Patent GB-601275-A (GB)
Title: Charge forming device for internal combustion engines
IPC: F02D19/12
Filed: 1945-09-27
Abstract: 601,275. Charge-forming devices. BENDIX AVIATION CORPORATION. Sept. 27, 1945, No. 25129. Convention date, June 9, 1944. [Class 7 (iii)] A charge-forming device is provided with means for supplying in the charge an auxiliary fluid automatically throughout substantially the entire range of power and speed operation of the engine, the rate of supply being regulated by passing the auxiliary fluid through a metering restriction and the pressure of the unmetered fluid is controlled independently of means which controls the pressure of metered fluid. The auxiliary fluid tends to maintain the engine operating temperatures at the point for most efficient operation and to prevent detonation. As it prevents overheating, heavier, less volatile fuels may be used. As shown (Fig. 1), auxiliary fluid from a tank 42 is supplied past valve 54, orifice 82 and valve 88 into a nozzle 84 in the induction passage 12 of a carburetter 10 during substantially the whole range of power and speed of the engine. The valve 54 is operated by a diaphragm 62 acted on by pressure of air entering the induction passage communicated to a chamber 68, the pressure of the fluid in a chamber 52 and a spring 72, a light spring 56 urging the valve in the closing direction. The valve 88 is operated by a diaphragm 90 acted on by the pressure of the fluid in a chamber 78, suction from the throat of a venturi 18 and a spring 96. Preferably, the strength of the spring 96 is arranged so that the valve 88 opens at low values of venturi suction so that as soon as a throttle 32 is opened past idling position the fluid commences to flow into the induction passage and continues to flow in all positions of the throttle past the idling position. Maximum flow will be attained at maximum venturi depression. A pump 106 maintains the tank 42 under air pressure. The carburetter 10 includes a float chamber 22 supplying a main fuel nozzle 20 and an idling port 29 formed in a rotatable plug 38. The air may be supplied under pressure to the induction passage 12 by a supercharger. Fig. 2 shows a modified arrangement for supplying the fluid, applied to a carburetter in which fuel is supplied under pressure. A pump 418 supplies the fluid from a tank 416 past valve 426, orifice 424 and a valve 456 into a fuel passage 204 leading past a valve 254 into a nozzle 270 in the induction passage. The fluid is thus mixed with the fuel and injected with it into the induction passage. The valve 456 is controlled similarly to the valve 88 previously described. The valve 426 is operated by two diaphragms 406, 404 which replace the single diaphragm of Fig. 1. These diaphragms are similar to diaphragms 148, 146 controlling a fuel valve 160. The pressure of entering air is supplied to a chamber 412 on one side of the diaphragm 406 and pressure derived from the throat of a venturi 114 of the carburetter is applied to a chamber 410 between the diaphragms. The valves 426 and 456 control the flow of fluid in accordance with the quantity of air flowing in the induction passage. The fluid commences to flow as soon as the throttle valve 120 of the carburetter moves from the idling range. As shown, the sizes of the diaphragms 404, 406 are the same as the diaphragms 146, 148 and the pressure of the fluid supply is the same as that of the fuel supply of the carburetter, but .modification of the sizes and pressures may be made. The arrangement and operation of the carburetter are similar to the arrangement and operation of the carburetters described in Specifications 590,493 and 591,471. The valve 160 operated by the diaphragms 146, 148 controls the fuel which is supplied to the inlet of the carburetter by a pump and enters by a pipe 162. From the valve 160 the fuel passes in turn to an orifice 220, passage 198, metering unit 134 and into the passage 202. The metering unit may be replaced by a single metering orifice. The chamber 142 between the diaphragms 146, 148 is connected to the chamber between diaphragms 404; 406 and is thus at the same pressure derived from the venturi throat. The chamber 144 on the left of the diaphragm 146 is connected to the chamber 402 by a pipe 442. The valve 160 is thus controlled by unmetered fuel pressure, i.e. the pressure of fuel on the upstream side of the metering unit 135, entering air pressure and pressure from the venturi throat. The valve 254 is controlled by metered fuel pressure and pressure from the venturi throat. The metering unit includes a stepped valve 210 which has three positions, one for idling controlled by a finger 230 on the throttle valve spindle, one for intermediate powers controlled by a sleeve 232 forming a stop and a third position for high powers which is obtained by venturi throat suction and unmetered fuel pressure compressing a spring 234 and moving the sleeve 232. The orifice 220 limits the fuel flow when the valve is in its high power position. A valve 182 when opened provides a connection between the venturi throat and the chamber at entering air pressure and thus modifies the throat pressure controlling the valves. An altitude control may be used to modify the pressure differential between chambers 142 and 144. When the valve 182 is moved past its open position, a cone 355 operates a lever 354 and plunger 126 to close the valve 160. A fuel well 314 supplies additional fuel during acceleration periods. A pipe 172 having a restricted communication with the top of the chamber 140 serves for the elimination of vapour. There may be a supercharger anterior to the venturi 114 in place of or in addition to the supercharger between the carburetter and the engine.