Patent GB-1329519-A (GB)
Title: Electronic fuel injection systems
IPC: F02D41/12
Filed: 1972-08-03
Abstract: 1329519 Fuel injection systems for I.C. engines GENERAL MOTORS CORP 3 Aug 1972 [7 Sept 1971] 36235/72 Heading G1N In an I.C. engine electronic fuel injection system, injection is prevented when the demand for engine power is decreased (i.e. the throttle is closed) and the engine speed is above a reference speed just above the idling speed by generating a speed voltage S which increases over a first fixed portion of engine rotation in each cycle, generating timing pulses P which occur at the end of a second fixed portion of engine rotation in each cycle, which end occurs during the first fixed portion, and disabling the fuel injection means when the amplitude of the speed voltage at the instant of occurrence of a timing pulse P is below a reference level R corresponding to the reference speed. As shown in Fig.1, a synchronizer 38 sequentially applies fuel injection pulses processed by a controller 36 under the control of a timer 34, Fig. 2 (not shown). A deceleration fuel control circuit 60 is responsive to signals A1 and A3 provided in the synchronizer 38, these signals having a pulse durations corresponding to 180 degrees engine rotation but displaced relatively by 90 degrees, and the position of the throttle 26 in the air intake manifold 20, to short circuit the injection pulses processed by the controller 36 when prevention of injection is desired. As shown in Fig. 4, the deceleration control circuit 60 includes a speed signal generator 80 which provides the signal S during the pulses of signal A1, a reference signal generator 90, a differential amplifier 106 which assumes a first or a second state depending upon the relative amplitudes of the speed signal and the reference signal, a differentiator 132 for providing the timing pulses P at the occurrence of the pulses of signal A3, AND gates 136, 138 responsive to the pulses P and the states of the transistors of the differential amplifier to control a bi-stable circuit 178, the bi-stable circuit in one state controlling the reference signal generator 90 to provide a first reference level Lu corresponding to the reference speed and in the other state to provide a second reference level Lo corresponding to a higher speed, and a switch L10 which is closed when the throttle 26 is closed. In operation, and with reference to Figs. 5 and 6, when the engine is accelerating towards a speed Nu and through Nu injection proceeds normally, the reference level being set at Lo, Figs. 5b and 5c. At the time t 1 , demand for engine power is decreased by closing the throttle 26, thereby closing switch 210. In this condition, since the amplitude of the speed signal at the occurrence of the pulses P is below the reference level, a transistor 224 is rendered conductive to by-pass the injection pulses from controller 36 to ground. The engine speed then decreases until, at the instant when the amplitude of the speed signal at the occurrence of the pulses P is above the reference value Lu, Fig.5a, and the bi-stable circuit is switched to its other state, fuel is re-supplied. This occurs between the instants t 2  and t 3  after which injection proceeds normally at the idling speed of the engine.