| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To accurately detect the deterioration state of an exhaust emission control catalyst of an internal combustion engine based on an oxygen storage amount of the catalyst. <P>SOLUTION: During a fuel cut, an exhaust air/fuel ratio becomes lean and the oxygen storage amount increases. When the storage amount of the oxygen stored in a precious metal catalyst layer (Pt and so on) of the catalyst in a state being highly reactive to oxidation or reduction with exhaust components to be purified (HC, CO, NOx) reaches its maximum level (saturation point), the oxygen starts to be released into an exhaust gas. Oxygen concentrations in the exhaust gas thereby increase suddenly and an air-fuel ratio sensor placed at the downstream of the catalyst detects the lean ratio. The oxygen storage amount calculated at this point is a maximum oxygen storage capacity OSCmax. Since the maximum oxygen storage capacity decreases as the catalyst deteriorates, it is determined that the catalyst deteriorates if the calculated maximum oxygen storage capacity is smaller than a slice level for deterioration determination. At the same time, the feedback control of the air-fuel ratio is performed, calculating the oxygen storage amount of the catalyst so as to adjust it to a target oxygen storage amount. <P>COPYRIGHT: (C)2004,JPO</p> |
