AIR-FUEL RATIO CONTROL DEVICE OF INTERNAL COMBUSTION ENGINE

PROBLEM TO BE SOLVED: To provide an air-fuel ratio control device capable of converging the air-fuel ratio to the target air-fuel ratio, while restraining an increase in an engine speed of an internal combustion engine. SOLUTION: This internal combustion engine 10 has a throttle valve 14 arranged in an intake passage 12 and capable of varying opening, an intake valve 30 communicating and cutting-off the intake passage 12 and a combustion chamber 18 and capable of varying a maximum lift quantity, a fuel injection valve 20 injecting fuel introduced to the combustion chamber 18, and an air-fuel ratio sensor 25 detecting the air-fuel ratio of an air-fuel mixture introduced to the combustion chamber 18. An electronic control device 70 controls quantity of the fuel injected by the fuel injection valve 20 in response to a driving state of the throttle valve 14 and the intake valve 30 so that the air-fuel ratio detected by the air-fuel ratio sensor 25 becomes the stoichiometric air-fuel ratio, and controls a lift quantity for reducing throttle opening and the throttle opening by setting the maximum lift quantity of the intake valve 30 to a predetermined minimum lift quantity or more, when the quantity of fuel of the fuel injection valve 20 is estimated as a minimum injection quantity or less. COPYRIGHT: (C)2008,JPO&INPIT