JPH0219694A - Oil-free vacuum pump - Google Patents

Abstract

PURPOSE:To improve the pumping effect and to achieve high vacuum by supporting the opposite ends of a rotary shaft on radial magnetic bearings and supporting the section between the rotor of a motor and the final stage pump of a multi-stage volute pump on a thrust magnetic bearing. CONSTITUTION:Viscous drag pump rotors 4, 4a, volute pump rotors 5a-5d of pumps I, II and the rotor of a motor 6 are formed integrally with a rotary shaft 1. The opposite ends of the rotary shaft 1 are supported by a magnetic radial bearing 2 while the section between the motor rotor 6 and the final sage rotor 5d of a multi-stage volute pump is supported by a magnetic thrust bearing 3. By such arrangement, the micro gap is reduced sufficiently to improve the pumping effect thus achieving high vacuum through a single unit.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention relates to a multi-stage vortex flow type rotor equipped with a plurality of rotors having a large number of radial blades and a casing surrounding the radial blades of the rotor to form a fluid flow path. A pump is provided on the exhaust side, and a plurality of discs rotating at the same speed as the rotor are provided on the upstream side of the multistage vortex pump, and a stationary disc with a flow groove formed opposite to the discs is combined, or It is equipped with a multi-stage viscous drag pump that combines a plurality of discs with flow passage grooves that rotate at the same speed as the rotor and a stationary disc facing the discs with flow passage grooves, and has a vacuum degree of 10'Torr or less as a single unit. Apply to the oil-free vacuum pump obtained.

[Prior Art] A vortex compressor equipped with a rotor having a large number of radial blades and a casing surrounding the radial blades of the rotor to form a fluid passage has a high compression ratio per stage, and has a typical volume. Unlike a type compressor, a non-contact type compressor does not particularly require a fluid seal, so it is used as a well-known oil-free type compressor or vacuum pump. Naturally, if the vortex type vacuum pump is provided with several stages, it is possible to obtain a higher degree of vacuum, but since the principle of pressure increase is different from that of the positive displacement type, the compression ratio per stage decreases at pressures below ITorr. However, it is difficult to obtain a higher degree of vacuum.

On the other hand, a viscous drag pump that combines a rotating disc and a stationary disc with a flow channel facing the disc is ITo
If the pressure range is below rr, the pressure ratio per stage will be large, and if this is combined with multiple stages and applied to a vacuum pump with an exhaust pressure near ITorr, a high degree of vacuum below 10'Torr can be easily obtained. is a known fact.

[Problems to be Solved by the Invention] In the conventional eddy current vacuum pump described above, the stage with high operating pressure generates a large amount of heat due to compression, and the rotor temperature -L
The rise value is also low, and of course, in a multi-stage vortex vacuum pump, the final stage pump, where the exhaust pressure is atmospheric pressure, has the highest temperature of 17.
The temperature of the upstream pump is low. The temperature of the rotating shaft is distributed such that it is highest at the final stage of the multi-stage vortex vacuum pump located at the center of the shaft, and decreases as it approaches both ends of the shaft.

The performance of the vortex vacuum pump is better as the minute gap between the disc-shaped rotor having a plurality of blades and the casing facing the disc-shaped rotor is small. However, in a multi-stage eddy current vacuum pump, the minute gap is affected by the elongation of the rotor shaft due to the thermal expansion that occurs during steady operation, and even in a viscous drag type vacuum pump, the small gap is affected by the elongation of the rotor shaft due to the thermal expansion that occurs during steady operation. Due to the above-mentioned influence, the small gap between the pump and the pump could not be made sufficiently small, and therefore the pumping effect was low.

It is an object of the present invention to provide an oil-free vacuum pump that suppresses the influence of pressure WI heat generation, improves the pumping effect, and that allows exhaust pressure to be atmospheric pressure and obtain a degree of vacuum of 10" rorr or less. .

[Means for Solving the Problems] According to the present invention, a multi-stage vortex pump is provided with a plurality of rotors having a large number of radial blades and a casing surrounding the radial blades of the rotor to form a fluid flow path. A combination of a plurality of discs rotating at the same speed as the rotor and a stationary disc with flow grooves facing the discs is provided on the upstream side of the multistage vortex pump, or the rotor and In a vacuum pump equipped with a multi-stage viscous drag pump that combines a plurality of disks with flow path grooves rotating at the same speed and a stationary disk facing the disks with flow path grooves, the rotor and the same are driven. A rotor shaft for an electric motor is formed into a single rotating shaft, both ends of the rotating shaft are supported by radial magnetic bearings, and supported by a thrust magnetic bearing between the electric motor rotor and a final stage pump of the multistage eddy current pump. are doing.

Here, the rotary shaft is formed hollow, a conduit for supplying liquid from the motor rotor side is provided in a non-contact state with the rotary shaft, and a cooling means is provided for cooling the rotary shaft with the liquid supplied through the conduit. It is preferable that

[Function] In the oil-free vacuum tube configured as described in Section 2, the thrust magnetic bearing serves as a reference position for the axial displacement of the rotating shaft, and relatively reduces the displacement of the rotating shaft due to thermal expansion.

Furthermore, when a cooling means is provided, the liquid cools the rotating shaft, and the absolute displacement of the rotating shaft due to thermal expansion can be further reduced.

Therefore, even if the gaps between the rotor and the casing of the vortex pump and between the rotating disk and the stationary disk of the drag pump are made sufficiently small, contactless operation is possible and the pumping effect can be improved.

[Example code] The present invention will be described in detail below with reference to the drawings.

In FIG. 1, the pump suction port 38 and the pump discharge port 39
Inside the housing, the whole of which is designated by the symbol A, is formed with a
From the pump suction port 38 side, there are provided a multi-stage viscous drag pump, which is generally indicated by the symbol I, and a multi-stage vortex pump, which is generally indicated by the symbol ■.

In the illustrated example, these pumps (1) and (2) are each configured in four stages, but this configuration changes depending on the rotational speed of the rotor and is not limited to what is illustrated.

Each of those pumps1. ■ Viscous dragbon rotor 4.
4a, eddy current pump rotors 5a, 5b, 5c, and 5d (hereinafter, reference numeral 5 will be used when collectively referring to them), and an electric motor rotor 6 are formed integrally with the rotating shaft 1.

A radial magnetic bearing 2.2a is provided between both ends of the rotating shaft 1 and the housing A, and a thrust bearing is provided between the final stage rotor 5d and the motor rotor 6 and the housing A. A magnetic bearing 3 and a thrust collar 3a are provided.

Further, the rotating shaft 1 is formed as a hollow shaft, and a conduit 7 is provided inside the rotating shaft 1 in a non-contact state.

This lead PF near is connected to a coolant pump (not shown) via a rotating shaft coolant port 51, and is connected to a coolant pump (not shown) through a rotating shaft coolant outlet 52.
The coolant pump, the inlet 51, the conduit 7, the outlet 52, the tank, and the circuit connecting them constitute a cooling means. In addition, the code 8 in the figure is 1! The motive stator, 53 is a casing cooling water passage, and 54 is an electric 9JJ machine cooling water passage.

The drag bomb rotor 4.4a faces the viscous drag bomb casing 10.10a with minute gaps 20.20a provided on both sides, and a two-stage pump is formed with one rotor.

These rotors 4.4a are formed into planar rotating disks,
As shown in FIG. 2, a channel groove 31 surrounded by a plurality of channel vanes 30 is formed in the casing 10.10a.

Therefore, when the rotor 4.4a rotates in the direction of arrow r1a,
The fluid flows in the channel groove 31 from the inside in the radial direction to the outside while increasing the pressure due to viscous force, and when the fluid rotates in the direction indicated by the arrow in the opposite direction, it flows in the opposite direction to the above-mentioned direction and the pressure increases in the flow direction.

This is known as a viscous drag bomb effect, and even if the same flow path groove 31 as described above is formed on the rotor 4.4a side,
Alternatively, the flow grooves may be formed on the rotor side and the planar disk on the casing side, and then the flow grooves may be formed on the casing side and the planar disk on the rotor side. 6. On the other hand, the vortex pump rotor 5 is formed with a large number of radial vanes 32, as shown in FIG. The rotor 5 faces the vortex type pump casings 12a, 12b, 12c, and 12d, which surround the radial blades 32 and form a fluid flow path 35, with a minute gap 22. A type pump is formed.

In FIG. 4, the fluid passage 35 is divided into a low pressure (suction) side and a high pressure (discharge) side by a stripper 33, and when the rotor 5a rotates in the direction of arrow C, the fluid flows while increasing its pressure and is guided to the discharge port 36. It will be destroyed. The discharge port 36 becomes a suction port of the casing 12b of the next stage, the pressure of the fluid is increased sequentially, and the fluid is discharged from the final stage to the atmosphere from the pump discharge port 39 formed in the casing 12d of the pump.

[Effects of the Invention] Since the present invention is configured as described above, by setting the reference position for axial displacement at the center of the shaft, the relative displacement of the rotating shaft due to pressure w4 heat generation is suppressed by the thrust magnetic bearing. The absolute displacement of the rotating shaft is made relatively small, and the minute gaps between the rotor and casing of a vortex pump and between the rotating disk and the stationary disk of a viscous drag pump are made sufficiently small. The effect is improved, the exhaust is set to atmospheric pressure, and a high altitude of 10'Torr or less can be achieved by itself.

[Brief explanation of the drawing]

Fig. 1 is a side sectional view showing an embodiment of the present invention, Fig. 2 is a plan view of a viscous drag pump casing, Fig. 3 is a plan view of a vortex type pump rotor, and Fig. 4 is a vortex type pump rotor showing a fluid passage. FIG. 3 is a cross-sectional view of the pump casing. ■... Multi-stage viscous drag pump ■... Multi-stage vortex pump 1... Rotating shaft 2.2a... Radial magnetic bearing 3... Thrust magnetic bearing 4.4a
... Viscous dragbon rotor 5a, 5b, 5C
15d--Eddy current pump rotor 6... Electric motor rotor 7... Conduit 10.10a... Viscous drag bomb casing 12a, 12b, 12c, 1
2d... Eddy current pump casing 20.20a,
22.22a...Minute gap 30...Flow path blade
31... Channel groove 32... Radial blade 35...
・Fluid passage patent applicant Ebara Research Institute Co., Ltd. Figure 1 Figure 1 "JQ"

Claims (2)

[Claims] (1) A multistage vortex pump equipped with a plurality of rotors having a large number of radial blades and a casing surrounding the radial blades of the rotor to form a fluid flow path is provided on the exhaust side, and the upstream side of the multistage vortex pump A combination of a plurality of disks rotating at the same speed as the rotor and a stationary disk with flow grooves formed opposite to the disk, or a plurality of disks with flow grooves rotating at the same speed as the rotor. In a vacuum pump equipped with a multistage viscous drag pump that combines a disk and a stationary disk facing the grooved disk, the rotor and a rotor shaft for an electric motor that drives the rotor are combined into one rotating shaft. 1. An oil-free type vacuum pump, characterized in that both ends of the rotating shaft are supported by radial magnetic bearings, and a thrust magnetic bearing is supported between the electric motor rotor and the final stage pump of the multistage eddy current pump. (2) forming the rotating shaft hollow and providing a conduit for supplying liquid from the motor rotor side in a non-contact state with the rotating shaft;
2. The oil-free vacuum pump according to claim 1, further comprising a cooling means for cooling the rotating shaft with the liquid supplied through the conduit.