Patent GB-652853-A (GB)
Title: Liquid fuel feeding systems for engines
IPC: F02D9/00
Filed: 1946-03-28
Abstract: 652,853. Spray carburetters; regulating. BENDIX AVIATION CORPORATION. March 28, 1946. No. 9624. Convention date, April 2, 1945. [Classes 7(iii) and 7(vi)] [Also in Group XXVI] In a system for supplying fuel under pressure to an engine wherein a fuel flow passage is provided with a restricted metering orifice from the downstream side of which metered fuel is led to the engine, a fuel flow controlling valve passes fuel to the passage or to a chamber forming part of the passage and the fuel valve is! subjected to a first controlling force varied in relation t o engine speed and a second controlling force dependent upon the difference between the pressure in a variable pressure regulator control chamber or passage connected to the metered and to the unmetered fuel chambers or passages by means of restricted orifices and a pressure in the fuel flow passage. As shown, fuel is maintained under pressure in a chamber 19 by an engine driven sliding vane type pump drawing from an inlet 12. From the chamber 19 fuel flows through a valve 28, Fig. 1a, to an unmetered fuel chamber 72 and from there passes through an orifice 107<SP>1</SP> controlled by a needle valve 107 to a conduit 84 leading to an engine. The valve 28 slides in a bushing 29 under the control of a diaphragm 47 connected to it by a cable 54 and a centrifugal governor 38 driven by an extension of the rotor 14 of the fuel pump. The right-hand side of the diaphragm is loaded by pressure of unmetered fuel in the chamber 72 while the other side is subjected to the pressure in a chamber 105. The chamber 105 is connected through a restriction 135 controlled by a valve 137 to the discharge side of the orifice 107<SP>1</SP> and through a restriction 100 to the chamber 72. The valve 28 takes up an equilibrium position when the force due to the governor is balanced by the difference of fuel pressures on the diaphragm and the force due to an idling spring 57. In order to maintain the pressure drop across the valve 28 substantially constant a byepess valve 62 is provided between the chamber 19 and a byepass chamber 61. This valve opens when the pressure in the chamber 19 exceeds by an amount determined by a spring 66 the pressure in the unmetered fuel chamber 72. This latter pressure is communicated by pipes 71, 71a and a port 86 in a slow running cut-off valve 81 to a chamber 70 separated from the chamber 61 by a diaphragm 68 which carries the valve. When the idle cut-off valve 81 is closed to cut off the fuel supply and stop the engine the port 86 is also closed. This prevents unduly high pressures in the chamber 19 when the engine continues to run under its own momentum after the fuel flow is cut off, which would otherwise be caused by the valve 62 requiring unduly high pressures to unseat it. The fuel flow to the engine can be varied by valves 107 and 137 which can more or less restrict orifice 107<SP>1</SP> and restriction 135 respectively. The valve 107, as shown, Fig. 1, is operated by capsules 108, 117 which are respectively subjected to supercharger pressure and exhaust manifold or atmospheric pressure. The supercharger pressure acts outside of the bellows 108 and the exhaust or atmospheric pressure acts inside the bellows 117. Preferably the combined unit is calibrated to produce constant travel of the needle 107 proportional to manifold pressure minus some predetermined increment of exhaust back pressure. The valve 135 controls the flow of fuel by varying the pressure in chamber 105 and consequently influencing the valve 28 through the diaphragm 47. The valve 135 may be employed to vary the fuel flow in accordance with changes of temperature of the entering air. A capsule is supplied with fluid from a thermal element at the outlet side of the supercharger. The fluid is temperatureresponsive so that changes of temperature vary the degree of compression of the capsule. The needle 137 is operated by the movements of the capsule. The conduit 84 may lead to a fuel injection nozzle on the intake side of a supercharger and between the supercharger and a throttle valve. In order to prevent fuel flow through the restriction 106 during idling this restriction may be provided with a valve operated by a diaphragm between the chambers 105 and 72. At high power this valve may reduce the area of the restriction in order to reduce the fuel flow. In a modification of this the area of the restriction 106 is varied by a needle valve operated by a temperature-responsive capsule and the needle valve 137 can be operated manually to control the fuel flow. Alternatively the orifice 106 could be retained as a fixed restriction and the restriction 135 and valve supplemented by a second restriction and valve in parallel with it. In another modification the chamber 72 is replaced by two chambers in series having a common wall with an orifice controlled by a needle valve operated by a temperature-responsive capsule the orifice 107<SP>1</SP> and needle 107 being located in the second chamber. If desired a second orifice may be located in the wall to ensure a minimum fuel metering area. This arrangement may be used alone or in conjunction with the restrictions 106 and 135. In a variation of the arrangement the orifice instead of being controlled by a needle valve co-operates with a valve connected to a diaphragm between the chambers 105 and the first of the two chambers referred to. This arrangement acts to maintain the operating speed of the engine within a predetermined limit. In another modification, Fig. 8, the orifice 106 is controlled by a needle valve 170 connected to a diaphragm 171. As the engine speed increases the fuel, pressures move the needle 170 to restrict the orifice 106 and thus reduce the fuel flow to compensate for the decreased volumetric efficiency. Compensation for volumetric efficiency variations may be accomplished throughout the entire speed range by properly contouring the needle 170. In the event of a change of speed due to a propeller pitch governor the governor 35 alters the fuel flow accordingly There may be control by a propeller pitch governor co-ordinated with throttle valve control. Fig. 9 shows the application of the apparatus of Fig. 1 to the control of the fuel supply to a supercharged engine in which the fuel is injected into the engine cylinders during the induction stroke. From the conduit 84, Fig. 1, the fuel flows by means of a pipe 213 to an inlet reservoir 215 of a wobble plate type fuel injection pump 214 which is similar to the pump described in Specification 611,402, (see Groups XXVIII and XXIX). This pump is driven by the engine and distributes the fuel to the respective cylinders of the engine one only 200 being shown through conduits such as 242. The pressure of the fuel in the reservoir 215 operates upon a .diaphragm 216 movements of which control the delivery of the pump by operating 'sleeves which co-operate one with each pump plunger. A fuel well is formed at the bottom of the reservoir 215 and a diaphragm operated by suction on the engine side of the throttle valve 212 draws fuel into the well and returns it during acceleration when the suction on the diaphragm is reduced. Arrangements for preventing vapour lock &c. are similar to those described in Specification 652,854. Specifications 604,466, [Group XXVI], and 625,889 also are referred to.