Stepper motor driven proportional fuel metering valve

摘要

A low energy stepper motor driven fuel metering valve (FMV) that eliminates the need for a position sensor is provided. The stepper motor rotates a cam that replaces the flapper valve used in conventional systems. The cam rotation increases the gap between the cam and nozzle on one side of the cam and decreases the gap between the cam and nozzle on the other side. The gap differences affect the pressures on the spool piston ends, which forces the piston in the direction that will re-equalize the cam-nozzle gaps. As a result, the relatively low energy stepper motor controls the relatively high energy hydromechanical system via the dual cam-nozzle-orifice system. The cam is precision machined and assures stroke/degree gain accuracy. The hydraulic system assures the piston tracks the cam essentially perfectly except for the effects of piston stiction forces.