| 摘要 |
PROBLEM TO BE SOLVED: To provide a deterioration detecting device for a linear air-fuel ratio sensor, capable of accurately detecting time constant deterioration of the linear air-fuel ratio sensor, without being affected by air-fuel ratio fluctuation (steady fluctuation) such as swell having a relatively large period, by providing an air-fuel ratio with disturbance, differentiating an output value of the linear air-fuel ratio sensor after forced change in the air-fuel ratio and determining time constant deterioration based on the differential value, at the time of deterioration detection of the linear air-fuel ratio sensor. SOLUTION: The deterioration detecting device for the linear air-fuel ratio sensor is equipped with the linear air-fuel ratio sensor provided in an exhaust system of an engine and outputting a value proportional to oxygen concentration in exhaust gas and with an air-fuel ratio control means for performing feedback of the air-fuel ratio of air-fuel mixture supplied to the engine to a target air-fuel ratio based on the detected value by the linear air-fuel ratio sensor. The deterioration detecting device for the linear air-fuel ratio sensor is further provided with air-fuel ratio changing means Q3, Q4 for forcibly changing an air-fuel ratio, a differential means Q6 for differentiating the output value of the linear air-fuel ratio sensor after the change in the air-fuel ratio and a deterioration determination means R1 for determining time constant deterioration of the linear air-fuel ratio sensor based on the value obtained by the differential means Q6. COPYRIGHT: (C)2006,JPO&NCIPI
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