JP2009191930A - Tapping screw - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tapping screw capable of causing smooth plastic flow of an object material and not causing notch effect on the root of a female screw formed in the object material without breaking or damaging the internal structure of the object material when being driven into an object material to thread the object material. <P>SOLUTION: In a longitudinal section including a shaft section 2 of a tapping screw 1, a root side section 5a of a root 5 formed between screw-threads 4 is made to be circular, furthermore a crest side section 4a of the screw-threads 4 is made to be circular also, additionally a straight line section is not arranged between both of them by directly connecting the root side section 5a and the crest side section 4a, or the straight line section longer than 20% or less of a height h of the screw-threads 4 is arranged between the root side section 5a and the crest side section 4a. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a fastening screw that can be tapped with a screw itself, that is, a tapping screw.

  In a conventional normal tapping screw, when viewed in a longitudinal section including the axis of the shaft, the flank (thread slope) and valley bottom form a straight line, and the vicinity of the top of the thread forms a sharp edge. Was. In addition, although a slight roundness was attached to the part where the top of the screw thread and the flank and the valley bottom intersect, these slight rounds are not intended to improve the performance of the screw, This was mainly for the purpose of manufacturing screws such as the service life of machining tools, and for the prevention of harm to workers due to edges.

  Further, the fastening male screw other than the tapping screw has a small roundness at the bottom of the valley, but this small rounding is not mainly intended to improve the performance of the screw. This was for the purpose of manufacturing the screw such as the life span, and for reducing the stress concentration at the bottom of the male screw valley in the male screw itself.

On the other hand, the present applicant previously proposed a tapping screw in which the bottom side portion of the valley formed between the screw threads has a large arc shape in the application according to Patent Document 1.
Japanese Utility Model Publication No. 56-162310

In the conventional normal tapping screw, when the screw is screwed into the mating material and tapped into the mating material, the direction of the plastic flow of the mating material will undergo a sudden change particularly at the portion where the flank and the valley bottom intersect, The plastic flow of the mating material is not smooth, and the top part of the pointed screw thread cuts and destroys the internal structure of the mating material (if the mating material is a metal, the fiber flow), In order to produce a notch effect at the bottom of the female thread formed in the mating material,
(A) The screwing torque increases.
(B) Small fastening force and holding force,
(C) If the mating material is plastic, the mating material may crack.
(D) Cannot be repeatedly screwed in and removed from the same part of the mating material,
(E) It is necessary to strictly manage the size of the pilot hole provided in the counterpart material within a narrow allowable range.
(F) When making by rolling, the wear of the mold is fast and the life of the mold is shortened.
There was a problem such as.

  On the other hand, in the tapping screw disclosed in Patent Document 1, since the valley bottom side portion of the valley formed between the screw threads has a large arc shape, the counterpart material is compared with the conventional normal tapping screw. Since the plastic flow of the mating material is relatively smoothly performed when screwed into the mating material, the problem of the conventional normal tapping screw can be reduced. However, when viewed in a longitudinal section including the axis of the shaft portion, most of the flank is linear, and the vicinity of the top of the screw thread constitutes a sharp edge. There was still a point that the screw problem could not be solved sufficiently.

  The present invention has been made in view of such conventional circumstances, and one of the objects of the present invention is to make the plastic flow of the mating material smoother when it is screwed into the mating material and tapped on the mating material. It is to provide a tapping screw that can be made to be performed.

  Another object of the present invention is to provide a tapping screw that does not cut or destroy the internal structure of the mating member due to the thread.

  Another object of the present invention is to provide a tapping screw that does not produce a notch effect at the bottom of the female thread formed in the mating member.

  Still other objects of the present invention will become apparent from the following description.

The tapping screw according to the present invention is a tapping screw having a shaft portion and a screw thread provided on the outer periphery of the shaft portion,
In the longitudinal section including the axis of the shaft portion, the valley bottom side portion of the valley formed between the screw threads has an arc shape, and the mountain peak side portion of the screw thread has an arc shape,
The valley bottom side portion and the thread peak side portion are directly connected to each other, and there is no linear portion between them, or the length between them is 20% or less of the height of the screw thread. A linear portion is provided.

  In the tapping screw according to the present invention, since it has the shape as described above, when screwed into the mating material, the mating material of the mating material is formed along the valley bottom side portion and the mountain top side portion, each of which has an arc shape Since the meat will plastically flow, the direction of the plastic flow of the meat of the counterpart material cannot be changed abruptly. Accordingly, the plastic flow of the mating material is performed very smoothly, the meat of the mating material is rotated as a whole with respect to the tapping screw, and the force is dispersed without being concentrated locally. Also, since the vicinity of the top of the screw thread does not constitute a sharp edge, this part cuts or destroys the internal structure of the mating member, or causes a notch effect at the bottom of the female screw formed on the mating member. There is nothing. Thereby, the conventional various problems can be solved.

  The tapping screw according to the present invention is particularly suitable when the mating material is made of a material that easily undergoes plastic flow, such as plastic or aluminum alloy.

When the tapping screw of the present invention is screwed into the mating material and tapped into the mating material, the plastic flow of the mating material can be performed more smoothly as described above, and the mating material can be formed by the thread. Streamlines can be prevented from breaking,
(A) Screwing torque is reduced,
(B) The fastening force and holding force are increased.
(C) Even when the mating material is made of plastic, the risk of causing cracks in the mating material is reduced.
(D) It will be possible to repeatedly screw and remove the same material from the same location.
(E) The allowable range of the size of the pilot hole provided in the counterpart material is increased, and it is not necessary to strictly manage the size of the pilot hole.
(F) When creating by rolling, the wear of the mold is delayed, and the life of the mold is prolonged.
It is possible to obtain excellent effects such as.

  Hereinafter, the present invention will be described based on embodiments shown in the drawings.

  1-3 show Example 1 of the present invention, which is an example in which the present invention is applied to a single tapping screw.

  As shown in FIG. 1, the tapping screw 1 includes a shaft portion 2 and a head portion 3 provided at one end portion of the shaft portion 2. A single thread 4 is spirally provided on the outer periphery of the shaft portion 2. In the longitudinal section including the axis of the shaft portion 2, the valley bottom side portion 5 a of the valley 5 formed between the screw threads 4 has an arc shape, and the mountain peak side portion 4 a of the screw thread 4 is also a valley bottom side portion 5 a. It has an arc shape that connects directly and smoothly to the arc.

  For reference, specific examples of dimensions and angles of the respective parts of the tapping screw 1 in this embodiment are shown below.

Outer diameter d ₁ = 1.65φmm
Valley diameter d ₂ = 1.21φmm
Thread height of thread 4 h = 0.22mm
Lead and pitch = 0.5mm
Thread angle α = 30 ° Radius of arc formed by the crest 4a of the thread 4 R _C = 0.033 mm
The radius R _{R of the} arc formed by the valley bottom portion 5a of the valley 5 = 0.22 mm.
However, it goes without saying that the tapping screw of the present invention is not limited to one having the above specific dimensions.

  In this tapping screw 1, the valley bottom side portion 5a of the valley 5 formed between the screw threads 4 has an arc shape, and the mountain peak side portion 4a of the screw thread 4 is also directly smooth to the arc formed by the valley bottom side portion 5a. Since it has an arc shape that leads to the material, when it is screwed into the mating material (not shown), the meat of the mating material plastically flows along these arcing portions that are smoothly connected to each other Therefore, the direction of the plastic flow of the mating material cannot be changed suddenly. Therefore, the plastic flow of the mating material is performed very smoothly, the meat of the mating material is rotated as a whole with respect to the tapping screw 1, and the force is dispersed without being concentrated locally. In addition, since the vicinity of the top of the thread 4 does not constitute a sharp edge, this portion cuts or destroys the internal structure of the mating member, or creates a notch effect at the bottom of the female screw formed on the mating member. I will not let you.

This
(A) Screwing torque is reduced,
(B) The fastening force and holding force are increased.
(C) Even when the mating material is made of plastic, the risk of causing cracks in the mating material is reduced.
(D) It will be possible to repeatedly screw and remove the same material from the same location.
(E) The allowable range of the size of the pilot hole provided in the counterpart material is increased, and it is not necessary to strictly manage the size of the pilot hole.
(F) When creating by rolling, the wear of the mold is delayed, and the life of the mold is prolonged.
An excellent effect such as can be obtained.

It should be noted that the radius R _c of the arc formed by the crest portion 4 a of the thread 4 is preferably 5% or more of the height h of the thread 4, and more preferably the height of the thread 4. It may be 10 to 20% of h. A better effect can be obtained by setting the radius R _c of the arc formed by the summit side portion 4a of the screw thread 4 within these ranges.

  In the present embodiment, in the longitudinal section including the axis of the shaft portion 2, the valley bottom side portion 5a and the mountain top side portion 4a of the screw thread 4 are directly connected, and there is no linear portion between them. A linear portion having a length of 20% or less of the height h of the thread 4 may be provided between the both. However, in order to obtain the above-mentioned effect better, the linear portion is preferably 10% or less of the height h of the thread 4, and more preferably no linear portion is provided as in this embodiment. It is good.

  Moreover, the tapping screw according to the present invention is particularly suitable when the counterpart material is made of a material that easily undergoes plastic flow such as plastic or aluminum alloy.

  4 to 6 show a second embodiment of the present invention, which is an example in which the present invention is applied to two tapping screws 1.

As shown in FIG. 4, also in this embodiment, the tapping screw 1 includes a shaft portion 2 and a head portion 3 provided at one end portion of the shaft portion 2. On the outer periphery of the shaft portion 2, two threads 4H and 4L, which are a thread 4H having a high thread height and a thread 4L having a low thread height, are provided in a spiral shape. In the longitudinal cross section including the axis of the shaft portion 2, the valley bottom side portion 5a of the valley 5 formed between the high thread 4H and the low thread 4L has an arc shape, and the high thread 4H and the low thread The summit-side portions 4Ha and 4La of the mountain 4L also have arc shapes that are directly and smoothly connected to the arc formed by the valley-bottom side portion 5a. The thread angle α _L of the low thread 4L is made larger than the thread angle α _H of the high thread 4H.

  For reference, specific examples of dimensions and angles of the respective parts of the tapping screw 1 in this embodiment are shown below.

Outer diameter d _{H1 at} high thread 4H = 1.65φmm
Outer diameter d _L1 = 1.493φmm at low thread 4L
Valley diameter d ₂ = 1.21φmm
High thread height 4H h _H = 0.22mm
Low thread 4L height h _L = 0.141mm
Lead = 1.0mm
Pitch P = 0.5mm
Thread angle α _H = 30 degrees of high thread 4H Thread angle α _L = 60 degrees of low thread 4L Radius of arc R _HC = 0.033 mm formed by peak side portion 4Ha of high thread 4H
Arc radius R _LC = 0.063 mm formed by the top 4La of the lower thread 4L
The radius R _{R of the} arc formed by the valley bottom portion 5a of the valley 5 = 0.22 mm.
However, it goes without saying that the tapping screw 1 of the present invention is not limited to the one having the above specific dimensions.

  Also in the tapping screw 1 of the present embodiment, the valley bottom side portion 5a of the valley 5 formed between the high thread 4H and the low thread 4L has an arc shape, and the high thread 4H and the low thread Since the 4L mountain top side portions 4Ha and 4La also have an arc shape that is directly and smoothly connected to the arc formed by the valley bottom side portion 5a, when they are screwed into a mating member (not shown), these circles smoothly connected to each other Since the meat of the mating material plastically flows along the arcuate portion, the mating material cannot be suddenly changed in the direction of plastic flow. Therefore, the plastic flow of the mating material is performed very smoothly, the meat of the mating material is rotated as a whole with respect to the tapping screw 1, and the force is dispersed without being concentrated locally. In addition, since the vicinity of the top of the thread 4 does not constitute a sharp edge, the internal structure can be cut or destroyed by this portion, or a notch effect can be produced at the bottom of the internal thread formed in the mating member. Absent.

  Thereby, like the case of Example 1, the outstanding effects, such as said (A)-(F), can be acquired.

  In this embodiment, the tapping screw 1 has a high thread 4H and a low thread 4L. However, in the present invention, two threads having the same height may be provided. However, if two threads of the high thread 4H and the low thread 4L are provided as in the present embodiment, the following more excellent operational effects can be obtained.

By separately controlling the heights h _H and h _L of the thread 4 of the high thread 4H and the low thread 4L, the amount of movement of the mating material can be adjusted. The flow can be made smoother.

  In addition, since the two screw threads, that is, the high screw thread 4H and the low screw thread 4L are provided, the contact resistance at the time of screwing is reduced, so that the screwing torque can be further reduced.

  Also, since it has two threads 4H and 4L, the lead can be enlarged even if the pitch is the same as that of a single tapping screw, so that the screwing can be performed quickly and the operation cost can be reduced. Can do.

Further, since the lower thread 4L is set larger the angle alpha _L of the thread higher thread 4H, since it is to increase the size of the flanks of the lower thread 4L, increasing the frictional resistance that, fastening The power can be further increased.

Preferably, the thread angle α _L of the lower thread 4L is 1.5 to 3 times larger than the thread angle α _{H of} the higher thread 4H, and the arc formed by the peak side portion 4Ha of the higher thread 4H. The radius R _HC is 5-30% of the height h _H of the high thread 4H, and the radius R _LC of the arc formed by the summit portion 4La of the low thread 4L is the height h of the low thread 4L. _It is good to set it as 20 to 70% of _L. More preferably, the thread angle α _L of the low thread 4L is 1.5 to 2.5 times larger than the thread angle α _{H of} the high thread 4H, and the summit portion 4Ha of the high thread 4H forms. The radius R _HC of the arc is 10-20% of the height h _H of the thread 4H of the high thread 4H, and the radius R _LC of the arc formed by the summit portion 4La of the low thread 4L is the height of the thread 4L of the low thread 4L. it may be 40 to 50 percent of the h _L. The ratio of the thread angles α _H and α _L of the high thread 4H and the low thread 4L, the radius R _{HC of the} arc formed by the peak part 4Ha of the high thread 4H, and the peak part 4La of the low thread 4L A better effect can be obtained by setting the radius R _{LC of the} formed arc within these ranges.

Also in this embodiment, in the longitudinal section including the axis of the shaft portion 2, the valley bottom portion 5a is directly connected to the peak portions 4Ha and 4La of the high thread 4H and the low thread 4L. There is no linear portion between them, but a straight line having a length of 20% or less of the height h _H of the high thread 4H is provided between the valley bottom part 5a and the summit part 4Ha of the high thread 4H. A straight part having a length of 20% or less of the height h _L of the low thread 4L may be provided between the shape part, the valley bottom part 5a and the peak part 4La of the low thread 4L.

However, in order to obtain the above-mentioned effect better, the linear portion between the valley bottom portion 5a and the peak portion 4Ha of the high thread 4H is 10% or less of the height h _H of the high thread 4H. The straight portion between the side portion 5a and the top portion 4La of the low thread 4L is preferably 10% or less of the height h _L of the low thread 4L, and more preferably as in this embodiment. It is better not to provide a straight portion.

  In addition, although each said Example is an example of a 1 item | strip | row and a 2 item | spinning tapping screw, respectively, this invention is applicable also to a multi-tapping tapping screw of 3 or more.

  In each of the above embodiments, each of the screw threads 4, 4H, 4L has a symmetrical shape in which the advance side flank angle and the follow side flank angle are equal. An asymmetrical shape in which the corner and the follower flank angle are not equal may be used.

  As described above, the tapping screw according to the present invention is useful as a fastening screw.

It is a front view which shows Example 1 of the tapping screw by this invention. FIG. 3 is an enlarged cross-sectional view showing a part of a shaft portion of the tapping screw of the first embodiment in a longitudinal section including the axis of the shaft portion. It is an expanded sectional view which expands and shows a part of FIG. It is a front view which shows Example 2 of the tapping screw by this invention. FIG. 6 is an enlarged cross-sectional view showing a part of the shaft of the tapping screw of the second embodiment in a longitudinal section including the axis of the shaft portion. It is an expanded sectional view which expands and shows a part of Drawing 5 further.

Explanation of symbols

1 Tapping screw 2 Shaft 4 Screw thread 4a Peak top part 4H High thread 4Ha High thread peak top part 4L Low thread 4La Low thread peak top part 5 Valley 5a Valley bottom side d ₁ Outer diameter d _H1 high Thread outer diameter d _L1 Lower thread outer diameter d ₂ Valley diameter h Thread height R _C Arc radius formed by the crest peak portion R _HC Arc radius formed by the higher thread crest portion R _LC Radius of the arc formed by the top of the lower thread R _R Radius of the arc formed by the bottom of the R _R valley α Thread angle α _H High thread angle α _L Low thread angle

Claims (9)

A tapping screw having a shaft portion and a screw thread provided on the outer periphery of the shaft portion,
In the longitudinal section including the axis of the shaft portion, the valley bottom side portion of the valley formed between the screw threads has an arc shape, and the mountain peak side portion of the screw thread has an arc shape,
The valley bottom side portion of the valley and the mountain top side portion of the screw thread are directly connected, and there is no linear portion between them, or 20% of the height (h) of the screw thread between them. A tapping screw provided with a linear portion having the following length.   In a longitudinal section including the axis of the shaft portion, a linear portion having a length of 10% or less of the height (h) of the screw thread is provided between the bottom side portion of the valley and the top portion of the screw thread. The tapping screw of Claim 1 provided. 2. In a longitudinal section including an axis of the shaft portion, a radius (R _C ) of an arc formed by a top portion of the thread is 5% or more of a height (h) of the thread. The tapping screw according to 1 or 2. In a longitudinal section including the axis of the shaft portion, the radius (R _C ) of the arc formed by the top portion of the thread is 10 to 20% of the height (h) of the thread. Item 3. A tapping screw according to item 1 or 2. It has two threads, a thread with a high thread height and a thread with a low thread height,
In a longitudinal section including the axis of the shaft portion, a valley bottom side portion formed between the high thread and the low thread has an arc shape, and the high thread and the low thread The summit side part of each also has an arc shape,
The valley bottom side portion of the valley and the mountain top side portion of the high screw thread are directly connected to each other, and there is no linear portion therebetween, or the height of the high screw thread (h _H ) therebetween. Is provided with a linear portion having a length of 20% or less,
The valley bottom side portion of the valley and the mountain top side portion of the low screw thread are directly connected to each other, and there is no linear portion therebetween, or the height of the low screw thread (h _L ) therebetween. The tapping screw of Claim 1 in which the linear part of the length of 20% or less of is provided. In a longitudinal section including the axis of the shaft portion, the height of the high thread height (h _H ) is 10% or less between the valley bottom side part of the valley and the peak side part of the high thread. A straight section is provided,
6. A linear portion having a length of 10% or less of the height (h _L ) of the low screw thread is provided between the bottom side part of the valley and the peak top part of the low screw thread. The tapping screw described. The tapping screw according to claim 5 or 6, wherein an angle (α _L ) of the lower thread is larger than an angle (α _H ) of the higher thread. The low thread thread angle (α _L ) is 1.5 to 3 times greater than the high thread thread angle (α _H );
In a longitudinal section including the axis of the shaft portion, the radius (R _HC ) of the arc formed by the top portion of the high thread is 5 to 30% of the height (h _H ) of the high thread, 8. The tapping screw according to claim 7, wherein a radius (R _LC ) of an arc formed by a peak portion of the low screw thread is 20 to 70% of a height (h _L ) of the low screw thread. The low thread thread angle (α _L ) is 1.5 to 2.5 times greater than the high thread thread angle (α _H );
The radius (R _HC ) of the arc formed by the top portion of the high thread in the longitudinal section including the axis of the shaft is 10 to 20% of the height (h _H ) of the high thread, 8. A tapping screw according to claim 7, wherein the radius (R _LC ) of the arc formed by the top portion of the low thread is 40 to 50% of the height (h _L ) of the low thread.

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