Exhaust Gas Purification System for Internal Combustion Engine

Abstract

It is an object of the present invention to suppress NOx emissions while also suppressing an increase in unburned fuel emission and accidental fire in an exhaust gas purification system for an internal combustion engine that has a super charger and an EGR apparatus, when the internal combustion engine is in a transient operating state. In the present invention, a target charging pressure and a target EGR gas amount are calculated based on the operating state of the internal combustion engine. If the actual charging pressure has not reached the target charging pressure when the internal combustion is operating in a transient state, then the EGR gas amount is controlled to an amount smaller than the target EGR gas amount.

1 . An exhaust gas purification system for an internal combustion engine, characterized by comprising:
 an EGR apparatus for introducing at least part of the exhaust gas of said internal combustion engine as EGR gas into an air intake system of said internal combustion engine;   a supercharger for supercharging intake air using energy from the exhaust gas of said internal combustion engine;   EGR gas amount control unit for controlling the EGR gas amount introduced into said air intake system of said internal combustion engine by said EGR apparatus;   target EGR gas amount calculation unit for calculating a target EGR gas amount that is a target value of the EGR gas amount, based on the operating state of said internal combustion engine;   target charging pressure calculation unit for calculating a target charging pressure that is a target value of the charging pressure, based on the operating state of said internal combustion engine; and   charging pressure detection unit for detecting the actual charging pressure, wherein   if the actual charging pressure detected by said charging pressure detection unit is lower than the target charging pressure when said internal combustion engine is in a transient operating state, said EGR gas amount control unit controls the EGR gas amount to an amount smaller than the target EGR gas amount.   
   
   
       2 . The exhaust gas purification system for an internal combustion engine according to  claim 1 , when the EGR gas amount is controlled to an amount smaller than the target EGR gas amount, said EGR gas amount control unit controls the EGR gas amount such that the lower the actual charging pressure, the smaller the EGR gas amount. 
   
   
       3 . The exhaust gas purification system for an internal combustion engine according to  claim 2 , further comprising:
 a fuel injection valve for directly injecting fuel into a cylinder of said internal combustion engine;   sub fuel injection execution unit for performing a sub fuel injection at a timing ahead of a main fuel injection that is performed by said fuel injection valve at a timing near top dead center in a compression stroke;   sub fuel injection timing control unit for controlling an execution timing of the sub fuel injection is performed by said sub fuel injection execution unit; and   target sub fuel injection timing calculation unit for calculating a target sub fuel injection timing that is a target value of the execution timing of the sub fuel injection, based on the operating state of said internal combustion engine, wherein   if the actual charging pressure detected by said charging pressure detection unit is lower than the target charging pressure when said internal combustion engine is in a transient operating state, said sub fuel injection timing control unit delays the execution timing of the sub fuel injection more than the target sub fuel injection timing.   
   
   
       4 . The exhaust gas purification system for an internal combustion engine according to  claim 3 , wherein when the execution timing of the sub fuel injection is delayed more than the target sub fuel injection timing, said sub fuel injection timing control unit controls the execution timing of the sub fuel injection such that the lower the actual charging pressure, the more delayed the execution timing of the sub fuel injection. 
   
   
       5 . The exhaust gas purification system for an internal combustion engine according to  claim 4 , further comprising:
 sub fuel injection amount control unit for controlling the sub fuel injection amount; and   target sub fuel injection amount calculation unit for calculating a target sub fuel injection amount that is a target value of the sub fuel injection amount, based on the operating state of said internal combustion engine, wherein   if the execution timing of the sub fuel injection is delayed more than the target sub fuel injection timing, said sub fuel injection amount control unit controls the sub fuel injection amount to an amount smaller than the target sub fuel injection amount.   
   
   
       6 . The exhaust gas purification system for an internal combustion engine according to  claim 5 , wherein when the sub fuel injection amount is controlled to an amount smaller than the target sub fuel injection amount, said sub fuel injection amount control unit controls the sub fuel injection amount such that the more delayed the execution timing of the sub fuel injection, the smaller the sub fuel injection amount. 
   
   
       7 - 10 . (canceled) 
   
   
       11 . The exhaust gas purification system for an internal combustion engine according to  claim 3 , further comprising:
 sub fuel injection amount control unit for controlling the sub fuel injection amount; and   target sub fuel injection amount calculation unit for calculating a target sub fuel injection amount that is a target value of the sub fuel injection amount, based on the operating state of said internal combustion engine, wherein   if the execution timing of the sub fuel injection is delayed more than the target sub fuel injection timing, said sub fuel injection amount control unit controls the sub fuel injection amount to an amount smaller than the target sub fuel injection amount.   
   
   
       12 . The exhaust gas purification system for an internal combustion engine according to  claim 11 , wherein when the sub fuel injection amount is controlled to an amount smaller than the target sub fuel injection amount, said sub fuel injection amount control unit controls the sub fuel injection amount such that the more delayed the execution timing of the sub fuel injection, the smaller the sub fuel injection amount. 
   
   
       13 . The exhaust gas purification system for an internal combustion engine according to  claim 1 , further comprising:
 a fuel injection valve for directly injecting fuel into a cylinder of said internal combustion engine;   sub fuel injection execution unit for performing a sub fuel injection at a timing ahead of a main fuel injection that is performed by said fuel injection valve at a timing near top dead center in a compression stroke;   sub fuel injection timing control unit for controlling an execution timing of the sub fuel injection is performed by said sub fuel injection execution unit; and   target sub fuel injection timing calculation unit for calculating a target sub fuel injection timing that is a target value of the execution timing of the sub fuel injection, based on the operating state of said internal combustion engine, wherein   if the actual charging pressure detected by said charging pressure detection unit is lower than the target charging pressure when said internal combustion engine is in a transient operating state, said sub fuel injection timing control unit delays the execution timing of the sub fuel injection more than the target sub fuel injection timing.   
   
   
       14 . The exhaust gas purification system for an internal combustion engine according to  claim 13 , wherein when the execution timing of the sub fuel injection is delayed more than the target sub fuel injection timing, said sub fuel injection timing control unit controls the execution timing of the sub fuel injection such that the lower the actual charging pressure, the more delayed the execution timing of the sub fuel injection. 
   
   
       15 . The exhaust gas purification system for an internal combustion engine according to  claim 14 , further comprising:
 sub fuel injection amount control unit for controlling the sub fuel injection amount; and   target sub fuel injection amount calculation unit for calculating a target sub fuel injection amount that is a target value of the sub fuel injection amount, based on the operating state of said internal combustion engine, wherein   if the execution timing of the sub fuel injection is delayed more than the target sub fuel injection timing, said sub fuel injection amount control unit controls the sub fuel injection amount to an amount smaller than the target sub fuel injection amount.   
   
   
       16 . The exhaust gas purification system for an internal combustion engine according to  claim 15 , wherein when the sub fuel injection amount is controlled to an amount smaller than the target sub fuel injection amount, said sub fuel injection amount control unit controls the sub fuel injection amount such that the more delayed the execution timing of the sub fuel injection, the smaller the sub fuel injection amount. 
   
   
       17 . The exhaust gas purification system for an internal combustion engine according to  claim 13 , further comprising:
 sub fuel injection amount control unit for controlling the sub fuel injection amount; and   target sub fuel injection amount calculation unit for calculating a target sub fuel injection amount that is a target value of the sub fuel injection amount, based on the operating state of said internal combustion engine, wherein   if the execution timing of the sub fuel injection is delayed more than the target sub fuel injection timing, said sub fuel injection amount control unit controls the sub fuel injection amount to an amount smaller than the target sub fuel injection amount.   
   
   
       18 . The exhaust gas purification system for an internal combustion engine according to  claim 17 , wherein when the sub fuel injection amount is controlled to an amount smaller than the target sub fuel injection amount, said sub fuel injection amount control unit controls the sub fuel injection amount such that the more delayed the execution timing of the sub fuel injection, the smaller the sub fuel injection amount. 
   
   
       19 . The exhaust gas purification system for an internal combustion engine according to  claim 1 , wherein if the actual charging pressure detected by said charging pressure detection unit is higher than the target charging pressure when said internal combustion engine is in a transient operating state, said EGR gas amount control unit controls the EGR gas amount to an amount larger than the target EGR gas amount. 
   
   
       20 . The exhaust gas purification system for an internal combustion engine according to  claim 19 , wherein when the EGR gas amount is controlled to an amount larger than the target EGR gas amount, said EGR gas amount control unit controls the EGR gas amount such that the higher the actual charging pressure, the larger the EGR gas amount. 
   
   
       21 . The exhaust gas purification system for an internal combustion engine according to  claim 20 , further comprising:
 a fuel injection valve for directly injecting fuel into a cylinder of said internal combustion engine;   fuel injection timing control unit for controlling a fuel injection timing by said fuel injection valve; and   target fuel injection timing calculation unit for calculating a target fuel injection timing that is a target value of the fuel injection timing, based on the operating state of said internal combustion engine, wherein   if the EGR gas amount is controlled to an amount larger than the target EGR gas amount, said fuel injection timing control unit delays the fuel injection timing more than the target fuel injection timing.   
   
   
       22 . The exhaust gas purification system for an internal combustion engine according to  claim 21 , wherein when the fuel injection timing is delayed more than the target fuel injection timing, said fuel injection timing control unit controls the fuel injection timing such that the larger the EGR gas amount, the more delayed the fuel injection timing. 
   
   
       23 . The exhaust gas purification system for an internal combustion engine according to  claim 19 , further comprising:
 a fuel injection valve for directly injecting fuel into a cylinder of said internal combustion engine;   fuel injection timing control unit for controlling a fuel injection timing by said fuel injection valve; and   target fuel injection timing calculation unit for calculating a target fuel injection timing that is a target value of the fuel injection timing, based on the operating state of said internal combustion engine, wherein   if the EGR gas amount is controlled to an amount larger than the target EGR gas amount, said fuel injection timing control unit delays the fuel injection timing more than the target fuel injection timing.   
   
   
       24 . The exhaust gas purification system for an internal combustion engine according to  claim 23 , wherein when the fuel injection timing is delayed more than the target fuel injection timing, said fuel injection timing control unit controls the fuel injection timing such that the larger the EGR gas amount, the more delayed the fuel injection timing.