Emission control system with altitude compensated purge valve

摘要

An altitude compensated purge valve is connected in parallel with the vacuum actuated purge valve in the evaporative emission control system for a vehicle engine whereby to control as a function of ambient pressure the purging of fuel vapors from a fuel vapor storage canister into the vehicle engine for combustion therein. The altitude compensated purge valve includes an aneroid actuated tapered valve to variably control the flow area through an inlet passage from the canister for controlling vapor purge therefrom to a common fuel vapor line connecting both the vacuum actuated purge valve and the altitude compensated purge valve to the induction system of the engine.