JPH0149561B2 - - Google Patents

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention provides a bend-formed part having a cross-sectional shape of a substantially constant curvature, and a bend-formed part having a curvature different from the above-mentioned curvature adjacent to both sides of the part, by a roll forming method. The present invention relates to a method of bending into a shape having a bent portion or a straight portion.

[Conventional technology]

Many of the shapes manufactured by the roll forming method have a cross-sectional shape that is a combination of a straight or nearly straight part and a bent part formed into an arc shape with an appropriate radius of curvature. Therefore, when the cross section of the material to be formed is developed, the radius of curvature changes in the width direction in the shape of a staircase or a step.

BACKGROUND ART Conventionally, the following methods have been employed singly or in combination as methods for bending arc-shaped parts such as sections.

(1) With a fixed radius of curvature, the bending arc length is sequentially expanded to both sides or either side in the width direction to obtain a bent portion with a predetermined radius of curvature, arc length, and bending angle.

(2) A predetermined bending portion is obtained by sequentially decreasing the radius of curvature over the entire arc length of the product, which will be the bending portion, from the larger radius of curvature to the radius of curvature of the product.

However, in these bending methods, the ratio R/t of the radius of curvature and the plate thickness, which is a large radius of curvature, is large.
When conditions such as a large bending angle are combined,
There were cases where the shape and precision of the bent portion was insufficient.

For example, in a bending portion, the amount of bending on both sides thereof is insufficient, and the center portion is likely to be bent excessively to compensate for the shortage of the amount of bending. In this case, of course, if the bending part contacts or engages with other parts of the product, errors may occur in the relative positions of the parts adjacent on both sides of the bending part, which may cause problems in use. may occur.

[Problem that the invention seeks to solve]

The present invention relates to a product having a shape having a bending part having a substantially constant curvature, and bending parts or linear parts having curvatures different from the curvature, respectively, adjacent to both sides of the bending part, the shape of the bending part, The purpose of the present invention is to provide a roll forming method that improves accuracy.

[Means for solving problems]

The present invention provides a method for bending and forming a cross-sectional shape having a bending portion having a substantially constant curvature, and bending portions or linear portions having curvatures different from the curvature, respectively, adjacent to both sides of the bending portion. This roll forming method is characterized in that, of the bending portion of the curvature, portions on both sides thereof are bent prior to the central portion excluding the portion.

[Effect]

The present inventors conducted experiments and studied the causes of incorrect molding shapes of bent portions in conventional roll forming methods. Next, we will discuss some of the findings obtained as a result.

As mentioned above, shapes, etc. are made up of straight parts and bent parts with various radii of curvature, and the radius of curvature changes in a staircase or step-like manner with respect to the position in the developed width direction of the material to be formed. ing.

On the other hand, in the normal roll forming method, the cross section of the material to be formed first contacts the hole molds of one or both of the upper and lower rolls at the roll entrance, and then is bent and formed by the roll hole molds while being fed from this position. It reaches a plane containing the upper and lower roll axes (hereinafter, the roll hole mold part within this plane will be referred to as directly below the roll), and the deformation at that forming stage ends. The cross section of the material to be formed during this deformation can be thought of as a beam in material mechanics.

In general, the bending moment diagram of a beam is continuous in the mathematical sense, meaning that the bending moment value does not change dramatically at a certain point along the length of the beam.

Therefore, due to the continuous bending moment, it is possible to correctly bend and form a cross-sectional shape in which the radius of curvature changes stepwise or stepwise as described above, that is, a shape in which the radius of curvature is discontinuous in the width direction of the material to be formed. In particular, the shape near the point where the radius of curvature changes will be incorrect.

Next, we will discuss the causes of irregular shapes due to the fact that when a material to be formed is bent, the formed part is subjected to bending action without being constrained on either the front or back surfaces.

Figures 3 and 4 are diagrams showing an example of the conventional roll forming method, and each shows a flower diagram of a hat section steel and the state of the forming roll and the material to be formed in the No. 4 stage of this flower. be.

No. 4 in Fig. 3 shows the cross-sectional shape of the finished product, in which there is a bent part a with a slightly large radius of curvature r4 in the center, and straight parts b adjacent to both sides of the formed part. , b, and has a cross-sectional shape in which leg bending portions c, c with a small radius of curvature and linear ear portions d, d are connected. The flower shown in FIG. 3 is made by bending the central bending portion a using the method (2) above, and the leg bending portions c and c using the method (1) above.

A, B1 and B2 in FIG. 4 are side views of the roll and the material to be formed in No. 4 forming in FIG. 3, respectively, and Y1-Y1' and Y in FIG.
2-Y2' cross-sectional blind view. An arbitrary cross section of the material to be formed into the cross-sectional shape No. 3 in Fig. 3 is first formed by bending the bending portion a, as shown in B1.
The boundary between the straight portions b and b comes into contact with the corner portions 13, 13 formed by connecting the grooved hole-shaped surfaces 9, 9 and the outer diameter surface of the No. 4 upper roll 7 with an arc from the outside of the bend. . Thereafter, the cross section of the material to be formed is formed into linear portions b, b, which are inclined to widen at the end, as shown in B2.
is strongly compressed downward by the corner portions 13, 13 of the roll 7, and a forward bending action is applied to the central bending portion a. However, this bending part a is not in contact with the roll hole die on either the front or the back, and therefore, the cross section is preferentially bent at the top point a', which is the part where the maximum bending moment is applied due to the compression. do.

For this reason, as mentioned above, among the bending and forming parts,
The central portion becomes excessively bent and deformed.

As can be seen from Figure 4A, the condition where the material to be formed is bent and deformed without being held by the roll hole die on either the front or back surface of the bending deformation section always occurs at the roll inlet. It is something to do.

The above-mentioned defective shape of the material to be formed can be somewhat corrected and improved by compressing the material directly under the rolls from both the front and back sides and restraining its cross-sectional shape to the correct shape, but R/t When is large, the amount of this correction is small, especially due to spring back.

According to the present invention, the vicinity of the point where the curvature changes, where the shape is likely to become incorrect, is bent before other parts are bent. This preliminary bending is at the early stage of forming, the cross-sectional shape is close to that of the material, and the height of the roll in the rolling direction is still low. Therefore, as can be seen from Figure 4A, the depth of the roll hole is small. The process is carried out at a shallow stage when the distance from the position where the cross section of the material to be formed starts contacting the roll hole die to just below the roll is small. For this reason, the cross section of the material to be formed during the bending deformation process is constrained from the front and back directly under the rolls, and tends to assume the correct shape under the influence of the portion of the material to be formed that is maintained in a relatively correct cross-sectional shape.

〔Example〕

Next, the present invention will be explained in detail with reference to Examples. FIG. 1 is a flower diagram of an example in which the present invention is applied to the central bending portion of a deformed hat-shaped steel having the same cross-sectional shape as FIG. 3 (the ear portions are different on the left and right sides).

Starting from the strip S, bend and form the strips in the order of No. 1 to No. 4.

For convenience, P1 to P on one side in the width direction of the material to be formed.
9, and the bending process will be explained for only one side thereof. In No. 4, the edge surface ~ P1 is the ear part and is a straight part, P1 to P4 are the leg bending part, P4 to P5 are the straight part, and the part from P5 to the apex P9 of the central bending part is the central bending part. be.

No. 1 pass is from the material S to the center bending part P5
-P9, only the portions P5 and P6 on both sides in the width direction are bent in an angle range of α1 with an inward bending radius of r1. Therefore, among the central bending portions P5 to P9, the portions P5 to P6 on both sides are bent prior to the central portions P6 to P9.

In this example, since the product is asymmetrical,
Since the material to be formed tends to meander, this No. 1 pass reduces the amount of bending (large r1, small α1, bending part (total width dimension is smaller).

In the No. 2 pass, the bending radius r2 of the parts on both sides of the central bending forming parts P5 to P9 is made to match the bending radius r4 of the product, and the width is also widened from P5 to P6 and up to P7. ~P9 is bent and formed with a radius of curvature t2, and P1
Among the leg bending forming portions of ~P4, portions P3 and P4 are bent. The molding method for this part is the conventional method (1) above. The description of the leg molding of P1 to P4 will be omitted below. Even this No. 2 pass is r2
<t2, and both side parts will be bent and formed before the central part.

Next, the No. 3 pass is the central bending part P5 to P
8 as r3 (=r4), and the other part P8
~P9 is set to a radius t3 smaller than t2. Therefore, also in this pass, both side portions are bent and formed first.

No. 4 pass r4 the entire area of the central bending part a
The bending radius is as follows.

In this example, the parts on both sides of the central bending parts P5 to P9, which are difficult to form into the correct shape, are passed through multiple times with the same radius of curvature, so the shape of the part is more accurate. be converted into

Next, Figure 2 shows the case where the present invention is applied to a shutter element. Figure A is the cross-sectional shape of the finished product, Figure B is the curvature distribution in the width direction, and Figure C is the cross-sectional shape of the finished product. Each cross-sectional shape is shown. In each figure, the materials to be formed are marked with symbols A to A in the width direction, and the correspondence of the positions in the width direction is shown. In the forming stage shown in Figure C, B,
The molding method of the present invention is applied to the areas F, T, R and W.
In addition, the conventional molding method (1) above is adopted for areas H and R, respectively. In addition, the present invention was adopted in the next molding stage for areas C and W.

〔Effect of the invention〕

As described above, the present invention eliminates the cause of shape defects in conventional forming methods, that is, bending and forming into a shape whose curvature changes in a staircase or step shape due to a continuously changing bending moment. This was done based on the confirmation that the material to be bent can be bent without coming into direct contact with the roll hole mold, which is the standard for the bending shape. Then, the present invention bends the part that is likely to have a defective shape at a part directly under the roll where the cross-sectional shape is maintained correctly because the material to be formed is restrained from the front and back. It was completed after experiments confirmed that by deforming it, it could be bent into a more accurate cross-sectional shape.

[Brief explanation of drawings]

1 and 2 are diagrams showing examples in which the present invention is applied to a deformed hat section and a shutter element, respectively, and FIGS. 3 and 4 are diagrams showing an example in which the embodiment of the present invention is applied to a deformed hat section and a shutter element, respectively, and FIGS. FIG. 3 is a diagram illustrating that an irregular shape occurs because the material to be formed is bent and deformed without being constrained by the roll hole shape. a: Central bending part, b: Straight part, c:
Leg bending molded part, d: ear part, 9, 9: slotted hole type, 13, 13: corner part, 10, 11: gap part.

Claims (1)

[Claims] 1. In a roll forming method in which a metal strip is passed through a number of roll stands arranged in tandem and bent in the width direction, the material to be formed is
When bending into a cross-sectional shape having a bend-formed part with a substantially constant curvature and a bend-formed part with a curvature different from the above-mentioned curvature or a linear part adjacent to both sides of the bend-formed part, the bend-formed part with a substantially constant curvature. A roll forming method characterized in that the parts on both sides are bent before the central part excluding the parts.