JPH0786357B2 - Oil-free vacuum pump - Google Patents

Description

TECHNICAL FIELD The present invention relates to a multi-stage vortex flow type in which a plurality of rotors having a large number of radial blades and a casing that surrounds the radial blades of the rotor to form a fluid flow path are provided. A pump is provided on the exhaust side, and a combination of a plurality of discs rotating at the same speed as the rotor and a stationary disc having flow passage grooves facing the discs is provided on the upstream side of the multistage vortex flow pump, or A multi-stage viscous drag pump combining a plurality of discs with flow passage grooves rotating at the same speed as the rotor and a stationary disc facing the flow passage grooved disc, and a vacuum degree of 10 ^-3 Torr or less. The present invention relates to an oil-free vacuum pump that can be obtained by itself.

[Prior Art] A vortex type compressor provided with a rotor having a large number of radial blades and a casing that surrounds the radial blades of the rotor to form a fluid passage has a large compression ratio per stage and a general volume. Unlike the type compressor, since it is a non-contact type compression mechanism that does not particularly require a fluid seal, it is used as an oil-free type compressor or a vacuum pump as is well known. Naturally, if the vortex flow type vacuum pump is provided in a few stages, a higher vacuum degree can be obtained, but since the principle of boosting is different from the volume type, the compression ratio per stage decreases at a pressure of 1 Torr or less. However, it is difficult to obtain a higher degree of vacuum.

On the other hand, a viscous drag pump that combines a rotating disk and a stationary disk having a flow channel groove facing the disk is 1 Torr
If the pressure range is below, the pressure ratio per stage will increase,
It is a known fact that a high vacuum degree of 10 ⁻³ Torr or less can be easily obtained by applying this to a vacuum pump having a discharge pressure of about 1 Torr by combining a plurality of stages.

[Problems to be Solved by the Invention] In the conventional vortex type vacuum pump described above, the higher the operating pressure, the larger the amount of heat generated by compression and the higher the temperature rise value of the rotor. Of course, in the multi-stage vortex flow type vacuum pump, the rotor temperature of the final stage pump in which the exhaust pressure is atmospheric pressure is the highest, and the temperature of the pump in the upstream stage is lower. The temperature of the rotating shaft has a distribution such that the position of the final stage of the multi-stage vortex flow type vacuum pump located at the center of the shaft is the highest and becomes lower toward the ends of both shafts.
The performance of the vortex flow type vacuum pump is better as the minute gap between the disk-shaped rotor having a plurality of blades and the casing facing the disk-shaped rotor is smaller. However, in a vortex flow type vacuum pump composed of multiple stages, the minute gap is affected by the elongation of the rotor shaft due to the thermal expansion that occurs during steady operation. The minute gap between and cannot be made sufficiently small under the influence of the above, and therefore the pump effect was low.

It is an object of the present invention to provide an oil-free vacuum pump that improves the pumping effect by suppressing the influence of compression heat generation, and that can achieve a vacuum degree of 10 ^-3 Torr or less by itself with exhaust pressure as atmospheric pressure. .

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

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

[Operation] In the oil-free vacuum pump configured as described above, the thrust magnetic bearing serves as a reference position for axial displacement of the rotary shaft, and relatively reduces displacement due to thermal expansion of the rotary shaft.

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

Therefore, even if the gaps between the rotor and the casing of the vortex flow pump and between the rotating disc and the stationary disc of the Drag pump are made sufficiently small, they can be operated without contact and the pump effect can be improved.

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

In FIG. 1, a multi-stage viscous drag pump generally designated by reference numeral I from the pump suction inlet 38 side and a whole by a reference numeral A in a housing in which a pump suction inlet 38 and a pump discharge outlet 39 are formed. A multi-stage vortex pump shown by reference numeral II is provided. Each of the pumps I and II has four stages in the illustrated example, but this configuration changes depending on the rotation speed of the rotor and is not limited to the illustrated one.

The viscous drag pump rotors 4 of the pumps I and II,
4a, vortex type pump rotors 5a, 5b, 5c, 5d (reference numeral 5 is used in the following description) and electric motor rotor 6 are formed integrally with the rotary shaft 1.

Radial magnetic bearings 2 and 2a are provided between both ends of the rotary shaft 1 and the housing A, and the rotor of the final stage is also provided.
Between 5d and the motor rotor 6 and the housing A,
A thrust magnetic bearing 3 and a thrust collar 3a are provided.

The rotary shaft 1 is formed as a hollow shaft, and a conduit 7 is provided inside the rotary shaft 1 in a non-contact state. This conduit 7 is connected to a cooling liquid pump (not shown) via a rotary shaft cooling liquid inlet 51, and is connected to a cooling liquid tank (not shown) via a rotary shaft cooling liquid outlet 52, and these cooling liquid pumps, inlets 51,
The cooling means is constituted by the conduit 7, the outlet 52, the tank and the circuit connecting them. In the figure, reference numeral 8 is an electric motor stator, 53 is a casing cooling water passage, and 54 is an electric motor cooling water passage.

The drag pump rotors 4 and 4a face the viscous drag pump casings 10 and 10a with minute gaps 20 and 20a on both sides, and two rotors are formed by one rotor. These rotors 4 and 4a are formed on a flat rotating disk, and the casings 10 and 10a are formed with flow passage grooves 31 surrounded by a plurality of flow passage vanes 30, as shown in FIG. Therefore, when the rotors 4 and 4a rotate in the direction of arrow a,
The fluid flows while increasing the pressure from the inner side to the outer side in the radial direction by the viscous force in the radial direction, and when the fluid rotates in the direction of the arrow b, it flows in the opposite direction to the above and increases in the flow direction. This is known as a viscous drag pump action, and even if the same flow passage groove 31 as described above is formed on the rotor 4, 4a side, or the flow passage groove is formed on the rotor side and the planar disk is the casing side, Next, even if the flow path grooves are formed on the casing side and the flat disk is formed on the rotor side alternately, the action as the viscous drag pump is the same.

On the other hand, the vortex pump rotor 5 is provided with a large number of radial blades 32 as shown in FIG. The rotor 5 is opposed to the vortex type pump casings 12a, 12b, 12c, 12d in which the fluid passages 35 are formed by surrounding the radial blades 32 with the minute gaps 22, 22a provided, and one rotor 5 makes one stage of vortex flow. A mold 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 the stripper 33, and when the rotor 5a rotates in the direction of arrow C, the fluid flows while increasing the pressure and is guided to the discharge port 36. Get burned. The discharge port 36 serves as a suction port of the casing 12b of the next stage, and the fluid is sequentially pressurized and 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, the relative displacement of the rotary shaft due to compression heat generation is suppressed by the thrust magnetic bearing by setting the reference position of the axial displacement at the center of the shaft. Smaller, the absolute displacement of the rotary shaft is relatively smaller,
Improved pumping effect with sufficiently small micro-gap between the rotary disk and between viscosity Doraguponpu the rotor and Keshinzu vortex pump a stationary disc, the exhaust and atmospheric pressure, alone at 10 ^- High accuracy of ³ Torr or less can be obtained.

[Brief description of drawings]

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 swirl pump rotor, and FIG. 4 is a swirl pump showing fluid passages. It is sectional drawing of a pump casing. I ... Multi-stage viscous drag pump, II ... Multi-stage vortex flow pump, 1 ... Rotating shaft, 2, 2a ... Radial magnetic bearing, 3 ...
… Thrust magnetic bearings 4,4a …… Viscous drag pump rotors, 5a, 5b, 5c, 5d …… Vortex flow pump rotors, 6 ……
Electric motor rotor, 7 ... Conduit, 10, 10a ... Viscous drag pump casing, 12a, 12b, 12c, 12d ... Eddy current type pump casing, 20, 20a, 22, 22a ... Micro gap, 30 ...
Flow path blade, 31 ...... Flow path groove, 32 ...... Radial blade, 35 ...... Fluid passage

Claims (2)

[Claims] 1. A multistage vortex flow pump provided with a plurality of rotors having a large number of radial vanes and a casing surrounding the radial vanes of the rotor to form a fluid flow path on the exhaust side, On the upstream side, a combination of a plurality of discs rotating at the same speed as the rotor and a stationary disc formed with passage grooves facing the discs, or with a passage groove rotating at the same speed as the rotor In a vacuum pump comprising a multi-stage viscous drag pump which is a combination of a plurality of discs and a stationary disc facing the disc with flow passage grooves, the rotor and a rotor shaft for an electric motor for driving the rotor are rotated by one rotation. An oil-free vacuum formed on a shaft, wherein both ends of the rotary shaft are supported by radial magnetic bearings, and thrust magnetic bearings are supported between the electric motor rotor and the final stage pump of the multi-stage eddy-current pump. pump. 2. A cooling means for forming a hollow rotation shaft, providing a liquid supply conduit from the electric motor rotor side in a non-contact state with the rotation shaft, and cooling the rotation shaft with a liquid supplied through the conduit. The oil-free vacuum pump according to claim 1, further comprising: