Patent ID: 8601793
Filing Date: 2013-12-10
Classification: F01N,F02D,Y02T

Abstract:
1. A malfunction diagnostic device for an exhaust gas control device, comprising: an electronic control unit configured to determine that an exhaust gas control device provided in an exhaust system of an internal combustion engine malfunctions when a parameter that indicates exhaust gas purification performance of the exhaust gas control device crosses a threshold; the electronic control unit being configured to determine a degree of deterioration of the exhaust gas control device; and the electronic control unit being configured to adjust the threshold based on the degree of deterioration of the exhaust gas control device in such a manner that a likelihood that the exhaust gas control device is determined to be malfunctioning is lower at lower degrees of deterioration of the exhaust gas control device, wherein when the exhaust gas control device is new, the electronic control unit is configured to set the threshold to a value that corresponds to a state where the exhaust gas control device is new, wherein as the degree of deterioration of the exhaust gas control device increases, the electronic control unit is configured to gradually change the threshold from the value that corresponds to the state where the exhaust gas control device is new in such a manner that the likelihood that the exhaust gas control device is determined to be malfunctioning increases, and wherein the electronic control unit is configured to set a limit value of the threshold, at which the threshold stops changing, to a value that corresponds to an upper limit of a certain range of degree of deterioration of the exhaust gas control device, in which the exhaust gas control device is able to purify exhaust gas.