A stator or a rotor for an electric motor

Abstract

A stator or rotor comprising a plurality of laminations that form a circumferential support, wherein each lamination includes a plurality of segments that include a subset of the plurality of teeth, wherein the circumferential start and finish of each of the plurality of segments of a first lamination are offset with respect to the circumferential start and finish of a plurality of segments of an adjacent lamination.

Description

[0001] A STATOR OR A ROTOR FOR AN ELECRIC MOTOR

[0002] The present invention relates to a stator or rotor, in particular a stator or rotor for an electric motor .

[0003] Stators are well known as the stationary part of an electric motor or electric generator relative to which a rotor turns .

[0004] Stators and rotors generally comprise a magnetic component and other structural components . Electric motors work on the principle that a current carrying wire will experience a force in the presence of a magnetic field . Typically, a rotor, carrying a set of permanent magnets , is arranged to rotate about a set of coils that are arranged to carry an electric current , resulting in the rotor rotating about the stator and generating movement . It will be appreciated that it is also possible for the rotor to carry a set of coils and the stator to carry a set of permanent magnets .

[0005] An example of a stator, which is arranged to be mounted within a rotor, is shown in Figure 1 . Figure 1 shows the back-iron of a stator formed of a single piece of material , for example from PM (powder metal ) or more commonly built up of a number of identical laminations made , for example , from electrical steel . The protrusions 100 from the circular support 150 ( also known as a back iron or back ring) are known as " teeth" and are used to receive a plurality of coil windings .

[0006] However, manufacturing costs for a stator and a rotor can be high .

[0007] It is desirable to improve this situation . In accordance with an aspect of the present invention there is provided a stator, rotor or method according to the accompanying claims .

[0008] The invention provides the advantage of allowing the manufacturing cost for a stator or a rotor to be reduced via the use of segmented laminations . Using segments to assemble a stator or rotor lamination allows the lamination reel width to be reduced . In other words , rather than needing to use a lamination reel width that is greater or equal to the diameter of a stator or rotor, the lamination reel with can be reduced to the width of a segment .

[0009] In accordance with an aspect of the present invention there is provided a stator comprising a plurality of laminations that form a circumferential support , wherein each lamination includes a plurality of segments that include a subset of the plurality of teeth, wherein the circumferential start and finish of each of the plurality of segments of a first lamination are of fset with respect to the circumferential start and finish of a plurality of segments of an adj acent lamination .

[0010] Preferably the arc formed by each of the plurality of segments is substantially the same .

[0011] Preferably the arc of each of the plurality of segments starts at substantially the centre of a first tooth and finishes at substantially the centre of a second tooth .

[0012] Preferably an aperture is formed on the inner radius of each of the plurality of segments to form a stress relief feature . Preferably the plurality of laminations are welded together .

[0013] Preferably a recess is formed on the inner radius of each of the plurality of segments that allow the plurality of laminations to be welded without the weld extending below the inner radius of the plurality of laminations .

[0014] Preferably the plurality of segments include one or more alignment features for aligning the plurality of segments with an adj acent lamination .

[0015] Preferably the alignment feature includes a portion of a segment that extends axially from a first radial surface that is arranged to engage with a recess formed on an adj acent lamination on a second radial surface .

[0016] In accordance with an aspect of the present invention there is provided a method of assembling a stator comprising forming a first circumferential lamination having a plurality of teeth using a first plurality of segments , wherein each segment includes a subset of the plurality of teeth and forming a second circumferential lamination having a plurality of teeth using a second plurality of segments , wherein each segment includes a subset of the plurality of teeth and placing the first circumferential lamination adj acent to the second circumferential lamination, wherein the start and end of each segment of the second circumferential lamination is of fset with respect to the start and end of each segment of the first circumferential lamination .

[0017] In accordance with an aspect of the present invention there is provided a rotor comprising a plurality of mounting locations , wherein each mounting location is arranged to mount a magnet , the rotor comprising a plurality of laminations that form a circumferential support , wherein each lamination includes a plurality of segments that include a subset of the mounting locations , wherein the circumferential start and finish of each of the plurality of segments of a first lamination are of fset with respect to the circumferential start and finish of a plurality of segments of an adj acent lamination .

[0018] Preferably, the arc formed by each of the plurality of segments is substantially the same .

[0019] Preferably the plurality of segments include one or more alignment features for aligning the plurality of segments with an adj acent lamination .

[0020] Preferably the alignment feature includes an aperture formed in the plurality of segments to allow a pin to be inserted through .

[0021] In accordance with an aspect of the present invention there is provided a method of assembling a rotor comprising a plurality of mounting locations , wherein each mounting location is arranged to mount a magnet , the method comprising forming a first circumferential lamination having a plurality of mounting locations using a first plurality of segments , wherein each segment includes a subset of the plurality of mounting locations and forming a second circumferential lamination having a plurality of mounting locations using a second plurality of segments , wherein each segment includes a subset of the plurality of mounting locations and placing the first circumferential lamination adj acent to the second circumferential lamination, wherein the start and end of each segment of the second circumferential lamination is of fset with respect to the start and end of each segment of the first circumferential lamination .

[0022] The present invention will now be described, by way of example , with reference to the accompanying drawings , in which :

[0023] Figure 1 illustrates a prior art stator configuration;

[0024] Figure 2 illustrates a stator for an electric motor according to an embodiment of the present invention;

[0025] Figure 3 illustrates a stator for an electric motor according to an embodiment of the present invention;

[0026] Figure 4 illustrates a lamination for a stator for an electric motor according to an embodiment of the present invention;

[0027] Figure 5 illustrates a stator for an electric motor according to an embodiment of the present invention;

[0028] Figure 6 illustrates a rotor for an electric motor according to an embodiment of the present invention;

[0029] Figure 7 illustrates a rotor for an electric motor according to an embodiment of the present invention .

[0030] Figure 2 illustrates a stator according to an embodiment of the present invention . The stator includes a plurality of laminations that form a circumferential support having a plurality of teeth that are arranged to receive coil windings (not shown) . The circumferential support is typically known as a backiron, where preferably the laminations are made from electrical steel . The inner surface of the circumferential support is typically called the interference face of the circumferential support , where the circumferential support is preferably interference fitted to a heat sink to allow cooling of the circumferential support .

[0031] For the purposes of the present embodiment , the stator includes forty eight teeth, however the stator may include any number of teeth .

[0032] Although in the present embodiment the stator teeth do not include tooth tips , thereby allowing bobbins to be mounted on the respective teeth as described in GB2616461 , in an alternative configuration tooth tips may be included on the respective teeth, where tooth tips extend laterally from the tip of a tooth, as illustrated in Figure 3 . For the corresponding features of the stator shown in Figures 3 and 5 to those shown in Figure 2 , the same reference numerals have been used .

[0033] As illustrated in Figure 2 , each lamination includes a plurality of segments ( 201 ) , where preferably for increased strength the arc of each segment ( 201 ) starts and finishes at substantially the centre of a tooth . However, the start and finish points of a segment may occur at any location .

[0034] Although each segment ( 201 ) may include any number of teeth, where the number of teeth between di f ferent segments may be di f ferent , for the purpose of the present embodiment , each segment ( 201 ) within a lamination is of equal si ze and includes eight teeth . Consequently, for the purposes of the present embodiment, each lamination includes six segments . The number of segments ( 201 ) that form a lamination will typically be determined by manufacturing cost to reduce lamination reel width, but will preferably be a whole number of the number of stator teeth and an even total tooth count per lamination segment .

[0035] For example , a stator design having forty eight teeth can be segmented six times so that each segment would have eight teeth, as illustrated in Figure 2 .

[0036] As illustrated in Figure 4 , preferably, each segment includes alignment / interlocking features that allow the segments of one lamination to be aligned / interlocked with an adj acent lamination .

[0037] Although the alignment / interlocking feature may take any form, for the purposes of the present embodiment radial semi-shears ( 301 ) are formed in the lamination . In other words , one lamination is punched / pressed in a way that partially shears the material , so that it can perfectly fit into an aperture ( 302 ) formed in the material placed beneath it . A semi-shear can partially, completely or surpass the surface the entire thickness of the material layered beneath it . For the purpose of the present embodiment , radial semishears are formed by punching a portion of the segment substantially 50 percent through to an adj acent lamination . However, the radial semi-shears may be punched through by any amount .

[0038] The radial semi-shear is arranged to fit within a corresponding recess formed on the adj acent lamination . Accordingly, each segment ( 201 ) will have one or more radial semi-shears arranged to engage or fit in a recess of an adjacent lamination and one or more recesses that are arranged to receive a radial semi-shear from another adjacent lamination.

[0039] As illustrated in Figure 2, for increased strength / rigidity, the segments (201) of a lamination are shifted with respect to the position of segments of an adjacent lamination.

[0040] Although the segments (201) may be rotationally shifted with respect to segments of an adjacent lamination by any amount, for the purposes of the present embodiment, the segments are rotationally shifted by 50 percent with respect to segments of an adjacent lamination. Although the embodiment illustrated in Figure 2 illustrates the segments of each lamination to be rotationally shifted with respect to segments of an adjacent lamination to form a brickwork of lamination segments, a stator may be formed from a blockwork of lamination segments, where a plurality of lamination segments are mounted on top of each other without a rotational shift, which is then rotationally shifted with respect to another block of lamination segments that have not been shifted with respect to each other.

[0041] To increase the rigidity of the stator, the plurality of laminations that form the stator are preferably welded together. Preferably a recess (401) is formed on the inner radius of each segment (201) , where the recess of the respective segments are arranged to be aligned when the stator is assembled to form a recess that runs axially along the inner radius of the stator, as illustrated in Figure 2 and Figure 5, which is used to weld the plurality of laminations without the weld extending below the inner radial surface of the stator. Preferably the inner radial surface of the respective segments (201) that form a lamination include one or more stress relief f eature / apertures (402) , where the stress relief features are designed in such a way to break the hoop-stress in the backiron and can be shaped in any number of ways. For example, a round cut above a thin slot protruding from the interference face of the circumferential support (i.e. the backiron) , a simple thin slot protruding from the interference face of the circumferential support, a "Zig-Zag" type of slot protruding from the interference face of the backiron.

[0042] Figure 6 illustrates a rotor back iron (600) according to an embodiment of the present invention. The rotor back iron (600) includes a plurality of laminations that form a circumferential support having a plurality of mounting locations / surf aces (601) for mounting a plurality of magnets (not shown) to the inner surface of the rotor back iron 600. The circumferential support is typically known as a backiron, where preferably the laminations are made from electrical steel. The outer surface of the circumferential support is typically called the interference face of the circumferential support, where the circumferential support is preferably interference fitted to a rotor housing (not shown) .

[0043] For the purposes of the present embodiment, the rotor back iron 600 includes 56 mounting locations for mounting magnets, however the rotor may include any number of mounting locations.

[0044] As illustrated in Figure 6, each lamination includes a plurality of segments (602) . However, the start and finish points of a segment (602) may occur at any location. Although each segment (602) may include any number of magnet mounting locations, where the number of magnet mounting locations between different segments (602) may be different, for the purpose of the present embodiment, each segment (602) within a lamination is of equal size and includes 8 mounting locations. Consequently, for the purposes of the present embodiment, each lamination includes 7 segments

[0045] (602) . Preferably the magnet mounting locations are wedged shaped to help retain a magnet.

[0046] The number of segments (602) that form a lamination will typically be determined by manufacturing cost to reduce lamination reel width.

[0047] As illustrated in Figure 6, preferably, each segment (602) includes alignment / interlocking features (603) that allow the segments (602) of one lamination to be aligned / interlocked with an adjacent lamination.

[0048] Although the alignment / interlocking feature (603) may take any form, for the purposes of the present embodiment the alignment / interlock feature is formed from an aperture (603) formed in each segment where the respective apertures in each lamination are aligned to allow a locking pin (604) to be inserted, thereby locking the respective laminations in place .

[0049] Additionally, or alternatively radial semi-shears (not shown) may be formed in the laminations of the rotor back- iron. In other words, one lamination is punched / pressed in a way that partially shears the material, so that it can perfectly fit into an aperture formed in the material placed beneath it. A semi-shear can partially, completely or surpass the surface the entire thickness of the material layered beneath it . For the purpose of the present embodiment , radial semi-shears are formed by punching a portion of the segment substantially 50 percent through to an adj acent lamination . However, the radial semi-shears may be punched through by any amount .

[0050] The radial semi-shear is arranged to fit within a corresponding recess formed on the adj acent lamination . Accordingly, each segment will have one or more radial semishears arranged to engage or fit in a recess of an adj acent lamination and one or more recesses that are arranged to receive a radial semi-shear from another adj acent lamination .

[0051] As illustrated in Figure 6 , for increased strength / rigidity, the segments of a lamination are shi fted with respect to the position of segments of an adj acent lamination .

[0052] Although the segments may be rotationally shi fted with respect to segments of an adj acent lamination by any amount , for the purposes of the present embodiment , the segments are rotationally shi fted by 50 percent with respect to segments of an adj acent lamination .

[0053] Although the embodiment illustrated in Figure 6 illustrates the segments of each lamination to be rotationally shi fted with respect to segments of an adj acent lamination to form a brickwork of lamination segments , a stator may be formed from a blockwork of lamination segments , where a plurality of lamination segments are mounted on top of each other without a rotational shi ft , which is then rotationally shi fted with respect to another block of lamination segments that have not been shi fted with respect to each other, as illustrated in Figure 7 .

[0054] To increase the rigidity of the rotor back-iron, the plurality of laminations that form the rotor back-iron are preferably welded together .

Claims

CLAIMS1 ) A stator back-iron having a plurality of teeth, the stator comprising a plurality of laminations that form a circumferential support , wherein each lamination includes a plurality of segments that include a subset of the plurality of teeth, wherein the circumferential start and finish of each of the plurality of segments of a first lamination are of fset with respect to the circumferential start and finish of a plurality of segments of an adj acent lamination .2 ) A stator back-iron according to claim 1 , wherein the arc formed by each of the plurality of segments is substantially the same .3 ) A stator back-iron according to claim 1 or 2 , wherein the arc of each of the plurality of segments starts at substantially the centre of a first tooth and finishes at substantially the centre of a second tooth .4 ) A stator back-iron according to any one of the preceding claims , wherein an aperture is formed on the inner radius of each of the plurality of segments to form a stress relief feature .5 ) A stator back-iron according to any one of the preceding claims , wherein the plurality of laminations are welded together .6 ) A stator back-iron according to any one of the preceding claims , wherein a recess is formed on the inner radius of each of the plurality of segmentsthat allow the plurality of laminations to be welded without the weld extending below the inner radius of the plurality of laminations .7 ) A stator back-iron according to any one of the preceding claims , wherein the plurality of segments include one or more alignment features for aligning the plurality of segments with an adj acent lamination .8 ) A stator back-iron according to claim 7 , wherein the alignment feature includes a portion of a segment that extends axially from a first axial surface that is arranged to engage with a recess formed on an adj acent lamination on a second axial surface .9 ) A method of assembling a stator comprising forming a first circumferential lamination having a plurality of teeth using a first plurality of segments , wherein each segment includes a subset of the plurality of teeth and forming a second circumferential lamination having a plurality of teeth using a second plurality of segments , wherein each segment includes a subset of the plurality of teeth and placing the first circumferential lamination adj acent to the second circumferential lamination, wherein the start and end of each segment of the second circumferential lamination is of fset with respect to the start and end of each segment of the first circumferential lamination .10 ) A rotor back-iron comprising a plurality of mounting locations , wherein each mounting location is arranged to mount a magnet , the rotor comprising a plurality of laminations that form acircumferential support , wherein each lamination includes a plurality of segments that include a subset of the mounting locations , wherein the circumferential start and finish of each of the plurality of segments of a first lamination are of fset with respect to the circumferential start and finish of a plurality of segments of an adj acent lamination .11 ) A rotor back-iron according to claim 10 , wherein the arc formed by each of the plurality of segments is substantially the same .12 ) A rotor back-iron according to claims 10 or 11 , wherein the plurality of segments include one or more alignment features for aligning the plurality of segments with an adj acent lamination .13 ) A rotor back-iron according to claim 12 , wherein the alignment feature includes an aperture formed in the plurality of segments to allow a pin to be inserted through .14 ) A rotor back-iron according to claim 12 or 13 , wherein the alignment feature includes a portion of a segment that extends axially from a first axial surface that is arranged to engage with a recess formed on an adj acent lamination on a second axial surface .15 ) A rotor back-iron according to any one of claims 10 to 14 , wherein plurality of laminations are welded together .16 ) A method of assembling a rotor comprising a plurality of mounting locations , wherein eachmounting location is arranged to mount a magnet , the method comprising forming a first circumferential lamination having a plurality of mounting locations using a first plurality of segments , wherein each segment includes a subset of the plurality of mounting locations and forming a second circumferential lamination having a plurality of mounting locations using a second plurality of segments , wherein each segment includes a subset of the plurality of mounting locations and placing the first circumferential lamination adj acent to the second circumferential lamination, wherein the start and end of each segment of the second circumferential lamination is of fset with respect to the start and end of each segment of the first circumferential lamination .

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