JP5074350B2 - Magnetic bearing - Google Patents

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 hybrid type magnetic bearing that uses a bias magnetic flux from a permanent magnet to reduce power consumption of an electromagnet.

  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, a hybrid type magnetic bearing using a bias magnetic flux of a permanent magnet whose performance is significantly improved has been used. Since the hybrid magnetic bearing uses a bias magnetic flux generated by a permanent magnet, there is an advantage that power consumption can be reduced and control characteristics are excellent.

  As this hybrid magnetic bearing, for example, a magnetic bearing disclosed in Patent Document 1 is known. This magnetic bearing has a plurality of salient poles (electromagnet cores) in which an annular stator that supports a rotor at the center portion projects toward the center rotor and is disposed at a predetermined interval in the circumferential direction. A magnetic circuit for bias magnetic flux is formed in a plane by coupling the base end portions with arc-shaped permanent magnets magnetized in the longitudinal direction.

  However, since this magnetic bearing is mostly occupied by long permanent magnets extending along the magnetic circuit, the overall magnetic resistance is large and the amount of leakage of control flux to the outside of the stator is large. There is a problem of inefficiency.

  Therefore, by using a bias permanent magnet with a thin and large area, the magnetic flux density of the main pole is increased, and the overall magnetic resistance of the magnetic circuit is reduced to reduce the leakage flux to the outside. A type magnetic bearing has also been proposed (Non-Patent Document 1).

FIG. 6 is a cross-sectional view showing this type of magnetic bearing.
The yoke 111 constituting the stator 110 includes four main salient poles 112 arranged at an angle of 90 ° around the rotor 120 so that the tip thereof faces the rotor 120 arranged at the center, and these main salient poles 112. And an annular connecting portion 113 that connects the base end portions of the salient poles 112. An excitation coil 114 is wound around the main salient pole 112 to constitute the main pole. The connecting portion 113 is divided between adjacent main salient poles 112, and a plate-like biasing permanent magnet 116 is inserted between the divided ends 113a. The permanent magnet 116 is thin and wide so as to sufficiently secure the bias magnetic flux indicated by the dotted arrow in the figure and to reduce the magnetic resistance to the control magnetic flux indicated by the solid arrow in the figure. The divided ends also have a shape projecting inward so as to cover both surfaces of the permanent magnet 116 for bias. In this magnetic bearing, the excitation control of the rotor 120 is performed by controlling the exciting coil 114 to generate a difference in magnetic attraction force between two opposing main poles.
JP 2001-041238 A (paragraphs 0011 to 0014, FIG. 1) “Development and Application of Parallel Permanent Magnet Type Hybrid Magnetic Bearing”, Koji Sagawa et al., Transactions of the Japan Society of Mechanical Engineers, Reprint, Volume 73, 733C, p81-87, Japan Society of Mechanical Engineers

In the conventional magnetic bearing described above, in order to secure a sufficient bias magnetic flux, it is necessary to extend the permanent magnet to the rotor side and increase the magnetic pole surface of the permanent magnet. There is a problem that the leakage magnetic flux to the rotor side increases and the bias magnetic flux cannot be strengthened, and at the same time, the negative spring force due to the leakage magnetic flux increases and adversely affects the control by the electromagnet.
In addition, since the split end that sandwiches the yoke permanent magnet needs to be extended to the rotor side, there is a problem that it is difficult to attach the exciting coil to the main salient pole.

  The present invention has been made in view of such problems, and provides a hybrid type magnetic bearing that can obtain a sufficient bias magnetic flux, has excellent controllability, and can be further reduced in size and weight. Objective.

  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 and rotated in a non-contact state, and the stator projects in a radial direction toward the rotor. A plurality of main poles having exciting coils whose leading magnetic flux concentrating portions face the rotor via a predetermined gap; a connecting part that connects base ends of the plurality of main poles in the circumferential direction; and the connecting part And is arranged along the radial direction so that one end protrudes from the connecting portion toward the rotor, and one surface is magnetized in the thickness direction with the first surface as the first polarity and the other surface as the second polarity. A plate-shaped biasing permanent magnet, and the one side of the radial protruding portion from the connecting portion of the biasing permanent magnet, the rotor side being a second polarity, and the connecting portion side being a first polarity First magnetic flux absorbing magnet And a second magnetic flux absorbing member disposed on the other surface side of the radially projecting portion of the biasing permanent magnet from the connecting portion and having the rotor side as a first polarity and the connecting portion side as a second polarity. And a magnet.

  The magnetic bearing according to the present invention is also a magnetic bearing having a stator and a rotor that rotates while being supported by the stator in a non-contact state by a magnetic force. The stator includes an annular connecting portion and an inner portion of the connecting portion. It has an even number of main salient poles that protrude from the circumferential side toward the center and are arranged at regular intervals in the circumferential direction of the connecting portion, and is divided at a position where the connecting portion deviates from the main salient pole in the circumferential direction. A yoke made of magnetic material, an exciting coil wound around the main salient pole, and inserted between the split ends of the connecting portion so that one end protrudes from the connecting portion toward the rotor. A plate-like bias permanent magnet that is arranged along the radial direction and supplies a bias magnetic flux magnetized in the thickness direction with one surface being a first polarity and the other surface being a second polarity; Radial protrusion from the connecting part A first magnetic flux absorbing magnet disposed on the one surface side and having the rotor side as the second polarity and the connecting portion side as the first polarity, and a radial protruding portion from the connecting portion of the biasing permanent magnet And a second magnetic flux absorbing magnet that is disposed on the other surface side and has the rotor side as a first polarity and the connecting portion side as a second polarity.

  In one embodiment of the present invention, the split end of the connecting portion protrudes toward the rotor. In another embodiment of the present invention, the first and second magnetic flux absorbing magnets cover the entire surfaces of the radially projecting portion from the connecting portion of the biasing permanent magnet.

  In still another embodiment of the present invention, the biasing permanent magnet protrudes from the connecting portion over the entire circumference, and the first magnetic flux absorbing magnet is the above-mentioned protruding portion of the biasing permanent magnet. Arranged on one surface side, magnetized with the second polarity on the outer side and the first polarity on the inner side, the second magnetic flux absorbing magnet is on the other surface side of the protruding portion of the permanent magnet for biasing It is characterized by being magnetized with the first polarity on the outside and the second polarity on the inside.

  In still another embodiment of the present invention, a magnetic flux detecting element is provided on a surface of the first and second magnetic flux absorbing magnets facing the rotor.

According to the present invention, both sides of the radial projection of the plate-shaped biasing permanent magnet that is inserted into the coupling portion and has one end projecting from the coupling portion toward the rotor are opposite in polarity to the magnetized surface of the biasing permanent magnet. Since the first and second magnetic flux absorbing magnets are arranged with the same polarity on the rotor side and the same polarity as the connecting portion side, the magnetic flux that leaks from the biasing permanent magnet to the rotor side is the first and second magnetic fluxes. The magnetic flux absorbing magnet is returned to the stator side. As a result, the leakage flux to the rotor side is reduced, and the bias flux density on the stator side can be further increased, so that the bias flux can be strengthened and the negative spring force due to the leakage flux can be reduced, enabling good bearing control. become.
In addition, since the protruding portion of the biasing permanent magnet to the rotor is sandwiched between the first and second magnetic flux absorbing magnets, there is no need to form a large protruding portion on the rotor side of the connecting portion. Thus, it is easy to mount the exciting coil on the main salient pole, and the magnetic bearing can be easily assembled.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a sectional view showing the configuration of a four-pole magnetic bearing according to the first embodiment of the present invention.
The magnetic bearing has an annular stator 10 disposed outside and a rotor 20 disposed inside the stator 10.
The stator 10 includes an annular yoke 11, an excitation coil 14, a biasing permanent magnet 15, first and second magnetic flux absorbing magnets 16 and 17, and a magnetic flux detection element 18.

  The yoke 11 is made of, for example, a magnetic material such as a laminated steel plate, and has an annular connecting part 12 and four main parts protruding from the inner peripheral side of the connecting part 12 toward the center and arranged at intervals of 90 ° in the circumferential direction. And a salient pole portion 13. An excitation coil 14 is wound around each of the four main salient pole portions 13, and the excitation coil 14 and the main salient pole portion 13 constitute a main pole. The connecting portion 12 is divided at a position shifted by 45 ° in the circumferential direction with respect to the four main salient pole portions 13. The split end 12 a of the connecting portion 12 projects radially toward the rotor 20.

  A plate-like biasing permanent magnet 15 is inserted between the adjacent divided ends 12 a of the connecting portion 12. The permanent magnet for bias 15 is arranged along the radial direction so that one end (side surface) protrudes in the radial direction from the inner peripheral side of the split end 12a of the connecting portion 12 toward the rotor 2, and one surface thereof Is magnetized in the thickness direction, with the S pole as the other and the N pole as the other surface.

First and second magnetic flux absorbing magnets 16 and 17 are arranged at a portion of the biasing permanent magnet 15 protruding from the connecting portion 12 toward the rotor 20 so as to be sandwiched from both surfaces. The first magnetic flux absorbing magnet 16 is in close contact with the south pole surface of the biasing permanent magnet 15 and is magnetized in the radial direction so that the rotor 20 side is the north pole and the yoke 11 side is the south pole. The second magnetic flux absorbing magnet 17 is in close contact with the N pole surface of the bias permanent magnet 16 and is magnetized in the radial direction so that the rotor 20 side is the S pole and the yoke 11 side is the N pole. Yes.
A magnetic flux detecting element 18 such as a Hall element is provided on the end face of the first and second magnetic flux absorbing magnets 16 and 17 on the rotor 20 side.
On the other hand, the rotor 20 has a magnetic body such as a laminated steel plate or electromagnetic material disposed at least on the outer peripheral portion, and is disposed rotatably inside the stator 10 via a predetermined gap from the tip of the main salient pole portion 12. Yes.

  According to such a magnetic bearing, as indicated by a dotted arrow in FIG. 1, the bias magnetic flux generated by the biasing permanent magnet 15 causes the N pole surface of the biasing permanent magnet 15, the connecting portion 12, and the main salient pole 13. A magnetic circuit reaching the S pole surface of the permanent magnet for bias 15 through the rotor 20, the main salient pole 13 and the connecting portion 12 is formed. Then, by controlling the exciting coil 14 wound around the main salient pole 13 to generate a control magnetic flux as shown by a solid line arrow in FIG. 1, for example, the main pole located on the upper side in the figure strengthens the magnetic flux, Since the main pole located on the lower side weakens the magnetic flux, a difference in magnetic attraction force is generated between the upper and lower main salient poles 13 and an upward force is generated in the rotor 20. By applying this to the two radial directions, the radial direction can be controlled.

  In the magnetic bearing according to the present embodiment, half of the biasing permanent magnet 15 protrudes from the yoke 11 to the rotor 20 side, and the first and second magnets magnetized in the radial direction are formed on both surfaces of the protruding portion. The second magnetic flux absorbing magnets 16 and 17 are arranged, and the magnetic flux absorbing magnets 16 and 17 have a function of confining the bias magnetic flux to the yoke 11 side. For this reason, it is possible to effectively prevent the magnetic flux from leaking to the rotor 20 side, and at the same time, the magnetic flux absorbing magnets 16 and 17 can also increase the magnetic flux density of the bias magnetic flux in the yoke 11, so that efficient control can be achieved. Is possible. According to this configuration, it is not necessary to use an expensive rare earth magnet, and a sufficient magnetic flux density can be obtained even with an inexpensive ferrite magnet.

Further, according to the magnetic bearing of the present embodiment, the magnetic flux detecting element 18 is attached to the tip of the first and second magnetic flux absorbing magnets 16 and 17 on the rotor 20 side, so that it is not affected by the control magnetic flux. In addition, the displacement of the rotor 20 can be accurately detected.
Furthermore, according to this embodiment, since the protruding amount of the split end 12b of the connecting portion 12 is smaller than that in the conventional example shown in FIG. 6, the excitation coil 14 can be easily wound around the yoke 11 in the split state. By assembling the biasing permanent magnet 15 after the coil 14 is mounted on the main salient pole 13, the magnetic bearing can be easily manufactured.

FIG. 2 is a cross-sectional view showing a configuration of a magnetic bearing according to the second embodiment of the present invention. The previous embodiment was a 4-pole type, but this embodiment has a 6-pole structure.
The stator 30 includes an annular yoke 31, an exciting coil 34, a biasing permanent magnet 35, and first and second magnetic flux absorbing magnets 36 and 37.
The yoke 31 has an annular connecting portion 32 and six main salient poles 33 that protrude from the inner peripheral side of the connecting portion 32 toward the center and are arranged at intervals of 60 ° in the circumferential direction. Other configurations are the same as in the previous embodiment.

  In this way, in the case of the 6-pole structure, unlike the 4-pole structure, the opposing pole pairs are arranged every 120 °, so the control in the xy direction is converted into two-phase three-phase, and U, V, W Although control for each phase is required, a general three-phase inverter used for motor control can be used for this control. FIG. 2 shows an example in which an upward force is generated by strengthening the magnetic flux with the upper two main poles and weakening the magnetic flux with the lower two main poles. Thus, it is desirable that the number of main salient poles is an even number.

FIG. 3 is a cross-sectional view showing a configuration of a magnetic bearing according to the third embodiment of the present invention. This embodiment is an example in which axial control is added to a four-pole structure.
The stator 50 includes an annular yoke 51, a radial control coil 54, an axial control coil 58, a bias permanent magnet 55, and first and second magnetic flux absorbing magnets 56 and 57.

The yoke 51 has an annular connecting portion 52 and four main salient poles 53 that protrude from the inner peripheral side of the connecting portion 52 toward the center and are arranged at intervals of 90 ° in the circumferential direction. As in the above-described embodiments, the main salient pole 53 is wound with a radial control coil 54 for radial control, and as shown in FIG. A groove is formed on the outer periphery of the portion, and an axial control coil 58 for axial control is wound. By making the thickness of the stator 50 slightly larger than the thickness of the rotor 60, the bias magnetic flux indicated by the dotted arrows in FIG.
As shown in the figure, when a current is passed through the axial control coil 58, a control magnetic flux as shown by a solid line arrow in the figure is generated, and the magnetic flux on the left side in the figure strengthens and the magnetic flux on the right side weakens. As a result, a rightward force in the axial direction is generated. Axial control can be performed in addition to radial control by performing this operation on other main poles.

FIG. 4 is a cross-sectional view showing a configuration of a magnetic bearing according to the fourth embodiment of the present invention. The previous embodiment was an inner rotor type, but this embodiment is an outer rotor type. That is, in the present embodiment, the stator 70 is disposed inside the cylindrical rotor 80.
The stator 70 includes a cross-shaped yoke 71, an exciting coil 74, a biasing permanent magnet 75, and first and second magnetic flux absorbing magnets 76 and 77.
The yoke 71 includes four main salient poles 73 that project radially outward from the center and are arranged at intervals of 90 ° in the circumferential direction, and a connecting portion 72 that connects the base ends of the main salient poles 73. Have. A position of the connecting portion 72 that is shifted from the main salient pole 73 by 45 ° in the circumferential direction is divided, and a plate-like biasing permanent magnet 75 is inserted therein. A part of the biasing permanent magnet 75 protrudes outward from the connecting portion 72, and the first and second magnetic flux absorbing magnets 76 and 77 are mounted on both surfaces of the protruding portion.
Also in this embodiment, a magnetic bearing with excellent controllability can be realized as in the previous embodiment.

  FIG. 5 is a cross-sectional view showing a configuration of a magnetic bearing according to the fifth embodiment of the present invention. In this embodiment, the biasing permanent magnet 95 protrudes from the connecting portion 92 over the entire circumference. The first magnetic flux absorbing magnet 96 is an annular magnet that is arranged on the S pole surface side of the protruding portion of the bias permanent magnet 95 and is magnetized with the outer side being the N pole and the inner side being the S pole. The second magnetic flux absorbing magnet 97 is an annular magnet that is arranged on the N pole face side of the protruding portion of the bias permanent magnet 95 and is magnetized with the S pole on the outside and the N pole on the inside. The magnetic flux absorbing magnets 96 and 97 may be a combination of bar magnets.

  According to the present embodiment, magnetic flux leakage can be prevented over the entire circumference of the biasing permanent magnet 95, so that a stronger bias magnetic flux can be formed.

It is sectional drawing of the magnetic bearing which concerns on the 1st Embodiment of this invention. It is sectional drawing of the magnetic bearing which concerns on the 2nd Embodiment of this invention. It is sectional drawing of the magnetic bearing which concerns on the 3rd Embodiment of this invention. It is sectional drawing of the magnetic bearing which concerns on the 4th Embodiment of this invention. It is sectional drawing of the magnetic bearing which concerns on the 5th Embodiment of this invention. It is sectional drawing of the conventional magnetic bearing.

Explanation of symbols

  10, 30, 50, 70, 90, 110 ... stator, 20, 40, 60, 80, 100, 120 ... rotor, 11, 31, 51, 71, 91, 111 ... yoke, 13, 33, 53, 73, 93, 113 ... main salient poles, 14, 34, 74, 94, 114 ... exciting coils, 15, 35, 55, 75, 95, 116 ... permanent magnets for bias, 16, 36, 56, 76, 96 ... 1st magnetic flux absorption magnet, 17, 67, 57, 77, 97 ... 2nd magnetic flux absorption magnet, 18 ... Magnetic flux detection element.

Claims (6)

In a magnetic bearing having a stator and a rotor that is supported and rotated in a non-contact state by magnetic force on the stator,
The stator is
A plurality of main poles having an exciting coil that protrudes in a radial direction toward the rotor and has a magnetic flux concentrating portion at a tip thereof facing the rotor via a predetermined gap;
A connecting portion for connecting the base ends of the plurality of main poles in the circumferential direction;
Inserted into the connecting portion and arranged in the radial direction so that one end protrudes from the connecting portion toward the rotor, and one surface is attached in the thickness direction with the first polarity and the other surface as the second polarity. A magnetized plate-shaped permanent magnet for bias;
A first magnetic flux absorbing magnet which is disposed on the one surface side of the radially projecting portion from the connecting portion of the biasing permanent magnet and has the rotor side as the second polarity and the connecting portion side as the first polarity; ,
A second magnetic flux absorbing magnet disposed on the other surface side of the radially projecting portion from the coupling portion of the biasing permanent magnet and having the rotor side as a first polarity and the coupling portion side as a second polarity; The magnetic bearing characterized by having. In a magnetic bearing having a stator and a rotor that is supported and rotated in a non-contact state by magnetic force on the stator,
The stator is
An annular connecting portion and an even number of main salient poles that protrude from the inner peripheral side of the connecting portion toward the center and that are arranged at regular intervals in the circumferential direction of the connecting portion, the connecting portion being the main impact A yoke made of a magnetic material divided at a position shifted in the circumferential direction from the pole,
An exciting coil wound around the main salient pole;
It is inserted between the split ends of the connecting portion, and one end is arranged along the radial direction so as to protrude from the connecting portion toward the rotor, and one surface has a first polarity and the other surface has a second polarity. A plate-like permanent magnet for bias that supplies a bias magnetic flux magnetized in the thickness direction;
A first magnetic flux absorbing magnet which is disposed on the one surface side of the radially projecting portion from the connecting portion of the biasing permanent magnet and has the rotor side as the second polarity and the connecting portion side as the first polarity; ,
A second magnetic flux absorbing magnet disposed on the other surface side of the radially projecting portion from the coupling portion of the biasing permanent magnet and having the rotor side as a first polarity and the coupling portion side as a second polarity; The magnetic bearing characterized by having.   The magnetic bearing according to claim 2, wherein a split end of the connecting portion protrudes toward the rotor.   The said 1st and 2nd magnet for magnetic flux absorption covers all the both surfaces of the radial direction protrusion part from the said connection part of the said permanent magnet for a bias, The any one of Claims 1-3 characterized by the above-mentioned. The magnetic bearing according to item. The permanent magnet for bias protrudes from the connecting portion over the entire circumference,
The first magnetic flux absorbing magnet is disposed on the one surface side of the projecting portion of the biasing permanent magnet, and is magnetized with a second polarity on the outer side and a first polarity on the inner side,
The second magnetic flux absorbing magnet is disposed on the other surface side of the protruding portion of the biasing permanent magnet, and is magnetized with the outer side being the first polarity and the inner side being the second polarity. The magnetic bearing according to claim 1, wherein:   6. The magnetic bearing according to claim 1, wherein a magnetic flux detecting element is provided on a surface of the first and second magnetic flux absorbing magnets facing the rotor.

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