| 摘要 |
PROBLEM TO BE SOLVED: To provide a heater controller which suppresses an excessive rise in the temperature of a sensor element and which protects the sensor element. SOLUTION: An A/F sensor 30 comprises a sensor element using a solid electrolyte body and a heater 39 used to heat the sensor element to an active state. A microcomputer 20 inside an air-fuel ratio detector 15 detects the element impedance of the A/F sensor 30, and it calculates a heater controlled variable on the basis of the deviation between the detected element impedance and a desired value. The microcomputer 20 calculates the heater controlled variable by limiting an integration term so as to restrain an increase in the integration term until the element impedance reaches a prescribed value on the halfway to the activation of the sensor when the sensor is activated. After the element impedance has reached the prescribed value, the limitation on the integration term is released, and the heater controlled variable is calculated. For example, until the element resistance reaches a prescribed value on the halfway to the activation of the sensor, the heater controlled variable is calculated without using the integration term. |
