Extended range proportional valve

摘要

An extended range proportional valve (10) which can control rates of mass flow over continuous low, intermediate, and high ranges has a pilot member (68) mounted on an armature (84) of a solenoid which can be dithered onto and off of a pilot opening (58) in a main valve member (30) which seals a main valve opening (18) to control mass flow rates over the low range by varying the duty cycle and/or frequency of a pulse width modulated current in the solenoid coil. Intermediate and high flow rates are achieved by dithering the pilot valve member (68) with a duty cycle and/or frequency sufficient to raise the main valve member (30) relatively short and relatively long respective distances from the main valve seat (18).