GB2353902A - Canned magnet structure for motor - Google Patents
Canned magnet structure for motor Download PDFInfo
- Publication number
- GB2353902A GB2353902A GB9920321A GB9920321A GB2353902A GB 2353902 A GB2353902 A GB 2353902A GB 9920321 A GB9920321 A GB 9920321A GB 9920321 A GB9920321 A GB 9920321A GB 2353902 A GB2353902 A GB 2353902A
- Authority
- GB
- United Kingdom
- Prior art keywords
- magnets
- rotor
- depression
- magnet
- assembly
- 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- Withdrawn
Links
Classifications
-
- 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
- H02K1/22—Rotating parts of the magnetic circuit
- H02K1/27—Rotor cores with permanent magnets
- H02K1/2706—Inner rotors
- H02K1/272—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis
- H02K1/274—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis the rotor consisting of two or more circumferentially positioned magnets
- H02K1/2753—Inner rotors the magnetisation axis of the magnets being perpendicular to the rotor axis the rotor consisting of two or more circumferentially positioned magnets the rotor consisting of magnets or groups of magnets arranged with alternating polarity
- H02K1/278—Surface mounted magnets; Inset magnets
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Permanent Field Magnets Of Synchronous Machinery (AREA)
- Iron Core Of Rotating Electric Machines (AREA)
- Permanent Magnet Type Synchronous Machine (AREA)
Abstract
An array of permanent magnets 13 is retained on a cylindrical rotor body 11 by a carbon fibre can assembly. Each magnet has a depression 14 at the centre section such that differential interference is established between the magnets and the can assembly, significant high pressure zones being established between the can assembly and the magnet at the axial ends thereof and a significant low pressure zone is established at the axial central portion. The depressions may be shaped so as to provide a continuous depressed band about the rotor and the transition 17 is designed with a sufficient length to avoid stress. The can may comprise two sections 19,20.
Description
3r, TITLE Rotor f or permanent magnet motor
DESCRIPTION
Field of the Invention The invention relates to an improvement in the structure for attaching permanent magnets of a rotor for a motor.
Description of the prior art
A conventional rotor for a permanent magnet motor is disclosed in USA-4,433,261. Referring to Figure 5,a rotor 61 is constructed in such a manner that permanent magnets 62 are adhered around a rotor shaft 63 with a adhesive (not shown) and are secured by a can 64 around the outer periphery thereof as well as by end plates 65 and 66 at the axial ends thereof. The end plates 65 and 66 play a very important role to hold the permanent magnets 62 as well as the can 64 and prevent the can 64 from moving outwards. Any component which moves will cause loss of the dynamic balance of the rotor and will thus cause a large vibration. Because of the necessity of having two end plates, there are the following disadvantages:
(a) the end plates increase the weight and the axial length of the motor rotor. They are not good f or rotor dynamics; (b) it is expensive to manufacture the rotor in order to control the correct interference between the shafts and the end plates, to eliminate the gaps between the end plates and the cans; (c) eddy current losses are expected in the end plates, reducing the efficiency of the motor.
Summary of the Invention
It is an object of the invention to omit any end plate from a rotor of a permanent magnet type motor.
The invention provides a rotor for a permanent magnet motor, comprising: a cylindrical rotor body; permanent magnets located around the periphery of the cylindrical rotor body, each magnet having a depression at an intermediate axial zone along its outer surface; and a can or can assembly surrounding the magnets to retain them on the rotor body, and establis hing different interference fits with the depressions in the magnets and the non-depression end portions of the magnets axially outwardly of the depressions.
Description of the Drawings
Figure 1 is an axial section through a rotor for a permanent magnet motor according to an embodiment of the invention; Figure 2 is an enlarged overview of a magnet and can assembly of the rotor of Figure 1; Figure 3 is a left half section of the magnet of Figure 1 and a graph of a pressure variation applied to the magnet at each axial position; Figure 4 is a section of the magnet when the magnet is deformed under the motor operation; and Figure 5 is a similar view to Figure 1, but showing the prior art rotor of USA-4433261.
Detailed Description of the Invention
Figure 1 shows an embodiment of a rotor of a permanent magnet motor. A cylindrical rotor body 11 is fixed to a rotor shaft (not shown) in such a manner that the rotor shaft is tightly inserted into a through hole 12 of the cylindrical rotor body 11. Permanent magnets 13, each of which is a sector of a cylinder are assembled together as a complete cylinder located around the outer periphery of the cylindrical rotor body 11. The number of sectors of the permanent magnets 13 depends on the number of poles of the motor.
Referring to Figure 2, a shallow depression 14 is formed around the outer periphery of the permanent magnets 13 at a central axial zone between the opposite axial ends. In Figure 2 the depressions of the different magnets link together so that in the assembled rotor the depressions form a continuous shallow annular depression around the entire magnet assembly. Alternatively, however, the depressions may be discrete indentations or depressions in the outer surfaces of the individual magnets so that when assembled into the complete rotor assembly there is provided a circular array of shallow dimple-like depressions around the magnet assembly. The full diameter portions of the magnets 13 at the opposite axial ends of each depression 14 will be referred to as non-depression portions 15 and 16. The depression 14 links smoothly to the non-depression portions 15 and 16 by transition slopes 17 and 18. A can assembly comprising two carbon-fibre can portions 19 and 20 is tightly assembled with a differential interference fit on the magnets 13 so as to retain the magnets 13 around the cylindrical rotor body 11. The interference fit is a differential interference, with the can portions 19 and 20 generally following the contour of the outer periphery of the magnets to establish different interference fits with the non-depression portions 15 and 16 and the depression 14. Theref ore a higher radial interference D1 is established between the can portions 19 and 20 and the magnet 13 at both the non-depression portions 15 and 16 at the axial end sections of the magnets 13, while a lower radial interference D2 is established between the can portions 19 and 20 and the magnets 13 at the depression 14, at the axial centre section of the magnets 13. Because of the -4 differential interference, a characteristic pressure variation at the inner diameter of the magnets 13, where they contact the cylindrical rotor body 11, is established axially along each magnet 13. As shown in Figure 3, high pressure bands are established corresponding to the non- depression portions 15 and 16 next to the transition slopes 17 and 18 at opposite axial ends of the magnet 13 and significant low pressure bands are established corresponding to the axially outer portions of the depression 14 next to the transition slopes 17 and 18 at the centre of the magnet 13. Figure 3 also shows the much smoother pressure variation a xially along the magnets of the prior art which establishes a more uniform interference between the magnets and the can or can assembly.
Because of the high pressure bands the following advantages are established.
(a) The outward radial bending or deformation of the magnets 13 at their axial ends is reduced as shown in Figure 4. This is a 129,.- reduction in comparison with the prior art. This outward radial bending is unfavourable in rotor dynamics, so that the reduced bending is advantageous.
(b) The stress distribution exerted on the can portions 16 and 17 is changed relative to the prior art so that the can portions 16 and 17 are prevented from moving axially outwards. Thus a self-locking mechanism for the can portions 16 and 17 is established, sufficient to permit the end plates of the prior art to be omitted according to the invention.
The maximum equivalent stress occury at the inner diameter of the can portions 16 and 17 and the maximum equivalent stress is reduced because of the differential interference, so that the fatigue life of the rotor is increased. Furthermore, the maximum stress point occurs at two zones each about one quarter of the total axial magnet length from the ends. In contrast, in the prior art the maximum stress point occurs at the centre of the total axial magnet length.
The axial length of each transition slope is preferably larger than a predetermined value, since a smaller axial length of slope means a steeper slope and thus an undesirable stress concentration at the inner diameter of the can or can assembly.
Since the above rotor uses no end plates, the weight and the axial length of the rotor are reduced, so that the manufacturing cost is significantly reduced. The above rotor is applicable for a high speed turbo alternator/motor shown in GB-A-2324913, for example. Such an alternator/motor could be driven at 120,000 rpm.
-6
Claims (4)
1 A rotor for a permanent magnet motor, comprising: a cylindrical rotor body; permanent magnets located around the periphery of the cylindrical rotor body, each magnet having a depression at an intermediate axial zone along its outer surface; and a can or can assembly surrounding the magnets to retain them on the rotor body, and establishing different interference fits with both the depressions in the magnets and the non-depression end portions of the magnets axially outwardly of the depressions.
2 A rotor according to claim 1, wherein the depression of each magnet links smoothly to non-depression end portions of the magnets by transition slopes.
3 A rotor according to claim 1, wherein the magnets are surrounded by a can assembly axially divided into two can portions.
4 A rotor according to any preceding claim, wherein the depressions of the different magnets link together so that in the assembled rotor the depressions form a continuous shallow annular depression around the entire magnet assembly.
A rotor for a permanent magnet motor, substantially as described herein with reference to Figures 1 to 4.
Priority Applications (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB9920321A GB2353902A (en) | 1999-08-28 | 1999-08-28 | Canned magnet structure for motor |
JP2000196035A JP2001069699A (en) | 1999-08-28 | 2000-06-29 | Rotor for permanent magnet type dynamo-electric machine |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB9920321A GB2353902A (en) | 1999-08-28 | 1999-08-28 | Canned magnet structure for motor |
Publications (2)
Publication Number | Publication Date |
---|---|
GB9920321D0 GB9920321D0 (en) | 1999-11-03 |
GB2353902A true GB2353902A (en) | 2001-03-07 |
Family
ID=10859924
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
GB9920321A Withdrawn GB2353902A (en) | 1999-08-28 | 1999-08-28 | Canned magnet structure for motor |
Country Status (2)
Country | Link |
---|---|
JP (1) | JP2001069699A (en) |
GB (1) | GB2353902A (en) |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2406000A (en) * | 2003-08-27 | 2005-03-16 | Freepower Ltd | Magnetic coupling for a turbo generator arrangement |
GB2414600A (en) * | 2004-05-26 | 2005-11-30 | Gen Electric | Multiple spaced ring coil retaining assembly with rings of different widths |
WO2020188006A1 (en) | 2019-03-20 | 2020-09-24 | Safran Electrical & Power | Improved method for manufacturing a rotor |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP4259548B2 (en) * | 2006-07-24 | 2009-04-30 | トヨタ自動車株式会社 | Rotor for motor and manufacturing method thereof |
JP2018085864A (en) * | 2016-11-24 | 2018-05-31 | アイシン・エィ・ダブリュ株式会社 | Rotor |
Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS63224640A (en) * | 1987-03-11 | 1988-09-19 | Isuzu Motors Ltd | Rotor structure for high speed rotary electric machine |
GB2299217A (en) * | 1995-03-23 | 1996-09-25 | Aisin Seiki | Method of assembling a permanent magnet rotor |
WO1997045917A1 (en) * | 1996-05-29 | 1997-12-04 | Empresa Brasileira De Compressores S/A. - Embraco | A rotor cover for an electric motor |
-
1999
- 1999-08-28 GB GB9920321A patent/GB2353902A/en not_active Withdrawn
-
2000
- 2000-06-29 JP JP2000196035A patent/JP2001069699A/en active Pending
Patent Citations (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS63224640A (en) * | 1987-03-11 | 1988-09-19 | Isuzu Motors Ltd | Rotor structure for high speed rotary electric machine |
GB2299217A (en) * | 1995-03-23 | 1996-09-25 | Aisin Seiki | Method of assembling a permanent magnet rotor |
WO1997045917A1 (en) * | 1996-05-29 | 1997-12-04 | Empresa Brasileira De Compressores S/A. - Embraco | A rotor cover for an electric motor |
Cited By (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2406000A (en) * | 2003-08-27 | 2005-03-16 | Freepower Ltd | Magnetic coupling for a turbo generator arrangement |
GB2406000B (en) * | 2003-08-27 | 2006-12-20 | Freepower Ltd | Working energy recovery system having rotary magnetic coupling |
GB2414600A (en) * | 2004-05-26 | 2005-11-30 | Gen Electric | Multiple spaced ring coil retaining assembly with rings of different widths |
GB2414600B (en) * | 2004-05-26 | 2007-10-24 | Gen Electric | Variable pitch manifold for rotor cooling in an electrical machine |
WO2020188006A1 (en) | 2019-03-20 | 2020-09-24 | Safran Electrical & Power | Improved method for manufacturing a rotor |
Also Published As
Publication number | Publication date |
---|---|
JP2001069699A (en) | 2001-03-16 |
GB9920321D0 (en) | 1999-11-03 |
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Legal Events
Date | Code | Title | Description |
---|---|---|---|
WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |