Electronic closed loop air-fuel ratio control system

Claim 1

An electronic closed loop air-fuel ratio control system for supplying an optimum air-fuel mixture to an internal combustion engine, which system comprises in combination: an air-fuel mixture supply assembly; an exhaust pipe; an exhaust gas sensor provided in the exhaust pipe for sensing the concentration of a component in exhaust gases, generating a first signal representative thereof characterized by upper and lower constant voltage maxima and an analog region as a function of air-fuel mixture therebetween, in the vicinity of stoichiometry; a difference detecting circuit responsive to said first signal for generating an analog second signal representative of the difference between magnitudes of the first signal from the exhaust gas sensor and a reference signal; a control signal generator responsive to said second signal, said control signal generator including first means for differentiating the second signal, second means for integrating the second signal, third means for proportionally amplifying the second signal, said first, second and third means being electrically connected in parallel and operating on said second signal simultaneously, and fourth means for summing the output signals of said first means, said second means of said third means to produce a control signal; and an actuator provided in the air-fuel mixture supply assembly responsive to the control signal for controlling the air-fuel ratio of an air-fuel mixture fed to the engine.