Patent ID: 6408617
Filing Date: 2002-06-25
Classification: F01N,F02D,Y02T

Abstract:
A diagnostic equipment for an exhaust gas cleaning apparatus for an engine system having an air-fuel-ratio controller which detects an air fuel ratio of exhaust gas emitted from an engine and which adjusts a quantity of fuel injection so as to hold the air fuel ratio of the exhaust gas at a predetermined value, and cleaning said exhaust gas with a catalyst, comprisinga first air-fuel-ratio sensor which detects the air fuel ratio of the exhaust gas upstream of said catalyst; a second air-fuel-ratio sensor which detects the air fuel ratio of the exhaust gas downstream of said catalyst; means for calculating a catalyst deterioration index indicative of a deterioration state of said catalyst from output signals of said first air-fuel-ratio sensor and said second air-fuel-ratio sensor; means using a predetermined threshold value for deciding a deterioration state of said catalyst through a comparison between threshold value and the catalyst deterioration index; means for detecting abnormality of said engine system affecting said catalyst deterioration index; and at least one member selected from the group consisting of means for correcting said catalyst deterioration index when the abnormality has been detected by said abnormality detection means, and means for interrupting a decision of said catalyst-deterioration decision means when the abnormality has been detected by said abnormality detection means, wherein said catalyst-deterioration-index correction means alters a correction coefficient used for correction in accordance with at least one of a temperature of the catalyst and operating conditions, when said catalyst deterioration index is corrected, and said catalyst-deterioration-decision interruption means alters a standard for interrupting said decision in accordance with at least one of said temperature of the catalyst and said operating conditions, when said decision is interrupted.