JPH0587140A - Magnetic bearing device - Google Patents

Abstract

PURPOSE:To simplify the structure around a control electromagnet while performing the position detection of a floating rotary shaft in a magnetic bearing device at the action point of the control electromagnet. CONSTITUTION:This magnetic bearing device is provided with a magnetic field generating coil 3 for generating the magnetic field for holding a rotary shaft, a power amplifier 22 for supplying a direct current to this magnetic field generating coil 3, a high frequency carrier oscillator 27, a band-pass filter 24, a rectifying circuit 25, a low-pass filter 26, and an offset-gain circuit 33. This magnetic field generating coil 3 is used in common as the coil of a control electromagnet and the coil for detecting the position of the rotary shaft 2.

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, and more particularly to a magnetic bearing device in which a rotating shaft floats from a bearing due to magnetic force and rotates in a non-contact state, and the rotating shaft stably rotates at a predetermined position. The present invention relates to a bearing device that can be used.

[0002]

2. Description of the Related Art Generally, a magnetic bearing device is composed of a rotating shaft placed on the center axis of the bearing and a permanent magnet or electromagnet mounted on a stator at a predetermined distance from the rotating shaft. Composed. This electromagnet consists of a yoke made of magnetic material and a coil wound on it. The yoke attracts the rotating shaft by the magnetic field generated by this coil.
To control this suction and to stably support it at any position,
It has a position sensor. Thus, in the magnetic bearing, the position sensor is indispensable for controlling the position of the rotary shaft.

[0003]

In order to detect the position of this rotary shaft, a position detection sensor has been conventionally provided. As the position detection sensor, for example, in an electromagnetic induction type sensor due to a change in inductance, a coil for detection is provided near the rotation axis and measurement is performed by a dedicated measurement system. Therefore, it is structurally difficult to match the portion of the rotating shaft, which is the point of action of the attraction force of the electromagnet, with the portion of the rotating shaft, which is the position detection point of the position sensor. In addition, there is a problem in that the position detection sensor must be installed around the control electromagnet, which complicates the configuration.

The present invention has been made in view of the above circumstances, and an object thereof is to enable position detection of a rotary shaft at an action point of a control electromagnet, and to eliminate a position detection coil. Another object of the present invention is to provide a magnetic bearing device capable of detecting the amount of movement of a magnetically levitated rotating shaft with a simple structure.

[0005]

A magnetic bearing device of the present invention is a magnetic bearing device comprising an electromagnet comprising a magnetic field generating coil and a yoke portion of a magnetic material, and a supported body, wherein the magnetic field generating coil comprises: The coil is also used as a coil for detecting the amount of movement of the supported body, so that the amount of movement of the rotary shaft is detected, and the rotary shaft is fixed at a predetermined position by the detected signal.

[0006]

In the present invention, when the rotary shaft moves from the central axis of the rotary shaft, this movement is regarded as a change in the inductance of the magnetic field generating coil 3, and the high frequency carrier signal, the high pass filter 24, the rectifier circuit 25, and the low pass filter. The detection is performed using the filter 26 or the like. A signal corresponding to the detected amount of movement of the rotating shaft is fed back to the control circuit 28. The phase and gain of the fed-back signal are adjusted by the control circuit 28 and the power amplifier 22.
Is amplified by. By feeding back the amplified current to the magnetic field generating coil 3 and applying it, the magnetic field generated by the magnetic field generating coil 3 is adjusted, and the rotating shaft is controlled so as to always be supported at the center of the bearing.

[0007]

Embodiments of the magnetic bearing device according to the present invention will be described below with reference to the drawings.

FIG. 5 is an explanatory view of a magnetic bearing device. A yoke part 1 around which a coil 3 mounted on a stator of the magnetic bearing device is wound, and a rotating shaft 2 which floats and rotates around the center of the bearing. Explain the relationship with.

In the magnetic bearing device having the above-described structure, when the coil 3 is energized, the yoke portion 1 is excited to generate a control magnetic field that always supports the rotating shaft at the center of the bearing.

If the rotary shaft 2 moves for some reason, the distance L between the rotary shaft 2 and the yoke portion 1 changes. In the present invention, when the rotating shaft 2 moves in the magnetic field of the magnetic field generating coil 3, the inductance of the magnetic circuit formed by the yoke part 1 changes to detect the position of the rotating shaft 2 with respect to the yoke part 1. It is a thing.

FIG. 1 shows a block diagram of the position detection of the magnetic field generating coil 3 according to the first embodiment of the present invention. In FIG. 1, 22 is a power amplifier, 3 is a magnetic field generating coil, 24 is a bandpass filter (BPF), 25 is a full-wave rectifier circuit, and 26
Is a low pass filter (LPF), and 33 is an offset / gain adjustment circuit. The magnetic field generating coil 3 in FIG. 1 is the same as the magnetic field generating coil 3 in FIG. 5, and is for holding and rotating the rotating shaft 2 at a predetermined position. The current for exciting the coil 3 is the power amplifier 2
2 supplies. On the other hand, the carrier oscillator 27 is 1 to 100k.
A high frequency signal of about Hz is generated, and this voltage is converted into a high frequency current by the power amplifier 22 and supplied to the magnetic field generating coil 3. The voltage at the lower end of the magnetic field generating coil 3, that is, the voltage of the detection resistor 35 (current detection resistor of about 0.1 to 0.3 ohm) is rectified by the full-wave rectification circuit 25 via a bandpass filter. The bandpass filter 24 is a filter that passes only a frequency band near the carrier frequency. The low-pass filter 26 extracts only the low-frequency component corresponding to the moving amount of the rotating shaft 2 from the voltage waveform rectified by the rectifying circuit 25. Offset / gain adjustment circuit 3
In step 3, the DC component and the gain are adjusted. still,
FIG. 2 shows the high-frequency current flowing through the coil 3 in the above-described embodiment taken from both ends of the detection resistor 35 through the differential circuit 37 (differential amplifier).

In FIG. 6, when the rotary shaft 2 approaches the yoke portion 1, the magnetic resistance of the magnetic circuit formed by the yoke portion 1 and the rotary shaft 2 becomes small, and the inductance of this magnetic circuit becomes large. Therefore, the high-frequency current flowing through the coil 3 decreases, the voltage across the detection resistor 35 decreases, and the rectified voltage output from the offset / gain adjusting circuit 33 decreases accordingly. That is, the offset
Since the voltage of the gain adjusting circuit 33 has decreased, it is detected that the rotating shaft 2 has approached the yoke portion 1 in FIG. In this case, the voltage waveform passing through the bandpass filter 24 is a carrier frequency waveform having an envelope formed by the magnetic circuit between the rotating shaft 2 and the magnetic field generating coil 3 and the rotating shaft 2. .. In this way, a signal corresponding to the amount of movement of the rotary shaft 2 is detected.

The amount of movement of the rotary shaft 2 detected by the offset / gain adjusting circuit 33 is fed back to the control circuit 28 to amplify the phase adjusted feedback signal to generate a direct current flowing through the magnetic field generating coil 3. By superimposing and applying, the generated magnetic field for holding the rotary shaft 2 at a predetermined position is adjusted by feedback, so that the movement of the rotary shaft 2 can be quickly restored.

A signal of the amount of movement of the rotary shaft 2 detected by the offset / gain adjusting circuit 33 is fed back to the control circuit 28 to advance or delay the phase thereof to adjust the gain / offset so that a more appropriate feed. With the back, delicate control is possible, and thereby the movement of the rotary shaft 2 can be optimally restored.

FIG. 3 is a block diagram of the position detection of the magnetic field generating coil according to the second embodiment of the present invention. In this embodiment, a signal obtained by amplifying the output of the control circuit 28 by the power amplifier 22a and a signal obtained by amplifying the output of the carrier oscillator 27 by the power amplifier 22b are superimposed and applied to the magnetic field generating coil 3. With this configuration, since the carrier oscillator has a dedicated power amplifier, there is an advantage that the frequency characteristic of the power amplifier 22a that handles a large current is not limited.

FIG. 4 is a block diagram of position control of the radial bearing according to the third embodiment of the present invention. In this embodiment, two yoke parts 1 are provided above and below the rotary shaft 2, and current is supplied to each yoke part 1 from the respective power amplifiers 22c and 22d, so that the moving amount of the rotary shaft 2 is changed. This is a magnetic bearing device that detects the distance on both sides and controls the distance between the yoke portion 1 and the rotary shaft 2. With such a configuration, more accurate position control of the rotary shaft 2 can be performed.

FIG. 5 shows a structure in which a part of the magnetic field generating coil 3 is used in place of the current detecting resistor 35 in the above embodiment of the present invention. With such a configuration, the resistor 35 for current detection can be omitted, and the circuit configuration is simplified.

[0018]

As described above, according to the present invention, when the rotary shaft is rotating at a predetermined position, the suction force is controlled when the rotary shaft moves for some reason. By sharing the magnetic field generating coil 3 as a detector,
The amount of movement of the rotating shaft can be detected at the point of action of the attractive force of the control electromagnet. Further, the coil for position detection is not required, and the structure of the magnetic bearing can be simplified. Therefore, it contributes to improvement of control accuracy, downsizing, and downsizing of the entire magnetic receiving device.

[Brief description of drawings]

FIG. 1 is a block diagram of position detection of a magnetic field generating coil according to a first embodiment of the present invention.

FIG. 2 is a block diagram of position detection of a magnetic field generation coil in which a high frequency current is taken out from both ends of a detection resistor through a differential amplifier circuit in the above embodiment.

FIG. 3 is a block diagram of position detection of a magnetic field generating coil according to a second embodiment of the present invention.

FIG. 4 is a block diagram of position control of a radial bearing according to a third embodiment of the present invention.

FIG. 5 is an explanatory diagram of a circuit in which a part of the magnetic field generating coil in the embodiment of the present invention is used for current detection of position detection.

FIG. 6 is an explanatory diagram showing a positional relationship between a yoke portion and a rotating shaft in the magnetic bearing device.

[Explanation of symbols]

 1 yoke part 2 rotating shaft 3 magnetic field generating coil 22 power amplifier 24 band pass filter 25 full wave rectifier circuit 26 low pass filter 27 high frequency carrier oscillator 28 control circuit 33 offset / gain adjusting circuit 35 detection resistor

Claims (2)

[Claims] 1. A magnetic bearing device comprising an electromagnet comprising a magnetic field generating coil and a yoke portion of a magnetic material and a supported body, wherein the magnetic field generating coil is a coil for detecting the amount of movement of the supported body. A magnetic bearing device that is commonly used as. 2. A carrier generating means for generating a high frequency carrier signal to be superimposed on the magnetic field generating coil, a detecting means for detecting only a component near a carrier signal frequency of a current flowing through the magnetic field generating coil, and the detected carrier. The moving amount of the supported body is detected by including rectifying means for rectifying a signal having a component near the signal frequency and detecting means for detecting a low frequency component of the rectified signal. The magnetic bearing device described.