Tool

Abstract

The problem addressed by the present disclosure is to suppress sound during the operation of a tool. This tool comprises a motor, a sun gear (41), an output shaft, a plurality of planetary gears, a planetary carrier (44), and an internal gear (43). A tip tool is attached to the output shaft, and the rotation of the sun gear (41) is transmitted to the output shaft. The internal gear (43) is held in a rotatable state. The internal gear (43) is fixed to the transmission body and rotates in accordance with the rotation of the transmission body. The internal gear (43) has a first engagement part (432). The planetary carrier (44) has a second engagement part (442). The first engagement part (432) of the internal gear (43) and the second engagement part (442) of the planetary carrier (44) can move relative to each other along the rotation direction of the transmission body, and come into contact with each other in accordance with the rotation of the internal gear (43).

Description

tool

[0001] FIELD OF THE DISCLOSURE The present disclosure relates generally to tools, and more particularly to tools including motors.

[0002] Patent Document 1 discloses a rotary impact tool including an impact mechanism, in which the impact mechanism applies a striking shock to an output shaft.

[0003] Incidentally, in the rotary impact tool as described in Patent Document 1, noise is generated when the impact mechanism applies a striking impact to the output shaft.

[0004] Japanese Patent Application Laid-Open No. 2017-132021

[0005] The present disclosure has been made in view of the above-mentioned circumstances, and aims to provide a tool that can suppress noise during operation.

[0006] A tool according to one aspect of the present disclosure includes a motor, a sun gear, an output shaft, multiple planetary gears, a planet carrier, and an internal gear. The motor rotates a transmission body that transmits torque to another member. A tool bit is attached to the output shaft, and the rotation of the sun gear is transmitted to the output shaft. The multiple planetary gears are arranged around the sun gear and mesh with the sun gear. The planet carrier rotatably supports the multiple planetary gears and rotates around the sun gear. The internal gear is arranged to surround the multiple planetary gears, meshes with the multiple planetary gears, and is held in a rotatable state. The internal gear is fixed to the transmission body and rotates in response to the rotation of the transmission body. The internal gear has a first engagement portion. The planet carrier has a second engagement portion. The first engagement portion of the internal gear and the second engagement portion of the planet carrier are relatively movable along the rotation direction of the transmission body and come into contact in response to the rotation of the internal gear.

[0007] FIG. 1 is a side view of a tool according to a first embodiment. FIG. 2 is a side cross-sectional view of a main portion of the tool. FIG. 3 is a cross-sectional view corresponding to line III-III in FIG. 2. FIG. 4 is a cross-sectional view corresponding to line IV-IV in FIG. 2. FIG. 5 is a cross-sectional view corresponding to line IV-IV in FIG. 2, showing a later time point than FIG. 4. FIG. 6 is a cross-sectional view corresponding to line IV-IV in FIG. 2, showing a later time point than FIG. 5. FIG. 7 is an exploded perspective view of the tool according to the first embodiment. FIG. 8 is an exploded perspective view of the tool according to the first embodiment. FIG. 9 is a block diagram showing the configuration of the tool according to the first embodiment. FIG. 10 is a timing chart showing the operation of the tool according to the first embodiment. FIG. 11 is a side cross-sectional view of a main portion of a tool according to a second embodiment. FIG. 12 is a cross-sectional view corresponding to line XII-XII in FIG. 11. FIG. 13 is a cross-sectional view corresponding to line XIII-XIII in FIG. 11. FIG. 14 is an exploded perspective view of the tool according to the first embodiment. FIG. 15 is a side cross-sectional view of a main portion of a tool according to a third embodiment. FIG. 16 is an exploded perspective view of the tool according to the first embodiment. FIG. 17 is a perspective view of the main part of the tool.

[0008] Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. Elements common to the embodiments described below are designated by the same reference numerals, and redundant descriptions of the common elements may be omitted. Each of the following embodiments is merely one of various embodiments of the present disclosure. Various modifications of each embodiment may be made depending on the design, etc., as long as the object of the present disclosure can be achieved. Furthermore, each embodiment (including each modified example) may be realized in appropriate combination.

[0009] The drawings described in this disclosure are schematic diagrams, and the ratios of the sizes and thicknesses of the components in the drawings do not necessarily reflect the actual dimensional ratios. The arrows indicating the directions in the drawings are merely examples and are not intended to define the directions in which the tool should be used. Furthermore, the arrows indicating the directions in the drawings are merely for explanatory purposes and do not have any substance.

[0010] In addition, "orthogonal (perpendicular)" as used herein does not only refer to a state in which the angle between two elements is strictly 90 degrees, but also includes a state in which two elements intersect within a certain range of difference. In other words, the angle between two elements that are perpendicular to each other falls within a certain range of difference from 90 degrees (for example, 10 degrees or less). In other words, "orthogonal" as used herein includes cases in which the angle between two elements is 80 degrees or more and 100 degrees or less.

[0011] First Embodiment (1) Overview First, an overview of the configuration of a tool 1 according to a first embodiment will be described with reference to FIGS. 1 to 4. FIG.

[0012] The tool 1 is, for example, a portable power tool and includes a motor 2, a planetary gear mechanism 4, and an output shaft 5.

[0013] The motor 2 rotates a transmission body (motor shaft 21) that transmits torque to other members.

[0014] The planetary gear mechanism 4 has a sun gear 41 , a plurality of planetary gears 42 (five in the example of FIG. 3 ), an internal gear 43 , and a planetary carrier 44 .

[0015] A tool bit is attached to the output shaft 5. The tool bit may be, for example, a driver bit, a socket bit, or a drill bit. A driver bit and a socket bit are bits used to tighten or loosen fastening members such as bolts. A drill bit is a bit used to drill holes in materials such as wood or metal. A tool bit appropriate for the intended use is attached to the output shaft 5 from among various tool bits. The rotation of the sun gear 41 is transmitted to the output shaft 5. As a result, the tool bit rotates integrally with the output shaft 5.

[0016] A tool tip may be attached to the output shaft 5 via an adapter.

[0017] A plurality of planetary gears 42 are arranged around the sun gear 41 and mesh with the sun gear 41 .

[0018] The planetary carrier 44 rotatably supports the plurality of planetary gears 42. The planetary carrier 44 rotates around the sun gear 41.

[0019] The internal gear 43 is disposed so as to surround the plurality of planetary gears 42 and meshes with the plurality of planetary gears 42. The internal gear 43 is held in a rotatable state.

[0020] The internal gear 43 is fixed to the transmission body (motor shaft 21) and rotates in response to the rotation of the transmission body.

[0021] The internal gear 43 has a first engagement portion 432. The planetary carrier 44 has a second engagement portion 442. The first engagement portion 432 of the internal gear 43 and the second engagement portion 442 of the planetary carrier 44 are relatively movable along the rotational direction of the transmission body (motor shaft 21), and come into contact with each other in response to the rotation of the internal gear 43.

[0022] Next, an overview of the operation of the tool 1 of the first embodiment will be described with reference to Figures 3 to 6. The overview of the operation of the tool 1 will be described on the assumption that a tool bit is attached to the output shaft 5 and is set on a work object such as a screw or a bolt, that is, the tool bit is in contact with the work object. The overview of the operation of the tool 1 will also be described on the assumption that the transmission body (motor shaft 21) is rotating in the first direction DR1 in Figure 3.

[0023] As shown in FIG. 3, the rotation of the motor 2 is transmitted to the internal gear 43 via the transmission body, causing the internal gear 43 to rotate in the first direction DR1.

[0024] Because the tool bit attached to the output shaft 5 is in contact with the work object, a force that suppresses rotation is applied to the output shaft 5. This suppresses rotation of the sun gear 41 that transmits rotation to the output shaft 5. In other words, when the motor 2 initially starts to rotate, the sun gear 41 in the planetary gear mechanism 4 is stopped, and the planet gears 42, the internal gear 43, and the planet carrier 44 are rotatable.

[0025] When the internal gear 43 rotates in the first direction DR1, the planetary gears 42 supported by the planetary carrier 44 rotate in the first direction DR1 while revolving in the first direction DR1, as shown in Figure 3. The planetary carrier 44 rotates in the first direction DR1. More specifically, the rotation of the internal gear 43 is decelerated to rotate the planetary carrier 44.

[0026] The rotational speed of the internal gear 43 is calculated by multiplying the rotational speed of the planetary carrier 44 by the gear ratio calculated by the following [Equation 1]. [Equation 1] (Z ａ +Z ｃ ) / Z ｃ Here, Z ａ is the number of teeth of the sun gear 41, and Z ｃ is the number of teeth of the internal gear 43. The number of teeth of the internal gear 43 is greater than the number of teeth of the sun gear 41.

[0027] Because the internal gear 43 rotates faster than the planetary carrier 44, after a period of time has passed while the motor shaft 21 is rotating, the first engagement portion 432 of the internal gear 43 comes into contact with the second engagement portion 442 of the planetary carrier 44, as shown in Figure 6. Then, the planetary carrier 44 is pushed by the first engagement portion 432 of the internal gear 43 at the second engagement portion 442, and rotates in the first direction DR1 at the same speed as the internal gear 43. Furthermore, when the force rotating the sun gear 41 exceeds the force suppressing the rotation of the output shaft 5, the sun gear 41 rotates in the first direction DR1 so as to cancel out the speed difference between the internal gear 43 and the planetary carrier 44.

[0028] In this way, when the tip tool is in contact with the work object and the first engagement portion 432 of the internal gear 43 is in contact with the second engagement portion 442 of the planetary carrier 44, the sun gear 41, the internal gear 43 and the planetary carrier 44 rotate in the same direction as the rotation direction (first direction DR1) of the transmission body (motor shaft 21).

[0029] As the sun gear 41 rotates, the rotation is transmitted from the sun gear 41 to the output shaft 5, and the tool bit rotates together with the output shaft 5. This allows the operator to perform work on the work object using the tool bit. The work is, for example, tightening a screw or other fastener on the work object.

[0030] The sun gear 41 and the output shaft 5 rotate due to the rotational energy (inertia torque) of the rotating body immediately before the first engagement portion 432 contacts the second engagement portion 442. The rotating body includes the internal gear 43, the planetary carrier 44, and the inertial body 3 (see FIG. 2 ), which will be described later. Compared to simply transmitting the rotational energy of the motor 2 to the output shaft 5, the rotational speed of the output shaft 5 instantaneously increases when the first engagement portion 432 contacts the second engagement portion 442 (see timings T7 and T9 in FIG. 10 ). In other words, a large rotational torque is generated. Therefore, a large rotational torque can be applied to the workpiece, similar to when the impact mechanism of a conventional impact rotary tool applies a striking impact to the output shaft. Therefore, fastening work, etc., on the workpiece can be performed with a large rotational torque. As such, the tool 1 of this embodiment can rotate the output shaft 5 due to the inertia torque of the rotating body.

[0031] The relative speed (speed difference) between the first engagement portion 432 of the internal gear 43 and the second engagement portion 442 of the planetary carrier 44 is slower than the rotational speed of the transmission body (motor shaft 21). Therefore, the noise generated when the first engagement portion 432 of the internal gear 43 and the second engagement portion 442 of the planetary carrier 44 come into contact with each other is much smaller than the noise generated when the impact mechanism of the rotary impact tool applies a striking impact to the output shaft. Therefore, noise can be suppressed compared to when a large torque is applied to the output shaft by the impact mechanism.

[0032] Furthermore, the impact generated when the first engagement portion 432 of the internal gear 43 and the second engagement portion 442 of the planetary carrier 44 come into contact with each other is much smaller than the impact generated when the impact mechanism of the rotary impact tool applies a striking impact to the output shaft. In other words, the tool 1 of this embodiment has a longer life than the rotary impact tool because wear on the output shaft 5 (or anvil) is suppressed.

[0033] Furthermore, in conventional rotary impact tools, the internal gear of the planetary gear mechanism is generally fixed to the housing so as not to rotate. Therefore, in conventional rotary impact tools, when performing a tightening operation or the like, a reaction force is transmitted from the internal gear to the housing, and the reaction force is transmitted to the operator. On the other hand, in the tool 1 of this embodiment, the internal gear 43 of the planetary gear mechanism 4 is held in a rotatable state relative to the housing 10 (see FIG. 2 ), so when performing a tightening operation or the like, the reaction force is less likely to be transmitted from the internal gear 43 to the housing 10. In other words, the tool 1 of this embodiment can reduce the reaction force transmitted to the operator when performing the operation.

[0034] Furthermore, in conventional rotary impact tools, after the hammer part of the impact mechanism collides with the anvil, the hammer part moves in a vibrating manner along the axial direction of the motor shaft due to its elastic force in order to release the engagement (contact) with the anvil, causing the entire rotary impact tool to vibrate along the axial direction of the motor shaft. However, in the tool 1 of this embodiment, the internal gear 43 does not move along the axial direction of the motor shaft 21 (axial movement is restricted), so vibration of the entire tool 1 along the axial direction of the motor shaft 21 is suppressed.

[0035] As described above, according to the tool 1 of this embodiment, noise during operation can be suppressed.

[0036] (2) Details The detailed configuration of the tool 1 according to the first embodiment will be described below with reference to FIGS. 1 to 10. In the following description, the direction from the motor shaft 21 of the motor 2 toward the output shaft 5 will be referred to as the forward direction, and the direction from the output shaft 5 toward the motor shaft 21 will be referred to as the rearward direction. In the following description, the forward direction and the rearward direction will sometimes be collectively referred to as the "front-rear direction." In the first embodiment, the rotation axis Ax1 (see FIG. 2) of the output shaft 5 is aligned along the front-rear direction. In the following description, the direction from the grip portion 102 of the housing 10 toward the body portion 101 of the housing 10 will be referred to as the upward direction, and the direction from the body portion 101 toward the grip portion 102 will be referred to as the downward direction. In the following description, the upward direction and the downward direction will sometimes be collectively referred to as the "vertical direction."

[0037] 1 and 2 , the tool 1 includes a housing 10, a motor 2, an inertial body 3, a planetary gear mechanism 4, an output shaft 5, a battery pack 11, and a trigger switch 12. Note that the tool 1 does not necessarily include the battery pack 11. Furthermore, as shown in FIG. 9 , the tool 1 further includes a storage unit 6, a control unit 7, and a torque sensor 14.

[0038] As shown in FIG. 1 , the housing 10 has a body portion 101 , a grip portion 102 , and a mounting portion 103 .

[0039] The body portion 101 accommodates the motor 2 , the inertial body 3 , and the planetary gear mechanism 4 .

[0040] The grip portion 102 protrudes downward from the body portion 101. The grip portion 102 of this embodiment is formed, for example, in a cylindrical shape with open top and bottom sides.

[0041] The attachment portion 103 is provided at the tip (lower end) of the grip portion 102. In other words, the body portion 101 and the attachment portion 103 are connected by the grip portion 102. The attachment portion 103 is configured so that the battery pack 11 can be removably attached thereto.

[0042] The battery pack 11 is a power source that supplies current to drive the motor 2. The battery pack 11 includes a battery pack configured by connecting multiple secondary batteries (e.g., lithium ion batteries or all-solid-state batteries) in series, and a case that houses the battery pack.

[0043] The trigger switch 12 protrudes from the grip portion 102. The trigger switch 12 is an operating portion that receives operations for controlling the rotation of the motor 2. The motor 2 can be switched on and off by pulling the trigger switch 12. The rotation speed of the motor 2 can also be adjusted by the amount of pulling of the trigger switch 12. The greater the amount of pulling, the faster the rotation speed of the motor 2.

[0044] The torque sensor 14 shown in Fig. 9 is, for example, a magnetostrictive torque sensor capable of detecting torsional distortion. The torque sensor 14 is disposed in a position where it can detect torsional distortion of the output shaft 5. The torque sensor 14 detects a change in magnetic permeability corresponding to distortion of the shaft caused by torque being applied to the output shaft 5 using a coil disposed in a non-rotating portion, and outputs a voltage signal proportional to the distortion to the torque detection unit 71. Note that the torque sensor 14 may also be a strain gauge torque sensor.

[0045] The storage unit 6 includes, for example, a read-only memory (ROM), a random access memory (RAM), or an electrically erasable programmable read-only memory (EEPROM). The storage unit 6 stores a control program executed by the control unit 7. The storage unit 6 also stores a tightening torque setting value (set torque), etc. Note that the term "tightening torque" used in this disclosure refers to a torque used to tighten a work object, and is a concept that includes the torque applied to the tool bit, the output shaft 5, or the motor shaft 21 when the tool 1 is operating.

[0046] The control unit 7 includes a computer system having one or more processors and a memory. At least some of the functions of the control unit 7 are realized by the processor of the computer system executing a program recorded in the memory of the computer system. The program may be recorded in the memory, or may be provided via a telecommunications line such as the Internet, or may be provided by being recorded on a non-transitory recording medium such as a memory card.

[0047] 9, the control unit 7 has a torque detection unit 71 and a drive control unit 72. Note that the torque detection unit 71 and the drive control unit 72 do not necessarily represent actual configurations, but represent functions realized by the control unit 7.

[0048] The torque detection unit 71 detects the tightening torque of the output shaft 5 based on the voltage signal output from the torque sensor 14 .

[0049] The drive control unit 72 controls the motor 2. The drive control unit 72 controls the motor 2, for example, by vector control. In vector control, the drive control unit 72 decomposes the motor current, which is the current supplied to the motor 2, into a torque current (q-axis current) that generates torque and an excitation current (d-axis current) that generates magnetic flux, and controls each current component independently. Note that the method by which the drive control unit 72 controls the motor 2 is not limited to vector control, and a control method other than vector control may also be used.

[0050] The drive control unit 72 controls the motor 2 so that the tightening torque measured by the torque detection unit 71 reaches a set torque that is pre-stored in the storage unit 6. When the tightening torque measured by the torque detection unit 71 reaches or exceeds the set torque, the drive control unit 72 controls the motor 2 to stop the rotation of the motor shaft 21.

[0051] When the operator pulls the trigger switch 12, the drive control unit 72 controls the motor 2 to rotate the motor shaft 21, for example, in a first direction DR1 (see FIG. 3 ). After the tightening torque increases and the internal gear 43 and the output shaft 5 stop rotating together, the drive control unit 72 controls the motor 2 to rotate the motor shaft 21 in a second direction opposite to the first direction DR1 for a predetermined time or a predetermined angle. After rotating the motor shaft 21 in the second direction for a predetermined time or a predetermined angle, the drive control unit 72 controls the motor 2 to rotate the motor shaft 21 again in the first direction DR1. The drive control unit 72 repeats this series of controls until the tightening torque measured by the torque detection unit 71 reaches or exceeds the set torque. Note that in the example of FIG. 3 , the first direction DR1 is clockwise as viewed from the rear, and the second direction is counterclockwise as viewed from the rear. However, the first direction DR1 may be counterclockwise as viewed from the rear, and the second direction may be clockwise as viewed from the rear.

[0052] The motor 2 is, for example, a brushless motor. As shown in Fig. 2, the motor 2 has a motor shaft 21. The motor 2 converts the power supplied from the battery pack 11 into a rotational driving force (torque) of the motor shaft 21. The motor shaft 21 functions as a transmission body that transmits the torque to other members. The front end of the motor shaft 21 is fixed to an internal gear 43.

[0053] The motor shaft 21 is rotatably supported by the housing 10. More specifically, the motor shaft 21 is supported by the housing 10 via a bearing 15. The bearing 15 is, for example, a ball bearing.

[0054] The inertial body 3 is disposed between the motor 2 and the planetary gear mechanism 4. More specifically, the inertial body 3 is disposed in front of the motor 2 and behind the planetary gear mechanism 4. The inertial body 3 is disposed between the motor 2 and the plurality of planetary gears 42. The inertial body 3 is also disposed between the motor 2 and the internal gear 43. The inertial body 3 is mechanically connected to the motor shaft 21, and rotates integrally with the motor shaft 21. The inertial body 3 is a so-called flywheel, and increases the inertial torque of the motor 2 (motor shaft 21).

[0055] The inertial body 3 has a disk-like shape, and the thickness direction of the inertial body 3 is along the front-rear direction.

[0056] The tool 1 further includes a fan 8 (see FIG. 2 ). The fan 8 is disposed between the motor 2 and the planetary gear mechanism 4. More specifically, the fan 8 is disposed in front of the motor 2 and behind the inertial body 3. The fan 8 is mechanically connected to the motor shaft 21, and rotates integrally with the motor shaft 21. Like the inertial body 3, the fan 8 increases the inertial torque of the motor 2 (motor shaft 21).

[0057] As shown in Figures 3, 7, and 8, the planetary gear mechanism 4 includes a shaft holding member 40, a sun gear 41, a plurality of planetary gears 42 (five in the example of Figure 3), an internal gear 43, and a planetary carrier 44.

[0058] The sun gear 41 is an external gear and has a main body 410 and a protrusion 412.

[0059] The main body 410 is formed in a cylindrical shape with its axial direction aligned with the front-rear direction, and a plurality of teeth are provided on the outer circumferential surface of the main body 410. Note that the main body 410 may be formed in an annular shape with its axial direction (thickness direction) aligned with the front-rear direction.

[0060] The protrusion 412 protrudes forward from the front end (front surface) of the main body 410. The shape of the protrusion 412 is a triangular prism. When viewed from the front-to-rear direction, the protrusion 412 is formed in a triangular shape with rounded apexes. The outer shape of the protrusion 412 and the edge of the recess 50 (see FIG. 8 ) of the output shaft 5 generally match in shape and size. The protrusion 412 is fitted into the recess 50 of the output shaft 5. By fitting the protrusion 412 into the recess 50 of the output shaft 5, the output shaft 5 and the sun gear 41 rotate integrally.

[0061] The multiple planetary gears 42 are arranged around the sun gear 41. The multiple planetary gears 42 are arranged at equal intervals on a circle centered on the central axis of the sun gear 41. The planetary gears 42 are external gears. Each of the multiple planetary gears 42 meshes with the sun gear 41 and the internal gear 43. The planetary gears 42 have through holes 422 (see FIG. 3 ) that penetrate the planetary gears 42 along the front-rear direction. When viewed from the front-rear direction, the through hole 422 is formed at the center of the planetary gear 42 and is a circular hole. A cylindrical or columnar shaft 421 whose axial direction is along the front-rear direction is passed through the through hole 422. The planetary gears 42 can rotate around the shaft 421. In other words, the planetary gears 42 can rotate around the shaft 421. The shaft 421 of the planetary gear 42 may be passed through the through hole 422 via a bearing.

[0062] The shaft 421 of the planetary gear 42 is supported by the shaft holding member 40 and the planet carrier 44. More specifically, a first end (front end) of the shaft 421 of the planetary gear 42 is inserted into a through-hole 401 formed in the shaft holding member 40. Furthermore, a second end (rear end) of the shaft 421 of the planetary gear 42 is inserted into a through-hole 4411 of the planet carrier 44.

[0063] The shaft holding member 40 is a member that supports the shafts 421 of the multiple planetary gears 42. The shaft holding member 40 is formed in an annular shape. The shaft holding member 40 is arranged so that the central axis of the shaft holding member 40 and the central axis of the sun gear 41 are concentric when viewed from the front-rear direction.

[0064] A plurality of through holes 401 (five in the example of FIG. 8 ) are formed in the shaft holding member 40. The plurality of through holes 401 are arranged at equal intervals on a circumference centered on the central axis of the sun gear 41. The plurality of through holes 401 penetrate the shaft holding member 40 in the front-to-rear direction. The front end of the shaft 421 of the planetary gear 42 is inserted into each of the plurality of through holes 401.

[0065] The shaft holding member 40 is rotatably supported by the internal gear 43. More specifically, the shaft holding member 40 is supported by the internal gear 43 via a bearing 17. The bearing 17 is, for example, a ball bearing.

[0066] The planetary carrier 44 is a member that supports the shafts 421 of the multiple planetary gears 42. The planetary carrier 44 has a carrier portion 441 and multiple (two in FIG. 8 ) second engagement portions 442.

[0067] The carrier portion 441 is formed in a disk shape with its thickness direction aligned with the front-rear direction. The planetary carrier 44 is arranged so that the central axis of the planetary carrier 44 and the central axis of the sun gear 41 are concentric when viewed from the front-rear direction.

[0068] A through-hole 4410 is formed in the center of the carrier portion 441 .

[0069] A plurality of through holes 4411 (five in the example of FIG. 8 ) are formed in the carrier portion 441. The plurality of through holes 4411 are arranged at equal intervals on a circumference centered on the central axis of the sun gear 41. The plurality of through holes 4411 penetrate the carrier portion 441 in the front-to-rear direction. The rear ends of the shafts 421 of the planetary gears 42 are inserted into each of the plurality of through holes 4411. In this way, the carrier portion 441 is connected to the shafts 421 of the plurality of planetary gears 42.

[0070] The two second engagement portions 442 protrude from the carrier portion 441 in a direction perpendicular to the rotation axis Ax1 of the output shaft 5. More specifically, the two second engagement portions 442 protrude outward from the outer edge of the disc-shaped carrier portion 441 in the radial direction of the carrier portion 441. The two second engagement portions 442 protrude in directions away from each other. The second engagement portions 442 protrude from part of the side surface of the carrier portion 441 and are formed in a rectangular parallelepiped shape.

[0071] The internal gear 43 is disposed around the plurality of planetary gears 42. The internal gear 43 meshes with the plurality of planetary gears 42. The internal gear 43 is rotatably supported by the housing 10. More specifically, the internal gear 43 of the first embodiment is supported by the housing 10 via a plurality of bearings 13 (two in FIG. 2 ) arranged side by side in the front-rear direction. The bearings 13 are, for example, ball bearings. The internal gear 43 may be supported by the housing 10 via one or three or more bearings 13.

[0072] The internal gear 43 has a main body portion 431 , a plurality of (two in the example of FIG. 8 ) first engagement portions 432 , and a plurality of (two in the example of FIG. 8 ) connecting portions 433 .

[0073] The main body 431 is formed in a cylindrical shape with its axial direction aligned with the front-rear direction, and a plurality of teeth are provided on the inner circumferential surface of the main body 431. The number of teeth of the main body 431 is greater than the number of teeth of the sun gear 41. The main body 431 is arranged so that the central axis of the main body 431 and the central axis of the sun gear 41 are concentric when viewed from the front-rear direction. The main body 431 may be formed in an annular shape with its axial direction (thickness direction) aligned with the front-rear direction.

[0074] The multiple first engagement portions 432 protrude rearward from the rear end (rear surface) of the main body portion 431. That is, the multiple first engagement portions 432 protrude from the main body portion 431 along the rotation axis Ax1 of the output shaft 5. The first engagement portions 432 protrude from part of the annular rear end of the main body portion 431 and are formed in a rectangular parallelepiped shape that is curved according to the curvature of the rear end of the main body portion 431. The two first engagement portions 432 in the first embodiment are arranged to face each other in a direction perpendicular to the front-rear direction. More specifically, the two first engagement portions 432 face each other so as to sandwich the rotation axis Ax1 of the output shaft 5 therebetween.

[0075] In the first embodiment, the first engaging portion 432 and the second engaging portion 442 protrude in directions perpendicular to each other, which allows the tool 1 to be made more compact in the front-rear direction than when both the first engaging portion 432 and the second engaging portion 442 protrude in the front-rear direction.

[0076] The two connecting portions 433 correspond one-to-one to the two first engaging portions 432. Each connecting portion 433 protrudes from the corresponding first engaging portion 432. More specifically, when viewed from the rear, each connecting portion 433 protrudes from the corresponding first engaging portion 432 toward the center of the main body portion 431. The two connecting portions 433 face each other with a gap between them. The tip of each of the two connecting portions 433 is formed in an arc shape that follows the shape of the motor shaft 21. The motor shaft 21 is fixed between the two connecting portions 433 by press-fitting. This allows the rotation of the motor shaft 21 to be transmitted to the internal gear 43.

[0077] The output shaft 5 is disposed in front of the planetary gear mechanism 4. The output shaft 5 rotates about a rotation axis Ax1 in accordance with the rotation of the sun gear 41. The rotation axis Ax1 of the output shaft 5 is also the rotation axis of the motor shaft 21, the sun gear 41, the internal gear 43, and the planetary carrier 44.

[0078] The output shaft 5 has a recess 50. The recess 50 is formed at the rear end of the output shaft 5. The edge of the recess 50 has a triangular shape with a rounded apex. The protrusion 412 of the sun gear 41 is fitted into the recess 50.

[0079] A tool tip is attached to the front end of the output shaft 5 .

[0080] The output shaft 5 is rotatably supported by the housing 10. More specifically, the output shaft 5 is supported by the housing 10 via a plurality of bearings 16 (two in FIG. 2 ) arranged side by side in the front-to-rear direction. The bearings 16 are, for example, ball bearings. The output shaft 5 may be supported by the housing 10 via one bearing 16 or three or more bearings 16.

[0081] (3) Operation of the Tool Next, the operation of the tool 1 will be described with reference to Figures 3 to 6 and 10. Since the planetary carrier 44 is connected to the shaft holding member 40 (see Figure 3) via the shaft 421 of the planetary gear 42, the planetary carrier 44 rotates integrally with the shaft holding member 40.

[0082] For example, at timing T0 in Fig. 10 , the operator pulls the trigger switch 12, for example, to its maximum, with the tip of the tool bit in contact with a workpiece such as a screw. Here, it is assumed that at timing T0, the second engagement portion 442 of the planetary carrier 44 is spaced apart from the first engagement portion 432 of the internal gear 43 by a certain distance or more in the rotational direction (first direction DR1) of the internal gear 43, as shown in Fig. 4 or 5 . In other words, it is assumed that the internal gear 43 is rotatable relative to the planetary carrier 44 in the first direction DR1 until the first engagement portion 432 and the second engagement portion 442 come into contact with each other.

[0083] When the trigger switch 12 is pulled, the drive control unit 72 rotates the motor shaft 21 in the first direction DR1 (forward direction). In the following description, it is assumed that the operator keeps the trigger switch 12 pulled to its fullest extent until the tightening operation of the work object is completed (until timing T10 in FIG. 10 ). Note that the trigger switch 12 may perform a so-called alternate operation in which it remains pulled to its fullest extent even when it is not operated by the operator.

[0084] When the motor shaft 21 rotates, the internal gear 43 fixed to the motor shaft 21 also rotates integrally with the motor shaft 21. That is, as shown in Figures 3 and 4, the internal gear 43 rotates in the first direction DR1 at the same rotational speed (or number of rotations [rpm]) as the motor shaft 21.

[0085] Furthermore, as the internal gear 43 rotates, the planetary gears 42 meshing with the internal gear 43 revolve in the first direction DR1 while rotating in the first direction DR1. In other words, the planetary carrier 44 rotates in the first direction DR1.

[0086] Here, the sun gear 41 is connected to the output shaft 5. Because the tool bit attached to the output shaft 5 is in contact with the work object, a force that inhibits rotation is applied to the output shaft 5. In other words, rotation of the sun gear 41 is inhibited. More specifically, the sun gear 41 receives forces from the multiple planetary gears 42 that tend to rotate the sun gear 41 in the second direction, but the sun gear 41 does not rotate before the first engagement portion 432 engages with the second engagement portion 442. Therefore, with the sun gear 41 fixed, the internal gear 43 and the planet carrier 44 rotate in the first direction DR1. The rotational speed of the internal gear 43 is faster than the rotational speed of the planet carrier 44.

[0087] Fig. 4 shows the state immediately before motor shaft 21 starts to rotate, Fig. 5 shows the state some time after motor shaft 21 starts to rotate in first direction DR1, and Fig. 6 shows the state after motor shaft 21 continues to rotate in first direction DR1 from the state shown in Fig. 5.

[0088] As shown in FIGS. 5 and 6 , as the internal gear 43 rotates in the first direction DR1 relative to the planetary carrier 44, the first engagement portion 432 of the internal gear 43 approaches the second engagement portion 442 located further ahead in the rotational direction. Then, for example, at timing T1 in FIG. 10 , the side of the first engagement portion 432 of the internal gear 43 comes into contact with the side of the second engagement portion 442 of the planetary carrier 44, as shown in FIG. 6 . In other words, the first engagement portion 432 of the internal gear 43 engages with the second engagement portion 442 of the planetary carrier 44. Note that during the period between timings T0 and T1, the rotational speed of the motor shaft 21 exceeds a certain value, and therefore the inertia torque of the motor shaft 21 increases above a certain value. In the following description, the period during which the rotational speed of the motor shaft 21 increases in the first direction DR1 is referred to as the charge period. The charge period is the period during which the inertia torque of the motor shaft 21 increases.

[0089] When the side surfaces of the first engagement portions 432 engage with the side surfaces of the second engagement portions 442, the planetary carrier 44 accelerates in the first direction DR1 due to the force applied from the first engagement portions 432 to the second engagement portions 442. This increases the force rotating the sun gear 41 in the first direction DR1. Therefore, the sun gear 41 and the output shaft 5 connected to the sun gear 41 rotate in the first direction DR1. The rotation of the output shaft 5 tightens the work object.

[0090] More specifically, when the planetary carrier 44 is accelerated in the first direction DR1 by the force applied from the first engagement portions 432 to the second engagement portions 442, a force acting on each of the planetary gears 42 to rotate in the second direction (opposite the first direction DR1) acts as a reaction force from the sun gear 41. Meanwhile, a force acting on each of the planetary gears 42 to rotate in the first direction DR1 is also acting on each of the planetary gears 42 due to the rotation of the internal gear 43 in the first direction DR1. Because both the force acting on the rotation in the first direction DR1 and the force acting on the rotation in the second direction are generated by the rotation of the internal gear 43 in the first direction DR1, the force acting on the rotation in the first direction DR1 and the force acting on the rotation in the second direction are counterbalanced. Therefore, each of the planetary gears 42 stops rotating (rotating) around the axis 421. As a result, the sun gear 41 rotates in the same direction and at the same speed as the internal gear 43.

[0091] Therefore, when the first engagement portion 432 and the second engagement portion 442 are engaged with each other, the planet carrier 44, the internal gear 43, the plurality of planet gears 42, and the sun gear 41 stop rotating relative to each other. In other words, when the first engagement portion 432 and the second engagement portion 442 are engaged with each other, the planet carrier 44, the internal gear 43, the plurality of planet gears 42, the sun gear 41, and the output shaft 5 are fixed to each other. When the planet carrier 44, the internal gear 43, the plurality of planet gears 42, the sun gear 41, and the output shaft 5 are fixed to each other, the planet carrier 44, the internal gear 43, the plurality of planet gears 42, the sun gear 41, and the output shaft 5 rotate integrally in the first direction DR1 around the rotation axis Ax1. Therefore, at timing T1 when the first engaging portion 432 and the second engaging portion 442 engage with each other, the rotation speed of the output shaft 5 becomes the same as the rotation speed of the motor shaft 21 .

[0092] In other words, when the tool bit is in contact with the work object and the first engagement portion 432 of the internal gear 43 is not in contact with the second engagement portion 442 of the planetary carrier 44, the internal gear 43 rotates in the same direction as the transmission body (motor shaft 21). When the tool bit is in contact with the work object and the first engagement portion 432 of the internal gear 43 is in contact with the second engagement portion 442 of the planetary carrier 44, the internal gear 43 and the output shaft 5 rotate integrally with the transmission body.

[0093] At timing T2 in Figure 10, the workpiece is seated. Here, "seated" means that if the workpiece is a screw or bolt, the head seating surface of the workpiece comes into contact with the mating member. Also, if the workpiece is a nut, it means that the workpiece comes into contact with the head seating surface of the mating member. When the workpiece is seated, the tool bit rotates against the frictional force generated between the workpiece and the mating member, causing a sudden increase in tightening torque.

[0094] The drive control unit 72 of this embodiment stops the power supply to the motor 2 in accordance with the magnitude or increase of the fastening torque detected by the torque detection unit 71 .

[0095] The drive control unit 72 stops the power supply to the motor 2 at the timing (e.g., timing T2) when the torque detection unit 71 detects that the work object has seated on the mating member. The torque detection unit 71 is configured to detect that the work object has seated when, for example, the increase in the tightening torque per unit time exceeds a specified value.

[0096] Furthermore, the drive control unit 72 stops the power supply to the motor 2 at the timing (for example, timing T7, T9) when the magnitude of the tightening torque detected by the torque detection unit 71 becomes equal to or greater than a specified value.

[0097] After the power supply to the motor 2 is stopped, the output shaft 5 and the tool bit attached to the output shaft 5 continue to rotate due to the inertial torque accumulated in the inertial body 3, etc., and tighten the workpiece. This reduces the reaction force that the operator receives from the tool 1 after the operator sits on the workpiece. Specifically, when power is not supplied to the motor 2, no electromagnetic interaction occurs between the rotor and stator of the motor 2. Therefore, the reaction force transmitted from the output shaft 5 to the rotor is not transmitted to the stator, and the reaction force that the operator receives from the tool 1 can be reduced.

[0098] As the tightening torque increases, the inertia torque of the motor shaft 21 is consumed, and at timing T3, the rotation of the motor shaft 21 and the output shaft 5 stops. At timing T4 after timing T3 when the rotation of the motor shaft 21 and the output shaft 5 stops, the drive control unit 72 of the first embodiment controls the motor 2 to rotate the motor shaft 21 in the second direction (reverse direction) for a predetermined time or a predetermined angle.

[0099] When the motor shaft 21 rotates, the internal gear 43 also rotates integrally with the motor shaft 21. That is, the internal gear 43 rotates in the second direction at the same rotational speed (or number of rotations [rpm]) as the motor shaft 21.

[0100] Since the tool bit attached to the output shaft 5 is in contact with the work object, a force that suppresses rotation is applied to the output shaft 5. In other words, rotation of the sun gear 41 connected to the output shaft 5 is suppressed.

[0101] Therefore, when the motor shaft 21 rotates in the second direction, the planetary carrier 44, the planetary gears 42, and the internal gear 43 each rotate in the opposite direction (second direction) to when the motor shaft 21 rotates in the first direction DR1 (as shown in FIG. 3 ). Because the rotational speed of the internal gear 43 is faster than the rotational speed of the planetary carrier 44, the first engagement portion 432 of the internal gear 43 and the second engagement portion 442 of the planetary carrier 44, which were in contact with each other, gradually move apart. The predetermined time during which the motor shaft 21 rotates in the second direction is the time during which the first engagement portion 432 moving away from the second engagement portion 442 does not come into contact with the other second engagement portions 442 within the predetermined time. The predetermined angle (predetermined number of rotations) is the angle (amount of rotation) during which the first engagement portion 432 moving away from the second engagement portion 442 does not come into contact with the other second engagement portions 442 until the motor shaft 21 rotates the predetermined angle (predetermined number of rotations).

[0102] The drive control unit 72 controls the motor 2 to stop the rotation of the motor shaft 21 at timing T5 when a predetermined time has elapsed since timing T4 or when the motor shaft 21 has rotated a predetermined angle.

[0103] At timing T6 after controlling the motor 2 to stop the rotation of the motor shaft 21, the drive control unit 72 controls the motor 2 to rotate the motor shaft 21 again in the first direction DR1. When the motor shaft 21 rotates in the first direction DR1, the internal gear 43 rotates in the first direction DR1 faster than the planetary carrier 44, as in the period between timing T0 and timing T1.

[0104] In other words, by the drive control unit 72 controlling the motor 2 to rotate the motor shaft 21 in the second direction, a charge period can be secured to increase the inertia torque again, and the work object can be tightened again using the inertia torque.

[0105] From time T6 onwards, the drive control unit 72 repeats the control performed from time T0 to time T5 until the tightening torque becomes equal to or greater than the set torque. In the example of Figure 10, times T7 and T8 in the second control correspond to times T2 and T3 in the first control, and times T9 and T10 in the third control correspond to times T2 and T3 in the first control. Because the work object is already seated in the first control, there is no period in the second and subsequent controls that corresponds to the period from time T1 to time T2 in the first control.

[0106] In the example of Figure 10, the first period from timing T2 to timing T3 is longer than the second period from timing T7 to timing T8. The second period is longer than the third period from timing T9 to timing T10. The peak value of the tightening torque in the first period is smaller than the peak value of the tightening torque in the second period. The peak value of the tightening torque in the second period is also smaller than the peak value of the tightening torque in the third period. The integrated value of the tightening torque in the first period, the integrated value of the tightening torque in the second period, and the integrated value of the tightening torque in the third period are all equal.

[0107] As described above, in the tool 1 of the first embodiment, the motor 2 operates in three operating states: a first operating state, a second operating state, and a third operating state. The first operating state is an operating state in which the motor shaft 21 rotates in the first direction DR1 and the output shaft 5 does not rotate (is stopped), as shown in the period from timing T0 to timing T1 in Fig. 10 . The second operating state is an operating state in which the motor shaft 21, the internal gear 43, the planetary carrier 44, and the output shaft 5 rotate integrally in the first direction DR1, as shown in the period from timing T1 to timing T2 in Fig. 10 . The third operating state is an operating state in which the motor shaft 21 rotates in the second direction and the internal gear 43 rotates in the second direction relative to the planetary carrier 44, as shown in the period from timing T4 to timing T5 in Fig. 10 . During the tightening operation using the tool 1 of embodiment 1, the operating state of the tool 1 transitions from the first operating state to the second operating state, from the second operating state to the third operating state, and from the third operating state to the first operating state.

[0108] (4) Modifications Modifications of the first embodiment are listed below.

[0109] The inertial body 3 may have multiple fins. For example, the multiple fins may be provided on the rear surface of the inertial body 3. By providing multiple fins on the rear surface of the inertial body 3, the inertial body 3 also functions as a fan for cooling the motor 2. When the motor shaft 21 rotates, the inertial body 3 also rotates, and cooling air is generated from the multiple fins toward the motor 2 as the inertial body 3 rotates. In this case, the tool 1 does not need to include the fan 8 shown in FIG. 2 .

[0110] In the first embodiment, the drive control unit 72 stops the power supply to the motor 2 when the torque detection unit 71 detects that the work object has seated on the mating member or when the magnitude of the tightening torque detected by the torque detection unit 71 exceeds a specified value. However, the drive control unit 72 may stop the power supply to the motor 2 when a predetermined time has elapsed since the torque detection unit 71 detected that the work object has seated on the mating member or when the magnitude of the tightening torque detected by the torque detection unit 71 exceeds a specified value. For example, the drive control unit 72 may stop the power supply to the motor 2 after the torque detection unit 71 detects that the work object has seated on the mating member or after the magnitude of the tightening torque detected by the torque detection unit 71 exceeds a specified value, but before the rotational speed of the output shaft 5 reaches zero. Alternatively, the drive control unit 72 may stop the power supply to the motor 2 when the rotational speed of the motor shaft 21 or the output shaft 5 exceeds a specified value, regardless of the tightening torque detected by the torque detection unit 71. In other words, the drive control unit 72 may stop the supply of power to the motor 2 when the rotational speed of the motor shaft 21 or the output shaft 5 reaches or exceeds a specified value, even if this is before the torque detection unit 71 detects that the work object has seated on the opposing member.

[0111] The tool 1 does not necessarily need to include the torque sensor 14. If the tool 1 does not include the torque sensor 14, the torque detection unit 71 may detect that the work object has seated on the mating member or that the magnitude of the tightening torque has reached a specified value or greater based on the rotational speed (or number of rotations [rpm]) of the motor shaft 21. The torque detection unit 71 may also calculate the tightening torque based on the amount of rotation (rotation angle) of the motor shaft 21 from the time when the torque detection unit 71 detects that the work object has seated on the mating member or the time when the magnitude of the tightening torque detected by the torque detection unit 71 reaches a specified value or greater until the motor shaft 21 stops. The torque detection unit 71 may also calculate the tightening torque by calculating the inertia torque of the output shaft 5 of the motor shaft 21 based on the rotational speed of the motor shaft 21 and the mass of the inertial body 3, etc.

[0112] The tool 1 is not limited to being powered by the battery pack 11, but may be powered by an AC power source (commercial power source).The tool 1 is also not limited to being an electric tool, but may be a pneumatic tool having an air motor (drive unit) that operates with compressed air (power) supplied from an air compressor as a power source.

[0113] Second Embodiment As shown in FIG. 11, a tool 1A according to a second embodiment differs from the tool 1 according to the first embodiment in that a planetary gear mechanism 4A has a multi-stage (two-stage) configuration.

[0114] (1) Configuration The planetary gear mechanism 4A, like the planetary gear mechanism 4 of embodiment 1, has a sun gear 41, a plurality of planetary gears 42 (five in the example of FIG. 14 ), an internal gear 43, and a planet carrier 44. Hereinafter, the sun gear 41, the plurality of planetary gears 42, and the planet carrier 44 will be referred to as the first sun gear 41, the plurality of first planetary gears 42, and the first planet carrier 44, respectively.

[0115] As shown in Figures 11 to 14, the planetary gear mechanism 4A further includes a second sun gear 41S, a plurality of second planetary gears 42S (five in the example of Figure 14), a second planetary carrier 44S, and a shaft holding member 45.

[0116] In the planetary gear mechanism 4A of this embodiment, the second sun gear 41S, not the first sun gear 41 , is fixed to the output shaft 5 .

[0117] The second sun gear 41S has a main body 410S and a protrusion 412S. The main body 410S and the protrusion 412S have the same shapes as the main body 410 and the protrusion 412 of the first sun gear 41, respectively, and therefore a description of the shape of the second sun gear 41S will be omitted.

[0118] The second sun gear 41S is disposed so that the central axis of the second sun gear 41S and the central axis of the first sun gear 41 are concentric when viewed from the front-rear direction.

[0119] The second sun gear 41S is disposed between the first sun gear 41 and the output shaft 5 in the front-rear direction. The protrusion 412S of the second sun gear 41S is fitted into the recess 50 (see FIG. 8 ) of the output shaft 5. By fitting the protrusion 412S into the recess 50 of the output shaft 5, the output shaft 5 and the second sun gear 41S rotate integrally.

[0120] The second planetary gear 42S has the same shape as the first planetary gear 42, and therefore a description of the shape of the second planetary gear 42S will be omitted.

[0121] The plurality of second planetary gears 42S are arranged around the second sun gear 41S and mesh with the second sun gear 41S.

[0122] The second planetary carrier 44S is formed in a disk shape with its thickness aligned with the front-rear direction. The second planetary carrier 44S is arranged so that its central axis is concentric with the central axis of the first sun gear 41 when viewed from the front-rear direction. The second planetary carrier 44S is arranged between the multiple first planetary gears 42 and the multiple second planetary gears 42S.

[0123] An insertion hole 440S is formed in the center of the second planetary carrier 44S. The protrusion 412 at the front end of the first sun gear 41 is inserted into the insertion hole 440S. This allows the second planetary carrier 44S and the first sun gear 41 to fit together. In other words, the second planetary carrier 44S is fixed to the first sun gear 41 and rotates around the first sun gear 41 in response to the rotation of the first sun gear 41.

[0124] The second planetary carrier 44S has a plurality of through holes 441S (five in the example of FIG. 12 ). The through holes 441S are arranged at equal intervals on a circle centered on the central axis of the first sun gear 41. The through holes 441S penetrate the second planetary carrier 44S in the front-to-rear direction. The rear ends of the shafts 421S of the second planetary gears 42S are inserted into each of the through holes 441S. Therefore, as the second planetary carrier 44S rotates, the second planetary gears 42S rotate (revolve) around the central axis of the second planetary carrier 44S. The second planetary carrier 44S also supports the second planetary gears 42S rotatably via the shafts 421S.

[0125] The shaft holding member 45 is formed in a disk shape with its thickness direction aligned with the front-rear direction. The shaft holding member 45 has a plurality of through holes 451 (five in the example of FIG. 14 ). The through holes 451 are arranged at equal intervals on a circumference centered on the central axis of the second sun gear 41S. The through holes 451 penetrate the shaft holding member 45 along the front-rear direction. The front end of the shaft 421S of the second planetary gear 42S is inserted into each of the through holes 451.

[0126] The first planetary carrier 44, the plurality of first planetary gears 42, and the first sun gear 41 are disposed between the motor 2 and the plurality of second planetary gears 42S. The first planetary carrier 44 rotatably supports the plurality of first planetary gears 42. The plurality of first planetary gears 42 are disposed around the first sun gear 41 and mesh with the first sun gear 41.

[0127] Similar to the first embodiment, the first planetary carrier 44 has a plurality of (two) second engagement portions 442 .

[0128] The internal gear 43 is fixed to the motor shaft 21. The internal gear 43 is arranged to surround the plurality of first planetary gears 42 and the plurality of second planetary gears 42S. The internal gear 43 meshes with the plurality of first planetary gears 42 and the plurality of second planetary gears 42S.

[0129] The rotation axis Ax1 of the output shaft 5 is also the rotation axis of the motor shaft 21, the first sun gear 41, the second sun gear 41S, the internal gear 43, the first planetary carrier 44, and the second planetary carrier 44S.

[0130] (2) Operation of the Tool Next, the operation of the tool 1A will be described.

[0131] 10, for example, the operator pulls the trigger switch 12 to its maximum, for example, with the tip of the tool bit in contact with a workpiece such as a screw. Here, it is assumed that at the time of timing T0, the second engagement portion 442 of the first planetary carrier 44 is spaced apart from the first engagement portion 432 of the internal gear 43 by a certain distance or more in the rotational direction of the internal gear 43 (first direction DR1), as shown in FIG.

[0132] When the trigger switch 12 is pulled, the drive control unit 72 rotates the motor shaft 21 in the first direction DR1 (forward direction). In the following description, it is assumed that the operator keeps the trigger switch 12 pulled to its fullest extent until the tightening operation of the work object is completed (until timing T10 in FIG. 10 ). Note that the trigger switch 12 may perform a so-called alternate operation in which it remains pulled to its fullest extent even when it is not operated by the operator.

[0133] When the motor shaft 21 rotates, the internal gear 43 fixed to the motor shaft 21 also rotates integrally with the motor shaft 21. That is, as shown in Fig. 12, the internal gear 43 rotates in the first direction DR1 at the same rotational speed (or number of rotations [rpm]) as the motor shaft 21. This causes the multiple first planetary gears 42 to rotate in the first direction DR1 while revolving in the first direction DR1. The planetary carrier 44 rotates in the first direction DR1.

[0134] The first sun gear 41, which is in mesh with the plurality of first planetary gears 42, rotates in a first direction DR1.

[0135] The second planetary carrier 44S, which is fixed to the first sun gear 41, rotates integrally with the first sun gear 41 in the first direction DR1. That is, the second planetary gears 42S revolve in the first direction DR1 (see FIG. 13). At this time, the second planetary gears 42S rotate on their axes in the first direction DR1.

[0136] The shaft holding member 45, to which the front ends of the shafts 421S of the plurality of second planetary gears 42S are connected, rotates in the first direction DR1 together with the second planetary carrier 44S.

[0137] Here, the second sun gear 41S is connected to the output shaft 5. Because the tool bit attached to the output shaft 5 is in contact with the workpiece, a force that inhibits rotation is applied to the output shaft 5. In other words, rotation of the second sun gear 41S is inhibited. More specifically, the second sun gear 41S receives forces from the multiple second planetary gears 42S that tend to rotate the second sun gear 41S in the second direction. However, the second sun gear 41S does not rotate before the first engagement portion 432 engages with the second engagement portion 442. Therefore, with the second sun gear 41S fixed, the internal gear 43, the first planetary carrier 44, the first sun gear 41, and the second planetary carrier 44S rotate in the first direction DR1. The rotational speed of the internal gear 43 is faster than the rotational speed of the first planetary carrier 44.

[0138] Fig. 4 shows the state immediately before motor shaft 21 starts to rotate, Fig. 5 shows the state some time after motor shaft 21 starts to rotate in first direction DR1, and Fig. 6 shows the state after motor shaft 21 continues to rotate in first direction DR1 from the state shown in Fig. 5.

[0139] 5 and 6, as the internal gear 43 rotates in the first direction DR1 relative to the first planetary carrier 44, the first engagement portion 432 of the internal gear 43 approaches the second engagement portion 442 located further ahead in the rotation direction. Then, for example, at timing T1 in Fig. 10, the side surface of the first engagement portion 432 of the internal gear 43 comes into contact with the side surface of the second engagement portion 442 of the first planetary carrier 44 as shown in Fig. 6.

[0140] When the side surfaces of the multiple first engagement portions 432 engage with the side surfaces of the multiple second engagement portions 442, the force applied from the multiple first engagement portions 432 to the multiple second engagement portions 442 accelerates the first planetary carrier 44 in the first direction DR1. This increases the force that rotates the first sun gear 41 and the second planetary carrier 44S fixed to the first sun gear 41 in the first direction DR1. In other words, this increases the force that revolves the multiple second planetary gears 42S in the first direction DR1. This causes the second sun gear 41S meshed with the multiple second planetary gears 42S and the output shaft 5 connected to the second sun gear 41S to rotate in the first direction DR1. The rotation of the output shaft 5 tightens the workpiece.

[0141] More specifically, when the second planetary carrier 44S is accelerated in the first direction DR1 by the force applied from the first engagement portions 432 to the second engagement portions 442, a force that tends to rotate in the second direction acts on each of the second planetary gears 42S as a reaction force from the second sun gear 41S. Meanwhile, a force that tends to rotate in the first direction DR1 acts on each of the second planetary gears 42S due to the second planetary carrier 44S indirectly receiving a force from the motor shaft 21 and rotating in the first direction DR1. Because both the force that tends to rotate in the first direction DR1 and the force that tends to rotate in the second direction are generated by the rotation of the second planetary carrier 44S in the first direction DR1, the force that tends to rotate in the first direction DR1 and the force that tends to rotate in the second direction are antagonistic. Therefore, each of the second planetary gears 42S stops rotating (rotating) about the axis 421S. As a result, the second sun gear 41S rotates at the same speed and in the same direction as the internal gear 43.

[0142] Because the first sun gear 41 is fixed to the second planetary carrier 44S, the first sun gear 41 also rotates at the same speed and in the same direction as the internal gear 43. Therefore, the multiple first planetary gears 42 meshed between the first sun gear 41 and the internal gear 43 stop rotating (spinning) around the axis 421.

[0143] Therefore, when the first engagement portion 432 and the second engagement portion 442 are engaged with each other, the first planetary carrier 44, the second planetary carrier 44S, the internal gear 43, the plurality of first planetary gears 42, the plurality of second planetary gears 42S, the first sun gear 41, and the second sun gear 41S stop rotating relative to each other. In other words, when the first engagement portion 432 and the second engagement portion 442 are engaged with each other, the first planetary carrier 44, the second planetary carrier 44S, the internal gear 43, the plurality of first planetary gears 42, the plurality of second planetary gears 42S, the first sun gear 41, and the second sun gear 41S are fixed to each other. When the first planetary carrier 44, the second planetary carrier 44S, the internal gear 43, the first planetary gears 42, the second planetary gears 42S, the first sun gear 41, and the second sun gear 41S are fixed to one another, the first planetary carrier 44, the second planetary carrier 44S, the internal gear 43, the first planetary gears 42, the second planetary gears 42S, the first sun gear 41, and the second sun gear 41S rotate together in the first direction DR1 around the rotation axis Ax1. Therefore, at timing T1 when the first engagement portion 432 and the second engagement portion 442 engage with each other, the rotational speed of the output shaft 5 becomes the same as the rotational speed of the motor shaft 21.

[0144] As with the tool 1 of the first embodiment, the tool 1A has three operating states: the first operating state, the second operating state, and the third operating state described in the first embodiment.

[0145] As described above, the planetary gear mechanism 4A has a two-stage configuration including a first-stage mechanism and a second-stage mechanism provided in front of the first-stage mechanism. The first-stage mechanism includes a first sun gear 41, a plurality of first planetary gears 42, and a first planetary carrier 44. The second-stage mechanism includes a second sun gear 41S, a plurality of second planetary gears 42S, and a second planetary carrier 44S. The first sun gear 41 is fixed to the second-stage mechanism (second planetary carrier 44S). By configuring the planetary gear mechanism 4A as a two-stage mechanism, the speed difference between the rotational speed of the internal gear 43 and the rotational speed of the first planetary carrier 44 is smaller than in the first embodiment, in which the planetary gear mechanism 4 has a single-stage configuration. More specifically, since the first sun gear 41 rotates in the same direction as the first planetary carrier 44 and the internal gear 43, the internal gear 43 slows down compared to embodiment 1, and the speed difference between the rotational speed of the internal gear 43 and the rotational speed of the first planetary carrier 44 becomes smaller.

[0146] The period of the first operating state (charge period) can be extended by reducing the speed difference between the rotational speed of the internal gear 43 and the rotational speed of the first planetary carrier 44. This allows the inertia torque of the motor shaft 21 to be sufficiently increased.

[0147] The planetary gear mechanism 4A may have a multi-stage configuration of three or more stages. By configuring the planetary gear mechanism 4A with a multi-stage configuration of three or more stages, the period of the first operating state (charge period) can be made longer. The number of internal gears included in the planetary gear mechanism 4A may be one regardless of the number of stages of the planetary gear mechanism 4A, or may be equal to the number of stages of the planetary gear mechanism 4A. When the planetary gear mechanism 4A has multiple internal gears held in a rotatable state, the multiple internal gears correspond one-to-one to multiple planet carriers, and each internal gear meshes with multiple planet gears supported by the corresponding planet carrier. Of the multiple internal gears, the first-stage internal gear has a first engagement portion 432 and is fixed to the motor shaft 21.

[0148] 15 to 17 illustrate a tool 1B according to embodiment 3. In this embodiment, the configurations of an internal gear 43B and a planetary carrier 44B of a planetary gear mechanism 4B are different from those of the internal gear 43 and the planetary carrier 44 of embodiment 1.

[0149] (1.1) Internal gear The internal gear 43B has a main body portion 431, a plurality of (two in the example of Figure 16) first engagement portions 432 protruding from the main body portion 431, and a plurality of (two in the example of Figure 16) third engagement portions 435 protruding from the main body portion 431.

[0150] The main body 431 is formed in a cylindrical shape with its axial direction aligned with the front-rear direction, and a plurality of teeth are provided on the inner circumferential surface of the main body 431. The number of teeth of the main body 431 is greater than the number of teeth of the sun gear 41B. The main body 431 is arranged so that the central axis of the main body 431 and the central axis of the sun gear 41B are concentric when viewed from the front-rear direction. The main body 431 may be formed in an annular shape with its axial direction (thickness direction) aligned with the front-rear direction.

[0151] The multiple first engagement portions 432 protrude rearward from the rear end (rear surface) of the main body portion 431. That is, the multiple first engagement portions 432 protrude from the main body portion 431 along the rotation axis Ax1 of the output shaft 5B. The first engagement portions 432 protrude from part of the annular rear end of the main body portion 431 and are formed in a rectangular parallelepiped shape that is curved according to the curvature of the rear end of the main body portion 431. The two first engagement portions 432 are arranged to face each other in a direction perpendicular to the front-rear direction. More specifically, the two first engagement portions 432 face each other so as to sandwich the rotation axis Ax1 of the output shaft 5B therebetween.

[0152] The multiple third engagement portions 435 protrude forward from the front end (front surface) of the main body portion 431. That is, the multiple third engagement portions 435 protrude from the main body portion 431 along the rotation axis Ax1 of the output shaft 5B. The third engagement portions 435 protrude from part of the annular front end of the main body portion 431 and are formed in a rectangular parallelepiped shape that is curved according to the curvature of the front end of the main body portion 431. The two third engagement portions 435 are arranged to face each other in a direction perpendicular to the front-rear direction. More specifically, the two third engagement portions 435 face each other so as to sandwich the rotation axis Ax1 of the output shaft 5B therebetween.

[0153] The direction in which the plurality of third engagement portions 435 protrude from the main body portion 431 is opposite to the direction in which the plurality of first engagement portions 432 protrude from the main body portion 431 .

[0154] The third engagement portions 435 correspond one-to-one to the first engagement portions 432. The third engagement portions 435 are aligned with the corresponding first engagement portions 432 in the front-rear direction.

[0155] (1.2) Transmission Body The tool 1B further includes a transmission body 941. The torque of the motor shaft 21 is transmitted to the internal gear 43B via the transmission body 941.

[0156] The transmitting body 941 has a disk shape. The transmitting body 941 has a plurality of (two in FIG. 16 ) recesses 9410. The recesses 9410 are provided on the side surface of the transmitting body 941.

[0157] The multiple first engagement portions 432 of the internal gear 43B correspond one-to-one to the multiple recesses 9410. Each first engagement portion 432 is inserted into the corresponding recess 9410. This connects the transmission body 941 and the internal gear 43B (see FIG. 17). The transmission body 941 and the internal gear 43B rotate integrally.

[0158] A gap is provided in the front-rear direction between the transmission body 941 and the main body 431 of the internal gear 43B. A plurality of second engagement portions 442 and a first carrier portion 441 (described later) are disposed in this gap.

[0159] (1.3) Planet Carrier The planetary gear mechanism 4B has a sun gear 41B, a plurality of planet gears 42 (six in the example of FIG. 16), an internal gear 43B, and a planet carrier 44B.

[0160] The planet carrier 44B has a first carrier portion 441, a second carrier portion 46, a plurality (two in Figure 16) of second engagement portions 442 protruding from the first carrier portion 441, and a plurality (two in Figure 16) of fourth engagement portions 464 protruding from the second carrier portion 46.

[0161] The second carrier portion 46 has a configuration corresponding to the shaft holding member 40 of the first embodiment.

[0162] The planetary carrier 44B is arranged so that the central axis of the planetary carrier 44B and the central axis of the sun gear 41B are concentric when viewed from the front-rear direction.

[0163] The first carrier portion 441 is formed in a disk shape with its thickness direction aligned with the front-rear direction.

[0164] A through-hole 4410 is formed in the center of the first carrier portion 441. The center pin 95 is inserted into the through-hole 4410.

[0165] The first carrier portion 441 has a plurality of (six) through holes 4411 formed therein. Note that FIG. 15 illustrates only two of the six through holes 4411. The through holes 4411 are arranged at equal intervals on a circumference centered on the central axis of the sun gear 41B. The through holes 4411 penetrate the first carrier portion 441 in the front-to-rear direction. The rear ends (first ends) of the shafts 421 of the planetary gears 42 are inserted into each of the through holes 4411. In this way, the first carrier portion 441 is connected to the rear ends (first ends) of the shafts 421 of the planetary gears 42.

[0166] The second carrier part 46 has a plurality of through holes 461 (six in FIG. 16 ). The through holes 461 are arranged at equal intervals on a circumference centered on the central axis of the sun gear 41B. The through holes 461 penetrate the second carrier part 46 in the front-to-rear direction. The front ends of the shafts 421 of the planetary gears 42 are inserted into each of the through holes 461. This connects the second carrier part 46 to the front ends (second ends) of the shafts 421 of the planetary gears 42.

[0167] The second carrier portion 46 is disposed in front of the first carrier portion 441. The second carrier portion 46 faces the first carrier portion 441 in the front-rear direction. The plurality of planetary gears 42 are disposed between the first carrier portion 441 and the second carrier portion 46.

[0168] The second carrier portion 46 is rotatably supported by the housing 10. More specifically, the second carrier portion 46 is supported by the housing 10 via a bearing 17.

[0169] The two second engagement portions 442 protrude from the first carrier portion 441 in a direction perpendicular to the rotation axis Ax1 of the output shaft 5B. More specifically, the two second engagement portions 442 protrude outward from the outer edge of the disk-shaped first carrier portion 441 in the radial direction of the first carrier portion 441. The two second engagement portions 442 protrude in directions away from each other. The second engagement portions 442 protrude from part of the side surface of the first carrier portion 441 and are formed in a rectangular parallelepiped shape.

[0170] The two fourth engagement portions 464 protrude from the second carrier portion 46 in a direction perpendicular to the rotation axis Ax1 of the output shaft 5B. More specifically, the two fourth engagement portions 464 protrude outward from the outer edge of the disk-shaped second carrier portion 46 in the radial direction of the second carrier portion 46. The two fourth engagement portions 464 protrude in directions away from each other. The fourth engagement portions 464 protrude from part of the side surface of the second carrier portion 46 and are formed in a rectangular parallelepiped shape.

[0171] The first carrier portion 441 and the second carrier portion 46 are connected via multiple shafts 421, thereby fixing the orientation of the second carrier portion 46 relative to the first carrier portion 441. The multiple (two) fourth engagement portions 464 correspond one-to-one to the multiple (two) second engagement portions 442. Each fourth engagement portion 464 is disposed in front of the corresponding second engagement portion 442. Each fourth engagement portion 464 faces the corresponding second engagement portion 442 in the front-rear direction.

[0172] As in embodiment 1, the multiple first engagement portions 432 of the internal gear 43B and the multiple second engagement portions 442 of the planetary carrier 44B are capable of relative movement along the rotational direction of the transmission body 941, and come into contact in response to the rotation of the internal gear 43B.

[0173] Furthermore, the plurality of third engagement portions 435 of the internal gear 43B and the plurality of fourth engagement portions 464 of the planetary carrier 44B are capable of relative movement along the rotational direction of the transmission body 941. When the plurality of first engagement portions 432 of the internal gear 43B and the plurality of second engagement portions 442 of the planetary carrier 44B come into contact in response to rotation of the internal gear 43B, the plurality of third engagement portions 435 of the internal gear 43B come into contact with the plurality of fourth engagement portions 464 of the planetary carrier 44B.

[0174] That is, similar to the first embodiment, the rotational force of the internal gear 43B is transmitted to the planet carrier 44B via the plurality of first engagement portions 432 and the plurality of second engagement portions 442. Furthermore, the rotational force of the internal gear 43B is also transmitted to the planet carrier 44B via the plurality of third engagement portions 435 and the plurality of fourth engagement portions 464. In this manner, in the present embodiment, the rotational force of the internal gear 43B is transmitted to the planet carrier 44B in a more dispersed manner than in the first embodiment. Therefore, stress concentration in the internal gear 43B and the planet carrier 44B can be suppressed. By suppressing stress concentration, the life of the tool 1B can be extended.

[0175] (2) Other Differences The following lists the configurations of the tool 1B of this embodiment that differ from the tool 1 of the first embodiment. However, it is not essential that the tool 1B differ from the tool 1 of the first embodiment in the matters described below. For example, the tool 1B may differ from the tool 1 of the first embodiment only in the matters described in "(1) Main Differences." Alternatively, the tool 1B may differ from the tool 1 of the first embodiment only in some of the matters described below.

[0176] (2.1) Sun Gear and Output Shaft The sun gear 41B has a main body portion 410 and a protrusion portion 413.

[0177] The main body 410 is formed in a cylindrical shape with an axial direction along the front-rear direction, and a plurality of teeth are provided on the outer peripheral surface of the main body 410. The protrusion 413 protrudes forward from the front end (front surface) of the main body 410. The shape of the protrusion 413 is cylindrical. The inner peripheral surface of the protrusion 413 is splined.

[0178] The output shaft 5B has a connecting portion 51. The connecting portion 51 is the rear end portion of the output shaft 5B. The connecting portion 51 has, for example, a cylindrical or columnar shape. The outer circumferential surface of the connecting portion 51 has a spline shape.

[0179] The connecting portion 51 of the output shaft 5B is connected to the protruding portion 413 of the sun gear 41B. That is, the connecting portion 51 is inserted into the inside of the protruding portion 413, and the connecting portion 51 and the protruding portion 413 are fitted together.

[0180] 15 , the tool 1B further includes a second planetary gear mechanism 9. The second planetary gear mechanism 9 includes a sun gear 91, a plurality of planetary gears 92, an internal gear 93, a planet carrier 94, a center pin 95, and a holder 96.

[0181] The sun gear 91 is a member that is integral with the motor shaft 21 of the motor 2. The sun gear 91 is provided at the front end of the motor shaft 21.

[0182] The plurality of planetary gears 92 are arranged around the sun gear 91 and mesh with the sun gear 91. Each of the plurality of planetary gears 92 rotates around a corresponding shaft 921. The shaft 921 is supported by the planetary carrier 94. More specifically, the shaft 921 is fixed to the planetary carrier 94 by being inserted into a through-hole formed in the planetary carrier 94.

[0183] As the sun gear 91 rotates, the multiple planet gears 92 revolve, and therefore the planet carrier 94 rotates.

[0184] The internal gear 93 is disposed so as to surround the plurality of planetary gears 92 and meshes with the plurality of planetary gears 92. The internal gear 93 is housed in a holder 96. The internal gear 93 is held by the holder 96.

[0185] The holder 96 is accommodated in the housing 10 of the tool 1B. The holder 96 is held by the housing 10. The holder 96 rotatably holds the planet carrier 94 via a bearing 18.

[0186] The planetary carrier 94 has a transmission body 941 and a carrier portion 942. The carrier portion 942 is disk-shaped. The shafts 921 of the multiple planetary gears 92 are fixed to the carrier portion 942. The transmission body 941 is disk-shaped. The transmission body 941 protrudes forward from the carrier portion 942.

[0187] The transmission body 941 and the carrier portion 942 are concentric. The diameter of the transmission body 941 is larger than the diameter of the carrier portion 942.

[0188] The planetary carrier 94 has a through hole 943 at its center. A center pin 95 is inserted into the through hole 943. The center pin 95 is inserted into the sun gear 41B and the output shaft 5B.

[0189] The planet carrier 94 is an example of an inertial body 3 used as a flywheel.

[0190] The rotation of the motor shaft 21 is reduced in speed by the second planetary gear mechanism 9 and transmitted from the transmission body 941 to the internal gear 43B.

[0191] (Summary) The above-described embodiments and the like disclose the following aspects.

[0192] A tool (1; 1A; 1B) according to a first aspect includes a motor (2), a sun gear (41; 41B), an output shaft (5; 5B), a plurality of planetary gears (42), a planetary carrier (44; 44B), and an internal gear (43; 43B). The motor (2) rotates a transmission body (motor shaft (21); (941)) that transmits torque to another member. A tool bit is attached to the output shaft (5; 5B), and the rotation of the sun gear (41; 41B) is transmitted to the motor shaft (21; (941)). The plurality of planetary gears (42) are arranged around the sun gear (41; 41B) and mesh with the sun gear (41; 41B). The planetary carrier (44; 44B) rotatably supports the plurality of planetary gears (42) and rotates around the sun gear (41; 41B). The internal gear (43; 43B) is arranged to surround the multiple planetary gears (42), meshes with the multiple planetary gears (42), and is held in a rotatable state. The internal gear (43; 43B) is fixed to the transmission body and rotates in response to the rotation of the transmission body. The internal gear (43; 43B) has a first engagement portion (432). The planetary carrier (44; 44B) has a second engagement portion (442). The first engagement portion (432) of the internal gear (43; 43B) and the second engagement portion (442) of the planetary carrier (44; 44B) are relatively movable in the rotational direction of the transmission body and come into contact in response to the rotation of the internal gear (43; 43B).

[0193] According to the above configuration, contact between the first engagement portion (432) and the second engagement portion (442) enables a large torque to be transmitted to the output shaft (5; 5B) based on the rotational energy of the planetary transmission mechanism (sun gear (41; 41B), planetary carrier (44; 44B), multiple planetary gears (42), and internal gear (43; 43B)). The relative speed between the first engagement portion (432) of the internal gear (43; 43B) and the second engagement portion (442) of the planetary carrier (44; 44B) is slower than the rotational speed of the transmission body (motor shaft (21); (941)). Therefore, the noise generated when the first engagement portion (432) and the second engagement portion (442) come into contact is smaller than the noise generated when the impact mechanism applies an impact to the output shaft (5; 5B). Therefore, compared to the conventional case where a large torque is applied to the output shaft (5; 5B) by an impact mechanism, noise generated during operation of the tool (1; 1A; 1B) can be suppressed.

[0194] In the tool (1; 1A; 1B) according to the second aspect, in the first aspect, when the tool bit is in contact with the work object and the first engagement portion (432) of the internal gear (43; 43B) and the second engagement portion (442) of the planetary carrier (44; 44B) are not in contact with each other, the internal gear (43; 43B) and the output shaft (5; 5B) rotate integrally with the transmission body when the tool bit is in contact with the work object and the first engagement portion (432) of the internal gear (43; 43B) and the second engagement portion (442) of the planetary carrier (44; 44B) are in contact with each other.

[0195] According to the above configuration, the internal gear (43; 43B) rotates in the same direction as the transmission body (motor shaft (21); (941)), and when the first engagement portion (432) and the second engagement portion (442) come into contact, the inertia torque of the internal gear (43; 43B) can be converted into torque to be transmitted to the output shaft (5; 5B), so that a large torque can be transmitted to the output shaft (5; 5B).

[0196] Furthermore, the tool (1; 1A; 1B) according to a third aspect is the tool of the first or second aspect, further including a control unit (7) that controls the motor (2). The control unit (7) controls the motor (2) to rotate the transmission body (motor shaft (21); (941)) in a first direction (DR1). After the integral rotation of the internal gear (43; 43B) and the output shaft (5; 5B) has stopped, the control unit (7) controls the motor (2) to rotate the transmission body in a second direction opposite to the first direction (DR1) for a predetermined time or by a predetermined angle. After rotating the transmission body in the second direction for a predetermined time or by a predetermined angle, the control unit (7) controls the motor (2) to rotate the transmission body in the first direction (DR1).

[0197] According to the above configuration, a period of time can be secured for increasing the inertia torque of the transmission body (motor shaft (21); (941)), and the work object can be tightened again by the inertia torque.

[0198] Furthermore, in a tool (1; 1A; 1B) according to a fourth aspect, in any one of the first to third aspects, the internal gear (43; 43B) further includes a main body portion (431) formed in an annular or cylindrical shape and having a plurality of teeth on its inner circumferential surface. The planetary carrier (44; 44B) further includes a carrier portion (441) coupled to each of the shafts of the plurality of planetary gears (42). A first engagement portion (432) of the internal gear (43; 43B) protrudes from the main body portion (431) along the rotation axis (Ax1) of the output shaft (5; 5B). A second engagement portion (442) of the planetary carrier (44; 44B) protrudes from the carrier portion (441) along a direction perpendicular to the rotation axis (Ax1).

[0199] According to the above configuration, the first engagement portion (432) and the second engagement portion (442) protrude in directions perpendicular to each other, so that the tool (1; 1A; 1B) can be made more compact than when they protrude in the same direction, for example.

[0200] Furthermore, a tool (1B) according to a fifth aspect is the tool of any one of the first to fourth aspects, wherein the internal gear (43B) further includes a main body portion (431) and a third engagement portion (435). The main body portion (431) is formed in an annular or cylindrical shape. A plurality of teeth are provided on the inner peripheral surface of the main body portion (431). The first engagement portion (432) and the third engagement portion (435) of the internal gear (43B) protrude from the main body portion (431). The planetary carrier (44B) further includes a first carrier portion (441) coupled to first ends of the shafts (421) of the plurality of planetary gears (42), a second carrier portion (46) coupled to second ends of the shafts (421) of the plurality of planetary gears (42), and a fourth engagement portion (464). The plurality of planetary gears (42) are disposed between a first carrier portion (441) and a second carrier portion (46). A second engagement portion (442) of the planetary carrier (44B) protrudes from the first carrier portion (441). A fourth engagement portion (464) of the planetary carrier (44B) protrudes from the second carrier portion (46). The third engagement portion (435) of the internal gear (43B) and the fourth engagement portion (464) of the planetary carrier (44B) are relatively movable along the rotation direction of the transmission body (941). When the first engagement portion (432) of the internal gear (43B) and the second engagement portion (442) of the planetary carrier (44B) come into contact with each other in response to rotation of the internal gear (43B), the third engagement portion (435) of the internal gear (43B) and the fourth engagement portion (464) of the planetary carrier (44B) come into contact with each other.

[0201] According to the above configuration, the rotational force of the internal gear (43B) is dispersed between the first carrier portion (441) and the second carrier portion (46) and transmitted to the planetary carrier (44B), thereby suppressing stress concentration on the internal gear (43B) and the planetary carrier (44B).

[0202] In addition, in a tool (1B) according to a sixth aspect, in the fifth aspect, the first engagement portion (432) and the third engagement portion (435) of the internal gear (43B) protrude from the main body portion (431) along the rotation axis (Ax1) of the output shaft (5B). The second engagement portion (442) of the planetary carrier (44B) protrudes from the first carrier portion (441) along a direction perpendicular to the rotation axis (Ax1). The fourth engagement portion (464) of the planetary carrier (44B) protrudes from the second carrier portion (46) along a predetermined direction perpendicular to the rotation axis (Ax1).

[0203] According to the above configuration, since the first engaging portion (432) and the second engaging portion (442) protrude in directions perpendicular to each other, the tool (1B) can be made more compact than when they protrude in the same direction. Also, since the third engaging portion (435) and the fourth engaging portion (464) protrude in directions perpendicular to each other, the tool (1B) can be made more compact than when they protrude in the same direction.

[0204] In addition, in the tool (1B) according to a seventh aspect, in the fifth or sixth aspect, the internal gear (43B) has a plurality of first engagement portions (432) including the first engagement portion (432) and a plurality of third engagement portions (435) including the third engagement portion (435). The planetary carrier (44B) has a plurality of second engagement portions (442) including the second engagement portion (442) and a plurality of fourth engagement portions (464) including the fourth engagement portion (464).

[0205] According to the above configuration, it is possible to further suppress the concentration of stress on the internal gear (43B) and the planetary carrier (44B).

[0206] Furthermore, the tool (1A) according to an eighth aspect is any one of the first to fourth aspects, further comprising: a second sun gear (41S) separate from the first sun gear (41) as the sun gear (41); a plurality of second planetary gears (42S) separate from the first planetary gears (42) as the planetary gears (42); and a second planetary carrier (44S) separate from the first planetary carrier (44) as the planetary carrier (44). The second planetary carrier (44S) is fixed to the first sun gear (41) and rotates around the first sun gear (41) in response to the rotation of the first sun gear (41). The second planetary carrier (44S) rotatably supports the plurality of second planetary gears (42S). The plurality of second planetary gears (42S) are arranged around the second sun gear (41S) and mesh with the second sun gear (41S). The internal gear (43) is arranged so as to surround the plurality of first planetary gears (42) and the plurality of second planetary gears (42S), and is in mesh with the plurality of first planetary gears (42) and the plurality of second planetary gears (42S).

[0207] According to the above configuration, the period until the first engagement portion (432) comes into contact with the second engagement portion (442) can be extended, and the inertia torque of the transmission body (motor shaft (21)) can be more reliably maintained at a certain value or above.

[0208] Furthermore, the tool (1; 1A; 1B) according to a ninth aspect is the tool according to any one of the first to fifth aspects, further comprising an inertial body (3). The inertial body (3) is disposed between the motor (2) and the internal gear (43; 43B) and rotates integrally with the transmission body (motor shaft (21); (941)).

[0209] According to the above configuration, the inertia torque of the transmission body (motor shaft (21); (941)) can be increased.

[0210] The configurations other than the first aspect are not essential to the tool (1; 1A; 1B) and can be omitted as appropriate.

[0211] 1; 1A; 1B Tool 2 Motor 3 Inertial body 5; 5B Output shaft 7 Control unit 21 Motor shaft (transmission body) 41; 41B Sun gear (first sun gear) 41S Second sun gear 42 Planet gear (first planet gear) 42S Second planet gear 43; 43B Internal gear 44; 44B Planet carrier (first planet carrier) 44S Second planet carrier 46 Second carrier portion 421 Shaft 431 Main body portion 432 First engagement portion 435 Third engagement portion 441 First carrier portion (carrier portion) 442 Second engagement portion 464 Fourth engagement portion 941 Transmission body Ax1 Rotation axis DR1 First direction

Claims

1. A tool comprising: a motor that rotates a transmission body that transmits torque to another member; a sun gear; an output shaft to which a tool tip is attached and to which the rotation of the sun gear is transmitted; a plurality of planetary gears arranged around the sun gear and meshing with the sun gear; a planetary carrier that rotatably supports the plurality of planetary gears and rotates around the sun gear; and an internal gear that is arranged to surround the plurality of planetary gears, meshes with the plurality of planetary gears and is held in a rotatable state, the internal gear is fixed to the transmission body and rotates in response to the rotation of the transmission body, the internal gear has a first engagement portion, and the planetary carrier has a second engagement portion, the first engagement portion of the internal gear and the second engagement portion of the planetary carrier are relatively movable along the rotational direction of the transmission body and come into contact in response to the rotation of the internal gear.

2. The tool described in claim 1, wherein the internal gear rotates in the same direction as the transmission body when the tool tip is in contact with a work object and the first engagement portion of the internal gear and the second engagement portion of the planetary carrier are not in contact, and the internal gear and the output shaft rotate integrally with the transmission body when the tool tip is in contact with a work object and the first engagement portion of the internal gear and the second engagement portion of the planetary carrier are in contact.

3. A tool as described in claim 1 or 2, further comprising a control unit that controls the motor to rotate the transmission body in a first direction, and after the integrated rotation of the internal gear and the output shaft stops, controls the motor to rotate the transmission body in a second direction opposite to the first direction for a predetermined time or by a predetermined angle, and after rotating the transmission body in the second direction for the predetermined time or by the predetermined angle, controls the motor to rotate the transmission body in the first direction.

4. A tool as claimed in any one of claims 1 to 3, wherein the internal gear further has a main body portion formed in an annular or cylindrical shape and having a plurality of teeth on its inner circumferential surface, the planetary carrier further has a carrier portion connected to each of the axes of the plurality of planetary gears, the first engagement portion of the internal gear protrudes from the main body portion along the rotation axis of the output shaft, and the second engagement portion of the planetary carrier protrudes from the carrier portion along a direction perpendicular to the rotation axis.

5. The internal gear further has a main body portion formed in an annular or cylindrical shape and having a plurality of teeth on its inner circumferential surface, and a third engagement portion, the first engagement portion and the third engagement portion of the internal gear protruding from the main body portion, the planetary carrier further has a first carrier portion connected to a first end of a shaft of each of the plurality of planetary gears, a second carrier portion connected to a second end of the shaft of each of the plurality of planetary gears, and a fourth engagement portion, the plurality of planetary gears are disposed between the first carrier portion and the second carrier portion, the second engagement portion of the planetary carrier protruding from the first carrier portion, and the fourth engagement portion of the planetary carrier protruding from the second carrier portion, the third engagement portion of the internal gear and the fourth engagement portion of the planetary carrier are relatively movable along the rotational direction of the transmission body, The tool according to claim 1 , wherein when the first engagement portion of the internal gear and the second engagement portion of the planetary carrier come into contact in response to rotation of the internal gear, the third engagement portion of the internal gear and the fourth engagement portion of the planetary carrier come into contact.

6. The tool described in claim 5, wherein the first engagement portion and the third engagement portion of the internal gear protrude from the main body portion along the rotation axis of the output shaft, the second engagement portion of the planetary carrier protrudes from the first carrier portion along a direction perpendicular to the rotation axis, and the fourth engagement portion of the planetary carrier protrudes from the second carrier portion along a predetermined direction perpendicular to the rotation axis.

7. A tool as described in claim 5 or 6, wherein the internal gear has a plurality of first engagement portions including the first engagement portion, and a plurality of third engagement portions including the third engagement portion, and the planetary carrier has a plurality of second engagement portions including the second engagement portion, and a plurality of fourth engagement portions including the fourth engagement portion.

8. The tool described in any one of claims 1 to 4, further comprising: a second sun gear separate from the first sun gear as the sun gear; a plurality of second planetary gears separate from the first planetary gears as the plurality of planetary gears; and a second planetary carrier separate from the first planetary carrier as the planetary carrier, wherein the second planetary carrier is fixed to the first sun gear and rotates around the first sun gear in response to the rotation of the first sun gear, and rotatably supports the plurality of second planetary gears, the plurality of second planetary gears are arranged around the second sun gear and mesh with the second sun gear, and the internal gear is arranged to surround the plurality of first planetary gears and the plurality of second planetary gears, and meshes with the plurality of first planetary gears and the plurality of second planetary gears.

9. The tool according to any one of claims 1 to 5, further comprising an inertia body disposed between the motor and the internal gear and rotating integrally with the transmission body.

Images