Epicyclic Gearbox Mesh Stiffness for Misalignment-Tolerant Load Sharing
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Solution Overview
Problem
Existing gearboxes for aircraft engines face challenges in maintaining optimal performance due to small errors in gear alignment and shape, which can lead to uneven wear and reliability issues.
Innovation Solution
An epicyclic gearbox with a specific range of overall gear mesh stiffness (between 1.05×10^9 N/m and 8.0×10^9 N/m) is designed to accommodate misalignments and shape errors, while maintaining sufficient stiffness to prevent excessive deformation and torsional vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the gear mesh stiffness is increased to reduce deformation and vibrations, then the reliability and efficiency improve, but the gearbox becomes less able to accommodate manufacturing errors and misalignments
Solution Approach 1:
The patent applies parameter changes by optimizing the gear mesh stiffness to a specific value or range that simultaneously achieves sufficient structural rigidity for reliable operation and adequate compliance to tolerate manufacturing errors. This involves carefully selecting material properties, gear geometry parameters, and mesh characteristics to reach an optimal stiffness value that balances both requirements.
2Manufacturing precision
If the gear mesh stiffness is decreased to accommodate misalignments, then the evenness of wear improves, but excessive flexibility leads to torsional vibrations and reduced efficiency
Solution Approach 1:
The patent uses parameter changes by adjusting the gear mesh stiffness to an optimal value that provides sufficient flexibility to accommodate misalignments and achieve even wear distribution, while preventing excessive flexibility that would cause harmful torsional vibrations and energy losses. This involves precise control of stiffness-related parameters within a specific range.
Data Source
AI summary
A gas turbine engine configured with an engine core. A fan located upstream of the engine core, the fan comprising a plurality of fan blades; and a gearbox arranged to receive an input from 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 being an epicyclic gearbox comprising a sun gear, a plurality of planet gears, a ring gear, and a planet carrier on which the planet gears are mounted, the planet carrier having an effective linear torsional stiffness and the gearbox having a gear mesh stiffness between the planet gears and the ring gear. Additionally, the product of the effective linear torsional stiffness of the planet carrier and the gear mesh stiffness between the planet gears and the ring gear is greater than or equal to 5.0×1018 N2m−2.