JP2002089488A - Fan device for circulating excimer laser gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress reduction of a bending natural frequency of a rotary shaft in a fan device for circulating an excimer laser gas, and to suppress aging bending of the rotary shaft itself. SOLUTION: This fan device for circulating the excimer laser gas has the rotary shaft 2 installed with a fan 3, and radial magnetic bearings 5, 13 and an axial magnetic bearing supporting the rotary shaft in a non-contact state. The rotary shaft 2 includes an austenitic stainless steel part; and a magnetic body 19 having high magnetic permeability fixed on the surface of the stainless steel part, opposite to electromagnets 4, 11 of the magnetic bearings 5, 13.

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 once-through fan device for circulating excimer laser gas, and more particularly to a structure of the device.
The present invention relates to a structure of a rotating shaft in the fan device.

[0002]

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

For example, Japanese Patent Application Laid-Open No. 11-87810 and Japanese Patent Application Laid-Open No. 11-303793 introduce examples of using magnetic bearings. These documents disclose a configuration in which a rotating shaft is non-contact supported by two radial magnetic bearings and two axial magnetic bearings, and a motor rotor fixed to the rotating shaft is rotationally driven by a motor stator on a stator side. I have.

FIG. 4 shows a once-through fan device for circulating laser gas having a structure different from that of the above-mentioned patent application, and its peripheral portion. As shown in FIG. 4, the fan 3 is installed in the chamber 1 and the chamber 1 is filled with a laser gas. The fan 3 is mounted on the rotating shaft 2 and rotates in the chamber 1.

[0005] Magnetic bearings supporting the rotating shaft 2 are arranged on both sides of the chamber 1. On the left side of the chamber 1, a radial magnetic bearing 5 composed of a radial electromagnet 4 and a position sensor 6, an axial electromagnet 16 and a position sensor 17 which are part of the axial magnetic bearing, and a motor stator 8
A motor 7 comprising a motor and a motor rotor 9;
And a protection bearing 10 that is arranged to protect the bearings and can be supported in the radial and axial directions.

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

As described above, the balance between the attraction force of the permanent magnet 14 and the attraction force of the axial electromagnet 16 is used for the axial magnetic bearing control, and the apparatus can be made compact by omitting one axial electromagnet. Further, there is no need for a power circuit for driving the axial electromagnet coil, and there is an advantage that cost can be reduced.

Here, the protective bearing 10, the motor stator 8
The radial electromagnet 4 is adjusted to be substantially coaxial. The clearance between the inner diameter of the protective bearing 10 and the rotating shaft 2 opposed thereto is set slightly smaller than the minimum dimension of the clearance between the inner diameter of the motor stator 8 and the radial electromagnet 4 and the rotating shaft 2 opposed thereto. 2 prevents contact with the motor stator 8 and each electromagnet.

Similarly, the protective bearing 15 and the radial electromagnet 1
1 is also adjusted to be substantially coaxial. The clearance between the inner diameter of the protective bearing 15 and the rotating shaft 2 opposed thereto is set slightly smaller than the clearance between the inner diameter of the radial electromagnet 11 and the rotating shaft 2 opposed thereto. To prevent contact.

The position of the rotating shaft 2 is detected 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, current-amplified by a power amplifier, and the electromagnet of each magnetic bearing. A predetermined current is applied to the coil.
Thereby, the magnetic bearing control is performed.

[0011]

As shown in FIG. 4, since the length of the fan 3 is long, the rotating shaft 2 is also long, and the bending natural frequency of the rotating shaft 2 is low. Therefore, it is difficult to secure control stability of the magnetic bearing. In addition, the electromagnets 4 and 1
A magnetic material having high magnetic permeability is used for the rotating shaft 2 facing the rotating shafts 1 and 16, but when the rotating shaft 2 itself is made of a magnetic material,
There is a problem that the cost is high, and furthermore, a magnetic material having a high magnetic permeability has a low elastic modulus, so that the bending natural frequency of the rotating shaft 2 is low.

Furthermore, since the rotating shaft 2 is long, for example, excessive stress such as bending is applied when the rotating shaft 2 is assembled, or the rotating shaft 2 is erroneously damaged or damaged during the assembly operation, or the rotating operation is performed. Excessive disturbance exceeding the magnetic bearing supporting capacity is suddenly applied to the rotating shaft 2 during rotation, and the rotating shaft 2
There is a possibility of deformation due to collision with 0,15. Furthermore, in the manufacturing process of the rotating shaft 2 itself, there are various deformation factors in the rotating shaft 2 such as plastic deformation of a material surface layer during cutting and grinding.

When the rotating shaft 2 is made of austenitic stainless steel, a slight plastic deformation as described above causes induced martensitic transformation, and martensite is scattered in austenite which is a main structure of the rotating shaft 2. become.

Since there is a positive change in volume due to a change in structure from austenite to martensite, the rotating shaft 2 is bent. When the temperature of the rotating shaft 2 increases, the rotating shaft 2 is further bent due to a difference in thermal expansion between austenite and martensite.

When the rotating shaft 2 is bent, the vibration of the fan 3 during rotation increases, causing a problem that the performance of an excimer laser device used for micromachining is deteriorated.

The present invention has been made to solve the above problems. An object of the present invention is to facilitate securing control stability of a magnetic bearing and to suppress bending of the rotating shaft 2.

[0017]

An excimer laser gas circulation fan apparatus according to the present invention includes a rotating shaft on which a fan is mounted, and a magnetic bearing for supporting the rotating shaft in a non-contact manner. And a magnetic part fixed on the surface of the austenitic stainless steel part and facing the electromagnet of the magnetic bearing.

As described above, austenitic stainless steel having a high elastic coefficient is mainly used as the material of the rotating shaft, and the magnetic body is selectively fixed only at the position facing the electromagnet, so that the magnetic body is positioned with respect to the rotating shaft. Acts as a spring system instead of an additional mass. Thereby, as shown in FIG. 3, it is possible to suppress a decrease in the bending natural frequency of the rotating shaft.

With the magnetic member fixed, the rotation axis is set to 300
It is preferable to anneal at a temperature of not less than ℃. Thereby, stress due to processing of the rotating shaft and stress due to sticking of the magnetic body portion can be removed, and bending of the rotating shaft can be suppressed.

On the rotating shaft, (% Ni + 30 ×% C + 0.5
×% Mn) is 16 or more,
And (% Cr +% Mo + 1.5 ×% Si + 0.5 ×% N
It is preferable to use a material whose Cr equivalent value given in b) is 18 or more. More preferably, the amount of Ni component on the rotating shaft is expressed as% Ni = (% Cr + 1.5 ×% Mo).
^{-20) 2/12 - (%} Mn / 2) -35 ×% C + 15
Is larger than% Ni calculated by

As a result, the austenite structure is stabilized, and the induced martensitic transformation can hardly occur. As a result, bending of the rotating shaft can be suppressed.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2,
An embodiment of the present invention will be described. FIG. 1 is a cross-sectional view of an excimer laser gas circulation fan device according to one embodiment of the present invention. The same components as those of the conventional example shown in FIG. 3 are denoted by the same reference numerals, and redundant description will be omitted as much as possible.

As shown in FIG. 1, a fan 3 mounted on a rotating shaft 2 is installed in a chamber 1. The rotating shaft 2 is supported in a non-contact manner by radial magnetic bearings 5 and 13 and an axial magnetic bearing as in the conventional example. Further, protective bearings 10 and 15 are provided as in the conventional example.

FIG. 1 is an explanatory diagram of the present invention. In this embodiment, the position of the motor 7 and the position of the radial magnetic bearing 5 are reversed from those of the conventional example. However, the intention of the present invention is not limited to such a configuration, and the present invention can be applied to the configuration shown in the conventional example. Can be applied.

The rotating shaft 2 is mainly made of austenitic stainless steel SUS304. Then, a magnetic body 19 having a high magnetic permeability such as permalloy is arranged at a position facing each of the electromagnets 4, 11, 16 and the magnetic body 19 is fixed to the austenitic stainless steel. Examples of the fixing method include welding and brazing. In the present embodiment, the magnetic body 19 is fixed to the austenitic stainless steel via the weld 20.

The magnetic body 19 facing the axial electromagnet 16, which is the electromagnet of the axial magnetic bearing, is not fixed in order to improve the assemblability of the apparatus. Also, welding or the like can be used for fixing the motor rotor 9.

Since the magnetic body 19 is fixed to the rotating shaft 2, the magnetic body 19 acts not as an additional mass but as a spring system with respect to the rotating shaft 2. Thus, it is possible to suppress a decrease in the bending natural frequency of the rotating shaft 2.

Since the workability of austenitic stainless steel is not good, internal stress may remain after working. Further, when the internal stress generated by welding or the like is released thereafter, the rotating shaft 2 may be bent.

Therefore, after the working of the rotary shaft 2 or after welding or the like, annealing is performed to remove the stress. The higher the annealing temperature, the better, but the annealing is preferably performed at a temperature of 300 ° C. or higher. Thereby, the stress can be removed, and the bending of the rotating shaft 2 can be suppressed.

Further, SUS304 has an unstable austenite structure and is apt to undergo martensitic transformation. In the case of martensite transformation, a positive volume change occurs, and the rotating shaft 2 is bent.

Therefore, the Ni equivalent (% Ni + 30 ×% C + 0.5 ×% Mn), which is an index of the stability of the austenitic structure, is 16 or more in the austenitic stainless steel material.
Cr equivalent (% Cr) which is an index of stability of ferrite structure
+% Mo + 1.5 ×% Si + 0.5 ×% Nb) is 18 or more.

FIG. 2 shows a structural diagram (Schaeffler diagram) of stainless steel. By selecting the above-mentioned material, there is no martensite structure inside in terms of histology, and it is possible to prevent the rotating shaft 2 from bending.

It is also important that the induced martensitic transformation is unlikely to occur in order to prevent the rotating shaft 2 from bending.

Therefore, C.I. B. Post can be introduced to TASM in 1947, and the concept of the necessary amount of Ni for preventing martensite from being produced at room temperature can be introduced to control the components.

That is, the required Ni component amount (% Ni) shown below is calculated from the material component amount, and the calculated% Ni
By using a material having a higher Ni content than in the above, it is possible to suppress the bending of the rotating shaft 2 due to the induced martensitic transformation.

% Ni = (% Cr + 1.5 ×% Mo-2)
^{0) 2/12 - (%} Mn / 2) -35 ×% C + 15 has been carried out described embodiments of the present invention as described above, the embodiments disclosed herein are illustrative in all respects limit Should not be considered as a matter of course. The scope of the present invention is defined by the appended claims, and includes all modifications within the scope and meaning equivalent to the claims.

[0037]

As described above, according to the present invention,
It is possible to suppress a decrease in the natural frequency of bending of the rotating shaft and also suppress a time-dependent bending of the rotating shaft itself. Thereby, not only can the control stability of the magnetic bearing be improved, but also the rotating shaft can be used for a long time.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an excimer laser gas circulation fan device according to the present invention.

FIG. 2 is a structural diagram (Schaeffler diagram) of stainless steel.

FIG. 3 is a diagram showing a change in a natural frequency of bending depending on a type of a rotating shaft.

FIG. 4 is a sectional view of a conventional fan device for excimer laser gas circulation.

[Explanation of symbols]

1 chamber, 2 rotating shafts, 3 fans, 4,11 radial electromagnet, 5,13 radial magnetic bearing, 6,1
2,17 position sensor, 7 motor, 8 motor stator, 9 motor rotor, 10,15 protective bearing, 14
Permanent magnet, 16 axial electromagnet, 19 magnetic body, 20
welded part.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01S 3/036 H01S 3/03 J 3/225 3/223 EF term (Reference) 3H022 AA02 BA06 CA01 CA16 CA50 CA51 DA13 3H031 AA04 BA05 3J102 AA01 BA03 BA19 CA02 CA14 CA18 DA02 DA03 DA09 DB05 FA03 GA20 5F071 AA06 DD08 FF09 JJ03 JJ05

Claims (4)

[Claims] A rotating shaft to which a fan is attached; and a magnetic bearing for supporting the rotating shaft in a non-contact manner, wherein the rotating shaft is provided on an austenitic stainless steel part and on a surface of the austenitic stainless steel part. A fan device for excimer laser gas circulation, comprising: a magnetic part fixed to a position facing an electromagnet of a magnetic bearing. 2. The excimer laser gas circulation fan device according to claim 1, wherein the rotating shaft is annealed at a temperature of 300 ° C. or more with the magnetic body fixed. 3. The method according to claim 1, wherein the rotating shaft includes (% Ni + 30 ×% C +
Ni equivalent value given by 0.5 ×% Mn) is 16 or more, and (% Cr +% Mo + 1.5 ×% Si + 0.5)
3. The fan apparatus for circulating excimer laser gas according to claim 1, wherein a material having a Cr equivalent value given by (×% Nb) is 18 or more is used. 4. The method according to claim 1, wherein the amount of the Ni component on the rotating shaft is% N.
i = (% Cr + 1.5 × % Mo-20) 2/12 - (%
The excimer laser gas circulation fan device according to claim 3, wherein the amount is larger than% Ni calculated by (Mn / 2) -35x% C + 15.