Electric tool

Abstract

According to the invention, the problem of work stabilization is solved. An electric power tool (1) is provided with a motor (2), an output shaft (6), a transmission mechanism (3), a first bearing (8A), a second bearing (8B), and a cover (10B). The output shaft (6) is coupled to the end tool (11). The transmission mechanism (3) is engaged with the output shaft (6) to transmit the torque generated by 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) accommodates the motor (2), the transmission mechanism (3), the first bearing (8A), and the second bearing (8B). The first bearing (8A) is arranged between the second bearing (8B) and the end tool (11). The second bearing (8B) is disposed at a portion where the transmission mechanism (3) is engaged with the output shaft (6) so as to be in contact with the transmission mechanism (3) and the cover (10B).

Description

Technical Field

[0001] The present disclosure relates generally to power tools, and more particularly to power tools including motors. Background Art

[0002] Patent document 1 discloses a portable electric tool. The portable electric tool includes: an electric motor as a driving source; a speed reduction mechanism for transmitting the rotational power generated by the electric motor; a drive unit for transmitting the rotational power from the speed reduction mechanism to the end tool; a body case for accommodating a bearing for rotatably holding the drive unit; and a handle case for accommodating a switch unit for controlling the power supply to the electric motor.

[0003] In a portable electric tool (electric tool) such as the portable electric tool disclosed in Patent Document 1, application of a radial load from a working object of the electric tool to the end tool and the drive unit may cause instability in the operation being performed.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2009-28840 Summary of the invention

[0007] In view of the foregoing background, it is therefore an object of the present disclosure to provide a power tool that helps stabilize the operation being performed.

[0008] An electric tool according to one aspect of the present disclosure includes a motor, an output shaft, a transmission mechanism, a first bearing, a second bearing, and a cover. The output shaft is coupled to an end tool. The transmission mechanism engages with the output shaft to transmit the torque generated by the motor to the output shaft. The first bearing and the second bearing are configured to rotatably support the output shaft. The cover accommodates the motor, the transmission mechanism, the first bearing, and the second bearing. The first bearing is between the second bearing and the end tool. The second bearing is configured to contact the transmission mechanism and the cover in the area where the transmission mechanism engages with the output shaft. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] [ Figure 1 ] Figure 1 is a cross-sectional view of an electric power tool according to an exemplary embodiment.

[0010] [ Figure 2 ] Figure 2 It is a perspective view illustrating the appearance of the electric tool.

[0011] [ Figure 3 ] Figure 3It is a cross-sectional view of the main parts of the power tool.

[0012] [ Figure 4 ] Figure 4 It is a block diagram of a power tool.

[0013] [ Figure 5 ] Figure 5 It is an exploded perspective view of a transmission mechanism included in the electric power tool when viewed from the front of the transmission mechanism.

[0014] [ Figure 6 ] Figure 6 is an exploded perspective view of a transmission mechanism included in an electric power tool when viewed from the rear of the transmission mechanism.

[0015] [ Figure 7 ] Figure 7 is a diagram illustrating how an adjustment structure provided for an electric power tool achieves the effect of a stable torque value.

[0016] [ Figure 8 ] Figure 8 is a diagram illustrating how an adjustment structure provided for an electric power tool achieves the effect of a stable torque value.

[0017] [ Fig. 9 ] Fig. 9 It is a cross-sectional view of the main parts of the power tool.

[0018] [ Fig.10 ] Fig.10 is a diagram illustrating the effect of how a second bearing provided for an electric power tool achieves a stable torque value.

[0019] [ Fig.11 ] Fig.11 is a diagram illustrating the effect of how a second bearing provided for an electric power tool achieves a stable torque value. DETAILED DESCRIPTION

[0020] The electric tool 1 according to an exemplary embodiment of the present disclosure will now be described in detail with reference to the accompanying drawings. It should be noted that the embodiments and modifications thereof to be described below are merely exemplary embodiments and modifications thereof of various embodiments of the present disclosure and should not be construed as restrictive. More specifically, the exemplary embodiments and modifications thereof can be easily changed in various ways based on design choices or any other factors without departing from the true spirit and scope of the present disclosure. The drawings mentioned in the following description of the embodiments are all schematic representations. Therefore, the proportions of the sizes (including thickness) of the various constituent elements shown in the drawings do not always reflect their actual size proportions. The arrows indicating various directions in the drawings are only examples and should not be construed as limiting the direction in which the electric tool 1 is used. In addition, the arrows indicating various directions in the drawings are merely shown in the drawings for illustration purposes only and are not physical arrows.

[0021] (1) Summary

[0022] First, refer to Figure 1 , Figure 2 and Fig. 9 An overview of an electric power tool 1 according to the exemplary embodiment will be described.

[0023] like Figure 1 As shown, the electric tool 1 according to the present embodiment 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.

[0024] The output shaft 6 is coupled to an end tool 11 such as a screwdriver bit for fastening a fastening member such as a screw or a bolt.

[0025] The transmission mechanism 3 engages with the output shaft 6 , and transmits the torque generated by the motor 2 to the output shaft 6 .

[0026] The first bearing 8A and the second bearing 8B rotatably support the output shaft 6 .

[0027] The cover 10B accommodates the motor 2 , the transmission mechanism 3 , the first bearing 8A, and the second bearing 8B.

[0028] The first bearing 8A is located between the second bearing 8B and the end tool 11 .

[0029] The second bearing 8B is arranged to be in contact with the transmission mechanism 3 and the cover 10B in a region where the transmission mechanism 3 engages with the output shaft 6 .

[0030] In the electric tool 1 according to the present embodiment, as Fig. 9As shown, the output shaft 6 is supported not only by the second bearing 8B but also by the cover 10B in contact with the second bearing 8B via the transmission mechanism 3. When a force (radial load) F3 is applied to the output shaft 6 in a direction intersecting the axis of the output shaft 6, this allows the cover 10B to receive the force F3, thereby reducing the degree of eccentricity of the output shaft 6, thereby helping to stabilize the operation being performed by the electric tool 1.

[0031] (2) Structure of power tools

[0032] Next, the configuration of the electric power tool 1 according to the present embodiment will be described in detail.

[0033] In the following instructions, Figure 1 As shown in other drawings, the direction from the motor 2 along the axis of the output shaft 6 to the output shaft 6 is defined as the "forward direction" herein, and the direction from the output shaft 6 along the axis of the output shaft 6 to the motor 2 is defined as the "rearward direction" herein. In addition, the direction from the handle 102 to the carcass 101 perpendicular to the front-to-back direction is defined as the "upward direction" herein, and the direction from the carcass 101 to the handle 102 perpendicular to the front-to-back direction is defined as the "downward direction" herein.

[0034] The electric tool 1 is a portable electric tool (such as a screwdriver bit) that can be held by an operator with one hand. Figure 1 , Figure 2 and Figure 4 As shown, the electric tool 1 includes a motor 2, an output shaft 6, a transmission mechanism 3, a bearing (first bearing) 8A, a cover 10B, an adjustment structure H0, a housing 10A, an inertial body 4, a switch 13, a control unit 7 and a storage unit 9. In addition, the electric tool 1 also includes a second bearing 8B housed in the cover 10B to rotatably support the output shaft 6.

[0035] The housing 10A includes a body portion 101, a handle 102, and an attachment portion 103. The body portion 101 is formed in a cylindrical shape with a bottom at the rear end.

[0036] The motor 2, the transmission mechanism 3, the first bearing 8A, and the second bearing 8B are housed in the body portion 101. More specifically, the body portion 101 houses the cover 10B and the transmission mechanism 3, and the first bearing 8A and the second bearing 8B are housed in the cover 10B.

[0037] The handle 102 protrudes downward from the body portion 101. The control unit 7 is accommodated in the handle 102.

[0038] The attachment portion 103 is provided at the end (ie, the bottom) of the handle 102. In other words, the carcass portion 101 and the attachment portion 103 are coupled to each other via the handle 102. The battery pack 14 is removably attached to the attachment portion 103.

[0039] The rechargeable battery pack 14 is removably attached to the power tool 1. The power tool 1 according to the present embodiment is powered by the battery pack 14 as a power source. That is, the battery pack 14 is a power source 14A that supplies current for driving the motor 2. In the present embodiment, the battery pack 14 is not a constituent element of the power tool 1. However, this is merely an example and should not be construed as limiting. Alternatively, the power tool 1 may include the battery pack 14 as one of its constituent elements. The battery pack 14 includes an assembled battery formed by connecting a plurality of secondary batteries (such as lithium-ion batteries) in series and a shell that accommodates the assembled battery therein.

[0040] The motor 2 is the power source of the electric tool 1. For example, the motor 2 may be a brushless motor. In particular, the motor 2 according to the present embodiment is a synchronous motor. More specifically, the motor 2 may be a permanent magnet synchronous motor (PMSM). The motor 2 includes: a rotor having a permanent magnet; a stator having a three-phase (i.e., U-phase, V-phase, and W-phase) armature winding. The rotor of the motor 2 has a drive shaft 21. The motor 2 converts the power supplied by the battery pack 14 into torque of the drive shaft 21.

[0041] like Figure 1 and Figure 2 As shown, an end tool 11 such as a screwdriver bit is coupled to the front end of the output shaft 6 via a chuck 12. That is, when the output shaft 6 rotates, the end tool 11 rotates. If the end tool 11 as a screwdriver bit is attached to the front end of the output shaft 6, rotating the end tool 11 set in place on a work object such as a screw allows an operation of tightening or loosening the work object relative to the workpiece to be performed.

[0042] In the present embodiment, neither the chuck 12 nor the end tool 11 is a constituent element of the electric tool 1 . However, this is merely an example and should not be construed as limiting. Alternatively, the electric tool 1 may include at least one of the chuck 12 or the end tool 11 .

[0043] The transmission mechanism 3 is arranged in front of the motor 2. The drive shaft 21 and the 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.

[0044] According to this embodiment, the transmission mechanism 3 includes: Figure 1 , Figure 3 , Figure 5 and Figure 6 The first reduction mechanism 3A, the second reduction mechanism 3B and the third reduction mechanism 3C are shown.

[0045] Each of the first reduction mechanism 3A, the second reduction mechanism 3B, and the third reduction mechanism 3C is a planetary gear mechanism for converting the rotation speed and torque of the drive shaft 21 of the motor 2 into the rotation speed and torque required for operating the working object (such as the operation of turning a screw, etc.). The third reduction mechanism 3C, the second reduction mechanism 3B, and the first reduction mechanism 3A are arranged in sequence from the front end to the rear end of the electric tool 1.

[0046] like Figure 1 , Figure 3 , Figure 5 and Figure 6 As shown, the first reduction mechanism 3A includes a first sun gear 31A, a plurality of (for example, three) first planetary gears 32A, a first internal gear 33A, and a first carrier 34A. Figure 1 As shown, the first sun gear 31A is coupled to the drive shaft 21 of the motor 2. Three first planetary gears 32A are arranged around the first sun gear 31A to mesh with the first sun gear 31A. The first internal gear 33A is arranged around the three first planetary gears 32A to mesh with the three first planetary gears 32A. The first carrier 34A supports the rotation shaft 35A of each of the three first planetary gears 32A. Specifically, the first carrier 34A supports the three first planetary gears 32A so that each of the three first planetary gears 32A is rotatable relative to the first carrier 34A. Specifically, the first carrier 34A supports each rotation shaft 35A in a manner that each rotation shaft 35A is rotatable relative to the first carrier 34A itself. In this case, each rotation shaft 35A is fixed to a corresponding one of the first planetary gears 32A. Alternatively, the rotation shaft 35A may be fixed to the first carrier 34A. In this case, the rotation shaft 35A will be supported in a rotatable manner 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.

[0047] like Figure 1 , Figure 3 , Figure 5 and Figure 6 As shown, the second speed reduction mechanism 3B includes a second sun gear 31B, a plurality of (for example, three) second planetary gears 32B, a second internal gear 33B, and a second carrier 34B. Figure 3 and Figure 5As shown, the second sun gear 31B is formed integrally with the first carrier 34A. That is, the first carrier 34A and the second sun gear 31B rotate integrally with each other. The three second planetary gears 32B are arranged around the second sun gear 31B to mesh with the second sun gear 31B. The second internal gear 33B is arranged around the three second planetary gears 32B to mesh with the three second planetary gears 32B. The second carrier 34B supports the rotation shaft 35B of each of the three second planetary gears 32B. Specifically, the second carrier 34B supports the three second planetary gears 32B in a manner that each of the three second planetary gears 32B is rotatable relative to the second carrier 34B itself. That is, the second reduction mechanism 3B converts the rotation of the first carrier 34A into the rotation of the second carrier 34B.

[0048] like Figure 1 , Figure 3 , Figure 5 and Figure 6 As shown, the third reduction mechanism 3C includes a third sun gear 31C, a plurality of (for example, five) third planetary gears 32C, a third internal gear 33C, and a third carrier 34C. Figure 3 and Figure 5 As shown, the third sun gear 31C is formed integrally with the second carrier 34B. The second carrier 34B and the third sun gear 31C rotate integrally with each other. That is, the third sun gear 31C is rotated by the power supplied by the motor 2 via the first reduction mechanism 3A and the second reduction mechanism 3B. Five third planetary gears 32C are arranged around the third sun gear 31C to mesh with the third sun gear 31C. The third internal gear 33C is arranged around the five third planetary gears 32C to mesh with the five third planetary gears 32C. The third carrier 34C supports the rotation shaft 35C of each of the five third planetary gears 32C. Specifically, the third carrier 34C supports the five third planetary gears 32C in a manner that each of the five third planetary gears 32C is rotatable relative to the third carrier 34C itself. More specifically, the third carrier 34C includes a circular ring disk portion 36 and a hollow cylinder portion 37 protruding forward from the disk portion 36. The rotation shaft 35C of each of the five third planetary gears 32C is rotatably supported by the disk portion 36. In addition, by engaging the protrusion provided for one selected from the output shaft 6 and the engaging hole 38 with the recess provided for the other in the circumferential direction, the output shaft 6 and the engaging hole 38 provided as the center hole for the cylinder 37 (see Figure 5and other figures) are combined with each other to adjust the rotation of the barrel 37 relative to the output shaft 6 in the circumferential direction. In addition, the engagement hole 38 and the output shaft 6 are matched with each other by a clearance fit. That is, the output shaft 6 and the transmission mechanism 3 are engaged with each other by a clearance fit. In other words, the output shaft 6 is engaged with the third carrier 34C to prevent the force transmitted to the output shaft 6 in the axial direction from being transmitted to the third carrier 34C. In addition, the output shaft 6 is engaged with the third carrier 34C when its rotation relative to the third carrier 34C is adjusted. Therefore, the output shaft 6 rotates integrally with the third carrier 34. That is, the third reduction mechanism 3C converts the rotation of the second carrier 34B into the rotation of the output shaft 6.

[0049] The first bearing 8A is housed in the distal end portion of the cover 10B and rotatably supports the output shaft 6. The first bearing 8A may be, for example, a hollow cylindrical ball bearing. Figure 3 As shown, the first bearing 8A includes an outer ring 81A, an inner ring 82A and a spherical rolling element. The first bearing 8A allows the inner ring 82A to rotatably support the output shaft 6 when the outer ring 81A is held by the cover 10B. In addition, the first bearing 8A also has a first end face S1 and a second end face S2 that are opposite to each other along the axis (i.e., the front-to-back direction) of the output shaft 6. The first end face S1 is an end face facing the motor 2. The second end face S2 is an end face facing the end tool 11. The first bearing 8A is provided with a first end face S1 that is kept out of contact with the third carrier 34C in the front-to-back direction.

[0050] In the present embodiment, the cover 10B includes a first retaining portion H1 configured to contact at least a portion of the first end surface S1. The first retaining portion H1 may be, for example, an annular portion protruding inward from the inner wall of the cover 10B. The first end surface S1 and the first retaining portion H1 are in contact with each other in the front-to-back direction. It should be noted that the first retaining portion H1 is not necessarily an annular portion, and may be, for example, a protruding portion.

[0051] At the same time, the output shaft 6 includes a second retaining portion H2 configured to contact at least a portion of the second end surface S2. The second retaining portion H2 may be, for example, an annular portion protruding outward from the surface of the output shaft 6. The second end surface S2 and the second retaining portion H2 are in contact with each other in the front-to-back direction. It should be noted that the second retaining portion H2 is not necessarily an annular portion, and may also be, for example, a protruding portion.

[0052] It can be seen that the first bearing 8A is sandwiched between the first retaining portion H1 and the second retaining portion H2 in the front-to-back direction so that its movement is adjusted in the front-to-back direction. That is, the first retaining portion H1 and the second retaining portion H2 form an adjustment structure H0, which is used to adjust the movement of the first bearing 8A along the axis of the output shaft 6 (i.e., the front-to-back direction).

[0053] The second bearing 8B is housed inside the cover 10B behind the first bearing 8A and the first retaining portion H1 and rotatably supports the output shaft 6. In the present embodiment, the end tool 11 is attached to the output shaft 6 via the chuck 12 in front of the first bearing 8A. Therefore, the first bearing 8A is between the second bearing 8B and the end tool 11.

[0054] The second bearing 8B may be, for example, a hollow cylindrical ball bearing. Figure 3 As shown, the second bearing 8B includes an outer ring 81B, an inner ring 82B, and a spherical rolling element. The second bearing 8B is configured such that the inner ring 82B supports the cylindrical portion 37 of the third carrier 34C when the outer ring 81B is held by the cover 10B. In this case, the cylindrical portion 37 is engaged with the output shaft 6. Therefore, the second bearing 8B is configured to contact the third carrier 34C and the cover 10B at the portion where the third carrier 34C is engaged with the output shaft 6. That is, the second bearing 8B is configured to contact the transmission mechanism 3 and the cover 10B at the portion where the transmission mechanism 3 is engaged with the output shaft 6.

[0055] like Figure 1 As shown, the inertial body 4 is between the first reduction mechanism 3A and the motor 2. Specifically, the inertial body 4 is arranged 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 integrally 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).

[0056] like Figure 1 As shown, the switch 13 protrudes forward from the handle 102. The switch 13 is an operating member that receives an operation command input by a user to control the motor 2. Specifically, the operator can turn the motor 2 on and off by pulling the switch 13. In addition, the rotation speed of the drive shaft 21 can also be adjusted depending on how deep the switch 13 is pulled. For example, the deeper the switch 13 is pulled, the higher the rotation speed of the drive shaft 21 becomes.

[0057] The storage unit 9 may be implemented as, for example, a read-only memory (ROM), a random access memory (RAM), or an electrically erasable programmable read-only memory (EEPROM). The storage unit 9 stores a control program to be implemented by the control unit 7. In addition, the storage unit 9 also stores a preset value of the tightening torque (ie, a preset torque value).

[0058] The control unit 7 comprises a computer system comprising one or more processors and a memory. At least some functions of the control unit 7 are performed by causing the processor of the computer system to implement a program stored in the memory of the computer system. The program may be stored in the memory. Alternatively, the program may also be downloaded via a telecommunication line such as the Internet or distributed after having been stored in a non-transient storage medium such as a memory card.

[0059] like Figure 4 As shown, the control unit 7 includes an acquisition section 71 and a drive control section 72. Note that the acquisition section 71 and the drive control section 72 do not necessarily have a physical configuration but merely represent functions to be performed by the control unit 7.

[0060] The acquisition unit 71 acquires a torque value associated with the output torque provided by the end tool 11 based on the amount of current flowing through the motor 2 .

[0061] The drive control unit 72 controls the motor 2. For example, the drive control unit 72 can control the motor 2 by vector control. The drive control unit 72 decomposes the motor current, which is the current to be supplied to the motor 2, into a torque current (q-axis current) for generating torque and an excitation current (d-axis current) for generating magnetic flux, and controls these current components independently of each other. It should be noted that the method by which the drive control unit 72 controls the motor 2 is not necessarily vector control, but may be a control method different from vector control.

[0062] The drive control section 72 controls the motor 2 so that the torque value measured by the acquisition section 71 is equal to the preset torque value pre-stored in the storage unit 9. For example, when the difference between the torque value detected by the acquisition section 71 and the preset torque value falls within a predetermined tolerance range (e.g., ±20% of the preset torque value), the drive control section 72 controls the motor 2 to stop rotating the drive shaft 21.

[0063] (3) Advantages

[0064] The electric tool 1 according to the present embodiment is used to perform an operation with the end tool pressed against a work object such as a screw or the like. Figure 3 In the direction (i.e., the front-to-back direction) aligned with the axis of the output shaft 6 shown, a thrust load F1 as a reaction force is applied from the work object to the end tool 11 and the output shaft 6 connected to the end tool 11. As described above, the electric tool 1 has an adjustment structure H0 (including a first retaining portion H1 and a second retaining portion H2) that clamps the first bearing 8A in the front-to-back direction. Therefore, the thrust load F1 applied to the output shaft 6 in the axial direction is transmitted from the second retaining portion H2 provided for the output shaft 6 to the second end face S2 of the first bearing 8A. Then, the thrust load F1 transmitted to the second end face S2 is transmitted as a force F2 from the first end face S1 to the first retaining portion H1 provided for the cover 10B. That is, the thrust load F1 applied to the output shaft 6 is decomposed into a force F2. This can reduce the degree of eccentricity of the output shaft 6, thereby helping to stabilize the operation being performed by the electric tool 1.

[0065] Furthermore, the transmission mechanism 3 is housed inside the cover 10B to prevent the force applied in the front-rear direction from being transmitted from the cover 10B. Therefore, the thrust load F1 transmitted to the first retaining portion H1 is not transmitted to the third carrier 34C of the transmission mechanism 3. Furthermore, the output shaft 6 and the engaging hole 38 of the third carrier 34C are engaged with each other by clearance fit, and therefore, the thrust load F1 applied to the output shaft 6 is not transmitted to the cylinder portion 37 of the third carrier 34C. In addition, the first bearing 8A and the third carrier 34C are spaced apart from each other in the front-rear direction. Therefore, for example, even if the first retaining portion H1 is deformed under the thrust load F1 transmitted from the first end surface S1, the first bearing 8A does not contact the third carrier 34C. Therefore, the thrust load F1 transmitted to the first bearing 8A is not transmitted from the first bearing 8A to the third carrier 34C.

[0066] This can reduce the chance of frictional force being generated between the plurality of gears included in the transmission mechanism 3 even if the thrust load F1 is applied to the transmission mechanism 3 in the front-rear direction, thereby stabilizing the torque value acquired by the acquisition portion 71. Specifically, the torque value can be stabilized by preventing the acquisition portion 71 from detecting a change in the amount of current flowing through the motor 2 due to the frictional force generated in the transmission mechanism 3.

[0067] Next, we will refer to Figure 7 and Figure 8 Explain how the adjustment structure H0 can achieve the advantage of a stable torque value. Figure 7 In FIG. 1 , the ordinate represents the torque value in the case where the thrust load F1 is applied to the output shaft in the electric tool according to the comparative example without the adjustment structure H0. Figure 8 In FIG. 1 , the ordinate represents the torque value when the thrust load F1 is applied to the output shaft in the electric tool 1 according to the present embodiment having the adjustment structure H0. Figure 7 and Figure 8 As shown. Compared with the case in the electric tool according to the comparative example, the dispersion of the torque value in the electric tool 1 according to the present embodiment is small. Therefore, Figure 8 Each torque value shown in is within the standard range.

[0068] In addition, when the electric tool 1 according to the present embodiment is used to perform an operation on a working object (such as a screw or the like), the force (radial load) F3 (see Fig. 9) may be applied to the end tool 11 and the output shaft 6 in a direction intersecting the axis of the output shaft 6 due to, for example, the movement of an operator holding the electric tool 1. As described above, the electric tool 1 includes the second bearing 8B configured to contact the transmission mechanism 3 and the cover 10B in the area where the transmission mechanism 3 engages with the output shaft 6. More specifically, the second bearing 8B is configured so that when viewed in a direction intersecting the axis of the output shaft 6, at least a portion of the output shaft 6, at least a portion of the third carrier 34C, and at least a portion of the second bearing 8B overlap each other. That is, the output shaft 6 is supported by the second bearing 8B via the third carrier 34C, and is further supported by the cover 10B in contact with the second bearing 8B.

[0069] This allows the cover 10B to receive the radial load F3 applied to the output shaft 6 even when the radial load F3 is applied to the output shaft 6, thereby reducing the external force applied to the transmission mechanism 3 under the radial load F3. This can reduce the chance of frictional force being generated between the plurality of gears included in the transmission mechanism 3, thereby stabilizing the torque value obtained by the obtaining portion 71.

[0070] Next, we will refer to Fig.10 and Fig.11 The following describes how the second bearing 8B achieves the advantage of a stable torque value. Fig.10 In FIG. 1 , the ordinate represents the torque value when the radial load F3 is applied to the output shaft in the electric tool according to the second comparative example without the second bearing 8B. Fig.11 In FIG. 1 , the ordinate represents the torque value when the radial load F3 is applied to the output shaft in the electric tool 1 according to the present embodiment having the second bearing 8B. Fig.10 and Fig.11 As shown, the dispersion of torque values ​​in the electric tool 1 according to the present embodiment is small compared to the case in the electric tool according to the second comparative example. Fig.11 Each torque value shown in is within the standard range.

[0071] As can be seen from the foregoing description, the electric power tool 1 according to the present embodiment helps to stabilize the operation being performed.

[0072] (4) Modification

[0073] It should be noted that the above embodiments are merely exemplary embodiments of various embodiments of the present disclosure and should not be interpreted as limiting. Specifically, the exemplary embodiments can be easily modified in various ways according to design choices or any other factors without departing from the scope of the present disclosure.

[0074] Next, modifications of the exemplary embodiment will be listed in order. Note that the modifications described below can be appropriately combined and adopted.

[0075] The electric tool 1 according to the present invention includes a computer system in its control unit 7. The computer system includes a processor and a memory as its main hardware components. The computer system performs the functions of the control unit 7 according to the present disclosure by causing the processor to implement a program stored in the memory of the computer system. The program can be pre-stored in the memory of the computer system. Alternatively, the program can also be downloaded through a telecommunication line or distributed after being recorded in a non-transient storage medium such as a memory card, an optical disk or a hard disk drive, any of which is readable by the computer system. The processor of the computer system can be composed of a single or multiple electronic circuits, including a semiconductor integrated circuit (IC) or a large-scale integrated circuit (LSI). As used herein, "integrated circuits" such as IC or LSI are called different names according to their degree of integration. Examples of integrated circuits such as IC or LSI include integrated circuits called "system LSI", "very large-scale integrated circuit (VLSI)" and "ultra-large-scale integrated circuit (ULSI)". Optionally, a field programmable gate array (FPGA) that is programmed after the LSI is manufactured or a reconfigurable logic device that allows the connection part or circuit part inside the LSI to be reconfigured can also be adopted as a processor. These electronic circuits can be integrated together on a single chip or distributed on multiple chips, as appropriate. These multiple chips can be combined together in a single device or distributed in multiple devices without restriction. As used herein, a "computer system" includes a microcontroller, which includes one or more processors and one or more memories. Therefore, a microcontroller can also be implemented as a single or multiple electronic circuits including semiconductor integrated circuits or large-scale integrated circuits.

[0076] Instead of a screwdriver bit, a socket may be attached to the power tool 1 as the end tool 11. Furthermore, the power tool 1 is not necessarily configured to use the battery pack 14 as a power source, and may be configured to use an AC power source (commercial power source) as its power source.

[0077] (5) Summary

[0078] As can be seen from the foregoing description, the electric tool (1) according to the first aspect 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 the end tool (11). The transmission mechanism (3) engages with the output shaft (6) to transmit the torque generated by the motor (2) to the output shaft (6). The first bearing (8A) and the second bearing (8B) are configured to rotatably support the output shaft (6). The cover (10B) accommodates the motor (2), the transmission mechanism (3), the first bearing (8A) and the second bearing (8B). The first bearing (8A) is between the second bearing (8B) and the end tool (11). The second bearing (8B) is configured to contact the transmission mechanism (3) and the cover (10B) in the area where the transmission mechanism (3) engages with the output shaft (6).

[0079] According to this aspect, the output shaft (6) is supported not only by the second bearing (8B) but also by the cover (10B) in contact with the second bearing (8B) via the transmission mechanism (3). When a force (F3) is applied to the output shaft (6) in a direction intersecting the axis of the output shaft (6), this can reduce the degree of eccentricity of the output shaft (6), thereby contributing to stabilizing the operation being performed by the electric tool (1).

[0080] According to the second aspect, which can be implemented in combination with the first aspect, the electric tool (1) further includes an acquisition unit (71) which acquires a torque value associated with an output torque provided by the end tool (11) based on current flowing through the motor (2).

[0081] This aspect allows an operation to be performed on a work object with an appropriate torque by comparing the torque value obtained by the obtaining unit (71) with a preset torque value.

[0082] In the electric tool (1) according to the third aspect that can be implemented in combination with the first aspect or the second aspect, 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) rotates using the power provided by the motor (2). The plurality of planetary gears (32C) are arranged around the sun gear (31C) to mesh with the sun gear (31C). The internal gear (33C) is arranged around the plurality of planetary gears (32C) to mesh with the plurality of planetary gears (32C). The carrier (34C) is engaged with the output shaft (6) to rotatably support each of the plurality of planetary gears (32C). The second bearing (8B) is configured to contact the carrier (34C) and the cover (10B) in the area where the carrier (34C) is engaged with the output shaft (6).

[0083] According to this aspect, the output shaft (6) is supported not only by the second bearing (8B) but also by the cover (10B) in contact with the second bearing (8B) via the carrier (34C). When a force (F3) is applied to the output shaft (6) in a direction intersecting the axis of the output shaft (6), this can reduce the degree of eccentricity of the output shaft (6), thereby helping to stabilize the operation being performed by the electric tool (1).

[0084] In an electric tool (1) according to a fourth aspect that can be implemented in combination with the third aspect, when viewed in a direction intersecting the axis of the output shaft (6), 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 configured to overlap each other.

[0085] According to this aspect, the output shaft (6) is supported not only by the second bearing (8B) but also by the cover (10B) in contact with the second bearing (8B) via the carrier (34C). When a force (F3) is applied to the output shaft (6) in a direction intersecting the axis of the output shaft (6), this can reduce the degree of eccentricity of the output shaft (6), thereby helping to stabilize the operation being performed by the electric tool (1).

[0086] It should be noted that the constituent elements according to the second to fourth aspects are not essential constituent elements for the electric tool (1) and can be appropriately omitted.

[0087] Description of Reference Numerals

[0088] 1. Power Tools

[0089] 2 Motor

[0090] 6 Output shaft

[0091] 3. Transmission mechanism

[0092] 31C Sun gear

[0093] 32C Planetary gear

[0094] 33C Internal gear

[0095] 34C Bearing

[0096] 8A bearing

[0097] 10B Cover

[0098] 11 End tool

[0099] 71 Acquisition Department

[0100] 8B Second bearing

[0101] F3 force

Claims

1. An electric tool comprising: motor; an output shaft configured to be coupled to an end tool; a transmission mechanism engaged with the output shaft to transmit the torque generated by the motor to the output shaft; a first bearing and a second bearing, each configured to rotatably support the output shaft; and a cover configured to accommodate the motor, the transmission mechanism, the first bearing, and the second bearing, The first bearing is between the second bearing and the end tool, and The second bearing is configured to be in contact with the transmission mechanism and the cover in a region where the transmission mechanism engages the output shaft. 2 . The electric power tool according to claim 1 , further comprising an acquisition unit configured to acquire a torque value associated with an output torque provided by the end tool based on a current flowing through the motor.

3. The electric tool according to claim 1 or 2, wherein: The transmission mechanism comprises: a sun gear configured to rotate using power provided by the motor; a plurality of planetary gears arranged around the sun gear to mesh with the sun gear; an internal gear disposed around the plurality of planetary gears to mesh with the plurality of planetary gears; and a carrier engaged with the output shaft to rotatably support each of the plurality of planetary gears, wherein The second bearing is configured to contact the carrier and the cover in an area where the carrier engages the output shaft.

4. The electric tool according to claim 3, wherein: When viewed in a direction intersecting the axis 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 each other.

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