JPH09285825A - Press forming method for square tube parts - Google Patents

Abstract

[PROBLEMS] To provide a press-molding method for finishing a corner portion bending radius as small as possible in press-molding a rectangular tubular component to obtain improved product quality and stable production conditions. A point a is located on a line segment ab connecting a center point a of an arc of a punch corner and a corner edge point b of a blank.
A point c having a predetermined length L is determined, and the intersections with the straight sides of the two perpendiculars drawn from the point c to the blank straight side are defined as n ₁ and n _2, and from these two points, the opposite direction to the point b. In addition, points m ₁ and m ₂ which are respectively separated by a predetermined dimension M are defined, and a perpendicular line is set up from these two points, and the intersection points c ₁ and c ₂ of this perpendicular line and the perpendicular line to the line segment ab pass through the point c. The above two blank straight sides bm ₁ and bm ₂ and two perpendiculars c ₁ m
_This is a method in which a blank corner portion region surrounded by ₁ , c ₂ m ₂ and line segments c ₁ c ₂ is cut out and press-molded.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a press forming method for drawing a metal plate into a rectangular tubular component, and more specifically, to a corner portion between a bottom portion and a side wall portion and / or a corner portion between side wall portions of the component. The present invention relates to a method for press-molding a rectangular tube component for finishing a bending radius as small as possible.

[0002]

2. Description of the Related Art For example, it is industrially well practiced to process a rectangular tubular component 10 as shown in FIG. 2 by drawing a metal plate. As a processing procedure for such a square tube component, first, a rectangular blank material 11 as shown in FIG. 3 is used, and as shown in FIG.
The flange part outside the part is cut to finish the product with a predetermined size and shape.

At that time, cracks may occur in the vicinity of the side wall portion 5 of the corner in the drawing step, but in order to avoid the cracks, reference books etc. (for example, "Technical guidance press work" issued by Engineering Book Co., Ltd.) It is known that the blank shape is not cut into a rectangular shape but is cut into an octagonal shape as shown in FIG.

Further, in JP-A-2-220720,
Disclosed is a technique in which the corners of the four corners of a blank are cut out at the tip of the punch corner into an arc shape that is 11 to 20 mm larger than the punch size to prevent cracks and to be formed without damaging the coating film. ing.

[0005]

However, in the above-mentioned conventional technique, the bending radius of the corner portion 3 of the rectangular tubular component 10 and the corner portion 3 of the side wall portion and / or the corner portion 4 between the side wall portions as shown in FIG. Is small, for example, if you want to finish less than 5mm,
If the depth is 20 mm or more, cracks 6 occur near the punch shoulders at the corners as shown in FIG. Further, when the cushion pressure is reduced to increase the inflow of the material so as not to cause cracks, wrinkles 7 are generated near the corner edges of the bottom of the panel.

In a press used for mass production, it is necessary to consider variations in cushion pressure and the like. Therefore, in order to perform stable production, there is a moldable range in which cracks and wrinkles do not occur. A molding method that can be 10% or more of the set value of the cushion pressure is required.

However, in mass production by the conventional method, there is a high risk that defects will occur during production, and it has been difficult to perform stable and favorable production. Further, if cracks and wrinkles cannot be avoided, the design of the parts must be redesigned, resulting in a marked deterioration in productivity and an increase in costs such as mold costs.

The present invention advantageously solves the above-mentioned problems, and can form a rectangular tubular component having a small bending radius at the corner between the bottom and the side wall and / or at the corner between the side walls without causing cracks or wrinkles. An object of the present invention is to provide a method for press-molding a rectangular tube part.

[0009]

SUMMARY OF THE INVENTION The gist of the present invention is, as shown in FIG. 1, a method of press-molding a rectangular tube part in which a rectangular or square blank is formed by cutting out four corners. Center point of arc of punch corner a
On the line segment ab connecting the corner edge point b of the blank and the point c of the dimension L satisfying the following formula (1) from the point a, and the straight line of the two perpendicular lines drawn from the point c to the straight side of the blank. The intersections with the sides are defined as n ₁ and n _2, and points m ₁ and m ₂ that are further apart from these points in the opposite direction of the point b by a dimension M that satisfies the following equation (2) are determined. Further, a perpendicular line is set up to define intersections c ₁ and c ₂ of this perpendicular line and a perpendicular line to the line segment ab passing through the point c, and the two blank straight sides bm ₁ and bm ₂ and the two perpendicular lines c ₁ m ₁ , c ₂ m ₂
And a section of a blank corner portion surrounded by line segments c _{1 and} c ₂ are cut out to be formed, and the method is a press forming method for a rectangular tubular component.

[0010]

[Formula 3] L ≤ (1 + √2) Rp + 2Rc + H / 2 ………… (1)

[0011]

[Equation 4] M <1 / √2 (Rc + L) ………… (2)

However, Rp: punch shoulder radius, Rc: punch corner radius, H:
It is the molding depth.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention are described below.
This will be described in detail.

According to the present invention, the bending radius of the corner between the bottom and the side wall of the rectangular tubular component and / or the corner between the side walls is 5 m.
The reason why the molding can be carried out at a depth of 20 mm or more when it is desired to finish as small as m or less is considered as follows.

In FIG. 1, reference numeral 1 is a punch shape as seen from the direction in which the punch advances, and 2 is a notch shape of a blank. Further, a is the center point of the arc of the punch corner, and L is the dimension from the center point a of the arc of the punch corner to the point c of the blank notch in the direction of the corner edge point b of the blank. In addition, _two perpendicular lines cn ₁ and cn ₂ passing through the point c to the straight sides of the blanks are separated from each other in the opposite direction to the point b.
Let M be the shortest dimension with respect to the perpendicular lines c ₁ m ₁ and c ₂ m ₂ of the blank of the book.

The blank size should be changed according to the shape of the mold and the molding depth, but according to the investigation by the present inventors, the corner portion and / or the side wall portion between the bottom portion and the side wall portion of the square tubular component are particularly preferable. When it is desired to finish the bending radius of the corners between them to be as small as 5 mm or less, it is necessary to satisfy the following conditions in advance as a blank shape in order to form a product having a depth of 20 mm or more without causing cracks.

That is, 4 of rectangular or square blanks
(A) A locus of a perpendicular line of a straight line ab passing through a point c having a dimension L satisfying the above expression (1) in the direction from the center point a of the arc of the punch corner to the corner edge point b of the blank, b) perpendicular lines cn ₁ and cn _{2 of the two} blank straight sides passing through the point c and two blank straight line perpendicular lines c distant in the opposite direction to the point b side by a dimension M satisfying the formula (2). That is, it is cut out along a locus composed of ₁ m ₁ and c ₂ m ₂ .

At this time, the notch dimensions L and M are limited to the following ranges. First, the center point a of the arc of the punch corner
To the blank cutout portion c point in the direction of the corner edge of the blank is (1 + √2) Rp + 2Rc +
It must be H / 2 (mm) or less.

Further, the shortest dimension M from the perpendicular of the blank straight side passing through the point c to the perpendicular of the blank straight side distant from the point b side in the opposite direction is less than 1 / √2 (Rc + L) (mm). There is a need to. Here, Rp is the punch shoulder radius, Rc is the punch corner radius, and H is the dimension of the forming depth.

The reason for limiting the dimension L is as follows. That is, since the inflow resistance from the flange portion to the wall portion increases as the dimension L increases, L> (1 + √2) Rp + 2Rc +
When it is H / 2, cracks occur in the punch shoulder. Further, the lower limit value of L may be determined according to the molding depth so that the blank edge does not enter the wall of the molded product.

Further, according to the investigation by the present inventors, the perpendicular lines cn ₁ and cn _{2 of the} straight side portion of the blank passing through the point c and the blank straight line separated from the point b by the dimension M satisfying the equation (2). The vertical lines c ₁ m ₁ and c ₂ m ₂ are notched loci, and instead of simply notching the blank into an octagon, the flange part to which cushion pressure is applied is increased to increase the flange part near the corner and the bottom of the punch. When the tensile force is applied, the wrinkles on the punch bottom can be suppressed.

At this time, the shortest dimension between the perpendiculars cn ₁ and cn _{2 of the} blank straight side passing through the point c and the perpendiculars c ₁ m ₁ and c ₂ m ₂ of the blank straight side distant from the point b in the opposite direction. The reason why M is limited is that when M ≧ 1 / √2 (Rc + L), wrinkles occur near the corner edge portion of the punch bottom. The lower limit of M is not specified, but any positive value will do.

As the method of cutting the designated blank shape, any of shearing, punching or laser cutting may be used.

[0024]

EXAMPLES The present invention will be specifically described below with reference to examples.

The cold-rolled steel sheet, the galvanized steel sheet, the coated steel sheet and the stainless steel sheet (SUS304) having the plate thicknesses shown in Table 2 are
A rectangular blank of 80 × 720 mm was cut with a shear, and a blank provided with notches shown in the same table (without notches, notches shown in FIGS. 1, 5 and 6) was obtained by laser cutting. It was

Further, a square tube deep-drawing die having a basic die shape as shown in Table 1 was manufactured, and these metal plates were subjected to square tube drawing under the forming conditions shown in Table 1. Occurrence of cracks and wrinkles in the molded product was observed, and the results are shown in Table 2 at the same time.
As is clear from the results in Table 2, when the method of the present invention is used for the conventional method, the metal plate can be formed without causing cracks or wrinkles.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

As described above, when the method for press-molding a rectangular tubular component according to the present invention is used, the bending radius of the corner between the bottom and the sidewall of the rectangular tubular component and / or the corner between the sidewalls. Even if is less than 5 mm, the flow resistance from the flange portion to the wall portion can be reduced, and molding can be performed without cracking.

Further, by providing the corner flange portion to which the cushion pressure is applied, by applying a tensile force to the wall portion near the corner and the punch bottom portion, the wrinkle of the punch bottom can be suppressed. Therefore, molded products can be obtained without cracks and wrinkles, and even when mass-produced, there is a remarkable effect that stable production conditions can be obtained along with improvement of product quality, which has high industrial value. .

[Brief description of drawings]

FIG. 1 is an explanatory view of a blank notch method of the present invention.

FIG. 2 is an explanatory diagram showing a perspective view of a rectangular tube component.

FIG. 3 is an explanatory view showing a perspective view of an initial blank shape for explaining a drawing process of a rectangular tube component.

FIG. 4 is an explanatory view showing a shape of a molded product after processing in a perspective view, for explaining a drawing process of a rectangular tubular component.

FIG. 5 is an explanatory diagram of a conventional blank cutout method.

FIG. 6 is an explanatory view of another conventional blank notching method.

FIG. 7 is a corner portion between a bottom portion and a side wall portion and / or a square tube formed by drawing.
It is an explanatory view of a defective phenomenon that often occurs when it is desired to reduce the bending radius of the corner between the side walls.

[Explanation of symbols]

1 Punch shape viewed from the direction of punch 2 Cutout shape of blank 3 Corner between bottom and side wall of square tubular component 4 Corner between side wall of square tubular component 5 Corner wall of drawn product 6 Square Cracks that often occur when it is desired to reduce the bending radius of the corner between the bottom portion and the side wall portion and / or the corner portion between the side wall portions in tubular drawing, 7 In the corner drawing between the bottom portion and the side wall, / Or wrinkles that often occur when you want to reduce the bending radius of the corners between the side walls 10 Square tube parts 11 Blanks

Claims (1)

[Claims] 1. A press-molding method for a rectangular tube part, which is formed by cutting out four corners of a rectangular or square blank, and a line segment connecting a center point a of an arc of a punch corner and a corner edge point b of a blank. On ab, a point c having a dimension L that satisfies the following formula 1 is defined from the point a, and the intersection point with the straight sides of the two perpendiculars drawn from the point c to the blank straight side is n ₁ ,
n ₂ and points m ₁ and m ₂ further apart from these two points in the opposite direction to the point b by a dimension M satisfying the following equation _2.
Then, a perpendicular line is set up from these two points, and the intersection points c ₁ and c _{2 of} this perpendicular line and the perpendicular line to the line segment ab passing through the point c.
And the above two blank straight sides bm ₁ and bm ₂ ,
A method for press-molding a rectangular cylinder part, characterized in that a blank corner area surrounded by _two perpendicular lines c ₁ m ₁ and c ₂ m ₂ and a line segment c ₁ c ₂ is cut out and molded. [Formula 1] L ≤ (1 + √2) Rp + 2Rc + H / 2 [Formula 2] M <1 / √2 (Rc + L) where Rp: punch shoulder radius, Rc: punch corner radius, H:
Forming depth