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Method and system for reducing vehicle emissions using a sensor downstream of an emission control device

  • US 6,546,718 B2
  • Filed: 06/19/2001
  • Issued: 04/15/2003
  • Est. Priority Date: 06/19/2001
  • Status: Expired due to Fees
First Claim
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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:

  • 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, wherein selecting includes calculating, during the lean operating condition, an efficiency value based on the first and second values; and

    terminating the lean operating condition when the efficiency value falls below a minimum efficiency value.

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