JP2001027238A - Magnetic bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the vibration of a housing to a minimum by controlling a rotor to rotate on a center of inertia on the basis of a detecting signal of a position detecting means capable of detecting a radial position of the rotor. SOLUTION: Output signals of radial sensors 8x, 8y are transformed from a static coordinate system to a rotary coordinate system by a coordinate transformation circuit 21. The signal is operated to allow only the DC components lx, ly corresponding to the number of revolutions by unbalancing by a low-pass filter circuit 22. The output signal is transformed into the static coordinate systems xl, yl by a coordinate inverse transformation circuit 23. The electric current corresponding to a calculated deflection signal around an inertia axis is allowed to flow to a coil of a radial magnetic bearing stator to control the radial position of a rotary shaft 3. As a result, the rotary shaft 3 can be rotated on a center of inertia. Whereby the vibration of a chamber housing can be reduced to a minimum though the deflection of the rotary shaft 3 is increased.

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 used for an excimer laser device or the like and having a magnetic bearing for supporting a rotating body in a non-contact manner.

[0002]

2. Description of the Related Art Generally, a bearing device for an excimer laser has a laser chamber for completely sealing a laser gas containing a highly corrosive halogen gas, and a gas circulation fan is installed in the laser chamber. This is a device that circulates the laser gas by rotating the rotation shaft. It is a well-known fact that in an excimer laser bearing device, when impurities are mixed into a laser gas to increase the amount thereof, discharge becomes unstable and laser output light energy decreases.

Conventionally, rolling bearings using ball bearings such as deep groove ball bearings have been used as bearings for this gas circulation fan. However, the grease required for the ball bearings is depleted, and the gas circulation fan becomes difficult to rotate, and mist and impurities that interfere with the operation of the excimer laser are generated from the grease, which are mixed into the gas laser medium circulating in the laser chamber. It has been difficult to use the rolling bearing for a long time for reasons such as unstable discharge. Therefore, in Japanese Patent Application Laid-Open No. 06-021543, a rolling bearing 19 for supporting a rotating shaft 18 of a blower fan 17 is provided with a casing 210 as shown in FIG.
One end of a gas purification tube 220 is connected to the casing 210, the other end is connected to the laser chamber 100, and an oil mist trap 230 and a circulation pump 240, which are a purification unit, are provided in the middle thereof. A rolling bearing device having a configuration in which one end of the drive bearing 18 is connected to a shaft 130 of a drive motor 120 is disclosed. In the process of circulating a part of the gas laser medium in the gas purifying pipe 220, impurities generated in the rolling bearing 19 are removed to prevent the impurities from entering the laser chamber 100.

[0004]

However, in the above-mentioned conventional rolling bearing device, the impurities cannot be completely removed in the gas purifying tube 220. Also,
Since it is necessary to control the laser beam with a submicron relative to the lens barrel, it is necessary to suppress the vibration around the support of the rotating shaft 18. However, the vibration of the blower fan 17 and the rotating shaft 18 is transmitted to the casing 210, Since it causes beam deflection, it cannot be applied to applications requiring precision such as machine tools. In addition, rolling bearing 1
No. 9 also had a problem that it had a short life because of contact support. On the other hand, in the case of a magnetic bearing that supports a rotating body (including a rotating shaft and a blower fan) in a non-contact manner, its vibration is much smaller than that of the rolling bearing 19 and has a longer life. Vibration is transmitted to the outside as in the case of a rolling bearing due to the unbalance force that agitates the laser beam, and in particular, the vibration is transmitted to the casing (housing), and the angle of the laser beam fluctuates.

According to the present invention, the disadvantages of the prior art are improved, and the vibration of the rotating body is allowed to some extent, but the vibration of the housing can be minimized, the power consumption is low, and the magnetic bearing device has a long life. The challenge is to provide

[0006]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a rotating body housed in a housing, and supports the rotating body in a non-contact manner so as to be adjustable in position. In a magnetic bearing device comprising: a plurality of mounted magnetic bearings; and a position detection unit that detects a radial position of the rotator, the rotator has a center of inertia based on a detection signal of the position detection unit. A rotation control means for controlling rotation as an axis is provided. Such rotation control means is preferably a coordinate conversion means for converting each position component in the stationary coordinate system of the rotating body, which is a value detected by the position detection means, into a rotation coordinate system, and a conversion result of the coordinate conversion means. Low-pass filter means for passing only a DC component corresponding to the number of rotations; and coordinate inverse transformation means for inversely transforming each position component of the rotating coordinate system that has passed through the low-pass filter means into a stationary coordinate system. Based on a value obtained by adding each position component obtained by the inversion means to the value detected by the position detection means with an inverse sign, control is performed so that the rotating body rotates around the center of inertia.

According to the present invention, since the rotating body is controlled to rotate around the center of inertia, the vibration of the housing is suppressed as much as possible even if the rotating body swings to some extent.

[0008]

An embodiment of the present invention will be described with reference to the drawings. 1 is a block diagram of a control circuit of a magnetic bearing device according to an embodiment of the present invention. FIG. 2 is an axial sectional view of a magnetic bearing device for an excimer laser according to the present invention. It is AA sectional drawing of a bearing device. This embodiment shows a case where the magnetic bearing device of the present invention is applied to a magnetic bearing device for an excimer laser. First, the configuration of a magnetic bearing device for an excimer laser will be described. In FIG. 2, 1 is a laser chamber, 2
Is a discharge excitation unit, 3 is a rotating shaft, 4 is a cross-flow fan for gas circulation mounted on the rotating shaft 3, 5 is a chamber housing, 6 is a radial magnetic bearing stator, 7 is a thrust magnetic bearing stator, and 8 is a radial sensor. , 9 is a thrust sensor, 11 is a coupling spacer, 12 is a drive side magnetic coupling, 13 is a drive motor, 31 is a thrust flange,
32 is a radial magnetic bearing rotor part of the rotating shaft 3, 33 is a rotating shaft side coupling magnet which is a rotor part for the drive motor 13, and 61 is a shield partition. The radial sensor 8 and the thrust sensor 9 are position detecting means.

The chamber housing 5 is a case that forms the entire laser chamber 1. The discharge excitation section 2 is attached to a predetermined position on the inner wall surface of the chamber housing 5. The rotating shaft 3 to which the thrust flanges 31 on both sides are fixed is rotatably supported in a non-contact state. A closed housing 10 is provided at a closed end 51 of the chamber housing 5 at the left end in the figure to seal one end of the laser chamber 1. A coupling spacer 11 made of non-magnetic ceramic is fixed to a laser chamber housing closed end 51 fixed to the right end side of the chamber housing 5 in the figure, and seals the other end of the laser chamber 1. .

A radial bearing rotor section 32 is provided on both sides of the cross-flow fan 4 of the rotating shaft 3. At a position on the chamber housing 5 side facing the radial bearing rotor section 32, a radial magnetic bearing stator 6 is provided at a predetermined interval, and a radial sensor 8 is provided adjacent thereto. A radial magnetic bearing coil 62 is attached to the radial magnetic bearing stator 6.
The radial bearing rotor section 32 and the radial magnetic bearing stator 6 constitute a magnetic bearing.

The shield partition wall 61 is made of a non-magnetic metal material and is welded and fixed to the chamber housing 5 and the chamber housing closed end 51 so as to surround the rotating shaft 3. As described above, the radial magnetic bearing stator 6 and the radial sensor 8 are disposed in a closed space formed by the radial partition wall 61 and the inner wall of the chamber housing 5. In this embodiment, the shield partition wall 61 is fixed by welding. However, the present invention is not limited to this configuration, and the shield partition wall 61 may be attached with a screw via an O-ring. The radial sensor 8 detects the displacement of the rotary shaft 3 in the radial direction as a change in inductance over the shield partition 61. By performing feedback control for controlling the current flowing through the coil 62 of the radial magnetic bearing in accordance with the change in the inductance, the rotating shaft 3
Of the shield wall 61 in the radial direction is kept constant.

The thrust magnetic bearing stator 7 is provided on the inner wall end face of the chamber housing 5 so as to face the thrust flange 31 of the rotating shaft 3, and is sealed by a thrust bearing inter-wall 71. The thrust sensor 9 is provided in the closed housing 10, and is sealed in the closed housing 10 by a thrust sensor partition 91. The thrust sensor 9 detects the axial displacement of the rotating shaft 3 as a change in inductance over the thrust sensor partition 91. By performing feedback control for controlling the current flowing through the coil of the thrust magnetic bearing stator 7 in accordance with the change in the inductance, the gap between the thrust sensor 9 side end surface of the rotating shaft 3 and the thrust sensor partition 91 in the axial direction is reduced. Try to keep it constant.

A rotating shaft-side coupling magnet 33 is attached to the outer peripheral surface of the end of the rotating shaft 3 on the coupling spacer 11 side, and is opposed to the inner peripheral surface of the coupling spacer 11 in a non-contact manner. The drive motor 13 is attached to the chamber housing closed end 51 by a motor attachment body 14, and a cylindrical drive-side magnetic coupling 12 is fixed to a tip of a shaft 131 of the drive motor 13. A drive-side magnetic coupling magnet 121 is attached to the inner peripheral surface side of the drive-side magnetic coupling 12, and this portion is arranged so as to face the outer peripheral surface of the coupling spacer 11 in a non-contact manner. The drive-side magnetic coupling magnet 121 and the rotating shaft-side coupling magnet 33 are arranged at a predetermined interval, and the drive-side magnetic coupling magnet 121, the coupling spacer 11, and the rotating shaft-side coupling magnet 33 provide: A magnetic coupling unit is configured.

A touchdown bearing 15 is provided in the chamber housing 5 in the vicinity of the thrust magnetic bearing stator 7, and has a function of stopping the rotation shaft 3 when it is abnormally rotated. Are located in
Thus, the rotating shaft 3 fitted inside the cross flow fan 4
It is held in a space sealed by the coupling spacer 11, the shield partition 61 of the chamber housing 5, the thrust bearing partition 71, and the thrust sensor partition 91 of the sealed housing 10, and has a radial bearing rotor portion 32 and a radial magnetic bearing stator. It is supported in a non-contact manner by a magnetic attraction force between the six.

In the above configuration, the rotating shaft 3 rotates when the driving force of the driving motor 13 is transmitted via the driving magnetic coupling 12 and the coupling spacer 11. At this time, the driving force of the driving motor 13 is controlled by the driving magnetic coupling magnet 121 of the driving magnetic coupling 12.
Is transmitted to the rotating shaft 3 by a non-contact coupling force due to a magnetic force between the rotating shaft 3 and the rotating shaft side coupling magnet 33. By the rotation of the gas circulation fan 4, as shown in FIG. 3, the laser gas containing the halogen gas in the closed space of the laser chamber 1 circulates as shown by the arrow.

Next, a control circuit for rotating the rotating shaft 3 supported in a non-contact manner around the center of inertia will be described with reference to FIG. In the figure, 3 is a rotation axis, 8
x and 8y are components of the radial sensor 8, 8x is an X component, 8y
Has a function of detecting each of the Y components. Reference numeral 21 denotes a coordinate conversion circuit as a coordinate conversion means, which converts a stationary coordinate system into a rotating coordinate system. Reference numeral 22 denotes a low-pass filter circuit (Low Pass Filter: LPF circuit) which is a low-pass filter means, and passes only a DC component corresponding to the rotation speed.
Reference numeral 23 denotes a coordinate inverse transformation circuit which is a coordinate inverse transformation means, which performs an inverse transformation from the rotating coordinate system to the stationary coordinate system. 77 is a current amplifier for amplification.

First, the output signals of the radial sensors 8x and 8y are converted by the coordinate conversion circuit 21 from a stationary coordinate system to a rotating coordinate system. Assuming that the angular velocity of rotation of the rotating shaft 3 is ω, the stationary coordinate system is (xs, ys), and the rotating coordinate system is (Lx, Ly), Lx = xs · cosωt + ys · sinωt Ly = −xs · sinωt + ys · cosωt

The coordinate conversion circuit 21 performs the calculation of these two equations and converts the rotation into a rotating coordinate system (Lx, Ly). The LPF circuit 22 converts the signal converted into the amount on the rotation coordinate into a DC component (I
x, Iy). If the filter constant is K and the time constant (cutoff frequency) is Ts,

The output signal of the LPF circuit 22, which has passed only the DC component corresponding to the rotation speed, is converted by the coordinate reverse conversion circuit 23 into a stationary coordinate system (xl, yl). xl = Ix.cos.omega.t-Iy.sin.omega.t yl = Ix.sin.omega.t + Iy.cos.omega.t The coordinate inverse conversion circuit 23 performs the operation of these two equations, and only the unbalanced DC component corresponds to the stationary coordinate system (xl, yl). And added to the detection signals of the radial sensors 8x and 8y with an opposite sign. A current corresponding to the shake signal about the inertial axis calculated in this way is passed through the coil 62 of the radial magnetic bearing stator 6 to control the radial position of the rotating shaft 3.

Accordingly, the component synchronized with the rotation is removed, and the BEF (Band E) having the center frequency synchronized with the rotation is removed.
A function similar to that of a limination filter (a filter that cuts off a specific frequency) can be obtained, and a state in which the gain of the control system is reduced only for the rotation synchronization frequency, that is, a state in which the rigidity is extremely reduced. As a result, the rotation shaft 3 can rotate around the center of inertia (control around the main axis of inertia). As a result, the run-out of the rotary shaft 3 becomes larger than in the case of the conventional control centered on the geometric center, but the reaction force acting on the radial magnetic bearing stator 6 becomes very small. , As much as possible. In addition, since the control of the rotational speed component is not performed, the power consumption can be suppressed.

FIG. 4A is a block diagram of a control processing procedure of the magnetic bearing device according to the present invention. In the figure,
The coordinate separation processing circuit 73 separates the axial displacement Z, the rotation angle θ about the X axis, the rotation angle φ about the Y axis, and the like from the sensor signal from the rotation detection circuit 72 in the coordinate separation processing circuit 73, and compensating circuit 7
5, the position correction amount is calculated.
Amplified by On the other hand, the displacements X and Y in the radial direction of the rotation shaft 3 are separated from the sensor signal of the rotation detection circuit 72 by the coordinate separation processing circuit 74, and the automatic balance control which is not included in the conventional control processing procedure of FIG. After the processing by the circuit 76, the position correction amount is calculated by the compensation circuit 75, and the calculation result is amplified by the current amplifier 77. This automatic balance control circuit 76
And the processing by the compensation circuit 75 are performed by the coordinate conversion circuit 2 described above.
1, low-pass filter circuit 22, and coordinate inverse transformation circuit 2
Perform in 3.

FIG. 5 shows the configuration of a test apparatus in which a rotation test was performed before the present invention was applied to an actual magnetic bearing apparatus for an excimer laser. In FIG. 9A, a rotor 81 as a rotating shaft is provided in the center of a magnetic bearing housing 80.
The two ends are disposed in a state of being supported in a non-contact manner by magnetic bearings (not shown).
The x, 8y, and rotation detectors 82 are arranged. In the same figure (b) showing the side surface of the magnetic bearing housing 80, 83
Is a disk for detecting rotation. Detection signals from the radial sensors 8x and 8y are output to a coordinate conversion circuit 86 via a sensor driver 84. On the other hand, the detection signal from the rotation detector 82 is output to the coordinate conversion circuit 86 in synchronization with the signal via the trigger circuit 87. The current flowing through the coil (not shown) of the magnetic bearing is controlled according to the components Xr and Yr of the calculation result by the coordinate conversion circuit 86. The coordinate conversion circuit 86 includes the coordinate conversion circuit 21, the low-pass filter circuit 22, and the coordinate inverse conversion circuit 23 described above. The dimensions of the rotor 81 used were 100 mm in diameter, 500 mm in length, and 50 mm in outer diameter of the magnetic bearing portion. The weight of the rotor 81 is about 8
The test was carried out at a rotational speed of kgf and the rotor 81 of about 5800 rpm.

As a result of the test using this test apparatus, the rotor 8
It was found that No. 1 was able to rotate around the center of inertia, and the reaction force acting on the bearing was extremely small. FIG. 7A shows a time waveform of a vertical vibration (G) of the magnetic bearing housing 80 in the test apparatus,
6 and the spectrum of the vibration (dB) in FIG.
The vertical vibration (G) time waveform of the magnetic bearing housing and the vibration (dB) of FIG. 6B in the case of the conventional control shown in FIG. It is clear when compared with the spectrum. That is, the amplitude of the vertical vibration of the magnetic bearing housing 80 in the test apparatus of FIG. 7 is smaller than the amplitude of the vertical vibration of the magnetic bearing housing in the case of the conventional control centered on the geometric center of FIG. It is getting smaller. Similarly, the time waveform of the horizontal vibration (G) of the magnetic bearing housing 80 in the test apparatus of FIG. 9A and the spectrum of the vibration (dB) of FIG. 9B are also shown in FIG.
The amplitude is clearly smaller than the horizontal time waveform and spectrum of the magnetic bearing housing by the conventional control centered on the geometric center shown in FIG.
Therefore, it can be seen that the vibration of the magnetic bearing housing 80 is smaller than in the case of the conventional control centered on the geometric center.

Further, as a result of the fact that the rotor 81 can rotate around the center of inertia, as shown in FIG. 10B, the rotating body ( The amplitude of the whirling resurge diagram of the rotor 81) has increased from 4 μm to 20 μm. That is, the run-out of the rotating body of the magnetic bearing device of the present invention is larger than in the conventional example.

However, in the case of the above-described test apparatus, a coil (not shown) of the radial magnetic bearing stator of the magnetic bearing is used.
As shown in FIG. 11B, the current flowing through the X-axis and the Y-axis components ranges from 2.5 to 2.8 A to 0.3 to 0.3 in both the X and Y components, as shown in FIG. Since it is reduced to 4A, which is about 1/7, it can be seen that power consumption is suppressed. This is because the conventional control of the rotational speed component is not performed.

As a matter of course, it has stiffness at frequencies other than the rotation speed, and as shown in FIG. 1, the deflection at frequencies other than the rotation frequency is controlled, so that the function as a bearing is not impaired. The attachment of the magnetic bearing to the housing 80 can be applied not only to the case where the magnetic bearing is directly attached as in this embodiment but also to the case where the magnetic bearing is attached via a non-magnetic material or a cushioning member therebetween. Further, the magnetic bearing device of the above embodiment is shown as a control circuit of a magnetic bearing device for an excimer laser. However, the present invention is not limited to this, and the vibration of the rotating body can be tolerated to some extent, but it is necessary to reduce the vibration of the housing. Can be applied to various uses.

[0027]

As described above, according to the present invention,
Since the rotating body is controlled so as to rotate around the center of inertia, the rotating body swings to some extent, but the vibration of the housing can be minimized and the power consumption can be greatly reduced accordingly. As a result, the life of the device can be extended.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a control circuit of a magnetic bearing device according to an embodiment of the present invention.

FIG. 2 is an axial cross-sectional configuration diagram of a magnetic bearing device for an excimer laser.

FIG. 3A shows the magnetic bearing device for the excimer laser of FIG. 2;
-A sectional view

FIG. 4 is a block diagram showing a control processing procedure of a magnetic bearing device according to the present invention (a) and a block diagram showing a control processing procedure of a conventional magnetic bearing device (b).

FIG. 5A is a block diagram showing the configuration of a test apparatus using the control circuit of the magnetic bearing device of the present invention, and FIG. 5B is a side view of the magnetic bearing housing.

FIG. 6 shows a time waveform (a) and a spectrum (b) showing vertical vibration of a magnetic bearing housing in a conventional geometric center control circuit.

FIG. 7 shows a time waveform (a) and a spectrum (b) showing vertical vibration of the magnetic bearing housing in the control circuit of the present invention.

FIG. 8 is a time waveform (a) and a spectrum (b) showing horizontal vibration of a magnetic bearing housing in a conventional geometric center control circuit.

FIG. 9 is a time waveform (a) and a spectrum (b) showing horizontal vibration of the magnetic bearing housing in the control circuit of the present invention.

FIG. 10 shows a whirling Lissajous figure of a rotating body by a conventional geometric center control circuit (a) and a whirling Lissajous figure of a rotating body by a control circuit of the present invention (b)

11 (a) is a waveform diagram of a current flowing through a coil of a radial magnetic bearing stator by conventional geometric center control, and FIG. 11 (b) is a waveform diagram of a current flowing through a coil of the radial magnetic bearing stator according to the control of the present invention.

FIG. 12 is a schematic configuration diagram in the axial direction showing a conventional rolling bearing device for an excimer laser.

[Explanation of symbols]

 3 Rotating body (rotary shaft and cross-flow fan) 6 Stator part (radial magnetic bearing stator) 8x, 8y Position detecting means (radial sensor) 32 Rotor part (radial magnetic bearing rotor part) 6,32 Magnetic bearing

Claims (1)

[Claims] 1. A rotating body housed in a housing, a plurality of magnetic bearings mounted in the housing for supporting the rotating body in a non-contact manner, and a radial position of the rotating body. And a position detecting means for detecting the rotation of the rotating body based on a detection signal of the position detecting means. Characteristic magnetic bearing device.