Patent ID: 8789357
Filing Date: 2014-07-29
Classification: F01N,F02D,Y02T

Abstract:
1. A catalyst deterioration detection apparatus comprising: an exhaust gas purification catalyst that is arranged in an exhaust passage of an internal combustion engine operable on both gas fuel and liquid fuel; an oxygen sensor that is arranged in said exhaust passage at a downstream side of said exhaust gas purification catalyst; and an electronic control unit (ECU) configured to execute catalyst deterioration determination control in which an air fuel ratio of an exhaust gas discharged from said internal combustion engine is changed to a rich side and a lean side, a comparison is made between a change of the air fuel ratio and a change of an output of said oxygen sensor, and a determination is made whether said exhaust gas purification catalyst has deteriorated; wherein the gas fuel is difficult to cause oxygen occluded in said exhaust gas purification catalyst to be released therefrom when the air fuel ratio of the exhaust gas discharged from said internal combustion engine is changed to the rich side in comparison to the liquid fuel, and when executing the catalyst deterioration determination control while said internal combustion engine is operated by using only the gas fuel, said ECU selects either one of determining whether said exhaust gas purification catalyst has deteriorated based on a change in the output of said oxygen sensor only at the lean side and determining whether said exhaust gas purification catalyst has deteriorated based on changes in the output of said oxygen sensor at the rich side and at the lean side.