Exhaust gas purification system for internal combustion engine

Abstract

There is provided a technology that enables easier adjustment of the temperature of an exhaust gas purification apparatus to a target value by supplying an appropriate quantity of fuel to the exhaust gas purification apparatus even in the case where sub-injection and exhaust addition are performed in an exhaust gas purification system for an internal combustion engine. The system includes a fuel addition valve that adds fuel to the exhaust gas in an exhaust passage upstream of the exhaust gas purification apparatus and unburned fuel discharge unit for discharging gas containing unburned fuel from the combustion chamber of the internal combustion engine to the exhaust passage, wherein when supplying fuel to the exhaust gas purification apparatus to make the temperature of the exhaust gas purification catalyst equal to a target temperature, the quantity of fuel supplied by the fuel addition valve is controlled by a feedback control, and the quantity of fuel supplied by the unburned fuel discharge unit is controlled by an open-loop control.

1 . An exhaust gas purification system for an internal combustion engine by comprising:
 an exhaust gas purification apparatus that is provided in an exhaust passage of the internal combustion engine and includes an oxidation catalyst and of which a purification capability is recovered by supply of fuel thereto;   a fuel addition valve that adds fuel to exhaust gas in the exhaust passage upstream of said exhaust gas purification apparatus; and   unburned fuel discharge unit for discharging gas containing unburned fuel from a combustion chamber of said internal combustion engine to the exhaust passage,   wherein when supplying fuel to said oxidation catalyst by at least one of said fuel addition valve and said unburned fuel discharge unit to make the temperature of the exhaust gas purification apparatus equal to a target temperature upon recovering the purification capability of the exhaust gas purification apparatus, the quantity of fuel supplied by said fuel addition valve is controlled by a feedback control, and the quantity of fuel supplied by said unburned fuel discharge unit is controlled by an open-loop control.   
     
     
         2 . An exhaust gas purification apparatus for an internal combustion engine according to  claim 1 , wherein when the temperature of the oxidation catalyst is not lower than an active temperature, supply of fuel by said unburned fuel discharge unit is stopped. 
     
     
         3 . An exhaust gas purification system for an internal combustion engine according to  claim 1 , wherein fuel is supplied at predetermined intervals by said unburned fuel discharge unit even while fuel is supplied by said fuel addition valve. 
     
     
         4 . An exhaust gas purification system for an internal combustion engine according to  claim 2 , wherein fuel is supplied at predetermined intervals by said unburned fuel discharge unit even while fuel is supplied by said fuel addition valve.