JP2018194079A - Thrust magnetic bearing and blower - Google Patents

Abstract

To provide a thrust magnetic bearing capable of making a size in an axial direction smaller for achieving miniaturization without increasing a size in a radial direction, and a blower thereof.SOLUTION: A thrust magnetic bearing includes a rotation shaft rotating around a center axis, a disk shaped disk arranged at a periphery of the rotation shaft coaxially with th rotation shaft, two electromagnets arranged facing each other while sandwiching the disk in the center axis direction and each having a magnetic pole and a core, a sensor arranged while facing the disk in the center axis direction and measuring a distance to the disk, and a control unit for adjusting a current for supplying the coil of the electromagnet on the basis of the measurement result of the sensor, and contactlessly supports the disk in the center axis direction. The electromagnet includes a gap at a position facing the disk and the sensor is arranged in the gap.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a thrust magnetic bearing for supporting a rotating body in a non-contact manner in the axial direction, and a blower provided with the thrust magnetic bearing.

  Generally, a magnetic bearing device for supporting a rotating shaft such as a blower (or a blower) has a thrust magnetic bearing that supports the rotating shaft in a non-contact manner from the axial direction (thrust direction), and a radial direction of the rotating shaft (radial). Direction) and a radial magnetic bearing supported in a non-contact manner from the outside. Each of the thrust magnetic bearing and the radial magnetic bearing has an electromagnet for generating a magnetic flux for supporting the rotating shaft and a sensor for detecting the displacement of the rotating shaft. Also, a general magnetic bearing device is provided with a touch-down bearing that supports the rotating shaft instead of the magnetic bearing when power supply is stopped or abnormal, a rotation speed sensor for detecting the rotation speed of the rotating shaft, and the like. ing.

JP 2000-216460 A Japanese Utility Model Publication No. 6-085755

  Since a magnetic bearing device including a thrust magnetic bearing and a radial magnetic bearing includes more components than a ball bearing or the like, the axial dimension of the rotating shaft is increased. As the axial dimension of the rotating shaft increases, the natural frequency of the rotating shaft decreases, so that the rotating shaft cannot be rotated at high speed while preventing resonance of the rotating shaft.

  In contrast, for example, Patent Document 1 discloses a thrust magnetic bearing in which a thrust sensor is disposed in a radial gap between a rotating shaft and a thrust magnetic bearing electromagnet. Further, for example, Patent Document 2 discloses a thrust magnetic bearing in which a thrust sensor is disposed on the radially outer side of a thrust magnetic bearing electromagnet. With these configurations, the axial dimension is prevented from being increased by the thrust magnetic bearing and the thrust sensor. However, in these configurations, there is a problem that the arrangement of the thrust magnetic bearing electromagnet or the thrust sensor is expanded in the radial direction, and the size in the radial direction of the thrust magnetic bearing disk installed on the rotating shaft is increased.

  Accordingly, the present invention provides a thrust magnetic bearing and a blower that can solve the above-described problems and can reduce the axial dimension without increasing the radial dimension and achieve downsizing. Objective.

  Therefore, the present invention provides a rotating shaft that rotates around the central axis, a disk-shaped disc that is provided around the rotating shaft and coaxially with the rotating shaft, and two opposingly arranged with the disc in the direction of the central axis. An electromagnet including a magnetic pole and a coil, a sensor that is arranged to face the disk in the direction of the central axis, and that measures the distance from the disk, and supplies the coil of the electromagnet based on the measurement result of the sensor And a thrust magnetic bearing for supporting the disk in the direction of the central axis in a non-contact manner. The electromagnet has a gap at a position facing the disk, and a sensor is disposed in the gap.

  According to the present invention, it is possible to obtain a thrust magnetic bearing and a blower that can reduce the axial dimension without increasing the radial dimension and can achieve downsizing.

It is sectional drawing which shows roughly the whole blower using the thrust magnetic bearing which concerns on Embodiment 1 of this invention. It is sectional drawing which looked at the blower of FIG. 1 in the II-II direction. It is sectional drawing of the thrust magnetic bearing electromagnet which concerns on Embodiment 2 of this invention.

Embodiment 1 FIG.
FIG. 1 is a cross-sectional view of a blower according to Embodiment 1 of the present invention, the whole being represented by 10. The blower 10 includes a rotating shaft 2 that rotates about a central axis X and a casing 1 that covers the periphery of the rotating shaft 2. A motor rotor 5 is attached around the rotary shaft 2. A motor stator 4 is provided outside the motor rotor 5 so as to surround the motor rotor 5 from the radial direction. By the motor stator 4, the motor rotor 5 and the rotating shaft 2 rotate around the central axis X. Blades 3 are attached to both ends of the rotating shaft 2 in the axial direction.

  In this specification, the direction parallel to the central axis X (the left-right direction in FIG. 1) may be referred to as the axial direction, the direction perpendicular to the axial direction as the radial direction, and the circumferential direction around the axis as the circumferential direction. is there.

  The rotating shaft 2 is supported by two radial magnetic bearings 100 and a thrust magnetic bearing 200. The two radial magnetic bearings 100 control two degrees of freedom in the radial direction and two degrees of freedom of inclination. The thrust magnetic bearing 200 controls one degree of freedom in the axial direction. That is, the blower 10 includes a so-called 5-axis control type magnetic bearing device. Further, the blower 10 includes touchdown bearings 13 and 14. The detailed configuration of each bearing will be described later.

  Each radial magnetic bearing 100 includes four radial magnetic bearing electromagnets 110 attached to the casing 1, a radial magnetic bearing rotor 120 attached to the rotating shaft 2, and a radial sensor 130.

  The radial magnetic bearing rotor 120 is formed of, for example, a laminated steel plate in order to suppress iron loss.

  The radial magnetic bearing electromagnets 110 are spaced radially apart from the radial magnetic bearing rotor 120 by a small predetermined dimension and spaced by 90 ° from each other so as to surround the radial magnetic bearing rotor 120. Are arranged in four directions.

  Each of the radial magnetic bearing electromagnets 110 includes two magnetic poles 112. The magnetic pole 112 is made of a magnetic material such as iron. A coil 116 is wound around the magnetic pole 112. Two magnetic poles 112 adjacent to each other form a pair, and currents in opposite directions are passed through the coils 116 wound around the pair of magnetic poles to constitute one magnetic circuit (radial magnetic bearing electromagnet 110). In this way, an attractive force is generated between the radial magnetic bearing rotor 120 and the magnetic pole 112.

  Four radial sensors 130 are arranged around the rotation axis 2 with an angular interval of 90 ° in the circumferential direction, for example. The radial sensor 130 is disposed, for example, at a 45 ° interval in the circumferential direction with respect to the radial magnetic bearing electromagnet. The radial sensor 130 measures the radial distance from the radial sensor 130 to the rotating shaft 2, and a control unit (not shown) connected to the radial sensor 130 determines the diameter of the rotating shaft 2 based on the measurement result. Calculate the displacement in the direction. Based on the calculated displacement, the control unit controls the current flowing through the coil 116, that is, the magnetic attraction force by which the radial magnetic bearing electromagnet 110 pulls the radial magnetic bearing rotor 120 by the footback control, and the radial magnetic bearing rotor. As a result, the radial position of the rotary shaft 2 is maintained at a desired position. In this manner, the radial magnetic bearing electromagnet 110 can support the radial magnetic bearing rotor 120 in a non-contact manner.

  The radial sensor 130 may be a general-purpose eddy current sensor, a capacitance sensor, or another sensor.

  As shown in FIG. 1, a pair of radial sensors 130 are arranged so as to face each other in the radial direction with the rotating shaft 2 interposed therebetween, and a sensor (not shown) resulting from a change in environmental temperature is detected by detecting the difference between the outputs of the two sensors. Measurement errors due to coil, cable, and amplifier drift can be reduced.

  The number of magnetic poles of the radial magnetic bearing electromagnet 110 is not limited to the eight poles as described above, but has two, four, six, eight, ten, twelve, fourteen, sixteen or more. May be. Further, in the above, the radial magnetic bearing 100 is a heteropolar type in which magnetic circuits are arranged in a circumferential direction in a plane perpendicular to the rotating shaft 2 (N poles and S poles are alternately arranged along the circumferential direction). However, it may be a shape (homopolar type) in which the magnetic circuit is arranged in a plane parallel to the rotation axis 2.

  The thrust magnetic bearing 200 includes a disc 260 attached to the rotary shaft 2, two thrust magnetic bearing electromagnets 220 and 240 that are attached to the casing 1 and face each other across the disc 260, and thrust magnetic bearing electromagnets 220 and 240. And a thrust sensor 280 disposed in each of the gaps 230 and 250.

  The disk 260 is attached to the rotary shaft 2 so as to be perpendicular to the central axis X, and has a disk shape centered on the central axis X when viewed in the axial direction. Therefore, the disk 260 rotates as the rotating shaft 2 rotates. The disk 260 is made of a ferromagnetic material.

  The thrust magnetic bearing electromagnets 220 and 240 are arranged perpendicularly to the central axis X and opposite to each other with the disk 260 interposed therebetween. Therefore, the thrust magnetic bearing electromagnets 220 and 240 are arranged so as to be parallel to the disk 260 when viewed from the radial direction. Further, the thrust magnetic bearing electromagnets 220 and 240 are arranged with a small predetermined gap from the axial surface of the disk 260, respectively.

  FIG. 2 is a cross-sectional view of the blower 10 of FIG. 1 as viewed in the II-II direction, and shows a cross section of the thrust magnetic bearing electromagnet 220. The thrust magnetic bearing electromagnet 220 has a gap 230 for disposing the thrust sensor 280 in a part of the annular shape surrounding the rotating shaft 2 in the circumferential direction. That is, as shown in FIG. 2, the cross section obtained by cutting the thrust magnetic bearing electromagnet 220 perpendicularly to the central axis X has a C-shape when viewed from the axial direction.

  The thrust magnetic bearing electromagnet 220 includes a magnetic pole 224 and a coil 226 made of a magnetic material such as iron. The magnetic pole 224 is provided with two grooves for accommodating the coil along the circumferential direction. This is different from a single thrust magnetic bearing having a single groove. The opening of the groove faces the direction of the disk 260 when the thrust magnetic bearing electromagnet 220 is disposed in the blower 10. Specifically, as shown in FIG. 2, a coil 226 is wound in a C-shape in a double groove. When the part below the rotating shaft 2 in the cross section of the magnetic poles 224 and 244 in FIG. 1 is seen, it can be seen that there are two grooves. Note that neither the magnetic pole nor the coil exists in the region of the gap 230. In other words, the annular magnetic pole 224 having two grooves has a gap 230 in a part of the circumferential direction, and the coil 226 passes through both of the two grooves. Further, it is wound so as not to pass through the gap portion 230.

  The thrust magnetic bearing electromagnet 240 also has the same structure as the thrust magnetic bearing electromagnet 220.

  As described above, the thrust magnetic bearing electromagnets 220 and 240 are arranged to face each other so as to sandwich the disk 260, and the openings of the grooves provided in the magnetic poles 224 and 244 face the disk 260. Therefore, when a current is supplied to the coils 226 and 246 disposed in the groove, a magnetic attractive force is generated, and the thrust magnetic bearing electromagnets 220 and 240 pull the disk 260.

  As shown in FIG. 1, the two thrust sensors 280 are disposed in the gap portions 230 and 250. The thrust sensor 280 measures the axial distance from the thrust sensor 280 to the disk 260. A control unit (not shown) connected to the thrust sensor 280 calculates the axial displacement of the disk 260 (that is, the axial displacement of the rotary shaft 2) based on the measurement result. Based on the calculated displacement, the control unit controls the current supplied to the coils 226 and 246, that is, the magnetic attraction force by which the thrust magnetic bearing electromagnets 220 and 240 pull the disk 260 based on the footback control. As a result, the axial position of the rotating shaft 2 is maintained at a desired position. In this way, the thrust magnetic bearing electromagnets 220 and 240 can support the disk 260 in a non-contact manner.

  Although two thrust sensors 280 are provided in FIG. 1, only one may be provided. As shown in FIG. 1, the advantage of the configuration in which the two thrust sensors 280 are arranged so as to face each other in the axial direction with the disk 260 interposed therebetween, and the advantage of detecting the difference between the outputs of the two sensors is not shown in FIG. It is possible to reduce measurement errors due to drift of sensor coils, cables, and amplifiers.

  The thrust sensor 280 is, for example, a general-purpose eddy current sensor.

  As shown in FIG. 1, the touchdown bearings 13 and 14 are attached to the casing 1. The touchdown bearings 13 and 14 are formed by the radial magnetic bearing 100 or the thrust magnetic bearing 200, for example, when power supply to the radial magnetic bearing electromagnet 110 or the thrust magnetic bearing electromagnet 220 or 240 is stopped or when an abnormality occurs. When the non-contact support state of the rotating shaft 2 cannot be maintained, the rotating shaft 2 is supported instead. The touchdown bearings 13 and 14 regulate the movable range in the axial direction and the radial direction of the rotary shaft 2. The touchdown bearings 13 and 14 mechanically support the rotary shaft 2 at the extreme position of the movable range. The touch-down bearing 13 has a configuration in which two angular ball bearings that face each other are used to support both the radial direction and the axial direction. On the other hand, the touchdown bearing 14 supports only the radial direction and has a configuration in which a deep groove ball bearing is used. In addition, the cross section of the touchdown bearings 13 and 14 in FIG. 1 shows the outline.

  The rotation speed sensor 12 is attached to the casing 1 and can detect (measure) the rotation speed of the rotary shaft 2. The rotation speed sensor 12 includes a permanent magnet as a detected portion and a Hall element or the like as a detecting portion, or includes a reflecting portion and a non-reflecting portion as a detecting portion, and a light projecting portion and a light receiving portion as detecting portions. It may be an optical sensor or the like.

  In addition, since the thrust magnetic bearing electromagnets 220 and 240 are C-shaped, the coil occupation area is reduced and the attractive force is reduced when compared with an annular shape having the same inner diameter and outer diameter. there's a possibility that. However, when the radial thickness of the thrust magnetic bearing electromagnets 220 and 240 is smaller than the circumferential length of the inner diameter of the thrust magnetic bearing electromagnets 220 and 240, the coil occupation area that is reduced by the C-shaped configuration is conventionally reduced. This is considered to be smaller than the coil occupying area which is reduced when the thrust magnetic bearing electromagnet is made smaller in the radial direction as in the technology and the thrust sensor is arranged on the outer side in the radial direction of the thrust magnetic bearing electromagnet. Therefore, a decrease in magnetic attractive force is not a problem. Therefore, it is possible to reduce the size of the magnetic bearing device.

  As described above, the thrust sensor 280 is not disposed inside or outside the thrust magnetic bearing electromagnets 220 and 240 but inside the gaps 230 and 250, so that the radial dimension of the thrust magnetic bearing can be reduced. The size in the axial direction can be reduced without increasing it. Therefore, it is possible to reduce the size of the thrust magnetic bearing and the blower including the thrust magnetic bearing.

  Further, the blower having the thrust magnetic bearing device as described above can increase the natural frequency of the rotary shaft 2 in order to reduce the weight of the thrust magnetic bearing disk, and therefore can withstand higher speed rotation. it can.

Embodiment 2. FIG.
3 is a cross-sectional view of a thrust magnetic bearing electromagnet 320 according to Embodiment 2 of the present invention at the same position as II-II in FIG. In the following description, differences from the first embodiment will be mainly described, and redundant description of other parts will be omitted in principle. Among the components in FIG. 3, the same reference numerals as those in FIGS. 1 and 2 are used for the same components as those in FIGS.

  The second embodiment differs from the first embodiment only in the configuration of the thrust magnetic bearing electromagnet. In the second embodiment, the magnetic poles of the thrust magnetic bearing electromagnet 320 are formed by assembling a plurality of magnetic poles. That is, as shown in FIG. 3, the thrust magnetic bearing electromagnet 320 includes a first electromagnet piece 322 and a second electromagnet piece 332. The electromagnet pieces 322 and 332 substantially cut the C-shaped thrust magnetic bearing electromagnet 220 of Embodiment 1 through a plane that passes through the radial center and the center of the gap 230 and is perpendicular to the radial direction. It is a shape (half-cracked shape) like that. In other words, when the half-cracked electromagnet pieces 322 and 332 are combined, a sufficient gap portion 330 for arranging the thrust sensor 280 is provided. The half-cracked coil structure has the advantage that it is easier to manufacture than the C-shaped coil structure. Further, the half-cracked structure can be assembled in the radial direction with respect to the rotating shaft 2 to form the thrust magnetic bearing electromagnet 320, and thus has an advantage of being easily assembled and disassembled.

  The thrust magnetic bearing electromagnet 320 has substantially the same structure as the thrust magnetic bearing electromagnet 220 except that it has a half crack shape. That is, the first electromagnet piece 322 of the thrust magnetic bearing electromagnet 220 includes the magnetic pole 324 and the coil 326 made of a magnetic material such as iron, and the second electromagnet piece 332 includes the magnetic pole 334 and the coil 336. The magnetic poles 324 and 334 are provided with double grooves for winding the coil. By supplying the same current to the coil 326 and the coil 336, the electromagnet pieces 322 and 332 function as one thrust magnetic bearing electromagnet 320.

  The thrust sensor 280 is disposed in the gap portion 330.

  Hereinafter, as described in the first embodiment, the control unit (not shown) calculates the axial displacement of the disk 260 based on the measurement result of the thrust sensor 280, and the coil 326, The current supplied to 336 is controlled. In this way, the thrust magnetic bearing electromagnet 320 can support the disk 260 in a non-contact manner.

  In the above description, the thrust magnetic bearing electromagnet 320 has been described as a half-cracked shape composed of two electromagnet pieces, but may have a structure composed of three or more electromagnet pieces.

  As described above, in the second embodiment, in addition to the effect shown in the first embodiment, there is an advantage that the shape of the coil is simple and the manufacture is easy. Moreover, since the electromagnet has a half-crack shape, the rotary shaft 2 can be assembled and disassembled from the radial direction and has excellent assemblability.

  1 casing, 2 rotating shafts, 3 blades, 4 motor stator, 5 motor rotor, 10 blower, 12 speed sensor, 13, 14 touchdown bearing, 100 radial magnetic bearing, 110 radial magnetic bearing electromagnet, 112 magnetic pole, 116 coil, 120 Radial magnetic bearing rotor, 130 Radial sensor, 200 Thrust magnetic bearing, 220, 240 Thrust magnetic bearing electromagnet, 224, 244 Magnetic pole, 226, 246 Coil, 230, 250 Gap, 260 Disc, 280 Thrust sensor, 320 Thrust magnetic bearing electromagnet 322, 332 Electromagnet piece, 324, 334 Magnetic pole, 326, 336 Coil, 330 Gap.

Claims (6)

A rotation axis that rotates about a central axis;
A disc-shaped disc provided coaxially with the rotating shaft around the rotating shaft;
Two electromagnets arranged opposite to each other across the disk in the direction of the central axis, the electromagnet including a magnetic pole and a coil;
A sensor that is disposed opposite to the disk in the direction of the central axis and measures a distance from the disk;
A control unit that adjusts a current supplied to the coil of the electromagnet based on a measurement result of the sensor, and a thrust magnetic bearing that supports the disk in the direction of the central axis in a non-contact manner,
The thrust magnet bearing according to claim 1, wherein the electromagnet has a gap portion at a position facing the disk, and the sensor is disposed in the gap portion.   2. The control unit according to claim 1, wherein the controller calculates an axial displacement of the disk based on a measurement result of the sensor, and adjusts a current supplied to the coil based on the displacement. Thrust magnetic bearings.   3. The thrust magnet according to claim 1, wherein the magnetic pole has two grooves formed along a circumferential direction centered on the central axis on one side surface in the axial direction. bearing.   The thrust magnetic bearing according to claim 3, wherein the coil is wound in the groove.   The electromagnet includes a plurality of electromagnet pieces divided along the direction of the central axis, and the coil is wound in the electromagnet pieces. Thrust magnetic bearings.   A blower comprising: the thrust magnetic bearing according to any one of claims 1 to 5; a radial magnetic bearing that supports the rotating shaft around the central shaft in a non-contact manner; and a blade attached to the rotating shaft.

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