Electronic controller for controlling the air/fuel ratio of the mixture supplied to an internal combustion engine

A digital electronic controller for regulating the air/fuel ratio of the mixture supplied to the cylinders of an internal combustion engine, having an EGO sensor situated on the exhaust path of the burned gases, at least one fuel supply device, such as a carburetor, whose fuel flow rate can be modified by an electrovalve controlled on the basis of an opening/closing cycle and a plurality of sensors for measuring operating conditions of this engine, said electronic controller comprising:

• a clock signal generator providing synchronous signals and a clock signal at the electrovalve cycle frequency;
• a closed loop digital circuit of the proportional integral type with variable gain, said closed loop being connected between said EGO sensor and said electrovalve and including a digital integrator having a gain control input receiving a digital signal representative of the rotation speed of the motor, a digital time duration modulator having a control input connected to the EGO sensor, and a multiplexer for opening said closed loop, said multiplexer having a command input connected to a logic circuit sensitive to operating conditions of said motor and at least a second input receiving a command signal sensitive to a motor physical parameter such as the temperature or the rotation speed of the motor.