JP4049531B2 - Magnetic bearing motor and excimer laser device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a magnetic bearing motor having a sealed structure and particularly an excimer laser device using the motor, in which the swinging of a rotating body and the vibration of a stator are reduced.
[0002]
[Prior art]
Unlike contact-type plain bearings and ball bearings, magnetic bearings support the rotor in a non-contact manner. Therefore, (1) there is little mechanical loss, (2) there is no friction or wear, and (3) no lubricating oil is required. (4) Low vibration and low noise, (5) Maintenance free, etc. Examples of using magnetic bearings having such characteristics include a turbo molecular pump that creates a vacuum environment with few impurities, and a spindle for machine tools that can perform ultra-high speed rotation.
[0003]
Here, when magnetic bearings are used in environments where impurities are extremely disliked or in corrosive environments, there is a problem of gas release and corrosion from the materials (for example, magnetic steel sheets, copper wire coils, organic materials). It becomes. For this reason, a coating material is provided on the surface of the magnetic bearing so as to protect the constituent materials from the corrosive environment. There is an excimer laser device as an example using a magnetic bearing motor having such a configuration, that is, a magnetic bearing having a sealed structure and a motor arranged at positions adjacent to each other.
[0004]
FIG. 5 shows a schematic structure of a conventional excimer laser device. As shown in FIG. 5, a conventional excimer laser device includes a laser container 101 in which a laser gas containing a halogen-based gas (F ₂ , C12 _2, etc.) is sealed, and a spare ionization apparatus that preliminarily ionizes the laser gas disposed inside the laser container 101. An ionization electrode (not shown) and a pair of main discharge electrodes 102 and 102 for obtaining a discharge capable of oscillating laser light disposed inside the laser container 101 are provided. Further, a circulation fan 103 for generating a high-speed laser gas flow is disposed in the laser container 101 between the pair of main discharge electrodes 102 and 102. Laser light extraction windows 105 and 105 are provided at both ends of the pair of main discharge electrodes 102 and 102.
[0005]
The circulation fan 103 has a rotating shaft 104 that passes through the inside and protrudes from both ends. The rotating shaft 104 has two radial magnetic bearings 106 and 107 provided at both ends of the laser container 101 and one axial shaft. The magnetic bearing 108 is levitated and supported so as to be rotatable without contact. A motor 109 for driving the circulation fan 103 is provided on the shaft end side of the radial magnetic bearing 107.
[0006]
Electromagnetic targets 106d, 107d and 108e and sensor targets 106c, 107c and 108d of magnetic bearings 106, 107 and 108 made of a magnetic material and a motor rotor 109b are fixed to the rotating shaft 104. Electromagnets 106b, 107b, 108b, and 108c, inductive displacement sensors 106a, 107a, and 108a, and a motor stator 109a are arranged at positions facing these, respectively. With the above configuration, the rotation shaft 104 is supported by the magnetic bearings 106, 107, and 108 with five degrees of freedom other than the movement around the rotation shaft 104 out of the six degrees of freedom of the object, so that stable rotation is obtained. .
[0007]
Electromagnetic magnets 106b and 107b of radial magnetic bearings 106 and 107, induction type displacement sensors 106a and 107a, and an inner peripheral surface of motor stator 109a have thin cylindrical partition walls 110 made of a nonmagnetic material such as austenitic stainless steel. 111 is provided, and a housing for housing each stator component and both ends are fixed by welding or the like to form a sealed structure. Similarly, in the axial magnetic bearing 108, the exposed surfaces of the electromagnets 108b, 108c, 108d and the inductive displacement sensor 108a are covered with thin disk-shaped partition walls 112, 113 made of a nonmagnetic metal material. Furthermore, a partition wall 114 made of a nonmagnetic metal material is also provided on the outer peripheral surface of the motor rotor 109b.
[0008]
[Problems to be solved by the invention]
In the magnetic bearing motor having the above-described conventional configuration, when a rotational drive current is excited in the motor stator 109a, eddy current, electromagnetic noise, or the like is generated in the partition 111 due to the AC magnetic flux of the motor, and this eddy current or electromagnetic noise is generated in the partition 111. It is easily transmitted and affects the detection signal of the inductive displacement sensor 107a. That is, there is a problem that the same noise as the excitation current frequency of the motor stator 109 a is added to the detection signal of the induction displacement sensor 107 a and the rotating shaft 104 is vibrated by the radial magnetic bearing 107.
[0009]
In order to solve this problem, the partition walls are also made of a non-conductive material such as Teflon, ceramics, or glass. However, the non-magnetic metal material is the best when it is desired to extremely reduce the emission gas in a special corrosive environment as in the excimer laser device. In addition, since the nonmagnetic metal material generally has superior mechanical strength as compared with the nonconductive material, the thickness of the partition wall can be reduced, and the manufacturing is easy and the cost is low.
[0010]
The present invention has been made in view of the above-described circumstances, and uses a nonmagnetic metal material as a partition wall, and can reduce the rotation of the rotating body and the vibration of the stator due to the rotational drive current applied to the motor stator. An object of the present invention is to provide a bearing motor and an excimer laser device using the motor.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a magnetic bearing motor according to the present invention includes a motor stator that rotates a rotating body, an induction displacement sensor and an electromagnet of a radial magnetic bearing that floats and supports the rotating body, with a sealant interposed. while by adjacent respectively accommodated in the motor housing main body and the bearing housing body arranged to one another, the inner circumferential surface of the motor housing main body, a first partition wall made of thin-walled cylindrical non-magnetic metal material, wherein the bearing housing The inner peripheral surface of the main body is hermetically sealed with a second partition made of a thin-walled cylindrical nonmagnetic metal material in a state in which the both partitions are separated from each other , and between the both partitions and the both partitions. The exposed motor housing body and the bearing housing body, and the sealing material interposed between the motor housing body and the bearing housing body, The serial motor rotor, and you characterized in that said displacement sensor targets and the electromagnet target of the radial magnetic bearing to form a hermetically enclosed by airtight space.
[0012]
Thus, the first partition that hermetically seals the inner peripheral surface of the motor stator and the second partition that hermetically seals the inner peripheral surface of the inductive displacement sensor are configured separately and separated from each other. Thus, when a rotational drive current is excited in the motor stator, the eddy current and electromagnetic noise generated in the first partition due to the AC magnetic flux of the motor are hardly transmitted to the second partition, and the detection signal of the inductive displacement sensor is used. The effect on it can be reduced.
[0013]
The excimer laser device according to the present invention includes a laser container that encloses a laser gas, a pair of main discharge electrodes that are disposed in the laser container to obtain a discharge that enables oscillation of laser light, and a rotating shaft. A circulation fan that creates a high-speed laser gas flow between the main discharge electrodes and a magnetic bearing motor according to any one of claims 1 to 4 that rotationally drives the rotating shaft.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to FIGS. 1 to 4.
1 and 2 show an excimer laser device provided with a magnetic bearing motor according to a first embodiment of the present invention. FIG. 1 is an overall cross-sectional view, and FIG. 2 is an enlarged view of a main part of FIG. is there.
[0015]
This excimer laser device includes a laser container 1 in which a halogen-based gas, for example, a laser gas containing fluorine gas, is sealed, a preionization electrode (not shown) for preionizing the laser gas disposed inside the laser container 1, and the laser container 1. Are provided with a pair of main discharge electrodes 2 and 2 for obtaining a discharge enabling oscillation of laser light. Furthermore, a circulation fan 3 for creating a high-speed laser gas flow is disposed between the pair of main discharge electrodes 2 and 2 in the laser container 1.
[0016]
The laser light is obtained by performing laser excitation discharge by applying a high voltage between the pair of main discharge electrodes 2 and 2. The generated laser light is taken out of the laser container 1 through the windows 5 and 5 provided on the side wall of the laser container 1. When the laser-excited discharge is performed, the laser gas existing between the pair of main discharge electrodes 2 and 2 deteriorates, and the deterioration deteriorates the discharge characteristics, so that repeated oscillation cannot be performed. For this reason, the laser gas in the laser container 1 is circulated by the circulation fan 3 and the laser gas between the pair of main discharge electrodes 2 and 2 is exchanged for each discharge to perform stable and repetitive oscillation.
[0017]
The circulation fan 3 has a rotating shaft 4 that penetrates the inside and projects from both ends. The rotating shaft 4 is rotatably supported in a non-contact manner by radial magnetic bearings 8 and 9 and an axial magnetic bearing 10 housed in a bearing housing 6 provided at both ends of the laser container 1 and a motor housing 7. The motor 11 gives rotational power to the rotating shaft 4 of the circulation fan 3.
[0018]
On the laser container 1 side of the bearing housing 6 and the motor housing 7, thread groove labyrinths 14 and 15 that prevent dust from entering the housing are provided. Thereby, it is possible to prevent dust generated in the laser container 1 from entering the bearing housing 6 and the motor housing 7 and from entering the rolling surfaces of the protective bearings 12 and 13. Further, the laser container 1 is provided with a gas outlet 16, and the laser gas flowing out from the gas outlet 16 is dust-removed by the dust removal filters 18 and 18 in the gas introduction chambers 17 and 17, and the gas introduction pipe is provided. 19 and 19 are introduced into the shaft ends of the bearing housing 6 and the motor housing 7. In other words, dust can be reliably prevented from entering the housings 6 and 7 by circulating the gas as indicated by the arrows in the figure.
[0019]
FIG. 2 is an enlarged view of a main part showing the periphery of the motor housing 7 in an enlarged manner. The motor housing 7 includes a bearing housing body 7a, a motor housing body 7b, and a bearing cover 7c. The bearing housing body 7 a is attached to the side wall of the laser container 1. A motor housing body 7b and a bearing cover 7c are sequentially attached to the bearing housing body 7a. Each mounting surface is provided with sealing grooves 52, 54, and 56, and sealing materials 53, 55, and 57 are attached to the sealing grooves 52, 54, and 56 to seal the laser gas. Note that as the sealing material, it is preferable to use a sealing material made of metal (for example, stainless steel or aluminum) that emits less gas such as moisture that contaminates the laser gas.
[0020]
An inductive displacement sensor 9a and an electromagnet 9b of the radial magnetic bearing 9 are accommodated in the bearing housing body 7a in a state where the relative positions are determined by the spacer 41 and the side plate 42. Thin cylindrical partition walls 44 are disposed on the inner peripheral surfaces of the inductive displacement sensor 9a and the electromagnet 9b, and both ends of the partition walls 44 are fixed to the bearing housing body 7a and the side plate 42 by welding or the like. Thus, by providing the partition wall 44, the inductive displacement sensor 9a and the electromagnet 9b having poor corrosion resistance against the laser gas do not come into contact with the laser gas. The partition walls 44 are resistant to laser gas and are made of a nonmagnetic material such as austenitic stainless steel.
[0021]
The motor housing body 7b accommodates the motor stator 11a and the side plate 43 of the motor 11. A thin cylindrical partition wall 45 is disposed on the inner peripheral surface of the motor stator 11a, and both ends of the partition wall 45 are fixed to the motor housing body 7b and the side plate 43 by welding or the like. This prevents the motor stator 11a from contacting the laser gas.
[0022]
As described above, the partition wall 45 that hermetically seals the inner peripheral surface of the motor stator 11a of the motor 11 and the partition wall 44 that hermetically seals the inner peripheral surface of the induction type displacement sensor 9a of the radial magnetic bearing 9 are separated. By configuring and separating them from each other, eddy currents and electromagnetic noise in the partition wall 45 generated by the AC magnetic flux of the motor are difficult to be transmitted to the partition wall 44 when the rotational drive current is excited in the motor stator 11a. The influence on the detection signal 9a can be reduced, whereby a displacement output signal with less noise can be extracted from the inductive displacement sensor 9a.
[0023]
On the other hand, the displacement sensor target 9e of the radial magnetic bearing 9, the electromagnet target 9f, and the motor rotor 11b of the motor 11 are fixed to the rotating shaft 4 of the circulation fan 3 with the relative positions determined by the rotor spacers 46 and 47. It is arranged in an airtight space that communicates with the interior of 1. Here, as the magnetic material constituting the displacement sensor target 9e and the electromagnet target 9f, permalloy (Fe—Ni alloy containing 30 to 80% Ni) having good corrosion resistance against the fluorine gas contained in the laser gas is used. is doing.
[0024]
Further, in the displacement sensor target 9e and the electromagnet target 9f, eddy current loss occurs due to a magnetic field change caused by rotation. In order to reduce this eddy current loss, a structure in which thin plates are stacked is adopted as the displacement sensor target 9e and the electromagnet target 9f. In addition, when problems such as gas accumulation between the laminated thin plates and contamination of the laser gas occur, the displacement sensor target 9e and the electromagnet target 9f may be made of an integral material.
[0025]
The motor rotor 11b of the motor 11 is composed of a composite material of laminated silicon steel plates and aluminum. Thus, when the motor rotor 11b is composed of a composite material of a silicon steel plate and aluminum, it is difficult to uniformly apply Ni plating suitable as a corrosion resistance treatment to the surface with good adhesion. Therefore, the partition wall 48 is disposed on the outer peripheral surface of the motor rotor 11b, both ends of the partition wall 48 are fixed to the side plates 49 and 50 by welding or the like, and the side plates 49 and 50 and the rotating shaft 4 of the circulation fan 3 are fixed by welding or the like. By doing so, an airtight space is formed so that the motor rotor 11b is not in contact with the laser gas. The partition wall 48 is made of austenitic stainless steel for the reasons described above.
[0026]
As the protective bearing 12, a rolling bearing is used in which the rolling elements 12 a are made of alumina ceramics, zirconia ceramics, or the like, and the outer ring 12 c and the inner ring 12 b are made of stainless steel such as SUS440C.
[0027]
3 and 4 show an excimer laser device provided with a magnetic bearing motor according to a second embodiment of the present invention. FIG. 3 is an enlarged sectional view (corresponding to FIG. 2), and FIG. FIG. 4 is a sectional view taken along line AA in FIG. 3.
[0028]
The difference of this embodiment from the first embodiment is that a radial magnetic bearing 9 is used in which the protruding portion in the iron core of the electromagnet 9b penetrates the partition wall 44 and the inner peripheral surface thereof is exposed. . Here, since the iron core of the electromagnet 9b is in contact with the laser gas, it needs to have corrosion resistance. For this reason, permalloy having good corrosion resistance against laser gas is used. The iron core of the electromagnet 9b is fixed to the partition wall 44 by welding or the like, thereby preventing the coil winding of the electromagnet 9b having poor corrosion resistance against the laser gas from coming into contact with the laser gas.
[0029]
According to this embodiment, the magnetic gap between the iron core of the electromagnet 9b and the electromagnet target 9f is prevented from expanding by the partition wall 44, the efficiency as a magnetic bearing is improved, and the power consumption is reduced and the size is reduced. Can do.
[0030]
【The invention's effect】
As described above, according to the present invention, the first partition that hermetically seals the inner peripheral surface of the motor stator and the second partition that hermetically seals the inner peripheral surface of the inductive displacement sensor are separated. When the rotational drive current is excited in the motor stator, the eddy current and electromagnetic noise in the first partition generated by the AC magnetic flux of the motor are difficult to be transmitted to the second partition. The influence on the detection signal of the inductive displacement sensor can be reduced. For this reason, it is possible to prevent the magnetic bearing from vibrating the rotating body at the same frequency as the rotational drive current of the motor, thereby reducing the swing of the rotating body and reducing the vibration of the stator. A bearing motor can be provided.
[Brief description of the drawings]
FIG. 1 is an overall cross-sectional view of an excimer laser device provided with a magnetic bearing motor according to a first embodiment of the present invention.
FIG. 2 is an enlarged view of a main part showing an enlarged main part of FIG. 1;
FIG. 3 is an enlarged cross-sectional view (corresponding to FIG. 2) of an essential part of an excimer laser device including a magnetic bearing motor according to a second embodiment of the present invention.
4 is a cross-sectional view taken along line AA in FIG.
FIG. 5 is an overall cross-sectional view of an excimer laser device provided with a conventional magnetic bearing motor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Laser container 2 Main discharge electrode 3 Circulation fan 4 Rotating shaft 7 Motor housing 8, 9 Radial magnetic bearing 9a Inductive displacement sensor 9b Electromagnet 9e Displacement sensor target 9f Electromagnet target 10 Axial magnetic bearing 11 Motor 11a Motor stator 11b Motor rotor 16 Gas flow Outlets 12 and 13 Protective bearings 14 and 15 Groove labyrinth 17 Gas introduction chamber 18 Dust removal filter 19 Gas introduction pipes 44, 45 and 48

Claims (5)

A motor housing body and a bearing housing body in which a motor stator of a motor that rotationally drives a rotating body and an inductive displacement sensor and an electromagnet of a radial magnetic bearing that floats and supports the rotating body are arranged adjacent to each other with a sealant interposed therebetween. Each housed inside ,
The inner peripheral surface of the motor housing body is a first partition made of a thin cylindrical nonmagnetic metal material, and the inner peripheral surface of the bearing housing body is a second partition made of a thin cylindrical nonmagnetic metal material. The both partition walls are individually hermetically sealed in a state of being separated from each other , the both partition walls, the motor housing body and the bearing housing body exposed between the both partition walls, and the motor housing body and the bearing housing. A magnetic bearing motor characterized in that an airtight space that hermetically surrounds the motor rotor of the motor, the displacement sensor target of the radial magnetic bearing, and the electromagnet target is formed by the sealing material interposed between the main body and the main body . The first partition wall, the motor housing main body and is fixed by welding the ends to the side plate disposed in the interior of the motor housing main body, the second partition wall, the inside of the bearing housing body and the bearing housing body The magnetic bearing motor according to claim 1, wherein both ends of the side plate are fixed to the arranged side plate by welding. Wherein the second partition wall, the magnetic bearing motor according to claim 1 or 2, wherein the iron core prior Symbol electromagnets, characterized in that the inner circumferential surface of the through and iron heart is exposed. The magnetic bearing motor according to claim 3, wherein the second partition wall and the iron core of the electromagnet are joined by welding. A laser container enclosing a laser gas;
A pair of main discharge electrodes for obtaining a discharge disposed in the laser container and capable of oscillating laser light;
A circulation fan having a rotating shaft and creating a high-speed laser gas flow between the pair of main discharge electrodes;
An excimer laser device comprising: the magnetic bearing motor according to any one of claims 1 to 4 that rotationally drives the rotating shaft.

Images