JP2001241440A - Magnetic bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic bearing device raising a natural frequency of a rotary body for suppressing resonance. SOLUTION: An offset axial sensor 4 is provided in the middle of two radial sensors 3 mutually adjacent in a circumferential direction. A target part 1b is shared by the radial sensors 3 and the offset axial sensor 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to the structure of a magnetic bearing device.

[0002]

2. Description of the Related Art FIG.
It is sectional drawing which shows simplified the structure of the conventional magnetic bearing device described in No. 80. In the figure, four electromagnets 2 constituting a radial magnetic bearing are arranged at equal intervals around a rotating body 1 having a columnar shape as a whole. In addition, four radial sensors 3 for detecting displacement of the rotating body 1 in the radial direction are provided at equal intervals around the rotating body 1 at a position slightly away from the electromagnet 2 in the axial direction of the rotating body 1. Are located. Furthermore, from these radial sensors 3, the rotating body 1
A pair of offset axial sensors 4 that detect displacement of the rotating body 1 in the axial direction are provided opposite to a part of the outer periphery of the rotating body 1 at a position separated in the axial direction. Target portions 1a, 1b, and 1c in which silicon steel plates or the like are stacked are provided at positions on the surface layer side of the rotating body 1 facing the electromagnet 2, the radial sensor 3, and the offset axial sensor 4, respectively. The position of the target portion 1 c facing the offset axial sensor 4 in the axial direction of the rotating body 1 corresponds to an intermediate position between the pair of offset axial sensors 4. When the rotating body 1 moves in the axial direction from this position, the reactance acting on the pair of offset axial sensors 4 changes. Therefore, by detecting this change, the displacement of the rotating body 1 in the axial direction can be detected.

[0003]

In the above-described conventional magnetic bearing device, not only the electromagnet 2 and the radial sensor 3 but also the offset axial sensor 4 are disposed so as to face the rotating body 1, so that the rotating body 1 Becomes longer in the axial direction. When the rotating body 1 is long in the axial direction, the natural frequency of the rotating body 1 decreases. If the natural frequency is low, resonance is likely to occur in relation to the rotation speed, and if the resonance occurs, the position of the rotating body 1 cannot be controlled.

[0004] In view of the above-mentioned conventional problems, an object of the present invention is to provide a magnetic bearing device that suppresses resonance by increasing the natural frequency of a rotating body.

[0005]

According to the present invention, there is provided a magnetic bearing device having an electromagnet for magnetically levitating a rotating body, and a position detecting means for the rotating body, wherein the position detecting means makes a round around the outer periphery of the rotating body. And a plurality of target portions provided around the target portion facing the target portion,
A radial sensor for detecting a displacement of the rotating body in a radial direction, between the two radial sensors adjacent to each other in a circumferential direction, provided opposite to the target portion, and in an axial direction of the rotating body. Is provided with a pair of axial sensors which are connected to each other and detect the displacement of the rotating body in the axial direction. In the magnetic bearing device configured as described above, the axial sensor includes:
It is located between two radial sensors adjacent to each other in the circumferential direction, and faces a common target portion with the radial sensors. Therefore, a target section dedicated to the axial sensor is not required, and the axial length of the rotating body is reduced.

[0006]

FIG. 1A is a cross-sectional view of a magnetic bearing device according to an embodiment of the present invention, and FIG.
It is a BB line sectional view in (a). (C)
FIG. 4 is a cross-sectional view of the same device corresponding to a cross section taken along line CC in FIG. In the figure, a rotating body 1 having a cylindrical shape as a whole is shown.
Are surrounded by 4 electromagnets 2 constituting a radial magnetic bearing.
And are arranged at equal intervals. In addition, these electromagnets 2
From the axial direction of the rotating body 1 (hereinafter simply referred to as the axial direction).
Four radial sensors 3 for detecting the displacement of the rotating body 1 in the radial direction are arranged at regular intervals around the rotating body 1 at a position slightly apart from the rotating body 1.

As shown in FIG. 1B, if the position of the radial sensor 3 is 0 degree right above the figure, the positions of 0 degree, 90 degrees, 180 degrees, and 270 degrees in the clockwise direction will be described. Are located in Further, a pair of offset axial sensors 4 for detecting the displacement of the rotating body 1 in the axial direction are provided so as to be continuous with each other in the axial direction, and their intermediate position in the axial direction is the same as the axial position of the radial sensor 3. (See (c)). Further, in the circumferential direction, the offset axial sensor 4
It is arranged in the middle of the two radial sensors 3, that is, in the vicinity of 225 degrees (see (b)). Note that the position at 225 degrees is an example, and other than that, near 45 degrees, near 135 degrees, and 3 degrees.
Any angle around 15 degrees may be used. Moreover, you may arrange | position in several places of a circumferential direction as needed.

On the other hand, the electromagnet 2 and the radial sensor 3
Target portions 1a and 1b, each of which is formed by stacking a silicon steel plate or the like, are provided at positions on the surface layer side of the rotating body 1 facing the rotating body 1. The target portion 1b is located at a position facing not only the radial sensor 3 but also the offset axial sensor 4. That is, the pair of offset axial sensors 4 are arranged such that their intermediate position in the axial direction coincides with the axial center position of the target portion 1b. When the rotating body 1 moves in the axial direction from this position, the reactance acting on the pair of offset axial sensors 4 changes. Therefore, by detecting this change, the displacement of the rotating body 1 in the axial direction can be detected. In this manner, the radial sensor 3, the offset axial sensor 4, and the common target 1
b constitutes a means for detecting the position of the rotating body 1 in the radial direction and the axial direction.

[0009] In the above-described configuration, between two radial sensors 3 adjacent to each other in the circumferential direction,
Since the offset axial sensor is arranged, the occupied area of the radial sensor 3 and the offset axial sensor 4 in the axial direction is shared, and the target portion 1b is also shared. Therefore, there is no need to separately provide a target for the offset axial sensor 4 at another position in the axial direction, and the axial length of the rotating body 1 can be made compact. Thereby, the natural frequency of the rotating body becomes higher than that of the conventional one, so that the occurrence of resonance can be suppressed.

[0010]

The present invention configured as described above has the following effects. According to the magnetic bearing device of the first aspect, since the radial sensor and the axial sensor share the target portion, the target portion dedicated to the axial sensor becomes unnecessary, so that the axial length of the rotating body is reduced. . Therefore, it is possible to increase the natural frequency of the rotating body and suppress occurrence of resonance.

[Brief description of the drawings]

1A is a cross-sectional view of a magnetic bearing device according to an embodiment of the present invention, and FIG. 1B is a cross-sectional view taken along line BB in FIG.
It is a line sectional view. Further, (c) is the C- value in (b).
FIG. 4 is a cross-sectional view of the device corresponding to a cross section taken along line C.

FIG. 2 is a cross-sectional view showing a simplified structure of a conventional magnetic bearing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotating body 1b Target part 2 Electromagnet 3 Radial sensor 4 Offset axial sensor

Claims (1)

[Claims] 1. A magnetic bearing device comprising: an electromagnet for magnetically levitating a rotating body; and a position detecting means for the rotating body.
The position detecting means includes: a target portion provided around the outer periphery of the rotating body; and a plurality of radial portions provided around the facing portion facing the target portion to detect a radial displacement of the rotating body. A sensor, which is located between the two radial sensors adjacent to each other in the circumferential direction and is provided so as to face the target portion, and is provided in a pair in the axial direction of the rotating body so as to be continuous with each other; A magnetic bearing device comprising: an axial sensor that detects displacement in an axial direction.