JPH08174086A - Press forming method for sheet metal - Google Patents

Abstract

PURPOSE: To enable strain-free press forming with an improved yield for a quadrangular press-formed product with walls at least on three sides. CONSTITUTION: At least adjacent two corners are notched on a quadrangular sheet metal work 10 for the hood outer of an automobile. One side 10a between these notched parts 12 and the other two sides 10b, 10b one end of which is each adjacent to the two corners are bent to the same side through overhang molding by the use of a press.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet metal stamping method, and more particularly to a sheet metal stamping product of a quadrilateral shape having three wall portions whose final shapes are adjacent to each other, which is not drawn by deep drawing. The present invention relates to a pressing method for forming by extrusion molding.

[0002]

2. Description of the Related Art As shown in FIG. 8, a hood outer 2 of an automobile generally has a front wall portion 2a having only a front portion hanging down. Such a shape is usually easily formed by an upper and lower molds sandwiching the peripheral portion of the sheet metal work, that is, an overmolding press in which the wrinkle holding surfaces of the upper mold and the blank holder are curved. That is, the upper die located on the left and right sides of the front wall 2a and the wrinkle holding surfaces of the blank holder are
The front wall portion 2a is bent in the same direction as the bending direction. In this way, at the stage of sandwiching the peripheral part of the sheet metal work by the upper and lower upper molds and the blank holder, the sheet metal work is clamped by the wrinkle holding surface that is bent only in the front-rear direction of the hood outer 2, and the sheet metal work is bent in the front-rear direction. In the state of being held, the punch is relatively elevated from the lower surface of the sheet metal work to form the hood outer. In this stretch forming, since the bending direction of the sheet metal work is one direction, an unreasonable force is not generated in the work and a good product finish with less distortion is obtained.

However, when the hood outer 4 having not only the front wall portion 4a but also the left and right side wall portions 4b and 4b is to be press-formed as shown in FIG. If the wrinkle holding surface of the upper and lower molds to be sandwiched is a curved surface that is close to the shape of the final product, a relatively large wrinkle (back ring) will occur in the sheet metal work when the peripheral part of the sheet metal work is sandwiched between the molds. If press molding is performed as it is, distortion that cannot be ignored remains in the product, and there is the inconvenience that it must be discarded because it does not meet the surface quality standard. The reason why such a large wrinkle occurs is that the curved surface of the wrinkle holding surface of the die extends in two directions, that is, the front-rear direction, the left-right direction, and the right-hand side of the sheet metal work.

On the other hand, when the hood outer 6 as shown in FIGS. 10 and 11 is formed by making the wrinkle holding surface of the mold flat, the large distortion as described above does not occur, but the sheet metal work for deep drawing. It is very difficult to control the material flow of the work in the peripheral walls 6a-6c within the normal range, and the pulling force of the front wall 2a, the left and right side walls 2b, 2b, and the rear wall 2c downward causes the material to flow. Excessively flow into these wall portions 2a-2c to cause distortion in the wall portions 2a-2c, and since the sheet metal work becomes bulky in the thickness direction in the distorted portion, seizure may occur in the mold due to friction. . If this burn-in occurs in a short period of time, it will be inevitable that productivity will drop and mold maintenance costs will rise.
Regarding the material yield, the inside of the wrinkle holding surface (the pressing surface of the die corresponding to the peripheral held portion 8 of the sheet metal work),
That is, since the amount of material drawn into the punch upper surface and the punch peripheral side surface is large, a margin must be taken into account for the size of the sheet metal work, and the material yield is inevitably low. The dotted line C in FIGS. 10 and 11 is a dividing line when the product is cut out from the work after pressing.

JP-A-62-107827 and JP-A-2-151322 are known as prior arts for molding automobile bodies and as prior arts for deep drawing.

An object of the present invention is to make it possible to form a quadrilateral sheet metal stamped product having walls on at least three sides without distortion and with good yield.

[0007]

In order to solve the above-mentioned problems, the present invention relates to at least two adjacent quadrilateral sheet metals.
The two corners are notched, and one side sandwiched by the notches and the other two sides of the sheet metal whose one ends are adjacent to the two corners are bent to the same side by bulging to form a wall. To form a part.

[0008]

[Function] Since the sides to be bent are separated from each other by the notches, when the sides are bent by bulging, the influence of the bending on one side does not affect the other side. Therefore, since the material flow is basically not generated, the sheet metal work is not wrinkled or distorted.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. As shown in FIG. 1, a sheet metal work 10 used in the present invention.
Has two corners adjacent to each other cut out in a substantially L shape. One side portion 10a of the sheet metal work sandwiched between the pair of cutout portions 12 is smoothly bent downward to form a front wall portion, and the other sides 10b, 10b adjacent to the cutout portion are smoothly bent downward to form left and right sides. Side wall.

A press device 14 as shown in FIG. 2 is used for press forming of the sheet metal work. This press device 14 is not much different from the conventional one, but it is not shown in FIG.
Further, as shown in FIG. 4, in order to support the lower surface of the peripheral edge of the notch 12 of the sheet metal work 10, that is, the lower end surfaces of the front wall and the lower front end of the side wall with curved surfaces, the lower die, that is, the blank holder, is left and right The new structure is that a pair of notched peripheral edge supports are provided upright. Further, as can be seen from FIG. 2, at the rear portion (right side in the figure) of the sheet metal work 10, a wall portion 6c (see FIG.
(See 0) is also new.
Along with this, the wrinkle holding surface 16 at the rear part of the upper and lower molds (right side in FIG. 2) is formed at a position slightly lower than the central flat surface portion 18 of the sheet metal work. In the conventional mold, the wrinkle holding surface 16 of this portion is formed at a position considerably lower than the central plane portion 18 of the sheet metal work, and forms a largely hanging rear wall portion 6c as shown in FIG. However, extra material was needed for that amount.

Other structures of the press device 14 will be briefly described. 20 is a fixed punch die, 22 is a vertically movable blank holder, and 24 is a blank holder which is urged upward by elastic means (not shown). A plurality of lifting rods that elastically support 22 are denoted by 26, an upper mold that can move up and down, and 28 is a vertically movable upper slide that supports the upper mold 26. The upper surface of the blank holder 22 and the peripheral area of the lower surface of the upper mold 26 are
In order to prevent large wrinkles from being generated in the sheet metal work 10 when the sheet metal work 10 is held in the vertical direction, the sheet metal work 10 is formed substantially flat except for the concave and convex grooves of the endless trim line along the outer shape of the product.

The side wall 4b of the sheet metal work 10 has a shelf 3 extending substantially horizontally as shown in FIGS. 5 and 6A.
0 is formed. The shelf portion 30 is for pulling the sheet metal material of the side wall portion 4b downward to exert a so-called wrinkle-extending action on the side wall portion 4b. It is also considered that the shape of the shelves 30 is more effective when the wrinkle-extending action is more effectively brought closer to the hood outer secant 32. Figure 6
Based on this idea, (B) shows the shelf portion 30 formed in a V shape so as to be close to the dividing line 32 of the hood outer 4. However, it has been found that when the V-shaped shelf 30 is press-molded, a so-called knockout mark 34 is distorted in the side wall 4b near the V-shaped bottom. The reason for this is that the sidewall portion 4 becomes closer to the final stage of pressing.
It is considered that the strains existing in b are gathered in the V-shaped bottom direction, and the strains that have no place to go at the end of the press stroke become knockout marks 34. The linear shelf 30 of FIG. 6 (A) was devised for the purpose of eliminating such a knockout mark 34. As a result, the distortion of the side wall 4b is dispersed along the long linear shelf 30. It was confirmed by experiments that the knockout mark 34 did not appear even at the end of the press stroke.

Next, the operation of this embodiment will be described. To press-form the sheet metal work 10, first, the press machine 1
The upper slide 28 and the upper die 26 of FIG. 4 are integrally moved upward and punched into the shape of FIG.
Is set on the punch die 20 as shown by the chain line in FIG. At this time, the blank holder 22 is raised to a position slightly lower than the upper surface of the punch die 20 by the pushing force of the elevating rod 24. When the upper mold 26 is lowered in this state, first, the peripheral part of the sheet metal work 10 is sandwiched by the peripheral parts of the upper mold 26 and the blank holder 22 from above and below, and the upper mold is maintained while maintaining this sandwiched state. When 26 is further lowered, only the peripheral portion of the sheet metal work 10 is pulled downward, and as a result, the central portion of the sheet metal work 10 is relatively pushed up by the punch die 20,
A hood outer 4 having a shape as shown in FIG. 5, that is, having a front wall portion 4a and a pair of left and right side wall portions 4b, 4b is formed. As shown in FIG. 7 (A), the rear portion of the hood outer 4 does not have a rear wall portion 6c (see FIG. 10) as in the related art, and is directed rearward in the horizontal direction at a position slightly lower than the central portion of the sheet metal work 10. Has ended.

The upper surface of the blank holder 22 is a flat surface,
In addition, as shown in FIG. 5, the sheet metal work 10 is between the front wall portion 4a and the left and right side wall portions 4b, that is, the quadrilateral sheet metal work 1 is formed.
Since the notch 12 is formed in the adjacent corners of 0,
Around the sheet metal work 10 is an upper die 26 and a blank holder 2.
It is possible to prevent large wrinkles from being generated in the sheet metal work 10 at the stage of being held between the sheet metal work 10 and the sheet metal work 10.
Even at the stage of pushing up with the punch die 20, the front wall portion 4a and the side wall portion 4b are not bent by deep drawing but bent and bent by bulging, and the wall portions 4a, 4b themselves and the front wall portion 4a are formed. The occurrence of strain in the intermediate portion between the side wall portion 4b and the side wall portion 4b is suppressed.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and various modifications can be made. For example, the above embodiment is an example applied to the hood outer of an automobile, but the quadrilateral sheet metal work 10 is used.
And with at least three walls,
The present invention is likewise applicable to other types of sheet metal presses.

[0016]

As described above, according to the present invention, at least two adjacent corner portions of a quadrilateral sheet metal are cut out, and one side portion sandwiched by the cutout portions and one end are adjacent to the two corner portions. Since the other two sides of the sheet metal to be bent are bent to the same side by stretch forming, it is possible to reduce the occurrence of strain in the wall portion of the sheet metal work. Also, since it is bulging instead of deep drawing, most of the sheet metal work inside the wrinkle holding surface can be used as the final product part, which is necessary for deep drawing, but scraps as scraps after pressing. Since it is not necessary to form an essentially unnecessary wall portion or peripheral portion that causes the above, the material yield can be increased.

[Brief description of drawings]

FIG. 1 is a plan view of a sheet metal work used in the present invention.

FIG. 2 is a sectional view of a press device.

FIG. 3 is a perspective view of a punch and a blank holder of the press device.

FIG. 4 is a perspective view of a punch and a blank holder of the press device.

FIG. 5 is a perspective view of a pressed product molded according to the present invention.

FIG. 6A is a perspective view of a pressed product molded according to the present invention seen from another angle, and FIG. 6B is a perspective view of another pressed product molded according to the present invention.

7A is a sectional view taken along the line AA of FIG. 5, and FIG. 7B is a sectional view taken along the line BB of FIG.

FIG. 8 is a perspective view of a conventional hood outer.

FIG. 9 is a perspective view of a new hood outer to be molded by the present invention.

FIG. 10 is a perspective view of a pressed product when a new hood outer is deep-drawn.

FIG. 11 is a perspective view of a pressed product when a new hood outer is deep-drawn and viewed from another angle.

[Explanation of symbols]

 4 Hood Outer 10 Sheet Metal Work 12 Notch 14 Press Device 15 Notch Peripheral Support 20 Punch Die 22 Blank Holder 26 Upper Die 30 Shelf 32 Split Line

Claims (1)

[Claims] 1. A quadrilateral sheet metal having at least two corners adjacent to each other cut out, and one side sandwiched between the cuts,
A method of pressing a sheet metal, wherein the two corner portions and the other two side portions of the sheet metal having one ends adjacent to each other are bent to the same side by bulging.