JP6239651B2 - Tapping screw - Google Patents

Description

  The present invention relates to a tapping screw that is fastened while forming a female thread on a mating material, and more particularly to a tapping screw that has excellent screwing characteristics for a wide range of mating materials from resin materials to metal materials.

In the past, tapping screws have been used for assembling machine parts, but in recent years, machine parts that have been partially made into resin parts for the purpose of weight reduction have increased. In these assembling operations, tapping pins for resin materials have been used. It was necessary to use different screws and metal tapping screws. For this reason, the work becomes complicated, and there is a demand for the development of a highly versatile tapping screw that can be shared by both resin and steel.
There are various differences between the tapping screw for resin materials and the tapping screw for metal materials, but the biggest difference is that the tapping screw for resin materials cannot increase the idling torque, and the creep phenomenon peculiar to resin materials does not occur. In order to generate and loosen easily, the thread is provided with a recess for preventing loosening.

As a conventional recess for preventing slack, for example, as described in Patent Document 1, a plurality of grooves serving as recesses are provided at the top of a thread in the winding direction, and even if the tightening force is reduced, a resin is provided in the groove. The material was hooked to prevent loosening.
However, when such a resin tapping screw is used for fastening a steel plate or the like, the concave portion becomes a large resistance, and the screwing torque increases. In addition, since the pressure receiving area of the screw thread becomes small, there is a problem that the screw thread cannot be broken with a low torque because it cannot withstand a high tightening force.

JP-A-7-139536

  The present invention was made in order to solve the above-described problems of the prior art, and the object of the present invention is to take sufficient fastening strength for a wide range of counterpart materials from resin materials to metal materials, Furthermore, it is to provide a tapping screw that can prevent loosening.

In order to achieve the above object, the present invention provides a tapping screw that performs fastening while forming a female screw by plastic deformation in a counterpart material.
At least on the pressure side flank surface of the thread in the mating part with the mating member, the outer diameter of the thread crest is kept in a cylindrical spiral shape and is localized in the circumferential direction of the thread diameter. Provided with a plurality of recesses,
The concave portion has a cross-sectional shape that gradually becomes deeper from the peak top side toward the screw root side, in a shape cut out in a fan shape when viewed from the central axis direction of the screw shaft,
The outer diameter end of the fan-shaped recess is along the outer diameter of the screw thread in a state shifted from the peak to the valley side, and the inner diameter of the fan-shaped recess is the sum of the peak and the screw root. Located in the middle of
The pressure side flank angle of the thread is smaller than the play side flank angle .

It is preferable that the outer diameter end of the recess is shifted to the valley side by about 0.1 times the thread height from the top of the thread.
The cross-sectional shape cut by the plane passing through the central axis N of the screw shaft on the bottom surface of the recess has an edge that hits the rear in the rotational direction when rotated in the tightening direction, and matches the pressure side flank surface of the thread. You may make it incline so that the base side may be cut deeply gradually toward the front of a fastening direction.
A recess can also be provided on the play-side flank surface.
Further, it is preferable that the screw outer diameter has a tolerance range in a direction smaller than the nominal size of the screw.
Further, it is preferable that the thread angle is 40 ° to 45 ° and the pressure side flank angle is smaller than the play side flank angle.
The screw pitch is preferably 0.27 to 0.33 times the nominal diameter.
Furthermore, the thread height may be 0.14 to 0.16 times the nominal diameter.

In the present invention, since the crest of the screw thread is formed continuously and spirally with the same diameter without being discontinuous by a groove or the like, the screw thread continuously bites into the counterpart material, Resistance is reduced and screwing torque can be reduced.
Further, since there is no notch such as a groove at the top of the thread, it is possible to strongly tighten against a metal material such as a steel plate that requires a high tightening force, and the idling torque can be increased. On the other hand, since there is a recess in the pressure side flank surface, it is possible to ensure the loosening resistance against the resin material.
Therefore, from resin materials with low idling torque to large metal materials, it has better characteristics than conventional products in screwing torque and loosening resistance.

In addition, if the recess has a cross-sectional shape that gradually deepens from the peak side toward the screw root, the pressure receiving area on the peak side can be increased, and the looseness resistance is also ensured. be able to.
If the bottom edge of the concave portion is matched with the pressure side flank surface of the screw thread at the edge that contacts the rear side in the rotation direction, the resistance decreases toward the front in the tightening direction and the screwing torque is small. On the other hand, with respect to the rotation on the slack side, since the rear portion is deeper than the rotation direction in the slack direction, the resistance is increased and the slack can be prevented.
If the concave portions are provided on both the pressure side flank surface and the play side flank surface, the screwing torque at the time of female screw molding can be further reduced.
In addition, since the outer diameter of the screw has a tolerance range in a direction smaller than the nominal size of the screw, when used for metal materials such as steel plates, interference with valleys can be avoided, and tightening with small diameter holes is also possible. Thus, the allowable range of the hole diameter of the pilot hole can be widened. On the other hand, since it has a tolerance in a small direction with respect to the nominal diameter as compared with the conventional resin material tapping screw, the screwing torque is small and the workability is excellent.

Also, if the thread angle is 40 ° to 45 ° and the pressure side flank angle is an asymmetrical shape smaller than the play side flank angle, the strength of the thread can be secured as a characteristic for the steel sheet, and the characteristic for the resin material Resin whitening and cracking can be prevented.
In addition, if the screw pitch is set to 0.27 to 0.33 times the nominal diameter (d), the idling torque and the holding force can be increased in comparison with the conventional steel plate screw, while the conventional resin is used. In contrast to the screw, since the pitch is small, the idling torque can be increased.
Furthermore, if the thread height is set to 0.14 to 0.16 times the nominal diameter, the idling torque and the holding force can be further increased in combination with the pitch.

1A and 1B show a tapping screw according to an embodiment of the present invention, in which FIG. 1A is a perspective view and FIG. 1B is a view of a recess viewed from an axial direction. 2A is a partially enlarged side view of the thread portion of the tapping screw of FIG. 1, and FIG. 2B is an enlarged view of the thread. FIG. 3 is a partial perspective view showing a tapping screw according to another embodiment of the present invention. 4A and 4B show a tapping screw according to still another embodiment of the present invention, in which FIG. 4A is a perspective view and FIG. 4B is a partially enlarged view of a recess.

EMBODIMENT OF THE INVENTION Below, the form for implementing this invention is demonstrated in detail with reference to drawings.
FIG. 1 shows a tapping screw according to an embodiment of the present invention. In the figure, reference numeral 1 denotes the entire tapping screw, which includes a screw shaft 5 on which a thread 3 is formed and a screw head 7. The thread 3 gradually increases in height from the distal end side toward the screw head 7 in the distal end thread portion 5A, which is a region of a predetermined axial length on the distal end side of the screw shaft 5, and the constant thread height is increased. It has shifted continuously to the parallel thread portion 5B. When screwed, the parallel thread portion 5B is fitted with a female screw formed on the mating member.
The pressure side flank surface 31 of the screw thread 3 in the parallel screw part 5B maintains a cylindrical spiral shape, which is a spiral shape in which the outer diameter of the screw peak part 33 is continuous, in the circumferential direction of the screw diameter. On the other hand, a plurality of recesses 9 are provided locally. In this embodiment, the concave portion 9 is provided in the entire parallel screw portion 5B, but it is sufficient that the concave portion 9 is provided at least in the fitting portion with the counterpart material.

A plurality of recesses 9 are provided at predetermined intervals in the direction in which the screw thread 3 is wound around the central axis of the screw shaft 5. In this example, as shown in FIG. 1B, the recesses 9 are formed at a period of 90 °, and four recesses 9 are formed for each turn of the thread.
The concave portion 9 has a shape in which the pressure-side flank surface 31 is cut away so as to gradually become deeper from the peak portion 33 side toward the root side (valley portion side). It is cut out. The outer diameter of the sector is along the outer diameter of the screw thread, the inner diameter is a circular arc shape concentrically with the peak of the screw thread in the middle of the screw thread, and both end edges 91 and 93 of the fan shape are screw shafts 5. Extends linearly from the central axis of the.
In the illustrated example, the outer diameter end of the concave portion 9 is the crest portion 33 of the screw thread, but it is shifted so as to be present on the trough side by about 0.1 H (H is the height of the screw thread) from the crest portion 33. Is preferred.

  Further, regarding the bottom surface 92 of the recess 9, the cross-sectional shape cut along the plane passing through the central axis N is formed in the same shape and the same depth at any phase angle around the central axis N. In this example, the cross-sectional shape cut by a plane passing through the central axis of the screw shaft 5 is a shape cut out in a triangular shape as shown in FIG. 2, and this cross-sectional shape has both end edges 91 and 93 in the spiral direction. A step portion is formed between the inner edge 94 on the root side and the pressure side flank surface 31.

  As shown in FIG. 2 (B), the screw thread 3 has a pressure-side flank angle α that is perpendicular to the center axis N of the screw shaft 5 and passes through the center of the peak portion 33. The asymmetrical angle is smaller than β. The ratio (α: β) between the pressure side flank angle α and the play side flank angle β is preferably set to 2: 8 to 3: 7.

The thread angle of the screw thread 3 is preferably set to 40 to 45 °, the play side flank angle β is set to about 30 °, and the pressure side flank angle α is preferably set to about 8 ° to 18 °.
The pitch p is preferably 0.25 to 0.29 times the nominal diameter d.
Furthermore, the thread height H is preferably 0.14 to 0.16 times the nominal diameter d.
Further, regarding the outer diameter of the screw, a tolerance range δ is set in a direction smaller than the nominal dimension.

The tapping screw of the present invention is to be fastened while forming a female screw on the mating member. In the present embodiment, the outer diameter of the crest portion 33 of the screw thread 3 is formed continuously and spirally with the same diameter without being discontinuous by a groove or the like. The resistance during screwing is reduced and the screwing torque can be lowered.
Further, since there is no notch such as a groove in the crest portion 33 of the screw thread 3, it is possible to strongly tighten against a metal material such as a steel plate that requires a high tightening force, and the idling torque can be increased. On the other hand, since the pressure side flank surface 31 has the concave portion 9, even if the tightening force is weakened, the resin material bites into the concave portion 9 provided on the pressure side flank surface, and the axial force is reduced due to creep or the like. It is possible to prevent the slack from being caught by the recess 9.
Therefore, from resin materials having low idling torque to large metal materials, the screwing torque and loosening resistance are superior to those of conventional products.

Moreover, since the concave portion 9 has a cross-sectional shape that gradually becomes deeper from the peak portion 33 side toward the screw root side, the pressure receiving area on the peak portion 33 side can be ensured.
In addition, since the outer diameter of the screw has a tolerance range δ in a direction smaller than the nominal size of the screw, when used for metal materials such as steel plates, interference with valleys can be avoided, and tightening is possible even with small diameter holes. It becomes possible, and the tolerance | permissible_range of the hole diameter of a pilot hole can be widened. On the other hand, since it has a tolerance in a small direction with respect to the nominal diameter as compared with the conventional resin material tapping screw, the screwing torque is small and the workability is excellent.

  That is, it is possible to strongly tighten a metal material such as a steel plate that requires a high tightening force, and the idling torque can be increased. On the other hand, the resin material can be prevented from loosening due to the presence of the recess 9, and has superior characteristics to conventional products in terms of screwing torque and loosening resistance.

Furthermore, in this embodiment, a suitable range is selected so that the thread angle (thread angle) θ, the thread height H, and the pitch p can be shared by both the steel plate and the resin material. doing.
Many tapping pins for steel plates have a thread angle of 60 °, and the thread height is in the range of 0.11 to 0.15 in terms of the outer diameter ratio. The screw pitch is in the range of 0.35 to 0.42 in terms of the outer diameter ratio in two types of JIS standards having the same pitch as the metric screw and in other cases.
In addition, in the ratio of the thread height to the pitch, there are three types of JIS standards with the same pitch as the metric thread, and the thread shape is 0.65 to 0.66, otherwise 0.31 to 0.43. It has a wide range of thicknesses and hole shapes.

On the other hand, many tapping screws dedicated to resin have a thread angle θ of 45 ° or less, and many thread heights are in the range of 0.16 to 0.21 in terms of the outer diameter ratio. The ratio is in the range of 0.35 to 0.45. The thread height is such that the thread height is 0.390 to 0.50 in terms of the ratio between the thread height and the pitch, and in order to provide the screw with a function to prevent loosening, the outer diameter of the thread is notched. Many of them have grooves or other indentations.
Further, as a feature of the resin-dedicated tapping screw, the outer diameter tolerance range with respect to the nominal diameter of the screw is located on the plus side with the nominal diameter as a reference dimension. Furthermore, since the thread height is higher than that of the steel plate tapping screw, the diameter of the trough is small when compared with the same nominal diameter.

When the above-mentioned conventional steel plate tapping screw is applied to a resin member, it has the following problems and is not used for fastening to the resin member.
i) Since the resin material is greatly deformed at the time of screwing and thread forming, phenomena such as resin cracking and whitening frequently occur.
ii) Since the strength of the resin material is lower than that of the steel material and the internal thread breaking torque (idling torque) is low, it is necessary to increase the fitting length and ensure the internal thread strength as the boss shape of the internal thread. .
The inner diameter part of this resin boss is tapered so that the resin member can be easily separated from the mold during injection molding, and this taper affects the inner diameter of the screw tip when screwing. And the screwing torque becomes very high, and in the extreme case, the phenomenon of not sitting occurs.
iii) Looseness occurs due to a creep phenomenon peculiar to a resin material at a high temperature. Even if the temperature is not high, the return torque ratio is low compared to steel, and it is easy to loosen.

On the other hand, when the conventional resin tapping screw is applied to a steel plate, it has the following problems and is not used for fastening to a steel plate member.
i) Since the pitch is large, sufficient internal thread strength cannot be ensured for tightening to a thin steel plate, the internal thread breaking torque (idling torque) is low, and the holding force is also low.
ii) The length of the screw becomes long to cope with the resin boss, and when applied to a steel plate, interference with peripheral members on the screw tip side occurs.
iii) Many of the threaded portions have notches and the thread height is small, so that the steel sheet cannot withstand the high tightening force of the steel sheet, and the thread breakage occurs with a low torque.
iv) Since the valley diameter is small, torsional breakage occurs when a thick plate is screwed.
v) Since the outer diameter is large compared to the steel plate screw, the screwing torque is increased under the same pilot hole conditions.
From the above, it has been necessary to use a tapping screw having a screw part shape that is different for each material as a tapping screw using a steel material and a resin material as a screwing material.

On the other hand, in the tapping screw of the present invention, if the thread angle θ, the thread height H, and the pitch p are set in the above ranges, the conventional tapping screw for steel (JIS standard) and resin Compared with the tapping screw, there are the following effects.
About the thread angle θ The thread angle θ is 40 to 45 °, which is set to the same level as the tapping screw for resin. The amount of biting into the resin is the same as before, and the resin material is whitened and cracked. Etc. can be prevented.
On the other hand, the screw thread 3 has a pressure side flank angle α smaller than the play side flank angle β and is asymmetric, and in particular, the play side flank angle is about 30 °, which is about the same as a conventional steel plate tapping screw. Therefore, even when it is used for a steel material, the play side flank surface side has a high strength, and the steel material can be plastically deformed without crushing the threads.

Thread height H In this embodiment, the thread height H is 0.14 to 0.16 times the nominal diameter d, and JIS standard tapping screws 0.11 to 0.15 and a tapping screw for resin Of 0.16 to 0.21.
Since the screw thread height H is higher than that of the JIS standard tapping screw, it can be screwed in even with a small hole diameter that interferes with the valley and generates seizure, and the allowable range of the applicable hole diameter is large. In particular, since the tolerance range is set in a direction in which the outer diameter of the screw is smaller than the nominal dimension, the structure is less likely to interfere.

Characteristics of Pitch p Also, the ratio (p / d) of the screw pitch (p) to the nominal diameter (d) is 0.27 to 0.33 times, and the pitch of 1 type, 2 types or 4 types of JIS standards. The ratio is set to be smaller than the ratio (0.31 to 0.43), so that the idling torque and holding force are high, especially the number of threads that engage with the thin plate increases, and compared with the conventional thin plate It is advantageous.
Further, since the pitch ratio is larger than the three types of JIS standard tapping screws, the screwing torque is lower than the third type, and the range of the prepared pilot holes is wider than the third type and is versatile.
Note that the thread angle θ, the thread height H, and the pitch p are not limited to these ranges, and it is a matter of course that an appropriate range can be selected according to the mating material.

Other Embodiments FIG. 3 shows another embodiment of the present invention.
In the above embodiment, the concave portion 9 is provided only on the pressure side flank surface 31, but in this embodiment, not only the pressure side flank surface 31 but also both the pressure side flank surface 31 and the play side flank surface 32. Is provided. Thus, if the recessed part 9 is provided also in the play side flank surface 32, the screwing torque at the time of internal thread shaping | molding can be made smaller.

FIG. 4 shows still another embodiment of the present invention.
In the above embodiment, the cross-sectional shape obtained by cutting the fan-shaped bottom surface 92 of the recess 9 with a plane passing through the central axis N of the screw shaft is the same shape at the same depth at any phase angle around the central axis N. In this embodiment, the cross-sectional shape of the bottom surface 292 of the fan-shaped recess 29 cut along the plane passing through the central axis N of the screw shaft is the screw shaft in the tightening direction, that is, toward the tip of the screw shaft 5 in the figure. When rotating clockwise around the central axis N, the second end edge 293 hitting the rear in the rotational direction coincides with the pressure side flank surface 31 of the thread. And it inclines so that the base side may be gradually cut deeply toward the front in the tightening direction, and a first step edge 291 that hits the front end has a triangular step on the base side. Further, the arcuate inner edge 294 on the root side is formed with a step which gradually deepens from the second end edge 293 toward the first end edge 291 with respect to the pressure side flank surface 31.
When screwing, in the embodiment shown in FIG. 1, the rear edge 93 is easily caught by the mating member and becomes resistant. In this embodiment, the rear second edge 293 is on the pressure side. Since it is the same surface as the flank surface 31, the resistance is small and the screwing torque is small. On the other hand, with respect to the rotation on the slack side, the first end edge 291 that is rearward with respect to the rotation direction of the slack direction is a step, so that the resistance increases and the slack can be prevented.

In addition, in the said embodiment, although demonstrated as a tapping screw which can be shared with both a resin material and a steel plate, it is not limited to a resin material and a steel plate, As a common product of a steel plate and an aluminum material, an aluminum material and a resin material Is also applicable.
In addition, it cannot be used for both resin and steel plates. In short, the outer diameter of the crest of the screw thread on the pressure flank surface of the screw thread is kept circular, and the thread diameter circle It is characterized in that a plurality of recesses are provided locally in the circumferential direction. By selecting the thread angle θ, thread height H, and pitch p, it can also be used as a tapping screw dedicated to resin materials. It can also be used as a tapping screw dedicated to steel plates. In short, the present invention can be applied to a wide range of counterpart materials from resin materials to metal materials.

DESCRIPTION OF SYMBOLS 1 Tapping screw 3 Thread 31 Pressure side flank surface, 32 Play side flank surface 33 Thread top part 5 Screw shaft 7 Screw head 9 Recessed part, 91, 93 Edge, 92 Bottom face, 94 Inner edge 29 Recessed part, 291 1st end Edge, 293 Second edge, 292 Bottom surface, 294 Inner edge d Nominal diameter G Mountain center line N Center axis p Pitch α Pressure side flank angle β Play side flank angle θ Mountain angle

Claims (8)

In a tapping screw that is fastened while forming a female thread by plastic deformation to the counterpart material,
At least on the pressure side flank surface of the thread in the mating part with the mating member, the outer diameter of the thread crest is kept in a cylindrical spiral shape and is localized in the circumferential direction of the thread diameter. Provided with a plurality of recesses ,
The concave portion has a cross-sectional shape that gradually becomes deeper from the peak top side toward the screw root side, in a shape cut out in a fan shape when viewed from the central axis direction of the screw shaft,
The outer diameter end of the fan-shaped recess is along the outer diameter of the screw thread in a state shifted from the peak to the valley side, and the inner diameter of the fan-shaped recess is the sum of the peak and the screw root. Located in the middle of
A tapping screw, wherein a pressure side flank angle of the thread is smaller than a play side flank angle . 2. The tapping screw according to claim 1, wherein an outer diameter end of the fan-shaped concave portion is shifted to a valley portion side by about 0.1 times a screw thread height from a peak portion of the screw thread.   The cross-sectional shape cut by the plane passing through the central axis of the screw shaft on the bottom surface of the recess has an edge that hits the rear in the rotational direction when rotated in the tightening direction, and matches the pressure side flank surface of the thread. The tapping screw according to claim 1, wherein the tapping screw is inclined so that the base side is gradually cut deeper toward the front in the tightening direction.   The tapping screw according to any one of claims 1 to 3, wherein a concave portion is also provided on the play-side flank surface. The tapping screw according to any one of claims 1 to 4 , wherein the screw outer diameter has a tolerance range in a direction smaller than a nominal size of the screw. The tapping screw according to any one of claims 1 to 5 , wherein a thread angle of the thread is 40 to 45 °. The tapping screw according to any one of claims 1 to 6, wherein the screw pitch is 0.27 to 0.33 times the nominal diameter.   The tapping screw according to any one of claims 1 to 7, wherein the thread height is 0.14 to 0.16 times the nominal diameter.

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