PURPOSE: To provide optimal control of air fuel ratio for the entire running range, by feedback-controlling air bleed of a variable Venturi tube type carburetor by means of an exhaust sensor.
CONSTITUTION: A variable Venturi tube type carburetor 5' contains a needle 5'-3 which moves back and forth in a fuel discharge port 5'-5 to control fuel flow. An air bleed inlet port 5'-6 which is controlled by a diaphragm device 9 is communicated with a portion downstream the discharge port 5'-5. A negative pressure chamber 9-3 of the diaphragm device 9 is equipped with a solenoid valve 6' selectively connected with a Venturi tube 5'-11 and air port 6'-6. The solenoid valve 6' is feedback-controlled by a control circuit 7 which receives signal from an exhaust sensor 4. Air bleed is regulated in accordance with the selective introduction of negative pressure and atmospheric air in the negative pressure chamber 9-3 through on-off control of a valve 6'-5 with a short period.
TAKADA SHIGETAKA
MORINO TOSHIHARU
