Load Balanced Journal Bearing Pin for Fan Drive Gear Systems
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Solution Overview
Problem
Existing fan drive gear systems in gas turbine engines face challenges in maintaining gear alignment under load, which can reduce propulsive efficiency due to misalignment caused by unsupported bearings, despite improvements in thermal and transfer efficiencies.
Innovation Solution
A fan drive gear system with beams of approximately equal stiffness that bend in opposite directions to maintain the bearing surface parallel to the gear rotation axis, supported by a torque frame and lubricant conduit for flexible movement, ensuring alignment and load accommodation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional bearings are used to support intermediate gears, then the gear assembly can rotate, but the bearings cannot accommodate loads and contribute to misalignment of meshing gears
Solution Approach 1:
The bearing support structure is segmented into multiple beams (first beam, second beam, third beam) that independently support different aspects of the bearing assembly, allowing each beam to be optimized for specific functions such as alignment maintenance or load accommodation
Solution Approach 2:
The beams are designed with different stiffness characteristics - some beams have higher stiffness to maintain alignment while others have lower stiffness to accommodate loads, creating an asymmetric support structure that addresses both requirements simultaneously
2Ease of operation
If beams of different stiffness are used to support the bearing, then load accommodation is improved, but gear alignment is compromised due to uneven bending
Solution Approach 1:
The first and second beams are positioned and designed to bend in opposite directions under load, creating a counterbalancing effect that maintains the bearing surface parallel to the gear rotation axis while accommodating the applied loads
Solution Approach 2:
The stiffness parameters of the beams are carefully controlled and differentiated - the first and second beams have approximately equal stiffness to enable opposite bending, while the third beam has different stiffness to provide additional support without disrupting the balance
3Reliability
If rigid support structures are used for bearings, then alignment is maintained, but the structure cannot accommodate operational loads
Solution Approach 1:
The support structure transitions from a rigid configuration to a dynamic one where the beams can bend and flex under load, allowing the system to adapt to operational conditions while maintaining alignment through the coordinated bending of multiple beams
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
This configuration maintains gear alignment and stability under load, enhancing propulsive efficiency and reducing misalignment issues, thereby improving overall engine performance.
Implementation Method 1
both the first beam and the second beam include an approximately common stiffness and bend in opposite directions to maintain the bearing surface substantially parallel to the intermediate gear rotation axis under a load applied to the bearing surface
Implementation Method 2
includes a passage for lubricant through the bearing surface and a lubricant conduit for communicating lubricant from the first beam to the passage in the bearing surface
Implementation Method 3
the lubricant conduit is flexible to enable relative bending of the first beam relative to the second beam
Data Source
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AI summary
A disclosed fan drive gear system includes a sun gear rotatable about an axis of rotation, a plurality of intermediate gears rotatable about an intermediate gear rotation axis in meshing engagement with the sun gear and a ring gear circumscribing the intermediate gears. A bearing assembly supports at least one of the plurality of intermediate gears and includes a first beam extending in a first direction and a second beam extending from an end of the first beam in a second direction. The bearing surface supported on the second beam such that first and second beams are configured to maintain the bearing surface substantially parallel to the intermediate gear rotation axis during operation.