Screw fastener and method for assembling the screw fastener

Abstract

To inhibit deterioration of detection accuracy of a torque sensor.SOLUTION: A screw tightening machine 1 includes: a motor 5 having a stator 51 and a rotor 52 which rotates around a rotation axis extending in an anteroposterior direction; a gear case 3 disposed at the front relative to the stator; a planetary gear which is housed in the gear case and rotated by the rotor; an internal gear which is housed in the gear case, connected to the planetary gear, and may rotate relative to the gear case; a torque sensor 9 having a front plate part 91 coupled to the internal gear, a rear plate part 92 disposed at a rear side relative to the front plate part and supported by the gear case, a hollow part 90 disposed between the front plate part and the rear plate part in the anteroposterior direction, and a strain gauge 93 fixed to the hollow part, the torque sensor 9 housed in the gear case; a bearing 54 which is disposed between the stator and the rear plate part in the anteroposterior direction and supports at least a part of the rotor; and a bearing box 6 which is disposed around the bearing and supports the bearing.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to a screw fastener and a method for assembling a screw fastener. [Background technology]

[0002] In the assembly process of a product, a screw driver is used to perform screw tightening work. For product management, a detection signal of the torque applied to the output part of the screw driver may be recorded. Patent Document 1 discloses a torque sensor that uses a motor as a drive source and detects the drive torque of a driven body. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2016-099163 A Summary of the Invention [Problem to be solved by the invention]

[0004] If vibrations of the motor are transmitted to the torque sensor, the detection accuracy of the torque sensor may decrease. Also, if the torque sensor is not twisted properly, the detection accuracy of the torque sensor may decrease.

[0005] The present disclosure aims to suppress a decrease in detection accuracy of a torque sensor. [Means for solving the problem]

[0006] According to the first disclosure, there is provided a screw fastener comprising: a motor having a stator and a rotor rotating around a rotation axis extending in the fore-and-aft direction; a gear case arranged forward of the stator; a planetary gear housed in the gear case and rotated by the rotor; an internal gear housed in the gear case, connected to the planetary gear and rotatable relative to the gear case; a front plate portion connected to the internal gear; a rear plate portion arranged rearward of the front plate portion and supported by the gear case; a hollow portion arranged between the front plate portion and the rear plate portion in the fore-and-aft direction; a torque sensor having a strain gauge fixed to the hollow portion and housed in the gear case; a bearing arranged between the stator and the rear plate portion in the fore-and-aft direction and supporting at least a part of the rotor; and a bearing box arranged around the bearing and supporting the bearing.

[0007] According to the second disclosure, there is provided a screw fastener comprising: a motor having a stator and a rotor rotating around a rotation axis extending in the fore-and-aft direction; a gear case arranged forward of the stator; a planetary gear housed in the gear case and rotated by the rotor; an internal gear housed in the gear case, connected to the planetary gear and rotatable relative to the gear case; a front plate portion connected to the internal gear; a rear plate portion arranged rearward of the front plate portion and supported by the gear case; a hollow portion arranged between the front plate portion and the rear plate portion in the fore-and-aft direction; a torque sensor housed in the gear case; and a fixing member arranged inward from the outer circumferential surface of the rear plate portion in the radial direction of the rotation axis, in contact with each of a first portion of the rear plate portion and a second portion of the gear case, and suppressing relative rotation between the rear plate portion and the gear case.

[0008] According to the third disclosure, there is provided a method for assembling a screw fastener, the method including: inserting into a gear case housing a planetary gear and an internal gear connected to the planetary gear a front plate portion, a rear plate portion arranged rearward of the front plate portion, a hollow portion arranged between the front plate portion and the rear plate portion in the fore-and-aft direction, and a torque sensor having a strain gauge fixed to the hollow portion; meshing the internal gear with a gear provided on the front plate portion; rotating the rear plate portion and the gear case relatively so that the rear plate portion and the gear case are aligned in the circumferential direction after the internal gear and the gear are meshed; and fixing the rear plate portion and the gear case after the rear plate portion and the gear case are aligned. Effect of the Invention

[0009] According to the present disclosure, deterioration in detection accuracy of the torque sensor is suppressed. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a perspective view showing a screw fastener according to an embodiment of the present invention, seen from the front left. [Diagram 2] FIG. 2 is a side view showing the screw fastener according to the embodiment. [Diagram 3] FIG. 3 is a cross-sectional view showing the screw fastener according to the embodiment. [Figure 4] FIG. 4 is a perspective view showing the inside of the motor housing portion according to the embodiment, seen from the left front. [Diagram 5] FIG. 5 is a perspective view showing the inside of the motor housing portion according to the embodiment, seen from the right rear. [Figure 6] FIG. 6 is an exploded perspective view showing the gear case and the planetary gear mechanism according to the embodiment. [Figure 7] FIG. 7 is a perspective view showing the torque sensor according to the embodiment, seen from the left front. [Figure 8] FIG. 8 is a side view showing the torque sensor according to the embodiment. [Figure 9] FIG. 9 is a cross-sectional view showing the torque sensor according to the embodiment. [Figure 10] FIG. 10 is a perspective view, seen from the front left, showing the fixing structure between the rear plate portion and the gear case according to the embodiment. [Figure 11] FIG. 11 is a perspective view from the right rear showing the fixing structure between the rear plate portion and the gear case according to the embodiment. [Figure 12] FIG. 12 is a rear view of the torque sensor housed in the gear case according to the embodiment. [Figure 13] FIG. 13 is a perspective view from the left front showing the fixing structure between the bearing box and the gear case according to the embodiment. [Figure 14] FIG. 14 is a perspective view from the right rear showing the fixing structure between the bearing box and the gear case according to the embodiment. [Figure 15] FIG. 15 is a perspective view from the left front showing a method of inserting the rotor shaft into the gear case according to the embodiment. [Figure 16] FIG. 16 is a perspective view from the right rear showing a method of inserting the rotor shaft into the gear case according to the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment according to the present disclosure will be described with reference to the drawings, but the present disclosure is not limited to the embodiment. The components of the embodiments described below can be appropriately combined. In addition, some components may not be used.

[0012] In the embodiment, the positional relationship of each part will be described using the terms "left," "right," "front," "rear," "upper," and "lower." These terms indicate relative positions or directions based on the center of the screw fastener 1.

[0013] The screw fastener 1 is a power tool powered by a motor 5. A direction parallel to the rotation axis AX of the motor 5 is referred to as the axial direction, a direction going around the rotation axis AX is referred to as the circumferential direction or the rotation direction, and a direction radial from the rotation axis AX is referred to as the radial direction.

[0014] The rotation axis AX extends in the front-rear direction. The axial direction and the front-rear direction are the same. One axial side is the front, and the other axial side is the rear. In addition, in the radial direction, a position closer to or approaching the rotation axis AX is appropriately referred to as the radial inner side, and a position farther from or away from the rotation axis AX is appropriately referred to as the radial outer side.

[0015] [Screw tightening machine] Fig. 1 is a perspective view of the screw driver 1 according to the embodiment, seen from the front left. Fig. 2 is a side view of the screw driver 1 according to the embodiment. Fig. 3 is a cross-sectional view of the screw driver 1 according to the embodiment.

[0016] The screw driver 1 is an industrial electric screwdriver used in a product assembly factory. In the product assembly process, a screw tightening operation is performed by the screw driver 1. An example of the assembly factory is an automobile assembly factory. An example of the product is an automobile.

[0017] As shown in Figures 1, 2, and 3, the screw fastener 1 includes a housing 2, a gear case 3, a battery mounting section 4, a motor 5, bearings 54 and 55, a bearing box 6, a planetary gear mechanism 7, an output section 8, a torque sensor 9, a fan 10, a trigger switch 11, a forward / reverse switching lever 12, an audio output section 13, a light-emitting section 14, and a controller 15.

[0018] The housing 2 is made of synthetic resin. The housing 2 includes a left housing 2L and a right housing 2R. The left housing 2L and the right housing 2R are fixed together with a screw 2S. The housing 2 is formed by fixing the left housing 2L and the right housing 2R together.

[0019] The housing 2 has a motor accommodating portion 21, a grip portion 22, and a controller accommodating portion 23.

[0020] The motor accommodating portion 21 accommodates the motor 5. The motor accommodating portion 21 has a cylindrical portion. The motor accommodating portion 21 is disposed above the grip portion 22. The motor accommodating portion 21 is provided with a screw boss portion 2B having an opening into which a screw 2S is inserted.

[0021] The grip portion 22 is held by the hand of an operator. The grip portion 22 is disposed below the motor accommodating portion 21. The grip portion 22 protrudes downward from the motor accommodating portion 21. The trigger switch 11 is disposed on the grip portion 22.

[0022] The controller accommodating section 23 accommodates the controller 15. The controller accommodating section 23 is disposed lower than the grip section 22. The controller accommodating section 23 is connected to the lower end of the grip section 22. The external dimensions of the controller accommodating section 23 are larger than the external dimensions of the grip section 22 in both the front-rear and left-right directions.

[0023] The gear case 3 houses the bearing box 6, the torque sensor 9, the planetary gear mechanism 7, and a portion of the output section 8. The gear case 3 is disposed forward of at least a portion of the motor 5. The gear case 3 is cylindrical. The gear case 3 is made of metal. In the embodiment, the gear case 3 is made of aluminum. The gear case 3 is disposed so as to cover the front opening of the motor accommodating section 21. The gear case 3 is fixed to the motor accommodating section 21. The rear portion of the gear case 3 is disposed inside the motor accommodating section 21. At least a portion of the motor accommodating section 21 is disposed around the gear case 3. The front portion of the gear case 3 is disposed forward of the motor accommodating section 21.

[0024] The battery mounting section 4 is formed at the bottom of the controller accommodating section 23. The battery mounting section 4 is connected to the battery pack 16. The battery pack 16 is mounted to the battery mounting section 4. The battery pack 16 is detachable from the battery mounting section 4. The battery pack 16 includes a secondary battery. In the embodiment, the battery pack 16 includes a rechargeable lithium-ion battery. By being mounted to the battery mounting section 4, the battery pack 16 can supply power to the screw fastener 1. The motor 5 is driven based on the power supplied from the battery pack 16. The controller 15 operates based on the power supplied from the battery pack 16.

[0025] The motor 5 is a power source of the screw fastener 1. The motor 5 is an electric motor. The motor 5 is an inner rotor type brushless motor. The motor 5 is accommodated in a motor accommodating portion 21.

[0026] Fig. 4 is a perspective view showing the inside of the motor accommodating section 21 according to the embodiment, as seen from the front left. Fig. 5 is a perspective view showing the inside of the motor accommodating section 21 according to the embodiment, as seen from the rear right.

[0027] As shown in Figs. 1, 2, 3, 4, and 5, the motor 5 has a stator 51 and a rotor 52. The stator 51 is disposed around the rotor 52. The rotor 52 rotates about a rotation axis AX. The gear case 3 is disposed forward of the stator 51. A recess 3R is provided in the upper part of the gear case 3, in which the screw boss portion 2B is disposed. In addition, a protrusion 3T that engages with at least a part of the motor accommodating portion 21 is provided in each of the left, right, and lower parts of the gear case 3. The protrusion 3T suppresses relative rotation between the gear case 3 and the motor accommodating portion 21.

[0028] The stator 51 includes a stator core 51A, a front insulator 51B, a rear insulator 51C, a coil 51D, a sensor board 51E, a short-circuit member 51F, and a fusing terminal 51G.

[0029] The stator core 51A is cylindrical. The stator core 51A includes a plurality of laminated steel plates. The front insulator 51B is fixed to the front part of the stator core 51A. The rear insulator 51C is fixed to the rear part of the stator core 51A. A plurality of coils 51D are provided. The plurality of coils 51D are wound around the teeth of the stator core 51A via the front insulator 51B and the rear insulator 51C. The sensor board 51E has a plurality of detection elements that detect the rotation of the rotor 52. The sensor board 51E is supported by the rear insulator 51C. The short-circuit member 51F connects the plurality of coils 51D via a fusing terminal 51G. The short-circuit member 51F is supported by the rear insulator 51C. The short-circuit member 51F is connected to the controller 15 via a lead wire (not shown).

[0030] The rotor 52 includes a rotor core 52A, a permanent magnet 52B, and a rotor shaft 53.

[0031] The rotor core 52A is disposed inside the stator core 51A and the coils 51D. The rotor core 52A is cylindrical. The rotor core 52A is disposed around the rotor shaft 53. The rotor core 52A includes a plurality of stacked steel plates. A plurality of permanent magnets 52B are provided. The permanent magnets 52B are held by the rotor core 52A. The rotor core 52A has through holes extending in the front-rear direction. A plurality of through holes are formed in the circumferential direction. The permanent magnets 52B are disposed in each of the plurality of through holes of the rotor core 52A.

[0032] The detection elements of the sensor board 51E detect the magnetic fields of the multiple permanent magnets 52B, thereby detecting the rotation of the rotor 52. The controller 15 supplies a drive current to the coil 51D based on the detection signals of the detection elements.

[0033] The rotor shaft 53 extends in the front-rear direction. The rotor shaft 53 rotates about a rotation axis AX. The rotation axis AX of the rotor shaft 53 coincides with the rotation axis of the output portion 8.

[0034] The bearing 54 supports at least a portion of the rotor 52. The bearing 54 rotatably supports a front portion of the rotor shaft 53. The bearing 54 supports a portion of the rotor shaft 53 forward of the stator 51.

[0035] The bearing 55 supports at least a portion of the rotor 52. The bearing 55 rotatably supports a rear portion of the rotor shaft 53. The bearing 55 supports a portion of the rotor shaft 53 rearward of the stator 51.

[0036] The bearing box 6 is disposed around the bearing 54. The bearing box 6 supports the bearing 54. The bearing box 6 is housed in the gear case 3. The bearing box 6 is fixed to the gear case 3.

[0037] The bearing 55 is held by a bearing holder 57 provided in the motor accommodating portion 21 .

[0038] The front end of the rotor shaft 53 is disposed forward of the bearing 54. The front end of the rotor shaft 53 is disposed inside the gear case 3.

[0039] A pinion gear 71S is attached to the front end of the rotor shaft 53. The pinion gear 71S is detachable from the rotor shaft 53. The pinion gear 71S is replaceable. The pinion gear 71S is cylindrical. The pinion gear 71S is attached to the rotor shaft 53 by being inserted into the front end of the rotor shaft 53 from a position forward of the rotor shaft 53. The pinion gear 71S attached to the front end of the rotor shaft 53 is removed from the rotor shaft 53 by being pulled forward from the rotor shaft 53. The rotor shaft 53 is connected to the planetary gear mechanism 7 via the pinion gear 71S.

[0040] The planetary gear mechanism 7 is housed in the gear case 3. The planetary gear mechanism 7 is disposed forward of the torque sensor 9. The planetary gear mechanism 7 connects the rotor shaft 53 and the output unit 8. The planetary gear mechanism 7 reduces the rotation speed of the rotor shaft 53 and rotates the output unit 8 at a lower rotation speed than the rotor shaft 53. The planetary gear mechanism 7 functions as a power transmission mechanism that transmits the rotational force generated by the motor 5 to the output unit 8.

[0041] FIG. 6 is an exploded perspective view showing the gear case 3 and the planetary gear mechanism 7 according to the embodiment.

[0042] 3 and 6, the planetary gear mechanism 7 has a planetary gear 71P, a carrier 71C, a sun gear 72S, a planetary gear 72P, a carrier 72C, and an internal gear 70. Each of the planetary gear 71P, the carrier 71C, the sun gear 72S, the planetary gear 72P, the carrier 72C, and the internal gear 70 is housed in a gear case 3.

[0043] A plurality of planetary gears 71P are provided. The plurality of planetary gears 71P are arranged around the pinion gear 71S. In the embodiment, three planetary gears 71P are arranged around the pinion gear 71S. Each of the plurality of planetary gears 71P meshes with the pinion gear 71S.

[0044] The carrier 71C rotatably supports a plurality of planetary gears 71P.

[0045] The sun gear 72S is disposed in front of the carrier 71C. The diameter of the sun gear 72S is smaller than the diameter of the carrier 71C. The carrier 71C and the sun gear 72S are integral with each other. The carrier 71C and the sun gear 72S rotate together.

[0046] A plurality of planetary gears 72P are provided. The plurality of planetary gears 72P are arranged around the sun gear 72S. In the embodiment, four planetary gears 72P are arranged around the sun gear 72S. Each of the plurality of planetary gears 72P meshes with the sun gear 72S. The planetary gears 72P are arranged between the sun gear 72S and the internal gear 70 in the radial direction.

[0047] The carrier 72C rotatably supports a plurality of planetary gears 72P. The carrier 72C is connected to the output unit 8. The carrier 72C is rotatable about a rotation axis AX.

[0048] The internal gear 70 is substantially cylindrical. The internal gear 70 is disposed around the planetary gears 72P. The internal gear 70 meshes with each of the planetary gears 72P. An inner peripheral surface 3D of the gear case 3 and an outer peripheral surface 70C of the internal gear 70 face each other. In the embodiment, the internal gear 70 is rotatable with respect to the gear case 3. The internal gear 70 is connected to a torque sensor 9.

[0049] A washer 73 is disposed behind the planetary gear 71P inside the internal gear 70. The washer 73 is disposed so as to surround the pinion gear 71S.

[0050] An elastic member 74 (first elastic member) is disposed inside the gear case 3. The elastic member 74 is ring-shaped. The elastic member 74 is disposed in a groove 31 provided in the inner circumferential surface 3D of the gear case 3. By disposing the elastic member 74 in the groove 31, the gear case 3 and the elastic member 74 are positioned. The rear end surface 70B of the internal gear 70 contacts the elastic member 74. An example of the elastic member 74 is a rubber O-ring.

[0051] An elastic member 75 (second elastic member) is disposed between the gear case 3 and the internal gear 70 in the radial direction. The elastic member 75 is ring-shaped. The elastic member 75 is disposed in a groove 76 provided in the outer circumferential surface 70C of the internal gear 70. By disposing the elastic member 75 in the groove 76, the internal gear 70 and the elastic member 75 are positioned. The inner circumferential surface 3D of the gear case 3 contacts the elastic member 75. An example of the elastic member 75 is a rubber O-ring. In the embodiment, two elastic members 75 are disposed in the front-rear direction.

[0052] The pinion gear 71S attached to the front end of the rotor shaft 53 is connected to the planetary gear 72P via the planetary gear 71P, the carrier 71C, and the sun gear 72S. The planetary gear 72P and the carrier 72C are each rotated by the rotor 52. The planetary gear 71P is connected to the internal gear 70 via the carrier 71C, the sun gear 72S, and the planetary gear 72P.

[0053] When the rotor shaft 53 is rotated by the driving of the motor 5, the pinion gear 71S rotates, and the planetary gear 71P revolves around the pinion gear 71S. The revolution of the planetary gear 71P causes the carrier 71C and the sun gear 72S to rotate at a rotational speed lower than the rotational speed of the rotor shaft 53. When the sun gear 72S rotates, the planetary gear 72P revolves around the sun gear 72S. The revolution of the planetary gear 72P causes the carrier 72C to rotate at a rotational speed lower than the rotational speed of the carrier 71C. In this way, when the motor 5 is driven, the carrier 72C rotates at a rotational speed lower than the rotor shaft 53.

[0054] The output unit 8 is driven by the rotor 52. The output unit 8 rotates based on the rotational force transmitted from the rotor 52 via the planetary gear mechanism 7. The output unit 8 rotates about the rotation axis AX. The output unit 8 is disposed forward of the stator 51. At least a portion of the output unit 8 is disposed forward of the planetary gear mechanism 7. A bit (a tool tip) is attached to the output unit 8. The output unit 8 rotates with the bit attached.

[0055] The output section 8 includes a spindle 81 and a chuck 82 .

[0056] The spindle 81 rotates around the rotation axis AX based on the rotational force transmitted from the rotor 52. The spindle 81 is rotatably supported by bearings 83 and 84. The spindle 81 is connected to the carrier 72C. The spindle 81 rotates around the rotation axis AX due to the rotation of the carrier 72C. The spindle 81 has an insertion hole 81A into which a bit is inserted. The insertion hole 81A is formed so as to extend rearward from the front end of the spindle 81. The cross section of the insertion hole 81A perpendicular to the rotation axis AX is hexagonal. The cross section of the bit is also hexagonal. The bit having a hexagonal cross section is inserted into the insertion hole 81A having a hexagonal cross section, so that the bit is fixed to the spindle 81 in the circumferential direction. The chuck 82 is disposed around the front part of the spindle 81. The chuck 82 prevents the bit from slipping out of the insertion hole 81A. A recess is provided on the side of the bit. The chuck 82 has a ball 82A that is disposed in a recess of the bit. When the bit is inserted into the insertion hole 81A, the ball 82A of the chuck 82 is disposed in the recess of the bit, thereby preventing the bit from falling out of the insertion hole 81A. When the spindle 81 rotates, the bit inserted in the insertion hole 81A rotates.

[0057] The torque sensor 9 detects the presence or absence of an abnormality in the operation performed by the output unit 8. The torque sensor 9 is connected to the output unit 8. In the embodiment, the operation performed by the output unit 8 includes a screw tightening operation. In the embodiment, the torque sensor 9 detects the torque applied to the output unit 8 during the screw tightening operation. The detection signal output from the torque sensor 9 indicates the torque applied to the output unit 8. The screw tightening operation is performed with a bit attached to the output unit 8. The torque detected by the torque sensor 9 includes the tightening torque of the screw applied to the output unit 8 during the screw tightening operation.

[0058] The torque sensor 9 is housed in the gear case 3. In the front-rear direction, the torque sensor 9 is disposed between the stator 51 and the output portion 8. In the embodiment, the torque sensor 9 is disposed between the fan 10 and the planetary gear mechanism 7.

[0059] The torque sensor 9 is cylindrical. The torque sensor 9 is disposed around the rotor shaft 53. The front end of the rotor shaft 53 is disposed forward of the front end of the torque sensor 9. The front end of the pinion gear 71S is disposed forward of the front end of the torque sensor 9. The fan 10 and the motor 5 are disposed rearward of the rear end of the torque sensor 9.

[0060] The fan 10 generates an airflow for cooling the motor 5. In the front-rear direction, the fan 10 is disposed between the stator 51 and the bearing box 6. The fan 10 is fixed to the rotor shaft 53. The fan 10 rotates by the rotation of the rotor shaft 53. The motor accommodating section 21 has an opening 24 connecting the internal space of the motor accommodating section 21 with the external space. The opening 24 includes an intake port 24A and an exhaust port 24B. The intake port 24A is provided behind the exhaust port 24B. When the fan 10 rotates, air in the external space of the housing 2 flows into the internal space of the housing 2 through the intake port 24A. The air that flows into the internal space of the housing 2 cools the motor 5 by circulating through the internal space of the housing 2. The air that circulates through the internal space of the housing 2 flows out to the external space of the housing 2 through the exhaust port 24B.

[0061] The trigger switch 11 is operated to start the motor 5. The trigger switch 11 is disposed in the grip portion 22. The trigger switch 11 includes a trigger member 11A and a switch body 11B. The switch body 11B is housed in the grip portion 22. The trigger member 11A protrudes forward from an upper portion of the front part of the grip portion 22. The trigger member 11A is operated by an operator. By operating the trigger member 11A, the motor 5 is switched between being driven and being stopped.

[0062] The forward / reverse switching lever 12 is operated to switch the rotation direction of the rotor 52. The forward / reverse switching lever 12 is provided on the upper part of the grip portion 22. The forward / reverse switching lever 12 is operated by an operator. By operating the forward / reverse switching lever 12, the rotation direction of the rotor 52 is switched between the forward direction and the reverse direction. By switching the rotation direction of the rotor 52, the rotation direction of the output portion 8 is switched.

[0063] The audio output unit 13 generates audio based on the detection signal of the torque sensor 9. The audio output unit 13 is housed in the motor housing portion 21.

[0064] The light-emitting unit 14 illuminates the output unit 8 or the area in front of the output unit 8. The light-emitting unit 14 is disposed in front of the motor housing unit 21. The light-emitting unit 14 emits illumination light forward. The light-emitting unit 14 includes, for example, a light-emitting diode (LED).

[0065] The controller 15 includes a computer system. The controller 15 outputs a control command for controlling the motor 5. The controller 15 is accommodated in the controller accommodation section 23. The controller 15 includes a board 15A on which a plurality of electronic components are mounted. At least a portion of the controller 15 is accommodated in a controller case 15B. Examples of the electronic components mounted on the board 15A include a processor such as a CPU (Central Processing Unit), a non-volatile memory such as a ROM (Read Only Memory) or storage, a volatile memory such as a RAM (Random Access Memory), a transistor, a capacitor, and a resistor.

[0066] [Torque sensor] Fig. 7 is a perspective view of the torque sensor 9 according to the embodiment, seen from the front left. Fig. 8 is a side view of the torque sensor 9 according to the embodiment. Fig. 9 is a cross-sectional view of the torque sensor 9 according to the embodiment.

[0067] As shown in FIGS. 3, 7, 8, and 9, the torque sensor 9 has a hollow portion 90, a front plate portion 91, a rear plate portion 92, a strain gauge 93, and lead wires 94.

[0068] The hollow portion 90 is cylindrical. In the front-rear direction, the hollow portion 90 is disposed between a front plate portion 91 and a rear plate portion 92. The central axis of the hollow portion 90 coincides with the rotation axis AX. The hollow portion 90 is disposed around the rotor shaft 53.

[0069] The front plate portion 91 is fixed to the front end of the hollow portion 90. The front plate portion 91 and the hollow portion 90 are integral. The front plate portion 91 is substantially annular. The central axis of the front plate portion 91 coincides with the rotation axis AX. The front plate portion 91 is disposed around the rotor shaft 53. At least a portion of the pinion gear 71S attached to the rotor shaft 53 is disposed forward of the front end of the front plate portion 91. The outer diameter of the front plate portion 91 is larger than the outer diameter of the hollow portion 90. The front plate portion 91 has a front surface 91A, a rear surface 91B, and an outer peripheral surface 91C. The front surface 91A faces forward. The rear surface 91B faces rearward. Each of the front surface 91A and the rear surface 91B is perpendicular to an axis parallel to the rotation axis AX. A gear 91D is provided on the outer peripheral surface 91C of the front plate portion 91.

[0070] The front plate portion 91 is coupled to the internal gear 70. At least a portion of the internal gear 70 is disposed around the front plate portion 91. The front plate portion 91 and the internal gear 70 are coupled to each other by meshing with a gear 91D of the front plate portion 91 and the internal gear 70. The torque sensor 9 is connected to the internal gear 70 via the front plate portion 91. As described above, the carrier 72C is connected to the output portion 8. The torque sensor 9 is connected to the output portion 8 via the planetary gear mechanism 7.

[0071] The rear plate portion 92 is disposed rearward of the front plate portion 91. The rear plate portion 92 is fixed to the rear end portion of the hollow portion 90. The rear plate portion 92 and the hollow portion 90 are integral with each other. The rear plate portion 92 is substantially annular. The central axis of the rear plate portion 92 coincides with the rotation axis AX. The rear plate portion 92 is disposed around the rotor shaft 53. The outer diameter of the rear plate portion 92 is larger than the outer diameter of the hollow portion 90. The outer diameter of the rear plate portion 92 is larger than the outer diameter of the front plate portion 91. The rear plate portion 92 has a front surface 92A, a rear surface 92B, and an outer peripheral surface 92C. The front surface 92A faces forward. The rear surface 92B faces rearward. Each of the front surface 92A and the rear surface 92B is perpendicular to an axis parallel to the rotation axis AX. A recess 92D (first recess) is provided in the outer peripheral surface 92C of the rear plate portion 92. The recessed portion 92D is recessed radially inward from the outer circumferential surface 92C. A plurality of recessed portions 92D are provided at intervals in the circumferential direction. In the embodiment, three recessed portions 92D are provided in the circumferential direction.

[0072] The rear plate portion 92 is supported by the gear case 3. At least a portion of the gear case 3 is disposed around the rear plate portion 92. The rear plate portion 92 is fixed to at least a portion of the gear case 3.

[0073] The torque sensor 9 has a through hole 96 that penetrates through a front surface 91A of the front plate portion 91 and a rear surface 92B of the rear plate portion 92. At least a portion of the through hole 96 is formed inside the hollow portion 90.

[0074] The strain gauge 93 is fixed to the hollow portion 90. The strain gauge 93 outputs a detection signal (voltage) indicating the torque applied to the output portion 8. In the embodiment, the strain gauge 93 is fixed to the outer surface of the hollow portion 90. A plurality of strain gauges 93 are provided. In the embodiment, four strain gauges 93 are arranged in the circumferential direction. The four strain gauges 93 are arranged at equal intervals in the circumferential direction.

[0075] The lead wire 94 is connected to the strain gauge 93. A plurality of lead wires 94 are provided. A detection signal output from the strain gauge 93 is transmitted to the controller 15 via the lead wire 94.

[0076] The torque applied to the output unit 8 during the screw tightening operation is transmitted to the internal gear 70 via the carrier 72C and the planetary gear 72P. A front plate portion 91 of the torque sensor 9 is connected to the internal gear 70, and a rear plate portion 92 of the torque sensor 9 is fixed to at least a part of the gear case 3. Therefore, when torque is applied to the internal gear 70, the hollow portion 90 is twisted in the rotational direction. When the hollow portion 90 is twisted in the rotational direction, the four strain gauges 93 arranged on the surface of the hollow portion 90 are deformed. As the strain gauges 93 are deformed, a detection signal (voltage) indicating the torque applied to the hollow portion 90 is output from the strain gauges 93. In this way, the torque applied to the output unit 8 is transmitted to the torque sensor 9 via the planetary gear mechanism 7, so that the torque sensor 9 can detect the torque applied to the output unit 8.

[0077] In the embodiment, the strain gauge 93 detects the torque applied to the hollow portion 90, thereby indirectly detecting the torque applied to the output portion 8. When the torque applied to the output portion 8 is large, the detection signal output from the strain gauge 93 becomes large, and when the torque applied to the output portion 8 is small, the detection signal (voltage) output from the strain gauge 93 becomes small.

[0078] [Fixing structure between rear plate and gear case] Fig. 10 is a perspective view from the left front showing the fixing structure between the rear plate portion 92 and the gear case 3 according to the embodiment. Fig. 11 is a perspective view from the right rear showing the fixing structure between the rear plate portion 92 and the gear case 3 according to the embodiment. Fig. 12 is a view of the torque sensor 9 housed in the gear case 3 according to the embodiment as seen from the rear.

[0079] An opening 32 is provided at the rear of the gear case 3. The planetary gear mechanism 7 is accommodated in the gear case 3 through the opening 32. After the planetary gear mechanism 7 is accommodated in the gear case 3, the torque sensor 9 is accommodated in the gear case 3 through the opening 32. The torque sensor 9 is inserted into the gear case 3 so that the internal gear 70 accommodated in the gear case 3 meshes with a gear 91G provided on the front plate portion 91. The front plate portion 91 is coupled to the internal gear 70 by the meshing of the internal gear 70 with the gear 91G.

[0080] After the torque sensor 9 is inserted into the gear case 3, the rear plate portion 92 and the gear case 3 are fixed together. The rear plate portion 92 and the gear case 3 are fixed together by a fixing member 17. The fixing member 17 suppresses at least relative rotation between the rear plate portion 92 and the gear case 3.

[0081] The fixing member 17 is disposed radially inward of an outer circumferential surface 92C of the rear plate portion 92. The fixing member 17 contacts each of the first portion 95 of the rear plate portion 92 and the second portion 34 of the gear case 3, thereby suppressing relative rotation between the rear plate portion 92 and the gear case 3.

[0082] A recess 92D (first recess) is provided on an outer peripheral surface 92C of the rear plate portion 92. The recess 92D is recessed radially inward from the outer peripheral surface 92C. A plurality of recesses 92D are provided in the circumferential direction. A recess 33 (second recess) is provided on an inner peripheral surface 3D of the gear case 3. A plurality of recesses 33 are provided in the circumferential direction. In the embodiment, three each of the recesses 92D and the recesses 33 are provided at intervals in the circumferential direction.

[0083] In the embodiment, the fixing member 17 includes a pin disposed in the recess 92D and the recess 33. Three fixing members 17 are provided. A first portion 95 of the rear plate portion 92 with which the fixing members 17 contact includes the inner surface of the recess 92D. A second portion 34 of the gear case 3 with which the fixing members 17 contact includes the inner surface of the recess 33. With the torque sensor 9 housed in the gear case 3, the fixing members 17 are disposed in the recess 92D and the recess 33, respectively, thereby suppressing relative rotation between the rear plate portion 92 and the gear case 3 around the rotation axis AX.

[0084] The torque sensor 9 and the gear case 3 rotate relative to each other in a state where the front plate portion 91 is coupled to the internal gear 70 and the fixing member 17 is not in contact with the first portion 95 of the rear plate portion 92 and the second portion 34 of the gear case 3. That is, after the torque sensor 9 is inserted into the gear case 3 so that the internal gear 70 and the gear 91G mesh with each other, the torque sensor 9 can rotate relative to the gear case 3 before the rear plate portion 92 and the gear case 3 are fixed by the fixing member 17. As described above, the internal gear 70 is rotatable relative to the gear case 3. Therefore, before the rear plate portion 92 and the gear case 3 are fixed by the fixing member 17, in a state where the front plate portion 91 and the internal gear 70 are coupled to each other, the torque sensor 9 can rotate together with the internal gear 70 relative to the gear case 3. The torque sensor 9 can rotate so that the recess 92D and the recess 33 are aligned in the circumferential direction.

[0085] After the torque sensor 9 is rotated with respect to the gear case 3 so that the recess 92D and the recess 33 are aligned in the circumferential direction, the fixing members 17 are inserted into the recess 92D and the recess 33. This suppresses relative rotation between the rear plate portion 92 and the gear case 3 around the rotation axis AX.

[0086] As shown in FIG. 12, the recess 92D including the first portion 95 and the recess 33 including the second portion 34 are arranged at unequal intervals in the circumferential direction. In the embodiment, the recess 92D includes a first recess 92D1, a second recess 92D2, and a third recess 92D3. The recess 33 includes a first recess 331, a second recess 332, and a third recess 333. In the radial direction, the distance between the rotation axis AX and the first portion 95 of the recess 92D1, the distance between the rotation axis AX and the first portion 95 of the recess 92D2, and the distance between the rotation axis AX and the first portion 95 of the recess 92D3 are equal. In the radial direction, the distance between the rotation axis AX and the second portion 34 of the recess 331, the distance between the rotation axis AX and the second portion 34 of the recess 332, and the distance between the rotation axis AX and the second portion 34 of the recess 333 are equal.

[0087] In the circumferential direction, the distance between the first portion 95 of the recess 92D1 and the first portion 95 of the recess 92D2 is different from the distance between the first portion 95 of the recess 92D2 and the first portion 95 of the recess 92D3. In the circumferential direction, the distance between the second portion 34 of the recess 331 and the second portion 34 of the recess 332 is different from the distance between the second portion 34 of the recess 332 and the second portion 34 of the recess 333.

[0088] In the circumferential direction, the distance between the first portion 95 of the recess 92D2 and the first portion 95 of the recess 92D3 may be different from or equal to the distance between the first portion 95 of the recess 92D3 and the first portion 95 of the recess 92D1. In the circumferential direction, the distance between the second portion 34 of the recess 332 and the second portion 34 of the recess 333 and the second portion 34 of the recess 331 may be different from or equal to the distance between the second portion 34 of the recess 333 and the second portion 34 of the recess 331.

[0089] When the recess 92D1 and the recess 331 are aligned, the recess 92D2 and the recess 332 are aligned, and the recess 92D3 and the recess 333 are aligned. Even when the recess 92D1 and the recess 332 are aligned, the recess 92D2 and the recess 331 and the recess 333 are not aligned, and the recess 92D3 and the recess 333 and the recess 331 are not aligned. Even when the recess 92D1 and the recess 333 are aligned, the recess 92D2 and the recess 331 and the recess 332 are not aligned, and the recess 92D3 and the recess 332 and the recess 331 are not aligned.

[0090] When the three recesses 92D and the three recesses 33 are aligned in the circumferential direction, the lead wires 94 extend downward from the hollow portion 90. A recess 3E through which the lead wires 94 pass is provided in the lower portion of the gear case 3.

[0091] [Bearing box and gear case fixing structure] Fig. 13 is a perspective view from the front left showing the fixing structure between the bearing box 6 and the gear case 3 according to the embodiment. Fig. 14 is a perspective view from the rear right showing the fixing structure between the bearing box 6 and the gear case 3 according to the embodiment.

[0092] The bearing box 6 is housed in the gear case 3. The bearing box 6 is fixed to the gear case 3. At least a portion of the bearing box 6 is housed in the gear case 3 through an opening 32 provided in the rear part of the gear case 3. After the planetary gear mechanism 7 is housed in the gear case 3 and the torque sensor 9 is housed in the gear case 3, the bearing box 6 is housed in the gear case 3 through the opening 32.

[0093] The bearing box 6 is substantially annular. The bearing box 6 has a front surface 6A, a rear surface 6B, and an outer peripheral surface 6C. The front surface 6A faces forward. The rear surface 6B faces rearward. An opening 64 is provided in the center of the bearing box 6.

[0094] A screw thread 60 is provided on at least a part of an outer peripheral surface 6C of the bearing box 6. A screw groove 35 is provided on at least a part of an inner peripheral surface 3D of the gear case 3. The screw thread 60 and the screw groove 35 are engaged with each other to fix the bearing box 6 to the gear case 3. That is, the bearing box 6 is fixed to the gear case 3 by screwing the bearing box 6 into the gear case 3. A nut portion 61 is provided at the rear of the bearing box 6. The nut portion 61 is disposed around an opening 64 at the rear of the bearing box 6. The outer shape of the nut portion 61 perpendicular to the rotation axis AX is hexagonal. A nut tightening tool is attached to the nut portion 61, and the bearing box 6 is rotated to screw the bearing box 6 into the gear case 3.

[0095] The bearing box 6 has a connecting portion 62 on which the thread 60 is provided, and a straight body portion 63 arranged forward of the connecting portion 62. The straight body portion 63 is arranged forward of the thread 60. No thread is provided on the straight body portion 63. The straight body portion 63 is cylindrical. The outer diameter of the straight body portion 63 is smaller than the outer diameter of the connecting portion 62.

[0096] The gear case 3 has a connecting portion 36 in which a screw groove 35 is provided, and a straight pipe portion 37 arranged forward of the connecting portion 36. The straight pipe portion 37 is arranged forward of the screw groove 35. No screw groove is provided in the straight pipe portion 37. The straight pipe portion 37 has a cylindrical shape. The inner diameter of the straight pipe portion 37 is smaller than the inner diameter of the connecting portion 36.

[0097] With the thread 60 of the coupling portion 62 and the thread groove 35 of the coupling portion 36 coupled to each other, the straight body portion 63 is disposed inside the straight pipe portion 37. The outer peripheral surface of the straight body portion 63 contacts the inner peripheral surface of the straight pipe portion 37. The contact between the outer peripheral surface of the straight body portion 63 and the inner peripheral surface of the straight pipe portion 37 positions the bearing box 6 and the gear case 3 in the radial direction.

[0098] The bearing box 6 is housed in the gear case 3 so that the front surface 6A of the bearing box 6 contacts the rear surface 92B of the rear plate portion 92. When the thread 60 of the coupling portion 62 and the thread groove 35 of the coupling portion 36 are coupled together, the front surface 6A of the bearing box 6 contacts the rear surface 92B of the rear plate portion 92. The contact between the front surface 6A of the bearing box 6 and the rear surface 92B of the rear plate portion 92 positions the bearing box 6, the gear case 3, and the torque sensor 9 in the axial direction.

[0099] The bearing box 6 is housed in the gear case 3 such that the rear surface 6B of the bearing box 6 is located forward of the rear end surface 3B of the gear case 3. In a state in which the thread 60 of the coupling portion 62 and the thread groove 35 of the coupling portion 36 are coupled together, the rear surface 6B of the bearing box 6 is located forward of the rear end surface 3B of the gear case 3. In other words, the entire bearing box 6 is located inside the gear case 3.

[0100] 3, the bearing box 6 and the bearing 54 supported by the bearing box 6 are disposed between the stator 51 and the rear plate portion 92 in the front-rear direction. In the embodiment, the bearing box 6 and the bearing 54 are disposed between the fan 10 and the rear plate portion 92 in the front-rear direction.

[0101] [Assembly method] Next, a method for assembling the screw fastener 1 will be described. Hereinafter, a method for assembling the components of the screw fastener 1 housed inside the motor housing 21 will be described. In the embodiment, the assembly work of the screw fastener 1 is performed by an assembly worker. Note that the assembly work of the screw fastener 1 may also be performed by an assembly robot.

[0102] As described with reference to Figs. 10 and 11, the opening 32 is provided at the rear of the gear case 3. The assembly worker inserts the output unit 8 into the gear case 3 through the opening 32. The assembly worker also inserts the planetary gear mechanism 7 into the gear case 3 through the opening 32. As described above, the planetary gear mechanism 7 has the planetary gear 71P meshing with the pinion gear 71S attached to the front end of the rotor shaft 53, the carrier 71C rotatably supporting the planetary gear 71P, the sun gear 72S integral with the carrier 71C, the planetary gear 72P meshing with the sun gear 72S, the carrier 72C rotatably supporting the planetary gear 72P, and the internal gear 70 meshing with the planetary gear 72P. The planetary gear 71P is connected to the internal gear 70 via the carrier 71C, the sun gear 72S, and the planetary gear 72P.

[0103] Next, the assembler inserts the torque sensor 9 through the opening 32 into the gear case 3 in which the planetary gear mechanism 7 is housed. As described above, the torque sensor 9 has the front plate portion 91, the rear plate portion 92 disposed rearward of the front plate portion 91, the hollow portion 90 disposed between the front plate portion 91 and the rear plate portion 92 in the front-rear direction, the strain gauge 93 fixed to the hollow portion 90, and the lead wire 94 connected to the strain gauge 93. The assembler inserts the torque sensor 9 into the gear case 3 so that the internal gear 70 housed in the gear case 3 and the gear 91G provided on the front plate portion 91 of the torque sensor 9 mesh with each other. The front plate portion 91 is coupled to the internal gear 70 by the internal gear 70 and the gear 91G meshing with each other.

[0104] After the internal gear 70 and the gear 91G of the front plate portion 91 are meshed, the assembly worker rotates the rear plate portion 92 and the gear case 3 relative to each other so that the rear plate portion 92 and the gear case 3 are aligned in the circumferential direction of the rotation axis AX. As described above, the internal gear 70 is rotatable with respect to the gear case 3. When the internal gear 70 and the gear 91G of the front plate portion 91 are meshed with each other, the rear plate portion 92 is rotated, whereby the torque sensor 9 can rotate together with the internal gear 70 with respect to the gear case 3.

[0105] As described above, the rear plate portion 92 is provided with a recess 92D (first recess). The gear case 3 is provided with a recess 33 (second recess). Aligning the rear plate portion 92 and the gear case 3 includes aligning the recess 92D and the recess 33. The assembly worker rotates the rear plate portion 92 with the internal gear 70 and the gear 91G of the front plate portion 91 engaged, so that the recess 92D and the recess 33 are aligned in the circumferential direction. As the rear plate portion 92 is rotated, the torque sensor 9 and the internal gear 70 rotate relative to the gear case 3.

[0106] 12, the recesses 92D and the recesses 33 are arranged at unequal intervals in the circumferential direction. The assembly worker rotates the rear plate 92 so that the recesses 92D1 and 331 are aligned, the recesses 92D2 and 332 are aligned, and the recesses 92D3 and 333 are aligned.

[0107] The lead wires 94 are preferably arranged so as to extend downward from the hollow portion 90. The lead wires 94 are arranged so as to extend downward from the hollow portion 90 when the three recesses 92D and the three recesses 33 are aligned. In the embodiment, the three recesses 92D and the three recesses 33 are arranged at unequal intervals in the circumferential direction, and therefore, an assembler can arrange the lead wires 94 so as to extend downward from the hollow portion 90 by aligning the three recesses 92D and the three recesses 33.

[0108] When the three recesses 92D and the three recesses 33 are arranged at equal intervals in the circumferential direction, when the recess 92D1 and the recess 331 are aligned, the recess 92D2 and the recess 332 are aligned, and the recess 92D3 and the recess 333 are aligned. When the recess 92D1 and the recess 332 are aligned, the recess 92D2 and the recess 333 are aligned, and the recess 92D3 and the recess 331 are aligned. When the recess 92D1 and the recess 333 are aligned, the recess 92D2 and the recess 331 are aligned, and the recess 92D3 and the recess 332 are aligned. In this way, when the three recesses 92D and the three recesses 33 are arranged at equal intervals in the circumferential direction, there are three patterns in which the three recesses 92D and the three recesses 33 are aligned. When there are a plurality of patterns in which the three recesses 92D and the three recesses 33 are aligned, even if the three recesses 92D and the three recesses 33 are aligned, the lead wires 94 may not be arranged to extend downward from the hollow portion 90. According to the embodiment, the recesses 92D and the recesses 33 are arranged at unequal intervals in the circumferential direction, and therefore, by aligning the three recesses 92D and the three recesses 33 in the circumferential direction, the lead wires 94 are arranged to extend downward from the hollow portion 90. This suppresses the occurrence of incorrect attachment by an assembly worker.

[0109] After the recess 92D and the recess 33 are aligned, the assembler fixes the rear plate portion 92 and the gear case 3 together. Fixing the rear plate portion 92 and the gear case 3 includes arranging a fixing member 17 in the aligned recess 92D and recess 33. The assembler inserts the fixing member 17 into each of the recess 92D and the recess 33 from behind the rear plate portion 92. By arranging the fixing member 17 in each of the recess 92D and the recess 33, relative rotation between the rear plate portion 92 and the gear case 3 about the rotation axis AX is suppressed.

[0110] After the rear plate portion 92 and the gear case 3 are fixed by the fixing member 17, the assembly worker inserts the bearing box 6 into the gear case 3.

[0111] 13 and 14 , a screw thread 60 is provided on at least a part of an outer circumferential surface 6C of the bearing box 6. A screw groove 35 is provided on at least a part of an inner circumferential surface 3D of the gear case 3. An assembly worker attaches a nut tightening tool to a nut portion 61 of the bearing box 6, and rotates the bearing box 6. By rotating the bearing box 6, the bearing box 6 is screwed into the gear case 3, and the bearing box 6 is fixed to the gear case 3.

[0112] The bearing box 6 is housed in the gear case 3 such that a front surface 6A of the bearing box 6 contacts a rear surface 92B of the rear plate portion 92. The bearing box 6 is housed in the gear case 3 such that a rear surface 6B of the bearing box 6 is disposed forward of a rear end surface 3B of the gear case 3.

[0113] After the bearing box 6 is inserted into the gear case 3 and the gear case 3 and the bearing box 6 are fixed, the assembly worker inserts the rotor shaft 53 into the inside of the hollow portion 90 of the torque sensor 9 so that the pinion gear 71S attached to the front end of the rotor shaft 53 meshes with the planetary gear 71P of the planetary gear mechanism 7.

[0114] Fig. 15 is a perspective view from the front left showing how to insert the rotor shaft 53 into the gear case 3 according to the embodiment. Fig. 16 is a perspective view from the rear right showing how to insert the rotor shaft 53 into the gear case 3 according to the embodiment.

[0115] 15 and 16, a bearing box 6 is fixed to the gear case 3. A pinion gear 71S is attached to the front end of the rotor shaft 53. A bearing 54 is disposed around the rotor shaft 53.

[0116] In the embodiment, the inner diameter of the bearing 54 is smaller than the outer diameter of the pinion gear 71S.

[0117] An assembly worker inserts the pinion gear 71S into the gear case 3 through the opening 64 of the bearing box 6. Inside the gear case 3, a torque sensor 9 is disposed in front of the bearing box 6, and the planetary gear mechanism 7 is disposed in front of the torque sensor 9. The pinion gear 71S inserted into the gear case 3 can pass through a through hole 96 of the torque sensor 9 and reach a planetary gear 71P of the planetary gear mechanism 7. An assembly worker can insert the rotor shaft 53 into the gear case 3 so that the pinion gear 71S attached to the front end of the rotor shaft 53 meshes with the planetary gear 71P of the planetary gear mechanism 7.

[0118] When the rotor shaft 53 is inserted inside the gear case 3, the bearing 54 is disposed in the opening 64 of the bearing box 6. The bearing 54 is supported by the bearing box 6.

[0119] [Operation] In a screw tightening operation, the controller 15 starts the motor 5 to rotate the output unit 8 based on an operation signal of the trigger switch 11. In a screw tightening operation, when a screw is screwed into a work object, the torque applied to the output unit 8 increases. The torque applied to the output unit 8 is transmitted to the internal gear 70 via the carrier 72C and the planetary gear 72P. The torque applied to the internal gear 70 is transmitted to the torque sensor 9 via the front plate portion 91. The torque applied to the output unit 8 is detected by the torque sensor 9.

[0120] The rear plate portion 92 of the torque sensor 9 is fixed to the gear case 3. The hollow portion 90 of the torque sensor 9 is twisted in the rotational direction by the internal gear 70. The front plate portion 91 and the rear plate portion 92 also receive torque, but each of the front plate portion 91 and the rear plate portion 92 has a larger diameter than the hollow portion 90. Therefore, the torsional deformation of the front plate portion 91 and the rear plate portion 92 is smaller than the torsional deformation of the hollow portion 90. When the hollow portion 90 of the torque sensor 9 is twisted in the rotational direction, four strain gauges 93 arranged on the surface of the hollow portion 90 are deformed. Due to the deformation of the strain gauges 93, a detection signal (voltage) indicating the torque applied to the hollow portion 90 is transmitted from the strain gauges 93 to the controller 15 via the lead wires 94.

[0121] The controller 15 acquires a detection signal of the torque sensor 9. The controller 15 calculates the torque applied to the output unit 8 based on the detection signal of the torque sensor 9. A target torque is registered in the controller 15. The controller 15 controls the motor 5 based on the detection signal of the torque sensor 9 so that the screw is tightened into the work object with the target torque.

[0122] When the controller 15 determines, based on the detection signal of the torque sensor 9, that the torque applied to the output unit 8 has reached the target torque, the controller 15 controls the motor 5 to stop the rotation of the rotor 52. In this way, the controller 15 can control the motor 5, based on the detection signal of the torque sensor 9, so that the screw is tightened into the work object at the target torque.

[0123] In the embodiment, the screw fastener 1 has a wireless communication device (not shown). The wireless communication device is disposed in a specified portion of the housing 2. The wireless communication device is capable of short-distance wireless communication using a communication method that does not require a wireless license. The wireless communication device is capable of wireless communication using a communication method that complies with the IEEE802.15.1 standard standardized by the Institute of Electrical and Electronics Engineers (IEEE).

[0124] The controller 15 transmits the detection signal of the torque sensor 9 to a wireless communication device. The wireless communication device transmits the detection signal of the torque sensor 9 to a management computer disposed outside the screw fastening machine 1. The management computer records the detection signal of the torque sensor 9 during the screw fastening operation.

[0125] [effect] As described above, according to the embodiment, the screw fastener 1 has the gear case 3 that houses the planetary gear mechanism 7 and the torque sensor 9, and the bearing box 6 that supports the bearing 54. The bearing 54 supports at least a part of the rotor 52. The gear case 3 and the bearing box 6 are separate members. Therefore, vibrations in the rotational direction generated in the rotor 52 are suppressed from being transmitted to the torque sensor 9. Since vibrations that function as disturbances are suppressed from being transmitted to the torque sensor 9, a decrease in the detection accuracy of the torque sensor 9 is suppressed.

[0126] At least a portion of the bearing box 6 is housed in the gear case 3 through an opening 32 provided in the rear of the gear case 3. Since at least a portion of the bearing box 6 is housed in the gear case 3, an increase in size of the screw fastener 1 in the axial direction is suppressed.

[0127] A rear surface 6B of the bearing box 6 is disposed forward of a rear end surface 3B of the gear case 3. Since the bearing box 6 is entirely housed in the gear case 3, an increase in size of the screw fastener 1 in the axial direction is suppressed.

[0128] The bearing box 6 is fixed to the gear case 3. This suppresses changes in the relative positions of the bearing box 6 and the gear case 3.

[0129] At least a portion of an outer circumferential surface 6C of the bearing box 6 is provided with a screw thread 60. At least a portion of an inner circumferential surface 3D of the gear case 3 is provided with a screw groove 35. The bearing box 6 is easily fixed to the gear case 3 by engagement between the screw thread 60 and the screw groove 35.

[0130] The bearing box 6 has a straight body portion 63 disposed forward of the thread 60. The gear case 3 has a straight pipe portion 37 disposed forward of the thread groove 35. When the thread 60 and the thread groove 35 are engaged, the outer peripheral surface of the straight body portion 63 comes into contact with the inner peripheral surface of the straight pipe portion 37. The contact between the outer peripheral surface of the straight body portion 63 and the inner peripheral surface of the straight pipe portion 37 positions the bearing box 6 and the gear case 3 at least in the radial direction.

[0131] The front surface 6A of the bearing box 6 contacts the rear surface 92B of the rear plate portion 92. Due to the contact between the front surface 6A of the bearing box 6 and the rear surface 92B of the rear plate portion 92, the bearing box 6, the gear case 3, and the torque sensor 9 are positioned at least in the axial direction.

[0132] An elastic member 74 (first elastic member) is disposed in a groove 31 provided in an inner peripheral surface 3D of the gear case 3. A rear end surface 70B of the internal gear 70 contacts the elastic member 74. This positions the internal gear 70 and the gear case 3 at least in the axial direction. In addition, transmission of vibrations of the internal gear 70 to the gear case 3 is suppressed.

[0133] The pinion gear 71S is detachable from the rotor shaft 53. The pinion gear 71S is replaceable. The planetary gear mechanism 7 is also replaceable. This allows the gear ratio between the rotor shaft 53 and the output unit 8 to be determined arbitrarily.

[0134] The inner diameter of the bearing 54 is smaller than the outer diameter of the pinion gear 71S. That is, the outer diameter of the rotor shaft 53 is smaller than the outer diameter of the pinion gear 71S. Since the rotor shaft 53 is thin, the inertia of the rotor shaft 53 in the rotation direction is small. In the screw tightening operation, the motor 5 is controlled so that the rotation of the rotor 52 is stopped. Since the inertia of the rotor shaft 53 in the rotation direction is small, when the controller 15 starts the control to stop the rotation of the rotor 52, the rotor 52 can immediately stop rotating. Therefore, the screw is tightened to the work object with the target torque.

[0135] An elastic member 75 (second elastic member) is disposed between the gear case 3 and the internal gear 70. This prevents vibrations of the internal gear 70 from being transmitted to the gear case 3 and prevents abnormal noise from being generated.

[0136] A gear 91G is provided on the front plate portion 91 of the torque sensor 9. The gear 91G of the front plate portion 91 meshes with the internal gear 70. Torque applied to the output portion 8 during a screw tightening operation is transmitted to the internal gear 70 via the carrier 72C and the planetary gear 72P. The torque sensor 9 and the internal gear 70 are connected via the gear 91G, so that the torque applied to the internal gear 70 is transmitted to the torque sensor 9.

[0137] The rear plate portion 92 of the torque sensor 9 and the gear case 3 are fixed by a fixing member 17. The fixing member 17 contacts each of the first portion 95 of the rear plate portion 92 and the second portion 34 of the gear case 3, thereby fixing the rear plate portion 92 of the torque sensor 9 and the gear case 3. As a result, the torque sensor 9 is appropriately twisted by the torque applied to the output portion 8. As the torque sensor 9 is appropriately twisted, a decrease in the detection accuracy of the torque sensor 9 is suppressed. In addition, the fixing member 17 is disposed radially inward of the outer circumferential surface 92C of the rear plate portion 92. As a result, an increase in size of the gear case 3 in the radial direction is suppressed.

[0138] A recess 92D (first recess) is provided on an outer peripheral surface 92C of the rear plate portion 92. A recess 33 (second recess) is provided on an inner peripheral surface 3D of the gear case 3. The fixing member 17 includes a pin that is disposed in the recess 92D and the recess 33. The first portion 95 includes an inner surface of the recess 92D. The second portion 34 includes an inner surface of the recess 33. As a result, the rear plate portion 92 of the torque sensor 9 and the gear case 3 are easily fixed together by simply inserting the fixing member 17 into the recess 92D and the recess 33 from the rear of the rear plate portion 92.

[0139] A plurality of first portions 95 and a plurality of second portions 34 are provided in the circumferential direction of the rotation axis AX. In the circumferential direction, the first portions 95 and the second portions 34 are arranged at unequal intervals. As a result, when the torque sensor 9 and the gear case 3 are fixed so that the lead wires 94 extend downward from the hollow portion 90, for example, an assembly worker can fix the torque sensor 9 and the gear case 3 so that the lead wires 94 extend downward from the hollow portion 90 by aligning the plurality of recesses 92D with the plurality of recesses 33. This suppresses the occurrence of human error by the assembly worker, and suppresses erroneous attachment of the torque sensor 9 to the gear case 3.

[0140] After the gear 91G of the front plate portion 91 and the internal gear 70 are coupled together and before the rear plate portion 92 and the gear case 3 are fixed by the fixing member 17, the torque sensor 9 and the gear case 3 rotate relative to each other. This allows an assembly worker to rotate the rear plate portion 92, thereby rotating the torque sensor 9 and the internal gear 70 together with respect to the gear case 3 so that the recess 92D and the recess 33 are aligned.

[0141] When assembling the screw fastener 1, the torque sensor 9 is inserted into the gear case 3 housing the planetary gear 71P and the internal gear 70 connected to the planetary gear 71P, and the internal gear 70 is meshed with the gear 91G provided on the front plate portion 91. After the internal gear 70 is meshed with the gear 91G, the rear plate portion 92 and the gear case 3 are rotated relative to each other so that the rear plate portion 92 and the gear case 3 are aligned in the circumferential direction. After the rear plate portion 92 and the gear case 3 are aligned in the circumferential direction, the rear plate portion 92 and the gear case 3 are fixed. This allows the screw fastener 1 to be assembled with good ease of assembly.

[0142] A recess 92D (first recess) is provided in the rear plate portion 92. A recess 33 (second recess) is provided in the gear case 3. Aligning the rear plate portion 92 and the gear case 3 in the circumferential direction includes aligning the recess 92D and the recess 33. Fixing the rear plate portion 92 and the gear case 3 includes placing a fixing member 17 in the recess 92D and the recess 33 that are aligned in the circumferential direction. This allows the screw fastener 1 to be assembled with good ease of assembly.

[0143] After the rear plate portion 92 and the gear case 3 are fixed, the bearing box 6 is inserted into the gear case 3. After the bearing box 6 is inserted into the gear case 3 and the gear case 3 and the bearing box 6 are fixed, the rotor shaft 53 is inserted into the inside of the hollow portion 90 so that the pinion gear 71S attached to the front end portion of the rotor shaft 53 meshes with the planetary gear 71P. In addition, the bearing 54 supporting the rotor shaft 53 of the motor 5 is inserted into the opening 64 of the bearing box 6. In this way, the screw fastener 1 can be assembled with good ease.

[0144] [Other embodiments] In the above-described embodiment, the planetary gear 71P meshing with the pinion gear 71S is connected to the internal gear 70 via the carrier 71C, the sun gear 72S, and the planetary gear 72P. The planetary gear 71P may mesh with the internal gear 70. The carrier 71C may be connected to the output unit 8. In other words, the sun gear 72S and the planetary gear 72P may be omitted.

[0145] In the above embodiment, the battery pack 16 mounted in the battery mounting section 4 is used as the power source for the screw fastener 1. A commercial power source (AC power source) may also be used as the power source for the screw fastener 1.

[0146] In the above embodiment, the screw driver 1 has been described as an example of the power tool. The power tool may have a motor 5 and an output unit 8 that rotates by the power generated by the motor 5. The power tool may be at least one of a vibration driver drill, a grinder, an angle drill, an impact driver, a hammer drill, a circular saw, and a reciprocating saw.

[0147] In the above-described embodiment, the power tool is an electric tool powered by the motor 5, which is an electric motor. The power tool may be a pneumatic tool powered by an air motor. The power source of the power tool is not limited to an electric motor or an air motor, and may be another power source. The power source of the power tool may be, for example, a hydraulic motor or a motor driven by an engine. [Explanation of symbols]

[0148] 1...screw tightening machine, 2...housing, 2B...screw boss portion, 2L...left housing, 2R...right housing, 2S...screw, 3...gear case, 3B...rear end surface, 3D...inner peripheral surface, 3E...recess, 3R...recess, 3T...protrusion, 4...battery mounting portion, 5...motor, 6...bearing box, 6A...front surface, 6B...rear surface, 6C...outer peripheral surface, 7...planetary gear mechanism, 8...output portion, 9...torque sensor, 10...fan, 11...trigger switch, 11A...trigger member, 11B...switch body, 12...forward / reverse switching lever, 13...audio output portion, 14...light emitting portion, 1 5...controller, 15A...board, 15B...controller case, 16...battery pack, 17...fixing member, 21...motor housing, 22...grip portion, 23...controller housing, 24...opening, 24A...intake port, 24B...exhaust port, 31...groove, 32...opening, 33...recess, 34...second portion, 35...thread groove, 36...connection portion, 37...straight tube portion, 51...stator, 51A...stator core, 51B...front insulator, 51C...rear insulator, 51D...coil, 51E...sensor board, 51F...short circuit member, 51G...fuse terminal, 52...rotor, 52A...rotor core, 52B...permanent magnet, 53...rotor shaft, 54...bearing, 55...bearing, 57...bearing retainer, 60...thread, 61...nut, 62...connection, 63...body, 64...opening, 70...internal gear, 70B...rear end surface, 70C...outer periphery, 71C...carrier, 71P...planetary gear, 71S...pinion gear, 72C...carrier, 72P...planetary gear, 72S...sun gear, 73...washer, 74...elastic member (first elastic member), 75...elastic member (second elastic member) elastic member), 76...groove, 81...spindle, 81A...insertion hole, 82...chuck, 82A...ball, 83...bearing, 84...bearing, 90...hollow portion, 91...front plate portion, 91A...front surface, 91B...rear surface, 91C...outer peripheral surface, 91D...gear, 92...rear plate portion, 92A...front surface, 92B...rear surface, 92C...outer peripheral surface, 92D...recess (first recess), 92D1...recess, 92D2...recess, 92D3...recess, 93...strain gauge, 94...lead wire, 95...first portion, 96...through hole, 331...recess, 332...recess, 333...recess, AX...rotating axis.

Claims

1. a motor having a stator and a rotor that rotates around a rotation axis extending in the front-rear direction; A gear case disposed forward of the stator; a planetary gear housed in the gear case and rotated by the rotor; an internal gear housed in the gear case, connected to the planetary gear, and rotatable relative to the gear case; a torque sensor housed in the gear case, the torque sensor having: a front plate portion connected to the internal gear; a rear plate portion disposed rearward of the front plate portion, supported by the gear case, and having an outer diameter larger than an outer diameter of the front plate portion; a hollow portion disposed between the front plate portion and the rear plate portion in the front-to-rear direction and integral with the front plate portion and the rear plate portion; and a strain gauge fixed to the hollow portion; a bearing disposed between the stator and the rear plate portion in the front-rear direction and supporting at least a portion of the rotor; a bearing box arranged around the bearing and supporting the bearing; A first elastic member is disposed in a groove provided on an inner circumferential surface of the gear case, A rear surface of the bearing box is disposed forward of a rear end surface of the gear case, a front surface of the bearing box contacts a rear surface of the rear plate portion; A rear end surface of the internal gear contacts the first elastic member. Screw tightening machine.

2. a motor having a stator and a rotor that rotates around a rotation axis extending in the front-rear direction; an output section disposed forward of the stator and driven by the rotor; A gear case disposed forward of the stator; a planetary gear mechanism including a planetary gear housed in the gear case and rotated by the rotor, and an internal gear housed in the gear case, connected to the planetary gear, and rotatable relative to the gear case, the planetary gear mechanism connecting the rotor and the output portion; a torque sensor that is housed in the gear case and has a front plate portion coupled to the internal gear, a rear plate portion disposed rearward of the front plate portion and supported by the gear case, a hollow portion disposed between the front plate portion and the rear plate portion in the front-rear direction, and a strain gauge fixed to the hollow portion; a bearing disposed between the stator and the rear plate portion in the front-rear direction and supporting at least a portion of the rotor; a bearing box arranged around the bearing and supporting the bearing; A grip portion that is held by the operator's hand; A first elastic member is provided on an inner circumferential surface of the gear case and positions the internal gear and the gear case at least in the axial direction, the planetary gear mechanism is disposed forward of the front plate portion of the torque sensor, At least a portion of the output portion is disposed forward of the planetary gear mechanism, the planetary gear mechanism reduces the rotation speed of the rotor and rotates the output portion at a lower rotational speed than the rotor; The planetary gear mechanism reduces the rotation speed of the rotor in two stages. Screw tightening machine.

3. At least a portion of the bearing box is accommodated in the gear case through an opening provided in a rear portion of the gear case. The screw fastener according to claim 1 or 2.

4. The bearing box is fixed to the gear case. The screw fastener according to claim 3.

5. At least a portion of the outer circumferential surface of the bearing box is provided with a screw thread; A thread groove is provided on at least a part of the inner circumferential surface of the gear case, The bearing box is fixed to the gear case by the engagement of the screw thread and the screw groove. The screw fastener according to claim 4.

6. The bearing box has a straight body portion disposed forward of the thread, The gear case has a straight pipe portion disposed forward of the screw groove, When the thread and the thread groove are coupled, the outer peripheral surface of the straight body portion and the inner peripheral surface of the straight pipe portion are in contact with each other. The screw fastener according to claim 5.

7. The rotor includes a rotor shaft, a rotor core disposed around the rotor shaft, and a permanent magnet held by the rotor core. the bearing supports a portion of the rotor shaft forward of the stator; A pinion gear connected to the planetary gear is attached to a front end of the rotor shaft, The pinion gear is detachable from the rotor shaft. The screw fastener according to any one of claims 1 to 6.

8. The inner diameter of the bearing is smaller than the outer diameter of the pinion gear. The screw fastener according to claim 7.

9. The inner circumferential surface of the gear case and the outer circumferential surface of the internal gear face each other, a second elastic member disposed between the gear case and the internal gear; The screw fastener according to any one of claims 1 to 8.

10. A gear is provided on the front plate portion, The gear of the front plate portion and the internal gear mesh with each other. A screw fastener according to any one of claims 1 to 9.

11. a fixing member disposed inside an outer circumferential surface of the rear plate portion in a radial direction of the rotation shaft, contacting each of a first portion of the rear plate portion and a second portion of the gear case, and suppressing relative rotation between the rear plate portion and the gear case; A screw fastener according to any one of claims 1 to 10.

12. a motor having a stator and a rotor that rotates around a rotation axis extending in the front-rear direction; A gear case disposed forward of the stator; a planetary gear housed in the gear case and rotated by the rotor; an internal gear housed in the gear case, connected to the planetary gear, and rotatable relative to the gear case; a torque sensor that is housed in the gear case and has a front plate portion coupled to the internal gear, a rear plate portion disposed rearward of the front plate portion and supported by the gear case, a hollow portion disposed between the front plate portion and the rear plate portion in the front-rear direction, and a strain gauge fixed to the hollow portion; a fixing member that is disposed inward of an outer circumferential surface of the rear plate portion in a radial direction of the rotation shaft, contacts each of a first portion of the rear plate portion and a second portion of the gear case, and suppresses relative rotation between the rear plate portion and the gear case; A first recess is provided on an outer peripheral surface of the rear plate portion, A second recess is provided on an inner circumferential surface of the gear case, the fixing member includes a pin disposed in the first recess and the second recess, the first portion includes an inner surface of the first recess, The second portion includes an inner surface of the second recess. Screw tightening machine.

13. The first portion and the second portion are each provided in a plurality of portions in a circumferential direction of the rotation shaft, The first portions and the second portions are arranged at unequal intervals in the circumferential direction. The screw fastener according to claim 11 or 12.

14. The front plate portion is coupled to the internal gear, and the torque sensor and the gear case rotate relative to each other in a state in which the fixing member is not in contact with the first portion and the second portion. A screw fastener according to any one of claims 11 to 13.

15. a gear case that houses a planetary gear and an internal gear connected to the planetary gear, the gear case including a front plate portion, a rear plate portion disposed rearward of the front plate portion, a hollow portion disposed between the front plate portion and the rear plate portion in the front-rear direction, and a torque sensor having a strain gauge fixed to the hollow portion; meshing the internal gear with a gear provided on the front plate portion; After the internal gear and the gear are engaged, the rear plate portion and the gear case are rotated relative to each other so that the rear plate portion and the gear case are aligned in a circumferential direction; and and fixing the rear plate portion and the gear case after the rear plate portion and the gear case are aligned. How to assemble a screwdriver.

16. A first recess is provided in the rear plate portion, A second recess is provided in the gear case, Aligning the rear plate portion and the gear case includes aligning the first recess and the second recess, Fixing the rear plate portion and the gear case includes disposing a fixing member in the aligned first recess and the aligned second recess. A method for assembling a screw fastener according to claim 15.

17. After the rear plate portion and the gear case are fixed, inserting a bearing box into the gear case; After the bearing box is inserted into the gear case, inserting the rotor shaft of a motor into the hollow portion so that a pinion gear attached to a front end of the rotor shaft meshes with the planetary gear; and inserting a bearing supporting the rotor shaft into the bearing box. The method for assembling a screw fastener according to claim 16.

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