Patent ID: 7313487

Claim:
A transpired fuel gas leak detecting device comprising: a valve that is provided in an transpiration purge system including a canister, which extends from a fuel tank to an internal combustion engine, and is capable of controlling the transpiration purge system to close; pressurizing means that leads an outside air in the transpiration purge system and pressurizes the transpiration purge system; internal pressure measuring means that detects an internal pressure of the transpiration purge system; and fuel volume detecting means that detects a fuel volume in the fuel tank; wherein the transpired fuel gas leak detecting device sets a decompression calculation value after a predetermined time, which is calculated using a pressurization measurement value measured by the internal pressure measurement means at the time when the transpiration purge system is brought into a closed state after intaking air via from the pressurizing means for a predetermined time, an air volume calculated by subtracting a fuel volume detected by the fuel volume detecting means from a capacity of the transpiration purge system set in advance, and an allowable leak hole diameter set in advance, as a judgment criteria pressure and judges that a leak is present on the basis of a holding pressure measurement value, which is measured by the internal pressure measuring means after a predetermined time from the state in which the transpiration purge system is closed, and the judgment criteria pressure.