Rotor Thermal Expansion Management via Segmented Gaps
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Solution Overview
Problem
Conventional rotors with embedded permanent magnets face issues due to thermal expansion differences between nonmagnetic and magnetic materials, leading to deformation and increased flux leakage, which results in iron loss and reduced output.
Innovation Solution
A rotor design incorporating a magnetic first member and a nonmagnetic second member with strategically placed gaps to manage thermal expansion, reducing deformation and flux leakage, while using materials with matching thermal expansion coefficients for the first member and shaft to maintain engagement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If nonmagnetic members and magnetic members are fixed in close contact over the whole circumference, then the structure is compact and simple, but excessive interference occurs between members due to thermal expansion differences causing deformation
Solution Approach 1:
The rotor structure is divided into multiple segments along the axial direction, with gaps introduced between the nonmagnetic member and magnetic member, and between the nonmagnetic member and laminated core. This segmentation allows each component to expand and contract independently during thermal cycles, preventing deformation while maintaining structural integrity.
Solution Approach 2:
The nonmagnetic member acts as an intermediary element positioned between the magnetic member and the permanent magnet. This intermediary structure provides thermal isolation and mechanical support, allowing the magnetic member to be securely held while preventing direct thermal contact that would cause deformation.
2Ease of manufacture
If soft nonmagnetic material such as resin or aluminum is used for the nonmagnetic member, then ease of manufacture is improved, but the member is deformed by thermal expansion
Solution Approach 1:
By dividing the nonmagnetic member into segments separated by gaps, soft materials like resin or aluminum can be used for ease of manufacture while the gaps prevent cumulative thermal expansion deformation. Each segment can expand independently without affecting the overall structural integrity.
Solution Approach 2:
The introduction of gaps changes the thermal expansion parameters of the system, allowing soft nonmagnetic materials to be used without deformation. The gaps provide expansion space that accommodates thermal growth while maintaining the mechanical function of holding the permanent magnet.
3Loss of energy
If the nonmagnetic member is pressed tightly against the magnetic member to reduce flux leakage, then magnetic efficiency is improved, but thermal expansion causes deformation and increased flux leakage
Solution Approach 1:
The nonmagnetic member serves as an intermediary that provides controlled magnetic isolation between the magnetic member and permanent magnet. The gaps in this intermediary structure allow thermal expansion while the nonmagnetic material properties reduce flux leakage, achieving both thermal and magnetic performance goals.
Solution Approach 2:
By changing the magnetic parameter (introducing nonmagnetic material with air gaps) rather than relying on tight mechanical contact, the system reduces flux leakage without causing thermal deformation. The gaps provide a magnetic path with higher reluctance that prevents flux leakage while accommodating thermal expansion.
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 design effectively reduces flux leakage and iron loss, maintains output levels, and prevents deformation of nonmagnetic members, even when using soft materials like resin or aluminum, by managing thermal expansion and enhancing cooling efficiency.
Implementation Method 1
the flux leakage from the permanent magnet into the second member can be reduced, and iron loss and decrease in output level can be suppressed
Implementation Method 2
when the temperature of the rotor increases owing to iron loss or the like during the operation of a motor, excessive interference occurs between the nonmagnetic members and the magnetic members, because the thermal expansion coefficients are greatly different between the nonmagnetic members and the magnetic members
Data Source
AI summary
A rotary electric machine is provided with a shaft which is a rotary shaft; a laminated core which has a permanent magnet embedded therein and is press-fitted to the shaft; a first member which is a magnetic member and is press-fitted to the shaft so as to hold an end portion of the laminated core; a second member which is a nonmagnetic member and is provided between the end portion of the laminated core and the first member so as to hold an end portion, with respect to the axial direction of the shaft, of the permanent magnet; and at least one of a first gap between the first member and the second member, and a second gap between the laminated core and the second member.