Patent ID: 6951209

Claim:
A fuel vapor processing system, comprising: a fuel tank; a canister for absorbing fuel vapor produced from said fuel tank; a first passage communicating a nominal full level of said fuel tank at one end thereof with said canister at the other end thereof; a float valve provided at the fuel tank end of said first passage; a second passage communicating a part slightly higher than said nominal full level of said fuel tank at one end thereof with said canister at the other end thereof; a check valve provided at the fuel tank end of said second passage; wherein said check valve comprises a low set-pressure valve that opens at a first threshold pressure P 1 substantially corresponding to a tank full state, a high set-pressure valve that opens at a second threshold pressure P 2 higher than said first threshold pressure P 1 and is connected in parallel with said low set-pressure valve, said high set-pressure valve being able to provide a larger flow rate than said low set-pressure valve.