Purge method of canister in ffv, and purge mechanism of canister in ffv using the method

Abstract

In an FFV (flexible fuel vehicle) on which an internal-combustion engine using alcohol blended fuel in mounted, the remaining amount of fuel vapor presumed to remain in a canister in accordance with a usual purge processing is presumed based on an alcohol concentration in the alcohol blended fuel. According to this remaining amount, the size of the tank side channel which is a channel in a canister near the connection section with a connection pathway (tank line) with a fuel tank is adjusted by a canister throttle control means, and/or, the timing of opening and closing of an intake valve is changed by a variable valve timing mechanism. Thereby, the desorption rate (the amount of desorption) of fuel vapor from adsorption material in a canister is adjusted, and the concentration of the fuel included in purge gas is adjusted. As a result, even when the change of the remaining amount of the fuel vapor adsorbed by the adsorption material in the canister and/or the uneven concentration distribution of an alcohol component within the canister occur, the accuracy of an air/fuel ratio control in the FFV can be raised, and the discharge of a toxic substance can be suppressed effectively.