Rotor Magnet Holder Assembly for Low Cogging Torque

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Solution Overview

Problem

Conventional rotors of rotating electric machines face issues with positioning accuracy of permanent magnets in the circumferential direction, leading to cogging torque and torque ripple, which deteriorate the performance of the machine.

Innovation Solution

A rotor design featuring a rotor core with press-fit pins and magnet holders with arm portions and base portions, where magnets are positioned between the rotor core and holders, with one end surface of the magnet contacting a pressing surface and the other end contacting core ribs, enhancing circumferential positioning accuracy.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If elasticity of bridge portions is used for positioning and fixation of magnets, then the structure is simple and easy to manufacture, but positioning accuracy of permanent magnets in the circumferential direction is deteriorated

Engineering Contradiction:

Improveease of manufactureVSAvoidpositioning accuracy

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The magnet holder is divided into a base portion and multiple arm portions that are independently positioned and fixed to the rotor core. Each arm portion can be separately adjusted and secured, allowing precise positioning of magnets while maintaining manufacturing simplicity through modular assembly

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent replaces the elastic bridge portion mechanism with a rigid arm portion structure that uses press-fit pins and insertion grooves for positioning. This mechanical substitution eliminates reliance on elastic deformation for positioning, thereby improving circumferential positioning accuracy while keeping the overall structure manufacturable

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Device complexity

If elasticity of bridge portions is used for positioning and fixation of magnets, then the structure is simple, but cogging torque and torque ripple are caused

Engineering Contradiction:

Improvestructure complexityVSAvoidcogging torque and torque ripple

Core Design Contradiction:

Device complexityVSObject-generated harmful factors

Solution Approach 1:

By segmenting the magnet holder into multiple independently positioned arm portions, the patent achieves precise alignment of magnets with rotor core slots. This segmentation allows each arm portion to be accurately positioned, reducing misalignment that causes cogging torque and torque ripple, while the overall structure remains relatively simple

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The replacement of elastic bridge portions with rigid arm portions featuring press-fit pins and insertion grooves eliminates the positioning errors and vibrations associated with elastic deformation. This mechanical substitution reduces cogging torque and torque ripple by ensuring stable, precise magnet positioning without the complexity of elastic components

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Manufacturing precision

If press-fit pins and insertion grooves are used for positioning, then positioning accuracy of magnets in the circumferential direction is improved, but device complexity increases

Engineering Contradiction:

Improvepositioning accuracyVSAvoiddevice complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The magnet holder is segmented into a base portion and multiple arm portions, each with its own press-fit pin and insertion groove configuration. This segmentation allows the complex positioning features to be distributed and standardized across multiple identical components, making the overall device more manageable and easier to manufacture despite the increased precision requirements

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The press-fit pins and insertion grooves are pre-configured during the molding of the base portion and arm portions. This preliminary action ensures that positioning features are accurately formed in advance, eliminating the need for complex post-assembly adjustments and reducing the overall device complexity by integrating positioning functions into the component geometry

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS12191716B2Rotor of rotating electric machine and rotating electric machine

Publication Date: 2025.01.07 MITSUBISHI ELECTRIC CORP

AI summary

A base portion of a magnet holder attached to a rotor core of a rotor has a press-fit pin press-fitted into a press-fit hole provided at an end surface of the rotor core. An arm portion of the magnet holder has a holder rib which protrudes inward in the radial direction of an output shaft and of which one end surface in the circumferential direction serves as a pressing surface, and a come-off prevention protrusion inserted into an insertion groove provided at an outer circumferential surface of the rotor core. Magnets are located between the rotor core and the magnet holders, one end surface in the circumferential direction of each magnet contacts with the pressing surface, and another end surface contacts with a core rib protruding from the rotor core.