JP2000291616A - Screw - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the inclination of a screw when the screw is inserted into an internal thread and prevent both locking of thread at its tip end and intersection of thread ridges. SOLUTION: A lead-in part 15 having a length of N, on which lead-in thread ridges (17) are formed, is formed on the tip end side of a shank 12 of a screw 10, while a pilot part 16 having a length of L is formed on the tip end side of the lead-in part 15. The outside diameter of the screw 10 at the pilot part 16 is formed so as to become almost the minimum of the fluctuating values of the inside diameters of an internal thread. As for the relations among a pitch P of thread ridges 14 of the shank 12, a length N of the lead-in part 15, and length L of the pilot part 16 are as follows: L/P>=1.6, N/P>=2.0. Moreover, regarding the thread of a coarse thread series, 6.0>=N/P+L/P>=5.0. Regarding the thread of fine thread series, 7.0>=N/P+L/P>=6.0. Regarding the thread of a 1/4-20 UNC series, 5.0>=N/P+L/P>=4.0.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw for preventing crossing of threads when screwing.

[0002]

2. Description of the Related Art For example, when a bolt is inserted into a nut and tightened, before the bolt is inserted, the axis of the male screw of the bolt and the axis of the female screw of the nut are not always arranged in a straight line. Inserted in a tilted state,
An intersection occurs between the thread of the male thread of the bolt and the thread of the female thread of the nut. Then, in the state where the thread crosses as described above, the thread is cut into the thread, and the fastening operation cannot be performed.

In this respect, conventionally, for example, International Publication No. WO9
As shown in JP-A-7 / 41360,
An introduction portion having a small outer diameter of the thread and a pilot portion not forming the thread are provided, and the insertion is performed with a reduced inclination.

[0004]

As described above, in order to provide the pilot portion and suppress the inclination by the pilot portion, the length of the pilot portion is sufficiently maintained, and the inner diameter of the internal thread for guiding the pilot portion is reduced. It is necessary to set a small difference from the outer diameter of the pilot section. However, when the length of the pilot portion is increased, there is a problem that the manufacturing cost of the screw increases. In addition, there is a variation in the inner diameter of the female screw, and there is a problem that it is difficult to always keep the distance between the female screw and the pilot portion small.

[0005] Further, even in a configuration in which an introduction portion having a small outer diameter of the thread is provided, if the length of the pilot portion is not sufficient, there is a possibility that the thread crosses at the introduction portion. Nothing is shown about the length relationship between the pilot section and the introduction section.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a screw which can prevent screw threads from intersecting at the time of screwing and can be screwed smoothly.

[0007]

A screw according to claim 1 is
A shaft portion provided with a thread of a coarse thread system, a pilot portion provided with no thread provided on the tip side of the shaft portion, and gradually located between the shaft portion and the pilot portion and facing the pilot portion. An introduction portion provided with an introduction portion thread having a reduced external dimension, wherein the length of the introduction portion is N, the length of the pilot portion is L, and the thread pitch is P,
P ≧ 1.6, N / P ≧ 2.0, 6.0 ≧ N / P + L / P
.Gtoreq.5.0.

In this configuration, in the coarse thread type screw, by setting L / P ≧ 1.6, the inclination at the time of inserting the tip of the screw into the screw hole is suppressed, and the screw thread of the introduction part is formed. Is prevented from being locked at the distal end of the cable. Furthermore, N / P
By setting ≧ 2.0 and N / P + L / P ≧ 5.0, the inclination of the screw is suppressed, and the thread of the introduction portion smoothly engages with the thread of the mating member, thereby preventing the thread from crossing. Is done. Further, it is not necessary to lengthen the introduction section and the pilot section more than necessary, and by setting 6.0 ≧ N / P + L / P, economical efficiency is secured.

A screw according to a second aspect of the present invention includes a shaft portion provided with a thread of a fine thread system, a pilot portion provided with no thread provided at a tip end side of the shaft portion, and a shaft portion and a pilot portion provided with the thread portion. An introduction part provided with an introduction part thread which is located between and is gradually reduced in outer dimensions toward the pilot part,
The length of the introduction section is N, the length of the pilot section is L,
When the thread pitch is P, L / P ≧ 1.6, N / P
P ≧ 2.0 and 7.0 ≧ N / P + L / P ≧ 6.0.

[0010] In this configuration, by setting L / P ≧ 1.6 in the thread of the fine thread system, the inclination at the time of inserting the tip of the screw into the screw hole is suppressed, and the thread of the introduction portion thread is reduced. Locking at the tip is prevented. Furthermore, N / P
By setting ≧ 2.0 and N / P + L / P ≧ 6.0, the inclination of the screw is suppressed, and the thread of the introduction portion smoothly engages with the thread of the mating member to prevent the thread from crossing. Is done. Further, it is not necessary to lengthen the introduction section and the pilot section more than necessary, and by setting 7.0 ≧ N / P + L / P, economical efficiency is secured.

The screw according to claim 3 is 1 / 4-20UN.
A shaft portion provided with a C-system thread, a pilot portion provided with no thread provided on the tip end side of the shaft portion, and an outer dimension gradually located between the shaft portion and the pilot portion and facing the pilot portion; Where the length of the introduction portion is N, the length of the pilot portion is L, and the thread pitch is P, L / P ≧
1.6, N / P ≧ 2.0, 5.0 ≧ N / P + L / P ≧
4.0.

In this configuration, 1 / 4-20 UN
By setting L / P ≧ 1.6 in the C-series screw, the inclination at the time of inserting the tip of the screw into the screw hole is suppressed, and the lock at the tip of the thread of the introduction portion is prevented. Further, by setting N / P ≧ 2.0 and N / P + L / P ≧ 4.0, the inclination of the screw is suppressed, and the thread of the introduction portion smoothly engages with the thread of the mating member. Mountain crossing is prevented. Further, it is not necessary to lengthen the introduction section and the pilot section more than necessary, and by setting 5.0 ≧ N / P + L / P, economical efficiency is secured.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the screw according to the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 10 denotes a screw.
Constitutes a hexagonal bolt having a substantially hexagonal column-shaped head 11 and a columnar shaft 12. The shaft portion 12 has a thread 14 which is a male screw having a predetermined outer diameter and pitch P, that is,
Coarse thread system, fine thread system, or 1 / 4-20UNC
(Unified coarse thread) system.

An introduction portion 15 having a length N is formed on the distal end side of the shaft portion 12. Further, on the distal end side of the introduction portion 15,
A pilot portion 16 having a length L is formed.

The introduction portion 15 is formed with an introduction portion thread 17 over the entire length. The introduction portion thread 17 is formed so as to be equal to the root diameter at the distal end portion of the introduction portion 15, gradually increase in outer diameter, and to have the proximal end portion continuous with the thread 14. Note that the trough diameter of the introduction portion 15 is equal to the trough diameter of the shaft portion 12.

The pilot portion 16 has no thread and is formed in a substantially columnar shape. Note that the outer diameter of the pilot portion 16 is formed close to the minimum of the inner diameter of the female screw that varies. In addition, a curved guide surface having a larger curvature at the distal end side than at the base end side is provided at the distal end of the pilot section 16.
18 are formed.

The relationship between the pitch P of the thread 14 of the shaft portion 12, the length N of the introduction portion 15, and the length L of the pilot portion 16 is L / P ≧ 1.6.
The length L is formed to be 1.6 times or more the pitch P,
N / P ≧ 2.0, that is, the length N of the introduction portion 15 is formed to be at least 2.0 times the pitch P.

Further, for the thread of coarse thread type, 6.0 ≧ N / P + L / P ≧ 5.0, for the thread of fine thread type, 7.0 ≧ N / P + L / P ≧ 6.0, For a 1 / 4-20UNC (Unified coarse thread) type screw, it is formed in the range of 5.0 ≧ N / P + L / P ≧ 4.0. Of the thread at the time of insertion into the screw hole
Can be prevented at the tip of the screw, the inclination of the screw 10 can be suppressed, the thread 17 of the introduction part can be smoothly screwed into the thread of the mating member, and the intersection of the thread 14 can be prevented. As described above, it is not necessary to form the introduction part 15 and the pilot part 16 long, and economical efficiency can be secured.

Next, with reference to FIGS. 1 to 3 and Table 1, the operation of screwing the screw 10 into the female screw portion 22 of the nut 21 as the mating member will be described.

The following is the calculation results of computer-based simulations of the coarse thread thread, the fine thread thread, and the 1 / 4-20 UNC, and the actual results of the coarse thread thread shown in Table 1. Table 1 shows the experimental results of whether the locked state shown in FIG. 2 and the thread crossing state shown in FIG. Also, in Table 1, the circles indicate the screws 10 that are screwed together without locking or thread crossing.

[0022]

[Table 1] That is, the screw 10 is desirably inserted with the axial direction A of the shaft portion 12 aligned with the axial direction B of the female screw portion 22 of the nut 21. However, in actual work, the screw 10 has an insertion angle θ of a predetermined size. Inserted.

When the insertion angle θ is large,
As shown in FIG. 2, in a state where the pilot portion 16 is inserted into the female screw portion 22 and the introduction portion thread 17 starts to engage with the female thread portion 22, the distal end of the pilot portion 16 is screwed into the female screw portion 22. In this embodiment, the outer diameter of the pilot portion 16 is set to an outer diameter close to the minimum inner diameter of the female screw portion 22 and the length L of the pilot portion 16 is set.
Is 1.6 times or more of the pitch P, the insertion angle θ can be reduced, and the introduction portion 15 of the screw 10 can be reliably guided into the female screw portion 22.

Then, the screw 10 having the leading end of the introduction portion 15 inserted into the female screw portion 22 advances the inside of the female screw portion 22 by rotating and screwing the screw 10.

The degree of suppression of the insertion angle θ of the screw 10 into the female screw portion 22 by the pilot portion 16 can be increased by increasing the inner diameter of the female screw portion 22 according to the variation in the inner diameter of the female screw portion 22. Female thread
If the inner diameter of 22 is close to the outer diameter of pilot section 16, the insertion angle θ
Is kept small.

When the insertion angle θ is small, even if the thread 14 of the shaft 12 which is a normal thread is introduced into the female thread 22 as it is, no intersection of the threads occurs. On the other hand, when the insertion angle θ is large, the thread 14 is directly introduced into the female screw portion 22, or when the length N of the introduction portion 15 is not sufficient, as shown in FIG. Screws inserted at 10
Moves forward before sufficient suppression of the angle is
Causes thread crossings that bite into the female screw portion 22.

Therefore, by providing the introduction portion 15 provided with the introduction portion thread 17 having a predetermined length N, the inclined screw 10 is advanced so as not to cause a thread intersection, and further, the insertion angle θ It is necessary to screw the screw thread 14 into the female screw portion 22 in a state where the inclination is sufficiently suppressed.

It is necessary to set the length N of the introduction portion 15 having an effect of not causing the lock or the thread crossing in accordance with the pitch P and the length L of the pilot portion 16, and as a result of the experiment, As described above, in addition to the condition of L / P ≧ 1.6, N / P ≧ 2.0, that is, the length N of the introduction portion 15 needs to be formed to be at least 2.0 times the pitch P. In addition, for coarse thread type screws, N / P +
L / P ≧ 5.0, N / P for fine thread thread
+ L / P ≧ 6.0, and it was found that it was necessary to form a screw of 1 / 4-20 UNC system within the range of N / P + L / P ≧ 4.0.

With such a configuration, even if the inclination is insufficient to prevent screw crossing only by the pilot section 16, the introduction section 15 can be introduced so as not to cause screw crossing.
To prevent thread crossing.

Further, the length of the introduction portion 15 and the pilot portion 16 is set to 6.0 ≧ N / P +
For L / P and fine thread type screws, 7.0 ≧ N / P
+ L / P, and for 1 / 4-20 UNC screws, the economy of the screw 10 can be secured by setting the range of 5.0 ≧ N / P + L / P.

In this manner, when the screw 11 is screwed into the female screw portion 22 such as the nut 21, it is possible to prevent the screw thread of the male screw portion from intersecting with the screw thread of the female screw and to reduce the manufacturing cost. A prevention screw can be provided.

In the above embodiment, the hexagonal bolt has been described. However, a bolt having a head of another shape,
Alternatively, the present invention can be applied to a member having a male screw thread, such as a so-called small screw.

The screw may be formed integrally or by welding a plurality of members.

[0034]

According to the screw of the first aspect, in the screw of the coarse thread system, the inclination at the time of inserting the tip of the screw into the screw hole is suppressed, and the screw at the tip of the thread of the introduction portion is locked. Can be prevented. Further, the inclination of the screw is suppressed, and the thread of the introduction portion is smoothly screwed into the thread of the mating member, so that the intersection of the threads can be prevented. In addition, it is not necessary to lengthen the introduction section and the pilot section more than necessary, and the economy can be secured.

According to the screw of the second aspect, in the screw of the fine thread system, the inclination at the time of inserting the tip of the screw into the screw hole can be suppressed, and locking at the tip of the thread of the introduction portion can be prevented. . Furthermore, it is possible to suppress the inclination of the screw, smoothly screw the thread of the introduction portion with the thread of the mating member, and prevent the thread from crossing. In addition, it is not necessary to lengthen the introduction section and the pilot section more than necessary, and the economy can be secured.

According to the screw of the third aspect, 1 / 4-2
In a 0UNC-type screw, the inclination at the time of inserting the tip of the screw into the screw hole can be suppressed, and locking at the tip of the thread of the introduction portion can be prevented. Further, the inclination of the screw is suppressed, and the thread of the introduction portion is smoothly screwed with the thread of the mating member, so that the intersection of the threads can be prevented. In addition, it is not necessary to lengthen the introduction section and the pilot section more than necessary, and the economy can be secured.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram showing an operation of the screw.

FIG. 3 is an explanatory diagram showing an operation of the screw.

[Explanation of symbols]

 10 Screw 12 Shaft 14 Thread 15 Inlet 16 Pilot 17 Inlet Thread

Claims (3)

[Claims] 1. A shaft portion provided with a thread of a coarse thread system, a pilot portion provided with no thread provided at a tip end side of the shaft portion, and a pilot portion located between the shaft portion and the pilot portion. An introduction section provided with an introduction section thread whose external dimensions gradually decrease toward the pilot section, wherein the length of the introduction section is N, the length of the pilot section is L, and the thread pitch is P , L / P ≧ 1.6, N / P ≧ 2.0, 6.0 ≧ N / P + L / P ≧ 5.0. 2. A shaft portion provided with a thread of a fine thread system, a pilot portion provided with no screw thread provided at a tip side of the shaft portion, and the pilot portion located between the shaft portion and the pilot portion. An introduction part provided with an introduction part thread whose external dimensions gradually decrease toward the part, wherein the length of the introduction part is N, the length of the pilot part is L, and the screw pitch is P, A screw characterized by the following range: L / P ≧ 1.6, N / P ≧ 2.0, 7.0 ≧ N / P + L / P ≧ 6.0. 3. A shaft portion provided with a 1 / 4-20 UNC thread, a pilot portion provided with no screw thread provided on a tip side of the shaft portion, and a position between the shaft portion and the pilot portion. And an introduction portion provided with an introduction portion thread whose external dimensions gradually decrease toward the pilot portion, wherein the length of the introduction portion is N, the length of the pilot portion is L, and the screw pitch is P. The screw according to claim 1, wherein L / P ≧ 1.6, N / P ≧ 2.0, 5.0 ≧ N / P + L / P ≧ 4.0.