JP2001090745A - Blastic arm type ratchet clutch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve problems of a conventional spring clutch comprising a number of parts in which sharp reduction of manufacturing cost is difficult, and in which actuation becomes unstable by thermal expansion difference between parts of synthetic resin and a coil spring of metal to deteriorate clutch characteristics. SOLUTION: This arm type ratchet clutch is an on/off type clutch, it comprises an input shaft 10 and an output shaft 20, and the input shaft 10 comprises an input gear 11, a hub part 12, and a ratchet gear 13. The output shaft 20 comprises a follower shaft part 21, a cylindrical part 22, a large diameter part 23, an elastic arm part 24, etc. A spiral slit 33 is formed between the cylindrical part 22 and the elastic arm part 24, and between the elastic arm part 24 and the large diameter part 23 for forming the elastic arm part 24 in arc form, a ratchet claw 25 is formed at an inner surface part of the elastic arm part 24, a control claw 26 controlled by a movable operation lever to be driven to advance/retract by a solenoid actuator, unillustrated, is formed at an outer circumferential part of the elastic arm part 24, and a stopper mechanism 27 is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an elastic arm type ratchet clutch to which an arcuate elastically deformable elastic arm having a ratchet pawl is applied.

[0002]

2. Description of the Related Art Heretofore, spring clutches of a type in which rotational torque of an input shaft is transmitted to an output shaft via a coil spring have been widely used. The spring clutch 100 shown in FIG. 5 is a one-way clutch. The spring clutch 100 includes an input shaft 101, a coil spring 102, an output shaft 103, and the like. The input shaft 101 has an input gear 104 to which a rotational driving force is input.
, A hub 105 and a central shaft hole 106.
Usually, each of the input shaft 101 and the output shaft 103 is an integrally molded product made of synthetic resin, and the coil spring 102 is made of metal. However, there is also a case where a coil spring made of synthetic resin is applied.

The output shaft 103 is provided with a shaft hole 10 of the input shaft 101.
6 has a driven shaft portion 106 inserted therethrough, and a clutch body 108 integrally formed on one end side of the driven shaft portion 106. The coil spring 102 is fitted to the hub 105 and the clutch body 108 so as to be able to make frictional contact. The left end of the coil spring 102 is connected to the hub 105, and the right end of the coil spring 102 is connected to the clutch body 108. In the spring clutch 100, when a rotational driving force for rotating the input shaft 101 in the direction of the arrow is input, the coil spring 102 is deformed to the diameter reduction side, and the hub portion 10
5, the rotational driving force is transmitted to the coil spring 102, and the rotational driving force is transmitted from the coil spring 102 to the clutch body 108. Further, when a rotational driving force for rotating the input shaft 101 in the direction opposite to the arrow is input, the coil spring 102 is deformed to the side with the larger diameter, so that the output shaft 1
No rotational force is transmitted to 03.

An on / off type spring clutch having the same principle as the spring clutch 100 is also widely applied to a paper feed mechanism of a printer or a copying machine. The on / off type spring clutch 110 shown in FIG.
1, coil spring 112, control cylinder 113, output shaft 1
14 and the like. Usually, the input shaft 111, the control cylinder 113, and the output shaft 114 are made of synthetic resin, and the coil spring 112 is made of metal. However, a coil spring made of synthetic resin is also used. The input shaft 111 has an input gear 115 to which a rotational force is input, a hub 116, and a shaft hole 117 at the center of the hub 116. Output shaft 1
14 has a driven shaft 118 inserted into a shaft hole 117 of the input shaft 111, and a clutch body 119 integrally formed on one end side of the driven shaft 118.

The coil spring 112 is fitted to the hub 116 and the clutch body 119 so as to be able to make frictional contact. The left end of the coil spring 112 is connected to the control cylinder 113, and the right end of the coil spring 112 is connected to the clutch body 119. You. The control cylinder 113 is externally fitted to the hub part 116 and the coil spring 112 externally fitted to the clutch body 119. A control claw 1 protruding outward is provided on the outer peripheral surface of the control cylinder 113.
20 is formed, and an external movable operation lever is appropriately advanced and driven by a solenoid actuator, and the control claw 120 can be stopped by the operation lever.

The on / off type spring clutch 11
0, when a rotational driving force for rotating the input shaft 111 in the direction of the arrow is input, the coil spring 112 is deformed toward the diameter reducing side by the frictional force acting on the coil spring 112 from the hub portion 116, and the coil Spring 11
2, the rotational driving force is transmitted from the coil spring 112 to the clutch body 119. When the control claw 120 is stopped by the operation lever driven by the solenoid actuator, the coil spring 112 does not deform to the diameter reduction side, so that the output shaft 114
The rotational driving force is not transmitted to the clutch 110
Turns off. On the other hand, when a rotation driving force for rotating the input shaft 111 in the direction opposite to the arrow is input, the coil spring 112 is deformed toward the diameter-enlarged side, so that the output shaft 1
The rotational driving force is not transmitted to 14.

[0007]

A conventional spring clutch applied as a one-way clutch includes at least three parts, an input shaft, a coil spring, and an output shaft. Costs and assembly costs are high. In addition, although the input shaft and the output shaft are usually made of synthetic resin, it is difficult to reduce the cost of manufacturing parts because an expensive coil spring made of metal is applied.

The conventional on / off type spring clutch is composed of four parts, an input shaft, a coil spring, a control cylinder, and an output shaft. Therefore, as described above, the number of parts is large, the structure is complicated, and the parts manufacturing cost and assembly are increased. Expensive. Also,
Usually, since an expensive coil spring made of metal is applied, it is difficult to reduce the cost of manufacturing parts. In addition, since the synthetic resin component has a significantly higher coefficient of thermal expansion (about 10 times) than the metal coil spring, the change in the diameter of the input shaft and the output shaft due to the thermal expansion is caused by the diameter of the coil spring. It is much larger than the change. The on / off characteristics of the clutch become unstable, and the stop phase angle of the output shaft tends to vary.

An object of the present invention is to provide a resilient arm type ratchet clutch having a novel structure capable of remarkably reducing manufacturing costs by reducing the number of parts and obtaining stable clutch characteristics.

[0010]

An elastic arm type ratchet clutch according to claim 1 is a ratchet clutch capable of transmitting a rotational driving force input to an input shaft to an output shaft.
The input shaft has a cylindrical hub portion, a ratchet gear,
A shaft portion, wherein the output shaft is externally fitted so as to be able to frictionally contact and relatively rotate with the hub portion, a driven shaft portion inserted through the shaft hole of the input shaft, and the driven shaft portion. A large-diameter portion having substantially the same diameter as the cylindrical portion, and being disposed between the cylindrical portion and the large-diameter portion in the vicinity of the outer peripheral surface of the ratchet gear, and a rotationally advanced end fixed to the cylindrical portion. An arc-shaped elastically deformable elastic arm having a rotation-direction following end fixed to the large-diameter portion; and an elastic arm formed on the elastic arm so as to protrude inward from an inner peripheral surface thereof and meshable with the ratchet gear. And at least one ratchet pawl.

The above "rotation direction" means the rotation direction of the input shaft. In order to reduce the manufacturing cost, it is desirable that both the input shaft and the output shaft are made of synthetic resin, and it is desirable that the output shaft is formed as an integrated product made of synthetic resin. In this elastic arm type ratchet clutch, when a rotational driving force is input to the input shaft, the cylindrical portion of the output shaft tends to rotate in the rotational direction due to frictional force acting between the output shaft and the hub. The elastic arm portion of the output shaft is near the outer peripheral surface of the ratchet gear portion, and since the rotationally advanced end of the elastic arm portion is fixed to the cylindrical portion, the elastic arm portion moves forward in accordance with the rotation of the cylindrical portion. The end moves in the direction of rotation.

Since the elastic arm portion is elastically deformed so as to approach the ratchet gear side and the ratchet pawl meshes with the ratchet gear, the trailing end of the elastic arm portion is connected to the large diameter portion of the output shaft. Therefore, the rotational driving force of the input shaft is transmitted from the ratchet gear to the ratchet pawl, transmitted from the ratchet pawl to the elastic arm, and transmitted from the elastic arm to the large-diameter portion of the output shaft, thus rotating the input shaft. The driving force is transmitted to the output shaft.

When the input shaft rotates in a direction opposite to the above-mentioned rotation direction, the cylindrical portion of the output shaft tries to rotate in the same direction as the input shaft due to the action of frictional force. The ratchet claw does not mesh with the ratchet gear, and the rotational driving force of the input shaft is not transmitted to the output shaft. That is, this elastic arm type ratchet clutch functions as a one-way clutch. In addition, the input shaft and the output shaft can each be integrally manufactured from a synthetic resin material. In this case, there is almost no difference between the thermal expansion of the input shaft and the thermal expansion of the output shaft. There is no instability of the operation or deterioration of the performance.

According to a second aspect of the present invention, there is provided an elastic arm type ratchet clutch according to the first aspect, wherein the output shaft is integrally formed of a synthetic resin material, and the output shaft is formed between the cylindrical portion, the elastic arm portion and the large diameter portion. A helical slit extending over half of the circumference is formed. Since the output shaft is integrally formed of a synthetic resin material, the production cost of the output shaft can be significantly reduced,
By forming a helical slit that extends over approximately one and a half turns between the cylindrical portion, the elastic arm portion, and the large diameter portion, the elastic arm portion can be easily formed.

According to a third aspect of the present invention, there is provided an elastic arm type ratchet clutch according to the first or second aspect of the present invention, wherein a control claw is provided on an outer peripheral portion of the elastic arm portion, the control claw being located closer to a rotationally forward end than the ratchet claw. By stopping the control claw by the movable operating lever of (1), the elastic arm portion is elastically deformed in a direction away from the ratchet gear, so that the ratchet clutch can be switched off. It is a feature.

The movable operation lever is driven forward and backward with respect to the elastic arm by, for example, a solenoid actuator. When the operation lever is advanced and driven by the solenoid actuator to stop the rotation of the control claw, the elastic arm portion is elastically deformed in a direction away from the ratchet gear, and the ratchet claw is disengaged from the ratchet gear. As a result, the ratchet clutch is turned off (a state in which the rotational driving force is not transmitted). In this off state, when the control lever is retracted by returning the operation lever to the rotation state, the rotation state of the input shaft is transmitted to the output shaft as described above. Thus, this clutch is an on / off type ratchet clutch.

According to a fourth aspect of the present invention, there is provided an elastic arm type ratchet clutch according to the third aspect of the present invention, wherein the elastic arm portion is prevented from being excessively elastically deformed when the clutch is switched off. A stop mechanism for restricting the relative rotation in the direction opposite to the rotation direction to a predetermined small angle. Here, when the clutch is switched off, the relative rotation of the cylindrical portion with respect to the large-diameter portion in the opposite direction to the rotation direction is restricted to a predetermined small angle by the stop mechanism, so that the elastic arm portion is separated from the ratchet gear. Since there is no excessive elastic deformation to
The responsiveness and durability of the elastic arm can be improved.

According to a fifth aspect of the present invention, in the elastic arm type ratchet clutch according to the fifth aspect of the present invention, the stop mechanism comprises:
A notch formed in one of the cylindrical portion and the large diameter portion, and a regulating portion formed in the other of the cylindrical portion and the large diameter portion and loosely fitted in the notch. It is. Therefore, the relative movement of the cylindrical portion with respect to the large diameter portion in the circumferential direction can be restricted by the notch portion and the restricting portion.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIGS.
The elastic arm type ratchet clutch 1 according to the present invention is an on / off type ratchet clutch suitable for a paper feeding mechanism such as a printer or a copying machine. The elastic arm type ratchet clutch 1 includes an input shaft 10, an output shaft 20, and a movable operation lever 40 (see FIG. 4) driven forward and backward by a solenoid actuator (not shown). here,
The input gear 10 side in FIGS. 1 and 2 is defined as the rear side, and the output shaft 20 side is defined as the front side.

The input shaft 10 is an integral part made of synthetic resin to which a rotational driving force is input. This input shaft 1
Reference numeral 0 denotes an input gear 11 to which a rotational driving force is input, and a cylindrical hub portion 1 protruding forward from a front end face of the input gear 11.
2, a ratchet gear 13 having the same outer diameter as the hub portion 12 and continuously connected to the front end of the hub portion 12, and a shaft hole 14 formed in the center portion. The tooth profile of the ratchet gear 13 may be a shape like a normal gear tooth or a shape specific to the ratchet gear such as a saw tooth.

The output shaft 20 is an integral part made of synthetic resin that outputs the rotational driving force transmitted from the input shaft 10. The output shaft 20 includes a driven shaft portion 21, a cylindrical portion 22, a large diameter portion 23, an elastic arm portion 24, a ratchet claw 25, a control claw 26, and a stop mechanism 27. The driven shaft portion 21 has a shaft shape inserted into the shaft hole 14 of the input shaft 10. Approximately two-thirds of the driven shaft portion 21 in the longitudinal direction are provided with the hub portion 12 and the ratchet gear 13 inside the cylindrical portion 22, the elastic arm portion 24, and the large-diameter portion 23.
Are formed so as to leave an annular gap in which they slide and fit.

A pair of elastically deformable engaging pieces 30 and engaging claws 31 are formed at the rear end of the driven shaft 21, and the front end of the driven shaft 21 is connected to an external shaft member. Connecting portion 32 is formed. Each engagement piece 30 is driven shaft portion 21
Each of the engaging pieces 30 has an engaging claw 31 formed in a protruding shape on the outer peripheral portion thereof through a pair of slits. In a state where the driven shaft portion 21 is inserted through the shaft hole 14, the pair of engagement claws 31 are locked at the rear end surface of the input gear 11, and the driven shaft portion 21 is prevented from coming off. When the driven shaft portion 21 is pulled out from the shaft hole 14, the driven shaft portion 21 can be pulled out by elastically deforming the pair of engagement pieces 30 toward the axis.

The rear end of the cylindrical portion 22 has an input gear 1
The cylindrical portion 22 is fitted on the hub portion 12 so as to be able to make frictional contact and to be relatively rotatable. The outer peripheral surface of the cylindrical portion 22 is formed as a cylindrical surface. The large diameter part 23 is formed integrally with the front part of the driven shaft part 21, and the outer diameter of the large diameter part 23 and the cylindrical part 22 are
Is formed substantially equal to the outer diameter of the.

The elastic arm portion 24 is elastically deformable in an arc shape over about a half circumference. The elastic arm portion 24 is disposed between the cylindrical portion 22 and the large-diameter portion 23 near the outer peripheral surface of the ratchet gear 13. The elastic arm portion 24 has a helical slit 33 extending approximately one and a half times between the cylindrical portion 22, the elastic arm portion 24, and the large diameter portion 23.
Is formed integrally with the tubular portion 22 and the large-diameter portion 23. Therefore, the cylindrical portion 22 is large-diameter portion 2
3, the elastic arm portion 24 moves to the side closer to the ratchet gear 13 when the cylindrical portion 22 rotates relatively to the large-diameter portion 23 in the rotationally forward direction. When elastically deformed and rotated in the opposite direction, the elastic arm portion 24 is elastically deformed to the side separated from the ratchet gear 13.

With reference to the rotational direction of the input shaft 10 (the direction of the arrow in FIGS. 1 and 2), the rotationally advanced end 33a of the slit 33 is located at the position shown in FIGS.
Is located on the opposite side of the rotation direction advancing end 33a with respect to the axis. The rotation-direction advancing end 24a of the elastic arm portion 24 is formed integrally with the tubular portion 22 via the connecting portion 34, and the rotation-direction following end of the elastic arm portion 24 is integrally connected to the large-diameter portion 23. I have. Note that the length of the elastic arm portion 24 in the circumferential direction is not limited to about a half circumference, and may be formed to be shorter or longer. The width in the front-rear direction of the elastic arm portion 24 is appropriately set so as to match the magnitude of the rotational driving force and the strength of the material forming the elastic arm portion 24.

The ratchet claw 25 is provided on the elastic arm 2.
4 at least one so as to protrude inward from its inner peripheral surface.
The ratchet claw 25 is formed so as to mesh with the ratchet gear 13. At least one ratchet claw 25 may be formed, but a plurality of ratchet claws 25 may be formed according to the magnitude of the rotational driving force. In the on / off type ratchet clutch 1, it is necessary to provide a control claw 26 for on / off switching. However, when the ratchet clutch 1 is used as a simple one-way clutch, the control claw 26 and the movable operation lever 40 may be omitted.

The control claw 26 is formed on the outer peripheral portion of the elastic arm 24 so as to be located closer to the rotationally forward end than the ratchet claw 25. The movable operation lever 40 is advanced toward the elastic arm portion 24 by a solenoid actuator (not shown), and the control claw 26 is received and stopped.
As shown in FIG.
The ratchet clutch 1 can be switched off (disconnected state) by elastically deforming in a direction away from the ratchet clutch 1. Conversely, when the movable operation lever 40 is driven backward to allow the control pawl 26 to rotate, the ratchet clutch 1 is switched on (connected state) (see FIG. 3).

The stop mechanism 27 is provided to prevent the elastic arm 24 from being excessively elastically deformed when the ratchet clutch 1 is switched off. The rotation is restricted to a predetermined small angle. The stop mechanism 27 is provided on one of the tubular portion 22 and the large-diameter portion 23 (in the present embodiment, the large-diameter portion 2
3) The notch 28 formed in 3), the cylindrical portion 22 and the large diameter portion 2
A restriction portion 29 is formed on the other of the three (in the present embodiment, the cylindrical portion 22) and is loosely fitted in the notch portion 28.

Next, the operation of the above-described elastic arm type ratchet clutch 1 will be described. FIG. 1 shows a state in which the ratchet clutch 1 is assembled, and a description will be given based on this figure. When a rotational driving force in a direction indicated by an arrow in FIG. 1 is input to the input shaft 10 through the input gear 11,
The cylindrical portion 22 of FIG. 3 is about to rotate in the rotation direction indicated by the arrow due to the frictional force acting between the cylindrical portion 22 and the hub portion 12. The elastic arm 24 is located in the vicinity of the outer peripheral surface of the ratchet gear 13, and the rotationally advanced end 24 a of the elastic arm 24 is connected to the cylindrical part 22. It rotates in the direction of rotation.

The elastic arm 24 is elastically deformed toward the ratchet gear 13 and the ratchet pawl 25 meshes with the ratchet gear 13, so that the trailing end of the elastic arm 24 has a large diameter of the output shaft 20. Since the rotation driving force of the input shaft 10 is connected to the ratchet gear 1
3 is transmitted to the ratchet pawl 25, transmitted from the ratchet pawl 25 to the elastic arm 24, transmitted from the elastic arm 24 to the large-diameter part 23 of the output shaft 20, and thus the rotational driving force of the input shaft 10 is output. It is transmitted to the shaft 20.

When the input shaft 10 rotates in a direction opposite to the above-described rotation direction, the cylindrical portion 22 of the output shaft 20 tries to rotate in the same direction as the input shaft 10 by the action of frictional force. The portion 24 is elastically deformed in a direction away from the ratchet gear 13, the ratchet claw 25 comes off the ratchet gear 13, and the rotational driving force of the input shaft 10 is not transmitted to the output shaft 20. That is, the ratchet clutch 1 functions as a one-way clutch. Further, the input shaft 10 and the output shaft 2
0 is formed integrally with the same kind of synthetic resin material, so that there is almost no difference in the thermal expansion between the input shaft 10 and the output shaft 20. , Performance does not decrease.

The movable operation lever 40 is driven in a radial direction with respect to the elastic arm portion 24 by, for example, a solenoid actuator. When the operation lever 40 is driven out to stop the rotation of the control claw 26, the cylindrical portion is moved. 22 rotates relative to the large-diameter portion 23 in the direction opposite to the rotation direction, the elastic arm portion 24 elastically deforms in a direction away from the ratchet gear 13, and the ratchet pawl 25
Get off. As a result, the ratchet clutch 1 is turned off (disconnected state) not transmitting the rotational driving force. In this off state, the operation lever 40 is moved backward to control the claw 2
6, the rotation driving force of the input shaft 10 is
It is turned on (connected state) transmitted to 0. When the control claw 26 is provided in this way and the control claw 26 can be controlled and released by the operation lever 40, this clutch is an on / off type ratchet clutch.

When the ratchet clutch 1 is switched off, the elastic arm portion 24 and the cylindrical portion 22 connected to the forward end thereof rotate relatively to the large-diameter portion 23 in the direction opposite to the rotation direction. . At this time, the stop mechanism 27 is
The rotation of the cylindrical portion 22 in the direction opposite to the rotation direction of the cylindrical portion 3 is restricted to a predetermined small angle. Therefore, the elastic arm 2
The responsiveness and durability of the elastic arm portion 24 can be enhanced without excessive elastic deformation of the elastic arm portion 4 outwardly away from the ratchet gear 13.

Since the input shaft 10 and the output shaft 20 are each formed integrally from a synthetic resin material, the number of parts can be reduced to two, the manufacturing cost of the input shaft 10 and the output shaft 20 can be reduced significantly, and assembly can be performed. The cost can be significantly reduced and the ratchet clutch 1
Can be significantly reduced. Moreover, there is no need to use metal coil springs that are expensive to manufacture,
Manufacturing costs can be further reduced. By forming a helical slit 33 that extends over approximately one and a half turns between the cylindrical portion 22, the elastic arm portion 24, and the large diameter portion 23, the elastic arm portion 24 is formed.
Therefore, the elastic arm portion 24 can be easily formed.

Since the input shaft 10 and the output shaft 20 are formed integrally from a synthetic resin material, respectively,
Since there is almost no difference in the thermal expansion of the clutch, the operation of the clutch does not become unstable or the performance does not deteriorate due to the influence of the thermal expansion. When it is configured as an on / off type ratchet clutch, the versatility of the ratchet clutch increases,
The clutch is suitable for a paper feeding mechanism such as a printer or a copying machine. Variations in the stop phase angle of the output shaft 20 caused by the influence of thermal expansion can be made very small.

Next, a description will be given of a modification in which the embodiment is partially modified. 1) The number of elastic arms 24 is not limited to one, and a plurality of elastic arms may be formed. The length in the circumferential direction of the elastic arm portion 24 is not limited to the length of about a half circumference, and may be formed to be shorter or longer. Further, the elastic arm portion 24 does not need to be formed to have the same diameter as the cylindrical portion 22 and the large-diameter portion 23, and can be formed to have different diameters. 2) It is desirable that the input shaft 10 and the output shaft 20 be made of a synthetic resin, but the output shaft 20 can be composed of a plurality of synthetic resin parts. The material of the input shaft 10 and the output shaft 20 is not limited to a synthetic resin material, but a metal material or a ceramic material is also applicable. The input gear 11 of the input shaft 10 is not essential.

3) The stop mechanism 27 may have any function as long as it has a function of restricting the relative rotation of the cylindrical portion 22 with respect to the large-diameter portion 23 to a predetermined small angle. It may be a mechanism. 4) Although the control claw 26 is formed on the elastic arm 24,
Since the forward end of the elastic arm 24 in the rotation direction and the tubular portion 22 are connected, almost the same function can be obtained even if the control claw 26 is formed on the tubular portion 22. In this case, since the cylindrical portion 22 is cylindrical, the control claw 26 may be formed on the cylindrical portion 22 at an arbitrary position in the circumferential direction. In addition, it is needless to say that the embodiment can be implemented with various modifications added thereto without departing from the technical idea of the present invention.

[0038]

According to the first aspect of the present invention, the input shaft is
A hub portion and a ratchet gear are provided, and the output shaft includes a cylindrical portion, a driven shaft portion, a large-diameter portion, and an elastic arm portion, and the elastic arm portion has a ratchet claw that can mesh with the ratchet gear.
Since the forward end of the elastic arm is connected to the cylindrical part and the trailing end of the elastic arm is connected to the large-diameter part, the number of parts can be minimized, and the production and assembly costs of the parts can be reduced. The production cost can be further reduced by omitting a high metal coil spring. In addition, the input shaft and the output shaft can each be manufactured integrally from a synthetic resin material. In this case, there is almost no difference between the thermal expansion of the input shaft and the thermal expansion of the output shaft. There is no unstable operation or performance degradation.

According to the second aspect of the present invention, since the output shaft is integrally formed of a synthetic resin material, the production cost of the output shaft can be significantly reduced. In addition, by forming a helical slit that extends over approximately one and a half turns between the cylindrical portion, the elastic arm portion, and the large diameter portion, the elastic arm portion can be easily formed. Other Claim 1
It has the same effect as.

According to the third aspect of the present invention, there is provided an on / off type ratchet clutch in which a control claw is formed on an elastic arm portion, and the control claw is stopped by an operation lever so that the clutch can be switched off. Therefore, the versatility of the ratchet clutch is enhanced, and a clutch suitable for a paper feeding mechanism such as a printer or a copying machine can be obtained. When applied to this paper feed mechanism, as described in the section of claim 1, if the input shaft and the output shaft are each formed integrally from a synthetic resin material, the difference between the thermal expansion of the input shaft and the thermal expansion of the output shaft is obtained. And the operation of the clutch is not unstable or the performance is not degraded due to the influence of thermal expansion. In addition, the same effect as the first or second aspect is obtained.

According to the fourth aspect of the present invention, since the stop mechanism is provided, the relative rotation in the direction opposite to the rotation direction of the cylindrical portion with respect to the large diameter portion when the clutch is switched off is restricted to a predetermined small angle. As a result, excessive elastic deformation of the elastic arm portion can be prevented, and the elastic arm portion is not excessively elastically deformed outward away from the ratchet gear, so that the responsiveness and durability of the elastic arm portion are improved. Can be. The other effects are the same as those of the third aspect.

According to the fifth aspect of the present invention, the stop mechanism includes a notch formed in one of the cylindrical portion and the large diameter portion, and a notch formed in the other of the cylindrical portion and the large diameter portion. The stop mechanism allows the relative movement of the cylindrical part relative to the large diameter part in the circumferential direction to be reliably restricted. Other effects similar to those of the fourth aspect are obtained.

[Brief description of the drawings]

FIG. 1 is a perspective view of an elastic arm type ratchet clutch according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view of the ratchet clutch.

FIG. 3 is a partially cutaway perspective view of the ratchet clutch in a connected state.

FIG. 4 is a partially cutaway perspective view of the ratchet clutch in a disengaged state.

FIG. 5 is an exploded perspective view of a conventional spring clutch.

FIG. 6 is an exploded perspective view of an on / off type spring clutch according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Elastic arm type ratchet clutch 10 Input shaft 12 Hub part 13 Ratchet gear 14 Shaft hole 20 Output shaft 21 Follower shaft part 22 Tubular part 23 Large diameter part 24 Elastic arm part 25 Ratchet pawl 26 Control pawl 27 Stop mechanism 28 Notch 29 Regulator 33 Slit

Claims (5)

[Claims] 1. A ratchet clutch capable of transmitting a rotational driving force input to an input shaft to an output shaft, wherein the input shaft includes a cylindrical hub portion, a ratchet gear, and a shaft hole. A cylindrical portion externally fitted to the hub portion so as to be able to frictionally contact and relatively rotate; a driven shaft portion inserted into a shaft hole of the input shaft; and a substantially same diameter as the cylindrical portion integrally formed with the driven shaft portion. The large-diameter portion is disposed between the cylindrical portion and the large-diameter portion in the vicinity of the outer peripheral surface of the ratchet gear, and the rotation-direction advancing end is fixed to the cylindrical portion, and the rotation-direction following end is provided in the large-diameter portion. An arcuately elastically deformable elastic arm fixed to the elastic arm; and at least one ratchet pawl formed on the elastic arm so as to protrude inward from an inner peripheral surface thereof and meshable with a ratchet gear. Elastic arm type ratchet characterized by the above-mentioned. Tokuratchi. 2. The apparatus according to claim 1, wherein the output shaft is integrally formed of a synthetic resin material, and a helical slit extending substantially one and a half turns is formed between the cylindrical portion, the elastic arm portion, and the large diameter portion. Item 2. An elastic arm type ratchet clutch according to Item 1. 3. A control claw, which is located closer to a rotation-advance end than the ratchet claw, is formed on an outer peripheral portion of the elastic arm portion,
An on-off type ratchet clutch configured to be able to switch off the ratchet clutch by stopping the control claw by an external movable operation lever to thereby elastically deform the elastic arm portion in a direction away from the ratchet gear. The elastic arm type ratchet clutch according to claim 1 or 2, wherein: 4. In order to prevent excessive elastic deformation of the elastic arm when the clutch is switched off, the relative rotation of the cylindrical portion relative to the large diameter portion in the direction opposite to the rotation direction is restricted to a predetermined small angle. The elastic arm type ratchet clutch according to claim 3, further comprising a stop mechanism. 5. A notch formed in one of a cylindrical portion and a large-diameter portion, and a regulating portion formed in the other of the cylindrical portion and the large-diameter portion and loosely fitted in the notch. The elastic arm type ratchet clutch according to claim 4, wherein the ratchet clutch comprises: