WO2011047483A1

WO2011047483A1 - Permanent magnet rotor assembly provided with welded magnet retaining elements

Info

Publication number: WO2011047483A1
Application number: PCT/CA2010/001681
Authority: WO
Inventors: Eric Latulippe; Martin Houle; George Bursuc; Sebastien Bigras; Bruno Carpenter; Diane Laflamme; Jane Roundell; Steve Fleming; Gerald Martin; Sylvain Rodier; Gervais Gagnon; Samuel Dubois
Original assignee: Tm4 Inc.
Priority date: 2009-10-22
Filing date: 2010-10-21
Publication date: 2011-04-28
Also published as: CN102577032A

Abstract

The present disclosure is concerned with a permanent magnet rotor for an electric machine provided with an internal stator and a coaxial external rotor. To overcome the drawbacks associated with the use of an adhesive to mount the permanent magnets to the rotor body, permanent magnet retaining elements are mounted to the inner surface of the rotor, between adjacent magnets.

Description

TITLE

Permanent Magnet Rotor Assembly provided with welded magnet retaining elements

FIELD

[0001] The present invention relates to permanent magnet electric machines. More specifically, the present invention is concerned with a permanent magnet rotor assembly including magnet retaining elements welded to the rotor.

BACKGROUND

[0002] Permanent magnet electric machines are well known in the art. They are usually provided with a stator and a rotor coaxially mounted to the stator so as to rotate thereabout.

[0003] Some permanent magnet electric machines are provided with an internal stator and an external rotor generally enclosing the stator. When this is the case, the rotor has a generally cylindrical body and the permanent magnets are positioned on the inner surface thereof. To properly mount the permanent magnet to the inner surface of the cylindrical rotor body it is conventional to use an adhesive to prevent relative movements of adjacent permanent magnets.

[0004] The use of an adhesive between the permanent magnets and the inner surface of the cylindrical rotor body has many drawbacks. First, an adequate adhesive must be selected since the operating temperature of an electric machine may be quite high. Second, the cost associated with the use of an adhesive is quite high when the price of the adhesive, the manual labour costs, the tooling costs and the parts cleaning costs are added. Indeed, for the adhesive to work properly, the mating surfaces of the permanent magnets and the cylindrical body are generally properly prepared and cleaned before the adhesive is applied, which is both time consuming and increases the manufacturing cost of the rotor.

BRIEF DESCRIPTION OF THE DRAWINGS [0005] In the appended drawings:

[0006] Figure 1 is a perspective view of a magnet retaining element according to a first illustrative embodiment;

[0007] Figure 2 is a perspective view of a portion of a rotor provided with magnet retaining elements as illustrated in Figure 1 , positioned between adjacent magnets;

[0008] Figure 3 is a sectional view taken along line 3-3 of Figure 2;

[0009] Figure 4 is a perspective view of a magnet retaining element according to a second illustrative embodiment;

[0010] Figure 5 is a perspective view of a portion of a rotor provided with magnet retaining elements as illustrated in Figure 4, positioned between adjacent magnets;

[0011] Figure 6 is a sectional view taken along line 6-6 of Figure 5; [0012] Figure 7 is a perspective view of a magnet retaining element according to a third illustrative embodiment;

[0013] Figure 8 is a perspective view of a portion of a rotor provided with magnet retaining elements as illustrated in Figure 7, positioned between adjacent magnets;

[001 ] Figure 9 is a sectional view taken along line 9-9 of Figure 8;

[0015] Figure 10 is a perspective view of a magnet retaining element according to a fourth illustrative embodiment;

[0016] Figure 11 is a perspective view of a portion of a rotor provided with magnet retaining elements as illustrated in Figure 10, positioned between adjacent magnets;

[0017] Figure 12 is a sectional view taken along line 12-12 of Figure

11;

[0018] Figure 13 is a perspective view of a magnet retaining element according to a fifth illustrative embodiment;

[0019] Figure 14 is a perspective view of a portion of a rotor provided with magnet retaining elements as illustrated in Figure 13, positioned between adjacent magnets;

[0020] Figure 15 is a sectional view taken along line 15-15 of Figure [0021] Figure 16 is a perspective view of a magnet retaining element according to a sixth illustrative embodiment;

[0022] Figure 17 is a perspective view of a portion of a rotor provided with magnet retaining elements as illustrated in Figure 16, positioned between adjacent magnets;

[0023] Figure 18 is a sectional view taken along line 18-18 of Figure

17;

[0024] Figure 19 is a perspective view of a magnet retaining element according to a seventh illustrative embodiment;

[0025] Figure 20 is a perspective view of a portion of a rotor provided with magnet retaining elements as illustrated in Figure 19, positioned between adjacent magnets;

[0026] Figure 21 is a sectional view taken along line 21-21 of Figure

20;

[0027] Figure 22 is a perspective view of a magnet retaining element according to a eighth illustrative embodiment;

[0028] Figure 23 is a perspective view of a portion of a rotor provided with magnet retaining elements as illustrated in Figure 22, positioned between adjacent magnets;

[0029] Figure 24 is a sectional view taken along line 24-24 of Figure [0030] Figure 25 is a perspective view of a magnet retaining element according to a ninth illustrative embodiment;

[0031] Figure 26 is a perspective view of a portion of a rotor provided with magnet retaining elements as illustrated in Figure 25, positioned between adjacent magnets;

[0032] Figure 27 is a sectional view taken along line 27-27 of Figure

29;

[0033] Figure 28 is a sectional view taken along line 28-28 of Figure

29;

[0034] Figure 29 is a perspective view of a magnet retaining element according to a tenth illustrative embodiment;

[0035] Figure 30 is a perspective view of a portion of a rotor provided with magnet retaining elements as illustrated in Figure 29, positioned between adjacent magnets;

[0036] Figure 31 is a sectional view taken along line 31-31 of Figure

30;

[0037] Figure 32 is a perspective view of a magnet retaining element according to a eleventh illustrative embodiment;

[0038] Figure 33 is a perspective view of a portion of a rotor provided with magnet retaining elements as illustrated in Figure 32, positioned between and on top of adjacent magnets; [0039] Figure 34 is a sectional view taken along line 34-34 of Figure

36;

[0040] Figure 35 is a perspective view of a magnet retaining element according to a twelfth illustrative embodiment;

[0041] Figure 36 is a perspective view of a portion of a rotor provided with magnet retaining elements as illustrated in Figure 35, positioned between adjacent magnets;

[0042] Figure 37 is a front elevational view of a portion of the stator of Figure 36;

[0043] Figure 38 is a perspective view of a magnet retaining element according to a thirteenth illustrative embodiment;

[0044] Figure 39 is a perspective view of a portion of a rotor provided with magnet retaining elements as illustrated in Figure 38, positioned between and on top of adjacent magnets;

[0045] Figure 40 is a sectional view taken along line 40-40 of Figure

39;

[0046] Figure 41 is a perspective view of a magnet retaining arrangement according to a fourteenth illustrative embodiment;

[0047] Figure 42 is a perspective view of a portion of a rotor provided with magnet retaining arrangements as illustrated in Figure 41 , positioned under the magnet ends; [0048] Figure 43 is a sectional view taken along line 43-43 of Figure

42;

[0049] Figure 44 is a perspective view of a magnet retaining arrangement according to a fifteenth illustrative embodiment;

[0050] Figure 45 is a perspective view of a portion of a rotor provided with magnet retaining arrangements as illustrated in Figure 44, positioned under the magnet ends;

[0051] Figure 46 is a sectional view taken along line 46-46 of Figure

45;

[0052] Figure 47 is a perspective view of a magnet retaining element according to a sixteenth illustrative embodiment;

[0053] Figure 48 is a perspective view of a portion of a rotor provided with magnet retaining elements as illustrated in Figure 47, positioned between adjacent magnets;

[0054] Figure 49 is a perspective view of a magnet retaining element according to a seventeenth illustrative embodiment;

[0055] Figure 50 is a perspective view of a portion of a rotor provided with magnet retaining elements as illustrated in Figure 49, positioned between adjacent magnets;

[0056] Figure 51 is a perspective view of a magnet retaining element according to a eighteenth illustrative embodiment; [0057] Figure 52 is a perspective view of a portion of a rotor provided with magnet retaining elements as illustrated in Figure 51 , positioned between adjacent magnets;

[0058] Figure 53 is a perspective view of a rotor provided with a magnet retaining cage according to a nineteenth illustrative embodiment; and

[0059] Figure 54 is a perspective view of a magnet retaining cage according to a twentieth illustrative embodiment.

DETAILED DESCRIPTION

[0060] In accordance with an illustrative embodiment, there is provided a rotor assembly for an external rotor electric machine, the rotor assembly comprising:

a generally cylindrical rotor body provided with an internal surface; the generally cylindrical rotor body defining a longitudinal rotation axis;

at least two permanent magnets longitudinally mounted to the internal surface of the rotor body, each at least two permanent magnets includes first and second longitudinally opposite ends and first and second opposite faces, the first face being configured and sized as to contact the internal surface of the rotor body; and

at least two spacing elements longitudinally mounted to the inner surface of the rotor body between adjacent permanent magnets via at least one respective spot weld; the at least two spacing elements being so configured and sized as to prevent relative circumferential and radial movements of the permanent magnets with respect to the rotor body. [0061] The use of the word "a" or "an" when used in conjunction with the term "comprising" in the claims and/or the specification may mean "one", but it is also consistent with the meaning of "one or more", "at least one", and "one or more than one". Similarly, the word "another" may mean at least a second or more.

[0062] As used in this specification and claims, the words

"comprising" (and any form of comprising, such as "comprise" and "comprises"), "having" (and any form of having, such as "have" and "has"), "including" (and any form of including, such as "include" and "includes") or "containing" (and any form of containing, such as "contain" and "contains"), are inclusive or open-ended and do not exclude additional, unrecited elements or process steps.

[0063] Generally stated, illustrative embodiments described herein are concerned with a permanent magnet rotor for an electric machine provided with an internal stator and a coaxial external rotor. To overcome the above- mentioned drawbacks associated with the use of an adhesive, permanent magnet retaining elements are mounted between adjacent permanent magnets via welds.

[0064] Turning now more specifically to Figures 1 to 3 of the appended drawings, a permanent magnet rotor 100 provided with magnet retaining elements 102 according to a first illustrative embodiment will be described.

[0065] The rotor 100 has an internal surface 104 configured to receive permanent magnets 106 thereon. As can be seen from Figure 3, the contact surfaces of the magnet 106 and the internal surface 104 of the stator 100 correspond to one another to adequately mount the magnet 106 to the stator 100.

[0066] The internal surface 104 also includes a shoulder 108 so positioned that the distal longitudinal ends 109 of the magnets 106 may be abutted thereon when the magnets 106 are correctly positioned onto the surface 104.

[0067] As can be better seen from Figure 1, the magnet retaining element 102 is a longitudinal element including a central portion 112 provided with two spot weld locations 114 (shown in dashed lines in Figure 1 ), a proximate T-shaped end 116 and a distal elevated and larger T-shaped end 118.

[0068] The proximate T-shaped end 116 is configured to receive the proximate corners 120, 122 of adjacent magnets 106 to prevent their longitudinal movements onto the surface 104 of the rotor 100. To prevent damaging the corners of the magnets 106, the T-shaped end 116 is provided with rounded cut-out portions 117 and 119.

[0069] The distal elevated larger T-shaped end 118 is configured to prevent the permanent magnets 106 from being removed from the surface 104 by an inwardly directed radial force. Indeed, its wide T-portion 124 overlaps a portion of the adjacent magnets 106 positioned on either side of the magnet retaining element 102, as can be seen from Figure 3. The elevation of the T- shaped end 118 is such that the magnets 106 are contacted by the underside [0070] As can be seen from Figure 3, the magnet retaining element

102 is spot welded to the surface 104 of the rotor 100 to adequately mount the magnet retaining element 102 to the rotor 100 between adjacent magnets 106.

[0071] The width of the central portion 112 of the magnet retaining element 102 is sized to circumferentially space adjacent magnets 106 of a predetermined distance, which depends on the design of the rotor. It is to be noted that the internal surface of the rotor 00 may optionally include markings to properly position the magnet retaining elements prior to the installation of the magnets 106.

[0072] The magnet retaining element 102 prevents longitudinal, circumferential and radial movements of the magnets 106 with respect to the rotor 100.

[0073] The magnet retaining element 102 may be made of various materials. It has been found that non-magnetic stainless steel is suitable for this element. Of course, other weldable materials materials such as conventional steel could be used.

[0074] Turning now to Figures 4 to 6 of the appended drawings, a permanent magnet rotor 200 provided with magnet retaining elements 202 according to a second illustrative embodiment will be described. Since the magnet retaining element 202 is very similar to the magnet retaining element 102 described hereinabove, only the differences therebetween will be described hereinbelow. [0075] Generally stated the main difference between the magnet retaining element 202 and the magnet retaining element 102 is the addition of a heat expansion stress relieving element.

[0076] The rotor 200 has an internal surface 204 configured to receive permanent magnets 206 thereon.

[0077] The magnet retaining element 202 is a longitudinal element including a central portion 212 provided with two spot weld locations 214 (shown in dashed lines in Figure 4), a proximate T-shaped end 216 and a distal elevated larger T-shaped end 218.

[0078] The heat expansion stress relieving element consists in a wave 220 provided in the central portion 212. The wave 220 is so configured that it allows the movement of the weld locations 214 towards and away from each other should the heat expansion of the magnet retaining element 202 and the heat expansion of the rotor 200 be different. In other words, the wave 220 allows the longitudinal heat expansion of the magnet retaining element 202 without the application of forces onto the welds. This prevents the welds from being damaged by the forces exerted onto them by the different heat expansion.

[0079] Turning now to Figures 7 to 9 of the appended drawings, a permanent magnet rotor 300 provided with magnet retaining elements 302 according to a third illustrative embodiment will be described. Since the magnet retaining element 302 is very similar to the magnet retaining elements 102 and 202 described hereinabove, only the differences therebetween will be described hereinbelow. [0080] Generally stated the main difference between the magnet retaining element 302 and the magnet retaining element 202 is the nature of the heat expansion stress relieving element.

[0081] The rotor 300 has an internal surface 304 configured to receive permanent magnets 306 thereon.

[0082] The magnet retaining element 302 consists in two longitudinal elements 312A and 312B each provided with a respective spot weld location 314 (shown in dashed lines in Figure 7). The longitudinal element 3 2A includes a proximate T-shaped end 316 and the longitudinal element 312B includes a distal elevated and larger T-shaped end 318.

[0083] The heat expansion stress relieving element consists in a tongue 320 and groove 322 arrangement provided between the adjacent ends of the longitudinal elements 312A and 312B. The tongue and groove arrangement is so configured and sized that when the longitudinal elements 312A and 312B are welded to the internal surface 304, there is a gap between the tongue 320 and the groove 322. This gap allows the longitudinal heat expansion of the magnet retaining element 302 without application of forces onto the welds. This prevents the welds 314 from being damaged by the forces exerted onto them by the different heat expansion.

[0084] Turning now to Figures 10 to 12 of the appended drawings, a permanent magnet rotor 400 provided with magnet retaining elements 402 according to a fourth illustrative embodiment will be described.

[0085] The rotor 400 has an internal surface 404 configured to receive permanent magnets 406 thereon. [0086] As can be better seen from Figure 10, the magnet retaining element 402 is a longitudinal element including a central portion 412 provided with two weld locations (illustrated in dashed lines in Figure 10), a proximate elevated double T-shaped end 416 and an identical distal elevated larger T- shaped end 418. For concision purpose, only the proximate elevated double T- shaped end 416 will be described hereinbelow.

[0087] The proximate T-shaped end 416 includes a first T-portion

420, similar to the T-portion 124 of Figure 1 , configured and sized as to apply pressure onto the adjacent magnets 406, and a second T-portion 422 having downwardly curved ends 424, 426 configured to contact the proximate longitudinal end 428 of the magnets 406 adjacent thereto to prevent longitudinal movement of the magnets 406.

[0088] Accordingly, the shoulder 108 of the internal surface of the rotor is not required, decreasing the required machining of the rotor.

[0089] The magnet retaining element 402 prevents longitudinal, circumferential and radial movements of the magnets 406 with respect to the rotor 400.

[0090] One skilled in the art will understand that a magnet retaining element according to an alternative embodiment (not shown) could be designed by combining the proximate end 416 of the magnet retaining element 406 (Figure 10) and the distal end 118 of the magnet retaining element 102 (Figure 1 ). [0091] Turning now to Figures 13 to 15 of the appended drawings, a permanent magnet rotor 500 provided with magnet retaining elements 502 according to a fifth illustrative embodiment will be described.

[0092] The rotor 500 has an internal surface 504 configured to receive permanent magnets 506 thereon. A shoulder 508 receives the distal longitudinal end 509 of the magnets 506.

[0093] As can be better seen from Figure 13, the magnet retaining element 52 is a longitudinal element including a central arc welding receiving aperture 514. The magnet retaining element 502 has a generally U-shaped cross-section defined by a bottom wall 520 and two angled side walls 522 and 524.

[0094] As can be seen from Figure 15, the angle of the angled side walls 522 and 524 is such that pressure is applied to the magnets 506 adjacent thereto when the magnet retaining element 502 is welded to the rotor 500.

[0095] The magnet retaining element 502 prevents circumferential and radial movements of the magnets 506 with respect to the rotor 500.

[0096] Turning now to Figures 16 to 18 of the appended drawings, a permanent magnet rotor 600 provided with magnet retaining elements 602 according to a sixth illustrative embodiment will be described.

[0097] The rotor 600 has an internal surface 604 configured to receive permanent magnets 606 thereon. A shoulder 608 receives the distal longitudinal end 609 of the magnets 606. [0098] The magnet retaining element 602 is a longitudinal element provided with two arc welding receiving apertures 614.

[0099] As can be better seen from Figure 18, the magnet retaining element 602 has a generally T-shaped cross-section. More specifically, the magnet contacting longitudinal sides of the magnet retaining element 602 include a shoulder 616 generally conforming to the profile of the magnets 606 to thereby prevent circumferential and radial movements of the magnets with respect to the rotor 600.

[0100] It is to be noted that longitudinal movements of the magnets

606 are not prevented by the magnet retaining element 602.

[0101] Turning now to Figures 19 to 21 of the appended drawings, a permanent magnet rotor 700 provided with magnet retaining elements 702 according to a seventh illustrative embodiment will be described.

[0102] The magnet retaining element 702 is a longitudinal element having a generally U-shaped cross-section defined by a bottom wall 722 and two side walls 724 and 726 each provided with respective flanges 728, 730 configured to prevent radial movements of the magnets 706. The free ends of the flanges 728 and 730 are folded to prevent the magnets 706 from being damaged.

[0103] The magnet retaining element 702 further includes two spot weld locations 714 (illustrated in dashed lines in Figure 19).

[0104] As can be seen from Figure 21 , the flanges 728 and 730 are elastically deformed when the magnet retaining element 702 is welded to the rotor 700, to adequately provide pressure on the magnets 706 towards the rotor 700.

[0105] The magnet retaining element 702 prevents circumferential and radial movements of the magnets 706 with respect to the rotor 700.

[0106] One skilled in the art will understand that the magnet retaining element 702 may be made of spring steel.

[0107] Turning now to Figures 22 to 24 of the appended drawings, a permanent magnet rotor 800 provided with magnet retaining elements 802 according to a eighth illustrative embodiment will be described.

[0108] The rotor 800 has an internal surface 804 configured to receive permanent magnets 806 thereon. A shoulder 808 receives the distal longitudinal end 809 of the magnets 806.

[0109] The magnet retaining element 802 is a longitudinal element provided with a central portion 812 and two end portions 816, 818 each provided with a spot weld location 84 (shown in dashed lines in Figure 22).

[0110] The two end portions 816, 818 have a U-shaped cross- section defined by a bottom wall 820 and two side walls 822 and 824, the free ends of which being folded to prevent the magnets 806 from being damaged. The side walls define a C-shaped spring configured and sized to apply pressure onto the magnets 806 to prevent their radial movements.

[0111] It is to be noted that longitudinal movements of the magnets

806 are not prevented by the magnet retaining element 802. [0112] Turning now to Figures 25 to 28 of the appended drawings, a permanent magnet rotor 900 provided with magnet retaining elements 902 according to a ninth illustrative embodiment will be described.

[0113] The rotor 900 has an internal surface 904 configured to receive permanent magnets 906 thereon. A shoulder 908 receives the distal longitudinal end 909 of the magnets 906.

[0114] The magnet retaining element 902 includes a central portion

912 provided with a spot weld location 914 (shown in dashed lines in Figure 25). The central portion 912 is generally U-shaped and provided with flanges 916, 918 configured to apply pressure onto the magnets 906 to prevent radial movements of the magnets 906. From the central portion 912 also extends two biasing assemblies 920, 922 each including two biasing arms 924, 926. As can be seen in Figure 28, the biasing arms 924, 926 apply pressure to a magnet 906 to ensure that the magnets 906 are correctly circumferentially positioned. Indeed, the tolerance used to manufacture the magnets and the magnet retaining elements are such that a small required play is present to allow the assembly of the rotor. The spring arms compensate the small play and prevent circumferential movements of the magnets 906.

[0115] One skilled in the art will understand that one of the biasing assemblies 920, 922 could be omitted.

[0116] The magnet retaining element 902 is made of spring steel or other similar materials.

[0117] It is to be noted that longitudinal movements of the magnets

906 are not prevented by the magnet retaining element 902. [0118] Turning now to Figures 29 to 31 of the appended drawings, a permanent magnet rotor 1000 provided with magnet retaining elements 1002 according to a tenth illustrative embodiment will be described.

[0119] The rotor 1000 has an internal surface 1004 configured to receive permanent magnets 1006 thereon. A shoulder 1008 receives the distal longitudinal end 1009 of the magnets 1006.

[0120] The magnet retaining element 1002 includes a central portion

1012 provided with an arc welding receiving apertures 1014. The central portion 1012 is provided with flanges 1016, 1018 configured to apply pressure onto the magnets 1006 to prevent radial movements of the magnets 1006. From the central portion 1012 also extends two biasing assemblies 1020, 022 each including two biasing arms 1024, 1026 that can be compressed inwardly when the magnet retaining element 1002 is mounted between magnets. As can be seen in Figure 31, the biasing arms 1024, 1026 ensure that the magnets 1006 are correctly circumferentially positioned. As mentioned hereinabove the tolerance used to manufacture the magnets and the magnet retaining elements are such that a small required play is present to allow the assembly of the rotor. The spring arms compensate the small play and prevent circumferential movements of the magnets 1006.

[0121] One skilled in the art will understand that one of the biasing assemblies 1020, 022 could be omitted.

[0122] The magnet retaining element 1002 is made of an aluminum alloy. Of course, other similar materials such as zinc and plastics could be used. [0123] It is to be noted that longitudinal movements of the magnets

1006 are not prevented by the magnet retaining element 1002.

[0124] Turning now to Figures 32 to 34 of the appended drawings, a permanent magnet rotor 1100 provided with magnet retaining assembly 1102 according to an eleventh illustrative embodiment will be described.

[0125] The rotor 1100 has an internal surface 1104 configured to receive permanent magnets 1106 thereon. A shoulder 1108 receives the distal longitudinal end 1109 of the magnets 1106.

[0126] The magnet retaining assembly 1102 includes a spacing element 1120 provided with a central portion 1112 and two longitudinal ends 1116 and 1118 each provided with a spot weld location 1114 (shown in dashed lines in Figure 32) to mount the spacing element 1120 to the internal surface 1104 of the rotor 1100. The central portion 11 12 includes a strap receiving deformation 1122 configured and sized to receive an end 1124 of a strap 1 126 that, when mounted thereto, prevent radial movements of the magnets 1106.

[0127] It is to be noted that the spacing element 1120 prevent circumferential movements of the magnets 1106.

[0128] It is to be noted that longitudinal movements of the magnets 106 are not prevented by the magnet retaining assembly 1102.

[0129] Turning now to Figures 35 to 37 of the appended drawings, a permanent magnet rotor 1200 provided with magnet retaining elements 1202 according to a twelfth illustrative embodiment will be described. [0130] The rotor 1200 has an internal surface 1204 configured to receive permanent magnets 1206 thereon. The internal surface 1204 includes a shoulder 1208 so positioned that the distal longitudinal ends 1209 of the magnets 1206 may be abutted thereon when the magnets are correctly positioned onto the surface 1204.

[0131] The magnet retaining element 1202 is a longitudinal element including a central portion 1212 provided with two spot weld locations 1214 (shown in dashed lines in Figure 35), a proximate elevated end 1216 provided with a stopper 1217 and a distal elevated T-shaped end 1218 similar to the elevated T-shaped end 118 of Figure 1.

[0132] The stopper 1217 is mounted to the proximate elevated end

1216 via a rivet 1219.

[0133] The distal elevated T-shaped end 1218 is configured to prevent the permanent magnets 1206 from being removed from the surface 1204 by an inward radial force.

[0134] As can be better seen from Figure 36, the stopper 1217 is so positioned as to contact the proximate end of adjacent magnets 1216 to thereby prevent the longitudinal movement of the magnets with respect to the rotor 1200. Accordingly, movements in the radial, longitudinal and circumferential directions are prevented by the magnet retaining element 1202.

[0135] Turning now to Figures 38 to 40 of the appended drawings, a permanent magnet rotor 1300 provided with magnet retaining elements 1202 according to a thirteenth illustrative embodiment will be described. [0136] The magnet retaining element 1202 is as described hereinabove with reference to Figures 35-37. However, the rotor 1300 is not provided with a shoulder such as 1208 (Figure 36). In place of this shoulder, some of the magnet retaining elements 1202 are alternatively installed with their stopper 1217 towards the distal end 1309 of the magnets 1306.

[0137] These upside down magnet retaining element 1202 may be mounted to the rotor 1300 first, then the permanent magnets 1306 may be installed and, finally the other magnet retaining elements 1202 may be installed, preventing longitudinal movements of the magnets 1306.

[0138] The stator 1300 therefore requires less machining than the stator 1200 while preventing movements in the radial, longitudinal and circumferential directions.

[0139] Turning now to Figures 41 to 43 of the appended drawings, a permanent magnet rotor 1400 provided with two identical magnet retaining elements 1403, 1405 according to a fourteenth illustrative embodiment will be described.

[0140] The internal surface 1404 includes two peripheral channels

1407, 1409 configured to respectively receive the magnet retaining element 1403 and 1405.

[0141] Since the magnet retaining element 1403 and 1405 are identical, only the magnet retaining element 1403 will be described hereinbelow. [0142] The magnet retaining element 1403 includes a thin web of material 1420 provided with arc welding receiving apertures 1422 allowing the web 420 to be welded to the channel 1407.

[0143] The web 1420 is provided with inwardly projecting integral hooks 1424 and the longitudinal ends of the permanent magnets 1406 are provided with corresponding hook receiving notches 1426.

[0144] Accordingly, the hook and notch arrangement prevent the movements of the magnets with respect to the rotor in the longitudinal, radial and circumferential directions.

[0145] Turning now to Figures 44 to 46 of the appended drawings, a permanent magnet rotor 1500 provided with two identical magnet retaining elements 1503, 1505 according to a fifteenth illustrative embodiment will be described.

[0146] The magnet retaining element 1503 and 1505 are very similar to the magnet retaining element 1403 and 1405 described hereinabove with reference to Figures 41-43. Accordingly, only the differences therebetween will be discussed hereinbelow.

[0147] Generally stated, the main difference concerns the location of the hook 1524 and notch 526 arrangement. Instead of being centrally located in the magnet 1506, these elements are located to one side thereof so that the hook 1526 does not exceed the height of the magnet 1506. This way, the air gap between the stator (not shown) and the rotor 1500 may be minimized if required. [0148] Turning now to Figures 47 and 48 of the appended drawings, a permanent magnet rotor 1600 provided with magnet retaining elements 102 as described hereinabove with reference to Figures 1 to 3 will be described.

[0149] The rotor 1600 is longitudinally longer than the previously described rotors and therefore includes two rows of magnets 1606A and 1606B. As discussed above, the magnet retaining element 102 are provided between each magnets of each row. Additionally, the proximate T-shaped end 116 of the magnet retaining element 102 is used as a spacer between the two rows of magnets 1606A and 1606B. Indeed, the distal ends of the magnets 1606B abut the T-shape ends 116 of the magnet retaining element 102.

[0150] Turning now to Figures 49 and 50 of the appended drawings, a permanent magnet rotor 1700 provided with magnet retaining elements 1702, according to a seventeenth illustrative embodiment will be described.

[0151] The rotor 1700 is very similar to the rotor 1600 described hereinabove with reference to Figures 47-48.

[0152] The magnet retaining element 1702 is very similar to the magnet retaining element 102 described hereinabove with reference to Figures 1 to 3. A difference between these magnet retaining elements is that the proximate end 1716 of the magnet retaining element 1706 is thinner than the proximate end 116 of the magnet retaining element 102. Accordingly, the two rows of permanent magnets 1706A and 1706B are longitudinally closer to one another. [0153] Turning now to Figures 51 and 52 of the appended drawings, a permanent magnet rotor 800 provided with magnet retaining elements 802, according to a eighteenth illustrative embodiment will be described.

[0154] The rotor 1800 is very similar to the rotor 1600 described hereinabove with reference to Figures 47-48.

[0155] The magnet retaining element 1702 is very similar to the magnet retaining element 102 described hereinabove with reference to Figures 1 to 3 except for the proximate end 816 that has a double-arrow shape formed by two triangles 1820 and 1822 integral with the magnet retaining element 1802.

[0156] The magnets of the two rows of magnets 1806A and 1806B are octagonal since the generally rectangular shape of the magnets has its corners removed. Accordingly, the magnets 1806 are less fragile than rectangular magnets.

[0157] It is to be note that the octagonal shape of the magnets 1806 and the double arrow shape of the proximate end 1816 of the magnet retaining element 1802 are generally complementary.

[0158] Turning now to Figure 53 of the appended drawings, a permanent magnet rotor 1900 provided with magnet retaining elements 1802, according to a eighteenth illustrative embodiment will be described.

[0159] The permanent magnet rotor 1900 includes a rotor body

1902, a plurality of permanent magnets 1904 mounted to the internal surface of the rotor body 1902 and a magnet retaining cage including a plurality of magnet retaining elements 1908 interconnected by integral top and bottom rings 1910, 1912. The top ring 1910 is generally circular while the bottom rings is so configured and sized that the magnet retaining cage 1906 can be mounted to the internal surface of the rotor body 1902 after the permanent magnets 1904 have ben mounted thereto.

[0160] The rotor body 1902 includes a keyway 1914 while the cage

1906 includes a corresponding key 1916 allowing the cage to be mounted at a known position in the rotor body.

[0161] The cage 1906 is made of a single piece of sheet metal that has appropriately been cut and folded. The joint between the two ends defining the key 1916.

[0162] It has to be noted that while the magnet retaining elements

1908 of the magnet retaining cage 1906 are generally modeled after the magnet retaining elements 702 of Figure 19, it will be apparent to one skilled in the art that many other magnet retaining elements described and illustrated herein could be interconnected as described hereinabove with a top ring and a bottom ring to define a magnet retaining cage. Similarly, other appropriate shapes of magnet retaining elements could be used.

[0163] Turning now briefly to Figure 54 of the appended drawings, an alternative magnet retaining cage 1906' very similar to the magnet retaining cage 1906 illustrated in Figure 53 will be described. Since the retaining cages 1906 and 1906' are very similar, only the differences will be described hereinbelow. [0164] Generally stated, a main difference between the cages 1906 and 1906' involves a bottom wall 1918 present in the cage 1906'. This bottom wall 1918 includes a central aperture 1920 allowing a shaft (not shown) therethrough and provided with a key 1922 corresponding to a key (not shown) of the rotor body.

[0165] It is to be noted that while some illustrative embodiment describe magnet retaining elements that are spot welded and some illustrative embodiment describe magnet retaining element that are arc welded, these two welding techniques are generally interchangeable. Furthermore, other types of welding techniques could also be used.

[0166] As will easily be understood by one skilled in the art, while one or two spot welds locations or arc welding receiving apertures are illustrated in the illustrative embodiments described hereinabove, more than two locations or apertures could be used. Similarly, while the arc welding receiving apertures are illustrated as being circular, other shapes, for example an oblong shape allowing a larger welding surface, can be used

[0167] It will be understood by one skilled in the art that the elements and features of the above illustrative embodiments could be combined. For example, the heat expansion stress relieving features of the magnet retaining element 202, 302 and 402 (Figures 4 to 12) could be applied to any magnet retaining element including two spaced apart welds.

[0168] It is to be understood that the invention is not limited in its application to the details of construction and parts illustrated in the accompanying drawings and described hereinabove. The invention is capable of other embodiments and of being practiced in various ways. It is also to be understood that the phraseology or terminology used herein is for the purpose of description and not limitation. Hence, although the present invention has been described hereinabove by way of illustrative embodiments thereof, it can be modified, without departing from the spirit, scope and nature of the subject invention as defined in the appended claims.

Claims

WHAT IS CLAIMED IS:

1. A rotor assembly for an external rotor electric machine, the rotor assembly comprising:

at least two permanent magnets longitudinally mounted to the internal surface of the rotor body, each at least two permanent magnets includes first and second longitudinally opposite ends and first and second opposite faces, the first face being configured and sized as to contact the internal surface of the rotor body;

at least two spacing elements longitudinally mounted to the inner surface of the rotor body between adjacent permanent magnets via at least one respective weld; the at least two spacing elements being so configured and sized as to prevent relative circumferential and radial movements of the permanent magnets with respect to the rotor body.

2. A rotor assembly as recited in claim 1 , wherein each at least two spacing elements includes a central portion and first and second opposite longitudinal ends.

3. A rotor assembly as recited in claim 2, wherein the first end of each spacing element is generally T-shaped and so configured as to contact the first end of two adjacent permanent magnets to thereby prevent longitudinal movements of the permanent magnet with respect to the rotor body.

4. A rotor assembly as recited in claim 2, wherein the second end of each spacing element is generally T-shaped and elevated so as to overlap the second face of adjacent permanent magnets to thereby prevent radial movements of the permanent magnets with respect to the rotor body.

5. A rotor assembly as recited in claim 2, wherein the central portion includes a heat expansion stress relieving element.

6. A rotor assembly as recited in claim 5, wherein the heat expansion stress relieving element includes an inwardly projecting wave in the central portion, allowing the heat expansion of the spacing element with respect to the rotor body.

7. A rotor assembly as recited in claim 5, wherein the central portion is circumferentially cut in first and second longitudinal elements and wherein the heat expansion stress relieving element includes a tongue and groove arrangement provided between the first and second longitudinal elements of the central portion.

8. A rotor assembly as recited in claim 2, wherein the first and second opposite ends of each spacing element is generally double T-shaped including an elevated T-portion and a downwardly curved T-portion; the elevated T-portion being so configured as to overlap the second face of adjacent permanent magnets to thereby prevent radial movements of the permanent magnets with respect to the rotor body and the downwardly curved T-portion being so configured as to contact the first end of two adjacent permanent magnets to thereby prevent longitudinal movements of the permanent magnet with respect to the rotor body.

9. A rotor assembly as recited in claim 2, wherein the first longitudinal end of each spacing element includes a stopper so configured as to contact the proximate end of adjacent permanent magnets to thereby prevent the longitudinal movement of the permanent magnets with respect to the rotor body.

10. A rotor assembly as recited in claim 2, wherein the central portion of each spacing element includes a strap receiving deformation spacing a portion fo the central portion from the internal surface of the rotor body; the rotor assembly including at least two straps so configured and sized as to be mounted to the strap receiving portions of the spacing element while overlapping the second face of a respective permanent magnet to thereby prevent the radial movement of the permanent magnet with respect to the rotor body.

11. A rotor assembly as recited in claim 1 , wherein each at least two spacing elements has a generally T-shaped cross-section defining longitudinal shoulders so configured as to overlap a portion of the second face of adjacent permanent magnets.

12. A rotor assembly as recited in claim 1 , wherein each spacing element includes a longitudinal body provided with lateral side walls so configured and sized as to overlap a portion of the second face of adjacent permanent magnets.

13. A rotor assembly as recited in claim 12, wherein the longitudinal body provided with lateral side walls of each spacing element define a generally U-shaped cross-section.

14. A rotor assembly as recited in claim 12, wherein each lateral side wall includes a flange so configured as to overlap a portion of the second face of adjacent permanent magnets; the flanges being plastically deformed when contacting the adjacent permanent magnets.

15. A rotor assembly as recited in claim 14, wherein the flanges define C-shaped springs.

16. A rotor assembly as recited in claim 1 , wherein each of the at least two spacing element includes a generally U-shaped central portion provided with flanges configured to overlap a portion of adjacent permanent magnets to thereby prevent radial movements of the permanent magnets; each of the at least two spacing element also includes first and second biasing assemblies extending from the central portion; each biasing assemblies including two biasing arms so configured as to apply circumferential pressure to adjacent permanent magnets.

17. A rotor assembly as recited in claim 2, further comprising a top ring and a bottom ring; the first end of each at least two spacing element being integral with the top ring and the second end of each at least two spacing element being integral with the bottom ring; the at least two spacing element and the top and bottom ring defining a magnet retaining cage.

18. A rotor assembly as recited in claim 17, wherein the bottom ring is so configured and sized as to allow the bottom ring to be mounted to the internal surface of the rotor while the at least two permanent magnets are mounted thereto.

19. A rotor assembly as recited in claim 17 wherein the rotor body and the cage further including a key and keyway arrangement.

20. A rotor assembly as recited in claim 17, wherein the cage further includes a bottom surface.

21. A rotor assembly as recited in claim 1 , wherein the at least two permanent magnets include a first circumferential row of a plurality of permanent magnets separated by spacing elements mounted to the internal surface of the rotor body via at least one respective spot weld and a second circumferential row of a plurality of permanent magnets separated by spacing elements mounted to the internal surface of the rotor body via at least one respective spot weld; the first and second row of permanent magnets being longitudinally separated by a portion of each spacing element.

22. A rotor assembly as recited in claim 1 , wherein the at least one weld mounting the at least two spacing elements longitudinally to the inner surface of the rotor body is a spot weld.

23. A rotor assembly as recited in claim 1 , wherein the at least one weld mounting the at least two spacing elements longitudinally to the inner surface of the rotor body is an arc weld.