Method of controlling operation of internal combustion engine

摘要

In an internal combustion engine utilizing an exhaust gas recirculation, an exhaust gas recirculation rate is set to a minimum or zero at a small engine load. The exhaust gas recirculation is carried out after lowering an exhaust gas temperature by a heat exchanger. An engine load smaller than a specified value is set to a small engine load operation region. A thermal efficiency is set to a desired value by controlling an excess air ratio and the exhaust gas recirculation rate. Further, when a NOx absorbing catalyst is installed in an exhaust gas passage, the exhaust gas temperature is raised by setting the exhaust gas recirculation rate to zero and regeneration of the NOx absorbing catalyst is accelerated. The exhaust gas recirculation rate is set to a minimum or zero at time of carrying out a rich spike work.