JP3640096B2 - Magnetic bearing control device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic bearing control device suitable for controlling a magnetic bearing such as a turbo molecular pump.
[0002]
[Prior art]
A magnetic bearing control device used for a turbo molecular pump or the like generally includes a magnetic bearing unit that levitates and supports a high-speed rotation shaft and a control unit that performs position control in response to a signal from the magnetic bearing unit. The magnetic bearing unit and the control unit are installed at a remote location and connected by a cable. Magnetic bearings are often installed in harsh environments such as high temperatures such as the exhaust area where turbomolecular pumps are installed, which is not preferable for the installation environment of control units consisting of electronic circuits including active elements. For this reason, the control unit is configured in a good environment far from the magnetic bearing unit and connected by a cable.
[0003]
[Problems to be solved by the invention]
However, the control device described above has a problem in that the matching (compatibility) between the magnetic bearing portion and the control portion is extremely poor because the adjustment portion of the magnetic bearing is in the control portion far from the magnetic bearing portion. In particular, when the cable length is changed by changing the installation location of the turbo molecular pump or the like, there is a disadvantage that the characteristics of the position detection circuit change. In addition, when the magnetic bearing unit or the control unit is replaced with another magnetic bearing unit or the control unit, the characteristics of the position detection circuit may change. Therefore, in order to emphasize compatibility, some turbo molecular pumps incorporate both a magnetic bearing unit and a control unit. However, as described above, a control unit composed of an electronic circuit including an active element is in a harsh environment. There is a possibility that the performance and life may be reduced by being exposed, and at the same time, there is a disadvantage that the pump becomes large in order to incorporate these into the pump.
[0004]
The present invention has been made to solve such a problem, and the control unit is installed in a good environment and is connected with a cable at a distance from the magnetic bearing unit. An object of the present invention is to provide a magnetic bearing control device that can be realized simultaneously.
[0005]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, a magnetic bearing control device according to the present invention is a magnetic bearing comprising a bridge circuit having at least one position detection coil for detecting the position of a rotating shaft pivotally supported by the magnetic bearing. And a control unit comprising an amplitude-controlled sine wave oscillation circuit for oscillating a sine wave in the bridge circuit, and a cable connecting the magnetic bearing unit and the control unit, and (1) a bridge of the magnetic bearing unit At least one side constituting the circuit is configured with a variable resistor to perform offset adjustment for position detection, and at the same time, a variable resistor is connected to the output terminal of the bridge circuit to perform gain adjustment (gain adjustment). It is characterized by that. (2) In addition, a feedback circuit for feeding back an excitation signal to the magnetic bearing portion from the magnetic bearing portion to the control portion via the cable is provided. (3) A synchronous detection circuit is provided in the control unit, and an excitation sine wave signal on the oscillation side and a sine wave signal fed back from the magnetic bearing unit are selectively applied as a synchronous signal input to the synchronous detection circuit. It is characterized by that.
[0006]
According to the configuration {circle around (1)} of this application, the magnetic bearing portion disposed on the pump side where the environment is harsh is composed of only passive elements such as a variable resistor, a fixed resistor, and a fixed inductor (coil). Wide operating temperature range. On the other hand, the active element sensitive to the environment of the electronic circuit is arranged on the control unit side and functions well in a good environment away from the pump. Further, since the offset adjustment and the gain adjustment are arranged on the pump side (magnetic bearing side), both the control devices are excellent in compatibility. Further, according to the above configuration (2), since the feedback signal of the excitation signal from the magnetic bearing unit is fed back to the control unit via the magnetic bearing unit and the cable, the characteristics of the adjustment component on the magnetic bearing side and the cable length The influence of the cable characteristics such as the length can be eliminated, and the cable compatibility is excellent. Further, according to the above configuration (3), the influence of noise can be reduced by synchronous detection. Of course, when an oscillation-side excitation sine wave signal is adopted as a synchronous signal, it is easily affected by external noise. Produces a signal that is in phase with the excitation signal. On the other hand, when a sine wave signal that is fed back from the magnetic bearing is used, a signal that is slightly out of phase but less affected by external noise is obtained. Therefore, a more desirable detection result can be obtained.
[0007]
Note that the configuration of the bridge circuit in this specification can be replaced with other components known to those skilled in the art that establish the circuit relationship.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0009]
FIG. 1 is a conceptual diagram showing the configuration of a magnetic bearing control device according to the present invention. In the figure, BD is a magnetic bearing part composed of a bridge circuit including two position detection coils L1 and L2 for detecting the position of the rotating shaft supported by the magnetic bearing, and MC is a control for controlling the magnetic bearing part BD. And CB are cables for connecting the magnetic bearing part BD and the control part MC. The configuration of the position detector of the magnetic bearing is as shown in FIG. 5. For example, in a turbo molecular pump or the like, a core 7, 7 ′ as an impedance type detector with respect to a rotating shaft 6 that rotates the rotor at a high speed, It consists of coils 8 and 9 wound around 7 '. The core 7 and the coil 8 constitute a positive detection coil L1, and the core 7 'and the coil 9 constitute a negative detection coil L2.
[0010]
In FIG. 1, the bridge circuit of the magnetic bearing portion BD includes two position detection coils L1 and L2 for detecting the position of the rotating shaft supported by the magnetic bearing, a variable resistor VR1, and fixed resistors connected to both sides thereof. R1 and R2 are connected in series. The bridge circuit is connected to the amplitude control sine wave oscillation circuit 1 in the control unit MC via the cable CB, and the sine wave signal from the amplitude control sine wave oscillation circuit 1 passes through the excitation line of the cable CB. When excited, the position of the rotating shaft supported by the magnetic bearing is detected.
[0011]
The fixed resistors R1 and R2 are set to a value of 0Ω or more, and the offset of the bridge circuit can be adjusted by operating the slider of the variable resistor VR1 to adjust the resistance value. . Further, fixed resistors R3 and R4 and a variable resistor VR2 are connected to a system connecting the position detection coils L1 and L2 and the variable resistor VR1. Lead wires connected to both sides of the variable resistor VR2 are connected to the differential amplifier 4 of the control unit MC via fixed resistors R5 and R6 and a cable CB, respectively, and constitute an output terminal of the bridge circuit. In other words, the variable resistor VR2 is connected to the output terminal of the bridge circuit. The fixed resistors R3 and R4 are set to values of 0Ω or more, and the gain of the bridge circuit can be adjusted by operating the slider of the variable resistor VR2 to adjust the resistance value. The fixed resistors R5 and R6 are also set to a value of 0Ω or more, and adjust the impedance to the output signal line. Furthermore, by providing such an offset adjustment mechanism and a gain adjustment mechanism on the magnetic bearing part BD side, even if the control part MC is replaced, it is not affected by these, and the control part MC can be compatible. ing.
[0012]
By the way, in this bridge circuit, a feedback circuit in which fixed resistors R11 and R12 are interposed is connected to the differential amplifier 3 of the control unit MC via a cable CB. The fixed resistors R11 and R12 are set to a value of 0Ω or more, and adjust the impedance to the signal line. These feedback circuits are feedback circuits for monitoring the excitation sine wave for the bridge circuit by the control unit MC. The feedback circuit is input from the differential amplifier 3 to the amplitude control sine wave oscillation circuit 1 and is supplied to the bridge circuit. Is kept constant. In such a configuration, since the excitation signal is also monitored through the cable CB, it is possible to control the excitation signal corresponding to a change in length or a change in cable characteristics due to cable replacement. Cable compatibility is obtained.
[0013]
In FIG. 1, the output signal of the position detection circuit (bridge circuit) is converted into a position signal by the synchronous detection circuit 2 and output to the terminal P. As the synchronization signal, either the excitation sine wave signal A fed back from the magnetic bearing side or the excitation sine wave signal B directly branched from the oscillation side can be selected and adopted by switching the switch 5. The feedback signal A is affected by external noise, but its phase matches well with the output signal. On the other hand, the phase of the oscillation signal B is slightly different from that of the output signal, but the influence of external noise is small, and the signals A and B can be selected according to the situation.
[0014]
【Example】
As for the configuration of the gain adjustment circuit which is one of the main parts of the magnetic bearing control device according to the present invention, various modified embodiments other than FIG. 1 can be considered. For example, as shown in FIG. 2A, the resistor VR2 is a slider type, and a resistor R7 for adjusting the impedance is added to the fixed resistor R4 side. In FIG. 2B, the resistor VR2 is of a slider type, and a resistor R7 for adjusting the impedance is added to the fixed resistor R3 side.
[0015]
As for the configuration of the offset adjustment circuit, various modified embodiments other than FIG. 1 can be considered. For example, FIG. 3 shows an example in which the resistor VR1 is a variable resistance type. FIG. 3A shows an example in which the upper part is connected to the gain adjustment circuit, and FIG. 3B shows an example in which the lower part is connected to the gain adjustment circuit.
[0016]
FIG. 4 shows a modified embodiment of the detection coils L1 and L2 in a bridge circuit configuration as a position detection circuit. In FIG. 4A, L1 is a fixed type, and in FIG. 4B, L2 is a fixed type. The resistor R8 is a resistor for adjusting the impedance.
[0017]
Needless to say, the magnetic bearing control device provided by the present invention is also applicable to control of magnetic bearings for uses other than those for turbo molecular pumps.
[0018]
【The invention's effect】
The magnetic bearing control device according to the present invention is configured so that the magnetic bearing portion disposed on the pump side, which is generally harsh in the environment, is composed of only passive elements such as variable resistors, fixed resistors, and fixed inductors (coils). The temperature range has been expanded. At the same time, since elements that are easily affected by the environment such as amplifiers and electronic circuits are arranged in the control unit installed in a good environment, the performance can be exhibited well. In addition, since the offset adjustment and gain adjustment can be performed only on the magnetic bearing side, the control devices of both the magnetic bearing unit and the control unit can be interchanged. In addition, the excitation voltage to the bridge circuit is monitored on the control unit side by a feedback circuit via the cable and is kept constant, so the characteristics of the adjustment parts on the magnetic bearing side and the effects of changing the cable length and the cable itself It is possible to eliminate the influence of the characteristics and the like, and there is a remarkable effect of realizing excellent compatibility.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram showing a configuration example of a magnetic bearing control device according to the present invention.
FIG. 2 is a view showing a modified embodiment of the magnetic bearing control device according to the present invention.
FIG. 3 is a view showing a modified embodiment of the magnetic bearing control device according to the present invention.
FIG. 4 is a view showing a modified embodiment of the magnetic bearing control device according to the present invention.
FIG. 5 is a view showing an example of a shaft position detection mechanism of a magnetic bearing according to the present invention.
[Explanation of symbols]
1 .... Amplitude control sine wave oscillation circuit 2 .... Synchronous detection circuit 3, 4 .... Differential amplifier 5 .... Switch 6 ... .... Rotating shaft 7 ... Core 8 ... Positive detection coil (L1)
9 ・ ・ ・ ・ ・ ・ ・ Negative detection coil (L2)
R1 to R11 ··· Fixed resistors VR1 and VR2 · Variable resistor BD ··· Magnetic bearing part MC ··· Control part CB ··· Cable

Claims (3)

A magnetic bearing portion comprising a bridge circuit having at least one position detection coil for detecting the position of a rotating shaft supported by the magnetic bearing, and an amplitude control sine wave oscillation circuit for oscillating a sine wave in the bridge circuit And a magnetic bearing control device comprising a cable connecting the magnetic bearing part and the control part, wherein at least one side constituting a bridge circuit of the magnetic bearing part is constituted by a variable resistor. The magnetic bearing control device is characterized in that the offset adjustment for position detection is performed, and at the same time, a gain is adjusted by connecting a variable resistor to the output terminal of the bridge circuit. A magnetic bearing portion comprising a bridge circuit having at least one position detection coil for detecting the position of a rotating shaft supported by the magnetic bearing, and an amplitude control sine wave oscillation circuit for oscillating a sine wave in the bridge circuit A magnetic bearing control device comprising: a control unit including: a cable that connects the magnetic bearing unit and the control unit; and an excitation signal to the magnetic bearing unit is transmitted from the magnetic bearing unit via the cable. And a feedback circuit for feeding back to the controller. A magnetic bearing portion comprising a bridge circuit having at least one position detection coil for detecting the position of a rotating shaft supported by the magnetic bearing, and an amplitude control sine wave oscillation circuit for oscillating a sine wave in the bridge circuit And a magnetic bearing control device comprising a cable connecting the magnetic bearing unit and the control unit, wherein the control unit is provided with a synchronous detection circuit and is input to the synchronous detection circuit A magnetic bearing control device configured to selectively apply an oscillation-side excitation sine wave signal and a sine wave signal fed back from a magnetic bearing portion.

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