Patent ID: 6330795
Filing Date: 2001-12-18
Classification: F01N,F02D,Y02T

Abstract:
A diagnostic equipment for an exhaust gas cleaning apparatus;said exhaust gas cleaning apparatus being usable in an engine system furnished with 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 by means of a catalyst;said diagnostic equipment, comprising:a 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;catalyst-deterioration-index calculation 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;catalyst-deterioration decision means endowed with a predetermined threshold value, for deciding the deterioration state of said catalyst through a comparison between the threshold value and the catalyst deterioration index;abnormally detection means for detecting any abnormality of said engine system as affects said catalyst deterioration index; andat least one member selected from the group consisting of catalyst-deterioration-index correction means for correcting said catalyst deterioration index when the abnormality has been detected by said abnormality detection means, and catalyst-deterioration-decision interruption means for interrupting the decision of said catalyst-deterioration decision means when the abnormality has been detected by said abnormality detection means, wherein said abnormality detection means comprises misfire detection means for detecting a combustion state of said engine so as to detect occurrence of misfire of said engine.