| 摘要 |
PROBLEM TO BE SOLVED: To treat fuel vapor in a back pressure chamber while maintaining the operation of a differential pressure valve. SOLUTION: A vent valve 131 is provided on a breather pipe 13 connecting the fuel tank 11 to a canister 10. The vent valve has a pressure chamber communicating with the fuel tank, isolated from the back pressure chamber with a diaphragm, and it is opened when a predetermined differential pressure is produced between the pressure chamber and the back pressure chamber. Since the fuel vapor exists on the side of the pressure chamber, the back pressure chamber in a sealed structure causes pressure in the back pressure chamber to be increased by the fuel vapor entering through the diaphragm into the back pressure chamber and pressure in the fuel tank to be increased with the vent valve opened. In order to prevent it, each diaphragm is provided with the back pressure chamber and the pressure chamber and a communication hole for communication between the back pressure chamber and the canister. Thus, the fuel vapor entering into the back pressure chamber is discharged to the sides of the canister and the fuel tank to keep the pressure in the back pressure chamber at an approximately atmospheric pressure without giving influences to the operation of the vent valve.
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