WO2005121561A1 - Vacuum pump impeller - Google Patents

Vacuum pump impeller Download PDF

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Publication number
WO2005121561A1
WO2005121561A1 PCT/GB2005/002005 GB2005002005W WO2005121561A1 WO 2005121561 A1 WO2005121561 A1 WO 2005121561A1 GB 2005002005 W GB2005002005 W GB 2005002005W WO 2005121561 A1 WO2005121561 A1 WO 2005121561A1
Authority
WO
WIPO (PCT)
Prior art keywords
shaft
impeller
titanium
alloy
arrays
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.)
Ceased
Application number
PCT/GB2005/002005
Other languages
French (fr)
Inventor
Emmanuel Uzoma Okoroafor
Paul Milner
Chan-Cheong Siew
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.)
BOC Group Ltd
Original Assignee
BOC Group 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 BOC Group Ltd filed Critical BOC Group Ltd
Publication of WO2005121561A1 publication Critical patent/WO2005121561A1/en
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

Links

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
    • F04D29/00—Details, component parts, or accessories
    • F04D29/02—Selection of particular materials
    • F04D29/023—Selection of particular materials especially adapted for elastic fluid 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
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C32/00—Bearings not otherwise provided for
    • F16C32/04—Bearings not otherwise provided for using magnetic or electric supporting means
    • F16C32/0406—Magnetic bearings
    • F16C32/0408—Passive magnetic bearings
    • F16C32/0423—Passive magnetic bearings with permanent magnets on both parts repelling each other
    • F16C32/0425—Passive magnetic bearings with permanent magnets on both parts repelling each other for radial load mainly
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05—INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05D—INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS
    • F05D2300/00—Materials; Properties thereof
    • F05D2300/10—Metals, alloys or intermetallic compounds
    • F05D2300/13—Refractory metals, i.e. Ti, V, Cr, Zr, Nb, Mo, Hf, Ta, W
    • F05D2300/133—Titanium
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C2360/00—Engines or pumps
    • F16C2360/44—Centrifugal pumps
    • F16C2360/45—Turbo-molecular pumps
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16C—SHAFTS; FLEXIBLE SHAFTS; ELEMENTS OR CRANKSHAFT MECHANISMS; ROTARY BODIES OTHER THAN GEARING ELEMENTS; BEARINGS
    • F16C35/00—Rigid support of bearing units; Housings, e.g. caps, covers

Definitions

  • the present invention relates to a vacuum pump impeller.
  • the invention relates to an impeller for a turbomolecular vacuum pump.
  • a standard turbomolecular pump includes an impeller comprising arrays of angled blades and arranged for rotation at high speed, for example up to ninety thousand revolutions per minute between alternately arranged arrays of stationary blades of a stator to convey gas from one end of the shaft to the other.
  • the arrays of impeller blades are formed from aluminium or an alloy thereof, and are mounted on an aluminium or stainless steel impeller shaft.
  • the shaft typically carries a set of magnetic bearing rings located in a bore co-axial with one or more of the arrays of impeller blades at the low-pressure end of the shaft.
  • Each array of impeller blades may be located on a discrete disc mounted on the shaft using a shrink-fitting technique.
  • a number of arrays of impeller blades may be located on a single block or sleeve similarly mounted on the shaft.
  • a problem encountered with this design is that during use of the pump, expansion of the aluminium discs or sleeves under a combination of centrifugal and thermal loads can increase the tendency for the bearing rings to become placed under tension. This can increase the likelihood of the relatively brittle rings cracking during use. Furthermore, the loads exerted on an aluminium shaft during use can cause the shaft to bend, which can result in increased noise and bearing damage during use of the pump.
  • the present invention provides an impeller for a vacuum pump, the impeller comprising a shaft having mounted thereon magnetic bearing means, wherein at least the part of the shaft which carries the bearing means is formed from titanium or an alloy thereof.
  • Forming at least the part of shaft from titanium or one of its alloys, for example Ti- 6AI-4V, having a relatively high stiffness and relatively low thermal expansion coefficient in comparison to aluminium and its alloys, can assist in maintaining the magnetic bearing means, for example magnetic rings carried by the shaft, under a state of compression during use of the pump, thereby inhibiting cracking of the rings.
  • Titanium and its alloys have comparable specific stiffness and strength as high tensile steels such as EN24T (AISI 4340), but are significantly lighter, thereby offering a reduction in impeller inertia in comparison to pumps having steel shafts.
  • the bearing rings are located within a bore of the shaft, the shaft extending around the bearing rings. Only the part of the shaft that extends around the rings may be formed from titanium or titanium alloy, or alternatively the majority, or all, of the shaft may be formed from titanium or titanium alloy.
  • Arrays of blades may be mounted on and/or integral with the shaft.
  • at least one of the arrays is integral with the titanium shaft, with at least one other of the arrays being mounted on the shaft and formed from material having a lower stiffness than said at least part of the shaft, such as aluminium, an aluminium alloy, for example Al 7075, 7175, 7475, 2024 or 2618, magnesium or a magnesium alloy.
  • all of the arrays of blades may be integral with the shaft, such that the entire impeller is formed from titanium or an alloy thereof.
  • the present invention provides an impeller for a vacuum pump, the impeller comprising a shaft, at least part of the shaft being formed from titanium or an alloy thereof, the shaft having mounted thereon one or more arrays of blades formed from material having a lower stiffness than said at least part of the shaft.
  • Figure 1 illustrates a cross-section through a first embodiment of an impeller for a turbomolecular vacuum pump
  • Figure 2 illustrates a cross-section through a second embodiment of an impeller for a turbomolecular vacuum pump.
  • impeller 10 comprises a shaft 12.
  • the shaft 12 has integral therewith a number of arrays or rows of impeller blades 14, three rows in the embodiment shown in Figure 1 although any number could be provided. Alternatively, there may be no rows of blades integral with the shaft 12.
  • each of these rows 16 may be located on a respective disc mounted on the shaft 12, again using a shrink-fitting technique.
  • the impeller 10 includes concentric magnetic bearing rings 20 located in a bore 22 formed at one end of the shaft 12. These rings 20 are retained in position by a retaining ring 24, which exerts a compressive force on the rings 20, and are arranged to co-operate with corresponding concentric rings provided on a stator of the pump to regulate the radial position of the impeller 10 relative to the stator.
  • An armature 26 of a motor for rotating the impeller 10 is also mounted on the shaft 12, a plastics sleeve 28, formed for example from carbon fibre reinforced plastic, being located around the armature 26.
  • the shaft 12 and rows 14 of impeller blades are formed from titanium or a titanium alloy, such as Ti-6AI-4V.
  • the shaft 12 and rows 14 of impeller blades are formed from titanium or a titanium alloy, such as Ti-6AI-4V.
  • part 30 of the shaft 12 that surrounds the bearing rings 20 may be formed from titanium or a titanium alloy, with the remainder of the shaft 12 being formed from other material, such as steel or aluminium.
  • the rows 16 of impeller blades and sleeve 18 mounted on the shaft 12 are formed from material that has a lower stiffness than part 30 of the shaft 12, for example aluminium or an aluminium alloy.
  • an impeller for a turbomolecular vacuum pump comprises a shaft having mounted thereon a plurality of rotor elements. Part of the shaft extends around magnetic bearing means located within a bore of the shaft. At least this 15 part of the shaft is formed from titanium or an alloy thereof so that the bearing means can remain in compression during use of the impeller, thereby inhibiting cracking of the bearing means.

Landscapes

  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Structures Of Non-Positive Displacement Pumps (AREA)
  • Non-Positive Displacement Air Blowers (AREA)

Abstract

An impeller (10) for a turbomolecular vacuum pump comprises a shaft (12) having mounted thereon a plurality of rotor elements (14, 16). Part of the shaft (12) extends around magnetic bearing means (20) located within a bore of the shaft (12). At least this part of the shaft (12) is formed from titanium or an alloy thereof so that the bearing means (20) can remain in compression during use of the impeller (10), thereby inhibiting cracking of the bearing means (20).

Description

VACUUM PUMP IMPELLER
The present invention relates to a vacuum pump impeller. In its preferred embodiment, the invention relates to an impeller for a turbomolecular vacuum pump.
A standard turbomolecular pump includes an impeller comprising arrays of angled blades and arranged for rotation at high speed, for example up to ninety thousand revolutions per minute between alternately arranged arrays of stationary blades of a stator to convey gas from one end of the shaft to the other.
Typically, the arrays of impeller blades are formed from aluminium or an alloy thereof, and are mounted on an aluminium or stainless steel impeller shaft. The shaft typically carries a set of magnetic bearing rings located in a bore co-axial with one or more of the arrays of impeller blades at the low-pressure end of the shaft. Each array of impeller blades may be located on a discrete disc mounted on the shaft using a shrink-fitting technique. Alternatively, or additionally, a number of arrays of impeller blades may be located on a single block or sleeve similarly mounted on the shaft.
A problem encountered with this design is that during use of the pump, expansion of the aluminium discs or sleeves under a combination of centrifugal and thermal loads can increase the tendency for the bearing rings to become placed under tension. This can increase the likelihood of the relatively brittle rings cracking during use. Furthermore, the loads exerted on an aluminium shaft during use can cause the shaft to bend, which can result in increased noise and bearing damage during use of the pump.
In one aspect, the present invention provides an impeller for a vacuum pump, the impeller comprising a shaft having mounted thereon magnetic bearing means, wherein at least the part of the shaft which carries the bearing means is formed from titanium or an alloy thereof. Forming at least the part of shaft from titanium or one of its alloys, for example Ti- 6AI-4V, having a relatively high stiffness and relatively low thermal expansion coefficient in comparison to aluminium and its alloys, can assist in maintaining the magnetic bearing means, for example magnetic rings carried by the shaft, under a state of compression during use of the pump, thereby inhibiting cracking of the rings. Titanium and its alloys have comparable specific stiffness and strength as high tensile steels such as EN24T (AISI 4340), but are significantly lighter, thereby offering a reduction in impeller inertia in comparison to pumps having steel shafts.
In the preferred embodiment, the bearing rings are located within a bore of the shaft, the shaft extending around the bearing rings. Only the part of the shaft that extends around the rings may be formed from titanium or titanium alloy, or alternatively the majority, or all, of the shaft may be formed from titanium or titanium alloy.
Arrays of blades may be mounted on and/or integral with the shaft. In the preferred embodiment at least one of the arrays is integral with the titanium shaft, with at least one other of the arrays being mounted on the shaft and formed from material having a lower stiffness than said at least part of the shaft, such as aluminium, an aluminium alloy, for example Al 7075, 7175, 7475, 2024 or 2618, magnesium or a magnesium alloy. Alternatively, all of the arrays of blades may be integral with the shaft, such that the entire impeller is formed from titanium or an alloy thereof.
In a second aspect, the present invention provides an impeller for a vacuum pump, the impeller comprising a shaft, at least part of the shaft being formed from titanium or an alloy thereof, the shaft having mounted thereon one or more arrays of blades formed from material having a lower stiffness than said at least part of the shaft.
Preferred features of the present invention will now be described, by way of example only, with reference to the accompanying figures, in which: Figure 1 illustrates a cross-section through a first embodiment of an impeller for a turbomolecular vacuum pump; and Figure 2 illustrates a cross-section through a second embodiment of an impeller for a turbomolecular vacuum pump.
With reference first to Figure 1 , impeller 10 comprises a shaft 12. The shaft 12 has integral therewith a number of arrays or rows of impeller blades 14, three rows in the embodiment shown in Figure 1 although any number could be provided. Alternatively, there may be no rows of blades integral with the shaft 12. In this embodiment, there are also a number of rows of impeller blades 16 which are mounted on the shaft 12, five rows in the embodiment shown in Figure 1 although again any number could be provided. As illustrated, these rows of impeller blades 16 may be integral with a sleeve or block 18 shrink-fitted on to the shaft 12.
Alternatively, each of these rows 16 may be located on a respective disc mounted on the shaft 12, again using a shrink-fitting technique.
The impeller 10 includes concentric magnetic bearing rings 20 located in a bore 22 formed at one end of the shaft 12. These rings 20 are retained in position by a retaining ring 24, which exerts a compressive force on the rings 20, and are arranged to co-operate with corresponding concentric rings provided on a stator of the pump to regulate the radial position of the impeller 10 relative to the stator. An armature 26 of a motor for rotating the impeller 10 is also mounted on the shaft 12, a plastics sleeve 28, formed for example from carbon fibre reinforced plastic, being located around the armature 26.
In this embodiment, the shaft 12 and rows 14 of impeller blades are formed from titanium or a titanium alloy, such as Ti-6AI-4V. Alternatively, only that part 30 of the shaft 12 that surrounds the bearing rings 20 may be formed from titanium or a titanium alloy, with the remainder of the shaft 12 being formed from other material, such as steel or aluminium. The rows 16 of impeller blades and sleeve 18 mounted on the shaft 12 are formed from material that has a lower stiffness than part 30 of the shaft 12, for example aluminium or an aluminium alloy. The higher stiffness (E = 125 GPa) and lower thermal expansion coefficient (α = 8.5x10"6 μm/m/°C) of titanium in comparison to aluminium (E = 72 GPa; α = 5 24x10"6 μm/m/°C) will tend to maintain the rings 20 in a state of compression during use of the pump, thereby inhibiting cracking of the bearing rings 20.
In the second embodiment illustrated in Figure 2, all of the rows 14, 16 of impeller blades are integral with the shaft 12, which is formed from titanium or a titanium 10. alloy, such as Ti-6AI-4V.
In summary, an impeller for a turbomolecular vacuum pump comprises a shaft having mounted thereon a plurality of rotor elements. Part of the shaft extends around magnetic bearing means located within a bore of the shaft. At least this 15 part of the shaft is formed from titanium or an alloy thereof so that the bearing means can remain in compression during use of the impeller, thereby inhibiting cracking of the bearing means.

Claims

1. An impeller for a vacuum pump, the impeller comprising a shaft having mounted thereon magnetic bearing means, wherein at least the part of the shaft which carries the bearing means is formed from titanium or an alloy thereof.
2. An impeller according to Claim 1 , wherein the bearing means are located within a bore of the shaft, said at least part of the shaft extending around the bearing means.
3. An impeller according to Claim 2, wherein the bore is located at one end of the shaft.
4. An impeller according to any preceding claim, wherein the majority of the shaft is formed from titanium or an alloy thereof.
5. An impeller according to any preceding claim, comprising a plurality of arrays of blades mounted or integral with the shaft.
6. An impeller according to Claim 5, wherein at least one of the arrays is integral with said at least part of the shaft.
7. An impeller according to Claim 5 or Claim 6, wherein at least one of the arrays is mounted on the shaft and formed from material having a lower stiffness than said at least part of the shaft.
8. An impeller for a vacuum pump, the impeller comprising a shaft, at least part of the shaft being formed from titanium or an alloy thereof, the shaft having mounted thereon one or more arrays of blades formed from material having a lower stiffness than said at least part of the shaft.
9. An impeller according to Claim 8, comprising one or more further arrays of blades integral with said at least part of the shaft.
10. An impeller according to any of Claims 5 to 9, wherein a sleeve having a plurality of arrays of blades integral therewith is mounted on the shaft, the sleeve being formed from material having a lower stiffness than said at least part of the shaft.
11. An impeller according to any of Claims 7 to 10, wherein said material comprises aluminium or an alloy thereof.
12. An impeller according to any of Claims 7 to 10, wherein said material comprises magnesium or an alloy thereof.
PCT/GB2005/002005 2004-06-07 2005-05-23 Vacuum pump impeller Ceased WO2005121561A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB0412667.8A GB0412667D0 (en) 2004-06-07 2004-06-07 Vacuum pump impeller
GB0412667.8 2004-06-07

Publications (1)

Publication Number Publication Date
WO2005121561A1 true WO2005121561A1 (en) 2005-12-22

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Family Applications (1)

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PCT/GB2005/002005 Ceased WO2005121561A1 (en) 2004-06-07 2005-05-23 Vacuum pump impeller

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GB (1) GB0412667D0 (en)
WO (1) WO2005121561A1 (en)

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103562554A (en) * 2011-06-16 2014-02-05 埃地沃兹日本有限公司 Rotor and vacuum pump
WO2015040022A1 (en) * 2013-09-23 2015-03-26 Oerlikon Leybold Vacuum Gmbh Rotor alloys of a turbo molecular pump
WO2015071143A1 (en) * 2013-11-12 2015-05-21 Oerlikon Leybold Vacuum Gmbh Rotor device for a vacuum pump, and vacuum pump
EP3088746A1 (en) * 2015-04-30 2016-11-02 Pfeiffer Vacuum Gmbh Vacuum pump
WO2022112212A1 (en) * 2020-11-25 2022-06-02 Edwards s.r.o. Rotor assembly for a turbomolecular pump

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3650581A (en) * 1969-06-30 1972-03-21 Karl Boden Wilhelm Groth & Die Bearing systems
US4579508A (en) * 1982-04-21 1986-04-01 Hitachi, Ltd. Turbomolecular pump
US5632597A (en) * 1995-03-31 1997-05-27 Osaka Vacuum, Ltd. Thread groove type vacuum pump
US20030155830A1 (en) * 2000-05-06 2003-08-21 Christian Beyer Magnetic bearing with damping

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3650581A (en) * 1969-06-30 1972-03-21 Karl Boden Wilhelm Groth & Die Bearing systems
US4579508A (en) * 1982-04-21 1986-04-01 Hitachi, Ltd. Turbomolecular pump
US5632597A (en) * 1995-03-31 1997-05-27 Osaka Vacuum, Ltd. Thread groove type vacuum pump
US20030155830A1 (en) * 2000-05-06 2003-08-21 Christian Beyer Magnetic bearing with damping

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103562554A (en) * 2011-06-16 2014-02-05 埃地沃兹日本有限公司 Rotor and vacuum pump
EP2722528A4 (en) * 2011-06-16 2014-12-03 Edwards Japan Ltd ROTOR AND VACUUM PUMP
CN103562554B (en) * 2011-06-16 2016-12-21 埃地沃兹日本有限公司 rotor and vacuum pump
EP2722528B1 (en) 2011-06-16 2018-05-30 Edwards Japan Limited Rotor assembly and vacuum pump there with
WO2015040022A1 (en) * 2013-09-23 2015-03-26 Oerlikon Leybold Vacuum Gmbh Rotor alloys of a turbo molecular pump
WO2015071143A1 (en) * 2013-11-12 2015-05-21 Oerlikon Leybold Vacuum Gmbh Rotor device for a vacuum pump, and vacuum pump
CN105765231A (en) * 2013-11-12 2016-07-13 厄利孔莱博尔德真空有限责任公司 Rotor device for a vacuum pump, and vacuum pump
US20160290343A1 (en) * 2013-11-12 2016-10-06 Oerlikon Leybold Vacuum Gmbh Rotor device for a vacuum pump, and vacuum pump
CN105765231B (en) * 2013-11-12 2018-10-26 莱宝有限公司 Rotor arrangement and vacuum pump for vacuum pump
EP3088746A1 (en) * 2015-04-30 2016-11-02 Pfeiffer Vacuum Gmbh Vacuum pump
WO2022112212A1 (en) * 2020-11-25 2022-06-02 Edwards s.r.o. Rotor assembly for a turbomolecular pump
US12345277B2 (en) 2020-11-25 2025-07-01 Edwards s.r.o. Rotor assembly for a turbomolecular pump

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Publication number Publication date
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