Resilient Ring Gear Mounting for Planetary Gearbox Stress Reduction

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Solution Overview

Problem

Current ring gear mounts in planetary gearboxes face challenges in accommodating build tolerances and avoiding stress on supporting structures, leading to deleterious effects on gears and bearings in high-power density applications.

Innovation Solution

A ring gear arrangement featuring a resiliently deformable connection using torsion bars and drive arms that allow the ring gear to move relative to the stator, distributing loads and reducing stress on gears, while maintaining axial and rotational stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the ring gear is rigidly fixed to the stator, then the structure is simple and stable, but build tolerances cannot be accommodated and stress concentrates on gears and bearings

Engineering Contradiction:

Improvegearbox component durabilityVSAvoidring gear mounting structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The ring gear mounting structure is transformed from a rigid static connection to a dynamic resilient connection. The resiliently deformable connection allows the ring gear to move relative to the stator in response to load variations and tolerance deviations, converting the static rigid structure into a dynamic adaptive system that maintains reliability while accommodating operational variations.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The physical state of the ring gear-stator connection is changed from rigid to resiliently deformable. This parameter change in the connection stiffness allows the system to accommodate build tolerances and distribute stresses, improving component durability while managing the complexity through a well-defined elastic deformation mechanism.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If the ring gear is allowed to move relative to the stator, then build tolerances are accommodated and stress is distributed, but the structure becomes more complex

Engineering Contradiction:

Improvestress distribution on gears and bearingsVSAvoidring gear mounting structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The resiliently deformable connection acts as an intermediary element between the ring gear and the stator. This intermediate component absorbs the complexity of tolerance accommodation and stress distribution, allowing the main gearbox structure to remain relatively simple while achieving improved reliability through the mediating resilient connection.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Power

If high-power density applications are used, then the gearbox size is reduced, but stress on supporting structures and bearings increases

Engineering Contradiction:

Improvepower density of gearboxVSAvoidstress on supporting structures and bearings

Core Design Contradiction:

PowerVSStress or pressure

Solution Approach 1:

The connection stiffness parameter is changed from rigid to resiliently deformable, allowing the system to accommodate the high stresses inherent in high-power density applications. The resilient connection distributes these stresses over time and space, enabling compact gearbox design while managing the increased stress levels on supporting structures and bearings.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The resiliently deformable connection provides beforehand cushioning against the high stresses that occur in high-power density applications. By incorporating this cushioning mechanism in advance, the gearbox can handle the increased power density while protecting supporting structures and bearings from excessive stress concentrations.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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 solution reduces loading on gearbox components, allows for self-centering of the ring gear, and improves load distribution, leading to a more efficient and durable gearbox operation with reduced stress on gears and bearings.

Implementation Method 1

The resiliently deformable connection is a torsion bar, the longitudinal axis of the torsion bar lying parallel to the principal axis

Methodology Applied

Scientific EffectTorsion: Torsion Spring

Implementation Method 2

each coupling having a resiliently deformable connection... movement of the drive arm from the first position to the second position loads the resiliently deformable connection against the ring gear

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Data Source

PatentEP3273093B1Ring gear arrangement

Publication Date: 2020.04.22 ROLLS ROYCE PLC

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AI summary

Disclosed is a ring gear arrangement (210), comprising: a ring gear mount (212) comprising: a ring gear (215) having at least one internal gear for interaction with one or more gear wheels; a ring gear stator (214); and, a plurality of couplings which locate the ring gear within the gear stator, each coupling having a drive arm (218) connected to the ring gear and a resiliently deformable connection (220), wherein the drive arm is movable between a first position in which the ring gear is in a rest position and a second position in which the ring gear has undergone some radial or rotational movement relative to the ring gear stator, wherein movement of the drive arm (218) from a the first position to the second position loads the resiliently deformable connection (220) against the ring gear, wherein the resiliently deformable connection (220) biases the drive arm (218) to return to the first position when in the second position.