Patent ID: 7117664
Filing Date: 2006-10-10
Classification: F01N,F02D,Y02T

Abstract:
1. A diagnostic equipment for an exhaust gas cleaning apparatus; said exhaust gas cleaning apparatus being directed toward 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 downstream 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; abnormality detection means for detecting any abnormality of said engine system as affects said catalyst deterioration index; catalyst-deterioration-decision interruption means for interrupting the decision of said catalyst-deterioration decision means when a frequency of detected by said abnormality detection means exceeds a predetermined frequency; and frequency changing means for changing said predetermined frequency according to an engine system state.