GB1306844A - Circuit arrangement for controlling the air-fuel ratioin an internal combustion engine - Google Patents

Abstract

1306844 Automatic air/fuel ratio control PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 19 March 1970 [22 March 1969] 13319/70 Heading G3R An arrangement for controlling automatically the air/fuel ratio of fuel mixture supplied to an internal combustion engine comprises a pick-up inserted in the exhaust gas duct and consisting of a solid substance coated on both sides with a porous electrode layer, one side being in contact with exhaust gases and the other contacting oxygen with a reference concentration whereby a potential difference is produced between the layers if they are subjected to different oxygen concentrations. This potential difference is used to control the air/ fuel ratio to attain a desired value thereof. In Fig. 2, a cylinder 1 of zirconium oxide inserted in the exhaust duct 6 of a four stroke engine has porous platinum electrode layers 2 and 3 the potential difference between which depends on the relation between oxygen concentrations outside and inside the exhaust duct. This difference is amplified at 9 and 11 and modified by the temperature detected by a thermocouple 7 to apply to a resistor 12 a voltage dependent on oxygen concentration, and thus carbon monoxide concentration which is complementary thereto. Any difference between this voltage and a reference voltage applied to a resistor 13 is effective through an integrating amplifier 14 to operate a follow-up servomotor 21 which differentially adjusts throttle valves 22, 23 associated with carburetters 24, 25 of different richness so that the air-fuel ratio is modified in such sense as to maintain a desired CO concentration in the exhaust and thereby avoid excessive pollution. Operation of an accelerator pedal 29 adjusts a main throttle 28 and also a potentiometer 31 the output of which is differentiated at 32 and applied through a limiter 33 to temporarily alter the reference voltage so as to produce an effect dependent on rate of accelerator operation. Instead of limiter 33 the movement of motor 21 or valves 22, 23 may be limited. If the inlet pressure drops, e.g. on overrun, a pressure responsive device 35 closes a valve 36 to cut off the fuel supply. A modification, having a single carburetter and no temperature compensation, servomotor follow-up, or accelerator rate effect, in which the servomotor controls an additional supply of air downstream of the carburetter, is described. The Specification also refers to pedal 29 operating valves 22 and 23 in the same direction instead of operating valve 28 and the servomotor 21 varying carburetter float chamber level instead of throttle valves. Applications to fuel injection engines in which the CO exhaust content controls the pressure in the fuel distributer, or the duration of electrical pulses controlling the periods of fuel injection and derived from an electromagnetic, Piezo-electric, capacitive, or Hall effective device driven by the engine, are described.