Power plants – Internal combustion engine with treatment or handling of... – Methods
Reexamination Certificate
1999-04-12
2001-09-25
Denion, Thomas (Department: 3748)
Power plants
Internal combustion engine with treatment or handling of...
Methods
C060S295000, C060S286000, C060S297000, C060S285000
Reexamination Certificate
active
06293092
ABSTRACT:
TECHNICAL FIELD
This invention relates to the control of an internal combustion engine and, more particularly, to the control of regeneration fuel supplied to an internal combustion engine during sequential regeneration events of a NOx adsorber to minimize engine emissions and maximize fuel economy.
BACKGROUND OF THE INVENTION
It is known in the art relating to internal combustion engines that by operating an engine with a less than stoichiometric (lean) mixture of fuel and air, efficiency of the engine is improved. This means that for a given amount of work performed by the engine, less fuel will be consumed, resulting in improved fuel efficiency. It is also well known that reduction of NOx emissions when the fuel rate is lean has been difficult to achieve, resulting in an almost universal use of stoichiometric operation for exhaust control of automotive engines. By operating an engine with a stoichiometric mixture of fuel and air, fuel efficiency is good and NOx emission levels are reduced by over 90% once the vehicle catalyst reaches operating temperatures.
Recent developments in catalysts and engine control technologies have allowed lean operation of the engine, resulting in improved fuel efficiency and acceptable levels of NOx emissions. One such development is a NOx adsorber which stores NOx emissions during fuel lean operations and allows release of the stored NOx during fuel rich conditions with conventional three-way catalysis to nitrogen and water. The adsorber has limited storage capacity and must be regenerated with a fuel rich reducing “pulse” as it nears capacity. It is desirable to control the efficiency of the regeneration event of the adsorber to provide optimum emission control and minimum fuel consumption.
SUMMARY OF THE INVENTION
The present invention is directed to a method for controlling NOx emissions from engines operating with lean fuel-air mixtures. The invention features a method for controlling regeneration fuel supplied to an internal combustion engine operating with a lean fuel-air mixture to obtain regeneration of a NOx adsorber to provide optimum emissions control and minimum fuel consumption. More specifically, the method monitors the exhaust gases flowing out of the adsorber during each regeneration event to detect when the fuel-air mixture is within an excessively lean or rich range. When the sensed exhaust gases contain an excessively lean fuel-air mixture, fuel is increased to the engine. Fuel is decreased when the sensed exhaust gases contain an excessively rich fuel-air mixture. The fuel can be increased or decreased by adjusting the duration or fuel rate of the regeneration event.
These and other features and advantages of the invention will be more fully understood from the following description of a certain specific embodiment of the invention taken together with the accompanying drawings.
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patent: 6023929 (2000-01-01), Ma
Ament Frank
Brown David Brian
Frank David Allen
Denion Thomas
General Motors Corporation
Simon Anthony Luke
Tran Binh
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