Rotor Magnet Tabs With Curved Tips for Secure IPM Retention

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Solution Overview

Problem

Interior permanent magnet electric machines face issues with magnet stabilization, leading to potential demagnetization due to voids in slots and damage from straight tabs, which also affect magnetic fields and increase manufacturing costs.

Innovation Solution

The use of pre-bent tabs in rotor slots that engage magnets without sharp edges, eliminating the need for epoxy and preventing magnet coating damage, while maintaining magnetic integrity.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Stability of the object's composition

If straight tabs are used to retain magnets in slots, then magnet positioning stability is improved, but magnet protective coating is damaged due to scraping

Engineering Contradiction:

Improvemagnet positioning stabilityVSAvoidmagnet coating damage

Core Design Contradiction:

Stability of the object's compositionVSObject-affected harmful factors

Solution Approach 1:

The tab tip is bent to form a curved surface instead of a straight edge, allowing the tab to engage the magnet without scraping the protective coating while still providing sufficient retention force

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Stability of the object's composition

If epoxy is used to secure magnets in slots, then magnet retention is improved, but manufacturing cost increases

Engineering Contradiction:

Improvemagnet retentionVSAvoidmanufacturing cost

Core Design Contradiction:

Stability of the object's compositionVSEase of manufacture

Solution Approach 1:

The epoxy adhesive is completely removed from the system and replaced with a mechanical retention solution using bent tabs that provide sufficient magnet retention through elastic deformation and geometric constraint

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The bent tabs provide self-retaining force through their pre-bent configuration, automatically securing magnets in slots without requiring additional adhesives or complex assembly processes

Inventive Principle:

Principle #25Self-service

3Adaptability or versatility

If slots are made longer than magnets to provide voids, then manufacturing flexibility is improved, but magnet stability deteriorates due to increased void space

Engineering Contradiction:

Improvemanufacturing flexibilityVSAvoidmagnet stability

Core Design Contradiction:

Adaptability or versatilityVSStability of the object's composition

Solution Approach 1:

The tabs are pre-bent before magnet insertion to a specific angle that optimizes retention force, allowing the slots to remain longer than magnets for manufacturing flexibility while ensuring stable magnet positioning through the pre-configured tab geometry

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS20260081489A1Electric machine with rotor magnet tabs

Publication Date: 2026.03.19 BORGWARNER INC

AI summary

An electric machine includes a stator having a plurality of windings and a rotor positioned within the stator. The rotor includes a lamination stack formed from a plurality of lamination sheets with a plurality of slots formed in the lamination stack. The rotor further includes a plurality of magnets arranged in the plurality of slots. At least one of the plurality of lamination sheets includes a tab extending into an associated one of the plurality of slots, the tab including a bent distal tip defining a distal curved surface and a bent proximal joint defining a proximal curved surface, wherein the distal curved surface engages one of the plurality of magnets positioned in the associated one of the plurality of slots.