PURPOSE: To prevent the occurence of idle hunting by a method wherein the constant of integration of the air-fuel ratio feedback control system of the engine using an air-fuel ratio sensor provided in exhaust gases is increased or decreased in proportion to the number of revolutions of the engine in the ordinary operation condition and the constant of integration is made to fall within a predetermined different range when the engine is idled.
CONSTITUTION: An air-fuel ration control device which receives as inputs the outputs of an air intake amount sensor, a throttle opening degree sensor, an r.p.m. sensor and etc. judges at Step 101 whether or not the engine is idled and if not, then it judges at Step 103 whether or not the engine r.p.m. (NE) is less than the proportional upper limit r.p.m. (NEU) corresponding to the upper limit value of the constant of integration of the air-fuel ratio feedback control system. Further, it judges at Step 105 whether or not the r.p.m. (NE) is larger than the proportional lower limit r.p.m. (NEL) corresponding to the lower limit value of the above mentioned constant of integration. Thus the air-fuel ratio control device calculates a value (K) to be added to, or deducted from, the constant of integration every single revolution of the engine, on the bases of the results of its judgements. On the other hand, when the engine is idled, the device calculates the value (K) at Step 102 by dividing a predetermined value (KI) fitted for the idle operation of the engine by the engine r.p.m. (NE).
MURAI TOSHIMI
DOUMIYOU HIROYUKI
MATSUOKA HIROKI
KINUGASA YUKIO
