Abstract:
A motor includes a rotor supported for rotation about a longitudinal axis, a stator including a magnetic core, a first end plate positioned at a first end of the magnetic core, and a second end plate positioned at a second end of the magnetic core. The magnetic core, first end plate, and second end plate cooperate to define a central opening. The motor also includes a plurality of rods each fixedly attached to the first end plate and the second end plate and including a first end that extends along the longitudinal axis beyond the first end plate and a second end that extends along the longitudinal axis beyond the second end plate. A first support disk is coupled to the first end of each of the rods and a second support disk is coupled to the second end of each of the rods.

Description:
RELATED APPLICATION DATA 
     This application claims priority to provisional application No. 61/592,465 filed Jan. 30, 2012, the entire contents of which are incorporated herein by reference. 
    
    
     BACKGROUND 
     The present invention relates to motors. More specifically, the present invention relates to electrically commutated motors supported in a housing. 
     SUMMARY 
     The present invention provides a motor that includes a rotor supported for rotation about a longitudinal axis, a stator including a magnetic core, a first end plate positioned at a first end of the magnetic core, and a second end plate positioned at a second end of the magnetic core. The magnetic core, the first end plate, and the second end plate cooperate to define a central opening. At least a portion of the rotor is disposed within the central opening. The motor also includes a plurality of rods. Each rod is fixedly attached to the first end plate and the second end plate and includes a first end that extends parallel to the longitudinal axis beyond the first end plate in a direction away from the magnetic core and a second end that extends parallel to the longitudinal axis beyond the second end plate in a direction away from the magnetic core. A first support disk is coupled to the first end of each of the plurality of rods such that the first support disk is spaced apart from the first end plate and a second support disk is coupled to the second end of each of the plurality of rods such that the second support disk is spaced apart from the second end plate. 
     In another construction, the invention provides a method of reducing vibration of a motor. The method includes supporting a rotor for rotation about a longitudinal axis, the rotor supported at a first end and a second end by an external housing. The method also includes selecting each of a plurality of rods, each of the rods having a length, a cross-sectional shape, a cross-sectional area, and a stiffness that define a natural frequency for each rod, each rod selected to have a desired natural frequency. The method further includes fixedly coupling each of the plurality of rods to a magnetic core of a stator such that a first end of each rod extends beyond the magnetic core and a second end of each rod extends beyond the magnetic core. The method also includes connecting a first support disk to the first ends of each of the rods, connecting a second support disk to the second ends of each of the rods, and engaging the first support disk, the second support disk and the external housing to support the magnetic core of the stator. The method further includes damping vibration of the motor by tuning the frequency of each of the plurality of rods to be different from the vibrational frequency of the magnetic core. 
     In still another construction, the invention provides a motor that includes a housing including an outer wall, a first end frame and a second end frame and a rotor supported by the first end frame and the second end frame for rotation about a longitudinal axis. A first support disk is coupled to the outer wall and the first end frame and a second support disk is coupled to the outer wall and the second end frame. A plurality of rods with each rod having a rod length measured between a first end fixedly attached to the first support disk and a second end fixedly attached to the second support disk. The outer wall inhibits radial movement of the first support disk and the second support disk with respect to the longitudinal axis and the first end frame and the second end frame cooperate to inhibit axial movement of the first support disk, the second support disk, and the plurality of rods along the longitudinal axis. A stator core surrounding a portion of the rotor and having a stator length measured between a first stator end and a second stator end, the rod length being about 1.1 to 2.5 times the stator length, the first stator end and the second stator end fixedly attached to each of the plurality of rods. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a perspective view of a portion of a stator core including longitudinal slots; 
         FIG. 1B  is a perspective view of the portion of the stator core of  FIG. 1 a    including end plates; 
         FIG. 1C  is a perspective view of the portion of the stator core of  FIG. 1 b    including a plurality of rods; 
         FIG. 1D  is a perspective view of the portion of the stator core of  FIG. 1 c    including support disks; 
         FIG. 1E  is a perspective view of the stator core of  FIG. 1 d    with a rotor positioned within the stator opening; 
         FIG. 1F  is a photograph of the stator core of  FIG. 1   d;    
         FIG. 2  is an end view of a first construction of a stator core; 
         FIG. 3  is an end view of a second construction of a stator core; 
         FIG. 4  is a longitudinal section view of the motor of  FIG. 1 e    installed in a housing; 
         FIG. 5  is a section view of the motor of  FIG. 1 e    installed in a housing and taken along a plane normal to the longitudinal axis; and 
         FIG. 6  is a cross-sectional view of a support disk taken along a central plane. 
     
    
    
     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. 
     DETAILED DESCRIPTION 
     The present invention provides a motor  10  that includes a support system that reduces the transmission of vibrations from the stator to the motor housing.  FIGS. 1A-1E  illustrate a stator core  15  for use with the invention, during the stator construction process, with  FIG. 1A  being the start of construction and  FIG. 1E  being the completed assembly. In the construction illustrated in  FIG. 1A , a portion of the core  20  is illustrated as being formed from a stack of laminations. The portion of the core  20  defined by the laminations (or other arrangement) sometimes referred to as a magnetic core  20   a . Preferably, electrical grade steel is employed to form the laminations and the number of laminations is selected to provide a desired length of the stator core  15 . In other constructions, other materials or arrangements are employed to form the illustrated portion of the stator core  20  or magnetic core  20   a . For example, powdered metal could be employed to form the portion of the core  20  or the portion of the core  20  could be machined from a single piece of material if desired. 
     In the construction of  FIG. 1A , the portion of the stator core  20  includes a plurality of longitudinally extending slots  25  on the exterior of the core  20 . In addition, the core  20  includes six teeth  30  that extend radially inward. In other constructions, the slots  25  can be eliminated. In addition, the number of teeth  30  can vary as desired for the particular motor application. 
     Turning to  FIG. 1B , two annular end plates  35  are shown attached to the ends of the portion of the core  20  of magnetic core  20   a  formed in  FIG. 1A . The end plates  35  have an outer diameter that is slightly larger than that of the portion of the stator core  20  and are fixed to the portion of the stator core  20  using the same methods that hold the various laminations together or other suitable methods. In preferred constructions, the end plates  35  include a plurality of apertures  40  or slots that extend axially through the plates  35 . In constructions in which the portion of the stator core  20  includes longitudinal slots  25 , the apertures  40  of the end plates  35  align with the slots  25 . In the illustrated construction, the end plates  35  are annular and include a circular central opening  45 . In still other constructions, the end plates  35  include teeth extending radially inward such that the end plates  35  are more similar to the laminations. In other constructions, the end plates  35  have the same diameter as the portion of the stator core  20  or even a slightly smaller diameter. In other constructions, the end plates  35  are formed as part of the portion of the stator core  20 . For example, in constructions in which the core  20  is formed from a powdered metal, the end plates  35  can be formed as one unitary piece with the remainder of the core  20 . 
     As illustrated in  FIG. 1C , a number of rods  50  extend longitudinally around the outside of the portion of the stator core  20 . The rods  50  pass through the apertures  40  in the end plates  35  and extend longitudinally beyond each end plate  35 . In constructions of the portion of the stator  20  that include slots  25 , at least a portion of the rods  50  are positioned within the slots  25 . Each rod  50  is cylindrical and includes threads  55  on either end. The diameter of the rod  50 , the length (effective length) of the rod  50 , and the material of the rod  50  are selected to provide the desired dynamic characteristics as will be discussed. In some constructions, the rod  50  has a circular cross section with other constructions having other cross sectional shapes. 
     A pair of support disks  60  attach to the ends of the rods  50  as illustrated in  FIG. 1D . In the illustrated construction, the support disks  60  are annular with other shapes being possible. The threaded ends  55  of the rods  50  pass through apertures  65  in the disk  60 . Nuts  70  are then threaded onto the rods  50  to rigidly attach the rods  50  to the support disks  60 . With the support disks  60  attached as illustrated in  FIG. 1D , the stator core  15  is complete and is ready to receive windings. 
     In some constructions such as the one shown in  FIG. 6 , the thickness of portions of one or both of the disks  60  is varied such that all of the rods  50  are not exactly the same length. In the construction of  FIG. 6 , each of the rods  50   a ,  50   b  is fixedly attached to the support disk  60   a  using two nuts  70 . The effective length of the uppermost rod  50   a  is twice the length  300  while the length of the lowermost rod  50   b  is twice the length  305 . As can be seen the thicker region of the support disk  60   a  adjacent the uppermost rod  50   a  when compared to the region adjacent the lowermost rod  50   b  results in an arrangement where the effective length of the lowermost rod  50   b  is longer than the uppermost rod  50   a . It should be noted that the term “length” as used herein should be interpreted as the effective length when it relates to the rods  50 ,  50   a ,  50   b . Thus, two rods having the same actual length can have a different effective length when attached to support disks  60   a  having varying thicknesses as illustrated in  FIG. 6 . 
       FIG. 1E  illustrates the stator core  15  of  FIG. 1D  with a rotor  75  positioned within the stator opening.  FIG. 1F  is a photograph of a completed stator core  15  including windings. 
     To assemble the stator core  15  according to one embodiment of the invention, the user first stacks a plurality of laminations to define the portion of the core  20  or forms the portion of a core  20  from a unitary piece of material. If the construction being assembled does not include longitudinal slots  25 , laminations or a unitary core piece having a cross section similar to that illustrated in  FIG. 2  can be employed. In constructions in which the slots  25  are employed, laminations or a unitary core piece having a cross section such as that shown in  FIG. 3  could be employed. The two end plates  35  are then attached to the portion of the core  20  using any suitable method (e.g., welding, adhesive, soldering, brazing, fasteners, etc.). The rods  50  are positioned within the apertures  40  of the end plates  35  such that they extend a desired distance in each direction (e.g., 1.1-2.5 times the stator core length). The rods  50  are then fixedly attached to the end plates  35  using any suitable method (e.g., welding, adhesive, soldering, brazing, fasteners, etc.). 
     Turning to  FIG. 5  and continuing with the assembly, the stator core  15  is positioned within a housing  80 . The illustrated housing  80  includes an outer wall  85  and two end frames  90  disposed at each end of the outer wall  85 . The stator core  15  fits within the outer wall  85  with each of the support disks  60  in contact with one of the end frames  90  and the outer wall  85 . Thus, the end frames  90  inhibit axial or longitudinal movement of the support disks  60  and the outer wall  85  inhibits radial movement of the support disks  60 . The rods  50 , the end plates  35 , and the portion of the stator core  20  are each sized to provide clearance (see  FIG. 4  and  FIG. 5 ) with respect to the outer wall  85  of the housing  80 . Thus, the support disks  60  are the only portions of the stator core  15  that are in direct contact with the housing  80 . The housing  80  supports the support disks  60 , which support the rods  50 , which in turn support the portion of the stator core  20  and the windings. The rotor  75  is in turn supported within the stator opening by a pair of bearings  95  that are supported by the end frames  90 . 
     The diameter, length, cross-sectional shape, and material used for the rods  50  are selected to support the stator core  15  and to dampen vibrations produced by the stator core  15  during operation. The rods  50 , in essence, are tuned to a desired frequency to reduce the transmission of vibrations from the stator core  15  to the housing  80 . By varying the length, the diameter, the shape, and/or the stiffness of the rods  50 , a user can greatly reduce the vibrations transmitted to the housing  80 . In some constructions, rods  50  having different characteristics are employed together to dampen vibrations at more than one frequency or across frequency ranges. For example, the support disks  60  can be formed to include steps at every other rod location. In this way, every other rod  50  will be a slightly different length and will therefore have a different natural frequency. The varying natural frequency will allow for the rods  50  to dampen different vibrations. Similarly, the diameter, or shape of the rods  50  could be varied to achieve similar results. 
     It should be noted that  FIG. 5  illustrates a switched reluctance motor  10  having a six pole stator  15  and a four pole rotor  75 . However, the invention described herein could be applied to motors having stators with more or fewer poles, rotors having more or fewer poles or motors other than switched reluctance motors.