Patent ID: 7877190

Claim:
A fuel control device for an internal combustion engine, comprising: an air-fuel ratio setting means which sets combustion air-fuel ratio depending on the operating state of the internal combustion engine, a standard fuel quantity setting means which sets standard fuel quantity on the basis of the combustion air-fuel ratio set by the air-fuel ratio setting means, a transient state determination means which determines whether or not the internal combustion engine is in a transient state, by a criterion, a fuel correction means which makes correction to the standard fuel quantity when the transient state determination means determines that the internal combustion engine is in a transient state, and an air-fuel ratio modulation means which oscillates the combustion air-fuel ratio of the internal combustion engine between rich and lean values, periodically, thereby oscillating exhaust air-fuel ratio between rich and lean values, periodically, wherein the transient state determination means includes a criterion setting means which sets said criterion, and the criterion setting means sets said criterion such that when the exhaust air-fuel ratio is being oscillated by the air-fuel ratio modulation means, whether or not the internal combustion engine is in a transient state is determined by a relaxed criterion, compared with when the exhaust air-fuel ratio is not being oscillated.