Method and apparatus for desulfating a no.sub.x 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 NO.sub.x trap is proposed wherein the SO.sub.x 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.
Claims17
A method of operating an engine supplied with a mixture of fuel and air and having a trap located in an exhaust path of the engine, said method comprising a sequence of the following steps:
- estimating the amount of contaminant accumulated in the trap;
- amplitude modulating the A/F of the mixture supplied to the engine between a lean and a rich mixture when the estimated amount of contaminant reaches a threshold amount to thereby raise the temperature of the trap to a predetermined temperature;
- purging the trap of contaminant when said predetermined temperature is reached;
- terminating the purging of said trap when a predetermined purge criteria is met.
Engine control apparatus comprising:
- a NO.sub.x trap located in the exhaust passage of a multi-cylinder engine;
- a catalytic converter located in said exhaust passage upstream of said NO.sub.x trap;
- a computer programmed to;
- estimate when the trap should be purged of accumulated SO.sub.x,
- modulate the amplitude of the A/F of the mixture supplied to the engine to raise the temperature of the trap to a purge temperature, and
- bias the modulation toward a rich A/F when the trap reaches said purge temperature to purge the trap of SO.sub.x.
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 NO.sub.x trap located in an exhaust passage thereof, said computer program comprising:
- code for causing the computer to estimate when the trap should be purged of accumulated SO.sub.x,
- code for causing the computer to modulate the amplitude of the A/F of the mixture supplied to the engine to raise the temperature of the trap to a purge temperature, and
- code for causing the computer to bias the modulation toward a rich A/F when the trap reaches said purge temperature to purge the trap of SO.sub.x.
Dependencies are inferred from the claim text.