Aircraft Reduction Gear Planet Geometry for Higher Ratios

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Solution Overview

Problem

Existing mechanical reduction gears in aircraft turbomachines face challenges in achieving higher reduction ratios while minimizing the moments generated in the planet gears.

Innovation Solution

The proposed solution involves a mechanical reduction gear design where each planet gear has a small-diameter central toothing meshing with the ring gear and a large-diameter lateral toothing meshing with the sun gear, with two guide bearings located in line with the large-diameter toothing.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If a double-stage meshing planet gear is used to increase the reduction ratio, then the reduction ratio is improved, but the moments generated in the planet gears increase

Engineering Contradiction:

Improvereduction ratioVSAvoidmoments in planet gears

Core Design Contradiction:

ProductivityVSForce

Solution Approach 1:

The planet gear is segmented into two distinct toothings: a first toothing with a larger diameter for meshing with the sun gear, and a second toothing with a smaller diameter for meshing with the ring gear. This segmentation allows each toothing to be optimized independently, enabling high reduction ratio while distributing and reducing the moments acting on the planet gear structure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the planet gear are given different properties: the first toothing has a larger diameter to handle the sun gear meshing, while the second toothing has a smaller diameter for ring gear meshing. This local differentiation of geometry allows the planet gear to achieve high reduction ratio without excessive moments, as each local region is optimized for its specific function.

Inventive Principle:

Principle #3Local quality

2Productivity

If the first toothing has a larger diameter than the second toothing, then the reduction ratio is increased, but the structural complexity of the planet gear increases

Engineering Contradiction:

Improvereduction ratioVSAvoidplanet gear structure

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent merges two toothings of different diameters into a single integrated planet gear body. This combination achieves the high reduction ratio benefits of different-sized toothings while avoiding the complexity of separate components, as both toothings are formed as one unified piece that rotates on a single axis.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The planet gear serves multiple functions simultaneously: it meshes with both the sun gear and ring gear, provides the reduction ratio through its dual toothings, and acts as a single rotating component. This multi-functionality reduces the overall device complexity compared to using separate components for each function.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS12221931B2Aircraft turbomachine with mechanical reduction gear

Publication Date: 2025.02.11 SAFRAN TRANSMISSIONS SYST

AI summary

An aircraft turbomachine including a mechanical reduction gear including one sun gear, a ring gear, planet gears which are meshed with the sun gear and the ring gear, each planet gear including a first toothing for meshing with the sun gear, and a second toothing for meshing with the ring gear, the first toothing of each planet gear having a diameter greater than that of the second toothing of the planet gear, and a planet carrier, wherein the sun gear is coupled to a first rotor shaft of the turbomachine, the planet carrier is coupled to a second rotor shaft of the turbomachine, the ring gear is fixed to a stator of the turbomachine.