System for controlling flow of intake air during start-up period of engine

摘要

A system for controlling a flow of intake air in a secondary intake air passage during a start-up period of an internal combustion engine. A main intake air passage extends to an intake port of the engine. A throttle valve is located in the main intake air passage. The secondary intake air passage connects to the main intake air passage at a position downstream of the throttle valve. The system includes a heater to heat a thermo-sensitive valve provided in the secondary intake air passage. A valve opening degree of the thermo-sensitive valve changes as the valve is heated by the heater. The system determines a duty ratio that controls a drive current supplied to the heater. The system supplies the drive current to the heater by applying a voltage pulse at a predetermined period. The voltage pulse has a pulse width determined by the duty ratio.