| 摘要 |
PROBLEM TO BE SOLVED: To provide an air/fuel ratio-detecting device that can accurately detect an air/fuel ratio in each state of a rich region, a theoretical air/fuel ratio, and a lean region. SOLUTION: A detection part 11 has a zirconium solid electrolyte 102, an atmosphere-side electrode 104, an exhaust-side electrode 105, and a diffusion resistor 106. An atmosphere-side application voltage VAF+ is applied to the non-inverted input terminal of an operational amplifier 82, and an exhaust-side application voltage VAF- is applied to the non-inverted input terminal of an operational amplifier 83. The operational amplifiers 82 and 83 are connected to a plus-side power supply VB and ground, respectively, power is supplied, and operation is made with a single power supply. In an A/D conversion part 84, a voltage V1 at the side of an operational amplifier 83 and a voltage V2 at the side of a detection part 101 are A/D-converted and are outputted to a microcomputer 85. The microcomputer 85 calculates a sensor current IP flowing between the electrodes 104 and 105 based on the voltages V1 and V2 and the resistance value of a resistor R1 and then calculates an air/fuel ratio according to the sensor current IP. |
