Hybrid Planet Gear Bearing Assembly for Misalignment Tolerance

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Solution Overview

Problem

Designing aircraft propulsion systems that accommodate misalignments between gears while minimizing weight and manufacturing complexity, as conventional cylindrical roller bearings are insufficient in handling wide torque bands and misalignments, and spherical roller bearings increase manufacturing costs and complexity.

Innovation Solution

A spherical mounted cylindrical roller bearing system that combines a spherical bearing assembly with a cylindrical roller bearing assembly for each planet gear, allowing tilting and rotational movements to accommodate misalignments without requiring a stiff carrier or complex pattern corrections.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional cylindrical roller bearings are used, then the structure is simple and manufacturing is easy, but they cannot handle wide torque bands and misalignments effectively

Engineering Contradiction:

Improveability to handle torque bands and misalignmentsVSAvoidmanufacturing complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent combines a spherical bearing assembly with a cylindrical roller bearing assembly into a hybrid bearing system. The spherical bearing portion accommodates misalignments and tilting movements, while the cylindrical roller bearing portion handles radial loads efficiently. This merging of two different bearing types into a single integrated system resolves the contradiction by achieving both misalignment tolerance and manufacturing feasibility.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent introduces a spherical bearing component with a curved spherical surface that interfaces with a corresponding spherical race. This spheroidal geometry enables the bearing system to accommodate misalignments and tilting movements of the planet gear relative to the sun gear, thereby improving reliability without requiring complex manufacturing of the entire gear system.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Reliability

If spherical roller bearings are used to handle misalignments, then misalignment accommodation is improved, but manufacturing costs and complexity increase significantly

Engineering Contradiction:

Improvemisalignment accommodation capabilityVSAvoidmanufacturing cost and complexity

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent divides the bearing system into two distinct segments: a spherical bearing assembly and a cylindrical roller bearing assembly. Each segment performs a specific function - the spherical portion handles misalignments while the cylindrical portion handles radial loads. This segmentation allows each component to be manufactured using simpler, more cost-effective processes compared to a complete spherical roller bearing, thereby reducing overall manufacturing complexity and cost.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The hybrid bearing system serves multiple functions within a single integrated structure. The spherical bearing portion provides misalignment accommodation and tilting capability, while the cylindrical roller bearing portion provides radial load support. This multi-functionality eliminates the need for separate misalignment bearings and radial load bearings, reducing the total number of components and simplifying the overall manufacturing process.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Manufacturing precision

If a stiff carrier is used to maintain gear alignment, then alignment precision is improved, but the weight of the propulsion system increases

Engineering Contradiction:

Improvegear alignment precisionVSAvoidcarrier weight

Core Design Contradiction:

Manufacturing precisionVSWeight of moving object

Solution Approach 1:

The patent uses a spherical bearing interface between the planet gear carrier and the sun gear that allows controlled tilting movements. This spherical geometry inherently accommodates misalignments without requiring the carrier to be excessively stiff or heavy. The curved spherical surfaces provide alignment tolerance while maintaining sufficient precision for proper gear meshing, thereby reducing the weight penalty associated with over-engineered stiff carriers.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Data Source

PatentUS11598412B2Spherical mounted cylindrical roller bearing system

Publication Date: 2023.03.07 TEXTRON INNOVATIONS INC

AI summary

A planetary gear system is provided in one example embodiment and may include a planet gear further comprising a bearing system, the bearing system further comprising an inner bearing assembly comprising a spherical bearing and an outer race; an outer bearing assembly comprising a plurality of cylindrical roller bearings, an inner race, and an outer race; and a race element comprising an inner surface and an outer surface, wherein the outer surface of the race element is the inner race for the outer bearing assembly and the inner surface of the race element is associated with the outer race for the inner bearing assembly.