AIR-FUEL RATIO CONTROLLER FOR MULTICYLINDER ENGINE

PURPOSE:To suppress the hunting phenomenon accompanied by closed-loop control by installing each exhaust sensor into the exhaust systems for the cylinder groups divided into two groups and suspending the closed-loop control for a prescribed time in one cylinder group and carrying-out air-fuel ration control by the opened-loop control. CONSTITUTION:A multicylinder engine E is divided into the first and the second cylinder groups 1 and 2, and exhaust sensors 6 and 7 are installed into the exhaust systems 3 and 4 for the cylinder groups 1 and 2, respectively. Fuel is supplied into each group 1, 2 from a fuel feeding apparatus 8 through the first and the second air-fuel ratio adjusting means 9 and 10. The first adjusting means 9 is controlled according to the integration signal on the basis of an exhaust sensor 6 by a closed-loop control means 11, and the second adjusting means 10 is controlled through an opened-loop control means 14 according to the integration signal on the basis of an exhuast sensor 7. An opened-loop control means 14 suspends the closed-loop control of the adjusting means 10 under a special operation condition, and performs reverse-phase control according to the opened-loop control signal supplied from an opened-loop control preparing means 13.