Multi-stage exhaust gas recirculation system
AssigneeFord Motor Company
InventorsDaniel C. Ahrns, Shane H. Rachedi
Life of this patent
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Abstract
An automotive type exhaust gas recirculation (EGR) system has two modes of operation, a first one that regulates EGR flow at a constant percentage rate as a function of throttle valve position independently of exhaust gas backpressure changes, and a second one that provides a variable percentage rate of flow of EGR gases in response to changes in exhaust gas backpressures, both modes utilizing carburetor ported vacuum modified by an air bleed device as the EGR valve opening force.
Claims7
A two-stage exhaust gas recirculation (EGR) system for use with an engine having intake and exhaust manifolds, including, an EGR passage connecting the manifolds for recirculating a portion of the exhaust gases into the engine, an air/fuel induction passage having a throttle valve variable movable across the induction passage to control flow therethrough, the induction passage having a pressure sensing port upstream of the edge of the throttle valve in its closed position to expose the port to essentially atmospheric pressure when the throttle valve is closed and progressively to the level of the manifold vacuum as the valve is opened, a spring closed EGR valve movably mounted in the EGR passage, an engine vacuum controlled first servo connected to the pressure sensing port and to the EGR valve to open the same in response to opening movements of the throttle valve, and an air bleed pressure regulating device in the connection between the first servo and port to regulate the level of vacuum applied to the servo,
- the air bleed device including an air vent and a spring opened bleed valve movably associated with the vent to control communication of air to the same, and second multi-stage servo means operably connected to the bleed valve to regulate movement of the same, the second servo means including first pressure responsive means connected to the bleed valve and responsive to the level of pressure in a constant pressure control chamber defined between the EGR valve and a flow restricting orifice located upstream of the EGR valve to constitute a first pressure regulating stage of movement of the bleed valve and EGR valve below predetermined exhaust manifold pressure levels, and second means movable in response to the pressure of the gases in the exhaust manifold acting thereon above the predetermined exhaust backpressure level to vary the movement of the bleed valve in a second regulatory stage of movement to provide a second regulatory movement of the EGR valve at a rate different than that of the first stage.
Dependencies are inferred from the claim text.