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Engine misfire detection with digital filtering

  • US 5,633,456 A
  • Filed: 08/04/1995
  • Issued: 05/27/1997
  • Est. Priority Date: 08/04/1995
  • Status: Expired due to Term
First Claim
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1. An apparatus for detecting misfire in individual cylinders of an internal combustion engine in a motor vehicle, comprising:

  • means for sensing rotation of a crankshaft;

    measuring means connected to the sensing means for determining changes in angular velocity corresponding to each of a plurality of cylinder firings;

    frequency analysis means for analyzing a frequency response of the engine in a frequency domain and determining a cut-off frequency between misfire signals and noise related signals;

    digital filtering means for digitally filtering out noise related signals from the determined changes in angular velocity as a function of the cut-off frequency; and

    means for comparing an output of said digital filtering means with a threshold value to detect the occurrence of a misfire for a selected cylinder as a result of said comparison.

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