Claims
- 1. A method for detecting deterioration of a catalyst for reducing nitrogen oxide, usable for an exhaust gas system of an internal combustion engine that operates mainly under a lean condition; said system comprising a nitrogen oxide reducing catalyst capable of adsorbing nitrogen oxide under lean atmosphere and nitrogen oxide sensor disposed downstream of the nitrogen oxide reducing catalyst; said method comprising the steps of:
- (a) switching temporarily the operation condition of said internal combustion engine into a stoichiometric condition or a rich condition so that the nitrogen oxide adsorbed to said nitrogen oxide reducing catalyst is detached or decomposed when an output of the nitrogen oxide sensor reaches a predetermined level, and
- (b) returning the operational condition back to a lean condition when an electromotive force, or a pumping current of a first pumping cell, of the nitrogen oxide sensor reaches a predetermined level,
- wherein the deterioration of the catalyst is detected based on an NOx exhaust amount (g/mile) that is calculated from at least nitrogen oxide sensor output, exhaust gas flow amount and a running distance of vehicle.
- 2. A method for detecting deterioration of a catalyst for reducing nitrogen oxide, usable for an exhaust gas system of an internal combustion engine that operates mainly under a lean condition; said system comprising a nitrogen oxide reducing catalyst capable of adsorbing nitrogen oxide under lean atmosphere and a nitrogen oxide sensor disposed downstream of the nitrogen oxide reducing catalyst; said method comprising the steps of:
- (a) injecting a fuel upstream of said nitrogen oxide reducing catalyst so that the nitrogen oxide adsorbed to said nitrogen oxide reducing catalyst is detached or decomposed when an output of the nitrogen oxide sensor reaches a predetermined level, and
- (b) returning the operational condition back to a lean condition when an electromotive force, or a pumping current of a first pumping cell, of the nitrogen oxide sensor reaches a predetermined level,
- wherein the deterioration of the catalyst is detected based on an NOx exhaust amount (g/mile) that is calculated from at least nitrogen oxide sensor output, exhaust gas flow amount and a running distance of vehicle.
Priority Claims (2)
Number |
Date |
Country |
Kind |
8-161219 |
Jun 1996 |
JPX |
|
9-139022 |
May 1997 |
JPX |
|
Parent Case Info
This is a continuation of application Ser. No. 09/315,358 filed May 17, 1999, now U.S. Pat. No. 6,026,640, which in turn is a divisional application of Ser. No. 08/876,285 filed Jun. 16, 1997, now U.S. Pat. No. 5,953,907.
US Referenced Citations (12)
Foreign Referenced Citations (2)
Number |
Date |
Country |
0690213 |
Jan 1996 |
EPX |
4411942 |
May 1995 |
DEX |
Non-Patent Literature Citations (4)
Entry |
"Evaluation of NOX Storage Catalysts as an Effective System for NOX Removal From the Exhaust Gas of Leanburn Gasoline Engines"; M.S. Brogan et al. |
Patent Abstracts of Japan, Vol. 096, No. 010, Oct. 31, 1996, JP 08-158917. |
Patent Abstracts of Japan, Vol. 095, No. 006, Jul. 31, 1995, JP 07-063096. |
Patent Abstracts of Japan, Vol. 018, No. 123, Feb. 28, 1994, JP 05-312024. |
Divisions (1)
|
Number |
Date |
Country |
Parent |
876285 |
Jun 1997 |
|
Continuations (1)
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Number |
Date |
Country |
Parent |
315358 |
May 1999 |
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