| 摘要 |
PURPOSE:To enable exhaust gas to be suitably recirculated by providing the first and second setting means for selective connection to an exhaust gas recirculation control valve through the opening and closing of an exhaust gas selector valve with a selector means as well as for setting the amount of recirculation exhaust gas at the time of opening and closing the exhaust gas selector valve. CONSTITUTION:An exhaust gas recirculation(EGR) operation zone is judged, according to the entry of an engine speed NE and an accelerator stepping opening Accp. Lines l1 to l5 show constant EGR rates when an exhaust gas selector valve 38 is closed. A maximum EGR rate of 20% is obtained in a zone below the line l1, and EGR stops in a zone above the line l5. When the exhaust gas selector valve 38 is closed in the EGR operation zone, constant EGR rate curves for the combination of an engine speed NE and the accelerator pedal opening Accp are shown by the lines l1 to l5, and the duty ratio of a drive signal for an electromagnetic valve 70 for EGR is so calculated and controlled as to obtain an EGR rate set with the aforesaid curves. When the exhaust gas selector valve 38 is judged to be open, the EGR rate calculates and controls the duty ratio of a drive signal for the electromagnetic valve 70, according to the lines l1 to l5. |
