Method and apparatus for accessing ability of lean NOx trap to store exhaust gas constituent

A method for controlling the operation of an internal combustion engine in a motor vehicle, wherein the engine generates exhaust gas including an exhaust gas constituent, and wherein exhaust gas is directed through an emissions control device before being exhausted to the atmosphere, the device storing a quantity of the exhaust gas constituent when the exhaust gas directed through the device is lean of stoichiometry and releasing a previously-stored amount of the exhaust gas constituent when the exhaust gas directed through the device is rich of stoichiometry, the method comprising:

• operating the engine in a first lean engine operating condition immediately following a first rich engine operating condition, the first rich engine operating condition being characterized by the release of substantially all of the previously-stored amount of the exhaust gas constituent from the device, the first lean operating condition operating to store an additional amount of the exhaust gas constituent in the device;
• determining a first measure representative of the instantaneous efficiency of the device to remove the exhaust gas constituent from the exhaust gas;
• discontinuing the first lean engine operating condition in favor of a second rich operating condition when the first measure falls below a reference value;
• and
• determining, during the second rich operating condition, a quantity of fuel in excess of a stoichiometric quantity of fuel sufficient to release substantially all of the additional amount of the exhaust gas constituent from the device.

A controller for controlling an engine operating in combination with an emissions control device that releases a previously-stored first exhaust gas constituent when the engine is operated at a rich operating condition for a predetermined duration, wherein the controller is arranged to determine that the engine is operating at a first lean operating condition immediately following a rich engine operating condition, the rich engine operating condition having been sufficient to release substantially all of the previously-stored amount of the exhaust gas constituent from the device, the first lean operating condition operating to store an additional amount of the exhaust gas constituent in the device;

• the controller being further arranged to determine a first measure representative of the instantaneous efficiency of the device to remove the exhaust gas constituent from the exhaust gas, and a second measure representative of the content of the exhaust gas constituent in exhaust gas exiting the device,
• to discontinue the first lean operating condition when the first measure falls below a reference value and the second measure is below a predetermined maximum threshold level,
• to initiate a subsequent rich operating condition characterized by the combustion of a quantity of fuel in excess of a stoichiometric quantity of fuel sufficient to release substantially all of the additional amount of the exhaust gas constituent from the device, and
• to determine an ability of the device based on the quantity of excess fuel.

A controller for controlling an engine operating in combination with an emissions control device that releases a previously-stored first exhaust gas constituent when the engine is operated at a rich operating condition for a predetermined duration, wherein the controller is arranged to determine that the engine is operating at a lean operating condition immediately following a rich engine operating condition, the rich engine operating condition having been sufficient to release substantially all of the previously-stored amount of the exhaust gas constituent from the device, the first lean operating condition operating to store an additional amount of the exhaust gas constituent in the device;

• the controller being further arranged to determine a first measure representative of the instantaneous efficiency of the device to remove the exhaust gas constituent from the exhaust gas,
• to initiate a subsequent rich operating condition when the first measure falls below a reference value, the subsequent rich operating condition being characterized by the combustion of a quantity of fuel in excess of a stoichiometric quantity of fuel sufficient to release substantially all of the additional amount of the exhaust gas constituent from the device, and
• to determine an ability of the device based on the quantity of excess fuel,
• wherein the reference value is significantly greater than a minimum value necessary to maintain the content of the exhaust gas constituent in the exhaust gas exiting the trap below a predetermined threshold level.