| 摘要 |
PROBLEM TO BE SOLVED: To provide an air-fuel ratio control device for an internal-combustion engine capable of establishing a control behavior with good stability and responsiveness suitable for a delay in the oxygen storage action of a catalyst and keeping the catalyst in good purified condition at all times. SOLUTION: The air-fuel ratio control device for internal-combustion engine is equipped with an upstream O2 sensor 13, a downstream O2 sensor 15, a first air-fuel ratio feedback control means 130 to regulate the fuel supply amount so that the air-fuel ratio in the upstream exhaust gas becomes identical to the target upstream air-fuel ratio AFobj, and a second air-fuel ratio feedback control means 150 to control the target upstream air-fuel ratio AFobj in accordance with the difference of the detected air-fuel ratio sensed by downstream air-fuel ratio sensor 15 and the target downstream air-fuel ratio so that the two become identical. The second air-fuel ratio feedback control means 150 makes setting larger the integral gain of the integrating computation with increasing rate of flow rate of the exhaust gas and also sets the proportional gain of the proportioning computation so as not to vary with respect to a change in the flow rate of the exhaust gas flow. COPYRIGHT: (C)2009,JPO&INPIT
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