Exhaust gas recirculation for engine

摘要

An exhaust gas recirculation system for an internal combustion engine employs an exhaust gas recirculation control valve in a passageway connecting the engine exhaust passage to the engine intake passage downstream from the throttle valve. The intake passage also provides a choke valve and a carburetor venturi section between the valves. An air conduit having an air control valve therein connects the intake passage between the throttle valve and the choke valve to the intake passage downstream from the throttle valve. Vacuum responsive actuators are provided for each of the control valves and they are operated by vacuum pressure regulated by a regulating valve, which is itself responsive to differential pressure between vacuum intensity in the intake passage upstream from said throttle valve and modified atmospheric pressure. The modified atmospheric pressure is obtained downstream of a restriction in the air conduit. Closing of the choke valve on a cold start of the engine causes high vacuum intake to the air conduit, reducing the exhaust gas recirculation through the exhaust gas recirculation control valve.