Electronic closed loop control system for internal combustion engine

Claim 1

An electronic closed loop control system for controlling an air-fuel ratio of the air-fuel mixture supplied to an internal combustion engine (1), which system includes: and exhaust gas sensor (3) for sensing a component of exhaust gases to generate an electrical signal representative thereof, a differential signal generator (4) fed by a source of single polarity and connected to said exhaust gas sensor for generating an electrical signal representative of a differential value between the signal from the sensor and a reference signal, control means (5) connected to the differential signal generator, and an actuator (6) connected between said control means and the engine, said control means controlling said actuator depending upon said differential value to optimally regulate the air-fuel ratio of the air-fuel mixture, wherein said electronic closed loop control system further comprises: clamping means (4') for clamping the signal from said differential signal generator to generate a signal therefrom, said clamping means being electrically interposed between said differential signal generator and said control means and including a first d.c. power source the potential of which is lower than that of a second d.c. power source provided for the differential signal generator, the potential of the signal from said clamping means ranging substantially from that of said first d.c. power source and zero potential, and the middle value of the signal from said clamping means substantially corresponding to the case where the potential of the signal from the sensor is equal to that of said reference signal.