JP2606443Y2 - Screw fastening structure - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw fastening structure in which a fastening member and a member to be fastened, both of which are made of a resin material, are overlapped and fastened by tapping screws.

[0002] For information processing equipment and the like, molded parts of a resin material are frequently used. For the attachment, a tapping screw that can be screwed into the prepared hole and fastened is used in view of assembly cost. However, since the expansion and contraction of the resin molded part due to the passage of time and the vertical movement of the environmental temperature are repeated, the screw fastening force is reduced and the tapping screw is loosened. Therefore, a structure capable of preventing the screw from being loosened is desired.

[0003]

2. Description of the Related Art As shown in an exploded side sectional view and an assembled side sectional view of a main part of FIGS. 2A and 2B, a conventional screw fastening structure has a structure in which a fastening member 11 and a member to be fastened 12 are both made of resin material. For example, when fastening with a tapping screw 13 (made of steel or stainless steel) having a nominal diameter of 4 mm, a pilot hole 11 having a diameter of 3.1 mm is used.
a, and a member to be fastened 12 having a fool hole 12a having a diameter of 5 mm is overlapped, and a tapping screw 13 is passed through the fool hole 12a of the to-be-fastened member 12 to form a lower hole 11a of the fastening member 11.
The screw is screwed while cutting the screw.

[0004]

However, according to the above-described screw fastening structure, the member to be fastened is screwed between the head of the tapping screw and the fastening member, and the screw of the tapping screw is tightened. Since the fastening force is maintained only by the frictional force generated between the lower surface of the head and the screw hole of the fastening member, the screw fastening force decreases due to expansion and contraction due to the passage of time and environmental temperature, and the tapping screw loosens. There was such a problem.

[0005] In view of the above problems, an object of the present invention is to provide a screw fastening structure that can prevent a tapping screw screwed into a resin material from being loosened.

[0006]

To achieve the above object, according to the solution to ## in the screw fastening structure of the present invention, the fastening member and the fastening member, <br/> threaded at tapping screw having threads of the same nominal diameter is bored down hole both being, and the diameter of the lower hole of the fastening member side (inside diameter) is, in so that a smaller than the screwing torque of the screwing torque fastening member of the fastening member, the fastening member side The diameter is larger than the diameter (inner diameter) of the pilot hole.

[0007]

In the present invention, not only the fastening member but also the member to be fastened is provided with a pilot hole which is threaded by a tapping screw, and the diameter of the pilot hole of the member to be fastened is at least larger than that of the fastening member. In addition to the frictional force between the head portion of the conventional tapping screw and the screw-down portion of the fastening member, the frictional force of the screw-down portion of the to-be-fastened member is further applied.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The gist of the present invention will be described below in detail with reference to the embodiments shown in the drawings. As shown in the exploded side sectional view and the assembled side sectional view of FIGS. 1 (a) and 1 (b), the screw fastening structure according to the present invention has a fastening member 1 which is formed of a resin material and has a boss. (Polycarbonate / ABS with a boss thickness of 13mm
When fastening a plate-shaped fastening member 2 (alloy resin) and a plate-shaped member to be fastened 2 (polycarbonate resin containing glass fiber with a thickness of 4.5 mm) with a tapping screw 3 having a nominal diameter of 4 mm and a length of 14 mm below the neck as in the conventional case, the fastening member 1 And the to-be-fastened member 2 both form pilot holes 1a, 2a for the tapping screw 3.

The fastening member 1 in this embodiment has a diameter of 3.1 m.
A hole (blind hole) 1a having a diameter of 15 mm and an effective depth of 15 mm is formed, and the member to be fastened 2 is formed with a hole (through hole) 2a having a diameter of 3.6 mm.
A member 2 to be fastened is closely attached to the fastening member 1, and a tapping screw 3 is screwed into the holes 1a and 2a from both sides of the member 2 to be fastened.

In this embodiment, in consideration of the workability, the screwing torque of the member 2 to be screwed first is made smaller than that of the member 1 to be screwed next, and the tapping screw 3 is easily closed. The diameter of the prepared hole 2a of the fastening member 2 is made larger than that of the prepared hole 1a of the fastening member 1, so that the screwing torque of the fastening member 2 alone is about 7.5 kgf · cm, and the screwing torque of the fastening member 1 alone is about 9.5 kgf · cm. cm, total screwing torque
It is about 17kgf ・ cm.

If the plate thickness of the member to be fastened 2 is smaller than the nominal diameter of the tapping screw 3, the diameter of the pilot hole 2a may be approximately the same as the diameter of the pilot hole 1a of the fastener 1. Also,
When screwing the tapping screw 3, it is important to firmly hold down the member to be fastened 2 so as not to float.

In order to conduct a comparative test of screw looseness, 10 samples each of the screw fastening structure of the present invention and a sample of the screw fastening structure according to the prior art were prepared, and the MIL standard 202F-1 of the United States was prepared.
Based on the temperature / humidity cycle test conditions of 06, the screw return torque after 7 cycles of 168 hours was 4.2 kgfcm for the screw fastening structure according to the conventional technology, whereas the screw fastening structure of the present invention An increase of about 20% was observed at 4.9 kgf · cm.

As described above, by forming a pilot hole screwed by a tapping screw into both the fastening member and the member to be fastened, and making the diameter of the hole of the member to be fastened at least larger than the diameter of the hole of the fastening member. In addition to the conventional frictional force between the lower surface of the head of the tapping screw and the threaded portion of the fastening member, in the present invention, the frictional force of the threaded portion threaded into the lower hole of the member to be fastened is added, so that the resin molded part It is possible to prevent the self-tapping screw from being loosened due to repetition of expansion and contraction due to aging or a temperature cycle.

[0014]

[Effect of the Invention] As described above, according to the present invention,
Since the tapping screw can be prevented from being loosened against the resin material, it can be applied to information processing equipment that is frequently used for resin molded products, and has an extremely useful effect in practical use such as improvement in quality and reliability. .

[Brief description of the drawings]

FIG. 1 is an exploded side sectional view of an essential part of an embodiment according to the present invention and an assembled side sectional view thereof.

FIG. 2 is an exploded side sectional view and an assembled side sectional view of a main part according to the prior art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fastening member 1a Prepared hole 2 Member to be fastened 2a Prepared hole 3 Tapping screw

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-167913 (JP, A) JP-A 52-106762 (JP, U) JP-A-6-73422 (JP, U) (58) Investigation Field (Int.Cl. ⁷ , DB name) F16B 5/00-5/12 F16B 25/00

Claims (1)

(57) [Scope of request for utility model registration] 1. A screw fastening structure for fastening a fastening member and a tapping screw overlapping the workpieces, the The fastening member and the fastening member, have the screw of the same nominal diameter
A pilot hole threaded with a self-tapping screw is formed on both sides , and the diameter of the pilot hole on the member-to-be-fastened is such that the screwing torque of the member-to-be-fastened is smaller than the screwing torque of the fastening member .
Remote on so that a smaller, than the diameter of the lower hole of the fastening member side
A screw fastening structure characterized by being enlarged .