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Method and arrangement for simulating the dynamic performance of an exhaust gas catalyzer

  • US 5,214,915 A
  • Filed: 04/17/1992
  • Issued: 06/01/1993
  • Est. Priority Date: 04/17/1991
  • Status: Expired due to Term
First Claim
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1. A method for simulating the time-dependent trace of the lambda value λ

  • -- H-- SIM at the outlet of an exhaust gas catalyzer in a motor vehicle equipped with an internal combustion engine, the method comprising the steps of;

    measuring the air-mass flow QS-- L-- AS inducted by the engine;

    computing the oxygen flow inducted by the engine as QS-- O2-- AS=k×

    QS-- L-- AS wherein k is the mass part of oxygen in air;

    determining the deviative Δ

    λ

    of the lambda value forward of the catalyzer from the lambda value one, said deviation being positive in the case of a lean mixture and said deviation being negative in the case of a rich mixture;

    computing the oxygen partial flow QS-- O2-- IN=Δ

    λ

    ×

    QS-- O2-- AS flowing from the engine into the catalyzer, said oxygen partial flow being a charging flow with respect to the action of the catalyzer in the case of positive values of Δ

    λ and

    , said oxygen partial flow being a depletion flow with respect to the action of the catalyzer in the case of negative values of Δ

    λ

    ;

    inputting the oxygen-storage capacity SPV-- O2 of the catalyzer as an oxygen quantity which the catalyzer can take up starting from an oxygen-free state up to an overflow threshold for a continuous charging flow while the gas flowing out through the outlet of the catalyzer has an oxygen concentration which exceeds a pregiven threshold; and

    ,computing the time-dependent trace of the lambda value λ

    -- H-- SIM at the outlet of the catalyzer by setting the lambda value to one as long as the oxygen store is in a charging state below the overflow threshold or is in a depletion state above a depletion threshold, said depletion threshold corresponding to a pregiven low oxygen concentration at the outlet of the catalyzer;

    or, at least temporarily setting the lambda value to the lambda value at the inlet of the catalyzer when the overflow threshold value is exceeded or there is a drop below the depletion threshold.

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