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Method and apparatus for desulfating a no.sub.x trap

  • US 5,974,788 A
  • Filed: 08/29/1997
  • Issued: 11/02/1999
  • Est. Priority Date: 08/29/1997
  • Status: Expired due to Term
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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