Epicyclic Gear Carrier Bushing Design for Thermal Stability

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Solution Overview

Problem

Conventional gear carriers in gas turbine engines face challenges with component movement due to tolerance issues in bolt connections, leading to reduced operational life under high thermal loads and pressure ratios.

Innovation Solution

A gear carrier design utilizing bushings with collars and chamfers to connect end plates to connector plates, along with temperature manipulation to ensure precise alignment and secure attachment, reducing relative movement and enhancing stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If bolt connections are used to connect end plates to connector plates, then the gear carrier can be assembled, but component movement occurs due to tolerance issues reducing operational life

Engineering Contradiction:
Improveoperational lifeVSAvoidcomponent movement
Core Design Contradiction:
ReliabilityVSStability of the object's composition

Solution Approach 1:

A bushing is introduced as an intermediary component between the end plates and connector plates. The bushing has a collar that fits over the connector plate and a chamfered end that fits into the end plate, creating a precise fit that eliminates tolerance-related movement while still allowing assembly. This intermediary component resolves the contradiction by providing both stability and assembly capability.

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The connection system is segmented into multiple components: the bushing, the collar, and the chamfered end. This segmentation allows each component to be optimized for its specific function - the bushing for precision fitting, the collar for connection, and the chamfer for alignment - thereby reducing overall component movement while maintaining assembly feasibility.

Inventive Principle:
Principle #1Segmentation

2Reliability

If traditional single-piece gear carrier design is used, then manufacturing is simpler, but component movement and tolerance issues occur under high thermal loads

Engineering Contradiction:
Improvestability under thermal loadsVSAvoidmulti-component structure
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The gear carrier is divided into multiple segments (end plates, connector plates, and bushings) that can be manufactured separately with precise tolerances and then assembled. This segmentation allows each component to be optimized for thermal stability while the precise fit of the bushing assembly eliminates movement issues that would occur in a single-piece design under thermal loads.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The design changes the physical parameters of the connection interface by introducing the bushing with specific geometric features (collar and chamfer). These parameter changes enable precise alignment and fitting that maintains stability under thermal expansion and contraction, while the modular nature manages the complexity through standardized components.

Inventive Principle:
Principle #35Parameter changes

3Manufacturing precision

If precise alignment is achieved through temperature manipulation, then component stability increases, but manufacturing process complexity increases

Engineering Contradiction:
Improvealignment precisionVSAvoidmanufacturing process
Core Design Contradiction:
Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The bushing is designed with preliminary geometric features (collar and chamfer) that guide alignment during assembly. The collar fits over the connector plate and the chamfered end fits into the end plate, creating self-aligning features that achieve precise alignment without requiring complex temperature manipulation or specialized manufacturing equipment.

Inventive Principle:
Principle #10Preliminary action

Solution Approach 2:

The bushing serves as an intermediary that provides built-in alignment features through its geometry. The collar and chamfered end create a mechanical guide system that ensures precise alignment during assembly, eliminating the need for complex temperature-based alignment processes while maintaining manufacturing simplicity.

Inventive Principle:
Principle #24Intermediary (Mediator)

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

The bushing-based gear carrier design reduces component movement, increases stability, and extends operational life by minimizing tolerance-related issues under high thermal and pressure conditions.

Implementation Method 1

a bushing configured to extend through the second end plate and into the connector plate to connect the second end plate to the connector plate

Methodology Applied
Scientific EffectMechanical Fastening: Mechanical Fastener

Implementation Method 2

The gear carrier may also include a bolt configured to extend through a bolt aperture of the bushing and be received by a bolt terminal of the connector plate for resisting movement of the bushing relative to the second end plate and the connector plate

Methodology Applied
Scientific EffectGeometric Fitting: Geometry

Implementation Method 3

connecting the first end plate to the connector plate using the bushing may include increasing a temperature of the first end plate and the connector plate, decreasing a temperature of the bushing, and inserting the bushing into the end bushing aperture of the first end plate and the connector bushing aperture of the connector plate

Methodology Applied
Scientific EffectThermal Expansion: Thermal Expansion

Data Source

PatentEP3260739B1Low-cost epicyclic gear carrier and method of making the same
Publication Date: 2020.04.29 RTX CORP
  • EP3260739B1 patent drawingFigure 1
  • EP3260739B1 patent drawingFigure 2~3
  • EP3260739B1 patent drawingFigure 4A~4B

AI summary

A gear carrier (200) includes a first end plate (202;502;602). The gear carrier (200) also includes a connector plate (208;508;608) connected to the first end plate (202;502;602). The gear carrier (200) also includes a second end plate (204;504;604). The gear carrier (200) also includes a bushing (212) configured to extend through the second end plate (204;504;604) and into the connector plate (208;508;608) to connect the second end plate (204;504;604) to the connector plate (208;508;608).