GB1340307A - Electronic fuel injection systems - Google Patents

Abstract

1340307 Electronic fuel injection systems for I C engines GENERAL MOTORS CORP 14 Sept 1972 [21 Oct 1971] 42638/72 Heading G1N In an I. C. engine electronic fuel injection system, an inductor 112 having an inductance proportional to the value of an engine operating parameter is supplied with, in synchronism with engine rotation, a voltage E having a constant magnitude thereby developing in the inductor a linearly varying magnitude current J whose constant rate of change is inversely proportional to the inductance of the inductor, the amount of fuel supplied being determined by this rate of change so as to be a linear function of the engine operating parameter. As shown, the conductor 112 has its inductance varied by a magnetic core 114 movable in dependence upon the negative pressure in the intake manifold 20 of the engine. Pulses P triggered in synchronism with engine rotation are supplied by a circuit 202, each pulse initiating the constant magnitude voltage E by switching a transistor 96. As the current J through the inductor increases the voltage drop K across a resistor 102 connected to the collector of transistor 96 decreases from a maximum value V u at a rate inversely proportional to the inductance value. This voltage is compared in a differential amplifier 156 with a reference voltage R determined by resistors 174, 176. When the voltage reaches the reference, the amplifier is switched to its original state to terminate the application of an injection pulse C supplied from the collector of a transistor 190. The duration of each pulse C is thus a linear function of the negative intake pressure. The duration of the pulses C may additionally be determined by other engine operating parameters, e.g. air temperature, output speed or battery voltage, by selectively shifting the level of the voltage E, the reference voltage R, or the voltage K.