WO2004097223A1 - Pompe turbomoleculaire a vide - Google Patents

Pompe turbomoleculaire a vide Download PDF

Info

Publication number
WO2004097223A1
WO2004097223A1 PCT/GB2004/001441 GB2004001441W WO2004097223A1 WO 2004097223 A1 WO2004097223 A1 WO 2004097223A1 GB 2004001441 W GB2004001441 W GB 2004001441W WO 2004097223 A1 WO2004097223 A1 WO 2004097223A1
Authority
WO
WIPO (PCT)
Prior art keywords
rotor
pump according
stator
yoke
teeth
Prior art date
Application number
PCT/GB2004/001441
Other languages
English (en)
Inventor
James Alexander Haylock
Ulrike Martina Hoefer
Nigel Paul Schofield
Original Assignee
The Boc Group Plc
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 The Boc Group Plc filed Critical The Boc Group Plc
Priority to US10/554,804 priority Critical patent/US20060210414A1/en
Publication of WO2004097223A1 publication Critical patent/WO2004097223A1/fr

Links

Classifications

    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K21/00—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets
    • H02K21/12—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets with stationary armatures and rotating magnets
    • H02K21/14—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets with stationary armatures and rotating magnets with magnets rotating within the armatures
    • H02K21/16—Synchronous motors having permanent magnets; Synchronous generators having permanent magnets with stationary armatures and rotating magnets with magnets rotating within the armatures having annular armature cores with salient poles
    • 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
    • F04D19/042—Turbomolecular vacuum pumps
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02K—DYNAMO-ELECTRIC MACHINES
    • H02K1/00—Details of the magnetic circuit
    • H02K1/06—Details of the magnetic circuit characterised by the shape, form or construction
    • H02K1/12—Stationary parts of the magnetic circuit
    • H02K1/14—Stator cores with salient poles
    • H02K1/146—Stator cores with salient poles consisting of a generally annular yoke with salient poles
    • H02K1/148—Sectional cores

Definitions

  • the invention relates to turbomolecular vacuum pumps and to high-speed electric motors for driving turbomolecular vacuum pumps.
  • High-speed motors for turbomolecular vacuum pumps must be capable of operating at very high speeds in difficult operating conditions.
  • the motor speed may be as low as 20,000 rpm, typically, the motor speed will be in excess of 50,000 rpm and may be up to 100,000 rpm.
  • An electric motor driving a turbomolecular pump is mounted within the pump casing in an area which experiences high vacuum. This gives rise to difficulties in cooling the rotor since the sole heat path for conduction of the heat generated when in use, is through the bearings of the shaft carrying the rotor and only a small amount of heat can be dissipated by radiation into the process gas. For this reason, brushless permanent magnet motors are usually used. In order to reduce eddy current losses and smooth the output of such motors, their stators conventionally have six or more teeth with distributed windings. These motors are specifically designed for application in turbomolecular vacuum pumps and their relatively complicated structure makes them expensive to produce, especially as the volumes required for use with turbomolecular pumps are relatively low. In particular, forming the windings in the limited spaces available within conventional stator designs is a difficult and expensive process involving dedicated machinery.
  • a further problem with motors for turbomolecular pumps is outgassing from the components of the motor. It is known that gas becomes lodged on or below the surfaces of the pump components and when the surfaces are placed under vacuum, gas evolves from those surfaces. This generation of gas by desorbtion is known as known outgassing. Outgassing is an increasingly important factor when pumps work at higher levels of vacuum and it is desirable to reduce outgassing levels to the extent this may be possible.
  • the invention also includes an electric motor for a turbomolecular vacuum pump, the motor comprising a stator having a plurality of teeth that have respective radially innermost surfaces that define an inside diameter of the stator, a motor shaft and a rotor comprising a permanent magnet mounted on a portion of the motor shaft, wherein a ratio of an outside diameter of the motor shaft portion and the inside diameter of the stator is less than or substantially equal to 2:3.
  • the invention also includes an electric motor for a turbomolecular vacuum pump, the motor comprising a stator having a plurality of teeth that each have a curved radially innermost surface and are arranged so as to define a substantially circular through-passage, a motor shaft and a rotor disposed in the through-passage and mounted on the motor shaft, the rotor having an outside diameter and comprising a permanent magnet that defines a through hole by which the rotor is mounted on the motor shaft and wherein the through hole defines an inside diameter of the rotor and a ratio of the inside diameter of the rotor and the outside diameter of the rotor is less than or substantially equal to 2:3.
  • the invention also includes an electric motor for a turbomolecular pump, the motor comprising a stator, a rotor and a motor shaft, the stator comprising three teeth made of a powdered magnetic material and each carrying an electrical winding, the teeth having concave radially innermost surfaces and being arranged such that the concave surfaces define a substantially circular passage for the rotor, the passage having a diameter, the rotor being mounted directly on the motor shaft and comprising a core made of a polymer bonded magnetic material and defining an axially extending through-passage for the motor shaft, the rotor further comprising a reinforcing sleeve for the core, the rotor being mounted on the motor shaft, which motor shaft has a diameter, and wherein a ratio of the motor shaft diameter to the passage diameter is less than or substantially equal to 2:3.
  • the invention also includes a turbomolecular vacuum pump comprising a casing having a pump inlet and a pump outlet, a pumping mechanism housed in the casing and connected with the inlet and the outlet and an electric motor housed in the casing and connected with the pumping mechanism, the electric motor comprising a motor shaft having a diameter, a rotor mounted directly on the motor shaft and consisting of an annular core and a reinforcing sleeve for the core, the core being a polymer bonded magnet and the sleeve being made of a material having low electrical conductivity, and a stator comprising three teeth held in a two-piece yoke and each carrying a wound non-distributed electrical winding, the teeth being made from a magnetic powder material and each comprising an arcuate portion having a concave surface and a convex surface opposite the concave surface and a projection projecting radially from the convex surface, the concave surfaces being arranged to define a substantially circular passage having an
  • the invention also includes an electric motor for a turbomolecular pump, the motor comprising a stator having a plurality of teeth for carrying respective electrical windings, a motor shaft comprising a hollow member made of a material having low electrical conductivity and a rotor comprising a permanent magnet housed in the hollow member.
  • the invention also includes an electric motor for a turbomolecular pump, the motor comprising a stator having a plurality of teeth for carrying the motor windings and a tooth holding unit by which the teeth are supported, the teeth and the tooth holding unit being made of a magnetic powder material.
  • Figure 1 is a schematic representation of a turbomolecular pump
  • Figure 2 is an exploded perspective view of a motor for a turbomolecular pump
  • Figure 3 is a perspective view of the motor in an assembled condition with the motor shaft omitted.
  • Figure 4 is a section on line IV - IV in Figure 2.
  • FIG. 1 shows a turbomolecular vacuum pump 2 that comprises a casing 4 having an inlet 5 and an outlet 6.
  • the casing 4 houses a pumping mechanism 8 connected with the inlet 5 and the outlet 6 and an electric motor 10 for driving the pumping mechanism 8.
  • Pumping mechanisms for turbomolecular vacuum pumps are know per se and will therefore not be described in any detail herein.
  • the pumping mechanism could, for example, be a mechanism such as that in the EXT250 made by BOC Edwards of the United Kingdom.
  • the motor 10 comprises a motor shaft 12, a rotor 14, a stator and stator windings ' 20.
  • the stator comprises three teeth 16 and a two-piece-split yoke 18(1), 18(2).
  • the teeth 16 are pressed, non-sintered, components made of soft magnetic powder, in which the powder particles are bonded by an electrically insulating binder.
  • An example of a suitable powder material provided with such a binder is Somaloy 500 made by Hoganas of Sweden. It is to be noted that although heat may be applied during the pressing process, it should be insufficient to cause fusion of the particles, which are held together by the binder.
  • Each tooth 16 comprises an arcuate segment 22 and a stepped projection 24 projecting from the convex side 26 of the arcuate segment.
  • the stepped projections 24 provide a locating point for the windings 20 in the form of a first portion 28 that is shaped such that it can be received in an elongate slot 30 defined by the windings 20.
  • the first portion 28 of the projection 24 is positioned on and extends radially outwardly from the convex side 26 of the arcuate segment 22.
  • a second portion 32 extends radially outwardly from the first portion 28.
  • the second portion 32 is generally circular and smaller in cross-section than the first portion 28.
  • the two-piece split yoke comprises two annular members 18(1), 18(2). Like the teeth 16, the annular members 18(1), 18(2) are pressed, non-sintered components made of soft magnetic powder, in which the powder particles are bonded by an electrically insulating binder. Each annular member 18(1), 18(2) has three semicircular cut-outs 34 at its axially inner end. The cut-outs 34 are equi-spaced about the circumference of the annular members 18(1), 18(2) at 120° intervals. The arrangement is such that when the innermost side faces 36 of the annular members are brought into abutting relationship, three circular holes 40 ( Figure 2) are provided for receiving the second portions 32 of the stepped projections 24.
  • the second portions 32 and the holes 40 are circular as a matter of convenience and that other shapes could be used if desired.
  • the second, free end, portions 32 of the stepped projections 24 are r held in the respective holes 40 defined by the opposed cutouts 34.
  • the teeth 16 are held such that the concave radially innermost surfaces 42 of the arcuate segments form a substantially continuous circular passage extending axially through the stator.
  • the passage defined by the concave surfaces 42 has a diameter corresponding to the radial distance R of the surfaces from the longitudinal axis of the stator and this diameter can be considered the inside diameter of the stator.
  • the electrical windings 20 are formed by entirely separate coils of wound wire that may be wound onto bobbins made of plastic to provide electrical insulation.
  • the windings each have tails (not shown) by which they are connected to an a.c. electrical supply.
  • stator parts the annular members 18(1), 18(2) and teeth 16
  • This sub- assembly is then assembled into the pump and preferably then set in resin.
  • other assembly techniques can be used.
  • the rotor 14 comprises an annular core 44 made of a magnetic material having low electrical conductivity.
  • the core 44 may be made of ferrite, but in a presently preferred embodiment is made of a polymer bonded magnetic material.
  • Polymer bonded magnetic materials are composites of non-conductive polymer and embedded magnetic particles. Such materials will be well known to those skilled in the art and will not be described detail herein.
  • An example of a suitable material is Vacobond (Trade Name) made by Vacuumschmelze of Hanau, Germany.
  • the core 44 has an axially extending through-hole 46 for receiving the motor shaft 12.
  • the rotor 14 additionally comprises a sleeve 48 for the core 44.
  • the diameter of the through-hole 46 essentially corresponds to the outside diameter of the motor shaft 12 so that the core 44 is a close sliding fit on the motor shaft and can be securely fixed thereon.
  • the motor shaft diameter is selected such that the ratio of the inside diameter of the stator and the outside diameter of the motor shaft, or at least the portion of the shaft on which the rotor 14 is mounted, is not greater than 3:2.
  • the shaft diameter is 14 mm and the outside diameter of the rotor 14 is 21 mm. Since there is just a very small running clearance between the surfaces 42 of the teeth 16 and the outer surface of the sleeve 48 (exaggerated in Figure 3), the inside diameter of the stator corresponds substantially to the outside diameter of the rotor.
  • the sleeve thickness will be approximately 1 mm and is preferably as thin as is possible within the constraints of providing the reinforcing desired.
  • a triangular plate 49 may be fitted to an end of the two-piece yoke 18(1), 18(2) by means of screws or the like.
  • the triangular plate would be provided with a through-hole for the motor shaft 12 and carry a sensor arranged to detect the rotational position of the shaft 12.
  • the sensor would provide signals for use in controlling the switching of the electrical windings 20.
  • the sensor may, for example, be a Hall sensor ring. It will, however, be understood that other sensors could be used and it is not essential that the sensor is carried by the two-piece split yoke 18(1), 18(2).
  • a stator consisting of parts made of a magnetic powder material in which the powder particles are bonded by an electrically insulating binder, is capable of providing the necessary electrical properties, while at the same time providing improvements in outgassing performance.
  • Tests have been carried out in which the outgassing performance of an embodiment provided with such a stator was compared with that of a pump having a stator comprising stacked, or laminated steel plates. It was found that the powdered metal stator provided a five-fold improvement in outgassing performance. That is, the amount of gas evolving from the stator made of magnetic powder material was approximately one-fifth of that evolving from the equivalent stator constructed as a- lamination of steel plates.
  • the modular construction of the stator makes the motor 10 more economic to produce than conventional motors, particularly if production levels are low, and provides considerable design flexibility.
  • forming the teeth 16 as separate components from magnetic powder material allows automated production using proven powder technology and the tailoring of the tooth shape to provide optimum electro-magnetic properties.
  • the modular construction also allows the electrical windings to be produced as individual coils 20 and then when complete, simply positioned on the teeth 16 prior to assembly of the stator. Once the coils are seated on the respective teeth, the stator can be readily assembled by clamping the required number of teeth between the annular members of the two-piece yoke 18(1), 18(2).
  • the modular construction makes it straight forward to produce motors having a different number of teeth so that again the freedom to design a motor having particular performance characteristics is enhanced.
  • the motor 10 has the twin advantage that it can be produced economically in small volumes and the design details can be easily modified to tailor the performance characteristics to the particular requirements of a given application.
  • the yoke of the embodiment is a two-piece split unit as shown, other configurations are possible.
  • the yoke could be made up of a plurality of arcuate segments that combine to form an annular part.
  • the recesses for the teeth would be provided between the abutting end surfaces of the segments.
  • the sleeve 48 is described as being as thin as practicable within the constraints of providing the reinforcement for the core 44 made of polymer bonded magnetic material.
  • the sleeve could be extended to serve as the motor shaft while still housing the magnetic core 44. In this case, the sleeve thickness would be increased to provide the necessary shaft stiffness for high speed motor operation.
  • the rotor magnet may be housed in a sleeve made of an electrically highly conductive sleeve made of a material such as aluminium. In this case, it would not be essential that the magnet was made of an electrically low conductive material.
  • a sleeve made of an electrically highly conductive material such as aluminium the stator flux is transmitted into the sleeve such that the eddy current losses found in the motor shaft are minimised. Since the resistivity of such a highly conductive sleeve will be low, heating of the sleeve component will be low.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Iron Core Of Rotating Electric Machines (AREA)

Abstract

L'invention concerne une pompe turbomoléculaire qui comprend un mécanisme de pompage et un moteur électrique (10) destiné à commander le mécanisme de pompage. Le moteur électrique comprend un rotor (14), un stator et des enroulements statoriques (20). Le stator comprend un collier de déviation (18(1), 18(2)) et plusieurs dents (16) en saille à partir du collier de déviation et supportant les enroulements statoriques. Le collier de déviation et les dents sont constitués d'un matériau de poudre magnétique non fritté dans lequel les particules de poudre sont liées par un liant isolant au niveau électrique.
PCT/GB2004/001441 2003-04-28 2004-04-01 Pompe turbomoleculaire a vide WO2004097223A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US10/554,804 US20060210414A1 (en) 2003-04-28 2004-04-01 Turbomolecular vacuum pump

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB0309644.3A GB0309644D0 (en) 2003-04-28 2003-04-28 Turbo-molecular vacuum pumps and motors for such pumps
GB0309644.3 2003-04-28

Publications (1)

Publication Number Publication Date
WO2004097223A1 true WO2004097223A1 (fr) 2004-11-11

Family

ID=9957271

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB2004/001441 WO2004097223A1 (fr) 2003-04-28 2004-04-01 Pompe turbomoleculaire a vide

Country Status (3)

Country Link
US (1) US20060210414A1 (fr)
GB (1) GB0309644D0 (fr)
WO (1) WO2004097223A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IT201900018461A1 (it) * 2019-10-10 2021-04-10 Texa Dynamics S R L “Componente di raffreddamento per motore elettrico”

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DD142409A1 (de) * 1979-03-07 1980-06-18 Karsten Pischang Verfahren zur herstellung von magnetkoerpern elektrischer maschinen
US5128574A (en) * 1989-04-11 1992-07-07 Canon Kabushiki Kaisha Brushless motor
JPH10288191A (ja) * 1997-04-16 1998-10-27 Daikin Ind Ltd ポンプ
US6081059A (en) * 1999-04-21 2000-06-27 Hsu; Chun-Pu Outer-rotor electric motor having inner-stator formed by concentrically wrapping flattened stator elements on stator core
EP1223662A1 (fr) * 2001-01-15 2002-07-17 N.V. Atlas Copco Airpower Procédé de fabrication d'un rotor à aimants permanents pour un moteur haute vitesse
US6472792B1 (en) * 1999-05-11 2002-10-29 Höganäs Ab Stator with teeth formed from a soft magnetic powder material

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2337226A1 (de) * 1973-07-21 1975-02-06 Maschf Augsburg Nuernberg Ag Vakuumpumpe mit einem im innenraum ihres gehaeuses gelagerten laeufer
EP0180330B1 (fr) * 1984-09-29 1989-11-15 Kabushiki Kaisha Toshiba Noyau annulaire d'armature
US5853513A (en) * 1995-02-22 1998-12-29 Mobile Storage Technology Inc. Method of producing a stator for a disk drive motor
US5980603A (en) * 1998-05-18 1999-11-09 National Research Council Of Canada Ferrous powder compositions containing a polymeric binder-lubricant blend
US6617740B2 (en) * 2000-12-01 2003-09-09 Petersen Technology Corporation D.C. PM motor and generator with a stator core assembly formed of pressure shaped processed ferromagnetic particles

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DD142409A1 (de) * 1979-03-07 1980-06-18 Karsten Pischang Verfahren zur herstellung von magnetkoerpern elektrischer maschinen
US5128574A (en) * 1989-04-11 1992-07-07 Canon Kabushiki Kaisha Brushless motor
JPH10288191A (ja) * 1997-04-16 1998-10-27 Daikin Ind Ltd ポンプ
US6081059A (en) * 1999-04-21 2000-06-27 Hsu; Chun-Pu Outer-rotor electric motor having inner-stator formed by concentrically wrapping flattened stator elements on stator core
US6472792B1 (en) * 1999-05-11 2002-10-29 Höganäs Ab Stator with teeth formed from a soft magnetic powder material
EP1223662A1 (fr) * 2001-01-15 2002-07-17 N.V. Atlas Copco Airpower Procédé de fabrication d'un rotor à aimants permanents pour un moteur haute vitesse

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN vol. 1999, no. 01 29 January 1999 (1999-01-29) *

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
IT201900018461A1 (it) * 2019-10-10 2021-04-10 Texa Dynamics S R L “Componente di raffreddamento per motore elettrico”
WO2021070017A1 (fr) * 2019-10-10 2021-04-15 Texa Dynamics S.R.L. Composant de refroidissement pour moteur électrique

Also Published As

Publication number Publication date
US20060210414A1 (en) 2006-09-21
GB0309644D0 (en) 2003-06-04

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