Rotor Core Groove Structure for Lower Keyway Stress

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing rotating electric machines face challenges in reducing stress within the rotor core, which limits the maximum rotation speed due to stress concentration and potential deformation under centrifugal forces.

Innovation Solution

The design incorporates a rotor core with a cylindrical shape, featuring key grooves, stress relaxation grooves, and protruding portions at the inner periphery, where the key portion is fitted into a key groove, and the stress relaxation grooves are strategically positioned to reduce stress concentration, with protruding portions between them to distribute stress evenly.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Strength

If a key portion is fitted into a key groove to fix the rotor core to the shaft, then the rotor core is securely fixed, but stress concentration occurs at the key portion leading to limited maximum rotation speed

Engineering Contradiction:

Improvefixing strength of rotor coreVSAvoidstress concentration at key portion

Core Design Contradiction:

StrengthVSStress or pressure

Solution Approach 1:

The invention divides the key portion into multiple segments along the axial direction, creating multiple key grooves instead of a single continuous key groove. This segmentation distributes the stress concentration points from a single location to multiple locations, reducing the stress magnitude at each individual key portion and allowing higher rotation speeds without failure.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention modifies the local geometry of the key grooves by making them curved rather than straight, and by positioning them at specific locations where stress distribution is optimized. This local geometric modification reduces stress concentration at critical points while maintaining the overall fixing function of the key portions.

Inventive Principle:

Principle #3Local quality

2Ease of manufacture

If the rotor core structure is simplified for ease of manufacture, then manufacturing cost decreases, but stress relaxation capability is reduced limiting maximum rotation speed

Engineering Contradiction:

Improvemanufacturing simplicity of rotor coreVSAvoidstress in rotor core under centrifugal force

Core Design Contradiction:

Ease of manufactureVSStress or pressure

Solution Approach 1:

The invention incorporates stress relaxation grooves that are pre-formed into the rotor core structure during manufacturing. These grooves are designed in advance to provide stress relaxation pathways before the rotor operates at high speeds, allowing the rotor core to naturally distribute and reduce stress during operation without requiring complex additional components or post-manufacturing modifications.

Inventive Principle:

Principle #10Preliminary action

3Stress or pressure

If the number of key grooves is increased to distribute stress, then stress concentration is reduced, but device complexity and manufacturing difficulty increase

Engineering Contradiction:

Improvestress distribution in rotor coreVSAvoidcomplexity of key groove structure

Core Design Contradiction:

Stress or pressureVSDevice complexity

Solution Approach 1:

The invention combines multiple functional features into the key groove structure itself: the key grooves serve both as fixing features (replacing a traditional keyway) and as stress relaxation features. By integrating these functions into a single structural element with optimized curvature and positioning, the invention achieves stress distribution without requiring separate stress relief grooves or additional complex components.

Inventive Principle:

Principle #5Merging (Combining)

Data Source

PatentUS11831205B2Rotating electric machine and rotor therefor

Publication Date: 2023.11.28 MITSUBISHI ELECTRIC MOBILITY CORP

AI summary

In a rotor for a rotating electric machine, a key portion, a first stress relaxation groove, a second stress relaxation groove, and a protruding portion are provided at an inner periphery of a rotor core. The first stress relaxation groove is formed to be adjacent to the key portion in a circumferential direction of the rotor core. The protruding portion is formed between the first stress relaxation groove and the second stress relaxation groove, and is in contact with an outer periphery of a shaft.