US Patent 7918085 Fuel-injection control device for internal-combustion engine

A fuel injection control device performs fuel injection only once corresponding to an over-rich air/fuel ratio immediately after the end of F/C as rich air/fuel ratio control after F/C. Such fuel injection is performed with a fuel amount which is the sum of a fuel amount corresponding to a shallow rich air/fuel ratio AFrich and a predetermined increment. Immediately after this operation, fuel injection is performed with a fuel amount corresponding to the shallow rich air/fuel ratio AFrich. This adjusts the air/fuel ratio of the engine to the over-rich air/fuel ratio for an extremely short period of time immediately after the end of F/C, following which the air/fuel ratio is immediately switched to the shallow rich air/fuel ratio AFrich.