Controller and control method for homogeneous charge compression ignition engine

A controller for a homogeneous charge compression ignition engine allowing a combustion operation of self-igniting, by a compression of a piston, a high-excess air ratio mixture, which being a mixture formed in a combustion chamber and having a mixture ratio of air and fuel of three times or more as large as a stoichiometric mixture ratio (having an excess air ratio of 3 or larger), the controller comprising:

• an ion-current detection section for detecting ions generated by combustion in the combustion chamber as an ion current;
• a combustion-timing detection section for detecting a timing at which the ion current becomes maximum;
• and
• a correction factor computing section for executing combustion control with the excess air ratio smaller than approximately 3 when a predetermined condition is satisfied and for computing a correction factor for correcting deviations between execution values of valve-opening timings and valve-opening periods of an intake valve and an exhaust valve and basic valve-opening timings and basic valve-opening periods of the intake valve and the exhaust valve which are previously determined for each operation condition, based on the timing at which the ion current becomes maximum detected by the combustion-timing detection section, in the combustion control with the excess air ratio smaller than approximately 3.