Patent GB-875287-A (GB)
Title: Improvements relating to the supply of fuel to internal combustion engines
IPC: F02M69/20
Filed: 1956-11-10
Abstract: 875,287. Supplying fuel. O'CONNOR, R. M., and NAYLOR, B. Nov. 11, 1957 [Nov. 10, 1956; Feb. 20, 1957], Nos. 34437/56 and 5732/57, Class 7(3). In a system for supplying fuel to a multi-cylinder engine, the fuel is metered so that the rate of flow varies directly with engine speed and the flow of fuel is divided into separate streams so that a predetermined proportion of the total flow is fed continuously into each air inlet tract receiving fuel and the fuel for each tract is provided from a common supply in a chamber into which fuel flows through a metering valve, positioned by a control pressure measured downstream of an air throttle, for governing the air flowing to one or more cylinders so that the fuel flowing to the chamber varies with the control pressure. In Fig. 1 a float chamber 1 is fed with fuel either by gravity or by a pump (not shown) and the fuel passes from the float chamber 1 through a pipe 2 to the eye of a centrifugal radial vaned pump 3 driven by the engine at a constant fraction of the engine rotational speed. The periphery of the centrifugal pump 3 is connected to the float chamber 1 by a pipe 18 through which trapped air can pass into the float chamber. From the periphery of the pump the fuel passes through pipe 4 into a control unit 5 in which the fuel flow is metered by the needle valve 11 before passing to the engine cylinders (not shown) by way of the pipes 7 and the inlet ports 8 of the engine only one of which is shown. The interior of the bellows 13 is subjected to the pressure existing at one or more of the engine inlet ports 8 downstream of the throttle so that the position of the needle 11 is adjusted against the restoring force of atmospheric pressure according to the pressure existing at the inlet ports 8. The division of the fuel between the cylinders depends upon the relative effective areas for flow of the jets 9 and can be adjusted by fitting different jets to give the desired distribution. An evacuated section may be incorporated in the bellows 13 so that the datum position of the needle 11 is varied with atmospheric pressure. In addition an element which decreases in length as the air temperature rises may be inserted between the bellows 13 and its anchorage to the casing. An accelerating device consists of a non-return spring actuated valve 16 and a restriction 19 in the pipe 14. To provide for the rich mixture necessary for starting the float chamber 1 may be provided with a stack pipe 17 so that when the float is depressed the fuel level will rise in the pipe 17 and thus fuel will flow under gravity to the inlet ports 8. In Fig. 2 the pump and metering valve are combined in a single control unit 21. The metering unit comprises a centrifugal pump 25 driven by the engine. The space between the bellows 37 and 38 is evacuated. The needle 39 is controlled by a temperature sensitive element 40. The element 40 which may be a gas filled bellows may be arranged as shown or may be connected with a bulb arranged in the manifold or in the air intake thereto. The height of the injection nozzle is arranged to be slightly above the fuel level in the float chamber 23. The mixture may also be enriched by opening a starting valve 42. In Fig. 3 fuel is supplied to the inlet chamber 26 under pressure through a pressure regulating valve 45 while the supply of fuel to the injection nozzles is controlled by pressure regulating valves 46 there being one such valve to each injection nozzle. The diaphragm control valves 47 are not essential but if they are used and are capable of controlling the injection pressure within fairly close limits the pressure regulating valves 46 need not be constructed as balanced valves or alternatively need not have large diaphragms. Alternatively for starting the engine means may be provided for injecting fuel under pressure into the control unit whereby some fuel will be delivered through the injection nozzles. Where the metering system is operated under pressure it is practical to control the air to the inlet manifolds for each cylinder by means of a common throttle valve. An injection nozzle may be provided for each cylinder and arranged on the downstream side of a single throttle valve. The needle valve may be controlled by a capsule or piston. It is possible to supply all the fuel through a smaller number of nozzles than there are cylinders, for example one nozzle to a pair of cylinders. The fuel may be petrol, paraffin or alcohol.