Epicyclic Gearbox Carrier Stiffness 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 distortion and reduced gearbox reliability.
Innovation Solution
The design of an epicyclic gearbox with a planet carrier having specific stiffness ranges for radial bending, tilt, and torsional stiffness, allowing for compensation of gear misalignment while maintaining even load distribution and reducing mass, thereby enhancing gearbox lifetime and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the planet carrier is designed with high stiffness to maintain gear alignment, then gear misalignment is reduced, but the mass of the planet carrier increases
Solution Approach 1:
The patent applies parameter changes by optimizing the stiffness values of the planet carrier within 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). This allows the carrier to have sufficient stiffness to maintain gear alignment while avoiding excessive mass that would result from overly high stiffness values.
2Reliability
If the planet carrier stiffness is increased to prevent distortion, then gear load distribution improves, but the mass of the gearbox increases
Solution Approach 1:
The patent uses parameter changes by defining specific stiffness ranges for the planet carrier that balance load distribution requirements with mass constraints. The radial bending stiffness range of 1.20×10^9 to 1.00×10^12 N/m ensures even load distribution across planet gears without unnecessarily increasing gearbox mass.
3Manufacturing precision
If the planet carrier is made more flexible to compensate for manufacturing tolerances, then gear misalignment is reduced, but the structural strength decreases
Solution Approach 1:
The patent resolves this contradiction through parameter changes by specifying minimum stiffness thresholds (radial bending stiffness ≥ 1.20×10^9 N/m, tilt stiffness ≥ 1.30×10^9 Nm/radian, torsional stiffness ≥ 1.60×10^8 Nm/radian) that provide enough flexibility to compensate for manufacturing tolerances while maintaining adequate structural strength to prevent excessive deformation under load.
Data Source
AI summary
An engine for an aircraft includes an engine core including a turbine, a compressor, and a core shaft connecting the turbine to the compressor; a fan located upstream of the engine core, the fan comprising a plurality of fan blades; and a gearbox. The gearbox receives an input from a gearbox input shaft portion of the core shaft and outputs drive to the fan so as to drive the fan at a lower rotational speed than the core shaft. The gearbox is an epicyclic gearbox including a sun gear, a plurality of planet gears, a ring gear, and a planet carrier on which the planet gears are mounted. The carrier and the gearbox input shaft each have a torsional stiffness, and a carrier to gearbox input shaft torsional stiffness ratio is greater than or equal to 70.