Combustion control apparatus for internal combustion engine

Abstract

A combustion control apparatus operates an internal combustion engine in a split retard combustion mode during regenerating an exhaust purifier such as a NOx trap. In the split retard combustion mode, the combustion control apparatus controls a first fuel injection to cause preliminary combustion at or near top dead center, and controls a second fuel injection to cause main combustion after an end of the preliminary combustion. In this manner, the combustion control apparatus controls an exhaust gas temperature, or an exhaust air-fuel ratio, without increasing exhaust smoke. During the split retard combustion mode, the combustion control apparatus controls the excess air ratio to vary the exhaust gas temperature, if there is a request for shifting the exhaust gas temperature. The combustion control apparatus adjusts the second fuel injection timing in accordance with the excess air ratio.

1 . A combustion control apparatus for an internal combustion engine, comprising: 
 a combustion controlling actuator for causing combustion in a combustion chamber of the engine;    a controller for controlling the combustion controlling actuator; and    the controller configured to perform the following: 
 switching a combustion mode between a normal combustion mode and a split retard combustion mode;  
 producing an increase request for an increase in an exhaust gas temperature of the engine, in accordance with an operating condition of the engine; and  
 performing the following in the normal combustion mode: 
 producing normal combustion to generate an output torque of the engine; and  
 
 performing the following in the split retard combustion mode in response to the increase request: 
 producing preliminary combustion at or near top dead center, to release a predetermined quantity of heat in the combustion chamber;  
 starting main combustion at a timing later than a start timing of the normal combustion in the normal combustion mode, after an end of the preliminary combustion, to generate the output torque of the engine; and  
 producing a shift request for shifting a target exhaust gas temperature, in accordance with the operating condition of the engine;  
 controlling an excess air ratio of the engine, to regulate the exhaust gas temperature in accordance with varying target exhaust gas temperature, in response to the shift request; and  
 adjusting the start timing of the main combustion in accordance with a change in the excess air ratio.  
 
   
   
   
       2 . A combustion control apparatus for an internal combustion engine, comprising: 
 a fuel injector for injecting fuel directly into a combustion chamber of the engine;    a controller for controlling the fuel injector; and    the controller configured to perform the following: 
 switching a combustion mode between a normal combustion mode and a split retard combustion mode, in accordance with an operating condition of the engine;  
 producing an increase request for an increase in an exhaust gas temperature of the engine, in accordance with an operating condition of the engine; and  
 performing the following in the normal combustion mode: 
 controlling a normal fuel injection to produce normal combustion to generate an output torque of the engine; and  
 
 performing the following in the split retard combustion mode in response to the increase request: 
 controlling a first fuel injection to produce preliminary combustion at or near top dead center, to release a predetermined quantity of heat;  
 starting a second fuel injection at a timing later than a start timing of the normal fuel injection in the normal combustion mode, to start main combustion after an end of the preliminary combustion, to generate the output torque of the engine;  
 determining a first target exhaust gas temperature and a second target exhaust gas temperature;  
 producing a shift request for shifting a target exhaust gas temperature from the first target exhaust gas temperature to the second target exhaust gas temperature when a predetermined condition is satisfied;  
 controlling an excess air ratio of the engine, to regulate the exhaust gas temperature from the first target exhaust gas temperature to the second target exhaust gas temperature, in response to the shift request; and  
 adjusting the timing of the second fuel injection, in accordance with a change in the excess air ratio.  
 
   
   
   
       3 . The combustion control apparatus as claimed in  claim 2 , further comprising a condition sensor for collecting information needed to determine the operating condition of the engine.  
   
   
       4 . The combustion control apparatus as claimed in  claim 3 , wherein: 
 the condition sensor senses the excess air ratio; and    the controller is configured to perform the following in the split retard combustion mode: 
 adjusting the timing of the second fuel injection in accordance with a change in the sensed excess air ratio.  
   
   
   
       5 . The combustion control apparatus as claimed in  claim 4 , wherein the controller is configured to perform the following, when the second target temperature is lower than the first target temperature: 
 increasing the excess air ratio to decrease the exhaust gas temperature from the first target temperature to the second target temperature; and    retarding the timing of the second fuel injection in accordance with an increase of the sensed excess air ratio.    
   
   
       6 . The combustion control apparatus as claimed in  claim 5 , wherein the controller is configured to retard the timing of the second fuel injection continuously in accordance with the increase in the sensed excess air ratio.  
   
   
       7 . The combustion control apparatus as claimed in  claim 4 , wherein the controller is configured to perform the following, when the second target temperature is higher than the first target temperature: 
 decreasing the excess air ratio to increase the exhaust gas temperature from the first target temperature to the second target temperature; and    advancing the timing of the second fuel injection in accordance with a decrease in the sensed excess air ratio.    
   
   
       8 . The combustion control apparatus as claimed in  claim 7 , wherein the controller is configured to advance the timing of the second fuel injection continuously in accordance with the decrease in the sensed excess air ratio.  
   
   
       9 . The combustion control apparatus as claimed in  claim 4 , further comprising an exhaust purifier in an exhaust gas passage of the engine, wherein the condition sensor senses information needed to determine the condition of the exhaust purifier; and the controller is configured to produce the increase request, in accordance with the condition of the exhaust purifier.  
   
   
       10 . The combustion control apparatus as claimed in  claim 9 , wherein the exhaust purifier includes at least one of a particulate filter and a NOx trap.  
   
   
       11 . The combustion control apparatus as claimed in  claim 9 , wherein the condition of the exhaust purifier includes a quantity of a substance trapped in the exhaust purifier.  
   
   
       12 . The combustion control apparatus as claimed in  claim 11 , wherein the trapped substance includes at least one of particulate matter and sulfur content.  
   
   
       13 . The combustion control apparatus as claimed in  claim 9 , wherein the exhaust purifier comprises a particulate filter; and the controller is configured to perform the following: 
 producing a regeneration request for removing particulate matter from the particulate filter, in accordance with the condition of the exhaust purifier; and    producing the increase request in response to the regeneration request.    
   
   
       14 . The combustion control apparatus as claimed in  claim 9 , wherein the exhaust purifier comprises a NOx trap; and the controller is configured to perform the following: 
 producing a regeneration request for removing sulfur content from the NOx trap, in accordance with the condition of the exhaust purifier; and    producing the increase request in response to the regeneration request.    
   
   
       15 . The combustion control apparatus as claimed in  claim 9 , wherein the exhaust purifier comprises a particulate filter and a NOx trap; and 
 the controller is configured to perform the following:    producing a first regeneration request for removing particulate matter from the particulate filter, in accordance with the condition of the exhaust purifier;    producing a second regeneration request for removing sulfur content from the NOx trap, in accordance with the condition of the exhaust purifier; and    producing the increase request in response to the first regeneration request and the second regeneration request.    
   
   
       16 . The combustion control apparatus as claimed in  claim 15 , wherein the predetermined condition is satisfied when both of the first regeneration request and the second regeneration request is present so that an operation of removing sulfur content from the NOx trap and an operation of removing particulate matter from the particulate filter are executed in succession.  
   
   
       17 . The combustion control apparatus as claimed in  claim 16 , wherein the controller is configured to determine an execution order of the operation of removing sulfur content from the NOx trap and the operation of removing particulate matter from the particulate filter, in accordance with the condition of the engine.  
   
   
       18 . A combustion control apparatus for an internal combustion engine, comprising: 
 combustion controlling means for causing combustion in a combustion chamber of the engine;    control means for controlling the combustion controlling means; and    the control means configured to perform the following: 
 switching a combustion mode between a normal combustion mode and a split retard combustion mode;  
 producing an increase request for an increase in an exhaust gas temperature of the engine, in accordance with an operating condition of the engine; and  
 performing the following in the normal combustion mode: 
 producing normal combustion to generate an output torque of the engine; and  
 
 performing the following in the split retard combustion mode in response to the increase request: 
 producing preliminary combustion at or near top dead center, to release a predetermined quantity of heat in the combustion chamber;  
 starting main combustion at a timing later than a start timing of the normal combustion in the normal combustion mode, after an end of the preliminary combustion, to generate the output torque of the engine; and  
 producing a shift request for shifting a target exhaust gas temperature, in accordance with the operating condition of the engine;  
 controlling an excess air ratio of the engine, to regulate the exhaust gas temperature in accordance with varying target exhaust gas temperature, in response to the shift request; and  
 adjusting the start timing of the main combustion in accordance with a change in the excess air ratio.  
 
   
   
   
       19 . A method of controlling combustion for an internal combustion engine, comprising: 
 switching a combustion mode between a normal combustion mode and a split retard combustion mode;    producing an increase request for an increase in an exhaust gas temperature of the engine, in accordance with an operating condition of the engine; and    performing the following in the normal combustion mode: 
 producing normal combustion to generate an output torque of the engine; and  
   performing the following in the split retard combustion mode in response to the increase request: 
 producing preliminary combustion at or near top dead center, to release a predetermined quantity of heat in the combustion chamber;  
 starting main combustion at a timing later than a start timing of the normal combustion in the normal combustion mode, after an end of the preliminary combustion, to generate the output torque of the engine; and  
 producing a shift request for shifting a target exhaust gas temperature, in accordance with the operating condition of the engine;  
 controlling an excess air ratio of the engine, to regulate the exhaust gas temperature in accordance with varying target exhaust gas temperature, in response to the shift request; and  
 adjusting the start timing of the main combustion in accordance with a change in the excess air ratio.