Patent ID: 6058701
Filing Date: 2000-05-09
Classification: B01D,F01N,F02D,F02M,Y02T

Abstract:
An exhaust purification apparatus for reducing nitrogen oxides in an exhaust gas emitted from an exhaust passage of an internal combustion engine, the apparatus comprising:a catalyst located in the exhaust passage, wherein the catalyst stores nitrogen oxides when the air-fuel ratio of an air-fuel mixture supplied to a combustion chamber is lean and reduces and emits the stored nitrogen oxides when the air-fuel ratio is rich;a rich spike controller that controls the air-fuel ratio of the air-fuel mixture to be rich when the nitrogen oxides stored in the catalyst is reduced and emitted;a determiner for judging whether the engine is operating in a stable manner;a changer for choosing among different combustion types and changing the engine combustion type according to varying loads on the engine; anda permitting means for permitting use of the rich spike controller only when the engine is judged to be operating in a stable manner by the determiner;wherein the determiner judges that the engine is operating in an unstable manner when the engine combustion type is being changed by the changer.