JP2012137174A - Loosening prevention bolt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a loosening prevention bolt, which can reliably prevent loosening in a simple constitution, has low cost, and is suitably structured to be applied especially to a long bolt.SOLUTION: The bolt includes: a fastening bolt wherein a closed-end space of a spindle form reduced in width in a conical shape from the tip end side toward the base end side is formed in the tip end shaft center of a shaft extending from a head, and a slit circumferentially dividing a tip end cylindrical portion at a circumferentially equally dividing position; a diameter expanding member positioned inside the space and having a spindle-like side circumferential surface touching the inside wall of the space; and a screwing means, coupled to a base of the space, for biasing toward the bolt head side by making the diameter expanding member touch the internal surface of the space.

Description

Detailed Description of the Invention

  The present invention relates to a loosening prevention bolt having a loosening prevention function.

  Between the female thread part engaged with the thread part of the bolt, the spiral thread / groove surface is generated based on the reaction in the longitudinal direction acting between the spiral thread / groove provided around the longitudinal axis. The mutual rotation is stopped by the component force of the friction force between them, and the fixed relationship is maintained. However, since the frictional force generated between the spiral strip and the groove surface is only generated between the smooth sloped surfaces, the tightening member expands and contracts due to temperature changes, and the vibration is repeated for a long time. The above-mentioned fixing condition between the bolt and nut may be broken based on slippage between the inclined surfaces, and the bolt may loosen or fall off, causing an accident.

  In order to prevent this type of accident, various types of locking structures have been conventionally proposed as means for fixing bolts and nuts. For example, Patent Document 1 discloses a locking bolt. As shown in FIG. 8A, the locking bolt of Patent Document 1 includes a headed bolt 201 having a truncated conical convex portion 2 concentric with the bolt shaft core on the lower surface of the tip, It consists of a disc-shaped receiving member 204 having a convex portion 202 and a symmetrical concave portion 203 on the upper surface. A disc-shaped receiving member is inserted into a bottomed screw hole in advance, and a truncated cone shape provided at the tip of the bolt. By causing the convex portion to be eccentrically fitted to the receiving member, the bolt is surely locked by applying a large shearing stress in a direction perpendicular to the axial direction to the bolt. In FIG. 8B, an outer screw having the same pitch as that of the bolt 1 is formed on the outer peripheral surface of the disc-shaped receiving member 204 ′, and a box wrench is formed on the upper surface of the convex portion of the disc-shaped receiving member 204 ′. An engaging portion for engaging the rotation B is provided, and the disc-shaped receiving member 204 ′ is screwed to the predetermined position of the bottomed screw hole 205 with the predetermined rotating tool B. I try to enter.

Japanese Patent Laid-Open No. 10-37936

  The bolts of this type that have been known so far have a complicated locking member / structure, which may increase costs, require too much work, or have a narrow scope of locking. There is a difficulty such as only corresponding to the bottom screw hole or conversely only to the through screw hole. Therefore, the present applicant has created a new structure of a loosening prevention bolt with a simple structure that can surely prevent loosening and has a wide construction range, and applied for a patent (Japanese Patent Application No. 2010-276347). A typical configuration example of the loosening prevention bolt of the existing application will be briefly described with reference to FIG. 9 (each code is associated with the specification of the existing application, and 500 is uniformly added to the number of the corresponding code. ) 9, (a) is a top view of the bolt 510, (b) is a partially sectional side view, (c) is a bottom view, (d) is a top view of the auxiliary bolt alone, and (e) is a diameter-enlarging member. It is a side view. 9 includes a fastening bolt (screw body) 511, a sub bolt (second bolt) 521, and a diameter-expanding member (so-called top) 531.

  As shown in FIG. 9, the fastening bolt 511 is a hexagon head type head fastening bolt in which a cylindrical fastening bolt shaft 511a protrudes from a hexagonal head 512 and is integrally formed, and has a through hole 511b in the shaft center. A spiral groove (male thread) 511c is formed at least at the tip of the outer peripheral surface of the fastening bolt shaft 511a, and a conically widened space is formed at the axial center of the tip of the spiral groove (thread) 511c. A portion 511d is formed. A side surface of the head 512 serves as a tool engaging portion 512a. In addition, a radial slit 511e is formed in the distal end cylindrical portion so as to divide the distal end portion of the screw portion into four in the circumferential direction including the distal end surface (annular surface) at the circumferentially equal division position. In addition, a concave portion 511f that accommodates a head portion 521b of a sub bolt 521, which will be described later, is formed at the center of the head portion 512 of the fastening bolt 511.

  In the space portion 511d, a diameter-enlarging member 531 having a truncated cone side surface (conical truncated cone portion) 531a that abuts against the inner wall of the space portion is disposed (see FIG. 1). This frustoconical diameter-expanding member 531 is a truncated cone in which, for example, the apex of a cone having an apex angle of 8 degrees (the angle is exaggerated in the drawing) is eliminated. A screw hole 531b that is screwed into the tip screw portion 521c of the sub bolt 521 is screwed in the shaft center portion of the diameter expanding member 531. Further, on the side peripheral surface, a protrusion that extends in the axial direction (length direction) corresponding to each slit 511e on the side surface of the diameter-expanding member and functions as rotation preventing means for preventing circumferential rotation. A long plate-like blade member 531c, which becomes a (locking protrusion), is formed. In the present embodiment, the blade member 531c is separately formed and fitted into a fitting groove extending in the axial direction, which is formed in the diameter-expanding member main body at four equally spaced positions, and is fixed. Of course, they may be integrally formed. In the embodiment, the blade member 531c is provided at four locations corresponding to all the slits. However, depending on the application of the loosening prevention bolt 510, it may be provided only at two axially symmetric locations and functions sufficiently. . The diameter-expanding member 531 can be expanded in diameter by pushing the tip threaded portion of the fastening bolt outwardly by moving it upward in the space portion 511d. Detailed description will be given to the specification of the application already filed, and will be omitted here.

  The structure of the above-mentioned loosening prevention bolt of the applicant of the present application has a wide target range of the locking prevention and can be applied to both the through screw hole and the bottomed screw hole, but requires advanced processing. In particular, application to long bolts increases the difficulty of processing and increases costs, and it is difficult to ensure the axial strength of the bolts.

  Therefore, the present invention has been made with the object of providing a loosening prevention bolt having a structure in which a through screw hole is an object to be screwed and is more easily processed, and particularly suitable for application to a long bolt.

  In order to solve the problem, the loosening prevention bolt according to the first aspect of the present invention is a weight reduced in a cone shape from a distal end side to a proximal end side at a distal end axial center portion of a shaft portion extending from a head portion. A trapezoidal bottomed space portion is formed, and a fastening bolt having a slit that divides the distal end cylindrical portion in the circumferential direction at a circumferentially equal division position, and an inner wall of the space portion that is positioned in the space portion. A diameter-enlarging member having a frustum-shaped side peripheral surface that is in contact with, and a threaded engagement for connecting the diameter-enlarging member to the bottom portion of the space portion and abutting against the inner surface of the space portion to urge the bolt head side And means.

  According to a second aspect of the present invention, in the loosening prevention bolt according to the first aspect, the screwing means includes a female screw portion screwed on an axial center portion of the bottom portion of the space portion, and the diameter-expanding member. It is characterized by comprising a sub-bolt that is inserted through a through-hole formed in the shaft center portion of the shaft and screwed into the female screw portion and biases the diameter-expanding member. According to a third aspect of the present invention, in the loosening prevention bolt according to the first aspect, the screwing means is erected on the axial center portion of the bottom portion of the space portion, and the axial center portion of the diameter-expanding member. An urging shaft portion having a male screw threaded at least at a tip end thereof, and an auxiliary nut that is screwed with the male screw at the tip end of the urging shaft portion to urge the diameter-expanding member. It is characterized by becoming.

  Further, the invention according to claim 4 is the loosening prevention bolt according to any one of claims 1 to 3, wherein the rotation preventing means for preventing circumferential rotation of the threaded enlarged diameter member is as described above. A locking projection that engages with the slit and prevents rotation is provided on a side surface of the diameter-expanding member. According to a fifth aspect of the present invention, in the loosening prevention bolt according to the fourth aspect, the locking protrusion is a protrusion formed in a side surface of the diameter-expanding member and extending in the length direction. And

  The loosening prevention bolt according to the present invention with the through screw hole as a screwing object is low-cost, and exhibits a strong rotation suppressing effect after final tightening, and can reliably prevent loosening of the bolt. In particular, it can be applied to a long bolt.

It is a figure which shows the loosening bolt of 1st embodiment which concerns on this invention, (a) is a partial cross section front view, (b) is a bottom view. The components in the first embodiment according to the present invention are shown, (a) is a front sectional view of the fastening bolt, (b) is a bottom view, (c) is a front view of the diameter-expanding member, (d ) Is a front view of the sub bolt, and (e) is a bottom view of the same. (A)-(e) is explanatory drawing which shows the example of the diameter expansion member which concerns on this invention. (A), (b) is a partially cutaway front view which shows the state which attached the loosening prevention bolt which concerns on this invention to the to-be-coupled object. It is a figure which shows the loosening prevention bolt of 2nd embodiment of this invention, (a) is a partial cross section front view, (b) is a bottom view similarly, (c) is explanatory drawing which shows a diameter-expansion member, (d) FIG. 3 is a front view of a sub bolt. It is a figure explaining the loosening prevention bolt of 3rd embodiment of this invention, (a) is front sectional drawing of a fastening bolt, (b) is a front view of a diameter-expansion member, (c) is a nut as a latching body. (D) is a front view of the whole loosening prevention bolt. It is a partial notch front view which shows the state which attached the loosening prevention volt | bolt which concerns on this invention to the thing to be joined. (A), (b) is a figure explaining a known locking bolt. (A) is a top view, (b) is a partially sectional front view, (c) is a bottom view, (d) is a front view of a sub-bolt alone, and (e) is a diameter-enlarging member. FIG.

[First Embodiment]
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a loosening prevention bolt 10 (hereinafter also simply referred to as a bolt) according to a first embodiment of the present invention, wherein (a) is a partially sectional side view and (b) is a bottom view. FIG. 2 shows each member, (a) is a side sectional view of the fastening bolt (screw body) 11, (b) is a bottom view, (c) is a top view of the diameter-expanding member, and (d) is a side view thereof. FIG. 4E is a side view of the sub bolt. The bolt 10 includes a fastening bolt (screw body) 11, a secondary bolt (second bolt) 21, and a diameter-expanding member (so-called top) 31.

  The fastening bolt 11 will be described with reference to FIGS. 1 and 2. As shown in the figure, the fastening bolt 11 is a hexagonal head-type long head fastening bolt in which a cylindrical fastening bolt shaft 11a protrudes from a hexagonal head 12 and is integrally formed, and the outer periphery of the fastening bolt shaft 11a. A spiral groove (male thread) 11c is engraved on the front end portion of the surface, and a frustum that is conically widened from the distal end side to the proximal end side at the axial center portion of the distal end portion of the spiral groove (thread portion) 11c. A bottomed space portion 11d is formed, and a female screw portion 11f that engages with the tip screw portion 21c of the sub bolt 21 is screwed in the axial center portion of the bottom portion of the space portion (expanded space portion) 11d. Has been. The side surface of the hexagonal head 12 is a tool engaging portion 12a. In addition, a radial slit 11e that divides the distal end portion of the screw portion into four in the circumferential direction including the distal end surface (annular surface) at the circumferentially equally divided position is formed in the distal end cylindrical portion so as to be easily expanded.

  In the space portion 11d, a diameter-expanding member 31 having a truncated cone-shaped side surface (side circumferential surface) 31a that abuts against the inner wall of the space portion is disposed (see FIG. 1). The diameter-expanding member 31 will be described with reference to a top view, a front view, and a bottom view shown in FIG. The frustoconical diameter expanding member 31 is, for example, a truncated cone in which the apex of a cone having an apex angle of 8 degrees (the angle is exaggerated in the drawing) is eliminated. A through hole 31b through which the shaft portion 21b of the sub bolt 21 is inserted is formed in the shaft center portion of the diameter expanding member 31, and a head portion 21a of the sub bolt 21 described later is accommodated in the center of the lower surface (bottom frustum bottom surface). A circular recess 31d is formed. Further, on the side peripheral surface 31a, a protrusion that extends in the axial direction (length direction) and prevents rotation in the circumferential direction corresponding to each slit 11e on the side surface of the diameter-expanding member. A long plate-like blade member 31c which is a (locking protrusion) is formed. In the present embodiment, the blade member 31c is formed separately and is fitted and fixed to a fitting groove extending in the axial direction that is formed in the diameter-enlarging member main body at a position equally divided into four in the circumferential direction. Of course, they may be integrally formed. In the embodiment, the blade member 31c is provided at four locations corresponding to all the slits. However, depending on the application of the loosening prevention bolt 10, it may be provided only at two axially symmetric locations. Function. The diameter-expanding member 31 is pushed upward in the space 11d in the drawing (the head side of the fastening bolt 11) so as to push the threaded end of the fastening bolt outward (expanded diameter, widened).

  As the above-mentioned diameter-expanding member, at least part of the frustum-shaped portion has a truncated cone-shaped portion, and the frustum side surface of the truncated cone-shaped portion is in contact with the side surface of the diameter-expanded space portion exclusively. If upward stress is applied to the member 31, it is sufficient if the tip end portion of the spiral groove 11c of the fastening bolt can be pressed radially outward. Further, the shape of the bottomed space portion 11d does not have to be a truncated cone shape, and can be a regular truncated pyramid shape (a frustum whose area is reduced uniformly in the central axis direction on the bottom surface of the regular polygon). good.

  As shown in FIG. 3 (b), instead of the protrusions as the rotation preventing means, the engaging pins are provided on the side surfaces of the diameter-expanding member 31 at positions corresponding to the slits as means for engaging the slits 11e and preventing the rotation. (Locking protrusion) 31c may be erected. Furthermore, in order to prevent the rotation of the diameter-expanding member 31 inserted into the space portion in place of such a locking protrusion, a streak extending in the axial direction on the truncated cone side surface 31a as shown in FIG. A protrusion may be formed on the entire surface by performing a knurling process or an eyelet knurling process, and a rotation preventing effect can be obtained by a simple method. If the auxiliary bolt 21 is shaped so that it cannot be easily removed, it can be used as an anti-theft bolt. As shown in FIG. 3D, a stepped portion is provided in the truncated cone side surface 31a in the axial direction so that the diameter-expanding member 31 does not return even if the urging force of the auxiliary bolt 21 is reduced. It may be possible to increase the reliability as a wedge stop for this purpose. Even when the sub bolt 21 is loosened or removed, the diameter-expanding member (piece) 31 does not return, so that the bolt is not loosened and is maintained in a strongly locked state.

  A sub-bolt (second bolt) 21 shown in FIG. 2 includes a sub-bolt shaft portion 21b that is slidably inserted into a through-hole 31b formed in the diameter-expanding member 31, and an upper end of the sub-bolt shaft portion 21b. The auxiliary bolt head 2b is integrally formed. The auxiliary bolt 21 has a head portion 21 a having a large-diameter flat cone shape, and a shaft portion 22 b in which a spiral groove (male screw) 21 c is engraved at a tip portion in a through hole 31 b provided in the diameter-expanding member 31. It is inserted and screwed to the female screw portion 11f at the bottom of the bottomed space portion 11d by the tip screw portion 21c. In the center of the head 21a of the sub bolt 21, a hexagonal engaging recess is formed as a tool engaging portion 21d that engages with an appropriate rotary tool. The head portion 21 a abuts on the bottom surface of the circular recess 31 d on the lower surface of the diameter-expanding member 31 that is assembled coaxially and generates a biasing force that pushes up the diameter-expanding member 31 to contact the screw of the fastening bolt 11. The distal end portion of the portion can be expanded from the inner side to the outer peripheral side.

  The fastening bolt shaft 11a, the sub bolt 21, and the diameter expanding member 31 in the present invention can be made of metal such as iron or stainless steel. In addition, it can be made of hard plastic with sufficient rigidity. In addition, although the direction of the screw of the spiral groove 11c of the sub bolt 21 is the same general right screw as that of the fastening bolt 11, it may be a reverse screw.

  The bolt 10 according to the embodiment is assembled by passing the auxiliary bolt 21 through the through-hole 31b of the diameter-expanding member 31, screwing the tip portion of the shaft portion 21a with the female screw portion 11f at the bottom portion of the bottomed space portion 11d, and lightly screwing. Temporarily fix and place (see Fig. 1). In this state, the tip thread portion of the fastening bolt 11 does not bulge radially outward (does not expand in diameter), maintains a normal dimension, and can be handled in the same manner as a normal bolt.

  To fasten the fastened object A and the fastened object B with the bolt 10 of the present embodiment, the fastening bolt 11 is inserted into the through-hole of the fastened object A as shown in FIG. The fastening bolt 11 is screwed into the spiral groove of the article to be fastened B on the base side (right side in the figure) that is inserted and threaded into the spiral groove 11c of the fastening bolt 11. Although not shown, in principle, a spring washer is used. When screwing, the bolt head is turned with a tool such as a wrench, the lower part of the bolt head is brought into contact with the surface of the article A to be fastened, and the articles A and B are fastened with a normal tightening strength.

  For further locking, the auxiliary bolt 21 is rotated by inserting and turning a hexagonal wrench (not shown) into a hexagonal hole provided in the head of the auxiliary bolt 21, for example, so that the tip of the auxiliary bolt 21 is connected to the female screw portion. (Screw hole) The upward stress is always applied to the diameter-expanding member 31 through which the sub bolt 21 is inserted by tightening the screw 11f. As a result, horizontal and vertical stresses are applied to the abutting space inner wall from the peripheral surface of the diameter expanding member 31 to expand the diameter of the tip threaded portion of the fastening bolt 11 (widen), and the entire outer periphery. It exerts a strong locking effect, and as a result, it is possible to reliably prevent the bolt from loosening. Thereafter, even if strong vibration is applied, the coupling of the fastening bolt 11 is loosened and does not rotate in the direction of disengagement, and the loosening can be prevented over a long period.

  When the operator wants to loosen, first, the secondary bolt 22 is loosened. As a result, the locking effect due to the widening of the tip end portion of the fastening bolt 11 is reduced and the normal holding force is restored. In this state, a general-purpose tool (driver, wrench, etc.) that can turn the fastening bolt is engaged, and the fastening bolt is engaged. The bolt 10 can be removed from the object to be fastened by rotating in the direction of removing the bolt 11 (the direction opposite to the direction of mounting). If necessary, the removed bolt 10 can be used again.

  FIG. 4B shows a case where the fastened object A and the fastened object B are fastened using the bolt 10 and the nut 41. In this case, after the bolt 10 is inserted into the through holes of the two fastened objects A and B, the fastened object is fastened by screwing and tightening the nut 41 to the spiral groove 11c at the tip. Similarly, in order to prevent loosening, an upward stress is always applied to the diameter-expanded member 31 through which the auxiliary bolt 21 is inserted by rotating the auxiliary bolt 21 and tightening the tip of the auxiliary bolt 21 into the female screw portion 11f. By doing so, the threaded end of the fastening bolt 11 is expanded and widened (widened), and the screwed portion of the fastening bolt 11 and the article B to be fastened is strongly locked to reliably prevent loosening. it can.

  In addition, the above-described loosening prevention bolt exhibits a sufficient bolting prevention effect even when used alone, but as shown in FIG. May be obtained. That is, the fastening bolt 11 is tightened by using the bolt 10 having a bolt length that protrudes from the fastened object, and further tightened by screwing the nut into the tip thread portion that protrudes from the fastened object. When 21 screws are tightened, a double lock is obtained, and the reliability of the screw fastening portion can be increased.

  In the embodiment described above, the sub bolt 21 has a hexagonal recess as the tool engaging portion 21d. However, the tool engaging portion may have any shape as long as the sub bolt 21 can be rotated. Of course there may be. The tool engaging portion may be a polygonal hole that fits a polygonal wrench, a minus or plus slot into which a minus or plus screwdriver can be inserted, or the like. Needless to say, the outer periphery of the head 21a of the sub bolt 21 is formed in, for example, a hexagonal shape and protrudes from the tip of the fastening bolt 11 so as to be rotated by a box spanner or the like. The secondary bolt 21 can be rotated with a commercially available tool, which is convenient and convenient. Depending on the application, a minus or plus groove into which a minus or plus screwdriver can be inserted may be sufficient.

  In this way, contrary to having versatility, the bolts may be loosened by a third party other than the administrator for the reason that the object to be fastened is an expensive one that may be stolen or for security reasons. When it is desired to eliminate the problem, it is preferable to make the tool engaging portion of the auxiliary bolt 21 special and add a crime prevention function / security function. For example, by making the tool engagement hole of a regular pentagonal system that can be rotated with a suitable dedicated wrench, a highly reliable bolt can be obtained in terms of crime prevention. In addition, also about the fastening bolt 11, as the tool engaging part 11h which rotates this, shapes other than hexagonal shape may be sufficient.

[Second Embodiment]
The loosening prevention bolt 10A of the second embodiment in which the sub bolt can be turned with a spanner or the like will be described with reference to FIG. As the sub bolt 21, a hexagon head type head fastening bolt is used. The fastening bolt 11 in this embodiment is the same as in the previous embodiment, and a description thereof is omitted. The diameter-expanding member 31 disposed in the space portion 11d is substantially the same as in the previous embodiment (see FIG. 3A), but has a flat surface with no circular recess on the lower surface. In addition, the dimensions of each part are designed so that the head of the sub bolt 21 protrudes sufficiently from the tip of the fastening bolt 11 in the raised state, and a spanner or a wrench can be used as a rotating tool. The bolt 10A of the second embodiment is also used in the same manner as in the case of the first embodiment described above, so that the same action and effect can be obtained and the loosening can be surely prevented. Of course, the effect of preventing loosening can be further enhanced by using a nut together. Even when the outer periphery of the head is used as the tool engaging portion, for example, a pentagonal shape may be used from the viewpoint of crime prevention, and the structure may be rotated by using a wrench suitable for this. It is also preferable to use a special shape with a tapered side engaging surface because a dedicated tool is required.

[Third Embodiment]
A loosening prevention bolt 10B according to a third embodiment will be described with reference to FIG. Also in this embodiment, the fastening bolt 11 is a hexagonal head-type long head fastening bolt as in the previous embodiment, and a spiral groove (male thread) 11c is engraved on the tip of the outer peripheral surface of the fastening bolt shaft 11a. A frustum-shaped bottomed space portion 11d is formed in the axial center portion of the tip portion of the spiral groove (screw portion) 11c, and the tip cylindrical portion is screwed at a circumferentially equally divided position. A radial slit 11e that divides the tip portion of the portion into four in the circumferential direction including the tip surface (annular surface) is formed. In the present embodiment, the space portion is configured as one of the screw members that connect the diameter-expanding member to the bottom portion of the space portion and abut against the inner side surface of the space portion to bias the bolt head side. A threaded shaft portion 11f having a diameter corresponding to the through hole 31b of the diameter-expanding member 31 is integrally formed from the center portion of the bottom portion of 11d so as to protrude from the tip of the spiral groove (male thread) 11c of the fastening bolt 11 by a certain length. In addition, a female screw is screwed at the tip of the screwing shaft portion 11f. A screwing means is constituted by the existing nut 41 as an auxiliary nut that is screwed into the female screw portion and biases the expanded member. The diameter-expanding member 31 disposed in the space portion 11d is substantially the same as in the previous embodiment (see FIG. 3A), but has a flat surface with no circular recess on the lower surface. The loosening prevention bolt 10B of the third embodiment can be used in the same manner as in the first embodiment, and the same operational effects can be obtained, and the loosening can be surely prevented.

  If a bolt 10 having a bolt length that protrudes from the object to be fastened and the diameter-expanding member 31 having the shape shown in FIG. In the diameter-expanding member 31 in FIG. 3 (e), for example, a truncated cone having a truncated apex having a top angle of 30 degrees, for example, is continuously connected to the lower bottom of the truncated cone having a truncated apex angle of 8 degrees. A blade member 31c is fixed to a frustoconical main body portion (the angle is exaggerated in the drawing) on the side peripheral surface having a constriction formed with an upper bottom. The diameter-expanding member 31 is inserted into the shaft portion 21a of the sub bolt 21, and the tip of the sub bolt 21 is screwed into the screwing screw hole 11f of the conical space portion 11d of the fastening bolt 11 and lightly screwed and assembled. Put (temporary fix). FIG. 7 shows the usage state of the bolt 10, and when the fastening bolt 11 and the sub bolt 21 are sequentially screwed in the same manner as described above, the distal end portion of the fastening bolt 11 is expanded and opened. Thus, a strong anti-loosening effect can be obtained, and the bolt 10 does not float by being locked by the bulged portion even in the event of loosening. In addition, reliability can be improved more by using together the nut tightening mentioned above at the time of use.

  The present invention has been described with reference to the embodiment. However, the present invention is not limited to the above-described embodiment, and various modifications can be made without changing the gist of the invention.

10, 10A ... Loosening prevention bolt 11 ... Fastening bolt (screw body)
11a ... Fastening bolt shaft 11b ... Head 11c ... Spiral groove (screw part)
11d ... Conical space (tip recess)
11e ... Slit 11f ... Screw screw hole (Female thread)
11g ... Screwed shaft (male thread)
11h ... Tool engaging portion 21 ... Sub bolt (second bolt)
21a ... Sub bolt head 21b ... Sub bolt shaft (connection shaft)
21c ... Threaded end portion 21d ... Tool engaging portion (engaging recess)
31 ... Diameter-expanding member (piece member)
31a ... frustoconical side surface (conical frustoconical part)
31b ... through hole 31c ... blade member (locking protrusion, rotation preventing means)
31d ... circular recess 41 ... nut

Claims (5)

A frustum-shaped bottomed space portion that is reduced in a cone shape from the distal end side toward the proximal end side is formed at the distal end axial center portion of the shaft portion extending from the head portion, and the distal end cylindrical portion is circumferentially equally divided. Fastening bolts with slits that divide in the circumferential direction at
A diameter-expanding member having a frustum-shaped side peripheral surface that is located in the space portion and contacts the inner wall of the space portion;
A screwing means for connecting to the bottom of the space, and abutting the diameter-expanding member on the inner surface of the space and urging it toward the bolt head;
A loosening prevention bolt, comprising:   The screwing means is inserted into a female screw part screwed to the shaft center part of the bottom part of the space part and a through hole formed in the shaft center part of the diameter-expanding member and screwed into the female screw part, The loosening prevention bolt according to claim 1, comprising a secondary bolt that urges the diameter-expanding member.   The energizing shaft in which the screwing means is inserted in the through hole formed in the shaft center portion of the diameter-expanding member so as to stand on the shaft center portion of the bottom portion of the space portion, and the male screw is screwed at least at the tip portion. 2. The loosening prevention bolt according to claim 1, comprising: a portion and an auxiliary nut that is screwed into a male screw at a tip of the biasing shaft portion and biases the diameter-expanding member.   The locking protrusion which engages with the slit and prevents rotation is provided on a side surface of the diameter increasing member as rotation preventing means for preventing rotation of the diameter expanding member in the circumferential direction. 4. The loosening prevention bolt according to any one of items 3.   The loosening prevention bolt according to claim 4, wherein the locking protrusion is a protrusion formed on a side surface of the diameter-expanding member and extending in the length direction.

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