Patent ID: 8899015
Filing Date: 2014-12-02
Classification: F01N,F02D,Y02T

Abstract:
1. A catalyst degradation detection device, comprising: a catalyst upstream sensor, which is provided on an upstream side of a catalyst in an exhaust passage of an internal combustion engine and which outputs a signal on the basis of an oxygen concentration in exhaust gas; a catalyst downstream sensor, which is provided on a downstream side of the catalyst in the exhaust passage and which outputs a signal on the basis of the oxygen concentration in the exhaust gas; a measuring unit, which measures a responsiveness of a change in the signal output from the catalyst downstream sensor in response to a change in the oxygen concentration in the exhaust gas on the downstream side of the catalyst; a calculating unit, which calculates an oxygen storage amount of the catalyst by forcing at least one of a rich-to-lean change and a lean-to-rich change to occur in an air-fuel ratio of the internal combustion engine; a correcting unit, which corrects the oxygen storage amount calculated by the calculating unit on the basis of the responsiveness measured by the measuring unit; and a determining unit, which determines whether the catalyst has degraded on the basis of the oxygen storage amount corrected by the correcting unit, wherein, when one of the responsiveness at the time of the lean-to-rich change in the air-fuel ratio of the internal combustion engine and the responsiveness at the time of the rich-to-lean change in the air-fuel ratio is measured by the measuring unit, the correcting unit corrects the oxygen storage amount on the basis of the measured responsiveness alone.