JP2002188615A - Tapping screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a tapping screw hardly causing an oblique tapping. SOLUTION: This tapping screw is formed with a head 3 and a shaft 5. The shaft 5 is equipped with an end side thread 6 formed by three threads in the end side and a base side thread 7 which is formed by six threads having the same lead angle as that of the three threads formed in the end side screw 7. That is, the shaft 5 is formed with the threads formed by two different kinds of pitch.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tapping screw, and more particularly, to a tapping screw capable of preventing oblique tapping.

[0002]

2. Description of the Related Art In general, a tapping screw is formed so as to be screwed into a pilot hole without being tapped.
JIS B 1115 (and 112)
It is specified in 2).

[0003] In recent years, in the industries of automobiles, home appliances, IT-related equipment, cooking equipment, etc., light, thin and small mechanical designs have been advanced, and thin steel plates are often used. It is getting screwed.

[0004]

However, conventionally, a tapping screw formed by a single thread is used, and when a tapping screw is used for a thin steel plate, the tapping screw is inclined obliquely to the thin steel plate. Diagonal tapping, which was driven in and tightened, frequently occurred. The oblique tapping is performed by turning the tapping screw on a thin steel plate that has not been pre-tapped in the pilot hole while rotating the tapping screw. Once the female screw is formed, it is difficult to correct.

[0005] When an oblique tapping occurs, a positional shift of the fastening member is likely to occur, resulting in poor mounting. In addition, the driving force of the fastening member is reduced by being driven obliquely. Furthermore, since a part of a gap is formed between the head portion of the self-tapping screw and the fastening member after tightening, the appearance is deteriorated, which is one of the causes of deterioration in quality.

Further, in the industries of automobiles, home appliances, IT-related equipment, cooking equipment, and the like, the production amount is large, and the use amount of the small screw tapping screw is extremely large. Moreover, in the above-mentioned industry, screw tightening work is often performed by a robot. When a large number of screws are tightened, the tightening work time is shortened to improve productivity and save energy. Was raised as an issue.

SUMMARY OF THE INVENTION The present invention solves the above-described problems, and does not generate an oblique tapping by being vertically tightened to a fastening member, has an appropriate fastening force, and improves workability in a fastening operation. It is an object of the present invention to provide a self-tapping screw.

[0008]

SUMMARY OF THE INVENTION A tapping screw according to the present invention is formed as follows in order to solve the above-mentioned problems. That is, a tapping screw having a head portion and a shaft portion, wherein a tip side threaded portion formed by a first multi-start thread is disposed at a tip side biting portion of the shaft portion, and A base-side threaded portion formed of a second multi-threaded screw having a greater number of threads than the first multi-threaded screw is provided at a portion of the head connected to the tip-side biting portion. It is characterized by the following.

[0009] Preferably, the distal-end-side screw portion includes:
What is necessary is just to form with the number of steps of twice the above-mentioned base part side screw part.

[0010] Further, it is desirable that the distal end side threaded portion is formed in a tapered shape having a smaller diameter toward the distal end, because it is likely to bite into the steel plate during tightening.

[0011]

Since the tapping screw of the present invention is constructed as described above, oblique biting can be corrected by the tip side threaded portion formed in the first multi-threaded screw, so that the vertical tapping can be performed. The tightening force is improved by the base side threaded portion formed of the second multi-threaded screw having a greater number of threads than the tip side threaded portion. In other words, when the tapping screw bites into the prepared hole, the leading end of the thread of each thread is disposed on the outer peripheral surface of the shaft at an equiangular position with respect to the shaft center. Are easily balanced and run in the vertical direction along the axis of the pilot hole, so that the internal thread formed in the pilot hole is formed concentrically with the pilot hole.

Further, the second multi-threaded screw formed in the base side threaded portion by tightening the tapping screw has a large lead of each thread, and the amount of tightening during one rotation is several times the conventional amount. Therefore, the fastening speed can be increased. As a result, the time for a large amount of tightening work can be shortened, the workability of the tightening work can be improved, and the electricity cost for the tightening work can be saved, and energy saving can be achieved. Also,
Because the number of threads on the base thread is greater than that on the tip,
Tightening force can be improved because the contact with the member to be tightened can be further increased and the member can be fixed.

[0013] Further, if the tapping screw is formed with a double number of threads of the base side threaded portion, it is formed with the number of threads of the base side threaded portion when forming the female screw. The screw can be screwed with the external thread having the same number of threads as the base side threaded part, and the experimental results show that the screw seat surface and the tightened member when the tapping screw is inclined by about 10 ° are inclined. It is suitable for preventing oblique tapping, since the vertical tightening property showing the adhesiveness with the adhesive is good. Further, the screwing torque has tapping performance equal to or higher than that of the JIS tapping screw. Moreover, the number of times of repeated tightening is good and can be improved.

Further, when the tapping screw is inserted into the pilot hole, the tapping of the shaft portion guides the insertion, so that the vertical tightening property can be further improved.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. The tapping screw 1 of the embodiment is formed from a head 3 and a shaft 5 as shown in FIGS.
The shaft portion 5 has a distal end side threaded portion 6 formed of a first multi-threaded screw (three-threaded thread in the illustrated example) from the intermediate portion toward the distal end biting side, and from the intermediate portion toward the end face of the head 3. It is formed to have a base part side screw part 7 formed by a second multi-threaded screw (six in the illustrated example) having a greater number of threads than the tip side screw part 6.

That is, as shown in FIG. 2, on the distal end surface of the distal end side screw portion 6, first screws 6a having the same lead angle rise from three places on substantially the same surface and are helically arranged. And is extended to the head 3 side. As shown in FIG. 3, in the cross section of the distal end portion of the base portion side screw portion 7, the second screw portion 7a is arranged in the same plane so as to be arranged in parallel with the intermediate portion of the first screw 6a. It is formed to have the same lead angle as one screw 6a. In other words, the six threaded portions are juxtaposed by the three threaded portions arranged side by side from the distal end side threaded portion 6 and the threaded portions which newly stand up from three places and are arranged side by side on the head 3 side. It is formed as follows.

Accordingly, in this tapping screw 1, the screw pitch of the distal screw portion 6 is different from that of the original screw portion 7, and the pitch P1 of the distal screw portion 6 is different from that of the original screw portion 7. Is formed twice as large as the pitch P2. Normally, since the lead of the screw is determined by the pitch P × the number of threads, the lead L of the self-tapping screw 1 is L = 3 × P1 at the tip side screw portion 6 and L = 6 at the base portion screw portion 7. × P2
(P1 / 2) = 3 × P1, and the lead L is 3P1 in all cases.

The pitch of the self-tapping screw 1 manufactured in this trial is such that the pitch of the base side screw part 7 is a general screw (JIS).
For example, in the case of a tapping screw 1 having an outer diameter of 3 mm, the pitch of the base side threaded portion 7 is 0.5 mm.
(The pitch of the tip side thread portion 6 is 1.0 mm), and the tapping screw having an outer diameter of 4 mm has a pitch of the base portion thread portion 7 of 0.7 mm.
(The pitch of the tip side screw portion 6 is 1.4 mm).

Further, the tapping screw 1 of the embodiment can be easily inserted into the prepared hole formed in the member to be fastened at the tip side screw portion 6 and the original side screw portion can be further improved in the vertical tightening property. A tapered taper 8 is formed from the connection part with the part 7 to the tip.

The prototype tapping screw 1 is made of three or four types of soft hard wire (SWRM), similarly to a general tapping screw.
As shown in Table 1 in FIG. 8, the maximum value of the tightening torque is 0.627 Nm with an M3 tapping screw (average value of ten prototype tapping screws). 0.737 with M4 tapping screw
Nm (average value of ten prototype tapping screws). The material may be, for example, brass / aluminum / resin base material as long as the torque value can be satisfied.

Tapping screws formed of a soft-hard wire or brass / aluminum can be processed by a commonly used machine tool such as rolling or lathe. In the case of a resin substrate, It can be manufactured by resin molding.

As shown in FIG. 4, the female screw 11 of the member 10 to be fastened with the tapping screw 1 having these two types of pitches is formed at the pitch of the base side thread portion 7 having a small pitch and fastened. The Rukoto.

FIG. 4A shows that when two fastening plates are fastened with the tapping screw 1, a screw having a hole diameter larger than the outer diameter of the tapping screw 1 is inserted into the first fastening plate 11 of the member 10 to be fastened. A hole 11 a is formed, and a second hole 12 a of the tapping screw 1 is formed in the second fastening plate 12. For example, if the tapping screw 1 is M4, the first fastening plate 11
Of the second fastening plate 12 is formed at 3.0 to 3.3 mm.

Then, the second fastening plate 1 is
When the female screw 12b is formed in the second fastening plate 12, as shown in FIG. 4 (b), the female screw 12b is first inserted into the second fastening plate 12 while being rotated. Is formed. After that, by further rotating the tapping screw 1, the base part side screw part 7 becomes the female screw 12 b
Is inserted to form six female threads 12c, and the tapping screw 1 is
0.

The applicable range of the tapping screw 1 is JIS B
It shall conform to the tapping screw specified in 1115 (or 1122).

The tapping screw (M) formed as described above
When an experiment was performed using two types of tapping screws 1) of 3 × 6 ZC and M4 × 8 ZC, results as shown in the experimental results of Tables 1 to 4 shown in FIGS. In each of the two types of tapping screws 1, the distal-side screw portion 6 is formed by a three-threaded screw, the base portion is formed by a six-threaded screw, and the member 10 to be fastened has a plate thickness of 0.8 mm. The diameter of the pilot hole 12a is 2.30 ° and 2.40 ° for the M3 tapping screw 1, and 3.20 for the M4 tapping screw 1.
鋼板 and 3.30ф steel plates are used. "ZC"
"" Indicates the type of plating, and indicates electrogalvanizing chromate treatment.

The experiment contents were as follows: maximum screwing torque (unit: Nm), maximum value of internal thread breaking torque (unit: Nm)
m), repeated use and vertical tightening. The repetitive usability is to check whether the product can be used repeatedly 20 times. The vertical tightening property is a tightening with a driver compulsory angle (about 10 °). Is to check if it is.

According to the result, the average value of the screwing torque maximum value (unit: Nm) is 0.6 mm for the M3 tapping screw.
27Nm and 0.598Nm (average value of 10 prototype tapping screws), 0.737 with M4 tapping screws
Nm (average value of ten prototype tapping screws), each of which has performance equal to or higher than that of JIS tapping screws.

The maximum value of the internal thread breaking torque (unit: N)
m) are also 2.248 Nm and 1.
968 Nm (average value for 10 prototype tapping screws) and 2.504 Nm for M4 tapping screw (average value for 10 prototype tapping screws). are doing.

Further, the number of times of repetitive tightening is 1.0 Nm in M3, and 1. Nm in M4.
With a tightening force of 8 Nm, no damage to the screws
It was confirmed that it could be reused and reused. Generally, it is considered that the number of times of repetitive tightening should be cleared 10 times, and it is confirmed that excellent properties are obtained by clearing 20 times.

In the case of vertical tightening, the screw is set at 10 °.
When the forcible tightening was performed by tilting, it was confirmed that the tightened state of the member to be fastened was completely adhered between the member to be fastened and the screw seat surface, and all were OK.

The tapping screw 1 can be integrally formed with a washer 9 at the lower end of the head 3 as shown in FIG.

As shown in FIG. 6, the tapping screw 1 is suitable as a small screw like a general tapping screw. It is formed with a cross-shaped hole (or slotted) and can be tightened with a tool such as a small Phillips screwdriver (or flat-blade screwdriver) or, as shown in FIG. (Or a hexagonal slot) so that it can be tightened not only with a Phillips screwdriver (or flathead screwdriver) but also with a tool such as a spanner. These shapes are not particularly limited, but are preferably formed as specified in JIS.

As described above, the tapping screw 1 of the present invention
In the first multi-threaded screw, the tip-side threaded portion 6 can correct oblique biting and can be tightened vertically, and the second threaded portion 6 has a larger number of threads than the tip-side threaded portion 6. The tightening force is improved by the base-side thread portion 7 formed of a multi-start thread. That is, when the tapping screw 1 bites into the prepared hole 12a of the second fastening hole 12 of the member 10 to be fastened, the leading end rising portion of each thread is formed by the shaft 5
Is arranged at an equiangular position with respect to the axis on the outer peripheral surface of the shaft, the tip of the rotating shaft portion 5 is easily balanced and progresses in the vertical direction along the axis of the pilot hole 12a, so that The female screw 12b formed in the pilot hole 12a
It is formed concentrically with respect to a.

Further, the second multi-threaded screw formed on the base side threaded portion 7 by tightening the tapping screw 1 has a large lead of each thread, and the amount of tightening during one rotation is limited to the conventional amount. Since it is several times, the fastening speed can be increased. As a result, the time for a large amount of tightening work can be reduced, the workability of tightening work can be improved, and the electricity cost associated with the tightening work can be saved, and energy can be saved. In addition, since the number of threads of the base portion side screw portion 7 is larger than that of the distal end side screw portion 6, it is possible to increase the tightness with the member 10 to be fastened and to fix the member, so that the tightening force can be improved.

In addition, this tapping screw 1 has a configuration in which the base side screw portion 7 is formed with twice the number of the front end side screw portions 6.
When forming the internal thread, it can be formed with the number of threads of the base side thread part 7, whereby it can be screwed with the same number of male threads as the base side thread part 7, and in the experimental results, Since the vertical tightening property indicating the close contact between the screw seat surface and the member to be fastened when the tapping screw is tilted at an angle of about 10 ° is good, it is suitable for preventing oblique tapping. Furthermore, the screwing torque is J
It has tapping performance equal to or better than that of IS tapping screws. Moreover, the number of times of repeated tightening is good and can be improved.

When the self-tapping screw 1 is inserted into the pilot hole 12a, the taper 8 at the tip of the shaft 5 guides the insertion, so that the vertical tightening property can be further improved.

The distal screw portion 6 is provided on the second fastening plate 1.
In order to improve the vertical tightening property with respect to 12a formed in 2, it is desirable to form it in multiple strips, and the number of strips is not limited. In addition, in order to improve the tightening force, it is desirable that the base side thread part 7 is formed with a greater number of threads than the tip side thread part 6, and the number of threads is not limited. In consideration of the above, it is preferable that the number is a multiple of the number of threads of the distal end side screw portion 6.

[Brief description of the drawings]

FIG. 1 is a front view of a tapping screw according to the present invention.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 is a sectional view taken along the line III-III in FIG. 1;

FIG. 4 is an operation view showing a state in which fastening is performed with the tapping screw of the present invention.

FIG. 5 is a front view showing a tapping screw in which a washer is integrated.

FIG. 6 is a plan view showing the head of the tapping screw.

FIG. 7 is a plan view showing a head of another form of the tapping screw.

FIG. 8 is a table showing experimental results obtained by fastening a fastening plate having a pilot hole of 2.3 mm with an M3 × 6 ZC tapping screw according to the present invention.

FIG. 9 is a table showing experimental results of fastening a fastening plate having a pilot hole of 2.4 mm with an M3 × 6 ZC tapping screw according to the present invention.

FIG. 10 is a table showing experimental results of fastening a fastening plate having a prepared hole of Φ3.2 mm with an M4 × 8 ZC tapping screw according to the present invention.

FIG. 11 is a table showing experimental results of fastening a fastening plate having a prepared hole of Φ3.3 mm with an M4 × 8 ZC tapping screw according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Tapping screw 3 ... Head 5 ... Shaft part 6 ... Tip side screw part 6a ... First screw 7 ... Base part side screw part 7a ... Second screw 8 ... Taper 10 ... Member to be fastened 11 ... First Fastening plate 12 ... Second fastening plate 12a ... Prepared hole 12b ... Three internal threads 12c ... Six internal threads

Claims (3)

[Claims] 1. A tapping screw having a head portion and a shaft portion, wherein a tip side biting portion of the shaft portion is provided with a tip side screw portion formed by a first multi-threaded screw. A base-side threaded portion formed of a second multi-threaded screw having a greater number of threads than the first multi-threaded screw is disposed at a portion of the head portion of the shaft connected to the tip-side biting portion. Tapping screw characterized by being made. 2. The device according to claim 1, wherein the base side threaded portion is formed with twice as many threads as the distal end side threaded portion.
Tapping screw described. 3. The self-tapping screw according to claim 1, wherein the distal-end-side screw portion is formed in a tapered shape having a smaller diameter toward the distal end.