System and method for determining a NOx storage capacity of a catalytic device
a technology of catalytic device and storage capacity, which is applied in the direction of electric control, machines/engines, mechanical equipment, etc., can solve the problems of increasing the cost of the lean aftertreatment system, nox emissions may be reduced, and the cost of no/sub>x /sub>sensors are typically high, so as to reduce nox emissions, reduce nox in the trap, and reduce nox emissions
Inactive Publication Date: 2007-04-19
FORD GLOBAL TECH LLC
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The patent text describes a method for accurately estimating the storage capacity of a NOx trap in a vehicle's exhaust system. This is important for determining when the trap needs to be purged, which can decrease NOx emissions. The method involves operating the engine at different non-stoichiometric relative air / fuel ratios and measuring the oxygen sensor output while doing so. By measuring the difference in oxygen sensor output between the two non-stoichiometric ratios, the NOx storage efficiency of the trap can be determined. This method is cost-effective and can be used in real-time emissions control systems.
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[0021]FIG. 1 shows a schematic depiction of an internal combustion engine 10. Engine 10 typically includes a plurality of cylinders, one of which is shown in FIG. 1, and is controlled by an electronic engine controller 12. Engine 10 includes a combustion chamber 14 and cylinder walls 16 with a piston 18 positioned therein and connected to a crankshaft 20. Combustion chamber 14 communicates with an intake manifold 22 and an exhaust manifold 24 via a respective intake valve 26 and exhaust valve 28. An exhaust gas oxygen sensor 30 is coupled to exhaust manifold 24 of engine 10. A three-way catalyst 32 is connected to and receives feedgas from exhaust manifold 24, and a NOx trap 34 is connected to and receives emissions from three-way catalyst 32. Furthermore, a first UEGO sensor 36 is positioned between three-way catalyst 32 and NOx trap 34, and a second UEGO sensor 38 is positioned downstream of NOx trap 34. Engine 10 is depicted as a port-injection spark-ignition gasoline engine. How...
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In an apparatus having an internal combustion engine, a method of operating the engine including operating the engine at a first non-stoichiometric relative air / fuel ratio for a first duration; operating the engine at a second non-stoichiometric relative air / fuel ratio for a second duration, wherein the second relative air / fuel ratio is on an opposite side of a stoichiometric relative air / fuel ratio as the first relative air / fuel ratio, and wherein the second duration is of sufficient length to allow at least one of one of a substantial saturation of oxygen storage sites in the catalytic device and a substantial regeneration of oxygen storage sites in the catalytic device; and operating the engine at a third non-stoichiometric relative air / fuel ratio for a third duration, wherein the third relative air / fuel ratio is on a same side of the stoichiometric relative air / fuel ratio as the second relative air / fuel ratio and is further from the stoichiometric relative air / fuel ratio than the second relative air / fuel ratio.
Description
TECHNICAL FIELD [0001] The present application relates to the field of automotive emission control systems and methods. BACKGROUND AND SUMMARY [0002] Lean-burning engines, or engines that run on an air / fuel mixture with a stoichiometrically greater amount of air than fuel, can offer improved fuel economy relative to engines configured to run on stoichiometric air / fuel mixtures. [0003] However, lean-burning engines also may pose various disadvantages. For example, burning a lean relative air / fuel mixture may decrease the reduction of nitrogen oxides (collectively referred to as “NOx”) [0004] Various mechanisms have therefore been developed to reduce NOx emissions in lean-burning engines. One mechanism is a catalyst known as a lean NOx trap. The NOx trap is a catalytic device typically positioned downstream of the catalytic converter in an emissions system, and is configured to retain NOx when the engine is producing a lean exhaust for eventual reduction when the engine produces a ric...
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IPC IPC(8): F01N3/00
CPCF01N3/0807F01N3/0842F01N3/106F01N11/007F01N2560/025F01N2560/14F02D41/0275F02D41/1441F02D41/1475F02D2200/0808F02D2200/0816Y02T10/47F01N13/009Y02T10/40
Inventor SURNILLA, GOPICHANDRAGORALSKI, CHRISTIAN T. JR.PATTERSON, JOSEPH E.THEIS, JOSEPH R.ELWART, SHANE
Owner FORD GLOBAL TECH LLC