JP2780003B2 - Manufacturing method of self-locking bolt - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a self-alignment device in which a slit is formed along the crest of a thread, and the flank of the thread is compressed by a nut-side flank and elastically deformed toward the slit when screwed into a nut. The present invention relates to a method for manufacturing a self-locking bolt having a locking function.

[0002]

2. Description of the Related Art There is known a self-locking bolt in which a slit is formed along the top of a thread of the bolt.
No. 58016). This bolt presses the flank on the bolt side to the slit side by the flank on the nut side to elastically deform, and prevents the bolt from being loosened by the restoring force of the elastically deformed flank on the bolt side.

As a method for manufacturing this type of self-locking bolt, Japanese Patent Publication No. 2-58016 has been proposed. In this method, after a two-thread screw is rolled, two threads are assembled using a mold having the same lead as the two-thread screw and rolled into one thread.

FIG. 6 is a view showing a first rolled bolt and a die used therein according to this method, FIG. 7 is a view showing a second rolled bolt and a die used therefor, and FIG. 9 is an enlarged view of the manufacturing process, and FIG.
0 is an enlarged view showing a nut fastening state.

In FIG. 6A, reference numeral 10 denotes a bolt material, and a bolt head 14 is formed on a bolt shaft 12 by cold forging or the like. Reference numeral 16 denotes a flat die used for the first rolling, and has a double thread type portion 18 extending in the rolling direction (horizontal direction in FIG. 6B).

[0006] The double thread type portion 18 is provided with the bolt shaft portion 12.
Of the thread relative to the outer peripheral length A = 2πR (see FIG. 8, where R is the radius of the bolt shaft portion 12), that is, the lead L
It is formed so that two threads may enter therein. This double-thread screw has two threads in the lead L, the pitch P and the lead.
The distance L and the outer peripheral length A have a relationship as shown in FIG. In FIG. 8, even (or odd) screw grooves g1 are indicated by solid lines, and odd (or even) screw grooves g2 are indicated by broken lines.

By holding the bolt shaft 12 between a pair of dies 16 and moving the dies 16 in opposite directions while pressing, as shown in FIG.
The double thread 20 is rolled. As shown in FIG. 9 (A), the shape of the double thread portion 20 includes all the thread grooves g1, g.
2 have the same shape and the same depth.

[0008] The second thread portion 20 is subjected to a second rolling process by a die 22 shown in FIG. 7 (B). The die 22 has a single-threaded portion 24 having the same lead as the double-threaded portion 18 of the die 16 and a double pitch. The single thread type portion 24 has a cross-sectional shape 24A shown by a virtual line in FIG.

[0009] A pair of dies 22 having the single-threaded portion 24 is prepared, and is superposed on the double-threaded portion 20 and moved in parallel in the opposite direction, whereby the single-threaded portion 26 shown in FIG. Built. That is, the shape of the thread of the single-threaded portion 24 engages with the even-numbered (or odd-numbered) thread groove g1 (or g2) of the double-threaded portion 20, and pushes the thread groove g1 (or g2) deeply. open. Therefore, as shown in FIGS. 9A and 9B, the two screw threads m1 and m2 are assembled to form
A single thread portion 26 having a cross-sectional shape 24A of No. 4 is formed.

The single thread portion 26 has a slit 28 at the thread groove g2, and elasticity is imparted to each portion m1, m2 sandwiching the slit 28 by performing a predetermined heat treatment.
In FIG. 9B, the same reference numerals are given to the corresponding parts in FIG. 9A.

Here, the cross-sectional shape 24A of the single thread type portion 24 is shown.
That is, as shown in FIG. 10, the shape of the thread of the single thread portion 26 is pressed by the flank 30 </ b> A of the nut 30 with the nut 30 screwed therein. That is, the single thread portion 2
The flank 26A of No. 6 is pressed by the flank 30A of the nut 30 and elastically deforms in a direction to narrow the slit 28.
For this reason, the flank 26A of the single thread portion 26 is
By pressing the flank 30A, frictional resistance is generated, and the nut 30 is prevented from loosening.

[0012]

In the conventional method, since the multi-threaded portion 20 having the same shape is formed in the first rolling, the depth x () of the slit 28 formed in the second rolling is used. FIG.
(B) is limited by the depth of the thread groove g2.

In general, the depth of the thread groove of the single thread portion 26 is much larger than the depth x of the slit 28, so that the slit 28 is very shallower than the height of the single thread portion 26. For this reason, the amount of elastic deformation of each part m1 and m2 sandwiching the slit 28 of the single thread part 26 is limited to a small amount. If the allowable deformation amount is small, it is necessary to increase the processing accuracy of the bolt and the nut, which lowers the productivity and lowers the production yield.
If the allowable elastic deformation amount is small, the variation in the force (tightening force) required for tightening the nut 30 becomes large, which may make it difficult to control the tightening torque and may lower the efficiency of the tightening operation.

[0014]

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and the slit 28 of the screw portion 26 formed by the second rolling can be made sufficiently deep, thereby enabling the bolt and nut to be allowed. A method of manufacturing a self-locking bolt that reduces processing accuracy to improve productivity and production yield, and reduces variation in tightening force to facilitate tightening torque management and improve tightening work efficiency. The purpose is to provide.

[0015]

SUMMARY OF THE INVENTION According to the present invention, there is provided a method of manufacturing a self-locking bolt having a self-locking screw portion having a slit formed along a crest of a screw thread, comprising the following steps. Manufacturing method of self-locking bolt: a. A first rolling step of forming a multi-start thread having a shallow thread every certain number of deep threads in the lead; b. Wherein with multiple thread and the same lead is engaged in the shallow thread groove, by Rukoto by assembling a plurality of threads across the deep screw groove of between the shallow thread groove, one with a deep slit <br/> of Threads and breaks along the centerline of the bolt
On the surface, insert the flank of this thread into the thread groove on the nut side.
Second rolling step that form less than the flank included angle, is achieved by.

Here, in the first rolling, a double thread having a shallow thread and a deep thread is formed alternately, and in the second rolling, a die is pressed into the shallow thread groove to form a deep thread groove therebetween. The threads on both sides can be assembled.

[0017]

FIG. 1 is a view showing a manufacturing process according to an embodiment of the present invention, and FIG. 2 is a view showing a state in which a nut is screwed onto the bolt. In FIG. 1A, reference numeral 120 denotes a double thread portion formed by the first rolling. In the double thread portion 120, shallow thread grooves g10 and deep thread grooves g20 are alternately formed.

In the double thread portion 120, the thread groove g
10, g20, that is, the angle α between the opposing flanks is constant, and only the depths a and b differ. Therefore, this first
A die (not shown) used for rolling can be easily manufactured by changing the biting amount for each strip using a cutting tool having the same blade shape.

A single thread 126 is rolled into the double thread 120 by a single thread 124 of a second rolling die (not shown). Here, since the slit 128 is formed by the deep screw groove g20,
Has a sufficiently large depth x0 as shown in FIG. Here, the thread of the single thread portion 126 is a bolt center line.
Between the two flanks of this thread on the section along
The angle is smaller than the flanking angle of the thread groove on the nut side.
Has been established.

For this reason, as shown in FIG. 2, the two slopes of the thread are screwed into the nut 130 and pressed against the slope of the valley of the nut.
And is displaced toward the slit 128 (see FIG. 2). When this is each unit to sandwich the slit 128 of 1-threaded screw portion 126 m
For 10, m20, large elastic deformation is allowed by the slit 128 which is sufficiently deep. This means that the tolerance of the machining accuracy of the bolt and the nut is also increased, and it is possible to improve the productivity, improve the production yield, and reduce the cost.

FIG. 3 is a view showing another embodiment of the double thread portion formed by the first rolling. Double thread section 220 of this embodiment
In the shallow thread groove g11 of the double thread portion 220, the flank angle β of the shallow thread groove g11 is larger than the flank angle γ of the deep thread groove g21. If the mountain shape of the mold part 224 is pressed and rolled,
A single thread portion (not shown) similar to that of FIG. 1B is formed.

FIG. 4 is a view showing another example of a bolt manufactured according to the present invention, and FIG. 5 is a view showing a die used for this manufacture. This bolt 10A has a normal screw portion 300 at the tip.
, And a self-locking screw part 3 with a slit on the other end side.
10 are formed. In the die 320 used for manufacturing the bolt 10A, the double thread type portion 322 and the single thread type portion 324 are formed continuously in the rolling direction.

Here, the double thread type portion 322 is the same as that shown in FIG.
(A) or the double threaded portions 120 and 220 shown in FIG.
This forms a double-threaded portion having the same shape as that of FIG. Therefore, if this die 320 is used, two dies
After forming the threaded portion, the self-locking threaded portion 310 and the ordinary threaded portion 300 can be continuously rolled in one operation by the single threaded portion 324.

According to this embodiment, since the ordinary screw portion 300 is formed at the tip of the bolt 10A, there is an effect that the screw can easily be screwed into the nut.

In the above embodiment, a double thread is formed by the first rolling. However, a multi-thread having three or more threads may be used. In this case, the lead is shallow with a constant number of thread grooves in the lead. Form a thread groove. Further, in the second rolling, two or more threads may be formed instead of the single thread, but the number of threads n in this case is larger than the number of threads N of the multi-thread in the first rolling. It needs to be small.

[0026]

As described above, according to the first aspect of the present invention, in the first rolling step, a multi- threaded screw having a shallow thread groove every predetermined number of deep thread grooves is formed in the lead, and the second rolling step is performed. In the manufacturing process, the same thread as the multi-threaded screw is engaged in a shallow thread groove, and a plurality of threads are assembled with a deep thread groove between the shallow thread grooves to form one thread with a deep slit. As a result, a deep slit can be formed at the top of the thread. Thus while ∎ it can <br/> the tolerance of elastic deformation of a portion sandwiching the slit in large flank included angle of the threaded slits Na
Machined smaller than the flank angle of the thread groove on the slot side.
Bolt thread easily displaces to deep slit side
I do. For this reason, it is possible to increase the tolerances during production, thus improving productivity and production step sump will be improved, which can contribute to significant reduction in cost.

Further, since the variation in the nut tightening force is reduced and the management of the tightening torque is facilitated, the efficiency of the tightening operation can be improved. Here, in the first rolling, a double thread screw is used.
In the second rolling, if a single thread is rolled, it is suitable for the production of a versatile bolt (claim 2).

[Brief description of the drawings]

FIG. 1 is an explanatory view of a manufacturing process of the present invention.

FIG. 2 is a view showing a fastening state of bolts and nuts;

FIG. 3 is a view showing another embodiment of the first rolling.

FIG. 4 is a diagram showing another embodiment of the bolt.

FIG. 5 is a view showing a die used in this manufacturing.

FIG. 6 is a diagram showing bolts and dies formed by first rolling in a conventional method.

FIG. 7 is a diagram showing bolts and dies similarly formed by second rolling;

FIG. 8 is a development view of a multi-start (two-start) screw.

FIG. 9 is an enlarged view of the same manufacturing process.

FIG. 10 is an enlarged view showing a nut fastening state.

[Explanation of symbols]

 10A Bolt 120, 220 Double thread 126 126 Single thread 128 Slit 130 Nut g10, g11 Shallow thread g20, g21 Deep thread

Claims (2)

(57) [Claims] 1. A method for manufacturing a self-locking bolt having a self-locking screw portion having a slit formed along a crest of a screw thread, comprising the following steps: a. A first rolling step of forming a multi-start thread having a shallow thread every certain number of deep threads in the lead; b. Wherein with multiple thread and the same lead is engaged in the shallow thread groove, by Rukoto by assembling a plurality of threads across the deep screw groove of between the shallow thread groove, one with a deep slit <br/> of Threads and breaks along the centerline of the bolt
On the surface, insert the flank of this thread into the thread groove on the nut side.
Second rolling step that form less than Frank nip angle. 2. The first rolling step forms a double thread having alternating shallow thread grooves and deep thread grooves, and the second rolling step collects shallow threads on both sides of one deep thread groove. Let me deep
2. The method for manufacturing a self-locking bolt according to claim 1, wherein the thread has one thread with a slit .