Patent ID: 6173570
Filing Date: 2001-01-16
Classification: F01N,F02D,Y02T

Abstract:
An exhaust gas purification device for an engine, comprising:a catalyst disposed in an exhaust passage of the engine, the catalyst trapping and storing NOx when an exhaust gas mixture flowing into the catalyst has a low reductant content, and the catalyst reducing NOx stored in the catalyst when the exhaust gas mixture has a high reductant content;an injector injecting fuel directly into a combustion chamber of the engine;a spark plug igniting the fuel in the combustion chamber; anda controller programmed:to detect an catalyst regeneration condition for regenerating the catalyst by reducing NOx stored in the catalyst;to calculate a first fuel injection quantity from fulfillment of the catalyst regeneration condition to the expiration of a first time period, the first fuel injection quantity being equal to or smaller than a stoichiometric fuel quantity required to set an average air fuel ratio in the combustion chamber equal to a stoichiometric air fuel ratio;to calculate a first fuel injection timing based on the first fuel injection quantity, the first fuel injection timing being such a fuel injection timing on a compression stroke as to produce an air fuel mixture having a rich air fuel ratio in a limited region around the spark plug; andto control the injector according to the first fuel injection quantity and the first fuel injection timing from the fulfillment of the catalyst regeneration condition to the expiration of the first time period.