| 摘要 |
PURPOSE:To attain recirculation of exhaust gas by an amount which is considered optimum, in various operating conditions of an engine. CONSTITUTION:A variable displacement turbocharger 81 is used as the turbocharger, and exhaust gas, taken out from an inlet side of this turbine 71, is recirculated through an exhaust gas recirculating pipe 13. In an exhaust pressure in the turbine inlet side, since an opening of a movable nozzle of the variable displacement turbocharger can be controlled by a step motor 23, a relation of exhaust pressure> boost pressure for enabling exhaust gas to recirculate can be easily obtained. A recirculating amount control valve 20 in the exhaust gas recirculating pipe 13 controls a recirculated exhaust gas amount so as to obtain an suitable value without worsening combustion of an engine. An exhaust pressure and boost pressure, in the case of excessive rising thereof to a hazardous degree, are decreased by opening an exhaust waste valve 21 in an exhaust waste pipe 22. |
