Rotor Non-Magnetic Ring Fixation Cogging Torque

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Solution Overview

Problem

Conventional rotors of rotating electrical machines face issues with secure fixation of permanent magnets, leading to fluctuations in cogging torque, noise, and increased costs due to the need for additional fixation members, which also result in physical enlargement of the machine.

Innovation Solution

A rotor design featuring a tube-shaped non-magnetic ring with inner-diameter bulging portions that securely fix magnetic poles on a rotor iron core, eliminating the need for additional fixation members and maintaining torque stability without physical enlargement or cost increase, achieved through press-fitting or shrinkage-fitting methods.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If adhesive is used to fix the non-magnetic cover on the permanent magnet, then the permanent magnet position can be fixed, but the fixing reliability is insufficient when adhesive hardens or lacks sufficient fixing power

Engineering Contradiction:

Improvefixing reliabilityVSAvoidpermanent magnet position precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent replaces the chemical bonding mechanism (adhesive) with a mechanical constraint mechanism. The non-magnetic cover is designed with a press-fit structure that mechanically constrains the permanent magnet through interference fit, eliminating reliance on adhesive bonding strength and curing processes.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The non-magnetic cover is segmented into multiple functional zones: a press-fit portion that mechanically constrains the permanent magnet, and a cover portion that protects the magnet. This segmentation allows the press-fit portion to provide reliable mechanical fixation while the cover portion provides protection.

Inventive Principle:

Principle #1Segmentation

2Reliability

If a fastening ring with fixation member (bolt) is used to secure the permanent magnet, then the permanent magnet position is secured, but material costs, processing costs increase and the machine size enlarges

Engineering Contradiction:

Improvepermanent magnet position stabilityVSAvoidfixation structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the fastening function and the protective cover function into a single integrated non-magnetic cover component. The press-fit structure of the cover itself provides the fixation mechanism, eliminating the need for separate fastening members like bolts, thereby reducing part count and assembly complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The non-magnetic cover is designed to be self-fixing through its press-fit structure. The interference fit between the cover's inner circumference and the permanent magnet's outer circumference, as well as between the cover and the yoke, enables the cover to secure the magnet without requiring external fixation members.

Inventive Principle:

Principle #25Self-service

3Reliability

If space between permanent magnets is increased to accommodate fixation member, then the fixation can be implemented, but the torque is deteriorated and physical enlargement occurs

Engineering Contradiction:

Improvefixation capabilityVSAvoidtorque

Core Design Contradiction:

ReliabilityVSPower

Solution Approach 1:

The patent transitions the fixation approach from the circumferential dimension (requiring space between magnets for bolts) to the radial dimension. The press-fit structure utilizes radial interference fit between the non-magnetic cover and both the permanent magnet and the yoke, enabling fixation without increasing circumferential spacing between magnets.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

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 ensures stable cogging torque and reduced noise by securely fixing magnetic poles, preventing torque deterioration and physical enlargement, while maintaining cost-effectiveness.

Implementation Method 1

achieved through press-fitting or shrinkage-fitting methods

Methodology Applied

Scientific EffectPress-fitting:

Implementation Method 2

achieved through press-fitting or shrinkage-fitting methods

Methodology Applied

Scientific EffectShrinkage-fitting: Thermal Contraction

Data Source

PatentUS7741747B2Rotor of rotating electrical machine and manufacturing method there for

Publication Date: 2010.06.22 MITSUBISHI ELECTRIC MOBILITY CORP

AI summary

A rotor of a rotating electrical machine is provided in which neither deterioration nor fluctuation in the cogging torque is caused and that causes neither physical enlargement nor cost increase. The rotor of a rotating electrical machine, provided with a plurality of magnetic poles 3 that are fixed on a rotor iron core 2 and arranged spaced apart from one another in the circumferential direction of the rotor iron core 2, is characterized by including a tube-shaped non-magnetic ring 4 mounted on the outer circumferential surfaces of the plurality of magnetic poles 3, and characterized in that the non-magnetic ring has a plurality of inner-diameter bulging portions 41 that abut on the corresponding outer circumferential surfaces of the plurality of magnetic poles.