METHOD AND DEVICE FOR IDLE FUEL CONSUMPTION RATE CONTROL FOR INTERNAL COMBUSTION ENGINE

PURPOSE: To optimize an air-fuel ratio in a method for controlling the air-fuel ratio by utilizing the gas storage capacity of a catalyzer by an oxygen sensor in front of the catalyzer of an exhaust system, by enriching or leaning the air-fuel ratio centering around a predetermined target value. CONSTITUTION: A signal from a subtracter 15 forming deviation Δλ between the λ value of an oxygen sensor in front of the catalyzer 16 of an exhaust pipe and a predetermined command λs is inputted to the integrator 22 of a controller 13, and areas FL matched to integration are counted from previous and late read time Δt. The area FL is inputted to an integration controller 23 and compared with a command IS, and when FL > IS, a control value FI is reduced by only one, and when FL < IS, the control value FI is increased by only one. Next, a dynamic control value FD is formed based on the deviation Δλby a dynamic characteristics circuit 21 and combined with the integration control value FI, thereby a control coefficient FR is formed. Subsequently, a basic injection time tp is multiplied by the control coefficient FR by a multiplier 12, and after correction, a value ti driving an injection valve is obtained and necessary fuel is supplied to an internal combustion engine.