Exhaust Purification System for Internal Combustion Engine

Abstract

An object of the present invention is to suppress a reduction in a NO x purification ratio accompanying filter regeneration processing in an exhaust gas purification system for an internal combustion engine that includes a filter carrying an SCR catalyst. In the present invention, the temperature of the filter is increased following completion of the filter regeneration processing by increasing the temperature of exhaust gas discharged from the internal combustion engine, and in so doing, HC adhered to the filter is removed.

1 . An exhaust gas purification system for an internal combustion engine, comprising:
 a pre-catalyst that is provided in an exhaust passage of the internal combustion engine and has an oxidation function;   a fuel supply apparatus configured to supply fuel to the pre-catalyst;   a filter provided in the exhaust passage on a downstream side of the pre-catalyst in order to trap particulate matter contained in exhaust gas, the filter carrying a selective catalytic reduction NO x  catalyst that reduces NO x  contained in the exhaust gas using ammonia as a reducing agent;   an ammonia supply apparatus configured to supply ammonia or an ammonia precursor to the filter;   a filter regeneration processing execution unit configured to execute filter regeneration processing for removing the particulate matter accumulated in the filter, by supplying fuel to the pre-catalyst from the fuel supply apparatus in order to increase a temperature of the filter; and   an HC poisoning recovery processing execution unit configured to execute HC poisoning recovery processing for removing HC adhered to the filter after the filter regeneration processing executed by the filter regeneration processing execution unit has been terminated, by increasing a temperature of the exhaust gas discharged from the internal combustion engine in order to increase the temperature of the filter.   
     
     
         2 . The exhaust gas purification system for an internal combustion engine according to  claim 1 , wherein the HC poisoning recovery processing is executed for a period corresponding to an amount of HC adhered to the filter at a start point of the HC poisoning recovery processing. 
     
     
         3 . The exhaust gas purification system for an internal combustion engine according to  claim 1 , wherein the HC poisoning recovery processing is executed for a period corresponding to an execution period of the filter regeneration processing. 
     
     
         4 . The exhaust gas purification system for an internal combustion engine according to  claim 1 , wherein during the filter regeneration processing, the ammonia or the ammonia precursor is supplied to the filter by the ammonia supply apparatus in an amount corresponding to the temperature of the filter until the temperature of the filter reaches a target temperature. 
     
     
         5 . The exhaust gas purification system for an internal combustion engine according to  claim 1 , wherein the fuel supply apparatus includes a fuel addition valve that adds the fuel to the exhaust gas,
 the filter regeneration processing execution unit executes the filter regeneration processing by adding the fuel to the pre-catalyst from the fuel addition valve in order to increase the temperature of the filter, and   the HC poisoning recovery processing execution unit executes the HC poisoning recovery processing by executing an auxiliary fuel injection in the internal combustion engine at a timing which is later than a main fuel injection and at which fuel injected in the auxiliary fuel injection contributes to combustion in a combustion chamber.   
     
     
         6 . The exhaust gas purification system for an internal combustion engine according to  claim 2 , wherein during the tiller regeneration processing, the ammonia of the ammonia precursor is supplied to the filter by the ammonia supply, apparatus in an amount corresponding to the temperature of the filter until the temperature of the filter reaches a target temperature. 
     
     
         7 . The exhaust gas purification system for an internal combustion engine according to  claim 3 , wherein during the filter regeneration processing, the ammonia or the ammonia precursor is supplied to the filter by the ammonia supply apparatus in an amount corresponding to the temperature of the filter until the temperature of the filter reaches a target temperature.