power tools

Abstract

To achieve stabilization of work.SOLUTION: An electric tool 1 includes a motor 2, an output shaft 6, a transmission mechanism 3, a first bearing 8A and a second bearing 8B, and a cover 10B. The output shaft 6 is connected to a tip tool 11. The transmission mechanism 3 engages with the output shaft 6 and transmits torque of the motor 2 to the output shaft 6. The first bearing 8A and the second bearing 8B rotatably support the output shaft 6. The cover 10B houses the motor 2, the transmission mechanism 3, and the first bearing 8A and the second bearing 8B. The first bearing 8A is disposed between the second bearing 8B and the tip tool 11. The second bearing 8B is disposed so as to contact with the transmission mechanism 3 and the cover 10B in an engagement portion between the transmission mechanism 3 and the output shaft 6.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure generally relates to power tools, and more particularly to power tools having a motor.

Background Art

[0002] The portable power tool described in Patent Document 1 includes a motor as a drive source, a speed reduction mechanism unit that transmits the rotational power of the electric motor, a drive unit that transmits the rotational power of the speed reduction mechanism unit to a tip tool, and a body outer shell that includes a bearing unit that rotatably holds the drive unit, and a grip outer shell that includes a switch unit that controls power supply to the electric motor.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a portable power tool (power tool) as described in Patent Document 1, when a radial load is applied to the tip tool and the drive unit from the work object of the power tool, the work may become unstable.

[0005] In view of the above reasons, the present disclosure is made, and an object thereof is to provide a power tool capable of stabilizing work.

Means for Solving the Problems

[0006] An electric tool according to one aspect of the present disclosure comprises a motor, an output shaft, a transmission mechanism, a first bearing and a second bearing, and a cover. The output shaft is connected to a tool tip. The transmission mechanism engages with the output shaft and transmits the torque of the motor to the output shaft. The first bearing and the second bearing rotatably support the output shaft. The cover houses the motor, the transmission mechanism, the first bearing, and the second bearing. The first bearing is positioned between the second bearing and the tool tip. The second bearing is positioned to contact the transmission mechanism and the cover at the engagement portion between the transmission mechanism and the output shaft. The transmission mechanism includes a sun gear that rotates by power from the motor, a plurality of planetary gears arranged around the sun gear and meshing with the sun gear, an internal gear arranged around the plurality of planetary gears and meshing with the plurality of planetary gears, and a carrier that engages with the output shaft and rotatably supports each of the plurality of planetary gears. The second bearing is positioned to contact the carrier and the cover at the engagement portion between the carrier and the output shaft. [Effects of the Invention]

[0007] According to this disclosure, it is possible to provide a power tool that can stabilize the operation. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a cross-sectional view of a power tool according to one embodiment of the present disclosure. [Figure 2] Figure 2 is a perspective view of the same power tool. [Figure 3] Figure 3 is a cross-sectional view of the main part of the same power tool. [Figure 4] Figure 4 is a block diagram of the same power tool. [Figure 5] Figure 5 is an exploded perspective view of the transmission mechanism of the power tool shown above, viewed from the front. [Figure 6] Figure 6 is an exploded perspective view of the transmission mechanism of the same power tool, seen from the rear. [Figure 7] Figure 7 is a graph illustrating the effect of torque value stabilization by the regulatory structure of the aforementioned power tool. [Figure 8] Figure 8 is a graph illustrating the effect of torque value stabilization by the regulatory structure of the aforementioned power tool. [Figure 9] Figure 9 is a cross-sectional view of the main part of the same power tool. [Figure 10] Figure 10 is a graph illustrating the effect of torque value stabilization provided by the second bearing in the same power tool. [Figure 11] Figure 11 is a graph illustrating the effect of torque value stabilization provided by the second bearing in the same power tool. [Modes for carrying out the invention]

[0009] A power tool 1 according to an embodiment of this disclosure will be described in detail with reference to the drawings. Note that the embodiments and modifications described below are merely examples of this disclosure, and this disclosure is not limited to these embodiments and modifications. Even outside of these embodiments and modifications, various modifications are possible depending on the design, etc., as long as they do not depart from the technical idea of ​​this disclosure. Furthermore, the figures described in the embodiments below are schematic diagrams, and the ratios of the size and thickness of each component in the figures do not necessarily reflect the actual dimensional ratios. The arrows indicating directions in the drawings are examples only and are not intended to define the orientation of the power tool 1 when in use. Also, the arrows indicating directions in the drawings are for illustrative purposes only and do not represent actual objects.

[0010] (1) Overview First, an overview of the power tool 1 of this embodiment will be described with reference to Figures 1, 2, and 9.

[0011] As shown in Figure 1, the power tool 1 of this embodiment comprises a motor 2, an output shaft 6, a transmission mechanism 3, a first bearing 8A and a second bearing 8B, and a cover 10B.

[0012] The output shaft 6 is connected to a tip tool 11, such as a driver bit, for tightening fastening components such as screws and bolts.

[0013] The transmission mechanism 3 engages with the output shaft 6 and transmits the torque of the motor 2 to the output shaft 6.

[0014] The first bearing 8A and the second bearing 8B rotatably support the output shaft 6.

[0015] The cover 10B houses the motor 2, the transmission mechanism 3, the first bearing 8A, and the second bearing 8B.

[0016] The first bearing 8A is disposed between the second bearing 8B and the tip tool 11.

[0017] The second bearing 8B is disposed so as to contact the transmission mechanism 3 and the cover 10B at the engagement portion between the transmission mechanism 3 and the output shaft 6.

[0018] According to the power tool 1 of the present embodiment, as shown in FIG. 9, the output shaft 6 is supported by the second bearing 8B and the cover 10B that contacts the second bearing 8B via the transmission mechanism 3. Therefore, when a force (radial load) F3 along a direction intersecting the axial direction of the output shaft 6 is applied to the output shaft 6, this force F3 can be received by the cover 10B, so that eccentricity of the output shaft 6 can be suppressed, and the operation of the power tool 1 can be stabilized.

[0019] (2) Configuration of the power tool Hereinafter, the configuration of the power tool 1 of the present embodiment will be described in detail.

[0020] In the following description, along the axial direction of the output shaft 6, as shown in FIG. 1 and the like, the direction from the motor 2 side to the output shaft 6 side is defined as the front, and the direction from the output shaft 6 side to the motor 2 side is defined as the rear. Also, along the direction orthogonal to the front and the rear, the direction from the grip portion 102 side to the body portion 101 is defined as the upper, and the direction from the body portion 101 side to the grip portion 102 side is defined as the lower.

[0021] The power tool 1 is a portable power tool such as a drill driver that can be gripped by an operator with one hand. As shown in FIGS. 1, 2, and 4, the power tool 1 includes a motor 2, an output shaft 6, a transmission mechanism 3, a bearing (first bearing) 8A, a cover 10B, a regulation structure H0, a housing 10A, an inertia body 4, a switch 13, a control unit 7, and a storage unit 9. The power tool 1 further includes a second bearing 8B that rotatably supports the output shaft 6 and is housed in the cover 10B.

[0022] The housing 10A has a body portion 101, a grip portion 102, and a mounting portion 103. The shape of the body portion 101 is cylindrical with a bottom at the rear end.

[0023] The fuselage section 101 houses the motor 2, the transmission mechanism 3, the first bearing 8A, and the second bearing 8B. More specifically, the fuselage section 101 houses the cover 10B, and the transmission mechanism 3, the first bearing 8A, and the second bearing 8B are housed in the cover 10B.

[0024] The grip section 102 protrudes downward from the body section 101. The grip section 102 houses the control unit 7.

[0025] The mounting section 103 is located at the tip (lower end) of the grip section 102. In other words, the body section 101 and the mounting section 103 are connected by the grip section 102. The mounting section 103 is configured so that the battery pack 14 can be detachably attached to it.

[0026] A rechargeable battery pack 14 is detachably attached to the power tool 1. In this embodiment, the power tool 1 operates using the battery pack 14 as a power source. That is, the battery pack 14 is a power supply unit 14A that supplies current to drive the motor 2. The battery pack 14 is not a component of the power tool 1. However, the power tool 1 may include the battery pack 14. The battery pack 14 comprises a battery pack configured by connecting a plurality of secondary batteries (e.g., lithium-ion batteries) in series, and a case that houses the battery pack.

[0027] Motor 2 is the power source in the power tool 1. Motor 2 is, for example, a brushless motor. In particular, motor 2 in this embodiment is a synchronous motor, and more specifically, a permanent magnet synchronous motor (PMSM). Motor 2 comprises a rotor equipped with permanent magnets and a stator equipped with armature windings for three phases (U phase, V phase, and W phase). The rotor of motor 2 has a drive shaft 21. Motor 2 converts the power supplied from the battery pack 14 into torque for the drive shaft 21.

[0028] As shown in Figures 1 and 2, a tip tool 11, such as a driver bit, is connected to the front end of the output shaft 6 by a mounting part 12. In other words, as the output shaft 6 rotates, the tip tool 11 rotates as well. When the tip tool 11, which is a driver bit, is attached to the front end of the output shaft 6, the rotation of the tip tool 11 while it is set on a workpiece such as a screw makes it possible to tighten or loosen the workpiece against the mating member.

[0029] The mounting portion 12 and the tip tool 11 are not components of the power tool 1. However, the power tool 1 may include at least one of the mounting portion 12 and the tip tool 11.

[0030] The transmission mechanism 3 is positioned in front of the motor 2. The drive shaft 21 and output shaft 6 of the motor 2 are mechanically connected to the transmission mechanism 3. The transmission mechanism 3 transmits the torque of the motor 2 to the output shaft 6.

[0031] As shown in Figures 1, 3, 5, and 6, the transmission mechanism 3 of this embodiment includes a first reduction mechanism 3A, a second reduction mechanism 3B, and a third reduction mechanism 3C.

[0032] The first reduction mechanism 3A, the second reduction mechanism 3B, and the third reduction mechanism 3C are each planetary gear mechanisms that convert the rotational speed and torque of the drive shaft 21 of the motor 2 to the rotational speed and torque required for the work on the workpiece (for example, screw-driving operation). The first reduction mechanism 3A, the second reduction mechanism 3B, and the third reduction mechanism 3C are arranged from front to back in the order of third reduction mechanism 3C, second reduction mechanism 3B, and first reduction mechanism 3A.

[0033] The first reduction gear 3A includes a first sun gear 31A, a plurality (e.g., three) first planetary gears 32A, a first internal gear 33A, and a first carrier 34A, as shown in Figures 1, 3, 5, and 6. The first sun gear 31A is coupled to the drive shaft 21 of the motor 2, as shown in Figure 1. The three first planetary gears 32A are arranged around the first sun gear 31A and mesh with the first sun gear 31A. The first internal gear 33A is arranged around the three first planetary gears 32A and meshes with the three first planetary gears 32A. The first carrier 34A supports the rotation axis 35A of each of the three first planetary gears 32A. In detail, the first carrier 34A rotatably supports each of the three first planetary gears 32A relative to the first carrier 34A. In this case, the first carrier 34A supports the rotating shaft 35A so that it can rotate relative to the first carrier 34A. In this case, the rotating shaft 35A is fixed to the first planetary gear 32A. Alternatively, the rotating shaft 35A may be fixed to the first carrier 34A. In this case, the rotating shaft 35A is supported so that it can rotate relative to the first planetary gear 32A. In this way, the first reduction mechanism 3A converts the rotation of the drive shaft 21 into the rotation of the first carrier 34A.

[0034] The second reduction gear 3B, as shown in Figures 1, 3, 5, and 6, includes a second sun gear 31B, a plurality (e.g., three) second planetary gears 32B, a second internal gear 33B, and a second carrier 34B. The second sun gear 31B is formed integrally with the first carrier 34A, as shown in Figures 3 and 5. That is, the first carrier 34A and the second sun gear 31B rotate together. The three second planetary gears 32B are arranged around the second sun gear 31B and mesh with it. The second internal gear 33B is arranged around the three second planetary gears 32B and meshes with them. The second carrier 34B supports the rotation axis 35B of each of the three second planetary gears 32B. In detail, the second carrier 34B is rotatably supported by each of the three second planetary gears 32B relative to the second carrier 34B. That is, the second reduction mechanism 3B converts the rotation of the first carrier 34A into the rotation of the second carrier 34B.

[0035] The third reduction mechanism 3C, as shown in Figures 1, 3, 5, and 6, includes a third sun gear 31C, a plurality (e.g., five) third planetary gears 32C, a third internal gear 33C, and a third carrier 34C. The third sun gear 31C is formed integrally with the second carrier 34B, as shown in Figures 3 and 5, and the second carrier 34B and the third sun gear 31C rotate together. In other words, the third sun gear 31C rotates due to power from the motor 2 via the first reduction mechanism 3A and the second reduction mechanism 3B. The five third planetary gears 32C are arranged around the third sun gear 31C and mesh with it. The third internal gear 33C is arranged around the five third planetary gears 32C and meshes with them. The third carrier 34C supports the rotation axis 35C of each of the five third planetary gears 32C. More specifically, the third carrier 34C rotatably supports each of the five third planetary gears 32C relative to the third carrier 34C. Specifically, the third carrier 34C has an annular disc portion 36 and a hollow cylindrical portion 37 projecting forward from the disc portion 36, with the disc portion 36 rotatably supporting the rotation axis 35C of each of the five third planetary gears 32C. Furthermore, the engagement hole 38 (see Figure 5, etc.) provided in the center of the cylindrical portion 37 and the output shaft 6 are combined in such a way that, in the circumferential direction, a projection on one side engages with a recess on the other side, thereby restricting the rotation of the cylindrical portion 37 relative to the output shaft 6 in the circumferential direction. In addition, the engagement hole 38 and the output shaft 6 are fitted together by clearance fitting. That is, the output shaft 6 and the transmission mechanism 3 are engaged by clearance fitting. In other words, the output shaft 6 is engaged with the third carrier 34C in a way that does not transmit the force transmitted to the output shaft 6 along the axial direction to the third carrier 34C. Furthermore, because the output shaft 6 is engaged with the third carrier 34C in a way that restricts its rotation relative to the third carrier 34C, the output shaft 6 rotates together with the third carrier 34C. That is, the third reduction mechanism 3C converts the rotation of the second carrier 34B into the rotation of the output shaft 6.

[0036] The first bearing 8A is housed at the tip of the cover 10B and rotatably supports the output shaft 6. The first bearing 8A is, for example, a hollow cylindrical ball bearing and, as shown in Figure 3, has an outer ring 81A, an inner ring 82A, and spherical rolling elements. The first bearing 8A rotatably supports the output shaft 6 by the inner ring 82A with the outer ring 81A held by the cover 10B. The first bearing 8A also has a first end face S1 and a second end face S2 that face each other in the axial direction (front-rear direction) of the output shaft 6. The first end face S1 is the end face on the motor 2 side, and the second end face S2 is the end face on the tip tool 11 side. The first bearing 8A is provided such that the first end face S1 is spaced apart from the third carrier 34C in the front-rear direction.

[0037] Here, the cover 10B is provided with a first retaining portion H1 that contacts at least a part of the first end face S1. The first retaining portion H1 is, for example, an annular portion that protrudes inward from the inner wall of the cover 10B. The first end face S1 and the first retaining portion H1 are in contact in the front-rear direction. Note that the first retaining portion H1 is not limited to an annular shape, but may be a protruding portion or the like.

[0038] Furthermore, the output shaft 6 is provided with a second retaining portion H2 that contacts at least a part of the second end face S2. The second retaining portion H2 is, for example, an annular portion that protrudes outward from the surface of the output shaft 6. The second end face S2 and the second retaining portion H2 are in contact in the front-rear direction. Note that the second retaining portion H2 is not limited to an annular shape, but may be a protruding portion or the like.

[0039] Thus, the first bearing 8A is sandwiched between the first holding part H1 and the second holding part H2 in the front-rear direction, and its movement in the front-rear direction is restricted. In other words, the first holding part H1 and the second holding part H2 constitute a restricting structure H0 that restricts the movement of the first bearing 8A in the axial direction (front-rear direction) of the output shaft 6.

[0040] The second bearing 8B is housed in the cover 10B behind the first bearing 8A and the first retaining portion H1, and rotatably supports the output shaft 6. Here, as shown in Figure 3, the tip tool 11 is attached to the output shaft 6 by the mounting portion 12 in front of the first bearing 8A. Therefore, the first bearing 8A is positioned between the second bearing 8B and the tip tool 11.

[0041] The second bearing 8B is, for example, a hollow cylindrical ball bearing, and as shown in Figure 3, has an outer ring 81B, an inner ring 82B, and spherical rolling elements. The second bearing 8B holds the cylindrical portion 37 of the third carrier 34C by the inner ring 82B, with the outer ring 81B held by the cover 10B. Here, the cylindrical portion 37 and the output shaft 6 are engaged. Therefore, the second bearing 8B is positioned to contact the third carrier 34C and the cover 10B at the engagement portion between the third carrier 34C and the output shaft 6. In other words, the second bearing 8B is positioned to contact the transmission mechanism 3 and the cover 10B at the engagement portion between the transmission mechanism 3 and the output shaft 6.

[0042] As shown in Figure 1, the inertial body 4 is positioned between the first reduction mechanism 3A and the motor 2. Specifically, the inertial body 4 is positioned in front of the motor 2 and behind the first reduction mechanism 3A. The inertial body 4 is mechanically connected to the drive shaft 21 and rotates together with the drive shaft 21. The inertial body 4 is a so-called flywheel and increases the inertial force of the torque of the motor 2 (drive shaft 21).

[0043] As shown in Figure 1, the switch 13 protrudes forward from the grip portion 102. The switch 13 is an operating part that receives operations performed by the user to control the motor 2. Specifically, the operator can switch the motor 2 on or off by pulling the switch 13. Furthermore, the amount the switch 13 is pulled can be used to adjust the rotation speed of the drive shaft 21; for example, the greater the amount the switch 13 is pulled, the faster the rotation speed of the drive shaft 21 becomes.

[0044] The memory unit 9 consists of ROM (Read Only Memory), RAM (Random Access Memory), EEPROM (Electrically Erasable Programmable Read Only Memory), etc. The memory unit 9 stores the control program executed by the control unit 7. The memory unit 9 also stores the tightening torque setting value (set torque), etc.

[0045] The control unit 7 includes a computer system having one or more processors and memory. At least some of the functions of the control unit 7 are realized by the computer system's processor executing a program recorded in the computer system's memory. The program may be recorded in memory, provided via a telecommunication line such as the Internet, or provided on a non-temporary recording medium such as a memory card.

[0046] As shown in Figure 4, the control unit 7 includes an acquisition unit 71 and a drive control unit 72. Note that the acquisition unit 71 and the drive control unit 72 do not necessarily represent actual physical configurations, but rather represent functions realized by the control unit 7.

[0047] The acquisition unit 71 acquires a torque value related to the output torque output by the tip tool 11 based on the amount of current flowing through the motor 2.

[0048] The drive control unit 72 controls the motor 2. The drive control unit 72 controls the motor 2, for example, using 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 may use a control method other than vector control.

[0049] The drive control unit 72 controls the motor 2 so that the torque value measured by the acquisition unit 71 matches the set torque stored in the storage unit 9 beforehand. For example, when the error between the torque value detected by the acquisition unit 71 and the set torque falls within a predetermined tolerance range (for example, ±20% of the set torque), the drive control unit 72 controls the motor 2 to stop the rotation of the drive shaft 21.

[0050] (3) Advantages In this embodiment, the power tool 1 performs work by pressing the tip tool against the workpiece (e.g., a screw). As shown in Figure 3, a thrust load F1 along the axial direction (front-rear direction) of the output shaft 6 is applied as a reaction force from the workpiece to the tip tool 11 and the output shaft 6 connected to the tip tool 11. As described above, the power tool 1 has a restricting structure H0 (first holding part H1 and second holding part H2) that clamps the first bearing 8A in the front-rear direction. As a result, the thrust load F1 applied to the output shaft 6 along the axial direction is transmitted from the second holding part H2 provided on the output shaft 6 to the second end face S2 of the first bearing 8A. The thrust load F1 transmitted to the second end face S2 is then transmitted as a force F2 from the first end face S1 to the first holding part H1 provided on the cover 10B. In other words, the thrust load F1 applied to the output shaft 6 is distributed into force F2. This suppresses eccentricity of the output shaft 6 and stabilizes the work performed by the power tool 1.

[0051] Furthermore, the transmission mechanism 3 is housed in the cover 10B so that forces along the front-rear direction are not transmitted from the cover 10B. Therefore, the thrust load F1 transmitted to the first holding part H1 is not transmitted to the third carrier 34C of the transmission mechanism 3. Also, since the engagement hole 38 of the output shaft 6 and the third carrier 34C are engaged by clearance fitting, the thrust load F1 applied to the output shaft 6 is not transmitted to the cylindrical part 37 of the third carrier 34C. Moreover, since the first bearing 8A and the third carrier 34C are spaced apart in the front-rear direction, the first bearing 8A and the third carrier 34C do not come into contact, for example, when the first holding part H1 is deformed by the thrust load F1 transmitted from the first end face S1. As a result, the thrust load F1 transmitted to the first bearing 8A is not transmitted from the first bearing 8A to the third carrier 34C.

[0052] As a result, even if a thrust load F1 in the longitudinal direction is applied to the transmission mechanism 3, the generation of frictional force between the multiple gears included in the transmission mechanism 3 can be suppressed, and the torque value acquired by the acquisition unit 71 can be stabilized. In particular, the acquisition unit 71 can stabilize the torque value by preventing the detection of changes in the amount of current flowing to the motor 2 caused by frictional force in the transmission mechanism 3.

[0053] The effect of torque value stabilization by the regulating structure H0 will be explained below with reference to Figures 7 and 8. The vertical axis of Figure 7 shows the torque value when a thrust load F1 is applied to the output shaft of a comparative example power tool that does not have the regulating structure H0. The vertical axis of Figure 8 shows the torque value when a thrust load F1 is applied to the output shaft of power tool 1 of this embodiment that has the regulating structure H0. As shown in Figures 7 and 8, in power tool 1 of this embodiment, the variation in torque value is smaller compared to the power tool of comparative example 1, and all torque values ​​shown in Figure 8 fall within the standard range.

[0054] Furthermore, when working on an object (e.g., a screw) with the power tool 1 of this embodiment, a force (radial load) F3 (see Figure 9) along a direction intersecting the axial direction of the output shaft 6 may be applied to the tip tool 11 and the output shaft 6, for example, by the movements of the worker holding the power tool 1. As described above, the power tool 1 is equipped with a second bearing 8B that is positioned to contact the transmission mechanism 3 and the cover 10B at the engagement portion between the transmission mechanism 3 and the output shaft 6. More specifically, the second bearing 8B is positioned such that, when viewed from a direction intersecting the axial direction of the output shaft 6, at least a part of the output shaft 6, at least a part of the third carrier 34C, and at least a part of the second bearing 8B overlap. That is, the output shaft 6 is supported by the second bearing 8B via the third carrier 34C, and further supported by the cover 10B which is in contact with the second bearing 8B.

[0055] As a result, even when a radial load F3 is applied to the output shaft 6, the cover 10B can receive the radial load F3 applied to the output shaft 6, thereby reducing the external force applied to the transmission mechanism 3 by the radial load F3. Therefore, the generation of frictional force between the multiple gears included in the transmission mechanism 3 can be suppressed, and the torque value acquired by the acquisition unit 71 can be stabilized.

[0056] The effect of torque value stabilization by the second bearing 8B will be explained below with reference to Figures 10 and 11. The vertical axis of Figure 10 shows the torque value when a radial load F3 is applied to the output shaft of the power tool of Comparative Example 2, which does not have the second bearing 8B. The vertical axis of Figure 11 shows the torque value when a radial load F3 is applied to the output shaft 6 of the power tool 1 of this embodiment, which has the second bearing 8B. As shown in Figures 10 and 11, the variation in torque values ​​in the power tool 1 of this embodiment is smaller compared to the power tool of Comparative Example 2, and all torque values ​​shown in Figure 11 are within the standard range.

[0057] Thus, the power tool 1 of this embodiment makes it possible to stabilize the work.

[0058] (4) Variations The above embodiments are merely one of many embodiments of this disclosure. The above embodiments can be modified in various ways depending on the design, etc., as long as they achieve the objectives of this disclosure.

[0059] The following lists some modifications of the above embodiment. The modifications described below can be combined and applied as appropriate.

[0060] The power tool 1 in this disclosure includes a computer system in its control unit 7. The computer system mainly consists of a processor and memory as hardware. The function of the control unit 7 in this disclosure is realized by the processor executing a program recorded in the memory of the computer system. The program may be pre-recorded in the memory of the computer system, provided via a telecommunications line, or provided on a non-temporary recording medium such as a memory card, optical disk, or hard disk drive that can be read by the computer system. The processor of the computer system consists of one or more electronic circuits including semiconductor integrated circuits (ICs) or large-scale integrated circuits (LSIs). The integrated circuits referred to here, such as ICs or LSIs, are named differently depending on the degree of integration. Integrated circuits such as ICs or LSIs include integrated circuits called system LSIs, VLSIs (Very Large Scale Integration), or ULSIs (Ultra Large Scale Integration). Furthermore, FPGAs (Field-Programmable Gate Arrays) that are programmed after the manufacture of the LSI, or logic devices that can reconfigure the junction relationships or circuit compartments inside the LSI, can also be used as processors. Multiple electronic circuits may be integrated onto a single chip or distributed across multiple chips. Multiple chips may be integrated onto a single device or distributed across multiple devices. The computer system referred to here includes a microcontroller having one or more processors and one or more memories. Therefore, the microcontroller also consists of one or more electronic circuits, including semiconductor integrated circuits or large-scale integrated circuits.

[0061] The power tool 1 may have a socket attached as the tool tip 11 instead of a driver bit. Furthermore, the power tool 1 is not limited to a configuration that uses a battery pack 14 as a power source, but may also use an AC power source (commercial power source) as a power source.

[0062] (5) Summary As described above, the power tool (1) of the first embodiment comprises a motor (2), an output shaft (6), a transmission mechanism (3), a first bearing (8A) and a second bearing (8B), and a cover (10B). The output shaft (6) is connected to the cutting tool (11). The transmission mechanism (3) engages with the output shaft (6) and transmits the torque of the motor (2) to the output shaft (6). The first bearing (8A) and the second bearing (8B) rotatably support the output shaft (6). The cover (10B) houses the motor (2), the transmission mechanism (3), the first bearing (8A), and the second bearing (8B). The first bearing (8A) is positioned between the second bearing (8B) and the cutting tool (11). The second bearing (8B) is positioned to contact the transmission mechanism (3) and the cover (10B) at the engagement portion between the transmission mechanism (3) and the output shaft (6).

[0063] In this embodiment, the output shaft (6) is supported by the second bearing (8B) and the cover (10B) that contacts the second bearing (8B) via the transmission mechanism (3). This makes it possible to suppress eccentricity of the output shaft (6) when a force (F3) is applied to the output shaft (6) in a direction intersecting the axial direction of the output shaft (6), thereby stabilizing the work performed by the power tool (1).

[0064] The power tool (1) in the second embodiment further comprises an acquisition unit (71) that acquires a torque value related to the output torque output by the tip tool (11) based on the current flowing through the motor (2).

[0065] According to this embodiment, by comparing the torque value acquired by the acquisition unit (71) with a preset torque, work can be performed on the work object with an appropriate torque.

[0066] In the third embodiment of the power tool (1), in the first or second embodiment, the transmission mechanism (3) includes a sun gear (31C), a plurality of planetary gears (32C), an internal gear (33C), and a carrier (34C). The sun gear (31C) is rotated by power from a motor (2). The plurality of planetary gears (32C) are arranged around the sun gear (31C) and mesh with the sun gear (31C). The internal gear (33C) is arranged around the plurality of planetary gears (32C) and meshes with the plurality of planetary gears (32C). The carrier (34C) engages with the output shaft (6) and rotatably supports each of the plurality of planetary gears (32C). A second bearing (8B) is positioned to contact the carrier (34C) and the cover (10B) at the engagement portion between the carrier (34C) and the output shaft (6).

[0067] In this embodiment, the output shaft (6) is supported by a second bearing (8B) and a cover (10B) that contacts the second bearing (8B) via a carrier (34C). This makes it possible to suppress eccentricity of the output shaft (6) when a force (F3) is applied to the output shaft (6) in a direction intersecting the axial direction of the output shaft (6), thereby stabilizing the operation by the power tool (1).

[0068] In the fourth embodiment of the power tool (1), as in the third embodiment, at least a portion of the output shaft (6), at least a portion of the carrier (34C), and at least a portion of the second bearing (8B) are arranged to overlap when viewed from a direction intersecting the axial direction of the output shaft (6).

[0069] In this embodiment, the output shaft (6) is supported by a second bearing (8B) and a cover (10B) that contacts the second bearing (8B) via a carrier (34C). This makes it possible to suppress eccentricity of the output shaft (6) when a force (F3) is applied to the output shaft (6) in a direction intersecting the axial direction of the output shaft (6), thereby stabilizing the operation by the power tool (1).

[0070] Furthermore, the second to fourth embodiments are not essential components of the power tool (1) and can be omitted as appropriate. [Explanation of symbols]

[0071] 1 Power tools 2 motors 6 Output shaft 3. Transmission mechanism 31C Sun Gear 32C Planetary Gear 33C Internal gear 34C Carrier 8A bearing 10B Cover 11 Tip tools 71 Acquisition Department 8B Second bearing F3 Power

Claims

1. Motor and, The output shaft connected to the tip tool, A transmission mechanism that engages with the output shaft and transmits the torque of the motor to the output shaft, The output shaft is rotatably supported by a first bearing and a second bearing, The system comprises the motor, the transmission mechanism, the first bearing, and the second bearing, and a cover that houses them. The first bearing is positioned between the second bearing and the tip tool. The second bearing is positioned to contact the transmission mechanism and the cover at the engagement portion between the transmission mechanism and the output shaft. The aforementioned transmission mechanism is A sun gear that rotates by power from the aforementioned motor, A plurality of planetary gears are arranged around the aforementioned sun gear and mesh with the sun gear, An internal gear is arranged around the plurality of planetary gears and meshes with the plurality of planetary gears, It has a carrier that engages with the output shaft and rotatably supports each of the plurality of planetary gears, The second bearing is positioned to contact the carrier and the cover at the engagement portion between the carrier and the output shaft. Power tools.

2. The system further includes an acquisition unit that acquires a torque value related to the output torque output by the tip tool based on the current flowing through the motor. The power tool according to claim 1.

3. When viewed from a direction intersecting the axial direction of the output shaft, at least a portion of the output shaft, at least a portion of the carrier, and at least a portion of the second bearing are arranged to overlap. The power tool according to claim 1 or 2.

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