JP4616122B2 - Magnetic bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic bearing with a rotor which is controlled in the axial direction and in the radial direction not to be subjected to magnetic attractive force of a permanent magnet, when machined and assembled. <P>SOLUTION: A stator 1 has: at least a pair of annular portions 12a, 12b; a first magnetic pole 13a and a second magnetic pole 13b provided on the inner peripheries of the annular portions 12a, 12b, respectively; and the annular permanent magnet 3 located between the annular portions 12a, 12b. A radial exciting coil 14 and an axial exciting coil 15 are wound in the first magnetic pole 13a and the second magnetic pole 13b, respectively, which generate a radial exciting magnetic flux &phiv;r and an axial exciting magnetic flux &phiv;a. <P>COPYRIGHT: (C)2007,JPO&amp;INPIT

Description

  The present invention relates to a magnetic bearing that supports a rotor in a non-contact state by a magnetic force, and particularly relates to a magnetic bearing capable of controlling the rotor position in an axial direction (axial direction) and a radial direction (radial direction).

  Since the magnetic bearing can support the rotating body in a non-contact manner, it has been used for various bearings as the control technology advances. 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 amount of electric power, a small gap between the rotor and the stator is required, and high machining accuracy is required.

As an effective method for solving these problems, in recent years, a hybrid type magnetic bearing using a bias magnetic flux of a permanent magnet whose performance is remarkably improved has been used. This hybrid type magnetic bearing is proposed by, for example, Patent Documents 1 and 2.
JP 2003-021140 A (paragraphs 0053 to 0056, FIG. 6) JP 2004-232740 A (paragraphs 0011 to 0021, FIG. 1)

However, the magnetic bearing disclosed in the above-mentioned patent document has a problem that there is a difficulty in processing and assembly.
The present invention has been made in view of such problems, and an object of the present invention is to provide a magnetic bearing with improved workability and assemblability.

  The 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 rotation shaft. The stator rotates to supply a bias magnetic flux. A permanent magnet formed in an annular shape around an axis and magnetized in the axial direction, and a magnetic material disposed in both ends of the permanent magnet in the axial direction and formed in an annular shape around the rotation axis, the diameter of the annular portion is The first annular portion and the second annular portion, which are substantially equivalent to the permanent magnet, are connected to the inner circumference of the first annular portion at a predetermined interval in the circumferential direction, while the second annular portion has a predetermined distance. A plurality of first magnetic poles made of a magnetic material disposed on the inner periphery of the second annular portion, and connected to the inner periphery of the second annular portion so as to sandwich the plurality of first magnetic poles at a predetermined interval in the circumferential direction. Is a magnet arranged at a predetermined distance A plurality of second magnetic poles made of a material, and formed on the first magnetic pole and the second magnetic pole so as to increase the bias magnetic flux on one side in the radial direction and weaken the bias magnetic flux on the other side. A radial excitation coil for generating a radial excitation magnetic flux that acts, and a bias magnetic flux formed on the first magnetic pole and the second magnetic pole so as to strengthen the bias magnetic flux on one side in the axial direction and the bias magnetic flux on the other side. And an axial excitation coil that generates an axial excitation magnetic flux that acts to weaken the magnetic field.

  According to the present invention, it is possible to provide a magnetic bearing that is excellent in controllability in the radial direction and the axial direction and that is not affected by a magnetic attractive force by a permanent magnet with improved workability and assembly.

(First embodiment)
First, a first embodiment of the present invention will be described with reference to FIG. 1, FIG. 2, and FIG. FIG. 1 is an exploded perspective view of the magnetic bearing according to the first embodiment, FIG. 2 is an assembled perspective view thereof, and FIG. 3 is a plan view seen from the direction of arrow A in FIG.
This magnetic bearing has an annular stator 1 disposed on the outside and a rotor 2 disposed on the inside of the stator 1. The rotor 2 is supported in a non-contact state by a magnetic flux applied from the stator 1 and is position-controlled.

The stator 1 is composed of a yoke. The yoke is made of a magnetic material such as a laminated steel plate. As shown in FIG. 1, the stator 1 is disposed between the first annular portion 12a, the second annular portion 12b, the first annular portion 12a, and the second annular portion 12b, and is formed in an annular shape around the rotation axis. The permanent magnet 3 is magnetized in the direction. The permanent magnet 3 is designed to be approximately equal to the diameter of the annular portions 12a and 12b.
Further, first magnetic poles 13a (1) and 13a (2) are formed integrally with the first annular portion 12a through the joint portion 18 at an interval of 180 ° on the inner periphery of the first annular portion 12a. Similarly, second magnetic poles 13b (1) and 13b (2) are formed integrally with the second annular portion 12b through the joint portion 18 at an interval of 180 ° on the inner periphery of the annular portion 12b (FIG. 2). As shown in FIG. 4, the magnetic poles 13a and 13b are spaced by 90 ° during assembly).
On the other hand, the rotor 2 has a magnetic material such as a laminated steel plate or electromagnetic material disposed on at least an outer peripheral surface thereof, and is disposed inside the stator 1 so as to be rotatable around a rotation axis.
Hereinafter, the intersection of the center plane of the permanent magnet 3 and the axis of the rotation axis is the origin, and a straight line connecting the center of the first magnetic pole 13a (1) to the center of the first magnetic pole 13a (2) is the x-axis, and the second magnetic pole 13b (1 ) To the center of the second magnetic pole 13b (2) is defined as the y-axis, and the rotation axis from the second annular portion 12b to the first annular portion 12a is defined as the z-axis.

Each of the magnetic poles 13 includes an axial excitation coil 14 and a radial excitation coil 15.
The axial excitation coil 14 is wound around the central portion of the magnetic pole 13 with the axial direction as the axis (axial center parallel to the z axis, wound on the xy plane). Further, the radial excitation coil 15 is wound around the magnetic pole 13 with the radial direction as an axial center (axial center in the x-axis parallel or y-axis parallel, wound in the zy plane or the zx plane).

Further, on the inner peripheral surface of each magnetic pole 13, two salient pole portions 16a (i), 16a (i) or 16b (i), 16b (i) (i = 1, 2) and a magnetic flux sensor 17a ( i), or 17b (i), (i = 1, 2).
These salient pole portions 16 have a shape protruding from the inside of the magnetic pole 13 toward the center of the rotation axis, and are outside the end in the axial direction (z axis) of the rotor 2 in the axial direction (z axis). Both are formed on the edge of the magnetic pole 13 so as to be separated from each other.
The magnetic flux sensor 17 is formed between two salient pole portions 16, and this magnetic flux sensor 17 is, for example, a Hall element. Note that the magnetic flux sensor 17 is not limited to the above-described arrangement, and may be any arrangement that can detect the magnetic flux. Further, a gap sensor or an inductance sensor can be used in place of the magnetic flux sensor 17.
Based on the change of the magnetic flux detected by the magnetic flux sensor 17, the current flowing through the exciting coils 14 and 15 is controlled. This control is performed by a control system described later.

2 and 3, when the magnetic bearing is assembled, the first magnetic poles 13a (1) and 13a (2) joined to the annular portion 12a are separated from the annular portion 12b, and similarly to the annular portion 12b. The joined second magnetic poles 13 b (1) and 13 b (2) are separated from the annular portion 12 a and form a gap 19. The air gap 19 only needs to have a structure that does not allow magnetic flux to pass through, and the magnetic pole 13 and the annular portion 12 can be joined using a low magnetic permeability material instead of the air gap 19. With these configurations, it is possible to generate a characteristic bias magnetic flux φb for controlling the position of the rotor 2 described later.
In addition, with the above configuration, the annular portions 12a and 12b, the permanent magnet 3, and the magnetic pole 13 can be assembled through independent manufacturing and processing steps. Therefore, it is possible to provide a magnetic bearing that is not affected by the magnetic attractive force of the permanent magnet during processing and assembly. Moreover, with such a structure, the winding process of each exciting coil 14 and 15 is also easy.

  Next, with reference to FIGS. 3, 4A, 4B, 4C, and 5, the exciting coils 14 and 15 are used for the axial excitation magnetic flux φa that forms the magnetic flux in the axial direction and the radial excitation that forms the magnetic flux in the radial direction. The relationship between the magnetic flux φr and the bias magnetic flux φb generated by the permanent magnet 3 will be described. 4A is an xz-axis cross-sectional view when current in the same rotational direction flows through the axial excitation coil 14 of the magnetic bearing, and FIG. 4B illustrates y when current in the same rotational direction flows through the axial excitation coil 14 of the magnetic bearing. FIG. 4C is a cross-sectional view taken along the z-axis, and FIG. 4C is a cross-sectional view taken along the z-axis when a current in a different rotational direction is passed through the axial excitation coil 14 of the magnetic bearing. It is xy sectional drawing of the rotor 2, annular part 12b, and 2nd magnetic pole 13b (1), 13b (2) in FIG.

As shown in FIGS. 3, 4A, and 4B, the bias magnetic flux φb by the permanent magnet 3 is supplied from the N pole of the permanent magnet 3 to the annular portion 12a and the magnetic pole 13a. Next, the bias magnetic flux φb supplied to the first magnetic pole 13a cannot be returned to the S pole shown in FIG. 4A because of the air gap 19, and is supplied to the rotor 2 through the salient pole portion 16a.
The bias magnetic flux φb supplied to the rotor 2 advances 90 degrees in the radial direction from the x axis to the y axis around the z axis in the rotor 2, and is supplied from the rotor 2 to the salient pole portion 16b and the magnetic pole 13b. Return to the south pole of the permanent magnet 3 through 12b.
Here, the pair of salient pole portions 16 are arranged so as to be aligned in the rotation axis (z-axis) direction on the surface of the magnetic pole 13 facing the rotor 2. Due to the structure of the salient pole portion 16, the bias magnetic flux φb has a vector from the edge in the z-axis direction of the rotor 2 toward the center of the rotor 2 on the first magnetic pole 13a side, and the bias magnetic flux φb on the second magnetic pole 13b side is It has a vector from the center of the rotor 2 toward the edge of the rotor 2 in the z-axis direction. Therefore, the bias magnetic flux φb includes an axial component.

  Next, with reference to FIG. 4A and FIG. 4B, the case where the control force is generated in the rotor 2 in the axial direction will be described. As described above, the bias magnetic flux φb includes an axial component. Here, when an exciting current in the same direction is passed through the axial exciting coil 14, an axially exciting magnetic flux φa rotating in the reverse direction is generated, and the magnetic flux on either the positive side or the negative side in the z-axis direction is intensified. The magnetic flux on the side weakens. As a result, an axial translational force Fa is generated in the z-axis direction, and axial control of the rotor 2 becomes possible.

  Further, as shown in FIG. 4C, when an exciting current is passed in the reverse direction, magnetic fluxes that strengthen in the y-axis + direction and the z-axis + direction, and the y-axis-direction and the z-axis-direction are generated. However, this magnetic flux differs from FIG. 4A and FIG. 4B and has vectors in opposite directions to each other, so that a counterclockwise moment M is generated. Therefore, the inclination of the rotor 2 can be controlled by this moment M.

  Next, with reference to FIG. 5, the case where the rotor 2 generates a control force in the radial direction will be described. As shown in FIG. 5, in addition to the bias magnetic flux φb, an exciting current is passed through the radial exciting coil 15 to generate a radial exciting magnetic flux φr. By this radial excitation magnetic flux φr, one side (y-axis + direction) of the magnetic flux strengthens and the other side (y-axis − direction) weakens. As a result, a radial control force Fr is generated in the radial direction (y-axis + direction).

Next, a configuration example of a control system for controlling the excitation current flowing in the axial excitation coil 14 and the radial excitation coil 15 according to the first embodiment of the present invention will be described with reference to FIG.
This control system includes an A / D converter 101 and a control unit 102 for controlling the excitation current of the radial excitation coil 14 and the radial excitation coil 15. The A / D converter 101 converts the analog signal detected by the magnetic flux sensor 17 into a digital signal and outputs it to the control unit 102. The control unit 102 controls the excitation current of the radial excitation coil 14 and the axial excitation coil 15 based on this digital signal. As a result, the radial excitation magnetic flux φr and the axial excitation magnetic flux φa change, and the radial and axial position control of the rotor 2 becomes possible. In FIG. 6, only the second magnetic poles 13b (1) and 13b (2) have been described for the sake of simplicity. Similarly, the magnetic fluxes of the first magnetic poles 13a (1) and 13a (2) are also controlled.

(Second Embodiment)
Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 7 is an exploded perspective view of a magnetic bearing according to the second embodiment of the present invention.
As shown in FIG. 7, a different point from 1st Embodiment is the structure of permanent magnet 3 'and the case 30 which accommodates it. A convex portion 31 and a concave portion 32 are formed in the case 30. The permanent magnet 3 ′ is divided in an arc shape and is stored in the recess 32 of the case 30. Further, the number of the permanent magnets 3 ′ and the recesses 32 is not limited to four.
With the above configuration, even after the annular portions 12a and 12b and the case 30 are joined, the arc-shaped permanent magnet 3 ′ can be inserted to manufacture a magnetic bearing.

(Third embodiment)
Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 8 is an exploded perspective view of a magnetic bearing according to the third embodiment of the present invention. The difference from the first embodiment is that the first magnetic pole 13a is not disposed in the annular portion 12a, and the first magnetic pole 13a and the second magnetic pole 13b are disposed in the annular portion 12b.
Further, the annular portion 12b, the magnetic pole 13a, and the magnetic pole 13b are processed in separate steps, and the second magnetic poles 13b (1) and 13b (2) are joined to the annular portion 12b by the joining portion 18 made of a material having high magnetic permeability. . On the other hand, the magnetic poles 13a (1) and 13a (2) are joined to the annular portion 12b by a joining portion 18 ′ made of a low magnetic permeability material.
Magnetic flux is not formed between the magnetic pole 13a (1) and the annular portion 12b and between the magnetic pole 13a (2) and the annular portion 12b by the joint 18 ′. Therefore, the joining portion 18 ′ has the same effect as the gap 19 described in the first embodiment, and joins the magnetic pole 13 and the annular portion 12.
Moreover, the junction part 18 is provided in the outer peripheral side of the magnetic poles 13a (1) and 13a (2) direction of the annular part 12a, respectively. When the magnetic bearing is assembled, the annular portion 12a comes into contact with the joint portion 18, and a magnetic flux can be formed between the magnetic pole 13a (1) and the annular portion 12b and between 13a (2) and the annular portion 12b.
The arrangement of the first magnetic pole 13a and the second magnetic pole 13b is not limited to this arrangement. One annular pole 12a has one first magnetic pole 13a, and the annular section 12b has one first magnetic pole 13a and two second magnetic poles 13b. It may be a configuration such as arranging.
As the shape of the annular portion 12 and the shape of the permanent magnet 3, the annular portion 12a ′ and the arc-shaped permanent magnet 3 ′ of FIG. 7 can be adopted. Further, the number of magnetic poles 13 is not limited to four, and a plurality of magnetic poles 13 may be arranged as long as the number is even.

  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.

It is a disassembled perspective view of the magnetic bearing which concerns on the 1st Embodiment of this invention. It is an assembly perspective view of the magnetic bearing which concerns on the 1st Embodiment of this invention. It is the top view seen from the arrow A direction in FIG. 2 of the magnetic bearing which concerns on the 1st Embodiment of this invention. In the magnetic bearing which concerns on the 1st Embodiment of this invention, it is the xz surface sectional drawing which sent the exciting current of the same rotation direction to the axial exciting coil. In the magnetic bearing which concerns on the 1st Embodiment of this invention, it is the yz surface sectional drawing which sent the exciting current of the same rotation direction to the axial exciting coil 14. FIG. In the magnetic bearing which concerns on the 1st Embodiment of this invention, FIG. In the magnetic bearing according to the first embodiment of the present invention, the xy section of the rotor 2, the annular portion 12b, the magnetic pole 13b (1), and the magnetic pole 13b (2) when a magnetic flux is applied in the + direction of the y-axis. FIG. FIG. 3 is a diagram illustrating a configuration example of a control system for controlling an excitation current flowing in an axial excitation coil 14 and a radial excitation coil 15 in the magnetic bearing according to the first embodiment of the present invention. It is a disassembled perspective view of the magnetic bearing which concerns on the 2nd Embodiment of this invention. It is a disassembled perspective view of the magnetic bearing which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Stator 12a ... 1st annular part 12b ... 2nd annular part 13a ... 1st magnetic pole 13b ... 2nd magnetic pole 14 ... Axial exciting coil 15 ... Radial exciting coil 16a , 16b ... salient pole part 17 ... magnetic flux sensor 18, 18 '... joint 19 ... air gap 2 ... rotor 3, 3' ... permanent magnet 30 ... case 31 ... -Convex part 32 ... Concave part 101 ... A / D converter 102 ... Control part φa ... Axial excitation magnetic flux φr ... Radial excitation magnetic flux φb ... Bias magnetic flux

Claims (3)

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
A permanent magnet formed in an annular shape around the rotation axis and magnetized in the axial direction to supply a bias magnetic flux;
A first annular portion and a second annular portion, which are made of a magnetic material which is arranged at both ends in the axial direction of the permanent magnet and which is formed in an annular shape around the rotation axis, and the diameter of the annular portion is substantially equal to that of the permanent magnet; ,
A plurality of first magnetic poles made of a magnetic material, which is connected to the inner periphery of the first annular portion at a predetermined interval in the circumferential direction, while being arranged at a predetermined distance from the second annular portion;
A plurality of magnetic materials that are connected to an inner periphery of the second annular portion so as to sandwich the plurality of first magnetic poles at predetermined intervals in the circumferential direction, and are made of a magnetic material arranged at a predetermined distance from the first annular portion. A second magnetic pole of
Radial excitation that is formed in the first magnetic pole and the second magnetic pole and that generates a radial excitation magnetic flux that acts to strengthen the bias magnetic flux on one side in the radial direction and acts to weaken the bias magnetic flux on the other side. Coils,
An axial that is formed in the first magnetic pole and the second magnetic pole and generates an axial excitation magnetic flux that acts to strengthen the bias magnetic flux on one side in the axial direction and acts to weaken the bias magnetic flux on the other side. A magnetic bearing comprising: an exciting coil. A sensor for detecting the magnitude of magnetic flux flowing through the rotor;
The magnetic bearing according to claim 1, further comprising: a control unit that controls an excitation current flowing through the radial excitation coil and the axial excitation coil based on a detection signal of the sensor. The magnetic bearing according to claim 1, wherein the annular permanent magnet is a plurality of arc-shaped permanent magnets.

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