JP2016161126A - Falling prevention device for fastening nut - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a falling prevention device for a fastening nut capable of preventing a nut fastened to a bolt, from being loosened by vibration and falling from the bolt.SOLUTION: In a restriction member 4 mounted on a bolt 3 for preventing falling of a fastening nut 2 loosened by vibration, the restriction member 4 is composed of a cylindrical body 5 having a bolt through hole 6 at the center, and a coil spring 10 accommodated in the bolt through hole 6. The coil spring 10 is composed of a coil portion 10a matching to pitches of a male screw 3a of the bolt 3, a fixed end portion 10b at one end of the coil spring 10, extended outward from an outer periphery of the coil portion 10a, and curved with a diameter larger than the coil portion 10a to be wound so as to be closely kept into contact with an outer periphery of the cylindrical body 5, and a free end portion 10c at the other end of the coil spring 10, faced outward from an opening 8 formed on one end of the cylindrical body 5.SELECTED DRAWING: Figure 1

Description

この発明は、振動などでボルトに螺合した締結ナットが緩み、ボルトから脱落することを防止するための締結ナット用脱落防止装置に関するものである。  The present invention relates to a fastening nut dropout prevention device for preventing a fastening nut screwed into a bolt by vibration or the like from loosening and dropping off from the bolt.

周知のように、ボルトに締結されたナットの緩みを止めて脱落防止するものとして、切欠きにより非連続のリングをなし、内周に雌ネジを有するものが多数提案されている（特許文献１）。このようなナット緩み止めリングは、それ自体が有する弾性により、内周の雌ネジをボルトの雄ネジに押圧することによって、雄ネジとの間に作用する摩擦力を大きくして、緩み止めの脱落を図ろうとするものである。  As is well known, as a means for preventing loosening of a nut fastened to a bolt and preventing it from falling off, a number of non-continuous rings formed by notches and having a female thread on the inner periphery have been proposed (Patent Document 1). ). Such a nut locking ring increases the frictional force acting between the male screw by pressing the inner female screw against the male screw of the bolt due to its own elasticity. It is intended to drop out.

特開昭５５−１１５６１３号公報Japanese Patent Application Laid-Open No. 55-115613

この特許文献１に記載のナット緩み止めリングでは、弾性力の大きさに限界があり、十分な緩み止め効果は得られず、しかも、通常のナットと同様に緩んでボルトから脱落してしまう虞があるので、抜け止め脱落の防止効果は得られないという問題があり、しかも、緩み止めリングの組み付けに手間がかかるなどの問題があった。  In the nut locking ring described in Patent Document 1, there is a limit to the magnitude of the elastic force, a sufficient locking effect cannot be obtained, and the nut may be loosened and fall off from the bolt in the same manner as a normal nut. Therefore, there is a problem that the effect of preventing the slipping-off and dropping cannot be obtained, and there is a problem that it takes time to assemble the locking ring.

この発明は、以上のようなことを考慮してなされたもので、ボルトにコイルバネが簡易に螺合され、長期間にわたって振動や外力等が作用することによる締結ナットの緩みによる脱落を確実に防止することができ、しかも、脱落を防止するための加工が少なく製作が容易な締結ナット用脱落防止装置を提供することを目的とする。  The present invention has been made in consideration of the above, and the coil spring is simply screwed onto the bolt, and it is reliably prevented from falling off due to loosening of the fastening nut due to vibration, external force, etc. acting over a long period of time. It is another object of the present invention to provide a fastening nut drop-off prevention device that can be manufactured and that is easy to manufacture with less processing for preventing the drop-off.

前記課題を解決し、かつ目的を達成するために、この発明は、以下のように構成した。  In order to solve the above-described problems and achieve the object, the present invention is configured as follows.

請求項１に記載の発明は、振動によって緩むナットの脱落を防ぐためにボルトに装着される規制部材であって、この規制部材は中央にボルト貫通孔を有する円筒体と、前記ボルト貫通孔内に収納されるコイルバネとよりなり、前記コイルバネは前記ボルトの前記雄ネジのピッチに整合するコイル部と、前記コイルバネの一方端を前記コイル部の外周より外方に延出して、前記コイル部より大径に湾曲させて前記円筒体の外周に密着するように卷装して固定端部とし、前記コイルバネの他方端を前記円筒体の一端に形成した開口より外方に臨ませて自由端部としてなることを特徴とする締結ナット用脱落防止装置である。  The invention according to claim 1 is a restricting member attached to the bolt to prevent the nut loosening due to vibration, and the restricting member has a cylindrical body having a bolt through hole in the center, and the bolt through hole. The coil spring includes a coil portion that matches the pitch of the male screw of the bolt, and one end of the coil spring extends outward from the outer periphery of the coil portion to be larger than the coil portion. It is curved to a diameter and is fitted so as to be in close contact with the outer periphery of the cylindrical body to be a fixed end, and the other end of the coil spring is faced outward from an opening formed at one end of the cylindrical body as a free end. This is a fastening nut dropout prevention device characterized in that.

請求項２に記載の発明は、前記コイルバネの他方端の自由端部が臨む前記開口の形成された前記円筒体の一端に多角形状の治具係合部を設けたことを特徴とする請求項１に記載の締結ナット用脱落防止装置である。  The invention according to claim 2 is characterized in that a polygonal jig engaging portion is provided at one end of the cylindrical body in which the opening facing the free end of the other end of the coil spring is formed. The fastening nut dropout prevention device according to claim 1.

請求項３に記載の発明は、前記円筒体は小径部と大径部よりなり、前記コイルバネの前記コイル部の外周より外方に延出して、前記コイル部より大径に湾曲される前記コイルバネの一方端を前記小径部の外周に密着するように卷装して前記固定端部としてなることを特徴とする請求項１または請求項２に記載の締結ナット用脱落防止装置である。  According to a third aspect of the present invention, the cylindrical body includes a small-diameter portion and a large-diameter portion, extends outward from the outer periphery of the coil portion of the coil spring, and is curved to have a larger diameter than the coil portion. 3. The fastening nut dropout prevention device according to claim 1, wherein one end of the fastening nut is fitted so as to be in close contact with the outer periphery of the small-diameter portion to serve as the fixed end portion.

前記構成により、この発明は、以下のような効果を有する。  With the above configuration, the present invention has the following effects.

請求項１に記載の発明では、振動によって緩むナットの脱落を防ぐためにボルトに装着される規制部材であって、この規制部材は中央にボルト貫通孔を有する円筒体と、前記ボルト貫通孔内に収納されるコイルバネとよりなり、前記コイルバネは前記ボルトの前記雄ネジのピッチに整合するコイル部と、前記コイルバネの一方端を前記コイル部の外周より外方に延出して、前記コイル部より大径に湾曲させて前記円筒体の外周に密着するように卷装して固定端部とし、前記コイルバネの他方端を前記円筒体の一端に形成した開口より外方に臨ませて自由端部とよりなるので、前記ボルトの振動などで、前記ボルトに螺合する前記締結ナットの脱落を確実に阻止でき、しかも、前記ボルトに装着する前記規制部材を前記ボルトの雄ネジに容易に螺合できる。  The invention according to claim 1 is a restricting member attached to the bolt to prevent the nut loosening due to vibration, and the restricting member has a cylindrical body having a bolt through hole in the center, and the bolt through hole. The coil spring includes a coil portion that matches the pitch of the male screw of the bolt, and one end of the coil spring extends outward from the outer periphery of the coil portion to be larger than the coil portion. It is curved to a diameter and is fitted so as to be in close contact with the outer periphery of the cylindrical body to be a fixed end, and the other end of the coil spring faces outward from an opening formed at one end of the cylindrical body, and a free end Therefore, it is possible to reliably prevent the fastening nuts screwed into the bolts from falling off due to vibrations of the bolts, and to easily attach the restricting member to be attached to the bolts to the male screws of the bolts. Possible case.

請求項２に記載の発明では、前記コイルバネの他方端の前記自由端部が臨む前記開口の形成された前記円筒体の一端に多角形状の治具係合部を設けるので、前記治具係止部と前記自由端部とが近接することになり、前記治具係合部の工具による締緩作業を前記自由端部の操作に容易に連繋させることができる。  According to a second aspect of the present invention, since a polygonal jig engaging portion is provided at one end of the cylindrical body in which the opening facing the free end of the other end of the coil spring is provided, Therefore, the tightening operation by the tool of the jig engaging portion can be easily linked to the operation of the free end portion.

請求項３に記載の発明では、前記円筒体は小径部と大径部よりなり、前記コイルバネの前記コイル部の外周より外方に延出して、前記コイル部より大径に湾曲される前記コイルバネの一方端を前記小径部の外周に密着するように卷装して前記固定端部としてなるので、前記固定端部を前記小径部から前記大径部に至る段部で位置決めでき、前記コイルバネの前記コイル部が前記ボルト貫通孔内で傾くことがなく、前記コイル部に対する前記ボルトの螺合が円滑になる。  According to a third aspect of the present invention, the cylindrical body includes a small-diameter portion and a large-diameter portion, and extends outward from the outer periphery of the coil portion of the coil spring, and is curved to a larger diameter than the coil portion. The one end of the coil spring is fitted so as to be in close contact with the outer periphery of the small-diameter portion and serves as the fixed end portion, so that the fixed end portion can be positioned at a stepped portion from the small-diameter portion to the large-diameter portion. The coil part does not tilt in the bolt through hole, and the screwing of the bolt to the coil part becomes smooth.

この発明における第１の実施の態様を示す断面図。Sectional drawing which shows the 1st embodiment in this invention. この発明における第１の実施の態様を示す平面図。The top view which shows the 1st embodiment in this invention. この発明におけるボルトに対する回転動作状態を示す断面図。Sectional drawing which shows the rotational operation state with respect to the volt | bolt in this invention. この発明の第２の実施の態様を示す断面図。Sectional drawing which shows the 2nd Embodiment of this invention. この発明における第２の実施の態様を示す平面図。The top view which shows the 2nd embodiment in this invention.

以下、この発明における締結ナットの脱落防止装置の実施の形態について説明する。この発明の実施の形態は、発明の最も好ましい形態を示すものであり、この発明はこれに限定されない。  Hereinafter, an embodiment of a fastening nut drop prevention device according to the present invention will be described. The embodiment of the present invention shows the most preferable mode of the present invention, and the present invention is not limited to this.

この発明における第１の実施の形態を、図１および図３に基づいて説明する。図１は締結ナット用脱落防止装置を実施した一例を示すもので、符号１で示されるものは被締結部材で、鋼板をプレス加工して形成され一対のブラケットよりなる。  A first embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows an example of a fastening nut drop prevention device. Reference numeral 1 denotes a member to be fastened, which is formed by pressing a steel plate and includes a pair of brackets.

前記被締結部材１は、締結ナット２をボルト３に螺合することにより組付けられる。前記ボルト３には、前記締結ナット２が振動などで緩み脱落を防止する規制部材４が装着される。  The fastened member 1 is assembled by screwing a fastening nut 2 into a bolt 3. A restriction member 4 is attached to the bolt 3 to prevent the fastening nut 2 from loosening due to vibration or the like and preventing it from falling off.

前記規制部材４は、前記ボルト３が挿通されるボルト貫通孔６を穿設する六角形状の円筒体５と、前記ボルト貫通孔６内に収納されるコイルバネ１０とよりなり、前記締結ナット２の端面に配置される。  The restricting member 4 includes a hexagonal cylindrical body 5 that has a bolt through hole 6 through which the bolt 3 is inserted, and a coil spring 10 that is housed in the bolt through hole 6. Arranged on the end face.

前記円筒体５の一端面５ｂには、半径方向の開口７を穿設するとともに、多角形状の治具係合部９を一体に設ける。なお、前記治具係合部９を六角形状にしたが、８角形状、１２角形状及び４角形状などの多角形でもよい。また、前記治具係合部９を多角形状の環状に形成して、前記円筒体５の外周に溶接などにより固着してもよい。  A cylindrical opening 5 is formed in one end surface 5b of the cylindrical body 5, and a polygonal jig engaging portion 9 is provided integrally therewith. Although the jig engaging portion 9 has a hexagonal shape, it may be a polygonal shape such as an octagonal shape, a dodecagonal shape, or a quadrangular shape. Further, the jig engaging portion 9 may be formed in a polygonal annular shape and fixed to the outer periphery of the cylindrical body 5 by welding or the like.

前記コイルバネ１０は前記ボルト３の雄ネジ３ａのピッチに整合するコイル部１０ａと、前記コイル部１０ａの一方端の固定端部１０ｂと、前記コイル部１０ａの他方端の自由端部１０ｃとを有する。  The coil spring 10 has a coil portion 10a that matches the pitch of the male screw 3a of the bolt 3, a fixed end portion 10b at one end of the coil portion 10a, and a free end portion 10c at the other end of the coil portion 10a. .

前記固定端部１０ｂは、前記コイルバネ１０の一方端を前記コイル部１０ａの外周より外方に延出し、前記円筒体５の他端面５ｂに形成した切欠き８を経て、前記コイル部１０ａより大径に湾曲させ、前記円筒体５の外周に密着するように卷装してなる。なお、前記固定端部１０ｂの巻き数を複数にしたが、一条の巻装でもよい。  The fixed end portion 10b extends from one end of the coil spring 10 outward from the outer periphery of the coil portion 10a, passes through a notch 8 formed in the other end surface 5b of the cylindrical body 5, and is larger than the coil portion 10a. It is curved to a diameter and is fitted so as to be in close contact with the outer periphery of the cylindrical body 5. In addition, although the winding number of the said fixed end part 10b was made into multiple, one winding may be sufficient.

前記自由端部１０ｃは、前記コイルバネ１０の他方端を前記円筒体５の前記一端面５ａ側に穿設した前記開口７より外方に非接触状態で臨ませてなり、前記円筒体５に伝わる振動によってコイルバネ１０が回動することがなく、前記円筒体５の緩みを確実に防止できる。
なお、前記開口７に対して前記切欠き８を同じ向きに形成にすると前記コイル部１０ａの巻き数を増やすことができる。The free end portion 10 c is formed such that the other end of the coil spring 10 faces in a non-contact state outwardly from the opening 7 formed on the one end surface 5 a side of the cylindrical body 5, and is transmitted to the cylindrical body 5. The coil spring 10 is not rotated by the vibration, and the cylindrical body 5 can be reliably prevented from loosening.
If the notch 8 is formed in the same direction with respect to the opening 7, the number of turns of the coil portion 10a can be increased.

前記規制部材４において、前記被締結部材１に貫挿した前記ボルト３に対して締付ナット２を螺合した後、メガネレンチなどの治具（図示せず）に保持された前記治具係合部９を介して、前記円筒体５を前記ボルト３に挿入する。  In the regulating member 4, after the fastening nut 2 is screwed to the bolt 3 inserted through the fastened member 1, the jig member held by a jig (not shown) such as a spectacle wrench. The cylindrical body 5 is inserted into the bolt 3 through the joint portion 9.

この際、前記コイルバネ１０の前記自由端部１０ｃをバネ力に抗して操作すると、前記コイルバネ１０は前記固定端部１０ｂを支点として前記コイルバネ１０の前記コイル部１０ａが拡径し、図３に示すように、前記ボルト３の前記雄ネジ３ａの谷に嵌る前記コイル部１０ａの素線と前記雄ネジ３ａの谷との間に隙間が生じて摩擦力が軽減され、前記コイルバネ１０が前記ボルト３の前記雄ネジ３ａに円滑にネジ込まれて前記円筒体５が前記ナット２の端面まで挿入される。  At this time, if the free end portion 10c of the coil spring 10 is operated against a spring force, the coil spring 10 has the fixed end portion 10b as a fulcrum, and the coil portion 10a of the coil spring 10 expands in diameter. As shown, a gap is created between the wire of the coil portion 10a that fits in the valley of the male screw 3a of the bolt 3 and the valley of the male screw 3a to reduce the frictional force, and the coil spring 10 is connected to the bolt. 3 and the cylindrical body 5 is inserted to the end face of the nut 2.

その後、前記コイルバネ１０の前記自由端部１０ｃの操作を解除すると、前記コイルバネ１０のバネ力により、前記コイルバネ１０の前記コイル部１０ａは前記ボルト３の軸芯方向に向って縮径し、前記円筒体５と一緒にネジ込まれた前記コイルバネ１０は、図１に示すように、前記ボルト３の前記雄ネジ３ａの谷に前記コイル部１０ａが嵌り込み密着して前記円筒体５の回転を不動にするとともに、前記円筒体５より前記締結ナット２の端面に向かう軸方向の力が作用する。  Thereafter, when the operation of the free end portion 10c of the coil spring 10 is released, the coil portion 10a of the coil spring 10 is contracted in the axial direction of the bolt 3 by the spring force of the coil spring 10, and the cylinder As shown in FIG. 1, the coil spring 10 screwed together with the body 5 has the coil portion 10 a fitted into the valley of the male screw 3 a of the bolt 3 so that the rotation of the cylindrical body 5 does not move. In addition, an axial force from the cylindrical body 5 toward the end face of the fastening nut 2 acts.

さらに、前記円筒体５を前記ボルト３より離脱する際には、前記コイルバネ１０の前記自由端部１０ｃをバネ力に抗して操作すると、前記コイルバネ１０の前記コイル部１０ａが拡径し、図３に示すように、前記ボルト３の前記雄ネジ３ａの谷と、前記コイル部１０ａとの密着を解除して摩擦が無くなり、あるいは軽減されて自由に回転を許容するようになるから、前記ボルト３の前記雄ネジ３ａを保護しながら簡単に前記円筒体５を回転して前記ボルト３から離脱することができる。  Further, when the cylindrical body 5 is detached from the bolt 3, if the free end portion 10c of the coil spring 10 is operated against a spring force, the coil portion 10a of the coil spring 10 is expanded in diameter. As shown in FIG. 3, the screw 3a of the bolt 3 is released from close contact with the coil portion 10a so that friction is eliminated or reduced, and the bolt is allowed to rotate freely. The cylindrical body 5 can be easily rotated and detached from the bolt 3 while protecting the male screw 3a.

次に、第２の実施の形態を、図４および図５に基づいて説明する。この実施の形態において第１の実施の形態と同じ構成は同一の符号を付して説明する。  Next, a second embodiment will be described based on FIG. 4 and FIG. In this embodiment, the same components as those in the first embodiment will be described with the same reference numerals.

この第２の実施の形態では、第１の実施の形態で説明している前記規制部材４と同様に円筒体５とコイルバネ１０とよりなり、前記円筒体５は小径部５１と大径部５２を有し、前記小径部５１から前記大径部５２に至る段部５３が形成される。  In the second embodiment, similarly to the restriction member 4 described in the first embodiment, the cylindrical body 5 includes a cylindrical body 5 and a coil spring 10, and the cylindrical body 5 includes a small diameter portion 51 and a large diameter portion 52. And a step portion 53 extending from the small diameter portion 51 to the large diameter portion 52 is formed.

前記コイルバネ１０の一方端は前記コイル部１０ａの外周より外方に延出して、前記コイル部１０ａより大径に湾曲させ前記小径部５１の外周に密着するように卷装して前記固定端部５ｂとし、コイルバネ１０の他方端は前記円筒体５の前記一端面５ａ側に穿設した前記開口７より外方に臨ませてなる。  One end of the coil spring 10 extends outward from the outer periphery of the coil portion 10a, is curved to have a larger diameter than the coil portion 10a, and is fitted so as to be in close contact with the outer periphery of the small diameter portion 51. 5b, and the other end of the coil spring 10 faces outward from the opening 7 formed on the one end face 5a side of the cylindrical body 5.

この実施の形態では、複数巻にした前記固定端部１０ｂが前記段部５３によって軸方向に位置決めされるので、前記コイルバネ１０の前記コイル部１０ａが前記ボルト貫通孔６内で傾くことがなく、前記コイル部１０ａに対する前記ボルト３の螺合が円滑になる。  In this embodiment, the fixed end portion 10b having a plurality of turns is positioned in the axial direction by the step portion 53, so that the coil portion 10a of the coil spring 10 is not inclined in the bolt through hole 6, The bolt 3 is smoothly screwed into the coil portion 10a.

以上の構成におけるナットの脱落防止装置において、前記規制部材４の前記コイルバネ１０の前記コイル部１０ａは、前記ボルト３の前記雄ネジ３ａに圧接して前記規制部材４の前記筒体５が回転不動に装着され、前記被締結部材１より伝わって生じる前記ボルト３の振動により緩む前記締結ナット２の脱落を前記規制部材４によって防止する。  In the nut drop prevention device having the above-described configuration, the coil portion 10a of the coil spring 10 of the restriction member 4 is pressed against the male screw 3a of the bolt 3 so that the cylinder 5 of the restriction member 4 does not rotate. The regulating member 4 prevents the fastening nut 2 from falling off due to the vibration of the bolt 3 generated by being transmitted from the fastened member 1.

また、前記コイルバネ１０の前記固定端部１０ｂは前記円筒体５の外周に密着させて保持され、しかも、前記開口８より外方に臨む前記コイルバネ１０の前記自由端部１０ｃを操作すれば、前記コイルバネ１０のコイル部が拡径し、前記筒体５を前記ボルト３に円滑に螺合できる。  Further, the fixed end portion 10b of the coil spring 10 is held in close contact with the outer periphery of the cylindrical body 5, and if the free end portion 10c of the coil spring 10 facing outward from the opening 8 is operated, The coil portion of the coil spring 10 is expanded in diameter, and the cylinder 5 can be smoothly screwed onto the bolt 3.

この発明は、ボルトの振動により緩んだナットの脱落を確実に防ぎ、ボルトへ簡単に装着でき、しかも製作が容易なナットの脱落防止装置である。  The present invention is a nut drop prevention device that reliably prevents the nut from falling off due to vibration of the bolt, can be easily attached to the bolt, and is easy to manufacture.

１ 被締結部材
２ 締結ナット
２ａ 雌ネジ
３ ボルト
３ａ 雄ネジ
４ 規制部材
５ 円筒体
５ａ 円筒体の一端面
５ｂ 円筒体の他端面
５１ 小径部
５２ 大径部
５３ 段部
６ ボルト貫通孔
７ 開口
８ 切欠き
９ 治具係合部
１０ コイルバネ
１０ａ コイル部
１０ｂ 固定端部
１０ｃ 自由端部DESCRIPTION OF SYMBOLS 1 Fastened member 2 Fastening nut 2a Female screw 3 Bolt 3a Male screw 4 Restriction member 5 Cylindrical body 5a One end surface 5b of a cylindrical body 51 Other end surface 51 of a cylindrical body Small diameter part 52 Large diameter part 53 Step part 6 Bolt through-hole 7 Opening 8 Notch 9 Jig engagement part 10 Coil spring 10a Coil part 10b Fixed end part 10c Free end part

Claims (3)

振動によって緩むナットの脱落を防ぐためにボルトに装着される規制部材であって、この規制部材は中央にボルト貫通孔を有する円筒体と、前記ボルト貫通孔内に収納されるコイルバネとよりなり、前記コイルバネは前記ボルトの前記雄ネジのピッチに整合するコイル部と、前記コイルバネの一方端を前記コイル部の外周より外方に延出して、前記コイル部より大径に湾曲させて前記円筒体の外周に密着するように卷装して固定端部とし、前記コイルバネの他方端を前記円筒体の一端に形成した開口より外方に非接触状態で臨ませて自由端部としてなることを特徴とする締結ナット用脱落防止装置。  A restricting member attached to the bolt to prevent the nut loosening due to vibration, the restricting member comprising a cylindrical body having a bolt through hole in the center and a coil spring housed in the bolt through hole, The coil spring has a coil portion that matches the pitch of the male screw of the bolt, and one end of the coil spring extends outward from the outer periphery of the coil portion, and is bent to a larger diameter than the coil portion. The fixed end portion is fitted so as to be in close contact with the outer periphery, and the other end of the coil spring is faced outwardly from the opening formed at one end of the cylindrical body in a non-contact state to form a free end portion. A drop prevention device for fastening nuts. 前記コイルバネの他方端の自由端部が臨む前記開口の形成された前記円筒体の一端に多角形状の治具係合部を設けたことを特徴とする請求項１に記載の締結ナット用脱落防止装置。  2. The fastening nut dropout prevention according to claim 1, wherein a polygonal jig engaging portion is provided at one end of the cylindrical body in which the opening facing the free end of the other end of the coil spring is formed. apparatus. 前記円筒体は小径部と大径部よりなり、前記コイルバネの前記コイル部の外周より外方に延出して、前記コイル部より大径に湾曲される前記コイルバネの一方端を前記小径部の外周に密着するように卷装して前記固定端部としてなることを特徴とする請求項１または請求項２に記載の締結ナット用脱落防止装置。  The cylindrical body includes a small-diameter portion and a large-diameter portion, extends outward from the outer periphery of the coil portion of the coil spring, and has one end of the coil spring curved to a larger diameter than the coil portion as an outer periphery of the small-diameter portion. 3. The fastening nut dropout prevention device according to claim 1, wherein the fastening end portion is provided so as to be in close contact with the fastening nut.

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