| 摘要 |
PURPOSE:To obtain a high output and a low fuel consumption under any load conditions and to prevent damage of an exhaust system by heat, by applying decremental correction to the air-fuel ratio when an internal-combustion engine is operated under a low load and the engine temperature is higher than a predetermined value. CONSTITUTION:When an engine is set into operation under a low load, the air- fuel ratio is controlled at a value in the vicinity of the theoretical air-fuel ratio until the exhaust temperature T representing the engine temperature is raised to 800 deg.C. Here, since the throttle opening TA is smaller than 40 deg.C and the exhaust temperature T is lower than 800 deg.C in the period from the time t1 to the time t2, a fuel increasing factor KF is set at 1.08 and the rate of rise of the exhaust temperature T is rendered moderate, so that degradation of the engine output and the specific fuel consumption, damage of the exhaust system by heat, etc. can be prevented. Further, since, from the time t2 to the time t3, the throttle opening TA is equal to or greater than 40 deg.C and the exhaust temperature T is lower than 850 deg.C, the fuel increasing factor KF is set at 1.15. In the period from the time t3 to the time t4, the fuel increasing factor KF is increased gradually at the rate of 0.01, and the exhaust temperature T is kept at a value in the vicinity of 850 deg.C.
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