Torque Path Coupling Assembly for Tiltrotor Mode Transition
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Solution Overview
Problem
Tiltrotor aircraft face limitations in maximum airspeed due to forward airspeed induced proprotor aeroelastic instability, which restricts their performance in forward flight.
Innovation Solution
A rotary propulsion system with a torque path coupling assembly that includes a freewheeling unit, such as a sprag clutch, and a shiftable torque path coupling assembly between the engine and proprotor assembly, allowing for synchronization and adjustment of rotating speeds to transition between non-rotary and rotary flight modes, thereby managing torque distribution and reducing instability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the proprotor operates in forward flight at high airspeed, then the fixed wing provides lift and the proprotor provides forward thrust, but forward airspeed induces proprotor aeroelastic instability that limits maximum airspeed
Solution Approach 1:
The patent applies dynamics by making the proprotor blade stiffness adjustable during flight. The variable stiffness mechanism allows the blade to be flexible at low speeds for stability and rigid at high speeds to overcome aeroelastic instability, enabling the aircraft to exceed the conventional speed limit while maintaining proprotor stability throughout the flight envelope.
2Reliability
If a torque path coupling assembly is added to manage torque distribution during mode transitions, then smoother transitions and reduced instability are achieved, but device complexity increases
Solution Approach 1:
The torque path coupling assembly acts as an intermediary mechanism between the engine and proprotor. It includes a freewheeling unit and synchronizing elements that mediate the torque transmission during mode transitions, allowing smooth engagement and disengagement while protecting the drivetrain from shock loads and instability.
3Adaptability or versatility
If the freewheeling unit allows the proprotor to rotate faster than the engine during transition, then non-rotary to rotary mode transition is enabled, but torque path control becomes more complex
Solution Approach 1:
The freewheeling unit provides dynamic torque path control that adapts to the relative speeds between engine and proprotor. During transition, it automatically engages or disengages based on speed differential, enabling the proprotor to rotate faster than the engine in non-rotary mode while maintaining controlled engagement when speeds synchronize.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables smoother transitions between flight modes, increases forward cruising speed by overcoming proprotor aeroelastic instability, and enhances the overall performance of tiltrotor aircraft by effectively managing torque and rotational energy distribution.
Implementation Method 1
a friction surface of the synchronizing ring is friction coupled to a conical face of the output of the first gear assembly
Data Source
Figure 1A~1B
Figure 1C~1D
Figure 2
AI summary
A rotary propulsion system (40) for a tiltrotor aircraft (10) operable to transition between rotary and non rotary flight modes. The rotary propulsion system (40) includes an engine (26a, 26b) that is coupled to a freewheeling unit (42a, 42b). A gear system has a torque path coupling assembly (46) between a first gear assembly (44) that is coupled to the freewheeling unit (42a, 42b) and a second gear assembly (48) that is coupled to a proprotor assembly (20a, 20b). The torque path coupling assembly (46) has an engaged position wherein the output of the first gear assembly (44) is coupled to the input of the second gear assembly (48) thereby providing a torque path between the engine (26a, 26b) and the proprotor assembly (20a, 20b). The torque path coupling assembly (46) also has a disengaged position wherein the output of the first gear assembly (44) is independent of the input of the second gear assembly (48) thereby interrupting the torque path between the engine (26a, 26b) and the proprotor assembly (20a, 20b).