Patent ID: 7987838

Claim:
A controller of an internal combustion engine that can use a blended fuel with alcohol blended therein, the controller comprising: a purge controller, operable to control opening and closing of a purge passage that connects a canister, storing a vaporized fuel, and an air intake system of the internal combustion engine, to control a purge amount of the vaporized fuel purged to the air intake system; an exhaust air-fuel ratio detector, operable to detect an exhaust air-fuel ratio of the internal combustion engine; an air-fuel ratio feedback controller, operable to perform feedback control of the internal combustion engine so as to make the exhaust air-fuel ratio, detected by the exhaust air-fuel ratio detector, approach a target air-fuel ratio; a period determiner, operable to determine whether it is an estimation enabling period, in which estimation of an alcohol concentration in the blended fuel is enabled, when a condition is met; and an alcohol concentration estimator, operable to estimate the alcohol concentration of the blended fuel based on the exhaust air-fuel ratio, detected by the exhaust air-fuel ratio detector, when the period determiner determines that it is the estimating enabling period, the air-fuel ratio feedback controller is in operation, and purge of the vaporized fuel is cut by the purge controller, wherein when the purge of the vaporized fuel is cut during the estimation enabling period, the purge controller: performs control so that the purge is cut with a large degree of tailing, in an operation region where a load of the internal combustion engine is high and a rotation speed is high; and performs control so that the purge is cut with a smaller degree of tailing than the large degree of tailing, in an operation region where the load of the internal combustion engine is low and the rotation speed is low.