U.S. patent application number 10/187566 was filed with the patent office on 2003-01-30 for vacuum pump.
Invention is credited to Maejima, Yasushi, Sakaguchi, Yoshiyuki.
Application Number | 20030021672 10/187566 |
Document ID | / |
Family ID | 19039128 |
Filed Date | 2003-01-30 |
United States Patent
Application |
20030021672 |
Kind Code |
A1 |
Maejima, Yasushi ; et
al. |
January 30, 2003 |
Vacuum pump
Abstract
To provide a vacuum pump in which destruction of a rotational
body due to corrosion can be prevented, and in which deposition of
product is reduced, preventing damage due to contact between the
rotational body and a fixed side. The pump case having the gas
inlet port opened on its upper surface, the rotor shaft supported
within the pump case such that it is capable of rotating, the
plurality of the rotor blades formed in the outer circumferential
surface of the rotor that is fixed to the rotor shaft, the
plurality of the stator blades fixed within the pump case,
positioned alternately with the plurality of the rotor blades, and
the driving motor for rotating the rotor shaft are provided. The
corrosion preventing film layer is formed on the inner
circumferential surface and the outer circumferential surface of
the rotor, and the balancing holes are formed by removing a portion
of the inner circumferential surface or the outer circumferential
surface of the rotor, and the thermosetting resin film layer is
formed on the surface of the balancing holes as an anti-corrosion
process.
Inventors: |
Maejima, Yasushi;
(Narashino-shi, JP) ; Sakaguchi, Yoshiyuki;
(Narashino-shi, JP) |
Correspondence
Address: |
ADAMS & WILKS
31ST FLOOR
50 BROADWAY
NEW YORK
NY
10004
US
|
Family ID: |
19039128 |
Appl. No.: |
10/187566 |
Filed: |
July 3, 2002 |
Current U.S.
Class: |
415/90 |
Current CPC
Class: |
F04D 29/662 20130101;
F04D 29/023 20130101; F05D 2300/44 20130101; F05D 2300/611
20130101; F05D 2230/90 20130101; F04D 19/04 20130101; F05D 2260/95
20130101 |
Class at
Publication: |
415/90 |
International
Class: |
F01D 001/36 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 3, 2001 |
JP |
2001-202297 |
Claims
What is claimed is:
1. A vacuum pump comprising: a pump case having a gas inlet port
opened in its top surface; a rotor shaft rotatably supported within
the pump case; a plurality of rotor blades formed on an outer
circumferential surface of a rotor that is fixed to the rotor shaft
and housed within the pump case; a plurality of stator blades fixed
within the pump case and positioned alternately with the plurality
of rotor blades; a driving motor for rotating the rotor shaft; an
anti-corrosive film layer formed on a surface of the rotor; and a
balancing hole formed by partially cutting off an inner
circumferential surface or an outer circumferential surface of the
rotor, and performed anti-corrosion process.
2. A vacuum pump according to claim 1, wherein the anti-corrosion
process comprises forming a thermosetting resin film layer on a
surface of the balancing hole.
3. A vacuum pump comprising: a pump case having a gas inlet port
opened in its top surface; a rotor shaft rotatably supported within
the pump case; a plurality of rotor blades formed on an outer
circumferential surface of a rotor that is fixed to the rotor shaft
and housed within the pump case; a plurality of stator blades fixed
within the pump case and positioned alternately with the plurality
of rotor blades; a driving motor for rotating the rotor shaft; a
balancing hole formed by partially cutting off an inner
circumferential surface or an outer circumferential surface of the
rotor; and an anti-corrosive film layer formed on a surface of the
rotor.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a vacuum pump used for a
semiconductor manufacturing apparatus, an electron microscope, a
surface analysis apparatus, a mass spectrometer, a particle
accelerator, an experimental fusion apparatus, or the like. In
particular, the invention relates to a vacuum pump in which
anti-corrosive processing is necessary, like one used in a
semiconductor manufacturing apparatus.
[0003] 2. Description of the Related Art
[0004] Conventionally, in a process step performing a processing
within a high vacuum chamber, such as a process step of dry etching
or CVD in a semiconductor manufacturing process, a vacuum pump such
as a turbo molecular pump is used as means for exhausting gas
within a processing chamber, for forming a given high vacuum
degree.
[0005] A rotational body of this type of vacuum pump is normally
formed of an aluminum alloy. However, in case of a vacuum pump that
is used under such a severe environment as a semiconductor
manufacturing process, in which the vacuum pump is exposed to
corrosive chlorine and fluorine sulfide gasses, an anti-corrosive
processing is performed in which the surface of a rotational body
made from an aluminum alloy is coated with an anti-corrosive
prevention film such as a nickel phosphorous alloy plating.
[0006] On the other hand, in vacuum pumps having a rotational body
as stated above, it becomes necessary to perform balancing of the
rotational body during high speed rotation at the pump assembly
stage of manufacturing. As a balancing method, a method is
generally known in which the mass of the rotational body is changed
by partially cutting off the outer circumferential surface or the
inner circumferential surface of the rotational body by using a
cutting tool such as a drill or a router, thus performing fine
adjustments of the balance.
[0007] However, balancing is performed by cutting in the
above-stated manner after conducting the anti-corrosion process,
and a portion of the anti-corrosive film coated on the surface of
the rotational body is removed by the cutting tool such as a drill
or a router. Therefore, corrosion develops in a cut off portion
where the aluminum alloy of the rotational body itself is exposed
due to a corrosive gas, stress corrosion cracks progress in the cut
off portion due to high speed rotation of the rotational body, and
in the worst case, this may lead to destruction of the rotational
body, affecting the outside of the vacuum pump as well.
[0008] Further, as stated above, the aluminum alloy of the
rotational body itself is exposed in the portion cut off for
balancing, and if debris or the like generated by etching a wafer
surface in a semiconductor manufacturing process is mixed into the
inside of the vacuum pump, then the debris will adhere to the
surface of the aluminum in the cut off portion, and will be
deposited as a product.
[0009] In particular, the debris will be easily deposited on the
surface of the deposited product, and if chain deposition of the
product on the surface of the rotational body progresses in this
manner, then the clearance between the fixed side of the vacuum
pump and the rotational body will become smaller. Accordingly,
there is a concern that the fixed side will have critical damage
when the product deposited on the rotating body contacts the fixed
side.
[0010] In view of the aforementioned matters in dispute, an object
of the present invention is to provide a vacuum pump in which
destruction of a rotational body due to corrosion can be prevented,
and in which the deposition of the product is reduced, preventing
damage due to contact between the rotational body and a fixed
side.
SUMMARY OF THE INVENTION
[0011] In order to achieve the aforementioned objective, a vacuum
pump according to the present invention is provided with: a pump
case having a gas inlet port opened in its top surface; a rotor
shaft rotatably supported within the pump case; a plurality of
rotor blades formed on an outer circumferential surface of a rotor
that is fixed to the rotor shaft and housed with in the pump case;
a plurality of stator blades fixed with in the pump case and
positioned alternately with the plurality of rotor blades; a
driving motor for rotating the rotor shaft; an anti-corrosive film
layer formed on a surface of the rotor; and a balancing hole formed
by partially cutting off an inner circumferential surface or an
outer circumferential surface of the rotor, the vacuum pump being
characterized in that anti-corrosion process is performed on the
balancing hole.
[0012] The anti-corrosion process employed here means a process in
which a thermosetting resin film layer is formed on a surface of
the balancing hole. Synthetic resins having superior heat
resistance characteristics and superior anti-corrosion
characteristics, such as epoxy resins and fluorine resins, for
example, can be used as the thermosetting resin.
[0013] Further, a vacuum pump according to the present invention is
provided with: a pump case having a gas inlet port opened in its
top surface; a rotor shaft rotatably supported within the pump
case; a plurality of rotor blades formed on an outer
circumferential surface of a rotor that is fixed to the rotor shaft
and housed within the pump case; a plurality of stator blades fixed
within the pump case and positioned alternately with the plurality
of rotor blades; a driving motor for rotating the rotor shaft; and
a balancing hole formed by partially cutting off an inner
circumferential surface or an outer circumferential surface of the
rotor; the vacuum pump being characterized in that an
anti-corrosive film layer is formed on a surface of the rotor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a vertical cross sectional diagram showing the
structure of a first embodiment of a vacuum pump according to the
present invention.
[0015] FIG. 2 is a blow-up cross sectional diagram of necessary
portions of the vacuum pump shown in FIG. 1, and is a diagram for
explaining an example of forming balancing holes in a rotor using a
cutting tool.
[0016] FIG. 3 is a blow-up cross sectional diagram of necessary
portions of the vacuum pump shown in FIG. 1, and is a diagram
showing a state after performing anti-corrosion process to the
rotor balancing holes.
[0017] FIG. 4 is a blow-up cross sectional diagram of necessary
portions of the vacuum pump shown in FIG. 1, and is a diagram
showing a second embodiment of an anti-corrosion process performed
on the rotor balancing holes.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0018] An embodiment of the present invention is explained in
detail below with reference to the attached drawings.
[0019] FIG. 1 is a vertical cross sectional diagram showing the
structure of a first embodiment of a vacuum pump according to the
present invention.
[0020] As shown in FIG. 1, a vacuum pump P of this embodiment is
roughly structured from a pump case 1 composed of a cylindrical
portion 1-1 and a base 1-2 attached to a lower end of the
cylindrical portion 1-1, and a pump mechanism portion housed in the
pump case 1.
[0021] An upper surface of the pump case 1 is opened, serving as a
gas inlet port 2, and a not shown vacuum container, such as a
process chamber, is screwed into the gas inlet port 2 and fixed
with a bolt, and an exhaust pipe that serves as a gas exhaust port
3 is formed in one side surface of a lower portion of the pump case
1.
[0022] A lower base of the pump case 1 is covered by a rear cover
1-3, and a stator column 4 is disposed above the rear cover 1-3 in
a standing manner toward an inside portion of the pump case 1 and
is screwed into and fixed to the base 1-2.
[0023] A rotor shaft 5 is bearing-supported in the radial direction
and in the axial direction by a radial direction electromagnet 6-1
and an axial direction electromagnet 6-2, respectively, which are
formed in an inside portion of the stator column 4 so that the
rotor 5 passing through between both ends of the stator column 4 is
able to rotate. Note that reference numeral 7 denotes a ball
bearing to which a dry lubricant has been applied. The ball bearing
7 protects the rotor shaft 5 and the electromagnets 6-1 and 6-2
from contacting and supports the rotor shaft 5 when an electric
power source for the magnetic bearings fails, the electromagnets
not being in contact with the rotor shaft 5 during normal
operation.
[0024] A rotor 8 formed in a cylindrical shape is disposed in the
inside portion of the pump case 1 so as to surround the stator
column 4, an upper end of the rotor 8 extends to the vicinity of
the gas inlet port 2, and is fixed to the rotor shaft 5 by screwing
with a bolt.
[0025] In a nearly center portion of the rotor shaft 5 in the axial
direction, a driving motor 9 composed of a high frequency motor or
the like is provided between the rotor shaft 5 and the stator
column 4, and the rotor shaft 5 and the rotor 8 are rotated at high
speed by the driving motor 9.
[0026] Further, the pump mechanism portion of the vacuum pump P of
this embodiment is housed within the pump case 1 and employs a
composite type pump mechanism composed of turbo molecular pump
mechanism portion P.sub.A of upper half, and thread groove pump
mechanism portion P.sub.B of lower half, which are defined between
an outer circumferential surface of the rotor 8 and an inner
circumferential surface of the pump case 1.
[0027] The turbo molecular pump mechanism portion P.sub.A is
structured by rotator blades 10 that rotate at high speed and
static stator blades 11 that are fixed.
[0028] That is, a plurality of processed blade shape rotor blades
10, 10, . . . are formed on the outer circumferential surface of
the upper half of the rotor 8 from the gas inlet port 2 side in a
direction to a central rotation axis L of the rotor 8. A plurality
of stator blades 11, 11, . . . disposed alternately between the
plurality of rotor blades 10, 10, . . . are formed on the inner
circumferential surface of the upper half of the pump case 1, and
are fixed through spacers 12, 12, . . .
[0029] On the other hand, the thread groove pump mechanism portion
P.sub.B is structured by a cylindrical surface 8a of the rotor 8
rotating at high speed and a static thread groove 13.
[0030] That is, the outer circumferential surface of the lower half
of the rotor 8 serves as the flat cylindrical surface 8a, and in
the inner circumferential surface of the lower half of the pump
case 1 a cylindrical screw stator 14 is disposed so as to oppose
the cylindrical surface 8a of the rotor 8 with a narrow gap. The
thread groove 13 is carved in the screw stator 14.
[0031] Note that the thread groove 13 can be carved in the outer
circumferential surface of the lower half of the rotor 8. Also, an
opposing surface of the screw stator 14 provided on the inner
circumference of the lower half of the pump case 1, to the rotor 8
can be formed in the flat cylindrical surface.
[0032] Incidentally, the vacuum pump P of this embodiment is used
under a severe environment exposed to corrosive chlorine and
fluorine sulfide gasses during semiconductor manufacturing
processes, an anti-corrosive process is performed as shown in FIG.
2 for forming an even coating of an anti-corrosive film layer 15 by
means of a plating, such as a nickel phosphorous oxide plating, at
a thickness on the order of 10 to 20 .mu.m on the outer
circumferential surface 8a and the inner circumferential surface 8b
of the rotor 8, which is formed by an aluminum alloy or the
like.
[0033] Further, the following may be performed as means for
performing balancing of the rotational body composed of the rotor
shaft 5, the rotor 8, and the rotor blades 10 during high speed
rotation: the stator blades 11 and the screw stator 14 fixed to the
cylindrical portion 1-1 of the pump case 1 may be temporarily
removed, and as shown in FIG. 2, balancing holes 16, 16, . . . may
be formed by partially cutting off the surface of the
anti-corrosive film layer 15 formed in the outer circumferential
surface 8a or the inner circumferential surface 8b of the rotor 8
using a cutting tool 20 such as a drill or a router; changing the
mass of the rotor 8 and performing fine adjustments of the balance
of the rotational body; and then an anti-corrosion process is
performed on the surface of the balancing holes 16.
[0034] The surface of the balancing holes 16 after performing the
rotational body balancing is in a state in which a portion of the
aluminum alloy of main body of the rotor 8 is exposed because a
portion of the anti-corrosive film layer 15 coated on the surface
of the outer circumferential surface 8a and the inner
circumferential surface 8b of the rotor 8 is cut off, as shown in
FIG. 2.
[0035] Therefore, in order to prevent stress corrosion cracking of,
and deposition of the product on the surface of the aluminum alloy
of the balancing holes 16, a thermosetting resin film layer 17
having superior heat resistance characteristics and superior
anti-corrosion characteristics, such as an epoxy resin, a fluorine
resin, or the like is formed on the surface of the balancing holes
16, as shown in FIG. 3.
[0036] The aforementioned thermosetting resin has good adhesive
characteristics with respect to metallic materials and has strong
adhesive force with respect to curved surfaces like the inner
circumferential surface 8b and the outer circumferential surface 8a
of the rotor 8, and therefore peeling due to centrifugal force of
the rotational body will not occur. Further, the thermosetting
resin has superior oxygen barrier characteristics, and therefore
anti-corrosion process can be performed by a relatively simple
method of only forming the thermosetting resin film layer 17 on the
surface of the balancing holes 16.
[0037] As a method of forming the thermosetting resin film layer
17, a known spray application process using a spray gun or the
like, followed by age hardening by the rotor 8 at room temperature
or a required temperature may be employed, whereby conducting a
uniform application at least on the surface of the aluminum alloy
of the balancing holes 16 at a thickness of 10 to 20 .mu.m.
[0038] Provided that the thermosetting resin film layer 17 is
formed into a thick film, anti-corrosion performance can be
increased, and corrosion of the balancing holes 16 can be prevented
over a long period of time. However, by reason that manufacturing
cost rises, the gap between the outer circumferential surface 8a of
the rotor 8 and the screw stator 14 becomes narrower, the
rotational body and the fixed side of the vacuum pump come into
contact, and the fixed side is damaged, the aforementioned film
thickness range is appropriate.
[0039] Further, the weight of the thermosetting resin film layer 17
after hardening and drying is set on the order of 1 to 10 mg with
respect to the number of balancing holes 16, and considering the
increase in weight due to the thermosetting resin film layer 17, it
is necessary to form the synthetic resin film layer 17 after
performing a little excess amount of material cutting for
balancing.
[0040] In accordance with the vacuum pump of this embodiment, the
aluminum alloy surface of the balancing holes 16 formed in the
surface of the outer circumferential surface 8a or the inner
circumferential surface 8b of the rotor 8 is covered by the
thermosetting resin film layer 17 as an anti-corrosion process, and
therefore corrosion due to a corrosive gas does not develop in the
aluminum alloy surface of the balancing holes 16, stress corrosion
cracking of the balancing holes due to high speed rotation of the
rotational body can be prevented, and rotor destruction due to
corrosion can be prevented from happening.
[0041] Further, as stated above, the thermosetting resin film layer
17 can be formed on the aluminum alloy surface of the balancing
holes 16b into a thin film as an anti-corrosion process, and
deposition of the product adhering to the aluminum alloy can be
reduced, and therefore damage due to contact between the rotational
body and the fixed side can be prevented.
[0042] Next, a second embodiment of a vacuum pump according to the
present invention is explained based on FIG. 4.
[0043] The basic structure of the vacuum pump in this second
embodiment is similar to the vacuum pump shown in FIG. 1, and
therefore identical reference numerals are attached to identical
portions, and a detailed explanation of those portions is
omitted.
[0044] The vacuum pump in this second embodiment is characterized
in that the balancing holes 16 are formed by removing a portion of
the inner circumferential surface 8b or the outer circumferential
surface 8a of the rotor 8, and in that the corrosion prevention
layer 15 is formed on the inner circumferential surface 8b and the
outer circumferential surface 8a of the rotor 8, as shown in FIG.
4.
[0045] That is, in this second embodiment, a portion of the outer
circumferential surface 8a or the inner circumferential surface 8b
of the rotor 8 formed by the aluminum alloy or the like is removed
by using the cutting tool 20 such as a drill or a router, changing
the mass of the rotor 8 and performing fine adjustments of the
balance of the rotational body, after which the corrosion
prevention film layer 15 is uniformly coated to a thickness on the
order of 10 to 20 .mu.m by plating a nickel phosphorous alloy
plating or the like, performing anti-corrosion process at the same
time to the rotor 8 and to the balancing holes 16.
[0046] In accordance with the vacuum pump of this second
embodiment, in addition to the effects obtained by the above stated
first embodiment, the process step for forming the thermosetting
resin film layer 17 for anti-corrosion process of the balancing
holes 16 can be omitted, anti-corrosion process of the balancing
holes 16 can be simplified, and the manufacturing costs of the
vacuum pump relating to anti-corrosion process can be lowered.
[0047] Further, the corrosion prevention film layer 15 is formed
uniformly over the entire surface of the rotor 8 after performing
balancing as stated above, and therefore it is not necessary to
remove an excess amount of material in order to adjust the
balance.
[0048] Note that although an example of applying the present
invention to a turbo molecular pump is explained in the
aforementioned embodiments, the present invention can also be
applied, of course, to other pumps that utilize rotation of a
rotating body, such as a drag pump, and it is also possible to
suitably change the locations in which the balancing holes are
formed for design reasons.
[0049] As explained in detail above, the following effects can be
obtained in accordance with the vacuum pump according to the
present invention.
[0050] (1) An effect in which corrosion due to corrosive gas does
not develop on the aluminum alloy surface of the balancing holes
formed in the rotor surface, stress corrosion cracking of the
balancing holes due to high speed rotation of the rotational body
can be prevented, and therefore, destruction of the rotor due to
corrosion can be prevented from happening.
[0051] (2) An effect in which the thermosetting resin film layer
can be formed as a thin film on the aluminum alloy surface of the
balancing holes for the heat resistance process, and deposition of
the product adhering to the aluminum alloy can be reduced, and
therefore damage due to contact between the rotational body and the
fixed side can be prevented.
[0052] (3) An effect in which anti-corrosion process of the
balancing holes can be simplified provided that the structure is
employed in which the corrosion prevention film is formed uniformly
over the entire surface of the rotor after performing balancing,
and manufacturing costs for the vacuum pump relating to
anti-corrosion process can be reduced.
* * * * *