Rotary Part Interference Fit Layout for Vibration Control

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Solution Overview

Problem

Aircraft engine rotary parts experience high centrifugal loads and thermal expansion, leading to variations in interference fits and induced vibrations due to radial pull, which existing technologies struggle to effectively control across a range of operating conditions.

Innovation Solution

A rotary assembly design featuring a shaft and rotary part with an interference fit interface spaced from the center of mass, incorporating an undercut to promote deflection and minimize radial pull, thereby stabilizing the fit and reducing vibrations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If the interference fit interface is located at the center of mass of the rotary part, then the assembly is simple and alignment is easy, but radial pull due to centrifugal loads and thermal expansion causes variations in the interference fit and induces vibrations

Engineering Contradiction:

Improvestability of interference fitVSAvoidcomplexity of rotary part structure

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The invention extracts the center of mass from the interference fit interface location. By positioning the interface away from the center of mass and creating an undercut that extends toward but does not include the center of mass, the design separates the mounting function from the mass center, thereby reducing radial pull variations while maintaining structural integrity

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The rotary part is segmented into distinct functional zones: the interference fit interface zone, the undercut zone extending toward the center of mass, and the axial end portion with reduced radial thickness. This segmentation allows each zone to perform its specific function - the interface provides stable mounting, the undercut reduces radial pull, and the thinned portion minimizes centrifugal effects

Inventive Principle:

Principle #1Segmentation

2Reliability

If an undercut is defined in the rotary part extending from the interface towards the center of mass, then radial pull is reduced and interference fit stability is improved, but the manufacturing complexity increases

Engineering Contradiction:

Improvereliability of interference fitVSAvoidease of manufacturing rotary part

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The undercut is implemented as a localized geometric feature with specific dimensional relationships (extending from the interface toward the center of mass but not including it, with the axial end portion having reduced radial thickness). This local modification provides the desired radial pull reduction while limiting the overall manufacturing complexity to a specific region rather than the entire component

Inventive Principle:

Principle #3Local quality

3Force

If the axial end portion has reduced radial thickness compared to the center of mass location, then centrifugal loads are reduced, but the structural strength at that location is compromised

Engineering Contradiction:

Improvecentrifugal loadVSAvoidstructural strength of rotary part

Core Design Contradiction:

ForceVSStrength

Solution Approach 1:

The reduced radial thickness of the axial end portion acts as a counterbalancing feature that offsets the centrifugal loads generated by the main body of the rotary part. By strategically thinning this specific portion, the design creates a counter-effect that reduces overall centrifugal force without significantly compromising the structural integrity provided by the fuller sections at the center of mass and interference fit interface

Inventive Principle:

Principle #8Anti-weight (Counterweight)

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

The solution effectively controls radial pull and maintains a stable interference fit across varying operating conditions, reducing vibrations and facilitating assembly/disassembly by optimizing the fit and reducing thermal expansion requirements.

Implementation Method 1

Aircraft engine parts rotating at high speed may experience high centrifugal loads and thermal expansion in normal operating conditions

Methodology Applied

Scientific EffectCentrifugal force: Centrifugal Force

Implementation Method 2

Aircraft engine parts rotating at high speed may experience high centrifugal loads and thermal expansion in normal operating conditions

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Data Source

PatentUS11525358B2Interference fit control for the assembly of rotary parts

Publication Date: 2022.12.13 PRATT & WHITNEY CANADA CORP

AI summary

A rotary assembly for an aircraft engine is disclosed. A shaft is mounted for rotation about a central axis and a rotary part is mounted on the shaft for common rotation therewith. The rotary part has an axial end portion extending away from a center of mass of the rotary part, the axial end portion having a radial thickness smaller than that of the rotary part at an axial location aligned with the center of mass. The shaft and the rotary part have an interface defining an interference fit between the shaft and the axial end portion of the rotary part. The interface is located at a distance along the central axis from the center of mass. An undercut is defined in the rotary part. The undercut extends axially from adjacent the interface towards the center of mass.