Abstract: In a vehicular electric power generation apparatus having an a.c. generator and an engine, a rotation speed of the a.c. generator at the idling rotation operation of the engine is set to be higher than a rotation speed, at which the driving torque of the a.c. generator becomes a maximum. Thus, the rotation speed of the a.c. generator does not change through the rotation speed at which the driving torque of the vehicle a.c. generator becomes a maximum, even when the rotation speed of the engine is raised high for running of a vehicle. Thus, changes in the load applied to the engine can be restricted.

Abstract: An automotive AC generator or alternator has a protective structure for fluid-tightly closing a brush unit and its associated components to thereby prevent water or oil from entering thereinto. The protective structure includes a brush holder for encasing brushes and a slip ring cover for covering slip rings. The brush holder and the cover are coupled to each other with axial recesses being engaged with associated projections. The thus coupled brush holder and slip ring cover are fixed while being pressed in the axial direction toward a rear frame of the alternator by a rear cover thereof with a seal member interposed between axial end faces of the brush holder and slip ring cover and the rear frame and with another seal member interposed between the other axial end faces of the brush holder and slip ring cover and the rear cover.