JPH0231606Y2 - - Google Patents

Description

[Detailed explanation of the idea] Industrial applications This invention relates to a self-tapping screw.

Prior Art Conventionally, when joining two members, as shown in FIG. 6, a pilot hole 22 or the like is provided in the member 21 on one side, and a self-tattle is provided in the through hole 24 of the member 23 on the other side. A self-tapping screw is known in which a pin screw 25 is inserted and the self-tapping screw 25 is screwed into the prepared hole 22 etc., thereby forming a female thread in the prepared hole 22 and tightening the screw. It is widely used because of its good workability.

Problems that the invention aims to solve However, in recent years, resins have come to be used extensively in components that make up equipment such as automobiles and electrical appliances. The boss 26, etc. on the pilot hole side may crack due to a low torque, the diameter of the pilot hole may expand due to over-tightening, making it impossible to tighten the screw, or the bolt may become loose due to insufficient holding force. It had disadvantages such as being easy to use. For this reason, various tapping screws have been provided with the aim of improving the fastening performance to resin, but all of them have advantages and disadvantages and have not been able to solve the above-mentioned drawbacks.

Means for Solving the Problems Therefore, in order to solve the problems of the conventional self-tapping screws mentioned above, this invention aims to solve the problems of the above-mentioned conventional self-tapping screws. and a second flank part that is disposed between the plurality of first flank parts and whose radial cross-sectional area is formed to be smaller than the radial cross-sectional area of the first flank parts. To provide a self-tapping screw characterized by forming a self-tapping screw.

Function In the self-tapping screw of this invention, since the pressure side flank surface is flat through the first flank part and the second flank part, screwing can be performed reliably. Even if the hole is cut deeply into the pilot hole, the recess is provided on the play side flank surface of the second flank part and the cross-sectional area is small, so it is possible to prevent the situation where the pilot hole side breaks. It is possible to avoid a situation where the screw cannot be tightened even if a certain amount of tightening force is applied.

Embodiment Referring to FIGS. 1, 2, and 3 showing an embodiment of this invention, a self-tapping screw 1 is
Generally, it consists of a head 2 and a shaft part 3 continuous to the center of the seat surface of the head 2, and a means 4 for engaging with a tightening rotary tool (not shown) is provided on the top surface of the head 2. The shaft portion 3 is provided with a spiral threaded portion 7 extending from the head and neck lower portion 5 to the distal end portion 6 of the shaft portion 3, and the threaded portion 7 has a thread angle approximately in the range of 45° to 55°. Pressure side flank surface 10 that intersects at any angle within
and a free side flank surface 11, the first flank portion 8 having an outer diameter equal to the nominal diameter of the screw, and a first flank portion 8 that is parallel to the play side flank surface 11 and has a small diameter. A depressed flank surface 1 arranged close to the pressure side flank surface 10 by the dimension
2, a recess 13 is provided extending in a direction intersecting the lead angle of the screw.
Second flank portions 9 having a smaller radial cross-sectional area than the flank portion 8 are provided alternately and in a continuous manner, and the recessed portion 13, that is, the installation position of the second flank portion 9 is the screw of the threaded portion 7. Provided at equal intervals along the direction. If desired, the recess 13
In other words, the length of the second flank portion 9 in the thread direction is 1/6 or less of the length of one screw lead, and the number of recesses 13 is set to be at least two or more per screw lead. do.

Referring to FIG. 4 showing another embodiment of this invention, in this embodiment, in forming the second flank part 9, the second flank part 9 and the first flank part 8 are
The peak portion 15 of the first flank portion 8 is made common, and the intersection angle between the depressed flank surface 12 and the pressure side flank surface 10 is roughly determined from the thread angle of the first flank portion 8.
The second flank portion 9 is formed smaller by 1° to 2.5°, thereby forming the recess 13, and the radial cross-sectional area of the second flank portion 9 is reduced.Other configurations are the same as in the first embodiment. The same is true.

Referring to FIG. 5 showing yet another embodiment of the invention, in this embodiment, in forming the second flank portion 9, the bottom edge 16 of the concave flank surface 12 of the second flank portion 9 and the The bottom edge 16 of the free side flank surface 11 of the first flank portion 8 is set at a common position, and the intersecting angle between the depressed flank surface 12 and the pressure side flank surface 10 is set so that the above free side flank surface 11 and the pressure side flank surface 10 intersect with each other. The second flank 9 is formed to be 1° to 2.5° larger than the thread angle that is the intersecting angle with the side flank surface 10, thereby forming a recess 13 and reducing the radial cross-sectional area of the second flank 9. in,
The other configurations are the same as those of the first embodiment.

If desired, the thread angle, the value of the recessed flank surface, the arrangement, etc. can be changed as appropriate depending on the location where the self-tapping screw is used.

Effects of the invention In the self-tapping screw of this invention, during screwing, the second flank has a recess on the play side flank surface, so that the second flank part presses into the surrounding material on the play side. is avoided,
The screw-in torque can be reduced by that amount, preventing the boss from cracking, and making it possible to tap the screws deeply and reliably. It is possible to avoid a situation where the screws cannot be tightened. Further, since the pressure side flank surfaces of the first flank part and the second flank part are common, screwing is reliable and the fastening force is strong, and it is suitable for use in fastening metal materials, and has a remarkable practical effect.

[Brief explanation of the drawing]

Fig. 1 is a side view of a self-tapping screw according to an embodiment of the invention, Fig. 2 is a partially cutaway enlarged perspective view of the self-tapping screw of Fig. 1, and Fig. 3 is a side view of the self-tapping screw of Fig. 2. 4 is a sectional view similar to FIG. 2 of another embodiment of this invention, and FIG. 5 is a sectional view similar to FIG. 2 of yet another embodiment of this invention. The cross-sectional view, FIG. 6, is a partially broken exploded cross-sectional view showing a conventional self-tapping screw in use. Explanation of symbols, 1...Self-tapping screw, 2
...Head, 3...Shaft, 7...Threaded part, 8...
First flank part, 9... Second flank part, 10...
... Pressure side flank surface, 11 ... Play side flank surface, 12 ... Concave flank surface, 13 ... Concavity, 1
4...Top line, 15...Mountain top, 16...Bottom edge.

Claims (1)

[Scope of Claim for Utility Model Registration] 1. A self-tapping screw having a head and a shaft continuous to the head, with a threaded portion formed in the shaft, the free side flank surface of the threaded portion having a Recesses extending in a direction that intersects the lead angle of the screw are formed at equal intervals along the thread direction, and the threaded portion is connected to the second flank portion in which the recess is formed, and the second
A self-tapping screw characterized in that it is divided into a first flank part between flank parts. 2. The concave portion of the second flank portion is formed by a recessed flank surface disposed closer to the pressure side flank surface by a dimension smaller than the play side flank surface. self-tapping screws. 3. The self-tapping screw according to claim 2, wherein the recessed flank surface is arranged parallel to the play side flank surface. 4. The crest of the second flank part is made common to the crest of the first flank part, and the intersection angle of the depressed flank surface and the pressure side flank surface is smaller than the thread angle of the first flank part. 3. A self-tapping screw according to claim 2, characterized in that the recess is provided by forming a self-tapping screw. 5 The bottom edge of the second flank portion is made common to the bottom edge of the first flank portion, and the intersection angle of the depressed flank surface and the pressure side flank surface is set to be smaller than the thread angle of the first flank portion. 3. The self-tapping screw according to claim 2, wherein the recess is provided with a larger diameter. 6. The first aspect of claim 1, wherein the length of the second flank in the thread direction is 1/6 or less of the length of one lead of the screw, and at least two flanks are provided for each lead of the screw. Term, 2nd term,
The self-tapping screw according to item 3, 4 or 5.