JPH062019Y2 - Tapping screw - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a tapping screw.

(Prior Art) Conventionally, when a metal part, a synthetic resin part, or the like is attached to a synthetic resin main body, a screw angle is 60 in a hole provided in a dowel, a boss, or a grommet integrated with the main body.
It is common practice to attach metal parts, synthetic resin parts, or the like to a synthetic resin body by screwing in and tightening a tapping screw formed in an equilateral angle at an angle of °.

(Problems to be solved by the invention) However, when tightening a pilot hole formed in a material having viscoelasticity such as synthetic resin with the above-mentioned conventional tapping screw, the residual volume corresponding to the part where the screw thread volume is excluded When the synthetic resin is plastically deformed and compressed, it recedes,
Therefore, the screw thread progresses and tightening is completed, but with the passage of time, the elasticity of the synthetic resin near the screw thread recovers, and the synthetic resin moves toward the center of the tapping screw in the radial direction. This becomes the residual stress. The movement that occurs in synthetic resin due to this residual stress is
Although it acts in the thread direction, it is blocked by the thread and as a result acts in the direction opposite to the thread and causes cracks in the dowels, bosses, and the like.

Alternatively, the synthetic resin slides irregularly on the side surface of the screw thread, creating a gap between the side surface of the screw thread and the synthetic resin, which reduces the tightening force and may cause vibration, impact, etc. In this case, there is a problem that the screw is loosened.

In view of this, the present invention has a thread angle of 30 ° instead of a tapping screw formed in an equilateral thread shape with a thread angle of 60 °.
Defects that form a continuous two-threaded thread of ~ 45 ° and have a predetermined length in the ridge direction at a position of 180 ° on the circumference of each thread and are perpendicular to the lead angle. Part is formed, and the thread missing portion is provided with a 90 ° phase difference with respect to the adjacent thread, so that the mating member does not crack and the tightening force decreases and loosens. The purpose is to provide a self-tapping screw.

[Constitution of device]

(Means for Solving the Problems) In order to achieve the above object, the present invention comprises a screw thread protruding in a spiral shape along a shaft, and a head having a tool engaging means at one end of the shaft. In the tapping screw, two continuous threads having a thread angle of 30 ° to 45 ° are formed on the shaft portion, and the thread missing portions having different phases are formed on the adjacent threads by the arrangement of the lead angle. It is characterized in that it is formed to be at a right angle to.

(Operation) According to the present invention, by forming a double thread having a thread angle of 30 ° to 45 °, the volume of the portion excluded by the thread volume is reduced to reduce the residual stress.
The use of thread threads prevents a decrease in thread strength and a decrease in workability due to an increase in pitch interval.Furthermore, a thread defect portion with a different phase is formed at a right angle to the lead angle, and The sliding power of synthetic resin can be released. Further, since the thread deficient portion which is perpendicular to the lead angle is formed, the end portion of the thread deficient portion is not chipped. Further, since the thread deficiency portion has a predetermined length in the ridge direction and is provided so as to be 90 ° out of phase with each other, the thread deficiency portion does not act on the mating member at the same time. With the rotation of, the mating member can be prevented from cracking due to the detent effect, and the tightening force will not decrease and will not loosen.

(Embodiment) Hereinafter, the present invention will be described with reference to an embodiment shown in the drawings.
1 is a front view of a tapping screw according to an embodiment of the present invention, FIG. 2 is a cross section of the thread shown in FIG. 1, and FIG.
The cross section of the screw thread having a phase different from that of the figure is shown, and further, FIG. 4 shows a cross section in which the screw thread is partially enlarged. In the embodiments shown in the above-mentioned drawings, a head 4 having a tool engaging means 3 (for example, a cross hole) for driving a screw is provided at one end of the shaft portion 2, and the other end is provided for facilitating introduction into a mating member. The tip portion 5 has an appropriate taper, and the diameter of the valley portion between the lower portion 6 of the shaft portion 2 and the tip portion 5 is almost equal to that of a standard product, and the thread angle θ is 30 °.
Form two continuous threads 7,8 of ~ 45 °,
As shown in FIG. 3 and FIG. 3, the thread deficient portions 9 and 10 having a predetermined length in the ridge direction are formed at positions 180 ° opposite to the thread ridges 7 and 8 at right angles to the lead angle of the thread ridges. At the same time, the adjacent threads 7 and 8 are configured so as to be 90 ° out of phase with each other.

Since the tapping screw 1 according to the present invention is constructed as described above, when the tapping screw 1 is screwed into the pilot hole formed in the mating member made of a material having viscoelasticity such as synthetic resin, the thread volume is increased. Excluded, but thread angle θ is 30 °
~ 45 °, which is smaller than the conventional 60 °.
8 is thin, therefore the amount of the mating member removed by the threads 7 and 8 is small, the residual stress that the residual synthetic resin tries to restore is small, and the mating member does not crack.

In addition, since the double thread is used, the decrease in the thread strength is prevented, and the irregular sliding of the synthetic resin on the side surfaces of the threads 7 and 8 due to a small amount of residual stress prevents the threads 7 and 8 from sliding.
Since it is released by the thread deficient portions 9 and 10 formed in the above, there is no gap between the resin and the synthetic resin.

[Effect of device]

As described above, the present invention has a thread angle of 30 ° to 4 °.
By forming the 5 ° double thread, the shear strength of the thread portion is slightly reduced, but the screwing torque is also reduced.
Then, the volume of the screw thread volume per pitch is eliminated, which reduces the residual stress of the mating member and improves the screwability, so that cracking does not occur and the thread strength decreases. It is possible to prevent the workability from deteriorating due to the increase of the pitch pitch and to further reduce the slipping force of the synthetic resin by forming the thread deficiency. A strong tapping screw can be provided. By forming the thread deficient portion at a right angle to the lead angle, the end portion of the thread deficient portion is formed at 90 ° rather than at an acute angle, and thus the end portion may be chipped as compared with the case of an acute angle. Absent. Furthermore, since the thread deficient portion has a predetermined length in the ridge direction and is provided so as to be 90 ° out of phase with the adjacent thread,
When the tapping screw is screwed in or returned, the thread missing portions of the two threads do not act at the same time, and the thread missing portion of the second thread acts after the thread missing portion of the first thread acts, resulting in a smooth screw. With the rotation of 1st article and 2
There is an effect such that the ridges and the creases alternately have a detent effect.

[Brief description of drawings]

1 is a front view of a self-tapping screw according to an embodiment of the present invention, FIG. 2 is a sectional view of the thread of FIG. 1, FIG. 3 is a sectional view of a thread having a phase different from that of FIG. 2, and FIG. The figure is a cross-sectional view in which a screw thread is partially enlarged. DESCRIPTION OF SYMBOLS 1 ... Tapping screw, 2 ... Shaft part, 3 ... Tool engaging means, 4 ...
Head, 5 ... Tip, 6 ... Under neck, 7, 8 ... Thread, 9, 1
0 ... thread missing part, θ ... thread angle.

Claims (1)

[Scope of utility model registration request] Claim: What is claimed is: 1. A screw thread that spirally protrudes along the shaft portion,
A tapping screw having a head having a tool engaging means at one end of a shaft portion, wherein the shaft portion has a thread angle of 30 ° to 4 °.
In addition to forming two consecutive threads of 5 °,
At a position of 180 ° on the circumference of each screw thread, a thread defect portion having a predetermined length in the ridge direction and being perpendicular to the lead angle is formed. To 9
A tapping screw characterized by being provided with 0 ° phase difference.