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Air-fuel ratio control device for an internal combustion engine

  • US 4,928,653 A
  • Filed: 03/27/1989
  • Issued: 05/29/1990
  • Est. Priority Date: 04/19/1988
  • Status: Expired due to Term
First Claim
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1. A control device for controlling an air-to-fuel ratio of a mixture of fuel and air supplied to an internal combustion engine, comprising:

  • air quantity detecting means for measuring a quantity of air supplied to said internal combustion engine;

    crank angle sensor means for detecting a crank angle (θ

    ) of said internal combustion engine;

    pressure sensor means for detecting a pressure (P) within a cylinder of said internal combustion engine;

    feedback value computation means, coupled to outputs of said pressure sensor means and said crank angle sensor means, for computing an actual ratio of a maximum rate of pressure change (dP/dθ

    )max within said cylinder with respect to said crank angle during a predetermined interval of time within a cycle of strokes in said cylinder to a maximum pressure (Pmax) within said cylinder during the same predetermined interval of time within a cycle of strokes in said cylinder;

    optimum air-to-fuel ratio computation means, coupled to outputs of said air quantity detecting means and said crank angle sensor means, for determining an optimum air-to-fuel ratio corresponding to an operating condition of said internal combustion engine determined by parameters including said outputs of said air quantity detecting means and said crank angle sensor means;

    conversion means, coupled to an output of said optimum air-to-fuel ratio computation means, for determining a value of a target ratio of the maximum rate of pressure change (dP/dθ

    )max within said cylinder with respect to said crank angle during said predetermined interval of time within a cycle of strokes in said cylinder to the maximum pressure (Pmax) within said cylinder during the same predetermined interval of time within a cycle of strokes in said cylinder by means of a relationship between values of air-to-fuel ratio and values of said ratio of the maximum rate of pressure change (dP/dθ

    )max within said cylinder with respect to the crank angle during said predetermined interval of time to the maximum pressure (Pmax) within said cylinder during the same predetermined interval of time within a cycle of strokes in said cylinder, said target ratio corresponding to said optimum air-to-fuel ratio determined by said optimum air-to-fuel ratio computation means;

    error computation means, coupled to said feedback value computation means and said conversion means, for computing a deviation of said actual ratio, computed by said feedback value computation means, with respect to said target value determined by said conversion means;

    fuel injection means for injecting an amount of fuel into an air intake passage coupled to said cylinder of the internal combustion engine; and

    control means, coupled to an output of said error computation means, for controlling said amount of fuel injected by said fuel injection means to reduce said deviation, outputted from said error computation means, of said actual ratio with respect to said target ratio.

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