GB1397502A - Closed loope engine control system - Google Patents

Abstract

1397502 Automatic control of exhaust gases BENDIXCORP 25 July 1973 [14 Sept 1972] 35417/73 Heading G3R The quantity of fuel which is periodically supplied to an internal combustion engine 10 is controlled at 50 in response to the integrated output of a comparator 40 which produces predetermined constant high or low level signals when a signal from a sensor 20 of the "quality" of combustion is above or below a predetermined limit. The sensor measures the oxygen concentration in the exhaust gas of the engine and it is explained that its output voltage will always be the same at a certain oxygen content (the "transitional" point) but the voltage at other concentrations will depend upon its age and temperature Fig. 4 (not shown). To render the system insensitive to these variations the comparator, Fig. 2 (not shown) produces an output voltage at 123 of +0.7, 0 or -0.7 according to whether the sensor voltage is below, at or above the transitional point. The comparator has a Zener controlled reference voltage and comprises an operational amplifier with positive feedback provided by diodes. Fuel injection is controlled by a circuit Fig. 3, (not shown) described in Specification 1367265 in which capacitors are charged at a regulated rate Fig. 6 (not shown). Initially this depends upon measured engine parameters, e.g. speed but when a timing signal is received to start injection the charging of the appropriate capacitor is increased by a ramp signal until its voltage reaches that set by another measured engine parameter, e.g. manifold pressure. The output of the comparator is integrated to modify the slope of the ramp signal. Thus, the amount of fuel injected depends upon the capacitor voltage at the start of injection (and this depends upon the first engine parameter) and the slope of the ramp signal, which depends upon the oxygen content of the exhaust gas.