Power tool

Abstract

To provide an electric tool equipped with a speed reducer that can change a speed reduction ratio, which is improved.SOLUTION: An electric tool is equipped with a motor, a speed reducer and a speed reduction ratio changing mechanism. The speed reducer includes a plurality of stages of planetary gear mechanisms. The speed reduction ratio changing mechanisms change a speed reduction ratio of the speed reducer in response to change in a rotating direction of a motor shaft. At least two stages of the plurality of stages of planetary gear mechanisms are configured so that respective internal gears thereof selectively function as fixed elements. The speed reduction ratio changing mechanism comprises a one-way clutch and a lock mechanism. The lock mechanism locks the internal gears of the at least two stages unrotatably, when the one-way clutch does not transmit rotation; and rotates the internal gears of the at least two stages, when the one-way clutch transmits rotation. The at least two stages of planetary gear mechanisms include a speed-increase planetary gear mechanism and a speed-decrease planetary gear mechanism.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a power tool, and more particularly to a power tool including a reducer capable of changing the reduction ratio. [Background technology]

[0002] There is known a power tool that is equipped with a motor that can rotate in two directions, a first direction and a second direction, and that can perform different operations when the motor rotates in the first direction and when the motor rotates in the second direction. For example, a hedge trimmer disclosed in Patent Document 1 switches the reduction ratio of a planetary gear type transmission mechanism when the motor rotates in the first direction and when the motor rotates in the second direction. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2005-269972 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-mentioned planetary gear type transmission mechanism, the reduction ratio is changed by switching the internal gear between a fixed state and a free state depending on the rotation direction of the motor. However, in this transmission mechanism, the change in the reduction ratio, and therefore the difference in the output speed, tends to be too large.

[0005] An object of the present disclosure is to provide an improvement to a power tool equipped with a reducer capable of changing the reduction ratio. [Means for solving the problem]

[0006] According to one aspect of the present disclosure, a motor, a reducer, Reduction ratioThe motor has a motor shaft rotatable in two opposite directions. The speed reducer is operably connected to the motor shaft. The speed reducer includes a multi-stage planetary gear mechanism. The speed reduction ratio change mechanism is configured to change the speed reduction ratio of the speed reducer in response to a change in the rotation direction of the motor shaft.

[0007] At least two stages of the multi-stage planetary gear mechanism are configured such that the respective internal gears selectively function as fixed elements. The reduction ratio change mechanism includes a one-way clutch and a lock mechanism. The one-way clutch is disposed in a torque transmission path and configured to transmit rotation only when the motor shaft rotates in a specific one of two directions. The lock mechanism is operably connected to the one-way clutch and at least two stages of the internal gears of the multi-stage planetary gears. The lock mechanism is configured to lock the at least two stages of internal gears so that they cannot rotate when the one-way clutch does not transmit rotation. The lock mechanism is also configured to rotate the at least two stages of internal gears when the one-way clutch transmits rotation. The at least two stages of planetary gear mechanism includes a speed-up planetary gear mechanism configured as a speed-up mechanism and a speed-down planetary gear mechanism configured as a speed-down mechanism.

[0008] The electric power tool of this embodiment includes a reducer including a multi-stage planetary gear mechanism and a reduction ratio change mechanism. The reduction ratio change mechanism switches the internal gears of at least two stages of the planetary gear mechanism between a non-rotatable state (locked state) and a rotating state in response to a change in the rotation direction of the motor shaft. In the locked state, the internal gears function effectively as fixed elements. On the other hand, when the internal gears are rotated, they cannot function as fixed elements. Therefore, the number of stages of the planetary gear mechanism that function effectively in the reducer is reduced by at least two, and the reduction ratio (speed transmission ratio) of the reducer is changed. In this way, the electric power tool of this embodiment does not require control of the rotation speed of the motor, and can selectively perform two operations with different required output speeds and output torques in response to only a change in the rotation direction of the motor.

[0009] The reduction ratio of the planetary gear mechanism having an internal gear as a fixed element is relatively large due to structural constraints. Therefore, when the reduction ratio is changed by enabling or disabling the function of at least one stage among the multiple planetary gear mechanisms, the change in the reduction ratio is likely to be large. In contrast, in this embodiment, the functions of at least two stages of planetary gear mechanisms including the speed-up planetary gear mechanism and the speed-down planetary gear mechanism are enabled or disabled. According to this configuration, by appropriately combining the speed-up ratio (<1) of the speed-up planetary gear mechanism and the speed-down ratio (>1) of the speed-down planetary gear mechanism, it is possible to more flexibly set the speed-up ratio or speed-down ratio of the at least two stages of planetary gear mechanisms as a whole. As a result, it is possible to reduce the change in the reduction ratio of the reducer as a whole, and therefore the rotational speed. Therefore, the electric power tool of this embodiment can selectively perform two operations with a relatively small difference in output speed depending on the change in the rotation direction of the motor.

[0010] According to another aspect of the present disclosure, there is provided an electric tool including a motor, a reducer, and a reduction ratio change mechanism. The motor has a motor shaft rotatable in two opposite directions. The reducer is operably coupled to the motor shaft. The reducer includes a planetary gear mechanism. The reduction ratio change mechanism is configured to change the reduction ratio of the reducer in response to a change in the rotation direction of the motor shaft. The planetary gear mechanism is configured such that a sun gear selectively functions as a fixed element and an internal gear selectively functions as an input element.

[0011] The reduction ratio change mechanism includes a one-way clutch and a lock mechanism. The one-way clutch is disposed in the torque transmission path and configured to transmit rotation only when the motor shaft rotates in one of two specific directions. The lock mechanism is operably connected to the one-way clutch and the sun gear. The lock mechanism is configured to lock the sun gear so that it cannot rotate when the one-way clutch does not transmit rotation, and to rotate the sun gear when the one-way clutch transmits rotation.

[0012] The electric power tool of this embodiment includes a reducer including a planetary gear mechanism, and a reduction ratio change mechanism. The reduction ratio change mechanism switches the sun gear of the planetary gear mechanism between a non-rotatable state (locked state) and a rotating state in response to a change in the rotation direction of the motor shaft. In the locked state, the sun gear effectively functions as a fixed element. On the other hand, when the sun gear is rotated, it cannot function as a fixed element. Therefore, the number of stages of the planetary gear mechanism that effectively function in the reducer is reduced by one, and the reduction ratio (speed transmission ratio) of the reducer is changed. In this way, the electric power tool of this embodiment does not require control of the rotation speed of the motor, and can selectively perform two operations with different required output speeds and output torques in response to only a change in the rotation direction of the motor.

[0013] Furthermore, since the planetary gear mechanism of this embodiment has a sun gear functioning as a fixed element, the reduction ratio is smaller than that of a reducer in which the internal gear is the fixed element. Therefore, the change in the reduction ratio caused by enabling or disabling the function of the planetary gear mechanism can be smaller than that of a reducer in which the internal gear is the fixed element. Therefore, the power tool of this embodiment can selectively perform two operations with a relatively small difference in output speed depending on the change in the rotation direction of the motor. [Brief description of the drawings]

[0014] [Figure 1] 1 is an overall perspective view of a hedge trimmer according to a first embodiment; [Diagram 2] FIG. [Diagram 3] FIG. 3 is a partially enlarged view of FIG. 2 (however, the main body housing and the connecting rod are omitted from the illustration). [Figure 4] FIG. 4 is a cross-sectional view taken along line IV-IV in FIG. [Diagram 5] FIG. 2 is an exploded perspective view of a reducer and a reduction ratio change mechanism. [Figure 6] FIG. 4 is an explanatory diagram of the operating principle of the locking mechanism, and is a schematic cross-sectional view of the locking mechanism in a locked state. [Figure 7]FIG. 4 is an explanatory diagram of the operating principle of the locking mechanism, and is a schematic cross-sectional view of the locking mechanism in an unlocked state. [Figure 8] FIG. 11 is a partial cross-sectional view of a hedge trimmer according to a second embodiment (however, a main body housing and a connecting rod are omitted from the illustration). [Figure 9] FIG. 2 is an exploded perspective view of a reducer and a reduction ratio change mechanism. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] In one or more embodiments of the present disclosure, the speed-up planetary gear mechanism may be disposed in front of (on the input side of) the speed-down planetary gear mechanism. With this configuration, the torque transmitted from the speed-up planetary gear mechanism to the speed-down planetary gear mechanism can be made smaller than the torque transmitted from the speed-up planetary gear mechanism to the speed-up planetary gear mechanism when the speed-down planetary gear mechanism is disposed in front of (on the input side of) the speed-up planetary gear mechanism. This allows the strength required for the gears to be smaller than the strength required when the speed-down planetary gear mechanism is disposed in front of the speed-up planetary gear mechanism, and thus allows the gears to be made compact.

[0016] In one or more embodiments of the present disclosure, the sun gear that functions as the output element of the speed-increasing planetary gear mechanism and the sun gear that functions as the input element of the speed-reducing planetary gear mechanism may be configured as a single member, which can simplify the configuration of the reducer and improve the ease of assembly.

[0017] In one or more embodiments of the present disclosure, the reducer may be configured to operate in a high-speed, low-torque mode when the locking mechanism locks the rotation of the at least two-stage internal gear, and to operate in a low-speed, high-torque mode when the locking mechanism rotates the at least two-stage internal gear. In other words, the reducer may be configured to operate in a high-speed, low-torque mode when the at least two-stage planetary gear mechanism functions effectively, and to operate in a low-speed, high-torque mode when the at least two-stage planetary gear mechanism does not function. In other words, the at least two-stage planetary gear mechanism may be configured as a speed-increasing mechanism as a whole. With this configuration, the torque can be effectively increased by the rotation of the internal gear in the low-speed, high-torque mode.

[0018] In one or more embodiments of the present disclosure, the power tool may further include a reduction gear disposed in the torque transmission path between the motor shaft and the internal gear, which allows further reduction in speed to be achieved prior to the reduction in speed achieved by the planetary gear mechanism.

[0019] In one or more embodiments of the present disclosure, the reducer may include only one planetary gear mechanism, which allows for a compact reducer.

[0020] In one or more embodiments of the present disclosure, the internal gear of the planetary gear mechanism may be rotatably supported by the first bearing. This configuration makes it possible to stabilize the rotation of the internal gear.

[0021] In one or more embodiments of the present disclosure, the one-way clutch may include a clutch member and a second bearing disposed on both sides of the clutch member in the axial direction of the one-way clutch. With this configuration, when the one-way clutch does not transmit rotation (when the one-way clutch rotates idly), the second bearing can ensure smooth rotation of the member that rotates relative to the one-way clutch.

[0022] In one or more embodiments of the present disclosure, the reduction ratio when the motor shaft is rotated in one of the two directions may be less than 2.5 times the reduction ratio when the motor shaft is rotated in the other of the two directions. This configuration provides a power tool that can selectively perform two operations with a relatively small difference in output speed depending on the change in the rotation direction of the motor.

[0023] In one or more embodiments of the present disclosure, the power tool may be a cutting tool configured to relatively reciprocate a first blade and a second blade attached to a body of the power tool in a linear manner, and to cut an object in both a stroke in which the first blade moves forward and a stroke in which the first blade moves backward relative to the second blade. With this configuration, a cutting tool capable of selectively performing two operations with different cutting speeds and cutting forces is realized by changing the rotation direction of the motor depending on the type of object.

[0024] Representative and non-limiting embodiments of the present disclosure will be specifically described below with reference to the drawings.

[0025] [First embodiment] A hedge trimmer 1A according to a first embodiment will be described below with reference to Fig. 1 to Fig. 7. The hedge trimmer 1A is an example of a power tool, and is mainly used for trimming and pruning hedges, trees, etc. The hedge trimmer 1A can cut an object (typically, tree branches and leaves) by relatively reciprocating two detachably attached blades 9 in a straight line.

[0026] First, a schematic configuration of the hedge trimmer 1A will be described.

[0027] As shown in FIG. 1 and FIG. 2, the outer shell of the hedge trimmer 1A is mainly formed by a main body housing 11 and two handles 17, 19 connected to the main body housing 11. A motor 2, a reduction gear 4, and a motion conversion mechanism 7 are arranged in the main body housing 11. A long plate-shaped blade 9 is operably connected to the motion conversion mechanism 7, protrudes from one end of the main body housing 11, and extends linearly in a direction perpendicular to a predetermined axis A1. The handle 17 is connected to an end of the main body housing 11 that is closer to the blade 9, and the handle 19 is connected to an end of the main body housing 11 that is farther from the blade 9. The handle 19 is provided with a switch lever (also called a trigger) 193 that is pressed by a user. When the switch lever 193 is pressed, the motor 2 is energized, and the two blades 9 are reciprocated relatively in the longitudinal direction.

[0028] For the sake of convenience, the direction in which the long axis of the blade 9 extends (also the longitudinal direction of the main housing 11) is defined as the front-rear direction of the hedge trimmer 1A. In the front-rear direction, the direction from the main housing 11 to the protruding end of the blade 9 is defined as the front direction, and the opposite direction (direction from the protruding end of the blade 9 to the main housing 11) is defined as the rear direction. In the following, the handle 17 closer to the blade 9 is referred to as the front handle 17, and the handle 19 farther from the blade 9 is also referred to as the rear handle 19. The direction perpendicular to the plate surface of the blade 9 (also the extension direction of the axis A1) is defined as the up-down direction of the hedge trimmer 1A. In the up-down direction, the direction from the blade 9 to the motor 2 is defined as the upward direction, and the opposite direction (direction from the motor 2 to the blade 9) is defined as the downward direction. The direction perpendicular to the front-rear direction and the up-down direction is defined as the left-right direction of the hedge trimmer 1A.

[0029] The detailed configuration of the hedge trimmer 1A will be described below.

[0030] First, the main housing 11 and the elements disposed within the main housing 11 will be described.

[0031] As shown in Fig. 2, the main body housing 11 is a hollow body and accommodates the motor 2, the reducer 4, and the motion conversion mechanism 7. The motor 2, the reducer 4, and the motion conversion mechanism 7 are disposed in the motor housing 20, the gear housing 40, and the crank housing 70, respectively. The motor housing 20, the gear housing 40, and the crank housing 70 are fixed to each other and integrated with screws. The motor housing 20, the gear housing 40, and the crank housing 70 are supported within the main body housing 11 so as to be substantially immovable relative to the main body housing 11.

[0032] The motor 2 is a brushless direct current (DC) motor. The motor 2 includes a stator 21, a rotor 22, and a motor shaft 23. The stator 21 is supported in a fixed manner within a motor housing 20. The motor shaft 23 is fixed to the rotor 22. The motor shaft 23 rotates integrally with the rotor 22 around an axis A1 extending in the vertical direction. The motor shaft 23 is rotatably supported at its upper and lower ends by bearings 201, 202. The bearings 201, 202 are supported by the motor housing 20. Note that in this embodiment, the motor shaft 23 is formed of a plurality of members connected to each other, but the motor shaft 23 may be a single member.

[0033] The reducer 4 is disposed below the motor 2 and coaxially with the motor 2. The reducer 4 is operably connected to the motor shaft 23 of the motor 2 and the motion conversion mechanism 7, and is configured to reduce the rotation speed of the motor shaft 23 and increase the torque to output to the motion conversion mechanism 7. As shown in FIG. 3, the reducer 4 is a multi-stage planetary reducer and includes a four-stage (four sets) planetary gear mechanism housed in a gear housing 40. Hereinafter, the four-stage (four sets) planetary gear mechanisms are referred to as a first planetary gear mechanism 41, a second planetary gear mechanism 42, a third planetary gear mechanism 43, and a fourth planetary gear mechanism 44, in that order from the first stage (input side, upper side).

[0034] A lower end of the motor shaft 23 protrudes into the gear housing 40. The input shaft of the reduction gear 4 is the motor shaft 23, and the final output shaft of the reduction gear 4 is a shaft 449 integrated with the fourth carrier 445 of the fourth planetary gear mechanism 44. The shaft 449 is supported rotatably around the axis A1 by two bearings 451, 452 supported by the crank housing 70. The lower end of the shaft 449 is disposed within the crank housing 70. The details of the reduction gear 4 will be described later.

[0035] As shown in Fig. 2, the motion conversion mechanism 7 is disposed in a crank housing 70 below the reducer 4. The motion conversion mechanism 7 is configured to convert the rotational motion of the final output shaft (shaft 449) of the reducer 4 into linear motion, and to linearly reciprocate the blades 9. Any known configuration may be adopted for the motion conversion mechanism 7. In this embodiment, the motion conversion mechanism 7 is configured as a so-called crank mechanism, and includes a cam plate 72 and two connecting rods 731, 732.

[0036] The cam plate 72 is a disk-shaped member fixed to the outer periphery of the shaft 449 of the fourth carrier 445, and rotates integrally with the fourth carrier 445 around the axis A1. Cylindrical eccentric parts 721, 722 protrude upward and downward from the upper and lower surfaces of the cam plate 72, respectively. The centers of the eccentric parts 721, 722 are offset from the axis A1 by the same distance and are located opposite each other across the axis A1. The rear ends of the connecting rods 731, 732 are operably connected to the eccentric parts 721, 722, respectively. The front ends of the connecting rods 731, 732 are operably connected to the two blades 9.

[0037] As shown in Figs. 1 and 2, the two blades 9 extend in the front-rear direction while overlapping each other in the up-down direction, and are supported by a blade guide 97. The blade guide 97 is fixed to the front end of the crank housing 70 and extends linearly forward from the crank housing 70. The blade guide 97 supports the blade 9 so that it can move linearly in the front-rear direction within a predetermined range. The two blades 9 reciprocate linearly in the front-rear direction in opposite phases (with a phase difference of 180 degrees) in response to the rotation of the cam plate 72. Each blade 9 has a plurality of blades (cutting portions) 90 formed along its left and right ends. As the two blades 9 move relatively in the front-rear direction, an object is pinched between the blades 90 of the upper blade 9 and the blades 90 of the lower blade 9, and cut.

[0038] The blades 90 are wedge-shaped and have cutting edges on both the front and rear sides. Therefore, the two blades 9 can cut an object regardless of the direction of their relative movement. In other words, the two blades 9 can cut an object both in a forward stroke in which the upper blade 9 moves forward relative to the lower blade 9, and in a return stroke in which the upper blade 9 moves backward relative to the lower blade 9.

[0039] In addition, the motion conversion mechanism 7 may be configured to reciprocate only one of the two blades 9 relative to the other, which is fixed, rather than reciprocating both of the two blades 9 back and forth relative to the main housing 11.

[0040] The front handle 17 will now be described.

[0041] 1, the front handle 17 is formed in a U-shape. The front handle 17 is formed integrally with the main body housing 11, and both ends thereof are connected to the left and right front ends of the main body housing 11, respectively. The center of the front handle 17 protrudes above the main body housing 11 and functions as a gripping part 171 to be gripped by the user.

[0042] The rear handle 19 and the elements disposed within the rear handle 19 will now be described.

[0043] As shown in FIG. 1 and FIG. 2, the rear handle 19 is a hollow body formed in a loop shape (D-shape) when viewed from the side, and is connected to the rear end of the main body housing 11. A portion of the rear handle 19 extending rearward from the upper rear end of the main body housing 11 functions as a grip part 191 to be gripped by a user. A switch lever 193 is disposed below the grip part 191. A switch 195 is disposed inside the rear handle 19. The switch 195 is normally maintained in an OFF state, and is turned ON in response to a pressing operation of the switch lever 193. The switch 195 is electrically connected to the controller 81 described below by an electric wire (not shown). When the switch 195 is turned ON, the switch 195 outputs a signal indicating the amount of operation (amount of pressing) of the switch lever 193 to the controller 81.

[0044] A controller 81 is housed within the lower front end of the rear handle 19. Although detailed illustration is omitted, the controller 81 includes a circuit board and a control circuit mounted on the circuit board. In this embodiment, the control circuit is configured as a microcomputer including a CPU, ROM, memory, timer, etc., and controls the operation of the hedge trimmer 1A including the driving of the motor 2. More specifically, when the controller 81 recognizes a signal from the switch 195, it drives the motor 2 at a rotation speed corresponding to the amount of operation of the switch lever 193 indicated by the signal.

[0045] An operation unit 85 is disposed on the upper surface of the rear handle 19. The operation unit 85 is an input device that allows a user to input various instructions by externally operating it. The operation unit 85 includes a plurality of push button switches, and is electrically connected to the controller 81 by wires (not shown). In this embodiment, the operation unit 85 includes a main power switch 851 and a reverse switch 855.

[0046] The main power switch 851 is a switch for inputting an instruction to turn on the main power. The main power switch 851 is configured to be switched between on and off in response to a long press, and to output a specific signal to the controller 81 in response to the switching. The controller 81 (control circuit) accepts the signal from the switch 195 as valid only while the main power switch 851 is in the on state. In other words, while the main power switch 851 is in the off state, the controller 81 does not drive the motor 2 even if the switch 195 is turned on.

[0047] The reverse switch 855 is a switch for inputting an instruction to reverse the rotation direction of the motor 2, and therefore the movement direction of the blade 9. The reverse switch 855 is configured to output a specific signal to the controller 81 in response to a pressing operation. In this embodiment, the rotation direction of the motor 2 (specifically, the rotor 22 and the motor shaft 23) can be switched between a first direction and a second direction opposite to the first direction. The controller 81 (control circuit) sets the rotation direction of the motor 2 to the first direction in response to the main power switch 851 being turned on. When the controller 81 subsequently recognizes a signal from the reverse switch 855, it changes the rotation direction of the motor 2 to the second direction. Thereafter, while the main power switch 851 is in the on state, the controller 81 switches the rotation direction of the motor 2 between the first direction and the second direction each time it recognizes a signal from the reverse switch 855.

[0048] Furthermore, a display unit 87 that displays various information is disposed adjacent to the operation unit 85 on the upper surface of the rear handle 19. Although detailed illustration is omitted, in this embodiment, the display unit 87 is configured to display the on / off state of the main power switch 851 and the rotation direction (operation mode) of the motor 2. The display unit 87 notifies such information by, for example, lighting up, flashing, changing the color of a lamp, or the like.

[0049] A battery attachment section 197 is provided at the lower rear end section of the rear handle 19. A battery 198 is removably attached to the battery attachment section 197. The battery 198 is a repeatedly rechargeable power source for supplying power to each section of the hedge trimmers 1A, 1B and the motor 2, and is also referred to as a battery pack. The configurations of the battery attachment section 197 and the battery 198 are well known, so a description thereof will be omitted.

[0050] The details of the reducer 4 will be described below.

[0051] As shown in Figs. 3 to 5, in the reduction gear 4, the first stage (input side) first planetary gear mechanism 41 includes a first sun gear 411, a first internal gear (also called a ring gear) 412, a first carrier 415, and a plurality of first planetary gears 418. In the first planetary gear mechanism 41, the first internal gear 412 is fixed, the first sun gear 411 is the input, and the first carrier 415 is the output. The first internal gear 412 is always in a fixed state. Therefore, the first planetary gear mechanism 41 always functions as a reduction mechanism.

[0052] The first internal gear 412 is supported within the gear housing 40 so as to be substantially non-rotatable around the axis A1 relative to the gear housing 40. The first sun gear 411 is fixed to a lower end of the motor shaft 23 (the input shaft of the reducer 4). The first planetary gear 418 is supported by the first carrier 415 and meshes with the first sun gear 411 and the first internal gear 412. A shaft 419 is fixed to the first carrier 415. The shaft 419 extends downward along the axis A1.

[0053] The second planetary gear mechanism 42 of the second stage is disposed below the first planetary gear mechanism 41. The second planetary gear mechanism 42 includes a second sun gear 421, a second internal gear (also called a ring gear) 422, a second carrier 425, and a plurality of second planetary gears 428. In the second planetary gear mechanism 42, the second internal gear 422 is fixed, the second carrier 425 is an input, and the second sun gear 421 is an output. However, the state of the second internal gear 422 is selectively switched between a fixed state (locked state) and a rotating state according to the rotation direction of the motor 2. Therefore, the second planetary gear mechanism 42 selectively functions as a speed increasing mechanism.

[0054] The second internal gear 422 is provided inside the sleeve 405. The sleeve 405 is a stepped cylindrical member, and is disposed within the gear housing 40 at a distance from the gear housing 40. The sleeve 405 is selectively rotatable around the axis A1 relative to the gear housing 40. The second internal gear 422 is configured to rotate integrally with the sleeve 405. Whether the second internal gear 422 rotates is switched by a reduction ratio change mechanism 6A according to the rotation direction of the motor 2. The reduction ratio change mechanism 6A will be described in detail later.

[0055] The second carrier 425 is fixed to a lower end of a shaft 419 extending from the first carrier 415. That is, the shaft 419 functions as an output shaft of the first planetary gear mechanism 41 and an input shaft of the second planetary gear mechanism 42. The second planetary gear 428 is supported by the second carrier 425 and meshes with the second internal gear 422 and the second sun gear 421. The second sun gear 421 is fixed to a shaft 429. The shaft 429 extends downward along the axis A1.

[0056] The third planetary gear mechanism 43 of the third stage is disposed below the second planetary gear mechanism 42. The third planetary gear mechanism 43 includes a third sun gear 431, a third internal gear (also called a ring gear) 432, a third carrier 435, and a plurality of third planetary gears 438. In the third planetary gear mechanism 43, the third internal gear 432 is fixed, the third sun gear 431 is an input, and the third carrier 435 is an output. As with the second planetary gear mechanism 42, the state of the third internal gear 432 is selectively switched between a fixed state (locked state) and a rotating state according to the rotation direction of the motor 2. Thus, the third planetary gear mechanism 43 selectively functions as a reduction mechanism.

[0057] The third internal gear 432 is provided below the second internal gear 422 and within the sleeve 405. Like the second internal gear 422, the third internal gear 432 is configured to rotate integrally with the sleeve 405. Therefore, whether or not the third internal gear 432 rotates is switched by a reduction ratio change mechanism 6A (described later) according to the rotation direction of the motor 2.

[0058] The third sun gear 431 is fixed to the lower end of the shaft 429. In other words, the second sun gear 421 and the third sun gear 431 are fixed to a common shaft 429 and constitute a single member. This improves the ease of assembly of the reducer 4. The shaft 429 functions as an output shaft of the second planetary gear mechanism 42 and an input shaft of the third planetary gear mechanism 43. The third planetary gear 438 is supported by the third carrier 435 and meshes with the third sun gear 431 and the third internal gear 432. The third carrier 435 has a shaft 439 extending downward along the axis A1.

[0059] The fourth planetary gear mechanism 44 of the fourth stage is disposed below the third planetary gear mechanism 43. The fourth planetary gear mechanism 44 includes a fourth sun gear 441, a fourth internal gear (also called a ring gear) 442, a fourth carrier 445, and a plurality of fourth planetary gears 448. In the fourth planetary gear mechanism 44, the fourth internal gear 442 is fixed, the fourth sun gear 441 is an input, and the fourth carrier 445 is an output. The fourth internal gear 442 is always in a fixed state. Therefore, the fourth planetary gear mechanism 44 always functions as a reduction mechanism.

[0060] The fourth internal gear 442 is supported in the gear housing 40 so as to be substantially non-rotatable around the axis A1 relative to the gear housing 40. The fourth sun gear 441 is fixed to the lower end of the shaft 439 extending from the third carrier 435. That is, the shaft 439 functions as the output shaft of the third planetary gear mechanism 43 and the input shaft of the fourth planetary gear mechanism 44. The fourth planetary gear 448 is supported by the fourth carrier 445 and meshes with the fourth sun gear 441 and the fourth internal gear 442. The fourth carrier 445 has a shaft 449 extending downward along the axis A1. As described above, the shaft 449 functions as the final output shaft of the reduction gear 4.

[0061] The reduction ratio change mechanism 6A will be described below. The reduction ratio change mechanism 6A is configured to selectively lock or rotate the second internal gear 422 of the second stage and the third internal gear 432 of the third stage of the reducer 4 with respect to the gear housing 40, depending on the rotation direction of the motor 2. When the states of the second internal gear 422 and the third internal gear 432 are 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.

[0062] As shown in FIGS. 3 to 5, the speed reduction ratio change mechanism 6A includes a one-way clutch 60 and a lock mechanism 61A.

[0063] The one-way clutch 60 is a clutch configured to transmit rotation in only one direction and rotate idly in the opposite direction. A general-purpose one-way clutch is used for the one-way clutch 60 of this embodiment. The one-way clutch 60 is a type in which bearings 605 (radial bearings) are arranged on both axial sides of a clutch member 601 (e.g., rollers, sprags). In other words, the one-way clutch 60 is configured as a single component (unit) with the bearings 605 built in.

[0064] The one-way clutch 60 is disposed on the torque transmission path of the reduction gear 4. More specifically, the one-way clutch 60 is fitted onto the outer periphery of the shaft 419 that is integrated with the first stage first carrier 415. When the shaft 419 rotates in a first direction, the one-way clutch 60 rotates idly relative to the shaft 419. That is, the one-way clutch 60 does not transmit rotation. On the other hand, when the shaft 419 rotates in a second direction opposite to the first direction, the one-way clutch 60 rotates integrally with the shaft 419. That is, the one-way clutch 60 is locked to the shaft 419 and rotates integrally with the shaft 419, enabling transmission of rotation.

[0065] The lock mechanism 61A is configured to switch the state of the second stage second internal gear 422 and the third stage third internal gear 432 between when the one-way clutch 60 does not transmit rotation and when it transmits rotation. The lock mechanism 61A includes a retainer 62A, two rollers 63, a lock sleeve 64A, and a lock cam 65A.

[0066] The retainer 62A is a cylindrical member having a through hole through which the shaft 419 is inserted. The retainer 62A holds the roller 63 so as to be movable in the circumferential direction around the axis A1 relative to the retainer 62A. The retainer 62A is configured to selectively engage with the lock cam 65A and rotate integrally with the lock cam 65A.

[0067] The retainer 62A includes a base portion 621, four protrusions 623, and a cylindrical portion 625. The base portion 621 is an annular portion. The protrusions 623 are arc-shaped wall portions arranged at approximately equal intervals on the outer edge of the base portion 621, and protrude downward from the outer edge of the base portion 621. The cylindrical portion 625 has an outer diameter smaller than the base portion 621, and protrudes forward from the center of the base portion 621 along the axis A1.

[0068] The one-way clutch 60 is fixed to the inside of the cylindrical portion 625 of the retainer 62A. That is, the retainer 62A is integrated with the one-way clutch 60 in terms of rotation. Therefore, the retainer 62A can selectively rotate with respect to the shaft 419. In detail, when the shaft 419 rotates in the first direction, the retainer 62A rotates idly with respect to the shaft 419 integrally with the one-way clutch 60. That is, the retainer 62A does not rotate together with the shaft 419. At this time, the bearing 605 of the one-way clutch 60 ensures smooth rotation of the shaft 419 with respect to the retainer 62A. On the other hand, when the shaft 419 rotates in the second direction, the retainer 62A rotates integrally with the shaft 419 together with the one-way clutch 60.

[0069] The rollers 63 are cylindrical members (pins). The diameter of each roller 63 is approximately uniform and is smaller than the interval between two adjacent protrusions 623 of the retainer 62A and is larger than the radial thickness of the protrusions 623. The two rollers 63 are disposed in two diagonally opposite corners of the four spaces formed between the protrusions 623 of the retainer 62A with their axes extending in the vertical direction.

[0070] The lock sleeve 64A is a substantially cylindrical member. The lock sleeve 64A is disposed coaxially with the retainer 62A and around (radially outwardly of) the retainer 62A below the first stage first internal gear 412. The lock sleeve 64A is supported within the gear housing 40 so as to be substantially unrotatable around the axis A1 relative to the gear housing 40. The protrusion 623 and roller 63 of the retainer 62A are disposed inside the lock sleeve 64A.

[0071] The locking cam 65A is operably connected to the retainer 62A and is selectively rotated by the retainer 62A. The locking cam 65A is a generally cylindrical member, and is disposed coaxially with the retainer 62A.

[0072] More specifically, the lock cam 65A includes a cylindrical portion 651 and two protrusions 656 protruding radially outward from the cylindrical portion 651. The cylindrical portion 651 has a through hole with a circular cross section extending along the axis A1. The outer peripheral surface of the cylindrical portion 651 includes two flat portions 652. The flat portions 652 are provided diagonally across the axis A1 and extend parallel to each other and parallel to the axis A1. The protrusions 656 are provided diagonally across the axis A1 and protrude radially outward from the outer peripheral surface of the cylindrical portion 651. The two protrusions 656 are each disposed between the two flat portions 652 in the circumferential direction of the cylindrical portion 651. Of the outer peripheral surface of the cylindrical portion 651, a portion between the flat portions 652 and the protrusions 656 is a curved surface that corresponds to the outer peripheral surface of a cylinder.

[0073] As shown in FIG. 6, the radial distance between the flat portion 652 and the inner peripheral surface of the lock sleeve 64A is maximum at the center of the flat portion 652 and is set to be slightly larger than the diameter of the roller 63. The radial distance between the flat portion 652 and the inner peripheral surface of the lock sleeve 64A decreases from the center to the end of the flat portion 652. The radial distance between the end of the flat portion 652 and the inner peripheral surface of the lock sleeve 64A is set to be smaller than the diameter of the roller 63. Note that FIG. 6 is a diagram that shows a schematic cross section of the lock mechanism 61A to explain the operating principle of the lock mechanism 61A, and does not strictly correspond to the shape of the actual lock mechanism 61A. This point is the same as FIG. 7, which will be referred to later.

[0074] The lock cam 65A having the above-mentioned configuration is fitted from below onto the outer periphery of the cylindrical portion 625 of the retainer 62A. The two protrusions 656 of the lock cam 65A are arranged in two of the four spaces (more specifically, two spaces in which the rollers 63 are not arranged) formed between the protrusions 623 of the retainer 62A in the circumferential direction. In addition, the portion of the cylindrical portion 651 other than the protrusions 656 is arranged in the space formed between the cylindrical portion 625 and the protrusions 623 of the retainer 62A in the radial direction. The rollers 63 are arranged between the flat portion 652 of the lock cam 65A and the inner circumferential surface of the lock sleeve 64A in the radial direction.

[0075] In addition, the lock cam 65A is connected to the sleeve 405 via the protrusion 656, and is selectively rotatable around the axis A1 relative to the gear housing 40 together with the sleeve 405. As described above, the second internal gear 422 and the third internal gear 432 are integrated with the sleeve 405 in terms of rotation, and therefore the lock cam 65A is selectively rotatable together with the second internal gear 422 and the third internal gear 432.

[0076] The operation of the speed reduction ratio change mechanism 6A (the one-way clutch 60 and the lock mechanism 61A) will now be described.

[0077] First, the operation when the rotation direction of the motor 2 is the first direction will be described.

[0078] When the motor shaft 23 starts to rotate in the first direction, the first stage first carrier 415 and shaft 419 also rotate in the first direction around the axis A1. At this time, as described above, the one-way clutch 60 rotates freely with respect to the shaft 419 and does not transmit the rotation to the retainer 62A. Therefore, the retainer 62A does not actively rotate.

[0079] The second stage second carrier 425 fixed to the shaft 419 also rotates in the first direction around the axis A1. The second planetary gear 428 supported by the second carrier 425 rotates the second internal gear 422 and the sleeve 405 in the second direction relative to the gear housing 40. At this time, the lock cam 65A connected to the sleeve 405 also rotates in the second direction (the direction of the arrow in FIG. 6). In response to the rotation of the lock cam 65A, the roller 63 moves relatively from the position indicated by the dotted line in FIG. 6 in the direction toward the end of the flat portion 652.

[0080] 6, before the projection 656 of the lock cam 65A abuts against the projection 623 of the retainer 62A, the roller 63 is wedged between the flat portion 652 and the inner circumferential surface of the lock sleeve 64A at a position closer to the end of the flat portion 652 than to the center of the flat portion 652. Hereinafter, the position of the roller 63 relative to the lock sleeve 64A and the lock cam 65A at this time will be referred to as the locked position, and the state of the lock mechanism 61A will be referred to as the locked state. As a result, the lock cam 65A is locked to the lock sleeve 64A and thus to the gear housing 40 via the roller 63, and rotation relative to the gear housing 40 is prohibited.

[0081] As the lock cam 65A is locked, the sleeve 405, and therefore the second internal gear 422 and the third internal gear 432 are also locked so as not to rotate relative to the gear housing 40. Therefore, from this point on, the second internal gear 422 and the third internal gear 432 function as fixed elements. The second planetary gear 428 revolves around the second sun gear 421 while rotating, causing the second sun gear 421 and the shaft 429 to rotate in the first direction. The third sun gear 431 fixed to the shaft 429 also rotates in the first direction, causing the third carrier 435 to rotate in the first direction via the third planetary gear 438.

[0082] As described above, when the motor shaft 23 rotates in the first direction and the one-way clutch 60 does not transmit the rotation to the retainer 62A, the lock mechanism 61A locks the second internal gear 422 of the second stage and the third internal gear 432 of the third stage so that they cannot rotate. This allows the second planetary gear mechanism 42 and the third planetary gear mechanism 43 to function effectively. Therefore, when the motor shaft 23 rotates in the first direction, the number of effective stages of the reducer 4 is four.

[0083] The operation when the rotation direction of the motor 2 is the second direction will be described.

[0084] When the motor shaft 23 starts to rotate in the second direction, the first stage first carrier 415 and shaft 419 also rotate in the second direction. At this time, the one-way clutch 60 is locked to the shaft 419 as described above, and transmits the rotation of the shaft 419 to the retainer 62A. Therefore, the retainer 62A also rotates in the second direction (the direction of the arrow in FIG. 7).

[0085] 7, two of the protrusions 623 of the retainer 62A come into contact with the protrusions 656 of the lock cam 65A and press them in the second direction. Meanwhile, the remaining two protrusions 623 come into contact with the roller 63 and press it in the second direction, moving it to a position (in this embodiment, a position roughly corresponding to the center of the flat portion 652) where the roller 63 is released from being clamped by the flat portion 652 and the inner circumferential surface of the lock sleeve 64A. Hereinafter, the position of the roller 63 relative to the lock sleeve 64A and the lock cam 65A at this time is also referred to as an unlocked position, and the state of the lock mechanism 61A is also referred to as an unlocked state.

[0086] As the roller 63 is placed in the unlocked position, the lock cam 65A becomes rotatable relative to the lock sleeve 64A and, in turn, the gear housing 40. Thus, the rotation of the retainer 62A is transmitted to the lock cam 65A, and the lock cam 65A rotates integrally with the shaft 419 and the retainer 62A in the second direction. As a result, the second stage second internal gear 422 and the third stage third internal gear 432 rotate integrally with the shaft 419 and the second stage second carrier 425 in the second direction.

[0087] The second planetary gear 428 supported by the second stage second carrier 425 cannot rotate (spin) because the second carrier 425 and the second internal gear 422 rotate integrally. As a result, the second stage second sun gear 421 rotates in the second direction integrally with the second carrier 425 and the second internal gear 422. The rotation speed of the shaft 429 (output shaft of the second planetary gear mechanism 42) is the same as that of the shaft 419 (input shaft of the second planetary gear mechanism 42), and the second planetary gear mechanism 42 does not function as a speed increasing mechanism.

[0088] The third planetary gear 438 supported by the third stage third carrier 435 cannot rotate (spin) either, because the third sun gear 431 and the third internal gear 432 fixed to the shaft 429 rotate integrally. As a result, the third stage third carrier 435 rotates in the second direction integrally with the third sun gear 431 and the third internal gear 432. The rotation speed of the shaft 439 (output shaft of the third planetary gear mechanism 43) is the same as that of the shaft 429 (input shaft of the third planetary gear mechanism 43), and the third planetary gear mechanism 43 does not function as a reduction mechanism.

[0089] As described above, when the motor shaft 23 rotates in the second direction and the one-way clutch 60 transmits the rotation to the retainer 62A, the lock mechanism 61A rotates the second internal gear 422 and the third internal gear 432 integrally with the shaft 419 in the same direction. As a result, the lock mechanism 61A disables the functions of the second planetary gear mechanism 42 and the third planetary gear mechanism 43. Therefore, when the motor shaft 23 rotates in the second direction, the number of effective stages of the reducer 4 is two.

[0090] As described above, the number of effective stages of the reduction gear 4 is switched between 4 and 2 depending on the rotation direction of the motor 2. In this embodiment, the second planetary gear mechanism 42 and the third planetary gear mechanism 43 are configured to function as a speed increasing mechanism as a whole (the output speed of the third planetary gear mechanism 43 is faster than the input speed of the second planetary gear mechanism 42). Specifically, the reciprocal of the speed increasing ratio (speed transmission ratio: less than 1) of the second planetary gear mechanism 42 when it functions effectively is greater than the reduction ratio (speed transmission ratio: 1 or more) of the third planetary gear mechanism 43 when it functions effectively. In other words, when the rotation speeds of the shaft 419, the shaft 429, and the shaft 439 are N1, N2, and N3, respectively, the relationship (N2 / N1)>(N2 / N3) is established. Although detailed description will be omitted, the reduction ratios of the first planetary gear mechanism 41 and the fourth planetary gear mechanism 44 are set so that the reducer 4 functions as a reduction mechanism as a whole.

[0091] Therefore, the shaft 449 rotates at a slower speed and exerts a higher torque when the number of effective stages of the reducer 4 is two (when the rotation direction of the motor 2 is the second direction and the second internal gear 422 and the third internal gear 432 rotate) than when the number of effective stages is four (when the rotation direction of the motor 2 is the first direction and the second internal gear 422 and the third internal gear 432 are locked). For this reason, the operation mode of the reducer 4 when the number of effective stages of the reducer 4 is two is called a low-speed / high-torque mode. Also, the operation mode of the reducer 4 when the number of effective stages is four is called a high-speed / low-torque mode. Particularly in this embodiment, in the low-speed / high-torque mode, the second internal gear 422 and the third internal gear 432 rotate, thereby effectively increasing the torque.

[0092] In this embodiment, the reducer 4 is configured so that the reduction ratio of the entire reducer 4 in the low-speed, high-torque mode is less than 2.5 times the reduction ratio of the entire reducer 4 in the high-speed, low-torque mode. The reduction ratio (speed transmission ratio) of the reducer is expressed as Ni / No, where Ni is the input rotation speed (input speed) and No is the output rotation speed (output speed). Therefore, when the input speed (rotation speed of the motor shaft 23) Ni of the reducer 4 is the same, the output speed Noh of the reducer 4 in the high-speed, low-torque mode is less than 2.5 times the output speed (rotation speed of the shaft 449) Nol of the reducer 4 in the low-speed, high-torque mode (that is, Nol and Noh satisfy the relationship Noh<(Nol×2.5)).

[0093] When the planetary gear mechanism is configured as a reduction mechanism with the internal gear fixed, the sun gear as the input, and the carrier as the output, the reduction ratio (speed transmission ratio) is determined by the number of teeth of the sun gear and the internal gear. Specifically, when the number of teeth of the sun gear and the internal gear are Zs and Zi, respectively, the reduction ratio (speed transmission ratio) is expressed as 1 + (Zi / Zs). Since the planetary gear is interposed between the sun gear and the internal gear, there is a limit to reducing Zi / Zs and thus the reduction ratio of each planetary gear mechanism. Therefore, in a multi-stage planetary reducer, when the reduction ratio is changed by enabling or disabling the function of at least one planetary gear mechanism with a fixed internal gear, the reduction ratio and therefore the output speed change relatively greatly.

[0094] Generally, the reduction ratio of each planetary gear mechanism is often about 3 or more. Therefore, when the function of one stage of a multi-stage planetary reducer is enabled or disabled, the reduction ratio (output speed) of the entire reducer 4 in the low-speed / high-torque mode is often about three times or more the reduction ratio (output speed) of the entire reducer 4 in the high-speed / low-torque mode.

[0095] In contrast, in the reducer 4 of this embodiment, of the four-stage (four sets) planetary gear mechanisms, the second planetary gear mechanism 42 is configured as a speed-increasing mechanism, and the remaining three stages are configured as speed-reducing mechanisms. The reduction ratio is changed by enabling or disabling the functions of the two-stage planetary gear mechanisms (the second planetary gear mechanism 42 and the third planetary gear mechanism 43) including the speed-increasing mechanism and the speed-reducing mechanism.

[0096] In this case, the speed increase ratio (speed transmission ratio) of the two stages as a whole can be flexibly set by appropriately combining the speed increase ratio of the second planetary gear mechanism 42 and the reduction ratio of the third planetary gear mechanism 43. Specifically, the reciprocal of the speed increase ratio of the two stages as a whole (<1) can be made smaller than the reduction ratio (>1) of the planetary gear mechanism with a fixed internal gear. This makes it possible to reduce the reduction ratio of the reducer 4 as a whole, and thus the change in output speed, compared to a case in which all stages of a multi-stage planetary reducer are reduction mechanisms with fixed internal gears, and the function of at least one of these stages is enabled or disabled.

[0097] In addition, in this embodiment, the second planetary gear mechanism 42, which is the speed-up mechanism, is disposed in front (on the input side) of the third planetary gear 43, which is the speed-reduction mechanism. Therefore, the torque transmitted from the second planetary gear mechanism 42 to the third planetary gear 43 can be made smaller than the torque transmitted from the speed-reduction mechanism to the speed-up mechanism when the speed-reduction mechanism is disposed in front (on the input side) of the speed-up mechanism. Therefore, the strength required for the gear can be made smaller than the strength required when the speed-reduction mechanism is disposed in front of the speed-up mechanism, and the gear can be made compact. However, contrary to this embodiment, the speed-reduction mechanism may be disposed in front (on the input side) of the speed-up mechanism. In this case, as in this embodiment, it is sufficient that the speed-up ratio or speed-reduction ratio (speed transmission ratio) of the two stages as a whole is appropriately set.

[0098] The operation of the hedge trimmer 1A when performing cutting work (pruning work, trimming work) will be described below.

[0099] The user presses and holds the main power switch 851 to turn it on, and then presses the reverse switch 855 as appropriate depending on the object to be cut. Specifically, when cutting relatively thin branches or leaves, a relatively small cutting force is required, and therefore the high speed / low torque mode is preferable from the viewpoint of cutting efficiency. Therefore, the user does not press the reverse switch 855, and keeps the rotation direction of the motor 2 in the first direction. On the other hand, when cutting relatively thick branches, a relatively large cutting force is required, and therefore the low speed / high torque mode is preferable. Therefore, the user presses the reverse switch 855 to change the rotation direction of the motor 2 from the first direction to the second direction.

[0100] Thereafter, when the switch lever 193 is pressed, the controller 81 (control circuit) drives the motor 2 at a rotation speed corresponding to the amount of operation of the switch lever 193. As described above, the reducer 4 operates at an effective stage number corresponding to the rotation direction (operation mode) of the motor 2. The shaft 449 reciprocates the two blades 9 relatively in the front-rear direction via the motion conversion mechanism 7. The reciprocating blades 9 cut the target object.

[0101] During cutting work, cut pieces of branches or leaves may become tangled between the blades 90 of the upper blades 9 and the blades 90 of the lower blades 9. In such a case, the user can switch the rotation direction of the motor 2 by pressing the reverse switch 855. When the switch lever 193 is then pressed, the movement direction of the two blades 9 is reversed, making it easier to remove the tangled branches or leaves. In particular, when the rotation direction of the motor 2 is switched from the first direction to the second direction (from the high-speed / low-torque mode to the low-speed / high-torque mode), the blades 90 that have bitten into the branch are more likely to come off the branch.

[0102] As described above, the reducer 4 of this embodiment is a multi-stage planetary reducer, and the number of effective stages is changed according to the rotation direction of the motor 2 (motor shaft 23), and the reduction ratio of the reducer 4, and therefore the output speed and output torque of the reducer 4, are changed. Thus, a hedge trimmer 1A is realized that can perform two operations with different required output speeds and output torques simply by changing the rotation direction of the motor 2, without controlling the rotation speed of the motor 2.

[0103] In addition, in the hedge trimmer 1A, the need for a significant increase in output torque is not so great, while a significant decrease in output speed is undesirable since it leads to a significant decrease in work efficiency. As described above, the speed reducer 4 of this embodiment has a relatively small change in the overall reduction ratio and therefore in the output speed, and therefore has characteristics that are preferable for the hedge trimmer 1A.

[0104] The correspondence between the configuration (features) of the first embodiment and the configuration (features) of this disclosure is shown below. However, the configuration (features) of the embodiment are merely examples and do not limit the configuration (features) of this disclosure or the present invention.

[0105] The hedge trimmer 1A is an example of an "electric tool" and a "cutting tool". The motor 2 and the motor shaft 23 are an example of a "motor" and a "motor shaft", respectively. The reducer 4 is an example of a "reduction gear". The reduction ratio change mechanism 6A is an example of a "reduction ratio change mechanism". The first planetary gear mechanism 41, the second planetary gear mechanism 42, the third planetary gear mechanism 43, and the fourth planetary gear mechanism 44 are an example of a "multiple-stage planetary gear mechanism". The one-way clutch 60 is an example of a "one-way clutch". Of the rotation directions (first direction and second direction) of the motor shaft 23, the second direction is an example of "a specific one of two directions". The lock mechanism 61A is an example of a "lock mechanism". The second planetary gear mechanism 42 and the third planetary gear mechanism 43 are an example of "at least two stages of a plurality of planetary gear mechanisms". The second internal gear 422 and the third internal gear 432 are an example of "at least two-stage internal gears". The second planetary gear mechanism 42 is an example of a "speed-increasing planetary gear mechanism". The third planetary gear mechanism 43 is an example of a "reduction planetary gear mechanism". The clutch member 601 and the bearing 605 are examples of a "clutch member" and a "bearing", respectively. The upper blade 9 and the lower blade 9 are examples of a "first blade" and a "second blade", respectively.

[0106] [Second embodiment] A hedge trimmer 1B according to the second embodiment will be described below with reference to Figures 8 and 9. The hedge trimmer 1B of this embodiment has a configuration that is substantially the same as that of the hedge trimmer 1A of the first embodiment in part. Therefore, in the following, the configuration of the hedge trimmer 1B that is substantially the same as that of the hedge trimmer 1A (including cases where the shape is slightly different) will be given the same reference numerals and description will be omitted or simplified, and different configurations will be mainly described.

[0107] Although not shown, the hedge trimmer 1B of the second embodiment includes a main body housing 11 and handles 17, 19 (see FIG. 2) similar to the hedge trimmer 1A of the first embodiment. As shown in FIG. 8, the main body housing 11 of the hedge trimmer 1B mainly includes a motor 2, a reduction gear 5, and a motion conversion mechanism 7. Note that the illustration of the connecting rods 731, 732 is omitted in FIG. 8. The motor 2, the reduction gear 5, and the motion conversion mechanism 7 are respectively arranged in the motor housing 20, the gear housing 50, and the crank housing 70. The motor housing 20, the gear housing 50, and the crank housing 70 are fixed to each other and integrated with screws, and are supported within the main body housing 11 so as to be substantially immovable relative to the main body housing 11.

[0108] The motor 2 is a brushless DC motor, similar to the first embodiment. The motor shaft 23 is supported rotatably around an axis A1 extending in the vertical direction. The lower end of the motor shaft 23 protrudes into the gear housing 50. The lower end of the motor shaft 23 is provided with a drive gear (pinion) 231. The rotation direction of the motor 2 (specifically, the rotor 22 and the motor shaft 23) can be switched between a first direction and a second direction opposite to the first direction.

[0109] The reducer 5 is disposed in front of the motor 2 in the front-rear direction. The reducer 5 is operatively connected to the motor shaft 23 of the motor 2 and the motion conversion mechanism 7, and is configured to reduce the speed of rotation of the motor shaft 23, increase the torque, and output it to the motion conversion mechanism 7. In this embodiment, the reducer 5 includes a reduction gear 53 and a one-stage (one set) planetary gear mechanism 55.

[0110] The reduction gear 53 is a large-diameter driven gear that meshes with the driving gear (pinion) 231 of the motor shaft 23. The reduction gear 53 is provided in the gear sleeve 51. More specifically, the gear sleeve 51 is a stepped cylindrical member and includes a large-diameter portion and a small-diameter portion having an inner diameter smaller than that of the large-diameter portion. The lower end of the gear sleeve 51 is the large-diameter portion, and the portion other than the lower end is the small-diameter portion. The gear sleeve 51 (internal gear 552) is supported rotatably around the axis A2 with respect to the gear housing 50 via a bearing 511 supported by the gear housing 50. The axis A2 extends in front of the axis A1 and parallel to the axis A1 (in the vertical direction). A flange portion that protrudes radially outward is provided on the outer periphery of the large-diameter portion of the gear sleeve 51. The reduction gear 53 is formed on this flange portion and meshes with the driving gear 231. The gear sleeve 51 rotates in the opposite direction to the rotation of the motor shaft 23 at a slower speed than the motor shaft 23 in response to the rotation of the motor shaft 23 .

[0111] The planetary gear mechanism 55 includes a sun gear 551, an internal gear (also called a ring gear) 552, a carrier 555, and a plurality of planetary gears 558. In the planetary gear mechanism 55, the sun gear 551 is fixed, the internal gear 552 is an input, and the carrier 555 is an output. However, the state of the sun gear 551 is selectively switched between a fixed state (locked state) and a rotating state according to the rotation direction of the motor 2. Thus, the planetary gear mechanism 55 selectively functions as a reduction mechanism.

[0112] The internal gear 552 is formed in the large diameter portion of the gear sleeve 51. Therefore, the internal gear 552 is stably supported by the bearing 511 so as to be rotatable relative to the gear housing 50. The shaft 52 is inserted into the gear sleeve 51 and extends along the axis A2. The one-way clutch 60 and the retainer 62B of the reduction ratio change mechanism 6B are interposed between the gear sleeve 51 and the shaft 52, as will be described in detail later. Whether the shaft 52, and therefore the sun gear 551, rotates is switched by the reduction ratio change mechanism 6B according to the rotation direction of the motor 2. The sun gear 551 is fixed to a lower portion of the shaft 52 (a portion disposed radially inward of the internal gear 552).

[0113] The planetary gear 558 is supported by a carrier 555 and meshes with the sun gear 551 and the internal gear 552. The carrier 555 is disposed below the sun gear 551 and coaxially with the shaft 52. The carrier 555 has a shaft 559 extending downward along the axis A2. The shaft 559 is supported rotatably around the axis A2 by two bearings 571 and 572 supported by the crank housing 70. The shaft 559 functions as the final output shaft of the reduction gear 5. In addition, a recess is formed at the upper end of the carrier 555. A bearing 574 is disposed in the recess and rotatably supports the lower end of the shaft 52.

[0114] In this embodiment, the reduction ratio change mechanism 6B is configured to selectively lock or rotate the shaft 52, and thus the sun gear 551, relative to the gear housing 50, depending on the rotation direction of the motor 2. When the state of the sun gear 551 is changed, the number of effective stages of the reducer 5 and thus the reduction ratio of the reducer 5 are changed. The basic configuration of the reduction ratio change mechanism 6B is the same as that of the reduction ratio change mechanism 6A of the first embodiment (see FIG. 3). Specifically, the reduction ratio change mechanism 6B includes a one-way clutch 60 and a lock mechanism 61B. The lock mechanism 61B includes a retainer 62B, two rollers 63, a lock sleeve 64B, and a lock cam 65B. Although the shapes and arrangements of these members are different from those of the lock mechanism 61A of the first embodiment, their functions are basically the same.

[0115] The retainer 62B includes an annular base portion 621, four projections 623 projecting from the base portion 621, and a sleeve portion 627. The sleeve portion 627 is formed in a cylindrical shape having an outer diameter smaller than that of the base portion 621, and extends coaxially with the base portion 621 from the center of the base portion 621 in the opposite direction to the projections 623. The sleeve portion 627 is inserted into the gear sleeve 51 along the axis A2. The base portion 621 and the projections 623 are disposed above the gear sleeve 51. The two rollers 63 are disposed in two diagonally opposite corners of the four spaces formed between the projections 623 of the retainer 62B, with their axes extending in the vertical direction.

[0116] The lock sleeve 64B is a cylindrical member with a bottom. The lock sleeve 64B is disposed above the gear sleeve 51, coaxially with the retainer 62B, and around (radially outwardly) the base portion 621 and the protrusion 623. The lock sleeve 64B is supported within the gear housing 40 so as to be substantially unrotatable around the axis A2 relative to the gear housing 40.

[0117] The lock cam 65B is operably engaged with the retainer 62B and is selectively rotated by the retainer 62B. The lock cam 65B is a cylindrical member as a whole and is arranged coaxially with the retainer 62B. As in the first embodiment, the lock cam 65B includes a cylindrical portion 651 and two protrusions 656 protruding radially outward from the cylindrical portion 651. The cylindrical portion 651 is arranged radially inside the protrusions 623 of the retainer 62B, and the two protrusions 656 are arranged in two of the four spaces formed between the protrusions 623 in the circumferential direction (more specifically, two spaces where the rollers 63 are not arranged).

[0118] In this embodiment, the lock cam 65B is connected to the shaft 52 and can selectively rotate around the axis A1 relative to the gear housing 40 together with the shaft 52. As described above, the sun gear 551 is fixed to the shaft 52, so the lock cam 65B can selectively rotate together with the sun gear 551.

[0119] The one-way clutch 60 is interposed between the small diameter portion of the gear sleeve 51 and the retainer 62B. The one-way clutch 60 is fixed in the small diameter portion of the gear sleeve 51 and is integrated with the gear sleeve 51 in terms of rotation. When the motor shaft 23 rotates in the first direction and the gear sleeve 51 rotates in the second direction, the one-way clutch 60 rotates idly with respect to the retainer 62B. That is, the one-way clutch 60 does not transmit rotation from the gear sleeve 51 to the retainer 62B. At this time, the bearing 605 of the one-way clutch 60 ensures smooth rotation of the gear sleeve 51 with respect to the retainer 62B. On the other hand, when the motor shaft 23 rotates in the second direction and the gear sleeve 51 rotates in the first direction, the one-way clutch 60 rotates integrally with the retainer 62B and transmits rotation from the gear sleeve 51 to the retainer 62B.

[0120] Hereinafter, the operation of the speed reduction ratio change mechanism 6B (the one-way clutch 60 and the lock mechanism 61B) will be described.

[0121] First, the operation when the rotation direction of the motor 2 is the first direction will be described.

[0122] When the motor shaft 23 rotates in the first direction, the gear sleeve 51 and the internal gear 552 rotate in the second direction. As described above, the one-way clutch 60 does not transmit rotation to the retainer 62B, so the retainer 62B does not actively rotate. The internal gear 552 rotates the sun gear 551 and the shaft 52 in the first direction via the planetary gear 558. At this time, the lock cam 65B connected to the shaft 52 also rotates in the first direction (the direction of the arrow in FIG. 6), and the roller 63 moves relatively from the dotted line position in the direction toward the end of the flat portion 652.

[0123] 6, when the roller 63 is placed in the locked position, the lock cam 65B is locked so as to be unable to rotate with respect to the gear housing 50, and the sun gear 551 is also unable to rotate with respect to the gear housing 50. Hence, from this point on, the sun gear 551 functions as a fixed element. As the internal gear 552 rotates in the second direction, the planetary gear 558 revolves around the sun gear 551 in the second direction while rotating on its own axis, causing the carrier 555 to rotate in the second direction.

[0124] As described above, when the motor shaft 23 rotates in the first direction, the lock mechanism 61B makes the planetary gear mechanism 55 function effectively. Therefore, when the motor shaft 23 rotates in the first direction, the number of effective stages of the reduction gear 5 is 1. Therefore, in the reduction gear 5, after the speed is reduced by the drive gear 231 and the reduction gear 53, the speed is further reduced by the planetary gear mechanism 55.

[0125] The operation when the rotation direction of the motor 2 is the second direction will be described.

[0126] When the motor shaft 23 rotates in the second direction, the gear sleeve 51 and the internal gear 552 rotate in the first direction. As described above, the one-way clutch 60 transmits the rotation of the gear sleeve 51 to the retainer 62B, so that the retainer 62B also rotates in the first direction (the direction of the arrow in FIG. 7). As shown in FIG. 7, two of the protrusions 623 of the retainer 62B come into contact with the protrusions 656 of the lock cam 65B and press them in the first direction. Meanwhile, the remaining two protrusions 623 come into contact with the roller 63 and press them in the first direction, moving the roller 63 to the unlock position. Therefore, thereafter, the lock cam 65B and the sun gear 551 rotate in the first direction together with the internal gear 552 and the retainer 62B. As a result, the carrier 555 also rotates in the first direction at the same rotational speed as the internal gear 552.

[0127] As described above, when the motor shaft 23 rotates in the second direction, the lock mechanism 61B disables the function of the planetary gear mechanism 55. Therefore, when the motor shaft 23 rotates in the second direction, the number of effective stages of the reducer 5 is 0. In other words, in the reducer 5, reduction in speed is performed only between the drive gear 231 and the reduction gear 53. Therefore, in this embodiment, when the number of effective stages is 1 (when the rotation direction of the motor 2 is the first direction and the sun gear 551 is locked), the reducer 5 operates in the low-speed, high-torque mode, and when the number of effective stages is 0 (when the rotation direction of the motor 2 is the second direction and the sun gear 551 rotates), Operates in high speed / low torque mode.

[0128] The planetary gear mechanism 55 of this embodiment is configured as a reduction mechanism with the sun gear fixed, the internal gear as input, and the carrier as output, and its reduction ratio (speed transmission ratio) is expressed as 1 + (Zs / Zi) (Zs and Zi are the number of teeth of the sun gear and the internal gear, respectively). Therefore, by enabling or disabling the function of the planetary gear mechanism 55, the reduction ratio of the entire reducer 5 and therefore the change in the output speed can be made smaller than that of a planetary gear mechanism with the internal gear fixed, the sun gear as input, and the carrier as output. The reducer 5 is configured so that the reduction ratio in the low-speed, high-torque mode is less than 2.5 times the reduction ratio in the high-speed, low-torque mode.

[0129] The operation of the hedge trimmer 1B when performing cutting work (pruning work, trimming work) is similar to that of the hedge trimmer 1A of the first embodiment. However, the operation modes corresponding to the rotation direction of the motor 2 are opposite between the hedge trimmer 1A and the hedge trimmer 1B.

[0130] As described above, the reducer 5 of this embodiment is a planetary reducer including only one planetary gear mechanism 55. The planetary gear mechanism 55 is enabled or disabled depending on the rotation direction of the motor 2 (motor shaft 23), and the reduction ratio of the reducer 5, and therefore the output speed and output torque of the reducer 5, are changed. Thus, this embodiment also realizes a hedge trimmer 1B that can perform two operations with different required output speeds and output torques by simply changing the rotation direction of the motor 2, without controlling the rotation speed of the motor 2.

[0131] In this embodiment, the number of planetary gear mechanisms included in the reducer 5 is limited to one, thereby realizing a compact reducer 5. Meanwhile, the reduction gear 53 disposed between the motor shaft 23 and the internal gear 552 can ensure the reduction function when the function of the planetary gear mechanism 55 is disabled.

[0132] The correspondence between the configuration (features) of the second embodiment and the configuration (features) of this disclosure is shown below. However, the configuration (features) of the embodiment are merely examples and do not limit the configuration (features) of this disclosure or the present invention.

[0133] The hedge trimmer 1B is an example of an "electric tool" and a "cutting tool". The motor 2 and the motor shaft 23 are an example of a "motor" and a "motor shaft", respectively. The speed reducer 5 is an example of a "speed reducer". The speed reduction ratio change mechanism 6B is an example of a "speed reduction ratio change mechanism". The planetary gear mechanism 55 is an example of a "planetary gear mechanism". The one-way clutch 60 is an example of a "one-way clutch". Of the rotation directions (first direction and second direction) of the motor shaft 23, the second direction is an example of "a specific one of two directions". The lock mechanism 61B is an example of a "lock mechanism". The sun gear 551 is an example of a "sun gear". The reduction gear 53 is an example of a "reduction gear". The bearing 511 is an example of a "first bearing". The clutch member 601 and the bearing 605 are an example of a "clutch member" and a "bearing", respectively. The upper blade 9 and the lower blade 9 are examples of the "first blade" and the "second blade", respectively.

[0134] It should be noted that the above-mentioned embodiment is merely an example, and the power tool according to the present disclosure is not limited to the illustrated hedge trimmers 1A and 1B. For example, the following modifications can be made. At least one of these modifications can be adopted in combination with the hedge trimmers 1A and 1B illustrated in the embodiment and any of the inventions described in the claims.

[0135] 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 198.

[0136] The number of planetary gear mechanisms included in the reduction gear 4 is not limited to four, and may be any number of two or more. In the reduction gear 4, the number of planetary gear mechanisms whose functions are enabled or disabled according to a change in the rotation direction of the motor 2 is also not limited to two, and may be three or more. The input shaft of the reduction gear 4 does not need to be the motor shaft 23, and another rotating shaft may be arranged in the torque transmission path between the motor shaft 23 and the reduction gear 5. The reduction gear 5 does not need to be arranged coaxially with the motor 2. Similarly, the configuration of the reduction gear 5 can also be changed as appropriate. For example, the reduction gear 5 may include another planetary gear mechanism in addition to the planetary gear mechanism 55.

[0137] In each of the reduction ratio change mechanisms 6A and 6B, the configuration and arrangement of the one-way clutch 60 and the locking mechanisms 61A and 61B may be appropriately changed. For example, the one-way clutch 60 may be a type in which the bearing 605 is not incorporated, and a bearing may be arranged separately from the one-way clutch 60. The shape, arrangement, number, etc. of each component of the locking mechanism 61A may be appropriately changed. For example, the number of rollers 63 may be three or more. The number of protrusions 656 of the locking cams 65A and 65B and the number of protrusions 623 of the retainers 62A and 62B may also be arbitrarily changed. The locking sleeves 64A and 64B may be omitted, and the rollers 63 may be arranged between the inner circumferential surfaces of the gear housings 40 and 50 and the flat surfaces 652 of the locking cams 65A and 65B, and may be movable between the locked position and the unlocked position. In the reducer 4, the locking cam 65A and the sleeve 405 may be formed as a single member. In the reducer 5, the lock cam 65B and the shaft 52 may be formed as a single member.

[0138] The control circuit of the controller 81 may be a control circuit other than a microcomputer including a CPU, etc. The operation member for inputting an instruction to change the rotation direction of the motor 2 (motor shaft 23) is not limited to the reverse switch 855, and may be, for example, a lever, a slider, a touch panel, etc.

[0139] Furthermore, in the above embodiment, the hedge trimmers 1A and 1B are given as examples of power tools, but the present disclosure may be applied to other power tools that perform two different operations depending on the rotation direction of the motor.

[0140] 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 at least two-stage planetary gear mechanism is configured as a speed increasing mechanism as a whole. [Aspect 2] The reciprocal of the speed-increasing ratio of the speed-increasing planetary gear mechanism is greater than the speed-reducing ratio of the speed-reducing planetary gear mechanism. [Aspect 3] the plurality of planetary gear mechanisms include at least three-stage planetary gear mechanisms; Among the at least three stages, planets other than the at least two stages gear Each of the mechanisms is configured as a speed reducing mechanism. [Aspect 4] In aspect 3, The speed-increasing planetary gear mechanism and the speed-reducing planetary gear mechanism are disposed in the second stage and the third stage, respectively. [Aspect 5] The one-way clutch is disposed around a shaft integrated with the carrier of the speed-increasing planetary gear mechanism, and is configured to transmit rotation to the motor shaft only when the motor shaft rotates in the specific one of the two directions. Shaft 419 is an example of a "shaft." [Aspect 6] The power tool includes: a controller configured to control operation of the power tool; and an operating member configured to be externally operated by a user, The control device is configured to change a rotation direction of the motor shaft in response to an operation of the operating member by the user. The controller 81 (control circuit) is an example of a "control device." The reverse switch 855 is an example of an "operation member." [Aspect 7] The reduction gear further includes a housing that accommodates the reduction gear. The at least two stages of the internal gears are selectively rotatable together with respect to the housing about a first axis, The locking mechanism includes: a roller movable in a circumferential direction about the first axis between a locked position and an unlocked position; a retainer that movably holds the roller between the locked position and the unlocked position and that is selectively rotatable about the first axis relative to the housing integrally with the one-way clutch; a lock cam configured to rotate integrally with the at least two stages of the internal gears about the first axis and engageable with the retainer; a lock sleeve disposed non-rotatably about the first axis relative to the housing and disposed at least partially around the roller, the retainer, and the lock cam; When the one-way clutch does not transmit rotation, the roller is sandwiched between the lock sleeve and the lock cam at the locked position, and locks the lock cam and the at least two stages of the internal gears so as not to rotate relative to the housing, When the one-way clutch transmits rotation, the roller is positioned loosely between the lock sleeve and the lock cam in the unlocked position, and the retainer rotates integrally with the one-way clutch, rotating the lock cam and the at least two stages of the internal gears. The gear housings 40, 50 are an example of a "housing." The roller 63 is an example of a "roller." The retainers 62A, 62B are an example of a "retainer." The locking cams 65A, 65B are an example of a "locking cam." The locking sleeves 64A, 64B are an example of a "locking sleeve." [Explanation of symbols]

[0141] 1A, 1B: hedge trimmer, 11: main body housing, 17: handle, 171: grip, 19: handle, 191: grip, 193: switch lever, 195: switch, 197: battery mounting part, 198: battery, 2: motor, 20: motor housing, 201: bearing, 202: bearing, 21: stator, 22: rotor, 23: motor shaft, 231: drive gear, 40: gear housing, 4: reducer, 405: sleeve, 41: first planetary gear mechanism, 411: first sun gear, 412: first internal gear, 41 5: first carrier, 418: first planetary gear, 419: shaft, 42: second planetary gear mechanism, 421: second sun gear, 422: second internal gear, 425: second carrier, 428: second planetary gear, 429: shaft, 43: third planetary gear mechanism, 431: third sun gear, 432: third internal gear, 435: third carrier, 438: third planetary gear, 439: shaft, 44: fourth planetary gear mechanism, 441: fourth sun gear, 442: fourth internal gear, 445: fourth carrier, 448: fourth planetary gear, 449: shaft shaft, 451: bearing, 452: bearing, 50: gear housing, 5: reducer, 51: gear sleeve, 511: bearing, 52: shaft, 53: reduction gear, 55: planetary gear mechanism, 551: sun gear, 552: internal gear, 555: carrier, 558: planetary gear, 559: shaft, 571: bearing, 572: bearing, 574: bearing, 6A, 6B: reduction ratio change mechanism, 60: one-way clutch, 601: clutch member, 605: bearing, 61A, 61B: lock mechanism, 62A, 62B: retainer, 621: base portion, 62 3: projection, 625: cylindrical portion, 627: sleeve portion, 63: roller, 64A, 64B: lock sleeve, 65A, 65B: lock cam, 651: cylindrical portion, 652: flat portion, 656: projection, 70: crank housing, 7: motion conversion mechanism, 71A: lock mechanism, 72: cam plate, 721: eccentric portion, 722: eccentric portion, 731: connecting rod, 732: connecting rod, 81: controller, 85: operation portion, 851: main power switch, 855: reverse switch, 87: display portion, 9: blade, 90: blade, 97: blade guide

Claims

1. a motor having a motor shaft rotatable in two opposite directions; a speed reducer operably connected to the motor shaft and including a multi-stage planetary gear mechanism; a reduction ratio change mechanism configured to change a reduction ratio of the reducer in response to a change in the rotation direction of the motor shaft, At least two stages of the multi-stage planetary gear mechanism are configured such that the respective internal gears selectively function as fixed elements; The reduction ratio change mechanism includes: A one-way clutch and a lock mechanism are provided. The one-way clutch is a torque transmission path configured to transmit the rotation transmitted by the rotation of the motor shaft to the lock mechanism only when the motor shaft is rotated in a specific one of the two directions; The locking mechanism includes: a one-way clutch that is operably connected to the at least two stages of the internal gears, and that is configured such that when the one-way clutch does not transmit the rotation transmitted by the rotation of the motor shaft to the lock mechanism and the rotation transmitted by the rotation of the motor shaft is transmitted to the at least two stages of the internal gears, the one-way clutch locks the at least two stages of the internal gears so that they cannot rotate, thereby allowing the at least two stages of the planetary gear mechanism to function effectively, and when the one-way clutch transmits the rotation transmitted by the rotation of the motor shaft to the lock mechanism, the one-way clutch rotates the at least two stages of the internal gears to disable the function of the at least two stages of the planetary gear mechanism, The power tool, wherein the at least two-stage planetary gear mechanism includes a speed-increasing planetary gear mechanism configured as a speed-increasing mechanism and a speed-reducing planetary gear mechanism configured as a speed-reducing mechanism.

2. The power tool according to claim 1, The power tool according to claim 1, wherein the speed-increasing planetary gear mechanism is disposed in front of the speed-reducing planetary gear mechanism.

3. The power tool according to claim 2, A power tool, characterized in that a sun gear functioning as an output element of the speed-increasing planetary gear mechanism and a sun gear functioning as an input element of the speed-reducing planetary gear mechanism are configured as a single member.

4. The power tool according to any one of claims 1 to 3, The power tool is characterized in that the reducer is configured to operate in a high-speed, low-torque mode when the locking mechanism locks the rotation of the at least two stages of the internal gears, and to operate in a low-speed, high-torque mode when the locking mechanism rotates the at least two stages of the internal gears.

5. a motor having a motor shaft rotatable in two opposite directions; a speed reducer operably connected to the motor shaft and including a planetary gear mechanism; a reduction ratio change mechanism configured to change a reduction ratio of the reducer in response to a change in the rotation direction of the motor shaft, the planetary gear mechanism is configured such that the sun gear selectively functions as a fixed element and the internal gear selectively functions as an input element; The reduction ratio change mechanism includes: A one-way clutch and a lock mechanism are provided. The one-way clutch is a torque transmission path configured to transmit the rotation transmitted by the rotation of the motor shaft to the lock mechanism only when the motor shaft is rotated in a specific one of the two directions; The locking mechanism includes: An electric tool characterized in that the one-way clutch is operably connected to the one-way clutch and the sun gear, and when the one-way clutch does not transmit the rotation transmitted by the rotation of the motor shaft to the lock mechanism, and when the rotation transmitted by the rotation of the motor shaft is transmitted to the sun gear, the sun gear is locked so that it cannot rotate, thereby allowing the planetary gear mechanism to function effectively, and when the one-way clutch transmits the rotation transmitted by the rotation of the motor shaft to the lock mechanism, the sun gear is rotated to disable the function of the planetary gear mechanism.

6. The power tool according to claim 5, The power tool further comprises a reduction gear disposed in the torque transmission path between the motor shaft and the internal gear.

7. The power tool according to claim 5 or 6, The power tool, wherein the reduction gear includes only one stage of the planetary gear mechanism.

8. The power tool according to any one of claims 5 to 7, The power tool, wherein the internal gear is rotatably supported by a first bearing.

9. The power tool according to any one of claims 1 to 8, The one-way clutch of the power tool comprises a clutch member and a second bearing disposed on both sides of the clutch member in the axial direction of the one-way clutch.

10. The power tool according to any one of claims 1 to 9, An electric power tool, characterized in that the reduction ratio of the reducer when the motor shaft is rotated in one of the two directions is less than 2.5 times the reduction ratio of the reducer when the motor shaft is rotated in the other of the two directions.

11. The power tool according to any one of claims 1 to 10, The power tool is characterized in that it is a cutting tool configured to move a first blade and a second blade attached to a main body of the power tool back and forth relative to one another in a linear manner, and to cut an object both in the stroke in which the first blade moves forward and backward relative to the second blade.

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