GB1365051A - Internal combustion engine fuel injection control system having a warm up fuel enrichment circuit - Google Patents

Abstract

1365051 Electronic fuel injection systems for I C engines BENDIX CORP 2 Jan 1973 [20 Jan 1972] 210/73 Heading G1N In an I.C. engine, electronic fuel injection system of the type having a computer 50 which develops a ramp voltage in synchronism with engine rotation and compares this voltage with a reference voltage, which is determined by the air pressure in the engine intake manifold, to provide injection valve opening pulses when the voltage is below the reference, a warm-up fuel enrichment circuit is provided to be responsive to engine temperature to control the variation rate of the ramp voltage so that the injection valve opening pulses are extended by an amount determined by the extent of the engine temperature below a pre-set temperature. As shown, a flip-flop 38 is triggered in synchronism with engine rotation to produce alternate signals 92, 94 on leads 40, 42, these leads being connected as shown to a pair of AND gates 46, 48 and to the computer 50, shown in Fig. 3. Upon receipt of signal 92, a capacitor 103 is charged by a current source 101 to provide the voltage shown at A to D in Fig. 4. When the signal 94 is received, capacitor 103 is then charged by a current source 102 to provide the voltage shown from point D onwards in Fig. 4. A second capacitor 104 also produces there across the voltage 90 shown in Fig. 4, but phase displaced therefrom by the width of pulse 92. A comparator 107 receives at the base of a transistor 171 the higher of the two voltages across the capacitors, and compares this voltage 90 with a reference voltage 98 which is provided at least by an intake air pressure sensor. The comparator provides a pulse to the AND gates 46, 48 from the instant of point D to the instant when the voltage 90 reaches the reference voltage 98. In order to provide warm-up fuel enrichment, the current source 102 is provided with a thermistor 14 as shown. This thermistor is responsive to engine temperature and causes a reduction in the charging current supplied by source 102 when the engine temperature is below a pre-set value determined by resistors 114, 115. Thus as engine temperature decreases from the pre-set value, the slope of the voltage 90 is reduced, as shown in Fig. 4, thereby providing longer duration pulses from the comparator 107. (For Figures see next page)