Patent GB-606451-A (GB)
Title: Fuel control system for internal combustion engines
IPC: F02D41/14
Filed: 1945-12-27
Abstract: 606,451. Automatic control of internalcombustion engines. SHELL DEVELOPMENT CO. Dec. 27, 1945, No. 34995. Convention date, Jan. 2. [Class 38 (iv)] [Also in Group XXVII]  An internal-combustion engine of the spark-  ignition type with fuel-metering means for adjusting the combustion mixture to a higher or lower fuel-air ratio, is provided with means which changes that ratio automatically in the necessary direction in response only to a decrease in the temperature of the engine. The system includes means for actuating the fuelmetering device periodically or cyclically, and is based on the consideration that the best engine fuel economy is obtained when the engine temperature is at a maximum. A thermo-couple 2 which may be located in the cylinder head, but preferably within the exhaust pipe or manifold, is connected to a measuring bridge unit 3 which may be of known commercial type embodying a self-balancing potentiometer whereby the thermo-couple voltage is balanced against a standard cell, and a pointer or mirror type galvanometer is deflected to produce a signal which operates a motor in the requisite direction to rebalance the bridge. A tapping 37 is taken from that side of the signal circuit to the motor which is energized only when rebalance is effected in response to a decrease of the engine temperature, and a signal is then fed to a timing or cycling unit 4 whereby switches 41, 42 are closed periodically at a constant relatively low frequency by rotating cams or the like driven by a motor which is fed independently over lines 13, 14. Alternatively, the timing unit may comprise a mechanical or electronic commutator of known type. The switch 42 is connected in one supply line 23 to the armature of a throttle controlling motor 6, while switch 41 is connected to supply unidirectional pulses to energize a relay unit 5 controlling the direction of energization of the motor field over leads 17, 19 or 18, 20. The shaft of motor 6 is connected through a torque-limiting clutch 25 to a lever 26 arranged to actuate a lever 27 which is linked to means for increasing or decreasing the fuel-air ratio of the mixture supplied to the engine by a fuel-injector device 7. A handle and locking device 29 on the lever 27 enable an operator to override the automatic control and determine the setting of the fuel-metering means manually. The operation of the automatic control is such that, due to the particular connection from the potentiometer unit 3 to the timing unit 4, an increase of temperature produces no signal over leads 37, 38, but a decreasing temperature due to the' fuel mixture being either too rich or too lean produces a signal in relay unit 5. The closing of switch 42 energizes both armature and field throughout the operative portion of each cycle of the timing unit, the direction of rotation being dependent on the way the field is connected during each period. In a modification, Fig. 8 (not shown), a unidirectional motor 6a is employed, and a relay 5a controls a gear-box which determines the direction of rotation of a screw-threaded shaft carrying a travelling nut linked to the fuel-metering device. A magnetic clutch controlled by the timing device may be interposed between the gear-box and the driving motor.