Thin Spindle Motor Stator Core Height Optimization
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Solution Overview
Problem
Conventional spindle motors in disk drive apparatuses face challenges in reducing thickness while maintaining sufficient torque and minimizing vibrations and noise, especially in 7 mm high disk drive applications where conventional motors with decreased thickness fail to produce adequate torque and increase noise.
Innovation Solution
A thin-type spindle motor design featuring a stator with a specific core-magnet height ratio, a neodymium bonded rotor magnet, and a bearing mechanism that supports the rotor hub and magnet to produce a torque constant of 3 mNm/A to 5 mNm/A, reducing vibrations and noise by optimizing the magnetic flux density and preventing stator core saturation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the motor thickness is reduced to meet the 7 mm high disk drive requirement, then the thickness is reduced, but the torque production becomes insufficient and vibrations and noise increase
Solution Approach 1:
The patent applies parameter changes by optimizing the height of the stator core relative to the rotor magnet height (setting it to 50-75% of magnet height) and controlling magnetic flux density within a specific range (1.5-2.5 T). These parameter optimizations enable the thin motor to achieve sufficient torque (3-5 mNm/A) while maintaining reduced thickness, directly resolving the contradiction between thickness reduction and torque production.
2Length of moving object
If the motor thickness is reduced, then the thickness is reduced, but vibrations and noise increase due to magnetic flux density variations
Solution Approach 1:
The patent controls magnetic flux density within a specific range (1.5-2.5 T) to prevent core saturation and reduce magnetic flux variations. This parameter control minimizes vibrations and noise while maintaining the reduced motor thickness, directly addressing the contradiction between thickness reduction and harmful factor generation.
3Length of moving object
If conventional motor designs are simply thinned down, then thickness is reduced, but torque constant decreases below acceptable levels
Solution Approach 1:
The patent achieves a torque constant of 3-5 mNm/A in a thin motor design by optimizing the stator core height to be 50-75% of the rotor magnet height and controlling magnetic flux density within 1.5-2.5 T. These parameter changes enable sufficient torque production while maintaining reduced thickness, resolving the contradiction between thickness reduction and torque constant maintenance.
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 motor achieves sufficient torque production while reducing vibrations and noise, maintaining efficiency with a torque constant within the desired range and limiting Total Harmonic Distortion (THD) below 4%, enhancing performance in thin disk drive applications.
Implementation Method 1
While the motor is driven, a magnetic action is produced between the driving magnet and the driving coils
Implementation Method 2
a magnetic action is produced between the driving magnet and the driving coils
Implementation Method 3
reducing occurrence of vibrations and noise
Data Source
AI summary
A spindle motor includes a base portion; a stator arranged above the base portion; a rotor hub including a cover portion positioned above the stator, and a side wall portion arranged to extend downward from an outer edge of the cover portion; a rotor magnet positioned radially outward of the stator, and fixed to an inner circumferential surface of the side wall portion of the rotor hub; and a bearing mechanism arranged to support the rotor hub and the rotor magnet to be rotatable. A height of the rotor magnet as measured in an axial direction is preferably in a range of about 2 mm to about 3 mm (both inclusive), and a height of a stator core of the stator as measured in the axial direction is preferably in a range of about 50% to about 75% (both inclusive) of the height of the rotor magnet.