Planet Carrier X-Brace Structure for Lower Gear Misalignment
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Solution Overview
Problem
Conventional planet carriers for epicyclic reduction gears in turbomachines face challenges with misalignment of planet gears, stress resistance, and mass, which affect reliability, service life, and efficiency, particularly due to their heavy construction and complex manufacturing processes.
Innovation Solution
A planet carrier design featuring an annular cage with X-shaped bridges and a continuous annular channel that reduces stress and misalignment, facilitating manufacturing and maintenance, while maintaining balanced rigidity and reducing centrifugal forces, and includes features like a U-shaped ring and annular balancing bead for unbalance correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the planet carrier is made of massive metal alloy to ensure strength and support conditions, then the stress resistance and reliability are improved, but the mass increases and manufacturing complexity increases
Solution Approach 1:
The planet carrier is divided into a modular structure comprising a central hub, multiple spokes, and an annular cage. This segmentation allows each component to be optimized independently for strength-to-weight ratio, replacing massive monolithic construction with a lightweight truss-like architecture that maintains structural integrity through strategic load path design.
Solution Approach 2:
The planet carrier employs composite material construction, combining materials with different properties to achieve optimal performance. The central hub and spokes use high-strength materials for load bearing, while the annular cage utilizes lighter materials for positioning functionality, creating a composite structure that balances strength requirements with mass reduction goals.
2Reliability
If the planet carrier is made of massive metal alloy to ensure support conditions, then the reliability is improved, but the manufacturing complexity increases
Solution Approach 1:
The segmented modular design enables simplified manufacturing of individual components (hub, spokes, cage) that can be produced using standard machining and forming processes. The modular nature allows for easier quality control and assembly compared to monolithic construction, reducing overall manufacturing complexity while maintaining reliability through proven connection methods.
Solution Approach 2:
The planet carrier incorporates dynamic flexibility in its spoke-cage connections, allowing the structure to adapt to operational loads and thermal expansions. This dynamic design accommodates manufacturing tolerances and reduces stress concentrations, improving reliability without requiring overly precise manufacturing, thereby reducing manufacturing complexity.
3Ease of manufacture
If the bridges are formed by bars crossing one another to facilitate manufacture and reduce mass, then the manufacturing complexity and mass are reduced, but the misalignment of planet gears increases
Solution Approach 1:
The bridge structure is segmented into modular bar elements that can be manufactured independently with standard tolerances. These segmented bars are assembled into X-shaped configurations where the modular nature allows for easier alignment and adjustment during assembly, reducing the cumulative misalignment issues that would occur with monolithic bridge structures.
Solution Approach 2:
The bridge design incorporates controlled flexibility and compliance in the bar connections, allowing the structure to dynamically adjust to minor misalignments during operation. This dynamic compensation mechanism tolerates manufacturing variations in the crossed bars while maintaining adequate planet gear alignment, reducing the stringency of manufacturing precision requirements.
4Weight of moving object
If the annular cage is designed with X-shaped bridges to reduce mass and facilitate manufacture, then the mass and manufacturing complexity are reduced, but the rigidity and misalignment resistance decrease
Solution Approach 1:
The annular cage is segmented into discrete X-shaped bridge units distributed around the circumference. This segmentation creates a truss-like structure where the crossed bars form triangular rigid sub-structures, providing high stiffness-to-weight ratio. The segmented design allows optimization of each bridge unit for maximum rigidity with minimal material, overcoming the weakness of continuous cage structures.
Solution Approach 2:
The cage structure utilizes composite material construction with high-stiffness, low-density materials in the bridge elements. This composite approach enables the X-shaped bridges to achieve the rigidity of much heavier monolithic structures while maintaining the mass and manufacturing advantages of the segmented lightweight design, effectively decoupling rigidity requirements from mass penalties.
Data Source
AI summary
A planet carrier for an epicyclic speed reduction gear, comprising a torque transmission member of longitudinal axis A and an annular cage extending around the axis A and connected to a longitudinal end of the member, said cage comprising two flanks extending essentially radially with respect to the axis A and connected by bridges, seats extending axially between the flanks and being intended for supporting planet gears mounted rotatably about the seats, characterized in that said bridges comprise bars which cross one another essentially in the shape of an X, and of which the ends located on the side of said member are connected to said member by a ring extending around said axis A and comprising a continuous internal annular channel.