Interior Magnet Rotor Corner Slopes for Demagnetization Resistance
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Solution Overview
Problem
Interior magnet rotors with permanent magnets face challenges such as demagnetization, chipping, and increased manufacturing costs due to the need for chamfering and division of magnets, which affect magnetic flux and efficiency in synchronous machines.
Innovation Solution
The design features a rotor with a rotor shaft and core housing multiple permanent magnets arranged in a row, each with 45-degree corner slopes on opposite corners, reducing the demagnetizing factor and eddy current without increasing the risk of chipping, and allowing for shorter positioning projections in the magnet housing hole.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If chamfering is performed on permanent magnets to prevent chipping, then chipping resistance is improved, but manufacturing time and cost increase
Solution Approach 1:
The patent forms the permanent magnets with rounded corners directly during the sintering process, rather than performing chamfering after manufacturing. This preliminary action eliminates the need for subsequent chamfering operations, preventing chipping while reducing manufacturing time and cost.
2Reliability
If chamfering is performed to prevent chipping, then chipping resistance is improved, but manufacturing cost increases
Solution Approach 1:
The patent forms the permanent magnets with rounded corners directly during the sintering process, rather than performing chamfering after manufacturing. This preliminary action eliminates the need for subsequent chamfering operations, preventing chipping while reducing manufacturing time and cost.
3Loss of energy
If permanent magnets are divided into multiple pieces to reduce eddy current, then efficiency is improved, but contact frequency between corners increases
Solution Approach 1:
The patent applies different corner radius values to different corners of the permanent magnets based on their position. Magnets at positions with higher contact frequency have larger corner radii, while others have smaller radii. This localized adaptation reduces eddy current through proper segmentation while minimizing chipping risk at critical contact points.
4Reliability
If corner slopes are formed by removing vertex portions, then chipping is prevented, but magnetic force is reduced
Solution Approach 1:
The patent changes the geometric parameter of corner radius to optimize the balance between chipping prevention and magnetic force maintenance. By forming rounded corners with specific radius values during sintering, the patent prevents chipping while minimizing the reduction in magnetic force compared to traditional chamfering that removes material.
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
This configuration reduces the demagnetizing factor by 33% for thin magnets and 9% for thick magnets, improves demagnetization resistance, and enhances torque-current characteristics by minimizing the reduction in magnetic force, while maintaining the same contact area and preventing corner chipping.
Implementation Method 1
a rotor shaft extending in a rotation axis direction; a rotor core that has at least one magnet housing hole formed in each magnetic pole
Implementation Method 2
a plurality of permanent magnets instead of a single permanent magnet are sometimes housed in a magnet hole of a rotor core, that is, the permanent magnet is practically divided into a plurality of pieces, whereby an eddy current generated in the permanent magnet is reduced
Data Source
AI summary
According to an embodiment, an interior magnet rotor includes a rotor shaft extending in a rotation axis direction, a rotor core, and a plurality of permanent magnets. The rotor core has at least one magnet housing hole formed in each magnetic pole and sandwiched by a first wall and a second wall, and is attached to the rotor shaft. The plurality of permanent magnets are housed in the magnet housing hole and are arranged in a row in one direction in a cross section of the magnet housing hole. The permanent magnets each have a substantially rectangular parallelepiped outer shape and have slopes formed over a longitudinal direction on two corners opposite to each other.