EXHAUST GAS TEMPERATURE DETECTION BY INJECTION OF TIME-VARYING CURRENT

摘要

A mixture control system for an internal combustion engine comprising an exhaust gas sensor and a source of time-varying current connected to the gas sensor to inject thereto a current which varies periodically between two constant values to develop a corresponding periodically varying voltage signal which superimposes a voltage signal developed in response to the ratio of mixture supplied to the engine. An amplitude detector is provided to detect the periodically varying voltage signal to develop a signal representative of the temperature of the gas sensor. The detected voltage signal is compared in a comparator with a reference level corresponding to the operating temperature of the gas sensor to operate the mixture control system in open-loop mode, when the gas sensor is operating below the operating temperature.