Transition Strategy for Engine Operation with Spark Ignition and Homogeneous Charge Compression Ignition Modes

Abstract

A method of operating an internal combustion engine having a combustion chamber with a piston and a spark plug, when transitioning between spark ignition combustion and autoignition combustion, creating a first mixture of air and fuel, adjusting an operating condition of the engine so that said first mixture of air and fuel in the combustion chamber approaches, but does not achieve, the autoignition temperature, and performing a spark from the spark plug so that at least a portion of said first mixture combusts to raise a remaining portion of said first mixture to said autoignition temperature.

1 . A method of operating an internal combustion engine having a combustion chamber with a piston and a spark plug, comprising: 
 when transitioning between spark ignition combustion and autoignition combustion, creating a first mixture of air and fuel, adjusting an operating condition of the engine so that said first mixture of air and fuel in the combustion chamber approaches, but does not achieve, the autoignition temperature, and performing a spark from the spark plug so that at least a portion of said first mixture combusts to raise a remaining portion of said first mixture to said autoignition temperature;    during said transition, performing an injection during a compression stroke so that a second stratified mixture of air and fuel is formed;    and performing a spark from the spark plug so that the second mixture combusts.    
   
   
       2 . The method of  claim 1  wherein said spark for said first mixture is performed after top dead center of piston position.  
   
   
       3 . The method of  claim 1  wherein said first mixture is created by performing a first injection during an intake stroke so that a lean homogeneous air and fuel region is created, performing a second injection during a compression stroke so that a less lean homogeneous air and fuel region is created substantially near the spark plug.  
   
   
       4 . A method of operating an internal combustion engine having a combustion chamber with a piston and a spark plug, comprising: 
 when transitioning between spark ignition combustion and autoignition combustion, creating a first mixture of air and fuel, adjusting an operating condition of the engine so that said first mixture of air and fuel in the combustion chamber approaches, but does not achieve, the autoignition temperature; wherein said first mixture is created by performing a first injection during an intake stroke so that a lean homogeneous air and fuel region is created, and performing a second injection during a compression stroke so that a less lean homogeneous air and fuel region is created substantially near the spark plug.    
   
   
       5 . The method of  claim 4  further comprising, during said transition, performing an injection during a compression stroke so that a second stratified mixture of air and fuel is formed; and performing a spark from the spark plug so that the second mixture combusts.  
   
   
       6 . The method of  claim 4  wherein said spark for said first mixture is performed after top dead center of piston position.