Patent ID: 8020371
Filing Date: 2011-09-20
Classification: F01N,F02D,Y02T

Abstract:
1. A catalyst deterioration detection device that detects catalyst deterioration by exercising active control for switching an exhaust air-fuel ratio prevailing upstream of a catalyst between a lean side and a rich side, the catalyst deterioration detection device comprising: an exhaust gas sensor, which is installed downstream of the catalyst and has an output value that varies in accordance with an exhaust air-fuel ratio prevailing downstream of the catalyst; and an electronic control unit that: (i) exercises control to set the exhaust air-fuel ratio prevailing upstream of the catalyst at a plurality of different lean side air-fuel ratios and rich side air-fuel ratios; (ii) calculates an oxygen excess-or-deficiency amount of an inflow to the catalyst before a change in the output value of the exhaust gas sensor at each of the plurality of different lean side air-fuel ratios and rich side air-fuel ratios, and calculates an oxygen storage amount of the catalyst for each of the plurality of different lean side air-fuel ratios and rich side air-fuel ratios in accordance with the oxygen excess-or-deficiency amount calculated for each of the plurality of different lean side air-fuel ratios and rich side air-fuel ratios; and (iii) detects whether the catalyst has deteriorated in accordance with the plurality of calculated oxygen storage amounts, wherein the plurality of calculated oxygen storage amounts used to determine whether the catalyst has deteriorated includes at least four oxygen storage amounts calculated from at least four oxygen excess-or-deficiency amounts obtained by causing the catalyst to go through at least two cycles of (a) storing oxygen until the catalyst is saturated with the oxygen and (b) releasing the stored oxygen until the oxygen stored in the catalyst has been consumed, such that the catalyst is saturated at least twice and the stored oxygen is consumed at least twice.