Electric control apparatus for carburetor

Abstract

In a carburetor having a flow control element axially movable within an air bleed passage in the carburetor body for controlling the cross-sectional area of the passage and a stepper motor on the body for effecting axial movement of the control element, an input circuit produces an electric signal indicative of the operating condition of an engine. A computer determines rotary steps of the motor in response to the electric signal for optimizing the cross-sectional area of the passage in relation to the operating condition of the engine, an a whether the number of the determined rotary steps is more than the actual rotary steps of the motor. A first command signal and a second command signal, and first and second control signals are produced respectively for effecting one rotary step of the motor in a direction defined by each of the command signals. The computer is responsive to one of the control signals to measure a first time duration for one rotary step of the motor to produce a first time signal upon lapse of the first time duration, responsive to change of one of the command signals to the other to measure a second time duration for one reverse rotary step of the motor to produce a second time signal upon lapse of the second time duration, and further responsive to one of the time signals to selectively apply the control signals to the motor.