The present invention, relates to a fuel cutoff valve 5 of the type shown in FIG. 1 disposed between a fuel tank 1 and a canister 3, where fuel evaporated in the fuel tank 1 (hereinafter referred to as "gas fuel") is allowed to pass through the valve to the canister 3, but when the fuel itself (hereinafter referred to as "liquid fuel") flows in, the gas flow is interrupted.
FIGS. 2 and 3 show a conventional fuel cutoff valve 5.
The fuel cutoff valve 5 includes a case member 7 and a float member 17.
The case member 7 is provided on its upper wall with a tapered outlet opening 9 pipe, which continues to a piping 11. The pipe 11 leads to the canister 3. An inner partition 13 is provided in case member 7 and a plurality of through holes 15 are formed therethrough.
The case member 7 communicates with the fuel tank 1 through an inlet opening 16 at the lower side of the inner partition 13.
The float member 17 is a box-shaped member and internally installed to the case member 7. A first seal member 19 of semicircular shape is formed on the upper surface of the float member 17. A compression coil spring 23 is inserted in a recess 21. The compression coil spring 23 urges the float member 17 upward.
The float member 17 is selected in its molding material so that the effective weight by substracting the biasing force of the spring 23 from the actual weight of the float member 17 is less than that of the liquid fuel having the same volume (e.g., high molecular material such as polyacetal). Consequently, when the liquid fuel flows from the fuel tank 1 into the case member 7, the float member 17 is floated.
That fuel cutoff valve 5 normally, allows the gas fuel to flow from the tank side to the canister side as shown by the arrows in FIG. 2.
When the vehicle is tilted or the like, if the liquid fuel from the tank 1 flows in, the float member 17 floats as shown in FIG. 3. Then the first seal member 19 closes the outlet opening 9, thereby the liquid fuel is not allowed to flow to the piping 11 (valve close state). If the liquid fuel is returned to the tank 1, the float member 17 falls and the valve is again opened.