GB1445933A - Exhaust gas recirculation system - Google Patents

Abstract

1445933 Exhaust gas recirculation FORD MOTOR CO Ltd 25 Oct 1974 [5 Nov 1973] 46200/74 Heading F1B [Also in Division G3] An I.C. engine has a valve 56 which governs the recirculation of exhaust gases into the inlet manifold as a function of throttle valve opening, the valve being operated by a servo 58 responsive to a pressure signal from the inlet manifold via port 80 and air lines 86, 74 connected by an air bleed device 84 which modifies the pressure signal at the servo and consequently the degree of exhaust gas recirculation in dependence on manifold pressure. Gases pass from the exhaust manifold 38 to the inlet manifold via duct 46 valve 56, normally closed by spring 77, and ducts 48, 50. The inlet manifold pressure is communicated via a line 118 to the bleed device 84 containing a spring loaded diaphragm 104 which governs the flow of air from a passage 106 open to the atmosphere, to line 74 via a flow restrictor 92. Servo 58 comprises chambers 70, 68 separated by a diaphragm 66, chamber 70 being connected to line 74 and chamber 68 being open to the atmosphere. During engine idling, throttle valves 26 are closed and the pressure in line 86 is atmospheric, this pressure being transmitted via a flow restrictor 90 to servo 58 which closes valve 56 preventing flow of exhaust gases into the inlet manifold. Under light acceleration, throttle valves 26 are open slightly, the edge of one of the valves being in the proximity of port 80 resulting in the pressure in lines 86 and 74 becoming subatmospheric; the inlet manifold pressure is sufficiently subatmospheric to hold bleed device 84 open allowing air to bleed into line 74, raising the pressure within it above that in line 86. Valve 56 therefore opens slightly allowing recirculation of exhaust gases. Under heavier acceleration, throttle valves 26 are opened wider thereby raising the inlet manifold pressure to a level which allows bleed device 84 to close. The subatmospheric pressure in line 86 is therefore transmitted directly to servo 58 which opens valve 56 fully, allowing maximum exhaust gas recirculation. When throttle valves 26 are wide open and no longer in the proximity of port 80, the pressures in lines 86, 118 become substantially atmospheric, bleed device 84 and valve 56 are therefore closed and no recirculation occurs. Under deceleration, when recirculation is not required, a non-return valve 124 allows by-pass of restrictor 90 so that valve 56 may close quickly.