Embedded Rotor Magnet Structure for Stress and Demagnetization Control
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Solution Overview
Problem
Rotors for rotary electric machines face challenges with permanent magnet damage due to stress concentration and demagnetization, particularly from assembling and environmental stresses such as vibrations and thermal changes, which existing designs fail to adequately address.
Innovation Solution
The rotor design incorporates a magnet-embedded structure with concave portions on the magnet surfaces and matching convex portions on the rotor core, which helps in stress dispersion, positional stabilization, and reduced contact friction, thereby enhancing anti-demagnetization performance and preventing damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the permanent magnet is made with a flat surface structure, then the manufacturing process is simple, but stress concentration occurs leading to magnet damage
Solution Approach 1:
The patent applies curvature by forming a concave portion with a curved surface in the middle portion of the magnet. This curved structure eliminates stress concentration points that would occur with flat surfaces, thereby improving the magnet's resistance to damage while maintaining manufacturing feasibility through standard forming processes.
Solution Approach 2:
The concave portion is specifically formed only in the middle portion of the magnet where stress concentration is most likely to occur, rather than changing the entire magnet structure. This localized modification optimizes stress distribution without unnecessarily complicating the overall manufacturing process.
2Weight of moving object
If the permanent magnet is made with a thin middle portion to reduce weight, then the weight is reduced, but the anti-demagnetization performance deteriorates
Solution Approach 1:
The magnet is designed with non-uniform thickness where the middle portion is thinner than the end portions. This localized thinning reduces overall weight while the thicker end portions maintain the anti-demagnetization performance by providing sufficient magnetic material depth at the critical regions where demagnetization risk is highest.
3Stability of the object's composition
If the permanent magnet is tightly fitted in the accommodation hole to improve positional stability, then the positional stability is improved, but stress concentration and damage risk increase
Solution Approach 1:
The concave portion with a curved surface provides a gradual transition in the magnet structure, which distributes assembly stress more evenly during insertion into the accommodation hole. This curved geometry prevents sharp stress concentrations that would occur with abrupt transitions, thereby reducing damage risk while maintaining positional stability through the engagement of the concave portion with the rotor core.
Data Source
AI summary
A rotor having a magnet-embedded structure includes a rotor core and a permanent magnet held in the rotor core. A permanent magnet is accommodated in an accommodation hole provided in the rotor core. The permanent magnet has a first surface and a second surface which extend in a direction intersecting with the magnetization direction, which is a direction of magnetic field lines inside the magnet and opposes each other. At least one of the first surface and the second surface is provided with a concave portion, which is provided with a curved surface in a concaved shape at a middle portion between both ends in a longitudinal cross-section.