Patent ID: 6814063
Filing Date: 2004-11-09
Classification: F02M

Abstract:
A fuel vapor processing device for use with an engine which burns air from an intake passage and fuel supplied from a fuel tank, comprising:a canister which adsorbs fuel vapor in the fuel tank, the canister having an air vent which communicates with the atmosphere; a first passage which connects the fuel tank and the canister; a second passage which connects the canister and the intake passage; a purge valve installed in the second passage; a pressure sensor which detects a negative pressure in a section leading from the purge valve to the fuel tank via the first passage, canister and second passage; and a programmable controller programmed to: compare the negative pressure, when the purge valve is open, with a reference negative pressure; and decrease an opening of the purge valve when a magnitude of the negative pressure is larger than a magnitude of the reference negative pressure by decreasing an upper limit of the opening of the purge valve according to a limit factor which gradually decreases at a predetermined reduction rate, and applying the limit factor immediately prior to a closure of the purge valve, to the limit factor when the purge valve is opened again after the closure.