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 misalignment and reduced gearbox reliability.
Innovation Solution
An epicyclic gearbox design with a planet carrier having specific radial bending, tilt, and torsional stiffness ranges, allowing for compensation of misalignment while maintaining even load distribution across gears, thereby reducing mass and improving reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the planet carrier is made with high stiffness to maintain gear alignment, then gear misalignment compensation is improved, 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 be stiff enough to maintain gear alignment and compensate for misalignment while avoiding excessive mass increase that would occur with higher stiffness values.
2Reliability
If the planet carrier stiffness is increased to ensure even load distribution, then gearbox reliability is improved, but the device complexity increases
Solution Approach 1:
The patent resolves this contradiction by defining specific stiffness parameter ranges for the planet carrier (radial bending: 1.20×10^9 to 1.00×10^12 N/m, tilt: 1.30×10^9 to 1.20×10^11 Nm/radian, torsional: 1.60×10^8 to 1.00×10^11 Nm/radian). These optimized parameters enable even load distribution across planet gears while avoiding the need for complex structural modifications that would increase device complexity.
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 is arranged to receive an input from a gearbox input shaft portion of the core shaft and to output 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 and has a sun gear, a plurality of planet gears, a ring gear, and a planet carrier. The planet carrier and the gearbox support each have a torsional stiffness, and a carrier to gearbox support torsional stiffness ratio is greater than or equal to 2.3.