Patent ID: 7128048

Claim:
A control apparatus for a multi-cylinder engine capable of performing compression ignition combustion, or selecting either the compression ignition combustion or spark ignition combustion, comprising: a cylinder-specific combustion state estimating means for estimating a combustion state for each cylinder; and a combustion state control means for controlling the combustion state for each cylinder; wherein the combustion state control means controls, during an engine operation in a compression ignition combustion mode, the combustion state for each cylinder based on the combustion state estimated by the cylinder-specific combustion state estimating means during the engine operation in the compression ignition combustion mode, wherein the combustion state control means controls at least one of a variable valve mechanism that varies an amount of internal EGR by changing at least one of the valve timing and an amount of valve lift of an intake valve and an exhaust valve, a fuel injection mechanism that directly or indirectly injects fuel into a combustion chamber of the multi-cylinder engine, and a transmission that transmits output shaft torque of the multi-cylinder engine to a power train mechanism of a vehicle through adjusting a gear ratio, and the combustion state control means controls the transmission so as to change the gear ratio, thereby decreasing an engine speed when it is estimated that the peak value of cylinder pressure of at least one of the plurality of cylinders is lower than a predetermined value, or the peak timing of cylinder pressure is retarded in relation to predetermined timing, based on the estimation made by the cylinder-specific combustion state estimating means.