Monitoring of fuel vapor pressure

A fuel vapor pressure monitoring device monitoring a pressure increase in a purge vent between a fuel tank and an intake passage of an engine, in a sealed state, the device comprising:

• a sensor which detects a pressure in the purge vent;
• and
• a programmable controller programmed to:
• calculate a pressure variation in the purge vent;
• calculate an error equivalence amount from the pressure variation in the purge vent, the error equivalence amount corresponding to an error amount in the pressure in the purge vent in the sealed state due to sloshing in the fuel tank;
• calculate a corrected pressure which corresponds to a pressure when sloshing does not occur, from the pressure in the purge vent in the sealed state and the error equivalence amount;
• seal the purge vent in a state where the pressure in the purge vent is equal to atmospheric pressure;
• determine whether or not a fixed vapor monitoring period has elapsed in a sealed state;
• and
• calculate the corrected pressure when the fixed vapor monitoring period has elapsed, as a vapor monitoring period temperature increase correction amount expressing a pressure variation resulting from a temperature variation during the vapor monitoring period.

A fuel vapor pressure monitoring device monitoring a pressure increase in a purge vent between a fuel tank and an intake passage of an engine, in a sealed state, the device comprising:

• means for determining a pressure in the purge vent;
• means for repeatedly calculating a pressure change rate in the purge vent in the sealed state at predetermined time intervals;
• means for updating a minimum value for the pressure change rate,
• means for calculating a difference of the minimum value and the pressure change rate,
• means for calculating an error equivalence amount based on a time integral of the difference, the error equivalence amount corresponding to an error amount in the pressure in the purge vent in the sealed state due to sloshing in the fuel tank;
• and
• means for calculating a corrected pressure which corresponds to a pressure when sloshing does not occur, from the pressure in the purge vent in the sealed state and the error equivalence amount.

A fuel vapor pressure monitoring method monitoring a pressure increase in a purge vent between a fuel tank and an intake passage of an engine, in a sealed state, the method comprising:

• determining a pressure in the purge vent;
• repeatedly calculating a pressure change rate in the purge vent in the sealed state at predetermined time intervals;
• updating a minimum value for the pressure change rate,
• calculating a difference of the minimum value and the pressure change rate,
• calculating an error equivalence amount based on a time integral of the difference, the error equivalence amount corresponding to an error amount in the pressure in the purge vent in the sealed state due to sloshing in the fuel tank;
• and
• calculating a corrected pressure which corresponds to a pressure when sloshing does not occur, from the pressure in the purge vent in the sealed state and the error equivalence amount.