Over-fueling prevention valve

An over-fueling prevention valve provided at an evaporation line of a fuel tank device including a full tank limit valve that closes a discharge port of fuel vapor when a fuel liquid level reaches a predetermined height at a time of filling fuel to a fuel tank and the evaporation line that enables an inner side of the fuel tank and a canister provided outside the fuel tank to communicate with each other, the over-fueling prevention valve comprising:

• a housing provided with a first opening that communicates with the fuel tank, a second opening that communicates with the canister, and a first valve seat provided at the first opening;
• a main valve that is slidably disposed in the housing, that is configured to be brought into contact with or separated from the first valve seat, that has an internal space inside the main valve, and that is provided with one end opening for communicating with the first opening, an other end opening for communicating with the second opening, and a second valve seat formed at the other end opening at a side close to the internal space;
• a first spring configured to bias the main valve toward the first valve seat;
• a sub valve that is slidably disposed in the internal space of the main valve and is configured to be brought into contact with or separated from the second valve seat;
• and
• a second spring that is disposed in the internal space of the main valve and is configured to bias the sub valve in a direction away from the second valve seat,
• wherein biasing forces of the first spring and the second spring are set such that a valve re-closing pressure when the main valve is brought into contact with the first valve seat again from a state in which the main valve is separated from the first valve seat against a biasing force of the first spring by a pressure in the fuel tank is higher than a valve re-opening pressure when the sub valve is separated from the second valve seat again from a state in which the sub valve is brought into contact with the second valve seat against a biasing force of the second spring by the pressure in the fuel tank, and
• wherein the first opening and the second opening are configured to communicate with each other via an external space between an inner periphery of the housing and an outer periphery of the main valve in a state in which the main valve is separated from the first valve seat.