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Feedback type air fuel ratio controlling system

  • US 4,278,060 A
  • Filed: 07/18/1980
  • Issued: 07/14/1981
  • Est. Priority Date: 05/02/1978
  • Status: Expired due to Term
First Claim
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1. A feedback type air fuel ratio controlling system comprising:

  • an exhaust gas sensor for supplying a sensor signal representative of an air fuel ratio,an automatic gain control (AGC) DC level amplifier having a gain changeable at a predetermined time constant in response to said sensor signal of said sensor, including;

    a variable gain DC amplifier having a signal input coupled to said sensor signal, an output, and a control input for controlling its gain,said variable gain DC amplifier being responsive to said sensor signal so as to (a) decrease its gain in accordance with said predetermined time constant when the output of said variable gain DC amplifier is greater than a fixed predetermined reference signal Vs so that a rich to lean change of air fuel ratio is detected earlier than it would be in the absence of such a gain change, and (b) increase its gain in accordance with said predetermined time constant when the output of said variable gain DC amplifier is less than Vs so that a lean to rich change of air fuel ratio is detected earlier than it would be in the absence of such a gain change,a comparator having a first input coupled to the output of said variable gain amplifier and a second input adapted to be coupled to a source of said reference signal Vs said comparator for producing a first signal whenever the output of said variable gain amplifier is greater than Vs and a second signal whenever the output of said variable gain amplifier is less than Vs, andan integrator having an input coupled to the output of said comparator, for generating an output signal Vc, responsive to said first and second signals, said output signal Vc being coupled to said control input of said variable gain amplifier whereby the gain of said variable gain amplifier is controlled in accordance with the time constant of said integrator and the output signals of said comparator,a deviation detector circuit for comparing the output of said automatic gain control DC level amplifier with a fixed reference signal Vp representing a stoichiometric air fuel ratio to produce a deviation signal, andan actuator for controlling the air fuel ratio in response to the deviation signal.

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