Patent ID: 6374810
Filing Date: 2002-04-23
Classification: F02M

Abstract:
A method of reducing gaseous phase presence in the liquid fuel metering chamber of a diaphragm carburetor for an internal combustion engine, such phase being in the form of air or fuel vapor agglomeration and/or bubble growth due to the same evaporating or effervescing from the liquid fuel during engine running and/or in the form of air when the chamber is not full of liquid fuel and hence air-filled due to carburetor fuel drain-down after engine-shut down, said method comprising the steps of:(a) providing a diaphragm type carburetor having a main air/fuel mixing through passageway, a fuel metering cavity formed in a carburetor body part and a metering diaphragm spanning said metering cavity and defining a fuel metering chamber therebetween, a liquid fuel supply passageway coupled between a pressurized source of liquid fuel and said metering chamber, an inlet valve disposed in said supply passage and being operably coupled to the diaphragm for controlling opening and closing of said inlet valve to admit pressurized liquid fuel from the fuel source to the metering chamber in response to pressure differential between atmospheric pressure and engine-intake-induced negative pressure in the carburetor mixing passageway acting on the metering diaphragm, an engine fuel feed metering circuit passageway system having a first inlet operably communicating with the metering chamber and outlet means operably communicating via check valve means with the carburetor mixing passageway for supplying and metering liquid fuel from the metering chamber via the outlet means into the mixing passageway to form therein an air/fuel mixture for operating the engine, and an air purge passageway system including a fuel vapor and air purge passageway having a second inlet operably communicating with the metering chamber and an outlet adapted for operably communicating with a return line leading to the fuel source, said air purge passageway system also including a pump and associated intake and outlet valves operably coupled in said purge passageway for pumping gas and/or liquid from the metering chamber into the return line, (b) determining what will be the highest elevation region in the metering chamber with the carburetor mounted on the engine and the mounted carburetor and engine together being oriented in the standard operating position of the engine, and (c) locating said first and second passageway inlets to communicate with said highest elevation region of the metering chamber to thereby insure that substantially all such gaseous phase presence is removed from the metering chamber by operation of the passageway systems associated with said inlets at least when said engine is oriented in the standard operating position.