Analog computer circuit for controlling a fuel injection system during engine cranking

An analog computer circuit for controlling a fuel injection system for an internal combustion engine during engine cranking, the fuel injection system being of the type including at least one electrically controllable fuel injector which, when energized, delivers a quantity of fuel to the engine that is proportional to the duration of the energization of the fuel injector, the fuel injection system further including circuit means coupled to the fuel injector for controlling the energization of the fuel injector in response to, and for the duration of, a cyclical logic level signal, applied by the aforementioned circuit means, the analog computer circuit generating the cyclical logic level signal and comprising:

• (a) means for supplying a DC voltage;
• (b) a plurality of switching
• (c) a capacitor;
• (d) a plurality of electrical impedances coupled to the switching devices, the electrical impedances being selectively switched into conductive circuit with the capacitor by the switching devices;
• (e) circuit means for controlling the switching devices as a function of the ratio of the voltage across the capacitor to the DC supply voltage;
• (f) circuit means for charging the capacitor from the DC supply voltage through the plurality of electrical impedances;
• (g) circuit means for discharging the capacitor at a frequency proportional to engine speed;
• and
• (h) circuit means coupled to the electrically controllable fuel injector for generating the cyclical logic level signal, the logic level signal having a cyclically recurring duration, at one logic voltage level, that is proportional to the time over which the capacitor is charged from the DC supply voltage prior to its being discharged by the discharge circuit means.