Oxygen sensor deterioration diagnosis apparatus

Abstract

An oxygen sensor deterioration diagnosis apparatus includes an oxygen sensor provided in an exhaust system of an internal combustion engine, an air-fuel ratio control unit for controlling an air-fuel ratio, an operation state detection unit for detecting an operation state of the internal combustion engine, an inversion period measurement unit for detecting an inversion period of an output signal of the oxygen sensor, an oxygen sensor deterioration diagnosis unit for performing a deterioration judgment by comparing the inversion period with a previously set judgment period, and a deterioration diagnosis inhibiting unit for inhibiting, when the operation state detection unit detects the operation state of the internal combustion engine having an influence on the inversion period, the measurement of the inversion period in a period of time of the detection.

Description

technical field [0001] The invention relates to an oxygen sensor degradation diagnosis device for diagnosing the degradation of an oxygen sensor used for controlling the air-fuel ratio of an internal combustion engine and arranged on an exhaust pipeline of the internal combustion engine. Background technique [0002] The structure of the oxygen sensor installed in the exhaust system of the internal combustion engine and detecting the oxygen concentration in the exhaust gas is usually to coat the porous platinum electrode on the inner and outer sides of the zirconia element, and to detect the air-fuel ratio relative to the theoretical air-fuel ratio according to the oxygen concentration in the exhaust gas After being rich or lean, the signal is sent to the ECU (Electronic Control Unit). Then, the ECU performs feedback control through proportional-integral control or the like based on this signal, so that the air-fuel ratio of the mixed gas becomes the theoretical air-fuel rat...

AI Technical Summary

Problems solved by technology

[0008] In this way, although the deterioration is judged by detecting the inversion cycle of the oxygen sensor, since the inversion cycle of the oxygen sensor has a great relationship with the operating state of the internal combustion engine, such as changes in the amount of fuel ejected and the amount of air intake, so in In the operating state that affects the inversion cycle of the oxygen sensor, there is a problem that the oxygen sensor that should be normal is misdiagnosed as deteriorated

Thus misdiagnosing a normal oxygen sensor as deteriorating

[0009] In addition, when the measurement condition of the inversion period is not satisfied continuously for a predetermined time or more, in the deterioration diagnosis device that invalidates the previously measured inversion period, since when the measured inversion period is invalid, the normal measurement to It is also invalid including the inversion cycle of , so there is a problem that the frequency of deterioration diagnosis is reduced

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