Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
2002-10-25
2004-10-26
Nguyen, Tran (Department: 2834)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S045000, C310S085000
Reexamination Certificate
active
06809448
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an excimer laser apparatus in which a rotary bearing of a laser gas circulating fan is supported by magnetic bearings.
BACKGROUND OF THE INVENTION
FIG. 12
is a first example of a basic arrangement of an excimer laser apparatus to which the present invention can be applied.
FIG. 13
shows an arrangement of a motor housing of the apparatus of FIG.
12
. In the excimer laser apparatus, a laser gas is sealably contained in a laser container
1
. The laser gas contains a halogen type gas, such as a fluorine gas. A pair of main discharge electrodes
2
,
2
are disposed in the laser container
1
so as to obtain an electric discharge for performing laser beam oscillation. Further, a circulation fan
3
is disposed in the laser container
1
, so as to generate a flow of laser gas having a high velocity between the main discharge electrodes
2
,
2
.
The circulation fan
3
has a rotary shaft
4
extending therethrough, which is projected beyond opposite end portions of the fan
3
. The rotary shaft
4
is rotatably supported by radial magnetic bearings
7
,
7
,
7
without making contact therewith, that is, in a floating condition. A motor
9
is provided so as to operate the circulation fan
3
.
A magnetic bearing generally includes, as basic elements, a rotor, stators made of electromagnets for effecting floating support of the rotor and position sensors for detecting the position of the rotor. The radial magnetic bearing
7
shown in
FIGS. 12 and 13
comprises a rotor
7
-
3
(
FIG. 13
) provided on the rotary shaft
4
, stators, i.e., electromagnets
7
-
1
,
7
-
1
arranged in a spaced relationship around the rotor, and displacement detection sensors
7
-
2
,
7
-
2
provided around a sensor target
7
-
4
on the rotary shaft so as to detect displacement of the rotary shaft
4
. Displacement signals from the displacement detection sensors
7
-
2
,
7
-
2
are input to a control circuit (not shown) for phase compensation and gain adjustment. Output from this control circuit is supplied to the electromagnets
7
-
1
,
7
-
1
, which generate a magnetic attraction force or a magnetic repellent force in accordance with this output, to thereby support the rotary shaft
4
so that it is floated at a predetermined position between the electromagnets
7
-
1
,
7
-
1
.
As mentioned above, the laser gas is a corrosive gas containing, for example, a fluorine gas. Therefore, the electromagnets
7
-
1
,
7
-
1
providing the radial magnetic bearing are subject to a corrosive environment. As shown in
FIG. 14
a
and
FIG. 14
b
, the electromagnet (stator)
7
-
1
comprises a stator core (iron core)
7
-
1
a
and excitation coils
7
-
1
b
attached to the stator core
7
-
1
a
. A separation wall
14
comprising a non-magnetic body is provided on an inner circumferential surface of the electromagnet
7
-
1
, which surface surrounds the magnetic bearing rotor
7
-
3
provided on the rotary shaft
4
. This prevents the electromagnet
7
-
1
(especially the excitation coils
7
-
1
b
which are liable to corrosion) from making contact with the laser gas. In
FIGS. 12
,
13
,
14
a
and
14
b
, reference numeral
6
denotes a motor housing;
8
a window through which a laser beam is emitted;
10
a protective bearing;
11
a gas inlet chamber;
12
a dust removing filter;
13
a gas inlet tube; and
15
a magnetic bearing frame.
When the separation wall
14
is provided on the inner circumferential surface of the electromagnet
7
-
1
, a problem arises, such that a magnetic gap between the electromagnet
7
-
1
and the magnetic bearing rotor
7
-
3
becomes large, thus reducing a magnetic attraction force or a magnetic repellent force obtained for effecting floating support of the rotary shaft
4
. Therefore, in order to obtain a desired magnetic force of the magnetic bearing for controlling floating support of the rotary shaft, it is required to increase the size of the electromagnet
7
-
1
. This is also problematic because the magnetic bearing inevitably becomes large.
In view of the above, the present invention provides an excimer laser apparatus in which an excitation coil of an electromagnet of a magnetic bearing has corrosion resistance against a laser gas, thus reducing the size of the magnetic bearing while increasing the life of the magnetic bearing, and preventing contamination of the laser gas.
FIG. 15
shows a second example of a basic arrangement of an excimer laser apparatus to which the present invention can be applied. As shown in
FIG. 15
, in this excimer laser apparatus, a laser gas containing a halogen type gas, such as a fluorine gas, is sealably contained in a laser container
201
. In the laser container
201
, there are provided pre-ionization electrodes (not shown) for pre-ionizing the laser gas and a pair of main discharge electrodes
202
,
202
for obtaining an electric discharge for performing laser beam oscillation. Further, a circulation fan
203
is provided in the laser container
201
, so as to generate a flow of the laser gas having a high velocity between the main discharge electrodes
202
,
202
.
The circulation fan
203
has a rotary shaft
204
extending therethrough, which is projected beyond opposite end portions of the circulation fan
203
. Radial magnetic bearings
206
,
207
and an axial magnetic bearing
208
are provided at opposite ends of the laser container
201
. The rotary shaft
204
is rotatably supported by these magnetic bearings
206
,
207
,
208
without making contact therewith, that is, in a floating condition. A motor
209
for operating the circulation fan
203
is provided on a shaft end side of the radial magnetic bearing
207
.
Displacement sensor targets
206
c
,
207
c
,
208
d
and magnetic bearing rotors
206
d
,
207
d
,
208
e
of the magnetic bearings are secured to the rotary shaft
204
. Further, a rotor
209
b
of the motor
209
is secured to the rotary shaft
204
. Displacement sensors
206
a
,
207
a
,
208
a
, electromagnets (i.e., magnetic bearing stators)
206
b
,
207
b
,
208
b
,
208
c
and a stator
209
a
of the motor
209
are provided so as to face the displacement sensor targets
206
c
,
207
c
,
208
d
, the magnetic bearing rotors
206
d
,
207
d
,
208
e
and the rotor
209
b
of the motor
209
, respectively.
Separation walls
210
,
211
in the forms of thin-walled cylinders are provided on inner circumferential surfaces of the displacement sensors
206
a
,
207
a
and the electromagnets
206
b
,
207
b
of the radial magnetic bearings
206
,
207
and the stator
209
a
of the motor
209
. The separation walls
210
,
211
are made of a material having corrosion resistance against a halogen type gas contained in a laser gas, for example, austenite type stainless steel such as SUS316L. Thus, the displacement sensors
206
a
,
207
a
, the electromagnets
206
b
,
207
b
and the stator
209
a
of the motor
209
, which comprise cores (iron cores) and coil wires having poor corrosion resistance against the laser gas, do not make contact with the laser gas.
In the axial magnetic bearing
208
, a separation wall
212
is provided so as to prevent the displacement sensor
208
a
from making contact with the laser gas, as in the case of the radial magnetic bearings
206
,
207
. With respect to the magnetic bearing stators of the axial magnetic bearing
208
, that is, the electromagnets
208
b
,
208
c
, the stator cores are made of a ferromagnetic material having corrosion resistance against a halogen type gas contained in a laser gas, such as a permalloy. Therefore, only the excitation coils are protected by separation walls
213
.
The displacement sensor targets
206
c
,
207
c
,
208
d
and the magnetic bearing rotors
206
d
,
207
d
,
208
e
of the magnetic bearings, which are secured to the rotary shaft
104
, are disposed within a sealed space communicated with the laser container
101
. Therefore, the displacement sensor targets
206
c
,
207
c
,
208
d
and the magnetic bearing rotors
206
d
,
207
d
,
208
e
are made of a ferroma
Barada Toshimitsu
Nakazawa Toshiharu
Nara Hisashi
Ooyama Atsushi
Sekiguchi Shinichi
Ebara Corporation
Nguyen Tran
Wenderoth , Lind & Ponack, L.L.P.
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