JP2004141896A - Burring method, and punch tip - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a burring method and a punch tip, by which an annular burr is not formed on the inner periphery of the tip end of the cylindrically projecting part formed by a burring process. <P>SOLUTION: The burring method comprises a process for inserting a projecting portion 25 provided at the tip end of the punch tip 21 into a prepared hole 11 formed on a workpiece W, a process for expanding the inlet side periphery of the prepared hole 11 outward when the edge of the prepared hole 11 is formed into a cylindrical shape by pushing the tip end side of the punch tip 21 into the prepared hole 11, and a process for forming the edge of the prepared hole 11 into the cylindrical shape by expanding the inlet side periphery of the prepared hole 11 outward and by pushing the tip end side of the punch tip 21 through the prepared hole 11. The punch tip 21 to be used has a tapered portion 23 formed at the tip end side thereof. An inlet side deformation preventing portion 25 for preventing the inward deformation of the inlet side periphery of the prepared hole 11 by being fitted into the prepared hole 11 formed on the plate shape workpiece W is protrusively provided at the tip end portion of the tapered portion 23. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a burring method for performing burring on a plate-like work and a punch tip used in the method, and more particularly, to forming an edge of a pilot hole formed in the work into a cylindrical shape (burring). The present invention relates to a burring method and a punch tip which can prevent the generation of an annular burr inside the tip of the cylindrical portion when the burring is performed.
[0002]
[Prior art]
The burring process is to form the edge of the pilot hole into a cylindrical shape by pushing a small-diameter pilot hole formed in a plate-shaped work through a punch tip having a larger diameter than the pilot hole, The cylindrical protrusion may be formed on the lower side of the work, or the protrusion may be formed on the upper side of the work.
[0003]
The difference between forming a cylindrical protruding part downward or protruding upward on the work is that the upper and lower dies for performing burring use the punching tip for burring on the upper die. Or the punch chip on the lower side.
[0004]
There is a known document as a configuration having a punch chip on the lower side (for example, see Patent Document 1).
[0005]
[Patent Document 1]
Japanese Utility Model Laid-Open No. 62-131732 [0006]
[Problems to be solved by the invention]
As shown in FIG. 2, the burring die 1 in the above-mentioned known document is provided with an ejector plate 7 surrounding a punch chip 5 erected and fixed at a central portion of a die base 3. It is urged upward by an elastic member 9 which is mounted.
[0007]
To perform burring on the plate-shaped work W in the above configuration, after positioning the small-diameter pilot hole 11 formed in the work W on the ejector plate 7 so as to correspond to the tip 5E of the punch chip 5, The die 15 having the hole 13 at the tip is relatively lowered, and the die 15 fixes the work W between the die 15 and the ejector plate 7.
[0008]
Thereafter, the die 15 is further lowered relatively against the urging force of the elastic member 9 so that the tip 5E of the punch chip 5 relatively pushes up the pilot hole 11 of the work W. Then, as shown in FIG. 2 (B), the work W is formed so that the pilot hole 11 of the work W projects into the hole 13 of the die 15. Then, when the tip 5E of the punch chip 5 pushes the pilot hole 11 through, the forming process of projecting the edge of the pilot hole 11 into the hole 13 of the die 15 into a cylindrical shape, that is, burring process is performed.
[0009]
As described above, when the cylindrical tip 17 is formed by performing burring by pushing the tip 5E having a larger diameter than the prepared hole 11 into the prepared hole 11 formed in the work W, the punch tip 5 is formed. 2B, the outer peripheral edge of the distal end portion 5E acts to handle the inner peripheral surface of the cylindrical projection 17 toward the distal end side, as indicated by the arrow in FIG. 2B. Since the projecting portion 17 is formed, an annular small burr 19 may be formed on the inner peripheral edge of the distal end of the cylindrical projecting portion 17 after the burring process, as shown in FIG.
[0010]
As described above, when an annular burr 19 is formed on the inner peripheral edge of the distal end of the cylindrical projection 17 formed by burring, when performing tapping on the inner peripheral surface of the projection 17, the annular burr 19 is formed. The burr 19 may fall from the tip of the projection 17 as a ring-shaped waste.
[0011]
If the ring-shaped residue falls on the product, it is not preferable because the surface of the product may be damaged. Therefore, it has been desired to prevent the generation of the annular burr during burring.
[0012]
[Means for Solving the Problems]
SUMMARY OF THE INVENTION The present invention has been made in view of the conventional problems as described above, and the invention according to claim 1 has a burring process in which a burring punch tip is inserted into a prepared hole formed in a plate-shaped work. In the method of performing, a step of inserting a protrusion having substantially the same diameter as the prepared hole provided at the tip of the punch chip from the entrance side of the prepared hole with respect to the prepared hole formed in the work, When the tip side is pushed into the pilot hole and the edge of the pilot hole is formed into a cylindrical shape, the step of expanding the entrance side peripheral edge of the pilot hole outward from the exit side peripheral edge, and the entrance side peripheral edge of the pilot hole A burring method comprising: a step of expanding outwardly from the peripheral edge on the outlet side and pushing a tapered portion on the tip end side of the punch tip through the prepared hole to form an edge of the prepared hole into a cylindrical shape.
[0013]
According to a second aspect of the present invention, in the punch tip used for burring, the tip side of the punch tip is formed in a tapered portion, and the tip end of the tapered portion is fitted into a pilot hole formed in a plate-shaped work. In addition, an inlet-side deformation preventing portion for preventing inward deformation of the entrance-side peripheral edge of the pilot hole is provided so as to protrude.
[0014]
According to a third aspect of the present invention, in the punch tip according to the second aspect, the tapered portion is a curved surface having a convex outer peripheral surface.
[0015]
According to a fourth aspect of the present invention, in the punch tip according to the second or third aspect, a boundary between the tapered portion and the entrance-side deformation preventing portion is formed as a concave curved surface.
[0016]
BEST MODE FOR CARRYING OUT THE INVENTION
In the present invention, the tip of the punch tip is formed in a special shape in order to prevent the occurrence of the above-mentioned small annular burrs during burring. Components having the same functions as those of the above-described conventional configuration are denoted by the same reference numerals, and redundant description will be omitted. Also, for convenience of explanation, a case where burring is performed on the lower side will be described.
[0017]
In the embodiment of the present invention, a punch tip 21 corresponding to the punch tip 5 is provided with a tapered portion 23 on the tip end side, and the tip end of the tapered portion 23 is fitted into the prepared hole 11 formed in the plate-shaped work W. This is a configuration including a freely protruding portion 25.
[0018]
More specifically, the tapered portion 23 is formed as a rotating body that rotates an arc drawn with a relatively large radius R1 so that the outside has a convex shape, that is, a curved surface having a convex outer peripheral surface. The protruding portion 25 has a columnar shape substantially equal to the diameter of the pilot hole 11, and its tip end is chamfered with a radius substantially equal to the radius of the protruding portion 25 or a radius slightly smaller than the radius of the protruding portion 25. I have. Therefore, the projection 25 has a substantially hemispherical shape.
[0019]
The connecting portion 27 between the tapered portion 23 and the protruding portion 25 is formed as a rotating body that rotates an arc drawn so as to have a concave shape with a small radius R3, that is, a curved surface having a concave outer peripheral surface. is there.
[0020]
To perform the burring process on the work W using the punch chip 21 as described above, the pilot hole 11 of the work W is positioned with respect to the hole 13 of the die 15. Thereafter, the protruding portion 25 provided at the tip of the punch chip 21 is inserted into the prepared hole 11 of the work W from the entrance side 11A of the prepared hole 11.
[0021]
As described above, when the projecting portion 25 of the tip of the punch chip 21 is inserted into the prepared hole 11 of the work W, the diameter of the prepared hole 11 and the diameter of the protruding portion 25 are substantially equal. The inner peripheral surface in the vicinity comes into contact with the outer peripheral surface of the protruding portion 25, and is prevented from being deformed so that the diameter of the peripheral edge on the entrance side of the prepared hole 11 becomes small during processing. Therefore, the projecting portion 25 constitutes an entrance-side deformation preventing portion for preventing the vicinity of the entrance side of the pilot hole 11 from being deformed inward.
[0022]
As described above, after the projecting portion 25 of the punch chip 21 is inserted (fitted) into the prepared hole 11 of the work W, the edge of the prepared hole 11 is projected into the hole 13 of the die 15 in a cylindrical shape. When the punch chip 21 is relatively lowered in FIG. 1, the periphery of the entrance side 11 </ b> A of the pilot hole 11 is enlarged and deformed by the connecting portion 27 so as to gradually increase in diameter, and is enlarged and deformed by the tapered portion 23. The diameter of the peripheral edge on the inlet side becomes larger than the peripheral edge on the outlet side 11B, and is gradually pressed and deformed downward.
[0023]
As described above, when the entrance side peripheral edge of the pilot hole 11 is enlarged and deformed by the connection portion 27 and the tapered portion 23, the metal of the entrance side peripheral edge is pressed outward, and a part of the metal decreases the diameter of the pilot hole 11. Although it tends to flow in the direction, a protruding portion 25 is fitted near the entrance side of the pilot hole 11 to prevent the peripheral edge of the pilot hole 11 on the entrance side from becoming small in diameter.
[0024]
Thereafter, when the punch chip 21 is further lowered as indicated by the reference numeral 21A, the entrance side peripheral edge of the prepared hole 11 of the work W is gradually projected into the hole 13 of the die 15 in a cylindrical shape. At this time, the inner peripheral surface of the portion protruding in the cylindrical shape comes into contact with the tapered surface 23 of the punch chip 21 and the diameter is gradually increased.
[0025]
That is, when the tapered portion 23 of the punch chip 21 is gradually inserted into the prepared hole 11 of the work W, the edge of the prepared hole 11 is expanded by the outer peripheral surface of the tapered portion 23 so as to move in the radial direction, and the tapered portion 23 is expanded. Is gradually formed into a cylindrical shape by moving into the hole 13 following the downward movement of the hole, and the relative sliding between the tapered portion 23 and the entrance side peripheral edge of the pilot hole 11, that is, the gripping action Is suppressed.
[0026]
Therefore, when the edge portion of the prepared hole 11 of the work W is formed into an inner cylindrical shape, the inner peripheral surface of the cylindrical portion is not squeezed toward the distal end unlike the conventional case, and the cylindrical protruding portion is not formed. The formation of small annular burrs at the inner peripheral portion of the tip of the fin is suppressed, and the conventional problem as described above can be solved.
[0027]
【The invention's effect】
As can be understood from the above description, according to the present invention, during burring, the workpiece is not handled by the tip of the punch tip, and the inner circumference of the tip of the projection formed into a cylindrical shape is not used. It is possible to prevent annular burrs from being generated in the portion, and to solve the conventional problems as described above.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a shape of a tip portion of a punch chip according to an embodiment of the present invention.
FIG. 2 is an explanatory sectional view showing a configuration of a conventional burring mold.
[Explanation of symbols]
W Workpiece 11 Preparatory hole 13 Hole 15 Die 21 Punch tip 23 Taper part 25 Projection part 27 Connection part

Claims (4)

A method of performing a burring process by inserting a punching tip for burring into a prepared hole formed in a plate-like workpiece, comprising the following steps: For the hole, provided at the tip of the punch tip, a step of inserting a protrusion having substantially the same diameter as the pilot hole from the entrance side of the pilot hole,
(B) a step of enlarging the peripheral edge of the pilot hole outward from the peripheral edge of the exit side when the tip end of the punch tip is pressed into the pilot hole and the edge of the pilot hole is formed into a cylindrical shape;
(C) a step of expanding the peripheral edge of the pilot hole into the outer side from the peripheral edge of the outlet side and pushing the tapered portion on the tip side of the punch tip through the pilot hole to form the edge of the pilot hole into a cylindrical shape; In a punch chip used for burring, the tip side of the punch chip is formed into a tapered portion, and the front end of the tapered portion is fitted into a prepared hole formed in a plate-shaped work, and the entrance of the prepared hole is formed. A punch chip comprising an inlet-side deformation preventing portion protrudingly provided to prevent inward deformation of a side peripheral edge. 3. The punch chip according to claim 2, wherein the tapered portion is a curved surface whose outer peripheral surface has a convex shape. 4. The punch chip according to claim 2, wherein a boundary between the tapered portion and the entrance-side deformation preventing portion is formed as a concave curved surface.

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