JP2006112490A - Magnetic bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a magnetic bearing device capable of performing precision control even with an A/D converter with a small number of digits, for safe operation even under disturbance. <P>SOLUTION: At such timing as a rotor 103 reaches a preset number of rotations, a gain signal setting part 11 specifies a gain signal 13 of high sensitivity in a high resolution mode. If a disturbance is applied, an A/D converter 10 overflows and a state signal 25 of the A/D converter 10 is set. The gain signal setting part 11 here specifies a gain signal 13 of low sensitivity to enter a normal mode. Thus, the incapability of measurement is avoided even a disturbance is applied, allowing a stable positioning. <P>COPYRIGHT: (C)2006,JPO&amp;NCIPI

Description

  The present invention relates to a magnetic bearing device, and more particularly to a magnetic bearing device that can perform high-precision control even with an A / D converter having a small number of digits and can operate safely even when subjected to disturbance.

With the recent development of electronics, the demand for semiconductors such as memories and integrated circuits is increasing rapidly.
These semiconductors are manufactured by doping impurities into a highly pure semiconductor substrate to impart electrical properties, or by forming fine circuits on the semiconductor substrate by etching.
These operations need to be performed in a high vacuum chamber in order to avoid the influence of dust in the air. A vacuum pump is generally used for evacuating the chamber. However, a turbo molecular pump, which is one of the vacuum pumps, is used frequently from the viewpoints of particularly low residual gas and easy maintenance.

In the semiconductor manufacturing process, there are a number of processes in which various process gases act on the semiconductor substrate. The turbo molecular pump not only evacuates the chamber, but also exhausts these process gases from the chamber. Also used.
Furthermore, turbo molecular pumps are also used in equipment such as electron microscopes to prevent the refraction of the electron beam due to the presence of dust, etc., so that the environment in the chamber of the electron microscope or the like is in a highly vacuum state. Yes.
Such a turbo molecular pump is composed of a turbo molecular pump main body for sucking and exhausting gas from a chamber of a semiconductor manufacturing apparatus or an electron microscope, and a control device for controlling the turbo molecular pump main body.

A longitudinal sectional view of the turbo molecular pump main body is shown in FIG.
In FIG. 5, the turbo molecular pump main body 100 has an intake port 101 formed at the upper end of a cylindrical outer cylinder 127. On the inner side of the outer cylinder 127, there is provided a rotating body 103 in which a plurality of rotating blades 102a, 102b, 102c,... By turbine blades for sucking and exhausting gas are formed radially and in multiple stages.
A rotor shaft 113 is attached to the center of the rotating body 103, and the rotor shaft 113 is levitated and supported in the air by a so-called 5-axis control magnetic bearing.

  In the upper radial electromagnet 104, four electromagnets are arranged in pairs on the X axis and the Y axis. Four upper radial sensors 107 are provided in close proximity to and corresponding to the upper radial electromagnet 104. The upper radial direction sensor 107 is configured to detect a radial displacement of the rotating body 103 and send a signal to a control device (not shown).

  In the control device, based on the displacement signal detected by the upper radial sensor 107, the excitation of the upper radial electromagnet 104 is controlled by the output of the amplifier via the magnetic bearing control circuit having the PID adjustment function, and the rotor shaft 113 Adjust the upper radial position. Here, the magnetic bearing control circuit converts the analog sensor signal of the displacement of the rotor shaft 113 detected by the upper radial sensor 107 into a digital signal by an A / D converter, processes the signal, and sends it to the upper radial electromagnet 104. The current to flow is adjusted, and the rotor shaft 113 is levitated.

Further, in order to finely adjust the current flowing through the upper radial electromagnet 104, the current flowing through the upper radial electromagnet 104 is measured and fed back to the magnetic bearing control circuit.
The rotor shaft 113 is formed of a high permeability material (such as iron) and is attracted by the magnetic force of the upper radial electromagnet 104. Such adjustment is performed independently in the X-axis direction and the Y-axis direction.
Further, the lower radial electromagnet 105 and the lower radial sensor 108 are arranged in the same manner as the upper radial electromagnet 104 and the upper radial sensor 107, and the lower radial position of the rotor shaft 113 is set to the upper radial direction. Like the position, it is adjusted in the control device.

  Furthermore, axial electromagnets 106A and 106B are arranged with a disk-shaped metal disk 111 provided at the lower part of the rotor shaft 113 sandwiched vertically. The metal disk 111 is made of a high permeability material such as iron. An axial sensor 109 is provided to detect the axial displacement of the rotor shaft 113, and the axial displacement signal is sent to the control device.

The axial electromagnets 106A and 106B are controlled to be excited by the output of the amplifier via the magnetic bearing control circuit having the PID adjustment function of the control device based on the axial displacement signal. The axial electromagnet 106A attracts the metal disk 111 upward by magnetic force, and the axial electromagnet 106B attracts the metal disk 111 downward.
As described above, in the control device, the magnetic force exerted on the metal disk 111 by the axial electromagnets 106A and 106B is appropriately adjusted, and the rotor shaft 113 is magnetically levitated in the axial direction and held in the space without contact.

The motor 121 includes a plurality of magnetic poles arranged circumferentially so as to surround the rotor shaft 113. These magnetic poles are controlled to rotate and drive the motor 121 by a power signal output from a drive circuit via a motor control circuit having a PWM control function of the control device.
The motor 121 is provided with a rotation speed sensor and a motor temperature sensor (not shown). Upon receiving detection signals from the rotation speed sensor and the motor temperature sensor, the rotation of the rotor shaft 113 is controlled by the control device. Yes.

A plurality of fixed blades 123a, 123b, 123c,... Are arranged with a slight gap from the rotor blades 102a, 102b, 102c,. The rotor blades 102a, 102b, 102c,... Are each inclined at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113 in order to transfer exhaust gas molecules downward by collision.
Similarly, the fixed blades 123 are also formed to be inclined at a predetermined angle from a plane perpendicular to the axis of the rotor shaft 113, and are arranged alternately with the stages of the rotary blades 102 toward the inside of the outer cylinder 127. ing.
And one end of the fixed wing | blade 123 is supported in the state inserted and inserted between the several fixed wing | blade spacer 125a, 125b, 125c ... stacked.

The fixed blade spacer 125 is a ring-shaped member and is made of a metal such as a metal such as aluminum, iron, stainless steel, or copper, or an alloy containing these metals as components.
An outer cylinder 127 is fixed to the outer periphery of the fixed blade spacer 125 with a slight gap. A base portion 129 is disposed at the bottom of the outer cylinder 127, and a threaded spacer 131 is disposed between the lower portion of the fixed blade spacer 125 and the base portion 129. An exhaust port 133 is formed below the threaded spacer 131 in the base portion 129 and communicates with the outside.

The threaded spacer 131 is a cylindrical member made of metal such as aluminum, copper, stainless steel, iron, or an alloy containing these metals as a component, and a plurality of spiral thread grooves 131a are formed on the inner peripheral surface thereof. It is marked.
The direction of the spiral of the thread groove 131 a is a direction in which molecules of the exhaust gas move toward the exhaust port 133 when the molecules of the exhaust gas move in the rotation direction of the rotating body 103.
A rotating blade 102d is suspended from the lowermost portion of the rotating body 103 following the rotating blades 102a, 102b, 102c. The outer peripheral surface of the rotating blade 102d is cylindrical and protrudes toward the inner peripheral surface of the threaded spacer 131, and is adjacent to the inner peripheral surface of the threaded spacer 131 with a predetermined gap. Yes.

The base portion 129 is a disk-like member that forms the base portion of the turbo molecular pump main body 100, and is generally made of a metal such as iron, aluminum, or stainless steel.
Since the base portion 129 physically holds the turbo molecular pump main body 100 and also has a function of a heat conduction path, a metal having rigidity such as iron, aluminum, and copper and high heat conductivity is used. Is desirable.
Further, a connector 160 is disposed on the base portion 129, and this connector 160 serves as an outlet of a signal line between the turbo molecular pump main body 100 and the control device.

In such a configuration, when the rotary blade 102 is driven by the motor 121 and rotates together with the rotor shaft 113, exhaust gas from the chamber is sucked through the intake port 101 by the action of the rotary blade 102 and the fixed blade 123.
Exhaust gas sucked from the inlet 101 passes between the rotary blade 102 and the fixed blade 123 and is transferred to the base portion 129. The exhaust gas transferred to the base portion 129 is sent to the exhaust port 133 while being guided by the thread groove 131a of the threaded spacer 131.
In the above description, it has been described that the threaded spacer 131 is disposed on the outer periphery of the rotating blade 102d, and the thread groove 131a is formed on the inner peripheral surface of the threaded spacer 131. However, conversely, a thread groove may be formed on the outer peripheral surface of the rotary blade 102d, and a spacer having a cylindrical inner peripheral surface may be disposed around the screw groove.

Further, the gas sucked from the intake port 101 enters the electrical component side including the motor 121, the lower radial electromagnet 105, the lower radial sensor 108, the upper radial electromagnet 104, the upper radial sensor 107, and the like. To prevent this, the pressure is maintained at a predetermined pressure with a purge gas.
For this reason, a pipe (not shown) is provided in the base portion 129, and the purge gas is introduced through this pipe. The introduced purge gas is sent to the exhaust port 133 through the clearance between the protective bearing 120 and the rotor shaft 113, between the rotor and the stator of the motor 121, and between the stator column 122 and the rotor blade 102.

  The protective bearing 120 is provided so that the rotor shaft 113 does not come into contact with each sensor or each electromagnet when the magnetic bearing cannot maintain the floating body 103 due to an apparatus abnormality or some disturbance. The clearance between the protective bearing 120 and the rotor shaft 113 is temporarily increased when the rotating body 103 passes through the resonance point during acceleration / deceleration, or when the protective bearing 120 and the rotor shaft 113 come into contact with each other due to a minute disturbance. Since it is inconvenient, it is considerably larger than the holding accuracy of the rotating body 103.

  For example, for a shaft holding accuracy of several μm, the clearance between the protective bearing 120 and the rotor shaft 113 is set to about 1 mm. Here, the rotor shaft 113 is supported by the protective bearing 120 in a state where the magnetic levitation is not performed. For this reason, in order to operate the magnetic bearing, a displacement sensor that can detect both the clearance (for example, 1 mm) between the protective bearing 120 and the rotor shaft 113 and the shaft holding accuracy (for example, several μm) is desired.

However, in general, a sensor that achieves both large full scale and high resolution is expensive and large. In addition, an A / D converter that captures a sensor signal into a digital control circuit also requires a large number of bits, which is expensive.
For example, assume that an 8-bit A / D converter (of -10 to 10 V full scale) is used for a sensor output of -10 to 10 V (the corresponding measurement distance range is -1 mm to 1 mm). When the measurement resolution in this case is calculated (20 V / 256), it is approximately 0.08 V, which corresponds to 0.008 mm (8 μm).

For this reason, a displacement of 8 μm or less cannot be detected. If not all 8 bits are used and 1 to 2 bits are used as code bits and status bits, the number of usable bits is reduced accordingly, and the resolution becomes worse.
Therefore, in order to cope with this problem, for example, a shift signal is added in accordance with the sensor output signal to obtain a pseudo signal near 0 that falls within the input range of the A / D converter, thereby obtaining high resolution. There is technology (Patent Document 1). The shift signal is a function of time.
Japanese Patent No. 3362996

  By the way, in Patent Document 1, it is considered to be applicable to a transient response whose behavior can be predicted in advance, such as when a magnetic bearing is started (at the start of levitation) or when it is accelerated or decelerated. If the sensor output signal is subjected to vibrations caused by contact, the sensor output signal may sufficiently exceed the input range of the A / D converter. In this case, the rotor shaft 113 may be in an uncontrollable state in an instant from the high speed rotation state.

  The present invention has been made in view of such a conventional problem. A magnetic bearing that can perform high-precision control even in an A / D converter with a small number of digits and can operate safely even when subjected to disturbance. An object is to provide an apparatus.

  For this reason, the present invention (Claim 1) provides a sensor and a first arithmetic unit capable of adjusting a first shift signal corresponding to a bias amount with respect to the input signal by using a signal output from the sensor as an input signal. A first amplifying unit capable of amplifying the output signal of the first arithmetic unit and changing the amplification degree, and a signal amplified by the first amplifying unit are input and subjected to analog / digital conversion A conversion unit, a second amplification unit that amplifies the signal converted by the conversion unit and can change the amplification degree, and a second corresponding to a bias for the signal amplified by the second amplification unit A second calculation unit that can adjust the shift signal of the first amplification unit, a gain signal setting unit that sets the amplification degree of the first amplification unit and each amplification degree of the second amplification unit, the first calculation unit, A shift signal setting unit that sets each shift signal of the second arithmetic unit, and the conversion unit. Are control signals with high precision based on the data is generated with the electromagnet is controlled by the control signal is performed, and constitute a rotor shaft which is floatingly supported by the electromagnet.

The first shift signal corresponding to the bias is adjusted with respect to the input signal. Then, the adjusted signal is amplified and input to the conversion unit. As a result, even if the analog / digital conversion performance of the conversion unit is limited, detection can be performed with high resolution and the accuracy can be improved.
Since the gain of the amplification unit can be set by the gain signal setting unit, the detection accuracy can be freely changed. For this reason, the amplification degree of the amplifying unit can be changed at any time according to changes in each situation, such as when the input signal fluctuates due to disturbance, etc., or when the input signal changes stably, and control becomes impossible. It can be done stably.

  Further, the present invention (Claim 2) includes detection means for detecting a maximum value and a minimum value of the change of the input signal, and each shift signal of the shift signal setting unit is detected by the detection means. It is set based on the minimum value.

  This makes it possible to efficiently acquire data that transitions between the maximum value and the minimum value.

  Furthermore, the present invention (Claim 3) includes detection means for detecting a maximum value and a minimum value of the change of the input signal, and the amplification factor of the first amplification unit of the gain signal setting unit and the second value Each amplification degree of the amplifying unit is set based on the maximum value and the minimum value detected by the detecting means and the performance of the converting unit.

  This makes it possible to accurately determine and set the amplification factor for data that changes between the maximum value and the minimum value.

  Further, according to the present invention (claim 4), the amplification factor of the first amplification unit is a reciprocal of the amplification factor of the second amplification unit, and the first shift signal and the second shift signal are It is characterized by being common.

  This can simplify the control.

  Further, according to the present invention (claim 5), the gain of the first amplification unit and the amplification of the second amplification unit by the gain signal setting unit can be switched based on the state signal of the conversion unit. Features.

  The state signal of the conversion unit is, for example, a signal that detects an overflow state at the time of analog / digital conversion, or a signal that exceeds a preset set value. As a result, even when the input signal to the conversion unit overflows due to disturbance or the like, it is possible to safely control without being affected by disturbance or the like by switching the amplification degree of the amplification unit.

As described above, according to the present invention, the first shift signal corresponding to the bias amount is adjusted with respect to the input signal, and the adjusted signal is amplified and then input to the conversion unit. Even if the analog / digital conversion performance is limited, detection can be performed with high resolution and the accuracy can be improved.
Further, since the gain of the amplification unit can be set by the gain signal setting unit, the detection accuracy can be freely changed.

  Hereinafter, embodiments of the present invention will be described. A block diagram of an embodiment of the present invention is shown in FIG. In FIG. 1, in the subtracter 1, signals detected by position sensors such as a lower radial sensor 108 and an upper radial sensor 107 are input as an input signal 3. On the other hand, the shift signal 7 calculated by the shift signal setting unit 5 is input to the subtracter 1 after being digital / analog converted by the D / A converter 6 and subtracted from the input signal 3. It is like that. The input signal 3 is appropriately biased by the shift signal 7.

  The signal biased by the subtractor 1 is amplified K times by the amplifier 9. In the amplifier 9, for example, the gain signal setting unit 11 updates the gain signal 13 so as to amplify the input full scale (or any amplification factor) of the A / D converter 10 in the next stage or to restore the amplification degree. It is like that. The gain signal 13 designates the amplification degree K of the amplifier 9. A simplified circuit diagram of the amplifier 9 can be configured as shown in FIG. At this time, the gain can be changed by switching the switch 12 with the gain signal 13.

  A signal 15 that is bias-adjusted by the subtracter 1 and amplified by the amplifier 9 is input to an A / D converter 10 for analog / digital conversion. Then, after the analog / digital converted signal is evaluated with high resolution, this signal is returned to its original unamplified state. For this reason, the amplifier 17 sets the amplification factor 1 / K with respect to the amplification factor K amplified by the amplifier 9 to return the signal to the state before amplification.

  The gain 1 / K is specified by the gain signal setting unit 11. However, the gain K may be designated from the gain signal setting unit 11 and may be read as amplification 1 / K inside the amplifier 17 (configured digitally). The signal 19 passing through the amplifier 17 is added with the shift signal 7 (digital value) by the adder 21 and returned before being biased.

  The signal 23 added by the adder 21 is input to the shift signal setting unit 5 and the gain signal setting unit 11, and the set value of the shift signal and the set value of the gain signal are determined, respectively. For this determination, the state signal 25 of the A / D converter 10 is input to the shift signal setting unit 5 and the gain signal setting unit 11. The state signal 25 of the A / D converter 10 is a signal output when the A / D converter 10 overflows or exceeds a certain set value, for example. The shift signal setting unit 5 and the gain signal setting unit 11 are further supplied with an operation state signal 27 indicating the operation state of the turbo molecular pump main body 100 from the outside.

  The operation state signal 27 is output, for example, when the rotating body 103 exceeds the resonance frequency of the rigid body mode, or is output when the steady operation is reached after the pump is started. The gain signal 13 is designated or switched by the gain signal setting unit 11 based on the operation state signal 27. Then, the digital value read with high precision by the signal 23 or the A / D converter 10 is transmitted to the control processing unit 24 and used for the subsequent control.

Next, the operation of this embodiment will be described.
In the following explanation, for the sake of simplicity, the sensitivity switching in the gain signal setting unit 11 is assumed to be two modes of low sensitivity and high sensitivity. However, the sensitivity may be finely set in a plurality of stages. The number of significant digits of the A / D converter 10 is 8 bits, for example.
FIG. 3 shows the operation flow (column B) and the relationship between the operation time and sensor output (column B) and the operation mode (column C) at this time. In the operation flow of FIG. 3, power is turned on in step 1 (abbreviated as S1 in the figure), and magnetic levitation is started in step 2. For example, the relationship diagram between the operation time and the sensor output in step 1 is shown in FIG. 1A, but is described so as to correspond to the right side of step 1 for the sake of easy understanding (the same applies hereinafter).
When the rotator 103 starts to float, the gain signal setting unit 11 designates the low-sensitivity gain signal 13 as the normal mode. Here, the normal mode refers to a state in which the full scale of the A / D converter 10 corresponds to the entire movable range of the rotor shaft 113.

  In addition, when the rotating body 103 is accelerated, the low gain signal 13 is designated as the normal mode by the gain signal setting unit 11 in the same manner as when the levitation starts. The reason why the sensitivity is low is that it is difficult to hold the rotor shaft 113 in a stable state from the beginning because it may pass through a resonance point or the like in the rigid body mode during the ascent (see step 3). That is, in the control during this time, the floating position of the rotor shaft 113 may swing in a considerably wide range. Therefore, it is necessary to detect the position covering the wide range, and the sensitivity of the amplifier 9 is low. On the contrary, if the sensitivity is set high, measurement may be impossible. In the A / D converter 10, a signal input with respect to full scale is detected with low resolution.

  Next, in step 4, the gain is obtained at a timing such as when the rotating body 103 reaches a preset rotation speed (for example, the rotation speed through the resonance point or the rated rotation speed) or when measurement is started with an electron microscope. A high-sensitivity gain signal 13 is designated as a high-resolution mode from the signal setting unit 11 (see FIG. 9E). These are desirably performed by automatically exchanging signals.

The concept of mode change and centering between the normal mode and the high resolution mode at this time will be described with reference to FIG. In the center alignment, in order to make the mode change effective, the center position determined from the sensor output and the structural center position 0 are first matched to try to change the mode.
For example, a sensor with a sensor output of −5 to 5 V (a corresponding measurement distance range at this time is −5 to 5 mm) and an A / D converter with an input full scale of −5 to 5 V are assumed. Note that the specifications here are used only to explain the concept in an easy-to-understand manner, and are different from the specifications of sensors and the like used for actual control.

  When opposed differential sensors such as the upper radial sensor 107 and the lower radial sensor 108 are used, it is ideal that the center position determined from the sensor output matches the structural center position 0, but actually Since there is an electromagnetic or mechanical center shift, the center position on the structure is usually slightly shifted from zero. In FIG. 4A, due to the presence of this deviation, the displacement of the rotor shaft 113 during rated operation is not 0, which is the center position determined from the sensor output. The rotor shaft 113 is rotated within a range of 2 to 3 mm. As described above, when the deviation between the virtual center and the center position on the true structure viewed from the sensor output is large, the shift signal setting unit 5 determines the deviation, and the subtractor 1 shifts the input signal 3 with respect to the shift signal. 7 to adjust with bias. In FIG. 4 (a), this bias is about 2.5V, and by adjusting this 2.5V with respect to the input signal 3, the output signal of the subtractor 1 is − as shown in FIG. 4 (b). 0.5 to 0.5V.

  As a method for determining this deviation, the shift signal setting unit 5 observes the maximum value and the minimum value of the input signal 23. Then, the center position of the maximum value and the minimum value is obtained to determine the deviation. The shift signal 7 designates the amount of deviation. The gain signal setting unit 11 sets the amplification degree K of the amplifier 9 to 10 times so that the output signal of the subtracter 1 becomes, for example, -5 to 5 V which is the input full scale of the A / D converter 10. In the state stabilized by rated operation, in the case of FIG. 4A, it is operated in the range of 2 to 3 mm, and it is sufficient to observe this range. For this reason, this range will be expanded and observed. If the signal from the amplifier 9 is taken into the A / D converter 10, as shown in FIG. 4C, the entire region can be used for an input full scale of -5 to 5V. As a result, the number of bits of the A / D converter 10 can be used effectively, and the resolution as a sensor can be increased.

In the description of this embodiment, the magnification of the gain signal 13 has been described as being set from low sensitivity to high sensitivity at once. However, the magnification may be gradually increased. Basically, the higher the resolution, the better the holding accuracy.
Note that the bias adjustment using the shift signal 7 and the sensitivity adjustment using the gain signal 13 described above are hypothetical because the entire area of the input full scale of the A / D converter 10 is used as much as possible without waste and is accurately detected. The signal is operated. Therefore, in order to restore and control the actual displacement signal, the magnification is returned to the state before amplification by the amplifier 9 by the amplifier 17 and before the bias by the subtractor 1 is applied by the adder 21.

  When a disturbance is applied in step 5 of FIG. 3, the A / D converter 10 overflows and the status signal 25 of the A / D converter 10 is set. At this time, the gain signal setting unit 11 designates the low-sensitivity gain signal 13 for the normal mode (see FIGS. (F) and (g)). To). Thus, even when a disturbance is applied, measurement is not disabled and stable position detection is possible.

In the present embodiment, the A / D converter 10 has been described as overflowing. However, when the A / D converter 10 exceeds a predetermined set value, a low-sensitivity gain signal 13 may be designated. At this time, the mode may be shifted to the normal mode at once, but the magnification may be gradually decreased toward the normal mode.
Further, if the A / D converter 10 is not over-ranged, normal magnetic levitation operation is possible. Therefore, if the runout of the rotor shaft 113 temporarily increases due to a disturbance, it will soon converge. Since this shake takes a little time to converge, for example, the high resolution mode may not be entered for a few seconds, or the resolution may be gradually increased as described above.

Next, when the transient state due to the disturbance returns to the steady state in step 6, the gain signal setting unit 11 designates the high-sensitivity gain signal 13 again as the high resolution mode (see FIG. (H)).
After that, when the measurement with the electronic mirror is completed in Step 7 or the deceleration of the turbo molecular pump main body 100 is started, the gain signal setting unit 11 sets the normal mode to the low-sensitivity gain signal. 13 is designated (transition from figure (h) to figure (i) by switching sensitivity).
As described above, the number of bits of the A / D converter 10 can be used effectively, and a high resolution can be obtained with an economical A / D converter with a small number of bits. Stable operation can be ensured by disturbances.

The magnetic bearing device of the present invention can be applied to a magnetic levitation type vibration isolation table, a spindle, and the like in addition to a turbo molecular pump.
In the present embodiment, the portion described as being configured digitally is configured with an analog circuit when noise or accuracy becomes a problem or when the D / A converter 6 is not desired to be used. Also good.

Block diagram of an embodiment of the present invention Simplified circuit diagram of the amplifier Operation flow (b), relationship diagram between operation time and sensor output (b) and operation mode at this time (c) Diagram showing the concept of mode change and centering Longitudinal section of turbo molecular pump body

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Subtractor 3 Input signal 5 Shift signal setting part 6 D / A converter 7 Shift signal 9, 17 Amplifier 10 A / D converter 11 Gain signal setting part 13 Gain signal 21 Adder 24 Control processing part 25 State signal 27 Operation state signal 100 Turbo molecular pump body

Claims (5)

A sensor,
A first arithmetic unit capable of adjusting a first shift signal corresponding to a bias with respect to the input signal, the signal output from the sensor as an input signal;
A first amplifying unit capable of amplifying the output signal of the first arithmetic unit and changing the amplification degree, and a converting unit that receives the signal amplified by the first amplifying unit and performs analog / digital conversion When,
A second amplifying unit capable of amplifying the signal converted by the converting unit and changing the amplification degree; and a second shift signal corresponding to a bias amount with respect to the signal amplified by the second amplifying unit. An adjustable second computing unit;
A gain signal setting unit for setting the amplification factor of the first amplification unit and each amplification factor of the second amplification unit;
A shift signal setting unit that sets each shift signal of the first calculation unit and the second calculation unit;
A control signal is generated based on highly accurate data obtained from the conversion unit, and an electromagnet controlled by the control signal;
A magnetic bearing device comprising: a rotor shaft that is levitated and supported by the electromagnet. Detecting means for detecting a maximum value and a minimum value of a change in the input signal;
2. The magnetic bearing device according to claim 1, wherein each shift signal of the shift signal setting unit is set based on a maximum value and a minimum value detected by the detecting means. Detecting means for detecting a maximum value and a minimum value of a change in the input signal;
Based on the maximum and minimum values detected by the detection means and the performance of the conversion unit, the amplification level of the first amplification unit and the amplification level of the second amplification unit of the gain signal setting unit are set. The magnetic bearing device according to claim 1, wherein the magnetic bearing device is set.   2. The amplification factor of the first amplification unit is an inverse of the amplification factor of the second amplification unit, and the first shift signal and the second shift signal are common. 2. The magnetic bearing device according to 2 or 3.   The amplification factor of the first amplification unit and the amplification factor of the second amplification unit by the gain signal setting unit are switched based on a state signal of the conversion unit. The magnetic bearing device according to item 1.

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