GB523895A - Improvements in or relating to the feeding of fuel to internal combustion engines - Google Patents

Abstract

523,895. Spray carburetters. CLEVELAND, F. J. (Bendix Aviation Corporation). Oct. 17, 1938. No. 30020. [Class 7 (iii)] A supercharger 12 is fed from an air inlet - conduit 10 supplied either by a second supercharger or by a scoop facing the direction of motion, the air being controlled by a throttle valve 16 above and below which are a fuel nozzle 34 and venturi tube 19 respectively. Tubes 81 expose to the atmosphere in the conduit 10 a space 82 behind the venturi 19 and the space communicates through a passage 80 with a pressure chamber 62. The throat 76 of a smaller venturi 74in the venturi 19 connects through a passage 78 with a suction chamber 56 separated by a diaphragm 60 from the chamber 62. A rod 50, secured to the diaphragm 60 and to a similar diaphragm 46 separating two fuel chambers 44, 28, carries a slide valve 52 displaceable to open a fuel port 59 by the pressure difference between the chambers 62, 56. Fuel is supplied from a pump 24 to the port 59 and flows through the chamber 28, a calibrated orifice 29 and valve-controlled passage 30 to the chamber 44 which is connected through a throttleactuated acceleration pump 96 and pipe 32 to the fuel nozzle 34. The nozzle 34 comprises an outlet valve 36 opening inwardly under pressure of the fuel on a diaphragm 39. The diaphragm 46, being exposed to the pressure of un-metered fuel in the chamber 28 on one side and to that of the metered fuel on the other side, co-operates with the diaphragm 60 in controlling the flow of fuel. Sealing diaphragms 58, 66 are disposed between the rod 50 and the chamber walls and a pressure equalizing passage 70 in the rod connects the chamber 28 with a chamber 68 beyond the chamber 62. A spring 69 in the chamber 68 increases the fuel flow during idling to give an over-rich mixture, the enrichment being accentuated by a passage 88 between the passages 78, 80 and a narrow bleed passage 83 leading from the passage 78 to a point above the throttle valve 16 when that valve approaches the closed position. The mixture is corrected by a valve 90 on the acceleration pump 96 which enters the passage 30 at small throttle openings. During normal working the mixture is corrected for altitude and temperature by a partially-evacuated bellows 84 which actuates a valve 86 in the passage 80, but this control may be overridden by a valve 112 having a lost motion connection with the control rod 106 of a manually operated fuel valve 108. The valve 108 serves to adjust the richness of the mixture and may put off entirely the flow through the passage 30. At wide throttle openings, additional fuel is fed through a byepass 120 controlled by a valve 122 operatively connected to a diaphragm 134 in a casing 136. A pipe 137 connects one side of the diaphragm to the outlet 15 of the supercharger 12, the other side being exposed to the induction pipe between the supercharger and the throttle valve while atmospheric pressure acts on a diaphragm 138 rigidly secured to the diaphragm 134. The diaphragm 134 may also control. a valve regulating a passage, between the passages 78, 80, which replaces the passage 88. In a modification of the fuel feed the sleeve valve 52 is replaced by a mushroom valve 144, Fig. 2, disposed in a chamber 142 filled with fuel from the pump 22. The valve stem 148 terminates in a. dashpot 143 and intermediate its ends engages a rocking lever 150 carrying a counterweight 152 to balance the diaphragm system 46 which actuates the mushroom valve 144, the valve itself being balanced by a diaphragm 145 connected to the lever 150 and disposed between the chambers 142 and 28. The. fuel supply unit 136, Fig. 1, may be replaced by a unit disposed in or connected to the air inlet, the unit comprising a bellows, exposed to the air inlet pressure and co-operating with a second bellows controlled by the supercharger outlet pressure to rock a spring pressed lever connected either to the valve 22 or to a valve controlling the passage 80. The additional fuel supply through the byepass may be controlled by the difference in pressure between the chambers 28 and 44 instead of by the unit 136. In another form, the fuel is fed to the nozzle from a chamber 374, Fig. 5, between two diaphragms 366, 368 which actuate the fuel valve 362. The diaphragm 368 forms one wall of a chamber 376 communicating with a fuel pump 398 drawing fuel from the chamber 374 and driven from the engine shaft, the pump creating a pressure in the chamber proportional to the square of the engine speed. The fuel supply pump 358 delivers .into a chamber 372 of which one wall is constituted by the diaphragm 366 and the fuel flows into the chamber 374 past a valve 380 actuated by a capsule in a casing 384 in communication with the supercharger outlet, the area of the orifice varying directly as the pressure in the inlet manifold of the engine. In addition, since the flow past the valve 380 varies as the square root of the pressure difference before and after it, the pressure in the chamber 376 co-operates therewith to feed the fuel to the nozzle at a rate corresponding directly with the engine speed.