power tools

Abstract

The present application provides an electric power tool. The electric power tool has a motor and a gear reducer. The motor has a motor shaft that is rotatable in two directions of a forward direction and a reverse direction. The gear reducer is operatively connected to the motor shaft. The gear reducer is configured to change a reduction ratio in accordance with a change in the rotational direction of the motor shaft. Accordingly, the electric power tool is capable of performing different operations in accordance with the rotational direction of the motor.

Description

TECHNICAL FIELD

[0001] The present application relates to an electric power tool. BACKGROUND

[0002] An electric power tool is known, which has a motor capable of rotating in two directions of a forward direction and a reverse direction, and is capable of performing different actions in a case where the motor rotates in the forward direction and in a case where the motor rotates in the reverse direction. For example, a fastening tool disclosed in Patent Literature 1 is configured to move a screw shaft to the rear to rivet a fastener in a case where the motor rotates in the forward direction, and to return the screw shaft to the initial position in the forward direction in a case where the motor rotates in the reverse direction.

[0003] [Related Art Documents]

[0004] [Patent Literature]

[0005] Patent Literature 1: Japanese Patent Application Laid-Open No. 2018-103257 SUMMARY

[0006] [Problems to be Solved by the Invention]

[0007] In the electric power tool such as the above-described fastening tool, which performs different actions depending on the rotation direction of the motor, the rotational speed and the output torque required depending on each action can be different.

[0008] An object of the present application is to provide an improved electric power tool, which performs different actions depending on the rotation direction of the motor.

[0009] [Means for Solving the Problems]

[0010] According to one embodiment of the present application, there is provided an electric power tool having a motor and a gear reducer. The motor has a motor shaft capable of rotating in two directions of a forward direction and a reverse direction. The gear reducer is connected to the motor shaft in an operable manner. In addition, the gear reducer is configured to change a reduction ratio depending on a change in the rotation direction of the motor shaft.

[0011] According to the present embodiment, the reduction ratio of the gear reducer, and further the rotational speed (output speed) of an output shaft of the gear reducer and the torque (output torque) output from the gear reducer can be changed in a case where the rotation direction of the motor shaft is the forward direction and in a case where the rotation direction is the reverse direction. Thereby, an electric power tool capable of performing two actions different in speed and torque required by changing only the rotation direction of the motor without controlling the rotational speed of the motor can be realized.

[0012] In one embodiment of the present invention, a gear reducer may include at least one planetary gear mechanism. Each of the at least one planetary gear mechanism includes a sun gear, an internal gear, a planetary carrier, and a plurality of planetary gears. The gear reducer may be configured to change the reduction ratio by varying the number of effective stages of the at least one planetary gear mechanism. This embodiment utilizes a planetary gear mechanism, enabling a smaller design and achieving a larger reduction ratio than a gear reducer composed of, for example, a combination of spur gears. Furthermore, by varying the number of effective stages of the planetary gear mechanism, the reduction ratio can be varied more efficiently.

[0013] In one embodiment of the present invention, the electric tool may further include a one-way clutch and a locking mechanism, wherein the locking mechanism is operatively 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 relative 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. In addition, the first direction is one of a positive direction and a reverse direction, and the second direction is the other of the positive direction and the reverse direction. The locking mechanism may be configured to lock the internal gear so as not to rotate when the one-way clutch allows relative rotation of the sun gear, and to allow the internal gear to rotate integrally with the sun gear when the one-way clutch rotates integrally with the sun gear.

[0014] According to this method, the one-way clutch and the locking mechanism work in coordination, enabling the planetary gear mechanism to function effectively when the motor shaft rotates in the first direction, and on the other hand, disabling the function of the planetary gear mechanism when the motor shaft rotates in the second direction. In particular, the one-way clutch is a clutch that automatically performs different actions depending on the direction of rotation, and thus can efficiently link the change in the rotation direction of the motor shaft with the change in the action of the locking mechanism. Through such a reasonable structure, the power tool of this method can perform actions requiring a relatively small speed and / or a relatively large torque when the motor shaft rotates in the first direction, and on the other hand, perform actions requiring a relatively large speed and / or a relatively small torque when the motor shaft rotates in the second direction.

[0015] In one embodiment of the present invention, the gear reducer may include a multi-stage (multi-set) planetary gear mechanism. The locking mechanism may be configured to act on the internal gear of the second stage or subsequent stages of the multi-stage planetary gear mechanism. According to this embodiment, after reduction by at least the first stage of the planetary gear mechanism, the locking mechanism acts on the internal gear of the second stage or subsequent stages of the planetary gear mechanism. This reduces the load on the locking mechanism, thereby improving durability.

[0016] In one embodiment of the present invention, a movable part may be further provided, which is connected to the gear reducer in an operative manner and is configured to move as the motor is driven. The electric tool may be configured to operate with a forward stroke and a return stroke as one cycle, wherein the forward stroke refers to a stroke in which the movable part moves in a prescribed direction, and the return stroke refers to a stroke in which the movable part moves in a direction opposite to the prescribed direction. Moreover, the rotation direction of the motor shaft can be changed between the forward stroke and the return stroke. According to this embodiment, it is possible to realize an electric tool that can exert the speed and torque required by each of the forward stroke and the return stroke simply by changing the rotation direction of the motor.

[0017] In one embodiment of the present invention, the power tool may be a fastening tool configured to fasten workpieces using a fastener. This fastening tool is a typical example of a power tool that performs different actions during the forward and return strokes of the fastening operation. This embodiment achieves a fastening tool capable of efficiently performing fastening operations.

[0018] In one embodiment of the present invention, the movable member can be configured to grip a portion of the fastener. Furthermore, the movable member can be configured to move in a predetermined direction from an initial position while pulling the fastener relative to the work material during a forward stroke, and to return to the initial position in a direction opposite to the predetermined direction without pulling the fastener during a return stroke. Furthermore, the reduction ratio during the forward stroke can be greater than the reduction ratio during the return stroke. This embodiment enables a fastening tool that can generate a relatively large torque during the forward stroke, in which the movable member pulls the fastener, and efficiently return to the initial position at a relatively high speed during the return stroke, in which the movable member returns to the initial position without pulling the fastener.

[0019] In one embodiment of the present invention, the power tool may further include a screw feed mechanism, which is disposed between the gear reducer and the movable member along a transmission path and is configured to convert the rotational motion of the output shaft of the gear reducer into linear motion of the movable member. According to this embodiment, the screw feed mechanism can efficiently convert relatively large torque into linear motion.

[0020] In one embodiment of the present invention, the reduction ratio when the motor shaft rotates in one of the forward and reverse directions can be 2.5 times or greater than the reduction ratio when the motor shaft rotates in the other of the forward and reverse directions. This embodiment enables a power tool capable of performing two actions with significantly different speeds and torques by changing the motor's rotational direction.

[0021] In one aspect of the present invention, a control device may be further provided, the control device being configured to control the operation of the power tool. The control device may be configured to change the rotational direction of the motor upon recognizing a predetermined event. According to this aspect, since the control device automatically switches the rotational direction of the motor upon recognizing the predetermined event, the reduction ratio can be appropriately and efficiently changed. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a cross-sectional view of the fastening tool.

[0023] Figure 2 It is a cross-sectional view of the reducer.

[0024] Figure 3 This is an exploded perspective view of the first-stage planetary carrier, the second-stage sun gear and internal gear, and the reduction ratio changing mechanism.

[0025] Figure 4 yes Figure 2 The cross-sectional view taken along line IV-IV is an explanatory diagram of the operation of the locking mechanism when the motor is driven in the forward direction.

[0026] Figure 5 yes Figure 4 Cross-sectional view of VV.

[0027] Figure 6 yes Figure 4 VI-VI cross-sectional view.

[0028] Figure 7 corresponds to Figure 3 The cross-sectional view is an explanatory diagram of the operation of the locking mechanism when the motor is driven in reverse.

[0029] [Explanation of Reference Numerals]

[0030] 1: Fastening tool; 11: Main body housing; 115: Recovery container; 13: Handpiece; 15: Handle; 151: Trigger; 152: Switch; 17: Battery housing; 170: Controller; 171: Control circuit; 181: Battery mounting portion; 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: Gearbox; 401: Slot; 41, 42, 43: Planetary gear mechanism; 411, 421, 431: Sun gear; 412, 422, 432: Internal gear; 423: Protrusion; 415, 425, 435: Planetary carrier; 416, 426, 436: 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 part; 63: pin holding part; 64: connecting part; 7: reduction ratio changing mechanism; 70: one-way clutch; 71: locking mechanism; 72: retaining frame; 721: cylindrical part; 723: base; 725: protrusion; 73: roller; 74: locking sleeve; 741: protrusion; 75: locking cam; 751: base; 753: flange part; 754: recessed part; 755: cam part; 756: protrusion; 757: flat part; 8: fastener; 81: pin; 85: sleeve; A1: drive axis; A2: rotation axis; W: working material. DETAILED DESCRIPTION

[0031] The following describes an embodiment with reference to the accompanying drawings. A fastening tool 1 of this embodiment is configured to fasten a workpiece using a fastener 8. The fastener 8 is a known fastener (specifically, a multi-piece swage-type fastener) consisting of a pin 81 and a sleeve 85.

[0032] First, the schematic structure of the fastening tool 1 will be described.

[0033] like Figure 1As shown, the outer contour of the fastening tool 1 is mainly formed by the main body shell 11, the head 13, the handle 15 and the battery shell 17. The main body shell (also called the tool body) 11 is formed as a rectangular box as a whole and extends along the specified drive axis A1. The main body shell 11 is used to accommodate the motor 2 and the drive mechanism 3. The head 13 protrudes from one end of the main body shell 11 in the long axis direction along the drive axis A1. The handle 15 protrudes from the central part of the main body shell 11 in the long axis direction in a direction intersecting with the drive axis A1 (specifically, a direction approximately orthogonal). A trigger 151 is provided on the handle 15, and the trigger 151 is operated by the user (pressing operation). The battery shell 17 is connected to the protruding end of the handle 15. The rechargeable battery 182 can be disassembled and installed relative to the battery shell 17.

[0034] When the user engages the fastener 8 with the top end of the nose 13 and pulls the trigger 151 , the motor 2 is driven, and the pin 81 is pulled axially relative to the sleeve 85 and the work material W, thereby fastening the work material W through the fastener 8 .

[0035] Below, regarding the direction of the fastening tool 1, for the sake of convenience, the extension direction of the drive axis A1 (or the long axis of the main body shell 11) is defined as the front-to-back direction of the fastening tool 1. In the front-to-back direction, the side where the head 13 is arranged is defined as the front side, and the opposite side is defined as the rear side. In addition, the direction that is orthogonal to the drive axis A1 and corresponds 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 shell 17 side) is defined as the lower side, and the base end side of the handle 15 (the main body shell 11 side) is defined as the upper side. In addition, the direction orthogonal to the front-to-back direction and the up-down direction is defined as the left-right direction.

[0036] Next, the detailed structure of the fastening tool 1 will be described.

[0037] First, the internal structure of the main body housing 11 is described. Figure 1 As shown, the main body housing 11 mainly accommodates a motor 2 and a drive mechanism 3 driven by the motor 2 .

[0038] The motor 2 is housed in the lower portion of the rear end portion of the main body housing 11. In this embodiment, a brushless 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 configured so that the rotation axis A2 of the motor shaft 23 extends below (specifically, directly below) the drive axis A1 and parallel to (i.e., in the front-to-back direction) the drive axis A1. The front end portion of the motor shaft 23 protrudes into the gear box 40 of the reducer 4. In addition, in this embodiment, the rotor 22 and the motor shaft 23 can rotate in both the forward and reverse directions. In addition, in this embodiment, the forward direction corresponds to the direction in which the screw shaft 56 and the pin holding portion 63 described later are moved backward. The reverse direction corresponds to the direction in which the screw shaft 56 and the pin holding portion 63 are moved forward. Hereinafter, the drive in which the motor 2 rotates in the forward direction is referred to as forward drive, and the drive in which the motor 2 rotates in the reverse direction is referred to as reverse drive.

[0039] Next, the drive mechanism 3 will be described. The drive mechanism 3 is configured to move the pin gripping portion 63 (described later) in the front-to-rear direction relative to the anvil 61 along the drive axis A1 using the power of the motor 2. In this embodiment, the drive mechanism 3 includes a speed reducer 4, a nut drive gear 311 provided on the first intermediate shaft 31, an idler gear 331 provided on the second intermediate shaft 33, and a ball screw mechanism 5. These components will be described below in order.

[0040] The reducer 4 is arranged in the main body housing 11, coaxially with the motor 2, and in front of the motor 2. The reducer 4 is a reducer using a planetary gear mechanism, and is configured to reduce the rotation of the motor shaft 23 according to the reduction ratio and increase the torque before outputting it to the first intermediate shaft 31. In this embodiment, the reducer 4 is a multi-stage planetary reducer. More specifically, Figure 2 As shown, the speed reducer 4 includes a gear box 40 and three-stage (three-set) planetary gear mechanisms 41, 42, and 43 housed in the gear box 40. The gear box 40 is supported by the main body case 11 in a non-rotatable manner.

[0041] The first-stage (input-side) planetary gear mechanism 41 includes a sun gear 411 , an internal gear (also referred to as a ring gear) 412 , a planetary carrier 415 , and a plurality of planetary gears 418 .

[0042] 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 relative to the reducer 4. The internal gear 412 is maintained in a fixed state in the gear box 40. That is, the internal gear 412 cannot substantially move in the front-to-back direction relative to the gear box 40, and cannot substantially rotate around the rotation axis A2. The planetary gear 418 is supported by the planetary carrier 415 and meshes with the sun gear 411 and the internal gear 412. The planetary carrier 415 has a shaft 416 extending forward along the rotation axis A2. When the motor 2 is driven, the planetary carrier 415 (shaft 416) rotates in the same direction as the motor shaft 23.

[0043] The second-stage planetary gear mechanism 42 includes a sun gear 421 , an internal gear (also referred to as a ring gear) 422 , a planet carrier 425 , and a plurality of planetary gears 428 .

[0044] The sun gear 421 is fixed to the front end of the shaft 416 of the first-stage planetary carrier 415. Consequently, when the motor 2 is driven, the sun gear 421 and the planetary carrier 415 rotate integrally in the same direction as the motor shaft 23. The internal gear 422 is embedded in the gearbox 40. Four protrusions 423 projecting rearward are provided at the rear end of the internal gear 422. The protrusions 423 are arranged at approximately equal intervals around the circumference of the internal gear 422. The internal gear 422 is essentially immovable in the front-to-rear direction relative to the gearbox 40 but can selectively rotate about the rotation axis A2. Furthermore, whether the internal gear 422 can rotate is switched by the reduction ratio changing mechanism 7 according to the rotation direction of the motor 2. The reduction ratio changing mechanism 7 will be described in detail later. The planetary gears 428 are supported by the planetary carrier 425 and mesh with the sun gear 421 and the internal gear 422. The planetary carrier 425 has a shaft 426 extending forward along the rotation axis A2.

[0045] The third-stage (final-stage, output-side) planetary gear mechanism 43 includes a sun gear 431 , an internal gear (also referred to as a ring gear) 432 , a planetary carrier 435 , and a plurality of planetary gears 438 .

[0046] Sun gear 431 is fixed to the front end of shaft 426 of second-stage planetary carrier 425. Similar to first-stage internal gear 412, internal gear 432 is held stationary within gearbox 40. Planetary gears 438 are supported by planetary carrier 435 and mesh with sun gear 431 and internal gear 432. Planetary carrier 435 includes shaft 436 extending forward along rotation axis A2. Third-stage (final-stage) shaft 436 serves as the final output shaft of reducer 4.

[0047] like Figure 1As shown, the first intermediate shaft 31 extends forward from the reducer 4 in the main body housing 11 in a coaxial manner with the motor shaft 23 and the reducer 4. The first intermediate shaft 31 is connected to the shaft 436 of the third stage planetary carrier 435 of the reducer 4 (see Figure 2 The first intermediate shaft 31 is supported by two bearings supported by the main body housing 11 so as to be rotatable about the rotation axis A2 and rotates integrally with the planetary 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.

[0048] The second intermediate shaft 33 extends above (specifically, directly above) the first intermediate shaft 31 and parallel to the first intermediate shaft 31. The idler gear 331 is supported on the second intermediate shaft 33 by a bearing and is rotatable about the axis of the second intermediate shaft 33. The idler gear 331 meshes with the nut drive gear 311 and the driven gear 511 of the nut 51 (described later), but does not affect the rotational speed ratio between the two.

[0049] The ball screw mechanism 5 is a well-known mechanism primarily 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 linear motion of the screw shaft 56, thereby causing the pin gripping portion 63, described later, to move linearly. Furthermore, the ball screw mechanism 5 is an example of a screw feed mechanism and can efficiently convert relatively large torque into linear motion.

[0050] The nut 51 is supported by the main housing 11 in a manner substantially immovable in the front-to-rear direction relative to the main housing 11 but rotatable about the drive axis A1. The nut 51 is cylindrical and has an integrally provided driven gear 511 on its outer periphery. The nut 51 is supported by a pair of radial bearings supported by the main housing 11 on the front and rear sides of the driven gear 511. Furthermore, the nut drive gear 311 and the driven gear 511 form a reduction gear mechanism.

[0051] The screw shaft 56 is engaged with the nut 51 in a state where it is substantially unable to rotate about the drive axis A1 relative to the main body housing 11 and can move in the front-to-back direction along the drive axis A1. More specifically, the screw shaft 56 is configured to be elongated and is inserted into the nut 51 in a manner extending along the drive axis A1. Although detailed illustrations are omitted, spiral grooves are formed on the inner circumference of the nut 51 and the outer circumference of the screw shaft 56. A plurality of balls are arranged in a rollable manner within the track defined by these spiral grooves. The screw shaft 56 is engaged with the nut 51 via these balls. In addition, although detailed illustrations are omitted, a pair of arms extending to the left and right from the screw shaft 56 are provided at the rear end of the screw shaft 56. Each arm supports a roller in a rotatable manner. The roller engages with the guide groove of the roller guide fixed to the main body housing 11. The roller can roll in the front-to-back direction along the guide groove while its movement in the up-and-down direction is restricted.

[0052] With such a structure, when the nut 51 rotates about the drive axis A1 , the screw shaft 56 moves linearly in the front-rear direction relative to the nut 51 and the main body housing 11 .

[0053] At the rear end portion of the screw shaft 56, an extension shaft 561 is connected and fixed in a coaxial manner, which is integrated with the screw shaft 56. Hereinafter, the screw shaft 56 and the extension shaft 561 formed as one body will also be 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 recovery container 115 is detachably mounted on the rear end portion of the main body shell 11. The recovery container 115 is a container for accommodating a portion of the shaft portion of the pin 81 separated from the fastener 8 (hereinafter referred to as the pin tail). The pin tail separated from the fastener 8 reaches the recovery container 115 through the through hole of the drive shaft 560, and is thereby accommodated in the recovery container 115.

[0054] Next, the machine head 13 will be described. Figure 1 As shown, the machine head 13 is mainly composed of an anvil 61 and a pin holding portion 63. The anvil 61 is constructed in a manner that can abut (engage) with the sleeve 85 of the fastener 8. The anvil 61 is connected to the main body shell 11 through the connecting component 62. The pin holding portion 63 is constructed in a manner that can hold the pin 81 of the fastener 8. The pin holding portion 63 is retained in a manner that can move relative to the anvil 61 in the front-to-rear direction along the drive axis A1. In addition, since the structures of the anvil 61 and the pin holding portion 63 are well-known structures, they will be briefly described below.

[0055] The anvil 61 is a cylindrical body as a whole and has a bore extending along the drive axis A1. The pin holding portion 63 is held in the bore in a coaxial manner with the anvil 61 and can slide in the bore. The top end of the bore is constructed in a manner that has a smaller diameter than other parts and can abut (engage) with the sleeve 85. Although detailed illustrations are omitted, the pin holding portion 63 has a plurality of claws (also called clamping claws) that can hold the shaft portion of the pin 81. The pin holding portion 63 is constructed in a manner that increases the holding force of the claws as it moves backward from the initial position relative to the anvil 61. The rear end portion of the pin holding portion 63 is connected to the front end portion of the screw shaft 56 via a connecting component 64. In addition, the connecting component 64 has a through hole that passes through the connecting component 64 along the drive axis A1 and is connected to the through hole of the drive shaft 560.

[0056] Next, the handle 15 will be described. Figure 1 As shown, the handle 15 is formed into an elongated cylindrical shape and extends continuously downward from the lower center portion of the main body housing 11 in the front-to-back direction. The handle 15 is the portion 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 within the handle 15. The switch 152 is normally maintained in an OFF state and becomes an ON state in response to the pulling operation of the trigger 151. The switch 152 is electrically connected to the controller 170 via an electric wire (not shown), and when it becomes the ON state, it outputs an ON signal to the controller 170.

[0057] Next, the battery case 17 will be described. Figure 1 As shown, the battery case 17 is a hollow body shaped like an inverted U, elongated in the front-to-back direction. A controller 170 is housed within the battery case 17. The controller 170 includes a control circuit 171 responsible for controlling the fastening tool 1. In this embodiment, the control circuit 171 comprises a microcomputer including a CPU, ROM, RAM, and other components. Although not shown in detail, the control circuit 171, along with the motor 2 drive circuit and other components, is mounted on a substrate housed within the case.

[0058] Two battery mounting portions 181 are provided at the lower end of the battery housing 17. Each battery mounting portion 181 is configured to allow for the removable installation of a battery 182. In other words, in this embodiment, two batteries 182 can be installed in the fastening tool 1. The batteries 182 are rechargeable power sources for supplying power to various components of the fastening tool 1 and the motor 2, and are also referred to as a battery pack. The structures of the battery mounting portions 181 and batteries 182 are well known, so their description is omitted.

[0059] Next, the reduction ratio changing mechanism 7 will be described. As described above, the reduction ratio changing mechanism 7 is configured to selectively permit or prohibit the rotation of the internal gear 422 of the second-stage planetary gear mechanism 42 of the speed reducer 4, depending on the rotation direction of the motor 2. By changing whether the internal gear 422 can rotate, the effective number of stages of the speed reducer 4 (the number of effectively functioning planetary gear mechanisms) is changed, thereby changing the reduction ratio of the speed reducer 4.

[0060] like Figure 2 and Figure 3 As shown, the speed reduction ratio changing mechanism 7 includes a one-way clutch 70 and a lock mechanism 71 .

[0061] The one-way clutch 70 is a clutch having a mechanism that transmits rotation in only one direction and idles in the opposite direction. In the present embodiment, the one-way clutch 70 is a general one-way clutch having a known structure in which a plurality of rollers biased by springs are supported in a cylindrical sleeve. The one-way clutch 70 is sleeved on the outer periphery of the shaft 416 of the first-stage planetary carrier 415. When the motor shaft 23 and the shaft 416 rotate in the positive direction, the one-way clutch 70 idles relative to the shaft 416 (i.e., it does not rotate with the planetary 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 and can transmit rotation).

[0062] The lock mechanism 71 is configured to switch whether the second-stage internal gear 422 can rotate when the one-way clutch 70 is idling or rotating integrally with the first-stage carrier 415 (shaft 416 ).

[0063] Next, the detailed structure of the locking mechanism 71 will be described. Figures 2 to 6 As shown, the locking mechanism 71 includes a retaining frame 72 , two rollers 73 , a locking sleeve 74 and a locking cam 75 .

[0064] The retainer 72 is a component that holds the roller 73 on the retainer 72 so that it can move in the circumferential direction around the rotation axis A2. The retainer 72 includes a cylindrical portion 721, a base 723, and four protrusions 725. The cylindrical portion 721 extends in the front-to-back direction along the rotation axis A2 to form the central portion of the retainer 72. The base 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 arranged at approximately equal intervals on the outer edge of the base 723, and protrude forward from the outer edge of the base 723. In the radial direction, a space is formed between the cylindrical portion 721 and the protrusions 725. The front end of the protrusion 725 is located further rearward than the front end of the cylindrical portion 721 (i.e., the protrusion 725 is shorter than the cylindrical portion 721 in the front-to-back direction).

[0065] 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 rotates integrally with the one-way clutch 70. Accordingly, the retainer 72 can selectively rotate with respect to the first-stage carrier 415. Specifically, in a case where the motor shaft 23 and the shaft 416 rotate in the forward direction, the retainer 72 idles with respect to the shaft 416 integrally with the one-way clutch 70 (i.e., does not rotate together with the shaft 416). On the other hand, in a case where the motor shaft 23 and the shaft 416 rotate in the reverse direction, the retainer 72 rotates integrally with the shaft 416 together with the one-way clutch 70.

[0066] The rollers 73 are cylindrical members (pins). The diameters of the respective rollers 73 are substantially uniform, are smaller than the intervals between the adjacent two protrusions 725 of the retainer 72, and are larger than the thicknesses of the protrusions 725 in the radial direction. In addition, the lengths of the rollers 73 are equal to the protruding lengths of the protrusions 725 of the retainer 72 that protrude from the front surface of the base portion 723. The two rollers 73 are disposed in two spaces diagonally among the four spaces formed between the protrusions 725 of the retainer 72 and extend in the front-rear direction.

[0067] The lock sleeve 74 is a substantially cylindrical member. The lock sleeve 74 is embedded in the gear case 40 in a coaxial manner with the reduction gear 4 on the front side of the first-stage inner gear 412. In addition, a plurality of protrusions 741 are provided on the outer peripheral surface of the lock sleeve 74, protrude to the radial outside, and extend from the front end to the rear end of the lock sleeve 74. These protrusions 741 are respectively engaged with a plurality of grooves 401 (refer to FIG. 6) formed in the inner peripheral surface of the gear case 40 and extending in the front-rear direction. Accordingly, the lock sleeve 74 is held to the gear case 40 in a manner that it cannot rotate with respect to the gear case 40. Figure 4

[0068] In addition, the lock sleeve 74 is disposed around (radially outside) the retainer 72. The front end of the lock sleeve 74 is located at a position further forward than the front ends of the protrusions 725 and the rollers 73, and the rear end of the lock sleeve 74 is located at a position further rearward than the rear end of the retainer 72. Accordingly, the protrusions 725 of the retainer 72 and the rollers 73 are disposed inside the lock sleeve 74 as a whole. The inner diameter of the lock sleeve 74 is set to be substantially the same as or slightly larger than the outer diameter of the base portion 723 of the retainer 72. The retainer 72 can selectively rotate with respect to the lock sleeve 74.

[0069] ​The locking cam 75 is operably connected to the retainer 72 and selectively rotated by the retainer 72. Furthermore, the locking cam 75 is connected to the second-stage internal gear 422 and is rotatable integrally with the internal gear 422 relative to the gearbox 40 about the rotation axis A2. The locking cam 75 is formed as a cylindrical member having a through hole with a circular cross section extending along the rotation axis A2, and includes a base portion 751, a flange portion 753, and a cam portion 755.

[0070] The base 751 is a disc-shaped portion and forms the front half of the locking cam 75. The flange portion 753 is a portion that protrudes radially outward from the outer peripheral surface of the base 751. The outer diameter of the flange portion 753 is set to be equal to the outer diameter of the second-stage internal gear 422. Four recesses 754 are provided on the flange portion 753 (see Figure 3 Each recess 754 is recessed radially inward from the outer edge of the flange portion 753. The recesses 754 are arranged at approximately equal intervals around the circumference of the flange portion 753. The recesses 754 have a shape that matches the protrusions 423 of the internal gear 422 and are constantly engaged with the protrusions 423. The locking cam 75 rotates integrally with the internal gear 422 through the engagement of the recesses 754 with the protrusions 423.

[0071] The cam portion 755 is a portion that protrudes rearward from the rear surface of the base 751 and forms the rear half of the locking cam 75. The cam portion 755 has two protrusions 756 and two flat portions 757. The protrusions 756 are arranged diagonally across the rotation axis A2 and protrude radially outward from the outer circumference of the cam portion 755. The two flat portions 757 are respectively arranged at approximately the middle position of the two protrusions 756 in the circumferential direction of the cam portion 755. The portion of the outer circumferential surface of the cam portion 755 located between the protrusions 756 and the flat portions 757 is a curved surface equivalent to the outer circumferential surface of a cylinder. The flat portions 757 are part of the outer circumferential surface of the cam portion 755 and are arranged diagonally across the rotation axis A2, extending in parallel with each other and in parallel with the rotation axis A2.

[0072] The radial distance between the flat portion 757 and the inner circumferential surface of the locking sleeve 74 is greatest at the center of the flat portion 757 and is set slightly larger than the diameter of the roller 73. The radial distance between the flat portion 757 and the inner circumferential surface of the locking 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 locking sleeve 74 is set smaller than the diameter of the roller 73.

[0073] The locking cam 75 having the above structure is fitted onto the outer circumference of the cylindrical portion 721 of the retainer 72 from the front. The two protrusions 756 of the locking cam 75 are circumferentially arranged in two of the four spaces formed between the protrusions 725 of the retainer 72 (specifically, the two spaces where the roller 73 is not arranged). Furthermore, the portion of the cam portion 755 other than the protrusions 756 is radially arranged in the space formed between the cylindrical portion 721 of the retainer 72 and the protrusions 725. The roller 73 is radially arranged between the flat portion 757 of the cam portion 755 of the locking cam 75 and the inner circumferential surface of the locking sleeve 74. Furthermore, the roller 73 is arranged in the front-to-back direction between the rear surface of the base 751 of the locking cam 75 and the front surface of the base 723 of the retainer 72.

[0074] Next, the operation of the reduction ratio changing mechanism 7 (the one-way clutch 70 and the lock mechanism 71 ) will be described.

[0075] First, the operation when the motor 2 is driven in the forward direction will be described.

[0076] When motor shaft 23 rotates in the forward direction, first-stage planetary carrier 415 (shaft 416) and second-stage sun gear 421 also rotate in the forward direction. At this time, as described above, one-way clutch 70 idles relative to shaft 416 and does not transmit rotation to retainer 72. Consequently, retainer 72 does not actively rotate.

[0077] The second stage sun gear 421 rotates the second stage planetary gear 428. Since the second stage planetary gear 428 is also meshed with the second stage internal gear 422, the second stage internal gear 422 rotates in the opposite direction relative to the gear box 40. At this time, the locking cam 75 also rotates in the opposite direction ( Figure 4 ) is rotated, thereby causing the roller 73 to move relative to the end portion of the flat portion 757.

[0078] like Figure 4 As shown, before the protrusion 756 of the locking cam 75 abuts the protrusion 725 of the retainer 72, the roller 73 is wedged between the flat portion 757 and the inner circumferential surface of the locking sleeve 74, at a position closer to the end than the center of the flat portion 757. Hereinafter, the position of the roller 73 relative to the locking sleeve 74 and the locking cam 75 at this time will be referred to as the locked position. Consequently, the locking cam 75 is locked to the locking sleeve 74 via the roller 73, thereby prohibiting rotation relative to the gearbox 40. When the locking cam 75 is locked, the internal gear 422 is also unable to rotate relative to the gearbox 40. Therefore, the planetary gears 428 then rotate while orbiting around the sun gear 421, causing the planetary carrier 425 to rotate in the forward direction.

[0079] As described above, when the motor shaft 23 rotates in the positive direction and the first-stage planetary carrier 415 and the second-stage sun gear 421 rotate relative to the one-way clutch 70, the locking mechanism 71 locks the second-stage internal gear 422 so that it cannot rotate. This lock mechanism 71 enables the second-stage planetary gear mechanism 42 to function effectively. Consequently, when the motor shaft 23 rotates in the positive direction, the number of effective stages of the speed reducer 4 is three.

[0080] The operation when the motor 2 is driven in reverse rotation will be described.

[0081] When the motor shaft 23 rotates in the reverse direction, the first stage planetary carrier 415 (shaft 416) and the second stage sun gear 421 also rotate in the reverse direction. At this time, as described above, the one-way clutch 70 is locked to the shaft 416, and the rotation of the shaft 416 is transmitted to the retainer 72, so the retainer 72 also rotates in the reverse direction ( Figure 7 to rotate in the direction of the arrow.

[0082] like Figure 7 As shown, two of the protrusions 725 of the retainer 72 respectively abut against the protrusions 756 of the locking cam 75, pushing the protrusions 756 of the locking cam 75 in the opposite direction. Simultaneously, the remaining two protrusions 725 abut against the roller 73, pushing it in the opposite direction, causing it to move to a position where the clamping of the roller 73 by the flat portion 757 and the inner circumference of the locking sleeve 74 is released (in this embodiment, a position corresponding to the approximate center of the flat portion 757). Hereinafter, the position of the roller 73 relative to the locking sleeve 74 and the locking cam 75 at this time will be referred to as the unlocked position. In the unlocked position, the roller 73 is loosely fitted between the flat portion 757 and the inner circumference of the locking sleeve 74, allowing the locking cam 75 to rotate relative to the locking sleeve 74. Consequently, the rotation of the retainer 72 is transmitted to the locking cam 75, causing the locking cam 75 and the retainer 72 to rotate in the opposite direction. As a result, the second-stage internal gear 422 rotates in the opposite direction integrally with the first-stage carrier 415 and the second-stage sun gear 421 .

[0083] Meanwhile, although the second-stage sun gear 421 attempts to rotate the second-stage planetary gears 428, the planetary gears 428 are unable to rotate (rotate on their own) because the sun gear 421 rotates integrally with the internal gear 422. Consequently, the second-stage planetary carrier 425 rotates integrally with the sun gear 421 and internal gear 422 in the opposite direction. The rotational speed of the planetary carrier 425 is the same as that of the sun gear 421 (the first-stage planetary carrier 415).

[0084] 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 planetary carrier 415 and the second-stage sun gear 421, the locking mechanism 71 causes the second-stage internal gear 422 to rotate at the same speed and in the same direction as the sun gear 421. Consequently, the locking mechanism 71 disables the functions (reduction and torque boosting functions) of the second-stage planetary gear mechanism 42. Consequently, when the motor shaft 23 rotates in the reverse direction, the effective number of stages of the speed reducer 4 is two.

[0085] As described above, when the motor shaft 23 rotates in the reverse direction, the number of effective stages of the reducer 4 is less than when the motor shaft 23 rotates in the forward direction. Accordingly, 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. That is, when the motor shaft 23 rotates in the reverse direction, the rotational speed of the shaft 436 of the third-stage planetary carrier 435 (the final output shaft of the reducer 4) (the output speed of the reducer 4) is greater than the rotational speed when the motor shaft 23 rotates in the forward direction. Furthermore, when the motor shaft 23 rotates in the forward direction, the torque output from the reducer 4 (the output torque of the reducer 4) is greater than the output torque when the motor shaft 23 rotates in the reverse direction. Furthermore, in this embodiment, the reducer 4 is configured so that the reduction ratio when the motor shaft 23 rotates in the forward direction is at least 2.5 times the reduction ratio when the motor shaft 23 rotates in the reverse direction.

[0086] Next, the operation of the fastening tool 1 during the operation of fastening a workpiece W using the fastener 8 (hereinafter referred to as the fastening operation) will be described. During the fastening operation, the screw shaft 56 and the pin gripping portion 63 perform a single cycle of motion consisting of a forward stroke, which moves backward from an initial position, and a return stroke, which moves forward to the initial position.

[0087] like Figure 1 As shown, in the initial state (with trigger 151 not pulled), the screw shaft 56 (i.e., drive shaft 560) and pin grip 63 are in their initial position (forwardmost position). The user pre-secures the fastener 8 to the work material W, and loosely grips the shaft of the pin 81 with the tip (claw) of the pin grip 63. When the user pulls the trigger 151, turning on the switch 152, the control circuit 171 of the controller 170 responds to the on signal from the switch 152 and begins driving the motor 2 in forward rotation. This initiates the forward stroke.

[0088] As described above, in response to the motor shaft 23 starting to rotate in the forward direction, the second-stage internal gear 422 is locked by the reduction ratio changing mechanism 7. The effective number of stages of the speed reducer 4 is made three. Accordingly, the shaft 436 of the speed reducer 4 rotates at a relatively low speed, and outputs a relatively large torque. The torque further increased is transmitted to the nut 51 via the nut driving gear 311, the idler gear 331, and the driven gear 511. With the rotation of the nut 51, the lead screw shaft 56 and the pin holding portion 63 move rearward relative to the main body case 11 and the nut 51. The shaft portion of the pin 81 is securely held by the pin holding portion 63, and is pulled rearward relative to the sleeve 85 and the work material W.

[0089] After the sleeve 85 is deformed and tightened to the shaft portion of the pin 81, and the work material W is clamped by the head portion of the pin 81 and the sleeve 85, a part of the shaft portion of the pin 81 is broken and separated, thereby ending the tightening of the work material W. In response to the lead screw shaft 56 and the pin holding portion 63 reaching a predetermined stop position, or in response to the user releasing the pressing of the trigger 151 to make the switch 152 an off state, the control circuit 171 stops driving the motor 2 in the forward direction. This ends the forward stroke. Furthermore, although detailed description and illustration are omitted, the control circuit 171 can determine whether the lead screw shaft 56 and the pin holding portion 63 reach the stop position based on the detection result of a position detector (for example, a Hall sensor, an optical sensor, a contact switch, or the like).

[0090] In addition, in response to the user releasing the pressing of the trigger 151 to make the switch 152 an off state, the control circuit 171 starts driving the motor 2 in the reverse direction. Accordingly, the return stroke is started.

[0091] As described above, in response to the motor shaft 23 rotating in the reverse direction, the second-stage internal gear 422 rotates integrally with the sun gear 421 by the reduction ratio changing mechanism 7, and the effective number of stages of the speed reducer 4 is changed to two. Accordingly, the shaft 436 of the speed reducer 4 rotates at a higher speed than that in the forward stroke, and outputs a smaller torque than that in the forward stroke. The torque is transmitted to the nut 51 via the nut driving gear 311, the idler gear 331, and the driven gear 511. The nut 51 rotates in the direction opposite to that in the forward stroke. Accordingly, the lead screw shaft 56 and the pin holding portion 63 move forward relative to the main body case 11 and the nut 51. In response to the lead screw shaft 56 and the pin holding portion 63 reaching the initial position, the control circuit 171 stops driving the motor 2 in the reverse direction. This ends the return stroke. Furthermore, as with the stop position, the control circuit 171 can determine whether the lead screw shaft 56 and the pin holding portion 63 reach the initial position based on the detection result of a position detector.

[0092] As explained above, the motor 2 (motor shaft 23) of the fastening tool 1 of the present embodiment can rotate in two directions of the forward direction and the reverse direction. In addition, the speed reducer 4 is configured so that the reduction ratio changes according to the change in the rotation direction of the motor shaft 23. Thereby, the output speed and the output torque of the speed reducer 4, and further the moving speed of the pin holding portion 63 and the traction force of the pin 81 can be changed in the case where the rotation direction of the motor shaft 23 is the forward direction and in the case where the rotation direction of the motor shaft 23 is the reverse direction. Therefore, the fastening tool 1 can perform two operations in which the moving speed of the pin holding portion 63 and the traction force of the pin 81 are different, according to the rotation direction of the motor shaft 23.

[0093] In addition, since the reduction ratio is changed by the reduction ratio changing mechanism 7, the control circuit 171 does not need to control the rotation speed of the motor 2. Thereby, the motor 2 can be driven with high efficiency at all times. In particular, in the present embodiment, when the control circuit 171 recognizes a specific event (specifically, the change in the pressing state of the trigger 151 (i.e., the switching of the on / off of the switch 152)), the driving mode (the rotation direction of the motor shaft 23) of the motor 2 is automatically changed. Thereby, the change in the reduction ratio can be performed appropriately and efficiently according to the change in the rotation direction of the motor shaft 23.

[0094] The fastening tool 1 is a typical example of a power tool that performs different operations in the forward stroke and the return stroke in the fastening work. In the forward stroke, the pin holding portion 63 moves to the rear from the initial position while drawing the pin 81, whereas in the return stroke, the pin holding portion 63 moves to the front to the initial position without drawing the pin 81. Moreover, the reduction ratio in the forward stroke is larger than the reduction ratio in the return stroke. Thereby, in the forward stroke in which a relatively strong force for drawing the pin 81 is required, the fastening tool 1 can exert a relatively large torque, and in the return stroke in which a large force is not particularly required, the fastening tool 1 can efficiently return the pin holding portion 63 to the initial position at a relatively high speed (i.e., the fastening work can be performed efficiently).

[0095] In particular, in the present embodiment, since 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, a relatively large difference can be made in the moving speed of the pin holding portion 63 and the traction force of the pin 81 in the forward stroke and the return stroke.

[0096] Further, in the present embodiment, the speed reducer 4 is a planetary speed reducer including three stages (three sets) of planetary gear mechanisms 41, 42, 43. The planetary speed reducer is smaller and can obtain a larger reduction ratio than a gear speed reducer formed by combining spur gears and the like. In the present embodiment, since the speed reducer 4 is a multi-stage planetary speed reducer, a particularly large reduction ratio can be obtained. Further, by changing the number of stages (effective stages) in which the planetary gear mechanisms 41, 42, 43 of the speed reducer 4 function effectively, a change in the reduction ratio can be achieved appropriately.

[0097] In the present embodiment, a structure is employed in which the one-way clutch 70 and the lock mechanism 71 function in cooperation to make the second-stage planetary gear mechanism 42 function effectively in the case where the motor 2 is driven in the forward direction, and on the other hand, to make the function of the planetary gear mechanism 42 ineffective in the case where the motor 2 is driven in the reverse direction. In particular, since the one-way clutch 70 is a clutch that automatically performs different actions depending on the rotation direction, the change in the rotation direction of the motor shaft 23 can be linked to the change in the action of the lock mechanism 71 efficiently. Further, the lock mechanism 71 is configured to lock and unlock the lock cam 75 by moving the roller 73 in the circumferential direction between the locked position and the unlocked position. Thereby, the lock mechanism 71 can be made compact in the front-rear direction and the radial direction. Moreover, the roller 73 functions as a wedge by a slight movement in the circumferential direction, so that the lock cam 75 can be locked reliably, and further, the inner gear 422 can be locked reliably.

[0098] Further, in the second-stage planetary gear mechanism 42, which is smaller in rotation speed than the first-stage planetary gear mechanism and smaller in torque than the third-stage planetary gear mechanism, the lock mechanism 71 acts on the sun gear 421 and the inner gear 422. Thereby, the load applied to the lock mechanism 71 can be reduced, so that the durability can be improved.

[0099] The correspondence between each of the components of the above-described embodiment and each of the components of the present application will be shown below. However, each of the components of the embodiment is merely an example, and each of the components of the present application is not limited thereto.

[0100] The fastening tool 1 is an example of an "electric power tool". The motor 2 and the motor shaft 23 are examples of a "motor" and a "motor shaft", respectively. The speed reducer 4 is an example of a "gear speed reducer". The planetary gear mechanisms 41, 42, and 43 are examples of a "planetary gear mechanism", respectively. The sun gears 411, 421, and 431 are examples of a "sun gear", respectively. The ring gears 412, 422, and 432 are examples of a "ring gear", respectively. The carriers 415, 425, and 435 are examples of a "carrier", respectively. The planetary gears 418, 428, and 438 are examples of a "planetary gear", respectively. 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 holding portion 63 is an example of a "movable member". The fastening member 8 is an example of a "fastening member". 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".

[0101] Further, the above-described embodiments are merely examples, and the electric power tool according to the present application is not limited to the fastening tool 1 exemplified above. For example, the following modifications can be implemented. In addition, at least one of these modifications can be combined with any of the fastening tool 1 exemplified in the embodiments and the inventions described in each technical solution.

[0102] For example, the motor 2 can be replaced with a brush motor instead of a brushless motor. The motor 2 can be driven by electric power supplied from an external alternating current power source instead of being driven by the battery 182.

[0103] In addition, in the drive mechanism 3, a screw feed mechanism having a nut and a screw shaft, in which the nut is formed with an internal thread at an inner peripheral portion and the screw shaft is formed with an external thread at an outer peripheral portion and directly screwed with the nut, can be used instead of the ball screw mechanism 5. In addition, the ball screw mechanism 5 can be configured such that the screw shaft 56 is supported so as to be restricted in movement in the front-rear direction and rotatable about the drive axis Al, and the nut 51 moves in the front-rear direction as the screw shaft 56 rotates. In this case, the pin holding portion 63 can be directly or indirectly connected to the nut 51, which is the final output shaft. The idler gear 331 provided between the nut drive gear 311 of the first intermediate shaft 31 and the driven gear 511 of the nut 51 can be omitted, the nut drive gear 311 and the driven gear 511 can be engaged, or another gear can be provided therebetween.

[0104] The number of stages of the reduction gear 4 (i.e., the number of planetary gear mechanisms included in the reduction gear 4), and the configuration of each of the planetary gear mechanisms 41, 42, 43 can be appropriately changed. For example, the reduction gear 4 can have only one planetary gear mechanism, or can have two or more than four planetary gear mechanisms. Further, in the case where only one planetary gear mechanism is provided, the effective number of stages is switched between zero and one in accordance with a change in the rotational direction of the motor 2. In addition, the change in the effective number of stages can also be achieved by moving any one of the inner gears 412, 422, 432 in the axial direction. Also, a gear reduction gear including a gear set (spur gear, helical gear, bevel gear, etc.) different from the planetary gear mechanism can be used instead of the reduction gear 4. In this case, the change in the reduction ratio can be achieved, for example, by causing a specific gear configured to be slidable to selectively engage one of two gears having different numbers of teeth.

[0105] The reduction ratio change mechanism 7 can be appropriately changed as long as it can act in accordance with a change in the rotational direction of the motor shaft 23 to switch the reduction ratio of the reduction gear 4. For example, the reduction ratio change mechanism 7 can be configured to move any one of the inner gears 412, 422, 432 of the reduction gear 4 in the axial direction using a gear set that is connected to the motor shaft 23 and the reduction gear 4 (or the gear shift of the above-described modification example) in an actable manner.

[0106] The one-way clutch 70 can be changed to a one-way clutch having any other arbitrary configuration (for example, a one-way clutch using a ball). The shape, arrangement, number, and the like of each of the configuration components of the locking mechanism 71 can also be appropriately changed. For example, the number of rollers 73 can be more than three. The number of protrusions 756 of the locking cam 75 and the protrusions 725 of the retainer 72 can also be changed. The locking sleeve 74 can be omitted, and the rollers 73 can be arranged between the inner peripheral surface of the gear case 40 and the flat portion 757 of the locking cam 75 and can be moved between the locked position and the unlocked position. In addition, the locking cam 75 and the inner gear 422 can be formed as one component.

[0107] In the above-described embodiments, an example in which the control circuit 171 is constituted by a microcomputer including a CPU or the like is cited. However, the control circuit 171 can also be constituted by a programmable logic device such as an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or the like. In addition, the driving of the motor 2 can be controlled by a plurality of control circuits. Furthermore, the event that becomes the trigger for the control circuit 171 to switch the driving mode of the motor 2 is not limited to the above-described example, and can be, for example, an operation performed on an operation section (for example, a push button switch, a touch panel, or the like) provided independently of the trigger 151.

[0108] Further, the fastening tool 1 can be configured to fasten the work material W using a fastener of a different type from the fastener 8 exemplified by the above-described embodiments (for example, a blind rivet, a fastener of a shaft-holding type among fasteners in which a plurality of members are riveted). The fastening tool 1 can correspond to a plurality of types of fasteners by replacing the anvil 61 and the pin holding portion 63.

[0109] In addition, in the above-described embodiments, the fastening tool 1 is cited as an example of the electric power tool, but the present application can also be applied to other electric power tools that perform different actions in correspondence with the rotation direction of the motor. For example, the electric power tool can be embodied as a pruning shear having a fixed blade and a movable blade constituted so as to rotate about a prescribed shaft with respect to the fixed blade between a closed position and an open position.

[0110] The pruning shear performs a forward stroke in which the movable blade rotates from the closed position toward the open position and a return stroke in which a tree branch is cut while returning from the open position to the closed position as one cycle. Accordingly, it is preferable that the movable blade be moved toward the open position quickly in the forward stroke and that the movable blade exert a relatively strong shearing force in the return stroke. Therefore, in the pruning shear, it can be changed so that the rotation direction of the motor is switched between the forward stroke and the return stroke and so that the reduction ratio of the reduction gear in the return stroke is greater than the reduction ratio in the forward stroke.

[0111] Further, the power tool is not limited to the power tool in which the forward stroke in which the movable member is moved in a predetermined direction and the return stroke in which the movable member is moved in the opposite direction to the predetermined direction are operated as one cycle, such as the tightening tool 1 and the trimmer scissors described above. For example, the power tool can be embodied as a rotary tool in which an output shaft to which a tip tool is detachably attached is rotated about a driving axis. The rotary tool reverses the rotation direction of the output shaft and the tip tool in accordance with the reversal of the rotation direction of the motor. Accordingly, by changing the reduction ratio of the speed reducer in correspondence with the change of the rotation direction of the motor, different operations can be performed in accordance with the rotation direction of the tip tool.

[0112] Further, the present application, in view of the gist of the above-described embodiments and modifications thereof, constructs the following modes. At least one of the following modes can be adopted in combination with at least one of the above-described embodiments and modifications thereof, and the inventions described in each technical solution.

[0113] [Mode 1]

[0114] The gear reducer includes a three-stage planetary gear mechanism,

[0115] A sun gear of a second-stage planetary gear mechanism is fixed to a shaft of a carrier of a first-stage planetary gear mechanism in the three-stage planetary gear mechanism,

[0116] The one-way clutch is mounted to the shaft of the carrier of the first-stage planetary gear mechanism.

[0117] [Mode 2]

[0118] Further, a housing for accommodating the motor and the speed reducer is provided,

[0119] The inner gear is selectively rotatable about a first axis relative to the housing,

[0120] The locking mechanism includes a cylindrical locking sleeve, a locking cam, a retainer, and at least one roller, wherein

[0121] The locking sleeve is not rotatable about the first axis relative to the housing;

[0122] The locking cam is connected to the inner gear and is selectively rotatable about the first axis relative to the locking sleeve integrally with the inner gear, and the locking cam is at least partially disposed radially inward of the locking sleeve;

[0123] The retainer is at least partially disposed radially inward of the locking sleeve and is selectively rotatable about the first axis relative to the locking sleeve integrally with the one-way clutch;

[0124] The at least one roller is held by the retaining frame between the locking sleeve and the locking cam in the radial direction and can selectively move circumferentially around the first axis relative to the locking sleeve and the locking cam between a locked position and an unlocked position, wherein, in the locked position, the at least one roller is clamped between the locking sleeve and the locking cam, locking the locking cam so as to be unable to rotate relative to the locking sleeve; in the unlocked position, the at least one roller is loosely fitted between the locking sleeve and the locking cam, allowing the locking cam to rotate relative to the locking sleeve.

[0125] When the motor shaft rotates in the first direction, the sun gear rotates, causing the internal gear and the locking cam to rotate around the first axis via the planetary gears. Accordingly, the at least one roller moves relatively to the locking position, thereby locking the internal gear so as to be unable to rotate via the locking cam.

[0126] When the motor shaft rotates in the second direction, the holder and the one-way clutch rotate integrally, and the lock cam causes the internal gear and the sun gear to rotate integrally.

[0127] The main body housing 11 , the lock sleeve 74 , the lock cam 75 , the holder 72 , and the roller 73 are examples of “housing”, “lock sleeve”, “lock cam”, “holder”, and “roller”, respectively, in this embodiment.

[0128] [Method 3]

[0129] The at least one roller is configured to lock the locking cam so as to be unable to rotate by a wedge effect when the at least one roller is arranged in the locking position.

Claims

1. An electric tool, characterized in that: Having a motor and a gear reducer, wherein The motor has a motor shaft that can rotate in both forward and reverse directions; The gear reducer is operably connected to the motor shaft. The gear reducer is configured to change the reduction ratio according to a change in the rotation direction of the motor shaft. The gear reducer has at least one stage planetary gear mechanism, which includes a sun gear, an internal gear, a planet carrier and a plurality of planetary gears. The gear reducer is configured to change the reduction ratio by changing the effective number of stages of the at least one planetary gear mechanism. It also has a one-way clutch and a locking mechanism, wherein The one-way clutch is provided on a transmission path from the motor shaft to the sun gear of any one stage of the at least one planetary gear mechanism, and the one-way clutch is configured to allow relative rotation of the sun gear of the stage with respect to the one-way clutch when the motor shaft rotates in a first direction, which is one of the positive direction and the reverse direction, and to rotate integrally with the sun gear of the stage when the motor shaft rotates in a second direction, which is the other of the positive direction and the reverse direction; The locking mechanism is connected to the one-way clutch in an operative manner, and is configured to lock the internal gear of the stage so as to be unable to rotate when the one-way clutch allows the sun gear of the stage to rotate relative to each other, and to allow the internal gear of the stage to rotate integrally with the sun gear of the stage when the one-way clutch rotates integrally with the sun gear of the stage.

2. The electric tool according to claim 1, wherein: The gear reducer has a multi-stage planetary gear mechanism. The locking mechanism is configured to act on the internal gear of the second stage or the planetary gear mechanism after the second stage in the multi-stage planetary gear mechanism.

3. The electric tool according to claim 1 or 2, characterized in that: The invention also includes a movable member that is movably connected to the gear reducer and is configured to move as the motor is driven. The electric tool is configured to operate by combining a forward stroke and a return stroke as one cycle, wherein the forward stroke refers to a stroke in which the movable member moves in a predetermined direction, and the return stroke refers to a stroke in which the movable member moves in a direction opposite to the predetermined direction. The rotation direction of the motor shaft changes between the forward stroke and the return stroke.

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

5. The electric tool according to claim 4, characterized in that 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 relative to 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 speed reduction ratio in the forward stroke is greater than the speed reduction ratio in the return stroke.

6. The electric tool according to claim 5, wherein: A screw feed mechanism is further provided. The screw feed mechanism is disposed between the gear reducer and the movable member on a transmission path and is configured to convert the rotational motion of the output shaft of the gear reducer into the linear motion of the movable member.

7. The electric tool according to claim 1 or 2, characterized in that: The 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 electric tool according to claim 1 or 2, characterized in that: It also includes a control device configured to control the operation of the electric tool. The control device is configured to change the rotation direction of the motor when a predetermined event is recognized.

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