Exhaust gas heating method

Abstract

A method according to the present invention of heating exhaust gas to be introduced into an exhaust gas purifying device from an internal combustion engine by heating and igniting fuel supplied into an exhaust passage from a fuel supply valve includes the steps of determining a necessity for supplying fuel into the exhaust passage, setting an amount of fuel to be supplied into the exhaust passage from the fuel supply valve, the amount being set when it is judged in the determining step that fuel needs to be supplied into the exhaust passage, checking an operating state of the engine, and controlling an air-fuel ratio of exhaust gas such that the air-fuel ratio falls within an area where amounts of both smoke and HC to be generated in the exhaust gas are low in the operating state of the engine checked in the checking step.

1 .- 8 . (canceled) 
     
     
         9 . A method of heating exhaust gas to be introduced into an exhaust gas purifying device from an internal combustion engine by supplying fuel into an exhaust passage from a fuel supply valve disposed upstream of the exhaust gas purifying device in an exhaust pipe upstream, and then by heating and igniting the fuel supplied into the exhaust passage, the method comprising steps of:
 determining a necessity for supplying fuel into the exhaust passage;   setting an amount of fuel to be supplied into the exhaust passage from the fuel supply valve, the amount being set when it is judged in the determining step that fuel needs to be supplied into the exhaust passage;   checking an operating state of the internal combustion engine; and   controlling an air-fuel ratio of exhaust gas to be released into the exhaust passage from a combustion chamber of the internal combustion engine such that the air-fuel ratio falls within an area where amounts of both smoke and HC to be generated in the exhaust gas flowing through the exhaust passage are low in the operating state of the internal combustion engine checked in the checking step.   
     
     
         10 . The method as claimed in  claim 9 , wherein the controlling step includes at least one of steps of:
 setting an amount of fuel to be injected into the combustion chamber of the internal combustion engine from a fuel injection valve such that an amount of oxygen to be released into the exhaust passage from the combustion chamber of the internal combustion engine is reduced;   setting an opening degree of a throttle valve; and   setting an opening degree of an EGR control valve.   
     
     
         11 . The method as claimed in  claim 10 , wherein the step of setting the fuel supply amount includes a step of correcting the fuel supply amount set in the step of setting the fuel supply amount by reducing the fuel supply amount in accordance with the fuel injection amount set in the step of setting the fuel injection amount. 
     
     
         12 . The method as claimed in  claim 10 , wherein
 the controlling step includes the step of setting the fuel injection amount,   the checking step includes a step of obtaining a temperature of the exhaust gas, and the method further comprising a step of   correcting the fuel injection amount set in the step of setting the fuel injection amount in accordance with the temperature of the exhaust gas obtained in the step of obtaining the temperature of the exhaust gas.   
     
     
         13 . The method as claimed in  claim 12 , wherein in the step of correcting the fuel injection amount, the fuel injection amount set in the step of the fuel injection amount is corrected by increasing the fuel injection amount during an operating state in which the temperature of the exhaust gas is high, while the fuel injection amount set in the step of setting the fuel injection amount is corrected by reducing the fuel injection amount during an operating state in which the temperature of the exhaust gas is low. 
     
     
         14 . The method as claimed in  claim 10 , wherein
 the controlling step includes the step of setting the fuel injection amount,   the checking step includes a step of obtaining an air-fuel ratio of the exhaust gas to be released into the exhaust passage from the combustion chamber of the internal combustion engine, and the method further comprising a step of   correcting the fuel injection amount set in the step of setting the fuel injection amount in accordance with the air-fuel ratio of the exhaust gas obtained in the step of obtaining the air-fuel ratio of the exhaust gas.   
     
     
         15 . The method as claimed in  claim 14 , wherein in the step of correcting the fuel injection amount, the fuel injection amount set in the step of setting the fuel injection amount is corrected by increasing the fuel injection amount when the air-fuel ratio of the exhaust gas is within a lean region, while the fuel injection amount set in the step of setting the fuel injection amount is corrected by reducing the fuel injection amount when the air-fuel ratio of the exhaust gas is within a rich region. 
     
     
         16 . The method as claimed in  claim 9 , wherein
 the exhaust gas purifying device includes a DPF, and   the step of setting the fuel injection amount includes a step of correcting the fuel injection amount set in the step of setting the fuel injection amount by reducing the fuel injection amount when it is judged that fuel needs to be supplied into the exhaust passage in the determining step during a regeneration process of the DPF.