JPH06307446A - Rotator having controlled type magnetic bearing - Google Patents

Abstract

PURPOSE:To prevent saturation of a magnetic bearing, and also increase current for controlling the other vibration component, in a control type magnetic bearing formed in such a type that suction force of an electromagnetic stone used in a rotator having function for carrying out feed back control on a setting rotator is controlled by the signal of a displacement sensor so as to maintain the rotator in non-contact condition. CONSTITUTION:In a control type magnetic bearing formed in such a type that suction force of an electromagnetic stone used in a rotator having function for carrying out feed back control on a set rotator is controlled by the signal of a displacement sensor so as to maintain the rotator in non-contact condition, notch filteres 11, 11 are inserted, and a notch filter center frequency tuning circuit 12 is provided to set center frequency of the notch filters 11, 11 in relation to rotation frequency of the rotator and frequency of the integer times magnification in the rotation frequency corresponding to a rotation frequency setting value as the target value of rotating speed control.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to various types of equipment such as turbo molecular pumps, machine tool spindles, centrifugal compressors and the like, which have controllable magnetic bearings for holding rotating bodies in a non-contact manner. The present invention relates to a rotating body having a magnetic bearing.

[0002]

2. Description of the Related Art Controlled magnetic bearings have advantages such as non-contact holding, cleanliness, and low loss. For example, in the field of vacuum equipment and high-speed rotating bodies, they can be used instead of conventional rolling bearings and sliding bearings. It's going on.

The structure of a conventional control type magnetic bearing of this type will be described in detail with reference to the drawings. FIG. 3 is a diagram for explaining the configuration of a conventional control type magnetic bearing. In the figure, 1 is a rotating shaft, 2 is a drive motor, 3 and 4 are electromagnets acting in the radial direction and the thrust direction, respectively, and 5 is a gear. 6M, 6R and 6T are drive circuits (DRV) for driving the motor 2, the radial direction electromagnet 3 and the thrust direction electromagnet 4, respectively. 7R and 7T are radial direction and thrust direction control circuits (CNT), respectively.
Reference numeral 8 is an automatic speed control circuit (ASC). 9 is a pulse sensor. 10R and 10T are radial directions,
It is a thrust direction displacement sensor.

The principle of operation in the radial direction will be described. The position of the rotary shaft 1 in the radial direction is measured by the displacement sensor 1.
Control circuit (CNT) 7R, drive circuit (DRV) so that the position is always kept in the same place
Control the radial electromagnet 3 through 6R. These two sets of radial magnetic bearings control translation in two directions and rotation in two directions.

Similarly in the thrust direction, the rotary shaft 1
The position in the thrust direction is detected by the displacement sensor 10T, and the thrust direction electromagnet 4 is controlled through the control circuit (CNT) 7T and the drive circuit (DRV) 6T so that the position is always held at the same position. This controls the translation in one direction. By controlling the five axes at the same time, the rotary shaft 1 can be held in a non-contact manner.

The rotary shaft 1 is rotated by a drive motor 2. In normal use, it is necessary to keep the number of revolutions accurately and constant, and the number of revolutions is detected by the pulse sensor 9 at the gear 5 attached to the rotary shaft 1, and the automatic speed control circuit (ASC) 8 and the motor drive circuit ( DRV)
Motor 2 is controlled via 6M. With these, it is possible to realize a rotating shaft that is completely non-contact and has a constant rotation speed.

[0007]

The above-mentioned magnetic bearing has the following drawbacks. FIG. 2 shows the relationship between the coil current and the attractive force in the electromagnet. The electromagnet has a saturation characteristic, and even if the current is increased to the saturation current ia or more, the attraction force does not increase accordingly. Therefore, the bias current io that is 1/3 to 1/5 of the saturation current ia is used. That is, in that state, the controllable coil current becomes ia-io, and the attraction force applied to the vibration of the rotating shaft becomes Fa-Fo. Therefore, the coil current in the normal state is i in the figure.

However, in a normal rotating shaft, the number of rotations N
Since (unbalance) and a vibration component of an integer multiple nN are involved, ia-io is often used up in order to control only that component, especially in a high-speed rotating shaft.

In that case, it becomes impossible to control other vibration components, which causes a problem in shaft vibration. In order to avoid this, there has been a problem that the balancing grade of the rotating shaft has to be unnecessarily raised.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned conventional problems, the present invention is directed to a rotational speed N and an integer multiple n thereof.
A notch filter having N as the center frequency is inserted. In addition, a circuit that can automatically tune the center frequency of the notch filter according to the rotational speed setting value of the rotating shaft is provided (Since the rotating speed of the rotating shaft is controlled by the automatic speed control circuit, Is almost equal to the number of revolutions).

[0011]

With the above configuration, the rotation speed N and its integral multiple n
It is possible to reduce the sensitivity to vibration of the N component and prevent the control current of the coil from decreasing. That is, it is possible to prevent saturation of the magnetic bearing itself and to increase the control current for other vibration components.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of a controlled magnetic bearing according to the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing the configuration of a controlled magnetic bearing according to the present invention.

In the figure, 1 is a rotary shaft, 2 is a drive motor,
Reference numerals 3 and 4 are electromagnets acting in the radial direction and the thrust direction, respectively, and 5 is a gear. 6M, 6R and 6T are drive circuits (DRV) for driving the motor 2, the radial direction electromagnet 3 and the thrust direction electromagnet 4, respectively. 7R and 7T are radial direction and thrust direction control circuits (CNT), respectively. Reference numeral 8 is an automatic speed control circuit (ASC). 9 is a pulse sensor, 10R, 10T
Are displacement sensors in the radial direction and the thrust direction, respectively. Reference numerals 11 and 12 are constituent elements provided in the present invention, and 11 is a notch filter (NT), 12
Is the notch filter center frequency tuning circuit (NF
T).

First, the operating principle of the radial direction will be described. The radial position of the rotary shaft 1 is measured by the displacement sensor 1
Notch filter 11 and control circuit (CNT) so that rotation axis 1 is always held at the same place
The drive circuit (DRV) 6R controls the electromagnet 3 in the radial direction by the signal passed through 7R.

A PID or the like is usually used for the control circuit 7R, and positive damping is applied to the natural frequency of the rigid body mode, and a similar filter is also used to perform the same for the bending first order.

The notch filter (NT) 11 has a rotary shaft 1
Number of revolutions N component of n and its integral multiple component nN (n is an integer)
A notch filter center frequency tuning circuit 12 is provided so that the center frequency is adjusted to reduce the sensitivity to the frequency component and the center frequency can be adjusted to an arbitrary rotation speed setting value of the rotary shaft 1.

Similarly in the thrust direction, the rotary shaft 1
Displacement sensor 10T detects the thrust direction position of
By controlling the electromagnet 4 in the thrust direction via the control circuit (CNT) 7T and the drive circuit (DRV) 6T, the rotary shaft 1 is always held at the same position. Although not shown here, a notch filter similar to that in the radial direction may be inserted in the thrust direction.

As described above, it is possible to hold the rotary shaft 1 in a non-contact manner by simultaneously controlling the three translational directions and the two rotational directions. The rotary shaft 1 is rotated by the drive motor 2. The rotation speed is detected by the pulse sensor 9 at the position of the gear 5 attached to the rotary shaft 1, and the automatic speed control circuit (ASC)
8. The motor drive circuit (DRV) 6M controls the rotation speed to be always the same.

The operation of the notch filter (NT) 11 will be described with reference to FIG. FIG. 2 shows the relationship between the coil current and the attractive force in the electromagnet. The electromagnet has a saturation characteristic, and even if the current is increased to the saturation current ia or more, the attraction force does not increase accordingly. Therefore, the bias current io of 1/3 to 1/5 of the saturation current ia is used. That is, in that state, the current that can effectively generate the attractive force in the electromagnet is ia-io, and the attractive force is Fa-Fo. On the other hand, the rotating shaft is often accompanied by a vibration component of a rotation speed N (unbalanced) component and its integer nN (n is an integer) component, and suppresses even a slight vibration particularly when rotating at a high speed. In order to do so, it requires a considerable amount of power. Therefore, the saturation current ia
, Or a coil current of ia or more is required,
Further control becomes difficult. However, due to the action of the notch filter (NT) 11 of the present invention, the saturation of the electromagnet can be reduced, and it becomes possible to control an arbitrary frequency component.

[0020]

As described above in detail, according to the rotating body mechanism having the controlled magnetic bearing of the present invention, the saturation of the electromagnet can be alleviated, and the control range of the coil current can be widened. In addition, high-precision balancing work is unnecessary.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a control type magnetic bearing according to an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between a coil current and an attractive force in an electromagnet.

FIG. 3 is a diagram showing a configuration of a conventional control type magnetic bearing.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Rotating shaft, 2 ... Drive motor, 3 ... Radial direction electromagnet, 4 ... Thrust direction electromagnet, 5 ... Gear, 6M, 6R,
6T ... Drive circuit (DRV), 7R, 7T ... Control circuit (C
NT), 8 ... Automatic speed control circuit (ASC), 9 ... Rotation pulse sensor, 10R, 10T ... Displacement sensor, 11 ... Notch filter (NT), 12 ... Notch filter center frequency tuning circuit (NFT).

Front page continuation (72) Koichi Tokiyasu 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima-shi, Hiroshima Mitsubishi Heavy Industries Ltd. Hiroshima Research Institute

Claims (1)

[Claims] 1. A control type magnetic bearing of a system in which a attracting force of an electromagnet used in a rotating body having a function of performing feedback control on a set rotating body is controlled by a signal of a displacement sensor to hold the rotating body in a non-contact manner. The notch filter is inserted for the rotation frequency of the rotating body and a frequency that is an integer multiple of the rotation frequency, and the center frequency of the notch filter is set according to the rotation frequency setting value that is the target value for rotation speed control. A rotating body having a control type magnetic bearing, which is provided with an adjusting circuit capable of performing the adjustment.