Composite VCM Magnet Assembly for Low-Coercivity Stability
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Solution Overview
Problem
The implementation of low-coercivity magnetic materials in hard disk drive (HDD) voice coil motors (VCMs) is challenging due to their susceptibility to demagnetization in low permeance coefficient applications, which are common in HDD VCMs.
Innovation Solution
A composite magnet assembly is used, where the weakest regions of low-coercivity magnets are replaced with high-coercivity magnets, effectively enhancing the permeance coefficient and stabilizing the magnetic field.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If low-coercivity magnetic materials are used in HDD VCMs, then cost and environmental benefits are achieved, but magnetic stability deteriorates due to susceptibility to demagnetization
Solution Approach 1:
The patent uses a composite magnet assembly combining low-coercivity magnets (cost-effective, environmentally friendly) with high-coercivity magnets (magnetically stable). This composite structure allows the system to achieve both cost benefits and magnetic stability by strategically placing different material types in regions where their specific properties are most beneficial.
Solution Approach 2:
The patent applies different magnetic material properties to different locations within the magnet assembly. High-coercivity materials are placed in regions requiring strong, stable magnetic fields, while low-coercivity materials are used in regions where cost effectiveness is prioritized and demagnetization risk is lower. This localized material selection optimizes both performance and cost.
2Object-generated harmful factors
If low-coercivity magnetic materials are used in HDD VCMs, then environmental benefits are achieved by reducing rare-earth materials, but magnetic stability deteriorates due to demagnetization susceptibility
Solution Approach 1:
The composite magnet assembly integrates environmentally friendly low-coercivity materials with high-coercivity materials in a strategic configuration. This allows the system to reduce overall rare-earth content and environmental impact while maintaining magnetic stability through the complementary high-coercivity components.
Solution Approach 2:
Environmental considerations are addressed by using low-coercivity, reduced rare-earth materials in appropriate locations within the magnet assembly, while high-coercivity materials are strategically placed only where their superior magnetic stability is critically needed for reliable operation.
3Ease of manufacture
If low-coercivity magnetic materials are used in HDD VCMs, then cost benefits are achieved, but permeance coefficient becomes insufficient leading to demagnetization
Solution Approach 1:
The composite magnet assembly combines low-coercivity and high-coercivity materials to achieve an overall permeance coefficient that is sufficient for reliable operation. The high-coercivity materials contribute their superior magnetic properties to boost the system's overall permeance coefficient, preventing demagnetization while keeping costs lower than using high-coercivity materials throughout.
Solution Approach 2:
The patent modifies the magnetic circuit design and geometry to optimize the permeance coefficient distribution throughout the assembly. By adjusting parameters such as magnet dimensions, spacing, and magnetic circuit path, the system compensates for the lower permeance coefficient of low-coercivity materials and prevents demagnetization.
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 approach enables the stable implementation of low-coercivity magnetic materials in HDD VCMs, improving magnetic stability and maintaining a suitable permeance coefficient, while also offering cost and environmental benefits by reducing the reliance on rare-earth materials.
Implementation Method 1
A composite magnet assembly is used, where the weakest regions of low-coercivity magnets are replaced with high-coercivity magnets, effectively enhancing the permeance coefficient and stabilizing the magnetic field.
Implementation Method 2
VCMs rely on permanent magnets for their own persistent magnetic fields. Such a field is typically strongest at the magnet surface and decreases with distance therefrom
Data Source
AI summary
A voice coil motor (VCM) includes a coil, and on a first side a first yoke having a coil-side facing the coil, a first low-coercivity permanent magnet positioned between the coil and the coil-side of the first yoke and having a yoke-side facing the first yoke and a coil-side opposing the yoke-side, and a first high-coercivity permanent magnet adjoining the coil-side of the first low-coercivity magnet. A second side of the VCM on the opposing side of the coil is similarly configured. The permeance coefficient of such a VCM enables magnetic stability of low-coercivity magnetic materials. Additional high-coercivity permanent magnets may be bonded to the coil-sides of each of the first and second yokes and adjoining the yoke-sides of each of the low-coercivity permanent magnets, if the relative thicknesses of the magnet materials so dictate by design.