Abstract:
According to aspects of the present invention there are provided synchronous electric machines including a stationary electromagnetic stator, a rotor having a rotational axis, wherein the rotor includes a cylindrically shaped structure comprising a plurality of concentric layers, and a plurality of permanent magnets disposed on the cylindrical shaped structure.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of priority from U.S. Provisional Application Ser. No. 61/874,180 filed Sep. 5, 2013 which is incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates generally to the field of synchronous electric machines, and, more particularly to the field of synchronous electric motors and synchronous electric generators. 
       BACKGROUND 
       [0003]    Synchronous electric machines include synchronous electric motors and synchronous electric generators. 
         [0004]    A brushless electric motor is a synchronous electric motor including a moving rotor and a stationary stator and electronic commutation. There are two common types of brushless electric motor configurations in use. In the outrunner configuration, a rotor with permanent magnets rotates about a stationary electromagnetic stator. In the inrunner configuration, a rotor with permanent magnets rotates within an electromagnetic stationary stator. In both motor configurations, an electrical current is applied to stator windings to make them into electromagnets to drive the rotor. 
         [0005]    Synchronous electric motors having an electromagnetic stator and a permanent magnet rotor can generally be operated as generators when the rotor is driven by a mechanical energy input. 
         [0006]    The maximum power that can be applied to or generated by a synchronous electric machine, including a brushless electric motor and a brushless electric generator, having an electromagnetic stator and a rotor with permanent magnets, is generally limited by the amount of heat generated by eddy currents. Too much heat weakens the permanent magnets for example. 
       SUMMARY 
       [0007]    According to one aspect of the present invention there is provided an electromechanical device including a stationary electromagnetic stator, a rotor having a rotational axis, wherein the rotor includes a cylindrically shaped structure comprising a plurality of concentric layers, and a plurality of permanent magnets disposed on the cylindrical shaped structure. 
         [0008]    According to another aspect of the present invention there is provided an electronically commutated motor which may be an outrunner brushless DC motor. The motor includes flux rings defined by steel rings with permanent magnets spaced around the inner circumferences of the steel rings and stators inside the rings. In certain embodiments of the present invention, the flux rings are formed using cylindrical laminated steel sections, preferably concentric layers of electric steel bonded together with structural epoxy. In certain embodiments, the permanent magnets may be super magnets. 
     
    
     
       DRAWINGS 
         [0009]    The invention is described below in greater detail with reference to the accompanying drawings which illustrate preferred embodiments of the invention, and wherein: 
           [0010]      FIG. 1  is a diagrammatic end view of an exemplary stator and rotor in accordance with embodiments of the present disclosure; 
           [0011]      FIG. 2  is a portion of a  FIG. 1  enlarged for magnification purposes; 
           [0012]      FIG. 3  is a diagrammatic view of an exemplary stator and rotor in accordance with embodiments of the present disclosure 
           [0013]      FIG. 4  is a diagrammatic view of an exemplary stator and rotor in accordance with embodiments of the present disclosure; 
           [0014]      FIG. 5  is a diagrammatic view of an exemplary stator and rotor in accordance with embodiments of the present disclosure; 
           [0015]      FIG. 6  is a diagrammatic end view of an exemplary stator and rotor in accordance with embodiments of the present disclosure; 
           [0016]      FIG. 7  is a rear perspective view of an exemplary motor in accordance with embodiments of the present disclosure; 
           [0017]      FIG. 8  is a front perspective view of the motor of  FIG. 7 ; 
           [0018]      FIG. 9  is a partial section of the motor of  FIG. 8  taken along 5-5; 
           [0019]      FIG. 10  is a block diagram of an exemplary electric generator set up in accordance with embodiments of the present disclosure; and 
           [0020]      FIG. 11  is a block diagram of an exemplary electric motor set up in accordance with embodiments of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0021]    The present invention will now be described more fully hereinafter with reference to the accompanying drawings, which are intended to be read in conjunction with both this summary, the detailed description and any preferred and/or particular embodiments specifically discussed or otherwise disclosed. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. 
         [0022]      FIG. 1  is a diagrammatic end view of an exemplary stator indicated generally at  4  and a rotor indicated generally at  6  in accordance with certain embodiments of the present disclosure. The stator  4  is an electromagnetic stator and is surrounded by the rotor  6  which is a permanent magnet rotor having a rotational axis  8 . 
         [0023]    The stator  4  includes a central hub  10  and radially outwardly projecting pole shoes  12  with wire windings  14  about the pole shoes  12 . The electrical connections to the windings  14  are not shown. In certain embodiments, of the present invention, the stator  4  may be wound as a conventional three-phase motor with a conventional three lead connection to connect the stator  4  to a motor controller which is connected to an electric energy source. In certain embodiments of the present invention, the stator  4  may also be wound and connected as a generator. Other suitable conventional stators may be used as the stator  4 . Novel stator configurations and/or stator windings may also be used. 
         [0024]    The permanent magnet rotor  6  includes a cylindrical shaped structure  16  (also sometimes referred to herein as a flux ring) that includes laminated concentric layers  18 ,  20 ,  22 ,  24  and  26 . The layers  18 ,  20 ,  22 ,  24  and  26  are made of electric steel. Other suitable electrically conductive materials may be used for the layers  18 ,  20 ,  22 ,  24  and  26 . In certain embodiments, the layers  18 ,  20 ,  22 ,  24  and  26  may all include identical materials, or alternating types of materials, or another suitable configuration. 
         [0025]    The layers  18 ,  20 ,  22 ,  24  and  26  may be coated with a C5 electrical insulator (not shown). Other non-conductive coatings, such as C1 to C4 or C6 coatings, may be used. 
         [0026]    The layers  18 ,  20 ,  22 ,  24  and  26  are bonded together with structural epoxy layers  27 . In certain embodiments, the laminated concentric layers of the cylindrical shaped structure  16  may be bonded, coupled or adhered together via one or more layers of other suitable bonding materials. In other embodiments, where the laminated concentric layers are not otherwise electrically insulated, such as via an insulating coating, the bonding material should be non-electrically conducting or minimally electrically conducting. In certain embodiments, the bonding material may be an adhesive which retains a degree of plasticity when cured such that the laminated layers can flex somewhat during use but remain sufficiently bonded together. In certain embodiments, the bonding material may be an epoxy which includes an elastomeric component which imparts flexibility when cured to the laminated layers which enables the laminated layers to flex or deform but still retain sufficient structural integrity. 
         [0027]    In other embodiments, the laminated concentric layers of the cylindrical shaped structure  16  may be coupled together by mechanical means such as a bolts  29 . Other suitable mechanical fasteners include screws, pins, clamps etc. provided that the layers are sufficiently physically separated, such as by a coating, to sufficiently electrically isolate the layers from each other. In other embodiments, both a bonding material and a mechanical fastener may be used. 
         [0028]    The layers  18 ,  20 ,  22 ,  24  and  26  each have a thickness of approximately 15 thousandths of an inch. Other suitable thicknesses may be used for the laminated concentric layers of the cylindrical shaped structure  16 , with some or all of the laminated concentric layers being of the same thickness or different thicknesses. 
         [0029]    The layers  18 ,  20 ,  22 ,  24  and  26  are each formed of a single sheet of electric steel with seams  28 ,  30 ,  32 ,  34  and  36  where the ends of the sheets meet. The seams  28 ,  30 ,  32 ,  34  and  36  are offset from one another but this is not essential. 
         [0030]    In certain embodiments of the present invention, the laminated concentric layers of the cylindrical shaped structure  16  may include a plurality of cylindrical or tubular shaped structures  35  disposed concentrically one after the other in a radial direction relative to the rotational axis  8 . In certain embodiments, each laminated concentric layer of the cylindrical shaped structure  16  may include concentric segments  36 . 
         [0031]    In certain other embodiments, the laminated concentric layers of the cylindrical shaped structure  16  may include a single continuous strip  38  of material wound successively about the rotational axis  8 . 
         [0032]    The cylindrical shaped structure  16  must include at least two laminated concentric layers. In further embodiments, the cylindrical shaped structure  16  may include more than two laminated layers, such as three, four, five, six or more layers. 
         [0033]    A plurality of magnets  40  lines the inside of the cylindrical shaped structure  16 . The magnets  40  are permanent types primarily made from rare earth materials, such as neodymium, samarium cobalt or similar material. The number of magnets  40  varies with a particular application, but is always a multiple of two. The magnets  40  are arranged with alternating pole orientation, north, south, north, south; and so on. The permanent magnet rotor  6  rotates in close proximity to stator  4 , separated by a continuous separating air gap  42  that permits the rotor  6  to rotate freely in close proximity to electromagnetic stator  4  without contact. 
         [0034]    In another embodiment of the present invention, the brushless DC electric motor generally is an inrunner type and includes a permanent magnet rotor  50  surrounded by an electromagnetic stator  52 . 
         [0035]    In one embodiment, the permanent magnet rotor  50  includes a cylindrical shaped structure  54  that includes three laminated concentric layers  56 ,  58  and  60 . The cylindrical shaped structure  54 , including the layers  56 ,  58  and  60 , may comprise configurations according to the teachings herein with respect to the laminated concentric layers of the cylindrical shaped structure  16 . The rotor  50  includes a central hub  62  and permanent magnets  64  arranged around the outside of the cylindrical shaped structure  16 . 
         [0036]    The stator  52  includes a cylindrical shaped structure  66  which includes two concentric laminated layers  68  and  70  and in certain embodiments, may comprise configurations according to the teachings herein with respect to the laminated concentric layers of the cylindrical shaped structure  16  or may be formed of a single unlaminated layer. 
         [0037]    The stator  52  includes radially inwardly projecting pole shoes  72  with wire windings  74  around the shoes  72 . A conventional stator may be used for the stator  52 . 
         [0038]    In certain embodiments of the present invention, a motor or generator may include a rotor having laminated concentric layers according to embodiments of the present invention. An exemplary motor including a rotor having laminated concentric layers is indicated generally at  100  in  FIGS. 3-5 . The motor  100  includes a rotor indicated generally at  105  which includes the cylindrical shaped structure  110  having five laminated layers  112  according to the embodiment described herein with respect to layers  18 ,  20 ,  22 ,  24  and  26 . It will be understood that the cylindrical shaped structure  110  may have layers according to other embodiments of the present invention, such as the embodiments illustrated in  FIGS. 3 to 5 . 
         [0039]    Rotor end caps  114  and  116  are provided and secured to the cylindrical shaped structure  110  by bolts  29  in holes  111 . End plate  114  with web  118  is provided on the front end of the motor  100  and end plate  116  with web  120  is provided on the rear end of the motor  100 . The web plate  118  includes a shaft  119  to which a propeller, axle etc. to be driven may be attached 
         [0040]    The end plates  118  and  120  connect the rotor  105  to the hub  122  of the stator indicated generally at  124 . The rotor  105  includes a plurality of permanent magnets  125 . The stator  124  is an electromagnetic stator including pole shoes  126  with windings  128 . The windings are not shown in  FIGS. 7 and 8  for simplicity. 
         [0041]    Without being bound by theory, the inventor believes that concentric layering of the cylindrical structure of the rotor reduces the size of eddy currents in the rotor and as a result, less heat is generated. 
         [0042]    In certain embodiments, a rotor with concentric layering according to embodiments of the present invention may be used as part of an otherwise conventional electromechanical device, including synchronous electric motors and generators, including in otherwise conventional brushless DC motors and generators of outrunner or inrunner configurations. 
         [0043]    In certain embodiments, a rotor with concentric layering according to embodiments of the present invention may be disposed in a motor  76  or generator  78  which includes otherwise conventional components known to persons skilled in the art such as one or more of a power source, such as energy source  80 , an energy storage  82 , an electrical power converter  84 , and a controller, such as motor controller  86 , for electronically controlling the motor  76 , such as by controlling motor position and/or rotational speed, and may be disposed in a motor or generator including in a power system, a vehicle, an automobile, a bus, an aircraft, a watercraft, or other suitable vehicle, and a non-vehicle application. 
         [0044]    While the present invention has been described above in terms of specific embodiments, it is to be understood that the invention is not limited to these disclosed embodiments. Many modifications and other embodiments of the invention will come to mind of those skilled in the art to which this invention pertains, and which are intended to be and are covered by both this disclosure and the appended claims. It is indeed intended that the scope of the invention should be determined by proper interpretation and construction of the appended claims and their legal equivalents, as understood by those of skill in the art relying upon the disclosure in this specification and the attached drawings.