Exhaust purification device of compression ignition type internal combustion engine

Abstract

In an internal combustion engine, an NO x selective reducing catalyst ( 15 ) is arranged in an engine exhaust passage and an oxidation catalyst ( 12 ) is arranged in the engine exhaust passage upstream of the NO x selective reducing catalyst ( 15 ). At the time of engine startup, HC is fed from a HC feed valve ( 28 ) to the oxidation catalyst ( 12 ), thereby raising the temperature of the NO x selective reducing catalyst( 15 ) by the heat of the oxidation reaction of HC. At this time, the temperature of the NO x selective reducing catalyst ( 15 ) is raised to a HC desorption range where HC is desorbed from the NO x selective reducing catalyst ( 15 ).

1 - 4 . (canceled) 
   
   
       5 . An exhaust purification device of a compression ignition type internal combustion engine arranging an NO x  selective reducing catalyst in an engine exhaust passage, arranging an oxidation catalyst in the engine exhaust passage upstream of the NO x  selective reducing catalyst, feeding urea to the NO x  selective reducing catalyst, and using an ammonia produced from the urea to selectively reduce NO x  contained in an exhaust gas, wherein HC is fed into the oxidation catalyst at the time of engine startup to raise a temperature of the NO x  selective reducing catalyst with a heat of oxidation reaction of HC, and at this time, the temperature of the NO x  selective reducing catalyst is increased to a HC desorption temperature range where HC is desorbed from the NO x  selective reducing catalyst, an amount of HC deposited at the NO x  selective reducing catalyst being calculated, and the feed of HC being stopped when a calculated HC amount becomes less than a predetermined set value. 
   
   
       6 . The exhaust purification device of the compression ignition type internal combustion engine as claimed in  claim 5 , wherein at the time of raising the temperature of the NO x  selective reducing catalyst, the temperature of the NO x  selective reducing catalyst is increased to a range within 350° C. to 650° C. 
   
   
       7 . The exhaust purification device of the compression ignition type internal combustion engine as claimed in  claim 5 , wherein there is a convergence temperature at which the temperature of the NO x  selective reducing catalyst ultimately converges when an idling operation is continued during warm-up operation and wherein the temperature of the NO x  selective reducing catalyst at the time of raising the temperature of the NO x  selective reducing catalyst is increased to a temperature at least 100° C. higher than the convergence temperature.