motor

Abstract

The present invention can provide a motor including a shaft, a rotor coupled to the shaft, and a stator arranged to correspond to the rotor, wherein the rotor includes a rotor core and a magnet coupled to the rotor core, the magnet including a first unit magnet and a second unit magnet arranged circumferentially on the outer peripheral surface of the rotor core so as to be adjacent to the first unit magnet, the first unit magnet including a first surface facing the rotor core and a first curved surface facing the stator, the second unit magnet including a second surface facing the rotor core and a second curved surface facing the stator, the circumferential length of the first surface being different from the circumferential length of the second surface, and the radius of curvature of the first curved surface being different from the radius of curvature of the second curved surface.

Description

[Technical Field]

[0001] The embodiment relates to a motor. [Background technology]

[0002] An electric steering system (EPS) is a device that ensures the vehicle's turning stability and provides quick righting force, allowing the driver to drive safely. Such an electric steering system controls the driving of the vehicle's steering shaft by driving the motor through an electronic control unit (ECU) according to driving conditions detected by a vehicle speed sensor, torque angle sensor, and torque sensor.

[0003] A motor includes a stator and a rotor. The stator may include teeth that form a number of slots, and the rotor may include a number of magnets that face the teeth. Adjacent teeth are spaced apart to form slot openings. As the rotor rotates, cogging torque may occur due to the difference in magnetic permeability between the metal stator and the air in the slot openings, which are empty spaces. This cogging torque can affect steering sensitivity or output. Summary of the Invention [Problem to be solved by the invention]

[0004] Therefore, the present embodiment is intended to solve the above-mentioned problems, and an object of the present invention is to provide a motor capable of reducing cogging torque.

[0005] The problems to be solved by the embodiments are not limited to those mentioned above, and other problems not mentioned here will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0006] An embodiment can provide a motor including a shaft, a rotor coupled to the shaft, and a stator arranged to correspond to the rotor, wherein the rotor includes a rotor core and a magnet coupled to the rotor core, the magnet including a first unit magnet and a second unit magnet arranged circumferentially on the outer peripheral surface of the rotor core so as to be adjacent to the first unit magnet, the first unit magnet including a first surface facing the rotor core and a first curved surface facing the stator, the second unit magnet including a second surface facing the rotor core and a second curved surface facing the stator, the circumferential length of the first surface being different from the circumferential length of the second surface, and the radius of curvature of the first curved surface being different from the radius of curvature of the second curved surface.

[0007] Preferably, the circumferential length of the first surface is within 91% to 97% of the length of the second surface, and the radius of curvature of the first curved surface is within 95% to 100% of the radius of curvature of the second curved surface.

[0008] Preferably, the circumferential length of the first surface is within 93% to 95% of the circumferential length of the second surface, and the radius of curvature of the second curved surface is within 95% to 100% of the radius of curvature of the first curved surface.

[0009] Preferably, the circumferential length of the first surface is within 91% to 93% of the circumferential length of the second surface, and the radius of curvature of the second curved surface is within 95% to 100% of the radius of curvature of the first curved surface.

[0010] Preferably, the circumferential length of the second surface is within 91% to 93% of the circumferential length of the first surface, and the radius of curvature of the second curved surface is within 100% to 105% of the radius of curvature of the first curved surface.

[0011] An embodiment can provide a motor including a shaft, a rotor coupled to the shaft, and a stator arranged to correspond to the rotor, wherein the rotor includes a rotor core and a magnet coupled to the rotor core, the magnet including a first unit magnet and a second unit magnet arranged circumferentially on the outer peripheral surface of the rotor core so as to be adjacent to the first unit magnet, wherein the surface of the first unit magnet that contacts the rotor core is different in size from the surface of the second unit magnet that contacts the rotor core, and the radius of curvature of the curved surface of the first unit magnet is different from the radius of curvature of the curved surface of the second unit magnet.

[0012] An embodiment can provide a motor including a shaft, a rotor coupled to the shaft, and a stator arranged to correspond to the rotor, wherein the rotor includes a rotor core and a magnet coupled to the rotor core, and the magnet includes a first unit magnet and a second unit magnet arranged circumferentially on the outer circumferential surface of the rotor core so as to be adjacent to the first unit magnet, wherein the length of the surface of the first unit magnet that contacts the rotor core in the circumferential direction is different from the length of the surface of the second unit magnet that contacts the rotor core, and the maximum thickness of the first unit magnet is different from the maximum thickness of the second unit magnet in the radial direction.

[0013] Preferably, the first unit magnets and the second unit magnets may be arranged alternately along the circumferential direction.

[0014] Preferably, the rotor core includes a third surface that contacts the magnet, and the third surface may be a flat surface.

[0015] Preferably, the minimum thickness of the first unit magnet may be different from the minimum thickness of the second unit magnet in the radial direction.

[0016] Preferably, the minimum distance between the first unit magnet and the teeth of the stator in the radial direction may be different from the minimum distance between the second unit magnet and the teeth of the stator.

[0017] Preferably, the pair of first unit magnets may be arranged symmetrically with respect to the axial center, and the pair of second unit magnets may be arranged symmetrically with respect to the axial center. [Effects of the Invention]

[0018] The embodiment provides the advantageous effect of reducing cogging torque. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a diagram illustrating a motor according to an embodiment. [Figure 2] 1 is a diagram illustrating a stator and a rotor. [Figure 3] FIG. 3 is an enlarged view of the magnet shown in FIG. 2. [Figure 4] 1 is a diagram illustrating the thickness of a magnet. [Figure 5] 4 is a graph comparing the cogging torque waveforms of the comparative example and the embodiment shown in FIG. 3. [Figure 6] 10 is a graph showing the cogging torque corresponding to the radius of curvature of the second curved surface of the motor according to the example under the first condition. [Figure 7] 10 is a table illustrating cogging torque corresponding to the radius of curvature of the second curved surface of the motor according to the embodiment under the first condition. [Figure 8] 1 is a diagram illustrating a rotor in which magnets having different shapes and sizes are arranged; [Figure 9] FIG. 9 is an enlarged view of the magnet in FIG. 8. [Figure 10] 9 is a diagram illustrating the thickness of the magnet in FIG. 8. [Figure 11] 10 is a graph comparing the cogging torque waveforms of the comparative example and the embodiment shown in FIG. 9. [Figure 12]10 is a graph showing the cogging torque corresponding to the radius of curvature of the second curved surface of the motor according to the example under the second condition. [Figure 13] 10 is a table illustrating cogging torque corresponding to the radius of curvature of the second curved surface of the motor according to the embodiment under the second condition. DETAILED DESCRIPTION OF THE INVENTION

[0020] The direction parallel to the length of the shaft (vertical direction) is called the axial direction, the direction perpendicular to the axial direction around the shaft is called the radial direction, and the direction along a circle with a radius in the radial direction around the shaft is called the circumferential direction.

[0021] FIG. 1 is a diagram illustrating a motor 1 according to an embodiment.

[0022] 1, a motor 1 according to the embodiment may include a shaft 10, a rotor 20, a stator 30, a housing 400, a bus bar 500, a sensing unit 600, and a substrate 700. Hereinafter, "inside" refers to the direction from the housing 400 toward the shaft 10, which is the center of the motor, and "outside" refers to the direction opposite to the inside, that is, the direction from the shaft 10 toward the housing 400.

[0023] The shaft 10 may be coupled to the rotor 20. When an electromagnetic interaction occurs between the rotor 20 and the stator 30 through the supply of current, the rotor 20 rotates, and the shaft 10 rotates accordingly. The shaft 10 is rotatably supported by bearings. The shaft 10 may be connected to a steering device of a vehicle to transmit power.

[0024] The rotor 20 rotates through electrical interaction with the stator 30. The rotor 20 may be disposed inside the stator 30. The rotor 20 may include a rotor core 21 and magnets 22 disposed in the rotor core 21. In this case, the rotor 20 may be an SPM type in which the magnets 22 are disposed on the outer circumferential surface of the rotor core 21.

[0025] The stator 30 is disposed outside the rotor 20. The stator 30 may include a stator core 31, an insulator 32 attached to the stator core 31, and a coil 33 attached to the insulator 32. The coil 33 may be wound around the insulator 32. The insulator 32 is disposed between the coil 33 and the stator core 31 and serves to electrically insulate the stator core 31 from the coil 33. The coil 33 induces electrical interaction with the magnet 22 of the rotor 20.

[0026] FIG. 2 is a diagram illustrating the stator 30 and the rotor 20.

[0027] Referring to FIG. 2, the stator core 31 may include a yoke 31a and teeth 31b. The teeth 31b may protrude from the inner circumferential surface of the yoke 31a. There may be a plurality of teeth 31b. The number of teeth 31b may vary depending on the number of magnets 22. For example, there may be 12 teeth 31b, forming 12 slots. The number of magnets may be 8. The stator core 31 may be formed by combining a plurality of split cores, each including the yoke 31a and teeth 31b. Meanwhile, notches 31c may be formed on the edges of the teeth 31b to reduce cogging torque.

[0028] The magnets 22 are disposed on the outer circumferential surface of the rotor core 21. Each of the magnets 22 may include a plurality of first unit magnets 100 and second unit magnets 200. The first unit magnets 100 and the second unit magnets 200 may be disposed adjacent to each other in the circumferential direction based on the axial center C0. The first unit magnets 100 and the second unit magnets 200 may be disposed alternately based on the axial center C0.

[0029] A pair of first unit magnets 100 may be arranged symmetrically with respect to the axial center C0. A pair of second unit magnets 200 may also be arranged symmetrically with respect to the axial center C0. For example, four first unit magnets 100 and four second unit magnets 200 may be arranged.

[0030] FIG. 3 is an enlarged view of the magnet 22 shown in FIG.

[0031] 3, the first unit magnet 100 and the second unit magnet 200 have different shapes and sizes in order to reduce the cogging torque by modifying the waveform of the cogging torque.

[0032] The first unit magnet 100 may include a first surface 110 and a first curved surface 120. The first surface 110 may be a flat surface that contacts the rotor core 21. The first curved surface 120 may be a curved surface that faces the teeth 31b of the stator core 31. The first surface 110 and the first curved surface 120 are connected at their sides. When viewed in the axial direction, the first surface 110 may be represented by a straight line, and the first curved surface 120 may be represented by a curve. Such a first unit magnet 100 may have a bread-type shape.

[0033] The second unit magnet 200 may include a second surface 210 and a second curved surface 220. The second surface 210 may be a flat surface that contacts the rotor core 21. The second curved surface 220 may be a curved surface that faces the teeth of the stator core 31. The second surface 210 and the second curved surface 220 are connected at their sides. When viewed from the axial direction, the second surface 210 may be represented by a straight line, and the second curved surface 220 may be represented by a curve. Such a second unit magnet 200 may also have a bread-type shape.

[0034] The circumferential length L1 of the first surface 110 may be different from the circumferential length L2 of the second surface 210. If the first surface 110 and the second surface 210 are flat, the circumferential length L1 of the first surface 110 and the circumferential length L2 of the second surface 210 each correspond to the linear distance from one end to the other end of the magnet 22 in the circumferential direction. The circumferential length L2 of the second surface 210 may be longer than the circumferential length L1 of the first surface 110.

[0035] The radius of curvature R1 of the first curved surface 120 may be different from the radius of curvature R2 of the second curved surface 220. The radius of curvature R1 of the first curved surface 120 corresponds to the radius from the first center of curvature C1 to the first curved surface 120. The radius of curvature R2 of the second curved surface 220 corresponds to the radius from the second center of curvature C2 to the second curved surface 220. The first center of curvature C1 and the second center of curvature C2 may each be located at a point offset by a certain distance in the radial direction from the axial center C0. The radius of curvature R1 of the first curved surface 120 may be greater than the radius of curvature R2 of the second curved surface 220.

[0036] Meanwhile, the rotor core 21 may include a third surface 21b that comes into contact with the magnet 22. The third surface 21b may be a flat surface.

[0037] FIG. 4 is a diagram illustrating the thickness of the magnet 22.

[0038] Referring to FIG. 4, the thickness of the first unit magnet 100 and the thickness of the second unit magnet 200 may be different in the radial direction.

[0039] For example, the maximum thickness T1 of the first unit magnet 100 and the maximum thickness T2 of the second unit magnet 200 may be different. Based on the radial direction, the maximum thickness of the magnet 22 may be the linear distance between the first surface 110 and the first curved surface 120 or the linear distance between the second surface 210 and the second curved surface 220, based on a reference line passing through the axial center C0 and the center of the circumferential length of the magnet 22. The maximum thickness T1 of the first unit magnet 100 may be greater than the maximum thickness T2 of the second unit magnet 200.

[0040] For example, the minimum thickness T3 of the first unit magnet 100 and the minimum thickness T4 of the second unit magnet 200 may be different. The minimum thickness of the magnet 22 in the radial direction may be the linear distance between the first surface 110 and the first curved surface 120 or the linear distance between the second surface 210 and the second curved surface 220, based on a reference line passing through the axial center C0 and the circumferential end of the magnet 22. The minimum thickness T3 of the first unit magnet 100 may be greater than the minimum thickness T4 of the second unit magnet 200.

[0041] FIG. 5 is a graph comparing the cogging torque waveforms of the comparative example and the embodiment shown in FIG.

[0042] FIG. 5(a) is a diagram illustrating the cogging torque waveform of the comparative example, and FIG. 5(b) is a diagram illustrating the cogging torque waveform of the example.

[0043] The comparative example is a motor in which all magnets 22 have the same shape and size. In contrast, the working example is a motor in which first unit magnets 100 and second unit magnets 200 with different shapes and sizes are alternately arranged in the circumferential direction. In the comparative example, it can be seen that the cogging torque waveform corresponding to the rotation angle approaches the maximum value (approximately 0.025 Nm) or the minimum value (approximately -0.025 Nm) many times, resulting in a high cogging torque. In contrast, in the working example, it can be seen that the cogging torque waveform corresponding to the rotation angle approaches the maximum value (approximately 0.005 Nm) or the minimum value (approximately -0.007 Nm) much less often, resulting in a significant reduction in cogging torque.

[0044] The difference in shape and size between the first unit magnet 100 and the second unit magnet 200 can determine the extent to which the cogging torque is reduced.

[0045] The circumferential length L1 of the first surface 110 may be within 91% to 97% of the circumferential length L2 of the second surface 210. Preferably, the circumferential length L1 of the first surface 110 may be within 93% to 95% of the circumferential length L2 of the second surface 210. In this case, the curvature radius R2 of the second curved surface 220 may be within 95% to 100% of the curvature radius R1 of the first curved surface 120.

[0046] FIG. 6 is a graph illustrating the cogging torque corresponding to the radius of curvature R2 of the second curved surface 220 of the motor according to the embodiment under the first condition, and FIG. 7 is a table illustrating the cogging torque corresponding to the radius of curvature R2 of the second curved surface 220 of the motor according to the embodiment under the first condition.

[0047] As shown in FIGS. 6 and 7, under the first condition, the cogging torque corresponding to the radius of curvature R2 of the second curved surface 220 was measured.

[0048] The first condition is a state in which the circumferential length L1 of the first surface 110 is 12.5 mm, the circumferential length L2 of the second surface 210 is 13.0 mm, the radius of curvature R1 of the first curved surface 120 is 10.0 mm, and there is no skew angle of the magnets 22. In the comparative example, the circumferential lengths of all magnets 22 in contact with the rotor core 21 are the same, 13.0 mm, and the radius of curvature of the curved surfaces of all magnets 22 facing the stator core 31 is the same, 10.0 mm, and there is also no skew angle of the magnets 22. Therefore, under the first condition, the radius of curvature of the first unit magnet 100 is the same as that of the comparative example, and the length of the second unit magnet 200 is the same as that of the comparative example. Furthermore, the length of the first unit magnet 100 is shorter than that of the comparative example. Under the first condition, the circumferential length L1 of the first surface 110 is 96.1% of the circumferential length L2 of the second surface 210.

[0049] 6 and 7, P1 in Fig. 6 indicates the cogging torque (44.4 Nm) of the comparative example. Under the first condition, it can be seen that the cogging torque decreases as the radius of curvature R2 of the second curved surface 220 changes from 9.5 mm to 9.9 mm, and that when the radius of curvature R2 of the second curved surface 220 is 9.6 mm and 9.7 mm, the measured cogging torque is lower than the cogging torque (44.4 Nm) of the comparative example.

[0050] The cogging torque measured when the radius of curvature R2 of the second curved surface 220 was 9.7 mm was 12.1 Nm, which was the largest reduction of 72.8% compared to the comparative example. When the radius of curvature R2 of the second curved surface 220 was 9.8 mm and 9.9 mm, the cogging torque increased compared to when it was 9.7 mm, but it was reduced by 58.3% and 50.2%, respectively, compared to the comparative example.

[0051] It can be seen that when the curvature radius R2 of the second curved surface 220 is smaller than 9.5 mm or larger than 10.2 mm, the cogging torque increases more than in the comparative example.

[0052] When the curvature radius of the comparative example and that of the first unit magnet 100 are the same at 10 mm, it can be confirmed that the cogging torque is measured to be lower than that of the comparative example in the range where the curvature radius R2 of the second curved surface 220 is within 95% to 100% of the curvature radius R1 of the first curved surface 120.

[0053] FIG. 8 is a diagram illustrating a rotor 20 in which magnets 22 of different shapes and sizes are arranged, FIG. 9 is an enlarged view of the magnet 22 in FIG. 8, and FIG. 10 is a diagram illustrating the thickness of the magnet 22 in FIG. 8.

[0054] 8 to 10 , the circumferential length L2 of the second surface 210 may be longer than the circumferential length L1 of the first surface 110. The difference between the circumferential length L2 of the second surface 210 and the circumferential length L1 of the first surface 110 may be greater than the difference between the circumferential length L2 of the second surface 210 and the circumferential length L1 of the first surface 110 of the magnet 22 shown in FIG. 4. Unlike the magnet 22 of FIG. 4 , the radius of curvature R2 of the second curved surface 220 may be greater than the radius of curvature R1 of the first curved surface 120. Unlike the magnet 22 of FIG. 4 , the maximum thickness T1 of the first unit magnet 100 may be smaller than the maximum thickness T2 of the second unit magnet 200. Conversely, the minimum thickness T3 of the first unit magnet 100 may be greater than the minimum thickness T4 of the second unit magnet 200.

[0055] FIG. 11 is a graph comparing the cogging torque waveforms of the comparative example and the embodiment shown in FIG.

[0056] FIG. 11(a) is a diagram illustrating the cogging torque waveform of the comparative example, and FIG. 11(b) is a diagram illustrating the cogging torque waveform of the example.

[0057] The comparative example is a motor in which all magnets 22 have the same shape and size. In contrast, the working example is a motor in which first unit magnets 100 and second unit magnets 200 with different shapes and sizes are alternately arranged in the circumferential direction. In the comparative example, it can be seen that the cogging torque waveform corresponding to the rotation angle approaches the maximum value (approximately 0.025 Nm) or the minimum value (approximately -0.025 Nm) many times, resulting in a high cogging torque. In contrast, in the working example, it can be seen that the cogging torque waveform corresponding to the rotation angle approaches the maximum value (approximately 0.008 Nm) or the minimum value (approximately -0.008 Nm) much less often, resulting in a significant reduction in cogging torque.

[0058] 9, the circumferential length L1 of the first surface 110 may be within 91% to 93% of the circumferential length L2 of the second surface 210. In this case, the curvature radius R2 of the second curved surface 220 may be within 95% to 100% of the curvature radius R1 of the first curved surface 120. Alternatively, the curvature radius R2 of the second curved surface 220 may be within 100% to 105% of the curvature radius R1 of the first curved surface 120.

[0059] FIG. 12 is a graph illustrating the cogging torque corresponding to the radius of curvature R2 of the second curved surface 220 of the motor according to the embodiment under the second condition, and FIG. 13 is a table illustrating the cogging torque corresponding to the radius of curvature R2 of the second curved surface 220 of the motor according to the embodiment under the second condition.

[0060] As shown in FIGS. 12 and 13, under the second condition, the cogging torque corresponding to the radius of curvature R2 of the second curved surface 220 was measured.

[0061] The second condition is a state in which the circumferential length L1 of the first surface 110 is 12.0 mm, the circumferential length L2 of the second surface 210 is 13.0 mm, and the radius of curvature R1 of the first curved surface 120 is 10.0 mm. In the comparative example, the circumferential lengths of all magnets 22 in contact with the rotor core 21 are the same, 13.0 mm, and the radius of curvature of the curved surfaces of all magnets 22 facing the stator core 31 is the same, 10.0 mm. Therefore, under the second condition, the radius of curvature of the first unit magnet 100 is the same as that of the comparative example, and the length of the second unit magnet 200 is the same as that of the comparative example. Furthermore, the length of the first unit magnet 100 is shorter than that of the comparative example. Under the second condition, the circumferential length L1 of the first surface 110 is 92.3% of the circumferential length L2 of the second surface 210.

[0062] 12 and 13, P2 in FIG. 12 indicates the cogging torque (44.4 Nm) of the comparative example. Under the second condition, the cogging torque decreases as the radius of curvature R2 of the second curved surface 220 changes from 9.5 mm to 9.9 mm. It can be seen that when the radius of curvature R2 of the second curved surface 220 is between 9.6 mm and 9.9 mm, the measured cogging torque is lower than the cogging torque (44.4 Nm) of the comparative example. When the radius of curvature R2 of the second curved surface 220 is 9.9 mm, the cogging torque is 19.7 Nm, which is 55.6% of the comparative example, and it can be seen that the greatest decrease occurs when the radius of curvature R2 of the second curved surface 220 is between 9.5 mm and 9.9 mm.

[0063] Meanwhile, when the radius of curvature R2 of the second curved surface 220 is in the range of 10.1 mm to 10.4 mm, the cogging torque is higher than when it is 9.9 mm, but it can be confirmed that the cogging torque is significantly lower than that of the comparative example. The cogging torque measured when the radius of curvature R2 of the second curved surface 220 is 10.1 mm is 16.8 Nm, which is 62.2% of that of the comparative example, and it can be confirmed that the cogging torque decreases most significantly when the radius of curvature R2 of the second curved surface 220 is in the range of 9.5 mm to 10.5 mm.

[0064] It can be seen that when the curvature radius R2 of the second curved surface 220 is smaller than 9.5 mm or larger than 10.5 mm, the cogging torque increases more than in the comparative example.

[0065] While the radius of curvature of the comparative example and that of the first unit magnet 100 are the same at 10 mm, it can be seen that the cogging torque is measured to be lower than that of the comparative example in the range where the radius of curvature R2 of the second curved surface 220 is within 95% to 100% of the radius of curvature R1 of the first curved surface 120 and in the range where it is within 100% to 105%.

[0066] The above-described embodiment can be used in a variety of devices such as vehicles or home appliances.

Claims

1. A shaft, a rotor coupled to the shaft; a stator disposed to correspond to the rotor, the rotor includes a rotor core and a magnet coupled to the rotor core; The magnets include a first unit magnet arranged in a circumferential direction on the outer circumferential surface of the rotor core and a second unit magnet arranged adjacent to the first unit magnet, The first unit magnet and the second unit magnet are spaced apart in a circumferential direction, the first unit magnet includes a first surface facing the rotor core and a first curved surface facing the stator, the second unit magnet includes a second surface facing the rotor core and a second curved surface facing the stator, a circumferential length of the first surface is different from a circumferential length of the second surface; the radius of curvature of the first curved surface is different from the radius of curvature of the second curved surface; the rotor core includes a third surface that contacts the magnet, the first surface, the second surface, and the third surface are each a flat surface, The maximum thickness of the first unit magnet is different from the maximum thickness of the second unit magnet in the radial direction, A motor, wherein the circumferential length of the third surface is greater than the circumferential length of the first surface and the circumferential length of the second surface.

2. the circumferential length of the first surface is within 91% to 97% of the circumferential length of the second surface; 2. The motor according to claim 1, wherein the radius of curvature of the first curved surface is within 95% to 100% of the radius of curvature of the second curved surface.

3. the circumferential length of the first surface is within 93% to 95% of the circumferential length of the second surface; 2. The motor according to claim 1, wherein the radius of curvature of the second curved surface is within 95% to 100% of the radius of curvature of the first curved surface.

4. the circumferential length of the first surface is within 91% to 93% of the circumferential length of the second surface; 2. The motor according to claim 1, wherein the radius of curvature of the second curved surface is within 95% to 100% of the radius of curvature of the first curved surface.

5. the circumferential length of the second surface is within 91% to 93% of the circumferential length of the first surface, 2. The motor according to claim 1, wherein the radius of curvature of the second curved surface is within 100% to 105% of the radius of curvature of the first curved surface.

6. The motor according to claim 1 , wherein a size of a plane where the first unit magnets and the rotor core are in contact is smaller than a size of a plane where the second unit magnets and the rotor core are in contact.

7. The motor according to claim 1 , wherein a maximum thickness of the first unit magnet is greater than a maximum thickness of the second unit magnet in the radial direction.

8. The motor according to claim 1 , wherein the first unit magnets and the second unit magnets are arranged alternately along the circumferential direction.

9. The pair of first unit magnets are arranged symmetrically with respect to the axial center, The motor according to claim 1 , wherein the pair of second unit magnets are arranged symmetrically with respect to the axial center.

10. The motor according to claim 1 , wherein a minimum thickness of the first unit magnet is different from a minimum thickness of the second unit magnet in the radial direction.

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