Rotary kinetic fluid motors or pumps – Including destructible – fusible – or deformable non-reusable...
Reexamination Certificate
2002-04-23
2004-03-16
Look, Edward K. (Department: 3745)
Rotary kinetic fluid motors or pumps
Including destructible, fusible, or deformable non-reusable...
C415S090000, C415S213100
Reexamination Certificate
active
06705830
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a vacuum pump used for a semiconductor manufacturing apparatus, and particularly, to a structure for preventing defect accompanied by a damage of a fastening-bolt that connects the pump and a process chamber, which is caused due to damaging torque.
2. Description of the Related Art
A vacuum pump such as a turbo molecular pump is employed as means for exhausting gas in a chamber in such a step that processes are performed in a process chamber (hereinafter, referred to as “chamber”) of high vacuum, such as a dry etching process of semiconductor manufacturing step or a CVD process.
FIG. 5
shows a conventional basic structure of this kind of vacuum pump. A pump case
1
of a vacuum pump shown in
FIG. 5
is provided with a gas inlet port
2
at the upper surface and an exhaust pipe that serves as an exhaust port
3
at one side portion of the lower portion, is formed in a cylindrical-shape and is attached to a base
1
—
1
.
The bottom portion of the base
1
—
1
is covered with an end plate
4
, and a stator column
5
is provided so as to be erected at the center portion of internal bottom surface thereof.
A rotor shaft
7
is rotatably bore through an upper ball bearing
6
and a lower ball bearing
6
at the center of the stator column
5
.
A driving motor
8
is arranged inside the stator column
5
. The driving motor
8
has a structure in which a stator element
8
a
is disposed inside the stator column
5
and a rotator element
8
b
is disposed on the rotor shaft
8
, and it is structured such that the rotor shaft
7
is rotated about the shaft.
A rotor
9
, which covers the outer circumference of the stator column
5
and is formed in a section-shape, is connected to the upper portion protrusion end from the stator column
5
of the rotor shaft
7
.
A plurality of rotor blades
10
and a plurality of stator blades
11
, which are processed and formed in a blade-shape, are alternately disposed along the rotation center shaft of the rotor
9
between the upper portion side outer circumferential surface of the rotor
9
and the upper portion side inner wall of the pump case
1
.
The rotor blades
10
are integrally processed with the rotor
9
, to thereby be integrally provided with the upper portion side outer circumferential surface of the rotor
9
. Further, the rotor blades
10
can be integrally rotated with the rotor
9
. However, the stator blades
11
are positioned and arranged between the upper stage and the lower stage of the rotor blades
10
,
10
through a spacer
11
a
positioned at the upper portion side inner wall of the pump case
1
. Further, the stator blades
11
are attached and fixed to the inner wall side of the pump case
1
.
A fixed screw stator
12
is arranged at the position opposing the lower portion side outer circumferential surface of the rotor
9
. The screw stator
12
is formed in a cylindrical-shape so that the entire shape thereof surrounds the lower portion side outer circumferential surface of the rotor
9
, and integrally attached and fixed to the base
1
—
1
. Note that a thread groove is formed inside the screw stator
12
, that is, at the surface side opposing the rotor
9
.
The vacuum pump shown in
FIG. 5
is employed as means for exhausting gas in the chamber
14
as described above. However, in this used state, the vacuum pump shown in
FIG. 5
is attached and fixed to the lower surface side opening portion of the chamber
14
. In the pump-attached and fixed structure, there is adopted a structure in which a flange
1
a
that is integrally provided with the peripheral end portion of the upper surface of the pump case
1
hits on the peripheral end of the lower surface side opening portion of the chamber
14
, and the flange
1
a
is fastened on the side of the chamber
14
by a plurality of bolts
15
in this state.
The operation of the above vacuum pump will be described. In the vacuum pump, an auxiliary pump (not shown) connected to the gas exhaust port
3
is operated to cause the inside of the chamber
14
to enter the vacuum state of some degree. Thereafter, the driving motor
8
is operated to rotate the rotor
9
and the rotor blades
10
at high speed integrated with the rotor shaft
7
.
Thus, the rotor blade
10
of the uppermost stage rotating at high speed imparts downward momentum to gas molecule entered from the gas inlet port
2
. The gas molecule including the downward momentum is guided to the stator blade
11
and sent into the side of the rotor blade
10
of the next lower stage. The above momentum impartment to gas molecule and the sending operation are repeated in a lot of stages. As a result, the gas molecule of the side of the gas inlet port
2
is sequentially moved to the inside of the screw stator
12
of the lower portion side of the rotor
9
. The exhausting operation of the gas molecule is a gas molecule exhausting operation, which is caused due to interaction between the rotating rotor blades
10
and the fixed stator blades
11
.
The gas molecule, which has reached the screw stator
12
of the lower portion side of the rotor
9
through the above-described gas molecule exhausting operation, is compressed by interaction between the rotating rotor
9
and the thread groove formed inside the screw stator
12
, and is moved to the side of the gas exhaust port
3
, and then is exhausted to the exterior through the auxiliary pump (not shown) from the gas exhaust port
3
.
Incidentally, as structural materials of the rotor
9
, the rotor blade
10
, and the stator blade
11
or the like, which compose the vacuum pump, light alloy, in particular, aluminum alloy is normally employed in many cases. This is because aluminum alloy is excellent in machining and can be precisely processed without difficulty. However, the hardness of aluminum alloy is relatively low as compared with the other materials and aluminum alloy may cause a damage depending on the operating condition. Further, in a rotation body composed of the rotor
9
and the rotor blades
10
, a minute drill hole is bored on the lower portion side outer circumferential surface of the rotor
9
, to thereby keep the dynamic balance at the time of high-speed rotation. Consequently, there are tendencies for stress to concentrate on the drill hole, and for the damage of the rotor
9
to occur from the drill hole.
However, the conventional vacuum pump shown in
FIG. 5
adopts the pump-attached and fixed structure in which the flange
1
a
of the pump case
1
is connected to the side of the chamber
14
by the bolt
15
, as described above. Therefore, for example, the above damage of the rotor
9
occurs during the high-speed rotation of the rotor
9
, to thereby generate a high rotation torque (hereinafter, referred to as “damaging torque”) for rotating the entire pump case
1
. Thus, the distortion of the pump case
1
is caused due to the damaging torque and a bolt shaft portion
15
a
of the bolt
15
fails due to the distortion force as shown in
FIG. 6
, resulting in causing such a defect that the entire pump together with the pump case
1
is released and dropped from the side of the chamber
14
. Also, it takes a lot of time to take out the failed bolt shaft
15
a
of the bolt
15
from the side of the chamber
14
. In the worst case, it is necessary that a new tap is built and a new screw hole is provided at the side of the chamber
14
. Therefore, the pump changing operation is performed with difficulty.
The present invention is made for solving the above described problems and an object of the present invention is to provide a vacuum pump in which dropping of the pump and troubles accompanied therewith can be prevented in advance even when an abnormality of the pump occurs only to generate damaging torque, and the changing operation of the pump causing the abnormality can be rapidly performed.
SUMMARY OF THE INVENTION
To attain the above described object, according to the present invention, there is provided a vacuum pump comprising: a pump case forming an i
Maejima Yasushi
Sakaguchi Yoshiyuki
Yamashita Yoshihiro
Adams & Wilks
BOC Edwards Techonlogies Limited
Edgar Richard A.
Look Edward K.
LandOfFree
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