Patent ID: 7225609

Claim:
A control apparatus for an internal combustion engine, comprising: an exhaust system of the internal combustion engine; a catalytic converter disposed in the exhaust system, for purifying an exhaust gas; upstream-side air-fuel ratio detecting means for detecting an air-fuel ratio upstream of the catalytic converter; downstream-side air-fuel ratio detecting means for detecting an air-fuel ratio in the exhaust gas downstream of the catalytic converter; air-fuel ratio adjusting means for adjusting the air-fuel ratio through adjustment of an amount of fuel supplied to the internal combustion engine; downstream-side target air-fuel ratio storing means for storing and retaining a target value for the air-fuel ratio downstream of the catalytic converter; downstream-side control means for calculating an upstream-side target air-fuel ratio through proportional calculation so that the downstream-side air-fuel ratio detected by the downstream-side air-fuel ratio detecting means coincides with the downstream-side target air-fuel ratio stored and retained by the downstream-side target air-fuel ratio storing means; upstream-side control means for controlling the air-fuel ratio adjusting means so that the upstream-side air-fuel ratio detected by the upstream-side air-fuel ratio detecting means coincides with the upstream-side target air-fuel ratio calculated by the downstream-side control means; fuel supply cut means for cutting the fuel supply performed by means of the air-fuel ratio adjusting means; and proportional gain changeover means for making a changeover in a proportional gain for proportional calculation in the downstream-side control means for a predetermined period from a normal proportional gain to a post-fuel-cut proportional gain set larger than the normal proportional gain by a predetermined value, when the fuel cutoff means starts cutting the fuel supply.