Method and apparatus for desulfating a NOx trap
AssigneeFord Global Technologies, LLC
InventorsJeffrey S. Hepburn, Garth M. Meyer, Joseph R. Asik
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Abstract
A method and apparatus for desulfating a NOx trap is proposed wherein the SOx purge temperature is achieved by modulating the amplitude of the A/F of the mixture supplied to the engine thereby storing oxygen in the trap during lean engine cylinder events and generating the required exotherm during rich engine cylinder events.
Claims12
A method of operating a motor vehicle having an engine supplied with a mixture of fuel and air and having a catalytic element located in an exhaust path of the engine, said method comprising a sequence of the following steps:
- detecting conditions requiring catalytic element desulfation;
- amplitude modulating the A/F of the mixture supplied to the engine to repeatedly switch the A/F between a lean and a rich mixture to create an exotherm in said catalytic element upon detection of said conditions to thereby raise the temperature of said catalytic element to a predetermined desulfation temperature;
- and
- performing a desulfation operation when said predetermined temperature is reached.
Engine control apparatus comprising:
- a catalytic element located in the exhaust passage of a multi-cylinder engine,
- a computer that is programmed to;
- detect conditions that indicate the catalytic element should be purged of accumulated SOx;
- amplitude modulate the A/F of the mixture supplied to the engine to repeatedly switch the A/F between a lean and a rich mixture to create an exotherm in said catalytic element upon detection of said conditions to thereby raise the temperature of the catalytic element to a predetermined desulfation temperature;
- and
- bias modulation toward a rich A/F when the catalytic element reaches said desulfation temperature to purge the catalytic element of SOx.
An article of manufacture comprising:
- a computer storage medium having a computer program encoded therein for causing the computer to control a multi-cylinder engine with a NOx trap located in an exhaust passage thereof, said computer program comprising:
- code for causing the computer to detect degraded tray efficiency resulting from SOx accumulation, and
- code for causing the computer to amplitude modulate the A/F of the mixture supplied to the engine between a lean and a rich mixture upon detection of said degraded trap efficiency to control the temperature of the catalytic element;
- and
- code for causing the computer to adjust spark advance during modulation of the A/F to prevent engine torque imbalance.
A method of operating a motor vehicle having au engine supplied with a mixture of fuel and air and having a NOx trap located in an exhaust path of the engine, said method comprising a sequence of the following steps:
- detecting trap efficiency reduction due to SOx accumulation;
- amplitude modulating the A/F of the mixture supplied to the engine between a lean and a rich mixture as a function of engine speed and load in response to detection of said trap efficiency reduction to raise the temperature of said trap to a predetermined temperature;
- adjusting engine spark timing during the lean and rich portions of the modulation period to prevent engine torque imbalance;
- trimming the amplitude and frequency of the modulation as a function of trap temperature;
- purging the trap of SOx when said predetermined temperature is reached;
- and
- terminating the purging of said trap when a predetermined purge criteria is met.
Dependencies are inferred from the claim text.