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Method and apparatus for detecting misfires in a controlled ignition internal combustion engine

  • US 5,606,119 A
  • Filed: 07/05/1995
  • Issued: 02/25/1997
  • Est. Priority Date: 01/08/1993
  • Status: Expired due to Fees
First Claim
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1. Method of detecting misfires in a controlled ignition internal combustion engine, comprising the steps of:

  • a) deriving, for each combustion-expansion phase in each cylinder of the engine, a signal representative of a measure of a gas torque produced in each corresponding cylinder during the corresponding combustion expansion phase,b) measuring a rotational speed of the engine and deriving (4) a signal representative of this rotational speed during at least an intake phase preceding the combustion-expansion phase of each corresponding cylinder,c) measuring a pressure at an air inlet manifold for each corresponding cylinder, and deriving a signal representative of this pressure during at least the intake phase preceding the combustion-expansion phase of the corresponding cylinder,d) entering speed and inlet manifold pressure signals as addresses in a map of reference theoretical gas torque, and deducing therefrom a signal representative of a reference torque,e) assigning the reference torque a multiplier weighting coefficient associated with each corresponding cylinder and/or a steady-state or transient operating mode of the engine, and deducing therefrom a signal representative of an expected theoretical torque, andf) comparing the signals of the measured gas torque and of the expected theoretical torque and concluding that there is a misfire when a ratio of the gas torque to the expected theoretical torque becomes less than a defined ratio threshold.

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