| 摘要 |
PURPOSE:To improve the accuracy of air fuel ratio measurement at the start of an engine by deciding the activation state of a sensor according to the time when the oxygen pump current value of a wide-range air fuel ratio sensor reaches a maximum value. CONSTITUTION:The wide-range air fuel ratio sensor consists of a solid electrolyte pump cell 81, a solid electrolyte oxygen battery cell 82, porous electrodes 83a-83c, a diffusion chamber 84, a reference voltage source 85, and a comparing amplifier 86 which compares the reference voltage of the reference voltage source 85 with the electromotive force of the oxygen battery cell 82. Then this sensor is provided with a pump driving circuit 87, a resistance 88 for detecting a pump current, a heater 89, and a heater control circuit 90. Heater control driving is started simultaneously with the start of the engine and an oxygen pump driving current is supplied. When this oxygen pump current reaches the maximum value, the oxygen pump driving current is stopped temporarily and the air fuel ratio detected when the oxygen pump cell 81 is started from being driven after a specific time determined according to the operation state of the engine is used to perform air fuel ratio feedback control. |
