CN111757793B - Working tool - Google Patents

Abstract

In a power tool having a planetary roller power transmission mechanism that performs power transmission in response to rearward movement of a main spindle, an improvement is provided for establishing stable frictional contact of a planetary roller with a driving surface. A power transmission mechanism (4) of an electric screwdriver (1) comprises a taper sleeve (41), a gear sleeve (47), a retainer (43) and a roller (45). The taper sleeve (41) and the gear sleeve (47) have taper surfaces (411, 475), respectively. The gear sleeve (47) is movable in the forward and backward directions relative to the tapered sleeve (41) integrally with the main shaft (3). At least a part of the roller (45) is disposed between the tapered surfaces (411, 475) in the radial direction with respect to the drive shaft (A1). The electric screwdriver (1) is provided with an urging spring (49), and the urging spring (49) limits the roller (45) to move in the front-back direction relative to the main body shell (11).

Description

Working tool

Technical Field

The present invention relates to a power tool configured to rotationally drive a tip tool.

Background

A power transmission mechanism (clutch) is known which is configured to rotationally drive a tool bit attached to a distal end portion of a spindle and to transmit power of a motor to the spindle in response to press-fitting of the spindle. For example, japanese patent laid-open publication No. 2012-135842 discloses a planetary power transmission mechanism having a fixed hub, a drive gear, a planetary roller (planetary roller), and a holding member for the planetary roller. The fixed hub has a tapered surface (tapered surface) on the outer periphery and is fixed to the housing. The cup-shaped drive gear has a tapered surface on an inner periphery and is rotatably held to the main shaft. The planetary rollers are disposed between the stationary hub and the tapered surface of the drive gear. The holding member of the planetary roller is fixed to the main shaft. The drive gear is rotated by power of the motor, and when the main shaft is pushed rearward, the planetary rollers revolve around the main shaft while rotating in frictional contact with the fixed hub and the tapered surfaces of the drive gear. Accordingly, the holding member of the planetary roller rotates around the shaft integrally with the main shaft.

Disclosure of Invention

In the above power transmission mechanism, when the main shaft moves in the axial direction, the drive gear held by the main shaft and the holding member of the planetary roller move in a direction approaching or separating from the fixed hub fixed to the housing. On the other hand, the planetary rollers are disposed in a groove formed in the holding member in a clearance fit manner. Therefore, the planetary roller may move in the axial direction and may be unstable in frictional contact with the tapered surface as the drive surface.

In view of the above, it is an object of the present invention to provide an improvement for establishing a stable frictional contact between a planetary roller and a driving surface in a power tool having a planetary roller type power transmission mechanism that transmits power in response to a backward movement of a main spindle.

According to an aspect of the present invention, there is provided a power tool configured to rotationally drive a tip tool. The work tool has a housing, a spindle, a motor, and a power transmission mechanism.

The spindle is supported by the housing so as to be movable in a front-rear direction along a predetermined drive shaft extending in the front-rear direction of the power tool and rotatable about the drive shaft. The spindle has a tip portion configured to be attachable to and detachable from the tip tool. The motor and the power transmission mechanism are housed in the case. The power transmission mechanism includes a sun member, a ring member, a carrier member, and planetary rollers. The sun member, the ring member, and the carrier member are disposed coaxially with the drive shaft. The planetary rollers are rotatably held by the carrier member. The sun member and the ring member have 1 st and 2 nd tapered surfaces, respectively, which are inclined with respect to the drive shaft. One of the sun member and the ring member is configured to be movable in the front-rear direction integrally with the main shaft relative to the other. At least a part of the planetary roller is disposed between the 1 st tapered surface and the 2 nd tapered surface in a radial direction with respect to the drive shaft.

The power transmission mechanism is configured to transmit power of the motor to the main shaft by relatively moving the sun member and the ring member in a direction to approach each other in response to backward movement of the main shaft, and bringing the planetary rollers into frictional contact with the sun member and the ring member. The power transmission mechanism is configured such that the sun member and the ring member are relatively moved in a direction away from each other in response to the forward movement of the main shaft, and the planetary rollers are brought into non-frictional contact with the sun member and the ring member, thereby blocking the transmission of power. The work tool further includes a regulating member configured to regulate the movement of the planetary roller in the forward and backward direction with respect to the housing. The term "restriction of movement" used herein is not limited to the complete prohibition of movement, but also includes the case where slight movement is permitted.

The power tool of the present embodiment includes a so-called planetary roller type power transmission mechanism. In the power transmission mechanism, at least a part of the planetary rollers is disposed between the 1 st tapered surface of the sun member and the 2 nd tapered surface of the ring member in a radial direction of the main shaft with respect to the drive shaft (a direction orthogonal to the drive shaft). One of the sun member and the ring member is movable in the front-rear direction integrally with the main shaft relative to the other. In contrast, the planetary rollers are restricted from moving in the front-rear direction by the restricting member. Therefore, the planetary rollers move in the front-rear direction in accordance with the relative movement of the sun member and the ring member, and the possibility that the frictional contact between the 1 st tapered surface and the 2 nd tapered surface becomes unstable can be reduced.

In one aspect of the present invention, the carrier member may be held to the main shaft so as to be movable in the front-rear direction with respect to the main shaft. In other words, the planet carrier member may be independent of the main shaft with respect to movement in the forward and rearward directions. The carrier member needs to be disposed at a position where the planetary rollers can be held so that the planetary rollers do not come off between the 1 st tapered surface of the sun member and the 2 nd tapered surface of the ring member. In contrast, according to the present embodiment, the carrier member can be held at an appropriate position regardless of the movement of the main shaft. Accordingly, compared to the case where the carrier member moves integrally with the main shaft, the restriction on the amount of movement of the main shaft in the front-rear direction can be reduced. In particular, when the planetary rollers or the 1 st and 2 nd tapered surfaces are worn, the main shaft needs to be pressed into a position where the sun member and the ring member are closer to each other in order to establish stable frictional contact. That is, the amount of movement of the main shaft in the front-rear direction needs to be increased, but this aspect can also appropriately cope with this demand.

In one aspect of the present invention, the carrier member may be held to the main shaft so as not to be rotatable about the drive shaft. The carrier member may be configured to rotate integrally with the main shaft by power transmitted via the planetary rollers. According to this aspect, a rational planetary roller type power transmission mechanism can be realized in which the carrier member is the output member.

In one aspect of the present invention, the restricting member may be configured to restrict the movement of the carrier member in the front-rear direction with respect to the case. According to this aspect, the movement of the planetary rollers and the carrier member in the front-rear direction is restricted by the restricting member, and therefore the proper positional relationship between the planetary rollers and the carrier member can be more reliably maintained.

In one aspect of the present invention, the restricting member may include a spring member that biases the main shaft and the carrier member away from each other in the front-rear direction. Also, the main shaft can be normally held at the most forward position by the urging force of the spring member. According to this aspect, when the main shaft is released from being pushed in while the movement of the carrier member is regulated by the biasing force of the spring member, the main shaft can be returned to the most forward position (i.e., the initial position).

In one aspect of the present invention, the ring member may be supported by the main shaft so as to be movable in the front-rear direction integrally with the main shaft and rotatable about the drive shaft. The spring member may be interposed between the carrier member and the ring member in the front-rear direction. The power tool may further include a receiving member that receives one end of the spring member on the ring member side in a state where the receiving member does not rotate with rotation of the ring member. According to this aspect, the spring member can be prevented from rotating together with the ring member (so-called co-rotation), or heat can be prevented from being generated at the sliding portion between the spring member and the ring member.

In one aspect of the present invention, the ring member may be configured to be rotated by power of a motor. The spring member may be configured to bias the ring member and the carrier member forward and backward so as to be away from each other. In other words, the spring member also has a function of biasing the ring member, which is the driving-side member in the power transmission mechanism, and the carrier member, which is the driven-side member, in the direction of interrupting the transmission. According to this aspect, a plurality of functions such as restriction of movement of the carrier member in the front-rear direction and interruption of power transmission can be achieved by the spring member without increasing the number of components.

In one aspect of the present invention, the annular member may have at least 1 communication hole that communicates the inside and the outside of the annular member. According to this aspect, the air flow can be generated through the communication hole by the centrifugal force generated in association with the driving of the power transmission mechanism (typically, the rotation of the ring member). This can suppress a local temperature rise in the power transmission mechanism and achieve smoother circulation of the lubricant disposed in the housing. As a result, wear of the planetary roller, the 1 st tapered surface, and the 2 nd tapered surface can be effectively reduced, and durability can be improved.

In an aspect of the present invention, the communication hole may be formed in a region of the annular member other than a region corresponding to the 2 nd tapered surface. According to this aspect, the communication hole can be easily formed in the ring member.

Drawings

Fig. 1 is a side view of an electric driver (Screwdriver) according toembodiment 1.

Fig. 2 is a longitudinal sectional view of the electric screwdriver.

Fig. 3 is a partially enlarged view of fig. 2.

Fig. 4 is a sectional view IV-IV of fig. 3.

Fig. 5 is a partially enlarged view of fig. 3.

Fig. 6 is a partially enlarged view of fig. 4.

Fig. 7 is an exploded perspective view of the main shaft, the power transmission mechanism, and the position switching mechanism.

Fig. 8 is a sectional view VIII-VIII of fig. 3, which corresponds to the roller, and is an explanatory diagram showing a non-frictional contact state between the roller, the tapered sleeve (tapered sleeve), and the gear sleeve (gear sleeve).

Fig. 9 is a longitudinal sectional view of the electric screwdriver in a state where the spindle is moved rearward from the home position and the power transmission mechanism is in a transmittable state.

Fig. 10 corresponds to the cross-sectional X-X view of fig. 9, and is an explanatory diagram showing a frictional contact state between the roller and the taper sleeve and the gear sleeve.

Fig. 11 is a cross-sectional view XI-XI of fig. 3, which is an explanatory diagram showing a state of the one-way clutch in a case where the gear sleeve is rotationally driven in the forward direction.

Fig. 12 is a cross-sectional view corresponding to fig. 11, and is an explanatory diagram showing a state of the one-way clutch in a case where the gear sleeve is rotationally driven in the reverse direction.

Fig. 13 is a cross-sectional view corresponding to fig. 4, and is an explanatory diagram showing a state in which a guide sleeve (lead sleeve) and a gear sleeve are moved rearward.

Fig. 14 is a longitudinal sectional view of the electric screwdriver in a state where the retainer (locator) is in contact with the workpiece and the screw tightening operation is completed.

Fig. 15 is a longitudinal sectional view of the electric screwdriver according toembodiment 2.

Fig. 16 is a cross-sectional view of XVI-XVI of fig. 15.

Fig. 17 is an exploded perspective view of the main shaft, the power transmission mechanism, and the position switching mechanism.

Fig. 18 is a sectional view corresponding to fig. 15, and is an explanatory diagram showing a state in which the gear sleeve is moved rearward.

Fig. 19 is a sectional view corresponding to fig. 16, and is an explanatory diagram showing a state in which the gear sleeve is moved rearward.

Fig. 20 is a longitudinal sectional view of the electric screwdriver according toembodiment 3.

Fig. 21 is a sectional view XXI-XXI of fig. 20.

Fig. 22 is an exploded perspective view of the main shaft, the power transmission mechanism, and the position switching mechanism.

Fig. 23 is a partially enlarged view of fig. 21.

Detailed Description

Embodiments of the present invention will be described below with reference to the drawings.

[ 1 st embodiment ]

Theelectric driver 1 according toembodiment 1 will be described with reference to fig. 1 to 14. Theelectric screwdriver 1 is an example of a power tool that rotationally drives a tip tool. More specifically, theelectric driver 1 is an example of a screw tightening tool capable of performing a screw tightening operation or a screw loosening operation by rotationally driving a driver bit (driver bit)9 attached to thespindle 3.

First, a schematic configuration of theelectric driver 1 will be explained. As shown in fig. 1 and 2, theelectric driver 1 includes: amain body 10 including amotor 2, aspindle 3, and the like; and ahandle portion 17 including agrip portion 171. Themain body portion 10 is formed in an elongated shape extending along a predetermined drive shaft a1 (drive axis a 1). Thedriver bit 9 is detachably attached to one end portion in the longitudinal direction of the main body 10 (the extending direction of the drive shaft a 1). Thegrip portion 17 is formed in a C-shape as a whole, and is annularly connected to the other end portion in the longitudinal direction of themain body portion 10. The portion of thegrip portion 17 that is separated from themain body portion 10 and linearly extends in a direction substantially orthogonal to the drive shaft a1 constitutes agrip portion 171 to be gripped by a user. Further, one end portion of thegrip 171 in the longitudinal direction is disposed on the drive shaft a 1. Atrigger 173 that can be operated by a user is provided at the one end portion. Apower cable 179 connectable to an external ac power source is connected to the other end of thegrip portion 171.

In theelectric screwdriver 1 of the present embodiment, themotor 2 is driven when the user pulls theoperation trigger 173. When thespindle 3 is pushed rearward, the power of themotor 2 is transmitted to thespindle 3 to rotate thedriver bit 9. Accordingly, the screw fastening operation or the screw loosening operation is performed.

Next, the detailed structure of theelectric driver 1 will be explained. In the following description, for convenience of explanation, the extending direction (axial direction) of the drive shaft a1 is defined as the front-rear direction of theelectric driver 1. In the front-rear direction, the side on which thedriver bit 9 is attached and detached is defined as the front side, and the side on which thegrip 171 is disposed is defined as the rear side. A direction perpendicular to the drive shaft a1 and corresponding to the extending direction of thegrip portion 171 is defined as the vertical direction. In the vertical direction, the side on which thetrigger 173 is disposed is defined as the upper side, and the side to which thepower cable 179 is connected is defined as the lower side. The directions orthogonal to the front-rear direction and the up-down direction are defined as the left-right direction.

First, themain body 10 and thegrip 17 will be briefly described. As shown in fig. 2, the outer contour of themain body portion 10 is mainly formed by themain body casing 11. Themain body casing 11 includes: a cylindricalrear housing 12 that houses themotor 2; a cylindricalfront housing 13 that houses thespindle 3; and acenter housing 14 disposed between therear housing 12 and thefront housing 13. The front end portion of thecenter housing 14 has apartition wall 141 disposed substantially orthogonal to the drive shaft a 1. Thecenter case 14 and thefront case 13 are fixed to therear case 12 with screws, whereby 3 cases are integrated into themain body case 11. Further, the details of the internal structure including themain body 10 will be described on the rear surface.

Acylindrical retainer 15 is detachably connected to a front end portion of thefront housing 13 so as to cover the front end portion. Theretainer 15 is movable relative to thefront housing 13 in the front-rear direction and is fixed at an arbitrary position by a user. Accordingly, the amount of protrusion of thedriver bit 9 from theretainer 15, that is, the depth of screw tightening is set.

As shown in fig. 2, the outer contour of thehandle portion 17 is mainly formed by thehandle housing 18. Thehandle case 18 is formed of a left and right split body. In addition, the left split body is formed integrally with therear housing 12. Thehandle housing 18 houses amain switch 174, arotation direction switch 176, and acontroller 178.

Themain switch 174 is a switch for starting themotor 2, and is disposed in thegrip 171 on the rear side of thetrigger 173. Themain switch 174 is normally maintained in an off state and is switched to an on state in response to a pulling operation of thetrigger 173. Themain switch 174 outputs a signal indicating an on state or an off state to thecontroller 178 through a wiring not shown.

A switchinglever 175 is provided in a portion of thehandle housing 18 connected to a lower end portion of thegrip portion 171 and a lower rear end portion of the main body portion 10 (rear housing 12), and the switchinglever 175 switches a rotation direction of the driver bit 9 (in detail, a rotation direction of the motor shaft 23). The user can set the rotational direction of themotor shaft 23 to one of the direction in which thedriver bit 9 fastens the screw 90 (forward direction, also referred to as screw fastening direction) and the direction in which thedriver bit 9 unscrews the screw 90 (reverse direction, also referred to as screw unscrewing direction) by operating the switchinglever 175. Therotation direction switch 176 outputs a signal corresponding to the rotation direction set via the switchinglever 175 to thecontroller 178 through a wiring not shown.

Acontroller 178 including a control circuit is disposed below themain switch 174. Thecontroller 178 is configured to drive themotor 2 in the rotation direction indicated by the signal from therotation direction switch 176 when the signal from themain switch 174 indicates the on state.

Next, a detailed structure of the internal structure including themain body 10 will be described.

As shown in fig. 2, themotor 2 is housed in therear housing 12. In the present embodiment, an ac motor is used as themotor 2. Themotor shaft 23 extending from therotor 21 of themotor 2 extends below the drive shaft a1 in parallel with the drive shaft a1 (in the front-rear direction). The front end portion and the rear end portion of themotor shaft 23 are rotatably supported bybearings 231, 233. Thefront bearing 231 is supported by thepartition wall 141 of thecenter housing 14, and therear bearing 233 is supported by the rear end of therear housing 12.Fan 25 for coolingmotor 2 is fixed to a portion ofmotor shaft 23 on the front side ofrotor 21 and is housed incenter housing 14. The front end portion of themotor shaft 23 protrudes into thefront housing 13 through a through hole provided in thepartition wall 141. Apinion 24 is formed at the front end of themotor shaft 23.

As shown in fig. 3 and 4, themain shaft 3, thepower transmission mechanism 4, and theposition switching mechanism 5 are housed in thefront housing 13. The detailed structure of these components will be described in turn.

As shown in fig. 3 and 4, themain shaft 3 is a substantially cylindrical elongated member extending in the front-rear direction along the drive shaft a 1. In the present embodiment, thespindle 3 is configured to be fixedly connected to and integrated with afront shaft 31 and arear shaft 32, which are formed separately. However, themain shaft 3 may be constituted by only a single shaft. Themain shaft 3 has aflange 34 protruding radially outward at a central portion in the front-rear direction (more specifically, a rear end portion of the front shaft 31).

Themain shaft 3 is supported by a bearing (specifically, an oilless bearing) 301 and a bearing (specifically, a ball bearing) 302 so as to be rotatable about a drive axis a1 and movable in the front-rear direction along a drive shaft a 1. Thebearing 301 is supported by thepartition wall 141 of thecenter housing 14. Thebearing 302 is supported at the front end of thefront housing 13. Thespindle 3 is normally biased forward by a biasing force of a biasingspring 49 described later, and is held at a position where the front end surface of theflange 34 abuts against astopper 135 provided in thefront housing 13. The position of thespindle 3 at this time is the most forward position (also referred to as the home position) within the movable range of thespindle 3. Further, the front end of the spindle 3 (front shaft 31) protrudes from thefront housing 13 into theretainer 15. A toolbit insertion hole 311 is provided along the drive shaft a1 at the tip end of the spindle 3 (the front shaft 31). A steel ball biased by a leaf spring (leaf spring) engages with the small diameter portion of thedriver bit 9 inserted into thebit insertion hole 311, whereby thedriver bit 9 is detachably held.

Next, thepower transmission mechanism 4 will be explained. As shown in fig. 3 and 4, thepower transmission mechanism 4 of the present embodiment is mainly configured by a planetary mechanism including ataper sleeve 41, a retainer (retainer)43, a plurality ofrollers 45, and agear sleeve 47. Thetaper sleeve 41, theretainer 43, and thegear sleeve 47 are arranged coaxially with the main shaft 3 (drive shaft a 1). Thetaper sleeve 41, thecage 43, therollers 45, and thegear sleeve 47 correspond to a sun member, a carrier member, a planetary member, and a ring member in the planetary mechanism, respectively. In the present embodiment, thepower transmission mechanism 4 is configured as a so-called sun planetary reduction mechanism in which theconical sleeve 41 as a sun member is fixed, thegear sleeve 47 as an annular member operates as an input member, and thecage 43 as a carrier member operates as an output member. Therefore, thegear sleeve 47 and the holder 43 (the spindle 3) rotate in the same direction.

Thepower transmission mechanism 4 is configured to transmit or block the power of themotor 2 to thespindle 3. Specifically, thepower transmission mechanism 4 is configured such that therollers 45 are brought into a frictional contact state or a non-frictional contact state with thetaper sleeve 41 and thegear sleeve 47 as thegear sleeve 47 moves in the front-rear direction relative to each other in a direction of approaching or separating from thetaper sleeve 41, theretainer 43, and therollers 45. Accordingly, thepower transmission mechanism 4 is switched between a transmittable state in which the power of themotor 2 can be transmitted to thespindle 3 and a blocked state in which the power of themotor 2 cannot be transmitted to thespindle 3. That is, thepower transmission mechanism 4 of the present embodiment can be configured as a planetary roller type friction clutch mechanism.

Next, the detailed structure and arrangement of the components of thepower transmission mechanism 4 will be described.

First, the taperedsleeve 41 will be explained. As shown in fig. 5 to 7, the taperedsleeve 41 corresponding to the sun member is configured as a cylindrical member. The taperedsleeve 41 is fixed to the main body case 11 (specifically, the partition wall 141) by the base 143 so as not to rotate around the drive shaft a 1. Thebase 143 is fixed to thepartition wall 141 on the front side of thebearing 301 that supports the rear end portion of the spindle 3 (rear shaft 32), and is integrated with themain body case 11. The spindle 3 (more specifically, the rear shaft 32) is inserted through the taperedsleeve 41 in a clearance fit manner, and is rotatable while being movable in the front-rear direction with respect to the taperedsleeve 41.

The outer peripheral surface of the taperedsleeve 41 is configured as atapered surface 411 inclined at a predetermined angle with respect to the drive shaft a 1. Specifically, the taperedsleeve 41 has a truncated cone shape whose outer shape is tapered (diameter is reduced) toward the front. Thetapered surface 411 is configured as a conical surface inclined in a direction approaching the drive shaft a1 as it approaches the front. In the present embodiment, the inclination angle of the taperedsurface 411 with respect to the drive axis a1 is set to approximately 4 degrees (approximately 8 degrees when viewed in a cross section of a cone).

Next, theretainer 43 will be explained. Thecage 43 as a carrier member is a member that rotatably holds therollers 45 as a planetary member. As shown in fig. 5 to 7, theretainer 43 includes: abottom wall 431 which is substantially circular and has a through hole; and a plurality of retainingarms 434 protruding from the outer edge of thebottom wall 431. The holdingarms 434 are arranged apart from each other in the circumferential direction. In the present embodiment, theretainer 43 has 10 holdingarms 434, but the number of the holding arms 434 (and the number of the rollers 45) can be changed as appropriate. Theholder 43 is disposed in such a direction that thebottom wall 431 is positioned on the front side (so that the holdingarm 434 protrudes rearward). Theholder 43 is supported by thespindle 3 so as to be unrotatable relative to thespindle 3 and movable in the forward-backward direction in a state where a part of the holdingarm 434 overlaps the taperedsleeve 41 in the radial direction. Each of the holdingarms 434 projects rearward from the outer edge of thebottom wall 431 at the same inclination angle as thetapered surface 411 of the taperedsocket 41 with respect to the drive shaft a1 (i.e., parallel to the tapered surface 411).

As shown in fig. 6 and 7, a pair ofgrooves 321 is formed in a front portion of a rear end portion of therear shaft 32 of themain shaft 3 with a drive shaft a1 interposed therebetween. Eachgroove 321 has a U-shaped cross section, and eachgroove 321 extends linearly in the front-rear direction.Steel balls 36 are arranged in eachgroove 321 in a rollable manner. Further, a pair ofrecesses 432 are formed on the rear surface (surface on the side of the holding arm 434) of thebottom wall 431 of theholder 43 with the drive shaft a1 interposed therebetween. A part of theballs 36 disposed in thegroove 321 is engaged with theconcave portion 432. Anannular recess 414 is formed in the center of the distal end surface of the taperedsleeve 41. Specifically, theretainer 43 is biased rearward by the biasingspring 49, and theballs 36 are disposed in the space defined by therecesses 414 and 432, and are held in a state where the rear surface of thebottom wall 431 is in contact with the front end surface of the taperedsleeve 41. Further, the rear end of the holdingarm 434 is disposed at a position separated from the base 143 toward the front side.

According to this configuration, thecage 43 is engaged with themain shaft 3 by theballs 36 in the radial direction and the circumferential direction of themain shaft 3, and is rotatable integrally with themain shaft 3. Theballs 36 are able to roll in theannular recess 414 of the taperedsleeve 41, and thecage 43 is able to rotate about the drive shaft a1 with respect to the taperedsleeve 41 together with thespindle 3. On the other hand, thespindle 3 is movable in the forward and backward directions with respect to theretainer 43 within a range in which theballs 36 can roll in thegrooves 321.

As shown in fig. 5 to 7, theroller 45 corresponding to the planetary member is a cylindrical member. In the present embodiment, eachroller 45 has a constant diameter and is held between the adjacent holdingarms 434 so as to be rotatable about a rotation axis substantially parallel to the taperedsurface 411. The length of theroller 45 is set to be longer than the holdingarm 434. As shown in fig. 8, in a state of being held by the holdingarm 434, a part of the outer peripheral surface of theroller 45 slightly protrudes in the radial direction of theholder 43 than the inner surface and the outer surface of the holdingarm 434.

Next, thegear sleeve 47 will be explained. As shown in fig. 5 to 7, thegear sleeve 47 corresponding to the ring member is configured as a substantially cup-shaped member having an inner diameter larger than the outer diameters of the taperedsleeve 41 and theretainer 43.

Thegear sleeve 47 has: abottom wall 471 having a through hole; and aperipheral wall 474 having a cylindrical shape and connected to thebottom wall 471. Theouter race 481 of the bearing (more specifically, ball bearing) 48 is fixed to a portion of the inner peripheral surface of theperipheral wall 474 near thebottom wall 471. Thegear sleeve 47 is disposed in a front direction (so as to open rearward) with thebottom wall 471 positioned at the front side. Thegear sleeve 47 is supported by thespindle 3 at a position forward of theholder 43 so as to be rotatable with respect to thespindle 3 and movable in the front-rear direction. More specifically, therear shaft 32 of thespindle 3 is inserted through the through hole of thebottom wall 471 in a clearance fit manner, and is inserted through theinner ring 483 of thebearing 48 so as to be slidable in the front-rear direction. Accordingly, a cylindrical inner space is formed between themain shaft 3 and theperipheral wall 474 on the rear side of thebearing 48. In the internal space, a part of thetaper sleeve 41, theretainer 43, and theroller 45, and an urgingspring 49 described later are disposed. Further,gear teeth 470 that constantly mesh with thepinion gear 24 are integrally formed on the outer periphery of the gear sleeve 47 (specifically, the peripheral wall 474). Therefore, thegear sleeve 47 is rotationally driven in accordance with the rotation of themotor shaft 23.

An inner peripheral surface of a portion (a portion on the opening end side) of theperipheral wall 474 of thegear sleeve 47 on the rear side of thebearing 48 includes atapered surface 475, and thetapered surface 475 is inclined at the same angle as thetapered surface 411 of the tapered sleeve 41 (i.e., is parallel to the tapered surface 411) with respect to the drive shaft a 1. That is, thetapered surface 475 is formed as a conical surface that is inclined in a direction away from the drive shaft a1 as it approaches the rear (the open end of the gear sleeve 47). Theroller 45 held by theholder 43 is held so that at least a part (specifically, a front part) thereof is positioned between thetapered surface 411 and thetapered surface 475 in the radial direction of the spindle 3 (a direction orthogonal to the drive shaft a 1).

In the present embodiment, thepower transmission mechanism 4 includes the biasingspring 49, and the biasingspring 49 is interposed between thegear sleeve 47, theholder 43, and theroller 45 in the front-rear direction. In the present embodiment, the biasingspring 49 is configured as a conical coil spring, and is disposed such that the end portion on the large diameter side is the rear side and the end portion on the small diameter side is the front side. More specifically, the end on the large diameter side abuts against thelarge diameter spacer 491, and the end on the small diameter side abuts against thesmall diameter spacer 493. Thespacer 491 is disposed so as to abut against the front end face of the holdingarm 434 of theholder 43. Thewasher 493 is disposed so as to abut against theinner ring 483 but not against theouter ring 481 of thebearing 48 mounted in thegear sleeve 47. That is, the biasingspring 49 is rotatable together with theholder 43, but is not rotated in association with the rotation of thegear sleeve 47.

The biasingspring 49 always biases theholder 43 and thegear sleeve 47 in the direction away from each other, that is, rearward and forward, through thespacers 491 and 493. Accordingly, theretainer 43 is held by the biasing force of the biasingspring 49 at a position where the rear surface of thebottom wall 431 abuts against the front end surface of the taperedsleeve 41, and is restricted from moving in the front-rear direction thereof. Theroller 45 is held between thespacer 491 and the front end face of the base 143 fixed to themain body case 11, and is restricted from moving in the front-rear direction. Here, the term "restricting movement" does not mean that movement is completely prohibited, and slight movement may be permitted. In the present embodiment, the distance between thepad 491 and the front end face of thebase 143 is set to be slightly longer than the roller 45 (i.e., a play is provided), and the movement of theroller 45 is allowed by the play. The biasingspring 49 may directly contact theholder 43 and theinner ring 483 without interposing thespacers 491, 493 therebetween.

Further, thegear sleeve 47 is biased forward by the biasing force of the biasingspring 49, whereby thespindle 3 is also biased forward by a thrust bearing (thrust bearing)53, aguide sleeve 500, andballs 508, which will be described later, and is held at an initial position where theflange 34 abuts against thestopper portion 135.

When thespindle 3 is disposed at the initial position, as shown in fig. 5 and 8, therollers 45 are disposed between thetapered surface 411 of the taperedsleeve 41 and thetapered surface 475 of thegear sleeve 47 in a clearance fit manner (more specifically, are separated from the tapered surface 475), and are in a non-frictional contact state with the taperedsleeve 41 and thegear sleeve 47. That is, thepower transmission mechanism 4 is in the disengaged state. On the other hand, when thegear sleeve 47 moves backward (approaches thetaper sleeve 41, theholder 43, and the rollers 45) with respect to themain body housing 11 as shown in fig. 9 and the interval between thetaper surface 411 of thetaper sleeve 41 and thetaper surface 475 of thegear sleeve 47 becomes narrow, therollers 45 are sandwiched between thetaper surface 411 and thetaper surface 475 and brought into a frictional contact state with thetaper sleeve 41 and thegear sleeve 47 as shown in fig. 10. Accordingly, thepower transmission mechanism 4 shifts to the transmittable state. The operation of thepower transmission mechanism 4 will be described later.

Next, theposition switching mechanism 5 will be explained. Theposition switching mechanism 5 is a mechanism that relatively moves thegear sleeve 47 and the tip end portion of themain shaft 3 in a direction away from each other in the front-rear direction when thegear sleeve 47 is rotationally driven in the reverse direction (screw loosening direction). According to this configuration, when thegear sleeve 47 is rotationally driven in the reverse direction (screw loosening direction) in a state where themain shaft 3 is disposed at the initial position, theposition switching mechanism 5 moves thegear sleeve 47 rearward with respect to themain shaft 3, and approaches theretainer 43 and theroller 45. Next, theposition switching mechanism 5 will be described in detail.

As shown in fig. 5 to 7, in the present embodiment, theposition switching mechanism 5 includes a one-way clutch 50, aguide sleeve 500 having a guide groove (lead groove)507, andballs 508.

In the present embodiment, the one-way clutch 50 includes acam groove 501 andballs 502 formed at the front end portion of thegear sleeve 47. The one-way clutch 50 is configured to rotate theguide sleeve 500 integrally with thegear sleeve 47 only when thegear sleeve 47 is rotationally driven in the reverse direction.

As shown in fig. 7 and 11, thecam groove 501 is a groove recessed inward in the radial direction of thegear sleeve 47 from the outer peripheral surface of theperipheral wall 474 of the front end portion of thegear sleeve 47. The depth of thecam groove 501 in the radial direction from the outer peripheral surface is smaller from the upstream side to the downstream side in the forward direction (screw tightening direction) of thegear sleeve 47 indicated by an arrow a in the figure (larger from the upstream side to the downstream side in the reverse direction (screw loosening direction) of thegear sleeve 47 indicated by an arrow B in the figure). In the present embodiment, 4cam grooves 501 are provided at equal intervals in the circumferential direction around the drive shaft a 1. Asteel ball 502 is disposed in eachcam groove 501. As shown in fig. 11, the diameter of theball 502 is set to be slightly larger than the depth of the deepest portion (i.e., the upstream side end portion in the positive direction) in thecam groove 501.

As shown in fig. 5 to 7, theguide sleeve 500 is formed into a substantially cup-shaped member, and includes: abottom wall 505 having a through hole; and aperipheral wall 504 having a cylindrical shape and protruding from an outer edge of thebottom wall 505. Theguide sleeve 500 is disposed between thegear sleeve 47 and theflange 34 of thespindle 3 in a state where thebottom wall 505 is disposed on the front side and therear shaft 32 of thespindle 3 is inserted into the through hole of thebottom wall 505 in a clearance fit manner. A thrust bearing (more specifically, a thrust ball bearing)53 is disposed between the rear surface of thebottom wall 505 and the front end surface of thebottom wall 471 of thegear sleeve 47. Thethrust bearing 53 receives a thrust load while allowing theguide sleeve 500 to rotate relative to thegear sleeve 47. Further, annular concave portions having a U-shaped cross section are formed on the rear surface of thebottom wall 505 and the front end surface of thebottom wall 471, respectively. Balls as rolling elements of thethrust bearing 53 can roll in a circular orbit defined by the concave portions.

The inner diameter of theperipheral wall 504 is set to be slightly larger than the outer diameter of the distal end portion of thegear sleeve 47 in which thecam groove 501 is formed, and theperipheral wall 504 is arranged so as to surround the outer peripheral surface of the distal end portion of thegear sleeve 47. As shown in fig. 11, the radial distance between the wall surface of thecam groove 501 and the inner peripheral surface of theperipheral wall 504 is set to be slightly larger than the diameter of theball 502 at the deepest portion of thecam groove 501.

With this configuration, the one-way clutch 50 rotates theguide sleeve 500 integrally with thegear sleeve 47 only when thegear sleeve 47 is rotationally driven in the reverse direction. Specifically, as shown in fig. 11, when thegear sleeve 47 is rotationally driven in the forward direction (the direction of arrow a in the figure), theballs 502 move relatively to the deepest portion (the upstream end portion in the forward direction (the direction of arrow a)) of thecam groove 501. Theballs 502 are disposed between the wall surface of thecam groove 501 and the inner peripheral surface of theperipheral wall 504 in a clearance fit manner, and rotate together with thegear sleeve 47 about the drive shaft a 1. That is, the one-way clutch 50 is in the disengaged state, and the rotational force of thegear sleeve 47 is not transmitted to theguide sleeve 500.

On the other hand, as shown in fig. 12, when thegear sleeve 47 is rotationally driven in the reverse direction (the direction of arrow B in the figure), theballs 502 move relatively from the deepest portion of thecam groove 501 to a shallower portion (the upstream side in the reverse direction (the direction of arrow B)). Accordingly, theballs 502 are sandwiched between the wall surface of thecam groove 501 and the inner peripheral surface of theperipheral wall 504, and thegear sleeve 47 and theguide sleeve 500 are integrated by theballs 502 due to a frictional force generated by the wedging action. That is, the one-way clutch 50 shifts to the transmittable state, and theguide sleeve 500 rotates in the reverse direction together with thegear sleeve 47.

Theguide grooves 507 and theballs 508 are configured to move theguide sleeve 500 relative to themain shaft 3 in the front-rear direction as theguide sleeve 500 rotates about the drive shaft a1, and to move thegear sleeve 47 relative to theholder 43 and therollers 45 in the front-rear direction as well. As shown in fig. 5 to 7, in the present embodiment, theguide groove 507 is formed as a spiral groove (strictly speaking, a groove having a shape corresponding to a part of a spiral) formed in the distal end surface of thebottom wall 505 of theguide sleeve 500. Theguide grooves 507 are provided at 3 equally spaced intervals in the circumferential direction apart from each other. More specifically, the depth of theguide groove 507 in the front-rear direction from the front end surface is smaller from the upstream side to the downstream side in the forward direction (screw tightening direction) of thegear sleeve 47 indicated by an arrow a in fig. 7 (larger from the upstream side to the downstream side in the reverse direction (screw loosening direction) of thegear sleeve 47 indicated by an arrow B in fig. 7). Asteel ball 508 is disposed in eachguide groove 507.

As described above, thegear sleeve 47 is always biased forward by the biasingspring 49 disposed between theholder 43 and the gear sleeve 47 (more specifically, the bearing 48). Therefore, as shown in fig. 5 and 6, thethrust bearing 53, theguide sleeve 500, and theballs 508 are also biased forward, and theballs 508 abut against the rear surface of theflange 34. Thespindle 3 is also biased forward by theflange 34 and normally held at the initial position.

With this configuration, the relative positional relationship between thespindle 3 and theguide sleeve 500 in the front-rear direction changes according to the position of theball 508 in theguide groove 507. More specifically, as shown in fig. 4, when theballs 508 are disposed at the deepest portion (i.e., the upstream end portion in the positive direction) of theguide grooves 507, the distance between theflange 34 and theguide sleeve 500 in the front-rear direction is smallest. That is, theguide sleeve 500 is disposed at the forefront position within the movable range with respect to thespindle 3. In a state where thespindle 3 is disposed at the initial position, thegear sleeve 47 is disposed at the farthest position from theretainer 43 and therollers 45 in the front-rear direction.

On the other hand, when the one-way clutch 50 is operated as described above and theguide sleeve 500 rotates in the reverse direction together with thegear sleeve 47, theballs 508 move relatively from the deepest portion of theguide groove 507 to the shallowest portion (upstream side in the reverse direction). Theballs 508 abut on the rear surface of theflange 34, and therefore, as shown in fig. 13, theguide sleeve 500 moves in a direction away from the flange 34 (rearward with respect to the main shaft 3) against the biasing force in response to the relative movement of theballs 508. Accordingly, theguide bush 500 moves thegear bush 47 rearward with respect to thespindle 3, i.e., in a direction approaching theretainer 43 and theroller 45 against the biasing force of the biasingspring 49. When theballs 508 are arranged at the shallowest portion, the distance between theflange 34 and theguide sleeve 500 in the front-rear direction is the largest. In the state where thespindle 3 is disposed at the initial position, thegear sleeve 47 is disposed at a position closer to the intermediate position between theretainer 43 and theroller 45 than the case where it is disposed at the farthest position. That is, the relative positions of thegear sleeve 47, theholder 43, and theroller 45 are switched from the farthest position to the intermediate position.

Next, the operations of thepower transmission mechanism 4 and theposition switching mechanism 5 that are associated with the driving of themotor 2 and the movement of themain shaft 3 will be described.

First, in an initial state where themotor 2 is not driven and no external force is applied to thespindle 3 in the rearward direction, thespindle 3 is disposed at the initial position by the biasing force of the biasingspring 49. As described above, at this time, as shown in fig. 5 and 8, therollers 45 are in a non-frictional contact state with thetaper sleeve 41 and thegear sleeve 47. That is, thepower transmission mechanism 4 is in the disengaged state.

When the switchinglever 175 sets the forward direction (screw tightening direction) as the rotation direction of themotor shaft 23, theelectric driver 1 operates as follows to perform the screw tightening operation.

When themain switch 174 is turned on by the user pulling theoperation trigger 173 in a state where thespindle 3 is disposed at the home position, thecontroller 178 starts driving themotor 2. As indicated by an arrow a in fig. 11, thegear sleeve 47 is rotationally driven in the forward direction (screw fastening direction). At this time, since the one-way clutch 50 is not operated as described above, the rotational force of thegear sleeve 47 is not transmitted to theguide sleeve 500. Thus, thegear sleeve 47, theretainer 43, theroller 45 are held in the most distant position. Further, since thepower transmission mechanism 4 is in the disengaged state, the rotational force of thegear sleeve 47 is not transmitted to thespindle 3, and thegear sleeve 47 idles in the forward direction.

As shown in fig. 12, in a state where theball 502 is held between the wall surface of thecam groove 501 and the inner peripheral surface of the peripheral wall 504 (that is, in a state where thegear sleeve 47, theholder 43, and theroller 45 are arranged at intermediate positions), a screw loosening operation described later may be ended. In this case, in response to thegear sleeve 47 rotating in the forward direction, theball 502 is released from being pinched, and theguide sleeve 500 returns to the forefront position by the biasing force of the biasingspring 49 and the action of theguide groove 507 and theball 508. Accordingly, thegear sleeve 47, theholder 43, and theroller 45 return from the intermediate position to the farthest position.

In the idle state of thegear sleeve 47, when the user moves theelectric screwdriver 1 forward (one side of the workpiece 900) and presses thescrew 90 engaged with thescrewdriver bit 9 against theworkpiece 900, thespindle 3 is pushed backward with respect to themain body housing 11 against the biasing force of the biasingspring 49. When pressed by theflange 34, theballs 508, theguide sleeve 500, thethrust bearing 53, and thegear sleeve 47 also move rearward relative to themain body housing 11 integrally with themain shaft 3. On the other hand, thetaper sleeve 41 is fixed to themain body housing 11, and theretainer 43 and theroller 45 are held in a state where movement in the front-rear direction with respect to themain body housing 11 is restricted. Therefore, thegear sleeve 47 approaches thetaper sleeve 41, theholder 43, and theroller 45 as it moves rearward, and the distance between thetaper surface 411 of thetaper sleeve 41 and thetaper surface 475 of thegear sleeve 47 in the radial direction gradually decreases.

Accordingly, as shown in fig. 9 and 10, theroller 45 held by theholder 43 is sandwiched between thetapered surface 411 and thetapered surface 475 to be in a frictional contact state (frictional force due to wedge action is generated at a contact portion between theroller 45 and thetapered surfaces 411 and 475). That is, thegear sleeve 47, theholder 43, and therollers 45 are arranged at positions where the rotational force can be transmitted from thegear sleeve 47 to theholder 43 via therollers 45. Theroller 45 revolves while rotating on thetapered surface 411 of the taperedsleeve 41 by the rotation of thegear sleeve 47, and rotates theretainer 43 about the drive shaft a 1. Theretainer 43 is integrated with thespindle 3 in the circumferential direction around the drive shaft a1, and therefore, thespindle 3 also rotates together with theretainer 43. In this way, in response to thespindle 3 moving rearward from the initial position, thepower transmission mechanism 4 shifts from the cut-off state to the transmission-enabled state, and starts screwing thescrew 90 into theworkpiece 900. Thespindle 3 rotates in the same direction as thegear sleeve 47 at a speed slower than the rotational speed of thegear sleeve 47.

When thescrew 90 is screwed into theworkpiece 900 and the distal end portion of thepositioner 15 abuts against theworkpiece 900 as shown in fig. 14, the portion receiving the pressing force is shifted from thespindle 3 to thepositioner 15, and thus the pressing force on thespindle 3 gradually decreases. Therefore, the force (corresponding to the sum of the pressing force of thespindle 3 and the force of biasing thespindle 3 forward by the biasing spring 49) of holding therollers 45 between thetapered surface 411 of the taperedsleeve 41 and thetapered surface 475 of thegear sleeve 47, and the rotational force transmitted from thegear sleeve 47 to thespindle 3 also gradually decreases. When the rotational force transmitted from thegear sleeve 47 to thespindle 3 is lower than the rotational force required to tighten thescrew 90, the rotation of thescrew 90 is stopped, and the screw tightening operation is completed.

On the other hand, when the reverse direction (screwing direction) is set as the rotation direction of themotor shaft 23 by the switchinglever 175, theelectric screwdriver 1 operates as follows to perform the screwing operation.

When themain switch 174 is turned on by the user pulling theoperation trigger 173 with thespindle 3 disposed at the initial position, thecontroller 178 starts driving themotor 2. As shown by an arrow B in fig. 12, thegear sleeve 47 is rotationally driven in the reverse direction (screw loosening direction). Accordingly, as described above, the one-way clutch 50 operates to rotate theguide sleeve 500 in the reverse direction. As shown in fig. 13, thegear sleeve 47 moves rearward with respect to themain shaft 3, i.e., in a direction approaching theretainer 43 and theroller 45, against the biasing force of the biasingspring 49 by the action of theguide groove 507 and theball 508. That is, during the screw loosening operation, regardless of the presence or absence of the backward movement of the spindle 3 (in a state where thespindle 3 is disposed at the initial position), the relative positions of thegear sleeve 47, theholder 43, and theroller 45 are switched from the farthest apart position to the intermediate position in response to thegear sleeve 47 being rotationally driven in the reverse direction.

As shown in fig. 13, even when thegear sleeve 47, theholder 43, and therollers 45 are disposed at the intermediate positions, therollers 45 are separated from the taperedsurface 475 and are in a non-frictional contact state with the taperedsleeve 41 and thegear sleeve 47, as in the case where therollers 45 are disposed at the farthest positions. Therefore, the rotational force of thegear sleeve 47 is not transmitted to thespindle 3. That is, thepower transmission mechanism 4 is in the disengaged state, and thegear sleeve 47 idles in the reverse direction.

When the user moves theelectric screwdriver 1 forward in the idling state of thegear sleeve 47 to press thedriver bit 9 against thescrew 90 fastened to theworkpiece 900 and engage thescrew 90 with the screw, thespindle 3 is pushed rearward with respect to themain body housing 11 against the biasing force of the biasingspring 49. Thegear sleeve 47 is close to thetaper sleeve 41, theholder 43, and theroller 45, and thegear sleeve 47, theholder 43, and theroller 45 are arranged at the transfer position. Theroller 45 is sandwiched between thetapered surface 411 and thetapered surface 475 to be in a frictional contact state, thepower transmission mechanism 4 is switched from the cut state to the transmission-enabled state, and thescrew 90 is loosened and removed from theworkpiece 900.

As described above, when the screw loosening operation is performed, thegear sleeve 47 is moved rearward relative to themain shaft 3 by theposition switching mechanism 5 than when the screw tightening operation is performed, and the distance between thegear sleeve 47 and theretainer 43 and theroller 45 in the front-rear direction is reduced. Therefore, the movement distance of themain shaft 3 in the front-rear direction until thegear sleeve 47, theholder 43, and theroller 45 are relatively moved from the intermediate position to the transmission position (in other words, the movement amount or the press-in amount of themain shaft 3 until thepower transmission mechanism 4 is transferred from the cut-off state to the transmittable state during the screw loosening operation) is smaller than the movement distance until thegear sleeve 47, theholder 43, and theroller 45 are relatively moved from the farthest position to the transmission position (the movement amount or the press-in amount of themain shaft 3 until thepower transmission mechanism 4 is transferred from the cut-off state to the transmittable state during the screw tightening operation). In the present embodiment, the moving distance during the screw loosening operation is set to be shorter than the moving distance of thespindle 3 during the screw tightening operation by about 1 mm. Accordingly, the user can unscrew thescrew 90 screwed into theworkpiece 900 without removing theretainer 15 from thefront housing 13.

In the above description, the operation in the case where themain shaft 3 is pushed backward after themotor 2 is started to be driven has been described, but the operation in the case where themotor 2 is started to be driven before themain shaft 3 is pushed backward and thepower transmission mechanism 4 shifts to the transmission-enabled state is basically the same. In addition, in the case of the screw loosening operation, depending on the position of themain shaft 3, thegear sleeve 47 may be moved rearward by theposition switching mechanism 5 in response to the start of driving of themotor 2, and thepower transmission mechanism 4 may be shifted to the transmission state. When themain shaft 3 is pushed backward and thepower transmission mechanism 4 is shifted to a transmission-enabled state and then themotor 2 is started to be driven, the rotation driving of themain shaft 3 is started in response to the start of the driving of themotor 2.

As described above, in thepower transmission mechanism 4 of theelectric screwdriver 1 according to the present embodiment, the rotational force is transmitted from thegear sleeve 47 to theholder 43 through therollers 45 in both the case where thegear sleeve 47 is rotationally driven in the forward direction in response to the screw tightening operation and the case where thegear sleeve 47 is rotationally driven in the reverse direction in response to the screw loosening operation. That is, the transmission of the power is performed through the same path during the screw tightening operation and the screw loosening operation. When thegear sleeve 47 is rotated in the reverse direction in a state where themain shaft 3 is located at the initial position in response to the screw loosening operation, theposition switching mechanism 5 moves thegear sleeve 47 in a direction (rearward) toward thecage 43 and theroller 45. That is, even if thespindle 3 is not pushed backward during the screw loosening operation, the distance between thegear sleeve 47 and theretainer 43 and the distance between thegear sleeve 47 and theroller 45 in the front-rear direction are shortened in response to thegear sleeve 47 being rotationally driven in the reverse direction. Accordingly, the amount of movement (the amount of press-fitting) of thespindle 3 to move backward, which is required to shift thepower transmission mechanism 4 to the transmittable state, can be set smaller than that in the screw fastening operation. As described above, according to the present embodiment, thepower transmission mechanism 4 can transmit power through the same path during the screw tightening operation and the screw loosening operation, and can perform the screw loosening operation with a smaller pressing amount than during the screw tightening operation.

In the present embodiment, theposition switching mechanism 5 is configured to convert the rotational motion around the drive shaft a1 into a linear motion in the front-rear direction in response to thegear sleeve 47 being rotationally driven in the reverse direction, and thereby move thegear sleeve 47 rearward with respect to themain shaft 3. That is, theposition switching mechanism 5 is configured as a motion conversion mechanism. In particular, in the present embodiment, thegear sleeve 47 is configured to move rearward with respect to themain shaft 3 by moving theguide sleeve 500 by the action of thespiral guide groove 507 formed in theguide sleeve 500 and theballs 508 rolling in theguide groove 507. Accordingly, theposition switching mechanism 5 can be operated smoothly.

In the present embodiment, only when thegear sleeve 47 is rotationally driven in the reverse direction, the one-way clutch 50 rotates theguide sleeve 500 around the drive shaft a1 integrally with thegear sleeve 47, and theposition switching mechanism 5 moves theguide sleeve 500 rearward with respect to themain shaft 3, thereby moving thegear sleeve 47 rearward. In this way, the following reasonable configuration is realized in the present embodiment: theguide sleeve 500 is rapidly rotated in response to thegear sleeve 47 being rotationally driven in the reverse direction, thereby moving thegear sleeve 47.

In the present embodiment, thepower transmission mechanism 4 is configured as a friction type clutch mechanism (specifically, a planetary roller type friction clutch mechanism). Therefore, compared to the case of using the clutch mechanism of the mesh engagement type, it is possible to reduce abnormal noise when thegear sleeve 47 engages with the roller 45 (at the time of frictional contact), and wear of theroller 45 or thetapered surfaces 411 and 475. Further, since thepower transmission mechanism 4 is configured as a planetary reduction mechanism, two functions of power transmission, power transmission interruption, and speed reduction can be realized by a single structure. In addition, thegear sleeve 47 hasgear teeth 470 that mesh with thepinion gear 24 provided on themotor shaft 23. This realizes a reasonable structure that can efficiently transmit the power from themotor 2 to thepower transmission mechanism 4.

[ 2 nd embodiment ]

Next, anelectric driver 100 according toembodiment 2 will be described with reference to fig. 15 to 19. Theelectric screwdriver 100 of the present embodiment includes apower transmission mechanism 6 and aposition switching mechanism 7 that are different from thepower transmission mechanism 4 and the position switching mechanism 5 (see fig. 5 to 7) ofembodiment 1, but the other configurations are substantially the same as those of theelectric screwdriver 1. Therefore, the same reference numerals are given to the same components as those ofembodiment 1 to omit or simplify the description, and different components will be mainly described below.

As shown in fig. 15 to 17, thepower transmission mechanism 6 of the present embodiment is mainly configured by a planetary mechanism including ataper sleeve 41, aretainer 43, a plurality ofrollers 45, and agear sleeve 67, which are coaxially arranged. The structure of thepower transmission mechanism 6 other than thegear sleeve 67 is substantially the same as that of thepower transmission mechanism 4 ofembodiment 1.

Thegear sleeve 67 of the present embodiment is configured as a substantially cup-shaped member having an inner diameter larger than the outer diameters of the taperedsleeve 41 and theretainer 43, and has the same configuration as thegear sleeve 47 ofembodiment 1 except for the configuration of the distal end portion of thegear sleeve 67. More specifically, thegear sleeve 67 includes: abottom wall 671 having a through hole; and aperipheral wall 674 which is cylindrical and connected to thebottom wall 671. Thegear sleeve 67 is supported by thespindle 3 at a position forward of theholder 43 so as to be rotatable with respect to thespindle 3 and movable in the forward and backward directions. In the inner space of thegear sleeve 67, the biasingspring 49 and the taperedsleeve 41, theretainer 43, and a part of theroller 45 are arranged. Further,gear teeth 670 that constantly mesh with thepinion gear 24 are integrally formed on the outer periphery of the gear sleeve 67 (specifically, the peripheral wall 674). Like theperipheral wall 474 of theembodiment 1, the inner peripheral surface of theperipheral wall 674 includes atapered surface 675, and thetapered surface 675 is inclined with respect to the drive shaft a1 at the same angle as thetapered surface 411 of the tapered sleeve 41 (i.e., parallel to the tapered surface 411).

Thegear sleeve 67 of the present embodiment has aguide groove 707 formed in a front end portion (specifically, a front end surface of the bottom wall 671), unlike thegear sleeve 47 ofembodiment 1. Theguide groove 707 has the same structure as theguide groove 507 of theguide sleeve 500 ofembodiment 1. That is, theguide groove 707 is formed as a spiral groove (strictly speaking, a groove having a shape corresponding to a part of a spiral). Theguide grooves 707 are provided with 3 strips away from each other and equally spaced in the circumferential direction. The depth of theguide groove 707 in the front-rear direction from the front end surface decreases from the upstream side to the downstream side in the forward direction (screw tightening direction) of thegear sleeve 67 indicated by an arrow a in fig. 17 (increases from the upstream side to the downstream side in the reverse direction (screw loosening direction) of thegear sleeve 67 indicated by an arrow B in fig. 17).

Theposition switching mechanism 7 of the present embodiment is configured to relatively move thegear sleeve 67 and the tip end portion of themain shaft 3 in the forward and backward direction in a direction away from each other when thegear sleeve 67 is rotationally driven in the reverse direction (screw loosening direction) as in theposition switching mechanism 5 ofembodiment 1. According to this configuration, when thegear sleeve 67 is rotationally driven in the reverse direction (screw loosening direction) in a state where themain shaft 3 is disposed at the initial position, theposition switching mechanism 7 moves thegear sleeve 67 rearward with respect to themain shaft 3, and approaches theretainer 43 and theroller 45.

As shown in fig. 15 to 17, in the present embodiment, theposition switching mechanism 7 is mainly configured by the one-way clutch 70, a flange sleeve (flange sleeve)700, aguide groove 707 formed in thegear sleeve 67, andballs 708.

In the present embodiment, a known general-purpose one-way clutch is used as the one-way clutch 70. The one-way clutch 70 is formed in a cylindrical shape and is externally attached to therear shaft 32 on the rear side of theflange 34 of themain shaft 3. The one-way clutch 70 is configured to be rotatable in the forward direction and not rotatable in the reverse direction with respect to themain shaft 3. Theflange sleeve 700 includes a cylindricalperipheral wall 701 and aflange 703 projecting radially outward from a distal end of theperipheral wall 701. An annular recess against which theballs 708 abut is formed in an outer edge portion of the rear surface of theflange 703. Theperipheral wall 701 is fixed to the outer periphery of the one-way clutch 70. In the front-rear direction, a thrust bearing (specifically, a thrust ball bearing)53 is disposed between the rear surface of theflange 34 of themain shaft 3 and the front surface of theflange 703 of theflange sleeve 700. Thethrust bearing 53 receives a thrust load while allowing theflange sleeve 700 to rotate with respect to themain shaft 3. Further, annular recesses having a U-shaped cross section are formed in the rear surface of theflange 34 and the front surface of theflange 703, respectively. Balls as rolling elements of thethrust bearing 53 can roll in a circular orbit defined by the concave portions.

Theguide groove 707 and theballs 708 are configured to move thegear sleeve 67 relative to themain shaft 3 in the forward and backward direction as thegear sleeve 67 rotates about the drive shaft a1 with respect to theflange sleeve 700, and thereby move thegear sleeve 67 relative to thecage 43 and therollers 45 in the forward and backward direction. As described above, in the present embodiment, theguide groove 707 is formed in the front end surface of thebottom wall 671 of thegear sleeve 67. Asteel ball 708 is disposed in eachguide groove 707.

As described above, thegear sleeve 67 is always biased forward by the biasingspring 49 disposed between theholder 43 and the gear sleeve 67 (more specifically, the bearing 48). Therefore, as shown in fig. 15 and 16, themain shaft 3 is also biased forward by theballs 708, theflange sleeve 700, and thethrust bearing 53, and is normally held at the initial position.

According to this structure, the relative positional relationship between themain shaft 3 and theflange sleeve 700 and thegear sleeve 67 in the front-rear direction changes in accordance with the position of theballs 708 in theguide grooves 707. More specifically, as shown in fig. 15 and 16, when theballs 708 are disposed at the deepest portion (i.e., the upstream end portion in the positive direction) of theguide groove 707, the distance between theflange 703 and thegear sleeve 67 in the front-rear direction is smallest. That is, thegear sleeve 67 is disposed at the foremost position within the movable range with respect to thespindle 3. In the state where thespindle 3 is arranged at the initial position, thegear sleeve 67 is arranged at the farthest position from theretainer 43 and therollers 45 in the front-rear direction.

At this time, theballs 708 disposed in theguide grooves 707 are pressed by the biasing force of the biasing springs 49 and engaged with annular recesses formed in the outer edge portion of the rear surface of theflange 703. As described above, the one-way clutch 70 and theflange sleeve 700 can rotate in the forward direction with respect to themain shaft 3. Therefore, when thegear sleeve 67 is rotationally driven in the forward direction, theflange sleeve 700 rotates in the forward direction together with thegear sleeve 67 due to the frictional force between theflange 703 and theballs 708 held in the deepest portion of theguide groove 707. That is, when thegear sleeve 67 is rotationally driven in the forward direction, the one-way clutch 70 allows theflange sleeve 700 to rotate integrally with thegear sleeve 67.

On the other hand, as described above, the one-way clutch 70 cannot rotate in the reverse direction with respect to themain shaft 3. Therefore, when thegear sleeve 67 is driven to rotate in the reverse direction, theflange sleeve 700 is inhibited from rotating in the reverse direction with respect to themain shaft 3 by the one-way clutch 70. Namely, theflange bushing 700 is integrated with themain shaft 3. Therefore, thegear sleeve 67 is relatively rotated in the reverse direction with respect to theflange sleeve 700. Along with this, theballs 708 move relatively from the deepest portion of theguide groove 707 to the shallowest portion (upstream side in the opposite direction). Since theballs 708 come into contact with the rear surface of theflange 703, thegear sleeve 67 moves in a direction away from the flange 703 (rearward with respect to the spindle 3), that is, in a direction approaching thecage 43 and therollers 45 against the biasing force of the biasingspring 49 while rotating in the reverse direction in response to the relative movement of theballs 708, as shown in fig. 18 and 19. When theballs 708 are arranged at the shallowest portion, the distance between theflange 703 and thegear sleeve 67 in the front-rear direction is the largest. In the state where thespindle 3 is arranged at the initial position, thegear sleeve 67 is arranged at a position closer to the intermediate position between theretainer 43 and theroller 45 than the case where it is arranged at the farthest position. That is, the relative positions of thegear sleeve 67, theholder 43, and theroller 45 are switched from the farthest position to the intermediate position.

As described above, in theelectric screwdriver 100 according to the present embodiment, when thegear sleeve 67 is rotationally driven in the reverse direction in a state where thespindle 3 is at the initial position in response to the screw loosening operation, theposition switching mechanism 7 moves thegear sleeve 67 in a direction (rearward) to approach theholder 43 and theroller 45. That is, even if thespindle 3 is not pushed backward during the screw loosening operation, the distance between thegear sleeve 67 and theretainer 43 in the front-rear direction and the distance between thegear sleeve 67 and therollers 45 in the front-rear direction are shortened in response to thegear sleeve 67 being rotationally driven in the reverse direction. Accordingly, the amount of movement (the amount of press-fitting) of thespindle 3 to move backward, which is required to shift thepower transmission mechanism 6 to the transmittable state, can be set smaller than that in the screw fastening operation.

In the present embodiment, theposition switching mechanism 7 is configured as a motion conversion mechanism that converts a rotational motion around the drive shaft a1 into a linear motion in the front-rear direction in response to thegear sleeve 67 being rotationally driven in the reverse direction, and thereby moves thegear sleeve 67 rearward relative to themain shaft 3. In particular, the following structure is adopted in the present embodiment: thegear sleeve 67 is moved rearward relative to themain shaft 3 by thespiral guide groove 707 formed in thegear sleeve 67 and theballs 708 rolling in theguide groove 707. This realizes theposition switching mechanism 7 that operates smoothly. In the present embodiment, when thegear sleeve 67 is driven to rotate in the reverse direction, the one-way clutch 70 prohibits theflange sleeve 700 from rotating relative to themain shaft 3 in the reverse direction (integrates theflange sleeve 700 with the main shaft 3), and theposition switching mechanism 7 rotates thegear sleeve 67 relative to theflange sleeve 700, thereby moving thegear sleeve 67 rearward relative to themain shaft 3. In this way, in the present embodiment, an appropriate configuration is achieved in which thegear sleeve 67 is quickly moved in the front-rear direction in response to thegear sleeve 67 being rotationally driven in the reverse direction.

[ embodiment 3]

Next, theelectric driver 110 according toembodiment 3 will be described with reference to fig. 20 to 23. Theelectric driver 110 of the present embodiment includes apower transmission mechanism 8 different from theelectric driver 100 of embodiment 2 (see fig. 15 to 17), but the configuration other than thepower transmission mechanism 8 is substantially the same as theelectric driver 100. Therefore, the same reference numerals are used to omit or simplify the description of the structure substantially the same as that of theelectric driver 100, and the description of the different structure will be mainly made below.

As shown in fig. 20 to 22, thepower transmission mechanism 8 of the present embodiment is mainly configured by a planetary mechanism including ataper sleeve 41, aholder 83, a plurality ofrollers 45, and agear sleeve 87, which are coaxially arranged. Thepower transmission mechanism 8 other than theholder 83 and thegear sleeve 87 has substantially the same configuration as the power transmission mechanism 6 (see fig. 15 to 17).

Thecage 83 of the present embodiment corresponds to a carrier member in the planetary mechanism, and is configured to rotatably hold therollers 45, as in thecage 43 of embodiment 2 (see fig. 15 to 17). Theholder 83 has the same structure as theholder 43 except for the structure of the tip end portion. More specifically, theholder 83 includes: abottom wall 831 having a substantially cylindrical shape and a through hole in a central portion thereof; aflange portion 832 having a ring shape and protruding radially outward from a front end portion of thebottom wall 831; and a plurality of holdingarms 834 projecting rearward from a rear surface of a peripheral portion of theflange portion 832. Thebottom wall 831 and the holdingarm 834 have substantially the same structure as thebottom wall 431 and the holdingarm 434 of theholder 43. According to this structure, the front ends of the holding spaces of therollers 45 formed between the circumferentially adjacent holdingarms 45 are closed by theflange portions 832. In the present embodiment, instead of omitting the spacer 491 (see fig. 15 to 17), the front surface of theflange portion 832 functions as a spring seat portion that receives a rearward biasing force of the biasingspring 49. The rear surface of theflange portion 832 abuts against the front end of theroller 45, and functions as a restricting surface for restricting the forward movement of theroller 45.

Theretainer 83 is disposed in a direction in which thebottom wall 831 is located on the front side (so that the retainingarm 834 protrudes rearward), similarly to theretainer 43. Theholder 83 is supported by thespindle 3 so as to be non-rotatable with respect to thespindle 3 and movable in the forward and backward directions in a state where a part of the holdingarm 834 overlaps thetaper sleeve 41 in the radial direction. Each of the retainingarms 834 protrudes rearward from the rear surface of the peripheral edge portion of theflange portion 832 so as to have the same inclination angle as thetapered surface 411 of the taperedsleeve 41 with respect to the drive shaft a 1.

Thegear hub 87 of the present embodiment is configured as a substantially cup-shaped member having substantially the same configuration as the gear hub 67 (see fig. 15 to 17) ofembodiment 2. More specifically, thegear sleeve 87 includes: abottom wall 871 having a substantially circular shape and a through hole in a central portion thereof; aperipheral wall 874, which is cylindrical, is connected to thebottom wall 871. Additionally, thebottom wall 871 has substantially the same result as thebottom wall 671 of thegear sleeve 67. Theperipheral wall 874 has the same basic structure as theperipheral wall 674 of thegear sleeve 67 except for having acommunication hole 878 described later. Specifically, theouter race 481 of thebearing 48 is fixed to the front end portion of theperipheral wall 874. Further,gear teeth 870 that constantly mesh with thepinion gear 24 are integrally formed on the outer periphery of the gear sleeve 87 (specifically, the peripheral wall 874).

As shown in fig. 23, the inner peripheral surface of theperipheral wall 874 includes atapered surface 875 and acylindrical surface 876 at a portion rearward of the rear end of thebearing 48. Thetapered surface 875 is a conical surface inclined with respect to the drive shaft a1 at the same angle as thetapered surface 411 of the taperedsleeve 41. Thetapered surface 875 occupies the rear half of the inner peripheral surface of theperipheral wall 874. Acylindrical surface 876 is attached to the forward end of the taperedsurface 875 and extends generally cylindrically along the drive axis a 1.

Thecommunication hole 878 is a through hole penetrating theperipheral wall 874 in the radial direction, and communicates the inside (inner space) and the outside of thegear sleeve 87. In the present embodiment, thecommunication hole 878 is provided in a region R3 corresponding to thecylindrical surface 876, which is a region different from the region R2 corresponding to the taperedsurface 875, in the region R1 (i.e., the region defining the internal space of the gear sleeve 87) between the rear end of theperipheral wall 874 and the rear end of thebearing 48. In other words, thecommunication hole 878 is arranged in a region that does not normally overlap with theroller 45 in the radial direction. In the present embodiment, the 4communication holes 878 are provided at equal intervals in the circumferential direction.

As shown in fig. 21 and 22, in the present embodiment, thegear sleeve 87 is also supported by thespindle 3 at a position forward of theholder 83 so as to be rotatable with respect to thespindle 3 and movable in the front-rear direction. Further, in the internal space of thegear sleeve 87, thetaper sleeve 41, theretainer 83, a part of theroller 45, and the biasingspring 49 are arranged.

In the present embodiment, the small-diameter side end portion (front end portion) of the biasingspring 49 abuts against thepad 493, and the large-diameter side end portion (rear end portion) abuts against the front surface of theflange portion 832 of theretainer 83, wherein thepad 493 abuts against theinner ring 483 of thebearing 48. The biasingspring 49 always biases theholder 83 and thegear sleeve 87 in directions away from each other, that is, in the rear and front directions. Accordingly, theretainer 83 is held by the biasing force of the biasingspring 49 at a position where the rear surface of thebottom wall 831 abuts on the front end surface of the taperedsleeve 41, and is restricted from moving in the front-rear direction. Theroller 45 is held between the rear surface of theflange portion 832 of theretainer 83 and the front end surface of thebase 143, and is restricted from moving in the front-rear direction. As described inembodiment 1, the term "restricting movement" herein does not mean that movement is completely prohibited, and may allow slight movement. Further, thegear sleeve 87 is biased forward by the biasing force of the biasingspring 49, so that thespindle 3 is also biased forward and held at the initial position.

The operation of thepower transmission mechanism 8 configured as described above is substantially the same as thepower transmission mechanisms 4 and 6 according toembodiments 1 and 2. Specifically, in the initial state, thespindle 3 is disposed at the initial position by the biasing force of the biasingspring 49, and therollers 45 are in a non-frictional contact state with thetapered surface 411 of the taperedsleeve 41 and thetapered surface 875 of thegear sleeve 87. That is, thepower transmission mechanism 8 is in the disengaged state. After that, as thespindle 3 is pushed rearward against the biasing force of the biasingspring 49, thegear sleeve 87 approaches thetaper sleeve 41, theholder 83, and theroller 45. Therollers 45 held by theretainer 83 are sandwiched between thetapered surface 411 and thetapered surface 875, and are in a frictional contact state. Accordingly, thepower transmission mechanism 8 can be shifted from the disengaged state to the transmittable state.

As described above, theelectric screwdrivers 1, 100, 110 according toembodiments 1 to 3 described above have the so-called planetary roller typepower transmission mechanisms 4, 6, 8, respectively. In thepower transmission mechanisms 4, 6, and 8, at least a part of theplanetary roller 45 is disposed between thetapered surface 411 of the taperedsleeve 41 as the sun member and thetapered surfaces 475, 675, and 875 of thegear sleeves 47, 67, and 87 as the ring members in the radial direction (direction orthogonal to the drive shaft a1) of themain shaft 3 with respect to the drive shaft a 1. Thegear sleeves 47, 67, 87 move in the front-rear direction integrally with themain shaft 3 with respect to thetaper sleeve 41. On the other hand, theroller 45 is restricted from moving in the front-rear direction with respect to themain body housing 11 by the biasing spring 49 (and thespacer 491 or the holder 83). Therefore, theroller 45 moves in the front-rear direction in association with the relative movement of thegear sleeves 47, 67, 87 and thetaper sleeve 41, and the possibility that the frictional contact between theroller 45 and thetaper surface 411 and the taper surfaces 475, 675, 875 becomes unstable can be reduced. Inembodiment 3, the movement of therollers 45 in the front-rear direction is restricted by theretainer 83 without using thespacers 491. Accordingly, the number of parts can be reduced, and the assembling property can be improved.

In addition, in the above-describedembodiments 1 to 3, theretainers 43, 83 as the carrier members are held by themain shaft 3 so as to be movable in the front-rear direction with respect to themain shaft 3. In other words, theretainers 43, 83 are independent of thespindle 3 with respect to the movement in the front-rear direction. Theretainers 43, 83 need to be arranged in positions that keep therollers 45 from disengaging from between thetapered surface 411 and thetapered surfaces 475, 675, 875. In contrast, in the above embodiment, theretainers 43 and 83 can be held at appropriate positions regardless of the movement of thespindle 3. Accordingly, compared to a structure in which theretainers 43 and 83 and thespindle 3 are moved integrally in the front-rear direction, the restriction on the amount of movement of thespindle 3 in the front-rear direction can be reduced. In particular, when therollers 45, thetapered surfaces 411, 475, 675, 875 wear, thespindle 3 needs to be pressed into a position where the taperedsleeve 41 and thegear sleeves 47, 67, 87 are closer to each other (i.e., more rearward) in order to establish stable frictional contact. That is, it is necessary to increase the amount of movement of themain shaft 3 in the front-rear direction, but this need can be met by thepower transmission mechanisms 4, 6, and 8 according to the above embodiments.

In the above-describedembodiments 1 to 3, theretainers 43 and 83 are held by themain shaft 3 so as to be unrotatable about the drive shaft a1, and are configured to rotate integrally with themain shaft 3 by the power transmitted via therollers 45. That is, in the above embodiment, the planetary roller typepower transmission mechanisms 4, 6, and 8 having theretainers 43 and 83 as output members are realized.

In addition, in the above-describedembodiments 1 to 3, the biasingspring 49 restricts the movement of theretainers 43 and 83 in the front-rear direction with respect to themain body housing 11 in addition to the movement of theroller 45. This makes it possible to more reliably maintain the proper positional relationship between theroller 45 and theretainers 43 and 83. In the above embodiment, the biasingspring 49 biases thespindle 3 and theretainers 43 and 83 forward and backward, respectively, so as to be spaced apart from each other. And, thespindle 3 is normally held at the most forward position (i.e., the initial position) by the urging force of the urgingspring 49. With this configuration, when the movement of theretainers 43 and 83 is restricted and the pushing of thespindle 3 is released, thespindle 3 can be returned to the initial position.

In the above-describedembodiments 1 to 3, thegear sleeves 47, 67, 87 are supported by themain shaft 3 so as to be movable in the front-rear direction integrally with themain shaft 3 and rotatable about the drive shaft a 1. The biasingspring 49 is disposed between theretainers 43, 83 and thegear sleeves 47, 67, 87 (more specifically, the biasing spring is disposed in thebearings 48 in thegear sleeves 47, 67, 87) in the front-rear direction, but the end portions on thegear sleeves 47, 67, 87 side are received byspacers 493, which do not rotate with the rotation of thegear sleeves 47, 67, 87. Therefore, the biasingspring 49 can be prevented from rotating together with thegear sleeves 47, 67, 87 (so-called co-rotation), or heat generation at the sliding portions of the biasingspring 49 and thegear sleeves 47, 67, 87 can be prevented.

In theabove embodiments 1 to 3, the biasingspring 49 biases thegear sleeves 47, 67, 87 and theretainers 43, 83 rearward and forward so as to be apart from each other. In other words, the biasingspring 49 also has a function of biasing thegear sleeves 47, 67, 87 serving as the driving-side members and theretainers 43, 83 serving as the driven-side members in thepower transmission mechanisms 4, 6, 8 in the direction of interrupting transmission. Thus, by using the biasingspring 49, it is possible to realize a plurality of functions such as restriction of movement of theretainers 43, 83 in the front-rear direction and interruption of power transmission without increasing the number of components.

In the above-describedembodiment 3, theperipheral wall 874 of thegear sleeve 87 is provided with thecommunication hole 878 for communicating the inside and the outside of thegear sleeve 87. Therefore, the air flow can be generated through thecommunication hole 878 by the centrifugal force generated by the rotation of thegear sleeve 87. This can suppress a local temperature rise and achieve smooth circulation of the lubricant (for example, grease) disposed in thefront housing 13. As a result, wear of theroller 45 and thetapered surfaces 411, 475, 675, 875 can be effectively reduced, and durability can be improved. Even when abrasion powder is generated, the abrasion powder can be efficiently discharged to the outside of thegear sleeve 87 through thecommunication hole 878 in association with the flow of air, and therefore thebearing 48 can be protected.

The above embodiments are merely examples, and the power tool according to the present invention is not limited to the configuration of the illustratedelectric screwdriver 1, 100, 110. For example, the variations exemplified below can be added. Any one or more of these modifications may be used independently or in combination with theelectric screwdriver 1, 100, or 110 described in the embodiments or the claims.

In the above-described embodiments, theelectric screwdrivers 1, 100, and 110 as the screw tightening tool are exemplified, but the present invention can be applied to other working tools configured to rotationally drive the tip tool. For example, the present invention can be applied to a punching tool (e.g., an electric drill) for performing a punching operation by rotationally driving a drill, a polishing tool (e.g., an electric sander) for performing a polishing operation by rotationally driving a polishing member (e.g., sandpaper), and the like.

In thepower transmission mechanisms 4, 6, and 8 as the friction clutch mechanisms of the planetary roller type, the configurations and arrangements of the sun member, the ring member, the carrier member, and the planetary rollers may be appropriately changed. For example, thepower transmission mechanisms 4, 6, and 8 may have a so-called planetary gear type in which a ring member is fixed or a so-called carrier type in which a carrier member is fixed, without having a so-called sun type in which a sun member is fixed to themain body case 11 so as not to be rotatable as in the above-described embodiments. In addition, although the above embodiment is a configuration example in which thegear sleeves 47, 67, 87 as the ring members are moved in the front-rear direction with respect to the taperedsleeve 41 as the sun member, any one of the sun member and the ring members may be moved integrally with themain shaft 3 as long as it has tapered surfaces parallel to each other and inclined with respect to the drive shaft a1 and is relatively movable in the front-rear direction. Further, one of the sun member and the ring member that moves integrally with themain shaft 3 may be formed integrally with themain shaft 3 as an output member.

In the above embodiment, the biasingspring 49 has a function of restricting the movement of theroller 45 as the planetary member in the front-rear direction, a function of biasing themain shaft 3 to the initial position, and a function of biasing thegear sleeve 47, 67, 87 as the driving-side member and theretainer 43, 83 as the driven-side member in thepower transmission mechanism 4, 6, 8 in the direction in which the power transmission is cut off, in addition to the function of restricting the movement of theretainer 43 as the planetary member in the front-rear direction. That is, thesingle urging spring 49 serves a plurality of functions. However, these functions may be realized by different members (for example, spring members), respectively.

When the communication holes 878 are provided, the number, arrangement position, shape, size, and the like thereof are not limited to those inembodiment 3, and may be appropriately changed. For example, at least 1communication hole 878 may be provided at any position in a region R1 (see fig. 23) from the rear end of theperipheral wall 874 to the rear end of thebearing 48. Thecommunication hole 878 may extend obliquely with respect to the radial direction, or may extend not linearly but curvedly.

The structure of themain body case 11, themotor 2, themain shaft 3, and theposition switching mechanisms 5 and 7 can be appropriately modified in addition to thepower transmission mechanisms 4, 6, and 8. For example, themotor 2 may be a dc brushless motor using a rechargeable battery as a power source. Theposition switching mechanisms 5 and 7 may be omitted.

The following shows the correspondence between each component of the above-described embodiment and modification and each component of the present invention. Theelectric screwdrivers 1, 100, and 110 are examples of the "power tool" of the present invention. Thedriver bit 9 is an example of the "tip tool" of the present invention. Themain body case 11 is an example of the "case" of the present invention. Thespindle 3 is an example of the "spindle" of the present invention. The drive shaft a1 is an example of the "drive shaft" of the present invention. Themotor 2 is an example of the "motor" of the present invention. Thepower transmission mechanisms 4, 6, and 8 are examples of the "power transmission mechanism" of the present invention. The taperedsleeve 41 is an example of the "sun member" of the present invention. Thegear sleeves 47, 67, 87 are examples of "ring members" of the present invention. Thecages 43 and 83 are an example of the "carrier member" of the present invention. Theroller 45 is an example of the "planetary roller" of the present invention. Thetapered surface 411 is an example of the "1 st tapered surface" of the present invention. The tapered surfaces 475, 675, 875 are examples of the "2 nd tapered surface" of the present invention. The biasingspring 49 is an example of the "regulating member" and the "spring member" in the present invention. Thespacer 493 is an example of a "receiving member" according to the present invention. Thecommunication hole 878 is an example of the "communication hole" of the present invention. The region R2 is an example of the "region corresponding to the 2 nd tapered surface" in the present invention. The region R3 is an example of the "region different from the region corresponding to the 2 nd tapered surface" in the present invention.

In view of the gist of the present invention and the above-described embodiments, the following structure (embodiment) is constructed. Any one or more of the following configurations can be used in combination with theelectric screw drivers 1, 100, and 110 of the embodiments and the modifications thereof, or the embodiments described in the claims.

[ means 1]

Can be as follows:

the annular member has a peripheral wall in a cylindrical shape surrounding the main shaft in a circumferential direction around the drive shaft and having an inner peripheral surface including the 2 nd taper surface,

at least a part of the carrier member is disposed in an inner space of the ring member defined by the main shaft and the inner peripheral surface,

the spring member is disposed in the internal space on a front side of the carrier member.

According to this aspect, the spring member can be disposed by effectively using the internal space of the annular member, and the power transmission mechanism can be kept compact.

[ means 2]

In themode 1, it may be:

the ring member has a stopper portion disposed on a front side of the spring member,

the spring member is interposed between the carrier member and the stopper portion in the front-rear direction.

[ means 3]

In themode 2, the following may be used:

the stopper portion is a bearing having an inner ring and an outer ring, wherein the inner ring is rotatably supported by the main shaft; the outer ring is fixed to the inner peripheral surface.

According toaspects 2 and 3, the spring member can be reasonably interposed between the carrier member and the ring member in the front-rear direction. Thebearing 48 is an example of the "stopper portion" and the "bearing" in theembodiments 1 and 2.

[ means 4]

Can be as follows: the annular member has a cylindrical peripheral wall portion centered on the drive shaft,

the communication hole is a through hole penetrating the peripheral wall portion.

[ means 5]

Can be as follows: the inner peripheral surface of the annular member includes the 2 nd taper surface and a cylindrical surface along the drive shaft,

the communication hole is provided in a region of the annular member corresponding to the cylindrical surface.

In view of the gist of the above-described embodiment, the followingembodiments 6 to 19 are constructed with the object of providing a screw fastening tool having a power transmission mechanism with a more rational structure. Any one or more of theembodiments 6 to 19 may be used independently of the claims, or may be used in combination with theelectric screwdrivers 1, 100, and 110 and the modifications thereof of the embodiments, or the claims.

[ means 6]

A screw tightening tool, characterized in that,

has a main shaft, a motor and a power transmission mechanism, wherein,

a spindle supported to be movable in a front-rear direction along a predetermined drive shaft extending in a front-rear direction of the screw tightening tool and rotatable about the drive shaft, and having a front end portion configured as a detachable tip tool;

the power transmission mechanism includes a driving member and a driven member, wherein the driving member is rotationally driven in a1 st direction or a 2 nd direction by power transmitted from the motor, the 1 st direction is a direction corresponding to a direction in which the tip tool fastens a screw, and the 2 nd direction is a direction opposite to the 1 st direction and corresponds to a direction in which the tip tool unscrews the screw; the driven member is configured to rotate around the drive shaft integrally with the main shaft by the power transmitted from the driving member rotating in the 1 st direction or the 2 nd direction,

the driving member and the driven member are arranged to be relatively movable in the front-rear direction, and are configured to move in a direction approaching each other in the front-rear direction in response to a backward movement of the main shaft, and to shift from a blocked state in which power transmission from the driving member to the driven member is disabled to a transmittable state in which power transmission from the driving member to the driven member is enabled,

the screw tightening tool includes a position switching mechanism configured to move one of the driving member and the driven member in the front-rear direction in a direction approaching the other of the driving member and the driven member when the driving member is rotationally driven in the 2 nd direction with the main shaft located at a foremost position.

In the power transmission mechanism of the screw tightening tool of this aspect, the rotational force is transmitted from the driving member to the driven member in both the case where the driving member is rotationally driven in the 1 st direction in response to the screw tightening operation and the case where the driving member is rotationally driven in the 2 nd direction in response to the screw loosening operation. That is, the transmission of the power is performed through the same path during the screw tightening operation and the screw loosening operation. When the driving member is driven to rotate in the 2 nd direction in accordance with the screw loosening operation with the main shaft located at the foremost position, the position switching mechanism moves one of the driving member and the driven member in the front-rear direction in a direction approaching the other of the driving member and the driven member. That is, even if the main shaft is not pushed backward during the unscrewing operation, the distance between the driving member and the driven member in the front-rear direction is shortened in response to the driving member being rotationally driven in the 2 nd direction. Accordingly, the amount of movement (press-in amount) of the spindle to move backward, which is required to shift the power transmission mechanism to the transmittable state, can be set smaller than that in the screw fastening operation. As described above, according to this aspect, it is possible to realize a rational power transmission mechanism that can transmit power through the same path during the screw tightening operation and the screw loosening operation and can perform the screw loosening operation with a smaller pushing amount than during the screw tightening operation.

Theelectric screwdrivers 1, 100, and 110 of the above embodiments are examples of the "screw fastening tool" of the present embodiment. Thespindle 3 is an example of the "spindle" of the present embodiment. The drive shaft a1 is an example of the "drive shaft" of the present embodiment. Themotor 2 is an example of the "motor" of the present embodiment. Thepower transmission mechanisms 4, 6, and 8 are examples of the "power transmission mechanism" of the present embodiment. Thegear sleeves 47, 67, and 87 are examples of the "driving member" of the present embodiment. Theretainers 43, 83 and therollers 45 are all an example of the "driven member" of the present embodiment, and theretainers 43, 83 and therollers 45 are also an example of the "driven member" of the present embodiment. Theposition switching mechanisms 5 and 7 are examples of the "position switching mechanism" of the present embodiment.

Note that, instead of the planetary roller type friction clutch mechanism, a mesh type clutch mechanism or another type of friction clutch mechanism may be employed as thepower transmission mechanisms 4, 6, and 8. For example, a single-plate or multi-plate type disc clutch mechanism or a cone clutch mechanism may be employed. In thepower transmission mechanisms 4, 6, and 8 as the planetary roller type friction clutch mechanisms, the configurations and arrangements of the sun member, the ring member, the carrier member, and the planetary rollers may be appropriately changed. For example, thepower transmission mechanisms 4, 6, and 8 may have a so-called planetary gear type in which a ring member is fixed or a so-called carrier type in which a carrier member is fixed, without having a so-called sun type in which a sun member is fixed to themain body case 11 so as not to be rotatable as in the above-described embodiments. In response to the change of thepower transmission mechanisms 4 and 6, a driving member (input member) driven by the power of themotor 2 and a driven member (output member) rotated integrally with themain shaft 3 by the power transmitted from the driving member can be changed. When thegear sleeve 47 is rotationally driven in the reverse direction in a state where themain shaft 3 is at the initial position, theposition switching mechanisms 5 and 7 may move either the driving member or the driven member relative to themain shaft 3, as long as one of the driving member and the driven member can be moved in a direction approaching the other in the front-rear direction.

[ means 7]

The screw tightening tool according tomode 6, characterized in that,

the position switching mechanism is configured to move the one of the driving member and the driven member by converting a rotational motion around the driving shaft into a linear motion in the front-rear direction in response to the driving member being rotationally driven in the 2 nd direction.

According to this aspect, the position switching mechanism is configured as a motion conversion mechanism. According to this aspect, one of the driving member and the driven member can be moved with a simple configuration.

[ means 8]

The screw tightening tool according tomode 7, characterized in that,

the position switching mechanism is configured to drive the one of the driving member and the driven member by an action of a guide groove extending spirally around the driving shaft and a ball; the ball is disposed in the guide groove.

According to this aspect, the position switching mechanism that can be operated smoothly by the rolling balls can be realized. Theguide grooves 507 and 707 are examples of "guide grooves" in the present embodiment, and theballs 508 and 708 are examples of "balls" in the present embodiment.

The structure for converting rotational motion into linear motion in response to the rotational motion of the driving member (thegear sleeve 47, 67, 87 of the above embodiment) in the opposite direction is not limited to theguide grooves 507, 707 and theballs 508, 708 of the above embodiment. For example, the driving member may be moved by the action of a guide surface configured as a spiral curved surface around the drive shaft a1, a screw groove, and a screw thread engaged with the screw groove. For example, inembodiment 1, a guide surface having a spiral curved shape around the drive shaft a1 may be provided on at least one of the front end surface of theguide sleeve 500 and the rear end surface of theflange 34 of themain shaft 3. The same modification can be made inembodiment 2. The number and structure of theguide grooves 507 and 707 and theballs 508 and 708 may be appropriately changed. The configuration of the one-way clutch 50 according toembodiment 1 may be appropriately modified so long as theguide sleeve 500 and thegear sleeve 47 are rotated integrally only when thegear sleeve 47 is driven to rotate in the reverse direction. Similarly, the configuration of the one-way clutch 70 according toembodiment 2 may be appropriately modified so long as theflange sleeve 700 is prohibited from rotating together with thegear sleeve 67 only when thegear sleeve 67 is rotationally driven in the reverse direction.

[ means 9]

The screw tightening tool according tomode 7 or 8, characterized in that,

the position switching mechanism includes a moving member and a one-way clutch, wherein,

the moving member is configured to move the driving member in a direction approaching the driven member in the front-rear direction by rotating about the driving shaft;

the one-way clutch is configured to rotate the moving member around the drive shaft integrally with the drive member only when the drive member is rotationally driven in the 2 nd direction.

According to this aspect, an appropriate configuration can be achieved in which the driving member is moved by rotating the moving member quickly in response to the driving member being rotationally driven in the 2 nd direction. Theguide sleeve 500 and the one-way clutch 50 are examples of the "moving member" and the "one-way clutch" in the present embodiment, respectively.

[ means 10]

The screw tightening tool according tomode 7 or 8, characterized in that,

the position switching mechanism includes a rotatable member and a one-way clutch, wherein,

the rotatable member is configured to be rotatable about the drive shaft;

the one-way clutch is configured to permit the rotatable member to rotate around the drive shaft integrally with the drive member relative to the spindle when the drive member is rotationally driven in the 1 st direction, and to prohibit the rotatable member from rotating around the drive shaft relative to the spindle when the drive member is rotationally driven in the 2 nd direction,

the position switching mechanism is configured to move the driving member, which is prevented from moving in the 2 nd direction relative to the rotatable member, which is prevented from rotating relative to the main shaft by the one-way clutch, in a direction to approach the driven member.

According to this aspect, an appropriate configuration can be achieved in which the driving member is driven to rotate in the 2 nd direction, and the driving member is quickly moved linearly in the front-rear direction. Theflange sleeve 700 and the one-way clutch 70 are examples of the "rotatable member" and the "one-way clutch" in the present embodiment, respectively.

[ means 11]

A screw tightening tool, characterized in that,

has a main shaft, a motor and a power transmission mechanism, wherein,

a spindle supported to be movable in a front-rear direction along a predetermined drive shaft extending in a front-rear direction of the screw tightening tool and rotatable about the drive shaft, and having a front end portion configured as a detachable tip tool;

the power transmission mechanism includes a driving member and a driven member, wherein the driving member is rotationally driven in a1 st direction and a 2 nd direction by power transmitted from the motor, the 1 st direction is a direction corresponding to a direction in which the tip tool fastens a screw, and the 2 nd direction is a direction opposite to the 1 st direction and corresponds to a direction in which the tip tool unscrews the screw; the driven member is configured to rotate around the drive shaft integrally with the main shaft by the power transmitted from the driving member rotating in the 1 st direction or the 2 nd direction,

the drive member and the driven member are arranged so as to be relatively movable in the front-rear direction, and are configured to move in a direction approaching each other in the front-rear direction in response to a backward movement of the main shaft, and to shift from a blocked state in which power transmission from the drive member to the driven member is disabled to a transmittable state in which power transmission from the drive member to the driven member is enabled,

the power transmission mechanism is configured such that the amount of movement when the drive member is rotationally driven in the 2 nd direction is smaller than the amount of movement when the main shaft is moved rearward from the cut-off state to the transmittable state when the drive member is rotationally driven in the 1 st direction.

In the power transmission mechanism of the screw tightening tool of this aspect, the rotational force is transmitted from the driving member to the driven member regardless of whether the driving member is rotationally driven in the 1 st direction in response to the screw tightening operation or in the 2 nd direction in response to the screw loosening operation. That is, the transmission of the power is performed through the same path during the screw tightening operation and the screw loosening operation. The power transmission mechanism is configured such that the amount of movement (the amount of pressing) of the rearward movement of the main shaft required to shift the power transmission mechanism to the transmittable state during the screw loosening operation can be made smaller than during the screw tightening operation. As described above, according to this aspect, it is possible to realize a rational power transmission mechanism that can transmit power through the same path during the screw tightening operation and the screw loosening operation, and that can perform the screw loosening operation with a smaller pushing amount than during the screw tightening operation.

[ means 12]

The screw tightening tool according to any one ofaspects 6 to 11, characterized in that,

the power transmission mechanism is configured as a friction clutch mechanism.

According to this aspect, noise and wear of the engagement portion when the driving member and the driven member are engaged can be reduced as compared with a mesh engagement type clutch mechanism.

[ means 13]

The screw tightening tool according to any one ofaspects 6 to 12, characterized in that,

the power transmission mechanism is configured as a planetary reduction mechanism.

According to this aspect, the power transmission cutoff function, and the deceleration function can be achieved by the single power transmission mechanism.

[ means 14]

The screw tightening tool according to any one ofaspects 6 to 13, characterized in that,

the driving part has a 2 nd gear tooth, and the 2 nd gear tooth is engaged with a1 st gear tooth provided on an output shaft of the motor.

According to this aspect, a reasonable structure for efficiently transmitting the power from the motor to the power transmission mechanism can be realized. Thepinion gear 24 and thegear teeth 470 are examples of "1 st gear tooth" and "2 nd gear tooth", respectively.

[ means 15]

Can be as follows:

the main shaft has a protruding portion that protrudes in a radial direction with respect to the drive shaft,

the position switching mechanism includes a moving member supported by the main shaft on a rear side of the projection and on a front side of the driving member so as to be rotatable about the drive shaft and movable in the front-rear direction,

the screw tightening tool further includes a biasing member for biasing the moving member and the spindle forward by the driving member,

the moving member rotates in response to the driving member being rotationally driven in the 2 nd direction, and moves backward with respect to the main shaft against the biasing force of the biasing member, thereby moving the driving member backward with respect to the main shaft.

According to this aspect, the position switching mechanism having a simple configuration can be realized by using the moving member and the urging member. Theflange 34 is an example of the "protruding portion" in the present embodiment. Theguide sleeve 500 is an example of the "moving member" in the present embodiment. The biasingspring 49 is an example of a "biasing member" in the present embodiment.

[ means 16]

In themode 15, the following may be used:

the position switching mechanism includes a guide groove and a ball, wherein,

the guide groove is formed on the front end surface of the moving component and extends spirally around the driving shaft;

the ball is disposed in the guide groove,

the moving member rotates in response to the rotational driving of the driving member in the 2 nd direction, and moves backward with respect to the main shaft by the guide groove and the balls.

[ means 17]

In themode 15 or 16, there may be:

the position switching mechanism includes a one-way clutch configured to rotate the moving member around the drive shaft integrally with the drive member only when the drive member is rotationally driven in the 2 nd direction.

[ means 18]

Can be as follows: the rotatable member has a protruding portion protruding in a radial direction with respect to the drive shaft and disposed on a front side of the drive member,

the screw tightening tool further includes a biasing member for biasing the rotatable member and the spindle forward by the driving member,

the driving member is configured to move rearward relative to the rotatable member against the biasing force of the biasing member while rotating in the 2 nd direction.

According to this aspect, the position switching mechanism having a simple structure can be realized by using the rotatable member and the urging member. Theflange 34 is an example of the "protruding portion" in the present embodiment. Theguide sleeve 500 is an example of the "moving member" in the present embodiment. The biasingspring 49 is an example of a "biasing member" in the present embodiment.

[ means 19]

In themode 18, the following may be used:

the position switching mechanism includes a guide groove and a ball, wherein,

the guide groove is formed on the front end surface of the driving part and extends spirally around the driving shaft,

the ball is disposed in the guide groove in a state of being in contact with a rear surface of the protruding portion,

the driving member is configured to move backward with respect to the main shaft by the guide groove and the balls while rotating in the 2 nd direction.

Description of the reference numerals

1. 100, and (2) a step of: an electric screwdriver; 10: a main body portion; 11: a main body housing; 12: a rear housing; 13: a front housing; 135: a limiting part; 14: a central housing; 141: a partition wall; 143: a base; 15: a positioner; 17: a handle portion; 171: a grip portion; 173: a trigger; 174: a master switch; 175: a switch lever; 176: a rotation direction switch; 178: a controller; 179: a power cable; 18: a handle housing; 2: a motor; 21: a rotor; 23: a motor shaft; 231: a bearing; 233: a bearing; 24: a pinion gear; 25: a fan; 3: a main shaft; 301: a bearing; 31: a front shaft; 311: a tool bit insertion hole; 32: a rear shaft; 321: a groove; 34: a flange; 36: a ball bearing; 4. 6: a power transmission mechanism; 41: a tapered sleeve; 411: a conical surface; 414: a recess; 43: a holder; 431: a bottom wall; 432: a recess; 434: a holding arm; 45: a roller; 47. 67: a gear sleeve; 470. 670: gear teeth; 471. 671: a bottom wall; 474. 674: a peripheral wall; 475. 675: a conical surface; 48: a bearing; 481: an outer ring; 483: an inner ring; 49: a force application spring; 491: a gasket; 493: a gasket; 5. 7: a position switching mechanism; 50. 70: a one-way clutch; 500: a guide sleeve; 501: a cam slot; 502: a ball bearing; 504: a peripheral wall; 505: a bottom wall; 507. 707: a guide groove; 508. 708: a ball bearing; 53: a thrust bearing; 700: a flange sleeve; 701: a peripheral wall; 703: a flange; 9: a screwdriver bit; 90: a screw; 900: a workpiece to be processed; a1: a drive shaft.

Claims (10)

1. A power tool configured to drive a tip tool to rotate,

the work tool is characterized in that the work tool is provided with a tool body,

comprises a shell, a main shaft, a motor and a power transmission mechanism, wherein,

a spindle supported by the housing so as to be movable in a front-rear direction along a predetermined drive shaft extending in a front-rear direction of the work tool and rotatable about the drive shaft, the spindle having a tip end portion to which the tip tool is detachably attached;

the motor is accommodated in the housing;

the power transmission mechanism includes a sun member, a ring member, and a carrier member disposed coaxially with the drive shaft, and a planetary roller rotatably held by the carrier member, and is housed in the housing,

the sun member and the ring member have 1 st and 2 nd tapered surfaces, respectively, that are inclined with respect to the drive shaft,

one of the sun member and the ring member is configured to be movable in the front-rear direction integrally with the main shaft relative to the other,

at least a part of the planetary roller is disposed between the 1 st tapered surface and the 2 nd tapered surface in a radial direction with respect to the drive shaft,

the power transmission mechanism is configured such that,

the sun member and the ring member are relatively moved in a direction to approach each other in response to the backward movement of the main shaft, and the planetary rollers are brought into frictional contact with the sun member and the ring member, whereby the power of the motor can be transmitted to the main shaft, and the power of the motor can be transmitted to the main shaft

The power transmission mechanism is configured such that,

the sun member and the ring member are relatively moved in a direction away from each other in response to the forward movement of the main shaft, and the planetary rollers are brought into non-frictional contact with the sun member and the ring member, thereby cutting off the transmission of the power,

the work tool has a restricting member configured to restrict movement of the planetary roller in the forward and backward directions with respect to the housing,

the carrier member is held by the main shaft so as to be movable in the front-rear direction with respect to the main shaft.

2. The work tool of claim 1,

the carrier member is held by the main shaft so as to be incapable of rotating around the drive shaft, and is configured to rotate integrally with the main shaft by the power transmitted via the planetary rollers.

3. The work tool of claim 1 or 2,

the restriction member is configured to restrict movement of the carrier member in the front-rear direction with respect to the case.

4. The work tool of claim 3,

the restricting member includes spring members that urge the main shaft and the carrier member forward and backward, respectively, so as to be apart from each other,

the spindle is normally held in a forwardmost position by the loading force of the spring member.

5. The work tool of claim 4,

the ring member is supported by the main shaft so as to be movable in the front-rear direction integrally with the main shaft and rotatable about the drive shaft,

the spring member is interposed between the carrier member and the ring member in the front-rear direction,

the power tool further includes a receiving member that receives one end of the spring member on the ring member side in a state where the receiving member does not rotate with rotation of the ring member.

6. The work tool of claim 5,

the ring member is configured to be rotated by the power of the motor,

the spring member is configured to urge the ring member and the carrier member away from each other in the front-rear direction.

7. The work tool according to any one of claims 1 to 6,

the annular member has at least 1 communication hole that communicates the inside and outside of the annular member.

8. The work tool of claim 7,

the communication hole is formed in a region of the annular member other than a region corresponding to the 2 nd tapered surface.

9. The work tool according to any one of claims 1 to 8,

the restricting member is configured to always restrict the planetary roller from moving in the front-rear direction with respect to the housing.

10. The work tool according to any one of claims 1 to 9,

the limiting member is a spring member.

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