Epicyclic Fan Drive Gear Assembly for Flexure Misalignment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Gas turbine engines with geared architectures face deformation issues due to torsional loads, leading to misalignment of gears and reduced operating life, as existing designs fail to maintain intermeshing alignment during flexure-induced deformation.
Innovation Solution
An epicyclic gear assembly with a carrier having first and second epicyclic gear sets, where the first and second ring gears extend from flexible flanges and include teeth that align with tooth roots of the second set, and spherical bearings between posts and intermediate gears allow for independent movement and alignment maintenance during carrier flexure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a geared architecture is used to increase fan efficiency, then the gas turbine engine efficiency is improved, but the gear structure becomes misaligned due to flexure-induced deformation from torsional loads
Solution Approach 1:
The patent changes the physical state of the ring gear from rigid to flexible by introducing a flexible flange. This allows the ring gear to deform elastically in response to torsional loads, maintaining gear mesh alignment despite carrier deformation. The flexible flange's ability to change shape under load directly addresses the misalignment problem while preserving the geared architecture's efficiency benefits.
Solution Approach 2:
The patent introduces dynamic adaptability to the gear system through the flexible flange, which can dynamically adjust its shape in response to varying torsional loads during operation. This dynamic response allows the gear assembly to maintain proper alignment under different operating conditions, resolving the contradiction between maintaining high efficiency and preventing misalignment.
2Manufacturing precision
If the carrier structure is made more flexible to accommodate deformation, then the gear alignment is maintained, but the structural strength decreases
Solution Approach 1:
The patent applies local quality by making only the ring gear flexible through the flexible flange, while keeping the rest of the carrier structure rigid. This localized flexibility allows the ring gear to accommodate deformation and maintain alignment without compromising the overall structural strength of the carrier. The flexibility is precisely where needed at the gear interface, not throughout the entire carrier.
3Manufacturing precision
If spherical bearings are used to allow independent gear movement, then alignment is maintained during flexure, but the device complexity increases
Solution Approach 1:
The spherical bearings act as intermediaries between the rigid carrier and the flexible ring gear, allowing relative movement while maintaining gear alignment. These bearings mediate the interaction between the deforming flexible flange and the intermediate gears, enabling the system to accommodate carrier deformation without increasing overall structural complexity. The spherical bearings provide a simple mechanical solution for maintaining alignment during flexure.
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
The solution effectively maintains relative intermeshing alignment of gears during deformation, reducing vibration and extending the operating life of gears and bearings by allowing for angular rotation and flexibility in the gear assembly.
Implementation Method 1
The first ring gear includes a first set of teeth that extends from a first flexible flange and the second ring gear includes a second set of teeth that extends from a second flexible flange
Implementation Method 2
at least one first spherical bearing is located between at least one first post and at least one of the first set of intermediate gears
Data Source
AI summary
An epicyclic gear assembly includes a carrier that includes a first plate axially spaced from a second plate by a connector. A first epicyclic gear set is supported adjacent the first plate and includes a first set of circumferentially offset intermediate gears meshing with a first sun gear and a first ring gear. A second epicyclic gear set is axially spaced from the first epicyclic gear set and supported adjacent the second plate and includes a second set of circumferentially offset intermediate gears meshing with a second sun gear and a second ring gear. The first epicyclic gear is set and the second epicyclic gear set maintain relative intermeshing alignment during flexure-induced deformation of the carrier. The first ring gear includes a first set of teeth that extends from a first flexible flange and the second ring gear includes a second set of teeth that extends from a second flexible flange.