EP1167772A1 - Vacuum pump - Google Patents

Vacuum pump Download PDF

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Publication number
EP1167772A1
EP1167772A1 EP00913011A EP00913011A EP1167772A1 EP 1167772 A1 EP1167772 A1 EP 1167772A1 EP 00913011 A EP00913011 A EP 00913011A EP 00913011 A EP00913011 A EP 00913011A EP 1167772 A1 EP1167772 A1 EP 1167772A1
Authority
EP
European Patent Office
Prior art keywords
cylindrical body
air gap
peripheral surface
stator
rotor
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Withdrawn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
EP00913011A
Other languages
German (de)
English (en)
French (fr)
Inventor
Akira Yamauchi
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.)
Seiko Instruments Inc
Original Assignee
Seiko Instruments Inc
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 Seiko Instruments Inc filed Critical Seiko Instruments Inc
Publication of EP1167772A1 publication Critical patent/EP1167772A1/en
Withdrawn legal-status Critical Current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
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D19/00—Axial-flow pumps
    • F04D19/02—Multi-stage pumps
    • F04D19/04—Multi-stage pumps specially adapted to the production of a high vacuum, e.g. molecular pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D19/00—Axial-flow pumps
    • F04D19/02—Multi-stage pumps
    • F04D19/04—Multi-stage pumps specially adapted to the production of a high vacuum, e.g. molecular pumps
    • F04D19/048—Multi-stage pumps specially adapted to the production of a high vacuum, e.g. molecular pumps comprising magnetic bearings
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D19/00—Axial-flow pumps
    • F04D19/02—Multi-stage pumps
    • F04D19/04—Multi-stage pumps specially adapted to the production of a high vacuum, e.g. molecular pumps
    • F04D19/044—Holweck-type pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04D—NON-POSITIVE-DISPLACEMENT PUMPS
    • F04D27/00—Control, e.g. regulation, of pumps, pumping installations or pumping systems specially adapted for elastic fluids
    • F04D27/02—Surge control
    • F04D27/0292—Stop safety or alarm devices, e.g. stop-and-go control; Disposition of check-valves

Definitions

  • the present invention relates to a vacuum pump which is composed of a rotor cylindrical body and a stator cylindrical body and which is provided with a thread groove pump portion in which a thread is formed in either the outer peripheral surface of the rotor cylindrical body or the inner peripheral surface of the stator cylindrical body and, in particular, to a measure for preventing the rotor cylindrical body and the stator cylindrical body from coming into contact with each other.
  • Examples of a vacuum pump provided with a thread groove pump portion include a composite-type turbo-molecular pump.
  • a composite-type turbo-molecular pump beats down molecules by a difference in speed between rotor blades, which rotate at high speeds of several tens of thousands of revolutions per minute, and stator blades, discharging gas through a flow passage formed by a thread groove portion formed in the inner peripheral surface of the stator and the outer peripheral surface of the rotor.
  • a turbine blade portion consisting of rotor blades in a number of stages and stator blades in a number of stages
  • a thread groove pump portion consisting of a rotor cylindrical body having a flat outer peripheral surface and a stator cylindrical body having an inner peripheral surface with a thread groove.
  • the rotor is rotatably supported by a bearing, such as a 5-axis control type magnetic bearing consisting of an active radial magnetic bearing and an active thrust magnetic bearing.
  • a touchdown bearing for supporting the rotor shaft in an emergency such as failure of the magnetic bearing.
  • the air gap between the two cylindrical bodies constituting the thread groove pump portion that is, the air gap between the thread groove portion of the stator cylindrical body and the outer peripheral surface of the rotor cylindrical body (hereinafter abbreviated to the "thread groove pump portion air gap" as needed) be large to some degree.
  • the thread groove pump portion air gap be as small as possible. Taking into account these two mutually contradictory conditions and other conditions, the air gap of the thread groove pump portion is determined.
  • the composite type turbo-molecular pump includes the air gap between the magnetic bearing and the rotor shaft, the air gaps between the rotor blades and the stator blades, the air gap between the inner ring of the touchdown bearing and the rotor shaft (hereinafter abbreviated to the "touchdown bearing air gap" as needed), etc.
  • the touchdown bearing air gap is set to be relatively small as compared with the air gap between the magnetic bearing and the rotor shaft, the air gaps between the rotor blades and the stator blades, the thread groove pump portion air gap, and the other air gaps.
  • the reason for this arrangement is to prevent the rotor side and the stator side from coming into contact with each other when the rotor shaft is supported by the touchdown bearing, which occurs when the magnetic bearing ceases to function as a result of failure of the vacuum pump, atmosphere intrusion, a power failure, etc.
  • the touchdown bearing is a consumable item; as the touchdown of the rotor shaft is repeated, the touchdown bearing is worn, the touchdown bearing air gap gradually increasing.
  • the touchdown bearing air gap has increased to become not smaller than a fixed size, it ceases to function as a touchdown bearing. Then, it can happen that the rotor side and the stator side come into contact with each other at the time of touchdown.
  • the thread groove pump portion air gap is not always equal to the design value. Actually, it differs from product to product depending on the parts accuracy, assembly condition, etc. Further, when operating the vacuum pump, the lower portion of the rotor cylindrical body, in particular, expands radially due to centrifugal force, heat, etc., whereby not only does it reduce the thread groove pump portion air gap, but in some cases it can be brought into contact with the thread groove portion of the stator cylindrical body.
  • the size of the thread groove pump portion air gap is determined such that the outer peripheral surface of the rotor cylindrical body and the thread groove portion of the stator cylindrical body are not brought into contact with each other during normal operation and at the time of touchdown, and that the gas taken in through the inlet of the vacuum pump does not flow in the reverse direction in the thread groove portion.
  • a number of methods for constantly monitoring a magnetic bearing for malfunction have been proposed, as disclosed in Japanese Patent Application Laid-Open No. 63-239397, Japanese Patent Application Laid-Open No. 2-221697, etc. According to these methods, malfunction of the magnetic bearing is detected to mitigate the impact imparted to the touchdown bearing, thereby reducing the wear of the touchdown bearing. In this way, the rotor side and the stator side are prevented from coming into contact with each other in an indirect fashion.
  • an air gap sensor for detecting an air gap between the outer peripheral surface of the rotor cylindrical body and the inner peripheral surface of the stator cylindrical body is provided at a predetermined position on the inner peripheral surface of the stator cylindrical body.
  • a plurality of the air gap sensors are arranged circumferentially at predetermined intervals on the inner peripheral surface of the stator cylindrical body. Further, the air gap sensor is arranged on the inner peripheral surface of the portion of the stator cylindrical body in the vicinity of the lower end thereof.
  • the air gap sensor there is employed any one of a contact sensor and an eddy current sensor.
  • the contact sensor is constructed of a pair of contacts arranged circumferentially at a minute interval on the inner peripheral surface of the stator cylindrical body.
  • a contact preventing device including: an air gap sensor for detecting an air gap between the outer peripheral surface of the rotor cylindrical body and the inner peripheral surface of the stator cylindrical body; a memory for storing the air gap value detected by the air gap detector; a discriminating device for comparing the detected air gap value with a set value; and an interlock circuit which causes an interlock operation to start when it is determined by the discriminating device that the detected air gap value is not higher than the set value.
  • Fig. 1 is a longitudinal sectional view of a composite type turbo-molecular pump according to an embodiment of the present invention.
  • This composite type turbo-molecular pump is a large capacity type turbo-molecular pump formed by combining a turbine blade portion with a thread groove pump portion, and comprises a rotor 10, a stator 20, and a magnetic bearing device 30 rotatably supporting the rotor 10.
  • the rotor 10 includes rotor blades 11 in a number of stages and a rotor cylindrical body 12 having a flat outer peripheral surface 12a.
  • the stator 20 includes stator blades 21 in a number of stages and a stator cylindrical body 22 having an inner peripheral surface 22a with a thread groove.
  • the rotor blades 11 in a number of stages and the stator blades 21 in a number of stages constitute the turbine blade portion, and the rotor cylindrical body 12 having the flat outer peripheral surface 12a and the stator cylindrical body 22 having the inner peripheral surface 22a with a thread groove constitute the thread groove pump portion.
  • the magnetic bearing device is a so-called 5-axis control type magnetic bearing device, and comprises a rotor shaft 31, a first radial magnetic bearing 32 consisting of a radial electromagnet 32a and a radial displacement sensor 32b, a second radial magnetic bearing 33 consisting of a radial electromagnet 33a and a radial displacement sensor 33b, a first thrust magnetic bearing 34 including an axial electromagnet, a second thrust magnetic bearing 35 including an axial electromagnet, an axial displacement sensor 36, a touchdown bearing 37, and a high frequency motor 38.
  • a gap sensor 40 serves to detect the air gap in the thread groove pump portion formed by the rotor cylindrical body 12 having the flat outer peripheral surface 12a and the stator cylindrical body 22 having the thread-grooved inner peripheral surface 22a. That is, it detects the air gap g shown in Fig. 2, which is an enlarged partial sectional view of the rotor cylindrical body and the stator cylindrical body in the thread groove pump portion. As is apparent from Fig. 2 and Fig. 3, which is a partial perspective view of the inner peripheral surface of the stator cylindrical body in the thread groove pump portion, the air gap g is formed in a spiral shape in the substantially cylindrical gap between the outer peripheral surface 12a of the rotor cylindrical body 12 and the inner peripheral surface 22a of the stator cylindrical body 22.
  • the air gap sensor 40 is installed on the thread-grooved inner peripheral surface 22a of the stator cylindrical body 22, as shown in Fig. 3.
  • the air gap sensor 40 consists, for example, of a contact sensor or an eddy current sensor.
  • the air gap sensor 40 is arranged on the inner peripheral surface of the portion of the stator cylindrical body 22 in the vicinity of the lower end thereof, thereby achieving an improvement in terms of reliability in gap detection.
  • a pair of contacts 41a and 41b constituting the contact sensor 41 are arranged circumferentially at a minute interval on the inner peripheral surface 22a of the stator cylindrical body 22, as shown in Fig. 3. That is, the air gap sensor having the first contact 41a is arranged on a thread groove portion B, and the air gap sensor having the second contact 41b is arranged on a thread ridge portion A.
  • the contacts are arranged on the inner peripheral surface 22a of the stator cylindrical body 22 such that they are in the same circumference in the gap between the stator cylindrical body 22 and the rotor cylindrical body 12, that is, the respective distances from the central axis of the stator cylindrical body 22 to the contacts are the same.
  • the second contact 41b protrudes to some degree from the thread ridge A, whereas the first contact 41a protrudes to a considerable degree from the thread groove B. Due to this arrangement, when the rotor 10 is supported in the normal position, the respective distances from the outer peripheral surface of the rotor cylindrical body 12 to the contacts are the same.
  • the contact sensor 41 Since the contact sensor 41 is arranged in the manner as described above, when the cylindrical body 12 of the rotor 10 formed of a metal such as aluminum comes into contact with the contact sensor 41 on the stator cylindrical body 22 side, the contacts 41a and 41b of the contact sensor 41 are electrically connected to each other to issue a detection signal.
  • This detection signal indicates that the air gap of the thread groove pump portion has become abnormally small, and consequently, there is a greater danger of the inner peripheral surface of the rotor cylindrical body coming into contact with the inner peripheral surface of the stator cylindrical body 22.
  • the eddy current sensor 42 is installed on the thread-grooved inner peripheral surface 22a of the stator cylindrical body 22 like the contact sensor 41. Unlike the contact sensor 41, the eddy current sensor 42 is capable of detecting an air gap value indicating the size of the air gap g.
  • Fig. 4 is a block diagram of a contact preventing device formed by using the eddy current sensor 42 as the air gap sensor 40
  • Fig. 5 is a flowchart showing the operation thereof.
  • the contact preventing device comprises the eddy current sensor 42 for detecting the air gap, a CPU 43 for performing various computing and control operations according to a program, a setting unit 45 serving as an input means for providing a set value, etc., and an interlock circuit 46 for bringing the operation of the vacuum pump to an emergency stop.
  • the CPU 43 reads the air gap value from the eddy current sensor 42, and stores it in a memory 44 (102). Next, the CPU 43 reads a set value and an air gap value from the memory 44, and compares them with each other (103). When, as a result of the comparison, it is determined that the air gap value is not larger than the set value, the interlock circuit is operated, and the operation of the vacuum pump is brought to an emergency stop (104), thereby completing the operational flow (105). It is also possible to provide the contact preventing device with an alarm unit, which issues an alarm when the air gap value becomes not larger than the set value. Further, it is also possible to use the contact sensor 41 as the air gap sensor and form a simplified contact preventing device which detects contact of the inner peripheral surface 12a of the rotor cylindrical body 12 with the contacts 41a and 41b of the sensor portion and issues an alarm.
  • the present invention is applied to a vacuum pump provided with a thread groove pump portion in which a thread groove is formed on the stator side
  • a vacuum pump in which a thread is formed on the outer peripheral surface of the rotor cylindrical body and in which this thread-grooved outer peripheral surface is opposed to a flat inner peripheral surface of the stator cylindrical body, there being provided a thread groove pump portion which maintains a predetermined air gap therebetween.
  • the present invention is also applicable to a vacuum pump in which the rotor is supported by a mechanical bearing, such as a rolling bearing or a sliding bearing. It goes without saying that the present invention is applicable to vacuum pumps in general including turbo-molecular pumps and drag pumps.
  • a vacuum pump provided with a thread groove pump portion, wherein an air gap sensor is provided at a predetermined position of the inner peripheral surface of the stator cylindrical body, whereby it is possible to directly and reliably detect the air gap between the outer peripheral surface of the rotor cylindrical body and the inner peripheral surface of the stator cylindrical body. Further, by operating the interlock by utilizing the output signal of the air gap sensor, it is possible to reliably prevent the rotor side and the stator side from coming into contact with each other. Thus, an improvement in terms of reliability and durability has been achieved in a vacuum pump provided with a thread groove pump portion.
  • the air gap sensor is something that is easily obtained, and the requisite number of man-hours for installing it in the thread groove pump portion is small, so that there is involved little increase in the production cost of a vacuum pump to which the present invention is applied, which leads to a substantial practical advantage.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Non-Positive Displacement Air Blowers (AREA)
EP00913011A 1999-03-31 2000-03-31 Vacuum pump Withdrawn EP1167772A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP9400799 1999-03-31
JP11094007A JP2000291586A (ja) 1999-03-31 1999-03-31 真空ポンプ
PCT/JP2000/002061 WO2000058628A1 (en) 1999-03-31 2000-03-31 Vacuum pump

Publications (1)

Publication Number Publication Date
EP1167772A1 true EP1167772A1 (en) 2002-01-02

Family

ID=14098397

Family Applications (1)

Application Number Title Priority Date Filing Date
EP00913011A Withdrawn EP1167772A1 (en) 1999-03-31 2000-03-31 Vacuum pump

Country Status (4)

Country Link
EP (1) EP1167772A1 (ja)
JP (1) JP2000291586A (ja)
KR (1) KR20020001816A (ja)
WO (1) WO2000058628A1 (ja)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102667169A (zh) * 2009-12-11 2012-09-12 埃地沃兹日本有限公司 螺纹槽排气部的筒形固定部件以及使用该部件的真空泵
CN105971905A (zh) * 2015-03-10 2016-09-28 株式会社岛津制作所 真空泵

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US10190597B2 (en) * 2011-06-17 2019-01-29 Edwards Japan Limited Vacuum pump and rotor thereof
JP6692635B2 (ja) * 2015-12-09 2020-05-13 エドワーズ株式会社 連結型ネジ溝スペーサ、および真空ポンプ
GB2552958B (en) 2016-08-15 2019-10-30 Edwards Ltd Turbo pump vent assembly and method

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS60104107U (ja) * 1983-12-23 1985-07-16 横河メディカルシステム株式会社 接触センサ
JP3825538B2 (ja) * 1997-08-29 2006-09-27 樫山工業株式会社 高真空ポンプ
JPH11280690A (ja) * 1998-03-27 1999-10-15 Ebara Corp ターボ分子ポンプ

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO0058628A1 *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN102667169A (zh) * 2009-12-11 2012-09-12 埃地沃兹日本有限公司 螺纹槽排气部的筒形固定部件以及使用该部件的真空泵
CN102667169B (zh) * 2009-12-11 2016-03-02 埃地沃兹日本有限公司 螺纹槽排气部的筒形固定部件以及使用该部件的真空泵
CN105971905A (zh) * 2015-03-10 2016-09-28 株式会社岛津制作所 真空泵

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Publication number Publication date
JP2000291586A (ja) 2000-10-17
WO2000058628A1 (en) 2000-10-05
KR20020001816A (ko) 2002-01-09

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