Epicyclic Gearbox Stiffness Tuning for Misalignment Compensation
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Solution Overview
Problem
Existing aircraft engine gearboxes face challenges in maintaining gear alignment and load distribution due to manufacturing tolerances and wear, leading to potential misalignment and reduced gearbox reliability.
Innovation Solution
An epicyclic gearbox design with a planet carrier having specific radial bending, tilt, and torsional stiffness ranges (e.g., ≥1.20×10^9 N/m, ≥6.00×10^8 Nm/rad) to compensate for misalignment and ensure even load distribution, reducing the risk of gear distortion and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the planet carrier stiffness is increased to maintain gear alignment, then gear misalignment compensation improves, but the mass of the gearbox increases
Solution Approach 1:
The patent applies parameter changes by optimizing the planet carrier stiffness to specific ranges (radial bending stiffness: 1.20×10^9 to 1.00×10^12 N/m, tilt stiffness: 1.30×10^9 to 1.20×10^11 Nm/radian, torsional stiffness: 1.60×10^8 to 1.00×10^11 Nm/radian). These controlled parameter changes enable the carrier to compensate for gear misalignment while preventing excessive stiffness that would increase mass, thus resolving the contradiction between reliability and weight.
2Manufacturing precision
If manufacturing tolerances are tightened to improve gear alignment, then gear misalignment reduces, but manufacturing cost and complexity increase
Solution Approach 1:
The patent implements self-service by designing the planet carrier with specific stiffness characteristics that enable it to automatically compensate for gear misalignment caused by manufacturing tolerances and wear. The carrier's controlled flexibility allows it to self-adjust and maintain even load distribution across planet gears without requiring complex active control systems or extremely tight manufacturing tolerances, thereby reducing manufacturing complexity while improving alignment.
3Adaptability or versatility
If the planet carrier is made more flexible to accommodate wear, then adaptability improves, but gear distortion increases
Solution Approach 1:
The patent resolves this contradiction through precise parameter control of the planet carrier stiffness within defined ranges. The radial bending stiffness (1.20×10^9 to 1.00×10^12 N/m), tilt stiffness (1.30×10^9 to 1.20×10^11 Nm/radian), and torsional stiffness (1.60×10^8 to 1.00×10^11 Nm/radian) are optimized to provide sufficient flexibility for wear compensation while maintaining structural integrity and preventing gear distortion. This balanced parameter selection enables adaptability without excessive flexibility.
Data Source
AI summary
An engine for an aircraft has an engine core having a turbine, a compressor, and a core shaft connecting the turbine to the compressor; a fan located upstream of the engine core, the fan having a plurality of fan blades; and a gearbox. The gearbox for an aircraft is arranged to receive an input from a core shaft and to output drive to a fan so as to drive the fan at a lower rotational speed than the core shaft. The gearbox is an epicyclic gearbox and has a sun gear, a plurality of planet gears, a ring gear, and a planet carrier having a plurality of pins, each pin being arranged to have a planet gear of the plurality of planet gears mounted thereon. A ratio of planet carrier torsional stiffness to pin stiffness is within a specified range.