Axial gap motor, robot, and robot system

Abstract

To reduce the outer diameter dimensions of axial gap motors.SOLUTION: A first motor 101 and a second motor 201 comprise: rotors 120, 220 rotating around the rotation axis AX3; stators 110, 210 opposing in the direction of the rotors 120, 220 and the rotation axis AX3; a back yoke section 403 provided in the stators 110, 210; a plurality of teeth 407 protruding from the back yoke section 403 toward one side in the direction of the rotation axis AX3; a plurality of coils 405 attached to the plurality of teeth 407; and a wiring board 413 located on the other side in the direction of the rotation axis AX3 with respect to the back yoke section 403 and connecting a plurality of drawn wires 411 drawn from the plurality of coils 405.SELECTED DRAWING: Figure 13

Description

[Technical field]

[0001] The disclosed embodiments relate to an axial gap motor, a robot, and a robot system. [Background technology]

[0002] Patent Document 1 describes an axial gap motor that includes a rotor fixed to a rotating shaft, and a first stator and a second stator that face each other on either axial side of the rotor with an air gap between them. In this axial gap motor, the first stator and the second stator have a back yoke, teeth that are axially provided on the rotor side of the back yoke, and coils wound around the teeth, and a connection plate that connects the neutral side of the coil and the power supply side is disposed radially outward of the teeth. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2008-172859 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the above-described conventional technology, the connection plate is disposed radially outside the teeth, which poses a problem of increasing the outer diameter of the motor.

[0005] The present invention has been made in consideration of such problems, and has an object to provide an axial gap motor, a robot, and a robot system that can reduce the outer diameter dimensions. [Means for solving the problem]

[0006] In order to solve the above problem, according to one aspect of the present invention, an axial gap motor is applied, which has a rotor that rotates around a rotation axis, a stator that faces the rotor in the direction of the rotation axis, a first back yoke provided on either the rotor or the stator, a plurality of teeth that protrude from the first back yoke toward one side in the direction of the rotation axis, a plurality of coils attached to the plurality of teeth, and a connecting portion that is arranged on the other side of the first back yoke in the direction of the rotation axis and connects a plurality of lead wires drawn from the plurality of coils.

[0007] According to another aspect of the present invention, there is provided a robot having an axial gap motor disposed at a joint, the axial gap motor having a rotor rotating around a rotation axis, a stator facing the rotor in the direction of the rotation axis, a first back yoke provided on either the rotor or the stator, a plurality of teeth protruding from the first back yoke toward one side in the direction of the rotation axis, a plurality of coils attached to the plurality of teeth, and a wiring connection portion disposed on the other side of the first back yoke in the direction of the rotation axis and connecting a plurality of lead wires drawn from the plurality of coils.

[0008] According to another aspect of the present invention, a robot system is provided, comprising the above-mentioned robot and a control device that controls the operation of the robot. Effect of the Invention

[0009] According to the axial gap motor etc. of the present invention, the outer diameter dimension can be reduced. [Brief description of the drawings]

[0010] [Figure 1] FIG. 1 is a diagram illustrating an example of an overall configuration of a robot system according to an embodiment. [Diagram 2]4 is a perspective view illustrating an example of an external configuration of a first motor unit and a second motor unit provided at a tip portion of a second arm. FIG. [Diagram 3] FIG. 4 is an exploded perspective view illustrating an example of an internal configuration of a first motor unit. [Figure 4] FIG. 4 is an exploded perspective view illustrating an example of an internal configuration of a second motor unit. [Diagram 5] 3 is a cross-sectional view illustrating an example of an internal configuration of a first motor unit and a second motor unit. FIG. [Figure 6] FIG. 1 is a perspective view illustrating an example of an overall configuration of a rotor. [Figure 7] 2 is a plan view showing an example of an overall configuration of a rotor, as viewed from the stator side in the axial direction. FIG. [Figure 8] FIG. 2 is a plan view illustrating an example of the shape of a magnet provided in a rotor. [Figure 9] 1 is a plan view showing an example of a manner in which a plurality of magnets provided in a rotor are cut out from a magnet sheet. FIG. [Figure 10] 1 is a graph showing an example of a relationship between cogging torque and a coefficient of a shift angle of a magnet. [Figure 11] FIG. 2 is a perspective view showing an example of an overall configuration of a stator, as viewed from the coil side. [Figure 12] FIG. 2 is a perspective view showing an example of an overall configuration of a stator, as viewed from the wiring board side. [Figure 13] 1 is a cross-sectional view illustrating an example of an overall configuration of a stator. [Figure 14] FIG. 2 is a perspective view illustrating an example of a configuration of a bobbin included in the stator. [Figure 15] FIG. 2 is a plan view illustrating an example of an arrangement of magnets in a rotor according to the embodiment. [Figure 16] 13 is a plan view showing an example of magnet arrangement of a rotor according to a modified example in which the magnets are not skewed. FIG. [Figure 17] 13 is a plan view showing an example of magnet arrangement of a rotor according to a modified example in which the radially outer and inner edges of the magnets are arc-shaped. FIG. [Figure 18]13 is a plan view showing an example of magnet arrangement of a rotor according to a modified example in which the radially outer and inner edges of the magnets are arc-shaped and the magnets are not skewed. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the embodiments will be described with reference to the drawings. In the embodiments, for convenience of explanation of the configuration of a robot, etc., a three-dimensional Cartesian coordinate system with X-axis, Y-axis, and Z-axis may be appropriately used. The Z-axis has a positive direction in the vertical upward direction, the X-axis is along the extension direction of the arm supporting the hand, and the tip side supporting the hand is the positive direction, and the Y-axis is perpendicular to the X-axis and Z-axis.

[0012] <1. Overall configuration of the robot system> An example of the overall configuration of a robot system 1 according to an embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram illustrating an example of the overall configuration of a robot system 1 according to an embodiment.

[0013] As shown in FIG. 1, the robot system 1 includes a transport robot 10 and a control device 20 that controls the operation of the robot 10. The transport robot 10 (an example of a robot) includes a main body 15 that is installed on a floor surface or the like, and a lifting unit 16 that moves up and down relative to the main body 15. The lifting unit 16 lifts and lowers a first arm 11 and a second arm 12 that are horizontal articulated arms. Two hands 13A and 13B, for example, are provided on the tip side of the second arm 12. The hands 13A and 13B can each hold a transported object such as a semiconductor substrate. The transport robot 10 includes three joints J1, J2, and J3, for example. At the joint J1, the first arm 11 rotates around a rotation axis AX1 of a motor relative to the lifting unit 16. At the joint J2, the second arm 12 rotates around a rotation axis AX2 of a motor relative to the tip of the first arm 11. At the joint J3, the hands 13A and 13B rotate coaxially around a rotation axis AX3 of a motor. The rotation axes AX1, AX2, and AX3 are substantially parallel to the Z axis.

[0014] Although two hands 13A, 13B are shown in Fig. 1, three or more hands may be used. Also, although the horizontal articulated arm is configured with two arms (first arm 11 and second arm 12) in Fig. 1, the arm may be one, or three or more arms.

[0015] The control device 20 is connected to the transfer robot 10. The control device 20 includes a control unit 21 and a storage unit 22. The control unit 21 includes an operation control unit 21a. The storage unit 22 stores teaching data 22a.

[0016] The operation control unit 21a controls the operation of the transport robot 10 based on the teaching data 22a. As an example, the operation control unit 21a causes the transport robot 10 to transport an object such as a substrate by issuing instructions to the motors corresponding to each axis of the transport robot 10 based on the teaching data 22a stored in the storage unit 22. The operation control unit 21a performs feedback control using detection values ​​of encoders in the motors. The operation control unit 21a may perform processing to stop or decelerate the operation of the transport robot 10 when an error occurs in the operation of the transport robot 10.

[0017] The teaching data 22a is generated by teaching the transport robot 10 to perform an operation. The teaching data 22a is information that specifies the operation of the transport robot 10, such as a moving trajectory of a hand. Note that the teaching data 22a generated by another computer connected via a wired or wireless network may be stored in the storage unit 22.

[0018] <2. Motor unit configuration> An example of the configuration of a motor unit for driving a hand provided in the joint J3 of the transport robot 10 will be described with reference to Figs. 2 to 5. Fig. 2 is a perspective view showing an example of the external configuration of a first motor unit and a second motor unit provided at the tip of the second arm. Fig. 3 is an exploded perspective view showing an example of the internal configuration of the first motor unit, and Fig. 4 is an exploded perspective view showing an example of the internal configuration of the second motor unit. Fig. 5 is a cross-sectional view that typically shows an example of the internal configuration of the first motor unit and the second motor unit. Note that Fig. 5 corresponds to a cross-sectional view cut along a plane parallel to the YZ plane at the position of the rotation axis AX3 when the second arm 12 is viewed from the tip side to the base end side.

[0019] As shown in FIG. 2, a first motor unit 100 and a second motor unit 200 for driving two hands 13A and 13B are provided on the tip side of the base frame 12A of the second arm 12. The first motor unit 100 and the second motor unit 200 are arranged in a stacked manner along the rotation axis AX3, and in the example shown in FIG. 2, the first motor unit 100 is arranged above the second motor unit 200. The first motor unit 100 includes a subframe 12S1 and a first motor 101 built into the subframe 12S1. The second motor unit 200 includes a subframe 12S2 and a second motor 201 built into the subframe 12S2. The base frame 12A and the subframes 12S1 and 12S2 form the housing of the second arm 12. In FIG. 2, the base frame 12A is indicated by a dashed line.

[0020] The first motor 101 and the second motor 201 are arranged side by side along the rotation axis AX3, with the rotation axis AX3 as a common axis. The first motor 101 drives the hand 13A, and the second motor 201 drives the hand 13B. The first motor 101 and the second motor 201 are so-called axial gap motors in which a rotor and a stator face each other along the rotation axis AX3. The first motor 101 and the second motor 201 directly drive the hands 13A and 13B, respectively.

[0021] The first motor 101 and the second motor 201 are so-called hollow motors having a hollow portion penetrating along the rotation axis AX3. The first motor 101 includes a hollow shaft 102, and the second motor 201 includes a hollow shaft 202. The hollow shaft 102 is connected to a rotor 120 of the first motor 101 (see Figs. 3 and 5 described later), and the hollow shaft 202 is connected to a rotor 220 of the second motor 201 (see Figs. 4 and 5 described later). The hollow shafts 102 and 202 extend along the rotation axis AX3 and rotate around the rotation axis AX3.

[0022] 2, the hollow shaft 102 of the first motor 101 protrudes to the upper surface side of the subframe 12S1 of the first motor unit 100. The hollow shaft 202 of the second motor 201 is inserted through the hollow shaft 102 of the first motor 101, passes through the first motor unit 100, and protrudes to the upper surface side of the subframe 12S1. A hand 13A is connected to the hollow shaft 102, and a hand 13B is connected to the hollow shaft 202. The inner hollow shaft 202 rotates the upper hand 13B, and the outer hollow shaft 102 rotates the lower hand 13A.

[0023] When there are three or more hands, the same number of motor units as the hands may be provided.

[0024] As shown in Fig. 3, the first motor unit 100 includes a first motor 101 and a subframe 12S1. Fig. 3 does not show a cover that is detachably attached to the top surface of the subframe 12S1, a communication hole that is provided on the side of the subframe 12S1 that is connected to the base frame 12A and through which a cable 103 (see Fig. 2) is inserted, and an inner wall that is provided inside the subframe 12S1 and to which each component of the first motor 101 is attached.

[0025] The first motor 101 (an example of an axial gap motor) includes a rotor 120 that rotates about a rotation axis AX3, and a stator 110 that faces the rotor 120 in the direction of the rotation axis AX3. The first motor 101 includes a shaft portion 102a and a boss portion 102b that configure the hollow shaft 102 shown in FIG. 2, a bearing 140, and a bearing presser 141. The first motor 101 includes an encoder 130. The encoder 130 includes a disk portion 131, a detection portion 132, and a support portion 133.

[0026] The stator 110 is disk-shaped with a hollow portion along the rotating axis AX3, and is provided with teeth and coils wound around the teeth on the end surface on the rotor 120 side. The detailed structure of the stator 110 will be described later. The rotor 120 is disk-shaped with a hollow portion along the rotating axis AX3 that communicates with the hollow portion of the stator 110, and a plurality of magnets are provided along the circumferential direction on the end surface on the stator 110 side. The detailed structure of the rotor 120 will be described later. A disk portion 131 of the encoder 130 is fixed to the end surface of the rotor 120 opposite to the stator 110. The disk portion 131 also has a hollow portion that communicates with the hollow portion of the rotor 120.

[0027] The shaft portion 102a of the hollow shaft 102 is fixed to the upper surface of the rotor 120. The stator 110 is disposed such that the inner circumference is spaced apart from the outer circumference of the shaft portion 102a. The bearing 140 is a so-called cross roller bearing. The inner circumference side of the bearing 140 is fixed to the outer circumference of the boss portion 102b of the hollow shaft 102, and the outer circumference side of the bearing 140 is fixed to the subframe 12S1 by a bearing holder 141. Note that in FIG. 3, the inner wall of the subframe 12S1 to which the bearing 140 is fixed is omitted. The boss portion 102b of the hollow shaft 102 is fixed to the upper surface of the shaft portion 102a such that the hollow portion communicates with the hollow portion of the shaft portion 102a.

[0028] The detection unit 132 of the encoder 130 is disposed so as to face the disk unit 131 provided on the end surface of the rotor 120. The support unit 133 supports the end surface side of the detection unit 132 opposite to the disk unit 131, and is fixed to the subframe 12S1. Note that the support unit 133 may be shaped so as to be fixable to the stator 110, and may be fixed to the stator 110.

[0029] As shown in Fig. 4, the second motor unit 200 includes a second motor 201 and a subframe 12S2. Note that Fig. 4 does not show a communication hole provided on the side surface of the subframe 12S2 connected to the base frame 12A for inserting a cable 203 (see Fig. 2), an inner wall provided inside the subframe 12S2 to which each component of the second motor 201 is attached, and the like.

[0030] The second motor 201 (an example of an axial gap motor) includes a rotor 220 that rotates about a rotation axis AX3, and a stator 210 that faces the rotor 220 in the direction of the rotation axis AX3. The second motor 201 includes the hollow shaft 202 shown in FIG. 2, a bearing 240, an outer periphery holder 241, and an inner periphery holder 242. The outer periphery holder 241 is a component that holds the outer periphery of the bearing 240, and the inner periphery holder 242 is a component that holds the inner periphery of the bearing 240. The second motor 201 includes an encoder 230. The encoder 230 includes a disk unit 231, a detection unit 232, and a support unit 233.

[0031] The stator 210 is disk-shaped with a hollow portion along the rotating axis AX3, and is provided with teeth and coils wound around the teeth on the end surface on the rotor 220 side. The detailed structure of the stator 210 will be described later. The rotor 220 is disk-shaped with a hollow portion along the rotating axis AX3 that communicates with the hollow portion of the stator 210, and a plurality of magnets are provided along the circumferential direction on the end surface on the stator 210 side. The detailed structure of the rotor 220 will be described later. A disk portion 231 of the encoder 230 is fixed to the end surface of the rotor 220 opposite to the stator 210. The disk portion 231 is provided with a hollow portion through which the hollow shaft 202 passes.

[0032] The hollow shaft 202 is fixed to the upper surface of the rotor 220. The bearing 240 is a so-called cross roller bearing. The inner periphery side of the bearing 240 is fixed to the outer periphery of the hollow shaft 202 by an inner periphery holder 242, and the outer periphery side of the bearing 240 is fixed to the subframe 12S2 by an outer periphery holder 241.

[0033] The detection unit 232 of the encoder 230 is disposed so as to face the disk unit 231 provided on the end surface of the rotor 220. The support unit 233 supports the end surface side of the detection unit 232 opposite to the disk unit 231, and is fixed to the subframe 12S2. Note that the support unit 233 may be shaped so as to be fixable to the stator 210, and may be fixed to the stator 210.

[0034] Next, the second arm 12 in a state in which the first motor unit 100 shown in FIG. 3 and the second motor unit 200 shown in FIG. 4 are assembled will be described with reference to FIG.

[0035] 5, the boss 102b of the hollow shaft 102 of the first motor unit 100 protrudes upward from the upper surface of the second arm 12. The hollow shaft 202 of the second motor unit 200 passes through the hollow shaft 102 of the first motor unit 100 and protrudes upward from the upper surface of the second arm 12.

[0036] The first motor 101 and the second motor 201 have their respective components arranged along the rotation axis AX3 from the lower surface to the upper surface of the second arm 12 in the following order: stator 210 of the second motor 201, rotor 220, rotor 120 of the first motor 101, and stator 110.

[0037] The encoder 130 of the first motor unit 100 is disposed at a position facing the lower surface side of the rotor 120 in the first motor unit 100, and the encoder 230 of the second motor unit 200 is disposed at a position facing the upper surface side of the rotor 220 in the second motor unit 200. As shown in Fig. 5, the encoder 130 and the encoder 230 are disposed at approximately the same height in the direction along the rotation axis AX3.

[0038] 5, the first motor 101 and the second motor 201 have a hollow portion 12H that penetrates from the lower surface side to the upper surface side of the second arm 12 along the rotation axis AX3. For example, a cable for the hand 13B connected to the hollow shaft 202 of the second motor unit 200 can be wired in the hollow portion 12H.

[0039] <3. Rotor configuration> With reference to Figs. 6 to 10, an example of the configuration of the rotor 120 of the first motor 101 and the rotor 220 of the second motor 201 will be described. The rotor 120 and the rotor 220 have the same configuration. Fig. 6 is a perspective view showing an example of the overall configuration of the rotors 120 and 220, Fig. 7 is a plan view showing an example of the overall configuration of the rotors 120 and 220 as seen from the stator side in the axial direction, Fig. 8 is a plan view showing an example of the shape of the magnets provided in the rotors 120 and 220, Fig. 9 is a plan view showing an example of a mode in which a plurality of magnets provided in the rotors 120 and 220 are cut out from a plate-shaped magnet sheet, and Fig. 10 is a graph showing an example of the relationship between the cogging torque and the coefficient of the shift angle of the magnet. In the description of Figs. 6 to 10, the "circumferential direction" refers to the circumferential direction centered on the rotation axis AX3, and the "radial direction" refers to the radial direction centered on the rotation axis AX3.

[0040] As shown in FIG. 6 and FIG. 7, the rotor 120, 220 has an annular rotor core 300. The rotor core 300 has a cylindrical hollow portion 301 extending along the rotation axis AX3 at its center. The rotor core 300 has a hub portion 302 connected to the shaft portion 102a described above, and a back yoke portion 303 (an example of a second back yoke) on whose surface magnets are arranged. The rotor core 300 is made of a magnetic material. A plurality of magnets 305 are arranged along the circumferential direction around the rotation axis AX3 on the surface of the back yoke portion 303 facing the stator 110 or the stator 210. In this embodiment, a case where the number of magnets 305 is 20 (20 poles) will be described as an example, but the number of magnets 305 may be other than 20. The magnets 305 include a plurality of first magnets 307 (half the number of magnets 305) arranged at equal angular intervals in the circumferential direction, and a plurality of second magnets 309 (half the number of magnets 305) arranged at equal angular intervals in the circumferential direction. The second magnets 309 are arranged one by one between the first magnets 307, and are arranged at positions shifted by a predetermined shift angle θ1 (an example of a first angle) from the central angle of two first magnets 307 adjacent to each other in the circumferential direction. The first magnets 307 and the second magnets 309 have the same shape. That is, the magnets 305 have the same shape. In this embodiment, when there is no need to distinguish whether a magnet is the first magnet 307 or the second magnet 309, it is described as a magnet 305.

[0041] In addition, when describing the arrangement of each magnet in this embodiment, the reference position may be any reference position that is uniquely and uniformly determined, such as the center of gravity of the magnet, the end position on one or the other side in the circumferential direction, or the end position on one or the other side in the radial direction. In this embodiment, for example, the center of gravity of the magnet is used as the reference. Specifically, as shown in FIG. 7, the center of gravity position PG2 of the second magnet 309 is disposed at an angle shifted by a shift angle θ1 to one side in the circumferential direction (clockwise direction in FIG. 7) from the bisector Lb of the angle 2θ0 between the center of gravity positions PG1 of two first magnets 307 adjacent in the circumferential direction, and at a position where the radial distance from the rotation axis AX3 is the same as the center of gravity position PG1.

[0042] The arrangement of the multiple magnets 305 can also be expressed as follows. As shown in Fig. 7, the multiple magnets 305 are arranged at unequal intervals such that the interval between two circumferentially adjacent magnets 305 alternates between a first interval D1 and a second interval D2 smaller than the first interval D1 in the circumferential direction. The first interval D1 and the second interval D2 are intervals when the same position is taken in the radial direction centered on the rotation axis AX3, such as the position of the center of gravity of the magnets or the position of the end on one or the other side in the radial direction.

[0043] The arrangement of the magnets 305 can also be expressed as follows. As shown in FIG. 7, the magnets 305 are arranged at unequal intervals such that the angle between two magnets 305 adjacent in the circumferential direction alternates between a first angle θA and a second angle θB smaller than the first angle θA in the circumferential direction. The reference position for the angle between the magnets may be any reference position that is uniquely and uniformly determined, such as the center of gravity of the magnets or the end position on one or the other side in the circumferential direction. In this embodiment, the angles are based on the center of gravity positions PG1 and PG2 of the magnets as shown in FIG. 7.

[0044] As a result of arranging the multiple magnets 305 as described above, the gap shapes between the first magnet 307 and the second magnet 309 are alternately different shapes in the circumferential direction. As shown in the partially enlarged view of Fig. 7, the gap shapes S1 and S2 adjacent in the circumferential direction are non-similar to each other, and are shapes that do not match even when rotated around the rotation axis AX3. Note that in Fig. 7, the gap shapes S1 and S2 are shaped as a space between the first magnet 307 and the second magnet 309 that extends to the outer periphery of the back yoke portion 303, but the same applies even if the shape of the space is only between the first magnet 307 and the second magnet 309.

[0045] As shown in FIG. 6 and FIG. 7, a first recess 311 in which the first magnet 307 is accommodated and a second recess 313 in which the second magnet 309 is accommodated are formed on the surface of the back yoke portion 303 on the side where the magnet 305 is arranged. The first recess 311 is formed in a shape corresponding to the first magnet 307, and the first magnet 307 is fixed thereto by, for example, adhesion or the like. As shown in FIG. 7, at least one end of the first magnet 307 on one circumferential side and the other circumferential side abuts against at least one step portion 311a on the one circumferential side and the other circumferential side of the first recess 311, thereby positioning the first magnet 307 in the circumferential direction. In addition, the radially inner end of the first magnet 307 abuts against a step portion 311b on the radially inner side of the first recess 311, thereby positioning the first magnet 307 in the radial direction.

[0046] The second recess 313 is formed in a shape corresponding to the second magnet 309, and the second magnet 309 is fixed thereto by, for example, adhesion or the like. At least one end of the second magnet 309 on one circumferential side and the other circumferential side abuts against at least one step 313a on one circumferential side and the other circumferential side of the second recess 313, thereby positioning the second magnet 309 in the circumferential direction. Also, the radially inner end of the second magnet 309 abuts against a radially inner step 313b of the second recess 313, thereby positioning the second magnet 309 in the radial direction.

[0047] FIG. 8 shows an example of the shape of the magnet 305 (first magnet 307, second magnet 309). As shown in FIG. 8, the magnet 305 has a so-called skewed shape in which a side 305a on one side in the circumferential direction and a side 305b on the other side are inclined in the same direction by a predetermined skew angle θ2 (an example of a second angle) with respect to a radial direction DR centered on the rotation axis AX3. The magnet 305 has a shape in which an outer side 305c and an inner side 305d in the radial direction are linear and parallel. That is, the magnet 305 has a trapezoidal shape in which one opposite side consisting of the sides 305c and 305d is parallel and the other opposite side consisting of the sides 305a and 305b is not parallel.

[0048] FIG. 9 shows an example of a manner in which a plurality of magnets 305 are cut out from a magnet sheet. As shown in FIG. 9, a plurality of magnets 305 (for example, 32 pieces) are manufactured from a parallelogram-shaped plate-like magnet sheet 315. The parallelogram of the magnet sheet 315 is similar in shape to a parallelogram (shape of the divided sheet 317) formed by arranging a pair of magnets 305, 305 with their sides 305b facing each other and their sides 305c, 305d oriented in a staggered direction. By equally dividing the magnet sheet 315 into a plurality of pieces in the vertical and horizontal directions, a plurality of (for example, 16) parallelogram-shaped divided sheets 317 having a shape similar to the parallelogram of the magnet sheet 315 are formed. Furthermore, the divided sheet 317 is bisected in the longitudinal direction along a cutting line CL inclined with respect to the sides 305a on both sides in the longitudinal direction to form a pair of magnets 305, 305. In this way, it is possible to prevent excess portions from being generated in the magnet sheet 315, and it is possible to cut out the magnets 305 from the magnet sheet 315 without any waste.

[0049] Fig. 10 shows an example of the relationship between the cogging torque generated in the rotors 120, 220 and the coefficient K of the shift angle θ1 of the second magnet 309. The shift angle θ1 is expressed by the following formula (1) where LCM is the least common multiple of the number of slots in the stators 110, 210 and the number of poles in the rotors 120, 220, and K is the coefficient. The number of slots is the number of teeth in the stator 110 or stator 210, and the number of poles is the number of magnets 305 in the rotor 120 or rotor 220. Fig. 10 shows the magnitude of the cogging torque when the coefficient K is changed from 0 to 1.0. θ1=K×{(360° / LCM) / 2}...Equation (1)

[0050] For example, if the number of slots of the stators 110 and 210 is 24 and the number of poles of the rotors 120 and 220 is 20, the least common multiple LCM is 120. It is preferable that the least common multiple LCM is 6 times or more the number of poles of the rotors 120 and 220. That is, if the skew angle θ2 of the magnets 305 is increased, the effect of reducing the cogging torque is enhanced, but depending on the slot combination of the motor, it may be difficult to arrange the multiple magnets 305 at unequal intervals. In that case, it is possible to arrange the magnets 305 by reducing their size, but this will result in a decrease in the output torque of the motor. If the least common multiple LCM is 6 times or more the number of poles, the shift angle θ1 can be reduced by the above formula (1). This makes it possible to simultaneously apply both a relatively large skew angle θ2 and an unequal arrangement of the magnets 305 while suppressing the size of the magnets 305 from being reduced.

[0051] One cycle of the waveform of the cogging torque generated in the rotors 120, 220 is expressed as (360° / LCM). Therefore, by setting the shift angle θ1 of the second magnet 309 to half the cycle of the waveform of the cogging torque {(360° / LCM) / 2}, that is, by setting the coefficient K=1 in the above formula (1), it is possible to reduce the cogging torque compared to when the shift angle θ1 is 0 degrees (when K=0), as shown in FIG.

[0052] As shown in Fig. 10, when the coefficient K is changed from 0 to 1.0, in other words when the shift angle θ1 is changed from 0 degrees to {(360° / LCM) / 2}, which is half one cycle of the cogging torque waveform, the cogging torque does not gradually decrease and reach its minimum value when the coefficient K=1.0, but rather reaches its minimum value when the coefficient K is less than 1.0. This is believed to be due to the following.

[0053] In general, in an axial gap motor with an open slot structure, the entire surface of the rotor magnet is not covered by the teeth of the stator (iron core of the stator), so the permeance fluctuation of the magnetic path passing through the rotor magnet and the teeth of the stator is large, which is one of the factors that increases the cogging torque. As in this embodiment, the cogging torque can be reduced by shifting the arrangement position of the second magnet 309 by a shift angle θ1, but the arrangement position of the second magnet 309 may have a manufacturing error, and this error may cause the cogging torque to increase due to an imbalance of forces acting on each magnet caused by permeance fluctuation. Therefore, in this embodiment, the first magnet 307 and the second magnet 309 are made into a skew shape inclined by a skew angle θ2 as described above. This makes it possible to make the first magnet 307 and the second magnet 309 into a shape that straddles adjacent teeth of the opposing stator, so that the force caused by the permeance fluctuation can be suppressed. Therefore, a configuration in which the arrangement position of the second magnet 309 is shifted by a shift angle θ1 is practically possible.

[0054] On the other hand, when the first magnet 307 and the second magnet 309 are skewed, the high frequency components (e.g., fourth and sixth order components) of the cogging torque may become large due to imbalance in the circumferential direction of the magnet shape. As described above, the first order component of the cogging torque can be reduced by setting the coefficient K=1.0, that is, by setting the shift angle θ1 of the second magnet 309 to {(360° / LCM) / 2}, which is half one cycle of the cogging torque waveform, but it is considered that the high frequency components can be effectively reduced in addition to the first order component of the cogging torque by setting the coefficient K to less than 1.0, that is, by setting the shift angle θ1 to less than {(360° / LCM) / 2}.

[0055] From the above, by setting the coefficient K to 1.0 or less, that is, by setting the shift angle θ1 to a range equal to but less than {(360° / LCM) / 2}, as shown in the following equation (2), the cogging torque can be effectively reduced in both cases where the cogging torque mainly contains a first-order component and where it contains harmonic components in addition to a first-order component. θ1≦(360° / LCM) / 2...Equation (2)

[0056] Furthermore, by setting the coefficient K to less than 1.0, that is, by setting the shift angle θ1 to a range less than {(360° / LCM) / 2} as shown in the following equation (3), the cogging torque can be effectively reduced, particularly in cases where the cogging torque contains harmonic components. θ1<(360° / LCM) / 2...Equation (3)

[0057] 10, the cogging torque value when coefficient K=1.0 is approximately equal to that when coefficient K=0.75, and the cogging torque value can be made equal to or less than the value when coefficient K=1.0 (the value when shift angle θ1 is {(360° / LCM) / 2}) when coefficient K is in the range of 0.75 to 1.0. Therefore, by setting coefficient K to 0.75 or more, that is, by setting shift angle θ1 to 0.75×{(360° / LCM) / 2} or more as shown in the following formula (4), the cogging torque can be suitably reduced. θ1≧0.75×{(360° / LCM) / 2}...Equation (4)

[0058] 10, the cogging torque value is at its minimum when the coefficient K is in the vicinity of 0.875. Therefore, by setting the coefficient K in the vicinity of 0.875, that is, by setting the shift angle θ1 in the vicinity of 0.875×{(360° / LCM) / 2} as shown in the following equation (5), both the first-order component and the high-frequency component of the cogging torque can be more effectively reduced. θ1≒0.875×{(360° / LCM) / 2}...Equation (5)

[0059] It should be noted that the above "vicinity" may have a certain degree of range as long as the value of the coefficient K or the shift angle θ1 is such that the value of the cogging torque is significantly suppressed compared to the value when the coefficient K=1.

[0060] In the above, the case where the first magnet 307 and the second magnet 309 have the same shape, i.e., the multiple magnets 305 have the same shape has been described, but this is not limiting, and the first magnet 307 and the second magnet 309 may have different shapes, i.e., the multiple magnets 305 may have different shapes. In this case, the graph in Fig. 10 changes, and when the coefficient K is less than 0.75, the value of the cogging torque may be equal to or less than the value when the coefficient K = 1.

[0061] <4. Stator configuration> An example of the configuration of the stator 110 of the first motor 101 and the stator 210 of the second motor 201 will be described with reference to Figs. 11 to 14. The stators 110 and 210 have the same configuration. Fig. 11 is a perspective view showing an example of the overall configuration of the stators 110 and 210 as seen from the coil side, Fig. 12 is a perspective view showing an example of the overall configuration of the stators 110 and 210 as seen from the wiring board side, Fig. 13 is a cross-sectional view showing an example of the overall configuration of the stators 110 and 210, and Fig. 14 is a perspective view showing an example of the configuration of the bobbin provided in the stators 110 and 210. In the description of Figs. 11 to 14, the "circumferential direction" refers to the circumferential direction centered on the rotation axis AX3, and the "radial direction" refers to the radial direction centered on the rotation axis AX3.

[0062] As shown in Figs. 11 to 13, the stator 110, 210 has an annular stator core 400. The stator core 400 has a cylindrical opening 401 extending along the rotation axis AX3 at its center. The stator core 400 has an annular back yoke part 403 (an example of a first back yoke), a plurality of teeth 407 to which coils 405 are attached, and an outer peripheral protrusion part 404 to which a wiring board 413 is accommodated on the radially inner side. The stator core 400 is made of a magnetic material. A plurality of coils 405 are arranged on the surface of the back yoke part 403 on the side facing the rotor 120 or the rotor 220. Specifically, as shown in Figs. 11 and 13, a plurality of teeth 407 are provided protruding from the back yoke part 403 toward one side in the direction of the rotation axis AX3 (upper side in Fig. 13). A cylindrical bobbin 409 with a coil 405 wound around its outer circumferential surface is attached to each of the teeth 407. The bobbin 409 is made of an insulating material. In this embodiment, a case where the number of coils 405, i.e., the number of teeth 407 is 24 (24 slots) will be described as an example, but the number of coils 405 may be other than 24.

[0063] As shown in FIG. 12 and FIG. 13, a wiring board 413 (an example of a wiring section) for connecting a plurality of lead wires 411 drawn from a plurality of coils 405 is disposed on the other side (lower side in FIG. 13) of the back yoke section 403 in the direction of the rotation axis AX3. The wiring board 413 is a ring-shaped board having a circular opening 413a on the radially inner side thereof, the circular opening 413a communicating with the opening 401 of the back yoke section 403. A predetermined wiring pattern for connecting the plurality of lead wires 411 is formed on the surface of the wiring board 413. The stator core 400 has a ring-shaped recess 415 on the other side (lower side in FIG. 13) in the direction of the rotation axis AX3, and the wiring board 413 is accommodated in the recess 415. The wiring section for connecting the plurality of lead wires 411 may be in a form other than a board.

[0064] Outer peripheral protrusion 404 is a generally C-shaped protrusion protruding from the outer periphery of back yoke portion 403 toward the other side in the direction of rotation axis AX3 (the lower side in FIG. 13). By providing outer peripheral protrusion 404 protruding from back yoke portion 403, stator core 400 (back yoke portion 403) is configured to be thick at the outer periphery where outer peripheral protrusion 404 is provided and to be thin at the inner periphery inside outer peripheral protrusion 404. Recess 415 is located radially inside outer peripheral protrusion 404 and is a region surrounded by outer peripheral protrusion 404.

[0065] 12, the wiring board 413 has terminal portions 413b protruding radially outward from a portion of its circumferential direction, and a power cable or the like is connected to the terminal portions 413b. The outer peripheral protrusion portion 404 has cutout portions 417 extending radially from a portion of its circumferential direction, and the terminal portions 413b of the wiring board 413 are housed in the cutout portions 417. The terminal portions 413b fit into the cutout portions 417, so that the wiring board 413 is positioned in the circumferential direction (angle) and is prevented from being displaced in the circumferential direction.

[0066] As shown in FIG. 12, the outer peripheral protrusion 404 is formed with a plurality of (for example, six) bolt holes 418 for fixing the stator core 400 to the subframes 12S1 and 12S2 described above. The plurality of bolt holes 418 are arranged, for example, at equal angular intervals along the circumferential direction. As shown in FIG. 13, the bolt holes 418 are formed with a depth that extends from the lower end of the outer peripheral protrusion 404 to the inside of the back yoke part 403. By providing the bolt holes 418 in the outer peripheral protrusion 404, the depth of the bolt holes 418 can be ensured and the bolt holes 418 can be prevented from interfering with the magnetic path in the back yoke part 403. On the other hand, the area on the inner peripheral side of the back yoke part 403 can be made thin because the bolt holes 418 are not formed and the magnetic path is not interrupted. Therefore, by using the portion as a recess 415 to accommodate the wiring board 413, the space on the other side (the lower side in FIG. 13) of the back yoke part 403 can be effectively utilized.

[0067] 13, the back yoke portion 403 has the opening 401 on the radially inner side of the teeth 407. That is, the inner peripheral surface 401a of the opening 401 is located radially inner than the radially inner end portion 407a of the teeth 407. The plurality of lead wires 411 drawn from the plurality of coils 405 are connected to the wiring board 413 through the opening 401. A protrusion 419 (an example of an insulating portion) provided on the bobbin 409 is disposed between the lead wires 411 and the inner peripheral surface 401a of the opening 401, and the lead wires 411 and the inner peripheral surface 401a of the opening 401 are insulated from each other by the protrusion 419.

[0068] An example of the structure of the bobbin 409 is shown in Fig. 14. As shown in Fig. 14, the coil 405 is wound around two adjacent bobbins 409A and 409B by continuous aligned winding (so-called double winding), with a winding start lead wire 411a at one end and a winding end lead wire 411b at the other end. The two bobbins 409A and 409B each have protrusions 419a and 419b protruding toward the inside of the opening 401. The protrusions 419a and 419b are made of an insulating material and are formed, for example, in a semi-cylindrical shape. A semi-cylindrical groove 401b into which the protrusions 419a and 419b fit is formed on the inner circumferential surface 401a of the opening 401 of the back yoke part 403. The projections 419a, 419b are fitted into the groove 401b, so that the projections 419a, 419b are positioned and are prevented from being displaced in the circumferential direction.

[0069] As shown in FIG. 14, the lead wire 411a is drawn from the coil 405 wound around the bobbin 409A along the protruding direction of the protruding portion 419a, and is connected to a pin 421 (so-called binding pin) provided at the tip of the protruding portion 419a, for example, by solder or the like. The protruding portion 419a has an end face 423 at the tip on the other side (lower side in FIG. 14) in the direction of the rotation axis AX3, and the pin 421 is erected on the end face 423. Similarly, the lead wire 411b is drawn from the coil 405 wound around the bobbin 409B along the protruding direction of the protruding portion 419b, and is connected to a pin 421 provided at the tip of the protruding portion 419b, for example, by solder or the like. The protruding portion 419b has an end face 423 at the tip on the other side (lower side in FIG. 14) in the direction of the rotation axis AX3, and the pin 421 is erected on the end face 423. The multiple pins 421 are connected to corresponding terminals 413c of the wiring board 413 by, for example, solder. The terminals 413c are formed as notches recessed radially outward in the opening 413a of the wiring board 413, and are capable of accommodating the pins 421. As shown in Fig. 13, the wiring board 413 is disposed such that a surface on one side (upper side in Fig. 13) of the wiring board 413 in the direction of the rotation axis AX3 abuts against an end face 423 of the protrusion 419.

[0070] The coil 405 may be wound continuously around three or more bobbins 409, or may be wound around a single bobbin 409 one by one instead of being wound continuously around a plurality of bobbins. A separate insulating part different from the protrusion 419a of the bobbin 409 may be provided between the lead wire 411 and the inner circumferential surface 401a of the opening 401. The two bobbins 409 may be integrally formed, or may be formed separately and connected. The bobbin 409 and the protrusion 419 may be integrally formed, or may be formed separately and connected. The wiring board 413 may be disposed such that a gap is provided between the end surface 423 of the protrusion 419 and the surface of the wiring board 413 and the end surface 423 of the protrusion 419 face each other via the gap.

[0071] <5. Effects of the embodiment> As described above, in the stator 110 of the first motor 101 and the stator 210 of the second motor 201 of this embodiment, the multiple coils 405 are arranged on one side in the direction of the rotation axis AX3 with respect to the back yoke portion 403, and the wire connection board 413 is arranged on the other side in the direction of the rotation axis AX3 with respect to the back yoke portion 403. This allows the coils 405, the back yoke portion 403, and the wire connection board 413 to be arranged in series in the axial direction, so that the outer diameter dimensions of the first motor 101 and the second motor 201 can be made smaller than when the wire connection board 413 is arranged radially outside the back yoke portion 403.

[0072] Furthermore, for example, when wiring board 413 is disposed between coil 405 and back yoke portion 403, the coil density in the slot decreases because coil 405 cannot be wound in the amount of space required for wiring board 413. In this embodiment, wiring board 413 is disposed on the side of back yoke portion 403 opposite to the side on which coil 405 is attached, thereby increasing the coil density.

[0073] Furthermore, in this embodiment, stator core 400 may be provided with a recess 415 on the other side of back yoke portion 403 in the direction of rotation axis AX3, and wire connection board 413 may be housed in recess 415. In this case, the axial dimensions of first motor 101 and second motor 201 can be made smaller than when wire connection board 413 is disposed on the other side of stator core 400. Furthermore, by effectively utilizing the space on the other side of back yoke portion 403, it is possible to prevent the occurrence of wasted space. Furthermore, wire connection board 413 can be protected.

[0074] Furthermore, in this embodiment, back yoke portion 403 may have openings 401 on the inside of teeth 407 in the radial direction centered on rotation axis AX3, and multiple lead wires 411 may pass through openings 401 and be connected to wiring board 413. In this case, lead wires 411 can be routed through the radial inside of back yoke portion 403 without being routed to the radial outside of back yoke portion 403. Therefore, the outer diameter dimensions of first motor 101 and second motor 201 can be reduced.

[0075] In this embodiment, the first motor 101 and the second motor 201 may have an insulating portion (protrusion 419 of bobbin 409 in the embodiment) that is disposed between the lead wire 411 and the inner circumferential surface 401a of the opening 401 and is made of an insulating material. In this case, insulation between the lead wire 411 and the back yoke portion 403 can be ensured.

[0076] Furthermore, in this embodiment, the first motor 101 and the second motor 201 may have a bobbin 409 made of an insulating material, with the coil 405 wound around the outer circumferential surface and attached to the teeth 407, and the insulating portion may be a protrusion 419 protruding from the bobbin 409 toward the inside of the opening 401. In this case, since the coil 405 is attached to the teeth 407 via the insulating bobbin 409, there is no need to insulate the surfaces of the back yoke portion 403 and the teeth 407. Furthermore, the use of the bobbin 409 makes it easier to wind the coil 405.

[0077] In this embodiment, the lead wire 411 may be drawn from the coil 405 along the protruding direction of the protrusion 419. In this case, the work of drawing out the lead wire 411 from the coil 405 becomes easier. Also, the lead wire 411 can be fixed by using the protrusion 419.

[0078] Furthermore, in this embodiment, grooves 401b into which protrusions 419 fit may be formed on inner circumferential surface 401a of opening 401 of back yoke portion 403. In this case, by fitting protrusions 419 of bobbin 409 into grooves 401b of back yoke portion 403, positioning of bobbin 409 and protrusions 419 and attachment to teeth 407 can be facilitated. Also, positional deviation and vibration of protrusions 419 and lead wires 411 can be suppressed.

[0079] In this embodiment, the plurality of lead wires 411 may be connected by a wiring board 413, the protrusion 419 may have an end face 423 at the tip on the other side in the direction of the rotation axis AX3, and the wiring board 413 may be arranged so as to contact the end face 423 of the protrusion 419. In this case, since the wiring section is configured as the wiring board 413, the wiring work is easier than when the wiring is performed manually using a lead wire or the like. In addition, the connection between the lead wires 411 and the wiring board 413 is easier, and the automation of the wiring work can be promoted. In addition, by bringing the wiring board 413 into contact with the end face 423 of the protrusion 419, the positioning of the wiring board 413 in the direction of the rotation axis AX3 is easier.

[0080] In this embodiment, the first motor 101 and the second motor 201 may be disposed in the joint J3 of the transport robot 10. In this case, the outer diameter dimensions of the first motor 101 and the second motor 201 can be reduced, so that the joint J3 of the transport robot 10 can be reduced in size.

[0081] As described above, in the rotor 120 of the first motor 101 and the rotor 220 of the second motor 201 of this embodiment, the multiple magnets 305 arranged along the circumferential direction on the back yoke portion 303 are configured with multiple first magnets 307 arranged at equal angular intervals in the circumferential direction and multiple second magnets 309 arranged one by one between the first magnets 307 and positioned at a position shifted by a predetermined shift angle θ1 from the central angle of two circumferentially adjacent first magnets 307. This allows the multiple magnets 305 on the back yoke portion 303 to be arranged at unequal intervals in the circumferential direction, thereby effectively reducing the cogging torque.

[0082] Furthermore, in this embodiment, when the least common multiple between the number of slots of the stators 110, 210 and the number of poles of the rotors 120, 220 is LCM, the shift angle θ1 may be set to be equal to or less than {(360° / LCM) / 2}. In this case, by setting the shift angle θ1 to a value including a range less than a value equivalent to {(360° / LCM) / 2}, which is half one cycle of the waveform of the cogging torque, even if the cogging torque includes harmonic components, these can be effectively reduced.

[0083] In this embodiment, the first magnet 307 and the second magnet 309 may be shaped such that the side 305a on one side in the circumferential direction and the side 305b on the other side are inclined by a predetermined skew angle θ2 in the same direction with respect to the radial direction DR centered on the rotation axis AX3. In this case, the first magnet 307 and the second magnet 309 can be shaped to straddle the adjacent teeth 407 in the stators 110 and 210, so that even if a manufacturing error occurs in the arrangement position of the second magnet 309, the force caused by the permeance variation can be suppressed. Therefore, it is practically possible to shift the arrangement position of the second magnet 309 by the shift angle θ1.

[0084] In this embodiment, the shift angle θ1 may be less than {(360° / LCM) / 2}. In this case, the high frequency components of the cogging torque can be effectively reduced. Therefore, by providing both a configuration in which the arrangement position of the second magnet 309 is shifted by the shift angle θ1 and a configuration in which the first magnet 307 and the second magnet 309 are skewed, it is possible to effectively reduce both the first component and the high frequency component of the cogging torque.

[0085] In this embodiment, the shift angle θ1 may be set to 0.75×{(360° / LCM) / 2} or more. In this case, the cogging torque can be set to a value equal to or less than the value of the cogging torque when the shift angle θ1 is {(360° / LCM) / 2}. This allows a certain degree of freedom in the value of the suitable shift angle θ1, making it practical to shift the position of the second magnet 309 by the shift angle θ1.

[0086] In this embodiment, the shift angle θ1 may be set to be close to 0.875×{(360° / LCM) / 2}. In this case, the shift angle θ1 can be set to be close to the center value of the preferable range {0.75×(360° / LCM) / 2≦θ1≦(360° / LCM) / 2}, so that both the first-order component and the high-frequency component of the cogging torque can be more effectively reduced.

[0087] In this embodiment, the first magnets 307 and the second magnets 309 may have the same shape. In this case, as shown in FIG. 10, when the coefficient K is changed from 0 to 1.0, that is, when the shift angle θ1 is changed from 0 degrees to half one cycle of the cogging torque waveform {(360° / LCM) / 2}, the value of the cogging torque may gradually decrease, reach a minimum value, and then increase again. This allows a certain degree of freedom for the value of the suitable shift angle θ1, so that it is practical to configure the second magnets 309 to be shifted by the shift angle θ1. In addition, since the magnets can be manufactured with the same shape, the manufacturing cost is low.

[0088] In this embodiment, the first magnets 307 and the second magnets 309 may be shaped such that the radial outer side 305c and the radial inner side 305d are parallel to each other. In this case, the magnet shape can be simplified and manufacturing becomes easier. In addition, the magnets 305 can be cut out from the magnet sheet 315 without waste, improving the yield and reducing the cost.

[0089] In this embodiment, the shape of the gap between the first magnet 307 and the second magnet 309 may be such that the gap shapes S1, S2 adjacent to each other in the circumferential direction are non-similar to each other and do not match even when rotated around the rotation axis AX3. In this case, the multiple magnets 305 on the back yoke portion 303 can be arranged at unequal intervals in the circumferential direction, so that the cogging torque can be effectively reduced.

[0090] In this embodiment, the least common multiple LCM between the number of slots of the stators 110 and 210 and the number of poles of the rotors 120 and 220 may be set to six or more times the number of poles. In this case, the shift angle θ1 can be made small, so that it is possible to simultaneously apply both a large skew angle θ2 and unequal spacing of the magnets 305 while preventing the size of the magnets 305 from becoming small.

[0091] In this embodiment, the first motor 101 and the second motor 201 may be disposed in the joint J3 of the transport robot 10. In this case, the cogging torque of the first motor 101 and the second motor 201 can be reduced, so that the joint J3 of the transport robot 10 can be driven smoothly.

[0092] <6. Variations> The disclosed embodiments are not limited to those described above, and various modifications are possible without departing from the spirit and technical concept thereof.

[0093] In the above embodiment, as shown in Fig. 15, the second magnet 309 is arranged at a position shifted by the shift angle θ1, and the first magnet 307 and the second magnet 309 are inclined by the skew angle θ2 with respect to the radial direction DR, but each magnet does not have to be skewed. For example, as shown in Fig. 16, the second magnet 309A may be arranged at a position shifted by the shift angle θ1, and both the first magnet 307A and the second magnet 309A may have a shape in which the side 305a on one side in the circumferential direction and the side 305b on the other side in the circumferential direction are aligned with the radial direction DR centered on the rotation axis AX3. Even in this case, the multiple magnets 305A on the back yoke portion 303A can be arranged at unequal intervals in the circumferential direction, so that the cogging torque can be effectively reduced.

[0094] In the above embodiment, the first magnet 307 and the second magnet 309 are described as having a shape in which the outer side 305c and the inner side 305d in the radial direction are linear and parallel, but the sides 305c and 305d do not have to be linear and parallel. For example, as shown in FIG. 17, the outer side 305c and the inner side 305d in the radial direction of the first magnet 307B and the second magnet 309B may have an arc shape centered on the rotation axis AX3. Also, as shown in FIG. 18, the outer side 305c and the inner side 305d may have an arc shape without providing a skew angle θ2 to each magnet. In the case of the shape shown in FIG. 17 and FIG. 18, the outer side 305c and the inner side 305d have a concentric arc shape. Even in the above case, the plurality of magnets 305B, 305C on the back yoke portions 303B, 303C can be arranged at unequal intervals in the circumferential direction, so that the cogging torque can be effectively reduced.

[0095] In the above, the configuration of the above embodiment is described as being applied to both the first motor 101 and the second motor 201 provided in the joint J3 of the transport robot 10, but it may be applied to either one of the motors. Also, the configuration of the above embodiment may be applied to the motors of the joints J1 and J2 other than the joint J3 of the transport robot 10.

[0096] In the above description, when "vertical", "parallel", "plane" and the like are used, the meanings are not strict. The terms "vertical", "parallel" and "plane" mean "substantially vertical", "substantially parallel" and "substantially plane" with allowance for design and manufacturing tolerances and errors.

[0097] In the above description, when the external dimensions, size, shape, position, etc. are described as "same", "equal", "different", etc., these descriptions are not intended to be strict. The terms "same", "equal", and "different" mean "substantially the same", "substantially the same", "substantially equal", and "substantially different", allowing for design and manufacturing tolerances and errors.

[0098] In addition to the above, the methods according to the above-mentioned embodiments and each modified example may be appropriately combined and used. Although not illustrated individually, the above-mentioned embodiments and each modified example may be implemented with various modifications without departing from the spirit thereof.

[0099] The problems and effects that the above-described embodiments and modifications are intended to solve are not limited to those described above. The embodiments and modifications may solve problems or achieve effects that are not described above, or may solve only some of the problems or achieve only some of the effects that are described. [Explanation of symbols]

[0100] 1. Robot System 10 Transport robot (example of robot) 20 Control device 101 First motor (an example of an axial gap motor) 110 Stator 120 rotor 201 Second motor (an example of an axial gap motor) 210 Stator 220 Rotor 300 rotor core 303 Back yoke part (an example of the second back yoke) 303A Back yoke 303B Back yoke 305 Magnet 305a One side 305A Magnet 305b Other side 305B Magnet 305c Outer edge 305d Inner edge 307 First Magnet 307A 1st magnet 307B 1st magnet 309 Second Magnet 309A 2nd magnet 309B 2nd magnet 400 stator core 401 Opening 401a Inner surface 401b Groove 403 Back yoke part (an example of the first back yoke) 404 Peripheral protrusion 405 Coil 407 Teeth 409 Bobbin 409A Bobbin 409B Bobbin 411 Lead Line 411a line 411b line 413 Wiring board (example of wiring part) 415 Recess 419 Protrusions (examples of insulating parts) 419a Protrusion 419b Protrusion 423 End face AX3 Rotation Axis DR Radial direction J3 Joint LCM least common multiple S1 Gap shape S2 Gap shape θ1 Shift angle (an example of the first angle) θ2 Skew angle (an example of the second angle)

Claims

1. A rotor that rotates around a rotation axis; a stator facing the rotor in the direction of the rotation axis; A first back yoke provided on either the rotor or the stator; a plurality of teeth protruding from the first back yoke toward one side in a direction of the rotation axis; A plurality of coils attached to the plurality of teeth; a connection portion that is disposed on the other side of the first back yoke in the direction of the rotation axis and that connects a plurality of lead wires that are led out from the plurality of coils; An axial gap motor having

2. The first back yoke is a recess on the other side in the direction of the rotation axis, The connection portion is The recess is accommodated in the recess.

2. The axial gap motor according to claim 1.

3. The first back yoke is an opening is provided on the inner side of the teeth in a radial direction about the rotation axis, The plurality of lead lines include The wire connection is connected through the opening.

3. The axial gap motor according to claim 1 or 2.

4. The insulating portion is disposed between the lead wire and an inner peripheral surface of the opening and is made of an insulating material. The axial gap motor according to claim 3 .

5. The coil is wound around an outer circumferential surface of a bobbin made of the insulating material and attached to the teeth. The insulating portion is A protrusion protruding from the bobbin toward the inside of the opening.

5. The axial gap motor according to claim 4.

6. The lead line is The coil is pulled out along the protruding direction of the protrusion. The axial gap motor according to claim 5 .

7. The inner circumferential surface of the opening has A groove into which the protrusion fits is formed. The axial gap motor according to claim 5 .

8. The connection portion is a wiring board on which a wiring pattern for connecting the plurality of lead wires is formed, The protrusion is an end face at a tip end on the other side in the direction of the rotation axis; The wiring board includes: The end surface is disposed so as to be in contact with the end surface or to face the end surface. The axial gap motor according to claim 5 .

9. A second back yoke provided on the other of the rotor and the stator; A plurality of magnets are arranged on the second back yoke along a circumferential direction around the rotation axis; and The plurality of magnets include A plurality of first magnets arranged at equal angular intervals in the circumferential direction; and a plurality of second magnets arranged one by one between the plurality of first magnets and at positions shifted by a predetermined first angle from a central angle of two of the first magnets adjacent in the circumferential direction.

2. The axial gap motor according to claim 1.

10. A robot in which an axial gap motor is disposed at a joint, The axial gap motor is A rotor that rotates around a rotation axis; a stator facing the rotor in the direction of the rotation axis; A first back yoke provided on either the rotor or the stator; a plurality of teeth protruding from the first back yoke toward one side in a direction of the rotation axis; A plurality of coils attached to the plurality of teeth; a connection portion that is disposed on the other side in the direction of the rotation axis with respect to the first back yoke and that connects a plurality of lead wires drawn from the plurality of coils, robot.

11. A robot according to claim 10; A control device for controlling the operation of the robot; A robot system having the above configuration.

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