JPH05118330A - Magnetic bearing device - Google Patents

Abstract

PURPOSE:To provide a magnetic bearing of a pulse width modulation (PWM) type by using a magnetic field generation coil of the magnetic bearing as a coil for a displacement amount detection sensor in common, and by using a switching ripple current of the electric power source of the pulse width modulation (PWM) bearing as a signal for measurement. CONSTITUTION:In a magnetic bearing device provided with a device to detect a displacement amount of a supported body and supporting the supported body 13 in non-contact by a magnetic force of an electromagnetic coil, a bearing electric power source 21 of a pulse width modulation (PWM) type is furnished and a displacement amount information detection means 15 of the supported body 13 to measure a switching ripple current of the electromagnetic coil 12 is arranged in the neighbourhood of the electromagnetic coil 12. Consequently, the displacement amount information detection means scarcely receives influence of the switching ripple current.

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,
In particular, the present invention relates to a magnetic bearing device that supports a supported body by a magnetic force in a non-contact state.

[0002]

2. Description of the Related Art FIG. 3 is an explanatory view of a conventional magnetic bearing device. In general, a magnetic bearing device includes an electromagnet coil 12 that exerts a supporting force by a magnetic force, a position sensor 10 that detects a moving amount of a supported body 13, and a control circuit that issues a control signal based on a signal detected by a sensor amplifier 11. 19 and a power amplifier 18 which supplies a current to the electromagnet coil 12 based on the control signal thereof.

The yoke portion 14 attracts the supported body 13 by the magnetic field generated by the electromagnet coil 12. In order to control this suction force and stably support it at an arbitrary position, the position sensor 10
Is equipped with. Thus, in the magnetic bearing,
The position sensor 10 is indispensable for controlling the position of the supported body 13.

[0004]

Conventionally, as a sensor for position detection, for example, in an electromagnetic induction type sensor due to a change in inductance, a special detection coil is provided in the vicinity of an electromagnet coil which gives a supporting force. The measurement was performed by a dedicated measuring system such as applying a detection signal. Therefore, it is structurally difficult to match the portion of the supported body, which is the point of action of the attraction force of the electromagnet, with the portion of the supported body, which is the position detection point of the position sensor. In addition, there is a drawback that the structure is complicated because a dedicated coil and a measuring system are required.

Therefore, a pulse width modulation system common to the coils shown in FIG. 2 was considered. That is, the electromagnet coil 12
Is also used as a coil for detecting the movement amount of the supported body 13, and the movement amount information detecting means 15 detects the movement amount from the switching ripple current from the pulse width modulation (PWM) type bearing power source 21. It is configured to support the supported body at a predetermined position by the signal. According to this configuration, since the electromagnet coil is also used as the position detection coil, the position of the supported body can be detected at the point of action of the control electromagnet, and the position detection coil is not used, resulting in magnetic levitation. The amount of movement of the supported object can be detected with a simple structure.

However, the controller 16 and the movement amount information detecting means 15 are generally separated from the electromagnet coil 12 and are connected by the signal cable 17, and a high frequency component or the like is generated from the pulse width modulated current flowing to the electromagnet coil. There is a case where a spike-shaped signal jumps in the signal cable 17 and enters the movement amount information detecting means 15. The present invention has been made in view of the above circumstances, and an object of the present invention is to improve the pulse width modulation method common to the coil shown in FIG. 2 and to reduce the influence of the long signal cable 17 between the electromagnet coil 12 and the controller 16. It is to provide a magnetic bearing device.

[0007]

According to another aspect of the present invention, there is provided a magnetic bearing device including a magnetic field generating coil, an electromagnet coil including a yoke portion, and a supported body, the magnetic field generating coil being the supported body. Is also used as a coil for detecting the amount of movement of the electromagnet coil, which has a pulse width modulation (PWM) type bearing power supply, measures the switching ripple current thereof, and detects the amount of movement of the supported body. Configured to be placed close to.

[0008]

In the present invention, the controller for moving amount information detecting means for measuring the switching ripple current of the pulse width modulation (PWM) type bearing power source is arranged near the electromagnet coil. It is possible to provide a magnetic bearing device in which the movement amount information detecting means is hardly affected by the switching ripple current due to the long cable from the bearing power source.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the magnetic bearing device according to the present invention will be described below with reference to FIG. When the controller 16 energizes the electromagnet coil 12, the yoke portion 14 is excited and a control magnetic field for supporting the supported body 13 at a predetermined position is generated.
If the supported body 13 moves for some reason, the distance X between the supported body 13 and the yoke portion 14 changes. When the supported body 13 moves in the magnetic field of the electromagnet coil 12, the position of the supported body 13 with respect to the yoke section 14 is detected by utilizing the fact that the inductance of the magnetic circuit formed by the yoke section 14 and the supported body 13 changes. To do.

That is, the electromagnet coil 12 serves both as a coil used for supporting the supported body 13 by generating a magnetic field and as a sensor coil for detecting the position of the supported body. The pulse width modulation (PWM) bearing power supply 21 supplies an exciting current for supporting the supported body 13 by pulse width modulation (PWM), and the current detector 23.
Is to detect the pulse-width modulated switching ripple current with a low resistance or the like.

A pulse width modulation (PWM) type bearing power supply 21
Is a bearing power supply whose current is controlled by modulating the pulse width by the control circuit 27. The output of the bearing power supply is a switching ripple current whose pulse width is modulated.
2 is applied. The switching ripple current applied to the electromagnet coil 12 is detected by the movement amount information detection means 15 arranged near the electromagnet coil 12. That is, a change in the position of the supported body 13 is recognized as a change in inductance, and the current detector 23 detects the current,
The output is fed back to the pulse width modulation (PWM) type bearing power supply 21, and the bandpass filter 2
4. Enter the rectifier circuit 25 and the low-pass filter 26. The bandpass filter 24 is a bandpass filter that allows the fundamental frequency of the pulse-modulated switching ripple current to pass, and a fundamental frequency of about 20 to 120 kHz is used. The fundamental frequency component of the switching ripple current is detected and rectified by the rectifier circuit 25. Low-pass filter 26
Is a filter that passes only a low-frequency component having a magnitude corresponding to the fundamental frequency component of the detected and rectified switching ripple current.

That is, in the magnetic circuit composed of the supported body 13 and the yoke portion 14, the inductance seen from the electromagnet coil 12 changes depending on the position of the supported body 13.
The change in the inductance is captured as a change in the magnitude of the fundamental frequency of the switching ripple current, and the rectifier circuit 25
The signal detected and rectified by the above becomes a signal corresponding to the change of the magnitude of the inductance. Therefore, the output signal of the low-pass filter 26 that removes the higher harmonic component becomes a signal having an amount corresponding to the change in the inductance, that is, the positional interval X between the supported body 13 and the yoke portion 14. When the supported object position X is detected by the movement amount information detecting means 15 in this way, the signal is fed back to the control circuit 27 constituting the controller 16 and a predetermined calculation is carried out so that the supported object should be present. The signal bearing the shaft in position is fed back to the pulse width modulation (PWM) bearing power supply 21 again. Thereby, the supported body 13 is supported at a predetermined position.

For example, in the case of a turbo molecular pump, as an example, the electromagnet coil 12 and the controller 16 are used.
Is a distance of several meters, and a high-frequency high-current switching ripple current from the PWM bearing power supply 21 is applied to the electromagnet coil 12 by the signal cable 17. Since the movement amount information detecting means 15 is arranged in the immediate vicinity of the electromagnet coil 12, spike noise and the like due to the switching ripple current of a high frequency large current can be greatly reduced from entering the movement amount information detecting means 15. The output of the movement amount information detecting means 15 is a few meters away from the controller 1
6 is sent by a signal cable, but the output of the movement amount information detecting means 15 is a low frequency signal, and therefore the influence of the switching ripple current of high frequency large current can be prevented by the filter of the controller.

By thus sharing the electromagnet coil with the position detecting coil, the position of the supported body can be detected at the point of action of the control electromagnet, and the position detecting coil is not used, and the magnetic levitation is performed. There is provided a magnetic bearing device capable of stably detecting the amount of movement of the supported body with a simple structure.

[0015]

INDUSTRIAL APPLICABILITY According to the present invention, the magnetic field generating coil of the magnetic bearing is also used as the coil of the movement amount detecting sensor, and the switching ripple current of the pulse width modulation (PWM) bearing power supply is used as the measurement signal. In a (PWM) type magnetic bearing, means for detecting the amount of movement of a supported body for measuring a switching ripple current is arranged near the electromagnet coil. Therefore, a stable magnetic bearing device is provided in which the movement amount information detecting means is hardly affected by the switching ripple current due to the long cable from the bearing power source of the controller.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a magnetic bearing device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a magnetic bearing device of a pulse width modulation type shared by coils.

FIG. 3 is an explanatory diagram of a conventional magnetic bearing device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Position sensor 11 Sensor amplifier 12 Electromagnet coil 13 Supported object 14 Yoke part 15 Moving amount information detecting means 16 Controller 17 Signal cable 18 Power amplifier 21 Pulse width modulation (PWM) bearing power supply 23 Current detector 24 Bandpass filter 25 Rectifier circuit 26 low-pass filter 27 control circuit

Claims (2)

[Claims] 1. A magnetic bearing device comprising a device for detecting the amount of movement of a supported body and supporting the supported body in a non-contact manner by the magnetic force of an electromagnet coil.
A magnetic bearing device having a M) type bearing power supply, and means for measuring switching ripple current of the electromagnet coil and detecting movement amount information of a supported body are arranged near the electromagnet coil. . 2. The means for measuring the switching ripple current and detecting the movement amount information of the supported body includes a detector and a bandpass filter for detecting a carrier signal component of the switching ripple current, and the carrier signal component. 2. The magnetic bearing device according to claim 1, comprising a rectifier circuit for rectifying and detecting to extract a low frequency component corresponding to the movement amount information, and a low pass filter.