JPH0295792A - Multistage root's-type vacuum pump - Google Patents

Abstract

PURPOSE:To perform the discharge of condensate continuously in a stable manner by setting up a peripheral gas passage and a cooling water passage, interconnecting a multi-stage pump section with each other, in an outer circumferential part of a housing with a built-in Root's-type rotor in order. CONSTITUTION:In a first pump section 1, suction gas G81 is inhaled out of each of suction ports 81, 13 and, after being transferred and compressed by an illustrated rotor, it is discharged to a peripheral gas passage 15A from a discharge port 14. At this time, this discharged gas is cooled by an outer wall of this peripheral gas passage 15A cooled by cooling water flowing in a cooling water passage 400. A part of condensed gas being contained in this discharged gas is guided into a suction port 23 of a second pump section 2 together with noncondensable gas. Even in this second pump section 2 and a third pump section 3, the same action as the first pump section 1 takes place. In addition, finally the discharge gas is guided in a gas-liquid separator 9 from each of discharge ports 34, 82, and then the noncondensable gas and condensate both are discharged out of an exhaust port 92 and a drain port 93.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention is applicable to suction of condensable gases such as water vapor in food drying equipment, methanol and hexane in pharmaceutical manufacturing equipment, and carbon tetrachloride in semiconductor manufacturing equipment. This invention relates to a multi-stage Roots-type vacuum pump. In the present invention, the suction pressure is
It can be applied to multistage Roots-type vacuum pumps that operate at high compression ratios in the range from atmospheric pressure to to-3 Torr level and suck condensable gases or gases that partially contain cE condensable gases. can.

[Prior art and problems to be solved by the invention] Generally, a part or all of the suction gas is a condensable gas, such as vacuum drying equipment for food drying, vacuum distillation equipment for pharmaceutical manufacturing equipment, and vacuum for semiconductor manufacturing equipment. When an oil rotary vacuum pump is used as a vacuum source machine for evaporation equipment, etc., condensate gets mixed into the sealing oil, causing significant deterioration of the sealing oil, making long-term continuous operation difficult, and it is difficult to extract only the condensate. Can not. Furthermore, when a water ring type vacuum pump is used, condensate gets mixed into the seal water used and is discharged together with the seal water, making it difficult to recover the condensate and also causing pollution due to the drainage water. be. Conventional backflow cooling multi-stage Roots vacuum pumps do not use sealing oil or sealing liquid inside, so they have often been used as vacuum source machines for devices that handle condensable gases.

In the three-stage counterflow-cooled Roots vacuum pump shown in FIG. 7, each pump section has two common horizontal shafts, a rotor supported on these shafts, and a rotor containing The first pump section 100 is configured by a housing.
and the suction port 201 of the second pump section 200.
are connected by connecting lines 103, 104, 105, a cooler 112 is provided between connecting lines 103 and 104, branching from connecting line 104, and leading backflow cooling gas to the housing of the first pump section 100. A backflow conduit 106 is provided,
Further, a condensate pipe line 10 branches from the connecting pipe 104 and leads the condensate to a condensate tank 113 provided at the bottom of the cooler 112.
7 is provided, and gate valves 114 and 115 are provided at the inlet and outlet of the condensate tank 113.

The outlet 202 of the second pump section 200 and the inlet 301 of the third pump section 300 are connected to the connecting pipe 203.204.20.
5, a cooler 212 is provided between the connecting pipes 203 and 204, and a backflow pipe 206 is provided which branches from the connecting pipe 204 and leads backflow cooling gas to the housing of the second pump section 200; Further, a condensate pipe line 207 is provided which branches from the connecting pipe 204 and leads the condensate to a condensate tank 213 provided at the lower part of the cooler 212. is provided.

The discharge port 302 of the third pump section 300 has a discharge conduit 30
3. 304, 305 are provided, and discharge pipes 303 and 30
A cooler 312 is provided between the discharge line 304 and a backflow line 306 is provided which branches off from the discharge line 304 and carries the backflow cooling gas to the housing of the third pump section 300.
A condensate pipe line 307 is provided which branches from 4 and leads the condensate to a condensate tank 313 provided at the bottom of the cooler 312.
Gate valves 314 and 315 are installed at the intake and outlet of the condensate tank 313.
is provided.

The operation of the three-stage counterflow cooling roots type vacuum pump shown in FIG. 7 is as follows. The compressed gas that flows in from the suction port of each pump section is discharged to the discharge connecting pipe, flows into the cooler through the connecting pipe, and is cooled, and a part of the condensable gas contained in the gas is It condenses according to pressure and temperature and flows into the condensate tank located at the bottom of the cooler. On the other hand, the non-condensable gas passes through the connecting line and is split again as counterflow cooling gas into gas that flows into each pump section and gas that flows into the suction of the next pump section. The above operations are repeated in sequence in each pump section to compress the suction gas from the pump suction pressure to atmospheric pressure.

In order to perform the above-mentioned functions, the three-stage reverse-cooled Roots vacuum pump shown in Fig. 7 radiates the compression heat generated in each pump section to the outside to prevent the pump from overheating. A plurality of external coolers are provided for cooling the gas flowing through the connecting conduit. Furthermore, since each pump section is arranged horizontally, condensate generated in the cooler of each pump section accumulates in the cooler and the connecting pipe, making it impossible to operate the pump normally. In order to prevent this, it is necessary to provide a condensate tank below the cooler of each pump section. For this reason, it is not necessarily advantageous in realizing downsizing of the pump device including each cooler and the condensate tank.

In addition, in order to operate the pump continuously, it is necessary to discharge the condensate from each condensate tank during pump operation. To discharge the condensate, close the gate valve provided at the inlet of the condensate tank, open the gate valve at the outlet, and discharge the condensate.
After discharging, valve operations are required to close the outlet gate valve and open the inlet gate valve again. This has been an obstacle to achieving unmanned operation and labor saving for continuous operation of the pump, and it has been difficult to continuously discharge the condensate. Furthermore, even if the gate valve is operated as described above, the condensate tank is temporarily brought to atmospheric pressure, so it is not possible to completely prevent atmospheric air from entering the pump. Fluctuations in suction pressure occur, which becomes an obstacle to achieving stable pump suction pressure.

The main object of the present invention is to provide a multi-stage Roots-type vacuum pump that sucks condensable gas or a gas containing condensable gas in part, in view of the above-mentioned problems with conventional pump devices. Cool the pump to a temperature that does not overheat it, without using a condensate tank, and arrange the pump sections vertically, with the pump suction in the top pump section, and The outer peripheral gas flow path that communicates the discharge port of the pump section with the suction port of the next pump section is sloped downward, so that the condensed liquid generated by compression and cooling in each pump section does not stagnate with non-condensable gas and flows inside the pump. The condensate flows down the outer peripheral gas flow path and is discharged from the discharge port of the pump provided in the lowest pump section, allowing the condensate to be continuously discharged without the need for special valve operation to discharge the condensate. The objective is to enable continuous operation of the pump under stable suction pressure conditions.

Another object of the present invention is to eliminate the need for multiple coolers and condensate tanks that were conventionally provided outside the pump.
The goal is to make the pump more compact.

[Means and operations for solving the problem] In the present invention, a roots-type vacuum pump is formed by a plurality of vertically arranged pump sections, the suction port is provided in the uppermost pump section, and the discharge port is provided in the uppermost pump section. The lowest pump section is provided with two vertical shafts common to each pump section, and a Roots-shaped rotor is provided that is supported on the two vertical shafts, constituting each pump section, and having a roots-shaped rotor. The housing that houses the rotor has a downwardly sloped outer gas flow path that communicates with the discharge port of each pump section and the suction port of the next stage pump section on the outer periphery of the housing. A multi-stage Roots-type vacuum pump is provided, which is characterized in that it is provided with a cooling channel located therein.

The multi-stage Roots vacuum pump according to the invention operates as follows.

The gas sucked from the suction port provided in the uppermost pump section is sucked into the housing from the suction port of each pump section, is transferred and compressed based on the operation of the rotor, and is discharged from the discharge port into the outer circumferential gas flow path. is discharged. The discharged gas is cooled by the outer wall of the peripheral gas flow path, which is sufficiently cooled by the cooling water flowing through the cooling waterway, and the condensable gas contained in the discharged gas is condensed according to its pressure and temperature, and together with the non-condensable gas, The gas flows without stagnation through the outer circumferential gas flow path, which has a downward slope, and reaches the suction port of the next stage pump section. The above action is reversed in each pump section sequentially from the top pump section, and the condensate and non-condensable gas condensed inside the pump are continuously discharged from the discharge port of the pump provided in the bottom pump section. It is discharged.

〔Example〕

As an embodiment of the invention, a three-stage Roots-type vacuum pump having a first pump section 1, a second pump section 2, and a third pump section 3 is shown in FIG. FIG. 2 is a cross-sectional view of the pump shown in FIG. 1, and FIG. 3 is a cross-sectional view of the pump shown in FIG.
FIG. 4 is a cross-sectional view taken along IV-1', and FIG. 5 is a cross-sectional view taken along line V-V.

The structure of this pump is as follows.

In FIG. 1, a partition wall 4 separates the first pump section 1 and a second pump section 2, and a corner wall 5 separates the second pump section 2 and the third pump section 2.
The first shaft 71 and the second shaft 72 are vertically provided in FIG. 2, pass through each pump section, and are supported by two upper and lower bearing mechanisms 74. They are assembled in a gear set 73 so that they rotate in opposite directions. 1st shaft 71
passes through the shaft sealing mechanism 75 and is driven by an electric motor.

The structure of each pump section is as follows.

1 and 3, the first pump section 1 consists of a housing 11 having a suction port 13 and a discharge port 14, and a rotor 12A12B supported on a pair of shafts 71 and 72. is an outer circumferential gas flow path 15A that communicates with the discharge port 14 and heads to the second pump section of the next stage.
, 15B, and the outer peripheral gas flow paths 15A, 15B.
It has a cooling water channel 400 on the outer periphery.

1 and 4, the second pump section 2 includes a housing 21 having an inlet 23 and an outlet 24, and a rotor 22A supported on a pair of shafts 71, 72.

22B, and on the outer periphery of the housing 21, there are outer circumferential gas flow paths 15A and 15B that communicate with the suction port 23 from the first pump section of the previous stage, and a third pump section that communicates with the discharge port 24 and the third pump section of the next stage.
It has an outer circumferential gas flow path 25A25B toward the pump section,
The peripheral gas flow paths 15A, 15B, 25A.

A cooling water channel 400 is provided on the outer circumferential portion of 25B.

1 and 5, the third pump section 3 includes a housing 31 having a suction port 33 and a discharge port 34, and a rotor 32A supported on a pair of shafts 71 and 72.

32B, and on the outer periphery of the housing 31 are outer circumferential gas passages 25A, 25B that communicate with the suction port 33 from the second pump section in the previous stage, and the outer circumferential gas passage 25A.

A cooling water channel 400 is provided on the outer circumferential portion of 25B.

In FIGS. 1 to 5, a cooling water inlet 401 communicates with a cooling water outlet 402 through a cooling water channel 400 provided on the outer periphery of the outer circumferential gas flow path.

The operation of this pump device will be explained below using FIGS. 1 to 6.

In the first pump section 1, as shown in FIG.
Suction gas G13 is sucked in from the suction port 13 of the pump section, transferred and compressed based on the operation of the rotors 12A, 12B, and discharged as discharge gas G14 from the discharge port 14 into the peripheral gas channels 15A, 15B. Discharged gas G
14 is caused by the cooling water W400 flowing through the cooling water channel 400,
A part of the condensed gas contained in the discharged gas G14, which was cooled by the sufficiently cooled outer walls of the peripheral gas channels 15A and 15B, condensed according to its pressure and temperature, and became a downward gradient together with the non-condensable gas G23. outer peripheral gas flow path 15A,
15B without stagnation and reaches the suction port 23 of the second pump section 2 at the next stage.

In the second pump section 2, as shown in FIG. 4, suction gas G23 is sucked in, transferred and compressed based on the operation of the rotor 22A22B, and discharged gas G24 from the discharge port 24 to the outer peripheral gas flow path 25A.

25B. The discharged gas G24 is a cooling water channel 400
A part of the condensed gas contained in the discharged gas G24 is cooled by the cooling water W400 flowing through the outer walls of the sufficiently cooled outer peripheral gas flow paths 25A and 25B, and some of the condensed gas contained in the discharged gas G24 is converted into non-condensable gas according to its pressure and temperature. Together with G33, the gas flows through the outer circumferential gas flow paths 25A and 25B, which have a downward slope, without stagnation, and reaches the suction port 33 of the third pump section 3 at the next stage.

In the third pump section 3, as shown in FIG. 5, suction gas 033 is drawn into the rotor 32A.

The discharged gas G34 is transferred and compressed based on the operation of 32B.
It is sent out from the discharge port 34 as a liquid.

The discharged gas and liquid from the discharge port 82 of the pump can be discharged to the outside as they are, and by connecting the gas-liquid separator 9, non-condensable gas and condensed liquid can be discharged from the exhaust port 92 and drain port 93, respectively. can do.

The gas-liquid separator 239 has a tubular drain port 93 at its lower part that opens downward from the inside and is led out to the outside, and an lj
A cylindrical body with an F air port 92 is formed. In the gas-liquid separator 9, as shown in FIG. 1 and FIG. The liquid is stored inside the gas-liquid separator up to the height of the drain port 93, and in order to prevent non-condensable gas from being discharged from the drain port 93, the liquid is sealed and drained outside according to the height of the condensate. Continuously discharged. A muffling chamber 94 can be provided in the upper part of the gas-liquid separator 9, and the non-condensable discharged gas G95 is muffled in the muffling chamber 94, and the exhaust port 9
2 can be exhausted to the outside.

In the multistage roots-type vacuum pump shown in Fig. 1, the gas sucked from the pump suction port provided in the uppermost pump section is sucked into the housing from the suction port of each pump section, and is used for the operation of the rotor. The gas is then transferred, compressed, and discharged from the discharge port into the outer peripheral gas flow path as discharged gas. The discharged gas is cooled by the cooling water flowing through the cooling channel and by the sufficiently cooled outer wall of the peripheral gas flow path, and a part of the 8Am gas contained in the discharged gas condenses according to its pressure and temperature and becomes non-condensed. It flows along with the condensable gas through the downwardly sloped peripheral gas flow path without stagnation, and reaches the suction port of the next stage pump section.

The above action is repeated in each pump section sequentially from the top pump section, and the condensate and non-condensable gas condensed inside the pump are discharged from the pump discharge port provided in the bottom pump section at atmospheric pressure. guided to a gas-liquid separator,
The condensate is stored inside the gas-liquid separator up to the height of the drain port, and to prevent non-condensable gas from being discharged from the drain port, the condensate is sealed and drained outside according to the height of the condensate. Continuously discharged. On the other hand, the valve condensable gas is discharged to the outside from an exhaust port provided at the top of the gas-liquid separator.

Note that the gas-liquid separator is not necessarily essential, and can be omitted depending on the case.

Although the above description has been made regarding the case where the pump section has three stages, the number is not limited to three stages, and it is possible to have four or more stages.

Note that even in the case of four or more stages, the first stage has the configuration shown in FIG. 3, and the last stage has the configuration shown in FIG. 5.

Further, it is also possible to apply a backflow cooling mechanism (see, for example, Japanese Patent Laid-Open No. 59-115489 and Japanese Patent Laid-open No. 63-154884) to the multi-stage Roots type vacuum pump shown in FIG.

〔Effect of the invention〕

According to the present invention, in a multi-stage Roots-type vacuum pump that sucks a condensable gas or a gas containing a condensable gas in a part thereof, the pump can be heated without using a special external cooler and a condensate tank. Each pump section that makes up the pump is arranged vertically, the uppermost pump section has a suction port, and the discharge port of each pump section and the suction port of the next pump section are connected to each other. The communicating outer gas flow path is sloped downward, and the condensate produced by compression and cooling in each pump section flows down inside the pump and through the outer gas flow path, and reaches the pump discharge port provided in the lowest pump section. By discharging the condensate from the pump, the condensate is continuously discharged without any special valve operation for discharging the condensate, and the pump can be operated continuously under stable suction pressure conditions.

Further, according to the present invention, there is no need for a plurality of coolers and condensate tanks that were conventionally provided outside the pump, and the pump can be made smaller.

[Brief explanation of the drawing]

FIG. 1 is a structural diagram of a multi-stage roots-type vacuum pump as an embodiment of the present invention, and FIG. 2 is a diagram showing the structure of the pump shown in FIG.
-II sectional view, Figure 3 is mm-m sectional view, Figure 4 is IV
-IV sectional view, FIG. 5 is a V-V sectional view, FIG. 6 is a diagram showing a gas-liquid separator, and FIG. 7 is a diagram showing an outline of a conventional backflow cooling multistage Roots vacuum pump. (Explanation of symbols) 1... First pump section, 11... Housing,
12A/12B...Rotor, 13...Suction port,
14...Discharge port, 15A-15B...Outer peripheral gas flow path between the first and second pump sections, 2...Second pump section, 21...Housing,
22A/22B... Rotor, 23... Suction port,
24...Discharge port, 25A/25B...Outer peripheral gas flow path between the second and third pump sections, 3...Third pump section, 3I...Housing,
32A/32B...Rotor, 33...Suction port,
34...Discharge port, 4...Partition wall of the first and second pump sections, 5...Second
, third pump section partition wall, 71... first shaft,
72... Second shaft, 73... Timing gear set, 74... Bearing mechanism, 75... Shaft sealing mechanism, 8
1... Suction port of the pump, 82... Discharge port of the pump, 013... Suction gas of the first pump section, G14...
Discharge gas of the first pump section, G23... Suction gas of the second pump section, G24... Discharge gas of the second pump section, G33... Suction gas of the third pump section, G34...
・Discharge gas of the third pump section, 081... Pump suction gas, G82... Condensate and non-condensable discharge gas, 9... Gas-liquid separator, 91... Gas-liquid separator Inlet, 92...Exhaust port, 93...Drain port, 94
...Muffling chamber, G95...Non-condensable discharge gas, 100...First pump section, 101...Suction port, 103, 104, 105...Connecting pipe line, 106...
・Reverse flow pipe line, 112...Cooler, 114.115...Gate valve, 201...Suction port, 203, 204, 205...Connection pipe line, 206...
...Reverse flow pipe line, 212...Cooler, 214.215...Gate valve, 301...Suction port, 303.304,305...Connection pipe line, 306...
Backflow pipe line, 312...Cooler, 314.315...Gate valve, W2O3...Cooling water, 102...Discharge port, 107...Condensate pipe line, 113...Condensate tank , 200...Second pump section, 202...Discharge port, 20? ...(Earache fluid pipe line, 213... Condensate tank, 300... Third pump section, 302... Discharge port, 307... Condensate pipe line, 313... Condensate tank , 400... Cooling water channel, 401... Cooling water inlet, 402... Cooling water outlet.

Claims (1)

[Claims] 1. A roots-type vacuum pump is formed by a plurality of vertically arranged pump sections, the suction port is provided in the top pump section, the discharge port is provided in the bottom pump section, and each The pump sections are provided with two common vertical axes, a Roots-shaped rotor supported on the two vertical axes is provided, and the housing constituting each pump section and containing the Roots-shaped rotor is provided with a roots-shaped rotor. A downwardly sloping peripheral gas flow path that communicates with the discharge port of each pump section and the suction port of the next stage pump section is provided on the outer peripheral portion of the housing, and a cooling water channel is provided on the outer periphery of the peripheral gas flow path. A multi-stage roots-type vacuum pump characterized by: 2. The multi-stage Roots vacuum pump according to claim 1, wherein a gas-liquid separator is provided on the discharge side of the lowest pump section.