| 摘要 |
PURPOSE:To enable to judge abrupt change in the output of an O2-sensor, by controlling a reference value to be compared with the output of the O2-sensor according to the level of current passed to the O2-sensor which determines an aimed air-fuel ratio at which output of the O2-sensor is changed drastically. CONSTITUTION:In case that a signal S1 is given to a current supply means 4 by determining an aimed air-fuel ratio suited for the operational conditions of an engine at a feedback control circuit 8 and an inflow current Is of a value corresponding to the signal S1 is supplied to an O2-sensor 1 from the current supply means 4, the value of current Is is detected by comparing the voltages at the opposite ends of a resistance R1 by a current detecting circuit 11, and a voltage Vi corresponding to the value of current Is is given to a reference value determining circuit 12. The circuit 12 gives a voltage obtained by adding KVi (K is a constant) to a voltage V0 determined by resistances R7, R8 through voltage division to a comparator 5 as a reference comparison value SL. The comparator 5 makes comparison between the reference value SL and the output Vs of the O2-sensor and produces an ''over-rich'' or ''lean'' signal. |
