System and method for diagnosing deterioration of NOx-occluded catalyst
First Claim
1. A system for diagnosing deterioration of a NOx-occluded catalyst installed in an exhaust stream of an internal combustion engine, said catalyst occluding NOx in the exhaust gas when the engine exhaust gas led to the catalyst shows a leaner air/fuel ratio and releasing NOx therefrom when said engine exhaust gas shows a stoichiometric and/or richer air/fuel ratio, said system comprising:
- an inlet NOx concentration estimating unit which estimates NOx concentration at an inlet part of said catalyst;
an outlet NOx concentration detecting unit which detects NOx concentration at an outlet part of said catalyst; and
a deterioration degree judging unit which judges a deterioration degree of the catalyst in accordance with a rate of the minimum value of NOx concentration detected by said detecting unit for a predetermined period to a value of NOx concentration estimated by said estimating unit at the time when said minimum value of NOx concentration is detected, said predetermined period being a period between a time when the engine exhaust gas shows the stoichiometric and/or richer air/fuel ratio and a subsequent time when the engine exhaust gas shows the stoichiometric and/or richer air/fuel ratio.
1 Assignment
0 Petitions
Accused Products
Abstract
A deterioration diagnosing system for a NOx-occluded catalyst comprises an inlet NOx concentration estimating unit which estimates NOx concentration at an inlet part of the catalyst; an outlet NOx concentration detecting unit which detects NOx concentration at an outlet part of the catalyst; and a deterioration degree judging unit which judges a deterioration degree of the catalyst in accordance with a rate of the minimum value of NOx concentration detected by the detecting unit for a predetermined period to a value of NOx concentration estimated by the estimating unit at the time when the minimum value of NOx concentration is detected. The predetermined period is a period between a time when the engine exhaust gas shows the stoichiometric and/or richer air/fuel ratio and a subsequent time when the engine exhaust gas shows the stoichiometric and/or richer air/fuel ratio.
37 Citations
9 Claims
-
1. A system for diagnosing deterioration of a NOx-occluded catalyst installed in an exhaust stream of an internal combustion engine, said catalyst occluding NOx in the exhaust gas when the engine exhaust gas led to the catalyst shows a leaner air/fuel ratio and releasing NOx therefrom when said engine exhaust gas shows a stoichiometric and/or richer air/fuel ratio, said system comprising:
-
an inlet NOx concentration estimating unit which estimates NOx concentration at an inlet part of said catalyst; an outlet NOx concentration detecting unit which detects NOx concentration at an outlet part of said catalyst; and a deterioration degree judging unit which judges a deterioration degree of the catalyst in accordance with a rate of the minimum value of NOx concentration detected by said detecting unit for a predetermined period to a value of NOx concentration estimated by said estimating unit at the time when said minimum value of NOx concentration is detected, said predetermined period being a period between a time when the engine exhaust gas shows the stoichiometric and/or richer air/fuel ratio and a subsequent time when the engine exhaust gas shows the stoichiometric and/or richer air/fuel ratio. - View Dependent Claims (2, 3, 4)
-
-
5. Method of diagnosing deterioration of a NOx-occluded catalyst installed in an exhaust stream of an internal combustion engine, said catalyst occluding NOx in the exhaust gas when the engine exhaust gas led to the catalyst shows a leaner air/fuel ratio and releasing NOx therefrom when said engine exhaust gas shows a stoichiometric and/or richer air/fuel ratio, said step comprising:
-
estimating NOx concentration at an inlet part of the catalyst; detecting NOx concentration at an outlet part of the catalyst; deriving a rate of the minimum value of the NOx concentration detected for a predetermined period to a value of NOx concentration estimated at the time when said minimum value is detected, said predetermined period being a period between a time when the engine exhaust gas shows the stoichiometric and/or richer air/fuel ratio and a subsequent time when the engine exhaust gas shows the stoichiometric and/or richer air/fuel ratio; and judging a deterioration degree of the catalyst in accordance with the derived rate. - View Dependent Claims (6, 7, 8)
-
-
9. A system for diagnosing deterioration of a NOx-occluded catalyst installed in an exhaust stream of an internal combustion engine, said catalyst occluding NOx in the exhaust gas when the engine exhaust gas led to the catalyst shows a leaner air/fuel ratio and releasing NOx therefrom when said engine exhaust gas shows a stoichiometric and/or richer air/fuel ratio, said system comprising:
-
first means for estimating NOx concentration at an inlet part of said catalyst; second means for detecting NOx concentration at an outlet part of said catalyst; and third means for judging a deterioration degree of the catalyst in accordance with a rate of the minimum value of NOx concentration detected by said second means for a predetermined period to a value of NOx concentration estimated by said first means at the time when said minimum value of NOx concentration is detected, said predetermined period being a period between a time when the engine exhaust gas shows the stoichiometric and/or richer air/fuel ratio and a subsequent time when the engine exhaust gas shows the stoichiometric and/or richer air/fuel ratio.
-
Specification