JP2004232740A - Magnetic bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic bearing device capable of reducing power consumption. <P>SOLUTION: A permanent magnet 21 is provided on a lower surface of a lower end flange part 23 of a rotary body 2. A permanent magnet 22 to add repulsive force to the permanent magnet 21 on the rotary body 2 is provided on an upper surface of a bottom wall 1a of a casing 1. A main body part of the rotary body 2 is formed of material having favorable magnetic characteristics. The lower end flange part 23 of the rotary body and the bottom wall 1a of the casing as parts of the rotary body 2 and the casing 1 close to the permanent magnets are formed of nonmagnetic material. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a magnetic bearing device in which a plurality of sets of magnetic bearings support a rotating body in a non-contact manner in an axial direction and a radial direction to magnetically levitate.
[0002]
[Prior art]
As this type of magnetic bearing device, there is a set of axial magnetic bearings that support the rotating body in a non-contact manner in the axial control axial direction, and a non-contact in two radial control axial directions orthogonal to each other at two locations in the axial direction. It is known to have two sets of supporting radial magnetic bearings. In the case of a magnetic bearing device in which a rotating body is arranged in a vertical direction, the support of the own weight of the rotating body has been performed by controlling an electromagnet of an axial magnetic bearing (Patent Document 1).
[0003]
[Patent Document 1]
JP-A-1-126423
[Problems to be solved by the invention]
In the above-described conventional magnetic bearing device, since the support of the rotating body by its own weight is performed by controlling the electromagnet of the axial magnetic bearing, it is necessary to constantly supply a control current for supporting the own weight, and as a result, the axial Since power consumption (copper loss) of the magnetic bearing increases and energy loss increases, improvement of the magnetic bearing has been an issue.
[0005]
An object of the present invention is to provide a magnetic bearing device capable of reducing power consumption.
[0006]
Means for Solving the Problems and Effects of the Invention
A magnetic bearing device according to the present invention detects a casing, a rotating body that rotates within the casing, a plurality of sets of magnetic bearings that support the rotating body in a non-contact manner in an axial direction and a radial direction, and detects an axial position of the rotating body. Sensor unit for detecting the radial position of the rotating body and a radial sensor unit for detecting the radial position of the rotating body, a permanent magnet is provided at a predetermined location of the rotating body, A permanent magnet for providing a repulsive force to the permanent magnet is provided, and a portion near the permanent magnet of the rotating body and the casing is formed of a non-magnetic material.
[0007]
The permanent magnet is provided, for example, on the lower end surface of the rotating body and the upper surface of the bottom wall of the casing, respectively. Then, the permanent magnet of the rotating body is formed by the lower N-pole layer (or S-pole layer) and the upper S-pole layer (or N-pole layer), and the permanent magnet of the casing is formed by the upper N-pole layer (or An S pole layer, that is, an pole layer that gives repulsive force to the permanent magnet of the rotating body) and a lower S pole layer (or an N pole layer) on the lower side. As a result, a magnetic repulsion acts on the rotating body in a direction opposite to its own weight.
[0008]
According to the magnetic bearing device of the present invention, the control of the rotating body in the axial direction and the radial direction is performed by supplying a control current to the electromagnets of the respective magnetic bearings. Since the magnetic repulsion acts, the control current for supporting the own weight of the rotating body can be reduced, and the power consumption (copper loss) of the axial magnetic bearing is reduced. The repulsive force between the permanent magnets is adjusted, for example, to have a magnitude corresponding to the weight of the rotating body (not only the rotating shaft but also the entire weight of the unit that rotates integrally with the rotating shaft). With this configuration, the control current for supporting the own weight of the rotating body can be made substantially zero. Since the rotating body and the portion near the permanent magnet of the casing are made of a non-magnetic material, this portion is not magnetized by the magnetic flux of the permanent magnet, and is kept permanent even if the non-operation state continues for a long time. The magnetized state in the vicinity of the magnet does not change, whereby the repulsive force between the permanent magnets for maintaining the weight of the rotating body between the permanent magnets is kept constant. After that, when the operating state is switched, the rotating body becomes stable. Ascent is possible.
[0009]
As the nonmagnetic material forming the portion near the permanent magnet of the rotating body and the casing, for example, A5056, A7075, SUS304 and the like are preferable. The body part of the rotating body excluding the part near the permanent magnet and the body part of the casing excluding the part near the permanent magnet are made of material for each part according to the necessity / unnecessity of good magnetic properties or high strength. Just select.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment in which the present invention is applied to a five-axis control type magnetic bearing device will be described with reference to the drawings.
[0011]
FIG. 1 is a longitudinal sectional view schematically showing a main part of a five-axis control type magnetic bearing device. This magnetic bearing device is of a vertical type in which a vertically rotating body (2) concentrically arranged inside a vertically cylindrical casing (1) rotates. In the following description, the control axis in the axial direction (vertical direction) of the rotating body is Z-axis, and two radial (horizontal) control axes orthogonal to the Z-axis and orthogonal to each other are X-axis and Y-axis, respectively. And
[0012]
In the casing (1), a control type axial magnetic bearing (4) for supporting the rotating body (2) in a non-contact manner in the Z-axis direction, and two upper and lower portions of the rotating body (2) in a non-contacting manner in the X-axis and Y-axis directions. Two sets of upper and lower controllable radial magnetic bearings (5) and (6), one set of axial sensor units (7) for detecting the position of the rotating body (2) in the axial direction, and upper and lower parts of the rotating body (2) Two sets of upper and lower radial sensor units (8) and (9) for detecting positions in the X-axis and Y-axis directions at two locations, a built-in type electric motor (10) for rotating the rotating body (2) at high speed, and a rotating body ( When the rotor (2) cannot be supported by the magnetic bearings (4), (5) and (6) in a non-contact manner by limiting the axial and radial displacements of (2), the rotor (2) is mechanically moved. Two sets of upper and lower touchdown bearings ( 1) (12) is provided.
[0013]
A flange (23) is provided at a lower end of the rotating body (2), and a permanent magnet (21) is provided on a lower surface thereof. Further, a permanent magnet (22) for applying a repulsive force to the permanent magnet (21) of the rotating body (2) is provided on the upper surface of the bottom wall (1a) of the casing (1). The two permanent magnets (21) and (22) constitute a rotating body supporting means for supporting the weight of the rotating body (2). Each of the permanent magnets (21) and (22) is formed in the same annular shape composed of an N-pole layer and an S-pole layer, so that the permanent magnets (21) and (22) repel each other. Both are concentric with the rotating body (2) and have the same pole (N pole in the drawing) facing each other. The distance between the permanent magnets (21) and (22) is set such that the repulsive force acting between the two magnets (21) and (22) has a magnitude corresponding to the weight of the rotating body (2). The flange portion (23) of the rotating body (2) is formed of a non-magnetic material while the other parts of the rotating body (2) are formed of a material having good magnetic properties. The bottom wall (1a) of the casing (1) is also formed of a non-magnetic material.
[0014]
The axial magnetic bearing (4) includes an axial electromagnet (4a) arranged such that a flange (2a) provided on an upper part of the rotating body (2) faces from above in the Z-axis direction. Each of the radial magnetic bearings (5) and (6) includes a pair of radial electromagnets (5a) and (6a) arranged so as to sandwich the rotating body (2) from both sides in the X-axis direction, and the rotating body (2). And a pair of radial electromagnets (not shown) arranged so as to be sandwiched from both sides in the Y-axis direction. The electric motor (10) includes a stator (10a) provided on the casing (1) side and a rotor (10b) provided on the rotating body (2) side.
[0015]
The upper radial sensor unit (8) is for detecting the position of the rotating body (2) in the X-axis and Y-axis directions near the upper radial magnetic bearing (5), and detects the position of the upper radial magnetic bearing (5). A pair of X-axis radial sensors (8a) arranged so as to sandwich a target portion (13) provided on the outer periphery of the rotating body (2) near the upper side from both sides in the X-axis direction, and a target portion (13) And a pair of Y-axis radial sensors (not shown) arranged so as to sandwich them from both sides in the Y-axis direction. The lower radial sensor unit (9) is for detecting the position of the rotating body (2) in the X-axis and Y-axis directions near the lower radial magnetic bearing (6). A pair of X-axis radial sensors (9a) arranged so as to sandwich the target portion (14) provided on the outer periphery of the rotating body (2) near the lower side from both sides in the X-axis direction; And a pair of Y-axis radial sensors (not shown) arranged so as to sandwich the) from both sides in the Y-axis direction. Each of the radial sensors (8a) and (9a) is a known one, and outputs a signal corresponding to the size of a radial gap between the rotating body (2) and the target portions (13) and (14). Therefore, the position of the rotating body (2) in the X-axis direction is detected by each pair of X-axis radial sensors (8a) and (9a), and the Y-axis of the rotating body (2) is detected by each pair of Y-axis radial sensors. An axial position is detected.
[0016]
A short columnar axial direction target (15) is concentrically attached to the upper end of the rotating body (2). The axial sensor unit (7) is for detecting the position of the rotating body (2) in the Z-axis direction, and is arranged to face the center of the upper end surface of the target (15) from above in the Z-axis direction. Axial sensor (7a). The axial sensor (7a) has a core wound with a coil. The axial sensor (7a) is a known sensor and outputs a signal corresponding to the position of the target (15) of the rotating body (2) in the Z-axis direction. Therefore, the position of the rotating body (3) in the Z-axis direction is detected by the axial sensor (7a).
[0017]
The upper touchdown bearing (11) limits the displacement of the rotating body (2) in the axial direction and the radial direction. The outer ring (11a) of the upper touch-down bearing (11) is fixed to the electromagnet core (4b) of the axial magnetic bearing (4), and the rotating body (2) of the inner ring (11b) has the magnetic bearing (4) ( 5) In the state of being supported in a non-contact manner by (6), a small gap is formed in the axial direction and the radial direction in the annular groove (16) formed on the outer periphery of the portion near the upper end of the rotating body (2). They are facing each other. The lower touch-down bearing (12) limits the radial displacement of the rotating body (2). The outer ring (12a) of the lower touchdown bearing (12) is fixed to the casing (1), and the rotating body (2) of the inner ring (12b) is non-contact supported by the magnetic bearings (4) (5) (6). In this state, the rotating body (2) is opposed to a shaft portion having a uniform outer diameter near the lower end with a slight gap in the radial direction. In a state where the rotating body (2) is supported in a non-contact manner by the magnetic bearings (4), (5) and (6), the axial direction and the radial direction between the inner ring (11b) of the upper touchdown bearing (11) and the rotating body (2). The radial gap and the radial gap between the inner ring (12b) of the lower touchdown bearing (12) and the rotating body (2) are actually very small, but they are exaggerated in FIG. . The space between the permanent magnet (21) at the lower end of the rotating body (2) and the permanent magnet (22) on the upper surface of the bottom wall (1a) of the casing (1) is also exaggerated.
[0018]
When the rotating body (2) is not supported by the magnetic bearings (4), (5), and (6) in a non-contact manner, such as when the magnetic bearing device stops operating, the rotating body (2) may be touch-down. It is mechanically supported by bearings (11) and (12). At this time, the dimensions of each part are determined so that the rotating body (2) does not contact the electromagnets (4a) (5a) (6a), the sensors (7a) (8a) (9a), and the like.
[0019]
During operation of the magnetic bearing device, the position of the rotating body (2) in the Z-axis direction detected by the axial sensor unit (7), and the position of the rotating body (2) detected by the radial sensor units (8) and (9). By controlling the electromagnets (4a), (5a), and (6a) of the magnetic bearings (4), (5), and (6) based on the positions in the X-axis and Y-axis directions, the rotating body (2) can move in the axial direction and in the axial direction. It is supported in a non-contact manner at a predetermined position in the radial direction. The rotating body (2) is rotated at high speed by the electric motor (10) while the rotating body (2) is supported in a non-contact manner by the magnetic bearings (4), (5) and (6).
[0020]
When controlling the electromagnets (4a) (5a) (6a) of the magnetic bearings (4) (5) (6), the permanent magnet (21) at the lower end of the rotating body (2) and the bottom wall (5) of the casing (1). 1a) Since a repulsive force is applied between the permanent magnet (22) on the upper surface and the self-weight of the rotating body (2), the rotating body (4a) is applied to the electromagnet (4a) of the axial magnetic bearing (4). No current for supporting the own weight of 2) is supplied, only a current for controlling displacement is supplied, and the control current for the axial magnetic bearing (4) is minimized.
[0021]
The air gap in the vicinity of the permanent magnets (21) and (22) arranged at the lower end differs by several 100 μm between when the magnetic bearing device is activated and when it is not activated. In this case, the state of magnetization of the portion near the permanent magnet of the rotating body (21), ie, the lower end flange portion (23), and the portion of the casing (1) near the permanent magnet, ie, the bottom wall (1a) is different from the state when the magnetic bearing device is operated. Although there is a possibility that the permanent magnets (23) and (1a) are made of a non-magnetic material, they are not magnetized by the magnetic flux of the permanent magnets (21) and (22). Therefore, even if the non-operating state continues for a long time, the magnetized state of the portion (23) (1a) near the permanent magnet does not change, whereby the permanent magnet (21) ( The repulsive force during the period 22) is kept constant, and thereafter, the stable floating of the rotating body (2) when switching to the operating state is ensured. The portion near the permanent magnet formed of a non-magnetic material is not limited to the lower end flange portion (23) of the rotating body (21) and the bottom wall (1a) of the casing (1), but may be formed of the rotating body (2). The non-magnetic portion is set so as to keep the repulsive force between the permanent magnets (21) and (22) holding the weight of the non-magnetic material constant. The annular permanent magnets (21) and (22) are provided integrally with a non-magnetic disc body, and this disc body is attached to the lower end surface of the rotating body (2) and the upper surface of the bottom wall of the casing (1). May be attached to the rotating body (2) and the casing (1) by being fitted into the recesses respectively provided in the casing.
[0022]
The configuration of each part of the magnetic bearing device is not limited to the above-described embodiment, and can be appropriately changed.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing mechanical parts of a five-axis control type magnetic bearing device according to an embodiment of the present invention.
[Explanation of symbols]
(1) Casing (1a) Bottom wall (near permanent magnet)
(2) Rotating body (4) Axial magnetic bearing (5) (6) Radial magnetic bearing (21) Permanent magnet (22) Permanent magnet (23) Lower end flange (part near permanent magnet)

Claims (1)

A casing, a rotating body that rotates within the casing, a plurality of sets of magnetic bearings that support the rotating body in a non-contact manner in the axial and radial directions, an axial sensor unit for detecting a position of the rotating body in the axial direction, and a rotation. In a magnetic bearing device having a radial sensor unit for detecting a position of a body in a radial direction, a permanent magnet is provided at a predetermined position of a rotating body, and a repulsive force acts on a permanent magnet of the rotating body on a casing. A magnetic bearing device, comprising: a permanent magnet to be provided; and a portion near the permanent magnet of the rotating body and the casing is formed of a nonmagnetic material.

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