JP2000161284A - Turbo vacuum pump - Google Patents

Abstract

[Problem] To provide a centrifugal impeller 4A, a centrifugal stator 4B, and a vortex impeller 5 even when a rotor 1 is extended by heat generated by a pump section.
The relative positional relationship between A and the vortex stator 5B is properly maintained so that the exhaust pump can be reliably protected in the event of an abnormality. A thrust protection bearing (17) is provided adjacent to a final impeller (5AE) near an exhaust port (8), and the thrust of this bearing (17) is obtained from the outputs of thrust direction position detection sensors (19A, 19B) provided on both shaft sides of a rotor (1). The direction position is detected, and the thrust magnetic bearing 14 is controlled so that the position does not move. In this way, the position of the bearing 17 becomes the base point of the elongation by heat of the rotor and substantially coincides with the base point of the elongation of the stator 5B by heat, so that the relative positional relationship between the impeller and the stator can always be properly maintained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an exhaust port having an atmospheric pressure,
Also, the present invention relates to a turbo vacuum pump that is operated to have a pressure close to the atmospheric pressure, and particularly relates to a turbo vacuum pump using a magnetic bearing that levitates a rotor by a magnetic force of an electromagnet and holds the rotor in a non-contact manner.

[0002]

2. Description of the Related Art As a turbo vacuum pump which supports a rotor by a magnetic bearing and operates an exhaust port at or near atmospheric pressure, for example, a vacuum pump described in Japanese Patent Application Laid-Open No. 4-72497 is known. ing. This conventional vacuum pump is provided with a pump section including a Siegbahn pump element and a vortex type pump element in a pump housing having an intake port and an exhaust port, and the pump rotor has an overhang structure, a radial magnetic bearing and a thrust magnetic element. It is supported by bearings. A recess is provided in the upper part of the pump portion of the pump rotor, and a cap-shaped fitting body having a detection surface for detecting the position in the thrust direction is fitted in the recess, and a thrust gap sensor for controlling the electromagnet of the thrust magnetic bearing detects the position in the thrust direction. It is installed at a position facing the surface, and further has a thrust touchdown bearing that regulates the position in the thrust direction. The thrust magnetic bearing controls the gap in the thrust direction of the pump unit to be constant based on the detection result of the thrust gap sensor.

In Japanese Patent Application Laid-Open No. 6-101689, an exhaust pump section is provided in a housing having an intake port and an exhaust port, and an integral rotor of the exhaust pump section and the motor is supported at both ends by bearing means. A sealing means comprising a screw seal is disposed in the vicinity of the intake port on the side opposite to the exhaust pump section, and the diameter of the sealing means comprising the screw seal is made larger than at least the outer diameter of the last stage impeller of the exhaust pump section. A disclosed turbo vacuum pump is disclosed.

[0004]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Laid-Open No. 4-7 is disclosed.
In the vacuum pump described in Japanese Patent No. 2497, when the rotor rotates, the gas flowing from the intake port is compressed by the Siegbahn pump element and the vortex pump element and exhausted to the atmosphere from the exhaust port. Since the thrust gap sensor and thrust protection bearing are located at the top of the pump, the pump must be supported in a cantilevered overhang structure, and the center of gravity of the pump rotor is higher than the radial magnetic bearing. There is a possibility that the rotor cannot be stably supported against an external force. In addition, a thrust gap sensor,
There is a problem that the thrust protection bearing is provided in the gas flowing pump and cannot be used in a film forming apparatus such as an etching apparatus using a corrosive gas or a CVD apparatus.

On the other hand, in Japanese Patent Application Laid-Open No. 6-101689, radial magnetic bearings are provided on both sides of the rotor, so that the rotor becomes stable even at high speed rotation. Also, a screw seal is interposed between the exhaust pump section and the bearing chamber or the motor chamber so that the exhaust gas does not enter the bearing chamber containing the bearing means, the gap sensor, etc., and the purge gas from the bearing chamber side. Because of the flowing structure, even a device using a corrosive gas can be used without any problem.

In the case of a turbo vacuum pump provided with radial bearings on both sides of the rotor, a thrust magnetic bearing is provided at one end closer to the intake port, and performs positioning control in the thrust direction using the output of a thrust sensor near the intake port. ing.
However, this control method has the following problems. That is, in this turbo vacuum pump, when the motor rotates, the radial magnetic bearings at both ends of the rotor and the rotor supported by the thrust magnetic bearings at the shaft end rotate with respect to the housing, and the exhaust pump operates to perform the exhaust action. This is done by setting the exhaust port to atmospheric pressure and evacuating the intake port side. At this time, a large amount of heat is generated by the compression action of the pump unit. In particular, the calorific value of the last stage of the exhaust pump stage operated near the atmospheric pressure is large, and the calorific value decreases as it goes upstream, that is, as the vacuum becomes lower. This heat causes the rotor to thermally expand, but this size gradually increases from the intake port to the exhaust port,
It extends from the end on the intake side as a base point. However, since the stator is fixed to the housing near the exhaust port, the stator extends toward the intake port from the fixing position. For this reason, the displacement of the impeller attached to the rotor and the stator facing the impeller due to the thermal expansion is reversed, which impairs the operation of the pump. further,
In an extreme case, a situation may occur in which the stator and the rotor come into contact with each other.

An object of the present invention is to use a magnetic bearing in a turbo vacuum pump capable of evacuating from atmospheric pressure, and to maintain a proper relative positional relationship between a rotor and a stator even when the rotor is extended by heat generated in a pump section. It is an object of the present invention to provide a turbo vacuum pump capable of reliably protecting a rotor and a stator of a pump section in an abnormal situation.

[0008]

SUMMARY OF THE INVENTION According to the present invention, an exhaust pump section is formed by a rotor having a stator and a rotor rotatably supported in a housing having an intake port and an exhaust port. In a turbo vacuum pump for compressing gas sucked in from and exhausting it to the atmosphere from an exhaust port, both ends of an integral rotor comprising an exhaust pump section and a motor for driving the exhaust pump section are supported by radial magnetic bearings, and one end of the integral rotor A turbo vacuum pump is disclosed in which a thrust magnetic bearing is supported by a thrust magnetic bearing, and a thrust protection bearing is arranged adjacent to a final stage impeller of the exhaust pump section.

Further, according to the present invention, a position detecting sensor in the thrust direction is provided at each of both ends of the integral rotor.
Disclosed is a turbo vacuum pump characterized in that control means is provided for detecting a thrust direction position of the thrust protection bearing from two sensor outputs and controlling the thrust magnetic bearing so that the detected thrust direction position becomes constant. I do.

Further, the present invention discloses a turbo vacuum pump wherein the axial distance between the thrust protection bearings is smaller than the distance between the impeller and the stator.

Further, the present invention discloses a turbo vacuum pump wherein the thrust protection bearing is a sliding type or rolling type bearing.

Further, according to the present invention, the purge gas is introduced into the exhaust pump section and exhausted together with the exhausted gas, and the installation position of the thrust protection bearing is located on the purge gas passage adjacent to the last stage impeller. A turbo vacuum pump is disclosed.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing a configuration example of a turbo vacuum pump according to the present invention. In FIG. 1, a pump rotor 1 is accommodated in a housing 3 having an intake port 2, and the pump rotor 1 is provided with a multi-stage centrifugal impeller 4A and a multi-stage vortex impeller 5A. The return flow path of the centrifugal impeller 4A is provided with a centrifugal stator 4B, and together with the centrifugal impeller 4A, constitutes a centrifugal pump stage 4. A vortex stator 5B is provided opposite to the vortex impeller 5A, and forms a vortex pump stage 5 together with the vortex impeller 5A. The centrifugal pump stage 4 and the vortex pump stage 5 form an exhaust pump section. The vortex stator 5B is provided with a ventilation path 5C, and a cooling jacket 6 is provided on the outer periphery. The vortex stator 5B and the housing 3 have a base 7
It is fixed to. An exhaust port 8 is provided in the base 7 and is connected in series with a ventilation path 5C provided in the vortex stator 5B.

A bearing chamber 9A is provided below the base 7, that is, on the opposite side of the exhaust pump section, and accommodates a radial magnetic bearing 10A for supporting the pump rotor 1 and a motor 11 for driving the pump rotor 1. A sliding type radial protection bearing 12A is provided at the shaft end, and is housed in a bearing chamber 9A. Swirl pump stage 5 and motor 1
1, a screw seal 13 is provided. Also,
On the rotor shaft side opposite to the bearing room 9A, a bearing room 9 in which a radial magnetic bearing 10B and a thrust magnetic bearing 14 are housed.
B is fixed to the housing 3. A sliding type radial protective bearing 12B is provided between the radial magnetic bearing 10B and the thrust magnetic bearing 14. A screw seal 15 is provided between the centrifugal pump stage 4 and the radial magnetic bearing 10B.

FIG. 2 is an enlarged view of the structure in the vicinity of the final stage (the eighth stage from the suction port 2 side in FIG. 1) of the vortex impeller 5A, which is a feature of the present invention. That is, a protrusion 16 is provided on the back surface of the last stage 5AE of the overflow impeller 5A, and a sliding type thrust protection bearing 17 is provided.
It is attached to the vortex stator 5B, and is arranged between the rear surface of the final stage 5AE of the vortex impeller 5A and the projection 16.
The axial clearance of the thrust protection bearing 17, that is, the back surface of the final stage of the vortex impeller 5A, the protection bearing 17, and the projection 16
The gap between the rotor and the thrust protection bearing 17 is set smaller than the axial gap between the impellers 4A and 5A and the stators 4B and 5B at each stage of the exhaust pump section. Further, radial position detection sensors 18A, 18B and thrust direction position detection sensors 19A, 19B are provided near the two radial magnetic bearings 10A, 10B, but the latter is also provided at two places. This is a feature of the present invention.

Next, the operation of the pump shown in FIG. 1 will be described. When the pump rotor 1 is driven at a high speed by the motor 11, the gas flowing from the intake port 2 is sequentially compressed in the ventilation path formed by the centrifugal pump stage 4 and the vortex pump stage 5, and is discharged to the atmosphere from the exhaust port 8. . Swirling pump stage 5
Covers a viscous flow region from atmospheric pressure to several hundred Pa, and the centrifugal pump stage 4 operates in a molecular flow and an intermediate flow region. The gas flowing in from the inlet port 2 of the turbo vacuum pump and compressed in the centrifugal pump stage 4 flows from the uppermost inlet of the vortex pump stage 5 to the ventilation passage 5.
C, and flows into the uppermost blade of the swirl impeller 5A. Here, gas is obtained in the circumferential direction by the high-speed rotating blades, is discharged radially from the space between the blades by centrifugal force, decelerates in the ventilation passage 5C, recovers pressure, and draws a vortex again in the next stage. Between the wings. The gas thus introduced repeats the above operation several times while sequentially passing through the ventilation passage 5C from the suction port to the discharge port, and flows in a spiral screw form in the ventilation passage 5C to obtain sufficient energy from the vortex impeller 5A. The air is exhausted to the atmosphere from an exhaust port 8 connected in series with the final exhaust duct 8A. The internal pressure of the vortex pump stage 5 is such that the final stage outlet is at atmospheric pressure and the uppermost stage inlet is several hundred Pa. In the steady state of the pump, when no gas flows from the pump suction port 2 and a desired pressure is obtained in the vortex pump stage 5, the centrifugal impeller 4A acts as a rotating disk having a spiral groove, Acts as a drag pump that acts from to the outer diameter side. Further, the plurality of blades of the centrifugal stator 5B function as a fixed disk having a spiral groove, function as a drag pump that compresses from the outer diameter side to the inner diameter side, compresses gas, and forms a turbo vacuum pump. The ultimate pressure can be sufficiently reduced.

In the above-described pumping operation, heat is generated by compressing the gas flowing from the intake port 2 by the centrifugal pump stage 4 and the vortex pump stage 5. In particular, the calorific value near the last stage of the vortex pump stage 5, which covers a pressure range from atmospheric pressure to several hundred Pa, is large, and the calorific value decreases as it goes upstream, that is, becomes more vacuum. When the pump rotor 1 and the overflow stator 5B expand due to thermal expansion due to uneven heat generation along the axial direction, the conventional technique has the above-described problem. In order to cope with this problem, in the present invention, the position of the vicinity of the thrust protection bearing 17 arranged on the back surface of the last stage impeller 5AE of the vortex pump stage 5 is set as the reference point by the output of the thrust position detection sensors 19A and 19B. The thrust magnetic bearing 14 is controlled so as not to change.
That is, the thrust position detection sensors 19A and 19B are connected in series to detect the amount of displacement, and control the thrust magnetic bearing 14 so that the position of the back surface of the last stage of the vortex impeller 5A does not change according to the amount of displacement. Then, the rotor is levitated. This control and the radial position detection sensors 18A, 18
The detection of the movement amount of the middle point of the sensors 18A and 18B of the pump rotor 1 from the B output and the control of the radial magnetic bearings 10A and 10B based on the detected movement amount are performed by a controller (not shown). In this way, by controlling the reference point of the pump rotor 1 near the thrust protection bearing 17 so as not to move in the thrust direction, the pump rotor 1 extends from the reference point to both shaft ends. On the other hand, since the vortex stator 5B is fixed to the base, it extends toward the intake port 2 due to thermal expansion. That is,
Exhaust pump part impellers 4A, 5A and stators 4B, 5B
Extend in the same direction, the impellers 4A, 5A and the stator 4B,
The relative positional relationship of 5B can be appropriately maintained. Also,
Since the thrust protection bearing 17 is arranged at the reference point of the axial floating position, in the axial gap of the turbo vacuum pump,
The axial clearance of the narrowest thrust protection bearing 17 can be kept substantially constant.
A, 12B and 17 can reliably protect the pump section.

In the example of the configuration shown in FIG.
Although A, 12B and 17 are of the sliding type, these protective bearings may be rolling bearings. Rolling bearings have bearing clearances between the outer ring and the ball, and between the ball and the inner ring, and the protection bearing itself requires a clearance, which has the disadvantage that the axial clearance between the rotor and stator in the pump must be increased accordingly. There is a point. On the other hand, in the sliding type protection bearing, since there is no gap in the protection bearing itself, the gap between the impellers 4A, 5A of the pump unit and the stators 4B, 5B is made narrower than when a rolling type protection bearing is used. Pump performance can be improved. On the other hand, when the rolling bearing type is used, the gap of the pump section must be widened.
A, 10B, and 14, when the pump cannot be supported, the pump rotor 1 can be stopped smoothly and the life of the protective bearing can be prolonged. That is, there is an advantage that the maintenance cycle such as replacement of the protective bearing can be lengthened, and the advantage of the maintenance-free magnetic bearing can be further utilized.

In addition to the above-described configuration and operation characteristic of the present invention, the configuration example shown in FIG.
Similarly to the technique disclosed in JP-A-89-89, the pump rotor 1 is supported by magnetic bearings at both ends, and the center of gravity of the pump rotor 1 is located between the two radial magnetic bearings 10A and 10B. Therefore, the pump rotor 1 can be stably supported even during acceleration of the pump rotor 1, during transient operation, or when an external force such as an earthquake is applied, and the turbo vacuum pump can be safely operated. Similarly, magnetic bearings 10A, 10B and 14 supporting the pump rotor 1 and sensors 18A, 18B and 19 for detecting the position of the pump rotor.
A, 19B, electrical components such as a motor 11 for driving the pump rotor 1, and protective bearings 12A, 12B, 17 are accommodated in bearing chambers 9A, 9B on both shaft sides of the pump rotor 1, and an exhaust pump section and a bearing chamber 9A are provided. , 9B, non-contact screw seals 13, 15 are arranged. Therefore, components such as electrical components are not in the pump flow path through which the corrosive gas flows, and there is no problem such as corrosion. Further, by purging an inert gas such as nitrogen into the bearing chambers 9A and 9B in which the bearings are housed, the magnetic bearings 10A and 9A are removed from the corrosive gas.
10B, 14 sensors 18A, 18B, 19A, 19B,
The motor 11 and the protective bearings 12A, 12B, 17 can be reliably protected, and can be used in a film forming apparatus such as an etching apparatus and a CVD apparatus.

Further, as shown in FIG. 2, an exhaust duct 8A communicating with an exhaust port 8 is provided at a portion of the overflow stator 5B which faces the final stage 5AE of the overflow impeller 5A in the rotor radial direction. The purge gas sent from the bearing 9A is sent from the exhaust duct 8A to the exhaust port 8. Therefore,
Although the thrust protection bearing 17 is provided in the exhaust pump section, the thrust protection bearing 17 does not corrode due to the corrosive gas or the like discharged by the purge gas flowing as shown by the arrow P in FIG. However, FIG. 2 is a sectional view including the exhaust duct 8A.

In the turbo vacuum pump shown in FIG.
Although the pump is composed of two stages of centrifugal pumps and eight stages of vortex pumps, the pump performance varies depending on the number of rotations of the pump rotor and the number of pump stages, and is not limited to the illustrated one. The thrust magnetic bearing 14 is
Although it is housed in the bearing chamber 9B and arranged at the end of the rotor shaft,
It is not limited to what is shown. Furthermore, although a description has been given of the case where the centrifugal pump stage 4 and the vortex pump stage 5 are used as a combination of pump elements, a turbo vacuum pump may be used by combining turbo-type elements such as an axial flow stage and a screw groove stage. . Further, although the screw seals 13 and 15 are used for sealing the exhaust pump section and the bearing chambers 9A and 9B, the same effect can be obtained by a floating ring seal, a labyrinth seal, or a non-contact sealing means combining them.

[0022]

According to the present invention, the relative positional relationship between the rotor and the stator can be properly maintained even when the rotor is stretched by the heat generated in the pump section. A magnetic bearing type turbo vacuum pump that can be protected can be realized. Further, it is possible to obtain a turbo vacuum pump which has good controllability of a magnetic bearing and can be evacuated from the atmospheric pressure and can be used in a film forming apparatus such as an etching apparatus or a CVD apparatus using a corrosive gas.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a configuration example of a turbo vacuum pump according to the present invention.

FIG. 2 is an enlarged longitudinal sectional view showing a thrust protection bearing portion.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 pump rotor 2 intake port 3 housing 4 centrifugal pump stage 4A centrifugal impeller 4B centrifugal stator 5 vortex pump stage 5A vortex impeller 5B vortex stator 5C stator ventilation path 6 cooling jacket 7 base 8 exhaust port 9A, 9B bearing chamber 10A, 10B Radial magnetic bearing 11 Motor 12A, 12B Radial protection bearing 13 Exhaust port side screw seal 14 Thrust magnetic bearing 15 Inlet port side screw seal 16 Projection 17 Thrust protection bearing 18A, 18B Radial position detection sensor 19A, 19B Thrust position detection sensor

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masahiro Mase 603, Kandachi-cho, Tsuchiura-shi, Ibaraki Inside the Tsuchiura Plant, Hitachi, Ltd. (72) Inventor Shinji Otani 4-3-1 Yashiki, Narashino-shi, Chiba Seiko Seiki Stock Within the company (72) Inventor Yuichi Kinoshita 4-3-1 Yashiki, Narashino-shi, Chiba Seiko Seiki Co., Ltd. (72) Inventor Shinichi Nomura 4-3-1 Yashiki, Narashino-shi, Chiba Seiko Seiki Co., Ltd. F-term (reference) 3H022 AA01 BA06 CA12 CA13 CA15 CA16 CA20 DA01 DA08 DA09 DA14 DA16 3H031 DA01 DA04 DA05 EA00 EA01 EA05 EA09 EA12 EA15 FA11 FA13 FA16 FA33 FA36

Claims (4)

[Claims] An exhaust pump section is formed by a stator and an impeller rotatably supported in a housing having an intake port and an exhaust port, and the action of the exhaust pump section compresses and sucks gas sucked from the intake port. In a turbo vacuum pump that exhausts gas from the mouth to the atmosphere, both ends of an integrated rotor composed of an exhaust pump section and a motor that drives the exhaust pump section are supported by radial magnetic bearings, and one end of the integrated rotor is supported by a thrust magnetic bearing. And a thrust protection bearing is arranged adjacent to the last stage impeller of the exhaust pump section. 2. A thrust-direction position detection sensor is provided at each of both ends of the integrated rotor, and a thrust-direction position of the thrust protection bearing is detected from outputs of the two sensors, and the detected thrust-direction position is fixed. 2. The turbo vacuum pump according to claim 1, further comprising control means for controlling the thrust magnetic bearing so as to satisfy the following condition. 3. The turbo vacuum pump according to claim 1, wherein the thrust protection bearing is a sliding type or rolling type bearing. 4. A purge gas is introduced into the exhaust pump section and exhausted together with the exhausted gas, and the installation position of the thrust protection bearing is a position adjacent to the last stage impeller on a path of the purge gas. Claim 1 characterized by the following:
A turbo vacuum pump according to one of the claims 1-3.