AIR/FUEL RATIO CONTROLLER FOR MULTI-CYLINDER ENGINE

PURPOSE:To suppress the hunting and to improve the control accuracy by performing the phase and period control such that the first and the second cylinder groups have the opposite phases and same inverting period. CONSTITUTION:Exhaust sensors 6, 7 are arranged respectively in the exhaust systems 3, 4 of the first and the second cylinder groups 1, 2. Both cylinder groups will perform closed-loop control by means of an integrated signal based on the output from respective exhaust sensor. Phase correction means 13 will vary the inverting timing such that the increasing/decreasing directions of the first and second integration signals will be in the opposite phase. Period correction means 15 will correct the control gain such that the varying periods of the first and the second integration signals will match. In such a manner, the control accuracy is improved while the hunting is suppressed.