Planetary Gearbox Assembly With Floating Sun Gears for Load Balance
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Solution Overview
Problem
Current gearbox assemblies for turbine engines face challenges with unbalanced load distribution due to misalignment of gears, leading to uneven wear and reduced efficiency, and they are often large, heavy, and inadequate in providing sufficient stiffness to counteract axial and radial loads.
Innovation Solution
The proposed gearbox assembly features two sun gears without a ring gear, utilizing compound planet gears with stiff and flexible shafts to distribute loads evenly and includes duplex bearings for additional flexibility, allowing the sun gears to float and realign radially, thereby improving stress distribution and gearbox life.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional gearbox assemblies use rigid shafts and fixed gear mounting, then structural stability is maintained, but load distribution becomes unbalanced due to misalignment, causing uneven wear and reduced efficiency
Solution Approach 1:
The patent applies the dynamics principle by transitioning from rigid fixed shafts to flexible shafts that can dynamically adjust their position. The flexible shafts allow the sun gears to float and self-align radially, enabling automatic compensation for misalignment and achieving balanced load distribution across all planet gears without requiring complex active control mechanisms.
Solution Approach 2:
The patent implements parameter changes by modifying the shaft's physical properties - specifically changing from a rigid structure to a flexible structure with controlled stiffness characteristics. This parameter change allows the shaft to deflect radially under load, enabling the gears to self-align and distribute loads evenly while maintaining structural integrity.
2Volume of moving object
If gearbox assembly size is reduced for compactness, then space efficiency improves, but stiffness becomes inadequate to counteract axial and radial loads
Solution Approach 1:
The patent applies local quality by creating non-uniform shaft structures with varying stiffness along their length. The shafts are designed with different wall thicknesses and diameters in different sections, providing localized flexibility where needed for radial deflection while maintaining sufficient stiffness in other areas to counteract axial and radial loads, thus resolving the contradiction between compact size and structural strength.
3Reliability
If sun gears are fixed rigidly to shafts, then positional stability is achieved, but load distribution becomes uneven due to inability to compensate for misalignment
Solution Approach 1:
The patent resolves this contradiction by making the gear-shaft connection dynamic rather than static. The flexible shafts enable the sun gears to float and move radially relative to the shafts, allowing automatic self-alignment that compensates for manufacturing tolerances and maintains uniform load distribution while preserving overall positional stability through the shafts' controlled flexibility.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design reduces the size and weight of the gearbox assembly, enabling lower gear ratios and improved load handling, resulting in enhanced efficiency and longer component life by evenly distributing loads across the planet gears.
Implementation Method 1
a first shaft flexible portion (336b) that extends axially from the first shaft stiff portion (336a). The first shaft flexible portion (336b) includes a greater flexibility than a flexibility of the first shaft stiff portion (336a) such that the first gear (352) moves in a radial direction with respect to the first shaft stiff portion (336a)
Data Source
AI summary
A gearbox assembly includes a first gear coupled to a first shaft, a second gear coupled to a second shaft, and a plurality of planet gears that mesh with the first gear and the second gear. The first shaft includes a first shaft stiff portion and a first shaft flexible portion that includes a greater flexibility than a flexibility of the first shaft stiff portion such that the first gear moves in a radial direction. The second shaft includes a second shaft stiff portion and a second shaft flexible portion that includes a greater flexibility than a flexibility of the second shaft stiff portion such that the second gear moves in the radial direction. The first gear and the second gear move to distribute loads substantially equally on the plurality of planet gears.