U.S. patent application number 10/244740 was filed with the patent office on 2003-01-23 for turbo-molecular pump.
This patent application is currently assigned to Ebara Corporation. Invention is credited to Kawasaki, Hiroyuki, Miyamoto, Matsutaro, Ogamino, Hiroaki, Shiokawa, Atsushi, Sobukawa, Hiroshi.
Application Number | 20030017047 10/244740 |
Document ID | / |
Family ID | 27474077 |
Filed Date | 2003-01-23 |
United States Patent
Application |
20030017047 |
Kind Code |
A1 |
Shiokawa, Atsushi ; et
al. |
January 23, 2003 |
Turbo-molecular pump
Abstract
A turbo-molecular pump includes a casing having an intake port,
a stator fixedly mounted in the casing, and a rotor supported in
the casing for rotation relatively to the stator. The stator and
the rotor make up a turbine blade pumping section and a groove
pumping section for evacuating gas. A scattering prevention member
is provided for preventing fragments of the rotor from being
scattered through the intake port.
Inventors: |
Shiokawa, Atsushi; (Tokyo,
JP) ; Miyamoto, Matsutaro; (Tokyo, JP) ;
Kawasaki, Hiroyuki; (Tokyo, JP) ; Sobukawa,
Hiroshi; (Tokyo, JP) ; Ogamino, Hiroaki;
(Tokyo, JP) |
Correspondence
Address: |
ARMSTRONG,WESTERMAN & HATTORI, LLP
1725 K STREET, NW.
SUITE 1000
WASHINGTON
DC
20006
US
|
Assignee: |
Ebara Corporation
Tokyo
JP
|
Family ID: |
27474077 |
Appl. No.: |
10/244740 |
Filed: |
September 17, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10244740 |
Sep 17, 2002 |
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09592411 |
Jun 13, 2000 |
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09592411 |
Jun 13, 2000 |
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09473137 |
Dec 28, 1999 |
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09473137 |
Dec 28, 1999 |
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09104171 |
Jun 25, 1998 |
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6332752 |
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Current U.S.
Class: |
415/90 |
Current CPC
Class: |
F04D 19/042 20130101;
F04D 29/522 20130101; F04D 29/701 20130101 |
Class at
Publication: |
415/90 |
International
Class: |
F01D 001/36 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 14, 1999 |
JP |
11-166637 |
Claims
What is claimed is:
1. A turbo-molecular pump comprising: a casing having an intake
port; a stator fixedly mounted in said casing; a rotor supported in
said casing for rotation relatively to said stator, said stator and
said rotor serving as at least one of a turbine blade pumping
section and a groove pumping section for evacuating gas; and a
scattering prevention members for preventing fragments of at least
one of said rotor and said stator from being scattered through said
intake port.
2. A turbo-molecular pump according to claim 1, wherein said rotor
comprises rotor blades and said stator comprises stator blades, and
said scattering prevention member comprises at least part of said
rotor blade or said stator blade
3. A turbo-molecular pump according to claim 1, wherein said
scattering prevention member includes at least one protrusion
projecting radially inwardly from an inner surface of said intake
port.
4. A turbo-molecular pump according to claim 1, wherein said
scattering prevention member is made of a high-strength
material.
5. A turbo-molecular pump according to claim 1, wherein said
scattering prevention member is made of a high-energy absorbing
material.
6. A turbo-molecular pump according to claim 1, wherein said
scattering prevention member has a shock absorbing structure.
Description
[0001] This is a continuation-in-part of application Ser. No.
09/473,137, filed Dec. 28, 1999.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a turbo-molecular pump for
evacuating gas with a rotor that rotates at a high speed.
[0004] 2. Description of the Related Art
[0005] FIG. 21 of the accompanying drawings shows a conventional
turbo-molecular pump. As shown in FIG. 21, the conventional
turbo-molecular pump comprises a rotor R and a stator S which are
housed in a pump casing 14. The rotor R and the stator S jointly
make up a turbine blade pumping section L1 and a thread groove
pumping section L2. The stator S comprises a base 15, a stationary
cylindrical sleeve 16 vertically mounted centrally on the base 15,
and stationary components of the turbine blade pumping section L1
and the thread groove pumping section L2. The rotor R mainly
comprises a main shaft 10 inserted coaxially in the stationary
cylindrical sleeve 16, and a rotary cylindrical sleeve 12 mounted
on the main shaft 10 and disposed around the stationary cylindrical
sleeve 16.
[0006] Between the main shaft 10 and the stationary cylindrical
sleeve 16, there are provided a drive motor 18, an upper radial
magnetic pole 20 disposed above the drive motor 18, and a lower
radial magnetic pole 22 disposed below the drive motor 18. An axial
bearing 24 is disposed at a lower portion of the main shaft 10, and
comprises a target disk 24a mounted on the lower end of the main
shaft 10, and upper and lower electromagnets 24b provided on the
stator side. By this magnetic bearing system, the rotor R can be
rotated at a high speed under 5-axis active control.
[0007] The rotary cylindrical sleeve 12 has rotor blades 30
integrally disposed on an upper outer circumferential portion
thereof. In the pump casing 14, there are provided stator blades 32
disposed axially alternately with the rotor blades 30. The rotor
blades 30 and the stator blades 32 jointly make up the turbine
blade pumping section L1 for evacuating gas by way of an
interaction between the rotor blades 30 and the stator blades
32.
[0008] The thread groove pumping section L2, which is disposed
downwardly of the turbine blade pumping section L1, includes a
thread groove section 34 of the rotary cylindrical sleeve 12 which
has thread grooves 34a defined in an outer circumferential surface
thereof and surrounds the stationary cylindrical sleeve 16. The
stator S has a spacer 36 disposed around the thread groove section
34. The thread groove pumping section L2 evacuates gas by way of a
dragging action of the thread grooves 34a in the thread groove
section 34 which rotates at a high speed in unison with the rotor
R. The stator blades 32 have outer edges clamped by either stator
blade spacers 38 or the stator blade spacer 38 and the spacer
36.
[0009] With the thread groove pumping section L2 disposed
downstream of the turbine blade pumping section L1, the
turbo-molecular pump is of the wide range type capable of handing a
wide range of rates of gas flows. In the conventional
turbo-molecular pump shown in FIG. 21, the thread grooves 34a of
the thread groove pumping section L2 are defined in the rotor R.
However, the thread grooves of the thread groove pumping section L2
may be defined in the stator S.
[0010] In such a turbo-molecular pump, if the rotor R is broken due
to corrosion or the like, then fragments of the rotor R may enter
an intake port 14a of the pump casing 14. When fragments of the
rotary cylindrical sleeve 12 or the rotor blades 30 which have
large kinetic energy are introduced into the chamber of a
processing apparatus that is connected to the intake port 14a of
the pump casing 14 through a flange 14b, the processing apparatus
may be broken or products that are being processed by the
processing apparatus may be damaged, and the overall evacuating
system may be destroyed, tending to cause a harmful processing gas
to leak into the surrounding environment.
SUMMARY OF THE INVENTION
[0011] It is therefore an object of the present invention to
provide a highly safe turbo-molecular pump which can prevent rotor
fragments from damaging the chamber in a processing apparatus and
products being processed by the processing apparatus even when a
rotor of the turbo-molecular pump is broken, and which can be
replaced in its entirety in case of destruction for quickly making
the processing apparatus reusable.
[0012] According to the present invention, there is provided a
turbo-molecular pump comprising a casing having an intake port, a
stator fixedly mounted in the casing, a rotor supported in the
casing for rotation relatively to the stator, the stator and the
rotor serving as at least one of a turbine blade pumping section
and a thread groove pumping section for evacuating gas, and a
scattering prevention member for preventing fragments of the rotor
from being scattered through the intake port.
[0013] If the rotor is broken, then fragments of the rotor, e.g., a
rotary cylindrical sleeve and rotor blades, or fragments of the
stator, e.g., stator blades, are blocked by the scattering
prevention member, or lose the kinetic energy toward the intake
port. Therefore, the scattering prevention member is effective to
prevent those fragments from damaging the chamber in a processing
apparatus connected to the intake port or devices and products
being processed in the chamber. The scattering prevention member
may be mounted on a stationary member such as the casing, or the
rotor.
[0014] The rotor comprises rotor blades and the stator comprises
stator blades, and the scattering prevention member comprises at
least part of the rotor blade or the stator blade. Therefore, at
least part of the rotor blade or the stator blade has a fragment
shield function.
[0015] The scattering prevention member includes at least one
protrusion projecting radially inwardly from an inner surface of
the intake port. If the rotor is broken, rotor fragments collide
with the protrusion, and are prevented from being scattered through
the intake port or kinetic energy of the rotor fragments is
reduced.
[0016] The scattering prevention member is made of a high-strength
material and/or a high-energy absorbing material. The high-strength
material may be stainless steel, titanium alloy, or the like which
is stronger than aluminum. The high-energy absorbing material may
be made of a relatively soft metal material such as lead, a polymer
material, or a composite material thereof, and shaped so as to be
effective to absorb shocks, e.g., shaped into a honeycomb structure
or an assembly of spherical members.
[0017] The scattering prevention member has a shock absorbing
structure. The shock absorbing structure is effective to absorb the
kinetic energy of rotor fragments which collide with the scattering
prevention member for better protection of the chamber in the
processing apparatus that is connected to the intake port.
[0018] The above and other objects, features, and advantages of the
present invention will become apparent from the following
description when taken in conjunction with the accompanying
drawings which illustrate preferred embodiments of the present
invention by way of example.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] FIG. 1 is an axial cross-sectional view of a turbo-molecular
pump according to a first embodiment of the present invention;
[0020] FIG. 2 is a plan view of the turbo-molecular pump shown in
FIG. 1;
[0021] FIG. 3 is an axial cross-sectional view of a turbo-molecular
pump according to a second embodiment of the present invention;
[0022] FIG. 4 is an axial cross-sectional view of a turbo-molecular
pump according to a third embodiment of the present invention;
[0023] FIG. 5 is an enlarged fragmentary cross-sectional view of
the turbo-molecular pump shown in FIG. 4;
[0024] FIG. 6 is an axial cross-sectional view of a turbo-molecular
pump according to a fourth embodiment of the present invention;
[0025] FIG. 7 is a plan view of the turbo-molecular pump shown in
FIG. 6;
[0026] FIG. 8 is an axial cross-sectional view of a turbo-molecular
pump according to a fifth embodiment of the present invention;
[0027] FIG. 9 is an axial cross-sectional view of a turbo-molecular
pump according to a sixth embodiment of the present invention;
[0028] FIG. 10 is an enlarged fragmentary cross-sectional view of
the turbo-molecular pump shown in FIG. 9;
[0029] FIG. 11 is a plan view of metal pipes of a shock absorbing
member used in the turbo-molecular pump shown in FIG. 9;
[0030] FIG. 12 is an axial cross-sectional view of a
turbo-molecular pump according to a seventh embodiment of the
present invention;
[0031] FIG. 13 is an axial cross-sectional view of a
turbo-molecular pump according to an eighth embodiment of the
present invention;
[0032] FIG. 14 is an axial cross-sectional view of a
turbo-molecular pump according to a ninth embodiment of the present
invention;
[0033] FIG. 15 is an enlarged fragmentary cross-sectional view of
the turbo-molecular pump shown in FIG. 14;
[0034] FIG. 16 is an axial cross-sectional view of a
turbo-molecular pump according to a tenth embodiment of the present
invention;
[0035] FIG. 17 is an axial cross-sectional view of a
turbo-molecular pump according to an eleventh embodiment of the
present invention;
[0036] FIG. 18 is a plan view of the turbo-molecular pump shown in
FIG. 17;
[0037] FIG. 19 is an axial cross-sectional view of a
turbo-molecular pump according to a twelfth embodiment of the
present invention;
[0038] FIG. 20 is a plan view of the turbo-molecular pump shown in
FIG. 19; and
[0039] FIG. 21 is an axial cross-sectional view of a conventional
turbo-molecular pump.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0040] Next, a turbo-molecular pump according to embodiments of the
present invention will be described below. Like or corresponding
parts are denoted by like or corresponding reference characters
throughout views. Those parts of turbo-molecular pumps according to
the present invention which are identical to those of the
conventional turbo-molecular pump shown in FIG. 21 are denoted by
identical reference characters, and will not be described in detail
below.
[0041] FIGS. 1 and 2 show a turbo-molecular pump according to a
first embodiment of the present invention. As shown in FIGS. 1 and
2, the turbo-molecular pump according to the first embodiment has a
protective cover 50 serving as a scattering prevention member
mounted on the flange 14b around the intake port 14a in the pump
casing 14. The protective cover 50 comprises a circular shield 52
disposed centrally in the intake port 14a in covering relationship
to an area directly above the rotary cylindrical sleeve 12 of the
rotor R, a ring-shaped rim 56 disposed concentrically with and
radially outwardly of the circular shield 52 and having an opening
whose size is the same as the size of the intake port 14a, and a
plurality of (three in FIG. 2) support bars 54 extending radially
outwardly from the circular shield 52 to connect the circular
shield 52 and the rim 56 to each other. In FIG. 1, the protective
cover 50 has a step 56a on the lower surface of the rim 56 which is
fitted over the flange 14b, so that the protective cover 50 is
fixed to the pump casing 14. However, the flange 14b may have a
step, and the protective cover 50 may be fitted in the step and
fastened to the flange 14b by bolts. Alternatively, the protective
cover 50 may be fitted in the step in the flange 14b and simply
sandwiched between the pump casing 14 and the chamber in the
processing apparatus to which the turbo-molecular pump is
connected.
[0042] The axially uppermost stator blade 32a of all the stator
blades 32 is made of a material stronger than aluminum, such as
stainless steel, titanium alloy, or the like, and the remaining
stator blades 32 are made of aluminum. Thus, the stator blade 32a
also serves as a scattering prevention member.
[0043] With the turbo-molecular pump having the above structure, if
the rotor R is broken due to corrosion or the like while it is
rotating, fragments of the rotary cylindrical sleeve 12 or the
rotor blades 30 in the rotor R collide with the shield 52 of the
protective cover 50, thereby losing their kinetic energy toward the
intake port 14a. Therefore, the chamber or the like connected to
the intake port 14a of the pump casing 14 is prevented from being
damaged, or the degree of damage of the chamber or the like is
reduced. In the embodiment shown in FIG. 1, the shield 52 covers
only the rotary cylindrical sleeve 12. However, the shield 52 may
cover not only the rotary cylindrical sleeve 12, but also part of
the rotor blades 30.
[0044] Since the axially uppermost stator blade 32a of the stator
blades 32 is made of a material stronger than aluminum, the stator
blade 32a is not broken or is broken to a lesser degree when it is
hit by fragments of the rotor blades 30 made of aluminum. The
stator blade 32a thus effectively serves as a scattering prevention
member for preventing fragments from being scattered through the
intake port 14a.
[0045] In the first embodiment, only the uppermost stator blade 32a
of the stator blades 32 is made of a high-strength material.
However, any other arbitrary stator blades 32, e.g., first- and
fourth-stage stator blades 32 may be made of a high-strength
material. This holds true for other embodiments of the present
invention.
[0046] In the first embodiment, the protective cover 50 is provided
as a scattering prevention member, and also the uppermost stator
blade 32a of the stator blades 32 is made of a material stronger
than aluminum as a scattering prevention member. However, either
protective cover 50 may be provided or the uppermost stator blade
32a may be made of a material stronger than aluminum. The
turbo-molecular pump in other embodiments described later may have
the same structure as the turbo-molecular pump in the first
embodiment.
[0047] FIG. 3 shows a turbo-molecular pump according to a second
embodiment of the present invention. According to the second
embodiment, the circular shield 52 of the protective cover 50
according to the first embodiment is replaced with a substantially
cylindrical shield 58. The substantially cylindrical shield 58 has
a substantially lower half disposed in a recess 13 defined
centrally in the rotary cylindrical sleeve 12. Other details of the
turbo-molecular pump according to the second embodiment are
identical to those of the turbo-molecular pump according to the
first embodiment.
[0048] With the turbo-molecular pump according to the second
embodiment, the gap between the shield 58 and the rotor R is
reduced to lower the possibility of fragments to be scattered
around for better protection of the chamber to which the
turbo-molecular pump is connected. The shield 58 also performs an
attitude maintaining function to keep the rotor R in its proper
attitude when the rotor R suffers abnormal rotation. Any unwanted
contact between the rotor R and the stator W can therefore be
minimized to reduce the possibility of fragment production.
[0049] FIGS. 4 and 5 shows a turbo-molecular pump according to a
third embodiment of the present invention. According to the third
embodiment, the turbo-molecular pump includes a scattering
prevention member having a shock absorbing structure. Specifically,
the protective cover 50 as a scattering prevention member has a
substantially circular shield 70 disposed centrally therein and
having a shank 70a projecting downwardly, and a shock absorbing
member 74 comprising metal pipes 72 wound in two coil-like layers
around the shank 70a. The shock absorbing member 74 is surrounded
by a cup-shaped cover 76 which is open upwardly. The shield 70 has
a peripheral edge fastened to a flange of the cover 76 by bolts 78.
The cover 76 is disposed so as to enter the recess 13 defined
centrally in the rotary cylindrical sleeve 12.
[0050] With the turbo-molecular pump of this embodiment, if the
rotor R is broken, then fragments of the rotor blades 30 or the
rotary cylindrical sleeve 12 collide with the shield 70 and the
cover 76. At this time, the shock absorbing member 74 can easily be
deformed or broken in both axial and radial directions to absorb
applied shocks. Therefore, the kinetic energy of the fragments is
absorbed to protect the chamber to which the turbo-molecular pump
is connected.
[0051] The shock absorbing member 74 may alternatively be made of a
relatively soft metal material such as lead, a polymer material, or
a composite material thereof, and shaped so as to be effective to
absorb shocks, e.g., shaped into a honeycomb structure or an
assembly of spherical members. In view of applications of the
turbo-molecular pump for evacuating corrosive gases, the shock
absorbing member 74 should preferably be made of a
corrosion-resistant material or be treated to provide a
corrosion-resistant surface such as a nickel coating.
[0052] FIG. 6 and 7 show a turbo-molecular pump according to a
fourth embodiment of the present invention. The turbo-molecular
pump according to the fourth embodiment differs from the
turbo-molecular pump according to the first embodiment in the
following: A plurality of (three in FIG. 7) protrusions 60, which
make up a scattering prevention member together with the protective
cover 50, are disposed at predetermined intervals on an inner
surface of the intake port 14a and project radially inwardly in
covering relationship to the outer circumferential edges of the
rotor blades 30 of the rotor R. While the protrusions 60 are shown
as being disposed on the inner surface of the intake port 14a, the
protrusions 60 may alternatively be disposed on the rim 56 of the
protective cover 50.
[0053] With the turbo-molecular pump according to the fourth
embodiment, if the rotor R is broken, then fragments of the rotor
blades 30 and the rotary cylindrical sleeve 12 collide with not
only the shield 52 but also the protrusions 60, thus reducing the
kinetic energy of the fragments introduced into the intake port
14a.
[0054] FIG. 8 shows a turbo-molecular pump according to a fifth
embodiment of the present invention. The turbo-molecular pump
according to the fifth embodiment has a scattering prevention
member 62 mounted on the upper end of the main shaft 10 of the
rotor R in covering relationship to the upper surface of the rotary
cylindrical sleeve 12 that faces the intake port 14a. The
scattering prevention member 62 is of a cup shape complementary to
the recess 13 in the rotary cylindrical sleeve 12 and has a flange
62a on its upper end which extends along the flat upper surface of
the rotary cylindrical sleeve 12. The scattering prevention member
62 has an internally threaded hole defined in a bottom thereof. The
main shaft 10 has a fixed portion 10a at the upper end thereof and
having an externally threaded surface. The scattering prevention
member 62 is fastened to the main shaft 10 by the fixed portion 10a
that is threaded into the internally threaded hole in the
scattering prevention member 62. The scattering prevention member
62 may alternatively be fastened to the main shaft 10 or the rotary
cylindrical sleeve 12 by other fasteners such as bolts.
[0055] With the turbo-molecular pump according to the fifth
embodiment, since the scattering prevention member 62 is mounted on
the rotor R, it is not necessary to provide an obstacle which would
otherwise extend across the intake port 14a for installing the
scattering prevention member 62. Therefore, the velocity of the gas
that is evacuated by the turbo-molecular pump is not lowered.
Furthermore, because the scattering prevention member 62 is
disposed in covering relationship to the recess 13 where fragments
of the rotor R tend to be scattered, the scattering prevention
member 62 is effective to efficiently prevent fragments of the
rotor R from being scattered. While the scattering prevention
member 62 is disposed in covering relationship to the rotary
cylindrical sleeve 12 in the illustrated embodiment, the scattering
prevention member 62 may be disposed so as to cover part of the
rotor blades 30.
[0056] FIGS. 9 through 11 show a turbo-molecular pump according to
a sixth embodiment of the present invention. The turbo-molecular
pump according to the sixth embodiment differs from the
turbo-molecular pump according to the fifth embodiment in that a
shock absorbing structure is added to the scattering prevention
member 62 according to the fifth embodiment. Other details of the
turbo-molecular pump according to the sixth embodiment are
identical to those of the turbo-molecular pump according to the
fifth embodiment.
[0057] In the sixth embodiment, the upwardly open scattering
prevention member 62 houses therein a shock absorbing member 82
comprising a pair of vertical stacks of semiannular metal pipes 80
(see FIG. 11) in radially confronting relationship to each other.
The main shaft 10 has a vertical extension having an externally
threaded upper end. A nut 84 as a shock absorbing member holder is
threaded over the externally threaded upper end of the extension of
the main shaft 10, thus holding the shock absorbing member 82
against removal. The nut 84 is fastened to cause the shock
absorbing member 82 to press the lower surface of the flange 62a
thereof against the rotary cylindrical sleeve 12 for thereby
securing the scattering prevention member 62.
[0058] If the rotor R is broken, then fragments of the rotor blades
30 or the rotary cylindrical sleeve 12 collide with the scattering
prevention member 62. At this time, the shock absorbing member 82
can easily be deformed or broken in both axial and radial
directions to absorb applied shocks. Therefore, the kinetic energy
of the fragments is absorbed to protect the chamber or the like to
which the turbo-molecular pump is connected.
[0059] The semiannular metal pipes 80 are used to make up the shock
absorbing member 82 for the reason of better productivity.
Alternatively, fully circular metal pipes, annular metal pipes with
open gaps, or coil-shaped metal pipes may also be employed. The
shock absorbing member 82 may alternatively be made of a relatively
soft metal material, a polymer material, or a composite material
thereof, and shaped so as to be effective to absorb shocks.
[0060] FIG. 12 shows a turbo-molecular pump according to a seventh
embodiment of the present invention. The turbo-molecular pump
according to the seventh embodiment differs from the
turbo-molecular pump according to the fifth embodiment in that the
cup-shaped scattering prevention member 62 is replaced with a
disk-shaped scattering prevention member 64 that is housed in the
recess 13 in the rotary cylindrical sleeve 12. Other details of the
turbo-molecular pump according to the seventh embodiment are
identical to those of the turbo-molecular pump according to the
fifth embodiment. Usually, the rotary cylindrical sleeve 12 has an
upper portion 12a integral with a hub 12b thereof. Therefore, only
by simply holding the hub 12b with the disk-shaped scattering
prevention member 64, rotor fragments is effectively prevented from
being scattered. The turbo-molecular pump according to the seventh
embodiment is less costly than the turbo-molecular pump according
to the fifth embodiment.
[0061] FIG. 13 shows a turbo-molecular pump according to an eighth
embodiment of the present invention. The turbo-molecular pump
according to the eighth embodiment differs from the turbo-molecular
pump according to the fifth embodiment in that the cup-shaped
scattering prevention member 62 is fastened to the rotary
cylindrical sleeve 12 by bolts 66 and also differs therefrom in the
following: A plurality of (three in the illustrated embodiment)
protrusions 60, which make up a scattering prevention member
together with the scattering prevention member 62, are disposed at
predetermined intervals on an inner surface of the intake port 14a
and project radially inwardly in covering relationship to the outer
circumferential edges of the rotor blades 30 of the rotor R.
[0062] With the turbo-molecular pump according to the eighth
embodiment, if the rotor R is broken, then fragments of the rotor
blades 30 or the rotary cylindrical sleeve 12 collide with not only
the scattering prevention member 62 but also the protrusions 60,
thus reducing the kinetic energy of the fragments introduced into
the intake port 14a. In all the embodiments, the scattering
prevention member including the protrusions should preferably be
made of a high-strength material such as stainless steel, titanium
alloy, or the like.
[0063] FIGS. 14 and 15 show a turbo-molecular pump according to a
ninth embodiment of the present invention. The turbo-molecular pump
according to the ninth embodiment differs from the turbo-molecular
pump according to the eighth embodiment in that a shock absorbing
structure is added to the scattering prevention member 62 fastened
to the rotary cylindrical sleeve 12 according to the eighth
embodiment. Other details of the turbo-molecular pump according to
the ninth embodiment are identical to those of the turbo-molecular
pump according to the eighth embodiment.
[0064] In the ninth embodiment, a support 90 having a shank 90a is
vertically mounted in the recess 13 in the rotary cylindrical
sleeve 12 and fastened to the bottom of the recess 13 by bolts 92.
The scattering prevention member 62 houses therein a shock
absorbing member 96 comprising a pair of vertical stacks of
semiannular metal pipes 80 (see FIG. 11) in radially confronting
relationship to each other and a plurality of O-rings 94 of
fluororubber interposed between the pipes 80 and the scattering
prevention member 62. The shank 90a has a vertical extension having
an externally threaded upper end. A nut 98 as a shock absorbing
member holder is threaded over the externally threaded upper end of
the extension of the shank 90a, thus holding the shock absorbing
member 96 against removal. The scattering prevention member 62 is
limited against its axial movement by the pipes 80 and limited
against its radial movement by the O-rings 94. The shock absorbing
structure is capable of absorbing shocks due to collision with
rotor fragments or stator fragments in both the axial and radial
directions.
[0065] As shown in FIG. 15, an annular ledge 12c is disposed on the
upper surface of the rotary cylindrical sleeve 12 around the recess
13, and an annular ridge 62c is disposed on the lower surface of a
peripheral edge of the flange 62a of the scattering prevention
member 62. The annular ridge 62c define a recess 62b in the lower
surface of the flange 62a. When the annular ledge 12c is fitted in
the recess 62b in the lower surface of the flange 62a, the
scattering prevention member 62 is coaxially aligned with the
rotary cylindrical sleeve 12 and held against radial movement.
[0066] With the turbo-molecular pump according to the ninth
embodiment, if the rotor R is broken, fragments of the rotor blades
30 or the rotary cylindrical sleeve 12 collide with the scattering
prevention member 62. At this time, the shock absorbing member 96
is deformed or broken to absorb the kinetic energy of the
fragments. Since fragments also collide with the protrusions 60,
the kinetic energy of the fragments introduced into the intake port
14a can further be reduced.
[0067] FIG. 16 shows a turbo-molecular pump according to a tenth
embodiment of the present invention. According to the tenth
embodiment, the axially uppermost rotor blade 30a of all rotor
blades 30 is separate from the other rotor blades 30 and is made of
a material stronger than aluminum, such as stainless steel,
titanium alloy, or the like, and the remaining rotor blades 30 are
made of aluminum. The uppermost rotor blade 30a is directly
fastened to the main shaft 10 by bolts 100, and serves as a
scattering prevention member.
[0068] Since the uppermost rotor blade 30a is made of a material
stronger than aluminum, the rotor blade 30a is not broken or is
broken to a lesser degree when it is hit by fragments of the
remaining rotor blades 30 made of aluminum. The rotor blade 30a
thus effectively serves as a scattering prevention member for
preventing fragments from being scattered through the intake port
14a.
[0069] FIGS. 17 and 18 show a turbo-molecular pump according to an
eleventh embodiment of the present invention.
[0070] The turbo-molecular pump comprises a cylindrical pump casing
114 housing a blade pumping section L1 and a groove pumping section
L2 which are constituted by a rotor (rotation member) R and a
stator (stationary member) S. The bottom portion of the pump casing
114 is covered by a base section 115 which is provided with an
exhaust port 115a. The top portion of the pump casing 114 is
provided with a flange section 114a for coupling the
turbo-molecular pump to an apparatus or a piping to be evacuated.
The stator S comprises a stator cylinder section 247 provided on
the center of the base section 115, and stationary sections of the
blade pumping section L1 and the groove pumping section L2.
[0071] The rotor R comprises a rotor cylinder section 112 attached
to a main shaft 110 which is inserted into the stator cylinder
section 247. Between the main shaft 110 and the stator cylinder
section 247, there are provided a drive motor 118, an upper radial
bearing 120 and a lower radial bearing 122 disposed on the upper
and lower sides of drive motor 118, respectively. At the lower part
of the main shaft 110, there is provided an axial bearing 124
having a target disk 124a at the bottom end of the main shaft 110
and an upper and lower electromagnets; 124b on the stator side. In
this configuration, the rotor R can be rotated at a high speed
under a five coordinate active control system.
[0072] Rotor blades (rotor vanes) 130 are provided integrally with
the upper external surface of the rotor cylinder section 112, and
on the inside of the pump casing 114, stator blades (stator vanes)
132 are provided in such a way to alternately interweave with the
rotor blades 130. These blade members constitute the blade pumping
section L1 which carries out gas evacuation by cooperative action
of the high-speed the rotor blades 130 and the stationary stator
blades 132. Below the blade pumping section L1, the groove pumping
section L2 is provided. The groove pumping section L2 comprises a
spiral groove section 134 having spiral grooves 134a on the outer
surface of the lower portion of the rotor cylinder section 112, and
the stator S comprises a spiral groove section spacer 251
surrounding the spiral groove section 134. Gas evacuation action of
the groove pumping section L2 is caused by the dragging effect of
the spiral grooves 134a of the spiral groove section 134.
[0073] By providing the groove pumping section L2 downstream of the
blade pumping section L1, a wide-range of the turbo-molecular pump
can be constructed so as to enable evacuation over a wide range of
gas flow rates using one pumping unit. In this example, the spiral
grooves of the groove pumping section L2 are provided on the rotor
side of the pump structure, but the spiral grooves may be formed on
the stator side of the pump structure.
[0074] The blade pumping section L1 comprises alternating rotor
blades 130 and stator blades 132, and the groove pumping section L2
comprises the spiral groove section 134 and the groove pumping
section spacer 251. The pump casing 114 is used to press down the
stator blades 132, the stator blade spacers 138 and the groove
pumping section spacer 251.
[0075] In this embodiment, the lower inner casing 250 and the
spiral groove section spacer 251 are separately provided. That is,
the stacked assembly comprising the stator blades 132 and the
stator blade spacers 138, and the spiral groove section spacer 251
are fixedly held by a lower inner casing 250 and an upper inner
casing 253, which are mutually fitted to construct an inner casing
252.
[0076] An impact absorbing member 286 is provided between the inner
surfaces of the lower inner casing 250 and the upper inner casing
253, and the outer surfaces of the stator blade spacers 138 and the
spiral groove section spacer 251. The impact absorbing member 286
is made of a material such as relatively soft metal, high polymer,
or composite material thereof.
[0077] The lower inner casing 250 comprises an outer cylindrical
portion 250A and an inner cylindrical portion 250B connected by a
connecting portion 250C having a communicating hole 250D. A
friction reducing structure (mechanical bearing) 285 is provided
between the inner surface of the inner cylindrical portion 250B and
the outer surface 247a of the stator cylinder section 247 of the
stator S.
[0078] In this embodiment, since a clearance T is formed between
the inner casing 252 and the pump casing 114, even when a part of
the inner casing 252 is broken or deformed, the impact is not
directly transmitted to the pump casing 114 to thus prevent
breakage of the pump casing 114 or its connection with other
facilities or devices.
[0079] In this embodiment, since the impact absorbing member 286 is
provided between the lower inner casing 250 and the upper inner
casing 253, and the stator blade spacers 138 and the spiral groove
section spacer 251, the amount of impact force transmitted to the
inner casing 252 is reduced, which has been transmitted from the
rotor R to the stator blade spacers 138 etc. Thus, the protection
function of the inner casing 252 is improved, and hence the
clearance T between the upper inner casing 253 or the lower inner
casing 250 and the pump casing 114 can be smaller to enable the
overall pump to be compact.
[0080] As shown in FIGS. 17 and 18, in this embodiment, another
impact absorbing structure 254 is provided at the upstream of the
blade pumping section L1, i.e., at an intake port 114b of the
turbo-molecular pump shown in FIG. 17. Specifically, an extended
portion 110a is provided at the top of the main shaft 110, and an
annular suppressing portion 254a is formed at the top of the upper
inner casing 253. Stay members 254b are provided to inwardly
protrude from the annular suppressing portion 254a and are
connected to a ring-shaped upper inner cylindrical portion 254c.
The ring-shaped upper cylindrical portion 254c surrounds the
extended portion 110a with a small gap t.
[0081] With the turbo-molecular pump according to the eleventh
embodiment, the separate impact absorbing structure 254 is provided
at the upstream of the blade pumping section L1, i.e., at the
intake port 114b of the turbo-molecular pump. The impact absorbing
structure 254 serves as a scattering prevention member for
preventing fragments of the rotor from being scattered through the
intake port 114b.
[0082] FIGS. 19 and 20 show a turbo-molecular pump according to a
twelfth embodiment of the present invention. In this embodiment,
the impact absorbing structure 254 at the entrance is mounted on a
shaft body fixed to the stator S by way of friction reducing
structure. That is, the upper end of the main shaft 110 is shorter,
and a bearing supporting member 290 is provided to protrude
inwardly from the top inner surface of the pump casing 114.
[0083] The bearing supporting member 290 comprises an annular
section 290a fixed to the pump casing 114, stay members 290b
extending radially inwardly from the annular section 290a, a disc
290c connected to the stay members 290b at the central region, and
a cylindrical shaft 290d extending downward from the disc 290c. On
the other hand, rectangular plate-like stay members 254b are
provided to radially inwardly extend from the annular suppressing
portion 254a of the upper inner casing 253, and an upper inner
cylindrical portion 254c is formed at the central region of the
stay members 254b above the main shaft 110. A mechanical bearing
(friction reducing mechanism) 292 is provided between the outer
surface of the shaft 290d and the upper inner cylindrical portion
254c.
[0084] The impact absorbing structure 254 serves as a scattering
prevention member for preventing fragments of the rotor from being
scattered through the intake port 114b. The bearing supporting
member 290 also serves as a scattering prevention member for
preventing fragments of the rotor from being scattered through the
intake port 114b.
[0085] As described above, according to the eleventh and twelfth
embodiments shown in FIGS. 17 through 20, if the rotor is broken,
then fragments of the rotor, e.g., a rotary cylindrical sleeve and
rotor blades, or fragments of the stator, e.g., stator blades, are
blocked by the scattering prevention member, or lose the kinetic
energy toward the intake port. Therefore, the scattering prevention
member is effective to prevent those fragments from damaging the
chamber in a processing apparatus connected to the intake port or
devices and products being processed in the chamber.
[0086] As described above, the various embodiments of the present
invention are applied to the wide-range turbo-molecular pump which
has the turbine blade pumping section L1 and the thread groove
pumping section L2. However, the principles of the present
invention are also applicable to a turbo-molecular pump having
either the turbine blade pumping section L1 or the thread groove
pumping section L2. Furthermore, the various embodiments of the
present invention may be used in any one of possible
combinations.
[0087] With the present invention, as described above, while the
rotor is rotated, fragments of the rotary cylindrical sleeve or the
rotor blades produced when the rotor is broken collide with the
scattering prevention member and are prevented from being scattered
through the intake port, or lose their kinetic energy. Thus, those
fragments are prevented from causing damage to the chamber
connected to the intake port or devices and products being
processed in the chamber. Therefore, even if the rotor is broken,
the turbo-molecular pump effectively prevents accidents which would
otherwise lead to damage to the chamber or destruction of the
evacuating system. Consequently, the turbo-molecular pump according
to the present invention is highly safe while it is in
operation.
[0088] Although certain preferred embodiments of the pre-sent
invention have been shown and described in detail, it should be
understood that various changes and modifications may be made
therein without departing from the scope of the appended
claims.
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