Variable venturi type carburetor

Claim 1

A variable venturi type carburetor of an internal combustion engine, said carburetor comprising: a housing; a bore extending through said housing and having an inner wall defining an intake passage; a suction piston movably mounted in said housing and having a head portion projecting into said intake passage, said head portion of the suction piston and said inner wall of the intake passage defining a venturi, said suction piston moving so as to change the cross-sectional area of said venturi in response to a change in the vacuum produced in said intake passage downstream of said venturi at a constant value; a fuel injection valve arranged at the position opposite to said head portion of the suction piston with regard to said intake passage, said fuel injection valve being electrically controlled so as to positively and directly inject the necessary amount of fuel into said intake passage in response to the engine running conditions from the opposite position without the need for venturi vacuum; said head portion of the suction piston having a recess therein which extends along a line crossing with the center axis of the suction piston and parallel to the direction of air flowing in said intake passage; and said head portion of the suction piston also having two fin members projecting therefrom, said fin members being on opposite sides of said recess and symmetrically disposed with respect to an imaginary surface passing through the central axis of said suction piston and extending along the direction of air flowing in said intake passage, said fin members defining a V-shaped passage therebetween.