Fuel vapor emission control device for an engine

摘要

Fuel vapor adsorbed by activated carbon 4a in a canister 4 is introduced to an engine 10 by a manifold vacuum in an intake air passage 8, and burnt. The controller 21 estimates the fuel amount desorbed from the canister 4 during purge, using a canister model (physical model) comprising an equation which computes the adsorption amount and an equation which computes the desorption amount from the adsorption amount and purge rate. An injection pulse width output to injectors 15 is corrected to reduce an air-fuel ratio fluctuation due to the supply of this desorbed fuel to the engine 10.