Abstract:
An axial flux electric machine and associated method of use that includes a shaft, a rotor attached to the shaft, a plurality of permanent magnets positioned underneath the rotor, an electrical winding positioned below the plurality of permanent magnets, a stator that encircles the shaft that is located below the rotor, a first bearing assembly located below the stator and encircling the shaft of the rotor, a second bearing assembly located below the first bearing assembly and encircling the shaft, and a spring mechanism, located between the first bearing assembly and the second bearing assembly, to distribute load placed on the shaft between the first bearing assembly and the second bearing assembly.

Description:
BACKGROUND OF THE INVENTION 
     A significant application for an electric motor is to operate a pump or a blower. This type of electric motor typically utilizes a permanent magnet electrical motor and would preferably utilize a planar array of magnets. A typical permanent magnet electrical motor can include an alternating current induction motor. One type of alternating induction motor is a radial flux motor, where the flux extends radially outward from the axis of rotation. Another type of electric motor is an electronically commutated motor. An electronically commutated motor may include a permanent magnet alternating current motor, a variable reluctance motor, and a brushless direct current motor. An electronically commutated motor typically operates at a higher efficiency than an alternating current induction motor. There is an axial flux configuration for an electronically commutated motor in which the flux in the air gap extends in a direction that is parallel to the axis of rotation for the rotor of the electronically commutated motor. 
     The electric motor could rotate an impeller within a pump or blower, which creates a flow of fluid. There are a variety of gas burning appliances that use an electric motor, which includes furnaces, radiant heaters, boilers, water heaters, and pool heaters. This also includes a wide variety of blower applications, where the electric motor powers a blower to move air and/or an air/fuel mixture either through or out of an appliance. 
     One typical type of axial flux configuration for an electronically commutated motor for the applications above includes an electric motor having a rotor comprising a rotor disk and a plurality of permanent magnets magnetically coupled to the rotor disk. The plurality of permanent magnets include a substantially flat profile and is aligned in a substantially planar array. The electric motor also includes a stator comprising a solid stator core and a plurality of coils each wound around a coil insulating member. The stator core includes a plurality of stator teeth extending substantially parallel to an axis of rotation of the rotor. This type of motor is disclosed in PCT Patent Application Publication No. WO 2011/119574 A1, International Application No. PCT/US2011/029378, which is incorporated herein by reference in its entirety. A major problem with this motor is that the load is placed on a single bearing on the shaft end of the motor. There is also a complex and costly sleeve and opposite end shaft plate. Moreover, the shaft for the rotor is a costly and complex structure to manufacture. 
     The present invention is directed to overcoming one or more of the problems set forth above. 
     SUMMARY OF INVENTION 
     In another aspect of the invention, an axial flux electric machine is disclosed. The axial flux electric machine includes a shaft, a rotor attached to the shaft, a plurality of permanent magnets positioned underneath the rotor, an electrical winding positioned below the plurality of permanent magnets, a stator that encircles the shaft that is located below the rotor, a first bearing assembly located below the stator and encircling the shaft of the rotor, a second bearing assembly located below the first bearing assembly and encircling the shaft, and a spring mechanism, located between the first bearing assembly and the second bearing assembly, to distribute load placed on the shaft between the first bearing assembly and the second bearing assembly. 
     In another aspect of the invention, an axial flux electric machine is disclosed. The axial flux electric machine includes a shaft, a rotor attached to the shaft, a plurality of permanent magnets positioned underneath the rotor, a plurality of coils positioned below the plurality of permanent magnets, a stator that encircles the shaft that is located below the rotor, a first ball bearing assembly located below the stator and encircling the shaft of the rotor; a second ball bearing assembly located below the first ball bearing assembly and encircling the shaft, a wave spring, located between the first bearing assembly and the second bearing assembly, to distribute load placed on the shaft between the first bearing assembly and the second bearing assembly, and a motor housing. 
     Still yet another aspect of the present invention is that a method for utilizing an axial flux electric machine is disclosed. The method includes utilizing a shaft with a rotor attached to the shaft and a plurality of permanent magnets positioned underneath the rotor, an electrical winding positioned below the plurality of permanent magnets, a stator that encircles the shaft that is located below the rotor, a first bearing assembly located below the stator and encircling the shaft of the rotor, a second bearing assembly located below the first bearing assembly and encircling the shaft, and a spring mechanism, located between the first bearing assembly and the second bearing assembly, to distribute load placed on the shaft between the first bearing assembly and the second bearing assembly. 
     These are merely some of the innumerable aspects of the present invention and should not be deemed an all-inclusive listing of the innumerable aspects associated with the present invention. These and other aspects will become apparent to those skilled in the art in light of the following disclosure and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       For a better understanding of the present invention, reference may be made to the accompanying drawings in which: 
         FIG. 1  is a partial cut-away, exploded side view of axial load sharing motor assembly of the present invention; 
         FIG. 2  is the partial cut-away, assemblied view of the axial load sharing motor assembly of the present invention shown in  FIG. 1 ; 
         FIG. 3  is a partial cut-away, exploded side view of the axial load sharing motor assembly of the present invention connected to a blower housing; 
         FIG. 4  is a perspective view of an exemplary embodiment of a rotor that may be included within the axial flux machine shown in  FIGS. 1 ,  2  and  3 ; 
         FIG. 5  is a bottom view of an exemplary embodiment of a magnet retention ring that may be included within the axial flux machine shown in  FIGS. 1 ,  2  and  3 ; 
         FIG. 6  is a side view of the magnet retention ring shown in  FIG. 5 ; 
         FIG. 7  is a perspective view of the magnet retention ring shown in  FIG. 5  and  FIG. 6 ; 
         FIG. 8A  is a perspective view of an exemplary embodiment of a rotor that may be included within the axial flux machine shown in  FIGS. 1 ,  2  and  3 ; 
         FIG. 8B  is a top view of the rotor shown in  FIG. 8A ; 
         FIG. 8C  is a side view of the rotor shown in  FIG. 8A ; 
         FIG. 8D  is a side view of a portion of the rotor shown in  FIG. 8A ; 
         FIG. 9  is a perspective view of an exemplary embodiment of a stator core that may be included within the axial flux machine shown in  FIGS. 1 ,  2  and  3 ; 
         FIG. 10  is a perspective view of an exemplary embodiment of a stator retention ring that may be included within the axial flux machine shown in  FIGS. 1 ,  2  and  3 ; 
         FIG. 11  is an exploded view of an exemplary embodiment of a bobbin assembly that may be included within the axial flux machine shown in  FIGS. 1 ,  2  and  3 ; and 
         FIG. 12  is a perspective view of an exemplary embodiment of a bobbin that is included within the bobbin assembly shown in  FIG. 11 . 
     
    
    
     Reference characters in the written specification indicate corresponding items shown throughout the drawing figures. 
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as to obscure the present invention. 
     Referring now to  FIGS. 1 and 2 , an axial flux load sharing machine of the present invention is generally indicated by numeral  10 .  FIG. 1  is an exploded, partially cut-away view of the axial flux load sharing machine  10  and  FIG. 2  is a partially cut-away view of the axial flux load sharing machine  10 . Components common to  FIGS. 1 and 2  are identified with the same reference numerals. Components are described herein as including a top surface  11  generally facing what is referred to herein as a top of the axial flux load sharing electric machine  10 , and a bottom surface  13  generally facing what is referred to herein as a bottom of axial flux load sharing electric machine  10 . In the exemplary embodiment, electric machine  10  is an electric motor, although, electric machine  10  may operate as either an electric motor or an electric generator. In the exemplary embodiment, electric machine  10  includes a housing (not shown), a rotor  39 , a bobbin assembly  32 , a stator core  20 , a stator core retaining spring, e.g., ring,  30 , a first bearing assembly, e.g., ball bearing,  14 , a second bearing assembly, e.g., ball bearing,  16 , and a spring mechanism, e.g., wave spring,  18  positioned between the first bearing assembly, e.g., ball bearing,  14 , and the second bearing assembly, e.g., ball bearing,  16 . This is followed by an end shield, e.g., motor housing,  12 . 
     In the exemplary embodiment, there is a rotor assembly  38  that includes a rotor  39  coupled to a shaft  22 . The rotor  39  is positioned adjacent to and directly above a plurality of permanent magnets  36 . The rotor assembly  38  is rotatable within the machine  10 , and more specifically, rotatable within the first bearing assembly, e.g., ball bearing,  14 , the second bearing assembly, e.g., ball bearing,  16 , and the spring mechanism, e.g., wave spring,  18 , about an axis  46  of rotation. Furthermore, in the exemplary embodiment, bobbin assembly  32  includes a plurality of coil insulating members  33  (also referred to herein as bobbins) and a stator core connection board  35 . 
     In the exemplary embodiment, the rotor  39  is manufactured using a sintering process from, for example, Soft Magnetic Alloy (SMA) or Soft Magnetic Composite (SMC) materials. In an alternative embodiment, the rotor  39  is machined and/or cast from, for example, steel. 
     In the exemplary embodiment, the plurality of permanent magnets  36  are neodymium magnets, although, any suitable permanent magnet may be included that allows the electric machine  10  to function as described herein. An air gap  48  exists between bottom surfaces of the plurality of permanent magnets  36  and top surface of the stator core  20 , as shown in  FIG. 2 . A flux within machine  10  extends between the plurality of permanent magnets  36  and the stator core  20  in a direction parallel to the axis of rotation  46 . In the exemplary embodiment, the plurality of permanent magnets  36  is symmetrical, which facilitates manufacturing a single magnet design for use as each of the magnets within the plurality of permanent magnets  36 . Furthermore, the plurality of permanent magnets  36  has a substantially flat profile which minimizes waste during manufacturing, and therefore, minimizes cost. 
     As shown in  FIGS. 1 and 2 , the shaft  22  is secured in position below the plurality of permanent magnets  36  and the rotor  39  and above the bobbin assembly  32  by a first shaft retaining ring  50 . The shaft  22  is also secured in position below the bobbin assembly  32  and the stator core connection board  35  and above the first bearing assembly, e.g., ball bearing,  14  by a second shaft retaining ring  52 . Moreover, the shaft  22  is secured in position adjacent to the spring mechanism, e.g., wave spring,  18 . The top of the shaft  22  is rotatably connected to a fan  40 . 
     Referring now to  FIG. 3 , the same structure shown in  FIGS. 1 and 2  is replicated with the sole exception that the axial flux load sharing machine  10  is mounted on a blower housing  44 , rather than the motor housing  12 , with a seal washer  42  located between the blower housing  44  and the second bearing assembly, e.g., ball bearing,  16 . 
     In the exemplary embodiment, the axial flux load sharing machine  10  is controlled by a sine drive controller (not shown). The sine drive controller produces essentially sine wave currents in the stator winding phases. Furthermore, in the exemplary embodiment, stator core  20  is formed using a sintering process from an SMC material, an SMA material, and/or a powdered ferrite material. The blower system is configured for use in gas burning appliances, for example, but not limited to, water heaters, boilers, pool heaters, space heaters, radiant heaters, and furnaces. 
       FIG. 4  is a perspective view of an exemplary embodiment of a rotor  39  that may be included within axial flux load sharing machine  10  (shown in  FIGS. 1 ,  2  and  3 ). In the exemplary embodiment, the rotor  39  includes a shaft opening  60 . Shaft opening  60  is located around the axis of rotation  46  and is configured to receive a shaft, for example, shaft  22  (shown in  FIGS. 1 ,  2  and  3 ). The rotor  39  also includes an outer rim  62  that extends axially from bottom surface  64  of the rotor  39 . In the exemplary embodiment, outer rim  62  is included within a permanent magnet retention system  66 , as shown in  FIG. 8A . Permanent magnet retention system  66  includes outer rim  62  and a magnet retention ring  68  (shown in  FIG. 5 ). Outer rim  62  includes an outer edge  70  and an inner edge  72 . In the exemplary embodiment, the rotor  39 , and more specifically, bottom surface  64 , includes a recessed area  74 . Recessed area  74  is a ring-shaped area having a depth  76 . Recessed area  74  and outer rim  62  are concentric. In the exemplary embodiment, outer rim  62  extends a distance  78  from recessed area  74 , wherein distance  78  is greater than depth  76 . 
       FIG. 5  is a bottom view of an exemplary embodiment of magnet retention ring  68 .  FIG. 6  is a side view of magnet retention ring  68 .  FIG. 7  is a perspective view of magnet retention ring  68 . In the exemplary embodiment, magnet retention ring  68  includes top surface  11  and bottom surface  13 , shown in  FIG. 6 . The magnet retention ring  68  also includes a plurality of magnet alignment features, for example, tabs  80 ,  82 ,  84 ,  86 ,  88 , and  90 . Tabs  80 ,  82 ,  84 ,  86 ,  88 , and  90  are configured to maintain a position of the plurality of permanent magnets  36  relative to the rotor  39 . The magnet retention ring  68  includes an outer edge  92  and an inner edge  94 . 
     In at least some embodiments, magnet retention ring  68  is manufactured from iron, steel, non-ferrous metal, and/or molded plastic. However, magnet retention ring  68  may be manufactured from any material that allows axial flux load sharing machine  10  to function as described herein. Furthermore, magnet retention ring  68  may be stamped, forged, blanked, or formed using any other suitable process to create a thin ring. Although described above as including a plurality of tabs  80 ,  82 ,  84 ,  86 ,  88 , and  90 , magnet retention ring  68  may include ribs, folded fingers, or any similar feature that facilitates maintaining the position of the plurality of permanent magnets  36  and keeping the plurality of permanent magnets  36  separated. The tabs, ribs, fingers, or other separation features are configured such that they do not cause magnetic shorting of the magnetic fields produced by the plurality of permanent magnets  36 . For example, the separation features may be sized such that shorting of the magnetic fields is minimized. Alternatively, non-ferrous and/or molded plastic separation features may be included, which will not cause shorting of the magnetic fields. 
     In at least some embodiments, magnet retention ring  68  has a thickness  96  (shown in  FIG. 6 ) that is substantially similar to depth  76  (shown in  FIG. 4 ). Substantially matching thickness  96  of magnet retention ring  68  and depth  76  of recessed area  74  minimizes an air gap between the plurality of permanent magnets  36 , magnet retention ring  68 , and rotor  39 . Such an air gap may reduce a torque constant generated by the rotor assembly  38 . 
       FIG. 8A  is a perspective view of an exemplary embodiment of the rotor assembly  38  (shown in  FIGS. 1 ,  2  and  3 ).  FIG. 8B  is a top view of an exemplary embodiment of the rotor assembly  38 .  FIG. 8C  is a side view of an exemplary embodiment of the rotor assembly  38 .  FIG. 8D  is a side view of a portion of the rotor assembly  38  shown in  FIG. 8C . In the exemplary embodiment, the rotor assembly  38  includes the plurality of permanent magnets  36  and magnet retention ring  68  coupled to a rotor  39 . The plurality of permanent magnets  36  includes a first permanent magnet  98  and a second permanent magnet  100 . In the exemplary embodiment, the rotor assembly  38  includes ten permanent magnets, evenly spaced around the rotor  39 . Other embodiments of the rotor assembly  38  include any suitable number of permanent magnets that allow the axial flux load sharing machine  10  to function as described here. 
     In the exemplary embodiment, at least a portion of magnet retention ring  68  fits within recessed area  74  (shown in  FIG. 4 ). More specifically, top surface  11  (shown in  FIG. 6 ) of magnet retention ring  68  is positioned adjacent to bottom surface  13  of the rotor  39 . Outer edge  70  of magnetic retention ring  68  may be positioned adjacent to inner edge  72  of outer rim  62 . Alternatively, outer edge  70  of magnetic retention ring  68  may be positioned adjacent to an inner edge of recessed area  74 . Magnet retention ring  68  may be secured adjacent to the rotor  39  by a magnetic force that couples the plurality of permanent magnets  36  to the rotor  39 . Magnet retention ring  68  may also be coupled to the rotor  39  using an adhesive. The adhesive is not necessary to retain magnet retention ring  68  within recessed area  74 , however, the adhesive may reduce fretting corrosion due to vibration during operation. 
     When the rotor  39  rotates about axis  46  (shown in  FIGS. 1 ,  2  and  3 ), forces act on the plurality of permanent magnets  36 . Outer rim  62  prevents the plurality of permanent magnets  36  from moving radially outward. Tabs  80 ,  82 ,  84 ,  86 ,  88 , and  90  maintain spacing between the plurality of permanent magnets  36 . In other words, tabs  80 ,  82 ,  84 ,  86 ,  88 , and  90  prevent first permanent magnet  98  from moving in a tangential direction relative to the rotor  39 . Furthermore, tabs  80 ,  82 ,  84 ,  86 ,  88 , and  90  and outer rim  62  eliminate the need for an adhesive to retain the plurality of permanent magnets  36  in the shaft axis direction while holding the plurality of permanent magnets  36  in the radial and tangential directions. An adhesive may be used to prevent fretting corrosion due to vibration during operation or to couple the plurality of permanent magnets  36  to the rotor disk  39  during handling and assembly of the axial flux load sharing machine  10 . 
       FIG. 9  is a perspective view of an exemplary embodiment of stator core  20  (shown in  FIGS. 1 ,  2  and  3 ). In the exemplary embodiment, stator core  20  includes a plurality of stator core teeth  102  that extend in an axial direction (i.e., parallel to axis of rotation  46 , shown in  FIGS. 1 ,  2  and  3 ) from a stator core base  104 . In the exemplary embodiment, the plurality of stator core teeth  102  includes a first tooth  106 , a second tooth  108 , a third tooth  110 , a fourth tooth  112 , a fifth tooth  114 , a sixth tooth  116 , a seventh tooth  118 , an eighth tooth  120 , a ninth tooth  122 , a tenth tooth  124 , an eleventh tooth  126  and a twelfth tooth  128 . Although described as including twelve teeth, stator core  20  may include any suitable number of teeth that allow axial flux load sharing machine  10  to function as described herein. In use, stator core base  104  is disposed perpendicularly about rotational axis  46  and the plurality of stator core teeth  102  extend axially from stator core base  104  and form a slot  130  between each adjacent tooth of the plurality of teeth  102 . In the exemplary embodiment, stator core  20  includes a flange  132  extending at least partially around an outside diameter of stator core  20 . Flange  132  may extend entirely around stator core  20 , or may extend only partially around stator core  20 . Flange  132  may also include a first section extending partially around stator core  20  and a second section extending partially around stator core  20 . Flange  132  may include any number of sections that allows the axial flux load sharing machine  10  to function as described herein. 
       FIG. 10  is a perspective view of an exemplary embodiment of magnetic retention ring  68  (shown in  FIGS. 1 ,  2  and  3 ). In the exemplary embodiment, magnetic retention ring  68  includes a lip  134 . Lip  134  may extend entirely around magnetic retention ring  68 , or may extend only partially around magnetic retention ring  68 . Furthermore, lip  134  may include a first section and a second section, each extending partially around magnetic retention ring  68 . Bottom surface  64  of lip  134  is configured to align with flange  132  of stator core  20 . When stator core retaining spring, e.g., ring,  30  is positioned around stator core  20  and is coupled to motor housing  12  (shown in  FIG. 1 ), stator core  20  is secured between stator core retaining spring, e.g., ring,  30  and the motor housing  12 . In the exemplary embodiment, stator core retaining spring, e.g., ring,  30  includes a first fastener opening  138 , a second fastener opening  140 , and a third fastener opening  142 . Fastener openings  138 ,  140 , and  142  align with openings within motor housing  12  (shown in  FIG. 1 ) with the plurality of attachment mechanisms, e.g., screws,  34  (shown in  FIGS. 1 ,  2  and  3 ), for example, a threaded fastener,  34  to couple stator core retaining spring, e.g., ring,  30  to the motor housing  12 . Although described as using screws for the attachment mechanisms  34  to couple the stator core retaining spring, e.g., ring,  30  to the motor housing  12 , any type of suitable fastener may be used that allows axial flux load sharing machine  10  to function as described herein. 
     In the exemplary embodiment shown in  FIG. 9 , flange  132 , in combination with stator core retaining spring, e.g., ring,  30  enables stator core  20  to be coupled to the motor housing  12  (shown in  FIG. 1 ) without an adhesive between the stator core  20  and the motor housing  12  or threaded fasteners passing directly through and/or into stator core  20  and into the motor housing  12 . In other words, stator core  20  is coupled to the motor housing  12  without the need for adhesives or screws into the stator core  20 . Securing stator core  20  in position adjacent to the motor housing  12  in this manner facilitates increasing reliability when compared to adhesively coupling stator core  20  to the motor housing  12 . The stator core retaining spring, e.g., ring,  30  prevents damage to stator core  20  that may be caused by using, for example, a threaded fastener into or through stator core  20  due to the relatively weak stator core material, which also leaves stator core  20  prone to thread failure. 
     In the exemplary embodiment shown in  FIG. 9 , stator core  20  includes a plurality of alignment features, for example, a first notch  144  and a second notch  146 . Furthermore, in the exemplary embodiment, stator core retaining spring, e.g., ring,  30  includes a plurality of corresponding alignment features, for example, a first protrusion  148  and a second protrusion  150 , shown in  FIG. 10 , configured to align with first notch  144  and the second notch  146 , respectively. The alignment features within stator core  20  and stator core retaining spring, e.g., ring,  30  prevent stator core  20  from rotating due to magnetic forces present during operation of axial flux load sharing machine  10 . Furthermore, the alignment features provide positive rotational alignment of stator core  20  within the axial flux load sharing machine  10  during assembly of axial flux load sharing machine  10 . The stator core retaining spring, e.g., ring,  30  may be manufactured from a variety of metals or plastics with elastic or non-elastic properties to absorb manufacturing tolerance accumulation. 
     In the exemplary embodiment, stator core  20  is a solid core. More specifically, as defined herein, a solid core is a non-laminated core. Furthermore, a solid core may be a complete, one-piece component, or may include multiple non-laminated sections coupled together to form a complete solid core. For example, stator core  20  may be constructed of an SMC or an SMA material. Such materials allow for three dimensional flux paths and facilitate reducing high frequency losses (e.g., losses at frequencies above 60 Hz) when compared with laminated stator cores. Use of the sintered SMC or SMA also facilitates increasing control of air gap  48  (shown in  FIG. 3 ) which improves performance and minimizes noise. 
       FIG. 11  is an exploded view of an exemplary embodiment of bobbin assembly  32 , shown in  FIGS. 1 ,  2  and  3 . In the exemplary embodiment, bobbin assembly  32  includes the plurality of bobbins  152  and the stator core connection board  35 . In the exemplary embodiment, the plurality of bobbins  152  includes a first bobbin  154 , a second bobbin  156 , a third bobbin  158 , a fourth bobbin  160 , a fifth bobbin  162 , and a sixth bobbin  164 . Although described as including six bobbins, bobbin assembly  32  may include any number of bobbins that allows axial flux load sharing machine  10  to function as described herein. Each of bobbins  154 ,  156 ,  158 ,  160 ,  162 , and  164  include an opening  166  that closely conforms to an external shape of the plurality of stator core teeth  102  (shown in  FIG. 4 ). Referring to  FIGS. 9 and 11 , the first tooth  106  is configured to be positioned at least partially within opening  166  of first bobbin  154 . Furthermore, third stator tooth  110  is configured to be positioned at least partially within opening  166  of second bobbin  156 . The axial flux load sharing machine  10  may include one bobbin per tooth, or one bobbin positioned on every other tooth. 
     In the exemplary embodiment, bobbin assembly  32  also includes an electrical winding  168  that includes a plurality of coils, for example, a first coil  170 , a second coil  172 , a third coil  174 , a fourth coil  176 , a fifth coil  178 , and a sixth coil  180 . In the exemplary embodiment, electrical winding  168  is made up of the six coils  170 ,  172 ,  174 ,  176 ,  178 , and  180  and creates a twelve-pole stator. Each coil  170 ,  172 ,  174 ,  176 ,  178 , and  180  is wound around a respective bobbin  154 ,  156 ,  158 ,  160 ,  162 , and  164 . Each bobbin  154 ,  156 ,  158 ,  160 ,  162 , and  164  electrically isolates one of coils  170 ,  172 ,  174 ,  176 ,  178 , and  180  from a respective stator tooth of the plurality of stator teeth  102 . 
     In the exemplary embodiment, coils  170 ,  172 ,  174 ,  176 ,  178 , and  180  are wound around bobbins  154 ,  156 ,  158 ,  160 ,  162 , and  164 . Each of coils  170 ,  172 ,  174 ,  176 ,  178 , and  180  include two ends, a start and a finish to the coil. The bobbins  154 ,  156 ,  158 ,  160 ,  162 , and  164  are coupled to stator core connection board  35 . In the exemplary embodiment, stator core connection board  35  is a printed circuit board (PCB). In the exemplary embodiment, each end of each of coils  170 ,  172 ,  174 ,  176 ,  178 , and  180  is coupled to stator core connection board  35  using an insulation displacement terminal  182  designed for directly soldering into stator core connection board  35 . In at least some embodiments, insulation displacement terminal  182  may be a Siameze terminal manufactured by Tyco Electronics Ltd., although, any other suitable connector may be used that allows the plurality of bobbins  152  to be coupled to stator core connection board  35  as described herein. In the exemplary embodiment, bobbin assembly  32  is manufactured as a complete component using printed circuit board processes using through-hole technology. In the exemplary embodiment, insulation displacement terminals  182  facilitate electrically coupling each of coils  170 ,  172 ,  174 ,  176 ,  178 , and  180  to stator core connection board  35 , and also mechanically coupling each of the plurality of bobbins  152  to stator core connection board  35  before and after soldering. In the exemplary embodiment, stator core connection board  35  includes a standard wiring connector (not shown in  FIG. 11 ) for directly connecting stator core connection board  35  to a motor control board. In an alternative embodiment, stator core connection board  35  is incorporated within a motor control board, thereby eliminating redundant mounting and connectors. Moreover, in the exemplary embodiment, bobbin assembly  32  also includes at least one spacer, for example, first spacer  184  and a second spacer  186 . First spacer  184  and second spacer  186  are coupled to stator core connection board  35  and maintain a distance between stator core connection board  35  and motor housing  12 . In some embodiments, spacers  184  and  186  each include an opening configured to allow a fastener to pass through. 
       FIG. 12  is a perspective view of an exemplary embodiment of bobbin  154 , also shown in  FIG. 11 . In the exemplary embodiment, bobbin  154  includes a first alignment post  188 , a second alignment post  190 , and a third alignment post  192 . Alignment posts  188 ,  190 , and  192  are configured to interact with corresponding stator core connection board  35  features, for example, a first opening  194 , a second opening  196 , and a third opening  198  (shown in  FIG. 11 ). Posts  188 ,  190 , and  192  in combination with first opening  194 , second opening  196 , and third opening  198 , facilitate proper coupling of the first bobbin  154  and stator core connection board  35 . Although described as including three alignment posts, the first bobbin  154  may include any number of alignment posts that allow the first bobbin  154  to be properly aligned with stator core connection board  35 . 
     In the exemplary embodiment, bobbin  154  also includes a first terminal opening  200  and a second terminal opening  202 . Each terminal opening  200  and  202  is configured to receive at least a portion of insulation displacement terminal  182 . A first end (not shown in  FIG. 12 ) of coil  170  is positioned at least partially within a first slit  204  and at least partially within a second slit  206 . Slit  206  is perpendicular to second terminal opening  202 . Second slit  206  facilitates aligning the first end of coil  170  in a manner that allows insulation displacement terminal  182  (shown in  FIG. 11 ) to electrically couple with the first end of coil  170  when positioned within second terminal opening  202 . 
     Although described above as including insulation displacement terminals  182 , in an alternative embodiment, bobbin assembly  32  does not include insulation displacement terminals  182 . In the alternative embodiment, the ends of each of coils  170 ,  172 ,  174 ,  176 ,  178 , and  180  are coupled directly to stator core connection board  35 , for example, through an electrical hole in a printed circuit board. The ends are then soldered to complete the electrical circuit and mechanically couple bobbin  154  to stator core connection board  35 . 
     An electric machine described herein includes a rotor comprising a rotor disk and a plurality of permanent magnets magnetically coupled to the rotor disk. The plurality of permanent magnets has a substantially flat profile and is aligned in a substantially planar array. The electric machine also includes a stator comprising a solid stator core and a plurality of coils each wound around a coil insulating member. The stator core includes a plurality of stator teeth extending substantially parallel to an axis of rotation of the rotor. 
     The electric machine described herein may include a stator connection board, wherein each of the coil insulating members is coupled to the stator connection board. The stator connection board mechanically and electrically couples together the plurality of coils. The electric machine may also include at least one insulation displacement terminal to facilitate coupling the plurality of coils to the stator connection board, wherein the coil insulating member includes an opening configured to receive the at least one insulation displacement terminal. The coil insulating member may include at least one alignment post for aligning the insulation member and the stator connection board. 
     The electric machine described herein may also include a stator retention ring configured to secure the stator core between the stator retention ring and an end shield of the machine. The stator retention ring may include at least one stator core alignment feature configured to interact with the stator core to prevent rotation of the stator core. Furthermore, the stator core may include at least one stator core alignment feature configured to interact with the stator core retention ring to prevent rotation of the stator core. 
     Moreover, the rotor may also include a permanent magnet retention system that includes an outer rim integrated within the rotor disk and configured to prevent the plurality of permanent magnets from moving in a radial direction relative to the rotor disk. The permanent magnet retention system may be integrated within the rotor disk. The permanent magnet retention system may also include a permanent magnet retention ring configured to be coupled between the rotor disk and the plurality of permanent magnets. The permanent magnet retention ring is configured to maintain a position of the permanent magnets relative to the rotor disk. The rotor disk further includes at least one balancing opening that facilitates balancing of the rotor. The electric machine described herein may be configured for use in a gas burning appliance. 
     A method for assembling an electric machine is described herein. The electric machine includes a rotor and a stator. The stator includes a solid stator core that includes a plurality of stator teeth extending substantially parallel to an axis of rotation of the rotor. The method described herein may include magnetically coupling a plurality of permanent magnets to a rotor, wherein the rotor includes a rotor disk and the permanent magnets have a substantially flat profile and are aligned in a substantially planar array. The method may also include winding a coil around each of a plurality of coil insulating members, wherein each of the plurality of coil insulating members includes an opening. The method may also include positioning at least one of the plurality of stator teeth at least partially within the coil insulating member opening. 
     The method for assembling an electric machine described herein may also include magnetically coupling a permanent magnet retention ring between the rotor disk and the plurality of permanent magnets. Furthermore, the plurality of coil insulating members may be mechanically coupled to a stator connection board, and the plurality of coils may be electrically coupled to the stator connection board. The method for assembling an electric machine may also include coupling the solid stator core to a machine end shield using a stator retention ring. Furthermore, the method may include positioning the electric machine in a gas burning appliance application. 
     A nonlimiting example of an axial flux electric machine that does not provide load sharing is found in International Application No. PCT/US2011/119574 for “Axial Flux Electric Machine and Methods of Assembling the Same,” filed Mar. 22, 2011, claiming a priority of Mar. 22, 2010, which is incorporated by referenced herein, in its entirety. 
     Furthermore, it should be understood that when introducing elements of the present invention in the claims or in the above description of the preferred embodiment of the invention, the terms “have,” “having,” “includes” and “including” and similar terms as used in the foregoing specification are used in the sense of “optional” or “may include” and not as “required.” Similarly, the term “portion” should be construed as meaning some or all of the item or element that it qualifies. 
     Thus, there has been shown and described several embodiments of a novel invention. As is evident from the foregoing description, certain aspects of the present invention are not limited by the particular details of the examples illustrated herein, and it is therefore contemplated that other modifications and applications, or equivalents thereof, will occur to those skilled in the art. Many changes, modifications, variations and other uses and applications of the present construction will, however, become apparent to those skilled in the art after considering the specification and the accompanying drawings. All such changes, modifications, variations and other uses and applications which do not depart from the spirit and scope of the invention are deemed to be covered by the invention which is limited only by the claims that follow.