JPH08193611A - Tapping screw for tightening synthetic resin material - Google Patents

Abstract

PURPOSE: To provide a tapping screw for tightening synthetic resin material having a serrate shape whose torque ratio is high and tightening characteristic is excellent, in spite of formation of protrusion parts in an unscrewing preventing direction at a bearing surface. CONSTITUTION: This tapping screw consists of a tapping screw element 1 and a head part 2 having a plurality of protrusion parts 4 and plane parts 5 on the bearing surface 3 side. The protrusion part 4 is an inclined part for forming it. There are also provided an inclined part 4L on the unscrewing direction side and an inclined part 4R on the screwing direction side. The inclination from the bearing surface 3 is large in the former and small in the latter. The plane part 5 is between adjacent protrusion parts 4. When the tapping screw is screwed in and tightening force works upon a member to be tightened, a synthetic resin material which has low elastic modulus and is a member to be tightened penetrates fully between the protrusion parts, and a contact area between the protrusion part 4 and the member to be tightened increases, thus increasing the friction coefficient of the bearing surface 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tapping screw for fastening synthetic resin materials together.

[0002]

2. Description of the Related Art Conventionally, in order to fasten two synthetic resin materials to each other, a resin boss is provided on one synthetic resin material, and a tapping screw is screwed into the resin boss through a hole of the other synthetic resin material. What is done is being done.
However, the resin boss that is a screw-in material has lower strength than steel plates, etc., and the strength of the female thread molded into the synthetic resin material by the tapping screw is also low, so the idling torque value and torque ratio are low, so tightening workability is low. Is bad. Moreover,
Since the tightening force generated is also low, the return torque rate is low, and there is also a problem in terms of slack resistance.

Therefore, in a conventional tapping screw for a synthetic resin for fastening such synthetic resin materials to each other, in order to improve the loosening resistance, the seating surface is provided with serrations in a detent direction. . Alternatively, in order to improve the tightening workability, the seat surface is provided with serrations in the torque braking direction. However, this serration in the detent direction, on the contrary, reduces the idling torque value and torque ratio, resulting in poor tightening workability, and the serration in the torque braking direction, conversely, has a low return torque ratio and a problem in terms of slack resistance. there were.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances, and has the same resistance to loosening as compared with the conventional serration in the detent direction, and
It is an object of the present invention to provide a tapping screw for synthetic resin having a serration shape having a high idling torque value and a high torque ratio and excellent tightening characteristics.

[0005]

According to a first aspect of the present invention, in a tapping screw for fastening a synthetic resin material having serrations on a seat surface of a head, the serrations include a plurality of protrusions. A flat surface portion, the inclination angle of the protrusion is large in the screw return direction side, small in the screw tightening direction side, and the flat surface portion is at least one position between adjacent ones of the plurality of protrusions. It is characterized by being in.

According to a second aspect of the present invention, in the tapping screw for fastening synthetic resin material according to the first aspect, the head portion is a head portion with a collar.

According to a third aspect of the present invention, in the tapping screw for fastening synthetic resin material according to the first or second aspect, the position of the protrusion is deviated in the tightening direction toward the lower neck. It is characterized by that.

According to a fourth aspect of the invention, in the tapping screw for fastening a synthetic resin material according to the third aspect, the deviation in the fastening direction is a spiral shape.

According to a fifth aspect of the present invention, in the tapping screw for fastening synthetic resin material according to the third or fourth aspect, a ring-shaped flat surface portion is provided around the lower portion of the neck. .

[0010]

According to the first aspect of the present invention, the tapping screw for fastening the synthetic resin material has serrations in the detent direction, thereby improving the loosening resistance. By providing a flat surface portion at at least one place between adjacent ones of the plurality of serrations, the synthetic resin material as the member to be tightened deeply enters between the protrusions of the serration during tightening.

According to the second aspect of the invention, since the head portion is the collared head portion, the contact area of the seat surface can be increased and the loosening resistance can be further improved.

According to the third aspect of the present invention, since the position of the protrusion of the serration deviates in the tightening direction toward the lower neck, the length of the protrusion can be increased and the contact area can be increased. Can be made bigger.

According to the invention described in claim 4, since the deviation in the tightening direction is formed in a spiral shape, the length of the protrusion can be made longer and the contact area can be made larger.

According to the fifth aspect of the present invention, since the ring-shaped flat surface portion is provided around the lower portion of the neck, the synthetic resin material swells inward and comes into contact with the ring-shaped flat surface portion when the screw is tightened. As a result, the friction coefficient of the seat surface increases, and despite the detent direction serration,
The idling torque value and torque rate increase.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic configuration diagram of an embodiment of a tapping screw for fastening a synthetic resin material according to the present invention.
Is a front view thereof, and FIG. 1 (B) is a bottom view thereof. In the figure, R is a screw tightening direction, L is a screw returning direction, 1 is a screw portion, 2 is a head portion, 3 is a seat surface portion, 4 is a protruding portion, 4R is a screw tightening direction side inclined portion, and 4L is a screw. On the inclined portion side in the returning direction, 5 is a flat surface portion, 5A is a flat surface portion between protrusions, 5B is a ring-shaped flat surface portion, and 6 is a flange portion.

The outline of the tapping screw for fastening the synthetic resin material of the present invention (hereinafter, simply referred to as "tapping screw") will be described. The tapping screw of the present invention comprises a screw portion 1 for tapping, a projection 4 having eight ridges and a flat surface portion 5 on the bearing surface 3 side.
And a head 2 having. The plane portion 5A is between adjacent ones of the plurality of protrusions 4. With the tapping screw of the present invention, for example, in order to fasten two synthetic resin materials to each other, a resin boss is provided in one synthetic resin material and a hole is opened in the other synthetic resin material which is a member to be tightened. To be Examples of the material of the synthetic resin material include polypropylene and ABS resin. The tapping screw of the present invention enters into the resin boss while being screwed through the hole of the other synthetic resin material, and a female screw is formed on the resin boss by the tapping screw. When the screwing is almost completed and the protrusion of the protrusion 4 comes into pressure contact with the member to be tightened, the synthetic resin material having a low elastic modulus, which is the member to be tightened, becomes deep between the protrusion 4 and the adjacent protrusion 4. The contact area between the member to be tightened and the protruding portion 4 increases when it enters. The shape of the head 2 is a pan head having a collar 6, and the collar 6 widens the seat surface 3, which is advantageous for the present invention focused on increasing the contact area between the seat surface 3 and the mounted member. . However, the present invention is not necessarily limited to this shape.

Next, the details of the protrusion 4 and the specific structure of the plane portion 5 will be described. FIG. 2 is a cross-sectional view showing a joint relationship between the protrusion 4 and a synthetic resin material that is a member to be tightened, and FIG. 2 (A) shows a conventional tapping screw with detent direction serration, and FIG. ) Is shown in FIG.
It is a tapping screw of the present invention showing an AA cross section shown in (B). In the figure, 7 is a protrusion of a tapping screw with a conventional detent direction serration, 7R is a screw tightening direction side inclined part of the protrusion 7, 7L is a screw return direction side inclined part, and 8 is a tightening member synthetic resin. It is a material.

As can be seen by comparing FIG. 2 (A) and FIG. 2 (B), the protrusion 4 of the tapping screw of the present invention is a protrusion in the detent direction and has a conventional detent direction serration. It is similar to the protrusion 7 of the tapping screw. Protrusion 4
Has a screw return direction side inclined portion 4L and a screw tightening direction side inclined portion 4R which are inclined portions forming the same. The inclination from the seat surface 3 is the screw return direction inclined portion 4L.
Is large, and is small in the screw tightening direction side inclined portion 4R. However, in the conventional tapping screw shown in FIG. 2 (A), the protrusions 7 are connected to each other, whereas in the tapping screw of the present invention shown in FIG. 2 (B), the protrusions 4 are adjacent to each other. A flat portion 5A is provided between the mating parts. Since the flat portion 5A widens the interval between the protrusions 4, the synthetic resin material 8 having a low elastic modulus, which is a member to be clamped, is deeply inserted between the protrusions 4 of the serration when a tightening force is applied to the screw. . As a result, the contact area between the protrusion 4 and the synthetic resin material 8 increases, and the coefficient of friction of the seat surface 3 increases. Therefore, despite the serration in the detent direction, the idling torque value and the torque ratio are increased, and the tightening workability is improved.

Next, the specific arrangement of the protrusions 4 will be described. FIG. 3 is a perspective view showing one serration,
FIG. 3A shows a case where the protrusion 4 is linear, and FIG. 3B is a view showing a case where the protrusion 4 is spiral. In each case, the protrusion 4 is in the direction intersecting the radius. That is, the protrusion 4 may be arranged in a straight line as shown in FIG. 3 (A) or in a spiral shape as shown in FIG. 3 (B). As the screw is displaced in the tightening direction R of the screw, the continuous line segment of the protrusion 4 becomes longer, and the area in which the protrusion 4 contacts the synthetic resin material 8 as the member to be tightened becomes wider, The friction coefficient of the seat surface 3 increases. The arrangement of the protrusions 4 is linear or spiral, but is not limited to this. For example, the protrusion 4 may be linearly displaced in the screw tightening direction R as it approaches the lower part of the neck. On the contrary, the protrusion 4 may be displaced linearly or spirally in the screw returning direction L as it gets closer to the lower part of the neck.

A ring-shaped flat surface portion 5B is provided from the lower part of the neck to the outer circumference. The protrusion 4 is shown in FIG.
As shown in FIG. 3B, when the screw deviates in the tightening direction R toward the lower part of the neck, the screw is rotated in the tightening direction and the tightening force increases, and the synthetic resin material that is the member to be tightened. Since the inner ring-shaped flat surface portion 5B comes into contact with the synthetic resin material 8 in order to swell the inner surface 8, the contact surface contact area at the time of screwing is further increased, and the seat surface 3
Increases the friction coefficient.

In the above-described embodiment, the number of peaks of the protrusion 4 is eight, but the number of peaks may be determined according to the degree of the detent action. Further, the flat surface portion 5A is provided between all the adjacent projection portions, but it is not necessarily required to be provided between all the projection portions depending on the degree of action thereof.

Next, the test results of the prototype are shown below. The synthetic resin boss is made of polypropylene,
The outer diameter is 12 mm and the prepared hole diameter is φ4.2 mm. The material to be tightened is polypropylene and the hole diameter is φ6.0 mm. The tapping screw is a pan head with a collar and the size is M5.
-14 peaks × 16, the surface treatment is black zinc chromate. The conventional serration has a detent direction of 18 ridges, screwing torque is 0.573 N · m, idling torque is 3.103 N · m, torque ratio is 5.42, tightening torque is 1.68 N · m, return torque. Was 2.020 N · m, and the return torque ratio was 120.24%. On the other hand, the protrusion of the embodiment of the present invention has eight peaks, the screwing torque is 0.602 N · m, the idling torque is 3.452 N · m, the torque ratio is 5.76, and the tightening torque is 1.89 N · m. m, return torque 2.45 Nm, return torque rate 129.6
It was 0%. From the above results, it can be seen that the tapping screw of the embodiment of the present invention has a higher torque ratio and a higher returning torque ratio than those of the conventional detent direction serrations.

[0023]

As is apparent from the above description, in the invention described in claim 1, the flat portion 5A is between the protrusions 4 in the detent direction, and the tapping screw for fastening the synthetic resin material is By providing the flat portion at least at one position between the detent direction serration and the adjacent one of the plurality of serrations, there is an effect that the loosening resistance is improved.

According to the second aspect of the invention, the use of the head portion with the collar has the effect of further improving the loosening resistance.

In the invention according to claim 3, since the position of the protrusion of the serration deviates in the tightening direction toward the lower neck, the length of the protrusion can be increased and the contact area can be increased. Since it can be increased, it has the effect of further improving the loosening resistance.

According to the fourth aspect, since the deviation in the tightening direction is formed in a spiral shape, the length of the protrusion can be increased and the contact area can be increased, so that the loosening resistance can be improved. There is an effect that can be further improved. .

According to the fifth aspect of the present invention, since the ring-shaped flat portion is provided around the lower portion of the neck, the idling torque value and the torque rate are increased, and the tightening workability is improved.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of a tapping screw for fastening a synthetic resin material of the present invention, FIG. 1 (A) is a front view, and FIG. 1 (B) is a bottom view.

FIG. 2 is a cross-sectional view showing a joint relationship between serrations and a synthetic resin material that is a member to be tightened, FIG. 2 (A) is for a conventional tapping screw, and FIG. 2 (B) is for FIG.
It is in the tapping screw of this invention showing the AA cross section shown to (B).

3 is a perspective view showing one serration, and FIG.
FIG. 3A is a diagram showing a case where the protrusion 4 is linear in the radial direction, and FIG. 3B is a diagram showing a case where the protrusion 4 is spiral.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Screw part, 2 ... Head part, 3 ... Seating surface, 4 ... Projection part, 5 ... Flat part, 5A ... Plane part between projection parts, 5B ... Ring-shaped flat part, 6 ... Tsuba, 7 ... Conventional Tapping screw protrusion, 8 ... Tightened member.

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Kazuhiko Shibata 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd.

Claims (5)

[Claims] 1. A tapping screw for fastening a synthetic resin material, which has serrations on a seat surface of a head, wherein the serration has a plurality of protrusions and a plane portion, and the inclination angle of the protrusions is in the screw return direction side. Is large and is small in the tightening direction of the screw, and the flat surface portion is on the seat surface and is at least at one position between the adjacent ones of the plurality of projection portions. Tapping screw for. 2. The tapping screw for fastening a synthetic resin material according to claim 1, wherein the head is a head with a collar. 3. The tapping screw for fastening a synthetic resin material according to claim 1, wherein the position of the protrusion is shifted in the tightening direction toward the lower part of the neck. 4. The tapping screw for fastening a synthetic resin material according to claim 3, wherein the deviation in the tightening direction is a spiral shape. 5. The tapping screw for fastening a synthetic resin material according to claim 3 or 4, wherein a ring-shaped flat surface portion is provided around a lower portion of the neck.