Patent ID: 7559193

Claim:
A control apparatus for an internal combustion engine having an oxygen storage volume computing unit for computing an oxygen storage volume of a catalyst by using a real air/fuel ratio detected by a front air/fuel ratio sensor for detecting exhaust components, said front air/fuel ratio sensor being installed on the upstream side of the catalyst, a center air/fuel ratio representing a stoichiometric air/fuel ratio of the catalyst, and an intake air volume obtained by means for estimating or detecting a flow rate of air flowing into the catalyst, the control apparatus comprising: center air/fuel ratio correcting means for correcting the center air/fuel ratio based on output of a rear air/fuel ratio sensor installed on the downstream side of the catalyst and an oxygen storage volume computed by the oxygen storage volume computing means; wherein said center air/fuel ratio correcting means includes a first catalyst air/fuel ratio estimating unit for estimating an air/fuel ratio in said catalyst based on output of the rear air/fuel ratio sensor; a second catalyst air/fuel ratio estimating unit for estimating an air/fuel ratio in said catalyst based on an oxygen storage volume computed by said oxygen storage volume computing means; and a center air/fuel ratio correction unit for correcting said center air/fuel ratio based on an estimated air/fuel ratio from said first catalyst air/fuel ratio estimating means and an estimated air/fuel ratio outputted from said second catalyst air/fuel ratio estimating unit.