Exhaust gas recirculation control device

An exhaust gas recirculation control device for use in an internal combustion engine having an intake manifold, an exhaust pipe and an exhaust gas recirculation pipe connecting said intake manifold to said exhaust pipe, said control device being operatively connected to said recirculation pipe and comprising:

• an exhaust gas flow restrictor in said recirculation pipe;
• an exhaust gas flow control valve mounted downstream of said restrictor;
• a pressure responsive membrane arranged to communicate with said recirculation pipe between said restrictor and said flow control valve to respond to pressure generated therebetween;
• a housing divides into a first chamber having an air bleed hole and a second chamber by a wall having a valve seat;
• a valve normally seated on said valve seat to block communication between the first and second chambers, and fixedly connected to said pressure responsive membrane, said valve being biased by a spring, the stiffness of said spring being selected such that when a predetermined pressure is reached to act on said pressure responsive membrane, said spring yields and said valve begins to open, and when the pressure acting on said pressure responsive membrane gradually increases above and beyond said predetermined pressure, the degree of opening of said valve is gradually increased;
• a diaphragm having a hole, disposed within the first chamber and dividing the first chamber into an atmospheric chamber communicating with the atmosphere through the air bleed hole and a vacuum chamber communicating with said atmospheric chamber through the hole, said diaphragm being engaged with said valve, said diaphragm preventing transmission of oscillations in the level of intake manifold vacuum to a vacuum responsive membrane and said flow control valve by dampening said oscillations;
• a said vacuum responsive membrane communicated with said vacuum chamber of said first chamber and linked with said flow control valve;
• the arrangement being such that when said predetermined pressure and pressures above and beyond said predetermined pressure act on said pressure responsive membrane, said valve leaves said valve seat causing intake manifold vacuum to communicate through said valve with said vacuum chamber of said first chamber and said air bleed hole and when air sucked through said air bleed hole reaches a predetermined maximum flow level, said intake manifold vacuum acts on said vacuum responsive membrane to open said flow control valve in dependence on the pressure level acting on said pressure responsive membrane.