JPH02229908A - Asymmetrical screw device - Google Patents

Abstract

PURPOSE:To make it possible to prevent slackening of a screw part by means of bend of thread ridge taking place at the time of tightening so as to hold the tightness by providing a clearance in such a way as gradually increasing, a space between slant surfaces of a thread ridge facing in the direction opposite to that of tightening, toward the low bending strength side in advance, in a screw part where thread ridges of mutually different bending strengths are combined together. CONSTITUTION:When the bending strength of a thread ridge of an enternal thread part 14 is smaller than that of an internal thread 16, a slope 15a, which faces the reverse direction L1 of the tightening, of the external thread part 14 is partially cut to form a slope 15b, thereby extending the bottom 18 of the external thread part 14 in tightening advancing direction T1. When this screw device is tightened, the part in the vicinity of the addendum 20 of a thread ridge 15 of the external thread 14 having lower bending strength is tightened in an almost point-contact state against a slope 17a of 17b of the thread ridge 17 of the internal thread part 16. The thread ridge 15 of the external thread part 14 is gradually bent toward the tightening advancing direction T1 side because of strong tightening force at the time of tightening. Thus, the slope 15a or 15b of the thread ridge 15 is brought in close contact with the slope 17a or 17b of the thread ridge 17 and is tightened. Accordingly, the friction area is enlarged, thereby preventing the slackening of the screw part.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a screw device for tightening, and in particular, in order to prevent the screw portion from loosening due to bending of the screw thread during tightening, the present invention relates to a screw device for tightening. This invention relates to an asymmetric screw device with different gaps.

[Prior Art] Conventionally, there have been various types of screw devices for this type of tightening.
N) is widely used.

In a combination of threaded parts with the same nominal diameter, the slope (flank) (3aH3b) of the thread (3) of the male threaded part (1),
Slope (41) (4b) of thread (4) of female thread (2)
are formed symmetrically so that their opposing surfaces are parallel. Then, screw the nut (N) larger toward the head (5) of the bolt, and further rotate the nut (N) at the position where it abuts the member to be tightened (6) as shown in Figure 8. and tighten. Therefore, the slope (3l) faces in the direction (Ll) opposite to the tightening direction (T1) of the male screw part (1).
) and the slope (4l) facing in the direction (L2) opposite to the tightening progress direction (T2) of the female screw portion (2) are in close contact with each other, and stress is generated between them to maintain the tightened state.

[Problems to be Solved by the Invention] As described above, in the conventional screw device, when screwing is performed, the slopes facing in the direction opposite to the tightening direction are in close contact with each other.

Here, in a normal screw device, the root area per pitch of male and female screw threads is different, and as shown in Fig. 9, the base length of the thread (3) of the male screw part (1) ( 11), the base length (l2) of the thread (4) of the female screw portion (2) is longer. Therefore, compared to the thread (3), the bottom area of the thread (4) is wider, the total volume of the thread per pitch is larger, and the bending strength of the thread is greater than that of the female thread (2). ) is larger. For this reason, the thread (3) of the male thread part (1) has a small bottom area (the bending strength of the thread is small), and the thread (3) of the male thread part (1) is Gradually bend in the tightening progress direction (TI). Therefore, the bottom of the valley of the male thread (1) (the slope (31) near η) and the female thread (2)
) is in point contact with the slope (41) near the top (4C), and the contact area becomes extremely small, making it easier to relax.

On the other hand, if the male and female thread parts are made of different materials and the bending strength of the female thread part (2) is lower than that of the male thread part (1),
As shown in the figure, the tightening direction (T2) of the female screw part (2)
The thread (4) of the female screw portion (2) is bent. Therefore,
The slope (3!) near the top (3C) of the male screw part (1),
The female screw portion (2) comes into point contact with the slope (4!) near the bottom (8), and the contact area becomes extremely small and loosens easily, similar to the state shown in FIG. 10.

In general screw devices, the male thread part (1) and the female thread part (2) are made of the same material, so there is a difference in bending strength due to the difference in the base area of the thread, and the above phenomenon is noticeable. Become.

Therefore, a technical problem arises that needs to be solved in order to prevent the screw portion from loosening due to the bending of the screw thread during tightening and maintain the tightened state.The present invention aims to solve this problem. With the goal.

[Means for Solving the Problems] The present invention was proposed to achieve the above object, and is a combination of a pair of male and female screw portions with the same nominal diameter, but with different bending strengths of both threads. In the thread part of
An asymmetrical screw device characterized in that the gap between the slopes of both the male and female threads facing in the opposite tightening direction is formed so as to gradually increase toward the lower bending strength side, and An asymmetrical screw device in which a part of the facing slope is removed and the bottom of the male thread part expands in the direction of tightening, and a part of the slope facing the opposite direction of the female thread part is removed and the top of the female thread part is tightened. An asymmetrical screw device that has been reduced in the tightening direction, and an asymmetrical screw device that has partially removed the slope facing the opposite tightening direction of the female screw portion and expanded the bottom of the female screw portion in the tightening direction, and an asymmetric screw device that has the male screw portion tightened in the opposite direction. It is an object of the present invention to provide an asymmetric screw device in which a part of the slope facing the direction is removed and the top of the male screw portion is reduced in the tightening direction.

[Function] The present invention gradually increases the gap between the slopes of both male and female threads facing in opposite tightening directions toward the lower bending strength side in a threaded portion having a combination of threads with different bending strengths. It is formed like this. That is, for example, if the bending strength of the thread of the male thread part is lower than that of the female thread part, the vicinity of the bottom of the slope of the male thread part facing the opposite direction of tightening may be expanded in the direction of tightening, or By reducing the vicinity of the top of the slope of the female screw portion facing in the direction opposite to the tightening direction in the tightening proceeding direction, the gap between the slopes is gradually increased toward the male screw portion.

In addition, if the bending strength of the male thread part is higher than that of the female thread part, the vicinity of the bottom of the slope of the female thread part facing in the opposite direction of tightening should be expanded in the tightening direction, or By reducing the vicinity of the top of the slope of the male screw portion facing in the tightening direction, the gap between the slopes is gradually increased toward the female screw portion.

In any of the above cases, both threaded portions are fastened in a state where the tops of the threads on the lower bending strength side are in close to point contact. Therefore, if the threads on the lower strength side are bent in the tightening direction due to the strong tightening force during tightening, the slopes of both male and female threads facing in the opposite direction of tightening will come into close contact and be tightened. , the friction area becomes large and loosening of the threaded portion can be prevented.

[Example 1] Hereinafter, an example of the present invention will be described in detail with reference to FIGS. 1 to 6 of the attached drawings. Figure 1 shows a state in which the nut (11) is screwed onto the bolt θ(1), and the head of the bolt (a) is in contact with the surface of the tightening member (1).Bolt 0(1) The bending strength of the male thread part (b) of the bolt (1) and the female thread part (lfD thread (0) of the nut (11) is as follows: If they are made of the same material, it is determined by the size of the bottom area of the thread, and the female thread part OQ is larger.

Figures 2 (A) and (8) show the male and female threads.
I1 is made of the same material, and the bending strength of the thread of the male thread part (B) is smaller than the female thread part (+110). Part of the slope (+51) facing the opposite tightening direction (L1) of the screw part (YU) is removed to form a slope (15b), and the bottom of the male screw part (→
1 in the tightening direction (T1). That is, the slopes (17cHI5c) facing the male and female threaded portions (10 (tightening direction of l<72) (TI) maintain their spacing in a parallel state, and face the opposite tightening direction (L2) (Ll). Slope (17
a)<15b) is formed so that the gap gradually increases toward the male thread part (10 Tightening in the opposite direction (L
2) Remove part of the slope (171) facing the slope (+?
b), and the female thread (1G) may be reduced in the direction of tightening progress (T2) at the top. Alternatively, the bottom of the slope (15a) may be ) by deleting a portion of the adjacent positions, and creating a gap between the slopes with the male screw part (I7
It may be gradually increased toward 0.

When the screw device formed as described above is fastened, the third
As shown in the figure, the area near the top of the male thread (G) of the male screw thread (0→) with low bending strength is connected to the female thread part (IED thread (slant slope <17!) or (+711)). Tighten in a state close to point contact. Then, due to the strong tightening force during tightening, the male screw part (four threads (one is in the tightening direction (T)
As shown in FIG. 4, the thread (one slope (15g) or (+5b)
? ) comes into close contact with the slope (171) or (+7b) and is tightened.

On the other hand, FIGS. 5(^) and (B) show that due to factors such as the difference in the materials of the male and female threads, the bending strength of the male and female threads is lower than that of the female thread. 10. As shown in Figure 5 (^), the female thread (l
A part of the slope (17m) facing the opposite tightening direction (L2) of f9 is removed to form a slope (17d), and the female screw part (bottom 01 of II) is expanded in the tightening proceeding direction (T1). That is,
Tightening direction (T2) of both male and female screws (IOQ4) (T
The slope ('I?cHI5c) facing I) maintains the distance parallel to each other, and the slope (t7d) (151) facing the opposite tightening direction (L2) (Ll) maintains the gap between the bends of the thread. The female thread part (formed so as to gradually increase toward the IQ side) has low strength. Also, as shown in Fig. 5(n), the male thread part (formed with an inclined surface (+5 ) is partially removed to form a slope (+5d), and the male screw part (top of the thread (
(to) may be reduced in the tightening progress direction (TI). Or,
The position near the valley bottom (21) of the slope (171) and the slope (15)
The gap between the slopes may be gradually increased toward the female screw portion (lfD side) by removing a portion of the positions near the tops (G) of &).

When the screw device formed as described above is fastened, the sixth
As shown in the figure, the female thread (10 threads) with low bending strength (near the top of the thread (c)) is placed on the male thread (15a) or (15d) on the slope (15d) of the zero thread. Tighten in a state close to contact.Thus, due to the strong tightening force when tightening,
The female screw portion (+19 thread U thread (r7)) gradually bends toward the tightening direction (T2), and as described above in FIG. 4, the slope (15a) or (15d) of the thread 09 The screw thread (b) comes into close contact with the slope (I7!) or (17d) and is tightened.

Thus, FIG. 2(A)(8) or FIG. 5(A)(B)
As explained in , if the gap between the slopes of both male and female threads is gradually increased toward the lower bending strength, the slopes will come into close contact with each other due to the bending of the threads during fastening, increasing the friction area. This can prevent the thread from loosening.

The gap between the slopes is set depending on the material of the male and female threaded parts, the difference in bending strength due to the shape of the threads, the tightening torque, etc. Further, the slope of the screw thread is not necessarily limited to a straight line, but a slope such as a curve or a straight line can also be effective.

[Effects of the Invention] As described in detail in the above-mentioned embodiment, the present invention has a screw portion having a combination of threads having different bending strengths, in which the bending strength is adjusted in advance between the slopes of the threads facing in the opposite tightening direction. The gap is set so that it gradually increases toward the lower strength side. Therefore, when the screw thread is bent in the tightening progress direction due to strong tightening force during tightening, the two slopes come into close contact with each other, increasing the friction area and preventing loosening of the threaded portion.

Note that this invention can be modified in various ways without departing from the spirit of the invention, and it goes without saying that this invention extends to such modifications.

[Brief Description of the Drawings] Figures 1 to 6 show an embodiment of the present invention, in which Figure 1 is a longitudinal cross-sectional side view of a bolt and nut, and Figure 2 (^) (B
) to FIG. 6 are longitudinal sectional side views showing the main parts of the screw thread. Figures 7 to 11 show conventional examples, Figures 7 and 8, Figures 10 and 11 are longitudinal sectional side views showing the main parts of the thread, and Figure 9 is a side view of the thread. FIG. (Yu... male screw part θ area...
Screw thread (15z) (15b) (15cHI5d)...
...Slope (17x) (17b) (Inc) (I'
d)......Slope (II...Female screw part
(III*l)... Valley bottom (II [phase]...
・・・Top

Claims (5)

[Claims] (1) In a pair of male and female screw threads with the same nominal diameter, but with different bending strengths of both threads, the gap between the slopes of both the male and female threads facing in opposite tightening directions. ,
An asymmetric screw device characterized in that the bending strength is formed so as to gradually increase toward a lower strength side. (2) Claim (1) in which a part of the slope facing the opposite direction of tightening of the male screw portion is removed and the valley bottom of the male screw portion is expanded in the direction of tightening progress.
) described asymmetric screw device. (3) Claim (1) in which a part of the slope facing the opposite direction of tightening of the female screw part is removed and the top of the female screw part is reduced in the tightening direction.
) or the asymmetric screw device described in (2). (4) Claim (1) in which a part of the slope facing the opposite direction of the tightening of the female thread is removed and the bottom of the female thread is expanded in the direction of tightening.
) described asymmetric screw device. (5) Claim (1) in which a part of the slope facing the opposite direction of tightening of the male screw portion is removed and the top of the male screw portion is reduced in the direction of tightening progress.
) or the asymmetric screw device described in (4).