JP2016118225A - Magnetic bearing and rotary machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an axial magnetic bearing for reducing the axial direction width of a rotor while maintaining a suction force of an electromagnet unit.SOLUTION: A magnetic bearing having a disc provided for a rotor and an electromagnet unit disposed to face the disc, and the electromagnet unit comprises a coil, a core which contains the coil and has an inter-magnetic-pole slit provided in a portion facing the disc, and a magnetic flux leakage prevention member which is disposed in the slit and is formed from a diamagnetic substance having a relative magnetic permeability lower than 1.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a magnetic bearing and a rotating machine.

  For example, as shown in Patent Document 1, in a rotary machine such as a turbo compressor and a motor, a magnetic bearing is used to support the rotor with as little rotational resistance as possible. In general, when a magnetic bearing is employed, a radial magnetic bearing that supports a load in the radial direction of the rotor and an axial magnetic bearing that supports a load in the axial direction of the rotor are provided as the magnetic bearing. .

JP 2001-214935 A

  By the way, in recent years, the rotation speed of the rotor has been increased, and the axial length of the rotor has been shortened from the viewpoint of improving the stability during rotation. Since the axial magnetic bearing is configured such that the disk fixed to the rotor is sandwiched from both sides by a certain gap with the electromagnet unit, the axial length of the rotor is shortened, so that the installation space for the electromagnet unit can be secured. It's getting harder. On the other hand, in order to ensure a constant magnetic flux in the electromagnet unit, it is necessary to maintain the coil line product ratio. For this reason, especially in rotating machines where the rotor rotates at high speeds, the electromagnet unit is expanded in the radial direction of the rotor, thereby maintaining the coil line area ratio and flattening in the axial direction of the rotor. It corresponds to.

  On the other hand, it is difficult to spread the disk in the radial direction in order to suppress the influence of centrifugal force. For this reason, when the electromagnet unit is flattened as described above, the electromagnet unit is larger in the radial direction than the disk, and only a part of the electromagnet unit on the inner diameter side faces the disk. In the axial magnetic bearing having such a configuration, the entire electromagnet unit coil is surrounded by a core so that the magnetic flux generated by the electromagnet unit efficiently passes through the disk, and the disk and the electromagnet are disposed in a region of the core facing the disk. The magnetic pole is formed by forming a slit having a width larger than the separation distance from the unit.

  However, in such a complex-shaped core, the shape of the magnetic flux is also distorted, and magnetic flux leakage increases. In particular, magnetic flux leakage between the magnetic poles increases. For this reason, the magnetic flux effective for generating the attractive force that supports the disk in the axial direction of the rotor is reduced, and as a result, the attractive force of the electromagnet unit is reduced.

  The present invention has been made in view of the above-described problems, and aims to reduce the axial width of a rotor in an axial magnetic bearing while maintaining the attractive force of an electromagnet unit.

  In order to achieve the above object, according to the present invention, as a first solution, a magnetic bearing having a disk provided to the rotor and an electromagnet unit that is disposed opposite to the disk and includes a region not facing the disk. The electromagnet unit includes a coil, a core that includes the coil and has an annular slit provided at a location facing the disk, and is disposed in the slit and has a relative permeability smaller than 1. A means of providing a magnetic flux leakage prevention member made of a magnetic material is adopted.

  As a second solving means, the first solving means is provided with a disk magnetic flux leakage preventing member provided on the peripheral surface of the disk and made of the diamagnetic material.

  As a third solution, in the first or second solution, the core surface is provided on a region of the core of the disk that is not opposed to the disk and is made of the diamagnetic material. A means of providing a magnetic flux leakage prevention member is adopted.

  As a fourth solution, a rotary machine including a rotor and a magnetic bearing that rotatably supports the rotor, the magnetic bearing according to any one of the first to third solutions as the magnetic bearing, Adopt the means.

  As a fifth solution, a disk, a core that includes an annular slit in a region facing the disk among a region facing the disk and a region not facing the disk, a coil included in the core, The magnetic flux leakage prevention member provided for the slit is used.

  According to the present invention, even when the electromagnet unit is flat in the axial direction of the rotor, the magnetic flux leakage prevention member can prevent the magnetic flux from leaking through the slit provided in the core. For this reason, the reduction | decrease of an effective magnetic flux can be suppressed and it can prevent that the attraction force of an electromagnet unit falls. Therefore, according to the present invention, in the magnetic bearing, the axial width of the rotor can be reduced while maintaining the attractive force of the electromagnet unit.

It is a longitudinal section showing a schematic structure of a motor concerning one embodiment of the present invention. It is a general view of the electromagnet unit with which the motor concerning one embodiment of the present invention is provided. It is a mimetic diagram containing a part of electromagnet unit and a disk with which a motor concerning one embodiment of the present invention is provided.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
A motor 1 (rotary machine) according to the present embodiment is mounted on, for example, an air compressor, and includes a housing 2, a stator 3, a rotor 4, a radial magnetic bearing 5, an axial magnetic bearing 6, and an auxiliary bearing 7. I have.

  The housing 2 is a casing that houses the stator 3, the rotor 4, the radial magnetic bearing 5, the axial magnetic bearing 6, and the auxiliary bearing 7. The housing 2 is provided with a through hole through which the rotor 4 passes in order to expose the tip of the rotor 4. The stator 3 is accommodated in the housing 2 and is supported by being fixed to the housing 2. The stator 3 includes a coil that is disposed so as to surround the rotor 4 at a predetermined interval, and a power supply state is controlled by a motor control device (not shown).

  The rotor 4 is a bar member and includes a permanent magnet at a location facing the stator 3. The rotor 4 is rotationally driven by a magnetic field generated by power feeding to the stator 3, and is rotatably supported by the radial magnetic bearing 5 and the axial magnetic bearing 6 at the time of rotation. The rotor 4 is supported by the auxiliary bearing 7 when stopped. The radial magnetic bearing 5 is provided for each end of the rotor 4. These radial magnetic bearings 5 generate magnetic force by being fed from a power feeding device (not shown), and support the load in the radial direction of the rotor 4 in a non-contact manner.

  As shown in FIG. 1, the axial magnetic bearing 6 includes a disk 6a, two electromagnet units 6b, and a magnetic flux leakage prevention member 6c. The disk 6 a is a disk-shaped member made of a magnetic material and is provided for the rotor 4. The disk 6 a has a larger diameter than the rotor 4 and is fixed concentrically to the rotor 4. Such a disk 6 a has an outer edge protruding outside the rotor 4 when viewed from the axial direction of the rotor 4. The two electromagnet units 6b are disposed to face the disk 6a so as to sandwich the disk 6a from the axial direction of the rotor 4, and are opposed to the housing 2 so as to face the disk 6a with a slight gap. Is fixed.

  2 is an overall view of the electromagnet unit 6b provided on one side (the left side in FIG. 1) of the disk 6a, (a) is a longitudinal sectional view, (b) is a front view, and (c). FIG. 3 is a cross-sectional view taken along line AA in FIG. FIG. 3 is an enlarged schematic view including the electromagnet unit 6b and a part of the disk 6a. As shown in these drawings, the electromagnet unit 6b includes a coil 6b1 and a core 6b2.

  The coil 6b1 is formed by a winding wound around the rotor 4, and power is supplied by a power supply device (not shown). The coil 6b1 is wound with a winding so as to have a predetermined line product ratio.

  The core 6b2 is an annular member made of a magnetic material and having an opening through which the rotor 4 is inserted at the center, and includes the coil 6b1. The core 6b2 has an annular slit 6b3 (a slit between the magnetic poles) provided at a location facing the area Ra facing the disk 6a. The slit 6b3 is provided in an annular shape with the rotor 4 as the center.

  The electromagnet unit 6b provided on the other side of the disk 6a (the right side in FIG. 1) has a symmetrical configuration around the electromagnet unit 6b provided on the one side of the disk 6a and the disk 6a. For this reason, detailed description of the electromagnet unit 6b provided on the other side of the disk 6a is omitted.

  The magnetic flux leakage prevention member 6c is a member made of a diamagnetic material having a relative permeability smaller than 1, and as shown in FIG. 3, the inner wall surface 6b4 of the slit 6b3, the peripheral surface 6a1 of the disk 6a, and the surface of the core 6b2. And provided in a region Rb of the disk 6a that does not face. Hereinafter, the magnetic flux leakage prevention member 6c1 provided on the inner wall surface 6b4 of the slit 6b3 is used as the magnetic flux leakage prevention member 6c1 for slit, and the magnetic flux leakage prevention member 6c provided on the peripheral surface 6a1 of the disk 6a is used as the magnetic flux leakage prevention member 6c2 for disk. And the magnetic flux leakage prevention member 6c provided in the area | region Rb which is the surface of the core 6b2 and does not oppose the disk 6a is called the magnetic flux leakage prevention member 6c3 for core surfaces.

  The slit magnetic flux leakage preventing member 6c1 is provided so as to cover the entire inner wall surface 6b4 (the radially inner wall surface 6b4 and the radially outer wall surface 6b4) of the opposing slit 6b3. As shown in FIG. 3, the slit magnetic flux leakage preventing member 6c1 prevents the magnetic flux from leaking through the slit 6b3 and guides the magnetic flux passing through the core 6b2 to the disk 6a. The magnetic flux leakage prevention member 6c2 for the disk and the magnetic flux leakage prevention member 6c3 for the core surface prevent the magnetic flux from leaking between the region Rb of the core 6b2 that does not face the disk 6a and the peripheral surface 6a1 of the disk 6a. Is guided to the disk 6a.

  Further, the magnetic flux leakage preventing member 6c2 for the disk is formed between the region Rb of the core 6b2 provided in the electromagnet unit 6b provided on the other side (the right side in FIG. 1) of the disk 6a and the peripheral surface 6a1 of the disk 6a. It also prevents leakage of magnetic flux between them. Similarly, the core surface magnetic flux leakage prevention member 6c3 is also provided in the electromagnet unit 6b provided on the other side of the disk 6a, and the electromagnet unit provided on the other side (right side in FIG. 1) of the disk 6a. The magnetic flux is prevented from leaking between the region Rb of the core 6b2 of the core 6b2 not facing the disk 6a and the peripheral surface 6a1 of the disk 6a.

  Such a magnetic flux leakage prevention member 6c can form the magnetic flux leakage prevention member 6c with, for example, behimas, lead, or a material containing these. However, the diamagnetic material forming the magnetic flux leakage prevention member 6c is not particularly limited.

  In the motor 1 of this embodiment having such a configuration, the rotor 4 is rotationally driven by supplying power to the stator 3, and further, the rotor 4 is supplied by supplying power to the radial magnetic bearing 5 and the axial magnetic bearing 6. Is supported in a non-contact manner. For this reason, the rotor 4 can be rotated in a state where the rotational resistance is extremely small.

  According to the motor 1 of the present embodiment as described above, even if the electromagnet unit 6b is flattened in the axial direction of the rotor 4 as shown in FIG. 1, the core 6b2 is prevented by the slit magnetic flux leakage preventing member 6c1. It is possible to prevent the magnetic flux from leaking through the slit 6b3 provided in (see FIG. 3). For this reason, the reduction | decrease of an effective magnetic flux can be suppressed and it can prevent that the attraction force of the electromagnet unit 6b falls. Therefore, according to the motor 1 of the present embodiment, in the axial magnetic bearing 6, the axial width of the rotor 4 can be reduced while maintaining the attractive force of the electromagnet unit 6b.

  In the motor 1 of the present embodiment, the disk magnetic flux leakage prevention member 6c2 made of a diamagnetic material is provided on the peripheral surface 6a1 of the disk 6a, and the surface of the core 6b2 on the disk 6a side is opposed to the disk 6a. And a core surface magnetic flux leakage preventing member 6c3 made of a diamagnetic material. For this reason, it is possible to prevent the magnetic flux from leaking between the region Rb of the core 6b2 that does not face the disk 6a and the peripheral surface 6a1 of the disk 6a, further suppressing the decrease in the effective magnetic flux, The suction force can be maintained at a higher level.

In addition, this invention is not limited to the said embodiment, For example, the following modifications can be considered.
(1) In the above embodiment, the magnetic flux leakage prevention member 6c is disposed in the slit 6b3 by providing the slit magnetic flux leakage prevention member 6c1 on the inner wall surface 6b4 of the opposed slit 6b3. However, the present invention is limited to this. Not. For example, a member made of a diamagnetic material that fills all or part of the slit 6b3 may be disposed in the slit 6b3, and this may be used as a magnetic flux leakage prevention member.

(2) In the above embodiment, the slit magnetic flux leakage preventing member 6c1 is provided for both the inner wall surfaces 6b4 of the opposed slits 6b3. However, the present invention is not limited to this. For example, the slit magnetic flux leakage prevention member 6c1 may be provided only on one of the inner wall surfaces 6b4 of the facing slit 6b3.

(3) In the above embodiment, the disk magnetic flux leakage prevention member 6c2 made of diamagnetic material and the surface of the core 6b2 on the disk 6a side that is provided on the peripheral surface 6a1 of the disk 6a and does not face the disk 6a. The core surface magnetic flux leakage prevention member 6c3 made of diamagnetic material is provided, but the present invention is not limited to this. For example, the disk magnetic flux leakage prevention member 6c2 and the core surface magnetic flux leakage prevention member 6c3 are not provided, or only the disk magnetic flux leakage prevention member 6c2 and the core surface magnetic flux leakage prevention member 6c3 are provided. You can also. When only one of the disk magnetic flux leakage prevention member 6c2 and the core surface magnetic flux leakage prevention member 6c3 is provided, it is preferable to provide only the disk magnetic flux leakage prevention member 6c2. This is because leakage of magnetic flux between the two electromagnet units 6b arranged with the disk 6a interposed therebetween can be prevented by one disk magnetic flux leakage prevention member 6c2.

(4) In the above embodiment, an example in which the present invention is applied to a motor has been described, but the present invention is not limited to this. For example, the present invention can be suitably applied to a rotating machine in which the natural frequency of the rotor is a major factor in determining characteristics, or a rotating machine that requires a predetermined suction force in a limited space. . Examples of such rotating machines include air compressors, turbo chillers, air separators, and gas turbines.

DESCRIPTION OF SYMBOLS 1 ... Motor (rotary machine), 2 ... Housing, 3 ... Stator, 4 ... Rotor, 5 ... Radial magnetic bearing, 6 ... Axial magnetic bearing, 6a ... Disk, 6a1 ... Peripheral surface, 6b ... Electromagnet unit, 6b1 ... Coil, 6b2 ... Core, 6b3 ... Slit, 6b4 ... Inner wall surface, 6c ... Magnetic flux leakage prevention member, 6c1 ... Magnetic flux leakage prevention member for slit, 6c2 ... Magnetic flux leakage prevention member for disk, 6c3 ... Magnetic flux leakage prevention member for core surface, 7 ... Auxiliary bearing, Ra ... area, Rb ... area

Claims (5)

A magnetic bearing having a disk provided to the rotor and an electromagnet unit that is disposed to face the disk and includes a region that does not face the disk,
The electromagnet unit is
Coils,
A core that includes the coil and has an annular slit provided at a location facing the disk;
A magnetic flux leakage preventing member that is disposed in the slit and is made of a diamagnetic material having a relative magnetic permeability smaller than 1.   The magnetic bearing according to claim 1, further comprising a magnetic flux leakage prevention member for a disk made of the diamagnetic material and provided on a peripheral surface of the disk.   3. The magnetic bearing according to claim 1, further comprising a core surface magnetic flux leakage prevention member provided on a surface of the core on the disk side and not facing the disk and made of the diamagnetic material. A rotary machine comprising a rotor and a magnetic bearing that rotatably supports the rotor,
A rotary machine comprising the magnetic bearing according to claim 1 as the magnetic bearing. A disc,
Of the area facing the disk and the area not facing the disk, a core including an annular slit in the area facing the disk;
A coil included in the core;
A magnetic flux leakage prevention member provided for the slit;
Magnetic bearing having.

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