Patent GB-929775-A (GB)
Title: Fuel and air supply system
IPC: F02M69/44
Filed: 1960-02-18
Abstract: 929,775. Fuel and air supply systems. ACF INDUSTRIES Inc. Feb. 18, 1960 [April 6, 1959], No. 5750/60. Class 7(3). A fuel and air supply system for an internalcombustion engine comprises conduit means connected to the engine and providing a flow of fuel to the engine in one stream and a flow of air to the engine in a separate stream, means for measuring the flow of air in the air stream, means for metering the flow of fuel in the fuel stream and a connection between the air measuring means and the fuel metering means adapted to maintain the flow of fuel proportional to the flow of air, the connection including an engine temperature responsive means for changing the phase of the fuel metering means relative to the air measuring means thereby to change the proportion of fuel to air flow. To start the engine E, ignition switch 323 is closed and starting switch 313 is closed to energize the starting motor 317 to crank the engine E. Relay 325 being normally closed as appears in Fig. 1, and oil pressure being developed to close the oil pressure switch 333, the electric pump 11 is energized to pump fuel to fuel metering chamber C and solenoid valve 40 is energized to open. With fuel being delivered by pump, chamber C is maintained full of fuel under pressure. Fuel also fills the datum pressure chambers 139 of nozzles N and the upper, intermediate and lower chambers 191, 193 and 195 of the datum pressure regulator R. Fuel for the engine E is delivered from chamber C through the orifices 19 and lines 25 to the charging fuel chambers 133 of nozzles N. Regulator R is adapted to maintain a predetermined pressure differential between the charging pressure (i.e., the pressure in fuel metering chamber C) and the datum pressure (i.e., the pressure in chambers 139 of nozzles N), with the datum pressure lower than the charging pressure during all normal rates of flow. This pressure differential may be about 1/2 p.s.i., for example, and it is maintained except during rotation of the cam 253, at which times it is reduced or raised (depending upon which way the cam rotates). The regulator R acts in accordance with variations in the pressure in chamber C to maintain the stated pressure differential as follows: Upon a decrease in charging pressure in chamber C, the pressure in regulator chambers 191 and 193 drops. Diaphragm 203 thereupon moves downward to move the regulator valve 233 farther away from its seat. This allows fuel to escape more readily from chamber 195 and datum line 37 so as to drop the datum pressure an amount equal to the drop in charging pressure, whereby the difference between charging pressure and datum pressure remains the same. Upon an increase in charging pressure in chamber C, the pressure in regulator chambers 191 and 193 increases. Diaphragm 203 thereupon moves upward to move the valve 233 closer to its seat. This increases the datum pressure an amount equal to the increase in charging pressure so that the difference between charging pressure and datum pressure remains the same. Thus, the regulator R reduces the charging pressure by a predetermined amount (1/2 p.s.i., for example) to convert it to datum pressure. As to each nozzle N, the nozzle diaphragm 135 is subject on one side to charging pressure in chamber 133 tending to move the nozzle needle 27 away from its seat 167, and subject on the other side to datum pressure in chamber 139 and the force of the nozzle spring 187 tending to move the nozzle needle toward its seat. With the charging pressure high enough to overcome the closing force on the nozzle needle 27 due to the datum pressure and spring 187, the needle is unseated, and fuel is discharged through the tip 159 of the nozzle. The rate of flow of fuel through a nozzle is dependent upon the position of the metering rod 21 related to that particular nozzle in relation to the metering rod orifice 19 and the pressure drop across the orifice. As long as the pressure differential between charging pressure and datum pressure remains substantially constant, the pressure drop across orifice 19 remains substantially constant, being equal to the stated pressure differential plus the pressure created by the nozzle spring 187 (which is a low rate spring). Thus, the pressure drop across orifice 19 is normally maintained substantially constant, and variations in the rate of flow of charging fuel are caused solely by moving the metering rods 21 in or out, the farther in the rods, the lower the rate of flow, and vice versa. The position of the metering rods 21 is dependent upon the position of air valve 7 and the temperature of thermosensitive member 127. The position of the air valve is dependent upon the rate of air flow through the conduit 1. The temperature of thermosensitive member 127 is dependent upon the temperature of engine E. Assuming that the engine is fully warmed up, the effect of temperature on the position of the rods may be disregarded, and it will be observed that with the air valve 7 closed, the metering rods 21 will occupy an advanced position wherein the effective area of each orifice 19 (the annular area round the rod within the orifice) is a minimum, for flow of charging fuel at a minimum rate corresponding to the rate of flow of air to the engine. As the air valve 7 opens with increase in the rate of air flow, the metering rods 21 are withdrawn an amount proportional to the opening of the air valve to increase the rate of flow of charging fuel proportionately to the increase in the rate of air flow. In the part throttle range, the opening of the air valve 7 is attenuated by the economizer 79 to attenuate the withdrawal of the metering rods to provide a lower rate of flow of charging fuel than would occur without such attenuation, so as to deliver an economy mixture of air and fuel to the engine. In the full throttle range of operation, wherein the air valve 7 has opened to the point where port 97 is downstream from the air valve, the attenuating effect of the economizer 79 is decreased, and the metering rods 21 are withdrawn to the point of providing the necessary rate of flow of charging fuel in relation to the rate of flow of air to deliver a richer mixture. A full rich mixture for power is delivered when manifold pressure increases to close valve 87. On starting a cold engine, valve 87 is closed to provide a richer mixture, and during starting and engine warm-up, the thermosensitive member 127 functions to provide for enrichment of the mixture by changing the phase of the metering rods 21 relative to the magnetic coupling member 121 and the air valve 7. As the engine warms up, the modulation of the metering rod position by the thermosensitive member 127 is lessened, and, once the engine has fully warmed up, the thermosensitive member has no further effect. On acceleration (pushing down the pedal 49), cam 253 is rotated clockwise as viewed in Fig. 9. The lower diaphragm 199 of regulator R is subject on both sides to charging pressure (regulator chambers 191 and 193 being in communication with fuel metering chamber C) and additionally subject to the downward force of spring 237. Accordingly, spring 237 drives the lower diaphragm 199 downward, forcing fuel out of chamber 191. Restriction 269 acts momentarily to prevent the fuel forced out of chamber 191 from entering chamber 193, most of the fuel being forced back to chamber C and increasing the pressure in chamber C. The pressure in the intermediate regulator chamber 193 is lowered, and the upper regulator diaphragm 203 is driven downward. This pulls valve 233 farther away from its seat, thereby reducing the datum pressure. Upon the drop in datum pressure in the nozzle datum pressure chambers 139, the nozzle diaphragms 135 respond to move the nozzle needles 27 farther away from their seats. This drops the pressure in the charging fuel chambers 133 of the nozzles. Thus, the pressure drop across metering orifices 19 is increased. As a result of this increase in the pressure drop across the orifices, charging fuel is delivered at a higher rate than it otherwise would have been delivered. This provides for momentary mixture enrichment on acceleration. The action on deceleration is the reverse. For unloading (i.e., clearing the engine of excess fuel), the pedal 49 is pushed all the way in, thereby closing the unloader switch U. This completes a circuit for the coil of relay 325, and the latter opens. This de-energizes the electric pump 11 and the solenoid valve 40. The valve 217 closes, thereby holding pressure in the datum system. With the pump cut off and increased pressure in the datum system, nozzles N close to cut off delivery of charging fuel to the engine. The engine is cranked by closing the starting switch 313, and this clears the engine of excess fuel. If heat should cause expansion of fuel in the datum system with resultant increase of pressure in the datum system, the pressure drives the upper regulator diaphragm 203 downward, thereby opening up the regulator valve 233 to relieve the excess pressure via passage 39 and return line 41 (the solenoid valve 40 being open). It will be observed that with solenoid valve 40 open, there is no restriction in the datum system downstream from the regulator R such as would inhibit relief of excess pressure. Fig. 14 shows a modified fuel system in which the fuel supply to the chamber C is heated in a water jacket 409. Other modifications are described. Specifications 830,305 and 929,776 are referred to.