GB1342705A - Injection control system for internal-combustion engines - Google Patents

Abstract

1342705 Regulating I C engine fuel supply SOC INDUSTRIELLE D'ELECTRONIQUE ET D'INFORMATIQUE 26 June 1972 29819/72 Heading F1B [Also in Division G1] In an I. C. engine, electrically controlled, intermittent fuel injection system, the duration of the injection valve energizing pulses is determined by the mass flow-rate of air into the engine cylinders measured by a corona effect ionization gauge 125 positioned in the air intake duct 301. The gauge includes an anode wire 15 centred on the axis of the duct, a pair of axially spaced conductive tubes 51', 51" surrounding the wire, and a helical cathode 16 lining the duct wall through insulation 17. As shown, the anode is energized by voltage stepped-up pulses P derived from an engine triggered pulse generator 1, the ends of the cathode leading to a differential amplifier 20, whose output pulses are integrated at 26, 27. The integrated voltage, representing the mass flow-rate is amplified at 28, 33 and 29 and combined with a temperature dependent voltage, derived from a thermistor 30 in the cooling system or on the engine wall, to provide at the output of an amplifier 31 a mass flow-rate and temperature dependent voltage. This voltage is compared at 323 with a sawtooth voltage on a capacitor 324 which is triggered by the pulses from generator 1. The pulses from generator 1 also trigger a flipflop 326 which operates a pre-energizing 358a and an energizing 359a injection coils through a monostable circuit 327 and a delay circuit 328 respectively, the flip-flop being reset to stop injection when the sawtooth voltage reaches the voltage level at the output of amplifier 31. When the throttle valve 304 is in its closed position as shown a stop 320 is engaged which grounds a line 329. Grounding of line 329 operates a relay 48, Fig.2, which switches the input of amplifier to a potentiometer 44. The low voltage supplied by potentiometer 44 causes the injection to be energized for a fixed brief period during each engine cycle. As shown, the pulse generator is a coil 114a operated by a magnet 115 on an engine driven shaft 111. In a multi-cylinder engine, the number of coils 114a equals the number of cylinders as does the number of transformers 10, and circuits 32a. In an alternative, the generator is provided by a constant current energized ionization gauge, similar to gauge 125, positioned in the duct downstream of the throttle valve, Fig. 3 (not shown). In order to compensate for varying air densities, a pair of ionization gauges are utilized, Fig.4 (not shown), to control capacitor 27.