| 摘要 |
PURPOSE:To improve the air-fuel ratio, by arranging such that an engine speed variation is utilized to check for the stability of combustion taking place in an engine, and the air-fuel ratio is controlled to shift into a lean side or a rich side respectively depending on whether the engine combustion state is stable or unstable. CONSTITUTION:In a step 311, a difference DELTANi between a momentary engine speed N1i at TDC and a momentary engine speed N2i at ATD 90 deg. CA is obtained. In a step 312, the difference DELTAN'i between an engine speed variation value prior to 4 ignitions and the engine speed variation value DELTANi-4 is obtained as DELTAN'i=DELTANi-DELTANi-4. The difference DELTANi is compared with a verification value alpha in a step 314. If the result is ¦DELTAN'i¦>alpha, the combustion state is judged to be unstable and a fuel injection amount is increased in a step 319. If the result is ¦DELTAN'i¦<=alpha, the combustion state is judged to be stable and the fuel injection amount is decreased in a step 320. In this manner, the air-fuel ratio is caused to shift into a lean side as much as possible, and thereby improving a fuel combustion. |
