Throttle valve for use in a gas turbine engine fuel control system

Claim 1

An internal combustion engine throttle control apparatus for selectively controlling a throttle valve to provide both high resolution control and rapid response control thereof, said throttle control apparatus comprising: a ported body, a throttle flow control member movable in the body so as to control the flow therethrough, a pair of electrical stepper motors, and means interconnected with said internal combustion engine throttle flow control valve for causing a high resolution movement of said throttle flow control member when said motors rotate in a first relative direction with respect to one another and for causing a high speed movement of said throttle flow control member when said motors rotate in a second relative direction with respect to one another, said means including first and second driving connections between respective ones of said stepper motors and said throttle flow control member, said first and second driving connections including a single differential gear mechanism having an output member coupled to the throttle flow control member and first and second input members drivingly coupled to the output member, said stepper motors being drivingly connected to the respective input members, and the gear ratio of said first driving connections being different from that of said second driving connection wherein the movement of said throttle flow control member is dependent upon the gear ratio difference when said stepper motors rotate in a first relative direction and the movement of said throttle flow control member is dependent upon the gear ratio sum when one of said stepper motors rotates in a second relative direction and wherein said gear ratio sum or difference is never zero.