JP7175362B2 - Radial magnetic bearings and blowers - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radial magnetic bearing for non-contact support of a rotating body from the radially outer side, and a blower provided with the radial magnetic bearing.

When a ball bearing is used as a bearing to support the rotating shaft of a blower (or fan), fretting fatigue and wear due to friction occur, making it impossible to rotate the rotating shaft at high speeds. need to do On the other hand, when using a magnetic bearing device (so-called active magnetic bearing) that levitates the rotating shaft by the attractive force of the electromagnet and supports the rotating shaft without contact (so-called active magnetic bearing), fretting fatigue and wear due to friction do not occur. The shaft can be rotated at high speed.

Here, the magnetic bearing device consists of a thrust magnetic bearing that supports the rotating shaft in the axial direction (rotating shaft direction, thrust direction) without contact, and a radial magnetic bearing that supports the rotating shaft from the outside in the radial direction (radial direction) without contact. and a bearing. Each of the thrust magnetic bearing and the radial magnetic bearing has an electromagnet for generating magnetic flux for supporting the rotating shaft and a displacement sensor for detecting displacement of the rotating shaft. In addition, a typical magnetic bearing device is equipped with a touchdown bearing that supports the rotating shaft in place of the magnetic bearing in the event of an abnormality such as when power supply is stopped, and a rotational speed sensor for detecting the rotational speed of the rotating shaft. .

In this way, a magnetic bearing device comprising an electromagnet, a displacement sensor, a touchdown bearing, a rotation speed sensor, etc. possessed by each of the thrust magnetic bearing and the radial magnetic bearing has more components than ball bearings. As a result, there is a problem that the axial dimension of the rotating shaft increases. Since the natural frequency of the rotating shaft decreases as the axial dimension of the rotating shaft increases, it is impossible to rotate the rotating shaft at high speed in order to prevent resonance of the rotating shaft.

In order to solve such problems, for example, in the radial magnetic bearing disclosed in Patent Document 1, the detecting surface of the displacement sensor and the acting surface of the attractive force of the electromagnet are arranged in the circumferential direction of the rotating shaft in a cross section cut along the axial direction. It is disclosed that they are arranged uniformly in the direction of the axis and at the same position in the axial direction. This technology can reduce the axial dimension of radial magnetic bearings.

JP 2005-233385

Here, the electromagnet of the radial magnetic bearing includes a back yoke portion, a pair of magnetic pole teeth portions that form a magnetic path together with the back yoke portion and the magnetic portion provided on the rotating body, and each magnetic pole tooth portion. and a coil. The pair of magnetic pole teeth extends from the back yoke toward the magnetic portion of the rotor.

Radial magnetic bearings are required to reduce their radial dimensions in addition to their axial dimensions. In the case where the displacement sensors are arranged uniformly in the circumferential direction of the rotating shaft, one method for reducing the radial dimension of the radial magnetic bearing is to arrange the adjacent magnetic pole tooth portions without sandwiching the displacement sensor. It is conceivable to bring it closer. As a result, the radial dimension of the radial magnetic bearing can be reduced without increasing the number of turns of the coil. However, in this case, the magnetic pole teeth are close to each other at the position on the rotating body side, and this increases the magnetic flux (leakage magnetic flux) that bypasses the pair of magnetic pole teeth without passing through the magnetic part of the rotating body (leakage magnetic flux), resulting in an attractive force. may decrease. In order to maintain the attractive force, it is necessary to increase the number of turns of the coil, but in this case, the radial magnetic bearing also becomes large in the radial direction or the axial direction.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems, and to reduce the size of a radial magnetic bearing while maintaining attractive force.

The present invention
A radial magnetic bearing for supporting a rotating body from the radially outer side without contact,
A plurality of electromagnets provided facing the rotating body and generating magnetic flux for supporting the rotating body,
Each of the plurality of electromagnets includes a back yoke portion, a pair of magnetic pole tooth portions forming a magnetic path together with the back yoke portion and the rotor, and a coil wound around each of the pair of magnetic pole tooth portions. and
Each of the pair of magnetic pole teeth has a base portion extending from the back yoke portion such that the gap between the pair of magnetic pole teeth narrows, and a gap between the pair of magnetic pole teeth that widens from the base toward the rotating body. , or a tip that extends to be maintained,
It relates to radial magnetic bearings.

According to the present invention, the tips of the pair of magnetic pole teeth provided on the electromagnet extend from the base toward the rotor so that the gap between the magnetic pole teeth widens or is maintained, thereby increasing the attractive force. It is possible to reduce the size of the radial magnetic bearing while maintaining the same.

1 is a cross-sectional view showing a blower provided with a radial magnetic bearing according to Embodiment 1 of the present invention; FIG. FIG. 2 is a cross-sectional view of the radial magnetic bearing according to Embodiment 1 of the present invention as seen from the axial direction; FIG. 4 is a diagram showing directions of magnetic fluxes formed in electromagnets of the radial magnetic bearing according to Embodiment 1 of the present invention; FIG. 5 is a diagram showing directions of magnetic fluxes formed in electromagnets of a radial magnetic bearing according to a comparative example of the present invention; 1 is a cross-sectional view of a radial magnetic bearing according to an embodiment of the present invention viewed from the axial direction; FIG. FIG. 5 is a cross-sectional view of a radial magnetic bearing according to another embodiment of the present invention as seen from the axial direction; FIG. 5 is a cross-sectional view of a radial magnetic bearing according to another embodiment of the present invention as seen from the axial direction;

Hereinafter, embodiments of the present invention will be specifically described with reference to the drawings. In the following description, terms indicating specific directions are used as necessary, but these terms are used to facilitate understanding of the present invention, and the scope of the present invention is defined by these terms. should not be understood as limiting.

Form 1.
(1. Overall structure of blower)
As shown in FIG. 1, the blower 1 has a cylindrical rotating shaft 2 . In the following description, the axial direction (thrust direction) of the rotating shaft 2 is called the Z direction, and the radial direction (radial direction) of the rotating shaft 2 is called the R direction.

The blower 1 further includes a motor 3 for rotating the rotating shaft 2, blades 4 fixed to both ends of the rotating shaft 2 in the axial direction Z, and magnetic bearing devices for supporting the rotating shaft 2 without contact. Prepare. The rotating shaft 2 and the magnetic bearing device are housed inside a casing 5 . The motor 3 has a stator 6 fixed to the casing 5 and a rotor 7 fixed to the rotating shaft 2 .

(2. Magnetic bearing device)
The magnetic bearing device includes radial magnetic bearings (hereinafter referred to as radial bearings) 10, 10 respectively provided at both ends of a rotating shaft 2 in the axial direction Z, and one thrust magnetic bearing (hereinafter referred to as a thrust bearing) 20. , a touchdown bearing 30 , and a rotational speed sensor 40 .

[2-1. Radial bearing]
The radial bearing 10 supports the rotating shaft 2 from the outside in the radial direction R without contact. In the present invention, the rotating shaft 2 is an example of a rotating body supported by the radial bearing 10 . The radial bearing 10 includes a plurality of electromagnets 11 that generate magnetic flux for supporting the rotating shaft 2, a magnetic portion 12 fixed to the peripheral surface of the rotating shaft 2, and a displacement of the rotating shaft 2 in the radial direction R. and a displacement sensor 13 for

Electromagnet 11 is fixed to casing 5 . As shown in FIG. 2, in form 1 , four electromagnets 11A, 11B, 11C, and 11D are arranged uniformly in the circumferential direction at an angle of 90° in a cross section cut along the axial direction Z. there is For example, the electromagnet 11A and the electromagnet 11B are arranged in the circumferential direction R with the displacement sensor 13 (specifically, a detection unit 13a described later) sandwiched therebetween. Electromagnet 11A and electromagnet 11D are arranged adjacent to each other. The four electromagnets have the same shape. The electromagnet 11 has back yoke portions 14 and 15, a pair of magnetic pole tooth portions 16 and 17, and coils 18 and 19 wound around the magnetic pole tooth portions 16 and 17, respectively. The back yoke portions 14 and 15 and the magnetic pole tooth portions 16 and 17 may be made of laminated steel plates. The back yoke portions 14 and 15 and the magnetic pole tooth portions 16 and 17 may be collectively referred to as the core of the electromagnet 11 .

Magnetic pole teeth portions 16 and 17 of electromagnet 11 extend from back yoke portions 14 and 15 respectively toward magnetic portion 12 provided on rotating shaft 2 . The magnetic pole tooth portions of the electromagnet 11 are unevenly arranged in the circumferential direction so as to avoid the displacement sensor 13 (specifically, a detection portion 13a described later) in a cross section taken along the axial direction Z. The electromagnets 11 (11A to 11D) are arranged uniformly in the circumferential direction in a cross section taken along the axial direction Z. As shown in FIG. In the embodiment, the back yoke portions 14 and 15 are divided for each magnetic pole tooth portion.

A minute gap is provided between the magnetic pole teeth portions 16 and 17 and the magnetic portion 12 . The magnetic pole tooth portion 16 has a base portion 16a on the back yoke portion 14 side and a tip portion 16b on the magnetic portion 12 side. Similarly, the magnetic pole tooth portion 17 has a base portion 17a on the back yoke portion 15 side and a tip portion 17b on the rotating shaft 2 side.

As illustrated, the distance L1 between the base portions 16a and 17a of the magnetic pole teeth portions 16 and 17 decreases from the back yoke portions 14 and 15 toward the tip portions 16b and 17b. Thus, the base portions 16a and 17a extend from the back yoke portions 14 and 15 toward the tip portions 16b and 17b so that the distance between the magnetic pole teeth portions 16 and 17 narrows.

In form 1 , the tip portions 16b and 17b of the magnetic pole teeth portions 16 and 17 are moved away from each other, that is, the distance L2 between them increases from the base portions 16a and 17a toward the magnetic portion 12 of the rotating shaft 2. It is bent with respect to 16a and 17a. Thus, the tip portions 16b and 17b extend from the base portions 16a and 17a toward the magnetic portion 12 so that the distance between the magnetic pole teeth portions 16 and 17 widens.

In the embodiment, the coils 18 and 19 are wound only around the base portions 16a and 17a of the magnetic pole teeth portions 16 and 17, and are not wound around the tip portions 16b and 17b. In order to increase the attractive force of the electromagnet 11 by increasing the area occupied by the coils 18 and 19, the coils 18 and 19 of adjacent electromagnets 11 and 11 are preferably close to each other.

The directions of the magnetic fluxes formed in the electromagnet 11 when the coils 18 and 19 are energized are indicated by arrows in FIG. In the embodiment, the winding direction of the coils 18 and 19 and the current direction are selected so that the magnetic poles of the magnetic pole teeth portions 16 and 17 of the electromagnets 11 and 11 adjacent in the circumferential direction are the same. As illustrated, the magnetic pole teeth portions 16 and 17 constitute a magnetic path together with the back yoke portions 14 and 15 and the magnetic portion 12 . In this manner, an attractive force is generated between the magnetic portion 12 provided on the rotary shaft 2 and the magnetic pole teeth portions 16 and 17 . In form 1 , the electromagnets 11 (11A to 11D) are arranged uniformly in the circumferential direction in a cross section taken along the axial direction Z, so the attractive force acts uniformly in the circumferential direction.

Here, as described above, the magnetic pole teeth portions 16 and 17 form a magnetic path together with the back yoke portions 14 and 15 and the magnetic portion 12, and when the magnetic pole teeth portions 16 and 17 come close to each other, the magnetic portion 12 is displaced. The magnetic flux (leakage magnetic flux) bypassing between the magnetic pole teeth portions 16 and 17 without intervening is increased (details will be described later). Therefore, it is preferable that the minimum distance L1 between the bases 16a and 17a of the magnetic pole teeth 16 and 17 and the minimum distance L2 between the tip parts 16a and 17a of the magnetic pole teeth 16 and 17 be such that the leakage magnetic flux can be ignored.

As described above, the tip portions 16b and 17b of the magnetic pole teeth portions 16 and 17 extend from the base portions 16a and 17a toward the magnetic portion 12 so that the distance between the magnetic pole teeth portions 16 and 17 widens. If the minimum value is such that the leakage magnetic flux can be ignored, the tip portions 16b and 17b maintain the distance between the magnetic pole teeth portions 16 and 17 from the base portions 16a and 17a toward the magnetic portion 12 (that is, spacing may be constant or substantially constant).

The magnetic portion 12 has a cylindrical shape and is provided coaxially with respect to the rotating shaft 2 . The magnetic portion 12 may be composed of laminated steel plates in order to suppress iron loss. The laminated steel plates of the magnetic portion 12 may be fixed directly to the rotating shaft 2 by shrink fitting. As described above, the magnetic portion 12 has a function of generating an attractive force with the magnetic pole teeth portions 16 and 17 . At least part of the rotating shaft 2 may be made of a magnetic material instead of providing the magnetic portion 12 on the rotating shaft 2 .

The displacement sensor 13 has a detecting portion 13a and a detected portion 13b that are arranged to face each other. In the embodiment, as the displacement sensor 13, an eddy current sensor that is less susceptible to the surface state of the object to be detected is used. The detector 13a is arranged in the space between the two adjacent electromagnets 11,11. In the embodiment, the four detectors 13a are evenly arranged in the circumferential direction at intervals of 90° in a cross section taken along the axial direction Z. As shown in FIG.

As shown in FIG. 1, the detection portion 13a of the displacement sensor 13 is arranged at a position overlapping the electromagnet 11 in the radial direction. In the embodiment, the detected portion 13 b of the displacement sensor 13 is provided on the outer peripheral surface of the magnetic portion 12 . The detected portion 13 b may be provided on the rotating shaft 2 . A pair of displacement sensors 13, 13 are constituted by two detecting portions 13a and the detected portion 13b facing each other across the rotation shaft 2 among the four detecting portions 13a. Two pairs of displacement sensors 13, 13 are configured by the four detecting portions 13a and the detected portion 13b.

A displacement in the radial direction R of the rotary shaft 2 detected by the displacement sensor 13 is coordinate-transformed into a displacement in the electromagnet 11 by a control device (not shown). Currents flowing in the coils 18 and 19 of the electromagnet 11 are fed back based on the coordinate-transformed displacement. Thereby, the magnetic attraction force acting between the electromagnet 11 and the magnetic portion 12 is controlled, and the size of the gap between the electromagnet 11 and the magnetic portion 12 is controlled so as to support the rotating shaft 2 without contact. .

By determining the difference between the outputs of a pair of displacement sensors 13, 13 facing each other across the rotating shaft 2, measurement errors due to drifts of sensor coils, cables, and amplifiers (all not shown) caused by environmental temperature changes can be reduced. ing.

As described above, the back yoke portions 14 and 15 of the electromagnet 11 are divided for each magnetic pole tooth portion. Therefore, the radial bearing 10 is assembled as a whole after the coils 18 and 19 are wound around the magnetic pole teeth portions 16 and 17, respectively.

[2-2. Thrust bearing]
The thrust bearing 20 supports the rotating shaft 2 in the axial direction Z. As shown in FIG. The thrust bearing 20 has a disk-shaped thrust disk 21 , a pair of annular electromagnets 22 , and a displacement sensor 23 . The thrust disk 21 is made of ferromagnetic material. The thrust disk 21 is mounted coaxially and perpendicularly to the rotating shaft 2 . The thrust disk 21 has circular main surfaces 21a and 21b.

The electromagnet 22 includes electromagnets 22a and 22b provided so as to sandwich the thrust disk 21 from the axial direction Z. As shown in FIG. An annular groove is formed in the electromagnets 22a and 22b. Annularly wound coils 24a and 24b are arranged in the groove. The electromagnets 22a and 22b are provided with a small predetermined gap between them and the main surfaces 21a and 21b of the thrust disk 21, respectively, and the coils 24a and 24b are positioned so as to face the main surfaces 21a and 21b of the thrust disk 21, respectively. , is attached to the casing 5 . An attractive force is generated between the electromagnets 22a and 22b and the main surfaces 21a and 21b of the thrust disk 21 by energizing the coils 24a and 24b.

In the embodiment, as the displacement sensor 23, an eddy current sensor that is less susceptible to the surface state of the object to be detected is used. Based on the displacement of the thrust disk 21 in the axial direction R detected by the displacement sensor 23, the current flowing through the electromagnets 22a and 22b is feedback-controlled, thereby acting between the electromagnet 22 and the main surfaces 21a and 21b of the thrust disk 21. The axial gap between the thrust disk 21 and the electromagnet 22 is controlled so that the thrust disk 21 is separated from the electromagnet 22 in the axial direction Z and supported without contact.

[2-3. touchdown bearing]
The touchdown bearing 30 is provided when the radial bearing 10 and the thrust bearing 20 stop and cannot support the rotating shaft 2 in an abnormal state such as when power supply to the electromagnet 11 of the radial bearing 10 and the electromagnet 22 of the thrust bearing 20 is stopped. supports the rotating shaft 2 instead of . The touchdown bearing 30 regulates the movable range of the rotating shaft 2 in the axial direction Z and the radial direction R, and mechanically supports the rotating shaft 2 at the extreme positions of the movable range of the rotating shaft 2 .

The touchdown bearing 30 is attached to the casing 5 . In the embodiment, the touchdown bearing 30 includes a deep groove ball bearing 31 that supports the rotating shaft 2 from the outside in the radial direction R, and two angular ball bearings 32 that support the rotating shaft 2 in both the radial direction R and the axial direction Z. including. The two angular ball bearings 32 are face-to-face. It should be understood that the cross-section of touchdown bearing 30 shown in FIG. 1 is only schematic.

[2-4. speed sensor]
The rotation speed sensor 40 is an optical encoder that detects the rotation speed or amount of rotation of the rotating shaft 2 . However, the present invention is not limited to this, and the rotational speed sensor 40 may use, for example, a sensor that has a Hall element as the detecting portion 41 and a permanent magnet as the detected portion 42 . Alternatively, an optical sensor or the like having a light projecting portion and a light receiving portion as a detecting portion and a reflecting portion and a non-reflecting portion as a detected portion may be used. The rotational speed sensor 40 has a detecting portion 41 that generates a pulse corresponding to the rotational speed of the rotating shaft 2 and a gear as a detected portion 42 attached to the rotating shaft 2 . The detector 41 is attached to the casing 5 .

(3. Action and effect)
As described above, the magnetic pole teeth portions 16 and 17 of the electromagnet 11 extend from the back yoke portions 14 and 15 respectively toward the magnetic portion 12 provided on the rotating shaft 2 . Further, in the embodiment, tip portions 16b and 17b are provided on the magnetic portion 12 side of the magnetic pole teeth portions 16 and 17, respectively. Here, as a comparative example, a configuration in which tip portions 16b and 17b are not provided on the magnetic portion 12 side of magnetic pole teeth portions 16 and 17 is considered. FIG. 4 shows the direction of the magnetic flux formed in the electromagnet 11 in the comparative example.

Consider bringing the magnetic pole teeth portions 16 and 17 closer to each other in order to reduce the dimension in the radial direction R of the radial bearing 10 . In the comparative example in which the tip portions 16b and 17b are not provided on the magnetic pole teeth portions 16 and 17, the ends of the magnetic pole teeth portions 16 and 17 on the magnetic portion 12 side are close to each other. At this time, the magnetic flux 201 passing through the magnetic path formed by the back yoke portions 14 and 15, the magnetic pole teeth portions 16 and 17, and the magnetic portion 12 decreases, while the magnetic pole teeth portions 16 17 (leakage magnetic flux) 202 increases. As the leakage magnetic flux increases, the attractive force of the electromagnet 11 decreases. 18 and 19), there is a problem that the radial bearing 10 becomes large.

In form 1 , the tip portions 16b and 17b extend from the base portions 16a and 17a toward the magnetic portion 12 so that the distance between the magnetic pole teeth portions 16 and 17 widens. are not adjacent to each other. As a result, the generation of leakage magnetic flux is suppressed, the magnetic flux 101 passing through the magnetic path formed by the magnetic pole teeth portions 16 and 17, the back yoke portions 14 and 15, and the magnetic portion 12 is maintained, and the attractive force of the electromagnet 11 is reduced. is suppressed or prevented. In this way, it is possible to reduce the size of the radial bearing 10 in the radial direction R while maintaining the attractive force of the electromagnet 11 .

Further, if the shape of the coils 18 and 19 is changed (if the shape of the coils 18 and 19 is made smaller in the axial direction Z), the radial dimension of the radial bearing 10 in the radial direction R can be maintained while the radial bearing 10 can be moved in the axial direction Z. It is also possible to reduce the size to As a result, the natural frequency of the rotating shaft 2 is increased, and the rotating shaft 2 can be rotated at a higher speed.

Further, in form 1 , the back yoke portions 14 and 15 of the electromagnet 11 are divided for each magnetic pole tooth portion. As a result, the winding of the coils 18 and 19 becomes easier than in the case where the back yoke portion is not divided, for example, and the occupied area of the coils 18 and 19 in the cross section taken along the axial direction Z is increased to increase the electromagnet. 11 suction force can be increased. In other words, the shape of the coils 18 and 19 can be reduced in the axial direction Z while maintaining the attractive force of the electromagnet 11, and as described above, the rotating shaft 2 can be rotated at a higher speed.

Further, the detected portion 13b of the displacement sensor 13 is provided on the outer peripheral surface of the magnetic portion 12 or the rotating shaft 2, and the detecting portion 13a is positioned so as to face the detected portion 8b at a position overlapping the electromagnet 11 in the radial direction R. Since they are arranged, the size of the radial bearing 10 can be reduced in the axial direction Z by the amount of overlap between the detection part 13a and the electromagnet 11, and as described above, the rotary shaft 2 can be rotated at a higher speed.

embodiment.
FIG. 5 is a cross-sectional view of the radial bearing 10 according to the embodiment of the present invention as seen from the axial direction Z. As shown in FIG. The embodiment has the same or corresponding configuration as form 1 , except for the points described below. In the description of the embodiment , the same reference numerals are given to the configurations that are the same as or correspond to those of the first embodiment .

In the embodiment , eight electromagnets 11A, 11B, 11C, 11D, 11E, 11F, 11G, and 11H are arranged side by side in the circumferential direction. The eight electromagnets have the same shape. As for the sensor 13, as in FIG. 2, four detectors 13a are arranged uniformly in the circumferential direction at angular intervals of 90°. In the embodiment , reference numerals 14, 16, and 18 are attached to the back yoke portion, the magnetic pole tooth portion, and the coil on the side closer to the detection portion 13a of the sensor 13 (hereinafter referred to as the detection portion side). Reference numerals 15, 17, and 19 are attached to the back yoke portion and the magnetic pole tooth portion on the far side (hereinafter referred to as the anti-detecting portion side), respectively.

In the embodiment , the circumferential length of the back yoke portion 14 on the detection portion side is greater than the circumferential length of the back yoke portion 15 on the anti-detection portion side. In the embodiment , the distance between the tip portions 16b and 17b of the magnetic pole teeth portions 16 and 17 is maintained from the base portions 16a and 17a toward the magnetic portion 12 of the rotating shaft 2 (that is, the distance is constant). is substantially constant). In FIG. 5, the bending angle of the tip 16b of the magnetic pole tooth 16 on the detection side with respect to the base 16a is larger than the bending angle of the tip 17b of the magnetic pole tooth 17 on the anti-detection side with respect to the base 17a. Thus, the tip portions 16b and 17b extend from the base portions 16a and 17a toward the magnetic portion 12 of the rotating shaft 2 so that the distance between the magnetic pole teeth portions 16 and 17 is kept constant.

In the embodiment , if the arrangement in the cross section of the radial bearing 10 taken along the axial direction Z is allowed, the tip portions 16b and 17b are arranged so that the distance between the magnetic pole teeth portions 16 and 17 from the base portions 16a and 17a toward the magnetic portion 12 is is maintained (that is, the distance between the two is constant or substantially constant).

According to the embodiment , even when five or more electromagnets 11 are provided in the radial bearing 10, the effects described in the first embodiment can be obtained.

Other embodiment.
Although the present invention has been described using embodiments, it should be understood that the present invention is not limited to the embodiments described above. Moreover, the features described in each embodiment may be freely combined. Also, various improvements, design changes, and omissions may be made to the above-described embodiments.

For example, in the above-described embodiment, the tip portions 16b and 17b of the magnetic pole teeth portions 16 and 17 of one electromagnet 11 are bent with respect to the base portions 16a and 17a, so that the distance between them is increased from the base portions 16a and 17a to the rotation axis. An example of spreading or maintaining toward two magnetic portions 12 has been described. The present invention is not limited to this, and the tip portions 16b and 17b of the magnetic pole teeth portions 16 and 17 of one electromagnet 11 are, for example, notched in the surfaces facing each other so that the distance between the two is increased from the base portions 16a and 17a. It may extend or be maintained toward the magnetic portion 12 .

Further, in the above-described embodiment, the example in which the back yoke portions 14 and 15 of the electromagnet 11 are divided into the magnetic pole tooth portions 16 and 17 has been described. The present invention is not limited to this. For example, the back yoke portion may be divided for each electromagnet 11 as shown in FIG. It may be divided with one back yoke portion as one unit. Also, the back yoke portions 14 and 15 may not be divided and may be integrated over the entire circumference of the radial bearing 10 .

In the above-described embodiment, a type (heteropolar type) radial magnetic bearing in which a magnetic path is formed in a plane perpendicular to the rotating shaft 2 is used. The present invention is not limited to this, and may be, for example, a type (homopolar type) radial magnetic bearing in which a magnetic path is formed in a plane parallel to the rotating shaft 2 .

In the above-described embodiment, eddy current sensors are used as the displacement sensor 13 of the radial bearing 10 and the displacement sensor 23 of the thrust bearing 20 . The present invention is not limited to this and, for example, a capacitive sensor may be used.

In the above-described embodiment, the radial bearing 10 is provided with a pair of displacement sensors 13, 13 facing each other across the rotating shaft 2, and the differential between the outputs of the two displacement sensors is obtained. The present invention is not limited to this, and only one of the pair of displacement sensors 13, 13 may be provided.

Further, in the above-described embodiment, an example in which four ( form 1 ) or eight ( embodiment ) electromagnets 11 are used for one radial bearing 10 has been described. The present invention is not so limited and may use 1 to 3, 5 to 7, or 9 or more electromagnets 11 .

Reference Signs List 1 Blower 2 Rotating shaft 3 Motor 4 Blades 5 Casing 6 Stator 7 Rotor 10 Radial magnetic bearing 11 Electromagnet 12 Magnetic part 13 Displacement sensor 13a Detecting part 13b Part to be detected 14,15 back yoke portion 16, 17 magnetic pole tooth portion 16a, 17a base portion 16b, 17b tip portion 18, 19 coil 20 thrust magnetic bearing 21 thrust disk 22 (22a, 22b) electromagnet 23 displacement sensor 24a, 24b coil, 30 (31, 32) touchdown bearing, 40 speed sensor

Claims (3)

A radial magnetic bearing for supporting a rotating body from the radially outer side without contact,
A plurality of electromagnets provided facing the rotating body and generating magnetic flux for supporting the rotating body,
Each of the plurality of electromagnets includes a back yoke portion, a pair of magnetic pole tooth portions forming a magnetic path together with the back yoke portion and the rotor, and a coil wound around each of the pair of magnetic pole tooth portions. and
Each of the pair of magnetic pole teeth has a base portion extending from the back yoke portion such that the gap between the pair of magnetic pole teeth is narrowed, and a gap between the pair of magnetic pole teeth is maintained from the base toward the rotating body. and a tip extending so as to be
a plurality of displacement sensors arranged uniformly in the circumferential direction of the rotating body for detecting displacement in the radial direction of the rotating body;
the plurality of electromagnets include a first electromagnet and a second electromagnet arranged with the displacement sensor sandwiched therebetween in the circumferential direction of the rotating body;
The plurality of electromagnets includes a third electromagnet positioned adjacent to the first electromagnet;
The first magnetic pole tooth portion of the first electromagnet and the second magnetic pole tooth portion of the third electromagnet are adjacent to each other,
Each of the first and second magnetic pole teeth has a base extending from the back yoke so that the distance between the first and second magnetic pole teeth narrows, and the first and second magnetic pole teeth extending from the base toward the rotor. and a tip portion that is bent with respect to the base portion so that the interval between the second magnetic pole tooth portions is maintained.
Radial magnetic bearing. The back yoke of each electromagnet is divided for each magnetic pole tooth,
A radial magnetic bearing according to claim 1. a rotating shaft of a motor as the rotating body;
A radial magnetic bearing according to claim 1 or 2;
A blade fixed to the rotating shaft;
blower with

Images