Electric machine-modular

Patent metadata

Field	Value
Publication number	US-9318938-B2
Application number	US-201013148897-A
Country	US
Kind code	B2
Filing date	Feb 12, 2010
Priority date	Feb 13, 2009
Publication date	Apr 19, 2016
Grant date	Apr 19, 2016

Abstract

An electric machine ( 100 ) comprises a stator ( 112 ) and a rotor ( 114 a, b ) mounted for rotation about a rotor axis ( 120 ) with respect to the stator. Permanent magnets ( 124 a, b ) are carried by the rotor. The rotor has an output ( 190 ). The stator has coils ( 122 ) wound on stator bars ( 116 ) for interaction with the magnets. The rotor has two stages ( 114 a,b ) arranged one at either end of the stator bars, with two air gaps ( 126 a,b ) between the ends of the bars and the rotor stages. An annular housing ( 102, 142 a, b, 146 ) retains and mounts the stator. A bearing ( 164 a, b ) is between the rotor and stator, the rotor being hollow around said rotor axis. There are two significant magnetic flux paths ( 30,30 ′) of the motor. The first passes between adjacent coils in a circuit on a substantially circumferential plane with respect to the axis ( 120 ). A second path 30 ′ is in an axial plane, passing around the bearing. The stator coils are spaced around the rotor axis and approach the rotor axis no closer than a first, stator radius (R 1 ) of the stator. The bearing comprises rolling elements rolling on a surface of the rotor that is no closer to the rotor axis than a second, rotor radius (r), which rotor radius is between 60% and 90% of the stator radius.

First claim

The invention claimed is:

1. A shaftless electric machine comprising a stator and a rotor mounted for rotation about a rotor axis with respect to the stator, permanent magnets being carried by the rotor, an output on the rotor, the stator comprising coils wound on stator bars for interaction with the magnets of the rotor, the rotor having two stages arranged one at either end of the stator bars, with air gaps between the ends of the bars and the rotor stages, an annular housing retaining and mounting the stator; a bearing radially between the rotor and stator, the rotor being hollow around said rotor axis, said output comprising flange connection means and a flange by which the flange is connectable to the rotor for transmitting rotary power to or from the rotor, wherein the entire load between the output and the annular housing is transmitted through the bearing between the stator and rotor, whereby no other mounting of the rotor or its output with respect to the annular housing is provided, and the rotor stages each comprise an inner radial portion and an outer radial portion, the outer radial portion being spaced axially further away from the stator than the inner radial portion, the outer radial portion having an annular section on which are mounted said permanent magnets, the inner radial portions of the rotor stages are connected together such that the rotor stages and said stator enclose said bearing and the bearing is mounted on the inner radial portions of the rotor stages.

2. The electric machine as claimed in claim 1 , in which there are at least two significant magnetic flux paths of the motor: a first passing through a first stator bar, across a first of the air gaps, through a first magnet on a first stage of the rotor into a back iron of the first stage, into an adjacent second magnet, across the first air gap into a second stator bar adjacent the first, across the second air gap, through a third magnet on second stage of the rotor into a back iron of the second stage, into an adjacent fourth magnet, across the second air gap and back into the first stator bar; and a second path passing through the first stator bar, across the first air gap and through the first magnet on the first stage and into the back iron of the first stage, through the first stage into the second stage of the rotor around said bearing into the back iron of the second stage, into the fourth magnet, across the second air gap and back into the first stator bar.

3. The electric machine as claimed in claim 1 , in which the stator coils are spaced around the rotor axis and said stator coils approach the rotor axis no closer than a first, stator radius (R 1 ) of the stator; and the bearing comprises rolling elements rolling on an inner race of said bearing, the inner race of the bearing being mounted to a surface of the rotor that is no closer to the rotor axis than a second, rotor radius (r), which rotor radius is between 60% and 90% of the stator radius.

4. The electric machine as claimed in claim 3 , in which the stator coils have a radial extent (C 1 ) such that the smallest circle enclosing the stator coils has a coil radius (R 2 ) where the stator radius (R 1 ) is between 50% and 80% of the coil radius (R 2 ) and the radial extent is equal to the difference of the coil radius and the stator radius (C 1 =R 2 −R 1 ).

5. The electric machine as claimed in claim 4 , in which the coils have a circumferential extent (C 2 ) that is between 50% and 150% of the radial extent.

6. The electric machine as claimed in claim 1 , in which the bars are axially aligned with the rotation axis of the rotor, the bearing being between two radial planes that intersect said air gaps.

7. The electric machine as claimed in claim 1 , in which said air gaps are axial air gaps extending in a radial direction.

8. The electric machine as claimed in claim 1 , in which the bearing is between two radial planes that intersect the coils, bars or a shoe of the stator.

9. The electric machine as claimed in claim 1 , in which the bearing is between two radial planes that intersect the coils of the stator.

10. The electric machine as claimed in claim 1 , in which the bars and coils thereon are enclosed by a stator housing that extends between the air gaps and defines a chamber incorporating cooling medium to cool the coils.

11. The electric machine as claimed in claim 10 , in which said stator housing comprises two annular plates and two cylindrical walls, the annular plates including recesses to locate the bars within the chamber.

12. The electric machine as claimed in claim 10 , in which the material of the stator housing is non-magnetic and electrically non-conducting.

13. The electric machine as claimed in claim 10 , in which the material of the stator housing in the air gaps is heat insulating.

14. The electric machine as claimed in claim 10 , in which said stator housing is thinned at the ends of the bar to minimize the gap between the bars and the magnets on the rotor.

15. The electric machine as claimed in claim 11 , in which said cylindrical walls are aluminium and said annular plates are plastics material.

16. The electric machine as claimed in claim 11 , in which said cylindrical walls are a radially inner and a radially outer wall, said radially outer wall comprising a portion of said annular housing and having means to mount the machine and said inner wall mounting said bearing.

17. The electric machine as claimed in claim 1 , in which each said inner radial portion comprises a cylindrical flange with an interface for mutual inter-engagement.

18. The electric machine as claimed in claim 17 , further comprising a spacer between the cylindrical flanges to adjust preload on the bearing.

19. The electric machine as claimed in 17 , in which said cylindrical flanges include bosses arranged parallel said rotor axis to receive fasteners for clamping said rotor stages together.

20. The electric machine as claimed in claim 1 , in which said flange connection means comprises an annular axial face of the rotor including fasteners for connection of said flange.

21. The electric machine as claimed in claim 20 , in which the flange comprises a disc and a hub.

22. The electric machine as claimed in claim 20 , in which said disc is connectible by said fasteners to bosses of the rotor.

23. The electric machine as claimed in claim 1 , in which the bearing comprises two bearings, one on either side of a flange on the stator, whereby axial location of the rotor stages with respect to the stator is determined.

24. The electric machine as claimed in claim 1 , in which said annular housing has axial interfaces enabling at least two such machines to be connected together sharing a common rotor axis.

25. The electric machine as claimed in claim 24 , in which the bearing comprises two bearings, one on either side of a flange on the stator, whereby axial location of the rotor stages with respect to the stator is determined and the rotors of the connected machines are interconnected by fasteners passing through bosses of adjacent rotors of adjacent machines, a spacer being disposed between them.

26. The electric machine as claimed in claim 1 , in which the exposed ends of the machine are closed by covers fitted on the annular housing, at least one having a central aperture through which said output is adapted to extend.

27. The electric machine as claimed in claim 1

Assignees

• Carpenter Nicholas
• Dowson Simon
• Woolmer Tim
• Leong Chee Yeow
• Treharne William
• Mcculloch Malcolm
• Isis Innovation

Inventors

• Carpenter Nicholas
• Dowson Simon
• Woolmer Tim
• Leong Chee Yeow
• Treharne William
• Mcculloch Malcolm

Classifications

• H02K1/28

  Means for mounting or fastening rotating magnetic parts on to, or to, the rotor structures · CPC title

• H02K7/083

  radially supporting the rotary shaft at both ends of the rotor (H02K7/086, H02K7/09 take precedence) · CPC title

• H02K1/2713

  the magnetisation axis of the magnets being axial, e.g. claw-pole type · CPC title

• H02K21/24 Primary

  with magnets axially facing the armatures, e.g. hub-type cycle dynamos · CPC title

• H02K9/197

  in which the rotor or stator space is fluid-tight, e.g. to provide for different cooling media for rotor and stator · CPC title