JP2785513B2 - Hole punch type - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a punching die used for punching a metal plate.

[0002]

2. Description of the Related Art Conventionally, an apparatus for punching a stamped product such as a door panel or a hood panel, which is an automobile part, is provided with an upper die which is vertically movable and opposed to a lower portion of the upper die. A punch having a lower die, a punch provided at a lower portion of the upper die, and a die corresponding to the punch and provided on the lower die is used. And when punching a pressed product, after placing the pressed product on the lower die, the upper die descends,
The punch presses the punched portion of the pressed product, and the shear stress generated from the punch and the edge (blade) of the die generates a crack from at least one of the punch side and the die side. Perform punching. However, since the crack generated in the punched portion is not constant between the product side and the remaining material side, when a break occurs on the remaining material side, burrs are generated on the product side. In order to solve this problem, for example, an apparatus as disclosed in Japanese Patent Application Laid-Open No. 1-293922 is used. The prior art will be described below with reference to FIGS. 5 and 6, reference numeral 1 denotes a punch, and 2 denotes a die. Then, one end of the punch 1 or the die 2 is uniformly chamfered, and the other end is formed with an edge (blade). By chamfering one of the punch 1 and the die 2, stress is always concentrated on the edge portion on the non-chamfered side, a crack is generated from the edge portion side, and the crack is generated on the non-chamfered side. Thereby,
The burrs can be concentrated on the chamfered side, the occurrence of burrs on the non-chamfered side is suppressed, and the occurrence of burrs on the product side is reduced.

[0003]

However, the material 6
When a hole having a contour different in curvature, such as a square hole or an elliptical hole, is punched out with a punch 1 having a uniform chamfer, the thickness of the material 6 is reduced by the pressing of the punch 1 in a portion having a small curvature,
If the thickness is less than a certain thickness, a crack is generated near the die edge 5 due to the shear stress from the die edge 5 and breaks. On the other hand, in a portion having a large curvature, the thickness of the material 6 gathers due to the shrinkage of the material 6 in the drawing line direction, so that the plate thickness near the die edge 5 decreases later than the portion having a small curvature. During this delay, the tensile stress in the vicinity of the punch 1 of the material 6 exceeds the necking occurrence value, and necking due to the tensile stress occurs in the vicinity of the punch 1 of the material 6 before the crack occurs near the die edge 5. Occurs, and the elongation concentrates and breaks. Burrs remain from the broken portion of the material 6 on the punch 1 side to the vicinity of the die edge 5. Therefore, in the hole punching processing of contours having different curvatures, burrs are generated on a product side at a portion having a large curvature. Therefore, the present invention reduces the tensile stress applied to the vicinity of the punch at a portion where the curvature of the material is large, such as a square hole, an elliptical hole, or another hole having a different curvature, so that the hole is always broken near the die edge, and a burr is formed. The purpose is to suppress the occurrence of.

[0004]

Means for Solving the Problems An upper die movably arranged up and down, a lower die facing the lower part of the upper die, and a lower edge of the upper die provided at a lower portion of the upper die. In a punching die in which a part is formed by a closed curve having a different curvature and is chamfered, and a die corresponding to the punch and provided in the lower die, a peripheral edge of a tip of the punch is provided. The chamfering amount of a portion having a large curvature is larger than that of a portion having a small curvature.

[0005]

The punch having the above structure presses the material by lowering the upper die in the punching of contours having different curvatures, such as a square hole and an elliptical hole. Cracks occur near the edge of the die and break. On the other hand, in a part where the curvature of the material is large, the thickness of the material near the edge of the die decreases with a delay because the material thickness gathers due to the shrinkage of the material in the direction of the drawing line, and cracks occur near the edge of the die. Timing is delayed. On the other hand, by increasing the amount of chamfering at the portion where the curvature of the punch is large, the amount of contact of the material with the vicinity of the chamfered portion (the amount of sticking) increases, and the sheet thickness is reduced while the punch descends a certain distance. Since the deformation of the material in the perpendicular direction is reduced, the reduction in the plate thickness of the abutting portion is delayed. This means that the rate of change of the tensile stress applied to the vicinity of the punch of the material is reduced. This makes it possible to delay the timing at which the material is stretched and concentrated in the vicinity of the punch, thereby first generating a crack near the edge of the die and breaking it near the edge of the die. Therefore, in a hole having a contour having a different curvature, a break can be uniformly generated in the vicinity of the edge of the die.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. FIGS. 1 and 2 show the configuration of the present invention. Reference numeral 7 denotes an upper die, which is fixed to a vertically movable ram (not shown). On the other hand, a lower mold 8 is fixedly mounted on a bolster (not shown) so as to face below the upper mold 7. At the lower part of the upper die 7, a punch 1 for removing a square hole having a rectangular tip is mounted, and the material 6 is pressed and fixed so as to surround the punch 1. A stripper 9 is provided. The stripper 9 is made of a cushion material such as urethane. The lower end of the stripper 9 is located slightly below the tip of the punch 1 and is compressed with the lowering of the upper die 7 to press and fix the material 6. The material 6 is paid by the elastic force. Reference numeral 2 denotes a die provided on the lower die 8 corresponding to the punch 1, and a die edge 5 is formed at the tip thereof. The shape of the tip of the punch 1 is a quadrangle formed by four punch corners 3 and other punch straight portions 4, and the periphery of the tip of the punch 1 is chamfered. This chamfer is
In both the punch corner portion 3 and the punch straight portion 4, the angle formed by the chamfered portion and the bottom surface of the punch 1 is constant.
The punch angle is set to a degree, and the chamfer amount of the punch corner portion 3 is formed in the longitudinal direction of the punch 1 larger than the chamfer amount of the punch straight portion 4, for example, two to three times.

The operation of the punching die configured as described above will be described. At the time of the square hole punching process, the upper die 7 descends while the material 6 is placed on the upper surface of the lower die 8, and accordingly, the stripper 9 and the punch 1 provided on the upper die 7 descend. The material 6 is pressed and fixed. Further, as the punch 1 descends, the material 6 starts to be pressed. At this time, at the portion of the material 6 pressed by the punch corner 3, the die edge 5
The decrease in the thickness of the nearby material is delayed, and the generation of cracks from the die edge 5 is delayed. However, as shown in FIG. 3, on the other hand, the large amount of chamfering of the punch 1 delays the reduction of the thickness of the material 6 in contact with the vicinity of the chamfered portion of the punch corner 3, and Such tensile stress is suppressed.

Accordingly, since the tensile stress applied to the material 6 is suppressed, the timing of concentration of the material 6 in the vicinity of the punch 1 is delayed, so that a crack can be generated in the vicinity of the die edge 5 first and the material 6 is broken. be able to. As a result, the square hole can be uniformly removed near the die edge, and the occurrence of burrs can be reduced.

An experiment was conducted using such a punching die. FIG. 4 shows the results. As shown in the experimental results of FIG. 4, when the chamfer amount of the punch straight portion is A and the chamfer amount of the punch corner portion is B, when B / A = 1.0 (the chamfer amount of the punch straight portion and the punch corner portion is The same), B / A = 2.0 (the amount of chamfer at the corner of the punch is twice that of the straight part of the punch), and B / A =
3.0 (The chamfer amount at the corner of the punch is 3 times that of the straight part of the punch)
By making the chamfer amount of the punch corner part larger than that of the punch straight part, the height of the burr can be increased over a wide range of clearance (clearance / plate thickness 5% to 50%).
It can be seen that a level of 0.1 mm or less can be secured.

In the present invention, the shape of the punch has been described as having a square shape. However, the technical idea of the present invention is not limited to a square shape. A similar effect can be obtained with a polygonal hole.

[0011]

As described above, when punching holes having different curvatures such as square holes and elliptical holes, the tensile stress applied to the vicinity of the punch of the material at the portion having a large curvature is reduced. Prior to the fracture on the side, a fracture from the vicinity of the die edge of the material can be generated. Thus, holes having contours having different curvatures can be uniformly broken near the die edge and removed, and the occurrence of burrs can be reduced. Also, since the clearance between the punch and the die is insensitive, the degree of freedom of the punch diameter with respect to the die diameter is high, and punches with different diameters can be used within the allowable limit of a certain hole tolerance dimension, which is spent on clearance management. The labor is reduced, and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a front view showing a configuration of the present invention.

FIG. 2 is a perspective view of a punch for removing square holes according to one embodiment of the present invention.

FIG. 3 is a diagram schematically illustrating the operation of the present invention.

FIG. 4 is a graph of an experimental result of the present invention showing a burr height according to a ratio of a chamfer amount between a punch straight portion and a punch corner.

FIG. 5 is a front view illustrating a configuration of a conventional technique.

FIG. 6 is a diagram schematically illustrating the operation of the related art.

FIG. 7 is a diagram schematically illustrating an operation of a conventional technique at a portion having a large curvature at a peripheral edge of a punch tip.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Punch 2 ... Die 3 ... Punch corner 4 ... Punch straight part 5 ... Die edge 6 ... Material 7 ... Upper 8 ... Lower 9 ... ·stripper

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) B21D 28/16 B21D 28/34 B21D 28/14

Claims (1)

(57) [Claims] 1. An upper die which is disposed movably up and down, a lower die which is disposed below and opposed to the upper die, and a lower end of the upper die which has a peripheral edge portion having a curvature. In a punching die formed of different closed curves and having a chamfered punch and a die provided in the lower die corresponding to the punch, the curvature of the peripheral edge of the tip of the punch is determined. A punching die, wherein the chamfering amount of a large portion is formed larger than the chamfering amount of a portion having a small curvature.