Permanent Magnet Rotor Projection Portions Cogging Force
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Solution Overview
Problem
Surface magnet type synchronous electric motor rotors face challenges in balancing the reduction of cogging force and maintaining demagnetization resistance capacity at the end portions of permanent magnets, as existing methods either reduce demagnetization resistance or increase cogging force.
Innovation Solution
A permanent magnet rotor design featuring a cylindrical core with sequentially disposed magnets and projection portions that include a base and cover portion, where the thickness of the magnets decreases towards the ends, and the cover portion reduces the radial height, along with a pressing portion to secure the magnets, addresses the issue by reducing cogging force while maintaining demagnetization resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the thickness of permanent magnets is reduced from center to end portion to reduce cogging force, then the cogging force is reduced, but the demagnetization resistant capacity at the end portion deteriorates
Solution Approach 1:
The patent applies local quality by providing projection portions specifically at the end portions of the permanent magnets where demagnetization risk is highest, while allowing the center portion to maintain optimal thickness for reducing cogging force. The projection portions create local structural reinforcement without affecting the overall magnet thickness distribution designed for cogging reduction.
Solution Approach 2:
The projection portions are designed to protrude from the rotor core surface before the permanent magnets are installed, creating predetermined engagement structures that guide and secure the magnets during assembly. This preliminary structural preparation ensures proper positioning and prevents demagnetization before operational stresses are applied.
2Reliability
If projection portions are designed to tightly engage with end portions of permanent magnets to prevent separation, then the demagnetization resistant capacity is improved, but the cogging force increases
Solution Approach 1:
The projection portions are localized specifically at the end portions of the magnets rather than extending across the entire magnet surface. This localized engagement approach provides necessary mechanical support where demagnetization risk is highest while leaving the main magnetic surface smooth to minimize cogging force generation.
Solution Approach 2:
The projection portions provide partial engagement rather than complete coverage of the magnet end surfaces. This partial action is sufficient to prevent demagnetization at the critical end portions while avoiding excessive engagement that would increase cogging force through surface irregularities.
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 effectively reduces the cogging force and restrains the reduction of demagnetization resistance capacity at the end portions of the permanent magnets in a balanced manner, enhancing the rotor's performance by minimizing magnetic flux leakage and maintaining magnetic force.
Implementation Method 1
a magnetic attraction force due to a magnetic field of a stator disposed around the rotor act on the permanent magnets
Implementation Method 2
synchronous electric motor
Implementation Method 3
a centrifugal force following rotation of the rotor and a magnetic attraction force due to a magnetic field of a stator disposed around the rotor act on the permanent magnets
Data Source
AI summary
Provided is a permanent magnet rotor that includes a plurality of magnets sequentially disposed on an outer circumferential surface of a core having a cylindrical shape along a circumferential direction of the core and a plurality of projection portions each disposed between the magnets adjacent to each other. Then a cover portion is formed such that a height of a space in a radial direction of the core is more reduced as from a base portion of the projection portions toward a tip end of the cover portion.