Magnetizing Yokes for Ring-Shaped BLDC Motor Magnets
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Solution Overview
Problem
The existing devices for magnetizing ring-shaped magnets in BLDC motors suffer from cogging and torque ripple phenomena due to rapid changes in magnetic flux densities at the ends of unit magnets, leading to rotation hunting issues.
Innovation Solution
The device includes a rotor with a ring-shaped magnet and magnetizing yokes spaced apart to face the magnet, magnetizing only regions except for the ends of the unit magnets, with a magnetizing angle of 0.7 to 0.8 times the pole pitch, and a rugged inner surface on the yokes to alleviate these issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the ring-shaped magnet is magnetized using conventional magnetizing yokes, then the magnetizing process is simple and efficient, but rapid changes in magnetic flux densities occur at the ends of unit magnets, causing cogging and torque ripple phenomena
Solution Approach 1:
The magnetizing yoke is designed with different magnetic permeability regions: a first region with high magnetic permeability for efficient flux generation, and a second region with low magnetic permeability at the ends to prevent rapid flux density changes. This local differentiation resolves the contradiction by maintaining overall magnetizing efficiency while eliminating harmful end effects.
Solution Approach 2:
The magnetic permeability parameter of the magnetizing yoke is varied along its length, with the first region having high permeability (for efficiency) and the second region having low permeability (to prevent flux density spikes). This parameter change approach allows the system to achieve both high productivity and reduced harmful factors.
2Manufacturing precision
If the magnetizing angle is increased to cover the entire pole pitch, then complete magnetization is achieved, but dead zones with rapid magnetic flux density changes are generated at the ends of unit magnets
Solution Approach 1:
The magnetizing yoke applies magnetization with different characteristics at different locations: the first region provides strong magnetization for completeness, while the second region at the ends provides reduced magnetization to maintain flux density stability and eliminate dead zones.
Solution Approach 2:
Instead of applying uniform magnetization across the entire pole pitch, the invention applies partial magnetization at the end regions (second region) to avoid excessive flux density changes, while maintaining sufficient magnetization in the central region for overall completeness.
3Power
If even-numbered unit magnets are coupled to create alternating N and S poles, then the motor generates rotational force, but rotation hunting phenomena occur due to rapid changes in magnetic resistance
Solution Approach 1:
The magnetizing yoke's second region with low magnetic permeability is positioned at the ends where unit magnets are coupled, locally reducing magnetic resistance changes at these critical locations. This maintains the alternating pole structure for power generation while stabilizing rotation by preventing hunting phenomena at the coupling points.
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 rapid changes in magnetic flux densities, minimizing cogging and torque ripple phenomena by maintaining consistent magnetic flux and resistance across the unit magnets, thereby enhancing motor performance.
Implementation Method 1
a magnetizing voltage is applied to the magnetizing yokes 30, such that a magnetic flux is generated through a magnetizing iron core, and even-numbered unit magnets 21 are magnetized in the ring-shaped magnet 20 by the magnetic flux
Data Source
AI summary
Provided is a device for magnetizing a ring-shaped magnet for a brushless direct current (BLDC) motor, including: a rotor having a ring-shaped magnet installed on an outer peripheral surface of a rotor core; and a plurality of magnetizing yokes disposed so as to be spaced apart from each other by a predetermined interval while facing an outer peripheral surface of the ring-shaped magnet, magnetizing the ring-shaped magnet to form even-numbered unit magnets, and magnetizing the ring-shaped magnet only in regions except for one end and the other end of the unit magnets.