WO2025109793A1 - Magnetic bearing apparatus - Google Patents

Abstract

This magnetic bearing apparatus is provided with a stator core (15) that accommodates axial coils (10A, 10B) and radial coils (12A-12D). The stator core (15) is provided with: second axial stator cores (17A, 17B) positioned on both sides of a second disk (8) and between the second disk (8) and the axial coils (10A, 10B); a plurality of radial stator cores (18) around which the radial coils (12A-12D) are wound; and first axial stator cores (19A, 19B) positioned on both sides of a first disk (7).

Description

Magnetic Bearing Device

The present invention relates to a magnetic bearing device that can support a rotor without contact.

Magnetic bearings are bearings that can support the rotor without contact using electromagnetic force, and can rotate the rotor at ultra-high speeds without friction loss. Magnetic bearings also have the advantage that they do not require lubricating oil, so they do not pollute the system environment, have a long life, and can be operated in vacuum, extremely low temperature, and high temperature environments.

FIG. 14 is a schematic diagram showing the structure of a conventional magnetic bearing. As shown in FIG. 14, the stator 500 of the magnetic bearing is composed of an axial stator section 501 and a radial stator section 502. The axial stator section 501 has two axial coils 512 wound around the rotor shaft 510. The radial stator section 502 has a four-slot structure and has four radial coils 513 (only two radial coils 513 are drawn in FIG. 14) for generating radial forces. The radial stator section 502 forms a magnetic circuit in a plane perpendicular to the axial direction of the rotor 520. The rotor 520 has a disk 525. This magnetic bearing supports the rotor 520 by generating a magnetic attraction force between the disk 525 of the rotor 520 and a stator core 526.

P. Imoberdorf, C. Zwyssig, S. D. Round and J. W. Kolar, "Combined Radial-Axial Magnetic Bearing for a 1 kW, 500,000 rpm Permanent Magnet Machine," APEC 07 - Twenty-Second Annual IEEE Applied Power Electronics Conference and Exposition, Anaheim, CA, USA, 2007, pp. 1434-1440, doi: 10.1109/APEX.2007.357705.

However, the magnetic bearing described above has a problem in that the opposing area between the disk 525 and the stator core 526 (the area of the region surrounded by the dotted line) is small, and the supporting force of the rotor 520 per unit volume (also called the supporting force density) is small.

The present invention provides an improved magnetic bearing device that can increase the bearing force (bearing force density).

In one aspect, a magnetic bearing device is provided that includes a rotor shaft, a first disk protruding radially outward from the outer circumferential surface of the rotor shaft, a second disk protruding radially outward from the outer circumferential surface of the first disk, an axial coil arranged on both sides of the second disk, a plurality of radial coils arranged radially outward of the axial coil, and a stator core that houses the axial coil and the plurality of radial coils, the stator core including a pair of first axial stator cores located on both sides of the first disk, a plurality of pairs of second axial stator cores located on both sides of the second disk and between the second disk and the axial coil, and a plurality of radial stator cores each wound with the plurality of radial coils.

In one aspect, the axial coil surrounds the periphery of the first disk.
In one embodiment, the thickness of the first disc is greater than the thickness of the second disc.
In one aspect, the plurality of radial coils surround the axial coil.
In one aspect, the magnetic bearing device further includes a pair of side disks protruding radially outward from the outer peripheral surface of the first disk, the second disk is positioned between the pair of side disks, and the stator core further includes a pair of side stator cores arranged outside the pair of side disks in the axial direction of the rotor shaft.

In one embodiment, the magnetic bearing device further includes a current controller that controls currents supplied to the axial coil and the plurality of radial coils.
In one aspect, the current controller is configured to supply current to one of the axial coils disposed on either side of the second disk while supplying current to the plurality of radial coils.
In one aspect, the current controller is configured to supply currents of the same magnitude and direction to the radial coils.
In one aspect, the current controller is configured to supply current to two radial coils located opposite each other among the plurality of radial coils while supplying current to the axial coil.
In one aspect, the current controller is configured to supply current to the two radial coils such that the two radial coils generate magnetic flux in the second disc in the same direction.
In one aspect, the current controller is configured to supply currents in opposite directions to the axial coils.

The magnetic bearing device has a first disk and a second disk that face the stator core. Therefore, compared to conventional magnetic bearings, the facing area between the stator core and the rotor is increased, resulting in a high bearing force (high bearing force density).

1 is a cross-sectional perspective view showing an embodiment of a magnetic bearing device. FIG. 2 is a vertical sectional view of the magnetic bearing device shown in FIG. 3 is a cross-sectional view taken along line AA in FIG. 2. FIG. 11 is a perspective view showing another embodiment of a magnetic bearing device. FIG. 5 is a vertical sectional view of the magnetic bearing device shown in FIG. 4 . 6 is a graph showing axial forces generated by the magnetic bearing device described with reference to FIGS. 1 to 3, the magnetic bearing device described with reference to FIGS. 4 and 5, and a conventional magnetic bearing device; 13 is a graph showing an example of radial force. 11A to 11C are diagrams illustrating an embodiment of a current supply method for generating a magnetic attraction force in the axial direction. 11A to 11C are diagrams illustrating an embodiment of a current supply method for generating a magnetic attraction force in the axial direction. 10 is a graph illustrating the axial force analysis results for the embodiment described with reference to FIGS. 8 and 9; 11A to 11C are diagrams illustrating an embodiment of a current supply method for generating a radial magnetic attraction force. 11A to 11C are diagrams illustrating an embodiment of a current supply method for generating a radial magnetic attraction force. 13 is a graph illustrating the radial force analysis results of the embodiment described with reference to FIGS. 11 and 12. FIG. 1 is a schematic diagram showing an example of a conventional magnetic bearing.

Below, an embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a cross-sectional perspective view showing one embodiment of a magnetic bearing device, Fig. 2 is a longitudinal cross-sectional view of the magnetic bearing device shown in Fig. 1, and Fig. 3 is a cross-sectional view taken along line A-A in Fig. 2. The magnetic bearing device comprises a rotor 1, a magnetic bearing 2 that supports the rotor 1 in a non-contact manner by magnetic attraction, and a current controller 3 that controls the operation of the magnetic bearing 2.

The rotor 1 is a rotatable structure. Applications of the rotor 1 rotatably supported by the magnetic bearing 2 are not particularly limited. For example, the rotor 1 is all or part of a rotor included in a rotating machine such as a liquid pump or a vacuum pump. In particular, the magnetic bearing device can support the rotor 1 without mechanically contacting the rotor 1, and therefore does not cause wear or frictional heat in the rotor 1. Therefore, the magnetic bearing device is suitable for applications in which it supports rotors that rotate at high speeds, such as the turbine of a turbomolecular pump or the impeller rotor of a liquid hydrogen pump that transports liquid hydrogen, which has a low specific gravity.

The rotor 1 has a rotor shaft 5, a first disk 7 protruding radially outward from the outer circumferential surface of the rotor shaft 5, and a second disk 8 protruding radially outward from the outer circumferential surface of the first disk 7. The rotor shaft 5, the first disk 7, and the second disk 8 are concentric. The rotor shaft 5, the first disk 7, and the second disk 8 are an integral structure and rotate together. The first disk 7 has a larger diameter than the rotor shaft 5, and the second disk 8 has a larger diameter than the first disk 7. The second disk 8 is located at the center of the first disk 7 in the axial direction of the rotor 1. The thickness (axial width) of the first disk 7 is larger than the thickness (axial width) of the second disk 8. The rotor 1 of this embodiment is a dual disk rotor having a first disk 7 and a second disk 8.

The magnetic bearing 2 includes a pair of axial coils 10A, 10B arranged on both sides of the second disk 8, a number of radial coils 12A, 12B, 12C, 12D arranged radially outside the axial coils 10A, 10B, and a stator core 15 that houses the axial coils 10A, 10B and the number of radial coils 12A, 12B, 12C, 12D. The pair of axial coils 10A, 10B are arranged to surround the first disk 7. More specifically, the axial coils 10A, 10B are arranged radially outside the first disk 7 and on both sides of the second disk 8 in the axial direction of the rotor 1. The central axes of the axial coils 10A, 10B coincide with the axis of the rotor 1.

The radial coils 12A to 12D surround the pair of axial coils 10A, 10B and are arranged along the outer circumferential surfaces of the axial coils 10A, 10B. As shown in FIG. 3, in this embodiment, four radial coils 12A, 12B, 12C, 12D are arranged at equal intervals along the circumferential direction of the rotor 1. In one embodiment, five or more radial coils may be provided. The central axis of each of the radial coils 12A, 12B, 12C, 12D is perpendicular to the axis of the rotor 1. Thus, each of the radial coils 12A, 12B, 12C, 12D forms a magnetic circuit in a plane perpendicular to the axial direction of the rotor 1.

The stator core 15 is made of a magnetic material such as silicon steel. The stator core 15 covers the axial coils 10A, 10B, the multiple radial coils 12A-12D, the first disk 7, and the second disk 8. As shown in FIG. 2, the stator core 15 has a pair of first axial stator cores 19A, 19B, multiple pairs of second axial stator cores 17A, 17B, and multiple radial stator cores 18.

The pair of first axial stator cores 19A, 19B are located on both sides of the first disk 7 in the axial direction of the rotor 1. More specifically, the first axial stator cores 19A, 19B have first opposing surfaces 19c, 19d that face both side surfaces 7a, 7b of the first disk 7. The first axial stator cores 19A, 19B extend radially inward from the outer wall portion 21 of the stator core 15.

Multiple pairs of second axial stator cores 17A, 17B are provided corresponding to the multiple radial coils 12A to 12D. In this embodiment, four radial coils 12A to 12D are provided, and therefore four pairs of second axial stator cores 17A, 17B are provided. In FIG. 2, only two pairs of second axial stator cores 17A, 17B are depicted. Each pair of second axial stator cores 17A, 17B is located on both sides of the second disk 8 and between a pair of axial coils 10A, 10B. More specifically, the second axial stator core 17A is located between the second disk 8 and the axial coil 10A, and the second axial stator core 17B is located between the second disk 8 and the axial coil 10B. The multiple pairs of second axial stator cores 17A, 17B have second opposing surfaces 17c, 17d that face both side surfaces 8a, 8b of the second disk 8.

The multiple radial stator cores 18 are provided corresponding to the multiple radial coils 12A-12D. In this embodiment, four radial coils 12A-12D are provided, and therefore four radial stator cores 18 are provided. In FIG. 2, only two radial stator cores 18 are illustrated. The multiple radial stator cores 18 are located radially outside the second disk 8 and the multiple pairs of second axial stator cores 17A, 17B.

As shown in FIG. 3, the multiple radial stator cores 18 surround the second disk 8. Each radial stator core 18 has an inner peripheral surface 18a that faces the outer peripheral surface 8c of the second disk 8. The multiple radial coils 12A to 12D are wound around the multiple radial stator cores 18, respectively. In this embodiment, four radial coils 12A to 12D are wound around four radial stator cores 18, respectively.

As shown in FIG. 2, the pairs of second axial stator cores 17A, 17B are each connected to a plurality of radial stator cores 18, which extend radially inward from the outer wall portion 21 of the stator core 15.

According to the embodiment described with reference to Figures 1 to 3, the thickness of the first disk 7 is greater than the thickness of the second disk 8, and the second disk 8 is located at the center of the outer circumferential surface of the first disk 7. This configuration reduces magnetic flux leakage from the radial stator core 18 to the first axial stator cores 19A and 19B.

The embodiment described with reference to Figures 1 to 3 has first opposing surfaces 19c, 19d and second opposing surfaces 17c, 17d, so the opposing area between the rotor 1 and the stator core 15 is increased. Specifically, the magnetic bearing 2 shown in Figures 1 to 3 has an opposing area that is three times or more the opposing area of the conventional magnetic bearing shown in Figure 14. Therefore, the magnetic bearing device according to the embodiment described with reference to Figures 1 to 3 can achieve a high supporting force (supporting force density).

The magnetic bearing device is equipped with multiple displacement sensors (not shown) for measuring the axial and radial displacements of the rotor 1. The measured values of the axial and radial displacements of the rotor 1 are sent to the current controller 3. The current controller 3 controls the currents to be supplied to the axial coils 10A, 10B and the multiple radial coils 12A-12D based on the measured values of the axial and radial displacements of the rotor 1. The rotor 1 is supported in a non-contact manner by the magnetic attraction forces generated by the axial coils 10A, 10B and the multiple radial coils 12A-12D.

The current controller 3 includes a storage device 3a that stores a program for controlling the position of the rotor 1, a calculation device 3b that executes calculations according to instructions included in the program, and a power source 3c that supplies current to the pair of axial coils 10A, 10B and the multiple radial coils 12A to 12D. The current controller 3 includes at least one computer. The storage device 3a includes a main storage device such as a random access memory (RAM) and an auxiliary storage device such as a hard disk drive (HDD) and a solid state drive (SSD). Examples of the calculation device 3b include a CPU (central processing unit) and a GPU (graphic processing unit). However, the specific configuration of the current controller 3 is not limited to these examples, as long as the current controller 3 can control the current to be supplied to the pair of axial coils 10A, 10B and the multiple radial coils 12A to 12D based on the measured values of the axial displacement of the rotor 1 and the radial displacement of the rotor 1.

FIG. 4 is a perspective view showing another embodiment of the magnetic bearing device, and FIG. 5 is a longitudinal cross-sectional view of the magnetic bearing device shown in FIG. 4. The configuration and operation of this embodiment not specifically described are the same as the embodiment described with reference to FIGS. 1 to 3, and therefore duplicated descriptions will be omitted. The cross-sectional view shown in FIG. 3 also applies to this embodiment shown in FIGS. 4 and 5.

The magnetic bearing device further includes a pair of side disks 24A, 24B in addition to the first disk 7 and second disk 8 described above. The rotor shaft 5, the first disk 7, the second disk 8, and the pair of side disks 24A, 24B are concentric. The rotor shaft 5, the first disk 7, the second disk 8, and the pair of side disks 24A, 24B are integrally constructed and rotate as a unit.

The side disks 24A and 24B protrude radially outward from the outer peripheral surface of the first disk 7. The second disk 8 is located between the pair of side disks 24A and 24B. In this embodiment, the side disks 24A and 24B are located at both ends of the first disk 7. The rotor 1 of this embodiment is a multi-disk rotor having the first disk 7, the second disk 8, and the side disks 24A and 24B.

In one embodiment, each of the side disks 24A, 24B has a diameter larger than the second disk 8. Furthermore, in one embodiment, the thickness of each of the side disks 24A, 24B is smaller than the thickness of the second disk 8. The pair of axial coils 10A, 10B and the multiple radial coils 12A to 12D are located between the pair of side disks 24A, 24B. In other words, the pair of side disks 24A, 24B are disposed outside the pair of axial coils 10A, 10B and the multiple radial coils 12A to 12D in the axial direction of the rotor 1.

The stator core 15 has a pair of side stator cores 26A, 26B arranged outside the pair of side disks 24A, 24B in the axial direction of the rotor shaft 5. The side stator cores 26A, 26B extend radially inward from the outer wall portion 21 of the stator core 15, and the first axial stator cores 19A, 19B extend radially inward from the side stator cores 26A, 26B. The side stator cores 26A, 26B have third opposing surfaces 26c, 26d that face the outer surfaces 24c, 24d of the side disks 24A, 24B.

The embodiment described with reference to Figures 4 and 5 has first opposing surfaces 19c, 19d, second opposing surfaces 17c, 17d, and third opposing surfaces 26c, 26d, so that the opposing area between the rotor 1 and the stator core 15 is increased. Specifically, the magnetic bearing 2 shown in Figures 4 and 5 has an opposing area that is about seven times that of the conventional magnetic bearing shown in Figure 14. Therefore, the magnetic bearing device according to the embodiment described with reference to Figures 4 and 5 can achieve a higher supporting force (supporting force density).

FIG. 6 is a graph showing an example of the axial force generated by the magnetic bearing device described with reference to FIGS. 1 to 3 (hereinafter referred to as Model A), the axial force generated by the magnetic bearing device described with reference to FIGS. 4 and 5 (hereinafter referred to as Model B), and the axial force generated by the conventional magnetic bearing described with reference to FIG. 14 (hereinafter referred to as Model C).

Models A, B, and C were designed so that they had the same outer diameter. Models A, B, and C generated axial forces by passing current through only one of the two axial coils. The current value was a low current of 0 to 0.1 A. As can be seen from Figure 6, models A and B can generate a large axial force with a relatively small current compared to model C. In addition, model B can generate a larger axial force than model A.

Figure 7 is a graph showing an example of the radial force generated by model A, the radial force generated by model B, and the radial force generated by model C.

Models A, B, and C were designed so that they had the same outer diameter. Models A, B, and C generated radial forces by passing current through only one of the four axial coils. The current value was a high current of 0 to 1 A. As can be seen from Figure 7, models A and B can generate a larger radial force than model C. In addition, model B can generate a larger radial force than model A.

Next, an embodiment of a novel method for supplying current to the axial coils 10A, 10B and the radial coils 12A to 12D will be described. The following description applies to each embodiment described with reference to Figures 1 to 5. The supply of current to the axial coils 10A, 10B and the radial coils 12A to 12D is controlled by the current controller 3.

With reference to Figures 8 and 9, one embodiment of a current supply method for generating a magnetic attraction force in the axial direction will be described. The current controller 3 is configured to supply current to one of the axial coils 10A, 10B while supplying current to all of the radial coils 12A to 12D. In the example shown in Figure 8, current is passed only to the right axial coil 10A, and no current is passed to the left axial coil 10B.

The current controller 3 is configured to supply current of the same magnitude and direction to all of the radial coils 12A-12D. In the example shown in FIG. 9, the radial coils 12A-12D generate radially outward forces, as indicated by the white arrows. These radially outward forces have the same magnitude and therefore cancel each other out.

When current is supplied to the axial coil 10A while current is supplied to the radial coils 12A to 12D, as shown in FIG. 8, magnetization and demagnetization occur at the first opposing surfaces 19c, 19d of the first axial stator cores 19A, 19B and the sides 7a, 7b of the first disk 7 (see the dotted circle). In the example shown in FIG. 8, the magnetic flux increases between the first opposing surface 19c of the first axial stator core 19A on the right side and the right side 7a of the first disk 7, while the magnetic flux decreases between the first opposing surface 19d of the first axial stator core 19B on the left side and the left side 7b of the first disk 7. Therefore, a difference in magnetic flux density occurs between the left and right sides of the rotor 1. As a result, in the example shown in FIG. 8, a magnetic attraction force toward the right is generated as shown by the white arrow, and the rotor 1 is displaced to the right.

Although not shown, when generating a magnetic attraction force toward the left side, the current controller 3 similarly supplies current to all of the radial coils 12A to 12D, while supplying current only to the left axial coil 10B. Although FIG. 8 shows the magnetic bearing device described with reference to FIGS. 1 to 3, the magnetic bearing device described with reference to FIGS. 4 and 5 also operates in the same manner.

FIG. 10 is a graph showing the analysis results of the axial force in the embodiment described with reference to FIG. 8 and FIG. 9. Current was passed only through one axial coil 10A while varying the current from 0 to 0.2A, and current was passed through four radial coils 12A-12D in four patterns of 0A, 0.1A, 0.2A, and 0.3A. As can be seen from FIG. 10, the axial force increased as the current passed through the four radial coils 12A-12D increased. This is because the increase in current passed through the four radial coils 12A-12D created a larger difference in magnetic flux density between the left and right sides of the rotor 1.

Next, one embodiment of a current supply method for generating a radial magnetic attraction force will be described with reference to Figures 11 and 12. The current controller 3 is configured to supply current to two radial coils located on opposite sides of the multiple radial coils 12A to 12D while supplying current to both axial coils 10A, 10B. As shown in Figure 11, the current controller 3 supplies currents in opposite directions to the axial coils 10A, 10B.

In the example shown in FIG. 12, the current controller 3 supplies current to two radial coils 12A, 12C located on opposite sides, and does not supply current to the other two radial coils 12B, 12D. The two radial coils 12A, 12C to which current is supplied generate magnetic flux in the same direction in the second disk 8. In the example shown in FIG. 11, the two radial coils 12A, 12C generate upward magnetic flux in the second disk 8. In addition to passing current through one radial coil 12A, current is passed through the radial coil 12C on the opposite side so that it generates magnetic flux in the same direction, thereby strengthening the radial magnetic flux. At the same time, current is passed through the two axial coils 10A, 10B so as to form a symmetrical magnetic circuit with respect to the second disk 8.

When current is supplied to the two radial coils 12A, 12C located on opposite sides while current is supplied to both axial coils 10A, 10B, magnetization and demagnetization occur at the opposing surfaces of the two radial stator cores 18 and the second disk 8 (see the dotted circle) as shown in FIG. 11. In the example shown in FIG. 11, the magnetic flux increases between the upper radial stator core 18 and the second disk 8, while the magnetic flux decreases between the lower radial stator core 18 and the second disk 8. Therefore, a difference in magnetic flux density occurs above and below the rotor 1. As a result, in the example shown in FIG. 11, an upward magnetic attraction force is generated, and the rotor 1 is displaced upward.

Although not shown, when generating a magnetic attraction force in a downward, rightward, or leftward direction, the current controller 3 similarly supplies current to both axial coils 10A, 10B while supplying current to two radial coils located on opposite sides. Although FIG. 11 shows the magnetic bearing device described with reference to FIGS. 1 to 3, the magnetic bearing device described with reference to FIGS. 4 and 5 operates in the same manner.

FIG. 13 is a graph showing the results of an analysis of the radial force in the embodiment described with reference to FIG. 11 and FIG. 12. Current was passed through the two radial coils 12A, 12C while varying the current from 0 to 1 A, and current was passed through the two axial coils 10A, 10B in three patterns of 0 A, 0.2 A, and 0.4 A. As can be seen from FIG. 13, the radial force increased as the current passed through the two axial coils 10A, 10B increased. This is because a larger difference in magnetic flux density was generated above and below the rotor 1 due to the increase in current passed through the two axial coils 10A, 10B.

The magnetic bearing device of each of the above-mentioned embodiments is a three-degree-of-freedom magnetic bearing device. The current application method described with reference to Figures 8 to 13 is suitable for a three-degree-of-freedom magnetic bearing device, and can improve the bearing force density.

The above-described embodiments have been described for the purpose of enabling a person having ordinary knowledge in the technical field to which the present invention pertains to practice the present invention. Various modifications of the above-described embodiments would naturally be possible for a person skilled in the art, and the technical ideas of the present invention may also be applied to other embodiments. Therefore, the present invention is not limited to the described embodiments, but is to be interpreted in the broadest scope in accordance with the technical ideas defined by the scope of the claims.

The present invention can be used in magnetic bearing devices that can support a rotor without contact.

REFERENCE SIGNS LIST 1 rotor 2 magnetic bearing 3 current controller 3a storage device 3b arithmetic device 3c power supply 5 rotor shaft 7 first disk 7a, 7b side surface of first disk 8 second disk 8a, 8b side surface of second disk 10A, 10B axial coil 12A, 12B, 12C, 12D radial coil 15 stator core 17A, 17B second axial stator core 17c, 17d second opposing surface 18 radial stator core 18a inner peripheral surface 19A, 19B of radial stator core first axial stator core 19c, 19d first opposing surface 21 outer wall portion 24A, 24B side disk 24c, 24d outer surface 26A, 26B of side disk side stator core 26c, 26d third opposing surface

Claims (11)

A rotor shaft;
a first disk protruding radially outward from an outer circumferential surface of the rotor shaft;
a second disk protruding radially outward from an outer circumferential surface of the first disk;
an axial coil disposed on both sides of the second disk;
A plurality of radial coils arranged radially outward of the axial coil;
a stator core that houses the axial coil and the plurality of radial coils;
The stator core is
A pair of first axial stator cores located on both sides of the first disk;
a plurality of pairs of second axial stator cores located on both sides of the second disk and between the second disk and the axial coil;
A magnetic bearing device comprising a plurality of radial stator cores around which the plurality of radial coils are wound respectively. The magnetic bearing device according to claim 1, wherein the axial coil surrounds the periphery of the first disk. The magnetic bearing device of claim 1, wherein the thickness of the first disk is greater than the thickness of the second disk. The magnetic bearing device according to claim 1, wherein the plurality of radial coils surround the axial coil. the magnetic bearing device further includes a pair of side disks protruding radially outward from an outer circumferential surface of the first disk,
The second disk is located between the pair of side disks,
2. The magnetic bearing device according to claim 1, wherein the stator core further comprises a pair of side stator cores arranged outside the pair of side disks in the axial direction of the rotor shaft. The magnetic bearing device of claim 1, further comprising a current controller that controls the current supplied to the axial coil and the plurality of radial coils. The magnetic bearing device according to claim 6, wherein the current controller is configured to supply current to one of the axial coils arranged on both sides of the second disk while supplying current to the plurality of radial coils. The magnetic bearing device of claim 7, wherein the current controller is configured to supply currents of the same magnitude and direction to the radial coils. The magnetic bearing device according to claim 6, wherein the current controller is configured to supply current to two radial coils located on opposite sides of the plurality of radial coils while supplying current to the axial coil. The magnetic bearing device of claim 9, wherein the current controller is configured to supply current to the two radial coils so that the two radial coils generate magnetic flux in the same direction within the second disk. 10. A magnetic bearing device according to claim 9, wherein the current controller is configured to supply currents in opposite directions to the axial coils.

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