JP2008002575A - Boss for self-tapping screw - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a boss for self tapping screw whose boss can be prevented from breaking using a simple metallic mold. <P>SOLUTION: The boss for self tapping screw includes a V-shaped groove 14 for preventing the boss axially extending in an inner cylindrical surface 12 from breaking and a reinforcing rib 18 formed in an outer cylindrical surface 16 opposed to the groove to prevent the boss from breaking. The groove reduces distortion and a rib for preventing the boss from breaking due to the presence of the groove is provided. As a result, the boss can be prevented from breaking. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a self-tapping screw boss, and more particularly to a resin-molded self-tapping screw boss that prevents cracking of the boss during self-tapping.

  When inserting the self-tapping screw into the self-tapping boss, the self-tapping screw is inserted while tapping the inner diameter of the self-tapping screw boss. Therefore, the inner diameter of the self-tapping boss is smaller than the outer diameter of the self-tapping screw.

  For this reason, the self-tap boss is distorted in accordance with the amount of overlap between the inner diameter of the self-tap screw boss and the outer diameter of the self-tap screw, causing cracks to occur from weak locations such as weld lines.

In order to cope with this, a self-tapping boss has been proposed in which a plurality of grooves are provided in the inner diameter of the self-tapping screw boss to release strain (Patent Document 1).
JP 2004-36655 A

  However, Patent Document 1 has the following drawbacks. Since the pin shape of the injection mold for creating a plurality of grooves is complicated, there has been a problem that mold preparation and maintenance are difficult. Moreover, since the thickness of the boss for self-tapping is not uniform, there is a possibility that strain concentrates on the thin-walled portion and a crack occurs. In addition, since the plurality of grooves are formed, the area on which the screw is applied is reduced, and the screw tightening torque may be insufficient. Moreover, in order to compensate for the shortage of the screw tightening torque, it is necessary to increase the screw length, and there is a problem that the size cannot be reduced.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a self-tap screw boss that prevents the boss from cracking with a simple mold.

  In order to achieve the object, the self-tap screw boss according to claim 1 is formed in a groove for preventing a boss crack extending in an axial direction on an inner cylinder surface and an outer cylinder surface facing the groove, and the groove It is characterized by having reinforcing ribs for preventing cracks at the top. Thereby, the boss | hub for self tap screws which prevents the crack of a boss | hub can be provided.

  The self-tap screw boss according to claim 2 is the self-tap screw boss according to claim 1, wherein the groove has a V-shape. Thereby, it is possible to concentrate stress in the groove more reliably.

  According to a third aspect of the present invention, there is provided the self-tapping screw boss according to the first aspect, wherein the groove has an arc shape. Thereby, since a mold shape can be made easy, the mold life is improved and a stable shape can be obtained.

  According to a fourth aspect of the present invention, there is provided a self-tapping screw boss according to any one of the first to third aspects, wherein a plurality of the grooves and the reinforcing ribs are provided. Thereby, it is possible to provide a self-tapping screw boss having a more appropriate shape and preventing cracking of the boss with respect to the self-tapping screw boss of various diameters.

  The self-tap screw boss according to claim 5 is the self-tap screw boss according to any one of claims 1 to 4, wherein the rib for preventing the boss from collapsing, or a rib for reinforcing the component on which the boss is arranged. It is characterized by being a reinforcing rib that is also used. Thereby, the width of the arrangement of the component shape elements is widened, and the degree of freedom in design can be increased.

  ADVANTAGE OF THE INVENTION According to this invention, the boss | hub for self tap screws which prevents the crack of a boss | hub with a simple metal mold | die can be provided. In addition, since the boss having a small outer diameter (thin wall thickness) can prevent cracking, the degree of freedom in design can be increased.

  The best mode for carrying out a self-tap screw boss according to the present invention will be described below in detail with reference to the accompanying drawings.

  FIG. 1 is a perspective view of a self-tap screw boss 10 according to a first embodiment of the present invention.

  A V-shaped groove 14 having a V-shape is formed on the inner cylindrical surface 12 of the self-tap screw boss 10. A reinforcing rib 18 is formed on the outer cylindrical surface 16 facing the V-shaped groove 14.

  When a tapping screw (not shown) is inserted into the inner cylinder surface 12 of the self-tap screw boss 10 while being rotated for fastening, the inner cylinder surface 12 is distorted by tapping. The inner cylindrical surface 12 expands in the circumferential direction due to strain, but the expansion is absorbed by the V-shaped groove 14, so that strain applied to the outer peripheral surface 16 is reduced.

  However, since stress concentrates on the V-shaped groove 14, the portion of the V-shaped groove 14 is likely to be cracked. Here, by installing the reinforcing ribs 18 that prevent cracks in the grooves, it is possible to provide sufficient strength so that cracks do not occur.

  According to the present embodiment, it is possible to provide a self-tap screw boss that prevents the boss from cracking. Further, since only a part of the outer cylindrical surface 16 needs to be enlarged, the entire outer diameter of the self-tap screw boss can be reduced.

  FIG. 2 is a perspective view of a self-tap screw boss 20 according to a second embodiment of the present invention.

  An R-shaped groove 24 having an arc shape is formed on the inner cylindrical surface 22 of the self-tap screw boss 20. A reinforcing rib 28 is formed on the outer cylindrical surface 26 facing the R-shaped groove 24.

  When a tapping screw (not shown) is inserted into the inner cylinder surface 22 of the self-tap screw boss 20 while rotating for fastening, the inner cylinder surface 22 is distorted by tapping. The inner cylindrical surface 22 expands in the circumferential direction due to strain, but since the expansion is absorbed by the R-shaped groove 24, strain on the outer peripheral surface 26 is reduced.

  At this time, stress concentrates on the R-shaped groove 24, so that the portion of the R-shaped groove 24 is likely to be cracked. However, the reinforcing ribs 28 can have sufficient strength to prevent cracking.

  The second embodiment is characterized in that the groove has an arcuate shape as compared with the first embodiment. Since the shape of the groove can be simplified by making the shape of the groove into an arc shape, the life of the mold can be prolonged and the shape can be stabilized. According to the present embodiment, it is possible to provide a self-tapping screw boss having a stable shape that prevents the boss from cracking.

  In addition, in the said embodiment, although the groove | channel and the reinforcement rib are formed in one place, you may install in not only one place but in multiple places.

  In the above embodiment, the V-shaped or arc-shaped groove is formed from the inner cylinder surface, but the straight portion is between the inner cylinder surface and the V-shaped or arc-shaped shape. May be provided.

  FIG. 3 is a perspective view of a self-tap screw boss 30 according to a third embodiment of the present invention.

  V-grooves 32 and 34 are provided on the inner cylindrical surface 31 of the self-tapping screw boss 30 for releasing strain caused by tapping. Reinforcing ribs 36 and 38 are formed on the outer cylindrical surface 35 facing the V-shaped grooves 32 and 34.

  The self-tap screw boss 30 is disposed integrally with a rib 40 that reinforces a component on which the self-tap screw boss 30 is disposed. The reinforcing rib 36 is disposed integrally with one end 42 of the rib 40, and the reinforcing rib 38 is disposed integrally with the other end 44 of the rib 40. According to the present embodiment, the width of the arrangement of component shape elements such as bosses and ribs is widened, and the degree of design freedom can be increased.

  In the above embodiment, the reinforcing rib is also used as a rib that reinforces the component on which the self-tap screw boss is disposed. However, the reinforcing rib may also be used as a rib that prevents the self-tapping screw boss from falling.

  Moreover, in the said embodiment, although the groove | channel and the reinforcement rib were installed in two places, you may install not only in two places but in one place or three places or more.

  In the above embodiment, the height of the upper end surface 30 ′ of the self-tap screw boss 30 is higher than the height of the upper end surface 40 ′ of the rib 40. And the height of the upper end surface 40 ′ of the rib 40 may be matched.

  Moreover, in the said embodiment, although it was set as the V-shaped groove | channel which has a V-shaped shape, the groove | channel which has an arc shape may be sufficient, and an inner cylinder surface and a V-shaped shape or circular arc shape may be sufficient. A straight portion may be provided between the two.

It is a perspective view of the boss | hub for self-tap screw which concerns on the 1st Embodiment of this invention. It is a perspective view of the boss | hub for self-tap screw which concerns on the 2nd Embodiment of this invention. It is a perspective view of the boss | hub for self-tap screw which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

10 ... Self-tapping screw boss, 14 ... V-shaped groove, 18 ... Reinforcing rib, 20 ... Self-tapping screw boss, 24 ... R-shaped groove, 28 ... Reinforcing rib, 30 ... Self-tapping screw boss, 40 ... Rib

Claims (5)

A groove for preventing boss cracks extending in the axial direction on the inner cylinder surface;
Reinforcing ribs formed on the outer cylinder surface facing the groove and preventing cracks in the groove;
A self-tapping screw boss that is provided.   The self-tapping screw boss according to claim 1, wherein the groove has a V-shape.   The self-tapping screw boss according to claim 1, wherein the groove has an arc shape.   The self-tapping screw boss according to any one of claims 1 to 3, wherein a plurality of the grooves and the reinforcing ribs are provided. 5. The reinforcing rib according to claim 1, wherein the reinforcing rib is a rib for preventing the boss from collapsing or a rib for reinforcing a component on which the boss is disposed. Boss for self-tapping screws.

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