Patent ID: 7520274
Filing Date: 2009-04-21
Classification: F01N,F02D

Abstract:
1. An air fuel ratio sensor deterioration determination system for a compression ignition internal combustion engine comprising: an NOx storage-reduction catalyst arranged on an exhaust passage of said compression ignition internal combustion engine; an air fuel ratio sensor arranged at a downstream side of said NOx storage-reduction catalyst for detecting an air fuel ratio corresponding to an oxygen concentration of an exhaust gas flowing out from said NOx storage-reduction catalyst; an exhaust gas air fuel ratio control section that controls an air fuel ratio of an exhaust gas flowing into said NOx storage-reduction catalyst by supplying fuel to said exhaust gas flowing into said NOx storage-reduction catalyst; a stoichiometric air fuel ratio shift response time detection section that detects a response time from a time point said air fuel ratio sensor detects a first air fuel ratio, which is leaner than a stoichiometric air fuel ratio, to a time point said air fuel ratio sensor detects a second air fuel ratio, which is leaner than the stoichiometric air fuel ratio and richer than said first air fuel ratio, when the air fuel ratio of said exhaust gas being in a lean state is controlled to a rich state by said exhaust gas air fuel ratio control section; and an air fuel ratio sensor deterioration determination section that makes a determination that said air fuel ratio sensor is degraded, when the response time detected by said stoichiometric air fuel ratio shift response time detection section exceeds a stoichiometric air fuel ratio shift reference time.