Method and system for reducing vehicle emissions using a sensor downstream of an emission control device
First Claim
1. A method of controlling an engine that operates at a plurality of engine operating conditions characterized by combustion of air-fuel mixtures having different air-fuel ratios to generate engine exhaust gas, wherein the exhaust gas is directed through an exhaust treatment system including an emission control device that stores a selected exhaust gas constituent when the exhaust gas is lean and releases the stored selected exhaust gas constituent when the exhaust gas is rich, and a sensor operative to generate an output signal representative of a concentration of the selected constituent in the exhaust gas exiting the device, the method comprising:
- determining a first value representative of an instantaneous concentration of the selected constituent in the engine exhaust gas when operating in the lean operating condition;
determining a second value representative of the instantaneous concentration of the selected constituent exiting the device based on the output signal generated by the sensor; and
selecting an engine operating condition as a function of the first and second values.
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Accused Products
Abstract
A system and method is provided for controlling a lean-burn engine whose exhaust gas is directed through an exhaust treatment system which includes an emission control device that alternately stores and releases a selected constituent of the exhaust gas, such as NOx, based on engine operating conditions, and a downstream NOx sensor. The system estimates the concentration of NOx flowing into the device based on engine operating conditions while determining a value for the concentration of NOx flowing out of the device based upon the output signal generated by NOx sensor. A device purge event is scheduled when the device efficiency, calculated based on the NOx concentrations flowing into and out of the device, falls below a predetermined minimum efficiency value. The length of a purge event is determined as a function of an accumulated measure based on the difference between the NOx concentrations into and out of the device.
2 Citations
15 Claims
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1. A method of controlling an engine that operates at a plurality of engine operating conditions characterized by combustion of air-fuel mixtures having different air-fuel ratios to generate engine exhaust gas, wherein the exhaust gas is directed through an exhaust treatment system including an emission control device that stores a selected exhaust gas constituent when the exhaust gas is lean and releases the stored selected exhaust gas constituent when the exhaust gas is rich, and a sensor operative to generate an output signal representative of a concentration of the selected constituent in the exhaust gas exiting the device, the method comprising:
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determining a first value representative of an instantaneous concentration of the selected constituent in the engine exhaust gas when operating in the lean operating condition;
determining a second value representative of the instantaneous concentration of the selected constituent exiting the device based on the output signal generated by the sensor; and
selecting an engine operating condition as a function of the first and second values. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A system for controlling an internal combustion engine that operates at a plurality of engine operating conditions characterized by combustion of air-fuel mixtures having different air-fuel ratios, wherein exhaust gas generated by such combustion is directed through an exhaust treatment system including an emission control device that stores a selected exhaust gas constituent when the exhaust gas is lean and releases the stored selected constituent when the exhaust gas is rich, and a sensor operative to generate an output signal representative of a concentration of a selected constituent of the exhaust gas exiting the device, the system comprising:
a controller including a microprocessor arranged to determine a first value representative of an instantaneous concentration of the selected constituent in the engine exhaust gas when operating in a lean operating condition, and to determine a second value representative of the instantaneous concentration of the selected constituent exiting the device based on the output signal generated by the sensor, and wherein the controller is further arranged to select an engine operating condition as a function of the first and second values. - View Dependent Claims (10, 11, 12, 13, 14, 15)
Specification