Jet control carburetor

A jet control type carburetor comprising:

• an intake pipe having an intake passage formed in an inner wall thereof, said intake passage allowing an intake air to flow therethrough;
• a venturi provided in said intake pipe, for increasing flow velocity of said intake air in said intake passage to reduce the pressure thereof;
• a fuel nozzle opened into said intake passage and connected to a fuel supply source through a fuel passage for supplying the fuel into said intake passage from said fuel nozzle in order to introduce the mixture of air and fuel into said intake passage;
• a throttle valve provided downstream of said venturi, for controlling the flow rate of said mixture of intake air and fuel;
• a control air nozzle opened into said intake passage at a point upstream from said throttle valve, said point including the position of said throttle valve, said nozzle being connected to an air supply source through a control air passage for directly jetting the flow of said control air to the fuel spurted from said fuel nozzle to afford a predetermined velocity component of said control air having a directional sense contrary to that of the spurted fuel, thereby to cause said control air to impinge upon said fuel spurted from said fuel nozzle and to restrain the fuel flow rate from said fuel nozzle, and
• a throttle means provided upstream of said control air nozzle in said control air passage, for controlling the flow rate of said control air in accordance with a driving condition of said engine;
• said control air nozzle having a predetermined inner diameter (d.sub.a), being provided at a portion spacing apart from said fuel nozzle with a predetermined distance (W), and
• a dimensional relationship of the spacing W between said fuel nozzle and said control air nozzle to the inner diameter d.sub.a of said control air nozzle being set as follows:
• W/d.sub.a .ltoreq.20,
• whereby the control air injected from said control air nozzle has enough flow rate and flow velocity to obtain its desired impinging force, penetrates the flow of the intake air and reaches the flow of the fuel spurted from the fuel nozzle, so that the flow rate of the fuel and the air-fuel ratio of the intake mixture are accurately controlled over a wide range of the driving conditions of said engine.