JPH10318182A - Dry turbo vacuum pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize a gas flow in a pump and improve exhaust efficiency of the pump, by forming a partition forward in the direction of rotation of a suction hole of a circular flow pump top step, when the gas sucked from a pump suction hole is compressed and exhausted through an exhaust hole to or near the atmospheric pressure condition. SOLUTION: In starting of a pump or in a transient condition that a large amount of gas flows from a pump intake hole 4A, a centrifugal pump step 3 acts as a centrifugal compressor because the pressure of the pump intake hole 4A becomes higher. A flow path between a centrifugal blade 3A and a blade placed on a centrifugal stator 3B acts as a return channel. The entered gas is compressed at the centrifugal pump step 3, and flows to a space between the centrifugal stator 3B and a centrifugal pump step 3 circumferentially and uniformly. By forming a partition 14 in the direction of rotation of a suction hole of the circular flow pump to step in a space 13 between the centrifugal pump step 3 and the circular flow step 2, the gas can flow uniformly in the direction of rotation of a pump rotor 1 in the space 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an exhaust port at atmospheric pressure,
Also, the present invention relates to a dry turbo vacuum pump which is operated near the atmospheric pressure, and more particularly to a dry turbo vacuum pump suitable for producing a clean vacuum, which is used in a manufacturing apparatus for semiconductors, foods, chemicals and the like.

[0002]

2. Description of the Related Art As a turbo-type vacuum pump in which the pressure at an exhaust port is set to atmospheric pressure, for example, the one described in Japanese Patent Application Laid-Open No. 8-86298 is known.

[0003] In this conventional dry turbo vacuum pump, a rotary shaft rotatably supported via bearings in a housing having an intake port and an exhaust port, and a housing between the intake port and the exhaust port are sequentially arranged. It has an arranged centrifugal pump stage and a circumferential flow pump stage. The rotating shaft is driven by a high frequency motor mounted on the shaft.

The centrifugal pump stage has an open type impeller having a plurality of retreating blades on a surface thereof and attached to a rotating shaft, and has an inwardly facing rotation direction on a surface facing the back surface of the impeller. A centrifugal stator having a plurality of blades is alternately combined.

The circumferential-flow pump stage is mounted on a rotating shaft, is fixed to a circumferential-flow impeller having a plurality of blades radially provided on an outer periphery thereof, and an inner wall of a housing, and faces the circumferential-flow impeller. A circumferential flow stator having a ventilation path on the surface is alternately combined.

[0006] The circumferential flow stator is opposed to the circumferential flow impeller with a small gap, and a partition is provided at one location in the circumferential direction of the ventilation passage. A suction port is provided at the front of the partition portion in the rotation direction of the circumferential flow impeller, and a discharge port is provided at the rear of the partition in the rotation direction.
The positions of the inlet and outlet of each stage are different for each stage, and the inlet is connected in series with the outlet of the preceding stage.

The turbo vacuum pump configured as described above rotates at a high speed by a special high-frequency input to a high-frequency motor, and the gas flowing from the suction port of the dry turbo vacuum pump is compressed by the centrifugal pump stage and the circumferential flow pump stage. Exhausted under atmospheric pressure.

[0008]

In the prior art dry turbo vacuum pump described in Japanese Patent Application Laid-Open No. H8-86298, the entire interior of the pump is at atmospheric pressure in an excessive state when the vacuum pump is started. The centrifugal pump stage acts as a centrifugal compressor because it is under close pressure and the gas flow is viscous. That is, the centrifugal impeller functions as a compressor impeller, and a flow path formed between the centrifugal impeller and the blade provided on the centrifugal stator serves as a return channel for guiding the flow from the outer diameter side to the inner diameter side. work. When the vacuum pump reaches a steady state and the pressure at the suction port of the circumferential flow pump stage becomes low and becomes an intermediate flow of several hundred Pa or less, the centrifugal pump stage acts as a drag pump. , And the pressure at the intake port can be made sufficiently low.

However, the above-mentioned prior art does not take into consideration the gas flow at the junction between the centrifugal pump stage and the circumferential flow pump stage. In this state, the gas flowing out of the centrifugal stator flows almost uniformly in the circumferential direction into the space between the centrifugal pump stage and the circumferential pump stage at a certain outflow angle. However, since there is one suction port in the circumferential flow pump stage, gas flows in a direction different from the outflow angle of the gas in front of the rotation direction of the suction port. For this reason, in the vicinity of the uppermost suction port of the circumferential flow pump, there is a problem that the gas flow is turbulent and cannot efficiently flow into the circumferential flow pump stage, and the pump performance cannot be sufficiently exhibited in an excessive state. Was.

[0010] It is an object of the present invention to form a stable gas flow inside a dry turbo vacuum pump even when the dry turbo vacuum pump is started or when it is operated in an excessive state where a large amount of flow is flowing. An object of the present invention is to provide a dry turbo vacuum pump capable of smoothly flowing gas into a stage and improving the pumping efficiency of the pump.

[0011]

In order to achieve the above object, a rotary shaft rotatably supported in a housing having an intake port and an exhaust port, and a multistage circumferential flow impeller supported by the rotary shaft. And a stator forming a multi-stage circumferential flow pump together with a circumferential flow impeller in the housing, and a centrifugal pump stage is disposed on the suction side of the circumferential flow pump stage, and suction is performed from a pump suction port. In a dry turbo vacuum pump that compresses gas and exhausts gas from the exhaust port to atmospheric pressure or near atmospheric pressure, in the rotational direction forward of the suction port at the top of the circumferential flow pump,
This is one in which a partition portion is formed.

In the dry turbo vacuum pump configured as described above, in the steady state of the pump, when gas does not flow from the pump inlet and the pressure at the uppermost inlet of the circumferential flow pump becomes several hundred Pa or less, The centrifugal pump stage acts as a drag pump. That is, the centrifugal impeller acts as a rotating disk having a spiral groove, and acts as a drag pump acting from the inner diameter side to the outer diameter side. In addition, the blades of the centrifugal stator act as a fixed disk with spiral grooves and act as a drag pump that compresses from the outer diameter side to the inner diameter side. ,
The pressure at the inlet can be made sufficiently low. At this time, almost no gas flows at the connection between the centrifugal pump stage and the circumferential flow pump stage because there is no gas flowing from the pump suction port.

Further, when the pump is started or in an excessive state where a large amount of flow is flowing from the pump suction port, the gas flow becomes a viscous flow, and the centrifugal pump stage acts as a centrifugal compressor. The centrifugal impeller functions as a compressor impeller, and a flow path formed between the centrifugal impeller and the blade provided on the centrifugal stator functions as a return channel for guiding a flow from an outer diameter side to an inner diameter side. The gas flowing in from the pump inlet is compressed by the centrifugal pump stage and flows out of the centrifugal stator into the space between the centrifugal pump stage and the circumferential pump stage at a uniform outflow angle in the circumferential direction. And since the partition part is formed in the rotation direction front of the suction port of the uppermost stage of the circumferential flow pump, it flows uniformly in the rotation direction in the space between the centrifugal pump stage and the circumferential flow pump stage, and smoothly flows in a circle. It can flow into a circumferential pump stage.

Therefore, even when the dry turbo vacuum pump is started or is operated in an excessive state in which a large amount of flow is flowing, a stable gas flow is maintained in the space between the centrifugal pump stage and the circumferential flow pump stage. Is formed, and the gas can smoothly flow into the circumferential flow pump stage, so that the exhaust efficiency can be improved.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing an entire structure of an embodiment of a dry turbo vacuum pump to which the present invention is applied. In this dry turbo vacuum pump, an intermediate portion and a lower end portion of the shaft 6 are supported by bearings 7A and 7B.
The high-frequency motor rotor 8A is press-fitted between B. On the upper side of the shaft 6, a multi-stage circumferential flow impeller 2A and a centrifugal impeller 3
A and the pump rotor 1 constituted by A are press-fitted and sintered. The centrifugal impeller 3A and the centrifugal stator 3B constitute a centrifugal pump stage 3, and the circumferential impeller 2A and the circumferential flow stator 2B constitute a circumferential pump stage 2. A cover 5 having an intake port 4A is mounted on the upper part of the centrifugal impeller 3A with security.

As shown in FIGS. 2 and 3, the circumferential flow impeller 2
A is provided with a plurality of blades 9. The circumferential flow stator 2B faces the circumferential flow impeller 2A with a small gap,
And a ventilation passage 10 surrounding the impeller 9 of the circumferential impeller 2A.
And a dam portion 11 is provided at one location in the circumferential direction. The suction port 1 is located in front of the damming portion 11 in the rotation direction.
A discharge port 12B is provided behind 2A in the rotation direction. The positions of the inlet 12A and the outlet 12B of each stage are different for each stage, and the inlet 12A is connected in series with the outlet 12B of the preceding stage. The final stage outlet 12B is connected to the pump outlet 4B.

A space 13 is formed between the centrifugal pump stage 3 and the circumferential pump stage 2 to allow the gas compressed by the centrifugal pump stage 3 to flow into the circumferential pump stage 2. As shown in (1), a partition portion 14 is provided in the rotation direction front of the suction port 12A at the uppermost stage of the circumferential flow pump.

Next, the operation of the above-described embodiment will be described.

When the dry turbo vacuum pump is in a steady state operation, the high-speed rotation of the pump rotor 1 by the high-frequency motor 8 causes the gas flowing in from the intake port 4A to flow.
The air is sequentially compressed in the ventilation path formed by the centrifugal pump stage 3 and the circumferential pump stage 2 and is discharged to the atmosphere from the exhaust port 4B. The circumferential pump stage 2 serves a viscous flow region from atmospheric pressure to several hundred Pa, and the centrifugal pump stage 3 operates in a molecular flow and intermediate flow region. The gas flowing from the inlet 4A of the dry turbo vacuum pump and compressed by the centrifugal pump stage 3 enters the ventilation passage 10 from the uppermost inlet 12A of the circumferential flow pump stage 2,
When the gas flows into the blade 9 of the circumferential flow impeller 2A, gas is obtained in the circumferential direction by the blade 9 rotating at a high speed, and is discharged in the radial direction from between the blades 9 by centrifugal force, and decelerated in the ventilation passage 10. After the pressure is recovered, the air enters the space between the blades 9 again by swirling. The gas flowing in from the suction port 12A repeats the above operation several times while passing through the ventilation path 10 from the suction port 12A to the discharge port 12B, flows in the ventilation path 10 in a spiral screw shape, and flows in the circumferential flow impeller 2A. From the exhaust port 4B directly connected to the final-stage exhaust port 12B. The internal pressure of the circumferential pump stage 2 is such that the final stage outlet 12B is at atmospheric pressure and the uppermost stage inlet 12A is several hundred Pa.

In the steady state of the pump, when no gas flows from the pump suction port 4A and a desired pressure is obtained in the circumferential pump stage 2, the centrifugal impeller 3A becomes a rotating disk having a spiral groove. Acts as a drag pump acting from the inner diameter side to the outer diameter side. Further, the plurality of blades 15 of the centrifugal stator 3B act as a fixed disk having a spiral groove, act as a drag pump that compresses from the outer diameter side to the inner diameter side, compress gas, and perform a dry turbo vacuum pump. Can be sufficiently reduced. At this time, in the space 13 at the connection between the centrifugal pump stage 3 and the circumferential pump stage 2, there is no gas flowing from the pump inlet 4A, so that almost no gas flows.

Further, when the pump is started or in an excessive state in which a large amount of gas is flowing from the pump suction port 4A, the pressure of the pump suction port 4A increases, and the gas flow becomes a viscous flow area. 3 acts as a centrifugal compressor. The centrifugal impeller 3A functions as a compressor impeller, and a flow path formed between the centrifugal impeller 3A and the blade provided on the centrifugal stator 3B forms a return channel for guiding the flow from the outer diameter side to the inner diameter side. Work as Pump inlet 4A
Is compressed in the centrifugal pump stage 3 and flows out of the centrifugal stator 3B into the space 13 between the centrifugal pump stage 3 and the circumferential flow pump stage 2 in the circumferential direction substantially uniformly at a certain outflow angle.

A partition 14 is formed in the space 13 between the centrifugal pump stage 3 and the circumferential pump stage 2 in the rotational direction forward of the uppermost suction port 12A of the circumferential pump as shown in FIG. Therefore, the gas compressed in the centrifugal pump stage 3 flows smoothly in the space 13 between the centrifugal pump stage 3 and the circumferential flow pump stage 2 in the rotation direction of the pump rotor 1. It can flow into stage 2. For this reason, it is possible to improve the pump exhaust efficiency in the excessive pump state.

FIG. 5 shows another embodiment of the present invention.
The upper part of the circumferential flow pump is divided at the front in the rotation direction of the suction port 12A, and the outer radius of the partition part is reduced in the rotation direction. With this configuration, the space 1 between the centrifugal pump stage 3 and the circumferential pump stage 2
The area of 3 increases in the rotational direction from the front in the rotational direction of the suction port 12A at the uppermost stage of the circumferential flow pump, and a volute flow path is formed so that the flow can be rectified.

FIG. 5 shows a centrifugal pump stage 3 and a circumferential pump stage 2
The area of the space 13 is enlarged in the radial direction, but as shown in FIG. 6, the outer radius of the partition portion is kept as it is, and the height of the partition portion is reduced in the rotation direction, and The same effect can be obtained by increasing the area in the direction. In the figure,
Although the height of the partition portion is reduced in the rotational direction from the tip of the blade 15, the height of the partition portion may be smaller than the root of the blade 15.

FIG. 7 shows another embodiment of the present invention.
The front of the suction port 12A at the top of the circumferential flow pump in the rotational direction is partitioned, and the area of the space 13 between the centrifugal pump stage 3 and the circumferential pump stage 2 is increased by the area of the suction port 12A at the top of the circumferential flow pump.
A is widened from the rear in the rotation direction of A to the suction port 12A side. With such a shape, the gas compressed in the centrifugal pump stage 3 can flow into the circumferential pump stage 2 smoothly. For this reason, it is possible to improve the pump exhaust efficiency in the excessive pump state.

Therefore, even when the dry turbo vacuum pump is started or is operated in an excessive state where a large amount of flow is flowing, the dry turbo vacuum pump is stable in the space 13 between the centrifugal pump stage 3 and the circumferential flow pump stage 2. Since a gas flow is formed and the gas can flow smoothly into the circumferential pump stage 2, the exhaust efficiency can be improved.

[0028]

As described above, according to the dry turbo vacuum pump of the present invention, a stable gas flow is formed at the junction between the centrifugal pump stage and the circumferential flow pump stage. The compressed gas is allowed to smoothly flow into the vortex pump stage, thereby improving the pumping efficiency of the pump.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of a dry turbo vacuum pump showing one embodiment of the present invention.

FIG. 2 is a vertical sectional view of a partition between a centrifugal pump stage and a circumferential flow pump stage according to an embodiment of the present invention.

FIG. 3 is a plan view of the circumferential flow pump stage shown in FIG.

FIG. 4 is a plan view of the circumferential flow pump stage shown in FIG.

FIG. 5 is a plan view of a partition between a centrifugal pump stage and a circumferential flow pump stage according to another embodiment of the present invention.

FIG. 6 is a view of the partition between the centrifugal pump stage and the circumferential pump stage according to another embodiment of the present invention, as viewed from the axial center.

FIG. 7 is a view from the axial center of a partition between a centrifugal pump stage and a circumferential pump stage according to another embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Pump rotor, 2 ... Circular flow pump stage, 2A ... Circular flow impeller, 2B ... Circular flow stator, 3 ... Centrifugal pump stage, 3
A: centrifugal impeller, 3B: centrifugal stator, 4A: intake port,
4B: exhaust port, 5: cover, 6: shaft, 7A, 7B: bearing, 8: high frequency motor, 8A: high frequency motor rotor, 9
... Vane, 10 ... Ventilation path, 11 ... Damper, 12A ... Inlet, 12B ... Outlet, 13 ... Space between centrifugal pump stage 3 and circumferential pump stage 2, 14 ... Partition, 15 ... Centrifugal stator Feather.

Claims (1)

[Claims] In a housing having an intake port and an exhaust port,
A rotary shaft rotatably supported, a multi-stage circumferential flow impeller supported by the rotary shaft, and a stator forming a multi-stage circumferential flow pump stage together with the circumferential flow impeller in the housing. In the dry turbo vacuum pump, a centrifugal pump stage is arranged on the suction port side of the circumferential flow pump stage, and compresses gas sucked from the suction port and exhausts the gas to or near atmospheric pressure from an exhaust port. A dry turbo vacuum pump characterized in that a partition section is provided in the rotation direction forward of the uppermost suction port of the circumferential flow pump.