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Diagnostic system for diagnosing deterioration of heated type oxygen sensor for internal combustion engines

  • US 5,928,303 A
  • Filed: 11/12/1997
  • Issued: 07/27/1999
  • Est. Priority Date: 11/12/1996
  • Status: Expired due to Fees
First Claim
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1. In a heated type oxygen sensor having a sensing element disposed in an exhaust passage for monitoring a content of oxygen contained within engine exhaust gases to generate an output signal in response to changes in the content of oxygen and a heating element inside for heating the sensing element, a diagnostic system for diagnosing deterioration of the oxygen sensor, comprising:

  • a diagnostic zone setting means for setting a diagnostic zone;

    a discrimination means being responsive to an engine temperature for discriminating that the engine is conditioned in one of a cold-engine state and a fully warmed-up state;

    a first warm-up time setting means being responsive to input information from said discrimination means, for setting a predetermined oxygen sensor'"'"'s warm-up time at a first delay time (ta) which is preset to be suitable for the cold-engine state, only when said discrimination means determines that the engine is in the cold-engine state, and there is a transition from a heater energization zone to the diagnostic zone;

    a second warm-up time setting means being responsive to the input information from said discrimination means, for setting said predetermined oxygen sensor'"'"'s warm-up time at a second delay time (tb) which is preprogrammed to be suitable for the fully warmed-up state, only when said discrimination means determines that the engine is in the fully warmed-up state, and there is a transition from a heater de-energization zone to the diagnostic zone; and

    a diagnostic means for executing a diagnosis on deterioration of the oxygen sensor under a particular condition in which an elapsed time, measured from a time when the heating element is turned on, reaches said predetermined oxygen sensor'"'"'s warm-up time set by one of said first and second warm-up setting means.

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