| 摘要 |
In the present invention, by means of injecting additional fuel into a cylinder during an expansion stroke or an exhaust stroke in the state of a throttle aperture being switched from a base throttle aperture to a rich control throttle aperture and an EGR rate being switched from a base EGR rate to a rich control EGR rate, rich control is performed that temporarily lowers the air-fuel ratio of exhaust gas discharged from an engine combustion chamber. When starting rich control, first the low-pressure-side EGR control valve aperture (VEGRL) is switched to a low-pressure-side EGR control valve aperture (VEGRLR) for rich control. Next, the high-pressure-side EGR control valve aperture (VEGRH) is switched to a high-pressure-side EGR control valve aperture (VEGRHR) for rich control. Next, the throttle aperture (VTH) is controlled, and then the injection of additional fuel (Qa) is started. |
