Magnetic geared bearingless motor

Abstract

In this magnetic geared bearingless motor, the supporting force and output torque of a magnetic bearing are increased. A motor (1) is provided with a first rotor (2), a stator (4) disposed, facing the first rotor (2), in the radial direction of the first rotor (2), and a second rotor (3) disposed between the first rotor (2) and the stator (4). The first rotor (2) includes a plurality of magnetic poles (24). The second rotor (3) includes a plurality of modulators (31). The stator (4) includes a stator core (41), a motor winding (42), a support winding (43), and a plurality of permanent magnets (44). The number of modulators (31) is equal to the sum of the number of magnetic pole pairs of the first rotor (2) and the number of magnetic pole pairs of the stator (4). The support winding (43) can apply a magnetic field with respect to either of pole pairs, the number of which is obtained by adding or subtracting one from the number of magnetic pole pairs of the first rotor (2), or one pole pair thereof. The ratio (gear ratio) of the number of the plurality of modulators (31) to the number of magnetic pole pairs of the first rotor (2) is 8.2-23.5.

Description

Magnetic-geared bearingless motor

[0001] The present disclosure relates to magnetic-geared bearingless motors.

[0002] Non-Patent Document 1 discloses a magnetic-geared bearingless motor. A bearingless motor is a motor that has a non-contact magnetic bearing. A magnetic-geared motor is a motor that incorporates a non-contact magnetic gear as a reducer. In a magnetic-geared bearingless motor, there is no mechanical contact between the bearing and the reducer, so wear is less likely to occur and the number of parts can be reduced and the motor can be made smaller.

[0003] Akira Kumashiro, et.al ,”Novel Reluctance-Type Magnetic-Geard Motor Integrated With High-Speed ​​Bearingless Motor”, IEEE Transactions on Industry Applications, Vol. 60, No.3, May-June 2024, P. 3808-3819

[0004] In a magnetic-geared bearingless motor, there are an infinite number of combinations of magnetic pole pairs for the high-speed rotor (first rotor), the low-speed rotor (second rotor), and the stator. However, in conventional magnetic-geared bearingless motors, the relationship between the magnetic pole pair combinations and the motor characteristics is not clear.

[0005] An object of the present disclosure is to provide a magnetic-geared bearingless motor having a sufficiently large supporting force of a magnetic bearing and a large output torque.

[0006] A magnetic-geared bearingless motor according to one aspect of the present disclosure includes a first rotor, a stator, and a second rotor. The first rotor is rotatable about its axis. The stator is disposed radially opposite the first rotor. The second rotor is disposed between the first rotor and the stator and is rotatable about its axis. The first rotor includes a rotor core. The first rotor has a plurality of magnetic poles. The plurality of magnetic poles are arranged in the circumferential direction of the rotor core. The second rotor includes a plurality of modulators. The plurality of modulators are arranged in the circumferential direction of the second rotor. The stator includes a stator core, motor windings, support windings, and a plurality of permanent magnets. The motor windings generate a magnetomotive force that generates torque in the first rotor. The support windings are independent of the motor windings and adjust the position of the axis of the first rotor relative to the stator. The plurality of permanent magnets are arranged in the circumferential direction of the second rotor. The number of the multiple modulators of the second rotor is equal to the sum of the number of pole pairs of the first rotor and the number of pole pairs of the stator. The support winding of the stator can provide a field for any one of the number of pole pairs of the first rotor plus one, the number of pole pairs of the first rotor minus one, or one pole pair. The gear ratio, which is the ratio of the number of the multiple modulators of the second rotor to the number of pole pairs of the first rotor, is 8.2 or more and 23.5 or less.

[0007] According to a magnetic-geared bearingless motor according to one aspect of the present disclosure, it is possible to sufficiently increase the supporting force of the magnetic bearing and increase the output torque.

[0008] FIG. 1 is a front view of a motor according to an embodiment. FIG. 2 is a cross-sectional view of the motor according to an embodiment, corresponding to the cross section II-II in FIG. 1. FIG. 3 is an enlarged cross-sectional view of the motor according to an embodiment, corresponding to area AR1 in FIG. 2. FIG. 4 is a side view of a second rotor of the motor according to an embodiment. FIG. 5 is a graph showing the relationship between the gear ratio of the motor and the torque of the second rotor. FIG. 6 is a graph showing the relationship between the gear ratio of the motor and the integrated value of the torque and gear ratio of the first rotor. FIG. 7 is a graph showing the relationship between the gear ratio of the motor and the support performance of the first rotor. FIG. 8 is a graph showing the relationship between the gear ratio of the motor and the estimated torque of the second rotor.

[0009] Magnetic-geared bearingless motors according to embodiments of the present disclosure will be described in detail below with reference to the drawings. However, the drawings described in the following embodiments are schematic diagrams, and the ratios of the sizes and thicknesses of the components do not necessarily reflect the actual dimensional ratios. Note that the configurations described in the following embodiments are merely examples of the present disclosure. The present disclosure is not limited to the following embodiments, and various modifications are possible depending on the design, etc., as long as the effects of the present disclosure can be achieved.

[0010] (Embodiment) (1) Configuration (1.1) Motor A magnetic-geared bearingless motor 1 (hereinafter referred to as "motor 1") according to an embodiment is shown in FIGS. 1 to 4. FIG. 1 is a front view of motor 1 according to an embodiment. FIG. 2 is a cross-sectional view of motor 1 according to an embodiment, corresponding to cross section II-II in FIG. 1. FIG. 3 is an enlarged cross-sectional view of motor 1 according to an embodiment, corresponding to area AR1 in FIG. 2. FIG. 4 is a side view of second rotor 3 of motor 1 according to an embodiment.

[0011] As shown in FIGS. 1 to 3, the magnetic-geared bearingless motor 1 includes a first rotor 2, a second rotor 3, and a stator 4. Note that the housing of the motor 1 is omitted from FIG. 1. The first rotor 2 is rotatable in a circumferential direction D1 about an axis A1 (see FIG. 2). The stator 4 is disposed opposite the first rotor 2 in a radial direction D2 (see FIG. 3) of the first rotor 2. The second rotor 3 is disposed between the first rotor 2 and the stator 4. The second rotor 3 is rotatable in the circumferential direction D1 about the axis A1. Note that in FIGS. 1 to 4, an XYZ Cartesian coordinate system is established, with the direction parallel to the axis A1 defined as the Z axis and the plane perpendicular to the axis A1 defined as the XY plane. The "circumferential direction" refers to the direction along the circumference of a circle centered on the axis A1 on the XY plane.

[0012] (1.2) First Rotor As shown in Figures 1 to 3, the first rotor 2 includes a rotor core 21, a first rotating shaft 22, and a plurality of (eight in Figure 2) permanent magnets 23. Note that the first rotating shaft 22 is omitted from Figures 2 and 3.

[0013] The rotor core 21 is formed in a cylindrical shape. The rotor core 21 is a so-called laminated core, which is formed by stacking a plurality of steel plates, each having a main surface and a back surface parallel to the XY plane, alternately stacking the main surfaces and back surfaces in the extension direction of the axis A1 (hereinafter referred to as "direction D3"). Note that direction D3 is parallel to the Z axis.

[0014] A shaft hole 25 is formed in the center of rotor core 21, passing through rotor core 21 in direction D3.

[0015] The first rotating shaft 22 is a rod-shaped member extending in the direction D3, and functions as an output shaft of the first rotor 2. The first rotating shaft 22 is disposed in the shaft hole 25 of the rotor core 21, for example.

[0016] The plurality of permanent magnets 23 are arranged on the outer peripheral surface of the rotor core 21. Note that in Figures 2 and 3, the polarities of the plurality of permanent magnets 23 on the outer peripheral surface of the rotor core 21 are indicated by two types of dot hatching with different densities. More specifically, in a plan view from direction D3, permanent magnets 23a with their north poles arranged on the outer peripheral surface side and permanent magnets 23b with their south poles arranged on the outer peripheral surface side are arranged alternately along the circumferential direction D1.

[0017] As a result, the first rotor 2 has a plurality of magnetic poles 24 (eight in FIG. 2 ) aligned along the circumferential direction D1. The plurality of magnetic poles 24 have magnetic poles 24 of mutually opposite polarities aligned alternately along the circumferential direction D1. Specifically, in the rotor core 21, north poles and south poles are aligned alternately along the circumferential direction D1 in a plan view from the direction D3. The plurality of magnetic poles 24 correspond, for example, one-to-one to the plurality of permanent magnets 23.

[0018] Here, a pair of two magnetic poles 24 of opposite polarity that the first rotor 2 has is called a magnetic pole pair. The first rotor 2 has a plurality of magnetic pole pairs. In FIGS. 1 and 2, the number N of magnetic pole pairs of the first rotor 2 is Ｈ is 4, which is the number of pairs of north and south poles included in the plurality of magnetic poles 24.

[0019] The first rotor 2 rotates about the axis A1 due to the interaction between the magnetic flux generated by the motor windings 42 (see FIGS. 2 and 3) of the stator 4 and the permanent magnets 23. The first rotating shaft 22 of the first rotor 2 is supported by the interaction between the magnetic flux generated by the support windings 43 (see FIGS. 2 and 3) of the stator 4 and the permanent magnets 23. In other words, the first rotating shaft 22 of the first rotor 2 is not mechanically supported by the stator 4.

[0020] (1.3) Second Rotor As shown in Figures 2 to 4, the second rotor 3 includes a plurality of (58 in Figures 2 to 4) modulators 31, a modulator holder 32, and a second rotating shaft 33. Note that the modulator holder 32 and the second rotating shaft 33 are not shown in Figures 2 to 4. In Figures 2 to 4, the number N of modulators 31 is Ｌ is 58.

[0021] Each of the multiple modulators 31 is made of a magnetic material and is, for example, a rectangular parallelepiped iron core. The multiple modulators 31 are lined up along the circumferential direction D1. For example, the multiple modulators 31 are arranged at intervals along the circumferential direction D1. For example, the multiple modulators 31 are arranged at equal intervals in the circumferential direction D1.

[0022] The modulator holding portion 32 is a member that holds the multiple modulators 31 and is made of a non-magnetic material such as aluminum, an aluminum alloy, or resin. The modulator holding portion 32 has a hollow cylindrical shape that extends in direction D3 and is open at one end in direction D3. The modulator holding portion 32 also has multiple recesses 34 for holding the multiple modulators 31.

[0023] The second rotating shaft 33 is a rod-shaped member extending in the direction D3, and functions as an output shaft of the second rotor 3. The second rotating shaft 33 is fixed to the modulator holding portion 32.

[0024] The second rotor 3 rotates about the axis A1 as a result of the magnetic flux between the plurality of magnetic poles 47 (see FIGS. 2 and 3) of the stator 4 and the plurality of magnetic poles 24 of the first rotor 2 penetrating the plurality of modulators 31. In other words, the first rotor 2, the second rotor 3, and the stator 4 function as a magnetic gear. In the magnetic gear, the first rotating shaft 22 of the first rotor 2 is the input shaft, and the second rotating shaft 33 of the second rotor 3 is the output shaft. The gear ratio of the magnetic gear is determined by the ratio of the number N of magnetic pole pairs of the first rotor 2 to the number N of magnetic pole pairs of the first rotor 2. Ｈ The number N of modulators 31 for Ｌ Ratio of N Ｌ / N Ｈ Here, the number of magnetic pole pairs of the first rotor 2 is N Ｈ is 4, and the number N of modulators 31 Ｌ Since the rotational speed of the second rotor 3 is 58, the magnetic gear is a reduction gear. Ｈ / N Ｌ The output torque of the second rotor 3 is N times that of the first rotor 2. Ｌ / N Ｈ It's double.

[0025] (1.4) Stator As shown in Figures 2 and 3, the stator 4 includes a stator core 41, a plurality of motor windings 42, a plurality of support windings 43, and a plurality of permanent magnets 44. In Figures 2 and 3, the polarities of the plurality of permanent magnets 44 on the inner circumferential surface 48 of the stator 4 are indicated by two types of dot hatching with different densities.

[0026] The stator core 41 is made of, for example, a magnetic material and has a plurality of teeth 45 (18 teeth in FIG. 2 ) and an outer circumferential portion 46 .

[0027] The teeth 45 protrude from the outer circumferential portion 46 in the radial direction D2 toward the first rotor 2 and the second rotor 3. The teeth 45 are, for example, arranged at equal intervals in the circumferential direction D1. Note that the "radial direction D2" refers to a direction perpendicular to the axis A1, with the axis A1 as the center.

[0028] The outer peripheral portion 46 has, for example, a hollow cylindrical shape. The teeth 45 are attached to the inner peripheral surface of the outer peripheral portion 46.

[0029] The plurality of motor windings 42 are provided in a one-to-one correspondence with the plurality of teeth 45. The plurality of motor windings 42 are windings for generating torque in the first rotor 2. Each of the plurality of motor windings 42 includes a linear conductor formed from, for example, copper or a copper alloy. Each motor winding 42 is wound around the corresponding tooth 45, for example, via an insulator (not shown).

[0030] The support windings 43 are provided in a one-to-one correspondence with the teeth 45. The support windings 43 are windings for generating a support force in the radial direction D2 that supports the first rotor 2. That is, the support windings 43 adjust the position of the first rotor 2 in the radial direction D2 relative to the stator 4. The support windings 43 are independent of the motor windings 42. More specifically, the support windings 43 magnetically support the first rotor 2. Each of the support windings 43 is wound around a corresponding tooth 45, for example, via an insulator (not shown). The support windings 43 generate a support force for the first rotor 2, for example, through feedback control based on the position and inclination of the first rotor 2. The motor 1 may include, for example, a sensor (not shown) that detects the position and inclination of the first rotor 2 and a control circuit (not shown), and the support windings 43 are supplied with power from the control circuit. Note that the motor 1 may not include a control circuit and may be connected to an external control circuit.

[0031] The plurality of permanent magnets 44 (90 in FIG. 2 ) are used as a plurality of magnetic poles 47 for generating torque in the second rotor 3 through interaction with the plurality of magnetic poles 24 of the first rotor 2. The plurality of magnetic poles 47 are arranged on an inner circumferential surface 48 of the stator 4.

[0032] The multiple magnetic poles 47 include magnetic poles 47 generated by the multiple motor windings 42 and the multiple teeth 45, and magnetic poles 47 generated by the multiple permanent magnets 44. The multiple magnetic poles 47 are provided on the inner circumferential surface 48 of the stator 4, between the center of each of the multiple teeth 45 and the centers of two teeth 45 adjacent to each other in the circumferential direction D1. The multiple magnetic poles 47 are provided, for example, at equal intervals along the circumferential direction D1.

[0033] Five of the permanent magnets 44 are arranged between two magnetic poles 47 at the centers of two teeth 45 adjacent to each other in the circumferential direction D1. The permanent magnets 44 are arranged such that the polarities of the two magnetic poles 47 adjacent to each other in the circumferential direction D1 are different. More specifically, permanent magnets 44a, whose north poles are arranged on the inner circumferential surface 48 of the stator 4, and permanent magnets 44b, whose south poles are arranged on the inner circumferential surface 48 of the stator 4, are arranged alternately along the circumferential direction D1.

[0034] 2 and 3, the number of magnetic pole pairs of the stator 4 is N Ｓ is 54, which is half of the number 108 of magnetic poles 47, which is the sum of the number 18 of the tips of the teeth 45 and the number 90 of the permanent magnets 44.

[0035] (2) Relationship between the number of magnetic poles and torque (2.1) Relationship between the number of magnetic poles Number N of modulators 31 of the second rotor 3 Ｌ , the number N of magnetic pole pairs of the first rotor 2 Ｈ , and the number N of magnetic pole pairs of the stator 4 Ｓ It is preferable that the following conditions are met:

[0036] As a first condition, the number N of modulators 31 of the second rotor 3 Ｌ is the number N of magnetic pole pairs of the first rotor 2 Ｈ and the number of magnetic pole pairs of the stator 4, N Ｓ That is, the following formula holds:

[0037] N Ｌ = N Ｈ +N Ｓ As a result, when the first rotor 2 is rotating, the magnetomotive force due to the magnetic poles 24 of the first rotor 2 and the magnetic flux density due to the interaction between the first rotor 2 and the second rotor 3 have the same magnetic flux distribution. Therefore, the rotation of the first rotor 2 causes the rotation of the second rotor 3. In the motor 1 described above, the number N of modulators 31 is Ｌ is 58, and the number of magnetic pole pairs of the first rotor 2, N Ｈ is 4, and the number of magnetic pole pairs of the stator 4, N Ｓ is 54. Therefore, the motor 1 satisfies the first condition.

[0038] As a second condition, the support winding 43 of the stator 4 must be equal to or larger than the number N of magnetic pole pairs of the first rotor 2. Ｈ or the number N of magnetic pole pairs of the first rotor 2 Ｈ It is preferable that the support winding 43 of the stator 4 is capable of providing a field for any one of the pole pairs, the number of which is M minus one. Here, "the support winding 43 of the stator 4 is capable of providing a field for M (M is an integer) pole pairs" means that the magnetic flux density distribution formed by the support winding 43 of the stator 4 inside the inner circumferential surface 48 of the stator 4 contains components of the M pole pairs as its main components. "The magnetic flux density distribution formed by the support winding 43 of the stator 4" means a component of the magnetic flux density distribution inside the inner circumferential surface 48 of the stator 4 that changes depending on whether or not a current is applied to the support winding 43 of the stator 4. Specifically, "the magnetic flux density distribution formed by the support winding 43 of the stator 4" means the difference between the magnetic flux density distribution when a current is applied to the support winding 43 of the stator 4 and the magnetic flux density distribution when no current is applied to the support winding 43 of the stator 4. For example, in the motor 1 , it is possible to pass a current through the support winding 43 of the stator 4 so that an M pole pair is formed inside the inner circumferential surface 48 of the stator 4 .

[0039] As a third condition, the gear ratio N of the motor 1 Ｌ / N Ｈ It is preferable that the gear ratio N is a non-integer value. Ｌ / N Ｈ If is a non-integer, the gear ratio N Ｌ / N Ｈ In comparison with the case where the gear ratio N is an integer, the periodicity of the magnetic field passing through the second rotor 3 in the circumferential direction D1 is reduced in a plan view from the direction D3, and therefore the cogging torque of the second rotor 3 can be reduced. Ｌ / N Ｈ is 58 / 4, or 14.5, which is a non-integer value. That is, motor 1 satisfies the third condition.

[0040] Furthermore, as a fourth condition, the number N of modulators 31 of the second rotor 3 Ｌ , the number N of magnetic pole pairs of the first rotor 2 Ｈ , and the number N of magnetic pole pairs of the stator 4 ＳIt is preferable that the number N of modulators 31 of the second rotor 3 has a common divisor of 2 or more. Ｌ , the number N of magnetic pole pairs of the first rotor 2 Ｈ , and the number N of magnetic pole pairs of the stator 4 Ｓ "have a common factor of 2 or more" means that the number N Ｌ , number N Ｈ , and the number N Ｓ The common factor of the three is 2 or more. Ｌ , number N Ｈ , and the number N Ｓ The greatest common divisor of the three is an integer greater than or equal to 2. Ｌ , number N Ｈ , and the number N Ｓ is K (K is an integer of 2 or more), the relative positional relationship between the multiple modulators 31 of the second rotor 3, the multiple magnetic poles 24 of the first rotor 2, and the multiple magnetic poles 47 of the stator 4 is K-fold rotationally symmetric in plan view from direction D3. Therefore, in plan view from direction D3, bias in the physical force applied to the multiple magnetic poles 24 of the first rotor 2 is less likely to occur. In other words, when the number N of modulators 31 of the second rotor 3 is Ｌ , the number N of magnetic pole pairs of the first rotor 2 Ｈ , and the number N of magnetic pole pairs of the stator 4 Ｓ However, if the number N has a common factor of 2 or more, the eccentric force of the first rotor 2 becomes small. Ｌ is 58, the number N Ｈ is 4, the number N Ｓ is 54, so the common divisor is 2. In other words, motor 1 satisfies the fourth condition.

[0041] (2.2) Relationship between the number of magnetic poles and torque Figure 5 shows the relationship between the number of magnetic poles and the torque of multiple magnetic-geared bearingless motors. Ｌ / N Ｈ 1 is a graph showing the relationship between the rated torque and the number of modulators 31 of the second rotor 3. The plurality of magnetic-geared bearingless motors includes the motor 1. The plurality of magnetic-geared bearingless motors also includes the plurality of magnetic-geared bearingless motors, each of which has a number N of modulators 31 of the second rotor 3. Ｌ , the number N of magnetic pole pairs of the first rotor 2 Ｈ , and the number N of magnetic pole pairs of the stator 4 ＳThe motor includes a motor in which one or more of the above components are different from motor 1. The rated torque of the magnetic-geared bearingless motor refers to the rated value of the output torque of the second rotating shaft 33. In Fig. 5, the rated torque is shown as a relative value, with the maximum value in Fig. 5 being 1. The vertical axis in Fig. 5 is in arbitrary units (au for short).

[0042] As shown in FIG. 5, the rated torque of the magnetic-geared bearingless motor is Ｌ / N Ｈ The gear ratio N Ｌ / N Ｈ When the gear ratio N is 16 or less, the rated torque of the magnetic-geared bearingless motor is Ｌ / N Ｈ The larger the gear ratio N Ｌ / N Ｈ is 16 or more, the rated torque of the magnetic-geared bearingless motor is Ｌ / N Ｈ The larger the gear ratio N of the motor 1, the smaller the rated torque. Ｌ / N Ｈ is greater than or equal to 8.2 and less than or equal to 23.5, the rated torque of the magnetic-geared bearingless motor is Ｌ / N Ｈ This is more than two-thirds of the rated torque of the magnetic-geared bearingless motor when the gear ratio N of the motor 1 is 16. Ｌ / N Ｈ is preferably 8.2 or more and 23.5 or less.

[0043] (2.3) Consideration The relationship between the number of magnetic poles and torque will now be considered.

[0044] FIG. 6 shows the gear ratio N Ｌ / N Ｈ and the average torque of the first rotor 2 and the gear ratio N Ｌ / N Ｈ 1 is a graph showing the relationship between the integrated value and the gear ratio N Ｌ / N ＨSince the magnetic gear is provided, the rotation speed of the second rotor 3 is N times the rotation speed of the first rotor 2. Ｈ / N L The output torque of the second rotor 3 is N times that of the first rotor 2. Ｌ / N Ｈ That is, the average torque of the first rotor 2 and the gear ratio N Ｌ / N Ｈ The integrated value of these indicates an estimated value of the average torque of the second rotor 3. Here, the average torque of the first rotor 2 does not take into consideration the support of the first rotor 2 by the multiple support windings 43. Also, in FIG. 6, the average torque of the first rotor 2 and the gear ratio N Ｌ / N Ｈ The integrated value is shown as a relative value with the maximum value in FIG.

[0045] As shown in FIG. 6, the average torque of the first rotor 2 and the gear ratio N Ｌ / N Ｈ The integrated value of gear ratio N Ｌ / N Ｈ It has the characteristic that it increases as

[0046] FIG. 7 shows the gear ratio N Ｌ / N Ｈ7 is a graph showing the relationship between the support performance of the first rotor 2 and the torque capacity of the first rotor 2. Here, the support performance of the first rotor 2 is the value obtained by dividing the value of the support force applied to the first rotor 2 from the multiple support windings 43 by the eccentric force generated in the first rotor 2. Therefore, the higher the support performance of the first rotor 2, the better the magnetic bearing function for the first rotor 2. Furthermore, for multiple magnetic-geared bearingless motors, if the magnetic bearing function is higher than necessary, reducing the number of turns of each of the multiple support windings 43 does not cause the posture of the first rotor 2 to become unstable, and therefore does not impede operation as a bearingless motor. In other words, if the support performance of the first rotor 2 is high, the torque of the first rotor 2 can be increased by reducing the number of turns of each of the multiple support windings 43 and instead increasing the number of turns of each of the multiple motor windings 42. In other words, the support performance of the first rotor 2 also indicates the room for improvement in the average torque of the first rotor 2. Note that in FIG. 7 , the support performance of the first rotor 2 is expressed as a relative value, with the maximum value in FIG. 7 being 1. The unit of the vertical axis in FIG. 7 is an arbitrary unit (au for short).

[0047] FIG. 8 shows the gear ratio N Ｌ / N Ｈ 6 is a graph showing the relationship between the average torque of the second rotor 3 and the integrated value of the support performance of the first rotor 2. Here, the average torque of the second rotor 3 is calculated by multiplying the average torque of the first rotor 2 shown in FIG. Ｌ / N Ｈ 8 is the product of the values ​​shown on the vertical axis in Fig. 6 and the values ​​shown on the vertical axis in Fig. 7. In Fig. 8, the product of the average torque of the second rotor 3 and the support performance of the first rotor 2 is shown as a relative value, with the maximum value in Fig. 8 being 1. The vertical axis in Fig. 8 is in arbitrary units (au for short).

[0048] As described above, the support performance of the first rotor 2 is a value that indicates the room for improvement in the average torque of the first rotor 2. Therefore, the product of the average torque of the second rotor 3 and the support performance of the first rotor 2 is considered to indicate the maximum value of the rated torque of the second rotor 3. Furthermore, from the similarity between the graphs of Fig. 5 and Fig. 8, it is considered that the rated torque of a magnetic-geared bearingless motor is significantly affected by the above-mentioned factors. In other words, the rated torque of a magnetic-geared bearingless motor is determined by the average torque of the first rotor 2 and the gear ratio N Ｌ / N Ｈ It is considered that the torque is determined by the balance between the average torque of the second rotor 3 determined by the above equation and the support performance of the first rotor 2.

[0049] (3) Effects The motor 1 according to the embodiment includes a first rotor 2, a stator 4, and a second rotor 3. The first rotor 2 is rotatable about an axis A1. The stator 4 is disposed opposite the first rotor 2 in a radial direction D2 of the first rotor 2. The second rotor 3 is disposed between the first rotor 2 and the stator 4 and is rotatable about the axis A1. The first rotor 2 includes a rotor core 21. The first rotor 2 has a plurality of magnetic poles 24. The plurality of magnetic poles 24 are aligned in the circumferential direction D1 of the rotor core 21. The second rotor 3 includes a plurality of modulators 31. The plurality of modulators 31 are aligned in the circumferential direction D1 of the second rotor 3. The stator 4 includes a stator core 41, a motor winding 42, a support winding 43, and a plurality of permanent magnets 44. The motor winding 42 generates a magnetomotive force that generates torque in the first rotor 2. The support winding 43 is independent of the motor winding 42 and adjusts the position of the axis of the first rotor 2 relative to the stator 4. The plurality of permanent magnets 44 are arranged in the circumferential direction D1 of the second rotor 3. The number N of the plurality of modulators 31 of the second rotor 3 Ｌ is the number N of magnetic pole pairs of the first rotor 2 Ｈ and the number of magnetic pole pairs of the stator 4, N Ｓ The support winding 43 of the stator 4 is equal to the sum of the number N of magnetic pole pairs of the first rotor 2. Ｈ or the number N of magnetic pole pairs of the first rotor 2 Ｈ The number of pole pairs of the first rotor 2 is N minus 1. ＨThe number N of the modulators 31 of the second rotor 3 Ｌ The gear ratio, which is the ratio of the above, is equal to or greater than 8.2 and equal to or less than 23.5. As a result, the motor 1 according to this embodiment can sufficiently increase the supporting force of the magnetic bearing and increase the output torque.

[0050] In addition, in the motor 1 according to the embodiment, the gear ratio N Ｌ / N Ｈ It is preferable that the value of π / 2 is a non-integer. As a result, the motor 1 according to this embodiment can reduce the cogging torque of the second rotor 3.

[0051] In the motor 1 according to the embodiment, the number N of the modulators 31 of the second rotor 3 is Ｌ and the number N of magnetic pole pairs of the first rotor 2 Ｈ and the number N of magnetic pole pairs of the stator 4 Ｓ and preferably have a common divisor of 2 or more. As a result, the motor 1 according to this embodiment reduces the eccentric force of the first rotor 2. Therefore, in the motor 1, by reducing the number and number of turns of the support windings 43 and increasing the number and number of turns of the motor windings 42, it is easy to improve the torque.

[0052] Furthermore, in the motor 1 according to this embodiment, it is preferable that the multiple modulators 31 are arranged at intervals from one another along the circumferential direction D1 of the second rotor 3. As a result, in the motor 1 according to this embodiment, the torque generated in the second rotor 3 in the circumferential direction D1 is less likely to vary, making it possible to reduce the cogging torque of the second rotor 3.

[0053] (Other Modifications According to the Embodiment) (1) In the motor 1 according to the embodiment, all of the multiple magnetic poles 24 of the first rotor 2 are permanent magnets 23. However, for example, the multiple magnetic poles 24 of the first rotor 2 may include consequent poles formed by iron cores. For example, in the rotor core 21, in a plan view from the direction D3, permanent magnets 23a whose north poles are arranged on the outer peripheral surface side and iron cores may be alternately arranged along the circumferential direction D1. Furthermore, in the rotor core 21, in a plan view from the direction D3, permanent magnets 23b whose south poles are arranged on the outer peripheral surface side and iron cores may be alternately arranged along the circumferential direction D1. When the first rotor 2 includes consequent poles, a pair of a consequent pole and one permanent magnet 23 adjacent to the consequent pole constitutes one magnetic pole pair.

[0054] Here, when the multiple magnetic poles 24 of the first rotor 2 include consequent poles, the support winding 43 of the stator 4 can generate a field for one pole pair, which makes it possible to sufficiently increase the supporting force of the magnetic bearing.

[0055] (2) In the motor 1 according to the embodiment, the multiple permanent magnets 23 in the first rotor 2 are arranged on the outer peripheral surface of the rotor core 21. However, for example, the rotor core 21 may have multiple magnet arrangement holes for respectively arranging the multiple permanent magnets 23, and the multiple permanent magnets 23 may be arranged one by one in the multiple magnet arrangement holes of the rotor core 21.

[0056] (3) In the motor 1 according to the embodiment, the first rotor 2 includes a plurality of permanent magnets 23. However, the first rotor 2 may have windings for forming magnetic poles 24 instead of some or all of the plurality of permanent magnets 23.

[0057] (4) In the motor 1 according to the embodiment, the multiple magnetic poles 24 of the first rotor 2 are arranged at equal intervals in the circumferential direction D1, but the multiple magnetic poles 24 do not have to be arranged at equal intervals in the circumferential direction D1.

[0058] (5) In the motor 1 according to this embodiment, the multiple modulators 31 of the second rotor 3 are arranged at intervals from one another in the circumferential direction D1. However, two or more of the multiple modulators 31 of the second rotor 3 may be connected in the circumferential direction D1. Furthermore, for example, the second rotor 3 may include a permanent magnet between two modulators 31 adjacent to each other in the circumferential direction D1. Furthermore, the multiple modulators 31 do not have to be arranged at equal intervals in the circumferential direction.

[0059] (6) In the motor 1 according to the embodiment, all of the magnetic poles 47 of the stator 4 other than the magnetic poles 47 formed by the motor windings 42 and the teeth 45 are permanent magnets 44. However, for example, the magnetic poles 47 of the stator 4 may include consequent poles formed by iron cores. For example, the stator 4 may have permanent magnets 44 and iron cores alternately arranged between the centers of two teeth 45 adjacent to each other in the circumferential direction D1. Here, the iron cores may be molded integrally with the stator core 41. When the stator 4 includes consequent poles, a pair of a consequent pole and one permanent magnet 44 adjacent to the consequent pole constitutes one magnetic pole pair.

[0060] (7) In the motor 1 according to this embodiment, the multiple motor windings 42 and the multiple support windings 43 all correspond one-to-one to the multiple teeth 45 in the stator 4. However, the multiple motor windings 42 and the multiple support windings 43 may be arranged on different teeth 45, for example. Also, for example, the number of motor windings 42 and the number of support windings 43 may be different. Also, one or both of the multiple motor windings 42 and the multiple support windings 43 do not have to be arranged at equal intervals in the circumferential direction D1.

[0061] (8) The motor 1 according to the embodiment is a so-called radial gap motor in which the multiple magnetic poles 24 of the first rotor 2, the multiple modulators 31 of the second rotor 3, and the multiple magnetic poles 47 of the stator 4 are aligned in the radial direction D2. However, the motor 1 may be a so-called axial gap motor in which the multiple magnetic poles 24 of the first rotor 2, the multiple modulators 31 of the second rotor 3, and the multiple magnetic poles 47 of the stator 4 are aligned in the direction D3 in which the axis A1 extends.

[0062] In this case, the stator 4 and the first rotor 2 are aligned in the direction D3 in which the axis A1 extends. The second rotor 3 is located between the stator 4 and the first rotor 2 in the direction D3. The stator core 41 of the stator 4 is, for example, disk-shaped, and the multiple teeth 45 protrude in the direction D3 toward the first rotor 2 and the second rotor 3. The rotor core 21 of the first rotor 2 is, for example, disk-shaped, and the multiple magnetic poles 24 are provided at one end of the rotor core 21 in the direction D3 so as to face the stator 4. The multiple modulators 31 of the second rotor 3 are, for example, arranged radially.

[0063] (Aspect) A magnetic-geared bearingless motor (1) according to a first aspect includes a first rotor (2), a stator (4), and a second rotor (3). The first rotor (2) is rotatable about an axis (A1). The stator (4) is disposed opposite the first rotor (2) in a radial direction (D2) of the first rotor (2). The second rotor (3) is disposed between the first rotor (2) and the stator (4) and is rotatable about the axis (A1). The first rotor (2) includes a rotor core (21). The first rotor (2) has a plurality of magnetic poles (24). The plurality of magnetic poles (24) are aligned in a circumferential direction (D1) of the rotor core (21). The second rotor (3) includes a plurality of modulators (31). The plurality of modulators (31) are aligned in the circumferential direction (D1) of the second rotor (3). The stator (4) includes a stator core (41), a motor winding (42), a support winding (43), and a plurality of permanent magnets (44). The motor winding (42) generates a magnetomotive force that generates torque in the first rotor (2). The support winding (43) is independent of the motor winding (42) and adjusts the position of the axis of the first rotor (2) relative to the stator (4). The plurality of permanent magnets (44) are arranged in the circumferential direction (D1) of the second rotor (3). The number of the plurality of modulators (31) of the second rotor (3) is equal to the sum of the number of magnetic pole pairs of the first rotor (2) and the number of magnetic pole pairs of the stator (4). The support winding (43) of the stator (4) can provide a field for any one of the number of pole pairs obtained by adding one to the number of magnetic pole pairs of the first rotor (2), the number of pole pairs obtained by subtracting one from the number of magnetic pole pairs of the first rotor (2), or one pole pair. A gear ratio, which is the ratio of the number of multiple modulators (31) of the second rotor (3) to the number of magnetic pole pairs of the first rotor (2), is 8.2 or more and 23.5 or less.

[0064] According to the magnetic-geared bearingless motor (1) according to the above aspect, it is possible to sufficiently increase the supporting force of the magnetic bearing and increase the output torque.

[0065] A magnetic-geared bearingless motor (1) according to a second aspect is the first aspect, in which the gear ratio is a non-integer value.

[0066] According to the magnetic-geared bearingless motor (1) according to the above aspect, it is possible to reduce the cogging torque of the second rotor (3).

[0067] The magnetic-geared bearingless motor (1) according to the third aspect is the first or second aspect, in which the number of the multiple modulators (31) of the second rotor (3), the number of magnetic pole pairs of the first rotor (2), and the number of magnetic pole pairs of the stator (4) have a common divisor of 2 or more.

[0068] The magnetic-geared bearingless motor (1) according to the above aspect reduces the eccentric force of the first rotor (2). Therefore, in the magnetic-geared bearingless motor (1), the torque can be easily improved by reducing the number and number of turns of the support windings (43) and increasing the number and number of turns of the motor windings (42).

[0069] The magnetic-geared bearingless motor (1) according to the fourth aspect is any one of the first to third aspects, in which a plurality of modulators (31) are arranged at intervals from one another along the circumferential direction (D1) of the second rotor (3).

[0070] According to the magnetic-geared bearingless motor (1) according to the above aspect, it is possible to reduce the cogging torque of the second rotor (3).

[0071] The magnetic-geared bearingless motor (1) according to the fifth aspect is any one of the first to third aspects, in which two or more of the multiple modulators (31) are connected in the circumferential direction (D1) of the second rotor (3).

[0072] According to the magnetic-geared bearingless motor (1) of the above aspect, it is possible to reduce the spacing between the multiple modulators (31) in the second rotor (3), thereby making it possible to reduce the size of the magnetic-geared bearingless motor (1).

[0073] The magnetic-geared bearingless motor of the present disclosure can provide a sufficiently large supporting force of the magnetic bearing and a large output torque, making the magnetic-geared bearingless motor of the present disclosure industrially useful.

[0074] REFERENCE SIGNS LIST 1 Motor (magnetic-geared bearingless motor) 2 First rotor 21 Rotor core 23, 23a, 23b, 44, 44a, 44b Permanent magnets 24, 47 Magnetic poles 3 Second rotor 31 Modulator 4 Stator 41 Stator core 42 Motor winding 43 Support winding A1 Axis center D1 Circumferential direction D2 Radial direction

Claims

1. A motor comprising: a first rotor rotatable about its axis; a stator disposed radially opposite the first rotor; and a second rotor disposed between the first rotor and the stator and rotatable about the axis, wherein the first rotor includes a rotor core having a plurality of magnetic poles arranged in the circumferential direction of the rotor core; the second rotor includes a plurality of modulators arranged in the circumferential direction of the second rotor; the stator includes a stator core, motor windings for generating magnetomotive force that generates torque in the first rotor, support windings that are independent of the motor windings and for adjusting the position of the axis of the first rotor relative to the stator, and a plurality of permanent magnets arranged in the circumferential direction of the second rotor; and the number of the plurality of modulators of the second rotor is equal to the sum of the number of magnetic pole pairs of the first rotor and the number of magnetic pole pairs of the stator, a magnetic-geared bearingless motor, wherein the support winding of the stator is capable of field magnetizing any one of the number of pole pairs obtained by adding one to the number of magnetic pole pairs of the first rotor, the number of pole pairs obtained by subtracting one from the number of magnetic pole pairs of the first rotor, or one pole pair, and wherein a gear ratio, which is the ratio of the number of the multiple modulators of the second rotor to the number of magnetic pole pairs of the first rotor, is 8.2 or more and 23.5 or less.

2. The magnetic-geared bearingless motor according to claim 1, wherein the gear ratio is a non-integer value.

3. A magnetic-geared bearingless motor according to claim 1 or 2, wherein the number of the plurality of modulators of the second rotor, the number of magnetic pole pairs of the first rotor, and the number of magnetic pole pairs of the stator have a common divisor of 2 or more.

4. A magnetic-geared bearingless motor according to claim 1 or 2, wherein the plurality of modulators are arranged at intervals from one another along the circumferential direction of the second rotor.

5. A magnetic-geared bearingless motor according to claim 1 or 2, wherein two or more of the plurality of modulators are connected in the circumferential direction of the second rotor.

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