| 摘要 |
<p>A catalyst poisoning detection device for detecting catalyst poisoning in an internal combustion engine, the catalyst poisoning detection device being provided with a catalyst downstream air-fuel ratio sensor, an air-fuel ratio control unit, and an estimation unit for making an estimation with regard to catalyst poisoning. The air-fuel ratio control unit performs a lean-rich control in which the air-fuel ratio of exhaust gas is changed from a lean air-fuel ratio to a rich air-fuel ratio and a rich-lean control in which the air-fuel ratio of exhaust gas is changed from a rich air-fuel ratio to a lean air-fuel ratio such that the air-fuel ratio of the exhaust gas on the upstream side of the catalyst is switched between a rich air-fuel ratio and a lean air-fuel ratio, the lean air-fuel ratio being a lean mixture relative to the ideal air-fuel ratio and the rich air-fuel ratio being a rich mixture relative to the ideal air-fuel ratio. The estimation unit makes an estimation with regard to catalyst poisoning on the basis of output values outputted by means of the catalyst downstream air-fuel ratio sensor in response to the lean-rich control during a period in which the lean air-fuel ratio converges to the ideal air-fuel ratio and/or output values outputted by means of the catalyst downstream air-fuel ratio sensor in response to the rich-lean control during a period in which the rich air-fuel ratio converges to the ideal air-fuel ratio.</p> |
