Patent ID: 7168240

Claim:
A control apparatus for an internal combustion engine comprising: a three-way catalyst disposed in an exhaust system of said internal combustion engine; a first air fuel ratio detection part disposed in said exhaust system at a location upstream of said three-way catalyst for detecting a first air fuel ratio of an exhaust gas; a second air fuel ratio detection part disposed in said exhaust system at a location downstream of said three-way catalyst for detecting a second air fuel ratio of said exhaust gas; a target oxygen change amount calculation part that calculates a target oxygen change amount of said three-way catalyst; an oxygen change amount calculation part that calculates an oxygen change amount of said three-way catalyst from an amount of exhaust gas passing through said three-way catalyst and said first air fuel ratio; and an air fuel ratio operation part that inversely operates said first air fuel ratio in accordance with said oxygen change amount; wherein said air fuel ratio operation part controls, in an inverting manner, said first air fuel ratio to a rich side and a lean side across a stoichiometric air fuel ratio with a prescribed air fuel ratio width each time said oxygen change amount in said three-way catalyst reaches said target oxygen change amount.