| 摘要 |
PURPOSE:To prevent an air-fuel ratio immediately after current supply front being mis-judged by detecting the heating condition of a heating means and starting current supply across electrodes of an oxygen pump element with the detected output. CONSTITUTION:A heater current feed circuit 51 supplies current to a heater element 20 by the instruction of a CPU47, and detects a voltage at both ends and a heater resistance from a reference resistance Rs. Also the value of a heater compensation resistance 53 is read through an A/D converter 52, variation in the heater resistance is compensated, and a judgment resistance value is obtained. When it is larger than the set value 1 at which blackening phenomenon may not be caused, the heater element is heated to a high temperature and the presence or absence of passing of a specified time is judged and, if it is passed, current is started to be supplied to a pump. When it is not passed, heater temperature is controlled while the judgment resistance value is compared with the set values 2 and 3 at which the heater temperature is raised. After warming up has been completed, the set value 4 is used to hold the heater temperature controllably to a target temperature. Thus an air-fuel ratio immediately after current supply to the element 20 is started can be prevented from being mis- judged. |
