JPH10328746A - Burring member and burring method of burring member - Google Patents

Abstract

(57) [Problem] To provide a burring member having a pilot hole shape of a burring member suitable for forming a screw insertion hole in which a large additional processing burr does not occur, and a burring method of the burring member. I do. SOLUTION: This burring member is provided with a prepared hole for burring, and the prepared hole has a substantially polygonal opening shape. Also, a burring method in which a prepared hole of a burring member provided with a prepared hole having a substantially polygonal opening shape is formed by drawing using a die (drawing die) and a burring punch to form a burring. A conical protrusion centered on the main axis at the tip end portion, and the apex angle of the cross section of the conical protrusion including the main axis forms an acute angle.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a burring member and a burring method of the burring member.
The present invention relates to a pilot hole shape of a burring member suitable for forming a screw insertion hole in which no additional burr is generated and a method of processing the same.

[0002]

2. Description of the Related Art Conventionally, when a screw hole is provided in a chassis or the like made of a relatively thin metal plate or the like used for electronic equipment and the like and a mounting screw is screwed into the screw hole to mount an electronic component or the like. The burring consisting of a cylindrical projection is formed integrally by burring the chassis in advance, and the burring is tapped to form a screw insertion hole that secures the vertical stroke of the mounting screw. Parts were stably mounted on the chassis.

FIG. 5 shows an example of a conventional burring method. FIG. 5 is a diagram showing an example of a processing step according to a conventional burring processing method. As shown in FIG. 5A, the chassis 101 for which burring is to be formed
For example, a burring member having a circular pilot hole 102 formed by punching or the like is prepared in advance, and the burring member is mounted on the die 103 in accordance with the guide hole 104 of the die (drawing die) 103.

[0005] Next, as shown in FIG.
While being inserted into the hole, the pilot hole 102 is pressed in the circumferential direction to expand the pilot hole 102 in the direction of the arrow, and the peripheral portion of the pilot hole 102 to be expanded is drawn along the guide hole 103a of the die 103. FIG. 5 (c)
As shown in FIG. 5, a cylindrical burring 105 is formed by drawing a part of the chassis 101.

In general, the burring punch 104 is provided with a conical inclined portion 104a and a projection 104b having substantially the same diameter as the pilot hole 102 at a tip portion of a cylindrical shaft. It is set to approximately 90 degrees. For this reason, the burring punch 104 first
After the protrusion 104b is fitted into the prepared hole 102, the inclined portion 104a further expands the prepared hole 102 so that the prepared hole 1
The periphery of 02 is pushed uniformly from the center of the pilot hole 102 and drawn along the guide hole 103a.

[0006]

As described above, the burring 105 includes the burring punch 104 and the die 10.
By drawing a part of the chassis 101 around the circular pilot hole 102 using the center hole 3, the cylindrical burring 10 having substantially the same diameter as the guide hole 103 a of the die 103 is formed.
5 are formed in a direction perpendicular to the chassis 101. In the above-described drawing, the inner wall of the burring 105 is formed by an annular area near a relatively cylindrical axis on the slope of the inclined portion 104a of the burring punch 104. Since the molding is performed while being squeezed, the portion that is squeezed by the inclined portion 104a on the inner wall side of the burring 105 being formed is subjected to the shearing force intensively.

As a result, near the inner wall outlet of the formed burring 105, as shown in FIG. 6 (a), a part of the inner wall side of the burring 105 pulled by the shearing force extends around the inner wall outlet. 6B, and protrudes from the inner wall outlet to form a ring-shaped sharp edge 105a. In some cases, as shown in FIG. 6B, an ironing burr 105b with a part of the sharp edge 105a cut off is formed. May be generated. FIG. 6 is a diagram showing an example of a sharp edge and an iron burr formed by a conventional burring process.

Further, when a screw insertion hole is formed by an additional process of tapping the inner wall side of the burring 105, the sharp edge 105a and the
In some cases, part or all of the ring-shaped part 5b may be detached from the burring 105 having the screw insertion hole, resulting in a large chassis burr.

When the chassis burr is large as described above, if it adheres to various parts in the electronic device, it may cause a malfunction of the circuit or the like. If exists,
It is necessary to remove this from the inside of the electronic device in advance, and the number of steps increases accordingly.

The present invention has been made in view of the above-mentioned problems, and has a burring member having a pilot hole shape of a burring member suitable for forming a screw insertion hole which does not generate large burrs, and a burring member of the burring member. It is intended to provide a processing method.

[0011]

According to the first aspect of the present invention,
A burring member provided with a pilot hole for burring, wherein the pilot hole has a substantially polygonal opening shape.

According to a second aspect of the present invention, a burring is formed by drawing a prepared hole of a burring member provided with a prepared hole having a substantially polygonal opening shape using a die (drawing die) and a burring punch. The burring punching method is characterized in that the burring punch has a conical projection centered on the main axis at the tip end portion, and the apex angle of the cross section of the conical projection including the main axis forms an acute angle.

[0013]

Since the present invention is constructed as described above, when forming a burring by drawing a prepared hole of a burring member, even if a shearing force is generated in the circumferential direction of the cylindrical burring being formed. Since the shearing force is dispersed within each side of the polygonal opening shape of the pilot hole,
Even when sharp edges and burrs are generated, the sharp edges and burrs are dispersed and small within the range of each side.

Further, when the pilot hole of the burring member is formed by drawing, the area where the conical projection of the burring punch comes into contact with the burring member during burring becomes large, and the force applied per unit contact area during the processing is small. Therefore, the shearing force applied to the burring member at the portion in contact with the burring punch is reduced. For this reason, when burring is formed, it is difficult to generate sharp edges and ironing burrs.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a preferred embodiment of the present invention will be described below with reference to the drawings. Drawing 1 is a figure showing an example of the principal part of the burring member in one embodiment of the present invention, (a) shows the sectional view of the burring member, and (b) shows the figure which looked at the burring member from the upper surface. ing.

The chassis 1 is a burring member made of a relatively thin metal plate, and is provided with a pilot hole 2 for burring as shown in FIG. The pilot hole 2 is formed by, for example, a punching process or the like.
As shown in (b), it has a substantially triangular opening shape inscribed in a circle about the axis X. Note that FIG.
It is sectional drawing represented by the cross section along AA of (b).

FIG. 2 is a sectional view of a burring punch and a die (drawing die) used for burring the burring member shown in FIG. 1. FIG. 2A is a sectional view of the burring punch. b) shows a sectional structural view of the die (drawing type). The burring punch 3 is shown in FIG.
As shown in FIG. 2, a conical projection 3b is provided continuously at the tip of a cylindrical shaft 3a having a predetermined outer diameter, and the apex angle θ is set to an acute angle (about 60 degrees in FIG. 2). ing.

Further, as shown in FIG. 2B, the die (drawing die) 4 is formed by a gate portion 4a having a predetermined inner diameter and a part of a conical shape gradually expanding continuously from the gate portion 4a. It has a guide hole 4b.

In the present embodiment, the burring member is burred by using the burring punch 3 and the die 4 described above, so that the inner diameter substantially equal to the outer diameter of the shaft 3a of the burring punch 3 and the gate portion 4a of the die 4 are formed. And a cylindrical burring 5 having an outer diameter substantially equal to the inner diameter of the burring 5.

Next, a burring method of the burring member shown in FIG. 1 will be described. FIG. 3 is a diagram showing an example of a burring method of the burring member of FIG. 1 in the order of steps by (a) to (c).

First, as shown in FIG. 3 (a), the prepared hole 2 is aligned so that the axis X passing through the substantially center of the prepared hole 2 becomes substantially the center of the gate portion 4a, and the chassis 1 is mounted on the die 4. Mount on top. Here, the pilot hole 2 is represented by a cross section shown in FIG.

Next, the burring punch 3 set coaxially with the center axis of the die 4 is moved vertically downward (in the direction of the arrow in the figure) toward the center of the pilot hole 2 while rotating from above the chassis 1.

In this case, since the prepared hole 2 has a substantially triangular opening shape, the slope of the conical projection 3b first comes into contact with each base of the substantially triangular shape of the prepared hole 2, and then the base of the prepared hole 2 is further lowered. It moves vertically downward while bending and pushing down. Therefore, first of all, the portion of the peripheral portion of the pilot hole 2 corresponding to the vicinity of substantially the center of each base of the substantially triangular shape is gradually pushed down by the slope of the conical projection 3b, and is sequentially pushed and spread along the rotation direction of the burring punch 3. It is stretched under shear forces along these directions.

At this time, since the apex angle of the conical projection 3b is set to an acute angle, when the peripheral portion of the pilot hole 2 is sequentially extended, the entire surface of the extended portion always comes into close contact with the slope of the conical projection 3b. Therefore, the shearing force does not concentrate locally.

As described above, when the burring punch 3 sequentially moves vertically downward while the portion corresponding to the vicinity of the approximate center of each base of the substantially triangular portion of the peripheral portion of the pilot hole 2 is stretched, the conical projection is formed. After the slope 3b abuts on a portion corresponding to each vertex of the substantially triangular shape in the peripheral portion of the pilot hole 2, the entire opening portion of the pilot hole 2 including this portion is pushed downward while being bent downward ( FIG. 3 (b)).

Also in this case, the portions corresponding to the vertices of the substantially triangular shape are subjected to the same shearing force as the portions at the bases of the above-described substantially triangular shape, so that the shearing force is stretched without being concentrated locally. Become.

Therefore, the portion of the peripheral portion of the pilot hole 2 which is successively stretched thereafter always has its entire surface in close contact with the slope of the conical projection 3b, and the above-mentioned shearing force does not concentrate locally.

Next, when the burring punch 3 moves further downward and the shaft 3a moves into the gate portion 4a, FIG.
As shown in FIG. 3 (b), when the peripheral portion of the pilot hole 2 which has already been stretched is narrowed down sequentially between the shaft 3a and the gate portion 4a, as shown in FIG.
A cylindrical burring 5 having an inner diameter substantially equal to the outer diameter of the shaft 3a and an outer diameter substantially equal to the inner diameter of the gate portion 4a of the die 4 is formed.

The burring 5 is formed by narrowing the substantially triangular opening shape of the pilot hole 2 in this manner. Of the peripheral portion of the pilot hole 2, the portion corresponding to the base of the substantially triangular shape is more suitable. Since the degree of squeezing is greater than the portion corresponding to the vertex of the substantially triangle, as shown in FIG.
The height of the cylinder of the formed burring 5 is higher in the partial area 5a of the cylindrical outlet corresponding to the central portion of the base of the substantially triangular shape than in the partial area 5b of the cylindrical outlet corresponding to the apex angle of the substantially triangular shape. Become.

Therefore, even if a shearing force is generated in the circumferential direction of the cylindrical burring during molding, the shearing force is limited to the area of the peripheral portion corresponding to each side of the substantially triangular opening shape of the pilot hole 2. Therefore, even when a sharp edge or an iron burr is generated, the sharp edge or the iron burr is dispersed and small within the range of each side.

FIG. 4 is an external view of the burring 5 thus formed. As shown in the figure, it can be seen that the cylindrical outlet of the burring 5 is formed in a shape in which the partial region 5a is a mountain and the partial region 5b is a valley.

As a result, the inner wall side of the burring 5 formed by squeezing the peripheral portion of the pilot hole 2 after being stretched does not receive the shearing force of the burring punch 3 intensively. At the cylindrical outlet,
The conventional ring-shaped sharp edge 105a is not formed.

Therefore, when a tapping process is further performed to form a screw insertion hole in the cylinder of the burring 5 thus formed, a part of the conventional ring-shaped sharp edge 105a or a part of the ironing burr 105b is formed. It does not create large chassis burrs for all.

In the above-described embodiment, the pilot hole of the burring member is substantially triangular. However, the pilot hole may have a polygonal shape. Has peaks and valleys corresponding to the vertices and sides of the polygon, and in this case, the same effect as that of the present embodiment can be obtained.

The conical projection of the burring punch only needs to have an acute apex angle θ, and in this case, the same effect as in the present embodiment can be obtained.

[0036]

According to the present invention, as described above, when a burring is formed by drawing a pilot hole of a burring member, a shearing force is generated in the circumferential direction of the cylindrical burring being formed. However, since the shearing force is dispersed within each side of the polygonal opening shape of the prepared hole, even when sharp edges and ironing burrs are generated, the sharp edges and ironing burrs are Are dispersed and smaller within the range.

Further, when the pilot hole of the burring member is formed by drawing, the area where the conical projection portion of the burring punch comes into contact with the burring member during burring becomes large, and the force applied per unit contact area during the processing is small. Therefore, the shearing force applied to the burring member at the portion in contact with the burring punch is reduced. For this reason, when burring is formed, it is difficult to generate sharp edges and ironing burrs. Therefore, even if a tapping process is additionally performed on the burring to form a screw insertion hole, a large additional processing burr does not occur.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating an example of a main part of a burring member according to an embodiment of the present invention.

FIG. 2 is a sectional structural view of a burring punch and a die (drawing type) used for burring.

FIG. 3 is a diagram illustrating an example of a burring method of a burring member.

FIG. 4 is an external view of a burring according to the present invention.

FIG. 5 is a diagram showing an example of a conventional burring method.

FIG. 6 is a view showing an example of a sharp edge and an iron burr formed by a conventional burring process.

[Explanation of symbols]

 1 ··· Chassis 2 ····· Prepared hole 3 ··· Burring punch 3a ··· Shaft 3b ··· Conical projection 4 ··· Die (drawing type) 4a ··· ..Gate portion 4b Guide hole 5 Burring 5a Partial area 5b Partial area

Claims (2)

[Claims] 1. A burring member provided with a pilot hole for burring, wherein the pilot hole has a substantially polygonal opening shape. 2. A burring method in which a burring is formed by drawing a prepared hole of a burring member provided with a prepared hole having a substantially polygonal opening shape using a die (drawing die) and a burring punch. The burring punch has a conical protrusion centered on a main axis at a tip portion, and a vertex angle of a cross section of the conical protrusion including the main axis forms an acute angle.