Monolithic Planet Carrier Structure for Twist-Controlled Gearboxes
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Solution Overview
Problem
Epicyclic gear trains in gas turbine engines face issues with torsional deflection due to planet carrier twisting, leading to inefficiency and reduced lifespan, and existing designs are not compact or lightweight enough to improve the power-to-weight ratio.
Innovation Solution
A monolithic planet carrier design with integrally formed torque transfer coupling, center arms, and carrier plates, where axially extending bridges connect the plates, forming a compact and lightweight structure that minimizes torsional deflection and optimizes torque path distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a traditional planet carrier design is used, then the structure is simple to manufacture, but the planet carrier is prone to torsional deflection and twisting under load
Solution Approach 1:
The planet carrier is divided into multiple functional segments including a central hub, multiple arms extending radially outward, and carrier plates at the ends of arms. Each segment is optimized independently to resist torsional loads while maintaining manufacturability. The segmentation allows strategic placement of reinforcement features without requiring complete redesign of the entire structure.
Solution Approach 2:
Reinforcement features such as ribs, gussets, and thickened sections are applied locally at critical stress points where torsional loads are highest, rather than uniformly throughout the entire planet carrier. This localized reinforcement increases torsional rigidity where needed while minimizing added weight and manufacturing complexity in non-critical areas.
2Weight of moving object
If a compact and lightweight planet carrier is designed, then the power to weight ratio improves, but the durability and resistance to torsional deflection may be compromised
Solution Approach 1:
The planet carrier design incorporates optimized arm thickness variations along their length, with thicker sections at the hub connection and carrier plate interfaces where stresses are highest, and gradually thinner sections toward the mid-spans. This dynamic thickness distribution minimizes weight while maintaining durability at critical locations.
Solution Approach 2:
The planet carrier utilizes composite construction combining different material properties in strategic locations, such as using high-strength alloys for the central hub and arm roots where torsional stresses concentrate, while employing lighter materials or reduced section thickness in less critical areas. This composite approach optimizes the strength-to-weight ratio across the entire component.
3Volume of moving object
If the planet carrier is made more compact, then the gearbox size is reduced, but the torque path distribution may be adversely affected
Solution Approach 1:
The planet carrier arms are positioned and dimensioned to nest efficiently within the epicyclic gear train geometry, with arms extending to刚好 reach the planet gear centers without excessive overhang. This nested arrangement minimizes the overall volume of the planet carrier while maintaining optimal torque distribution paths from the sun gear through the planet gears to the ring gear.
Solution Approach 2:
The design optimizes the three-dimensional arrangement of arms and carrier plates to create efficient torque transmission paths in multiple dimensions. The arms are angled and positioned to distribute torque loads across different spatial dimensions, allowing compact packaging while maintaining robust torque path distribution through the gear train.
Data Source
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AI summary
A planet carrier (40; 140; 240) for an epicyclic gear train (27) of a gas turbine engine gearbox (12) includes a centrally disposed torque transfer coupling (44; 144; 244), a pair of carrier plates (48a, 48b; 148a, 148b; 248a, 248b) parallel to each to each other and perpendicular to a longitudinal axis (37), and center arms (50; 150; 250) radially extending radially outward from the torque transfer coupling (44; 144; 244) to the carrier plates (48a, 48b; 148a, 148b; 248a, 248b). A central bore (45) is concentric with the longitudinal axis (37) and forming a torque transmission point (54) on the planet carrier(40; 140; 240). The center arms (50; 150; 250) are axially disposed between the axially spaced apart carrier plates (48a, 48b; 148a, 148b; 248a, 248b) and have radially outer ends (52) which terminate at an outer perimeter (60) of the carrier plates (48a, 48b; 148a, 148b; 248a, 248b). The center arms (50; 150; 250) are thus entirely radially disposed within a radial outer perimeter (60) of the carrier plates (48a, 48b; 148a, 148b; 248a, 248b).