Venturi vacuum responsive exhaust gas recirculation control system

Claim 1

In an internal combustion engine having an intake manifold having an exhaust crossover passage through which exhaust gases flow, an exhaust gas recirculation passage fluidly connecting the intake manifold and the exhaust crossover passage, a carburetor fluidly connected with the intake manifold, said carburetor having a venturi section with a vacuum signal proportional to engine air consumption and a throttle bore with a varying vacuum signal having a movable throttle plate; an exhaust gas recirculation control system, comprising: a first valve in the recirculation passage, said first valve including a first valve member movable between a maximum opening and a minimum opening with respect to said recirculation passage to restrict flow of exhaust gases therethrough; a first vacuum motor having a first diaphragm means defining a first vacuum chamber; means connecting said first valve member to said first diaphragm means for moving the former between said minimum and maximum openings in accordance with applied vacuum in said first vacuum chamber; first conduit means fluidly connecting the throttle bore with said first vacuum chamber; a second valve associated with said first conduit means, said second valve movable between a first position for admitting air into said first conduit means to reduce the vacuum therein and movable to a second position for preventing the flow of air to said first conduit means, said second valve being biased to said first position by the pressure differential thereacross between atmosphere and vacuum in said first conduit means; a second vacuum motor having second diaphragm means defining a second vacuum chamber; output means connected to said second diaphragm means; second conduit means fluidly connecting the venturi section with said second vacuum chamber whereby said output means moves in accordance with vacuum conditions at said venturi section; yieldable means connecting said output means and said second valve for biasing the latter against the pressure differential in accordance with applied vacuum at said second vacuum chamber, the arrangement being such that the greatest air flow past said second valve is at the lowest applied vacuum in said second vacuum chamber and the applied vacuum in said first vacuum chamber is lowest sucH that said first valve moves to said minimum opening position, said venturi vacuum signal increasing and said throttle bore signal decreasing upon increasing throttle plate opening whereby the pressure differential decreases and the applied vacuum at said second vacuum chamber increases such that said air flow past said second valve is reduced and the vacuum at said first vacuum chamber increases thereby causing said first valve to move to said maximum opening position at an opening rate proportional to engine air consumption.