JPH10103322A - Fastening structure of tapping screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a screw from loosening due to time elapsed without using other parts by making the hole diameter of a soft material smaller than the diameter of a tapping screw thread when the soft material is fastened together to a metal material with the tapping screw from the side of the soft material. SOLUTION: A hole 4 of ϕ dC which is smaller than the outside diameter ϕdA of the screw thread of a tapping screw 3 is opened on an iron plate 1 and a female screw is constituted by fastening the screw 3. A hole 5 of ϕ dB which is smaller than the outside diameter ϕ dA of the screw thread is provided also on a plastic parts 2 and the female screw is formed to the hole 5 by fastening the screw 3. At this time, a pawl 6 is provided to prevent the parts 2 from revolving together with the screw 3. When the tip part of the screw 3 passes the parts 2 and enters the hole 4, the formation of the female screw can not be smoothly performed and the screw 3 occasionally idles. A pawl 7 is provided to prevent the parts 2 from floating from the iron plate 1 at this time. Thus, the screw part comes into contact with the parts 2, friction is increased and the screw loosening can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure in which a soft member is jointly fastened to a metal member by tapping screws.

[0002]

2. Description of the Related Art Generally, when a soft member is fastened to a metal member with a self-tapping screw, a hole larger than the thread outer diameter is provided in the soft member, and a lower hole of the metal member having a diameter smaller than the screw outer diameter. The tapping screw is tightened while forming the female screw, and the soft member is sandwiched between the screw head and the metal member. In this structure, the soft member is deformed due to the creep phenomenon with the passage of time, the force for pushing back the screw is lost, the frictional force of the contact portion of the screw thread with the metal member is reduced, and the screw is loosened in a place accompanied by vibration. Sometimes. When the first tightening is performed while forming the female screw, there is no looseness due to the large frictional force between the tapping screw and the metal member. After the second tightening, since the frictional force between the tapping screw and the metal member is obtained by the repulsive force of the soft member against the screw head, the soft member is loosened due to the deformation. As means for preventing this, there are methods such as using a spring washer having elasticity in a thrust direction, a washer with a blade having sharp unevenness in a thickness direction, or applying an adhesive to a screw portion.

[0003]

However, these methods increase the number of parts and increase the cost, and it is difficult to automatically supply these parts together with screws when tightening by an automatic machine. . In addition, when applying the adhesive, there is a drawback that the detachment is not easy and the adhesive must be applied again when the adhesive is attached again.

An object of the present invention is to provide a tightening structure that can prevent loosening of a screw with the passage of time without using a separate part.

[0005]

A feature of the present invention resides in that the hole diameter of the soft member is smaller than the thread diameter of the tapping screw.

[0006]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a state in which a plastic part 2 is attached to an iron plate 1 with a tapping screw 3. The iron plate 1 has a hole 4 of φd _C smaller than the thread outer diameter φd _A , and a female screw is formed when the tapping screw 3 is tightened. In the plastic part 2 will form a female screw into the hole 5 when tightened tapping screw 3 is provided with a hole of smaller .phi.d _B than the thread outer diameter .phi.d _A. At this time, a claw 6 is provided to prevent the plastic part 2 from rotating together with the tapping screw 3. When the tip of the tapping screw 3 passes through the plastic part 2 and enters the hole 4 of the iron plate 1, the female screw cannot be formed smoothly, and the tapping screw 3 may idle. At this time, the plastic part 2 may rise from the iron plate 1.
Is provided.

As described above, the iron plate 1 and the plastic part 2 fastened together by the self-tapping screw 3 are (thread outer diameter φd
_A)> (prevents the pilot hole diameter .phi.d _B) and to screw loosening increases the contact and friction screw portion and the plastic part 2 shown in 8 of Fig. 2 by the plastic parts. In addition, when the screw is once removed and the screw is tightened again, the female screw of the iron plate and the female screw of the plastic are not aligned. As a result, the female screw portion of the plastic forms a new crest and a friction force can be obtained. However, if the diameter of the prepared hole 5 of the plastic is a hole diameter for forming an ideal female screw like the prepared hole 4 of the metal member, it is difficult to collapse.
It is preferable to make the diameter larger than the prepared hole diameter φd _{C of the} metal member because the close contact with the metal member 1 cannot be performed. In the above embodiment, a tapping screw having a continuous thread is illustrated. However, a tapping screw having a discontinuous thread may be used.

[0009]

As described in detail above, according to the present invention, the screw can be prevented from being loosened due to vibration or the like without using a separate part. .

[Brief description of the drawings]

FIG. 1 is a sectional view of a state before a self-tapping screw is tightened.

FIG. 2 is a cross-sectional view in a state where the screw is tightened by a tapping screw.

[Explanation of symbols]

1 ... iron plate, 2 ... plastic parts, 3 ... tapping screw,
Reference numeral 4: Prepared hole of iron plate, 5: Prepared hole of plastic parts, 6: Claw for rotation prevention, 7: Claw for preventing lifting, 8: Contact part of screw.

Claims (5)

[Claims] 1. A structure for fastening a soft member to a metal member with a tapping screw from the side of the soft member, wherein the diameter of the hole of the soft member is smaller than the outer diameter of the thread of the tapping screw. 2. The tapping screw tightening structure according to claim 1, wherein the hole diameter of the soft member is smaller than the thread outer diameter of the tapping screw and larger than the hole diameter of the metal member. 3. A tapping screw tightening structure according to claim 1, wherein a plastic material is used as the soft member and an iron plate material is used as the metal member. 4. The tapping screw tightening structure according to claim 1, wherein the tapping screw is formed of a material harder than the metal member and the soft member. 5. The tightening structure for a tapping screw according to claim 1, wherein a lifting prevention claw for preventing the metal member from lifting when forming the tapping screw is formed on the soft member.