ES346729A1 - Fuel injection control system - Google Patents

Abstract

The duration of the period in each cycle during which the valves of the fuel injection system of an I. C. engine are open is determined by a transistor circuit in accordance with the degree of vacuum in the inlet manifold, and is provided with a fuel inhibition facility when the acceleration pedal is not depressed, the engine temperature is above a preset minimum and the engine speed is above a preset minimum idling value. Normally the solenoids 13 of the fuel injection valves are energized by the amplified pulses from monostable multi-vibrator 18, which receives input pulses from engine driven contact breaker 20, giving two pulses per revolution, and delivers synchronous pulses whose duration is controlled by the pressure in the inlet manifold 12. These pulses are fed through synchronous change-over switch 24, alternately to transistor 27, energizing the left hand solenoids 13, and to transistor 28, energizing the right hand solenoids 13. The base of transistors 27, 28 is connected to a bi-stable multi-vibrator 38 which inhibits energization of solenoids 13 when accelerator pedal 87 is not depressed and associated switch 86 is closed and when the engine temperature, as used by a bimetallic switch 85, is above a minimum and switch 85 is closed. When either switch is open, diode 70 conducts, transistor 46 conducts, its collector is earthed and fuel injection proceeds normally as above. When both switches are closed diode 70 is blocked, and the operation of multi-vibrator 38 is dependent on the frequency of the pulses from contact breaker 20 fed in via capacitor 59 and resistor 62. If the frequency is lower than that of normal idling speed, components 52-59 pass the pulses to block transistor 45, transistor 46 conducts and fuel injection proceeds normally. If the frequency is above that of idling speed components 62-69 pass the pulses to block transistor 46 and fuel injection is inhibited.