Patent ID: 6933635

Claim:
An automotive alternator, comprising: a rotor; a stator disposed in an opposed relationship with said rotor; a frame supporting said rotor and said stator; a rectifying unit converting an alternating-current output of said stator into a direct-current output; a rear cover disposed outside said frame so as to cover said rectifying unit; and a cooling fan introducing cooling air from the outside into an inside space of said frame via said rear cover, said rectifying unit, and a cooling air inlet window of said frame, wherein said rectifying unit has a positive-electrode side heat radiation fin to which a positive-electrode side rectifying element is fixed, a negative-electrode side heat radiation fin to which a negative-electrode side rectifying element is fixed, and a terminal platform having a connecting terminal providing wiring for said positive-electrode side rectifying element and said negative-electrode side rectifying element, said positive-electrode side heat radiation fin and said negative-electrode side heat radiation fin are disposed in a radial direction with respect to a rotary shaft of said rotor, said negative-electrode side heat radiation fin is interposed between said frame and said positive-electrode side heat radiation fin and is partly overlapped with said positive-electrode side heat radiation fin in an extending direction of said rotary shaft, said negative-electrode side heat radiation fin has a projected portion at a position overlapping with said cooling air inlet window in the extending direction of the rotary shaft of said rotor so as to protrude toward an inner side of said rotor in the radial direction, said cooling air inlet window has an inner radius R 1 and an outer radius R 3 , and said projected portion has an inner radius R 2 so as to satisfy a relationship R 1 +(R 3 −R 1 )/2≧R 2 >R 1 .