JPH03213695A - Turbo vacuum pump - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a turbo vacuum pump whose exhaust port is at atmospheric pressure, particularly for use in semiconductor manufacturing equipment and the like.

This invention relates to a turbo vacuum pump suitable for creating a clean vacuum.

[Conventional technology]

BACKGROUND ART Conventionally, a turbo vacuum pump whose exhaust port pressure is close to atmospheric pressure is known, for example, as described in Japanese Patent Laid-Open No. 61-247893.

This turbo-type vacuum pump consists of a housing with an intake port and an exhaust port, a rotary shaft rotatably supported within the housing via a bearing, and a rotating shaft installed in the housing from the intake port side to the exhaust port side. , a centrifugal compression pump stage, and a circumferential flow compression pump stage. The rotating shaft is driven by a motor connected thereto. Since it is driven at high speed, an O-ring is attached to the outer periphery of the bearing holder to act as a damper.

Gas flowing in from the inlet near the top of the centrifugal compression pump stages is sufficiently compressed by each pump stage and exhausted to atmospheric pressure from the exhaust port.

[Problem to be solved by the invention]

In the conventional turbo vacuum pump described above, when the vacuum pump reaches a steady operating state, the centrifugal compression pump stage mainly works with molecular flow and intermediate flow, and the circular homogeneous compression pump stage works with viscous flow, so the exhaust port The pressure can be maintained at atmospheric pressure and the inlet pressure can be made sufficiently low.

However, the circumferential flow compression pump stage has multiple stages because the compression ratio per single stage is small, and the positions of the inlet and discharge ports of each stage of the circumferential flow compression pump stage are generally shifted in the circumferential direction. Due to the circumferential pressure distribution of each stage, a unidirectional force acts on the rotor of the pump stage. As a result, the O-ring that acts as a damper deforms, causing the rotor to tilt and the clearance between the rotor and stator to become uneven in the circumferential direction, making it difficult to obtain the desired performance.In extreme cases, the rotor and stator may come into contact with each other. was there.

An object of the present invention is to provide a turbo vacuum pump that can maintain an appropriate clearance between a rotor and a stator.

[Means for Solving the Problems] In order to achieve the above object, the turbo vacuum pump of the present invention includes a centrifugal compression pump stage and a circumferential flow compression pump stage formed in a housing having an intake port and an exhaust port. a pump mechanism section that connects to the rotor of the pump stage, a rotary shaft that is connected to the rotor of the pump stage, a damper bearing that supports the rotary shaft, and an electric motor section that drives the rotor, and the gas sucked in from the suction port is discharged to the atmosphere from the exhaust port. In a turbo vacuum pump that can
The rotor bearing and the center of the stator were made eccentric.

[Effect]

According to the above technical means, in a turbo vacuum pump whose exhaust port has atmospheric pressure, the resultant force of forces generated by the circumferential pressure distribution of each stage of the circumferential flow compression pump acts on the rotor in one direction. As a result, the O-ring of the damper bearing is deformed (
Even if the rotor is tilted in one direction, the rotor axis and stator center are eccentric, so the clearance between the rotor and stator can be maintained uniform in the circumferential direction.

The second solution will be explained one after another. Turbo vacuum pumps must exceed several critical speeds before reaching their rated speed. Once the last critical speed has been exceeded, the control circuit applies a predetermined voltage to the piezoelectric actuator and distorts the piezoelectric actuator by a predetermined amount, which disables the O-ring of the damper bearing, preventing the rotor from tilting and preventing the rotor from tilting. Clearance between stators can be kept uniform in the circumferential direction.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a longitudinal sectional view of a turbo vacuum pump according to an embodiment of the present invention.

The turbo vacuum pump shown in FIG. 1 has a pump mechanism section that forms a pump flow path by a rotor and a stator, and an electric motor section that drives the rotor, in a housing 1 that has an intake port IA and an exhaust port IB.

More specifically, bearings 2a and 2b are provided within the housing 1.
The housing 1 includes a rotary shaft 3 rotatably supported via a rotary shaft 3, and a centrifugal compression pump stage 4 and a circumferential flow compression pump stage 5 arranged in sequence within the housing 1. The rotating shaft 3 is driven by a motor 6 connected thereto.

The centrifugal compression pump stage 4 has a plurality of retreating vanes on its surface,
Moreover, an open type impeller 4A related to the rotor attached to the rotating shaft 3, and blades attached in the housing 1 and facing inward with respect to the rotation direction on a surface facing the back surface of the impeller 4A. Fixed disk 4B related to a plurality of stators
It is constructed by arranging them alternately.

The circumferential flow compression pump stage 5 includes an impeller 5A that is attached to the rotating shaft 3 and is connected to a rotor having a plurality of blades radially provided on the outer circumferential surface, and an impeller 5A that is integrally formed on the inner surface of the housing 1, facing the impeller 5A. It consists of a shaped stator arranged. FIG. 2 is an axial view of a circumferential flow compression pump stage. As shown in FIG. 2, the stator of the circumferential flow compression pump stage 5 is provided with partitions 7 at two locations in the circumferential direction of the ventilation passage. A suction port 8 is provided at the front of the partition portion 7 in the rotational direction, and a discharge port 9 is provided at the rear in the rotational direction. The positions of the inlet and outlet ports of each stage are shifted from each other. For example, if you look at the fifth row,
The fourth stage discharge port and the fifth stage suction port are connected, the fifth stage discharge port and the sixth stage suction port are connected, and the final stage discharge port is the exhaust port IB.
is connected to

The rotating shaft 3 is supported by bearings 2a and 2b, and the bearing 2a is supported by the housing 1 via a bearing holder 10a and a ring lla that functions as a damper. The bearing 2b is supported by the motor case 12 via a bearing holder 10b and a ring llb that functions as a damper. The fine point of the rotating shaft and the center of the stator are eccentrically arranged.

Next, the operation of this embodiment will be explained. Gas sucked in from the intake port IA is sequentially compressed within a flow path formed by the centrifugal compression pump stage 4 and the circumferential flow compression pump stage 5, and is discharged to the atmosphere from the exhaust port IB. The circumferential flow compression pump stage receives a viscous flow ranging from atmospheric pressure to several Torr, and a unidirectional force acts on the rotor due to the circumferential pressure distribution of each stage. Therefore, the O-ring 11. which acts as a damper.
a is deformed and the rotor tilts in one direction, but since the precision of the rotating shaft to which the rotor is attached and the center of the stator are eccentric in the direction in which the rotor is tilted, the clearance between the rotor and stator is uniform in the circumferential direction. can be kept.

Next, other embodiments will be explained using FIGS. 3, 4, and 5. Figure 3 is an example, Figure 4 is an enlarged view of the main parts,
FIG. 5 is a signal system diagram. The overall configuration of this embodiment is essentially the same as that in FIG. However, the rotor axis and the stator center are aligned, and a piezoelectric actuator is provided on the outer periphery of the bearing holder 10a.

A turbo-type vacuum pump can obtain the desired performance by rotating the rotor at high speed, but it must exceed several critical speeds before reaching the rated rotational speed, and the outer periphery of the bearing holders 10a, 10b 0 ring l in the part
Vibration is prevented by using la and llb as dampers. When the last critical speed before reaching the rated rotational speed is exceeded, the voltage generator is controlled by the control circuit to generate a voltage sufficient to distort the piezoelectric actuator. As a result, the piezoelectric actuator is distorted, and the bearing holder 10a and the housing 1
is fixed via a piezoelectric actuator, the O-ring lla will not plow, and even if the force due to the circumferential pressure distribution of the circumferential flow compression pump stage acts on the rotor, the rotor will not tilt, and the rotor and Clearance between stators can be kept uniform in the circumferential direction.

〔Effect of the invention〕

According to the present invention, the clearance between the rotor and stator of the turbo vacuum pump can be maintained uniform, so that stable pump performance can be obtained.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of a turbo vacuum pump of the present invention, FIG. 2 is an axial view of a circumferential flow compression pump stage constituting the present invention, and FIG. FIG. 4 is a vertical cross-sectional view showing an enlarged main part of the present invention shown in FIG. 3, and FIG. 5 is a signal system diagram. 1... Housing, IA... Intake port, IB... Exhaust port, 2... Bearing, 3... Rotating shaft, 4... Centrifugal compression pump stage, 5... Circumferential flow compression Pump stage, 6...motor,...partition section. 1o... Bearing holder, 1...○ ring, 12... 2nd 3rd 4th

Claims (1)

[Scope of Claims] 1. A housing having an intake port and an exhaust port, and a rotating shaft to which the rotor is fastened to a pump mechanism section in which a pump flow path is formed by multi-stage rotors and stators within the housing; A turbo vacuum pump that includes a damper bearing that supports the rotating shaft and an electric motor that drives the rotor, and that discharges gas sucked in from the intake port to the atmosphere from the exhaust port, wherein the axial center of the rotor and the A turbo vacuum pump characterized by an eccentric center of the stator.