Patent Publication Number: US-2006012254-A1

Title: Finned rear housing for alternator

Description:
BACKGROUND  
      1. Field of the Invention  
      The present invention relates generally to an alternator with improved cooling characteristics.  
      2. Description of Related Technology  
      In most alternators, internal fans pull ambient air into openings in the rear of the alternator. As the air flows through the alternator and across the components of the alternator the air heats up. This heated air exits from the inside of the alternator through openings in the outer diameter of the rear housing, but the difference between the heated air and the hot housing is not large enough to provide sufficient cooling to the housing. Therefore, there is a need for an alternator with more efficient and effective cooling of the alternator components and the housing.  
     SUMMARY  
      An alternator incorporating the features of the present application includes a generally cylindrically-shaped main housing and stator and a fan extending from a rear end of the rotor. A rear housing is mounted onto the rear end of the stator and encloses the fan. The rear housing including a rear plate having an outer surface and an inner surface and a support rim that is mounted onto the stator to secure the rear housing to the main housing. A plurality of axially extending ribs are spaced circumferentially around and interconnect the support rim and the rear plate.  
      In an aspect of the present application, the outer surface of the rear plate includes a plurality of axially extending radially aligned cooling fins positioned radially outward of and spaced circumferentially around openings formed within the rear plate, such that when the fan draws air inward through the openings in the rear plate, air is drawn over and between the cooling fins, providing ambient air cooling of the rear housing.  
      In another aspect of the present application, the alternator includes an end cap mounted onto the rear housing. The end cap includes a rim portion attached to the rear housing, and a dome portion including a cylindrical side wall and an end face. The end face includes a plurality of vents formed therein to allow ambient air be drawn inward. The end cap may further include a plurality of slots formed within said side wall to allow ambient air to be drawn inward.  
      In yet another aspect of the present application, a heat sink is mounted onto the rear housing, within the end cap. The heat sink includes a plurality of axially extending radially aligned cooling fins. The cooling fins of the heat sink are axially aligned with the vents in the end cap such that ambient air drawn in through the vents passes over and between the cooling fins of the heat sink. The heat sink provides further cooling of the components within the rear housing of the alternator. 
    
    
     DESCRIPTION OF THE DRAWINGS  
      The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of the embodiments when considered in the light of the accompanying drawings in which:  
       FIG. 1  is a perspective view of an alternator having features of the present application;  
       FIG. 2  is a side sectional view of an the alternator of  FIG. 1 ;  
       FIG. 3  is a schematic illustration of the portion of the alternator enclosed within the circle  3 - 3  of  FIG. 2 ;  
       FIG. 4  is an exploded view of an alternator having features of the present invention;  
       FIG. 5  is a perspective view of a rear housing as described in the present application;  
       FIG. 6  is a perspective view of an end cap as described in the present application;  
       FIG. 7  is a perspective view of a heat sink as described in the present application; and  
       FIG. 8  is a perspective view of the rear housing, the heat sink, and the end cap wherein a portion of the end cap is broken away to illustrate the position of the heat sink on the rear housing and the end cap enclosing the heat sink. 
    
    
     DESCRIPTION OF THE EMBODIMENTS  
      Referring now to  FIGS. 1 and 2 , an electric machine of the present application is shown generally at  10 . Referring to  FIG. 3 , a simplified view of a portion of  FIG. 2  is shown to more clearly illustrate the features of the present application. The electric machine  10 , in this instance an alternator, includes a generally cylindrically-shaped main housing and stator  12  and a fan  14  attached to the rear end of the rotor  16 . A rear housing  18  is mounted onto the rear end of the stator  12  and encloses the fan  14 . The rear housing  18  includes a rear plate  20  having an outer surface  22  and an inner surface  24 . A plurality of axially extending ribs  28  extend from the inner surface  24 , and are spaced circumferentially around the rear plate. A support rim  26  is mounted onto the distal ends of the ribs  28 . The support rim  26  is mounted onto the stator  12  to secure the rear housing  20  to the stator  12 .  
      The rear plate  20  includes a central bore  30  formed therein to accommodate a bearing  32  for the alternator  10 . A plurality of openings  34  are formed within the rear plate  20  to allow ambient air to be drawn into the alternator  10 , as indicated by arrows  35  in  FIG. 3 . The openings  34  are positioned radially outward of and spaced circumferentially around the central bore  30 . Ambient air is drawn inward through the openings  34  in the rear plate  20  of the rear housing  18  and is exhausted outward from the alternator  10  through the openings  33  defined between adjacent ribs  28  of the rear housing  18 , as indicated by arrow  37  in  FIG. 3 .  
      As also seen in  FIGS. 3 and 5 , the outer surface  22  of the rear plate  20  further includes a plurality of axially extending, radially aligned cooling fins  36 . The cooling fins  36  are positioned radially outward of and spaced circumferentially around the openings  34  in the rear plate  20 . When the fan  14  draws air inward through the openings  34 , the air is drawn over and between the cooling fins  36 , thereby providing cooling of the rear housing  18  with air that is not already pre-heated by the internal components of the alternator  10 .  
      The alternator  10  further includes a plurality of rectifying diodes  38  mounted thereon. As shown in  FIGS. 2 and 5 , the rectifying diodes  38  can be mounted within pockets  39  directly onto the rear plate  20 . Alternatively, the rectifying diodes  38  can be mounted onto a diode plate  40 .  
      Referring to  FIG. 3 , a diode plate  40  is shown mounted onto the rear housing  18  axially outward of the cooling fins  36  such that the cooling fins  36  are positioned between the diode plate  40  and the outer surface  22  of the rear plate  20 . To mount and support the diode plate  40 , the rear housing  18  includes a plurality of supports  42  extending axially from the outer surface  22  of the rear plate  20 , axially outward further than the cooling fins  36 , with the diode plate  40  mounted onto the supports  42 . A gap  44  is defined between the diode plate  40  and a top surface  46  of the cooling fins  36 , to allow ambient air to flow therebetween.  
      An end cap  48  is mounted onto the rear housing  18  to enclose the previously mentioned components. As seen in  FIGS. 3 and 6 , the end cap  48  includes a rim portion  50  attached to the rear housing  18 , and a dome portion  52  including a cylindrical side wall  54  and an end face  56 . The end face  56  includes a plurality of vents  58  formed therein to allow ambient air be drawn inward. The end cap  48  further includes a plurality of slots  60  formed within the side wall  54  to also allow ambient air to be drawn inward. Preferably, the slots  60  within the side wall  54  of the end cap  48  are radially aligned with the cooling fins  36  such that ambient air drawn inward through the slots  60  passes over and between the cooling fins  36  of the rear housing  18 , as indicated by arrow  62  of  FIG. 3 .  
      The end cap  48  may also include flared out portions  63  which allow ambient air to be drawn into the end cap  48 . Referring to  FIGS. 1 and 2 , the flared portions  63  define an air gap  65  between the end cap  48  and the rear housing  18  that allows air to flow inward within the end cap  48 .  
      A heat sink  64  may be mounted onto the rear housing  18  within the end cap  48 . As seen in  FIGS. 3 and 7 , the heat sink  64  is generally ring shaped having a outer rim  66 , and inner rim  68 , and a plurality of axially extending radially aligned cooling fins  70 , the later of which extend radially between the inner rim  68  and the outer rim  66 . The cooling fins  70  of the heat sink  64  are aligned with the vents  58  formed within the end face  56  of the end cap  48 . Ambient air drawn in through the vents  58  passes over and between the cooling fins  70  of the heat sink  64 , as indicated by arrows  72  of  FIG. 3 .  
      In accordance with the provisions of the patent statutes, the features of the present application have been described in various specific embodiments. However, it should be noted that the features of the present application can be practiced otherwise than as specifically illustrated and described herein.