Engine emission control system

Claim 1

An emission control system for an internal combustion engine having intake and exhaust manifolding, a carburetor mounted on the engine and having a throttle valve controlled air/fuel mixture induction passage, the passage being open at one end to air essentially at atmospheric pressure and connected at its opposite end to the engine intake manifold, a pressure sensing port in the passage adapted to be traversed by the edge of the throttle valve as the valve moves from an idle speed closed throttle position to an open throttle position whereby the port pressure varies progressively from an essentially atmospheric pressure level to the subatmospheric pressure level of the intake manifold, the system including an air pump driven by the engine providing a source of superatmospheric pressure varying as a function of engine speed, means for modifying the air pump pressure as a function of changes in engine manifold vacuum to provide a signal pressure that varies as a function of both engine speed and load, an engine ignition timing distributor breaker plate movable in opposite directions to operably advance and retard the engine ignition timing, multi-stage servo means connected to the breaker plate to move the same, an exhaust gas recirculating (EGR) system including a first conduit connecting exhaust gases to the intake manifold, an (EGR) valve in the conduit movable between a closed and open position to control flow through the conduit, second servo means connected to the (EGR) valve for moving the same between the open and closed positions, first conduit means operatively connecting the carburetor induction passage pressure port to a first part of the distributor multi-stage servo to effect a first stage part throttle movement of the same in an advance direction to provide part throttle ignition timing advance as a function of increases in the port vacuum level, second conduit means operatively connecting the air pump pressure to the (EGR) second servo means to actuate the (EGR) valve at times to an open position to permit the flow of exhaust gases to the manifold as a function of the level of the air pump pressure, control means operatively connected both to a second part of the multi-stage servo and to the second servo means for simultaneously controlling a second stage supplemental movement of the distributor multi-stage servo in an advance direction and the operativeness of the second servo means, and further conduit means connecting the signal pressure to the control means to control the actuation of the servo in timed relation to the actuation of the (EGR) valve by the air pump pressure.