Double Helical Gear Reduction for Turbine Gearbox Vibration
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Solution Overview
Problem
The existing gearbox designs in gas turbine engines experience vibrations due to variations in torque transfer and manufacturing tolerances, which affect the durability and life of both the gearbox and associated turbine engine components.
Innovation Solution
The implementation of a gear reduction system using double helical gears with specific tooth configurations and an epicyclic gear system, including a sun gear, ring gear, and intermediate gears, to achieve a gear ratio greater than 2.3:1, which reduces transmission error and vibration by optimizing the helix angle and circumferential offset of gear teeth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If conventional single helical gears are used, then the structure is simple, but vibrations occur due to variations in torque transfer and manufacturing tolerances
Solution Approach 1:
The gear teeth are segmented into two distinct helices with different hand orientations (left-handed and right-handed). Each helix carries a portion of the load, and their combined effect balances the axial forces and reduces torque transfer variations, thereby reducing vibrations while maintaining structural complexity at an acceptable level.
Solution Approach 2:
The double helical gear introduces asymmetry in the tooth configuration by having two helices with opposite handedness. This asymmetric design allows the gears to counterbalance each other's axial thrust and reduce vibrations caused by manufacturing tolerances and torque variations, improving reliability without excessive complexity.
2Reliability
If double helical gears with circumferential offset are used, then vibrations are reduced, but manufacturing precision requirements increase
Solution Approach 1:
The invention specifies a circumferential offset parameter between the two helices that is optimized to balance vibration reduction benefits against manufacturing precision requirements. By carefully selecting this parameter, the design achieves vibration reduction while keeping manufacturing precision requirements at practical levels.
3Power
If high gear ratio greater than 2.3:1 is achieved through epicyclic gear system, then torque transfer efficiency improves, but device complexity increases
Solution Approach 1:
The epicyclic gear system employs a nested configuration where planet gears are positioned around and mesh with both the sun gear and the ring gear. This nested arrangement enables high torque transfer efficiency through multiple simultaneous gear contacts while containing the overall system within a compact space, managing complexity effectively.
Solution Approach 2:
The gear system merges multiple gear functions into a single integrated epicyclic assembly. The sun gear, planet gears, and ring gear work together as a unified system to achieve the required gear ratio greater than 2.3:1, improving torque transfer efficiency while avoiding the need for separate多级 gear trains that would increase complexity.
Data Source
AI summary
A gas turbine engine according to an example of the present disclosure includes, among other things, a fan section, a compressor section, and a turbine section including a fan drive turbine that drives the fan through a gear reduction. The gear reduction includes at least two double helical gears in meshed engagement, each of the at least two double helical gears having a first plurality of gear teeth separated from a second plurality of gear teeth such that a first end of the first plurality of gear teeth and a first end of the second plurality of gear teeth are spaced apart by an axial distance. Each of the first plurality of gear teeth is offset a first circumferential offset distance in relation to the next gear tooth of the second plurality of gear teeth when moving in a circumferential direction relative to respective axes.