Abstract:
A retainer in the stator of an electrical machine holds a plurality of stacked stator laminations in compression at an inner diameter of a stator core. The plurality of laminations have a central aperture and a plurality of teeth circumferentially spaced about the central aperture. The plurality of stacked laminations forms a contiguous stator core with a central aperture for housing a rotor and stator winding slots extending from one axial face of the stator core to an opposite axial face of the stator core. The retainer is adapted to be fitted in the stator slots adjacent the windings and adjacent the central aperture. The retainer extends from one axial face of the stator core to the opposite axial face of the stator core. The retainer has opposite longitudinal ends abutting the axial opposite faces of the stator core that hold the laminations in compression.

Description:
BACKGROUND 
       [0001]    The disclosure relates generally to the field of electric motors and generators and, particularly, to the construction of stators for such motors and generators. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0002]      FIG. 1  is a partial cross-sectional view of an electric motor; 
           [0003]      FIG. 2  is partial cross-sectional view of a stator core of the electric motor taken along section  2 - 2  of  FIG. 1 ; 
           [0004]      FIG. 3  is partial cross-sectional view of the stator core of the electric motor taken along section  3 - 3  of  FIG. 1  and represents a view opposite that of  FIG. 2 ; 
           [0005]      FIG. 4  is a side view of a clip comprising a retainer assembly; 
           [0006]      FIG. 5  is a perspective view of the retainer assembly of  FIG. 4 ; 
           [0007]      FIG. 6  is a partial cross-sectional view of the motor taken along section  6 - 6  of  FIG. 1 ; 
           [0008]      FIG. 7  is partial cross-sectional view of the motor with detailed areas showing the configuration of the retainer assembly. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    Electric motors of various types are commonly found in industrial, commercial, and consumer settings. In industry, such motors are employed to drive various kinds of machinery, such as pumps, conveyors, compressors, fans and so forth, to mention only a few. Turning to the drawings,  FIG. 1  illustrates an exemplary electric motor  10 . To simplify the discussion, only the top portion of the motor  10  is shown, as the structure of the motor  10  is essentially mirrored along its centerline. In the embodiment illustrated, the motor  10  comprises a switched reluctance motor housed in a motor housing. However, the principles disclosed herein may also be used with other motors and generators, for instance, induction motors or permanent magnet motors. The exemplary motor  10  comprises a frame  12  capped at each end by front and rear end caps  14 , 16 , respectively. The frame  12  and the front and rear end caps  14 , 16  cooperate to form the enclosure or motor housing for the motor. The frame  12  and the front and rear end caps  14 , 16  may be formed of any number of materials, such as steel, aluminum, or any other suitable structural material. The end caps  14 , 16  may include mounting and transportation features, such as the illustrated mounting flange  18  and eyehook  20 . Those skilled in the art will appreciate in light of the following description that a wide variety of motor configurations and devices may employ the construction techniques outlined below. 
         [0010]    Within the frame  12 , there are a stator  22  and rotor  24 . Rotation of the rotor is effected by routing current through the stator. A rotor shaft  26  coupled to the rotor rotates in conjunction with the rotor. That is, rotation of the rotor translates into a corresponding rotation of the rotor shaft  26 . As appreciated by those of ordinary skill in the art, the rotor shaft  26  may couple to any number of drive machine elements, thereby transmitting torque to the given drive machine element. By way of example, machines such as pumps, compressors, fans, conveyors, and so forth, may harness the rotational motion of the rotor shaft  26  for operation. 
         [0011]    The stator  22  comprises a plurality of stator laminations  30  juxtaposed and aligned with respect to one another to form a lamination stack, such as a contiguous stator core  32 . In the exemplary motor  10 , the stator laminations  30  are substantially identical to one another, and each includes features that cooperate with adjacent laminations to form cumulative features for the contiguous stator core  32 . For example, each stator lamination  30  includes a central aperture that cooperates with the central aperture of adjacent laminations to form a rotor chamber  34  that extends the length of the stator core  32  and that is sized to receive the rotor. Additionally, each stator lamination  30  includes a plurality of stator slots disposed circumferentially about the central aperture. These stator slots cooperate to receive two or more stator windings  36 , which are illustrated as coil sides in  FIG. 1 , that extend the length of the stator core  32  from a first axial face  38  to an opposite axial face  40 . The stator laminations of an electrical machine such as a switch reluctance motor may be held together with a weld bead  41  extending axially on the outer diameter of the contiguous stator core  32 . 
         [0012]    The rotor  24  resides within the rotor chamber  34 . Similar to the stator core  32 , the rotor  24  comprises a plurality of rotor laminations  42  aligned and adjacently placed with respect to one another. Thus, the rotor laminations  42  cooperate to form a contiguous rotor core  44 . The exemplary rotor  24  also includes an end plate assembly  46 , disposed on each end of the rotor core  44 , that cooperates to secure the rotor laminations  42  with respect to one another. When assembled, the rotor laminations  42  cooperate to form a shaft chamber that extends through the center of the rotor core  44  and that is configured to receive the rotor shaft  26  therethrough. The rotor shaft  26  is secured with respect to the rotor core  44  such that the rotor core  44  and the rotor shaft  26  rotate as a single entity—the rotor  24 . 
         [0013]    To support the rotor, the exemplary motor  10  includes front and rear bearing sets  50 ,  52 , respectively, that are secured to the rotor shaft  26  and that facilitate rotation of the rotor within the stationary stator core  32 . During operation of the motor  10 , the bearing sets  50 ,  52  facilitate transfer of the radial and thrust loads produced by the rotor to the motor housing. Each bearing set  50 , 52  includes an inner race  54  disposed circumferentially about the rotor shaft  26 . The tight fit between the inner race  54  and the rotor shaft  26  causes the inner race  54  to rotate in conjunction with the rotor shaft  26 . Each bearing set  50 ,  52  also includes an outer race  56  and ball bearings  58 , which are disposed between the inner and outer races  54 ,  56 . The ball bearings  58  facilitate rotation of the inner races  54  while the outer races  56  remain stationary and mounted with respect to the end caps  14 , 16 . Thus, the bearing sets  50 ,  52  facilitate rotation of the rotor while supporting the rotor within the motor housing, i.e., the frame  12  and the end caps  14 , 16 . To reduce the coefficient of friction between the races  54 , 56  and the ball bearings  58 , the ball bearings may be coated with a lubricant. 
         [0014]    To maintain the stator laminations in compression at the stator tooth tips, a retainer  100  is used. As will be explained below in greater detail, the retainer  100  may be fitted in the stator slots adjacent the windings to hold the stack of laminations of the contiguous stator core  32  in compression at the stator tooth tips. Thus, the retainer  100  together with the axial weld bead  41 , or other outer diameter fixation means, provide improved structural integrity for the stator  22 . 
         [0015]      FIGS. 2-7  show the retainer or clip  100 . Preferably, the retainer or clip  100  comprises a non-conductive, structurally rigid material with a high shear strength. The retainer preferably comprises an assembly with a first retainer portion  102  and a second retainer portion  104 . The first retainer portion  102  comprises an elongated strip of material generally rectangular in shape with a face capturing surface  106  on an axial end  108 . The second retainer portion  104  also comprises a rectangular elongated strip of material with a face capturing surface  110  on its axial end  112 . Preferably, the first and second retainer portions  102 ,  104  have interlocking features that enable the first and second portions to be assembled together to form a retainer assembly with the face capturing surface  110  of the second retainer portion  104  longitudinally opposite the face capturing surface  106  of the first retainer portion  102 . 
         [0016]    As best shown in  FIGS. 4 and 5 , the first retainer portion  102  and second retainer portion  104  may be interlocked together to form the assembly with a notch and detent arrangement. The first retainer portion  102  preferably has a rectangular tab  114  which is punched through the mid section of the elongated section and deflected (downward in  FIGS. 4 and 5 ) so as to project from the mid section (bottom in  FIGS. 4 and 5 ) of the first retainer portion. The second retainer portion  104  is formed with a plurality of serrations  116  extending across its width at its mid section (top in  FIGS. 4 and 5 ) that cooperate with the tab  114  formed in the first retainer portion to lock the assembly together. The distal end of the tab  114  is formed into a tip  118  that cooperates with the serrations  116 . The interlocking features may reversed between the first and second retainer portions, and instead of a tab and serrations, may comprise a system of cooperating tabs and slots, nubs and holes, etc. 
         [0017]    During installation, the second retainer portion  104  is received in the stator slot  90  adjacent the windings  36  and preferably toward or adjacent the distal end of adjacent stator teeth  92  with the second retainer portion face capturing surface  110  engaging the axial face  38  of the stator core. The second retainer portion  104  may abut the windings  36  extending through the stator slot  90 . The first retainer portion  102  is received in the stator slot  90  adjacent the second retainer portion  104  preferably closer in distance toward the central aperture  34  than the second retainer portion and adjacent the distal end of adjacent stator teeth  92 . The first retainer portion  102  may then be moved axially relative to the stator core centerline such that the first retainer portion face capturing surface  106  engages the opposite axial face  40  of the stator. As the first retainer portion  102  is moved into position, the serrations  116  of the second retainer portion engage the first retainer portion tab  114 , locking the assembly with the first retainer portion face capturing surface  106  engaging one axial face  40  of the stator and the second retainer portion face capturing surface  110  engaging the opposite axial face  38  of the stator. By providing a plurality of rows serrations  116 , the length of the retainer assembly may be adjusted as necessary to accommodate variations in manufacturing tolerances in the axial dimension of the contiguous stator core. The clip or retainer may also be formed monolithically at a dimension that enables the face capturing surfaces of the retainer to abut the axial opposite faces of the stator to hold the stator laminations in compression. The configuration may also be reversed among the first and second retainer portions. 
         [0018]    In some constructions of electrical machine stators, such as that shown in  FIGS. 2 and 3 , the distal end of each stator tooth  92  has a notch  94  to provide a locating surface for a stator slot insulator. The retainer  100  may cooperate with the pattern of notches  94  at the distal end of each stator tooth  94  to assist in maintaining the retainer  100  in the stator slot  90 . For instance, for retainer or clip  100  comprising an assembly, the first and second portions may be configured so that the first retainer portion  102  may fit within the existing pattern of notches  94  provided on the distal end of each stator tooth  92 . The second retainer portion  104  may have a width less than a stator slot width dimension at the distal end of each stator tooth, thereby allowing the second retainer portion to fit within the stator slot immediately adjacent the first retainer portion fitted in the stator tooth tip notches. The generally narrowing of the stator slot at the distal end of the stator teeth also allows the retainer to be fitted in the stator slot, with or without the use of a stator slot insulator, with or without the notches, and with or without force from the windings pushing the retainer against the opposing walls of the stator slot. Force from the windings may be used to assist in maintaining the first and second portions of the retainer assembly in a locked configuration. 
         [0019]    As best shown in  FIGS. 6 and 7 , a retainer (i.e., clip) or retainer assembly may be fitted in one or more of the slots of the stator to hold a stator stack in compression at the stator tooth tips. The retainer may comprise a slot insulator. Combined with the weld extending on the outer diameter of the stator core, the stator stack may be held in compression around its complete periphery, thereby preventing teeth from flaring outward during final assembly or operation of the motor. 
         [0020]    While specific embodiments have been described in detail in the foregoing detailed description and illustrated in the accompanying drawings, those with ordinary skill in the art will appreciate that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed were meant to be illustrative only and not limited as to the scope of the invention which is to be given the full breadth of the appended claims and any equivalents thereof.