JP3386202B2 - Two-stage oil rotary vacuum pump - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-stage oil rotary vacuum pump, and more particularly to a two-stage oil rotary vacuum pump having an improved cooling method. 2. Description of the Related Art Oil rotary vacuum pumps capable of rotating a rotor in a cylinder to discharge a volume while releasing lubrication and sealing with oil and discharging the volume to the atmosphere are simple and widely used. Among them, a two-stage type in which two pumps are connected in series has a high compression ratio and a high degree of ultimate vacuum, and is therefore commonly used in various fields. FIG. 4 shows a cross-sectional view of a typical two-stage oil rotary vacuum pump, and FIG. 5 shows a vertical cross-sectional view thereof. As shown in FIG. 4, the first-stage pump 10 having a large volume and the second-stage pump 20 having a small volume include the front cover 2, the intermediate plate 3,
It is sandwiched between the rear covers 4, connected in series with the same main shaft 5, and almost immersed in oil inside the pump case 21. A cooling fan 7 is attached to the main shaft 5 coming out of the front cover 2.
Is connected to a motor 9 via a coupling 8. FIG. 5 shows a cross section of the first stage pump 10.
It generally comprises a cylinder 12 and a rotor 14 which is rotated in an eccentric position within it. The rotor 14 has the two vanes 15 projecting in the opposite direction by an internal coil spring. When the rotor 14 is rotated clockwise in FIG. Slides on the inner wall of the air intake port 11 to inhale and compress the gas from the intake port 11,
It functions as a pump by discharging to The principle of this evacuation is the same for the second stage pump 20. The pump 20 includes a rotor 24 having vanes 25 and a cylinder 22.
And the exhaust port 16 of the first-stage pump 10 is connected to an intake port (not shown) of the second-stage pump 20. While the rotor 14 is rotating, oil in the pump case 21 is supplied and circulated for lubrication and sealing of the sliding portion. This oil passes through an oil feed pump, that is, the inside of the rear cover 4. A small oil feed pump (not shown) having the main shaft 5 as a drive shaft is provided at a rear end of the main shaft 5 through a path (not shown) from the cylinder 22 of the second-stage pump 20 through the center plate 3. It is sent to the cylinder 12 of the single-stage pump 10. The above is a typical example of the two-stage oil rotary vacuum pump. As is well known, the ultimate pressure of the oil rotary vacuum pump is determined by the vapor pressure of the oil used, and during operation of the pump, As the temperature rises, the ultimate pressure rises, so cooling of the oil, especially of the oil in the cylinder, which is directly related to the ultimate pressure, i.e. the cooling of the cylinder, has a very important significance, and as described above Has a cooling fan installed. [0007] From the standpoint of cooling the cylinder, the assembling structure of the above-described two-stage oil rotary vacuum pump of the representative example will be described first.
FIG. 2 shows a conventional example. That is, the cooling fan 7 is attached to the main shaft 5 connected to the motor 9, and the first-stage pump 10 and the second-stage pump 20 are connected by using the main shaft 5 in common. (Not shown), the cylinders 12 and 22 are arranged in the case 21 so as to be almost immersed in the oil o. A large number of fins 26 are provided on the outer periphery of the pump case 21.
Is provided. To explain the operation of the first conventional example, when the motor 9 is rotated, the wind generated by the cooling fan 7 attached to the main shaft 5 causes the fins 2 of the pump case 21 to rotate.
The oil flows in the pump case 12 and the oil contained therein by flowing along the arrow 6 as shown by the arrow, and the first cylinder 12 and the second cylinder 22 are indirectly cooled by the cooled oil. Since the cooling efficiency of the indirect cooling using oil is low, both the first cylinder 12 and the second cylinder 22 are kept at a relatively high temperature. The high temperature of each cylinder 12, 22 means that the oil for lubrication and sealing existing inside them is in a state of high vapor pressure, thereby limiting the ultimate pressure. In particular, the high vapor pressure of the oil in the first cylinder 12 causes a reverse flow of oil vapor to the container to be evacuated (so-called vapor back) and contaminates the container to be evacuated. Since the circulating oil amount is small at the farthest position, there is a problem that the oil film is apt to be broken, and sometimes the first stage pump 10 is seized. Above all, contamination of the container to be evacuated is a fatal defect when used in a semiconductor production line that requires high purity. As a countermeasure for this, there is a second prior art two-stage oil rotary vacuum pump using a direct air cooling system, and its assembling structure is shown in FIG. The first stage pump 10 and the second stage pump 20 directly connect the common main shaft 5 to the motor 9, and the cooling fan 7 is attached to the main shaft 5 as in the first conventional example. , Each stage pump 1
First cylinder 12 and second cylinder 2 constituting 0, 20
2 are in direct contact with the atmosphere, and fins 33 are provided on their surfaces. The entire periphery is covered with a side panel 34 as a structure with a gap (atmosphere) therebetween. An oil tank 35 is provided integrally with a part of the side panel 34, and the oil o stored therein is supplied and circulated to each of the cylinders 12 and 22 by an oil feed pump. The operation of the second conventional example will be described.
The wind generated by the cooling fan 7 due to the rotation of the first and second cylinders 12 and 22 flows along the fins 33 between the surfaces of the first and second cylinders 12 and 22 and the side panel 34 as shown by arrows, so that the cylinders 12 and 22 are directly connected to each other. Is cooled. When air is directly cooled in this manner, the first cylinder 12 and the second cylinder 22 are both kept at a relatively low temperature, and the oil present in each of the cylinders 12 and 22 is kept at a low vapor pressure. It is. In this respect, unlike the first conventional example, the ultimate pressure is reduced, and the vapor back and the breakage of the oil film of the lubricating oil are also suppressed. It has the disadvantage that gas liquefaction is large. That is, when the condensable gas (for example, water vapor) is liquefied and mixed into the oil, the pumping performance represented by the ultimate pressure and the pumping speed is reduced, and the lubricity and rust prevention of the oil are also reduced. Therefore, it is necessary to disassemble and maintain the pump within a short period of time. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to prevent mechanical seizure due to a vapor back or oil film shortage and also prevent liquefaction of condensable gas. It is an object of the present invention to provide a two-stage oil rotary vacuum pump that can perform the above. [0014] The object of the present invention is to solve the above problems.
A first stage pump connected to the container side, and the first stage pump
The second that inhales the gas exhausted from the pump and releases it to the atmosphere
Two-stage oil rotary vacuum pump having a two-stage pump
Te, the cylinder of the first stage of the pump is your contact with the atmosphere
And is directly cooled by air, and is cooled by the cylinder of the second stage pump.
And the cylinder of the second stage pump is
Immersed and cooled indirectly through the oil
This is achieved by a two-stage oil rotary vacuum pump characterized in that the temperature is higher than the cylinder of the first stage pump . Since the cylinder of the first-stage pump on the side of the container to be evacuated, that is, on the high vacuum side, is directly air-cooled, it is indirectly oil-cooled.
It is kept at a lower temperature than the cylinder of the second stage pump, and it is possible to prevent vapor back and oil film shortage of the cylinder,
Since the cylinder of the second-stage pump on the low vacuum side is indirectly oil-cooled, the cylinder of the first-stage pump directly cooled by air is used.
Is also kept at a high temperature, and liquefaction of the condensable gas can be prevented. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A two-stage oil rotary vacuum pump according to an embodiment of the present invention will be described below with reference to the drawings, particularly from the standpoint of cooling a cylinder. That is, FIG. 1 shows an embodiment 2 of the present invention.
It is a figure which shows the assembly structure of a step type oil rotary vacuum pump. The first-stage pump 10 and the second-stage pump 20 are connected in series, and are directly connected to the motor 9 by the common main shaft 5 (the pumps 10 and 20 are not shown). The first cylinder 1 which is the cylinder of the first stage pump 10
2 has a fin 43 on its surface and is in contact with the atmosphere, and its periphery is covered by a side panel 44 also serving as a structure with a gap (atmosphere). A second cylinder 22, which is a cylinder of the second stage pump 20, is disposed in a pump case 41, and most of the second cylinder 22 is immersed in oil o.
A large number of fins 46 are provided on the outer periphery of one. First
The cooling fan 7 is attached to the main shaft 5 directly connecting the second-stage pump 10 and the second-stage pump 20 to the motor 9 as in the first conventional example and the second conventional example. The operation of the present embodiment will be described below. The wind generated by the cooling fan 7 mounted on the main shaft 5 when the motor 9 is rotated is as shown by the arrow in FIG.
First, after flowing between the first cylinder 12 and the side panel 44 along the fins 43 to directly air-cool the first cylinder 12, the outer periphery of the pump case 41 in which the second cylinder 22 is immersed in oil o The oil flows along the fins 46 provided to cool the pump case 41 and the oil o stored therein, and the cooled oil o cools the second cylinder 22. That is, the wind from the cooling fan 7 indirectly cools the second cylinder 22 via the oil o. According to the two-stage oil rotary vacuum pump of this embodiment, the oil vapor pressure is kept low in order to prevent reverse flow (vapor back) of oil vapor to the container to be evacuated and also to prevent oil film shortage. In other words, the first cylinder 12 whose oil temperature is to be kept low is kept relatively low and the second cylinder 2 whose temperature is kept high to prevent liquefaction of condensable gas.
2 can be kept relatively high and their temperature difference can be as high as 20-30 ° C. The effect is, for example, that the vapor pressure of the oil in the first cylinder 12 can be reduced by one to two digits compared to the case of the first conventional example.
Liquefaction of the condensable gas is small as in the first conventional example. Although the embodiments of the present invention have been described above, the present invention is, of course, not limited thereto, and various modifications can be made based on the technical concept of the present invention. For example, in the embodiment, the first-stage pump 10 and the second-stage pump 20 are directly connected, and the common main shaft 5 is directly connected to the motor 9 for operation. Pumps are independently installed and operated, and the exhaust port of the first stage pump 10 is connected to the second stage pump 20.
May be connected to the intake port. In the embodiment, the oil feed pump is provided at the end of the main shaft 5, but may be provided at another location. In that case, the driving force is transmitted from the main shaft to the oil feed pump. In the embodiment, the pump 1 of each stage is used.
Although the motor 9 is directly connected to the main shaft 5 that drives 0 and 20 by the coupling 8, the transmission may be performed by a belt instead of the coupling 8. Further, in the embodiment, the rotary vane type oil rotary vacuum pump is adopted, but the technical idea of the present invention can be applied to a cam type and a oscillating piston type two-stage oil rotary vacuum pump. . As described above, according to the two-stage oil rotary vacuum pump of the present invention, the cylinder of the second-stage pump is connected to the cylinder of the second-stage pump.
In comparison, the first stage pump cylinder, whose temperature is to be cooled lower, can be kept at a low temperature, preventing vapor back and running out of oil film in the cylinder, preventing contamination of the container to be exhausted and mechanical seizure of the pump. it can be, and the first
Cooling to a higher temperature compared to a single-stage pump cylinder
Since the temperature of the cylinder of the second stage pump can be kept high and the liquefaction of the condensable gas can be prevented, the interval of the disassembly and maintenance due to the decrease in the pumping performance of the pump can be prolonged. In addition, when replenishing oil, there is also an effect of removing water contained in the new oil.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic sectional view showing an assembly structure of a two-stage oil rotary vacuum pump according to an embodiment of the present invention. FIG. 2 is a schematic sectional view showing an assembling structure of a two-stage oil rotary vacuum pump of a first conventional example which is indirectly oil-cooled. FIG. 3 is a schematic sectional view showing an assembly structure of a two-stage oil rotary vacuum pump of a second conventional example which is directly cooled by air. FIG. 4 is a cross-sectional view of a typical indirect oil-cooled two-stage oil rotary vacuum pump. FIG. 5 shows a vertical cross section of the pump, [5]-of FIG.
[5] FIG. 5 is a cross-sectional view in the line direction. [Description of Signs] 7 Cooling fan 9 Motor 12 First cylinder 22 Second cylinder 41 Pump case o Oil

Continuation of the front page (72) Inventor Shunichi Tateno 3313 Ueno, Yokokawa-cho, Aira-gun, Kagoshima Prefecture Inside Albac Seiki Co., Ltd. (56) References JP-A-3-279683 (JP, A) JP-A-61-87991 ( JP, A) JP-A-60-212687 (JP, A) JP-A-55-123389 (JP, A) Actually open Showa 49-142608 (JP, U) Actually open Showa 53-39807 (JP, U) Actually open 1980 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) F04C 23/00-29/10

Claims (1)

(57) [Claim 1] The first stage pump connected to the container to be evacuated
And the gas exhausted from the first stage pump
Two-stage oil circuit having a second-stage pump discharging to the atmosphere
In the rotary vacuum pump, the cylinder of the first stage pump is in contact with the atmosphere,
Air-cooled and lower than the cylinder of the second stage pump
And the second stage pump cylinder is immersed in oil,
Indirectly cooled through the oil, the first stage pump
A two-stage oil rotary vacuum pump characterized in that the temperature is higher than that of the cylinder .