GB1483355A - Internal combustion engine having an exhaust gas recirculating system - Google Patents

Abstract

1483355 Controlling exhaust gas recirculation FORD MOTOR CO Ltd 2 Sept 1974 [24 Sept 1973] 38243/74 Heading F1B An I.C. engine comprises a carburetter having an induction passage 18 containing a Venturi 22, a passage 44, 42, 46, 48, 50 connected to recirculate exhaust gases from exhaust manifold 38 to intake manifold 30, the passage containing a valve 56 responsive to both inlet manifold vacuum and Venturi vacuum and being movable between open and closed positions in dependence thereon by a servo 58 having a movable member (diaphragm 86) acted on on one side by the manifold vacuum and on the other side by the Venturi vacuum. The Venturi vacuum depends on the air flow to the engine and hence on the engine speed and acts in a chamber 80 whereas the manifold vacuum depends on the opening of throttle valve 24 and hence on engine load and acts in a chamber 70. Chambers 68 and 82 are open to atmospheric pressure and the diameters of diaphragms 68, 86 and 79 separating the various chambers are chosen so that a given depression at the Venturi would result in a force ten times as great being exerted on the valve 56 as would be exerted if the same depression occurred in the inlet manifold, to compensate for the fact that during part-throttle operation, the Venturi depression is much smaller than the inlet manifold depression as illustrated in Fig. 3 (not shown). At idle the manifold vacuum is high enough to lower valve 56 so that the valve land 92 closes on to seat 96 preventing exhaust gas recirculation and at maximum speed with wide open throttle recirculation is prevented by the valve's being raised until land 94 closes on to seat 98. At intermediate loads and speeds, recirculation is permitted.