Air-fuel detection system using a limit current sensor

摘要

A/F sensor (30) outputs a linear air-fuel ratio detection signal proportional to the oxygen concentration in an exhaust gas from an engine (10) upon application of a voltage. A computer (20) controls the applied-voltage in a stoichiometric control region, a lean burn control region, an atmosphere detection region and a rich control region to have a fixed value such that the change rate of the applied-voltage is reduced to be less than that in other regions. In addition, when changing the voltage applied to the A/F sensor (30), the computer 20 variably sets the voltage change speed sequentially. Thus, the influence of the capacitive characteristic of the A/F sensor (30) is eliminated.