Web Gear Wheel Structure for Lightweight High-Load Transmissions

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Solution Overview

Problem

Gears used in transmissions, particularly for gas turbine engines, face a challenge in being both lightweight and resilient enough to withstand high loads, as traditional web gears are typically lighter but less resilient compared to solid wheels, and optimizing tooth base curves is complex due to varying stiffness in axial and circumferential directions.

Innovation Solution

A gear design featuring a ring with a circumferential toothing and a support point connected via a web, where the geometry varies periodically in the axial direction to reinforce heavily stressed tooth areas, increasing stiffness and load capacity while minimizing material usage in other sections, allowing for a lightweight yet robust gear.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Weight of moving object

If a web gear design is used to reduce weight, then the weight of the gear is reduced, but the load capacity and stiffness are decreased

Engineering Contradiction:
Improvegear weightVSAvoidload capacity
Core Design Contradiction:
Weight of moving objectVSStrength

Solution Approach 1:

The patent applies local quality by varying the web thickness in specific regions rather than uniformly. The web thickness is increased in areas where teeth are attached to provide local reinforcement for load-bearing, while remaining thinner in other areas to maintain weight reduction. This creates non-uniform stiffness distribution that optimizes both weight and load capacity.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The web is segmented into multiple regions with different thicknesses corresponding to different functional requirements. Each segment is optimized independently - regions under teeth have greater thickness for strength, while regions between teeth have reduced thickness for weight savings. This segmentation allows the gear to achieve optimal performance across different zones.

Inventive Principle:
Principle #1Segmentation

2Strength

If the tooth root curve is optimized to increase stress in the tooth base area, then the tooth strength is improved, but the stiffness requirements become more complex due to varying axial and circumferential stiffness

Engineering Contradiction:
Improvetooth root strengthVSAvoidstiffness optimization complexity
Core Design Contradiction:
StrengthVSDevice complexity

Solution Approach 1:

The patent addresses the complexity by implementing local quality variations in the web structure. By making the web thickness position-dependent (thicker near tooth roots, thinner elsewhere), the design locally enhances stiffness where needed for tooth root strength while avoiding uniform complexity throughout the entire gear structure.

Inventive Principle:
Principle #3Local quality

Data Source

PatentEP4004407B1Tooth wheel
Publication Date: 2024.03.27 ROLLS ROYCE DEUT LTD & CO KG
  • EP4004407B1 patent drawingFigure 1
  • EP4004407B1 patent drawingFigure 2~3
  • EP4004407B1 patent drawingFigure 4

AI summary

The invention relates to a gear wheel (50) for a transmission (30), comprising: a rim (51) on which a toothing (52) with a plurality of teeth (53) is provided; a support point (54); and a web (55) via which the rim (51) is connected to the support point (54); wherein, on a side (56) of the rim (51) opposite the toothing (52) and next to the web (55), a periodic variation of the geometry is formed that is aligned with the teeth (53) of the toothing (52).