JP7424687B2 - locking bolt - Google Patents

Description

The present invention relates to a locking bolt having a locking function.

Conventionally, in order to prevent bolts from loosening, various locking nuts and locking washers having a locking function have been developed and put into practical use. Known locking nuts include U-nuts and Hardlock nuts (“Hardlock” and “HARDLOCK” are trademarks of the applicant). Furthermore, examples of the locking washer include a taper washer and a washer having an uneven shape such as serrations on the seat surface.

In recent years, in order to reduce the burden of installation work and reduce weight, screw holes are formed in the equipment frame or other object to be installed by tapping, etc., and screwed into the screw holes, without using nuts or washers. 2. Description of the Related Art There is an increasing demand in various industries for fastening and fixing a mounting part to an object to be mounted using bolts. In order to prevent the bolt from loosening even in such a case, a locking bolt that has a locking function by itself is required.

Generally, male threads and female threads are formed with dimensional accuracy within a range of dimensional tolerances in accordance with required standards such as ISO standards. The dimensional tolerances of the male thread and the female thread are determined so that the nut can be screwed onto the threaded shaft of the bolt. For general metric threads, the dimensional tolerance of male threads is, for example, the tolerance range class of JIS B0209-2:2001 (ISO 965-2:1998) 6g, and the dimensional tolerance of female threads is, for example, JIS B0209-2:2001 (ISO 965-2:1998). 965-2:1998) 6H tolerance zone class. the result,
Play occurs between the male thread and the female thread.

If there is any play between the male thread and the female thread, the bolt will loosen in a short period of time in a situation where the bearing surface pressure is intermittently lost due to vibration.

Patent Document 1 discloses a technique for eliminating play between a male thread and a female thread by providing a "bump 16" on the flank surface of the female thread, thereby preventing loosening.

Patent Document 2 discloses that the flank face of the male thread of the bolt shaft is composed of a top flank face (13) with a gentler slope than the female thread, and a valley side flank face (12) with a steeper slope than the female thread. A technique has been disclosed in which a connection is made using an arcuate surface (15) and this arcuate surface portion interferes with the female thread to prevent loosening.

Patent Document 3 discloses that a protrusion (9) is provided on the compression side flank at the end of the female thread of the nut, and by deforming the end of the female thread when fastening is completed, the play side flank of the female thread becomes the play side flank of the male thread. Techniques have been disclosed for applying pressure and thereby preventing loosening.

Patent Document 4 discloses a grounding bolt that increases the contact area with the nut when fastened to the nut and increases the amount of current flowing through the fastened portion with the nut. This earthing bolt has a convex portion (18) formed on the head side flank surface (15a) of the thread.

Patent Document 5 discloses a technique for preventing loosening by providing a convex curved surface on the compression flank of a male thread or a female thread.

Patent Document 6 discloses a technique in which the flank surface of the male screw is configured with a convex curved surface, while the flank surface of the female screw is configured with a concave curved surface that matches the convex curved surface of the male screw, thereby increasing the strength of the screw connection. .

Patent Document 7 discloses that the screw threads are formed in an inclined shape, and when the screw threads are deformed when the fastening is completed, not only the compression side flank surfaces but also the play side flank surfaces are brought into contact with each other, thereby preventing loosening. A technique for performing this is disclosed.

Special Publication No. 2001-512807 Japanese Patent Application Publication No. 2019-113156 Japanese Patent Application Publication No. 2018-100765 Japanese Patent Application Publication No. 2015-137700 Special Publication No. 2013-543962 Japanese Patent Application Publication No. 2008-151346 JP2014-206234A

An object of the present invention is to provide a locking bolt that is excellent in fastening workability and has a locking function in the bolt itself.

The locking bolt according to the present disclosure has a threaded shaft with a male thread formed on the outer peripheral surface so as to be screwed into a threaded hole having a female thread. The male thread includes an R threaded portion located in the middle of the threaded shaft in the axial direction, and a distal end threaded portion located further toward the distal end in the axial direction than the R threaded portion.

At least one of the compression side flank surface and the play side flank surface of the R threaded portion is arranged such that there is no play with respect to the female thread (that is, the R threaded portion of the male thread and the compression side flank surface of the female thread are in contact with each other, and It may have a convex flank surface portion having a convex arc shape in a cross section along the axial direction (so that the R threaded portion of the male thread and the free side flank surface of the female thread come into contact with each other). This convex flank surface portion may be spirally continuous over at least 1/2 pitch of the male thread. Preferably, the entire compression side flank surface of the R threaded portion may be the convex flank surface portion. Further, the entire play side flank surface of the R threaded portion may be the convex flank surface portion.

The distal end threaded portion does not have the convex flank surface portion. Preferably, when the screw shaft is completely fastened to the screw hole, the distal end threaded portion of the male thread and the compression side flank surface of the female thread are in contact with each other, but there is no contact between the distal end threaded portion of the male thread and the play side flank surface of the female thread. A gap is formed. The distal end side threaded portion may be designed according to a standard thread shape defined in a general standard, for example, JIS B 0205-1. For example, the compression side flank surface and the play side flank surface of the tip side threaded portion may be flat or concave in a cross section along the axial direction of the bolt. On the other hand, the convex flank surface portion of the R threaded portion can be designed to slightly protrude outward in the radial direction from the dimensional tolerance of the reference thread shape.
According to the locking bolt of the present invention, the distal end threaded portion can be smoothly threaded into the screw hole at the initial stage of bolt fastening work. When the R thread part fits into the threaded hole, not only the compression side flank surfaces of the R thread part and the female thread contact each other, but also the play side flank surfaces contact each other, so the contact friction resistance increases and the predetermined prevailing occurs. Torque is generated, but since the tip threaded portion is already fitted into the threaded hole, rotating the bolt generates a threading force in the axial direction, and the R threaded portion is fitted into the threaded hole.

The convex flank surface portion of the R thread portion may be spirally continuous over at least 3/4 pitch of the male thread, or may be spirally continuous over at least one pitch of the male thread. According to this, an alignment effect occurs when the R threaded portion fits into the female thread, and it is possible to prevent the axial center of the screw shaft from being eccentric with respect to the axial center of the screw hole. In addition, when only one R threaded portion is provided, by continuing this only R threaded portion in a spiral over at least one pitch of the male thread, the necessary prevailing torque can be applied by the only R threaded portion. can be caused.

Preferably, each of the compression side flank surface and the play side flank surface of the R threaded portion may have the convex flank surface portion. That is, both the compression side flank surface and the play side flank surface of the R threaded portion are arranged such that there is no play with respect to the female thread (that is, the R threaded portion of the male thread and the compression side flank surface of the female thread are in contact with each other, and It may have a convex flank surface portion having a convex arc shape in a cross section along the axial direction (so that the R threaded portion of the male thread and the free side flank surface of the female thread come into contact with each other). According to this, contact between the compression-side flank surfaces of the R-threaded portion and the female thread, and contact between the free-side flank surfaces of the R-threaded portion and the female thread, can occur more reliably.

Preferably, the male thread may further include a proximal threaded portion located on the proximal end side in the axial direction than the R threaded portion. This proximal threaded portion does not have the convex flank surface portion. Preferably, when the screw shaft is completely fastened to the screw hole, the proximal threaded portion of the male thread and the compression side flank surface of the female thread are in contact with each other, but the proximal threaded portion of the male thread and the free side flank surface of the female thread are in contact with each other. A gap is formed between them. The proximal threaded portion may be designed according to a standard thread shape defined in a general standard, for example, JIS B 0205-1. For example, the compression side flank surface and the play side flank surface of the proximal threaded portion may be flat or concave in a cross section along the axial direction of the bolt. By providing the proximal threaded part in this way, the proximal threaded part can bear most of the axial force of the screw shaft, and by reducing the axial force generated in the R threaded part, the R It is possible to prevent seizure from occurring in the threaded portion.

Preferably, the proximal threaded portion, the R threaded portion, and the distal threaded portion may be spirally continuous to form one thread. Alternatively, the proximal threaded portion may be a part of another thread spaced apart in the axial direction from the R threaded portion. Further, the proximal threaded portion may be a part of another thread spaced apart in the axial direction from the R threaded portion.

The male thread may further include a second R threaded portion different from the R threaded portion (hereinafter referred to as “first R threaded portion”) and an intermediate threaded portion. The second R threaded portion and the intermediate threaded portion may be located between the first R threaded portion and the proximal threaded portion in the axial direction. The intermediate threaded portion may be located between the first R threaded portion and the second R threaded portion in the axial direction. At least one of the compression side flank surface and the play side flank surface of the second R threaded portion may have a convex flank surface portion having a convex arc shape in a cross section along the axial direction so as to eliminate play with respect to the female thread. The convex flank surface portion of the second R threaded portion may be spirally continuous over at least 1/2 pitch of the male thread. The intermediate threaded portion does not have the convex flank surface portion. For example, the convex flank surface portion of the second R threaded portion can be designed to slightly protrude outward in the radial direction from the dimensional tolerance of the reference thread shape of the male thread.

In this manner, by providing the second R threaded portion and the intermediate threaded portion, it is possible to generate the necessary prevailing torque while preventing the prevailing torque from becoming excessively large.

The intermediate threaded portion may be spirally continuous over at least 0.9 pitch of the male thread. If the intermediate threaded portion is spirally continuous over at least one pitch of the male thread, the distal end of the first R thread and the proximal end of the second R thread will not be adjacent to each other, and any cross-section Also, an intermediate threaded portion is interposed between the first R threaded portion and the second R threaded portion.

Preferably, each of the compression side flank surface and the play side flank surface of the second R threaded portion may have the convex flank surface portion.

The convex flank surface portion of the second R threaded portion may be spirally continuous over at least 3/4 pitch of the male thread, or may be spirally continuous over at least one pitch of the male thread.

Preferably, the proximal threaded portion, the first R threaded portion, the intermediate threaded portion, the second R threaded portion, and the distal threaded portion are spirally continuous to form one thread. good.

According to the present invention, it is possible to provide a locking bolt that has excellent fastening workability and has a locking function in the bolt itself.

FIG. 1 is a front view and an enlarged view of essential parts of a locking bolt according to a first embodiment of the present invention. FIG. 2 is a sectional view of the same locking bolt fastened to a screw hole. FIG. 3 is a front view and an enlarged view of essential parts of a locking bolt according to a second embodiment of the present invention. FIG. 4 is a schematic diagram of the bolt rolling device. FIG. 5 is an enlarged side view of a main part of a rolling round die for rolling a locking bolt according to a second embodiment. FIG. 6 is a graph showing the test results of a repeated attachment and detachment test of the locking bolt according to the second embodiment.

Hereinafter, preferred embodiments of the present invention will be described based on the drawings.

1 and 2 show a locking bolt according to a first embodiment of the present invention. This locking bolt is used to fasten and fix the attachment part 4 to an attachment target 3 such as a device frame or a steel plate. A screw hole 31 is previously formed in the object to be mounted 3 by tapping or the like, and a bolt insertion hole is formed in the mounting component 4.

The locking bolt is made of metal such as SS or SUS, and has a threaded shaft 1 with a male thread 2 formed on its outer circumferential surface so as to be screwed into a threaded hole 31 having a female thread. The male thread 2 includes an R threaded portion 21 located halfway in the axial direction of the screw shaft 1, a distal end threaded portion 22 extending from the axial end of the R threaded portion 21 toward the distal end side, and an axial end of the R threaded portion 21. It includes a proximal threaded portion 23 extending from the proximal end toward the proximal side.

The distal end threaded portion 22 and the proximal threaded portion 23 have a general thread shape, for example, a triangular thread shape, and have a compression side flank surface (the upper side surface of the thread in the figure) and an idle side flank. All of the surfaces (lower side surfaces of the threads in the figure) are flat in cross section along the axial direction. Note that the flank angle of each flank surface is, for example, 30°.

In the illustrated embodiment, each of the compression side flank surface and the play side flank surface of the R threaded portion 21 is formed as a convex flank surface having a convex arc shape in a cross section along the axial direction so that play with respect to the female thread of the screw hole 31 is eliminated. ing. In this embodiment, the compression side flank surface and the play side flank surface of the R threaded portion 21, which are convex flank surfaces, are spirally continuous over about two pitches of the male thread.

When the threaded shaft 1 of the locking bolt is fastened to the threaded hole 31, as shown in FIG. The flank surfaces touch each other. On the other hand, in the distal end threaded part 22 and the proximal threaded part 23 that are formed as general threads, the compression side flank surfaces of the male thread 2 and the female thread contact each other, but there is a gap between the play side flank surfaces of the male thread 2 and the female thread. It is formed. In such a fastened state, most of the axial force of the screw shaft 1 is borne by the proximal threaded portion 23, and an excessive force is borne by the R threaded portion 21 whose compression side and play side flank surfaces are in contact with the female thread. It is possible to avoid the occurrence of stress. On the other hand, in the initial stage of bolt fastening work, the screwing is started from the tip end threaded portion 22 made of a general thread, so the R threaded portion 21 is fitted into the screw hole 31 by the threading force of the tip end threaded portion 22. be able to. Therefore, although the R threaded portion 21 exhibits a large loosening prevention effect, the fastening workability is excellent.

FIG. 3 shows a locking bolt according to a second embodiment of the present invention. Structures similar to those of the first embodiment are given the same reference numerals and detailed explanations are omitted, and different structures and effects will be explained. do.

The locking bolt according to the second embodiment has two R threaded portions 21', 21'' (shown as shaded areas in FIG. 3) spaced apart in the axial direction, and two R threaded portions 21', 21''. and an intermediate threaded portion 24 provided therebetween.

Each of the R threaded portions 21', 21'' continues spirally over approximately one pitch of the male thread.The shape of each R threaded portion may be the same as that of the first embodiment.

The intermediate threaded portion 24 continues spirally over approximately one pitch of the male thread. The thread shape of the intermediate threaded portion 24 may be the same as that of the distal threaded portion 22 and the proximal threaded portion 23. That is, when the screw shaft 1 of the bolt is fastened to the screw hole 31, the compression side flank surface of the intermediate threaded portion 24 contacts the compression side flank surface of the female thread, but there is no play between the play side flank surface of the intermediate threaded portion 24 and the female thread. Each flank surface of the intermediate threaded portion 24 is formed flat in a cross section along the axial direction so that a gap is formed between the flank surfaces and the side flank surfaces.

According to the locking bolt according to the second embodiment, the two R threaded portions generate prevailing torque to prevent the bolt from loosening. Furthermore, by providing the intermediate threaded portion between the two R threaded portions, it is possible to prevent the prevailing torque from becoming excessively large due to manufacturing errors or the like.

The locking bolts according to each of the embodiments described above can be manufactured using a bolt rolling apparatus shown in FIG. 4. This bolt rolling device includes two rolling round dies, and forms a male thread on the outer periphery of the blank by rolling the blank (bar material) between the rolling round dies.

FIG. 5 shows an example of a rolling round die for rolling the locking bolt according to the second embodiment. This die has a diameter that is n times (for example, 8 times) that of the screw shaft 1, and a multi-thread thread having n threads is formed on the outer circumferential surface. When the die rotates once, the screw shaft rotates n times. That is, when the die rotates 1/n, the screw shaft rotates once, and the thread shape on the outer periphery of the die is transferred to the screw shaft.

A part of the multi-thread thread of the die is provided with a plurality of R flank surface forming portions (shown as braided portions in FIG. 5) for forming flank surfaces of the two R threads. Since the number of threads of the male thread of the die is n, when forming an R thread portion of approximately 1 pitch, each R flank surface forming portion only needs to be continuous over approximately 1/n circumference of the die.

By using the two rolling dies shown in FIG. 5, a locking nut having an R threaded portion can be manufactured with high productivity. Although it is important to synchronize the axial positioning of each die and the rotation period of each R flank surface forming part between the two dies, it is possible to intentionally shift the rotation period slightly. It is also possible to finely adjust the length of the R threaded portion.

FIG. 6 shows the results of measuring residual prevailing torque through repeated attachment and detachment tests of the locking bolt according to the second embodiment. The size of the bolt used in the test was M20, and the thread pitch was 2.5 mm. From the test results, the prevailing torque decreased to about 60% after the first 10 times of attachment and detachment, but the prevailing torque remained at about 60% even after repeated attachment and detachment. This confirmed that the locking bolt of this embodiment exhibits a sufficient locking function even if it is repeatedly attached and detached.

The present invention is not limited to the above embodiments, and the design can be changed as appropriate. For example, if the axial force acting on the threaded shaft of the bolt is relatively small, the proximal threaded portion may not be provided.

1 Threaded shaft 2 Male thread 21 R threaded part 22 Distal threaded part 23 Proximal threaded part 24 Intermediate threaded part 31 Screw hole

Claims (10)

a threaded shaft with a male thread formed on the outer circumferential surface so as to be screwed into a threaded hole having a female thread;
The male thread includes an R threaded portion located in the middle of the threaded shaft in the axial direction, and a distal threaded portion located on the distal end side of the R threaded portion in the axial direction,
At least one of the compression side flank surface and the play side flank surface of the R threaded portion has a convex flank surface portion having a convex arc shape in a cross section along the axial direction so as to eliminate play with respect to the female thread, and the convex flank surface The portion is spirally continuous over at least 1/2 pitch of the male thread,
the distal end threaded portion does not have the convex flank surface portion;
Locking bolt. The locking bolt according to claim 1, wherein the convex flank surface portion of the R threaded portion continues spirally over at least one pitch of the male thread. The locking bolt according to claim 1 or 2, wherein each of the compression side flank surface and the play side flank surface of the R thread portion has the convex flank surface portion. The locking bolt according to any one of claims 1 to 3, wherein the male thread further includes a proximal threaded portion located on the proximal end side in the axial direction than the R threaded portion, and the proximal threaded portion The locking bolt does not have the convex flank surface portion. The locking bolt according to claim 4, wherein the proximal threaded portion, the R threaded portion, and the tip threaded portion are spirally continuous to form one thread. . The locking bolt according to claim 4 or 5, wherein the male thread further includes a second R threaded portion different from the R threaded portion (hereinafter referred to as “first R threaded portion”) and an intermediate threaded portion, The second R threaded portion and the intermediate threaded portion are located between the first R threaded portion and the proximal threaded portion in the axial direction, and the intermediate threaded portion is located between the first R threaded portion and the proximal threaded portion in the axial direction. At least one of the compression side flank surface and the play side flank surface of the second R thread section has a convex arc shape in a cross section along the axial direction so as to eliminate play with respect to the female thread. The locking device has a convex flank surface portion, the convex flank surface portion is spirally continuous over at least 1/2 pitch of the male thread, and the intermediate thread portion does not have the convex flank surface portion. bolt. The locking bolt according to claim 6, wherein the intermediate threaded portion continues spirally over at least 0.9 pitch of the male thread. The locking bolt according to claim 6 or 7, wherein each of the compression side flank surface and the play side flank surface of the second R threaded portion has the convex flank surface portion. The locking bolt according to any one of claims 6 to 8, wherein the convex flank surface portion of the second R threaded portion continues spirally over at least 3/4 pitch of the external thread. bolt. In the locking bolt according to any one of claims 6 to 9, the proximal threaded portion, the first R threaded portion, the intermediate threaded portion, the second R threaded portion, and the distal threaded portion are A locking bolt that has two continuous threads in a spiral pattern.

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