| 摘要 |
PURPOSE:To obtain an oxygen concentration determination apparatus in which the time interval, when the oxygen concentration can not be determined, is shortened significantly by setting the temperature detection timing appropriately. CONSTITUTION:A circuit 50 detects the current during a period before finishing the current increase of a sensor body 20 after negative biasing through a bias control circuit 40. A microcomputer 70 then estimates the saturation current based on the detected current thus determining the temperature of the sensor body 20. Immediately after elapse of the period, the sensor body 20 is biased positively through the bias control circuit 40 and when the current decrease of the sensor body 20 due to the positive bias is ended, the microcomputer 70 determines the air/fuel ratio based on the current at that time. The microcomputer 70 also sets an appropriate period for applying the negative bias variably depending on the variation in the engine temperature or intake air flow. |
