JP2001221187A - Turbo dry pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a turbo dry pump for preventing cooling gas for cooling a bearing from mixing with exhaust gas. SOLUTION: A stator 1L disposed on an axial direction the other end side from an exhaust port 1H of a turbo pump mechanism, namely disposed downward, and a rotor 2L are disposed near to each other and opposed to each other so as to constitute a seal mechanism. A blade 2Y is disposed aside on the rotor 2L so as to generate a function of a centrifugal blade at the time of rotation. It is blocked by the seal mechanism and the centrifugal blade function that exhaust gas flows out to the sides of bearings 5, 6, and it is also blocked that exhaust gas is mixed with cooling gas of the bearings 5, 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a turbo-type dry pump which operates without bringing oil into a housing and is used for applications requiring an oil-free environment.

[0002]

2. Description of the Related Art In a dry pump of this type, a rotor is axially mounted in a cylindrical housing via a bearing, and a pump action for gas compression is performed between the rotor and a stator formed on the inner periphery of the housing. A plurality of circumferential flow pumps are provided to compress the gas from the intake port at one axial end of the housing and discharge it to the exhaust port at the other axial end of the housing.
This circumferential pump is a non-contact type and belongs to a turbo type pump. In addition, this turbo type dry pump can evacuate from the state of atmospheric pressure and can create a vacuum region. Mechanical ball bearings, magnetic bearings, or hydrostatic bearings have been used as bearings in such dry pumps, but these days they are convenient for maintenance, have a long life, and reduce initial costs and running costs. Dynamic pressure gas bearings that can be developed have been proposed.

The dynamic pressure gas bearing includes a foil bearing using a thin piece, ie, a foil, a tilting pad bearing using a tilting pad, and a spiral bearing employing a spiral system. For example, in the case of a foil bearing, the foil is installed in a cantilever shape while the supporting surface to be supported and the surface of the rotating body to be supported are closely opposed to each other, and the foil forms a wedge-shaped gap that gradually narrows in the rotation direction. . And gas (gas)
And generate a dynamic pressure to support the rotating body against the substrate surface. Therefore, a completely oil-free environment (dry) is realized instead of using oil like a ball bearing.

[0004]

A dynamic pressure gas bearing generates an air flow by the rotation of a rotating body to generate a dynamic pressure, so that the friction of the air flow generates heat. The heat generated may cause deformation of the instrument, and play (looseness), thereby generating noise and reducing the function of the circumferential flow pump. For this reason, the cooling gas is usually circulated through the bearing to cool it. An inert gas such as a nitrogen gas is used as the cooling gas.

In this type of dry pump, the structure of the circumferential flow pump is non-contact, and the bearing for supporting the rotating body of the circumferential flow pump is in communication with the circumferential flow pump. Therefore, mixing of the cooling gas of the bearing portion and the exhaust gas by the circumferential flow pump portion may occur. For cooling gas,
The amount of gas (gas) to be evacuated is extremely small and very small. Therefore, for example, when this kind of dry pump is used in a semiconductor manufacturing apparatus or the like, when the gas to be evacuated to be evacuated is a corrosive gas, the evacuated gas needs to be appropriately treated. After discharging the cooling gas mixed with the corrosive gas to the outside, it is necessary to appropriately treat the cooling gas. For this reason, the processing facility became large. Further, when a corrosive gas handled on the semiconductor manufacturing apparatus flows into and comes into contact with the bearing portion, the durability of the bearing is reduced and the bearing cannot be used. An object of the present invention is to provide a turbo type dry pump which solves such a problem.

[0006]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a turbo-type dry pump provided by the present invention has a seal mechanism in which a rotating body and a stator at the other end in the axial direction from the exhaust port side are brought close to and opposed to each other. And a discharge port for discharging a cooling gas for cooling the bearing to the outside of the housing is provided in the housing on the other end side from the position of the sealing mechanism. Therefore, the circumferential flow pump side and the cooling gas section side are separated by the sealing mechanism, so that gas mixing on both sides can be reduced, and gas mixing from the circumferential flow pump side to the cooling gas section side can be eliminated.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A turbo type dry pump according to the present invention will be described below with reference to an embodiment shown in the drawings. FIG. 1 is a diagram showing a basic configuration of a turbo type dry pump DP provided by the present invention, and shows a vertical cross section of the entire pump.

The dry pump DP is mainly composed of a cylindrical housing 1 and a rotating body (hereinafter referred to as a rotor) 2 rotatably mounted on the inside of the housing 1 by a bearing. Specifically, the housing 1 has a bottomed shape as shown in the figure, and an opening at one axial end (upper side) is an intake port 1K, and an exhaust port at the other axial end (lower side) is in the middle. 1H is installed. A circumferential pump is constituted by a combination of a circumferential portion of the rotor 2 and a stator formed on the inner circumference of the housing 1. The circumferential flow pump is provided in a plurality of stages, that is, in a plurality of stages in the axial direction of the rotor 2. In the embodiment shown in FIG.
An example of a so-called hybrid dry pump in which a thread groove pump is installed above a circumferential flow pump is shown.

In the following, this structure will be described in detail. First, a thread groove 1M is formed in the upper inner peripheral portion of the housing 1, and the upper cylindrical portion 2P of the rotor 2 is opposed to approach the thread groove 1M. I have. A combination of the screw groove 1M and the cylindrical portion 2P of the rotor 2 constitutes a so-called screw groove pump mechanism NP. The rotation of the rotor 2 compresses the molecules in the viscous flow region of the gas and sends it downward.

[0010] Further, in the middle stage of the inner circumference of the housing 1, a plurality of stator units 1T, specifically, seven stages, are stacked in the axial direction. On the other hand, the rotor circumferential portion 2B, which is inserted between the stators 1T, is provided facing the rotor 2 from the middle to the lower side. A groove 1G is formed at the inner peripheral end of the stator portion 1T, and a groove 2G is also formed at the outer peripheral end of the rotor circumferential portion 2B. An air flow is generated by the relative displacement between the two grooves 1G and 2G, and the pump function is activated. This pump function is sequentially connected to the subsequent stage via the flow path 1N, and the gas is compressed as a whole. These two are of course non-contact, but depending on the combination, the circumferential pump S
P is formed. By the operation of this multi-stage circumferential flow pump SP, the gas pumped by the screw groove pump mechanism NP is
The air is further compressed and sent downward to be exhausted to the exhaust port 1H via the exhaust path 1R. That is, the circumferential flow pump SP of each stage compresses the gas on its circumference, and sends the gas to the next stage circumferential flow pump SP via the flow path 1N at the end,
This is sequentially performed for each stage to exhaust gas.

The basic principle and operation of the turbo-type dry pump have been described above. The rotor 2 has an H-shaped cross section as shown in the drawing, and a central portion thereof is connected to a rotary drive mechanism and a shaft is provided. Is being worn. That is, reference numeral 3 denotes a rotary drive shaft which is arranged on the axis of the housing 1. The rotary drive shaft 3 is provided with a flange portion 3F for a bearing at a middle stage, and an electric motor (motor) 4 is integrally installed below the flange portion 3F. The electric motor 4 includes an armature winding 4M provided on the inner periphery of the housing 1 corresponding to the armature and a rotor winding 3M provided on the rotary drive shaft 3 corresponding to the rotor.
The rotation driving shaft 3 is rotated at a high speed by the supply of electric energy 9 from the outside. In the drawing, reference numeral 3S denotes a screw portion at the upper end of the rotary drive shaft 3 which cooperates with the nut 3N to fix the rotor 2 to the rotary drive shaft 3.

The rotating body, that is, the rotor 2 is mounted on the housing 1 by a bearing mechanism composed of a dynamic pressure gas bearing. That is, the hydrodynamic gas bearing in the illustrated example is a foil-type bearing, and more specifically, a plurality of thrust foil bearings 5 as thrust bearings are uniformly arranged around the upper and lower gaps between the flange portion 3F and the cylindrical portion 1E of the housing 1. is set up. By being installed above and below the flange portion 3F, it is possible to cope with a strong thrust force. On the other hand,
Above and below the rotary drive shaft 3, radial foil bearings 6 are installed in two vertical stages in a gap between the cylindrical portion 1 </ b> E of the housing 1. The rotor 2 is smoothly and non-contacted by these two foil bearings 5 and 6. Although the dynamic pressure gas bearings 5 and 6 are non-contact bearings, they generate heat due to gas flow. This heat must be removed. Therefore, as shown in FIG. 1, a cooling gas supply port 1F is provided, and the two gas bearings 5 and 6 are cooled by the cooling gas supplied from the cooling gas supply port 1F.

The above configuration is a configuration of a conventional turbo-type dry pump. In the present invention, in these configurations, a cooling gas for cooling the foil bearings 5 and 6 and a gas (gas) to be exhausted are used. A means for preventing mixing is added. That is, in the turbo-type dry pump provided by the present invention, a combination of a rotating body (rotor) and a stator is provided further on the other end side from the outlet 1H, that is, in the downward direction in the illustrated example, and a seal mechanism is provided in this portion. There is a basic feature of the present invention in the configuration. This basic configuration is shown in FIG. 2, and FIG. 2 is an enlarged sectional view showing a main part of the present invention in FIG.

As shown in FIG. 2, the rotor 2 extends below the exhaust port 1H (toward the other end of the housing 1) and has a rotor 2M at the lower end. On the other hand, the stator portion 1T also has a one-stage stator 1L below the exhaust port 1H.
Is provided. The rotor 2M and the stator 1L are combined with each other in an uneven manner, and are opposed to each other in close proximity to each other. That is, the two 2M and 1L are close to each other and have a small gap therebetween. In the drawings, the gap is shown with a certain interval for easy understanding, but the gap is such that an air flow is unlikely to occur, and both of them constitute a sealing mechanism.

A cooling gas outlet 1Z is formed below the seal mechanism (toward the other end of the housing 1). The cooling gas is supplied to the supply port 1 shown in FIG.
F, cools the foil bearings 5 and 6, and then flows downward from outside the cylindrical portion 1 </ b> E of the housing 1 to reach the discharge port 1 </ b> Z. At this time, the rotor 2L and the stator 1L are not in contact with each other, and the cooling gas normally tries to flow into the circumferential flow pump SP from this gap. The cooling gas is discharged to the outside from the discharge port 1Z.

The outlet 1Z is provided with an orifice OF. The orifice OF is provided to make the internal pressure of the gas in the cooling gas flow path equal to or higher than the atmospheric pressure.
The reason that the pressure is equal to or higher than the atmospheric pressure is that the pressure of the outlet 1Z is the atmospheric pressure,
If the pressure at the cooling gas discharge portion is lower than that, the gas to be exhausted flows out to the cooling gas discharge portion even if the sealing mechanism is interposed. This is because the inflow of the exhaust gas into the exhaust portion has a problem as described above.

Further, the present invention is characterized in that a blade 2Y is attached to the lower surface of the rotor 2L immediately below the exhaust port 1H. The blades 2Y are arranged around the rotor 2L with a certain interval, and function as centrifugal blades by the rotation of the rotor 2L. That is, the rotation of the rotor 2L causes the centrifugal wing 2Y to generate air blowing in the outer circumferential direction. By this blowing, the exhaust gas is prevented from flowing out to the discharge portion side of the cooling gas. In FIG. 3, a thread groove 2m is formed on the outer peripheral side of a rotor cylindrical portion connecting the rotor 2L and the rotor 2M.
Are arranged, and function as a thread groove pump by the rotation of the rotor 2. That is, the thread groove pump generates a blow from the rotor 2M toward the rotor 2L. The exhaust gas tends to flow out to the cooling gas discharge portion side by this air blowing, but is blocked.

The turbo type dry pump provided by the present invention is as described in detail above, but is not limited to the above and illustrated examples, but includes various modified embodiments. First, a dry pump is used. The illustrated example is a hybrid type in which the pump is combined with a thread groove pump NP as shown in FIG. 1. However, it is not essential that the thread groove pump is provided, and only a circumferential flow pump may be used. Next, as for the bearing mechanism, the illustrated example is a dynamic pressure gas bearing, specifically, a foil bearing. However, the present invention is applicable to a dry pump using a bearing such as a ball bearing, and is not limited to the illustrated example bearing. Alternatively, a magnetic bearing system may be employed. Regarding the configuration of the housing, the installation of the cylindrical portion 1E is not always necessary. Also,
2 and 3, the blade 2Y and the thread groove 2m are provided on the rotor side, but may be formed on the stator side. The present invention covers all these modified embodiments.

[0019]

The turbo type dry pump provided by the present invention is as described in detail above, so that the mixture of the cooling gas and the exhaust gas can be prevented. Therefore, when the exhaust gas is a corrosive gas, such a gas does not enter the bearing portion, so that corrosion of the bearing can be reduced and durability can be improved. Further, since the corrosive gas is not discharged from the cooling gas discharge section, there is no need to provide a facility for treating the corrosive gas, thereby providing an economical dry pump.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a turbo type dry pump provided by the present invention.

FIG. 2 is an enlarged view showing a configuration of a main part of a turbo type dry pump provided by the present invention.

FIG. 3 is an enlarged view showing a configuration of a main part of a turbo type dry pump provided by claim 3 of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Housing 1E ... Cylindrical part 1G ... Groove 1K ... Intake port 1Z ... Discharge port 1H ... Exhaust port 1L ... Stator 2 ... Rotor 2L ... Rotor 2G ... Groove 2m ... Thread groove 2Y … Wings 3… rotating drive shaft 4… motor 5… foil thrust bearings 6… radial foil bearings 9… electrical energy

Claims (4)

[Claims] 1. A rotating body is axially mounted in a cylindrical housing via a bearing, and a gas compression pumping action is performed between a circumferential portion of the rotating body and a stator formed on an inner circumference of the housing. Turbo-type dry pump in which a circumferential flow pump is provided in multiple stages in the axial direction of the rotating body, and compresses gas from an intake port at one axial end of the housing and discharges the gas to an exhaust port at the other axial end of the housing. In the pump, a seal mechanism is provided with the rotating body and the stator at the other end in the axial direction closer to each other than the exhaust port, and a cooling gas for cooling the bearing is externally provided to a housing at the other end from the position of the seal mechanism. A turbo-type dry pump characterized in that a discharge port is provided to discharge the cooling gas, and the cooling gas for cooling the bearing is prevented from entering the circumferential flow pump side by the seal mechanism. 2. A rotator according to claim 1, wherein a wing is attached to the rotating body of the seal mechanism, and the wing functions as a centrifugal wing by rotation of the rotating body, so that air is generated in the cooling gas. Turbo dry pump. 3. The turbo-type dry pump according to claim 1, wherein a screw groove is provided between the rotating body and the stator of the sealing mechanism, and the rotation of the rotating body generates air in the cooling gas. 4. The turbocharger according to claim 1, wherein an orifice is provided at an outlet for discharging the cooling gas to the outside, and a pressure of the cooling gas is maintained at a pressure higher than the atmospheric pressure at a portion of the seal mechanism. Type dry pump.