Three-way flow valve with variable drain orifice area

Abstract

A solenoid valve for use in a fuel system includes a valve body with a central core and three interconnected passageways. A spool is disposed within the central core and by means of enlarged and reduced diameter portions controls the flow through the solenoid valve. Solenoid armatures cooperatively control movement of the valve spool which is sized and shaped so as to provide a fuel flow path from an inlet passageway to an outlet passageway when the solenoid valve is in an opened condition. When the spool is shifted to a closed condition, incoming fuel is blocked and a flow path is created from the output passageway to a drain passageway, The drain passageway allows excess fuel in the injector to drain to relieve fuel pressure on the metering plunger. As the spool moves from a closed condition to an opened condition, some fuel flows to the drain passageway. The amount of fuel 'loss' depends on the speed of the spool and the size of the drain passageway. In order to avoid the higher cost associated with drilling a small diameter hole through the valve body, a larger drilled hole is used. The enlarged end of the valve spool is extended so as to block a substantial portion of the drain passageway orifice. The blocked orifice yields a smaller flow through area and this reduced flow orifice area reduces transition loss and cavitation.