1. Field of the Invention
The present invention relates to a fuel check valve assembly for use in a fuel tank of an automotive vehicle or the like.
2. Description of the Prior Art
As is well known, a fuel tank of an automotive vehicle is equipped with a fuel check valve assembly for preventing outflow of fuel from the fuel tank when the vehicle is inclined or overturned.
An example of a fuel check valve assembly is disclosed in U.S. Pat. No. 4,000,828 and includes a float valve and a valve seat which cooperate to constitute a check valve for preventing outflow of fuel from the fuel tank. The valve seat is movable upwardly so as to constitute a relief valve for venting the fuel tank when the check valve is closed and the pressure within the fuel tank rises.
Another example of a fuel check valve assembly is disclosed in Japanese Utility Model Provisional Publication No. 62-75278 and includes two pairs of valve seats and valves which cooperate to constitute a check valve and a relief valve, respectively.
In either of the fuel check valve assemblies, the valve opening pressure of the relief valve needs to be set low so that the pressure within the fuel tank does not become so high for thereby preventing the float valve from being strongly pressed; against the valve seat to and sticking same.
The valve opening pressure of the relief valve can be set high if the pressure which causes the float valve to stick to the valve seat can be set high. To this end, it is considered to increase the size of the float valve, i.e., to increase the weight of the float valve for thereby making it difficult for the float valve to stick to the valve seat by the effect of the heavy weight. However, this inevitably causes an increase in the weight and coast of the vehicle and is therefore undesirable.