Patent GB-1367264-A (GB)
Title: Information s'ignal generating circuitry for electronic fuel cont rol system
IPC: F02D41/00
Filed: 1973-01-22
Abstract: 1367264 Electronic fuel injection systems for I C engines BENDIX CORP 22 Jan 1973 [15 Feb 1972] 3220/73 Heading G1N In an I.C. engine, intermittant fuel injection system of the type in which a computer is responsive to engine triggered signals to generate a voltage which is compared with a reference level determined by signals from engine condition sensors, the period from the initiation of the voltage to the instant it reaches the reference level determining the duration of injection valve energizing pulses, a circuit is provided which controls the level of the voltage at its initiation point in dependence upon engine speed. As shown, alternate high level signals F, G are supplied at input locations 40, 42 in synchronism with engine rotation. Current sources 101, 102 in association with a switching circuit 220 are operative to control the voltage appearing across capacitors 103, 104, the voltage D appearing across capacitor 103 being determined by the current source 101 and the switching circuit 220, as described below, and the voltage E across capacitor 103 being determined by current source 102. Voltages E', D' appear across capacitor 104 in similar manner. A comparator 107 is responsive to the higher of the two instantaneous voltages appearing across capacitors 103, 104 and compares this voltage with a reference voltage at terminal 170, established by at least a signal representative of intake manifold pressure, to determine the injection duration. The voltage D across capacitor 103 and D' across capacitor 104, are determined as follows. The circuit shown in Fig. 4 receives the signals F and G at terminals 40, 42 respectively to charge a capacitor 312. The voltage appearing across capacitor 312 is compared with two reference levels determined respectively by resistive networks 330, 336. Immediately the high level voltage F is received, the capacitor 312 begins to charge and a low signal appears at a terminal 244. When the voltage across capacitor 312 reaches the first reference level, set by network 330, and indicative of an engine speed lower that a first pre-set value, a high level signal appears at terminal 244 and a low level signal appears at a terminal 250. When the voltage across capacitor 312 exceeds the second reference level set by network 336 and indicative of an engine speed lower than a second pre-set value, a high level signal appears at terminal 250. The terminals 244, 250 are respectively connected to reference level establishing circuits 210, 214, a third such circuit 212 also being provided. These circuits are associated with the switching circuit 220 so as to control the voltages D, D' appearing across the capacitors 103, 104. The voltage which appear on the bases of transistors 230, 232 and 234 of the circuits 210, 212 and 214 are shown respectively at A, B and C in Fig. 5. The switching circuit 220 is responsive to the lowest instantaneous voltage appearing at the bases of transistors 230-234 to establish the voltage D and D' across capacitors 103, 104. Portions 401, 403, 405 of these voltages correspond to the portions 401, 403, 405 of the voltages A, B and C. The portions 402, 404 correspond to discharging and charging periods of capacitors 103 and 104.