JPH02146291A - Vacuum pump - Google Patents

Abstract

PURPOSE:To prevent the adhesion of a reaction product and suppress the temperature rise of a bearing by boring a shaft seal gas passage from a stator outer wall to the inside of the wall such as to guide the shaft seal gas supplied in a space part into the stator wall and communicating the shaft seal gas passage with a discharge opening part. CONSTITUTION:The temperature of N2 gas which entered a space part 12 rises at the space part 12 by heat absorption, becomes even higher by letting the N2 gas pass through a shaft seal gas passage 13 via a stator wall part, and the N2 gas is then exhausted from a discharge port part 2a and a discharge opening 2. Accordingly, the exhausted gas, the N2 gas which passes through the shaft seal part 9a and the high temperature gas which passed through the stator wall are collected at the discharge port part 2a and exhausted from the discharge opening 2. As a result, a pump passage, the discharge port part 2a and the discharge opening 2 are prevented from the adhesion of a reaction product by the effect of temperature rise for adding the high temperature N2 gas. In addition, as the shaft seal reaching the bearing part has normal temperature, the temperature of the bearings 7a, 7b is prevented from rising.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a vacuum pump, which operates its discharge port at atmospheric pressure, and is particularly suitable for exhausting corrosive gas that tends to accumulate. It is related to.

[Conventional technology]

Conventional dry vacuum pumps do not use oil in the pump flow path through which corrosive gases and reactive products sucked in from the intake port pass, so they have the excellent feature of being maintenance-free with little oil deterioration. . However, since it is necessary to supply lubricating oil to the bearings that support the rotor, it is necessary to prevent this lubricating oil or its oil vapor from entering the pump flow path, and to prevent the gas passing through the pump flow path from entering the bearing. Special consideration had to be given to the shaft seal to prevent it from flowing into the shaft.

A vacuum pump that takes this type of shaft seal into consideration is 1.
For example, a technique described in Japanese Unexamined Patent Publication No. 153597/1982 is known, and its outline will be explained with reference to FIG. 3.

FIG. 3 is a longitudinal sectional view of a conventional vacuum pump.

Pump mechanism section 6 composed of rotor 4 and stator 5
Pump flow path section and oil-lubricated bearing (hereinafter simply referred to as bearing) 7
to the shaft sealing portion 9a located between the

A shaft sealing gas supply port 9 is provided for supplying shaft sealing gas from outside the vacuum pump, and this shaft sealing gas is configured to flow separately to both the pump flow path side and the bearing 7a side.

Therefore, the gas passing through the pump flow path portion does not come into contact with the bearing lubricating oil.

In this prior art, a part of the shaft sealing gas that has flowed into the pump flow path is mixed with the gas sucked in from the intake port 1 and is exhausted from the discharge port 2. On the other hand, the shaft sealing gas that has flowed into the bearing 7a side is exhausted from an exhaust port provided in the lower casing 3b.

[Problem to be solved by the invention]

The shaft sealing mechanism using shaft sealing gas of the above-mentioned prior art exhibits its function sufficiently when handling clean gas. but,
If the suction gas contains substances that tend to adhere to and accumulate on the wall surface of the flow path, the products will accumulate in the pump flow path and impede the flow.

If the pump flow path is clogged, the rotor may become locked or the pressure balance may be disrupted, causing problems such as lubricating oil flowing out from the shaft seal into the pump flow path.

The present invention provides l! ! This was developed to solve the problem, and even if the gas passing through the pump flow path contains substances that tend to accumulate, it can be easily removed from the pump flow path or the discharge port without adding any external equipment. It is an object of the present invention to provide a vacuum pump which prevents the deposition of reactive products in a vacuum pump.

[Means to solve the problem]

In order to achieve the above object, the configuration of the vacuum pump according to the present invention includes a casing having an intake port and a discharge port.
A pump mechanism section that forms a pump flow path with a stator and a rotor, an electric motor section that drives the rotor, and an oil-lubricated bearing that is located below the pump mechanism section and supports the electric motor section, are housed outside the vacuum pump. a shaft sealing gas system that supplies shaft sealing gas from the shaft sealing gas, and a shaft sealing portion of the shaft sealing gas system located between the pump flow path and the oil-lubricated bearing, and the gas sucked from the intake port In a vacuum pump that is evacuated to the atmosphere from a discharge port, a shaft sealing gas system from outside the vacuum pump is branched, and one end is connected to a space formed by the casing and the stator, and the shaft sealing gas system is connected to the space formed by the casing and the stator. In order to conduct the shaft sealing gas supplied to the stator wall into the stator wall, a shaft sealing gas flow passage is bored in the stator outer wall and communicated with the discharge port.

As an additional note, the above purpose is to inject a portion of the shaft sealing gas into the outer wall and inside of the stator section, which is heated by the compression action of the pump, and then discharge the shaft sealing gas heated to a high temperature to the discharge port. This is achieved by preventing a rapid temperature drop in the pump flow path.

[Effect]

The movements based on the above technical means are as follows.

For example, in semiconductor manufacturing equipment, when a gas exiting a processing chamber is evacuated, it is necessary to raise the temperature according to the vapor pressure of the gas, and if this operation is not performed, the gas will transform into a solid. In particular, since there is no heat generating part in the atmospheric pressure discharge part, the gas temperature cools down and transforms into a solid, causing it to adhere and deposit on the wall surface.

Vacuum pumps that discharge to the atmosphere generate a large amount of heat due to the compression action. At this time, the temperature of the stator outer wall is 130 to 17
The temperature is around 0℃.

Therefore, a part of the shaft sealing gas is branched into the space formed by the casing and the outer wall of the stator, where it freezes, absorbs heat with the gas, and transfers the shaft sealing gas from the outside of the stator to the shaft sealing gas drilled into the wall. It flows into the discharge port through the flow path. The temperature of the shaft sealing gas further increases while passing through the stator wall, which is at a higher temperature, and the temperature of the discharge port portion is not cooled by the gas. Therefore, it is possible to prevent one reactive product from adhering to the pump channel or the discharge port.

〔Example〕

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

FIG. 1 is a longitudinal sectional view of a vacuum pump according to an embodiment of the present invention, and FIG. 2 is a line flow diagram showing the flow of shaft sealing gas in the vacuum pump of FIG.

In FIG. 1, 1 is an intake port, 2 is a discharge port, and 3 is a casing. 4 is a rotor, 5 is a stator, and these stator 4 and rotor 5 face each other to form a pump flow path,
A pump mechanism section 6 is configured.

7 (generic name for 7a and 7b) is a rotating body part casing 3
7a is a ball bearing (hereinafter simply referred to as a bearing) related to an oil-lubricated bearing supported on the motor section 8,
b is the lower bearing. 8a is a rotor, 8b is a stator, and these constitute the electric motor section 8. 10 is a rotating shaft to which the rotor 8a of the electric motor section 8 and the rotor 4 of the pump mechanism section 6 are each integrally attached.

9 is a shaft sealing gas supply port provided in the casing 3 and connected to a line for supplying shaft sealing gas from outside the vacuum pump, and 9a is a shaft sealing portion. Further, 11 is a gas supply port provided in the upper casing 3a, and 12 is a space formed by the upper casing 3a and the outer periphery of the stator 5. The shaft sealing gas flows into the space 12 through. Furthermore, 13
13a is a shaft sealing gas flow passage bored in the wall of the stator 5;
is a gas supply port that opens in the outer wall of the stator 5 and communicates with the shaft sealing gas flow passage 13, and the shaft sealing gas flow passage 13 communicates with the discharge port portion 2a.

The discharge port section is composed of a discharge port boat section 2a and a discharge port 2.

To explain it more systematically, as shown in Figure 1.

Inside the casing 3 having an intake port 1 and a discharge port 2, there is a pump mechanism section 6 consisting of a rotor 4 supported by a bearing 7 and driven by an electric motor section 8, and a stator 5 provided opposite to the rotor 4. be.

Gas sucked in from the intake port 1 passes through the pump channel of the pump mechanism 6, passes through the discharge port 2a and the discharge port 2, and is exhausted to the atmosphere. Although not shown in the figure, the shaft sealing gas line that supplies shaft sealing gas from outside the vacuum pump is branched in front of the vacuum pump, and one line runs from the shaft sealing gas supply port 9 to the shaft sealing portion 9a.
Shaft sealing gas is supplied to the upper casing 3a, and shaft sealing gas is poured into the space 12 through the gas supply port 11 provided in the upper casing 3a.

Gas supply port 13a provided on the outer wall of stator 5, stator 5
The gas is exhausted from the discharge port portion 2a and the discharge port 2 through the shaft sealing gas flow passage 13 penetrating the inside of the wall.

The effect will be explained by operating the kiln in Fig. 2.

FIG. 2 shows an N2 gas line using nitrogen Nz as a shaft sealing gas. The symbols in FIG. 1 correspond to the symbols in FIG. 1. This shows the state of the gas: the normal temperature Nz gas related to the shaft sealing gas is supplied to the shaft sealing part 9a before the vacuum pump, and the other is supplied to the space 12 between the upper casing and the outer circumference of the stator. It is branched into.

The NZ gas supplied to the shaft sealing section 9a is divided into the bearing 7a and the pump mechanism section 6, and the gas that has entered the pump mechanism section 6 is
together with the gas sucked in from the intake port 1, the discharge port portion 2a;
The gas is exhausted to the discharge section formed by the discharge port 2, and the gas that has entered the bearing section 7a is exhausted from the lower casing 3b. The N2 gas used here is at room temperature when it reaches the bearing section, and at a slightly higher temperature when it reaches the discharge port.

On the other hand, the N2 gas that has entered the space 12
The temperature rises due to heat absorption, and when the gas passes through the shaft sealing gas flow passage 13 in the stator wall, the temperature becomes even higher and is exhausted to the discharge port section consisting of the discharge port section 2a and the discharge port section 2.

Therefore, the exhaust gas, the N2 gas that has passed through the shaft seal, and the high-temperature gas that has passed through the stator wall gather in the discharge port 2a and are exhausted from the discharge port 2.

In the conventional method, the exhaust gas and the gas passing through the shaft seal are mixed, so the effect of increasing the temperature of the exhaust gas is small, but the method of this example has a temperature increasing effect by adding high-temperature Nz. It's coming. Therefore, the pump flow path or discharge port portion 2a
, it is possible to prevent reactive products from adhering to the discharge port 2.

In addition, since the shaft sealing gas that reaches the bearing part is at room temperature,
The temperature of the bearing also does not rise.

According to this embodiment, the following effects are achieved.

1) Adhesion of reactive products can be prevented by increasing the gas temperature at the discharge port.

2) Although the gas temperature at the discharge port is increased, the temperature of the bearing does not rise because the gas supplied to the bearing is at room temperature.

3) Since the structure is simple and it is possible to prevent the adhesion of reactive products, the overall cost can be reduced.

〔Effect of the invention〕

As described above, according to the present invention, even if the gas passing through the pump flow path contains substances that tend to accumulate, it is possible to do so without adding an external device.

It is possible to provide a vacuum pump that prevents the deposition of reactive products in the pump flow path section or discharge section.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal cross-sectional view of a vacuum pump according to an embodiment of the present invention, FIG. 2 is a line flow diagram showing the flow of shaft sealing gas in the vacuum pump of FIG. 1, and FIG. 3 is a conventional vacuum pump. FIG. 3 is a longitudinal cross-sectional view of the vacuum pump. 1...Intake port, 2...Discharge 0.2a 3...Casing, 4...Rotor,...Pump mechanism section, 7.7a, 7 Motivation section, 9...Shaft sealing gas supply port , 11.13a... Gas supply port, 1... Shaft sealing gas flow path. ...Discharge boat section. 5... Stator, 6 b... Bearing, 8... Electric 9a... Shaft sealing part, 2... Space part, 13th /i 2nd concave↑

Claims (1)

[Claims] 1. A pump mechanism section that forms a pump flow path with a stator and a rotor in a casing having an intake port and a discharge port, an electric motor section that drives the rotor, and a motor section that is located below the pump mechanism section. a shaft sealing gas system that houses the supporting oil-lubricated bearing and supplies shaft sealing gas from outside the vacuum pump; and a shaft sealing part of the shaft sealing gas system that is located between the pump flow path and the oil-lubricated bearing. In the vacuum pump, in which gas sucked in from the intake port is exhausted to the atmosphere from the discharge port, a shaft sealing gas system from outside the vacuum pump is branched, and one of the systems is connected to the casing and the stator. A discharge port is connected to the space formed by drilling a shaft sealing gas flow path from the outer wall of the stator into the wall so as to conduct the shaft sealing gas supplied to the space into the stator wall. A vacuum pump characterized by being connected to.