Interior Permanent Magnet Motor Rotor Core Bridge Design
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Solution Overview
Problem
Existing interior permanent magnet motor designs face challenges in improving rotor core strength and magnetic flux efficiency while maintaining low manufacturing costs, as gaps between permanent magnets and bridges lead to reduced magnetic flux and increased costs due to complex magnet shapes.
Innovation Solution
The design features a rotor core with separated magnet insertion holes and bridges formed by parallel linear portions and curved portions, allowing for efficient magnet placement and stress distribution without increasing manufacturing costs, by ensuring the magnets are fully utilized and the bridge's shape alleviates stress concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a thin portion is designed between the magnet insertion hole and outer circumferential surface to serve as a leakage flux path, then magnetic flux efficiency is improved, but rotor core strength deteriorates due to insufficient centrifugal force resistance
Solution Approach 1:
The magnet insertion hole is divided into multiple segments in the circumferential direction, creating multiple smaller holes instead of one large hole. This segmentation allows bridges to be formed between adjacent holes, providing structural reinforcement while maintaining the thin portion for leakage flux paths
Solution Approach 2:
Bridges are formed within the rotor core structure, nesting additional structural elements between the magnet insertion holes and the outer circumferential surface. These bridges provide strength without increasing the overall rotor dimensions
2Strength
If bridges are formed to connect radially outer and inner portions of the rotor core, then rotor core strength is improved, but manufacturing cost increases due to complex magnet shapes required to eliminate gaps
Solution Approach 1:
By segmenting the magnet insertion holes circumferentially, the bridge structure can be formed using simple rectangular magnets without requiring complex curved shapes. The segmentation allows straight bridges to connect between holes, simplifying magnet manufacturing
Solution Approach 2:
Instead of making the magnets complex to fit around bridges, the invention inverts the approach by making the bridges simple structural elements and positioning rectangular magnets in segmented holes, eliminating the need for complex magnet geometries
3Strength
If the number of permanent magnets is increased by dividing magnet insertion holes, then rotor core strength is improved through bridge formation, but magnetic flux amount decreases due to gaps between magnets and bridges
Solution Approach 1:
The bridges are formed as preliminary structural elements before magnet insertion, creating defined pathways and positioning structures that guide magnet placement. This preliminary bridge formation ensures minimal gaps without requiring complex magnet shapes
Solution Approach 2:
The thin portions are strategically positioned only where needed for leakage flux paths, while other areas maintain full magnet-to-bridge contact. This local differentiation optimizes both magnetic flux efficiency and structural strength
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 enhances rotor core strength and magnetic flux efficiency while preventing a rise in permanent magnet manufacturing costs, achieving improved motor performance without complex or costly magnet shapes.
Implementation Method 1
a portion between both the ends of the magnet insertion hole and the outer circumferential surface of the rotor core serves as a path for a so-called leakage magnetic flux, which is a magnetic flux flowing out of a surface of the permanent magnet and into another surface of the permanent magnet without passing through a stator core and contributing to an output
Implementation Method 2
when an upper limit on the number of revolutions of a motor is raised, the strength of the rotor core is required to be improved because the magnitude of a centrifugal force acting on a rotor is proportional to the square of the number of revolutions
Data Source
AI summary
Provided is an interior permanent magnet motor including: a stator; and a rotor, the rotor including separated permanent magnets for one magnetic pole, in which: a rotor core includes the same number of separated magnet insertion holes as that of the plurality of permanent magnets for one magnetic pole; bridges are formed between respective adjacent ones of the magnet insertion holes in each magnetic pole; each of the bridges includes a pair of parallel linear portions and two pairs of curved portions; under a state in which the permanent magnets are inserted into the magnet insertion holes, the pair of linear portions are in contact with edge surfaces of the permanent magnets; the pair of curved portions are connected to ends of the linear portions; and an interval between the pair of curved portions becomes larger as the interval becomes away from the linear portions.