Patent GB-1500814-A (GB)
Title: Method and apparatus for providing a periodic control signal especially for controlling the ignition of an internal combustion engine
IPC: F02P5/155
Filed: 1975-03-26
Abstract: 1500814 Timing ignition; controlling fuel injection SOC ANON POUR L'EQUIPEMENT ELECTRIQUE DES VEHICULES SEV MARCHAL 26 March 1975 [28 March 1974 29 March 1974] 12725/75 Heading F1B The timing of a periodic control signal, e.g. for an I.C. engine ignition timing or fuel injection, in dependence at least on the speed of rotation of a shaft, is effected by generating a signal P of duration q at a pick-up 2 in response to the passage of a segment on the shaft 1, and by generating a signal P of duration q during the absence of signal P; the signal P being fed to an integrator 18 receiving also a fixed voltage, and the output thereof being fed to an adder 21 together with a characteristic voltage K and a fixed voltage to produce a signal during a period q or q dependant on q or q and representing the required ignition advance, and storing the signal until a subsequent period q or q when the signal P is similarly fed to an integrator 32 and adder 38 to produce a signal dependent on time; the two output signals then being compared at a comparator 23 and, when equal, producing an ignition advance signal E2. The advance signal is fed also to an AND gate 28 receiving also signal P, the output of which gate is fed to the base of a field effect transistor 26 to discharge a condenser 27 storing the output of integrator 18. As shown, the advance curve produced as a function of speed is a linear curve with positive slope but, Fig. 6, (not shown), by feeding the voltage K to the positive terminal of adder 21, a curve with negative slope is produced. Also, Fig. 8 shows a speed discriminating circuit which allows selection of a particular calculating circuit as described to allow the ignition advance to function over selected speed ranges. An operational amplifier 66 is supplied with the signal P and a fixed voltage, the storage capacitor 73 being controlled_by a field effect transistor 72 receiving the signal P at its base. The output 68 of amplifier 66 is fed to three comparators 69, 70, 71 also connected to different points 75a, 75b, 75c and 75d on a resistor. The comparator outputs are each fed to four AND gates 79, 80, 81 and 82, the three inputs of each of which have a different number of invertors so that one only of the flipflop circuits 87, 88, 89 and 90 will produce an output 91, 92, 93 or 94 to a calculating circuit in dependence on the respective speed range. The flip-flops have inputs H from signal P, reset inputs R from signal P and ground terminal S. A further supply input, not shown on Fig. 8, to each flipflop may be varied, Fig. 10, (not shown), in accordance with any other parameter, e.g. inlet manifold depression. Again, Fig. 12, (not shown) illustrates a complete circuit including a speed discriminator and the calculating circuits in which many components function in more than one circuit. Also, Fig. 17, an identical pick-up 200 produces a signal P fed to sawtooth generator 202a, b, c, to the output of which is added a constant voltage at 203a, b, c, the outputs of which are fed to comparators 204a, b, c, which also receive the stored outputs from sawtooth generators 201a, b, c, fed from pick-up 200 with signal P. To modify the timing in dependence on the inlet manifold depression, a pressure responsive pick-up 208 feeds a signal to amplifiers 207a, b, c, the outputs of which have been multiplied by coefficients which may differ if required.