Accessory Gearbox with Constant Speed Drive for Turbine Engines

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Solution Overview

Problem

Turbine engines face challenges in maintaining consistent speed variations for accessory components, leading to inefficiencies and compromises in component design due to wide-ranging shaft speeds during operation.

Innovation Solution

A constant speed drive system, such as a continuously variable transmission (CVT), is integrated into the accessory gearbox to provide a constant or near-constant speed to accessory components, independent of varying engine shaft speeds, and is controlled by a controller like FADEC to optimize operation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If accessory components are driven directly by the engine shaft through a conventional accessory gearbox, then the structure is simple and easy to manufacture, but the accessory components must accommodate significant speed variations which compromises their design and performance

Engineering Contradiction:

Improveaccessory component performance consistencyVSAvoidaccessory drive system complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

A constant speed drive mechanism is introduced as an intermediary between the variable-speed engine shaft and the accessory components. This mediator converts the variable input speed into a constant output speed, allowing accessory components to operate at consistent speeds regardless of engine shaft variations, thereby improving reliability without requiring changes to the accessory component designs

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system changes the speed parameter from variable to constant through the constant speed drive mechanism. By transforming the speed characteristic of the drive input, the system enables accessory components to operate within a limited, optimized speed range, improving performance consistency while the drive system absorbs the speed variations

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If accessory components are designed to accommodate extremes in shaft speed variations, then the system can handle all operating conditions, but the component structure requires compromises that reduce efficiency and performance

Engineering Contradiction:

Improveaccessory drive adaptability to speed variationsVSAvoidaccessory component efficiency

Core Design Contradiction:

Adaptability or versatilityVSProductivity

Solution Approach 1:

The constant speed drive acts as a mediator that decouples the accessory components from engine shaft speed variations. This allows the accessories to operate at their optimal, consistent speed for maximum efficiency, while the intermediary handles the adaptability to varying engine speeds

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The drive system is segmented into two functional parts: the constant speed drive mechanism that handles speed conversion, and the accessory components that operate at constant speed. This segmentation allows each part to be optimized for its specific function, with accessories designed for efficiency rather than speed accommodation

Inventive Principle:

Principle #1Segmentation

3Device complexity

If the accessory gearbox handles wide-ranging shaft speeds directly, then no additional components are needed, but the accessory components experience significant speed variations that require design compromises

Engineering Contradiction:

Improveaccessory gearbox structureVSAvoidaccessory component operation consistency

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

A constant speed drive is introduced as an intermediary component between the engine shaft and accessory gearbox. This additional component converts variable input speed to constant output speed, ensuring reliable and consistent accessory operation while the gearbox structure remains relatively simple

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system replaces the direct mechanical connection between the engine shaft and accessory components with a constant speed drive mechanism. This substitution eliminates the transmission of speed variations to the accessories, improving operation consistency while maintaining a manageable gearbox structure

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 solution allows accessory components to operate efficiently within a limited speed range, enhancing performance and reducing inefficiencies by enabling optimized design and operation.

Implementation Method 1

a heat exchanger that transfers heat that is generated within the constant speed drive into a cooling flow

Methodology Applied

Scientific EffectHeat transfer: Heat Exchanger

Data Source

PatentUS12553380B2Constant speed accessory gearbox for turbine engine

Publication Date: 2026.02.17 RTX CORP

AI summary

An accessory drive system for a turbine engine includes a first input shaft that is coupled to a first engine drive shaft, a constant speed drive that is driven at an input speed by the first input shaft that varies, the constant speed drive includes an output that rotates at a constant speed independent of the input speed, an accessory gearbox that includes a first gear system that is driven by the output from the constant speed drive, and a first accessory component that is mounted to the accessory gearbox and driven by the gear system.