Patent ID: 8812214

Claim:
A control device for an internal combustion engine that can be operated with a different air-fuel ratio at each of a plurality of cylinder groups, and is configured to control quantities of air that is taken into respective cylinders of the plurality of cylinder groups with one throttle, comprising: request torque acquiring means for acquiring request torque to the internal combustion engine; request air-fuel ratio acquiring means for acquiring a request air-fuel ratio to each of the plurality of cylinder groups; reference air-fuel ratio setting means for setting a reference air-fuel ratio within a range from the leanest air-fuel ratio to the richest air-fuel ratio out of the request air-fuel ratios to the respective cylinder groups; target air quantity calculating means for calculating a target air quantity for realizing the request torque under the reference air-fuel ratio, based on data that defines a relation between torque generated by the internal combustion engine and an air quantity in relation to an air-fuel ratio; throttle opening control means for controlling an opening of the throttle in accordance with the target air quantity; fuel injection amount control means for controlling fuel injection amounts of the respective cylinders in accordance with the request air-fuel ratios to the respective cylinder groups; estimated torque calculating means for calculating an estimated torque, which is a torque estimated to be achieved under an optimum ignition timing, based on an estimated air quantity calculated from a current opening of the throttle and the reference air-fuel ratio; ignition timing controlling efficiency calculating means for calculating an ignition timing controlling efficiency, which is a ratio of the request torque to the estimated torque; combustion limit guard means for specifying a combustion limit efficiency corresponding to the reference air-fuel ratio, based on a data which defines for every air-fuel ratio a minimum efficiency with which suitable combustion is secured, and limiting a minimum value of the ignition timing controlling efficiency with the combustion limit efficiency as a guard value; and ignition timing control means for calculating a retard amount with respect to the optimal ignition timing from the ignition timing controlling efficiency, and controlling ignition timing of the respective cylinders in accordance with the retard amount.