| 摘要 |
PROBLEM TO BE SOLVED: To well control a heater while simplifying constitution. SOLUTION: The sensor element part 60 of an A/F(air/fuel ratio) sensor 30 is constituted by laminating a solid electrolyte and a heater 64 to integrate them. The A/F sensor 30 outputs a linear A/F detection signal proportional to the concn. of oxygen in exhaust gas accompanied by the application of voltage. A microcomputer 20 operates the heater 64 through a heater control circuit 25 to hold the sensor element part 60 (solid electrolyte) to predetermined active temp. In this case, the microcomputer 20 detects element resistance on the basis of the voltage applied to the sensor element part 60 and the sensor current flowing accompanied by the applied voltage, and controls the supply of a current to the heater 64 on the basis of the element resistance. That is, the open control of heater working current is performed corresponding to the temp. rising capacity of the heater until effective element resistance becomes detectable, and the control for feeding back element resistance to an objective value is performed when the effective element resistance becomes detectable. |
