Front fan retention in dual internal fan alternator

Abstract

An alternator has a pole segment with a collar, an axially outward surface, and at least one key extending radially outward from the collar along the surface. A fan has a keying slot extending radially outward from a center ring, and a fan body including protrusions. The fan is mounted to the segment whereby the collar fits inside the ring and the key fits inside the keying slot, and the fan is welded to the segment at the protrusions. A method includes securing a fan to a pole segment by mating a radially-extending key formed on the segment to a keying slot of the fan and by welding the fan to the segment.

What is claimed is: 
     
         1 . An alternator having a center axis, comprising:
 a pole segment having a collar, a plurality of claw poles, an axially outward segment surface connecting the claw poles, and at least one key extending radially outward from the collar along the segment surface;   a fan having an inside diameter formed as a ring, a keying slot positioned radially outward from the ring, a plurality of blades, and a fan body connecting the blades and including a plurality of protrusions;   wherein the fan is mounted to the segment so that the collar fits inside the ring and the key fits inside the keying slot, and wherein the fan is welded to the segment at the protrusions.   
     
     
         2 . The alternator of  claim 1 , wherein the at least one key comprises a plurality of keys symmetrically arranged about the center axis and the keying slot comprises a corresponding plurality of slots aligned with the keys and mated thereto. 
     
     
         3 . The alternator of  claim 2 , wherein the protrusions are symmetrically arranged about the center axis. 
     
     
         4 . The alternator of  claim 1 , wherein the keying slot comprises a pair of opposed axially-extending tabs. 
     
     
         5 . The alternator of  claim 1 , wherein the key is mated to the keying slot by an interference fit. 
     
     
         6 . The alternator of  claim 1 , wherein the collar is formed as an integral part of the segment. 
     
     
         7 . The alternator of  claim 1 , wherein the protrusions are formed on an axially inward surface of the fan body. 
     
     
         8 . A method of cooling an alternator, comprising:
 providing a pole segment having a raised collar, a plurality of claw poles, an axially outward segment surface connecting the claw poles, and at least one key extending radially outward from the collar;   providing a fan having an inside diameter formed as a ring, a keying slot positioned radially outward from the ring, a plurality of blades, and a fan body connecting the blades and including a plurality of protrusions;   placing the fan onto the segment so that the collar fits inside the ring and the key fits inside the keying slot; and   welding the fan to the segment at the protrusions.   
     
     
         9 . The method of  claim 8 , wherein the welding comprises brazing an interface of the fan and the segment. 
     
     
         10 . The method of  claim 8 , further comprising placing a thermally conductive material at an interface of the fan and the segment. 
     
     
         11 . The method of  claim 8 , wherein the welding comprises axially clamping the fan and segment toward one another. 
     
     
         12 . The method of  claim 8 , wherein the keying slot includes a pair of axially extending tabs that engage the key, whereby the key is substantially isolated from the remainder of the fan. 
     
     
         13 . The method of  claim 12 , wherein the welding comprises placing a welding electrode proximate the protrusions to thereby substantially isolate the welding to the protrusions. 
     
     
         14 . The method of  claim 13 , further comprising filling gaps between isolated welds with a thermally conductive material. 
     
     
         15 . The method of  claim 8 , wherein the key is secured inside the keying slot by press fitting. 
     
     
         16 . The method of  claim 15 , wherein the welding and the press fitting are substantially simultaneous. 
     
     
         17 . A method of assembling a rotor of an alternator, comprising securing a fan to a drive end (DE) pole segment by mating a radially-extending key formed on the segment to a keying slot of the fan and by welding the fan to the segment. 
     
     
         18 . The method of  claim 17 , wherein the fan has an axially inward surface containing a plurality of projections, and wherein the welding comprises projection welding. 
     
     
         19 . The method of  claim 17 , wherein the welding comprises brazing. 
     
     
         20 . The method of  claim 17 , wherein the mating comprises press fitting a plurality of the radially-extending keys to a corresponding plurality of the keying slots.