Epicyclic Gearbox Planet Carrier Stiffness for Gear Alignment
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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 radial bending, tilt, and torsional stiffness ranges, which allows 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
1Reliability
If the planet carrier stiffness is increased to reduce gear misalignment and improve load distribution, then gearbox reliability is improved, but the mass of the gearbox increases
Solution Approach 1:
The patent applies parameter changes by optimizing the stiffness values of the planet carrier within specific ranges (radial bending stiffness: 0.5-2.0x10^9 N/m, tilt stiffness: 0.2-0.8x10^9 N/m, torsional stiffness: 0.1-0.5x10^9 N/m). This allows the carrier to be stiff enough to maintain gear alignment and load distribution while avoiding excessive mass increase that would occur with higher stiffness values.
2Weight of moving object
If the planet carrier stiffness is decreased to reduce mass, then gearbox mass is reduced, but gear misalignment and distortion increase
Solution Approach 1:
The patent uses parameter changes by establishing minimum stiffness thresholds for the planet carrier (radial bending stiffness ≥ 0.5x10^9 N/m, tilt stiffness ≥ 0.2x10^9 N/m, torsional stiffness ≥ 0.1x10^9 N/m). These parameter boundaries ensure the carrier maintains sufficient rigidity to prevent gear misalignment and distortion while allowing mass reduction compared to conventional designs.
Data Source
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AI summary
An engine (10) for an aircraft comprises an engine core (11) comprising a turbine (19), a compressor (14), and a core shaft (26) connecting the turbine to the compressor; a fan (23) located upstream of the engine core, the fan comprising a plurality of fan blades; and a gearbox (30). The gearbox (30) is an epicyclic gearbox and comprises a sun gear (28), a plurality of planet gears (32), a ring gear (38), and a planet carrier (34) on which the planet gears (32) are mounted. The radial bending stiffness of the planet carrier (34) is equal to or greater than 1.20x109 N/m, and/or the tilt stiffness of the planet carrier (34) is greater than or equal to 6.00x108 Nm/rad. A method of operation of such an engine (10) is also disclosed.