Method of controlling an engine exhaust gas system and method of detecting deterioration of catalyst/adsorbing means

• US 6,026,640 A
• Filed: 05/17/1999
• Issued: 02/22/2000
• Est. Priority Date: 06/21/1996
• Status: Expired due to Term

• Current Assignee: NGK Insulators Limited
• Original Assignee: NGK Insulators Limited
• Inventors: Kato, Nobuhide, Kurachi, Hiroshi
• Primary Examiner(s): ARGENBRIGHT, TONY MICHAEL
• Application Number:
  US09/315,358
• Time in Patent Office: 281 Days
• Field of Search: 60/274, 60/276, 60/277, 60/285, 60/286, 60/297, 60/301, 60/311
• US Class Current: 60/274
• CPC Class Codes: B01D 53/9431 Processes characterised by a specific device
• CPC Class Codes: B01D 53/9495 Controlling the catalytic process
• CPC Class Codes: F01N 11/00 Monitoring or diagnostic devices for exhaust-gas treatment apparatus , e.g. for catalytic activity safety, indicating or supervising devices for internal combustion engines F02B77/08; testing of machines G01M13/00
• CPC Class Codes: F01N 2250/12 absorption or adsorption, and catalytic conversion
• CPC Class Codes: F01N 2430/06 by varying fuel-air ratio, e.g. by enriching fuel-air mixture
• CPC Class Codes: F01N 2550/02 Catalytic activity of catalytic converters
• CPC Class Codes: F01N 2550/03 of sorbing activity of adsorbents or absorbents
• CPC Class Codes: F01N 2610/03 the substance being hydrocarbons, e.g. engine fuel
• CPC Class Codes: F01N 3/0814 combined with catalytic converters, e.g. NOx absorption/storage reduction catalysts
• CPC Class Codes: F01N 3/0842 Nitrogen oxides
• CPC Class Codes: F01N 3/0871 Regulation of absorbents or adsorbents, e.g. purging by electrically controlling the supply of combustible mixture or its constituents only F02D41/0235
• CPC Class Codes: F02B 1/04 with fuel-air mixture admission into cylinder
• CPC Class Codes: F02D 41/0275 the exhaust gas treating apparatus being a NOx trap or adsorbent
• CPC Class Codes: F02D 41/1441 Plural sensors
• CPC Class Codes: F02D 41/146 the characteristics being an NOx content or concentration
• CPC Class Codes: F02D 41/1463 of the exhaust gases downstream of exhaust gas treatment apparatus
• CPC Class Codes: Y02T 10/12 Improving ICE efficiencies
• CPC Class Codes: Y02T 10/40 Engine management systems

Abstract

In a method of controlling an exhaust gas system of an internal combustion engine including a nitrogen oxide reducing catalyst capable of adsorbing nitrogen oxide under a lean atmosphere and a nitrogen oxide sensor disposed downstream of the nitrogen oxide reducing catalyst, the nitrogen oxide reducing catalyst and the nitrogen oxide sensor are disposed in the exhaust gas system operated mainly under a lean condition, respectively. An output value of the nitrogen oxide sensor is compared with a predetermined value, and an operation condition of the internal combustion engine is temporarily changed into a stoichiometric condition or a rich condition, or a fuel is injected upstream of the nitrogen oxide reducing catalyst, so that the nitrogen oxide adsorbed to the nitrogen oxide reducing catalyst is detached or decomposed, and again the internal combustion engine is operated under the lean condition.

Claims

1. A method of controlling an exhaust gas system of an internal combustion engine which operates mainly under a lean condition, which system comprises a nitrogen oxide reducing catalyst capable of adsorbing nitrogen oxide under a lean atmosphere and a 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,

(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.

3. A method of detecting deterioration of a catalyst usable for an exhaust gas system of an internal combustion engine which operates mainly under a lean condition;

said system comprising a nitrogen oxide reducing catalyst capable of adsorbing nitrogen oxide under a lean atmosphere and a nitrogen oxide sensor disposed downstream of the nitrogen oxide reducing catalyst characterized in that deterioration of the catalyst is detected based on a length of a period between the step (a) and the step (b) in claim 1.

5. A method of detecting deterioration of a catalyst/adsorption means, usable for an exhaust gas system of an internal combustion engine which operates mainly under a lean condition;

said system comprising a nitrogen oxide reducing catalyst capable of adsorbing nitrogen oxide under a lean atmosphere and a nitrogen oxide sensor disposed downstream of the nitrogen oxide reducing catalyst, characterized in that deterioration of the catalyst is detected based on a length of a period between the step (a) and the step (b) in claim 1.

2. A method of controlling an exhaust gas system of an internal combustion engine which operates mainly under a lean condition, which system comprises a nitrogen oxide reducing catalyst capable of adsorbing nitrogen oxide under a 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.

4. A method of detecting deterioration of a catalyst usable for an exhaust gas system of an internal combustion engine which operates mainly under a lean condition;

said system comprising a nitrogen oxide reducing catalyst capable of adsorbing nitrogen oxide under a lean atmosphere and a nitrogen oxide sensor disposed downstream of the nitrogen oxide reducing catalyst characterized in that deterioration of the catalyst is detected based on a length of a period between the step (a) and the step (b) in claim 2.

6. A method of detecting deterioration of a catalyst/adsorption means, usable for an exhaust gas system of an internal combustion engine which operates mainly under a lean condition;

said system comprising a nitrogen oxide reducing catalyst capable of adsorbing nitrogen oxide under a lean atmosphere and a nitrogen oxide sensor disposed downstream of the nitrogen oxide reducing catalyst, characterized in that deterioration of the catalyst is detected based on a length of a period between the step (a) and the step (b) in claim 2.