JP3636964B2 - Counterbore forming method and press apparatus for thick sheet metal - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a counterbore forming method for forming a counterbore on a thick sheet metal and a press apparatus for counterbore formation.
[0002]
[Prior art]
Generally, a through hole for inserting a bolt is formed on a thick sheet metal, and a counterbore is formed around the through hole to improve the sitting of the bolt or a nut screwed to the bolt. To be done.
[0003]
As a conventional example for forming the counterbore, after the through hole is formed, the thick sheet metal is plastically deformed to a predetermined depth by using a second punch having an outer diameter larger than the through hole. And forming a spot face.
However, as described above, in the case of a thick sheet metal, when the counterbore is to be formed by one-step press molding, a great amount of pressure is required, resulting in a problem that the press device is enlarged. .
[0004]
Therefore, a method of reducing the pressing force in each process by performing the pressing process using the second punch in a plurality of times has been attempted.
[0005]
[Problems to be solved by the invention]
Incidentally, as described above, when the pressing process using the second punch is performed in a plurality of steps, the following problems to be improved arise.
That is, in the second and subsequent press processes, if the second punch and the recessed portion formed in advance are not aligned with high accuracy, the second punch collides with the opening edge of the recessed portion and It is a problem that it is assumed that the two punches are damaged.
In addition, when a position shift occurs between the previously formed recess and the second punch, the recess is enlarged by the press in the next process, and a problem that the dimensional accuracy of the spot facing is lowered is also assumed.
[0006]
The present invention has been made in view of such conventional problems, and provides a counterbore forming method and a press device for a thick sheet metal that can suppress an increase in power required for pressing and can obtain high dimensional accuracy. It is intended to do.
[0007]
[Means for Solving the Problems]
According to a first aspect of the present invention, there is provided a counterbore forming method for a thick-walled sheet metal in which a through-hole is formed in the thick-walled sheet metal and an end side of the through-hole of the thick-walled sheet metal is achieved. A first punch having the same outer diameter as the inner diameter of the through hole, a second punch having an outer diameter larger than the inner diameter of the counterbore to be formed, A third punch having an outer diameter substantially equal to the inner diameter of the counterbore to be formed, the through hole is formed by punching out the thick sheet metal with the first punch, and the second punch is formed with the through hole. In addition to being installed on the same axis, the second punch is used to plastically deform the thick metal plate to a predetermined depth to form a first recess, and then the third punch is installed on the same axis as the first recess. Along with this third punch, And forming a counterbore to form a second recess by plastically deforming the bottom surface of the first concave portion to a predetermined depth.
According to claim 2 of the present invention, the counterbore forming method for the thick sheet metal is such that the outer peripheral portion of the tip of the second punch according to claim 1 is chamfered with an arc-shaped cross section. The bottom periphery of the first recess to be formed is formed in a cross-sectional arc shape.
According to a third aspect of the present invention, in the method of forming a counterbore in the thick sheet metal, the upper edge of the second concave portion according to the second aspect and the surface of the thick metal plate are located on the periphery of the first concave portion. It is connected by the circular arc surface formed.
A press apparatus according to a fourth aspect of the present invention is a press apparatus for forming a through hole in a thick sheet metal and forming a counterbore on the surface of the end of the through hole of the thick sheet metal. A die on which the thick sheet metal is placed, a first punch having the same outer diameter as the inner diameter of the through hole, and a second punch having an outer diameter larger than the inner diameter of the counterbore to be formed A third punch having an outer diameter substantially equal to the inner diameter of the counterbore, and these first to third punches are selectively opposed to the thick sheet metal on the die and pressed toward the die. A press mechanism, which presses down the first punch to punch out the thick sheet metal, and then presses down the second punch to form a first recess having a predetermined depth around the through hole. Forming, and then pressing the third punch to A first recess, characterized in that it is adapted to form a second recess having a predetermined depth concentrically.
A press apparatus according to a fifth aspect of the present invention is characterized in that a tip outer peripheral portion of the second punch according to the fourth aspect is chamfered in an arc shape.
According to a sixth aspect of the present invention, the diameter of a circle obtained by connecting the inner edges of the chamfers of the second punch according to the fifth aspect is substantially equal to the inner diameter of the counterbore to be formed. It is characterized by being made.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
First, an embodiment of the press apparatus of the present embodiment will be described. A die 2 on which a thick sheet metal 1 is placed, a first punch 3 (see FIG. 1) disposed opposite to the die 2, and formation. A second punch 4 (see FIG. 2) having an outer diameter larger than the inner diameter of the counterbore to be formed, a third punch 5 (see FIG. 3) having an outer diameter substantially equal to the inner diameter of the counterbore to be formed, and these A press machine (not shown) is provided for selectively causing the first to third punches 3, 4, and 5 to face the die 2 and to be pressed toward the thick sheet metal 1 on the die 2.
[0009]
Next, the counterbore forming method according to the present embodiment will be described together with the operation of the press device according to the present embodiment configured as described above.
First, after placing the thick metal plate 1 on the die 2 and aligning the first punch 3 at a predetermined position of the thick metal plate 1 as shown in FIG. The through-hole 6 is formed by pressing down and punching out the thick sheet metal 1 in the thickness direction.
[0010]
Next, the second punch 4 is aligned coaxially with the through-hole 6, and the second punch 4 is pressed down by a press machine as indicated by an arrow in FIG. The first recess 7 is formed by plastic deformation to the depth.
[0011]
Further, as shown in FIG. 3, after the third punch 5 is positioned coaxially with the through hole 6 and the first recess 7 in place of the second punch 4, the third punch 5 is pressed by a press machine. To form a second recess 8 by plastically deforming the bottom of the first recess 7 of the thick sheet metal 1 to a predetermined depth to form a counterbore.
[0012]
When the counterbore (second concave portion 8) is formed in this way, first, the large second punch 4 is plastically deformed to the middle of the thickness of the thick sheet metal 1, and then the small third punch 5 is used. Since the counterbore is formed by plastic deformation to a predetermined depth, the pressing force required in each step is suppressed to a low level, and as a result, an increase in the size of the press device is suppressed.
[0013]
Prior to the formation of the counterbore (second recess 8), preforming is performed by the second punch 4 having a large outer diameter, and the third punch 5 having a smaller outer diameter than the second punch 4 is used to perform the seating. Since the hole (second recess 8) is formed, there is no interference between the third punch 5 and the inner peripheral wall of the first recess 7 formed previously when the third punch 5 is formed. Therefore, the third punch 5 is prevented from being damaged and the dimensional accuracy of the counterbore (second recess 8) to be formed is ensured.
[0014]
On the other hand, in the present embodiment, a chamfer 9 having a circular arc shape is applied to the outer peripheral edge of the tip of the second punch 4 over the entire circumference.
When the first recess 7 is formed by the second punch 4 as described above, as shown in FIGS. 2 and 3, the inner surface shape of the intersecting portion between the bottom wall and the outer peripheral wall of the first recess 7 is an arc shape. Become.
Furthermore, by matching the diameter of the circle obtained by connecting the inner edge of the chamfer 9 with the outer diameter of the third punch 5, the upper peripheral edge of the first recess 7, The upper peripheral edge of the two recesses 8 are connected by a circular arc surface.
As a result, the change in the cross-sectional shape of the portion of the thick sheet metal 1 where the counterbore (second concave portion 8) is formed becomes moderate, and the strength reduction of the thick sheet metal 1 is suppressed.
[0015]
Note that the shapes, dimensions, and the like of the constituent members shown in the embodiment are examples, and can be variously changed based on design requirements and the like.
[0016]
【The invention's effect】
As described above, according to the counterbore forming method for a thick sheet metal according to the present invention, the thick sheet metal is plastically deformed in the sheet thickness direction by a plurality of pressing processes, and after the punch used in the previous process. By reducing the diameter of the punch used in this process, it is possible to suppress an increase in power required for pressing, to prevent damage to the punch used in the subsequent process, and to improve the dimensional accuracy of the counterbore formed. Can be increased.
In addition, by providing an arc-shaped chamfer at the peripheral edge of the punch used in the previous process, the continuous part between the counterbore and the thick sheet metal surface becomes a smooth arc surface. The change of the cross-sectional shape of the part where the spot face is formed can be moderated, the stress generated in the thick sheet metal can be smoothly transmitted, and the strength can be ensured.
[Brief description of the drawings]
FIG. 1 shows an embodiment of the present invention and is a longitudinal sectional view for explaining a process of forming a through hole by a first punch.
FIG. 2, showing an embodiment of the present invention, is a longitudinal sectional view for explaining a process of forming a first recess by a second punch.
FIG. 3, showing an embodiment of the present invention, is a longitudinal sectional view for explaining a step of forming a second recess (counterbore) using a third punch.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Thick sheet metal 2 Die 3 1st punch 4 2nd punch 5 3rd punch 6 Through-hole 7 1st recessed part 8 2nd recessed part (counterbore)
9 Chamfer

Claims (6)

A method for forming a through hole in a thick sheet metal and forming a counterbore on a surface of the thick sheet metal on an end side of the through hole, the first having the same outer diameter as the inner diameter of the through hole Using the punch, the second punch having an outer diameter larger than the inner diameter of the counterbore to be formed, and the third punch having an outer diameter substantially equal to the inner diameter of the counterbore to be formed, the thick sheet metal is used as the first sheet metal. The through hole is formed by punching with a punch, the second punch is placed coaxially with the through hole, and the thick metal plate is plastically deformed to a predetermined depth by the second punch to form a first recess. Then, the third punch is placed on the same axis as the first recess, and the third recess is used to plastically deform the bottom surface of the first recess to a predetermined depth. Form a counterbore Counterbore method of forming the thick sheet metal, characterized in that. The tip outer peripheral portion of the second punch is chamfered in an arc shape in cross section, and the bottom peripheral edge of the first recess formed by the second punch is formed in an arc shape in cross section. A method of forming a spot face in the thick sheet metal according to 1. 3. The thick sheet metal according to claim 2, wherein the upper edge of the second recess and the surface of the thick sheet metal are connected by an arc surface formed at the periphery of the first recess. Counterbore formation method. A press apparatus for forming a through hole in a thick sheet metal and forming a counterbore on a surface of the thick sheet metal on an end side of the through hole, the die on which the thick sheet metal is placed, A first punch having the same outer diameter as the inner diameter of the through hole, a second punch having an outer diameter larger than the inner diameter of the counterbore to be formed, and a third punch having an outer diameter substantially equal to the inner diameter of the counterbore to be formed A punch and a pressing mechanism that selectively opposes the first to third punches to the thick metal plate on the die and presses them toward the die, and the pressing mechanism includes the first punch Depressing one punch to punch out the thick sheet metal, then depressing the second punch to form a first recess having a predetermined depth around the through hole, and then depressing the third punch The second recess having a predetermined depth is formed in the first recess. Press apparatus characterized by being adapted to form a heart shape. The press apparatus according to claim 4, wherein the outer peripheral portion of the tip end of the second punch is chamfered in an arc shape. 6. The press apparatus according to claim 5, wherein a diameter of a circle obtained by connecting inner edges of the chamfers of the second punch is substantially equal to an inner diameter of a counterbore to be formed.

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