JPH04203564A - Oil seal for vacuum pump - Google Patents

Abstract

PURPOSE:To obtain a clean vacuum pump and contribute to improvement in product yield by arranging a sub lip part on the inner peripheral surface inside of a rotor machine for oil seal so as to extend in the opposite direction, and forming its slidably moving tip of resin having an excellent lubricating ability. CONSTITUTION:At the same time when lubricating oil 14 passed through an oil filler port 2a is supplied to a bearing 10, entrance of the lubricating oil into a rotor machine 15 is prevented by means of oil seal 16. The tip of a main lip 16a seals up the lubricating oil 14 by means of rubber elasticity and tensile force of a coil spring 19 wound round the circumference while contacting slidably with a fellow sleeve 17. A sub lip 16b is arranged as a preparatory measure in case the lubricating oil is leaked from the main lip 16a, and the configuration is formed on the inner peripheral surface inside of the rotor machine so as to extend in the opposite direction to the inside of the rotor machine by considering that the rear side is put in a vacuum atmosphere, and further, the constitution is set in such a way that resin 16c having an excellent lubricating ability such as PTFE or polyimide used widely as dry seal is coated thereon.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an oil seal that is effective in drum vacuum pumps used in semiconductor manufacturing equipment and the like, particularly when the back side of the seal is in a vacuum atmosphere.

[Conventional technology]

In the conventional device, as described in Japanese Utility Model Application Publication No. 63-162168, the dust lip portion extends in the opposite direction to the main lip portion, and the lip is lubricated by grease instead of a drum. That is, when the back side of the seal becomes vacuum, the tension of the dust lip decreases, resulting in a structure in which sealing oil, grease, etc. tend to leak.

[Problem to be solved by the invention]

The above conventional technology does not take into consideration backup measures to prevent oil from leaking into the rotor machine in a vacuum atmosphere in the event that oil leaks from the main lip. There was a problem in that lubricating oil entered the vacuum chamber and contaminated the product.

An object of the present invention is to provide a backup means to absolutely prevent oil from entering the rotor machine even if oil leaks from the main lip.

[Means to solve the problem]

In order to achieve the above object, the present invention installs a sub lip part extending in the opposite direction to the inside of the rotor machine on the inner circumferential surface of the oil seal inside the rotor machine, or on the rear part. The sliding tip of the part is made of resin with good lubricity.

[Effect]

In the conventional dust lip, when the back surface becomes vacuum, the tip of the lip opens in the direction, but in the sub-lip as a backup means of the present invention, the lip extends in the opposite direction to the inside of the rotor machine, which is a vacuum atmosphere. Even if the lubricating oil side of the bearing is at atmospheric pressure, during operation, in addition to the lip elasticity, the tension force increases due to the differential pressure between the vacuum and atmospheric pressure. In addition, with conventional seal shapes, there was a large possibility that grease as a lubricant would be sucked into the vacuum side, but in the present invention, the sliding tip is made of resin with good lubricity instead of a grease pack, so grease can be sucked into the vacuum side. There is no trouble as if it is leaking Vl.

〔Example〕

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

FIG. 4 is a sectional view of a screw type dry vacuum pump embodying the present invention. The screw type rotor 1 only shows one shaft in the figure, but it has two shafts, a male rotor and a female rotor.
It is fixed to a rotating shaft 2 and rotates synchronously with a timing gear 3 in a non-contact manner. Further, another pinion gear 4 mounted on the rotating shaft 2 receives power from the motor 5 and speeds it up by a pull gear 6 and an idle gear 7. In this way, when the rotor 1 rotates, the gas sucked in from the intake port 8 is compressed and transferred by both rotors, and the pressure is increased to atmospheric pressure from the exhaust port 9 and exhausted. .11- is supported. The lower bearing 1] is lubricated by immersion.
The upper shaft ] 0 and the gears 3 , 4 , 6 , and 7 are lubricated by an eccentric pump attached to the lower end of the rotary shaft 2 through an oil supply hole 2 a provided inside the rotary shaft to lubricate the oil tank 13 . This is done by feeding oil 14. An oil seal 16 is installed between the sleeve 17 and the housing 18 in order to prevent this lubricating oil 14 from entering the rotor interior 15 which must be kept clean. In the dry vacuum pump shaft sealing device constructed as described above, if a conventional oil seal as shown in Fig. 3 is used, in the event that oil leaks from the main lip 23a, the grease will be removed. Reservoir 2
4 and the dust lip 231), and there was a possibility that the leaked oil could enter into the rotor machine. That is,
With conventional oil seals, if the back side becomes vacuum,
Since the dust lip 23b extends in the direction where the tension force is weakened, it appears to be in an open state between it and the sleeve, and oil easily leaked out. Further, even when there is no oil leakage from the main lip 23a, the grease sealed between the lips may be sucked out to the vacuum side and scattered, contaminating the vacuum chamber. In any case, with conventional oil seals, there is a problem of oil leakage when the back side is in a vacuum atmosphere.

As described above, the present invention was devised as a backup measure in case oil leaks from the oil seal, and the structure, operation, and effects will be explained next.

A first embodiment of the present invention will be explained with reference to FIG.

This figure is an enlarged view of the vicinity of the oil seal portion in FIG. 4. The upper side of the drawing is the inside of the rotor machine, which is 2500 to 60
A low vacuum atmosphere of 0 cmHg is created. The lower side is the bearing lubricating oil side, and the lubricating oil 14 that has passed through the oil supply hole 2a is transferred to the bearing 1.
At the same time, the oil seal 16 prevents the oil from entering the rotor interior 15. The tip of the main lip 16a of the oil seal seals the lubricating oil 14 while slidingly contacting the mating sleeve 17 due to the elasticity of the rubber and the tension of the coil spring 19 wound around the circumference. However, in the event that the lubricating oil 14 passes through the main lip 16a, if there is no lip that comes into sliding contact after that, the oil will continue to flow into the rotor interior 1.
2, that is, the sub lip 16b that is sucked into the
This is provided as a backup measure in case there is leakage from the main lip 16a. Considering that the back side is in a vacuum atmosphere, the shape of the lip is such that a sub-lip 16b is provided on the inner circumferential surface inside the rotor machine that extends in the opposite direction to the inside of the rotor machine, and there is a possibility of grease leaking between the lips 22. Instead, the sub lip 16b is coated with a resin 16e having good lubricity, such as PTFE or polyimide, which is often used as a dry seal. By adopting such a shape and configuration, even if the rear side of the seal 7 is in a vacuum, the tension force on the sub lip 16b is increased compared to when it is in the atmosphere, making it difficult to leak. 6 Furthermore, the grease itself contains oil. , there is a high possibility that the oil will be sucked into the vacuum side, so in consideration of this, the sub lip]-6
It was decided that the lubrication of b was performed using resins 1 and 6c.

Next, a second embodiment of the present invention is shown in FIG.

While the sub lip in the first embodiment was provided on the inner peripheral surface of the oil seal, in the second embodiment it was provided on the back surface of the oil seal. That is, the lubricating oil 14 leaking from the main lip 20a to the oil seal 20 passes between the lips 21 and is sealed between the sub lip 20b as a backup means and the end surface of the sleeve [7a], preventing oil from entering the vacuum side. is prevented.

The shape of the auxiliary lip was also designed to extend in the inner diameter direction so that the tension on the sealing surface increases when a vacuum is created.

Further, the sliding tip of the sub lip 20b is coated with a resin 20c having good lubricity as in the first embodiment.

〔Effect of the invention〕

According to the present invention, even if oil leaks from the main lip of the oil seal, it is possible to prevent the oil from leaking into the rotor machine with the sub-snow f, making it possible to supply a clean vacuum pump. Therefore, it can contribute to improving product yield.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a shaft sealing part showing an embodiment of the present invention;
Fig. 2 is a vertical cross-sectional view of the shaft sealing part showing the second embodiment; Fig. 3 is a longitudinal cross-sectional view of the shaft sealing part showing the conventional example; and Fig. 4 is a longitudinal cross-sectional view of the shaft sealing part showing the conventional example. FIG. 16.20-oil seal, 16a, 20b-main lip, 16b, 20b-auxiliary lip 1cc.

Claims (1)

[Claims] 1. A screw vacuum pump with a pair of right-handed and left-handed rotors, each rotor supported by a bearing, and an oil seal provided to prevent the bearing lubricating oil from entering the rotor machine. In the shaft sealing device for a pump, a sub lip portion extending in a direction opposite to the inside of the rotor machine is provided on an inner circumferential surface of the oil seal inside the rotor machine, and a sliding tip of the sub lip part is made of resin with good lubricity. An oil seal for a vacuum pump characterized by a