Geared unison ring for variable vane actuation
A variable vane system includes a harmonic drive driven by an actuator, and a drive gear driven by the harmonic drive. A geared unison ring includes an actuator gear rack driven by the drive gear and a multiple of vane gears, each of the multiple of vane gears mounted to one of a multiple of variable vanes, the multiple of vane gears driven by a gear rack of the geared unison ring.
1. A variable vane system, comprising: an actuator; a harmonic drive driven by the actuator; a drive gear driven by the harmonic drive; a geared unison ring comprising an actuator gear rack driven by the drive gear; and a multiple of vane gears, each of the multiple of vane gears mounted to one of a multiple of variable vanes, the multiple of vane gears driven by a gear rack of the geared unison ring, wherein the geared unison ring spans a first variable vane stage of the multiple of variable vanes and a second variable vane stage of the multiple of variable vanes.
2. The system as recited in claim 1 , wherein the harmonic drive includes a strain wave gearing mechanism.
3. The system as recited in claim 2 , wherein the strain wave gearing mechanism include a fixed circular spline, a flex spline attached to an output shaft, and a wave generator attached to an input shaft, the flex spline driven by the wave generator with respect to the fixed circular spline.
4. The system as recited in claim 1 , wherein the harmonic drive provides between a 30:1-320:1 gear ratio.
5. The system as recited in claim 1 , wherein the drive gear is a gear segment.
6. The system as recited in claim 5 , wherein the drive gear is operable to rotate through 90 degrees.
7. The system as recited in claim 5 , wherein the drive gear is operable to rotate through 0-40 degrees.
8. The system as recited in claim 1 , wherein the geared unison ring includes an interface with an engine case of a gas turbine engine to restrain axial motion.
9. The system as recited in claim 8 , wherein the interface is a flange to restrain axial movement of the geared unison ring.
10. The system as recited in claim 1 , wherein the geared unison ring spans the first variable vane stage with a vane gear for each first stage variable vane, and the second variable vane stage with a vane gear for each second stage variable vane.
11. The system as recited in claim 1 , wherein the actuator gear rack is shorter than the gear rack.
12. The system as recited in claim 1 , wherein the actuator gear rack is on the same plane as the gear rack.
13. The system as recited in claim 1 , wherein the actuator gear rack is opposite the gear rack.
14. A gas turbine engine, comprising: an engine case; a multiple of variable vanes at least partially within the engine case; and a harmonic drive operable to drive a variable vane system through a geared unison ring that surrounds said engine case, each of a multiple of vane gears mounted to one of the multiple of variable vanes, each of the multiple of vane gears driven by a gear rack of the geared unison ring, the geared unison ring driven by an actuator gear rack that extends from the geared unison ring, wherein the geared unison ring spans a first variable vane stage of the multiple of variable vanes and a second variable vane stage of the multiple of variable vanes.
15. The gas turbine engine as recited in claim 14 , wherein the actuator gear rack is meshed with a drive gear.
16. The gas turbine engine as recited in claim 14 , wherein the geared unison ring includes an interface with an engine case of a gas turbine engine to restrain axial motion.
17. A gas turbine engine, comprising: an engine case; a multiple of variable vanes; a multiple of vane gears, each of the multiple of vane gears mounted to one of a multiple of variable vanes; a geared unison ring that surrounds said engine case, the multiple of vane gears driven by the geared unison ring; and an actuator gear rack that extends from the geared unison ring to drive the geared unison ring, wherein the geared unison ring spans a first variable vane stage of the multiple of variable vanes and a second variable vane stage of the multiple of variable vanes.
18. The system as recited in claim 17 , wherein the geared unison ring comprises a first gear rack that meshes with the first variable vane stage and a second gear rack that meshes with the second variable vane stage.
19. The system as recited in claim 18 , wherein the actuator gear rack is driven by a drive gear, the actuator gear rack shorter than the first gear rack.
20. The system as recited in claim 18 , wherein the actuator gear rack is driven by a drive gear, the actuator gear rack opposite the first gear rack.
21. The system as recited in claim 17 , further comprising a drive gear to drive the actuator gear rack.
22. The system as recited in claim 21 , wherein the actuator gear rack is shorter than the gear rack that drives the multiple of actuator gears.
23. The system as recited in claim 21 , further comprising:
an actuator;
a harmonic drive driven by the actuator; and
the drive gear driven by the harmonic drive to drive the geared unison ring through the actuator gear rack.