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Exhaust gas purification device for an engine

  • US 5,740,669 A
  • Filed: 11/16/1995
  • Issued: 04/21/1998
  • Est. Priority Date: 11/25/1994
  • Status: Expired due to Term
First Claim
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1. An exhaust gas purification device for an internal combustion engine comprising:

  • a NOx absorbent disposed in an exhaust passage of an internal combustion engine, wherein the NOx absorbent absorbs NOx in exhaust gas from the engine when the air-fuel ratio of the exhaust gas flowing into the NOx absorbent is lean, and releases the absorbed NOx when the oxygen concentration in the exhaust gas becomes lower;

    temperature detecting means for detecting a temperature of the NOx absorbent;

    regenerating means for causing the air-fuel ratio of the exhaust gas flowing into the NOx absorbent to become one of a rich air-fuel ratio and a stoichiometric air-fuel ratio to cause the NOx accumulated in the NOx absorbent to be released from the NOx absorbent and to be reduced to nitrogen; and

    regeneration control means for activating the regenerating means to cause the air-fuel ratio of the exhaust gas flowing into the NOx absorbent to become one of a rich air-fuel ratio and a stoichiometric air-fuel ratio only when the temperature of the NOx absorbent is lower than a predetermined temperature and an amount of NOx accumulated in the NOx absorbent is at least a predetermined amount.

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