Curved Shaft-Gearbox Coupling for High Torsional Stiffness
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Solution Overview
Problem
Geared turbo fan engines require effective torque transmission between the turbine section and the propulsive fan, which existing coupling devices fail to achieve efficiently while minimizing weight and maintaining structural integrity under mechanical loads.
Innovation Solution
A coupling device with a logarithmic or power profile design that maximizes torsional stiffness over lateral stiffness, featuring a curved shape with varying cross-sectional thickness and asymptotic approaches to the rotational axis, allowing for efficient torque transmission and reduced weight penalty.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a conventional coupling device design is used, then the structure is simple and manufacturing is easier, but the ratio of torsional stiffness to lateral stiffness is low and weight penalty increases
Solution Approach 1:
The coupling device employs a curved shape with logarithmic or power profile instead of straight or conventional geometric profiles. This curvature optimization maximizes the ratio of torsional stiffness to lateral stiffness while minimizing weight, directly resolving the contradiction between strength and weight.
Solution Approach 2:
The patent applies mathematical parameter changes by using logarithmic or power functions to define the coupling device geometry. By varying the profile parameters according to these functions, the design achieves optimal torsional stiffness-to-weight ratio that conventional constant-profile designs cannot achieve.
2Strength
If the coupling device uses a curved shape with logarithmic or power profile, then torsional stiffness is maximized, but manufacturing complexity increases
Solution Approach 1:
The logarithmic or power profile is defined by simple mathematical parameters that can be directly input into modern CNC machining systems. This allows complex curved geometries to be manufactured with standard equipment, reducing the actual manufacturing complexity despite the non-linear profile.
Solution Approach 2:
The coupling device design serves multiple functions: it provides optimal torsional stiffness, defines precise alignment through the asymptotic approach to the rotational axis, and maintains structural integrity under mechanical loads. This multi-functionality in a single geometric form reduces the need for additional components or complex assembly procedures.
3Strength
If the coupling device has varying cross-sectional thickness, then stress distribution is optimized, but manufacturing precision requirements increase
Solution Approach 1:
The cross-sectional thickness varies according to the logarithmic or power profile parameters, allowing stress optimization through controlled thickness variation. The mathematical definition provides clear tolerances and transition zones that guide manufacturing precision requirements.
Solution Approach 2:
The coupling device has different thicknesses at different locations along its length, with thicker sections where stress is highest and thinner sections where less strength is required. This local quality optimization ensures stress distribution is maximized while material is used efficiently, with precision requirements focused only where critical.
4Volume of moving object
If the coupling device approaches the rotational axis asymptotically, then space utilization is optimized, but the structural integrity under load may be compromised
Solution Approach 1:
The asymptotic approach to the rotational axis creates a curved profile that efficiently utilizes the available radial space. The curve is designed to maintain adequate thickness and structural section modulus even as it approaches the axis, ensuring integrity is maintained while maximizing space utilization.
Solution Approach 2:
The mathematical parameters of the logarithmic or power profile are optimized to balance two competing requirements: approaching the rotational axis closely for space efficiency while maintaining sufficient cross-sectional properties for structural integrity under the applied mechanical loads.
Data Source
AI summary
A coupling device for rotably coupling a shaft with a gearbox in a geared turbo fan aircraft engine, wherein the coupling device includes a connection to the shaft at a first end and a connection to the gearbox at a second end, the first and the second ends being axially separated and at least one curved shape between the first end and the second end extending from the gearbox radially inwards to the shaft and the at least one curved shape including at least one cross-section in the axial direction of the engine with a logarithmic profile or a power profile.