Exhaust gas recirculation mechanism for engine and method for controlling exhaust gas recirculation valve

摘要

An exhaust gas recirculation (EGR) mechanism of an engine. Some of exhaust gas discharged from combustion chambers (5) is recirculated to the combustion chambers (5) through an EGR passage (29a). An EGR valve (29) is located in the EGR passage (29a) for adjusting the amount of recirculated exhaust gas. Foreign matter contained in exhaust gas in the EGR passage (29a) adheres to a valve shaft (56a) of the EGR valve (29) that is exposed in the EGR passage (29a). Normally, the opening amount of the EGR valve (29) is controlled in accordance with the running state of the engine. If the opening amount of the EGR valve (29), which is determined based on the running state of the engine, is greater than a predetermined value, an ECU (30) judges that the EGR ratio will fall within an acceptable range even if the EGR valve (29) is fully opened from the current position. The ECU (30) therefore forces the EGR valve (29) to open fully. As a result, the foreign matter adhered to the valve shaft (56a) is removed without deteriorating the running condition of the engine.