| 摘要 |
PROBLEM TO BE SOLVED: To provide a heater control device for an air-fuel ratio sensor which can supply an optimum amount of electric power regardless of the temperature of cooling water at the start of an internal combustion engine. SOLUTION: Immediately after the start of an internal combustion engine, a switching element 122 is kept turned on to pass current continuously to the heater 12 of an air-fuel ratio sensor 11. The switching element is duty-ratio controlled so that the heater temperature is kept at 1100 deg.C after the heater resistance calculated from the voltage applied to the heater and the current flowing through the heater has reached a predetermined value, and so that a detecting element 111 is kept at 710 deg.C after the air-fuel ratio sensor has become active. In that case, the power supplied to the heater is increased in accordance with the temperature of cooling water detected by a cooling water temperature sensor 142 and with compensated power calculated as a function of the time elapsed after the start of the internal combustion engine, so as to prevent excessive heating of the heater and delay of the activation of the air-fuel ratio sensor. |
