ES346778A1 - Fuel injection system for internal combustion engines - Google Patents

Abstract

In an I. C. engine with fuel injection controlled electrically in accordance with the degree of vacuum in the inlet manifold, the fuel pump is automatically switched off at speeds below idling, to reduce loss of fuel due to faulty functioning, the switch circuit being cut-out at starting. As shown (Fig. 1), the four cylinders of an engine 10 are supplied with fuel through valves 13, obtained from tank 17 by pump 16 driven by motor 18. The engine drives a contact breaker 56, 57, 58 feeding two pulses per revolution to a monostable multi-vibrator 25 to produce a pulse train synchronous with the engine rotations whose durations are determined by the pressure in the inlet manifold 12, as measured by the displacement of core 41 of transformer 39, and extended when the engine temperature is low, as sensed by a temperaturesensitive resistor 67. These pulses are fed through synchronous switch 29 to the solenoid windings of the valves 13, and also to an averaging circuit comprising capacitor 72 in parallel with resistor 71. When the engine speed is above idling, the charge on capacitor 72 causes transistors 21, 22 to conduct and relay winding R is energized, contact r is closed and motor 18 is energized. When the speed falls below idling, the charge on capacitor 72 does not maintain transistor 21, 22 conducting and contact r opens, stopping the fuel pump 16. A switch 80 in the base circuit of transistor 21 is closed when starting, causing the transistor to conduct and close contact r independently of speed. In a modification the averaging circuit is fed from a separate monostable multi-vibrator so that the pulses being averaged are of constant duration.