Exhaust gas recirculation system for internal combustion engine

Claim 1

In an internal combustion engine having an intake passage for delivering an air-fuel mixture into the engine, the intake passage having a throttle valve and having a Venturi portion, the combination of: an exhaust passage for carrying exhaust gases from the engine, means including a passageway connecting said exhaust passage to said intake passage downstream from said throttle valve for recirculating exhaust gases into the engine, a first control valve in said passageway, an air conduit connecting said intake passage to atmosphere, a second control valve in said air conduit, each of said control valves having a vacuum-responsive actuator, an electrically operated valve for venting to atmosphere the actuator for the first control valve, means responsive to an engine operating condition for actuating said electrically operated valve, and a regulating valve for controlling vacuum intensity in the actuator for each said control valve, said regulating valve being responsive to differential vacuum pressure between vacuum pressure in said Venturi portion and vacuum pressure in said air conduit.