Exhaust gas purification device for an internal combustion engine

  • US 5,974,793 A
  • Filed: 04/11/1997
  • Issued: 11/02/1999
  • Est. Priority Date: 04/19/1996
  • Status: Expired due to Term
First Claim
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1. An exhaust gas purification device for an internal combustion engine comprising:

  • conversion means for converting, when the air-fuel ratio of exhaust gas supplied to the conversion means is rich, at least a portion of NOX contained in the exhaust gas to NH3 ;

    NOX purification means disposed in an exhaust gas passage of the engine for causing the NOX in the exhaust gas to react with the NH3 produced by the conversion means and for causing the NOX to be reduced to N2 by the NH3 ; and

    NOX increasing means for adjusting an air-fuel ratio of the exhaust gas supplied to the conversion means to a rich air-fuel ratio and, at the same time, increasing a concentration of NOX in the exhaust gas supplied to the conversion means to a value higher than a normal concentration of NOX in the exhaust gas of the engine, the normal concentration of NOX being defined as a concentration of NOX when the engine is operated at an air-fuel ratio the same as that of the exhaust gas adjusted by the NOX increasing means.

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