JP2007016844A - Torque limiter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a torque limiter capable of achieving high torque by using a plurality of stepped coil springs, and adjusting a generated torque value in a spring-type torque limiter applying the stepped coil springs. <P>SOLUTION: This torque limiter is composed of an outer circular member 1, an inner ring 2 concentrically fitted and supported inside of the outer circular member 1, two stepped coil springs 3a, 3b mounted in the axial direction of an outer diameter face of the inner ring 2, and cover members 4a, 4b forcibly rotatably fitted to both end portions of the outer circular member 1. Small-diameter portions 12 of the coil springs 3a, 3b are respectively bonded to the outer diameter face of the inner ring 2 with required elasticity, hooks 15 at a large-diameter portion 13 side, of the coil springs 3a, 3b are respectively engaged with the cover members 4a, 4b, hooks 14 at a small-diameter portion 12 side are respectively engaged with a circular portion 8 formed on an inner diameter face of the outer circular member 1, and the winding directions of the coil springs 3a, 3b are respectively determined to simultaneously produce diameter enlarging action on the small-diameter portions 12 in accompany with the relative unidirectional rotation to the outer circular member 1 of the inner ring 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a coil spring type torque limiter used for a torque transmission unit in a copying machine, a printer, or the like, and particularly enables generation of high torque.

  FIG. 8A shows a coil spring type torque limiter that has been widely used conventionally. The torque limiter 40 is attached to the outer ring member 41, an inner ring 43 inserted into the outer ring member 41 and supported in a relatively rotatable manner at a boss portion 42 at one end, and an outer diameter surface of the inner ring 43 with a required tightening allowance. The left-handed coil spring 44 and the other end of the outer ring member 41 are fitted and fixed to the inner diameter surface of the outer ring member 41 so as to close the outer ring surface of the inner ring 43 and the other end of the inner ring 43 is freely rotatable. And a lid member 45 to be supported.

  The coil spring 44 is a stepped coil spring having a large-diameter portion 44a and a small-diameter portion 44b. The large-diameter portion 44a is arranged in a direction that faces the boss portion 42 and the small-diameter portion 44b faces the lid member 45. The small diameter portion 44b is bound to the outer diameter surface of the inner ring 43 with a required tightening allowance.

  A hook 46 bent in the axial direction is provided at the end of the large-diameter portion 44 a and is engaged with the boss portion 42 of the outer ring member 41. A hook 47 bent in the axial direction is also provided at the end of the small diameter portion 44b, and is engaged with the lid member 45 (see Patent Document 1).

  When the inner ring 43 and the shaft 49 inserted and integrated with the outer ring member 41 rotate relative to the outer ring member 41, the torque limiter 40 is viewed from the direction of the large diameter portion 44a of the coil spring 44 ( When the coil spring 44 is rotated in the same direction (left direction) as that of the coil spring 44, a diameter expansion action occurs in the small diameter portion 44b. Due to the diameter expansion action, the binding force with respect to the outer diameter surface of the inner ring 43 is reduced to generate a constant magnitude of torque, that is, a specified torque value. When the inner ring 43 and the shaft 49 rotate in the opposite direction, a diameter reducing action occurs in the small diameter portion 44b and a large binding force acts to lock the inner ring 43. In this case, the function as a torque limiter cannot be achieved. That is, the torque limiter 40 functions as a one-way torque limiter.

  The regulation torque value is adjusted by fixing the outer ring member 41 and rotating the lid member 45 from the outside using a required tool, and the diameter of the large-diameter portion 44a of the coil spring 44 changes. Accordingly, the tightening allowance of the small diameter portion 44b changes, so that the specified torque value is adjusted. In this case, since the change in the adjustment amount due to the rotation of the lid member 45 due to the presence of the large diameter portion 44a has little influence on the change in the tightening allowance of the small diameter portion 44b (that is, a part of the rotation amount of the lid member 45 has a large diameter). Therefore, it is possible to adjust the torque over a wider range than a coil spring (single-diameter coil spring) having only the small-diameter portion 44b without the large-diameter portion 44a.

  As shown in FIG. 8B, there may be a torque limiter in which the arrangement of the large diameter portion 44a and the small diameter portion 44b of the coil spring 44 is opposite. In this case, a right-handed coil spring 44 is used. When the inner ring 43 and the shaft 49 rotate counterclockwise in the same manner as described above, a diameter expanding action is generated in the small diameter portion 44b, and a constant torque is generated. When the inner ring 43 and the shaft 49 are rotated to the right, they are locked.

  As described above, when the axial orientation of the small diameter portion 44b and the large diameter portion 44a of the coil spring 44 is reversed, the winding direction of the coil spring 44 is not reversed when the rotation direction of the inner ring 43 is constant. And a predetermined torque cannot be generated. However, in the arrangement of FIG. 8B in which the small diameter portion 44b is on the boss 42 side, it is difficult to adjust the torque by rotating the lid member 45, so this type of torque limiter adjusts the torque value. Adopted when is unnecessary.

  The above torque limiter 40 includes, for example, an end portion of the outer ring member 41 on the boss portion 42 side connected to one end portion of a paper separating roller 48 of an office machine or the like, and a shaft 49 inserted through the inner ring 43 is engaged with the inner ring 43. Combined for use.

On the other hand, a coil spring type torque limiter is also known in which a plurality of single-diameter coil springs (single-diameter coil springs composed of only the small-diameter portion 44b of the coil spring 44) that generate torque are arranged in the axial direction. (Patent Document 2). In the case of a single-diameter coil spring, since the large-diameter portion 44a does not exist, the change in the adjustment amount directly affects the tightening force of the coil spring, and the change in the tightening force becomes steep, so that the torque adjustment is practical. Is impossible. Further, even if it is possible to adjust the tightening allowance by some means, it is not practical due to high cost, and high accuracy is desired because of the variation in the torque generated per spring. Can not.
JP-A-8-270673 (see FIG. 4) JP-A-8-74889 (see FIG. 1)

  As the speed of copying machines, printers, etc. increases, the torque limiter is required to have high-speed rotation and high-torque performance in order to improve paper handling performance. From this point of view, when the torque limiter using the conventional stepped coil spring 44 is used, when it is used under high speed rotation and high torque, there is a problem that the load on the coil spring is increased and the durability is lowered. That is, the amount of heat generation increases under high speed rotation and high torque, resulting in a high surface pressure, so that the lubricating performance of the lubricant deteriorates early. As a result, the load on the coil spring increases, resulting in an early decrease in torque.

  As a measure for improving the durability of the coil spring, it is conceivable to use a plurality of coil springs as in Patent Document 2 in order to disperse the load on the coil spring. There is a problem that torque adjustment is substantially impossible.

  Therefore, the present invention achieves higher torque by using a plurality of stepped coil springs capable of adjusting torque, while reducing the burden on each coil spring to increase durability and further adjusting the generated torque value. It is an object of the present invention to provide a torque limiter as described above.

  In order to solve the above problems, the torque limiter according to the present invention uses two stepped coil springs. That is, two coil springs are axially disposed on the outer diameter surface of the inner ring, hooks on the inner end side in the axial direction of each coil spring are respectively engaged with the outer ring members, and hooks on the outer end side in the axial direction are respectively A structure in which the winding direction of each coil spring is determined to be a direction in which a diameter expanding action is simultaneously generated in each small diameter portion with rotation in a certain relative direction with respect to the outer ring member of the inner ring. Consists of.

  In the torque limiter having the above configuration, the hook of the large-diameter portion is engaged with the lid member for at least one of the two coil springs, so that the torque can be adjusted by rotating the lid member. . Further, the winding direction of the coil spring is uniquely determined according to the rotation direction of the inner ring.

  That is, when the rotation direction of the inner ring is determined to be a fixed direction (for example, left rotation, see FIG. 8A), the winding direction of one coil spring is the same as the rotation direction (left winding). The winding direction of the other coil spring is opposite (right winding) (see FIG. 8B). When the inner ring rotates in the above-described direction, the diameter-expanding action is simultaneously generated in both small-diameter portions, and a predetermined torque is generated respectively. The total torque of the torque limiter as a whole becomes a specified torque value.

  The relationship between the direction of the large diameter part and the small diameter part of the two coil springs and the winding direction of the coil springs are the direction in which the large diameter part of the two coil springs is axially outside and the small diameter part is axially inside. And both coil springs are disposed in the same direction, and the coil springs are disposed in the same orientation in the axial direction of the small diameter portion and the large diameter portion of the two coil springs. The winding direction is the same. In either case, the total torque can be obtained.

  It is also possible to use three or more coil springs. That is, in this case, for the convenience of storing the coil spring, the outer ring member is constituted by a combination of divided bodies divided into a plurality of parts in the axial direction. Of the three or more coil springs arranged in the axial direction on the outer diameter surface of the inner ring, the two coil springs arranged at both ends are respectively engaged with the hook members on the axial outer end side. The hooks on the inner end sides of these two coil springs and the hooks on both ends of the other coil springs arranged between these coil springs are both engaged with the outer ring member, and the windings of the respective coil springs are wound. The direction is determined to be a direction in which a diameter expanding action is simultaneously generated in each small-diameter portion with relative rotation of the inner ring with respect to the outer ring member.

  The torque limiter having the above configuration generates a predetermined torque in the small diameter portions of all the coil springs when the inner ring rotates in a certain direction, and a large total torque is obtained.

  In addition, the arrangement | positioning relationship of the two coil springs arrange | positioned at both ends is the same as that of the case where the above-mentioned two coil springs are used.

  As described above, in the torque limiter according to the present invention, a plurality of stepped coil springs are arranged in series, and the winding direction of these coil springs is a direction in which a small diameter portion tightly bound to the inner ring simultaneously produces a diameter expanding action. In this way, it is possible to obtain a large specified torque value that combines the torque generated in each small diameter portion, to increase the torque limiter, and at the same time, to reduce the burden on each coil spring. , Durability can be improved. Further, since the large diameter portion of at least one coil spring is engaged with the lid member, there is a convenience that the generated torque value can be adjusted.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The torque limiter of the first embodiment shown in FIGS. 1 and 2 uses two stepped coil springs 3a and 3b.

  As in the conventional case, the basic structure includes the outer ring member 1, the inner ring 2 fitted and supported in a concentric state inside the outer ring member 1, and the outer ring member 1 and the inner ring 2. The left-handed first coil spring 3 a and the right-handed second coil spring 3 b fitted to the outer diameter surface of the inner ring 2, and the outer ring member 1 between the inner ring 2 at both ends of the outer ring member 1. It consists of the 1st cover member 4a and the 2nd cover member 4b which were fitted so that forced rotation was possible.

  The outer ring member 1 has a cylindrical shape and is provided with gripping cut portions 5 and 5 at the time of torque adjustment at opposite positions of the outer diameter surface, and fitting grooves 6 and 7 are formed on inner diameter surfaces of both end portions. Provided. Further, an annular portion 8 projecting from the central portion of the inner surface of the outer ring member 1 is provided, and engaging recesses 9 and 9 ′ are provided in two axially symmetrical positions of the annular portion 8 in the axially opposite direction.

  The inner ring 2 is fitted into the outer ring member 1, and the outer diameter surface of the intermediate part thereof is supported concentrically by the annular part 8. The annular portion 8 serves as a radial bearing portion that rotatably supports an intermediate portion of the inner ring 2. One end portion of the inner ring 2 is inside the outer ring member 1, but the other end portion protrudes to the outside of the outer ring member 1. The protruding portion is provided with a notch 11 for engaging with the shaft.

  The first coil spring 3a and the second coil spring 3b are of the same size opposite to the winding direction, and both are stepped coil springs having a small diameter portion 12 and a large diameter portion 13 formed by a material wire having a square cross section. The hooks 14 and 15 projecting in the axial direction are provided at the ends of the small diameter portion 12 and the large diameter portion 13, respectively. These coil springs 3a, 3b are arranged symmetrically on the outer diameter surface of the inner ring 2 in the direction in which the small diameter portions 12, 12 are inside on both sides of the annular portion 8, that is, with respect to the annular portion 8. The small diameter portions 12 and 12 are attached to the outer diameter surface of the inner ring 2 with a required binding force. The hooks 14 and 14 of the small diameter portions 12 and 12 are respectively inserted into the engaging recesses 9 and 9 ′ of the annular portion 8 and engaged with the annular portion 8 in the radial direction.

  At the end of the outer ring member 1 on the first coil spring 3 a side, an annular first lid member 4 a is fitted between the inner diameter surface and the outer diameter surface of the inner ring 2. Engaging ribs 16 provided on the outer diameter surface of the first lid member 4a are forcibly fitted into the fitting groove 6. The strength of the fitting is a strong frictional force that does not rotate when performing a normal operation as a torque limiter, but the frictional force can be rotated by holding a tool from the outside for torque adjustment. Set as much as possible. Further, a pair of engaging projections 19 for the biting roller 31 are provided on the outer end surface of the first lid member 4a so as to protrude in the axial direction.

  The first lid member 4a has a small-diameter portion 17 (see FIG. 1) having the same diameter as the inner ring 2 on the inner surface side, and the tip surface of the small-diameter portion 17 is abutted against one end surface of the inner ring 2 and is thrust. A bearing portion 18 is formed. Further, an engagement recess 21 that is opened inward in the axial direction is provided on the inner surface of the first lid member 4a on the outer diameter side of the small diameter portion 17, and the hook 15 of the first coil spring 3a is provided in the engagement recess 21. Inserted and engaged in radial direction.

  On the other hand, an annular second lid member 4b is fitted between the inner diameter surface and the end surface of the inner ring 2 at the end of the outer ring member 1 on the second coil spring 3b side. An engagement rib 22 is provided on the outer diameter surface of the second lid member 4b, and the engagement rib 22 is fitted into the fitting groove 7 with the same frictional force as the first lid member 4a. Further, an engagement recess 23 that is opened inward in the axial direction is provided on the inner surface of the second lid member 4b, and the hook 15 of the second coil spring 3b is inserted and engaged therewith.

  The torque limiter according to the first embodiment is as described above. The projection 33 is provided on the shaft 32 inserted through the inner diameter surface of the inner ring 2, and the projection 33 is engaged with the cutout portion 11 of the inner ring 2. The protrusion 19 is engaged with the paper separating roller 31 and the like for use. The inner ring 2 is positioned and freely rotatable along with the shaft at the radial bearing portion on the inner surface of the second lid member 4b and the inner surface of the annular portion 8 and the thrust bearing portion 18 on the abutting surface of the first lid member 4a. Supported by

  When the inner ring 2 is rotated in the winding direction (left-handed) of the first coil spring 3a when viewed from the direction of arrow A in FIG. 1, in the small diameter portion 12 of the first coil spring 3a and the small diameter portion 12 of the second coil spring 3b. The diameter expansion action occurs, and the total torque generated in both the small diameter portions 12 and 12 is obtained as the specified torque value in the inner ring 2.

  For adjusting the torque value, for the first coil spring 3a, the gripping cut portions 5, 5 of the outer ring member 1 are gripped and fixed with a tool or the like, and then the first lid member 4a is rotated with an appropriate tool. By doing. When the first lid member 4a is rotated in the direction opposite to the winding direction of the coil spring 3a (right direction), the large-diameter portion 13 is reduced in diameter, and the small-diameter portion 12 is also reduced in diameter with the reduced diameter, so that the generated torque Is adjusted to increase. When the rotation operation is performed in the opposite direction, the diameter of the small diameter portion 12 is expanded, and as a result, the generated torque is adjusted to decrease. Similarly, the torque adjustment of the second coil spring 3b can be performed by rotating the second lid member 4b.

  If the inner ring 2 rotates in the opposite direction (right rotation), the small-diameter portions 12 and 12 are locked and the inner ring 2 cannot be rotated, and cannot function as a torque limiter.

  When the rotation direction of the inner ring 2 is opposite to the above, the same specified torque value can be obtained by using the winding directions of the first and second coil springs 3a and 3b in the opposite directions.

  Next, in the torque limiter of the second embodiment shown in FIGS. 3 and 4, the direction of the second coil spring 3b in the axial direction is opposite to that in the first embodiment. That is, the small diameter portion 12 is arranged so as to be on the second lid member 4b side (outward). The winding direction is left-handed for both the first and second coil springs 3a and 3b. The configuration other than the above is the same as that of the first embodiment.

  In the torque limiter according to the second embodiment, when the inner ring 2 rotates relatively counterclockwise as viewed from the direction of the arrow A, a diameter expanding action occurs in the small diameter portions 12 and 12 of the first and second coil springs 3a and 3b. A specified torque value is obtained by integrating the generated torques. However, the torque adjustment in this case can be performed only for the first coil spring 3a from the first lid member 4a side.

  Next, the torque limiter according to the third embodiment will be described with reference to FIGS. 5 and 6. This torque limiter is obtained by adding another similar coil spring, that is, a third coil spring 3c in series to the first and second coil springs 3a and 3b to the torque limiter of the first embodiment. is there.

  The outer ring body member 1a and the outer ring auxiliary member 1b, which are divided in two in the axial direction, are connected and integrated in the axial direction to constitute the outer ring member 1, and the inner ring is formed inside the outer ring member 1. 2 is fitted and supported in a concentric state.

  The first and second coil springs 3a and 3b are fitted to the inner ring 2 in the outer ring main body member 1a. The specific configuration is the same as that in the first embodiment.

  The outer ring auxiliary member 1b is formed to have a length sufficient to accommodate the third coil spring 3c, and an annular connecting portion 25 fitted to the inner diameter surface of the end portion of the outer ring main body member 1a is provided at the inner end portion thereof. In addition, an engagement rib 26 that is forcedly fitted into the fitting groove 6 is provided on the outer diameter surface of the annular coupling portion 25. An inner diameter surface of the annular coupling portion 25 forms a radial bearing portion for the inner ring 2. The annular connecting portion 25 is provided with engaging concave portions 27 and 27 ′ opened in opposite directions in the axial direction at positions that are symmetrical with respect to the center. A fitting groove 28 is provided on the inner diameter surface of the outer end portion of the outer ring auxiliary member 1b. The first lid member 4a is fitted to the outer end portion of the outer ring auxiliary member 1b, and the engagement rib 29 formed on the outer diameter surface thereof is forcibly fitted into the fitting groove 28. The first lid member 4a has the same structure as that of the first embodiment, has a small diameter portion 17 on the inner surface, and forms a thrust bearing portion 18 in contact with the end surface of the inner ring 2.

  The first coil spring 3a, the second coil spring 3b, and the third coil spring 3c are of the same size, and each of them has a stepped coil spring having a small diameter portion 12 and a large diameter portion 13 formed by a material wire having a square cross section. It is. In the illustrated case, the first coil spring 3a and the third coil spring 3c are left-handed, and the second coil spring 3b is right-handed. Hooks 14 and 15 protruding in the axial direction are provided at the ends of the small diameter portion 12 and the large diameter portion 13 of the coil springs, respectively. The first coil spring 3a and the third coil spring 3c have a large-diameter portion 13 arranged toward the first lid member 4a, and the second coil spring 3b has a large-diameter portion 13 on the second lid member 4b side. It is arranged toward.

  The hook 14 of the first coil spring 3 a is inserted and engaged with the engaging recess 9 of the annular portion 8, and the other hook 15 is inserted and engaged with the engaging recess 27 ′ of the annular connecting portion 25. The hook 14 of the second coil spring 3b is inserted and engaged with the engaging recess 9 'of the annular portion 8, and the other hook 15 is inserted and engaged with the engaging recess 23 of the second lid member 4b. The hook 14 of the third coil spring 3c is inserted and engaged with the engaging recess 27 of the annular connecting portion 25, and the hook 15 is engaged with the engaging recess 21 of the first lid member 4a.

  The small diameter portions 12 of the coil springs 3a to 3c are bound to the outer diameter surface of the inner ring 2 with a predetermined elasticity.

  The large-diameter portion 13 of the first coil spring 3 a does not contact either the inner diameter surface of the outer ring member 1 or the outer diameter surface of the inner ring 2.

  The torque limiter according to the third embodiment is as described above, and the inner ring 2 has the shaft 32 and the radial bearing portions on the inner diameter surface of the second lid member 4b, the inner diameter surface of the annular portion 8 and the inner diameter surface of the annular connecting portion 25. And it rotates in the state positioned in the thrust bearing part 18 in the contact surface with the 1st cover member 4a.

  When the inner ring 2 relatively rotates counterclockwise together with the shaft 32, a diameter expanding action occurs in the small diameter portions 12 of the coil springs 3a to 3c, and a specified torque value based on the total torque generated in the three small diameter portions 12 is obtained.

  The adjustment of the torque value is performed on the second coil spring 3b by gripping and fixing the gripping cut portions 5 and 5 of the outer ring main body member 1a and rotating the second lid member 4b with an appropriate tool. . For the third coil spring 3c, the cut portion 5 'of the outer ring auxiliary member 1b is similarly fixed, and the first lid member 4a is rotated. Since the first coil spring 3a is not connected to any lid member, torque adjustment cannot be performed.

  Next, in the fourth embodiment shown in FIG. 7, the second coil spring 3b in the third embodiment (see FIGS. 5 and 6) is changed to the left-handed, and the arrangement of the small diameter portion 12 and the outer diameter portion 13 in the axial direction is changed. This is the same as the other first coil spring 3a and third coil spring 3c. Also in this case, when the inner ring 2 rotates counterclockwise, a specified torque value based on the total torque by the three coil springs 3a, 3b, 3c is obtained. However, in this case, the torque adjustment of the first coil spring 3a and the second coil spring 3b cannot be performed, and the torque adjustment is performed only for the third coil spring 3c.

  When the inner ring 2 rotates clockwise, the winding directions of the coil springs 3a to 3c are reversed.

  When the number of coil springs further increases, the number of divisions of the outer ring member 1 can be increased so that the coil springs can be accommodated, and the winding direction of each coil spring and the large diameter portion and the small diameter portion The direction can be uniquely determined by the rotation direction of the inner ring 2 as in the case of the above embodiments.

Sectional drawing of Embodiment 1 Exploded perspective view Sectional drawing of Embodiment 2 Exploded perspective view Sectional drawing of Embodiment 3 Exploded perspective view Sectional drawing of Embodiment 4 (A) (b) Cross-sectional view of a conventional example

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Outer ring member 1a Outer ring main body member 1b Outer ring auxiliary member 2 Inner ring 3a First coil spring 3b Second coil spring 3c Third coil spring 4a First lid member 4b Second lid member 5, 5 ′ Grasp cut portion 6 Fitting groove 7 Fitting groove 8 Annular portion 9, 9 'Engaging recess 11 Notch portion 12 Small diameter portion 13 Large diameter portion 14 Hook 15 Hook 16 Engaging rib 17 Small diameter portion 18 Thrust bearing portion 19 Engaging protrusion 21 Engagement Recess 22 Engagement rib 23 Engagement recess 25 Annular connecting part 26 Engagement ribs 27 and 27 'Engagement recess 28 Fitting groove 29 Engagement rib 31 Paper separating roller 32 Shaft 33 Projection

Claims (7)

  An outer ring member, an inner ring fitted and supported concentrically inside the outer ring member, a coil spring mounted on the outer surface of the inner ring between the outer ring member and the inner ring, and the outer ring member The coil spring has a large-diameter portion and a small-diameter portion that are fitted at both ends so as to be able to rotate forcibly, and the coil spring has a large-diameter portion and a small-diameter portion. In the torque limiter in which the hook at one end of the coil spring is engaged with the lid member and the hook at the other end is engaged with the outer ring member, the coil spring is disposed axially on the outer diameter surface of the inner ring. Each of the coil springs is engaged with the outer ring member, and each of the hooks on the axial outer end side is engaged with the lid member. The winding direction of the coil spring is against the outer ring member of the inner ring Torque limiter, characterized in that the diameter acting simultaneously defined in a direction that occurs in the relative respective small-diameter portion with the rotation of the certain direction.   2. The coil springs according to claim 1, wherein the two coil springs are arranged in a direction in which a large-diameter portion is axially outer and a small-diameter portion is axially inner, and the winding directions of both coil springs are opposite. Torque limiter.   2. The coil springs according to claim 1, wherein the two coil springs are arranged in the same direction in the axial direction of the small diameter portion and the large diameter portion, and the winding directions of both the coil springs are the same. Torque limiter.   The hook on the inner end side of each of the coil springs is respectively engaged with a radial bearing portion formed in an annular shape on the inner diameter surface of the outer ring member. Torque limiter.   An outer ring member, an inner ring fitted and supported concentrically inside the outer ring member, a coil spring mounted on the outer surface of the inner ring between the outer ring member and the inner ring, and the outer ring member The coil spring has a large-diameter portion and a small-diameter portion that are fitted at both ends so as to be able to rotate forcibly, and the coil spring has a large-diameter portion and a small-diameter portion. In the torque limiter in which the hooks at both ends of the coil spring are directly or indirectly engaged with the outer ring member at least one end via the lid member, the outer ring member is a shaft. The coil spring is composed of three or more coil springs arranged in the axial direction on the outer diameter surface of the inner ring, and two of them are arranged at both ends. Each coil spring has a hook on its axially outer end side. Are engaged with the lid members, and hooks on the inner ends of these two coil springs and hooks on both ends of the other coil springs arranged between these coil springs are all engaged with the outer ring member. A torque limiter characterized in that the winding direction of each of the coil springs is determined in a direction in which a diameter-expanding action occurs simultaneously in each small-diameter portion with relative rotation of the inner ring with respect to the outer ring member.   The large diameter portions of the two coil springs arranged at both ends are arranged in an orientation in which the small diameter portion is on the outside in the axial direction and the small diameter portion is on the inside in the axial direction, and the winding directions of both the coil springs are opposite. The torque limiter according to claim 5.   The small diameter part and the large diameter part of the three or more coil springs are arranged in the same direction in the axial direction, and the winding directions of the coil springs are all the same. The described torque limiter.

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