IRREGULARITY DIAGNOSING DEVICE FOR EXHAUST GAS SENSOR

摘要

PROBLEM TO BE SOLVED: To accurately determine regularity/irregularity of an exhaust gas sensor (catalyst downstream gas sensor) installed downstream of a catalyst for exhaust gas purification without deteriorating exhaust emission in a device performing irregularity diagnosis of a catalyst downstream side sensor. SOLUTION: Air fuel ratio is temporally controlled to rich after recovery from fuel cut to promote reaction of occluded lean composition (occluded oxygen) of the catalyst and rich composition of exhaust gas and reduce lean composition occlusion quantity of the catalyst and a condition of the catalyst is quickly recovered to a near stoichiometric condition for reducing emission of lean composition such as NOx after recovery from fuel cut (after fuel injection restart). Response time between a predetermined voltage (in a embodiment 0.3 V→0.5 V) of the catalyst downstream sensor from lean to rich is measured by using air fuel ratio rich control temporally executed after recovery from fuel cut and irregularity diagnosis of the catalyst downstream sensor based on the response time. COPYRIGHT: (C)2006,JPO&NCIPI