Patent ID: 6422004
Filing Date: 2002-07-23
Classification: F01N,F02B,F02D,F02M,Y02T

Abstract:
A fuel injection control system for an internal combustion engine equipped with a fuel injector through which fuel is sprayed directly into a combustion chamber of the internal combustion engine and a catalyst disposed in an exhaust passage which contains a NOx trapping substance operative to absorb NOx in an exhaust gas containing oxygen in excess and to release NOx into the exhaust gas when the oxygen content of the exhaust gas lowers, said fuel injection control system comprising:detecting means for detecting a value relating to an amount of NOx absorbed by said NOx trapping substance which represents a trapped amount of NOx; fuel injection control means for repeatedly performing fuel injection through primary fuel injection which is made at a primary fuel injection timing near a top dead center of a compression stroke when said trapped amount of NOx is larger than a specified amount and post-fuel injection at a post-fuel injection timing retarded by a predetermined time from said top dead center of compression stroke after said primary fuel injection when causing a fall in said oxygen concentration so as to release NOx from said NOx trapping substance; wherein said control means controls a retardation of said post-fuel injection timing so as to be large for a specified period of time from a detection of said trapped amount of NOx larger than said specified amount than after a lapse of said specified period of time so as thereby to make an amount of HC in an exhaust gas from said combustion chamber larger for a period of time from said detection of said trapped amount of NOx larger than said specified amount to said lapse of said specified period of time than after said lapse of said specified period of time.