Patent ID: 7901562
Filing Date: 2011-03-08
Classification: G01N

Abstract:
1. A degradation detection method for an oxygen sensor, comprising the steps of: calculating an element impedance real value from a value related to an electric power supplied to the oxygen sensor, and acquiring the calculated value as a first judgment value; calculating an element temperature estimated value of the oxygen sensor from a factor that affects a temperature of the oxygen sensor, and acquiring the calculated value as a second judgment value; and determining whether the oxygen sensor has an abnormality based on the first judgment value and the second judgment value, wherein, in the abnormality determining step, it is determined that the oxygen sensor has an abnormality if a relationship between the first judgment value and the second judgment value does not agree with a normal temperature characteristic that is exhibited by an element impedance of the oxygen sensor, wherein the oxygen sensor comprises a sensor element that exhibits the temperature characteristic, and a heater for heating the sensor element, wherein the factor that affects the temperature of the oxygen sensor includes at least a factor related to a state of operation of the heater, and wherein the abnormality determining step comprises the step of detecting a state of electrification of the heater, and the step of, if it is determined that the oxygen sensor has an abnormality in a situation where the heater is not electrified, identifying the abnormality as an abnormality of the sensor element.