Exhaust gas purification device

Abstract

An ECU corrects a fuel addition interval, based on an amount of change between a present backpressure and a basic backpressure obtained when a basic addition interval is set, to reduce the fuel addition interval with an increase in the amount of change in the backpressure (steps ST 1 -ST 4 ). Thereby, a required fuel addition amount can be secured even if a pressure in an exhaust path provided with a fuel addition valve is increased and thus the backpressure at an ejection hole portion of the fuel addition valve is increased. Consequently, an increase in a catalyst bed temperature required for an exhaust gas purifying function of a catalyst can be ensured. Further, a temperature at a tip of the fuel addition valve can be maintained at not more than a predetermined value (i.e., a temperature at which production of deposits can be suppressed), and thus clogging of the ejection hole of the fuel addition valve with the deposits can be avoided.

1 . An exhaust gas purification device having a catalyst provided in an exhaust path of an internal combustion engine and a fuel addition valve adding fuel to said exhaust path, comprising:
 detection means for detecting a pressure in the exhaust path provided with said fuel addition valve; and   correction means for correcting an addition amount of the fuel to be added to said exhaust path based on said detected pressure.   
   
   
       2 . The exhaust gas purification device according to  claim 1 , wherein said correction means includes means for correcting the addition amount of the fuel to be added to said exhaust path based on said detected pressure, taking into account a timing when the fuel is injected into a cylinder of said internal combustion engine. 
   
   
       3 . The exhaust gas purification device according to  claim 1 , wherein said detection means includes means for calculating the pressure in said exhaust path based on at least one of an exhaust gas flow volume and an exhaust gas temperature. 
   
   
       4 . The exhaust gas purification device according to  claim 3 , wherein said correction means includes means for correcting the addition amount of the fuel to be added to said exhaust path based on said detected pressure, taking into account a timing when the fuel is injected into a cylinder of said internal combustion engine. 
   
   
       5 . The exhaust gas purification device according to any of  claims 1  to  4 , wherein said correction means includes means for correcting an injection amount of the fuel to be injected to said exhaust path by multiplying at least one of a basic injection time interval and a basic injection time period by a correction coefficient according to the pressure in said exhaust path. 
   
   
       6 . An exhaust gas purification device having a catalyst provided in an exhaust path of an internal combustion engine and a fuel addition valve adding fuel to said exhaust path, comprising:
 a detection unit detecting a pressure in the exhaust path provided with said fuel addition valve; and   a control unit controlling said exhaust gas purification device,   wherein said control unit corrects an addition amount of the fuel to be added to said exhaust path based on said detected pressure.   
   
   
       7 . The exhaust gas purification device according to  claim 6 , wherein said control unit corrects the addition amount of the fuel to be added to said exhaust path based on said detected pressure, taking into account a timing when the fuel is injected into a cylinder of said internal combustion engine. 
   
   
       8 . The exhaust gas purification device according to  claim 6 , wherein said detection unit calculates the pressure in said exhaust path based on at least one of an exhaust gas flow volume and an exhaust gas temperature. 
   
   
       9 . The exhaust gas purification device according to  claim 8 , wherein said control unit corrects the addition amount of the fuel to be added to said exhaust path based on said detected pressure, taking into account a timing when the fuel is injected into a cylinder of said internal combustion engine. 
   
   
       10 . The exhaust gas purification device according to any of  claims 6  to  9 , wherein said control unit corrects an injection amount of the fuel to be injected to said exhaust path by multiplying at least one of a basic injection time interval and a basic injection time period by a correction coefficient according to the pressure in said exhaust path.