JPH04258320A - Method for bending negative angle part - Google Patents

Abstract

PURPOSE:To prevent a product surface from rolling over. CONSTITUTION:In bending a product which is formed with a vertical wall part 11 and a flange part 12 with an acute angle between the product surface 10 on the peripheral apart of the product surface 10, when these vertical wall part 11 and flange part 12 are bent preliminarily, a projecting part 22 running to both sides with the boundary line 21 put between is formed and when the vertical wall part 11 and the flange part 12 are bent again, the projecting part 22, is also pressurized to prevent tensile stress from becoming excessive by flow of the material from the projecting part 22 and the product surface 10 is prevented from rolling over.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a bending method for forming a vertical wall portion and a flange portion following the wall portion by bending the peripheral portion of a product surface in two steps in opposite directions, and particularly relates to The present invention relates to a method for forming a negative corner part in which the angle between the wall part and the product surface is an acute angle.

0002

BACKGROUND OF THE INVENTION It is well known that when bending is performed using a press, elongation and contraction occur in a complicated manner depending on the shape of the bend. The stress associated with elongation and shrinkage acts on the surrounding area, causing wrinkles and cracks, and for this reason, it has conventionally been done to control the flow of material or provide extra thickness in advance.

[0003] As an example, Utility Model Application Publication No. 59-93322
The publication describes a flange processing device configured to prevent cracks caused by stretch flanges. This is because the flange 2 in the curved part 1 shown in FIG.
First, a wave shape with a higher height on the side is formed on the flange 2,
Next, a method of bending the flange 2 is carried out.

[0004] Therefore, in the method using the apparatus described in the above publication, the elongation of the material due to bending of the flange 2 is
Since the uneven portions formed in advance are flattened, the uneven portions are formed smoothly, so that excessive tension is not generated in the flange 2, and the occurrence of cracks and the like is prevented.

[0005]

[Problems to be Solved by the Invention] When bending a flange as shown in FIG. 8, since the elongation is the largest at the edge 3, it is necessary to form a wave shape in advance that increases the height on the edge 3 side. However, this is to allow smooth elongation in the direction parallel to the edge 3.

However, when flange bending is performed, a tensile force is also generated in a direction perpendicular to the bending line (line indicated by reference numeral 4 in FIG. 8), and the material is stretched. This problem occurs more clearly as the bending angle of the flange increases, that is, as the angle between the flange and the product surface (pinching angle) decreases, and also when the edge of the flange is further folded in a direction parallel to the product surface. occurs noticeably.

[0007] The above-mentioned wavy shape hardly acts as an extra wall portion with respect to elongation in the direction perpendicular to the end edge (ie, the bending direction). Therefore, in the past, elongation in the bending direction affected the product surface, and it was not possible to avoid the so-called surface-down phenomenon in which the peripheral portion of the product surface was bent toward the flange side.

The present invention was made against the background of the above-mentioned circumstances, and its object is to provide a method that can prevent the phenomenon of product surface sagging accompanying flange forming.

[0009]

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a vertical wall portion forming an acute angle with respect to the product surface in the peripheral portion of the product surface, and furthermore, the vertical wall portion When bending a product that has a flange bent in the opposite direction to the bending direction of the vertical wall with respect to the product surface, the vertical wall and flange are bent at the final bending angle. In addition to bending and forming at a smaller angle, the part that spans both sides of the boundary between the vertical wall and flange is
This method is characterized by forming recesses or protrusions, and then pressing the vertical wall part together with the recesses or protrusions to form an acute angle with the product surface.

0010

[Operation] In the method of the present invention, the peripheral portion of the material plate is bent in two stages to form a vertical wall portion continuous to the product surface and a flange portion following this, and the product surface of the vertical wall portion is The angle with respect to the angle (the pinching angle) ultimately becomes an acute angle, and this portion becomes a so-called negative angle portion. These vertical wall parts and flange parts are pre-bent to a small bending angle, and then bent to the final angle in the subsequent process.
A concave portion or a convex portion is formed on both sides of the boundary line between the vertical wall portion and the flange portion. These recesses or protrusions are pressed simultaneously when bending the vertical wall to the final angle, and at that time, the recesses or protrusions are stretched in the plane direction, and the extra thickness secured here is Since it flows in the same direction, the product surface is prevented from sagging.

[0011]

EXAMPLES Next, the method of the present invention will be explained based on examples.

FIGS. 1 to 3 are cross-sectional views showing the bending process according to the present invention, and the example shown in these figures is a method of bending into the shape shown in FIG. 4. That is, the shape shown in FIG.
and a flange portion 12 are formed, the vertical wall portion 11 is bent toward the lower surface side of the product surface 10, and the angle θ (the sandwiching angle between the product surface 10 and the vertical wall portion 11) is an acute angle. Further, the flange portion 12 has a shape in which the end edge portion of the vertical wall portion 11 is folded back toward the upper surface side and extends in a direction substantially parallel to the product surface 10.

FIG. 1 shows the first forming process for obtaining the above shape, in which a panel 1 made of a pressed material such as a steel plate is
3 is placed on the die 14, and its peripheral portion is pressed and fixed by a wrinkle suppressing ring 15. By lowering the punch 16 in this state, a drawing force is applied to the panel 13 to form it into a predetermined shape. In FIG. 1, the part indicated by numeral 17 corresponds to the product surface, and the part indicated by numeral 18 corresponds to the vertical wall, numeral 19.
The part indicated by is the part corresponding to the flange, and the part indicated by the symbol 20
The area indicated by is the trimming line.

In the so-called preforming step shown in FIG. 1, the bending angles of the vertical wall portion 18 and the flange portion 19 are set to be smaller than the bending angle of the product. Simultaneously with the bending and forming of each of these corresponding portions 17, 18, and 19, convex portions 22 are formed on both sides of the boundary line 21 between the vertical wall portion 17 and the flange portion 18. FIG. 5 is a partial perspective view showing the shape of the convex portion 22. As shown in FIG.

As is clear from FIGS. 5 and 1, the end of the convex portion 22 on the side corresponding to the flange 19 is located inside the trimming line 20 (on the boundary line 21 side), and even after the next punching process, the end thereof is located on the inside of the trimming line 20 (on the boundary line 21 side). Maintain shape.

In the punching process, as shown in FIG.
is placed on the lower die 23 and pressed and fixed with a pad 24, and in this state it is sheared along the trimming line 20 with a cutting blade 25. Here, the appropriate dimension from the protrusion 22 to the trimming line 20 is, for example, about 3 mm to 5 mm.

Next, the vertical wall portion 18 and the flange portion 19 are bent to form the final shape shown in FIG. 4. FIG. 3 shows the state in which the punched panel 13 is placed on the lower die 26 and is pressed and fixed by the pad 27. In this state, the processing cam (shifting cam) 28 is moved laterally toward the lower die 26, and the processing cam 28 moves the portion corresponding to the vertical wall 1.
8 and the flange-equivalent portion 19 are pressed and formed into the shape shown in FIG.

In this way, when bending the vertical wall portion 11 to the extent that it forms an acute angle with respect to the product surface 10, the vertical wall portion 1
1 and the flange portion 12 in the plane direction, the extra thickness for this is secured by the convex portion 22,
By stretching the convex portion 22 to become a flat surface during the bending process shown in FIG. 3, excessive tensile stress is not generated on the product surface 10 or the flange portion 12. As a result, product aspect 10
is not pulled strongly in the direction of the arrow in Figure 3, so
The product surface 10 is prevented from falling down.

[0019] Here, the position where the convex portion 22 is provided will be explained. As mentioned above, the position where the convex portion 22 is provided is, for example, 3 to 5 mm from the trimming line 20.
It is preferable that it be on the inside, and at least in this invention, it is on the inside of the trimming line. In other words, as shown in FIG. 6, if the convex part 22 is formed beyond the trimming line 20, a part of the convex part 22 will be cut off during the punching process, and as a result, the convex part will be cut off during the bending process. 2
The extra thickness secured in step 2 is used as an extension of the flange portion and does not contribute to the extension in the bending direction (in the direction of the arrow in FIG. 6), making it impossible to prevent the surface-sagging phenomenon.

Also, as shown in FIG. 7, the trimming line 2
Even if the convex part 2 is inside the flange-equivalent part 19,
2, this is no different from the conventional general countermeasure against excess thickness and helps prevent cracking of the flange portion 12, but it cannot prevent the phenomenon of surface sagging in the peripheral portion of the product surface 10.

As mentioned above, the convex portion 22 has a great effect on preventing the product surface from sagging, and in addition to this, the convex portion 22
By forming 2 in advance, it is possible to prevent the flange part 12 from cracking or wrinkling during the bending process, and the excess thickness due to the convex part 22 prevents the elongation of the vertical wall part 11 and the flange part 12 during the bending process. Therefore, there is no direct influence on the trimming line, that is, the edge of the flange portion 12, and therefore the trimming line can be developed linearly. By securing extra thickness by the convex portions 22, the tensile stress at each portion can be relaxed, so that changes in the product shape can be suppressed.

[0022] In the above embodiment, the protrusion 22 is formed, but since the main purpose of this is to secure extra thickness, a recess may be formed instead of the protrusion. Moreover, the shape may be any shape such as a spherical shape or a wavy shape.

[0023]

[Effects of the Invention] As explained above, in the method of the present invention, the uneven portion is formed in advance in the portion from the vertical wall portion to the flange portion, so that when these portions are bent again, the product surface is A large tensile stress is not generated, so the method of the present invention reliably prevents or suppresses the phenomenon of bending of the product surface, making it possible to obtain a product with the desired shape.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a so-called preforming step in an example of the method of the present invention.

FIG. 2 is a sectional view showing a so-called punching step in an example of the method of the present invention.

FIG. 3 is a sectional view showing a so-called collapsing bending step in an example of the method of the present invention.

FIG. 4 is a partially sectional perspective view showing the product shape.

FIG. 5 is a partially sectional perspective view showing the shape of a convex portion.

FIG. 6 is a cross-sectional view showing a convex portion formed beyond the trimming line.

FIG. 7 is a sectional view showing a convex portion formed on the flange portion.

FIG. 8 is a schematic exploded perspective view showing a bending shape that becomes a stretch flange.

[Explanation of symbols]

10 Product side 11 Vertical wall section 12 Flange part 21 Boundary line 22 Convex part

Claims (1)

[Claims] [Claim 1] A vertical wall portion forming an acute angle with respect to the product surface is provided at the periphery of the product surface, and furthermore, a vertical wall portion is provided at the edge of the vertical wall portion in the direction of bending of the vertical wall portion with respect to the product surface. When bending a product with a flange bent in the opposite direction, the vertical wall and flange are bent at an angle smaller than the final bending angle, and the vertical wall and flange are bent at an angle smaller than the final bending angle. A concave part or a convex part is formed on both sides of the boundary line, and then the vertical wall part is pressed together with the concave part or convex part to form an acute angle with the product surface. A method for bending and forming negative corners.