PURPOSE: To ensure stability of operation at the time of executing open-loop control, by using a value stored and learnt as the center value of a correction value for the air fuel ratio in feedback control region as an initial value of the correction value for the air-fuel ratio in open-loop control region.
CONSTITUTION: In operation of an engine, a control unit 44 controls the air-fuel ratio according to the operational conditions of the engine by way of open-loop control or fedback control based on the output of an O2-sensor 30. When the operational conditions of the engine are changed from feedback control region to open-loop control region, a value stored and learnt as the center value of a correction value for the air-fuel ratio in the feedback control region is used as an initial value of the correction value for the air-fuel ratio in the open-loop control region. In case that these two correction values are different to each other, the initial correction value is brought gradually closer to a reference correction value by a time constant greater than that used when the above learnt value is stored and learnt, and the air-fuel ratio in the open-loop control region is controlled on the basis of the correction value brought closer to the reference correction value.
TAKEDA YUUJI
ITOU YOSHIYASU
ANZAI KATSUSHI
