Ring-Shaped Motor Magnet Mitigating Cogging Torque
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Solution Overview
Problem
Conventional small-sized motors face challenges in assembling and fixing multiple C-shaped stator pole magnets, leading to increased production costs and inefficiencies due to excessive magnetic flux reduction, which results in high cogging torque and reduced motor torque.
Innovation Solution
A small-sized motor design featuring a single ring-shaped magnet with thin portions between magnetic poles, allowing for efficient assembly and fixation, reducing cogging torque without significantly lowering motor torque, by maintaining a constant gap between the magnet and rotor pole core.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If multiple C-shaped stator pole magnets are assembled into the yoke, then the magnetic field can be distributed across multiple poles, but the positioning and fixing become difficult, increasing production cost and reducing quality
Solution Approach 1:
Multiple C-shaped magnets are merged into a single ring-shaped magnet member with multiple poles. This integration eliminates the need to assemble and fix multiple separate magnets, simplifying the assembly process while maintaining the multi-pole magnetic field configuration necessary for motor torque generation.
Solution Approach 2:
The ring-shaped magnet member is segmented into multiple magnetic poles (four or more) with thin portions between adjacent poles. This segmentation creates distinct magnetic regions that generate the multi-pole magnetic field, achieving the same functional effect as multiple separate C-shaped magnets but with a single integrated component.
2Object-generated harmful factors
If the gap between the magnet and rotor is increased from central portion to end portions, then cogging torque is reduced, but magnetic flux is reduced excessively, lowering motor torque efficiency
Solution Approach 1:
The ring-shaped magnet member has non-uniform thickness with thin portions at specific locations between magnetic poles. This local variation in thickness creates a constant gap between the magnet and rotor at critical positions, reducing cogging torque by preventing abrupt magnetic field changes, while maintaining sufficient magnetic flux in the pole regions to preserve motor torque efficiency.
3Power
If four or more magnets are assembled into the yoke, then multi-pole magnetic field is achieved, but positioning and fixing become difficult, increasing production cost
Solution Approach 1:
Multiple magnets are merged into a single ring-shaped magnet member that can be assembled into the motor casing as one piece. This eliminates the complex positioning and fixing operations required for multiple separate magnets, significantly improving ease of manufacture and reducing production cost while maintaining the multi-pole configuration for adequate motor torque.
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
The design effectively mitigates cogging torque while maintaining motor torque performance, simplifies assembly, and reduces production costs by using a ring-shaped magnet with thin and cut portions, ensuring efficient magnetic flux distribution.
Implementation Method 1
The magnetization is performed in the radial direction so as to alternately form S poles and N poles in the circumferential direction
Implementation Method 2
through formation of thin portions between the poles of the multi-pole magnet, generation of cogging torque can be mitigated
Data Source
AI summary
A small-sized motor includes a field magnet attached to an inner circumferential surface of a metallic motor casing and having four or more magnetic poles. The field magnet is formed of a single ring-shaped magnet member having a predetermined thickness with respect to the radial direction and a predetermined length with respect to the thrust direction. At each of portions between the magnetic poles formed through magnetization, the magnet member has a thin portion having a reduced thickness with respect to the radial direction, the thin portion being formed by cutting the magnet member from the radially outward side. The magnetization is performed in the radial direction so as to alternately form S poles and N poles in the circumferential direction. At each of portions between the magnetic poles, the magnet member may have cut portions formed at opposite end portions of the magnet member with respect to the thrust direction.