Abstract:
A housing assembly for an electric motor having a rotor shaft rotatable about an axis includes a housing cover and a housing case. The housing cover defines a first bearing seat for rotatably supporting a first portion of the rotor shaft. The housing case defines a second bearing seat for rotatably supporting a second portion of the rotor shaft. At least one of the housing cover and the housing case includes a plurality of mounting lugs substantially circumferentially evenly spaced about the shaft axis for mounting the electric motor to a surface.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims priority to U.S. Provisional Patent Application No. 61/587,482, filed Jan. 17, 2012, the contents of which are herein incorporated by reference. 
     
    
     BACKGROUND  
       [0002]    The present invention relates to electric motors, such as a brushless DC (BLDC) motor. Electric motors include a rotor that is rotatably supported in a housing by one or more bearings. A stator is fixed to the housing and surrounds a portion of the rotor. Stator windings provide an electro-magnetic field to the rotor. The housing protects and supports the rotor and stator. 
       SUMMARY  
       [0003]    In one embodiment, the invention provides a housing assembly for an electric motor having a rotor shaft rotatable about an axis. A housing cover defines a first bearing seat for rotatably supporting a first portion of the rotor shaft. A housing case defines a second bearing seat for rotatably supporting a second portion of the rotor shaft. At least one of the housing cover and the housing case includes a plurality of mounting lugs substantially circumferentially evenly spaced about the shaft axis for mounting the electric motor to a surface. 
         [0004]    In another embodiment, the invention provides a housing assembly for an electric motor having a rotor shaft. A housing cover defines a first bearing seat rotatably supporting a first portion of the rotor shaft for rotation about a shaft axis. The housing cover includes a plurality of cover assembly lugs. A housing case defines a second bearing seat rotatably supporting a second portion of the rotor shaft. The housing case includes a plurality of case assembly lugs and further includes a plurality of mounting lugs substantially circumferentially evenly spaced about the shaft axis for mounting the electric motor to a surface. The plurality of cover assembly lugs align with the corresponding case assembly lugs such that the housing case and the housing cover may be coupled together. The mounting lugs are configured for mounting the electric motor to a surface. 
         [0005]    Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0006]      FIG. 1  is a perspective view of a motor assembly. 
           [0007]      FIG. 2  is an alternative perspective view of the motor assembly of  FIG. 1 . 
           [0008]      FIG. 3  is a cross-sectional view along line  3 - 3  of the motor assembly of  FIG. 1 . 
           [0009]      FIG. 4  is a cross-sectional view along line  4 - 4  of the motor assembly of  FIG. 2 . 
           [0010]      FIG. 5  is a perspective view of a rotor assembly, a stator assembly, and a printed circuit board of the motor assembly of  FIG. 1 . 
           [0011]      FIG. 6  is a perspective view of a bobbin of the stator of  FIG. 5 . 
           [0012]      FIG. 7  is a cross-sectional view along section line  7 - 7  of the bobbin of  FIG. 6 . 
           [0013]      FIG. 8  is a cross-sectional view along section line  8 - 8  of the bobbin of  FIG. 6 , including an exemplary stator winding arrangement. 
           [0014]      FIG. 9  is an exploded view of a bearing assembly. 
           [0015]      FIG. 10  is a cross sectional view of a bearing spring of the bearing assembly of  FIG. 9 . 
           [0016]      FIG. 11  is a detailed view of a portion of  FIG. 3 , illustrating a bearing assembly and bearing seat. 
           [0017]      FIG. 12  is a front view of a motor housing cover according to another aspect of the invention. 
       
    
    
     DETAILED DESCRIPTION  
       [0018]    Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. 
         [0019]    Referring to  FIG. 3 , a motor  10  includes a stator assembly  14 , a rotor assembly  18 , a housing cover  22 , and a housing case  26 . The motor  10  may be, for example, a single phase, four pole brushless DC (BLDC) motor. 
         [0020]    Referring to  FIG. 1 , the housing cover  22  includes a cover body  30 . The cover body  30  defines a shaft aperture  34  disposed about a rotor shaft axis  38 . Three cover assembly lugs  42  extend outwardly from edges of the cover body  30 . Referring to  FIG. 2 , the three cover assembly lugs  42  align with corresponding case assembly lugs  46  defined by the housing case  26 . The housing cover  22  may be joined to the housing case  26  with fasteners  48  extending across the assembly lugs  42  and  46 . The housing case  26  further includes three mounting lugs  50  disposed circumferentially about the shaft axis  38 , approximately 120 degrees apart. Each mounting lug  50  defines a mounting aperture  54  for receiving, for example, a self-tapping mounting screw. 
         [0021]    Referring to  FIG. 3 , each of the housing cover  22  and the housing case  26  defines a bearing seat  58  and  62 , respectively. Referring to  FIG. 11 , housing case bearing seat  62  defines a thrust support surface  66 , a sleeve bearing support surface  70 , a pad support surface  74 , a spring support surface  78 , and a spring centering surface  82 . The thrust support surface  66 , the pad support surface  74 , and the spring support surface  78  are substantially perpendicular to the shaft axis  38  ( FIG. 3 ). Referring to  FIG. 11 , the spring centering surface  82  is substantially perpendicular to the spring support surface  78 . The sleeve bearing surface  70  is substantially oblique to the pad support surface  74 . 
         [0022]    Each of the housing cover  22  and the housing cover  26  may be unitarily formed by, for example, injection molding a thermoplastic. 
         [0023]    Referring to  FIG. 5 , the stator assembly  14  includes a laminate core  86  (i.e., stator core) and a coil assembly  90 . The laminate core includes a stack of wafer-like laminations  94 . Referring to  FIG. 4 , each lamination  94  includes an outer ring  98  and four substantially radial teeth  102 . In the illustrated construction, the outer ring  98  is divided into four ring segments  104 . The ring segments  104  are coupled together with portions of the radial teeth  102 . 
         [0024]    Referring to  FIG. 4 , the coil assembly  90  includes four bobbins  106 . As illustrated in  FIGS. 4-5 , the bobbins  106  are arranged circumferentially about the shaft axis  38 . Referring to  FIG. 7 , each bobbin  106  includes bobbin body  110  having a winding hub  114 , an inner flange  118 , and an outer flange  122 . 
         [0025]    The winding hub  114  includes an inner hub portion  124  adjacent the outer flange  122  and a flared portion  126  adjacent the inner flange  118 . A winding span  130 , defined between the flared portion  126  and the outer flange  122 , tapers from an outer portion  134  of the bobbin body  110  from inner flange the  118  to inner hub portion  124 . As illustrated in  FIG. 7 , this arrangement provides for a long winding span  130  away from the winding hub  114  and a short winding span  130  adjacent the inner hub portion  124 . 
         [0026]    Referring to  FIG. 6 , an inner surface  135  of the winding hub  114  defines a rectangular aperture  136  through the bobbin body  110 . The rectangular aperture  136  is configured to receive the radial teeth  102  of the laminations  94  (see  FIG. 4 ). Referring to  FIG. 6 , a rib  138  extends in cantilever fashion from the inner surface  135  into the rectangular aperture  136 . The rib  138  facilitates a secure fit with the radial teeth  102  of the laminate core  86 , despite dimensional variations of the laminate core  86 . As shown in  FIG. 4 , the flared portion  126  of the winding hub  114  closely matches the profile of the radial teeth  102  of the laminations  94 , thereby substantially improving slot fill around the laminate core  86  ( FIG. 4 ) and lowering winding resistance. 
         [0027]    Referring to  FIG. 6 , each bobbin  106  includes a pair of bobbin terminals  142  coupled to the outer flange  122 . The bobbin terminals  142  are electrically conductive members that may be inserted into the bobbin body  110  during an injection molding process. The bobbin terminals  142  may be coated with tin in order to facilitate soldering. 
         [0028]    Referring to  FIG. 8 , a coil of wire  146 , forming a stator winding, is wrapped around each bobbin  106 , with wire ends  148  connected to the bobbin terminals  142 . Referring to  FIG. 3 , the bobbin terminals  142  of each bobbin  106  extend through a printed circuit board assembly (PCBA)  150 . The PCBA  150  connects the bobbin terminals  142 , and thereby the windings, to power electronics coupled to the PCBA  150 . The bobbin terminals  142  of all four bobbins  106  may be connected in series on the PCBA  150 . 
         [0029]    Referring to  FIG. 3 , the rotor assembly  18  includes a shaft  154  and a rotor  158  fixedly coupled to the shaft  154  for rotation with the shaft  154  relative to the stator assembly  14  about the shaft axis  38 . The shaft  154  has a load end  160 , for receiving a load to be driven, a case end  162 , and an intermediate portion  163  between the load end  160  and the case end  162 . The rotor  158  may include, for example, a plurality of permanent magnets. 
         [0030]    The rotor assembly  18 , more specifically the shaft  154 , is rotatably coupled to the housing cover  22  with a cover bearing assembly  164  and rotatably coupled to the housing case  26  with a case bearing assembly  166 . The cover bearing assembly  164  rotatably supports the intermediate portion  163  of the shaft  154 , while case bearing assembly  166  rotatably supports the case end  162  of the shaft  154 . The cover bearing assembly  164  and case bearing assembly  166  are substantially similar in most respects, with each bearing assembly  164  and  166  seated within the respective bearing seats  58  and  62  of the housing cover  22  and housing case  26 . 
         [0031]      FIG. 9  is an exploded view of the case bearing assembly  166 . The case bearing assembly  166  includes a thrust plate  170 , a felt pad  174 , a sleeve bearing  178 , and a bearing spring  182 . The thrust plate  170  is a substantially planar, disk like member. Referring to  FIG. 11 , the sleeve bearing  178  includes a substantially cylindrical body with an outer surface  186  having tapered end portions  190 . The sleeve bearing  178  defines a shaft aperture  194 . The felt pad  174  is a washer like member with pad aperture  198  sized to receive the outer surface  186  of the sleeve bearing  178 . The felt pad  174  may be formed, for example, of a wool or synthetic felt. A lubricant may be applied to the felt pad  174  to lubricate the sleeve bearing. 
         [0032]    Referring to  FIG. 10 , the bearing spring  182  includes a unitarily formed body having a substantially planar base wall  202 , and a substantially planar support wall  206 . An oblique connecting wall  210  connects the base wall  202  and the support wall  206 . An oblique outer wall extends  214  circumferentially about the support wall  206 . Eight talon members  218  are coupled to the base wall  202  and surround a bearing spring aperture  222  ( FIG. 9 ). The talon members  218  are bent away from the planar base wall  202  in a profile corresponding to the tapered end portions  190  of the sleeve bearing  178 . 
         [0033]    Referring to  FIGS. 3 and 11 , the thrust plate  170  is seated on the thrust support surface  66 . The thrust plate  170  thus provides a bearing surface for the case end  162  of the rotor shaft  154 . The felt pad  174  is seated on the pad support surface  74 . The case end  166  of the rotor shaft  154  extends through the shaft aperture  194  of the sleeve bearing  178 . The sleeve bearing  178  is seated upon the sleeve bearing support surface  70 , and centered within the pad aperture  198 . The bearing spring  182  is then seated such that the talon members  218  engage the sleeve bearing  178 , the support wall  206  engages the spring support surface  78 , and the oblique outer wall  214  resiliently engages the spring centering surface  82 . 
         [0034]      FIG. 12  illustrates a housing cover  226  according to another aspect of the invention. The housing cover  226  may be used with the motor assembly  10  in place of the housing cover  22  of  FIGS. 1-3 . The housing cover  226  includes a cover body  230  formed, for example, of a thermoplastic. The cover body  230  defines a shaft aperture  234  disposed about a rotor shaft axis  238 . Three cover assembly lugs  242  extend outwardly from edges of the cover body  230 , for alignment with the case assembly lugs  46  of  FIG. 2 . Referring to  FIG. 12 , the housing cover  226  further includes three mounting lugs  246  disposed circumferentially about the shaft axis  238 , approximately 120 degrees apart. Each mounting lug  246  defines a mounting aperture  250  for receiving, for example, a self-tapping mounting screw. The mounting lugs  246  are provided as an alternative mounting structure to the mounting lugs  50  of the housing case  36  ( FIG. 2 ). 
         [0035]    Thus, the invention provides, among other things, a new and useful electric motor. Various features and advantages of the invention are set forth in the following claims.