GB1458503A - - Google Patents

Abstract

1458503 Controlling fuel injection systems PETROL INJECTION Ltd and HE JACKSON 31 Dec 1973 [4 Jan 1973] 569/73 Heading F1B A fuel injection system for an I.C. engine comprises supply and return conduits 3 and 7, at least one injector 5 connected to receive fuel from the supply conduit and a fuel pressurizing device (pump 2) to supply fuel to the supply conduit, the return conduit 7 including a valve closure member 402 resiliently biased towards a closed position and movable against the bias by pressure in the return conduit and means (diaphragm 407 and chamber 408) connectible to the engine intake manifold and operable to increase the resilient bias in response to a drop in manifold vacuum below a predetermined value. Chambers 408, 409 are connected via conduits 410, 411 to the engine inlet manifold and a point immediately down- stream of the air cleaner, respectively. Under partload, the intake manifold vacuum raises diaphragm 407 and holds rod 412 out of engagement with diaphragm 402. The characteristics of a spring 406 are such that the biasing force it exerts is substantially constant over the range of positions of diaphragm 402, so that a substantially constant fuel pressure is maintained upstream of the relief valve 6 while rod 412 remains clear of the diaphragm 402. Thus the amount of fuel issuing from injectors 5 depends only on the period for which they are open. When the throttle valve 12 is nearing its fully open position, the low inlet manifold vacuum is insufficient to keep rod 412 clear of diaphragm 402, so that the biasing force on the latter is increased, thereby increasing fuel pressure upstream of the valve 6 ensuring increased fuel injection from the injectors 5. The length of time for which injectors 5 discharge fuel is determined by the engine air intake flow-rate by electrical pulses produced by a switching unit 8 controlled by a timing switch 14 as described in Specification 1363631. The control pulse length may be varied in response to engine conditions e.g. intake manifold temperature and cooling water temperature by valves 400, 401 as described in that Specification.