EP0674106A1 - Mehrstufige Vakuumpumpe - Google Patents

Mehrstufige Vakuumpumpe Download PDF

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Publication number
EP0674106A1
EP0674106A1 EP95103183A EP95103183A EP0674106A1 EP 0674106 A1 EP0674106 A1 EP 0674106A1 EP 95103183 A EP95103183 A EP 95103183A EP 95103183 A EP95103183 A EP 95103183A EP 0674106 A1 EP0674106 A1 EP 0674106A1
Authority
EP
European Patent Office
Prior art keywords
pump
vacuum pump
rotors
stage
multistage
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP95103183A
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English (en)
French (fr)
Inventor
Morinobu Esaki
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
CHEMITEC Co Ltd
Original Assignee
CHEMITEC Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by CHEMITEC Co Ltd filed Critical CHEMITEC Co Ltd
Publication of EP0674106A1 publication Critical patent/EP0674106A1/de
Withdrawn legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2/00—Rotary-piston machines or pumps
    • F04C2/24—Rotary-piston machines or pumps of counter-engagement type, i.e. the movement of co-operating members at the points of engagement being in opposite directions
    • F04C2/28—Rotary-piston machines or pumps of counter-engagement type, i.e. the movement of co-operating members at the points of engagement being in opposite directions of other than internal-axis type
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C28/00—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids
    • F04C28/08—Control of, monitoring of, or safety arrangements for, pumps or pumping installations specially adapted for elastic fluids characterised by varying the rotational speed
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04C—ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C23/00—Combinations of two or more pumps, each being of rotary-piston or oscillating-piston type, specially adapted for elastic fluids; Pumping installations specially adapted for elastic fluids; Multi-stage pumps specially adapted for elastic fluids
    • F04C23/001—Combinations of two or more pumps, each being of rotary-piston or oscillating-piston type, specially adapted for elastic fluids; Pumping installations specially adapted for elastic fluids; Multi-stage pumps specially adapted for elastic fluids of similar working principle

Definitions

  • the present invention relates to multistage vacuum pumps and, more particularly, to a multistage vacuum pump having a plurality of Roots vacuum pump units which are arranged so that the rotation speeds of the rotors of these pump units can be individually set.
  • Vacuum environments are required in many systems such as a CVD system, a dry etching system, a sputtering system, etc. which are used, for example, in semiconductor producing processes.
  • Vacuum pumps are used to produce vacuum environments.
  • Oil-sealed rotary vacuum pumps are generally known as vacuum pumps which are capable of starting operation with the pump inlet placed under atmospheric pressure.
  • this type of pump uses oil in the pump chamber, the vacuum environment obtained with the pump may be contaminated with oil. Therefore, the oil-sealed rotary vacuum pumps are unsuitable for use in systems such as those described above.
  • Roots vacuum pumps have recently been used as one type of dry-sealed vacuum pump. To obtain a high vacuum, a plurality of Roots vacuum pump units are disposed in series to form a multistage Roots vacuum pump.
  • Such a conventional multistage Roots vacuum pump is disclosed, for example, in Japanese Patent Application Public Disclosure (KOKAI) Nos. 04-8891 and 04-311696.
  • the interior of a single casing is divided into a plurality of pump chambers, and a pair of rotors are disposed in each pump chamber. These rotors are fitted on mutual driving and driven shafts so as to rotate at the same speed of rotation.
  • This type of pump will be referred to as "single-shaft multistage vacuum pump" in the following description.
  • the single-shaft multistage vacuum pump a single mutual shaft is used as each of the driving and driven shafts, and therefore, the driving and driven shafts are long, as a matter of course. Accordingly, when the pump is run for a long time, particularly in a low-vacuum region where the heat generation rate is relatively high, the rotors are displaced to a considerable extent by the thermal expansion of the shafts, so that the rotors may contact the casing. Thus, the conventional single-shaft multistage vacuum pump cannot practically perform a continuous operation for a long time.
  • an exhaust passage which connects each pair of adjacent pump chambers is formed in the casing which is integrated one for all the pump chambers as has been described above.
  • three-lobe rotors which have a complicated configuration, are used in order to raise the compression ratio.
  • the whole pump system must be disassembled because of the single-shaft arrangement.
  • the amount of heat generated in a Roots vacuum pump is known to be proportional to the inlet pressure, the pumping speed and the compression ratio. It is also known that, in a relatively low-pressure region, no large amount of heat is generated even if the compression ratio is high, but a large amount of heat is generated at the high-pressure side. That is, in the conventional single-shaft multistage Roots vacuum pump, it is mainly at the rear-stage side that the heat generation gives rise to a problem.
  • Roots vacuum pumps are also used as superchargers for automotive engines.
  • two-lobe rotors having a simple configuration, that is, hourglass-shaped or cocoon-shaped rotors, are used.
  • the whole structure is also simplified, and thus the quality is stabilized.
  • the compression ratio varies according to the speed of rotation in each pressure region.
  • the present invention has been made to solve the problems of the conventional single-shaft multistage Roots vacuum pump on the basis of the above-described knowledge.
  • An object of the present invention is to provide a multistage vacuum pump which is greatly improved in its pump efficiency, facilitates the temperature control, provides a high pumping speed and is capable of attaining a high ultimate vacuum.
  • Another object of the present invention is to provide a multistage vacuum pump which generates a minimal amount of heat and is capable of continuously operating for a long time.
  • Still another object of the present invention is to provide a multistage vacuum pump which facilitates repair and maintenance operations.
  • a further object of the present invention is to provide a multistage vacuum pump which is capable of starting operation with its inlet placed under atmospheric pressure and of attaining a high vacuum without the need for any auxiliary equipment.
  • the present invention provides a multistage vacuum pump which includes a plurality of Roots vacuum pump units each having a pair of rotors.
  • the Roots vacuum pump units have respective casings which are formed as discrete structures.
  • the pump units are disposed in series, and for each pair of adjacent pump units, the outlet of the front-stage pump unit and the inlet of the rear-stage pump unit are connected by piping for exhaust.
  • the multistage vacuum pump is arranged so that the rotation speed of the rotors of each pump unit can be individually set, thereby enabling the rotors in each stage to be rotated at a desired speed.
  • the rotation speed of the rotors of the front-stage pump unit may be set higher than that of the rotors of the rear-stage pump unit.
  • the plurality of pump units used in the multistage vacuum pump may have the same pump capacity.
  • the rotors may be two-lobe rotors.
  • the clearance between the rotors and the casing is not greater than 0.1 millimeter.
  • Fig. 1 is a graph showing the relationship between the rotation speed and the compression ratio in each pressure region of a two-lobe rotor Roots vacuum pump.
  • Fig. 2 schematically shows the arrangement of one embodiment of the multistage vacuum pump according to the present invention.
  • Fig. 3 schematically shows the way in which an ultimate vacuum is measured at each stage.
  • Fig. 4 is a graph showing the ultimate vacuum measured at each stage.
  • Fig. 2 is a schematic view showing the arrangement of a multistage vacuum pump 1 according to one embodiment of the present invention.
  • the multistage vacuum pump 1 has four Roots vacuum pump units 3, 5, 7 and 9 which are disposed in series to form a 4-stage vacuum pump structure. Identical Roots pumps are used for the Roots vacuum pump units 3, 5, 7 and 9. That is, the pump units 3, 5, 7 and 9 have the same pump capacity.
  • Each Roots vacuum pump unit has a casing 11 which defines a pump chamber 13 in the inside thereof.
  • a pair of two-lobe rotors (generally known as hourglass-shaped or cocoon-shaped rotors) 15 and 17 are carried on driving and driven shafts (not shown), respectively, in the pump chamber 13 so as to mesh with each other and rotate synchronously.
  • End portions of the driving and driven shafts extend into a gear chamber (not shown) which is provided adjacently to each pump chamber 13.
  • the end portions of the driving and driven shafts have timing gears fitted thereon which are in mesh with each other to rotate the driving and driven shafts synchronously.
  • Roots vacuum pump structure is known, and Roots vacuum pumps used in the multistage vacuum pump of the present invention may have such a known structure, illustration of specific arrangement thereof and further description thereof are omitted.
  • the inlet 19 of the first-stage pump unit 3 is communicated with a closed chamber (not shown) which is to be evacuated through an exhaust pipe 35.
  • a closed chamber (not shown) which is to be evacuated through an exhaust pipe 35.
  • the outlet of the front-stage pump unit and the inlet of the rear-stage pump unit are connected by an exhaust pipe 37, 39 or 41.
  • the outlet 33 of the fourth-stage pump unit 9 releases exhaust gas into the atmosphere through a pipe 43.
  • a heat exchanger 45 is equipped with an oil pump to circulate cooling oil, as shown by the dotted-line arrows in the figure, so that the cooling oil is sent to the gear chamber for the pump unit in each stage to cool the timing gears.
  • the heat exchanger 45 is supplied with cooling water through a pipe 47 as shown by the solid-line arrow in the figure.
  • Intercoolers 49, 51 and 53 are disposed at the outlets25, 29 and 31 of the second-, third- and fourth-stage pump units 5, 7 and 9. A part of the exhaust gas cooled in each of the intercoolers 49, 51 and 53 is returned to the pump chamber 13 in each of the second, third and fourth stages, thereby suppressing heat generation from the rotors 15 and 17. Since such intercoolers have also heretofore been used, detailed description thereof is omitted.
  • a check valve 55 is provided in the exhaust pipe 43 to prevent back-flow of the gas when the operation of the multistage vacuum pump 1 is suspended.
  • the rotation speeds of the rotors 15 and 17 in each of the first-, second-, third- and fourth-stage pump units 3, 5, 7 and 9 can be set independently of each other. That is, unlike those in the above-described conventional single-shaft multistage vacuum pump, the driving and driven shafts in the pump units 3, 5, 7 and 9 are discrete from each other and capable of being rotated at different speeds.
  • the device for individually rotating the driving and driven shafts may be realized in various forms. That is, the pump units 3, 5, 7 and 9 in the four stages may be driven by respective motors.
  • a single motor is used, and the rotation speed of the pump unit in each stage is varied in an appropriate speed reduction ratio by using a combination of a belt and a belt pulley, or other appropriate motion transmitting device. It is also possible to use a gearbox, as a matter of course.
  • the rotation speeds are set so that the rotation speed of the first-stage pump unit 3 is the highest, and the rotation speed reduces as the ordinal number of the stages increases.
  • the generation of heat is low and gives rise to no significant problem at the upstream side of the multiple stages, that is, at the lower-pressure side where the degree of vacuum is relatively high, even if the pumping speed is raised to provide an extremely high compression ratio, as has been described above. Therefore, the rotation speeds may be set, for example, as follows: 3,600 rpm for the first-stage pump unit 3; 1,800 rpm for the second-stage pump unit 5; 1,170 rpm for the third-stage pump unit 7; and 765 rpm for the fourth-stage pump unit 9.
  • the pumping speed of the first stage is set at an extremely high level, thereby enabling the multistage vacuum pump 1 to attain an extremely high ultimate vacuum.
  • the rotation speed of the fourth stage is set at a relatively low level, and the compression ratio is set at 2 or lower, thereby enabling the generation of heat to be markedly suppressed.
  • Roots pumps having a pump capacity of 300 liters/minute when used as a supercharger.
  • the Roots pumps which were used in the first, second, third and fourth stages were run at 3,600 rpm, 3,600 rpm, 1,800 rpm and 1,800 rpm, respectively, and ultimate vacuums were measured at the exhaust pipes 35, 37, 39, 41 and 43 with vacuum gauges 57, 59, 61, 63 and 65, as shown in Fig. 3.
  • vacuum gauges 57, 59, 61, 63 and 65 as shown in Fig. 3.
  • values such as those shown in the graph of Fig. 4 were obtained.
  • Roots vacuum pumps used in all the stages have the same capacity
  • Roots vacuum pumps having different capacities may also be used, as a matter of course.
  • Roots vacuum pumps used in the present invention are not necessarily limited to two-lobe rotor pumps such as those described above. Three- or four-lobe rotor Roots vacuum pumps may also be used, as a matter of course.
  • a device for introducing an inert gas into the pump system or a trap can be readily attached to the piping for exhaust, not to the pump body.
  • Roots vacuum pumps per se cannot evacuate with the inlet thereof placed under atmospheric pressure, and an auxiliary pump or other equipment is required.
  • it has been proved to be possible to start operation with the inlet of the pump placed under atmospheric pressure and to attain a high vacuum even with Roots vacuum pumps having two-lobe rotors by providing a plurality of such Roots vacuum pumps in a multistage structure with the clearance between the rotors and the casing of each pump being set not greater than 0.1 millimeter, and by setting the rotation speed of the pump in each stage at an appropriate value, as described above.
  • a vacuum gauge is provided at a proper position in association with the pump in each stage to measure the vacuum obtained by the pump.
  • a vacuum gauge may be installed in the pipe between each pair of adjacent pump units, as shown in Fig. 3.
  • the pump unit that has a failure can be instantaneously identified by the indication of the vacuum gauge associated with that pump unit.
  • the vacuum gauge 59 gives an abnormal indication.
  • the vacuum gauge 57 may also gives an abnormal indication.
  • the rotation speed of the rotors of the Roots vacuum pump unit in each stage can be individually set. Accordingly, the pump unit in each stage can be run at an optimal pumping speed, and efficient evacuation can be effected with minimal power supplied to the driving shafts. Thus, the overall pump efficiency can be improved, and the overall pumping speed can be increased. In addition, the ultimate vacuum of the multistage vacuum pump can be raised to a high level. In particular, if the pumping speed and temperature in each stage are controlled in view of the change of the compression ratio according to the speed of rotation, a multistage vacuum pump having extremely superior pump performance can be obtained.
  • a high pumping speed and a high ultimate vacuum are obtained by increasing the rotation speed of the pump unit at the higher-vacuum side, that is, in the first stage, where the heat generation rate is relatively low even if the compression ratio is high.
  • the rotation speed of the pump is reduced to lower the compression ratio, thereby enabling the heat generation to be suppressed to a considerable extent. Accordingly, it is possible to eliminate the problems associated with the conventional multi stage vacuum pumps, such as the problem that the lubricating oil may enter the pump chamber because of destruction of the shaft seal.
  • the casings of the pump units in all the stages are discrete from each other, and therefore, the pump casings can be cooled advantageously. In this regard also, the temperature control is facilitated. Since the heat generation can be suppressed, the pump can be continuously run for a long time.
  • the multistage vacuum pump of the present invention need not entirely be disassembled when it is to be repaired, but only the portion that needs repair may be disassembled.
  • the present invention enables the degree of freedom of the pump configuration to be increased by appropriately drawing exhaust piping in accordance with the place for installation. Accordingly, it is possible to construct a pump system which is appropriate for each particular purpose.
  • the present invention enables the pump performance to be readily modified by changing the speed of rotation, the pump capacity of pump units used, or the number of stages of pump units to be installed.
  • the multistage vacuum pump of the present invention includes a plurality of Roots vacuum pump units, and the Roots vacuum pump units are driven through respective discrete shafts. Accordingly, when repair is needed, it is only necessary to disassemble and repair the pump unit in the stage that has a failure. Therefore, the above-described advantage that the pump that is attributable to a system failure can be instantaneously identified is extremely useful from the viewpoint of repairs.
  • the multistage vacuum pump of the present invention can be formed by using a plurality of pump units having the same pump capacity, if pump units of the same capacity are prepared as spares, when the system has a failure, the system operation can be immediately resumed simply by replacing the pump unit that has a failure with a spare pump unit.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Applications Or Details Of Rotary Compressors (AREA)
EP95103183A 1994-03-16 1995-03-06 Mehrstufige Vakuumpumpe Withdrawn EP0674106A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP70200/94 1994-03-16
JP7020094 1994-03-16

Publications (1)

Publication Number Publication Date
EP0674106A1 true EP0674106A1 (de) 1995-09-27

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ID=13424643

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EP95103183A Withdrawn EP0674106A1 (de) 1994-03-16 1995-03-06 Mehrstufige Vakuumpumpe

Country Status (3)

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EP (1) EP0674106A1 (de)
KR (1) KR950033092A (de)
CN (1) CN1112649A (de)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2349426A (en) * 1999-03-30 2000-11-01 Aisin Seiki A multi-stage pump assembly with flexible fluid connections between pumps
EP1291527A2 (de) * 2001-09-08 2003-03-12 SGI-PROZESSTECHNIK GmbH Zweistufige Vakuumpumpe
EP1304484A3 (de) * 2001-10-17 2003-09-03 Kabushiki Kaisha Toyota Jidoshokki Vakuumpumpe
CN109237959A (zh) * 2018-09-07 2019-01-18 华电电力科学研究院有限公司 一种多级干式罗茨真空泵双背压凝汽器抽真空系统及方法
CN110360112A (zh) * 2019-05-28 2019-10-22 上海伊莱茨真空技术有限公司 一种多级罗茨泵真空节能系统
CN110645176A (zh) * 2019-10-12 2020-01-03 常州市金坛区维格生物科技有限公司 一种真空机组连续排料装置

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE10150015A1 (de) * 2001-10-11 2003-04-17 Leybold Vakuum Gmbh Mehrkammeranlage zur Behandlung von Gegenständen unter Vakuum, Verfahren zur Evakuierung dieser Anlage und Evakuierungssystem dafür
FR2888894A1 (fr) * 2005-07-20 2007-01-26 Alcatel Sa Pompage rapide d'enceinte avec economie d'energie
WO2017031807A1 (zh) * 2015-08-27 2017-03-02 上海伊莱茨真空技术有限公司 一种多驱动腔非共轴真空泵

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB809443A (en) * 1954-02-27 1959-02-25 Heraeus Gmbh W C Improvements in or relating to rotary high-vacuum pumps
US2936107A (en) * 1956-06-14 1960-05-10 Nat Res Corp High vacuum device
DE3444169A1 (de) * 1984-12-04 1986-06-12 Loewe Pumpenfabrik GmbH, 2120 Lüneburg Anordnung zur optimierung des betriebes von vakuumpumpenanlagen
DE9306559U1 (de) * 1992-06-10 1993-07-01 Siemens AG, 8000 München Anordnung bestehend aus wenigstens zwei in Reihe geschalteten Flüssigkeitsringmaschinen

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB809443A (en) * 1954-02-27 1959-02-25 Heraeus Gmbh W C Improvements in or relating to rotary high-vacuum pumps
US2936107A (en) * 1956-06-14 1960-05-10 Nat Res Corp High vacuum device
DE3444169A1 (de) * 1984-12-04 1986-06-12 Loewe Pumpenfabrik GmbH, 2120 Lüneburg Anordnung zur optimierung des betriebes von vakuumpumpenanlagen
DE9306559U1 (de) * 1992-06-10 1993-07-01 Siemens AG, 8000 München Anordnung bestehend aus wenigstens zwei in Reihe geschalteten Flüssigkeitsringmaschinen

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2349426A (en) * 1999-03-30 2000-11-01 Aisin Seiki A multi-stage pump assembly with flexible fluid connections between pumps
US6305910B1 (en) 1999-03-30 2001-10-23 Aisin Seiki Kabushiki Kaisha Multi-stage pump device
GB2349426B (en) * 1999-03-30 2003-08-27 Aisin Seiki A multi-stage pump assembly
EP1291527A2 (de) * 2001-09-08 2003-03-12 SGI-PROZESSTECHNIK GmbH Zweistufige Vakuumpumpe
EP1291527A3 (de) * 2001-09-08 2003-07-02 SGI-PROZESSTECHNIK GmbH Zweistufige Vakuumpumpe
EP1304484A3 (de) * 2001-10-17 2003-09-03 Kabushiki Kaisha Toyota Jidoshokki Vakuumpumpe
CN109237959A (zh) * 2018-09-07 2019-01-18 华电电力科学研究院有限公司 一种多级干式罗茨真空泵双背压凝汽器抽真空系统及方法
CN110360112A (zh) * 2019-05-28 2019-10-22 上海伊莱茨真空技术有限公司 一种多级罗茨泵真空节能系统
CN110645176A (zh) * 2019-10-12 2020-01-03 常州市金坛区维格生物科技有限公司 一种真空机组连续排料装置

Also Published As

Publication number Publication date
KR950033092A (ko) 1995-12-22
CN1112649A (zh) 1995-11-29

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