Control system for hybrid vehicles

摘要

There is provided a control system for a hybrid vehicle including an internal combustion engine, a drive shaft driven by the engine, a motor operable on electrical energy for driving the drive shaft, and electrical storage device for supplying electrical energy to the motor. An amount of assistance of the motor to the engine by driving the drive shaft is calculated based at least on load on the engine. An output from the motor is controlled based on the amount of assistance of the motor to the engine. It is determined whether conditions are satisfied for a lean operating mode of the engine in which an air-fuel ratio of a mixture supplied to the engine is controlled to a leaner value than a stoichiometric value. Changeover of an operating mode of the engine is carried out between a stoichiometric operating mode in which the air-fuel ratio of the mixture supplied to the engine is controlled to a value at or close to the stoichiometric value and the lean operation or the lean operating mode, based on the amount of assistance of the motor to the engine and results of the determination of the lean operating condition.