| 摘要 |
An apparatus is provided for controlling discharge of fuel vapors from a fuel tank during refueling. The apparatus includes a conduit for conducting fuel vapor between the fuel tank and a first destination such as a vapor treatment canister situated outside of the fuel tank, a valve operable between a flow-blocking position and a flow-delivery position for selectively blocking flow of fuel vapor through the conduit, and a spring for yieldably biasing the valve toward its flow-blocking position. A venting control chamber is situated in communication with the valve for receiving and using fuel vapor pressure from the fuel tank having a magnitude in excess of a predetermined threshold level to exert an opening force on the valve in opposition to the spring so that the valve is moved to its flow-delivery position. Such movement of the valve permits discharge of pressurized fuel vapor in the tank to said first destination through the conduit. In addition to the foregoing primary venting system, the apparatus is made stageable by including an optional auxiliary system for venting the fuel tank to a second destination.
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