Apparatus for detecting fuel-vapor gas leaks, and vent valve apparatus applied to this apparatus

An apparatus for detecting fuel-vapor gas leaks, comprising:

• a valve for performing shut-off control of a vapor purge system that includes a canister that connects a fuel tank to an internal combustion engine;
• an open/close controllable reference orifice having a reference leak hole, said reference orifice for causing leakage from the vapor purge system through the reference leak hole;
• a jet pump for introducing outside air to the vapor purge system and for pressurizing the vapor purge system by gasoline flow from a submerged fuel pump in the fuel tank;
• an internal pressure sensor for detecting the internal pressure of the fuel tank;
• a vent valve arranged between the fuel tank and the canister, for shutting off the fuel tank from the canister according to an external signal;
• a control valve for open/close control of air flow to the canister and the jet pump;
• and
• a storage device for storing pressure values, in an increasing pressure condition as an increasing pressure initial curve, during pressurization by the jet pump over a first predetermined time period with the vent valve closed and the reference orifice opened and for storing as a decreasing pressure initial curve, after halting the pressurization after the first predetermined time period has elapsed, pressure values under a decreasing pressure condition by means of leakage through the reference orifice, in a time series over a second predetermined time period;
• wherein
• judgement of leak existence in the fuel tank side of the vapor purge system is performed by comparing a time series in an increasing pressure curve obtained by the jet pump pressurizing the fuel tank in a closed condition, with the time series in the increasing pressure initial curve;
• and
• judgement of leak existence in the canister side of the vapor purge system is performed, when an actual pressure value exceeds the pressure value of the increasing pressure initial curve at the first predetermined time, by halting the pressurization and comparing a time series in a decreasing pressure curve with the purge system being completely shut-off, with the time series in the decreasing pressure initial curve.

A vent valve device in an apparatus for detecting fuel-vapor gas leaks, comprising:

• a vent valve for shutting off a fuel tank from a canister by buoyancy of a float that rises with rising liquid surface level in the fuel tank;
• a control valve body for moving, according to a control signal from outside, in a direction in which a control valve, which communicates with a jet pump, opens;
• and
• a linking member that pulls the vent valve so as to shut it off when the control valve body moves in its opening direction, wherein
• the linking member has an engagement structure for not letting the control valve body move in its opening direction with the float rising with the liquid surface.