Low Temperature Emission Control
AssigneeFord Global Technologies, LLC
InventorsShane Elwart, Jason Aaron Lupescu, Joseph Robert Theis, Gopichandra Surnilla
Life of this patent
Estimating the term…
Abstract
A method of controlling an engine having a lean NOx trap in the exhaust is described. The method comprises during a first mode, at a first temperature, storing NOx at a lean condition and then purging stored NOx from the NOx trap at a rich condition without concurrently supplying oxygen to the trap during the purging and during a second mode, at a second, lower temperature, storing NOx at a lean condition and then purging stored NOx from the NOx, where an exothermic reaction is generated to temporarily raise the temperature of the trap by supplying oxygen and reductants with an overall rich mixture to the trap during the purging.
Claims19
A method of controlling an engine having a lean NOx trap in the exhaust, the method comprising:
- during a first mode, at a first temperature, storing NOx at a lean condition and then purging stored NOx from the NOx trap at a rich condition without concurrently supplying oxygen to the trap during the purging;
- and
- during a second mode, at a second, lower temperature, storing NOx at a lean condition and then purging stored NOx from the NOx, where an exothermic reaction is generated to temporarily raise the temperature of the trap by supplying oxygen and reductants with an overall rich mixture to the trap during the purging.
A method for controlling engine operation, the engine having an emission control device coupled in an engine exhaust, the method comprising:
- during a first mode when temperature of the emission control device is greater than a threshold, purging NOx stored by at least one of:
- operating a first and second cylinder group rich for at least a portion of the purge;
- and
- operating the first cylinder group stoichiometric and the second cylinder group rich for at least a portion of the purge;
- and
- during a second mode when temperature of the emission control device is less than a threshold, operating at least one of the cylinder groups lean and operating another cylinder group rich, where a mixture of at least the cylinder groups is rich of stoichiometry, for at least a portion of the purge.
A system for an engine, comprising:
- a first bank of cylinders of the engine;
- a second bank of cylinders of the engine;
- a first catalyst coupled to the first bank;
- a second catalyst coupled to second bank;
- a NOx trap coupled downstream of the first and second catalyst;
- and
- a controller to:
- during a first mode at a first temperature of the NOx trap:
- transition from operating the first and second banks lean of stoichiometry to operating both the first and second bank rich to purge stored NOx;
- and
- during a second mode at a second temperature of the NOx trap below the first temperature:
- transition from operating both the first and second banks lean to operating the first bank rich of stoichiometry and the second bank slightly lean of stoichiometry for a first duration with an overall rich air-fuel ratio, and then operating the second bank stoichiometric or rich for a second duration following the first duration, where length of the first duration is adjusted with temperature of the NOx trap.
Dependencies are inferred from the claim text.