JPH0599176A - Screw type dry vacuum pump - Google Patents

Abstract

PURPOSE:To provide a screw type dry vacuum pump which regulates a seal gas feed amount to a trace amount without lowering performance of a pump. CONSTITUTION:Sealing is effected by a sealing part 16b on the suction side and a sealing part 16a on the delivery side so that oil and grease from a bearing part 15 is prevented from entering a rotor chamber. The shaft sealing part is provided with a screw type dry vacuum pump being of structure where seal gas is fed from a seal gas feed part The pressure of seal gas from the seal gas feed part is regulated to a specified value by a gas pressure regulating means, such as regulator 1. The seal gas is branched through a flow rate regulating valve or a throttle valve 2. The branched seal gas is fed to the shaft sealing part on the delivery side and the other one is further fed to the shaft sealing part on the suction side through a flow rate regulating valve or a throttle valve 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a screw type dry vacuum pump used in a semiconductor manufacturing apparatus or the like.

[0002]

2. Description of the Related Art A screw type dry vacuum pump is a bearing,
A shaft sealing mechanism is provided in order to minimize the intrusion of oil or grease that lubricates the timing gear into the rotor chamber, and a seal gas is supplied to the shaft sealing mechanism. As shown in FIG. 5, this seal gas is adjusted to a constant pressure (positive pressure) by a regulator 101 or the like, and is passed through a flow rate adjusting valve or throttle valves 102 and 103 to a suction side shaft sealing mechanism and a discharge side shaft. Supplying to the sealing mechanism.

[0003]

However, in the conventional screw type dry vacuum pump described above, the flow rate adjusting valve or the throttle valve 1 is adjusted to a constant pressure (positive pressure).
Since it is supplied to each shaft sealing mechanism via 02 and 103, on the suction side, the flow rate control valve or the throttle valve 10
Before and after 3, the pressure ratio was large, and the seal gas was largely expanded and supplied, so that there was a problem that the performance of the pump deteriorates. Moreover, it was difficult to adjust the amount of the seal gas supplied to a very small amount.

The present invention has been made in view of the above points, and an object thereof is to provide a screw type dry vacuum pump capable of adjusting a seal gas supply amount to a minute amount without deteriorating the performance of the pump. To do.

[0005]

In order to solve the above problems, the present invention comprises a pair of a male rotor and a female rotor that rotate in mesh with each other in a rotor chamber of a casing, and a fluid sucked from a casing suction port is rotated by the male rotor. It is configured so that it is sucked into the tooth space formed by the female rotor and the female rotor and discharged from the casing outlet, and the oil and grease from the bearing and other parts enter the rotor chamber by the shaft seal on the suction side and the shaft seal on the discharge side. In a screw type dry vacuum pump having a structure that is sealed so as not to enter and a seal gas is supplied to the shaft seal portion from a seal gas supply portion, as shown in FIG. 1, the seal gas from the seal gas supply portion is regulated by a regulator. The pressure is adjusted to a constant pressure by a gas pressure adjusting means such as 1, and then branched via a flow rate adjusting valve or a throttle valve 2, one of which is supplied to the discharge side shaft seal portion, Cormorants One and supplying to the shaft sealing portion of the suction side further through the flow control valve or throttle valve 3.

[0006]

The seal gas adjusted to a constant pressure as described above is branched after passing through the flow rate control valve or the throttle valve 2, one of which is supplied to the shaft seal portion on the discharge side, and the other is further supplied to the flow rate control valve or Since it is supplied to the shaft seal portion on the suction side via the throttle valve 3, the flow rate control valve or the throttle valves 2 and 3 of 2 on the suction side.
It becomes a step adjustment, the pressure ratio is small before and after the flow rate control valve or the throttle valve 3, the seal gas does not greatly expand, and the performance of the pump does not deteriorate.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an outline of a seal gas supply system used in the screw type dry vacuum pump of the present invention. This seal gas supply system regulates the seal gas from the seal gas supply unit to a constant pressure by a regulator 1, and further branches it through a flow rate control valve or a throttle valve 2, one of which supplies the discharge side shaft sealing mechanism. On the other hand, the other is further supplied to the suction side shaft sealing mechanism via the flow rate adjusting valve or the throttle valve 3.

FIG. 2 is a side sectional view showing the structure of the screw type dry vacuum pump of the present invention. This screw type dry vacuum pump has a main casing 11 and a discharge casing 12.
In the space formed by and, the male rotor 17a and the female rotor 1
7b are rotatably supported by bearings 15a and 15b, respectively, and the bearing 15 is supported by shaft sealing mechanisms 16a and 16b.
It is sealed from the lubricating oils a and 15b.

The shaft of the male rotor 17a is directly connected to the shaft of the electric motor 22, and the female rotor 17b is rotated by the timing gears 20, 20 with a slight gap from the male rotor 17a.

The gas sucked from the suction port 18a passes through the suction port 18b and is sucked into the tooth space formed by the inner wall of the rotor of the main casing 11 and the male and female rotors 17a and 17b. The liquid is discharged from the discharge port 19a via 19b. Reference numeral 13 in the figure is a gear cover, and 14 is an electric motor casing.

1 is branched through the flow control valve or throttle valve 2 of the seal gas supply system of FIG.
It is supplied to the shaft sealing mechanism 16a on the discharge side of the screw type dry vacuum pump having the structure shown in (1) and further supplied to the shaft sealing mechanism 16b on the suction side through the flow rate control valve or the throttle valve 3.

FIG. 3 is a diagram showing a schematic structure of a shaft sealing mechanism to which a sealing gas is supplied. In the figure, the schematic structure of the shaft sealing mechanism 16b on the suction side is shown. As shown in the drawing, the shaft seal member 16b1 is provided around the shaft 17c of the male rotor 17a.
16b2 and 16b3 are provided, and the male rotor 17a
Through the seal gas supply hole 11a provided in the casing 11 between the side shaft seal members 16b1 and 16b2,
The seal gas that has passed through the flow control valve or the throttle valve 3 in FIG. 1 is supplied. This prevents the lubricating oil of the bearing 15 from entering the rotor chamber. In addition, 22 is a bearing 15
It is an oil drain chamber that stores the lubricating oil that intrudes from.

The structure of the suction side shaft sealing mechanism of the female rotor 17b and the discharge side shaft sealing mechanism 16a of the male and female rotors is also shown in FIG.
Since it is almost the same as the above, its illustration and description are omitted.

FIG. 4 is a diagram showing a schematic structure of a seal gas supply system in the case where the screw type dry vacuum pump has a multi-stage (two stages in the figure) structure. The present seal gas supply system regulates the seal gas from the seal gas supply unit to a constant pressure by the regulator 1, and further branches it through the flow rate control valve or the throttle valve 2, one of which is on the discharge side of the first stage pump. The shaft sealing mechanism on the suction side of the first-stage pump is further supplied via the flow rate adjusting valve or the throttle valve 3. Further, the seal gas that has passed through the flow rate control valve or throttle valve 2 is branched via the flow rate control valve or throttle valve 4, one of which is supplied to the shaft sealing mechanism on the discharge side of the second stage pump, and the other is further supplied. It is supplied to the suction side shaft sealing mechanism of the first stage pump via a flow rate adjusting valve or a throttle valve 5.

In FIG. 4, the mounting position of the flow rate control valve or throttle valve 3 is the flow rate control valve or throttle valve 2
It may be inserted in series between 4 and 4.

Even if the vacuum pump has multiple stages, by constructing the seal gas supply system as shown in FIG. 4, the pressure ratio is large on the suction side before and after the flow rate control valve or the throttle valve, and the seal gas expands greatly. The performance of the pump does not deteriorate.

[0017]

As described above, according to the present invention, the seal gas adjusted to a constant pressure is branched after passing through the flow rate adjusting valve or the throttle valve, and one is supplied to the shaft seal portion on the discharge side. The other one is further supplied to the shaft seal portion on the suction side via the flow rate control valve or throttle valve, so that the suction side has two stages of adjustment of the flow rate control valve or throttle valve, and the pressure control valve before or after the flow rate control valve 3 Since the ratio is small and the seal gas does not greatly expand, the excellent effect that the performance of the pump is not deteriorated is obtained.

[Brief description of drawings]

FIG. 1 is a diagram showing an outline of a seal gas supply system used in a screw type dry vacuum pump of the present invention.

FIG. 2 is a side sectional view showing the structure of the screw type dry vacuum pump of the present invention.

FIG. 3 is a diagram showing a schematic structure of a shaft sealing mechanism to which a seal gas is supplied.

FIG. 4 is a diagram showing a schematic configuration of a seal gas supply system when the screw type dry vacuum pump has a multi-stage (two stages in the figure) configuration.

FIG. 5 is a diagram showing an outline of a seal gas supply system used in a conventional screw type dry vacuum pump.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 regulator 2 flow control valve or throttle valve 3 flow control valve or throttle valve 4 flow control valve or throttle valve 5 flow control valve or throttle valve 11 main casing 12 discharge casing 13 gear cover 14 electric motor casing 15a bearing 15b bearing 16a shaft seal mechanism 16b Shaft sealing mechanism 17a Male rotor 17b Female rotor 18a Suction port 18b Suction port 19a Discharge port 19b Discharge port 20 Timing gear 22 Electric motor

Claims (1)

[Claims] 1. A casing comprising a pair of male rotor and female rotor which rotate in mesh with each other in a rotor chamber of the casing, and sucks fluid sucked from a casing suction port into a tooth space formed by the male rotor and the female rotor. It is configured to discharge from the discharge port, and is sealed by the suction side shaft seal portion and the discharge side shaft seal portion so that oil and grease from the bearing portion and the like do not enter the rotor chamber, and the shaft seal portion is In a screw type dry vacuum pump having a structure for supplying a seal gas from a seal gas supply unit, the seal gas from the seal gas supply unit is adjusted to a constant pressure by a gas pressure adjusting means, and then a flow control valve or a throttle valve is used. While branching, one is supplied to the discharge side shaft seal portion, and the other is supplied to the suction side shaft seal portion via a flow rate control valve or a throttle valve. Screw-type dry vacuum pump to butterflies.