Method for heating exhaust

Abstract

A method according to the present invention heats exhaust introduced to an exhaust emission purifier by injecting fuel into an exhaust passage through a fuel addition valve toward a heat generating portion of a glow plug disposed in the exhaust passage located upstream of the exhaust emission purifier, and then igniting the fuel. In the method, a rate of the fuel injected through the fuel addition valve which directly contacts the heat generating portion is set to between 8% and 55%.

1 . A method for heating exhaust introduced to an exhaust emission purifier by injecting fuel into an exhaust passage through a fuel addition valve toward a heat generating portion of an ignition device disposed in the exhaust passage located upstream of the exhaust emission purifier, and then igniting the fuel, the method comprising:
 setting a rate of the fuel injected through the fuel addition valve which directly contacts the heat generating portion to between 8% and 55%.   
     
     
         2 . The method for heating exhaust as claimed in  claim 1 , wherein an amount of fuel injected, during a single injection operation, through the fuel addition valve when the fuel is intermittently injected into the exhaust passage, is set to between 10 mm 3  and 75 mm 3 . 
     
     
         3 . The method for heating exhaust as claimed in  claim 2 , wherein duration of injection through the fuel addition valve during a single injection operation is set to between 1.5 ms and 15 ms. 
     
     
         4 . The method for heating exhaust as claimed in  claim 1 , wherein an amount of fuel injected through the fuel addition valve per unit time is set to between 80 cc and 1,000 cc per minute. 
     
     
         5 . The method for heating exhaust as claimed in  claim 1 , wherein the fuel injected through the fuel addition valve diffuses in conical form, and an area of the heat generating portion which overlaps the conical fuel injection region projected on a plane perpendicular to a center axis of the fuel injection region and containing an axis of the heat generating portion is set to between 8% and 55% of an area of the fuel injection region. 
     
     
         6 . The method for heating exhaust as claimed in  claim 1 , wherein the fuel injected though the fuel injection valve is light oil or biofuel. 
     
     
         7 . The method for heating exhaust as claimed in  claim 1 , wherein the heat generating portion of the ignition device is heated and the fuel is injected into the exhaust passage through the fuel addition valve only if exhaust flowing through the exhaust passage has a flow rate of 50 grams per second or less. 
     
     
         8 . The method for heating exhaust as claimed in  claim 5 , wherein the heat generating portion of the ignition device is heated and the fuel is injected into the exhaust passage through the fuel addition valve only if exhaust flowing through the exhaust passage has a flow rate of 50 grams per second or less.