Aircraft Turbine Accessory Gearbox Nested Reducer

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Solution Overview

Problem

Aircraft gear chains require a compact structure that integrates speed-increasing or reducer functions while allowing for disconnection to reduce dimensions and weight, particularly for turbine engine accessories, as existing solutions do not efficiently manage the decoupling of drive and slave members during start-up.

Innovation Solution

The integration of a speed-increasing or reducer gear system within the aircraft gear chain, utilizing a decoupling member such as an overrunning clutch device, allows for mechanical power transfer between drive and slave members, reducing volume and weight by positioning the decoupling mechanism within the gear itself, enabling operation under specific rotation conditions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If a speed-increasing or reducer function is integrated into the drive chain, then mechanical power transfer efficiency is improved, but the volume and weight of the drive chain increases

Engineering Contradiction:

Improvemechanical power transfer efficiencyVSAvoiddrive chain volume

Core Design Contradiction:

PowerVSVolume of moving object

Solution Approach 1:

The gear system is built into the inner space of the first main gear, creating a nested configuration where the speed-increasing/reducer mechanism is housed within the existing gear structure. This eliminates the need for separate external gearboxes and reduces overall drive chain volume while maintaining power transfer efficiency

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The patent combines the first main gear and the gear system into a single integrated unit, where both components work together to form the speed-increasing or reducer mechanism. This merging of functions into one compact assembly reduces the number of separate components and optimizes space utilization

Inventive Principle:

Principle #5Merging (Combining)

2Device complexity

If the drive member and slave member are permanently connected, then structural simplicity is improved, but the ability to disconnect for start-up phase operation is lost

Engineering Contradiction:

Improvestructural simplicityVSAvoiddecoupling capability

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The decoupling member is designed to dynamically change its state between connected and disconnected positions based on operational requirements. During start-up, it allows disconnection; during normal operation, it provides rigid connection. This dynamic adaptability resolves the contradiction between structural simplicity and operational versatility

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The decoupling member acts as an intermediary element between the drive member and slave member, controlling the transmission of mechanical power. It can selectively engage or disengage to allow the drive chain to operate in different modes (connected during normal operation, disconnected during start-up), providing the needed adaptability without complicating the overall structure

Inventive Principle:

Principle #24Intermediary (Mediator)

3Volume of moving object

If accessories are positioned in cantilever position, then space utilization is improved, but stress on supporting couplings increases

Engineering Contradiction:

Improvespace utilizationVSAvoidcoupling stress

Core Design Contradiction:

Volume of moving objectVSStress or pressure

Solution Approach 1:

By merging the gear system with the first main gear into a single integrated unit, the patent creates a more rigid and stable structure. This integration provides better structural support for cantilever-mounted accessories, reducing the stress on supporting couplings while maintaining optimal space utilization

Inventive Principle:

Principle #5Merging (Combining)

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 reduces stress on supporting couplings, optimizes the gear chain's inner volume, and allows for efficient operation of accessories like aircraft turbine engine starters during start-up, enabling two members to operate at different speeds within a minimal space.

Implementation Method 1

said gear system being mounted onto the wall by means of a decoupling member... the decoupling member enables a drive member or a slave member to only operate under certain rotation conditions... could advantageously only operate on turbine engine start-up

Methodology Applied

Scientific EffectOverrunning clutch mechanism:

Data Source

PatentUS10323576B2Compact structure for accessory gearbox of an aircraft turbine engine

Publication Date: 2019.06.18 SAFRAN TRANSMISSION SYST

AI summary

An aircraft drive chain including a plurality of main gears engaging with each other, a first main gear including a wall defining an inner space, an outer set of gear teeth being placed on an outer surface of the wall, the outer set of gear teeth engaging with at least one second main gear, a gear system being built into the inner space, the first main gear and the gear system being jointly configured so as to form a gearbox or reducer and ensure mechanical power transfer between a drive member and a slave member, the gear system being mounted onto the wall with a decoupling member.