Patent ID: 8561638

Claim:
A check valve connected to a pipe communicating with an interior of a fuel tank, the check valve including a main-casing having a positive-pressure valve seat formed in an interior thereof, a sub-casing assembled to the main-casing so as to form a valve chamber and communicating with an outside of the fuel tank, and a positive-pressure valve and a negative-pressure valve disposed slidably in the valve chamber, wherein the positive-pressure valve is formed into a cylindrical shape, a plurality of through holes communicating with an interior thereof and a negative-pressure valve seat to and from which the negative-pressure valve is attached and detached are formed on a distal end side of the positive-pressure valve, and an outer circumference of the positive-pressure valve is attached to and detached from the positive-pressure valve seat, wherein the negative-pressure valve is disposed on an outer side of a distal end of the positive-pressure valve so as to be attached to and detached from the negative-pressure valve seat to thereby close and open the through holes and has a plurality of leg portions which are inserted into the interior of the positive-pressure valve through the through holes, wherein a cap, which is connected to the plurality of leg portions of the negative valve via a locking unit and which holds the negative-pressure valve slidable with respect to the positive-pressure valve, is disposed in the interior of the positive-pressure valve, wherein a positive-pressure valve spring, which biases the positive-pressure valve towards the positive-pressure valve seat in the main-casing, is disposed between the positive-pressure valve and the sub-casing, wherein a negative-pressure valve spring, which biases the negative-pressure valve towards the negative-pressure valve seat in the positive-pressure valve, is disposed between the positive-pressure valve and the cap, wherein the positive-pressure valve is detached from the positive-pressure valve seat when a pressure within the fuel tank is equal to or larger than a certain value, and the negative-pressure valve is detached from the negative-pressure valve seat when the pressure within the fuel tank decreases to a certain value or lower than the atmospheric pressure, wherein a positive-pressure flow path for allowing fuel vapor to flow out from the fuel tank when the positive-pressure valve is detached from the positive-pressure valve seat is formed so as to pass by an outer side of the positive-pressure spring between the outer circumference of the positive-pressure valve and an inner circumference of the main-casing, and wherein a negative-pressure flow path for allowing outside air to flow into the fuel tank when the negative-pressure valve is detached from the negative-pressure valve seat is formed so as to pass by an outer side of the negative-pressure spring between an inner circumference of the positive-pressure valve, and the leg portions and an outer circumference of the cap and between the through holes and the leg portions.