Patent ID: 7392800

Claim:
A fuel vapor treatment system treating a fuel vapor which is combusted with injected fuel of an internal combustion engine, comprising: a canister containing an adsorbent which temporarily adsorbs fuel vapor generated in a fuel tank; a detection means for detecting a fuel vapor condition quantity of a mixture gas of air and the fuel vapor desorbed from the adsorbent; a purge passage for introducing the mixture gas into the internal combustion engine; a control means for performing a purge of the mixture gas into the internal combustion engine through the purge passage and controlling the purge based on the fuel vapor condition quantity detected by the detection means; and a learning means for learning a fuel vapor condition quantity of the mixture gas purged by the control means based on a driving condition quantity of the internal combustion engine; wherein under a condition that a difference between a learned condition quantity which is the fuel vapor condition quantity learned by the learning means at a previous purge and a detection condition quantity which is the fuel vapor condition quantity detected by the detection means after the previous purge is not less than a specified value, the control means controls the purge based on the learned condition quantity prior to a purge control based on the detection condition quantity.