| 摘要 |
PURPOSE:To prevent exhaust gas temperature from becoming high because of an air-fuel ratio transiently becoming the theoretical air fuel ratio in accordance with changeover of the air fuel ratio when rich air fuel ratio and lean air fuel ratio are changed over to each other in accordance with operation condition, in a high road operation range. CONSTITUTION:In an engine with a supercharger, rich air fuel ratio (A/F = about 13) is set in a high load low revolution speed range II (range in which supercharging ability is not exhibited sufficiently) and lean air fuel ratio (A/F = about 16) is set in a high road high revolution speed range III. Although a supercharger 32 slowly starts to exhibit its supercharging ability following a rise of engine revolution speed when a full open acceleration (a throttle valve is in a full open condition) is active, EGR is started by utilizing remaining power of intake air prior to shift of operation condition to that in the range III from that in the range II. As this EGR gas is cooled in an EGR cooler 72, exhaust gas temperature is lowered, and a shift of a temperaturize to a level of the exhaust gas temperature following the changeover to lean air fuel ratio is suppressed thereafter. |
