Patent ID: 7751966
Filing Date: 2010-07-06
Classification: G01M

Abstract:
1. An abnormality diagnostic device for an air-fuel ratio sensor that detects air-fuel ratio of exhaust gas of an internal combustion engine, comprising: an ECU including an identification portion that causes the ECU to model a system extending from a fuel injection valve to the air-fuel ratio sensor by a first order response delay, and that identifies a parameter in the first order response delay based on an input air-fuel ratio that is given to the air-fuel ratio sensor and an output air-fuel ratio that is output from the air-fuel ratio sensor; a waste time correction portion that causes the ECU to calculate a waste time that elapses between the input air-fuel ratio and the output air-fuel ratio, and performs a shift correction of at least one of the input air-fuel ratio and the output air-fuel ratio by an amount of the waste time; and an abnormality determination portion that causes the ECU to determine presence/absence of abnormality regarding a predetermined characteristic of the air-fuel ratio sensor based on the parameter identified by the identification portion, wherein the waste time correction portion calculates a dispersion value of the input air-fuel ratio and a dispersion value of the output air-fuel ratio, and if a peak of the dispersion value of the output air-fuel ratio is greater than a predetermined value, the waste time correction portion calculates the waste time based on a time difference between a peak of the dispersion value of the input air-fuel ratio and the peak of the dispersion value of the output air-fuel ratio.