Control apparatus for internal combustion engine

A control apparatus for an internal combustion engine, the control apparatus controlling the internal combustion engine including an intake pipe and a throttle valve disposed in the intake pipe, the throttle valve controlling an air flow rate, the control apparatus comprising:

• an introduction port that is disposed in the intake pipe and through which a gas other than fresh air flows in the intake pipe, wherein
• the control apparatus controls the internal combustion engine using detection values of humidity sensors disposed upstream and downstream, respectively, of the introduction port,
• a purge system disposed in the intake pipe, the purge system including:
• a canister that adsorbs fuel evaporative emissions to thereby allow the internal combustion engine to draw air while diluting the fuel evaporative emissions with atmosphere;
• and a purge flow rate estimation unit that introduces a purge gas as the gas other than fresh air, wherein
• the purge gas is connected to a connection with the intake pipe via a purge introduction pipe, and
• the internal combustion engine is controlled using the detection values of the humidity sensors disposed upstream and downstream, respectively, of the connection, and
• wherein a purge air-fuel ratio as a ratio of air to the fuel evaporative emissions contained in the purge gas at a position downstream of the connection is obtained using the detection values of the respective humidity sensors.