To provide an operation control method for an internal combustion engine that ensures stabilized combustion during operations under light loads.
In an internal combustion engine using EGR, an EGR rate is set to a minimum or zero during operations under light loads. EGR is performed after the temperature is decreased by a heat exchanger. Any loads under a predetermined level are set as a light load operating range. Thermal efficiency is set to any desired value by operating an air excess ratio and the EGR rate. In addition, when a NOX occlusion catalyst is provided in an exhaust passageway, the EGR rate is zeroed so as to increase an exhaust temperature, thereby promoting regeneration of the NOX occlusion catalyst. When a rich spike is executed, the EGR rate is set to minimum or zero.
NAKAZONO TORU
MATSUBAYASHI SHOGO
