Patent ID: 8813477
Filing Date: 2014-08-26
Classification: F01N,Y02T

Abstract:
1. An exhaust purification system for an internal combustion engine equipped with a selective reduction catalyst provided in an exhaust channel of an internal combustion engine that reduces NOx in exhaust flowing through the exhaust channel under the presence of a reducing agent, and a reducing agent supply means for supplying a reducing agent or an additive serving as a source to the selective reduction catalyst, the system comprising: a reducing agent detection means for detecting a reducing agent amount or reducing agent concentration of exhaust in the exhaust channel on a downstream side of the selective reduction catalyst; a slip determination means for determining an occurrence of reducing agent slip in the selective reduction catalyst based on an output value of the reducing agent detection means; a storage amount estimation means for calculating an estimated value of a storage amount, with an amount of reducing agent stored in the selective reduction catalyst as the storage amount; a storage capacity estimation means for calculating an estimated value of a storage capacity, with an amount of reducing agent that can be stored by the selective reduction catalyst as the storage capacity; and a supply amount determination means for determining a supply amount of the reducing agent supply means, wherein the supply amount determination means determines a supply amount by decreasing in amount, relative to a reference supply amount calculated based on a parameter correlating to an operating state of the internal combustion engine, in response to having determined that the reducing agent slip has occurred, and increasing in amount in response to an estimated amount of the storage amount falling below a predetermined switch determination value, and wherein the reference supply amount is determined to be an amount appropriate for a NOx amount discharged from the engine, and the switch determination value is set to a value that is somewhat smaller than the estimated value of the storage capacity.