the fourth step of roll forming.   In the first step, the curved surface lengths of the two types of large and small convex curves are approximately matched to the circumferential length of the curved edge and bag portion of the deformed trapezoidal tube and the circumferential length excluding the short side of the trapezoidal portion. The manufacturing method of the deformed pipe | tube for motor vehicle structural members of Claim 1 which carries out roll forming to.   Before the fourth step, from the left and right rolls having a tapered portion and a curved portion, the lower roll having a curved portion having a curvature radius smaller than the radius of curvature of the lower roll used in the fourth step, and the upper roll used in the fourth step The manufacturing method of the deformed pipe | tube for motor vehicle structural members of Claim 1 or 2 which pinches | interposes the process of roll-forming with an upper roll with a wide flat width.   A first forming stand comprising a concave upper roll having a concave portion with a large curvature radius and a concave lower roll having a concave portion having a small curvature radius, which are arranged in the circumferential direction of the raw tube, and also arranged in the circumferential direction of the raw tube. Further, a second forming stand comprising a concave lower roll having a concave portion having a curvature radius smaller than or equal to the concave lower roll having a concave portion having a small curvature radius and a disk-like convex upper roll having a small curvature radius at the end portion. And a third molding stand in which a pair of concave rolls having concave portions with the same radius of curvature as the concave lower roll of the second molding stand are arranged on the left and right sides, and a taper having a larger higher diameter than a lower diameter An apparatus for manufacturing a deformed pipe for automobile structural members, comprising a fourth forming stand in which rolls are arranged on the left and right, and a flat upper roll and a concave lower roll having a large radius of curvature are arranged vertically. .   In addition to the left and right rolls, the third forming stand has a disk-shaped flat upper roll whose flat width is narrower than the width of the convex upper roll of the second forming stand and a smaller radius of curvature than the concave lower roll of the second forming stand. The manufacturing apparatus of the deformed pipe | tube for motor vehicle structural members of Claim 4 with which the concave lower roll which has the said recessed part is arrange | positioned up and down. Between the third molding stand and the fourth molding stand, a roll having a tapered portion having a larger diameter than the central portion and a curved portion curved from the central portion to the bottom portion is disposed on the left and right, and the third A flat upper roll with a flat width that is narrower than the flat upper roll of the forming stand and wider than the flat upper roll of the fourth forming stand, and a fourth forming stand that is equal to or larger than the concave lower roll of the third forming stand. The manufacturing apparatus of the deformed pipe | tube for motor vehicle structural members of Claim 4 or 5 in which the shaping | molding stand by which the concave lower roll which has a smaller curvature radius than the concave lower roll of this is arrange | positioned up and down is interposed.

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