JP2002089489A - Structure of once-through fan for excimer laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a structure of a once-through fan for an excimer laser device capable of securing control stability of magnetic bearing control. SOLUTION: In this structure, both ends of a rotary shaft 2 are disposed with first and second radial magnetic bearings 101, 103, first and second protection bearings 11, 15 are disposed near the radial magnetic bearings 101, 103, and a third radial magnetic bearing 102 is disposed on a fan side near a motor 104. The third radial magnetic bearing 102 corrects a negative spring element of the motor 104.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a cross-flow fan for an excimer laser device, and more particularly to a structure for supporting and rotating a rotating shaft in the fan device.

[0002]

2. Description of the Related Art A cross-flow fan for laser gas circulation of an excimer laser device is required to have low vibration characteristics and durability.
In order to cope with this, a magnetic bearing capable of realizing maintenance-free with non-contact support has been studied for a bearing used for a once-through fan.

[0003] For example, JP-A-11-087810 and JP-A-11-307933 show examples of the use of magnetic bearings. In these publications, a rotating shaft is supported in a non-contact manner by an axial magnetic bearing composed of two radial magnetic bearings and two axial electromagnets, and a motor rotor fixed to the rotating shaft is driven to rotate by a motor stator on the stator side. The configuration is shown.

FIG. 14 is a cross-sectional view showing a basic structure of a fan for circulating excimer gas and its peripheral portion. FIG.
In 4, the fan 203 is disposed in the chamber 201, and a laser gas is sealed in the chamber 201. The fan 203 attached to the rotation shaft 202 rotates in the chamber 201. Magnetic bearings for supporting the rotating shaft 202 are arranged on both sides of the chamber 201, and on the left side of FIG.
5, a magnetic magnetic bearing 206 composed of axial electromagnets 207 and 208 and a position sensor 209, and a motor 211 composed of a motor rotor 218 and a motor stator 217.
And a protective bearing 212 as a touch-down bearing capable of supporting the radial direction and the axial direction to protect the rotating shaft 202.

[0005] On the right side of FIG.
A radial magnetic bearing 215 including a position sensor 214 and a protective bearing 216 capable of supporting only in the radial direction are provided.

Here, the inner diameters of the protective bearing 212, the motor stator 217, and the radial electromagnet 204 are adjusted to be substantially coaxial. The gap between the inner diameter of the protective bearing 212 and the opposing rotating shaft 202 is
Is set slightly smaller than the minimum size of the gap between each inner diameter of the radial electromagnet 204 and the rotating shaft 202 opposed thereto, thereby preventing the rotating shaft 202 from contacting the radial electromagnet 204 and the motor stator 217.

[0007] The axial magnetic bearing 210 and the radial magnetic bearings 206 and 215 are provided with position sensors 209 and 209, respectively.
The position of the rotary shaft 202 is detected by 205 and 214, and the signal obtained by comparing the output of each position sensor with the command value is phase-compensated by a control circuit (not shown), the current is amplified by the power amplifier, and the current is amplified by the corresponding electromagnet coil. Current is applied.

[0008]

In the cross-flow fan for laser gas circulation of the excimer laser device shown in FIG.
As a result, the pressure of the gas to flow through is as high as 5000 hPa at maximum, and in order to rotate the fan 203 under this high output,
It is necessary to increase the output of the motor 211 that drives the rotating shaft 202. However, since the motor output is high, the attraction between the motor rotor 218 and the motor stator 217 constituting the motor 211 is increased.
This is simply a rotating shaft 2 having a built-in motor rotor 218.
Not only increases the disturbance to the rotation axis 202
This also affects the control stability of the radial magnetic bearing 206 that supports the motor.

The radial magnetic bearing is supported by a motor 211.
It is necessary to control stably in both the non-rotational state where the motor is not affected and the maximum rotation state where the influence of the motor is large. Further, it is necessary to rotate the gas flowing through all pressure ranges of 5000 hPa or less at the maximum, and it has been difficult to secure the stability of the magnetic bearing control.

FIG. 15 shows a structure near the radial magnetic bearing portion, and FIG. 16 is a block diagram of a magnetic bearing control system for explaining the influence of the motor based on the radial magnetic bearing of FIG.

In FIG. 15, a distance between a desired radial magnetic bearing electromagnet 204 and a rotating shaft 202 is represented by Xo,
The floating position of the rotating shaft 202 is controlled by measuring the displacement x from the distance Xo and adjusting the attractive force of the radial magnetic bearing electromagnet 204 based on the measured value. Here, a motor 211 is arranged near the radial magnetic bearing 206, and the motor 211 affects the control of the radial magnetic bearing 206.

In FIG. 16, P (s) is the motor 211
Represents the control target of the magnetic bearing alone without considering
(S) shows the transfer function of the magnetic bearing control circuit, and x shows the displacement of the rotary shaft from the position of a predetermined floating distance Xo.
After a comparison operation is performed between the output x 'of the position sensor for detecting the displacement x of the rotating shaft and the command value r, a magnetic bearing control circuit G (s) composed of a control circuit composed of proportional, integral and differential elements
The electromagnetic force Fa calculated in (1) acts on the rotating shaft 202 to support the rotating shaft 202 at a predetermined position. Here, km is a negative spring constant of the motor 211.

In FIG. 15, when the rotating shaft 202 moves downward, the suction force F from the lower motor stator 217 is obtained.
m increases, resulting in an apparently negative spring constant. The value of km increases as the output of the motor 211 increases, that is, as the suction force between the motor rotor 218 and the motor stator 217 increases. In other words, the control of the magnetic bearing requires a design taking this km into consideration.
Greatly fluctuates (this km becomes 0 when the rotational drive is stopped), so it is difficult to ensure the stability of the magnetic bearing support in all the states.

FIG. 17 shows a gain curve of a Bode diagram of a control target (a transfer function from Fa to x in FIG. 16) of the magnetic bearing when the motor is driven and when the motor is not driven. In FIG. 17, a solid line a is a gain curve when the motor is not rotating, and a solid line b is a gain curve when the motor is driven. It can be seen that the gain curve at the time of driving the motor decreases in the low frequency range. Since the gain decreases in the low frequency range and the gain curve has a flat characteristic (the frequency gradient of the gain is almost 0) in a wide range of the low frequency range, the controllability of the magnetic bearing deteriorates.

FIG. 18 is a diagram showing an open-loop transfer function when a magnetic bearing control circuit that ensures stability in both states (when the motor is driven and when it is not driven) is designed based on the control target of the magnetic bearing. Yes, (a) shows gain characteristics, and (b) shows phase characteristics.

In FIG. 18 (a), a solid line c indicates a state where the motor is not driven, and a solid line d indicates an open loop transfer function when the motor is driven. By driving the motor 211, the gain margin shown in FIG. 18A is reduced from A to A ', and it can be seen that the margin for control stability is greatly reduced. As a countermeasure against this, there is a method in which the crossover frequency is set to a high frequency side to suppress the influence of the motor. However, in the excimer laser device, a laser gas is discharged by a high voltage for laser oscillation to excite the laser gas. For this reason, in the magnetic bearing used in the excimer laser device, it is necessary to reduce the control gain of the magnetic bearing as much as possible so as not to be affected by the high frequency noise.

Further, the fan 203 used is long in the axial direction, and the rotating shaft 202 itself becomes long. As a result, there is a problem that the bending mode holding frequency of the rotating shaft 202 is reduced. Also, it is necessary to lower the gain of the magnetic bearing control system. For these reasons, it is not possible to take a method of setting the crossover frequency, which would increase the gain in the high frequency range, on the high frequency side.

As described above, the cross-flow fan for circulating the laser gas of the excimer laser apparatus has a maximum gas pressure of 5 through.
000 hPa, and the output of the motor 211 that drives the rotary shaft 202 to rotate the fan 203 on this high output side becomes higher, resulting in a negative spring constant k
There is a problem inherent to the excimer laser device that m becomes large, a high frequency noise generation source is located in the vicinity, and it becomes difficult to secure control stability of the magnetic bearing control because the rotating shaft 202 becomes long.

In addition, since the rotating shaft 202 is long, the bending natural frequency of the rotating shaft 202 is low, and there is a problem that the controllability of the magnetic bearing is poor and the rotating shaft 202 is easily bent.

SUMMARY OF THE INVENTION It is, therefore, a primary object of the present invention to provide a structure of a cross-flow fan for an excimer laser device capable of performing stable magnetic bearing control without increasing the gain of the magnetic bearing even when driving a motor.

[0021]

SUMMARY OF THE INVENTION The present invention provides a rotary shaft to which a fan is mounted, a control type magnetic bearing for supporting the rotary shaft in a non-contact manner, and a control type magnetic bearing which cannot support the rotary shaft. In the structure of a cross-flow fan for an excimer laser device, comprising a protective bearing for supporting the rotating shaft and a motor for rotating the rotating shaft, and circulating the laser gas in the chamber by rotation of the fan by rotation of the motor, the control type magnetic bearing is An axial magnetism including radial electromagnets arranged at three locations in the axial direction, a radial magnetic bearing including a position detection sensor arranged around each radial electromagnet, one axial electromagnet, and at least one permanent magnet Bearings, the axial electromagnet is arranged opposite one end face of the rotating shaft, the permanent magnet is arranged opposite the other end face of the rotating shaft, A first radial magnetic bearing of the radial magnetic bearings is disposed near the axial electromagnet, and a second radial magnetic bearing is disposed on the inner side of the rotating shaft with respect to a permanent magnet disposed opposite to the end surface of the rotating shaft. The third radial magnetic bearing is disposed between the motor and the fan.

The protective bearing supports both the axial direction and the radial direction of the rotating shaft, a first protective bearing disposed near the axial electromagnet and the motor, and supports only the radial direction of the rotating shaft. And a second protective bearing disposed near the radial electromagnet.

Further, a third protection bearing is provided between the third radial magnetic bearing and the fan and can support only the radial direction.

Further, a soft magnetic material is provided on a portion of the rotating shaft facing the radial electromagnet, the axial electromagnet, and the permanent electromagnet, and the soft magnetic material of the rotating shaft facing the axial electromagnet is fixed to the rotating shaft. Except for the magnetic material, the rotating shaft has the same or smaller diameter from the axial electromagnet side to the permanent magnet side, and has a protection fixing the axial electromagnet and the first protection bearing or the first protection bearing. By removing the bearing housing from the housing and further removing the soft magnetic material, the stator and the fan of the rotating shaft facing the axial electromagnet from the rotating shaft, the rotating shaft is removed from the chamber and the outside of the housing without removing the housing from the chamber. It is characterized by being able to.

Further, the radial electromagnet has eight magnetic poles in the circumferential direction, and an electromagnetic force is generated on the rotating shaft by two adjacent magnetic poles, or four magnetic poles in the circumferential direction and the magnetic force are generated in the axial direction. Each of the radial magnetic bearings has two control shafts, each of which has two control poles, and each control shaft supports its own weight. It is characterized by doing.

Further, the control axis direction of the radial electromagnet of each radial magnetic bearing is 45 ° ± 2 with respect to the anti-vertical direction.
It is characterized by being within 2.5 °.

Further, a part of the radial electromagnet of the radial magnetic bearing is characterized in that a coil is not wound around a magnetic pole that does not support the weight of the rotating shaft.

Further, the radial electromagnet has four magnetic poles in the circumferential direction, and an electromagnetic force is generated on the rotating shaft by the two adjacent magnetic poles, or two magnetic poles in the circumferential direction and the magnetic force are generated in the axial direction. It is characterized in that each of the magnetic poles has two magnetic poles, and a set of two magnetic poles close to each other in the axial direction applies an electromagnetic force to the rotating shaft, and the center of each magnetic pole is all above a horizontal plane.

Further, a radial magnetic bearing which is composed of a proportional element, an integral element and a differential element and is close to the first and second protective bearings, a control circuit for controlling the axial magnetic bearing, and a proportional element or a differential element And a control circuit for controlling the third radial magnetic bearing.

Further, the magnetic bearing is controlled by software processing. Further, a soft magnetic member having a notch or a hole is provided on a rotating shaft facing the electromagnet of the axial magnetic bearing, and a magnetic rotation sensor is provided at a position facing the soft magnetic member. .

Further, the control parameter of the third radial magnetic bearing is changed according to the number of rotations obtained by the rotation sensor.

[0032]

FIG. 1 is a longitudinal sectional view of a cross-flow fan for an excimer laser device according to an embodiment of the present invention. FIG.
, A laser gas is sealed in a chamber 1, and a fan 3 attached to a rotating shaft 2 rotates in the chamber 1. Magnetic bearings supporting the rotating shaft 2 are arranged on both sides of the chamber 1. On the left side of FIG. 1, two radial magnetic bearings 101, 102, an axial electromagnet 8, a position sensor 9, and a motor 1 which are part of the axial magnetic bearing.
The motor stator 10 and the protective bearing 11 included in the electric motor 04 are provided. The radial magnetic bearing 101 is composed of the radial electromagnet 4 and the position sensor 6, and the radial magnetic bearing 102 is composed of the radial electromagnet 5 and the position sensor 7. The protection bearing 11 supports the rotating shaft 2 in the radial direction and the axial direction.
When the radial magnetic bearings 101 and 102 cannot support the rotating shaft 2 in a non-contact manner, the rotating shaft 2 is supported when the non-operating or abnormal state occurs or when the radial magnetic bearings 101 and 102 cannot support the rotating shaft 2 in a non-contact manner.

On the right side of FIG. 1, one radial magnetic bearing 103 composed of a radial electromagnet 12 and a position sensor 13 is provided.
And a permanent magnet 14 on the stator side, which is a part of the axial magnetic bearing, and a suction mechanism composed of a magnetic body on the rotating shaft side, and a protective bearing 15 capable of supporting only in the radial direction.

Here, the protective bearing 11 and the motor stator 1
0 and the inner diameters of the radial electromagnets 4 and 5 are adjusted to be substantially coaxial. The gap between the inner diameter of the protective bearing 11 and the opposing rotary shaft is set slightly smaller than the initial dimension of the gap between each inner diameter of the motor stator 10 and the radial electromagnets 4 and 5 and the opposing rotary shaft. The shaft 2 is prevented from contacting the motor 104 and the electromagnet member.

Similarly, the protective bearing 15 is adjusted substantially coaxially with the inner diameter of the radial electromagnet 12. Protection bearing 1
5 is set slightly smaller than the gap between the inner diameter of the radial electromagnet 12 and the opposing rotating shaft 2 to prevent contact between the rotating shaft 2 and the electromagnet member. .

In FIG. 1, the protective bearings are arranged at two places, but the third protective bearing 16 may be arranged at an intermediate portion in consideration of the fact that the rotating shaft is long and long. Such an embodiment is shown in FIG.

Each magnetic bearing unit detects the position of the rotating shaft by each position sensor, and a signal obtained by comparing the output of each position sensor with a command value is phase-compensated by a control circuit (not shown). When the current is amplified and a current flows through the coil of the electromagnet, the rotating shaft 2 is supported by the radial magnetic bearings 101, 102, 103 and the axial magnetic bearing in a non-contact manner. Here, a radial magnetic bearing 102 is used to compensate for the negative spring element of the motor.
The control circuit used for the radial magnetic bearings 101 and 103 is composed of proportional and differential elements, and further includes an integral element to perform fixed position control with a small deviation from a command value, thereby supporting the rotating shaft 2. The radial magnetic bearing 102 has a control circuit including only a proportional element and a differential element, and not only compensates for a negative spring element of the motor 104 but also improves controllability of the radial magnetic bearing 101.

FIG. 3 shows the radial magnetic bearing 101 and the motor 1.
FIG. 4 is a schematic view of a radial magnetic bearing 102 and a radial magnetic bearing 102, and FIG. 5 to 8 are Bode diagrams of the control target of the radial magnetic bearing 101.

Next, the two radial magnetic bearings 101, 1
02 will be described.

In FIG. 3, as shown in FIG. 1, since the rotating shaft 2 for excimer gas flow of the excimer laser device is long, when the rigid mode of the rotating shaft 2 is considered, the rotating shaft 2 is detected. The output x1 of the position sensor 6 and the output x2 of the position sensor 7 have substantially the same value. Taking advantage of this,
FIG. 4 shows a block diagram in which the displacement of the rotating shaft 2 is x. However, the sensor amplifier is omitted for simplification.

In FIG. 4, P (s) indicates a control target of the radial magnetic bearing 101 when the motor 104 is not affected, G1 (s) indicates a control circuit of the radial magnetic bearing 101, and G2 (s) indicates a control circuit. The control circuit of the radial magnetic bearing 102 is shown, km indicates a negative spring constant by the motor 10, r1 is a command value of the radial magnetic bearing 101, and r
Reference numeral 2 denotes a command value of the radial magnetic bearing 102.

G1 (s) is composed of a proportional element, an integral element and a differential element. The control target P (s) of the magnetic bearing is
It is represented by 1 / (Ms2-k). Here, the magnetic bearing also has a negative spring element, and k corresponds to this negative spring constant. Therefore, the control object in consideration of the influence of the motor 104 and the influence of the radial magnetic bearing 102, that is, the transfer function from Fa to x is P1 (s) = 1 / (Ms2-k-k).
m + G2 (s)).

Here, FIG. 5 shows a transfer function from Fa to x (only the gain curve) when G2 (s) is constituted only by the proportional element.

In FIG. 5, the solid line a represents the transfer function in the case of G2 (s) = 0 without the influence of the motor (km = 0) and (P1 (s) = 1 / (Ms ² -k)). b includes the influence of the motor, and the transfer function (P1) when G2 (s) = 0
(S) = 1 / (Ms ² -k-km)), and the solid line c includes the influence of the motor 104, and further, G2 (s) = (k + k)
m), the transfer function (P1 (s) = 1 / Ms ² ) is shown, and the solid line d includes the influence of the motor 104 and G2
(S) = ky, transfer function (P1 (s) = 1 / (Ms ² −k−km + ky) in the case of 0 <ky <(k + km)), and the solid line e includes the influence of the motor 104 and further includes G2
The transfer function (P1 (s) = 1 / (Ms ² -k-km + ke)) is shown when (s) = ke, ke> (k + km).

As shown in FIG. 5, when the control circuit of the radial magnetic bearing 102 is composed of only the proportional element, and when the gain of the proportional element is not less than 0 and not more than (k + km), the control target P1 (s ) Can increase the gain in the low frequency range.

On the other hand, the gain of the proportional element is (k + k
m) or more, a peak (A in FIG. 5) may be generated in the control target P1 (s) of the radial magnetic bearing 101, and the magnetic bearing controllability may be impaired.

As described above, the control circuit of the radial magnetic bearing 102 is constituted by only the proportional element and the gain of the proportional element is set to be equal to or greater than 0 (k + km), whereby the control object P1 (s) of the radial magnetic bearing 101 is controlled. As a result, the gain of the low frequency range can be increased, and as a result, the stability of the magnetic bearing can be improved.

FIG. 6 shows a transfer function from Fa to x when G2 (s) is composed of only the differential element, where (a) is a gain characteristic and (b) is a phase characteristic. In FIG. 6, the solid line a includes the influence of the motor, and the transfer function (P1 (s) = 1 / (Ms ² −k−k) when G2 (s) = 0.
m)), including the effect of motor 104 and G2
Transfer function when (s) = cs and the value of c is increased (P1 (s) = 1 / (Ms ² + cs−k−km))
The characteristics are shown by solid lines b, c, d and e. Here, c is called a differential gain.

As shown in FIG. 6, as c becomes larger, the gradient of the gain flat portion in the low-frequency region of the control target P1 (s) of the radial magnetic bearing 101 becomes larger, and the phase also shows the phase advance characteristic. That is, by configuring the control circuit of the magnetic bearing with the differential element, the gain curve in the low frequency region can be improved, and at the same time, since the phase is advanced, the control performance of the radial magnetic bearing 101 is greatly improved.

FIGS. 7 and 8 show transfer functions from Fa to x when G2 (s) is composed of both a proportional element and a differential element.

In FIG. 7, the solid line a shows the case where the differential element is not included for comparison, includes the influence of the motor 104, and further, the transfer function (P1) when G2 (s) = (k + km).
(S) = 1 / Ms ² ). The solid line b includes the transfer function (P1 (s) = 1 / (Ms ² + cs) in the case of G2 (s) = (cs + k + km) including the influence of the motor.

By incorporating this differential element, the slope of the gain curve on the low frequency side becomes small, but the phase in the low frequency region can be advanced. That is, by configuring the control circuit of the radial magnetic bearing with the proportional element and the differential element, the gain curve in the low frequency region can be improved, and the control performance of the radial magnetic bearing 101 is greatly improved because the phase is advanced. .

Further, in FIG. 8, the solid line a indicates the motor 1
G2 (s) = ke, ke> (k
+ Km) (P1 (s) = 1 / (Ms^Two
−k−km + ke)), and the solid line b represents the motor 104
G2 (s) = cs + ke, ke> (k
+ Km) (P1 (s) = 1 / (Ms ^Two
+ Cs-k-km + ke)).

Although the gain curve has a maximum in the solid line a in FIG. 8, the characteristics can be improved and the phase can be advanced by adding a differential element. That is, in the control circuit of the radial magnetic bearing 102, the differential element must be added even under the condition that the proportional constant ke is equal to or greater than the value obtained by adding the negative spring constant of the magnetic bearing and the negative spring constant of the motor 104. Thus, the peak appearing in the gain curve can be suppressed, the phase advance characteristic can be obtained, and the control performance of the radial magnetic bearing 101 can be greatly improved.

Here, although the spring element of the motor 104 has been treated as being constant, it actually varies depending on the motor speed and the motor current. In FIG. 1, a rotation sensor 21 is provided at the end of the rotation shaft, and this rotation sensor 21 is constituted by a magnetic sensor, and the number of rotations of the rotation shaft 2 can be measured by forming a notch 22 on the opposite rotation shaft surface. . By changing the transfer function G2 (s) of the control circuit of the radial magnetic bearing 102 according to the measured rotation speed, optimal control can always be performed.

In general, the negative spring constant km of the motor 104 increases as the rotational speed increases.
It is preferable to increase the proportional gain of (s). Also,
As the motor current value increases, the negative spring constant of the motor 104 increases. By changing the transfer function G2 (s) of the control circuit of the radial magnetic bearing 102 according to the monitored current value of the motor 104, optimal control can always be performed. In any case, the transfer function G2 (s) may be changed continuously according to the rotation speed or the motor current value, or may be changed in several steps.

As described above, in order to change the control depending on the number of revolutions or the motor current value, the CPU is used as the control means.
It is preferable to use software control using a DSP.

Further, since the rotating shaft 2 is long, the coaxiality of the surface of each of the radial magnetic bearings 101, 102, 103 facing the electromagnet and the surface of each of the radial magnetic bearings 101, 102, 103 facing the position sensors 6, 7, 13 are determined. Difficult to secure. For this reason, when the rotating shaft 2 is rotated while being supported by the radial magnetic bearing 101 and the radial magnetic bearing 103 which are the basis of the rotating shaft support, the rotating shaft portion of the radial magnetic bearing 102 is rotated synchronously or at a cycle of an integral multiple thereof. The whirling is highly likely to occur. If the radial magnetic bearing 102 is controlled in this state, the control force is highly likely to be a disturbance to the radial magnetic bearing 101 and the radial magnetic bearing 103, and stable rotation cannot be obtained. Therefore, by selectively removing the rotation synchronization component or its higher-order component from the radial magnetic bearing 102, stable rotation and magnetic bearing support performance can be obtained.

Here, the method of selectively removing the rotation synchronous component or its higher-order component is not limited, but a method using a switched capacitor filter or a method incorporating this in the software control described above may be used.

In FIG. 1, the control circuit of the radial magnetic bearing 102 is composed of a proportional element and a differential element. However, the control circuit of the radial magnetic bearing 101 is composed of a proportional element and a differential element, and the radial magnetic bearing 102 includes an integral element. Alternatively, fixed position control with a small deviation from the command value may be performed to support the rotating shaft 2. In this case, the protective bearings 11 and 15 are indispensable.

Thus, by arranging three radial magnetic bearings, the magnetic bearing and the motor 10 can be slightly reduced.
4 is large, and the output is large. As a result, it is difficult to remove the housing 200 from the chamber 1 due to the attachment and detachment of the rotating shaft, and the structure in which the rotating shaft 2 can be attached and detached without removing the housing 200 is incorporated in the embodiment of FIGS. It is rare.

That is, a soft magnetic member 51 is fastened to the rotating shaft 2 by bolts on the rotating shaft 2 opposed to the axial electromagnet 8, and the rotating shaft 2 is permanently removed from the axial electromagnet 8 side except for the soft magnetic member 51. The diameter is equal or smaller toward the magnet 14 side.
Then, the axial electromagnet 8 and the first protection bearing 11
Alternatively, the protective bearing housing 50 fixing the first protective bearing 11 is removed from the housing 200, and the fan 3 is further removed from the rotary shaft 2, so that the rotary shaft 2 is not removed from the chamber 1 and the chamber 30 is removed. 1 and the outside of the housing 200.

Further, in the embodiment shown in FIGS. 1 and 2, measures against damage to the magnetic bearing and the motor due to the corrosive laser gas in the chamber 1 are not included, but are disclosed in JP-A-11-087810. As described above, the area around the rotating shaft 2 may be covered with a can to protect against corrosive laser gas.

Further, in the above description, a method of compensating for the influence of the motor has been described. However, an eddy current motor which does not generate an attractive force between the motor rotor 17 and the motor stator 10 is used to eliminate the influence of the motor itself. It may be.

Further, by arranging three radial magnetic bearings, the coil winding work of the radial electromagnet is increased and the cost is increased. In the case of a cross-flow fan for laser gas circulation of an excimer laser device, the weight of the rotating shaft 2 is large, and the radial magnetic bearings 101, 102, 10
The current flows through the coil 3 in the direction of supporting its own weight, but does not flow in the opposite direction. In addition, since its own weight is large, the current of the electromagnet coil that makes full use of its own weight is large, and problems such as heat generation occur.

Therefore, as a technique for reducing the heat generation of the electromagnet coil and further reducing the number of coil winding steps, three radial magnetic bearings are used according to the arrangement of each electromagnet and the method of reducing the total number of coil turns of each radial electromagnet. A method that does not increase the number of steps of coil winding even in the case of performing will be described.

FIGS. 9 to 11 are sectional views of an electromagnet of the radial magnetic bearing. FIG. 9 shows an example in which the magnetic force of the rotating shaft 2 is generated by two magnetic poles having eight magnetic poles in the circumferential direction and two magnetic poles close to each other. FIG. 10 shows four magnetic poles in the circumferential direction and two magnetic poles in the axial direction. An electromagnetic force is applied to the rotating shaft 2 by two sets of magnetic poles having a magnetic pole and approaching in the axial direction. FIG. 11 is a cross-sectional view taken along line AA and line CC in FIG.

In FIG. 10, the directions A and B are arranged so as to support their own weight. Specifically, the control axis direction of the radial electromagnet of each radial magnetic bearing is 45 ° ± 22 ° with respect to the anti-vertical direction. By setting the angle to be within 0.5 °, the concentration of current to the electromagnet coil of one control shaft can be suppressed, and heat generation can be reduced. Further, it is not necessary to wind a coil around a magnetic pole that is not supported by its own weight of the rotating shaft. Thereby, the number of steps of coil winding can be reduced.

FIGS. 12 and 13 show another example of the electromagnet of the radial magnetic bearing. FIG. 12 shows a case where two magnetic poles having four magnetic poles in the circumferential direction and two magnetic poles close to each other generate electromagnetic force on the rotating shaft 2. FIG. 13 shows two magnetic poles in the circumferential direction and two magnetic poles in the axial direction. With magnetic poles and close in the axial direction 2
An electromagnetic force is applied to the rotating shaft by a set of two magnetic poles, and the centers of the magnetic poles may be all arranged above a horizontal plane.

The embodiments disclosed this time are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

[0071]

As described above, according to the present invention, the first and second radial magnetic bearings are arranged at both ends of the rotary shaft, and the third radial magnetic bearing is provided near the motor. Since the negative spring element of the motor is corrected by the radial magnetic bearing, the magnetic bearing can be stably controlled without increasing the gain of the magnetic bearing when driving the motor.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a cross-flow fan for an excimer laser device according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a cross-flow fan for an excimer laser device according to another embodiment of the present invention.

FIG. 3 is a schematic diagram of a radial magnetic bearing and a motor.

FIG. 4 is a block diagram of a control system of a rotating shaft including a radial magnetic bearing and a motor.

FIG. 5 is a diagram showing a transfer function from Fa to x when G2 (s) is constituted only by a proportional element.

FIG. 6 is a diagram illustrating a transfer function from Fa to x when G2 (s) is configured only with a differential element.

FIG. 7 is a diagram showing a transfer function from Fa to x when G2 (s) is composed of both a proportional element and a differential element.

FIG. 8 is a diagram showing a transfer function from Fa to x when G2 (s) is composed of both a proportional element and a differential element.

FIG. 9 is a sectional view of an electromagnet of a radial magnetic bearing having eight magnetic poles in a circumferential direction.

FIG. 10 is a sectional view of an electromagnet of a radial magnetic bearing having four magnetic poles in the circumferential direction and two magnetic poles in the axial direction.

FIG. 11 is a sectional view taken along lines AA and CC of FIG. 10;

FIG. 12 is a diagram showing an electromagnet of a radial magnetic bearing having four magnetic poles in the circumferential direction and generating electromagnetic force on a rotating shaft by two magnetic poles close to each other.

FIG. 13 is a view showing an electromagnet of a radial magnetic bearing having two magnetic poles in a circumferential direction and two magnetic poles in an axial direction.

FIG. 14 is a cross-sectional view of a conventional fan for circulating excimer gas and its peripheral portion.

FIG. 15 is a view showing a structure near a radial magnetic bearing portion.

16 is a block diagram of a magnetic bearing control system for explaining the effect of the motor shown in FIG.

FIG. 17 is a diagram illustrating a gain curve of a Bode diagram of a control target of the magnetic bearing when the motor is driven and when the motor is not driven.

FIG. 18 is a diagram showing an open-loop transfer function when a magnetic bearing control circuit is designed.

[Explanation of symbols]

1 chamber, 2 rotation axes, 3 fans, 4, 5, 12
Radial electromagnet, 6, 7, 9, 13 Position sensor, 8
Axial electromagnet, 10 motor stator, 14 permanent magnet, 11, 15, 16 protective bearing, 21 rotation sensor, 22 notch, 23 motor rotor, 51, 52, 5
3 Soft magnetic member, 200 housing, 101, 10
2,103 radial magnetic bearing, 104 motor.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hironori Tokunaga 1578 Higashikaizuka, Iwata City, Shizuoka Prefecture Inside (72) Inventor Koji Yamada 1578 Higashikaizuka, Iwata City, Shizuoka Prefecture F Term (in reference) 3H022 AA02 BA06 CA16 CA19 DA09 DA11 DA13 3H031 AA11 BA05 3J102 AA01 BA03 BA19 CA10 CA14 DA02 DA03 DA09 DB05 DB10 DB11 GA20

Claims (12)

[Claims] 1. A rotating shaft to which a fan is attached, a control type magnetic bearing for supporting the rotating shaft in a non-contact manner, and a protection for supporting the rotating shaft when the control type magnetic bearing cannot support the rotating shaft. In a structure of a cross-flow fan for an excimer laser device, comprising a bearing and a motor for rotating the rotating shaft, and circulating a laser gas in a chamber by rotation of the fan driven by the motor, the control-type magnetic bearing has an axial direction. A radial magnetic bearing including three radial electromagnets and a position detection sensor disposed around each radial electromagnet; an axial magnetic bearing including one axial electromagnet and at least one permanent magnet. The axial electromagnet is disposed so as to face one end face of the rotating shaft, and the permanent magnet is facing the other end face of the rotating shaft. A first radial magnetic bearing of the radial magnetic bearing is disposed near the axial electromagnet, and a second radial magnetic bearing is disposed on the rotating shaft more than a permanent magnet disposed on an end face of the rotating shaft. Wherein the third radial magnetic bearing is disposed between the motor and the fan, wherein the third radial magnetic bearing is disposed between the motor and the fan. 2. The protection bearing, which supports both the axial direction and the radial direction of the rotating shaft, a first protective bearing disposed near the axial electromagnet and the motor, and a radial direction of the rotating shaft. 2. The structure of the cross-flow fan for an excimer laser device according to claim 1, further comprising a second protective bearing that supports only the other radial electromagnet and that is disposed near the other radial electromagnet. 3. 3. The apparatus according to claim 2, further comprising a third protective bearing disposed between said third radial magnetic bearing and said fan and capable of supporting only in a radial direction.
4. The structure of the cross-flow fan for an excimer laser device according to item 1. 4. A soft magnetic material is provided on a portion of the rotating shaft facing the radial electromagnet, the axial electromagnet, and the permanent electromagnet, and the soft magnetic material of the rotating shaft facing the axial electromagnet is a soft magnetic material. The rotating shaft is fixed to a shaft, and except for the soft magnetic material, the rotating shaft has the same or smaller diameter from the axial electromagnet side toward the permanent magnet side, and the axial electromagnet and the first protective bearing Alternatively, the housing for the protective bearing that fixes the first protective bearing is removed from the housing, and the soft magnetic material of the rotating shaft facing the axial electromagnet, the stator, and the fan are removed from the rotating shaft. The rotation shaft can be removed outside the chamber and the housing without removing the rotation shaft. It characterized Rukoto, structure of the cross-flow fan excimer laser device according to claim 1 or 3. 5. The radial electromagnet has eight magnetic poles in a circumferential direction, and generates electromagnetic force on a rotating shaft by two adjacent magnetic poles, or has four magnetic poles in a circumferential direction and an axial direction. Each of the radial magnetic bearings has two control shafts, and each of the radial magnetic bearings has two control shafts, and each of the control shafts has two magnetic poles. The structure of a cross-flow fan for an excimer laser device according to any one of claims 1 to 4, wherein the structure supports the own weight. 6. The control axis direction of the radial electromagnet of each of the radial magnetic bearings is 45 ° ± 22.
The structure of the cross-flow fan for an excimer laser device according to any one of claims 1 to 5, wherein the angle is within 5 °. 7. The excimer laser device according to claim 5, wherein a coil is not wound around a magnetic pole of the radial magnetic bearing that does not support the weight of the rotating shaft, which is a part of the radial electromagnet. For once-through fan. 8. The radial electromagnet has four magnetic poles in a circumferential direction, and generates electromagnetic force on the rotating shaft by two adjacent magnetic poles, or two magnetic poles and a shaft in the circumferential direction. 2. A magnetic head according to claim 1, wherein two magnetic poles are provided in each direction, and an electromagnetic force is applied to the rotation axis by a set of two magnetic poles which are close to each other in the axial direction, and the centers of the magnetic poles are all above a horizontal plane. 6. The structure of the cross-flow fan for an excimer laser device according to any one of items 1 to 5. 9. A radial magnetic bearing comprising a proportional element, an integral element, and a differential element, the radial magnetic bearing being close to the first and second protective bearings, a control circuit for controlling the axial magnetic bearing, The structure of the cross-flow fan for an excimer laser device according to any one of claims 1 to 8, further comprising a control circuit configured with a differentiating element and controlling the third radial magnetic bearing. 10. The structure of the cross-flow fan for an excimer laser device according to claim 1, wherein the control of the magnetic bearing is performed by software processing. 11. A soft magnetic member having a notch or a hole is provided on a rotating shaft facing an electromagnet of the axial magnetic bearing, and a magnetic rotation sensor is provided at a position facing the soft magnetic member. The structure of a cross-flow fan for an excimer laser device according to any one of claims 1 to 10, characterized in that: 12. The cross-flow fan for an excimer laser device according to claim 11, wherein a control parameter of said third radial magnetic bearing is changed according to a rotation speed obtained by said rotation sensor. Construction.