Method and apparatus for desulfating a no.sub.x trap
First Claim
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1. 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.
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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.
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Citations
17 Claims
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1. 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:
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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. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. Engine control apparatus comprising:
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a NOx trap located in the exhaust passage of a multi-cylinder engine; a catalytic converter located in said exhaust passage upstream of said NOx trap; a computer programmed to; estimate when the trap should be purged of accumulated SOx, 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 SOx.
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16. An article of manufacture comprising:
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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 estimate when the trap should be purged of accumulated SOx, 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 SOx. - View Dependent Claims (17)
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Specification