Exhaust gas purification system and method of purifying exhaust gas

Abstract

Decreases in the volume of intake air to an engine in response to environmental changes results in an increase in amount of PM emissions. In view of this situation, a correction coefficient of fuel supply interval is calculated based on the variation in amount of PM emissions to adjust a reference fuel supply interval in order to determine an target fuel supply interval. By adjusting the fuel supply interval, a fuel supply amount appropriate to the variation in amount of PM emissions, thereby preventing clogging of the injection hole of a supplemental fuel valve, while maintaining fuel economy.

1 . An exhaust gas purification system comprising:
 a catalyst disposed in an exhaust passage of an internal combustion engine;   a supplemental fuel valve that supplies fuel to the exhaust passage; and   an adjusting portion that adjusts a supplemental amount of fuel that is supplied from the supplemental fuel valve based on a variation in an amount of particulate matter emitted from a combustion chamber of the internal combustion engine.   
   
   
       2 . The exhaust gas purification system according to  claim 1 , wherein
 the adjusting portion adjusts the supplemental amount of fuel that is supplied from the supplemental fuel valve to the exhaust passage per unit time.   
   
   
       3 . The exhaust gas purification system according to  claim 2 , wherein
 the adjusting portion multiplies a reference fuel supply interval by a correction coefficient that depends on the variation in amount of particulate matter emitted to determine a target fuel supply interval.   
   
   
       4 . The exhaust gas purification system according to  claim 3 , wherein
 the adjusting portion multiplies the reference fuel supply interval by a correction coefficient to change the fuel supply interval to determine the target fuel supply interval, when an actual intake air volume to the internal combustion engine is smaller than a reference intake air volume.   
   
   
       5 . The exhaust gas purification system according to  claim 1 , wherein:
 the adjusting portion adjusts a fuel supply interval of fuel that is supplied from the supplemental fuel valve to the exhaust passage per unit time.   
   
   
       6 . The exhaust gas purification system according to  claim 5 , further comprising:
 a supplemental fuel valve temperature estimating portion for estimating a temperature of the supplemental fuel valve, wherein   the adjusting portion compares a first correction coefficient with a second correction coefficient each other, the first correction coefficient is used to change the fuel supply interval when the actual intake air volume to the internal combustion engine is smaller than the reference intake air volume, the second correction coefficient is used to change the fuel supply interval when the estimated temperature of the supplemental fuel valve rises, and multiplies the reference fuel supply interval by the correction coefficient of the first and second correction coefficients that yields a shorter fuel supply interval to determine the target fuel supply interval.   
   
   
       7 . The exhaust gas purification system according to  claim 1 , further comprising:
 a catalyst temperature detecting portion for detecting a temperature of the catalyst, wherein   the adjusting portion reduces the supplemental amount of fuel per unit time according to the detected catalyst temperature when the detected catalyst temperature is equal to or higher than a preset value.   
   
   
       8 . The exhaust gas purification system according to  claim 1 , further comprising:
 a catalyst temperature detecting portion for detecting a temperature of the catalyst, wherein
 the adjusting portion reduces the supplemental amount of fuel per unit time according to the detected catalyst temperature when the variation in the detected catalyst temperature is equal to or greater than a preset value. 
   
   
   
       9 . The exhaust gas purification system according to  claim 1 , further comprising:
 a coolant temperature detecting portion for detecting a coolant temperature in the internal combustion engine, wherein   the adjusting portion reduces the supplemental amount of fuel per unit time according to the detected catalyst temperature when the variation in the detected coolant temperature is equal to or greater than a preset value.   
   
   
       10 . The exhaust gas purification system according to  claim 7 , wherein
 a fuel injection amount per unit time is reduced by shortening the fuel supply interval, while the fuel supply duration per interval is reduced.   
   
   
       11 . The exhaust gas purification system according to  claim 1 , wherein
 the internal combustion engine is a diesel engine.   
   
   
       12 . The exhaust gas purification system according to  claim 1 , wherein
 the internal combustion engine is mounted on a vehicle.   
   
   
       13 . The exhaust gas purification method comprising:
 supplying fuel to an exhaust passage of an internal combustion engine, the exhaust passage having a catalyst disposed therein; and   adjusting an supplemental amount of fuel that is supplied from the supplemental fuel valve based on a variation in an amount of particulate matter emitted from a combustion chamber of the internal combustion engine.   
   
   
       14 . The exhaust gas purification method according to  claim 13 , wherein
 the supplemental amount of fuel that is supplied from the supplemental fuel valve to the exhaust passage per unit time is adjusted in order to adjust the supplemental amount of the fuel.   
   
   
       15 . The exhaust gas purification method according to  claim 14 , wherein
 a reference fuel supply interval is multiplied by a correction coefficient that depends on the variation in amount of particulate matter emitted to determine a target fuel supply interval in order to adjust the supplemental amount of the fuel.   
   
   
       16 . The exhaust gas purification method according to  claim 15 , wherein
 the reference fuel supply interval is multiplied by a correction coefficient that adjusts the fuel supply interval to determine the target fuel supply interval when an actual intake air volume to the internal combustion engine is smaller than a reference intake air volume in order to adjust the amount of the fuel.   
   
   
       17 . The exhaust gas purification method according to  claim 13 , wherein
 the degree of fuel is an interval of fuel that is supplied from the supplemental fuel valve to the exhaust passage.   
   
   
       18 . The exhaust gas purification method according to  claim 17 , further comprising:
 estimating a temperature of the supplemental fuel valve, wherein   a first correction coefficient and a second correction coefficient are compared with each other, the first correction coefficient is used to change the fuel supply interval when the actual intake air volume to the internal combustion engine is smaller than the reference intake air volume, and the second correction coefficient is used to change the fuel supply interval when the estimated temperature of the supplemental fuel valve rises; and wherein the reference fuel supply interval is multiplied by the correction coefficient of the first and second correction coefficients that yields a shorter fuel supply interval, whereby the target fuel supply interval is determined.   
   
   
       19 . The exhaust gas purification method according to  claim 13 , further comprising:
 detecting the catalyst temperature, wherein   the supplemental amount of the fuel per unit time is reduced when the detected catalyst temperature is equal to or higher than a preset value in order to adjust the supplemental amount of the fuel.   
   
   
       20 . The exhaust gas purification method according to  claim 19 , wherein
 a fuel injection amount per unit time is reduced by shortening the fuel supply interval, while the fuel supply duration per interval is reduced.