CATALYST DETERIORATION DETECTION DEVICE AND METHOD

摘要

The purpose of the present invention is to provide a technique to accurately detect the deterioration of an exhaust gas purification catalyst applied to an internal combustion engine capable of using a gas fuel and a liquid fuel. When using only the gas fuel which is less likely to release oxygen occluded in the exhaust gas purification catalyst even when the air/fuel ratio of the exhaust gas discharged from the internal combustion engine is changed to a rich side, a catalyst deterioration discrimination unit discriminates whether the exhaust gas purification catalyst is deteriorated, according to either the change only on a lean side of the output of an oxygen concentration detection unit or the changes on the rich side and the lean side of the output of the oxygen concentration detection unit.