Device for purifying exhaust gas discharged from internal combustion engine

摘要

Disclosed is an improvement of an exhaust gas purifying device for use with an internal combustion engine incorporating both an exhaust gas recirculation system and a secondary air supply system, the improvement comprising variable restriction means disposed in an exhaust pipe downstream of an exhaust gas intake port of the exhaust gas recirculation system for varying the flow cross sectional area of the exhaust pipe and control means responsive to the difference between the signal representative of the volume of exhaust gas and the signal representative of the volume of intake air for controlling the variable restriction means in such a way that the former signal may be proportional to the latter signal, whereby the volume of exhaust gas to be recirculated may be made optimumly proportional to the volume of intake air independently of the variation in rotational speed and load of the engine.