JP3290362B2 - Tapping screw for soft metal material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tapping screw which is screwed into a screw hole formed in a work in advance while forming a female screw, and more particularly to a tapping screw suitable for a metal material whose work is relatively soft.

[0002]

2. Description of the Related Art Conventionally, when a screw is screwed into a work made of a relatively soft metal material, particularly a work made of an aluminum die cast or a zinc die cast, a tapping screw is used as the screw. This is such as shown in FIG. 13, in which works 140 made of a soft metal material are overlapped with each other, and the work 140 is fastened by screwing the tapping screw 101 into the work. The self-tapping screw 101 is now in the screw hole 1 of the work 140.
41 is screwed in while forming a female screw 142,
The tip of the leg 103 of the screw 101 has a relatively low thread and has a tapered shape in which the thread is gradually increased, so that a thread having a desired size is finally formed in the screw hole 141. .

[0003]

However, when a tapping screw having such a shape is used for a work made of a relatively hard metal material, the screwing operation can be performed without any obstacle, but the soft metal is used. When screwed into a screw hole of a material work, a tapping screw is first screwed into the screw hole while forming a female screw in the screw hole. However, when the tapping screw is screwed in, it adheres to the work and the tightening torque increases, so that the tapping screw is not completely screwed in and the head seat surface does not sit on the work, a so-called screw floating state occurs. Is rattled without being completely fixed. Further, even if the tapping screw in this state is removed and the screwing operation is performed again, the tapping screw cannot be removed, and the head is destroyed. There is.

[0004] A first object of the present invention is to solve the above-mentioned problems and to enable a screw to be smoothly screwed in with a low tightening torque without adhering a tapping screw to a screw hole of a work made of a soft metal material. A second object of the present invention is to enable screwing with a lower torque, and a third object of the present invention is to provide a self-tapping screw in a screw hole. The fourth object of the present invention is to obtain a secure locking torque for a workpiece made of a soft metal material.

[0005]

SUMMARY OF THE INVENTION The purpose of the present invention is as follows.
A leg 3 having a crest and one end of the leg 3
Tappy consisting of a large diameter integrally formed head 2
On the outer circumference of the leg 3 that continues from the head 2
A thread body 10 having a crest angle of 50 ° is formed.
Continuously connect the top of the thread of the thread body 10 to the tip of 3
Parallel to the straight line and smaller than the thread outer diameter D of the thread body 10
A screw having a large thread outside diameter d and a thread crest angle of 60 °
A thread guide 20 is formed, and the thread body 10 and the thread plan are formed.
Connect these to the interior 20 and the threads
The apex angle is larger than the crest angle of the thread of the thread body 10 and is half a circumference
Thread connection portion 30 is formed, and further, the thread body portion 1 is formed.
0, the thread connection section 30 and the thread of the thread guide section 20
And at the same pitch, and at least the thread body
Flat relief with upper thread removed along lead 10
By obtaining a tapping screw for soft metal material with a groove 4
Achieved. Also, in addition to the above, the threaded leg 3
And one end of the leg 3 with a diameter larger than the diameter of the leg.
A self-tapping screw comprising a shaped head 2
The screw crest angle is 50 ° on the outer circumference of the leg 3 which continues from 2
A thread body 10 is formed, and a thread body is formed at the tip of the leg 3.
10 screws parallel to a straight line connecting the thread crests continuously
Has a screw thread outer diameter d smaller than the screw thread outer diameter D of the screw body 10
Forming the screw guide portion 20 with a screw crest angle of 60 °
Between the thread body 10 and the thread guide 20.
These are connected and the crest angle of the screw is
Side that is larger than the thread crest angle of 0 and that faces the axis.
Alternatively, each of the thread body portions 10 may be positioned at equal positions on the circumference.
A thread formed with a protruding edge portion 31 having a larger outer diameter than a part thereof
A connecting portion 30 is formed, and further, the threaded body 10 and the threaded connection are formed.
All the threads of the connecting part 30 and the thread guide part 20 have the same pitch.
And at least lead to the thread body 10
Cut a flat relief groove 4 with the upper side of the thread removed along
Also achieved by obtaining a tapping screw for soft metal
You. Furthermore, in addition to these configurations, the thread guide
The thread diameter is only half the thread height of thread body 10
It is formed small in the radial direction and
Soft metal tapping formed within two peaks from the tip
Achieved by obtaining screw threads.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 1 and 2, reference numeral 1 denotes a tapping screw including a head 2 and a leg 3;
A head 2 having a diameter larger than the diameter of the leg is integrally formed at one end of the head. On the head side of the leg 3, a thread body 10 having a crest angle of 50 ° is formed.
A thread guide portion 20 having a thread crest angle of about 60 [deg.] Of about one or two threads is formed at the tip of the thread. This thread guide 20
Is parallel to a straight line continuously connecting the thread crests of the thread body 10, and the thread height of the thread body 10 is larger than the thread outer diameter D of the thread body 10. It is formed to have a small diameter by about half. A thread connection portion 30 for connecting these threads is provided between the thread guide portion 20 and the thread body portion 10. The thread connection portion 30 has a thread crest angle of 60 ° and at least a thread. It is formed at the same mountain height as the trunk 10. The thread connection portion 30 is at most about a half circumference of the leg portion 3, and the female screw 42 of the screw hole 41 of the work 40 is formed at this portion. The thread body 10, the thread connection part 30, and the thread guide part 2
All the 0 threads have the same pitch, and may be a single or double thread.

A relief groove 4 is formed in the thread body 10 and the thread connection part 30 along the axis of the leg 3, and the depth of the relief groove 4 is at most equal to the depth of the thread. Approximately half of the height from the ridgeline to the thread valley is used as the thread lead
It has a flat shape along . Both ends of the escape groove 4 along the thread are on the line where the extension of the end face intersects the center of the leg 3, and this escape groove 4 may be a single groove, as shown in FIGS. 3, 4 and 5. Usually, there are two to four strips, which are formed at equal intervals in the circumferential direction. Although the clearance groove 4 is formed parallel to the axis, the clearance groove 4 may be formed in a direction perpendicular to the lead angle of the screw thread. You may form only in the part 10. Further, the surface on the advancing side when screwing the escape groove 4 may be a gentle slope, that is, an extension of the slope may be on a line that does not intersect with the center of the leg 3, thereby reducing resistance when screwing.
The tightening torque is reduced.

FIGS. 6 and 7 show two escape grooves 4 formed in the same manner as described above. The thread connection portions 30 are opposed to each other with the center line of the leg portion 3 interposed therebetween. Part 10
The height of the thread ridge line is partially higher than the height of the protrusion edge portion 31 to protrude slightly outward. For this reason, in this protruding edge portion 31, the angle of the screw crest angle is 50 ° to 6 °.
The projecting edge portions 31 are provided so as to oppose each other so as to uniformly apply the screwing force in the leg portion 3 when screwing in, but this is a circumferential edge. The same operation can be obtained in the female screw forming operation of the screw hole 41 of the work 40 even if only one of them is provided, and even if it is at a position equally divided into three or four.

Using the tapping screw 1 obtained as described above, as shown in FIG. 8, the tapping screw 1 is screwed into a screw hole 41 previously formed in a work 40 made of a soft metal material. In the initial stage of screwing, the screw is guided by the thread guide portion 20 and the screw hole 4 is formed.
Enter 1. At this time, since the screw hole 41 has a slightly smaller diameter than the thread diameter of the thread guide section 20, the female screw 42 is formed in a streak shape in the thread guide section 20. Thereafter, the thread connection portion 30 is screwed into the streaky female screw 42 to form the female screw 42 having a vertical angle of 60 °.

The threaded body 10 of the self-tapping screw 1 is continuously screwed into the female screw 42 thus formed, and the crest angle of the threaded body 10 is 50 mm.
雌, the internal thread 4 formed by the thread connection portion 30 is formed on the flank 11 of the thread of the thread body 10.
Since almost no contact occurs, the contact resistance is reduced, and no adhesion occurs between the thread of the tapping screw 1 and the female screw 42 of the screw hole 41. On the other hand, since the female screw 42 is formed in the screw hole 41 by the thread connection portion 30, the largest resistance is applied to this portion when screwing.

In this embodiment, the operation has been described with respect to a screw thread having a thread connection portion 30 of 60 °.
As shown in the figure, when the projecting edge portion 31 is formed so that the diameter of the thread connection portion 30 becomes slightly larger, the female screw 42 has a deep trough as a whole. Therefore, the female screw 42 does not come into contact with the thread of the thread body 10 of the tapping screw 1 as in the above-described embodiment, and the same operation is performed.

As described above, the tapping screw 1 is screwed into the screw hole 41 of the work 40 while forming the female screw 42, and a screwing action with a low tightening torque is obtained. On the other hand, when the tapping screw 1 is screwed in, the bearing surface of the head 2 of the screw 1 is seated on the surface of the work 40 due to the axial force of the screw. It will move to the 2nd side. As a result, the flank surface 43 of the female screw 42 comes into contact with the upper flank surface 11 of the thread of the tapping screw 1.
As shown in FIG. 11, when the predetermined tightening torque is reached, at the same time, the flank face 43 of the female screw 42 is fitted into the clearance groove 4 of the tapping screw 1. For this reason,
Even if the work 40 vibrates and acts on the tapping screw 1 to loosen, a loosening preventing action occurs between the clearance groove 4 and the meat fitted therein.

The following Table 1 shows, in order to show this loosening prevention effect, experimental data showing a return torque for loosening a screwed tapping screw, and a ratio of a return torque to a tightening torque, a so-called looseness ratio (%). Is shown.

[0014]

[Table 1]

FIG. 12 shows the torque curves of the tightening torque (TS) and the internal thread breaking torque (TM) of the tapping screw of the present invention and the conventional tapping screw. The experimental conditions are the same as those in Table 1. Nominal dimensions: 4 mm, screw hole diameter: 3.8 mm, Work: An experiment was conducted with an aluminum plate. The tightening torque (Ts) has conventionally fluctuated greatly and shows a high value (average 21.50 Kgfcm). However, in this case, the tightening torque (TS) is a low value with little fluctuation (average 7.65 kgfcm). Moreover, the internal thread breaking torque (T _M ) has a low value conventionally (average 43.45 Kg).
fcm), but in this case, the internal thread breaking torque (T
_M ) is a high value (average 76.35 Kgfcm). This proves that the screwing workability is stable, and that it is functionally superior, for example, the thread is not broken within the range of the normal tightening torque.

Further, in Table 1 above, when the tightening torque of the conventional tapping screw is 40 kgfcm, the female screw in the screw hole of the work is near the limit of breaking, and the return torque is half of the tightening torque. I have. In addition, the self-tapping screw of the present invention does not break the internal thread of the screw hole even if it is screwed into the screw hole of the work by changing the tightening torque in three ways, and the fluctuation of the return torque is smaller and the tightening torque is higher than before As the return torque becomes higher, the return torque corresponding to the tightening torque is constantly obtained, indicating that the loosening prevention effect is higher.

[0017]

As described above, according to the present invention, a thread body 10 having a thread crest angle of 50 ° is formed on the outer periphery of a leg 3 continuous from the head 2 and the tip of the leg 3 is formed. A thread outer diameter d that is parallel to a straight line continuously connecting the thread crests of the thread body 10, is smaller than the thread outer diameter D of the thread body 10, and has a thread crest angle of 60 °. A thread guide section 20 is formed, these are connected between the thread body section 10 and the thread guide section 20 and the crest angle of the thread body section 1 is changed.
The thread connecting portion 30 which is larger than the thread crest angle of 0 and within half a circumference or the thread body 1 on the side opposite to the axis center.
Threaded connection part formed with a protruding edge part 31 partly larger in diameter than 0
30 and the thread body 10 and the thread connection 3
0 and the threads of the thread guide 20 are all configured with the same pitch
And, moreover, along at least a screw Yamado unit 10 to rie de
This is a tapping screw for a soft metal material in which a flat relief groove 4 in which the upper side of the thread is removed is cut.

[0018] Therefore, relatively if screwed into threaded hole of the work of the soft metal material, a female thread in contact throughout the during screwing except thread crest of the threaded Yamado portion of tapping screw
The same as the screw body with a screw crest angle of 60 ° and less than half a circumference
Since the internal thread is formed at the thread connection of the diameter, the contact resistance
Anti-can be reduced and the tightening torque is lowered. In addition, the generation of frictional heat between the thread of the tapping screw and the female screw is small.
The screw surface does not adhere to the female screw. For this reason, the tightening torque increases during screwing, the tapping screw is not completely screwed in, the head seating surface does not sit on the work, and a screw floating state occurs, and the work is not completely fixed and there is no backlash. become. Meanwhile, thread
Female thread at the thread connection of the protruding edge part that protrudes from the body
When the female screw is formed,
Since the valleys are all deep, the threads on the thread body are screwed
Sometimes it does not come into contact with the internal thread, further reducing the tightening torque.
It is. Further, a tapping screw having these thread connection portions
Even if the tightening failure occurs for some reason, the tapping screw can be removed and the screwing operation can be performed again, so that many product defects do not occur. In addition, when the screw is screwed in and an axial force is applied, the pressure-side flank face located at the base side of the internal thread is slightly fitted into the flat-shaped relief groove of the leg. As a result, the screws do not become loose with respect to the work that is constantly vibrated, and the reliability of the product is improved. In addition, since a screw thread having a diameter smaller than the diameter of the thread body is formed at the tip of the leg, the tapping screw can be easily screwed accurately without inclining into the screw hole of the work, and a reliable screwing operation can be provided. And the like.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of the present invention.

FIG. 2 is an enlarged front view of a main part of FIG.

FIG. 3 is an enlarged bottom view of FIG. 1;

FIG. 4 is an enlarged front view of a main part showing another embodiment of the present invention.

FIG. 5 is a bottom view of FIG. 4;

FIG. 6 is an enlarged front view of a main part showing another embodiment of the present invention.

FIG. 7 is a bottom view of FIG. 6;

FIG. 8 is an enlarged sectional view of a main part of FIG. 2, showing a state where the work is screwed into a work.

FIG. 9 is a cross-sectional view of a main part showing a screw tightening completed state in FIG. 8;

FIG. 10 is an enlarged cross-sectional view of a main part of FIG. 6, showing a state where it is screwed into a work.

FIG. 11 is a cross-sectional view of a main part showing a screw tightening completion state of FIG. 10;

FIG. 12 is a torque curve diagram showing a tightening torque and a female screw breaking torque of the present and conventional tapping screws.

FIG. 13 is a sectional front view of a main part showing a conventional example of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 tapping screw 2 head 3 leg 4 relief groove 10 thread body 11 flank face 20 thread guide section 30 thread connection section 31 protrusion 40 work 41 screw hole 42 internal thread 43 flank face

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-50-35567 (JP, A) JP-A-3-103607 (JP, A) Fully open 1980-13069 (JP, U) Really open 133013 (JP, U) Actually open 62-2819 (JP, U) Actually open 60-169415 (JP, U) Actually open 58-178514 (JP, U) Actually open 1-80811 (JP, U) JP 50-21123 (JP, B1) (58) Fields investigated (Int. Cl. ⁷ , DB name) F16B 25/00-25/08

Claims (3)

(57) [Claims] 1. A threaded leg 3 and a head 2 integrally formed at one end of the leg 3 with a diameter larger than the diameter of the leg.
In the tapping screw consisting of the following, the screw crest angle is 50 ° on the outer periphery of the leg 3 continuous from the head 2.
Is formed in parallel with a straight line continuously connecting the thread crest of the thread body 10 to the tip of the leg 3 and having a diameter smaller than the thread outer diameter D of the thread body 10. Thread outer diameter d
Forming a thread guide 20 having a thread crest angle of 60 °, connecting these between the thread body 10 and the thread guide 20 and having a thread crest angle of the thread body 20 Forming a thread connection portion 30 which is larger than and within half a circumference of the thread crest angle of the thread 10, and further, the thread body portion 10 and the thread connection portion
30 and all the threads of the thread guide section 20 are formed at the same pitch.
Form, moreover, along to lead to at least a screw Yamado section 10
A tapping screw for a soft metal material, wherein a flat relief groove 4 in which an upper side of a thread is removed is cut. 2. A leg 3 having a thread formed thereon, and the leg 3
Head 2 integrally molded at one end with a diameter larger than the leg diameter
In tapping screw made of a, screw summit angle to the outer periphery of the leg portion 3 continuous from the head 2 is 50 °
The thread body 10 is formed with a thread
Parallel to a straight line connecting the thread crests of the body 10 continuously;
Thread outer diameter d smaller than thread outer diameter D of thread body 10
And a thread guide portion 20 having a thread crest angle of 60 ° is formed.
Between the thread body 10 and the thread guide 20.
These are connected and the crest angle of the screw is
It is larger than 10 thread crest angles and faces each other across the axis.
Thread body at the side or at equally spaced positions on the circumference
The protruding edge 31 having a larger outer diameter than the part 10 was formed.
A thread connection part 30 is formed, and the thread body part 10 and a screw
All the threads of the thread connection section 30 and thread guide section 20
And at least a threaded body 10
Cut a flat relief groove 4 along the lead
A tapping screw for a soft metal material, which is provided. 3. The thread guide section has a thread diameter of the thread.
Small in the radial direction by half the thread height of the body 10
Claim, characterized in that it is formed within two mountain from the tip of the leg portion 3 with being Ku formed 1 or claim 2
5. A tapping screw for a soft metal material according to item 1.