JP2002202089A - Turbo dry vacuum pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a turbo dry vacuum pump preventing a compound generated from reaction gas from accumulating in a narrow opening in a pump, and preventing bearing lubricating oil from mixing in. SOLUTION: A hanging bell shaped rotor 1b connected to a shaft 21 of a high frequency motor 3a is provided with a multi stage circumferential flow pump part 16 at the outer circumference part and rotates at a high speed. Reaction gas is sucked from a suction opening 6 and is compressed between a screw groove pump part 18 and the multi stage circumferential flow pump part 16. Inert gas is supplied in a labyrinth seal 19 part of a shaft seal part 5a from a gas supply passage 22, flows in a gas flow passage 23, passes through plural through holes 17 provided on cylindrical part of the rotor 1b in a radius and rotation direction, flows in a narrow opening connecting between gas compression parts at a high speed, and is discharged with reaction gas sucked from an upper part, in order to prevent lubricating oil 10 from leaking out during rotating.

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 vacuum pump, and more particularly to a turbo-type dry vacuum pump for dealing with a reaction product gas generated in a process of a semiconductor manufacturing apparatus or the like.

[0002]

2. Description of the Related Art There are dry vacuum pumps, molecular drag pumps, turbo molecular pumps and the like as vacuum pumps for transporting gas by mechanically imparting momentum in a certain direction to gas molecules by a rotary blade or the like. Dry vacuum pump
It exhausts gas from atmospheric pressure to low vacuum, and exhausts gas using a mechanism such as a rotary wing, screw wing, or mechanical booster without using any oil in a gas passage in the pump. A molecular drag pump is a type in which a high-speed rotor surface for giving momentum to gas molecules always moves parallel to the surface.For example, a screw-shaped wing is attached to a high-speed rotating body, and the high-speed High vacuum can be obtained by rotation. The turbo-molecular pump is composed of a rotor blade with a slanted slit in a disk under conditions of low pressure such that collisions between gas molecules can be ignored.
The fixed blades, which have the same shape as the rotating blades and have the same inclination as the rotating blades, are arranged alternately.The rotating blades are driven at an extremely high rotational speed, and gas molecules pass through the gap between the two blades. Then, it is evacuated to a vacuum and an ultra-high vacuum can be obtained. Molecular pumps generally include a molecular drag pump and a turbo molecular pump. These vacuum pumping systems require an oil rotary pump, a mechanical booster pump, a dry vacuum pump, or the like as a back pressure pump.

FIG. 3 shows a cross section of a turbo type dry vacuum pump. This vacuum pump is provided with a gas intake port 6 at an upper portion to inhale gas, and a gas exhaust port 1 on a side surface of the case 13.
4 is to discharge gas from the cylindrical portion 2 in the case 13.
Inside, the rotating body 1 is held by an upper rolling bearing 7 and a lower rolling bearing 8 via a shaft 4, and the lower shaft 4 of the rotating body 1 is provided with a rotor of the high-frequency motor 3, and a case 12 is provided.
Rotating at high speed by the high frequency motor 3 of
The rotating blades 1a are arranged in a plurality of stages on the outer peripheral portion of the upper part of the upper surface, and the stationary blades 2a are arranged in a plurality of stages inside the cylindrical portion 2 in opposition thereto. By rotating the rotating body 1 at a high speed,
A pump action occurs, and the gas inlet 6 side and the gas outlet 1
A pressure difference on the four side occurs. A space for storing the lubricating oil 10 is provided in a case 12 provided below the motor chamber 9, and the lubricating oil 10 is provided in the rolling bearings 8 and 7.
Is supplied. On the other hand, the gas supply port 15 prevents the mist of the lubricating oil 10 from entering the exhaust chamber from the motor chamber 9 through the rolling bearing 7 provided in the shaft seal portion 5.
For example, an inert gas such as nitrogen is introduced, and the gas is forced to flow in the direction of the exhaust port 14.

[0004]

The conventional turbo-type dry vacuum pump is constructed as described above. However, when a turbo-type dry vacuum pump is used as an exhaust pump for a CVD apparatus or an etching apparatus, the source gas is pumped. Decomposes in the inside, the product is deposited in the pump, or the gas of the reaction product in the process, the solid precipitates inside the pump, filling the gaps inside the pump, There is a problem that the pump cannot be operated. In order to prevent this, in order to change the gas composition in the exhaust gas, an inert gas is supplied from the stator side (fixed side) of the pump toward the gas compression section (gas compression flow path). In order to supply gas to the portion where the gap is filled with the deposit, it is necessary to provide an inert gas flow path in a narrow portion, and there is a problem that the processing is difficult and time-consuming. Further, when a rolling bearing is used separately from the inert gas flow path, it is necessary to provide an inert gas flow path so that lubricating oil does not enter the vacuum gas flow path.

The present invention has been made in view of such circumstances, and when used as an exhaust pump in a gas reaction generating apparatus such as a CVD apparatus, the product of the reaction gas is generated between the gas compression sections in the pump. It is an object of the present invention to provide a turbo-type dry vacuum pump which is easy to work and which is prevented from accumulating in a narrow gap connecting between the bearings and lubricating oil from a bearing into a vacuum gas flow path.

[0006]

In order to achieve the above-mentioned object, a turbo-type dry vacuum pump according to the present invention comprises a multi-stage circumferential pump having a plurality of stages of rotating disks capable of compressing gas by rotation. And a rotary body consisting of a shaft to which a rotor of a high-frequency motor driving the rotor is connected is held by upper and lower bearings, and the multi-stage circumferential flow pump is a turbo-type dry vacuum pump capable of taking in gas. The rotating body of the portion has a cylindrical shape of a bell, and a plurality of through holes are provided in the radial direction on the circumference between the rotating disks provided in a plurality of stages in the cylinder.

The direction of the plurality of through holes provided in the cylinder of the rotating body of the multi-stage circumferential flow pump is set to the same direction as the rotating direction of the rotating body, so that the gas flows from the inside to the outside by the rotation. Things.

Further, a rolling bearing is used as a bearing for holding the rotating body, and an inert gas is supplied to the bearing from the outside so that lubricating oil for the bearing does not mix into the gas compression section. It has a gas flow path passing through the inner surface of the cylinder of the body.

Further, a dynamic pressure gas bearing is used as a bearing for holding the rotating body, and an inert gas is supplied to the bearing portion from the outside, and the inert gas is provided with a gas flow path passing through the inner side surface of the cylinder of the rotating body. Things.

In addition, a static pressure gas bearing is used as a bearing for holding the rotating body, an inert gas is supplied to the bearing portion from the outside, and a gas flow path is provided through which the inert gas passes through the inner surface of the cylinder of the rotating body. Things.

The turbo-type dry vacuum pump of the present invention is constituted as described above. The rotary body of the pump has a cylindrical shape of a bell, and a disk having a plurality of stages of rotary blades is provided on the outer periphery of the cylinder. A plurality of through-holes are provided in the radial direction on the circumference between each of the rotating disks, and the direction of the through-holes is adjusted so that gas flows outward from a gas flow path provided inside by rotation. And the same direction. A rolling bearing is used as the bearing that holds the rotating body, and an inert gas is supplied to the bearing from the outside so that lubricating oil for the bearing does not enter the gas compression section. It passes through the gas flow path on the inner surface. In addition, a dynamic pressure gas bearing or a static pressure gas bearing is used as a bearing for holding the rotating body, and an inert gas is supplied to the bearing portion from the outside, and the inert gas passes through a gas flow path on the inner surface of the cylinder of the rotating body. I do. With the above-described structure, the multi-stage circumferential flow pump section that enables gas compression performs gas compression on the outside, provides an inert gas flow path on the inside, and supplies inert gas from the outside to the bearing section. The active gas channel side is equal to the gas compression channel side or has a high pressure. Due to the pressure difference, the inert gas flows from the inert gas channel to the plurality of through holes,
The inert gas can be reliably supplied at a high speed to a narrow gap between the bearing portion and the gas compression portion in the pump, and the intrusion of lubricating oil and the accumulation of gaseous reaction products can be prevented. Further, since the multi-stage circumferential flow pump section can be assembled by laminating a plurality of rotating disks, the processing of the gas supply path, the gas flow path, the through hole, etc. of the inert gas can be easily performed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a turbo-type dry vacuum pump according to the present invention will be described with reference to FIGS.
FIG. 1 is a view showing a cross section of a turbo type dry vacuum pump of the present invention. FIG. 2A is a vertical cross-sectional view of the multistage circumferential pumping unit 16 of the bell-shaped rotating body 1b, and FIG. 2B is a plan cross-sectional view. The turbo-type dry vacuum pump has a rotating body 1 having a cylindrical grooved pump portion 18 on a cylindrical outer peripheral portion.
a, a rotating disk having a plurality of stages of rotating blades (pump grooves 20) on the outer periphery of a bell-shaped cylindrical shape below, and a plurality of through holes 17 in the radial direction on the circumference between each rotating disk. Rotator 1b provided with a multi-stage circumferential pump section 16 provided in the rotation direction
The rotor 1a and the rotor 1b are combined into one, and the rotor of the high-frequency motor 3a is attached below, and the shaft 21 supported and rotated by the rolling bearings 7a and 8a, and the high-frequency rotating the shaft 21 at high speed. A motor 3a, an intake port 6 for taking in external gas at an upper part, a thread groove pump part 18 and a multi-stage circular pump part 16 at an inner part, and an exhaust part for exhausting compressed gas at a lower side part. A gas supply port 15a for supplying an inert gas to the labyrinth seal 19 and the shaft sealing portion 5a of the rolling bearing 7a;
2 and a gas flow path 23 inside the bell-shaped rotator 1b.
And a cylindrical portion 2a in which a lubricating oil 10 is stored at a lower portion.

[0013] The turbo-type dry vacuum pump comprises a rotating body 1
a, a thread groove pump section 18 is mounted on the rotating body 1b, and a multi-stage circumferential pump section 16 is mounted on the rotating body 1b, and the rotating bodies 1a, 1b are rotated at a high speed of tens of thousands of rpm by the high frequency motor 3a. That the body 1b has a bell shape, that a bearing is selected and that a gas supply passage 22 and a gas passage 23 for flowing an inert gas are provided so that the lubricating oil 10 does not leak from the shaft sealing portion 5a; The through-hole 17 is provided in the same direction as the rotation direction so that the gas reaction product does not accumulate in the gap of the multi-stage circumferential flow pump section 16.

The thread groove pump section 18 is provided on the upper part of the pump, and has a spiral groove on the side of the cylindrical section 2a. When the rotating body 1a rotates at a high speed, the gas after the reaction from the gas reaction apparatus is removed. The suction is performed through the intake port 6. The multi-stage circumferential flow pump section 16 is provided at the lower part of the pump, and is provided at a plurality of stages on the outer periphery of the cylindrical portion of the bell-shaped rotating body 1b. It consists of a ring-shaped grooved member provided on the cylindrical portion 2a opposite thereto, and compresses and sucks gas from the preceding thread groove pump portion 18 by rotating the rotating body 1b at high speed. The gas supply passage 22 is provided with an inert gas at a predetermined pressure from the outside of the cylindrical portion 2 a through the gas supply port 15 a to the shaft sealing portion 5.
This is a passage for introduction into the cylindrical portion 2a, and is formed by machining in the cylindrical portion 2a. The shaft sealing portion 5a includes a rolling bearing 7a for holding an upper portion of a shaft 21 rotating at a high speed, and a lubricating oil 10 for a high frequency motor.
Shows a part constituted by a labyrinth seal 19 provided so as not to leak to the gas flow passage 23 through the rolling bearing 7a. Labyrinth seal 19
Is a non-contact seal that provides a small stagger gap (maze: Labyrinth) between two surfaces that move relative to each other, and seals the fluid. The effect of this is that gas leaking through a narrow gap has a constant outflow area. The amount of leakage depends on the pressure difference before and after the leakage and the flow resistance to the flow.
In order to reduce the amount of leakage, it is necessary to make the gap as small as possible. However, since there is a limit, it is necessary to increase the flow resistance of the passage. Therefore, as the flow path becomes more complicated, the amount of leakage decreases. Here, by introducing an inert gas at a predetermined pressure into the gas flow path 23, a pressure difference between the gas flow path 23 and the space of the high-frequency motor 3a is provided, so that the lubricating oil 10 23 so as not to leak. The gas passage 23 is provided between the inside of the bell-shaped rotator 1b and the fixed-side cylindrical portion 2a that holds the shaft 21 with the rolling bearing 7a and holds the rolling bearing 7a. Through the gas supply passage 22,
This is a flow path through which the introduced inert gas flows. Through hole 17
Are arranged on the outer periphery of the cylindrical shape of the bell of the rotating body 1b, on the circumference between the rotating disks stacked in a plurality of stages, a plurality of them in the radial direction,
And it is provided toward the rotation direction. The introduction of the inert gas increases the gas pressure in the gas flow path 23, and the through holes 17 are formed in the direction of rotation, so that the flow of the gas flow is increased during rotation. The inner side becomes high pressure with respect to the outer side (pump compression side) to generate a pressure difference, and the inert gas passes through the through hole 17 and a narrow upper and lower gap (0.1-0.
(About 4 mm) at a high speed. This prevents gas reaction products from being deposited in the narrow gap. The processing of the through-holes 17 is such that the through-holes 17 are formed for each stage of the rotating disk and are stacked in multiple stages, whereby the bell-shaped multi-stage circumferential pumping unit 16 can be easily formed.

Next, the flow of the inert gas will be described. The inert gas is supplied from the gas supply port 15a to the gas supply path 2
2 and is introduced into the gas passage 23 of the shaft sealing portion 5a. Then, it flows over the labyrinth seal 19 and the upper part of the rolling bearing 7a, and the cylindrical portion 2a
And a gas flow path 23 is provided between them, and the inert gas introduced by the external pressure flows therethrough. A plurality of through holes 17 are provided in the radial direction and in the rotation direction on the circumference between the rotating disks of the rotating body 1b. Side), the inert gas passes through the through-holes 17 and the narrow upper and lower gaps (about 0.1 to 0.4 mm) connecting between the gas compression parts, and rotates due to the pressure difference between the inside and outside. It is further pushed out by the pump groove 20 of the body 1b, and finally the exhaust port 14a
And is exhausted to the outside together with the intake gas from above. As described above, the inert gas passes through the shaft sealing portion 5a, flows through the gas passage 23, passes through the through hole 17, and passes through the narrow gap connecting the gas compression portions at a high speed. Accumulation of gaseous reaction products can be prevented.

In this turbo type dry vacuum pump, the rolling bearing 7a has been described as a bearing for the shaft sealing portion 5a, but a dynamic pressure gas bearing or a static pressure gas bearing can also be used. The dynamic pressure gas bearing is a bearing in which a lubricant is pushed into a wedge-shaped bearing clearance by rotation of a shaft, and pressure is generated. Since the shaft 21 rotates at high speed at tens of thousands of rpm, by flowing an inert gas through the shaft sealing portion 5a,
The radial pressure can be supported by the gas pressure generated by the rotation. A hydrostatic gas bearing is a bearing that forcibly supplies a pressurized lubricant from outside the bearing. In this case, a mechanism for forcibly applying an inert gas pressure to the bearing portion is required. These bearings are operated in fluid lubrication,
The load is supported by the pressure generated in the lubricating film. Claim 3
In the rolling bearings 7a and 8a described in (1), a liquid lubricating bearing using the lubricating oil 10 is used, and in the dynamic pressure gas bearing and the static pressure gas bearing according to claims 4 and 5, an inert gas is used. Gas lubricated bearings (gas bearings) are used.

In the above embodiment, the thread groove pump portion 18 is provided on the upper portion. However, the present invention can be applied to a turbo type dry vacuum pump having no thread groove pump portion 18.

[0018]

The turbo-type dry vacuum pump according to the present invention is constructed as described above, and is provided between a plurality of rotating disks having rotating blades, which are provided in a plurality of stages on the outer periphery of a bell-shaped cylindrical shape. A plurality of through-holes are provided in the rotation direction on the circumference of in the radial direction so that the gas flows from the inside to the outside by the rotation. Then, a rolling bearing is used as the bearing, and an inert gas is supplied to the bearing portion from the outside so that lubricating oil for the bearing does not enter the gas compression portion, and the inert gas is provided on a cylindrical inner surface of the rotating body. The gas is flowed through the gas flow path, and the gas is flowed through the above-mentioned through hole at a high speed, so that the gas reaction product can be prevented from being deposited in a narrow gap connecting the gas compression parts. In addition, since the multi-stage circumferential flow pump section can be assembled in a laminated structure, the processing of the gas supply path, the gas flow path, the through hole, and the like of the inert gas can be easily performed.

[Brief description of the drawings]

FIG. 1 is a view showing one embodiment of a turbo type dry vacuum pump of the present invention.

FIG. 2 is a view for explaining a structure of a multistage circumferential flow pump section of the turbo type dry vacuum pump of the present invention.

FIG. 3 is a diagram showing a cross-sectional structure of a conventional turbo-type dry vacuum pump.

[Explanation of symbols]

 1, 1a, 1b ... Rotating body 2, 2a ... Cylindrical part 3, 3a ... High frequency motor 4, 21 ... Shaft 5, 5a ... Shaft sealing part 6 ... Intake port 7, 7a, 8, 8a ... Rolling bearing 9 ... Motor chamber DESCRIPTION OF SYMBOLS 10 ... Lubricating oil 12, 13 ... Case 14, 14a ... Exhaust port 15, 15a ... Gas supply port 16 ... Multistage circular flow pump part 17 ... Through-hole 18 ... Screw groove pump part 19 ... Labyrinth seal 20 ... Pump groove 21 ... Shaft 22: gas supply path 23: gas flow path

Claims (5)

[Claims] 1. A rotating body comprising a multi-stage circumferential pump having a plurality of stages of rotating disks capable of compressing gas by rotation and a shaft connected to a rotor of a high-frequency motor for driving the pump. And a turbo-type dry vacuum pump which is held by a lower bearing and allows gas to be taken in, wherein the rotating body of the multi-stage circumferential flow pump section has a bell-shaped cylindrical shape, and the rotating circle provided in a plurality of stages in the cylinder. A turbo-type dry vacuum pump characterized in that a plurality of through holes are radially provided on the circumference between each of the plates. 2. The direction of a plurality of through holes provided in a cylinder of a rotating body of a multi-stage circumferential flow pump unit is set to be the same direction as the rotating direction of the rotating body, so that the gas flows from the inside to the outside by the rotation. The turbo-type dry vacuum pump according to claim 1, wherein: 3. A rolling bearing is used as a bearing for holding a rotating body, and lubricating oil for the bearing is prevented from being mixed into the gas compression section.
2. The turbo-type dry vacuum pump according to claim 1, further comprising a gas flow path that supplies an inert gas to the bearing portion from the outside, and the inert gas passes through a cylindrical inner surface of the rotating body. 4. A dynamic pressure gas bearing is used as a bearing for holding a rotating body, an inert gas is supplied to the bearing portion from the outside, and a gas flow path through which the inert gas passes through a cylindrical inner surface of the rotating body is provided. The turbo-type dry vacuum pump according to claim 1, wherein: 5. A static pressure gas bearing is used as a bearing for holding a rotating body, an inert gas is supplied from outside to a bearing portion, and the inert gas is provided with a gas flow path passing through a cylindrical inner surface of the rotating body. The turbo-type dry vacuum pump according to claim 1, wherein: