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Catalyst deterioration detection device for internal combustion engine

  • US 5,737,916 A
  • Filed: 10/24/1996
  • Issued: 04/14/1998
  • Est. Priority Date: 10/26/1995
  • Status: Expired due to Term
First Claim
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1. A catalyst deterioration detection device for an internal combustion engine, comprising:

  • a three-way catalyst mounted in an exhaust passage of said internal combustion engine and having an O2 storage capability;

    an air-fuel ratio sensor, mounted upstream of said three-way catalyst, for linearly detecting air-fuel ratio;

    air-fuel ratio feedback control means for, based on the output of said air-fuel ratio sensor, calculating a feedback correction amount consisting of a proportional term for bringing the air-fuel ratio to stoichiometry and an integral term for bringing an integrated value of an error between the air-fuel ratio and stoichiometry to zero;

    an O2 sensor, mounted downstream of said three-way catalyst, for detecting whether the air-fuel ratio is rich or lean;

    catalyst deterioration determining means for determining deterioration of said three-way catalyst on the basis of the length of a response curve that the output of said O2 sensor describes during the time that air-fuel ratio feedback control is being performed by said air-fuel ratio feedback control means; and

    a response curve length calculation interrupting means for interrupting the calculation of the response curve length being performed by said catalyst deterioration determining means for a predetermined length of time when the output of said air-fuel ratio sensor or the amount of change of said output has exceeded a preset value.

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