High flow, low vacuum carbon canister purge valve

摘要

A technique is provided for purging an adsorption canister in a fuel tank vent system. The technique provides a relatively high purge flow under conditions wherein the intake manifold vacuum is relatively low. A sonic nozzle is placed in the purge line between the existing purge valve and the adsorption canister. The sonic nozzle includes a tap at its throat for producing a vacuum in response to flow in the purge line. The vacuum is used to control a vacuum operated diaphragm valve in a parallel purge line. The system therefore supplements purge flow through the adsorption canister to the intake manifold.