Axial gap motor, robot, and robot system

Abstract

The invention discloses an axial clearance motor, a robot and a robot system. The cogging torque of the axial clearance motor is effectively reduced. The first motor (101) and the second motor (201) have: rotors (120, 220) that rotate about a rotation axis (AX3); stators (110, 210) facing the rotor in the direction of the rotation axis (AX3); a back yoke (303) provided to the rotor; and a plurality of magnets (305) disposed on the back yoke (303) in the circumferential direction around the rotation axis, the plurality of magnets (305) having: a plurality of first magnets (307) disposed at equal angular intervals in the circumferential direction; and a plurality of second magnets (309) disposed one between each of the plurality of first magnets (307) and disposed at a position deviated by a predetermined deviation angle ([theta] 1) from the center angle of two circumferentially adjacent first magnets (307).

Description

Technical Field

[0001] Embodiments of the present disclosure relate to an axial-gap motor, a robot, and a robot system. Background Art

[0002] Patent Document 1 discloses a flat rotary motor in which a rotor and a stator are arranged with an axial air gap therebetween. By forming a permanent magnet forming a magnetic pole into a skewed shape, smooth operation with low cogging torque can be achieved.

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Patent Laid-Open No. 58-222766 Summary of the Invention

[0006] Problems to be Solved by the Invention

[0007] In the above prior art, there are cases where the cogging torque cannot be sufficiently reduced, and there has been a continuous search for a motor that can more effectively reduce the cogging torque.

[0008] The present invention has been made in view of such problems, and an object thereof is to provide an axial-gap motor, a robot, and a robot system that can effectively reduce the cogging torque.

[0009] Means for Solving the Problems

[0010] To solve the above problems, according to one aspect of the present invention, an axial-gap motor is applied, which includes: a rotor that rotates about 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; and a plurality of magnets arranged along the circumferential direction around the rotation axis on the first back yoke. 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, each of which is arranged between two adjacent first magnets and is arranged at a position deviated from the center angle of two adjacent first magnets in the circumferential direction by a predetermined first angle.

[0011] Further, according to another aspect of the present invention, a robot is applied, which is provided with an axial clearance motor at a joint portion. The axial clearance motor has: a rotor that rotates about a rotation axis; a stator that faces the rotor in the direction of the rotation axis; a first back yoke that is provided on either the rotor or the stator; and a plurality of magnets that are arranged along the circumferential direction around the rotation axis on the first back yoke. The plurality of magnets have: a plurality of first magnets that are arranged at equal angular intervals in the circumferential direction; and a plurality of second magnets, with one second magnet arranged between each pair of adjacent first magnets and located at a position deviated from the central angle of two adjacent first magnets in the circumferential direction by a specified first angle.

[0012] Further, according to still another aspect of the present invention, a robot system is applied, which has: the above-mentioned robot; and a control device that controls the operation of the above-mentioned robot.

[0013] Advantages of the Invention

[0014] According to the axial clearance motor and the like of the present invention, cogging torque can be effectively reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 FIG. is an example showing the overall structure of the robot system according to the embodiment.

[0016] Figure 2 FIG. is a perspective view showing an example of the external structure of the first motor unit and the second motor unit provided at the end portion of the second arm.

[0017] Figure 3 FIG. is an exploded perspective view showing an example of the internal structure of the first motor unit.

[0018] Figure 4 FIG. is an exploded perspective view showing an example of the internal structure of the second motor unit.

[0019] Figure 5 FIG. is a cross-sectional view schematically showing an example of the internal structure of the first motor unit and the second motor unit.

[0020] Figure 6 FIG. is a perspective view showing an example of the overall structure of the rotor.

[0021] Figure 7 FIG. is a plan view showing an example of the overall structure of the rotor as observed from the stator side in the axial direction.

[0022] Figure 8 FIG. is a plan view showing an example of the shape of the magnets provided in the rotor.

[0023] Figure 9It is a plan view showing an example of a method of cutting out a plurality of magnets provided in a rotor from a magnet sheet.

[0024] Figure 10 It is a graph showing an example of the relationship between cogging torque and the coefficient of the offset angle of the magnet.

[0025] Figure 11 It is a perspective view seen from the coil side showing an example of the overall structure of the stator.

[0026] Figure 12 It is a perspective view seen from the wiring board side showing an example of the overall structure of the stator.

[0027] Figure 13 It is a cross-sectional view showing an example of the overall structure of the stator.

[0028] Figure 14 It is a perspective view showing an example of the structure of the bobbin provided in the stator.

[0029] Figure 15 It is a plan view showing an example of the arrangement of the magnets of the rotor of the embodiment.

[0030] Figure 16 It is a plan view showing an example of the arrangement of the magnets of a modified example rotor in which the magnets are not in a skewed shape.

[0031] Figure 17 It is a plan view showing an example of the arrangement of the magnets of a modified example rotor in which the outer and inner edges in the radial direction of the magnet are arc-shaped.

[0032] Figure 18 It is a plan view showing an example of the arrangement of the magnets of a modified example rotor in which the outer and inner edges in the radial direction of the magnet are arc-shaped and the magnets are not in a skewed shape.

[0033] Reference Numeral Explanation

[0034] 1: Robot system

[0035] 10: Handling robot (an example of a robot)

[0036] 20: Control device

[0037] 101: First motor (an example of an axial-gap motor)

[0038] 110: Stator

[0039] 120: Rotor

[0040] 201: Second motor (an example of an axial-gap motor)

[0041] 210: Stator

[0042] 220: Rotor

[0043] 300: Rotor core

[0044] 303: Back yoke part (an example of the first back yoke)

[0045] 303A: Back yoke part

[0046] 303B: Back yoke part

[0047] 305: Magnet

[0048] 305a: One side

[0049] 305A: Magnet

[0050] 305b: The other side

[0051] 305B: Magnet

[0052] 305c: Outer side

[0053] 305d: Inner side

[0054] 307: First magnet

[0055] 307A: First magnet

[0056] 307B: First magnet

[0057] 309: Second magnet

[0058] 309A: Second magnet

[0059] 309B: Second magnet

[0060] 400: Stator core

[0061] 401: Opening part

[0062] 401a: Inner peripheral surface

[0063] 401b: Groove part

[0064] 403: Back yoke part (an example of the second back yoke)

[0065] 404: Outer peripheral protrusion part

[0066] 405: Coil

[0067] 407: Tooth

[0068] 409: Bobbin

[0069] 409A: Bobbin

[0070] 409B: Bobbin

[0071] 411: Lead wire

[0072] 411a: Wire

[0073] 411b: Wire

[0074] 413: Wiring substrate (an example of a wiring portion)

[0075] 415: Recess

[0076] 419: Protrusion (an example of an insulating portion)

[0077] 419a: Protrusion

[0078] 419b: Protrusion

[0079] 423: End face

[0080] AX3: Axis of rotation

[0081] DR: Radial direction

[0082] J3: Joint portion

[0083] LCM: Least common multiple

[0084] S1: Gap shape

[0085] S2: Gap shape

[0086] θ1: Offset angle (an example of a first angle)

[0087] θ2: Skew angle (an example of a second angle) Detailed implementation manners

[0088] Hereinafter, the implementation manners will be described with reference to the drawings. In the implementation manners, for the sake of convenience in explaining the structure of a robot or the like, a three-dimensional rectangular coordinate system of the X-axis, Y-axis, and Z-axis is sometimes appropriately used. The Z-axis is in the vertically upward positive direction, the X-axis is along the extending direction of the arm that supports the hand, and the positive direction is the end side that supports the hand, and the Y-axis is orthogonal to the X-axis and the Z-axis.

[0089] <1. Overall structure of the robot system>

[0090] Refer to Figure 1 , and an example of the overall structure of the robot system 1 of the implementation manner will be described. Figure 1 is a diagram showing an example of the overall structure of the robot system 1 of the implementation manner.

[0091] As Figure 1As shown in the figure, the robot system 1 includes a transfer robot 10 and a control device 20 that controls the operation of the robot 10. The transfer robot 10 (an example of a robot) includes a main body 15 disposed on the ground or the like and a lifting part 16 that moves up and down relative to the main body 15. The lifting part 16 moves the first arm 11 and the second arm 12, which are horizontal multi-joint type arms, up and down. For example, two end effectors 13A and 13B are provided on the end side of the second arm 12. The end effectors 13A and 13B can respectively hold an object to be transferred, such as a substrate for semiconductors. The transfer robot 10 includes, for example, three joint parts J1, J2, and J3. At the joint part J1, the first arm 11 rotates around the rotation axis AX1 of the motor relative to the lifting part 16. At the joint part J2, the second arm 12 rotates around the rotation axis AX2 of the motor relative to the end part of the first arm 11. At the joint part J3, the end effectors 13A and 13B rotate coaxially around the rotation axis AX3 of the motor. The rotation axes AX1, AX2, and AX3 are substantially parallel to the Z axis.

[0092] In addition, Figure 1 shows two end effectors 13A and 13B, but the number of end effectors can also be three or more. In addition, Figure 1 shows a horizontal multi-joint type arm composed of two arms (the first arm 11 and the second arm 12), but the number of arms can also be one, or three or more.

[0093] 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. In addition, the storage unit 22 stores teaching data 22a.

[0094] The operation control unit 21a controls the operation of the transfer robot 10 based on the teaching data 22a. As an example, the operation control unit 21a instructs the motors corresponding to the respective axes in the transfer robot 10 based on the teaching data 22a stored in the storage unit 22, thereby causing the transfer robot 10 to transfer an object to be transferred, such as a substrate. The operation control unit 21a performs feedback control using the detection values of the encoders in the motors. The operation control unit 21a can also perform processing to stop or decelerate the operation of the transfer robot 10 when an error occurs in the operation of the transfer robot 10 or the like.

[0095] The teaching data 22a is generated by teaching the operation to the transfer robot 10. The teaching data 22a is information that defines the operation of the transfer robot 10, such as the movement trajectory of the end effector. In addition, the teaching data 22a generated by another computer connected by a wired or wireless network can also be stored in the storage unit 22.

[0096] <2. Structure of the motor unit>

[0097] Refer to Figures 2 to 5, showing an example of the structure of the motor unit for driving the hand provided at the joint portion J3 of the transfer robot 10. Figure 2 It is a perspective view showing an example of the external structure of the first motor unit and the second motor unit provided at the end portion of the second arm. Figure 3 It is an exploded perspective view showing an example of the internal structure of the first motor unit, Figure 4 It is an exploded perspective view showing an example of the internal structure of the second motor unit. Figure 5 It is a cross-sectional view schematically showing an example of the internal structure of the first motor unit and the second motor unit. In addition, Figure 5 It is a cross-sectional view obtained by cutting in a plane parallel to the YZ plane at the position of the rotation axis AX3 when observing the base end side from the end side of the second arm 12.

[0098] As Figure 2 shown, a first motor unit 100 and a second motor unit 200 for driving two hands 13A and 13B respectively are provided at the end side of the base frame 12A of the second arm 12. The first motor unit 100 and the second motor unit 200 are overlapped and arranged in the direction along the rotation axis AX3. In the Figure 2 example shown, the first motor unit 100 is arranged above the second motor unit 200. The first motor unit 100 includes a sub-frame 12S1 and a first motor 101 built in the sub-frame 12S1. The second motor unit 200 includes a sub-frame 12S2 and a second motor 201 built in the sub-frame 12S2. The base frame 12A and the sub-frames 12S1 and 12S2 constitute the housing of the second arm 12. In addition, in Figure 2 the base frame 12A is shown by a one-dot chain line.

[0099] The first motor 101 and the second motor 201 are arranged in a posture where they are aligned in the direction 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 the rotor and the stator are opposed to each other in the direction along the rotation axis AX3. The first motor 101 and the second motor 201 directly drive the hands 13A and 13B respectively.

[0100] The first motor 101 and the second motor 201 are so-called hollow motors provided with 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 the rotor 120 of the first motor 101 (refer to Figure 3 , Figure 5 described later), and the hollow shaft 202 is connected to the rotor 220 of the second motor 201 (refer to Figure 4 ,Figure 5 ) Connection. The hollow shafts 102 and 202 extend along the rotation axis AX3 and rotate about the rotation axis AX3.

[0101] As Figure 2 shown, the hollow shaft 102 of the first motor 101 protrudes toward the upper surface side of the sub-frame 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, penetrates the first motor unit 100, and protrudes toward the upper surface side of the sub-frame 12S1. The hand 13A is connected to the hollow shaft 102, and the 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.

[0102] In addition, when the number of hands is three or more, motor units having the same number as the hands can also be provided.

[0103] As Figure 3 shown, the first motor unit 100 includes a first motor 101 and a sub-frame 12S1. In addition, in Figure 3 , illustrations of a cover that is attached and detached to the upper surface of the sub-frame 12S1, a communication hole provided on the side surface of the sub-frame 12S1 on the side connected to the base frame 12A and used for inserting and penetrating a cable 103 (refer to Figure 2 ), and an inner wall of the sub-frame 12S1 that is provided inside the sub-frame 12S1 and mounts various components of the first motor 101 are omitted.

[0104] The first motor 101 (an example of an axial clearance motor) includes a rotor 120 that rotates about the rotation axis AX3 and a stator 110 that faces the rotor 120 in the direction of the rotation axis AX3. The first motor 101 has a shaft portion 102a and a shaft hub portion 102b that constitute the Figure 2 shown hollow shaft 102, a bearing 140, and a bearing pressing member 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.

[0105] The stator 110 is in the shape of a circular plate having a hollow portion along the rotation axis AX3, and has teeth on the end face on the side closer to the rotor 120 and coils wound around the teeth. In addition, the detailed structure of the stator 110 will be described later. The rotor 120 is in the shape of a circular plate having a hollow portion along the rotation 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 face on the side closer to the stator 110. In addition, the detailed structure of the rotor 120 will be described later. The disk portion 131 of the encoder 130 is fixed to the end face of the rotor 120 on the side opposite to the stator 110. A hollow portion that communicates with the hollow portion of the rotor 120 is also provided in the disk portion 131.

[0106] The shaft portion 102a of the hollow shaft 102 is fixed to the upper surface of the rotor 120. The stator 110 is arranged in such a manner that its inner circumference is separated from the outer circumference of the shaft portion 102a. The bearing 140 is a so-called crossed roller bearing. The inner circumferential side of the bearing 140 is fixed to the outer circumference of the hub portion 102b of the hollow shaft 102, and the outer circumferential side of the bearing 140 is fixed to the sub-frame 12S1 by the bearing presser 141. In addition, in Figure 3 the illustration of the inner wall of the sub-frame 12S1 that fixes the bearing 140 is omitted. The hub portion 102b of the hollow shaft 102 is fixed to the upper surface of the shaft portion 102a in such a manner that the hollow portion communicates with the hollow portion of the shaft portion 102a.

[0107] The detection portion 132 of the encoder 130 is arranged to face the disk portion 131 provided on the end face of the rotor 120. The support portion 133 supports the end face side of the detection portion 132 opposite to the disk portion 131 and is fixed to the sub-frame 12S1. In addition, the support portion 133 may be formed in a shape that can be fixed to the stator 110 and fixed to the stator 110.

[0108] As Figure 4 shown, the second motor unit 200 includes a second motor 201 and a sub-frame 12S2. In addition, in Figure 4 the illustration of the communication hole provided on the side surface of the sub-frame 12S2 connected to the base frame 12A for passing through and inserting the cable 203 (refer to Figure 2 ), and the inner wall of the sub-frame 12S2 provided inside and mounting the components of the second motor 201 is omitted.

[0109] The second motor 201 (an example of an axial gap motor) includes a rotor 220 that rotates about the 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 Figure 2 the hollow shaft 202, the bearing 240, the outer circumferential presser 241, and the inner circumferential presser 242 as shown. The outer circumferential presser 241 is a component that presses the outer circumference of the bearing 240, and the inner circumferential presser 242 is a component that presses the inner circumference of the bearing 240. The second motor 201 includes an encoder 230. The encoder 230 includes a disk portion 231, a detection portion 232, and a support portion 233.

[0110] The stator 210 is in the shape of a circular plate with a hollow portion along the rotation axis AX3, and has teeth and coils wound around the teeth on the end face on the side closer to the rotor 220. The detailed structure of the stator 210 will be described later. The rotor 220 is in the shape of a circular plate with a hollow portion along the rotation axis AX3 that communicates with the hollow portion of the stator 210, and has a plurality of magnets provided along the circumferential direction on the end face on the side closer to the stator 210. The detailed structure of the rotor 220 will be described later. A disk portion 231 of the encoder 230 is fixed to the end face of the rotor 220 on the side opposite to the stator 210. A hollow portion through which the hollow shaft 202 passes is provided in the disk portion 231.

[0111] The hollow shaft 202 is fixed to the upper surface of the rotor 220. The bearing 240 is a so-called crossed roller bearing. The inner circumferential side of the bearing 240 is fixed to the outer circumference of the hollow shaft 202 by an inner circumferential pressing member 242, and the outer circumferential side of the bearing 240 is fixed to the sub-frame 12S2 by an outer circumferential pressing member 241.

[0112] The detection portion 232 of the encoder 230 is arranged to face the disk portion 231 provided on the end face of the rotor 220. The support portion 233 supports the end face side of the detection portion 232 on the side opposite to the disk portion 231 and is fixed to the sub-frame 12S2. In addition, the support portion 233 may be formed in a shape that can be fixed to the stator 210 and fixed to the stator 210.

[0113] Next, use Figure 5 to illustrate Figure 3 the assembled Figure 4 state of the first motor unit 100 and

[0114] As Figure 5 shown, the hub portion 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.

[0115] The first motor 101 and the second motor 201 are arranged in the order of the stator 210, rotor 220, rotor 120 of the first motor 101, and stator 110 of the first motor 101 along the rotation axis AX3 from the lower surface to the upper surface of the second arm 12.

[0116] The encoder 130 of the first motor unit 100 is arranged 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 arranged at a position facing the upper surface side of the rotor 220 in the second motor unit 200. As Figure 5As shown, the encoder 130 and the encoder 230 are arranged at substantially the same height in the direction along the rotation axis AX3.

[0117] As Figure 5 shown, 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. Wires such as those for the hand 13B connected to the hollow shaft 202 of the second motor unit 200 can be routed through the hollow portion 12H.

[0118] <3. Structure of the Rotor>

[0119] Refer to Figures 6 to 10 and describe an example of the structures of the rotor 120 of the first motor 101 and the rotor 220 of the second motor 201. The structures of the rotor 120 and the rotor 220 are the same as each other. Figure 6 is a perspective view showing an example of the overall structure of the rotors 120 and 220, Figure 7 is a plan view showing an example of the overall structure of the rotors 120 and 220, observed from the stator side in the axial direction, Figure 8 is a plan view showing an example of the shape of the magnets included in the rotors 120 and 220, Figure 9 is a plan view showing an example of the manner in which a plurality of magnets included in the rotors 120 and 220 are cut out from a plate-shaped magnet sheet, Figure 10 is a graph showing an example of the relationship between the cogging torque and the coefficient of the magnet offset angle. In addition, in the Figures 6 to 10 description, the "circumferential direction" is the circumferential direction centered on the rotation axis AX3, and the "radial direction" is the radial direction centered on the rotation axis AX3.

[0120] As Figure 6 and Figure 7As shown, the rotors 120 and 220 have an annular rotor core 300. The rotor core 300 has a cylindrical hollow portion 301 extending along the rotation axis AX3 at the 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 the first back yoke) on the surface where magnets are arranged. The rotor core 300 is made of a magnetic material. On the surface of the back yoke portion 303 on the side facing the stator 110 or the stator 210, a plurality of magnets 305 are arranged along the circumferential direction around the rotation axis AX3. In the present embodiment, the case where the number of the magnets 305 is 20 (20 poles) is described as an example, but the number of the magnets 305 may also be other than 20. The plurality of magnets 305 include: a plurality of (half the number of the magnets 305) first magnets 307, which are arranged at equal angular intervals every other one in the above-mentioned circumferential direction; and a plurality of (half the number of the magnets 305) second magnets 309, which are arranged at equal angular intervals every other one in the above-mentioned circumferential direction. One second magnet 309 is arranged between each pair of the first magnets 307 and is arranged at a position deviated from the central angle (representing the central position between two adjacent first magnets 307 in the circumferential direction as the central angle in the circumferential direction) of two adjacent first magnets 307 in the above-mentioned circumferential direction by a prescribed deviation angle θ1 (an example of the first angle). The first magnets 307 and the second magnets 309 have the same shape as each other. That is, the plurality of magnets 305 have the same shape respectively. In addition, in the present embodiment, without distinguishing whether the magnet is the first magnet 307 or the second magnet 309, it is described as the magnet 305.

[0121] In addition, in the present embodiment, when explaining the arrangement of each magnet, the reference position as long as it is a uniquely and uniformly determined reference position such as, for example, the center-of-gravity position of the magnet, the position of one end or the other end in the circumferential direction, or the position of one end or the other end in the radial direction, etc., can be any position. In the present embodiment, for example, the center-of-gravity position of the magnet is used as the reference. Specifically, as Figure 7 shown, the center-of-gravity position PG2 of the second magnet 309 is arranged at a position such that this position is at an angle deviated from the bisector Lb of the angle 2θ0 between the center-of-gravity positions PG1 of two adjacent first magnets 307 in the circumferential direction ( Figure 7 in the clockwise direction in the figure) by the deviation angle θ1, and the radial distance from the rotation axis AX3 is the same as the distance of the center-of-gravity position PG1.

[0122] In addition, the arrangement of the plurality of magnets 305 can also be described in other words as follows. As Figure 7As shown, a plurality of magnets 305 are arranged at unequal intervals in such a manner that a first interval D1 and a second interval D2 smaller than the first interval D1 are alternately repeated in the circumferential direction at intervals between two circumferentially adjacent magnets 305. Further, the first interval D1 and the second interval D2 are, for example, intervals when taking the same position in the radial direction centered on the rotation axis AX3, such as the position of the center of gravity of the magnet, or the position of the end on one or the other side in the radial direction.

[0123] In addition, the arrangement of the plurality of magnets 305 can also be described in other words as follows. As Figure 7 shown, a plurality of magnets 305 are arranged at unequal intervals in such a manner that a first angle θA and a second angle θB smaller than the first angle θA are alternately repeated in the circumferential direction at angles formed by two circumferentially adjacent magnets 305. Further, the position serving as a reference for the angle between the magnets can be any position as long as it is a uniquely and uniformly determined reference position such as, for example, the position of the center of gravity of the magnet, or the position of the end on one or the other side in the circumferential direction. In the present embodiment, as Figure 7 shown, the angles are based on the center-of-gravity positions PG1, PG2 of the magnets.

[0124] As a result of arranging the plurality of magnets 305 as described above, the gap shape between the first magnet 307 and the second magnet 309 becomes alternately different shapes in the circumferential direction. As Figure 7 shown in the partial enlarged view of, the circumferentially adjacent gap shapes S1 and S2 are shapes that are not similar to each other and are shapes that do not coincide even when rotated around the rotation axis AX3. Further, in Figure 7 , the gap shapes S1, S2 are set as the shapes of the space obtained by extending the space between the first magnet 307 and the second magnet 309 to the outer periphery of the back yoke portion 303, but the same applies when setting the shape of only the space between the first magnet 307 and the second magnet 309.

[0125] As Figure 6 and Figure 7 shown, a first recess 311 for accommodating the first magnet 307 and a second recess 313 for accommodating the second magnet 309 are formed on the surface of the back yoke portion 303 on the side where the magnets 305 are arranged. The first recess 311 is formed in a shape corresponding to the first magnet 307, and the first magnet 307 is fixed, for example, by adhesion or the like. As Figure 7 shown, at least one end of the first magnet 307 on one or the other side in the circumferential direction abuts against at least one stepped portion 311a on one or the other side in the circumferential direction of the first recess 311, whereby the circumferential position of the first magnet 307 is positioned. Further, the end of the first magnet 307 on the inner side in the radial direction abuts against the stepped portion 311b on the inner side in the radial direction of the first recess 311, whereby the radial position of the first magnet 307 is positioned.

[0126] The second recess 313 is formed in a shape corresponding to the second magnet 309, and the second magnet 309 is fixed, for example, by adhesion or the like. At least one end of one circumferential side and the other circumferential side of the second magnet 309 abuts against at least one step portion 313a of one circumferential side and the other circumferential side of the second recess 313, whereby the circumferential position of the second magnet 309 is positioned. In addition, the end portion on the radially inner side of the second magnet 309 abuts against the step portion 313b on the radially inner side of the second recess 313, whereby the radial position of the second magnet 309 is positioned.

[0127] Figure 8 An example of the shape of the magnet 305 (the first magnet 307, the second magnet 309) is shown. As Figure 8 shown, the magnet 305 has a so-called skewed shape in which one side 305a and the other side 305b in the circumferential direction are inclined by a predetermined skew angle θ2 (an example of the second angle) in the same direction with respect to the radial direction DR centered on the rotation axis AX3. In addition, the magnet 305 has a shape in which the outer side 305c and the inner side 305d in the radial direction are linear and parallel. That is, the magnet 305 has a trapezoidal shape in which one pair of opposite sides formed by the sides 305c, 305d are parallel, and the other pair of opposite sides formed by the sides 305a, 305b are not parallel.

[0128] Figure 9 An example of a method of cutting out a plurality of magnets 305 from a magnet sheet is shown. As Figure 9 shown, a plurality of (for example, 32) magnets 305 are manufactured from a parallelogram-shaped magnet sheet 315. The parallelogram of the magnet sheet 315 is a shape similar to the parallelogram (the shape of the divided sheet 317) formed by arranging a pair of magnets 305, 305 with the sides 305b facing each other and the sides 305c, 305d staggered. By equally dividing the magnet sheet 315 in the longitudinal and transverse directions into a plurality of parts, 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. Further, by bisecting the divided sheet 317 in the longitudinal direction along a cutting line CL inclined with respect to the sides 305a on both sides in the length direction, a pair of magnets 305, 305 are formed. Thereby, it is possible to prevent a remaining portion from being generated in the magnet sheet 315, and the magnets 305 can be cut out from the magnet sheet 315 without waste.

[0129] Figure 10An example of the relationship between the cogging torque generated in the rotors 120 and 220 and the coefficient K of the offset angle θ1 of the second magnet 309 is shown. When the least common multiple of the number of slots of the stators 110 and 210 and the number of poles of the rotors 120 and 220 is set as LCM and the coefficient is set as K, the offset angle θ1 is represented by the following formula (1). The number of slots is the number of teeth in the stator 110 or the stator 210, and the number of poles is the number of magnets 305 in the rotor 120 or the rotor 220. Figure 10 The magnitude of the cogging torque when the coefficient K is changed from 0 to 1.0 is shown.

[0130] θ1 = K × {(360° / LCM) / 2} … Formula (1)

[0131] For example, when the number of slots of the stators 110 and 210 is set as 24 and the number of poles of the rotors 120 and 220 is set as 20, the least common multiple LCM is 120. In addition, the least common multiple LCM is preferably 6 times or more the number of poles of the rotors 120 and 220. That is, if the skewing angle θ2 of the magnet 305 is increased, the effect of reducing the cogging torque is improved, but depending on the slot combination of the motor, it is sometimes difficult to arrange a plurality of magnets 305 at unequal intervals. In this case, the size of the magnet 305 can also be reduced for arrangement, but it will result in a decrease in the output torque of the motor. When the least common multiple LCM is set as 6 times or more the number of poles, the offset angle θ1 can be reduced by the above formula (1). Thereby, it is possible to suppress the size of the magnet 305 from becoming small, and it is possible to apply both a relatively large skewing angle θ2 and the unequal interval arrangement of the magnets 305 at the same time.

[0132] One cycle of the waveform of the cogging torque generated in the rotors 120 and 220 is represented by (360° / LCM). Therefore, by setting the offset angle θ1 of the second magnet 309 as half of one cycle of the waveform of the cogging torque, that is, {(360° / LCM) / 2}, that is, when the coefficient K = 1 in the above formula (1), as Figure 10 shown, compared with the case where the offset angle θ1 is set as 0 degrees (the case where K = 0), the cogging torque can be reduced.

[0133] In addition, as Figure 10 shown, when the coefficient K is changed from 0 to 1.0, in other words, when the offset angle θ1 is changed from 0 degrees to half of one cycle of the waveform of the cogging torque, that is, {(360° / LCM) / 2}, the cogging torque does not gradually decrease and becomes the lowest value when the coefficient K = 1.0, but becomes the lowest value when the coefficient K is less than 1.0. It is considered that this is due to the following reasons.

[0134] Generally, in an axial-gap motor with an open-slot structure, the surface of the magnets of the rotor is not entirely covered by the teeth (the iron core of the stator) of the stator. Therefore, the magnetic conductance of the magnetic circuit passing through the magnets of the rotor and the teeth of the stator varies greatly, which is one of the reasons for the increase in cogging torque. As in the present embodiment, by staggering the arrangement position of the second magnet 309 by the offset angle θ1, the cogging torque can be reduced. However, sometimes there are manufacturing errors in the arrangement position of the second magnet 309. Due to this error, there may be a situation where the cogging torque becomes larger due to the imbalance of the forces acting on each magnet caused by the variation of magnetic conductance. Therefore, in the present embodiment, as described above, the first magnet 307 and the second magnet 309 are formed into a skewed shape with a skewing angle θ2. Thereby, the first magnet 307 and the second magnet 309 can be made to straddle adjacent teeth of the opposing stator, so that the force caused by the variation of magnetic conductance can be suppressed. Thus, in practice, a structure in which the arrangement position of the second magnet 309 is staggered by the offset angle θ1 can be realized.

[0135] On the other hand, when the first magnet 307 and the second magnet 309 are formed into a skewed shape, the harmonic components (such as the 4th component, 6th component, etc.) of the cogging torque may increase due to the imbalance in the circumferential direction of the magnet shape. As described above, by setting the coefficient K = 1.0, that is, the offset angle θ1 of the second magnet 309 is half of one cycle of the waveform of the cogging torque, i.e., {(360° / LCM) / 2}, the 1st component of the cogging torque can be reduced. However, by setting the coefficient K less than 1.0, that is, the offset angle θ1 is less than {(360° / LCM) / 2}, in addition to effectively reducing the 1st component of the cogging torque, the harmonic components can also be effectively reduced.

[0136] Based on the above, by setting the coefficient K to 1.0 or less, that is, setting the offset angle θ1 as in the following formula (2) to a range that not only includes the same range as {(360° / LCM) / 2} but also includes a range less than {(360° / LCM) / 2}, the cogging torque can be effectively reduced corresponding to both the case where the cogging torque mainly includes the 1st component and the case where it includes harmonic components in addition to the 1st component.

[0137] θ1 ≤ (360° / LCM) / 2 ··· Formula (2)

[0138] In addition, by setting the coefficient K less than 1.0, that is, setting the offset angle θ1 as in the following formula (3) to a range less than {(360° / LCM) / 2}, the cogging torque can be effectively reduced corresponding to the case where the cogging torque includes harmonic components in particular.

[0139] θ1 < (360° / LCM) / 2 ··· Formula (3)

[0140] In addition, asFigure 10 As shown, when the coefficient K = 1.0, the value of the cogging torque is approximately equal to the value of the cogging torque when the coefficient K = 0.75. In the range where the coefficient K is 0.75 or more and 1.0 or less, the value of the cogging torque can be set to be below the value when the coefficient K = 1.0 (the value when the offset angle θ1 is {(360° / LCM) / 2}). Therefore, by setting the coefficient K to 0.75 or more, that is, by setting the offset angle θ1 to be 0.75×{(360° / LCM) / 2} or more as in the following formula (4), the cogging torque can be appropriately reduced.

[0141] θ1≥0.75×{(360° / LCM) / 2}…Formula (4)

[0142] In addition, as Figure 10 shown, when the coefficient K is near 0.875, the value of the cogging torque becomes the minimum value. Therefore, by setting the coefficient K to be near 0.875, that is, by setting the offset angle θ1 to be near 0.875×{(360° / LCM) / 2} as in the following formula (5), both the fundamental component and the harmonic component of the cogging torque can be more effectively reduced.

[0143] θ1≈0.875×{(360° / LCM) / 2}…Formula (5)

[0144] In addition, as long as the "near" mentioned above is a value of the coefficient K or the offset angle θ1 at which the value of the cogging torque is significantly suppressed compared to the value when the coefficient K = 1, there can also be a certain degree of range.

[0145] In addition, the above description has been made for the case where the first magnet 307 and the second magnet 309 have the same shape, that is, where the plurality of magnets 305 have the same shape as each other, but it is not limited to this. The first magnet 307 and the second magnet 309 can also have different shapes, that is, the plurality of magnets 305 can have different shapes from each other. In this case, Figure 10 the graph changes, and when the coefficient K is less than 0.75, the value of the cogging torque may become below the value when the coefficient K = 1.

[0146] <4. Structure of the stator>

[0147] With reference to Figures 11 to 14 , an example of the structure of the stator 110 of the first motor 101 and the stator 210 of the second motor 201 will be described. The structures of the stator 110 and the stator 210 are the same as each other. Figure 11 is a perspective view observed from the coil side showing an example of the overall structure of the stators 110 and 210, Figure 12 is a perspective view observed from the wiring board side showing an example of the overall structure of the stators 110 and 210, Figure 13 is a cross-sectional view showing an example of the overall structure of the stators 110 and 210,Figure 14 FIG. 1 is a perspective view showing an example of the structure of the bobbin included in the stators 110 and 210. In addition, in the description of Figures 11 to 14 , the "circumferential direction" is the circumferential direction centered on the rotation axis AX3, and the "radial direction" is the radial direction centered on the rotation axis AX3.

[0148] As Figures 11 to 13 shown, the stators 110 and 210 have an annular stator core 400. The stator core 400 has a cylindrical opening 401 extending along the rotation axis AX3 at the center. The stator core 400 has an annular back yoke portion 403 (an example of the second back yoke portion), a plurality of teeth 407 for mounting the coils 405 respectively, and an outer peripheral protrusion portion 404 for accommodating the wiring substrate 413 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 portion 403 on the side facing the rotor 120 or the rotor 220. Specifically, as Figure 11 and Figure 13 shown, a plurality of teeth 407 protrude on one side in the direction from the back yoke portion 403 toward the rotation axis AX3 ( Figure 13 the upper side in FIG. 2). A cylindrical bobbin 409 having a coil 405 wound around its outer peripheral surface is mounted on each of the plurality of teeth 407. The bobbin 409 is made of an insulating material. In the present embodiment, the case where the number of coils 405, that is, the number of teeth 407 is 24 (24 slots) is described as an example, but the number of coils 405 may be other than 24.

[0149] As Figure 12 and Figure 13 shown, on the other side of the back yoke portion 403 in the direction of the rotation axis AX3 ( Figure 13 the lower side in FIG. 2), a wiring substrate 413 (an example of a wiring portion) for connecting a plurality of lead wires 411 led out from the plurality of coils 405 is arranged. The wiring substrate 413 is an annular substrate having a circular opening 413a communicating with the opening 401 of the back yoke portion 403 on the radially inner side. A predetermined wiring pattern for connecting the plurality of lead wires 411 is formed on the surface of the wiring substrate 413. The stator core 400 has an annular recess 415 on the other side in the direction of the rotation axis AX3 ( Figure 13 the lower side in FIG. 2), and the wiring substrate 413 is accommodated in the recess 415. In addition, the wiring portion for connecting the plurality of lead wires 411 may be in a form other than a substrate.

[0150] The outer peripheral protrusion portion 404 is on the other side in the direction from the outer peripheral portion of the back yoke portion 403 toward the rotation axis AX3 ( Figure 13A substantially C-shaped protruding portion protruding from the lower side in []. By protruding the outer peripheral protruding portion 404 from the back yoke portion 403, the stator core 400 (back yoke portion 403) is configured to have a thick wall at the outer peripheral portion where the outer peripheral protruding portion 404 is provided, and a thin wall at the inner peripheral portion inside the outer peripheral protruding portion 404. The concave portion 415 is located radially inside the outer peripheral protruding portion 404 and is an area surrounded by the outer peripheral protruding portion 404.

[0151] As Figure 12 shown, the wiring board 413 has a terminal portion 413b protruding radially outward in a part of the circumferential direction, and a cable or the like is connected to the terminal portion 413b. The outer peripheral protruding portion 404 has a notch portion 417 extending in the radial direction in a part of the circumferential direction, and the terminal portion 413b of the wiring board 413 is received in the notch portion 417. By fitting the terminal portion 413b into the notch portion 417, the circumferential orientation (angle) of the wiring board 413 is positioned, and the circumferential position deviation of the wiring board 413 is prevented.

[0152] As Figure 12 shown, a plurality of (for example, six) bolt holes 418 for fixing the stator core 400 to the above-mentioned sub-frames 12S1 and 12S2 are formed in the outer peripheral protruding portion 404. The plurality of bolt holes 418 are arranged at equal angular intervals along the circumferential direction. As Figure 13 shown, the bolt holes 418 are formed to a depth from the lower end portion of the outer peripheral protruding portion 404 to the inside of the back yoke portion 403. By providing the bolt holes 418 in the outer peripheral protruding portion 404, the depth of the bolt holes 418 can be ensured, and the bolt holes 418 can be prevented from obstructing the magnetic path in the back yoke portion 403. On the other hand, since the bolt holes 418 are not formed in the inner peripheral side region of the back yoke portion 403, the magnetic path is not obstructed, and a thin wall can be provided. Therefore, by using this portion as the concave portion 415 to receive the wiring board 413, the space on the other side ( Figure 13 the lower side in []) of the back yoke portion 403 can be effectively utilized.

[0153] As Figure 13 shown, the back yoke portion 403 has the above-mentioned opening portion 401 at a position radially inside the teeth 407. That is, the inner peripheral surface 401a of the opening portion 401 is located radially inside the radially inner end portion 407a of the teeth 407. A plurality of lead wires 411 respectively led out from the above-mentioned plurality of coils 405 are connected to the wiring board 413 through the opening portion 401. A protruding portion 419 (an example of an insulating portion) provided in the bobbin 409 is disposed between the lead wire 411 and the inner peripheral surface 401a of the opening portion 401, and the lead wire 411 is insulated from the inner peripheral surface 401a of the opening portion 401 by the protruding portion 419.

[0154] Figure 14 Shows an example of the structure of the bobbin 409. AsFigure 14 As shown, the coil 405 is wound continuously by regular winding with respect to two adjacent bobbins 409A and 409B (so-called two-consecutive winding). A lead wire 411a for starting winding is provided on one end side, and a lead wire 411b for ending winding is provided on the other end side. The two bobbins 409A and 409B respectively have protruding portions 419a and 419b protruding toward the inside of the opening 401. The protruding portions 419a and 419b are made of an insulating material and are formed, for example, in a semi-cylindrical shape. On the inner peripheral surface 401a of the opening 401 of the back yoke portion 403, a semi-cylindrical groove portion 401b for fitting the protruding portions 419a and 419b is formed. By fitting the protruding portions 419a and 419b into the groove portion 401b, the protruding portions 419a and 419b are positioned and the circumferential position deviation is prevented.

[0155] As Figure 14 shown, the lead wire 411a is led out from the coil 405 wound around the bobbin 409A along the protruding direction of the protruding portion 419a and is connected, for example, by solder or the like to a pin 421 (so-called connection pin) provided at the end of the protruding portion 419a. The protruding portion 419a has an end face 423 at the end on the other side ( Figure 14 the lower side in Figure 14 ) of the direction of the rotation axis AX3, and the pin 421 is erected on the end face 423. Similarly, the lead wire 411b is led out from the coil 405 wound around the bobbin 409B along the protruding direction of the protruding portion 419b and is connected, for example, by solder or the like to a pin 421 provided at the end of the protruding portion 419b. The protruding portion 419b has an end face 423 at the end on the other side ( Figure 13 the lower side in Figure 13 ) of the direction of the rotation axis AX3, and the pin 421 is erected on the end face 423. The plurality of pins 421 are connected, for example, by solder or the like to corresponding terminals 413c of the wiring substrate 413. The terminal 413c is formed as a notch portion recessed toward the radially outer side in the opening 413a of the wiring substrate 413 and can accommodate the pin 421. As Figure 13 shown, the wiring substrate 413 is arranged such that the surface on one side ( Figure 13 the upper side in

[0156] In addition, the coil 405 can also be continuously wound around more than three bobbin holders 409, or it can be wound around each bobbin holder 409 one by one instead of continuously wound around multiple bobbin holders. Additionally, another insulating member different from the protrusion 419a of the bobbin holder 409 can be provided between the lead wire 411 and the inner peripheral surface 401a of the opening 401. Further, the two bobbin holders 409 can be integrally formed or separately formed and connected. Moreover, the bobbin holder 409 and the protrusion 419 can be integrally formed or separately formed and connected. Also, the wiring substrate 413 can be arranged such that a gap is provided between the end face 423 of the protrusion 419, and the surface of the wiring substrate 413 faces the end face 423 of the protrusion 419 with a gap therebetween.

[0157] <5. Effects of the Embodiment>

[0158] As described above, for the rotor 120 of the first motor 101 and the rotor 220 of the second motor 201 in this embodiment, the plurality of magnets 305 arranged circumferentially on the back yoke portion 303 are composed of a plurality of first magnets 307 and a plurality of second magnets 309. The plurality of first magnets 307 are arranged at equal angular intervals in the circumferential direction, and one second magnet 309 is arranged between each pair of adjacent first magnets 307 and is arranged at a position deviated from the center angle of two adjacent first magnets 307 in the circumferential direction by a specified offset angle θ1. Thereby, the plurality of magnets 305 on the back yoke portion 303 can be arranged at unequal intervals in the circumferential direction, and thus the cogging torque can be effectively reduced.

[0159] In addition, in this embodiment, when the least common multiple of the number of slots of the stators 110 and 210 and the number of poles of the rotors 120 and 220 is set as LCM, the offset angle θ1 can also be set to be {(360° / LCM) / 2} or less. In this case, by setting the offset angle θ1 to include values in a range less than {(360° / LCM) / 2} in addition to values equal to half of one period of the cogging torque waveform, i.e., {(360° / LCM) / 2}, the cogging torque can be effectively reduced including harmonic components when they are present.

[0160] In addition, in the present embodiment, the first magnet 307 and the second magnet 309 may be formed in such a shape 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 formed to straddle the adjacent teeth 407 in the stators 110 and 210. Therefore, even when a manufacturing error occurs in the arrangement position of the second magnet 309, the force caused by the change in magnetic permeance can be suppressed. Thus, in practice, a structure in which the arrangement position of the second magnet 309 is shifted by the offset angle θ1 can be realized.

[0161] In addition, in the present embodiment, the offset angle θ1 may be made smaller than {(360° / LCM) / 2}. In this case, the harmonic components of the cogging torque can be effectively reduced. Therefore, by providing both a structure in which the arrangement position of the second magnet 309 is shifted by the offset angle θ1 and a structure in which the first magnet 307 and the second magnet 309 are skew-shaped, both the fundamental component and the harmonic components of the cogging torque can be effectively reduced.

[0162] In addition, in the present embodiment, the offset angle θ1 may be set to be 0.75×{(360° / LCM) / 2} or more. In this case, the cogging torque can be set to be equal to or less than the value of the cogging torque when the offset angle θ1 is {(360° / LCM) / 2}. Thereby, a certain range can be set for the preferred value of the offset angle θ1. Thus, in practice, a structure in which the arrangement position of the second magnet 309 is shifted by the offset angle θ1 can be realized.

[0163] In addition, in the present embodiment, the offset angle θ1 may be set to be around 0.875×{(360° / LCM) / 2}. In this case, the offset angle θ1 can be made around the central value of the preferred range {0.75×(360° / LCM) / 2 ≤ θ1 ≤ (360° / LCM) / 2}. Therefore, both the fundamental component and the harmonic components of the cogging torque can be reduced more effectively.

[0164] In addition, in the present embodiment, the plurality of first magnets 307 and the plurality of second magnets 309 may be formed in the same shape as each other. In this case, as Figure 10As shown, when the coefficient K is changed from 0 to 1.0, that is, when the offset angle θ1 is changed from 0 degrees to half of one cycle of the cogging torque waveform {(360° / LCM) / 2}, the value of the cogging torque can change in such a way that it gradually decreases to a minimum value and then increases again. Thus, a certain range can be set for the value of the preferred offset angle θ1, and therefore, in practice, a structure in which the arrangement position of the second magnet 309 is offset by the offset angle θ1 can be realized. In addition, since it can be made of magnets with the same shape, the manufacturing cost is low.

[0165] In addition, in the present embodiment, the plurality of first magnets 307 and the plurality of second magnets 309 may be formed in a shape in which the outer side 305c and the inner side 305d in the radial direction are parallel. In this case, the magnet shape can be simplified and the manufacturing becomes easy. In addition, the magnets 305 can be cut out from the magnet sheet 315 without waste, the yield can be increased, and the cost can be reduced.

[0166] In addition, in the present embodiment, the gap shape between the first magnet 307 and the second magnet 309 may also be set to a shape such that the gap shapes S1 and S2 adjacent in the circumferential direction are not similar to each other and do not coincide even when rotated around the rotation axis AX3. In this case, the plurality of magnets 305 on the back yoke portion 303 can be arranged at unequal intervals in the circumferential direction, and thus the cogging torque can be effectively reduced.

[0167] In addition, in the present embodiment, the least common multiple LCM of 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 6 times or more the number of poles. In this case, the offset angle θ1 can be reduced, so that the size reduction of the magnet 305 can be suppressed, and both a large skewing angle θ2 and the unequal interval arrangement of the magnets 305 can be applied simultaneously.

[0168] In addition, in the present embodiment, the first motor 101 and the second motor 201 may be arranged at the joint portion J3 of the transfer robot 10. In this case, since the cogging torque of the first motor 101 and the second motor 201 can be reduced, the joint portion J3 of the transfer robot 10 can be driven smoothly.

[0169] In addition, as described above, in the stator 110 of the first motor 101 and the stator 210 of the second motor 201 in the present embodiment, the plurality of 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 wiring substrate 413 is arranged on the other side in the direction of the rotation axis AX3 with respect to the back yoke portion 403. Thereby, the coil 405, the back yoke portion 403, and the wiring substrate 413 can be arranged in a straight line along the axial direction. Therefore, compared with the case where the wiring substrate 413 is arranged on the radially outer side of the back yoke portion 403, the outer diameter dimensions of the first motor 101 and the second motor 201 can be reduced.

[0170] In addition, for example, when the wiring substrate 413 is arranged between the coil 405 and the back yoke portion 403, it is impossible to wind the coil 405 in an amount corresponding to the arrangement space of the wiring substrate 413, so the coil density in the slot is reduced. In the present embodiment, since the wiring substrate 413 is arranged on the side of the back yoke portion 403 opposite to the side where the coil 405 is installed, the coil density can be increased.

[0171] In addition, in the present embodiment, the stator core 400 may also have a recess 415 on the other side in the direction of the rotation axis AX3 of the back yoke portion 403, and the wiring substrate 413 may also be accommodated in the recess 415. In this case, compared with the case where the wiring substrate 413 is arranged at a position on the other side of the stator core 400, the axial dimensions of the first motor 101 and the second motor 201 can be reduced. In addition, by effectively using the space on the other side of the back yoke portion 403, useless space can be prevented from being generated. In addition, the wiring substrate 413 can be protected.

[0172] In addition, in the present embodiment, the back yoke portion 403 may also have an opening 401 at a position radially inside the teeth 407 with respect to the rotation axis AX3, and the plurality of lead wires 411 may also be connected to the wiring substrate 413 through the opening 401. In this case, the lead wires 411 can be routed through the radially inner side of the back yoke portion 403 instead of routing the lead wires 411 on the radially outer side of the back yoke portion 403. Therefore, the outer diameter dimensions of the first motor 101 and the second motor 201 can be reduced.

[0173] In addition, in the present embodiment, the first motor 101 and the second motor 201 may also have an insulating portion (the protrusion 419 of the bobbin 409 in the embodiment) made of an insulating material and arranged between the lead wire 411 and the inner peripheral surface 401a of the opening 401. In this case, insulation between the lead wire 411 and the back yoke portion 403 can be ensured.

[0174] In addition, in the present embodiment, the first motor 101 and the second motor 201 may also have a bobbin 409 made of an insulating material on which the coil 405 is wound on the outer circumference and mounted on the tooth 407, and the insulating portion may be provided as a protrusion 419 protruding from the bobbin 409 toward the inner side of the opening 401. In this case, the coil 405 is mounted on the tooth 407 via the insulating bobbin 409, so it is not necessary to perform insulation treatment on the surface of the back yoke 403 and the tooth 407. In addition, by using the bobbin 409, the winding operation of the coil 405 becomes easy.

[0175] In this embodiment, the lead wire 411 may be led out from the coil 405 along the protruding direction of the protrusion 419. In this case, the lead wire 411 of the coil 405 can be easily led out. In addition, the protrusion 419 can be used to fix the lead wire 411.

[0176] In addition, in the present embodiment, a groove 401b into which the protrusion 419 fits may be formed on the inner circumferential surface 401a of the opening 401 of the back yoke 403. In this case, by fitting the protrusion 419 of the bobbin 409 into the groove 401b of the back yoke 403, positioning of the bobbin 409 and the protrusion 419 and mounting work on the teeth 407 are facilitated. In addition, positional deviation and vibration of the protrusion 419 and the lead wire 411 can be suppressed.

[0177] In addition, in the present embodiment, a plurality of lead wires 411 may be connected by using a connection substrate 413, the protrusion 419 may have an end face 423 at the end on the other side in the direction of the rotation axis AX3, and the connection substrate 413 may be configured to contact the end face 423 of the protrusion 419. In this case, since the connection portion is configured as the connection substrate 413, the connection work becomes easier than when the connection is performed manually using a lead wire or the like. In addition, the connection between the lead wire 411 and the connection substrate 413 becomes easier, which can promote the automation of the connection work. In addition, by making the connection substrate 413 contact the end face 423 of the protrusion 419, the positioning of the connection substrate 413 in the direction of the rotation axis AX3 becomes easier.

[0178] In the present embodiment, the first motor 101 and the second motor 201 may be disposed at the joint J3 of the transfer robot 10. In this case, since the outer diameters of the first motor 101 and the second motor 201 can be reduced in size, the size of the joint J3 of the transfer robot 10 can be reduced in size.

[0179] <6. Modifications>

[0180] Embodiments of the present disclosure are not limited to the above, and various modifications can be made without departing from its gist and technical idea.

[0181] In the above embodiment, it has been described that as shown in Figure 15 , the second magnet 309 is arranged at a position deviated from the offset angle θ1, and the first magnet 307 and the second magnet 309 are formed into a skewed shape inclined by the skew angle θ2 with respect to the radial direction DR. However, each magnet may not be formed into a skewed shape. For example, as shown in Figure 16 , the second magnet 309A is arranged at a position deviated from the offset angle θ1, and both the first magnet 307A and the second magnet 309A are formed into a shape in which one side 305a and the other side 305b in the circumferential direction are along the radial direction DR centered on the rotation axis AX3. In this case, the plurality of magnets 305A on the back yoke portion 303A can also be arranged at unequal intervals in the circumferential direction, so that the cogging torque can be effectively reduced.

[0182] In addition, in the above embodiment, it has been described that both the first magnet 307 and the second magnet 309 are in a shape in which the outer side edge 305c and the inner side edge 305d in the radial direction are straight and parallel, but the edges 305c and 305d may not be straight and parallel. For example, as shown in Figure 17 , both the first magnet 307B and the second magnet 309B are in a shape in which the outer side edge 305c and the inner side edge 305d in the radial direction are arc-shaped centered on the rotation axis AX3. In addition, for example, as shown in Figure 18 , it can be in the following shape: the outer side edge 305c and the inner side edge 305d are arc-shaped, and no skew angle θ2 is provided in each magnet. In the cases of the shapes shown in Figure 17 and Figure 18 , the outer side edge 305c and the inner side edge 305d become concentric arc-shaped. In the above cases, the plurality of magnets 305B and 305C on the back yoke portions 303B and 303C can also be arranged at unequal intervals in the circumferential direction, so that the cogging torque can be effectively reduced.

[0183] In addition, the above has described the case where the structure of the above embodiment is applied to both the first motor 101 and the second motor 201 provided in the joint portion J3 of the handling robot 10, but it can also be applied to any one of the motors. In addition, the structure of the above embodiment can also be applied to the motors of the joint portions J1 and J2 other than the joint portion J3 of the handling robot 10.

[0184] In the above description, when there are descriptions such as "vertical", "parallel", "plane", etc., these descriptions do not have a strict meaning. These "vertical", "parallel", "plane" allow for tolerances and errors in design and manufacturing, and refer to "substantially vertical", "substantially parallel", "substantially plane".

[0185] In the above description, when there are descriptions such as "identical", "the same", "equal", "different", etc. regarding the dimensions, sizes, shapes, positions, etc. in appearance, these descriptions do not have a strict meaning. These "identical", "the same", "equal", "different" allow for tolerances and errors in design and manufacturing, and refer to "substantially identical", "substantially the same", "substantially equal", "substantially different".

[0186] In addition to the above, the methods of the above-described embodiments and each modification example can also be used in appropriate combinations. Furthermore, although not exemplified one by one, the above-described embodiments and each modification example can be implemented with various changes within the scope not departing from their gist.

[0187] The problems to be solved and the effects of the embodiments, modification examples, etc. described above are not limited to the above content. Through the embodiments, modification examples, etc., it is also possible to solve problems not mentioned above, or achieve effects not mentioned above, and sometimes only solve a part of the problems described, or only achieve a part of the effects described.

Claims

1. An axial gap motor, comprising: a rotor that rotates about a rotation axis; a stator, which is opposite to the rotor in the direction of the rotation axis; a first back yoke provided on either one of the rotor and the stator; as well as a plurality of magnets arranged on the first back yoke along a circumferential direction around the rotation axis, The plurality of magnets have: a plurality of first magnets arranged at equal angular intervals in the circumferential direction; as well as The plurality of second magnets are disposed one by one between the plurality of first magnets and are disposed at positions offset by a predetermined first angle from a center angle of two of the first magnets adjacent to each other in the circumferential direction.

2. The axial gap motor according to claim 1, wherein: When the first angle is θ and the least common multiple of the number of slots of the stator and the number of poles of the rotor is LCM, θ≤(360° / LCM) / 2.

3. The axial gap motor according to claim 1 or 2, wherein: The first magnet and the second magnet have the following shapes: The side on one side and the side on the other side in the circumferential direction are inclined in the same direction at a predetermined second angle with respect to a radial direction centered on the rotation axis.

4. The axial gap motor according to claim 3, wherein: When the first angle is θ and the least common multiple of the number of slots of the stator and the number of poles of the rotor is LCM, θ<(360° / LCM) / 2.

5. The axial gap motor according to claim 4, wherein: When θ≥0.75×{(360° / LCM) / 2}, the value of the cogging torque generated between the rotor and the stator when the rotor is rotated about the rotation axis is equal to or less than the value of the cogging torque when θ is (360° / LCM) / 2.

6. The axial gap motor according to claim 5, wherein: The above θ is approximately 0.875×{(360° / LCM) / 2}.

7. The axial gap motor according to claim 5, wherein: The plurality of first magnets and the plurality of second magnets have the same shape as each other.

8. The axial gap motor according to claim 5, wherein: The plurality of first magnets and the plurality of second magnets have shapes in which outer sides and inner sides in the radial direction are parallel to each other.

9. The axial gap motor according to claim 1 or 2, wherein: The shape of the gap between the first magnet and the second magnet is such that the shapes of the gaps adjacent to each other in the circumferential direction are not similar to each other and are not consistent even when the gaps are rotated around the rotation axis.

10. The axial gap motor according to claim 2, wherein: The least common multiple is greater than 6 times the number of poles.

11. The axial gap electric machine according to claim 1, wherein: The axial gap motor also has: a second back yoke provided on the other of the rotor and the stator; a plurality of teeth protruding from one side of the second back yoke in a direction toward the rotation axis; a plurality of coils mounted on the plurality of teeth; and The connecting portion is disposed on the other side of the second back yoke in the direction of the rotation axis and is used to connect a plurality of lead wires led out from the plurality of coils.

12. A robot having an axial gap motor disposed at a joint, wherein: The axial gap motor has: a rotor that rotates about a rotation axis; a stator, which is opposite to the rotor in the direction of the rotation axis; a first back yoke provided on either one of the rotor and the stator; as well as a plurality of magnets arranged on the first back yoke along a circumferential direction around the rotation axis, The plurality of magnets have: a plurality of first magnets arranged at equal angular intervals in the circumferential direction; as well as The plurality of second magnets are disposed one by one between the plurality of first magnets and are disposed at positions offset by a predetermined first angle from a center angle of two of the first magnets adjacent to each other in the circumferential direction.

13. A robot system comprising: The robot according to claim 12; and A control device controls the actions of the robot.

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