Closed-loop method and system for purging a vehicle emission control
AssigneeFord Global Technologies, LLC
InventorsDavid George Farmer, Gopichandra Surnilla
Life of this patent
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Abstract
A vehicle exhaust treatment system includes an emission control device featuring at least one upstream NOx-storing “brick,” and a downstream NOx-storing “brick” that is substantially smaller in nominal capacity than the upstream brick. An oxygen sensor positioned between the upstream and downstream bricks generates an output signal representing the concentration of oxygen in the device. A controller selects a rich operating condition to purge the device of stored NOx, and deselects the rich, NOx-purging engine operating condition in response to the sensor output signal, preferably after an additional time delay calculated to provide sufficient excess hydrocarbons to release substantially all stored NOx from the downstream brick.
Claims21
A system for controlling the operation of an internal combustion engine, wherein the engine operates at a plurality of operating conditions characterized by combustion of a range of air-fuel mixtures to generate exhaust gas, the exhaust gas flowing through an emission control device for storing a constituent of the exhaust gas when the exhaust gas is lean of a stoichiometric air-fuel mixture and of releasing the stored constituent when the exhaust gas is rich of a stoichiometric air-fuel mixture, the system comprising:
- a controller including a microprocessor arranged to select a first operating condition, characterized by combustion of a first air-fuel mixture lean of a stoichiometric air-fuel ratio, for a first time period sufficient to store a significant amount of the constituent in both an upstream portion of the device material and a downstream portion of the device material, and to select a second operating condition, characterized by combustion of a second air-fuel mixture rich of the stoichiometric air-fuel ratio, and wherein the controller is further arranged to deselect the second operating condition based upon a detected characteristic of the exhaust gas flowing through the device at a first position between an upstream portion of the device and a downstream portion of the device.
A method for controlling the operation of an internal combustion engine, wherein the engine operates at a plurality of operating conditions characterized by combustion of a range of air-fuel mixtures to generate exhaust gas, the exhaust gas flowing through an emission control device for storing a constituent of the exhaust gas when the exhaust gas is lean of a stoichiometric air-fuel mixture and for releasing the stored constituent when the exhaust gas is rich of a stoichiometric air-fuel mixture, the method comprising:
- selecting a first operating condition, characterized by combustion of a first air-fuel mixture lean of a stoichiometric air-fuel ratio, for a first time period sufficient to store a significant amount of the constituent in both an upstream portion of the device and a downstream portion of the device;
- selecting a second operating condition, characterized by combustion of a second air-fuel mixture rich of the stoichiometric air-fuel ratio;
- detecting, during the second operating condition, a concentration of oxygen in the exhaust gas flowing through the device at a first position within the device located between the upstream portion of the device and a downstream portion of the device;
- and
- deselecting the second operating condition based upon a comparison of the detected concentration to a reference value.
A method for releasing, from an emission control device receiving exhaust gas generated by an internal combustion engine, an amount of a constituent of the exhaust gas that is stored in the device, the method comprising:
- generating, during a first time period, a first flow of exhaust gas through the device that is rich of a stoichiometric air-fuel ratio;
- and
- detecting a characteristic of the first flow of exhaust gas at a position within the device between an upstream portion of the device and a downstream portion of the device;
- and
- determining the first time period on the basis of the detected characteristic.
A method for purging, from an emission control device receiving exhaust gas generated by an internal combustion engine that includes NOx, an amount of NOx stored in the device, wherein the device includes an upstream portion and a downstream portion, the method comprising:
- operating the engine with an air-fuel mixture rich of a stoichiometric air-fuel mixture for a first time period;
- and
- simultaneously detecting, at a first position within the device located between the upstream portion and the downstream portion, a concentration of oxygen in the exhaust gas,
- wherein the first time period is determined on the basis of the detected concentration.
Dependencies are inferred from the claim text.