Rotor Magnet Layout for Lower-Cost Motor Output Retention
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Solution Overview
Problem
The high cost of manufacturing motors due to the use of rare-earth bonded magnets, which are more expensive than ferrite bonded magnets, is a challenge in rotor design.
Innovation Solution
A rotor design incorporating a ferrite bonded magnet with polar-anisotropic orientation and rare-earth bonded magnets distributed in grooves on the outer circumference, where the volume ratio of rare-earth magnets is lower in the overhang portion than in the stator-facing portion, reducing the overall use of rare-earth magnets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If rare-earth bonded magnets are used to enhance magnetic force, then motor output and efficiency are improved, but manufacturing cost increases
Solution Approach 1:
The patent applies local quality by differentiating the rotor structure into two regions: a stator-facing portion with a higher concentration of rare-earth magnets for optimal magnetic interaction, and an overhang portion with fewer or no rare-earth magnets. This spatial differentiation of material quality maintains motor output while reducing the total amount of expensive rare-earth material used.
Solution Approach 2:
The rotor magnet structure is segmented into the stator-facing portion and the overhang portion, with distinct rare-earth magnet arrangements in each. The stator-facing portion contains rare-earth magnets positioned to maximize magnetic flux interaction with the stator, while the overhang portion has reduced rare-earth magnet content, thereby segmenting the magnetic field generation function across different spatial zones.
2Loss of energy
If rare-earth bonded magnets are used to enhance magnetic force, then motor efficiency is improved, but manufacturing cost increases
Solution Approach 1:
By concentrating rare-earth magnets in the stator-facing portion where they directly interact with the stator core, the patent optimizes magnetic flux density and reduces energy losses in the primary magnetic interaction zone. The overhang portion uses fewer rare-earth magnets since it contributes less to the productive magnetic flux, thereby reducing material cost while maintaining efficiency.
3Ease of manufacture
If the volume of rare-earth magnets is reduced to lower cost, then manufacturing cost decreases, but magnetic flux flow into the stator core may be compromised
Solution Approach 1:
The patent optimizes magnetic flux generation by transitioning from a uniform axial distribution of rare-earth magnets to a differentiated spatial arrangement where magnet density varies along the axial direction. The stator-facing portion maintains high magnet density for effective flux transfer, while the overhang portion reduces density, achieving cost reduction without compromising the critical magnetic flux flow into the stator core.
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 design reduces manufacturing costs without compromising motor output or efficiency by minimizing the use of rare-earth magnets while maintaining effective magnetic flux flow into the stator core.
Implementation Method 1
A rotor (1) including a shaft (10) and a rotor magnet (50) fixed with respect to the shaft (10), and a stator (6) surrounding the rotor (1) in a radial direction about the shaft (10)
Implementation Method 2
The rotor magnet (50) includes a first magnet (20) magnetized so as to have polar-anisotropic orientation, and second magnets (30), the number of which is P (P is an even number), provided on an outer circumference of the first magnet (20)
Data Source
AI summary
A motor includes a rotor having a shaft and a rotor magnet, and a stator. The rotor magnet includes a first magnet magnetized so as to have polar-anisotropic orientation, and second magnets, the number of which is P (P is an even number), provided on an outer circumference of the first magnet, magnetized so as to have polar-anisotropic orientation, and having a stronger magnetic pole than the first magnet. A length Hr of the rotor magnet in the axial direction and a length Hs of a stator core in the axial direction satisfy Hr>Hs. The rotor magnet includes, in the axial direction, a stator-facing portion facing the stator core in the radial direction and an overhang portion protruding from the stator core in the axial direction. A volume ratio of the second magnets to the first magnet is smaller in the overhang portion than in the stator-facing portion.