Power tool

Abstract

To provide improvement on an electric tool performing different actions according to a rotative direction of a motor.SOLUTION: An electric tool includes a motor and a gear reducer. The motor has a motor shaft rotatable in two directions of a normal direction and a reverse direction. The gear reducer is connected operably to the motor shaft. The gear reducer is constituted so that a reduction ratio is changed according to change of the rotation direction of the motor shaft.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to power tools. [Background technology]

[0002] There are known power tools that are equipped with a motor that can rotate in two directions, forward and reverse, and that can perform different operations when the motor rotates in the forward direction and when the motor rotates in the reverse direction. For example, a fastening tool disclosed in Patent Document 1 is configured to move a screw shaft backward to tighten a fastener when the motor rotates in the forward direction, and to return the screw shaft forward to its initial position when the motor rotates in the reverse direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-103257 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a power tool that performs different operations depending on the rotation direction of a motor, such as the fastening tool described above, the required rotation speed and output torque may differ depending on each operation.

[0005] The present disclosure aims to provide an improvement to a power tool that performs different operations depending on the rotation direction of a motor. [Means for solving the problem]

[0006] According to one aspect of the present disclosure, there is provided a power tool including a motor having a motor shaft rotatable in two directions, a forward direction and a reverse direction, the gear reducer operably coupled to the motor shaft, and the gear reducer configured to change a reduction ratio in response to a change in the direction of rotation of the motor shaft.

[0007] According to this aspect, the reduction ratio of the gear reducer, and therefore the rotation speed (output speed) of the output shaft of the gear reducer and the torque (output torque) output from the gear reducer can be changed depending on whether the rotation direction of the motor shaft is forward or reverse. Therefore, it is possible to realize a power tool that can perform two operations requiring different speeds and torques by simply changing the rotation direction of the motor without controlling the rotation speed of the motor.

[0008] In one aspect of the present disclosure, the gear reducer may include at least one planetary gear mechanism. Each of the at least one planetary gear mechanisms includes a sun gear, an internal gear, a carrier, and a plurality of planetary gears. The gear reducer may be configured to be able to change the reduction ratio by changing the number of effective stages of the at least one planetary gear mechanism. According to this aspect, by using the planetary gear mechanism, it is possible to obtain a large reduction ratio with a small size compared to a gear reducer combined with a spur gear or the like. In addition, the reduction ratio can be changed rationally by changing the number of effective stages of the planetary gear mechanism.

[0009] In one aspect of the present disclosure, the power tool may further include a one-way clutch and a locking mechanism operably connected to the one-way clutch. The one-way clutch may be provided on a transmission path from the motor shaft to the sun gear. The one-way clutch may be configured to allow relative rotation of the sun gear with respect to the one-way clutch when the motor shaft rotates in a first direction, and to rotate integrally with the sun gear when the motor shaft rotates in a second direction. The first direction is one of the forward direction and the reverse direction, and the second direction is the other of the forward direction and the reverse direction. The locking mechanism may be configured to lock the internal gear so that it cannot rotate when the one-way clutch allows relative rotation of the sun gear, and to rotate the internal gear integrally with the sun gear when the one-way clutch rotates integrally with the sun gear.

[0010] According to this aspect, the one-way clutch and the locking mechanism work together to enable the planetary gear mechanism to function effectively when the motor shaft rotates in a first direction, and disable the function of the planetary gear mechanism when the motor shaft rotates in a second direction. In particular, the one-way clutch is a clutch that automatically performs different operations depending on the rotation direction, so that a change in the rotation direction of the motor shaft can be efficiently linked to a change in the operation of the locking mechanism. With such a rational configuration, the electric tool of this aspect can perform an operation requiring a relatively low speed and / or a relatively high torque when the motor shaft rotates in the first direction, and can perform an operation requiring a relatively high speed and / or a relatively low torque when the motor shaft rotates in the second direction.

[0011] In one aspect of the present disclosure, the gear reducer may include a multi-stage (multiple sets) planetary gear mechanism. The lock mechanism may be configured to act on an internal gear of a second-stage or subsequent-stage planetary gear mechanism among the multi-stage planetary gear mechanisms. According to this aspect, after being reduced in speed by at least the first-stage planetary gear mechanism, the lock mechanism acts on the internal gear in the second-stage or subsequent-stage planetary gear mechanism, thereby reducing the load on the lock mechanism and improving its durability.

[0012] In one aspect of the present disclosure, the power tool may further include a movable member operably connected to the gear reducer and configured to move with the drive of the motor. The power tool may be configured to operate in one cycle including a forward stroke in which the movable member moves in a predetermined direction and a return stroke in which the movable member moves in a direction opposite to the predetermined direction. The rotation direction of the motor shaft may be changed between the forward stroke and the return stroke. According to this aspect, a power tool capable of exhibiting the required speed and torque in the forward stroke and the return stroke can be realized by simply changing the rotation direction of the motor in each of the forward stroke and the return stroke.

[0013] In one aspect of the present disclosure, the power tool may be a fastening tool configured to fasten a work material via a fastener. The fastening tool is a typical example of a power tool that performs different operations in a forward stroke and a return stroke in a fastening operation. According to this aspect, a fastening tool that can efficiently perform the fastening operation can be realized.

[0014] In one aspect of the present disclosure, the movable member may be configured to grip a portion of the fastener. The movable member may be configured to move from an initial position in a predetermined direction while pulling the fastener against the work material in a forward stroke, and to return to the initial position in a direction opposite to the predetermined direction without pulling the fastener in a return stroke. The reduction ratio in the forward stroke may be greater than the reduction ratio in the return stroke. According to this aspect, a fastening tool can be realized that exerts a relatively large torque in a forward stroke in which the movable member pulls the fastener, and can return to the initial position relatively quickly and efficiently in a return stroke in which the movable member returns to the initial position without pulling the fastener.

[0015] In one aspect of the present disclosure, the power tool may further include a screw feed mechanism disposed on the transmission path between the gear reducer and the movable member and configured to convert the rotational motion of the output shaft of the gear reducer into the linear motion of the movable member. According to this aspect, by using the screw feed mechanism, a relatively large torque can be efficiently converted into the linear motion.

[0016] In one aspect of the present disclosure, the reduction ratio when the rotation direction of the motor shaft is one of the forward and reverse directions may be 2.5 times or more of the reduction ratio when the rotation direction of the motor shaft is the other of the forward and reverse directions. According to this aspect, it is possible to realize a power tool capable of performing two operations with relatively large differences in speed and torque by changing the rotation direction of the motor.

[0017] In one aspect of the present disclosure, the power tool may further include a control device configured to control an operation of the power tool. The control device may be configured to change a rotation direction of the motor when a predetermined event is recognized. According to this aspect, the control device that recognizes the predetermined event automatically switches the rotation direction of the motor, so that the reduction ratio can be changed appropriately and efficiently. [Brief description of the drawings]

[0018] [Figure 1] FIG. [Diagram 2] FIG. [Diagram 3] FIG. 2 is an exploded perspective view of a first-stage carrier, a second-stage sun gear and an internal gear, and a reduction ratio change mechanism. [Figure 4] 4 is a cross-sectional view taken along line IV-IV in FIG. 2, illustrating the operation of the locking mechanism when the motor is driven in the forward direction. FIG. [Diagram 5] 5 is a cross-sectional view taken along line VV in FIG. 4. [Figure 6] 6 is a cross-sectional view taken along line VI-VI in FIG. [Figure 7] FIG. 4 is a cross-sectional view corresponding to FIG. 3, illustrating the operation of the locking mechanism when the motor is driven in the reverse direction. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, an embodiment will be described with reference to the drawings. A fastening tool 1 of this embodiment is configured to fasten a work material using a fastener 8. The fastener 8 is a well-known fastener (more specifically, a multi-piece swage type fastener) composed of a pin 81 and a collar 85.

[0020] First, a schematic configuration of the fastening tool 1 will be described.

[0021] As shown in FIG. 1, the outer shell of the fastening tool 1 is mainly formed by a main body housing 11, a nose 13, a handle 15, and a battery housing 17. The main body housing (also called a tool body) 11 is formed in a rectangular box shape as a whole and extends along a predetermined drive axis A1. The main body housing 11 accommodates a motor 2 and a drive mechanism 3. The nose 13 protrudes from one end of the main body housing 11 in the longitudinal direction along the drive axis A1. The handle 15 protrudes from a central portion of the main body housing 11 in the longitudinal direction in a direction intersecting the drive axis A1 (more specifically, in a direction roughly perpendicular to the drive axis A1). The handle 15 is provided with a trigger 151 that is pulled (pushed) by a user. The battery housing 17 is connected to the protruding end of the handle 15. A rechargeable battery 182 can be attached to and detached from the battery housing 17.

[0022] When the user engages the fastener 8 with the tip of the nose 13 and pulls the trigger 151, the motor 2 is driven, the pin 81 is pulled axially against the collar 85 and the work material W, and the work material W is fastened by the fastener 8.

[0023] In the following, for the sake of convenience, the direction of the fastening tool 1 is defined as the extension direction of the drive axis A1 (or the long axis of the main body housing 11) as the front-rear direction of the fastening tool 1. In the front-rear direction, the side where the nose 13 is arranged is defined as the front side, and the opposite side is defined as the rear side. In addition, the direction perpendicular to the drive axis A1 and corresponding to the extension direction of the long axis of the handle 15 is defined as the up-down direction. In the up-down direction, the protruding end side of the handle 15 (the battery housing 17 side) is defined as the lower side, and the base end side of the handle 15 (the main body housing 11 side) is defined as the upper side. In addition, the direction perpendicular to the front-rear direction and the up-down direction is defined as the left-right direction.

[0024] The detailed configuration of the fastening tool 1 will be described below.

[0025] First, a description will be given of the internal structure of the main body housing 11. As shown in Fig. 1, the main body housing 11 mainly accommodates a motor 2 and a drive mechanism 3 driven by the motor 2.

[0026] The motor 2 is accommodated in the lower part of the rear end of the main body housing 11. In this embodiment, a brushless direct current (DC) motor is used as the motor 2. The motor 2 includes a stator 21, a rotor 22, and a motor shaft 23 that rotates integrally with the rotor. The motor 2 is disposed such that the rotation axis A2 of the motor shaft 23 extends below (specifically, directly below) the drive shaft A1 and parallel to the drive shaft A1 (that is, in the front-rear direction). The front end of the motor shaft 23 protrudes into the gear case 40 of the reduction gear 4. In this embodiment, the rotor 22 and the motor shaft 23 can rotate in two directions, a forward direction and a reverse direction. In this embodiment, the forward direction corresponds to a direction in which the screw shaft 56 and the pin gripping portion 63 described later are moved backward. The reverse direction corresponds to a direction in which the screw shaft 56 and the pin gripping portion 63 are moved forward. Hereinafter, driving the motor 2 to rotate in the forward direction is also referred to as forward driving, and driving the motor 2 to rotate in the reverse direction is also referred to as reverse driving.

[0027] The drive mechanism 3 will be described below. The drive mechanism 3 is configured to move a pin gripping portion 63, which will be described later, in the front-rear direction relative to the anvil 61 along the drive shaft A1 by the power of the motor 2. In this embodiment, the drive mechanism 3 includes a reducer 4, a nut drive gear 311 provided on the first intermediate shaft 31, an idle gear 331 provided on the second intermediate shaft 33, and a ball screw mechanism 5. These components will be described in order below.

[0028] The reducer 4 is disposed coaxially with the motor 2 in front of the motor 2 within the main housing 11. The reducer 4 is a reducer using a planetary gear mechanism, and is configured to reduce the rotation speed of the motor shaft 23 according to a reduction ratio, increase the torque, and output the torque to the first intermediate shaft 31. In this embodiment, the reducer 4 is a multi-stage planetary reducer. More specifically, as shown in FIG. 2, the reducer 4 includes a gear case 40 and three-stage (three sets of) planetary gear mechanisms 41, 42, 43 housed in the gear case 40. The gear case 40 is supported by the main housing 11 so as not to rotate.

[0029] The first stage (input side) planetary gear mechanism 41 includes a sun gear 411 , an internal gear (also called a ring gear) 412 , a carrier 415 , and a plurality of planetary gears 418 .

[0030] The sun gear 411 is fixed to the front end of the motor shaft 23. That is, in this embodiment, the motor shaft 23 functions as an input shaft for the reduction gear 4. The internal gear 412 is held fixedly within the gear case 40. That is, the internal gear 412 is substantially immovable in the front-rear direction relative to the gear case 40, and is substantially immovable around the rotation axis A2. The planetary gear 418 is supported by the carrier 415 and meshes with the sun gear 411 and the internal gear 412. The carrier 415 has a shaft 416 that extends forward along the rotation axis A2. When the motor 2 is driven, the carrier 415 (shaft 416) rotates in the same direction as the motor shaft 23.

[0031] The second stage planetary gear mechanism 42 includes a sun gear 421 , an internal gear (also called a ring gear) 422 , a carrier 425 , and a plurality of planetary gears 428 .

[0032] The sun gear 421 is fixed to the front end of the shaft 416 of the first stage carrier 415. Therefore, when the motor 2 is driven, the sun gear 421 rotates integrally with the carrier 415 in the same direction as the motor shaft 23. The internal gear 422 is fitted into the gear case 40. Four protrusions 423 protruding rearward are provided at the rear end of the internal gear 422. The protrusions 423 are arranged at approximately equal intervals in the circumferential direction of the internal gear 422. The internal gear 422 is substantially immovable in the front-rear direction relative to the gear case 40, but is selectively rotatable around the rotation axis A2. The internal gear 422 is allowed to rotate or not by the reduction ratio change mechanism 7 depending on the rotation direction of the motor 2. The reduction ratio change mechanism 7 will be described in detail later. The planetary gear 428 is supported by the carrier 425 and meshes with the sun gear 421 and the internal gear 422. The carrier 425 has a shaft 426 that extends forward along the rotation axis A2.

[0033] The third stage (final stage, output side) planetary gear mechanism 43 includes a sun gear 431 , an internal gear (also called a ring gear) 432 , a carrier 435 , and a plurality of planetary gears 438 .

[0034] The sun gear 431 is fixed to the front end of the shaft 426 of the second-stage carrier 425. The internal gear 432, like the first-stage internal gear 412, is held fixed within the gear case 40. The planetary gear 438 is supported by the carrier 435 and meshes with the sun gear 431 and the internal gear 432. The carrier 435 has a shaft 436 that extends forward along the rotation axis A2. The third-stage (final-stage) shaft 436 functions as the final output shaft of the reducer 4.

[0035] As shown in Fig. 1, the first intermediate shaft 31 extends forward from the reducer 4 coaxially with the motor shaft 23 and the reducer 4 within the main housing 11. The first intermediate shaft 31 is coupled to a shaft 436 (see Fig. 2) of a third-stage carrier 435 of the reducer 4. The first intermediate shaft 31 is rotatably supported around the rotation axis A2 by two bearings supported by the main housing 11, and rotates integrally with the carrier 435. The nut drive gear 311 is provided integrally with the first intermediate shaft 31 on the outer periphery of the first intermediate shaft 31.

[0036] The second intermediate shaft 33 extends parallel to the first intermediate shaft 31 above (specifically, directly above) the first intermediate shaft 31. The idle gear 331 is supported by the second intermediate shaft 33 via a bearing and is rotatable around the axis of the second intermediate shaft 33. The idle gear 331 meshes with the nut drive gear 311 and a driven gear 511 of a nut 51 (described later), but does not affect the ratio of the rotation speeds of the two.

[0037] The ball screw mechanism 5 is a well-known mechanism mainly composed of a nut 51 and a screw shaft 56. In this embodiment, the ball screw mechanism 5 is configured to convert the rotational motion of the nut 51 into the linear motion of the screw shaft 56, and to linearly move a pin gripping portion 63, which will be described later. The ball screw mechanism 5 is an example of a screw feed mechanism, and can efficiently convert a relatively large torque into linear motion.

[0038] The nut 51 is supported relative to the main body housing 11 in a state where it is substantially immovable in the front-rear direction and rotatable around the drive shaft A1. The nut 51 is formed in a cylindrical shape and has a driven gear 511 provided integrally on the outer periphery. The nut 51 is supported by a pair of radial bearings supported by the main body housing 11 on the front and rear sides of the driven gear 511. The nut drive gear 311 and the driven gear 511 are configured as a reduction gear mechanism.

[0039] The screw shaft 56 is engaged with the nut 51 in a state where it is substantially unable to rotate around the drive axis A1 with respect to the main housing 11 and is movable in the front-rear direction along the drive axis A1. More specifically, the screw shaft 56 is configured as an elongated body and is inserted into the nut 51 so as to extend along the drive axis A1. Although detailed illustration is omitted, a spiral groove is formed on the inner peripheral surface of the nut 51 and the outer peripheral surface of the screw shaft 56. A large number of balls are arranged to be able to roll within the track defined by these spiral grooves. The screw shaft 56 is engaged with the nut 51 via these balls. Although detailed illustration is omitted, a pair of arms extending left and right from the screw shaft 56 are provided at the rear end of the screw shaft 56. Each arm rotatably supports a roller. The roller is engaged with a guide groove of a roller guide fixed to the main housing 11. The roller is able to roll in the front-rear direction along the guide groove in a state where the movement in the up-down direction is restricted.

[0040] With this configuration, when the nut 51 is rotated around the drive shaft A1, the screw shaft 56 moves linearly in the front-rear direction relative to the nut 51 and the main housing 11.

[0041] An extension shaft 561 is coaxially connected and fixed to the rear end of the screw shaft 56, and is integrated with the screw shaft 56. Hereinafter, the integrated screw shaft 56 and the extension shaft 561 are collectively referred to as the drive shaft 560. The drive shaft 560 has a through hole that passes through the drive shaft 560 along the drive axis A1. A collection container 115 is removably attached to the rear end of the main body housing 11. The collection container 115 is a container for storing a part of the shaft portion of the pin 81 (hereinafter, referred to as the pintail) that has been separated from the fastener 8. The pintail that has been separated from the fastener 8 reaches the collection container 115 through the through hole of the drive shaft 560, and is stored in the collection container 115.

[0042] The nose 13 will be described below. As shown in FIG. 1, the nose 13 is mainly composed of an anvil 61 and a pin gripping portion 63. The anvil 61 is configured to be able to abut (engage) with a collar 85 of the fastener 8. The anvil 61 is connected to the main body housing 11 via a connecting member 62. The pin gripping portion 63 is configured to be able to grip a pin 81 of the fastener 8. The pin gripping portion 63 is held so as to be able to move relatively to the anvil 61 in the front-rear direction along the drive shaft A1. Note that the configurations of the anvil 61 and the pin gripping portion 63 are known, so they will be briefly described below.

[0043] The anvil 61 is generally a cylindrical body, and has a bore extending along the drive shaft A1. The pin gripping portion 63 is held in the bore coaxially with the anvil 61, and can slide in the bore. The tip of the bore is configured to have a smaller diameter than the other portions, and can abut (engage) with the collar 85. Although detailed illustration is omitted, the pin gripping portion 63 has a plurality of claws (also called jaws) capable of gripping the shaft portion of the pin 81. The pin gripping portion 63 is configured such that the gripping force of the claws increases as the pin gripping portion 63 moves rearward from the initial position relative to the anvil 61. The rear end of the pin gripping portion 63 is connected to the front end of the screw shaft 56 via a connecting member 64. The connecting member 64 has a through hole that penetrates the connecting member 64 along the drive shaft A1 and communicates with the through hole of the drive shaft 560.

[0044] The handle 15 will be described below. As shown in FIG. 1, the handle 15 is formed in a long cylindrical shape, and extends downward from the lower center in the front-rear direction of the main body housing 11. The handle 15 is a portion that is held by the user, and a trigger 151 that can be pulled by the user is provided at its upper end. A switch 152 is housed inside the handle 15. The switch 152 is normally maintained in an OFF state, and is turned ON in response to the pulling of the trigger 151. The switch 152 is electrically connected to the controller 170 by an electric wire (not shown), and outputs an ON signal to the controller 170 when turned ON.

[0045] The battery housing 17 will be described below. As shown in Fig. 1, the battery housing 17 is configured as an inverted U-shaped hollow body that is long in the front-rear direction. A controller 170 is accommodated in the battery housing 17. The controller 170 includes a control circuit 171 that controls the fastening tool 1. In this embodiment, the control circuit 171 is configured as a microcomputer including a CPU, a ROM, a RAM, and the like. Although detailed illustration is omitted, the control circuit 171 is mounted on a board accommodated in a case together with a drive circuit for the motor 2, and the like.

[0046] Two battery attachment parts 181 are provided at the lower end of the battery housing 17. Each battery attachment part 181 is configured to allow a battery 182 to be attached and detached. That is, in this embodiment, two batteries 182 can be attached to the fastening tool 1. The battery 182 is a repeatedly rechargeable power source for supplying power to each part of the fastening tool 1 and the motor 2, and is also called a battery pack. Note that the configurations of the battery attachment parts 181 and the battery 182 are well known, so a description thereof will be omitted.

[0047] The following describes the reduction ratio change mechanism 7. As described above, the reduction ratio change mechanism 7 is configured to selectively permit or prohibit rotation of the internal gear 422 of the second-stage planetary gear mechanism 42 of the reducer 4 in accordance with the rotation direction of the motor 2. When the permission or prohibition of rotation of the internal gear 422 is changed, the number of effective stages of the reducer 4 (the number of planetary gear mechanisms that function effectively) and therefore the reduction ratio of the reducer 4 are changed.

[0048] As shown in FIGS. 2 and 3, the speed reduction ratio change mechanism 7 includes a one-way clutch 70 and a lock mechanism 71.

[0049] The one-way clutch 70 is a clutch having a mechanism for transmitting rotation in only one direction and rotating freely in the opposite direction. In this embodiment, the one-way clutch 70 is a general-purpose one-way clutch having a well-known configuration in which a number of rollers biased by springs are supported in a cylindrical sleeve. The one-way clutch 70 is fitted to the outer periphery of the shaft 416 of the first-stage carrier 415. When the motor shaft 23 and the shaft 416 rotate in the forward direction, the one-way clutch 70 rotates freely with respect to the shaft 416 (i.e., it does not rotate together with the carrier 415 and does not transmit rotation). On the other hand, when the motor shaft 23 and the shaft 416 rotate in the opposite direction, the one-way clutch 70 rotates integrally with the shaft 416 (i.e., it is locked to the shaft 416 and rotates integrally with the shaft 416, enabling transmission of rotation).

[0050] The lock mechanism 71 is configured to switch between allowing and disallowing rotation of the second-stage internal gear 422 depending on whether the one-way clutch 70 rotates freely relative to the first-stage carrier 415 (shaft 416) or rotates integrally therewith.

[0051] The following describes in detail the configuration of the lock mechanism 71. As shown in FIGS.

[0052] The retainer 72 is a member that holds the roller 73 so as to be movable in the circumferential direction around the rotation axis A2 relative to the retainer 72. The retainer 72 includes a cylindrical portion 721, a base portion 723, and four protrusions 725. The cylindrical portion 721 extends in the front-rear direction along the rotation axis A2 and forms the center portion of the retainer 72. The base portion 723 is an annular portion that protrudes radially outward from the rear end of the cylindrical portion 721. The protrusions 725 are arc-shaped wall portions that are arranged at approximately equal intervals on the outer edge of the base portion 723 and protrude forward from the outer edge of the base portion 723. A space is formed between the cylindrical portion 721 and the protrusions 725 in the radial direction. The front end of the protrusions 725 is located rearward of the front end of the cylindrical portion 721 (i.e., the protrusions 725 are shorter in the front-rear direction than the cylindrical portion 721).

[0053] The cylindrical portion 721 of the retainer 72 is fixed to the outer periphery of the sleeve of the one-way clutch 70 by press-fitting. That is, the retainer 72 is integrated with the one-way clutch 70 in terms of rotation. Therefore, the retainer 72 can selectively rotate with respect to the first-stage carrier 415. In detail, when the motor shaft 23 and the shaft 416 rotate in the forward direction, the retainer 72 rotates idly with respect to the shaft 416 together with the one-way clutch 70 (that is, does not rotate together with the shaft 416). On the other hand, when the motor shaft 23 and the shaft 416 rotate in the reverse direction, the retainer 72 rotates integrally with the one-way clutch 70 and the shaft 416 together with the one-way clutch 70.

[0054] The rollers 73 are cylindrical members (pins). The diameter of each roller 73 is approximately uniform, and is smaller than the distance between two adjacent protrusions 725 of the retainer 72, and is larger than the radial thickness of the protrusions 725. The length of the rollers 73 is approximately the same as the length of the protrusions 725 protruding from the front surface of the base portion 723 of the retainer 72. The two rollers 73 are disposed in two diagonally opposite corners of the four spaces formed between the protrusions 725 of the retainer 72, and extend in the front-rear direction.

[0055] The lock sleeve 74 is a substantially cylindrical member. The lock sleeve 74 is fitted coaxially with the reducer 4 inside the gear case 40, in front of the first-stage internal gear 412. The outer circumferential surface of the lock sleeve 74 is provided with a plurality of protrusions 741 that protrude radially outward and extend from the front end to the rear end of the lock sleeve 74. These protrusions 741 are formed on the inner circumferential surface of the gear case 40 and engage with a plurality of grooves 401 (see FIG. 4) that extend in the front-rear direction. This holds the lock sleeve 74 non-rotatably relative to the gear case 40.

[0056] Furthermore, the lock sleeve 74 is disposed around (radially outward from) the retainer 72. The front end of the lock sleeve 74 is located forward of the front ends of the projection 725 and the roller 73, and the rear end of the lock sleeve 74 is located rearward of the rear end of the retainer 72. Thus, the entire projection 725 and roller 73 of the retainer 72 are disposed inside the lock sleeve 74. The inner diameter of the lock sleeve 74 is set to be roughly the same as or slightly larger than the outer diameter of the base portion 723 of the retainer 72. The retainer 72 is selectively rotatable with respect to the lock sleeve 74.

[0057] The lock cam 75 is operably connected to the retainer 72 and is selectively rotated by the retainer 72. The lock cam 75 is also connected to the second stage internal gear 422 and is rotatable around the rotation axis A2 relative to the gear case 40 together with the internal gear 422. The lock cam 75 is formed as a whole as a tubular member having a through hole with a circular cross section that extends along the rotation axis A2, and includes a base portion 751, a flange portion 753, and a cam portion 755.

[0058] The base portion 751 is a disk-shaped portion and forms the front half of the lock cam 75. The flange portion 753 is a portion that protrudes radially outward from the outer circumferential surface of the base portion 751. The outer diameter of the flange portion 753 is set to be approximately the same as the outer diameter of the second stage internal gear 422. The flange portion 753 is provided with four recesses 754 (see FIG. 3). Each recess 754 is recessed radially inward from the outer edge of the flange portion 753. The recesses 754 are disposed at approximately equal intervals in the circumferential direction of the flange portion 753. The recesses 754 have a shape that matches the protrusion 423 of the internal gear 422, and are always engaged with the protrusion 423. The lock cam 75 is integrated with the internal gear 422 in terms of rotation by the engagement between the recesses 754 and the protrusion 423.

[0059] The cam portion 755 is a portion that protrudes rearward from the rear surface of the base portion 751, and forms the rear half of the lock cam 75. The cam portion 755 has two protrusions 756 and two flat portions 757. The protrusions 756 are provided diagonally across the rotation axis A2, and protrude radially outward from the outer circumferential surface of the cam portion 755. The two flat portions 757 are respectively disposed at approximately intermediate positions between the two protrusions 756 in the circumferential direction of the cam portion 755. Of the outer circumferential surface of the cam portion 755, a portion between the protrusions 756 and the flat portions 757 is a curved surface that corresponds to the outer circumferential surface of a cylinder. The flat portions 757 are part of the outer circumferential surface of the cam portion 755, are provided diagonally across the rotation axis A2, and extend parallel to each other and parallel to the rotation axis A2.

[0060] The radial distance between the flat portion 757 and the inner circumferential surface of the lock sleeve 74 is maximum at the center of the flat portion 757 and is set to be slightly larger than the diameter of the roller 73. The radial distance between the flat portion 757 and the inner circumferential surface of the lock sleeve 74 decreases toward the end of the flat portion 757. The radial distance between the end of the flat portion 757 and the inner circumferential surface of the lock sleeve 74 is set to be smaller than the diameter of the roller 73.

[0061] The lock cam 75 having the above configuration is fitted from the front into the outer periphery of the cylindrical portion 721 of the retainer 72. The two protrusions 756 of the lock cam 75 are arranged in two of the four spaces (specifically, two spaces in which the rollers 73 are not arranged) formed between the protrusions 725 of the retainer 72 in the circumferential direction. In addition, the portion of the cam portion 755 other than the protrusions 756 is arranged in the space formed between the cylindrical portion 721 and the protrusions 725 of the retainer 72 in the radial direction. The roller 73 is arranged between the flat portion 757 of the cam portion 755 of the lock cam 75 and the inner circumferential surface of the lock sleeve 74 in the radial direction. In addition, the roller 73 is arranged between the rear surface of the base portion 751 of the lock cam 75 and the front surface of the base portion 723 of the retainer 72 in the front-rear direction.

[0062] Hereinafter, the operation of the speed reduction ratio change mechanism 7 (the one-way clutch 70 and the lock mechanism 71) will be described.

[0063] First, the operation when the motor 2 is driven in the forward direction will be described.

[0064] When the motor shaft 23 rotates in the forward direction, the first stage carrier 415 (shaft 416) and the second stage sun gear 421 also rotate in the forward direction. At this time, as described above, the one-way clutch 70 rotates idly relative to the shaft 416 and does not transmit rotation to the retainer 72. Therefore, the retainer 72 does not actively rotate.

[0065] The second-stage sun gear 421 rotates the second-stage planetary gear 428. The second-stage planetary gear 428 also meshes with the second-stage internal gear 422, and therefore rotates the second-stage internal gear 422 in the reverse direction relative to the gear case 40. At this time, the lock cam 75 also rotates in the reverse direction (the direction of the arrow in FIG. 4), and accordingly the roller 73 moves relatively in the direction toward the end of the flat portion 757.

[0066] As shown in FIG. 4, before the projection 756 of the lock cam 75 abuts against the projection 725 of the retainer 72, the roller 73 is wedged between the flat portion 757 and the inner peripheral surface of the lock sleeve 74 at a position closer to the end of the flat portion 757 than the center of the flat portion 757. Hereinafter, the position of the roller 73 relative to the lock sleeve 74 and the lock cam 75 at this time is also referred to as the locked position. As a result, the lock cam 75 is locked to the lock sleeve 74 via the roller 73, and rotation relative to the gear case 40 is prohibited. When the lock cam 75 is locked, the internal gear 422 is also unable to rotate relative to the gear case 40, so that thereafter, the planetary gear 428 revolves around the sun gear 421 while rotating on its own axis, and the carrier 425 rotates in the forward direction.

[0067] As described above, when the motor shaft 23 rotates in the forward direction and the first-stage carrier 415 and the second-stage sun gear 421 rotate relative to the one-way clutch 70, the lock mechanism 71 locks the second-stage internal gear 422 so that it cannot rotate. This allows the second-stage planetary gear mechanism 42 to function effectively. Therefore, when the motor shaft 23 rotates in the forward direction, the number of effective stages of the reducer 4 is three.

[0068] The operation when the motor 2 is driven in the reverse direction will be described.

[0069] When the motor shaft 23 rotates in the reverse direction, the first stage carrier 415 (shaft 416) and the second stage sun gear 421 also rotate in the reverse direction. At this time, the one-way clutch 70 is locked to the shaft 416 as described above and transmits the rotation of the shaft 416 to the retainer 72, so that the retainer 72 also rotates in the reverse direction (the direction of the arrow in FIG. 7).

[0070] As shown in FIG. 7, two of the protrusions 725 of the retainer 72 come into contact with the protrusions 756 of the lock cam 75 and press them in the opposite direction. At the same time, the remaining two protrusions 725 come into contact with the roller 73 and press it in the opposite direction, moving it to a position where the roller 73 is released from being sandwiched between the flat portion 757 and the inner circumferential surface of the lock sleeve 74 (a position corresponding to approximately the center of the flat portion 757 in this embodiment). Hereinafter, the position of the roller 73 relative to the lock sleeve 74 and the lock cam 75 at this time is also referred to as an unlocked position. At the unlocked position, the roller 73 is disposed loosely between the flat portion 757 and the inner circumferential surface of the lock sleeve 74, so that the lock cam 75 is rotatable relative to the lock sleeve 74. Thus, the rotation of the retainer 72 is transmitted to the lock cam 75, and the lock cam 75 rotates in the opposite direction together with the retainer 72. As a result, the second stage internal gear 422 rotates integrally with the first stage carrier 415 and the second stage sun gear 421 in the opposite direction.

[0071] On the other hand, the second-stage sun gear 421 tries to rotate the second-stage planetary gear 428, but the planetary gear 428 cannot rotate (spin) because the sun gear 421 and the internal gear 422 rotate integrally. As a result, the second-stage carrier 425 rotates in the opposite direction integrally with the sun gear 421 and the internal gear 422. The rotational speed of the carrier 425 is the same as that of the sun gear 421 (first-stage carrier 415).

[0072] As described above, when the motor shaft 23 rotates in the reverse direction and the one-way clutch 70 rotates integrally with the first-stage carrier 415 and the second-stage sun gear 421, the lock mechanism 71 rotates the second-stage internal gear 422 in the same direction and at the same speed as the sun gear 421. As a result, the lock mechanism 71 disables the functions (speed reduction function and torque increase function) of the second-stage planetary gear mechanism 42. Therefore, when the motor shaft 23 rotates in the reverse direction, the number of effective stages of the reducer 4 is two.

[0073] As described above, the number of effective stages of the reducer 4 is smaller when the motor shaft 23 rotates in the reverse direction than when the motor shaft 23 rotates in the forward direction. Therefore, the reduction ratio of the reducer 4 when the motor shaft 23 rotates in the reverse direction is smaller than the reduction ratio of the reducer 4 when the motor shaft 23 rotates in the forward direction. In other words, the rotation speed (output speed of the reducer 4) of the shaft 436 (final output shaft of the reducer 4) of the third stage carrier 435 is higher when the motor shaft 23 rotates in the reverse direction than when it rotates in the forward direction. In addition, the torque output from the reducer 4 (output torque of the reducer 4) is higher when the motor shaft 23 rotates in the forward direction than when it rotates in the reverse direction. Note that, in this embodiment, the reducer 4 is configured so that the reduction ratio when the motor shaft 23 rotates in the forward direction is 2.5 times or more the reduction ratio when the motor shaft 23 rotates in the reverse direction.

[0074] The operation of the fastening tool 1 when performing the operation of fastening the work material W using the fastener 8 (hereinafter referred to as the fastening operation) will be described below. When performing the fastening operation, the screw shaft 56 and the pin gripping portion 63 perform one cycle of operation consisting of a forward stroke in which they move backward from the initial position, and a return stroke in which they move forward to the initial position.

[0075] As shown in Fig. 1, in the initial state where the trigger 151 is not pulled, the screw shaft 56 (i.e., the drive shaft 560) and the pin gripping portion 63 are located in the initial position (forward-most position). The user temporarily fastens the fastener 8 to the work material W, and loosely grips the shaft portion of the pin 81 with the tip portion (claw) of the pin gripping portion 63. When the user pulls the trigger 151 and the switch 152 is turned on, the control circuit 171 of the controller 170 starts driving the motor 2 in the forward direction in response to the on signal from the switch 152. This starts the forward stroke.

[0076] As described above, as the motor shaft 23 starts to rotate in the forward direction, the second-stage internal gear 422 is locked by the reduction ratio change mechanism 7. The number of effective stages of the reducer 4 becomes three. Therefore, the shaft 436 of the reducer 4 rotates at a relatively low speed and outputs a relatively large torque. The increased torque is transmitted to the nut 51 via the nut drive gear 311, the idle gear 331, and the driven gear 511. As the nut 51 rotates, the screw shaft 56 and the pin gripping portion 63 move backward relative to the main body housing 11 and the nut 51. The shaft portion of the pin 81 is firmly gripped by the pin gripping portion 63 and pulled backward relative to the collar 85 and the work material W.

[0077] The collar 85 is deformed and swaged to the shaft of the pin 81, and the work material W is clamped between the head of the pin 81 and the collar 85, and then a part of the shaft of the pin 81 is torn off and separated, completing the fastening of the work material W. The control circuit 171 stops the forward rotation of the motor 2 in response to the screw shaft 56 and the pin gripping portion 63 reaching a predetermined stop position, or in response to the user releasing the pressure on the trigger 151 and turning off the switch 152. This ends the forward stroke. Although detailed explanation and illustration are omitted, the control circuit 171 can determine whether the screw shaft 56 and the pin gripping portion 63 have reached the stop position based on the detection result of a position detector (e.g., a hall sensor, an optical sensor, a contact switch, etc.), for example.

[0078] Furthermore, when the user releases the pressure on the trigger 151 and the switch 152 turns off, the control circuit 171 starts driving the motor 2 in the reverse direction, thereby starting the return stroke.

[0079] As described above, in response to the motor shaft 23 rotating in the reverse direction, the second-stage internal gear 422 is rotated integrally with the sun gear 421 by the reduction ratio change mechanism 7, and the number of effective stages of the reducer 4 is changed to two. Therefore, the shaft 436 of the reducer 4 rotates faster than in the forward stroke and outputs a smaller torque than in the forward stroke. The torque is transmitted to the nut 51 via the nut drive gear 311, the idle gear 331, and the driven gear 511. The nut 51 rotates in the direction opposite to the forward stroke. As a result, the screw shaft 56 and the pin gripping portion 63 move forward relative to the main body housing 11 and the nut 51. The control circuit 171 stops the reverse drive of the motor 2 in response to the screw shaft 56 and the pin gripping portion 63 reaching the initial position. This ends the return stroke. The control circuit 171 can determine whether or not the screw shaft 56 and the pin gripping portion 63 have reached the initial position based on, for example, the detection result of a position detector, in the same manner as the stop position.

[0080] As described above, the motor 2 (motor shaft 23) of the fastening tool 1 of this embodiment can rotate in two directions, the forward direction and the reverse direction. The reducer 4 is configured so that the reduction ratio is changed in response to a change in the rotation direction of the motor shaft 23. Therefore, the output speed and output torque of the reducer 4, and further the moving speed of the pin gripping portion 63 and the tensile force of the pin 81, are changed depending on whether the rotation direction of the motor shaft 23 is the forward direction or the reverse direction. For this reason, the fastening tool 1 can perform two operations with different moving speeds of the pin gripping portion 63 and different tensile forces of the pin 81 depending on the rotation direction of the motor shaft 23.

[0081] Furthermore, since the reduction ratio is changed by the reduction ratio change mechanism 7, the control circuit 171 does not need to control the rotation speed of the motor 2. This makes it possible to drive the motor 2 with high efficiency at all times. Particularly in this embodiment, when the control circuit 171 recognizes a specific event (more specifically, a change in the pressing state of the trigger 151 (i.e., switching of the switch 152 between on and off)), it automatically changes the driving mode of the motor 2 (the rotation direction of the motor shaft 23). This makes it possible to appropriately and efficiently change the reduction ratio in response to the change in the rotation direction of the motor shaft 23.

[0082] The fastening tool 1 is a typical example of a power tool that performs different operations in a forward stroke and a backward stroke during a fastening operation. In a forward stroke, the pin gripping portion 63 moves backward from an initial position while pulling the pin 81, whereas in a backward stroke, the pin gripping portion 63 moves forward to the initial position without pulling the pin 81. The reduction ratio in the forward stroke is greater than that in the backward stroke. Thus, the fastening tool 1 exerts a relatively large torque in a forward stroke in which a relatively strong force is required to pull the pin 81, and can return the pin gripping portion 63 to the initial position relatively quickly and efficiently in a backward stroke in which no particularly large force is required (i.e., the fastening operation can be performed efficiently).

[0083] In particular, in this embodiment, the reduction ratio when the motor shaft 23 rotates in the forward direction is 2.5 times or more the reduction ratio when the motor shaft 23 rotates in the reverse direction, so that the moving speed of the pin gripping portion 63 and the tensile force of the pin 81 can be made to differ relatively greatly between the forward stroke and the return stroke.

[0084] Moreover, in this embodiment, the reducer 4 is a planetary reducer including three-stage (three sets) planetary gear mechanisms 41, 42, and 43. A planetary reducer is small in size and can obtain a large reduction ratio compared to a gear reducer combined with a spur gear or the like. In this embodiment, the reducer 4 is a multi-stage planetary reducer, and therefore can obtain a particularly large reduction ratio. Moreover, the reducer 4 can rationally change the reduction ratio by changing the number of planetary gear mechanisms 41, 42, and 43 that function effectively (number of effective stages).

[0085] In this embodiment, the one-way clutch 70 and the lock mechanism 71 work together to make the second stage planetary gear mechanism 42 function effectively when the motor 2 is driven in the forward direction, while disabling the function of the planetary gear mechanism 42 when the motor 2 is driven in the reverse direction. In particular, the one-way clutch 70 is a clutch that automatically performs different operations depending on the rotation direction, so that a change in the rotation direction of the motor shaft 23 can be efficiently linked to a change in the operation of the lock mechanism 71. In addition, the lock mechanism 71 is configured to lock and unlock the lock cam 75 by the roller 73 moving in the circumferential direction between the lock position and the unlock position. This realizes a lock mechanism 71 that is compact in the front-rear and radial directions. Furthermore, the roller 73 exerts a wedge effect with a slight movement in the circumferential direction, and can reliably lock the lock cam 75 and therefore the internal gear 422.

[0086] Furthermore, the lock mechanism 71 acts on the sun gear 421 and the internal gear 422 in the second stage planetary gear mechanism 42, which has a lower rotation speed than the first stage and a lower torque than the third stage. This reduces the load on the lock mechanism 71 and improves its durability.

[0087] The correspondence between each component of the above embodiment and each component of the present invention is shown below. However, each component of the embodiment is merely an example and does not limit each component of the present invention.

[0088] The fastening tool 1 is an example of an "electric tool". The motor 2 and the motor shaft 23 are examples of a "motor" and a "motor shaft", respectively. The reducer 4 is an example of a "gear reducer". The planetary gear mechanisms 41, 42, and 43 are an example of a "planetary gear mechanism". The sun gears 411, 421, and 431 are an example of a "sun gear". The internal gears 412, 422, and 432 are an example of an "internal gear". The carriers 415, 425, and 435 are an example of a "carrier". The planetary gears 418, 428, and 438 are an example of a "planetary gear". The one-way clutch 70 is an example of a "one-way clutch". The lock mechanism 71 is an example of a "lock mechanism". The pin gripping portion 63 is an example of a "movable member". The fastener 8 is an example of a "fastener". The ball screw mechanism 5 is an example of a “screw feed mechanism.” The control circuit 171 of the controller 170 is an example of a “control device.”

[0089] It should be noted that the above embodiment is merely an example, and the power tool according to the present disclosure is not limited to the illustrated fastening tool 1. For example, the following modifications can be made. Furthermore, at least one of these modifications can be adopted in combination with the fastening tool 1 illustrated in the embodiment and any of the inventions described in the claims.

[0090] For example, a motor with brushes may be used instead of a brushless motor for the motor 2. The motor 2 may be driven by power supplied from an external AC power source instead of the battery 182.

[0091] In addition, in the drive mechanism 3, instead of the ball screw mechanism 5, a screw feed mechanism including a nut having a female screw formed on the inner periphery and a screw shaft having a male screw formed on the outer periphery and directly screwed into the nut may be adopted. In addition, in the ball screw mechanism 5, the screw shaft 56 may be configured such that the movement in the front-rear direction is restricted and the screw shaft 56 is supported rotatably around the drive shaft A1, while the nut 51 moves in the front-rear direction with the rotation of the screw shaft 56. In this case, the pin gripping portion 63 may be directly or indirectly connected to the nut 51 as the final output shaft. The idle gear 331 arranged between the nut driving gear 311 of the first intermediate shaft 31 and the driven gear 511 of the nut 51 may be omitted, and the nut driving gear 311 and the driven gear 511 may be meshed with each other, or another gear may be interposed.

[0092] The number of stages of the reducer 4 (i.e., the number of planetary gear mechanisms included in the reducer 4) and the configuration of each of the planetary gear mechanisms 41, 42, and 43 may be changed as appropriate. For example, the reducer 4 may include only one planetary gear mechanism, or may include two or four or more planetary gear mechanisms. When only one planetary gear mechanism is provided, the number of effective stages is switched between zero and one according to a change in the rotation direction of the motor 2. The number of effective stages may be changed by axial movement of any one of the internal gears 412, 422, and 432. Furthermore, instead of the reducer 4, a gear reducer including a gear train (a gear train such as a spur gear, a helical gear, or a bevel gear) different from the planetary gear mechanism may be employed. In this case, the reduction ratio can be changed by, for example, selectively meshing a specific gear arranged to be slidable with one of two gears having a different number of teeth.

[0093] The reduction ratio change mechanism 7 operates in response to a change in the rotation direction of the motor shaft 23, and can be changed as appropriate as long as it is possible to switch the reduction ratio of the reducer 4. For example, the reduction ratio change mechanism 7 may be configured to move one of the internal gears 412, 422, 432 of the reducer 4 in the axial direction by using a gear train operatively connected to the motor shaft 23 and the reducer 4 (or the gear transmission of the modified example described above).

[0094] The one-way clutch 70 may be changed to a one-way clutch having any other configuration (for example, a one-way clutch using balls). The shape, arrangement, number, etc. of each component of the lock mechanism 71 may also be changed as appropriate. For example, the number of rollers 73 may be three or more. The number of protrusions 756 of the lock cam 75 and the number of protrusions 725 of the retainer 72 may also be changed. The lock sleeve 74 may be omitted, and the roller 73 may be disposed between the inner circumferential surface of the gear case 40 and the flat portion 757 of the lock cam 75, and may be movable between the locked position and the unlocked position. In addition, the lock cam 75 and the internal gear 422 may be formed as a single member.

[0095] In the above embodiment, an example is given in which the control circuit 171 is configured by a microcomputer including a CPU and the like. However, the control circuit 171 may be configured by a programmable logic device such as an ASIC (Application Specific Integrated Circuits) or an FPGA (Field Programmable Gate Array). Furthermore, a plurality of control circuits may control the driving of the motor 2. Furthermore, the event that triggers the control circuit 171 to switch the driving mode of the motor 2 is not limited to the above example, and may be, for example, an operation on an operation unit (e.g., a push button switch, a touch panel, etc.) provided separately from the trigger 151.

[0096] Furthermore, the fastening tool 1 may be configured to fasten the work material W using a type of fastener (e.g., a blind rivet, a axially-maintained fastener among multiple-component swaging fasteners) different from the fastener 8 exemplified in the above embodiment. The fastening tool 1 may be compatible with multiple types of fasteners by replacing the anvil 61 and the pin gripping portion 63.

[0097] In addition, in the above embodiment, the fastening tool 1 is given as an example of the power tool, but the present disclosure may be applied to another power tool that performs different operations depending on the rotation direction of a motor. For example, the power tool may be embodied as pruning scissors including a fixed blade and a movable blade configured to rotate around a predetermined axis between a closed position and an open position relative to the fixed blade.

[0098] Such pruning scissors operate in a cycle consisting of a forward stroke in which the movable blade rotates from the closed position to the open position, and a return stroke in which the movable blade cuts the branch while returning from the open position to the closed position. Therefore, it is preferable that the movable blade quickly moves to the open position in the forward stroke, and that the movable blade exerts a relatively strong cutting force in the return stroke. Therefore, in the pruning scissors, the rotation direction of the motor is switched between the forward stroke and the return stroke, and the reduction ratio of the reducer in the return stroke is changed to be larger than that in the forward stroke.

[0099] Furthermore, the power tool is not limited to a power tool that operates in one cycle, such as the fastening tool 1 and the above-mentioned pruning shears, in which a forward stroke in which the movable member moves in a predetermined direction and a return stroke in which the movable member moves in a direction opposite to the predetermined direction. For example, the power tool may be embodied as a rotary tool that rotates an output shaft to which a tool tip is removably attached around a drive shaft. In the rotary tool, the rotation direction of the output shaft and the tool tip is reversed in response to a reversal of the rotation direction of the motor. Thus, by changing the reduction ratio of the reducer in response to a change in the rotation direction of the motor, different operations can be performed in response to the rotation direction of the tool tip.

[0100] Furthermore, in consideration of the spirit of the present invention, the above-mentioned embodiment and its modified examples, the following aspects are constructed. At least one of the following aspects may be adopted in combination with the above-mentioned embodiment and its modified examples, and at least one of the inventions described in each claim. [Aspect 1] The gear reducer includes a three-stage planetary gear mechanism, In the three-stage planetary gear mechanism, a second-stage sun gear is fixed to the shaft of the first-stage carrier, The one-way clutch is attached to the shaft of the first stage carrier. [Aspect 2] The motor and the reducer are further provided with a housing. the internal gear is selectively rotatable relative to the housing about a first axis, The locking mechanism includes: a cylindrical lock sleeve that cannot rotate about the first axis relative to the housing; a lock cam coupled to the internal gear and selectively rotatable about the first axis relative to the lock sleeve integrally with the internal gear, the lock cam being at least partially disposed radially inward of the lock sleeve; a retainer disposed at least partially radially inward of the lock sleeve and selectively rotatable about the first axis relative to the lock sleeve and integral with the one-way clutch; at least one roller held by the retainer between the lock sleeve and the lock cam in the radial direction, the at least one roller being sandwiched between the lock sleeve and the lock cam and selectively movable in the circumferential direction around the first axis relative to the lock sleeve and the lock cam between a locked position at which the lock cam is locked so as not to rotate relative to the lock sleeve and an unlocked position at which the lock cam is loosely fitted between the lock sleeve and the lock cam and allows rotation of the lock cam relative to the lock sleeve; When the motor shaft rotates in the first direction, the internal gear and the lock cam are rotated around the first axis via the planetary gear by the rotation of the sun gear, and in response, the at least one roller moves relatively to the lock position, thereby locking the internal gear non-rotatably via the lock cam, When the motor shaft rotates in the second direction, the retainer rotates integrally with the one-way clutch, and causes the internal gear to rotate integrally with the sun gear via the lock cam. The main body housing 11, the lock sleeve 74, the lock cam 75, the retainer 72, and the roller 73 are examples of the "housing", "lock sleeve", "lock cam", "retainer", and "roller" of this embodiment, respectively. [Aspect 3] The at least one roller is configured to lock the locking cam against rotation by a wedge effect when disposed in the locked position. [Explanation of symbols]

[0101] 1: Fastening tool 11: main body housing, 115: collection container, 13: nose, 15: handle, 151: trigger, 152: switch, 17: battery housing, 170: controller, 171: control circuit, 181: battery mounting part, 182: battery, 2: motor, 21: stator, 22: rotor, 23: motor shaft, 3: drive mechanism, 31: first intermediate shaft, 311: nut drive gear, 33: second intermediate shaft, 331: idle gear, 4: reducer, 40: gear case, 401: groove, 41, 42, 43: planetary gear mechanism, 411, 421, 431: sun gear, 412, 422, 432: internal gear, 423: protrusion, 415, 425, 435: carrier, 416, 426, 43 6: shaft, 418, 428, 438: planetary gear, 5: ball screw mechanism, 51: nut, 511: driven gear, 56: screw shaft, 560: drive shaft, 561: extension shaft, 61: anvil, 62: connecting member, 63: pin gripping portion, 64: connecting member, 7: reduction ratio change mechanism, 70: one-way clutch, 71: lock mechanism, 72: retainer, 721: cylindrical portion, 723: base portion, 725: projection, 73: roller, 74: lock sleeve, 741: projection, 75: lock cam, 751: base portion, 753: flange portion, 754: recess, 755: cam portion, 756: projection, 757: flat portion, 8: fastener, 81: pin, 85: collar, A1: drive shaft, A2: rotating shaft, W: work material

Claims

1. A power tool, a motor having a motor shaft that can rotate in two directions, forward and reverse; a gear reducer operably coupled to the motor shaft, the gear reducer configured to change a reduction ratio in response to a change in a direction of rotation of the motor shaft; A one-way clutch; a locking mechanism operably connected to the one-way clutch, the gear reducer includes a one-stage or multiple-stage planetary gear mechanism, and is configured to be able to change the reduction ratio by changing the number of effective stages of the one-stage or multiple-stage planetary gear mechanism; Each stage of the one-stage or multi-stage planetary gear mechanism includes a sun gear, an internal gear, a carrier, and a plurality of planetary gears; The electric power tool is configured such that the one-way clutch and the locking mechanism perform different operations depending on a rotation direction of the motor shaft, The direction of rotation of the motor shaft is determined by a user setting or a sensor; the one-way clutch is provided on a transmission path from the motor shaft to a sun gear of a specific stage of the one-stage or multiple-stage planetary gear mechanism, and is configured to allow relative rotation of the sun gear of the specific stage with respect to the one-way clutch in a first case in which the motor shaft rotates in a first direction that is one of the forward direction and the reverse direction, and to rotate integrally with the sun gear of the specific stage in a second case in which the motor shaft rotates in a second direction that is the other of the forward direction and the reverse direction, The locking mechanism is configured such that, in the first case, when the one-way clutch allows relative rotation of the sun gear of the specific stage, the internal gear of the specific stage is locked so as to prevent rotation, thereby allowing the specific stage to function effectively, and, in the second case, when the one-way clutch rotates integrally with the sun gear of the specific stage, the internal gear of the specific stage is rotated integrally with the sun gear of the specific stage, thereby disabling the function of the specific stage.

2. The power tool according to claim 1, The gear reducer includes a multi-stage planetary gear mechanism, The power tool, wherein the specific stage is a second stage or a stage subsequent thereto.

3. The power tool according to claim 1 or 2, a movable member operably connected to the gear reducer and configured to move in response to the driving of the motor; The electric power tool is configured to operate in a cycle including a forward stroke in which the movable member moves in a predetermined direction and a return stroke in which the movable member moves in a direction opposite to the predetermined direction, A power tool, characterized in that the rotation direction of the motor shaft is changed between the forward stroke and the return stroke.

4. The power tool according to claim 3, The electric power tool is a fastening tool configured to fasten a work material via a fastener.

5. The power tool according to claim 4, the movable member is configured to grip a portion of the fastener; The movable member is configured to move from an initial position in the predetermined direction while pulling the fastener against the work material during the forward stroke, and to return to the initial position in a direction opposite to the predetermined direction without pulling the fastener during the return stroke, The power tool according to claim 1, wherein the reduction ratio during the forward stroke is greater than the reduction ratio during the return stroke.

6. The power tool according to claim 5, An electric power tool further comprising a screw feed mechanism disposed on a transmission path between the gear reducer and the movable member and configured to convert the rotational motion of an output shaft of the gear reducer into linear motion of the movable member.

7. The power tool according to any one of claims 1 to 6, An electric power tool characterized in that a reduction ratio when the rotation direction of the motor shaft is one of the forward direction and the reverse direction is 2.5 times or more of the reduction ratio when the rotation direction of the motor shaft is the other of the forward direction and the reverse direction.

8. The power tool according to any one of claims 1 to 7, a controller configured to control operation of the power tool; The control device is configured to change the rotation direction of the motor in response to an operation of an operating unit by a user.

Images