Spindle Motor Torque Optimization Using Nd-Fe-B Bond Magnets
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Solution Overview
Problem
The challenge is to design a spindle motor for disk drive apparatuses that is thinner while maintaining sufficient torque and reducing startup time, as existing motors face difficulties in achieving these requirements due to limited space constraints.
Innovation Solution
The spindle motor design includes a stator core with a height of 50% to 70% of the total stator height, a rotor magnet made of Nd—Fe—B bond magnet, and a bearing mechanism that supports the rotor hub and magnet to be rotatable, with a torque constant of 4 mN·m/A to 6 mN·m/A and a motor constant of 2 mN·m/(A·√Ω) to 4 mN·m/(A·√Ω), optimizing the thickness and magnetic flux density to generate sufficient torque and reduce startup time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the motor thickness is reduced to meet thinner disk drive demands, then the motor size is reduced, but the torque generation capability deteriorates
Solution Approach 1:
The patent changes the material parameter of the rotor magnet from conventional magnets to Nd-Fe-B bond magnet, which has superior magnetic properties. This allows the motor to maintain sufficient torque generation capability even with reduced thickness, as the high-performance magnet material compensates for the reduced size.
Solution Approach 2:
The patent uses Nd-Fe-B bond magnet, which is a composite material combining neodymium, iron, and boron. This composite material provides enhanced magnetic flux density and torque constant, enabling the thin motor to achieve the required torque output without increasing size.
2Length of moving object
If the motor thickness is reduced, then the motor size is reduced, but the startup time increases
Solution Approach 1:
By changing the magnet material to Nd-Fe-B bond magnet with optimized magnetic parameters, the motor achieves higher torque constant and motor constant. This allows the thin motor to maintain fast startup performance despite the reduced thickness.
Solution Approach 2:
The patent optimizes the stator core height ratio to 50-70% of the total stator height, redistributing the magnetic circuit dimensions. This dimensional optimization, combined with the high-performance magnet material, ensures sufficient torque and fast startup in a thin profile.
3Power
If the stator core height is optimized to 50-70% of total stator height, then the magnetic flux density is optimized, but the structural design complexity increases
Solution Approach 1:
The patent optimizes the stator core height as a key geometric parameter (50-70% of total stator height) to achieve optimal magnetic flux density. This parameter optimization balances performance with manufacturability, as it involves simple dimensional specification rather than complex structural design.
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 design efficiently generates sufficient torque and shortens startup time by optimizing the magnetic flux density and motor constants, preventing the motor from increasing in size while maintaining performance within the limited space constraints.
Implementation Method 1
When the motor is driven, a magnetic action is generated between the drive magnet and the drive coil
Implementation Method 2
a magnetic action is generated between the drive magnet and the drive coil
Implementation Method 3
The rotor magnet is made of an Nd—Fe—B bond magnet
Implementation Method 4
a permanent magnet is disposed to face an outer circumferential side of an electromagnet
Data Source
AI summary
A spindle motor of a disk drive apparatus includes a base unit, a stator core, a covered cylindrical rotor hub, a rotor magnet, and a bearing mechanism. The height of the stator core in an axial direction is about 50% or more and about 70% or less of the height of the stator. A torque constant Kt of torque generated between a stator and a rotor magnet is about 4 mN·m/A or more and about 6 mN·m/A or less. A motor constant Km is about 2 mN·m/(A·√Ω) or more and about 4 mN·m/(A·√Ω) or less.