Composite Permanent Magnet for Hard Disk Drive Voice Coil Motor
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current hard disk drives face challenges in increasing the efficiency of voice coil motors (VCM) due to limitations in magnetic field strength and gradient, which are affected by the scarcity and cost of rare earth materials, and the difficulty in optimizing permanent magnets within a confined space.
Innovation Solution
A composite permanent magnet structure is introduced, comprising core magnets with opposite magnetization directions and cladding magnets, which are deposited, bonded, or placed next to each other, and attached to a soft magnetic yoke, optimizing magnetic field distribution and strength without increasing material costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If NdFeB magnets are used to increase magnetic strength, then the magnetic flux density increases, but the cost increases significantly due to the scarcity of Neodymium
Solution Approach 1:
The patent uses a composite magnet structure combining ferrite and SmCo materials with different magnetization directions to achieve high magnetic flux density without relying on expensive NdFeB magnets. The composite structure leverages the complementary magnetic properties of different materials to reach performance targets at lower cost.
Solution Approach 2:
The patent applies different magnetic materials (ferrite and SmCo) to different regions of the magnet assembly, with each material optimized for its specific location to maximize overall magnetic field strength while controlling costs. The cladding magnet and core magnet use different materials strategically placed to optimize field distribution.
2Productivity
If the magnetic field strength is increased by using higher grade magnets, then the motor efficiency increases, but the cost increases in proportion with the grade
Solution Approach 1:
The patent creates a composite magnet system using ferrite and SmCo materials arranged in a specific configuration with opposite magnetization directions. This composite approach achieves high motor efficiency by optimizing the magnetic field gradient without requiring a single high-grade expensive magnet, thereby reducing overall material costs while maintaining productivity.
3Ease of operation
If two pieces of permanent magnet are glued together to provide necessary magnetic field, then the VCM operation is enabled, but the magnetic field optimization in confined space is limited
Solution Approach 1:
The patent divides the magnet system into multiple segments including core magnets and cladding magnets with different magnetization directions. This segmentation allows independent optimization of each segment's magnetic contribution, enabling better control over the overall magnetic field gradient within the confined VCM space while ensuring proper operation.
Solution Approach 2:
The patent introduces a cladding magnet layer that adds a new dimensional aspect to the magnet structure. The cladding magnet is positioned and magnetized in a direction substantially perpendicular to the core magnet, creating a three-dimensional magnetic field optimization that enhances the magnetic field gradient without increasing the footprint area, thus improving productivity within confined space.
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 composite magnet design enhances magnetic field and flux density, leading to a 20% increase in torque and efficiency, reducing energy consumption and improving seek times in hard disk drives.
Implementation Method 1
Permanent magnets (PM) create their own persistent magnetic fields and are typically used in electromagnetic induction devices such as motors and generators
Implementation Method 2
Permanent magnets are typically used in electromagnetic induction devices such as motors and generators
Implementation Method 3
The composite permanent magnet is attached to a soft magnetic yoke and form a composite permanent magnet component
Data Source
AI summary
A hard disk drive includes a drive case and a cover plate, the storage media platers and a spindle, the recording heads and actuators, the connection port, the control logic board and one or more voice coil motor, where the actuators are operated via a voice coil motor; wherein the voice coil motor magnets comprise of a pair of composite permanent magnets on both sides of the voice coil, where each piece of composite permanent magnet comprising: a first core magnet M1, a cladding magnet Mc12 and a second core magnet M2; the magnetization direction of M1 and M2 are opposite to each other; the magnetization direction of Mc12 is substantially perpendicular to the magnetization direction of M1 and M2; the ratio of the width of Mc12 to the thickness or the height of Mc12 is 4:1 or less as seen from the back view.