GB1337529A - Electronic fuel ejection systems - Google Patents

Abstract

1337529 Electrical fuel Injection systems for I.C. engines GENERAL MOTORS CORP 26 Oct 1972 [15 Nov 1971] 49470/72 Heading G1N In an I.C. engine, intermittent, electrical fuel injection system, the duration of injection control pulses C, initiated at a frequency proportional to engine speed, is determined by at least one engine operating parameter, e.g. intake air pressure, and is compensated for engine speed, the compensation being determined by the amplitude of a speed voltage S during each control pulse C, the speed voltage being provided by a generator so as to have an amplitude which varies at a constant rate over a time period which is a function of the interval between the termination of successive control pulses, to provide a first order compensation, the constant rate of change being a function of the frequency of the control pulses to provide a second order compensation. As shown in Fig.1, the control pulses C are provided by a generator 88 which is triggered in synchronism with engine rotation by a pulse former 164. Upon each triggering, the voltage at a junction 118 is compared with a reference voltage in a differential amplifier 126, the time taken for the voltage at 118 to fall to the reference voltage determining the duration of the control pulses. The initial voltage at junction 118 is determined by a voltage developed by a speed compensator circuit 166, Fig.7, and the rate of fall of the voltage is determined by the value of an inductor which in turn is determined by the intake air pressure (sensor 112). The speed compensator is connected to receive the control pulses C, the termination of each pulse C initiating a constant duration speed pulse P, Fig. 5 at a junction 180. The speed voltage S is developed across a capacitor 188, this capacitor being discharged during each pulse P and being charged at a constant rate, determined by the voltage at a junction 194, during a period Tc between the pulses P. The bias voltage B developed at the junction 118 at the output of the speed compensator is inversely proportional to the speed voltage S. Thus, the bias voltage B at the junction 118 at the initiation of each pulse C determines the duration of the pulse C and it will be seen that as the frequency of the pulses C increases, the bias voltage at the initiation of each pulse C increases and thus the duration of each pulse C increases, thus providing a first order compensation. To provide the second order compensation, the charging rate of capacitor 188 is determined by the engine speed. To thus end, the pulses P at junction 180 are applied to an integrator 312, 314 to provide a voltage at junction 308 representing engine speed. As the engine speed increases, a resistor 230 and subsequently a resistor 226 of a resistor chain which determine the charging rate of capacitor 188, are by-passed thereby changing the charging rate of capacitor 188 at a speed N 3 and at a speed N 5 . The purpose of this is to provide a speed compensation which approximates an optimum linear speed compensation X between two speeds No and Nu, as shown in Fig.6. Additional resistors may be provided in the chain and sequentially by-passed to provide more steps in the actual approximate compensation curve.