Exhaust gas purification apparatus for an internal combustion engine

摘要

A decrease in an NOx removal or reduction rate at the time of filter regeneration is suppressed. To this end, provision is made for an NOx selective reduction catalyst, a filter arranged at the upstream side of the NOx selective reduction catalyst, an NH3 generation catalyst arranged at the upstream side of the NOx selective reduction catalyst to generate NH3 when the air fuel ratio of an exhaust gas is equal to or less than a stoichiometric air fuel ratio, a regeneration unit to carry out regeneration of the filter, and a generation unit to make the air fuel ratio of the exhaust gas equal to or less than the stoichiometric air fuel ratio, thereby causing NH3 to be generated in the NH3 generation catalyst, wherein the regeneration unit inhibits the regeneration of the filter until the generation of NH3 by the generation unit is completed.

主权项

1. An exhaust gas purification apparatus of an internal combustion engine comprising:
an NOx selective reduction catalyst that is arranged in an exhaust passage of the internal combustion engine and reduces NOx by using NH3 as a reducing agent; a filter that is arranged in the exhaust passage at the upstream side of said NOx selective reduction catalyst and traps particulate matter contained in the exhaust gas; an NH3 generation catalyst that is arranged in the exhaust passage at the upstream side of said NOx selective reduction catalyst and generates NH3 when the air fuel ratio of the exhaust gas is equal to or less than a stoichiometric air fuel ratio; a regeneration unit that regenerates said filter by supplying oxygen to said filter while raising the temperature of said filter; and a generation unit that makes the air fuel ratio of the exhaust gas equal to or less than the stoichiometric air fuel ratio, thereby causing NH3 to be generated in said NH3 generation catalyst; wherein said regeneration unit inhibits the regeneration of said filter until the generation of NH3 by said generation unit is completed; and said generation unit does not carry out the generation of NH3 during the regeneration of said filter.