Patent GB-681346-A (GB)
Title: Fuel metering device for an internal-combustion engine
IPC: F02D9/00
Filed: 1948-11-29
Abstract: 681,346. Spray carburetters. BENDIX AVIATION CORPORATION. Nov. 29, 1948 [Dec. 11, 1947], No. 30952/48. Class 7 (iii) [Also in Group XXIX] A fuel metering device comprises a fuel conduit with a fixed metering restriction therein and a valve connected to a pressure responsive element which is controlled by a liquid pressure differential varying with variations in engine speed and modified in response to changes in engine variables indicative of mass air intake, said valve being positioned by said element to maintain the metering head across said restriction proportional. to said modified pressure differential. A valve 24 is actuated by diaphragms 30, 31 to maintain the fuel differential pressure across the diaphragm 30, and hence across the metering jet system 52, equal to that across diaphragm 31, which latter differential is maintained proportional to the square of engine speed by a centifrugal pump 10 and corrected for variations in mass air flow by a valve 132 controlled by capsules 133, 137 ac- :ording to intake pressure and exhaust back presure and by a valve 143 controlled by a thermally esponsive bulb according to intake air temperature. The pressure differential is also corrected for variations in the volumetric efficiency of the engine by a contoured valve 121 actuated by a diaphragm 122 subject to the inlet and outlet pressures of the pump 110. The fuel, supplied to the valve 24 by a constant pressure pump 21 flows through a pipe 51 to the jet system 52 from which i flows through a manually operated valve 59 and an idling valve 95 to a pipe 18 leading to a spray nozzle situated adjacent the inlet of a centrifugal supercharger. The pump 110 operates in a closed crcuit and maintains a pressure differential proportional to the square of engine speed across an orifice 117 connecting chambers 49 and 50, the pump drawing fuel from chamber 49 through a pipe 112 and returning it to chamber 50 through pipes 114, 115 in which are arranged in parallel the valves 121, 132, and 141. The metering jet system 52 comprises a jet 53 in a pipe 57 in parallel with jets 55, 54 in a pipe 58 leading to a port 65 controlled by the valve 59, actuated by a lever 59<SP>1</SP> which determines which jets are in action. At high power outputs a normally closed valve 71, actuated by a diaphragm 73 subject to the metering differential, is opened to increase the fuel flow, and a derichment jet 56 in the pipe 58 may be closed when anti-detonant is supplied to the engine by a valve 85 actuated by the anti-detonant pressure on a diaphragm 87. The spring-loaded idling valve 95, normally held open by the outlet pressure of pump 110 acting through pipe 108 on a diaphragm 101, moves towards closing to meter the fuel at idling, a slow-running spring holding the valve 24 open. An accelerating pump 150 comprises a throttle-valve operated piston 164 which draws fuel into chamber 160 through a check valve 163 when the throttle valve is closed, the pressure of which fuel on diaphragm 156 when the throttle valve is opened forces open a valve 151 to allow accelerating fuel to flow through a pipe 176. A float operated valve 182 controls the escape of fuel vapour accumulating in a chamber 180 connected to the pipe 20.