Epicyclic Gearbox Carrier Stiffness for Alignment Under Load
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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 distortion and reduced gearbox reliability.
Innovation Solution
The design of an epicyclic gearbox with a planet carrier having specific stiffness ranges, including radial bending stiffness between 1.20×10^9 N/m and 1.00×10^12 N/m, tilt stiffness greater than 6.00×10^8 Nm/rad, and torsional stiffness between 1.60×10^8 Nm/rad and 1.00×10^11 Nm/rad, which allows for compensation of gear misalignment and maintains even load distribution across gears.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the planet carrier stiffness is increased to maintain gear alignment, then gear misalignment compensation is improved, but the gearbox mass increases
Solution Approach 1:
The patent applies parameter changes by optimizing the planet carrier stiffness to specific numerical ranges (radial bending stiffness: 1.20×10^9 to 1.00×10^12 N/m, tilt stiffness: ≥6.00×10^8 Nm/rad, torsional stiffness: 1.60×10^8 to 1.00×10^11 Nm/rad). These precise parameter specifications resolve the contradiction by finding the optimal stiffness values that provide sufficient gear alignment compensation while avoiding excessive mass increase.
2Manufacturing precision
If the planet carrier stiffness is increased to maintain load distribution, then gear load sharing is improved, but the gearbox reliability decreases due to distortion
Solution Approach 1:
The patent resolves this contradiction by specifying optimal stiffness parameter ranges that balance load distribution and distortion prevention. The radial bending stiffness (1.20×10^9 to 1.00×10^12 N/m), tilt stiffness (≥6.00×10^8 Nm/rad), and torsional stiffness (1.60×10^8 to 1.00×10^11 Nm/rad) are tuned to provide sufficient rigidity for even load sharing across planet gears while maintaining enough flexibility to avoid harmful distortions that would reduce reliability.
3Productivity
If the planet carrier mass is reduced to improve efficiency, then gearbox efficiency is improved, but the gear alignment stability deteriorates
Solution Approach 1:
The patent resolves this contradiction by optimizing the stiffness-to-mass ratio through precise stiffness parameter specifications. By defining radial bending stiffness (1.20×10^9 to 1.00×10^12 N/m), tilt stiffness (≥6.00×10^8 Nm/rad), and torsional stiffness (1.60×10^8 to 1.00×10^11 Nm/rad), the invention enables the planet carrier to achieve maximum alignment stability with minimum necessary mass, thereby improving gearbox efficiency while maintaining gear alignment stability.
Data Source
AI summary
An engine for an aircraft includes 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 is an epicyclic gearbox and comprises a sun gear, a plurality of planet gears, a ring gear, and a planet carrier on which the planet gears are mounted. The radial bending stiffness of the planet carrier is equal to or greater than 1.20×109 N/m, and/or the tilt stiffness of the planet carrier is greater than or equal to 6.00×108 Nm/rad. A method of operation of such an engine is also disclosed.