JPH08332529A - Die for working pierce hole and method thereof - Google Patents

Abstract

PURPOSE: To provide a die for working a pierce hole, by which the fatigue strength of a work with the pierce hole can be enhanced. CONSTITUTION: In a die 10, for working a pierce hole, with die 11 and punch 12 provided, a projecting edge 16 is provided on the whole periphery of an opening edge part on the punch side of a die hole 15. The outer peripheral surface of the projecting edge 16 is formed of a tapered part 18 whose root side is flared from the tip 17 of the projecting edge 16. The punch 12 is equipped with a base part 25 with a width larger than the hole width of the die hole 15 and a tip part 26 with a dimension possible to insert it into the die hole 15. A tapered part 27 is provided over the whole periphery of the punch 12 between the base part 25 and the tip part 26. This tapered part 27 is positioned opposite to the tapered part 18 on the die side. After punching a pierce hole by the punch 12, the inner peripheral part of the pierce hole is pressurized by the tapered part 18 on the die side and the tapered part 27 on the punch side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hole forming die suitable for forming a pierce hole on a relatively thick metal plate and a method for forming a pierce hole.

[0002]

2. Description of the Related Art When it is necessary to form a hole at a predetermined position in a metal plate-like structural material used in various machines, in a normal piercing hole processing by shear punching, a work is performed by using a die and a punch. I try to make a hole in it. In the normal piercing hole processing, as shown in FIG. 6, a pitted portion having a depth d called "drip" is formed around the piercing hole 2 to some extent in the opening edge 3 on the punch side. , The height h called "burr" at the opening edge 4 on the die side
The protruding part of

As described above, mere piercing hole processing inevitably causes a defect portion around the piercing hole, and in particular in a high-strength steel sheet, the above-mentioned "dag" or "burr" tends to appear remarkably. When a durability test is performed on a work with such pierced holes, there are some cases where the shear separation surface or the above-mentioned defective part becomes the starting point of rupture and early destruction occurs. There is a problem that it is not preferable for strength.

Therefore, as shown in FIG. 7 (a), a coining punch 6 is used to mold a portion 7 coined into a concave annular shape on the surface of the work 1, and then as shown in FIG. 7 (b). It is also practiced to punch the above portion 7 with a piercing punch 8 and a die 9. In this case, compared to mere piercing hole processing, the occurrence of "sag" and "burr" is reduced, and since the area around the piercing hole is coined beforehand to cause work hardening, durability can be improved. It is possible.

[0005]

However, when the two steps of coining and piercing are separately performed as described above, the number of steps is increased by that much, and the equipment cost and working time required for processing are increased. Is larger than normal piercing. Further, it is inevitable that the above-mentioned defective portions (sags, burrs, etc.) will be produced to some extent after the piercing process, which causes a decrease in fatigue strength.

Therefore, an object of the present invention is to process a die and a piercing hole so that the working of the piercing hole which can improve the fatigue strength of the work having the piercing hole can be carried out in one pressing step. To provide a method.

[0007]

A die for forming a pierce hole of the present invention, which has been developed to achieve the above object, comprises a die having a die hole having a shape corresponding to the pierce hole, and a die width of the die hole. Also has a base having a large width and has a tip portion having a width that can be inserted into the die hole, and a punch in which the tip portion is inserted into the die hole in a state of being advanced to a predetermined position with respect to the die. A punch edge having a die side taper portion that projects toward the punch side and inclines so that the outer peripheral surface tapers toward the die surface from the tip thereof is provided at the punch side opening edge portion of the die hole. A punch-side taper portion that is opposed to the die-side taper portion and has a taper width that widens from the tip-end portion of the punch toward the base portion between the tip portion and the base portion of the punch. .

Further, in the hole drilling method of the present invention using the die and the punch, the work is arranged between the die and the punch, and the tip of the punch is inserted into the die hole to pierce the work. By punching the punch and advancing the punch further to a predetermined position, the die side taper portion and the punch side taper portion pressurize the inner peripheral portion of the piercing hole to form a shape corresponding to these tapered portions. Is a molding method.

[0009]

[Function] The work is placed on the die, and the punch is lowered with respect to the die. The tip of the punch punches a piercing hole in the work. The inner peripheral part of the die is pressed by the die side taper part and the punch side taper part, and
Occurrence of defective portions such as “blur” and the like is avoided. Moreover, work hardening occurs in the inner peripheral part of the piercing hole, and the surface of the inner peripheral part of the piercing hole becomes smooth and dense.
A favorable surface condition is obtained. The pierce hole processed in this manner has a significantly improved fatigue strength as compared with a work that has been subjected to normal hole processing, and since the above pierce hole processing can be performed in one pressing step, the work efficiency is high.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. As shown in FIG. 1, a die 10 for piercing holes includes a die 11 located on the lower side in the drawing,
The punch 12 is provided above the die 11. The punch 12 can reciprocate vertically with a predetermined stroke by a punch driving mechanism of a press machine (not shown).

A die hole 15 is provided in the die 11. A projecting edge 16 protruding outward is provided at an opening edge portion of the die hole 15 on the punch side. This tongue 16 is
The die hole 15 is continuously annularly formed around the entire circumference. The cross-sectional shape of the projecting edge 16 is a shape close to a triangle with a sharp tip 17. The outer peripheral surface of the projecting edge 16 is a tapered portion 18 that is inclined so as to spread in a taper shape from the tip 17 toward the root side (die surface side). This taper part 1
The angle θ1 formed by 8 with the axis of the die 11 is about 45 °.
Is.

The inner surface of the die hole 15 has a hole width W1 in the region extending from the intermediate portion 20 in the vertical direction to the tip 17 of the projecting edge 16.
Is substantially constant and has a tapered shape such that the hole width W2 slightly increases from the middle portion 20 to the lower side as it goes downward.

The punch 12 has a base portion 25 having a width D1 larger than the hole width W1 of the die hole 15 and a tip portion 2 connected to the lower side of the base portion 25 and having a width D2 smaller than the width D1 of the base portion 2.
6, and a taper portion 27 which is continuous between the base portion 25 and the tip portion 26 over the entire circumference of the punch 12.
It has.

The shapes of the die hole 15 and the punch 12 correspond to the shape of the pierce hole to be punched. For example, when punching out a circular piercing hole, the die hole 15 is also circular, so that both the base portion 25 and the tip portion 26 of the punch 12 are cylindrical. When the pierce hole is non-circular, the punch 12 having the base portion 25 and the tip portion 26 having a shape corresponding to the shape is adopted.

The width D2 of the punch tip 26 is defined by the die hole 15
Is slightly smaller than the hole width W1 of the punch hole, and when this tip portion 26 enters the die hole 15, a clearance of a proper size (difference between W1 and D2) between the inner surface of the die hole 15 and the punch tip portion 26. Is being secured. The angle θ2 formed by the punch side taper portion 27 and the axis of the punch 12 is, for example, 4
Although it is about 5 °, this angle θ2 is appropriately set as necessary.

Next, the die 10 for forming a pierce hole having the above structure.
The operation of will be described. An example of the work 1 set on the die 11 is, for example, a high-tensile steel plate having a plate thickness of about several mm used for a structural material. As shown in FIG. 1, the work 1 is set on the die 11, and the punch 12 is lowered by a punch driving mechanism (not shown). In addition, work 1
The upper surface side of the above is pressed around the punch 12 by a work pressing ring or a stripper (not shown).

When the punch 12 descends, the tip portion 26 of the punch 12 enters the die hole 15 as shown in FIG. 2, whereby the work 1 is punched out to form the pierce hole 30 and the scrap 1a is punched. Dropped below.

As the punch 12 further descends to a predetermined stroke end on the descending side, the inner peripheral portions 31, 32 of the piercing hole 30 are formed by the die side taper portion 18 and the punch side taper portion 27 as shown in FIG. Is pressurized. As shown in FIG. 4, in the pierce hole 30 thus processed, the inner peripheral portions 31 and 32 are formed in a tapered shape to prevent the occurrence of defects such as “dare” and “burr”, and Work hardening occurs in the peripheral portion of the piercing hole 30 including the peripheral portions 31 and 32. Moreover, the surfaces of the inner peripheral portions 31 and 32 of the piercing hole 30 are smooth and dense. Further, if the piercing hole processing using the mold 10 is performed cold, a preferable fiber flow (flow of the fiber structure of the material) for increasing the fatigue strength is generated in the peripheral portion of the piercing hole 30, which is further effective. Fatigue strength is improved.

FIG. 5 shows the results of carrying out durability tests on various works. In this durability test, a tensile load was repeatedly applied to a test piece made of a rectangular high-strength steel plate (HTP55 material) with a prescribed stress amplitude, and the number of repetitions until fracture was investigated. In FIG. 5, line segment A
Is a test piece with no holes and has the highest fatigue strength.

On the other hand, the test piece having the piercing hole 30 formed by using the mold 10 of this embodiment can exhibit fatigue strength comparable to the test piece having no hole as shown by the line segment B. confirmed. The line segment C is obtained by performing piercing hole processing after coining processing (FIG. 7), and has much lower durability than that of the present embodiment. A line segment D is a chamfer around the hole after machining the piercing hole. The line segment E is the one that has been subjected to the pierce hole processing, and the shear separation surface of the hole is in a considerably rough state, so that the durability is low.

[0021]

According to the present invention, it is possible to prevent the occurrence of defects such as "sag" and "burr" at the peripheral portion of the piercing hole, and to improve the fatigue strength of the surface condition of the inner peripheral portion of the piercing hole. In addition to being able to be processed into a preferable state, the fatigue strength can be increased by work hardening around the pierce holes. In particular, when the high-strength steel plate is cold-worked with the pierce hole, the above effect is remarkable. Further, in the present invention, the above-mentioned piercing hole processing can be performed in one pressing step, and the work efficiency is extremely high compared to the case where two steps of coining processing and piercing hole processing are conventionally performed.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a part of a die for piercing holes showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view in the process of punching out a pierce hole with the mold shown in FIG.

FIG. 3 is a cross-sectional view showing a state where a pierce hole is punched out by the mold shown in FIG.

FIG. 4 is a cross-sectional view of a work in which pierce holes are punched out by the mold shown in FIG.

FIG. 5 is a diagram showing the fatigue strength of various test pieces.

FIG. 6 is a cross-sectional view of a part of a conventional work in which pierce holes are formed.

FIG. 7 is a cross-sectional view showing an example of a conventional piercing hole processing method in the order of steps.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Work 10 ... Mold 11 ... Die 12 ... Punch 15 ... Die hole 16 ... Projection edge 18 ... Die side taper part 25 ... Punch base part 26 ... Punch tip part 27 ... Punch side taper part 30 ... Pierce hole

Claims (4)

[Claims] 1. A die for forming a piercing hole in a plate-shaped work, the die having a die hole having a shape corresponding to the piercing hole, and a base having a width larger than the hole width of the die hole. And a punch having a tip portion having a width that can be inserted into the die hole and being advanced to a predetermined position with respect to the die, the tip portion being inserted into the die hole. At the punch edge of the hole, there is provided a projecting edge having a die side taper portion that projects toward the punch side and inclines so that the outer peripheral surface tapers from the tip toward the die surface. A piercing hole drilling characterized in that a punch side taper portion is provided between the base portion and the base portion so as to face the die side taper portion and widen in a taper shape from the tip end portion of the punch toward the base portion. Money Type. 2. The tip of the punch has a cylindrical shape, the base of the punch has a cylindrical shape with a diameter larger than that of the tip, and the punch side taper portion is the entire circumference of the punch. 2. The die side taper portion is provided on the entire circumference of the die.
Mold for piercing hole described. 3. A die having a projecting edge projecting toward the punch side at an opening edge portion of the die hole, and an outer peripheral surface of the projecting edge being a taper portion expanding in a taper shape from a tip end thereof toward a root side. A punch having a base portion having a width larger than the hole width of the die hole and a tip portion having a width insertable into the die hole, and having a taper portion having a taper width between the tip portion and the base portion. By using, and arranging a work between the die and the punch, by making the tip of the punch enter the die hole to punch out the pierce hole in the work and further advancing the punch to a predetermined position, A method for processing a pierce hole, characterized in that the die-side taper portion and the punch-side taper portion press the inner peripheral portion of the pierce hole to form the inner peripheral portion of the pierce hole into a shape corresponding to these tapered portions. 4. The method of processing a piercing hole according to claim 3, wherein the work is a high-strength steel plate, and the piercing hole processing is performed cold.