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Air-to-fuel ratio control system for internal combustion engines

  • US 4,129,105 A
  • Filed: 06/22/1977
  • Issued: 12/12/1978
  • Est. Priority Date: 06/29/1976
  • Status: Expired due to Term
First Claim
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1. An air-to-fuel ratio control system for internal combustion engines comprising:

  • a carburetor, positioned upstream of an engine of a vehicle and having a throttle valve therein, for supplying said engine with air-fuel mixture corresponding to the opening angle of said throttle valve;

    a speed detector for generating a speed voltage indicative of the speed of said vehicle;

    a pressure detector, provided in an intake passage connecting said carburetor with said engine, for generating a pressure voltage indicative of the pressure in said intake passage;

    an oxygen detector, provided in the exhaust passage of said engine, for generating an oxygen voltage indicative of the air-to-fuel ratio of the mixture supplied to said engine;

    a speed function generator, connected to be responsive to said speed voltage, for generating a speed function voltage the level of which is constant while the speed of said vehicle is lower than a lower preset speed and is higher than a higher preset speed;

    a pressure function generator, connected to be responsive to said pressure voltage, for generating a pressure function voltage which varies in accordance with the pressure in said intake passage;

    an oxygen function generator, connected to be responsive to said oxygen voltage, for generating an oxygen function voltage which varies in accordance with the air-to-fuel ratio of said mixture;

    a selection circuit, adapted to select one of said pressure function voltage and said oxygen function voltage in response to the level of said speed function voltage, said selection circuit selecting said oxygen function voltage while the speed of said vehicle is lower than said lower preset speed and said pressure function voltage while the speed of said vehicle is higher than said higher preset speed; and

    an air addition passage, positioned to by-pass said carburetor and connected to be responsive to the function voltage selected by said selection circuit, for supplying said engine with air to thereby control the air-to-fuel ratio of said mixture in response to the speed of said vehicle, the amount of said air being controlled by said oxygen function voltage and said pressure function voltage while the speed of said vehicle is lower and higher than said respective lower preset speed and higher preset speed, respectively.

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