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Internal combustion engine misfire detection

  • US 5,668,725 A
  • Filed: 11/13/1995
  • Issued: 09/16/1997
  • Est. Priority Date: 11/13/1995
  • Status: Expired due to Term
First Claim
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1. In an internal combustion engine having a plurality of cylinders each cylinder having a piston mechanically linked to a crankshaft and reciprocally driven in the cylinder to rotate the crankshaft by cylinder combustion events in which an air-fuel mixture provided to the engine cylinders is ignited by timed application of an ignition drive signal to cylinder spark plugs, a method for diagnosing improper combustion conditions in the engine cylinders, comprising the steps of:

  • generating fuel injection control commands;

    outputting the fuel injection control commands to control delivery of fuel to the engine;

    generating ignition control commands;

    outputting the ignition control commands to drive spark plugs of the engine cylinders;

    generating reference signals at predetermined angular positions of the crankshaft;

    determining reference periods as timed durations between each adjacent reference signal;

    diagnosing an improper combustion condition in a selected engine cylinder, by (a) identifying a first and second determined reference period corresponding to the selected engine cylinder, (b) calculating an ideal reference period for the identified first and second determined reference periods, (c) estimating noise and disturbance content in the identified first and second reference periods, (d) processing the identified first and second reference periods by removing the ideal reference period and the estimated noise and disturbance content from said first and second reference periods, (e) forming a misfire component as a difference between the processed first and second reference periods, (f) comparing the magnitude of the misfire component to a predetermined threshold component, and (g) diagnosing an improper cylinder combustion condition in the selected engine cylinder when the magnitude of the misfire component exceeds the predetermined threshold component.

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