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AssigneeNippondenso Co., Ltd.
InventorsTomomichi Mizoguchi, Masayuki Takami, Kazuhiro Okazaki
Estimating the term…
An oxygen sensor has a detecting device unit for outputting a sensor current such as a limiting current of which a value is constant even though a sensing voltage applied to the oxygen sensor changes in a limiting current generating region and corresponds to an air-fuel ratio of a combustion gas and a heater for heating the detecting device unit to keep a resistance of the detecting device unit even though the oxygen sensor is degraded. When the sensing voltage is changed to a second sensing voltage of a resistance governing region, a current peak occurs in the sensor current, and a peak current value is detected. Because the peak current value decreases as the oxygen sensor is gradually degraded, when the peak current value is lower than a degradation judging value, it is judged that the oxygen sensor is degraded. Therefore, the diagnosis of the degradation of the oxygen sensor can be performed with a high accuracy.
A method for diagnosing degradation of an oxygen sensor from which a limiting current corresponding to an oxygen concentration is output according to a voltage-current characteristic by applying a sensing voltage placed in a limiting current generating region, comprising the steps of:
A method for diagnosing malfunction of an oxygen sensor from which a limiting current corresponding to an oxygen concentration is output according to a voltage-current characteristic by applying a sensing voltage placed in a limiting current generating region, comprising the steps of:
An apparatus for diagnosing degradation of an oxygen sensor from which a limiting current corresponding to an oxygen concentration is output according to a voltage-current characteristic by applying a sensing voltage placed in a limiting current generating region, comprising:
Dependencies are inferred from the claim text.