1.  Field of the Invention
The present invention relates to carburetion and more particularly to the improvement of the qualities of atomization and the homogeneity of the mixture in a carburetor having a diffuser with a sonic throat through which the fuel mixture passes. 
2.  Description of the Prior Art
The atomization obtained with conventional carburetors with butterfly valves is not generally sufficient for perfect combustion and distribution, particularly at low speeds where the amount and the velocity of the intake air are too small to homogenize and disperse the fuel coming from the idle or main jets.  Better atomization can be obtained using the so-called "Cannot shock" produced downstream of a throat with supersonic flow.  This technique has been applied to a passage for the injection of the idle mixture, where the slow flow and the vacuum of the main intake have allowed the realization of the idle atomizer in a sonic-flow throat.  Also known is a variable section nozzle obtained by transverse sliding of a gate or shell.  Technological difficulties and mechanical friction reduce their utilization, however, particularly at low flows, where they inferfere with the smooth and continuous functioning of the controls and constitute the source of numerous instabilities.