Power plants – Internal combustion engine with treatment or handling of... – By means producing a chemical reaction of a component of the...
Patent
1998-04-20
2000-03-07
Denion, Thomas
Power plants
Internal combustion engine with treatment or handling of...
By means producing a chemical reaction of a component of the...
60285, 701201, F01N 300
Patent
active
060324619
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an exhaust gas purifying system for an internal combustion engine or, more particularly, to an exhaust gas purifying system for an internal combustion engine in which a poisonous gas component in the exhaust gas is trapped, stored and periodically removed.
BACKGROUND ART
Various types of exhaust gas purifying systems, for purifying the exhaust gas emitted from an internal combustion engine, are used according to the properties of the exhaust gas, and many of them trap a poisonous component contained in the exhaust gas and require regeneration operation at appropriate time intervals.
For example, an exhaust gas purifying system, for a gasoline engine or, especially, for a gasoline engine which executes lean burning for most of the running period, except accelerating periods or the like, which absorbs nitrogen oxide for the lean burning period and releases the absorbed nitrogen oxide for the short rich burning period has already proposed (Refer to International Publication No. W093/07363).
The above-mentioned exhaust purifying system absorbs nitrogen oxide contained in the exhaust gas in an absorbent incorporated in the exhaust gas purifying system for the lean burning period, which accounts for most of the running period, and executes a regeneration operation which releases the nitrogen oxide from the absorbent by increasing an amount of fuel to make air-fuel ratio rich when it is determined that the absorbing power has deteriorated. Note, nitrogen oxide released during the regeneration operation is not directly emitted into the air because it is deoxidized by unburned hydrocarbon and carbon monoxide and converted to nitrogen gas, carbon dioxide and water in the exhaust gas with rich air-fuel ratio. The nitrogen oxide released for the regeneration operation is dioxidized by unburned hydrocarbon in the exhaust gas, the air-fuel ratio thereof being rich, and thus is converted into nitrogen gas, carbon dioxide and water. The nitrogen oxide, therefore, is not emitted into the air.
However, if the remaining absorbing power of the absorbent is evaluated based on the integrated value of the product of the intake air flow rate which is proportional to the amount of nitrogen dioxide in the exhaust gas and the engine load or in a more simplistic manner, based on the integrated value of the engine speed, and a regeneration operation is executed when it is determined that the remaining absorbing power decreases below a fixed level, it is not avoidable that the nitrogen oxide is emitted in the air depending on the exhaust gas temperature.
Because the air-fuel ratio in the absorbent gradually changes from the lean state to the rich state when the air-fuel ratio is controlled from the lean state to the rich state, nitrogen oxide is not completely deoxidized and is liable to be emitted in the air before the actual air-fuel ratio has been completely transferred to the rich state.
However, it is known that the discharge amount of nitrogen oxide when switching the air-fuel ratio from rich to lean depends mainly on the temperature of the absorbent and becomes almost zero when the temperature of the absorbent is lower than 200.degree. C.
Therefore, the present applicant has already proposed stopping the regeneration operation as long as the absorbent has a residual absorption power when the temperature of the absorbent (or the exhaust gas) rises over the temperature where the regeneration operation is permitted.
However, the regeneration operation of the exhaust gas purifying system based on the current temperature of the absorbent is not always optimal.
Namely, even if the regeneration timing of the exhaust gas purifying system is controlled based on the current temperature of the exhaust gas in addition to the integrated value of the engine speed, the nitrogen oxide is liable to be emitted into the air when the exhaust gas temperature suddenly rises while the exhaust gas purifying system is regeneration, and when the exhaust gas temperature becomes the temperature where reg
REFERENCES:
patent: 5319930 (1994-06-01), Shinzawa et al.
patent: 5711149 (1998-01-01), Araki
patent: 5740669 (1998-04-01), Kinugasa et al.
patent: 5815824 (1998-09-01), Saga et al.
Igarashi Kouhei
Itou Takaaki
Kinugasa Yukio
Denion Thomas
Toyota Jidosha & Kabushiki Kaisha
Tran Binh
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