Variable-speed gear box with hydraulic system for tiltrotor aircraft
An aircraft includes a variable-speed gearbox. The variable-speed gearbox includes a low-speed gear train and a high-speed gear train, each gear train of which is configured to selectively provide torque from an engine of the aircraft to a proprotor. The variable-speed gearbox also includes a hydraulic system configured to provide torque to the proprotor. The hydraulic system includes a hydraulic pump driven by the engine of the tiltrotor aircraft and a variable-displacement motor driven by a hydraulic fluid from the hydraulic pump.
1. A variable-speed gearbox for an aircraft, the variable-speed gearbox comprising:
a low-speed gear train and a high-speed gear train, each of which is configured to selectively provide torque from an engine of the aircraft to a proprotor;
a hydraulic system configured to provide torque to the proprotor;
a hydraulic pump driven by the engine of the aircraft;
a variable-displacement motor driven by a hydraulic fluid from the hydraulic pump;
a hydraulic pump gear train that meshes with at least one of the high-speed and low-speed gear trains and is coupled to the hydraulic pump; and
a variable-displacement motor gear train that meshes with the hydraulic pump gear train and is coupled to an output shaft of the variable-displacement motor.
2. The variable-speed gearbox of claim 1 , wherein the low-speed gear train comprises a sprag clutch coupled between the low-speed gear train and the engine of the aircraft.
3. The variable-speed gearbox of claim 1 , wherein the high-speed gear train comprises a sprag clutch coupled between the high-speed gear train and the engine of the aircraft.
4. The variable-speed gearbox of claim 1 , wherein the hydraulic system comprises a bypass valve coupled between the hydraulic pump and the variable-displacement motor and configured to allow hydraulic fluid to bypass the variable-displacement motor.
5. The variable-speed gearbox of claim 1 , wherein the variable-displacement motor gear train comprises a sprag clutch coupled to the variable-displacement motor.
6. The variable-speed gearbox of claim 1 , wherein the hydraulic system further comprises:
a heat exchanger coupled between the variable-displacement motor and the hydraulic pump; and
a hydraulic fluid reservoir coupled between the variable-displacement motor and the hydraulic pump.
7. A tiltrotor aircraft comprising:
a first and a second variable-speed gearbox, each gearbox comprising:
a low-speed gear train and a high-speed gear train, each of which is configured to selectively provide torque from an engine of the tiltrotor aircraft to a proprotor;
a hydraulic system configured to provide torque to the proprotor, the hydraulic system comprising a hydraulic pump driven by the engine of the tiltrotor aircraft and a variable-displacement motor driven by a hydraulic fluid from the hydraulic pump;
a hydraulic pump gear train that meshes with at least one of the high-speed and low-speed gear trains and is coupled to the hydraulic pump; and
a variable-displacement motor gear train that meshes with the hydraulic pump gear train and is coupled to an output shaft of the variable-displacement motor.
8. The tiltrotor aircraft of claim 7 , wherein the low-speed gear train comprises a sprag clutch coupled between the low-speed gear train and the engine of the tiltrotor aircraft.
9. The tiltrotor aircraft of claim 7 , wherein the high-speed gear train comprises a sprag clutch coupled between the high-speed gear train and the engine of the tiltrotor aircraft.
10. The tiltrotor aircraft of claim 7 , wherein a variable-displacement motor gear train coupled to the variable-displacement motor comprises a sprag clutch coupled to the variable-displacement motor.
11. The tiltrotor aircraft of claim 7 , wherein the hydraulic system comprises a bypass valve coupled between the hydraulic pump and the variable-displacement motor and configured to allow hydraulic fluid to bypass the variable-displacement motor.