Epicyclic Gear Support Structure for Backbone Bending Misalignment

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Solution Overview

Problem

Misalignment caused by backbone bending in gas turbine engine structures leads to efficiency losses and reduced gear train life due to deflection of sun or planet gear axes, resulting in misalignment at gear train journal bearings and teeth mesh in epicyclic gear systems.

Innovation Solution

The epicyclic gear system incorporates a structural oil baffle housing with spherical joints and flexible carrier posts that allow angular movement, reducing misalignment and enabling the use of larger rolling element bearings, along with an oil management system to enhance gear mesh efficiency and reduce heat loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If the engine case assembly is made lightweight, then weight is reduced, but backbone bending deflection increases causing gear misalignment

Engineering Contradiction:

Improveengine case assembly weightVSAvoidgear alignment precision

Core Design Contradiction:

Weight of moving objectVSManufacturing precision

Solution Approach 1:

The patent applies the dynamics principle by making the gear carrier and planet gear supports flexible rather than rigid. The planet gear supports are mounted on flexible arms that can dynamically adjust their position to compensate for case deflection, allowing the gear train to maintain proper alignment despite backbone bending in the lightweight engine case.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes the structural parameters of the gear support system from rigid fixed mounts to flexible mounted supports. This parameter change allows the support structure to adapt its stiffness and positioning characteristics, enabling it to accommodate case deflection while maintaining gear mesh quality.

Inventive Principle:

Principle #35Parameter changes

2Stability of the object's composition

If rigid fixed mounts are used for planet gears, then structural stability is improved, but misalignment losses increase due to backbone bending

Engineering Contradiction:

Improvegear train structural stabilityVSAvoidmisalignment loss

Core Design Contradiction:

Stability of the object's compositionVSLoss of energy

Solution Approach 1:

The flexible mounted supports replace rigid fixed mounts, transforming the gear train from a statically rigid structure to a dynamically adaptable one. The flexible arms can deflect and reposition themselves to maintain optimal gear alignment under varying load and deflection conditions, reducing misalignment losses while preserving structural stability.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The flexible arms act as intermediary elements between the engine case and the planet gear supports. These intermediaries absorb and compensate for case deflection, isolating the gear train from misalignment caused by backbone bending while maintaining the overall structural stability of the system.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Weight of moving object

If smaller bearings are used to reduce weight, then weight is reduced, but durability decreases under misalignment conditions

Engineering Contradiction:

Improvebearing weightVSAvoidgear train durability

Core Design Contradiction:

Weight of moving objectVSReliability

Solution Approach 1:

The flexible mounted supports provide beforehand cushioning by pre-accommodating case deflection and misalignment tendencies. This prevents excessive misalignment loads from developing during operation, allowing smaller lightweight bearings to maintain adequate durability by protecting them from peak misalignment stresses.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Solution Approach 2:

The patent changes the operational parameters of the bearings by reducing misalignment through flexible mounting. This parameter change in alignment quality allows the use of smaller bearings with reduced load capacity while maintaining durability, as the bearings operate under more favorable alignment conditions.

Inventive Principle:

Principle #35Parameter changes

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 configuration increases gear system efficiency from 98% to 99.5%, reduces weight and complexity in the engine, and minimizes loads on intermediate gears, leading to improved durability and operational efficiency.

Implementation Method 1

structural oil baffle housing with spherical joints and flexible carrier posts that allow angular movement

Methodology Applied

Scientific EffectAngular movement:

Implementation Method 2

an oil management system to enhance gear mesh efficiency and reduce heat loss

Methodology Applied

Scientific EffectHeat transfer: Conduction (thermal)

Data Source

PatentEP3936711B1An epicyclic gear system

Publication Date: 2023.04.12 RTX CORP

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AI summary

A gas turbine engine includes a structural oil baffle housing which at least partially supports a set of intermediate gears.