Abstract:
An electro-dynamic machine including a rotor shaft extending along an axis and a bearing rotatably supporting the rotor shaft for rotation about the axis. An inner housing has an outer surface and defines a bearing bore. The bearing bore receives and supports the bearing. An outer housing surrounds the inner housing. A plurality of non-radial ribs extends from the outer housing to the inner housing. The non-radial ribs are coupled to the inner housing substantially tangential to the outer surface.

Description:
BACKGROUND 
       [0001]    The present invention relates to electric motors. More particularly, the invention relates to an electric motor that includes an end frame. 
         [0002]    An end frame for an electric motor should generally be rigid in order to minimize vibration and other adverse effects. In some cases, it is desirable to provide a flow path through the end frame for air cooling of the motor components. Some electric motors may also require periodic maintenance at the end frame, including the addition of grease to one or more shaft bearings. 
       SUMMARY 
       [0003]    In one embodiment, the invention provides an electro-dynamic machine including a rotor shaft extending along an axis and a bearing rotatably supporting the rotor shaft for rotation about the axis. An inner housing has an outer surface and defines a bearing bore. The bearing bore receives and supports the bearing. An outer housing surrounds the inner housing. A plurality of non-radial ribs extends from the outer housing to the inner housing. The non-radial ribs are coupled to the inner housing substantially tangential to the outer surface. 
         [0004]    In another embodiment the invention provides a motor including a rotor and a bearing. A cylindrical inner housing has an outer surface and an inner bore is disposed along an axis and sized to receive and support the bearing. An annular outer housing is disposed concentrically about the inner housing. A first non-radial rib extends from the outer housing to the inner housing. The first non-radial rib is arranged substantially tangentially to the outer surface. A second non-radial rib extends from the outer housing to the inner housing. The second non-radial rib is arranged substantially tangentially to the outer surface. The second non-radial rib cooperates with the first non-radial rib to define a V-shaped rib pair having a vertex adjacent the outer housing. 
         [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 cross-sectional view of an electric motor. 
           [0007]      FIG. 2  is an exploded perspective view of a sub-assembly of the electric motor of  FIG. 1 . 
           [0008]      FIG. 3  is a top view of an end frame of the sub-assembly of  FIG. 2 . 
           [0009]      FIG. 4  is a top view of a bearing lubrication system of the end frame of  FIG. 3 . 
           [0010]      FIG. 5  is a bottom perspective view of the end frame of  FIG. 3 . 
           [0011]      FIG. 6  is a cross sectional view of the bearing lubrication system of  FIG. 4  taken along section line  6 - 6 . 
       
    
    
     DETAILED DESCRIPTION 
       [0012]    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. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. 
         [0013]      FIG. 1  is a schematic cross section of an electric motor  10 . The electric motor  10  includes an end frame  14  and an opposite end frame  18 . A rotor shaft  22  is rotatably supported by an end frame bearing  26  and an opposite end frame bearing  30 . The rotor shaft  22  supports a rotor  34  for rotation about an axis  38 . The rotor  34  rotates relative to a stator  42 . The stator  42  is enclosed within a stator housing  44  and is disposed between the end frame  14  and the opposite end frame  18 . 
         [0014]      FIG. 2  is an exploded perspective view of a sub-assembly  46  of the electric motor  10 . More specifically, the sub-assembly  46  includes the rotor shaft  22 , the end frame bearing  26 , and the end frame  14 . The end frame  14  includes an outer housing  50  and an inner housing  54 . The outer housing  50  includes four mounting flanges  58 . Each mounting flange  58  includes a through-hole  62 . The through-holes  62  are provided, for example, to receive assembly bolts for coupling the end frame  14  to the opposite end frame  18 . Fewer than four through-holes  62  or more than four may alternatively be provided, as required. 
         [0015]    The inner housing  54  defines a bearing cavity  66 . The bearing cavity  66  includes a precision bearing bore  70 . The bearing bore  70  is configured to receive the end frame bearing  26 . A shaft aperture  74  of the inner housing  54  allows an extension  76  of the shaft  22  to pass through the end frame  14  and couple to the load. 
         [0016]    A ventilated lattice  78  connects the outer housing  50  and inner housing  54 . The lattice  78  facilitates the flow of air (or other fluids) through the motor to cool the rotor, stator, and bearings during motor operation. With reference to  FIG. 3 , the lattice  78  is formed by a combination of radial ribs  82 , non-radial ribs  86 , and annular ribs  90 . As used herein, “non-radial” ribs do not include annular ribs. The lattice  78  is sufficiently rigid to substantially minimize oscillation of the end frame  14 , while at the same time allowing for adequate cooling flow through the motor, thereby improving the life of the end frame bearing  26 . While the radial ribs  82 , non-radial ribs  86 , and annular ribs  90  are described herein as discrete elements, in the illustrated embodiment, the entire end frame  14  is formed as a single component. The inner housing  54 , outer housing  50 , and lattice  78  may be formed by casting, forging, machining, injection molding, or other known manufacturing methods. 
         [0017]    During assembly of the electric motor  10 , the end frame  14  should slide freely over the end frame bearing  26 . If the bearing bore  70  is out of round, a number of assembly problems may result. For example, if the end frame  14  is forced over the bearing  26  with a mallet, the resulting impact forces may dent the balls and/or raceways of the bearing assembly, which may result in premature bearing wear. The non-radial ribs  86  are configured to reduce deformation of the bearing bore  50  during machining of the end frame  22 . 
         [0018]    As best illustrated in  FIG. 3 , the non-radial ribs  86  are arranged in three pairs  94 . The three pairs  94  of non-radial ribs  86  are arranged symmetrically (i.e., each pair  94  is approximately 120 degrees apart from the next pair). This symmetrical arrangement of the three pairs  94  corresponds generally to contact points  96  ( FIGS. 2 and 5 ) for a three jawed chuck, such as is used to hold the end frame  14  when machining the bearing bore  70  and other surfaces of the end frame  14 . Referring back to  FIG. 3 , the non-radial ribs  86  of each pair  94  form a “V” shape, with a vertex  98  adjacent the outer housing  50 . In the illustrated embodiment, the vertex  98  is illustrated radially outward of the outer housing  50 . In other embodiments, the vertex may lie on or in the housing  50 . Each of the non-radial ribs  86  contacts the inner housing  54  substantially tangentially, as opposed to radially. With this arrangement, the non-radial ribs  86  transmit clamping forces to the inner housing and apply them in a direction that is tangent to the bore, thereby reducing deformation of the inner housing  54  when chucked. The resulting bearing bore  70  can be machined with a roundness having a tighter tolerance than would otherwise be possible with radial ribs that transmit the chuck clamping forces to radially to the bore. 
         [0019]    In addition to the non-radial ribs  86 , three of the radial ribs  82  are arranged symmetrically between non-radial ribs  86 . Additional radial ribs  82  cross, or intersect, several of the non-radial ribs  86 . 
         [0020]    The bearing cavity  66  includes a bearing lubrication system  102 . With reference to  FIGS. 4 and 6 , the bearing lubrication system  102  extends from a base wall  106  of the bearing cavity  66  toward an axial seating surface  108  of the bearing bore  70 . The base wall  106  surrounds the shaft aperture  74 . When the end frame bearing  26  is installed in the bearing bore  70 , the bearing  26  encloses the bearing lubrication system  102 . The bearing lubrication system  102  includes a grease storage chamber  112 , a charging chamber  116 , and a metering wall  118 . The charging chamber  116  extends circumferentially about the shaft aperture  74  from a first boundary wall  120  to the metering wall  118 . The grease storage chamber  112  extends circumferentially about the shaft aperture  74  from the metering wall  118  to a second boundary wall  122 . The first boundary wall  120  and second boundary wall  122  extend axially to the same level as the axial seating surface  108 , and therefore define a portion of the seating surface  108  and make contact with the end frame bearing  26  when installed. As shown in  FIG. 6 , the metering wall  118  does not extend all the way to the axial seating surface  108  of the bearing bore  70 . 
         [0021]    The charging chamber  116  and storage chamber  112  are both bounded by an inner annular wall  128  and an outer annular wall  132 . In the illustrated embodiment, the inner annular wall  128  of the charging chamber  116  and storage chamber  112  is not parallel to the axis  38  (i.e., frusto-conical). When the motor assembly  10  is mounted with the axis  38  horizontal, the shape of the inner annular wall  128  assists grease in from the charging chamber and a portion of the storage chamber migrating toward the bearing  26  during motor operation. 
         [0022]    As shown in  FIGS. 4 and 5 , the charging chamber  116  receives grease from a grease inlet port  136 . The grease inlet port  136  may be threaded for a screw-in grease fitting (such as a “Zerk” fitting), or it may be otherwise coupled to a grease conduit or other source of grease. The metering wall  118  acts as a flow restrictor between the charging chamber  116  and the storage chamber  112 . Fresh grease entering the charging chamber  116  from the inlet port  136  will have a tendency to enter the bearing  26 . As voids between ball bearings within the bearing  26  fill with grease, excess grease from the charging chamber  116  will migrate over the metering wall  118  and into the storage chamber  112 . New grease entering the storage chamber  112  from the charging chamber  90  will force old grease out. Grease exits the storage chamber  112  through an exit port  140 . 
         [0023]    As best illustrated in  FIG. 4 , the charging chamber  116  and storage chamber  112  together do not provide a full 360 degrees of grease to the bearing bore  70 . Rather, a bounded area  144  between the first boundary wall  120  and the second boundary wall  122 , in the clockwise direction from the perspective of  FIG. 2 , is intended to remain free of grease. The storage chamber  112  plus the charging chamber  116  provides an optimal amount of grease to the bearing  18 . Because the first boundary wall and second boundary extend to the same level as the axial bearing seating surface, they substantially inhibit grease from entering the bounded area  144 . By maintaining the bounded area  144  of the bearing lubrication system  102  grease-free, heat transfer from the bearing  26  to the end-frame  14  is improved, thereby improving bearing life. 
         [0024]    Thus, the invention provides, among other things, an end-frame  14  for an electric motor assembly  10 . Various features and advantages of the invention are set forth in the following claims.