Bi-Conical Planet-Carrier Axes for Turbine Gear Misalignment

Solution Overview

Problem

Existing reduction gears in turbine engines face misalignment issues due to deformation under load, leading to increased contact pressures and overload on gearings, which can cause misalignment of planet gears and generate excessive stress.

Innovation Solution

A planet-carrier design with bi-conical inner frustoconical surfaces that adjust the stiffness ratio between upstream and downstream sides, allowing for ±10% movement in the bi-cone length without affecting roller clamping, thereby rebalancing the assembly and reducing overload on gearings.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If the planet-carrier is made more rigid to reduce deformation under load, then the misalignment of tracks is reduced, but the stiffness ratio between upstream and downstream sides becomes unbalanced, causing overload on gearings

Engineering Contradiction:

Improvealignment stabilityVSAvoidload bearing capacity

Core Design Contradiction:

Stability of the object's compositionVSStrength

Solution Approach 1:

The guiding axes are designed with non-uniform thickness along their length, creating local variations in stiffness. The thickness is greater in the upstream portion and smaller in the downstream portion, which allows each region to have different rigidity characteristics tailored to its specific functional requirements, thereby balancing the stiffness ratio between upstream and downstream sides while maintaining overall alignment stability

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention changes the geometric parameter of the guiding axes by varying their thickness profile along the length. This parameter modification adjusts the stiffness characteristics of the planet-carrier to achieve an optimal balance between reducing track misalignment and preventing overload on gearings

Inventive Principle:

Principle #35Parameter changes

2Strength

If the planet-carrier is made more flexible to reduce overload on gearings, then the stiffness ratio is balanced, but the misalignment of tracks increases, causing excessive contact pressures

Engineering Contradiction:

Improveload bearing capacityVSAvoidalignment stability

Core Design Contradiction:

StrengthVSStability of the object's composition

Solution Approach 1:

The guiding axes are designed with non-uniform thickness along their length, creating local variations in stiffness. The thickness is greater in the upstream portion and smaller in the downstream portion, which allows each region to have different rigidity characteristics tailored to its specific functional requirements, thereby balancing the stiffness ratio between upstream and downstream sides while maintaining overall alignment stability

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention changes the geometric parameter of the guiding axes by varying their thickness profile along the length. This parameter modification adjusts the stiffness characteristics of the planet-carrier to achieve an optimal balance between reducing track misalignment and preventing overload on gearings

Inventive Principle:

Principle #35Parameter changes

3Ease of manufacture

If cylindrical guiding axes are used for simplicity, then the manufacturing is easier, but the misalignment reduction is insufficient under load

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidalignment precision

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The guiding axes are designed with non-uniform thickness along their length, creating local variations in stiffness. The thickness is greater in the upstream portion and smaller in the downstream portion, which allows each region to have different rigidity characteristics tailored to its specific functional requirements, thereby balancing the stiffness ratio between upstream and downstream sides while maintaining overall alignment stability

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The guiding axes transition from a simple cylindrical shape to a more complex profile with varying thickness. This curved or non-uniform geometry optimizes the stiffness distribution to reduce misalignment under load while remaining manufacturable

Inventive Principle:

Principle #14Spheroidality (Curvature)

Data Source

PatentUS10989119B2Planet-carrier for a mechanical reduction gear of an aircraft turbine engine

Publication Date: 2021.04.27 SAFRAN TRANSMISSION SYST

AI summary

A planet-carrier for a mechanical reduction gear of a turbine engine, in particular of an aircraft, this planet-carrier having a rotation axis and comprising axes for guiding the planet gears that are arranged around and parallel with the rotation axis, each guiding axis having a general tubular shape of which the outer periphery comprises only two coaxial and adjacent cylindrical tracks of the respective rollers of two annular rows of rollers, wherein each axis has an inner periphery that is substantially bi-conical and comprising two coaxial and adjacent frustoconical surfaces, these inner frustoconical surfaces converging towards one another and extending respectively radially inside the tracks.