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Air-fuel ratio control system for internal combustion engines

  • US 5,732,689 A
  • Filed: 02/23/1996
  • Issued: 03/31/1998
  • Est. Priority Date: 02/24/1995
  • Status: Expired due to Term
First Claim
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1. An air-fuel ratio control system for an internal combustion engine having a plurality of cylinders, and an exhaust passage connected to said plurality of cylinders, comprising:

  • air-fuel ratio-detecting means arranged in said exhaust passage, for detecting an air-fuel ratio of exhaust gases emitted from said cylinders;

    sampling means for sampling an output from said air-fuel ratio-detecting means whenever said engine rotates through a predetermined crank angle, and for sequentially storing sampled values of said output from said air-fuel ratio-detecting means;

    output characteristic-detecting means for detecting an output characteristic of said air-fuel ratio-detecting means;

    selecting means for selecting one of said sampled values of said output from said air-fuel ratio-detecting means at least depending on said output characteristic of said air-fuel ratio-detecting means detected by said output characteristic-detecting means;

    cylinder-by-cylinder air-fuel ratio-estimating means for estimating an air-fuel ratio of a mixture supplied to each of said cylinders, separately from other ones of said cylinders, based on selected ones of said sampled values of said output from said air-fuel ratio-detecting means and a model representative of a behavior of said exhaust passage; and

    cylinder-by-cylinder feedback control means for controlling said air-fuel ratio of said mixture supplied to said each of said cylinders in a feedback manner responsive to the estimated air-fuel ratio of said mixture such that the estimated air-fuel ratio of said mixture supplied to said each of said cylinders is converged to a desired air-fuel ratio.

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