Arcuate Magnet Molding Die with Ferromagnetic Field Shaping
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Solution Overview
Problem
Current methods for producing arcuate magnets with polar-anisotropic orientation are challenging due to difficulties in adjusting magnetic-field-generating coils and voltage, leading to suboptimal orientation and increased risk of cracking, especially for large magnets, which affects the reduction of cogging torque in motors.
Innovation Solution
A die apparatus with an arcuate-cross-sectional cavity, a central ferromagnetic body, and symmetrically arranged side ferromagnetic bodies, all positioned within a parallel magnetic field, is used to produce arcuate magnets with polar-anisotropic orientation, ensuring the magnetic powder is oriented circumferentially at the ends and radially at the center, mimicking the orientation of polar-anisotropic ring magnets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If arcuate magnets with polar-anisotropic orientation are produced using conventional die apparatus with coils, then magnetic powder orientation can be achieved, but it is difficult to adjust coil arrangement and voltage to obtain ideal orientation, increasing device complexity and reducing manufacturing precision
Solution Approach 1:
The patent replaces the electromagnetic field generation system (coils and power supply) with a permanent magnet-based field generation system. The die apparatus uses permanent magnets arranged in specific patterns to generate the necessary magnetic fields for orienting magnetic powder, eliminating the need for complex coil arrangements and voltage adjustments while achieving precise control over magnetic field distribution.
Solution Approach 2:
The patent introduces ferromagnetic bodies as intermediaries between the permanent magnets and the magnetic powder. These ferromagnetic bodies concentrate and guide the magnetic field lines, enabling precise control over the magnetic field distribution in the die cavity without requiring direct adjustment of coil parameters. The ferromagnetic bodies act as field-shaping elements that simplify the overall system complexity.
2Manufacturing precision
If polar-anisotropic ring magnets are produced, then surface magnetic flux density waves have higher peaks and closer to sinusoidal wave, but orientation cracking occurs easily during sintering, particularly in large ring magnets
Solution Approach 1:
The patent applies different magnetic field orientations to different regions of the arcuate magnet. By using multiple permanent magnets arranged in specific patterns, the magnetic field direction varies locally across the die cavity, creating the desired polar-anisotropic orientation where different portions of the magnet have different orientation directions. This local variation in field orientation enables the sinusoidal flux density waveform while the gradual transition reduces stress concentration.
Solution Approach 2:
The patent divides the die apparatus into multiple independent magnetic field generation zones using separate permanent magnets. Each permanent magnet or group of magnets creates a localized magnetic field that contributes to the overall polar-anisotropic orientation. This segmentation allows independent optimization of each zone's magnetic field to minimize local stress concentrations that could lead to cracking.
3Ease of manufacture
If arcuate magnets with radial orientation are produced, then production is simpler, but surface magnetic flux density waves have trapezoidal form, unable to provide sinusoidal waveform needed for low cogging torque
Solution Approach 1:
The patent replaces the simple single-direction magnetic field generation (suitable for radial orientation) with a multi-component permanent magnet system that generates complex spatially-varying magnetic fields. This substitution enables the creation of polar-anisotropic orientation with sinusoidal flux density waveform while maintaining relative manufacturing simplicity through the use of permanent magnets rather than complex electromagnetic systems.
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 produced arcuate magnets exhibit ideal polar-anisotropic orientation, resulting in a sinusoidal surface magnetic flux density distribution when assembled into a ring, reducing cogging torque and enhancing motor performance.
Implementation Method 1
magnetic powder charged into the cavity being oriented to have multi-pole orientation by a magnetic field generated from coils 360 disposed in grooves 350 on the inner surface of the die apparatus 340
Implementation Method 2
a die apparatus with an arcuate-cross-sectional cavity, a central ferromagnetic body, and symmetrically arranged side ferromagnetic bodies, all positioned within a parallel magnetic field
Data Source
AI summary
A die apparatus for molding an arcuate magnet having polar-anisotropic orientation in a magnetic field, which comprises a die made of non-magnetic cemented carbide, which is arranged in a parallel magnetic field generated by a pair of opposing magnetic field coils; an arcuate-cross-sectional cavity having an inner arcuate wall, an outer arcuate wall and two side walls, which is disposed in the die; a central ferromagnetic body arranged on the side of the outer arcuate wall of the cavity; and a pair of side ferromagnetic bodies symmetrically arranged on both side wall sides of the cavity; the cavity being arranged such that its radial direction at a circumferential center thereof is identical with the direction of the parallel magnetic field; the width of the central ferromagnetic body being smaller than the width of the cavity in a direction perpendicular to the parallel magnetic field; and a pair of the side ferromagnetic bodies being arranged such that the cavity is positioned in a region sandwiched by a pair of the side ferromagnetic bodies.