Patent ID: 7367184

Claim:
A fuel injection amount control device for an internal combustion engine, the fuel injection amount control device comprising: a secondary air supply device that supplies secondary air into an exhaust passage of the internal combustion engine; flow amount calculating means that calculates a secondary air flow amount, the secondary air flowing into the exhaust passage; target air fuel ratio setting means that sets a target air fuel ratio when secondary air is supplied; fuel amount correcting means that corrects a fuel injection amount in accordance with a current value of the secondary air flow amount such that the air fuel ratio on a downstream side of an inlet of secondary air in the exhaust passage becomes the target air fuel ratio when secondary air is supplied; target changing means that monitors increase and decrease in the secondary air flow amount, the target changing means changing the target air fuel ratio to one of a rich side and a lean side in accordance with the increase and decrease in the secondary air flow amount; means for setting a guard value of the target air fuel ratio on at least the rich side in accordance with the secondary air flow amount calculated using the flow amount calculating means, and wherein the target changing means restricts the target air fuel ratio with the guard value when the target air fuel ratio reaches the guard value.