JPH1089284A - Turbo-molecular pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a turbo-molecular pump to improve exhaust performance and relieve the load of a rotation generating source to rotate a rotor vane. SOLUTION: Rotor vanes 141-144 are attached on a rotor shaft 12 supported at a magnetic bearing 20, and stator vanes 181-184 surely positioned between the rotor vanes are arranged. An exhaust stage, an intermediate stage, and a compression stage at which gas is exhausted and compressed by the rotor vanes and the stator vanes are formed, in the order named. The blades of the rotor vane 144 of which the compression stage consists are radially arranged in a state to be inclined based on the rotor shaft 12, and the width direction of each blade is curved such that the rear side in the rotation direction of the blade is formed in a protrusionform state. Thereby, since gas flows along a plate surface at the periphery of each blade 144b, gas is movable from the upper side to the lower side and exhaust performance of a turbo-molecular pump is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbo molecular pump used as a vacuum apparatus such as a semiconductor manufacturing apparatus and an electron microscope.

[0002]

2. Description of the Related Art A turbo-molecular pump has rotor blades attached to a rotor shaft rotating at high speed and stator blades fixed to a casing arranged alternately, and a plurality of pairs of rotor blades and stator blades are provided. Thus, an exhaust stage, an intermediate stage, and a compression stage for exhausting and compressing gas in the molecular flow region are formed. As shown in FIG. 7, the rotor blade 1 includes an annular ring portion 1a, and a plurality of flat blades (blades) 1b radially provided on the outer peripheral surface of the ring portion 1a. Each blade 1b
Is inclined at a predetermined angle with respect to the rotation axis R, as shown in FIG. 7, and has a substantially uniform thickness.
FIG. 8 is a partial plan view of the rotor blade 1, and FIG.
It is sectional drawing of each position in the length direction of the blade 1b.

In a turbo-molecular pump, the blades of the rotor blades have different sizes and inclination angles in an exhaust stage, an intermediate stage, and a compression stage, but have a flat plate-like shape as shown in FIG. It is. In the turbo molecular pump having such a configuration, the rotor blades are rotated by the rotation of the rotor shaft, and the blades of the rotor blades move the gas molecules in the axial direction by hitting the gas molecules in the rotation direction, thereby exhausting. .

[0004]

However, the gas density on the compression stage side of the turbo-molecular pump is higher than the gas density on the exhaust stage side, and it is considered that the gas generates a viscous flow property. Even if it is attempted to move by striking the gas like the side, the movement becomes difficult. That is, as shown in FIG. 10, the gas cannot move along the surface of the blade 1b, causing separation, particularly on the rear side (the right side of the blade in the drawing) with respect to the rotation direction of the blade 1b, and the gas is stirred. As a result, the exhaust performance cannot be improved. In addition, the load on the motor that rotates the rotor blades increases due to the turbulence of the gas, causing a problem that the motor generates more heat than necessary.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a turbo-molecular pump capable of improving the exhaust performance and reducing the load on a rotation source for rotating a rotor blade.

[0006]

In order to achieve the above object, the present invention provides a rotor shaft, a bearing rotatably supporting the rotor shaft, and a motor for rotating the rotor shaft supported by the bearing. A plurality of rotor blades attached to the rotor shaft and provided with a plurality of blades radially inclined at a predetermined angle with respect to the rotor shaft, and a plurality of stators arranged between the plurality of rotor blades At least a part of the rotor blade is curved so that a width direction of the blade is convex rearward with respect to a rotation direction of the blade.

As described above, in the present invention, as shown in FIG. 4, for example, each blade 144b of the rotor blade 144 has its width direction convex rearward with respect to the rotation direction of the blade 144b. It is curved. Therefore, when each blade 144b is rotated by the rotation of the rotor blade 144, the gas flows along the plate surface without separating around the blade 144b as shown in FIG. It can be moved, and the exhaust performance of the turbo molecular pump as a whole is improved. Also, blade 1
Since there is no turbulent flow downstream of 44b and gas separation does not occur, the load on the motor, which is the drive source for rotating the rotor blades 144, is reduced, and this reduction can prevent heat generation of the motor.

Further, according to the present invention, each blade 144b of the rotor blade 144 forming the compression stage has a rounded tip or improves the surface roughness of the surface of each blade 144b, thereby achieving the above effects. Further improvements are being made.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, a preferred embodiment of the present invention will be described with reference to FIGS. FIG.
FIG. 1 is a cross-sectional view illustrating an entire configuration of a turbo-molecular pump according to a first embodiment of the present invention. FIG. 2 is a partial plan view of a rotor blade in a compression stage of the turbo molecular pump. FIG. 3 is a sectional view of each part of the blade of the rotor blade. The turbo molecular pump 10 according to the first embodiment
Is, as shown in FIG. 1, a substantially cylindrical rotor shaft 12;
A rotor blade 14 attached to the rotor shaft 12;
A stator blade 18 fixed to the inner periphery of a substantially cylindrical exterior body 16, a magnetic bearing 20 for supporting the rotor shaft 12 by magnetic force, and a motor 21 for generating torque on the rotor shaft 12
And

The rotor blade 14 has four types of rotor blades 14.
1, 142, 143, 144, and the stator blade portion 18 has its rotor blades 141, 142, 143, 144.
Types of stator blades 181, 182, 18 corresponding to
3, 184. And the rotor blade 141
To 144 and the corresponding stator blades 181 to 184 are arranged alternately in the vertical direction with a slight gap. With such an arrangement, for example, an exhaust stage is formed by the rotor blades 141 and the stator blades 181, and the rotor blades 142 and 1
43 and the stator blades 182 and 183 form an intermediate stage, and the rotor blade 144 and the stator blade 184 form a compression stage. The rotor blades 144 and the stator blades 184 forming the compression stage are provided with blades described later in a denser state than other blades in order to prevent gas from flowing backward from the exhaust port 39 side.

[0011] The rotor blades 141, 142, 143 are shown in FIG.
As in the case of the rotor blade 1 shown in FIG. 1, an annular ring portion and a plurality of flat blades (blades) radially provided on the outer peripheral surface of the ring portion. The size and inclination angle of the blades are controlled by the rotor blades 141, 14
2,143. Stator blades 181, 18
2, 183 have blades similar to the rotor blades 141, 142, 143, and the inclination direction of each blade is opposite to the inclination direction of the blades of the rotor blades 141, 142, 143.

Next, the detailed configuration of the rotor blade 144 will be described with reference to FIGS. This rotor blade 1
Reference numeral 44 denotes an annular ring portion 144a as shown in FIG.
And a plurality of blades 144b radially provided on the outer peripheral surface of the ring portion 144a. As shown in FIG. 3, each blade 144b is inclined at a predetermined angle with respect to the rotation axis.
The width direction of 4b is curved so as to protrude rearward with respect to the rotation direction of blade 144b. Further, as shown in FIG.
b-1 is formed round, and the surface roughness of the surface 144b-2 on the rear side in the rotation direction of the blade is improved. The stator blades 184 are connected to the stator blades 181, 18
2, 183.

The above-described magnetic bearing 20 is provided on the rotor shaft 1.
2, a radial electromagnet 22, 24 and an axial electromagnet 26 for generating a radial magnetic force and an axial magnetic force, respectively, and a radial direction for detecting the radial position and the axial position of the rotor shaft 12, respectively. Sensors 30, 32, and an axial sensor 34, and these radial sensors 30, 3
2, and a control system 36 for performing feedback control of exciting currents of the radial electromagnets 22 and 24 and the axial electromagnet 26 based on detection signals of the axial sensor 34, respectively.

Next, the operation of the first embodiment having such a configuration will be described with reference to the drawings. When the turbo molecular pump 10 of this embodiment is driven, the rotor shaft 12 is held in a non-contact state at a predetermined floating position by the magnetic bearing 20, and the motor 21 is driven in this state, whereby the rotor shaft 12 is driven. 12 rotates. And
As shown in FIG. 1, when each rotor blade 14 rotates between the stator blades 18, gas is taken in from the intake port 38 and is compressed and discharged from the exhaust port 39.

Incidentally, the rotor blade 141 and the stator blade 1
81 and the rotor blades 142, 143
Since the gas flow can be handled as a molecular flow in the intermediate stage formed by the rotor blades 182 and 183, the gas molecules are hit by the blades of the rotor blades 141, 142 and 143 and move toward the exhaust port 39 side. I do. However, in the compression stage formed by the rotor blades 144 and the stator blades 184,
The gas density becomes higher than that in the exhaust stage or the intermediate stage, and it cannot be handled as a molecular flow.

However, in the first embodiment, as shown in FIG. 3, the width direction of each blade 144b of the rotor blade 144 forming the compression stage is convex rearward with respect to the rotation direction of the blade 144b. The shape is curved. Therefore, when each blade 144b is rotated by the rotation of the rotor blade 144, gas flows along the plate surface around each blade 144b and does not cause separation,
The upper gas can be moved downward, and the exhaust performance is improved.

Further, since the turbulence on the downstream side of the blade 144b is eliminated and the gas is not separated, the load on the motor which is the driving source for rotating the rotor blades is reduced, and the heat generation of the motor can be prevented by this reduction. . Further, in this embodiment, each blade 144b has a tip side 144b-1 having a rounded shape and a surface 144b-2.
Since the surface roughness is improved, the exhaust performance is further improved.

Next, a second embodiment of the present invention will be described with reference to FIGS. The second embodiment is different from the rotor blade 144 according to the first embodiment.
Is replaced with a rotor blade 145 as shown in FIG. 5 and FIG. That is, in the second embodiment, as shown in FIG.
45a, and a plurality of blades 145b radially provided on the outer peripheral surface of the ring portion 145a. Each blade 145b is inclined at a predetermined angle with respect to the rotation axis as shown in FIG.
The width direction of the blade 44b is curved so as to protrude rearward with respect to the rotation direction of the blade 144b, and at the same time, a twist is applied in the length direction. The configuration of other parts of the second embodiment is the same as that of the first embodiment, and a description thereof will be omitted.

[0019]

As described above, in the present invention, the width direction of the blade of the rotor blade is curved so as to protrude backward with respect to the rotation direction of the blade, so that the exhaust performance can be improved. In addition, the load on the rotor blade rotation source can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of a turbo-molecular pump according to a first embodiment of the present invention.

FIG. 2 is a partial plan view of a rotor blade in a compression stage.

FIG. 3 is a sectional view of a blade of the rotor blade.

FIG. 4 is a diagram illustrating the operation of the blade.

FIG. 5 is a partial plan view of a rotor blade in a compression stage according to a second embodiment of the present invention.

FIG. 6 is a sectional view of each part of a blade of the rotor blade.

FIG. 7 is a perspective view of a rotor blade of a conventional turbo-molecular pump.

FIG. 8 is a partial plan view of the rotor blade.

FIG. 9 is a sectional view of a blade of the rotor blade.

FIG. 10 is a diagram illustrating the operation of the blade.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Turbo molecular pump 12 Rotor axis 14 Rotor blade part 141, 142, 143, 144, 145 Rotor blade 144a, 145a Ring part 144b, 145b Blade 18 Stator blade part 181, 182, 183, 184 Stator blade 20 Magnetic bearing

Claims (4)

[Claims] A rotor shaft; a bearing rotatably supporting the rotor shaft; a motor rotating the rotor shaft supported by the bearing; a predetermined angle attached to the rotor shaft; A plurality of rotor blades in which a plurality of blades are provided radially in a slanted manner, and a plurality of stator blades arranged between the plurality of rotor blades, at least a part of the rotor blades, A turbo molecular pump characterized in that the width direction of the blade is curved so as to be convex rearward with respect to the rotation direction of the blade. 2. The turbo-molecular pump according to claim 1, wherein the curved blade is twisted in a length direction thereof. 3. The turbo-molecular pump according to claim 1, wherein the curved blade has a rounded tip. 4. The curved blade according to claim 1, wherein the surface roughness of the surface on the rear side with respect to the rotation direction of the blade is improved.
The turbomolecular pump as described.