A flow regulator for controlling the purging of fuel vapours into an intake of an engine and evaporative emission control system having such a regulator

摘要

A flow regulator for automotive vehicles of the type having a computer-controlled emission control system. The flow regulator has an electric vacuum regulator (EVR) valve that regulates the vacuum signal provided to a vacuum regulator valve in accordance with the current signal supplied to the EVR valve by the engine controller unit. The vacuum regulator valve includes a control chamber and a valve chamber that are separated by a movable diaphragm valve assembly. The preload on a biasing spring acting on the diaphragm valve assembly can be adjusted during calibration of the flow regulator for setting a first calibration point. An adjustable flow restrictor provided in the inlet portion of the vacuum regulator valve can be varied during calibration for setting a second calibration point. In addition, an anti-permeation filter is provided for inhibiting the venting of fuel vapors to atmosphere that have permeated through the diaphragm valve. In operation, the flow regulator is operable to generate substantially linear output flow characteristic between the two calibration points as a function of the current signal in a manner that is independent of changes in manifold vacuum.