JP2002217475A - Gas-circulating fan for excimer laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gas-circulating fan, for an excimer laser, in which it is not required to stop the rotation of the fan once when a gas is replaced and by which the gas can be replaced safely, by a method wherein the speed of rotation of the fan is set, when a vacuum is evacuated and the fan is controlled in such a way that the speed of rotation will not be increased any further. SOLUTION: In this fan, a rotary shaft 7 is magnetically born by magnetic bearings 9, 10; the speed of rotation of the fan 6 attached to the rotary shaft 7 is detected by a rotation detector 17, when the gas is replaced; the detected speed of rotation and the allowable speed of rotation are compared by a speed- of-rotation determining circuit 22; and a current flowing to a motor 8 is interrupted by a rotary switch 23, in such a way that the fan 6 is not turned at a tolerance or more, and the speed of rotation of the fan 6 is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a gas recirculation fan of an excimer laser device, and more particularly to a gas recirculation fan of an excimer laser device for recirculating a laser gas in a laser chamber.

[0002]

2. Description of the Related Art In an excimer laser apparatus, as shown in FIG. 4, a laser gas 2 containing a halogen gas is sealed in a laser chamber 1, and a predetermined high voltage is applied between discharge electrodes 3 to cause discharge. This excites the laser gas 2 to generate a laser. The generated laser light is emitted to the outside of the laser chamber 1 via the window 5 provided on the side wall 4 in the optical axis direction.

[0003] A fan 6 is rotatably provided at a predetermined position in the laser chamber 1, and circulates the laser gas 2 in the laser chamber 1 to guide it between the discharge electrodes 3. Outside the laser chamber 1, a motor 8 for driving the fan 6 to rotate around a rotation shaft 7 is provided.
The rotating shaft 7 penetrates the left and right side walls 4 of the laser chamber 1,
Each is rotatably supported by a bearing.

Recently, in order to eliminate generation of impurity gas and dust from the bearing portion, magnetic bearings 9 and 10 are adopted for the bearing of the fan 6 to take measures to prevent the laser gas 2 from deteriorating.

[0005]

The laser oscillation is performed at a gas pressure of about 3000 to 4000 Hpa in the chamber 1. However, if the laser is operated for a long time, the laser gas 2 is deteriorated, and a gas replacement operation is required. . The conventional replacement work procedure is performed as follows. The rotation of the gas circulation fan 6 is stopped, the chamber 1 is evacuated, the laser gas 2 is filled to about 3000 to 4000 Hpa, and the circulation fan 6 is rotated to emit laser light.

In this method, it is necessary to stop the fan 6 once in the gas exchange operation, and the workability is not good. Further, if the gas is exchanged while the fan 6 is rotating, the gas load on the fan 6 during vacuum evacuation becomes very small, and the fan 6 rises sharply from a predetermined rotation speed. Bearing control) becomes difficult, and the rotating shaft 7, the fan 6, and the bearings 9 and 10 may be damaged.

[0007] Therefore, a main object of the present invention is to set the rotation speed of the fan at the time of evacuation and perform control so that the rotation speed does not increase any more, so that the rotation of the fan is temporarily stopped at the time of gas exchange. An object of the present invention is to provide a gas recirculation fan of an excimer laser device that does not need to be replaced and can safely exchange gas.

[0008]

SUMMARY OF THE INVENTION The present invention comprises a rotating shaft on which a fan is mounted, a control type magnetic bearing for supporting the rotating shaft in a non-contact manner, and a motor for rotating the rotating shaft. In an excimer laser device that circulates a laser gas in a chamber by rotation of a fan by driving, a rotation speed detection unit that detects a rotation speed of the fan, and a fan that does not rotate beyond an allowable value of the rotation speed detected by the rotation speed detection unit. And limiting means for controlling the fan speed by interrupting the current flowing through the motor between the allowable speed and the normal operation speed.

According to another aspect of the present invention, there is provided a mechanical body comprising a chamber and a housing, a rotating shaft provided through the chamber and the housing, a fan mounted on the rotating shaft to circulate gas in the chamber, In an excimer laser device including a control type magnetic bearing for supporting a shaft in a non-contact manner, a motor for rotating a rotary shaft, an inverter for driving the motor to rotate, and control means for controlling the magnetic bearing, Control means for comparing the detection signal from the rotation number detecting means with a preset allowable number of rotations. A signal for stopping the rotation of the motor when it is determined that the allowable rotation speed has been exceeded, and a signal for rotating the motor when the rotation speed falls below a preset normal operation speed. Characterized in that a limit means for outputting the over data.

The rotation number detecting means includes a rotation detection target made of a magnetic material attached to one end face of the rotation shaft, and a non-contact position sensor facing the rotation detection target and fixed to the housing. It is characterized by.

Further, the rotation detection target includes a notch in the circumferential direction, and the non-contact position sensor detects the notch.

Furthermore, the control type magnetic bearing is characterized in that it is a five-axis control type.

[0013]

FIG. 1 is a diagram showing a configuration of a gas circulation fan according to an embodiment of the present invention. According to the present invention, when the internal gas pressure fluctuates during gas exchange in the laser chamber 1, the rotation speed of the fan 6 is monitored and the rotation speed becomes higher than an upper limit rotation speed (a dangerous rotation speed if the temperature is further increased). It is controlled so as not to have.

In FIG. 1, a gas circulating fan device includes a chamber 1 and a housing 1 constructed in the same manner as in FIG.
A controller 20 for controlling the floating of the five-axis control type magnetic bearings 9, 10; monitoring the rotation speed of the fan 6;
And an inverter 21 that drives the motor 8 to rotate.

The magnetic bearing 9 includes an electromagnet 13 and a position sensor 15 provided in a housing 11.
Includes an electromagnet 14 and a position sensor 16 provided in the housing 12. The current flowing through the electromagnets 13 and 14 of these magnetic bearings 9 and 10 is controlled by the controller 20 based on the outputs of the position sensors 15 and 16 so that the rotating shaft 7 magnetically floats. A rotation detection target 18 is attached to the end surface of the rotation shaft 7 on the housing 11 side, and the rotation number of the fan 6 is taken into the controller 20 by the rotation number detector 17.

The controller 20 compares a rotation speed detection output of the rotation speed detector 17 with a predetermined upper limit rotation speed to thereby control a rotation speed judging circuit 22 for monitoring the rotation speed of the fan 6, A motor rotation switch 23 for stopping current supply to the motor 8 and stopping rotation of the fan based on the output of the number judgment circuit 22.

FIG. 2 is a diagram showing the structure of the fan rotation speed monitoring unit. In FIG. 2A, a rotation detection target 18 made of a magnetic material is attached to an end face of the rotating shaft 7. As shown in FIG. 2B, two notches 25 are formed in the rotation detection target 18 in the circumferential direction.
A rotation detector 17 which is a non-contact magnetic (reluctance) position sensor is arranged at a position of the housing 11 opposite to the rotation detection target 18. The rotation detector 17 is configured such that a coil 27 is wound around a sensor core 26, and the coil 27 is connected to a sensor circuit 28. The rotation detector 17 is provided with a notch 25 of the rotation detection target 18.
The number of rotations of the rotating shaft 7 is detected based on the difference between the sensor output when the sensor faces the portion other than the notch 25 and when the sensor outputs the sensor. The number of the notches 25 is not limited to two but may be any number.

FIG. 3 is a diagram for explaining the fluctuation of the fan speed in one embodiment of the present invention. When the inside of the chamber 1 is evacuated during gas exchange, the load applied to the fan 6 decreases, and the rotation speed of the fan 6 starts to increase. If the fan 6 rises above a certain rotation speed, the fan 6 and the bearings 9 and 10 may be damaged. Therefore, the rotation speed determination circuit 22 inside the controller 20 always monitors the rotation speed of the fan 6 and is predetermined. Maximum rotation speed (fan 6
When the rotation speed of the fan 6 exceeds the upper limit rotation speed, a motor-off command signal is immediately sent to the inverter 21 to turn off the motor rotation switch 23, and the motor is turned off. The supply of the current to the fan 8 is stopped, and the fan 6 starts to decrease in rotation in the free run.

Thereafter, when the rotation speed of the fan 6 decreases to the normal rotation speed, the rotation speed determination circuit 22 sends a motor-on command to the inverter 21 again to rotate the fan 6. By repeating the above operation, the rotation speed of the fan 6 can be maintained between the normal use rotation speed and the safe upper limit rotation speed regardless of the gas pressure in the chamber 11.

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.

[0021]

As described above, according to the present invention, the rotation speed of the fan is detected, and the rotation between the allowable rotation speed and the normal operation rotation speed is controlled so that the fan does not rotate beyond the allowable value of the detected rotation speed. The fan speed is controlled by interrupting the current flowing through the motor, so it is possible to set the fan speed during evacuation and control so that the speed does not rise any further Thus, there is no need to temporarily stop the rotation of the fan at the time of gas exchange, and it is possible to maintain a safe rotation speed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a gas circulation fan according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a structure of a fan rotation speed monitoring unit.

FIG. 3 is a diagram for explaining a change in a fan speed according to the embodiment of the present invention;

FIG. 4 is a diagram showing a configuration of a conventional gas circulation fan.

[Explanation of symbols]

1 chamber, 2 laser gas, 3 discharge electrodes, 4 side walls, 5 windows, 6 fans, 7 rotating shafts, 8 motors,
9,10 Magnetic bearing, 11,12 Housing, 13,
14 electromagnet, 15, 16 position sensor, 17 rotation detector, 18 rotation detection target, 20 controller, 21 inverter, 22 rotation number judgment circuit, 23
Motor rotation command switch, 25 notch, 26 sensor core, 27 coil, 28 sensor circuit.

Claims (5)

[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 motor for rotating the rotating shaft, the rotation of the fan driven by the motor. In an excimer laser device that circulates a laser gas in the chamber by: a rotation speed detection unit that detects the rotation speed of the fan; and the rotation speed detection unit detects the rotation speed so that the fan does not rotate more than an allowable value. A gas recirculation fan for an excimer laser device, comprising: limit means for controlling the number of rotations of the fan by intermitting a current flowing through the motor between an allowable rotation number and a normal operation number of rotations. 2. A mechanical body comprising a chamber and a housing, a rotating shaft provided through the chamber and the housing, and a fan mounted on the rotating shaft and circulating gas in the chamber, An excimer laser including a control type magnetic bearing for supporting the rotating shaft in a non-contact manner, a motor for rotating the rotating shaft, an inverter for driving the motor to rotate, and control means for controlling the magnetic bearing. The apparatus, further comprising: a rotation speed detection unit that detects a rotation speed of the rotation shaft; the control unit; a comparison unit that compares a detection signal from the rotation speed detection unit with a preset allowable rotation speed; When the comparing means determines that the rotation speed of the rotating shaft has exceeded the allowable rotation speed, a signal for stopping the rotation of the motor is sent to the predetermined communication. Characterized in that a limit means for outputting a signal for rotating the motor to the inverter when below the working rotational speed, gas recirculation fan of the excimer laser device. 3. The rotation number detection means includes: a rotation detection target made of a magnetic material attached to one end surface of the rotation shaft; and a non-contact position sensor facing the rotation detection target and fixed to the housing. Characterized by including
A gas recirculation fan for the excimer laser device according to claim 1. 4. The gas recirculation of the excimer laser device according to claim 3, wherein the rotation detection target includes a notch in a circumferential direction, and the non-contact position sensor detects the notch. fan. 5. The gas recirculation fan of an excimer laser device according to claim 1, wherein said control type magnetic bearing is a five-axis control type.