Patent GB-1471449-A (GB)
Title: Internal combustion engines having a fuel injection system
IPC: F02D9/02
Filed: 1974-04-30
Abstract: 1471449 Regulating IC engines ROBERT BOSCH GmbH 30 April 1974 [2 May 1973 1 March 1974] 18799/74 Heading FIB [Also in Division G3] An I.C. engine comprises an exhaust gas recirculation pipe extending between an inlet manifold and an exhaust pipe, adjustable throttle means being arranged in the inlet manifold upstream of the recirculation pipe and/or in the exhaust pipe or in the recirculation pipe determining the quantity of exhaust gas relative to the quantity of air drawn into the inlet manifold, means being arranged in the inlet manifold for continuously monitoring the air flow-rate, and a fuel injection control being arranged to control the quantity of fuel injected, the throttle means or the fuel injection control being arbitrarily operable in dependence on the monitored air flow-rate to obtain the desired ratio of injected fuel to the quantity of air. Exhaust gas is recirculated to the inlet manifold 2, Fig. 1, via a pipe 10, the throttle pedal 15  controlling the usual air throttle valve 5 or, instead, a throttle valve 11 in the exhaust pipe 6 or a throttle valve 12 in the pipe 10. The air-flow determined by the throttle valve 5 and the engine speed is measured by a pivoted flap 20 which controls a fuel metering valve 22 downstream of the fuel pump 23. The metered fuel is distributed to the engine cylinders by an injection pump 17. The discharge pressure of the pump 23 is stabilized by a relief valve 24, while the pressure drop across the metering valve 27 is stabilized by a throttle valve 25 in series with the metering valve and operated by a diaphragm 27 subjected to the pressure drop. The intermittent flow through the injection pump 17 is accommodated by an accumulator 30. In Fig. 3, the air-flow is measured by a flap 35 which operates a potentiometer 38 to provide a voltage input to an electronic control unit 39 varying substantially linearly with the airflow. A potentiometer 46 connected to the control rod 47 of the fuel injection pump 8 provides a voltage input to the control unit 39 varying linearly with the fuel flow. A further input representing the engine speed is fed to the control unit 39 by a signal generator 45. A cam 50 linked to the throttle valve 5 acts via a lever 51 to provide a coarse adjustment of the fuel flow, a fine adjustment being provided by a servo solenoid 52 acting on the lever 51 and controlled by the control unit 39.Overspeeding is prevented by a governor 53. In a modification, Fig. 2 (not shown), the control unit 39 controls solenoid-operated fuel injection valves (40). In Fig. 5, the fuel flow is determined by the pedal 15 acting on the fuel injection pump, and the air-flow is adjusted correspondingly by a throttle valve 5 operated by a hydraulic actuator 90. The actuator is controlled by an hydraulic bridge comprising a throttle valve 77 controlled in accordance with air-flow by a pivoted plate 80, a throttle valve 65 controlled by the fuel flow, and a pair of fixed throttles 86, 87. In an electrical version of this arrangement, Fig. 4 (not shown), the actuator 90 is replaced by a solenoid (64) controlled by a Wheatstone bridge comprising two fixed resistors (59, 60) and two variable resistors (56, 58), the latter being in the form of heated  wires which are inserted in the fuel flow and air-  flow respectively whereby their resistances vary with the flows. Variable resistor (58) may be replaced by a potentiometer arrangement 35-38 as in Fig. 3.In Fig. 7, throttle valve 77, actuated in accordance with air-flow by pivoted plate 80, is connected in series with the fuel injection pump 55 so as to produce a pressure drop which is a function of both the air-flow and the fuel flow. This pressure drop is compared with a fixed pressure drop produced across one limb 106 of an hydraulic potentiometer 106, 108 for the purpose of adjusting the air-flow by means of throttle valve 5 operated by actuator 90. The comparison is effected by a metal diaphragm 110 which, when not in the neutral position, contacts one or other of two electrodes 111, 112 so as to energize one or other of two solenoid valves 113, 114 whereby the actuator 90 is moved in one direction or the other to adjust the throttle valve 5. In a modification, Fig. 8 (not shown), the electrical components 110-114 are replaced by an arrangement of diaphragm-operated valves. In a further modification, Fig. 9, the pressure drop across the throttle valve 77, which as in Fig. 8 is a function of air-flow and fuel flow, is sensed by a diaphragmactuated valve 143 which controls the flow from the fuel pump 68 to the actuator 90. The flow returns to the fuel pump inlet via a variable throttle passage in the piston 147 of the actuator and a fixed restrictor 151. When the engine is on full load, the exit end of the exhaust gas recirculation pipe 10 is closed by the portion 153 of the throttle 5. This feature may be incorporated in the other embodiments.