Patent ID: 6966214
Filing Date: 2005-11-22
Classification: F02M

Abstract:
1. A leakage diagnosis apparatus for a fuel vapor purge system, in which fuel vapor generating in a fuel tank is trapped in a canister via an evaporation passage, and the fuel vapor trapped in said canister is purged, via a purge passage, into an intake passage of an internal combustion engine, comprising: a blocking device configured to block a diagnosis zone containing at least one of said fuel tank, said evaporation passage, said canister and said purge passage; a pressurizer that pressurizes said diagnosis zone; a pressure detector configured to detect a pressure in said diagnosis zone; and a diagnosis unit that outputs control signals to said blocking device and said pressurizer, and also receives a detection signal as an input signal from said pressure detector, to diagnose an occurrence of leakage in said diagnosis zone, wherein said diagnosis unit blocks said diagnosis zone by said blocking device, and detects data indicating a pressure rise characteristic in said diagnosis zone for when said diagnosis zone is pressurized by said pressurizer based on the detection signal from said pressure detector and also detects data indicating a pressure drop characteristic in said diagnosis zone after the pressurization by said pressurizer is stopped, and diagnoses an occurrence of leakage in said diagnosis zone based on the data indicating said pressure rise characteristic and the data indicating said pressure drop characteristic, wherein said diagnosis unit: detects the curvature of a pressure change curve during the pressurization by said pressurizer as the data indicating said pressure rise characteristic, and detects a pressure drop amount within a period of time after the stop of pressurization by said pressurizer as the data indicating said pressure drop characteristic; judges that there is no leakage, when an absolute value of said curvature is smaller than a first threshold, and also said pressure drop amount is smaller than a second threshold; judges an occurrence of leakage when the absolute value of said curvature is equal to or larger than the first threshold; and judges an occurrence of leakage when said pressure drop amount is equal to or larger than the second threshold.