Fuel-air ratio automatic control system using variable venturi structure

Claim 1

An automatic control system for supplying a fuel-air mixture to the intake manifold of the internal combustion engine of a vehicle for regulating the ratio of air to fuel so that this ratio is optimized for prevailing conditions of engine speed and load, said system comprising: A. a variable Venturi structure whose inlet is coupled to a source of incoming combustion air and whose outlet is coupled to said intake manifold, said structure including concentric passages constituted by a primary Venturi passage having a throat and leading to a secondary Venturi passage having a variable area throat, and a tertiary Venturi passage having a throat, incoming air flowing through an inlet into all three passages to said intake manifold, and a mechanism for adjusting said variable area throat; B. a servo motor operatively coupled to said mechanism to adjust said variable throat area; C. means to supply fuel into said primary passage to intermingle with the air passing therethrough to produce an air-fuel mixture; D. means communicating with said inlet and the throat of the tertiary passage to sense the pressure difference between that of the air at the inlet and that at the tertiary passage throat to produce a command signal that depends on the velocity of air flow through the Venturi structure; and E. a controller responsive to said command signal to govern said servo motor to adjust the area of the variable area throat and thereby change said air velocity so as to bring about the desired ratio of air and fuel in said mixture.