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Exhaust gas purifying device for engine

  • US 5,996,338 A
  • Filed: 10/28/1997
  • Issued: 12/07/1999
  • Est. Priority Date: 11/01/1996
  • Status: Expired due to Fees
First Claim
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1. An exhaust gas purifying device for an engine having an exhaust passage comprising:

  • an exhaust gas purifying catalyst arranged in the exhaust passage wherein a NOX adsorbing capacity of the exhaust gas purifying catalyst increases as a temperature of the exhaust gas purifying catalyst decreases, and wherein when the catalyst temperature increases toward a first threshold temperature, the NOX previously adsorbed therein is desorbed therefrom, wherein, at the first threshold temperature, the NOX adsorbing capacity of the exhaust gas purifying catalyst is substantially zero; and

    catalyst temperature control means for controlling the catalyst temperature, the catalyst temperature control means alternately and repeatedly decreasing the catalyst temperature below and increasing the catalyst temperature above the first threshold temperature to adsorb NOX therein when the catalyst temperature falls below the first threshold temperature, and to desorb therefrom NOX previously adsorbed therein when the catalyst temperature increases above the first threshold temperature, wherein the desorbed NOX is reduced.

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