Patent ID: 6782694
Filing Date: 2004-08-31
Classification: F01N,F02D,F02M,Y02T

Abstract:
A control method of an engine, having at least an HC adsorbing catalyst including an HC adsorbing function for adsorbing HC in an exhaust gas pipe of the engine at a low temperature and for emitting the adsorbed HC at a high temperature, and a three-way purifying function on the same carrier; and an NOx adsorbing (occluding) catalyst having an NOx adsorbing (occluding) function for adsorbing or occluding NOx in oxidizing atmosphere and for emitting NOx in reducing atmosphere, and a three-way purifying function, said method comprising the steps of:driving the engine in a stoichiometric air-fuel ratio or a rich air-fuel ratio when a temperature of the HC adsorbing catalyst and a temperature of the NOx adsorbing (occluding) catalyst is equal to/lower than a predetermined value; and driving the engine in a lean air-fuel ratio when the temperature of the HC adsorbing catalyst and a temperature of the NOx adsorbing (occluding) catalyst is equal to/higher than the predetermined value.