Power tool

Abstract

The present invention provides a power tool. The power tool includes a motor, a speed reducer, and a reduction ratio changing mechanism. The speed reducer includes a multi-stage planetary gear mechanism. The reduction ratio changing mechanism changes the reduction ratio of the speed reducer according 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 their respective internal gears selectively function as fixed structural elements. The reduction ratio changing mechanism has a one-way clutch and a locking mechanism. When the one-way clutch does not transmit rotation, the locking mechanism locks at least two stages of the internal gears so that they cannot rotate, and when the one-way clutch transmits rotation, the locking mechanism causes at least two stages of the internal gears to rotate. At least two stages of the planetary gear mechanism include a speed increasing planetary gear mechanism and a speed reducing planetary gear mechanism. Accordingly, an improved power tool having a speed reducer capable of changing the reduction ratio can be provided.

Description

Technical Field

[0001] The present invention relates to a power tool. More specifically, the present invention relates to a power tool having a speed reducer capable of changing a reduction ratio. Background Art

[0002] There is known a power tool having a motor capable of rotating in two directions, a first direction and a second direction, and capable of performing different operations when the motor rotates in the first direction and when the motor rotates in the second direction. For example, in the hedge trimmer disclosed in Patent Document 1, the reduction ratio of the planetary gear type speed change mechanism is switched when the motor rotates in the first direction and when the motor rotates in the second direction.

[0003] [Prior Art Documents]

[0004] [Patent Documents]

[0005] Patent Document 1: Japanese Patent Application Laid-Open Publication No. 2005-269972 Summary of the Invention

[0006] [Technical Problem to be Solved by the Invention]

[0007] In the above-described planetary gear type speed change mechanism, the reduction ratio can be changed by switching the internal gear between a fixed state and a free state in response to the rotation direction of the motor. However, in this speed change mechanism, there is a tendency that the change in the reduction ratio becomes too large and the difference in the output speed becomes too large.

[0008] An object of the present invention is to provide an improved power tool having a speed reducer capable of changing a reduction ratio.

[0009] [Technical Solution for Solving the Technical Problem]

[0010] According to one aspect of the present invention, there is provided a power tool having a motor, a speed reducer, and a reduction ratio changing mechanism. The motor has a motor shaft capable of rotating in two opposite directions. The speed reducer is operably connected to the motor shaft. In addition, the speed reducer includes a multi-stage planetary gear mechanism. The reduction ratio changing mechanism is configured to change the reduction ratio of the speed reducer according to a change in the rotation direction of the motor shaft.

[0011] At least two stages of the multi-stage planetary gear mechanism are configured such that their internal gears selectively act as fixed structural elements. The reduction ratio change mechanism has a one-way clutch and a locking mechanism. The one-way clutch is configured to be disposed on the torque transmission path and transmit rotation only when rotating in a specific one of the two directions of the motor axis. The locking mechanism is operably connected to the one-way clutch and at least two internal gears of the multi-stage planetary gear. The locking mechanism is configured to lock at least two internal gears so that they cannot rotate when the one-way clutch does not transmit rotation. Further, the locking mechanism is configured to rotate at least two internal gears when the one-way clutch transmits rotation. 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.

[0012] The power tool of this embodiment has a speed reducer including a multi-stage planetary gear mechanism and a reduction ratio change mechanism. The reduction ratio change mechanism switches at least two internal gears of the multi-stage planetary gear mechanism between a non-rotating state (locked state) and a rotating state according to a change in the rotation direction of the motor shaft. The internal gear effectively acts as a fixed structural element in the locked state. On the other hand, when the internal gear rotates, it cannot act as a fixed structural element. Therefore, the number of stages of the planetary gear mechanism that effectively acts in the speed reducer is at least reduced by 2 stages, and the reduction ratio (transmission ratio) of the speed reducer is changed. Thus, the power tool of this embodiment does not require speed control of the motor and can selectively perform two operations with different required output speeds and output torques only according to a change in the rotation direction of the motor.

[0013] Due to structural limitations, the reduction ratio of the planetary gear mechanism with the internal gear as a fixed structural element becomes large. Therefore, when changing the reduction ratio by enabling or disabling the function of at least one stage of the multiple planetary gear mechanisms, the change in the reduction ratio tends to be large. In contrast, in this embodiment, the functions of at least two stages of the planetary gear mechanism including the speed-increasing planetary gear mechanism and the speed-reducing planetary gear mechanism are enabled or disabled. According to this structure, by appropriately combining the speed-increasing ratio (<1) of the speed-increasing planetary gear mechanism and the reduction ratio (>1) of the speed-reducing planetary gear mechanism, the overall speed-increasing ratio or reduction ratio of at least two stages of the planetary gear mechanism can be set more flexibly. As a result, the overall reduction ratio of the speed reducer can be reduced, and further, the change in the rotational speed can be reduced. Therefore, the power tool of this embodiment can selectively perform two operations with a smaller difference in output speed according to a change in the rotation direction of the motor.

[0014] According to another aspect of the present invention, there is provided a power tool having a motor, a speed reducer, and a reduction ratio changing mechanism. The motor has a motor shaft that can rotate in two opposite directions. The speed reducer is operably connected to the motor shaft. The speed reducer includes a planetary gear mechanism. The reduction ratio changing mechanism is configured to change the reduction ratio of the speed reducer according 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 structural element and the internal gear functions as an input structural element.

[0015] The reduction ratio changing mechanism has a one-way clutch and a locking mechanism. The one-way clutch is configured to be disposed on the torque transmission path and transmit rotation only when the motor shaft rotates in a specific one of the two directions. The locking mechanism is operably connected to the one-way clutch and the sun gear. The locking 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.

[0016] The power tool of this aspect has a speed reducer including a planetary gear mechanism and a reduction ratio changing mechanism. The reduction ratio changing mechanism switches the sun gear of the planetary gear mechanism between a non-rotating state (locked state) and a rotating state according to a change in the rotation direction of the motor shaft. The sun gear effectively functions as a fixed structural element in the locked state. On the other hand, when the sun gear rotates, it cannot function as a fixed structural element. Therefore, the number of stages of the planetary gear mechanism that effectively functions in the speed reducer is reduced by one stage, and the reduction ratio (transmission ratio) of the speed reducer is changed. In this way, the power tool of this aspect does not require speed control of the motor, and can selectively perform two operations with different required output speeds and output torques only according to a change in the rotation direction of the motor.

[0017] In addition, since the sun gear functions as a fixed structural element, the reduction ratio of the planetary gear mechanism of this aspect is smaller than that of a speed reducer in which the internal gear is a fixed structural element. Therefore, the change in the reduction ratio caused by enabling or disabling the function of the planetary gear mechanism can also be reduced compared to the case of a speed reducer in which the internal gear is a fixed structural element. Therefore, the power tool of this aspect can selectively perform two operations with a smaller difference in output speed according to a change in the rotation direction of the motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is an overall perspective view of a hedge trimmer according to the first embodiment.

[0019] Figure 2 is a cross-sectional view of the hedge trimmer.

[0020] Figure 3 isFigure 2 Partial enlarged view (wherein, the illustrations of the main body housing and the connecting rod are omitted).

[0021] Figure 4 is Figure 3 IV-IV sectional view of

[0022] Figure 5 Stereoscopic exploded view of the speed reducer and the reduction ratio change mechanism

[0023] Figure 6 Explanation diagram of the operation principle of the locking mechanism, which is a diagram schematically showing the cross-section of the locking mechanism in the locked state

[0024] Figure 7 Explanation diagram of the operation principle of the locking mechanism, which is a diagram schematically showing the cross-section of the locking mechanism in the unlocked state

[0025] Figure 8 Partial sectional view of the hedge trimmer according to the second embodiment (wherein, the illustrations of the main body housing and the connecting rod are omitted).

[0026] Figure 9 Stereoscopic exploded view of the speed reducer and the reduction ratio change mechanism

[0027] [Explanation of reference numerals]

[0028] 1A, 1B: Hedge trimmer; 11: Main body housing; 17: Handle; 171: Gripping part; 19: Handle; 191: Gripping part; 193: Switch operating 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: Driving gear; 40: Gear housing; 4: Reducer; 405: Sleeve; 41: First planetary gear mechanism; 411: First sun gear; 412: First internal gear; 415: First planet carrier; 418: First planetary gear; 419: Shaft; 42: Second planetary gear mechanism; 421: Second sun gear; 422: Second internal gear; 425: Second planet carrier; 428: Second planetary gear; 429: Shaft; 43: Third planetary gear mechanism; 431: Third sun gear; 432: Third internal gear; 435: Third planet carrier; 438: Third planetary gear; 439: Shaft; 44: Fourth planetary gear mechanism; 441: Fourth sun gear; 442: Fourth internal gear; 445: Fourth planet carrier; 448: Fourth planetary gear; 449: 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: Planet carrier; 558: Planetary gear; 559: Shaft; 571: Bearing; 572: Bearing; 574: Bearing; 6A, 6B: Reduction ratio change mechanism; 60: One-way clutch; 601: Clutch part; 605: Bearing; 61A, 61B: Locking mechanism; 62A, 62B: Retaining member; 621: Base; 623: Protrusion; 625: Cylindrical part; 627: Sleeve part; 63: Roller; 64A, 64B: Locking sleeve; 65A, 65B: Locking cam; 651: Cylindrical part; 652: Flat part; 656: Protrusion; 70: Crank housing; 7: Motion conversion mechanism; 71A: Locking mechanism; 72: Cam plate; 721: Eccentric part; 722: Eccentric part; 731: Connecting rod; 732: Connecting rod; 81: Controller; 85: Operating part; 851: Main power switch; 855: Reverse switch; 87: Display part; 9: Blade; 90: Blade edge; 97: Blade guide. Detailed implementation mode

[0029] In one or more embodiments of the present invention, the speed-increasing planetary gear mechanism may be configured at the front stage (input side) of the speed-reducing planetary gear mechanism. According to this structure, compared with the torque transmitted from the speed-reducing planetary gear mechanism to the speed-increasing planetary gear mechanism when the speed-reducing planetary gear mechanism is configured at the front stage (input side) of the speed-increasing planetary gear mechanism, the torque transmitted from the speed-increasing planetary gear mechanism to the speed-reducing planetary gear mechanism can be made smaller. Therefore, compared with the strength required when the speed-reducing planetary gear mechanism is configured at the front stage of the speed-increasing planetary gear mechanism, the strength required for the gears can be reduced, and thus the gears can be made more compact.

[0030] In one or more embodiments of the present invention, the sun gear that functions as an output structural element of the speed-increasing planetary gear mechanism and the sun gear that functions as an input structural element of the speed-reducing planetary gear mechanism may form a single component. According to this structure, the structure of the speed reducer can be simplified and the assemblability can be improved.

[0031] In one or more embodiments of the present invention, the speed reducer may be configured such that when the locking mechanism locks the rotation of at least two internal gears, the speed reducer operates in a high-speed and low-torque mode, and when the locking mechanism allows at least two internal gears to rotate, the speed reducer operates in a low-speed and high-torque mode. In other words, the speed reducer may be configured such that when at least two planetary gear mechanisms function effectively, the speed reducer operates in a high-speed and low-torque mode, and when at least two planetary gear mechanisms do not function, the speed reducer operates in a low-speed and high-torque mode. That is, at least two planetary gear mechanisms as a whole may also be configured as a speed-increasing mechanism. According to this structure, in the low-speed and high-torque mode, the torque can be effectively increased by the rotation of the internal gears.

[0032] In one or more embodiments of the present invention, the power tool may further include a reduction gear that is disposed between the motor shaft and the internal gear in the torque transmission path. According to this structure, further reduction can be achieved before the reduction by the planetary gear mechanism.

[0033] In one or more embodiments of the present invention, the speed reducer may include only one set of planetary gear mechanisms. According to this structure, a compact speed reducer can be achieved.

[0034] In one or more embodiments of the present invention, the internal gear of the planetary gear mechanism may also be rotatably supported by a first bearing. According to this structure, the rotation of the internal gear can be stabilized.

[0035] In one or more embodiments of the present invention, the one-way clutch may have a clutch member and a second bearing, and the second bearing is axially disposed on both sides of the clutch member in the one-way clutch. According to this structure, when the one-way clutch does not transmit rotation (idle rotation), the second bearing can ensure smooth rotation of the member rotating relative to the one-way clutch.

[0036] In one or more embodiments of the present invention, the reduction ratio when the motor rotates in one direction in the motor axis direction may be less than 2.5 times the reduction ratio when the motor rotates in the other direction in the motor axis direction. According to this structure, an electric tool can be realized that can selectively perform two operations with a small difference in output speed in response to a change in the rotation direction of the motor.

[0037] In one or more embodiments of the present invention, the power tool may also be a cutting tool configured to linearly reciprocate a first blade and a second blade mounted on the main body of the power tool relative to each other, and cut an object in both a forward stroke and a return stroke of the first blade relative to the second blade. According to this structure, by changing the rotation direction of the motor according to the type of the object, a cutting tool can be realized that can selectively perform two operations with different cutting speeds and cutting forces.

[0038] Hereinafter, representative and non-limiting embodiments of the present invention will be specifically described with reference to the drawings.

[0039] [First Embodiment]

[0040] Hereinafter, reference will be made to Figures 1 to 7 The hedge trimmer 1A according to the first embodiment will be described. 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, a branch or leaf of a tree) by linearly reciprocating two blades 9 detachably mounted relative to each other.

[0041] First, the schematic structure of the hedge trimmer 1A will be described.

[0042] As Figure 1 and Figure 2As shown, the outer contour of the hedge trimmer 1A is mainly formed by the main body housing 11 and two handles 17 and 19 connected to the main body housing 11. A motor 2, a speed reducer 4, and a motion conversion mechanism 7 are arranged in the main body housing 11. The long plate-shaped blade 9 is movably connected to the motion conversion mechanism 7 and protrudes from one end of the main body housing 11, extending linearly in a direction orthogonal to the specified axis A1. The handle 17 is connected to the end of the main body housing 11 closer to the blade 9, and the handle 19 is connected to the end farther from the blade 9. A switch operating lever (also called a trigger) 193 for the user to press is provided on the handle 19. When the switch operating lever 193 is pressed, the motor 2 is energized, and the two blades 9 reciprocate relative to each other along their long axis directions.

[0043] Hereinafter, for the sake of convenience of explanation, the extending direction of the long axis of the blade 9 (which is also the length direction of the main body housing 11) is defined as the front-rear direction of the hedge trimmer 1A. In the front-rear direction, the direction from the main body housing 11 toward the protruding end of the blade 9 is defined as the front, and the opposite direction (from the protruding end of the blade 9 toward the main body housing 11) is defined as the rear. In addition, hereinafter, the handle 17 close to the blade 9 is called the front-side handle 17, and the handle 19 far from the blade 9 is called the rear-side handle 19. The direction orthogonal to the plate surface of the blade 9 (which is also the extending 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 toward the motor 2 is defined as the upper side, and the opposite direction (from the motor 2 toward the blade 9) is defined as the lower side. The direction orthogonal to the front-rear direction and the up-down direction is defined as the left-right direction of the hedge trimmer 1A.

[0044] Hereinafter, the detailed structure of the hedge trimmer 1A will be described.

[0045] First, the main body housing 11 and the structural elements arranged in the main body housing 11 will be described.

[0046] As Figure 2 shown, the main body housing 11 is a hollow body and houses the motor 2, the speed reducer 4, and the motion conversion mechanism 7. The motor 2, the speed reducer 4, and the motion conversion mechanism 7 are respectively arranged in the motor housing 20, the gear housing 40, and the crank housing 70. In addition, the motor housing 20, the gear housing 40, and the crank housing 70 are fixed to each other by screws and integrated. The motor housing 20, the gear housing 40, and the crank housing 70 are supported in the main body housing 11 in a manner that they cannot move substantially relative to the main body housing 11.

[0047] 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 state within the motor housing 20. The motor shaft 23 is fixed to the rotor 22. The motor shaft 23 rotates integrally with the rotor 22 about an axis A1 extending in the vertical direction. The upper and lower ends of the motor shaft 23 are rotatably supported by bearings 201 and 202. The bearings 201 and 202 are supported by the motor housing 20. In addition, in the present embodiment, the motor shaft 23 is formed of a plurality of components connected to each other, but the motor shaft 23 may also be a single component.

[0048] The speed reducer 4 is disposed below the motor 2 coaxially with the motor 2. The speed reducer 4 is configured to be operably connected to the motor shaft 23 of the motor 2 and the motion conversion mechanism 7, reduce the rotational speed of the motor shaft 23, and increase the torque and output it to the motion conversion mechanism 7. As Figure 3 shown, the speed reducer 4 is a multi-stage planetary speed reducer, including four stages (four sets) of planetary gear mechanisms housed in the gear housing 40. Hereinafter, the four stages (four sets) of planetary gear mechanisms will be sequentially referred to as 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 from the first stage (input side, upper side).

[0049] The lower end of the motor shaft 23 projects into the gear housing 40. The input shaft of the speed reducer 4 is the motor shaft 23, and the final output shaft of the speed reducer 4 is a shaft 449 integrated with the fourth planet carrier 445 of the fourth planetary gear mechanism 44. The shaft 449 is rotatably supported about the axis A1 by two bearings 451 and 452, and the two bearings 451 and 452 are supported by the crank housing 70. The lower end of the shaft 449 is disposed within the crank housing 70. In addition, the details of the speed reducer 4 will be described later.

[0050] As Figure 2 shown, the motion conversion mechanism 7 is disposed within the crank housing 70 below the speed reducer 4. The motion conversion mechanism 7 is configured to convert the rotational motion of the final output shaft (shaft 449) of the speed reducer 4 into a linear motion, causing the blade 9 to reciprocate linearly. The motion conversion mechanism 7 may adopt any known structure. In the present embodiment, the motion conversion mechanism 7 is configured as a so-called crank mechanism, having a cam plate 72 and two linkages 731 and 732.

[0051] The cam plate 72 is a disc-shaped component fixed to the outer periphery of the shaft 449 of the fourth planet carrier 445, and rotates integrally with the fourth planet carrier 445 about the axis A1. The cylindrical eccentric portions 721, 722 project upward and downward from the upper and lower surfaces of the cam plate 72, respectively. The centers of the eccentric portions 721, 722 are offset from the axis A1 by the same distance and are located at positions facing each other across the axis A1. The rear ends of the link rods 731, 732 are movably connected to the eccentric portions 721, 722, respectively. The front ends of the link rods 731, 732 are movably connected to the two blades 9.

[0052] As Figure 1 and Figure 2 shown, the two blades 9 extend in the front-rear direction in a state of overlapping in the up-down direction and are supported by the blade guide 97. The blade guide 97 is fixed to the front end portion of the crank case 70 and extends linearly forward from the crank case 70. The blade guide 97 supports the blade 9 in such a manner that it can linearly move within a specified range in the front-rear direction. The two blades 9 linearly reciprocate in the front-rear direction with opposite phases (a phase difference of 180 degrees) according to the rotation of the cam plate 72. On each blade 9, a plurality of cutting edges (cutting portions) 90 are formed along its left and right ends. As the two blades 9 relatively move in the front-rear direction, the object is clamped between the cutting edges 90 of the upper blade 9 and the cutting edges 90 of the lower blade 9 and is cut.

[0053] The cutting edge 90 is wedge-shaped and has a cutting tip on both the front side and the rear side. Therefore, the two blades 9 can cut the object regardless of the relative movement direction. That is, the two blades 9 can cut the object in both the forward stroke in which the upper blade 9 moves forward relative to the lower blade 9 and the return stroke in which the upper blade 9 moves backward relative to the lower blade 9.

[0054] In addition, the motion conversion mechanism 7 may also be configured such that instead of reciprocating both of the two blades 9 in the front-rear direction relative to the main body case 11, only one of the two blades 9 reciprocates relative to the other fixed blade.

[0055] Next, the front handle 17 will be described.

[0056] As Figure 1 shown, the front handle 17 is formed in the shape of a capital letter U. The front handle 17 is integrally formed with the main body case 11, and its two end portions are respectively connected to the left front end portion and the right front end portion of the main body case 11. The central portion of the front handle 17 projects upward from the main body case 11 and functions as a grip portion 171 for the user to hold.

[0057] Next, the rear handle 19 and the structural elements disposed within the rear handle 19 will be described.

[0058] As Figure 1 and Figure 2 shown, the rear handle 19 is a hollow body that forms a ring shape (in the shape of a capital letter D when viewed from the side) and is connected to the rear end portion of the main body housing 11. The portion of the rear handle 19 that extends rearward from the upper rear end portion of the main body housing 11 functions as a grip portion 191 that is gripped by the user. A switch operating lever 193 is disposed below the grip portion 191. A switch 195 is disposed inside the rear handle 19. The switch 195 is always kept in an off state during normal times and becomes an on state in response to the pressing operation of the switch operating lever 193. The switch 195 is electrically connected to a controller 81 (to be described later) through a wire (not shown). In response to the switch 195 becoming an on state, a signal indicating the operation amount (pressing amount) of the switch operating lever 193 is output to the controller 81.

[0059] The controller 81 is housed inside the lower front end portion 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 addition, in the present embodiment, the control circuit is configured as a microcomputer including a CPU, a ROM, a memory, a timer, etc., and is used to control the operation of the hedge trimmer 1A including the drive of the motor 2. More specifically, when the controller 81 recognizes a signal from the switch 195, the motor 2 is driven at a rotational speed corresponding to the operation amount of the switch operating lever 193 indicated by the signal.

[0060] An operation unit 85 is disposed on the upper surface of the rear handle 19. The operation unit 85 is an input device that can input various instructions through external operations by the user. The operation unit 85 includes a plurality of push-button switches and is electrically connected to the controller 81 through a wire (not shown). In the present embodiment, the operation unit 85 includes a main power switch 851 and a reverse switch 855.

[0061] 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 switch the on / off state in response to a long press operation and output a specific signal to the controller 81 in response to the switching. The controller 81 (control circuit) receives the signal from the switch 195 as a valid signal only during the period when the main power switch 851 is in the on state. That is, during the period when 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 in the on state.

[0062] The reverse switch 855 is a switch for input indication that reverses the rotation direction of the motor 2 and thus the moving 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 the present 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. In response to the main power switch 851 being set to the ON state, the controller 81 (control circuit) sets the rotation direction of the motor 2 to the first direction. Thereafter, when the controller 81 recognizes a signal from the reverse switch 855, the controller 81 changes the rotation direction of the motor 2 to the second direction. Thereafter, during the period when the main power switch 851 is in the ON state, each time the controller 81 recognizes a signal from the reverse switch 855, the controller 81 switches the rotation direction of the motor 2 between the first direction and the second direction.

[0063] Further, on the upper surface of the rear handle 19, a display unit 87 for displaying various information is disposed adjacent to the operation unit 85. Omitting the detailed illustration, in the present 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 these information, for example, by lighting, flashing, or changing the color of a lamp.

[0064] In addition, a battery mounting portion 197 is provided at the lower rear end portion of the rear handle 19. The battery 198 is detachably mounted on the battery mounting portion 197. The battery 198 is a rechargeable power source for supplying electric power to each part of the hedge trimmers 1A and 1B and the motor 2, and is also referred to as a battery pack. The structures of the battery mounting portion 197 and the battery 198 are well known, and thus the description thereof is omitted.

[0065] Next, the details of the speed reducer 4 will be described.

[0066] As Figures 3 to 5 shown, in the speed reducer 4, the first planetary gear mechanism 41 at the first stage (input side) includes a first sun gear 411, a first internal gear (also referred to as a ring gear) 412, a first planet carrier 415, and a plurality of first planetary gears 418. In the first planetary gear mechanism 41, the first internal gear 412 is in a fixed state, the first sun gear 411 is in an input state, and the first planet carrier 415 is in an output state. In addition, the first internal gear 412 is always in a fixed state. Therefore, the first planetary gear mechanism 41 always functions as a speed reduction mechanism.

[0067] The first internal gear 412 is supported in the gear housing 40 in a manner that it cannot rotate substantially about the axis A1 relative to the gear housing 40. The first sun gear 411 is fixed to the lower end of the motor shaft 23 (the input shaft of the speed reducer 4). The first planetary gear 418 is supported by the first planet carrier 415 and meshes with the first sun gear 411 and the first internal gear 412. A shaft 419 is fixed to the first planet carrier 415. The shaft 419 extends downward along the axis A1.

[0068] The second-stage second planetary gear mechanism 42 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 referred to as a ring gear) 422, a second planet carrier 425, and a plurality of second planetary gears 428. In the second planetary gear mechanism 42, the second internal gear 422 is in a fixed state, the second planet carrier 425 is in an input state, and the second sun gear 421 is in an output state. 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.

[0069] The second internal gear 422 is disposed inside the sleeve 405. The sleeve 405 is a stepped cylindrical member and is disposed in the gear housing 40 in a manner separated from the gear housing 40. The sleeve 405 can selectively rotate about 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 according to the rotation direction of the motor 2 by the reduction ratio change mechanism 6A. The reduction ratio change mechanism 6A will be described in detail later.

[0070] The second planet carrier 425 is fixed to the lower end of the shaft 419 extending from the first planet carrier 415. That is, the shaft 419 functions as the output shaft of the first planetary gear mechanism 41 and the input shaft of the second planetary gear mechanism 42. The second planetary gear 428 is supported by the second planet carrier 425 and meshes with the second internal gear 422 and the second sun gear 421. The second sun gear 421 is fixed to the shaft 429. The shaft 429 extends downward along the axis A1.

[0071] 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 referred to as a ring gear) 432, a third planet carrier 435, and a plurality of third planetary gears 438. In the third planetary gear mechanism 43, the third internal gear 432 is in a fixed state, the third sun gear 431 is in an input state, and the third planet carrier 435 is in an output state. Similar to 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. Therefore, the third planetary gear mechanism 43 selectively functions as a reduction mechanism.

[0072] The third internal gear 432 is disposed within the sleeve 405 below the second internal gear 422. Similar to the second internal gear 422, the third internal gear 432 is configured to rotate integrally with the sleeve 405. Thus, whether the third internal gear 432 rotates is also switched according to the rotation direction of the motor 2 and by a reduction ratio changing mechanism 6A described later.

[0073] The third sun gear 431 is fixed to the lower end portion of the shaft 429. That is, the second sun gear 421 and the third sun gear 431 are fixed to the common shaft 429 to form a single component. Accordingly, the assemblability of the speed reducer 4 can be improved. 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 planet carrier 435 and meshes with the third sun gear 431 and the third internal gear 432. The third planet carrier 435 has a shaft 439 extending downward along the axis A1.

[0074] 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 referred to as a ring gear) 442, a fourth planet carrier 445, and a plurality of fourth planetary gears 448. In the fourth planetary gear mechanism 44, the fourth internal gear 442 is in a fixed state, the fourth sun gear 441 is in an input state, and the fourth planet carrier 445 is in an output state. Additionally, the fourth internal gear 442 is always in a fixed state. Therefore, the fourth planetary gear mechanism 44 always functions as a reduction mechanism.

[0075] The fourth internal gear 442 is supported in the gear housing 40 in a manner that it cannot substantially rotate about 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 planet 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 planet carrier 445 and meshes with the fourth sun gear 441 and the fourth internal gear 442. The fourth planet 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 speed reducer 4.

[0076] Next, the reduction ratio change mechanism 6A will be described. 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 speed reducer 4 relative to the gear housing 40 according to the rotation direction of the motor 2. When the states of the second internal gear 422 and the third internal gear 432 change, the effective number of stages (the number of planetary gear mechanisms that effectively function) of the speed reducer 4 changes, and thus the reduction ratio of the speed reducer 4 changes.

[0077] As Figures 3 to 5 shown, the reduction ratio change mechanism 6A includes a one-way clutch 60 and a locking mechanism 61A.

[0078] The one-way clutch 60 is a clutch configured to transmit rotation only in one direction and idle in the opposite direction. The one-way clutch 60 of the present embodiment uses a general one-way clutch. The one-way clutch 60 is of a type in which bearings 605 (radial bearings) are arranged on both sides in the axial direction of a clutch member 601 (such as a roller, a sprag). That is, the one-way clutch 60 is configured as a single component (unit) in which the bearings 605 are assembled.

[0079] The one-way clutch 60 is disposed on the torque transmission path of the speed reducer 4. More specifically, the one-way clutch 60 is fitted onto the outer periphery of the shaft 419 integrated with the first planet carrier 415 of the first stage. When the shaft 419 rotates in the first direction, the one-way clutch 60 idles 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 the 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, so that rotation can be transmitted.

[0080] The locking mechanism 61A is configured to switch the states of the second-stage second internal gear 422 and the third-stage third internal gear 432 when the one-way clutch 60 does not transmit rotation and when it transmits rotation. The locking mechanism 61A includes a holding member 62A, two rollers 63, a locking sleeve 64A, and a locking cam 65A.

[0081] The holding member 62A is a cylindrical member having a through-hole through which the shaft 419 is inserted. The holding member 62A holds the rollers 63 so that they can move circumferentially around the axis A1 relative to the holding member 62A. In addition, the holding member 62A is configured to selectively engage with the locking cam 65A and rotate integrally with the locking cam 65A.

[0082] The holding member 62A includes a base portion 621, four protrusions 623, and a cylindrical portion 625. The base portion 621 is an annular part. The protrusions 623 are arc-shaped wall portions arranged at substantially equal intervals on the outer edge portion of the base portion 621 and protrude downward from the outer edge portion of the base portion 621. The cylindrical portion 625 has an outer diameter smaller than that of the base portion 621 and protrudes forward along the axis A1 from the central portion of the base portion 621.

[0083] The one-way clutch 60 is fixed inside the cylindrical portion 625 of the holding member 62A. That is, the holding member 62A rotates integrally with the one-way clutch 60. Therefore, the holding member 62A can selectively rotate relative to the shaft 419. Specifically, when the shaft 419 rotates in the first direction, the holding member 62A idles relative to the shaft 419 integrally with the one-way clutch 60. That is, the holding member 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 relative to the holding member 62A. On the other hand, when the shaft 419 rotates in the second direction, the holding member 62A rotates integrally with the shaft 419 together with the one-way clutch 60.

[0084] The rollers 63 are cylindrical members (pins). The diameters of the respective rollers 63 are substantially equal, smaller than the interval between two adjacent protrusions 623 of the holding member 62A, and larger than the thickness in the radial direction of the protrusions 623. The two rollers 63 are arranged in two diagonal spaces out of the four spaces formed between the protrusions 623 of the holding member 62A with their axes extending in the vertical direction.

[0085] The locking sleeve 64A is a substantially cylindrical member. The locking sleeve 64A is arranged around (radially outside) the holding member 62A coaxially with the holding member 62A below the first-stage first internal gear 412. The locking sleeve 64A is supported by the gear housing 40 in the gear housing 40 so as not to be able to rotate substantially around the axis A1 relative to the gear housing 40. The protrusions 623 and the rollers 63 of the holding member 62A are arranged inside the locking sleeve 64A.

[0086] The locking cam 65A is operably connected to the holding member 62A and selectively rotated by the holding member 62A. The locking cam 65A is an integral cylindrical member and is arranged coaxially with the holding member 62A.

[0087] More specifically, the locking 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 arranged diagonally across the axis A1, parallel to each other and extending parallel to the axis A1. The protrusions 656 are arranged diagonally across the axis A1 and protrude radially outward from the outer peripheral surface of the cylindrical portion 651. The two protrusions 656 are respectively arranged between the two flat portions 652 in the circumferential direction of the cylindrical portion 651. In the outer peripheral surface of the cylindrical portion 651, the portion between the flat portion 652 and the protrusion 656 is a curved surface corresponding to the outer peripheral surface of a cylinder.

[0088] As Figure 6 shown, the radial distance between the flat portion 652 and the inner peripheral surface of the locking sleeve 64A is the largest 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 locking sleeve 64A decreases as it moves from the center of the flat portion 652 towards the end. The radial distance between the end of the flat portion 652 and the inner peripheral surface of the locking sleeve 64A is set to be less than the diameter of the roller 63. In addition, Figure 6 is a diagram schematically showing a cross-section of the locking mechanism 61A for explaining the operating principle of the locking mechanism 61A and does not strictly correspond to the actual shape of the locking mechanism 61A. The same applies to Figure 7 referred to later.

[0089] The locking cam 65A having the above structure is inserted into the outer periphery of the cylindrical portion 625 of the holding member 62A from below. The two protrusions 656 of the locking cam 65A are arranged in two of the four spaces (specifically, the two spaces where the roller 63 is not arranged) formed between the protrusions 623 formed on the holding member 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 holding member 62A in the radial direction. The roller 63 is arranged in the radial direction between the flat portion 652 of the locking cam 65A and the inner peripheral surface of the locking sleeve 64A.

[0090] In addition, the locking cam 65A is connected to the sleeve 405 via the protrusion 656 and can selectively rotate integrally with the sleeve 405 relative to the gear housing 40 about the axis A1. As described above, since the second internal gear 422 and the third internal gear 432 rotate integrally with the sleeve 405, the locking cam 65A can selectively rotate integrally with the second internal gear 422 and the third internal gear 432.

[0091] Next, the operation of the reduction ratio change mechanism 6A (the one-way clutch 60 and the locking mechanism 61A) will be described.

[0092] First, the operation when the rotation direction of the motor 2 is the first direction will be described.

[0093] When the motor shaft 23 starts to rotate in the first direction, the first planetary carrier 415 and the shaft 419 of the first stage also rotate in the first direction about the axis A1. At this time, as described above, the one-way clutch 60 idles relative to the shaft 419 and does not transmit rotation to the holder 62A. Therefore, the holder 62A does not rotate actively.

[0094] The second planetary carrier 425 of the second stage fixed to the shaft 419 also rotates in the first direction about the axis A1. The second planetary gear 428 supported by the second planetary carrier 425 causes the second internal gear 422 and the sleeve 405 to rotate in the second direction relative to the gear housing 40. At this time, the locking cam 65A connected to the sleeve 405 also rotates in the second direction ( Figure 6 in the direction of the arrow). In response to the rotation of the locking cam 65A, the roller 63 moves relatively from the position shown by the dotted line in Figure 6 toward the end of the plane portion 652.

[0095] As Figure 6 shown by the solid line, before the protrusion 656 of the locking cam 65A abuts against the protrusion 623 of the holder 62A, the roller 63 is wedged and clamped between the plane portion 652 and the inner peripheral surface of the locking sleeve 64A at a position closer to the end than the center of the plane portion 652. Hereinafter, the position of the roller 63 relative to the locking sleeve 64A and the locking cam 65A at this time will also be referred to as the locked position, and the state of the locking mechanism 61A will also be referred to as the locked state. Accordingly, the locking cam 65A is locked to the locking sleeve 64A via the roller 63, and further locked to the gear housing 40, thereby prohibiting the rotation of the locking cam 65A relative to the gear housing 40.

[0096] In response to the locking cam 65A being locked, the sleeve 405 is locked against rotation relative to the gear housing 40, and thus the second internal gear 422 and the third internal gear 432 are also locked against rotation relative to the gear housing 40. Therefore, thereafter, the second internal gear 422 and the third internal gear 432 function as fixed structural elements. The second planetary gear 428 revolves around the second sun gear 421 while rotating on its own axis, 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, and via the third planetary gear 438, causes the third planet carrier 435 to rotate in the first direction.

[0097] As described above, when the motor shaft 23 rotates in the first direction and the one-way clutch 60 does not transmit rotation to the holder 62A, the locking mechanism 61A locks the second internal gear 422 of the second stage and the third internal gear 432 of the third stage against rotation. Accordingly, the locking mechanism 61A enables 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 effective number of stages of the speed reducer 4 is 4.

[0098] The operation when the rotation direction of the motor 2 is the second direction will be described.

[0099] When the motor shaft 23 starts to rotate in the second direction, the first planet carrier 415 and the shaft 419 of the first stage also rotate in the second direction. At this time, as described above, the one-way clutch 60 is locked to the shaft 419 and transmits the rotation of the shaft 419 to the holder 62A. Therefore, the holder 62A also rotates in the second direction ( Figure 7 in the direction of the arrow in).

[0100] As Figure 7 shown, two of the protrusions 623 of the holder 62A come into contact with the protrusions 656 of the locking cam 65A and press in the second direction. During this period, the remaining two protrusions 623 come into contact with the roller 63 and press in the second direction, causing it to move to a position where the release plane portion 652 and the inner peripheral surface of the locking sleeve 64A no longer clamp the roller 63 (in this embodiment, a position corresponding to approximately the center of the plane portion 652). Hereinafter, the position of the roller 63 relative to the locking sleeve 64A and the locking cam 65A at this time will also be referred to as the unlocking position, and the state of the locking mechanism 61A will also be referred to as the unlocked state.

[0101] In response to the roller 63 being configured in the unlocked position, the locking cam 65A can rotate relative to the locking sleeve 64A and, thus, can rotate relative to the gear housing 40. Accordingly, the rotation of the holding member 62A is transmitted to the locking cam 65A, and the locking cam 65A rotates integrally with the shaft 419 and the holding member 62A in the second direction. As a result, the second internal gear 422 of the second stage and the third internal gear 432 of the third stage rotate integrally with the shaft 419 and the second planet carrier 425 of the second stage in the second direction.

[0102] Since the second planet carrier 425 rotates integrally with the second internal gear 422, the second planet gear 428 supported by the second planet carrier 425 of the second stage cannot rotate (self-rotate). As a result, the second sun gear 421 of the second stage rotates integrally with the second planet carrier 425 and the second internal gear 422 in the second direction. The rotational 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.

[0103] Since the third sun gear 431 fixed to the shaft 429 rotates integrally with the third internal gear 432, the third planet gear 438 supported by the third planet carrier 435 of the third stage also cannot rotate (self-rotate). As a result, the third planet carrier 435 of the third stage rotates integrally with the third sun gear 431 and the third internal gear 432 in the second direction. The rotational 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 speed reducing mechanism.

[0104] As described above, when the motor shaft 23 rotates in the second direction and the one-way clutch 60 transmits the rotation to the holding member 62A, the locking mechanism 61A causes the second internal gear 422 and the third internal gear 432 to rotate integrally with the shaft 419 in the same direction. Accordingly, the locking mechanism 61A invalidates 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 effective number of stages of the speed reducer 4 is 2.

[0105] As described above, the effective number of stages of the speed reducer 4 switches between 4 and 2 according to the rotation direction of the motor 2. Further, in the present 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 higher than the input speed of the second planetary gear mechanism 42). Specifically, the reciprocal of the speed increasing ratio (transmission ratio: less than 1) of the second planetary gear mechanism 42 when functioning effectively is larger than the reduction ratio (transmission ratio: greater than 1) of the third planetary gear mechanism 43 when functioning effectively. That is, when the rotational speeds of the shafts 419, 429, and 439 are set to N1, N2, and N3, respectively, the relationship (N2 / N1) > (N2 / N3) holds. In addition, detailed description is omitted, and the reduction ratios of the first planetary gear mechanism 41 and the fourth planetary gear mechanism 44 are each set so that the speed reducer 4 functions as a reduction mechanism as a whole.

[0106] Therefore, when the effective number of stages of the speed reducer 4 is 2 (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), the shaft 449 rotates at a lower speed than when the effective number of stages is 4 (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), and a higher torque is exerted. Thus, the operation mode of the speed reducer 4 when the effective number of stages is 2 is referred to as the low speed - high torque mode. In addition, the operation mode of the speed reducer 4 when the effective number of stages is 4 is referred to as the high speed - low torque mode. In particular, in the present embodiment, in the low speed - high torque mode, the torque can be effectively increased by the rotation of the second internal gear 422 and the third internal gear 432.

[0107] In the present embodiment, the speed reducer 4 is configured such that the overall reduction ratio of the speed reducer 4 in the low speed - high torque mode is less than 2.5 times the overall reduction ratio of the speed reducer 4 in the high speed - low torque mode. Further, when the input rotational speed (input speed) is set to Ni and the output rotational speed (output speed) is set to No, the reduction ratio (transmission ratio) of the speed reducer is represented by Ni / No. Therefore, when the input speed (rotational speed of the motor shaft 23) Ni of the speed reducer 4 is the same, the output speed Noh of the speed reducer 4 in the high speed - low torque mode is less than 2.5 times the output speed (rotational speed of the shaft 449) Nol of the speed reducer 4 in the low speed - high torque mode (that is, Nol and Noh satisfy the relationship Noh < (Nol × 2.5)).

[0108] In the case where a planetary gear mechanism is configured as a reduction mechanism in which the internal gear is in a fixed state, the sun gear is in an input state, and the carrier is in an output state, the reduction ratio (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 set to Zs and Zi, respectively, the reduction ratio (transmission ratio) is expressed as 1 + (Zi / Zs). Since the planetary gears are interposed between the sun gear and the internal gear, there is a limit to reducing Zi / Zs, and thus there is a limit to reducing 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 stage of the planetary gear mechanism fixed by the internal gear, the reduction ratio changes greatly, and thus the output speed changes greatly.

[0109] Generally, the reduction ratio of each planetary gear mechanism is mostly about 3 or more than 3. Therefore, when enabling or disabling the function of one stage of a multi-stage planetary reducer, the reduction ratio (output speed) of the entire reducer 4 in the low-speed / high-torque mode is mostly about 3 times or more than the reduction ratio (output speed) of the entire reducer 4 in the high-speed / low-torque mode.

[0110] In contrast, in the reducer 4 of the present embodiment, the second planetary gear mechanism 42 in the four-stage (four sets) planetary gear mechanism is configured as a speed increasing mechanism, and the remaining three stages are configured as reduction mechanisms. And the reduction ratio is changed by enabling or disabling the function of 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 reduction mechanism.

[0111] In this case, by appropriately combining the speed increasing ratio of the second planetary gear mechanism 42 and the reduction ratio of the third planetary gear mechanism 43, the speed increasing ratio (transmission ratio) of the two stages as a whole can be flexibly set. Specifically, the reciprocal of the speed increasing ratio (<1) of the two stages as a whole can be made smaller than the reduction ratio (>1) of the planetary gear mechanism with the internal gear fixed. Accordingly, compared with the case where all stages of a multi-stage planetary reducer are reduction mechanisms with the internal gear fixed and the function of at least one stage is enabled or disabled, the reduction ratio of the entire reducer 4 can be reduced, and thus the change in the output speed can be reduced.

[0112] In addition, in the present embodiment, the second planetary gear mechanism 42 serving as a speed increasing mechanism is disposed at the front stage (input side) of the third planetary gear 43 serving as a speed reducing mechanism. Therefore, when the speed reducing mechanism is disposed at the front stage (input side) of the speed increasing mechanism, 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 reducing mechanism to the speed increasing mechanism. Therefore, the required strength of the gears can be made smaller than that required when the speed reducing mechanism is disposed at the front stage of the speed increasing mechanism, and thus the gears can be made more compact. However, contrary to the present embodiment, the speed reducing mechanism may be disposed at the front stage (input side) of the speed increasing mechanism. In this case, similar to the present embodiment, it is only necessary to appropriately set the overall speed increasing ratio or speed reducing ratio (transmission ratio) of the two stages.

[0113] Next, the operation of the hedge trimmer 1A during a cutting operation (pruning operation, trimming operation) will be described.

[0114] After the user long-presses the main power switch 851 to turn it on, the reverse switch 855 is appropriately pressed according to the cutting object. Specifically, when cutting relatively thin branches or leaves, the cutting force can be relatively small, so from the perspective of cutting efficiency, the high-speed·low-torque mode is preferred. 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, so the low-speed·high-torque mode is preferred. 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.

[0115] Then, when the switch operating lever 193 is pressed, the controller 81 (control circuit) drives the motor 2 at a rotational speed corresponding to the operation amount of the switch operating lever 193. As described above, the speed reducer 4 operates with an effective number of stages corresponding to the rotation direction (operation mode) of the motor 2. The shaft 449 causes the two blades 9 to reciprocate relatively in the front-rear direction through the motion conversion mechanism 7. The object to be cut is cut by the reciprocating blades 9.

[0116] In addition, during the cutting operation, sometimes debris of branches or leaves may be wound between the cutting edges 90 of the upper blade 9 and the cutting edges 90 of the lower blade 9. In this case, the user can switch the rotation direction of the motor 2 by pressing the reverse switch 855. After that, when the switch operating lever 193 is pressed, since the moving directions of the two blades 9 are reversed, the wound branches or leaves can be easily removed. In particular, when the rotation direction of the motor 2 is switched from the first direction to the second direction (switching from the high-speed·low-torque mode to the low-speed·high-torque mode), the cutting edge 90 biting into the branch can be easily detached from the branch.

[0117] As described above, the speed reducer 4 of the present embodiment is a multi-stage planetary speed reducer, which changes the effective number of stages according to the rotation direction of the motor 2 (motor shaft 23), thereby changing the reduction ratio of the speed reducer 4, and further changing the output speed and output torque of the speed reducer 4. Therefore, it is possible to realize a hedge trimmer 1A that can perform two operations with different required output speeds and output torques only by changing the rotation direction of the motor 2 without performing speed control of the motor 2.

[0118] In addition, in the hedge trimmer 1A, the demand for a significant increase in output torque is not so large. On the other hand, a significant reduction in output speed will lead to a significant decrease in work efficiency, so it is not preferred. As described above, since the change in the overall reduction ratio of the speed reducer 4 of the present embodiment is small, and further the change in output speed is small, it has the characteristics preferred by the hedge trimmer 1A.

[0119] The correspondence between the structure (feature) of the first embodiment and the structure (feature) of the present invention is as follows. However, the structure (feature) of the embodiment is only an example and does not limit the present invention or the structure (feature) of the present invention.

[0120] The hedge trimmer 1A is an example of an "electric tool" and a "cutting tool". The motor 2 and the motor shaft 23 are examples of a "motor" and a "motor shaft", respectively. The speed reducer 4 is an example of a "speed reducer". 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 examples of a "multi-stage planetary gear mechanism". The one-way clutch 60 is an example of a "one-way clutch". The second direction in the rotation direction (the first direction and the second direction) of the motor shaft 23 is an example of "a specific one of the two directions". The locking mechanism 61A is an example of a "locking mechanism". The second planetary gear mechanism 42 and the third planetary gear mechanism 43 are examples of "at least two stages of multiple planetary gear mechanisms". The second internal gear 422 and the third internal gear 432 are examples of "at least two stages of 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 "speed reducing 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.

[0121] [Second Embodiment]

[0122] Next, refer to Figures 8 to 9The hedge trimmer 1B according to the second embodiment will be described. The hedge trimmer 1B of this embodiment has a structure substantially the same as that of the hedge trimmer 1A of the first embodiment in part. Therefore, hereinafter, the same reference numerals are assigned to the structures (including cases where the shapes are slightly different) substantially the same as those of the hedge trimmer 1A in the hedge trimmer 1B, and the description thereof is omitted or simplified, and mainly the different structures will be described.

[0123] Although not shown in the drawings, the hedge trimmer 1B of the second embodiment has a main body housing 11 and handles 17 and 19 in the same manner as the hedge trimmer 1A of the first embodiment (see Figure 2 ). As Figure 8 shown, a motor 2, a speed reducer 5, and a motion conversion mechanism 7 are mainly arranged in the main body housing 11 of the hedge trimmer 1B. In addition, in Figure 8 , the illustration of the link rods 731 and 732 is omitted. The motor 2, the speed reducer 5, and the motion conversion mechanism 7 are respectively arranged in a motor housing 20, a gear housing 50, and a crank housing 70. The motor housing 20, the gear housing 50, and the crank housing 70 are fixed to each other by screws and integrated, and are supported in the main body housing 11 in a manner that cannot move substantially relative to the main body housing 11.

[0124] Similar to the first embodiment, the motor 2 is a brushless DC motor. The motor shaft 23 is supported so as to be rotatable about an axis A1 extending in the vertical direction. The lower end portion of the motor shaft 23 projects into the gear housing 50. The lower end portion of the motor shaft 23 has 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.

[0125] The speed reducer 5 is arranged in front of the motor 2 in the front-rear direction. The speed reducer 5 is configured to be operably connected to the motor shaft 23 of the motor 2 and the motion conversion mechanism 7, decelerate the rotation of the motor shaft 23, and increase the torque and output it to the motion conversion mechanism 7. In this embodiment, the speed reducer 5 includes a reduction gear 53 and a first-stage (one set) planetary gear mechanism 55.

[0126] The reduction gear 53 is a large-diameter driven gear that meshes with the drive gear (pinion) 231 of the motor shaft 23. The reduction gear 53 is provided on the gear sleeve 51. More specifically, the gear sleeve 51 is a stepped cylindrical member that 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 portion of the gear sleeve 51 is the large-diameter portion, and the portion other than the lower end portion is the small-diameter portion. The gear sleeve 51 (inner gear 552) is supported by the gear housing 50 via a bearing 511 so as to be rotatable relative to the gear housing 50 about the axis A2. The axis A2 extends parallel (in the vertical direction) to the axis A1 in front of the axis A1. 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 drive gear 231. The gear sleeve 51 rotates in the direction opposite to the motor shaft 23 at a speed lower than that of the motor shaft 23 according to the rotation of the motor shaft 23.

[0127] The planetary gear mechanism 55 includes a sun gear 551, an inner gear (also referred to as a ring gear) 552, a planet carrier 555, and a plurality of planet gears 558. In the planetary gear mechanism 55, the sun gear 551 is in a fixed state, the inner gear 552 is in an input state, and the planet carrier 555 is in an output state. 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. Therefore, the planetary gear mechanism 55 can selectively function as a reduction mechanism.

[0128] The inner gear 552 is formed inside the large-diameter portion of the gear sleeve 51. Therefore, the inner gear 552 is supported by the bearing 511 so as to be able to rotate stably relative to the gear housing 50. In addition, a shaft 52 is inserted through the inside of 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, and the details will be described later. Whether the shaft 52 rotates, and thus whether the sun gear 551 rotates, is switched according to the rotation direction of the motor 2 by the reduction ratio change mechanism 6B. The sun gear 551 is fixed to the lower portion of the shaft 52 (the portion disposed radially inside the inner gear 552).

[0129] The planetary gear 558 is supported by the planet carrier 555 and meshes with the sun gear 551 and the internal gear 552. The planet carrier 555 is coaxially arranged with the shaft 52 below the sun gear 551. The planet carrier 555 has a shaft 559 extending downward along the axis A2. The shaft 559 is supported by two bearings 571, 572 on the crank case 70 so as to be rotatable about the axis A2. The shaft 559 functions as the final output shaft of the speed reducer 5. In addition, a recess is formed at the upper end of the planet carrier 555. A bearing 574 is arranged in the recess, and the bearing 574 rotatably supports the lower end of the support shaft 52.

[0130] In the present embodiment, the reduction ratio change mechanism 6B is configured to selectively lock or rotate the shaft 52 and even the sun gear 551 relative to the gear housing 50 according to the rotation direction of the motor 2. When the state of the sun gear 551 is changed, the effective number of stages of the speed reducer 5 is changed, and further the reduction ratio of the speed reducer 5 is changed. The basic structure of the reduction ratio change mechanism 6B is the same as that of the reduction ratio change mechanism 6A of the first embodiment (refer to Figure 3 ). Specifically, the reduction ratio change mechanism 6B includes a one-way clutch 60 and a locking mechanism 61B. The locking mechanism 61B includes a holding member 62B, two rollers 63, a locking sleeve 64B, and a locking cam 65B. The respective shapes and configurations of these components are different from those of the locking mechanism 61A of the first embodiment, but their functions are basically the same.

[0131] The holding member 62B includes an annular base 621, four protrusions 623 protruding from the base 621, and a sleeve portion 627. The sleeve portion 627 is formed in a cylindrical shape with an outer diameter smaller than that of the base 621, and extends coaxially with the base 621 from the central portion of the base 621 in the direction opposite to the protrusions 623. The sleeve portion 627 penetrates the gear sleeve 51 along the axis A2. The base 621 and the protrusions 623 are arranged above the gear sleeve 51. The two rollers 63 are arranged in two diagonal spaces out of the four spaces formed between the protrusions 623 of the holding member 62B in such a way that their axes extend in the vertical direction.

[0132] The locking sleeve 64B is a bottomed cylindrical member. The locking sleeve 64B is coaxially arranged with the holding member 62B above the gear sleeve 51 around (radially outside) the base 621 and the protrusions 623. The locking sleeve 64B is supported by the gear housing 40 in the gear housing 40 so as not to substantially rotate about the axis A2 relative to the gear housing 40.

[0133] The locking cam 65B is movably engaged with the holding member 62B and is selectively rotated by the holding member 62B. The locking cam 65B is an integral cylindrical member and is arranged coaxially with the holding member 62B. Similar to the first embodiment, the locking 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 protrusion 623 of the holding member 62B, and the two protrusions 656 are arranged in two of the four spaces formed between the protrusions 623 in the circumferential direction (specifically, the two spaces where the rollers 63 are not arranged).

[0134] In addition, in the present embodiment, the locking cam 65B is connected to the shaft 52 and can selectively rotate integrally with the shaft 52 relative to the gear housing 40 about the axis A1. As described above, since the sun gear 551 is fixed to the shaft 52, the locking cam 65B can selectively rotate integrally with the sun gear 551.

[0135] A one-way clutch 60 is interposed between the small-diameter portion of the gear sleeve 51 and the holding member 62B. The one-way clutch 60 is fixed inside the small-diameter portion of the gear sleeve 51 and rotates integrally with the gear sleeve 51. 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 idles relative to the holding member 62B. That is, the one-way clutch 60 does not transmit rotation from the gear sleeve 51 to the holding member 62B. At this time, the bearing 605 of the one-way clutch 60 ensures smooth rotation of the gear sleeve 51 relative to the holding member 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 holding member 62B and transmits rotation from the gear sleeve 51 to the holding member 62B.

[0136] Hereinafter, the operation of the reduction ratio change mechanism 6B (one-way clutch 60 and locking mechanism 61B) will be described.

[0137] First, the operation when the rotation direction of the motor 2 is the first direction will be described.

[0138] 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, since the one-way clutch 60 does not transmit rotation to the holding member 62B, the holding member 62B does not rotate actively. The internal gear 552 causes the sun gear 551 and the shaft 52 to rotate in the first direction via the planetary gear 558. At this time, the locking cam 65B connected to the shaft 52 also rotates in the first direction ( Figure 6 in the direction of the arrow), and the roller 63 relatively moves in the direction toward the end of the flat surface portion 652 from the position of the dotted line.

[0139] As Figure 6As shown by the solid line, as the roller 63 is disposed at the locked position, the locking cam 65B is locked and cannot rotate relative to the gear housing 50, and the sun gear 551 also cannot rotate relative to the gear housing 50. Therefore, after this, the sun gear 551 functions as a fixed structural 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 planet carrier 555 to rotate in the second direction.

[0140] As described above, when the motor shaft 23 rotates in the first direction, the locking mechanism 61B enables the planetary gear mechanism 55 to function effectively. Therefore, when the motor shaft 23 rotates in the first direction, the effective number of reduction stages of the speed reducer 5 is 1. Therefore, in the speed reducer 5, after deceleration by the drive gear 231 and the reduction gear 53, further deceleration is performed by the planetary gear mechanism 55.

[0141] The operation when the rotation direction of the motor 2 is the second direction will be described.

[0142] 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 holder 62B, so the holder 62B also rotates in the first direction ( Figure 7 in the arrow direction). As Figure 7 shown, two of the protrusions 623 of the holder 62B respectively abut against the protrusions 656 of the locking cam 65B and press in the first direction. During this period, the remaining two protrusions 623 abut against the roller 63 and press in the first direction, causing the roller 63 to move to the unlocking position. Therefore, after this, the locking cam 65B and the sun gear 551 rotate integrally with the internal gear 552 and the holder 62B in the first direction. As a result, the planet carrier 555 also rotates in the first direction at the same rotational speed as the internal gear 552.

[0143] As described above, when the motor shaft 23 rotates in the second direction, the locking mechanism 61B invalidates the function of the planetary gear mechanism 55. Therefore, when the motor shaft 23 rotates in the second direction, the effective number of reduction stages of the speed reducer 5 is 0. That is, in the speed reducer 5, deceleration is only performed between the drive gear 231 and the reduction gear 53. Therefore, in the present embodiment, the speed reducer 5 operates in a low-speed and high-torque mode when the effective number of reduction stages is 1 (when the rotation direction of the motor 2 is the first direction and the sun gear 551 is locked), and operates in a high-speed and low-torque mode when the effective number of reduction stages is 0 (when the rotation direction of the motor 2 is the second direction and the sun gear 551 rotates).

[0144] The planetary gear mechanism 55 of the present embodiment is configured as a reduction mechanism in which the sun gear is in a fixed state, the internal gear is in an input state, and the carrier is in an output state, and its reduction ratio (transmission ratio) is represented by 1+(Zs / Zi) (Zs and Zi are the number of teeth of the sun gear and the internal gear, respectively). Therefore, by making the function of the planetary gear mechanism 55 effective or ineffective, compared with the case of a planetary gear mechanism in which the internal gear is in a fixed state, the sun gear is in an input state, and the carrier is in an output state, the reduction ratio of the entire reducer 5 can be reduced, and thus the change in the output speed can be reduced. The reducer 5 is configured such 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.

[0145] Regarding the operation of the hedge trimmer 1B during the cutting operation (pruning operation, trimming operation), it is the same as the operation of the hedge trimmer 1A of the first embodiment. However, in the hedge trimmer 1A and the hedge trimmer 1B, the operation modes corresponding to the rotation direction of the motor 2 are opposite.

[0146] As described above, the reducer 5 of the present embodiment is a planetary reducer including only one set of planetary gear mechanisms 55. And, according to the rotation direction of the motor 2 (motor shaft 23), by making the planetary gear mechanism 55 effective or ineffective, the reduction ratio of the reducer 5 can be changed, and thus the output speed and output torque of the reducer 5 can be changed. Therefore, in the present embodiment, it is also possible to realize a hedge trimmer 1B that can perform two operations with different required output speeds and output torques only by changing the rotation direction of the motor 2 without controlling the rotational speed of the motor 2.

[0147] In addition, in the present embodiment, by making the number of planetary gear mechanisms included in the reducer 5 only one, a compact reducer 5 can be realized. On the other hand, 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 ineffective.

[0148] The correspondence between the structure (feature) of the second embodiment and the structure (feature) of the present invention is as follows. However, the configuration (feature) of the embodiment is only an example and does not limit the present invention or the structure (feature) of the present invention.

[0149] The hedge trimmer 1B is an example of an "electric tool" and a "cutting tool". The motor 2 and the motor shaft 23 are examples of a "motor" and a "motor shaft", respectively. The speed reducer 5 is an example of a "speed reducer". The reduction ratio change mechanism 6B is an example of a "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". The second direction among the rotation directions (the first direction and the second direction) of the motor shaft 23 is an example of "a specific one of the two directions". The locking mechanism 61B is an example of a "locking 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 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.

[0150] In addition, the above-described embodiments are merely illustrative, and the electric tool according to the present invention is not limited to the illustrated hedge trimmers 1A and 1B. For example, the following-described changes can be added. In addition, at least one of these changes can be combined with any one of the hedge trimmers 1A and 1B illustrated in the embodiments and the inventions described in each technical solution and adopted.

[0151] For example, the motor 2 can also be a brushed motor instead of a brushless motor. The motor 2 can also be driven not by the battery 198 but by the electric power supplied from an external AC power source.

[0152] The number of planetary gear mechanisms included in the speed reducer 4 is not limited to 4, and can also be any number of 2 or more. In the speed reducer 4, the number of planetary gear mechanisms whose functions are made effective or ineffective according to the change in the rotation direction of the motor 2 is not limited to 2, and can also be 3 or more. The input shaft of the speed reducer 4 does not need to be the motor shaft 23, and other rotating shafts can also be arranged on the torque transmission path between the motor shaft 23 and the speed reducer 5. The speed reducer 5 does not need to be coaxially arranged with the motor 2. Similarly, the structure of the speed reducer 5 can also be appropriately changed. For example, the speed reducer 5 can also include other planetary gear mechanisms in addition to the planetary gear mechanism 55.

[0153] In each of the reduction ratio change mechanisms 6A and 6B, the structures and arrangements of the one-way clutches 60 and the locking mechanisms 61A and 61B can be appropriately changed. For example, the one-way clutch 60 is of a type without the assembled bearing 605, and the bearing can also be arranged separately and independently from the one-way clutch 60. The shapes, arrangements, numbers, etc. of the respective structural components of the locking mechanism 61A can be appropriately changed. For example, the number of rollers 63 can also be three or more. The numbers of the protrusions 656 of the locking cams 65A and 65B and the protrusions 623 of the holding members 62A and 62B can also be arbitrarily changed. The locking sleeves 64A and 64B can also be omitted, and the rollers 63 can be arranged between the inner peripheral surfaces of the gear housings 40 and 50 and the flat portions 652 of the locking cams 65A and 65B and can move between the locking position and the unlocking position. In addition, in the speed reducer 4, the locking cam 65A and the sleeve 405 can also be formed as a single component. In the speed reducer 5, the locking cam 65B and the shaft 52 can also be formed as a single component.

[0154] The control circuit of the controller 81 can also 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 can also be, for example, a lever, a slider, a touch panel, etc.

[0155] In addition, in the above-described embodiment, as examples of the power tool, the hedge trimmers 1A and 1B are listed, but the present invention can also be applied to other power tools that perform two different operations according to the rotation direction of the motor.

[0156] Furthermore, in view of the gist of the above-described embodiment and its modified examples, the present invention can construct the following modes. At least one of the following modes can be adopted in combination with at least one of the above-described embodiment and its modified examples and the inventions described in the respective technical solutions.

[0157] [Mode 1]

[0158] The entire at least two-stage planetary gear mechanism is configured as a speed increasing mechanism.

[0159] [Mode 2]

[0160] The reciprocal of the speed increasing ratio of the speed increasing planetary gear mechanism is larger than the reduction ratio of the reduction planetary gear mechanism.

[0161] [Mode 3]

[0162] The plurality of planetary gear mechanisms include at least a three-stage planetary gear mechanism,

[0163] In the at least three-stage planetary gear mechanism, each of the planetary gear mechanisms other than the at least two stages is configured as a reduction mechanism.

[0164] [Mode 4]

[0165] In Mode 3,

[0166] the speed-increasing planetary gear mechanism and the speed-decreasing planetary gear mechanism are respectively arranged at the second stage and the third stage.

[0167] [Mode 5]

[0168] The one-way clutch is configured to be arranged around the shaft integrated with the planet carrier of the speed-increasing planetary gear mechanism, and transmit rotation to the shaft only when the motor rotates in the specific one of the two directions along the motor axis.

[0169] Shaft 419 is an example of the "shaft".

[0170] [Mode 6]

[0171] The power tool further includes:

[0172] a control device configured to control the operation of the power tool; and

[0173] an operation member configured to be externally operated by a user,

[0174] The control device is configured to change the rotation direction of the motor shaft in response to the operation of the operation member by the user.

[0175] Controller 81 (control circuit) is an example of the "control device". Reverse switch 855 is an example of the "operation member".

[0176] [Mode 7]

[0177] It further includes a housing for accommodating the speed reducer,

[0178] the internal gears of at least two stages can selectively rotate integrally relative to the housing about the first axis,

[0179] The locking mechanism includes: a roller that can move between a locking position and a locking release position in the circumferential direction around the first axis;

[0180] a holder that holds the roller so that it can move between the locking position and the locking release position, and can selectively rotate integrally with the one-way clutch relative to the housing about the first axis;

[0181] a locking cam configured to rotate integrally with the internal gears of at least two stages about the first axis and be able to engage with the holder; and

[0182] A locking sleeve, which is configured not to rotate relative to the housing about the first axis and is at least partially disposed around the roller, the holding member, and the locking cam,

[0183] When the one-way clutch does not transmit rotation, the roller is clamped between the locking sleeve and the locking cam in the locked position, locking the locking cam and the at least two-stage internal gear so as not to rotate relative to the housing.

[0184] When the one-way clutch transmits rotation, the roller is disposed between the locking sleeve and the locking cam in a clearance fit (loosely fitted) state in the unlocked position, and the holding member rotates integrally with the one-way clutch to rotate the locking cam and the at least two-stage internal gear.

[0185] The gear housings 40, 50 are an example of the "housing". The roller 63 is an example of the "roller". The holding members 62A, 62B are an example of the "holding member". The locking cams 65A, 65B are an example of the "locking cam". The locking sleeves 64A, 64B are an example of the "locking sleeve".

Claims

1. An electric tool, characterized in that, it has a motor, a speed reducer and a reduction ratio change mechanism, wherein, the motor has a motor shaft capable of rotating in two opposite directions; the speed reducer is movably connected to the motor shaft and includes a multi-stage planetary gear mechanism; the reduction ratio change mechanism is configured to change the reduction ratio of the speed reducer according to the change of the rotation direction of the motor shaft, at least two stages of the multi-stage planetary gear mechanism are configured such that their internal gears selectively act as fixed structural elements, the reduction ratio change mechanism has a one-way clutch and a locking mechanism, wherein, the one-way clutch is configured to be arranged on the torque transmission path and transmit rotation only when the motor shaft rotates in a specific one of the two directions; the locking mechanism is movably connected to the one-way clutch and the at least two stages of the internal gears, and the locking mechanism is configured to lock the at least two stages of the internal gears from rotating when the one-way clutch does not transmit rotation, and to rotate the at least two stages of the internal gears when the one-way clutch transmits rotation, the at least two stages of planetary gear mechanisms include 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 electric tool according to claim 1, characterized in that, the speed increasing planetary gear mechanism is arranged at the front stage of the speed reducing planetary gear mechanism.

3. The electric tool according to claim 2, characterized in that, the sun gear acting as the output structural element of the speed increasing planetary gear mechanism and the sun gear acting as the input structural element of the speed reducing planetary gear mechanism form a single component.

4. The electric tool according to any one of claims 1 to 3, characterized in that, the speed 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. An electric tool, characterized in that, it has a motor, a speed reducer and a reduction ratio change mechanism, wherein the motor has a motor shaft capable of rotating in two opposite directions; the speed reducer is movably connected to the motor shaft and includes a planetary gear mechanism; the reduction ratio change mechanism is configured to change the reduction ratio of the speed reducer according to the change of the rotation direction of the motor shaft; the planetary gear mechanism is configured such that the sun gear selectively acts as a fixed structural element and the internal gear acts as an input structural element, the reduction ratio change mechanism has a one-way clutch and a locking mechanism, wherein, the one-way clutch is configured to be arranged on the torque transmission path and transmit rotation only when the motor shaft rotates in a specific one of the two directions; The locking mechanism is operably connected to the one-way clutch and the sun gear. The locking mechanism is configured to lock the sun gear against rotation when the one-way clutch does not transmit rotation, and to allow the sun gear to rotate when the one-way clutch transmits rotation.

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

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

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

9. The power tool according to any one of claims 1 to 8, wherein: The one-way clutch has a clutch member and a second bearing, and the second bearing is 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, wherein: The reduction ratio of the speed reducer when the motor rotates in one of the two directions is less than 2.5 times the reduction ratio of the speed reducer when the motor rotates in the other of the two directions.

11. The power tool according to any one of claims 1 to 10, wherein: The power tool is a cutting tool, and is configured to cause a first blade and a second blade mounted on the main body of the power tool to perform a reciprocating linear relative movement, and to cut an object to be cut during both a forward stroke and a return stroke of the first blade relative to the second blade.

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