JPH0264296A - Turbo-type vacuum pump - Google Patents

Abstract

PURPOSE:To stabilize the pump performance and facilitate assembling by arranging a centrifugal compression pump stage, a circumferential flow compression pump stage and an axial flow vane type circumferential compression pump stage from the suction port 21A side. CONSTITUTION:A centrifugal compression pump stage 24, a circumferential flow compression pump stage 25 and an axial flow vane type circumferential compression pump stage 27 are arranged in sequence in a housing 21 from the suction port 21A side to the discharge port 21B side. The circumferential flow compression pump stage 25 and the axial flow vane type circumferential compression pump stage 27 operated in a viscous flow are used in the proper pressure area. The pump performance can be thereby stabilized. When the same compression ratio as that of only the circumferential flow compression pump stage 25 is obtained in the viscous flow, the number of stages can be decreased, and the cost can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a vacuum pump whose exhaust port is at atmospheric pressure, and particularly to a turbo vacuum pump suitable for creating a clean vacuum.

[Conventional technology]

As a conventional turbo vacuum pump, JP-A-61-247
The one described in Publication No. 893 is known.

This conventional turbo-type vacuum pump consists of a housing having an intake port and an exhaust port, a rotary shaft rotatably supported within the housing via a bearing, and a shaft extending from the intake port side to the exhaust port side. It includes a centrifugal compression pump stage and a circumferential flow compression pump stage arranged in sequence. The rotating shaft is driven by a motor connected thereto.

[Problem to be solved by the invention]

In the above-mentioned prior art turbo vacuum pump, when the vacuum pump reaches a steady operating state, the centrifugal compression pump stage mainly works in molecular flow and intermediate flow, and the circumferential flow compression pump stage works in viscous flow. The mouth pressure can be maintained at atmospheric pressure and the inlet pressure can be made sufficiently low.

But for the centrifugal compression pump stage to work.

It is necessary to increase the compression ratio of the circumferential flow compression pump stage, and it is unavoidable to make one circumferential flow compression pump multistage, but considering the critical speed of the shaft system, the axial dimension cannot be increased, i.e. It is not possible to increase the number of stages very much,
Therefore, in order to increase the compression ratio per stage of one circumferential flow compression pump stage, efforts were made to improve the blade shape and narrow the gap between the impeller and the fixed disk. However, this has led to problems such as difficulty in managing the gap between the impeller and the fixed disk, requiring time to assemble and increasing costs, and making it difficult to stabilize performance.

An object of the present invention is to provide a device that can achieve a large compression ratio in a viscous flow, provide stable performance, reduce the number of stages, and facilitate assembly.

[Means to solve the problem]

The above purpose is to install an axial vane-shaped circumferential flow compression pump stage with a large cut-off compression ratio on the high pressure side of the viscous flow on the exhaust port side in a turbo vacuum pump that can exhaust air directly from the exhaust port to the atmosphere. This is achieved by arranging a circumferential flow compression pump stage with the maximum cut-off compression ratio on the low pressure side of the flow, and sequentially arranging centrifugal compression pump stages that can obtain a large compression ratio in the molecular flow and intermediate flow. Ru.

[Effect]

The turbo-type vacuum pump of the present invention has an axial airfoil type same-circumferential pressure line pump stage that can obtain a large compression ratio from atmospheric pressure up to 30 Torr (about 30 Torr) near the floating pressure port, and a circular airfoil type pump stage that has a large compression ratio at lower pressures. By combining circumferential flow compression pump stages, the inlet pressure of the circumferential flow compression pump stage can be reduced to several T with fewer stages than before.
orr or less, and the pressure at the pump inlet can be brought to a sufficiently low pressure by the action of the centrifugal compression pump stage.

(Example〕 Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows an embodiment of the turbo vacuum pump of the present invention. In FIG. 1, this vacuum pump includes a housing 21 having an intake port 21A and an exhaust port 21B, and a bearing 22 inside the housing. A centrifugal compression pump stage 249, a circumferential flow compression pump stage 25, and a shaft are sequentially disposed within the housing 21 between the intake port 21A side and the exhaust port 21B side. A vane-shaped circumferential compression pump stage 27 is provided. The rotating shaft 23 is driven by a motor 26 connected thereto. The centrifugal compression pump stage 24, as shown in FIGS. 2 and 3,
An open impeller 24A having a plurality of retreating blades 28 on its surface and attached to the rotating shaft 23, and an open impeller 24A attached to the housing 21 as shown in FIGS. 2 and 4, and a back surface of the impeller 24A. A fixed disk 24B having a plurality of blades 29 provided on the opposite surface thereof are arranged alternately in series. As shown in FIGS. 5 and 6, the circumferential flow compression pump stage 25 is attached to the rotating shaft 23, and is attached to the housing 21 and an impeller 25A having a plurality of blades 30 radially provided on the outer circumferential surface. .

Further, fixed disks 25B having U-shaped grooves 31 on the surfaces facing the impeller 25A are arranged alternately to form a ventilation passage 32.

The axial airfoil circumferential compression pump stage 27 is shown in FIGS.
As shown in the figure, an impeller 27A is attached to a rotating shaft 23 and has a plurality of arc-shaped blades 32 that are concave with respect to the rotation direction on the outer periphery of the cylindrical impeller 27A, and the blades 3
Closely on the entire circumference of 2.

A ring-shaped core 33 is attached and the impeller 27
A fixed disk 27 having a groove 34 surrounding the blade 32 of A
B are arranged alternately.

Next, the operation of the embodiment of the present invention described above will be explained.

In a transient state at the beginning of pump operation, the entire inside of the pump is under pressure close to atmospheric pressure and the gas flow becomes a viscous flow, so that the centrifugal compression pump stage 24 acts as a centrifugal compressor. That is, the impeller 24A of the centrifugal compression pump stage 24
works as a compressor impeller, 1 impeller 24A and fixed disc 2
The flow path formed by being sandwiched between the blades 29 and 4B is
When the vacuum pump is in steady operation, it acts as a return channel that guides the flow from the outer diameter side to the inner diameter side.

Since the gas is sufficiently compressed by the centrifugal compression pump stage 24,
A circumferential flow compression pump stage 25 downstream of the centrifugal compression pump stage 24. The volumetric flow rate of the gas flowing into the axial vane-shaped circumferential compression pump stage 27 is almost zero, and the matching of feeding it into the circumferential compression pump stage with a large cut-off compression ratio is very successful. The gas flowing into the circumferential flow compression pump stage 25 receives centrifugal force from the impeller 25A and flows from dimming to dimming to the fixed disc 25B. U-shaped groove 3
1. The gas that has flowed out into the U-shaped groove 31 of the fixed disk 25B flows through the ventilation passage 32 along the groove 31 due to the self-velocity component in one circumference, flows into the impeller 25A again along the groove 31, and repeats the same movement.

By repeatedly going in and out of the impeller 25A,
Obtaining a large pressure rise, the axial airfoil circumferential flow compression pump stage 2
7. The gas flowing into the axial airfoil circumferential compression pump stage 27 receives energy from the single impeller 27A and flows along the core 33 from the blades 32 of the impeller 27A to the groove 34 of the fixed disk 27B. The gas molecules that have flowed into the grooves 34 of the fixed disk 27B are caused to move toward the fixed disk 27B due to the circumferential velocity component.
While moving in the circumferential direction through the grooves 34, the gas molecules rotate around the core 33 and return to the blades 32 of the impeller 27A, repeating the same movement, and while flowing through the grooves 34, the gas molecules draw a whirlpool and move over and over again. The pump of this embodiment is a circumferential flow compression pump that operates in a viscous flow, which moves in and out of the blades 32 of the impeller 27A and the grooves 34 of the fixed disc 27B, obtains a large pressure rise, and is discharged from the exhaust port. Stages and axial airfoil circumferential flow compression pump stages can be used in the appropriate pressure range and the pump performance can be stabilized. Also, in a viscous flow, to obtain the same compression ratio as with only the circumferential flow compression pump stage,
The number of stages can be reduced and costs can be lowered.

〔Effect of the invention〕

According to the present invention, by optimizing the pressure range of the viscous flow pump element, the compression ratio per stage of the viscous flow pump element can be made larger than that of the conventional type.

Stable pump performance can be obtained. Furthermore, when obtaining the same compression ratio, the number of stages can be reduced, making assembly easier and reducing costs.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an embodiment of the turbo vacuum pump of the present invention, FIG. 2 is an enlarged sectional view of a part of the centrifugal compression pump stage constituting the present invention, and FIG. 4 is a plan view of its fixed disk, FIG. 5 is a sectional view of the circumferential flow compression pump stage of the present invention, and FIG. 6 is a circular FIG. 7 is a plan view of the impeller of the circumferential flow compression pump stage, FIG. 7 is a sectional view of the axial airfoil type circumferential flow compression pump stage constituting the present invention, and FIG. 8 is a plan view of the axial airfoil type circumferential flow compression pump stage. It is a front view of an impeller. 21...Housing, 21A...Intake port, 21B.
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Claims (1)

[Claims] 1. A housing having an intake port and an exhaust port, a rotating shaft rotatably supported within the housing, a plurality of fixed bodies attached to the inner wall of the housing, and a plurality of rotating bodies attached to the rotating shaft. In a turbo vacuum pump, the pump stage is configured by alternately combining the fixed body and the rotary body, and the gas sucked from the intake port can be discharged directly to the atmosphere from the exhaust port, wherein the intake port A turbo vacuum pump characterized by having a centrifugal compression pump stage, a circumferential flow compression pump stage, and an axial vane-shaped circumferential flow compression pump stage arranged from the side.