Evaporated fuel treatment device of an engine

摘要

An evaporated fuel treatment device comprising a purge control valve arranged between a canister and an intake passage of an engine. A drive pulse of the purge control valve is controlled by a duty ratio. When the purge action starts, the duty ratio is gradually increased. In the region of a small duty ratio where the flow rate of the purge control valve becomes unstable, the duty ratio is either increased or else held constant so that the duty ratio is not allowed to fall.