JP2003148469A - Magnetic bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic bearing device capable of preventing an oscillation in a high frequency area. SOLUTION: Electromagnets X1, X1', Y1, and Y1' in radial direction are formed of the assembly of a plurality of small electromagnets (for example, 401, 402, 409, 410). Since a magnetic paths in the cores of the small electromagnets are rather short, the lowering of inductance in the high frequency area is suppressed, and an electromagnetic force is assured. Thus, the natural frequency of the rotating body 6 in bending mode can be prevented from being excited.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic bearing device.

[0002]

2. Description of the Related Art FIG. 4 is a schematic view of a conventional magnetic bearing device as seen from an axial end of a rotating body. In addition, FIG.
5 is a sectional view taken along line VV in FIG. 4 and 5, the rotating body 101 is a cylindrical stator housing 10
The four electromagnets 103, which are equally arranged on the inner circumference of 2, are supported in a non-contact manner in a magnetically levitated state. The electromagnet 103 includes, for example, a horseshoe-shaped core 103a as shown in FIG.
3b is wound. In the case of a control type magnetic bearing device, the magnetic force of these electromagnets 103 is controlled to rotate the rotor 1.
01 has a position control function of levitating to a desired position. However, the position control of the levitated rotating body 101 is originally an unstable control system, and oscillates if the natural frequency of the bending mode is excited. Therefore, conventionally, an optimum control constant is determined in the control system so as not to excite the natural frequency, and thereby stable levitation of the rotating body 101 is realized.

[0003]

When the conventional magnetic bearing device as described above becomes large in size, the rotating body 101 is accompanied by it.
The electromagnet 103 that attracts is also upsized. The magnetic path of the magnetic flux passing through the core of the electromagnet 103 having such a large size has a long magnetic path, resulting in a large iron loss. Therefore, as the frequency of the current flowing through the coil of the electromagnet 103 becomes higher, the inductance decreases and the electromagnetic force relatively decreases. Therefore, in a high frequency region (for example, 500 Hz or more), even if a predetermined current is passed through the coil to generate a desired electromagnetic force, the desired electromagnetic force cannot be obtained. As a result, there is a problem that the natural frequency of the bending mode existing in the high frequency region is excited and oscillates.

In view of the above-mentioned conventional problems, an object of the present invention is to provide a magnetic bearing device which prevents oscillation in a high frequency region.

[0005]

According to the present invention, in a magnetic bearing device for magnetically non-contact supporting a rotating body by a plurality of sets of electromagnets, the plurality of sets of electromagnets are arranged in the radial direction across the rotating body. Each of the at least one set of electromagnets is composed of an assembly of a plurality of small electromagnets. In the magnetic bearing device configured as described above, since the electromagnet is composed of an assembly of small electromagnets, the magnetic path in the core of the small electromagnet is shorter than that of an appropriately sized electromagnet composed of a single body. Also, there is almost no decrease in inductance even in the high frequency range. Therefore, the reduction of the electromagnetic force in the high frequency region is suppressed, and the excitation of the natural frequency of the bending mode in the rotating body is suppressed.

Further, in the above magnetic bearing device, a displacement sensor may be arranged close to an electromagnet composed of an assembly, and the electromagnetic force of the electromagnet may be controlled based on the output of the displacement sensor. (Claim 2). In this case, the plurality of small electromagnets can be controlled in common or individually based on the output of the displacement sensor.

[0007]

1 is a view of a magnetic bearing device according to an embodiment of the present invention as seen from an axial end of a rotating body (partially cut away and shown). In addition, FIG. 2 corresponds to FIG.
It is a II-II sectional view taken on the line. In FIGS. 1 and 2, a pair of annular members 2 is axially mounted in a cylindrical stator housing 1. In FIG. 2, a plurality of electromagnet mounting seats 3 are fixed between a pair of annular members 2 in the axial direction, and a small electromagnet is attached to each of them.
In this embodiment, eight small electromagnets are equally arranged in the circumferential direction,
In addition, these are provided in two rows in the axial direction (one row: 40
1 to 408, 2 rows: 409 to 416), a total of 16 small electromagnets 401 to 416 are arranged. The small electromagnets 401 to 416 are, for example, a horseshoe-shaped core 4a as shown in FIG. 2 and a coil 4b wound around the core 4a. Further, a total of four displacement sensors 5 are arranged at intervals of 90 degrees in the circumferential direction. The rotating body 6 has these small electromagnets 401 to
It is magnetically supported in a contactless manner by 416.

Here, as shown in FIG.
When the axial direction of is the Z-axis direction (axial direction), and the radial direction orthogonal to this is the X-axis direction and the Y-axis direction (the X-axis and the Y-axis are orthogonal to each other), four small electromagnets 401, The assembly of 402, 409, 410 constitutes one electromagnet X1 as a whole, while the other four electromagnets 4 are arranged.
05, 406, 413, 414 constitute one electromagnet X1 'as a whole. And both electromagnets X1, X1 '
Are arranged to face each other with the rotating body 6 interposed therebetween in the X-axis direction,
By attracting the rotating body 6 with an electromagnetic force, the rotating body 6
Is levitated on the X-axis. Similarly, four small electromagnets 40
7, 408, 415, and 416 constitute one electromagnet Y1 as a whole, while four small electromagnets 403 and 40 are provided.
4,411,412 are one electromagnet Y1 'as a whole
Make up. The two electromagnets Y1, Y1 'are arranged to face each other with the rotor 6 interposed therebetween in the Y-axis direction, and the rotor 6 is attracted by an electromagnetic force to levitate the rotor 6 on the Y-axis. A displacement sensor 5 corresponding to each electromagnet is disposed in the vicinity of an intermediate position in the circumferential direction of each electromagnet X1, X1 ', Y1, Y1' so as to be close to the electromagnet. Is detected. Further, the displacement sensor 5 includes the electromagnets X1, X1 ′, Y1, Y
It is preferable that the axial position of 1'is also arranged at an intermediate position.

Another set of the magnetic bearing device configured as described above is provided at another position in the axial direction of the rotating body 6. Each magnetic bearing device applies an electromagnetic force of electromagnets X1, X1 ', Y1, Y1' to the coil 4b by a control device (not shown) based on the displacement signals of the X-axis and the Y-axis captured by the displacement sensor 5. The rotating body 6 is controlled to be levitated at a desired position by controlling the applied current. In addition,
The electric currents applied to the coils 4b of the small electromagnets of the electromagnets X1, X1 ′, Y1, Y1 ′ may all be commonly applied, or may be applied independently depending on the individual small electromagnets.

FIG. 3 shows the electromagnets X1, X1 ', Y1,
It is a graph which shows the frequency characteristic of an inductance in Y1 '. In the figure, the solid line indicates the electromagnet X in the present embodiment.
1, X1 ', Y1, Y1' are shown, and the broken line shows the characteristics of the conventional electromagnet 103 (FIG. 4) for comparison. As is clear from this graph, in the case of the conventional electromagnet, when the frequency increases from 1 Hz, the inductance gradually decreases up to 500 Hz, and sharply decreases at 500 Hz. On the other hand, the electromagnet X in the present embodiment
In the case of 1, X1 ', Y1, Y1', 1 Hz to 10
Inductance hardly decreases up to about 00Hz,
After that, when the frequency further increases, the frequency gradually decreases.

The difference in characteristics as described above occurs because the electromagnets X1, X1 ', Y1, Y1' are composed of an assembly of small electromagnets, as compared with an electromagnet of a proper size composed of a single body. This is because the magnetic path in the core of the small electromagnet is short and the iron loss is small. That is, such a small electromagnet has a small decrease in inductance even if the frequency increases. Therefore, the electromagnets X1, X in the present embodiment
1 ', Y1, Y1' can be used up to about 1000 Hz as a control band. Therefore, 500-1000Hz
Electromagnets X1, X1 ', even in high frequency range
The electromagnetic forces of Y1 and Y1 'are hardly reduced, and the excitation of the natural frequency of the bending mode of the rotating body 6 existing in the high frequency region can be hindered and the oscillation can be prevented. The characteristic of the electromagnet of the present embodiment is a low level corresponding to about half that of the conventional electromagnet at the DC level (for example, 1 Hz), but this can be easily compensated by increasing the exciting current. Therefore, this point does not pose any problem.

In this embodiment, all electromagnets X1,
Each of X1 ', Y1, and Y1' is configured by a small electromagnet, but only one set of the X-axis and Y-axis electromagnets is configured by an assembly of small electromagnets, and the other sets are the same as those of the conventional one. Even if the electromagnet is composed of a single body, a certain oscillation preventing effect can be obtained. Further, in the present embodiment, two in the circumferential direction,
The electromagnets X1, X1 ', Y1, Y1' were composed of a total of four small electromagnets in two rows in the axial direction, but if necessary, the number of elements of the small electromagnets as an assembly forming the electromagnets. Can be increased or decreased in the radial direction or in the axial direction. Further, in the above embodiment, the displacement sensor 5 is
The electromagnets X1, X1 ', Y1, Y1' are arranged at intermediate positions in the circumferential direction, and the electromagnets X1, X1 ', Y are arranged.
Although it is preferable that the electromagnets X1, X1 ′, Y1, and Y1 ′ are also arranged at intermediate positions in the axial direction,
A configuration may be employed in which a pair of sensors are provided so as to be close to each of Y1 ′ and sandwich the Y1 ′ in the circumferential direction or the axial direction, and the displacement of the rotating body 6 at the position corresponding to each electromagnet is obtained by calculation.

[0013]

The magnetic bearing device of the present invention constructed as described above has the following effects. According to the magnetic bearing device of claim 1, since the electromagnet is composed of an assembly of small electromagnets, as compared with an electromagnet of a corresponding size composed of a single body,
Since the magnetic path in the core of the small electromagnet is short, the inductance hardly decreases even in the high frequency region. For this reason, the reduction of the electromagnetic force in the high frequency region is suppressed, and the excitation of the natural frequency of the bending mode in the rotating body is suppressed, so that the oscillation in the high frequency region can be prevented.

According to the magnetic bearing device of the second aspect, it is easy to control the plurality of small electromagnets in common or individually based on the output of the displacement sensor.

[Brief description of drawings]

FIG. 1 is a view of a magnetic bearing device according to an embodiment of the present invention as seen from an axial end of a rotating body.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3 shows electromagnets X1, X1 ′, Y1, Y1 ′ shown in FIG.
3 is a graph showing frequency characteristics of inductance in FIG.

FIG. 4 is a schematic view of a conventional magnetic bearing device as seen from an axial end of a rotating body.

5 is a sectional view taken along line VV in FIG.

[Explanation of symbols]

5 displacement sensor 6 rotating body 401-416 small electromagnet X1, X1 ', Y1, Y1' electromagnets

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Claims (2)

[Claims] 1. A magnetic bearing device for magnetically non-contact supporting a rotating body by a plurality of sets of electromagnets, wherein each of at least one set of electromagnets among the plurality of sets of electromagnets is arranged in the radial direction with the rotating body interposed therebetween. The magnetic bearing device comprises an assembly of a plurality of small electromagnets. 2. A displacement sensor is arranged in the vicinity of the electromagnet composed of the aggregate, and based on the output of the displacement sensor,
The magnetic bearing device according to claim 1, wherein the electromagnetic force of the electromagnet is controlled.