Patent ID: 8590289
Filing Date: 2013-11-26
Classification: F01N,F02D,Y02T

Abstract:
1. A deterioration diagnostic device for diagnosing a deterioration condition of an exhaust gas purifier disposed in an exhaust passage in an internal-combustion engine based on an output of a first exhaust gas sensor that is disposed downstream of the exhaust gas purifier, comprising: detecting-signal generating means for generating a detecting-signal having particular frequency components and multiplying the generated detecting-signal by a basic fuel injection amount so as to calculate a fuel injection amount, said detecting-signal being a fixed signal obtained by adding a single trigonometric function wave or a composite wave formed by two or more trigonometric function waves to a predetermined offset value; exhaust gas purifier evaluating means for extracting a frequency response corresponding to the fixed detecting-signal from an output of the first exhaust gas sensor of the engine, the output being in response to the calculated fuel injection amount, so as to determine a condition of the exhaust gas purifier based on the extracted frequency response; a second exhaust gas sensor disposed upstream of the exhaust gas purifier in the exhaust gas passage; air-fuel ratio controlling means for controlling an air-fuel ratio to be supplied to the engine to a predetermined value based on at least an output of the second exhaust gas sensor, wherein the fuel injection amount is corrected in accordance with a feedback coefficient that is determined based on the output of the second exhaust gas sensor; and responsiveness evaluating means for performing a bandpass filtering of an output from the first exhaust gas sensor.