JPH0436091A - Oil-sealed rotary vacuum pump - Google Patents

Abstract

PURPOSE:To prevent an oil-sealed rotary vacuum pump from seizure and so forth during operation under load and from lowering its performance during operation under no load, by connecting a forced oil supply means to a first stage pump chamber by way of a valve adapted to be opened and closed in accordance with a pressure at the suction port the first stage pump chamber. CONSTITUTION:A second stage pump chamber P2 connected thereto with a forced oil feed means 7 is connected to a first pump chamber P1 through a differential pressure oil feed passage 8. The forced oil feed means 7 is connected to the first pump chamber P1 by way of a valve 11 which is adapted to be opened and closed in accordance with a pressure at the suction port 41 of the first pump chamber P1. With this arrangement in which a large volume of oil can be introduced into the first pump chamber 1 from the forced oil feed means 7 during operation under load, the lubrication for the first pump chamber P1 is sufficiently made so as to prevent seizure or the like. Further, since the forced oil feed means 7 is shut off so that the operating mode is shifted into a differential pressure oil feed mode during operation under no load, i is possible of prevent the performance from lowering in a case such as oil being fed after deaeration in order to carry out high vacuum discharge.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a two-stage oil rotary vacuum pump that can be used in various vacuum application fields.

[Prior Art] Oil rotary vacuum pumps often have a pump chamber configured in two stages, as shown in FIG. 2, in order to increase exhaust capacity.

Each pump chamber Pe (P2) is cylinder 1□ (1□)
, rotor 2□ (22) inscribed in the eccentric position of this cylinder z (12), and this rotor 21 (
22), the vane 3 is accommodated in a radially projectable and retractable manner and has its tip slidingly contacted with the inner periphery of the cylinder 11 (12).
□ It is separated by (32). Then, both pump chambers P1 and P2 are filled with pump oil, and the rotor 21.2 is filled with pump oil.
2, the gas taken in from the intake port 41 is first compressed and exhausted in the first stage pump chamber P1, and then,
From the first stage pump house outlet 51 to the second stage via the intermediate communication path 6.
By transferring the gas to the stage pump chamber 4□ and continuing to compress and exhaust it in the second stage pump chamber P2, the well-known pump action of exhausting the gas to the outside through the exhaust port 52 can be performed. It looks like this.

By the way, since the intake port 41 of the first stage pump chamber P1 is connected to the purpose of exhausting a chamber or the like, if oil containing air is supplied to the first pump chamber P1, the air in the oil will have a negative effect on the ultimate pressure of the pump. affect For this reason, there is a restriction that more oil than necessary must not be supplied. Also, this pump chamber P
1, there is also the aspect that if the second stage pump chamber P2 is filled with sufficient pump oil and backed up by this, even if the amount of oil filled is small, there will be no particular problem in the operation of the pump. . For this reason, in the conventional oil supply system, a forced oil supply means 7 consisting of an oil passage 7a''-hydraulic pump 7b, a filter 7C% tank T, etc. is connected to the second stage pump chamber P2 to ensure sufficient oil supply. However, for the first stage pump chamber P1, the oil that has been introduced into the second stage pump chamber P2 and degassed is sent to the differential pressure oil supply path 8.
Only the amount of oil required for lubrication and sealing can be sent into the first stage pump chamber P1 through the pump.

[Problems to be Solved by the Invention] However, with such a configuration, a problem arises in that lubrication is not performed at the beginning of pumping, etc., when a large load is applied to the pump and high lubricity is required.

In other words, conventional differential pressure oil supply aims at the point when exhaust has progressed to a certain extent, and uses the differential pressure between both pump chambers P, 22 to supply an appropriate amount from the second stage pump chamber P2 to the first stage pump chamber P1. It is set so that the oil is supplied. For this reason,
At the beginning of exhaustion when the intake port 4 is at atmospheric pressure or close to atmospheric pressure, the differential pressure between both pump chambers P1.22 is extremely small, and effective differential pressure oil supply cannot be performed. As a result, there is a problem that seizure is likely to occur due to poor lubrication, and there is a high possibility that the pump will be damaged at an early stage.

In addition, the purpose of use is not limited to high vacuum evacuation, but also in situations where a constant load is always applied, such as in semiconductor manufacturing equipment that deposits a film under a constant pressure without allowing reactive gas to flow into the chamber. There are also some that perform exhaust, in which case lubrication is an important factor throughout. Moreover, the gas exhausted from such devices is often condensable (water vapor or reactive gas), and a larger amount of oil must be supplied to prevent deterioration of lubricity.

However, even if the conventional differential pressure oil supply functioned effectively, it would be impossible to supply such an amount of oil; Even if a situation arises that requires refueling, it is impossible to accomplish this.

The present invention aims to effectively solve these problems.

[Means for Solving the Problems] In order to achieve the above object, the present invention takes the following measures.

That is, in the oil rotary vacuum pump according to the present invention, a forced oil supply means is connected to a second stage pump chamber, and the second stage pump chamber is communicated with a first stage pump chamber via a differential pressure oil supply path.
In the step-type oil rotary vacuum pump, the forced oil supply means is connected to the first stage pump chamber via a valve, and the valve is opened and closed according to the level of the intake port pressure of the first stage pump chamber. It is characterized by what it did.

[Function] With this configuration, the valve is opened during load operation with high intake port pressure, and the first stage pump chamber is directly supplied with oil from the forced oil supply means, and the amount of oil is adjusted accordingly. Because it can be set to do not have). Next, when the pressure at the intake port becomes low and the air in the oil approaches a no-load operating condition where it affects the exhaust, the valve closes and the forced lubrication means is cut off. Only the degassed oil is supplied to the first stage pump chamber through the conventional differential pressure oil supply path. For this reason, it becomes possible to suppress the air introduced through refueling to the necessary minimum, and to perform high vacuum evacuation effectively.

[Example] An embodiment of the present invention will be described below with reference to FIG.

Note that parts common to those in FIG. 2 are denoted by the same reference numerals, and their explanations will be omitted.

20 Oil rotary vacuum pump has the above-mentioned configuration.
The stage pump chamber P1 and the forced oil supply means 7 are connected by an oil passage 12 with an electromagnetic valve 11 interposed therebetween, and the valve 11 is connected to a vacuum switch P attached to the intake port 4 of the first pump chamber P1. They are designed to open and close in conjunction with each other. Specifically, when the vacuum switch P does not operate, the valve 11 is kept open, and when the vacuum switch P senses the set pressure and operates, the valve 11 is switched to the closed position. The set pressure is set at such a pressure that the exhaust performance begins to deteriorate due to the air in the oil supplied to the first stage pump chamber P (for example, about ITorr for a pump with an exhaust capacity of 10-'Torr). It is.

With such an oil rotary vacuum pump, the valve 1 is closed while the pressure in the intake port 41 is high during load operation at the beginning of exhaust.
1 is "open", and a large amount of oil is directly supplied to the first stage pump chamber P1 from the forced oil supply means 7. Therefore, insufficient lubrication can be effectively resolved. Next, when the pressure in the intake port 41 falls below the set pressure, the vacuum switch P is activated and the valve 11 is closed, and the second stage pump is supplied to the first stage pump chamber P1 via the conventional differential pressure oil supply path 8. Only the degassed oil is supplied from the chamber P2 to the minimum necessary extent. Therefore, it becomes possible to effectively perform vacuum evacuation at, for example, 10' Torr, which is the ultimate pressure of this pump.

Further, such a configuration can be suitably applied to semiconductor manufacturing equipment and the like. In other words, the pressure of the inlet port 4 connected to the chamber in which gas is constantly flowing does not decrease significantly even when the operation enters a steady state, and the pump is forced to operate under a continuous load. Therefore, if you adjust the set pressure so that the vacuum switch P does not operate,
The valve 11 can be kept in the "open" state from beginning to end,
By continuously introducing a large amount of oil from the forced oil supply means 7 into the first stage pump chamber P1, it becomes possible to maintain a high lubrication function. Of course, such a method can also be effectively used when exhausting condensable gas.

Although one embodiment of the present invention has been described above, the configuration of each part is not limited to the illustrated example, and various modifications can be made without departing from the spirit of the present invention.

[Effects of the Invention] Since the oil rotary vacuum pump of the present invention has the above-described configuration, a large amount of oil can be introduced into the first stage pump chamber from the forced oil supply means during load operation. It is possible to effectively lubricate the chamber and prevent seizure and the like. Therefore, it is possible to effectively improve the reliability of the pump at the beginning of general vacuum evacuation, when evacuating a chamber of semiconductor manufacturing equipment, or when evacuating condensable gas. Additionally, during no-load operation, the forced lubrication means can be shut off and the system can shift to conventional differential pressure lubrication, allowing oil to be pumped in after degassing, which prevents performance deterioration when performing high-vacuum exhaust. be able to.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an embodiment of the present invention, and FIG. 2 is a schematic diagram corresponding to FIG. 1 showing a conventional example.

Claims (1)

[Claims] A two-stage oil rotary vacuum pump in which a forced oil supply means is connected to the second stage pump chamber, and the second stage pump chamber is communicated with the first stage pump chamber via a differential pressure oil supply path.
An oil rotary vacuum pump characterized in that the forced oil supply means is connected to the stage pump chamber via a valve, and the valve is opened and closed depending on the level of the intake port pressure of the first stage pump chamber.