| 摘要 |
PURPOSE:To prevent a change as time proceeds, by correcting a correction value per unit time of an integral term and a proportional term for feedback control according to a ratio between a time when an exhaust gas concentration detected value changes from a rich maximum value to a reference value and a time when the detected value changes from a lean minimum value to the reference value. CONSTITUTION:Detection values from a throttle valve opening sensor 4, an intake pipe absolute pressure sensor 8, a water temperature sensor 9, an engine speed sensor 10, an O2 sensor 13, etc. are input to an electronic control unit 5. Then, a valve open time of a fuel injection valve 6 is feedback controlled so that an air-fuel ratio becomes a target value according to an operational condition. The electronic control unit 5 computes a ratio between a time when the output from the O2 sensor changes from a maximum value to a reference value and a time when the output changes from a minimum value to the reference value. When the ratio exceeds a predetermined range, the control unit 5 corrects a lean proportional control term and integral control term or a rich proportional control term or integral control term.
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