JP2928694B2 - Screw and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw suitable for tapping screws and the like and a method of manufacturing the same, in which the contour formed by the crest of the screw thread is non-circular when viewed from the axial direction.

[0002]

2. Description of the Related Art Conventionally, as a screw of this kind and a method of manufacturing the same, Japanese Patent Publication No. 37-4608 and Japanese Patent Publication No.
As disclosed in U.S. Pat. No. 22,637, there is known a blank formed by rolling a blank having a polygonal cross section.

[0003]

However, in the conventional screw and the method for manufacturing the same, a special header die is first required to obtain a blank having a polygonal cross section, and a rolling die having a special shape is required. However, there is a problem that the production cost becomes high.

The present invention has been made in view of such circumstances, and can be manufactured from a blank having a circular cross section. At least for each lead of the thread, the top of the thread is viewed from the axial direction. An object of the present invention is to provide a screw having a non-circular contour line and a method of manufacturing the same.

[0005]

SUMMARY OF THE INVENTION A screw according to the present invention is formed by rolling a screw thread and a reverse spiral groove forming a spiral opposite to the screw thread, so that at least the screw thread is formed. For each lead, the contour formed by the crest of the thread when viewed from the axial direction has a non-circular shape.

Further, in the method of manufacturing a screw according to the present invention, at least one lead of the screw thread is formed by forming a screw thread and a reverse spiral groove which forms a spiral opposite to the screw thread. With respect to every minute, the contour line formed by the crest of the thread when viewed from the axial direction has a non-circular shape.

At the intersection of the screw thread and the reverse spiral groove, the screw thread may be continuous and the reverse spiral groove may be discontinuous, or conversely, the reverse spiral groove may be continuous. The thread may be discontinuous.

[0008]

The reverse spiral groove is provided by rolling as in the present invention.
In the case, the material of the inverted spiral groove is mainly the width of the inverted spiral groove.
Extruded in the direction. This means that at both ends of the reverse spiral groove,
The material is extruded in multiple directions because there is a shelter in multiple directions
However, the width of the reverse spiral groove is not
Since there is only a place for material to escape in the direction, the width direction of the reverse spiral groove
Because they are extruded. When the thread is continuous at the intersection of the thread and the reverse spiral groove to make the reverse spiral groove discontinuous, the thread is separated from the intersection of the thread and the reverse spiral groove at the thread. Since the material corresponding to the depression of the reverse spiral groove in the vicinity thereof is extruded in the width direction of the reverse spiral groove, the material is raised by a volume corresponding to the depression of the reverse spiral groove, so the reverse spiral groove is provided. Higher than if not possible,
Since there is a portion where the reverse spiral groove does not exist on both sides of the intersection portion of the screw thread and the reverse spiral groove, the protrusion due to the depression of the reverse spiral groove is small. Therefore, while the screw thread is higher at the part away from the intersection with the reverse spiral groove,
Since it becomes lower at the intersection with the reverse spiral groove, at least for every one lead of the thread, the contour line formed by the top of the thread when viewed from the axial direction becomes non-circular. For example, thread 1
If the number of intersections between the thread and the reverse spiral groove for each lead is two, the contour is elliptical, and if the number of intersections is an integer M of 3 or more, the contour is approximately M square. (However, the number of intersections between the thread and the reverse spiral groove for each lead of the thread is not necessarily an integer).

On the other hand, in the case where the reverse spiral groove is made continuous at the intersection of the screw thread and the reverse spiral groove so that the screw thread is discontinuous, the thread of the screw thread and the reverse spiral groove are connected to each other. Is higher than in the case where the reverse spiral groove is not provided, as described above, while there is no thread at the intersection of the thread and the reverse spiral groove. Therefore, also in this case, at least for every one lead of the thread, the contour line formed by the top of the thread when viewed from the axial direction is non-circular.

In this way, according to the present invention, it is possible to manufacture a screw having a non-circular contour line formed by the crest of the thread when viewed from the axial direction from a blank having a circular cross section.

Further, when the contour of the thread crest as viewed from the axial direction becomes non-circular, the contact portion between the screw and the mating member into which the screw is screwed is reduced, and thus the screw is used as a tapping screw, for example. In this case, advantages such as a reduced screwing torque can be obtained.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the embodiments shown in the drawings. FIG. 1 shows a blank 1 according to an embodiment of the present invention.
FIG. 2 is a bottom view of the blank 1. The blank 1 has a screw head 2 and a shaft portion 3 having a circular cross section. The screw head 2 has a driver fitting hole 4. FIG. 3 shows a screw 5 manufactured from the blank 1, wherein the screw 5 has a single thread 6 and two reverse spiral grooves which form a spiral opposite to this thread 6. 7 and
It is formed by rolling as will be described in detail later.
At the intersection 12 between the thread 6 and the reverse spiral groove 7,
The thread 6 is continuous, and the reverse spiral groove 7 is discontinuous. The pitch between the thread 6 and the reverse spiral groove 7 is the same.

In this embodiment, the thread shape of the thread 6 is triangular as shown in FIG. 4 and the groove shape of the reverse spiral groove 7 is trapezoidal as shown in FIG.
In the present invention, the thread shape of the thread 6 and the groove shape of the reverse spiral groove 7 may be other types of shapes.

FIG. 7 is a front view of a fixed die 8 of a flat rolling die for manufacturing the screw 5 from the blank 1, and has a thread forming groove 9 having a shape corresponding to the thread 6 and a thread forming groove 9. A reverse spiral groove forming ridge 10 corresponding to the reverse spiral groove 7 is provided (in FIG. 7, the thread forming groove 9 and the reverse spiral groove forming ridge 10 are simply represented by one line, respectively). ing). FIG. 8 shows an enlarged front view of the thread forming groove 9 and the reverse spiral groove forming ridge 10.

FIG. 9 shows the state of rolling in the present embodiment. The moving die 11 is provided with a thread forming groove 9 and a reverse spiral groove forming ridge 10 like the fixed die 8. By moving the movable die 11 and rolling the blank 1 between the movable die 11 and the fixed die 8 in exactly the same manner as in the case of normal thread rolling, the thread 6 and the reverse spiral groove 7 are formed. The screw 5 can be manufactured from the blank 1. Although a flat die is used in the present embodiment, a round die or the like may be used in the present invention.

In the screw 5, the portion of the screw thread 6 that is apart from the intersection 12 between the screw thread 6 and the reverse spiral groove 7 is made of the reverse material of the reverse spiral groove 7 in the vicinity. By being pushed out in the width direction of the spiral groove 7, the spiral groove 7 is raised by a volume corresponding to the depressed portion of the reverse spiral groove 7, so that the height is higher than when the reverse spiral groove 7 is not provided. The intersection 12 between the thread 6 and the reverse spiral groove 7 is the same as FIG.
As is apparent from the figure, since there are portions on both sides where the reverse spiral groove 7 does not exist, the uplift of the reverse spiral groove 7 due to the depression is small.
Therefore, the thread 6 is higher at a portion away from the intersection 12 with the reverse spiral groove 7, but is lower at the intersection 12 with the reverse spiral groove 7.

In the case of this embodiment, the thread 6 has a single thread,
Since the reverse helical groove 7 has two threads and the pitch of the thread 6 and the reverse helical groove 7 are the same pitch, the thread 6 and the reverse helical are provided every one lead (in this case, equal to one pitch) of the thread 6. Three intersections 12 with the grooves 7 occur at intervals of 120 degrees. The intersections 12 between the thread 6 and the reverse spiral groove 7 are aligned on three straight lines extending in a direction parallel to the axis of the screw 5.
As a result, as shown in FIG. 6, the contour 13 formed by the top of the thread 6 as viewed from the axial direction is rounded at the intersection 12 between the thread 6 and the reverse spiral groove 7. Triangular shape.

In the embodiment described above, the thread 6 has one thread and the reverse spiral groove 7 has two threads as described above. However, in the present invention, the number of threads of the thread 6 and the reverse spiral groove 7 is Any number can be used as needed. Next, this will be described.

The lead L _a of the thread 6, pitch P _a of the thread 6, Article number N _a of the thread 6, the lead of the reverse helical grooves 7 L _b, the pitch of the reverse helical grooves 7 P _b when the number of threads of opposite helical grooves and N _b, (the case of N _a = 1) when the thread 6 is Paragraph, of 1 per lead of the thread 6, the thread 6 and all of the reverse helical grooves 7 number Z of the intersection 12 becomes _{Z = N b (1 + L} a / L b) = N b (1 + P a / N b · P b) = N b + P a / P b (1).

In general, when the number of threads of the thread 6 is N _a , the number Z of the intersections 12 between the thread 6 and all the reverse spiral grooves 7 per lead of one thread 6 is: _{Z = N b (1 + L} a / L b) = N b (1 + N a · P a / N b · P b) = N b + N to become _{a · P a / P b (} 2).

Therefore, for example, the number of threads N _a of the thread 6
= 1, the inverse spiral groove 7 of the number of threads N _b = 1, and the reverse spiral groove 7 of the pitch P when _b the pitch of the thread 6 and a half of P _a and number of threads of the thread 6 N _a = 2, Article number N _b of the reverse helical grooves 7
= 1, and even when the pitch P _b of a pitch P _a = reverse helical groove 7 of the thread 6, the 1 per lead of one thread 6,
The number Z of the intersections 12 between the thread 6 and all the reverse spiral grooves 7 is 3
And the contour line 13 formed by the top of the thread 6 as viewed from the axial direction.
Has a rounded triangular shape in which the intersection 12 between the thread 6 and the reverse spiral groove 7 forms three sides thereof.

Further, for example, the number of threads N _a = 1 of the thread 6,
Article number N _b = 1 reverse spiral groove 7, and the pitch P _a of the thread 6
= If the pitch P _b of the reverse helical grooves 7, one thread 6
The number Z of the intersections 12 between the thread 6 and all the reverse spiral grooves 7 per lead is 2, and as shown in FIG. 10, a contour 13 formed by the top of the thread 6 when viewed from the axial direction. Is thread 6
And the reverse spiral groove 7 has a substantially elliptical shape in which the intersection portion 12 becomes a short diameter portion.

Further, for example, the number of threads N _a =
1, the number of threads N _b = 4 reverse spiral groove 7, and when the pitch P _b of a pitch P _a = reverse helical groove 7 of the thread 6, the 1 per lead of one thread 6, the thread 6 The number of intersections 12 with all the reverse spiral grooves 7 is 5, and as shown in FIG. 11, the contour line 13 formed by the top of the screw thread 6 is formed between the screw thread 6 and the reverse spiral groove 7 when viewed from the axial direction. The intersection 12 has a rounded pentagonal shape forming the five sides. FIG. 12 shows an embodiment of a flat die for rolling such a screw.

As described above, by appropriately selecting the number of threads N _a and N _{b of the} thread 6 and the reverse spiral groove 7 and the pitches P _a and P _b of the thread 6 and the reverse spiral groove 7, one The number Z (the number is not necessarily an integer) of the intersection 12 between the thread 6 and the reverse spiral groove 7 per lead of the thread 6 is appropriately selected, and at least when viewed from the axial direction, The shape of the contour 13 formed by the top of the thread 6 for each lead can be an elliptical shape (when Z is near 2) or a substantially polygonal shape (when Z is close to 3 or 3 or more). ).

[0025] In addition, the pitch P _a and reverse the spiral groove 7 of the thread 6
When the pitch P _b of an integer ratio, intersection 12 between the threads 6 and reverse helical grooves 7 are aligned on a straight line extending parallel to the axis direction of the screw. Therefore, in this case, not only for each lead, but also when the entire screw is viewed in the axial direction, the contour line 13 formed by the top of the screw thread 6 has an elliptical or polygonal shape.

[0026] In addition, the pitch P _a and reverse the spiral groove 7 of the thread 6
When the pitch P _b of so as not an integer ratio, the intersection 12 between the threads 6 and reverse helical groove 7 is as arranged spirally, for this case, every lead, viewed in the axial direction When the thread is formed, the contour 13 formed by the top of the thread 6 has an elliptical shape or a substantially polygonal shape. However, when the entire screw is viewed in the axial direction, the contour 13 formed by the top of the thread 6 is almost circular.

In any case, when the contour 13 formed by the top of the screw thread 6 as viewed from the axial direction has a non-circular shape as described above, the contact portion between the screw and the mating member into which the screw is screwed is reduced. Therefore, for example, when used as a tapping screw, advantages such as a reduced screwing torque can be obtained.

In the above embodiment, the screw thread is made continuous at the intersection of the screw thread and the reverse spiral groove so that the reverse spiral groove is discontinuous. The reverse spiral groove may be continuous at the intersection of the reverse spiral groove and the thread may be discontinuous. in this case,
The part of the thread that is away from the intersection between the thread and the reverse spiral groove is higher than the case where the reverse spiral groove is not provided, as described above, while at the intersection between the thread and the reverse spiral groove. Has no threads. Therefore, also in this case, at least for every one lead of the thread, the contour line formed by the top of the thread when viewed from the axial direction is non-circular.

[0029]

As described above, the present invention relates to a screw having a non-circular cross section when viewed from the axial direction, wherein the contour formed by the crest of the thread at least per lead of the thread. It can be manufactured from a circular blank, and does not require a special header die or a specially formed rolling die, and can provide an excellent effect that the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a front view of a blank in an embodiment of a screw manufacturing method according to the present invention.

FIG. 2 is a bottom view of the blank.

FIG. 3 is a front view showing an embodiment of the screw of the present invention manufactured by the embodiment of the screw manufacturing method.

FIG. 4 is a cross-sectional view showing a thread shape of the thread in the embodiment of the screw.

FIG. 5 is a sectional view showing a groove shape of a reverse spiral groove in the embodiment of the screw.

FIG. 6 is a diagram showing a contour line formed by a crest of a screw thread in the embodiment of the screw, as viewed from an axial direction.

FIG. 7 is a front view showing a mobile rolling die in the embodiment of the screw manufacturing method.

FIG. 8 is an enlarged front view showing a thread forming groove and a reverse spiral groove forming groove of the rolling die.

FIG. 9 is a plan view showing a state of rolling in the embodiment of the screw manufacturing method.

FIG. 10 is a view showing a contour line formed by a crest of a screw thread in another embodiment of the screw of the present invention as viewed from an axial direction.

FIG. 11 is a view of a contour line formed by a crest of a screw thread in still another embodiment of the screw of the present invention, as viewed from an axial direction.

FIG. 12 is a front view of an embodiment of a rolling die for manufacturing the screw of FIG. 11;

[Explanation of symbols]

 5 Screw 6 Thread 7 Reverse Spiral Groove 12 Intersection of Thread and Reverse Spiral Groove 13 Contour Line Formed by Thread Top

Claims (2)

(57) [Claims] 1. A thread and a reverse spiral groove forming a spiral in a direction opposite to the thread are formed by rolling.
A screw according to at least one lead of the screw thread, wherein a contour line formed by the crest of the screw thread when viewed from the axial direction has a non-circular shape. 2. A thread and a reverse spiral groove forming a spiral in a direction opposite to the thread are formed by rolling, so that at least every one lead of the thread is viewed from the axial direction. A method for manufacturing a screw, characterized in that a contour line formed by the crest of the screw thread has a non-circular shape.