Exhaust-gas recirculation system for internal combustion engine

摘要

An exhaust-gas recirculation (EGR) system has a main control device that supplies a control signal to an EGR valve actuating device that opens an EGR valve to a desired extent. Under normal conditions, a pulse actuating signal having a time-width corresponding to a difference between the actual opening of the EGR valve and the desired opening is supplied to the valve actuating device. Then, the next actuating signal is fed to the valve actuating device after a given length of quiescent time. When the desired opening changes suddenly, however, the normal operation is discontinued and an actuating signal corresponding to a new desired opening is supplied to the valve actuating device. By so doing, the EGR valve is at all times opened to the desired extent, not only under normal conditions but also when the desired amount of valve opening changes suddenly.