Abstract: A housing of a motor generator is integrally coupled to an end of an internal combustion engine. The internal combustion engine includes an oil pan and a cylinder block which have arcuate stiffener ribs and radial stiffener ribs on end surfaces thereof for increased mechanical strength of the internal combustion engine. The motor generator has a housing that is directly coupled to the internal combustion engine with a relatively small number of parts.

Abstract: In an engine including a variable timing/lift mechanism for an intake valve, journal portions of a valve-operating cam shaft are supported on cam bearing portions integrally provided in a cylinder head, and an intake rocker shaft is fixed by bolts to rocker shaft fixing portions provided on an upper surface of the cam bearing portions. By bringing opposite sides of intake rocker arms swingably supported on the intake rocker shaft into slidable abutment against positioning faces integrally formed on opposite sides of the cam bearing portions, the intake rocker arms are positioned in a thrust direction. Thus, it is possible to accurately and easily position the intake rocker arms in the thrust direction without the need for a special member.

Abstract: A misfire-detecting system for an internal combustion engine detects occurrence of a misfire in the engine, based on voltage between both ends of a spark plug assumed when sparking discharge takes place at the spark plug. A diode is arranged in an ignition secondary circuit of the engine, for checking reverse current flowing in the circuit in a direction reverse to the direction of flow of current occurring when spark ignition takes place at the spark plug. An ECU detects reverse current flowing in the ignition secondary circuit, and detects an abnormality of the diode, based on the detected reverse current.