JP2004270787A - Clutch mechanism of power tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve durability of a clutch mechanism by reducing effect of abrasion of a clutch pin and a driven-side clutch tooth by meshing, in the clutch mechanism that moves a drive-side clutch tooth forward to mesh with the driven-side clutch tooth by meshing the driven-side clutch tooth on a spindle side with the clutch pin disposed on the drive gear side and falling it, moves the drive-side clutch tooth backward by separating the clutch pin from the driven-side clutch tooth and erecting it to instantly generate a clearance between it and the driven-side clutch tooth to quietly idle the drive gear side. <P>SOLUTION: A falling direction of the clutch pin is set appropriately, and the clutch pin is separated at a position (C) displaced from a contact position (A) of mesh starting with the drive-side clutch tooth 22. Thus, separating timing of the clutch pin is kept for a long time by reducing the effect of the abrasion at the mesh starting position (A). <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a clutch mechanism in an electric tool such as an electric screwdriver.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, for example, Japanese Patent No. 2867107 discloses a technique related to a clutch mechanism of an electric screwdriver. The clutch mechanism is interposed between a drive gear that is rotated by a motor and can move in the axial direction and a spindle that is rotatably and axially movably supported on the housing, and supplies power on the drive gear side to the spindle. It has the function of transmitting and blocking to
In this clutch mechanism, a plurality of clutch pins as axial displacement means are arranged on the drive gear side so as to be tiltable in the circumferential direction, and the clutch pins in the upright state are engaged with the driven clutch teeth on the spindle side. The clutch pin is tilted, whereby the driving clutch teeth on the driving gear side are immediately moved forward to quickly mesh with the driven clutch teeth, while the driven clutch teeth are disengaged from the clutch pins as the screw tightening progresses. The clutch pin is instantly returned to the upright state, whereby the drive-side clutch teeth are instantaneously retracted to generate an appropriate gap with the driven-side clutch teeth.
According to this clutch mechanism, the drive-side clutch teeth and the driven-side clutch teeth are instantaneously engaged and disengaged. In the disengaged state, an appropriate gap is generated between the two clutch teeth. And improved the durability of the clutch teeth (silent clutch mechanism).
[0003]
[Patent Document 1]
Japanese Patent No. 2867107 [0004]
[Problems to be solved by the invention]
However, the above-mentioned conventional silent clutch mechanism also has a point to be improved. That is, in recent years, there has been an increasing tendency to rotate the spindle at a higher speed than in the past, from the viewpoint of speeding up the screw tightening operation. If the drive gear and, consequently, the clutch pin are rotated at a higher speed than before in order to rotate the spindle at a higher speed than before, the impact when the driven clutch teeth engage with the tips of the clutch pins will increase, and as a result, the driven clutch The wear of the teeth and the clutch pins progresses in a shorter time than before.
As the wear of the driven clutch teeth and the clutch pins increases, the timing at which the driven clutch teeth are disengaged from the clutch pins and the clutch pins are returned to the upright state with the progress of the screw tightening becomes earlier. Is returned in the direction away from the driven clutch teeth, a sufficient gap is not generated between the two clutch teeth, and the two clutch teeth come into contact with each other to generate noise. In this state, the original function of the silent clutch mechanism is not exhibited (lifetime of the clutch mechanism), so that the power transmission function (basic function of the screw tightening machine) by the engagement of the clutch teeth is not impaired at all, but conventionally, The life of the screw tightening machine was at the stage.
SUMMARY OF THE INVENTION The present invention has been made in view of the above problem, and the function of the clutch mechanism is not limited to the life of the screw tightening machine due to the progress of wear of both the driven clutch teeth and the clutch pin, but to the wear of the driven clutch teeth. It is an object of the present invention to provide a clutch mechanism capable of increasing the durability of a power tool such as a screw tightening machine by preventing the influence of the power tool.
[0005]
[Means for Solving the Problems]
For this reason, the present invention provides a clutch mechanism having the configuration described in the claim.
According to the clutch mechanism of the first aspect, the position where the clutch pin starts to engage with the driven clutch teeth and the position where the clutch pin disengages are different. For this reason, even if the driven clutch teeth and the clutch pin are worn by receiving a large impact from each other at the beginning of the engagement, the clutch pin relatively moves to a different portion of the driven clutch tooth and disengages from the driven clutch tooth. Therefore, even if the clutch pin and a part of the driven clutch teeth (the position where the meshing starts) are worn due to the impact at the start of the meshing, the clutch pin passes through a different part (a part that is not worn) from the driven clutch teeth. Therefore, the above-mentioned wear can be affected only by the wear of the clutch pin and not by the wear of the driven clutch teeth. From this, the timing at which the driven clutch teeth disengage from the clutch pins can be maintained for a longer period of time than before without being affected by the wear at the position where the driven clutch teeth start to mesh, so that the clutch The durability (life) of the power tool as a whole can be improved.
According to the clutch mechanism of the second aspect, the clutch pin falls down in the direction orthogonal to the meshing surface of the driven clutch teeth at the position where the meshing starts, so that the relative rotational force of the drive gear with respect to the spindle (the driven gear) The relative rotation force of the clutch teeth) is efficiently received, and the clutch is tilted to the tilting position. According to this, the wear of the clutch pin itself can be reduced.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a front part of a screw tightening machine 1 provided with a clutch mechanism 20 of the present embodiment. The present embodiment is characterized by the clutch mechanism 20, and the entire configuration of the screw tightening machine 1 does not need to be particularly changed, but will be briefly described below.
In FIG. 1, reference numeral 2 denotes a housing. An electric motor 3 is built in the housing 2. A gear portion 3b is formed on the output shaft 3a of the electric motor 3. The drive gear 4 is meshed with the gear portion 3b. The drive gear 4 is supported rotatably with respect to the drive shaft 5 and movable in the axial direction. The rear end of the drive shaft 5 is rotatably supported by the housing 2 via a bearing 6. The front end of the drive shaft 5 is supported coaxially with the spindle 8 via a bearing 7 attached to the spindle 8. The bearing 7 is accommodated in a recess 8 a provided coaxially on the rear surface of the spindle 8. The front side of the drive shaft 5 enters the recess 8a.
The spindle 8 is supported by the housing 2 via a bearing 9 so as to be rotatable and movable in the axial direction. A compression spring 10 is interposed between the spindle 8 and the drive gear 4. Therefore, the spindle 8 is biased in the forward direction (left side in the figure), and the drive gear 4 is biased in the backward direction (right side in the figure).
[0007]
A thrust bearing 11 is interposed between the rear surface of the drive gear 4 and the housing 2. The thrust bearing 11 does not move in the axial direction. The drive gear 4 is pressed against the thrust bearing 11 by the compression spring 10. The clutch mechanism 20 of the present embodiment is provided between the drive gear 4 and the rear surface of the spindle 8. This will be described later.
At the front end of the spindle 8, a bit (tip tool) 12 for screwing is mounted. On the other hand, a stopper sleeve 13 is mounted on the front end of the housing 2. The position of the stopper sleeve 13 can be adjusted in the axial direction with respect to the housing 2 by rotating the stopper sleeve 13. By adjusting the position of the stopper sleeve 13 in the axial direction with respect to the housing 2, it is possible to adjust the timing of the completion of the tightening of the screw (not shown) and the disconnection of the clutch mechanism 20.
When the screw tightening machine 1 is pressed in the screw tightening direction to relatively retract the spindle 8 against the compression spring 10, the clutch mechanism 20 meshes and the spindle 8 starts rotating, whereby the screw tightening proceeds.
As the screw tightening progresses, the tip of the stopper sleeve 13 comes into contact with the screw tightening target, and in this state, the spindle 8 further rotates and moves forward to complete the screw tightening. When the screw tightening is completed, the clutch mechanism 20 is disconnected, and the rotation of the spindle 8 is stopped.
[0008]
The clutch mechanism 20 according to the present embodiment includes the drive clutch teeth 21 to 21 provided on the front surface of the drive gear 4, the driven clutch teeth 22 to 22 provided on the rear end face of the spindle 8, and the drive gear 4. The clutch pins 23 to 23 are provided. As shown in FIG. 2, three drive-side clutch teeth 21 to 21 are provided at three equally-divided positions in the circumferential direction on the same circumference around the axis of the drive shaft 5. The respective meshing surfaces 21 a of the three drive-side clutch teeth 21 to 21 are provided radially around the axis of the drive shaft 5.
Further, the clutch pins 23 to 23 and the holding holes 24 to 24 for holding the same are arranged one by one between the drive-side clutch teeth 21 and 21. The three sets of clutch pins 23 to 23 and holding holes 24 to 24 are also arranged at three equally circumferential positions about the axis of the drive shaft 5. 4 to 6 show the drive gear 4 and the spindle 8 developed in the circumferential direction. 4 to 6, when the rotation of the drive gear 4 is moved to the right in the drawing, it can be considered that the spindle 8 rotates relative to the drive gear 4 in the direction indicated by the white arrow in the drawings.
[0009]
As shown in the drawing, each clutch pin 23 has a cylindrical engaging portion 23a and a hemispherical holding portion 23b. The holding hole 24 has a guide portion 24a for accommodating the engaging portion 23a of the clutch pin 23 and a hemispherical concave portion 24b communicating with the guide portion 24a for accommodating the holding portion 23b of the clutch pin 23. Each clutch pin 23 is tiltably held in the holding hole 24 in a state in which the engaging portion 23a is upright and a state in which it is tilted backward in the rotation direction of the drive gear 4.
For this reason, the guide portion 24a of each holding hole 24 is formed so that its mouth is long in the shape of a long slot (oval shape). That is, the mouth of each guide portion 24a is tangent from its front end 24c in the rotational direction of the drive gear 4 (counterclockwise direction in FIG. 2, rightward in FIGS. 4 to 6) as shown in FIG. It is formed long in the rotation direction rear side along the S direction. Accordingly, as described later, when the driven clutch teeth 22 start to engage with the engaging portions 23a of the clutch pins 23, each clutch pin 23 is tilted down in the tangent S direction.
As shown in FIG. 3, six driven clutch teeth 22 to 22 are provided at six equally divided positions on the same circumference centered on the axis of the spindle 8. The respective meshing surfaces 22a of the six driven clutch teeth 22 to 22 are provided radially around the axis of the spindle 5.
[0010]
With the clutch mechanism 20 configured as described above, the screw tightening machine is operated as follows. As shown in FIG. 1, when the screw tightening machine 1 is not used, the drive gear 4 and the spindle 8 are axially separated from each other by a compression spring 10. For this reason, an appropriate gap is generated between the driving-side clutch teeth 21 to 21 and the driven-side clutch teeth 22 to 22. For this reason, even if the electric motor 3 is started in this non-use state, the drive gear 4 idles quietly because the drive-side clutch teeth 21 to 21 and the driven-side clutch teeth 22 to 2 are not engaged with each other. Does not rotate.
Further, since the drive gear 4 is pressed by the compression spring 10 in a state where the rear surface thereof is in contact with the bearing 11, the clutch pins 23 to 23 are maintained in an upright state as shown in FIG. .
When the screw is set to the bit 12 and the screw is applied to the object to be screwed, and then the electric motor 3 is started, the drive gear 4 idles first and the spindle 8 does not rotate as described above. It becomes. When the screw tightening machine 1 is pressed in the screw tightening direction in this state, the spindle 8 relatively moves backward, whereby the distance between the drive-side clutch teeth 21 to 21 and the driven-side clutch teeth 22 to 22 decreases. To go. Further, the distance between the upright clutch pins 23 to 23 and the driven clutch teeth 22 to 22 also decreases. Even in this state, the drive gear 4 is idling and the spindle 8 is not rotating.
[0011]
Further, when the screw tightening machine 1 is pressed, the driven clutch teeth 22 to 22 start to engage with the clutch pins 23 to 23 which are rotating (revolving around the drive shaft 5) integrally with the drive gear 4. The state at this moment is shown in FIG. When the driven clutch teeth 22 are engaged with the respective clutch pins 23, the three clutch pins 23 to 23 are simultaneously tilted rearward in the rotation direction of the drive gear 4 by the relative rotation of the drive gear 4 and the spindle 8. The state at this stage is shown in FIG. As shown in the drawing, when the clutch pins 23 to 23 are tilted rearward in the rotational direction, the ends of the respective holding portions 23b protrude from the rear end surface of the drive gear 4. Therefore, the drive gear 4 is lifted by a distance D from the bearing 11 against the compression spring 10, whereby the drive-side clutch teeth 21 to 21 and the driven-side clutch teeth 22 to 22 are instantaneously engaged. In this meshing state, the three driven clutch teeth 22-22 mesh with the three drive clutch teeth 21-21, and the remaining three driven clutch teeth 22-22 mesh with the clutch pins 23-23.
Through the above process, all the rotational power of the drive gear 4 is transmitted to the spindle 8, and screw tightening proceeds.
[0012]
As the screw tightening proceeds, the tip of the stopper sleeve 13 abuts against the object to be screwed. In this abutting state, the spindle 8 is further rotated to tighten the screw, and the lead of the screw causes the spindle 8 to be compressed by the compression spring 10. It is pushed by and gradually moves forward. When the spindle 8 starts to move forward by the compression spring 10, the driven clutch teeth 22 to 22 are displaced gradually in a direction away from the drive clutch teeth 21 to 21, and the mutual meshing becomes shallower. FIG. 6 shows a state immediately before the completion of the screw tightening. In this state, the driven clutch teeth 22 to 22 are in a state immediately before disengagement from the clutch pins 23 to 23.
When the driven clutch teeth 22 to 22 are disengaged from the clutch pins 23 to 23, no external force is applied to hold down the clutch pins 23 to 23. As a result, there is no gap between the drive gear 4 and the bearing 11, and the bearing 11 is returned to the upright position. In this way, at the moment when the engaged state of the driven clutch teeth 22 to 22 to the clutch pins 23 to 23 is released, the drive gear 4 retreats, and thereby the drive clutch teeth 21 to 21 to the driven clutch teeth 22 to 22. Is instantaneously released and an appropriate gap is instantaneously provided between the two clutch teeth 21 and 22, and the drive gear 4 quietly idles.
[0013]
According to the screw tightening machine 1 configured as described above, the driven side clutch teeth 22 to 22 are engaged with the upright clutch pins 23 to 23 by the retraction of the spindle 8 due to the pressing of the screw tightening machine 1, whereby the clutch The pins 23 to 23 are tilted backward in the rotation direction of the drive gear 4. The direction in which the clutch pins 23 to 23 fall is such that the clutch pins 23 to 23 fall along the mouth of the guide portion 24a that holds the engaging portion 23a, so that the tangent S direction at the rotation direction front end portion 24c of the guide portion 24a. It becomes. Therefore, the clutch pin 23 falls down in a direction orthogonal to the meshing surface 22a of the driven clutch tooth 22. In FIG. 2, this point is such that the tangent S to the line M representing the surface direction of the meshing surface 22 a of the driven clutch tooth 22 coincides with the axis J of the clutch pin 23 corresponding to the direction in which the clutch pin 23 falls. Can be understood.
On the other hand, the driven clutch teeth 22 to 22 move in an arc. Therefore, at the moment when the driven clutch teeth 22 start to be engaged (FIG. 4), the contact position (meshing start position) of the clutch pin 23 with the meshing surface 22a and the moment when the driven clutch teeth 22 disengage (FIG. 6). The contact position (disengagement position) of the clutch pin 23 with the engagement surface 22a is largely shifted radially outward of the spindle 8.
[0014]
That is, as shown in FIG. 7, the position where the clutch pin 23 starts to mesh with the meshing surface 22a of the driven clutch tooth 22 is located on the inner peripheral side, and the disengaged position is located on the outer peripheral side. The contact point gradually displaces to the outer peripheral side with the inclination of the clutch pin 23 and with the separation of the driven clutch teeth 22 to 22 from the drive clutch teeth 21 to 21.
In FIG. 7, the movement trajectory L of the contact point of the clutch pin 23 with the engagement surface 22a from when the driven clutch tooth 22 starts to engage with the clutch pin 23 until it disengages is shown by a solid line. In FIG. 7, the position indicated by reference numeral (A) is at a position relative to the meshing surface 22 a of the clutch pin 23 at the moment when the driven clutch tooth 22 starts to mesh with the clutch pin 23 in the upright state (FIG. 4). The position at which the engagement starts is shown. The position indicated by reference numeral (B) is in a state where the clutch pin 23 is tilted to the inclined position and the drive-side clutch teeth 21 to 21 are completely meshed with the spindle clutch teeth 22 to 22 (FIG. 5). The engagement position of the clutch pin 23 with respect to the engagement surface 22a is shown. Further, the position indicated by the reference numeral (C) indicates the engagement of the clutch pin 23 with the engagement surface 22a at the moment when the screw tightening advances and the driven clutch teeth 22 are disengaged from the drive clutch teeth 21 (FIG. 6). It shows the off position.
[0015]
A movement trajectory L 'indicated by a broken line with respect to the movement trajectory L is due to the clutch mechanism 30 having the conventional structure shown in FIG. 8, and shows a movement trajectory of a contact point of the clutch pin 31 with the driven clutch teeth 22. . The movement trajectory L 'is a trajectory from the meshing start position (A) to the meshing position (C') via the meshing position (B '). Are in almost the same position.
As shown in FIG. 8, the clutch pin 31 of the conventional clutch mechanism 30 at the engagement start position (A) is orthogonal to the engagement surface 22 a (the direction indicated by line M) of the driven clutch teeth 22 (tangential direction). It was not configured to fall along S).
The conventional clutch pin 31 is configured to fall along an axis J that is coincident with or parallel to the chord of the arc-shaped movement trajectory of the driven clutch tooth 22 that moves while the driven clutch tooth 22 is engaged with the clutch pin 31. It was. For this reason, in the conventional clutch mechanism 30, the contact position of the clutch pin 31 with the meshing surface of the driven clutch tooth moving along the arc-shaped trajectory is defined as the meshing start position (A) and the meshing disengagement position (C '). And the clutch pin is disengaged from the clutch teeth 22 in a state where the clutch pin is greatly affected by the wear at the position where the meshing starts, and as a result, the timing of the disengagement of the clutch pin 31 from the driven clutch teeth 22 becomes earlier. There was a problem. If the clutch pin is quickly disengaged from the driven clutch teeth, the clutch pin is returned to the upright position, and the drive gear retreats earlier.Therefore, the drive clutch teeth and the driven clutch teeth are retracted when the drive gear is retracted. Therefore, an appropriate gap is not generated between the clutch clutch and the clutch clutch. As a result, the two clutch teeth come into contact with each other to generate an abnormal noise, which makes it impossible to perform the silent idle function which is a feature of the silent clutch mechanism.
Also, if the timing of disengagement of the clutch pin from the driven clutch teeth is advanced, the transmission of power is interrupted at the time when the screw tightening is not completed, and as a result, poor screwing occurs.
[0016]
As described above, according to the clutch mechanism 20 of the present embodiment, the engagement position (engagement position) of the clutch pin 23 with respect to the engagement surface 22a of the driven-side clutch teeth 22 is greatly different between the start of engagement and the stage of disengagement. . Therefore, the driven clutch teeth 22 to 22 are repeatedly engaged with the clutch pins 23 to 23 in a state where the drive gear 4 is rotated at a high speed, whereby the engagement start position (A) of the driven clutch teeth 22 to 22 and the clutch pin Even when the clutch pin 23 is worn by the impact, the clutch pin 23 is displaced radially outward from the meshing start position (A) and disengages from the meshing disengaging position (C) where there is almost no wear.
Thus, the timing at which the clutch pin 23 is disengaged from the driven clutch teeth 22 can be maintained at an appropriate timing for a long period of time, as compared with the conventional configuration in which the engagement is disengaged from substantially the same position as the engagement start position (A). Thus, the function as the silent clutch mechanism 20 can be maintained for a long time, and the life of the screw tightening machine 1 can be extended.
Further, since the clutch pin 23 falls down from the engagement start position in the tangent S direction (the direction orthogonal to the engagement surface 22a indicated by the line M), the engagement angle of the clutch pin 23 with the driven clutch tooth 22 (the collision of the engagement surface 22a). As a result, the operating direction of the rotational force applied to the clutch pin 23) can be made to coincide with the falling direction (tangential line S direction) of the clutch pin 23, whereby the clutch pin is tilted by efficiently receiving the relative rotational force on the spindle side. The clutch pin 23 can be efficiently moved down to the position, and the wear itself of the clutch pin 23 can be reduced as compared with the related art.
[0017]
Various modifications can be made to the embodiment described above. For example, although the configuration in which each clutch pin 23 is tilted in the direction orthogonal to the meshing surface 22a (line M) of the driven clutch teeth 22 at the meshing start position (A) is illustrated, the clutch pin according to the present invention is other than the above. Can be configured to be tilted in the angle direction. In addition to the conventional case of tilting outward (radially outward) with respect to the tilting direction (direction of line J in FIG. 8), a configuration of tilting inward (toward the center of rotation) may be employed. In short, the contact angle of the clutch pin with the driven clutch tooth (the angle between the line M and the axis J in FIG. 8) is appropriately set, and the contact position of the clutch pin with the driven clutch tooth 22 is changed to the contact at the beginning of engagement. The clutch pin 23 may be displaced largely from the position (for example, from (A) to (C) in FIG. 7), and the clutch pin 23 may be disengaged from a portion of the meshing surface 22a of the clutch tooth 22 where wear is small.
Further, the configuration in which the three clutch pins 23 to 23 are provided is illustrated, but a configuration in which two or four or more clutch pins are provided may be employed.
In addition, the clutch pins 23 to 23 and the driving clutch teeth 21 to 21 are provided directly on the drive gear 4 to displace the drive gear 4 in the axial direction. The clutch plate may be provided so as to be movable in the direction and rotatable integrally with the drive gear 4, and the clutch plate may be provided with clutch pins and drive-side clutch teeth. In this case, the drive gear can be configured not to be displaced in the axial direction.
Furthermore, although the screw tightening machine has been exemplified as the electric tool, the present invention can be similarly applied to a clutch mechanism of another electric tool.
[Brief description of the drawings]
FIG. 1 is a view showing an embodiment of the present invention, and is a side view showing an internal structure of a front part of a screw tightening machine.
FIG. 2 is a front view of a drive gear, and is a plan view of drive-side clutch teeth and clutch pins in an upright state. In this drawing, a state is shown in which each clutch pin has fallen to the inclined position.
FIG. 3 is a rear view of the spindle and a plan view of a driven clutch tooth.
FIG. 4 is a development view of a clutch mechanism. This figure shows a state at the moment when the driven clutch teeth start engaging with the clutch pins. The clutch pin is in an upright state immediately before being brought down.
FIG. 5 is a development view of a clutch mechanism. This figure shows a state in which the driven clutch teeth mesh with the drive clutch teeth. The clutch pin is shown in a state where the clutch pin is tilted to the tilt position.
FIG. 6 is a development view of a clutch mechanism. This drawing shows a state immediately before disengagement from the clutch pin in a state where the driven clutch teeth are tilted.
FIG. 7 is a front view showing a movement trajectory of a contact position of a clutch pin with respect to an engagement surface, which is a view taken along line (7)-(7) of FIG. 3;
FIG. 8 is a view showing a conventional clutch mechanism, and is a plan view of a front end face of a drive gear. In this drawing, a state is shown in which each clutch pin has fallen to the inclined position.
[Explanation of symbols]
1. Screwdriver (power tool)
2 ... Housing 3 ... Electric motor, 3a ... Output shaft, 3b ... Gear part 4 ... Drive gear 5 ... Drive shafts 6,7 ... Bearing 8 ... Spindle, 8a ... Recess 9 ... Bearing 10 ... Compression spring 11 ... Thrust bearing 12 ... Bit (tip tool)
13: stopper sleeve 20: clutch mechanism (silent clutch mechanism)
Reference numeral 21: drive side clutch teeth, 21a: meshing surface 22: driven side clutch teeth, 22a: meshing surface 23: clutch pin, 23a: engaging portion, 23b: holding portion 24: holding hole, 24a: guide portion, 24b: concave portion .., 24c... Front end (A)... Meshing start position (B)... Meshing position (C). Conventional clutch mechanism

Claims (2)

A drive clutch tooth on the drive gear side and a driven clutch tooth on the spindle side interposed between a drive gear rotated by a motor and a spindle rotatably and axially movably supported by a housing. A clutch mechanism of an electric tool for transmitting rotation of the drive gear to the spindle by meshing with the spindle.
The drive gear includes a clutch pin that is tiltably held between an upright position that stands upright toward the spindle and a tilt position that is tilted rearward in the rotation direction of the drive gear,
When the clutch pin is tilted to the tilted position due to meshing with the driven clutch teeth, the driving clutch teeth approach the driven clutch teeth and both clutch teeth are engaged, while the clutch pin is driven by the driven pin. When the clutch pin is disengaged from the side clutch teeth and the clutch pin is returned to the upright position, the drive side clutch teeth are separated from the driven side clutch teeth and a gap is generated between the two clutch teeth.
When the clutch pin is tilted from the upright position toward the tilt position, the contact position with respect to the driven clutch tooth is displaced, and the clutch pin is disengaged from the driven clutch tooth at a position different from the contact position at which meshing starts. Clutch mechanism. 2. The clutch mechanism according to claim 1, wherein the clutch pin is tilted from a position where the clutch pin starts to mesh with the driven clutch tooth in a direction orthogonal to a meshing surface of the driven clutch tooth.

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