Starter-Dedicated Accessory Gearbox for Reduced Axial Space

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Solution Overview

Problem

Existing aircraft turbomachines face a significant challenge in reducing the axial space requirement of accessory gearboxes, which are often too large for installation in inter-path or fan compartments.

Innovation Solution

The integration of a reduction gear and freewheel directly into the accessory gearbox casing, along with a pinion shaft and freewheel dedicated to the starter, reduces the overall axial space requirement by optimizing the layout and allowing for more efficient use of space within the turbomachine.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Length of moving object

If the reduction gear and freewheel are integrated into the accessory gearbox casing, then the axial space requirement is reduced, but the device complexity increases

Engineering Contradiction:

Improveaxial space requirementVSAvoiddevice complexity

Core Design Contradiction:

Length of moving objectVSDevice complexity

Solution Approach 1:

The reduction gear and freewheel are permanently integrated into the accessory gearbox casing, merging multiple functions (starter drive, reduction gearing, freewheel mechanism) into a single unified structure. This eliminates the need for separate housings and mounting arrangements, thereby reducing the overall axial space requirement while consolidating components.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The accessory gearbox casing serves multiple functions simultaneously: it houses the reduction gear, accommodates the freewheel mechanism, provides mounting surfaces for the starter, and structures the pinion shaft alignment. This multi-functionality reduces the need for additional dedicated components, optimizing space utilization.

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Volume of moving object

If the pinion shaft extends between opposing walls perpendicular to the starter interface wall, then the starter size is reduced, but the manufacturing precision requirements increase

Engineering Contradiction:

Improvestarter sizeVSAvoidmanufacturing precision

Core Design Contradiction:

Volume of moving objectVSManufacturing precision

Solution Approach 1:

The pinion shaft is nested within the accessory gearbox casing structure, with its ends disposed on opposite sides of the casing walls. This nesting arrangement allows the pinion shaft to be precisely positioned and supported by the casing itself, reducing the starter size while the rigid casing provides stable reference surfaces for manufacturing.

Inventive Principle:

Principle #7Nested doll (Nesting)

Solution Approach 2:

The reduction gear and pinion shaft are pre-integrated into the accessory gearbox casing during manufacturing, establishing precise geometric relationships and alignment features before final assembly. This preliminary integration ensures that critical dimensions and tolerances are controlled during the manufacturing process rather than during field assembly.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS20250283434A1Accessory gearbox and aircraft turbine engine comprising such a box

Publication Date: 2025.09.11 SAFRAN AIRCRAFT ENGINES SAS

AI summary

Accessory gearbox for an aircraft turbine engine, including: a casing, a reduction gear, and a freewheel which are permanently integrated into the casing, the accessory gearbox being configured to interface with a starter of the turbomachine that is intended to start up the turbomachine, the reduction gear and the freewheel being dedicated to the starter of the turbomachine.