Screw tightening tool

Abstract

To provide a technique conducible to efficiency of operation by a screw fastening tool.SOLUTION: A screw fastening tool includes: a housing; a motor; a spindle; a first clutch; and a second clutch. The first clutch is operably coupled to an output shaft and a spindle so that power transmission from the output shaft to the spindle is possible only when the output shaft rotates in a first direction. The second clutch is operably coupled to the output shaft and the spindle so that power transmission from the output shaft to the spindle is possible only when the output shaft rotates in a second direction. Output rotational speed of the spindle corresponding to the same rotational speed of the output shaft is different when the power transmission is performed through the first clutch or when the power transmission is performed through the second clutch.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a screwing tool.

Background Art

[0002] The screwing tool rotates the spindle in the reverse direction during the screwing operation and the unscrewing operation. Patent Document 1 discloses a screwing tool configured to start rotating the spindle in response to the pushing of the spindle. During the unscrewing operation, the pressing force on the screw may be smaller than during the screwing operation. Therefore, this screwing tool starts rotating the spindle in response to a smaller pushing of the spindle during the unscrewing operation than during the screwing operation.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The screwing tool described in Patent Document 1 can reduce the pushing amount of the spindle during the unscrewing operation. However, there is room for further improvement in this screwing tool.

[0005] In view of the above situation, one non-limiting object of the present disclosure is to provide a technique that contributes to improving the efficiency of operations by a screwing tool.

Means for Solving the Problems

[0006] In one aspect of the present disclosure, the screwing tool includes a housing, a motor, a spindle, a first clutch, and a second clutch.

[0007] The motor is housed in a housing. The motor has an output shaft configured to be selectively rotationally driven in a first direction and a second direction opposite to the first direction. The first direction corresponds to the direction of tightening a screw. The second direction corresponds to the direction of loosening a screw. The spindle is supported by the housing so as to be movable along the drive shaft and rotatable about the drive shaft. The drive shaft defines the longitudinal direction of the screw tightening tool. The front end portion of the spindle is configured to be detachable from the tip tool.

[0008] The first clutch is operably connected to the output shaft and the spindle. The first clutch is configured to enable power transmission from the output shaft to the spindle only when the output shaft is rotationally driven in the first direction. The second clutch is operably connected to the output shaft and the spindle. The second clutch is configured to enable power transmission from the output shaft to the spindle only when the output shaft is rotationally driven in the second direction. Further, the screw tightening tool is configured such that the output rotational speed of the spindle with respect to the rotational speed of the same output shaft is different when power is transmitted via the first clutch and when power is transmitted via the second clutch.

[0009] In the screw tightening tool of this aspect, during the screw tightening operation, power is transmitted from the motor to the spindle via the first clutch, while during the screw loosening operation, power is transmitted from the motor to the spindle via the second clutch. That is, power is transmitted via different paths during the screw tightening operation and the screw loosening operation. Also, even when the rotational speed of the output shaft of the motor is the same, the output rotational speed during power transmission via the first clutch and the output rotational speed during power transmission via the second clutch are different. That is, even when the rotational speed of the output shaft of the motor is the same, the spindle (and thus the screw) can be rotated at a rotational speed suitable for each operation during the screw tightening operation and the screw loosening operation. Thereby, it becomes possible to optimize the efficiency in each operation.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

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Figure 11

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Figure 17

Best Mode for Carrying Out the Invention

[0011] In a non-limiting embodiment of the present disclosure, the first clutch may be configured to selectively transmit power according to the longitudinal position of the spindle. The second clutch may be configured to transmit power regardless of the longitudinal position of the spindle. According to this embodiment, during the screwing operation, the spindle can be selectively rotated according to the longitudinal position of the spindle, that is, whether or not the screw is pressed against the workpiece. On the other hand, during the unscrewing operation, the spindle can be rotated even without the screw being pressed against the workpiece, so that the operation can be started quickly.

[0012] In addition to or in place of the above embodiment, the screwing tool may further include a regulating mechanism configured to regulate the longitudinal movement of the spindle only when the output shaft is rotationally driven in the second direction. According to this embodiment, when the output shaft is rotationally driven in the second direction, the regulating mechanism can surely prevent the first clutch from operating.

[0013] In addition to or in place of the above embodiment, the regulating mechanism may include a first regulating portion and a second regulating portion. The first regulating portion may be rotatable circumferentially around the drive shaft between a first position and a second position. The first regulating portion may be configured to be disposed at the first position in response to the rotation of the output shaft in the first direction and at the second position in response to the rotation of the output shaft in the second direction. The second regulating mechanism may be configured to allow the longitudinal movement of the spindle when the first regulating portion is at the first position and to regulate the longitudinal movement of the spindle when the first regulating portion is at the second position. According to this embodiment, a regulating mechanism with a simple configuration can appropriately allow or regulate the longitudinal movement of the spindle according to the rotational direction of the output shaft of the motor.

[0014] In addition to or instead of the above-described embodiment, the screw tightening tool may further include a rotating member disposed between the output shaft and the spindle on the power transmission path and configured to be rotated by the output shaft. The first restricting portion may be disposed around the rotating member so as to be selectively rotatable with respect to the rotating member and configured to rotate together with the rotating member only between the first position and the second position. Note that "rotating together" means that a second member in contact with a first member rotates together with the first member in accordance with the rotation of the first member due to the frictional force between the respective contact surfaces. The second restricting portion may be substantially immovable with respect to the housing. Note that the second restricting portion may be a member separate from the housing and may be directly or indirectly fixed to the housing, or may be a part of the housing. According to this embodiment, by using the rotating member, it is possible to easily realize the first restricting portion that is rotatable in the circumferential direction between the first position and the second position.

[0015] In addition to or instead of the above-described embodiment, the second restricting portion may include a wall portion disposed behind the first restricting portion and extending in the circumferential direction. The front end surface of the wall portion may include a first surface extending in a direction orthogonal to the drive shaft and a second surface extending obliquely rearward from one end of the first surface in the circumferential direction. The first surface may be configured to abut against the first restricting portion disposed at the second position from behind. The second surface may be configured to allow movement of the spindle in the front-rear direction. According to this embodiment, the second restricting portion having a simple configuration can surely prevent the operation of the first clutch when the output shaft is rotationally driven in the second direction.

[0016] In addition to or instead of the above-described embodiment, the first clutch may be configured to also serve as a speed reduction mechanism. According to this embodiment, since there is no need to provide a speed reduction mechanism separately from the first clutch, a compact screw tightening tool can be realized.

[0017] In addition to or instead of the above-described embodiments, the speed reduction mechanism may include a sun member, a ring member, and a carrier arranged coaxially with the drive shaft, and a plurality of planetary rollers rotatably held by the carrier. The ring member may be configured to be rotated by the output shaft. The carrier may be configured to rotate integrally with the spindle. The plurality of planetary rollers may be at least partially disposed between the tapered outer peripheral surface of the sun member and the tapered inner peripheral surface of the ring member in the radial direction of the ring member. The ring member may be movable in the front-rear direction relative to the sun member integrally with the spindle. The first clutch may be configured to transmit power by selectively frictionally contacting the plurality of planetary rollers with the outer peripheral surface of the sun member and the inner peripheral surface of the ring member in response to the rearward movement of the spindle from its initial position. According to this embodiment, a so-called planetary roller type speed reduction mechanism that operates in response to the movement of the spindle in the front-rear direction is adopted as the first clutch, and a screw tightening tool with a reasonable configuration can be realized.

[0018] In addition to or instead of the above-described embodiments, the spindle may have a first hole extending forward from the rear end of the spindle, and a second hole communicating with the first hole and extending in a direction intersecting the first hole and opening to the outer peripheral surface of the spindle. The screw tightening tool may further include a circulation path in the housing for returning the lubricant discharged from the spindle through the first hole and the second hole to the rear end of the spindle. According to this embodiment, the lubricant discharged from the second hole by the centrifugal force during the rotation of the spindle can flow back into the first hole of the spindle again and circulate in the housing. Therefore, the components in the housing can be efficiently lubricated.

[0019] In addition to or instead of the above-described embodiments, a lubricant storage portion may be provided on the circulation path. According to this embodiment, the lubricant can be stored in the storage portion and circulated efficiently. Note that a member (for example, felt) capable of absorbing and holding the lubricant may be disposed in the storage portion.

[0020] Hereinafter, with reference to the drawings, the screw driver 1 according to representative and non-limiting embodiments of the present disclosure will be specifically described. The screw driver 1 is an example of a screw tightening tool that can selectively perform screw tightening work and screw loosening work by rotationally driving a tip tool (specifically, a driver bit 9) removably attached to a spindle 3.

[0021] First, the schematic configuration of the screw driver 1 will be described.

[0022] As shown in FIG. 1, the outer contour of the screw driver 1 is formed by a long main body housing (also referred to as a tool body) 11 and a handle 17.

[0023] The main body housing 11 houses a motor 2, a long spindle 3, etc. The spindle 3 is arranged such that the rotation axis of the spindle 3 (that is, the drive axis A1 of the driver bit 9) extends in the longitudinal axis direction of the main body housing 11. One end of the spindle 3 is arranged inside one end in the longitudinal axis direction of the main body housing 11. This one end of the spindle 3 is configured to be detachable from the driver bit 9.

[0024] The handle 17 is generally formed in a C shape as a whole and is connected in a loop shape to the other end in the longitudinal axis direction of the main body housing 11. The handle 17 includes a gripping portion 171 that is gripped by the user. The gripping portion 171 extends linearly in a direction generally perpendicular to the drive axis A1, spaced apart from the main body housing 11. One end in the longitudinal axis direction of the gripping portion 171 is arranged on the drive axis A1, and a trigger 173 is provided at this one end. Also, a power cord 179 that can be connected to an external AC power supply is connected to the other end of the gripping portion 171.

[0025] When the trigger 173 is pressed by the user, the motor 2 is driven and the spindle 3 is rotationally driven integrally with the driver bit 9. Thereby, the screw 90 engaged with the driver bit 9 is rotated.

[0026] In the following description, for the sake of convenience, the extending direction of the drive shaft A1 is defined as the front-rear direction of the screwdriver 1. In the front-rear direction, the side where the driver bit 9 is mounted is defined as the front side, and the side where the gripping portion 171 is disposed is defined as the rear side. Further, the direction orthogonal to the drive shaft A1 and generally corresponding to the extending direction of the gripping portion 171 is defined as the up-down direction of the screwdriver 1. In the up-down direction, the side where the trigger 173 is disposed is defined as the upper side, and the side where the power cord 179 is connected is defined as the lower side. Also, the direction orthogonal to the front-rear direction and the up-down direction is defined as the left-right direction of the screwdriver 1.

[0027] Hereinafter, the detailed configuration of the screwdriver 1 will be described.

[0028] First, the detailed configuration of the main body housing 11 and the components within the main body housing 11 will be described.

[0029] As shown in FIG. 1, the main body housing 11 mainly includes a cylindrical rear housing 12 that houses the motor 2, a cylindrical front housing 13 that mainly houses the spindle 3, and a central housing 14 disposed between the rear housing 12 and the front housing 13. Note that the front end portion of the central housing 14 has a partition wall 141 disposed so as to intersect the drive shaft A1. By fixing the central housing 14 and the front housing 13 to the rear housing 12 with screws, the three housings are integrated to form the main body housing 11.

[0030] The rear housing 12 mainly houses the motor 2. The output shaft 23 of the motor 2 extends parallel to the spindle 3 below the spindle 3. That is, the axis of rotation of the output shaft 23 is parallel to the drive shaft A1. The output shaft 23 is rotatably supported by bearings 231 and 233 at its front end and rear end. The front bearing 231 is supported by the partition wall 141. The rear bearing 233 is supported by the rear end of the rear housing 12. The front end of the output shaft 23 projects forward (inside the front housing 13) through a through hole provided in the partition wall 141. A pinion gear 24 is fixed to the front end of the output shaft 23.

[0031] As shown in FIGS. 2 and 3, the front housing 13 mainly houses the spindle 3, the first clutch 4, and the second clutch 5.

[0032] The spindle 3 is generally a columnar (round bar-shaped) long member (shaft). The spindle 3 extends in the front-rear direction along the drive shaft A1. In the present embodiment, the spindle 3 is formed by connecting and fixing two separate members (two shafts 31 and 32) in the front-rear direction and integrating them. However, the spindle 3 may originally be a single member. A flange 34 is provided at the central portion of the spindle 3 in the front-rear direction.

[0033] The spindle 3 is rotatably supported around the drive shaft A1 and slidably supported in the front-rear direction along the drive shaft A1 with respect to the main body housing 11 by bearings 301 and 302 at its front end and rear end. The front bearing 301 is a ball bearing and is supported by the front end of the front housing 13. The rear bearing 302 is a sliding bearing (also called a plain bearing or a bush). The bearing 302 is press-fitted and supported in a recess (hereinafter referred to as the bearing housing portion 143) defined by the front surface of the partition wall 141 and a cylindrical portion 142 protruding forward from the front surface of the partition wall 141 (see FIG. 5).

[0034] As will be described later, the spindle 3 is always biased forward. Therefore, in the initial state where no external force acting rearward on the spindle 3 is present, the spindle 3 is held at a position where the front end face of the flange 34 abuts against a stopper portion 131 provided in the front housing 13. The position of the spindle 3 at this time is the foremost position (hereinafter also referred to as the initial position) within the movable range of the spindle 3.

[0035] A cylindrical locator 15 is removably connected to the front end portion of the front housing 13 so as to cover the front end portion. The front end portion of the spindle 3 protrudes from the front housing 13 into the locator 15. A bit insertion hole 311 is formed in the front end portion of the spindle 3. The driver bit 9 is held in a state where the rear portion thereof is inserted into the bit insertion hole 311. Note that the user can relatively move the locator 15 in the front-rear direction with respect to the front housing 13 and fix it at an arbitrary position. Thereby, the protruding amount of the driver bit 9 from the locator 15, that is, the tightening depth of the screw 90 is set.

[0036] The first clutch 4 and the second clutch 5 are both configured to selectively transmit power from the output shaft 23 of the motor 2 to the spindle 3. Details of the first clutch 4 and the second clutch 5 will be described later.

[0037] Hereinafter, the configuration inside the handle 17 will be described.

[0038] As shown in FIG. 1, the handle 17 houses a main switch 174, a forward / reverse switch 176, and a controller 178.

[0039] The main switch 174 is a switch for starting the motor 2, and is disposed inside the upper end of the grip portion 171 and behind the trigger 173. The main switch 174 is normally maintained in an off state and is switched to an on state in response to the pressing of the trigger 173. The main switch 174 is connected to the controller 178 via a wire (not shown) and outputs a signal indicating the on / off state to the controller 178.

[0040] At the portion connecting the lower end of the grip portion 171 of the handle 17 and the lower rear end of the main body housing 11 (rear housing 12), a forward / reverse lever 175 is provided. The forward / reverse lever 175 is an operating member for switching the rotation direction of the motor 2 (the rotation direction of the output shaft 23), and is operably connected to the forward / reverse switch 176. The user can set the rotation direction of the motor 2 to one of the direction in which the driver bit 9 tightens the screw 90 (hereinafter referred to as the forward direction, the screw tightening direction) and the direction in which the driver bit 9 loosens the screw 90 (hereinafter referred to as the reverse direction, the screw loosening direction) according to the operation of the forward / reverse lever 175. The forward / reverse switch 176 is connected to the controller 178 via a wire (not shown). The forward / reverse switch 176 outputs a predetermined signal to the controller 178 according to the rotation direction set via the forward / reverse lever 175.

[0041] The controller 178 is disposed below the main switch 174 inside the grip portion 171. The controller 178 includes a control circuit configured to control the drive of the motor 2. The controller 178 is configured to rotationally drive the motor 2 in the forward direction or the reverse direction according to the signal from the forward / reverse switch 176 when the main switch 174 is in the on state.

[0042] Hereinafter, the detailed configuration of the first clutch 4 will be described.

[0043] As shown in FIGS. 2 and 3, the first clutch 4 is operably connected to the output shaft 23 and the spindle 3. That is, the first clutch 4 is arranged in the power transmission path from the output shaft 23 to the spindle 3. The first clutch 4 is configured to selectively transmit power from the output shaft 23 to the spindle 3 according to the position of the spindle 3 in the longitudinal direction.

[0044] Further, the first clutch 4 of the present embodiment also functions as a speed reduction mechanism. Specifically, the first clutch 4 is configured as a planetary speed reduction mechanism including a tapered sleeve 41, a retainer 43, a plurality of rollers 45, and a gear sleeve 47.

[0045] The tapered sleeve 41, the retainer 43, and the gear sleeve 47 are arranged coaxially with the spindle 3 (along the drive shaft A1). The tapered sleeve 41, the retainer 43, the roller 45, and the gear sleeve 47 respectively correspond to the sun member, the carrier, the planetary member, and the ring member in the planetary speed reduction mechanism. In the first clutch 4, the tapered sleeve 41, the gear sleeve 47, and the retainer 43 function as a fixed element, an input element, and an output element, respectively. Therefore, the gear sleeve 47 and the retainer 43 (spindle 3) rotate in the same direction.

[0046] Hereinafter, when the motor 2 (output shaft 23) is rotationally driven in the forward direction (screw tightening direction), the rotational directions of the gear sleeve 47, the retainer 43, and the spindle 3 are referred to as the forward directions (screw tightening directions) of the gear sleeve 47, the retainer 43, and the spindle 3. When the motor 2 is rotationally driven in the reverse direction (screw loosening direction), the rotational directions of the gear sleeve 47, the retainer 43, and the spindle 3 are referred to as the reverse directions (screw loosening directions) of the gear sleeve 47, the retainer 43, and the spindle 3. However, the rotational direction of the output shaft 23 and the rotational directions of the gear sleeve 47, the retainer 43, and the spindle 3 are always opposite.

[0047] As shown in FIGS. 2 to 4, the tapered sleeve 41 is a cylindrical member. The tapered sleeve 41 is held by the main body housing 11 via the base 40.

[0048] The base 40 is formed as a separate member from the main body housing 11 and is connected to the main body housing 11 (specifically, the partition wall 141) coaxially with the drive shaft A1. More specifically, the base 40 includes an annular portion 401 and four legs 407 protruding rearward from the peripheral edge of the annular portion 401. On the other hand, as shown in FIG. 5, a plurality of recesses 80 partitioned by a plurality of ribs are formed around the cylindrical portion 142 surrounding the bearing housing portion 143. As shown in FIG. 6, the legs 407 of the base 40 are respectively fitted into the recesses 80. Thereby, the base 40 is held by the main body housing 11 (partition wall 141) in a state where rotation around the drive shaft A1 is restricted.

[0049] In addition, in the present embodiment, the recess 80 is also used as a storage portion (oil sump) for a lubricant (for example, grease, lubricating oil), and a felt 801 for absorbing and holding the lubricant is fitted into the recess 80. Note that there are gaps between the rear end (protruding end) of the leg 407 and the bottom surface of the recess 80, and between the radially inner surface of the leg 407 and the outer peripheral surface of the cylindrical portion 142 within the recess 80 (see FIG. 15). The felt 801 is disposed in these gaps.

[0050] As shown in FIGS. 2 to 4, a plurality of protrusions 412 are provided at the rear end of the tapered sleeve 41. These protrusions 412 are fitted into a recess 405 formed in the inner peripheral portion of the base 40. Thereby, the tapered sleeve 41 is held by the main body housing 11 (partition wall 141) via the base 40 in a state where rotation around the drive shaft A1 is restricted. The outer peripheral surface of the tapered sleeve 41 is configured as a tapered surface 411 that is inclined at a predetermined angle with respect to the drive shaft A1. More specifically, the outer shape of the tapered sleeve 41 is in the shape of a frustum of a cone that becomes narrower (smaller in diameter) toward the front, and the tapered surface 411 is configured as a conical surface that is inclined in a direction approaching the drive shaft A1 toward the front.

[0051] The retainer 43 is configured to rotatably hold the roller 45. The retainer 43 of the present embodiment includes an annular portion 431 and a plurality of holding arms 434.

[0052] The annular portion 431 is a wall portion having a through hole at the center. The plurality of holding arms 434 are arranged at intervals from each other in the circumferential direction, and each projects generally rearward from the rear surface of the peripheral edge portion of the annular portion 431. Each holding arm 434 extends at the same inclination angle as the tapered surface 411 of the tapered sleeve 41 with respect to the drive shaft A1 (that is, parallel to the tapered surface 411). The space formed between the holding arms 434 adjacent to each other in the circumferential direction functions as a holding space for the roller 45. The front end of this space is closed by the peripheral edge portion of the annular portion 431.

[0053] In the present embodiment, the retainer 43 is supported by the spindle 3 so as not to be rotatable and to be movable in the front-rear direction with the holding arms 434 disposed on the radially outer side of the tapered sleeve 41. More specifically, as shown in FIGS. 3 and 4, two grooves 321 are formed at the rear end portion of the spindle 3 (shaft 32) with the drive shaft A1 interposed therebetween. Each groove 321 extends linearly in the front-rear direction. A ball 36 is disposed in each groove 321 so as to be rollable. Further, two recesses 432 are formed on the inner peripheral surface of the annular portion 431 of the retainer 43 with the drive shaft A1 interposed therebetween. A part of the ball 36 disposed in the groove 321 is engaged with the recess 432. Furthermore, an annular recess 414 is formed at the central portion of the front surface of the tapered sleeve 41. Although details will be described later, the retainer 43 is biased rearward by a biasing spring 49, the ball 36 is disposed in the space defined by the recesses 414 and 432, and the rear surface of the annular portion 431 is held in contact with the front surface of the tapered sleeve 41.

[0054] With such a configuration, the retainer 43 engages with the spindle 3 via the ball 36 and can rotate integrally with the spindle 3. The ball 36 can roll within the annular recess 419 of the tapered sleeve 41, and the retainer 43 can rotate around the drive shaft A1 with respect to the tapered sleeve 41 together with the spindle 3. On the other hand, the spindle 3 can move in the front-rear direction with respect to the retainer 43 and the tapered sleeve 41 within the range where the ball 36 can roll within the groove 321.

[0055] As shown in FIGS. 2 to 4, the roller 45 is a cylindrical member. Each roller 45 has a constant diameter and is rotatably held between adjacent holding arms 434. Also, as shown in FIG. 7, the outer peripheral surface of the roller 45 partially and slightly protrudes from the inner and outer surfaces of the holding arm 434 in the radial direction of the retainer 43.

[0056] As shown in FIGS. 2 to 4, the gear sleeve 47 is configured as a stepped cylindrical member as a whole. More specifically, the front end portion of the gear sleeve 47 has an inner diameter and an outer diameter that are smaller than the portion extending rearward from the front end portion. Hereinafter, the front end portion of the gear sleeve 47 is referred to as the small diameter portion 471, and the portion extending rearward from the front end portion is referred to as the large diameter portion 474. Also, the stepped portion connecting the small diameter portion 471 and the large diameter portion 474 is referred to as the shoulder portion 472. Both the small diameter portion 471 and the large diameter portion 474 are cylindrical tube walls and have an inner diameter larger than the diameter of the spindle 3.

[0057] The outer ring of a bearing (specifically, a ball bearing) 48 is fixed to the inner peripheral surface of the front end portion (the portion adjacent to the shoulder portion 472) of the large diameter portion 474. The spindle 3 is inserted through the inner ring of the bearing 48. Thereby, the gear sleeve 47 is rotatably supported around the drive shaft A1 with respect to the spindle 3 by the spindle 3.

[0058] On the rear side of the bearing 48, a space is formed radially between the spindle 3 and the large-diameter portion 474 (cylindrical wall). A part of the tapered sleeve 41, the retainer 43, and the roller 45 are arranged in this space. Further, gear teeth 470 are integrally provided on the outer periphery of the rear end portion of the gear sleeve 47 (specifically, the large-diameter portion 474). The gear teeth 470 are always meshed with the pinion gear 24. Therefore, the gear sleeve 47 is rotationally driven in the direction opposite to the output shaft 23 in accordance with the rotation of the output shaft 23.

[0059] As shown in FIGS. 2 and 3, the inner peripheral surface of the rear end portion of the large-diameter portion 474 of the gear sleeve 47 is formed as a tapered surface 475. The tapered surface 475 is inclined at the same angle as the tapered surface 411 of the tapered sleeve 41 with respect to the drive shaft A1 (parallel to the tapered surface 411). That is, the tapered surface 475 is formed as a conical surface that inclines in a direction away from the drive shaft A1 toward the rear (the open end of the gear sleeve 47). The front portion of the roller 45 held by the retainer 43 is located between the tapered surface 411 and the tapered surface 475 in the radial direction of the spindle 3 (the direction perpendicular to the drive shaft A1).

[0060] Also, the first clutch 4 includes a biasing spring 49 disposed between the gear sleeve 47 and the retainer 43 in the front-rear direction (specifically, between the bearing 48 and the retainer 43). In this embodiment, a conical coil spring is adopted for the biasing spring 49, but other types of springs may be adopted. The biasing spring 49 always biases the retainer 43 and the gear sleeve 47 away from each other, that is, rearward and forward, respectively. Therefore, the tapered sleeve 41, the retainer 43, and the roller 45 are each restricted in their movement in the front-rear direction and are held at predetermined positions in the front-rear direction with respect to the main body housing 11.

[0061] In the front-rear direction, a thrust bearing 35 is disposed between the front surface of the gear sleeve 47 (small-diameter portion 471) and the flange 34 of the spindle 3. When the gear sleeve 47 is biased forward by the biasing force of the biasing spring 49, the spindle 3 is also biased forward via the thrust bearing 35. As a result, in the initial state, the spindle 3 is held at the most forward position (initial position). Further, as the spindle 3 moves in the front-rear direction, the gear sleeve 47 also moves in the front-rear direction. That is, the gear sleeve 47 and the spindle 3 are configured to move integrally in the front-rear direction with respect to the main body housing 11.

[0062] The first clutch 4 having the above configuration transmits power by the frictional force between the roller 45 and the taper sleeve 41 (taper surface 411), and the frictional force between the roller 45 and the gear sleeve 47 (taper surface 475). That is, the first clutch 4 of the present embodiment is a so-called planetary roller type friction clutch.

[0063] Hereinafter, the front-rear positions of the spindle 3 and the gear sleeve 47 and the operation of the first clutch 4 will be described.

[0064] First, when the spindle 3 is disposed at the initial position, as shown in FIGS. 2 and 7, the roller 45 is held in a state where a slight movement is allowed between the taper surface 411 of the taper sleeve 41 and the taper surface 475 of the gear sleeve 47. Therefore, the first clutch 4 is in a state where the power of the motor 2 cannot be transmitted to the spindle 3 (hereinafter referred to as a cut-off state). Therefore, even if the gear sleeve 47 rotates, the rotation is not transmitted to the retainer 43.

[0065] On the one hand, as shown in FIG. 8, when the user presses the screw 90 engaged with the driver bit 9 against the workpiece 91, the spindle 3 is pushed backward with respect to the main body housing 11 against the biasing force of the biasing spring 49. The gear sleeve 47 moves backward integrally with the spindle 3 with respect to the main body housing 11, the tapered sleeve 41, the retainer 43, and the roller 45. As the gear sleeve 47 moves backward, it approaches the tapered sleeve 41, and the radial distance between the tapered surface 411 of the tapered sleeve 41 and the tapered surface 475 of the gear sleeve 47 gradually decreases.

[0066] In response to the backward movement of the spindle 3 and the gear sleeve 47, as shown in FIGS. 8 and 9, the roller 45 comes into frictional contact with the tapered surface 411 and the tapered surface 475. When the frictional force increases and reaches a predetermined threshold value, the roller 45 revolves while rotating on its own axis in response to the rotation of the gear sleeve 47, and rotates the retainer 43 and the spindle 3 in the same direction as the gear sleeve 47. That is, the first clutch 4 shifts from the disengaged state to a state in which power transmission to the spindle 3 is possible (hereinafter referred to as the transmission state). Hereinafter, the front-rear positions of the spindle 3 and the gear sleeve 47 at this time are referred to as the operating positions. Since the first clutch 4 is a speed reduction mechanism, the rotational speed of the spindle 3 is slower than the rotational speed of the gear sleeve 47.

[0067] In addition, the first clutch 4 of the present embodiment enables power transmission from the output shaft 23 to the spindle 3 only when the motor 2 is rotationally driven in the forward direction (screw tightening direction). In other words, the first clutch 4 cannot shift from the disengaged state to the transmission state when the motor 2 is rotationally driven in the reverse direction (screw loosening direction). This point will be described in detail later.

[0068] Hereinafter, the detailed configuration of the second clutch 5 will be described.

[0069] As shown in FIGS. 2 to 4, the second clutch 5 is operably connected to the output shaft 23 and the spindle 3. That is, the second clutch 5 is disposed in the power transmission path from the output shaft 23 to the spindle 3. Different from the first clutch 4, the second clutch 5 is configured to transmit power from the output shaft 23 to the spindle 3 regardless of the position of the spindle 3 in the front-rear direction. Further, the second clutch 5 of the present embodiment is configured to transmit power from the output shaft 23 to the spindle 3 only when the rotation direction of the motor 2 (output shaft 23) is the reverse direction (the direction of loosening the screw).

[0070] The second clutch 5 of the present embodiment is composed of a one-way clutch 51. The one-way clutch 51 is a clutch configured to transmit rotation only in one direction and idle in the reverse direction. The one-way clutch 51 of the present embodiment is a general-purpose one-way clutch and includes a cylindrical outer ring and a plurality of rolling elements (clutch members) disposed inside the outer ring. Rollers (specifically, needle rollers) are employed as the rolling elements.

[0071] The one-way clutch 51 is disposed between the small-diameter portion 471 of the gear sleeve 47 and the spindle 3 in the radial direction of the spindle 3. More specifically, the outer ring of the one-way clutch 51 is press-fitted and fixed to the inner peripheral surface of the small-diameter portion 471 of the gear sleeve 47. The spindle 3 is inserted through the one-way clutch 51.

[0072] When the motor 2 (output shaft 23) is rotationally driven in the forward direction (screw tightening direction), the one-way clutch 51 rotates together with the gear sleeve 47 but idles with respect to the spindle 3. That is, when the motor 2 is rotationally driven in the forward direction, the one-way clutch 51 does not transmit the rotation of the gear sleeve 47 to the spindle 3. On the other hand, when the motor 2 is rotationally driven in the reverse direction (screw loosening direction), the one-way clutch 51 is locked to the spindle 3 and rotates integrally with the gear sleeve 47 and the spindle 3. That is, when the motor 2 is rotationally driven in the reverse direction, the one-way clutch 51 transmits the rotation of the gear sleeve 47 to the spindle 3. The rotational speed of the gear sleeve 47 and the rotational speed of the spindle 3 are the same.

[0073] Furthermore, the screw driver 1 includes a regulating mechanism 6 configured to selectively regulate the forward and backward movement of the spindle 3 and the gear sleeve 47. More specifically, when the motor 2 is rotationally driven in the forward direction (screw tightening direction), the regulating mechanism 6 allows the forward and backward movement of the spindle 3 and the gear sleeve 47, thereby putting the first clutch 4 in an operable state. Also, when the motor 2 is rotationally driven in the reverse direction (screw loosening direction), the regulating mechanism 6 regulates (prevents) the forward and backward movement of the spindle 3 and the gear sleeve 47, thereby putting the first clutch 4 in an inoperable state. That is, the regulating mechanism 6 is configured to switch the state of the first clutch 4 between an operable state and an inoperable state according to the rotational direction of the motor 2. Hereinafter, the detailed configuration of the regulating mechanism 6 will be described.

[0074] As shown in FIGS. 2 to 4, FIG. 10, and FIG. 11, the regulating mechanism 6 includes a rotating sleeve 61 and a regulating frame 62.

[0075] The rotating sleeve 61 is a member (sleeve, collar) that is generally cylindrical (annular) in shape. More specifically, the rotating sleeve 61 includes a cylindrical barrel wall 611 and two protrusions 613 that protrude radially outward from the outer peripheral surface of the barrel wall 611. The barrel wall 611 is disposed around the small-diameter portion 471 of the gear sleeve 47 (fitted onto the outer periphery of the small-diameter portion 471). The outer diameter of the barrel wall 611 is set such that the outer peripheral surface of the barrel wall 611 does not protrude radially from the outer peripheral surface of the large-diameter portion 474 of the gear sleeve 47. The two protrusions 613 are symmetrically arranged with the axis (drive shaft A1) of the rotating sleeve 61 in between. The protrusions 613 protrude radially outward beyond the outer peripheral surface of the large-diameter portion 474. Note that the rear end surface of each protrusion 613 includes an inclined surface 614 that is slightly inclined in the circumferential direction (see FIG. 11).

[0076] The rotating sleeve 61 is configured to rotate together with the rotation of the gear sleeve 47 when no external force acts on the rotating sleeve 61 and when the external force is relatively small. The rotating sleeve 61 of the present embodiment can rotate around the drive shaft A1 with respect to the main body housing 11 together with the gear sleeve 47 due to the frictional force between the inner peripheral surface of the rotating sleeve 61 (barrel wall 611) and the outer peripheral surface of the gear sleeve 47 (small-diameter portion 471). On the other hand, when an external force that exceeds the frictional force causing co-rotation acts on the rotating sleeve 61, the rotating sleeve 61 and the gear sleeve 47 can rotate relative to each other around the drive shaft A1.

[0077] The rotating sleeve 61 is disposed in the front-rear direction between the shoulder portion 472 of the gear sleeve 47 and a retaining ring 473 (and washer) fixed to the outer periphery of the gear sleeve 47 (small-diameter portion 471). Therefore, the movement of the rotating sleeve 61 in the front-rear direction with respect to the gear sleeve 47 is restricted. Thus, the rotating sleeve 61 moves in the front-rear direction with respect to the main body housing 11 integrally with the gear sleeve 47 and thus the spindle 3.

[0078] The regulation frame 62 is a member that is supported in a substantially non-movable manner with respect to the main body housing 11. The regulation frame 62 is configured to selectively regulate (inhibit) the forward and backward movement of the rotation sleeve 61 (and thus the spindle 3 and the gear sleeve 47) with respect to the main body housing 11 according to the rotational position of the rotation sleeve 61 with respect to the main body housing 11 (the circumferential position of the protrusion 613).

[0079] More specifically, the regulation frame 62 is generally a cylindrical member with a larger diameter than the rotation sleeve 61. More specifically, the regulation frame 62 has a cylindrical wall 620 arranged coaxially with the gear sleeve 47 around the gear sleeve 47, two protrusions 625 protruding forward from the front end of the wall 620, and two protrusions 627 protruding radially outward from the outer peripheral surface of the wall 620.

[0080] As shown in FIGS. 3 and 12, two grooves 133 corresponding to the protrusions 627 of the regulation frame 62 are formed inside the front housing 13. Each groove 133 is a groove extending in the front-back direction and has a cross-sectional shape that matches the protrusion 627. The protrusions 627 are respectively fitted into the grooves 133. Also, each protrusion 627 is sandwiched and held in the front-back direction between the surface defining the front end of the groove 133 and the front end of the arm portion 661 (see FIG. 10) of the holding member 66 arranged on the front side of the partition wall 141. With such a configuration, the regulation frame 62 is held in a substantially non-movable manner with respect to the main body housing 11. However, the regulation frame 62 may be directly connected and fixed to the main body housing 11 (front housing 13) without using the holding member 66.

[0081] The two protrusions 625 project forward from the front end of the cylindrical wall 620 at positions symmetric with respect to the drive shaft A1. That is, in the circumferential direction of the regulating frame 62, the two protrusions 625 and the two portions of the cylindrical wall 620 without the protrusions 625 are alternately arranged. The portion of the cylindrical wall 620 without the protrusion 625 (hereinafter referred to as the regulating portion 621) is located behind the rear end of the protrusion 613 of the rotating sleeve 61 in the front-rear direction when the spindle 3 and the gear sleeve are in the initial positions. On the other hand, each protrusion 625 of the regulating frame 62 projects forward of the rear end of the protrusion 613 of the rotating sleeve 61.

[0082] The position of the front end face of the regulating portion 621 in the front-rear direction is configured to change in the circumferential direction of the cylindrical wall 620. More specifically, the front end face of each regulating portion 621 includes a first face 622 (flat face) substantially orthogonal to the drive shaft A1 and a second face 623 (inclined face) extending obliquely rearward in the circumferential direction from one end in the circumferential direction of the first face 622. More specifically, the second face 623 is connected to the end on the positive direction (the direction of arrow D1 in FIG. 11) side of the first face 622 with respect to the rotation direction of the gear sleeve 47 and is inclined rearward as it advances in the positive direction. Each protrusion 625 is disposed between the first face 622 of one regulating portion 621 and the second face 623 of the other regulating portion 621 in the circumferential direction of the regulating frame 62.

[0083] In addition, the inner diameter of the cylindrical wall 620 of the regulating frame 62 is set larger than the outer diameter of the large-diameter portion 474 of the gear sleeve 47. Therefore, the inner peripheral surface of the cylindrical wall 620 is always separated from the large-diameter portion 474, and the gear sleeve 47 can rotate around the drive shaft A1 with respect to the main body housing 11 and the regulating frame 62 without interfering with the cylindrical wall 620. On the other hand, the inner diameter of the cylindrical wall 620 is smaller than the distance between the protruding ends of the two protrusions 613 of the rotating sleeve 61 (the maximum diameter of the rotating sleeve 61). Therefore, the protrusion 625 can interfere with the protrusion 613 of the rotating sleeve 61 when the rotating sleeve 61 rotates with respect to the regulating frame 62 by co-rotation. Also, when the spindle 3 and the gear sleeve move rearward from the initial position, the regulating portion 621 can interfere with the protrusion 613 of the rotating sleeve 61.

[0084] Specifically, as shown in FIG. 11, when the gear sleeve 47 rotates in the forward direction (the direction of arrow D1), the rotating sleeve 61 rotates in the same direction as the gear sleeve 47 with respect to the main body housing 11 and the regulating frame 62 due to co-rotation. The rotating sleeve 61 is rotatable to a position where the protrusion 613 abuts against the protrusion 625 on the forward side, as shown by the dotted line in FIG. 11. The rotational position (circumferential position) of the rotating sleeve 61 at this time is referred to as the first position.

[0085] When the rotating sleeve 61 is disposed at the first position, the protrusion 613 is just in front of the end on the forward side (the direction of arrow D1) of the second surface 623 of the regulating portion 621. When the spindle 3 is in the initial position, the protrusion 613 is separated from the second surface 623. Therefore, as shown in FIG. 13, the rotating sleeve 61 is movable rearward with respect to the regulating frame 62. That is, the regulating portion 621 (specifically, the second surface 623) of the regulating frame 62 allows the spindle 3 to move rearward from the initial position when the rotating sleeve 61 is at the first position. Note that the regulating portion 621 (the second surface 623) is configured to allow the spindle 3 to move from the initial position to at least the operating position (putting the first clutch 4 in an operable state).

[0086] On the other hand, when the gear sleeve 47 rotates in the reverse direction (the direction of arrow D2) with the spindle 3 in the initial position, the rotating sleeve 61 is rotatable, due to co-rotation, to a position where the protrusion 613 abuts against the protrusion 625 on the reverse side, as shown by the solid line in FIG. 11. The rotational position (circumferential position) of the rotating sleeve 61 at this time is referred to as the second position.

[0087] When the rotation sleeve 61 is disposed at the second position, the protrusion 613 is just in front of the first surface 622 of the restricting portion 621. At this time, in the front-rear direction, there is only a slight gap between the protrusion 613 and the first surface 622. For this reason, even when the spindle 3 attempts to move rearward from the initial position, the first surface 622 abuts against the protrusion 613 from the rear, preventing the rotation sleeve 61 from moving further rearward. That is, the restricting portion 621 (specifically, the first surface 622) restricts (inhibits) the spindle 3 from moving rearward from the initial position when the rotation sleeve 61 is at the second position (rendering the first clutch 4 inoperative).

[0088] Hereinafter, the operations of the restricting mechanism 6, the first clutch 4, and the second clutch 5 during the screw tightening operation and the screw loosening operation will be described in detail.

[0089] First, the screw tightening operation (that is, the case where the motor 2 is rotationally driven in the forward direction (screw tightening direction)) will be described.

[0090] As shown in FIG. 2, when the spindle 3 is disposed at the initial position, the first clutch 4 is in the disengaged state. When the user presses the trigger 173 in this state, the main switch 174 is turned on, and the controller 178 starts driving the motor 2. The gear sleeve 47 is rotationally driven in the forward direction (screw tightening direction). As described above, at this time, the second clutch 5 (one-way clutch 51) does not operate, and the gear sleeve 47 idles relative to the spindle 3.

[0091] As described above, the rotation sleeve 61 of the restricting mechanism 6 is disposed at the first position by co-rotation. As shown by the dotted line in FIG. 11, since the protrusion 613 of the rotation sleeve 61 abuts against the protrusion 625 of the restricting frame 62, further rotation of the rotation sleeve 61 in the forward direction is prevented, and the rotation sleeve 61 is held at the first position. The gear sleeve 47 continues to idle in the forward direction relative to the spindle 3 while rotating relative to the rotation sleeve 61.

[0092] Since the rotating sleeve 61 is in the first position, the restricting portion 621 (second surface 623) allows the spindle 3 to move rearward without interfering with the projection 613 of the rotating sleeve 61. That is, the first clutch 4 is in an operable state. Thus, as shown in FIGS. 8 and 13, as the user presses the screw 90 against the workpiece 91, the spindle 3, the gear sleeve 47, and the rotating sleeve 61 move rearward with respect to the main body housing 11 and the restricting frame 62. When the spindle 3 moves rearward to the operating position, the first clutch 4 shifts from the disengaged state to the engaged state, and the tightening of the screw 90 against the workpiece 91 is started.

[0093] As the tightening of the screw 90 onto the workpiece 91 progresses and the tip of the locator 15 abuts against the workpiece 91, the part receiving the pressing force shifts from the spindle 3 to the locator 15. Therefore, the pressing force on the spindle 3 gradually decreases. For this reason, the force with which the tapered surface 411 of the tapered sleeve 41 and the tapered surface 475 of the gear sleeve 47 sandwich the roller 45, and thus the torque transmitted from the gear sleeve 47 to the spindle 3 also gradually decreases. When the torque transmitted from the gear sleeve 47 to the spindle 3 falls below the torque required for tightening the screw 90, the rotation of the spindle 3 is stopped. With this, the screw tightening operation ends.

[0094] Next, the screw loosening operation (that is, the case where the motor 2 is rotationally driven in the reverse direction (screw loosening direction)) will be described.

[0095] With the spindle 3 positioned at the initial position, when the user presses the trigger 173, the main switch 174 is turned on, and the controller 178 starts driving the motor 2. The gear sleeve 47 is rotationally driven in the reverse direction (the screw loosening direction). As described above, since the second clutch 5 (one-way clutch 51) operates, the spindle 3 rotates integrally with the gear sleeve 47 simultaneously with the start of rotation of the gear sleeve 47, and begins to loosen the screw 90. That is, when the motor 2 is rotationally driven in the reverse direction, the screw 90 can be loosened without the user pressing the screw 90 against the workpiece 91. Therefore, the user can quickly start the screw loosening operation.

[0096] Also, as described above, the rotating sleeve 61 of the regulating mechanism 6 is arranged at the second position by co-rotation. Before the rotating sleeve 61 reaches in front of the first surface 622, if the spindle 3 is pushed backward and the protrusion 613 abuts against the second surface 623, the rotating sleeve 61 can be guided to the second position by the action of the second surface 623 (and the inclined surface 614 of the protrusion 613), which is an inclined surface. As shown by the solid line in FIG. 11, when the rotating sleeve 61 is arranged at the second position, the protrusion 613 of the rotating sleeve 61 abuts against the protrusion 625 of the regulating frame 62, so that further reverse rotation of the rotating sleeve 61 is prevented, and the rotating sleeve 61 is held at the second position. The gear sleeve 47 continues to rotate in the reverse direction integrally with the spindle 3 while rotating with respect to the rotating sleeve 61.

[0097] The screw 90 moves backward as it is loosened. Therefore, the spindle 3 is pressed backward. However, since the rotating sleeve 61 is in the second position, the restricting portion 621 (the first surface 622) abuts against the protrusion 613, restricting (inhibiting) the backward movement of the spindle 3. That is, the first clutch 4 is maintained in an inoperable state, and it is prevented that the first clutch 4 operates during the operation of the second clutch 5. Thus, the power of the output shaft 23 is transmitted to the spindle 3 only through the second clutch 5, the screw 90 is loosened, and removed from the workpiece 91. As described above, since the first clutch 4 is a speed reduction mechanism, if the first clutch 4 and the second clutch 5 operate simultaneously, slippage may occur in either of them, which may cause a problem. In the present embodiment, such a problem is appropriately avoided.

[0098] As described above, in the screw driver 1 of the present embodiment, during the screw tightening operation, power is transmitted from the motor 2 to the spindle 3 via the first clutch 4, while during the screw loosening operation, power is transmitted from the motor 2 to the spindle 3 via the second clutch 5. That is, power is transmitted through different paths during the screw tightening operation and the screw loosening operation. Further, since the first clutch 4 is also a speed reduction mechanism, even if the rotational speed of the output shaft 23 of the motor 2 is the same, the rotational speed of the spindle 3 during power transmission via the first clutch 4 and the rotational speed of the spindle 3 during power transmission via the second clutch 5 are different. Specifically, when the motor 2 is rotationally driven at the same rotational speed, the screw 90 can be rotated at a higher speed during the screw loosening operation than during the screw tightening operation. The torque required for the screw loosening operation is smaller than the torque required for the screw tightening operation. Therefore, as in the present embodiment, by varying the output rotational speed with respect to the same rotational speed of the motor 2 according to the rotational direction of the motor 2, the efficiency in each operation can be optimized.

[0099] In addition, the first clutch 4 that operates only when the motor 2 is rotationally driven in the forward direction (screw tightening direction) also serves as a speed reduction mechanism, so there is no need to provide a speed reduction mechanism separately from the first clutch 4. Therefore, a compact screw driver 1 is realized. On the other hand, when the motor 2 is rotationally driven in the reverse direction (screw loosening direction), the required torque is relatively small. For this reason, a one-way clutch 51 that simply transmits rotation is used for the second clutch 5, and no speed reduction is performed. As a result, a compact and relatively inexpensive second clutch 5 is realized.

[0100] In addition, the first clutch 4 starts power transmission in response to the rearward pushing of the spindle 3. The regulation mechanism 6 regulates the forward and backward movement of the spindle 3 only when the motor 2 (output shaft 23) is rotationally driven in the reverse direction. Thereby, the regulation mechanism 6 can surely prevent the first clutch 4 from operating when the motor 2 (output shaft 23) is rotationally driven in the reverse direction.

[0101] In particular, in the present embodiment, the regulation mechanism 6 includes a rotation sleeve 61 that is rotatable between a first position and a second position, and a regulation frame 62 that is fixed to the main body housing 11 and regulates the forward and backward movement of the spindle 3 only when the rotation sleeve 61 is in the second position. The rotation sleeve 61 is rotatable between the first position and the second position by utilizing the co-rotation with the gear sleeve 47 rotated by the output shaft 23, so the configuration is simple. Further, the regulation frame 62 (regulation portion 621) has a simple configuration of a first surface 622 that abuts against the rotation sleeve 61 from the rear, and can surely prevent the spindle 3 from moving backward.

[0102] Furthermore, in the present embodiment, the regulation frame 62 is provided with a protrusion 625 that can abut against the protrusion 613 of the rotation sleeve 61 in the circumferential direction. Thereby, without preventing the rotation of the gear sleeve 47, the rotation sleeve 61 can be prevented from co-rotating beyond the first position and the second position, and the rotation sleeve 61 can be held at the first position and the second position.

[0103] Incidentally, in the screwdriver 1, since various mechanisms and components that require lubrication are housed in the front housing 13, a lubricant (e.g., grease, lubricating oil) is introduced into the front housing 13. In the present embodiment, a circulation path 8 for effectively circulating the lubricant is provided in the front housing 13. Hereinafter, the circulation path 8 will be described in detail.

[0104] As shown in FIGS. 14 and 15, the circulation path 8 mainly includes a path 81 passing through the inside of the spindle 3 and various paths 82 to 86 for guiding the lubricant to the rear end of the spindle 3 outside the spindle 3.

[0105] The path 81 inside the spindle 3 is defined by a first hole 811 and a second hole 812. The first hole 811 extends forward along the axis (drive axis A1) of the spindle 3 from the rear end of the spindle 3. The first hole 811 is a bottomed hole with a closed front end and an opening at the rear end to the rear end of the spindle 3. The second hole 812 penetrates the spindle 3 in the diameter direction of the spindle 3. Note that both ends of the second hole 812 open to the outer peripheral surface of the spindle 3 (specifically, inside the groove 321). Both ends of the second hole 812 are located inside the radial direction of the first clutch 4 (surrounded by the first clutch 4) regardless of the position of the spindle 3 in the front-rear direction. Also, the central portion of the second hole 812 communicates with the front end portion of the first hole 811. That is, the first hole 811 and the second hole 812 are arranged in a T shape as a whole.

[0106] The lubricant flowing into the first hole 811 from the rear end of the spindle 3 can flow out to the outside of the spindle 3 through the openings at both ends of the second hole 812. More specifically, the lubricant is discharged radially outward of the spindle 3 through the path 81 by the centrifugal force during the rotation of the spindle 3. Thereby, components (particularly, the first clutch 4) arranged around the spindle 3 can be lubricated.

[0107] Path 82 is a path that allows the lubricant that has flowed out of the spindle 3 through path 81 to flow out radially outward of the gear sleeve 47. Specifically, as shown in FIG. 15, two communication holes 478 are provided in the large-diameter portion 474 of the gear sleeve 47. The communication hole 478 penetrates the large-diameter portion 474 (cylindrical wall), and communicates the space inside the large-diameter portion 474 (the internal space of the gear sleeve 47) with the space outside the radial direction (the external space of the gear sleeve 47). Therefore, the lubricant that has flowed into the internal space of the gear sleeve 47 through path 81 can flow out radially outward of the gear sleeve 47 through the communication hole 478. In particular, when the gear sleeve 47 rotates, due to centrifugal force, a flow of air is generated through the communication hole 478, so that the lubricant can be effectively discharged to the outside of the gear sleeve 47.

[0108] Path 83 is a path for guiding the lubricant that has flowed out of the spindle 3 through path 81 to the periphery of the roller 45 through the space between the tapered sleeve 41 and the retainer 43. Specifically, as shown in FIG. 16, a plurality of shallow grooves 433 are formed on the rear surface of the annular portion 431 of the retainer 43. The groove 433 extends radially from the inner edge to the outer edge of the annular portion 431 between the holding arms 434. As shown in FIG. 14, the path 83 is defined by the front surface of the tapered sleeve 41 and the groove 433. As described above, the retainer 43 is held in a state where the rear surface of the annular portion 431 is in contact with the front surface of the tapered sleeve 41. However, the lubricant that has flowed out of the spindle 3 through path 81 can move to the periphery of the roller 45 through path 83 and lubricate the roller 45 and the tapered surfaces 411 and 475.

[0109] Note that the roller 45 rotates and revolves while rubbing against the tapered surface 411 of the tapered sleeve 41 and the tapered surface 475 of the gear sleeve 47. For this reason, there is a difference in rotation between the front portion and the rear portion of the roller 45, so slippage occurs. Therefore, the lubricant supplied via path 81 can effectively reduce the wear of the roller 45 and the tapered surfaces 411 and 475, and contribute to improving the durability of the first clutch 4.

[0110] When the lubricant passing through paths 82, 83, etc. moves to the recess 80 (oil reservoir) of the partition wall 141 (see Fig. 15), it is absorbed and held by the felt 801 disposed in the recess 80. In this way, by storing the lubricant in the recess 80 using the felt 801, the lubricant can be circulated efficiently.

[0111] Path 84 is a path for guiding the lubricant from the recess 80 to the opening of the bearing housing portion 143. Specifically, as shown in Fig. 17, two shallow grooves 406 are formed on the rear surface of the annular portion 401 of the base 40. The two grooves 406 extend in the diameter direction across the central portion of the annular portion 401 so as to be orthogonal to each other (in a cross shape). As shown in Figs. 14 and 15, path 84 is defined by the front surface of the cylindrical portion 142 and the grooves 406. As described above, the base 40 is held in a state where the rear surface of the annular portion 401 is in contact with the front surface of the cylindrical portion 142. However, the lubricant absorbed and held by the felt 801 in the recess 80 can reach the opening of the bearing housing portion 143 through path 84.

[0112] Paths 85 and 86 are paths for guiding the lubricant from the opening of the bearing housing portion 143 to the inside (specifically, the periphery of the rear end of the spindle 3).

[0113] Specifically, as shown in Fig. 5, a shallow groove 144 is formed on the surface defining the bearing housing portion 143. The groove 144 extends from the front end (projecting end) of the cylindrical portion 142 to the central portion of the bottom surface of the bearing housing portion 143. As shown in Fig. 14, path 85 is defined by the outer surface of the bearing 302 and the groove 144. The lubricant that has reached the opening of the bearing housing portion 143 through path 84 enters the bearing housing portion 143 and then the inside of the bearing 302 through path 85 and reaches the periphery of the rear end of the spindle 3. Therefore, the lubricant can enter path 81 inside the spindle 3 again.

[0114] Also, as shown in FIGS. 14 and 15, the front end of the bearing 302 (sliding bearing) is positioned slightly rearward of the front end of the cylindrical portion 142 of the partition wall 141. The path 86 is formed by a gap between the front end of the bearing 302 and the rear ends of the base 40 and the tapered sleeve 41. The lubricant that has reached the opening of the bearing housing portion 143 through the path 84 moves to the outer peripheral surface of the spindle 3 through the path 86, and can further reach the periphery of the rear end of the spindle 3 through the space between the bearing 302 and the spindle 3. Therefore, the lubricant can enter the path 81 inside the spindle 3 again.

[0115] In this embodiment, due to the rotation of the spindle 3, the pressure inside the bearing 302 becomes lower than the external pressure. In this embodiment, since the felt 801 can be used to store the lubricant in the recess 80, by providing the paths 84, 85, and 86, this pressure difference can be utilized to guide the lubricant from the recess 80 into the bearing 302. Also, since the spindle 3 reciprocates in the front-rear direction with respect to the bearing 302, the lubricant can also be guided from the recess 80 into the bearing 302 by the pump effect.

[0116] As described above, in this embodiment, the components (especially the first clutch 4) in the front housing 13 can be effectively lubricated by the circulation path 8 including the path 81 passing through the inside of the spindle 3 and the paths 82 to 86 outside the spindle 3. Note that the circulation path 8 may include a path different from this example, or an oil reservoir may be arranged at a position different from this example.

[0117] The correspondence between each component (feature) of the above embodiment and each component (feature) of the present disclosure or invention is shown below. However, each component of the embodiment is merely an example and does not limit each component of the present disclosure or the present invention.

[0118] The screwdriver 1 is an example of a "screw tightening tool". The main body housing 11 is an example of a "housing". The motor 2 and the output shaft 23 are examples of a "motor" and an "output shaft", respectively. The forward direction (screw tightening direction) is an example of a "first direction". The reverse direction (screw loosening direction) is an example of a "second direction". The spindle 3 is an example of a "spindle". The drive shaft A1 is an example of a "drive shaft". The first clutch 4 is an example of a "first clutch". The second clutch 5 is an example of a "second clutch".

[0119] The regulating mechanism 6 is an example of a "regulating mechanism". The rotating sleeve 61 (projection 613) is an example of a "first regulating portion". The regulating frame 62 (regulating portion 621) is an example of a "second regulating portion". The gear sleeve 47 is an example of a "rotating member". The regulating portion 621 is an example of a "wall portion". The first surface 622 and the second surface 623 are examples of a "first surface" and a "second surface", respectively. The tapered sleeve 41 is an example of a "sun member". The gear sleeve 47 is an example of a "ring member". The retainer 43 is an example of a "carrier". The roller 45 is an example of a "planetary roller". The tapered surface 411 is an example of a "tapered outer peripheral surface of the sun member". The tapered surface 475 is an example of a "tapered inner peripheral surface of the ring member". The first hole 811 and the second hole 812 are examples of a "first hole" and a "second hole", respectively. The circulation path 8 is an example of a "circulation path". The recess 80 is an example of a "storage portion".

[0120] Note that the above embodiments are merely illustrative, and the screw tightening tool according to the present disclosure is not limited to the illustrated screwdriver 1. For example, the following modifications can be made. Also, at least one of these modifications can be adopted in combination with at least one of the screwdriver 1 illustrated in the embodiments and the features described in each claim.

[0121] For example, in the above embodiment, the first clutch 4 employs a so-called planetary roller friction clutch. Instead of this, when the spindle 3 is in the initial position, it may be in the disengaged state, and when the spindle 3 moves rearward from the initial position, another type of clutch configured to shift to the engaged state may be employed. For example, a single-plate or multi-plate friction clutch or a cone friction clutch may be employed. Alternatively, a meshing type clutch may be employed. Also, when a so-called planetary roller friction clutch is employed, the configurations (shape, size, number, etc.) and arrangements of the sun member, ring member, carrier, and planetary rollers may be appropriately changed.

[0122] Similarly, for the second clutch 5, a clutch of a type different from the example of the above embodiment (for example, a sprag type one-way clutch) may be employed. Also, the arrangement of the second clutch 5 can be appropriately changed according to or regardless of the change of the first clutch 4.

[0123] Also, for the regulating mechanism 6, any configuration may be employed as long as it can regulate the forward and backward movement of the spindle 3 only when the motor 2 (output shaft 23) is rotationally driven in the forward direction.

[0124] For example, the rotating sleeve 61 may be operably connected to another member rotated by the output shaft 23 instead of the gear sleeve 47. Also, the number of protrusions 613 of the rotating sleeve 61 may be 1 or 3 or more. Alternatively, a portion of the rotating sleeve 61 other than the protrusion 613 may be capable of abutting against the regulating frame 62 (regulating portion 621). According to the change of the rotating sleeve 61, the regulating portion 621 of the regulating frame 62 and the number of protrusions 625 may also be changed.

[0125] Also, when the rotating sleeve 61 is disposed at the second position, the configuration that abuts against a part of the rotating sleeve 61 from the rear and restricts (hinders) the backward movement of the spindle 3 is not limited to the restricting frame 62 (restricting portion 621). For example, such a configuration may be provided integrally with the main body housing 11 (front housing 13) inside the main body housing 11. For example, a protrusion protruding toward the rotating sleeve 61 may be provided on the inner surface of the main body housing 11. Then, this protrusion may be disposed immediately behind the protrusion 613 of the rotating sleeve 61 only when the rotating sleeve 61 is disposed at the second position, and may be configured to abut against the protrusion 613 from the rear to restrict the backward movement of the spindle 3.

[0126] Furthermore, the configuration that restricts (hinders) the rotation of the rotating sleeve 61 beyond the first position and the second position by co-rotation is not limited to the protrusion 625 of the restricting frame 62. For example, similar to the modification example of the restricting portion 621 described above, at least one protrusion that abuts against a part of the rotating sleeve 61 and prevents further rotation may be provided on the inner surface of the main body housing 11 (front housing 13) when the rotating sleeve 61 is disposed at the first position and the second position.

[0127] Also, the screwdriver 1 may be configured to operate with power supplied from a DC power source instead of an external AC power source. In this case, the main body housing 11 is provided with, for example, a battery mounting portion that removably receives a rechargeable battery. The shape, connection structure of the main body housing 11 and the handle 17, the type and arrangement of the motor 2 can also be appropriately changed. For example, a DC motor (for example, a brushless DC motor) may be adopted for the motor 2. Also, the motor 2 may be arranged such that the rotation axis of the output shaft 23 intersects the drive shaft A1.

[0128] Furthermore, in view of the gist of the present invention and the above-described embodiment, the following aspects are constructed. Any one or a plurality of the following aspects may be adopted in combination with the screwdriver 1 of the embodiment and its modification examples, or the invention described in each claim. [Aspect 1] The output rotational speed during power transmission via the second clutch is higher than the output rotational speed during power transmission via the first clutch. According to this aspect, the rotational speed of the screw during the screw loosening operation can be made higher than that during the screw tightening operation, and the efficiency of the screw loosening operation can be realized. [Aspect 2] The spindle is always held at the initial position and is configured to move to an operating position behind the initial position in response to a rearward pressing. The first clutch is configured to cut off power transmission when the spindle is in front of the operating position, and to transmit power as the spindle is arranged at the operating position. [Aspect 3] The first restricting portion is configured to move in the front-rear direction integrally with the spindle. The second restricting portion is configured to inhibit the rearward movement of the spindle by abutting against the first restricting portion arranged at the second position from the rear. According to this aspect, by the second restricting portion abutting against the first restricting portion, the rearward movement of the spindle can be surely inhibited. [Aspect 4] The screw tightening tool further includes a first abutting portion configured to abut against the first restricting portion arranged at the first position in response to the rotation of the output shaft in the first direction and to restrict the rotation of the first restricting portion in the first direction, and a second abutting portion configured to abut against the first restricting portion arranged at the second position in response to the rotation of the output shaft in the second direction and to restrict the rotation of the first restricting portion in the second direction. The protrusion 625 of the embodiment is an example of the "first abutting portion" and "second abutting portion" of this aspect. According to this aspect, the first restricting portion can surely prevent the co-rotation from rotating beyond the first position and the second position. [Aspect 5] The second surface is on the rotation direction side of the first restricting portion when the output shaft is rotationally driven in the first direction with respect to the first surface in the circumferential direction, and is inclined rearward as it goes in the rotation direction of the first restricting portion when the output shaft is rotationally driven in the first direction. [Aspect 6] The second clutch is a one-way clutch configured to transmit rotation only in one direction and idle in the reverse direction. [Aspect 7] The one-way clutch is disposed radially inside the ring member and radially outside the spindle, and is configured to transmit the rotation of the ring member to the spindle only when the output shaft is rotationally driven in the second direction. [Aspect 8] The second hole opens to the outer peripheral surface of the spindle within the first clutch. [Aspect 9] The rear end portion of the spindle is supported slidably along the drive shaft and rotatably around the drive shaft by a bearing fixed to the housing. The reservoir portion is disposed radially outside the bearing. [Aspect 10] The circulation path includes at least one first path between the second hole and the reservoir portion and at least one second path between the reservoir portion and the inside of the bearing.

Explanation of Reference Numerals

[0129] 1: Screwdriver, 11: Body housing, 12: Rear housing, 13: Front housing, 131: Stopper portion, 133: Groove, 14: Central housing, 141: Partition wall, 142: Cylindrical portion, 143: Bearing housing portion, 144: Groove, 15: Locator, 17: Handle, 171: Gripping portion, 173: Trigger, 174: Main switch, 175: Forward / reverse lever, 176: Forward / reverse switch, 178: Controller, 179: Power cord, 2: Motor, 23: Output shaft, 231: Bearing, 233: Bearing, 24: Pinion gear, 301: Bearing, 302: Bearing, 3: Spindle, 31: Shaft, 311: Bit insertion hole, 32: Shaft, 321: Groove, 34: Flange, 35: Thrust bearing, 36: Ball, 4: First clutch, 40: Base, 401: Annular portion, 405: Concave portion, 406: Groove, 407: Leg, 41: Taper sleeve, 411: Tapered surface, 412: Projection, 414: Concave portion, 419: Concave portion, 43: Retainer, 431: Annular portion, 432: Concave portion, 433: Groove, 434: Holding arm, 45: Roller, 47: Gear sleeve, 470: Gear teeth, 471: Small diameter portion, 472: Shoulder portion, 473: Stop ring, 474: Large diameter portion, 475: Tapered surface, 478: Communication hole, 48: Bearing, 49: Biasing spring, 5: Second clutch, 51: One-way clutch, 6: Regulation mechanism, 61: Rotating sleeve, 611: Cylindrical wall, 613: Projection, 614: Inclined surface, 62: Regulation frame, 620: Cylindrical wall, 621: Regulation portion, 622: First surface, 623: Second surface, 625: Projection, 627: Projection, 66: Holding member, 661: Arm portion, 8: Circulation path, 80: Concave portion, 801: Felt, 81: Path, 811: First hole, 812: Second hole, 82: Path, 83: Path, 84: Path, 85: Path, 86: Path, 9: Driver bit, 90: Screw, 91: Workpiece, A1: Drive shaft

Claims

1. A screw tightening tool, comprising a housing, a motor housed in the housing and having an output shaft configured to be selectively rotationally driven in a first direction corresponding to the direction of tightening a screw and a second direction corresponding to the direction of loosening the screw and opposite to the first direction, a spindle supported by the housing so as to be movable along a drive shaft defining the front-rear direction of the screw tightening tool and rotatable around the drive shaft, the spindle having a front end portion configured to detachably attach a tip tool, a first clutch operably connected to the output shaft and the spindle and configured to enable power transmission from the output shaft to the spindle only when the output shaft is rotationally driven in the first direction, a second clutch operably connected to the output shaft and the spindle and configured to enable power transmission from the output shaft to the spindle only when the output shaft is rotationally driven in the second direction, wherein the output rotational speed of the spindle with respect to the rotational speed of the same output shaft is different between the power transmission via the first clutch when the output shaft is rotationally driven in the first direction corresponding to the direction of tightening the screw and the power transmission via the second clutch when the output shaft is rotationally driven in the second direction corresponding to the direction of loosening the screw. A screw tightening tool characterized by this.

2. The screw tightening tool according to claim 1, wherein the first clutch is configured to selectively transmit power according to the position of the spindle in the front-rear direction, and the second clutch is configured to transmit the power regardless of the position of the spindle in the front-rear direction. A screw tightening tool characterized by this.

3. The screw tightening tool according to claim 2, further comprising a regulating mechanism configured to regulate the movement of the spindle in the front-rear direction only when the output shaft is rotationally driven in the second direction.

4. The screw tightening tool according to claim 3, wherein the regulating mechanism is A first restricting portion rotatable in the circumferential direction around the drive shaft between a first position and a second position, the first restricting portion being arranged at the first position in response to rotation of the output shaft in the first direction and arranged at the second position in response to rotation of the output shaft in the second direction. A second restricting portion configured to allow movement of the spindle in the front-rear direction when the first restricting portion is in the first position and to restrict movement of the spindle in the front-rear direction when the first restricting portion is in the second position. The screwing tool is characterized by including the second restricting portion. **Claim 5** The screwing tool according to claim 4, further comprising a rotating member arranged between the output shaft and the spindle on the power transmission path and configured to be rotated by the output shaft. The first restricting portion is arranged around the rotating member so as to be selectively rotatable with respect to the rotating member, and is configured to rotate together with the rotating member only between the first position and the second position. The second restricting portion is substantially immovable with respect to the housing. The screwing tool is characterized by this. **Claim 6** The screwing tool according to claim 4 or 5, the second restricting portion includes a wall portion arranged behind the first restricting portion and extending in the circumferential direction, a front end face of the wall portion extends in a direction orthogonal to the drive shaft and includes a first face configured to abut against the first restricting portion arranged at the second position from behind, and a second face extending obliquely rearward from one end of the first face in the circumferential direction and configured to allow movement of the spindle in the front-rear direction. The screwing tool is characterized by this. **Claim 7** The screwing tool according to any one of claims 1 to 6, the first clutch is configured to also serve as a speed reduction mechanism. The screwing tool is characterized by this. **Claim 8** The screwing tool according to claim 7, the speed reduction mechanism includes a sun member, a ring member, and a carrier arranged coaxially with the drive shaft, and a plurality of planetary rollers rotatably held by the carrier. The ring member is configured to be rotated by the output shaft. The carrier is configured to rotate integrally with the spindle. The plurality of planetary rollers are at least partially disposed between the tapered outer peripheral surface of the sun member and the tapered inner peripheral surface of the ring member in the radial direction of the ring member. The ring member is integrally movable with the spindle in the front-rear direction with respect to the sun member. The first clutch is configured to transmit power by selectively bringing the plurality of planetary rollers into frictional contact with the outer peripheral surface of the sun member and the inner peripheral surface of the ring member in response to the rearward movement of the spindle from its initial position. A screw tightening tool characterized by that.

9. A screw tightening tool according to any one of claims 1 to 8, The spindle has a first hole extending forward from the rear end of the spindle and a second hole communicating with the first hole and extending in a direction intersecting the first hole and opening to the outer peripheral surface of the spindle. The screw tightening tool further includes a circulation path that returns the lubricant discharged from the spindle through the first hole and the second hole to the rear end of the spindle in the housing. A screw tightening tool characterized by that.

10. A screw tightening tool according to claim 9, A screw tightening tool characterized in that a storage portion for the lubricant is provided on the circulation path.

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