Controller for internal combustion engine

Abstract

To provide a controller that can slow down progression of deterioration of an internal combustion engine caused by repeated occurrence of LSPI. An index value of the degree of deterioration of the internal combustion engine caused by LSPI is calculated. If the index value exceeds a first threshold, when the temperature of cooling water that cools a part of the peripheral wall of a cylinder that is close to a combustion chamber is lower than a threshold temperature, and the internal combustion engine is running in a determined operational region set in a low speed and high load region, the proportion of fuel injection by an in-cylinder injection valve is reduced to increase the proportion of fuel injection by a port injection valve compared with before the index value exceeds the first threshold, thereby suppressing occurrence of LSPI.

What is claimed is: 
     
         1 . A controller for an internal combustion engine, the internal combustion engine comprising:
 an in-cylinder injection valve that directly injects fuel into a combustion chamber formed in an upper part of a cylinder;   a port injection valve that injects the fuel into an intake port;   a first cooling water flow channel used to cool a part of a peripheral wall of the cylinder; and   a second cooling water flow channel used to cool, with second cooling water, the intake port or a part of the peripheral wall of the cylinder that is closer to the combustion chamber than the part cooled by the first cooling water flow channel, the second cooling water flowing in the second cooling water flow channel being at a lower temperature than first cooling water flowing in the first cooling water flow channel,   wherein the controller is configured
 to calculate an index value of a degree of deterioration of the internal combustion engine caused by LSPI; and 
 to reduce a proportion of fuel injection by the in-cylinder injection valve to increase a proportion of fuel injection by the port injection valve compared with before the index value exceeds the first threshold, wherein if the index value exceeds a first threshold, when the temperature of the second cooling water is lower than a threshold temperature, and the internal combustion engine is running in a determined operational region set in a low speed and high load region. 
   
     
     
         2 . The controller for an internal combustion engine according to  claim 1 , further configured, wherein if the index value exceeds a second threshold that is greater than the first threshold, when the internal combustion engine is running in the determined operational region, to increase the temperature of the second cooling water compared with before the index value exceeds the second threshold.