CONTROL DEVICE FOR INTERNAL COMBUSTION ENGINE

An EGR rate estimation method using an EGR valve opening area involves aggravated EGR rate estimation accuracy as an EGR valve is deteriorated and is unable to satisfy required accuracy when a target EGR rate is high. With a method for correcting a fuel injection amount by a fuel injection valve through estimation of a purge air-fuel ratio on the basis of variations in an air-fuel ratio variable depending on whether purging is performed, the fuel injection correction fails to accommodate the change in the air-fuel ratio when concentration of fuel evaporative emissions adsorbed by an activated carbon of a canister is high, resulting in reduced conversion efficiency of a catalyst. An arrangement includes an introduction port that is disposed in an intake pipe and through which a gas other than fresh air flows in the intake pipe and humidity sensors disposed upstream and downstream, respectively, of the introduction port. The EGR rate or the purge air-fuel ratio in the intake pipe is estimated using detection values of the respective humidity sensors.