Patent ID: 7888828

Claim:
A starter generator which operates as a brushless motor at start of an engine to drive a crankshaft of the engine in order to start the engine and is driven by the engine after the starting operation of the engine is completed to operate as a magneto generator, which comprises: a rotor which includes a rotor yoke having a peripheral wall portion and a bottom wall portion closing one axial end of said peripheral wall portion, permanent magnets being attached on an inner peripheral of the peripheral wall portion of said rotor yoke, and in which a boss portion to be connected to a crankshaft of said engine is provided at a center of the bottom wall portion of the rotor yoke; a stator bracket to be fixed to a case of said engine; a stator having an armature core and a multi-phase armature coil wound around said armature core and being arranged inside of the rotor, in which the armature core is fixed to the stator bracket; and a protective cover having an end wall portion which is opposed to the bottom wall portion of the rotor yoke and a cylindrical side wall portion surrounding said peripheral wall portion of the rotor yoke, said protective cover being fixed to said engine so as to be sealed in liquid-tight manner with respect to said engine, in which a rotor/stator containing space for containing said rotor and stator is formed, wherein: a plurality of fans arranged so as to be arrayed in circumferential direction of the rotor yoke are formed on an outer surface of a portion close to the outer periphery of the bottom wall portion of the rotor yoke; each vent hole which penetrates the bottom wall portion of the rotor yoke is formed at a position adjacent to the fan, respectively, and a centrifugal fan for leading air inside of the rotor yoke out through the vent holes and sending the air to the outer peripheral side of the rotor yoke is constituted by said fans; and a guide surface is provided on the stator bracket, which guides, into the inside of the rotor yoke, said air being sent to the outer peripheral side of the rotor yoke by the centrifugal fan and flowed to the stator bracket side through a gap between the side wall portion of the protective cover and the peripheral wall portion of the rotor yoke.