Abstract:
A compacted magnetic powder metal component stator for use in an electrical machine is provided. Each stator is comprised of a plurality of stator core assemblies. Each stator core assembly forms an arcuate section of the stator core itself. Each stator core assembly is comprised of an inner shoe component, with winding guides supporting a winding, and at least one back piece and two end caps fitted to the winding on the outer radial edge of the stator assembly.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to core components for use in electrical machines and, more particularly, a stator assembly for use in an electrical machine, most typically an electric motor.  
         [0002]     Electrical machines such as motors and generators have a stationary element, usually termed a stator, and movable or rotating elements, typically termed the rotor. The interaction between the stator and the rotor is caused by the interaction of a magnetic field generated by either the stator or the rotor. Such magnetic field is usually generated or induced by electric currents in a winding placed on either the stator or the rotor. Such winding usually comprises a plurality of coils wound about a winding support. The winding support is usually comprised of a soft magnetic material which traditionally is made of laminations of selected steel materials. The laminations are insulated from each other in order to reduce eddy currents.  
         [0003]     One concern in the design of such electrical machines is the need or desire to reduce the free space by improving the fill factor of the windings. It is desirable that the windings fill as much of the open space as practical to improve the inter action between the electromagnetic field between the stator and the rotor. This produces a more efficient motor or generator. Such terminology is deemed as the power density of the motor.  
         [0004]     It has become known also to replace the laminated steel materials of the stator or rotor cores with ferro-magnetic powder particles that are compacted in a powder metallurgy operation to form the winding support. The ferro-magnetic powder particles themselves are electrically insulated from each other so that the resulting compacted product exhibits a low eddy current loss in a manner similar to the use of stacks of laminated steel materials. Such use of compacted metal powders comprised of ferro-magnetic powder particles for cores in electrical machines is disclosed in U. S. Pat. Nos. 6,956,307, 6,300,702 and 6,441,530.  
         [0005]     Accordingly, it is an object of the present invention to provide an improved stator assembly for use in an electrical machine wherein the fill factor of the windings is reduced and accordingly, the power density of the motor itself is improved.  
         [0006]     It is another object of the present invention to provide an improved stator assembly for use in electrical machines wherein the stator assembly utilizes components comprised of compacted ferrous-magnetic powder.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention provides an improved stator assembly for an electrical machine and, more specifically, an improved stator assembly for use in an electrical motor or generator. The improved stator assembly comprises a plurality of components. Each stator assembly forms an arcuate section of the stator itself, which is understood to be generally cylindrical structure. Each stator assembly comprises an inner shoe, a winding assembly, a back piece, and two end caps. Each stator assembly is adjacent another similar stator assembly along a circumferential plane of the stator itself.  
         [0008]     Further, each of the inner shoe component, back piece, and end cap are formed of ferrous magnetic powder particles. Such ferrous magnetic powder particles are mutually insulated. The ferrous magnetic metal powder particles are pressure formed in a powder metal operation into a solid form.  
         [0009]     It is a feature of the present invention that such an improved stator assembly comprised of a plurality of sections formed of mutually insulated ferrous magnetic powder metal particles provides improved performance due to the reduced eddy current losses in the electrical machine. Such improved performance is mainly due to the elimination of open spaces by improving the fill factor of the windings within the stator assembly. Such improved filling of open spaces within the stator assembly also improves the power density of the motor. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     In the drawings,  
         [0011]      FIG. 1  is a perspective view, with individual components shown separated, of a stator assembly is accordance with an embodiment of the present invention;  
         [0012]      FIG. 2  is a perspective view of a stator assembly in accordance with an embodiment of the present invention;  
         [0013]      FIG. 3  is a perspective view of a stator assembly with a bonding agent encapsulating the stator assembly components, and  
         [0014]      FIG. 4  is a cross sectional view of a stator comprised of a plurality of stator assemblies in accordance with an embodiment of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0015]     Referring now to  FIG. 1  of the drawings, a stator assembly is shown generally at  10 . Stator assembly  10  is seen to be generally comprised of an inner shoe component  24  which is generally rectangular in shape, having an inwardly arcuate inner surface  28  and an outwardly arcuate outer surface  30 . Another way of viewing inner shoe component  24  is to say that inner surface  28  is concave along a longitudinal axis of inner component  24  and outer surface  30  is convex along a longitudinal axis of inner shoe component  24 . Winding guides  26  are seen to be raised and extending from outer surface  30  of inner shoe component  24 . Each winding guide  26  is seen to have an arcuate or circular section outer surface and a generally straight inner surface.  
         [0016]     Winding  20  is seen to be generally oval in shape, and is comprised of numerous windings of insulated electrical wire. A winding lead  22  extends outwardly from winding  20  to allow and appropriate electrical connection in the final configuration of stator assembly  10 . Winding  20  is seen to fit about guides  26  in order to allow the close spacing of inner shoe component  24  adjacent winding  20 .  
         [0017]     End caps  12  and  18  are seen to be identical, with an outer surface  13  for end cap  12  and  19  for end cap  18 , which is outwardly arcuate, or generally convex along a longitudinal axis of stator assembly  10 . Further, end cap  18  is seen to have a cut out  34  that is formed to fit about an end of winding  20 . Accordingly, end cap  18  is seen to provide a snug fit, as is end cap  12 , about the ends of winding  20 . Further, end caps  12  and  18  are seen to be in close proximity to the outer surface  30  of inner shoe component  24 .  
         [0018]     Back pieces  14  and  16  are identical, and are seen to be adjacent each other and located inwardly and adjacent to end caps  12  and  18 . Each back piece  14  and  16  is seen to have an outwardly arcuate outer surface  21  for back piece  14  and  23  for back piece  16 . Further, back piece  16  is shown to have a cut out section  36  located near a lateral edge of back piece  16  and another cut out section adjacent the other lateral edge of back piece  16 . Back piece  14  has similar cut out sections. Cut out section  36  and the similar cut out section adjacent the other lateral edge of back piece  16  are preferably arcuate in form to adapt as closely as possible to the top surface of winding  20 . However, if for some reason winding  20  were to take an other than arcuate shape, then cut out openings  36  and the other cut out opening in back piece  16  would be similarly complementary to the shape of the top of winding  20 .  
         [0019]     Further, back piece  16  is also seen to have inner support  38  that extend adjacent cut out section  36  and, with a similar inner support adjacent the other cut out section in back piece  16 . Such inner support acts to form part of cut out  36  as well as assure the physical location of a portion of back piece  16  as near as possible to outer surface  30  of inner shoe component  24 .  
         [0020]     It should be understood that end caps  12  and  18 , back pieces  14  and  16 , and inner shoe component  24  are all comprised of a compacted ferrous magnetic powder comprised of insulated powder particles formed to the shape of the particular component of stator assembly  10 . Such forming is done in known powder metal operations, which include die compacting and heat treating. It is important such that the ferrous magnetic metal powder particles used to form the components of stator assembly  10  are insulated electrically from each other so as to diminish the build up of eddy currents within the fully assembled stator.  
         [0021]     It should also be understood that appropriate insulating material such as an oxide layer can be utilized between adjacent surfaces of end cap  12 , back piece  14 , back piece  16  and end cap  18 .  
         [0022]     Further, each of end pieces  12  and  18  are seen to include mating surface  52  which can be a ledge or similar ridge or depression in the lateral face of end cap  18  adjacent back piece  16 . Back piece  16  would include a complementary edge surface to assure a complementary fitting between back piece  16  and end cap  18 . End cap  12  and back piece  14  would have similar complementary surfaces.  
         [0023]     Referring now to  FIG. 2 , the stator assembly  10  is shown with inner shoe component  24 , winding  20 , and back pieces  14  and  16  fitted thereon. It is readily apparent that there is a virtual elimination of any open spaces between back pieces  14  and  16  and inner shoe component  24 . Winding  20  is seen to be occupying virtually the entire space between back pieces  14  and  16  and inner shoe component  24 . This assures a high fill factor and an improved power density of the motor into which stator assembly  10  would be used.  
         [0024]     Referring now to  FIG. 3 , a fully assembled stator assembly  10  is shown. Stator assembly  10  is seen to comprise inner shoe component  24 , with winding  20  placed thereon fitted about winding guides  26 , which are not seen in this view. Stator assembly  10  also comprises end cap  12 , back piece  14 , back piece  16  and end cap  18 , all of which are fitted about and onto winding  20  as described above. A bonding agent or resin, at  56  and  58  to encapsulize stator assembly  10  and to ensure the thermal management and strength of the unit of components. Such resin is also provided between end cap  12 , back piece  14 , back piece  16  and end cap  18  to further assure the bonding and encapsulation of these components. Further, a channel  57  is seen to exist between end cap  12  and inner shoe component  24  to further allow the impregnation and movement of the bonding agent therein. A similar channel  59  provides a similar channel for allowing the bonding agent and resin to further secure and provide good thermal management and strength to stator assembly  10 .  
         [0025]     Referring now to  FIG. 4 , an assembled complete stator is shown generally at  50 . Such stator is seen to comprise a plurality of stator assemblies  10  which are formed in a circular arrangement, which is typical for a motor or generator. Each stator assembly  10 , as described above in  FIG. 1-3 , is seen to be comprised of an inner shoe component  24 , which faces inwardly toward the axis of stator  50 . Winding  20  is seen to be placed radially outwardly on inner shoe component  24 . Although not shown in this view, it is understood that winding  20  is fitted about winding guides  26  which protrude from outer surface  30  of inner shoe component  24 . Further, each stator assembly  10  is seen, as described above in  FIGS. 1-3 , to be further comprised of end cap  12 , adjacent back piece 14 , adjacent back piece  16 , and end cap  18 . It is seen that end caps themselves are adjacent each other in the final assembly of the complete stator  50 .