Control apparatus for an internal combustion engine

A control apparatus for an internal combustion engine which learns a concentration of a single composition of fuel in a fuel tank according to air fuel ratio feedback control, estimate a concentration change delay from the fuel tank to a fuel supply device, and calculates a concentration of said composition in said fuel supply device, said apparatus comprising:

• an air fuel ratio detection unit that is arranged in an exhaust system of said internal combustion engine for detecting an air fuel ratio in an exhaust gas from said internal combustion engine;
• a fuel concentration change delay behavior estimation unit that estimates a delay behavior of a concentration change of the single composition until the fuel in said fuel tank, of which the concentration of the single composition has been changed due to refueling of said fuel tank, arrives at said fuel supply device;
• an air fuel ratio correction amount calculation unit that calculates an amount of air fuel ratio correction for correcting an amount of fuel to be supplied in said fuel supply device based on the air fuel ratio detected by said air fuel ratio detection unit;
• an in-tank concentration learning unit that estimates the concentration of the single composition of fuel in said fuel tank based on the amount of air fuel ratio correction calculated by said air fuel ratio correction amount calculation unit and the delay behavior of the single composition concentration change estimated by said fuel concentration change delay behavior estimation unit;
• a supplied fuel concentration calculation unit that calculates the single composition concentration of fuel to be supplied to the internal combustion engine, from the single composition concentration of the fuel in the fuel tank learned by said in-tank concentration learning unit and the delay behavior of the single composition concentration change estimated by said fuel concentration change delay behavior estimation unit;
• and
• a fuel control unit that calculates a single composition concentration correction coefficient based on the supplied fuel concentration calculated by said supplied fuel concentration calculation unit, and corrects the amount of fuel supplied to the internal combustion engine by said single composition concentration correction coefficient thus calculated.