Patent attributes
In an evaporative fuel treatment device, a differential pressure specifying unit specifies a differential pressure between a pressure in a diagnosis target system and the atmosphere, and a pressure target setting unit sets a pressure target value so that the differential pressure attains a predetermined differential pressure value. A pump pressurizes or depressurizes the pressure in the diagnosis target system to the pressure target value, and a leakage diagnosis unit performs a leakage diagnosis based on a pressure change relation value related to the pressure change in the diagnosis target system and the leakage diagnosis threshold value. The fuel partial pressure estimation unit estimates a first partial pressure of fuel vapor in the fuel tank from a tank inside concentration and a tank absolute pressure of a specific component. A corresponding partial pressure specifying unit specifies a second partial pressure of the fuel vapor in the fuel tank based on a relation between the tank absolute pressure and the first partial pressure when the second partial pressure of the fuel vapor in the fuel tank when the pressure is increased or reduced to the target pressure value. A comparison unit compares the first partial pressure and the second partial pressure. A correction unit corrects, based on a comparison result of the comparison unit, a leakage diagnosis threshold value or the pressure change relation value used for the leakage diagnosis.
