| 摘要 |
An evaporative control system for a multicylinder internal combustion engine makes the driving period of a purge control valve (4) for asynchronous to an engine cycle when controlling purged fuel, to keep an air-fuel ratio in the engine stabilized, improve exhaust purifying performance, and prevent lean misfires. The engine has a canister (37) for storing evaporated fuel from a fuel tank (15), a purge pipe (39) for connecting the canister to an intake duct of the engine, and a purge control valve (41) disposed in the purge pipe. A driving period changing unit (A) sequentially changes the driving period of the purge control valve from one to another, or changes it so that the start of the driving period may not continuously agree with a crank angle of the engine. A valve controlling unit (B) opens and closes the purge control valve according to the driving period set by the driving period changing unit. A duty factor setting unit sets (C) a minimum valve open time for the purge control valve. A timer unit (D) measures an interval of purge control. A restricting unit (E) restricts the change of the driving period of the purge control valve according to a duty factor. <IMAGE> |
