GB560196A - Improvements in or relating to carburetters for internal-combustion engines - Google Patents

Abstract

560,196. Spray carburetters. BEDALE, P. W. June 22, 1942, No. 8548. [Class 7 (iii)] A carburetter is of the type in which liquid fuel is supplied by a pump 20 to chambers 12, 32 and through a metering orifice and a meteredfuel chamber 35 to a spray nozzle 37 in the combustion-air inlet of the engine, the admission of fuel to the chamber 12 being restricted by a valve 23 adjusted by a diaphragm 13, which is loaded by an engine-driven governor 14 and is subjected on its opposite faces to the pressures in the chambers 32, 35. The valve 23 is thus adjusted to keep the pressure difference between'the chambers proportional to the square of the engine speed. The total effective area of the orifice 33 is controlled by means responsive to atmospheric pressure amd to the charge pressure maintained in the induction pipe 50 by a supercharger 39, the area being maintained proportional to the "adjusted charge-pressure"; this is defined as the charge-pressure less 1 /nth of the atmospheric pressure, n being a constant approximately equal to the compression ratio of the engine. According to the invention, the pressure-responsive means is arranged so to vary the effective area of the metering orifice 33 that it is a function of the " adjusted chargepressure " so long as that pressure is below a predetermined value and is another function, higher in value, when the said pressure exceeds that value, so that the fuel-air mixture is enriched at high charge-pressures. As shown, pipes 31, 40 connect the chambers 12, 11 respectively to the chambers 32, 35, which communicate through a metering orifice constituted by a main jet 33 and an enrichment jet 34. The jet 33 is adjusted by a needle'41 having a parabolic tip and connected through a link 42 to evacuated capsules 43 and a capsule 143 open to the atmosphere, the capsules being enclosed in a chamber 48 connected to the induction pipe 50. A slot 44 in the link 42 is engaged by a pin on a lever 46 connected to a rod 51 between capsules 52, 53 ; the capsule 52 is gas-filled and connected to a sealed bulb 55 in the induetion pipe in order to respond to the temperature therein, while the capsule 53 is evacuated and sealed in order to balance the effect of changes of atmospheric pressure on the capsule 52. A needle valve 56 for the enrichment jet 34 has a tapered tip and is connected through a lever 57 pivoted at 58 to the capsule stack 43 so as to open the jet under high boost conditions. Fuel-collecting grooves 62, 64, 65 around the governor shaft, 16 and the needles 41, 56 are connected at 63 to the supercharger inlet 38. A relief valve 26 in the pump outlet 21 is connected to a diaphragm 27 subjected to the pressure in the chamber 12.