To provide an internal combustion engine controller capable of making an occluded oxygen amount of a catalyst rapidly approach an appropriate value by decreasing a mechanical compression ratio to promptly raise a catalyst temperature after the end of a fuel cutting (FC) operation only when the catalyst temperature is lowered during the fuel cutting (FC) operation.
The controller is applied to an engine equipped with a compression ratio varying mechanism for varying the mechanical compression ratio and a catalyst in an exhaust passage. The controller determines a basic target mechanical compression ratio mtgtb at a normal operation depending on the operational state of the engine (step 710). When the catalyst temperature has reached a temperature below, e.g., a given temperature during the fuel cutting operation, a compression ratio drop flag XD is set at "1". When the flag is set to "1", the controller sets, as "a final target mechanical compression ratio mtgt", "a compression ratio created by decreasing "the basic target mechanical compression ratio mtgtb" by a given mechanical compression ratio B (steps 720, 750 or 770).
CHIBA FUMITO
NAKASAKA YUKIHIRO
KUROKI RENTARO
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