Patent ID: 7162863
Filing Date: 2007-01-16
Classification: F01N,F02D

Abstract:
1. An exhaust gas purifying apparatus for an internal combustion engine having an exhaust system, comprising: NOx purifying means provided in said exhaust system for purifying NOx in exhaust gases, said NOx purifying means having NOx adsorbing capacity; temperature detecting means for detecting a temperature of said NOx purifying means; and enriching means for setting an air-fuel ratio of an air-fuel mixture, which burns in said engine, to a value on a rich side with respect to a stoichiometric ratio so as to increase an amount of reducing components in the exhaust gases flowing into said NOx purifying means, wherein said NOx purifying means generates ammonia from the adsorbed NOx and retains the generated ammonia when the air-fuel ratio is set to a value on the rich side with respect to the stoichiometric ratio, said NOx purifying means purifying NOx with the retained ammonia when the air-fuel ratio is set to a value on a lean side with respect to the stoichiometric ratio, wherein said enriching means comprises conversion rate calculating means for calculating a rate of conversion from the adsorbed NOx to ammonia in said NOx purifying means according to the temperature detected by said temperature detecting means, and enrichment parameter setting means for setting an enrichment parameter according to the calculated conversion rate, and wherein said enriching means performs the enrichment based on the set enrichment parameter.