CA2950308A1

CA2950308A1 - Inserted permanent magnet rotor for an external rotor electric machine

Info

Publication number: CA2950308A1
Application number: CA2950308A
Authority: CA
Inventors: Eric Latulipe; Martin Houle; Luc CHAMPOUX; Jean-philippe DEXTRAZE
Original assignee: TM4 Inc
Current assignee: Dana TM4 Inc
Priority date: 2014-05-27
Filing date: 2015-05-13
Publication date: 2015-12-03
Also published as: WO2015179966A1; CN106537730A; CN106537730B

Abstract

The external rotor for an electric machine includes a cylindrically shaped receptacle having a peripheral wall and a lamination assembly including lamination segments assembled to the peripheral wall inside the receptacle so as to define a cylindrically shaped stack. The lamination segments are shaped so as to yield magnet-receiving portions in the ring-shaped stack, and permanent magnets are secured to the lamination assembly in the magnet-receiving portions. The lamination elements are flexible so as to be movable during the assembly thereof to the peripheral wall between a deployed configuration and an arcuate configuration wherein each of the lamination elements conforms to the peripheral wall inside the receptacle.

Description

TITLE
Inserted Permanent Magnet Rotor for an External Rotor Electric Machine FIELD
[0001] The present disclosure generally relates to electric machines.
More specifically, the present disclosure is concerned with an inserted permanent magnet (IPM) rotor for an external rotor electric machine.
BACKGROUND

[0002] The use of inserted permanent magnet (IPM) in electric machines is well known. Such technology allows the reduction of the number and/or sizes of magnets and has been essentially used in conventional electric machines, i.e. those including a rotor mounted inside a stator for coaxial rotation therein.

[0003] It has been found desirable to provide the rotor of an external rotor electric machine with IPM.
SUMMARY

[0004] The difficulty of providing an external rotor electric machine with IPM is solved by mounting permanent magnets in a ring-shaped lamination assembly secured to the rotor inner wall. In order to facilitate and speed up the mounting of the magnets to the ring-shaped lamination assembly and the ring-shaped assembly to the rotor inner wall, each layer of the lamination of the ring-shaped lamination assembly is assembled from one or more flexible members.

[0005] In accordance with an illustrative embodiment, there is provided an external rotor for an electric machine comprising a cylindrically shaped receptacle including a peripheral wall provided with an inner surface, a lamination assembly including lamination elements assembled to the inner surface of the peripheral wall so as to define a cylindrically shaped stack;
the lamination elements being shaped so as to yield magnet-receiving portions in the cylindrically shaped stack and permanent magnets secured to the lamination assembly in the magnet-receiving portions. The lamination elements are flexible so as to be movable between a deployed configuration and an arcuate configuration wherein the lamination elements generally conforms to the inner surface of the peripheral wall.

[0006] Other objects, advantages and features will become more apparent upon reading of the following non-restrictive description of illustrative embodiments thereof, given by way of example only with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In the appended drawings:

[0008] Figure 1 is a cross section of an external rotor electric machine according to a first illustrative embodiment;

[0009] Figure 2 is a perspective view of the rotor of the electric machine from Figure 1;

[0010] Figure 3A is a top plan view of the external rotor from Figure 2;

[0011] Figures 3B-3C are top plan views of the external rotor from Figure 2, illustrating the mounting of the lamination assembly and permanent magnets to the cylindrically shaped receptacle of the rotor;

[0012] Figure 4A is a top plan view of an external rotor for an electric machine according to a second illustrative embodiment;

[0013] Figures 4B-4C are top plan views of the external rotor from Figure 4A, illustrating the mounting of the lamination assembly and permanent magnets to the cylindrically shaped receptacle of the rotor;

[0014] Figure 5A is a top plan view of an external rotor for an electric machine according to a third illustrative embodiment;

[0015] Figures 5B-5C are top plan views of the external rotor from Figure 5A, illustrating the mounting of the lamination assembly and permanent magnets to the cylindrically shaped receptacle of the rotor;

[0016] Figure 6A is a top plan view of an external rotor for an electric machine according to a fourth illustrative embodiment;

[0017] Figures 6B-6C are top plan views of the external rotor from Figure 6A, illustrating the mounting of the lamination assembly and permanent magnets to the cylindrically shaped receptacle of the rotor;

[0018] Figure 7A is a top plan view of an external rotor for an electric machine according to a fifth illustrative embodiment;

[0019] Figure 7B is top plan view of the external rotor from Figure 7A, illustrating the mounting of the lamination assembly and permanent magnets to the cylindrically shaped receptacle of the rotor;

[0020] Figure 70 is a close up view taken within line 70-70 from Figure 7A, showing the locking elements of the lamination assembly in an unlocked configuration;

[0021] Figure 7D is a close up view similar to Figure 70, showing the locking elements in a locked configuration;

[0022] Figures 7E and 7F are close up views similar to Figures 70 and 7D, showing locking elements of the lamination assembly according to a sixth illustrative embodiment; and

[0023] Figure 8 is a perspective view of an external rotor for an electric machine according to a seventh illustrative embodiment.
DETAILED DESCRIPTION

[0024] 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.

[0025] As used in this specification and claim(s), 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.

[0026] The expression "electric machine" should be construed herein and in the appended claims broadly so as to include electric motors, electric generators and the like.

[0027] The expression "connected" should be construed herein and in the appended claims broadly so as to include any cooperative or passive association between mechanical parts or components. For example, such parts may be connected together by direct coupling, or indirectly coupled using further parts therebetween.

[0028] With reference first to Figures 1, 2, 3A, 3B and 30 of the appended drawings, a first illustrative embodiment of an external rotor electric machine 10 will now be described.

[0029] The external rotor electric machine 10 comprises an external rotor 12 provided with an integral coaxial hub 14, an internal stator 16 coaxial with the rotor 12, and a generally cylindrical cooling member 18 secured to the stator 16 therein.

[0030] It is to be noted that the stator 16 is not limited to the illustrated embodiment. Since stators are believed to be well known in the art, the stator 16 will not be further described herein for concision purposes.
Furthermore, many conventional elements of an electric machine are omitted from the appended drawings for concision and clarity purposes. For example, bearings (not shown) are routinely used to coaxially mount a rotor to a stator for coaxial alignment and a casing is generally used to enclose the electric machine.

[0031] As can be better seen from Figure 2, the external rotor 12 comprises a cylindrically shaped receptacle 20 including a peripheral wall 22 provided with an inner surface 34 and an integral cap 24 provided at its longitudinal end 26. The hub 14 is provided in the cap 24 coaxially with the wall 22. The hub 14 allows receiving an input/output shaft (not shown) internally and/or externally to the receptacle.

[0032] The rotor 12 further includes i) a lamination assembly 28, including lamination segments 30 that are assembled into a cylindrically shaped stack and secured to the inner surface 34 of the peripheral wall 22, and ii) permanent magnets 32 that are secured to the lamination assembly 28. For that purpose, the lamination segments 30 are shaped so as to yield magnet-receiving portions 36 therein (see Figure 3B).

[0033] The lamination segments 30 are in the form of flexible ring sections resulting for example from stamping or cutting magnetically susceptible strips of material. The segments 30 may, of course, result from other manufacturing processes.

[0034] According to the first illustrated embodiment, each lamination layer includes two lamination segments 30, each having a semi-circular configuration when secured to the inner surface 34 of the peripheral wall 22.

[0035] Prior to their mounting onto the inner surface 34, the ring segments 30 can be pre-assembled into sub-stacks 35.

[0036] According to the first illustrative embodiment, multiple segments 30 are assembled into a sub-stack 35 having a thickness equivalent to the height of the magnets 32 received therein. All layers of the overall assembly 28 or all layers of a semi-circular side thereof are secured to the wall 22 before the magnets 32 are secured therein.

[0037] According to another embodiment (not shown), the thickness of the sub-stacks 35 receives two or more longitudinally abutted permanent magnets.

[0038] With reference more specifically to Figure 30, showing a segment 30 in its deployed configuration, one can see that the ring segments 30 are so shaped as to define central protrusions 38 that are shaped so as to yield rounded notches 40 between the central protrusion 38 and respective lateral magnet-receiving portions 36. Within a sub-stack 35, the notches 40 define together a channel 42 between the central protrusion 38 and respective magnets 32 that prevents the magnetic field to directly go from the magnets 32 to the central protrusions 38.

[0039] Each notch 40 defines, with the magnet-receiving portion 36, a small shoulder 44 that helps positioning and maintaining in place the magnet 32. In other words, the shoulder 44 delimits the magnet-receiving portion.

[0040] The segments 30 include thinner portions 46 in the center of the magnet-receiving portions 36. The thinner portions 46 define flexible portions of the segments 30 that allows moving the segments 30 for example during the mounting thereof to the peripheral wall 22 between a deployed configuration (see at the top of Figure 30) and an arcuate configuration wherein each of the lamination segments 30 conforms to the inner surface 34 of the peripheral wall 22 of the receptacle 20.

[0041] A person skilled in the art will now appreciate that the segments 30 can be obtained by metal sheet cutting the generally linear deployed configuration thereof. Cutting the segments 30 into their generally linear deployed configuration allows minimizing cutting waste and therefore generally decreases the manufacturing cost.

[0042] The permanent magnets 32 are secured to the sub-stack 35 of segments 30 using adhesive. The resulting sub-stack assembly 35 is secured to the receptacle 20 using adhesive. Other fastening means than adhesive can also be used, such as other mechanical or chemical fastening, including soldering.

[0043] The thickness and configuration of the magnets 32, and segments 30 are such that the resulting assembly 28 yields a generally evenly rounded internal surface of the rotor 12, with the exception of the channels 42, thereby improving the electric machine efficiency.

[0044] Both the inner surface 34 of the receptacle 20 and the facing contacting side of the segments 30 can be provided with cooperating guiding elements such as tongues and grooves (not shown) to help position and assemble the segments 30 within the receptacle 20.

[0045] Since the permanent magnets 32 are mounted to the receptacle 20 of the rotor 12 via a lamination assembly, the receptacle 20 is not limited to being made from magnetically susceptible metals and can be made of other materials such as plastics, non magnetically susceptible metals such as aluminum and aluminum alloys, and fiber reinforced plastics, amongst others.

[0046] A possible sequence of assembly of the rotor 12 provided with inserted permanent magnets as described herein is as follows:

[0047] ¨ The segments 30, in their deployed configuration, are assembled into a plurality sub-stacks 35 having a thickness equal to the length of the magnets 32;

[0048] ¨ The segments 30 forming the sub-stacks 35 are maintained together, for example by creating a partial and localized deformation of a portion thereof;

[0049] ¨ The sub-stacks 35 are then curved to their arcuate configuration to conform to the inner surface 34 of the peripheral wall 22;

[0050] - The arcuate sub-stacks are applied to the inner surface 34 and secured thereto via an adhesive; and

[0051] The magnets 32 are mounted to the magnet-receiving portions 36.

[0052] An external rotor 50 for an electric machine according to a second illustrative embodiment will now be described with reference to Figures 4A, 4B and 40. Since the rotor 50 is similar to the rotor 12 described hereinabove, only the differences therebetween will be described herein in more detail for concision purposes.

[0053] Each of the two ring segments 52 includes pairs of adjacent protrusions 54 (four pairs of protrusions according to the illustrated embodiment) that are separated by a thin slit 56. Each slit 56 ends by an enlargement 58 near the outer side 60 of the segment 52. The enlargement 58 defines with a facing notch 61 a thinner portion of the ring segment 52 where it can be bent to move the segment 52 from the generally deployed configuration shown at the top of Figure 40 to the arcuate configuration that conforms to the inner surface 34 of the peripheral wall 22of the receptacle 20.

[0054] The magnet-receiving portions are defined by V-shaped depressions 62 between the pairs of protrusions 54. Each magnet-receiving portion 62 receives two magnets 66, one on each leg side of the V-shaped depressions. The magnet-receiving portions 62 and the protrusions 54 are separated by the rounded notches 40 defining shoulders 41.

[0055] A first longitudinal end 68 of each segment 52 is flat, while the opposite end 70 is slanted with the larger portion 72 on the inner side of the segment 52 when it is mounted to the receptacle 22.

[0056] As illustrated in Figure 4B, such configurations of the ends 68-70 allow to ease the mounting of the second segment 52 as follow:

[0057] - the flat end 68 of the second segment 52 is first abutted to the slated end 70 of the first segment (see arrow 74);

[0058] ¨ then the second segment 52 is gradually pressed onto the receptacle 22 from the flat end side 68 to the slanted end side thereof (see arrows 76).

[0059] The configuration of the slanted end 70 allows pushing press-fitting of the second segment 52 against the first, already-positioned, segment 52 (see arrow 78).

[0060] The number, configuration and size of the magnet-receiving portions 62 and of the magnets 66 are not limited to those illustrated in Figures 4A-4C.

[0061] As described with reference to the first illustrated embodiment, the lamination segments 52 can be secured to the receptacle after their sub-assembly into sub-stacks. Since they do not span two adjacent segments, the magnets 66 can be secured to such sub-stacks before the complete lamination assembly is secured to the receptacle, as shown in the top portion of Figure 40, therefore facilitating the assembly of the rotor 50.

[0062] An external rotor 80 for an electric machine according to a third illustrative embodiment will now be described with reference to Figures 5A, 5B and 50. Since the rotor 80 is similar to the rotors 12 and 50 described hereinabove, only the differences therebetween will be described herein in more detail for concision purposes.

[0063] Instead of the longitudinal ends 84 and 86 of the lamination segments 82 ending in the middle of the protrusions 88 as in the case of the segments 52, the ends 84 and 86 are registered with the lateral side of a magnet 66 within the magnet-receiving portions 90. This yields two gaps 92 between the two lamination segments 82 that allow each segment 82 to be given an arcuate shape that conforms to the peripheral wall 22 inside the receptacle 20 (see arrows 94) when it is secured thereto. The inner surface 34 of the receptacle 20 and the facing contacting side of the segments 82 are provided with cooperating guiding elements such as tongues and grooves 96 and 98 to help position and assemble the segments 82 within the receptacle 20. It is to be noted that the number and position of the cooperating tongues and grooves can be different than illustrated.

[0064] An external rotor 100 for an electric machine according to a fourth illustrative embodiment will now be described with reference to Figures 6A, 6B and 60. Since the rotor 100 is similar to the rotor 50 described hereinabove, only the differences therebetween will be described herein in more detail for concision purposes.

[0065] According to this embodiment, the longitudinal ends 102 and 104 of both lamination segments 106 are so shaped as to complement a dovetail member 108. During assembly, an adhesive is applied to the segments 106 (or to a sub-stack thereof) and/or to the wall 22 and the segments 106 are positioned onto the wall 22 (see arrows 110). Before the adhesive cures, a dovetail member 108 is positioned in each gap 112 between the two segments 106. The segments 106 and dovetail members 108 are configured and sized so as to yield a tight assembly once mounted to the wall 22.

[0066] An external rotor 120 for an electric machine according to a fifth illustrating embodiment will now be described with reference to Figures 7A, 7B, 70 and 7D. Since the rotor 120 is similar to the rotor 50 described hereinabove, only the differences therebetween will be described herein in more detail for concision purposes.

[0067] The rotor 120 includes a single lamination segment 122 in each lamination layer.

[0068] Similarly to the previously described embodiments, sub-stacks of segments 122 are secured to the inner surface 34 of the peripheral wall 22 using for example an adhesive. Starting at one longitudinal end 124 of the segment 122 and ending at the other end 126, the segment 122, in its arcuate configuration, is gradually positioned in place so that it conforms to the cylindrical wall 22 (see arrow 128). As described hereinabove, the magnets 66 can be mounted to pre-assembled sub-stacks (not shown) of segments 122 or be mounted after the assembly of segments 122 is secured to the wall 22.

[0069] As can be better seen in Figure 70, both longitudinal ends 124-126 of the segments 122 are provided with cooperative locking elements 130 and 132.

[0070] The first locking element 130 includes an acute skew edge 134 with regards to the inner longitudinal sides 136 and an abutting portion defined by a small protrusion 138 that extends generally perpendicularly from the edge 134.

[0071] The second locking element 132 is in the form of a foldable tongue defined by a groove 140 near the end 126 of the segment 122.

[0072] As illustrated in Figures 70-7D, the segment 122 is locked to itself once it is positioned against the wall 22 by inserting a tool (not shown) in the groove 140 (see arrow 142) that causes the folding of the tongue 132 so that it is generally parallel the skew edge 134 (see arrow 144). The tongue and overall segment 122 is thus prevented to move out of place by the protrusion 138.

[0073] The above-described locking process can be done one segment 122 at a time or for a sub-stack thereof.

[0074] As shown in Figures 7E-7F, the second locking element can be provided with a tongue 146 so angled as to be pre-positioned for inter-locking with the first locking element 148 when the segment 149 is positioned against the wall 22.

[0075] The locking elements are not limited to the illustrated embodiment and may be in the form of other interlocking or cooperating elements.

[0076] Figure 8 shows an external rotor 150 for an electric machine according to a sixth illustrative embodiment. Since the rotor 150 is similar to the rotor 50, only the differences therebetween will be described herein in more detail for concision purposes.

[0077] According to this embodiment, a first row of sub-stack 152 is assembled to the inner surface 34 of the receptacle 20 inside thereof and the next adjacent row is similarly assembled to the receptacle 20 so as to be angularly shifted with regards to the previous adjacent row. While this angular shift is of three (3) degrees according to the illustrative embodiment, other angular shift angles can also be foreseen.

[0078] This shifting from one row of lamination segment stack to the next has been found to cancel harmonics and to reduce cogging torque.

[0079] Also, caps 154 are provided onto adjacent magnets 66. The caps 154 are made of metallic powder, which allows a functional magnetic permeability and a low electric conductivity. A person skilled in the art will also appreciate that there is no direct connection between the caps 152 and the segments 52, thereby preventing magnetic short circuit. It will also be apparent to one skilled in the art that the caps 154 could be made of stacks of laminations.

[0080] The thickness and configuration of the magnets 66, caps 154, and segments 52 are such that the resulting assembly yields a generally evenly rounded surface of the rotor 150, with the exception of the channels 156, thereby improving the electric machine efficiency by reducing the air gap between the magnets and the stator, thereby increasing the torque capacity of the machine.

[0081] It is to be noted that some of the caps 152 have been omitted in Figure 8 to alleviate the drawing.

[0082] One skilled in the art will understand that other configurations of a rotor for an external rotor electric machine using some of the various features of the above-described illustrative embodiments can be conceived.

[0083] It is to be understood that the rotor for an external rotor electric machine is not limited in its applications to the details of construction and parts illustrated in the accompanying drawings and described hereinabove.
The rotor for an external rotor electric machine 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 rotor for an external rotor electric machine 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.

Claims

16

1. An external rotor for an electric machine comprising:
a cylindrically shaped receptacle including a peripheral wall provided with an inner surface;
a lamination assembly including lamination elements assembled to the inner surface of the peripheral wall so as to define a cylindrically shaped stack; the lamination elements being shaped so as to yield magnet-receiving portions in the cylindrically shaped stack; and permanent magnets secured to the lamination assembly in the magnet-receiving portions;
wherein the lamination elements are flexible so as to be movable between a deployed configuration and an arcuate configuration wherein the lamination elements generally conforms to the inner surface of the peripheral wall.

2. The external rotor of claim 1, wherein the lamination elements are assembled into sub-stacks of laminations.

3. The external rotor of claim 2, wherein the sub-stacks of laminations are maintained together by a partial and local deformation.

4. The external rotor of claim 1, wherein the cylindrically shaped receptacle includes an integral cap and a hub coaxially therewith and configured to receive an input/output shaft.

5. The external rotor of claim 1, wherein the lamination elements include protrusions separating the magnets receiving portions.

6. The external rotor of claim 5, wherein the lamination elements includes thinner portions allowing the lamination elements to be movable between the deployed and arcuate configurations.

7. The external rotor of claim 6, wherein the thinner portions are provided in the magnet-receiving portions, thereby separating each magnet-receiving portion in two.

8. The external rotor of claim 6, wherein the thinner portions are provided in the protrusions, thereby separating each protrusion in two.

9. The external rotor of claim 1, wherein each magnet-receiving portion is so configured as to receive two magnets.

10. The external rotor of claim 1, wherein each lamination element includes opposite ends including corresponding interlocking elements.

11. The external rotor of claim 1, wherein each lamination element includes opposite ends so configured as to receive a spacing element.

12. The external rotor of claim 1, wherein the lamination elements further includes rounded notches provided between magnet receiving portions and adjacent protrusions.

13. The external rotor of claim 1, wherein the lamination elements further include a magnet positioning shoulder delimiting the magnet-receiving element.

14. The external rotor of claim 1, further comprising caps mounted to adjacent magnets provided.

15. The external rotor of claim 14, wherein the caps are made of magnetic powders.

16. The external rotor of claim 2, wherein the cylindrically shaped stack is defined by more than one row of adjacently assembled sub-stacks.

17. The external rotor of claim 16, wherein the consecutive rows forming the cylindrically shaped stack are angularly shifted.

18. The external rotor of claim 1, wherein the cylindrically shaped receptacle is made of a material selected from the group consisting of plastics, aluminum, non-magnetically susceptible alloys and fiber reinforced plastics.