JPS60252197A - Vacuum pump - Google Patents

Abstract

PURPOSE:To reduce the power required for a vacuum pump by employing a volute compression pump achievable of the compression ratio with relatively small diameter as the pump stage at the atmospheric pressure side while arranging an ejector of low heat production at the pre-stage thereby reducing the number of stages of a centrifugal pump and suppressing heat production. CONSTITUTION:Upon starting of drive motor 10 to start respective pump thus to inject the driving gas through a nozzle 51 and to operate an ejector 50 having relatively high compression ratio and low heat production, the gas in a chamber to be evacuated will enter through a suction port 2 then compressed by means of a siegbahn pump 20 and fed to a centrifugal pump 30 where the number of stage is reduced through the ejector 50. The gas is further compressed and fed through an intermediate delivery port 4 to the negative pressure generating section 51 of the ejector 50 where the gas compressed through the prestage pump is sucked and fed to the final stage volute compression pump 40 having shorter dimater of rotor than the pre-stage pump. With such arrangement, the number of stage of the centrifugal compression pump 30 is reduced to suppress heat production in this pump stage resulting in reduction of power required for the vacuum pump.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] This invention is a vacuum pump whose exhaust port is at atmospheric pressure, for example, a system for creating a clean vacuum by excluding air from a closed chamber in semiconductor manufacturing equipment, electron microscopes, etc. This invention relates to a vacuum pump suitable for discharging air.

[Background of the invention]

As an example of this type of vacuum pump, JP-A-51-381
There is one disclosed in Publication No. 13.

This vacuum pump has an axial flow turbo-molecular pump all arranged in the first stage, followed by an additional molecular pump, a centrifugal compression pump, and a vortex compression pump, which are successively installed in the housing from the intake port to the exhaust port. It has a similar structure.

In the vacuum pump mentioned above, the largest disk friction loss occurs in the vortex compression pump stage located on the exhaust port side near atmospheric pressure, but the same occurs in the centrifugal compression pump located before the vortex compression pump. do. This loss is proportional to the fifth power of the radius of the impellers of both pumps, and is also proportional to the density of the gas.

Therefore, the present applicant first proposed a vacuum pump in which the diameter of the impeller of a vortex-type compression pump was reduced by 1" in order to reduce the disc friction loss in this part.

(Japanese Patent Application No. 58-224157), this vacuum pump consists of an impeller having a large number of blades on the entire outer peripheral surface of the vortex type compression pump stage, and a fixed disk surrounding the impeller. The diameter is smaller than that of the impeller of the preceding centrifugal compression pump, and a ventilation path is formed by the impeller and the fixed disc. In this vacuum pump, the disc friction loss generated in the final stage pump can be reduced to a large extent, but it is necessary to reduce the disc friction loss in the centrifugal compression pump in the previous stage of the pump, especially the centrifugal It is not possible to suppress heat generation in the impeller located downstream of the compressor pump. Therefore, in order to further reduce the required power of the pump and increase the energy saving effect, measures have been desired to reduce the disk friction loss in the centrifugal compression pump stage.

[Object of the Invention] An object of the present invention is to completely reduce disk friction loss in a centrifugal compression pump stage without impairing pump performance in a vacuum pump whose discharge outlet pressure is near atmospheric pressure.

[Summary of the invention]

The vacuum pump of the present invention has an intermediate discharge port and an intermediate suction port between the suction port and the discharge port, and a Siegbahn pump, a centrifugal compression pump, and an intermediate suction port between the suction port and the intermediate discharge port. Centrifugal compression pumps and vortex-type compression pumps are sequentially arranged between the exhaust port and the ejector, each having a rotor with a diameter smaller than that of the preceding pump. It is fully connected to the compression pump.

According to the above configuration, all the pump stages on the atmospheric pressure side, which account for most of the power loss, are vortex type compression pumps with a relatively small diameter and a good compression ratio. By arranging all the ejectors, the number of stages of the centrifugal compression pump can be reduced, heat generation in the pump stages can be suppressed as much as possible, and the power required for the vacuum pump can be reduced.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, the casing 1 forming the main body support frame includes:
Gas that should be exhausted? A suction port 2 for sucking in the gas and an exhaust port 3 for discharging the gas are provided, and an intermediate discharge port 4 and an intermediate suction port 5 are formed between the suction port 2 and the exhaust port 3. A drive motor 10 is mounted outside the casing opposite to the suction port 2, and the rotation shaft 1 of the drive motor 10 extends toward the suction port 2.

The rotors of a Siegbahn pump 20, a centrifugal compression pump 30, and a vortex compression pump 40 are sequentially attached to this rotating shaft (from a position close to the suction port 2). Stakes are fixed opposite to each other.In other words, between the suction port 2 and the intermediate valve rotor 21 and the intermediate discharge shaft 1, the rotary shaft 1 is adjacent to the suction port 2. Adjacent to the outlet 4, a centrifugal FiE compression pump rotor 31 is fixed by a nut 6, and a Siegbahn bomb stator 22 having a spiral groove and a centrifugal compression pump stator 32 are mounted on the rounded casing 1. A device is fixed at a fixed interval from each rotor.In this way, a Siegbahn pump 20 and a centrifugal compression pump 22 are connected to the outside and inside of the casing between the suction port 2 and the intermediate discharge port 4. The gas is sucked in from the Siegbahn pump 20 at the first stage, passes through the subsequent centrifugal compression pump 30, and is discharged from the intermediate discharge port 4.A rotor 41 is installed between the intermediate suction port 5 and the exhaust port 3. A vortex compression pump 40 is mounted on the rotating shaft 11 and fixed in the housing 1 with a stator 42 spaced apart from the rotor 41 at a constant distance. An ejector 50 is provided whose discharge side is connected to the suction side and the intermediate suction port 5.This ejector 50 includes a negative pressure generating section 52 provided with a nozzle x51, and a diffuser communicating with the discharge port of the negative pressure generating section. 55. High-pressure driving gas sent from a high-pressure gas supply source (not shown) is injected from the nozzle 51 into the negative pressure generating section 52 through the supply port 53, and the negative pressure generated at this time is The gas compressed by the pre-stage pump is sucked through the intermediate discharge port 4, and is sent to the diffuser 5 together with the driving gas.
Send to 5. The diffuser 55 is used for the hole gas at the intermediate suction port 5.
It is sent to the vortex compression pump 40 through the .

Next, the operation of the above embodiment will be explained.

When the drive motor 1 (l) is started, each pump is started, and the drive gas is injected from all nozzles 51 to operate the ejector 50, the gas in the vacuum chamber enters the suction port 2 and flows through the Siegbahn pump 20. The gas is compressed by the action of the stator 22 with swirl grooves and the rotor 21, and is transferred to the next stage centrifugal compression pump 30.Then, the gas is further compressed by the rotor 31 and stator 32 of the centrifugal compression pump, and the gas is It is sent to the negative pressure generating section 51 of the ejector 50 via the discharge port 4.

Here, all of the gas compressed by the pre-stage pump is sucked by the negative pressure generated by the driving gas injected from the nozzle 51, and is sent to the final-stage vortex type compression pump 40 via the diffuser 55. Note that the ejector 50 has the characteristics that it can have a relatively high compression ratio, and that it generates a small amount of heat because it has no rotating parts. For example, while the compression ratio in each stage of a centrifugal compression pump is approximately 1.5, the compression ratio in the ejector can be approximately 5. Therefore, several stages of a centrifugal compression pump can be replaced by the ejector.

The gas sent from the ejector 50 to the vortex compression pump via the intermediate suction port 5 is compressed to approximately atmospheric pressure and is discharged to the atmosphere from the exhaust port 3.

In this way, the rotor diameter of the vortex compression pump is made smaller by /j% than the rotor diameter of the preceding pump, and at the same time, heat generation due to disc friction in this area is suppressed as much as possible, and at the same time, part of the compression in the centrifugal compression pump stage is By having all the ejectors share the load, the number of stages in the centrifugal compression pump can be completely eliminated, and the disc friction in the pump can be reduced.

In the embodiment described above, the driving gas for the ejector 50 is supplied from the outside, but as shown in FIG. It is operated by a vortex compression pump 60 configured with a stator 62 provided at intervals, and connected to a supply pipe 6.
Alternatively, the liquid may be supplied from the supply port 53 of the ejector 50 via the ejector 3 .

64 is an intake port, and 65 is an exhaust port.

〔Effect of the invention〕

As described above, according to the present invention, disc friction loss can be reduced without impairing pump performance, and in particular, the required power can be further reduced compared to that of the prior application.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view showing one embodiment of the vacuum pump of the present invention, and FIG. 2 is a longitudinal sectional view of another embodiment. 20...Siegbahn pump, 3o...centrifugal expansion compressor, 40...vortex expansion compressor, 5o...ejector. Agent Tatsuyuki Unuma Figure 1

Claims (2)

[Claims] (1) Inside the housing, which has an intake port and an exhaust port,
In the vacuum pump in which a Siegbahn pump, a centrifugal compression pump, and a vortex compression pump are sequentially arranged from the suction port side, the housing is provided with an intermediate discharge port and an intermediate suction port, and an ejector is provided at the intermediate discharge port and the intermediate suction port. connection,
A vacuum pump characterized in that the ejector is fully valved to connect the centrifugal compression pump and the whirlpool compression pump, and the rotor diameter k of the whirlpool compression pump is smaller than the rotor diameter of a 7M 1-stage pump. (2) The vacuum pump according to claim 1, further comprising a pump for supplying driving gas for the ejector into the housing.