Patent ID: 7834493

Claim:
A vehicle alternator rotor, the rotor having an axis of rotation and comprising: a pair of magnetic pole pieces, each having a plurality of claw-like magnetic pole fingers, each claw-like magnetic pole finger being oriented in a radial direction with the claw-like magnetic pole fingers of the pair of magnetic pole pieces alternately intermeshed with the claw-like magnetic pole fingers of the other pole piece of the pair of magnetic pole pieces; a field coil wound on boss portions of the magnetic pole pieces; and a pair of cooling fans fixedly mounted on the magnetic pole pieces, respectively; wherein each of the cooling fans includes a central disc portion, a plurality of fan base portions formed on the central disc portion at circumferentially spaced intervals, and a plurality of axially outward extending fan blades standing upright from the fan base portions in an axially outward direction, respectively; the central disc portion has an outer circumferential periphery formed with a plurality of cutout portions to be contiguous with roots of the fan base portions, respectively, and placed in areas radially inward of the fan blades, respectively; each of the cutout portions extends in a direction perpendicular to the radial direction on which each claw-like magnetic pole finger is oriented; and each of the fan blades has a root portion having a curved shape with a given radius and having a length of a value 2.2r or less where “r” represents a given radius of the curved shape.