Patent attributes
An evaporative fuel treatment system is disclosed that includes a canister, a detection passage having a reduced area portion, and switching device that switches fluid communication. Also included is a depressurizing device for depressurizing the detection passage coupled to the detection passage on a side of the reduced area portion opposite to the switching device, and a pressure detecting device. Moreover, the system includes an evaporative fuel state calculating device for calculating an evaporative fuel state in the mixture based on a cutoff pressure, an air pressure, and a mixture pressure of a mixture of air and the evaporative fuel. In one embodiment, the cutoff pressure, the air pressure, and the mixture pressure are detected independently and discontinuously. In another embodiment, the cutoff pressure and the air pressure are detected on a continual basis during purge of the evaporative fuel.
