Abstract:
An electric machine that includes a stator and a rotor. The rotor includes a shaft and a lamination assembly coupled to the shaft and is configured and disposed to rotate relative to the stator, the rotor lamination assembly including a plurality of laminations that define an outer periphery having an outer surface and an inner surface. The electric machine also includes a resolver rotor coil at least partially radially inwardly disposed of the inner surface and formed in the rotor lamination assembly and a resolver stator located between the resolver rotor coil and the shaft.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to electric machines and, in particular, to electric machines having a resolver. 
         [0002]    Electric machines such as motors and generators include a rotor that rotates relative to a stator. In the case of a motor, electrical current passing though the stator is influenced by a magnetic field developed in the rotor. The interaction of the current and the magnetic field creates an electro-motive force that causes the rotor to rotate. Certain electric motors/generators employ permanent magnets in the rotor. The permanent magnets are mounted in magnet slots formed in the rotor and that are covered by a plurality of stacked laminations. 
         [0003]    Some electric machines are coupled to a resolver. A resolver also includes a stator and a rotor. Generally, a resolver is a type of rotary electrical transformer used for measuring degrees of rotation of a rotor. In a resolver, the stator typically houses three windings: an exciter winding and two two-phase windings (usually labeled “x” and “y”). The exciter winding is located on the top and functions as an input coil of a turning (rotary) transformer. The exciter winding couples energy to the rotor. Thus, there is no need for brushes, or limit to the rotation of the rotor. The two other windings (x and y) are on the bottom, wound on a lamination. They are configured at  90  degrees from each other. The rotor houses a coil, which is the secondary winding of the turning transformer, and a separate primary winding in a lamination, exciting the two two-phase windings on the stator. 
         [0004]    In operation, the primary winding of the transformer, fixed to the stator, is excited by a sinusoidal electric current that, by electromagnetic induction, induces current in the rotor. This current then flows through the input coil on the rotor. This current, in turn, induces currents in the x and y windings of the stator. The x any y windings, thus, produce a sine and cosine feedback current. The relative magnitudes of the two-phase voltages are measured and used to determine the angle of the rotor relative to the stator. 
         [0005]    In some cases, the position of the rotor of the electric machine needs to be known. In such cases, the rotor of a resolver is typically connected to the rotor of the electric machine. This adds additional parts and may lead to alignment difficulties. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0006]    Disclosed is an electric machine that includes a stator and a rotor. The rotor includes a shaft and a lamination assembly coupled to the shaft and is configured and disposed to rotate relative to the stator, the rotor lamination assembly including a plurality of laminations that define an outer periphery having an outer surface and an inner surface. The electric machine also includes a resolver rotor coil at least partially radially inwardly disposed of the inner surface and formed in the rotor lamination assembly and a resolver stator located between the resolver rotor coil and the shaft. 
         [0007]    Also disclosed is a method of forming an electric machine. The method includes: arranging a plurality of laminations to form a rotor lamination assembly, the rotor lamination assembly including having an outer surface and an inner surface; forming a resolver rotor coil in the lamination assembly; and arranging a resolver stator in a region at least partially radially inwardly disposed from the inner surface. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
           [0009]      FIG. 1  is a partial, cross-sectional view of an electric machine according to an embodiment of the present invention; and 
           [0010]      FIG. 2  is an end view of a rotor according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0011]    A detailed description of one or more embodiments of the disclosed apparatus and method are presented with reference to the Figures by way of exemplification and not limitation. 
         [0012]    In some cases, the stator of the resolver is integrated into the housing of an electric machine. In such cases, the stator of the resolver surrounds the rotor of the electric machine. Currently, the resolver rotor is placed inside of the resolver stator. This requires the resolver rotor to be a separate component mounted on the rotor shaft of the electric machine and either mechanically or electrically aligned to it. According to an embodiment of the present invention, the orientation of the resolver rotor and stator are inverted. That is, the resolver stator is located inside of the resolver rotor. In doing this, the resolver rotor can then be integrated into the rotor of the machine. This integration eliminates the resolver rotor as a separate component. To this end, the laminations of the machine rotor can include the resolver rotor windings. In one embodiment, such an inverted structure eliminates the need to align the resolver rotor to the machine rotor and reduces the piece count. 
         [0013]    An electric machine constructed in accordance with an exemplary embodiment is indicated generally at  2  in  FIG. 1 . Electric machine  2  includes a housing  4  having a first end wall  6  that is joined with first and second opposing sidewalls  8  and  9  that form an interior portion  10 . A second, detachable, end wall  12  is secured to first and second opposing sidewalls  8  and  9 . Second end wall  12  serves as a cover that provides access to interior portion  10 . 
         [0014]    Electric machine  2  includes a shaft  20  having a first end  22  that extends through first end wall  6  to a second end  24  through an intermediate portion  26 . First end  22  is rotatably supported relative to first end wall  6  through a first bearing  30  and second end  24  is rotatably supported relative to second end wall  12  through a second bearing  32 . A seal  34  extends about first end  22  at first end wall  6 . Seal  34  is provided to contain any fluid, such as lubricant and/or coolant, present within interior portion  10 . Shaft  20  rotatably supports a hub  40  which, in turn, supports rotor windings  44 . Rotor windings  44  rotate relative to a stator  50  that is supported relative to housing  4 . The hub  40  can be formed of one or more laminations in one embodiment. 
         [0015]    As illustrated, the hub  40  includes an outer periphery  61 . The outer periphery includes an outer surface  63 . Opposite the outer surface  63 , the outer periphery  61  of the hub  40  also includes an inner surface generally indicated by reference numeral  66 . It shall be understood that the inner and outer surfaces  63 ,  61  can be formed by a plurality of laminations in one embodiment. 
         [0016]    In one embodiment, the hub  40  includes a resolver rotor coil  64 . The resolver rotor coil  64  is located at least partially within the inner surface  66  in one embodiment. As illustrated, the resolver rotor coil  64  is located on the inner surface  66  generally at an end  70  of the hub  40 . Of course, the resolver rotor coil  64  could be located at any location on the inner surface  66 . 
         [0017]    The electric machine  2  also includes a resolver stator  80 . The resolver stator  80  includes three windings: an exciter winding and two two-phase windings. The windings are shown, generally, as being contained in stator windings  82 . According to one embodiment, one or more of the three stator windings  82  are located within the outer periphery  61 . In one embodiment, the stator windings  82  are located between the resolver rotor coil  64  and the rotor  20 . In one embodiment, the resolver rotor coil  64  is arranged such that current or voltages induced therein do not interfere with either the rotor windings  44  or the stator  50 . 
         [0018]    It shall be understood that the resolver rotor coil  64  is, as illustrated, fixed to the hub  40 . As such, the alignment of the resolver rotor coil  64  and the rotor  20  is guaranteed and cannot change. Voltages are applied to the stator windings  82  in the manner described above in one embodiment. 
         [0019]      FIG. 2  shows an end view of a rotor  100  according to one embodiment of the present invention.  FIG. 2  also schematically illustrates the location of stator windings  102 ,  104 ,  106  of a stator assembly  108  according to an embodiment of the present invention. The rotor  100  includes an outer periphery  109  that includes an outer surface  110  and an inner surface  112 . Rotor coil  114  is located at least partially within the outer periphery  109  of the rotor  100  and outside of the rotor shaft  116 . In one embodiment, the rotor coil  114  is located within a lamination assembly that makes up the rotor  100 . 
         [0020]    The windings  102 ,  104 ,  106  are illustrated as the exciter ( 102 ), and the x ( 104 ) and y ( 106 ) phase windings of a resolver stator. As such, coils  104  and  106  are arranged perpendicularly to each other. According to an embodiment of the present invention, the windings  102 ,  104 ,  106  are between the rotor shaft  116  and the rotor coil  114  and at least partially within the inner surface  66 . 
         [0021]    While the invention has been described with reference to an exemplary embodiment or embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention, but that the invention will include all embodiments falling within the scope of the claims.