Cannister purge valve assembly

Abstract

A cannister purge valve assembly for a vehicle emissions control system is disclosed which includes a housing defining a chamber which is divided into a pair of sections by a diaphragm carried by the valve housing. One of the sections has inlets communicated to the vehicle fuel tank and to the vapor absorbing cannister and an outlet which is communicated to engine intake manifold vacuum when the vehicle engine is operating. The other section is provided with an inlet which is communicated to the spark port on the vehicle carburetor so that the other section is communicated to a vacuum level when the engine is running. The inlet communicated to the cannister and the outlet communicated to the intake manifold terminate in a pair of coaxial tubes which extend into the chamber. Corresponding ends of the tube are substantially coplanar to define a valve seating area. A spring yieldably urges the diaphragm into sealing engagement with the valve seating area on the coplanar ends of the tubes, to thereby prevent communication between the two inlets and between either of the inlets and the outlet unless the pressure level in the vehicle fuel tank raises above a predetermined pressure level sufficient to actuate the diaphragm, whereupon the vapor in the fuel tank is absorbed by the cannister. When the vehicle engine is started, the diaphragm moves away from the valve seating area to permit purging of the cannister through the outlet.