JP2006162049A - Magnetic bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic bearing having superior axial controllability and capable of reducing its size and weight. <P>SOLUTION: A rotor 2 comprises a rotating shaft 2a, and a pair of discs 2b, 2b' held by the rotating shaft 2a in a state of being located on positions axially shifted inside with respect to a main pole 3. An axial control coil 15 is wound on a connecting portion 21 constituting a part of a stator 1, thereby axial control magnetic flux ψca is generated. Radial control magnetic flux ψr is enhanced at one side of a pair of annular portions 12, 12' and weakened at the other side by the axial control magnetic flux ψca to control an axial position of the rotor 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a magnetic bearing that supports a rotor in a non-contact state by a magnetic force, and more particularly to a magnetic bearing that can control the rotor in an axial direction (axial direction).

  Since the magnetic bearing can support the rotating body in a non-contact manner, it has been used for various bearings with the development of control technology. Recently, there has been a demand for magnetic bearings for micro rotating bodies. However, since the magnetic bearing using an electromagnet requires a large current to float the rotor, the power consumption increases. Further, in order to increase the magnetic force with a small current, it is required that the gap between the rotor and the stator is small, and high machining accuracy is required.

As a promising method for solving these problems, in recent years, a hybrid type magnetic bearing using a bias magnetic flux of a permanent magnet whose performance has been remarkably improved has been used. This hybrid type magnetic bearing is proposed by patent documents 1-3, for example.
JP 2003-21140 (paragraphs 0053 to 0056, FIG. 6) Japanese Patent Laid-Open No. 2001-41138 (paragraphs 0011 to 0014, FIG. 1) Japanese Patent Laid-Open No. 2001-101234 (paragraph 0009, FIG. 1)

  However, in the magnetic bearing disclosed in the above-mentioned patent document, it is necessary to rely on passive stability for the stability in the axial direction (axial direction). For this reason, when an axial load is applied to the rotor, the magnetic bearing is inclined and rotated. There is a problem that control becomes difficult due to vibration or vibration.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a magnetic bearing that is excellent in axial controllability and can be reduced in size and weight.

  A magnetic bearing according to the present invention is a magnetic bearing having a stator and a rotor that is supported by the stator in a non-contact state by a magnetic force and rotates about a rotating shaft. The stator has a predetermined interval in the axial direction. And controlling the radial position of the rotor made of a magnetic material arranged at a predetermined interval in the circumferential direction on the inner circumference of each of the pair of annular portions. A plurality of main poles through which a bias magnetic flux and a radial control magnetic flux pass, and a connection portion made of a magnetic material that magnetically connects the pair of annular portions, and the rotor is a rotation made of a magnetic material. And a pair of discs made of a magnetic material held by the rotating shaft so as to be positioned inwardly with respect to the axial direction from the main pole, and the bias magnetic flux A permanent magnet to be fed, a radial control coil that generates the radial control magnetic flux, and an axial control magnetic flux that is wound around the connection portion and uses a closed circuit by the annular portion, the connection portion, and the rotor as a magnetic circuit An axial control coil for controlling the position of the rotor in the axial direction by strengthening the radial control magnetic flux on one side of the pair of annular portions and weakening the other side by the axial control magnetic flux. Features.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the magnetic bearing which is excellent in controllability of an axial direction, and can be reduced in size and weight.

First, a magnetic bearing according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1A is a plan view of the magnetic bearing as viewed from the axial direction, and FIG. 1B is a cross-sectional view taken along the line AA ′ in FIG.
This magnetic bearing has an annular stator 1 disposed outside and a rotor 2 disposed inside the stator 1. The rotor 2 is controlled in rotation by the rotation driving unit 100 and is held and controlled in position by a magnetic flux applied from the stator 1.

  The stator 1 is composed of a yoke 11. The yoke 11 is made of a magnetic material such as a laminated steel plate. As shown in FIG. 1 (b), by this yoke 11, two annular portions 12, 12 ′ and a plurality of (2 in FIG. 1) projecting toward the center on the inner periphery of the annular portions 12, 12 ′. × 4 poles = 8) main salient pole portions 13 (i), 13 ′ (i) (i = 1 to 4) and a plurality of projections toward the center on the inner periphery of the annular portion 12 (FIG. 1). Then, 2 × 4 poles = 8) complementary salient pole parts 14 (i) and 14 ′ (i) (i = 1 to 4) and a connection part 21 connecting the two annular parts 12 and 12 ′ are formed. Has been.

  The main salient pole portions 13 (i) and 13 ′ (i) have a magnetic concentration portion facing the outer peripheral surface of the rotor 2 with a predetermined gap, and are arranged at intervals of 90 ° in the circumferential direction. Yes. A radial control coil 18 wound around the radial direction as an axis is installed on the main salient pole portions 13 (i) and 13 '(i). The radial control coil 18 is for generating a radial excitation magnetic flux φr for strengthening or weakening the magnetic pole of the magnetic flux concentrating portion. The main salient pole portions 13 (i), 13 '(i) and the radial control coil 18 form main poles 3 (i), 3' (i). The position of the rotor 2 in the radial direction is controlled by controlling the magnetic pole of the main pole 3 based on the change in the radial excitation magnetic flux φr. This control is performed by a control system described later.

  Further, the complementary salient pole portions 14 (i) and 14 ′ (i) are shifted by 45 ° in the circumferential direction from the main salient pole portions 13 (i) and 13 ′ (i) on the inner circumference of the annular portions 12 and 12 ′. The permanent magnet 16 is attached to the tip of the tip. The complementary salient poles 14 (i) or 14 '(i) and the permanent magnets 16 form complementary poles 4 (i) and 4' (i). The permanent magnet 16 is for providing a bias magnetic flux φb to the main poles 3 (i), 3 '(i). The permanent magnet 16 is mounted with the first polarity (for example, the S pole) set to the tip side toward the rotor 2. When the south pole is on the tip side, the bias magnetic flux φb is changed from the bottom of the auxiliary salient pole part 14 (i) or 14 ′ (i) to the adjacent main salient pole part 13 (i) or via the annular part 12 or 12 ′. 13 ′ (i), and is further formed in a path returning to the complementary salient pole portion 14 (i) or 14 ′ (i) via the rotor 2. As a result, the magnetic flux concentrating portion that is the tip of the main pole 3 (i), 3 '(i) becomes the N pole.

  Further, magnetic flux sensors 17A (i) and 17B (i) for detecting magnetic flux are attached to the tip of each auxiliary pole 4 (i), that is, the tip of the permanent magnet 16 (i = 1 to 4). Similarly, magnetic flux sensors 17A '(i) and 17B' (i) are attached to the tips of the respective complementary poles 4 '(i). These magnetic flux sensors 17 are, for example, Hall elements. The magnetic flux sensors 17A (i) and 17B (i) attached to one permanent magnet 16 are attached at different positions in the axial direction (Z direction) as shown in FIG. 1 (b). Here, it is assumed that the magnetic flux sensor 17A (i) is present inside the Z direction with respect to 17B (i). The same applies to the magnetic flux sensors 17A '(i) and 17B' (i).

  On the other hand, the rotor 2 is provided with a magnetic material such as a laminated steel plate or an electromagnetic material at least on the outer periphery, and has a rotating shaft 2a and two disks 2b and 2b '. The two discs 2b and 2b ′ are disposed inside the stator 1 so as to be rotatable around the rotation shaft 2a, and the axial position thereof is slightly inside the annular portions 12 and 12 ′. Yes. That is, the axial distance between the two disks 2b and 2b 'is shorter than the distance between the two annular portions 12 and 12'. For this reason, the radial excitation magnetic flux φr between the main pole 3 and the disc 2b or 2b ′ becomes magnetic fluxes φra and φrb having axial components (axial components) (see FIG. 1B). In this embodiment, the position control (axial control) of the rotor 2 in the axial direction is performed by increasing or decreasing the magnetic fluxes φra and φrb.

  In order to strengthen or weaken the magnetic fluxes φra and φrb, and as shown in FIG. 1A, the connection portion 21 is axially excited around an axis parallel to the axial direction of the rotor 2 (Z-axis direction). A coil 15 is wound. When an exciting current flows through the axial control coil 15, an axial control magnetic flux φca is generated in a magnetic circuit formed by the connection portion 21, the upper and lower annular portions 12, 12 ′, the main poles 3, 3 ′, and the rotor 2. To do. The direction and magnitude of the magnetic flux φca varies depending on the direction and magnitude of the excitation current flowing in the axial control coil 15. The axial control magnetic flux acts to strengthen either one of the magnetic fluxes φra or φrb and weaken either one. As a result, an axial force F is applied to the rotor 2 to control the axial position of the rotor 2.

Next, a configuration example of a control system for controlling the excitation current of the radial control coil 18 and the axial control coil 15 will be described with reference to FIG.
This control system includes comparators 101 and 102, a coordinate conversion circuit 103, and controllers 104 and 105 for controlling the excitation current of the radial control coil 18. Further, adders 106 and 107, a comparator 108, and a controller 109 are provided for controlling the excitation current of the axial control coil 15.

  The comparator 101 outputs a differential signal of the magnetic flux sensors 17A (1) and 17A (3) formed on the opposing complementary electrodes 4 (1) and 4 (3). Similarly, the comparator 102 outputs a differential signal of the magnetic flux sensors 17A (2) and 17A (4) formed on the opposing complementary electrodes 4 (2) and 4 (4). The coordinate conversion circuit 103 performs coordinate conversion of these difference signals to generate a y-direction displacement signal and an x-direction displacement signal, and outputs them to the controllers 104 and 105. The controllers 104 and 105 control the excitation current of the radial control coil 18 based on these displacement signals. Thereby, the radial excitation magnetic flux φr changes, and the radial position control of the rotor 2 becomes possible.

  The adder 106 calculates the sum of the magnetic flux sensors 17B (i) formed on the complementary pole 4 (i) provided on the annular portion 12 side, while the adder 107 is on the annular portion 12 ′ side. The total of the magnetic flux sensors 17B ′ (i) formed on the provided complementary poles 4 ′ (i) is obtained. The comparator 108 outputs a z displacement signal that is a difference signal between the output signals of the one adders 106 and 107. The controller 109 controls the excitation current of the axial control coil 15 based on this z displacement signal. As a result, the axial excitation magnetic flux φca is changed, and one of the magnetic fluxes φra and φrb is strengthened and the other is weakened, so that an axial force is applied to the rotor 2 and the axial position control of the rotor 2 becomes possible. . In this embodiment, since the axial control coil 15 is wound around the connection portion 21 between the annular portions 12 and 12 ', an increase in size and weight is avoided.

  In FIG. 2, the detection output of the magnetic flux sensor 17A (i) is used for controlling the excitation current of the radial control coil 18, and the detection output of the magnetic flux sensor 17B (i) is used for controlling the excitation current of the axial control coil 15. However, conversely, the detection output of the magnetic flux sensor 17B (i) is used for controlling the excitation current of the radial control coil 18, and the detection output of the magnetic flux sensor 17A (i) is used for the excitation of the axial control coil 15. You may utilize for control of an electric current.

  Although the embodiments of the invention have been described above, the present invention is not limited to these embodiments, and various modifications, additions, substitutions, and the like can be made without departing from the spirit of the invention. For example, in the above embodiment, the permanent magnet 16 is formed at the tip of the complementary poles 4 (i) and 4 ′ (i). However, as shown in FIG. '(I) is abolished, the permanent magnet 16 is formed at the tip of the main pole 3 (i), 3' (i), and the magnetic flux sensors 17A (i), 17B (i), 17A '(i), 17B ′ (i) may be formed at the tip of the permanent magnet 16. In FIG. 3, a notch is formed on the left side of the main poles 3 (i) and 3 ′ (i), and a gap g is formed in the notch with respect to the main poles 3 (i) and 3 ′ (i). The permanent magnet 16 is provided while remaining. According to this configuration, the bias magnetic flux φb generated by the permanent magnet 16 is emitted from the N pole of the permanent magnet 16, passes through the right side of the main poles (i) and 3 ′ (i) (the portion that is not a notch), and goes to the S pole. Returning magnetic flux. The gap g is set to a sufficient size so that such a circuit of the bias magnetic flux φb is formed.

It is the top view and sectional drawing of the magnetic bearing which concern on embodiment of this invention. 2 shows a configuration example of a control system for controlling the excitation current of coils 15 and 18 in FIG. The modification of embodiment of this invention is shown.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Stator, 2 ... Rotor, 3 ... Main pole, 4 ... Supplementary pole, 11 ... Relay, 12 ... Annular part, 13 ... Main salient pole part, 14・ ・ ・ Supplementary salient pole part, 15 ... Axial control coil, 16 ... Permanent magnet, 17 ... Magnetic flux sensor, 18 ... Radial control coil.

Claims (6)

In a magnetic bearing having a stator and a rotor that is supported by the stator in a non-contact state by a magnetic force and rotates about a rotation axis,
The stator is
At least a pair of annular portions made of a magnetic material coaxially arranged at a predetermined interval in the axial direction;
A plurality of main poles made of a magnetic material arranged at a predetermined interval in the circumferential direction on the inner circumference of each of the pair of annular portions, through which a bias magnetic flux and a radial control magnetic flux for controlling the radial position of the rotor pass When,
A connecting portion made of a magnetic material for magnetically connecting between the pair of annular portions,
The rotor is
A rotating shaft made of magnetic material;
A pair of discs made of a magnetic material held by the rotating shaft so as to be located at a position shifted inward in the axial direction from the main pole,
A permanent magnet for supplying the bias magnetic flux;
A radial control coil for generating the radial control magnetic flux;
An axial control magnetic flux that is wound around the connection portion and uses a closed circuit by the annular portion, the connection portion, and the rotor as a magnetic circuit is generated, and the radial control magnetic flux is generated by the axial control magnetic flux between the pair of annular portions. A magnetic bearing comprising: an axial control coil that controls the position of the rotor in the axial direction while strengthening on one side and weakening on the other side. A magnetic flux sensor for detecting magnetic flux;
The magnetic bearing according to claim 1, further comprising: a control unit that controls an exciting current flowing in the axial control coil based on a detection output of the magnetic flux sensor. The control unit includes a difference between a sum of detection outputs of the magnetic flux sensors provided on one side of the pair of annular portions and a sum of detection outputs of the magnetic flux sensors provided on the other side of the pair of annular portions. The magnetic bearing according to claim 2, wherein an excitation current of the axial control coil is controlled based on the magnetic field. A plurality of complementary poles made of a magnetic material arranged at predetermined intervals in the circumferential direction so as to be adjacent to the plurality of main poles on the inner circumference of each of the pair of annular portions;
The magnetic bearing according to claim 2, wherein the magnetic flux sensor is provided at a tip portion of the auxiliary pole.   5. The magnetic bearing according to claim 4, wherein the permanent magnet supplies the bias magnetic flux so that a tip end portion of the auxiliary pole has a first polarity and a magnetic flux concentration portion of the adjacent main pole has a second polarity. The magnetic bearing according to claim 1, wherein the permanent magnet is provided on a part of the main pole.

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