Exhaust gas purification system for an internal combustion engine

摘要

An engine exhaust gas purification system comprises an E.G.R. passage for the recirculation of engine exhaust gases from an exhaust system of an engine back into an intake system downstream of an engine throttle valve. A first E.G.R. control valve is provided in the E.G.R. passage and operatively connected to the throttle valve to control E.G.R. flow through the E.G.R. passage. A second E.G.R. control valve is provided in the E.G.R. passage upstream of the first E.G.R. control valve to control E.G.R. flow toward the first E.G.R. control valve. A valve controller is provided for the second E.G.R. control valve and operative in response to the variation in the pressure in the E.G.R. passage between the first and second E.G.R. control valves to control the second E.G.R. control valve so that the pressure is maintained substantially constant.