Patent GB-1374446-A (GB)
Title: Apparatus for supplying fuel to the atomisers of a combustion engine
IPC: F02M69/00
Filed: 1971-11-11
Abstract: 1374446 Fuel injection apparatus PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 11 Nov 1971 [14 Nov 1970] 52409/71 Heading F1B [Also in Division F2] An apparatus for supplying fuel to I. C. engine atomizers comprises a fuel pump, drawing from a tank and feeding at constant pressure to the inlet of a flow restrictor, the bore of which is continuously controlled by an electrical control element between the fully-closed and fully-open positions, the restrictor outlet communicating with a first pressure control valve which maintains at the restrictor outlet a constant pressure which is lower than the constant pressure at the restrictor inlet, the valve comprising a casing having a fuel inlet chamber connected to the restrictor, a fuel outlet chamber and a valve seating between the chambers which co-operates with a valve body, the valve body tending to move in the valve opening direction under the influence of the pressure of the fuel, against a resilient means having a small spring constant for providing a flat fuel pressure-flow characteristic, the valve also being constructed so that the opening forces exerted by the fuel in the outlet chamber are small compared with those exerted by the fuel in the inlet chamber, the outlet chamber communicating with a fuel distributer which connects each of the atomizers periodically to the outlet chamber for equal periods of time. Pump 1 feeds fuel via an accumulator 4 to restrictor 5, the bore of which is varied by an electric controller. From the restrictor fuel passes to a first pressure control valve 6 and then to a cam-shaft driven distributer connected by pipes 9 to the atomizers (10). A spring-loaded relief valve 12 is connected to the fuel feed line upstream of the restrictor and by-passes excess fuel back to the tank. The pressure control valve ensures that a constant pressure differential prevails across the restrictor for all rates of fuel flow, and the distributer supplies an equal quantity of fuel to each atomizer. The restrictor consists of a casing 15 having an inlet 16 and outlet 17, a valve seat 18 and a valve element 19 which is mounted on a shaft 20 supported at opposite ends by diaphragms 22 and 26 and having an enlarged end which is acted on by an electromagnet 21 energized through leads 22.' When the electromagnet is not energized the resilience of the diaphragm 22 moves the valve element 19 into the bore of the seat 18. When the valve is opened, fuel flows through apertures 25 in diaphragm 26 and also passes through a duct 24 into chamber 23, the cross-sections of diaphragm 22 and valve element 19 being so chosen that the forces exerted thereon are balanced and the position of the valve is independent of the pressure differential across the restrictor. The pressure control valve consists of a casing 30 having an inlet chamber 31 separated from an outlet chamber 32 by a valve seating 33 which co-operates with a valve body 35 rigidly attached to a piston 37. Above the piston is a space which is open to atmosphere and contains a constant rate spring 38. The pressure of fuel on the underside of the piston tends to move the valve body 35 to the open position, and this force is in the same direction as, and is greater than the force exerted on the valve body 35 by the pressure of fuel in the outlet chamber 32. A small variation in the fuel pressure in the inlet chamber results in a large displacement of the valve body and hence a large variation in the flow of fuel permitted. Modifications of the valve are shown in Figs. 3b and 3c. Due to manufacturing variations the atomizers fitted to an engine will open at slightly different pressures and Fig. 4 shows the use of a second pressure control valve 50 in a circuit which is otherwise similar to Fig. 1, in order to compensate for these variations and thus ensure that each atomizer passes the same quantity of fuel. The valve 50 is generally similar to the first pressure control valve, except that the piston 57 is biased towards the valve open position by a spring 58, and the space above the piston is connected to the inlet chamber 31 of the first pressure control valve. If the distributer after feeding fuel to an atomizer which opens at a pressure p, then has to feed fuel to an atomizer which opens at a pressure p + #p, then the pressure in the outlet chamber of the second valve 50 increases and lifts the piston 57. The resulting increase in the volume of the inlet chamber 53 results in a temporary reduction in the amount of fuel passing to the outlet chamber 54, but this is compensated by fuel being displaced from the space 56 above the piston, through a restrictor 60 to the inlet chamber of the first valve 6. This fuel reaches the distributer within the period of time during which the distributer is supplying fuel to the atomizer which opens at the pressure p + #p. Flow restrictor 60 damps oscillations of the control valves.